JP4845606B2 - refrigerator - Google Patents

Description

  The present invention relates to a refrigerator incorporated in an air conditioning system of a vehicle, and more particularly to a refrigerator that uses carbon dioxide as a refrigerant.

The refrigerator for the main vehicle air conditioning system includes a variable capacity compressor, a gas cooler, an electric expansion valve and an evaporator inserted in the refrigerant circulation path, and the pressure of the high-pressure side refrigerant at the gas cooler outlet. Is maintained at a critical pressure or higher (Patent Documents 1 and 2).
Specifically, in the refrigerators of Patent Documents 1 and 2, in order to achieve the optimum COP (coefficient of performance), the electric expansion valve is opened to maintain the pressure of the high-pressure side refrigerant at the target pressure. The degree is controlled.
Japanese Patent Laid-Open No. 11-304268 Japanese Patent Laid-Open No. 2002-22288

  Even if the refrigerator of the above-mentioned patent document is operated to achieve the optimum COP, if the temperature of the passenger compartment exceeds the set temperature due to load fluctuations, a variable displacement compressor is provided accordingly. Adjusts the discharge capacity to increase the refrigerating capacity. For this reason, the pressure of the high-pressure side refrigerant deviates from the target pressure, and the electric expansion valve adjusts the valve opening to compensate for this, and changes the pressure on the suction side of the compressor, that is, the pressure of the low-pressure side refrigerant. .

Thus, the compressor varies the discharge amount in accordance with the required refrigeration capacity, that is, the pressure of the low-pressure side refrigerant, whereas the expansion valve adjusts the valve opening degree by the pressure of the high-pressure side refrigerant. The refrigerant pressure is varied on both the low-pressure side and the low-pressure side.
In order to avoid the above-described pressure fluctuation, the refrigerator disclosed in Patent Document 1 is not implemented simultaneously with the valve opening control of the electric expansion valve and the capacity control of the compressor. Since it is a pressure, if one of the high-pressure side refrigerant and the low-pressure side refrigerant is controlled, the pressure on the other side will inevitably fluctuate, causing the operation of the refrigerator to become unstable.

  Also, considering the situation where the set temperature in the passenger compartment falls below its target value, in this case, the compressor decreases its discharge amount, which increases the pressure of the low-pressure side refrigerant while Reduce pressure. Since the pressure drop of the high-pressure side refrigerant means a deviation from the target pressure that achieves the optimum COP, the electric expansion valve reduces the valve opening and increases the pressure of the high-pressure side refrigerant to the target pressure. Let Along with this, the pressure of the low-pressure side refrigerant decreases, so that the evaporation temperature of the refrigerant in the evaporator decreases, and in order to compensate for this, the compressor further reduces the discharge amount. The desired operation is repeated. Therefore, the electric expansion valve is finally fully closed, and the compressor is driven with the minimum discharge amount.

When such a situation occurs, the temperature in the passenger compartment drops below the set temperature, and the compressor tries to increase the discharge amount, and the above operation is repeated in the reverse direction. As a result, the pressure control of the refrigerant does not converge but diverges, causing the refrigerant pressure to fluctuate significantly.
Furthermore, in the refrigerators of Patent Documents 1 and 2, when the pressure of the high-pressure side refrigerant is equal to or higher than the critical pressure, the valve opening degree of the electric expansion valve is controlled to achieve the optimum COP. However, in actual operation of the refrigerator, the pressure of the high-pressure side refrigerant may be lower than the critical pressure, and establishment of control under such a situation is desired.

  The present invention has been made based on the above-mentioned circumstances, and its object is to suppress undesired pressure fluctuations of the refrigerant and achieve optimum COP even in supercritical and subcritical states. It is in providing the refrigerator which can do.

In order to achieve the above object, the refrigerator of the present invention includes a refrigerant circulation path divided into a high pressure path portion and a low pressure path portion, and a variable capacity type that is inserted in the high pressure path portion and compresses and discharges the refrigerant. A compressor, a gas cooler that is interposed downstream of the compressor in the high-pressure path portion and cools the high-pressure refrigerant discharged from the compressor, and an upstream end of the high-pressure path portion and a downstream end of the low-pressure path portion An expansion means having an opening provided therein, the expansion means capable of adjusting the opening degree of the opening, and an evaporation which is inserted in the low-pressure path portion and evaporates the low-pressure side refrigerant flowing out from the opening of the expansion means and cools the conditioned air , A conditioned temperature setting means for setting a set temperature of the conditioned air to be supplied from the evaporator, an air temperature detecting means for detecting the actual temperature of the conditioned air, and the actual temperature of the high-pressure side refrigerant in the high-pressure path portion Detect That a refrigerant temperature detecting means, and the refrigerant pressure detecting means for detecting the actual pressure of the high-pressure side refrigerant in the high pressure path portion, the opening of the refrigerant discharge amount and expansion means of the compressor in order to match the actual temperature to the target temperature of the conditioned air A discharge amount control device for performing a discharge amount control for controlling the opening degree, and a valve opening degree control for controlling the opening degree of the opening in the expansion means , which is operated periodically by interrupting the discharge amount control. a practice that the valve opening control device, the valve opening control device, when the high-pressure side refrigerant is in a state of supercritical, based on the pressure of the high-pressure side refrigerant, to achieve optimum coefficient of performance (COP) The target temperature calculating means for calculating the target temperature of the high-pressure side refrigerant and the opening setting for setting the target opening degree of the opening in the expansion means based only on the deviation between the target temperature of the high-pressure side refrigerant and its actual temperature Means and target opening Based on, and an opening signal output means for outputting the opening signals to the expansion means (claim 1).

Specifically, the discharge amount control device includes a discharge amount calculating means for calculating a target discharge amount of the compressor based on a deviation between the target temperature of the conditioned air and the actual temperature, and a compressor based on the target discharge amount. Capacitance signal output means for outputting a capacitance signal can be further included.
According to the refrigerators of claims 1 and 2 described above, when the valve opening degree control device is implemented, the opening degree of the opening in the expansion means matches the actual temperature with the target temperature of the high-pressure side refrigerant, not the pressure of the high-pressure side refrigerant. Therefore, the valve opening control here does not interfere with the discharge amount control of the compressor.

Further, the valve opening degree control device is configured to calculate target pressure calculating means for calculating a target pressure of the high-pressure side refrigerant when the discharge amount of the compressor is maintained at or near an allowable maximum value, and based on the target pressure, Second opening signal output means for outputting an opening signal to the means can further be included.
Furthermore, the valve opening degree control device can further include third opening degree signal output means for outputting a predetermined opening degree signal to the expansion means when the discharge amount of the compressor is maintained at or near the minimum value. (Claim 4) In this case, the predetermined opening signal is preferably a full opening signal (Claim 5).

According to the refrigerators of claims 3 to 5, even if the opening degree of the opening in the expansion means is controlled by the opening degree signal based on the target pressure of the high-pressure side refrigerant or the predetermined opening degree signal, at this time, the discharge amount of the compressor Is not substantially changed, and the valve opening control does not interfere with the discharge amount control of the compressor.
Furthermore, the opening degree setting means, actual pressure of the high-pressure side refrigerant when lower than the critical pressure for setting a predetermined fixed opening degree to the target opening (Claim 6).

If the actual pressure of the high-pressure side refrigerant is lower than the critical pressure, specific be varied opening degree of the expansion means, since the increase or decrease of the capacity in the gas cooler and the evaporator cancel each other, the opening of the opening in the refrigerator A substantially optimal COP is achieved by the fixed opening.

Since the refrigerators according to claims 1 to 5 do not interfere with the valve opening control of the opening in the expansion means and the discharge amount control of the compressor, when performing these valve opening control and discharge amount control, The refrigerant pressure fluctuation can be effectively suppressed without hunting, and the optimum COP can be achieved.
In the refrigerator of claim 6, even when the pressure of the high-pressure side refrigerant is in a subcritical state lower than the critical pressure, an optimum COP can be obtained only by setting the opening degree of the expansion means to a fixed degree. Control in the critical state becomes simple.

FIG. 1 schematically shows a refrigerator incorporated in a vehicle air conditioning system, and this refrigerator uses, for example, carbon dioxide as a refrigerant. The basic configuration of this type of refrigerator is known, and therefore the basic configuration of the refrigerator will be briefly described below.
The refrigerator includes a refrigerant circulation path 2, which is divided into a high-pressure path portion 2a and a low-pressure path portion 2b. A variable displacement compressor 4 is inserted in the high-pressure path portion 2 a, and this compressor 4 is connected to an engine 8 via an electromagnetic clutch 6, and power from the engine 8 is transmitted via the electromagnetic clutch 6. Driven.

A gas cooler 10 is inserted in the high-pressure path portion 2a. The gas cooler 10 is a radiator and is compressed by the compressor 4 and cools the high-pressure side refrigerant discharged from the compressor 4.
On the other hand, an evaporator 12 and an accumulator 14 are sequentially inserted in the refrigerant circulation direction in the low pressure path portion 2b, and as an expansion means between the upstream end of the low pressure path portion 2b and the downstream end of the high pressure path portion 2a. The electric expansion valve 16 is arranged. The expansion valve 16 is adjustable in its opening (opening), that is, its opening. The accumulator 14 performs a gas-liquid separation action on the refrigerant flowing out of the evaporator 12 and supplies only the gas phase portion toward the compressor 4.

Further, in the high pressure path portion 2a between the gas cooler 10 and the expansion valve 16 and in the low pressure path portion 2b between the accumulator 14 and the compressor 4, the high pressure path portion 2a and the low pressure path portion 2b are part of each other. Adjacent to each other, the internal heat exchanger 18 is configured.
The discharge amount of the compressor 4 and the opening / closing of the electromagnetic clutch 6 and the opening degree of the expansion valve 16 are controlled in response to a control signal from the controller 20. For this reason, the controller 20 is electrically connected to various sensors and switches. It is connected. The controller 20 includes a microprocessor (MPU), a storage device such as a ROM and a RAM, an input / output port (I / O), and various drivers.

  Specifically, the sensor includes an air temperature sensor 22 that detects the temperature of the conditioned air after passing through the evaporator 12, that is, the conditioned air supplied to the vehicle interior of the vehicle, and the inlet side (suction side) of the compressor 4. The refrigerant pressure sensor 24 and the refrigerant temperature sensor 26 for detecting the pressure and temperature of the low-pressure side refrigerant at the gas cooler 10, respectively, and the refrigerant pressure sensor 28 and the refrigerant temperature sensor 30 for detecting the pressure and temperature of the high-pressure side refrigerant at the outlet of the gas cooler 10, respectively. The switches include a room temperature setting switch 32 for setting the temperature in the passenger compartment and an A / C switch 34 for switching the air conditioning system on and off.

The controller 20 controls the operation of the refrigerator based on the detection signals from the sensors and switches described above and the setting or switching signal, and the operation control will be described in detail below.
FIG. 2 shows a main routine executed by the controller 20.
In the main routine, the controller 20 first performs initialization processing (step S1) and then performs signal processing (step S2). In step S2, a predetermined process for reading signals from sensors and switches is performed.

Next, the controller 20 performs clutch control (step S3) for the electromagnetic clutch 6.
The discharge amount control for the compressor 4 (step S4) and the valve opening degree control for the expansion valve 16 (step S5) are sequentially performed.
The clutch control is performed based on the switching signal from the A / C switch 34 described above. When the A / C switch 34 is turned on, the controller 20 transmits a control signal to the electromagnetic clutch 6 to turn off the electromagnetic clutch 6. The power of the engine 8 is transmitted to the compressor 4 through the electromagnetic clutch 6. Therefore, from this point, the compressor 4 is driven, the refrigerant circulates in the circulation path 2, and cooling of the passenger compartment is started.

The discharge amount control is specifically shown in FIG.
A discharge rate control, first, on the basis of a setting signal from the temperature setting switch 32 described above, the target temperature T _O of the conditioned air is read (step S40), and, the conditioned air based on the detection signal from the air temperature sensor 22 actual temperature _{T A} is read (step S41). Thereafter, the controller 20 on the basis of the target temperature _{T O,} and the actual temperature _{T A,} calculates a target discharge amount _{Q O} of the compressor 4 (step S42), and the control amount of the compressor 4 according to the target discharge quantity _{Q O} Is output. Accordingly, the compressor 4 is controlled to be driven so that the actual discharge amount coincides with the target discharge amount Q _O , and step S4 is repeatedly performed, so that the temperature in the passenger compartment is maintained at the target temperature T _O.

Note that the controller 20 also adjusts the valve opening of the expansion valve 16 when the above-described discharge amount control is performed. Specifically, the initial value of the valve opening of the expansion valve 16 is determined by the target temperature T _O, which is set at room temperature setting switch 32, thereafter, the valve opening degree with the increase in the discharge pressure in the compressor 4 The pressure is adjusted according to a discharge pressure-valve opening degree map determined in advance by experiments.

The next valve opening degree control is performed at regular intervals after the above-described discharge amount control is performed for a predetermined time, and details thereof are shown in FIG.
In the valve opening control, the controller 20 first determines whether or not the drive of the compressor (comp) is started (ON) (step S50), and if the determination result here is true (Yes), the compressor 20 It is determined whether or not the discharge amount is the maximum discharge (step S51). When the determination result here is false (No), the controller 20 further determines whether or not the pressure of the refrigerant flowing through the high-pressure path portion 2a of the circulation path 2, that is, the pressure of the high-pressure side refrigerant is equal to or higher than the critical pressure. A determination is made (step S52). Determination here is performed based on the detection signal from the refrigerant pressure sensor 28 described above, the refrigerant pressure sensor 28 detects the pressure at the outlet of the gas cooler 10 as the pressure P _H of the high-pressure side refrigerant.

If the decision result in the step S52 is Yes, that is, when the high-pressure side refrigerant is in a supercritical state, the controller 20 calculates a target temperature TT _G of the high-pressure side refrigerant (step S60), in FIG. 5 for details of this step It is shown.
Upon calculating the target temperature TT _G of the high-pressure side refrigerant, the controller 20 is the refrigerant flowing through the low-pressure path section in 2b of the circulation path 2, i.e., it reads the pressure P _S in the low-pressure refrigerant (step S61). Specifically, here, it is read detection signals from refrigerant pressure sensor 24 described above, the refrigerant pressure sensor 24 for detecting the pressure of low-pressure refrigerant sucked into the compressor 4 as a pressure P _S.

Next, the controller 20 detects the superheat degree of the low-pressure refrigerant (SH) (Step S62), and, on the basis of the pressure _{P S} and the degree of superheat (SH), select the best line to achieve optimal COP (Step S63). Here, the optimal line, shows the relationship between the pressure P _H of the high-pressure side refrigerant at the outlet of the gas cooler 10 to achieve optimal COP and its temperature T _G. Specifically, when 6 superheat (SH) is 0, it represents an example of a best line the pressure P _S in the low-pressure refrigerant as a parameter, contrast, FIG. 7 is a pressure P _S is constant ( When P _S = 3.5 MPa), an example of an optimum line with the degree of superheat (SH) as a parameter is shown.

Accordingly, the controller 20 may elect one of the best lines from the pressure P _S and the degree of superheat (SH), and, on the basis of the pressure P _H of the high-pressure side refrigerant read and selected the best line _(step S64), the optimal setting a target temperature TT _G of the high-pressure side refrigerant to achieve a COP (step S65).
As is apparent from FIGS. 6 and 7, the pressure P _H and the temperature T _G of the high-pressure side refrigerant represented by the optimum line does not change much with respect to differences in the pressure P _S and the degree of superheat (SH) Linear since a Do relationship, it is also possible to ignore the pressure P _S and the degree of superheat of (SH), in this case, the target temperature TT _G is based on the pressure P _H, it can be calculated from the following equation.

TT _G = A × P _H + B
Here, A and B are constants.
When the target temperature TT _G of the high-pressure side refrigerant in the manner described above is set, the controller 20 in the next step S53 (see FIG. 4), calculates a target valve opening O _E on the basis of the target temperature TT _G . Specifically, here, the deviation between the target temperature TT _G and the actual temperature TG _A high-pressure side refrigerant is calculated, the target valve opening O _E of the expansion valve 16 required to eliminate the deviation is calculated The The actual temperature TG _A is detected by the refrigerant temperature sensor 30 described above.

Thereafter, the controller 20, in order to match the current Miben opening to the target valve opening O _E, sends a control signal to the expansion valve 16, and drives the expansion valve 16 (step S54).
More specifically, the target valve opening O _E apparent as expansion valve 16 from FIG. 8, the higher the real temperature TG _A high-pressure side refrigerant to the target temperature TT _G, closed to reduce Genben opening is set to a direction, conversely, the lower the actual temperature TG _a high-pressure side refrigerant to the target temperature TT _G, is set in the opening direction to increase Genben opening.

Further, valve opening of the expansion valve 16, rather than being immediately changed to the target valve opening O _E, is increased or decreased little by little toward the target valve opening O _E, thereby, the refrigerant in the circulation path 2 Pressure fluctuation is suppressed.
Table 1 below shows the pressure P _H , the temperature _TG of the high-pressure side refrigerant at the outlet of the gas cooler 10 and the circulation amount of the refrigerant when the valve opening degree of the expansion valve 16 is changed.

  Moreover, the Mollier diagrams corresponding to the states (i) to (v) in Table 1 are shown in (i) to (v) of FIG. 9, a to f indicate the positions of the inlet of the evaporator 12, the outlet of the evaporator 12, the suction port of the compressor 4, the discharge port of the compressor 4, the outlet of the gas cooler 10, and the outlet of the internal exchanger 18, respectively. These positions are also shown in FIG. 1 with the same reference numerals. Further, in FIG. 9, reference symbol L indicates the optimum line described above.

As can be seen from FIG. 9, if the valve opening of the expansion valve 16 changes, the state of the high-pressure side refrigerant at the outlet of the gas cooler 10 also changes. Here, if the change valve opening degree of the expansion valve 16, although the pressure P _S in the low-pressure side refrigerant also change, change in the pressure P _S in order to correspond to the temperature of the conditioned air, the compressor 4 is pressure P _S The amount of discharge is changed in the direction to cancel out, and only the temperature _TG changes in the state of the high-pressure side refrigerant. Therefore, the optimal COP ((iv in FIG. 9) is controlled by controlling the valve opening degree of the expansion valve 16 so that the target temperature TT _G on the optimum line L matches the high-temperature refrigerant temperature _TG . ), (v) state) can be achieved.

That is, when the high-pressure side refrigerant is in a supercritical state during operation of the refrigerator, the valve opening of the expansion valve 16 is controlled according to the temperature _TG of the high-pressure side refrigerant, and the discharge amount of the compressor 4 is low-pressure side. since is controlled according to the pressure P _S of the refrigerant, it will not be such that these control interfere with each other.
On the other hand, the valve opening control routine of FIG. 4, if the determination result in step S52 is false, that is, if the pressure P _H of the high-pressure side refrigerant is lower than the critical pressure, the controller 20 is the step S55 from step S52 In this step, the opening degree of the expansion valve 16 is set to a predetermined fixed opening degree. Therefore, in the next step S54, the expansion valve 16 is controlled so that its valve opening is fixed.

The situation in which the determination result in step S52 is false indicates that the high-pressure side refrigerant is in a subcritical state. In the Mollier diagram of FIG. 10, the outlet (e position) in the gas cooler 10 is temporarily on the saturated liquid line. Positioned and shown.
Since the pressure P _H and the temperature T _G of the high-pressure side refrigerant at the outlet (e position) entering the two-phase region, it is not possible to substantially grasp these pressures P _H and temperature T _G. However, when the capacity of the gas cooler 10 is measured and the state of the high-pressure side refrigerant at the inlet and outlet of the gas cooler 10 is calculated, the actual outlet is at the position α in FIG.

If the valve opening of the expansion valve 16 is varied under the above-described circumstances, the α position changes to the left and right as viewed in FIG. 10, and the outlet of the evaporator 12 is actually connected by the action of the internal heat exchanger 18. It has been confirmed by experiments that the β position shown also changes from side to side as seen in FIG.
Table 2 below shows the behavior of the refrigerator when the opening degree of the expansion valve 16 is variously changed.

Further, Mollier diagrams corresponding to (i) to (viii) in Table 2 are shown in (i) to (iii) of FIG. 11, respectively.
Referring to the capacity of the evaporator 12 and the capacity of the gas cooler 10 in Table 2, when the valve opening degree of the expansion valve 16 is changed, the above-described α position and β position are estimated to move left and right, respectively. Therefore, in achieving the optimum COP, the opening degree of the expansion valve 16 can be set to a fixed opening degree, and this has been confirmed by experiments. In the case of the refrigerator used in the experiment, the optimum COP was achieved when the valve opening at which the valve opening instruction value was about 28 was set as a fixed opening.

Referring to the valve opening control routine of FIG. 4 again, when the determination result in step S50 is false, that is, when the discharge amount of the compressor 4 is maintained at or near the minimum value, the expansion valve 16 is set to fully open (step S56), and after step S54, the expansion valve 16 is driven to fully open the valve opening.
On the other hand, if the determination result in step S51 becomes Yes, that is, when in the situation in which the discharge amount of the compressor 4 is kept maximum or near its permissible at step S70, the high-pressure side refrigerant target pressure TP _G The details are shown in FIG.

Upon calculation of the target pressure TP _G is implemented steps S61~S63 the same steps S71~S73 in calculation routine of the target temperature TT _G described above, and, with the selected optimum line and pressure _{T G} (step S74) based on the target pressure TP _G is set (step S75).
The target pressure TP _G may be calculated from the following equation.

TP _G = C × T _G + D
C and D are constants.
Thereafter, in the next step S57, the target valve opening O _E of the expansion valve 16 based on the target pressure TG _P is calculated, through the implementation of step S54, the valve opening of the expansion valve 16 is a target valve opening O It is changed in small increments to match _E.

If the opening degree of the expansion valve 16 is fully opened through the above-described step S56, the initial value of the opening degree of the expansion valve 16 is set to full opening, so that the COP of the refrigerator quickly reaches the optimum value. Can be made.
On the other hand, even if the valve opening degree of the expansion valve 16 is controlled through step S70, the compressor 4 is not in a state in which the discharge amount can be substantially varied at this time. They do not interfere with each other, so that an optimal COP can be achieved.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, a compressor of the present invention is applicable refrigerator one whose discharge quantity temperature T _A, the pressure P _S, is controlled to be maintained a differential pressure of the discharge pressure P _D or P _D -P _S constant Needless to say, the refrigerator may be provided with an oil palator or a receiver.

  Furthermore, the expansion valve is not limited to the electric type, and the valve opening degree may be mechanically controlled.

It is the schematic block diagram which showed the refrigerator of one Example. It is the flowchart which showed the main routine which the controller of FIG. 1 implements. It is the flowchart which showed the detail of discharge amount control of FIG. It is the flowchart which showed the detail of the valve opening degree control of FIG. Is a flowchart showing details of the operation of TT _G in FIG. Is a graph showing the optimum line in which the pressure P _S as a parameter. It is a graph which shows the optimal line which used the superheat degree as a parameter. It is a graph which shows that the valve opening degree of an expansion valve is changed with the target temperature of a high voltage | pressure side refrigerant | coolant. It is a Mollier diagram when the high-pressure side refrigerant is in a supercritical state, and (i) to (v) respectively show states accompanying changes in the valve opening of the expansion valve. It is a Mollier diagram when the high-pressure side refrigerant is in a subcritical state. It is a Mollier diagram when the high-pressure side refrigerant is in a subcritical state, and (i) to (viii) respectively show states associated with changes in the opening degree of the expansion valve. Is a flowchart showing details of the operation of TP _G in FIG.

Explanation of symbols

2 Circulation path 2a High pressure path part 2b Low pressure path part 4 Compressor 6 Electromagnetic clutch 10 Gas cooler 12 Evaporator 14 Accumulator 16 Expansion valve 18 Internal heat exchanger 20 Controller (control device)
22 Air temperature sensors 26 and 30 Refrigerant temperature sensors 24 and 28 Refrigerant pressure sensor 32 Room temperature setting switch 34 A / C switch

Claims (6)

A refrigerant circulation path divided into a high-pressure path part and a low-pressure path part;
A variable displacement compressor that is inserted into the high-pressure path portion and compresses and discharges the refrigerant;
A gas cooler that is inserted in the high-pressure path portion at a position downstream of the compressor and cools the high-pressure side refrigerant discharged from the compressor;
An expansion means having an opening provided between a downstream end of the high-pressure path portion and an upstream end of the low-pressure path portion, the opening degree of the opening being adjustable;
An evaporator interposed in the low-pressure path portion, evaporating the low-pressure side refrigerant flowing out from the opening of the expansion means, and cooling conditioned air;
Conditioned temperature setting means for setting a target temperature of the conditioned air to be supplied from the evaporator;
Air temperature detecting means for detecting the actual temperature of the conditioned air;
Refrigerant temperature detecting means for detecting an actual temperature of the high-pressure side refrigerant in the high-pressure path portion;
Refrigerant pressure detection means for detecting an actual pressure of the high-pressure side refrigerant in the high-pressure path portion;
A discharge amount control device for performing discharge amount control for controlling the refrigerant discharge amount of the compressor and the opening of the opening of the expansion means so as to make the actual temperature coincide with the target temperature of the conditioned air;
A valve opening degree control device that is operated by periodically interrupting during the discharge amount control, and performs valve opening degree control for controlling the opening degree of the opening in the expansion means;
The valve opening control device is:
When the high-pressure side refrigerant is in a state of supercritical, based on the pressure of the high-pressure side refrigerant, the target temperature calculating means for calculating the target temperature of the high-pressure side refrigerant in achieving optimum coefficient of performance (COP) When,
An opening setting means for setting a target opening degree of the opening in the expansion means based only on a deviation between the target temperature of the high-pressure side refrigerant and the actual temperature;
A refrigerator including an opening signal output means for outputting an opening signal to the expansion means based on the target opening. The discharge amount control device comprises:
A discharge amount calculating means for calculating a target discharge amount of the compressor based on a deviation between the target temperature of the conditioned air and the actual temperature;
Capacity signal output means for outputting a capacity signal to the compressor based on the target discharge amount;
Refrigerator according to claim 1, characterized in including Mukoto a. The valve opening control device is:
Target pressure calculating means for calculating a target pressure of the high-pressure side refrigerant when the discharge amount of the compressor is maintained at or near an allowable maximum value;
The refrigerator according to claim 1 or 2, further comprising: a second opening degree signal output means for outputting an opening degree signal to the expansion means based on the target pressure. The valve opening control device is:
4. A third opening signal output means for outputting a predetermined opening signal to the expansion means when the discharge amount of the compressor is maintained at a minimum value or in the vicinity thereof. A refrigerator according to any one of the above.   The refrigerator according to claim 4, wherein the predetermined opening degree signal is a full open signal. The opening degree setting means, when the actual pressure before Symbol high-pressure side refrigerant is lower than the critical pressure, to claim 1, characterized by setting a predetermined fixed opening degree to the target opening The refrigerator as described.

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