JPH0518350A - Capacity control device of variable capacity type axial piston machine - Google Patents

Abstract

PURPOSE:To attempt the simplification of the constitution of an increase/ decrease operation mechanism of the slant angle of a swash plate, the commonalization of parts, the reduction of a contact surface pressure between a connecting arm and an operation piston and the deterioration prevention of the operation piston. CONSTITUTION:Plural pistons 11 are provided respectively in plural cylinder blocks 17 rotating with a shaft 8 in one body. Plural pistons 11 are provided in nearly parallel with the shaft 8 and come in contact with a swash plate 25 by a compression soil spring. In the swash plate 25 which has a slant surface 25a slanting in relation to the axle center of the shaft 8, when the slant surface 25a is used slanting between alpha1 and alpha2 (alpha1>alpha2) in relation to the axial center of the shaft 8, a connecting arm 26 is fixed to the swash plate 25 shifting only an angle of 1/2(alpha1-alpha2) in relation to the normal line of the slant surface 25a of the swash plate 25.

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 pump or motor, and more particularly to a mechanism for increasing / decreasing an inclination angle of a swash plate.

[0002]

2. Description of the Related Art Generally, an axial piston pump or motor has a large load on the swash plate because of its structure, and therefore a large operating force is required to increase or decrease the tilt angle of the swash plate.
Further, there is a problem that the operating mechanism is complicated and the physique becomes large. For this problem, for example,
The mechanism of Japanese Patent No. 1354 has been proposed.

However, this mechanism has the following problems. The operating piston is divided into three parts, and the spherical shape and the connecting pin are used, and the structure is also complicated. The layout space of the operating piston that increases the tilt angle of the swash plate with respect to the connecting arm and the layout space of the operating piston that decreases the tilt angle are asymmetric, and the same parts cannot be used for the operating piston.

If the operation piston is brought into direct contact with both end surfaces of the connecting arm to simplify the structure, the contact surface pressure becomes high, and the operation piston is more likely to be twisted.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and simplifies the configuration of the swash plate tilt angle increasing / decreasing operation mechanism and makes the parts common, and further, An object of the present invention is to provide a displacement control device for a variable displacement axial piston machine, which reduces contact surface pressure between a connecting arm and an operating piston and prevents twisting of the operating piston.

[0006]

A displacement control device for a variable displacement axial piston machine according to the present invention for achieving the above object comprises a shaft, a shaft that rotates integrally with the shaft, and a shaft that surrounds the shaft. A cylinder block having a plurality of cylinders having an axis parallel to the axis, a plurality of pistons slidably fitted in the cylinders, and an inclined surface inclined with respect to the axis of the shaft. A variable displacement axial piston including a swash plate having the swash plate, urging means for urging the plurality of pistons to the inclined surface, and a connecting arm that is connected to the swash plate and changes an inclination angle of the swash plate. In the machine, the inclined surface of the swash plate has inclination angles α ₁ to α ₂ (α ₁
When used at an inclination angle between> α ₂ ), the axis of the connecting arm and the normal to the inclined surface of the swash plate form an angle of 1/2 (α ₁ −
The connecting arm is fixed to the swash plate so as to form α ₂ ).

According to the displacement control device for a variable displacement axial piston machine of the present invention, as will be described later, the movable region of the connecting arm is symmetric with respect to the axial center of the shaft. The range of motion of the operating piston such as the angle increasing side piston and the swash plate angle decreasing side piston can also be symmetrical. Therefore, the same parts can be used for the operation piston and the like.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. 1 and 2 show a first embodiment when the present invention is applied to an axial piston pump. In FIG. 1, a housing 2 of an axial piston pump 1 has a cup-shaped body 3 and a seal member 4 at an opening of the body 3.
And the cover 5 fitted via the
Has an intake port and a discharge port (not shown) provided on opposite sides of the center thereof. An annular valve plate 6 is attached to the surface of the cover 5 on the body 3 side.
Are integrally connected to the cover 5 by pins. The valve plate 6 is also provided with an intake port and a discharge port corresponding to the intake port and the discharge port provided in the cover 5. As will be described later, as the shaft 8 rotates, the plurality of pistons 11 advance and retreat and the piston chamber 12 expands and contracts, which causes fluid to flow from the suction port to the piston chamber 12.
It is sucked in, compressed, and discharged from the discharge port.

The shaft 8 is rotatably supported around its axis by a bearing 14 provided in the opening 13 of the body 3 and a bearing 15 fixed to the cover 5. One end of the shaft 8 projects from the opening 13 of the body 3 and is connected to a rotary drive source (not shown). An oil seal 16 is fitted on the inner side of the body 3 with respect to the bearing 14 of the shaft 8 to prevent the fluid in the housing 2 from flowing out of the opening 13.

The cylinder block 17 is connected to the shaft 8 in the housing 2 by a spline 18,
It rotates integrally with this shaft 8. A plurality of cylinder bores 21 extending parallel to the axis of the shaft 8 are formed in the cylinder block 17, and pistons 11 are slidably accommodated in these cylinder bores 21 to form a piston chamber 12. The piston chamber 12 can communicate with the valve plate 6 and the suction port and the discharge port provided in the cover 5 through the port 22 formed in the cylinder block 17.

A portion of the piston 11 opposite to the piston chamber 12 projects from the cylinder block 17, and a spherical head portion 23 is formed at the tip thereof, and a shoe 24 is rotatably fitted to the spherical head portion 23. Since the elastic force of the compression coil spring 50 is transmitted to the shoe 24 via the plate 51, the pin 52 and the spherical seat 53, the shoe 24 is slidably engaged with the inclined surface 25a of the swash plate 25. When the shaft 8 rotates, the shoe 24 slides on the inclined surface 25a of the swash plate 25 and the piston 1
1 moves forward in the cylinder bore 21 substantially parallel to the shaft 8,
Reciprocate back and forth. At this time, oil is sucked from the suction port (not shown) into the piston chamber 12 in the forward stroke of the piston 11, and is discharged from the piston chamber 12 to the discharge port (not shown) in the backward stroke.

A cylindrical convex surface 25b is formed on the opposite side of the inclined surface 25a of the swash plate 25, and the cylindrical convex surface 25b slidably contacts a cylindrical concave surface 27a provided on the holder 27.
Connection arm 26 fixed to swash plate 25 with bolts 28
Is rotatably fitted to a pin 29 fixed to the body 3. The swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40 are in contact with both side surfaces 26a and 26b of the connecting arm 26 opposite to the swash plate angle increasing side piston 30 and the swash plate angle increasing side piston 30, respectively. The reducing side pistons 40 each have a collar 3
It is slidably fitted into the insides of 1, 41.

Inside the collars 31 and 41, the swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40 are connected.
The compression coil springs 32 and 42 are provided to urge the side surfaces 26a and 26b of the contact member 6 so as to abut. Color 3
O-rings 45 and 46 are provided on the outer circumferences of 1 and 41. The swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40 correspond to the collar inner peripheral walls 31a and 41a according to the pressure oil supplied from the control valve (not shown) into the collars 31 and 41 through the oil passages 33 and 34. The inside of each is moved forward or backward in the direction of the color axis. As the pistons 30 and 40 move forward and backward, the connecting arm 26 swings around the pin 29 as the center of rotation, and the swash plate 25 also swings while sliding along the cylindrical surface, and tilts with respect to the axis of the shaft 8. Change the angle α.

Next, the mounting relationship between the swash plate 25 and the connecting arm 26, which is one of the characteristic features of the present invention, will be described. In FIG. 1, first, the maximum inclination angle of the swash plate 25 is αmax. The connecting arm 26 is fixed to the swash plate 25 by being shifted by αmax / 2 with respect to the normal line of the inclined surface 25a of the swash plate 25.

Here, from the control valve (not shown) to the oil passage 33,
When the pressure oil is supplied into the collars 31 and 41 via 34, the swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40 retreat or advance in the collar axial direction according to the decrease in the pressure oil. To do. The connecting arm 26, which contacts the swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40, rotates about the pin 29 as a fulcrum to reduce the inclination angle of the swash plate 25. Then, the swash plate inclination angle α is reduced from the maximum inclination angle αmax, and the pump capacity is reduced.

Therefore, the swash plate inclination angle α of the swash plate 25 changes within the following range. 0 ≦ α ≦ αmax The angle β of the connecting arm 26 with respect to the axis of the shaft 8 is
It changes in the following range. It changes within the range of −αmax / 2 ≦ β ≦ + αmax / 2. This is because the connecting arm 26 is a swash plate 25.
This is because they are assembled by being shifted by αmax / 2 with respect to the inclined surface 2a.

Therefore, since the movable area of the connecting arm 26 is symmetrical with respect to the axis of the shaft 8, the movable areas of the swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40 are also symmetrical, and the same parts are used. Since it can be used, the collars 31 and 41 can be manufactured by the same part. Next, the contact surface pressure between the connecting arm 26 and the swash plate angle increasing side piston 30 and the swash plate angle decreasing side piston 40, and each piston 3
The twist of 0 and 40 and the collars 31 and 41 will be described with reference to FIG.

Assuming that the inclination angle of the connecting arm 26 is β, the inclination angle β changes in the following range. −αmax / 2 ≦ β ≦ αmax / 2 Here, as shown in FIG. 3, the swash plate angle increasing side piston 30
Let F be the force that urges the connecting arm 26, the force F is
Force F _{1 in} the normal direction to the contact surface and swash plate angle increasing side piston 30
F ₂ which acts laterally against the collar 31
Is decomposed into. F ₁ and F ₂ are expressed as follows.

F ₁ = F / cos β, F ₂ = F · tan β Therefore, when β increases, cos β decreases and F ₁ increases, so that the contact surface pressure increases and tan β increases and F ₂ increases. Is increased, the swash plate angle increasing side piston 30 and the collar 31 are easily twisted. According to this embodiment, the maximum value of F ₁ ,
The maximum value of F ₂ is as follows.

(F ₁ ) max = F / cos αmax / 2, (F ₂ ) max = F · tan αmax / 2 In the conventional configuration, since 0 ≦ β ≦ αmax, the maximum value of F ₁ , F ₂ The maximum value of is _{(F 1) max = F /} cos αmax, hence _{(F 2) max = F ·} tan αmax, in this embodiment, compared with the conventional configuration, the maximum value of F ₁ (F ₁₎ the maximum value of the max and F ₂ Since (F ₂ ) max can be significantly reduced, it is possible to reduce contact surface pressure and prying force between the connecting arm 26 and the swash plate angle increasing side piston 30. It should be noted that the connecting arm 26 and the swash plate angle reducing side piston 40 also similarly have the effect of achieving a reduction in contact surface pressure and a reduction in prying force.

A second embodiment of the present invention is shown in FIG. In the second embodiment, as shown in FIG. 4, the connecting arm 26 is assembled to the swash plate 25 while being shifted by α / 4 with respect to the normal line of the inclined surface. In this example, under actual usage conditions,
This is effective when the pump displacement is changed within the range where the swash plate inclination angle is α / 2 to α. Since the movable region of the connecting arm 26 can be made symmetrical with respect to the axis of the shaft 8 within the range of the inclination angle β of −α / 4 ≦ β ≦ α / 4, the contact surface pressure and the prying force can be reduced.

Generally, the swash plate inclination angle is from α ₁ to α ₂ (α ₁
For pumps used in the range of> α ₂ ), if the connecting arm is attached to the swash plate by shifting the connecting arm by 1/2 (α ₁ −α ₂ ) with respect to the normal to the inclined surface of the swash plate, the connecting arm will be -1/2 (α ₁ -α ₂ ) to 1/2 (α _{1 with} respect to the shaft center
Since it moves symmetrically within the range of −α ₂ ), the same effect as that of the first embodiment can be obtained.

A third embodiment of the present invention is shown in FIGS. In the third embodiment, as shown in FIG. 5, both ends of the swash plate 60 are supported by trunnion support pins 61 and 62, and the swash plate 60 is swung with the pins 61 and 62 as rotation axes. Like the connecting arms 26 of the first and second embodiments, the connecting arm 63 is assembled so as to deviate from the normal line of the inclined surface of the swash plate. FIG. 6 shows the swash plate 60 and the connecting arm 63.

In the above embodiment, the connecting arm and the swash plate are fixed by bolts. However, in the present invention, the connecting arm and the swash plate may be fixed by using a key member or a groove structure. The connecting arm may be integrally cut. In FIGS. 1 to 6, substantially the same components are designated by the same reference numerals.

[0024]

As described above, according to the displacement control device for a variable displacement axial piston machine of the present invention, simplification can be achieved by using common parts in the displacement control mechanism, and the contact surface between the connecting arm and the piston can be simplified. By reducing the pressure and the twisting force between the piston and the collar, it is possible to improve the durability of the capacity control mechanism and the capacity control characteristics.

[Brief description of drawings]

FIG. 1 shows a displacement control device for a variable displacement axial piston machine according to a first embodiment of the present invention.
It is a sectional view taken along the line A.

FIG. 2 is a sectional view showing a displacement control device for a variable displacement axial piston machine according to a first embodiment of the present invention.

FIG. 3 is an explanatory view showing a mounting relationship between a connecting arm and a swash plate angle increasing side piston according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a displacement control device of a variable displacement axial piston machine according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a displacement control device for a variable displacement axial piston machine according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing a swash plate according to a third embodiment of the present invention.

[Explanation of symbols]

 8 shaft 11 piston 17 cylinder block 21 cylinder bore (cylinder) 25 swash plate 25a inclined surface 26 connecting arm 50 compression coil spring (biasing means)

Claims (1)

Claim: What is claimed is: 1. A shaft, and a cylinder block having a plurality of cylinders that rotate integrally with the shaft and that have a shaft center around the shaft and that is parallel to the shaft center. Pistons slidably fitted in the respective cylinders, a swash plate having an inclined surface inclined with respect to the axis of the shaft, and an urging means for urging the plurality of pistons to the inclined surface. And a connecting arm that is connected to the swash plate and that changes an inclination angle of the swash plate, wherein the inclined surface of the swash plate has an inclination angle with respect to a shaft axis. When used at an inclination angle between α ₁ and α ₂ (α ₁ > α ₂ ), the axis of the connecting arm and the normal to the inclined surface of the swash plate form an angle of 1
2. A displacement control device for a variable displacement axial piston machine, wherein the connecting arm is fixed to the swash plate so as to form ½ (α ₁ −α ₂ ).