JP2009250590A - Expansion valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expansion valve capable of stabilizing pressure on the low pressure side and increasing beforehand a flow rate capable of flowing at high load start. <P>SOLUTION: A pressure sensitive actuator 33 is provided. Pressure on the low pressure side of the expansion valve 3 introduced via a through-hole 44 is sensed by a diaphragm 35, and lift of a valve element 28 is controlled so as to maintain the pressure on the low pressure side at a predetermined level. Thus, since the pressure on the low pressure side is stabilized, blow-out temperature of air passed through an evaporator can be stabilized. Since a shape memory alloy spring 41 enables lift of the valve element 28 at high load start, large amount of a refrigerant can be made to flow simultaneously with the start. Thus, time required for reducing the blow-out temperature of the air is shortened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an expansion valve, and more particularly to an expansion valve used in a refrigeration cycle of a vehicle air conditioner using a natural refrigerant such as carbon dioxide.

  2. Description of the Related Art A refrigeration cycle for a vehicle air conditioner is known that includes an accumulator that performs gas-liquid separation of refrigerant on the outlet side of an evaporator. As an apparatus for expanding the refrigerant in the refrigeration cycle, a fixed orifice such as an orifice tube not having a refrigerant flow rate control function or a variable orifice having a control function is used. In this variable orifice expansion valve (see, for example, Patent Document 1), the valve body has a structure of a differential pressure valve urged in a valve closing direction by a spring, and a fixed orifice is formed so as to bypass the differential pressure valve. ing. The fixed orifice is for flowing a refrigerant having a minimum flow rate necessary for circulating the lubricating oil of the compressor when the differential pressure valve is closed.

  In the expansion valve of such a variable orifice, when the differential pressure between the refrigerant inlet pressure and the refrigerant outlet pressure is small, the differential pressure valve is closed and the refrigerant flows through the fixed orifice. When the differential pressure exceeds a predetermined value, the differential pressure valve opens against the biasing force of the spring in the valve closing direction. Therefore, when the differential pressure before and after the expansion valve is small, the expansion valve controls the flow rate of the refrigerant so that the flow rate increases as the differential pressure increases.

  On the other hand, in the refrigeration cycle, there is a point where the coefficient of performance of the refrigeration cycle becomes maximum with respect to the pressure with respect to the refrigerant temperature on the inlet side of the expansion valve, and optimal control in which such a change in pressure point is plotted on the Mollier diagram A line is known. Therefore, by making the refrigerant temperature and pressure on the inlet side of the expansion valve change along the optimum control line, the refrigeration cycle is operated with the maximum coefficient of performance, and the compressor is driven. It is possible to minimize the load on the vehicle running engine.

As the compressor, there is generally known a suction capacity control type variable capacity compressor that senses the suction pressure on the low pressure side and variably controls the discharge capacity so that the suction pressure is maintained at a preset value. . Controlling the variable capacity compressor so that the suction pressure on the low pressure side is stabilized is that the temperature of the air blown into the passenger compartment after heat exchange in the evaporator disposed on the low pressure side of the variable capacity compressor is It will be stable. However, in a refrigeration cycle that uses a refrigerant with a very high operating pressure, such as carbon dioxide, it is difficult to use a capacity control valve for a variable capacity compressor with a suction pressure control type because of the pressure resistance of the pressure sensing element and cost. It has become to.
JP 2006-189240 A

  For this reason, it is difficult to adopt a control method in which the pressure on the low-pressure side is stabilized on the variable capacity compressor side of the refrigeration cycle, and there is a problem that the temperature of the air passing through the evaporator is not stable. It was.

  Further, since the expansion valve having the differential pressure valve cannot be operated so that the refrigerant temperature and pressure on the inlet side thereof are along the optimum control line, it is difficult to operate the refrigeration cycle in a state where the coefficient of performance is maximized. There was a problem.

  Furthermore, the expansion valve having the differential pressure valve is closed at the time of starting without the differential pressure and is in a state in which the refrigerant does not flow easily, so that even when the cooling load is very high, it is not possible to flow the corresponding amount of refrigerant. For this reason, there is a problem that it takes time to lower the blowing temperature of the air that has passed through the evaporator.

  The present invention has been made in view of such a point, and the pressure on the low pressure side can be stabilized regardless of the control method of the variable capacity compressor, and the refrigeration cycle is operated in a state where the coefficient of performance is maximized. An object of the present invention is to provide an expansion valve that can increase the flow rate that can be allowed to flow and that can be increased in advance when a high load is started.

  In the present invention, in order to solve the above problems, in an expansion valve having a valve unit for controlling the flow rate of the refrigerant, the pressure or temperature sensed by sensing the pressure or temperature of the expanded low-pressure side refrigerant is supported. An actuator that controls the valve unit so that the pressure is maintained at a predetermined pressure; and a temperature-sensitive actuator that senses the temperature of the refrigerant on the low-pressure side and biases the valve unit in the valve opening direction. An expansion valve is provided.

  According to such an expansion valve, since an actuator is provided and control is performed so that the pressure on the low pressure side is maintained at a predetermined pressure, the pressure on the low pressure side is stabilized, and the blowing temperature of the air passing through the evaporator is stabilized. Can be made. Further, since the temperature-sensitive actuator can be opened at the time of high load startup, it becomes possible to flow a large amount of refrigerant at the same time as startup, thereby reducing the time taken to lower the air blowing temperature. Shortened.

  The expansion valve having the above-described configuration includes an actuator that controls the pressure on the low-pressure side to be constant, so that even if a control method for controlling the pressure on the low-pressure side on the variable displacement compressor side is not used, The pressure on the low-pressure side can be stabilized, and the provision of a temperature-sensitive actuator allows the valve section to be kept open at the time of high load startup, so the temperature of air blown through the evaporator can be reduced. There is an advantage that it can be lowered in a short time.

  When a diaphragm having a pressure receiving area larger than that of the valve body is used as the pressure sensing element, the actuator can greatly increase the power for driving and controlling the valve portion. Therefore, the valve body having a small pressure receiving area has a high pressure. Even if it receives a pressure fluctuation or a fluid force such that the valve body itself moves freely due to the high-speed flow of the refrigerant in the valve portion, it is substantially not affected.

  In addition, since the expansion valve has a function of controlling the pressure on the low pressure side to be constant, when combined with a variable capacity compressor by a control method other than the suction pressure control type, the expansion valve inlet It becomes easy to control the refrigerant so that the temperature and pressure of the refrigerant change along an optimum control line that is considered to be efficient.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking as an example a case where the present invention is applied to a refrigeration cycle of a vehicle air conditioner using a natural refrigerant such as carbon dioxide.
FIG. 1 is a diagram showing a refrigeration cycle to which the expansion valve according to the first embodiment is applied.

  The refrigeration cycle includes a compressor 1 that compresses the refrigerant, a gas cooler 2 that cools the compressed refrigerant, an expansion valve 3 that adiabatically expands the cooled refrigerant, an evaporator 4 that evaporates the expanded refrigerant, and a refrigeration cycle. The accumulator 5 that stores the excess refrigerant and separates the vapor-phase refrigerant from the evaporated refrigerant and sends it to the compressor 1, the high-temperature refrigerant that flows from the gas cooler 2 to the expansion valve 3, and the low-temperature that flows from the accumulator 5 to the compressor 1. And an internal heat exchanger 6 for exchanging heat with the other refrigerant. In the figure, solid arrows indicate the direction of refrigerant flow.

  The expansion valve 3 includes a valve unit that controls the flow rate of the refrigerant, and an actuator that senses the pressure of the expanded refrigerant and controls the valve unit so that the pressure is maintained at a predetermined pressure. Has a function of controlling the pressure of the gas at a constant level. The compressor 1 is a variable capacity compressor whose capacity can be varied so as to obtain a predetermined compression capacity regardless of the rotational speed of the vehicle running engine that drives the compressor 1, and a capacity capable of controlling the discharge capacity. A control valve 7 is provided. The capacity control valve 7 is connected to a capacity control unit 8 that controls the compressor 1 by a control method other than the suction pressure control type.

  The capacity control unit 8 includes a pressure sensor 9 that senses the discharge pressure Pd of the compressor 1, a temperature sensor 10 that senses the outlet temperature Tg of the gas cooler 2, and a temperature sensor that senses the blowing temperature Te of air exchanged by the evaporator 4. 11 is connected. Based on the signals from the pressure sensor 9 and the temperature sensors 10 and 11, the capacity control unit 8 determines that the refrigerant temperature and pressure on the inlet side of the expansion valve 3 are on the Mollier diagram within a range where the discharge pressure Pd does not become abnormally high. It is controlled so as to change along the optimal control line. The control by the capacity control unit 8 is, for example, a differential pressure that controls so that the differential pressure (Pd−Ps) between the discharge pressure Pd and the suction pressure Ps of the compressor 1 is maintained at a predetermined differential pressure set by an external signal. Control, flow rate control for controlling the flow rate of the refrigerant discharged from the compressor 1 to be maintained at a predetermined flow rate set by an external signal, or the discharge pressure Pd of the refrigerant discharged from the compressor 1 is the outlet of the gas cooler 2 It can be set as control which maintains the capacity | capacitance which becomes the optimal pressure on the optimal control line corresponding to temperature Tg.

FIG. 2 is a central longitudinal sectional view showing the configuration of the expansion valve according to the first embodiment.
The expansion valve 3 has a body 21, and a refrigerant inlet 22 is formed in the upper part of the figure of the body 21, and a strainer 23 is attached so as to cover this. The body 21 also has a refrigerant outlet 24 formed through the body 21. At the center of the body 21, a valve hole 25 that communicates the refrigerant inlet 22 and the refrigerant outlet 24 is formed, and a fixed orifice 26 is provided in parallel so as to bypass the valve hole 25. In the refrigerant inlet 22, the edge of the valve hole 25 constitutes a valve seat 27, and a ball-shaped valve body 28 is disposed so as to be able to contact with and separate from the valve seat 27. The valve body 28 constitutes the valve portion of the expansion valve 3 together with the valve seat 27. The valve body 28 is also urged by a biasing spring 29 in a direction to be seated on the valve seat 27, and the side of the spring 29 opposite to the valve body 28 is a spring receiver screwed to the refrigerant inlet 22. Received by member 30.

  The body 21 has a hollow cylindrical portion formed in the lower half thereof, and a low pressure chamber 31 is formed therein. A shaft 32 is disposed at the axial position of the body 21 and is held by the body 21 so as to be movable forward and backward in the axial direction. One end of the shaft 32 is in contact with the valve body 28 in the valve hole 25, and the other end is in contact with the pressure sensitive actuator 33 through the low pressure chamber 31.

  The pressure-sensitive actuator 33 includes a first housing 34 that is screwed to the lower end portion of the body 21, a diaphragm 35 that is displaced in the axial direction in response to pressure, and a second housing 36, and the diaphragm 35 is disposed in the first housing. These outer peripheral portions are joined together by welding in a state of being sandwiched by 34 and the second housing 36. A plurality of snap plates 37 are stacked in the second housing 36 so as to receive the diaphragm 35 therein. The snap plate 37 is used to support the diaphragm 35 on the surface opposite to the pressure receiving surface when the high pressure refrigerant cannot be received only by the diaphragm 35. The number of the snap plates 37 depends on the spring load characteristics. Is adjusted. In the second housing 36, a hollow cylindrical portion is formed in a lower portion of the drawing than the accommodating portion of the snap plate 37, and a spring 38 is accommodated therein. One end of the spring 38 is brought into contact with the center portion of the snap plate 37 via a spring receiving member 39, and the other end is received by an adjustment screw 40 screwed into the hollow cylindrical portion of the second housing 36. . The adjustment screw 40 adjusts the spring load of the spring 38 according to the screwing amount.

  The low pressure chamber 31 houses therein a shape memory alloy spring 41 that functions as a temperature sensitive actuator. One end of the shape memory alloy spring 41 is received by the spring receiving member 42, and the other end is received by the first housing 34 of the pressure sensitive actuator 33. The spring receiving member 42 is locked by an E-ring 43 fitted to the shaft 32, and the shape memory alloy spring 41 attaches the shaft 32 when the refrigerant in the low-pressure chamber 31 reaches a predetermined temperature or higher. Thus, the valve body 28 can be forcedly urged in the valve opening direction to open the valve portion. A through-hole 44 communicating with the low-pressure chamber 31 is formed in the hollow cylindrical portion of the body 21 so that the pressure on the low-pressure side of the expansion valve 3 can be introduced to the diaphragm 35 of the pressure-sensitive actuator 33. .

  In the expansion valve 3 having the above configuration, the high-pressure refrigerant from the internal heat exchanger 6 is introduced into the refrigerant inlet 22, and the expanded low-pressure refrigerant is led out from the refrigerant outlet 24 and sent to the evaporator 4. The low pressure chamber 31 receives a refrigerant pressure of a low pressure pipe extending from the refrigerant outlet 24 of the expansion valve 3 to the suction port of the compressor 1, for example, the refrigerant pressure of the refrigerant outlet 24, through the through hole 44.

  Here, when the operation of the vehicle air conditioner is stopped, the pressures in the refrigeration cycle are all in a balanced state. Therefore, the diaphragm 35 of the pressure sensitive actuator 33 is more than that during operation of the vehicle air conditioner. It is displaced in a direction away from the valve part under high pressure. As a result, the pressure sensitive actuator 33 cannot drive the valve body 28 in the lift direction via the shaft 32, so the valve body 28 is seated on the valve seat 27 by the biasing force of the spring 29, and the expansion valve 3 is Fully closed.

  When the vehicle air conditioner starts operation and the refrigeration cycle starts, the refrigerant inlet 22 side of the expansion valve 3 in the fully closed state is pressurized by the compressor 1 to become high pressure, and conversely, the refrigerant outlet 24 side is It is sucked by the compressor 1 and becomes a low pressure. When the pressure on the low-pressure side falls below a predetermined pressure, the pressure-sensitive actuator 33 detects the pressure drop in the low-pressure chamber 31 by displacing the diaphragm 35 in the direction of the valve portion, so that the valve element is connected via the shaft 32. 28 is lifted from the valve seat 27. As a result, the valve portion is opened, and the high-temperature and high-pressure refrigerant introduced into the refrigerant inlet 22 flows out to the refrigerant outlet 24 through the gap between the valve seat 27 and the valve body 28. At this time, the refrigerant adiabatically expands to become a low-temperature / low-pressure refrigerant and is sent to the evaporator 4.

  After the expansion valve 3 is opened, the pressure on the low pressure side is sensed by the pressure-sensitive actuator 33. When the pressure becomes higher than a predetermined pressure, the valve portion is driven in the valve closing direction. Since the section is driven in the valve opening direction, the expansion valve 3 controls the refrigerant flow rate so that the low-pressure side pressure maintains a predetermined pressure. In the present embodiment, the predetermined pressure on the low pressure side is set to about 3.5 MPa, which is the pressure when the carbon dioxide refrigerant reaches 0 ° C., and therefore the pressure on the low pressure side is about 3.5 MPa. The refrigerant flow rate is controlled to be constant.

  Since the pressure-sensitive actuator 33 includes the diaphragm 35 having a pressure receiving area sufficiently larger than that of the valve body 28, the pressure-sensitive actuator 33 has sufficient power to drive the valve body. For this reason, even if the phenomenon that the valve body is pulled in the valve closing direction by the fluid due to the high flow rate of the refrigerant passing through the valve portion, it is stable without being affected by such fluid force. It becomes possible to obtain an operation.

  The expansion valve 3 includes a shape memory alloy spring 41 in the low pressure chamber 31 and senses the installation environment temperature of the expansion valve 3. The shape memory alloy spring 41 directly senses the temperature of the refrigerant in the low-pressure chamber 31 and forcibly opens the valve when the refrigerant in the low-pressure chamber 31 reaches a predetermined temperature or higher. Like to do. Therefore, when starting the operation of the vehicle air conditioner in a normal environment, the refrigeration cycle starts from a state in which the expansion valve 3 is fully closed. For example, when the temperature is very high as in a desert area in summer, The refrigeration cycle starts when the temperature is sensed and the expansion valve 3 is open. The purpose of this is to eliminate the time required for lowering the blowing temperature Te of the air that has passed through the evaporator 4 when the refrigeration cycle is started with a very high cooling load. Thereby, at the time of high load start-up, the expansion valve 3 is opened in advance and can flow a large amount of refrigerant, so that the blowing temperature Te can be reduced in a short time.

  In this embodiment, the shape memory alloy spring 41 is used as a temperature-sensitive actuator that senses the temperature of the refrigerant on the low-pressure side and urges the expansion valve 3 to open at the time of high load startup. A bimetal whose load changes can be used, or a temperature-sensitive actuator configured by enclosing a wax whose volume changes with temperature in a container sealed with a diaphragm can be used.

  3 is a central longitudinal sectional view showing the configuration of the expansion valve according to the second embodiment, and FIG. 4 is a central longitudinal sectional view showing a configuration example of the expansion valve and the expansion valve mounting block according to the second embodiment. is there. 3 and 4, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The expansion valve 3a according to the second embodiment prevents the valve element 28 from being affected by high pressure fluctuations. That is, in the expansion valve 3 according to the first embodiment, since the valve element 28 receives the high-pressure refrigerant in the closing direction, it is directly influenced by the fluctuation of the high pressure. The expansion valve 3a is configured to cancel the influence of the high pressure.

  The expansion valve 3 a has a refrigerant inlet 22 on the side surface of the body 21, and the refrigerant outlet 24 is formed on the front end side of the body 21. Therefore, the strainer 23 is locked to the body 21 so as to cover the annular groove communicating with the refrigerant inlet 22, and the spring 29 that urges the valve body 28 in the valve closing direction is accommodated in the space of the refrigerant outlet 24. . The valve body 28 is formed integrally with a shaft 45 that extends through the valve hole 25 in the direction of the pressure-sensitive actuator 33. The shaft 45 has a portion indicated by the body 21 having an outer diameter substantially equal to the inner diameter of the valve hole 25. As a result, the pressure receiving area that the valve body 28 receives in the valve opening direction is substantially equal to the pressure receiving area that the shaft 45 receives in the valve closing direction of the valve body 28, so that the valve body 28 and the shaft 45 are hardly affected by high pressure. It has a back pressure cancellation structure that does not receive it.

  However, strictly speaking, the shaft 45 is formed with an outer diameter slightly smaller (for example, about 4%) than the inner diameter of the valve hole 25. As a result, the load that causes the valve element 28 to act in the valve opening direction is larger than the load that causes the shaft 45 to act in the valve closing direction, so that the expansion valve 3a becomes easier to open little by little as the pressure of the introduced refrigerant increases. It has a high-pressure-dependent characteristic.

  The end portion of the shaft 45 opposite to the valve body 28 is fitted to the spring receiving member 42 of the shape memory alloy spring 41. The spring receiving member 42 is formed integrally with a shaft 46 that transmits the displacement of the diaphragm 35 to the shaft 45. The valve body 28 and the shaft 45 are formed with a communication hole 47 penetrating along the axis thereof, and further, a through hole 48 is formed in the shaft 45 so that the communication hole 47 communicates with the low pressure chamber 31. As a result, the low pressure chamber 31 communicates with the refrigerant outlet 24 via the communication hole 47 and the through hole 48, so that the pressure of the low pressure side refrigerant immediately after expansion can be directly introduced into the low pressure chamber 31.

  The operation of the expansion valve 3a is also controlled so as to maintain the low-pressure side pressure at a predetermined pressure, and when the high load is started, the operation starts from the open state. Further, the expansion valve 3a has a back pressure canceling structure so that it is not easily affected by high pressure fluctuations, and has a high pressure dependency characteristic that makes it easy to open the valve at a high pressure at the refrigerant inlet 22. However, unlike the expansion valve 3 in which the first housing 34, the diaphragm 35, and the second housing 36 are joined by welding, the pressure-sensitive actuator 33 is assembled as shown in FIG. 3 when incorporated into the refrigeration cycle. It is said. For this reason, an O-ring 49 is disposed between the first housing 34 and the diaphragm 35 to seal the refrigerant in the low pressure chamber 31 from leaking outside.

  The expansion valve 3a is attached to the expansion valve mounting block 50 as shown in FIG. The expansion valve mounting block 50 is formed with a mounting hole 51 for accommodating the expansion valve 3a, and a high-pressure refrigerant inlet 52 and a low-pressure refrigerant outlet 53 are formed so as to communicate with the mounting hole 51. The high-pressure refrigerant inlet 52 is a pipe joint to which a high-pressure pipe from the internal heat exchanger 6 is connected, and the low-pressure refrigerant outlet 53 is a pipe joint to which a low-pressure pipe toward the evaporator 4 is connected.

  The expansion valve 3 a is inserted into the mounting hole 51 of the expansion valve mounting block 50, and the fixing plate 54 is locked to the expansion valve mounting block 50 with a bolt 55 while the fixing plate 54 is locked to the second housing 36 of the pressure-sensitive actuator 33. By fixing, it is attached to the expansion valve mounting block 50, thereby constituting an expansion device. At this time, the pressure-sensitive actuator 33 is coupled by the first housing 34, the diaphragm 35, and the second housing 36 being sandwiched between the expansion valve mounting block 50 and the fixed plate 54.

  In the example of FIG. 4, the spring 29 that biases the valve body 28 in the valve closing direction is changed from a taper spring shown in FIG. 3 to a coil spring. In this example, the expansion valve mounting block 50 is shown as an independent member, but it may be formed integrally with the body of the internal heat exchanger 6, for example. Thereby, the connection location of a high voltage | pressure piping reduces by one and the site | part which may have an external leakage can be reduced.

  FIG. 5 is a central longitudinal sectional view showing a configuration example of the expansion valve and the expansion valve mounting block according to the third embodiment. In FIG. 5, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The expansion valve 3b according to the third embodiment forms a low-pressure chamber 31 that is closed by press-fitting the lower end portion of the body 21 into the first housing 34 of the pressure-sensitive actuator 33. The pressure-sensitive actuator 33 is formed by forming the second housing 36 with a bottomed closed container by deep drawing processing, housing a spring 38 for supporting the diaphragm 35 therein, and deforming the bottom portion from the outside to the inside, The spring load of the spring 38 is adjusted by changing the axial position of the spring receiving member 56 receiving the spring 38 on the side opposite to the diaphragm 35 side.

  In this embodiment, the expansion valve 3b is completely accommodated in the expansion valve mounting block 50 to constitute the expansion device. In the expansion valve mounting block 50, the low-pressure refrigerant outlet 53 and the mounting hole 51 are formed coaxially, and the high-pressure refrigerant inlet 52 is formed in a direction perpendicular to the axis thereof. Since the expansion valve 3b is entirely accommodated in a mounting hole 51 formed in the central portion of the expansion valve mounting block 50, there is no refrigerant leakage site other than the pipe joints of the high-pressure refrigerant inlet 52 and the low-pressure refrigerant outlet 53. Absent.

  FIG. 6 is a central longitudinal sectional view showing a configuration example of the expansion valve and the expansion valve mounting block according to the fourth embodiment. In FIG. 6, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The expansion valve 3c according to the fourth embodiment is configured to sense the pressure at the outlet of the evaporator 4 as the low pressure side pressure. Therefore, the valve body 28 and the shaft 45 formed integrally therewith are formed by a solid member so that the refrigerant outlet 24 and the low pressure chamber 31 do not communicate with each other, and the low pressure chamber 31 is connected via the through hole 44. It communicates with the outside. In the expansion valve 3c, the mechanism for adjusting the spring load of the snap plate 37 is omitted, and the pressure-sensitive actuator 33 has a simple configuration.

  The expansion valve 3c is also completely accommodated in the expansion valve mounting block 50. In the expansion valve mounting block 50, a return low-pressure refrigerant outlet 57 and a mounting hole 51 are formed coaxially, and a high-pressure refrigerant inlet 52, a low-pressure refrigerant outlet 53, and a return low-pressure refrigerant inlet 58 are formed in a direction orthogonal to the axis. . The entire expansion valve 3 c is accommodated in a mounting hole 51 formed in the central portion of the expansion valve mounting block 50.

  The refrigerant introduced into the high-pressure refrigerant inlet 52 is adiabatically expanded by the expansion valve 3 c, is sent from the low-pressure refrigerant outlet 53 to the evaporator 4, and is evaporated by the evaporator 4. The refrigerant evaporated by the evaporator 4 is introduced into the return low-pressure refrigerant inlet 58 and sent from the return low-pressure refrigerant outlet 57 to the accumulator 5. At this time, the pressure is introduced into the low pressure chamber 31 of the expansion valve 3c through the through hole 44 while the refrigerant flows from the return low pressure refrigerant inlet 58 to the return low pressure refrigerant outlet 57 in the expansion valve mounting block 50, and pressure sensitive. It is sensed by the actuator 33. Therefore, the expansion valve 3c senses the outlet pressure of the evaporator 4 as the low-pressure side pressure, and controls the refrigerant flow rate so that the pressure maintains a predetermined pressure. Further, the shape memory alloy spring 41 forcibly opens the valve element 28 when the load is activated.

  FIG. 7 is a central longitudinal sectional view showing a configuration example of an expansion valve and an expansion valve mounting block according to the fifth embodiment. In FIG. 6, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the expansion valve 3d according to the fifth embodiment, the pressure sensitive actuator 33 uses a bellows 59 as a pressure sensitive member. The bellows 59 is housed in a bottomed cylindrical housing 60 that is screwed to the body 21 and constitutes the low-pressure chamber 31 in a state in which the expansion / contraction direction thereof coincides with the axis of the valve body 28 and the shafts 45 and 46. . One end of the bellows 59 is in contact with the bottom of the housing 60, and the other end is in contact with the shaft 46. A shape memory alloy spring 41 is disposed between a bottom portion of the housing 60 and a flange portion formed at the other end of the bellows 59, and a shaft 45 is interposed between the other end of the bellows 59 and the spring receiving member 42. A spring 61 that urges the valve body 28 in the valve opening direction is disposed.

The expansion valve 3d is attached to the expansion valve mounting block 50 by a fixing plate 54 and a bolt 55.
The refrigerant introduced into the high-pressure refrigerant inlet 52 is adiabatically expanded by the expansion valve 3 d and is sent from the low-pressure refrigerant outlet 53 to the evaporator 4. At this time, the pressure of the adiabatically expanded refrigerant is introduced into the low pressure chamber 31 through the valve body 28 and the communication hole 47 and the through hole 48 of the shaft 45, and the pressure is detected by the bellows 59. Therefore, the expansion valve 3d senses the pressure of the adiabatically expanded refrigerant and controls the flow rate of the refrigerant so that the pressure maintains a predetermined pressure.

  FIG. 8 is a central longitudinal sectional view showing a configuration example of the expansion valve and the expansion valve mounting block according to the sixth embodiment. In FIG. 8, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The expansion valve 3e according to the sixth embodiment uses a shape memory alloy spring 62 as an actuator for controlling the pressure on the low pressure side to be constant. That is, the expansion valve 3e is a bias spring stored in the refrigerant outlet 24 so as to remove the pressure-sensitive actuator 33 from the expansion valve 3a shown in FIG. 4 and urge the valve body 28 in the valve closing direction. 29 is replaced with a shape memory alloy spring 62. The shape memory alloy spring 62 senses the temperature of the expanded low-pressure refrigerant, and controls the valve portion so that the pressure corresponding to the sensed temperature is maintained at a predetermined pressure.

  Here, the expansion valve 3e is controlled on the basis of the temperature of the refrigerant on the low-pressure side, for the following reason. That is, the refrigerant on the low-pressure side immediately after expansion is in a gas-liquid two-phase state in a vapor state. While the vapor refrigerant evaporates, its temperature and pressure do not change and have a one-to-one correspondence with each other. Therefore, if the temperature of the vapor refrigerant is read, the pressure directly You can know. Therefore, the expansion valve 3e is controlled by the pressure-sensitive actuator 33 by combining the temperature-load characteristic of the shape memory alloy spring 62 so as to be similar to the pressure-load characteristic that the pressure-sensitive actuator 33 has. Similar control is possible.

  Next, the coefficient of performance of the refrigeration cycle is exhibited while exhibiting the functional characteristics of the actuator that the expansion valve 3, 3a, 3b, 3c, 3d, 3e as described above is controlled so as to maintain the pressure on the low pressure side constant. A method for operating the refrigeration cycle that maintains the state in which the maximum value will be described. In this description, reference is made to the refrigeration cycle having the configuration shown in FIG.

FIG. 9 is a Mollier diagram for explaining the operation control method of the refrigeration cycle.
In the refrigeration cycle using carbon dioxide as a refrigerant, as shown by ABCD-A in FIG. 9, the refrigerant in the gas phase is compressed by the compressor 1 to be a high-temperature / high-pressure refrigerant (A− B) The high-temperature / high-pressure refrigerant is cooled by the gas cooler 2 and the internal heat exchanger 6 (BC), and the cooled refrigerant is adiabatically expanded by the expansion valve 3 to be a low-temperature / low-pressure refrigerant ( CD), the low-temperature / low-pressure refrigerant is evaporated by the evaporator 4 and returned to the compressor 1 through the accumulator 5 and the internal heat exchanger 6 (D-A). When the expansion valve 3 expands the refrigerant and the pressure falls below the saturated liquid line SL, the refrigerant enters a gas-liquid two-phase state, and when it evaporates in the evaporator 4, it takes away latent heat of vaporization from the air in the passenger compartment. Thus, the cooling operation is performed.

  Here, the expansion valve 3 is controlled so that the low pressure side, that is, the pressure between D and A maintains a predetermined pressure (for example, 3.5 MPa). On the other hand, the discharge capacity of the compressor 1 is controlled by the capacity control unit 8. Here, a difference (Pd−Ps) between the discharge pressure Pd and the suction pressure Ps is first set by a predetermined difference set by an external signal. A control method is adopted so as to maintain the pressure ΔP. This differential pressure control is described in Japanese Patent No. 3963619, and the difference between the discharge pressure Pd and the suction pressure Ps can be maintained at a predetermined differential pressure ΔP, and the predetermined differential pressure ΔP is It can be freely set by an external signal.

  The pressure of the refrigerant inlet 22 of the expansion valve 3 is substantially equal to the discharge pressure Pd of the compressor 1 and the pressure of the refrigerant outlet 24 of the expansion valve 3 if the pressure loss of the gas cooler 2, the internal heat exchanger 6 and these pipes is ignored. Is substantially equal to the suction pressure Ps of the compressor 1 if the pressure loss of the evaporator 4, the accumulator 5, the internal heat exchanger 6 and these pipes is ignored, and the suction pressure Ps is set to a predetermined pressure by the expansion valve 3. Controlled to maintain. For this reason, the pressure at the refrigerant inlet 22 of the expansion valve 3 becomes a pressure (discharge pressure Pd) obtained by adding a predetermined differential pressure ΔP to control the compressor 1 to the predetermined pressure. This means that the pressure at the refrigerant inlet 22 of the expansion valve 3 can be freely set by an external signal of the capacity control unit 8 that sets the differential pressure ΔP.

  In order to operate the refrigeration cycle in a state where the coefficient of performance is maximized, the temperature and pressure of the refrigerant at the refrigerant inlet 22 of the expansion valve 3 are on the optimum control line CL indicated by the wavy line on the Mollier diagram of FIG. It is said that it is good. For this purpose, a set pressure (3.5 MPa) to be controlled from the pressure on the optimum control line CL corresponding to the temperature of the refrigerant at the refrigerant inlet 22 of the expansion valve 3 or the outlet of the gas cooler 2 on the low pressure side of the expansion valve 3. The differential pressure obtained by subtracting () may be the set differential pressure for controlling the discharge capacity of the compressor 1.

  For this reason, when the cooling load becomes low, the set differential pressure of the capacity control valve 7 that controls the compressor 1 is set to a small value. The set differential pressure ΔP1 is the low pressure side pressure controlled by the expansion valve 3, and What is necessary is just to make it the difference with the pressure on the optimal control line CL corresponding to the temperature of the refrigerant | coolant in the refrigerant inlet 22 of the expansion valve 3. FIG. Thereby, a refrigerating cycle changes according to A1-B1-C1-D1-A1 on a Mollier diagram.

  Here, regarding the control of the capacity control unit 8 of the compressor 1, the differential pressure control for setting the difference between the discharge pressure Pd and the suction pressure Ps to the predetermined differential pressure ΔP has been described. However, the suction pressure Ps is set to the predetermined pressure. Except for a general suction pressure control method which is maintained, the control is not limited to the differential pressure control as long as the discharge pressure Pd can be achieved. As the capacity control unit 8, for example, an ON-OFF control or a flow rate control for controlling the discharge flow rate to be constant can be used while monitoring the discharge pressure Pd of the compressor 1.

Next, the capacity control unit 8 that controls the capacity control valve 7 of the compressor 1 will be described.
FIG. 10 is a diagram illustrating a configuration example of the capacity control unit.
The capacity control unit 8 includes a central processing unit (CPU) 71 that controls the entire system, a ROM (read only memory) 72 that stores programs necessary for differential pressure control, and the central processing unit 71. Includes a random access memory (RAM) 73 for storing a program for executing operations and data being processed, and an input / output interface 74 for inputting / outputting signals, which are connected to each other via a bus. The input / output interface 74 is connected to the pressure sensor 9 and the temperature sensors 10 and 11 and has a function of receiving these detection signals and converting them into digital signals. The capacity control unit 8 also includes a valve drive unit 75 that controls and drives the capacity control valve 7 of the compressor 1 based on the calculation result of the central processing unit 71 received via the input / output interface 74. The ROM 72 stores data of a pressure correspondence table on the optimum control line CL corresponding to the outlet temperature of the gas cooler 2. Although not shown, the input / output interface 74 is connected to a main controller of a vehicle air conditioner that is a host controller of the capacity controller 8.

  With the hardware configuration as described above, it is possible to realize a processing function related to the operation method of the refrigeration cycle. Next, the capacity control unit 8 controls the compressor 1 so that the coefficient of performance of the refrigeration cycle is maximized by exerting a function specific to the expansion valve 3 that controls the low-pressure side pressure constant. A specific example of the operation control method will be described.

FIG. 11 is a flowchart showing a first operation control method of the refrigeration cycle.
First, the central processing unit 71 acquires the outlet temperature Tg of the gas cooler 2 acquired from the temperature sensor 10 and the blowing temperature Te of air that has passed through the evaporator 4 (steps S1 and S2). Next, the discharge pressure Pd of the compressor 1 acquired from the pressure sensor 9 is detected (step S3), and the discharge pressure Pd and a predetermined allowable value (for example, 13.5 MPa) allowed in the high-pressure circuit of the refrigeration cycle are obtained. Compare (step S4). Here, when the discharge pressure Pd exceeds the permissible value, it is a very dangerous state. Therefore, the set differential pressure of the capacity control valve 7 is changed to be small, and the valve drive unit 75 is changed. The capacity control valve 7 is driven with a current corresponding to the set differential pressure (step S5).

  In the normal case where the discharge pressure Pd does not exceed the allowable value, the target differential pressure is calculated (step S6). That is, the central processing unit 71 refers to the data in the correspondence table stored in the ROM 72 and determines the pressure on the optimum control line CL corresponding to the outlet temperature Tg of the gas cooler 2 (ie, the isothermal line and the optimum control line CL). The pressure at the intersecting position) is calculated, the evaporation pressure corresponding to the air blowing temperature Te is calculated, and the target differential pressure is obtained from these differences. The central processing unit 71 changes the set differential pressure of the capacity control valve 7 to the target differential pressure, and the valve driving unit 75 drives the capacity control valve 7 with a current corresponding to the changed set differential pressure ( Step S7). Thereby, the capacity of the compressor 1 is controlled so that the difference between the discharge pressure Pd and the suction pressure Ps becomes the set pressure, and the lower limit of the differential pressure is set to a constant pressure by the low-pressure side control function by the expansion valve 3. By fixing, the upper limit of the differential pressure is controlled to the pressure on the optimum control line CL.

FIG. 12 is a flowchart showing a second operation control method of the refrigeration cycle.
This operation control method is different from the operation control method shown in FIG. 11 in that the temperature detection procedure is performed after the abnormal high pressure determination step. First, the central processing unit 71 detects the discharge pressure Pd of the compressor 1 acquired from the pressure sensor 9 (step S11), and compares the discharge pressure Pd with a predetermined allowable value (for example, 13.5 MPa) (step S11). S12). Here, when the discharge pressure Pd exceeds the allowable value, the set differential pressure of the capacity control valve 7 is changed to be small, and the valve drive unit 75 drives the capacity control valve 7 with a current corresponding thereto. (Step S13).

  Next, the central processing unit 71 acquires the outlet temperature Tg of the gas cooler 2 acquired from the temperature sensor 10 (step S14), acquires the blowing temperature Te of the air that has passed through the evaporator 4 (step S15), and the target differential pressure Is calculated (step S16). The central processing unit 71 changes the set differential pressure of the capacity control valve 7 to the target differential pressure, and the valve drive unit 75 drives the capacity control valve 7 with a current corresponding to the changed set differential pressure ( Step S17).

FIG. 13 is a flowchart showing a third operation control method of the refrigeration cycle.
In this operation control method, first, the central processing unit 71 detects the discharge pressure Pd of the compressor 1 acquired from the pressure sensor 9 (step S21), and the discharge pressure Pd and a predetermined allowable value (for example, 13.5 MPa). ) Is compared (step S22). Here, when the discharge pressure Pd exceeds the allowable value, the setting of the capacity control valve 7 is changed so that the discharge capacity decreases, and the valve drive unit 75 drives the capacity control valve 7 with a current corresponding thereto. (Step S23).

  In the normal case where the discharge pressure Pd does not exceed the allowable value, the central processing unit 71 acquires the outlet temperature Tg of the gas cooler 2 acquired from the temperature sensor 10 (step S24), and calculates the optimum outlet pressure Pg of the gas cooler 2. (Step S25). That is, the central processing unit 71 refers to the data in the correspondence table stored in the ROM 72 and obtains the optimum outlet pressure Pg that is the pressure on the optimum control line CL from the outlet temperature Tg of the gas cooler 2. Then, the central processing unit 71 compares the determined optimum outlet pressure Pg with the previously detected discharge pressure Pd of the compressor 1 (step S26). Here, when the discharge pressure Pd is higher than the optimum outlet pressure Pg, the central processing unit 71 changes the setting of the capacity control valve 7 so that the discharge capacity decreases (step S23), and the discharge pressure Pd becomes the optimum outlet pressure Pg. If it is lower, the setting of the capacity control valve 7 is changed so as to increase the discharge capacity (step S27). In this way, when the setting of the capacity control valve 7 is changed so that the discharge pressure Pd approaches the optimum outlet pressure Pg, the valve drive unit 75 causes the capacity control valve 7 to be turned on with a current corresponding to the changed set capacity. Will drive. Here, in this operation control method, it is based on the assumption that the discharge pressure Pd, the outlet pressure of the gas cooler 2 and the pressure of the refrigerant outlet 24 of the expansion valve 3 are substantially equal, whereby the discharge pressure Pd becomes the outlet of the gas cooler 2. Feedback control is performed so that the optimum outlet pressure Pg corresponding to the temperature Tg is obtained, and the pressure of the refrigerant outlet 24 of the expansion valve 3 is controlled to the pressure on the optimum control line CL.

It is a figure which shows the refrigerating cycle to which the expansion valve which concerns on 1st Embodiment is applied. It is a center longitudinal cross-sectional view which shows the structure of the expansion valve which concerns on 1st Embodiment. It is a center longitudinal cross-sectional view which shows the structure of the expansion valve which concerns on 2nd Embodiment. It is a center longitudinal cross-sectional view which shows the structural example of the expansion valve which concerns on 2nd Embodiment, and an expansion valve attachment block. It is a center longitudinal cross-sectional view which shows the structural example of the expansion valve and expansion valve attachment block which concern on 3rd Embodiment. It is a center longitudinal cross-sectional view which shows the structural example of the expansion valve which concerns on 4th Embodiment, and an expansion valve attachment block. It is a center longitudinal cross-sectional view which shows the structural example of the expansion valve which concerns on 5th Embodiment, and an expansion valve attachment block. It is a center longitudinal cross-sectional view which shows the structural example of the expansion valve which concerns on 6th Embodiment, and an expansion valve attachment block. It is a Mollier diagram explaining the operation control method of a refrigerating cycle. It is a figure which shows the structural example of a capacity | capacitance control part. It is a flowchart which shows the 1st operation control method of a refrigerating cycle. It is a flowchart which shows the 2nd operation control method of a refrigerating cycle. It is a flowchart which shows the 3rd operation control method of a refrigerating cycle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Gas cooler 3, 3a, 3b, 3c, 3d, 3e Expansion valve 4 Evaporator 5 Accumulator 6 Internal heat exchanger 7 Capacity control valve 8 Capacity control part 9 Pressure sensor 10, 11 Temperature sensor 21 Body 22 Refrigerant inlet 23 Strainer 24 Refrigerant outlet 25 Valve hole 26 Fixed orifice 27 Valve seat 28 Valve element 29 Spring 30 Spring receiving member 31 Low pressure chamber 32 Shaft 33 Pressure sensitive actuator 34 First housing 35 Diaphragm 36 Second housing 37 Snap plate 38 Spring 39 Spring receiving member 40 Adjust Screw 41 Shape memory alloy spring 42 Spring receiving member 43 E ring 44 Through hole 45, 46 Shaft 47 Communication hole 48 Through hole 49 O-ring 50 Expansion valve mounting block 51 Mounting hole 52 High pressure refrigerant inlet 53 Low Coolant outlet 54 fixing plate 55 bolt 56 spring receiving member 57 returns low pressure refrigerant outlet 58 returns low pressure refrigerant inlet 59 bellows 60 housing 61 spring 62 SMA spring

Claims (12)

In the expansion valve having a valve part for controlling the refrigerant flow rate,
An actuator that controls the valve unit so that the pressure or temperature corresponding to the sensed temperature or the sensed temperature is maintained at a predetermined pressure by sensing the pressure or temperature of the expanded low-pressure refrigerant;
A temperature-sensitive actuator that senses the temperature of the refrigerant on the low-pressure side and biases the valve portion in the valve opening direction;
An expansion valve characterized by comprising:   The valve section includes a valve body that is disposed downstream of the valve hole and receives high-pressure refrigerant in the valve opening direction, and a shaft that is disposed upstream of the valve hole and receives high-pressure refrigerant in the valve closing direction. The expansion valve according to claim 1, wherein the valve body and the shaft are formed so as to operate integrally with a substantially equal pressure receiving area.   The valve portion includes a valve body that is disposed downstream of the valve hole and receives high-pressure refrigerant in the valve opening direction, and a shaft that is disposed upstream of the valve hole and receives high-pressure refrigerant in the valve closing direction. The valve body and the shaft are formed so as to operate integrally, and the pressure receiving area of the valve body is made larger than the pressure receiving area of the shaft so that the valve can be easily opened as the pressure increases. Expansion valve.   The actuator includes a pressure-sensitive member that displaces in the valve opening direction of the valve unit when a pressure drop of the low-pressure side refrigerant is sensed, and a shaft that transmits the displacement of the pressure-sensitive member to the valve body. The expansion valve according to claim 1.   The expansion valve according to claim 4, wherein the pressure-sensitive member is a diaphragm.   6. The expansion valve according to claim 5, wherein the diaphragm is supported by a snap plate on a surface opposite to a surface receiving the pressure of the refrigerant on the low pressure side.   2. The temperature sensing member according to claim 1, wherein the actuator is a temperature-sensitive member having a characteristic that a load changes so as to urge the valve body of the valve portion in a valve closing direction when a temperature rise of the low-pressure side refrigerant is detected. Expansion valve.   The expansion valve according to claim 7, wherein the temperature sensitive member is a shape memory alloy spring. Detecting the pressure or temperature of the expanded low-pressure side refrigerant and controlling the refrigerant flow rate so that the pressure sensed or the pressure corresponding to the sensed temperature is maintained at a predetermined pressure, and the temperature of the low-pressure side refrigerant An expansion valve comprising a temperature sensing actuator configured to sense and set a flow rate that can be increased as the sensed temperature increases;
An expansion valve mounting block in which a first piping joint and a mounting hole for accommodating the entire expansion valve therein are formed coaxially, and a second piping joint is formed in a direction perpendicular to the axis;
An inflating device comprising: Detecting the pressure or temperature of the expanded low-pressure side refrigerant and controlling the refrigerant flow rate so that the pressure sensed or the pressure corresponding to the sensed temperature is maintained at a predetermined pressure, and the temperature of the low-pressure side refrigerant An expansion valve comprising a temperature sensing actuator configured to sense and set a flow rate that can be increased as the sensed temperature increases;
A first pipe joint and a second pipe joint in which a mounting hole for accommodating the entire expansion valve is coaxially formed and a high-pressure pipe is connected in a direction orthogonal to the axis thereof, for sending out the expanded refrigerant A third pipe joint to which the low-pressure pipe is connected and a fourth pipe joint to which a return low-pressure pipe for receiving the refrigerant evaporated by the evaporator is connected are formed, and the fourth pipe joint and the first pipe joint are formed. An expansion valve mounting block in which a pressure-sensitive actuator of the expansion valve is arranged so as to sense the pressure of the passage communicating with the pipe joint;
An inflating device comprising: A variable capacity compressor controlled to maintain a difference between the discharge pressure and the suction pressure at a predetermined set differential pressure set by an external signal; a gas cooler for cooling the refrigerant discharged from the variable capacity compressor; An actuator for controlling the flow rate of the refrigerant so that the pressure or temperature corresponding to the sensed temperature or the sensed temperature is maintained at a predetermined pressure by sensing the pressure or temperature of the low-pressure side refrigerant expanded while the refrigerant is expanded. Control of a refrigeration cycle comprising an expansion valve having a temperature-sensitive actuator that is set so that the flow rate that can be passed increases as the temperature of the refrigerant increases, and an evaporator that evaporates the refrigerant maintained at a predetermined pressure A method,
Detecting the outlet temperature of the gas cooler and the blowing temperature of the air that has passed through the evaporator;
Calculate the target differential pressure from the pressure on the optimal control line corresponding to the outlet temperature and the pressure corresponding to the blowing temperature,
Setting the set differential pressure of the variable displacement compressor to the target differential pressure;
An operation control method for a refrigeration cycle, comprising: a step. A variable capacity compressor whose capacity is controlled to a predetermined capacity set by an external signal, a gas cooler that cools the refrigerant discharged from the variable capacity compressor, and a low-pressure side refrigerant that is expanded while expanding the cooled refrigerant. A flow rate that can flow as the temperature of the low-pressure-side refrigerant increases, and an actuator that controls the flow rate of the refrigerant so that the pressure sensed or the pressure corresponding to the sensed temperature is maintained at a predetermined pressure. An operation control method for a refrigeration cycle, comprising: an expansion valve having a temperature-sensitive actuator that is set so as to increase; and an evaporator that evaporates the refrigerant maintained at a predetermined pressure,
Detecting the discharge pressure of the variable capacity compressor and the outlet temperature of the gas cooler;
Calculate the optimum pressure on the optimum control line corresponding to the outlet temperature,
Changing the predetermined capacity of the variable capacity compressor so that the discharge pressure becomes the optimum pressure;
An operation control method for a refrigeration cycle, comprising: a step.

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