JPH0792045B2 - 2-speed variable swash plate hydraulic motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable type swash plate type hydraulic motor capable of changing displacement, and more specifically, the swash plate can be tilted about a tilt fulcrum located between the swash plate and an inner wall of a casing. The present invention relates to an improvement of a variable swash plate type hydraulic motor which is disposed in the vehicle and performs variable speed control by tilting the swash plate by a hydraulically driven tilt angle control member.

[0002]

2. Description of the Related Art As those similar to the above, those disclosed in, for example, British Patent No. 1055286 and Japanese Patent Application Publication No. 10784 of 1964 are conventionally known.

Although both of them are swash plate type hydraulic pumps whose disclosure contents are variable, the swash plate is attached to the inner wall of the casing through two balls provided between the swash plate and the inner wall of the casing. The swash plate is arranged so as to be capable of tilting with the line connecting the centers of these balls leaning against it as the tilting fulcrum.

Then, the tilting angle of the swash plate is switched by a hydraulically driven tilting angle control member using hydraulic pressure to change the discharge amount of hydraulic oil (displacement volume in hydraulic motor). It is configured to control.

[0005]

This type of swash plate support structure is simpler than that of a swash plate support structure using a trunnion shaft as disclosed in, for example, Japanese Patent Application Publication No. 122405 of 1979. It is excellent in that it can be configured in a small size, and as a result, the form of the entire hydraulic pump or motor can be downsized.

On the other hand, on the other hand, the swash plate has a structure in which it leans against the inner wall of the casing and is supported, and moreover, it swings around the tilting fulcrum, so that the swash plate lacks stability. There is a face.

In this case, in the case of the hydraulic pump, since the active control operation is to change the amount of hydraulic oil discharged according to the switching operation of the tilt angle of the swash plate, this discharged hydraulic oil is used. Even if there is a certain amount of pulsation, the pulsation is absorbed by the accumulator effect due to the expansion and contraction of the hydraulic oil in the actuator and the expansion and contraction of the piping itself from the hydraulic pump, and is driven by the hydraulic pump. The instability of the swash plate does not matter so much since it has almost no effect on the actuator side.

Instead, the tilt angle of the swash plate can be steplessly switched from the maximum position (maximum discharge amount) to zero (no discharge state) or beyond zero to the opposite direction (reverse discharge state). It is generally desired to do so, and in fact, the conventional example given at the beginning also has such a configuration.

On the other hand, the hydraulic motor receives the pressure hydraulic oil sent from the hydraulic pump, converts it into a rotational force by the swash plate, and adjusts the tilt angle of the swash plate and the amount of supplied oil. It is a device that passively operates by rotating at a rotational speed.

Moreover, if the hydraulic motor is used as a motor for driving a vehicle such as a bulldozer or a shovel dozer, the pressure of the hydraulic oil acting on the hydraulic motor greatly fluctuates due to changes in the vehicle running resistance depending on the working condition.
Depending on the case, a remarkably high pressure often acts on the hydraulic motor due to a reaction applied to the vehicle body.

As a result, if the support of the swash plate is unstable, the tilt angle of the swash plate changes due to these pressure fluctuations and peak pressure, and the displacement volume of the hydraulic motor changes, causing the vehicle to rattle or run left or right. Therefore, there arises a problem that the traveling motor has a difference in rotational speed and impairs the straightness of the vehicle.

From this, in the hydraulic motor, the swash plate can be changed in a large amount from the pressure of the hydraulic oil which fluctuates greatly, as compared with the case where the tilt angle of the swash plate is changed steplessly and the gear shifting operation is continuously performed. How to keep the surface pressure of the swash plate low is a problem in maintaining a stable state and ensuring durability as a hydraulic motor.

In addition to this, when the pressure oil of the hydraulically driven tilt angle control member for changing the tilt angle of the swash plate has run out, the tilt angle of the swash plate is automatically set to the maximum position. It is desired to reduce the rotational speed of the hydraulic motor, that is, the traveling speed of the vehicle by returning to the above, and to take a so-called fail-safe structure for ensuring safety.

Therefore, an object of the present invention is to secure the stability of the swash plate at the tilt angle switching position and to reduce the surface pressure, and to tilt the swash plate when the hydraulic drive type tilt angle control member releases pressure. It is an object of the present invention to provide a two-speed variable swash plate hydraulic motor that can automatically and surely switch the turning angle to the maximum position.

[0015]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide a first rear surface of the swash plate having a different angle of selectively abutting against the inner wall of the casing with the tilt fulcrum as a boundary. The seat surface and the second seat surface are formed symmetrically, and the surfaces of the inner wall of the casing with which the first seat surface and the second seat surface contact each other and the tilting fulcrum of the swash plate are the same. Place it on the level plane.

Moreover, when the first seat surface abuts the inner wall of the casing, the inclination angle of the inclined plane formed on the surface side of the swash plate is large, and the second seat surface is the inner wall of the casing. The angles of the front side inclined plane and the back side first and second seat surfaces of the swash plate are formed so that the inclination angle of the front side inclined plane becomes small when they abut. .

In addition to the above, a hydraulic drive type tilt angle control member for switching the tilt angle of the swash plate is provided on the surface side of the swash plate when hydraulic pressure is applied to the tilt angle control member. The tilt plane of the swash plate is associated with the swash plate so that the tilt angle of the swash plate is small. It is achieved by displacing the action center line of the pressing force on the outer peripheral side of the swash plate so that the action center line of the pressing force always passes through the first sheet surface of the swash plate.

[0018]

In other words, with the above construction, the first seat surface and the second seat surface formed on the back surface side of the swash plate are the surfaces of the inner wall of the casing with which they selectively abut. And the tilting fulcrum of the swash plate are arranged on the same level plane, the entire first or second seat surface inevitably goes to each surface of the inner wall of the casing at each tilting position of the swash plate. It comes into surface contact with and abuts.

As a result, the swash plate is in a low-speed rotation state in which the first seat surface is in contact with the inner wall of the casing by the pressing force from the plunger, and the second swash plate is in the second state by the force of the hydraulically driven tilt angle control member. At each switching position where the seat surface is in contact with the inner wall of the casing in the high-speed rotation state, the first or second seat surface is firmly pressed against the inner wall of the casing while keeping a surface contact state, and positioned in a stable state. To be done.

Not only that, but also in this state, the contact portion of the first or second seat surface on the swash plate side with the inner wall on the casing side inevitably makes surface contact as described above, so that the contact is concerned. The surface pressure at the contact area is also kept low.

Thus, the swash plate type hydraulic motor of this type can be constructed as a two-speed variable type hydraulic motor which is stable in performance and has high durability.

Further, in addition to the above, pressure oil is sent to a hydraulically driven tilt angle control member to keep the tilt angle of the swash plate, that is, the tilt angle of the inclined plane on the surface side of the swash plate small, whereby It is assumed that the tilt angle control member causes a pressure drop accident for some reason while the hydraulic motor is being driven at a high speed.

However, even when such an abnormal situation occurs, the tilting fulcrum of the swash plate is always tilted around the tilting fulcrum due to the positional relationship between the pressing force from the plunger and the tilting fulcrum of the swash plate during operation. Since a moment acts to increase the turning angle,
The swash plate tilts in the direction of increasing the tilt angle while removing the oil in the tilt angle control member.

As a result, the so-called fail-safe effect is achieved in which the hydraulic motor is automatically switched to the low speed rotation state to reduce the traveling speed of the vehicle and to ensure safety.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the preferred embodiments shown in the drawings.

FIG. 1 is a hydraulic circuit diagram when the two-speed variable type swash plate hydraulic motor A according to the present invention is used as a vehicle running motor such as a bulldozer or a shovel dozer.

That is, the hydraulic pump C, which is rotationally driven by the vehicle-mounted engine B, discharges the pressure working oil to the side of the conduit D or the conduit E according to the operating direction of the forward / reverse switching lever (not shown). The pressure hydraulic oil reaches the hydraulic motor A via the pipeline D or E.

The pressure hydraulic oil flowing into the hydraulic motor A drives the hydraulic motor A to rotate in the forward or reverse direction to move the vehicle forward or backward, and then to the hydraulic pump C via the pipeline E or D. Return.

In the above, the two-speed variable type swash plate hydraulic motor A, which is a vehicle traveling motor, has a casing 1, a rotating shaft 2 rotatably supported by the casing 1, and a rotating shaft 2 as shown in FIG. A cylinder block 3 connected to the shaft 2 and a casing 1 facing the cylinder block 3
And the swash plate 4 arranged on the inner wall 1a side.

A valve plate 5 fixed to the casing 1 is disposed on the end surface of the cylinder block 3 on the side opposite to the swash plate 4, and the cylinder block 3 is mounted on the surface of the valve plate 5. It is in sliding contact.

In the casing 1, supply / discharge passages 11 and 12 communicating with the pipes D and E and a control passage 13 separate from them.
And the supply / discharge passages 11 and 12 communicate with the kidney ports 5a and 5b formed in the valve plate 5, respectively, and the control passage 13 has one end on the back side of the swash plate 4. And a control cylinder 14 provided in the inner wall 1a of the casing 1 so as to face the above.

The control cylinder 14 is a hydraulic pump C.
Has a piston 15 that is pushed forward by the pressure oil sent to the control passage 13 through a separate path from a universal shoe 16 provided at the tip of the piston 15.
The one end on the back side of the swash plate 4 is pushed through.

Thus, the control cylinder 14, the piston 15 and the shoe 16 constitute a hydraulically driven tilt angle control member P.

The rotating shaft 2 is rotatably supported by the bearings 20 and 21 provided in the casing 1 so as to penetrate the inner wall 1a of the casing 1 and the swash plate 4 and between the inner wall 1a of the casing 1. The inner space 10 inside the casing 1 is sealed from the outside by a seal 22 interposed in the casing 1.

A joint hole 23 for connecting the input shaft of the speed reducer is formed at one end of the rotary shaft 2.

On the other hand, the cylinder block 3 is arranged in the inner space 10 of the casing 1 and is coupled to the rotary shaft 2 by splines or serrations, and the rotary shaft 2
The rotation of the cylinder block 3 is transmitted to the speed reducer side through.

The cylinder block 3 has a plurality of odd-numbered cylinders (usually an odd number such as 5, 7 or 9).
0 are concentric circles at equal intervals and are bored in the axial direction,
Plunger 31 is slidably inserted into the inside of one end opening of each cylinder 30.

Each of the plungers 31 has a universal shoe 32 at the tip thereof, and is in sliding contact with the surface side of the swash plate 4 via these shoes 32.

Ports 33 are formed in the bottom of the cylinder 30, and these ports 33 are sequentially opened at fixed timings in the kidney ports 5a and 5b of the valve plate 5 as the cylinder block 3 rotates. ,
The inside of the cylinder 30 is selectively communicated with the supply / discharge passages 11 and 12 through these kidney ports 5a and 5b.

The cylinder block 3 presses the cylinder block 3 against the valve plate 5 even when pressure hydraulic oil does not act on the cylinder 30 to prevent the hydraulic oil from leaking between the two as much as possible, and at the same time. , Plunger 3
A pressing device Q for pressing the shoe 32 of No. 1 to the swash plate 4 side to facilitate starting of the hydraulic motor A is provided.

The pressing device Q has a stop ring 34 fitted to the inner wall of the expanded diameter hole of the cylinder block 3 formed between the rotary shaft 2 and the cylinder block 3 through the expanded diameter hole.
A plurality of pins 3 that penetrate through and project slidably
7 and a cap 38 that is interposed between the holding plate 39 that connects the shoes 32 to each other and the pin 37.

Located in the expanded hole, between the stop ring 34 and the pin 37, spring supports 35a and 35b are provided.
The spring 36 is inserted through the
The cylinder block 3 is pressed against the valve plate 5 by the repulsive force of, and the shoe 32 is pressed against the surface side of the swash plate 4 from the pin 37 through the cap body 38 and the holding plate 39.

As shown in FIG. 3, the swash plate 4 has an annular disk shape when viewed from the front, and has a wedge shape when viewed from the side as shown in FIG. It has a shape.

As is apparent from FIG. 2, the shoe 32 provided at the tip of the plunger 31 in the cylinder block 3 is shown.
The surface side of the swash plate 4 facing the is formed as a series of inclined planes 42.

On the other hand, the rear surface side of the swash plate 4 opposite to the inclined flat surface 42 has a first seat surface 40 and a second seat surface 41 which are different in angle of selectively contacting the inner wall 1a of the casing 1. have.

In the case of this embodiment, the swash plate 4 has the tilt fulcrum O as the intersection line of the first and second seat surfaces 40, 41 shown in FIG. As shown in FIG. 2, the swash plate 4 is tiltable with respect to the inner wall 1a of the casing 1 so that the first seat surface 40 and the second seat surface 41 selectively contact the inner wall 1a of the casing 1. It is placed leaning against it.

Thus, according to this embodiment, the swash plate 4 is
The first and second seat surfaces 40, 41 are formed on the back side of the
The tilt fulcrum O is automatically formed during the period 1.

Therefore, not only the shape of the swash plate 4, that is, the angular relationship between the first and second seat surfaces 40, 41 on the rear surface side and the inclined flat surface 42 on the front surface side, but also the first and second seat surfaces The positional relationship between the tilt fulcrums O and 40 and 41 can also be processed easily and accurately.

In order to hold the swash plate 4 at a predetermined position with respect to the inner wall 1a of the casing 1 and to allow only the tilting movement in a predetermined direction, the embodiment is shown in FIG. As can be seen, the swash plate 4 has a pair of left and right hemispherical recesses 43 located at the tilt fulcrum (intersection line) O and centered on a point on the tilt fulcrum O.

As is apparent from FIG. 4, the recess 43 is formed.
Are opposed to a pair of left and right hemispherical recesses (not shown) formed in the inner wall 1a of the casing 1, and the balls 44 are interposed by leaving a slight gap between these recesses. This prevents the rotational movement of the swash plate 4 and at the same time positions the swash plate 4.

As a positioning member using the balls 44, a hemispherical projection or a cylindrical or semi-cylindrical member is provided at a position corresponding to the recess 43 of the swash plate 4, and the other inner wall of the casing 1 is adjacent. A receiving portion corresponding to 1a may be formed to serve as a positioning member.

As shown in FIG. 2, a through hole 45 having an inner diameter larger than the outer diameter of the rotary shaft 2 is bored in the shaft center portion of the swash plate 4, and the bearing 21 and the cap body 38 are formed.
A large-diameter portion 46 and a notch 47 are provided for avoiding interference with the swash plate 4, and the swash plate 4 is supported by the inner wall 1a of the casing 1 so as to be tiltable only.

On the other hand, the first seat surface 40 on the swash plate 4 side
The inner wall 1a of the casing 1 with which the first seat surface 41 and the second seat surface 41 contact each other have the same level with respect to the respective surfaces with which the first and second seat surfaces 40 and 41 contact and the tilt fulcrum O of the swash plate 4. It is formed so as to be arranged on a plane (in this embodiment, the entire surface of the inner wall 1a is formed as a plane as shown in FIG. 2).

As a result, when the swash plate 4 tilts about the tilt fulcrum O, the first and second seat surfaces 4 are moved.
0 and 41 inevitably come into contact with the inner wall 1a of the casing 1 while maintaining a surface contact state, and hold the swash plate 4 in a stable state.

In this state, as described above,
Since the first or second seat surface 40, 41 of the swash plate 4 is in surface contact with the inner wall 1a of the casing 1, the surface pressure of the abutting portion is also kept low.

Thus, according to this embodiment, in combination with the fact that the shape of the swash plate 4 described above can be easily and accurately processed, a highly accurate displacement volume important for the performance of the hydraulic motor is provided. In addition, it becomes possible to obtain a variable type swash plate hydraulic motor with high and low speeds that is highly durable.

An inclined flat surface 42 on the surface side of the swash plate 4
As shown in FIGS. 5 and 6, the first and second seat surfaces 40 and 41 on the rear side and the back surface side of the inclined flat surface 42 when the first seat surface 40 contacts the inner wall 1a of the casing 1. The inclination angle is large, and conversely, when the second seat surface 41 contacts the inner wall 1a of the casing 1, the respective inclination angles are set so that the inclination angle becomes small.

Further, in the hydraulic drive type tilt angle control member P provided on the side of the casing 1, the control cylinder 14 is arranged so as to face the end of the first seat surface 40 of the swash plate 4, When hydraulic pressure is applied to the control cylinder 14, the second seat surface 41 is brought into contact with the inner wall 1a of the casing 1 and the swash plate 4
It is positioned with respect to the swash plate 4 so that the inclination angle of the inclined plane 42 on the surface side of the is kept small.

Moreover, in this state, FIG.
As is clear from FIG. 6 and FIG. 6, with respect to the pressing force F exerted on the swash plate 4 by the plunger 31 at the tilt fulcrum O of the swash plate 4, regardless of the tilt position of the swash plate 4, the action center of the pressing force F is always The line is shifted to the outer peripheral side of the swash plate 4 by a distance b≈b1 from the action center line so that the line passes through the first seat surface 40 of the swash plate 4.

Thus, when hydraulic pressure is not acting on the control cylinder 14 of the tilt angle control member P, the swash plate 4
Shows the shoe 3 on the cylinder block 3 side, as shown in FIG.
The first seat surface 40 is moved to the casing 1 by a rotational moment in the clockwise direction around the tilt fulcrum O due to the pressing force F from the casing 1.
The surface-side inclined flat surface 42 is kept in a state of having a large inclination angle by making surface contact with the inner wall 1a of the above.

On the other hand, when pressure operating oil is sent from the control passage 13 to the control cylinder 14 and the piston 15 is pushed out by overcoming the rotational moment due to the pressing force F from the cylinder block 3 side, the force of this piston 15 The swash plate 4 tilts counterclockwise around the tilt fulcrum O, the first seat surface 40 separates from the inner wall 1a of the casing 1, and this time the second seat surface 41 as shown in FIG.
Makes surface contact with the inner wall 1a of the casing 1 and keeps the inclined plane 42 on the front surface side in a state where the inclination angle is small.

Therefore, the force f from the tilt angle control member P
Between the pressing force F from the cylinder block 3 and “(b /
a) × F <f <{(b + c) / (a + c)} × F ”, the swash plate 4 does not tilt too much with the lower end as a fulcrum, and The second seat surface 41 is stable in a state of being in surface contact with the inner wall 1a of the casing 1.

Next, the operation of the two-speed variable type swash plate hydraulic motor A having the above-described structure according to the embodiment of the present invention will be described.

When pressure hydraulic oil is sent from the hydraulic pump C toward the supply / discharge passage 11 side of the hydraulic motor A, at that time,
The pressure-operated oil is sent into the cylinder 30 of the cylinder block 3 that faces the kidney port 5a of the valve plate 5, and the cylinder 30 is operated by the pressure-operated oil.
The inner plunger 31 is pressed against the inclined flat surface 42 on the surface side of the swash plate 4 to exert a pressing force F on the swash plate 4.

At this time, the pressure hydraulic oil fed into the cylinder 30 leaks through the sliding contact surfaces of the cylinder block 3, the valve plate 5, the swash plate 4, and the shoe 32, and these leaks cause the hydraulic motor A to move. The pressing device Q described above is used so that the engine cannot be started.
Prevents them from leaking.

Thus, the cylinder block 3 starts to rotate about the axis, and the plunger 31 in the cylinder 30 on the side of the valve plate 5 facing the kidney port 5b is pushed by the swash plate 4 while the internal hydraulic oil is removed. The hydraulic motor A is pushed to the side of the supply / discharge passage 12 to start the start.

After this start, as is well known in the prior art in this type of hydraulic motor, the port 33 of each cylinder 30 in the cylinder block 3 has a predetermined timing and the kidney port 5 of the valve plate 5 has a predetermined timing.
The hydraulic motor A continues to rotate in that direction in the same manner as above, while sequentially communicating with a and 5b and repeating the operation of supplying and discharging the hydraulic oil.

The rotation of the cylinder block 3 is transmitted from the rotary shaft 2 integrally connected to the cylinder block 3 to the drive wheels of the vehicle through the reduction gear, and the vehicle is made to travel.

In the above description, if the pressure hydraulic oil from the hydraulic pump C is sent to the supply / discharge passage 12 side of the hydraulic motor A, the pressure hydraulic oil is opposite to the piston 31 of the cylinder block 3 from the previous one. The cylinder block 3 is rotated in the opposite direction to drive the vehicle in the opposite direction, for example, in the backward direction.

When stopping the running vehicle,
From the hydraulic pump C to the supply / discharge passage 11 or 1 of the hydraulic motor A
When the supply of the pressure hydraulic oil to be sent to 2 is cut off, the pressing force F acting on the swash plate 4 from the plunger 31 of the cylinder block 3 disappears, so the rotational force acting on the cylinder block 3 also disappears and the torque of the hydraulic motor A becomes zero. And the vehicle stops.

The above operation is the same when the swash plate 4 is in the state of FIG. 5 or in the state of FIG.

However, the tilt angle control member P with respect to the swash plate 4 is
In the case of FIG. 5 in which the pressure hydraulic oil does not act on, that is,
The first seat surface 40 of the swash plate 4 is the inner wall 1a of the casing 1.
In the state in which the inclined plane 40 is in surface contact with the inclined plane 40, the inclined angle of the inclined plane 40 on the front surface side of the swash plate 4 is large.

Therefore, the stroke length of the plunger 31 in the cylinder block 3 becomes long and the displacement volume of the hydraulic motor A is large, so that the hydraulic motor A is kept in the low speed rotation state.

On the other hand, when pressure oil is sent to the control cylinder 14 of the tilt angle control member P, the piston 15 is pushed out to tilt the swash plate 4 around the tilt fulcrum O, and It stabilizes in the state of FIG. 6 in which the second seat surface 41 of No. 4 is in surface contact with the inner wall 1a of the casing 1.

As a result, the inclination angle of the inclined plane 40 on the surface side of the swash plate 4 is switched to a small state, the stroke length of the plunger 31 is shortened, the displacement of the hydraulic motor A is reduced, and the hydraulic motor A operates at high speed. It will rotate.

In this way, the stroke length of the plunger 31 of the cylinder block 3 is changed by changing the inclination angle of the inclined plane 42 on the surface side of the swash plate 4 in two steps, and the displacement volume of the hydraulic motor A is reduced to two. By changing the number of stages, the rotation speed of the hydraulic motor A changes and the output torque also changes, so that the second speed variable control is performed.

Moreover, in the above high-speed rotation state, if a pressure drop accident occurs in the tilt angle control member P for some reason, and the force pushing the swash plate 4 by the tilt angle control member P disappears, The pressing force F by 31 causes the swash plate 4 to
However, the tilting operation is performed in a direction in which the oil in the control cylinder 14 of the tilting angle control member P is removed and the tilting angle of the tilted flat surface 42 on the front surface side is increased.

Therefore, the hydraulic motor A is automatically switched to a low speed rotation state to reduce the traveling speed of the vehicle, and exhibits a so-called fail-safe effect for ensuring safety.

[0079]

As described above, according to the present invention, the following effects can be exhibited.

The first sheet surface and the second sheet surface formed on the back surface side of the swash plate are at the same level with the respective surfaces of the inner wall of the casing with which they selectively abut and the tilt fulcrum of the swash plate. By simply arranging the swash plate on the plane, the entire surface of the first or second seat surface inevitably comes into surface contact with the inner wall of the casing at the two tilt positions of the swash plate, and the swash plate is always intended. It becomes possible to hold it stably under the condition.

Further, as described above, since the contact portion of the first or second seat surface on the swash plate side with the inner wall on the casing side is inevitably in surface contact, the surface pressure of that portion is kept low. It is possible to improve the durability of the hydraulic motor by preventing wear and fatigue of the abutting portion.

As a result, the swash plate type hydraulic motor having the swash plate structure of this type can be made stable in performance and highly durable, and therefore, it is important for the performance of the hydraulic motor. It becomes possible to obtain a high / low two-speed variable type swash plate hydraulic motor having a displacement of precision.

From this, even if the two-speed variable type swash plate hydraulic motor is used for the left and right drive wheels as a vehicle running hydraulic motor such as a bulldozer or a shovel dozer, the left and right hydraulic motors are pushed away. Since there is no difference in volume, excellent straightness as a vehicle can be obtained.

Further, even when the tilt angle control member causes a pressure drop accident while the hydraulic motor is rotating at a high speed while the tilt angle of the swash plate is kept small by the tilt angle control member, the plunger does not come out. Depending on the positional relationship between the pressing force from the swash plate and the tilt fulcrum of the swash plate and the action direction of the tilt angle control member with respect to the swash plate, the swash plate tilts while removing oil in the tilt angle control member. The tilting operation is performed in the direction of increasing the turning angle, and the hydraulic motor can be automatically switched to the low speed rotation state on the safe side to exhibit the fail-safe effect.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram when a two-speed variable swash plate hydraulic motor according to the present invention is used as a vehicle running motor such as a bulldozer or a shovel dozer.

FIG. 2 is a vertical cross-sectional side view showing only a main part of the hydraulic motor in the above.

FIG. 3 is a rear view of the swash plate showing only the swash plate.

FIG. 4 is a side view of the same swash plate.

FIG. 5 is a side view showing a tilted state of a swash plate.

FIG. 6 is a side view showing a tilted state of the swash plate to the other side.

[Explanation of symbols]

 1 Casing 1a Inner wall of casing 2 Rotating shaft 3 Cylinder block 4 Swash plate 31 Plunger 40 First seat surface formed on the back side of the swash plate 41 Second seat surface formed on the back side of the swash plate 42 Surface of the swash plate The inclined plane formed on the side F The pressing force exerted on the swash plate by the plunger O The tilt fulcrum of the swash plate P The hydraulic drive tilt angle control member

Claims (1)

[Claims] 1. A casing 1, a rotary shaft 2 rotatably supported by the casing, a cylinder block 3 connected to the rotary shaft, a plunger 31 inserted in the cylinder block, and the plunger and the casing.
Swash plate 4 located between the inner wall 1a of the swash plate and tiltable about a tilt fulcrum, and a hydraulic drive type tilt angle control member for switching the tilt angle of the swash plate by hydraulic pressure. In the variable swash plate hydraulic motor composed of P and P, the swash plate is symmetrical with the inclined plane 42 formed on the surface side facing the plunger and the tilt fulcrum O on the back side opposite to the inclined plane. Of the casing having a first seat surface 40 and a second seat surface 41, which are arranged at a different angle and selectively abut against the inner wall of the casing, and in which the first and second seat surfaces abut. with arranging the tilting supporting point of each surface and the swash plate of the inner wall on the same level plane, the inclination angle of the inclined plane of the surface side when the first sheet surface is in surface contact with the inner wall of the casing Largely, the second seat surface is in surface contact with the inner wall of the casing. In this case, the angles of the front side inclined plane and the back side first and second seat surfaces of the swash plate are formed so that the inclination angle of the front side inclined plane is small, and the hydraulic drive is used. The tilt angle control member is arranged so that the tilt angle of the tilt plane on the surface side of the swash plate becomes small when hydraulic pressure is applied to the tilt angle control member, while the tilt angle of the swash plate is changed. rolling the fulcrum to the pressing force F on-flops plunger is in the swash plate
In contrast, the pressing force is always applied regardless of the tilted position of the swash plate.
The action center is so that the core wire passes through the first sheet surface of the swash plate.
A two-speed variable swash plate hydraulic motor characterized in that it is displaced from the line to the outer peripheral side of the swash plate.