JP2007071453A - Refrigeration cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly control returning quantity of liquid refrigerant in accordance with a refrigerant inlet temperature of a compressor in a refrigeration cycle applying a carbon dioxide gas as the refrigerant. <P>SOLUTION: The refrigerant inlet temperature Ts of the compressor 11 is detected by a temperature sensor 19, and a controller 20 outputs a prescribed flow rate adjustment signal to a bypass control valve 18 on the basis of the refrigerant inlet temperature Ts to control a flow rate of the liquid refrigerant returned to an internal heat exchanger 13 from an accumulator 16 through a liquid refrigerant returning flow channel 17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle that uses carbon dioxide gas or the like as a refrigerant, and more particularly, to a refrigeration cycle that appropriately controls the refrigerant outlet temperature of a compressor using liquid refrigerant accumulated in an accumulator.

  In recent years, for example, in the refrigeration cycle of a vehicle air conditioner, a refrigerant that has a low global warming potential and is used at a gas-liquid critical temperature or pressure, such as carbon dioxide, has been used. Measures are also taken to reduce the impact on the environment.

  In such a refrigeration cycle using carbon dioxide gas as a refrigerant, when an air-cooled radiator is employed, when the operating temperature is higher than the critical pressure and the refrigerant from the radiator is adiabatically expanded from the outside temperature, the inlet of the evaporator Since the dryness of the side refrigerant increases (liquid refrigerant decreases), there is a problem that the heat exchange efficiency in the evaporator decreases. Therefore, an internal heat exchanger for exchanging heat between the refrigerant on the outlet side of the radiator and the refrigerant on the outlet side of the evaporator is provided to lower the temperature during adiabatic expansion. According to this, since the dryness of the inlet refrigerant of the evaporator can be reduced, the efficiency of the evaporator can be improved.

However, if such an internal heat exchanger is provided, the refrigerant on the outlet side of the evaporator is overheated, so that the specific volume of the refrigerant is increased on the inlet side of the compressor, and the volume efficiency of the compressor is reduced. was there. In order to solve this, a refrigerant return hole is provided in the outlet pipe in the accumulator storage chamber, and the liquid refrigerant is returned from the refrigerant return hole to the inlet side of the compressor so as to suppress the temperature of the refrigerant discharged from the compressor. A refrigeration cycle apparatus has been proposed (see Patent Document 1).
JP 2003-90651 A

  In the conventional example proposed in the above Japanese Patent Laid-Open No. 2003-90651, the liquid refrigerant is returned from the refrigerant return hole when the liquid level of the liquid refrigerant rises and falls according to the outside air temperature, so the outside air temperature is the liquid in the accumulator. There was a time lag in transferring to the refrigerant, and it was difficult to return an appropriate amount of liquid refrigerant.

  An object of the present invention is to appropriately control the temperature of the refrigerant discharged from the discharge port of the compressor by appropriately controlling the return amount of the liquid refrigerant in accordance with the refrigerant inlet temperature of the compressor. Is to provide.

  In order to solve the above problems, a refrigeration cycle according to the present invention includes at least a compressor that compresses a refrigerant, a radiator that exchanges heat between the refrigerant compressed by the compressor and outside air, and the radiator. A decompression unit that decompresses the refrigerant that has passed, an evaporator that exchanges heat between the refrigerant decompressed by the decompression unit and the supply air, and a refrigerant that has passed through the radiator and a refrigerant that has passed through the evaporator. The internal heat exchanger that exchanges heat with the gas and the refrigerant that has passed through the evaporator are gas-liquid separated, and the gas-phase refrigerant is sent to the internal heat exchanger to temporarily store the liquid-phase refrigerant (hereinafter, liquid refrigerant). A refrigerant inlet temperature detecting means for detecting a refrigerant inlet temperature of the compressor, and the gas-liquid separator according to a flow rate adjustment signal given from the outside. Return flow of liquid refrigerant to the internal heat exchanger And a predetermined flow rate adjusting signal is output to the flow rate adjusting unit based on the refrigerant inlet temperature detected by the refrigerant inlet temperature detecting unit, and the internal heat exchange is performed from the gas-liquid separator. And a control means for controlling the flow rate of the liquid refrigerant returned to the vessel.

  According to the above configuration, since the return amount of the liquid refrigerant from the gas-liquid separator to the internal heat exchanger is controlled according to the refrigerant inlet temperature of the compressor, the return amount of the liquid refrigerant is appropriately controlled. Can do. As a result, when a large amount of liquid refrigerant needs to be returned, the amount of liquid refrigerant returned can be increased, and the discharge temperature of the refrigerant discharged from the compressor can be reduced. Further, since the return of the liquid refrigerant is not performed when the return of the liquid refrigerant is unnecessary, the discharge temperature of the refrigerant discharged from the compressor can be increased. Therefore, the temperature of the refrigerant discharged from the compressor can be controlled appropriately.

  Embodiments of the refrigeration cycle according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a circuit diagram of a refrigeration cycle according to the first embodiment, and particularly shows an example of a refrigeration cycle using carbon dioxide gas as a refrigerant.

  The refrigeration cycle 10 of the present embodiment includes a compressor 11 that compresses a refrigerant, a radiator 12 that cools the refrigerant compressed by the compressor 11 with outside air, and an expansion that depressurizes the refrigerant cooled by the radiator 12. Heat exchange between the valve (decompression unit) 14, the evaporator 15 that evaporates the refrigerant depressurized by the expansion valve 14, and the low-pressure refrigerant returning to the compressor 11 and the refrigerant cooled by the radiator 12 The refrigerant that has passed through the evaporator 15 includes a heat exchanger 13 and an accumulator (gas-liquid separator) 16 that gas-liquid separates the refrigerant that has passed through the evaporator 15 and sends only the refrigerant in the gas phase state to the compressor 11. Is returned to the compressor 11 and the refrigerant to which the kinetic energy (pressure) is given by the compressor 11 is circulated in the cycle.

  Further, in the refrigeration cycle 10 of this embodiment, as a configuration for returning a part of the liquid refrigerant stored in the accumulator 16 to the inlet side of the internal heat exchanger 13, a liquid refrigerant return flow path 17 and a bypass control valve 18 are used. And a temperature sensor 19 and a controller 20. Hereinafter, each part will be described.

  The compressor 11 obtains a driving force from a motor (not shown) or an engine, compresses gas phase carbon dioxide, and discharges it as a high-temperature and high-pressure refrigerant.

  The radiator 12 cools the temperature of the refrigerant to near the outside temperature by dissipating the heat of the high-temperature and high-pressure refrigerant discharged from the compressor 11 to the outside air. For example, an electric fan or the like is driven to the radiator 12 to blow outside air. The high-temperature and high-pressure refrigerant is cooled to an intermediate temperature by causing heat exchange between the high-temperature and high-pressure refrigerant passing through the radiator 12 and the outside air to be blown.

  The internal heat exchanger 13 further exchanges heat between the refrigerant cooled by the radiator 12 and the low-temperature and low-pressure refrigerant evaporated by the evaporator 15 described later, and further sends the refrigerant sent from the radiator 12 to the expansion valve 14. It is cooling.

  The expansion valve 14 depressurizes (expands) the medium-temperature and high-pressure refrigerant cooled by the internal heat exchanger 13 and sends it to the evaporator 15 as a low-temperature and low-pressure gaseous refrigerant.

  The evaporator 15 is a heat exchanger that exchanges heat between the low-temperature and low-pressure refrigerant decompressed by the expansion valve 14 and the conditioned air supplied from the blower fan. The refrigerant that has become low temperature and low pressure by the expansion valve 14 takes the heat of the conditioned air flowing in the air conditioning duct and evaporates (evaporates) when passing through the evaporator 15. The conditioned air absorbed by the refrigerant in the evaporator 15 is cooled and dehumidified to be cooled and supplied to the passenger compartment.

  The accumulator 16 gas-liquid separates the refrigerant discharged from the evaporator 15 and sends out a gas-phase refrigerant (hereinafter referred to as a gas refrigerant) to the internal heat exchanger 13, and a liquid-phase refrigerant (hereinafter referred to as a liquid refrigerant). Is temporarily stored. Here, the configuration of the accumulator 16 in this embodiment will be described with reference to FIG.

  FIG. 2 is a cross-sectional view showing the internal configuration of the accumulator 16. A storage tank 26 is formed inside the accumulator 16, and an inlet pipe 21 for taking in the refrigerant discharged from the evaporator 15 is installed above the storage tank 26. Further, a substantially U-shaped outlet pipe 22 through which only the gas refrigerant is circulated is installed inside the storage tank 26. One end of the outlet pipe 22 opens to the upper part of the storage tank 26 so that the gas refrigerant is sucked, and the other end is connected to the pipe to the internal heat exchanger 13. Further, an oil bleed hole 24 for returning the lubricating oil staying inside together with the liquid refrigerant 23 to the compressor 11 is formed at a bent portion in the substantially U shape of the outlet pipe 22.

  According to the above configuration, the gas-liquid two-phase refrigerant discharged from the evaporator 15 flows from the inlet pipe 21 into the storage tank 26 of the accumulator 16, where it is separated from the gas and liquid and sucked from one end of the outlet pipe 22. And returned to the internal heat exchanger 13. On the other hand, the liquid refrigerant 23 is stored in the lower part of the storage tank 26.

  Further, the refrigeration cycle 10 of the present embodiment is provided with a liquid refrigerant return channel 17 for returning a part of the liquid refrigerant 23 stored in the accumulator 16 to the internal heat exchanger 13. As shown in FIG. 2, one end of the liquid refrigerant return channel 17 is connected to the lower part of the storage tank 26 of the accumulator 16, and the other end is connected to the low-pressure side inlet pipe of the internal heat exchanger 13 as shown in FIG. It is connected to the.

  A bypass control valve (flow rate adjusting means) 18 is connected in the middle of the liquid refrigerant return flow path 17. The bypass control valve 18 adjusts the return amount of the liquid refrigerant flowing through the liquid refrigerant return flow path 17 by opening and closing an internal valve in accordance with a valve opening / closing signal (flow rate adjustment signal) sent from the controller 20. Yes.

  FIG. 5 shows a configuration example for returning the liquid refrigerant flowing through the liquid refrigerant return flow path 17 to the middle of the pipe 27 extending from the accumulator 16 to the internal heat exchanger 13. As shown in FIG. 5, a throttle portion 28 is provided in the middle of the pipe 27. Since the flow velocity of the refrigerant increases in the throttle portion 28, the pressure at the return port of the liquid refrigerant decreases and a differential pressure can be generated between the accumulator 16 and the liquid refrigerant can be taken into the pipe 27.

  The position where the throttle portion 28 is provided is not limited to the inlet pipe of the internal heat exchanger 13, and may be the middle of the internal heat exchanger 13 or the outlet pipe.

  The temperature sensor (refrigerant inlet temperature detection means) 19 is connected to the inlet side piping of the compressor 11, detects the refrigerant inlet temperature Ts of the compressor 11, and outputs it to the controller 20.

  The controller 20 is constituted by a microcomputer including a CPU, a ROM, a RAM, and the like. The controller 20 takes in the refrigerant inlet temperature Ts periodically (or continuously) sent from the temperature sensor 19 and performs arithmetic processing based on the control program. As a result, an open / close valve opening / closing signal is output to the bypass control valve 18.

  Next, control for returning an appropriate amount of liquid refrigerant from the accumulator 16 to the inlet side of the internal heat exchanger 13 will be described. FIG. 3 is a flowchart showing a processing procedure for controlling the return amount of the liquid refrigerant by the controller 20.

  First, the controller 20 takes in the refrigerant inlet temperature Ts detected by the temperature sensor 19 (step S101), and determines whether it is larger than a threshold value ts1 set in advance by the outside air temperature (step S102). Here, when the refrigerant inlet temperature Ts is larger than the threshold value ts1, a valve opening / closing signal for opening the bypass control valve 18 is sent (step S103). When the bypass control valve 18 opens the valve in response to this valve opening / closing signal, a part of the liquid refrigerant stored in the accumulator 16 flows into the liquid refrigerant return flow path 17 and is returned to the inlet pipe of the internal heat exchanger 13.

  On the other hand, when the refrigerant inlet temperature Ts is not larger than the threshold value ts1, it is determined whether or not the threshold value ts1-a is larger than the refrigerant inlet temperature Ts (step S104). Here, “a” is a set value for preventing the liquid refrigerant returned to the inlet side of the internal heat exchanger 13 from being below the saturation temperature so that it does not return to the compressor 11 as liquid refrigerant. Therefore, when the detected refrigerant inlet temperature Ts is lower than the threshold value ts1-a, the temperature of the refrigerant becomes equal to or lower than the saturation temperature, and the evaporation of the liquid refrigerant stops and returns to the compressor 11 in the liquid state. A valve opening / closing signal is sent (step S105). When the bypass control valve 18 closes the valve in response to this valve opening / closing signal, the liquid refrigerant stored in the accumulator 16 is blocked from flowing into the liquid refrigerant return flow path 17. In step S104, when the refrigerant inlet temperature Ts is larger than the threshold value ts1-a, the valve opening / closing signal is not sent to the bypass control valve 18, and the process returns to step S101 and continues.

  As described above, according to this embodiment, the threshold value ts1 determined by the outside air temperature is set, and the return amount of the liquid refrigerant from the accumulator 16 to the internal heat exchanger 13 is controlled according to the refrigerant inlet temperature Ts of the compressor 11. Therefore, the return amount of the liquid refrigerant can be appropriately controlled following the change in the outside air temperature. Thereby, when returning the liquid refrigerant to the internal heat exchanger 13, the specific volume of the refrigerant is reduced on the inlet side of the compressor 11 and the volume efficiency of the compressor 11 can be improved, so that the refrigerant circulation in the refrigeration system The amount increases, and the heat dissipation amount in the radiator 12 can be maintained.

  Moreover, the heating efficiency can be improved by improving the mechanical efficiency of the compressor 11 by making the return amount of the liquid refrigerant larger during heating than when cooling. Furthermore, since the difference in the specific volume of the refrigerant during cooling and heating can be reduced, it is possible to suppress an increase in the capacity of the compressor 11.

  In particular, in this embodiment, the bypass control valve 18 can be installed outside the system, so that the return amount of the liquid refrigerant can be easily controlled.

  In the present embodiment, an example is shown in which a part of the liquid refrigerant stored in the accumulator 16 is returned from the liquid refrigerant return flow path 17 to the inlet pipe of the internal heat exchanger 13, but the return position of the liquid refrigerant is in this example. It is not limited to. For example, as shown by the symbol A in FIG. 1, it may be in the middle of the internal heat exchanger, or may be the outlet side of the internal heat exchanger, similarly as shown by the symbol B in FIG.

  FIG. 4 is a cross-sectional view illustrating the internal configuration of the accumulator according to the second embodiment. In FIG. 4, the same parts as those in FIG. 2 (Example 1) are denoted by the same reference numerals.

  In the accumulator 16 </ b> A of this embodiment, a liquid refrigerant bleed hole 25 is formed in the vicinity of the oil bleed hole 24, and a part of the liquid refrigerant is returned from the liquid refrigerant bleed hole 25 to the outlet pipe 22. For this reason, the liquid refrigerant return flow path 17 and the bypass control valve 18 of the first embodiment are excluded from the system configuration.

  The liquid refrigerant bleed hole 25 is provided with an opening / closing mechanism (not shown). This opening / closing mechanism is constituted by an electromagnetic valve or the like that can be controlled from the outside by an electric signal, and is controlled by giving an opening / closing signal from the controller 20 shown in FIG. When the diameter of the oil bleed hole 24 is, for example, 1 mm, the diameter of the liquid refrigerant bleed hole 25 is about 2 to 3 mm.

  Also in this embodiment, by applying the processing procedure of FIG. 3, a predetermined electrical signal is output from the controller 20 to the opening / closing mechanism of the liquid refrigerant bleed hole 25, and the accumulator 16A is connected to the inlet side of the internal heat exchanger 13. The return amount of the liquid refrigerant to can be controlled. As a result, the specific volume of the refrigerant is reduced on the inlet side of the compressor 11 and the volume efficiency of the compressor 11 can be improved. Therefore, the refrigerant circulation amount in the refrigeration system is increased, and the heat dissipation amount in the radiator 12 is increased. Can be maintained.

  Moreover, the heating efficiency can be improved by improving the mechanical efficiency of the compressor 11 by making the return amount of the liquid refrigerant larger during heating than when cooling. Furthermore, since the difference in the specific volume of the refrigerant during cooling and heating can be reduced, it is possible to suppress an increase in the capacity of the compressor 11.

  In particular, in the present embodiment, the liquid refrigerant return flow path 17 and the bypass control valve 18 as in the first embodiment are not required, so that the system configuration can be simplified.

  In the present embodiment, the outlet pipe 22 is formed in a substantially U shape inside the accumulator, so that the flow velocity increases at the bottom of the U shape, so that the liquid refrigerant stored in the accumulator 16 is discharged from the liquid refrigerant bleed hole 25 to the outlet. It can be taken into the flow path of the pipe 22. Thereby, the liquid refrigerant is returned to the inlet side of the internal heat exchanger 13.

1 is a circuit diagram of a refrigeration cycle according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view illustrating an internal configuration of the accumulator according to the first embodiment. The flowchart which shows the process sequence for controlling the return amount of a liquid refrigerant by a controller. FIG. 6 is a cross-sectional view showing an internal configuration of an accumulator according to a second embodiment. Sectional drawing which shows the structure of an aperture_diaphragm | restriction part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Refrigeration cycle 11 ... Compressor 12 ... Radiator 13 ... Internal heat exchanger 14 ... Expansion valve 15 ... Evaporator 16, 16A ... Accumulator 17 ... Liquid refrigerant return flow path 18 ... Bypass control valve 19 ... Temperature sensor 20 ... Controller DESCRIPTION OF SYMBOLS 21 ... Inlet piping 22 ... Outlet piping 24 ... Oil bleed hole 25 ... Bleed hole for liquid refrigerants 26 ... Reservoir 28 ... Restriction part

Claims (1)

At least a compressor (11) that compresses the refrigerant, a radiator (12) that exchanges heat between the refrigerant compressed by the compressor and the outside air, and a decompression unit (10) that depressurizes the refrigerant that has passed through the radiator. 14), an evaporator (15) for exchanging heat between the refrigerant decompressed by the decompression means and the supply air, and heat exchange between the refrigerant that has passed through the radiator and the refrigerant that has passed through the evaporator The internal heat exchanger (13) that performs the gas-liquid separation of the refrigerant that has passed through the evaporator and the refrigerant in the gas phase state is sent to the internal heat exchanger, and the refrigerant in the liquid phase state (hereinafter, liquid refrigerant) is temporarily In a refrigeration cycle comprising a gas-liquid separator (16) for storing automatically,
Refrigerant inlet temperature detection means (19) for detecting the refrigerant inlet temperature of the compressor;
A flow rate adjusting means (18) for adjusting a return flow rate of the liquid refrigerant from the gas-liquid separator to the internal heat exchanger according to a flow rate adjustment signal given from the outside;
The flow rate of the liquid refrigerant returned from the gas-liquid separator to the internal heat exchanger by outputting a predetermined flow rate adjustment signal to the flow rate adjustment unit based on the refrigerant inlet temperature detected by the refrigerant inlet temperature detection unit Control means (20) for controlling
A refrigeration cycle comprising:

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