JP2000303961A - Absorption control device for variable displacement type axial piston motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts to simplify the constitution to prevent the device from being projected and damaged. SOLUTION: In this device, an annular recessed groove 25 is formed around the circumference of the large diameter end part of a control piston 7 as an absorption control device of a motor 1, a control chamber 27 is formed to be continued to the bore 26 of the control piston, capable of appearing/ disappearing in such a way that the recessed groove is opened/closed, and the device is provided with a counter pressure leading circuit 30 leading the counter pressure of the motor to a tank by a check valve 31, a first throttle 28, and a second throttle 29 sufficiently smaller than the first one. By this constitution, pressure between the first and second throttles is led to the recessed groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption control device for controlling the speed of a variable displacement axial piston motor mainly used for running a vehicle such as a wheel shovel.

[0002]

2. Description of the Related Art Conventionally, a variable displacement axial piston motor has been used for running a wheel shovel or the like, and when the load pressure of the motor is small, the absorption amount of the motor is reduced to reduce the speed (rotational speed). ) Is generally controlled by an absorption amount control device. One specific example is as shown in FIGS. 1 and 2, in which a cylinder block b integrated with an output shaft v of a variable displacement axial piston motor a slides in a bore d formed in a casing c of the motor a. And a control piston g for adjusting the absorption amount of the cylinder block b having the large and small pressure receiving surfaces e and f on which the operating circuit pressure of the motor acts.

As shown in FIG. 3, the operating circuit pressure is led to the large-diameter pressure receiving surface e through an introduction circuit h.
The introduction circuit h is provided with a servo valve k having a spool j having a control surface i on which the operating circuit pressure is applied. A force of a feedback spring m provided on the piston is applied in the same direction as the piston, and the servo valve k introduces the operating circuit pressure into the introduction circuit h and the introduction circuit h
Is connected to the tank s. The movement distance of the control piston g in the direction of the large-diameter pressure receiving surface is limited by the movement control means n composed of a plunger provided to face the large-diameter pressure receiving surface.

The motor a is connected to a variable displacement hydraulic pump (not shown) rotated by a traveling engine via operation circuits o and p with a counter balance valve q interposed therebetween. Is extracted from a shuttle valve r provided between the operation circuits o and p via an extraction circuit t.

When fluid is supplied from the hydraulic pump to the operating circuit o, the counterbalance valve q switches to the position I. In this case, if the operating circuit pressure extracted from the shuttle valve r is large, the spool j of the servo valve k moves by bending the feedback spring m by the operating circuit pressure acting on the control surface i, and the operating circuit pressure is increased. Is introduced into the large-diameter pressure-receiving surface e through the introduction circuit h, so that the control piston g moves so as to increase the absorption amount of the cylinder block b. As a result, the motor a rotates at a low speed. The movement of the piston g stops at a position where the force generated on the control surface i and the force generated on the large-diameter pressure receiving surface e are balanced.

If the extracted operating circuit pressure is small,
The spool j is pushed by the force of the adjusting spring l and moves to the position shown in the figure. Since the introduction circuit h is connected to the tank s, the force generated on the large-diameter pressure receiving surface e disappears, and the control piston g Is moved by the force of the feedback spring m so as to reduce the absorption amount of the cylinder block b.

When the motor a is used for running the vehicle, when the vehicle having a large operating circuit pressure is started, the output shaft v of the motor a rotates at a low speed and a large torque by the control operation of the absorption control device. When the vehicle is accelerated and the operating circuit pressure is reduced, the motor a rotates at high speed and low torque, so that the vehicle speed can be automatically controlled according to the acceleration state. Usually, the output shaft v is connected to a traveling device via a speed reducer w. Further, it is preferable to make the engine brake easy to use at the time of deceleration without affecting during acceleration as a running control. For this purpose, a piston opposed to the large-diameter pressure receiving surface e of the control piston g at an appropriate interval is preferable. And a counter pressure from the counter pressure circuit x is applied to the limiter u to increase the absorption amount of the motor a. As the counter pressure, the pressure generated in the operation circuit by deceleration is used, and in the illustrated example, the pressure generated between the operation circuit p on the outflow side of the motor a and the counter balance valve q is used.
Also, if the limiter u operates when the speed reduction ratio of the speed reducer w is large (at the first speed), the engine brake is too effective and the shock at the time of deceleration of the vehicle is large. ) So that the limiter u operates
An on-off valve y that opens and closes in accordance with the reduction ratio is interposed in the counter pressure introduction circuit x to obtain the rotation characteristics of the output shaft as shown in FIG.

[0008]

In the absorption control device for the motor a, a control piston g is provided with a piston-like retarder stroke limiter u for receiving a counter pressure in order to perform a deceleration control of its rotation. However, there is a disadvantage that the limiter u and a case for accommodating the limiter u are required, the number of parts is large, the assembly is complicated, and the cost increases. In addition, the limiter u needs to be long enough to reliably apply a stroke to the control piston g and strong enough to withstand the counter pressure, and is relatively large. Therefore, the limiter u projects from one side of the casing c. The motor a is generally mounted on the bottom of a vehicle such as a wheel shovel with its output shaft v being horizontal. The motor a is likely to collide with a projection such as irregular terrain because it is close to the ground, and the protruding limiter If u is damaged, it hinders the running of the vehicle, which is not preferable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable displacement axial piston motor absorption control device which has a small number of parts, has a simple structure, does not protrude from the casing, and is not easily damaged.

[0010]

According to the present invention, there is provided a cylinder block of a variable displacement axial piston motor which has a large diameter which slides in a bore formed in a casing of the motor and on which an operating circuit pressure of the motor acts. A control piston connected to a control piston for adjusting the absorption amount of the cylinder block having a small-diameter pressure-receiving surface and having the operating circuit pressure applied to an introduction circuit for guiding the operating circuit pressure to the large-diameter pressure-receiving surface. A servo valve having a spool is provided, and the force of an adjustable adjustment spring is opposed to the force generated on the control surface, and the force of a feedback spring provided on the piston is opposed to the large-diameter pressure receiving surface. On the spool, the servo valve controls the introduction of the operating circuit pressure to the introduction circuit and the connection of the introduction circuit to the tank, and the direction of the large-diameter pressure receiving surface of the control piston In an absorption amount control device provided with a movement control means for controlling a movement distance, an annular concave groove is provided on a peripheral surface of a large-diameter end portion on which a large-diameter pressure receiving surface of the control piston is formed. A control chamber which is continuous with the bore and whose large-diameter end protrudes and retracts to open and close the concave groove is formed, and the counter pressure of the motor is set to a check valve, a first throttle, and a second throttle which is sufficiently smaller than the first throttle. A counter pressure introducing circuit for guiding the tank through the throttle to introduce an intermediate pressure between the first and second throttles into the groove, so that the control piston increases the absorption amount of the axial piston motor; The above object is achieved by moving in the direction of the pressure receiving surface and moving the absorption amount to an intermediate point between the maximum and the minimum, whereby the connection between the concave groove and the control chamber is cut off. It is advantageous to provide an on-off valve in the circuit for introducing counter pressure from the point of extraction of the counter pressure to the groove.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In FIGS. 5 and 6, reference numeral 1 denotes a variable displacement axial piston motor.
A drive plate 4 provided at one end of an output shaft 3 extending inward and outward of the casing 2, a cylinder block 6 in which a plurality of pistons 5 whose heads are fitted to the drive plate 4 protrude and retract, and the cylinder block 6 is connected to the output shaft. A control piston 7 for tilting with respect to 3, a lens-shaped control plate 9 slidable along an arc-shaped groove 8 formed on the inner surface of the casing 2 and in contact with the rear end of the cylinder block 6. The piston 7 and the plate 9 are connected to each other by a pin 10, and the angle between the output shaft 3 and the cylinder block 6, that is, the tilt angle, is changed by moving the piston 7 inside the casing 2. . By changing the tilt angle, the absorption amount of the cylinder block 6, that is, the absorption amount of the motor 1 is changed.

As shown in FIG. 7, a counterbalance valve 15, a directional control valve, a relief valve and other control devices are provided in the cylinder block 6 from a variable displacement hydraulic pump 12 driven by an engine 11 of the vehicle. Operating circuit 1 provided
The working fluid is supplied through one of two ports (not shown) of the control plate 9 connected to 3, 14. The piston 5 is pushed out of the cylinder block 6 by the pressure of the working fluid to rotate the output shaft 3, and the working fluid whose work has been completed returns from the other port to the tank 16 via the working circuit 14.

The control piston 7 has a large-diameter pressure receiving surface 17 and a small-diameter pressure receiving surface 18 on which the operating circuit pressure of the motor 1 extracted via the shuttle valve 37 acts. Introductory circuit 1 that guides operating circuit pressure to surface 17
9 is provided with a servo valve 22 provided with a spool 21 having a control surface 20 on which the operating circuit pressure has acted. Force and a feedback spring 23 provided opposite the large-diameter pressure receiving surface 17 of the piston 7.
To actuate the spool 21 to introduce the operating circuit pressure into the introduction circuit 19 by operating the servo valve 22 or to connect the introduction circuit 19 to the tank 1 via the tank circuit 36.
6 to control the movement of the control piston 7 and the cylinder block 6.
Is controlled.

Although such a configuration also includes a conventional absorption amount control device, in the present invention, a large-diameter pressure receiving surface 17 of the control piston 7 is formed in order to control the absorption amount as required. An annular concave groove 25 is provided around the large-diameter end portion 24, and the large-diameter end portion 24 is continuous with the bore 26 in which the piston 7 slides and has the same area as the cross-sectional area of the large-diameter pressure receiving surface 17. Control chamber 27 in which the groove 25 is opened and closed
Was formed. A counter pressure introducing circuit 30 for guiding the counter pressure of the motor 1 to the tank 16 through a check valve 31, a first throttle 28 and a second throttle 29 having a sufficiently smaller throttle area than the first throttle is provided. The intermediate pressure between the first and second throttles 28 and 29 acts on the large-diameter pressure receiving surface 17. When the control piston 7 moves in the decreasing direction of the absorption amount and the connection between the concave groove 25 and the control chamber 27 is closed, the counter pressure does not enter the control chamber 27 and the control piston 7 stops.

The counter pressure is generated by the counter balance valve 15 in the operation circuit 14 when the fluid from the hydraulic pump 12 is supplied to the operation circuit 13 in FIG.
The counter pressure was guided from the operation circuit 14 to the groove 25 through the check valve 31. An on-off valve 32 is interposed in a counter pressure introducing circuit 30 from the extraction point of the counter pressure of the operation circuit 14 to the control chamber 27, and the output shaft 3 of the motor 1 is connected to a traveling means 34 such as a wheel via a speed reducer 33. When connected, the on-off valve 32 can be opened and closed in conjunction with the selection of the reduction ratio of the speed reducer 33.

The operation of the illustrated embodiment applied to vehicle running will be described. When hydraulic fluid is supplied from the hydraulic pump 12 to the operating circuit 13, the hydraulic motor 1 is rotated to operate from the operating circuit 14 to the tank 16. Fluid returns. The rotation of the hydraulic motor 1 is transmitted to the traveling means 34 via the reduction gear 33, and the vehicle travels. When the vehicle is started or running at low speed, a relatively large operating circuit pressure is generated in the operating circuit 13, and the force generated on the control surface 20 of the servo valve 22 by the action of the operating circuit pressure is larger than the force of the adjustment spring 35. Then, the spool 21 moves to introduce the operating circuit pressure into the introduction circuit 19, and the large-diameter pressure receiving surface 17 of the control piston 7
The working circuit pressure acts on. The operating circuit pressure also acts on the small-diameter pressure receiving surface 18 of the control piston 7, and the control piston 7 increases the absorption amount of the cylinder block 6 by the thrust generated by the area difference between the two pressure receiving surfaces 17, 18. Go to As a result, the motor 1 rotates at low speed and large torque according to the running state of the vehicle. The spool 21 of the servo valve 22 is pushed back to the equilibrium position by the force of the feedback spring 23 transmitting the movement of the control piston 7.

When the operating circuit pressure decreases due to acceleration of the vehicle, the spool 21 of the servo valve 22
5, the introduction circuit 19 is connected to the tank 16, so that the tank pressure acts on the large-diameter pressure receiving surface 17, and the control piston is actuated by the operating circuit pressure acting on the small-diameter pressure receiving surface 18. 7 moves so as to enter the control chamber 27 so as to reduce the absorption amount of the cylinder block 6.
As a result, the motor 1 rotates with high speed and low torque, and the vehicle speed increases.

When the speed reducer of the vehicle is set to the second speed (small reduction ratio), the on-off valve 32 is opened, and preparation is made to guide the counter pressure to the concave groove 25 of the control piston 7.
When the concave groove 25 is open, when the accelerator pedal is released, the flow rate from the hydraulic pump 12 decreases, the pressure of the operation circuit 14 becomes higher than that of the operation circuit 13, and a counter pressure is generated. Since the concave groove 25 is open to the control chamber 25, the counter pressure increases via the check valve 31 to the pressure receiving surface 1 having a large diameter.
7, the control piston 7 is forcibly pushed in a direction to increase the absorption amount, and the concave groove 25 and the control chamber 2
7 stops at the position where it is closed, the absorption amount is halfway between the maximum and the minimum, the absorption torque of the motor 1 increases, and the engine brake becomes easy to use. The aperture 28 is made sufficiently larger than the aperture 29 so as not to prevent the control piston 7 from being pushed in a direction to increase the absorption of the motor 1. When the speed reducer is set to the first speed (large reduction ratio), by closing the on-off valve 32, the counter pressure from the check valve 31 is not introduced into the large-diameter pressure receiving surface 17, so that the forced absorption amount is reduced. Is not increased, and there is no shock due to excessive application of the engine brake at low speed. The relationship between the absorption amount of the motor 1 and the motor inlet pressure is substantially the same as that of the conventional motor shown in FIG.

Large diameter end 24 of the control piston 7
Is formed with an annular concave groove 25 around it, and the check valve 31 and the first and second throttles 28 and 29 are provided in the counter pressure introducing circuit 30. It can be manufactured more easily than the configuration provided, and the length of the device in the direction of the large-diameter end can be shortened so as not to protrude from the casing 2. The inconvenience of colliding with leveling and damage is unlikely to occur.

In a specific example, when the diameter of the large-diameter end portion 24 is set to 28 mm, the diameter of the first diaphragm 28 is set to 1.
By forming the diameter of the second throttle 29 to 4 mm and the diameter of the second throttle 29 to 1 mm, the control piston 7 can be moved to a position in the middle of the stroke at a pressure intermediate to the pressure generated by a normal engine braking operation. There was no problem in the operation of reducing vehicle speed and increasing vehicle speed.

[0021]

As described above, according to the present invention, an annular concave groove is provided on the peripheral surface of the large-diameter end of the control piston constituting the absorption control device for the variable displacement axial piston motor. The first and second throttles are provided in a counter pressure introduction circuit which forms a control chamber which is continuous with the bore and whose large-diameter end protrudes and retracts to open and close the concave groove, and which guides the counter pressure of the motor to the tank. Since an intermediate pressure is introduced into the groove, the piston can be moved to a position where the absorption amount is halfway between the maximum and the minimum with a simple structure that is small and has a small number of parts, and controls the movement of the piston. Since the components to be formed are housed in the casing of the motor to prevent the protrusion to the outside, damage to the control device due to collision with the motor can be prevented, and the control device can be easily assembled at low cost. There is.

[Brief description of the drawings]

FIG. 1 is a cut-away side view of a conventional variable displacement axial piston motor absorption control device.

FIG. 2 is a left side view of FIG. 1;

FIG. 3 is a diagram of a control circuit using the absorption control device of FIG. 1;

FIG. 4 is a diagram showing a relationship between an absorption amount and a motor inlet pressure.

FIG. 5 is a cutaway side view showing an embodiment of the present invention.

FIG. 6 is a right side view of FIG.

FIG. 7 is a diagram of a control circuit using the absorption control device of FIG. 5;

[Explanation of symbols]

1 Variable displacement axial piston pump, 2 casing, 3 output shafts, 5 pistons, 6 cylinder block, 7 control piston, 13/14 operation circuit, 16 tank, 17 large pressure receiving surface, 18 small pressure receiving surface, 19 introduction Circuit, 20 control valve, 21 spool, 22 servo valve, 23 feedback spring, 24 large diameter end, 25 concave groove, 26 bore, 27
Control room, 28 first throttle, 29 second throttle, 30 counter pressure introduction circuit, 31 check valve, 32 on-off valve, 3
5 adjustment spring, 36 tank circuit,

Claims (2)

[Claims] A cylinder block of a variable displacement axial piston motor having a large-diameter and a small-diameter pressure-receiving surface which slides in a bore formed in a casing of the motor, and on which an operating circuit pressure of the motor acts. A control valve for adjusting the absorption amount of the cylinder block is connected, and a servo valve having a spool having a control surface on which the operating circuit pressure is applied is provided in an introduction circuit for guiding the operating circuit pressure to the large-diameter pressure receiving surface. A force of an adjustable spring that is opposed to a force generated on the control surface, and a force of a feedback spring provided on the piston opposed to the large-diameter pressure-receiving surface, acting on the spool; Controlling the introduction of the operating circuit pressure to the introduction circuit and the connection of the introduction circuit to the tank by a servo valve,
In an absorption amount control device provided with a movement control means for controlling a moving distance of the control piston in a direction of a large-diameter pressure receiving surface, a peripheral surface of a large-diameter end portion on which a large-diameter pressure receiving surface of the control piston is formed. An annular concave groove is provided to form a control chamber which is continuous with the bore of the control piston and whose large-diameter end protrudes and retracts to open and close the concave groove. The control pressure of the motor is checked by a check valve and a first throttle. And a counter pressure introducing circuit for guiding the tank through a second throttle, which is sufficiently smaller than the first throttle, to introduce an intermediate pressure between the first and second throttles into the concave groove. A variable displacement, wherein the connection between the groove and the control chamber is interrupted when the piston moves toward the small-diameter pressure receiving surface increasing the absorption of the piston motor and the absorption moves to an intermediate point between the maximum and the minimum. Axial pis Absorption-controlled device Nmota. 2. An absorption amount control device for a variable displacement axial piston motor according to claim 1, wherein an on-off valve is provided in a counter pressure circuit from the extraction point of the counter pressure to the groove.