CONTROL VALVE FOR SCROLL COMPRESSOR

Abstract

 A control valve (1) includes: a body (2) having a discharge pressure chamber (20), a first pressure chamber (22), a suction pressure chamber (28), a second pressure chamber (30), a valve hole (24), and a reference pressure chamber (S); and a valve element (36) that moves toward and away from the valve hole (24) to adjust the opening degree of the valve section. The reference pressure chamber (S) is a sealed space formed between any two of the pressure chambers. The valve element (36) operates depending on the pressures in at least the two pressure chambers.

Description

[0001] The present invention relates to a control valve for a scroll compressor and, in particular, to a structure of a control valve for controlling back pressure for pressing a fixed scroll and a movable scroll of a scroll compressor against each other.

[0002] A scroll compressor including a fixed scroll and a movable scroll is known as an example of a motor compressor (refer to JP 2018-150835 A). In the compressor, fluid introduced into a suction chamber is guided into a compression chamber formed between the scrolls, and the movable scroll is then rotated. By gradually reducing the volume of the compression chamber in this manner, the fluid can be compressed. The compressed fluid is led out from the discharge chamber. A back pressure chamber is formed on a side opposite the fixed scroll with respect to the movable scroll. The pressure in the back pressure chamber (also referred to as "back pressure") presses the scrolls against each other, which ensures the compression performance. Thus, this prevents poor compression due to separation of the scrolls caused by increased pressures during compressing operation.

[0003] In order to increase the responsiveness of control on the back pressure, such a compressor typically uses the high pressure in the discharge chamber (also referred to as "discharge pressure") to increase the back pressure. If the back pressure becomes higher than necessary, however, the frictional resistance between the scrolls increases, and the power loss increases. A control valve is therefore provided between the discharge chamber and the back pressure chamber to control the back pressure depending on the discharge pressure. Thus, such control characteristics in which the discharge pressure and the back pressure are substantially proportional to each other are achieved (refer to JP 2018-536110 A).

[0004] In the control valve of JP 2018-536110 A, a valve hole communicating with the discharge chamber, a first pressure chamber communicating with the back pressure chamber, a suction pressure chamber communicating with the suction chamber, a reference pressure chamber into which air is introduced at a reference pressure, and a second pressure chamber communicating with the back pressure chamber are arranged in this order from one end side of a body. A movable member that can shift integrally with the valve element along the axis of the body is provided. The movable member is constituted by three segments (first to third segments) connected in series. The first segment slidably extends through a partition in the body, and a valve element is formed at a leading end of the first segment. The second segment and the third segment each have a rubber at its periphery and are connected with an inner face of the body at the rubbers in a fluid seal manner.

[0005] The first pressure chamber is formed between the valve hole and the partition, and the suction pressure chamber is formed between the partition and the second segment. The reference pressure chamber is formed between the second segment and the third segment, and the second pressure chamber is formed on a side opposite the reference pressure chamber with respect to the third segment. The reference pressure chamber is open to the atmosphere. Such a structure enables the second segment to sense the suction pressure in the compressor to control the back pressure. As the back pressure increases, the pressure acting on the valve element in the valve closing direction increases, which properly suppresses the increases of the back pressure.

Related Art List

[0006] 

(1) JP 2018-150835 A

(2) JP 2018-536110 A

[0007] In order to fix the rubbers of the segments to the inner face of the body, however, a troublesome process is required. Furthermore, if refrigerant in the suction pressure chamber of the second pressure chamber leaks into the reference pressure chamber owing to a defect or the quality of the rubber, the refrigerant may be released to the atmosphere.

[0008] The present invention has been made in view of such circumstances, and one object thereof is to prevent external leakage of fluid via a reference pressure chamber in a control valve for a scroll compressor.

[0009] A control valve according to an aspect of the present invention is to be applied to a scroll compressor in which a fixed scroll and a movable scroll are pressed against each other by a pressure in a back pressure chamber and in which a fluid introduced into a suction chamber is compressed in a compression chamber between the fixed scroll and the movable scroll and discharged from a discharge chamber, and controls the pressure in the back pressure chamber. The control valve includes: a body including a discharge pressure chamber communicating with the discharge chamber, a first pressure chamber communicating with the back pressure chamber, a suction pressure chamber communicating with the suction chamber, a second pressure chamber communicating with the back pressure chamber, a valve hole through which the discharge pressure chamber and the first pressure chamber communicate with each other, and a reference pressure chamber being a sealed space formed between any two of the pressure chambers; and a valve element that operates depending on pressures in at least the two pressure chambers, and moves toward or away from the valve hole to adjust an opening degree of a valve section.

[0010] As a result of applying the control valve according to this aspect to a scroll compressor, the back pressure that varies depending on the discharge pressure and the suction pressure can be achieved. Because the reference pressure chamber is a sealed space inside the body, air need not be introduced. Because the sealed space is formed between two pressure chambers, the reference pressure chamber is included in the inside of the body. Therefore, even if the reference pressure chamber is damaged, fluid is not released from the reference pressure chamber to the atmosphere.

FIG. 1 is a cross-sectional view of a structure of a control valve according to an embodiment.

FIG. 2 is an exploded view illustrating a method of assembly of the control valve.

[0011] An embodiment of the invention will now be described. The description is not intended to limit the scope of the present invention, but to exemplify the invention.

[0012] The embodiment of the present invention will now be described in detail with reference to the drawings. In the description below, for convenience of description, the positional relationship in each structure may be expressed with reference to how the structure is depicted in the drawings.

[0013] FIG. 1 is a cross-sectional view of a structure of a control valve according to the embodiment.

[0014] The control valve 1 is applied to a scroll compressor (hereinafter also simply referred to as a "compressor") driven by a motor. The compressor is installed in a refrigeration cycle of an automotive air conditioner. The refrigeration cycle is a so-called supercritical refrigeration cycle in which carbon dioxide is used as refrigerant, and the pressure of the refrigerant is therefore increased to a supercritical range exceeding its critical temperature. Thus, the control valve 1 is also required to have a high pressure resistance strength.

[0015] In the compressor, a fixed scroll and a movable scroll are pressed against each other by the pressure (back pressure) in a back pressure chamber. The compressor compresses refrigerant, which has been introduced into the suction chamber, in the compression chamber formed between the scrolls, and discharges the compressed refrigerant through a discharge chamber. Part of the discharged refrigerant is introduced into the back pressure chamber via the control valve 1. The control valve 1 is integrated with the compressor and controls back pressure therein. Because such a compressor is known as described in JP 2018-150835 A, for example, detailed description thereof is omitted.

[0016] The control valve 1 has a body 2 having a stepped cylindrical shape. The body 2 includes a first body 4 and a second body 6, which are coaxially connected with each other. An external thread portion 5 is formed at a lower end of the first body 4, an internal thread portion 7 is formed at an upper end of the second body 6, and the first body 4 is screwed into the second body 6. The first body 4 and the second body 6 are thus connected in series. A power element 8 is mounted in lower part of the second body.

[0017] The body 2 has ports 10, 12, and 14 arranged in this order from an upper end thereof. Among these ports, the port 10 is formed at an upper end of the first body 4 and the port 12 is formed at a lateral side of the first body 4. The port 14 is located at a lateral side of the second body 6. The port 10 functions as a "discharge chamber communication port", which communicates with the discharge chamber of the compressor. The port 12 functions as a "back pressure chamber communication port", which communicates with the back pressure chamber of the compressor. The port 14 functions as a "suction chamber communication port", which communicates with the suction chamber of the compressor.

[0018] Partitions 16 and 18 are formed to axially divide the inside of the first body 4 into three regions. A discharge pressure chamber 20 is formed on the upper side of the partition 16, and a first pressure chamber 22 is formed on the lower side of the partition 16. In addition, a valve hole 24 is formed to axially pass through the center of the partition 16. The discharge pressure chamber 20 and the first pressure chamber 22 communicate with each other through the valve hole 24. A valve seat 26 is formed at an open end of the valve hole 24 of the side of the first pressure chamber 22. The discharge pressure chamber 20 communicates with the discharge chamber of the compressor through the port 10. The first pressure chamber 22 communicates with the back pressure chamber through the port 12. A discharge pressure Pd introduced into the discharge pressure chamber 20 changes to a back pressure Pb as a result of passing through a valve section (valve hole 24), and then delivered from the first pressure chamber 22 toward the back pressure chamber.

[0019] A suction pressure chamber 28 is formed on the lower side of the partition 18. More specifically, the suction pressure chamber 28 is formed as a space surrounded by the first body 4, the second body 6, and the power element 8. The suction pressure chamber 28 communicates with the suction chamber through the port 14, and a suction pressure Ps is introduced into the suction pressure chamber 28. A second pressure chamber 30 is formed below the power element 8 in the second body 6. Specifically, the power element 8 is mounted in the body 2 in a manner that the power element 8 separates the suction pressure chamber 28 from the second pressure chamber 30. A plurality of slits 31 that are open radially are formed at a lower end of the second body 6. The second pressure chamber 30 communicates with the back pressure chamber through the opening at the lower end of the second body 6, and the back pressure Pb is thus introduced into the second pressure chamber 30.

[0020] A guiding passage 32 is formed to axially pass through the center of the partition 18. An elongated valve drive member 34 axially extends through the guiding passage 32. The valve drive member 34 is slidably supported in the guiding passage 32. The valve drive member 34 has a valve element 36 having a tapered shape at one end (upper end) thereof, and is in contact with the power element 8 at the other end (lower end) thereof. The valve element 36 moves toward or away from the valve hole 24 to adjust the opening degree of the valve section.

[0021] The valve drive member 34 has, at the lower end thereof, a flange portion 38 radially extending outward. A spring 40 (biasing member) for biasing the valve drive member 34 in the valve opening direction is provide between a bottom face of the first body 4 and the flange portion 38. The characteristics of the control valve 1 can be adjusted by adjustment of the insertion amount of the first body 4 into the second body 6. A lower end face of the valve drive member 34 is a spherical surface that is in smooth contact with the center of an upper face of the power element 8. Even when the power element 8 is inclined, this structure can absorb the inclination for operable coupling of the valve drive member 34 and the power element 8.

[0022] In the present embodiment, a clearance between the valve drive member 34 and the guiding passage 32 is set to be narrow, which achieves a so-called clearance seal that prevents leakage of refrigerant from the first pressure chamber 22 to the suction pressure chamber 28. Alternatively, in a modification, a sealing member such as an O ring may be provided between the valve drive member 34 and the guiding passage 32 to prevent flow of refrigerant.

[0023] A filter member 42 for preventing entry of foreign materials through the port 10 is fitted into an upper end opening of the first body 4. Refrigerant discharged from the compressor may contain foreign materials such as metal powder, and the filter member 42 prevents or reduces entry of such foreign materials into the control valve 1. The filter member 42 has a filter 44 having a bottomed cylindrical shape, and a metal plate 46 having a ring shape that reinforces the open end of the filter 44. The filter 44 is made of a metal mesh. The filter member 42 with its bottom side up is fixed in such a manner that the metal plate 46 is press-fitted into the body 2. The filter member 42 is mounted inside the body 2 s illustrated in FIG. 1, which prevents the filter member 42 from being deformed by contact with external structures.

[0024] A filter member 43 having a cylindrical shape is also mounted at the port 12. The filter member 43 includes a mesh for preventing entry of foreign materials into the body 2.

[0025] The power element 8 has a housing 50 having a cylindrical shape. An upper end opening of the housing 50 is sealed by a diaphragm 52, and a lower end opening thereof is sealed by a diaphragm 54. A reference pressure chamber S in a vacuum state is formed inside the power element 8. The reference pressure chamber S is a sealed space filled with a reference pressure Po. The diaphragm 52 functions as a "first diaphragm", and the diaphragm 54 functions as a "second diaphragm". The diaphragms 52 and 54 are both metal diaphragms.

[0026] An upper part and a lower part of an inner face the housing 50 are annularly cut out to form stepped portions 56 and 58. In addition, a disc spring 60 is fitted to the stepped portion 56, and a disc spring 62 is fitted to the stepped portion 58. The disc springs 60 and 62 constitute a "spring member", the disc spring 60 functions as a "first disc spring", and the disc spring 62 functions as a "second disc spring". In the present embodiment, the disc springs 60 and 62 are both layered disc springs to ensure a high pressure resistance strength. In a modification, however, at least one of the disc springs 60 and 62 may be a disc spring of a single layer (single disc).

[0027] A thin-film abrasion-resistant sheet (thin film member) may be provided between the disc spring 60 and the diaphragm 52 so as to minimize abrasion therebetween. Similarly, an abrasion-resistant sheet may also be provided between the disc spring 62 and the diaphragm 54. An abrasion-resistant sheet may also be provided between the disc springs constituting the layers of disc springs. For the abrasion-resistant sheet, a thin sheet made of fluororesin such as polytetrafluoroethylene or a polyimide film may be used, for example.

[0028] A core 64 having a stepped columnar shape is provided between the disc spring 60 and the disc spring 62. The core 64 has a flange portion 66 extending radially outward at a central part in the axial direction. A clearance between the inner face of the housing 50 and the outer face of the flange portion 66 is set to be narrow, which restrict shifting of the core 64 in the radial direction. Thus, the core 64 is shifted along the axis in the power element 8.

[0029] The disc spring 60 has a substantially disc shape, but the periphery thereof has a tapered portion 61 that is slightly inclined downward. The whole disc spring 60 therefore has a shape that slightly expands toward the suction pressure chamber 28. In contrast, the disc spring 62 also has a substantially disc shape, but the periphery thereof has a tapered portion 63 that is slightly inclined upward. The whole disc spring 62 therefore has a shape that slightly expands toward the second pressure chamber.

[0030] The diaphragm 52 is arranged to press the disc spring 60 from above, and the periphery thereof is annularly welded along the contact with the upper face of the housing 50. Thus, the diaphragm 52 has a shape along the upper face of the disc spring 60. The disc spring 60 is arranged to be in contact with the lower face of the diaphragm 52. In contrast, the diaphragm 54 is arranged to press the disc spring 62 from below, and the periphery thereof is annularly welded along the contact with the lower face of the housing 50. Thus, the diaphragm 54 has a shape along the lower face of the disc spring 62. The disc spring 62 is arranged to be in contact with the upper face of the diaphragm 54.

[0031] The upper face of the core 64 is in contact with a flat portion on the inner side of the tapered portion 61 of the lower face of the disc spring 60, and the lower face of the core 64 is in contact with a flat portion on the inner side of the tapered portion 63 of the upper face of the disc spring 62. Even when the diaphragms 52 and 54 are shifted (deformed) by the refrigerant pressure, this structure makes the shift be along the axis and thus enables the valve drive member 34 to be stably driven in the axial direction.

[0032] In the present embodiment, the stepped portion 56 has an inner diameter larger than the inner diameter of the stepped portion 58, and the disc spring 60 has an outer diameter larger than the outer diameter of the disc spring 62. In other words, an upper end face of the housing 50 has an inner diameter larger than the inner diameter of a lower end face thereof. Thus, the two diaphragms have different effective pressure-receiving diameter (effective pressure-receiving area) from each other. The effective pressure-receiving area A1 of the diaphragm 52 is larger than the effective pressure-receiving area A2 of the diaphragm 54 (A1 > A2). The diaphragm 52 senses the suction pressure Ps and is thus shifted in the axial direction of the valve drive member 34 (the opening and closing directions of the valve section) . The diaphragm 54 senses the back pressure Pb and is thus shifted in the axial direction of the valve drive member 34 (the opening and closing directions of the valve section). Because a rigid member (core 64) is present between the diaphragm 52 and the diaphragm 54, the movements of the two diaphragms are linked with each other. Thus, the power element 8 is moved (in tandem) by sensing two pressures, which are the suction pressure Ps and the back pressure Pb.

[0033] In addition, the effective pressure-receiving area A1 of the diaphragm 52 is larger than the cross-sectional area B of the guiding passage 32, and the effective pressure-receiving area A2 of the diaphragm 54 is larger than the difference between the cross-sectional area B of the guiding passage 32 and the cross-sectional area C of the valve hole 24 (A1 > B, A2 > B-C). According to this structure, the back pressure Pb substantially acts on the valve drive member 34 in the valve closing direction, and the suction pressure Ps and the discharge pressure Pd acts on the valve drive member 34 in the valve opening direction. When the effective pressure-receiving areas (the pressure-receiving areas after being balanced out) of the valve drive member 34 and the power element 8 are referred to as the effective pressure-receiving area Ad on which the discharge pressure Pd acts, the effective pressure-receiving area As on which the suction pressure Ps acts, and the effective pressure-receiving area Ab on which the back pressure Pb, the following relation is satisfied: As > Ab > Ad. The control valve 1 therefore senses the suction pressure Ps and thus operates to open/close the valve section. Note that, in the present embodiment, in order to achieve predetermined characteristics of the control valve 1, the cross-sectional area B of the guiding passage 32 is larger than the cross-sectional area C of the valve hole 24 and smaller than the effective pressure-receiving areas of the diaphragms 52 and 54 (A1 > A2 > B > C). The relation of these effective pressure-receiving areas can be adjusted depending on desired characteristics of the control valve 1.

[0034] FIG. 2 is an exploded view illustrating a method of assembly of the control valve 1.

[0035] For assembly of the control valve 1, the body 2 and the power element 8 are prepared individually. In addition, the spring 40 is mounted on the valve drive member 34 in advance. Then, as illustrated in FIG. 2, the valve drive member 34 and the power element 8 are inserted in this order from below the body 2. The power element 8 is press-fitted into the lower part of the body 2 in an airtight manner. In this manner, because the power element 8 is a single independent component, the power element 8 can be easily mounted in the body 2 and the control valve 1 can be achieved with a simple structure.

[0036] Next, operations for controlling the control valve 1 will be explained with reference to FIG. 1.

[0037] When the compressor is driven, the movable scroll revolves about the axis of the fixed scroll, and the refrigerant pressure is increased from the suction pressure Ps to the discharge pressure Pd. An air conditioner for a vehicle performs air conditioning by the discharged refrigerant circulating in the refrigeration cycle. In this process, part of the discharged refrigerant is supplied through the port 10 of the control valve 1.

[0038] At this point, the back pressure Pb of the compressor is controlled by the control valve 1. The valve element 36 is maintained at a valve lifted position at which the force in the valve opening direction caused by the discharge pressure Pd, the force in the valve opening direction caused by the suction pressure Ps, the force in the valve closing direction caused by the back pressure Pb, and the force in the valve opening direction caused by the spring 40 are balanced.

[0039] When either of the discharge pressure Pd and the suction pressure Ps is increased in the process of control of the back pressure Pb, the force acting on the valve element 36 in the valve opening direction increases. Thus, the back pressure Pb also increases to increase the force in the valve closing direction that balances the load on the valve element 36 in the valve opening direction. The present embodiment achieves the control characteristics in which the back pressure Pb increases with the increase in the discharge pressure Pd and the suction pressure Ps.

[0040] As described above, in the present embodiment, application of the control valve 1 to the scroll compressor enables the back pressure Pb to change with the discharge pressure Pd and the suction pressure Ps. Because the power element 8 is provided, the reference pressure chamber S is a sealed space in the body 2, which eliminates the need for leading air into the body 2. Because the sealed space is formed between the suction pressure chamber 28 and the second pressure chamber 30, the reference pressure chamber S is included in the inside of the body 2. Thus, even if the reference pressure chamber S is damaged because a diaphragm is broken or in a case like that, refrigerant is not released from the reference pressure chamber S to the atmosphere.

[0041] More specifically, because a closed reference pressure chamber S is formed inside the power element 8, the need for a passage between the reference pressure chamber S and the outside is eliminated. This reduces the risk for external leakage of refrigerant. Because the reference pressure chamber S is in a vacuum state, the control accuracy is improved as compared with a case where a pressure medium such as air is led in. Specifically, in a case where air is led in, the reference pressure (atmospheric pressure) is affected by the climate change. In the case where a pressure medium including air is enclosed, the reference pressure is affected by the temperature. In this regard, in the present embodiment, because the reference pressure chamber S is in a vacuum state, which is less likely to be affected by these factors. In addition, because the power element 8 that senses the suction pressure Ps and the back pressure Pb is designed as a single component, the power element 8 can be easily mounted in the body 2 and the control valve 1 can be achieved with a simple structure. Because the reference pressure need not be introduced from the outside to the control valve 1, and as a result, the need for also providing a passage for introducing the reference pressure in the compressor is eliminated. This also enables the structure of the compressor to be simplified.

[0042] In addition, the housing 50 is fixed (sealed) to the body 2 and the chambers on respective sides of the housing 50 are pressure chambers separate from each other, which enables a single power element 8 to sense two pressures. The rigid member (core 64) is placed in the middle of the power element 8 and connect the two diaphragms 52 and 54, which enables the movement of the diaphragm 54 to be also transmitted to the valve drive member 34. In other words, the movements of the two diaphragms 52 and 54 can be linked with each other. Because two diaphragms 52 and 54 are included in one power element 8, which eliminates the need for providing two power elements. The control valve 1 can therefore be reduced in size, simplified, and reduced in cost. Furthermore, movements caused by the respective pressures can be transmitted to the valve drive member 34 without any complicated connecting means. This also leads to reduction in size, a simpler structure, and lower cost of the control valve 1.

[0043] Furthermore, the effective pressure-receiving area A1 of the diaphragm 52 and the effective pressure-receiving area A2 of the diaphragm 54 can be individually adjusted (changed). Thus, the degree of dependence of the characteristics on the two pressures (the suction pressure Ps and the back pressure Pb in the present embodiment) that act on the power element 8 can be freely designed.

[0044] In addition, in the refrigeration cycle of the present embodiment, because the pressure of the refrigerant is increased to a supercritical range exceeding its critical temperature, the refrigerant pressure becomes very high. In this regard, because all the components of the power element 8 are made of metal, which ensures a sufficient pressure resistance strength.

[0045] The description of the present invention given above is based upon a certain embodiment. The embodiment is intended to be illustrative only and it will be obvious to those skilled in the art that various modifications could be further developed within the technical idea underlying the present invention.

[0046] In the embodiment described above, an example of a structure in which the first body 4 and the second body 6 are connected with each other with a screw structure (thread portions 5 and 7) has been presented. In a modification, the first body 4 and the second body 6 may be fixed to each other by press fitting. The characteristics of the control valve 1 can be adjusted by adjustment of the amount of press fitting.

[0047] In the embodiment described above, an example in which the power element 8 is press-fitted into the body 2 to achieve sealing therebetween has been presented. In a modification, a sealing member such as an O ring may be provided between the body 2 and the power element 8 to achieve sealing therebetween. In this case, an internal thread portion may be formed on the inner face of the body 2 and an external thread portion may be formed on the outer face of the power element 8, so that the body 2 and the power element 8 are fixed to each other by being screwed together.

[0048] In the embodiment described above, an example in which the valve element 36 is formed integrally with the valve drive member 34 has been presented. In a modification, a valve element and a rod-like transmitting member may be connected to form a valve drive member. In other words, a valve drive member may include a plurality of members.

[0049] In the embodiment described above, the power element 8 is designed so that the effective pressure-receiving area A1 of the diaphragm 52 is larger than the effective pressure-receiving area A2 of the diaphragm 54 (A1 > A2). Depending on the characteristics required of the control valve 1, the effective pressure-receiving area A1 may conversely be smaller than the effective pressure-receiving area A2 (A1 < A2). Alternatively, the effective pressure-receiving area A1 and the effective pressure-receiving area A2 may be equal to each other (A1 = A2). The relation of the effective pressure-receiving areas can be adjusted depending on desired characteristics of the control valve 1.

[0050] In the embodiment described above, an example in which the control valve is applied to a supercritical refrigeration cycle in which carbon dioxide is used as refrigerant has been presented. In a modification, the control valve may be applied to a supercritical refrigeration cycle using refrigerant other than carbon dioxide. Alternatively, the control valve may be applied to a refrigeration cycle that does not function in a supercritical range but in which the pressure of refrigerant becomes high. For example, the control valve may be applied to a refrigeration cycle in which HFC-134a or HFO-1234yf, for example, is used as refrigerant. If a sufficient pressure resistance strength can be achieved, diaphragms made of resin may also be used for the two diaphragms included in the power element.

[0051] While the inside of the power element 8 is in a vacuum state in the embodiment described above, a pressure medium such as air or the like may be enclosed to fill the power element with the reference pressure.

[0052] In the embodiment described above, an example in which the core 64 (rigid member) is provided between the disc spring 60 (first disc spring) and the disc spring 62 (second disc spring) has been presented. In a modification, a different spring (a coil spring, a leaf spring, etc.) may be provided between the first disc spring and the second disc spring.

[0053] Although not mentioned in the embodiment described above, a connecting member such as a shock absorbing member (rubber, for example) may be provided between the valve drive member 34 and the power element 8. This prevents or reduces breakage and damage of the diaphragm 52. The valve drive member may have a shock absorbing member or the like on an end face thereof.

[0054] Although not described in detail in the embodiment, the diaphragm 54, which is an end of the power element 8, is located near the open end (lower end) of the body 2 (see FIG. 1). Thus, the open end of the body 2 can be pressed against a wall face of the fixed scroll, the housing, or the like of the compressor, so that the wall face functions as a stopper that defines the maximum opening degree of the valve section, for example.

[0055] Specifically, when an increase in the discharge pressure Pd causes the valve drive member 34 to move in the valve opening direction, the positions of the diaphragms 52 and 54 of the power element 8 are shifted but the wall face stops the diaphragm 54. In this manner, the positional shift can be restricted to the maximum displacement, that is, the opening degree of the valve section can be restricted to the maximum opening degree. In this case, a connecting member such as a shock absorbing member may be provided between the power element 8 and the stopper (wall face). This prevents or reduces breakage and damage of the power element 8.

[0056] In the embodiment described above, an example of a structure in which the discharge pressure chamber 20, the first pressure chamber 22, the suction pressure chamber 28, and the second pressure chamber 30 are arranged in this order from the leading end of the body 2 has been presented. In a modification, a structure in which the first pressure chamber 22, the discharge pressure chamber 20, the suction pressure chamber 28, and the second pressure chamber 30 are arranged in this order from the leading end of the body 2 may be used. In this case, the effective pressure-receiving areas of the valve drive member 34 and the power element 8 are adjusted, so that the control characteristics similar to that in the embodiment can be achieved.

[0057] In the embodiment described above, a compressor mounted in an automotive air conditioner has been presented as an example of a scroll compressor to which the control valve 1 is applied. In a modification, the control valve 1 may be applied to a scroll compressor to be mounted on an air conditioner for general use (household use or professional use). In addition, the control valve 1 may be applied to a scroll compressor in which working fluid other than refrigerant is used.

Claims

1. A control valve (1) to be applied to a scroll compressor in which a fixed scroll and a movable scroll are pressed against each other by a pressure in a back pressure chamber and in which a fluid introduced into a suction chamber is compressed in a compression chamber between the fixed scroll and the movable scroll and discharged from a discharge chamber, the control valve (1) controlling the pressure in the back pressure chamber, the control valve (1) comprising:

a body (2) including a discharge pressure chamber (20) communicating with the discharge chamber, a first pressure chamber (22) communicating with the back pressure chamber, a suction pressure chamber (28) communicating with the suction chamber, a second pressure chamber (30) communicating with the back pressure chamber, a valve hole (24) through which the discharge pressure chamber (20) and the first pressure chamber (22) communicate with each other, and a reference pressure chamber (S) being a sealed space formed between any two of the pressure chambers; and

a valve element (36) that operates depending on pressures in at least the two pressure chambers, and moves toward or away from the valve hole (24) to adjust an opening degree of a valve section.

2. The control valve (1) according to claim 1, further comprising:

a power element (8) including the reference pressure chamber (S) therein, and being mounted in the body (2), the power element (8) separates the suction pressure chamber (28) from the second pressure chamber (30); and

a valve drive member (34) including the valve element (36) at one end thereof and coming in contact with the power element (8) at another end thereof, wherein

the power element (8) includes:

a housing (50) having a cylindrical shape and being mounted on an inner face of the body (2);

a first diaphragm (52) that seals an end opening of the housing (50), senses a pressure in the suction pressure chamber (28) and is thus shifted in an axial direction of the valve drive member (34);

a second diaphragm (54) that seals another end opening of the housing (50), senses a pressure in the second pressure chamber (30), and is thus shifted in the axial direction of the valve drive member (34); and

a spring member (60, 62) placed between the first diaphragm (52) and the second diaphragm (54).

3. The control valve (1) according to claim 2, wherein
the first diaphragm (52) and the second diaphragm (54) are metal diaphragms that are welded to the housing (50).

4. The control valve (1) according to claim 2 or 3, wherein
the housing (50) is press-fitted into the body (2).

5. The control valve (1) according to claim 2 or 3, wherein
the spring member (60, 62) includes:

a first disc spring (60) positioned to be in contact with the first diaphragm (52); and

a second disc spring (62) positioned to be in contact with the second diaphragm (54).

6. The control valve (1) according to claim 5, wherein
the power element (8) includes a core (64) between the first disc spring (60) and the second disc spring (62).

Drawing