JPH06103026B2 - Swash plate piston pump - Google Patents

Description

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

(Prior Art) As a swash plate piston pump, there is one as shown in FIG. 7, for example. In the figure, 1 is a housing, and 2 is a trunnion pin 3 which is axially fixed to a bearing 4 provided in the housing 1.
And is a swash plate that is rotatable around the trunnion pin 3. Reference numeral 6 denotes a cylinder block which is coupled to an input shaft 7 driven by a driving means (not shown) and rotated. A cylinder (not shown) provided in the cylinder block 6 has a shoe 8 at its head. Swash plate 2 through shoe 8
A piston 9 that is in sliding contact with is inserted. Housing 1
The port block 11 is provided with a valve plate 10, and the valve plate 10 is in surface contact with the cylinder block 6.

Then, the swash plate 2 is rotated, the maximum stroke of the piston 9 is adjusted according to the inclination angle, and the discharge amount is controlled.
That is, if the tilt angle is increased, the stroke of the piston 9 is increased, so that the discharge amount is increased, and if the tilt angle is zero (neutral state), the stroke is zero.

This type of swash plate piston pump may be used in a hydrostatic transmission of a vehicle or the like, but in this case, the vehicle can be moved forward by changing the inclination direction of the swash plate.
Controls backward or stop. That is, when the tilt angle of the swash plate is set to 0 degree while keeping the operation lever in the neutral position, the stop function is exerted, and the vehicle is moved forward by tilting from this tilt angle of 0 degree in any direction. Move it backwards. Therefore, when the operation lever is held at the neutral position, a good stopping function cannot be obtained unless the inclination angle of the swash plate is surely 0 degree.

However, if there is only one point on the operation lever for stopping the vehicle, etc., if the point is displaced due to mechanical vibration, etc., or if the driver is inexperienced, the operation lever is surely put in the stop point. It becomes difficult, and there is a problem in safety.

Therefore, when the operating lever is located near the neutral position,
A device that provides a certain amount of play (with play) in the linkage mechanism between the operating lever and the swash plate so that the vehicle etc. can be stopped reliably and uses the self-recovery force generated within that range has been proposed previously. Has been done.

It is generally known that a swash plate piston pump generates a self-returning force that attempts to return to the neutral state when the swash plate reaches near the neutral state. The mechanism will be described with reference to FIGS.

FIG. 8 shows the force relationship when the piston is extended, and FIG. 9 shows the force relationship when the piston is contracted.

The drag force Ft acting on the swash plate is Ft = ApPb−Ff ... (1) at the time of extension and Ft = ApPb + Ff ... (2) at the time of 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 Ff is larger 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, actually, due to the strength and weakness of this drag force, a tilt β in the left-right direction of the swash plate is generated as shown in FIGS. 10 to 12. This inclination angle β is substantially
Since it can be grasped as the tilt angle of the thrust plate, the same description will be made below.

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 Fig. 10, when the tilt angle α >> β of the swash plate, the effect of β can be ignored, and the bottom dead center and 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. 11, when α is reduced (close to the neutral position) and α≈β, the bottom dead center and top dead center of the piston are
Each moves clockwise. 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.

Further, as shown in FIG. 12, when the tilt angle α of the swash plate approaches the vicinity of the neutral position (α≈0), the bottom dead center and the top dead center of the piston move on the X axis, and the left and right half surfaces of the swash plate are moved. The acting piston thrusts become equal, β = 0 following α = 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 approaches 0 °, the influence of the left and right inclination β of the swash plate becomes non-negligible, and the bottom dead center and the 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.

(Problems to be Solved by the Invention) However, in the conventional device as described above, vibration is easily generated in the operation lever and the swash plate due to the provision of backlash, and wear of the linkage mechanism between the operation lever and the swash plate. However, there is a problem in that the control accuracy of the swash plate inclination angle decreases due to the deformation.

Further, 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 where α = 0 ° that there is no discharge condition. Even if the neutral point return moment of is used, difficult lever operation is required.

(Means for Solving Problems) The present invention is directed to a cylinder block that is rotationally driven by an input shaft, a piston that is slidably mounted on the cylinder block, and a thrust member that is slidably contacted with a shoe provided on the piston head. A plate, a swash plate that directly contacts the thrust plate on the opposite side of the piston shoe, and a valve plate that is in surface contact with the cylinder block on the opposite side of the thrust plate. In the swash plate piston pump in which the discharge amount is controlled by controlling the swash plate, the thrust plate is supported with respect to the swash plate through a detent mechanism that restricts rotation around the input shaft. It has a feature in that it can be tilted only in the tilt direction.

(Operation) According to the swash plate piston pump of the present invention, when the operation lever is positioned in the vicinity of the neutral position, the thrust plate causes the relative inclination angle with respect to the cylinder block by the self-returning force of the pump itself to the neutral state. If it is set to 0 degree, the pump is in a neutral state, that is, in a state of no discharge. Then, the thrust plate rotates in the tilting direction of the swash plate within a certain range even if the operating lever is operated near the tilt angle of 0 ° by lever operation, so that so-called play occurs. The non-ejection range becomes large. This non-ejection range can be changed by adjusting the rotation range of the thrust plate with respect to the swash plate. Therefore, since the non-ejection range, that is, the neutral width can be set relatively freely, it is possible to increase the neutral range in the lever operation, the influence due to the vibration of the machine is reduced, and the operator can be surely inexperienced. The discharge amount of the pump can be completely set to 0 and the vehicle or the like can be stopped.

(Embodiment) Hereinafter, the present invention will be described with reference to the drawings. However, the same parts as in the related art will be designated by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described.

1 (a) and 1 (b) show a first embodiment of the present invention, in which 12 is a swash plate, and the swash plate 12 extends through the center of the swash plate 12 in parallel with the trunnion pin 3. Semicircular ridge
13 are provided. A thrust plate 17 is provided on the swash plate 12 so as to face the thrust plate 17.
A recess 18 corresponding to the protrusion 13 is formed in the protrusion 17, and the recess 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 together, a gap 1 is formed between the swash plate 12 and the thrust plate 17. The thrust plate 17 can be rotated within the range. The thrust plate 17 can rotate within the range of the gap 1 as described above, but in consideration of its localization, the thrust plate 17 is provided on the side facing the swash plate 12 in the plurality of spring holes 20 provided in the swash plate 12. The urging force of the compressed spring 21 is applied. The biasing force of the spring 21 can be freely adjusted by the set length adjusting screw 22.

In this first embodiment, the ridge 13 is formed on the swash plate 12 side,
Although the recess 18 is formed on the thrust plate 17 side, it goes without saying that they may be reversed. Further, a connector may be fixed to either the swash plate 12 or the thrust plate 17 and a recess corresponding to this connector may be formed on the other one. In short, any structure may be used as long as the thrust plate 17 can rotate in the tilt direction.

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, if a detent mechanism around the axis is installed so as not to prevent the thrust plate from moving in the tilting direction, only the protrusion is provided on either the thrust plate or the swash plate in a direction parallel to the axis of the trunnion pin 3. It may be provided in the. The second embodiment of FIG. 2 is a specific example of this.
In FIG. 2, 24 is a swash plate, 25 is a thrust plate, and 25
Reference numeral a denotes a protrusion provided on the thrust plate 25, and reference numeral 26 denotes a steel ball provided between the swash plate 24 and the thrust plate 25 as a mechanism for preventing the axial rotation of the thrust plate 25.

The third embodiment shown in FIG. 3 is a swash plate 27 and a thrust plate.
A gap l is provided between the thrust plate 28 and the trunnion pins 29 on both ends of the thrust plate 28, and a bearing 30 is provided on the swash plate 27. The bearing 30 holds the thrust plate 28 rotatably. Is.

The fourth embodiment shown in FIGS. 4 (a), (b) and (c) is
Four piston holes are symmetrically located on the swash plate 32 with respect to its center.
A pressing piston 34 is slidably fitted in the hole 33 while forming 33. Then, a biasing force of a spring 36 that can be adjusted by an adjusting screw 35 is applied to the pressing piston 34, and the hydraulic pressure by the piston 9 provided in the cylinder block 6 is applied to the housing 1 and the swash plate 32. The pressure piston 34 is acted on via the passage 37.

In the fourth embodiment, the facing surface of the thrust plate 38, which faces the swash plate 32, is composed of two flat surfaces protruding from the end portion toward the central portion as shown in the figure.
The same function as the protrusion 13 of the embodiment is achieved. And
In the fourth embodiment, the hydraulic pressure acts on the pressing piston 34 to press the thrust plate 38, so that the thrust plate 38 can maintain its orientation, and the pressing force causes a sliding contact force between the swash plate 32 and the thrust plate 38. The load on the bearing can be reduced.

In addition, in order to apply a pressing force to the thrust plate 38, various methods other than the pressing piston 34 are conceivable, but any method is acceptable as long as it can offset the hydraulic thrust of the piston 9. . For example, thrust plate
A pressing piston may be provided on the 38 side and the thrust plate 38 may be pressed by the action of the pressure supplied from the swash plate 32 side. Also, the number of pistons can be appropriately determined.

In the fifth embodiment shown in FIG. 5, a pair of piston holes 33 are formed in the swash plate 42 at vertically symmetrical positions with respect to the center thereof, and the pressing piston 34 is slidably fitted in the holes 33. It is a thing. This embodiment is basically the same as the above-mentioned fourth embodiment, but both are adjusted so that the fluid pressure supplied to the pressing piston 34 becomes the average value of the pressures of the suction and discharge ports 45, 46 of this pump. Ports 45 and 46 with two identical apertures 47
The channel 48 is provided so as to communicate with the channel 37. As a result, the hydraulic thrust of the piston 9 can be canceled and the moment balance in the inclination direction due to the hydraulic thrust of the pressing piston 34 can be achieved.

The sixth embodiment shown in FIGS. 6 (a), (b) and (c) is
The swash plate 52 is provided with a pair of spring holes 20 at vertically symmetrical positions with respect to the center thereof, and the localization adjusting springs 21 of the thrust plate 53 are contracted in the holes 20, and And a pair of piston holes 33 are provided at symmetrical positions, and a pressing piston 34 is provided in this hole 33.

In any case, in the fourth, fifth and sixth embodiments, the thrust plates 38 and 53 are pushed by the pushing piston 34, but the effective area of the pushing piston 34 is reduced and the spring
The spring force of 36 may be increased to bear a part of the hydraulic pressure on the pressing piston 34.

Further, although the swash plate shown in each of the above embodiments is a trunnion type, it may be a swash plate of any shape such as a half-moon swash plate.

(Effects of the Invention) As described above, according to the present invention, in the swash plate piston pump that changes the stroke of the piston according to the inclination angle of the swash plate to control the discharge amount, a thrust plate is provided on the swash plate. Since the swash plate is provided so as to be rotatable in the tilt direction, if the operating lever is positioned near the neutral position, the thrust plate will move relative to the cylinder block by the self-returning force of the pump itself to the neutral state. If it is set to 0 degree, the pump is in a neutral state, that is, in a state of no discharge. This non-ejection range can be changed by adjusting the rotation range of the thrust plate with respect to the swash plate.
Therefore, since the non-ejection range, that is, the neutral width can be set relatively freely, it is possible to increase the neutral range in the lever operation, the influence due to the vibration of the machine is reduced, and the operator can be surely inexperienced. It is possible to stop the vehicle by completely setting the discharge amount of the pump to zero. Further, when the detent mechanism is used to maintain the neutral position, the detent mechanism can be sufficiently used even if the accuracy of the neutral position is lower than the conventional one, and the zero point adjustment becomes very easy. Furthermore, since the thrust plate is installed in an environment filled with hydraulic oil in the pump case, a damping effect occurs, vibration of the swash plate and lever is greatly reduced, and the tilt angle of the swash plate due to wear and deformation is reduced. Various effects are obtained such that the influence on the control accuracy is significantly reduced.

[Brief description of drawings]

1 to 6 show the respective embodiments of the swash plate piston pump according to the present invention, and FIG. 1 (a) is a partially cutaway front view of the main part of the first embodiment, (b) ) Is the front view of the swash plate,
FIG. 2 is a front sectional view of the main part of the second embodiment, FIG. 3 is a partially cutaway front view of the main part of the third embodiment, and FIG. 4 shows the fourth embodiment. ) Is a partial sectional plan view,
(B) is a partially cutaway front view of a main part, (c) is a front view of a swash plate, FIG. 5 is a partially sectional plan view of a fifth embodiment, and FIG. 6 shows a sixth embodiment. Here, (a) is a partial sectional plan view, (b) is a partially cutaway front view of a main part, (c) is a front view of a swash plate, and FIG. 7 is a conventional swash plate piston pump. 8 and 9 are explanatory views of the swash plate drag force, FIGS. 10 to 12 are explanatory views of the neutral point return moment generating mechanism, and FIG. 10A is a front view of the swash plate. (B) is a plan view,
(C) is a side view. 9 ... Piston, 12, 24, 27, 32, 42, 52 ... Swash plate, 17, 25, 28, 38, 53 ... Thrust plate.

Claims (1)

[Claims] 1. A cylinder block rotatably driven by an input shaft, a piston slidably mounted on the cylinder block, a thrust plate on which a shoe provided on the piston head is in sliding contact, and an opposite side of the piston shoe. The swash plate that directly contacts the thrust plate and the valve plate that is in surface contact with the cylinder block on the opposite side of the thrust plate are provided, and the discharge amount can be varied by controlling the tilt angle of the swash plate. In the swash plate piston pump described above, the thrust plate is supported with respect to the swash plate via a rotation stop mechanism that restricts rotation around the input shaft, and the thrust plate can be tilted only in the tilt direction of the swash plate. A swash plate piston pump that is characterized.