JPH0333480A - Swash plate type piston motor - Google Patents

Abstract

PURPOSE:To change over the revolving speed to high, medium, and low by forming a plurality of cylinder holes at the inner and outer circumference of a cylinder block, inserting a piston slidable along a fixed swash plate in each cylinder hole, thus forming an inner and an outer cylinder chamber, and supplying pressure oil to the chambers selectively with a selector valve. CONSTITUTION:A plurality of inner cylinder holes 15 are formed at the inner circumference of a cylinder block 14, while outer cylinder holes 16 are provided at the outer circumference, and pistons 17, 19 are inserted therein, and an inner and an outer cylinder chamber 18, 20 are partitioned. These pistons 17, 19 are slidable with shoes 21, 22 on a swash plate 23 fixed at a certain angle. When a selector valve supplies pressure oil to both the inner and outer cylinder chambers 18, 20, the sweep-aside capacity maximizes to put the block 14 into low speed, while the chamber 18 is solely supplied to get a high speed, and only supplying to the chamber 20 generates medium speed. Accordingly the revolving speed of the output shaft 13 can be changed over in three steps only through operation of the selector valve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a swash plate type piston motor used as a travel motor for power shovels, bulldozers, agricultural vehicles, and the like.

[Conventional technology]

A swash plate type piston motor used as a travel motor for a vehicle can change the rotation speed between high and low speeds by changing the swash plate angle in order to change the travel speed.

For example, as shown in FIG. 6, the arc surface 2 of the swash plate 1 can be swung along the cradle 3, and the rocker cam 2 can be swung by the variable piston 4 to change the swash plate angle. By varying the stroke of the piston 7 fitted into the cylinder hole 6 of the cylinder block 5, the rotational speed of the output shaft 8 is switched between high and low speeds.

[Problem to be solved by the invention]

In such a swash plate type piston motor, the stroke of the piston 7 is varied by changing the angle of the swash plate 1, and the rotation speed of the output shaft 8 is changed by increasing or decreasing the displacement for pushing and pushing. , arc surface 2, cradle 3
The need for a member to swingably support the swash plate 1 such as L and the variable piston 4 not only increases the number of parts, making the assembly work troublesome, but also increases the overall size, and the arc surface 2 of the swash plate 1 If the sliding part of the cradle 3 seizes up, the swash plate 1
It becomes impossible to change the angle, and durability deteriorates.

Also, since the angle of the swash plate 1 is changed by the variable piston 4,
The angle of the swash plate 1 is switched between the maximum and minimum angles at the end of the extension stroke and the end of the contraction stroke of the variable piston 4, and it is difficult to stop the swash plate 1 at an angle between the maximum and minimum. Therefore, it is virtually impossible to shift to three speeds: high speed, medium speed, and low speed.

Furthermore, it is necessary to form a plurality of drill hole passages 9 for supplying pressure oil to the variable piston 4, which makes the machining very troublesome.

Therefore, an object of the present invention is to provide a swash plate type piston motor that can solve the above-mentioned problems.

[Means and effects for solving the problem] A plurality of inner and outer cylinder holes are formed on the inner and outer circumferential sides of the cylinder block L, and inner and outer pistons are fitted and pushed into the inner and outer cylinder holes respectively to form inner and outer cylinders. L forming a chamber,
The tips of the inner and outer pistons are slidable along a swash plate fixed to the motor case, and a speed switching valve is provided to control the supply of pressure oil to the inner and outer cylinder chambers,
By supplying pressure oil to both or one of the inner and outer cylinder chambers, the displacement volume is changed, the swash plate angle is kept constant, and the rotational speed of the cylinder block is switched between high speed, medium speed, and low speed. can.

〔Example〕

As shown in FIGS. 1 to 3, the end cover 11 is bolted to the motor case 10, and the output shaft 13 is rotatably supported between the motor housings 12 and L, and between the motor case 10 and the end cover 11. A cylinder block 14 is spline-fitted to this output shaft 13, so that the cylinder block 14 can freely rotate together with the output shaft 13 within the motor housing 12, and the cylinder block 14 has an inner cylinder hole 15 and an outer cylinder hole 16.
As shown in the figure, a plurality of inner cylinder holes 15 are formed at equal intervals on a concentric circle, and each inner cylinder hole 15 is connected to a pair of adjacent outer cylinder holes 1.
The inner and outer cylinder holes are formed between 6゜16 and 15゜1.
6 overlaps in the radial direction and the cylinder block 1
4 can be made smaller.

An inner piston 17 is slidably fitted into each inner cylinder hole 15 to form an inner cylinder chamber 18 L, and an outer piston 19 is slidably fitted into each outer cylinder hole 16 to form an outer cylinder chamber 20. The inner piston shoe 21 provided on the inner piston 17 and the outer piston shoe 22 provided on the outer piston 19 can freely slide along a swash plate 23, and the swash plate 23 is fixed to the motor case 10 at a predetermined angle. It is.

Each inner cylinder chamber 18 is connected to the cylinder block 14.
A substantially arc-shaped inner suction boat 2 is formed on the valve plate 25 and the end cover 11 from the cocoon-shaped inner boat 24.
6 and the inner discharge port 27, and each outer cylinder chamber 20 has two substantially arc-shaped outer suction boats formed on the valve plate 25 and the end cover 11 than the cocoon-shaped outer boat 28 formed on the cylinder block 14. The outer discharge boats 30 are opened alternately.

Brake plates 31 are provided alternately between the motor case 10 and the cylinder block 14, and the brake plates 31 are pressed together with a piston 32 to close the cylinder block 14.
The piston 32 is adapted to brake the spring 3.
3 in the crimping direction, and is moved in the separating direction by pressure oil supplied to the pressure receiving chamber 34, thereby forming the parking brake A.

A valve hole 40 is bored in the end cover 11 as shown in FIG. 3, and a spool 4I is fitted into the valve hole 40 to form a quick-skin switching valve 42 for communicating and blocking the respective ports.

The spool 41 has first to fifth small diameter portions 43° to 435°.
are formed in the valve hole 40, and the first to sixth ports 441 to 44 are formed in the valve hole 40.
6 and a tank boat 45 are formed, and the spool 41 is held at the low speed position shown by the spring 46, and moved to the medium speed position by pilot pressure oil supplied to the first pressure receiving chamber 47, and the second pressure receiving chamber 48. It moves to a high-speed position using pilot pressure oil supplied to the

The first port 441 has the outer suction boat 29, the second boat 442 has four suction boats, the third port 443 has the inner suction port 26, the fourth port 444 has the inner discharge boat 27, the fifth port 445 has the discharge boat 50, The sixth boat 446 is connected to the outer discharge boat 30, and the suction boat 49 and the discharge boat 50 are connected to the first main circuit 51 and the second main circuit 52, as shown in FIG.
The first main circuit 51 and the second main circuit 52 are connected to a variable hydraulic pump.

When the spool 41 is in the low speed position, the outer suction boat 29 and the inner suction boat 26 are connected to the first m2 small diameter portion 4.
31 * 432 communicates with the suction boat 49 L, and the outer discharge boat 30 and the inner discharge boat 27 are connected to the fourth small diameter portion 434
It communicates with the discharge boat 50.

As a result, the discharge pressure oil of the reversible hydraulic pump is transferred to the first main circuit 5.
1 and the inner/outer suction boat via the suction boat 49)26.
29 as well as the inner and outer discharge boats 27.3
0 communicates with the suction side of the reversible hydraulic pump via the discharge boat 50 and the second main circuit 52, so that the inner and outer cylinder chambers 1
Pressure oil is supplied to 8゜20 and the inner and outer pistons 17゜1
9 expands and contracts, so the cylinder block 14 is the output shaft 13
rotates with

At this time, the pressure oil discharged from the hydraulic pump 32 is supplied to the inner and outer cylinder chambers 18 and 20, so the volume of the displacement is maximized, and the amount of oil supplied to one cylinder chamber is the amount of oil discharged from the hydraulic pump 32. , the stroke speed of the inner and outer pistons 17 and 19 becomes slower and the output sleeve 13
has high torque at low speed rotation.

Pilot pressure oil is supplied to the first pressure receiving chamber 47 and the spool 4
2 is the medium speed position M, the two outer suction boats are the first
The small diameter portion 431 communicates with the four suction boats L, the two inner suction boats L communicate with the tank boat 45 through the second small diameter portion 43□, and the inner discharge boat 27 communicates with the tank boat 45 through the third small diameter portion 433. Communication L with two inner suction boats,
The outer suction boat 30 communicates with the discharge boat 50 at a fourth reduced diameter section 434 .

As a result, the discharge pressure oil of the reversible hydraulic pump is transferred to the first main circuit 5.
1. It is supplied to the outer suction boat 29 via the suction boat 49, the outer discharge boat 30 is connected to the suction side of the reversible hydraulic pump via the discharge boat 50 and the second main circuit 52, and the inner suction boat 26 is supplied to the inner discharge boat 27. communicates with the tank side, so pressure oil is supplied only to the outer cylinder chamber 20, the outer piston 19 expands and contracts, and the output shaft 13 rotates together with the cylinder block 14.

At this time, the volume of the push and release becomes smaller than the above, and the output shaft 1
3 has medium torque at medium speed rotation.

Further, when pilot pressure oil is supplied to the second pressure receiving chamber 48, the spool 41 is suppressed to the left and reaches the high speed position H, and the two outer suction boats are connected to the tank boat 45 at the first small diameter section 431.
The inner suction boat 26 communicates with the suction boat 49 L, the inner discharge boat 27 communicates with the discharge boat 50 at the fourth small diameter section 434, and the outer discharge boat 30 communicates with the fifth small diameter section 435.
It communicates with the tank boat 45 and with the outer suction boat 29.

As a result, the discharge pressure oil of the reversible hydraulic pump is transferred to the first main circuit 5.
1. It is supplied to the inner suction boat 29 through four suction boats, and the inner discharge boat 27 is connected to the suction side of the reversible extraction pump via the discharge boat 50 and the second main circuit 52 L, and the outer suction boat 29 and the outer discharge Since the boat 30 communicates with the tank side, pressure oil is supplied only to the inner cylinder chamber 18, the inner piston 17 expands and contracts, and the output shaft 13 rotates together with the cylinder block 14.

At this time, the volume of the displacement becomes smaller than the above, and the output shaft 1
3 has high speed rotation and low torque.

FIG. 5 is a circuit diagram in which a counterbalance valve 60 and a shaft brake switching valve 61 are provided.
When the shaft brake switching valve 6 changes from the neutral position N to the operating position due to the differential pressure between the first main circuit 51 and the second main circuit 52,
1, hydraulic oil is supplied to the oil chamber 34 of the shaft brake A, and the shaft brake A is released.

〔Effect of the invention〕

If the speed selector valve 42 is switched and pressure oil is supplied to the outer cylinder chamber 20 and the inner cylinder chamber 18, the displacement will be maximized, and if the speed selector valve 42 is switched and pressure oil is supplied to the outer cylinder chamber 20, For pushing and removing, the volume will be an intermediate value,
If the speed switching valve 42 is switched to supply pressure oil only to the inner cylinder chamber 18, the volume of displacement will be minimized.

Therefore, the rotational speed of the cylinder block 14 can be switched between high speed, medium speed, and low speed without changing the angle of the swash plate 23, and members that swingably support the swash plate, such as an arcuate portion or a cradle, and the swash plate can be changed. There is no need to provide a variable piston to swing, the number of parts can be reduced, assembly work can be simplified, and the whole can be made compact.

Further, since the swash plate is not rocked by simply switching the speed switching valve 42, durability can be improved.

In addition, instead of changing the displacement by changing the stroke of the piston, the displacement changes the volume by selecting the outer piston and the inner piston, which always reciprocate with a constant stroke. The volume can be changed accurately, improving reliability. When used as a motor for left and right travel, the left and right rotational speeds can be made the same, improving straight-line performance.

In addition, by switching the pressure supply to the outer cylinder chamber and the inner cylinder chamber with the speed switching valve 42, the displacement can be changed in three stages, so the speed can be changed to three speeds: high speed, medium speed, and low speed with a simple operation. Not only is this possible, but the speed difference can be changed by changing the difference between the volume of the outer cylinder chamber and the volume of the inner cylinder chamber, so the speed difference can be set arbitrarily.

Furthermore, since a variable piston is not required, a drilled hole is also not required, making machining easier.

[Brief explanation of drawings]

Figures 1 to 5 show embodiments of the present invention, Figure 1 is a longitudinal sectional view, Figure 2 is a sectional view of the cylinder block, Figure 3 is a sectional view of the end cover, and Figure 4 is the hydraulic pressure. Circuit diagram, Figure 5 is a hydraulic circuit diagram when a counterbalance valve is installed, Figure 6
The figure is a sectional view of a conventional example. 10 is a motor case, 11 is an end cover 13 is an output shaft, 14 is a cylinder block, 15 is an inner cylinder hole, 16 is an outer cylinder hole, 17 is an inner piston, 18
19 is an inner cylinder chamber, 19 is an outer piston, 20 is an outer cylinder chamber, and 42 is a speed switching valve.

Claims (1)

[Claims] An inner cylinder hole 1 is provided on the inner peripheral side of the cylinder block 14.
5, a plurality of outer cylinders 16 are formed on the outer peripheral side, an inner piston 17 is fitted into each inner cylinder hole 15 to form an inner cylinder chamber 18, and an outer piston 19 is fitted into each outer cylinder hole 16. The tips of each of the inner pistons 17 and the tips of each outer piston 19 are slidable along a swash plate 23 fixed to the motor case 10 to form an outer cylinder chamber 20. Speed switching that can be switched to a low speed position L that supplies pressure oil to the outer cylinder chamber 20, a medium speed position M that supplies pressure oil only to the outer cylinder chamber 20, and a high speed position H that supplies pressure oil only to the inner cylinder chamber 18. A swash plate type piston motor characterized by being provided with a valve 42.