JP2009062834A - Coolant intake structure of fixed capacity type piston compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the mitigating effect of startup shocking in a fixed capacity type piston compressor using a rotary valve. <P>SOLUTION: A first rotary valve 35 and a second rotary valve 36 are provided to a rotary shaft 21 in correspondence with cylinder blocks 11, 12, and a cylinder 41 is integrally formed on the inner wall surface 401 of the plinth 40 which is formed in the rear housing 14. A valve body 42 is inserted to the inner surface 411 of the cylinder 41 in a state where the valve body 42 partitions a back pressure chamber 412, and the valve body 42 is energized toward the bottom wall surface 402 of the back pressure chamber 412 by a spring force of a return spring 47. The back pressure chamber 412 is connected to an intake chamber 142 through an extracting passage 48, and a check valve G1 is arranged on the extracting passage 48. The fluid in the back pressure chamber 412 can flow out into the intake chamber 142 via the extracting passage 48. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a fixed capacity type comprising a rotary valve having an introduction passage for introducing a refrigerant from a suction pressure region into a compression chamber defined in a cylinder bore by a piston, and the rotary valve rotates integrally with the rotary shaft. The present invention relates to a refrigerant suction structure in a piston type compressor.

  A piston compressor using a rotary valve (see, for example, Patent Documents 2 and 5) has a larger cylinder bore than a piston compressor using a reed valve type suction valve (see, for example, Patent Documents 1 and 4). There is little inhalation resistance when inhaling inhalation gas, and energy efficiency is excellent.

  As described in paragraph [0006] of Patent Document 2, when the compressor is started, the torque rapidly increases as the gas is compressed, and this is added to the vehicle engine (internal combustion engine) as a load. Therefore, a starting shock occurs in which the traveling speed of the vehicle decreases for a moment and the vehicle occupant feels a shock.

  In the piston compressor disclosed in Patent Document 2, a rotary valve that rotates integrally with the rotary shaft is provided so as to be movable in the axial direction of the rotary shaft, and the rotary valve has a pressure supplied to the control pressure chamber. Accordingly, the position of the rotating shaft in the axial direction can be changed. In addition, a bypass groove is formed in the rotary valve so that almost all cylinder bores can communicate with a suction port provided to the center of the cylinder block. The rotary valve is disposed at a position in the axial direction of the rotary shaft so that the bypass groove comes to a position where almost all cylinder bores can communicate with the suction port when the operation is stopped and started. Therefore, even when the piston performs an operation of compressing the gas in the cylinder bore at the time of activation, the gas in the cylinder bore returns to the suction port via the bypass groove, so that the activation shock does not occur.

  The clearance on the peripheral surface of the rotary valve needs to be as small as possible so that gas does not leak along the peripheral surface and the rotary valve can rotate. However, in the configuration in which the rotary valve can be moved in the axial direction of the rotary shaft, a clearance that enables the rotary valve to be moved in the axial direction of the rotary shaft is required, but such clearance management is very difficult. It is.

  The piston compressor disclosed in Patent Document 4 is provided with a differential pressure sensing on / off valve that opens and closes by a differential pressure between a discharge pressure and a suction pressure. The differential pressure sensing on / off valve is interposed between the low-pressure refrigerant line for introducing refrigerant from the outside of the compressor and the suction chamber in the compressor, and when the compressor is started from a pressure balanced state, the differential pressure The sensing on / off valve is closed, and the flow of refrigerant from the outside of the compressor into the suction chamber is stopped. Thereby, the starting shock is relieved.

In the compressor disclosed in Patent Document 3, a starting load reducing device is provided in the middle of the suction passage leading to the suction chamber. The starting load reducing device includes a spool valve that constitutes an oil damper, and a gap is provided between the damper portion of the spool valve and the housing. When the spool valve moves in the direction to open the suction passage, the oil in the damper chamber is gradually discharged from the gap into the intermediate chamber. Therefore, the moving speed of the spool valve becomes gradual, and the opening speed of the suction passage becomes gradual. Thereby, the starting shock is relieved.
JP-A 64-88064 Japanese Patent Laid-Open No. 7-119631 Japanese Patent Laid-Open No. 7-139474 JP 2000-145629 A JP 2006-83835 A

  However, in the compressor disclosed in Patent Document 3, the refrigerant remains in the suction chamber even when the suction passage is closed by the spool valve, and the residual refrigerant is sucked into the cylinder bore and compressed. In the compressor disclosed in Patent Document 4, the refrigerant remains in the suction chamber even when the differential pressure sensing on / off valve is closed, and the residual refrigerant is sucked into the cylinder bore and compressed. Since the volume of the suction chamber is increased in order to suppress suction pulsation, a large amount of refrigerant is sucked into the cylinder bore when the differential pressure sensing on / off valve is closed or when the suction passage is closed, The effect of starting shock mitigation is not sufficient.

  An object of this invention is to raise the effect of starting shock mitigation.

  In the present invention, pistons are accommodated in a plurality of cylinder bores arranged around the rotation shaft, and the piston is interlocked with the rotation of the rotation shaft through a cam body integrated with the rotation shaft. A rotary valve having an introduction passage for introducing a refrigerant from a suction pressure region into a compression chamber defined in the cylinder bore by the piston, wherein the rotary valve rotates integrally with the rotary shaft, and the rotation The shaft is directed to a refrigerant suction structure in a fixed displacement piston compressor connected to an external drive source via a clutch, and the invention of claim 1 includes a suction pressure region in the compressor and an outlet of the introduction passage. Switching means for switching between a communicating state and a blocking state is provided, and the switching means communicates a suction pressure region in the compressor and an outlet of the introduction passage. A valve body that is switched between a position to be shut off and a position to be shut off, a return spring that returns the valve body from the communicating position to the shut-off position, a back pressure chamber that is partitioned by the valve body, and the interior of the compressor A back pressure passage that communicates the suction pressure region and the back pressure chamber, and the back pressure chamber and the suction pressure region are communicated by a vent passage, and fluid from the back pressure chamber to the vent passage A check valve is provided to allow the flow of air.

  When the operation of the compressor is stopped, the valve body is in a position where the suction pressure region in the compressor and the outlet of the introduction passage are shut off, but when the operation of the compressor is started, the valve body is located downstream of the valve body. The pressure in the introduction passage decreases, and the valve body moves from a position where it is shut off to a position where it is communicated. Since the communication between the suction pressure region in the compressor and the outlet of the introduction passage is interrupted when the compressor is started, the amount of refrigerant compressed when the switching means is in the shut-off state is small, and the effect of reducing the start shock is reduced. high.

  When the compressor is in operation, oil that flows together with the refrigerant accumulates in the back pressure chamber. However, when the operation of the compressor is stopped, the oil accumulated in the back pressure chamber moves from a communicating position to a position where it is blocked. It is discharged to the extraction passage by the movement of the valve body. Therefore, when the operation of the compressor is stopped, the valve body is reliably returned to the shut-off position by the spring force of the return spring. The use of the return spring is a simple configuration for returning the valve body to the position where it is shut off.

  In a preferred example, the valve body has a piston portion that defines the back pressure chamber, the back pressure chamber has a bottom wall surface, and the pressure receiving end surface of the piston portion that receives the pressure of the back pressure chamber is In surface contact with the bottom wall surface of the back pressure chamber.

  When the valve body is in a position where it is shut off, the pressure receiving end face comes into surface contact with the bottom wall surface of the back pressure chamber. The oil accumulated in the back pressure chamber is discharged to the vent passage, but when the valve body is in a position where it is shut off, an oil film is formed between the pressure receiving end surface and the bottom wall surface. The oil film brakes the valve body at the start of the movement of the valve body, and the time required to shift from the position where the valve body is shut off to the communicating position after the start of operation of the compressor is increased. This contributes to mitigating the start-up shock.

In a preferred example, the pressure receiving end surface and the bottom wall surface are planes parallel to each other.
The configuration in which the pressure receiving end surface and the bottom wall surface are parallel to each other is suitable for increasing the contribution of the start-up shock due to the oil film.

In a preferred example, the inlet of the extraction passage opens on the bottom wall surface.
In a preferred example, the valve body is switched between the communicating position and the blocking position by moving in the direction of the axis of the rotating shaft.

The extraction passage passes through a housing constituting the fixed displacement type piston compressor and communicates with a suction pressure region in the compressor.
In a preferred example, the back pressure passage is above the back pressure chamber.

Oil that flows with the refrigerant tends to accumulate in the lower part of the compressor. The configuration in which the back pressure passage is provided above the back pressure chamber is suitable for reducing the inflow of oil into the back pressure chamber.
In a preferred example, a descending step is provided that goes around the inlet of the back pressure passage.

The descending step is a step that falls from the entrance side to the back pressure passage side in the direction away from the entrance. Such a descending step reduces the inflow of oil into the back pressure chamber.
In a preferred example, when the switching means is in the shut-off state, the valve body is disposed at a position for shutting off the inlet of the introduction passage from the suction pressure region in the compressor.

  Since the communication between the suction pressure region in the compressor and the inlet of the introduction passage is cut off when the compressor is started, the amount of refrigerant compressed when the switching means is in the cut-off state is small, and the effect of reducing the start shock is reduced. high.

  In a preferred example, a rear housing is connected to a cylinder block forming the cylinder bore, a suction chamber is formed in the rear housing, and the valve body is provided in the rear housing.

  The present invention has an excellent effect that the effect of reducing the start-up shock can be enhanced.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a front housing 13 is connected to one cylinder block 11 of a pair of connected cylinder blocks 11, 12, and a rear housing 14 is connected to the other cylinder block 12. The cylinder blocks 11, 12, the front housing 13 and the rear housing 14 constitute an entire housing of the fixed displacement piston compressor 10. A discharge chamber 131 as a discharge pressure region in the compressor is formed in the front housing 13, and a discharge chamber 141 as a discharge pressure region in the compressor and a suction chamber 142 as a suction pressure region in the compressor are formed in the rear housing 14. Is formed. The inside of the compressor means the inside of the entire housing of the fixed displacement type piston compressor 10, and the outside of the compressor means the outside of the entire housing of the fixed capacity type piston type compressor 10.

  A valve plate 15, a valve forming plate 16 and a retainer forming plate 17 are interposed between the cylinder block 11 and the front housing 13. A valve plate 18, a valve forming plate 19, and a retainer forming plate 20 are interposed between the cylinder block 12 and the rear housing 14. Discharge ports 151 and 181 are formed on the valve plates 15 and 18, and discharge valves 161 and 191 are formed on the valve forming plates 16 and 19. The discharge valves 161 and 191 open and close the discharge ports 151 and 181. Retainers 171 and 201 are formed on the retainer forming plates 17 and 20. The retainers 171 and 201 regulate the opening degree of the discharge valves 161 and 191.

  A rotating shaft 21 is rotatably supported on the cylinder blocks 11 and 12. Shaft holes 111 and 121 are provided through the cylinder blocks 11 and 12, and a rotating shaft 21 is passed through the shaft holes 111 and 121. The outer peripheral surface of the rotating shaft 21 is in contact with the inner peripheral surfaces of the shaft holes 111 and 121, and the rotating shaft 21 is directly supported by the cylinder blocks 11 and 12 through the inner peripheral surfaces of the shaft holes 111 and 121. . The outer peripheral surface portion of the rotating shaft 21 in contact with the shaft hole 111 is a seal peripheral surface 211, and the outer peripheral surface portion of the rotating shaft 21 in contact with the shaft hole 121 is a seal peripheral surface 212.

  A swash plate 23 as a cam body is fixed to the rotating shaft 21. The swash plate 23 is accommodated in a swash plate chamber 24 between the cylinder blocks 11 and 12. A lip seal type shaft seal member 22 is interposed between the front housing 13 and the rotating shaft 21. The shaft seal member 22 prevents gas leakage from between the front housing 13 and the rotating shaft 21. A protruding end portion of the rotating shaft 21 that protrudes outward from the front housing 13 is connected to a vehicle engine 26 that is an external drive source via an electromagnetic clutch 25. The rotating shaft 21 obtains a rotational driving force from the vehicle engine 26 via the electromagnetic clutch 25.

  As shown in FIG. 2A, the cylinder block 11 is formed with a plurality of cylinder bores 27 arranged around the rotation shaft 21. As shown in FIG. 2B, the cylinder block 12 is formed with a plurality of cylinder bores 28 arranged around the rotation shaft 21. A double-headed piston 29 is accommodated in the cylinder bores 27 and 28 that form a pair in the front and rear (the front housing 13 side is the front side and the rear housing 14 is the rear side).

  As shown in FIG. 1, the rotational movement of the swash plate 23 that rotates integrally with the rotary shaft 21 is transmitted to the double-headed piston 29 via the shoe 30, and the double-headed piston 29 reciprocates back and forth in the cylinder bores 27 and 28. To do. The double-headed piston 29 partitions compression chambers 271 and 281 in the cylinder bores 27 and 28.

  An in-axis passage 31 is formed in the rotating shaft 21 along the rotating axis 210 of the rotating shaft 21. An inlet 311 of the in-shaft passage 31 is in the end surface 213 of the rotating shaft 21 in the cylinder block 12 and opens to the suction chamber 142 in the rear housing 14. An outlet 312 of the in-shaft passage 31 is formed on the rotating shaft 21 in the shaft hole 111 so as to open to the seal peripheral surface 211 of the rotating shaft 21. An outlet 313 of the in-shaft passage 31 is formed in the rotating shaft 21 in the shaft hole 121 so as to open to the seal peripheral surface 212 of the rotating shaft 21.

  As shown in FIG. 2A, a communication path 32 is formed in the cylinder block 11 so as to communicate with the cylinder bore 27 and the shaft hole 111. As shown in FIG. 2B, a communication passage 33 is formed in the cylinder block 12 so as to communicate with the cylinder bore 28 and the shaft hole 121. As the rotary shaft 21 rotates, the outlets 312 and 313 of the in-shaft passage 31 communicate with the communication passages 32 and 33 intermittently.

  When the double-headed piston 29 is in the intake stroke state on the cylinder bore 27 side (stroke in which the double-headed piston 29 moves from the left side to the right side in FIG. 1), the outlet 312 and the communication path 32 communicate with each other. When the double-headed piston 29 is in the suction stroke state on the cylinder bore 27 side, the refrigerant in the in-shaft passage 31 of the rotating shaft 21 is sucked into the compression chamber 271 of the cylinder bore 27 via the outlet 312 and the communication passage 32.

  When the double-headed piston 29 is in the discharge stroke state on the cylinder bore 27 side (stroke in which the double-headed piston 29 moves from the right side to the left side in FIG. 1), the communication between the outlet 312 and the communication path 32 is blocked. When the double-headed piston 29 is in the discharge stroke state on the cylinder bore 27 side, the refrigerant in the compression chamber 271 pushes the discharge valve 161 away from the discharge port 151 and is discharged into the discharge chamber 131. The refrigerant discharged into the discharge chamber 131 flows out to the external refrigerant circuit 34 through the passage 341.

  When the double-headed piston 29 is in the intake stroke state on the cylinder bore 28 side (stroke in which the double-headed piston 29 moves from the right side to the left side in FIG. 1), the outlet 313 and the communication path 33 communicate with each other. When the double-headed piston 29 is in the suction stroke state on the cylinder bore 28 side, the refrigerant in the in-shaft passage 31 of the rotating shaft 21 is sucked into the compression chamber 281 of the cylinder bore 28 via the outlet 313 and the communication passage 33.

  When the double-headed piston 29 is in a discharge stroke state on the cylinder bore 28 side (stroke in which the double-headed piston 29 moves from the left side to the right side in FIG. 1), the communication between the outlet 313 and the communication path 33 is blocked. When the double-headed piston 29 is in the discharge stroke state on the cylinder bore 28 side, the refrigerant in the compression chamber 281 pushes the discharge valve 191 away from the discharge port 181 and is discharged into the discharge chamber 141. The refrigerant discharged into the discharge chamber 141 flows out to the external refrigerant circuit 34 through the passage 342.

Oil is put in the compressor and the external refrigerant circuit 34, and this oil flows together with the refrigerant and lubricates the lubrication necessary portion in the compressor.
A heat exchanger 37 for removing heat from the refrigerant, an expansion valve 38, and a heat exchanger 39 for transferring ambient heat to the refrigerant are interposed on the external refrigerant circuit 34. The expansion valve 38 controls the flow rate of the refrigerant according to the change in the gas temperature on the outlet side of the heat exchanger 39. The refrigerant that has flowed into the external refrigerant circuit 34 returns to the suction chamber 142.

  A portion of the seal peripheral surface 211 of the rotary shaft 21 becomes a first rotary valve 35 integrally formed with the rotary shaft 21, and a portion of the seal peripheral surface 212 of the rotary shaft 21 is a second rotary integrally formed with the rotary shaft 21. It becomes the valve 36. That is, the rotating shaft 21 is a rotary valve. The rotation axis 210 is the rotation axis of the rotary valve, and the end surface 213 of the rotation shaft 21 (that is, the end surface of the rotary valve) intersects the rotation axis 210 of the rotary valve. The in-shaft passage 31 and the outlets 312 and 313 constitute an introduction passage for the rotary valve, the shaft hole 111 is a valve housing chamber for housing the first rotary valve 35, and the shaft hole 121 is for the second rotary valve 36. It is a valve storage chamber for storing.

  As shown in FIGS. 3 and 4, the pedestal 40 is integrally formed on the end wall of the rear housing 14 that forms the suction chamber 142, and the cylinder 41 is integrally formed on the inner wall surface 401 of the pedestal 40. The rotation axis 210 of the rotation shaft 21 intersects the inner wall surface 401 perpendicularly.

  A spool-shaped valve element 42 is slidably fitted in the cylinder 411 of the cylinder 41. The valve body 42 includes a disk-shaped piston portion 43 and a cylindrical portion 44, and the cylindrical portion 44 has an introduction port 441 that opens to the outer peripheral surface of the cylindrical portion 44 and communicates with the cylinder interior 442 of the cylindrical portion 44. It is formed as follows. The cylinder interior 442 is an internal passage of the valve body 42. The piston portion 43 partitions the back pressure chamber 412 in the cylinder 411 of the cylinder 41. The back pressure chamber 412 communicates with the suction chamber 142 via the back pressure passage 413. The inlet 414 of the back pressure passage 413 is above the back pressure chamber 412. The inner wall surface 401 of the cylinder interior 411 is the bottom wall surface 402 of the back pressure chamber 412, and the bottom wall surface 402 is a flat surface.

  A cylindrical guide tube 45 is integrally formed on the end surface of the cylinder block 12 on the rear housing 14 side so as to face the cylinder 41. A cylinder 451 of the guide cylinder 45 communicates with an inlet 311 of the in-axis passage 31 (introduction passage). The distal end of the guide cylinder 45 and the distal end of the cylinder 41 are separated from each other, and the cylindrical portion 44 of the valve body 42 is slidably fitted to the guide cylinder 45. A circlip 46 is attached to the inner peripheral surface of the guide tube 45, and a return spring 47 is interposed between the circlip 46 and the piston portion 43. The return spring 47 urges the valve body 42 so as to approach the bottom wall surface 402. When the valve body 42 approaches the bottom wall surface 402, the volume of the back pressure chamber 412 decreases.

  The piston portion 43 of the valve body 42 has a flat pressure receiving end surface 431 that receives the pressure of the back pressure chamber 412. The planar pressure receiving end surface 431 and the planar bottom wall surface 402 are parallel to each other, and the parallel pressure receiving end surface 431 and the bottom wall surface 402 are perpendicular to the rotation axis 210, and the pressure receiving end surface 431 and the bottom wall surface 402 are Surface contact is possible.

  An extraction passage 48 is formed in the wall of the base 40. The vent passage 48 includes a valve hole 481 that opens to the back pressure chamber 412, an outlet passage 482 that has an outlet that opens to the suction chamber 142, and a valve storage chamber 483 that connects the valve hole 481 and the outlet passage 482. ing. The valve hole 481 is an inlet of the extraction passage 48.

  A ball valve body 49 is accommodated in the valve accommodating chamber 483 so that the valve hole 481 can be opened and closed. The valve storage chamber 483 is blocked from the outside of the compressor by a lid 51, and a compression spring 50 is interposed between the ball valve body 49 and the lid 51. The ball valve body 49 is urged toward the position where the valve hole 481 is closed by the spring force of the compression spring 50. The valve hole 481, the valve storage chamber 483, the ball valve body 49, and the compression spring 50 constitute a check valve G 1 that allows the flow of fluid from the back pressure chamber 412 to the extraction passage 48.

  In the state shown in FIG. 4, the entire introduction port 441 is in a position where it is exposed in the suction chamber 142, and the in-shaft passage 31 passes through the inside 451 of the guide tube 45, the inside 442 of the cylinder portion 44 and the introduction port 441. And communicated with the suction chamber 142. In this state, the valve body 42 is separated from the bottom wall surface 402, and FIG. 4 shows a state in which the valve body 42 is in a position where the in-shaft passage 31 and the suction chamber 142 are communicated. In the state shown in FIG. 3, the entire introduction port 441 is in a position where it enters the cylinder 411, and communication between the in-shaft passage 31 and the suction chamber 142 is blocked. In this state, the pressure receiving end surface 431 of the piston portion 43 of the valve body 42 is in surface contact with the bottom wall surface 402, and FIG. 3 shows a state where the valve body 42 is in a position where the shaft passage 31 and the suction chamber 142 are blocked. Indicates. The surface contact between the pressure receiving end surface 431 and the bottom wall surface 402 is based on the fact that oil as a fluid that flows with the refrigerant (oil Y accumulated in the lower portion of the suction chamber 142 is shown in FIGS. Including the case in between.

  As shown in FIG. 1, the electromagnetic clutch 25 is subjected to excitation / demagnetization control by the control computer C. An air conditioner operation switch W, a room temperature setter S, and a room temperature detector F are signal-connected to the control computer C. When the air conditioner operation switch W is in the ON state, the control computer C uses the electromagnetic clutch 25 based on the temperature difference between the target room temperature set by the room temperature setter S and the detected room temperature detected by the room temperature detector F. Controls current supply (excitation demagnetization) to.

  When the detected temperature is lower than the target temperature, or when the detected temperature is higher than the target temperature and the temperature difference between the detected temperature and the target temperature is less than the tolerance, the control computer C supplies current to the electromagnetic clutch 25. To stop. At this time, the electromagnetic clutch 25 is disengaged and the rotational driving force of the vehicle engine 26 is not transmitted to the rotating shaft 21. When the detected temperature is higher than the target temperature and the temperature difference between the detected temperature and the target temperature exceeds the allowable difference, the control computer C supplies current to the electromagnetic clutch 25. At this time, the electromagnetic clutch 25 is in a connected state, and the rotational driving force of the vehicle engine 26 is transmitted to the rotating shaft 21.

  It is assumed that the fixed displacement piston compressor 10 is in an operation stop state (a state where the electromagnetic clutch 25 is disconnected). In this state, the pressure in the compressor is balanced, and the valve body 42 is in the position to be blocked as shown in FIG. 3 by the spring force of the return spring 47. When the valve body 42 is in the blocking position, the pressure receiving end surface 431 and the bottom wall surface 402 are in surface contact via the oil film.

  When the operation of the fixed displacement piston compressor 10 is started, the refrigerant in the shaft passage 31 and the refrigerant in the cylinders 451 and 442 are sucked into the compression chamber 271 (see FIG. 1) and the compression chamber 281. Therefore, the pressure in the in-shaft passage 31 and the in-cylinders 451 and 442 is reduced by this suction action. That is, the pressure in the in-shaft passage 31 and the cylinders 451 and 442 is lower than the pressure in the suction chamber 142. The pressure in the suction chamber 142 has spread to the back pressure chamber 412, and the pressure in the back pressure chamber 412 corresponds to the pressure in the suction chamber 142. The pressure in the back pressure chamber 412 is opposed to the pressure in the cylinders 451 and 442 and the spring force of the return spring 47 via the valve body 42.

  The oil film between the pressure receiving end surface 431 and the bottom wall surface 402 causes the piston portion 43 to be adsorbed to the bottom wall surface 402. The sum of the adsorption force by the oil film and the spring force of the return spring 47 is the difference generated between the pressure in the back pressure chamber 412 and the pressure in the cylinders 451 and 442 when the fixed displacement piston compressor 10 is operated. It is set to lose pressure. Therefore, the differential pressure generated between the pressure in the back pressure chamber 412 and the pressure in the cylinders 451 and 442 when the operation of the fixed displacement piston compressor 10 is started is determined by the spring force of the return spring 47 and the oil film. Overcome with the adsorption power by As a result, the valve body 42 moves from the blocking position shown in FIG. 3 to the communicating position shown in FIG. When the valve body 42 is in a communicating position, the refrigerant in the suction chamber 142 passes to the compression chambers 271 and 281 via the introduction port 441, the cylinder interior 442, the cylinder interior 451, the shaft passage 31, and the communication passages 32 and 33. Inflow.

  When the operation of the fixed displacement piston compressor 10 is stopped, the refrigerant in the in-shaft passage 31 and the refrigerant in the cylinders 451 and 442 are not sucked into the compression chamber 271 (see FIG. 1) and the compression chamber 281. The pressures in the in-shaft passage 31 and the cylinders 451 and 442 increase. Therefore, the pressure in the in-shaft passage 31 and the cylinders 451 and 442 and the pressure in the back pressure chamber 412 are balanced, and the valve body 42 is viewed from the position shown in FIG. It moves to the position shown in FIG.

  When the valve body 42 moves from the position where it is shut off to the position where it communicates, the oil in the suction chamber 142 is sucked into the back pressure chamber 412 via the back pressure passage 413. As shown in FIG. 4, the oil in the suction chamber 142 flows into the back pressure chamber 412 via the back pressure chamber 412 even when the valve body 42 is in the blocking position. Therefore, the oil Y accumulates in the back pressure chamber 412. Since the pressure in the back pressure chamber 412 is equal to the pressure in the outlet passage 482, the valve hole 481 is closed by the ball valve body 49 receiving the spring force of the compression spring 50, and the suction chamber 142. The oil Y inside does not flow into the back pressure chamber 412 through the drain passage 48. When the operation of the fixed capacity type piston compressor 10 is stopped, when the valve body 42 is moved from the communicating position to the shut-off position, the oil Y accumulated in the back pressure chamber 412 flows out from the back pressure passage 413 to the suction chamber 142. To do. Further, the oil Y accumulated in the back pressure chamber 412 flows out from the extraction passage 48 to the suction chamber 142 while pushing the ball valve body 49 away from the valve hole 481.

  The valve body 42 has a suction chamber 142 (suction pressure) in the compressor according to the pressure level in the introduction passage (in-shaft passage 31) corresponding to the operation state and the operation stop state of the fixed displacement piston compressor 10. The area) and a position where the outlets 312 and 313 of the introduction passage are communicated with each other and a position where they are blocked are arranged. The valve body 42, the return spring 47, the back pressure chamber 412, and the back pressure passage 413 are in a state where the suction chamber 142 (suction pressure region) in the compressor communicates with the outlets 312 and 313 of the introduction passage and is shut off. The switching means 52 to be switched is configured.

  In the state of FIG. 3, the switching means 52 is in a state in which the outlet 312 (see FIG. 1) and outlet 313 of the introduction passage and the suction chamber 142 are shut off. In the state of FIG. The outlet 312 (see FIG. 1) and the outlet 313 are in communication with the suction chamber 142.

In the first embodiment, the following effects can be obtained.
(1) Since the amount of refrigerant compressed while the communication between the suction chamber 142 and the inlet 441 in the fixed displacement piston compressor 10 is interrupted is small, the effect of suppressing torque fluctuations, that is, starting shock mitigation Is highly effective.

  (2) If the time required for the valve body 42 to move from the blocking position to the communicating position is long, the effect of mitigating the start-up shock becomes high. The valve element 42 in the position where the fixed capacity type piston compressor 10 is shut off when the operation is started is moved from the shut-off position to the position where it is communicated by the adsorption force by the oil film between the pressure receiving end surface 431 and the bottom wall surface 402. It is delayed to start moving towards. The delay in the movement of the valve element 42 from the shut-off position to the communicating position due to the oil film adsorption force after the fixed displacement piston compressor 10 starts operation contributes to the mitigation of the starting shock.

  (3) If the oil Y accumulated in the back pressure chamber 412 is not discharged from the back pressure chamber 412, the valve body 42 cannot return to the blocking position. When the operation of the fixed displacement piston compressor 10 is started, if the valve body 42 has not returned to the position where it is shut off, the fixed displacement piston compressor 10 is compressed when the operation of the fixed displacement piston compressor 10 is started. The amount of refrigerant to be increased is larger than that in the case where the valve body 42 is returned to the position where the valve body 42 is shut off, and the effect of mitigating the starting shock cannot be obtained.

  In this embodiment, when the operation of the fixed displacement piston compressor 10 is stopped, the oil Y accumulated in the back pressure chamber 412 is moved by the movement of the valve body 42 from the communicating position to the blocking position. The air is discharged from the passage 413 and the extraction passage 48 to the suction chamber 142. Therefore, when the operation of the fixed displacement piston compressor 10 is stopped, the valve body 42 is reliably returned to the position where it is shut off by the spring force of the return spring 47.

  (4) When the pressure receiving end surface 431 and the bottom wall surface 402 that are parallel to each other are in surface contact with each other and the valve body 42 is in a position where the valve body 42 is blocked, an oil film is formed on the entire bottom wall surface 402 except for the opening of the valve hole 481 facing the back pressure chamber 412. Occurs. The configuration in which the pressure receiving end surface 431 and the bottom wall surface 402 are parallel to each other maximizes the adsorption force by the oil film, and delays the movement of the valve body 42 from the blocking position to the communicating position. The configuration in which the pressure receiving end surface 431 and the bottom wall surface 402 are parallel to each other is a preferable configuration for increasing the contribution to the relaxation of the starting shock.

  (5) The oil Y accumulated in the back pressure chamber 412 can be discharged from the back pressure passage 413 and the extraction passage 48 to the suction chamber 142. Therefore, the passage cross-sectional area of the back pressure passage 413 can be set to a minimum size necessary for spreading the pressure in the suction chamber 142 to the back pressure chamber 412. This contributes to making it difficult for oil in the suction chamber 142 to flow into the back pressure passage 413.

  (6) When the operation of the fixed displacement piston compressor 10 is stopped, the valve body 42 returns to the shut-off position by the spring force of the return spring 47. The use of the return spring 47 is a simple configuration for returning the valve body 42 to the position where it is shut off.

  (7) Oil that flows together with the refrigerant tends to accumulate in the lower portion of the suction chamber 142. The configuration in which the inlet 414 of the back pressure passage 413 is provided above the back pressure chamber 412 is suitable for reducing the inflow of oil into the back pressure passage 413, that is, the inflow of oil into the back pressure chamber 412.

  (8) When the valve body 42 is in a position where the valve body 42 is blocked, the introduction port 441 which is the inlet of the cylinder body 442 of the valve body 42 enters the cylinder 411 and is shielded, and when the valve body 42 is in a position where it communicates, It is outside the cylinder 411 and exposed in the suction chamber 142. The configuration in which the introduction port 441 enters and exits the cylinder 411 is suitable for increasing the introduction port 441 and securing a sufficient cross-sectional area of the introduction passage.

Next, a second embodiment shown in FIGS. 5A and 5B will be described. The same reference numerals are used for the same components as those in the first embodiment.
A communication chamber 53 and a valve hole 541 are formed in the rear housing 14, and a plate-shaped opening / closing plate 55 made of a magnetic material is accommodated in the communication chamber 53 so that the valve hole 541 can be opened and closed. The valve hole 541 extends through the partition wall 54 that separates the communication chamber 53 and the suction chamber 142. An inlet 311 of the in-shaft passage 31 is in the end surface 213 of the rotating shaft 21 in the cylinder block 12 and opens to the communication chamber 53 in the rear housing 14.

  A piston portion 56 is fitted into the cylinder 411, and a transmission rod 57 is integrally formed with the piston portion 56. An opening / closing plate 55 is secured to the tip of the transmission rod 57. The opening / closing plate 55 contacts and separates from the valve seat surface 542. The sealing surface 551 of the opening / closing plate 55 that is in contact with the valve seat surface 542 is formed as a flat surface. That is, when the opening / closing plate 55 closes the valve hole 541, the seal surface 551 of the opening / closing plate 55 is in surface contact with the valve seat surface 542. The piston portion 56, the transmission rod 57, and the opening / closing plate 55 constitute a valve body 59 that opens and closes the valve hole 541, and the valve body 59 partitions the back pressure chamber 412 in the cylinder 411.

  A column base 58 protrudes from the inner wall surface 401 around the cylinder 41, and an inlet 414 of the back pressure passage 413 opens on the end surface of the column base 58. The peripheral surface of the columnar table 58 is an annular descending step 581 that goes around the inlet 414.

  A return spring 60 is interposed between the piston portion 56 and the partition wall 54. The return spring 60 biases the piston portion 56 in a direction to push it into the cylinder 411. 5B, the valve body 59 is in a position where the valve hole 541 is opened and the communication chamber 53 communicates with the suction chamber 142. In FIG. 5A, the valve body 59 closes the valve hole 541 and the communication chamber 53 is opened. And the suction chamber 142 are disconnected from each other. The return spring 60 biases the valve body 59 from the communicating position toward the blocking position.

  A plurality of stoppers 552 protrude from the back surface of the opening / closing plate 55 facing the end surface 213 of the rotating shaft 21. The stopper 552 can be brought into contact with and separated from the tip of the cylindrical portion 123 protruding from the end surface 122 of the cylinder block 12. In a state where the valve body 59 is disposed at the communicating position shown in FIG. 5B, the stopper 552 is in contact with the tip of the cylindrical portion 123, and the valve body 59 is blocked at the position shown in FIG. The stopper 552 is separated from the tip of the cylindrical portion 123 in the state of being disposed at the position.

  When the fixed displacement piston compressor 10 is in the operation stop state, the valve element 59 is arranged at the position shown in FIG. 5A by the spring force of the return spring 60, and the refrigerant in the suction chamber 142 is connected to the communication chamber. Inflow to 53 is impossible. In this state, the pressure receiving end surface 561 of the piston portion 56 is in surface contact with the bottom wall surface 402.

  When the operation of the fixed displacement piston compressor 10 is started, the refrigerant in the shaft passage 31 and the refrigerant in the communication chamber 53 are sucked into the compression chamber 271 (see FIG. 1) and the compression chamber 281. By this suction action, the pressure in the in-shaft passage 31 and the communication chamber 53 is lowered. That is, the pressure in the shaft passage 31 and the communication chamber 53 is lower than the pressure in the suction chamber 142. Therefore, the valve body 59 is disposed at a communicating position shown in FIG. 5B, and the refrigerant in the suction chamber 142 passes through the valve hole 541, the communication chamber 53, and the in-shaft passage 31, and the compression chamber 271 (see FIG. 1). ) And the compression chamber 281.

  The valve body 59, the return spring 60, the back pressure chamber 412 and the back pressure passage 413 communicate with the suction chamber 142 (suction pressure region) in the compressor and the outlet 312 (see FIG. 1) and the outlet 313 of the introduction passage. The switching means 52A that can be switched to the shut-off state is configured.

  In the second embodiment, since the volume of the communication chamber 53 that accommodates the plate-shaped opening / closing plate 55 can be reduced, the effect of reducing the start-up shock is high as in the case of the first embodiment. Further, since the descending step 581 is provided around the inlet 414 of the back pressure passage 413, it is difficult for oil transmitted along the inner wall surface 401 around the cylinder 41 to enter the back pressure passage 413. That is, the configuration in which the descending step 581 is provided around the inlet 414 of the back pressure passage 413 makes it difficult for oil in the suction chamber 142 to flow into the back pressure chamber 412. This is preferable for reliably returning the valve body 59 to the position where the valve body 59 is shut off.

Next, a third embodiment shown in FIGS. 6A and 6B will be described. The same reference numerals are used for the same components as those in the first embodiment.
A piston portion 61 is slidably fitted into the cylinder 41, and the piston portion 61 defines a back pressure chamber 412 in the cylinder 411. A transmission rod 62 is connected to the piston portion 61. The transmission rod 62 enters the in-axis passage 31A. The in-shaft passage 31A includes a small-diameter passage 314 and a large-diameter passage 315 having a larger diameter than the small-diameter passage 314. A disc 63 is fixed to the tip of the transmission rod 62 in the small diameter passage 314, and a cylindrical circumferential surface 64 is fixed to the transmission rod 62 in the large diameter passage 315.

  The disc 63 is fitted in the small diameter passage 314 so as to be slidable in the direction of the rotation axis 210 of the rotary shaft 21, and the cylindrical circumferential surface body 64 is slidable in the direction of the rotary axis 210 of the rotary shaft 21, and The outlet 313 is fitted in the large-diameter passage 315 so that it can be opened and closed. In the cylinder of the cylindrical circumferential surface body 64, an in-axis passage 31A between the disc 63 and the circumferential surface body 64, and an in-axis passage 31A between the inlet 311 of the in-axis passage 31A and the circumferential surface body 64 are provided. And communicate with.

  As shown in FIG. 6B, when the circumferential surface body 64 is in a position to close the outlet 313, the disk 63 is upstream of the outlet 312 in the in-shaft passage 31A, and the refrigerant in the in-shaft passage 31A. Cannot flow into the compression chamber 271 through the outlet 312. As shown in FIG. 6A, when the circumferential surface body 64 is in a position to open the outlet 313, the disc 63 is located downstream of the outlet 312 in the in-shaft passage 31A, and the refrigerant in the in-shaft passage 31A. Can flow into the compression chamber 271 through the outlet 312.

  A return spring 65 is interposed between the step 316 between the small diameter passage 314 and the large diameter passage 315 and the circumferential surface body 64. The return spring 65 urges the disc 63, the circumferential surface body 64, the transmission rod 62, and the entire piston portion 61 toward the back pressure chamber 412 so as to push the piston portion 61 into the cylinder 411.

  A ball valve body 49 is accommodated in the valve accommodating chamber 483A constituting the extraction passage 48A so that the valve hole 481A can be closed by its own weight. The valve hole 481A, the valve accommodating chamber 483A, and the ball valve body 49 constitute a check valve G2 that allows the flow of fluid from the back pressure chamber 412 to the extraction passage 48A.

  An inlet 414 of the back pressure passage 413 opens on the inner wall surface 401 around the cylinder 41, and an annular groove 66 is formed around the inlet 414 around the inlet 414 of the back pressure passage 413. Yes. The inner peripheral surface of the groove 66 is an annular descending step 661 that goes around the inlet 414.

  When the fixed displacement piston compressor 10 is in the operation stop state, the disc 63 and the circumferential surface body 64 are held at the blocking position shown in FIG. 6B by the spring force of the return spring 65. In this state, the pressure receiving end surface 611 of the piston portion 61 is in surface contact with the bottom wall surface 402.

  When the operation of the fixed displacement piston compressor 10 is started, the refrigerant in the space 317 (a part of the shaft passage 31A) between the disc 63 and the end of the shaft passage 31A is sucked into the compression chamber 271. As a result, the pressure in the space 317 decreases. Therefore, the disc 63 and the circumferential surface body 64 are arranged from the blocking position shown in FIG. 6B against the spring force of the return spring 65 to the communicating position shown in FIG.

  When the operation of the fixed displacement type piston compressor 10 is stopped, the disk 63 and the circumferential surface body 64 are returned to the blocking position shown in FIG. 6B by the spring force of the return spring 65. The oil accumulated in the back pressure chamber 412 flows out from the extraction passage 48 </ b> A to the suction chamber 142 while pushing up the ball valve body 49.

  The disc 63, the circumferential surface body 64, the transmission rod 62, and the piston portion 61 constitute a valve body that partitions the back pressure chamber 412 in the cylinder 411. The valve body is provided in the compressor according to the pressure in the space 317 [part of the introduction passage (in-shaft passage 31A)] corresponding to the operation state and the operation stop state of the fixed displacement piston compressor 10. The suction chamber 142 (suction pressure region) and the outlets 312 and 313 of the introduction passage are switched between a position where the suction chamber 142 is communicated with a position where the suction passage 142 is blocked. The valve body, the return spring 65, the back pressure chamber 412 and the back pressure passage 413 are switched between a state in which the suction chamber 142 (suction pressure region) in the compressor communicates with the outlets 312 and 313 of the introduction passage and a state in which the suction passage 142 is shut off. The switching means 52B is configured.

  In the third embodiment, the same effect as in the first embodiment can be obtained. Further, the refrigerant that can flow into the compression chambers 271 and 281 when the disk 63 and the circumferential surface body 64 are blocked is only the refrigerant in the space 317, the outlets 312 and 313, and the communication passages 32 and 33. Therefore, the effect of mitigating the startup shock is higher than in the first and second embodiments.

  Since the ball valve body 49 closes the valve hole 481A by its own weight, the configuration of the check valve G2 is simpler than the check valve G1 in the first and second embodiments. Further, since a step 661 is provided around the inlet 414 of the back pressure passage 413, oil transmitted along the inner wall surface 401 around the cylinder 41 is difficult to enter the back pressure passage 413. That is, the configuration in which the step 661 is provided around the inlet 414 of the back pressure passage 413 makes it difficult for oil in the suction chamber 142 to flow into the back pressure chamber 412.

Next, a fourth embodiment shown in FIGS. 7A and 7B will be described. The same reference numerals are used for the same components as those in the first embodiment.
An accommodation cylinder part 67 is formed on the back side of the pressure receiving end surface 431 of the piston part 43, and a ball valve body 49 is accommodated in the valve accommodation chamber 671 in the accommodation cylinder part 67. A valve hole 432 that opens on the pressure receiving end surface 431 is formed in the piston portion 43. A circlip 68 is attached to the inner peripheral surface of the accommodating cylinder portion 67, and a compression spring 50 is interposed between the circlip 68 and the ball valve body 49. The ball valve body 49 can open and close the valve hole 432, and the compression spring 50 biases the ball valve body 49 toward the position where the valve hole 432 is closed. The valve storage chamber 671 communicates with the cylinder interior 442 of the cylindrical portion 44, and the valve storage chamber 671 and the valve hole 432 constitute an extraction passage 69 extending from the back pressure chamber 412 into the cylinder interior 442. The valve hole 432, the valve storage chamber 671, the ball valve body 49, and the compression spring 50 constitute a check valve G <b> 3 that allows fluid flow from the back pressure chamber 412 to the extraction passage 69.

  When the fixed displacement piston compressor 10 is in the operation stop state, the valve element 42 is held at the blocking position shown in FIG. 7A by the spring force of the return spring 47. In this state, the pressure receiving end surface 431 is in surface contact with the bottom wall surface 402.

  When the operation of the fixed displacement piston compressor 10 is started, the valve element 42 resists the spring force of the return spring 47 and the adsorption force by the oil film between the pressure receiving end surface 431 and the bottom wall surface 402. It arrange | positions from the position to interrupt | block shown to (a) to the position to communicate shown in FIG.7 (b).

  When the operation of the fixed displacement piston compressor 10 is stopped, the valve element 42 returns to the blocking position shown in FIG. 7A by the spring force of the return spring 47. The oil accumulated in the back pressure chamber 412 flows out from the drain passage 69 into the cylinder 442 while pushing the ball valve body 49 away from the valve hole 432.

In the fourth embodiment, the same effect as in the first embodiment can be obtained.
Next, a fifth embodiment of FIG. 8 will be described. The same reference numerals are used for the same components as those in the first embodiment.

  The entire housing of the fixed displacement piston compressor 10A is composed of a cylinder block 12, a front housing 13, and a rear housing 14. A swash plate 23 is provided in a swash plate chamber 24 between the cylinder block 12 and the front housing 13. Contained. The single-headed piston 70 linked to the swash plate 23 reciprocates in the cylinder bore 28 as the swash plate 23 rotates. The rotary shaft 21 is provided with a rotary valve 36 corresponding to the cylinder block 12, and the rear housing 14 is provided with a valve body 42, a vent passage 48 and a check valve G <b> 1.

In the fifth embodiment, the same effect as in the first embodiment can be obtained.
In the present invention, the following embodiments are also possible.
The first rotary valve 35 and the second rotary valve 36 may be formed separately from the rotary shaft 21.

O The extraction passage may be opened at the lowest part of the back pressure chamber 412.
In the first embodiment, the pressure-receiving end surface 431 may be a conical concave surface, the bottom wall surface 402 may be a conical convex surface, and the concave surface and the convex surface may be in surface contact. In this way, the area of the pressure receiving end surface 431 increases, and the adhesion force due to the oil film increases.

The technical idea that can be grasped from the embodiment described above will be described below.
[1] The introduction passage has an inlet on an end surface of the rotary valve and an outlet on a peripheral surface of the rotary valve, and the introduction passage has a direction of a rotation axis of the rotation shaft inside the rotation shaft. And an outlet of the introduction passage passes through a peripheral surface of the rotating shaft and communicates with the passage in the shaft, and the valve body is connected to the introduction passage from the inlet of the introduction passage. The valve body is fitted in the shaft passage so as to be slidable in the direction of the rotation axis, and the valve body is moved in the direction of the rotation axis in the shaft passage to shut off the communicating position. The fixed capacity according to any one of claims 1 to 10, wherein the shut-off position is a position where the valve body blocks the outlet of the introduction passage from the in-shaft passage. Refrigerant suction in a piston-type compressor Elephants.

The side sectional view of the whole compressor which shows a 1st embodiment. (A) is the sectional view on the AA line of FIG. (B) is the BB sectional drawing of FIG. FIG. FIG. (A), (b) is a partial expanded sectional side view which shows 2nd Embodiment. (A), (b) is the partial expanded sectional view which shows 3rd Embodiment. (A), (b) is a fragmentary sectional side view which shows 4th Embodiment. The sectional side view of the whole compressor which shows a 5th embodiment.

Explanation of symbols

  10, 10A ... Fixed capacity piston type compressor. 11, 12 ... Cylinder block. 131, 141: Discharge chamber as a discharge pressure region. 14: Rear housing. 142: A suction chamber as a suction pressure region in the compressor. 21 ... Rotating shaft. 210: A rotational axis. 23 ... A swash plate as a cam body. 25: Electromagnetic clutch. 26: Vehicle engine as an external drive source. 27, 28 ... Cylinder bore. 271,281 ... Compression chamber. 29 ... Double-headed piston. 31, 31 </ b> A.. 311 ... Entrance. 312,313 ... Exit. 35: First rotary valve. 36: Second rotary valve. 402 ... A flat bottom wall surface. 412 ... Back pressure chamber. 413 ... Back pressure passage. 414 ... Entrance. 42, 59 ... Valve body. 43, 56, 61 ... piston part. 431: Flat pressure-receiving end face. 47, 60, 65... Return spring. 48, 48A, 69 ... extraction passage. 52, 52A, 52B... Switching means. 581,661… Descent step. 70: One-headed piston. G1, G2, G3 ... check valves.

Claims (10)

Pistons are accommodated in a plurality of cylinder bores arranged around the rotation shaft, and the piston is interlocked with the rotation of the rotation shaft through a cam body integrated with the rotation shaft. A rotary valve having an introduction passage for introducing a refrigerant from a suction pressure region into a compression chamber defined in the cylinder bore, wherein the rotary valve rotates integrally with the rotary shaft; In the refrigerant suction structure in the fixed displacement piston compressor connected to the external drive source via
Switching means for switching between a state in which the suction pressure region in the compressor and the outlet of the introduction passage communicate and a state in which the suction passage is shut off is provided, and the switching means is provided between the suction pressure region in the compressor and the introduction passage. A valve body that is switched between a position for communicating with the outlet and a position for blocking, a return spring that returns the valve body from the communicating position to the position for blocking, and a back pressure chamber defined by the valve body; A back pressure passage communicating the suction pressure region in the compressor and the back pressure chamber, the back pressure chamber and the suction pressure region being communicated by a vent passage, A refrigerant suction structure in a fixed displacement piston compressor provided with a check valve that allows a fluid flow to a passage.   The valve body has a piston portion that defines the back pressure chamber, the back pressure chamber has a bottom wall surface, and the pressure receiving end surface of the piston portion that receives the pressure of the back pressure chamber is the back pressure chamber. The refrigerant suction structure in the fixed displacement piston compressor according to claim 1, which is in surface contact with the bottom wall surface of the fixed capacity type piston compressor.   The refrigerant suction structure for a fixed displacement piston compressor according to claim 2, wherein the pressure receiving end surface and the bottom wall surface are flat surfaces parallel to each other.   4. The refrigerant suction structure in the fixed displacement piston compressor according to claim 2, wherein an inlet of the extraction passage is opened on the bottom wall surface. 5.   5. The refrigerant suction structure in a fixed displacement piston compressor according to claim 4, wherein the valve body is moved in the direction of the axis of the rotating shaft and is switched between the communicating position and the blocking position.   The fixed displacement according to any one of claims 1 to 5, wherein the extraction passage passes through a housing constituting the fixed displacement type piston compressor and communicates with a suction pressure region in the compressor. Refrigerant intake structure for type piston compressor.   The refrigerant suction structure in the fixed displacement piston compressor according to any one of claims 1 to 6, wherein an inlet of the back pressure passage is above the back pressure chamber.   The refrigerant suction structure in the fixed displacement piston compressor according to any one of claims 1 to 7, wherein a descending step is provided around the inlet of the back pressure passage.   9. The valve body according to claim 1, wherein when the switching unit is in the shut-off state, the valve body is disposed at a position for shutting off the inlet of the introduction passage from the suction pressure region in the compressor. A refrigerant suction structure in the fixed displacement piston compressor described in 1.   The rear housing is connected to a cylinder block forming the cylinder bore, a suction chamber is formed in the rear housing, and the valve body is provided in the rear housing. 10. A refrigerant suction structure in a fixed displacement piston compressor according to any one of items 9 to 9.

Images