JP5887902B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a technique for preventing overheating of a compressor of a refrigeration cycle apparatus using a refrigerant such as R32 that has a low warming coefficient and easily increases the discharge temperature.

In recent years, global warming has become a major problem, and the movement to use refrigerants with low global warming potential has become prominent. As alternative refrigerants for hydrofluorocarbon (HFC), natural refrigerants and refrigerants such as hydrofluoroolefins having a double bond between carbon and carbon have attracted attention. As for HCFC-22 (R22), from the viewpoint of protection of the ozone layer, conversion to a refrigerant that does not destroy the ozone layer has been urged, and in Japan, the use of new devices such as air conditioners has ended.

  Hydrofluoroolefin has attracted particular attention as an alternative refrigerant for HFC-134a, and its practical application to an air conditioner for automobiles is being promoted. The global warming potential (GWP) is extremely small compared to 4 for HFO-1234yf, 1430 for HFC-134a, and 2090 for HFC-410A used in air conditioners. This characteristic that the warming coefficient is small is attributed to the fact that there is a double bond between carbon and it is easy to decompose.

  Moreover, as HFC which can be used as a refrigerant with a relatively low global warming potential, it accounts for 50% of HFC-410A and has slightly flammable HFC-32 (GWP675), weakly flammable HFC-152a (GWP124), etc. Strongly flammable hydrocarbons also have excellent characteristics as refrigerants.

  However, in the case of HFO-1234yf, the pressure loss is large and it is not suitable for a separate type room air conditioner where the indoor unit and the outdoor unit are installed apart from each other. For HFC-152a and hydrocarbons, it is flammable. However, there are problems such as a decrease in performance and an increase in cost, and the fact that carbon dioxide has a large decrease in performance and it is difficult to obtain practical performance. HFC-32 (R32) is promising.

  When R32 is used as a refrigerant, its global warming potential is low and the global environmental load can be reduced. However, since the discharge temperature rises compared to the case of using R22 or HFC-410A (R410A), It is necessary to cope with the increase in the discharge temperature, that is, against the overheating of the compressor as well as the slight flammability.

  In the conventional air conditioner, there is an optimum value as the discharge temperature of the compressor, and the optimum discharge temperature is realized by adjusting the opening degree of the expansion valve to prevent overheating of the compressor (for example, patent document). 1). If the opening of the expansion valve is opened, the discharge temperature decreases, and if the opening is reduced, the discharge temperature increases. Therefore, in a situation where it is desired to lower the discharge temperature, the expansion valve may be opened. When the expansion valve is opened, the refrigerant does not completely evaporate at the intake port of the compressor, resulting in a wet state, and the discharge temperature decreases.

  On the other hand, if a large amount of liquid refrigerant is sucked into a compressor, liquid compression may occur and reliability may not be ensured. Therefore, in conventional devices, gas-liquid separation is usually performed to mainly suck gas-phase refrigerant. An accumulator is provided to prevent a decrease in reliability.

  This accumulator introduces a refrigerant into a container with a cylindrical body, slows the flow rate of the refrigerant, collects liquid refrigerant at the bottom of the container due to the effect of gravity, and selectively sucks and compresses gas-phase refrigerant A refrigerant outlet pipe to be sent to a machine or the like is provided. In order to return the refrigeration oil discharged and returned during the cycle to the compressor, a small hole is provided in the lower part of the refrigerant outlet pipe, and is mixed with the gas-phase refrigerant and sent to the compressor. At this time, if the liquid refrigerant is accumulated, the liquid refrigerant also returns to the compressor, but this is limited to small amounts. That is, normally, one small hole at the lower part of the refrigerant outlet pipe is provided with a predetermined size.

  In order to wet the refrigerant sucked in the compressor, there is also a method of directly returning the liquid refrigerant by providing a bypass path with a control valve to the accumulator immediately before or after the expansion valve.

Japanese Patent Publication No. 3-40295

  In the conventional discharge temperature control by adjusting the expansion valve opening, the accumulator basically has a structure for storing liquid refrigerant, and the liquid refrigerant return port has only one small hole in the lower part of the refrigerant outlet pipe. The return amount of the refrigerant is determined by the diameter of the small hole and the head difference of the liquid refrigerant. Therefore, even if it becomes a situation where the discharge temperature of the compressor is to be lowered, the amount of liquid return to the compressor cannot be increased, and if it is attempted to make this possible, that is, the refrigerant becomes wet at the inlet of the compressor. In order to increase the amount of liquid return when it enters, it is necessary to accumulate a large amount of liquid refrigerant in the accumulator constantly to ensure a head difference.

  However, if liquid refrigerant is accumulated in the accumulator, there is a problem in that the amount of refrigerant in the cycle is insufficient and performance is deteriorated.

  Here, in anticipation of the shortage of refrigerant, if a large amount of refrigerant is filled in advance, the refrigerant is overfilled in a situation where it is not necessary to store the liquid refrigerant in the accumulator, and as a result, the performance deteriorates.

  In addition, there is a method of providing a bypass path provided with a control valve and returning the liquid refrigerant directly. However, in this method, the problem of lack of refrigerant is the same, and it is avoided that the number of components increases and the cost of the apparatus increases. Absent.

  The present invention solves such a conventional problem, and in a refrigeration cycle apparatus using a refrigerant whose discharge temperature is likely to rise, overheating of the compressor is prevented without causing an increase in cost and a decrease in performance, and high reliability. It aims at providing the refrigerating-cycle apparatus which has property.

In order to solve the above-described conventional problems, the present invention provides a refrigeration cycle apparatus in which a refrigerant circulates through a compressor, a condenser , an expansion valve, an evaporator, and an accumulator, and the accumulator is provided immediately before the refrigerant suction port of the compressor. The accumulator has an opening provided in the upper portion and a plurality of small holes provided in the lower portion and having different height positions in the vertical direction, and a refrigerant outlet pipe provided in the accumulator, and the plurality of the accumulators An accumulator throttle portion provided around the small hole and having a diameter that is smaller than the outer diameter of the accumulator, and the height of the liquid level with respect to a change in the amount of liquid refrigerant in the accumulator by the accumulator throttle portion It amplifies the change, with the refrigerant within the accumulator and configured to be introduced into the compressor, on the basis of the discharge refrigerant temperature of the compressor Rise It is constituted to adjust the degree of opening of the valve.

  As a result, the amount of liquid return greatly changes with respect to a slight change in the liquid level of the liquid refrigerant accumulated in the accumulator, and the wetness of the refrigerant sucked into the compressor can be greatly changed. In addition, since the space around the plurality of small holes arranged in the accumulator is narrowed down, the liquid level of the liquid refrigerant can be greatly changed with respect to a slight change in the amount of liquid refrigerant accumulated. it can. As a result, the wetness of the refrigerant sucked into the compressor can be greatly changed more effectively.

The air conditioner of the present invention can greatly change the wetness of the refrigerant sucked into the compressor just by accumulating a small amount of liquid refrigerant in the accumulator. Even if a refrigerant with a small global warming potential is used, the cost can be reduced. An increase in the discharge temperature of the compressor can be prevented without causing an increase or a decrease in performance, and a refrigeration cycle apparatus having high reliability and a small environmental load can be provided.

The block diagram of the air conditioner to which the refrigeration cycle apparatus in Embodiment 1 of this invention is applied.

A first invention is a refrigeration cycle device in which a refrigerant circulates through a compressor, a condenser , an expansion valve, an evaporator, and an accumulator, wherein the accumulator is disposed immediately before a refrigerant suction port of the compressor, and the accumulator is an opening provided in the upper portion, and a plurality of different small holes height position in the vertical direction is provided in the lower part, a refrigerant outlet pipe provided in the accumulator, is provided around the plurality of small holes, An accumulator throttle portion having a diameter that is narrower than the outer diameter of the accumulator, wherein the accumulator throttle portion amplifies a change in liquid level with respect to a change in the amount of liquid refrigerant in the accumulator, and the accumulator And a configuration in which the opening of the expansion valve is adjusted based on the refrigerant discharge temperature of the compressor. And Aru.

Thereby, the liquid return amount can be greatly changed with respect to a slight change in the liquid level of the liquid refrigerant accumulated in the accumulator, and the wetness of the refrigerant sucked into the compressor can be greatly changed. Therefore, even with a small refrigerant global warming coefficient, prevents a rise in discharge temperature of the compressor without lowering the growth and performance of the cost, Ru can provide a device having a high reliability.

According to a second invention, in the first invention, the refrigerant discharge temperature of the compressor is configured to control the expansion valve so as not to exceed a predetermined upper limit value, and while preventing an increase in the temperature of the compressor, Under the condition that the discharge temperature is equal to or lower than the upper limit value, it is possible to operate with the optimum performance at the optimum discharge temperature. Therefore, it is possible to ensure both reliability and operation with optimum performance.

According to a third invention, in the first and second inventions, the refrigerant uses a refrigerant having a warming coefficient of at least 750 or less, and the compressor does not cause an increase in cost or a decrease in performance. Therefore, it can be used with high reliability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a configuration diagram of an air conditioner to which a refrigeration cycle apparatus according to an embodiment of the present invention is applied.

  As shown in FIG. 1, this air conditioner is configured by connecting an outdoor unit 100 and an indoor unit 101 with connection pipes, that is, a liquid side connection pipe 126 and a gas side connection pipe 127, and performs heating / cooling operation. Do. As the refrigerant, a low-warming refrigerant having a smaller warming coefficient than R22 or R410A and having a warming coefficient of 5 or more and 750 or less, preferably 350 or less is used. For example, there is a single refrigerant such as HFC-32 (R32), HFC-152a, HFO-1234yf, HFO-1234ze, or the like as a main component, and a mixed refrigerant in which two components are mixed or three components are mixed. In the embodiment, R32 is used as an example.

  The indoor unit 101 includes an indoor blower 116, an indoor heat exchanger 115, and an indoor heat exchanger temperature sensor 124 that detects the evaporation temperature of the refrigerant in the indoor heat exchanger 115.

  The outdoor unit 100 includes a compressor 111, an outdoor heat exchanger 112 that is a condenser, an outdoor blower 113, an expansion valve 114 that decompresses and expands the refrigerant, an accumulator 117, and a discharge that detects the temperature of the refrigerant discharged from the compressor 111. Ideal discharge from the outputs of the temperature sensor 122, the outdoor heat exchanger temperature sensor 123, which is a condensation temperature sensor for detecting the condensation temperature in the outdoor heat exchanger 112, and the outdoor heat exchanger temperature sensor 123 and the indoor heat exchanger temperature sensor 124. And a control device 125 that calculates the temperature and adjusts the opening degree of the expansion valve 114 according to the difference from the discharge temperature sensor 122.

  The accumulator 117 has a refrigerant outlet pipe 118 provided with a plurality of small holes 119 positioned at different heights in the vertical direction. The refrigerant outlet pipe 118 opens at the upper part of the accumulator 117 and is drawn out from the lower part to introduce the refrigerant into the compressor 111. .

  Further, the accumulator 117 is configured such that the periphery of the lower small hole 119 is narrowed as shown by the accumulator restricting portion 117S, and the space around the small hole 119 is reduced so that a head difference is generated with a small amount when the liquid refrigerant is accumulated. Has been.

  The compressor 111 is a hermetic rotary compressor, and a rotating piston is rotated by a DC brushless motor driven by an inverter at an arbitrary number of rotations to compress the refrigerant. The refrigerant sucked into the compressor 111 from the refrigerant outlet pipe 118 is compressed by the compressor 111, sent out into the sealed shell of the compressor 111, and discharged after cooling the motor unit.

  Accordingly, the discharge temperature of the compressor 111 is substantially equal to the maximum temperature of the refrigerant, and the temperature inside the compressor can be estimated by looking at the output of the discharge temperature sensor 122.

  When the internal temperature of the compressor 111 rises, problems such as deterioration of the resin material and refrigerating machine oil and demagnetization of the magnetic body constituting the motor rotor arise.

  The upper limit of the discharge temperature is determined by the material being used. For example, if the insulating material used for the winding of the motor is type E, the allowable temperature is 120 ° C., and it is desirable to keep the discharge temperature below 110 ° C. become.

  On the other hand, due to the physical properties of R32 used as a refrigerant, there is a characteristic that the discharge temperature rises compared to R22 and R410A.

  For example, assuming that ideal adiabatic compression is performed from a state where the saturation temperature of suction of the compressor is 10 ° C. and the degree of heating is 5K and the state is compressed to a state where the saturation temperature is 45 ° C., the discharge temperatures of R22 and R410A are about 65. And R32 is about 76 ° C.

  Actually, as a result of the drop-in test, in the operation for obtaining the same cooling capacity, the discharge temperature of R32 was about 10 ° C. higher than the discharge temperature of R410A.

  Therefore, since the discharge temperature rises more easily in the apparatus using R32 than in the apparatus using R410A, a technique for lowering the discharge temperature is necessary to ensure reliability.

  As described in the prior art, it is known that the discharge temperature can be lowered by opening the expansion valve 114 or lowering the rotational speed of the compressor 111. However, if the rotation speed of the compressor 111 is lowered, the capacity of the air conditioner is lowered.

Further, in the conventional method of opening the expansion valve, the accumulator basically has a structure for accumulating liquid refrigerant, and the liquid refrigerant return port has only one small hole in the lower part of the refrigerant outlet pipe, and refrigerant is used to lower the discharge temperature. In order to obtain a wet state, it is necessary to accumulate a large amount of liquid refrigerant and increase the head difference. However, this causes a shortage of refrigerant in the cycle, resulting in a reduction in capacity.

  Further, in the prior art, there is also known a technique for reducing the discharge temperature by configuring an injection cycle or by providing a bypass provided with an adjustment valve to the accumulator immediately before or immediately after the expansion valve to return the liquid refrigerant. The cost of the device increases.

  Therefore, in the air conditioner shown in the first embodiment, the refrigerant outlet pipe 118 of the accumulator 117 is provided with a plurality of small holes 119 at different heights in the vertical direction, and the liquid level of the liquid refrigerant in the accumulator 117 rises. Since the liquid return amount increases, the liquid refrigerant accumulation amount can be reduced. As a result, it is possible to prevent performance degradation caused by accumulating liquid refrigerant.

  On the other hand, when the discharge temperature deviates from the optimum value, the performance decreases. Therefore, if the diameter of the small hole is increased and the liquid return amount is increased, the variation in the wetness of the refrigerant flowing into the accumulator will affect the discharge temperature, so it is necessary to set the average value of the discharge temperature lower. In this respect, it is desirable to adjust the liquid return by providing a plurality of small holes 119 at different heights in the vertical direction because the performance is deteriorated.

  Furthermore, the accumulator 117 shown in the first embodiment is narrowed so that the periphery of the lower small hole 119 is indicated by the accumulator restricting portion 117S, and the space around the small hole 119 is reduced so that a small amount of head can be obtained when liquid refrigerant is accumulated. Since the difference is configured, the liquid refrigerant accumulation amount for adjusting the liquid return amount can be minimized, and the performance degradation can be minimized.

  Furthermore, if the optimum discharge temperature calculated by the control device 125 from the outputs of the outdoor heat exchange temperature sensor 123 and the indoor heat exchange temperature sensor 124 is equal to or lower than the upper limit temperature (eg, 110 ° C.), the optimum discharge temperature is set as the target value. If the opening degree of the expansion valve 114 is adjusted and exceeds the upper limit temperature, the opening degree of the expansion valve 114 is adjusted with the upper limit temperature as a target value. Thereby, the best performance can be realized while ensuring reliability.

  As described above, the air conditioner of the first embodiment uses R32 having a small warming coefficient with high reliability while suppressing an increase in the temperature of the compressor without causing an increase in cost or a decrease in performance. An apparatus with a small environmental load can be provided.

  In the first embodiment, an air conditioner that performs cooling has been described. However, the present invention is also effective in a device that performs heating or cooling and heating. In this case, the indoor heat exchanger and the outdoor heat exchanger are replaced with a condenser and an evaporator by heating and cooling.

  In addition, the basic shape of the refrigerant outlet pipe 118 in FIG. 1 is a straight pipe, but even if it is a U-shaped pipe shape, the same effect can be obtained if small holes are provided at different heights in the vertical direction.

  As described above, the present invention is an environmental load that can be used with high reliability by suppressing a rise in the temperature of the compressor without incurring an increase in cost and a decrease in performance without causing a refrigerant with a small warming potential. A small device can be provided, and it is effective not only for an air conditioner but also for a separate type showcase or a refrigerator.

DESCRIPTION OF SYMBOLS 100 Outdoor unit 101 Indoor unit 111 Compressor 112 Outdoor heat exchanger 113 Outdoor blower 114 Expansion valve 115 Indoor heat exchanger 116 Indoor blower 117 Accumulator 117S Accumulator throttle part 118 Refrigerant outlet pipe 119 Small hole 122 Discharge temperature sensor 123 Outdoor heat exchanger temperature sensor 124 indoor heat exchange temperature sensor 125 control device 126 liquid side connection pipe 127 gas side connection pipe

Claims (3)

A refrigeration cycle device in which a refrigerant circulates through a compressor, a condenser , an expansion valve, an evaporator, and an accumulator, wherein the accumulator is disposed immediately before a refrigerant suction port of the compressor, and the accumulator is provided at an upper portion An opening and a plurality of small holes provided at a lower portion and having different height positions in the vertical direction; a refrigerant outlet pipe provided in the accumulator; and provided around the plurality of small holes; from an outer diameter of the accumulator An accumulator throttle portion having a small throttle diameter, and the accumulator throttle portion amplifies a change in height of the liquid level with respect to a change in the amount of liquid refrigerant in the accumulator, and the liquid refrigerant in the accumulator is The cooling valve is configured to be introduced into a compressor, and the opening degree of the expansion valve is adjusted based on a refrigerant discharge temperature of the compressor. Cycle device. The refrigeration cycle apparatus according to claim 1, wherein the expansion valve is controlled so that a refrigerant discharge temperature of the compressor does not exceed a predetermined upper limit value. The refrigeration cycle apparatus according to claim 1 or 2 , wherein the refrigerant has a warming coefficient of at least 750 or less.