JP3092042B2 - Control device for variable displacement axial piston 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 control device for a variable displacement axial piston motor mainly used for running a vehicle.

[0002]

2. Description of the Related Art Conventionally, a variable displacement axial piston motor has been used for running a vehicle such as a wheel loader. When the load pressure of the motor is small, the motor is designed to reduce the absorption of the motor. It is generally controlled by a control device. One specific example is as shown in FIG.
A control piston e having large and small pressure receiving surfaces c and d on which a load pressure of the motor acts is connected to a cylinder block b of a variable displacement axial piston motor a,
The load pressure of the motor is directly introduced into the small-diameter pressure receiving surface d,
In the circuit f for guiding the load pressure to the large-diameter pressure receiving surface c, the force of a feedback spring g provided in connection with the end of the piston e facing the large-diameter pressure receiving surface c is the same as that of the feedback spring g. Valve k with a spool j that moves with the force of an adjustable adjusting spring h acting on the ring and a force generated by an annular control surface i on which the load pressure has been applied opposing these forces.
To control the introduction of load pressure to the large-diameter pressure receiving surface c. The outer diameter of the land portion o of the spool j having the control surface i is formed larger than the outer diameter of the end portion p of the spool j, and the chambers l, m, and n are open to the tank. .

[0003] With this configuration, the spool j of the servo valve k is the resultant force of the force F ₂ of the force F ₁ and the adjusting spring h feedback spring g is acting on the control surface i
Moves to be balanced with the force F ₃ which is generated by the load pressure that either directs the load pressure to the pressure receiving surface c of the large diameter, or to determine whether to connect the receiving surfaces c to the tank. If the load pressure is high and the force F ₃ is larger than該合force, the spool j
Moves to guide the load pressure to the pressure receiving surface c via the circuit f, and the control piston e flexes the feedback spring g to increase the absorption amount of the motor a so that the tilt angle of the cylinder block b is increased. Move to increase. With this movement, the spool j is pushed back, and when the circuit f is closed, the movement of the piston e stops, and the motor rotates at an increased absorption amount, that is, at a low speed, so that the vehicle speed can be reduced. When the load pressure decreases and F ₃ becomes smaller than the resultant force, the spool j connects the circuit f to the tank.
The control piston e moves in the direction of the large-diameter pressure receiving surface c above the drawing due to the load pressure acting on the small-diameter pressure receiving surface d, whereby the tilt angle of the cylinder block b is reduced, and the motor absorption amount is reduced. As the vehicle speed decreases, the vehicle speed increases.

[0004]

When the flow rate supplied to the motor is large, no load pressure is generated when the motor is stopped. Therefore, the tilt angle of the cylinder block b is minimized and the absorption amount is minimized. When starting, the vehicle tries to start at a high speed because the absorption amount is in the minimum state. However, the running resistance is high, so the vehicle does not start in the minimum absorption state, and the load pressure moves the spool j to increase the diameter. To the pressure introduced into the pressure receiving surface c, that is, the tilting start pressure, and the control piston e operates so as to increase the tilting angle before starting. Therefore, there is an inconvenience that a smooth start cannot be performed and a time lag until the start is large.

[0005] Further, since the tilting start pressure is adjusted by setting the force of the adjusting spring h of the spool j, when the flow rate supplied to the motor is small and the running resistance is small, the absorption is reduced. The vehicle travels at a relatively high speed with a minimum amount, and has a drawback that it is not suitable for the purpose when it is desired to run slowly with a small supply flow rate to the motor.

Further, since the pressure on the high pressure side of the inflow port and the outflow port of the motor is generally selected as the load pressure of the motor, the pressure on the high pressure side is used as the load pressure during deceleration. If the selected load pressure is higher than the tilt start pressure, the absorption amount of the motor increases, and it is difficult to decelerate the vehicle smoothly due to excessive braking by the motor.

According to the present invention, when the load pressure of a variable displacement axial piston motor is zero, the amount of absorption of the motor is controlled to the maximum, and the load pressure of the motor decreases and the flow rate supplied to the motor decreases. A first object is to provide a control device that can also reduce the amount of absorption, and a second object is to provide a control device that can smoothly decelerate in addition to this purpose.

[0008]

According to the present invention, the absorption amount of a cylinder block of a variable displacement axial piston motor having large and small pressure receiving surfaces on which a load pressure of the motor acts is adjusted. A control piston connected to the large-diameter pressure receiving surface and a spool having a control surface on which the load pressure is applied.
Servo valve, and an adjustable adjustment spur
A ring of the force, by the action of a force feedback spring provided connected to the pressure receiving surface opposing ends of the large-diameter <br/> in the same direction of the piston, the load pressure of the said servo valve to said circuit In the control device that controls the introduction and connection of the circuit to the tank, the control piston and the cylinder block are reduced in the absorption amount of the cylinder block by the load pressure acting on the large-diameter pressure receiving surface of the control piston. In such a direction as to move in the direction of
Of the adjusting spring and the feedback spring
The control surface so that a force in the same direction as the force is generated.
And the force generated on the control surface by the load pressure
The first object is achieved by forming a pressure control surface on the spool which generates a force in the opposite direction by the action of the pilot pressure . This object is achieved by selecting the higher pressure of the fluid inlet and outlet pressures of the variable displacement type axial piston motor with a high-pressure selection valve such as a shuttle valve or a check valve to obtain the load pressure. The second object can be achieved by extracting the load pressure from the inlet of the variable displacement axial piston motor through a switching valve in accordance with the forward rotation and the reverse rotation of the motor.

[0009]

When the pilot pressure and the load pressure of the motor are zero, the spool of the servo valve is pushed by the force of the adjusting spring, and the large-diameter motor is used. The circuit for guiding the load pressure to the pressure receiving surface is moved so as to connect to the tank, and the control piston is in a state where the cylinder block has been moved to a position where the absorption amount is maximized by the force of the feedback spring. When a certain amount of fluid is supplied from the pump to the motor to start the motor, the motor rotates at a low speed because the absorption amount of the motor is maximum, and the vehicle can be started at a low speed. Thereafter, when a pilot pressure having a pressure superior to the force of the feedback spring and the adjustment spring is applied to the pressure control surface, the spool
The control piston moves so as to introduce a load pressure into the circuit by bending a spring , and the control piston receives the load pressure having a small diameter.
Introduced to the pressure receiving surface with a diameter larger than the force generated by acting on the pressure surface.
Since the force generated by the applied load pressure is larger,
Since the cylinder block is tilted by moving in the direction of decreasing the absorption amount, the rotation speed of the motor increases, and the traveling speed of the vehicle increases. If the load pressure increases after the start of traveling, the force generated on the control surface of the spool increases, and this force
And the total force of each spring is generated on the pressure control surface
When the force exceeds the force, the spool transfers the circuit to the tank.
The control piston moves to connect
Is the force generated on the small-diameter pressure receiving surface to which the load pressure has acted.
Move the cylinder block so that the
Therefore, the traveling speed decreases, and the vehicle travels at a torque corresponding to the load pressure.

[0010] When sudden acceleration, although large flow rate so that rapid load pressure is supplied to the motor is increased, since in this case also initially no load pressure, the position of the spool of the servo valve
No matter where the control piston is
The amount of the cylinder block absorbed by the force of the lock spring
Is moved to the position where
The pilot pressure acts on the pressurization control
The pool receives the large pressure of the control piston from the circuit
Movement to induce a sudden rise in load pressure on the surface
Troll piston maximizes the absorption of the cylinder block
Since there is a moment of time to a minimum from, this
In the meantime, a large torque that overcomes the large running resistance at the start of running is obtained by the motor, and its starting is slowed down. Thereafter, the absorption amount is minimized, and the rotation of the motor becomes high speed, so that the starting is shocking. No, the ride is better.

By changing the pilot pressure acting on the pressurization control surface of the servo valve, the rotation of the motor can be controlled according to the condition of use. For example, if the pilot pressure is reduced when the supply flow rate to the motor is small, the tilt start pressure of the motor is reduced, and the spool pressure is reduced even when the load pressure is low.
Can be moved to connect the circuit to the tank.
Therefore, the operability of the vehicle at low speeds is improved because the amount of absorption of the motor can be increased , and when the supply flow rate is large, increasing the pilot pressure and increasing the tilt start pressure can increase the traveling speed of the vehicle. Can be raised.

When the motor is rotated in the forward or reverse direction, if the load pressure is always selected from the inlet side of the motor by the switching valve,
When the rotation is decelerated, the pressure on the inlet side is reduced, so that the force generated on the control surface of the spool is reduced.
The spool moves to introduce load pressure to the circuit,
The control piston acts on its large-diameter pressure receiving surface
It operates on the side where the absorption amount is reduced by the load pressure. Therefore, the braking force due to the hydraulic pressure during deceleration (the engine braking force via the motor) is reduced, and smooth running can be performed without abrupt engine braking during high-speed running.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described based on an embodiment applied to a variable displacement axial piston motor 1 for traveling of a hydraulic traveling vehicle such as a wheel loader shown in FIG. A plurality of axial pistons 4 each having a head mounted on a driving plate 3 of the cylinder block 5, a control piston 6 for tilting the cylinder block 5 with respect to the output shaft 2, and a motor 1
And a lens-shaped control plate 9 movable along an arc-shaped groove 8 formed in the inner surface of the casing 7 and in contact with the rear end of the cylinder block 5. The piston 6 and the plate 9 The tilt angle between the cylinder block 5 and the output shaft 2 is changed with the movement of the piston 6. The cylinder block 5 has two ports (not shown) formed in the control plate 9 from a hydraulic pump 12 driven by an engine 11.
The axial piston 4 is sequentially pushed out of the cylinder block 5 by the fluid pressure, the output shaft 2 is rotated by the pushing force, and the fluid that has finished the work is supplied from the other port. Rejected to tank 22.

As shown in FIG. 7, the control piston 6 has a large-diameter pressure receiving surface 14 and a small-diameter pressure receiving surface 15 on which the load pressure of the motor 1 acts. 14, a circuit 16 for introducing the load pressure to the large-diameter pressure receiving surface 14.
And a control surface 20 on which the load pressure of the motor 1 acts by receiving the force of the feedback spring 17 provided in connection with the end facing the motor and the force of the adjustable adjustment spring 18 acting in the same direction. A servo valve 21 having a spool 19 is provided .
Circuit 1 from the closed state, that is, the neutral state where the circuit 16 is closed.
Or the circuit 16 introduces a load pressure to 6 tanks 22
Control operation to connect to the control piston 6
And the movement of the cylinder block 5 is controlled to control the tilt angle of the cylinder block 5, that is, the amount of absorption of the motor 1.

[0015] Although this configuration is where also comprises conventional control system, the conventional ones, when the load pressure to the pressure receiving surface 14 of the large diameter does not act, or when no load, the absorption amount of the motor 1 is minimum What Do and the above-mentioned disadvantages, it means that produce defect, in the present invention, the control piston 6 and the cylinder block 5, the load pressure acting on the pressure receiving surface 14 of the large diameter of the control piston 6 in the absorption of the cylinder block 5 and connected so as to move in the direction of the small, the control surface 20 provided on the spool 19 of the servo valve 21, the feedback spring 17 and when this load pressure is applied It provided a force in the same direction as the force of the adjustment spring 18 so that it can generate, the control surface 20
Work of a force in the opposite direction of the force of the pilot pressure generated by the
A pressure control surface 30 generated by use is provided, and the absorption amount is maximized when no load pressure acts on the large-diameter pressure receiving surface 14 or the like. Small pressure receiving surface 15
, The load pressure is constantly acting.

More specifically, the servo valve is connected to the end of the control piston 6 on the side of the small-diameter pressure receiving surface 15 via a feedback spring 17 and a connecting rod 25 with a flange 24 through which a fixed bush 23 is inserted. 21 is brought into contact with one end of a spool 19, and an adjusting spring 18 is interposed between a flange 24 of the connecting rod 25 and a bush 23. The adjusting spring 18 is moved to the bush 23 in the axial direction to perform the adjustment. An adjusting screw 26 for adjusting the spring force of the spring 18 is provided. The servo valve 21 is constituted by three connection ports 27 cylindrical barrel 28 in spool 19 of the stepped inserted through the inside of and its provided with, the spool 19 land portion 19
The outer diameter of the end portion 19b is made larger than that of the end portion 19a so that the shoulder of the end portion 19b becomes the control surface 20, and pressure is applied to the end of the spool 19 facing the feedback spring 17 and the adjustment spring 18. The control surface 30 was formed. A pilot pressure is introduced into the pressurization control surface 30 through a port 35. The pilot pressure may be a known hydraulic pump such as a known hydraulic pump whose pressure increases in accordance with the number of revolutions of the engine 11, for example. By using the pressure from the hydraulic device in which the valve is combined, the pilot pressure can be increased by depressing the accelerator of the vehicle driver. A leak discharge hole 31 extending in the axial direction was formed inside the spool 19, and the discharge hole 31 was connected to a chamber 32 opened to the tank. The chambers 33 and 34 are also opened to the tank.

In the embodiment shown in FIG. 2, when the flow rate is not supplied from the hydraulic pump 12 to the motor 1, or in the no-load operation state where no load pressure is generated even if the flow rate is supplied, the pilot pressure is reduced. The spool 19 of the servo valve 21 is operated by the action or the action of the feedback spring 17.
Connects the circuit 16 to the large-diameter pressure receiving surface 14 through the spool 19.
As a result, the control piston 6 is opened to the small-diameter pressure receiving surface 15, and the control piston 6 is set to the pilot pressure or the feedback.
By the force of the click spring 17 Before moving the cylinder block 5 in a position to maximize the absorption of the motor 1. And this
When the flow rate is supplied from the pump 12 to the motor 1 for running the vehicle in the state described above, the motor 1 rotates at a low speed because the absorption amount is maximum, and the vehicle starts at a low speed. Thereafter, when a pilot pressure having a pressure more predominant than the total force of the feedback spring 17 and the adjustment spring 18 is applied to the pressurization control surface 30, the spool 19 causes the load pressure of the motor 1 to increase to a large diameter of the control piston 6. Of the large-diameter pressure receiving surface 14
The load pressure acts on both the surface 14 and the small-diameter pressure receiving surface 15.
Therefore , the control piston 6 tilts the cylinder block 5 so that the absorption amount of the motor becomes small . So
As a result, the rotation speed of the motor increases, and the traveling speed of the vehicle increases. When the load pressure rises after the start of traveling, the sp
The force generated on the control surface 20 of the tool 19 increases, and this force is
Since the force generated on the pressure control surface 30 is reduced,
19 is a feedback spring 17 and an adjustment spur.
The circuit 16 is moved by the force of the ring 18 to connect the circuit 16 to the tank 22 . As a result , the absorption amount of the motor 1 increases, the traveling speed decreases, and the vehicle travels with a torque corresponding to the load pressure. When the load pressure, the force of the springs 17, 18 and the pilot pressure are balanced, the spool 19
Closes the circuit 16 as shown in FIG. 2 and the vehicle runs at a constant speed.

[0018] During startup of the vehicle, when a large flow rate from the pump 11 to supply to the motor 1, as shown in FIG. 3, but rapidly load pressure is increased, since its activation before no load pressure, scan
The control piste irrespective of the position of the pool 19
6 is the action of pilot pressure or feedback
Moved to maximize the amount of absorption by the action of the pulling 17
When starting, the pilot pressure is increased
0 and the spool 19 as feedback spring 17
And even when moved against the force of the adjusting spring 18,
Since the control piston 6 rises to the load pressure acts on the pressure receiving surface 14 of the larger diameter while the move to minimize the suction yields a state absorption amount is large, while the large running resistance at the start of travel Start with high torque to overcome
Is ensured, then no shocking starting from suction yield rotates at a high speed at the minimum, ride is improved.
On the other hand, in the conventional motor shown in FIG. 1, as shown in FIG. 4 , a large flow rate is supplied when the motor absorption amount is at a minimum, so that the vehicle suddenly starts suddenly, Since the amount is maximized, the acceleration is reduced and the driving state is not suitable for the driver's intention.

By changing the pilot pressure acting on the pressure control surface 30, the cylinder block 5 starts tilting.
Load pressure can be changed. If the pilot pressure is reduced when the number of revolutions of the engine 11 is small and the supply flow rate to the motor is small, the tilt start pressure of the cylinder block 5 of the motor is reduced, and the circuit 16 is operated even if the load pressure is low . N
Move the spool 19 so that it connects to the
Since the amount of absorption of the motor 1 can be increased by the wheel piston 6, the running torque of the vehicle at low speed increases and the operability is improved, and when the engine 11 rotates at a high speed and the supply flow rate is high, the pilot pressure increases. When the tilt start pressure is increased by increasing the vehicle speed, the traveling speed of the vehicle is increased and the riding comfort is improved.

FIG. 5 shows that the higher one of the pressures of the inlet 35 and outlet 36 shown symbolically of the motor 1 is selected as a load pressure by a high-pressure selection valve 37 such as a shuttle valve or a check valve. Thus, even if the motor 1 rotates forward and backward, it is possible to extract the load pressure and control the axial piston motor control device. In addition, according to the forward / reverse rotation of the motor 1, the inlet 35 of the motor 1 is selected by a switching valve 38 which automatically switches and operates with an external pressure as shown in FIG.
By introducing the selected pressure to the control device as the load pressure, the fluid inlet 3 when decelerating the vehicle by loosening the accelerator
I also Do low pressure 5 side, it is the this <br/> to reduce the absorption of the motor 1 of this low pressure during deceleration using a load pressure. Therefore, the hydraulic braking force, that is, the engine braking force by the motor during the deceleration becomes small, and the engine braking does not work too much during high-speed running, so that no jerky movement is generated, and the riding comfort is improved.

[0021]

As described above, according to the present invention, the control piston and the cylinder block of the control device for the variable displacement axial piston motor are driven by the load pressure acting on the large-diameter pressure receiving surface of the control piston. And the control surface of the servo valve that controls the piston, on which the load pressure is applied, generates a force in the same direction as the force of the feedback spring and the adjustment spring. Formed on the spool, and further generated on the spool by the load pressure on the control surface.
Since the force in the direction opposite to the force forms a pressurization control surface generated by the action of the pilot pressure, when there is no load pressure, the absorption amount is maximized and the motor can start rotating at a low speed. When the flow rate supplied to the motor is small and the load is small, the amount of absorption can be increased to rotate at a relatively low speed, control can be performed according to the driver's intention, and sudden start rotation becomes smooth, The responsiveness is also improved, the tilting start pressure of the cylinder block can be arbitrarily changed by changing the pilot pressure, and the rotation state can be changed according to the use state of the motor, which is convenient. According to the configuration, the load can be reliably obtained and the control can be performed. With the configuration of the third aspect, there is an effect that a good deceleration state of the motor can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a conventional example.

FIG. 2 is a cutaway side view of an embodiment of the present invention.

3 shows a diagram of the control characteristics of the device of FIG. 2;

FIG. 4 is a diagram showing control characteristics of the conventional example of FIG. 1;

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

FIG. 6 is a cutaway side view of yet another embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Variable displacement axial piston motor 5 Cylinder block 6 Control piston 10 Pin 12 Hydraulic pump 14 Large-diameter pressure receiving surface 15 Small-diameter pressure receiving surface 16 Circuit 17 Feedback spring 18 Adjusting spring 19 Spool 20 Control surface 21 Servo valve 22 Tank 30 Pressurization Control surface 37 High pressure selection valve 38 Switching valve

Claims (3)

(57) [Claims] 1. A control piston for adjusting an absorption amount of a cylinder block having a large-diameter and a small-diameter pressure-receiving surface on which a load pressure of the motor is applied, is connected to a cylinder block of a variable displacement axial piston motor. In the circuit for guiding the load pressure to the large-diameter pressure receiving surface, the
Providing a servo valve having a spool having
In, and power of adjustable adjusting spring, and a force feedback spring provided connected to the pressure receiving surface opposing ends of the large diameter of the piston to act in the same direction, by the servo valve to the circuit In a control device that controls the introduction of the load pressure and the connection of the circuit to the tank, the control piston and the cylinder block are subjected to the load pressure acting on the large-diameter pressure receiving surface of the control piston to absorb the cylinder block. Are connected so as to move in the direction in which
The adjusting spring and the feed are actuated by the load pressure acting on
The force in the same direction as the force of the dback spring is generated
Forming the control surface on the spool and applying the load pressure
The force in the opposite direction to the force generated on the control surface is
A control device for a variable displacement axial piston motor, wherein a pressurization control surface generated by the action of (1) is formed on the spool. 2. A high-pressure selection valve such as a shuttle valve or a check valve to select a higher one of pressures at a fluid inlet and a fluid outlet of the variable displacement axial piston motor to obtain the load pressure. The control device for a variable displacement axial piston motor according to claim 1, wherein: 3. A variable displacement axial piston according to claim 1, wherein said load pressure is extracted by a switching valve from an inlet of said variable displacement axial piston motor in accordance with normal rotation and reverse rotation of said motor. Control device for piston motor.