JPH073218B2 - 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 tilting 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 stop point of the operation lever for stopping the vehicle, if the point is displaced due to mechanical vibration, etc., or if the driver is inexperienced, the operation lever must be set to the stop point securely. It becomes difficult to do it, and there is a problem in safety.

Therefore, when the operating lever is located near the neutral position,
In order to reliably stop the vehicle or the like, there has been conventionally known a device that uses a self-restoring force by providing a backlash in a linkage mechanism between an operation lever and a swash plate.

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

Reference FIG. 1 shows a force relationship at the time of piston extension, and Reference FIG. 2 shows a force relationship at the time of piston contraction.

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, Ff: = frictional force between piston and cylinder block.

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

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, in actuality, the strength of this drag causes a lateral inclination β of the swash plate as shown in Reference FIGS. 3 to 5. The inclination angle β can be substantially grasped as the inclination angle of the thrust plate, and therefore will be described below as the same.

Due to the occurrence 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 Reference FIG. 3, when the tilt angle α >> β of the swash plate, the effect of β can be ignored, 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, and 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. 5, 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 movement of the piston in the axial direction also disappears, and the swash plate tilting moment I does not occur.

That is, when the tilt angle α, 0 ° is approached, the influence of the left / 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 / right direction of the swash plate, and the X axis rotation 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 device as described above, the magnitude of the self-restoring force varies depending on the characteristics of individual pumps, operating conditions, etc., and thus the desired restoration characteristic cannot be obtained. There were many cases.

Further, there is a problem that the operating lever and the swash plate are likely to vibrate due to wear and deformation of the linking portion, and the control accuracy of the tilt angle of the swash plate is reduced.

It should be noted that when the tilt angle α of the swash plate becomes 0 ′, the pump is in a neutral state, that is, there is no discharge, but there is only one point at α = 0 ° where there is no discharge condition. Even if the neutral point return moment of is used, difficult lever operation is required.

It is an object of the present invention to provide a device in which the thrust plate provided on the swash plate can be swung in a predetermined direction to eliminate the above-mentioned conventional drawbacks.

(Means for Solving Problems) In order to achieve the above object, the present invention provides a cylinder block which is rotationally driven by an input shaft, a piston slidably provided on the cylinder block, and a head of the piston. A thrust plate that is in sliding contact with the shoe provided on the
The thrust plate is provided with a swash plate adjacent to the shoe on the side opposite to the shoe, and a valve plate on the side opposite to the thrust plate that is in surface contact with the cylinder block. The stroke of the piston is adjusted according to the tilt angle of the swash plate. In the swash plate piston pump configured to change and control the discharge amount thereof, the thrust plate can swing about the thrust plate swing axis, and the thrust plate swing axis is the tilt axis of the swash plate. And an angle larger than 0 degree and smaller than 90 degrees in the direction opposite to the rotation direction of the cylinder block.

(Operation of the Present Invention) According to the swash plate piston pump of the present invention, when the swing axis of the thrust plate is set to 0 degrees with respect to the swash plate tilt axis, the pump is in a non-discharge range. The neutral width can be increased, while the self-restoring force can be increased by setting it to 90 degrees. Therefore, if the swing axis is determined within the range of 0 ° to 90 ° rotation according to the required accuracy, the neutral width can be increased and at the same time, the self-restoring force to the neutral point can be increased.

(Effect of the present invention) As described above, if the swing axis of the thrust plate is set within the range of 0 to 90 degrees with respect to the tilt axis of the swash plate, a large self-restoring force can be achieved while maintaining a sufficient neutral width. It can be exhibited, and good neutral characteristics can be secured.

As a result, the influence of vibration of the machine is reduced, and even if the operator is inexperienced, the discharge amount of the pump can be completely reduced to 0 and the vehicle or the like can be stopped. Further, when the detent mechanism is used to maintain the neutral position, even if the accuracy of the neutral position is lower than the conventional one, the detent mechanism can be sufficiently put into practical use, and the zero point adjustment becomes very easy.

(Embodiment of the present invention) FIG. 1 shows a relative relationship between a swash plate 12 and a cylinder block 6. Trunnion pins 3 and 3 are provided at both ends of the swash plate 12, and the swash plate tilt axis is used as the tilt axis. The trunnion pins 3 and 3 are supported by bearings 4 and 4. Then, place the swash plate 12 around the trunnion pins 3 and 3 with an arrow 15
The tilt angle α is adjusted by tilting in the direction.

The arrow 15 indicates the tilt direction. Further, the arrow 16 direction indicates the left-right direction that is substantially orthogonal to the tilt direction.

2 to 4 show a first embodiment of the present invention, in which 12 is a swash plate, and the swash plate 12 has a circular cross section passing through the central portion thereof which is the swing axis of the thrust plate 17. The ridge 13 is provided. And this ridge 13 is the trunnion pin 3,
Although the angle γ is maintained with respect to the axis x of 3, the angle γ is set in the range of 0 ° <γ <90 °.

However, at this time, the direction of rotation of the cylinder block is indicated by the arrow 45.
And the angle γ is the axis x that is the tilt axis of the swash plate.
The arrow 45 with reference to is the angle rotated in the opposite direction. If the rotation direction of the cylinder block is the opposite direction of the arrow 45, the angle γ is the opposite direction, and therefore the range in which the ridge 13 is provided is different from that of the present embodiment.

Further, the thrust plate 17 provided facing the swash plate 12
A concave portion 18 corresponding to the protrusion 13 is formed in the groove, and the concave portion 18 and the protrusion 13 are fitted to each other. And
When the swash plate 12 and the thrust plate 17 are made vertical with the protrusion 13 and the recess 18 fitted to each other, a gap 1 is formed between them and the thrust plate 17 falls within the range of the gap 1. It can be rocked.

The thrust plate 17 swings in the 14 directions around the protrusion 13 in the figure, which is different from the tilting direction of the swash plate and the left-right direction.

Further, although the thrust plate 17 can swing within the range of the gap 1 as described above, the spring force of the spring 21 is applied to the surface facing the swash plate 12 to secure its localization. . The springs 21 are contracted in the spring holes 20 provided in the swash plate 12.

However, since the thrust plate 17 can swing, there is no problem if the spring 21 is not provided.
Is provided to improve its localization.
Further, the spring force of the spring 21 can be freely adjusted by the illustrated set length adjusting screw 22.

In the first embodiment, the ridges 13 are formed on the swash plate 12 side and the recesses 18 are formed on the thrust plate 17 side, but it goes without saying that they may be reversed. Further, a single member (connector) having the same shape as the ridge 13 may be fixed to either the swash plate 12 or the thrust plate 17, and a recess corresponding to this connector may be formed in the other one. . In short, any structure may be used as long as the thrust plate 17 can swing within the range of 0 ° <γ <90 ° which is the middle of the tilting direction of the swash plate and the left-right direction.

A piston 9 is slidably provided on the cylinder block 6, and a shoe 8 provided on the head of the piston 9 is brought into sliding contact with the thrust plate 17.

Therefore, in the first embodiment described above, the contact surface between the protrusion 13 and the recess 18 has a semi-cylindrical shape, but it may have another shape such as a mountain shape. Further, as long as the rotation stopping mechanism around the axis is installed so as not to hinder the swinging of the thrust plate, only the protrusion may be provided on either the thrust plate or the swash plate. Also in this case, the protrusion must be provided in a direction intersecting with the trunnion pins 3 and 3 at an angle γ.

The second embodiment shown in FIGS. 5 to 8 is a specific example thereof, in which the facing surface of the thrust plate 25 facing the swash plate 24 is composed of two flat surfaces which are raised from the end portion toward the central portion, and the two flat surfaces intersect each other. The projecting portion 35 formed in the portion fulfills the same function as that of the ridge 13 of the first embodiment. Further, in the figure, reference numeral 26 denotes a steel ball as a shaft rotation preventing mechanism of the thrust plate 25, which is inserted into a recess formed in both the swash plate 24 and the thrust plate 25.

In the second embodiment, the thrust plate 25 is attached to the swash plate.
Although the protrusion 35 that contacts the 24 is provided, it goes without saying that this may be provided on the swash plate 24 side.

In the third embodiment shown in FIGS. 9 and 10, while the gap 1 is provided between the swash plate 27 and the thrust plate 28, the trunnion pins 29 are provided at both ends of the thrust plate 28, and the bearing of the swash plate 27 is provided.
The trunnion pin 29 is supported by 30, and the thrust plate 28 is held so as to be capable of swinging in any one direction between the tilt of the swash plate and the horizontal direction.

In the fourth embodiment shown in FIGS. 11 and 12, a protrusion 32 is formed in the center of a swash plate 31, a self-aligning type bearing 33 is provided on this protrusion 32, and this self-aligning type bearing 33 is used. The thrust plate 17 is configured to be swingably supported in a direction intersecting with the axis of the trunnion pin 3 of the swash plate at an angle γ.

Further, although a detent 34 around the shaft is provided at the swing center of the thrust plate 17, the other configurations are similar to those of the first embodiment.

Although the protrusion 32 is formed on the swash plate 31 in the fourth embodiment, the protrusion 32 may be formed on the thrust plate to perform the same function.

The fifth embodiment shown in FIGS. 13 and 14 is a specific example.

That is, the protrusion 36 formed on the thrust plate 38,
While the self-aligning type bearing 33 is provided, the swash plate 39 has this bearing.
A hole 37 for inserting and supporting 33 is formed. Other configurations are similar to those of the fourth embodiment.

The sixth embodiment shown in FIGS. 15 and 16 is the same as the first embodiment except that a mechanism for canceling the hydraulic thrust of the piston 9 of the cylinder block 6 is added.

That is, the pressing piston holes 40 are placed at the symmetrical positions of the swash plate 12.
And a pressing piston 41 is housed in the hole 40.

Then, the pressing piston 41 is caused to act by a spring 43 whose spring force can be adjusted by an adjusting screw 42, and the hydraulic pressure (discharge pressure, suction pressure) of the piston 9 provided in the cylinder block 6 is The pressing piston 41 is made to act via the flow path 44.

In this sixth embodiment, the discharge pressure and the suction pressure act on the respective pressing pistons 41, so that the moment thrust in the lateral direction of the swash plate can be balanced by the hydraulic thrust of the piston 9 of the cylinder block 6. At the same time, the pressing force can reduce the sliding contact force between the swash plate 12 and the thrust plate 17.

In addition, in order to apply a pressing force to the thrust plate 17, various methods can be considered as the pressing piston 41. In short, if the hydraulic thrust of the piston 9 can be canceled, that method is used. It doesn't matter. Furthermore, the number of pressing pistons 41 can be appropriately determined.

Further, in the sixth embodiment, the pressing piston 41 cancels the hydraulic thrust of the piston 9 of the cylinder block 6, but the effective area of the pressing piston 41 is reduced and the spring force of the spring 43 is reduced. The pressure may be increased to bear a part of the hydraulic pressure of the piston 9.

Further, it goes without saying that the hydraulic thrust canceling mechanism for the piston 9 shown in the sixth embodiment is applicable to the second to fifth embodiments.

As described above, the swash plate shown in each of the above embodiments is a trunnion type, but it goes without saying that a swash plate of any shape such as a half-moon swash plate may be used.

Further, in each of the above-described embodiments, the thrust plate is swingable with respect to the trunnion pin about an axis formed by inclining the thrust plate in a range larger than 0 degree and smaller than 90 degrees. At this time, if the swing axis is closer to 0 degree, the neutral width, which is the non-discharge range of the pump, can be increased, but the self-restoring force tends to be small, and conversely, if it is closer to 90 degrees. The self-recovery force can be increased, but the neutral width tends to decrease.

Therefore, by setting the angle of the swing axis of the thrust plate according to the characteristics of the pump, a large self-restoring force can be exerted while maintaining a sufficient neutral width.

[Brief description of drawings]

FIG. 1 is a perspective view showing a relative relationship between a swash plate and a cylinder block, and FIGS. 2 to 4 show a first embodiment.
Figure is a side view of the swash plate side, Figure 3 is a partially cutaway front view,
FIG. 4 is a sectional view of the swash plate, FIGS. 5 to 8 show a second embodiment, and FIGS. 5 and 6 are sectional views showing different phases of the swash plate.
FIG. 7 is a side view of the swash plate side, FIG. 8 is a side view of the thrust plate, and FIGS. 9 and 10 are side and front views of the swash plate side showing the third embodiment. 12 is a side view and a front view on the side of the swash plate showing the fourth embodiment, and FIGS. 13 and 14 are the fifth view.
A side view and a front view of the swash plate side showing an embodiment, FIG.
FIG. 16 is a side view and a sectional view of the swash plate showing the sixth embodiment,
17 and 18 are explanatory views of the swash plate drag force, FIGS. 19 to 21 are explanatory views of the neutral point return moment generating mechanism, (a) is a front view of the swash plate, (b) is a plan view, and (c) is a plan view. ) Is a side view. 3 ... Trunnion pin, 9 ... Piston, 12, 24, 27,
31, 39 …… Swash plate, 17, 25, 28, 38 …… Thrust plate, 45 …… Arrow.

Claims (1)

[Claims] 1. A cylinder block rotatably driven by an input shaft, a piston slidably mounted on the cylinder block, a thrust plate slidably contacting a shoe provided on the head of the piston, and a shoe of the thrust plate. A swash plate adjacent to the swash plate, and a valve plate on the side opposite to the thrust plate and in surface contact with the cylinder block.The stroke of the piston is changed according to the tilt angle of the swash plate, and its discharge In a swash plate piston pump configured to control the amount, the thrust plate can swing about a thrust plate swing axis, and the thrust plate swing axis is the tilt axis of the swash plate and the cylinder block. The swash plate piston pump is characterized in that it makes an angle greater than 0 degrees and less than 90 degrees in the opposite direction to the rotation direction of.