JPH1037848A - Axial piston type hydraulic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial piston type hydraulic device of variable displacement type having a simple configuration and a small-size, producing a high output and also showing a high efficiency. SOLUTION: A piston 13 is reciprocated within a cylinder bore 7a of a cylinder block 7 rotated in synchronous with a main shaft 1, thereby a shoe block 12 having a spherical part 13b held at a slant plate 10 through a connecting rod 13a is rotated, seven steel balls 9 held at a cage member 8 slidably installed between an inner circumferential surface 12a if the shoe block 12 provided with an inner circumferential groove 12b and an outer circumferential surface of a bulged-out out 1a of the main shaft 1 having an outer circumferential groove 1b are held between the outer circumferential groove 1b and the inner circumferential groove 12b, thereby constant constant velocity joint mechanism is configured. Rotation of the shoe block 12 is transmitted to the main shaft 1 through steel balls 9, a slant angle of the slant plate 10 is changed to adjust output torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement axial piston type hydraulic device in which the displacement is changed by changing the inclination angle of a swash plate.

[0002]

2. Description of the Related Art Generally, in an axial piston type hydraulic device such as a piston pump or a piston motor in which the direction of reciprocation of a piston is substantially parallel to the center axis of a cylinder block, the drive shaft and the center axis of the cylinder block are the same. The swash plate type, which is not on a straight line, and the swash plate type, in which both axes are on the same straight line, are classified.

[0003] The oblique axis type axial piston type hydraulic device does not apply a radial load between the cylinder block and the piston, is suitable for high pressure and can rotate at high speed with high efficiency. However, the variable capacity type requires a large cylinder block to be tilted, so the size is significantly increased, the variable capacity mechanism becomes complicated and expensive, and the pressure loss in the oil passage increases. It is also disadvantageous in terms of efficiency.

On the other hand, a swash plate type axial piston type hydraulic device tends to be relatively large in a fixed displacement type.
In addition, a radial load acts between the cylinder block and the piston, making it unsuitable for high pressure and high speed rotation and having a large pressure loss as compared with the oblique shaft type. The capacity mechanism is simple and can be produced at low cost.

Conventionally, as a swash plate type axial piston type hydraulic apparatus which has solved the above-mentioned problems to some extent, for example, a so-called jaw type hydraulic apparatus as shown in FIG. 9 is widely known. In this embodiment, a variable displacement pump is formed in the left half and a fixed displacement motor is formed in the right half with the intermediate plate 101 as a boundary. However, the pump or the motor alone may be used. The inclination angle of the swash plate 102A on the pump side is adjusted by control means (not shown), and the discharge direction and the discharge flow rate change with a constant rotation of the input shaft 103, thereby controlling the rotation direction and the rotation speed of the motor output shaft 104. Intermediate plate 1
Both sides 105A and 105B of 01 constitute a valve surface, each valve surface 105A and 105B has two kidney ports, and a supply valve, a relief valve, an air release valve and the like are incorporated in these ports.

[0006] The main power is supplied from the input shaft 103 to the universal joint 106.
A, shoe block 108 via intermediate ring 107A
A to the piston 110 via the rod 109A.
A reciprocates in a cylinder block 111A that is rotationally driven from the input shaft 103 by a pin 112A. Since a single universal joint is used for the universal joint 106A, the shoe block 108A
Instantaneously changes twice per rotation. The pressure fluid discharged from the cylinder block 111A is
1, is introduced into the motor side cylinder block 111B and pushes out the piston 110B, and the shoe block 108B supported by the swash plate 102B, the intermediate ring 107B,
The motor output shaft 104 is rotated via the universal joint 106B. And with such a configuration, no radial load acts between the bore of the cylinder block and the piston,
As a result, the inclination angle of the swash plate can be increased, and a small-sized, large-capacity swash plate type axial piston hydraulic device can be obtained.

[0007]

However, in such a conventional axial piston type hydraulic apparatus, the one on the pump side is described in terms of the pump side. The torque between the intermediate ring 107A and the shoe block 108A is transmitted from the shear pin 113A fixed to the shaft 103 to the intermediate ring 107A, and further by the shear pin (not shown) fixed to the shoe block 108A and orthogonal to the shear pin 113A. Is transmitted. As described above, due to the function of the universal joint, the shaft torque is transmitted through the two pairs of shear pins. The shaft torque is transmitted by the shear force of at most two shear pins, and the shear pins receive the torque. Accordingly, the roller slides while receiving a high surface pressure. Therefore, it is not possible to obtain a large output by increasing the tilt angle of the swash plate to form a large displacement volume (capacity), or by increasing the pressure of the output (input in the case of a motor) hydraulic fluid. It was difficult. The present invention has been made in view of the above points, and has as its object to provide a high-efficiency axial-piston hydraulic device capable of obtaining high output (large capacity / high pressure) with a simple configuration at a low cost. I do.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a cylinder block having a plurality of cylinder bores which rotate together with a main shaft and are substantially parallel to the main shaft on the same circumference; Pistons slidably fitted into the cylinder bores of the block, a shoe block slidably holding the other end of each piston, and changing the angle of the shoe block with the main shaft, A swash plate for changing the stroke of the piston with the rotation of the cylinder block, a variable displacement axial piston type hydraulic device having an arc-shaped cross-section extending in the axial direction formed on the outer peripheral surface of the main shaft. A plurality of outer peripheral grooves, and a cross-sectional arc formed on the inner peripheral surface of the shoe block and extending in the axial direction of the shoe block so as to face the outer peripheral groove, respectively. A constant velocity joint mechanism comprising the same number of inner circumferential grooves, steel balls rotatably held in the respective outer circumferential grooves and inner circumferential grooves, and a cage member for holding the axial position of each steel ball is provided. An axial piston type hydraulic device is provided.

In the above axial piston type hydraulic device, the axial trajectories of the contact points between the outer circumferential groove and the inner circumferential groove and the steel balls may be linear or arcuate, respectively. It doesn't matter.

[0010]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention in a state where a swash plate is in a maximum inclination state, and FIG.
FIG. 4 is a cross-sectional view showing a state where the swash plate inclination angle is zero.

In FIG. 1, a main shaft 1 is attached to a body 4 made up of two members, left and right, via a main shaft bearing 2 and a seal member 3.
Attach freely around. A valve plate 5 having a plano-convex lens shape in cross section is fixed to the left end of the inner surface of the body 4.
A pair of non-illustrated kidney ports for fluid supply and fluid discharge are provided on the same pitch circle.

A fixed shaft 6 is implanted at the left end of the body 4 in FIG. 1 through a valve plate 5 concentrically with the main shaft 1, and a cylinder block 7 is rotatably mounted on the fixed shaft 6. The circumference is divided into seven equal parts on the same pitch circle from the axis X of the cylinder block 7, and seven cylinder bores 7a that can communicate with the kidney port of the valve plate 5 are formed substantially parallel to the axis X. Is spline-coupled to one end of the main shaft 1 to rotate the cylinder block 7 in synchronism with the main shaft 1.

A bulged portion 1a having a spherical outer shape is formed substantially at the center of the main shaft 1 in FIG. 1, and the circumference is divided into seven equal parts on the same pitch circle from the axis X of the outer peripheral surface of the bulged portion 1a. Thus, an outer circumferential groove 1b extending in the axial direction and having an arc-shaped cross section is formed. Bulge 1a
A cage member 8 whose inner surface has the same spherical surface is slidably and slidably contacted with the outer peripheral surface of the cage member, and the circumferential direction of the cage member 8 is divided into seven equal parts to form through holes 8a. 9 is rollably held.

An outer peripheral surface of the cage member 8 is also formed in a spherical shape, and this outer peripheral surface is rotatably mounted via a needle bearing 11 on a swash plate 10 provided to be tiltable in the body 4. 12 and is slidable on the cylindrical inner peripheral surface 12a. The inner circumferential surface 12a of the shoe block 12 has a circumferential surface 7a facing the outer circumferential groove 1b of the bulging portion 1a of the main shaft 1.
At the equally divided positions, there are seven inner circumferential grooves 12b extending in the axial direction of the shoe block 12 and having a circular arc cross section.

The cylinder block 7 of the shoe block 12
As shown in FIG. 2, the surface facing the inner peripheral groove 12b is adjacent to the inner peripheral groove 12b on the same pitch circle outside the pitch circle of the inner peripheral groove 12b.
A spherical hole 12c is formed in an intermediate portion between b and 12b. The piston 13 having the outer peripheral portion slidably mounted on the cylinder bore 7a of the cylinder block 7 in a sealed state in a sealed state forms a spherical portion 13b on the other end side via an integrally formed connecting rod portion 13a, and the spherical portion 13b is formed. It is slidably mounted and held in the spherical hole 12c of the shoe block 12. The piston 13, the connecting rod portion 13a, and the spherical portion 13b have a communication hole (not shown) penetrating in the longitudinal direction in the central shaft portion.

The bulging portion 1a of the main shaft 1 and the outer circumferential groove 1
b, the cage member 8, the steel ball 9, the inner peripheral surface 12a of the shoe block 12, and the inner peripheral groove 12b constitute a bar-field type sliding constant velocity joint mechanism. At this time, spindle 1
The bulging portion 1a and the shoe block 12 constitute the inner ring and the outer ring of the constant velocity joint, respectively. The steel ball 9 and the spindle 1 and the cage member 8 can move freely in the axial direction on the inner peripheral surface 12a of the shoe block 12 integrally. Although FIGS. 1 and 2 do not show the swash plate angle operating means including a hydraulic cylinder or the like, they are all publicly known, and any operating means including an electric motor may be used. .

The axial piston type hydraulic device having the above-described configuration can be used for either a pump or a motor. The operation when the device is used as a piston motor will be described below. When the hydraulic fluid acts on one of the pair of ports of the hydraulic device and the hydraulic fluid is introduced into the cylinder bore 7a of the cylinder block 7 communicating with the port, the piston 13 is pressed in the direction of being pushed out of the cylinder block 7. .

This pressing force is applied to the connecting rod portion 13.
a, a radial load is transmitted along the swash plate 10 to the shoe block 12 via the spherical portion 13b, and generates a radial load as a component force in a direction orthogonal to the axis X of the main shaft 1. The torque becomes the fulcrum, and the torque of the shoe block 12 is transmitted to the main shaft 1 via the steel ball 9 and becomes the output torque of the main shaft 1. At this time, the swash plate 10
The output shaft torque can be varied by changing the angle formed with respect to a plane Y (FIG. 1) orthogonal to the axis X of the main shaft 1.

Here, output shaft torque T (N · m) Port pressure P (Pa) Motor capacity (displacement capacity) V (m ³ / rad) Piston cross-sectional area a (m ² ) Number of pistons n Cylinder block pitch circle D (M) Swash plate angle β (rad)

Then, T = PV (N · m) (1) V = a · D · tan β / 2π (2)

From the above equations (1) and (2), the output shaft torque T increases and decreases in proportion to the port pressure P and the motor capacity V, and the motor capacity V is the cross-sectional area a and the number n of the piston 13 and the cylinder. It can be seen that it increases or decreases in proportion to the pitch circle D of the cylinder bore 7a in the block 7 and the inclination angle β of the swash plate 10.

Next, an example of the specifications of the axial piston type hydraulic device shown in the above embodiment is as follows. Swash plate maximum inclination angle ± 30 ° Number of pistons 7 Piston diameter 20mm Maximum piston stroke 42mm (at β = 30 °) Maximum displacement 92.4cm ³ / rev. Maximum theoretical torque 51.5 kgf · m (at 350 kgf / cm ² ) Maximum output 216 PS (at 350 kgf / cm ² , 3000 rpm)

Here, the bulging portion 1a of the main shaft 1 and the outer circumferential groove 1
b, the cage member 8, the steel ball 9, the inner peripheral surface 12a of the shoe block 12, and the inner peripheral groove 12b will be described with reference to FIGS. 3 (a) and 3 (b) are a longitudinal sectional view and a transverse sectional view showing the configuration of a known fixed type constant velocity joint 20, and are shown on the same pitch circle of the inner ring 21 and the outer ring 22 in the axial direction. A plurality of (six in FIG. 3) outer peripheral grooves 21a extending
And an inner peripheral groove 22a.
The steel balls 24 held by the cage 23 are clamped by a and 22a. The outer peripheral surface of the inner ring 21 and the inner peripheral surface of the outer ring 22 are spherical surfaces having the same center as the pitch circle of the steel balls 24,
Cage 23 having the same spherical surface in the gap between inner and outer rings 21 and 22
Are slidably fitted.

The inner and outer circumferential grooves 21a and 22a are arcuate in the axial direction, and the centers A and B of the respective arcs are shifted from the center O (center of the joint angle) of the pitch circle of the steel balls 24 by the same distance to the left and right. A and B, the shape is expanded in one direction (right direction in FIG. 3) between the inner race 21 and the outer race 22. This expanded shape, as shown in FIG.
At every intersection angle θ between both axes, the steel ball 24 is
And the two halves make the angular velocity of both axes the same, and facilitate the movement of the steel ball 24 when the intersection angle θ between the two axes changes.

FIG. 5 shows the inner and outer peripheral grooves 2 shown in FIG.
FIG. 3 is an enlarged explanatory view showing a holding portion between the steel balls 1a and 22a and the steel balls 24. Each of the grooves 21a and 22a has an elliptical cross section, and the contact between the steel balls 24 and the grooves 21a and 22a. Each of the points 21b, 21b, 22b, and 22b has two points. The torque is applied to the inner ring 21 as indicated by the arrow T.
From the outer ring 22 or from the outer ring 22 to the inner ring 21 via the contact points 21b and 22b.

When the torque is 0, the steel ball 24 and the inner and outer circumferential grooves 2
1a and 22a make point contact at contact points 21b and 22b, respectively, but when torque is applied, the contact points 21b and 22b become elliptical, and the contact ellipse increases as the torque increases. If the inner and outer grooves 21a and 22a are circles having the same radius of curvature as the steel ball 24, even if the torque is small, the contact point between the steel ball 24 and the groove bottom of the inner and outer grooves 21a and 22a is extremely large. An edge load occurs and both contacts are damaged early, resulting in a significant reduction in life.

As described above, when the cross-sectional shapes of the inner and outer peripheral grooves 21a and 22a are made elliptical and the contact points 21b and 22b are located at an effective position, an extremely large torque can be transmitted, and the groove bottom and the groove bottom can be connected. A gap is formed between the steel ball 24 and the lubrication property can be improved.

FIGS. 6 and 7 are longitudinal sectional views showing the structure of the sliding type constant velocity joint 30. FIG. Inner ring 31 and outer ring 3
6, six inner and outer grooves 31a and 32a are provided on the same pitch circle in parallel with each axis.
The torque is transmitted by sandwiching the steel ball 34 held by the cage 33 by a and 32a. The inner peripheral surface of the outer ring 32 is cylindrical, and the outer peripheral surface of the inner ring 31 is spherical.

In this sliding type constant velocity joint, the inner peripheral surface of the outer race 32 is cylindrical and the inner peripheral groove 32 formed in the inner peripheral surface of the outer race 32 is provided.
a, the steel ball 34, the inner race 31 and the cage 3
3 can integrally move the inner peripheral surface of the outer race 32 freely in the axial direction, and can provide an angle and slide in the axial direction. As shown in FIG. It can be positioned on the bisecting plane of the intersection angle θ between both axes, and has extremely high uniformity.

The embodiment of the present invention shown in FIGS. 1 and 2 is based on the principle of the latter sliding type constant velocity joint, and transmits a large torque while taking an arbitrary swash plate inclination angle. And excellent in uniformity.

In the above embodiment, the needle bearing 1 interposed between the swash plate 10 and the shoe block 12 is used.
1 is used to convert the radial force of the shoe block 12 into torque, but it is also possible to obtain the above function with a main shaft bearing 2 that rotatably supports the main shaft 1.
However, in this case, since a very high moment is generated, a spindle bearing that can withstand the moment is required. Since a thrust load acts on the cage member 8 of the constant velocity joint, the constant velocity joint is preferably a fixed type rather than a sliding type.

FIG. 8 shows another embodiment of the present invention in which the sliding type constant velocity joint is changed to a fixed type constant velocity joint. Parts corresponding to FIG. 1 are denoted by the same reference numerals. Is shown. In this embodiment, the needle bearing 11 of the shoe block 12 in FIG.
Is a pair of tapered roller bearings 2A and 2B.

In each of the above embodiments, the bulging portion 1a and the shoe block 12 formed integrally with the main shaft 1 are applied to the inner ring and the outer ring of the constant velocity joint, respectively. It may be integrally fixed to the device. Further, the above-mentioned axial piston type hydraulic device can be used as a piston pump.

[0034]

As described above, the axial piston type hydraulic device according to the present invention is excellent in constant velocity by using a constant velocity joint and is capable of transmitting torque by a large number of steel balls. The transmission torque under the contact surface pressure can be increased, and a small, high-efficiency, high-output hydraulic device can be obtained. Further, since the constant velocity joint used for the hydraulic device has been conventionally used for driving an axle of a front wheel drive automobile, it can be supplied at a low cost.

In the above hydraulic apparatus, if the axial trajectories of the contact points between the outer circumferential groove and the inner circumferential groove and the steel ball are respectively linear, an arbitrary intersection angle between the main shaft and the shoe block is provided. And the relative movement of the two in the axial direction is also possible. If the axial trajectories are each formed in an arc shape, the thrust load generated in the cage of the constant velocity joint can be effectively received.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention in a state where a swash plate is in a maximum inclination state.

FIG. 2 is a cross-sectional view showing the swash plate at a tilt angle of 0;

FIG. 3 is a sectional view showing a configuration of a fixed type constant velocity joint applied to the present invention.

FIG. 4 is a longitudinal sectional view showing the state of crossing the axis.

FIG. 5 is an enlarged sectional view of a main part showing the relationship between the steel balls sandwiched between the outer circumferential groove and the inner circumferential groove and the respective grooves.

FIG. 6 is a longitudinal sectional view showing a configuration of a sliding type constant velocity joint applied to the present invention.

FIG. 7 is a vertical sectional view showing the state of crossing the axis.

FIG. 8 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing an example of a conventional axial piston type hydraulic device.

[Explanation of symbols]

 1: Main shaft 1a: Swelling portion 1b: Outer peripheral groove 4: Body 5: Valve plate 7: Cylinder block 7a: Cylinder bore 8: Cage member 9, 24, 34: Steel ball 10: Swash plate 11: Needle bearing 12: Shoe block 12b: inner circumferential groove 13: piston 23, 33: cage 20: fixed type constant velocity joint 30: sliding type constant velocity joint

Claims (3)

[Claims] A cylinder block provided with a plurality of cylinder bores which rotate together with the main shaft and are substantially parallel to the main shaft on the same circumference, and slidably fitted into the cylinder bores of the cylinder block, respectively. A piston, a shoe block that slidably holds the other end of each piston, and a tilt that changes a stroke of the piston accompanying rotation of the cylinder block by changing an angle between the shoe block and the main shaft. A variable displacement axial piston type hydraulic device having a plate and a plurality of axially extending outer circumferential grooves formed in an outer circumferential surface of the main shaft and having an arc-shaped cross section, and formed in an inner circumferential surface of the shoe block. And the same number of inner circumferential grooves having an arc-shaped cross section extending in the axial direction of the shoe block opposite to the outer circumferential grooves, and freely rolling into each of the outer circumferential grooves and the inner circumferential grooves. And clamping steel balls, axial piston type hydraulic apparatus characterized in that a constant velocity joint mechanism comprising a cage member for holding the axial position of the steel ball. 2. The axial piston type hydraulic device according to claim 1, wherein the axial trajectories of the contact points between the outer circumferential groove and the inner circumferential groove and the steel ball are respectively linear. 3. The axial piston type hydraulic device according to claim 1, wherein the axial trajectories of the contact points between the outer circumferential groove and the inner circumferential groove and the steel ball are each arc-shaped.