JP2008267766A - Vapor compression refrigeration cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor compression refrigeration cycle, constituted so as to optimally control differential pressure before and after passing through an expansion mechanism according to the pressure of a refrigerant. <P>SOLUTION: The vapor compression refrigeration cycle having a supercritical operation region of the refrigerant comprises a differential pressure type expansion means capable of adiabatically expanding the refrigerant circulating in the refrigeration cycle and adjusting the amount of refrigerant passing through the expansion mechanism, according to the differential pressure between the inlet side refrigerant pressure and outlet-side refrigerant pressure of the expansion mechanism. The differential pressure expansion means comprises a differential pressure valve which is opened with the increase in the differential pressure, and the differential pressure valve is constituted so as to satisfy 5 MPa≤Po≤6 MPa condition, when the pressure for starting the opening the valve is set as the valve-opening pressure Po. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vapor compression refrigeration cycle, and particularly to a vapor compression refrigeration cycle suitable for a vehicle air conditioner having a refrigeration cycle using carbon dioxide, which is a natural refrigerant.

  In the case of a vapor compression refrigeration cycle in a vehicle air conditioner, when carbon dioxide, which is a natural refrigerant, is used as the refrigerant, the valve opening of the expansion device is controlled by an external control signal. One that adjusts the pressure of the high-pressure side line is known (for example, Patent Document 1).

  In such a refrigeration cycle, the high pressure side pressure at which the coefficient of performance (COP) of the refrigeration cycle is optimal is calculated by referring to the high pressure side refrigerant temperature of the refrigeration cycle, and the high pressure side pressure is optimal. Thus, the valve opening degree of the expansion device is controlled.

In addition, there has also been proposed a system in which the refrigeration cycle is efficiently operated by changing the passage cross-sectional area of the orifice of the expansion device according to the pressure and temperature of the refrigerant at the outlet of the radiator (gas cooler) in the refrigeration cycle. An expansion device having a valve biased by a shape memory alloy spring is also proposed (for example, Patent Document 2). In such a configuration, the refrigerant pressure and temperature at the gas cooler outlet side are controlled along the optimal control line obtained from the refrigerant temperature and the pressure at which the coefficient of performance is maximized at the gas cooler outlet side. This enables efficient operation of the refrigeration cycle using carbon.
Japanese Patent Laid-Open No. 7-294033 JP 2007-46808 A

  As described above, as an expansion device for controlling the pressure to be the optimum high-pressure side pressure calculated by referring to the temperature of the gas cooler outlet refrigerant, a method for controlling an electrically controlled expansion mechanism, pressure, and temperature are used. A mechanical expansion mechanism in which the passage cross-sectional area of the orifice is changed accordingly is known. The former detects the gas cooler outlet refrigerant temperature and pressure, and controls the electric expansion valve according to the detected amount, so that the apparatus becomes complicated and large, the control method becomes complicated, and the cost is also increased. It is supposed to rise. In the latter, the passage cross-sectional area of the orifice is varied according to the gas cooler outlet refrigerant temperature and pressure, and since the refrigerant temperature of the gas cooler outlet is sensed, the piping connection structure of the refrigeration cycle is particularly complicated and the number of fastening parts is also increased. There are concerns and the cost is expected to rise. In general, a vapor compression refrigeration cycle using carbon dioxide includes an internal heat exchanger for exchanging heat between a high-pressure side refrigerant and a low-pressure side refrigerant. Therefore, the refrigerant that has flowed out of the gas cooler is circulated through the internal heat exchanger and then flows into the expansion device. As a result, after detecting the refrigerant at the outlet of the gas cooler, the internal heat exchanger is circulated again and then flows into the expansion device. Therefore, in the mechanical expansion mechanism described above, compared to the advantages in terms of application It is thought that there are major drawbacks.

  FIG. 1 shows the relationship between the refrigerant pressure and the coefficient of performance (COP) of the refrigeration cycle with respect to the gas cooler outlet refrigerant temperature. From FIG. 1, when the gas cooler outlet refrigerant temperature is equal to or lower than the critical temperature (about 31 ° C.), the coefficient of performance improves as the value of the high-pressure side refrigerant pressure decreases. In addition, there is a certain high-pressure refrigerant pressure (location on the dotted line in FIG. 1) at which the coefficient of performance is maximum above the critical temperature, and the coefficient of performance is maximized as the gas cooler outlet refrigerant temperature rises. It can be seen that the pressure rises more. In addition, when the gas cooler outlet refrigerant temperature exceeds a predetermined temperature (about 40 ° C.), it can be confirmed that the superiority or inferiority of the coefficient of performance due to the change in the high-pressure side pressure becomes small. From these facts, it is considered important to actively control the high-pressure side refrigerant pressure (about 8 to 10 MPa as the pressure control range) when the gas cooler outlet refrigerant temperature is in the range of about 30 ° C to 40 ° C.

  However, in the above temperature range, although the coefficient of performance improves if it can be controlled to the high-pressure side refrigerant pressure at which the coefficient of performance is maximized, when the control is performed at a pressure lower than the optimum high-pressure side refrigerant pressure, the coefficient of performance of It can be seen that the decrease is significant. Therefore, in the method of controlling the high-pressure side refrigerant pressure by the gas cooler outlet refrigerant temperature, the effect can be expected in a specific temperature range (a range of about 30 ° C. to 40 ° C.) and at that time It is considered that the high-pressure side control pressure needs to be controlled above the optimum pressure (for example, the region A shown in FIG. 1).

  However, the expansion mechanism as described above is an expansion mechanism and a control method for the purpose of controlling the high-pressure side pressure to an optimal high pressure as a whole, so the complexity of the apparatus and the refrigeration cycle, the difficulty of control, Each problem such as high cost is large. Therefore, there is a trade-off between the effect of improving the coefficient of performance by detecting the refrigerant temperature at the gas cooler outlet and controlling the refrigerant pressure on the high pressure side, the simplicity of the piping configuration of the refrigeration cycle, the simplicity of control, etc. Is considered to exist. Therefore, it is desired to develop an expansion mechanism that simplifies the piping configuration of the refrigeration cycle and aims to improve the coefficient of performance.

  Accordingly, an object of the present invention is to provide a vapor compression refrigeration cycle in which the differential pressure before and after passing through the expansion mechanism can be optimally controlled according to the pressure of the refrigerant in order to meet the above demand. It is in.

  Moreover, the subject of this invention can change differential pressure control before and behind expansion mechanism according to the refrigerant | coolant temperature after expansion mechanism passage, and can control differential pressure more appropriately according to the conditions at that time. An object of the present invention is to provide a vapor compression refrigeration cycle.

  In order to solve the above-described problems, the vapor compression refrigeration cycle according to the present invention may adiabatically expand the refrigerant circulating in the refrigeration cycle during the vapor compression refrigeration cycle having a supercritical operating region of the refrigerant. And a differential pressure type expansion means capable of adjusting the amount of refrigerant passing through the expansion mechanism in accordance with a differential pressure between the inlet side refrigerant pressure and the outlet side refrigerant pressure of the expansion mechanism. A differential pressure valve that opens as the differential pressure increases, and when the pressure at which the differential pressure valve starts to open is set to “Po”, 5 MPa ≦ Po ≦ 6 MPa It consists of what is characterized by comprising.

  In such a vapor compression refrigeration cycle, the differential pressure across the expansion mechanism of the differential pressure expansion means is changed by a change in the refrigerant flow path cross-sectional area due to the opening of the differential pressure valve, but the refrigerant flow path cross-sectional area changes. The differential pressure before and after the expansion mechanism when starting to start is taken as the valve opening pressure. As shown in FIG. 4 to be described later, when the refrigerant flow passage cross-sectional area (in FIG. 4, the orifice diameter as will be described later) in which an optimum coefficient of performance is obtained under various conditions, the set value of the valve opening pressure is determined. By setting the optimum valve opening pressure “Po” as shown in FIG. 4, that is, by setting so as to satisfy 5 MPa ≦ Po ≦ 6 MPa, it is possible to suppress the decrease in the coefficient of performance (COP). I found out that

  In the vapor compression refrigeration cycle according to the present invention, the differential pressure type expansion means includes a refrigerant communication passage through which the refrigerant flowing in can constantly flow and adiabatically expand (for example, as shown in an embodiment described later). A refrigerant communication passage (that is, a fixed orifice) that extends through the differential pressure valve is provided. When the equivalent cross-sectional diameter of the communication passage is “Dp”, 0.4 mm ≦ Dp ≦ 0.6 mm is satisfied. It is preferable. This range is also obtained as a result of investigating the diameter (fixed orifice diameter) of the refrigerant communication passage that provides the optimum coefficient of performance under various conditions, as shown in FIG. 5 described later.

  In addition, when the differential pressure exceeds a predetermined valve opening pressure and the differential pressure valve is opened, the maximum equivalent cross-sectional diameter of the refrigerant flow path passing through the expansion mechanism is “Dx”. , 1.0 mm ≦ Dx ≦ 2.0 mm is preferably satisfied. That is, when the differential pressure valve is opened, the cross-sectional area of the flow path of the refrigerant passing through the expansion mechanism is enlarged. The maximum value of the cross-sectional area of the flow path is set to the maximum flow path cross-section equivalent diameter “Dx”. The preferred range is defined by. For example, when an extremely high pressure rise occurs such as when the heat load is high, the maximum flow path cross-section equivalent diameter “Dx” is set within an appropriate range, so that the refrigeration cycle can be reliably protected.

Moreover, it can also be set as the structure provided with the valve opening pressure temperature correction | amendment means which changes the valve opening pressure of the said differential pressure valve according to the temperature of the refrigerant | coolant which flowed out from the said expansion mechanism. The valve opening pressure temperature correcting means has a characteristic of lowering the valve opening pressure from a predetermined set value as the temperature of the refrigerant flowing out of the expansion mechanism increases. ”, The corrected valve opening pressure is“ Poc ”(where Poc is 0 or more), the predetermined constant is“ Kx ”, the temperature of the refrigerant flowing out of the expansion mechanism is“ Txo ”, When the correction coefficient is “S” and the correction start temperature is “Txc”,
Poc = Po−Kx × S
S = Txo-Txc (when Txo> Txc [° C])
S = 0 (when Txo ≤ Txc [° C])
0 ≦ Txc ≦ 20
0.2 ≦ Kx ≦ 0.8
It is preferable to be configured to satisfy the above. An example of changing the valve opening pressure by the valve opening pressure temperature correcting means is shown in FIG. By such control, smooth start-up of the refrigeration cycle and more efficient operation can be realized.

  Further, when the differential pressure between the inlet side refrigerant pressure and the outlet side refrigerant pressure of the expansion mechanism exceeds a predetermined valve opening pressure, the amount of change in the differential pressure [MPa] and the refrigerant flow path in the expansion mechanism When the relationship between the change amount of the channel cross-section equivalent diameter [mm] and “K” is “K”, it is preferably configured to satisfy 0.1 mm / MPa ≦ K ≦ 0.3 mm / MPa. This K needs to be changed depending on the generation capacity of the refrigeration cycle, etc., but as shown in FIG. 6 described later, by setting it within the above range, it is possible to improve the coefficient of performance of the refrigeration cycle.

  Further, it may be configured to include a valve opening pressure external temperature correcting means for changing the valve opening pressure of the differential pressure valve in accordance with the temperature outside the differential pressure type expansion means (for example, the outside air temperature). The valve opening pressure external temperature correcting means has a characteristic that the valve opening pressure is lowered from a predetermined set value as the external temperature of the differential pressure type expansion means increases. By such control, for example, it is possible to avoid a high pressure increase in the refrigeration cycle at the initial start-up time under a high heat load, and a smooth start-up characteristic can be obtained.

  The vapor compression refrigeration cycle according to the present invention is particularly suitable for use as a refrigeration cycle for a vehicle air conditioner, and is particularly suitable when the refrigerant used is made of carbon dioxide.

  According to the vapor compression refrigeration cycle according to the present invention, in particular, in a vehicle air conditioner that uses carbon dioxide, which is a natural refrigerant, as a refrigerant in the vapor compression refrigeration cycle, the difference between before and after passing through the expansion mechanism according to the refrigerant pressure. The pressure can be optimally controlled, the optimum design of the differential pressure type expansion means is enabled, and the efficient operation and safety of the refrigeration cycle can be ensured.

  Further, if a temperature correction means is provided for the valve opening pressure, the differential pressure can be more appropriately controlled according to the conditions at that time.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 2 shows the entire mechanical components when a vapor compression refrigeration cycle using carbon dioxide, which is a natural refrigerant, is incorporated in a vehicle air conditioner according to an embodiment of the present invention. In the refrigeration cycle, a fixed capacity type or capacity driven by a belt 12 driven by pulleys 2 and 3 by a vehicle engine 1 as a driving source (however, another driving source such as an electric motor is also possible). Variable compressor 4, high pressure side pressure detecting means 5 for detecting the pressure of the high pressure refrigerant discharged from compressor 4, and radiator for cooling the refrigerant by heat exchange between the high pressure refrigerant from compressor 4 and external air 6 (gas cooler), a radiator cooling fan 7, an internal heat exchanger 8 for exchanging heat between the high-pressure refrigerant flowing out of the radiator 6 and the low-pressure refrigerant flowing out of the gas-liquid separator 11 (accumulator), and heat radiation Expansion means 9 for adiabatic expansion of the refrigerant sent from the vessel 6 through the internal heat exchanger 8 is provided, and in the present invention, the expansion means 9 is provided with an inlet side refrigerant pressure and an outlet side refrigerant pressure of the expansion mechanism. According to differential pressure An amount of refrigerant passing through the expansion mechanism can be adjusted, and a differential pressure valve that opens as the differential pressure increases is provided. The differential pressure valve opens the pressure at which the valve starts to open. When the pressure is “Po”, the pressure differential expansion means 9 is configured so as to satisfy 5 MPa ≦ Po ≦ 6 MPa. The refrigerant from the differential pressure expansion means 9 is sent to the evaporator 10 to cool the conditioned air, and the refrigerant that has flowed out of the evaporator 10 is separated into gas and liquid by the gas-liquid separator 11, and the liquid refrigerant is stored and vaporized. The refrigerant flows out, and the discharged gas refrigerant is sent to the compressor 4 through the internal heat exchanger 8 and is compressed again. Thus, the refrigeration cycle 13 is configured.

  The evaporator 10 is arrange | positioned in the ventilation duct 14 which sends an air conditioned wind into a vehicle interior. Air is introduced into the ventilation duct 14 from the outside air introduction port 15 and the inside air introduction port 16 via the inside / outside air switching damper 17, and the operation of the inside / outside air switching damper 17 is controlled by the inside / outside air switching damper actuator 18. The introduced air is sucked by the blower fan 19 and is pumped toward the evaporator 10 on the downstream side. An evaporator outlet air temperature sensor 20 is provided on the outlet side of the evaporator 10, and a heater core 21 as a heater is provided on the downstream side of the evaporator 10. The ratio of the air passing through the heater core 21 and the bypassing air is adjusted by the air mix damper 22, and the opening degree of the air mix damper 22 is controlled by the air mix damper actuator 23. The temperature-adjusted air is blown out from the outlets 27, 28, 29 through the dampers 24, 25, 26 toward the vehicle interior.

  Reference numeral 31 denotes an air conditioning control device. The air conditioning control device 31 includes an outside air temperature signal from the outside air temperature sensor 32, a solar radiation amount signal from the solar radiation sensor 33, a vehicle interior temperature signal from the vehicle interior temperature sensor 34, and a high pressure side. The high pressure side refrigerant pressure signal 35 of the pressure detection means 5 and the evaporator outlet air temperature signal from the evaporator outlet air temperature sensor 20 are input. From the air conditioning controller 31, a clutch control signal 37 is sent to the clutch controller 36 that controls the drive of the compressor 4, a compressor capacity control signal 38 is sent to the compressor 4, and an air mix damper control signal 39 is sent to the air mix damper actuator 23. The inside / outside air switching damper control signal 40 is output to the inside / outside air switching damper actuator 18.

  FIG. 3 shows an example of the expansion mechanism 41 of the differential pressure type expansion means 9 (the arrow indicates the flow direction of the refrigerant). However, FIG. 3 is a conceptual diagram of the mechanism, and is not limited to the illustrated structure. The differential pressure type expansion mechanism 41 in FIG. 3 has a fixed orifice portion 42 as a refrigerant communication path through which refrigerant always flows, and the inlet side refrigerant pressure of the expansion mechanism 41 and the expansion mechanism refrigerant outlet at the expansion mechanism refrigerant inlet 43. The amount of refrigerant passing through the expansion mechanism 41 can be adjusted according to the pressure difference between the outlet side refrigerant pressure of the expansion mechanism 41 at 44 and the differential pressure valve 45 is opened as the differential pressure increases. The differential pressure valve 45 is urged in the valve closing direction by a spring 46.

  The refrigerant that has flowed in from the upstream side of the differential pressure type expansion mechanism 41 passes through the fixed orifice portion 42 as a refrigerant communication path provided in the differential pressure valve 45 and is sent to the evaporator 10 from the expansion mechanism refrigerant outlet 44. The differential pressure valve 45 having the fixed orifice portion 42 receives pressure from the refrigerant from the upstream side, and the pressure acts as a force in the valve opening direction on the spring 46 connected to the differential pressure valve 45. The spring 46 acts as a force toward the upstream side, that is, a force in the valve closing direction. When the force relationship in the valve closing direction is stronger than the force in the valve opening direction, the differential pressure valve 45 having the fixed orifice portion 42 does not open, and the fixed orifice is used as the refrigerant channel cross-sectional area. The expansion mechanism has the flow path cross-sectional area of the portion 42. On the other hand, when the force in the valve opening direction is stronger than the force in the valve closing direction, the differential pressure valve 45 is opened, and in addition to the flow path cross-sectional area of the fixed orifice portion 42, the housing of the differential pressure valve 45 and the expansion mechanism 41 is opened. The expansion mechanism has a refrigerant flow path cross-sectional area to which a gap with the body is added. According to such an operating principle, the refrigerant flow passage cross-sectional area is changed by the differential pressure across the fixed orifice portion 42, and the differential pressure across the front or back side or the high-pressure side pressure is controlled. By defining the condition values for the design of the differential pressure type expansion mechanism 41 as follows, an optimum coefficient of performance or high pressure control close thereto is achieved.

First, in the differential pressure type expansion mechanism 41, when the refrigerant flow path cross-sectional area changes due to the opening of the differential pressure valve 45 due to the differential pressure across the fixed orifice portion 42, the refrigerant flow cross-sectional area starts to change. The differential pressure across the orifice is called the valve opening pressure. From the result of investigating the orifice diameter of the fixed orifice portion 42 (that is, the diameter equivalent to the passage cross section of the refrigerant communication passage) from which the optimum coefficient of performance can be obtained for various conditions, the set value of the valve opening pressure is shown in FIG. It was decided to set the optimal valve opening pressure “Po” as shown in FIG. The set optimal valve opening pressure is in the following range.
5MPa ≦ Po ≦ 6MPa
At this time, the pressure control accuracy is desirably within 0.5 MPa. This pressure control accuracy can be achieved by mechanical accuracy.

  This set value can suppress a decrease in the coefficient of performance (COP) by opening the valve within the set range. As is clear from FIG. 4, when the lower limit value (5MPa) is lower than the lower limit value (5MPa), the COP decreases significantly, and when the upper limit value (6MPa) is higher, there is a concern about higher pressure than the COP decrease. become. As a result, it is desirable that the set value range be the valve opening pressure.

As for the orifice diameter of the fixed orifice portion 42, as shown in FIG. 5, the orifice diameter as a passage cross-section equivalent diameter “Dp” of the refrigerant communication passage capable of obtaining an optimum coefficient of performance was investigated. As a result, when the heat load of the refrigeration cycle is relatively small (region shown in A), the coefficient of performance (COP) is not improved when the orifice diameter is smaller than 0.4 mm. In addition, when the refrigeration cycle heat load was large (region indicated by B), it was confirmed that the coefficient of performance (COP) decreased when the orifice diameter was larger than 0.6 mm. Therefore, it is desirable to set the fixed orifice diameter “Dp” within the following range.
0.4mm ≦ Dp ≦ 0.6mm
Alternatively, this range can also be applied as the minimum orifice equivalent diameter.

Further, in the differential pressure type expansion mechanism 41, when the differential pressure across the orifice further exceeds the valve opening pressure of the differential pressure valve 45 and the refrigerant flow passage cross-sectional area is enlarged by opening the differential pressure valve 45, it corresponds to the maximum flow passage cross section. The diameter (maximum orifice equivalent diameter) “Dx” was set as follows.
1.0mm ≦ Dx ≦ 2.0mm
In this embodiment, this setting is made from the value of the orifice diameter when the pressure across the orifice is 11 MPa in FIG. Here, when an extreme high pressure rise occurs such as when the heat load is high, the refrigeration cycle can be reliably protected by setting the maximum equivalent diameter of the orifice within the appropriate range as described above.

Further, the relationship between the change amount of the differential pressure across the orifice and the change amount of the orifice equivalent diameter after the differential pressure across the orifice in the differential pressure type expansion mechanism 41 exceeds the valve opening pressure of the differential pressure valve 45 is expressed as “K”. In this case, the range of the optimum inclination of both changes was set as follows from the results shown in FIG.
0.1mm / MPa ≦ K ≦ 0.3mm / MPa
This setting value should be set so that the coefficient of performance of the system is higher. As shown in FIG. 6, it is considered that about 0.15 mm / MPa is desirable in one system, and another value is desirable in another system. It is expected that In other words, it is considered that this K needs to be changed depending on the generation capability of the system, but if it is set within the above range, the coefficient of performance of the system can be improved.

Further, valve opening pressure temperature correction means for changing the valve opening pressure of the differential pressure valve 45 according to the temperature of the refrigerant flowing out from the differential pressure type expansion mechanism 41 (for example, by detecting the refrigerant temperature immediately after the orifice) is provided. It can also be configured. As described above, the valve opening pressure temperature correcting means has a characteristic of decreasing the valve opening pressure from a predetermined set value as the temperature of the refrigerant flowing out from the expansion mechanism 41 increases. The value is “Po”, the corrected valve opening pressure is “Poc” (where Poc is 0 or more), the predetermined constant is “Kx”, and the temperature of the refrigerant flowing out of the expansion mechanism is “ Toc ”, correction coefficient“ S ”, and correction start temperature“ Txc ”, Poc = Po−Kx × S
S = Txo-Txc (when Txo> Txc [° C])
S = 0 (when Txo ≤ Txc [° C])
0 ≦ Txc ≦ 20
0.2 ≦ Kx ≦ 0.8
It is configured to satisfy An example of changing the valve opening pressure by this valve opening pressure temperature correcting means is shown in FIG. In this example, the correction start temperature Txc is 15 ° C. In other words, when Txo = 15 ° C or less, it is set to be a constant characteristic line represented by a solid line, while when it exceeds Txo = 15 ° C, it becomes a characteristic line like a dotted line according to the value of Txo at that time It is corrected. As an example of operation by such control, immediately after the start of the refrigeration cycle under the hot summer heat, the refrigerant temperature immediately after the orifice rises, so the orifice opening pressure at this time is lower than the normal opening pressure. By correcting, a rise in high pressure at the start of startup is suppressed, and stable startup performance can be obtained. In addition, when the operating time has elapsed for several minutes after the start of the refrigeration cycle, the refrigerant temperature immediately after the orifice gradually decreases, so the valve opening pressure and differential pressure control characteristics aiming at the optimum coefficient of performance described above are achieved. Get closer. Therefore, smooth start-up and efficient operation of the refrigeration cycle can be realized.

  Also, in the differential pressure type expansion mechanism 41, for example, the valve opening pressure of the differential pressure valve 45 is controlled based on a predetermined characteristic in accordance with the external temperature of the expansion mechanism 41 corresponding to the outside air temperature. Can do. In this embodiment, it is assumed that the valve opening pressure decreases as the expansion mechanism external temperature increases. As a result, as described above, it is possible to avoid an increase in the high pressure of the refrigeration cycle at the initial stage of startup under a high heat load, and smooth startup characteristics can be obtained.

  An example of a temperature correction type differential pressure type expansion mechanism is shown in FIG. The differential pressure type expansion mechanism 51 in FIG. 8 has a fixed orifice portion 52 as a refrigerant communication path through which refrigerant constantly flows, and the inlet side refrigerant pressure of the expansion mechanism 51 and the expansion mechanism refrigerant outlet at the expansion mechanism refrigerant inlet 53. 54 is provided with a differential pressure valve 55 that can adjust the amount of refrigerant passing through the expansion mechanism 51 in accordance with the differential pressure with respect to the outlet side refrigerant pressure of the expansion mechanism 51 at 54, and opens as the differential pressure increases. The differential pressure valve 55 is urged in the valve closing direction by springs 56 and 57 with a moving plate 58 interposed therebetween. The spring 57 is a shape memory alloy spring and expands and contracts depending on the temperature of the refrigerant on the outlet side of the expansion mechanism 51 at the expansion mechanism refrigerant outlet 54. The spring 56 is an ordinary spring. Usually, as described in paragraph [0018] of Patent Document 2, the shape memory alloy spring is generally extended at a temperature higher than the transformation point and contracted at a lower temperature. For example, as can be seen from the [Action] column of JP-A-1-125570 and from the upper right column to the lower left column of the third publication page, it can be set to shrink at a temperature higher than the transformation point and to extend at a lower temperature. . In the embodiment shown in FIG. 8, the latter setting is adopted. That is, when the temperature of the refrigerant on the outlet side of the expansion mechanism 51 at the expansion mechanism refrigerant outlet 54 increases, the spring 57 is urged in the left direction (the valve opening direction) in the figure, and the valve opening pressure decreases. Such a configuration makes it possible to correct the temperature of the valve opening pressure.

  Furthermore, an example of a differential pressure type expansion mechanism of an outside air temperature correction type is shown in FIG. The differential pressure type expansion mechanism 61 in FIG. 9 has a fixed orifice portion 62 as a refrigerant communication passage through which refrigerant constantly flows, and the inlet side refrigerant pressure of the expansion mechanism 61 and the expansion mechanism refrigerant outlet at the expansion mechanism refrigerant inlet 63. 64 is provided with a differential pressure valve 65 that can adjust the amount of refrigerant passing through the expansion mechanism 61 in accordance with the differential pressure from the outlet side refrigerant pressure of the expansion mechanism 61 at 64, and opens as the differential pressure increases. The differential pressure valve 65 is urged in the valve closing direction by springs 66 and 67 with a moving plate 68 interposed therebetween. The spring 67 is a shape memory alloy spring, and the spring 66 is an ordinary spring. Heat from the outside air temperature is transmitted to the heat transfer sleeve 70 provided around the spring 67 from the temperature sensing portion 69 of the outside air temperature, and heat is transferred from the sleeve 70 to the spring 67 so that the spring 67 expands and contracts. It has become. With such a configuration, temperature correction according to the outside air temperature of the valve opening pressure becomes possible.

  The structure of the differential pressure type expansion mechanism in the vapor compression refrigeration cycle according to the present invention can be applied to any vapor compression refrigeration cycle, and is particularly suitable for a refrigeration cycle of a vehicle air conditioner using a carbon dioxide refrigerant. .

It is a relationship figure of the refrigerant | coolant pressure and the coefficient of performance (COP) of a refrigerating cycle regarding a gas cooler exit | outlet refrigerant | coolant temperature. It is an equipment distribution diagram of a vehicle air conditioner incorporating a vapor compression refrigeration cycle according to an embodiment of the present invention. It is a schematic sectional drawing which shows an example of a differential pressure type expansion mechanism. FIG. 6 is a relationship diagram between the differential pressure across the orifice, the orifice diameter, and the coefficient of performance (COP), showing the examination result of the optimum valve opening pressure. It is a relationship figure of an orifice front-back differential pressure, an orifice diameter, and a coefficient of performance (COP) which shows the examination result of the optimal orifice diameter. FIG. 6 is a relationship diagram between an orifice front-rear differential pressure and an orifice diameter showing a result of examination of a differential pressure change amount and an orifice equivalent diameter. FIG. 5 is a relationship diagram between an orifice front-rear differential pressure and an orifice diameter showing an example of temperature correction characteristics. It is a schematic sectional drawing which shows an example of the temperature-correction type differential pressure type expansion mechanism. It is a schematic sectional drawing which shows an example of the differential pressure type expansion mechanism of an outside temperature correction type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2, 3 Pulley 4 Compressor 5 High pressure side pressure detection means 6 Radiator (gas cooler)
7 Radiator Cooling Fan 8 Internal Heat Exchanger 9 Differential Pressure Type Expansion Mechanism 10 Evaporator 11 Gas-Liquid Separator (Accumulator)
12 Belt 13 Refrigeration cycle 14 Ventilation duct 15 Outside air introduction port 16 Inside air introduction port 17 Inside / outside air switching damper 18 Inside / outside air switching damper actuator 19 Blower fan 20 Evaporator outlet air temperature sensor 21 Heater core 22 Air mix damper 23 Air mix damper actuator 24 25, 26 Dampers 27, 28, 29 Air outlet 31 Air conditioning control device 32 Outside air temperature sensor 33 Solar radiation sensor 34 Car interior temperature sensor 35 High pressure side refrigerant pressure signal 36 Clutch controller 37 Clutch control signal 38 Compressor capacity control signal 39 Air mix damper Control signal 40 Inside / outside air switching damper control signal 41, 51, 61 Differential pressure type expansion mechanism 42, 52, 62 Fixed orifice part 43, 53, 63 as refrigerant communication passage Expansion mechanism refrigerant inlet 44, 54, 64 Expansion mechanism refrigerant Outflow Ports 45, 55, 65 Differential pressure valves 46, 56, 66 Springs 47, 57, 67 Shape memory alloy springs 58, 68 Moving plate 69 Temperature sensing part 70 for outside air temperature Sleeve

Claims (8)

  During the vapor compression refrigeration cycle having the supercritical operating region of the refrigerant, the refrigerant circulating in the refrigeration cycle can be adiabatically expanded, and the differential pressure between the inlet side refrigerant pressure and the outlet side refrigerant pressure of the expansion mechanism And a differential pressure expansion means capable of adjusting the amount of refrigerant passing through the expansion mechanism according to the differential pressure expansion means. The differential pressure expansion means includes a differential pressure valve that opens as the differential pressure increases. The vapor compression refrigeration cycle, wherein the differential pressure valve is configured to satisfy 5 MPa ≦ Po ≦ 6 MPa when the valve opening pressure is “Po”.   The differential pressure type expansion means includes a refrigerant communication passage through which the flowing refrigerant can be circulated and adiabatically expanded, and when the equivalent cross-sectional diameter of the communication passage is “Dp”, 0.4 mm ≦ Dp ≦ 0.6 mm The vapor compression refrigeration cycle according to claim 1, wherein the vapor compression refrigeration cycle is configured to satisfy the following.   When the differential pressure exceeds a predetermined valve opening pressure, and when the differential pressure valve is opened, the maximum flow path equivalent diameter of the flow path of the refrigerant passing through the expansion mechanism is `` Dx '', 1.0 The vapor compression refrigeration cycle according to claim 1, wherein the vapor compression refrigeration cycle is configured to satisfy mm ≦ Dx ≦ 2.0 mm. Valve opening pressure temperature correcting means for changing the valve opening pressure of the differential pressure valve in accordance with the temperature of the refrigerant flowing out of the expansion mechanism, the valve opening pressure temperature correcting means being a temperature of the refrigerant flowing out of the expansion mechanism; The valve opening pressure has a characteristic of lowering from a predetermined set value as the value becomes higher. The predetermined set value is “Po”, and the corrected valve opening pressure is “Poc” (however, Poc Is a predetermined constant “Kx”, the temperature of the refrigerant flowing out of the expansion mechanism is “Txo”, the correction coefficient is “S”, and the correction start temperature is “Txc” ,
Poc = Po−Kx × S
S = Txo-Txc (when Txo> Txc [° C])
S = 0 (when Txo ≤ Txc [° C])
0 ≦ Txc ≦ 20
0.2 ≦ Kx ≦ 0.8
The vapor compression refrigeration cycle according to claim 1, wherein the vapor compression refrigeration cycle is configured to satisfy the above.   When the differential pressure between the inlet side refrigerant pressure and the outlet side refrigerant pressure of the expansion mechanism exceeds a predetermined valve opening pressure, the amount of change in the differential pressure [MPa] and the flow path of the refrigerant flow path in the expansion mechanism 5. The structure according to claim 1, wherein when the relationship with the amount of change in cross-sectional equivalent diameter [mm] is “K”, 0.1 mm / MPa ≦ K ≦ 0.3 mm / MPa is satisfied. The vapor compression refrigeration cycle described.   A valve opening pressure external temperature correcting means for changing a valve opening pressure of the differential pressure valve in accordance with a temperature outside the differential pressure expansion means; and the valve opening pressure external temperature correcting means is external to the differential pressure expansion means. The vapor compression refrigeration cycle according to any one of claims 1 to 5, which has a characteristic of lowering the valve opening pressure from a preset value as the temperature increases.   The vapor compression refrigeration cycle according to any one of claims 1 to 6, which is used as a refrigeration cycle of a vehicle air conditioner.   The vapor compression refrigeration cycle according to any one of claims 1 to 7, wherein the refrigerant used is made of carbon dioxide.

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