Variable capacity swash plate compressor

Abstract

[Problem] To provide a variable-capacity swash-plate-type compressor that can store, in a crank chamber, an appropriate amount of a lubricant with respect to a change in operation state of a refrigeration circuit while ensuring lubricant supply to a sliding part and that can suppress excessive emission of the lubricant to the refrigeration circuit. [Solution] A first bleed-air passage 50 that always communicates between a crank chamber 2 and a suction chamber 31 and a second bleed-air passage 60 that always communicates between the crank chamber 2 and the suction chamber 31 are provided; the first bleed-air passage 50 is made to communicate with the crank chamber 2 via a space (central-hole space 54) defined by an insertion end section of a shaft 7 in a central hole 12 that is formed at least at the center of a cylinder block 1 and into which the shaft 7 is inserted; and the second bleed-air passage 60 is made to open in an end surface 1a of the cylinder block 1 that faces a swash plate 19.

Description

[Technical Field]

[0001] The present invention relates to a variable displacement swash plate compressor having a configuration for appropriately adjusting oil in a crank chamber defined by a cylinder block and a housing assembled thereto. [Background technology]

[0002] This type of compressor comprises a cylinder block in which multiple cylinder bores are formed, a front housing attached to the front side of the cylinder block to define a crank chamber, and a rear housing attached to the rear side of the cylinder block via a valve plate and in which a suction chamber and a discharge chamber are formed. Pistons are arranged so that they can move back and forth in each cylinder bore of the cylinder block, a shaft is rotatably supported by the front housing and the cylinder block, and a swash plate is provided on this shaft that rotates integrally with the shaft and has a variable inclination angle relative to the shaft. The engaging portions of the pistons are anchored to the peripheral part of the swash plate via shoes, and the rotational movement of the swash plate is converted into reciprocating movement of the pistons via the shoes.

[0003] This type of compressor has an intake passage connecting the discharge chamber and the crank chamber, and a bleed passage connecting the crank chamber and the suction chamber. A control valve is also provided in the intake passage, which controls the pressure in the crank chamber by adjusting the amount of working fluid flowing from the discharge chamber to the crank chamber. This changes the inclination angle of the swash plate relative to the shaft, thereby controlling the discharge rate. Since the working fluid flowing in through the intake passage contains oil, supplying this working fluid to the crank chamber also supplies oil to the crank chamber.

[0004] The fluids that enter the crank chamber include intake gas supplied from the discharge chamber and blow-by gas that enters through the clearance between the cylinder bore and the piston. The fluids that leave the crank chamber include bleed gas that flows through a bleed passage into the intake chamber formed in the rear housing. Therefore, the amount of oil (lubricating oil) in the crank chamber fluctuates depending on the operating conditions due to the flow of these fluids.

[0005] However, if the amount of oil in the crankcase is low, the sliding parts such as the swash plate will not be sufficiently lubricated, which may result in a loss of reliability. Therefore, in the past, in order to prevent oil from being taken out of the crankcase (to keep the oil in the crankcase), measures such as providing an oil separation function within the crankcase have been considered.

[0006] For example, in the piston-type compressor shown in Patent Document 1 below, a bleed hole that forms part of a bleed passage for releasing the working fluid that has flowed into the crank chamber into the suction chamber is formed in the shaft, and the bleed hole formed in this shaft is composed of an axial passage that is provided along the axis from the rear end to the front end of the shaft and a radial passage that communicates with this axial passage, opens to the crank chamber, and forms the inlet of the bleed passage, and oil is separated from the working fluid that is sucked in from the radial passage by centrifugal force generated by rotation of the shaft. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-343440 [Patent Document 2] International Publication No. WO2015 / 199207 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in a variable displacement swash plate compressor in which a portion of the bleed passage that guides the working fluid from the crank chamber to the suction chamber is formed on the shaft and the centrifugal force generated by the rotation of the shaft is used to separate the oil, the oil separation function increases as the rotation speed increases, making it easier for oil to accumulate in the crank chamber.If too much oil accumulates in the crank chamber, the swash plate will stir the highly viscous oil, causing heat generation due to shear friction between the swash plate and the oil, which in turn increases the temperature inside the crank chamber.

[0009] To address this problem, the applicant has proposed a configuration in which, in addition to a bleed passage that connects the crank chamber and the suction chamber via a hole in the shaft, a bypass passage is provided that constantly connects the crank chamber and the suction chamber, and the portion of this bypass passage that connects to the crank chamber is located radially outside the rotational trajectory of the swash plate, for example, in the lower part of the crank chamber, at the position of the bolt holes through which bolts that fasten the housing are inserted (see Patent Document 2).

[0010] According to the configuration of Patent Document 2, the bypass passage is located in the lower part of the crank chamber and opens at the position of the bolt hole through which the bolt is inserted, so oil can be stably discharged into the suction chamber from the part of the crank chamber where the oil concentration is highest.

[0011] However, because the oil is sucked from areas where it has not turned into mist, too much oil is discharged. This can lead to a shortage of oil in the crankcase, resulting in insufficient lubrication of the sliding parts, during high-load operation when the pressure control valve in the intake passage closes and oil cannot be supplied from the discharge chamber, or during low-flow (low-load) operation when the oil discharged into the refrigeration circuit does not return to the compressor.

[0012] The present invention has been made in consideration of the above circumstances, and its main objective is to provide a variable displacement inclined plate compressor that can store an appropriate amount of lubricating oil in the crank chamber in response to changes in the operating state of the refrigeration circuit, and can constantly ensure a supply of lubricating oil to the sliding parts by suppressing excessive discharge of lubricating oil into the refrigeration circuit. [Means for solving the problem]

[0013] In order to achieve the above object, a variable displacement swash plate compressor according to the present invention comprises: a cylinder block having a plurality of cylinder bores; a front housing attached to the front side of the cylinder block to define a crank chamber; a rear housing attached to the rear side of the cylinder block to define a suction chamber and a discharge chamber; a shaft rotatably supported by the front housing and a central hole formed in the center of the cylinder block; a swash plate that rotates integrally with the shaft and is attached so as to have a variable inclination angle relative to the shaft; pistons disposed in a plurality of cylinder bores formed around the central hole of the cylinder block and reciprocate with the rotation of the swash plate; an intake passage communicating the discharge chamber with the crank chamber; a pressure control valve provided in the intake passage to adjust the opening degree of the intake passage; a first bleed passage constantly communicating the crank chamber with the suction chamber; and a second bleed passage constantly communicating the crank chamber with the suction chamber. the first bleed passage communicates with the crankcase via at least a space defined by an insertion end of the shaft within the central hole; The second bleed passage is open to an end surface of the cylinder block facing the swash plate.

[0014] Here, the space defined by the insertion end of the shaft in the central hole of the cylinder block (hereinafter also referred to as the central hole space) is, for example, the space formed between the rear end of the shaft in the central hole and the valve plate when the central hole is formed through the center of the cylinder block and a rear housing is assembled to the cylinder block via a valve plate. The first bleed passage, which is connected to the crankcase via this central hole space, is formed by connecting the central hole space to the crankcase via a gap between the central hole and the shaft, and / or by connecting the central hole space to the crankcase via a hole formed in the shaft, which will be described later.

[0015] The end face of the cylinder block facing the swash plate is the front end face that defines the crank chamber of the cylinder block, avoiding the cylinder bores and center hole. Furthermore, if the cylinder block has a recess on the crank chamber side that opens into the center hole or bolt holes for inserting bolts to fasten the housing, the end face that faces the swash plate is the part that avoids these recesses and bolt holes.

[0016] In the above configuration, the oil inside the crankcase is stirred by the oscillating rotating swash plate and mixed with the refrigerant inside the crankcase, forming a mist of working fluid. This mist of refrigerant and oil rotates inside the crankcase due to the rotation of the swash plate, causing a centrifugal force. As a result, the working fluid has a high oil content in the radially outer region of the crankcase and a low oil content in the radially inner region of the crankcase.

[0017] The first bleed passage communicates with the crankcase via a space (central bore space) defined by the insertion end of the shaft in the central bore of the cylinder block, enabling stable discharge of working fluid with a low oil concentration, i.e., refrigerant gas, from the crankcase. Meanwhile, the second bleed passage opens on the end face of the cylinder block facing the swash plate, radially outward of the central bore, allowing discharge of working fluid with a relatively high oil concentration. This allows oil mist generated by oil agitation to be discharged, thereby suppressing an increase in oil temperature due to oil agitation. Meanwhile, oil radially outward of the swash plate's rotation path (e.g., oil flowing into the inner surfaces of bolt holes through which bolts fastening the housing are inserted) is hardly agitated and does not become mist, so it is not discharged from the second bleed passage, preventing excessive oil depletion in the crankcase.

[0018] Here, it is preferable that the first bleed passage and the second bleed passage each have an orifice with a reduced passage area. With this configuration, an orifice is provided in each of the first bleed passage, which releases refrigerant gas from the crank chamber into the suction chamber, and the second bleed passage, which releases working fluid containing mist-like oil from the crank chamber into the suction chamber. This makes it possible to set a preferred orifice area for each, enabling stable discharge of refrigerant gas and excess oil.

[0019] The shaft may be configured to have an axial hole of finite length that opens into a space defined by the insertion end of the shaft within the central hole and extends along the axis from the insertion end of the shaft, and a crank chamber side hole that extends radially from the axial hole and opens into the crank chamber. In this configuration, communication from the crank chamber to the central hole space is via the crank chamber side hole connected to the axial hole of the shaft, so that the centrifugal force caused by the rotation of the shaft can further dilute the oil concentration of the working fluid flowing into the central hole space.

[0020] The shaft may also have a finite-length axial hole that opens into a space defined by the insertion end of the shaft within the central hole and extends along the axis from the insertion end of the shaft, and a shaft seal chamber side hole that extends radially from the axial hole, houses a seal member that seals between the shaft and the front housing, and opens into a shaft seal chamber that communicates with the crank chamber. In this configuration, communication from the crank chamber to the central bore space is via the shaft seal chamber side hole connected to the axial hole of the shaft, so that the working fluid discharged from the crank chamber to the suction chamber can pass through the shaft seal chamber, making it possible to effectively cool and lubricate the shaft seal.

[0021] Furthermore, the shaft may have a finite-length axial hole that opens into a space defined by the insertion end of the shaft within the central hole and extends along the axis from the insertion end of the shaft, a crank chamber side hole that extends radially from the axial hole and opens into the crank chamber, and a shaft seal chamber side hole that extends radially from the axial hole, houses a seal member that seals between the shaft and the front housing, and opens into a shaft seal chamber that communicates with the crank chamber. In such a configuration, both of the effects described above (the oil concentration of the working fluid flowing into the central hole space can be reduced, thereby cooling and lubricating the shaft seal) can be achieved.

[0022] The opening of the intake passage on the crank chamber side is located radially inward of the portion of the end face of the cylinder block on the crank chamber side where the distance between adjacent cylinder bores of the cylinder block is shortest, and the opening of the second bleed passage on the crank chamber side is located in an area on the end face of the cylinder block facing the swash plate, radially outward of an imaginary circle connecting the portions of the end face that face the swash plate where the distance to the central holes of each cylinder bore is shortest, and radially inward of the portion of the end face that faces the swash plate where the distance between adjacent cylinder bores is shortest. Here, the end face on the crank chamber side where the intake passage opens includes the end face where the cylinder bores of the cylinder block are formed (the end face facing the swash plate), and, in the case where the cylinder block has a recess with a central hole opening on the crank chamber side, the bottom face where the central hole of this recess opens.

[0023] In this configuration, the oil-mixed working fluid returning from the discharge chamber to the crankcase through the intake passage is sprayed toward the swash plate from the intake passage outlet, lubricating the swash plate's sliding surface. The oil in the working fluid that lubricates the swash plate tends to move radially outward due to the centrifugal force of the rotating working fluid as the swash plate rotates. However, it cannot move radially outward unless it passes between the pistons inserted in the multiple cylinder bores. Therefore, the oil mist in the working fluid must pass in front of the second bleed passage. As it passes in front of the second bleed passage, it is sucked into the second bleed passage and effectively discharged into the suction chamber.

[0024] The opening of the second bleed passage on the crank chamber side is preferably positioned at a phase offset of 180 degrees or more in the rotation direction of the swash plate from the opening of the intake passage on the crank chamber side. With this configuration, the opening position of the second bleed passage is more than 180 degrees away from the opening position of the intake passage in the rotational direction, so there is no risk that oil in the working fluid that has returned from the intake passage to the crank chamber will be sucked out of the second bleed passage before it can lubricate the swash plate.

[0025] The opening of the second bleed passage on the crankcase side should be positioned lower in the direction of gravity than the first bleed passage. The oil in the crankcase is blown away by the rotation of the swash plate and becomes mist-like. The oil density near the bottom of the crankcase becomes high due to the effect of gravity. Therefore, by positioning the opening of the second bleed passage on the crankcase side lower in the direction of gravity than the first bleed passage, the mist-like oil in the crankcase can be effectively discharged. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view showing a first configuration example of a compressor according to the present invention. [Figure 2] FIG. 2(a) is a diagram showing an end face (end face defining the crank chamber) of the cylinder block used in the compressor of FIG. 1 that faces the swash plate and faces the crank chamber, and FIG. 2(b) is a perspective view in which the cylinder block is cut so that the second bleed passage is visible. [Figure 3] FIG. 3(a) is a diagram showing the end face of the cylinder block used in the compressor of FIG. 1 on the valve plate side, and FIG. 3(b) is a perspective view in which the cylinder block is cut so that the second bleed passage is visible. [Figure 4] FIG. 4 is a cross-sectional view showing a second configuration example of a compressor according to the present invention. [Figure 5]FIG. 5(a) is a diagram showing an end face (end face defining the crank chamber) of the cylinder block used in the compressor of FIG. 3 that faces the swash plate and faces the crank chamber, and FIG. 5(b) is a perspective view in which the cylinder block is cut so that the second bleed passage is visible. [Figure 6] FIG. 6(a) is a diagram showing the end face on the valve plate side of the cylinder block used in the compressor of FIG. 3, and FIG. 6(b) is a perspective view in which the cylinder block is cut so that the second bleed passage is visible. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0028] 1, the variable displacement swash plate compressor is configured to include a cylinder block 1, a front housing 3 assembled to cover the front side of the cylinder block 1 and defining a crank chamber 2 between the cylinder block 1, and a rear housing 5 assembled to the rear side of the cylinder block 1 via a valve plate 4. The front housing 3, cylinder block 1, valve plate 4, and rear housing 5 are fastened together in the axial direction by fastening bolts 6.

[0029] A shaft 7, the front end of which protrudes from the front housing 3, is housed in a crank chamber 2 defined by the front housing 3 and the cylinder block 1. A drive pulley (not shown) is provided on the portion of the shaft 7 that protrudes from the front housing 3, and rotational power applied to the drive pulley is transmitted to the shaft 7 via engagement of a clutch plate.

[0030] The front end of the shaft 7 is airtightly sealed from the front housing 3 via a seal member 10 provided between the shaft 7 and the front housing 3, and is rotatably supported by a radial bearing 11. The rear end of the shaft 7 is rotatably supported by a radial bearing 13 housed in a central hole 12 formed in approximately the center of the cylinder block 1. Here, the radial bearings 11 and 13 may be rolling bearings or plain bearings.

[0031] 2 and 3, the cylinder block 1 is provided with a recess 14, into which a central hole 12 for accommodating a radial bearing 13 opens, and which opens into the crank chamber 2. A plurality of cylinder bores 15 are arranged at equal intervals on a circumference centered on the central hole 12. Each cylinder bore 15 is formed to pass through the cylinder block 1 in the axial direction, and a piston 20 is inserted into each cylinder bore 15 so as to be able to slide back and forth.

[0032] A thrust flange 16 that rotates integrally with the shaft 7 is fixed to the shaft 7 within the crank chamber 2. The thrust flange 16 is rotatably supported via a thrust bearing 17 on the inner wall surface of the front housing 3 that is formed substantially perpendicular to the shaft 7. A swash plate 19 is connected to the thrust flange 16 via a link member 18.

[0033] The swash plate 19 is tiltably supported by a hinge ball 21 provided on the shaft 7, and rotates integrally with the thrust flange 16 in synchronization with its rotation.

[0034] The piston 20 is constructed by joining a head 20a inserted into the cylinder bore 15 and an engagement portion 20b protruding into the crank chamber 2 in the axial direction, and the engagement portion 20b is anchored to the peripheral portion of the swash plate 19 via a pair of shoes 22.

[0035] Therefore, when the shaft 7 rotates, the swash plate 19 rotates accordingly, and the rotational motion of the swash plate 19 is converted into the reciprocating linear motion of the piston 20 via the shoe 22, thereby changing the volume of the compression chamber 25 defined between the piston 20 and the valve plate 4 within the cylinder bore 15.

[0036] The rear housing 5 is formed with a suction chamber 31 and a discharge chamber 32 formed outside the suction chamber 31, and the valve plate 4 is formed with a suction hole 26 that connects the suction chamber 31 and the compression chamber 25 via a suction valve (not shown), and a discharge hole 27 that connects the discharge chamber 32 and the compression chamber 25 via a discharge valve (not shown).

[0037] In this configuration example, a supply passage 40 that connects the discharge chamber 32 and the crank chamber 2 is formed by passages 41, 42, and 43 formed in the rear housing 5, the valve plate 4, and the cylinder block 1. A pressure control valve 44 is also arranged in the rear housing 5, and is provided midway through the supply passage 40 (passage 41). A valve mechanism (not shown) is provided inside the pressure control valve 44, and by adjusting the opening degree of this valve mechanism, the flow rate of refrigerant flowing from the discharge chamber 32 through the supply passage 40 to the crank chamber 2 is adjusted, thereby controlling the pressure in the crank chamber 2.

[0038] As shown in Figures 2 and 3, the passage 43 is composed of an axial hole 43a for the intake passage that is formed from the end face 1b of the cylinder block 1 on the valve plate side and is generally parallel to the central hole 12, and an oblique hole 43b for the intake passage that is drilled from the end face 1a on the crank chamber side of the cylinder block 1 toward the rear side so as to pass through the gap between adjacent cylinder bores 15 and is connected to the axial hole 43a for the intake passage.

[0039] The intake passage 40 (oblique intake passage hole 43b) has an opening on the crank chamber side formed in the end face 1a of the cylinder block 1 on the crank chamber side. In this example, the opening is on the end face 1a of the cylinder block 1 facing the swash plate 19, i.e., the end face on which the cylinder bores 15 and the recesses 14 are formed, slightly inside the sliding contact portion of the swash plate 19 that slides against the shoes 22. Therefore, the intake passage 40 supplies oil mixed with the refrigerant delivered from the discharge chamber 32 via the pressure control valve 44 to the sliding contact surface of the swash plate 19 with the shoes 22. In particular, in this example, the intake passage 40 opens radially inward from the narrowest portion between adjacent cylinder bores 15 (the portion where the distance between adjacent cylinder bores is shortest) and radially outward from the recesses 14 where the central hole 12 opens (see FIG. 2(a)).

[0040] The shaft 7 is provided with a fluid discharge passage 51, which will be described below. This fluid discharge passage 51 is composed of an axial hole 51a of finite length formed on the axis of the shaft 7, extending from the rear end to about the middle of the front end, a crank chamber side hole 51b that communicates with the axial hole 51a, extends radially, and opens into the crank chamber 2, and a shaft seal chamber side hole 51c that communicates with the axial hole 51a, extends radially, and opens into a shaft seal chamber 52 that houses the seal member 10.

[0041] Here, the shaft seal chamber 52 communicates with the crank chamber 2 above it via a communication hole 53 drilled in the front housing 3. A portion of the oil flowing down the inner wall surface of the front housing 3 is guided to the shaft seal chamber 52 via the communication hole 53.

[0042] In addition, the space defined by the insertion end of the shaft 7 into the central hole 12, i.e., the space between the rear end of the shaft 7 and the valve plate 4 (hereinafter referred to as the central hole space 54), is connected to the suction chamber 31 via an orifice hole 55 formed in the valve plate 4. Therefore, in this configuration example in which the above-mentioned fluid discharge passage 51 is formed in the shaft 7, the fluid discharge passage 51, the central hole space 54, and the orifice hole 55 form the first bleed passage 50 that constantly connects the crank chamber 2 and the suction chamber 31.

[0043] The crank chamber side hole 51b of the first bleed passage 50 (fluid discharge passage 51) has the function of separating oil from the working fluid that flows in through it by centrifugal force generated by the rotation of the shaft 7, and mainly functions to allow working fluid with a low oil content to flow in. In addition, the shaft seal chamber side hole 51c has the function of sucking in and discharging excess oil that accumulates in the shaft seal chamber 52.

[0044] In the above-described configuration, the working fluid flows from the crank chamber 2 to the central hole space 54 via the fluid discharge passage 51, and also from the recess 14 via the gap between the central hole 12 in which the radial bearing 13 is housed and the shaft 7. Therefore, even in a compressor in which a fluid discharge passage 51 is not formed in the shaft 7, the recess 14, the gap between the central hole 12 and the shaft 7, the central hole space 54, and the orifice hole 55 form a first bleed passage 50 that constantly connects the crank chamber 2 and the suction chamber 31.

[0045] Furthermore, in this compressor, a second bleed passage 60 is formed in addition to the first bleed passage 50, which constantly connects the crank chamber 2 and the suction chamber 31. This second bleed passage 60 is configured to have a passage 61 formed in the cylinder block 1 and an orifice hole 62 formed in the valve plate 4 and communicating with this passage 61.

[0046] The passage 61 is formed from the end face 1b of the cylinder block 1 on the valve plate 4 side substantially parallel to the central hole 12, and is composed of: a second bleed passage axial hole 61a into which the filter 56 is removably inserted; and a second bleed passage oblique hole 61b which is drilled from the end face 1a on the crank chamber 2 side of the cylinder block 1 toward the rear side so as to pass between the adjacent cylinder bores 15 and which communicates with the second bleed passage axial hole 61a.

[0047] The portion of the second bleed passage 60 that communicates with the crank chamber 2 (the portion where the passage 61 formed in the cylinder block 1 communicates with the crank chamber 2, i.e., the opening on the crank chamber side) is formed on the end face 1a of the cylinder block 1 that faces the crank chamber 2 and faces the swash plate 19. That is, the portion of the second bleed passage 60 that communicates with the crank chamber 2 is located radially inward of the positions of the bolt holes 28, through which the bolts 6 that fasten the housing are inserted. In particular, in this example, the portion is located in a triangular region 1c (shown by hatching in FIG. 2(a)) that is radially outward of an imaginary circle α that connects the positions where the distance between each cylinder bore 15 and the central hole 12 is shortest, in this example, radially outward of the recess 14 where the central hole 12 opens, and radially inward of an imaginary circle β that connects the positions where the distance between adjacent cylinder bores is shortest (the positions where the distance between the bores is shortest).

[0048] The air supply passage oblique hole 43b is formed with a smaller diameter than the air supply passage axial hole 43a, and the second bleed passage oblique hole 61b is formed with a smaller diameter than the second bleed passage axial hole 61a, so that the passage components can be connected to each other even if differences in shape occur due to manufacturing variations.

[0049] The positional relationship between the portion where the intake passage 40 opens into the crank chamber 2 and the portion where the second bleed passage 60 opens into the crank chamber 2 is such that the crank chamber side opening of the second bleed passage 60 is out of phase with the crank chamber side opening of the intake passage 40 by 180 degrees or more in the rotation direction 19a of the swash plate 19 (in the example shown in FIG. 2, it is out of phase by about 240 degrees).

[0050] Furthermore, while maintaining this phase relationship, with the compressor installed, the opening of the second bleed passage 60 on the crank chamber side is positioned lower than the first bleed passage 50 in the direction of gravity.

[0051] In the above-described configuration, when the shaft 7 is rotated by the rotational power applied to the drive pulley, the swash plate 19 is rotated. This rotational motion of the swash plate 19 is converted via the shoes 22 into reciprocating linear motion of the pistons 20, causing the pistons 20 to reciprocate within the cylinder bores 15. This reciprocating motion of the pistons 20 changes the volume of the compression chambers 25 formed between the pistons 20 and the valve plate 4 within the cylinder bores 15, thereby performing the suction, compression, and discharge strokes of the working fluid. That is, during the suction stroke, the pistons 20 move to increase the volume of the compression chambers 25, and working fluid is drawn from the suction chamber 31 to the compression chamber 25 through the suction hole 26, which is opened and closed by the suction valve. During the compression stroke, the pistons 20 move to decrease the volume of the compression chambers 25, and compressed working fluid is discharged from the compression chambers 25 to the discharge chamber 32 through the discharge hole 27, which is opened and closed by the discharge valve.

[0052] The discharge volume of the compressor is determined by the stroke of the piston 20. This stroke is determined by the pressure difference between the pressure on the front surface of the piston 20, i.e., the pressure in the compression chamber 25, and the pressure on the back surface of the piston 20, i.e., the pressure in the crank chamber 2. Specifically, if the pressure in the crank chamber 2 is increased, the pressure difference between the compression chamber 25 and the crank chamber 2 decreases, reducing the inclination angle (oscillation angle) of the swash plate 19. As a result, the stroke of the piston 20 decreases and the discharge volume decreases. Conversely, if the pressure in the crank chamber 2 is decreased, the pressure difference between the compression chamber 25 and the crank chamber 2 increases, increasing the inclination angle (oscillation angle) of the swash plate 19. As a result, the stroke of the piston 20 increases and the discharge volume increases.

[0053] During high rotation speeds such as during acceleration, the pressure control valve 44 increases the amount of refrigerant gas supplied from the discharge chamber 32 to the crank chamber 2 via the supply passage 40 to reduce the power load on the compressor, thereby increasing the crank chamber pressure. Therefore, the swing angle of the swash plate 19 becomes smaller (the piston stroke becomes shorter), and the discharge amount becomes smaller. At this time, the rotation speed of the shaft 7 becomes faster, so the oil separation function of the fluid discharge passage 51 becomes stronger, and oil tends to accumulate in the crank chamber 2.

[0054] At this time, the oil in the crank chamber 2 is agitated by the oscillating and rotating swash plate 19 and mixes with the refrigerant inside the crank chamber, forming a mist. This mist of working fluid, a mixture of oil and refrigerant, rotates inside the crank chamber as the swash plate 19 rotates, and as a result of the centrifugal force, the working fluid in the radially outer region of the crank chamber is rich in oil, while the working fluid in the radially inner region of the crank chamber is lean in oil.

[0055] The first bleed passage 50 communicates with the crank chamber 2 via the central hole space 54 of the central hole 12 of the cylinder block 1, so that the working fluid (i.e., refrigerant gas) with a low oil concentration in the crank chamber can be stably discharged. Moreover, when the working fluid that flows into the central hole space 54 is introduced from the crank chamber side hole 51b, the oil concentration can be further reduced by the centrifugal force.

[0056] This configuration makes it easier for oil to accumulate in the crank chamber. However, because the second bleed passage 60 opens to the end face 1a of the cylinder block 1 that faces the crank chamber 2 and faces the swash plate 19 (the end face located radially inward from the position where the bolt holes 28 of the cylinder block 1 are open), it becomes possible to discharge a working fluid with a relatively high oil content due to the pressure difference between the crank chamber 2 and the suction chamber 31. This allows the oil mist generated by the agitation by the swash plate 19 to be discharged, preventing excess oil from accumulating in the crank chamber 2 and suppressing an increase in oil temperature due to oil agitation. On the other hand, the oil on the radially outer side that flows into the bolt holes 28 (oil radially outward from the rotational path of the swash plate 19) remains there without being stirred by the swash plate 19 and does not turn into mist, so it is not discharged from the second bleed passage 60. Therefore, regardless of the operating conditions, the problem of excessive oil reduction in the crankcase is eliminated.

[0057] The crank chamber-side opening of the intake passage 40 is located radially inward of the crank chamber-side end face of the cylinder block 1 at the point where the distance between adjacent cylinder bores is shortest. The crank chamber-side opening of the second bleed passage 60 is located in the triangular region 1c on the end face of the cylinder block 1 facing the swash plate 19. Therefore, oil-mixed working fluid is ejected from the intake passage 40 toward the swash plate 19, lubricating the sliding surface of the swash plate 19. The working fluid that lubricates the swash plate 19 rotates with the swash plate 19, and centrifugal force causes the oil in the working fluid to move radially outward. However, it cannot move radially outward unless it passes between the pistons 20 inserted in the cylinder bores 15. Therefore, the oil in the working fluid travels along the triangular region 1c of the cylinder block 1 between the adjacent pistons 20, weakening its rotation by collisions with the adjacent pistons. This allows the oil in the working fluid to more easily pass in front of the second bleed passage 60. In particular, in this example, the crank chamber-side opening of the second bleed passage is located lower in the direction of gravity than the first bleed passage, so that the oil in the working fluid blown radially outward by the rotation of the swash plate 19, combined with the effect of gravity, more easily passes in front of the second bleed passage 60. As the oil in the working fluid passes in front of the second bleed passage 60, it is sucked into the second bleed passage 60 and discharged into the suction chamber 31. That is, the working fluid that mainly contains oil after lubricating the swash plate 19 is discharged from the second bleed passage.

[0058] Furthermore, in the above example, the crank chamber-side opening of the second bleed passage 60 is positioned at a phase offset of 180 degrees or more with respect to the rotational direction 19a of the swash plate 19 relative to the crank chamber-side opening of the intake passage 40. Therefore, there is no risk that oil in the working fluid returning from the intake passage 40 to the crank chamber 2 will be sucked out of the second bleed passage before it has time to lubricate the swash plate 19, and there is no risk that the lubrication of the swash plate 19 will be impaired.

[0059] As described above, this configuration ensures sufficient lubrication of the swash plate 19 by opening the intake passage 40 opposite the swash plate 19. Furthermore, the oil mist generated after lubricating the swash plate 19 is discharged through the second bleed passage 60, preventing excess oil from accumulating in the crank chamber 2. Furthermore, oil that is not misted by the agitation of the swash plate 19 remains in the crank chamber and is not discharged through the second bleed passage 60. As a result, it is possible to avoid the inconvenience of oil depletion in the crank chamber depending on the operating conditions, and it is possible to constantly maintain an appropriate amount of oil in the crank chamber.

[0060] Furthermore, in the above-described configuration, the orifice hole 55 of the first bleed passage 50 and the orifice hole 62 of the second bleed passage 60 are provided separately. Therefore, the amount of bleed gas introduced into the suction chamber 31 via the fluid discharge passage 51 (first bleed passage 50) and the amount of oil introduced into the suction chamber 31 via the second bleed passage 60 can be independently adjusted by adjusting the sizes of the orifice holes 55, 62. Therefore, in this compressor, the amount of bleed gas and the amount of oil discharged can be independently adjusted to obtain desired characteristics.

[0061] In the above example, the intake passage 40 is opened to the end face 1a where the cylinder bores 15 facing the swash plate 19 of the cylinder block 1 are formed. However, the intake passage 40 does not have to be opened to the end face 1a facing the swash plate 19, and may be opened to another end face radially inward from the point where the distance between adjacent cylinder bores of the cylinder block 1 is shortest, as long as it can introduce high-pressure gas from the discharge chamber 32 into the crank chamber 2. An example of this is shown in FIG. 4, where the opening of the supply passage 40 to the crank chamber 2 side is open to the bottom surface 14a of the recess 14 where the central hole 12 opens.

[0062] In this example, a valve housing space 71 is provided in a portion of the supply passage 40 downstream of the pressure control valve 44, and a bleed control valve 72 is slidably accommodated in this valve housing space 71. The valve housing space 71 extends substantially parallel to the shaft 7 from an end face 1b of the cylinder block 1 that faces the valve plate 4. The upstream end of this valve housing space 71 (the open end facing the valve plate 4) communicates with the through hole 42 formed in the valve plate 4 that constitutes part of the supply passage 40. The downstream end of the valve housing space 71 is connected to a passage 73 that leads to the crank chamber 2. In addition, a branch passage 75 is formed in the cylinder block 1 near the downstream end of the valve housing space 71. The branch passage 75 is connected to a communication hole 74 formed in the valve plate 4 and communicates with the suction chamber 31 via the communication hole 74. This branch passage 75 and the communication hole 74 formed in the valve plate 4 form a third bleed passage 70 that branches off from the supply passage 40 downstream of the pressure control valve 44, communicates with the suction chamber 31, and is opened and closed by the bleed control valve 72.

[0063] The opening degree of this bleed control valve 72, which communicates between the crank chamber 2 and the branch passage 75 via the portion of the supply passage 40 downstream of the bleed control valve 72, changes depending on the difference between the pressure downstream of the pressure control valve 44 in the supply passage and the pressure in the crank chamber 2. When the pressure downstream of the pressure control valve 44 in the supply passage 40 is lower than the pressure in the crank chamber 2, the compressor increases the opening degree of communication between the crank chamber 2 and the branch passage 75, so that the pressure in the crank chamber 2 is quickly discharged to the suction chamber 31. When the pressure downstream of the pressure control valve 44 is higher than the pressure in the crank chamber 2, the compressor decreases the opening degree of communication between the crank chamber 2 and the branch passage 75, so that the original function of the supply passage, which is to flow working fluid from the upstream side to the downstream side of the supply passage 40 via the bleed control valve 72 and introduce it into the crank chamber 2, can be achieved.

[0064] The specific configuration, operation, and function of such a bleed control valve 72 are the same as those in Japanese Patent Application No. 2018-13851, and therefore will not be described here. Furthermore, other components such as the first bleed passage 50 and the second bleed passage 60 are similar to those in the example of the configuration shown in FIG. 1, so the same components are denoted by the same reference numerals and a description thereof will be omitted.

[0065] In this configuration, the intake passage 40 opens to the bottom surface 14a of the recess 14 where the central hole 12 of the cylinder block 1 opens, so oil supplied through the intake passage 40 is unlikely to be sprayed directly onto the outer periphery of the swash plate 19. However, the second bleed passage 60 opens to the end surface 1a of the cylinder block 1 facing the crank chamber 2, which faces the swash plate 19 (opens radially inward from the location where the bolt holes 28, which are located radially outward from the rotational path of the swash plate 19, open). Therefore, as mentioned above, an appropriate amount of oil remains in the crank chamber 2, enough to immerse the outer periphery of the swash plate 19. This, combined with the oil supplied from the intake passage 40, allows sufficient oil to be supplied to the swash plate 19, ensuring lubrication of the swash plate 19.

[0066] Furthermore, since the compressor having such a configuration is provided with the third bleed passage 70, which is opened and closed by the bleed control valve 72, in addition to the second bleed passage 60, the second bleed passage 60 can discharge excess oil from the crank chamber while preventing excessive oil discharge. Furthermore, when the pressure downstream of the pressure control valve 44 in the supply passage 40 is lower than the pressure in the crank chamber 2, the bleed control valve 72 increases the opening degree of communication between the crank chamber 2 and the branch passage 75, thereby enabling the pressure in the crank chamber 2 to be quickly discharged to the suction chamber 31. Therefore, at the start of the compressor, the amount of oil in the crank chamber can be maintained at an appropriate level while the time until the liquid refrigerant accumulated in the crank chamber is vaporized and discharged to the suction chamber 31 can be shortened, thereby shortening the time until the compressor's discharge capacity can be controlled. [Explanation of symbols]

[0067] 1 Cylinder block 1a End face 2 crankcase 3 Front housing 4 valve plates 5 Rear housing 7 shaft 12 Central hole 15 cylinder bore 19 Swash plate 20 pistons 25 compression chamber 31 Suction chamber 32 Discharge chamber 40 Air supply passage 50 First bleed passage 51 Fluid discharge passage 51a Shaft hole 51b Crankcase side hole 51c Shaft seal chamber side hole 52 Shaft seal chamber 54 Central hole space 55 Orifice 60 Second bleed passage 62 Orifice hole 70 Third bleed passage

Claims

1. a cylinder block having a plurality of cylinder bores formed therein; a front housing attached to the front side of the cylinder block to define a crank chamber; a rear housing attached to a rear side of the cylinder block and having a suction chamber and a discharge chamber formed therein; a shaft rotatably supported in the front housing and a central hole formed in the center of the cylinder block; a swash plate that rotates integrally with the shaft and is attached so that its inclination angle with respect to the shaft can be varied; Pistons are arranged in a plurality of cylinder bores formed around the central hole of the cylinder block, and reciprocate with rotation of the swash plate; an air supply passage communicating the discharge chamber and the crank chamber; a pressure control valve provided in the air supply passage and configured to adjust the opening degree of the air supply passage; a first bleed passage that constantly connects the crank chamber and the suction chamber; a second bleed passage that constantly connects the crank chamber and the suction chamber, the first bleed passage communicates with the crankcase via at least a space defined by an insertion end of the shaft within the central hole; The second bleed passage opens to an end surface of the cylinder block facing the swash plate. A variable displacement swash plate compressor characterized by:

2. 2. The variable displacement swash plate compressor according to claim 1, wherein the first bleed passage and the second bleed passage each have an orifice with a reduced passage area, independently of each other.

3. The shaft an axial hole of finite length that opens into a space defined by an insertion end of the shaft within the central hole and extends from the insertion end of the shaft along an axis; a crank chamber side hole extending radially from the axial hole and opening into the crank chamber; 3. The variable displacement swash plate compressor according to claim 1, further comprising:

4. The shaft an axial hole of finite length that opens into a space defined by an insertion end of the shaft within the central hole and extends from the insertion end of the shaft along an axis; a shaft seal chamber side hole that extends radially from the shaft hole, accommodates a seal member that seals between the shaft and the front housing, and opens into a shaft seal chamber that communicates with a crank chamber; 3. The variable displacement swash plate compressor according to claim 1, further comprising:

5. The shaft an axial hole of finite length that opens into a space defined by an insertion end of the shaft within the central hole and extends from the insertion end of the shaft along an axis; a crank chamber side hole extending radially from the axial hole and opening into the crank chamber; a shaft seal chamber side hole that extends radially from the shaft hole, accommodates a seal member that seals between the shaft and the front housing, and opens into a shaft seal chamber that communicates with a crank chamber; 3. The variable displacement swash plate compressor according to claim 1, further comprising:

6. an opening of the supply passage on the crank chamber side is located radially inward of a portion of an end face of the cylinder block on the crank chamber side where the distance between adjacent cylinder bores of the cylinder block is shortest, The opening of the second bleed passage on the crank chamber side is located in a region on the end face of the cylinder block facing the swash plate, radially outward from an imaginary circle connecting the portions of the cylinder bores where the distance from the center hole is shortest, and radially inward from a portion where the distance between adjacent cylinder bores is shortest.

6. A variable displacement swash plate compressor according to claim 1.

7. 7. The variable displacement swash plate compressor according to claim 6, wherein the opening of the second bleed passage on the crank chamber side is positioned at a phase offset of 180 degrees or more in the rotation direction of the swash plate from the opening of the supply passage on the crank chamber side.

8. 8. The variable displacement swash plate compressor according to claim 1, wherein an opening of the second bleed passage on the crank chamber side is located lower than the first bleed passage in the direction of gravity.

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