JP2002242825A - Swash plate type piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a passage structure and to inhibit an abrasion of a bearing in a swash plate type piston pump. SOLUTION: The swash plate type piston pump 1 is provided with a swash plate 4 reciprocating a piston 8 so as to enlarge/shrink a volume chamber 7 by a rotation of a cylinder block 3; a first bearing 42 inclinably supporting the swash plate 4 in opposition to a discharge area where the piston 8 shrinks the volume chamber 7; and a second bearing 32 inclinably supporting the swash plate 4 in opposition to a suction area where the piston 8 enlarges the volume chamber 7. The piston pump 1 is provided with a first pressure introduction passage 50 for introducing a hydraulic oil from the volume chamber 7 in the discharge area to the first bearing 42 opposed to the discharge area; and a second pressure introduction passage 60 for introducing the hydraulic oil from the volume chamber 7 in the suction area to the second bearing 32 opposed to the suction area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a swash plate type piston pump in which the back surface of a swash plate is suspended and supported via a static pressure bearing.

[0002]

2. Description of the Related Art Heretofore, as this type of swash plate type piston pump, for example, there is the following one.

[0003] A device having a pair of hydrostatic bearings for floatingly supporting the rear surface of a swash plate, and having a passage for guiding the discharge pressure of a piston pump in a pocket of each hydrostatic bearing.

[0006] As shown in FIGS. 16 and 17, a hydrostatic bearing 104 which floats and supports a back surface 102 of a swash plate 101 in opposition to a discharge area of a cylinder block 103, Back surface 10 of plate 101
And a sliding bearing 106 for floatingly supporting the bearing 5.

[0005]

However, in the piston pump, a passage for guiding the discharge pressure of the piston pump to the pair of hydrostatic bearings is formed in the swash plate or the pump housing. There was a problem that the cost of the product was increased.

In the piston pump [0006] is simplified passage structure by providing the sliding bearing 106 can be achieved, is actuated for a long time oil film of the sliding bearing 106 is likely to occur. FIG. 18 shows the expected surface pressure distribution of the sliding bearing 106. When the sliding bearing 106 is operated for a long time, a portion where the contact of the sliding bearing 106 becomes uniform occurs due to initial adaptation, and an oil film breakage occurs at this portion. Sliding bearing 10 despite the low surface pressure
The wear amount of No. 6 increased, and the durability of the piston pump could be impaired.

The present invention has been made in view of the above problems, and has as its object to simplify a passage structure and suppress bearing wear in a swash plate type piston pump.

[0008]

According to a first aspect of the present invention, there is provided a cylinder accommodating a piston and defining a volume chamber, a cylinder block having the cylinder, and a volume chamber expanded and contracted with rotation of the cylinder block. A swash plate that reciprocates the piston, a first bearing that tiltably supports the swash plate in opposition to a discharge area in which the piston contracts the volume chamber, and a swash plate that faces a suction area in which the piston expands the volume chamber. The present invention is applied to a swash plate type piston pump including a second bearing that tiltably supports a plate.

The first pressure introducing passage for guiding hydraulic oil from the volume chamber in the discharge area to the first bearing facing the discharge area, and the hydraulic oil from the volume chamber in the suction area to the second bearing facing the suction area. And a second pressure introducing passage for guiding the pressure.

In a second aspect based on the first aspect, the second pressure introducing passage is formed through the piston and the swash plate.
An oil sump pocket communicating with the second pressure introducing passage is formed on the back surface of the swash plate, and the oil sump pocket is arranged at a central portion where the surface pressure on the back surface of the swash plate is high.

According to a third aspect of the present invention, in the first or second aspect, a second pressure introduction passage is formed through the piston and the swash plate, and a pair of the second pressure introduction passage communicate with the second pressure introduction passage on the back surface of the swash plate. forming a sump pockets, and shall be characterized by being arranged so as to sandwich the central portion of the Kakuaburatamari pocket surface pressure on the rear of the swash plate increases.

[0012] The fourth aspect, in the third any one invention of the first, characterized in that the swash plate is configured to tilt in both directions from the neutral position perpendicular to the axis of rotation of the cylinder block It was taken.

According to a fifth aspect of the present invention, a cylinder accommodating a piston to define a volume chamber, a cylinder block having the cylinder, and an oblique piston for reciprocating the piston so as to expand and contract the volume chamber as the cylinder block rotates. A plate, a first bearing that tiltably supports the back surface of the swash plate in opposition to a discharge region in which the piston contracts the volume chamber, and a back surface of the swash plate in opposition to a suction region in which the piston expands the volume chamber. The present invention is applied to a swash plate type piston pump including a second bearing that is supported to be tiltable and a housing chamber that accommodates a cylinder block and a swash plate.

A first pressure introducing passage for guiding hydraulic oil from the volume chamber in the discharge area to the first bearing facing the discharge area, and a second pressure guiding path for guiding hydraulic oil from the housing chamber to the second bearing facing the suction area. And a pressure introducing passage.

[0015]

According to the first aspect of the present invention, when the piston pump operates, the point of application of the load acting on the swash plate from each piston is located in the discharge area, so that the load received by the first bearing opposed to the discharge area. Is larger than the load received by the second bearing facing the suction area.

In the first bearing opposed to the discharge area, a part of the hydraulic oil pressurized in the volume chamber is guided through the first pressure introduction passage, and the back surface of the swash plate is floated and supported via an oil film, so that friction is generated. And durability can be ensured.

In the second bearing opposed to the suction area, a part of the hydraulic oil supplied to the volume chamber is guided through the second pressure introduction passage, and floats and supports the rear surface of the swash plate via an oil film. Thus, the pressure guided to the second bearing via the second pressure introduction passage is smaller than the pump discharge pressure guided to the first bearing via the first pressure introduction passage, but the second pressure facing the suction area. Since the load received by the bearing is smaller than that of the first bearing facing the discharge area, sufficient hydraulic pressure can be obtained to maintain the oil film on the back of the swash plate, and control of pump discharge pressure by suppressing friction of the second bearing Accuracy can be improved and durability can be ensured.

According to the second aspect of the present invention, the structure of the passage is simplified and the cost of the product is reduced as compared with the conventional device in which a passage for guiding the discharge pressure of the piston pump is provided between the pair of bearings. When the through hole of the swash plate communicates with the through hole of the piston, the operating oil sent to the volume chamber by means such as a position head applied to the volume chamber in the suction area or a pressure head by a charge pump is stored in the oil reservoir of the second bearing. Guided intermittently in the pocket. Hydraulic oil supplied to the second bearing via the second pressure introduction passage is guided to a portion of the back surface with high surface pressure through the oil reservoir pocket, the second bearing maintains an oil film, suppresses friction and controls accuracy And durability can be ensured.

According to the third aspect of the present invention, the cylinder block is rotated and the swash plate communicates with the piston through-hole, so that a means such as a position head applied to the volume chamber of the suction area or a pressure head by a charge pump is provided. As a result, the hydraulic oil sent to the volume chamber is intermittently guided to each oil reservoir pocket of the second bearing. As the swash plate tilts, hydraulic fluid guided to the oil reservoir pocket is supplied to the second bearing, which maintains the oil film, suppresses friction, improves control accuracy, and has the highest surface pressure. Since the area of the central portion can be secured, the durability of the second bearing can be secured.

According to the fourth aspect, as the tilt angle of the swash plate switches from the neutral position to the boundary, the discharge region and the suction region are switched, and the first and second pressure introduction passages are switched from the first and second pressure introduction passages. The pressure guided to the second bearing is switched, so that the first and second bearings maintain an oil film, suppress friction, increase control accuracy, and ensure durability.

According to the fifth aspect, when the piston pump is operated, the point of action of the load acting on the swash plate from each piston is located in the discharge area, so that the load received by the first bearing facing the discharge area is applied to the suction area. It is larger than the load received by the opposed second bearing.

In the first bearing opposed to the discharge area, a part of the hydraulic oil pressurized in the volume chamber is guided through the first pressure introduction passage, and the back surface of the swash plate is suspended and supported via an oil film, so that friction is generated. , Control accuracy can be increased, and durability can be ensured.

In the second bearing facing the suction area, a part of the working oil in the housing chamber is continuously guided through the second pressure introducing passage, and supports the back surface of the swash plate in a floating manner via an oil film. Thus, the pressure guided to the second bearing via the second pressure introduction passage becomes the pressure of the housing chamber, but the load received by the second bearing facing the suction area is smaller than that of the first bearing facing the discharge area. As a result, the hydraulic pressure sufficient to maintain the oil film on the back surface of the swash plate is obtained, the friction of the second bearing is suppressed, the control accuracy is improved, and the durability is secured.

Furthermore, since the hydraulic oil guided to the second bearing does not pass through the piston shoe rotating at high speed on the swash plate, foreign matter mixed in the hydraulic oil may be caught by the piston shoe and damage the swash plate and the like. Can be prevented.

Also, the structure of the passage is simplified as compared with the conventional device in which a passage for guiding the discharge pressure of the piston pump is provided between the pair of bearings, and the cost of the product can be reduced.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the swash plate type piston pump 1 has a cylinder block 3 and a swash plate 4 housed in a housing chamber 24 formed by a pump housing 2 and a cover 10.

The cylinder block 3 is driven to rotate via a shaft 5. One end of the shaft 5 is supported by the pump housing 2 via a bearing 12, and the shaft 5 is supported by the cover 10 via a bearing 11. Rotation is transmitted from an engine (not shown) as a power source to one end of the shaft 5 protruding from the cover 10 to the outside.

In the cylinder block 3, a plurality of cylinders 6 are arranged substantially in parallel with the rotation axis thereof and at regular intervals on substantially the same circumference centered on the rotation axis.

A piston 8 is inserted into each cylinder 6, and a volume chamber 7 is defined between them. One end of each piston 8 protrudes from the cylinder block 3 and the swash plate 4
Is supported via a shoe 9 which is in contact with. When the cylinder block 3 rotates, each piston 8 reciprocates with the swash plate 4 to expand and contract the volume chamber 7 of the cylinder 6.

Here, in the cylinder block 3, an area where the piston 8 contracts the volume chamber 7 is defined as a discharge area, and an area where the piston 8 expands the volume chamber 7 is defined as a suction area.

A second port 13 communicating with each volume chamber 7 in the suction area and a first port 14 communicating with each volume chamber 7 in the discharge area are formed in the port plate 15 with which the cylinder block 3 slides. With the rotation of the cylinder block 3, hydraulic oil pressure-fed from a means such as a position head applied to the second port 13 or a pressure head by a charge pump is supplied from the second port 13 to each volume chamber 7 through the passage 18. On the other hand, the hydraulic oil discharged from each volume chamber 7 to the first port 14 is guided to the hydraulic device through the passage 19.

In order to make the discharge amount of the piston pump 1 variable, as shown in FIG. 3, the back surfaces 31 and 41 of the swash plate 4 are formed in a cylindrical shape, and are interposed via first and second bearings 42 and 32. And tiltably supported. A tilt spring 21 for biasing the swash plate 4 in a direction in which the tilt angle increases is provided in the pump housing 2. Then, a drive piston 23 for driving the swash plate 4 against the tilt spring 21 in the direction of tilting angle is increased. The drive piston 23 drives the swash plate 4 in a direction in which the tilt angle increases by the pump discharge pressure guided from the first port 14. In the present embodiment, the tilt angle of the swash plate 4 is limited so that the discharge area and the suction area do not change.

As shown in FIG. 4, the back surfaces 31, 4 of the swash plate 4
1 is formed with the rotation axis of the cylinder block 3 interposed therebetween.
The second bearing 32 faces the suction area of the cylinder block 3, and the first bearing 42 faces the discharge area of the cylinder block 3.

The first and second bearings 42, 32 are provided with bushes 43, 33 which are in sliding contact with the cylindrical rear surfaces 41, 31 of the swash plate 4, and the bushes 43, 33 are respectively connected to the cover 10 via screws 45, 35. Is concluded.

As a gist of the present invention, a first pressure introducing passage 50 for guiding hydraulic oil from the volume chamber 7 in the discharge area to the first bearing 42 facing the discharge area, and a volume chamber in the suction area. And a second pressure introducing passage 60 that guides the hydraulic oil from the seventh to the second bearing 32 facing the suction area.

The first pressure introducing passage 50 has a through hole 51 passing through the piston 8, a through hole 53 passing through the spherical seat 22,
The through hole 54 penetrates the shoe 9 and the through hole 55 penetrates the swash plate 4 (see FIGS. 1 and 2). Through hole 5
An orifice 56 is interposed in the middle of 5. When the shoe 9 slides on the swash plate 4 with the rotation of the cylinder block 3, the through hole 55 of the swash plate 4 communicates with the through hole 54 of the shoe 9, and the hydraulic oil pressurized in the cylinder 6 is released. First bearing 42
Is intermittently led to As a result, the first bearing 42 functions as a static pressure bearing that floats and supports the back surface 41 of the swash plate 4 via the oil film.

As shown in FIGS. 3 (c), 3 (D) and 4, the back surface 41 of the swash plate 4 is formed with two oil guide grooves 46 extending in the circumferential direction. The first pressure introduction passage 50 is located on the back surface 41.
Are formed at the center where the surface pressure is highest. The hydraulic oil supplied to the first bearing 42 via the first pressure introducing passage 50 is guided in the circumferential direction of the back surface 41 via the oil guide groove 46.

The second pressure introducing passage 60 has a through hole 51 passing through the piston 8, a through hole 53 passing through the spherical seat 22,
It is constituted by a through hole 54 penetrating the shoe 9 and a single through hole 61 penetrating the swash plate 4 (see FIGS. 1 and 2).
When the shoe 9 slides on the swash plate 4 with the rotation of the cylinder block 3, the through hole 61 of the swash plate 4 communicates with the through hole 54 of the shoe 9, and the hydraulic oil sent into the cylinder 6 It is guided intermittently to the two bearings 32. Thereby, the second bearing 3
Numeral 2 functions as a hydrostatic bearing that floats and supports the back surface 41 of the swash plate 4 via an oil film.

As shown in FIG. 3A, FIG. 3D and FIG. 4, an oil reservoir pocket 36 is formed on the back surface 31 of the swash plate 4 so as to extend in the circumferential direction. The oil reservoir pocket 36 is formed at the center of the rear surface 31 where the surface pressure is highest. The second pressure introduction passage 60 opens at the center of the oil reservoir pocket 36. The hydraulic oil supplied to the first bearing 42 via the second pressure introducing passage 60 is guided in the circumferential direction of the back surface 31 via the oil reservoir pocket 36.

Next, the operation of the embodiment of the present invention configured as described above will be described.

The piston pump 1 has a cylinder block 3
Each rotation of the piston 6 causes the piston 6 to reciprocate once in the cylinder 6. In the suction stroke in which the volume chamber 7 of the cylinder 6 expands, hydraulic oil is supplied from the second port 13 to the volume chamber 7. In the discharge stroke in which the volume chamber 7 of the cylinder 6 contracts, pressurized hydraulic oil is discharged from the volume chamber 7 to the first port 14.

When the piston pump 1 is operated, the point of application of the load acting on the swash plate 4 from each piston 8 is located in the discharge area, so that the load received by the first bearing 42 facing the discharge area is opposed to the suction area. It is larger than the load that the second bearing 32 receives.

A part of the hydraulic oil pressurized in the volume chamber 7 in the cylinder 6 is intermittently guided to the first bearing 42 facing the discharge area through the first pressure introducing passage 50. The hydraulic oil supplied to the first bearing 42 via the first pressure introducing passage 50 is guided in the circumferential direction of the back surface 41 via the oil guide groove 46.
Thus, the first bearing 42 is a back 41 of the swash plate 4 suspended supported through the oil film, can secure durability by suppressing friction.

The relation of the discharge pressure and discharge flow rate of the piston pump 1 (displacement) is determined by the balance of forces of the elastic restoring force and the driving piston 23 of the tilt spring 21, the friction of the first bearing 42 as described above Is suppressed, the smooth operation of the swash plate 4 is maintained, and characteristics close to the set target characteristics are obtained.

The second bearing 32 facing the suction area is configured such that part of the hydraulic oil supplied to the volume chamber 7 in the cylinder 6 is intermittently guided through the second pressure introducing passage 60, and 3
1 is suspended and supported via an oil film. As described above, the pressure guided to the second bearing 32 via the second pressure introduction passage 60 is smaller than the pump discharge pressure guided to the first bearing 42 via the first pressure introduction passage 50, but is reduced to the suction area. Since the load applied to the opposed second bearing 32 is smaller than that of the first bearing 42 opposed to the discharge area, sufficient hydraulic pressure is obtained to float and support the back surface 31 of the swash plate 4 via an oil film.

The second bearing 3 through the second pressure introducing passage 60
The hydraulic oil supplied to 2 is guided through the oil reservoir pocket 36 to a portion of the back surface 31 where the surface pressure is high. Thereby, the oil film is maintained in the second bearing 32, friction can be suppressed, control accuracy of the pump discharge pressure can be improved, and durability can be ensured.

[0048] Further, the passage structure in comparison with the conventional apparatus provided with a passage for guiding the discharge pressure of the piston pump to the pair of bearings is simplified, FIG. 5 in the following the cost of products can be achieved, Fig. 6
Another embodiment shown in FIG. The same components as those in the above-described embodiment are denoted by the same reference numerals.

The second pressure introduction passage 60 is constituted by a pair of through holes 63 and 64 through the swash plate 4. Swash plate 4
A pair of oil reservoirs 65 and 66 are formed in the rear surface 31 of the oil reservoir. Each sump pocket 6
Reference numerals 5 and 66 are arranged so as to sandwich the central portion of the back surface 31 where the surface pressure is highest.

In this case, when the shoe slides on the swash plate 4, the through holes 63 and 64 of the swash plate 4 communicate with the through holes of the shoe, and the operating oil sent into the cylinder 6 is supplied to the second bearing. It is guided intermittently to each of the 32 oil sump pockets 65 and 66. Swash plate 4
Hydraulic oil guided to the oil reservoir pockets 65 and 66 is supplied to the second bearing 32 along with the tilting, the oil film is maintained in the second bearing 32, friction is suppressed, and control accuracy of the pump discharge pressure is increased. In addition, since the area of the central portion where the surface pressure is highest can be secured, the durability of the second bearing 32 can be secured.

Next, another embodiment shown in FIGS. 7 to 9 will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals.

The first pressure introducing passage 50 includes a through hole 57 formed in the pump housing 2 and communicating with the first port 14, and a through hole 58 formed in the cover 10. Thereby, when the piston pump 1 is operated, a part of the hydraulic oil pressurized in the volume chamber 7 in the cylinder 6 is continuously guided to the first bearing 42 through the first pressure introducing passage 50, and the high pressure is applied to the first bearing 42. It can also maintain the oil film during the load.

The second pressure introducing passage 60 is formed by a through hole 61 penetrating through the swash plate 4 as in the above embodiment. A part of the hydraulic oil sent into the cylinder 6 is intermittently guided to the second bearing 32.

Next, another embodiment shown in FIGS. 10 to 13 will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals.

The swash plate 4 is configured to tilt in both directions from a neutral position orthogonal to the rotation axis of the cylinder block 3.
The discharge area and the suction area are switched.

First and second pressure introduction passages 71 and 72 for guiding the hydraulic oil from each of the chambers 7 to the first and second bearings 42 and 32 are formed. The first and second pressure introduction passages 71 and 72 are formed through the piston pump 1 and the swash plate 4 and have the same structure as the first pressure introduction passage 50.

On the back surfaces 41 and 31 of the swash plate 4, two oil guide grooves 46 extending in the circumferential direction are provided with first and second pressure introduction passages 71 and 7, respectively.
2 is formed so as to sandwich the open end. The first and second pressure introduction passages 71 and 72 are opened at the center of each of the back surfaces 41 and 31 where the surface pressure is highest.

In this case, as shown in FIG. 8, as the tilt angle of the swash plate 4 is switched from the neutral position to the boundary, the discharge region and the suction region are switched, and the first and second pressure introduction are performed. The pressure guided from the passages 71 and 72 to the first and second bearings 42 and 32 is switched. Thereby, the first and second bearings 42, 3
In No. 2, the oil film is maintained, the friction is suppressed, the control accuracy of the pump discharge pressure is improved, and the durability can be ensured.

Next, another embodiment shown in FIGS. 14 and 15 will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals.

The first pressure introducing passage 50 for guiding hydraulic oil from the volume chamber 7 in the discharge area to the first bearing 42 facing the discharge area.
And a second bearing 32 facing the suction area from the housing chamber.
And a second pressure introducing passage 80 for guiding the hydraulic oil to the second pressure introducing passage.

The first pressure introducing passage 50 is formed through the piston and the swash plate 4 in the same manner as in the above-described embodiment, and the shoe is slid on the swash plate 4 to be pressurized in the volume chamber. The hydraulic oil is intermittently guided to the first bearing 42.

The second pressure introducing passage 80 is provided on the side surface 8 of the swash plate 4.
1 and a through hole 82 opened in the shaft insertion hole 28 and a through hole 83 opened in the second bearing 32.
Thereby, a part of the operating oil in the housing chamber is continuously guided through the second pressure introduction passage 80.

As shown in FIG. 14A, FIG. 14D and FIG. 15, an oil reservoir pocket 84 extending in the circumferential direction is formed on the back surface 31 of the swash plate 4. Oil pocket 84 is on back 31
Are formed at the center where the surface pressure is highest. The second pressure introduction passage 68 opens at the center of the oil reservoir pocket 84. The hydraulic oil supplied to the first bearing 42 via the second pressure introducing passage 80 is guided in the circumferential direction of the back surface 31 via the oil reservoir pocket 84.

As described above, the pressure guided to the second bearing 32 through the second pressure introduction passage 80 becomes the pressure of the housing chamber, but the load received by the second bearing 32 facing the suction area is opposed to the discharge area. Since the first bearing 42 is smaller than the first bearing 42, sufficient hydraulic pressure is obtained to float and support the rear surface 31 of the swash plate 4 via an oil film. Thereby, the oil film is maintained in the second bearing 32, friction can be suppressed, control accuracy of the pump discharge pressure can be improved, and durability can be ensured.

In this case, since the hydraulic oil guided to the second bearing 32 does not pass through the piston shoe rotating at high speed on the swash plate 4, foreign matter mixed in the hydraulic oil is caught by the piston shoe and the piston shoe or the swash plate 4 can be prevented from being damaged.

It is apparent that the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the technical idea.

[Brief description of the drawings]

FIG. 1 is a plan view of a piston pump showing an embodiment of the present invention.

FIG. 2 is a side view of the piston pump.

FIG. 3 is a four side view of the swash plate.

FIG. 4 is a rear view of the swash plate.

FIG. 5 is a four-sided view of a swash plate showing another embodiment.

FIG. 6 is a rear view of the swash plate.

FIG. 7 is a plan view of a piston pump according to another embodiment.

FIG. 8 is a side view of the piston pump.

FIG. 9 is a four side view of the swash plate.

FIG. 10 is a plan view of a piston pump according to another embodiment.

FIG. 11 is a side view of the piston pump.

FIG. 12 is a four side view of the swash plate.

FIG. 13 is a rear view of the swash plate.

FIG. 14 is a four-sided view of a swash plate showing another embodiment.

[15] same rear view of the swash plate.

FIG. 16 is a plan view of a piston pump showing a conventional example.

FIG. 17 is a side view of the piston pump.

FIG. 18 is a view showing a surface pressure distribution of the swash plate.

[Explanation of symbols]

 Reference Signs List 1 swash plate piston pump 2 pump housing 3 cylinder block 4 swash plate 6 cylinder 7 volume chamber 8 piston 9 shoe 31 back 32 second bearing 36 oil reservoir pocket 41 back 42 first bearing 46 oil guide groove 50 first pressure introduction passage 60 second pressure introduction passage

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H070 AA01 BB04 CC27 CC31 CC35 DD13 DD47 DD94 3H071 AA03 BB01 CC26 CC27 CC31 CC34 DD01 DD46

Claims (5)

[Claims] A cylinder for accommodating a piston to define a volume chamber; a cylinder block having the cylinder; and an oblique reciprocating piston for expanding and contracting the volume chamber with rotation of the cylinder block. A plate, a first bearing that tiltably supports the rear surface of the swash plate in opposition to a discharge area in which the piston contracts the volume chamber, and a first bearing that opposes a suction area in which the piston expands the volume chamber. And a second bearing that tiltably supports a rear surface of the swash plate.The swash plate type piston pump further comprising: supplying hydraulic oil to the first bearing facing the discharge region from the volume chamber in the discharge region. A swash plate, comprising: a first pressure introduction passage that guides; and a second pressure introduction passage that guides hydraulic oil from the volume chamber in the suction area to the second bearing facing the suction area. Piston pump. 2. The oil reservoir according to claim 2, wherein the second pressure introducing passage is formed through the piston and the swash plate, and an oil reservoir pocket communicating with the second pressure introducing passage is formed on a rear surface of the swash plate. The swash plate type piston pump according to claim 1, wherein a pocket is disposed at a central portion of the rear surface of the swash plate where the surface pressure is high. 3. The second pressure introduction passage is formed through the piston and the swash plate, and a pair of oil reservoir pockets communicating with the second pressure introduction passage are formed on the back surface of the swash plate. 2. The oil reservoir pockets are arranged so as to sandwich a central portion of the rear surface of the swash plate where the surface pressure is high.
Or the swash plate type piston pump according to 2. 4. The swash plate type piston according to claim 1, wherein the swash plate is tilted in both directions from a neutral position orthogonal to the rotation axis of the cylinder block. pump. 5. A cylinder accommodating a piston to define a volume chamber, a cylinder block having the cylinder, and an oblique piston for reciprocating the piston so as to expand and contract the volume chamber as the cylinder block rotates. A plate, a first bearing that tiltably supports the rear surface of the swash plate in opposition to a discharge area in which the piston contracts the volume chamber, and a first bearing that opposes a suction area in which the piston expands the volume chamber. A swash plate type piston pump comprising: a second bearing that tiltably supports a rear surface of the swash plate; and a housing chamber that accommodates the cylinder block and the swash plate, wherein the volume chamber in the discharge region is provided. A first pressure introducing passage for guiding hydraulic oil from the housing chamber to the first bearing facing the discharge area; and guiding hydraulic oil from the housing chamber to the second bearing facing the suction area. Swash plate type piston pump, characterized in that it comprises two pressure introduction passage, the.