JPH0660629B2 - Swash plate piston pump - Google Patents

Description

TECHNICAL FIELD The present invention relates to a swash plate piston pump that controls a discharge amount by adjusting a tilt angle of a swash plate.

(Prior Art) This type of swash plate piston pump is sometimes used in a hydrostatic transmission. In this case, forward, backward, or stop control is performed by changing the tilt direction of the swash plate. In other words, when the tilt angle of the swash plate is set to 0 degree while keeping the operation lever at the neutral position, the stop function is exerted, and the tilt angle of 0 degree is used to tilt the vehicle in any direction. To move forward or backward.

Therefore, when the operation lever is held at the neutral position, a good stopping function cannot be obtained unless the tilt angle of the swash plate pump is definitely 0 degree.

However, if there is only one point on the operation lever for stopping the vehicle, if the point is displaced due to mechanical vibration or the driver is inadequate, the operation lever will be set at the stop point without fail. It becomes difficult to do it, and there is a problem in safety.

Therefore, when the operating lever is located near the neutral position,
2. Description of the Related Art There is conventionally known a device in which a linkage mechanism between an operation lever and a swash plate is provided with a backlash in order to surely stop the vehicle or the like.

It is generally known that when the swash plate pump reaches the vicinity of the neutral point, a self-returning force that tries to return to the neutral point is generated, but this conventional device uses the self-returning force within the range of rattling. It is something that is done.

(Problems to be Solved by the Present Invention) In the conventional device as described above, vibration of the operation lever and the swash plate is likely to occur, and the tilt angle of the swash plate is changed due to wear and deformation of the linkage portion. There is a problem that the control accuracy is reduced.

Therefore, when the present inventors repeated various experiments, it was found that the cylinder block easily tilted in the tilting direction of the swash plate.
It was found that the range without pump discharge, the so-called neutral width, expands.

On the other hand, in a swash plate piston pump, generally, there is rattling between the cylinder block and the input shaft, but the present invention utilizes this rattling to make the cylinder block easier to move. .

That is, an object of the present invention is to provide a swash plate piston pump in which the cylinder block can be easily rotated in the tilting direction and the non-discharge range near the neutral point is increased.

(Means for Solving Problems) The present invention is rotationally driven by an input shaft, and
A cylinder block that keeps play with respect to the input shaft, a piston that is slidably mounted on this cylinder block, a swash plate that a shoe provided on the head of this piston slidably contacts, and this swash plate A valve plate that is in surface contact with the cylinder block on the opposite side to the valve block, and a valve plate that is adjacent to the valve plate on the opposite side to the cylinder block and that guides the fluid discharged from this valve plate to the outside and the fluid from the outside. It is premised on a swash plate piston pump which has a port block formed with a port leading to the swash plate and which has a variable discharge amount by controlling the tilt angle of the swash plate.

While assuming the above-mentioned swash plate piston pump, the present invention interposes a restricting means for restricting rotation of the valve plate around the input shaft between the valve plate and the port block, while the cylinder block and the valve plate are It is characterized in that it rotates integrally and the rotation axis of the swash plate and the rotation axes of the cylinder block and the valve plate are substantially orthogonal to the input shaft and parallel to each other.

(Operation of the present invention) In the present invention, since the valve plate can be rotated in the tilting direction, the rotation of the cylinder block is not restricted by the valve plate, and the cylinder block can be rotated more easily.

(Effect of the present invention) As described above, since the cylinder block easily rotates in the tilting direction, the neutral width is expanded. Therefore, if the operation lever is returned to the neutral position to some extent, it can be easily set in the neutral region and the vehicle or the like can be reliably stopped.

(Embodiment of the present invention) In the first embodiment shown in FIGS. 1 and 2, since the cylinder block 11 is connected to the input shaft 12 by a spline, the cylinder block 11 rattles with respect to the input shaft 12. I am trying.

The cylinder block 11 thus constructed has a shoe on the head.
A plurality of pistons 14 forming 13 are provided, and the shoes 13 are brought into sliding contact with the swash plate 15.

The swash plate 15 rotates about the trunnion pin 16,
The maximum stroke of the piston 14 is adjusted according to the tilt angle so that the discharge amount can be controlled. That is,
If the tilt angle is increased, the stroke of the piston also increases, so the discharge amount also increases and the speed of the vehicle etc. also increases.On the other hand, if the tilt angle is set to zero, the stroke also becomes zero. The amount becomes zero and the vehicle etc. stops.

A valve plate 17 is provided on the side surface of the cylinder block 11 on the side opposite to the swash plate 15, and these cylinder block 11 and valve plate
17 is in surface contact with.

On the side surface of the valve plate 17 opposite to the contact surface of the cylinder block 11 and in the radial direction thereof, a semi-cylindrical convex portion 18 is formed, and in the port block 19 facing the cylinder block 11, A concave portion 20 that engages with the convex portion 18 is formed.

The convex portion 18 and the concave portion 20 constitute the rotation restricting means of the present invention. That is, the rotation restricting means restricts the rotation of the valve plate 17 around the rotation axis.

Then, a gap is formed between the valve plate 17 and the port block 19 so that the valve plate 17 can rotate about the convex portion 18 within the range of the gap.

However, since the convex portion 18 is formed parallel to the trunnion pin 16 of the swash plate 15, the valve plate 17 can rotate only in the tilting direction of the swash plate 15. Thus, the fact that the valve plate 17 rotates only in the tilting direction of the swash plate means that the cylinder block 11 that makes surface contact with the valve plate is also restricted in its rotating direction. In other words, this cylinder block 11
As described above, since the play is held against the input shaft, it is possible to rotate in all directions within the range of the play.
As described above, since the rotation direction of the valve plate 17 is restricted,
The cylinder block 11 can also rotate only in the tilting direction together with the valve plate.

The port block 19 has a pressing spring 21
Is provided, and the pressing spring acts on the valve plate 17, and the adjusting screw 22 for adjusting the spring force of the spring 21 is provided.
Is provided.

The reason why the spring force of the pressing spring 21 acts on the valve plate 17 in this manner is to maintain the stability of the valve plate 17 and the close contact between the cylinder block 11 and the valve plate 17. Also, by adjusting the spring force of the spring 21 with the adjusting screw 22, the contact resistance between the convex portion 18 and the concave portion 20 can be adjusted.

Then, by operating the operating lever (not shown), the swash plate 15
When the tilt angle of is larger than zero, since the cylinder block 11 is rotating together with the input shaft 12, the piston 14 is guided by the swash plate 15 to reciprocate, and the discharge amount according to the tilt angle is discharged. However, since the pump function itself is exactly the same as the conventional one, its detailed description is omitted.

Then, when the operation lever is returned from the above state to the vicinity of the neutral position and the tilt angle of the swash plate 15 is made close to zero, the cylinder block 11 is integrated with the valve plate 17 as described above, and tilting is performed. The neutral width increases because it tends to tilt in the direction. Therefore, the operation lever can be easily set in the neutral zone, and the vehicle or the like can be reliably stopped.

In order to improve the followability between the cylinder block 11 and the valve plate 17, the diameter of the cylindrical surface of the convex portion 18 must be equal to or smaller than the pitch circle diamond at the arrangement position of the pistons 14 with respect to the cylinder block 11.

As described above, in this first embodiment, the convex portion 18 is formed on the valve plate 17 and the concave portion 20 is formed on the port block 19. However, the concave portion is formed on the valve plate and the convex portion is formed on the port block. Of course it is good.

Further, although the convex portion 18 is formed integrally with the valve plate 17 or the port block, a connector is provided on either one of the valve plate and the port block and a concave portion is formed on the other one, and the connector and the concave portion are engaged with each other. You may allow it.

Further, although the convex portion 18 is formed long in the radial direction of the valve plate 17, the convex portion or the connector may be spherical. When the convex portion or the connector has a spherical shape as described above, it is necessary to provide a rotation preventing mechanism such as a pin that restricts the rotation around the input shaft without hindering the rotation of the valve plate and the connector in the tilting direction. If the anti-rotation mechanism is provided in this way, the cylinder block 11 can be rotated only in the tilting direction by the thrust of the piston 14 even if the convex portion and the connector are spherical.

In the second embodiment shown in FIG. 3, a trunnion 23 is provided on the valve plate 17, the trunnion 23 rotatably supports the valve plate 17, and the trunnion 23 has a flow passage 24 for discharge and suction. Is formed. A pressing spring 21 is provided on a body 25 provided so as to face the valve plate 17, and the spring force of the pressing spring 21 is applied to the valve plate 17. Other configurations are similar to those of the first embodiment. Is.

In each of the above-described embodiments, an oil film is formed on the convex portion 18 or the sliding contact portion of the connector, and this oil film fulfills the lubricating function.

However, if the thrust of the piston 14 due to hydraulic pressure increases,
The pressing force of the sliding contact portion is increased, and thus the frictional force is increased, which may hinder the smooth movement of the sliding contact portion.

Therefore, in order to prevent such a phenomenon, the piston 14
The means for canceling the thrust force must be provided to ensure the smooth movement of the sliding contact portion. An embodiment provided with this means is the third embodiment shown in FIG.

In the third embodiment, the valve plate 17 is provided with a piston 26 for canceling the thrust of the piston 14. That is, four pressure chambers 27 communicating with the piston 14 side are formed in the valve plate 17 at symmetrical positions in the left, right, up, and down directions, and the pistons 26 are mounted in these pressure chambers 27 via springs 28. It is in contact with 19.

Therefore, a thrust force substantially equal to the thrust force of the piston 14 acts on the port block via the piston 26, so that the thrust force of the piston 14 is canceled and the convex portion or the connector portion is smoothly lubricated.

It should be understood that the number of pistons 26 and the size thereof may be determined according to the thrust of the piston 14.

In the fourth embodiment shown in FIG. 5, adjusting screws 29 and 29 are provided on the port block side, and adjusting pistons 30 and 30 are provided at the tips of the screws 29 and 29, and the adjusting pistons 30 and 30 are provided according to the position of the adjusting piston. The pressing force of the piston 26 can be adjusted.

Other configurations are similar to those of the third embodiment.

In the fifth embodiment shown in FIG. 6, the port block 19 side is
The hollow pistons 31, 31 are provided, and this hollow piston 3
1 and 31 ensure a certain clearance with the pressure chambers 32 and 32 so that the hollow pistons 31 and 31 can follow even if the valve plate 17 is tilted.

Therefore, in the fifth embodiment, the thrust force is canceled by the pressure introduced into the hollow pistons 31, 31, but the spring force of the pressing spring 28 can be adjusted by the adjusting screws 29, 29. There is.

Of course, the hollow piston 31 may be replaced by the piston 26 shown in the third and fourth embodiments.

The sixth embodiment shown in FIG. 7 uses a hollow piston 31 having the same structure as the fifth embodiment as a flow path connecting the valve plate 17 and the port block 19. Then, the valve plate 17
The convex portion 18, which is the center of rotation of the
In order to prevent the rotation of the pin, a pin 33 is provided as a restricting means of the present invention.

In the sixth embodiment, unlike the first to fifth embodiments,
Since the flow path is not formed at the center of rotation of the valve plate 17, the shape of the convex portion 18 may be determined as long as the valve plate 17 can be rotated in the tilting direction.

Further, although the pin 33 is provided in order to prevent the valve plate 17 from rotating, if, for example, a V-shaped convex portion is formed on one side and a V-shaped groove is formed on the other side, the above is described. Pin 33 is also unnecessary.

In the seventh embodiment shown in FIGS. 8 and 9, a piston 26 for canceling the thrust of the piston 14 is provided at vertically symmetrical positions in the center of the valve plate.

Then, in the port block 19, depending on the rotation direction of the cylinder block 11, flow paths 34 and 35 are formed, one of which is on the discharge side and the other is on the suction side, and both flow paths 34 and 35 are formed. A conduction path 37 for communicating with each other is formed. Further, a pair of throttles 36 are provided in the conduction path 37, and a piston is provided between these throttles 36 via a communication path 38.
Supplying to the 26 side. Therefore, the average pressure of the discharge pressure and the suction pressure acts on the piston 26.

The piston 26, the communication passage 37, and the communication passage 38 are connected to the valve plate 17
May be provided.

In the eighth embodiment shown in FIGS. 10 and 11, the hollow piston 26 for canceling the thrust of the piston 14 is provided at the symmetrical position in the center of the valve plate, and at the same time the valve plate 17 is symmetrically arranged in the vertical direction. A spring 21 is provided to maintain the orientation of the plate. Then adjust the spring force of this spring 21
It is possible to adjust with 22.

The ninth embodiment shown in FIG. 12 is a valve plate 17 and a port block.
Flow paths 34 and 35 connecting to 19 are provided at both end portions of the cylindrical convex portion 18, and pistons 26 that cancel thrust of the piston 14 are provided inside the flow paths 34 and 35.

In any case, in each of the above-described embodiments, the neutral width, which is the range in which the pump does not discharge, expands when the lever is operated near the neutral point.

[Brief description of drawings]

FIGS. 1 and 2 show a first embodiment of the present invention.
FIG. 1 is a front view, FIG. 2 is a sectional view of an essential part, and FIGS. 3 to 12 are sectional views of an essential part showing second to ninth embodiments of the present invention. 11 …… Cylinder block, 12 …… Input shaft, 13 …… Shoe, 14 …… Piston, 15 …… Swash plate, 17 …… Valve plate.

Claims (1)

[Claims] 1. A rotary drive by an input shaft,
A cylinder block that keeps play with respect to the input shaft, a piston that is slidably mounted on this cylinder block, a swash plate that a shoe provided on the head of this piston slidably contacts, and this swash plate A valve plate that is in surface contact with the cylinder block on the opposite side to the valve block, and a valve plate that is adjacent to the valve plate on the opposite side to the cylinder block and that guides the fluid discharged from this valve plate to the outside and the fluid from the outside. In a swash plate piston pump in which a discharge amount is variable by controlling a tilt angle of the swash plate, a port block having a port leading to a valve plate is provided between the valve plate and the port block. While interposing a restricting means for restricting rotation around the axis, the cylinder block and the valve plate rotate integrally, and the rotation axis of the swash plate and the rotation axis of the cylinder block and the valve plate Substantially perpendicular to and swash plate piston pump was configured to be parallel to each other and the input shaft.