JP2000205119A - Swash plate type piston pump motor - Google Patents

Abstract

(57) [Summary] In a swash plate type piston pump / motor, an action point of a lifting force supporting a swash plate of each hydrostatic bearing is made to coincide with an action point of a concentrated load of a piston. SOLUTION: A large pocket 12 and a small pocket 13 for guiding the pressure for floatingly supporting the swash plate 50 are formed in each of the hydrostatic bearings 9 side by side in the circumferential direction. When formed at a position close to the point and divided into two port areas having different stroke directions of the piston, the large pocket 13 in the second port area E is formed.
Is connected to the second port 42 in the second port area E, and the small pocket 13 in the second port area E is connected to the first port 41 in the first port area D.
And a pressure-introducing passage 16 communicating with the pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston pump / motor for supporting a back surface of a swash plate via a hydrostatic bearing.

[0002]

2. Description of the Related Art Conventionally, a swash plate type piston pump of this kind
The motors disclosed in, for example, Japanese Patent Publication No. 4-47152 and Japanese Patent Laid-Open Publication No. Hei 7-317651 are provided with a pair of hydrostatic bearings for floatingly supporting the rear surface of a swash plate. The pressure generated in each cylinder of the plate-type piston pump / motor is guided.

[0003]

However, in such a conventional swash plate type piston pump / motor,
As the swash plate tilt direction reverses, the point of application of each hydrostatic bearing receiving the concentrated piston load moves greatly, so the point of application of the lifting force supporting the swash plate becomes the point of application of the concentrated load of the piston. Otherwise, the efficiency of the piston pump / motor may decrease, and the durability of each hydrostatic bearing may decrease.

The present invention has been made in view of the above problems, and in a swash plate type piston pump / motor, the point of action of a lifting force for supporting a swash plate of each hydrostatic bearing is determined by the action of a concentrated load on the piston. The aim is to match points.

[0005]

According to a first aspect of the present invention, there are provided a plurality of cylinders rotating integrally with a main shaft, a piston slidably interposed in each cylinder, and a tip end side of a piston protruding from each cylinder. A swash plate, a pair of hydrostatic bearings that support the swash plate in a tiltable manner with the main shaft interposed therebetween, and a pair of ports that allow fluid to flow into and out of each cylinder as each piston slides. Applies to plate type piston pumps and motors.

A large pocket and a small pocket for guiding the pressure for floatingly supporting the swash plate are formed in each of the hydrostatic bearings so as to be arranged side by side in the circumferential direction. Formed at a position close to
When the piston is divided into two port regions having different stroke directions, a large pocket communicates with a port in the same port region as the pressure introduction passage, and a small pocket communicates with a port in a different port region from the pressure introduction passage. And a passage.

According to a second aspect of the present invention, in the first aspect, the point of action of the resultant force Fp of the lifting force for supporting the swash plate by the pressure guided to the large pocket and the small pocket substantially coincides with the point of action of the piston concentrated load Fd. The ratio of the opening area of the large pocket and the small pocket is set so as to perform the above.

According to a third aspect, in the first or second aspect, the large pocket and the small pocket are formed symmetrically with respect to the rotation center line S of the main shaft.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the back surface of the swash plate is formed in a cylindrical surface, and the hydrostatic bearing includes a bush opposed to the back surface of the swash plate. A large pocket and a small pocket.

In a fifth aspect based on the fourth aspect, the bearing surface of the bush is formed of resin.

In a sixth aspect based on any one of the first to fifth aspects, the pressure introducing passage is formed by penetrating a member having a bearing surface facing the back surface of the swash plate.

According to a seventh aspect of the present invention, in any one of the first to fifth aspects, the pressure introducing passage is formed so as to penetrate through the distal end portion of the piston and the swash plate.

[0013]

When the present invention is applied to a piston pump, the point of application of the concentrated load Fd of the piston moves along the trunnion center line T as the tilt angle of the swash plate changes across the neutral position. The region moves from one region to the other region across the trunnion, and the region where the pump discharge pressure is guided through the pressure introduction passage and the region where the charge pressure is guided are switched across the trunnion center line T. For this reason,
The point of application of the resultant force Fp of the floating force of each hydrostatic bearing and the point of application of the concentrated piston load Fd are located in the same area separated by the trunnion center line T, and the two points of action can be substantially matched.

As the tilt angle of the swash plate changes across the neutral position, the point of application of the piston concentrated load Fd moves from one area to the other across the pump boundary surface C.
Since the large pocket having a large opening area is closer to the point of application of the piston concentrated load Fd than the small pocket, the point of application of the resultant force Fp of the floating force of each hydrostatic bearing and the piston concentrated load Fd
The action point of d is located in the same area separated by the pump boundary line C, so that the two action points can be made substantially coincident.

Since the point of action of the floating force Fp of each hydrostatic bearing substantially coincides with the point of action of the concentrated load Fd of the piston, the clearance of each hydrostatic bearing is made uniform and the fluid flows out of the large pocket and the small pocket. Reduce the amount of oil,
The efficiency of the piston pump / motor can be increased, the friction of each hydrostatic bearing can be equalized, the durability can be increased, and the operating force for tilting the swash plate can be properly maintained.

In the second invention, by setting the ratio of the opening areas of the large pocket and the small pocket, the point of action of the resultant force Fp of the floating force of each hydrostatic bearing substantially coincides with the point of action of the concentrated piston load Fd. Can be done.

According to the third aspect of the present invention, the trajectory in which the point of application of the concentrated load Fd of the piston moves as the tilt angle of the swash plate changes becomes symmetric with respect to the rotation center line S of the main shaft. By forming the large pocket and the small pocket symmetrically with respect to the rotation center line S of the main shaft, the point of action of the resultant force Fp of the lifting force can be made substantially coincident with the point of action of the piston concentrated load Fd.

In the fourth aspect of the present invention, by forming a large pocket and a small pocket in the bush, the processing thereof can be facilitated and the productivity can be increased.

In the fifth aspect, by forming the bearing surface of the bush with resin, vibration of the swash plate can be suppressed, durability can be enhanced, and noise can be reduced.

In the sixth aspect of the present invention, the pressure introduction passage is formed through the bearing surface facing the back surface of the swash plate, whereby the pressure of each port is continuously guided to the large pocket or the small pocket, Pressure fluctuations occurring in the hydrostatic bearing can be suppressed, and durability can be improved.

In the seventh aspect, the processing for forming the pressure introducing passage can be reduced, and the cost of the product can be reduced.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a piston pump provided in an HST (continuously variable transmission) mounted on a vehicle such as a forklift will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a main shaft. The main shaft 1 has bearings 6, 7 on the flange 55 and the port block 40.
And rotatably driven by an engine (not shown).

A cylinder block 2 is attached to the main shaft 1 so as to rotate integrally therewith. The cylinder block 2 has the same circumference (PC.
D) Nine cylinders 4 are formed at equal intervals on the top, and the pistons 3 are slidably interposed in each cylinder 4.

Reference numeral 50 denotes a swash plate. The swash plate 50 is brought into contact with the tip of the piston 3 protruding from each cylinder 4.
The tip of each piston 3 contacts the swash plate 50 via the spherical seat 26 and the shoe 27, and expands and contracts with the rotation of the cylinder block 2 by a stroke amount corresponding to the tilt angle of the swash plate 50. By changing the tilt angle of the swash plate 50, the stroke of each piston 3 changes, the discharge amount per rotation of the main shaft 1 changes, and the gear ratio of the HST changes.

In FIG. 4A, T is a trunnion centerline which is the center of tilting of the swash plate 50, and C is orthogonal to the trunnion centerline T and the main shaft 1 and the cylinder block 2
Is the pump interface that bisects The first port region D and the second port region E are separated by the pump boundary surface C,
The stroke direction of each piston 3 reverses around the pump boundary surface C.

A port block 40 is provided in sliding contact with the bottom surface of the cylinder block 2. The port block 40 has a crescent-shaped first port 41 and a second port 42. The first port 41 is arranged in the first port area D, and the second port 42 is arranged in the second port area E, and communicates with each cylinder 4 as the cylinder block 2 rotates. The first port 41 and the second port 42 communicate with each port of the piston motor via a hydraulic circuit (not shown), and charge pressure is guided to the hydraulic circuit from a charge pump.

The rear surface 51 of the swash plate 50 is formed in a cylindrical shape, and is supported by the flange 55 in a floating manner via a pair of hydrostatic bearings 9. Each hydrostatic bearing 9 is arranged in the first port area D and the second port area E, respectively.

The back surface 51 of the swash plate 50 has a trunnion center line T
Is formed on the flange 55, and a semi-cylindrical recess is also formed on the flange 55 centered on the trunnion center line T, and a set having a predetermined thickness therebetween is formed. Semi-cylindrical bush 10 is interposed. The bush 10 is positioned with respect to the flange 55 via the knock pin 18 fitted to the center.

As shown in FIG. 2 and FIG.
The resin layer 17 is formed by coating the inner peripheral surface of a strip-shaped back metal 16 with Teflon, and the inner peripheral surface of the resin layer 17 forms the bearing surface 11 facing the swash plate 50.

A large pocket 12 and a small pocket 1 are formed in the bearing surface 11 of the bush 10 as oil grooves for guiding pressurized hydraulic oil.
3 are formed side by side in the circumferential direction.

In FIG. 4A, the bearing surface 11 is bisected by the trunnion center line T, and the large pocket 12 and the small pocket 13 are arranged so as to sandwich the trunnion center line T. And large pocket 12 is small pocket 1
3 is closer to the trunnion center line T.

Assuming that the point at which the hydrostatic bearing 9 receives the concentrated load of each piston 3 that strokes on the compression side is the point of application of the concentrated piston load Fd, the large pocket 12 is closer to the point of application of the concentrated piston load Fd than the small pocket 13. Formed in position.

A pressure introduction passage 15 communicating with each port 41 or 42 in the same port area separating the large pocket 12 by the pump boundary C is provided, and the small pocket 13 is separated by the pump boundary C. A pressure introduction passage 16 is provided which communicates with each port 41 or 42 in a different port area. That is, the large pocket 12 located in the second port area E and the small pocket 13 located in the first port area D communicate with the second port 42 located in the second port area E and are located in the first port area D. The large pocket 12 and the small pocket 13 located in the second port area E communicate with the first port 41 located in the first port area D.

The pressure introduction passages 15 and 16 are provided with a flange 55
, And through holes 19, 20 formed in the bush 10 and penetrating the bearing surface 11, and the pressure of each port 41 or 42 is applied to the large pocket 1.
It is designed to be continuously guided to two or small pockets 13.

The pressure introduction passage 16 connecting the ports 41, 42 and the small pocket 13 branches from the middle of the pressure introduction passage 15 connecting the ports 41, 42 to the large pocket 12, and the length of the pressure introduction passage 15 is changed to the pressure introduction passage 16 Is formed shorter than the length of the passage.

The large pocket 12 and the small pocket 13
By properly setting the opening area ratio of the large pocket 12 and the opening position of the large pocket 12 and the small pocket 13 with respect to the trunnion center line T, the lifting force due to the pressure guided to the large pocket 12 as shown in FIGS. The point of application of the resultant force Fp with the lifting force due to the pressure guided to the small pocket 13 substantially coincides with the point of application of the piston concentrated load Fd.

The operation as described above will now be described.

As shown in FIG. 4, when the main shaft 1 rotates in the direction of arrow A in a state where the swash plate 50 is tilted, the piston 3 strokes in the first port region D toward the extension side, and hydraulic oil is supplied. While being sucked into the cylinder 4 from the first port 41,
In the second port region E, each of the pistons 3 strokes to the pressure side, and sends out hydraulic oil from each of the cylinders 4 to the second port 42.

At this time, the point of application of the piston concentrated load Fd is located in a region G on the left side of the trunnion center line T as shown in FIG. Large pocket 1 in this area G
The pump discharge pressure is led from the second port 42 to the second and small pockets 13, and the charge pressure is led from the first port 41 to the large pockets 12 and the small pockets 13 in the region F on the right side of the trunnion center line T in the figure. As a result, the resultant force F of the lifting force generated in the large pocket 12 and the small pocket 13
The point p is opposed to the concentrated load Fd of each piston 3 when its action point is located in the region G.

As shown in FIG. 8, the point of application of the piston concentrated load Fd is located in the second port region E on the left side of the pump boundary surface C in the figure. The opening area of the large pocket 12 near the point of application of the piston concentrated load Fd in the region G is made larger than the opening area of the small pocket 13 far from the point of application of the piston concentrated load Fd, and the opening area ratio between the two is set appropriately. As a result, the point of action of the resultant force Fp of the lifting force due to the pressure guided to the large pocket 12 and the lifting force due to the pressure guided to the small pocket 13 is determined by the piston concentrated load F.
It can be made to substantially coincide with the action point of d.

As shown in FIG. 5, when the swash plate 50 is in the neutral position, the piston 3 does not make a stroke, and the flow of the hydraulic oil in the first port 41 and the second port 42 stops. At this time, the point of action of the piston concentrated load Fd is located on the rotation center line S of the main shaft 1. However, the charge pressure is guided to all the large pockets 12 and the small pockets 13, and the point of action of the resultant force Fp of the lifting force. Substantially coincides with the point of action of the piston concentrated load Fd of each piston 3 on the rotation center line S of the main shaft 1.

As shown in FIG. 6, while the swash plate 50 is tilted, the piston 3 strokes in the pressure side in the first port region D, and hydraulic oil is sent from each cylinder 4 to the first port 41. In the second port region E, the piston 3 strokes to the extension side, and hydraulic oil is sucked into each cylinder 4 from the second port 42.

At this time, the point of action of the piston concentrated load Fd is determined in the area F on the right side of the trunnion center line T in FIG.
The pump discharge pressure is guided from the first port 41 to the large pocket 12 and the small pocket 13 in this area F, and the large pocket 12 and the small pocket 13 in the area G on the left side of the trunnion center line T When the charge pressure is led from the two ports 42, the resultant force F of the lifting force
The action point of p is located in the area F, and the piston concentrated load Fd
Approximately coincides with the action point of.

The locus of movement of the point of application of the concentrated load Fd of the piston as the tilt angle of the swash plate 50 changes becomes symmetric about the rotation center line S of the main shaft 1. By forming the small pockets 13 symmetrically with respect to the rotation center line S of the main shaft 1, it is possible to make the point of application of the resultant force Fp of the lifting force substantially coincide with the point of application of the concentrated piston load Fd.

In practice, as shown in FIG. 4, when the swash plate 50 is tilted, the number of the pistons 3 located in the second port area E with the rotation of each cylinder 4 is four to five. Even if the tilt angle of the swash plate 50 is constant, the discharge amount generated at the second port 42 fluctuates, and the point of application of the piston concentrated load Fd slightly moves along the locus of the swash plate 50 as indicated by the arrow in the figure. But each large pocket 12 and small pocket 13
Are arranged so as to surround the point of action of the piston concentrated load Fd, so that the point of action of the resultant force Fp of the lifting force is largely prevented from deviating from the point of action of the piston concentrated load Fd.

Further, since the passage length of the pressure introduction passage 15 is shorter than the passage length of the pressure introduction passage 16, the pressure guided to the small pocket 13 is higher than the pressure guided to the large pocket 12, and the resultant force Fp of the lifting force is increased. Is brought closer to the point of application of the piston concentrated load Fd.

In this manner, the point of application of the floating force Fp of each hydrostatic bearing 9 substantially coincides with the point of application of the concentrated load Fd of the piston, so that the clearance of each hydrostatic bearing 9 is made uniform, and the large pocket 12 and the small pocket 13 are made uniform. The pump efficiency can be increased by reducing the amount of hydraulic oil flowing out of the compressor, and the durability of each hydrostatic bearing 9 can be increased by equalizing the friction of each hydrostatic bearing 9.

As shown in FIG. 11, the pressing ratio (Fd / Fp), which is the ratio of the lifting force Fp for supporting the swash plate 50 of each hydrostatic bearing 9 to the concentrated load Fd of each piston 3, increases. Accordingly, while the noise generated from the piston pump is reduced, the operating force for tilting the swash plate 50 increases. Based on this characteristic, the range of the pressing ratio (Fd / Fp) that can suppress both noise and operating force is set as shown in the figure, and the opening areas of the large pocket 12 and the small pocket 13 are determined so as to fall within this range. .

By forming the bearing surface 11 of the bush 10 with the resin layer 17, vibration of the swash plate 50 can be suppressed, durability can be enhanced, and noise can be reduced.

By forming the pressure introduction passages 15 and 16 through the bearing surface 11, the pressure of each port 41 or 42 is continuously guided to the large pocket 12 or the small pocket 13, and each of the hydrostatic bearings 9. Pressure fluctuations caused by
Durability can be increased.

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

The pressure introducing passage 15 connecting the port and the large pocket 12 has a through hole 60 passing through the piston 3 and a spherical seat 2.
6 and the through hole 6 through the shoe 27.
2 and a through hole 63 penetrating the swash plate 50. One end of the through hole 63 of the swash plate 50 is open facing the large pocket 12. A check valve 64 is interposed in the middle of the through hole 63.

The pressure introducing passage 16 connecting the port and the small pocket 13 is provided with a through hole 63 forming the other pressure introducing passage 16.
Is formed by a through hole 65 connected in the middle of the process. Swash plate 5
One end of the through hole 64 formed in the opening 0 always faces the small pocket 13 regardless of the tilt angle of the swash plate 50.

In this case, when the shoe 27 slides on the swash plate 50, the through hole 62 of the shoe 27 communicates with the through hole 63 of the swash plate 50, and the hydraulic oil in the cylinder 4 flows into the large pocket 1.
2 and the small pocket 13 are intermittently guided.

Since it is not necessary to form the pressure introducing passages 15 and 16 in the flange 55 and the like, the processing for forming the pressure introducing passages 15 and 16 can be reduced, and the cost of the product can be reduced.

The present invention can be applied to a piston motor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of the present invention.

FIG. 2 is a plan view of the bush.

FIG. 3 is a sectional view of the bush.

FIG. 4 is a diagram showing an operating state when hydraulic oil is discharged from a second port.

FIG. 5 is a diagram showing an operation state when the swash plate is at a neutral position.

FIG. 6 is a diagram showing an operation state when hydraulic oil is discharged from a first port.

FIG. 7 is a side view showing the applied state of the load.

FIG. 8 is a front view showing an applied state of the load.

FIG. 9 is a diagram showing a locus of an action point of a piston concentrated load Fd of the piston.

FIG. 10 is a characteristic diagram showing the relationship between the pressing ratio (Fd / Fp), noise, and operating force.

FIG. 11 is a plan view showing another embodiment.

FIG. 12 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 2 Cylinder block 3 Piston 4 Cylinder 9 Static pressure bearing 10 Bush 11 Bearing surface 12 Large pocket 13 Small pocket 15 Pressure introduction passage 16 Pressure introduction passage 40 Port block 41 First port 42 Second port 50 Swash plate 51 Back

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H070 AA01 BB04 BB06 CC07 CC21 DD33 3H084 AA08 AA45 BB09 BB16 CC33

Claims (7)

[Claims] 1. A plurality of cylinders rotating integrally with a main shaft, a piston slidably interposed in each of the cylinders, a swash plate projecting from each of the cylinders, the swash plate being in contact with a tip end side of the piston. A swash plate type piston comprising: a pair of hydrostatic bearings that support the swash plate in a tiltable manner with the main shaft interposed therebetween; and a pair of ports that allow fluid to flow into and out of the cylinders as the pistons slide. In the pump / motor, a large pocket and a small pocket for guiding the pressure for floatingly supporting the swash plate in each of the hydrostatic bearings are formed side by side in the circumferential direction. When the piston is divided into two port regions having different stroke directions of the piston, the large pocket is located in the same port region as the piston. A pressure introduction passage for over preparative communication with, the swash plate type piston pump motor, characterized in that a pressure introduction passage communicating with the port on the small pockets and different port regions. 2. The large pocket so that the point of action of a resultant force Fp of a lifting force for supporting the swash plate by the pressure guided to the large pocket and the small pocket substantially coincides with the point of action of the piston concentrated load Fd. 2. The swash plate type piston pump / motor according to claim 1, wherein a ratio between an opening area of the small pocket and an opening area of the small pocket is set. 3. The swash plate type piston pump motor according to claim 1, wherein the large pocket and the small pocket are formed symmetrically with respect to a rotation center line S of the main shaft. 4. The swash plate according to claim 1, wherein a back surface of the swash plate is formed in a cylindrical shape, a bush opposed to the back surface of the swash plate is provided on the hydrostatic bearing, and the large pocket and the small pocket are formed in the bush. The swash plate type piston pump motor according to any one of claims 1 to 3, wherein: 5. The swash plate type piston pump motor according to claim 4, wherein a bearing surface of said bush is formed of resin. 6. The swash plate type piston according to claim 1, wherein the pressure introducing passage is formed by penetrating a member having a bearing surface facing the back surface of the swash plate. Pump and motor. 7. The swash plate type piston pump motor according to claim 1, wherein the pressure introduction passage is formed through the piston and the swash plate.