Valve

Abstract

The present invention provides a valve that can smoothly change the pressure of a back pressure fluid.　A valve V1 comprises: a housing 60 having a high-pressure space S2 into which a high-pressure fluid Pd flows, back-pressure spaces S3, S3' into which a back-pressure fluid Pb flows, and a low-pressure space S1 into which a low-pressure fluid Ps flows; and a valve body 61 disposed so as to be movable relative to the housing 60. The housing 60 has a first passage 73 provided between the high-pressure space S2 and the back-pressure space S3, and a second passage 78 provided between the back-pressure space S3' and the low-pressure space S1. The valve body 61 has a first valve body part 72 for controlling the opening degree of the first passage 73, and a second valve body part 77 for controlling the opening degree of the second passage 78. The first valve body part 72 and the second valve body part 77 are linked together so that the respective movement directions thereof are opposite to each other in the opening direction and the closing direction.

Description

valve

[0001] The present invention relates to valves, for example, valves for controlling pressure.

[0002] Scroll compressors are one type of compressor used in various industrial fields. This type of compressor is not only highly efficient but also quiet, and is therefore used in a wide range of applications, such as refrigeration cycles.

[0003] A scroll compressor is equipped with a scroll compression mechanism consisting of a fixed scroll with a spiral wrap and a movable scroll with a spiral wrap, a rotating shaft that rotates the movable scroll eccentrically, and the movable scroll slides relative to the fixed scroll while rotating eccentrically, thereby pressurizing the refrigerant fluid supplied from the suction chambers on the outer diameter sides of both scrolls and discharging the high-pressure refrigerant from a discharge port formed in the center of the fixed scroll.

[0004] In this type of scroll compressor, when the pressure in the discharge chamber, from which the refrigerant compressed by the scroll compression mechanism is discharged, increases, a force acts in a direction that separates the movable scroll from the fixed scroll.

[0005] The scroll compressor of Patent Document 1 has an air supply passage that connects the discharge chamber with a back pressure chamber formed on the back side of the movable scroll. Part of the air supply passage is a slit that functions as a fixed throttle. A portion of the compressed refrigerant in the discharge chamber is decompressed and adjusted by the slit and supplied to the back pressure chamber, pressing the movable scroll toward the fixed scroll, preventing the movable scroll from separating from the fixed scroll.

[0006] The scroll compressor also has a bleed passage connecting the back pressure chamber and the suction chamber. A back pressure control valve is provided in the bleed passage. The back pressure control valve includes a front housing, a case, and a valve element. The front housing and the case define a first valve chamber communicating with the discharge chamber, a second valve chamber communicating with the back pressure chamber, and a third valve chamber communicating with the suction chamber. The valve element is housed within the front housing and the case so as to be reciprocable. Together with a valve seat provided between the third valve chamber and the second valve chamber, the valve element forms a BS valve that adjusts the flow rate in the bleed passage between the back pressure chamber and the suction chamber. The valve element moves in an open or closed direction depending on the discharge pressure, back pressure, and suction pressure, thereby adjusting the aperture of the BS valve.

[0007] JP 2010-150967 A (pages 5 to 8, Figure 1)

[0008] In the scroll compressor of Patent Document 1, when the back pressure becomes insufficient, the valve element of the back pressure control valve moves in the closing direction, causing the BS valve to open to a small degree or close. At this time, in the scroll compressor, refrigerant continues to be supplied to the back pressure chamber through the supply passage, so the pressure in the back pressure chamber can be increased.

[0009] Furthermore, if the back pressure becomes excessive, the valve element of the back pressure control valve moves in the open direction, widening the BS valve and reducing the pressure in the back pressure chamber. However, even if the back pressure is excessive and the BS valve is wide open, refrigerant continues to be supplied to the back pressure chamber through the supply passage, which causes a problem in that it takes time for the pressure in the back pressure chamber to reach the appropriate pressure.

[0010] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a valve that can smoothly change the pressure of the back pressure fluid.

[0011] To solve the above problems, the present invention provides a valve including a housing having a high-pressure space into which a high-pressure fluid flows, a back-pressure space into which a back-pressure fluid flows, and a low-pressure space into which a low-pressure fluid flows, and a valve element arranged to be movable relative to the housing. The housing has a first passage between the high-pressure space and the back-pressure space and a second passage between the back-pressure space and the low-pressure space. The valve element has a first valve element portion that controls the aperture of the first passage and a second valve element portion that controls the aperture of the second passage. The first valve element portion and the second valve element portion are linked so that their respective movement directions are opposite to each other in an opening direction and a closing direction. This allows for smooth changes in the pressure of the back-pressure fluid. Furthermore, because back pressure can be adjusted using only the valve, the configuration of the device to which the valve is attached can be simplified.

[0012] The back pressure space may be a first back pressure space that can communicate with the first passage, and a second back pressure space that can communicate with the second passage and is partitioned from the first back pressure space, thereby preventing fluid from flowing directly from a space with a relatively high pressure to a space with a low pressure.

[0013] The valve body may have a connecting portion that connects the first valve body portion and the second valve body portion, thereby allowing the first valve body portion and the second valve body portion to be easily interlocked.

[0014] The housing and the connecting portion may be sealed to prevent fluid from flowing directly from a space with a relatively high pressure to a space with a low pressure.

[0015] a pressure Pd of the high-pressure fluid, a pressure Pb of the back-pressure fluid, a pressure Ps of the low-pressure fluid, an effective cross-sectional area A of the first valve body portion, an effective cross-sectional area B of the connecting portion, an effective cross-sectional area C of the second valve body portion, and a biasing force F of the biasing means; ｓｐ and may be configured to satisfy the following equation: According to this, the pressure Pd of the high-pressure fluid, the pressure Pb of the back-pressure fluid, the pressure Ps of the low-pressure fluid, and the biasing force F of the biasing means ｓｐ The valve body can be moved smoothly in accordance with the above.

[0016] The effective cross-sectional areas A and C may be larger than the effective cross-sectional area B. This allows the influence of the back pressure fluid and the low pressure fluid to be greater than that of the high pressure fluid.

[0017] The housing may have a first valve seat provided in the first passage and a second valve seat provided in the second passage. With this, the first valve body and the second valve body come into contact with the first valve seat and the second valve seat, respectively, to reliably close the first passage and the second passage, thereby enabling the pressure of the backpressure fluid to be changed more smoothly.

[0018] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be construed as limiting the invention.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A valve according to the present invention will be described below with reference to the following examples.

[0020] A valve according to a first embodiment will be described with reference to Figures 1 and 2. The valve of the present invention is applied to a rotary machine including an eccentric mechanism, for example, a scroll compressor C that draws in, compresses, and discharges a refrigerant as a fluid used in an air conditioning system of an automobile, etc. In this embodiment, the refrigerant is a gas mixed with a mist of lubricating oil.

[0021] First, a description will be given of the scroll compressor C. As shown in Fig. 1 , the scroll compressor C is mainly composed of a housing 1, a rotating shaft 2, an inner casing 3, a scroll compression mechanism 4, a side seal 7, a thrust plate 8, and a drive motor M.

[0022] The housing 1 is composed of a cylindrical casing 11 and a cover 12 that closes an opening of the casing 11. An opening in the casing 11 on the axially opposite side to the opening closed by the cover 12 is closed by a drive motor M.

[0023] The casing 11 is provided with a low-pressure chamber 20 to which low-pressure refrigerant, i.e., intake fluid Ps as a low-pressure fluid, is supplied through the intake port 10 from a refrigerant circuit (not shown), a high-pressure chamber 30 serving as a discharge chamber from which high-pressure refrigerant compressed by the scroll compression mechanism 4, i.e., a discharge fluid Pd as a high-pressure fluid, is discharged, and a back-pressure chamber 50 to which a portion of the refrigerant compressed by the scroll compression mechanism 4 together with lubricating oil, i.e., a control fluid Pb as a back-pressure fluid, is supplied via a back-pressure control valve V1. The back-pressure chamber 50 is formed inside a cylindrical inner casing 3 housed inside the casing 11.

[0024] A discharge communication passage 13 is formed in the cover 12, connecting a refrigerant circuit (not shown) with the high-pressure chamber 30. A back-pressure communication passage 14 is also formed in the cover 12, connecting the high-pressure chamber 30 with the back-pressure chamber 50, and is branched off from the discharge communication passage 13. An oil separator 6 is provided in the discharge communication passage 13 to separate lubricating oil from the refrigerant.

[0025] The inner casing 3 is fixed with its axial end abutting against an end plate 41a of a fixed scroll 41 that constitutes the scroll compression mechanism 4. A suction communication passage 15 that penetrates radially is formed in the side wall of the inner casing 3. That is, the low-pressure chamber 20 is formed from the outside of the inner casing 3 to the inside of the inner casing 3 via the suction communication passage 15. The suction fluid Ps that is supplied to the inside of the inner casing 3 through the suction communication passage 15 is drawn into the scroll compression mechanism 4.

[0026] The scroll compression mechanism 4 is mainly composed of a fixed scroll 41 that is fixed to the cover 12 in a sealed manner, and a movable scroll 42 that is housed inside the inner casing 3 .

[0027] The fixed scroll 41 is made of metal and has a spiral wrap 41b that protrudes from the surface of a disk-shaped end plate 41a, i.e., the end face of the end plate 41a that faces the movable scroll 42, toward the movable scroll 42. The fixed scroll 41 also has a recess 41c that is recessed in the opposite direction to the cover 12 on the inner diameter side of the back surface of the end plate 41a, i.e., the end face of the end plate 41a that abuts against the cover 12, and this recess 41c and the cover 12 define the high-pressure chamber 30.

[0028] The movable scroll 42 is made of metal and has a spiral wrap 42b that protrudes from the surface of a disk-shaped end plate 42a, i.e., the end face of the end plate 42a that faces the fixed scroll 41, toward the fixed scroll 41. The movable scroll 42 also has a boss 42c that protrudes from the center of the back surface of the end plate 42a. An eccentric portion 2a formed on the rotating shaft 2 is inserted into the boss 42c so as to be rotatable relative to the boss 42c. In this embodiment, the eccentric portion 2a of the rotating shaft 2 and a counterweight portion 2b that protrudes radially outward from the rotating shaft 2 constitute an eccentric mechanism that rotates the rotating shaft 2 eccentrically.

[0029] When the rotary shaft 2 is driven to rotate by the drive motor M, the eccentric portion 2a rotates eccentrically, and the movable scroll 42 slides relative to the fixed scroll 41 while maintaining its posture with the eccentric rotation. At this time, the movable scroll 42 rotates eccentrically relative to the fixed scroll 41, and as this rotation occurs, the contact position of the wraps 41b, 42b moves sequentially in the rotation direction, and the compression chamber 40 formed between the wraps 41b, 42b moves toward the center and gradually shrinks. As a result, the intake fluid Ps sucked into the compression chamber 40 from the low-pressure chamber 20 formed on the outer diameter side of the scroll compression mechanism 4 is compressed, and finally, a high-pressure discharge fluid Pd is discharged into the high-pressure chamber 30 through the discharge hole 41d provided in the center of the fixed scroll 41.

[0030] The side seal 7 is made of resin, has a rectangular cross section, and is annular when viewed in the axial direction, and is fixed to the back surface of the end plate 42a of the movable scroll 42. The side seal 7 is formed with a sliding surface 7a that abuts against a sliding surface 8a formed on the thrust plate 8.

[0031] The thrust plate 8 is made of metal, has an annular shape, and has a seal ring 43 fixed thereto. The seal ring 43 abuts against the inner peripheral end surface of the inner casing 3. As a result, the thrust plate 8 functions as a thrust bearing that receives the axial load of the movable scroll 42 via the side seal 7.

[0032] Additionally, the side seal 7 and the seal ring 43 divide the interior of the inner casing 3 into a low-pressure chamber 20 formed on the outer diameter side of the movable scroll 42 and a back pressure chamber 50 formed on the back surface side of the movable scroll 42. The back pressure chamber 50 is formed as an enclosed space by a seal ring 44 fixed to the inner periphery of a through hole 3 a provided in the center of the inner casing 3, sealing between the back pressure chamber 50 and the rotating shaft 2 inserted through the through hole 3 a.

[0033] A back pressure control valve V1 is provided in a back pressure communication passage 14 that is formed across the cover 12, the fixed scroll 41, and the inner casing 3 and that connects the high pressure chamber 30 and the back pressure chamber 50. In other words, the back pressure control valve V1 is provided inside the housing 1 that is isolated from the outside air.

[0034] A portion of the discharge fluid Pd from the high pressure chamber 30 that is supplied to the back pressure control valve V1 together with the lubricating oil separated by the oil separator 6 is adjusted in pressure to a control fluid Pb and is supplied to the back pressure chamber 50.

[0035] The inner casing 3 is also formed with a pressure relief hole 16 that connects the back pressure control valve V1 and the low pressure chamber 20.

[0036] Next, the back pressure control valve V1 as a valve in this embodiment will be described with reference to Fig. 2. In the following description, the left and right sides as viewed from the front side of Fig. 2 will be referred to as the left and right sides of the back pressure control valve V1.

[0037] As shown in FIG. 2, the back pressure control valve V1 of the first embodiment is mainly composed of a housing 60, a rod 61 serving as a valve body, and a coil spring 62 serving as a biasing means for pressing the rod 61 in one direction.

[0038] The housing 60 defines a low pressure space S1 communicating with the low pressure chamber 20, a high pressure space S2 communicating with the high pressure chamber 30, and back pressure spaces S3, S3' communicating with the back pressure chamber 50. The housing 60 only needs to define at least a portion of the low pressure space S1, the high pressure space S2, and the back pressure spaces S3, S3'.

[0039] The housing 60 is composed of a first divided body 63, a second divided body 64, and a third divided body 65, in that order from the right side.

[0040] The first divided body 63 has a peripheral wall 63a and a side wall 63b, and is formed in a cylindrical shape with a side wall that is open toward the left in the axial direction.

[0041] The peripheral wall 63a is formed in a cylindrical shape extending in the axial direction. The peripheral wall 63a is provided with communication holes 63c that penetrate radially and communicate with the low pressure chamber 20 and the low pressure space S1. In this embodiment, the communication holes 63c are equally spaced, but the number and arrangement of the communication holes 63c may be changed as appropriate. The same applies to communication holes 64f and 64k, which will be described later.

[0042] The inner diameter of the peripheral wall 63a is substantially constant along the axial direction.

[0043] The side wall 63b is formed in a disk shape that closes the right end of the peripheral wall 63a in the axial direction.

[0044] The side wall 63b has a cylindrical protrusion 63d that protrudes axially leftward from the center of its left end face. The right axial end of the coil spring 62 is fitted onto the protrusion 63d. This positions the right axial end of the coil spring 62 in the radial direction. The right axial end of the coil spring 62 abuts against the side wall 63b.

[0045] The second partition 64 is formed in a cylindrical shape extending in the axial direction and includes, in order from the left axial direction, a left large inner diameter peripheral wall 64a, a left medium inner diameter peripheral wall 64b, a small inner diameter peripheral wall 64c, a right medium inner diameter peripheral wall 64d, and a right large inner diameter peripheral wall 64e.

[0046] The left large inner diameter peripheral wall 64a is cylindrical and extends in the axial direction. A communication hole 64f is formed in the left large inner diameter peripheral wall 64a, which passes through in the radial direction and communicates with the high pressure space S2.

[0047] The outer diameter end of the communication hole 64f is an annular recess 64g that is expanded in diameter and opens toward the outer diameter side, and communicates with the high-pressure chamber 30. A filter 66 is provided in the recess 64g to remove foreign matter such as contaminants contained in the refrigerant.

[0048] The left middle inner diameter peripheral wall 64b is cylindrical and extends axially rightward from the right end of the left large inner diameter peripheral wall 64a. The inner diameter of the left middle inner diameter peripheral wall 64b is smaller than the inner diameter of the left large inner diameter peripheral wall 64a. The left middle inner diameter peripheral wall 64b also has an annular eaves portion 64h that extends inward from its left end.

[0049] The small inner diameter peripheral wall 64c is cylindrical and extends axially rightward from the right end of the left-side intermediate inner diameter peripheral wall 64b. A through-hole 64j is formed in the radial center of the small inner diameter peripheral wall 64c, penetrating the wall in the axial direction. The inner diameter of the small inner diameter peripheral wall 64c is smaller than the inner diameter of the left-side intermediate inner diameter peripheral wall 64b, more specifically, the inner diameter of the eaves portion 64h.

[0050] The right middle inner diameter peripheral wall 64d is cylindrical and extends axially rightward from the right end of the small inner diameter peripheral wall 64c. A second back pressure space S3′ and a second valve hole 64m are formed in the radial center of the right middle inner diameter peripheral wall 64d.

[0051] The second back pressure space S3' has a larger diameter than the through hole 64j to the right in the axial direction, and further extends axially to the right with approximately the same diameter.

[0052] The second valve hole 64m has a diameter that increases from the second back pressure space S3' toward the right in the axial direction. The tapered surface that defines the second valve hole 64m is a second valve seat 76.

[0053] A second valve body portion 77 of the rod 61 comes into contact with and separates from the second valve seat 76. In other words, the second valve seat 76 and the second valve body portion 77 come into contact with and separate from each other to form a BS valve 75 serving as a second valve that controls the opening and closing of a second passage 78 between the second valve seat 76 and a curved surface 77a of the second valve body portion 77. The second valve body portion 77 is also capable of adjusting the opening degree of the second passage 78 in accordance with the movement of the rod 61, thereby adjusting the flow rate passing through. Hereinafter, adjustment of the opening degree of the second passage 78 by movement of the rod 61 may also be described as adjustment of the opening degree of the BS valve 75.

[0054] Further, a communication hole 64k is formed in the right middle inner diameter peripheral wall 64d so as to penetrate radially and communicate with the back pressure chamber 50 and the second back pressure space S3'.

[0055] The right large inner diameter peripheral wall 64e is cylindrical and extends axially rightward from the right end of the right intermediate inner diameter peripheral wall 64d. The inner diameter of the right large inner diameter peripheral wall 64e is larger than the inner diameter of the right intermediate inner diameter peripheral wall 64d, more specifically, the maximum diameter of the second valve seat 76.

[0056] The outer diameter of the right end of the second divided body 64 is substantially constant along the axial direction, and is substantially the same as or slightly larger than the inner diameter of the peripheral wall 63 a of the first divided body 63 .

[0057] The right end of the second division 64 is press-fitted and fixed inside the peripheral wall 63a of the first division 63. The space surrounded by the peripheral wall 63a and side wall 63b of the first division 63 and the right-side medium-inner-diameter peripheral wall 64d and right-side large-inner-diameter peripheral wall 64e of the second division 64 forms a low-pressure space S1 into which the intake fluid Ps flows.

[0058] The third divided body 65 is formed in a cylindrical shape with an outer step and includes, in order from the left in the axial direction, a large outer diameter peripheral wall 65a and a small outer diameter peripheral wall 65b.

[0059] The large outer diameter peripheral wall 65a is cylindrical and extends in the axial direction.

[0060] The small outer diameter peripheral wall 65b is cylindrical and extends axially rightward from the right end of the large outer diameter peripheral wall 65a. The small outer diameter peripheral wall 65b has a smaller outer diameter than the large outer diameter peripheral wall 65a.

[0061] The outer diameter of the small outer diameter peripheral wall 65 b is substantially constant along the axial direction, and is substantially the same as or slightly larger than the inner diameter of the left large inner diameter peripheral wall 64 a of the second divided body 64 .

[0062] The third divider 65 has its small outer diameter peripheral wall 65b press-fitted and fixed inside the left large inner diameter peripheral wall 64a of the second divider 64. The third divider 65 is also positioned in the axial direction with its large outer diameter peripheral wall 65a abutting against the left large inner diameter peripheral wall 64a of the second divider 64. The space surrounded by the left large inner diameter peripheral wall 64a, left medium inner diameter peripheral wall 64b, and small inner diameter peripheral wall 64c of the second divider 64 and the third divider 65 forms a high-pressure space S2 into which the discharge fluid Pd flows.

[0063] A first valve hole 65c is formed in the radial center of the large outer diameter peripheral wall 65a and the small outer diameter peripheral wall 65b, that is, in the radial center of the third divided body 65.

[0064] The first valve hole 65c extends from the high-pressure space S2 toward the left in the axial direction with a substantially constant diameter, and then expands in diameter toward the left in the axial direction. The tapered surface that defines the portion that expands in diameter toward the left in the axial direction is the first valve seat 71.

[0065] A first valve body 72 of the rod 61 moves toward and away from the first valve seat 71. In other words, the first valve seat 71 and the first valve body 72 move toward and away from each other to form the DB valve 70 as a first valve that controls the opening and closing of a first passage 73 between the first valve seat 71 and a curved surface 72 a of the first valve body 72. The first valve body 72 is also capable of adjusting the opening degree of the first passage 73 in accordance with the movement of the rod 61, thereby adjusting the flow rate of the passing fluid. Hereinafter, the adjustment of the opening degree of the first passage 73 by the movement of the rod 61 may also be described as adjustment of the opening degree of the DB valve 70.

[0066] A first back pressure space S3 is formed in the radial center of the large outer diameter peripheral wall 65a. The first back pressure space S3 is recessed axially rightward from the left end face of the large outer diameter peripheral wall 65a and opens axially leftward. The first back pressure space S3 communicates with the back pressure chamber 50 and the first valve hole 65c.

[0067] The rod 61 is composed of a base material 67 and an annular member 68 .

[0068] The base material 67 has a stepped cylindrical shape, and an annular member 68 (described later) is fixed to its right end. The left end of the base material 67 constitutes a first valve body 72. The right end of the base material 67 and the annular member 68 constitute a second valve body 77. A shaft 67a serves as a connecting portion connecting the first valve body 72 and the second valve body 77 of the base material 67.

[0069] The first valve body portion 72 has a curved surface 72a that is formed as part of a spherical shape and whose diameter decreases from its left end toward the right in the axial direction.

[0070] The first valve body 72 is disposed across the first back pressure space S3 and the first valve hole 65c. That is, the pressure of the discharge fluid Pd and the pressure of the control fluid Pb act on the first valve body 72. The effective cross-sectional area A1 of the first valve body 72 is substantially the same as the cross-sectional area of ​​the first valve body 72 at a point of circumferential line contact with the first valve seat 71 when the first valve body 72 is seated on the first valve seat 71.

[0071] The shaft portion 67a extends from the right end of the first valve body portion 72 toward the right in the axial direction with approximately the same diameter, expands toward the right in the axial direction, extends further toward the right in the axial direction with approximately the same diameter, and then is formed into a stepped cylindrical shape with a reduced diameter toward the right in the axial direction.

[0072] The shaft portion 67a is inserted into the housing 60 from the first backpressure space S3 side and is disposed across the first valve hole 65c, the high-pressure space S2, the through-hole 64j, the second backpressure space S3′, the second valve hole 64m, and the low-pressure space S1. In other words, the pressures of the discharge fluid Pd, the backpressure fluid Pb, and the suction fluid Ps act on the shaft portion 67a. The effective cross-sectional area B1 of the shaft portion 67a is the cross-sectional area of ​​the portion inserted into the through-hole 64j, i.e., the cross-sectional area of ​​the large-diameter body portion 67b, which has the largest diameter of the shaft portion 67a. The effective cross-sectional area B1 of the shaft portion 67a is narrower than the effective cross-sectional area A1 of the first valve body portion 72 (A1 > B1).

[0073] The outer circumferential surface of the large-diameter body portion 67b and the inner circumferential surface of the small-inner-diameter peripheral wall 64c that defines the through-hole 64j are smooth surfaces with the same diameter in the axial direction, allowing the two surfaces to slide relative to each other. Furthermore, because the gap between the outer circumferential surface of the large-diameter body portion 67b and the inner circumferential surface of the small-inner-diameter peripheral wall 64c is very small, there is almost no movement of refrigerant between the high-pressure space S2 and the second back-pressure space S3′ through this gap.

[0074] Furthermore, an O-ring 69 serving as a sealing means is fitted onto the outside of the large-diameter body portion 67b. The O-ring 69 is fitted into the left-hand middle inner-diameter peripheral wall 64b of the second divided body 64. The O-ring 69 seals between the shaft portion 67a and the left-hand middle inner-diameter peripheral wall 64b while allowing axial movement of the rod 61. In other words, the O-ring 69 seals between the high-pressure space S2 and the second back-pressure space S3'.

[0075] As described above, the left-side intermediate inner diameter peripheral wall 64b has a left end formed with the eaves portion 64h. The small inner diameter peripheral wall 64c continues axially to the right of the left-side intermediate inner diameter peripheral wall 64b, i.e., toward the low-pressure space S1. In other words, the O-ring 69 is positioned axially between the eaves portion 64h and the small inner diameter peripheral wall 64c, preventing it from moving axially outward beyond the left-side intermediate inner diameter peripheral wall 64b.

[0076] The right axial end of the large-diameter body portion 67b of the shaft portion 67a is press-fitted and fixed into an annular member 68. The annular member 68 is formed in an annular shape. The inner diameter of the annular member 68 is approximately the same as or slightly smaller than the outer diameter of the large-diameter body portion 67b.

[0077] The right end of the shaft portion 67a protrudes axially to the right beyond the right axial edge of the annular member 68, and the left axial end of the coil spring 62 is extrapolated thereto. This determines the radial position of the left axial end of the coil spring 62. The left axial end of the coil spring 62 also abuts against the annular member 68.

[0078] The annular member 68 has a curved surface 77a that is formed as part of a spherical shape and whose diameter increases from its left end toward the right in the axial direction.

[0079] The second valve body 77 is disposed across the second back pressure space S3′ and the low pressure space S1. That is, the pressure of the control fluid Pb and the pressure of the suction fluid Ps act on the second valve body 77. The effective cross-sectional area C1 of the second valve body 77 is the cross-sectional area of ​​the second valve body 77 on the inner diameter side of the point of circumferential line contact between the second valve body 77 and the second valve seat 76 when the second valve body 77 is seated on the second valve seat 76. In other words, the effective cross-sectional area C1 is approximately the same as the sum of the cross-sectional area of ​​the annular member 68 and the cross-sectional area of ​​the large diameter body 67b.

[0080] The effective cross-sectional area C1 of the second valve body portion 77 is larger than the effective cross-sectional area A1 of the first valve body portion 72 and the effective cross-sectional area B1 of the shaft portion 67a (C1>A1>B1).

[0081] The effective pressure-receiving area of ​​the rod 61 on which the pressure of the control fluid Pb in the first back pressure space S3 acts is the effective cross-sectional area A1 of the first valve body portion 72.

[0082] The effective pressure-receiving area of ​​the rod 61 on which the pressure of the discharge fluid Pd acts is the portion (A1-B1) of the effective cross-sectional area A1 of the first valve body portion 72 that is located radially outward of the effective cross-sectional area B1 of the shaft portion 67a.

[0083] The effective pressure-receiving area A1 of the rod 61 on which the pressure of the control fluid Pb in the first back pressure space S3 acts is larger than the effective pressure-receiving area (A1-B1) of the rod 61 on which the pressure of the discharge fluid Pd acts (A1>(A1-B1)).

[0084] The effective pressure-receiving area of ​​the rod 61 on which the pressure of the control fluid Pb in the second back pressure space S3' acts is the portion (C1-B1) of the effective cross-sectional area C1 of the second valve seat 76 that is located radially outward of the effective cross-sectional area B1 of the shaft portion 67a.

[0085] The effective pressure-receiving area (C1-B1) of the rod 61 on which the pressure of the control fluid Pb in the second back pressure space S3' acts is larger than the effective pressure-receiving area (A1-B1) of the rod 61 on which the pressure of the discharge fluid Pd acts ((C1-B1) > (A1-B1)).

[0086] The effective pressure-receiving area of ​​the rod 61 on which the pressure of the intake fluid Ps acts is the effective cross-sectional area C1 of the second valve body portion 77.

[0087] Next, the opening and closing operation of the back pressure control valve V1 will be described. In this embodiment, the pressure of the discharge fluid Pd is written as Pd in ​​the formula, the pressure of the control fluid Pb is written as Pb in the formula, and the pressure of the suction fluid Ps is written as Ps in the formula.

[0088] In the housing 60, the intake fluid Ps flows into the low pressure space S1, the discharge fluid Pd flows into the high pressure space S2, and the control fluid Pb flows into the back pressure spaces S3 and S3'.

[0089] The rod 61 receives a force (F Ｐｄ = Pd × (A1 - B1)) and the force (F Ｐｓ = Ps × C1) and the biasing force F of the coil spring 62 ｓｐ The rod 61 is pushed to the left in the axial direction by a force F １ =F Ｐｄ +F Ｐｓ +F ｓｐ is at work).

[0090] The rod 61 also receives a force (F Ｐｂ１ = Pb × A1), and the force (F Ｐｂ２ = Pb × (C1 - B1)) is pushed to the right in the axial direction (i.e., the right direction is positive, and the rod 61 is subjected to a force F ２ =F Ｐｂ１ +F Ｐｂ２ is at work).

[0091] Force F １ and force F ２ The balance equation for F is as follows, and it can be seen that it satisfies Equation 1. １ =F ２ Pd×(A1-B1)+Ps×C1+F ｓｐ =Pb×A+Pb×(C1-B1) (A1-B1+C1)Pb=Pd×(A1-B1)+Ps×C1+F ｓｐPb=C1÷(A1-B1+C1)×Ps+(A1-B1)÷(A1-B1+C1) +F ｓｐ ÷(A1-B1+C1)

[0092] The rod 61 is subjected to a force F １ and force F ２ From the balanced state, force F １ The force F ２ When the force F １ >Force F ２ ). And the force F １ and force F ２ is the balance (F １ =F ２ ) or the second valve body portion 77 is seated on the second valve seat 76 in the housing 60, so that the rod 61 is stationary.

[0093] The rod 61 is subjected to a force F １ and force F ２ From the balanced state, force F １ The force F ２ When the force becomes smaller than １ <Force F ２ ). And the force F １ and force F ２ is the balance (F １ =F ２ ) or the first valve body portion 72 is seated on the first valve seat 71 in the housing 60, so that the rod 61 is stationary.

[0094] In this way, the back pressure control valve V1 can smoothly move the rod 61 according to the pressure of the discharge fluid Pd, the pressure of the control fluid Pb, the pressure of the intake fluid Ps, and the biasing force of the coil spring 62.

[0095] When the first valve body portion 72 is located at a position spaced apart from the first valve seat 71 and the second valve body portion 77 is located at a position spaced apart from the second valve seat 76, the DB valve 70 and the BS valve 75 are in an open state.

[0096] More specifically, as the rod 61 moves axially to the left, the first valve body portion 72 moves away from the first valve seat 71, widening the valve opening of the DB valve 70, and the second valve body portion 77 moves closer to the second valve seat 76, narrowing the valve opening of the BS valve 75.

[0097] In this embodiment, when the second valve body portion 77 is seated on the second valve seat 76 and the BS valve 75 is in a closed state, the first valve body portion 72 is at the farthest position from the first valve seat 71, and the valve opening of the DB valve 70 is at its maximum.

[0098] As the rod 61 moves axially to the right, the first valve body portion 72 approaches the first valve seat 71, narrowing the valve opening of the DB valve 70, and the second valve body portion 77 moves away from the second valve seat 76, widening the valve opening of the BS valve 75.

[0099] In this embodiment, when the first valve body portion 72 is seated on the first valve seat 71 and the DB valve 70 is in a closed state, the second valve body portion 77 is at the position farthest from the second valve seat 76, and the valve opening of the BS valve 75 is at its maximum.

[0100] The valve openings of the DB valve 70 and the BS valve 75 vary from a maximum opening that is wider than the opening of a fixed throttle such as the slit in Patent Document 1, to the opening of the fixed throttle, to an opening that is narrower than the opening of the fixed throttle, and finally to a closed valve state.

[0101] The range of valve opening of the DB valve 70 and the BS valve 75 may be adjusted as appropriate, but it is preferable that it be at least narrower than the opening of a fixed throttle such as the slit in Patent Document 1.

[0102] As described above, in the back pressure control valve V1 of this embodiment, when the opening degree of the first passage 73 is narrowed, the opening degree of the second passage 78 is widened, and when the opening degree of the second passage 78 is narrowed, the opening degree of the first passage 73 is widened.

[0103] For example, the force F １ and force F ２When the pressure of the control fluid Pb becomes relatively higher than the pressures of the discharge fluid Pd and the suction fluid Ps from a state in which these are balanced, the opening of the first passage 73 narrows, while the opening of the second passage 78 widens. By making the opening of the first passage 73 narrower than that of a fixed throttle such as the slit in Patent Document 1, the amount of refrigerant flowing into the first back pressure space S3 can be reduced more than with the fixed throttle, and the pressure of the control fluid Pb can be smoothly reduced.

[0104] Furthermore, since the opening of the second passage 78 is wider than the opening of a fixed throttle such as the slit in Patent Document 1, the pressure of the control fluid Pb can be reduced more smoothly.

[0105] Also, the force F １ and force F ２ When the pressure of the control fluid Pb becomes relatively smaller than the pressures of the discharge fluid Pd and the suction fluid Ps from a state in which these are balanced, the aperture of the first passage 73 widens, while the aperture of the second passage 78 narrows. By making the aperture of the first passage 73 wider than the aperture of a fixed throttle such as the slit in Patent Document 1, the amount of refrigerant flowing into the first back pressure space S3 can be increased compared to the fixed throttle, and the pressure of the control fluid Pb can be smoothly increased.

[0106] Furthermore, since the opening of the second passage 78 is narrower than the opening of a fixed throttle such as the slit in Patent Document 1, the pressure of the control fluid Pb can be increased more smoothly.

[0107] As described above, the back pressure control valve V1 can smoothly change the pressure of the control fluid Pb. Furthermore, since the back pressure can be adjusted only by the back pressure control valve V1, the configuration of the scroll compressor C can be simplified.

[0108] Furthermore, since the rod 61 is configured such that the first valve body portion 72 and the second valve body portion 77 are connected by the shaft portion 67a, the first valve body portion 72 and the second valve body portion 77 can be easily linked together.

[0109] The second back pressure space S3' is a space separated from the first back pressure space S3. The refrigerant flowing from the high pressure space S2 into the first back pressure space S3 first flows into the back pressure chamber 50, flows from the back pressure chamber 50 into the second back pressure space S3', and then flows into the low pressure space S1. In this way, the back pressure control valve V1 can prevent the discharge fluid Pd from flowing directly into the low pressure space S1, thereby preventing a decrease in the operating efficiency of the refrigeration cycle.

[0110] Furthermore, since the space between the first back pressure space S3 and the second back pressure space S3' is sealed by the O-ring 69, it is possible to more reliably prevent the discharge fluid Pd from flowing directly into the low pressure space S1.

[0111] Furthermore, since the effective cross-sectional areas A1 and C1 are larger than the effective cross-sectional area B1, the influence of the control fluid Pb and the intake fluid Ps can be made greater than that of the discharge fluid Pd.

[0112] Additionally, in the back pressure control valve V1, a high pressure space S2 is provided between the first back pressure space S3 and the second back pressure space S3', and a low pressure space S1 is provided on the opposite side of the second back pressure space S3' from the high pressure space S2. Also, a rod 61 is inserted from the first back pressure space S3 to the low pressure space S1.

[0113] This allows the effective pressure-receiving area on which the pressure of the discharge fluid Pd acts to be reduced by the effective cross-sectional area B1 (A1-B1), making it possible to easily increase the influence of the control fluid Pb and the intake fluid Ps more than that of the discharge fluid Pd.

[0114] Furthermore, since the first valve body portion 72 is provided at the tip of the rod 61, the pressure of the control fluid Pb can be applied to the entire effective cross-sectional area A1.

[0115] Furthermore, since the second valve body 77 is provided at the tip of the rod 61, the pressure of the intake fluid Ps can be applied to the entire effective cross-sectional area C1.

[0116] The housing 60 also has a first valve seat 71 and a second valve seat 76. That is, the opening of the first passage 73 and the second passage 78 is adjusted by a so-called poppet system. This allows the back pressure control valve V1 to reliably close the first passage 73 and the second passage 78, thereby enabling the pressure of the control fluid Pb to be changed more smoothly.

[0117] Furthermore, since the back pressure control valve V1 has a first valve body portion 72 and a second valve body portion 77 provided at both axial ends of the rod 61, they can function as stoppers for each other, and therefore the maximum opening degrees of the first passage 73 and the second passage 78 can be kept approximately constant.

[0118] The back pressure control valve V1 is biased by the biasing force (F ｓｐ ) acts to press the rod 61 to the left in the axial direction. ｓｐ ) acts in the opening direction of the DB valve 70 and acts in the closing direction of the BS valve 75. In other words, the DB valve 70 of this embodiment is a normally open type, and the BS valve 75 is a normally closed type.

[0119] With this, even if the scroll compressor C has been stopped for a long period of time and the pressures of the suction fluid Ps, the discharge fluid Pd, and the control fluid Pb are balanced and substantially the same, the back pressure control valve V1 can quickly increase the control fluid Pb because the opening degree of the first passage 73 is properly guaranteed and the second passage 78 is closed when the scroll compressor C is started. As a result, the pressure of the control fluid Pb can be adjusted in a short time when the scroll compressor C is started.

[0120] Furthermore, the housing 60 has the second divided body 64 press-fitted into the first divided body 63, and the amount of press-fitting is variable within the range of the press-fitting allowance, which not only makes it possible to adjust the biasing force of the coil spring 62 but also to adjust the axial length of the housing 60. Note that the first divided body 63 and the second divided body 64 may be fixed together by screwing instead of by press-fitting.

[0121] Furthermore, the base material 67 of the rod 61 is press-fitted into the annular member 68, and the amount of press-fitting is variable within the range of the press-fitting allowance, so that it is possible to adjust the stroke amount of the rod 61, in other words, the maximum opening degree of the DB valve 70 and the BS valve 75. Note that the annular member 68 and the base material 67 may be fixed by screwing, adhesive fixation, shrink fit fixation, or other suitable means, instead of press-fitting.

[0122] Next, a valve according to a second embodiment will be described with reference to Fig. 3. Note that a description of the same configuration as in the previous embodiment will be omitted.

[0123] As shown in FIG. 3, the back pressure control valve V2 of the second embodiment is mainly composed of a housing 160, a rod 161, and a coil spring 62.

[0124] The housing 160 is composed of a first divided body 63 , a second divided body 164 , a third divided body 165 , and a cover member 169 .

[0125] The second partition 164 has an inner peripheral surface that defines the second back pressure space S13', and the diameter of the uniform diameter portion 164n that extends in the axial direction with approximately the same diameter is approximately the same as or slightly larger than the effective cross-sectional area C1 of the second valve body portion 177.

[0126] The third divided body 165 has an inner surface that defines the first valve hole 165c, and the diameter of the uniform diameter portion 165d that extends in the axial direction with approximately the same diameter is approximately the same as or slightly larger than the effective cross-sectional area A1 of the first valve body portion 172.

[0127] A lid member 169 is attached by screwing to the inner circumferential surface of the left end opening of the third division 165. The space surrounded by the third division 165 and the lid member 169 is the first back pressure space S13. Note that the lid member 169 may be fixed to the third division 165 by various fixing means other than screwing, but it is preferable that the axial position of the lid member 169 be adjustable.

[0128] A communication hole 169a is formed in the lid member 169, penetrating the axial direction on the outer diameter side. The communication hole 169a communicates with the first back pressure space S13 and the back pressure chamber 50.

[0129] The rod 161 serving as a valve body is composed of a base material 167 and an annular member 168 .

[0130] The base material 167 is formed in a stepped cylindrical shape and includes, from the left axial side, a small diameter body portion 167a as a connecting portion, a left large diameter body portion 167b as a connecting portion, a second valve body portion 177, and a right large diameter body portion 167c.

[0131] The small diameter body portion 167a is formed in a cylindrical shape extending in the axial direction. The left end of the small diameter body portion 167a is press-fitted and fixed into the annular member 168. The left end of the small diameter body portion 167a and the annular member 168 constitute a first valve body portion 172.

[0132] The left large-diameter body portion 167b is formed in a cylindrical shape that expands in diameter toward the right in the axial direction from the right end of the small-diameter body portion 167a and extends toward the right in the axial direction with approximately the same diameter. The maximum cross-sectional area of ​​the left large-diameter body portion 167b is the effective cross-sectional area B1.

[0133] The second valve body 177 is formed in a cylindrical shape that extends axially rightward from the right end of the left large-diameter body 167b with a substantially constant diameter. The cross-sectional area of ​​the second valve body 177 is an effective cross-sectional area C1.

[0134] The outer peripheral surface of the second valve body portion 177 and the constant diameter portion 164n of the second divided body 164 in the housing 160 are smooth surfaces with the same diameter along the axial direction, and the two surfaces are capable of sliding relative to each other.

[0135] The opening of the second passage 178 narrows as the rod 161 moves to the left and the area where the second valve body portion 177 overlaps with the same diameter portion 164n in the radial direction increases, and the opening of the first passage 173 widens as the rod 161 moves to the right and the area where the overlapping in the radial direction decreases. In other words, the opening of the second passage 178 is adjusted by a so-called spool mechanism.

[0136] The right large-diameter body portion 167c is formed in a cylindrical shape that extends axially rightward from the right end of the second valve body portion 177 with approximately the same diameter and then decreases in diameter toward the right in the axial direction. The maximum cross-sectional area of ​​the right large-diameter body portion 167c is the effective cross-sectional area B1.

[0137] The annular member 168 extends axially rightward with approximately the same diameter. The cross-sectional area of ​​the first valve body 172 is an effective cross-sectional area A1, which is approximately the same as the sum of the cross-sectional area of ​​the annular member 168 and the cross-sectional area of ​​the small-diameter body 167a.

[0138] The outer peripheral surface of the first valve body portion 172 and the constant diameter portion 165d of the third divided body 166 of the housing 160 are smooth surfaces with the same diameter along the axial direction, and the two surfaces are capable of sliding relative to each other.

[0139] The opening of the first passage 173 narrows as the rod 161 moves to the right and the area where the first valve body portion 172 overlaps with the same diameter portion 165d in the radial direction increases, and the opening of the first passage 173 widens as the rod 161 moves to the left and the area where the overlapping in the radial direction decreases. In other words, the opening of the first passage 173 is adjusted in a so-called spool manner.

[0140] The rod 161 is restricted from moving axially leftward when its small-diameter body portion 167a abuts against the cover member 169. At this time, the opening degree of the first passage 173 is at its maximum, and the opening degree of the second passage 178 is at its minimum and closed.

[0141] Furthermore, by adjusting the axial position of the cover member 169, the maximum opening degree of the first passage 173 can be varied.

[0142] Furthermore, the rod 161 is restricted from moving axially to the right when its right large-diameter body portion 167c abuts against the protrusion 63d of the housing 160. At this time, the opening degree of the second passage 178 is at its maximum, and the opening degree of the first passage 173 is at its minimum and closed.

[0143] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0144] For example, in the first and second embodiments, the first and second valve bodies are described as being connected by a connecting portion and integrated into one body. However, this is not limited thereto. The first and second valve bodies may be disposed separately without being connected by a connecting member. For example, the first and second valve bodies may be pressed against each other by an elastic member that presses the first valve body toward the second valve body and a biasing means that presses the second valve body toward the first valve body, and move together. Furthermore, the first and second valve bodies may be disposed separately and not in direct or indirect contact with each other, as long as they move in conjunction with each other in directions opposite to the valve opening and closing directions due to a pressure difference.

[0145] Furthermore, in Examples 1 and 2, the rod was described as being composed of one base material and one annular member, but this is not limited to this and the rod may be composed of one base material and two annular members.

[0146] Furthermore, in the first and second embodiments, the first and second passages are described as being blockable, but the present invention is not limited to this, and the first and second passages may be configured not to be blockable.

[0147] In addition, in the above-described Examples 1 and 2, the first valve body portion and the second valve body portion are described as each functioning as a stopper that restricts the movement of the valve body, but this is not limited to this, and a stopper that restricts the movement of the valve body may be provided separately from the first valve body portion and the second valve body portion.

[0148] In addition, in the first and second embodiments, the biasing means is described as a coil spring, but is not limited to this and may be a coiled wave spring, a leaf spring, an air spring, or any other suitable change. As an example of an air spring, a pressure-sensitive body such as a bellows filled with a gas such as nitrogen may be disposed.

[0149] In addition, in the first and second embodiments, the biasing means functions as a compression spring, but is not limited to this and may be an extension spring. If the biasing means is an extension spring, the biasing means may be disposed in the first back pressure space.

[0150] In addition, in the first and second embodiments, the biasing means biases the valve element in the opening direction of the DB valve and the closing direction of the BS valve. However, this is not limited to this, and the biasing means may bias the valve element in the closing direction of the DB valve and the opening direction of the BS valve. In other words, the DB valve may be a normally closed type and the BS valve may be a normally open type. This configuration makes it easier to prevent the pressure of the back pressure fluid from increasing excessively.

[0151] Furthermore, in the first and second embodiments, the back pressure control valve has been described as having a configuration in which a first back pressure space, a high pressure space, a second back pressure space, and a low pressure space are arranged in that order from the left side, but this is not limited to this, and the configuration may also be such that a high pressure space, a first back pressure space, a low pressure space, and a second back pressure space are arranged in that order from the left side, or a high pressure space, a back pressure space, and a low pressure space are arranged in that order from the left side, and this may be changed as appropriate.

[0152] In addition, in the first and second embodiments, the effective cross-sectional area A of the first valve body and the effective cross-sectional area C of the second valve body are described as being larger than the effective cross-sectional area B of the connecting portion, but this is not limited to this and may be changed as appropriate. For example, in a configuration in which a high-pressure space, a first back-pressure space, a low-pressure space, and a second back-pressure space are arranged in this order from the left, the effective cross-sectional area A of the first valve body can be made smaller than the effective cross-sectional area B of the connecting portion and the effective cross-sectional area C of the second valve body, thereby making the influence of the back-pressure fluid and the low-pressure fluid greater than that of the high-pressure fluid.

[0153] Furthermore, in the first and second embodiments, the sealing means is described as an O-ring, but this is not limited thereto, and as long as it is capable of sealing between the high-pressure space and the low-pressure space, it may be a lip packing, a gland packing, a labyrinth seal, or the like, and may be modified as appropriate.

[0154] In addition, in the first and second embodiments, the coil spring is described as being in contact with the second valve body portion, but this is not limiting, and a receiving member on which the biasing force of the coil spring acts may be provided separately from the second valve body portion. In such a configuration, the biasing force of the coil spring can be varied by adjusting the position of the receiving member.

[0155] In the first and second embodiments, only the back pressure communication passage in which the valve is disposed has been described, but this is not limited thereto, and a separate back pressure communication passage that connects the high pressure chamber and the back pressure chamber may be provided, and an orifice and a valve may also be provided in the separate back pressure communication passage.

[0156] In addition, in the first and second embodiments, the pressure relief hole is described as connecting the valve and the low-pressure chamber, but this is not limiting, and a separate pressure relief hole may be provided connecting the back pressure chamber and the low-pressure chamber. The separate pressure relief hole may also be provided with an orifice or a valve.

[0157] Furthermore, in the first and second embodiments, the valve is described as being applied to a scroll compressor used in an air conditioning system of an automobile or the like, but the present invention is not limited to this, and the valve may be used to control various working fluids.

[0158] In addition, in the first and second embodiments, the valve is a back pressure control valve. However, the valve may be, for example, an expansion valve disposed between a condenser and an evaporator in an air conditioning system, or a displacement control valve incorporated in a variable displacement compressor in an air conditioning system.

[0159] The intake fluid, discharge fluid, and control fluid may each be in the form of gas, liquid, or a mixture of gas and liquid.

[0160] 60 Housing 61 Rod (valve body) 62 Coil spring (biasing means) 67a Shaft portion (connecting portion) 69 O-ring (sealing means) 70 DB valve 71 First valve seat 72 First valve body portion 73 First passage 75 BS valve 76 Second valve seat 77 Second valve body portion 78 Second passage 160 Housing 161 Rod (valve body) 167a Small diameter body portion (connecting portion) 167b Left large diameter body portion (connecting portion) 172 First valve body portion 173 First passage 177 Second valve body portion 178 Second passage A1 Effective cross-sectional area B1 Effective cross-sectional area C1 Effective cross-sectional area S1 Low pressure space S2 High pressure space S3, S13 First back pressure space S3', S13' Second back pressure space V1, V2 Back Pressure Control Valve

Claims

1. A valve comprising a housing having a high pressure space into which a high pressure fluid flows, a back pressure space into which a back pressure fluid flows, and a low pressure space into which a low pressure fluid flows, and a valve body arranged to be movable relative to the housing, wherein the housing has a first passage provided between the high pressure space and the back pressure space, and a second passage provided between the back pressure space and the low pressure space, the valve body has a first valve body portion which controls the opening degree of the first passage, and a second valve body portion which controls the opening degree of the second passage, and the first valve body portion and the second valve body portion are linked so that their respective movement directions are opposite to each other in an opening direction and a closing direction.

2. The valve according to claim 1, wherein the back pressure space comprises a first back pressure space capable of communicating with the first passage, and a second back pressure space capable of communicating with the second passage and separated from the first back pressure space.

3. The valve according to claim 1, wherein the valve body has a connecting portion connecting the first valve body portion and the second valve body portion.

4. The valve of claim 3, wherein a seal is provided between said housing and said connection.

5. A biasing means is provided for biasing the valve body in one direction, and the pressure Pd of the high pressure fluid, the pressure Pb of the back pressure fluid, the pressure Ps of the low pressure fluid, the effective cross-sectional area A of the first valve body portion, the effective cross-sectional area B of the connecting portion, the effective cross-sectional area C of the second valve body portion, and the biasing force F of the biasing means. ｓｐ 4. The valve of claim 3, wherein:

6. The valve of claim 5, wherein the effective cross-sectional area A and the effective cross-sectional area C are greater than the effective cross-sectional area B.

7. A valve as claimed in any one of claims 1 to 6, wherein said housing has a first valve seat provided in said first passage and a second valve seat provided in said second passage.