JP2014129986A - Refrigeration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration device using R32 as refrigerant, and capable of improving the COP of the refrigeration device if a compressor operates in a small number-of-revolutions range and the pressure difference is large between the high pressure side and the low pressure side of the compressor.SOLUTION: An air conditioner 10 using R32 as refrigerant includes: a compressor 31; an outdoor heat exchanger; expansion valves 23 and 36; an indoor heat exchanger; a determination unit 41a; and a lower-limit change unit 41c. The compressor attracts low-pressure refrigerant from a suction tube, compresses the refrigerant, and discharges high-pressure refrigerant. The determination unit determines whether the compressor is in a differential pressure state, that is, whether a pressure difference between a pressure of the high-pressure refrigerant discharged from the compressor and that of the low-pressure refrigerant attracted by the compressor is equal to or larger than a predetermined value. The lower-limit change unit changes a lower-limit number of revolutions of the compressor from a first lower limit to a second lower limit greater than the first lower limit if the determination unit determines that the compressor is in the differential pressure state.

Description

  The present invention relates to a refrigeration apparatus.

  Conventionally, a refrigeration apparatus using R32 as a refrigerant is known. For example, Patent Literature 1 (Japanese Patent Laid-Open No. 2001-194015) discloses an air conditioner using R32.

  By the way, at present, refrigeration apparatuses are required to operate a compressor in a lower rotational speed range than before in order to cope with a wide range of loads with a single compressor. Even in an air conditioner using R32 as a refrigerant, such as Patent Document 1 (Japanese Patent Laid-Open No. 2001-194015), it is required to operate the compressor in a low rotation speed range.

  However, when the compressor is operated in a low rotation speed range, there is a problem that the supply of refrigeration oil to the compression mechanism is likely to be insufficient, and the refrigerant is likely to leak from the gap in the compression mechanism. Such a problem is remarkable when the pressure difference between the high pressure side and the low pressure side of the compressor is large. Furthermore, when R32 is used as the refrigerant, the refrigerant is liable to leak from the gap in the compression mechanism, and the COP of the refrigeration apparatus is likely to be deteriorated, compared to the case where R410A is used.

  An object of the present invention is a refrigeration apparatus that uses R32 as a refrigerant, and when the compressor is operated in a low speed range and the pressure difference between the high pressure side and the low pressure side of the compressor is large, An object of the present invention is to provide a refrigeration apparatus capable of improving COP.

  The refrigeration apparatus according to the first aspect of the present invention is a refrigeration apparatus that uses R32 as a refrigerant. The refrigeration apparatus includes a compressor, a condenser, an expansion mechanism, an evaporator, a determination unit, and a lower limit changing unit. The compressor sucks low-pressure refrigerant from the suction flow path, compresses the refrigerant, and discharges high-pressure refrigerant. The condenser condenses the high-pressure refrigerant discharged from the compressor. The expansion mechanism expands the high-pressure refrigerant that has exited the condenser. The evaporator evaporates the refrigerant expanded by the expansion mechanism. The determination unit determines whether the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is equal to or greater than a predetermined value. Determine. The lower limit changing unit changes the lower limit rotation speed of the compressor from the first lower limit value to a second lower limit value larger than the first lower limit value when the determination unit determines that the differential pressure state is present.

  Here, when the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is equal to or greater than a predetermined value, the compressor Is changed to a large value. By changing the lower limit rotational speed of the compressor to a large value, the amount of refrigeration oil supplied to the compressor's compression mechanism can be easily secured even when the compressor is operated in a low rotational speed range. It becomes possible to suppress the gap of the mechanism to be small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor can be suppressed and the COP of the refrigeration apparatus can be improved in the low speed range.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, further comprising a condensation temperature detection unit and an evaporation temperature detection unit. The condensation temperature detector detects the condensation temperature of the condenser. The evaporation temperature detector detects the evaporation temperature of the evaporator. A determination part determines whether it is in a differential pressure state using condensation temperature and evaporation temperature.

  Here, using the condensation temperature and the evaporation temperature, the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor becomes a predetermined value or more. It is determined whether or not there is a differential pressure state. It is possible to determine whether or not there is a differential pressure state without using a pressure sensor that measures the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant. When operated in the rotational speed range, the refrigerant leakage of the compressor compression mechanism can be suppressed, and the COP of the refrigeration apparatus can be improved.

  The refrigeration apparatus according to the third aspect of the present invention is the refrigeration apparatus according to the second aspect, and the determination unit converts the condensation temperature and the evaporation temperature into a condensation pressure and an evaporation pressure, respectively. A determination part determines whether it is in a differential pressure state using the converted condensing pressure and evaporation pressure.

  Here, it is determined whether or not there is a differential pressure state by converting the condensation temperature into the condensation pressure and the evaporation temperature into the evaporation pressure, and using the condensation pressure and the evaporation pressure. Therefore, when the compressor is operated in a low speed range, the refrigerant leakage of the compressor compression mechanism is suppressed while suppressing the cost of the refrigeration apparatus without using the pressure sensor for measuring the pressure. The COP of the refrigeration apparatus can be improved.

  The refrigeration apparatus according to the fourth aspect of the present invention is the refrigeration apparatus according to the second aspect, and the determination unit determines whether or not the differential pressure state is established using a temperature difference between the condensation temperature and the evaporation temperature. To do.

  Here, it is determined from the temperature difference between the condensation temperature and the evaporation temperature whether or not a differential pressure state exists. Therefore, when the compressor is operated in a low speed range, the refrigerant leakage of the compressor compression mechanism is suppressed while suppressing the cost of the refrigeration apparatus without using the pressure sensor for measuring the pressure. The COP of the refrigeration apparatus can be improved.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the first aspect, further comprising a discharge pressure detection unit and a suction pressure detection unit. The discharge pressure detection unit detects the pressure of the high-pressure refrigerant discharged from the compressor. The suction pressure detection unit detects the pressure of the low-pressure refrigerant sucked into the compressor. A determination part determines whether it is in a differential pressure state using the detection result of a discharge pressure detection part and a suction pressure detection part.

  Here, the differential pressure state can be accurately determined by actually measuring the discharge pressure and the suction pressure. Therefore, it is easy to improve the COP of the refrigeration apparatus by suppressing the leakage of the refrigerant of the compressor compression mechanism in the low rotation speed range.

  In the refrigeration apparatus according to the first aspect of the present invention, the difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is a predetermined value or more. When in the pressure state, the lower limit rotational speed of the compressor is changed to a large value. By changing the lower limit rotational speed of the compressor to a large value, the amount of refrigeration oil supplied to the compressor's compression mechanism can be easily secured even when the compressor is operated in a low rotational speed range. It becomes possible to suppress the gap of the mechanism to be small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor can be suppressed and the COP of the refrigeration apparatus can be improved in the low speed range.

  In the refrigeration apparatus according to the second to fourth aspects of the present invention, the refrigerant leakage of the compression mechanism of the compressor is suppressed when the compressor is operated in a low speed range while suppressing the cost of the refrigeration apparatus. In addition, the COP of the refrigeration apparatus can be improved.

  In the refrigeration apparatus according to the fifth aspect of the present invention, it is easy to improve the COP of the refrigeration apparatus by suppressing the leakage of the refrigerant in the compression mechanism of the compressor in the low speed range.

It is a schematic block diagram of the air conditioning apparatus as a freezing apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of the air conditioning apparatus of FIG. It is a flowchart of the determination process of a differential pressure state of the air conditioning apparatus of FIG. 1, and the change process of the minimum rotation speed of a compressor. In the air conditioning apparatus of FIG. 1, it is an image figure for demonstrating the effect of changing a minimum rotation speed from a 1st lower limit to a 2nd lower limit (> 1st lower limit). A graph when the compressor is operated at the first lower limit value is shown on the left side, and a graph when the compressor is operated at the second lower limit value is shown on the right side. The graph shows that when the pressure difference between the discharge pressure and the suction pressure of the compressor is a predetermined value, how much of the energy consumption (power consumption of the compressor) is used effectively (for air conditioning) It shows how much energy was wasted due to leakage of refrigerant from the gap of the compression mechanism. It is a flowchart of the determination process of the differential pressure state concerning the modification A, and the change process of the minimum rotation speed of a compressor. The temperature difference between the detected temperature of the outdoor heat exchanger sensor and the detected temperature of the indoor heat exchanger sensor is converted into a pressure difference, and the pressure difference is determined using the pressure difference. It is a flowchart of the determination process of the differential pressure state concerning the modification A, and the change process of the minimum rotation speed of a compressor. The differential pressure state is determined using the temperature difference between the temperature detected by the outdoor heat exchanger sensor and the temperature detected by the indoor heat exchanger sensor. It is a schematic block diagram of the air conditioning apparatus as a freezing apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram of the air conditioning apparatus of FIG. It is a flowchart of the determination process of a differential pressure state of the air conditioning apparatus of FIG. 7, and the change process of the minimum rotation speed of a compressor.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the following embodiment of this invention can be suitably changed in the range which does not deviate from the meaning of this invention.

<First Embodiment>
(1) Overall Configuration The air conditioner 10 as a refrigeration apparatus according to the first embodiment of the present invention is an air conditioner that can be operated by switching between a cooling operation and a heating operation. However, the air conditioner 10 may not be operable by switching between the cooling operation and the heating operation, and may be an air conditioner capable of performing only the cooling operation or the heating operation.

  As shown in FIGS. 1 and 2, the air conditioner 10 mainly includes an indoor unit 20, an outdoor unit 30, and a control unit 40. In the present embodiment, the number of indoor units 20 is one, but a plurality of units may be used.

  The air conditioner 10 has a refrigerant circuit 1 filled with R32 as a refrigerant. The refrigerant circuit 1 has an indoor circuit 1 a accommodated in the indoor unit 20 and an outdoor circuit 1 b accommodated in the outdoor unit 30. The indoor side circuit 1a and the outdoor side circuit 1b are connected by a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72.

(2) Detailed configuration (2-1) Indoor unit The indoor unit 20 is installed in the room which is the object of air conditioning. The indoor unit 20 includes an indoor heat exchanger 21, an indoor fan 22, an indoor expansion valve 23, and an indoor heat exchange temperature sensor 24.

  The indoor heat exchanger 21 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of heat transfer fins. During the cooling operation, the indoor heat exchanger 21 functions as an evaporator that evaporates refrigerant expanded by an outdoor expansion valve 36 and an indoor expansion valve 23 described later, and cools indoor air. The indoor heat exchanger 21 functions as a condenser that condenses high-pressure refrigerant discharged from a compressor 31 described later during heating operation, and heats indoor air. The liquid side of the indoor heat exchanger 21 is connected to the liquid refrigerant communication pipe 71, and the gas side of the indoor heat exchanger 21 is connected to the gas refrigerant communication pipe 72.

  The indoor fan 22 is rotated by a fan motor, takes in indoor air, blows it to the indoor heat exchanger 21, and promotes heat exchange between the refrigerant flowing through the indoor heat exchanger 21 and the indoor air.

  The indoor expansion valve 23 is an example of an expansion mechanism, and is an electric expansion valve with a variable opening provided for adjusting the pressure and flow rate of the refrigerant flowing in the indoor circuit 1a. During the cooling operation, the indoor expansion valve 23 expands (depressurizes) the refrigerant flowing from the outdoor heat exchanger 34 of the outdoor unit 30 described later, which functions as a condenser, to the indoor heat exchanger 21 that functions as an evaporator. . During the heating operation, the indoor expansion valve 23 expands (depressurizes) the refrigerant flowing from the indoor heat exchanger 21 that functions as a condenser to the outdoor heat exchanger 34 that functions as an evaporator.

  The indoor heat exchanger temperature sensor 24 is a thermistor that measures the temperature of the indoor heat exchanger 21. The indoor heat exchanger temperature sensor 24 is attached to the indoor heat exchanger 21. When the indoor heat exchanger 21 functions as a condenser, the indoor heat exchanger temperature sensor 24 functions as a condensing temperature detector that detects the condensing temperature Tc. When the indoor heat exchanger 21 functions as an evaporator, the indoor heat exchanger temperature sensor 24 functions as an evaporation temperature detection unit that detects the evaporation temperature Te.

(2-2) Outdoor unit The outdoor unit 30 mainly includes a compressor 31, a four-way switching valve 33, an outdoor heat exchanger 34, an outdoor fan 35, an outdoor expansion valve 36, an outdoor heat exchanger temperature sensor 37, and a discharge. A temperature sensor 51 is provided. The compressor 31, the four-way switching valve 33, the outdoor heat exchanger 34, and the outdoor expansion valve 36 are connected by refrigerant piping.

(2-2-1) Connection of component equipment by refrigerant piping Connection by refrigerant piping of the component equipment of the outdoor unit 30 will be described.

  The suction port of the compressor 31 and the four-way switching valve 33 are connected by a suction pipe 81. The discharge port of the compressor 31 and the four-way switching valve 33 are connected by a discharge pipe 82. The four-way switching valve 33 and the gas side of the outdoor heat exchanger 34 are connected by a first gas refrigerant pipe 83. The outdoor heat exchanger 34 and the liquid refrigerant communication pipe 71 are connected by a liquid refrigerant pipe 84. The liquid refrigerant pipe 84 is provided with an outdoor expansion valve 36. The four-way switching valve 33 and the gas refrigerant communication pipe 72 are connected by a second gas refrigerant pipe 85.

(2-2-2) Compressor The compressor 31 drives the compression mechanism with a motor, thereby sucking low-pressure gas refrigerant from the suction pipe 81, and supplying the high-pressure gas refrigerant compressed by the compression mechanism to the discharge pipe 82. Discharge. Although the compressor 31 is a rotary compressor, it is not limited to this, For example, a scroll compressor may be sufficient.

  The compressor 31 is an inverter type compressor capable of changing the rotational speed N (the rotational speed of the motor of the compressor 31). The movement of the compressor 31 is controlled by a compressor control unit 41b described later. The compressor control unit 41b controls the rotational speed N of the compressor 31 according to the degree of divergence between the temperature (room temperature) of the air conditioning target space and the set temperature.

(2-2-3) Four-way switching valve The four-way switching valve 33 switches the flow direction of the refrigerant when the air-conditioning apparatus 10 is switched between the cooling operation and the heating operation. During the cooling operation, the discharge pipe 82 and the first gas refrigerant pipe 83 are connected, and the suction pipe 81 and the second gas refrigerant pipe 85 are connected (see the solid line in FIG. 1). On the other hand, during the heating operation, the discharge pipe 82 and the second gas refrigerant pipe 85 are connected, and the suction pipe 81 and the first gas refrigerant pipe 83 are connected (see the broken line in FIG. 1).

(2-2-4) Outdoor Heat Exchanger The outdoor heat exchanger 34 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of heat transfer fins. The outdoor heat exchanger 34 functions as a condenser that condenses the high-pressure refrigerant discharged from the compressor 31 by exchanging heat between the outdoor air and the refrigerant during the cooling operation. The outdoor heat exchanger 34 functions as an evaporator that evaporates the refrigerant expanded by the indoor expansion valve 23 and the outdoor expansion valve 36 by exchanging heat between the outdoor air and the refrigerant during heating operation.

(2-2-5) Outdoor Fan The outdoor fan 35 is rotated by a fan motor and takes outdoor air into the outdoor unit 30. The taken outdoor air passes through the outdoor heat exchanger 34 and is finally discharged out of the outdoor unit 30. The outdoor fan 35 promotes heat exchange between the refrigerant flowing in the outdoor heat exchanger 34 and outdoor air.

(2-2-6) Outdoor Expansion Valve The outdoor expansion valve 36 is an example of an expansion mechanism, and an electric expansion with a variable opening provided for adjusting the pressure and flow rate of the refrigerant flowing in the outdoor circuit 1b. It is a valve. During the cooling operation, the outdoor expansion valve 36 expands (depressurizes) the refrigerant flowing from the outdoor heat exchanger 34 functioning as a condenser to the indoor heat exchanger 21 functioning as an evaporator. During the heating operation, the outdoor expansion valve 36 expands (depressurizes) the refrigerant flowing from the indoor heat exchanger 21 that functions as a condenser to the outdoor heat exchanger 34 that functions as an evaporator.

(2-2-7) Outdoor Heat Exchange Temperature Sensor The outdoor heat exchange temperature sensor 37 is a thermistor that measures the temperature of the outdoor heat exchanger 34. The outdoor heat exchange temperature sensor 37 is attached to the outdoor heat exchanger 34. When the outdoor heat exchanger 34 functions as a condenser, the outdoor heat exchanger temperature sensor 37 functions as a condensing temperature detector that detects the condensing temperature Tc. The outdoor heat exchanger temperature sensor 37 functions as an evaporation temperature detection unit that detects the evaporation temperature Te when the outdoor heat exchanger 34 functions as an evaporator.

(2-2-8) Discharge pipe temperature sensor The discharge temperature sensor 51 is a thermistor for detecting the temperature of the refrigerant discharged from the compressor 31. The discharge temperature sensor 51 is provided outside the compressor 31, more specifically, near the discharge port of the compressor 31 in the discharge pipe 82. The temperature detected by the discharge temperature sensor 51 is used for control of the compressor 31 (including protection control of the compressor 31).

(2-3) Control Unit The control unit 40 controls the movement of the air conditioner 10. In FIG. 2, the block diagram of the air conditioning apparatus 10 containing the control unit 40 is shown.

  The control unit 40 includes a control unit 41 made up of a microcomputer or the like, a storage unit 42 made up of a memory such as RAM or ROM, and an input unit 43 (remote control). The control unit 40 includes each configuration of the indoor unit 20 and the outdoor unit 30, a compressor 31, a four-way switching valve 33, an outdoor fan 35, an outdoor expansion valve 36, an indoor fan 22, an indoor expansion valve 23, a discharge temperature sensor 51, an outdoor The heat exchange temperature sensor 37, the indoor heat exchange temperature sensor 24, and the like are electrically connected.

  The control unit 41 controls the air conditioner 10 by reading and executing the program stored in the storage unit 42. The control unit 41 exchanges control signals with the input unit 43 in order to operate the indoor unit 20. And the control part 41 controls the driving | operation of the air conditioning apparatus 10 according to the input (The operation / stop of the air conditioning apparatus 10, an operation mode (cooling mode / heating mode), preset temperature, etc.) to the input part 43. . The control unit 41 controls various devices of the indoor unit 20 and the outdoor unit 30 according to operating conditions (for example, according to the degree of deviation between the temperature (room temperature) of the air-conditioning target space and the set temperature).

  In addition, the control part 41 has the determination part 41a, the compressor control part 41b, and the lower limit change part 41c as a function part. The determination unit 41a, the compressor control unit 41b, and the lower limit changing unit 41c will be described later.

  The storage unit 42 stores a program to be executed by the control unit 41 and various information. The storage unit 42 includes a conversion information storage area 42 a that stores temperature-pressure conversion information, and an upper and lower limit storage area 42 b that stores the lower limit rotation speed NL and the upper limit rotation speed NH of the compressor 31. The conversion information storage area 42a and the upper / lower limit storage area 42b will be described later.

(2-3-1) Control part (2-3-1-1) Determination part The determination part 41a is the pressure (discharge pressure Po) of the high pressure refrigerant | coolant discharged from a compressor, and the low pressure suck | inhaled by a compressor. It is determined whether or not the pressure difference between the refrigerant and the refrigerant pressure (suction pressure Pi) is in a differential pressure state such that the pressure difference is equal to or greater than a predetermined value A (eg, 0.3 MPa). Specifically, the determination unit 41a includes the condensation temperature Tc (measured value of the indoor heat exchanger temperature sensor 24 or the measured value of the outdoor heat exchanger temperature sensor 37) and the evaporation temperature Te (measured value of the outdoor heat exchanger temperature sensor 37 or The measured value of the indoor heat exchanger temperature sensor 24) is used to determine whether or not it is in a differential pressure state.

  The determination of the differential pressure state by the determination unit 41a will be described later.

(2-3-1-2) Compressor Control Unit The compressor control unit 41b is configured to start / stop the compressor 31 and to control the compressor 31 according to the operating conditions of the air conditioner 10, various control signals, and the like. The rotational speed N (the rotational speed of the motor of the compressor 31) is determined and controlled. For example, the compressor control unit 41b controls the rotation speed N of the motor of the compressor 31 according to the degree of deviation between the temperature (room temperature) of the space that is the air-conditioning target of the air conditioner 10 and the set temperature. The rotation speed N of the compressor 31 is controlled by a value between a lower limit rotation speed NL and an upper limit rotation speed NH stored in an upper / lower limit storage area 42b described later.

(2-3-1-3) Lower limit change unit The lower limit change unit 41c changes the lower limit rotation number NL of the compressor 31 by rewriting the value of the lower limit rotation number NL stored in the upper and lower limit storage area 42b.

  When the determination unit 41a determines that the differential pressure state is in the differential pressure state, the lower limit change unit 41c changes (sets) the lower limit rotation speed NL of the compressor to the second lower limit value N2. The lower limit changing unit 41c changes (sets) the lower limit rotation speed NL of the compressor to the first lower limit value N1 when the determination unit 41a determines that the differential pressure state is not present.

  The change of the lower limit rotational speed NL by the lower limit changing unit 41c will be described later.

(2-3-2) Storage Unit (2-3-2-1) Conversion Information Storage Area In the conversion information storage area 42a, the condensation temperature (evaporation temperature) of R32 that is a refrigerant, the condensation pressure (evaporation pressure), and Temperature pressure conversion information related to the relationship is stored. Specifically, the conversion information storage area 42a stores the condensation pressure (evaporation pressure) for each condensation temperature (evaporation temperature) as temperature-pressure conversion information.

  However, the present invention is not limited to this. For example, the conversion information storage area 42a may store a relational expression between the condensation temperature (evaporation temperature) and the condensation pressure (evaporation pressure) as temperature pressure conversion information. .

(2-3-2-2) Upper / lower limit storage area The upper / lower limit storage area 42b stores an upper limit (upper limit rotational speed NH) and a lower limit (lower limit rotational speed NL) of the rotational speed N of the compressor 31. .

  When the determination part 41a determines that it is not in the differential pressure state, the first lower limit value N1 is stored as the lower limit rotation speed NL in the upper and lower limit storage area 42b. On the other hand, when the determination unit 41a determines that the pressure difference is present, the upper and lower limit storage area 42b stores the second lower limit value N2 as the lower limit rotation speed NL. The second lower limit value N2 is larger than the first lower limit value N1. For example, the first lower limit value N1 is 4 rps, and the second lower limit value N2 is 6 rps. The lower limit rotation speed NL in the upper / lower limit storage area 42b is set to the first lower limit value N1 or the second lower limit value N2 by being changed by the lower limit changing unit 41c.

(2-3-3) Input Unit The input unit 43 is a remote controller for the air conditioning apparatus 10. The input unit 43 receives various inputs from the user of the air conditioning apparatus 10. Various inputs received from the user by the input unit 43 include an operation / stop command for the air conditioner 10, an operation mode (heating mode / cooling mode) of the air conditioner 10, a set temperature of the air conditioner 10, and the like.

(3) Differential Pressure State Determination Process and Compressor Lower Limit Rotation Speed Change Process Hereinafter, the differential pressure state determination process and the lower limit rotation speed NL change process of the compressor 31 will be described with reference to the flowchart of FIG. To do. The process for determining the differential pressure state and the process for changing the lower limit rotational speed NL are performed periodically (for example, at intervals of 30 seconds) while the air conditioner 10 is in operation.

  In step S <b> 1, the determination unit 41 a acquires measurement values of the indoor heat exchange temperature sensor 24 and the outdoor heat exchange temperature sensor 37. If the air conditioner 10 is in the cooling operation, the measured value of the outdoor heat exchanger temperature sensor 37 is acquired as the condensation temperature Tc, and the measured value of the indoor heat exchanger temperature sensor 24 is acquired as the evaporation temperature Te. If the air conditioner 10 is in the heating operation, the measured value of the indoor heat exchanger temperature sensor 24 is acquired as the condensation temperature Tc, and the measured value of the outdoor heat exchanger temperature sensor 37 is acquired as the evaporation temperature Te. Thereafter, the process proceeds to step S2.

  In step S2, the determination unit 41a converts the aggregation temperature Tc obtained in step S1 into the aggregation pressure Pc using the temperature / pressure conversion information stored in the conversion information storage area 42a, and converts the evaporation temperature Te into the evaporation pressure Pe. Convert to. Thereafter, the process proceeds to step S3.

  In step S3, the determination unit 41a calculates a pressure difference ΔP between the condensation pressure Pc obtained in step S2 and the evaporation pressure Pe. The pressure difference ΔP is calculated by subtracting the evaporation pressure Pe from the condensation pressure Pc. Note that the pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe approximates the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31. Thereafter, the process proceeds to step S4.

  In step S4, the determination unit 41a determines whether or not the pressure difference ΔP is equal to or greater than a predetermined value A. If the pressure difference ΔP is determined to be greater than or equal to the predetermined value A, it is determined that the pressure difference is present (the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is greater than or equal to the predetermined value A), and step Proceed to S5. When it is determined that the pressure difference ΔP is smaller than the predetermined value A, it is determined that the pressure difference state is not established, and the process proceeds to step S7.

  In step S5, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the first lower limit value N1. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the first lower limit value N1, the process proceeds to step S6. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the first lower limit value N1 (the second lower limit value N2), the process is terminated.

  In step S6, the lower limit changing unit 41c changes the lower limit rotation speed NL to the second lower limit value N2. Thereafter, the process ends.

  In step S7, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the second lower limit value N2. If it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the second lower limit value N2, the process proceeds to step S8. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the second lower limit value N2 (is the first lower limit value N1), the process ends.

  In step S8, the lower limit changing unit 41c changes the lower limit rotation speed NL to the first lower limit value N1. Thereafter, the process ends.

  By performing the above processing, when the determination unit 41a determines that the air conditioner 10 is in the differential pressure state, the lower limit rotation speed NL of the compressor 31 is set to the second lower limit value N2 (change). ) On the other hand, when the determination unit 41a determines that the air conditioner 10 is not in the differential pressure state, the lower limit rotation speed NL of the compressor 31 is set (changed) to the first lower limit value N1.

  As described above, the lower limit rotational speed NL of the compressor 31 is variable between the first lower limit value N1 and the second lower limit value N2, and the lower limit rotational speed NL of the compressor 31 is set to the first lower limit value N1 when in the differential pressure state. By setting the second lower limit value N2 to be larger, the following effects can be obtained.

  It is desirable that the compressor 31 can be operated at the lowest possible rotation speed NL as much as possible in order to meet a wide range of air conditioning capabilities with a single compressor 31. Therefore, it is desirable that the lower limit rotation speed NL of the compressor 31 is basically a small value (first lower limit value N1).

  By the way, in the compressor 31, in order to prevent the refrigerant from leaking from the high pressure side to the low pressure side through the gap of the compression mechanism, refrigeration oil is supplied to the compression mechanism and an oil film is formed in the gap of the compression mechanism. doing. The clearance of the compression mechanism is, for example, a clearance between a roller and a cylinder in the case of a rotary compressor as in this embodiment. The supply of the refrigerating machine oil to the compression mechanism of the compressor 31 uses a centrifugal force or the like generated by the rotation of the motor as a driving force. In the state where the lower limit rotational speed NL is reached, the supply amount of refrigerating machine oil tends to decrease. Therefore, when the rotation speed N of the compressor 31 reaches the lower limit rotation speed NL, the refrigerant is likely to leak from the gap of the compression mechanism. In particular, in a differential pressure state where the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is equal to or greater than a predetermined value A, the refrigerant is likely to leak. Moreover, in this embodiment, since R32 is used as a refrigerant, the refrigerant is more likely to leak from the gap of the compression mechanism than when R410A is used as the refrigerant.

  As a result, when the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is a certain value B (value B ≧ predetermined value A which is a reference value of the differential pressure state), the lower limit rotation speed of the compressor 31 is reached. Assuming that NL is the first lower limit value N1, for example, as shown in the graph on the left side of FIG. 4, the proportion of energy wasted due to refrigerant leaking from the gap of the compression mechanism with respect to energy consumption (power consumption). Cheap. In other words, the ratio of energy (shaded area in FIG. 4) that actually contributes to air conditioning tends to be small with respect to energy consumption (power consumption).

  On the other hand, when the lower limit rotational speed NL of the rotational speed N of the compressor 31 is changed to the second lower limit value N2 larger than the first lower limit value N1, the amount of oil supplied to the compression mechanism of the compressor 31 at the lower limit rotational speed NL. Will increase. As a result, an oil film is formed in the gap of the compression mechanism, and the amount of refrigerant leaking is reduced. As a result, for example, as shown in the graph on the right side of FIG. 4, less energy is wasted due to refrigerant leaking from the gaps in the compression mechanism. In other words, by changing the lower limit rotational speed NL from the first lower limit value N1 to the second lower limit value N2, energy actually consumed for air conditioning (hatched portion in FIG. 4) with respect to energy consumption (power consumption). The proportion increases. That is, in the air conditioning apparatus 10 of the present embodiment, it is possible to improve the efficiency of the compressor 31 when the compressor 31 is operated in the differential pressure state and in the low rotation speed region. As a result, the COP of the air conditioner 10 is improved, and energy can be effectively used.

  Note that the determination of whether or not the differential pressure state is present is made in order to prevent the refrigerant from leaking from the gap of the compression mechanism as described above and the COP of the air conditioner 10 from being excessively deteriorated. Therefore, the reference value (predetermined value A) as to whether or not the differential pressure state exists may be appropriately determined according to the characteristics of the compressor 31 and the like.

(4) Features (4-1)
The air conditioning apparatus 10 of the present embodiment is a refrigeration apparatus that uses R32 as a refrigerant. The air conditioner 10 includes a compressor 31, a condenser (indoor heat exchanger 21 or outdoor heat exchanger 34), an indoor expansion valve 23 and an outdoor expansion valve 36 as an expansion mechanism, and an evaporator (outdoor heat exchanger). 34 or the indoor heat exchanger 21), a determination unit 41a, and a lower limit changing unit 41c. The compressor 31 sucks low-pressure refrigerant from a suction pipe 81 serving as a suction flow path, compresses the refrigerant, and discharges high-pressure refrigerant. The condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34) condenses the high-pressure refrigerant discharged from the compressor 31. The indoor expansion valve 23 and the outdoor expansion valve 36 expand the high-pressure refrigerant that has exited the condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34). The evaporator (the outdoor heat exchanger 34 or the indoor heat exchanger 21) evaporates the refrigerant expanded by the indoor expansion valve 23 and the outdoor expansion valve 36. The determination unit 41a is in a differential pressure state in which the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. It is determined whether or not there is. When the determination unit 41a determines that the differential pressure state exists, the lower limit changing unit 41c changes the lower limit rotation speed NL of the compressor 31 from the first lower limit value N1 to a second lower limit value that is larger than the first lower limit value N1. Change to N2.

  Here, when the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. The lower limit rotational speed NL of the compressor 31 is changed to a large value (second lower limit value N2). By changing the lower limit rotational speed NL of the compressor 31 to a large value, the amount of refrigerating machine oil supplied to the compression mechanism of the compressor 31 is ensured even when the compressor 31 is operated in a low rotational speed range. It becomes easy and it becomes possible to suppress the clearance gap of a compression mechanism small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor 31 can be suppressed and the COP of the air conditioner 10 can be improved in the low speed range.

(4-2)
In the air conditioning apparatus 10 of the present embodiment, the condensation temperature detection unit (the indoor heat exchange temperature sensor 24 or the outdoor heat exchange temperature sensor 37) and the evaporation temperature detection unit (the outdoor heat exchange temperature sensor 37 or the indoor heat exchange temperature sensor 24). And prepare. The condensation temperature detector (the indoor heat exchanger temperature sensor 24 or the outdoor heat exchanger temperature sensor 37) detects the condensation temperature Tc of the condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34). The evaporation temperature detection unit (outdoor heat exchange temperature sensor 37 or indoor heat exchange temperature sensor 24) detects the evaporation temperature Te of the evaporator (outdoor heat exchanger 34 or indoor heat exchanger 21). The determination part 41a determines whether it is in a differential pressure state using the condensation temperature Tc and the evaporation temperature Te.

  Here, the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor using the condensation temperature Tc and the evaporation temperature Te is equal to or greater than a predetermined value A. It is determined whether or not the differential pressure state is as follows. It is possible to determine whether or not there is a differential pressure state without using a pressure sensor that measures the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant, and while reducing the cost of the air conditioner 10, the compressor When 31 is operated in a low rotation speed range, leakage of the refrigerant of the compression mechanism of the compressor 31 can be suppressed, and the COP of the air conditioner 10 can be improved.

(4-3)
In the air conditioning apparatus 10 of the present embodiment, the determination unit 41a converts the condensation temperature Tc and the evaporation temperature Te into a condensation pressure Pc and an evaporation pressure Pe, respectively. The determination part 41a determines whether it is in a differential pressure state using the converted condensing pressure Pc and evaporation pressure Pe.

  Here, the condensing temperature Tc is converted into the condensing pressure Pc, the evaporating temperature Te is converted into the evaporating pressure Pe, and the condensing pressure Pc and the evaporating pressure Pe are used to determine whether or not there is a differential pressure state. Is called. Therefore, when the compressor 31 is operated in a low speed range while suppressing the cost of the air conditioner 10 without using a pressure sensor for measuring pressure, the refrigerant of the compression mechanism of the compressor 31 is reduced. Leakage can be suppressed and the COP of the air conditioner 10 can be improved.

(5) Modifications Modifications of the present embodiment are shown below. A plurality of modified examples may be appropriately combined.

(5-1) Modification 1A
In the above embodiment, the determination unit 41a converts the condensation temperature Tc and the evaporation temperature Te into the condensation pressure Pc and the evaporation pressure Pe, respectively, and is in a differential pressure state using the converted condensation pressure Pc and the evaporation pressure Pe. However, the present invention is not limited to this.

  For example, in the conversion information storage area 42a, information (for example, a mathematical expression) for converting the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te into the pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe is stored. 41a may determine whether or not it is in a differential pressure state by using the information.

  In this case, unlike the flowchart of the above-described embodiment (see FIG. 3), step S12 for calculating the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te is performed instead of step S2, as in the flowchart of FIG. Step S13 is executed instead of step S3, in which a pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe is calculated from the temperature difference ΔT.

  In addition, for example, the condensation temperature Tc and the evaporation temperature Te are highly likely to be in a differential pressure state, that is, the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is likely to be a predetermined value A or higher. The reference value C of the temperature difference ΔT is stored in the storage unit 42 in advance, and the determination unit 41a determines whether or not the temperature difference ΔT is greater than or equal to the reference value C to determine whether or not the differential pressure state exists. May be.

  In this case, unlike the flowchart of the above-described embodiment (see FIG. 3), step S12 for calculating the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te is performed instead of step S2, as in the flowchart of FIG. After that, the differential pressure state is determined based on whether or not the temperature difference ΔT is greater than or equal to the reference value C in step S14.

(5-2) Modification 1B
In the above embodiment, the determination unit 41a considers that the calculated ΔP of the condensation pressure Pc and the evaporation pressure Pe is equal to the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31, and ΔP is equal to or greater than the predetermined value A. At this time, it is determined that there is a differential pressure state (a state in which the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is equal to or greater than a predetermined value A), but is not limited thereto. For example, it may be determined that the differential pressure state is present when ΔP is equal to or greater than the product of the predetermined value A and the predetermined coefficient.

(5-3) Modification 1C
In the above embodiment, the determination unit 41a determines whether or not the differential pressure state is present using the condensation temperature Tc and the evaporation temperature Te, but the determination method for the differential pressure state is not limited to this. . For example, it may be determined whether or not the pressure is in a differential pressure state using the opening degree of the indoor expansion valve 23 and / or the outdoor expansion valve 36 and the rotational speed N of the compressor 31. Moreover, in addition to the condensation temperature Tc or the evaporation temperature Te, it may be determined whether or not a differential pressure state is established using room temperature or an outside air temperature.

(5-4) Modification 1D
In the above embodiment, one differential pressure such that the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. The lower limit rotational speed NL is set to one of the first lower limit value N1 and the second lower limit value N2 depending on whether or not the state is determined and the differential pressure state, but the present invention is not limited to this. It is not something. For example, by providing a plurality of predetermined values, a first differential pressure state in which the pressure difference is greater than or equal to the predetermined value A1, a second differential pressure state in which the pressure difference is greater than or equal to the predetermined value A2, and so on are determined. The lower limit rotational speed NL may be set (changed) to a plurality of values depending on whether the state is in effect.

(5-5) Modification 1E
In the said embodiment, although the indoor expansion valve 23 and the outdoor expansion valve 36 are provided as an expansion mechanism, it is not limited to this. For example, the expansion mechanism may be only the outdoor expansion valve 36.

Second Embodiment
An air conditioner 110 as a refrigeration apparatus according to a second embodiment of the present invention will be described. In addition, since the air conditioning apparatus 110 of this embodiment has many points in common with 1st Embodiment, it mainly demonstrates a different point. In the description of the second embodiment, the same reference numerals as those in the first embodiment may be used, but the configuration using the same reference numerals means the same as the configuration in the first embodiment.

(1) Overall Configuration The air conditioning apparatus 110 is a refrigeration apparatus that uses R32 as a refrigerant. As shown in FIG. 1, the air conditioner 110 mainly includes an indoor unit 20, an outdoor unit 130, and a control unit 140. Since the air conditioner 10 of the first embodiment and the indoor unit 20 are the same, only the outdoor unit 130 and the control unit 140 will be described here.

(2) Detailed configuration (2-1) Outdoor unit The outdoor unit 130 mainly includes a compressor 31, a four-way switching valve 33, an outdoor heat exchanger 34, an outdoor fan 35, an outdoor expansion valve 36, and an outdoor heat exchange temperature sensor. 37, a discharge temperature sensor 51, a discharge pressure sensor 61, and a suction pressure sensor 62. The outdoor unit 130 is the same as the outdoor unit 30 of the first embodiment except that the outdoor unit 130 has a discharge pressure sensor 61 and a suction pressure sensor 62. Therefore, only the discharge pressure sensor 61 and the suction pressure sensor 62 will be described here. To do.

(2-1-1) Discharge Pressure Sensor The discharge pressure sensor 61 is an example of a discharge pressure detection unit that detects the pressure of the high-pressure refrigerant discharged from the compressor 31 (discharge pressure Po). The discharge pressure sensor 61 is provided outside the compressor 31, more specifically, near the discharge port of the compressor 31 in the discharge pipe 82.

(2-1-2) Suction Pressure Sensor The suction pressure sensor 62 is an example of a suction pressure detection unit that detects the pressure (suction pressure Pi) of the low-pressure refrigerant sucked into the compressor 31. The suction pressure sensor 62 is provided outside the compressor 31, more specifically, near the suction port of the compressor 31 in the suction pipe 81.

(2-2) Control Unit The control unit 140 controls the air conditioner 110. FIG. 8 shows a block diagram of the air conditioner 110 including the control unit 140.

  The control unit 140 includes a determination unit 141a using the control unit 40 according to the first embodiment, the point where the suction pressure sensor 61 and the suction pressure sensor 62 are electrically connected, and the measured values of the pressure sensors 61 and 62. Is different in that it determines the differential pressure state. Since the other points are the same, only the determination unit 141a will be described here. In addition, since the conversion information storage area 42a of the storage unit 42 is not used for the determination of the differential pressure state by the determination unit 141a, it may not be provided.

(2-2-1) Determination Unit The determination unit 41a includes the pressure of the high-pressure refrigerant discharged from the compressor (discharge pressure Po), the pressure of the low-pressure refrigerant sucked into the compressor (intake pressure Pi), It is determined whether or not the pressure difference is equal to or greater than a predetermined value A. Specifically, the determination unit 41a determines whether or not a differential pressure state exists using the discharge pressure Po measured by the discharge pressure sensor 61 and the suction pressure Pi measured by the suction pressure sensor 62. To do.

(3) Differential Pressure State Determination Process and Compressor Lower Limit Rotation Speed Change Process Hereinafter, the differential pressure state determination process and the lower limit rotation speed NL change process of the compressor 31 will be described with reference to the flowchart of FIG. To do. The process for determining the differential pressure state and the process for changing the lower limit rotational speed NL are performed periodically (for example, at intervals of 30 seconds) while the air conditioner 110 is in operation.

  In step S101, the determination unit 141a acquires the measurement values of the discharge pressure sensor 61 and the suction pressure sensor 62 as the discharge pressure Po and the suction pressure Pi. Thereafter, the process proceeds to step S102.

  In step S102, the determination unit 141a calculates a pressure difference ΔP1 between the discharge pressure Po obtained in step S101 and the suction pressure Pi. The pressure difference ΔP1 is calculated by subtracting the suction pressure Pi from the discharge pressure Po. Thereafter, the process proceeds to step S103.

  In step S103, the determination unit 141a determines whether or not the pressure difference ΔP1 is equal to or greater than a predetermined value A. If it is determined that the pressure difference ΔP1 is greater than or equal to the predetermined value A, it is determined that the pressure difference is present, and the process proceeds to step S104. If it is determined that the pressure difference ΔP1 is smaller than the predetermined value A, it is determined that the pressure difference state is not established, and the process proceeds to step S106.

  In step S104, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the first lower limit value N1. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the first lower limit value N1, the process proceeds to step S105. On the other hand, when it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the first lower limit value N1 (the second lower limit value N2), the process is terminated.

  In step S105, the lower limit changing unit 41c changes the lower limit rotation speed NL to the second lower limit value N2. Thereafter, the process ends.

  In step S106, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the second lower limit value N2. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the second lower limit value N2, the process proceeds to step S107. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the second lower limit value N2 (is the first lower limit value N1), the process ends.

  In step S107, the lower limit changing unit 41c changes the lower limit rotation speed NL to the first lower limit value N1. Thereafter, the process ends.

(4) Features The air conditioner 110 of the second embodiment has the following features in addition to the features of (4-1) of the first embodiment.

(4-1)
The air conditioning apparatus 110 according to the present embodiment includes a discharge pressure sensor 61 as a discharge pressure detection unit, and a suction pressure sensor 62 as a suction pressure detection unit. The discharge pressure sensor 61 detects the pressure of the high-pressure refrigerant discharged from the compressor 31. The suction pressure sensor 62 detects the pressure of the low-pressure refrigerant sucked into the compressor 31. The determination unit 141a determines whether or not a differential pressure state exists using the detection results of the discharge pressure sensor 61 and the suction pressure sensor 62.

  Here, the differential pressure state can be accurately determined by actually measuring the discharge pressure Po and the suction pressure Pi. Therefore, it is easy to improve the COP of the air conditioner 110 by suppressing the leakage of the refrigerant of the compression mechanism of the compressor 31 in the low rotation speed range.

(5) Modifications Modifications of the present embodiment are shown below. A plurality of modified examples may be appropriately combined.

(5-1) Modification 2A
In the above embodiment, the discharge pressure sensor 61 and the suction pressure sensor 62 are provided, but the present invention is not limited to this.

  For example, only one of the discharge pressure sensor 61 or the suction pressure sensor 62 may be provided. For the pressure not detected by the pressure sensor, as in the first embodiment, the condensation pressure Pc or the evaporation pressure Pe is calculated using the condensation temperature Tc or the evaporation temperature Te, and the value is not detected by the pressure sensor. As a substitute. For example, when the suction pressure sensor 62 is not provided, the evaporation pressure Pe is calculated by converting the evaporation temperature Te detected by the indoor heat exchange temperature sensor 24 or the outdoor heat exchange temperature sensor 37, and the value is calculated as the suction pressure Pi. It may be used as

(5-2) Modification 2B
In the above embodiment, one differential pressure state is determined such that the pressure difference ΔP1 between the discharge pressure Po and the suction pressure Pi of the compressor 31 is greater than or equal to the predetermined value A, and depending on whether or not the differential pressure state is present. The lower limit rotational speed NL is set to one of the first lower limit value N1 and the second lower limit value N2, but is not limited to this. For example, by providing a plurality of predetermined values, a first differential pressure state in which the pressure difference is greater than or equal to the predetermined value A1, a second differential pressure state in which the pressure difference is greater than or equal to the predetermined value A2, and so on are determined. The lower limit rotational speed NL may be set (changed) to a plurality of values depending on whether the state is in effect.

(5-3) Modification 2C
In the said embodiment, although the indoor expansion valve 23 and the outdoor expansion valve 36 are provided as an expansion mechanism, it is not limited to this. For example, the expansion mechanism may be only the outdoor expansion valve 36.

  According to the present invention, in a refrigeration apparatus that uses R32 as a refrigerant, when the compressor is operated in a low rotation speed range and the pressure difference between the high pressure side and the low pressure side of the compressor is large, the COP of the refrigeration apparatus Improvements can be made.

10,110 Air conditioning equipment (refrigeration equipment)
21 Indoor heat exchanger (condenser, evaporator)
23 Indoor expansion valve (expansion mechanism)
24 Indoor heat exchange temperature sensor (condensation temperature detector, evaporating temperature detector)
31 Compressor 34 Outdoor heat exchanger (evaporator, condenser)
36 Outdoor expansion valve (expansion mechanism)
37 Outdoor heat exchange temperature sensor (evaporation temperature detection unit, condensation temperature detection unit)
41a, 141a determination unit 41c lower limit change unit 61 discharge pressure sensor (discharge pressure detection unit)
62 Suction pressure sensor (suction pressure detector)
81 Suction pipe (suction channel)

JP 2001-194015 A

  The present invention relates to a refrigeration apparatus.

  Conventionally, a refrigeration apparatus using R32 as a refrigerant is known. For example, Patent Literature 1 (Japanese Patent Laid-Open No. 2001-194015) discloses an air conditioner using R32.

  By the way, at present, refrigeration apparatuses are required to operate a compressor in a lower rotational speed range than before in order to cope with a wide range of loads with a single compressor. Even in an air conditioner using R32 as a refrigerant, such as Patent Document 1 (Japanese Patent Laid-Open No. 2001-194015), it is required to operate the compressor in a low rotation speed range.

  However, when the compressor is operated in a low rotation speed range, there is a problem that the supply of refrigeration oil to the compression mechanism is likely to be insufficient, and the refrigerant is likely to leak from the gap in the compression mechanism. Such a problem is remarkable when the pressure difference between the high pressure side and the low pressure side of the compressor is large. Furthermore, when R32 is used as the refrigerant, the refrigerant is liable to leak from the gap in the compression mechanism, and the COP of the refrigeration apparatus is likely to be deteriorated, compared to the case where R410A is used.

  An object of the present invention is a refrigeration apparatus that uses R32 as a refrigerant, and when the compressor is operated in a low speed range and the pressure difference between the high pressure side and the low pressure side of the compressor is large, An object of the present invention is to provide a refrigeration apparatus capable of improving COP.

The refrigeration apparatus according to the first aspect of the present invention is a refrigeration apparatus that uses R32 as a refrigerant. The refrigeration apparatus includes a rotary or scroll compressor, a condenser, an expansion mechanism, an evaporator, a determination unit, and a lower limit changing unit. The compressor sucks low-pressure refrigerant from the suction flow path, compresses the refrigerant, and discharges high-pressure refrigerant. The condenser condenses the high-pressure refrigerant discharged from the compressor. The expansion mechanism expands the high-pressure refrigerant that has exited the condenser. The evaporator evaporates the refrigerant expanded by the expansion mechanism. The determination unit determines whether the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is equal to or greater than a predetermined value. Determine. The lower limit changing unit changes the lower limit rotation speed of the compressor from the first lower limit value to a second lower limit value larger than the first lower limit value when the determination unit determines that the differential pressure state is present.

  Here, when the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is equal to or greater than a predetermined value, the compressor Is changed to a large value. By changing the lower limit rotational speed of the compressor to a large value, the amount of refrigeration oil supplied to the compressor's compression mechanism can be easily secured even when the compressor is operated in a low rotational speed range. It becomes possible to suppress the gap of the mechanism to be small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor can be suppressed and the COP of the refrigeration apparatus can be improved in the low speed range.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, further comprising a condensation temperature detection unit and an evaporation temperature detection unit. The condensation temperature detector detects the condensation temperature of the condenser. The evaporation temperature detector detects the evaporation temperature of the evaporator. A determination part determines whether it is in a differential pressure state using condensation temperature and evaporation temperature.

  Here, using the condensation temperature and the evaporation temperature, the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor becomes a predetermined value or more. It is determined whether or not there is a differential pressure state. It is possible to determine whether or not there is a differential pressure state without using a pressure sensor that measures the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant. When operated in the rotational speed range, the refrigerant leakage of the compressor compression mechanism can be suppressed, and the COP of the refrigeration apparatus can be improved.

  The refrigeration apparatus according to the third aspect of the present invention is the refrigeration apparatus according to the second aspect, and the determination unit converts the condensation temperature and the evaporation temperature into a condensation pressure and an evaporation pressure, respectively. A determination part determines whether it is in a differential pressure state using the converted condensing pressure and evaporation pressure.

  Here, it is determined whether or not there is a differential pressure state by converting the condensation temperature into the condensation pressure and the evaporation temperature into the evaporation pressure, and using the condensation pressure and the evaporation pressure. Therefore, when the compressor is operated in a low speed range, the refrigerant leakage of the compressor compression mechanism is suppressed while suppressing the cost of the refrigeration apparatus without using the pressure sensor for measuring the pressure. The COP of the refrigeration apparatus can be improved.

  The refrigeration apparatus according to the fourth aspect of the present invention is the refrigeration apparatus according to the second aspect, and the determination unit determines whether or not the differential pressure state is established using a temperature difference between the condensation temperature and the evaporation temperature. To do.

  Here, it is determined from the temperature difference between the condensation temperature and the evaporation temperature whether or not a differential pressure state exists. Therefore, when the compressor is operated in a low speed range, the refrigerant leakage of the compressor compression mechanism is suppressed while suppressing the cost of the refrigeration apparatus without using the pressure sensor for measuring the pressure. The COP of the refrigeration apparatus can be improved.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the first aspect, further comprising a discharge pressure detection unit and a suction pressure detection unit. The discharge pressure detection unit detects the pressure of the high-pressure refrigerant discharged from the compressor. The suction pressure detection unit detects the pressure of the low-pressure refrigerant sucked into the compressor. A determination part determines whether it is in a differential pressure state using the detection result of a discharge pressure detection part and a suction pressure detection part.

  Here, the differential pressure state can be accurately determined by actually measuring the discharge pressure and the suction pressure. Therefore, it is easy to improve the COP of the refrigeration apparatus by suppressing the leakage of the refrigerant of the compressor compression mechanism in the low rotation speed range.

  In the refrigeration apparatus according to the first aspect of the present invention, the difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is a predetermined value or more. When in the pressure state, the lower limit rotational speed of the compressor is changed to a large value. By changing the lower limit rotational speed of the compressor to a large value, the amount of refrigeration oil supplied to the compressor's compression mechanism can be easily secured even when the compressor is operated in a low rotational speed range. It becomes possible to suppress the gap of the mechanism to be small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor can be suppressed and the COP of the refrigeration apparatus can be improved in the low speed range.

  In the refrigeration apparatus according to the second to fourth aspects of the present invention, the refrigerant leakage of the compression mechanism of the compressor is suppressed when the compressor is operated in a low speed range while suppressing the cost of the refrigeration apparatus. In addition, the COP of the refrigeration apparatus can be improved.

  In the refrigeration apparatus according to the fifth aspect of the present invention, it is easy to improve the COP of the refrigeration apparatus by suppressing the leakage of the refrigerant in the compression mechanism of the compressor in the low speed range.

It is a schematic block diagram of the air conditioning apparatus as a freezing apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of the air conditioning apparatus of FIG. It is a flowchart of the determination process of a differential pressure state of the air conditioning apparatus of FIG. 1, and the change process of the minimum rotation speed of a compressor. In the air conditioning apparatus of FIG. 1, it is an image figure for demonstrating the effect of changing a minimum rotation speed from a 1st lower limit to a 2nd lower limit (> 1st lower limit). A graph when the compressor is operated at the first lower limit value is shown on the left side, and a graph when the compressor is operated at the second lower limit value is shown on the right side. The graph shows that when the pressure difference between the discharge pressure and the suction pressure of the compressor is a predetermined value, how much of the energy consumption (power consumption of the compressor) is used effectively (for air conditioning) It shows how much energy was wasted due to leakage of refrigerant from the gap of the compression mechanism. It is a flowchart of the determination process of the differential pressure state concerning the modification A, and the change process of the minimum rotation speed of a compressor. The temperature difference between the detected temperature of the outdoor heat exchanger sensor and the detected temperature of the indoor heat exchanger sensor is converted into a pressure difference, and the pressure difference is determined using the pressure difference. It is a flowchart of the determination process of the differential pressure state concerning the modification A, and the change process of the minimum rotation speed of a compressor. The differential pressure state is determined using the temperature difference between the temperature detected by the outdoor heat exchanger sensor and the temperature detected by the indoor heat exchanger sensor. It is a schematic block diagram of the air conditioning apparatus as a freezing apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram of the air conditioning apparatus of FIG. It is a flowchart of the determination process of a differential pressure state of the air conditioning apparatus of FIG. 7, and the change process of the minimum rotation speed of a compressor.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the following embodiment of this invention can be suitably changed in the range which does not deviate from the meaning of this invention.

<First Embodiment>
(1) Overall Configuration The air conditioner 10 as a refrigeration apparatus according to the first embodiment of the present invention is an air conditioner that can be operated by switching between a cooling operation and a heating operation. However, the air conditioner 10 may not be operable by switching between the cooling operation and the heating operation, and may be an air conditioner capable of performing only the cooling operation or the heating operation.

  As shown in FIGS. 1 and 2, the air conditioner 10 mainly includes an indoor unit 20, an outdoor unit 30, and a control unit 40. In the present embodiment, the number of indoor units 20 is one, but a plurality of units may be used.

  The air conditioner 10 has a refrigerant circuit 1 filled with R32 as a refrigerant. The refrigerant circuit 1 has an indoor circuit 1 a accommodated in the indoor unit 20 and an outdoor circuit 1 b accommodated in the outdoor unit 30. The indoor side circuit 1a and the outdoor side circuit 1b are connected by a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72.

(2) Detailed configuration (2-1) Indoor unit The indoor unit 20 is installed in the room which is the object of air conditioning. The indoor unit 20 includes an indoor heat exchanger 21, an indoor fan 22, an indoor expansion valve 23, and an indoor heat exchange temperature sensor 24.

  The indoor heat exchanger 21 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of heat transfer fins. During the cooling operation, the indoor heat exchanger 21 functions as an evaporator that evaporates refrigerant expanded by an outdoor expansion valve 36 and an indoor expansion valve 23 described later, and cools indoor air. The indoor heat exchanger 21 functions as a condenser that condenses high-pressure refrigerant discharged from a compressor 31 described later during heating operation, and heats indoor air. The liquid side of the indoor heat exchanger 21 is connected to the liquid refrigerant communication pipe 71, and the gas side of the indoor heat exchanger 21 is connected to the gas refrigerant communication pipe 72.

  The indoor fan 22 is rotated by a fan motor, takes in indoor air, blows it to the indoor heat exchanger 21, and promotes heat exchange between the refrigerant flowing through the indoor heat exchanger 21 and the indoor air.

  The indoor expansion valve 23 is an example of an expansion mechanism, and is an electric expansion valve with a variable opening provided for adjusting the pressure and flow rate of the refrigerant flowing in the indoor circuit 1a. During the cooling operation, the indoor expansion valve 23 expands (depressurizes) the refrigerant flowing from the outdoor heat exchanger 34 of the outdoor unit 30 described later, which functions as a condenser, to the indoor heat exchanger 21 that functions as an evaporator. . During the heating operation, the indoor expansion valve 23 expands (depressurizes) the refrigerant flowing from the indoor heat exchanger 21 that functions as a condenser to the outdoor heat exchanger 34 that functions as an evaporator.

  The indoor heat exchanger temperature sensor 24 is a thermistor that measures the temperature of the indoor heat exchanger 21. The indoor heat exchanger temperature sensor 24 is attached to the indoor heat exchanger 21. When the indoor heat exchanger 21 functions as a condenser, the indoor heat exchanger temperature sensor 24 functions as a condensing temperature detector that detects the condensing temperature Tc. When the indoor heat exchanger 21 functions as an evaporator, the indoor heat exchanger temperature sensor 24 functions as an evaporation temperature detection unit that detects the evaporation temperature Te.

(2-2) Outdoor unit The outdoor unit 30 mainly includes a compressor 31, a four-way switching valve 33, an outdoor heat exchanger 34, an outdoor fan 35, an outdoor expansion valve 36, an outdoor heat exchanger temperature sensor 37, and a discharge. A temperature sensor 51 is provided. The compressor 31, the four-way switching valve 33, the outdoor heat exchanger 34, and the outdoor expansion valve 36 are connected by refrigerant piping.

(2-2-1) Connection of component equipment by refrigerant piping Connection by refrigerant piping of the component equipment of the outdoor unit 30 will be described.

  The suction port of the compressor 31 and the four-way switching valve 33 are connected by a suction pipe 81. The discharge port of the compressor 31 and the four-way switching valve 33 are connected by a discharge pipe 82. The four-way switching valve 33 and the gas side of the outdoor heat exchanger 34 are connected by a first gas refrigerant pipe 83. The outdoor heat exchanger 34 and the liquid refrigerant communication pipe 71 are connected by a liquid refrigerant pipe 84. The liquid refrigerant pipe 84 is provided with an outdoor expansion valve 36. The four-way switching valve 33 and the gas refrigerant communication pipe 72 are connected by a second gas refrigerant pipe 85.

(2-2-2) Compressor The compressor 31 drives the compression mechanism with a motor, thereby sucking low-pressure gas refrigerant from the suction pipe 81, and supplying the high-pressure gas refrigerant compressed by the compression mechanism to the discharge pipe 82. Discharge. Although the compressor 31 is a rotary compressor, it is not limited to this, For example, a scroll compressor may be sufficient.

  The compressor 31 is an inverter type compressor capable of changing the rotational speed N (the rotational speed of the motor of the compressor 31). The movement of the compressor 31 is controlled by a compressor control unit 41b described later. The compressor control unit 41b controls the rotational speed N of the compressor 31 according to the degree of divergence between the temperature (room temperature) of the air conditioning target space and the set temperature.

(2-2-3) Four-way switching valve The four-way switching valve 33 switches the flow direction of the refrigerant when the air-conditioning apparatus 10 is switched between the cooling operation and the heating operation. During the cooling operation, the discharge pipe 82 and the first gas refrigerant pipe 83 are connected, and the suction pipe 81 and the second gas refrigerant pipe 85 are connected (see the solid line in FIG. 1). On the other hand, during the heating operation, the discharge pipe 82 and the second gas refrigerant pipe 85 are connected, and the suction pipe 81 and the first gas refrigerant pipe 83 are connected (see the broken line in FIG. 1).

(2-2-4) Outdoor Heat Exchanger The outdoor heat exchanger 34 is a cross-fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of heat transfer fins. The outdoor heat exchanger 34 functions as a condenser that condenses the high-pressure refrigerant discharged from the compressor 31 by exchanging heat between the outdoor air and the refrigerant during the cooling operation. The outdoor heat exchanger 34 functions as an evaporator that evaporates the refrigerant expanded by the indoor expansion valve 23 and the outdoor expansion valve 36 by exchanging heat between the outdoor air and the refrigerant during heating operation.

(2-2-5) Outdoor Fan The outdoor fan 35 is rotated by a fan motor and takes outdoor air into the outdoor unit 30. The taken outdoor air passes through the outdoor heat exchanger 34 and is finally discharged out of the outdoor unit 30. The outdoor fan 35 promotes heat exchange between the refrigerant flowing in the outdoor heat exchanger 34 and outdoor air.

(2-2-6) Outdoor Expansion Valve The outdoor expansion valve 36 is an example of an expansion mechanism, and an electric expansion with a variable opening provided for adjusting the pressure and flow rate of the refrigerant flowing in the outdoor circuit 1b. It is a valve. During the cooling operation, the outdoor expansion valve 36 expands (depressurizes) the refrigerant flowing from the outdoor heat exchanger 34 functioning as a condenser to the indoor heat exchanger 21 functioning as an evaporator. During the heating operation, the outdoor expansion valve 36 expands (depressurizes) the refrigerant flowing from the indoor heat exchanger 21 that functions as a condenser to the outdoor heat exchanger 34 that functions as an evaporator.

(2-2-7) Outdoor Heat Exchange Temperature Sensor The outdoor heat exchange temperature sensor 37 is a thermistor that measures the temperature of the outdoor heat exchanger 34. The outdoor heat exchange temperature sensor 37 is attached to the outdoor heat exchanger 34. When the outdoor heat exchanger 34 functions as a condenser, the outdoor heat exchanger temperature sensor 37 functions as a condensing temperature detector that detects the condensing temperature Tc. The outdoor heat exchanger temperature sensor 37 functions as an evaporation temperature detection unit that detects the evaporation temperature Te when the outdoor heat exchanger 34 functions as an evaporator.

(2-2-8) Discharge pipe temperature sensor The discharge temperature sensor 51 is a thermistor for detecting the temperature of the refrigerant discharged from the compressor 31. The discharge temperature sensor 51 is provided outside the compressor 31, more specifically, near the discharge port of the compressor 31 in the discharge pipe 82. The temperature detected by the discharge temperature sensor 51 is used for control of the compressor 31 (including protection control of the compressor 31).

(2-3) Control Unit The control unit 40 controls the movement of the air conditioner 10. In FIG. 2, the block diagram of the air conditioning apparatus 10 containing the control unit 40 is shown.

  The control unit 40 includes a control unit 41 composed of a microcomputer or the like, a storage unit 42 composed of a memory such as a RAM or ROM, and an input unit 43 (remote control). The control unit 40 includes each configuration of the indoor unit 20 and the outdoor unit 30, a compressor 31, a four-way switching valve 33, an outdoor fan 35, an outdoor expansion valve 36, an indoor fan 22, an indoor expansion valve 23, a discharge temperature sensor 51, an outdoor The heat exchange temperature sensor 37, the indoor heat exchange temperature sensor 24, and the like are electrically connected.

  The control unit 41 controls the air conditioner 10 by reading and executing the program stored in the storage unit 42. The control unit 41 exchanges control signals with the input unit 43 in order to operate the indoor unit 20. And the control part 41 controls the driving | operation of the air conditioning apparatus 10 according to the input (The operation / stop of the air conditioning apparatus 10, an operation mode (cooling mode / heating mode), preset temperature, etc.) to the input part 43. . The control unit 41 controls various devices of the indoor unit 20 and the outdoor unit 30 according to operating conditions (for example, according to the degree of deviation between the temperature (room temperature) of the air-conditioning target space and the set temperature).

  In addition, the control part 41 has the determination part 41a, the compressor control part 41b, and the lower limit change part 41c as a function part. The determination unit 41a, the compressor control unit 41b, and the lower limit changing unit 41c will be described later.

  The storage unit 42 stores a program to be executed by the control unit 41 and various information. The storage unit 42 includes a conversion information storage area 42 a that stores temperature-pressure conversion information, and an upper and lower limit storage area 42 b that stores the lower limit rotation speed NL and the upper limit rotation speed NH of the compressor 31. The conversion information storage area 42a and the upper / lower limit storage area 42b will be described later.

(2-3-1) Control part (2-3-1-1) Determination part The determination part 41a is the pressure (discharge pressure Po) of the high pressure refrigerant | coolant discharged from a compressor, and the low pressure suck | inhaled by a compressor. It is determined whether or not the pressure difference between the refrigerant and the refrigerant pressure (suction pressure Pi) is in a differential pressure state such that the pressure difference is equal to or greater than a predetermined value A (eg, 0.3 MPa). Specifically, the determination unit 41a includes the condensation temperature Tc (measured value of the indoor heat exchanger temperature sensor 24 or the measured value of the outdoor heat exchanger temperature sensor 37) and the evaporation temperature Te (measured value of the outdoor heat exchanger temperature sensor 37 or The measured value of the indoor heat exchanger temperature sensor 24) is used to determine whether or not it is in a differential pressure state.

  The determination of the differential pressure state by the determination unit 41a will be described later.

(2-3-1-2) Compressor Control Unit The compressor control unit 41b is configured to start / stop the compressor 31 and to control the compressor 31 according to the operating conditions of the air conditioner 10, various control signals, and the like. The rotational speed N (the rotational speed of the motor of the compressor 31) is determined and controlled. For example, the compressor control unit 41b controls the rotation speed N of the motor of the compressor 31 according to the degree of deviation between the temperature (room temperature) of the space that is the air-conditioning target of the air conditioner 10 and the set temperature. The rotation speed N of the compressor 31 is controlled by a value between a lower limit rotation speed NL and an upper limit rotation speed NH stored in an upper / lower limit storage area 42b described later.

(2-3-1-3) Lower limit change unit The lower limit change unit 41c changes the lower limit rotation number NL of the compressor 31 by rewriting the value of the lower limit rotation number NL stored in the upper and lower limit storage area 42b.

  When the determination unit 41a determines that the differential pressure state is in the differential pressure state, the lower limit change unit 41c changes (sets) the lower limit rotation speed NL of the compressor to the second lower limit value N2. The lower limit changing unit 41c changes (sets) the lower limit rotation speed NL of the compressor to the first lower limit value N1 when the determination unit 41a determines that the differential pressure state is not present.

  The change of the lower limit rotational speed NL by the lower limit changing unit 41c will be described later.

(2-3-2) Storage Unit (2-3-2-1) Conversion Information Storage Area In the conversion information storage area 42a, the condensation temperature (evaporation temperature) of R32 that is a refrigerant, the condensation pressure (evaporation pressure), and Temperature pressure conversion information related to the relationship is stored. Specifically, the conversion information storage area 42a stores the condensation pressure (evaporation pressure) for each condensation temperature (evaporation temperature) as temperature-pressure conversion information.

  However, the present invention is not limited to this. For example, the conversion information storage area 42a may store a relational expression between the condensation temperature (evaporation temperature) and the condensation pressure (evaporation pressure) as temperature pressure conversion information. .

(2-3-2-2) Upper / lower limit storage area The upper / lower limit storage area 42b stores an upper limit (upper limit rotational speed NH) and a lower limit (lower limit rotational speed NL) of the rotational speed N of the compressor 31. .

  When the determination part 41a determines that it is not in the differential pressure state, the first lower limit value N1 is stored as the lower limit rotation speed NL in the upper and lower limit storage area 42b. On the other hand, when the determination unit 41a determines that the pressure difference is present, the upper and lower limit storage area 42b stores the second lower limit value N2 as the lower limit rotation speed NL. The second lower limit value N2 is larger than the first lower limit value N1. For example, the first lower limit value N1 is 4 rps, and the second lower limit value N2 is 6 rps. The lower limit rotation speed NL in the upper / lower limit storage area 42b is set to the first lower limit value N1 or the second lower limit value N2 by being changed by the lower limit changing unit 41c.

(2-3-3) Input Unit The input unit 43 is a remote controller for the air conditioning apparatus 10. The input unit 43 receives various inputs from the user of the air conditioning apparatus 10. Various inputs received from the user by the input unit 43 include an operation / stop command for the air conditioner 10, an operation mode (heating mode / cooling mode) of the air conditioner 10, a set temperature of the air conditioner 10, and the like.

(3) Differential Pressure State Determination Process and Compressor Lower Limit Rotation Speed Change Process Hereinafter, the differential pressure state determination process and the lower limit rotation speed NL change process of the compressor 31 will be described with reference to the flowchart of FIG. To do. The process for determining the differential pressure state and the process for changing the lower limit rotational speed NL are performed periodically (for example, at intervals of 30 seconds) while the air conditioner 10 is in operation.

  In step S <b> 1, the determination unit 41 a acquires measurement values of the indoor heat exchange temperature sensor 24 and the outdoor heat exchange temperature sensor 37. If the air conditioner 10 is in the cooling operation, the measured value of the outdoor heat exchanger temperature sensor 37 is acquired as the condensation temperature Tc, and the measured value of the indoor heat exchanger temperature sensor 24 is acquired as the evaporation temperature Te. If the air conditioner 10 is in the heating operation, the measured value of the indoor heat exchanger temperature sensor 24 is acquired as the condensation temperature Tc, and the measured value of the outdoor heat exchanger temperature sensor 37 is acquired as the evaporation temperature Te. Thereafter, the process proceeds to step S2.

  In step S2, the determination unit 41a converts the aggregation temperature Tc obtained in step S1 into the aggregation pressure Pc using the temperature / pressure conversion information stored in the conversion information storage area 42a, and converts the evaporation temperature Te into the evaporation pressure Pe. Convert to. Thereafter, the process proceeds to step S3.

  In step S3, the determination unit 41a calculates a pressure difference ΔP between the condensation pressure Pc obtained in step S2 and the evaporation pressure Pe. The pressure difference ΔP is calculated by subtracting the evaporation pressure Pe from the condensation pressure Pc. Note that the pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe approximates the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31. Thereafter, the process proceeds to step S4.

  In step S4, the determination unit 41a determines whether or not the pressure difference ΔP is equal to or greater than a predetermined value A. If the pressure difference ΔP is determined to be greater than or equal to the predetermined value A, it is determined that the pressure difference is present (the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is greater than or equal to the predetermined value A), and step Proceed to S5. When it is determined that the pressure difference ΔP is smaller than the predetermined value A, it is determined that the pressure difference state is not established, and the process proceeds to step S7.

  In step S5, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the first lower limit value N1. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the first lower limit value N1, the process proceeds to step S6. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the first lower limit value N1 (the second lower limit value N2), the process is terminated.

In step S6, the lower limit changing unit 41c, to change the lower limit rotational speed NL to the second lower limit value N2. Thereafter, the process ends.

  In step S7, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the second lower limit value N2. If it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the second lower limit value N2, the process proceeds to step S8. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the second lower limit value N2 (is the first lower limit value N1), the process ends.

In step S8, the lower limit changing unit 41c, to change the lower limit rotational speed NL to the first lower limit value N1. Thereafter, the process ends.

  By performing the above processing, when the determination unit 41a determines that the air conditioner 10 is in the differential pressure state, the lower limit rotation speed NL of the compressor 31 is set to the second lower limit value N2 (change). ) On the other hand, when the determination unit 41a determines that the air conditioner 10 is not in the differential pressure state, the lower limit rotation speed NL of the compressor 31 is set (changed) to the first lower limit value N1.

  As described above, the lower limit rotational speed NL of the compressor 31 is variable between the first lower limit value N1 and the second lower limit value N2, and the lower limit rotational speed NL of the compressor 31 is set to the first lower limit value N1 when in the differential pressure state. By setting the second lower limit value N2 to be larger, the following effects can be obtained.

  It is desirable that the compressor 31 can be operated at the lowest possible rotation speed NL as much as possible in order to meet a wide range of air conditioning capabilities with a single compressor 31. Therefore, it is desirable that the lower limit rotation speed NL of the compressor 31 is basically a small value (first lower limit value N1).

  By the way, in the compressor 31, in order to prevent the refrigerant from leaking from the high pressure side to the low pressure side through the gap of the compression mechanism, refrigeration oil is supplied to the compression mechanism and an oil film is formed in the gap of the compression mechanism. doing. The clearance of the compression mechanism is, for example, a clearance between a roller and a cylinder in the case of a rotary compressor as in this embodiment. The supply of the refrigerating machine oil to the compression mechanism of the compressor 31 uses a centrifugal force or the like generated by the rotation of the motor as a driving force. In the state where the lower limit rotational speed NL is reached, the supply amount of refrigerating machine oil tends to decrease. Therefore, when the rotation speed N of the compressor 31 reaches the lower limit rotation speed NL, the refrigerant is likely to leak from the gap of the compression mechanism. In particular, in a differential pressure state where the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is equal to or greater than a predetermined value A, the refrigerant is likely to leak. Moreover, in this embodiment, since R32 is used as a refrigerant, the refrigerant is more likely to leak from the gap of the compression mechanism than when R410A is used as the refrigerant.

  As a result, when the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is a certain value B (value B ≧ predetermined value A which is a reference value of the differential pressure state), the lower limit rotation speed of the compressor 31 is reached. Assuming that NL is the first lower limit value N1, for example, as shown in the graph on the left side of FIG. 4, the proportion of energy wasted due to refrigerant leaking from the gap of the compression mechanism with respect to energy consumption (power consumption). Cheap. In other words, the ratio of energy (shaded area in FIG. 4) that actually contributes to air conditioning tends to be small with respect to energy consumption (power consumption).

  On the other hand, when the lower limit rotational speed NL of the rotational speed N of the compressor 31 is changed to the second lower limit value N2 larger than the first lower limit value N1, the amount of oil supplied to the compression mechanism of the compressor 31 at the lower limit rotational speed NL. Will increase. As a result, an oil film is formed in the gap of the compression mechanism, and the amount of refrigerant leaking is reduced. As a result, for example, as shown in the graph on the right side of FIG. 4, less energy is wasted due to refrigerant leaking from the gaps in the compression mechanism. In other words, by changing the lower limit rotational speed NL from the first lower limit value N1 to the second lower limit value N2, energy actually consumed for air conditioning (hatched portion in FIG. 4) with respect to energy consumption (power consumption). The proportion increases. That is, in the air conditioning apparatus 10 of the present embodiment, it is possible to improve the efficiency of the compressor 31 when the compressor 31 is operated in the differential pressure state and in the low rotation speed region. As a result, the COP of the air conditioner 10 is improved, and energy can be effectively used.

  Note that the determination of whether or not the differential pressure state is present is made in order to prevent the refrigerant from leaking from the gap of the compression mechanism as described above and the COP of the air conditioner 10 from being excessively deteriorated. Therefore, the reference value (predetermined value A) as to whether or not the differential pressure state exists may be appropriately determined according to the characteristics of the compressor 31 and the like.

(4) Features (4-1)
The air conditioning apparatus 10 of the present embodiment is a refrigeration apparatus that uses R32 as a refrigerant. The air conditioner 10 includes a compressor 31, a condenser (indoor heat exchanger 21 or outdoor heat exchanger 34), an indoor expansion valve 23 and an outdoor expansion valve 36 as an expansion mechanism, and an evaporator (outdoor heat exchanger). 34 or the indoor heat exchanger 21), a determination unit 41a, and a lower limit changing unit 41c. The compressor 31 sucks low-pressure refrigerant from a suction pipe 81 serving as a suction flow path, compresses the refrigerant, and discharges high-pressure refrigerant. The condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34) condenses the high-pressure refrigerant discharged from the compressor 31. The indoor expansion valve 23 and the outdoor expansion valve 36 expand the high-pressure refrigerant that has exited the condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34). The evaporator (the outdoor heat exchanger 34 or the indoor heat exchanger 21) evaporates the refrigerant expanded by the indoor expansion valve 23 and the outdoor expansion valve 36. The determination unit 41a is in a differential pressure state in which the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. It is determined whether or not there is. When the determination unit 41a determines that the differential pressure state exists, the lower limit changing unit 41c changes the lower limit rotation speed NL of the compressor 31 from the first lower limit value N1 to a second lower limit value that is larger than the first lower limit value N1. Change to N2.

  Here, when the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. The lower limit rotational speed NL of the compressor 31 is changed to a large value (second lower limit value N2). By changing the lower limit rotational speed NL of the compressor 31 to a large value, the amount of refrigerating machine oil supplied to the compression mechanism of the compressor 31 is ensured even when the compressor 31 is operated in a low rotational speed range. It becomes easy and it becomes possible to suppress the clearance gap of a compression mechanism small. As a result, even when R32 is used as the refrigerant, leakage of the refrigerant in the compression mechanism of the compressor 31 can be suppressed and the COP of the air conditioner 10 can be improved in the low speed range.

(4-2)
In the air conditioning apparatus 10 of the present embodiment, the condensation temperature detection unit (the indoor heat exchange temperature sensor 24 or the outdoor heat exchange temperature sensor 37) and the evaporation temperature detection unit (the outdoor heat exchange temperature sensor 37 or the indoor heat exchange temperature sensor 24). And prepare. The condensation temperature detector (the indoor heat exchanger temperature sensor 24 or the outdoor heat exchanger temperature sensor 37) detects the condensation temperature Tc of the condenser (the indoor heat exchanger 21 or the outdoor heat exchanger 34). The evaporation temperature detection unit (outdoor heat exchange temperature sensor 37 or indoor heat exchange temperature sensor 24) detects the evaporation temperature Te of the evaporator (outdoor heat exchanger 34 or indoor heat exchanger 21). The determination part 41a determines whether it is in a differential pressure state using the condensation temperature Tc and the evaporation temperature Te.

  Here, the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor using the condensation temperature Tc and the evaporation temperature Te is equal to or greater than a predetermined value A. It is determined whether or not the differential pressure state is as follows. It is possible to determine whether or not there is a differential pressure state without using a pressure sensor that measures the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant, and while reducing the cost of the air conditioner 10, the compressor When 31 is operated in a low rotation speed range, leakage of the refrigerant of the compression mechanism of the compressor 31 can be suppressed, and the COP of the air conditioner 10 can be improved.

(4-3)
In the air conditioning apparatus 10 of the present embodiment, the determination unit 41a converts the condensation temperature Tc and the evaporation temperature Te into a condensation pressure Pc and an evaporation pressure Pe, respectively. The determination part 41a determines whether it is in a differential pressure state using the converted condensing pressure Pc and evaporation pressure Pe.

  Here, the condensing temperature Tc is converted into the condensing pressure Pc, the evaporating temperature Te is converted into the evaporating pressure Pe, and the condensing pressure Pc and the evaporating pressure Pe are used to determine whether or not there is a differential pressure state. Is called. Therefore, when the compressor 31 is operated in a low speed range while suppressing the cost of the air conditioner 10 without using a pressure sensor for measuring pressure, the refrigerant of the compression mechanism of the compressor 31 is reduced. Leakage can be suppressed and the COP of the air conditioner 10 can be improved.

(5) Modifications Modifications of the present embodiment are shown below. A plurality of modified examples may be appropriately combined.

(5-1) Modification 1A
In the above embodiment, the determination unit 41a converts the condensation temperature Tc and the evaporation temperature Te into the condensation pressure Pc and the evaporation pressure Pe, respectively, and is in a differential pressure state using the converted condensation pressure Pc and the evaporation pressure Pe. However, the present invention is not limited to this.

  For example, in the conversion information storage area 42a, information (for example, a mathematical expression) for converting the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te into the pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe is stored. 41a may determine whether or not it is in a differential pressure state by using the information.

  In this case, unlike the flowchart of the above-described embodiment (see FIG. 3), step S12 for calculating the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te is performed instead of step S2, as in the flowchart of FIG. Step S13 is executed instead of step S3, in which a pressure difference ΔP between the condensation pressure Pc and the evaporation pressure Pe is calculated from the temperature difference ΔT.

  In addition, for example, the condensation temperature Tc and the evaporation temperature Te are highly likely to be in a differential pressure state, that is, the pressure difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is likely to be a predetermined value A or higher. The reference value C of the temperature difference ΔT is stored in the storage unit 42 in advance, and the determination unit 41a determines whether or not the temperature difference ΔT is greater than or equal to the reference value C to determine whether or not the differential pressure state exists. May be.

  In this case, unlike the flowchart of the above-described embodiment (see FIG. 3), step S12 for calculating the temperature difference ΔT between the condensation temperature Tc and the evaporation temperature Te is performed instead of step S2, as in the flowchart of FIG. After that, the differential pressure state is determined based on whether or not the temperature difference ΔT is greater than or equal to the reference value C in step S14.

(5-2) Modification 1B
In the above embodiment, the determination unit 41a considers that the calculated ΔP of the condensation pressure Pc and the evaporation pressure Pe is equal to the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31, and ΔP is equal to or greater than the predetermined value A. At this time, it is determined that there is a differential pressure state (a state in which the difference between the discharge pressure Po and the suction pressure Pi of the compressor 31 is equal to or greater than a predetermined value A), but is not limited thereto. For example, it may be determined that the differential pressure state is present when ΔP is equal to or greater than the product of the predetermined value A and the predetermined coefficient.

(5-3) Modification 1C
In the above embodiment, the determination unit 41a determines whether or not the differential pressure state is present using the condensation temperature Tc and the evaporation temperature Te, but the determination method for the differential pressure state is not limited to this. . For example, it may be determined whether or not the pressure is in a differential pressure state using the opening degree of the indoor expansion valve 23 and / or the outdoor expansion valve 36 and the rotational speed N of the compressor 31. Moreover, in addition to the condensation temperature Tc or the evaporation temperature Te, it may be determined whether or not a differential pressure state is established using room temperature or an outside air temperature.

(5-4) Modification 1D
In the above embodiment, one differential pressure such that the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor 31 and the pressure of the low-pressure refrigerant sucked into the compressor 31 is equal to or greater than a predetermined value A. The lower limit rotational speed NL is set to one of the first lower limit value N1 and the second lower limit value N2 depending on whether or not the state is determined and the differential pressure state, but the present invention is not limited to this. It is not something. For example, by providing a plurality of predetermined values, a first differential pressure state in which the pressure difference is greater than or equal to the predetermined value A1, a second differential pressure state in which the pressure difference is greater than or equal to the predetermined value A2, and so on are determined. The lower limit rotational speed NL may be set (changed) to a plurality of values depending on whether the state is in effect.

(5-5) Modification 1E
In the said embodiment, although the indoor expansion valve 23 and the outdoor expansion valve 36 are provided as an expansion mechanism, it is not limited to this. For example, the expansion mechanism may be only the outdoor expansion valve 36.

Second Embodiment
An air conditioner 110 as a refrigeration apparatus according to a second embodiment of the present invention will be described. In addition, since the air conditioning apparatus 110 of this embodiment has many points in common with 1st Embodiment, it mainly demonstrates a different point. In the description of the second embodiment, the same reference numerals as those in the first embodiment may be used, but the configuration using the same reference numerals means the same as the configuration in the first embodiment.

(1) Overall Configuration The air conditioning apparatus 110 is a refrigeration apparatus that uses R32 as a refrigerant. As shown in FIG. 1, the air conditioner 110 mainly includes an indoor unit 20, an outdoor unit 130, and a control unit 140. Since the air conditioner 10 of the first embodiment and the indoor unit 20 are the same, only the outdoor unit 130 and the control unit 140 will be described here.

(2) Detailed configuration (2-1) Outdoor unit The outdoor unit 130 mainly includes a compressor 31, a four-way switching valve 33, an outdoor heat exchanger 34, an outdoor fan 35, an outdoor expansion valve 36, and an outdoor heat exchange temperature sensor. 37, a discharge temperature sensor 51, a discharge pressure sensor 61, and a suction pressure sensor 62. The outdoor unit 130 is the same as the outdoor unit 30 of the first embodiment except that the outdoor unit 130 has a discharge pressure sensor 61 and a suction pressure sensor 62. Therefore, only the discharge pressure sensor 61 and the suction pressure sensor 62 will be described here. To do.

(2-1-1) Discharge Pressure Sensor The discharge pressure sensor 61 is an example of a discharge pressure detection unit that detects the pressure of the high-pressure refrigerant discharged from the compressor 31 (discharge pressure Po). The discharge pressure sensor 61 is provided outside the compressor 31, more specifically, near the discharge port of the compressor 31 in the discharge pipe 82.

(2-1-2) Suction Pressure Sensor The suction pressure sensor 62 is an example of a suction pressure detection unit that detects the pressure (suction pressure Pi) of the low-pressure refrigerant sucked into the compressor 31. The suction pressure sensor 62 is provided outside the compressor 31, more specifically, near the suction port of the compressor 31 in the suction pipe 81.

(2-2) Control Unit The control unit 140 controls the air conditioner 110. FIG. 8 shows a block diagram of the air conditioner 110 including the control unit 140.

The control unit 140 uses the control unit 40 according to the first embodiment, the point where the discharge pressure sensor 61 and the suction pressure sensor 62 are electrically connected, and the determination values 141a using the measured values of the pressure sensors 61 and 62. Is different in that it determines the differential pressure state. Since the other points are the same, only the determination unit 141a will be described here. In addition, since the conversion information storage area 42a of the storage unit 42 is not used for the determination of the differential pressure state by the determination unit 141a, it may not be provided.

(2-2-1) Determination Unit The determination unit 41a includes the pressure of the high-pressure refrigerant discharged from the compressor (discharge pressure Po), the pressure of the low-pressure refrigerant sucked into the compressor (intake pressure Pi), It is determined whether or not the pressure difference is equal to or greater than a predetermined value A. Specifically, the determination unit 41a determines whether or not a differential pressure state exists using the discharge pressure Po measured by the discharge pressure sensor 61 and the suction pressure Pi measured by the suction pressure sensor 62. To do.

(3) Differential Pressure State Determination Process and Compressor Lower Limit Rotation Speed Change Process Hereinafter, the differential pressure state determination process and the lower limit rotation speed NL change process of the compressor 31 will be described with reference to the flowchart of FIG. To do. The process for determining the differential pressure state and the process for changing the lower limit rotational speed NL are performed periodically (for example, at intervals of 30 seconds) while the air conditioner 110 is in operation.

  In step S101, the determination unit 141a acquires the measurement values of the discharge pressure sensor 61 and the suction pressure sensor 62 as the discharge pressure Po and the suction pressure Pi. Thereafter, the process proceeds to step S102.

  In step S102, the determination unit 141a calculates a pressure difference ΔP1 between the discharge pressure Po obtained in step S101 and the suction pressure Pi. The pressure difference ΔP1 is calculated by subtracting the suction pressure Pi from the discharge pressure Po. Thereafter, the process proceeds to step S103.

  In step S103, the determination unit 141a determines whether or not the pressure difference ΔP1 is equal to or greater than a predetermined value A. If it is determined that the pressure difference ΔP1 is greater than or equal to the predetermined value A, it is determined that the pressure difference is present, and the process proceeds to step S104. If it is determined that the pressure difference ΔP1 is smaller than the predetermined value A, it is determined that the pressure difference state is not established, and the process proceeds to step S106.

  In step S104, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the first lower limit value N1. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the first lower limit value N1, the process proceeds to step S105. On the other hand, when it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the first lower limit value N1 (the second lower limit value N2), the process is terminated.

In step S105, the lower limit changing unit 41c, to change the lower limit rotational speed NL to the second lower limit value N2. Thereafter, the process ends.

  In step S106, the lower limit changing unit 41c determines whether or not the lower limit rotational speed NL stored in the upper and lower limit storage area 42b is the second lower limit value N2. When it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is the second lower limit value N2, the process proceeds to step S107. On the other hand, if it is determined that the lower limit rotational speed NL stored in the upper / lower limit storage area 42b is not the second lower limit value N2 (is the first lower limit value N1), the process ends.

In step S107, the lower limit changing unit 41c, to change the lower limit rotational speed NL to the first lower limit value N1. Thereafter, the process ends.

(4) Features The air conditioner 110 of the second embodiment has the following features in addition to the features of (4-1) of the first embodiment.

(4-1)
The air conditioning apparatus 110 according to the present embodiment includes a discharge pressure sensor 61 as a discharge pressure detection unit, and a suction pressure sensor 62 as a suction pressure detection unit. The discharge pressure sensor 61 detects the pressure of the high-pressure refrigerant discharged from the compressor 31. The suction pressure sensor 62 detects the pressure of the low-pressure refrigerant sucked into the compressor 31. The determination unit 141a determines whether or not a differential pressure state exists using the detection results of the discharge pressure sensor 61 and the suction pressure sensor 62.

  Here, the differential pressure state can be accurately determined by actually measuring the discharge pressure Po and the suction pressure Pi. Therefore, it is easy to improve the COP of the air conditioner 110 by suppressing the leakage of the refrigerant of the compression mechanism of the compressor 31 in the low rotation speed range.

(5) Modifications Modifications of the present embodiment are shown below. A plurality of modified examples may be appropriately combined.

(5-1) Modification 2A
In the above embodiment, the discharge pressure sensor 61 and the suction pressure sensor 62 are provided, but the present invention is not limited to this.

  For example, only one of the discharge pressure sensor 61 or the suction pressure sensor 62 may be provided. For the pressure not detected by the pressure sensor, as in the first embodiment, the condensation pressure Pc or the evaporation pressure Pe is calculated using the condensation temperature Tc or the evaporation temperature Te, and the value is not detected by the pressure sensor. As a substitute. For example, when the suction pressure sensor 62 is not provided, the evaporation pressure Pe is calculated by converting the evaporation temperature Te detected by the indoor heat exchange temperature sensor 24 or the outdoor heat exchange temperature sensor 37, and the value is calculated as the suction pressure Pi. It may be used as

(5-2) Modification 2B
In the above embodiment, one differential pressure state is determined such that the pressure difference ΔP1 between the discharge pressure Po and the suction pressure Pi of the compressor 31 is greater than or equal to the predetermined value A, and depending on whether or not the differential pressure state is present. The lower limit rotational speed NL is set to one of the first lower limit value N1 and the second lower limit value N2, but is not limited to this. For example, by providing a plurality of predetermined values, a first differential pressure state in which the pressure difference is greater than or equal to the predetermined value A1, a second differential pressure state in which the pressure difference is greater than or equal to the predetermined value A2, and so on are determined. The lower limit rotational speed NL may be set (changed) to a plurality of values depending on whether the state is in effect.

(5-3) Modification 2C
In the said embodiment, although the indoor expansion valve 23 and the outdoor expansion valve 36 are provided as an expansion mechanism, it is not limited to this. For example, the expansion mechanism may be only the outdoor expansion valve 36.

  According to the present invention, in a refrigeration apparatus that uses R32 as a refrigerant, when the compressor is operated in a low rotation speed range and the pressure difference between the high pressure side and the low pressure side of the compressor is large, the COP of the refrigeration apparatus Improvements can be made.

10,110 Air conditioning equipment (refrigeration equipment)
21 Indoor heat exchanger (condenser, evaporator)
23 Indoor expansion valve (expansion mechanism)
24 Indoor heat exchange temperature sensor (condensation temperature detector, evaporating temperature detector)
31 Compressor 34 Outdoor heat exchanger (evaporator, condenser)
36 Outdoor expansion valve (expansion mechanism)
37 Outdoor heat exchange temperature sensor (evaporation temperature detection unit, condensation temperature detection unit)
41a, 141a determination unit 41c lower limit change unit 61 discharge pressure sensor (discharge pressure detection unit)
62 Suction pressure sensor (suction pressure detector)
81 Suction pipe (suction channel)

JP 2001-194015 A

Claims (5)

A refrigeration apparatus (10, 110) using R32 as a refrigerant,
A compressor (31) for sucking low-pressure refrigerant from the suction flow path (81), compressing the refrigerant and discharging high-pressure refrigerant;
A condenser (21, 34) for condensing the high-pressure refrigerant discharged from the compressor;
An expansion mechanism (23, 36) for expanding the high-pressure refrigerant exiting the condenser;
An evaporator (34, 21) for evaporating the refrigerant expanded by the expansion mechanism;
Determining whether or not the pressure difference between the pressure of the high-pressure refrigerant discharged from the compressor and the pressure of the low-pressure refrigerant sucked into the compressor is equal to or greater than a predetermined value. A determination unit (41a, 141a) to perform,
When the determination unit determines that the differential pressure state exists, a lower limit change unit that changes the lower limit rotational speed of the compressor from a first lower limit value to a second lower limit value that is larger than the first lower limit value ( 41c)
A refrigeration apparatus comprising: A condensation temperature detector (24, 37) for detecting the condensation temperature of the condenser;
An evaporation temperature detecting section (37, 24) for detecting the evaporation temperature of the evaporator;
Further comprising
The determination unit (41a) uses the condensation temperature and the evaporation temperature to determine whether or not the differential pressure state exists.
The refrigeration apparatus (10) according to claim 1. The determination unit
The condensation temperature and the evaporation temperature are converted into a condensation pressure and an evaporation pressure, respectively.
Using the converted condensing pressure and the evaporation pressure, it is determined whether or not the differential pressure state.
The refrigeration apparatus according to claim 2. The determination unit determines whether or not the differential pressure state is present using a temperature difference between the condensation temperature and the evaporation temperature.
The refrigeration apparatus according to claim 2. A discharge pressure detector (61) for detecting the pressure of the high-pressure refrigerant discharged from the compressor;
A suction pressure detector (62) for detecting the pressure of the low-pressure refrigerant sucked into the compressor;
Further comprising
The determination unit (141a) determines whether or not the differential pressure state exists using detection results of the discharge pressure detection unit and the suction pressure detection unit.
The refrigeration apparatus (110) of claim 1.

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