JPH0739897B2 - Refrigeration cycle equipment - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention includes a refrigeration cycle in which a compressor, a condenser, a decompression device, an evaporator, and the like are sequentially connected, and a defrosting function for the evaporator. Refrigeration cycle device.

[Technical background of the invention]

Generally, in an air conditioner that includes a heat pump type refrigeration cycle and enables cooling operation and heating operation, during heating operation, frost will gradually adhere to the outdoor heat exchanger that acts as an evaporator, If it is left as it is, the amount of heat drawn up will decrease and the heating capacity will decline.

Therefore, conventionally, the frosting amount of the outdoor heat exchanger is detected by the following methods, and when the frosting amount exceeds a certain amount, the four-way valve is returned to change the heating cycle to the defrosting cycle (cooling cycle). By switching, the outdoor heat exchanger is defrosted by the heat of the high-temperature refrigerant.

A sensor that detects the frost itself is attached to the outdoor heat exchanger, and this sensor directly detects the amount of frost.

The amount of frost is indirectly detected by the change in ventilation resistance of the outdoor heat exchanger and the difference in enthalpy of the refrigerant.

As shown in Japanese Patent Publication No. 57-47822, the amount of frost formation is indirectly detected by the amount of change in the temperature of the outdoor heat exchanger (hereinafter referred to as the evaporator temperature). For example, as shown in FIG. 6, the evaporator temperature Te changes from the state at the start of operation to the set value Δ
When Te drops, it is considered that the amount of frost is above a certain level.

[Problems of background technology]

However, the methods (1) and (2) have the drawbacks that the device is large and complicated, and the detection error is large, resulting in poor reliability.

In addition, the method (1) has a drawback that a detection error occurs due to the temperature change of the outdoor air that affects the amount of frost formation, because the set value ΔTe of the difference is always fixed. In particular, when the outdoor air temperature is low, defrosting does not start easily despite rapid frost formation. I will invite you.

[Object of the Invention]

The present invention has been made in view of the above circumstances,
The purpose of this is to make it possible to accurately detect the frosted state of the evaporator without being affected by the outdoor air temperature, even though it has a simple structure. Another object of the present invention is to provide a refrigerating cycle device capable of suppressing a decrease in temperature.

[Outline of Invention]

The present invention relates to a refrigeration cycle in which a compressor, a condenser, a decompression device, an evaporator and the like are sequentially connected, a temperature detecting means for detecting the temperature of the evaporator, and a detection of the temperature detecting means after a certain time has passed from the start of operation A storage unit that stores the result, a unit that calculates the ratio between the temperature stored in the storage unit and the detection result of the temperature detection unit during operation, and defrosts the evaporator when the calculation result reaches a set value. It consists of means.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the compressor 1, the four-way valve 2, the outdoor heat exchanger 3,
A pressure reducing device such as an expansion valve 4 and an indoor heat exchanger 5 are sequentially connected to form a heat pump type refrigeration cycle. That is, during the cooling operation, the refrigerant flows in the direction indicated by the solid line arrow to form a cooling cycle, and the outdoor heat exchanger 3 acts as a condenser and the indoor heat exchanger 5 acts as an evaporator. There is. During the heating operation, the switching operation of the four-way valve 2 causes the refrigerant in the direction of the broken line arrow to flow to form a heating cycle, and the outdoor heat exchanger 3 functions as an evaporator and the indoor heat exchanger 5 condenses. It works as a container. An outdoor fan 6 is provided near the outdoor heat exchanger 3, and an indoor fan 7 is provided near the indoor heat exchanger 5.

An evaporator temperature sensor (thermistor) 8 is attached to the refrigerant pipe on the refrigerant inlet side of the outdoor heat exchanger 3 during the heating operation, and the temperature detected by the evaporator temperature sensor 8 is detected by the evaporator temperature detection circuit 9. It is converted into an electric signal (digital signal) and supplied to the controller 10 as evaporator temperature data.
The control unit 10 is composed of a microcomputer and its peripheral circuits and the like, and stores the operating state of the driving operation unit 11, the temperature detected by the indoor temperature sensor (thermistor) 12, the evaporator temperature data from the evaporator temperature detection circuit 9 and the like. Various operation controls are performed accordingly.

By the way, the control unit 10 has a built-in defrosting operation control circuit, and its concrete configuration is shown in FIG. That is, reference numeral 21 is an arithmetic circuit, and a timer circuit 22, a temperature storage unit 23, a four-way valve drive circuit 24, etc. are connected to the arithmetic circuit 21. The calculation circuit 21 determines the frosting state of the outdoor heat exchanger 3 by calculation based on the evaporator temperature data from the evaporator temperature detection circuit 9, and issues a defrosting command as necessary. The timer circuit 22 starts at the same time as the heating operation starts, and the arithmetic circuit
It manages the time of 21 processes. Temperature storage unit 23
Is based on the processing of the arithmetic circuit 21, and stores the evaporator temperature Te after a fixed time t ₁ (for example, 15 minutes) from the start of the heating operation as Te ₀ . The four-way valve drive circuit 24 drives the four-way valve 2 according to the processing of the arithmetic circuit 21.

Next, the operation of the above configuration will be described with reference to FIG.

The operation unit 11 sets the heating operation and the desired room temperature, and performs the operation start operation. Then, the control unit 10
The compressor 1, the outdoor fan 6, and the indoor fan 7 are each turned on, and the four-way valve 2 is switched. In this way, a heating cycle is formed, the outdoor heat exchanger 3 acts as an evaporator, the indoor heat exchanger 5 acts as a condenser, and the condensing action and operation of the indoor fan 7 blow hot air into the room. It That is, the heating operation is started.

By the way, during the heating operation, the frost gradually adheres to the outdoor heat exchanger 3 acting as an evaporator, and the amount of heat pumped up is reduced as it is, and the heating capacity is deteriorated.

Therefore, during the heating operation, the arithmetic circuit 21 monitors the elapsed time from the start of operation by the output of the timer circuit 22 which is started at the same time as the start of operation. Then, for a fixed time t ₁ (for example, 15
Minutes), the temperature of the outdoor heat exchanger 3, that is, the evaporator temperature Te is detected by the signal from the evaporator temperature detection circuit 9 at that time, and it is stored in the temperature storage unit 23 as Te ₀ . In this case, the constant time t ₁ is the time until the evaporator temperature Te stabilizes. Further, the arithmetic circuit 21 is arranged so that the evaporator temperature Te
Are sequentially detected and the next calculation is performed.

B = Note (Te + A) / (Te 0 + A), A is a specific number, for example, to "20".

That is, the ratio of the value obtained by adding the numerical value A to the evaporator temperature Te ₀ after the fixed time t ₁ and the value obtained by adding the numerical value A to the sequentially detected evaporator temperature Te is calculated.

The arithmetic circuit 21 then calculates the value B and the set value C
(For example, 0.5), if B is larger than C, the heating operation is continued and the above calculation is repeated (1
A few times a second). However, if B is the same as C or smaller than C, it is considered that the amount of frost is above a certain level and defrosting is necessary, and a four-way valve return command is issued to the four-way valve drive circuit 24.

For example, if Te ₀ is -5 ° C and the evaporator temperature Te is -5 ° C, B = (-0.5 + 20) / (-0.5 + 20) = 1 and B> C
Therefore, heating operation continues.

If Te ₀ is -5 ° C and the evaporator temperature Te is -12.5 ° C, B = (-12.5 + 20) / (-0.5 + 20) = 0.5 and B =
Since it is C, a four-way valve return command is issued.

When a four-way valve return command is issued, the four-way valve 2 is restored by the operation of the four-way valve drive circuit 24, the heating cycle so far is switched to the defrost cycle (cooling cycle), and the high temperature discharged from the compressor 1 The high-pressure refrigerant flows into the outdoor heat exchanger 3. In this way, the frost adhering to the outdoor heat exchanger 3 is gradually removed by the heat of the high-temperature refrigerant. That is, the defrosting operation is performed on the outdoor heat exchanger 3.

In this case, the evaporator temperature drop width ΔTe (= Te ₀ −Te) when the amount of frost is above a certain level and defrosting is considered necessary is proportional to Te ₀ as shown in FIG. Change. That is, if Te ₀ = 0 ° C., ΔTe = 10 ° C., and if Te ₀ = −10 ° C., ΔTe = 5 ° C.

Thus, as shown in FIG. 5, when the temperature of the outdoor air passing through the outdoor heat exchanger 3 is high and Te ₀ is high, the evaporator temperature drop width is ΔTe ₁ and the defrosting operation is started. In contrast,
When the outdoor air temperature is low and Te ₀ is low, the defrosting operation starts with a smaller evaporator temperature drop width ΔTe ₂ (<ΔTe ₁ ) than when Te ₀ is high. As a result, when the outdoor air temperature is high, the decrease in the heat radiation amount Q due to frost (the heat radiation amount of the indoor heat exchanger 5 acting as a condenser) is ΔQ ₁ , but when the outdoor air temperature is low, the heat radiation amount is low. The decrease in Q is ΔQ ₂ (<ΔQ ₁ ). That is, in a situation where the outdoor air temperature is low and the amount of heat pumped up is small, it is possible to suppress a decrease in the amount of heat radiation Q due to frost formation.

In this way, the evaporator temperature Te after a certain time t ₁ from the start of operation
_{Using 0} as a reference, the ratio between Te ₀ plus the specific value A and the sequentially detected evaporator temperature Te plus the specific value A is calculated, and the calculated result is compared with the set value C. By performing the defrosting operation control by the above, it is possible to perform the optimum defrosting operation according to the frosted state of the outdoor heat exchanger 3 without being affected by the outdoor air temperature. Moreover, according to the embodiment of the optimum defrosting operation, when the outdoor air temperature is low and the pumping heat amount is small, the heat radiation amount Q due to frost formation
Of the heating capacity can be suppressed to a small level, and thus the deterioration of the heating capacity can be suppressed as much as possible.

It should be noted that, in the above-described embodiment, a certain time t _{1 has} elapsed since the start of the heating operation.
The subsequent evaporator temperature is stored as Te ₀ , but the maximum value of the evaporator temperature at the start of operation (constant time t ₁ = zero) may be stored as Te ₀ . Zero hours from the start of operation, that is, the evaporator temperature detected at the same time when the operation switch is turned on is the same as the outdoor temperature because the refrigeration cycle itself is not operated, and can be a sufficiently stable reference value. Further, although the reverse cycle defrosting is performed by returning the four-way valve 2, the defrosting may be performed by the bypass system of the gas refrigerant or the heater heating.
Further, the numerical values A and C used for the calculation may be appropriately determined according to the condition of the refrigeration cycle and the like. Further, although the air conditioner has been described as an example, the present invention is not limited to this, and is similarly applicable to a refrigerator or a refrigerating showcase.

〔The invention's effect〕

As described above, according to the present invention, it is possible to accurately detect the frosted state of the evaporator without being affected by the outdoor air temperature, even though it has a simple structure, and thereby always perform optimum defrosting. It is possible to provide a refrigeration cycle device capable of suppressing a decrease in heating capacity.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the operation of an embodiment of the present invention, FIG. 2 is a diagram showing a schematic configuration of a refrigeration cycle and a control circuit in the embodiment, and FIG. 3 is a control in the embodiment. FIG. 4 is a diagram showing a configuration of a main part of a portion, FIG. 4 is a diagram for explaining an evaporator temperature drop width when defrosting is considered necessary in the same embodiment, and FIG. 5 is a diagram showing evaporator temperature in the same embodiment. FIG. 6 is a diagram showing changes and changes in the amount of heat radiation, and FIG. 6 is a diagram for explaining defrosting operation control of a conventional refrigeration cycle apparatus. 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4
...... Expansion valve (pressure reducing device), 5 ...... Indoor heat exchanger, 8 ......
Evaporator temperature sensor, 10 ... control unit, 21 ... arithmetic circuit, 22
...... Timer circuit, 23 ...... Temperature storage unit, 24 ...... Four-way valve drive circuit.

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, a decompression device, an evaporator and the like are sequentially connected, a temperature detecting means for detecting the temperature of the evaporator, and the temperature after a lapse of a predetermined time from the start of operation. A storage unit that stores the detection result of the detection unit,
During operation, a means for calculating the ratio between the temperature stored in the storage unit and the detection result of the temperature detecting means and a means for defrosting the evaporator when the calculation result reaches a set value are provided. Refrigeration cycle device characterized by.