JPH0549822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a swash plate plunger pump used in a hydrostatic transmission (hereinafter referred to as HST) or the like.

(Prior art) HST generally comprises a closed circuit with a variable displacement type swash plate plunger pump and a fixed displacement type swash plate plunger motor, and controls the operating speed of the plunger motor according to the discharge amount of the plunger pump. .

In this case, the control lever is operated to change the tilting direction of the swash plate plunger pump to move the vehicle forward or backward, and to bring the tilting angle to zero to stop the vehicle. Therefore, the stopping characteristics when the operating lever is held at the neutral position greatly affect the safety of the vehicle.

At this time, if there is only one point on the operating lever to stop the vehicle, if that point shifts due to mechanical vibrations, etc., or the driver is inexperienced, the operating lever will be reliably set to the stopping point. This makes it difficult to set the correct position, which also poses a safety problem.

Therefore, in order to ensure that the vehicle etc. stops when the operating lever is located near the neutral position,
2. Description of the Related Art Devices in which a linkage mechanism between an operating lever and a swash plate is provided with play are conventionally known.

It is generally known that when a swash plate plunger pump reaches near the neutral point, it generates a self-returning force that tries to return to the neutral point, but this conventional device only generates a self-returning force within the above-mentioned wobbling range. It was designed to be used.

However, in such a device, the magnitude of the neutral point return moment of the swash plate varies depending on the characteristics and operating conditions of individual pumps, so there is a problem that stable return characteristics cannot be obtained.

Therefore, the inventors of the present invention repeatedly conducted various experiments and found that when the cylinder block easily moves in a direction perpendicular to the tilting direction of the swash plate, the neutral point return moment of the pump increases.

And in this type of swash plate plunger pump,
Generally, the cylinder block is connected to the input shaft using a spline or the like, and there is some play in both, but the inventors of the present invention have made use of this play to make the cylinder block easier to move. I thought about it.

That is, the idea was to make the cylinder block and the valve plate rotatable in a direction substantially perpendicular to the direction of tilting of the swash plate.

(Problems to be Solved by the Present Invention) To rotate the cylinder block and the valve plate as one unit as described above means that the valve plate and the port block must be rotated relative to each other. It won't happen. Therefore, the sliding surfaces of both had to be made relatively small, and there was a problem in that the thrust on the cylinder block side was concentrated on the sliding surfaces.

Also, in the contact area between the valve plate and the port block,
Although it is necessary to form a supply/discharge flow path for the cylinder block, since the sliding surface is not large as described above, the flow path cannot be made large either, which poses the problem of reduced self-priming performance.

The object of the present invention is to provide a swash plate plunger pump which is capable of canceling thrust on the cylinder block side and ensuring a sufficiently large flow path.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a cylinder block that maintains play against an input shaft, a plunger slidably provided on the cylinder block, and a plunger that is slidably provided on the cylinder block. It is equipped with a swash plate on the head of which the shu slides, and a valve plate on the opposite side of the swash plate that makes surface contact with the cylinder block, and the discharge amount can be varied by controlling the tilt angle of the swash plate. In this type of swash plate plunger pump, the cylinder block and the valve plate are integrated and can be rotated only in a direction substantially perpendicular to the direction of tilting of the swash plate. One or more pairs of piston mechanisms for canceling thrust are provided, and a supply/discharge passage for the cylinder block is formed in the piston mechanism or the trunnion.

(Operation of the present invention) Since the present invention is configured as described above, the thrust of the cylinder block can be canceled by the piston mechanism, and a sufficient supply and discharge flow path for the cylinder block can also be secured.

(Effects of the present invention) Since the thrust of the cylinder block can be canceled as described above, even if the discharge pressure or suction pressure of the pump changes, the hydraulic balance state with respect to the port block does not change, and the valve plate and The thrust force on the cylinder block side will not be concentrated at the contact area with the port block.

Furthermore, since the supply and discharge passages are formed at locations other than this contact portion, the supply and discharge passages can be sufficiently secured, and the self-priming performance does not deteriorate.

(Embodiment of the present invention) In the first embodiment shown in FIGS. 1 and 2, the cylinder block 1 is connected to the input shaft 2 by a spline, so that the cylinder block 1 may have some play with respect to the input shaft 2. I try to stick to it.

The cylinder block 1 thus constructed is provided with a plurality of plungers 4 each having a shoe 3 formed on its head, and the shoe 3 is brought into sliding contact with a swash plate 5.

The swash plate 5 rotates around the trunnion pin 6, and the maximum stroke of the plunger 4 is adjusted according to its tilt angle, so that its discharge amount can be controlled. In other words, if you increase the tilt angle,
As the stroke of the plunger becomes larger, the discharge amount also increases, and the speed of the vehicle increases.
If the tilt angle is set to zero, the stroke will also be set to zero, so the discharge amount will be set to zero, and the vehicle or the like will stop.

A valve plate 7 is provided on the side surface of the cylinder block 1, that is, on the side opposite to the swash plate 5, and the cylinder block 1 and the valve plate 7 are brought into surface contact.

A semi-cylindrical protrusion 8 is formed in the radial direction on the side surface of the valve plate 7 opposite to the contact surface of the cylinder block 1, and a port block 9 facing the cylinder block 1 has a protrusion 8 formed therein. A recess 10 that engages with the protrusion 8 is formed.

A gap l is formed between the valve plate 7 and the port block 9, so that the valve plate 7 can rotate around the protrusion 8 within the range of this gap l.

However, since the protrusion 8 is formed in a direction perpendicular to the trunnion pin 6 of the swash plate 5, the valve plate 7 can only rotate in a direction substantially perpendicular to the tilting direction of the swash plate 5. It will be possible. The fact that the valve plate 7 rotates only in the direction orthogonal to the direction of tilting of the swash plate means that the cylinder block 1 that is in surface contact with the valve plate is also restricted in its rotational direction. In other words, as described above, this cylinder block 1 maintains a play with respect to the input shaft, so it can rotate in all directions within the range of the play, but as described above, the valve plate 7 rotates the cylinder block 1. Since the direction of movement is restricted, the cylinder block 1 can also rotate integrally with the valve plate only in a direction orthogonal to the tilting direction.

The port block 9 is provided with one or more pairs of hollow pistons 11 at symmetrical positions, and a hollow bolt 1 is provided on the outside of the hollow piston 11.
An adjustment spring 13 is interposed between the piston 11 and the bolt 12.

The hollow part of the piston 11 and bolt 12 as described above is connected to the supply/discharge passage 14 of the cylinder block 1.
It communicates with the port 15 formed in the port block 9 as well.

The total effective pressure receiving area of the plurality of hollow pistons 11 is made equal to the total pressure receiving area of the plungers 4 provided in the cylinder block 1. Therefore, even if the discharge pressure or suction pressure of the pump changes, the hydraulic pressure will not become unbalanced.

Note that the adjustment spring 13 acting on the hollow piston 11 is for finely adjusting the pressing force of the hollow piston 11, but the effective pressure receiving area of the hollow piston 11 is reduced to reduce the spring force of the adjustment spring 13. The force may be increased so that part of the thrust on the cylinder block 1 side is borne by this spring load.

In addition, in this embodiment, when the valve plate 7 and the port block 9 rotate relative to each other, the hollow piston 11 follows the rotation, so that the clearance between the bore of the port block 9 is increased, and the sealing member is 16 elastic deformations are utilized.

The second embodiment shown in FIG. 3 is similar to the first embodiment in that a hollow piston 11 is provided in the port block 9, but the hollow piston 11 is engaged with the port block 9 with a small clearance. While ensuring sealing performance, a shoe 17 is interposed between the hollow piston 11 and the valve plate 7 to prevent relative rotation between the valve plate 7 and the port block 9. This is different from the first embodiment.

To explain this in more detail, the above screen 1
7, a sphere 18 is fixed thereto, and this sphere 18 is rotatably engaged with the inner opening of the hollow piston 11, and the above-mentioned shoe 17 and the sphere 1
8 is hollow, and the other structure is the same as that of the first embodiment.

In the third embodiment shown in FIG. 4, the piston mechanism is provided on the valve plate 7.

That is, the valve plate 7 is equipped with a hollow piston 11 together with an adjustment spring 13, and the port block 9 is equipped with a hollow bolt 12 that is pressed against the hollow piston 11. The hollow piston 11 also has a large clearance with the bore provided in the valve plate 7, and is also made tiltable by utilizing the elastic deformation of the seal member 16.

It goes without saying that the valve plate 7 can be provided with a type using the shoe 17 of the second embodiment.

Further, in each of the above embodiments, one or more pairs of supply/discharge channels 14 are provided at locations other than the engagement portion between the protrusion 8 and the recess 10.
Since the ports 15 and 15 are formed, the range of shapes of the protrusion 8 and the recess 10 can be selected from a wide range. for example,
It is also possible to make the protrusion 8 wedge-shaped, or to make the protrusion and the recess a combination of spherical surfaces.

In the fourth embodiment shown in FIG. 5, the valve plate 7 is supported by a trunnion 19 provided in a direction perpendicular to the trunnion 6 of the valve plate 7, and the trunnion 19 is made hollow, and the hollow part is used as a port. 15. Since the port 15 is formed in the trunnion 19 in this way, the piston 20 is made into a ram shape unlike the previous embodiments, and the contact surface with the port block 9 is made into an arc shape, but this may also be a hollow piston. Of course.

In this way, the valve plate 7 is supported by the trunnion 19,
Moreover, the only difference from the above-mentioned embodiments is that the hollow portion is made into a port 15, and the other configurations are substantially the same.

Therefore, it goes without saying that a pump of the type in which the valve plate 7 is supported by the trunnion 19 can also adopt a configuration corresponding to each of the above embodiments.

[Brief explanation of the drawing]

Drawings 1 and 2 show a first embodiment of the present invention, in which Fig. 1 is a front view, Fig. 2 is a sectional view of the main part, and Figs. 3 to 5 are main points of the second to fourth embodiments. FIG. 1...Cylinder block, 2...Input shaft, 3...Shu, 4...Plunger, 5...Swash plate, 7...Valve plate, 11
and 20... a piston constituting a piston mechanism, 1
4... Supply/discharge channel, 19... Trunnion supporting the valve plate.

Claims (1)

[Claims] 1 A cylinder block that maintains play against the input shaft, a plunger that is slidably provided on this cylinder block, a swash plate that is provided on the head of this plunger on which the shoe slides, and a cylinder that is opposite to this swash plate. In a swash plate plunger pump that includes a valve plate that makes surface contact with the cylinder block on the side, and that controls the tilt angle of the swash plate to make the discharge amount variable, the cylinder block and the valve plate that are in surface contact with each other have an inclined surface. The valve plate is configured to be rotatable only in a direction substantially perpendicular to the direction of tilting of the plate, and is equipped with a piston mechanism that presses the valve plate toward the cylinder block under the pressure of the supply and discharge passage formed in the cylinder block. At least one pair is provided, and the total effective pressure receiving area of the piston mechanism is
A swash plate plunger pump that is equal to the total pressure receiving area of the plungers above.