JP2521073B2 - Axial piston pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a swash plate axial piston pump that controls a discharge amount by adjusting a tilt angle of a swash plate or a cylinder block.

(Prior Art) This type of axial piston pump is sometimes used for a hydrostatic transmission, but in this case, forward, backward, or stop control can be performed by changing the tilt direction of the swash plate or cylinder block. To do.
That is, when the tilt angle of the swash plate or the cylinder block is set to 0 degree while keeping the operation lever in the neutral position, the stop function is exerted, and the tilt angle is tilted in either direction from 0 degree. Move the vehicle or the like forward or backward.

Therefore, when the operating lever is held in the neutral position,
A good stopping function cannot be obtained unless the tilt angle of the swash plate pump is surely set to 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, conventionally, there is known a device in which a rattling is provided in a linkage mechanism between the operation lever and the swash plate in order to surely stop the vehicle or the like when the operation lever is positioned near the neutral position.

The mechanism of generating the neutral point restoring moment that produces this self-restoring force will be described with reference to FIGS. 12 to 16.

FIG. 12 shows the force relationship when the piston is extended, and FIG. 13 shows the force relationship when the piston is contracted.

 The drag force Ft acting on the swash plate is Ft = ApPb−Ff (1) during extension and Ft = ApPb + Ff (2) during contraction.

However, ApPb: hydraulic thrust, Ft: frictional force between piston and cylinder block.

From the above equations (1) and (2), it can be seen that the drag force Ft acting on the swash plate is greater when the piston is contracted than when the piston is contracted.

Then, with respect to this extension and contraction, with the diameter line connecting the bottom dead center and the top dead center on the swash plate as a boundary, one half side of the swash plate corresponds to the extension of the piston, and the other half side corresponds to the contraction side. .

Therefore, a strong force acts on one side and a weak force acts on the other side of the swash plate with the diameter line connecting the bottom dead center and the top dead center as a boundary. Then, actually, due to the strength of this drag force, a tilt β in the left-right direction of the swash plate is generated as shown in FIGS. 14 to 16. This inclination angle β can be substantially grasped as the inclination angle of the valve plate, and therefore,
The same description will be made.

According to the invention of β, the bottom dead center and the top dead center on the Y axis when β = 0 move clockwise (same as the cylinder block rotation direction).

As shown in FIG. 14, when the tilt angle α >> β of the swash plate, the effect of β can be neglected, and the bottom dead center and the top dead center of the piston are at the upper and lower positions of the swash plate, respectively. Since it is on the Y-axis, the piston thrust forces above and below the swash plate are in equilibrium, and the moment about the X-axis is almost zero.

Next, as shown in FIG. 15, when α is decreased (close to the neutral position) and α≈β, the bottom dead center and the top dead center of the piston move clockwise, respectively. This movement moves the position of large thrust, and the lower half surface of the swash plate becomes larger than the piston thrust of the upper half surface. Therefore, a moment I about the X axis is generated.

Furthermore, the tilt angle α of the swash plate approaches the vicinity of the neutral point (α≈0)
And the bottom dead center and top dead center of the piston move on the X-axis, and the piston thrust forces acting on the left and right half surfaces of the swash plate become equal.
Following = 0, β = 0. Further, the piston does not move in the axial direction, and the tilting moment I of the swash plate is not generated (Fig. 16).

That is, when the tilt angle α approaches 0 °, the influence of the left and right inclination β of the swash plate becomes non-negligible, and the bottom dead center and top dead center of the piston move in the left and right direction of the swash plate, and the X axis A surrounding moment I is generated. This moment I is the neutral point return moment.

The conventional device utilizes the self-restoring force within the range of rattling.

(Problems to be Solved by the Present Invention) In the conventional apparatus as described above, the magnitude of the self-restoring force may vary depending on the characteristics of individual pumps and operating conditions, and the desired restoration characteristic may not be obtained. Many.

Also, vibration of the operating lever and the swash plate easily occurs,
Further, there is a problem that the accuracy of controlling the tilt angle of the swash plate or the cylinder block is deteriorated due to wear and deformation of the linking portion.

Therefore, the inventors of the present invention repeated various experiments and found that when the cylinder block was likely to move in the tilting direction of the swash plate and in the left-right direction, the neutral point return moment increased and the range without pump discharge (neutral It was found that the width) increased.

On the other hand, in an axial piston pump, generally, there is looseness between the cylinder block and the input shaft,
The present invention utilizes this backlash to make the cylinder block easier to move.

That is, an object of the present invention is to provide a device in which the cylinder block is tilted and rotatable in both left and right directions, and the above-mentioned conventional drawbacks are eliminated.

(Means for Solving the Problem) In order to achieve the above object, the present invention relates to an axial piston pump configured to change the stroke of a piston and control the discharge amount thereof, so as to rotate in any one direction. It is equipped with two or more valve plates that are made possible, the valve plates are rotatable in different directions, and the sliding surface of the valve plate with respect to the cylinder block rotates in any direction with respect to the swash plate or cylinder block. It is movable.

(Operation of the Present Invention) The present invention provides a valve plate that is rotatable in one arbitrary direction.
Since they rotate in different directions, as a result, the sliding surface of the valve plate with respect to the cylinder block can rotate in any direction with respect to the swash plate. As a result, the cylinder block can be tilted both in the tilting direction and in the left-right direction.

Also, when the operation lever is near the neutral position, the tilting range in which the generated neutral point return moment is large can be widened,
Moreover, the value of the return moment increases significantly.

Further, due to this return moment, the cylinder block easily keeps the relative tilt angle with the swash plate to zero, and the neutral width also increases.

The range of generation of the return moment and the neutral width can be easily changed by adjusting the range of rotation and the direction of rotation of the valve plate.

(Effect of the present invention) As described above, since the range of generation of the return moment and the range of no discharge can be set relatively freely, it is possible to obtain a desired return characteristic with respect to the lever operation and also to increase the neutral width. It becomes easy to obtain a good neutral characteristic.

In addition, this will reduce the influence of machine vibration, etc., and even if the operator is inexperienced, if the operating lever is returned to the neutral position to some extent, it can be easily set in the neutral range and the vehicle etc. can be stopped reliably. You can

Further, when the detent mechanism is used to maintain the neutral position, it can withstand practical use even if the accuracy of the neutral position is lower than the conventional one, and the zero point adjustment becomes very easy.

(Embodiment of the present invention) FIG. 1 shows the relative relationship between the swash plate 15 and the cylinder block 11. The trunnion pins 16 and 16 are provided at both ends of the swash plate 15 and the trunnion pins 16 and 16 are provided. Bearing 10,
It is configured to be supported by 10. The swash plate 15 is rotated about the trunnion pins 16 in the direction of arrow 5 to adjust the tilt angle α, and the direction of arrow 5 is the tilt direction. The arrow 6 direction is the left-right direction that is substantially orthogonal to the tilt direction.

In the first embodiment shown in FIGS. 2 to 5, since the cylinder block 11 and the input shaft 12 are connected by a spline, the cylinder block 11 can rattle with respect to the input shaft 12.

The cylinder block 11 thus configured is provided with a plurality of pistons 14 each having a shoe 13 formed on the head thereof, and the shoes 13 are brought into sliding contact with the swash plate 15.

On the other hand, an upper valve plate 17a is provided on the side surface of the cylinder block 11 on the side opposite to the swash plate 15, and the cylinder block 11 and the upper valve plate 17a are in surface contact with each other. A semi-cylindrical convex portion 18a parallel to the trunnion pin 16 is formed on the side surface of the upper valve plate 17a opposite to the contact surface of the cylinder block 11, and the upper valve plate 17a is formed.
The lower valve plate 17b opposed to the above is formed with a concave portion 20a that fits with the convex portion 18a.

Further, in the lower valve plate 17b, a convex portion 18b is formed on a surface opposite to the concave portion 20a in a direction orthogonal to the trunnion pin 16, and the port block facing the lower valve plate 17b has the above convex portion. A concave portion 20b that fits with the portion 18b is formed.

The upper valve plate 17a, the lower valve plate 17b, and the lower valve plate
When the upper valve plate 17a and the lower valve plate 17b are kept horizontal with the 17b and the port block 19 fitted together, the gap 1a is held between the upper valve plate 17a and the lower valve plate 17b. In addition, the gap 1b is held between the lower valve plate 17b and the port block 19, but the upper valve plate 17a and the lower valve plate 17b are configured to rotate within the range of the gaps 1a and 1b. .

However, the convex portion 18a and the convex portion 18b are provided in a direction orthogonal to each other, the upper valve plate 17a rotates in the tilting direction which is the arrow 5 direction, and the lower valve plate 17b rotates in the left and right direction which is the arrow 6 direction. I am trying to move.

Therefore, the sliding surface of the upper valve plate 17a with the cylinder block 11 becomes rotatable in all directions in combination with the rotation of the lower valve plate 17b.

As a result, the cylinder block 11 that is in surface contact with the upper valve plate 17a can also rotate in all directions together with the upper valve plate 17a within the range of play with the input shaft.

The upper valve plate 17a, the lower valve plate 17b configured as described above,
Although it can rotate in the range of the above-mentioned gaps 1a and 1b, in consideration of its localization, between the upper valve plate 17a and the lower valve plate 17b, and
Between the lower valve plate 17b and the port block 19, the spring 2
The spring force of 1a and 21b is applied. However, this spring is for ensuring the localization of both valve plates as described above, and when such a function is not required, this spring is unnecessary. And this spring 21a, 2
The spring force of 1b can be freely adjusted by the set length adjusting screws 22a and 22b.

In order to improve followability between the cylinder block 11 and each valve plate 17a, 17b, the diameter of the cylindrical surface of the convex portions 18a, 18b should be equal to or less than the arrangement pitch circle diamond of the pistons 14 with respect to the cylinder block 11. I have to.

In the first embodiment, the upper valve plate 17a is rotated in the tilting direction and the lower plate plate 17b is rotated in the left-right direction.
You may reverse those rotation directions.

Further, the valve plates 17a, 17b are not limited to the tilting direction and the left-right direction, but may be rotated in any intermediate direction. Also,
The rotation directions of the valve plates may be orthogonal to each other as in this embodiment, or may intersect at other angles.

Further, in the first embodiment, the convex portion 1 is provided on the side of the upper valve plate 17a.
8a is formed and the concave portion 20a is formed on the side of the lower valve plate 17b facing the concave portion 8a, but they may be reversed. Also, the upper valve plate
A single member having a shape similar to that of the convex portion 18a, for example, a connector may be fixed to either 17a or the lower valve plate 17b, and a concave portion corresponding to the connector may be formed on either of the other members.

This is the same between the lower valve plate 17b and the port block 19.

Further, although the convex portions 18a and 18b are formed to be long in the radial direction of the valve plates 17a and 17b, the convex portions or the connector may be spherical. When the convex portion or the connector is thus spherical, it is necessary to provide a rotation stopping mechanism such as a pin that restricts rotation around the input shaft without hindering the rotation of each valve plate and the connector in any one direction. .

In the second embodiment shown in FIG. 6, the trunnion pins 23b are provided on both sides of the lower valve plate 17b, while the body 25 has a bearing piece 9b.
b is provided, and the trunnion pin 23b is rotatably supported by the bearing provided on the bearing piece 9b.

Further, trunnion pins 23a are provided on both sides of the valve plate 17a, while a bearing 9a is provided on the lower valve plate 17b.
The trunnion pin 23a is rotatably supported by a bearing provided in the.

Then, the two valve plates 17a, 17b are made to rotate in different directions, and the two are combined so that the surface of the upper valve plate 17a, which is the sliding surface with the cylinder block 11, rotates in all directions as in the first embodiment. I am trying to be free.

The discharge and suction flow paths 24 are formed via the trunnion portions of each valve plate.

 Other configurations are similar to those of the first embodiment.

In the second embodiment, both valve plates 17a and 17b are of the trunnion type, but it goes without saying that either one may have the structure shown in the first embodiment.

In each of the above-described embodiments, the thrust of the piston 14 acting on the cylinder block 11 acts on the convex portion or connector of each valve plate, or the trunnion bearing of each valve plate, so that the piston 14 is hydraulically operated. It can be considered that when the thrust becomes large, the smooth rotation of each valve plate is hindered.

Therefore, in order to prevent such a phenomenon, the piston
The means for canceling the thrust of 14 must be provided to ensure the smooth rotation of each valve plate. The embodiment provided with this means is the third to seventh embodiments shown in FIGS. Is.

The third embodiment shown in FIG. 7 is a case where the upper valve plate 17a can be rotated in the left-right direction, and the thrust of the piston 14 is canceled by the upper valve plate 17a so as not to hinder the rotation of the lower valve plate 17b. This is provided with a pressing piston 26 for doing so. That is, the pressure chamber 27 communicating with the piston 14 side is connected to the upper valve plate 17a.
Is formed at the left and right symmetrical positions of the upper valve plate, and these pressure chambers 27 are internally provided with a pressing piston 26 via a spring 28,
The pressure piston is brought into contact with the port block 19 through the pressure piston through hole 31 provided in the lower valve plate.

Therefore, the thrust that is almost equal to the thrust of the piston 14 is
Since it acts on the port block via the pressing piston 26, the thrust force of the piston 14 is canceled and lubrication of each convex portion or connector portion is smoothly performed.

It should be understood that the number and size of the pressing pistons 26 may be set according to the thrust of the pistons 14.

Further, in order to apply a pressing force to the port block 19, various methods can be considered as the pressing piston, but any method can be used as long as the hydraulic thrust of the piston 14 can be canceled.

Further, as shown in the fourth embodiment of FIG. 8, an adjusting screw 29 is provided on the port block side and
An adjusting piston 30 may be provided at the tip of 29 so that the pressing force of the pressing piston 26 can be adjusted according to the position of the adjusting piston.

As shown in the fifth embodiment of FIG. 9, the pressing piston 26 may be provided on the port block side and the upper valve plate 17a may be pressed by the action of the pressure supplied from the port block 19 side. .

In addition, in the third to fifth embodiments, the pressing force of the pressing piston 26 is applied to the lower valve plate 17b which can be rotated in the left-right direction, but the invention is not limited to this, and the lower valve plate 17b can be rotated in the tilting direction. The above pressing force may be applied to a possible upper valve plate. further,
The pressing force of the pressing piston 26 may be applied to not only the upper valve plate 17a but also the lower valve plate 17b.

Further, the hydraulic thrust canceling mechanism of the piston 14 shown in the third to fifth embodiments is applied to the first embodiment, but is also applicable to the trunnion type valve plate of the second embodiment. It is natural.

In the sixth embodiment shown in FIG. 10, as a mechanism for canceling the hydraulic thrust of the piston 14, a hollow type pressing piston 32 is provided so as not to hinder the rotation of the lower valve plate 17b. 32 is used as the flow path 24 connecting the upper valve plate 17a and the port block 19.

Then, the convex portion, which is the center of rotation of each valve plate 17a, 17b, is formed into a V-shaped convex portion 33a, 33b, and the pin 34a for preventing the rotation of each valve plate 17a, 17b around the input shaft. 34b is provided.

The hollow pistons 32, 32 secure some clearance with the pressure chambers 27, 27 so that the hollow pistons 32, 32 can follow even if the upper valve plate 17a is tilted.

Further, in this sixth embodiment, since no flow path is formed at the center of rotation of each valve plate 17a, 17b, if each valve plate can be rotated in one arbitrary direction, the convex portions 33a, 33b can be formed. Any shape may be defined.

Further, pins 34a and 34b are provided to prevent rotation of each valve plate around the input shaft. For example, a V-shaped convex portion is formed on one side and a V-shaped groove is formed on the other side. If so, the above-mentioned pins 34a and 34b become unnecessary.

In the seventh embodiment shown in FIG. 11, a trunnion type valve plate is acted on by a hollow piston 32 which also serves as a flow passage.
The hydraulic thrust of the piston 14 of the cylinder block 11 is canceled, and the hollow piston 32 discharges and suctions the flow path 24.
Is formed.

In the sixth and seventh embodiments, the hollow piston 32 is used as the pressing piston that also serves as the flow passage, but the present invention is not limited to this, and any piston having a flow passage may be used. For example, the shoe type piston shown in the fourth embodiment may be used.

In the third to seventh embodiments described above, the pressing piston 26 or 32 presses the valve plate 17a or 17b. However, the effective area of the pressing piston is reduced and the spring 28
Needless to say, the spring force may be increased to bear a part of the hydraulic pressure of the piston 14.

In any case, in the first to seventh embodiments described above, an appropriate return moment can be obtained for the lever operation near the neutral point, and the neutral width, which is the range in which the pump does not discharge, increases.

In each of the above embodiments, the valve plate 17a and the lower valve plate 17b are
The above two valve plates were used, but it goes without saying that the number of valve plates may be three or more.

[Brief description of drawings]

Drawing FIG. 1 is a perspective view showing a relative relationship between a swash plate and a cylinder block, FIGS. 2 to 5 show a first embodiment of the present invention, FIG. 2 is a partial sectional view, and FIG. FIG. 2 is a partial sectional view in the state of being rotated by 90 °, FIG. 4 is a front view of the upper valve plate taken along the line IV-IV in FIG. 3, and FIG. 5 is VV in FIG.
Front view of the lower valve plate based on the line, Figures 6-11 are
7 is a partial sectional view of FIG. 12, FIG. 12 and FIG. 13 are explanatory diagrams of swash plate drag force, and FIGS. 14 to 16 are explanatory diagrams of a neutral point return moment generating mechanism, and (a) is a front view of the swash plate. Figure, (b) is a plan view,
(C) is a side view. 11 …… Cylinder block, 15 …… Swash plate A, 17a …… Upper valve plate, 17b …… Lower valve plate.

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. An axial piston pump configured to change the stroke of a piston and control the discharge amount thereof, comprising two or more valve plates rotatable in one arbitrary direction, and the valve plates differ from each other. Axial piston pump that is rotatable in any direction and the sliding surface of the valve plate with respect to the cylinder block is rotatable in any direction with respect to the swash plate or cylinder block.