JP6594698B2 - Refrigeration and air conditioning equipment - Google Patents

Description

  The present invention relates to a refrigeration / air-conditioning apparatus using a refrigerant whose discharge temperature Td is likely to rise, for example, an R32 refrigerant.

  In various refrigerators, air conditioners, heat pumps, etc. (hereinafter collectively referred to as refrigeration / air conditioners), etc., by controlling the opening of the expansion valve so that the suction superheat degree SH is constant, Liquid back was prevented and reliability was ensured. On the other hand, in order to reduce environmental impact, recently, a mixture of R32 refrigerant or R32 refrigerant rich in which the global warming potential (GWP) is as low as about 1/3 of that of R410A refrigerant and the ozone depletion potential (ODP) is zero. A refrigerant (hereinafter simply referred to as R32 refrigerant in the present invention) is used.

  However, the discharge temperature Td of the R32 refrigerant is higher by about 10 to 20 ° C. than the R410A refrigerant due to physical properties, and the discharge temperature Td tends to increase as the difference between the high and low pressures of the refrigerant increases. For this reason, in the case of the R410A refrigerant, as shown in the Mollier diagram of FIG. 6, the discharge temperature Td can be controlled within a temperature range that does not break the insulation of the compressor motor in the normal use range, but when the R32 refrigerant is used, As shown in the Mollier diagram of FIG. 7, in the control with the constant suction superheat degree SH, the discharge temperature Td exceeds the temperature at which the insulation of the compressor motor is broken, and the discharge temperature Td is likely to rise (high and low pressure difference large ), There is a possibility that the motor efficiency may be lowered and the capacity cannot be secured. In addition, in order to solve this problem and secure the operating range, there is a problem that it is necessary to increase the insulation grade of the motor winding gland and the cost is increased.

  Therefore, the opening degree of the electronic expansion valve (EEV) is controlled so that the suction superheat degree SH becomes a predetermined temperature. On the other hand, when the discharge temperature Td of the compressor exceeds the upper limit value, the electronic expansion valve ( Patent Document 1 discloses a configuration in which the opening degree of EEV) is controlled. Further, in Patent Document 2, in order to set the refrigerant dryness at the compressor inlet to 0.85 or more, the compressor rotation speed is adjusted so that the compression ratio of the compressor becomes smaller than the upper limit value, and the discharge overheating is also performed. A configuration in which the degree of opening of the electronic expansion valve (EEV) is adjusted so that the degree TdSH approaches the target value is shown.

JP 2001-174075 A JP 2014-190632 A

  However, although those disclosed in Patent Documents 1 and 2 can prevent an excessive increase in the discharge temperature Td and a decrease in the motor efficiency associated therewith, the suction superheat degree SH associated with a change in the operation state or the operation point can be prevented. Not only can it not cope sufficiently with an increase, a decrease in operation efficiency resulting from this, an impediment to stable operation due to the occurrence of excessive liquid back, or a limit value of the discharge temperature Td due to a change in the outside air temperature. In addition to the opening degree control, the rotation speed control of the compressor must be used in combination, which causes problems such as a complicated control system.

  The present invention has been made in view of such circumstances, and it is possible to ensure an appropriate operating state with respect to changes in operating conditions and operating points only by controlling the opening degree of the electronic expansion valve, and compression. An object of the present invention is to provide a refrigeration / air-conditioning apparatus that can operate a machine within the usage limits and ensure reliability.

In order to solve the above-described problems, the refrigeration / air-conditioning apparatus of the present invention employs the following means.
That is, in the refrigeration / air conditioning apparatus according to the present invention, at least the compressor, the heat source side heat exchanger, the electronic expansion valve, and the use side heat exchanger are connected via the refrigerant pipe, and the discharge temperature Td is higher than that of the R410A refrigerant. When the refrigeration cycle is filled with a refrigerant that tends to rise and the discharge temperature Td is less than or equal to the upper limit value, the opening of the electronic expansion valve is controlled at a constant intake gas superheat degree SH, and the discharge temperature Td reaches the upper limit value. Expansion valve control means for controlling the degree of opening of the electronic expansion valve at a discharge superheat degree TdSH constant or discharge temperature Td constant when the discharge superheat degree exceeds the discharge superheat degree TdSH constant or the discharge When the discharge superheat degree TdSH constant control is being performed during the control at the constant temperature Td, the target discharge superheat degree TdSH + high pressure saturation temperature obtained from the calculation of the compressor rotation speed, and the discharge temperature When the discharge superheat degree TdSH constant control or the discharge temperature Td constant control with the lower one of the upper limit values of the temperature Td as a target value is switched and the discharge temperature Td constant control is performed, It comprises target value switching means for comparing the target discharge temperature Td obtained from the calculation with the high pressure saturation temperature and the upper limit value, and adopting the lower one as the target discharge temperature Td. To do.

  According to the present invention, when the discharge temperature Td of the refrigerant discharged from the compressor during operation is equal to or lower than a preset upper limit value, the opening of the electronic expansion valve is controlled at a constant suction gas superheat degree SH, and the discharge When the temperature Td exceeds the upper limit value, the opening degree of the electronic expansion valve is controlled with the discharge superheat degree TdSH constant or the discharge temperature Td constant, so that even when the R32 refrigerant that easily increases the discharge temperature Td is used The temperature Td is prevented from exceeding the upper limit of use, and the compressor motor insulation grade can be used as it is, thereby avoiding an increase in cost and making the discharge temperature Td difficult to increase. Deterioration can be prevented. Further, when the discharge superheat degree TdSH is constant or the discharge temperature Td is constant and the discharge superheat degree TdSH is constant, the target discharge superheat degree TdSH + high pressure saturation temperature obtained from the calculation of the compressor rotation speed, When the discharge superheat degree TdSH constant control or the discharge temperature Td constant control with the lower one of the upper limit values of the temperature Td as the target value is switched and the target discharge temperature Td constant control is performed, the compressor rotational speed and the high pressure The target discharge temperature Td obtained from the calculation with the saturation temperature is compared with the upper limit value, and the lower one is adopted as the target discharge temperature Td. Therefore, the compressor rotation speed is not changed. Even when the point changes, the opening of the electronic expansion valve is controlled with the lower of the allowable upper limit value of the discharge temperature Td and the target discharge superheat degree TdSH + high pressure saturation temperature as the target value. Rukoto can, by suppressing discharge temperature Td below the upper limit value of the compressor can be protected reliably use restrictions.

  Furthermore, in the refrigeration / air conditioning apparatus according to the present invention, in the above-described refrigeration / air conditioning apparatus, the expansion valve control means further changes a target discharge superheat degree TdSH or a target discharge temperature Td according to the rotation speed of the compressor. A value variable means is provided.

  According to the present invention, since the expansion valve control means further includes the target value variable means for changing the target discharge superheat degree TdSH or the target discharge temperature Td according to the rotational speed of the compressor, the opening degree of the electronic expansion valve If the compressor rotation speed decreases and the compression ratio decreases during the control with the discharge superheat degree TdSH constant or the discharge temperature Td constant, the opening degree of the electronic expansion valve becomes too narrow, resulting in the intake superheat degree SH becoming too large. Although the heat exchange performance is deteriorated, by varying the target discharge superheat degree TdSH or the discharge temperature Td according to the compressor rotational speed, it is possible to prevent the electronic expansion valve from being excessively throttled and maintain an appropriate operation state. . Therefore, it is possible to suppress the deterioration of the heat exchange performance due to the excessive suction superheat degree SH and to perform an efficient operation.

Furthermore, in the refrigeration / air-conditioning apparatus according to the reference example of the present invention, at least a compressor, a heat source side heat exchanger, an electronic expansion valve, and a use side heat exchanger are connected via a refrigerant pipe, and a discharge temperature Td is R410A inside. When the refrigeration cycle is filled with a refrigerant that is more likely to rise than the refrigerant and the discharge temperature Td is less than or equal to the upper limit, the opening of the electronic expansion valve is controlled at a constant intake gas superheat degree SH, and the discharge temperature Td Expansion valve control means for controlling the degree of opening of the electronic expansion valve at a discharge superheat degree TdSH constant or a discharge temperature Td constant when the upper limit value is exceeded, and the expansion valve control means further rotates the compressor There is provided a target value varying means for varying the target discharge superheat degree TdSH or the target discharge temperature Td according to the number.

According to the reference example of the present invention , when the discharge temperature Td of the refrigerant discharged from the compressor during operation is equal to or lower than a preset upper limit value, the opening degree of the electronic expansion valve is controlled at a constant intake gas superheat degree SH. When the discharge temperature Td exceeds the upper limit value, the opening degree of the electronic expansion valve is controlled with the discharge superheat degree TdSH constant or the discharge temperature Td constant. However, by preventing the discharge temperature Td from exceeding the upper limit of use and making the insulation grade of the compressor motor usable as it is, it is possible to avoid an increase in cost and to make the discharge temperature Td difficult to increase. Deterioration of refrigeration oil can be prevented. In addition, when the opening degree of the electronic expansion valve is controlled with the discharge superheat degree TdSH constant or the discharge temperature Td constant, if the compressor speed decreases and the compression ratio becomes small, the opening degree of the electronic expansion valve is reduced too much. Although the degree of superheat SH becomes too large and the heat exchange performance deteriorates, by varying the target discharge superheat degree TdSH or the discharge temperature Td according to the compressor rotational speed, the electronic expansion valve is prevented from being excessively throttled and appropriately The driving state can be maintained. Therefore, it is possible to suppress the deterioration of the heat exchange performance due to the excessive suction superheat degree SH and to perform an efficient operation.

  According to the present invention, even when the R32 refrigerant that easily increases the discharge temperature Td is used, the discharge temperature Td is prevented from exceeding the upper limit of use, and the insulation grade of the compressor motor can be used as it is. Cost increase can be avoided and deterioration of the refrigerating machine oil can be prevented by making it difficult to raise the discharge temperature Td. Even when the operating point changes without changing the compressor rotation speed, the lower of the allowable upper limit value of the discharge temperature Td and the target discharge superheat degree TdSH + high pressure saturation temperature is set to the target value. As a result, the opening degree of the electronic expansion valve can be controlled, and the discharge temperature Td can be kept below the upper limit value for use of the compressor, so that the use limit can be reliably observed.

  Further, according to the present invention, when the opening degree of the electronic expansion valve is controlled at a constant discharge superheat degree TdSH or a constant discharge temperature Td, the opening degree of the electronic expansion valve is reduced when the compressor rotation speed is reduced and the compression ratio is reduced. As a result of excessive throttle, the suction superheat degree SH becomes too large and the heat exchange performance deteriorates. However, by varying the target discharge superheat degree TdSH or the discharge temperature Td according to the compressor rotation speed, the electronic expansion valve can be over throttled. Therefore, it is possible to prevent the heat exchange performance from being deteriorated due to excessive increase in the suction superheat degree SH, and to perform efficient operation.

1 is a refrigerant circuit diagram of a refrigeration / air conditioning apparatus according to an embodiment of the present invention. FIG. 5 is Mollier diagrams (A) and (B) for explaining the significance of switching control of the electronic expansion valve of the above apparatus between suction superheat degree SH control and discharge superheat degree TdSH or discharge temperature Td. FIG. 6 is a Mollier diagram illustrating the significance of controlling the target value switching of the electronic expansion valve between the upper limit discharge temperature Td of the compressor and the calculated target discharge superheat degree TdSH or the discharge temperature Td. It is a Mollier diagram explaining the significance of controlling the electronic expansion valve by varying the target discharge superheat degree TdSH or the discharge temperature Td according to the rotation speed of the compressor. It is a graph which shows the relationship between the said compressor rotation speed and the target discharge superheat degree TdSH or discharge temperature Td which changes according to it. It is a Mollier diagram of the refrigerating cycle using R410A refrigerant. It is a Mollier diagram of the refrigerating cycle using R32 refrigerant.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5.
FIG. 1 shows a refrigerant circuit diagram of a refrigeration / air-conditioning apparatus according to an embodiment of the present invention.
The refrigeration / air conditioning apparatus 1 according to the present embodiment includes a heat source side unit (outdoor unit) 2 installed outdoors and a use side unit (indoor unit) 3 installed in an indoor air-conditioned space. The units 2 and 3 are connected via a liquid side pipe 4 and a gas side pipe 5.

  The heat source side unit (outdoor unit) 2 includes a compressor 6 that compresses the refrigerant, a four-way switching valve 7 that switches the circulation direction of the refrigerant, a heat source side heat exchanger (outdoor heat exchanger) 8 that exchanges heat between the refrigerant and the outside air, A heating electronic expansion valve (EEVH) 9 that depressurizes the refrigerant during heating, a receiver 10 that temporarily stores liquid refrigerant, a cooling electronic expansion valve (EEVC) 11 that depressurizes the refrigerant during cooling, and a liquid side pipe 4. A liquid side operation valve 12 to be connected, a gas side operation valve 13 to which the gas side pipe 5 is connected, an accumulator 14 for separating the liquid component and sucking only the gas refrigerant into the compressor 6 and the like are provided. The heat source side refrigerant circuit 16 is configured by connecting the refrigerant pipes 15 as illustrated.

  The heat source side refrigerant circuit 16 of the heat source side unit 2 has a high pressure switch 17 that opens and closes the pressure of the high pressure refrigerant gas discharged from the compressor 6 at a set high pressure with respect to the refrigerant discharge pipe 15A from the compressor 6. And a discharge temperature sensor (Td temperature sensor) 18 for detecting the temperature of the refrigerant gas discharged from the compressor 6 and a low-pressure refrigerant sucked into the compressor 6 with respect to the refrigerant suction pipe 15B of the compressor 6 A low-pressure sensor 19 that detects the gas pressure and a suction temperature sensor 20 that detects the temperature of the refrigerant gas sucked into the compressor 6 are provided.

  Further, the heat source side heat exchanger 8 is provided with a heat exchange temperature sensor 21 for detecting the temperature of the intermediate part and a heat exchange temperature sensor 22 for detecting the temperature of one end part, and for the heat source side heat exchanger 8. An outside air temperature sensor 23 is provided for detecting the temperature of outside air that is ventilated through an outdoor blower (not shown).

  On the other hand, the use side unit (indoor unit) 3 is provided in the use side refrigerant circuit 24, and exchanges heat between the refrigerant and indoor air circulated through an indoor fan (not shown) to cool or heat the indoor air. A side heat exchanger (outdoor heat exchanger) 25 is provided, and the air cooled or heated by the use side heat exchanger 25 is blown into the room to be used for indoor cooling or heating. .

  The use side heat exchanger 25 is provided with a heat exchange temperature sensor 26 for detecting the temperature of the intermediate part and a heat exchange temperature sensor 27 for detecting the temperature of one end part. A suction temperature sensor 28 is provided for detecting the temperature of room air sucked through the air.

  Then, the heat source side refrigerant circuit 16 and the use side refrigerant circuit 24 are connected to the liquid side pipe 4 and the gas side pipe 5 by using the liquid side operation valve 12 and the gas side operation valve 13, thereby refrigeration in a closed cycle. The refrigeration / air-conditioning apparatus 1 is configured by filling the refrigeration cycle 29 with a required amount of refrigerant, such as R32 refrigerant, whose discharge temperature Td is likely to rise higher than that of the R410A refrigerant. Yes.

  In the refrigeration cycle 29, the refrigerant compressed by the compressor 6, as indicated by a solid arrow by the four-way switching valve 7, is a heat source side heat exchanger 8, a receiver 10, a cooling electronic expansion valve 11, a liquid side pipe 4, A cooling / cooling cycle is formed by circulating the use side heat exchanger 25, the gas side pipe 5, the four-way switching valve 7, the accumulator 14, and the compressor 6 in this order, and the heat source side heat exchanger 8 is a condenser, use side heat. The exchanger 25 is made to function as an evaporator, and air cooled by the endothermic action of the refrigerant in the evaporator is blown into the room so that the cooling / cooling operation can be performed.

  Further, the refrigerant compressed by the compressor 6 is indicated by broken arrows by the four-way switching valve 7, as shown by the gas side pipe 5, the use side heat exchanger 25, the liquid side pipe 4, the receiver 10, and the heating electronic expansion valve 9. , Liquid side piping 4, heat source side heat exchanger 8, four-way switching valve 7, accumulator 14, compressor 6 are circulated in this order to form a heating / heating cycle, and use side heat exchanger 25 is connected to the condenser, heat source side The heat exchanger 8 is made to function as an evaporator, and air heated by the heat radiation action of the refrigerant in the condenser is blown into the room so that heating / heating operation can be performed.

  The heat source side unit (outdoor unit) 2 and the use side unit (indoor unit) 3 are provided with heat source side and use side controllers 30, 31 for controlling the operation of the units 2, 3. Are connected to each other via a communication line 32. The controllers 30 and 31 receive detection signals from the sensors, and are stored in the storage units 33 and 34 based on the detected values and operation signals and setting signals input from a remote controller (not shown). In accordance with the control program, the compressor 6 is turned on / off and the rotational speed, the four-way switching valve 7 is switched, the outdoor blower on / off and the rotational speed are omitted, the heating electronic expansion valve 9 and the cooling electronic expansion valve. The operation of the refrigeration / air-conditioning apparatus 1 is controlled by appropriately controlling the opening degree of 11, the on / off of the indoor blower (not shown), the rotational speed, and the like.

  In the present embodiment, the heat source side controller 30 includes a detected value of the suction temperature sensor 20 and a detected value of the heat exchanger temperature sensor 26 or a saturation temperature of the pressure detected by the low pressure sensor 19 during normal cooling operation. On the other hand, during heating operation, the degree of suction superheat obtained from the difference between the detected value of the suction temperature sensor 20 and the detected value of the heat exchanger temperature sensor 21 or the saturation temperature of the pressure detected by the low pressure sensor 19 Expansion valve control means 35 for controlling the opening degree of the cooling electronic expansion valve (EEVC) 11 or the heating electronic expansion valve (EEVH) 9 is provided so that SH is constant.

The expansion valve control means 35 is preset with the temperature (discharge temperature) Td of the refrigerant discharged from the compressor 6 detected by the discharge temperature sensor (Td temperature sensor) 18 during normal cooling / heating operation. When the temperature (for example, 95 ° C.) is exceeded, it has a function of switching from the suction superheat degree SH constant control to the discharge superheat degree TdSH constant control or the discharge temperature Td constant control.
The discharge superheat degree TdSH is a difference between the detection value of the discharge temperature sensor 18 and the detection value of the heat exchange temperature sensor 21 during cooling, and the detection value of the heat exchange temperature sensor 26 during heating (a high pressure sensor is provided. In this case, the saturation temperature of the detected pressure (high pressure saturation temperature) may be used).

  In the above switching control, as shown in FIG. 2A, during the suction superheat degree SH constant control, for example, when the rotation speed of the compressor 6 increases and the compression ratio increases as shown by the white arrow. If the suction superheat degree SH is kept constant, the discharge temperature Td may exceed the use upper limit value (thick one-dot chain line). Thus, when the discharge temperature Td exceeds a preset temperature (upper limit value; for example, 95 ° C.), the opening degree control of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is controlled to a constant discharge superheat degree TdSH. Or it switches to discharge temperature Td fixed control.

  In this way, by switching the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 to the discharge superheat degree TdSH constant control or the discharge temperature Td constant control, as shown in FIG. 6 can be controlled as indicated by white arrows, and the discharge temperature Td can be suppressed to a temperature within the usage limit that does not break the insulation of the motor winding of the compressor 6. In this case, as shown in FIG. 2 (B), the suction superheat degree SH becomes 0 or less (the left side region from the saturated gas line), the wet gas is sucked, and a slight liquid back operation is performed. Reliability can be ensured by keeping TdSH sufficiently high.

  Further, while the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is controlled by the expansion valve control means 35 at a constant discharge superheat degree TdSH or a constant discharge temperature Td, the compressor rotational speed remains unchanged. When the operating point changes (for example, when the outside air temperature rises and the high pressure rises during the cooling operation), the operating point may change as shown by a broken line in FIG. Even if TdSH is controlled to be constant, the discharge temperature Td may exceed the upper limit of use.

  In order to avoid such a situation, target value switching means 36 is provided for expansion valve control means 35. When the target value switching means 36 is performing control with the discharge superheat degree TdSH constant or the discharge temperature Td constant, and the control with the discharge superheat degree TdSH constant, the target discharge superheat degree TdSH + high pressure obtained by calculation from the compressor rotational speed. The pressure saturation temperature is compared with the upper limit value of the discharge temperature Td allowed for the compressor 6, and the lower value is set as a target value to control the discharge superheat degree TdSH constant, or the discharge temperature Td constant control. It is to switch whether to do.

  Further, the target value switching means 36 can be obtained by calculation from the compressor rotational speed and the high pressure saturation temperature when the control is performed at the discharge temperature Td constant during the control at the discharge superheat degree TdSH constant or the discharge temperature Td constant. The target discharge temperature Td and the upper limit value of the discharge temperature Td allowed for the compressor 6 are compared, and the control is performed with the discharge temperature Td constant with the lower value as the target value.

Further, in the reference example of the present embodiment, the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is being controlled by the expansion valve control means 35 at a constant discharge superheat degree TdSH or a constant discharge temperature Td. In addition, a target value variable means 37 for changing the target value of the discharge superheat degree TdSH or the discharge temperature Td according to the rotation speed of the compressor 6 is provided.

  Generally, when the rotational speed of the compressor 6 decreases, the performance of the heat exchanger increases, so the high pressure decreases, the low pressure increases, and the compression ratio decreases. Therefore, as shown in FIG. 4, if the target discharge superheat degree TdSH or the target discharge temperature Td remains constant, as a result, the suction superheat degree SH is controlled to be constant as shown by a fine broken line. It may be larger than the control value of the hour. Therefore, a target value variable means 37 for changing the target value of the discharge superheat degree TdSH or the discharge temperature Td according to the rotation speed of the compressor 6 is provided, and the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is excessively throttled. I try to prevent it.

  At this time, as shown in FIG. 5, the relationship between the compressor rotational speed and the discharge superheat degree TdSH or the discharge temperature Td is such that the target value of the discharge superheat degree TdSH or the discharge temperature Td changes linearly within a certain rotational speed range. If the discharge superheat degree TdSH or the discharge temperature Td becomes too small, the liquid back state occurs. Therefore, a target value (discharge superheat degree TdSH or discharge temperature Td) equal to or higher than a certain value is secured and discharged. If the degree of superheat TdSH or the discharge temperature Td becomes too high, the discharge temperature Td exceeds the upper limit value for use, so that the value reaches a certain value.

  Further, as shown in FIG. 4, when the suction superheat degree SH becomes larger, basically, the control is returned from the discharge superheat degree TdSH constant control or the discharge temperature Td constant control to the suction superheat degree SH constant control. If the control is frequently switched, stable operation is hindered. Therefore, hysteresis is provided, and once the control is switched, the suction superheat degree SH rises to some extent or the discharge superheat degree TdSH or the discharge temperature Td is specified. Control may not be switched until the value drops by more than the value.

According to the embodiment described above, the following operational effects are obtained.
In the refrigeration / air-conditioning apparatus 1, the high-temperature and high-pressure refrigerant gas discharged from the compressor 6 is circulated in the direction of the solid arrow by the four-way switching valve 7 to form a cooling / cooling cycle, and the heat source side heat exchanger 8 is condensed. The cooling / cooling operation can be performed by making the use side heat exchanger 25 function as an evaporator, while the high-temperature and high-pressure refrigerant gas discharged from the compressor 6 is fed by the four-way switching valve 7 in the direction of the broken line arrow It is possible to perform heating / heating operation by forming a heating / heating cycle and causing the use side heat exchanger 25 to function as a condenser and the heat source side heat exchanger 8 as an evaporator.

  During these cooling / cooling and heating / heating operations, the cooling electronic expansion valve (EEVC) 11 or the heating electronic expansion valve (EEVH) 9 has a constant suction superheat degree SH via the expansion valve control means 35. The opening degree is controlled. When the refrigerant discharge temperature Td detected by the discharge temperature sensor 18 during such operation exceeds a preset use upper limit value (95 ° C. in this embodiment), the discharge superheat from a constant suction superheat degree SH. The control is switched to constant TdSH control or discharge temperature Td constant control.

  As a result, even when the R32 refrigerant whose discharge temperature Td is likely to rise as compared with the R410A refrigerant is used, in the low compression ratio region, by controlling the suction superheat degree SH to be constant, the liquid back is surely prevented and the reliability is improved. In a region where the discharge temperature Td is likely to rise at a high compression ratio, the discharge temperature Td can be prevented from exceeding the upper limit of use by operating with a slight liquid back. The cost increase can be avoided by making the insulation grade of the machine motor usable as it is. Moreover, deterioration of the refrigerating machine oil can be prevented by making it difficult to raise the discharge temperature Td.

  Further, when the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is controlled at a constant discharge superheat TdSH or a constant discharge temperature Td, the discharge temperature Td may change depending on the high pressure level during operation. For example, when the outside air temperature rises and the high pressure rises during cooling, the operating point changes without changing the compressor rotation speed, and only the discharge superheat degree TdSH is controlled as shown in FIG. There is a possibility that the discharge temperature Td may exceed the allowable upper limit value.

  However, during the control with the discharge superheat degree TdSH constant or the discharge temperature Td constant as described above, when the target value switching means 36 performs the control with the discharge superheat degree TdSH constant, the target obtained by calculation from the compressor rotational speed. Comparing the discharge superheat degree TdSH + high pressure saturation temperature with the upper limit value of the discharge temperature Td allowed for the compressor 6, and controlling the discharge superheat degree TdSH constant with the lower value as the target value Switches whether to control at a constant temperature Td. Further, when the control is performed with the discharge temperature Td constant, the target discharge temperature Td obtained by calculation from the compressor rotation speed and the high pressure saturation temperature, and the upper limit value of the discharge temperature Td allowed for the compressor 6 are set. In comparison, the lower value is adopted as the target value, and the discharge temperature Td is controlled to be constant.

  Therefore, as described above, even when the operating point changes without changing the rotation speed of the compressor 6, the lower of the upper limit value of the allowable discharge temperature Td and the target discharge superheat degree TdSH + high pressure saturation temperature. By controlling the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 with the value of the value as a target value, the discharge temperature Td can be kept below the upper limit of use of the compressor 6 and the use limit can be observed. Can do.

Further, in the reference example of the present embodiment, the target value variable means 37 for changing the target value of the discharge superheat degree TdSH or the discharge temperature Td according to the rotation speed of the compressor 6 is provided for the expansion valve control means 35. Yes. That is, when the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is controlled with the discharge superheat degree TdSH constant or the discharge temperature Td constant, when the rotation speed of the compressor 6 decreases and the compression ratio decreases, When the target discharge superheat degree TdSH or the discharge temperature Td is constant, the opening degree of the cooling electronic expansion valve 11 or the heating electronic expansion valve 9 is excessively narrowed. As a result, the intake superheat degree SH becomes too large and the heat exchange performance deteriorates. .

  However, by changing the target value discharge superheat degree TdSH or the discharge temperature Td as shown in FIG. 5 according to the number of rotations of the compressor 6 by the target value variable means 37, an appropriate operation state is maintained and efficiency is improved. Can perform good driving.

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above-described embodiment, the discharge superheat degree TdSH and the discharge temperature Td are arranged in the same row for convenience in the form in which the discharge superheat degree TdSH or the discharge temperature Td, which is the control target value, is varied according to the rotation speed of the compressor 6. In this example, the discharge superheat degree TdSH is variable and the discharge temperature Td is constant. However, the relationship between the high pressure saturation temperature and the target discharge temperature Td is used as a map without using the discharge superheat degree TdSH. Of course, the configuration may be good.

  Furthermore, although the said embodiment demonstrated the example of the freezing / air-conditioning apparatus 1 which provided the electronic expansion valve for heating (EEVH) 9 and the electronic expansion valve for cooling (EEVC) 11 separately, single electronic expansion valve (EEV) may be used, or a cooling electronic expansion valve (EEVC) 11 may be provided in the use side unit (indoor unit) 3. Further, the refrigeration cycle 29 only needs to have a basic cycle including a compressor, a heat source side heat exchanger, an electronic expansion valve, and a use side heat exchanger, and is not limited to the refrigeration cycle of the above embodiment. It goes without saying that it can be transformed into a cycle of construction.

1 Refrigeration / air-conditioning device 6 Compressor 8 Heat source side heat exchanger 9 Heating electronic expansion valve (EEVH)
11 Electronic expansion valve for cooling (EEVC)
15 Refrigerant piping 18 Discharge temperature sensor 19 Low pressure sensor 20 Suction temperature sensors 21, 22, 26, 27 Heat exchange temperature sensor 29 Refrigeration cycle 30 Heat source side controller 31 Use side controller 35 Expansion valve control means 36 Target value switching means 37 Target value Variable means

Claims (2)

A refrigeration cycle in which at least a compressor, a heat source side heat exchanger, an electronic expansion valve, and a use side heat exchanger are connected via a refrigerant pipe, and the inside is filled with a refrigerant whose discharge temperature Td is more likely to rise than the R410A refrigerant;
When the discharge temperature Td is equal to or lower than the upper limit value, the opening degree of the electronic expansion valve is controlled at a constant suction gas superheat degree SH, and when the discharge temperature Td exceeds the upper limit value, the discharge superheat degree TdSH constant or the discharge temperature is controlled. Expansion valve control means for controlling the opening of the electronic expansion valve at a constant Td,
When the expansion valve control means performs the discharge superheat degree TdSH constant control during the discharge superheat degree TdSH constant or the discharge temperature Td constant control, the target discharge superheat degree obtained from the calculation of the compressor rotation speed is performed. Switching to the discharge superheat degree TdSH constant control or the discharge temperature Td constant control with the lower one of TdSH + high pressure saturation temperature and the upper limit of the discharge temperature Td as a target value, and performing the discharge temperature Td constant control If it is, the target discharge temperature Td obtained from the calculation of the compressor speed and the high pressure saturation temperature is compared with the upper limit value, and the lower one is adopted as the target discharge temperature Td. A refrigeration / air-conditioning device comprising means.   2. The refrigeration according to claim 1, wherein the expansion valve control means further comprises target value variable means for varying the target discharge superheat degree TdSH or the target discharge temperature Td in accordance with the rotational speed of the compressor.・ Air conditioning equipment.

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