JP2005241169A - Refrigerant circuit of air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerant circuit of an air conditioner which can be stably operated at a low manufacturing cost. <P>SOLUTION: In the refrigerant circuit of the air conditioner in which a compressor 2, condenser 3 (or 5), an expansion valve 7b (or 7a) and an evaporator 5 (or 3) are sequentially connected by a refrigerant flow passage, a flow passage L for bypassing a space B between the evaporator 5 and the compressor 2 and a space A between the condenser 3 and the expansion valve 7b are provided and an electromagnetic opening/closing valve 10 and a capillary tube 9 are provided at the bypassing flow passage L with the capillary tube 9 on the B side and the electromagnetic opening/closing valve 10 on the A side. A pressure sensor 11 is provided between the electromagnetic opening/closing valve 10 and the capillary tube 9 and "fixed evaporating pressure control" is conducted during cooling operation and "fixed condensing pressure control" is conducted during heating operation by work control of the electromagnetic opening/closing valve 10. In addition, in the case that temperature of discharging refrigerant from the compressor 2 abnormally rises, liquid refrigerant is introduced to the compressor 2 through the bypassing flow passage for cooling down the compressor 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a refrigerant circuit of an air conditioner capable of stable operation.

  FIG. 4 is a schematic configuration diagram of a refrigerant circuit of a conventional vapor compression air conditioner used for indoor air conditioning. Below, the refrigerating cycle of this refrigerant circuit is demonstrated.

  The refrigerant circuit includes a four-way valve 21 that controls the refrigerant flow in the refrigerant circuit during cooling and heating, a compressor 22, and an indoor heat exchanger 23 that functions as an evaporator during cooling and as a condenser during heating. The indoor fan 24 for sending wind to the indoor heat exchanger 23, the outdoor heat exchanger 25 acting as a condenser during cooling and as an evaporator during heating, and sending the wind into the outdoor heat exchanger 25 The outdoor fan 26, an expansion valve 27a that acts as an expansion valve during cooling and is fully opened during heating and becomes part of the piping, and an expansion valve that is fully opened during cooling and becomes part of the piping and acts as an expansion valve during heating. 27b, an accumulator 28, and piping connecting them.

  For the purpose of stable operation of the refrigerant circuit, the heat exchangers 23 and 25 are provided with thermistor temperature detectors 29a and 29b, and the condensation pressure or the evaporation pressure is detected by detecting the condensation temperature or the evaporation temperature. By presuming, the rotation speed of the compressor 22 and the fans 24 and 26 are controlled.

  During cooling, the four-way valve 21 is set to a solid line state, whereby the refrigerant discharged from the compressor 22 flows from the outdoor heat exchanger 25 to the indoor heat exchanger 23 as indicated by a solid line arrow. On the other hand, during heating, the four-way valve 21 is set in a broken line state so that the refrigerant discharged from the compressor 22 flows in the opposite direction to that during cooling, as indicated by a broken line arrow.

  Next, the state change of the refrigerant in the refrigeration cycle will be described with reference to the Mollier diagram shown in FIG. In FIG. 5, the vertical axis represents pressure and the horizontal axis represents enthalpy. In the figure, x is a curve indicating the boundary between the gas phase state, the liquid phase state and the gas-liquid two-phase state of the refrigerant, the vertex y indicates the critical point, and the curve portion on the right side of this indicates the saturated vapor line. The curve portion on the left shows a saturated liquid line, and the inside thereof shows gas-liquid two-phase wet steam in which a gas-phase refrigerant and a liquid-phase refrigerant are mixed. The right side of the saturated vapor line is a superheated steam region, and the left side of the saturated liquid line is a supercooled liquid region.

  In the wet steam range, the temperature is constant when the pressure is constant, and there is a one-to-one correspondence. This relationship is the basis of a method of measuring the temperature, which will be described in detail in the embodiments of the invention, to indirectly know the pressure, that is, a method of indirectly measuring the pressure.

  Between a and b in the figure, the refrigerant is compressed by the compressor 22 to become high-temperature and high-pressure superheated steam. Moreover, between bc in a figure, a refrigerant | coolant is condensed in the condenser 23 (at the time of heating) or 25 (at the time of air_conditioning | cooling), and becomes a supercooled liquid state from a superheated steam state through a two-phase state. . And between cd in a figure, a refrigerant | coolant is pressure-reduced by the expansion valve 27a (at the time of cooling) or 27b (at the time of heating), and is a low-temperature low-pressure gas-liquid two-phase state (mixed state of a liquid refrigerant and a gas refrigerant) ) Is a two-phase refrigerant with a high wetness. Between da in the figure, the wet refrigerant evaporates by removing heat from the surroundings in the evaporator 25 (during heating) or 23 (during cooling), and the wetness decreases (dryness increases). It becomes superheated superheated steam. Then, the refrigerant that has become superheated steam is sent again into the compressor 22 via the accumulator 28.

  Actually, as described above, the refrigerant returned from the evaporator 25 (during heating) or 23 (during cooling) may not be superheated steam as described above, and may be partially in the liquid state. Therefore, in order to prevent the liquid refrigerant from returning to the compressor 22 and damaging the compressor 22, the gas refrigerant is separated by the accumulator 28 and only the gas refrigerant is supplied to the compressor 22.

  The refrigerant flowing through the heat exchanger changes from a gas refrigerant to a gas-liquid two-phase state and a liquid refrigerant, or conversely changes from a liquid refrigerant to a gas-liquid two-phase state and a gas refrigerant. The thermistor temperature detector 29a is provided in the bend of the outdoor heat exchanger 25, particularly in the bend corresponding to the location where the refrigerant is in a gas-liquid two-phase state. The thermistor temperature detector 29b is provided on the bend of the indoor heat exchanger 23, particularly on the bend corresponding to the location where the refrigerant is in a gas-liquid two-phase state.

  During the cooling operation, the outdoor heat exchanger 25 functions as a condenser, and the indoor heat exchanger 23 functions as an evaporator. Therefore, the thermistor temperature detector 29a detects the condensation temperature, and the thermistor temperature detector 29b detects the evaporation temperature. . It is relatively stable by performing indirect measurement of the condensation pressure and evaporation pressure from each detected temperature and maintaining the refrigerant evaporation pressure at a predetermined constant pressure to ensure stable cooling capacity, that is, "evaporation pressure constant control". Has been realized. The reason why the pressure can be indirectly measured through the temperature is clear from the description of the Mollier diagram.

  Further, during the heating operation, the indoor heat exchanger 23 functions as a condenser, and the outdoor heat exchanger 25 functions as an evaporator. Therefore, the thermistor temperature detector 29b indicates the condensation temperature, and the thermistor temperature detector 29a indicates the evaporation temperature. To detect. Indirect measurement of condensing pressure and evaporating pressure from each detected temperature, and control to maintain stable heating capacity by maintaining the condensing pressure of the refrigerant at a predetermined constant pressure, that is, "Condensing pressure constant control", is relatively stable Has been realized.

  As described above, it is indispensable to know the refrigerant pressure during operation in order to realize the operational control requirements of the air conditioner. That is, the refrigerant pressure on the suction side of the compressor 22 (hereinafter referred to as “low pressure”) during the cooling operation, and the refrigerant pressure on the discharge side of the compressor 22 (hereinafter referred to as “high pressure”) during the heating operation. Necessary.

JP 2002-350004 A

  However, in the conventional method of indirectly measuring the refrigerant pressure using the thermistor temperature detector, it is difficult to control the transient state because the response of the thermistor temperature detector is slow with respect to the start of operation of the apparatus and the load fluctuation of the compressor. there were.

  Further, in the pressure indirect measurement method using the thermistor temperature detector, the refrigerant is installed in the heat exchanger where the refrigerant is assumed to be in the gas-liquid two-phase state, but in the portion that forms the gas-liquid two-phase state depending on the operating state. When the position of the gas-liquid two-phase state fluctuates and deviates from the installation location of the thermistor temperature detector, there is instability that it is difficult to accurately indirectly measure the refrigerant pressure.

  In addition, even if the refrigerant pressure is indirectly measured from the condensation temperature or evaporation temperature in the heat exchanger, pressure loss may occur depending on the layout of the pipes that make up the refrigerant circuit, and the actual low and high pressure values before and after the compressor May be different.

  On the other hand, a method of directly detecting low pressure and high pressure by installing pressure sensors in the pipes before and after the compressor is also conceivable, but in this case, two relatively expensive pressure sensors are required. Therefore, there has been a problem of incurring a cost increase.

  The present invention has been made in view of the above situation, and an object thereof is to provide a refrigerant circuit of an air conditioner capable of stably controlling operation by measuring a low pressure and a high pressure while suppressing manufacturing costs. To do.

The refrigerant circuit of the air conditioner according to the present invention for solving the above problems is as follows.
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
The bypass channel has an on-off valve and a pressure reducing means, the pressure reducing means is on the suction pipe side between the evaporator and the compressor, and the on-off valve is a liquid between the condenser and the expansion valve. A refrigerant circuit for an air conditioner, wherein the refrigerant circuit is provided so as to be positioned on the pipe side, and a pressure sensor is further disposed between the on-off valve and the pressure reducing means.

The refrigerant circuit of another air conditioner according to the present invention that solves the above problems is as follows.
In the refrigerant circuit of the air conditioner,
The bypass flow path is further provided with temperature detection means on the suction pipe side between the evaporator and the compressor than the decompression means,
An air conditioner refrigerant circuit having a function of indirectly measuring and controlling an evaporation pressure based on a refrigerant temperature detected by the temperature detecting means.

The refrigerant circuit of another conditioner according to the present invention that solves the above problems is as follows.
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. A refrigerant circuit for an air conditioner, wherein the refrigerant circuit is provided so as to be positioned on the pipe side, and a pressure sensor is further disposed between the on-off valve and the pressure reducing means.

The refrigerant circuit of another air conditioner according to the present invention that solves the above problems is as follows.
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the bottom of the liquid receiver provided between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. Provided on the pipe side so as to be located respectively, and further arranged a pressure sensor between the on-off valve and the pressure reducing means,
A refrigerant circuit for an air conditioner, characterized in that a temperature detection means is provided at the bottom of the liquid receiver, and the condensation pressure is indirectly measured and controlled based on the refrigerant temperature detected by the temperature detection means. is there.

According to the refrigerant circuit of the air conditioner according to the present invention,
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
The bypass channel has an on-off valve and a pressure reducing means, the pressure reducing means is on the suction pipe side between the evaporator and the compressor, and the on-off valve is a liquid between the condenser and the expansion valve. Since it is provided so as to be located on the pipe side, and a pressure sensor is further arranged between the on-off valve and the pressure reducing means,
In the cooling operation, the refrigerant evaporating pressure can be maintained at a predetermined constant pressure to perform stable control, that is, "evaporation pressure constant control" can be performed. In the heating operation, the refrigerant condensing pressure is set to a predetermined value. Control that maintains a constant pressure and secures stable heating capability, that is, "condensation pressure constant control" can be performed. In addition, when the temperature of refrigerant discharged from the compressor rises abnormally, liquid refrigerant is introduced into the compressor through the bypass channel by opening the on-off valve regardless of the cooling operation and heating operation. This can be cooled. That is, since the high pressure can be measured when the on-off valve is in the open state and the low pressure can be measured when the on-off valve is in the closed state, the pressure sensor can be reduced because high pressure and low pressure can be measured with one pressure sensor. Thereby, it can manufacture at low cost.

According to the refrigerant circuit of another air conditioner according to the present invention,
In the refrigerant circuit of the air conditioner,
The bypass flow path is further provided with temperature detection means on the suction pipe side between the evaporator and the compressor than the decompression means,
Since it has a function of indirectly measuring and controlling the evaporation pressure based on the refrigerant temperature detected by the temperature detection means,
In addition to the above effects, even when it is necessary to detect the high pressure with the on-off valve opened, or when it is necessary to cool the liquid refrigerant by introducing it into the compressor, Control using low pressure can be performed, and a refrigerant circuit of an air conditioner capable of more stable operation control can be obtained.

According to the refrigerant circuit of another air conditioner according to the present invention,
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. Since it is provided so as to be located on the pipe side, and a pressure sensor is further arranged between the on-off valve and the pressure reducing means,
In the cooling operation, the refrigerant evaporating pressure can be maintained at a predetermined constant pressure to perform stable control, that is, "evaporation pressure constant control" can be performed. In the heating operation, the refrigerant condensing pressure is set to a predetermined value. Control that maintains a constant pressure and secures stable heating capability, that is, "condensation pressure constant control" can be performed. In addition, when the temperature of refrigerant discharged from the compressor rises abnormally, liquid refrigerant is introduced into the compressor through the bypass channel by opening the on-off valve regardless of the cooling operation and heating operation. This can be cooled. Moreover, since many pressure sensors are not required, it can manufacture at low cost.

According to the refrigerant circuit of another air conditioner according to the present invention,
In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the bottom of the liquid receiver provided between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. Provided on the pipe side so as to be located respectively, and further arranged a pressure sensor between the on-off valve and the pressure reducing means,
Since the temperature detection means is provided at the bottom of the liquid receiver, and it has the function of indirectly measuring and controlling the condensation pressure based on the refrigerant temperature detected by the temperature detection means,
In addition to the above effects, even when it is necessary to detect the low pressure with the open / close valve opened, or when it is necessary to cool the liquid refrigerant by introducing it into the compressor, Control using high pressure can be performed, and a refrigerant circuit of an air conditioner capable of more stable operation control can be provided.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of a refrigerant circuit of the air conditioner according to the first embodiment. Below, the refrigerating cycle of this refrigerant circuit is demonstrated.

  The refrigerant circuit includes a four-way valve 1 that controls the refrigerant flow in the refrigerant circuit during cooling and heating, a compressor 2, and an indoor heat exchanger 3 that functions as an evaporator during cooling and as a condenser during heating. The indoor fan 4 for sending wind to the indoor heat exchanger 3, the outdoor heat exchanger 5 acting as a condenser during cooling and acting as an evaporator during heating, and sending the wind into the outdoor heat exchanger 5 The outdoor fan 6, an expansion valve 7a that acts as an expansion valve during cooling and is fully opened during heating and becomes part of the piping, and an expansion valve that is fully opened during cooling and becomes part of the piping and acts as an expansion valve during heating 7b, accumulator 8, piping connecting them, and the liquid pipe side between the condenser and the expansion valve (between 5 and 7a during cooling and between 3 and 7b during heating) A and compressor (Specifically between the compressor 2 and the accumulator 8) of the suction pipe side B consists of a flow path L to bypass the.

  In a flow path L that bypasses the liquid pipe side A between the condenser and the expansion valve and the suction pipe side B between the compressor 2 and the accumulator 8, an electromagnetic on-off valve 10 and a capillary having a predetermined passage resistance are provided. A tube 9 (pressure reducing means) is provided so that the electromagnetic opening / closing valve 10 is located on the A side and the capillary tube 9 is located on the B side. Further, a pressure sensor is provided between the electromagnetic opening / closing valve 10 and the capillary tube 9. 11 is interposed.

  In this case, when the on-off valve is in the “open state”, the liquid refrigerant flows to the suction side through the capillary tube 9 that is a throttling element, but pressure loss occurs predominantly in the capillary tube 9, so that a high pressure is measured. . On the other hand, when the on-off valve is in the “closed state”, the capillary tube 9 serving as the throttle element acts as a communication pipe, and thus the low pressure is measured.

  At the time of cooling, the refrigerant discharged from the compressor 2 flows as indicated by solid line arrows by setting the four-way valve 1 to the solid line state. On the other hand, at the time of heating, the refrigerant discharged from the compressor 2 flows as indicated by broken line arrows by setting the four-way valve 1 to the broken line state.

  About the state change of the refrigerant | coolant in a refrigerating cycle, it is the same as that of the past, and if it demonstrates with reference to FIG.1 and FIG.5, between a and ab in a figure, a refrigerant | coolant is compressed by the compressor 2, and it is high temperature. High pressure superheated steam. Moreover, between bc in a figure, a refrigerant | coolant is condensed in the condenser 3 (at the time of heating) or 5 (at the time of air_conditioning | cooling), and becomes a supercooled liquid state from a superheated steam state. And between cd in a figure, a refrigerant | coolant is pressure-reduced with the expansion valve 7a (at the time of cooling) or 7b (at the time of heating), and is a low-temperature low-pressure gas-liquid two-phase state (mixed state of a liquid refrigerant and a gas refrigerant) ). Between da in the figure, the refrigerant in the two-phase state evaporates by taking heat away from the surroundings in the evaporator 5 (during heating) or 3 (during cooling), and gradually increases its dryness and overheats moderately. It becomes steam. Then, the refrigerant that has become superheated steam is sent again into the compressor 2 via the accumulator 8.

  Here, in the present embodiment, a flow path L that bypasses the liquid pipe side A between the condenser and the expansion valve and the suction pipe side B of the compressor 2 is provided. By setting the operation mode of the electromagnetic on-off valve 10 in the flow path L as described below, stable operation control is realized in the cooling operation and the heating operation.

  That is, the electromagnetic on-off valve 10 is kept in the closed state during the cooling operation, and is temporarily opened at a predetermined timing with the closed state being the normal state during the heating operation. Furthermore, regardless of the cooling operation and the heating operation, when the load state of the refrigerant circuit changes and the temperature of the refrigerant discharged from the compressor 2 rises abnormally, the electromagnetic on-off valve 10 is held in the open state. .

  As described above, in the cooling operation, it is necessary to know the low-pressure pressure in order to perform a control for maintaining a stable cooling capacity by maintaining the evaporation pressure of the refrigerant at a predetermined constant pressure, that is, “evaporation pressure constant control”. By holding the electromagnetic on-off valve 10 in a closed state, the low pressure pressure of the refrigerant sucked into the compressor 2 acts on the pressure sensor 11 in the flow path L via the capillary tube 9, and the pressure sensor 11 A low pressure is detected. By performing the rotational speed control of the compressor 2 based on the detected low pressure, “evaporation pressure constant control” for making the evaporation pressure of the refrigerant in the indoor heat exchanger 3 constant is realized, and the indoor heat exchanger 3 is stable, and a stable cooling operation is realized.

  Further, as described above, in the heating operation, it is necessary to know the high-pressure pressure in order to perform control for maintaining stable heating capacity by maintaining the refrigerant condensing pressure at a predetermined constant pressure, that is, “constant condensing pressure control”. Become. By temporarily opening the electromagnetic on-off valve 10 at a predetermined timing, the refrigerant discharged from the compressor 2 is introduced into the pressure sensor 11 in the flow path L from the A, and the capillary tube 9 Since the passage resistance is applied, a high pressure is applied, and the high pressure of the refrigerant is detected by the pressure sensor 11.

  The reason why the high pressure can be detected by sampling the refrigerant in A is that the refrigerant passing through A flows before the pressure is reduced in the expansion valve 7b, and the pressure drop is caused exclusively in the capillary tube 9 which is a throttle element. This is because the pressure discharged from the compressor 2 can be detected. In addition, the reason why the electromagnetic on-off valve 10 is not always opened in the heating operation is that the A side is in a higher pressure state than the B side, so that the high pressure refrigerant is introduced more than necessary into the suction side B of the compressor 2. This causes a loss of capacity, and is to suppress this.

  By performing the rotational speed control of the compressor 2 based on the high pressure detected by the pressure sensor 11, “constant condensation pressure constant control” that makes the condensation pressure of the refrigerant in the indoor heat exchanger 3 constant is realized. The condensation action in the heat exchanger 3 is stabilized, and a stable heating operation is realized.

  Basically, the above-described opening / closing control is performed on the electromagnetic opening / closing valve 10 according to the cooling operation and the heating operation. However, the load state of the refrigerant circuit changes and the temperature of the refrigerant discharged from the compressor 2 abnormally increases. In this case, the electromagnetic on-off valve 10 is held in the open state regardless of the cooling operation and the heating operation. Since the A side is at a higher pressure than the B side, the A-side liquid refrigerant is introduced into the compressor 2 through the flow path L to cool it by opening the electromagnetic on-off valve 10. Can do.

  The basic control for stable operation is “evaporation pressure constant control” in cooling operation and “condensation pressure constant control” in heating operation, but the high pressure is detected in the cooling operation, and the condensation pressure is determined based on this. If it is possible to control or detect the low pressure in the heating operation and control the evaporation pressure based on this, it is possible to realize a more stable operation.

  Therefore, the high pressure may be detected by temporarily opening the electromagnetic on-off valve 10 in a closed state during the cooling operation instead of holding the electromagnetic on-off valve 10 at a predetermined timing. However, since the “evaporation pressure constant control” is controlled by the rotation speed of the compressor 2 as described above, the rotation speed of the outdoor fan 6 is controlled when the condensation pressure is controlled based on the detected high pressure. Thus, the condensation efficiency of the outdoor heat exchanger 5 is changed.

  Further, during the heating operation, the low pressure pressure may be detected at a time other than the timing when the electromagnetic on-off valve 10 is opened, and the evaporation pressure may be controlled based on the low pressure. However, since the “condensation pressure constant control” is controlled by the rotation speed of the compressor 2 as described above, the rotation speed of the outdoor fan 6 is controlled when the evaporation pressure is controlled based on the detected low pressure. By doing this, the evaporation efficiency of the outdoor heat exchanger 5 is changed.

  The refrigerant pressure can be controlled by changing the rotation speed of the compressor 2 or the rotation speed of the outdoor fan 6, but the pressure control can be performed more directly by controlling the rotation speed of the compressor 2. Therefore, the compressor 2 may be used mainly to control the pressure to be controlled depending on the operating state, and the outdoor fan 6 may be used to control the pressure to be controlled as a slave.

<Second Embodiment>
FIG. 2 is a schematic configuration diagram of a refrigerant circuit of the air conditioner according to the second embodiment. Below, the refrigerating cycle of this refrigerant circuit is demonstrated. In addition, since the refrigerant circuit of the air conditioner which concerns on this embodiment is based on 1st Embodiment, the same code | symbol is attached | subjected to the member which has the same function, and the overlapping description is abbreviate | omitted.

  In the present embodiment, a thermistor 12 serving as a temperature detecting means is provided on the B side of the capillary tube 9 in the flow path L that bypasses A between the condenser and the expansion valve and B between the compressor 2 and the accumulator 8. It is installed.

  As described in the first embodiment, the pressure sensor 11 has a function capable of detecting both a low pressure and a high pressure by opening and closing the electromagnetic on-off valve 10. However, this means that when one pressure is detected, the other pressure cannot be detected. When it is desired to detect both pressures for a certain period of time, the electromagnetic on-off valve 10 It is required to open and close frequently.

  On the other hand, in this embodiment, the temperature after being squeezed and expanded by the capillary tube 9 by the thermistor 12 is measured, and the evaporation pressure is indirectly measured by the temperature. In the capillary tube 9, as shown in FIG. 5, Hd is constant and expands to the evaporation pressure. Therefore, in the state before mixing with the gas refrigerant exiting the evaporator, the saturation temperature shown at point d in FIG. 5 can be detected. Thereby, the evaporation pressure can be indirectly detected and used as a control signal. As a result, the low pressure can be indirectly measured. The method for controlling the evaporation pressure using the indirectly measured low pressure is as described above.

  That is, in this embodiment, even when the electromagnetic on-off valve 10 is in the open state and it is necessary to detect a high pressure or when it is necessary to cool the liquid refrigerant by introducing it into the compressor 2. At the same time, it is possible to provide a refrigerant circuit of an air conditioner that can perform control using low-pressure and can perform more stable operation control.

<Third Embodiment>
FIG. 3 is a schematic configuration diagram of a refrigerant circuit of an air conditioner according to the third embodiment. Below, the refrigerating cycle of this refrigerant circuit is demonstrated. In addition, since the refrigerant circuit of the air conditioner which concerns on this embodiment is based on 1st Embodiment, the same code | symbol is attached | subjected to the member which has the same function, and the overlapping description is abbreviate | omitted.

  In the present embodiment, a flow path L that bypasses A between the condenser and the expansion valve and B between the compressor 2 and the accumulator 8 is provided. The capillary tube 15 (pressure reducing means) having the passage resistance is provided so that the capillary tube 15 is located on the A side and the electromagnetic opening / closing valve 16 is located on the B side. A pressure sensor 17 is interposed therebetween. Further, in the flow path L, a thermistor 18 as a temperature detecting means is installed on the A side of the capillary tube 15.

  In this embodiment, since the electromagnetic on-off valve 16 is closed, the refrigerant discharged from the compressor 2 is introduced from the A through the capillary tube 15 into the pressure sensor 17 in the flow path L. The high pressure acts, and the high pressure of the refrigerant is detected by the pressure sensor 17. On the other hand, by opening the electromagnetic opening / closing valve 16, low pressure refrigerant sucked into the compressor 2 is introduced from the B into the pressure sensor 17 in the flow path L, and a predetermined passage resistance is given by the capillary tube 15. Therefore, the low pressure acts, and the low pressure of the refrigerant is detected by the pressure sensor 17.

  “Condensation pressure constant control” that makes the condensation pressure of the refrigerant in the indoor heat exchanger 3 constant by performing the rotational speed control of the compressor 2 based on the high pressure or the low pressure detected as described above. Or "evaporation pressure constant control" which makes the evaporation pressure of the refrigerant in the indoor heat exchanger 3 constant is realized, and a stable cooling operation or heating operation is realized. This control method is as described above. Further, by opening the electromagnetic on-off valve 17, the liquid refrigerant can be introduced into the compressor 2 to cool it.

  Further, as described, if a liquid receiver (receiver) 30 is provided for the refrigerant circuit shown in FIG. 3, a bypass pipe is provided from the bottom, and the temperature at the bottom is measured (see FIG. 4). The thermistor 18 detects a saturation temperature corresponding to the condensation pressure. As a result, the high pressure can be indirectly measured. The method for controlling the condensation pressure using the indirectly measured high pressure is as described above.

  That is, in the present embodiment, even when the electromagnetic on-off valve 16 is in the open state and it is necessary to detect the low pressure or when it is necessary to cool the liquid refrigerant by introducing it into the compressor 2. At the same time, it is possible to provide a refrigerant circuit for an air conditioner that can perform control using high pressure and can perform more stable operation control.

It is a schematic block diagram of the refrigerant circuit of the air conditioner which concerns on 1st Embodiment. It is a schematic block diagram of the refrigerant circuit of the air conditioner which concerns on 2nd Embodiment. It is a schematic block diagram of the refrigerant circuit of the air conditioner which concerns on 3rd Embodiment. It is a schematic block diagram of the refrigerant circuit of the air conditioner which concerns on the modification of 3rd Embodiment. It is a schematic block diagram of the refrigerant circuit of the conventional vapor compression type air conditioner. It is a Mollier diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Four-way valve 2 Compressor 3 Indoor heat exchanger 4 Indoor fan 5 Outdoor heat exchanger 6 Outdoor fan 7a, 7b Expansion valve 8 Accumulator 9, 15 Capillary tube 10, 16 Electromagnetic on-off valve 11, 17 Pressure sensor 12, 18 Thermistor

21 Four-way valve 22 Compressor 23 Indoor heat exchanger 24 Indoor fan 25 Outdoor heat exchanger 26 Outdoor fan
27a, 27b Expansion valve 28 Accumulator
29a, 29b Thermistor temperature detector 30 Receiver

Claims (4)

In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
The bypass channel has an on-off valve and a pressure reducing means, the pressure reducing means is on the suction pipe side between the evaporator and the compressor, and the on-off valve is a liquid between the condenser and the expansion valve. A refrigerant circuit for an air conditioner, wherein the refrigerant circuit is provided on a pipe side so as to be positioned, and a pressure sensor is further disposed between the on-off valve and the pressure reducing means. In the refrigerant circuit of the air conditioner according to claim 1,
The bypass flow path is further provided with temperature detection means on the suction pipe side between the evaporator and the compressor than the decompression means,
A refrigerant circuit for an air conditioner having a function of indirectly measuring and controlling an evaporation pressure based on a refrigerant temperature detected by the temperature detection means. In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the liquid pipe between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. A refrigerant circuit for an air conditioner, wherein the refrigerant circuit is provided on a pipe side so as to be positioned, and a pressure sensor is further disposed between the on-off valve and the pressure reducing means. In the refrigerant circuit of the air conditioner in which the compressor, the condenser, the expansion valve, and the evaporator are sequentially connected by the refrigerant flow path,
Providing a flow path that bypasses the suction pipe between the evaporator and the compressor and the bottom of the liquid receiver provided between the condenser and the expansion valve;
An opening / closing valve and a pressure reducing means are provided in the bypass flow path, the opening / closing valve is disposed on the suction pipe side between the evaporator and the compressor, and the pressure reducing means is provided between the condenser and the expansion valve. Provided on the pipe side so as to be located respectively, and further arranged a pressure sensor between the on-off valve and the pressure reducing means,
A refrigerant circuit for an air conditioner, characterized in that a temperature detection means is provided at the bottom of the liquid receiver, and the condensation pressure is indirectly measured and controlled based on the refrigerant temperature detected by the temperature detection means.

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