CN115807749A

CN115807749A - Fluid machine and construction machine

Info

Publication number: CN115807749A
Application number: CN202210942202.2A
Authority: CN
Inventors: 赤见俊也; 高梨幸治
Original assignee: Nabtesco Corp
Current assignee: Nabtesco Corp
Priority date: 2021-09-15
Filing date: 2022-08-08
Publication date: 2023-03-17
Also published as: JP2023042733A; KR20230040264A

Abstract

The present invention relates to a fluid machine and a construction machine. The main pump of the embodiment is provided with: a cylinder body; a piston housed in the cylinder chamber so as to be slidable; a housing that houses a cylinder; and a valve plate (19) disposed between the cylinder block and the housing. The valve plate (19) has: a suction inlet; a discharge port formed on the opposite side of the suction port with a pair of switching land portions formed on the 1 st surface (41 a) therebetween; a piston housing recess (49) which houses the pressing piston; and a valve plate communication hole (51) which communicates the piston housing recess (49) with the switching land portion.

Description

Fluid machine and construction machine

Technical Field

The present invention relates to a fluid machine and a construction machine.

Background

As a fluid machine, there is a so-called swash plate type hydraulic piston pump (hereinafter, simply referred to as a hydraulic pump) mounted on a construction machine such as a hydraulic excavator. Such a hydraulic pump includes, for example: a shaft rotatably supported within the pump housing; a cylinder fixed to an outer peripheral surface of the shaft; and a plurality of pistons. The cylinder block has a plurality of cylinder chambers formed therein. Pistons are housed in the cylinder chambers so as to be slidable in an axial direction of the shaft (hereinafter, simply referred to as an axial direction).

The hydraulic pump is provided with: a swash plate disposed on the 1 st end side in the axial direction of the cylinder block; and a valve plate disposed on the 2 nd end portion side opposite to the 1 st end portion. The swash plate restricts sliding movement of the pistons in the cylinder chambers by the end portions of the pistons that are movable on the surface of the swash plate. The swash plate changes a volume of a space formed by the cylinder chamber and the piston according to an inclination angle with respect to the pump housing. The valve plate has suction ports and discharge ports through which the hydraulic oil flows, formed at positions corresponding to the plurality of cylinder chambers of the cylinder block. The suction port communicates with a suction path of the pump casing. The ejection port communicates with an ejection path of the pump housing. A switching land portion facing the No. 2 end of the cylinder is formed between the suction port and the discharge port on the end surface of the valve plate on the cylinder side.

With this configuration, when the cylinder block rotates around the axis of the shaft, each cylinder chamber revolves around the shaft, and alternately communicates with the suction port and the discharge port via the switching land portion of the valve plate. At the time when the cylinder chamber communicates with the suction port, the piston slides in the cylinder chamber so as to increase the volume of the space in the cylinder chamber. Thereby, the working oil is sucked into the cylinder chamber from the outside of the pump housing through the suction path and the suction port (suction step). At the time when the cylinder chamber communicates with the discharge port, the piston slides in the cylinder chamber so as to reduce the volume of the space in the cylinder chamber. Thereby, the working oil is discharged from the cylinder chamber to the outside of the pump case through the discharge port and the discharge path (discharge step).

Here, since the cylinder chamber is rapidly opened through the discharge port at the timing when the cylinder chamber communicates with the discharge port, there is a possibility that the working oil is reversely injected into the cylinder chamber due to the pressure difference. In such a case, the high-speed fluid (hydraulic oil) collides with the inner wall surface of the cylinder chamber, and cavitation (hereinafter, referred to as corrosion) occurs. Therefore, a technique of forming a hole for communicating the discharge port of the valve plate with the switching land portion of the valve plate is disclosed (for example, see patent document 1). A technique of forming a notch in a switching land portion of a valve plate, the switching land portion being located at a bottom dead center position at which switching from a suction process to a discharge process is performed, is disclosed (for example, see patent document 2). In both techniques, a pressure of a fluid on the outlet side is introduced into the cylinder chamber, thereby suppressing a rapid pressure change in the cylinder chamber.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 57-171086

Patent document 2: japanese patent application laid-open No. 2010-174690

Disclosure of Invention

Problems to be solved by the invention

However, in the above-mentioned patent document 1, it is difficult to easily machine the hole, which may increase the machining cost of the valve plate.

In the above-mentioned patent document 2, since the pressure of the discharge port is branched to the cylinder chamber at a position immediately adjacent to the discharge port, there is a possibility that the effect of corrosion prevention is hardly obtained.

The invention provides a fluid machine and a construction machine, which can restrain the processing cost of a valve plate and can obtain sufficient anticorrosion effect of a cylinder chamber.

Means for solving the problems

A fluid machine according to an aspect of the present invention includes: a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber, the piston performing a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber; a housing that houses the cylinder, the housing having an intake path and a discharge path formed therein; a valve plate disposed between the cylinder block and the housing; and an urging member that urges the valve plate toward the cylinder block side, the valve plate having: a suction port that communicates the cylinder communication hole with the suction path; a discharge port formed on the opposite side of the suction port so as to sandwich the pair of switching land portions formed on the 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path; a pressing member accommodating recess formed in a position of a 2 nd surface of the valve plate on a side opposite to the 1 st surface, the position avoiding the suction path and the discharge path, the pressing member accommodating recess accommodating the pressing member; and a valve plate communication hole that communicates the pressing member housing recess with the switching land portion.

In this way, the valve plate communication hole is formed by the pressing member accommodating recessed portion, and the pressure of the discharge port can be branched to the switching land portion side via the valve plate communication hole. Therefore, an abrupt pressure change in the cylinder chamber can be suppressed. Therefore, the processing cost of the valve plate can be suppressed, and a sufficient anti-corrosion effect of the cylinder chamber can be obtained.

In the above-described configuration, the valve plate may be provided with a notch, a land portion of the pair of switching land portions, which is located at a bottom dead center position at which the piston is switched from the suction process to the discharge process, may be defined as a bottom dead center switching land portion, the notch may extend from the discharge port toward the bottom dead center switching land portion, the valve plate communication hole may be disposed at a position separated from a tip of the notch toward the suction port, and the tip of the notch may be defined as an end portion on a side opposite to the discharge port.

In the above-described configuration, the valve plate may be provided with a notch, a land portion of the pair of switching land portions, which is located at a bottom dead center position at which the piston switches from the suction process to the discharge process, may be defined as a bottom dead center switching land portion, the notch may extend from the discharge port toward the bottom dead center switching land portion, the valve plate communication hole may be disposed at a tip of the notch, and the tip of the notch may be defined as an end portion on a side opposite to the discharge port.

In the above configuration, the pressing member may be a disc-shaped small piston.

Another aspect of the present invention provides a fluid machine including: a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber; a piston which is slidably housed in the cylinder chamber and which performs a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber; a housing that houses the cylinder, the housing having a suction path and a discharge path formed therein; a valve plate disposed between the cylinder block and the housing; and a pressing member that presses the valve plate toward the cylinder block side, the valve plate having: a suction port that communicates the cylinder communication hole with the suction path; a discharge port that is formed on the opposite side of the suction port so as to sandwich a pair of switching land portions formed on a 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path; a pressing member accommodating recess portion formed in a 2 nd surface of the valve plate on a side opposite to the 1 st surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess portion accommodating the pressing member; a notch extending from the ejection port toward the bottom dead center switching land portion; and a valve plate communication hole disposed at a position away from a front end of the cutout toward the suction port side, the valve plate communication hole communicating the pressing member accommodating recessed portion with the switching land portion, the bottom dead center switching land portion being defined as a land portion, out of the pair of switching land portions, disposed at a bottom dead center position at which the piston is switched from the suction process to the discharge process, the front end of the cutout being defined as an end portion on a side opposite to the discharge port.

With this configuration, the valve plate communication hole is formed by the pressing member accommodating recess, and the pressure of the discharge port can be branched to the bottom dead center switching land portion side by the valve plate communication hole. Therefore, the reverse ejection of the fluid into the cylinder chamber in the ejection step can be prevented. Therefore, the processing cost of the valve plate can be suppressed, and a sufficient corrosion prevention effect of the cylinder chamber can be obtained.

A fluid machine according to another aspect of the present invention includes: a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber, the piston performing a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber; a housing that houses the cylinder, the housing having an intake path and a discharge path formed therein; a valve plate disposed between the cylinder block and the housing; and a pressing member that presses the valve plate toward the cylinder block side, the valve plate having: a suction port that communicates the cylinder communication hole with the suction path; a discharge port that is formed on the opposite side of the suction port so as to sandwich a pair of switching land portions formed on a 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path; a pressing member accommodating recess portion formed in a 2 nd surface of the valve plate on a side opposite to the 1 st surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess portion accommodating the pressing member; a notch extending from the ejection port toward the bottom dead center switching land portion; and a valve plate communication hole disposed at a front end of the cutout, the valve plate communication hole communicating the pressing member accommodating recess with the switching land portion, the bottom dead center switching land portion being defined as a land portion disposed at a bottom dead center position at which the piston is switched from the suction step to the discharge step, of the pair of switching land portions, and the front end of the cutout being defined as an end portion on a side opposite to the discharge port.

The switching land portion is formed by grinding the valve plate at the time of finish machining of the valve plate. At this time, by forming the valve plate communication hole at the tip of the notch, it is possible to prevent the distance between the notch and the valve plate communication hole from changing due to the amount of grinding. That is, although the position of the front end of the notch changes due to the amount of grinding, the valve plate communication hole is formed at the front end of the notch, thereby preventing the distance between the notch and the valve plate communication hole from changing. Therefore, the effect of the valve plate communication hole can be stabilized regardless of the amount of grinding.

The construction machine according to another aspect of the present invention includes: a vehicle body; and a fluid machine that sucks and discharges a fluid that is a drive source of the vehicle body, the fluid machine including: a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber; a piston which is slidably housed in the cylinder chamber and which performs a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber; a housing that houses the cylinder, the housing having an intake path and a discharge path formed therein; a valve plate disposed between the cylinder block and the housing; and an urging member that urges the valve plate toward the cylinder block side, the valve plate having: a suction port that communicates the cylinder communication hole with the suction path; a discharge port that is formed on the opposite side of the suction port so as to sandwich a pair of switching land portions formed on a 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path; a pressing member accommodating recess portion formed in a 2 nd surface of the valve plate on a side opposite to the 1 st surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess portion accommodating the pressing member; a notch extending from the discharge port toward the bottom dead center switching land portion; and a valve plate communication hole disposed at a position away from a front end of the cutout toward the suction port side, the valve plate communication hole communicating the pressing member accommodating recessed portion with the switching land portion, the bottom dead center switching land portion being defined as a land portion, out of the pair of switching land portions, disposed at a bottom dead center position at which the piston is switched from the suction process to the discharge process, the front end of the cutout being defined as an end portion on a side opposite to the discharge port.

With such a configuration, it is possible to provide a construction machine capable of suppressing the processing cost of the valve plate and obtaining a sufficient corrosion prevention effect of the cylinder chamber.

The construction machine according to another aspect of the present invention includes: a vehicle body; and a fluid machine that sucks and discharges a fluid that is a drive source of the vehicle body, the fluid machine including: a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber; a piston which is slidably housed in the cylinder chamber and which performs a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber; a housing that houses the cylinder, the housing having an intake path and a discharge path formed therein; a valve plate disposed between the cylinder block and the housing; and an urging member that urges the valve plate toward the cylinder block side, the valve plate having: a suction port that communicates the cylinder communication hole with the suction path; a discharge port that is formed on the opposite side of the suction port so as to sandwich a pair of switching land portions formed on a 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path; a pressing member accommodating recess portion formed in a 2 nd surface of the valve plate on a side opposite to the 1 st surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess portion accommodating the pressing member; a notch extending from the ejection port toward the bottom dead center switching land portion; and a valve plate communication hole disposed at a distal end of the cutout, the valve plate communication hole communicating the pressing member accommodating recess portion with the switching land portion, the bottom dead center switching land portion being defined as a land portion of the pair of switching land portions disposed at a bottom dead center position at which the piston is switched from the suction process to the discharge process, the distal end of the cutout being defined as an end portion on a side opposite to the discharge port.

With such a configuration, it is possible to provide a construction machine in which the effect of the valve plate communication hole can be stabilized regardless of the polishing amount.

ADVANTAGEOUS EFFECTS OF INVENTION

The fluid machine and the construction machine described above can obtain a sufficient anti-corrosion effect of the cylinder chamber while suppressing the processing cost of the valve plate.

Drawings

Fig. 1 is a schematic configuration diagram of a construction machine according to an embodiment of the present invention.

Fig. 2 is a partially cut-away view of the pump unit according to the embodiment of the present invention.

Fig. 3 is a plan view of the 1 st surface side of the valve plate in embodiment 1 of the present invention.

Fig. 4 is a plan view of the 2 nd surface side of the valve plate in embodiment 1 of the present invention.

Fig. 5 isbase:Sub>A sectional view taken along linebase:Sub>A-base:Sub>A of fig. 4.

Fig. 6 is a sectional view taken along line B-B of fig. 3.

Fig. 7 is a sectional view of a main portion of a valve plate in embodiment 2 of the present invention.

Description of the reference numerals

1. A main pump (fluid machine); 2. a main housing (casing); 4. a cylinder body; 17. a cylinder chamber; 18. a communication hole (cylinder body communication hole); 19. 219, a valve plate; 19a, a suction inlet; 19b, a discharge port; 21. a piston; 41a, 1 st surface; 41b, face 2; 46. a pressing piston (pressing member); 47a, a bottom dead center switching land portion; 47b, an upper dead point switching land portion; 49. a piston housing recess (pressing member housing recess); 50. a notch; 51. a valve plate communication hole; 101. a swivel body (vehicle body); 102. a traveling body (vehicle body); 122. the 1 st suction path (suction path); 123. an ejection path.

Detailed Description

Next, an embodiment of the present invention will be described based on the drawings.

< construction machinery >

Fig. 1 is a schematic configuration diagram of a construction machine 100.

As shown in fig. 1, the construction machine 100 is, for example, a hydraulic excavator or the like. The construction machine 100 includes a revolving body (an example of a vehicle body in the claims) 101 and a traveling body (an example of a vehicle body in the claims) 102 provided under the revolving body 101. The revolving unit 101 revolves on the upper part of the traveling unit 102. The rotary body 101 includes a pump unit (an example of a fluid machine in the claims) 110.

The rotary body 101 includes: a cab 103 for supporting an operator on the revolving unit 101; a boom 104 having one end connected to the cab 103; an arm 105 having one end connected to the other end of the boom 104; and a bucket 106 coupled to the other end of arm 105. Boom 104 swings with respect to cab 103. The arm 105 swings with respect to the boom 104. The bucket 106 swings with respect to the stick 105.

The pump unit 110 is disposed in the cab 103. The hydraulic oil supplied from pump unit 110 serves as a drive source for cab 103, boom 104, arm 105, and bucket 106.

< Pump Unit >

Fig. 2 is a partially cut-away view of the pump unit 110.

The pump unit 110 is a so-called hydraulic pump. The pump unit 110 sucks and discharges the working oil. As shown in fig. 2, the pump unit 110 includes a main pump (an example of a fluid machine in the claims) 1 as a fluid machine, and a gear pump 111 provided on one side of the main pump 1. Fig. 2 shows the main pump 1 only in a cross section along the axial direction. In fig. 2, the scale of each member is appropriately changed to facilitate understanding of the description.

Main pump

The main pump 1 is a so-called swash plate type variable displacement hydraulic pump. The main structure of the main pump 1 is: a main housing (an example of a housing in claims) 2; a shaft 3 supported by the main casing 2 so as to be rotatable about a central axis C with respect to the main casing 2; a cylinder 4 housed in the main casing 2 and fixed to the shaft 3; a swash plate 5 housed in the main casing 2 and provided to be tiltable with respect to the main casing 2; a piston 21 provided in the cylinder 4; a valve plate 19 disposed between the main casing 2 and the cylinder block 4; and a pressing piston (an example of a pressing member in claims) 46 provided to the valve plate 19.

In fig. 2, the scale of each member is appropriately changed to facilitate understanding of the description. In the following description, a direction parallel to the central axis C of the shaft 3 is referred to as an axial direction, a rotation direction of the shaft 3 is referred to as a circumferential direction, and a radial direction of the shaft 3 is simply referred to as a radial direction.

The main casing 2 includes: a box-shaped case main body (an example of a case in claims) 9 having an opening 9a; and a front flange 10 for closing the opening 9a of the housing main body 9.

The case body 9 includes a bottom wall 119 provided on the opposite side of the opening 9a. The bottom wall 119 is a wall portion of the housing main body 9 located on the central axis C of the shaft 3. The cylinder 4 is disposed on the inner surface 119a side of the bottom wall 119. The gear pump 111 is attached to an outer surface 119b of the bottom wall 119.

A rotation shaft insertion hole 121 through which the shaft 3 is inserted is formed in the bottom wall 119 so as to penetrate in the plate thickness direction of the bottom wall 119. A bearing 11 for rotatably supporting one end side of the shaft 3 is provided in the rotation shaft insertion hole 121 at a position close to the inner surface 119a of the bottom wall 119.

The bottom wall 119 is formed with a 1 st suction path 122 (an example of a suction path in claims) and a discharge path 123 on both sides in the radial direction with a rotation shaft insertion hole 121 interposed therebetween. The 1 st suction path 122 has an opening 122a formed in the 1 st side surface 119c of the bottom wall 119. The opening 122a of the 1 st suction path 122 communicates with a tank not shown. The 1 st suction path 122 extends in the bottom wall 119 so that an opening area thereof becomes gradually smaller from the 1 st side surface 119c toward the rotation shaft insertion hole 121.

A 1 st communication path 124 for communicating the 1 st suction path 122 with the inner surface 119a of the bottom wall 119 is formed at an end of the 1 st suction path 122 on the rotation shaft insertion hole 121 side. The 1 st communication path 124 communicates the 1 st suction path 122 with a suction port 19a of the valve plate 19 described later.

The end of the 1 st suction path 122 on the side of the rotation shaft insertion hole 121 does not communicate with the rotation shaft insertion hole 121. A 2 nd communication path 125 for communicating the 1 st suction path 122 with the outer surface 119b of the bottom wall 119 is formed at an end of the 1 st suction path 122 on the rotation shaft insertion hole 121 side. The 2 nd communication path 125 communicates the 1 st suction path 122 with a 2 nd suction path 144 of the gear pump 111, which will be described later.

An O-ring groove 118 is formed in an outer surface 119b of the bottom wall 119 so as to surround the rotation shaft insertion hole 121 and the 2 nd communication path 125. An O-ring 117 is attached to the O-ring groove 118. The O-ring 117 ensures sealing between the main casing 2 and a gear casing 141 of the gear pump 111, which will be described later.

With this configuration, the working oil is sucked into the 1 st suction path 122 from a tank not shown. The working oil sucked into the 1 st suction path 122 flows to the 1 st communication path 124 and the 2 nd communication path 125.

The discharge path 123 has an opening 123a formed in a 2 nd side surface 119d of the bottom wall 119 on the opposite side of the 1 st side surface 119c with the rotation axis insertion hole 121 interposed therebetween. Opening 123a is connected to cab 103, boom 104, arm 105, and bucket 106 via a control valve or the like, not shown. The discharge path 123 extends from the 2 nd side surface 119d toward the rotation shaft insertion hole 121 in the bottom wall 119.

The end of the discharge path 123 on the side of the rotation shaft insertion hole 121 does not communicate with the rotation shaft insertion hole 121. A 3 rd communication path 128 for communicating the discharge path 123 with the inner surface 119a of the bottom wall 119 is formed at an end of the discharge path 123 on the rotation shaft insertion hole 121 side. The 3 rd communication path 128 communicates the discharge path 123 with a discharge port 19b of the valve plate 19, which will be described later.

The front flange 10 is formed with a through hole 13 through which the shaft 3 passes. A bearing 14 for rotatably supporting the other end side of the shaft 3 is provided in the through hole 13. An oil seal 15 is provided in the through hole 13 on the opposite side of the bearing 14 from the housing main body 9 (outside the front flange 10). The oil seal 15 prevents the working oil from flowing out from the inside, and prevents foreign matters and the like from entering between the shaft 3 and the front flange 10.

Two attachment plates 137 are formed integrally with the front flange 10 on the front flange 10. The two mounting plates 137 are disposed on both sides in the radial direction with the shaft 3 interposed therebetween. The mounting plate 137 extends toward the radially outer side. The two attachment plates 137 are used to fix the main pump 1 to a drive source such as an engine provided in the revolving unit 101.

The shaft 3 is formed to have a step shape. The shaft 3 is integrally formed by a shaft main body 131, a 1 st bearing portion 132, a transmission shaft 133, a 2 nd bearing portion 134, and a coupling shaft 135, which are coaxially arranged, the 1 st bearing portion 132 extending from the shaft main body 131 toward one end side of the shaft 3 (the side of the bottom wall 119 of the main casing 2), the transmission shaft 133 extending from the 1 st bearing portion 132 toward the side opposite to the shaft main body 131, the 2 nd bearing portion 134 extending from the shaft main body 131 toward the other end side of the shaft 3 (the side of the front flange 10), and the coupling shaft 135 extending from the 2 nd bearing portion 134 toward the side opposite to the shaft main body 131.

The shaft main body 131 is disposed in the main casing 2. Shaft body 131 is formed with 1 st spline 131a. A cylinder 4 is fitted to the 1 st spline 131a. A pressing member 27 is fitted to the outer peripheral surface of the shaft main body 131 at a position close to the 2 nd bearing 134. The pressing member 27 presses a shoe holding member 29 described later.

The shaft diameter of the 1 st bearing portion 132 is smaller than the shaft diameter of the shaft main body 131. The 1 st bearing portion 132 is rotatably supported by the bearing 11 of the bottom wall 119.

The transmission shaft 133 transmits the rotational force of the shaft 3 to the gear pump 111. The shaft diameter of the transmission shaft 133 is smaller than the shaft diameter of the 1 st bearing 132. The transmission shaft 133 protrudes to the gear pump 111 side through the bearing 11. The transmission shaft 133 is disposed in the rotation shaft through hole 121 of the bottom wall 119. A cylindrical coupling 136 is fitted to the outer peripheral surface of the transmission shaft 133. The coupling 136 rotates integrally with the transmission shaft 133. An end portion of the coupling 136 opposite to the 1 st bearing portion 132 protrudes outward from the bottom wall 119 through the rotation shaft insertion hole 121. The protruding portion is connected to the gear pump 111.

The shaft diameter of the 2 nd bearing part 134 is larger than the shaft diameter of the 1 st bearing part 132. The 2 nd bearing portion 134 is rotatably supported by the bearing 14 of the front flange 10.

The coupling shaft 135 is coupled to a power source such as an engine, not shown. The shaft diameter of the coupling shaft 135 is smaller than the shaft diameter of the 2 nd bearing 134. The distal end portion of the coupling shaft 135 on the opposite side to the 2 nd bearing portion 134 protrudes outward from the front flange 10 via the bearing 14. A 2 nd spline 135a is formed at a distal end portion of the coupling shaft 135. A power source such as an engine, not shown, is coupled to the shaft 3 via the 2 nd spline 135a.

The cylinder 4 fixed to the shaft 3 is formed in a cylindrical shape. A through hole 16 into which the shaft 3 is inserted or press-fitted is formed in the radial center of the cylinder 4. A spline 16a is formed on an inner wall surface of the through hole 16. The spline 16a is coupled to the 1 st spline 131a of the shaft body 131. The shaft 3 and the cylinder 4 rotate integrally via the

respective splines

16a, 131a.

A recess 20 is formed between the axial center of the through hole 16 and the end 4a on the bottom wall 119 side so as to surround the shaft 3. A through hole 25 penetrating the cylinder 4 in the axial direction is formed in a part of the inner wall surface between the axial center of the through hole 16 and the front flange 10 side. The recess 20 accommodates a spring 23 and

races

24a and 24b, which will be described later. A coupling member 26, which will be described later, is accommodated in the through hole 25 so as to be movable in the axial direction.

The cylinder block 4 has a plurality of cylinder chambers 17 formed to surround the shaft 3. The plurality of cylinder chambers 17 are arranged at equal intervals in the circumferential direction on a predetermined pitch circle concentric with the center axis C. The cylinder chamber 17 is a recess opened on the front flange 10 side and closed on the bottom wall 119 side. A communication hole (an example of a cylinder communication hole in claims) 18 for communicating each cylinder chamber 17 with the outside of the cylinder block 4 is formed in the end portion 4a of the cylinder block 4 at a position corresponding to each cylinder chamber 17.

A piston 21 is housed in each cylinder chamber 17 so as to be slidable in the axial direction. Thereby, the piston 21 rotates so as to revolve around the center axis C in accordance with the rotation of the shaft 3 and the cylinder 4.

A cavity for storing the hydraulic oil in the cylinder chamber 17 is formed inside the piston 21. The sliding movement of the piston 21 is associated with the suction and discharge of the hydraulic oil with respect to the cylinder chamber 17.

That is, when the piston 21 is pulled out from the cylinder chamber 17, the spatial volume in the cylinder chamber 17 increases, and the hydraulic oil is sucked into the cylinder chamber 17 through the communication hole 18 (suction step). From the bottom dead center at which the piston 21 is drawn out from the cylinder chamber 17 to the maximum, the piston 21 moves into the cylinder chamber 17. When the piston 21 enters the cylinder chamber 17, the volume of the space in the cylinder chamber 17 decreases, and the hydraulic oil is discharged from the cylinder chamber 17 through the communication hole 18 (discharge step). The piston 21 moves to the top dead center where the piston 21 enters the cylinder chamber 17 to the maximum extent, and the motion of the piston 21 is again shifted to the bottom dead center.

A spherical projection 28 is integrally formed at the end of the piston 21 on the front flange 10 side. A plurality of shoes 22 are attached to the boss 28. The shoe 22 is used to correlate the amount of sliding movement of the piston 21 with the inclination of the swash plate 5. A spherical recess 22a is formed in the surface of the shoe 22 on the side of the receiving projection 28 so as to correspond to the shape of the projection 28. The convex portion 28 of the piston 21 is fitted into the inner wall surface of the concave portion 22a. The shoe 22 is coupled to the convex portion 28 of the piston 21 so as to be rotatable with respect to the convex portion 28 of the piston 21.

The spring 23 accommodated in the recess 20 of the cylinder 4 is, for example, a coil spring. The spring 23 is compressed between two

races

24a, 24b housed in the recess 20. The spring 23 generates an urging force in a direction in which it is extended by an elastic force. The urging force of the spring 23 is transmitted to the coupling member 26 via one 24b of the two

races

24a, 24b. The pressing force of the spring 23 is transmitted to the pressing member 27 fitted to the outer peripheral surface of the shaft main body 131 via the connecting member 26.

The swash plate 5 is provided on an inner surface 10a of the front flange 10 on the housing main body 9 side. The swash plate 5 is inclined with respect to the front flange 10, thereby restricting displacement of each piston 21 in the axial direction. A through hole 32 through which the shaft 3 passes is formed in the radial center of the swash plate 5. The swash plate 5 includes a flat sliding surface 5a formed on the cylinder block 4 side. The plurality of shoes 22 move on the sliding surface 5a.

The shoes 22 are integrated by a shoe holding member 29. The pressing member 27 is in contact with the shoe holding member 29 to press the shoe holding member 29 toward the swash plate 5 side. The shoe 22 moves so as to follow the sliding surface 5a of the swash plate 5. Thereby, the piston 21 revolving around the center axis C slides with respect to the cylinder chamber 17. That is, the amount of sliding movement of the pistons 21 is controlled by the swash plate 5. In other words, the amount of sliding movement of the pistons 21 is determined by the inclination angle of the swash plate 5. In other words, the swash plate 5 controls the discharge amount of the hydraulic oil discharged from the main pump 1. The inclination angle of the swash plate 5 is controlled by an actuator not shown. Their details are described later.

[ embodiment 1 ]

< valve plate >

The valve plate 19 is disposed between the end surface 4b of the end 4a of the cylinder block 4 and the inner surface 119a of the bottom wall 119 of the housing main body 9. The valve plate 19 is formed in a disc shape. The valve plate 19 is provided in a bottom wall 119 of the housing main body 9 so as not to rotate. That is, the valve plate 19 may be separated from the inner surface 119a of the bottom wall 119, although not rotating with respect to the bottom wall 119 of the housing main body 9.

The valve plate 19 is stationary with respect to the main casing 2 (casing main body 9) even in the case where the cylinder block 4 and the shaft 3 rotate about the center axis C. The cylinder block 4 is supported by static pressure of an oil film of the hydraulic oil formed between the valve plate 19 and the end surface 4b of the cylinder block 4.

Fig. 3 is a plan view of the valve plate 19 viewed from the 1 st surface 41a side of the cylinder 4. Fig. 4 is a plan view of the valve plate 19 viewed from the 2 nd surface 41b on the bottom wall 119 side. Fig. 5 isbase:Sub>A sectional view taken along linebase:Sub>A-base:Sub>A of fig. 4.

As shown in fig. 3 to 5, a through hole 42 through which the shaft 3 penetrates is formed in the radial center of the valve plate 19 so as to penetrate in the plate thickness direction of the valve plate 19. An inner recess 43 having an annular shape in axial view is formed on the 1 st surface 41a of the valve plate 19 so as to surround the periphery of the through hole 42 and communicate with the through hole 42. An annular outer recess 44 is formed along the outer peripheral portion on the 1 st surface 41a of the valve plate 19.

The valve plate 19 is formed with suction ports 19a that communicate with the communication holes 18 of the cylinder block 4 so as to penetrate through the valve plate 19 in the thickness direction. The outer shape of the suction port 19a is, for example, an arc shape within a predetermined angular range around the center axis C, and is formed in an oblong shape.

Each cylinder chamber 17 communicates with the 1 st communication path 124 formed in the housing main body 9 via the suction port 19a of the valve plate 19 and the communication hole 18 of the cylinder block 4.

A discharge port 19b is formed from the 2 nd surface 41b of the valve plate 19 to the thickness direction center of the valve plate 19. The discharge port 19b is formed in a circular shape as viewed in the axial direction. The discharge port 19b is disposed on the opposite side of the circumferential center of the suction port 19a with the through hole 42 interposed therebetween.

An elongated recess 45 communicating with the discharge port 19b is formed on the side opposite to the suction port 19a with the through hole 42 interposed therebetween, between the 1 st surface 41a of the valve plate 19 and the thickness direction center of the valve plate 19.

The long concave portion 45 communicates with the ejection port 19b, and therefore, the long concave portion 45 is a part of the ejection port 19b. The long concave portion 45 is, for example, arc-shaped within a predetermined angular range around the center axis C, and is formed in an oblong shape. The long concave portion 45 and the suction port 19a are arranged on the same pitch circle.

Each cylinder chamber 17 communicates with the 3 rd communication path 128 formed in the housing main body 9 via the discharge port 19b of the valve plate 19, the elongated recess 45, and the communication hole 18 of the cylinder block 4.

A pair of switching

land portions

47a, 47b (a bottom dead center switching land portion 47a, a top dead center switching land portion 47 b) are formed on the 1 st surface 41a of the valve plate 19 between both ends in the longitudinal direction of the suction port 19a and both ends in the longitudinal direction of the elongated recess 45. In other words, the suction port 19a and the long concave portion 45 are formed on both sides with the pair of switching

land portions

47a, 47b interposed therebetween. The pair of switching

land portions

47a and 47b are flush with the 1 st surface 41 a. The communication hole 18 of the cylinder 4 is switched to communicate with the suction port 19a or the elongated recess 45 by the pair of switching

land portions

47a and 47b when the cylinder 4 rotates.

In the following description, the switching land portion 47a of the pair of switching

land portions

47a and 47b corresponding to a portion where the motion of the piston 21 shifts from the bottom dead center to the top dead center is referred to as a bottom dead center switching land portion 47a. Of the pair of switching

land portions

47a, 47b, the switching land portion 47b corresponding to a portion where the operation of the piston 21 shifts from the top dead center to the bottom dead center is referred to as a top dead center switching land portion 47b.

Between the 2 nd surface 41b of the valve plate 19 and the thickness direction center of the valve plate 19, piston accommodating recesses (an example of a pressing member accommodating recess in the claims) 49 are formed at positions corresponding to both ends in the longitudinal direction of the long recess 45. These piston housing recesses 49 are also formed at positions avoiding the 1 st suction path 122 and the discharge path 123 formed in the housing main body 9. The avoided position is a position not communicating with the 1 st suction path 122 and the discharge path 123. That is, the piston accommodating recess 49 is formed at a position not communicating with the 1 st suction path 122 and the discharge path 123.

The piston housing recess 49 is formed in a circular shape as viewed in the axial direction. The diameter of the piston accommodating recess 49 is larger than the diameter of the discharge port 19b. The piston accommodating recess 49 communicates with both longitudinal ends of the long recess 45.

The piston accommodating recess 49 accommodates a disk-shaped pressing piston 46. The center axis Co of the pressing piston 46 is in the axial direction. The diameter of the pressing piston 46 is substantially the same as the diameter of the piston housing recess 49 or slightly smaller than the diameter of the piston housing recess 49.

Fig. 6 is a sectional view taken along line B-B of fig. 3.

As shown in fig. 3, 4, and 6, the notch 50 extending from the end portion of the long concave portion 45 on the bottom dead center switching land portion 47a side out of the longitudinal both ends of the long concave portion 45 toward the bottom dead center switching land portion 47a (the longitudinal end portion of the suction port 19 a) is formed in the 1 st surface 41a of the valve plate 19. Notch 50 is formed so that its tip becomes narrower from the longitudinal end of elongated recess 45 toward the longitudinal end of suction port 19a as viewed in the axial direction. The notch 50 is formed such that the notch depth gradually becomes shallower from the longitudinal direction end of the long recessed portion 45 toward the longitudinal direction end of the suction port 19a.

In the valve plate 19, a valve plate communication hole 51 for communicating the bottom surface 49a with the bottom dead center switching land portion 47a is formed in the bottom surface 49a of the piston housing recess 49 disposed on the bottom dead center switching land portion 47a side. The valve plate communication hole 51 is a fine hole. The valve plate communication hole 51 extends in the axial direction. The valve plate communication hole 51 is disposed slightly apart from the tip of the notch 50 toward the longitudinal end of the suction port 19a. The valve plate communication hole 51 communicates with each communication hole 18 of the cylinder block 4.

< Gear Pump >

As shown in fig. 2, the gear pump 111 provided on one side of the main pump 1 functions as an additional pump. The gear pump 111 includes a gear housing 141, and a drive gear and a driven gear, which are not shown.

The gear housing 141 having a rectangular parallelepiped shape is disposed on the outer surface 119b of the bottom wall 119 of the main housing 2. A 2 nd suction path 144 communicating with the 2 nd communication path 125 of the main casing 2 is formed in the 1 st wall surface 141a of the gear casing 141 overlapping the main casing 2. The 2 nd suction path 144 communicates the inside and outside of the 1 st wall surface 141a of the gear housing 141.

A coupling through-hole 149 is formed in the 1 st wall surface 141a of the gear case 141 at a position corresponding to the rotation shaft through-hole 121 of the main case 2. The end of the coupling 136 on the gear pump 111 side protrudes into the gear case 141 through the coupling through hole 149.

A 3 rd discharge path, not shown, is formed on a 2 nd wall surface 141b of the gear case 141, which is orthogonal to the 1 st wall surface 141a and faces in the same direction as the 2 nd side surface 119d of the main case 2. The opening of the 3 rd discharge path is formed in the 2 nd wall surface 141b.

A drive gear and a driven gear, not shown, are rotatably supported in the gear housing 141 and mesh with each other. The drive gear is coupled to a coupling 136 protruding from the main casing 2 through a coupling through-hole 149. The rotational force of the shaft 3 in the main pump 1 is transmitted to the drive gear via the coupling 136. The driven gear is meshed with the drive gear, and therefore, the driven gear rotates in synchronization with the drive gear.

< action of Pump Unit >

Next, the operation of the pump unit 110 will be described.

First, the operation of the main pump 1 will be described.

The main pump 1 outputs driving force generated by discharge of hydraulic oil from the cylinder chamber 17 and suction of hydraulic oil into the cylinder chamber 17.

More specifically, the cylinder 4 rotates integrally with the shaft 3 as the shaft 3 rotates due to power from a power source such as an engine. As the cylinder 4 rotates, the piston 21 orbits around the central axis C of the shaft 3.

Due to the urging force of the spring 23, the shoes 22 attached to the convex portions 28 of the pistons 21 appropriately follow and are pressed against the sliding surface 5a of the swash plate 5 regardless of the inclination angle of the swash plate 5. The convex portion 28 of the piston 21 is formed in a spherical shape, and the concave portion 22a of the shoe 22 into which the convex portion 28 is fitted is also formed in a spherical shape. The pressing member 27 applies a pressing force to the swash plate 5 side to each shoe 22 via the shoe holding member 29. Even if the inclination angle of the swash plate 5 changes, the shoes 22 follow the inclination of the swash plate 5 and appropriately follow and press against the sliding surface 5a.

When the piston 21 rotates around the center axis C of the shaft 3 as the cylinder block 4 rotates, the shoes 22 also move on the sliding surface 5a of the swash plate 5 while rotating around the center axis C of the shaft 3. Thereby, each piston 21 slides in the axial direction in each cylinder chamber 17 to reciprocate.

When the piston 21 shifts from the top dead center to the bottom dead center, the cylinder chamber 17 (the communication hole 18) in which the piston 21 is housed passes through the suction port 19a from the elongated recess 45 of the valve plate 19 via the top dead center switching land portion 47b. At this time, the working oil is sucked into the cylinder chamber 17 from the 1 st suction path 122 of the main casing 2 through the 1 st communication path 124, the suction port 19a, and the communication hole 18 (suction step).

When the piston 21 transitions from the bottom dead center to the top dead center, the cylinder chamber 17 (communication hole 18) in which the piston 21 is housed passes over the long concave portion 45 from the suction port 19a of the valve plate 19 via the bottom dead center switching land portion 47a. At this time, the hydraulic oil is discharged from the cylinder chamber 17 through the communication hole 18, the elongated recess 45, the discharge port 19b, the 3 rd communication path 128, and the discharge path 123 (discharge step).

When the inclination angle of the swash plate 5 (sliding surface 5 a) changes, the stroke (moving distance) of the reciprocating motion of the piston 21 changes. The larger the inclination angle of the swash plate 5, the larger the suction amount and discharge amount of the hydraulic oil with respect to the cylinder chamber 17, which are generated as the pistons 21 reciprocate. As the inclination angle of the swash plate 5 decreases, the suction amount and discharge amount of the hydraulic oil with respect to the cylinder chamber 17, which are generated as the pistons 21 reciprocate, decrease. When the inclination angle of the swash plate 5 is zero, the pistons 21 do not reciprocate even if the pistons 21 rotate around the center axis C of the shaft 3. When the inclination angle of the swash plate 5 is zero, the discharge amount of the hydraulic oil from each cylinder chamber 17 is also zero.

In the discharge step, the hydraulic oil discharged from the cylinder chamber 17 to the elongated recess 45 is discharged to the piston accommodating recess 49 in addition to the discharge port 19b. The push piston 46 is housed in the piston housing recess 49, and therefore, due to the pressure of the working oil, the push piston 46 is pushed toward the inner surface 119a of the bottom wall 119 in the main casing 2. Due to the reaction force generated by the pressing piston 46 being pressed against the inner surface 119a of the bottom wall 119, a pressing force is generated that presses the valve plate 19 against the end surface 4b of the cylinder 4.

The hydraulic oil discharged from the cylinder chamber 17 forms an oil film between the portion of the 2 nd surface 41b of the valve plate 19 other than the through hole 42, the suction port 19a, the discharge port 19b, and the piston accommodating recess 49 and the inner surface 119a of the bottom wall 119.

The pressing force is generated as a force that presses the cylinder block 4 against the valve plate 19 by the piston 21 housed in each cylinder chamber 17 of the cylinder block 4. The pressing force is a force of the valve plate 19 toward the cylinder block 4, and includes a reaction force of a force of pressing the piston 46 by the hydraulic oil acting on the cylinder chamber 17.

The hydraulic oil discharged from the cylinder chamber 17 forms an oil film between the portion of the 1 st surface 41a of the valve plate 19 other than the through hole 42, the suction port 19a, the elongated recess 45, the inner recess 43, and the outer recess 44, and the end surface 4b of the cylinder block 4. The reaction force of the oil film becomes a separating force to separate the valve plate 19 from the end surface 4b of the cylinder 4. Further, the deviating force is hydraulic force acting on the end surface 4b of the cylinder 4 from the suction port 19a and the discharge port 19b of the valve plate 19. By balancing these urging force and the deviating force, the positional relationship between the cylinder block 4 and the valve plate 19 is appropriately ensured.

However, at the time when the cylinder chamber 17 (the communication hole 18) communicates with the long concave portion 45 (the discharge port 19 b) through the bottom dead center switching land portion 47a, the cylinder chamber 17 is rapidly opened by the long concave portion 45 (the discharge port 19 b), and therefore, there is a possibility that the working oil is reversely injected into the cylinder chamber 17 due to a pressure difference. The notch 50 formed in the 1 st surface 41a of the valve plate 19 functions to alleviate rapid pressure fluctuations in the cylinder chamber 17.

In addition, in the valve plate 19 of embodiment 1, a valve plate communication hole 51 for communicating the bottom surface 49a with the bottom dead center switching land portion 47a is formed in the bottom surface 49a of the piston accommodating recess 49. Therefore, immediately before the cylinder chamber 17 (the communication hole 18) communicates with the long concave portion 45 (the discharge port 19 b), the cylinder chamber 17 (the communication hole 18) communicates with the valve plate communication hole 51. As a result, the pressure of the hydraulic oil in the piston accommodating recess 49 (the discharge port 19 b) (hereinafter referred to as the discharge pressure of the hydraulic oil) is introduced into the cylinder chamber 17, and the pressure in the cylinder chamber 17 is slightly increased. Therefore, the reverse injection of the hydraulic oil into the cylinder chamber 17 can be prevented at the timing when the cylinder chamber 17 (the communication hole 18) communicates with the long concave portion 45 (the discharge port 19 b).

Next, the operation of the gear pump 111 will be described.

Since the drive gear of the gear pump 111 is coupled to the shaft 3 of the main pump 1 via the coupling 136, the drive gear rotates integrally with the shaft 3. The driven gear engaged with the driving gear also rotates in synchronization with the driving gear. The working oil flowing through the 1 st suction path 122 is sucked into the 2 nd suction path 144 through the 2 nd communication path 125 of the main casing 2. The hydraulic oil flows between the gears and the inner surface of the gear case 141 to the 3 rd discharge path side, not shown. The working oil is discharged through the opening of the 3 rd discharge path.

As described above, the valve plate 19 in embodiment 1 has the valve plate communication hole 51, and the valve plate communication hole 51 is formed in the bottom surface 49a of the piston housing recess 49 so that the bottom surface 49a communicates with the bottom dead center switching land portion 47a. Therefore, immediately before the cylinder chamber 17 (the communication hole 18) and the long concave portion 45 (the discharge port 19 b) communicate with each other through the bottom dead center switching land portion 47a, the discharge pressure of the hydraulic oil can be introduced into the cylinder chamber 17 through the valve plate communication hole 51. As a result, the reverse injection of the hydraulic oil into the cylinder chamber 17 can be prevented at the timing when the cylinder chamber 17 (the communication hole 18) communicates with the elongated recess 45 (the discharge port 19 b). Therefore, corrosion of the cylinder chamber 17 due to back injection of the hydraulic oil into the cylinder chamber 17 can be reliably suppressed.

The valve plate communication hole 51 is formed by the piston housing concave portion 49 for generating the pressing force to the cylinder block 4 in the valve plate 19, and the pressure of the hydraulic oil at the discharge port 19b can be easily introduced into the valve plate communication hole 51. Therefore, the processing cost of the valve plate 19 can be suppressed.

The valve plate communication hole 51 is disposed slightly apart from the front end of the notch 50 toward the longitudinal end of the suction port 19a. Therefore, the discharge pressure of the hydraulic oil can be reliably introduced into the cylinder chamber 17 immediately before the cylinder chamber 17 (the communication hole 18) and the elongated recess 45 (the discharge port 19 b) communicate with each other through the bottom dead center switching land portion 47a.

A disk-shaped pressing piston 46 is accommodated in a piston accommodating recess 49 formed in the valve plate 19. By applying the discharge pressure of the hydraulic oil to the pressing piston 46, the pressing force toward the cylinder 4 can be easily applied to the valve plate 19.

[ 2 nd embodiment ]

Next, embodiment 2 of the present invention will be described with reference to fig. 7.

Fig. 7 is a sectional view of a main portion of a valve plate 219 in embodiment 2. Fig. 7 corresponds to the aforementioned fig. 6. The same reference numerals are given to the same aspects as those of embodiment 1, and the description thereof is omitted.

As shown in fig. 7, the difference between embodiment 1 and embodiment 2 is as follows: in the valve plate 19 of embodiment 1, the valve plate communication hole 51 is disposed at a position slightly separated from the tip of the notch 50, whereas in the valve plate 219 of embodiment 2, the valve plate communication hole 52 is disposed at the tip of the notch 50. In embodiment 2, the valve plate communication hole 52 communicates with the notch 50 on the 1 st surface 41a side of the valve plate 219.

The switching

land portions

47a, 47b of the valve plate 219 are formed by grinding the valve plate 219 at the finish machining of the valve plate 219. At this time, by forming the valve plate communication hole 52 at the tip of the notch 50, it is possible to prevent the distance between the notch 50 and the valve plate communication hole 52 from changing due to the amount of grinding. That is, although the position of the front end of the notch 50 changes depending on the amount of grinding, the valve plate communication hole 52 is formed at the front end of the notch 50, thereby preventing the distance between the notch 50 and the valve plate communication hole 52 from changing. In other words, the valve plate communication hole 52 always communicates with the notch 50 on the 1 st surface 41a side of the valve plate 219 regardless of the amount of grinding. Therefore, the effect of the valve plate communication hole 52 can be stabilized regardless of the amount of grinding.

The present invention is not limited to the above-described embodiments, and various modifications may be made to the above-described embodiments without departing from the scope of the present invention.

For example, in the above-described embodiment, the description has been given of the case where the construction machine 100 is a hydraulic excavator. However, the present invention is not limited to this, and various kinds of construction machines can be used.

In the above-described embodiment, the main pump 1 using the working oil as the fluid is described as the fluid machine. However, the present invention is not limited to this, and the above-described configuration of the

valve plates

19 and 219 can be adopted in various fluid machines using various fluids other than the working oil.

In the above-described embodiment, the case where the valve plate 19 has the valve plate communication hole 51 formed in the bottom surface 49a of the piston housing recess 49 disposed on the bottom dead center switching land portion 47a side, so that the bottom surface 49a and the bottom dead center switching land portion 47a communicate with each other, has been described. However, the present invention is not limited to this, and a valve plate communication hole 51 that communicates the bottom surface 49a with the top dead center switching land portion 47b may be formed in the bottom surface 49a of the piston housing recess 49 disposed on the top dead center switching land portion 47b side.

In the above-described embodiment, the case where the disk-shaped pressing piston 46 is accommodated in the piston accommodating recess 49 formed in the valve plate 19 is described. However, a pressing force toward the cylinder 4 may be generated in the valve plate 19 by the pressure of the hydraulic oil discharged to the piston accommodating recess 49. For example, the pressing piston 46 may not be provided in the piston housing recess 49. Instead of pressing the piston 46, a compression coil spring or the like may be housed in the piston housing recess 49. The valve plate 19 may be urged toward the cylinder 4 by the elastic force of the compression coil spring.

In the above-described embodiment, the case where the piston accommodating recess portion 49 is formed in the valve plate 19 at the position corresponding to both ends in the longitudinal direction of the long recess portion 45 has been described. However, the piston housing recess 49 is not limited to this, and may be formed at a position avoiding the 1 st suction path 122 and the discharge path 123 (a position not communicating with the 1 st suction path 122 and the discharge path 123). The pressure of the hydraulic oil discharged to the piston housing recess 49 through the valve plate communication hole 51 may be used to generate a pressing force on the valve plate 19 toward the cylinder 4.

This is because, when the piston accommodating recess 49 communicates with the 1 st suction path 122 and the discharge path 123, the hydraulic oil discharged to the piston accommodating recess 49 leaks to the 1 st suction path 122 and the discharge path 123. With such a configuration, it is difficult to generate a pressing force on the valve plate 19 toward the cylinder 4 by the pressure of the hydraulic oil discharged to the piston housing recess 49.

In the above-described embodiment, the case where the valve plate communication hole 51 formed in the valve plate 19 extends in the axial direction has been described. However, it is not limited thereto as long as the valve plate communication hole 51 is formed so as to communicate the piston housing recess 49 of the valve plate 19 with the switching

land portions

47a, 47b.

In the embodiment disclosed in the present specification, a member made of a plurality of objects may be formed by integrating the plurality of objects, and conversely, a member made of one object may be divided into a plurality of objects. Whether integrated or not, may be configured to achieve the object of the invention.

Claims

1. A fluid machine in which, in a fluid machine,

the fluid machine includes:

a cylinder block having a cylinder chamber and a cylinder block communication hole for communicating the inside and outside of the cylinder chamber;

a piston which is slidably housed in the cylinder chamber and which performs a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber;

a housing that houses the cylinder, the housing having a suction path and a discharge path formed therein;

a valve plate disposed between the cylinder block and the housing; and

an urging member that urges the valve plate toward the cylinder block side,

the valve plate has:

a suction port that communicates the cylinder communication hole with the suction path;

a discharge port formed on the opposite side of the suction port so as to sandwich the pair of switching land portions formed on the 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path;

a pressing member accommodating recess portion formed in a position avoiding the suction path and the discharge path on a 2 nd surface of the valve plate on a side opposite to the 1 st surface, the pressing member accommodating recess portion accommodating the pressing member; and

a valve plate communication hole communicating the pressing member housing concave portion with the switching land portion.

2. The fluid machine according to claim 1,

a notch is formed in the valve plate,

a land portion of the pair of switching land portions, which is located at a bottom dead center position at which the piston is switched from the intake process to the discharge process, is defined as a bottom dead center switching land portion,

the notch extends from the ejection port toward the bottom dead center switching land portion,

the valve plate communication hole is disposed at a position separated from the front end of the notch toward the suction port,

the front end of the notch is defined as an end portion on the opposite side to the ejection port.

3. The fluid machine according to claim 1,

a notch is formed in the valve plate,

the valve plate communication hole is configured at the front end of the notch,

4. The fluid machine according to any one of claims 1 to 3,

the pressing member is a disc-shaped small piston.

5. A fluid machine in which, in a fluid machine,

the fluid machine includes:

a piston slidably housed in the cylinder chamber, the piston performing a discharge step of compressing the cylinder chamber and an intake step of expanding the cylinder chamber;

a housing that houses the cylinder, the housing having an intake path and a discharge path formed therein;

a valve plate disposed between the cylinder block and the housing; and

an urging member that urges the valve plate toward the cylinder block side,

the valve plate has:

a discharge port that is formed on the opposite side of the suction port so as to sandwich a pair of switching land portions formed on a 1 st surface of the valve plate on the cylinder side with the suction port, the discharge port communicating the cylinder communication hole with the discharge path;

a pressing member accommodating recess portion formed in a 2 nd surface of the valve plate on a side opposite to the 1 st surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess portion accommodating the pressing member;

a notch extending from the discharge port toward the bottom dead center switching land portion; and

a valve plate communication hole disposed at a position separated from the front end of the notch toward the suction port, the valve plate communication hole communicating the pressing member accommodating recess portion with the switching land portion,

the bottom dead center switching land portion is defined as a land portion of the pair of switching land portions, which is disposed at a bottom dead center position where the piston is switched from the intake process to the discharge process,

6. A fluid machine in which, in a fluid machine,

the fluid machine includes:

a valve plate disposed between the cylinder block and the housing; and

an urging member that urges the valve plate toward the cylinder block side,

the valve plate has:

a notch extending from the ejection port toward the bottom dead center switching land portion; and

a valve plate communication hole disposed at a front end of the cutout, the valve plate communication hole communicating the pressing member accommodating recess portion with the switching land portion,

the lower dead center switching land portion is defined as a land portion of the pair of switching land portions, which is disposed at a lower dead center position at which the piston is switched from the suction process to the discharge process,

7. A construction machine in which, in a construction machine,

the construction machine is provided with:

a vehicle body; and

a fluid machine that sucks and discharges fluid that is a drive source of the vehicle body,

the fluid machine is provided with:

a valve plate disposed between the cylinder block and the housing; and

an urging member that urges the valve plate toward the cylinder block side,

the valve plate has:

8. A construction machine in which, in a construction machine,

the construction machine is provided with:

a vehicle body; and

a fluid machine that sucks and discharges a fluid that is a drive source of the vehicle body,

the fluid machine is provided with:

a valve plate disposed between the cylinder block and the housing; and

an urging member that urges the valve plate toward the cylinder block side,

the valve plate has: