JPS629003A - Displacement control device for variable displacement motor - Google Patents

Abstract

PURPOSE:To make it possible to change a rotational speed of a motor easily by changing a set pressure of a fixed power control valve by the use of a pilot pressure from a remote control valve. CONSTITUTION:On one side of the spool 19 of a constant power control valve 18 elastic force of a spring 30 and a supply pressure to a motor 1 are applied and on the other side a pilot pressure from a remote control valve is also applied. For this reason, even if a motor load is constant, an optional rotational speed of the motor can be gotten by controlling the lever 8 of a remote control valve 7 and simultaneously, at the stoppage of the motor, it is possible to change the displacement of the motor to the maximum easily for the next start-up.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a displacement control device for a variable displacement motor in a hydraulic drive control device used for hoisting various cranes and winches, running construction machines, etc.

[Previous technology]

In cranes, winches, etc., load is controlled at high speed and low torque.
By driving at medium speed and medium torque, and low speed and large torque, we aim to improve work efficiency and effectively utilize the horsepower of the prime mover.

This is shown in Fig. 3 in Japanese Unexamined Patent Publication No. 58-32974
To explain this using the device shown in the figure, liquid discharged from the pump 3 is supplied to the variable displacement motor 1 via a flow path 61 or 62 by a directional control valve 60, and is also supplied from a shuttle valve 20 connected to the flow paths 61 and 62. The motor supply pressure is controlled by the eccentricity switching valve 63.
is led to the constant horsepower control valve 64 via the.

In this case, when the eccentric amount switching valve 63 is in position A, the motor supply pressure is guided to the liquid chamber 65 and the liquid chamber 66 communicates with the tank 4, so the constant horsepower control valve 64 is in the position, and the hydraulic cylinder of the eccentric mechanism 67 is As a result of introducing the motor supply pressure to 69 and communicating the hydraulic cylinder 68 to the tank 4, the displacement per revolution of the motor is maximized. When the eccentric amount switching valve 63 is set to position B, the motor supply pressure is introduced to the liquid chamber 66, and the liquid chamber 64 is transferred to the tank 4.
In order to communicate with the tank 4, the constant horsepower control valve 64 assumes position a, and as a result, the motor supply pressure is introduced into the hydraulic cylinder 68 and the hydraulic cylinder 69 is communicated with the tank 4, so that the displacement volume is minimized.

When the eccentricity switching valve 63 is placed in the neutral position, the motor supply pressure is guided to the liquid chambers 66 and 65, and the spring 70 is set to the set spring force. When the pressing force of the pilot piston 71 overcomes this set spring force, the constant horsepower control valve 64 assumes position a, and the displacement per revolution of the motor increases. Accordingly, when the motor rotation speed and motor supply pressure decrease and the pressing force of the virofft piston 71 balances the set spring force of the spring 70, the constant horsepower control valve 64 assumes the neutral position and the hydraulic cylinders 68 and 69 are As a result of pressure locking, the displacement volume remains constant. Furthermore, when the motor supply pressure decreases from this state, the constant horsepower control valve 64 is displaced and the displacement volume decreases. Along with this, the motor rotation speed and the motor supply pressure increase, and the pressing force of the pilot piston 71 is increased by the spring 70.
When balanced with the set spring force, the constant horsepower control valve 64 assumes a neutral position and the displacement becomes constant. If the eccentricity switching valve 63 is set in the neutral position in this manner, the displacement per motor rotation can be obtained in accordance with the motor supply pressure, so that constant horsepower control is possible.

[Problem that the invention seeks to solve]

However, in the conventional device as described above, the constant horsepower control valve 64
If the set spring force is constant and the opposing load pressure is constant, the displacement will not change. Therefore, it is not possible to improve work efficiency by adjusting the motor rotation speed under a constant load. In addition, an eccentric amount switching valve is required to maximize the displacement volume when the hydraulic motor is stopped.

SUMMARY OF THE INVENTION An object of the present invention is to provide a displacement control device for a variable displacement motor that eliminates the above-mentioned drawbacks.

[Means for solving problems]

The structure of the present invention for achieving the above object will be explained using FIG. 1 and FIG. 2 which correspond to embodiments. The constant horsepower control valve 18 counteracts the spring 30 and motor supply pressure with a pilot pressure proportional to the operating angle of the operating lever 8 from the remote control valve 7 via the spool 19, and also controls the pressure per rotation of the variable displacement motor. When the pilot pressure overcomes the spring 30 and motor supply pressure, the displacement decreases,
The volume control cylinder 22 of the variable displacement motor 1 is controlled so that the volume increases when the pressure is lost, and remains constant when balanced.

[For production]

When the operating lever 8 of the remote control valve 7 is operated in the direction of the arrow,
A pilot pressure Pi proportional to the operating angle of the operating lever 8 is applied to the pressure chamber 14 of the directional control valve 2 and the liquid chamber 3 of the constant horsepower control valve 18.
I am guided by 3. As a result, the directional control valve 2 is switched to position A, and the fluid discharged from the pump 3 is supplied to the variable displacement motor 1, and the motor supply pressure is guided to the constant horsepower control valve 18 via the spool 19 to the pilot pressure Pi. to compete with.

The constant horsepower control valve 18 is at position A in the initial stage when the spool pressing force due to the spring 30 and the motor supply pressure overcomes the spool pressing force due to the pilot pressure, and guides the motor supply pressure to the large volume port 47 of the volume control cylinder 22. The displacement per revolution of the variable displacement motor 1 is maximum, and the motor 1 starts slowly. When the spool pressing force caused by the pilot pressure overcomes the spool pressing force caused by the spring 30 and the motor supply pressure, the constant horsepower control valve 18 switches to position B and guides the motor supply pressure to the small capacity boat 50 (thereby reducing the amount of power per revolution of the motor). The displacement volume decreases and the motor 1 is accelerated. When the motor is accelerated to a predetermined speed, the operation lever 8 is
When the operation of the constant horsepower control valve 8 is stopped, the pilot pressure becomes constant, and when the spool pushing force due to this pilot pressure is balanced by the spool pushing force at the other end, the constant horsepower control valve 8 assumes a neutral position, and the displacement per revolution of the motor becomes constant. The motor is driven at a constant speed. When the motor supply pressure changes from this state due to a change in load, the constant horsepower control valve 18 is switched from the neutral position to the functional position, and the displacement of the motor changes. Along with this, the motor rotation speed and the motor supply pressure change, and when the motor supply pressure returns to the pressure before the change, the constant horsepower control valve 18 takes the neutral position again. Therefore, the displacement per rotation of the motor corresponds to the load pressure. That is, constant horsepower characteristics are obtained when the pilot pressure is constant.

Next, if the pilot pressure is changed when the motor supply pressure is constant, the constant horsepower control valve 18 is switched to the functional position, so the displacement per motor rotation changes and the motor rotation speed changes. Therefore, even when the motor supply pressure is constant, any desired motor rotation speed can be obtained using the operating lever 8.

When the operating lever 8 is returned to the neutral position, the pilot pressure becomes zero and the directional control valve 2 assumes the neutral position, so the motor 1 is hydraulically locked and stopped. On the other hand, the constant horsepower control valve 18 is switched to position fiA by the spring 30 and the motor supply pressure, so that the displacement of the motor 1 is maximized.

〔Example〕

Embodiments of the present invention will be described based on the drawings. In FIG. 1, a variable displacement motor 1 is connected to a pump 3 and a tank 4 via a directional valve 2. As shown in FIG. In the illustrated neutral state, the directional switching valve 2 communicates the pump 3 with the tank 4, and blocks the passages 5 and 6 connecting the motor 1 and the directional switching valve 2 by cutting off communication with the pump 3 and the tank 4. There is. The remote control valve 7 consists of an operating raper 8 and variable pressure reducing valves 9 and 10, and the primary boat of the variable pressure reducing valves 9 and 10 is connected to the pump 11.
The secondary port is connected to the fluid chamber 14.15 of the directional valve 2 by a passage 12.13.

Reference numeral 18 denotes a constant horsepower control valve that controls the displacement control cylinder 22 of the variable displacement motor 1, and pilot pressure from the remote control valve 7 led through the shuttle valve 16 and the passage 17 whose primary port is connected to the passage 12.13. A shuttle valve 20 with a primary boat connected to the flow paths 5 and 6, a motor supply pressure led through a passage 21, and a spring 30 are opposed to each other via a spool 19.

A specific example of the configuration of the constant horsepower control valve 18 will be explained with reference to FIG.
, an annular groove 34 and a through hole 35 are formed in the main body 24.
The motor supply pressure from the through hole 21 and the ring groove 52 is guided to the through hole 3.
The pilot piston 36 fitted into the spring bearing is connected to the shaft 2.
The annular grooves 39 and 40 are in contact with the annular grooves 53 and 5 of the main body 24 and are spaced apart from the annular groove 34 by lands 37 and 38.
4, together with the spring chamber 28, constantly communicates with the tank 4 via a passage 41,42. The spring holder attached to one end of the spool 19 is set to a predetermined spring force by a screw 32, and the spring 30 interposed between the seat 27 and the spring holder shaft 29 is tightened with a lock nut 31. The other end of the spool 19 is positioned in a liquid chamber 33 to which pilot pressure from the remote control valve 7 is introduced.

While the spool pressing force caused by the spring 30 and the motor supply pressure overcomes the spool pressing force caused by the pilot pressure, the spool 19 is positioned at the left stroke end as shown in the figure, and the ring grooves 34 and 44 and the ring grooves 40 and 45 are connected to each other. The motor supply pressure from the passage 21 is guided to the large volume port 47 of the volume control cylinder 22 via the annular groove 34, 44 and the passage 46, and the small volume port 50 is connected from the passage 49 to the annular grooves 45, 40, 54, Passage 41
．． It communicates with tank 4 via 42. The balance between the pressing forces at both ends of the spool is lost, causing the spool 19 to move to the right and land 3.
When the annular grooves 44 and 45 are closed at 7.38, the port 47.50 of the volume control cylinder 22 is disconnected from the passage 21 and the tank 4. Moving further to the right, the annular grooves 52 and 45 and the annular grooves 53 and 44 communicate with each other to guide the motor supply pressure from the passage 21 to the small volume port 50 via the passage 49, and to connect the large volume port 47 connected to the passage 46 to the tank 4. It will be communicated to.

Since this embodiment has the above-mentioned configuration, when the operating lever 8 of the remote control valve 7 is operated in the direction of the arrow, the variable pressure reducing valve 9 is operated and the pump 11 and the passage 12 are connected to each other, so that the operating angle of the operating lever 8 is changed. A pilot pressure Pi proportional to is guided to the liquid chamber 14 of the directional control valve 2 and the liquid chamber 33 of the constant horsepower control valve 18.

As a result, the directional control valve 2 is switched to position A, and the liquid discharged from the pump 3 is supplied to the variable displacement motor 1 from the flow path 5, and the motor supply pressure is changed to the shuttle valve 20 and the passage 21.
It is led to the constant horsepower control valve 18 through the. Constant horsepower control valve 18
At the initial stage when the spool pressing force due to the spring 30 and the motor supply pressure overcomes the spool pressing force due to the pilot pressure, the motor supply pressure is guided to the large capacity boat 47 of the capacity control cylinder 22 and the small capacity boat 50 is transferred to the tank. 4, the displacement per revolution of the motor is maximum, and the motor 1 starts slowly.When the spool pressing force caused by the pilot pressure overcomes the spool pressing force caused by the spring 30 and the motor supply pressure, the constant horsepower control valve 18 Switching to position B, the motor supply pressure is guided to the small volume port 50 and the large volume boat 47 is communicated with the tank 4, so the displacement per revolution of the motor is reduced and the motor 1 is accelerated. When the operation of the operating lever 8 is stopped after accelerating the motor to a predetermined speed, the spool pressing force due to the pilot pressure becomes constant, and when this spool pressing force is balanced by the spool pressing force due to the spring 30 and the motor supply pressure, the constant horsepower control valve 18 is activated. is in a neutral position, the displacement of the motor 1 is constant, and the motor is driven at a constant speed. From this state, when the motor supply pressure decreases due to a decrease in load and the constant horsepower control valve 18 switches from the neutral position to position B, the motor supply pressure is introduced to the small volume port 50 and the large volume boat 47 communicates with the tank 4. Therefore, the displacement per rotation of the motor decreases. Along with this, the motor rotation speed and motor supply pressure increase, and when the motor supply pressure returns to the pressure before the decrease, the constant horsepower control valve 1
8 assumes the neutral position again, so the displacement per revolution of the motor corresponds to the motor supply pressure. That is, constant horsepower characteristics are obtained when the pilot pressure is constant.

Next, if the pilot pressure is changed when the motor supply pressure is constant, the pressing force applied to the spool 19 will be unbalanced and the constant horsepower control valve 18 will be switched to the functional position A or B, so the displacement of the motor l will change. The motor rotation speed changes accordingly. Therefore, even when the motor supply pressure is constant, it is possible to obtain an arbitrary motor rotation speed using the operating lever 8.

When the operating lever 8 is returned to the neutral position, the pilot pressure becomes zero, and the directional control valve 2 assumes the neutral position, so the motor 1
is hydraulically locked and stopped, and the constant horsepower control valve 18 is switched to position A by the spring 30 and motor supply pressure, so that the displacement of the remoter 1 is maximized.

〔Effect of the invention〕

As explained above, according to the present invention, since the set pressure of the constant horsepower control valve is made variable by the pilot pressure from the remote control valve, constant horsepower characteristics can be obtained when the pilot pressure is constant, and when the load is constant, However, by operating the lever, you can obtain any desired motor rotation speed, which helps improve work efficiency.

Furthermore, since the displacement volume when the motor is stopped can be maximized without adding a switching valve, costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention, FIG. 2 is a vertical sectional view of a constant horsepower control valve, and FIG. 3 is a hydraulic circuit diagram of a conventional device. 1..Variable displacement motor, 7..Remote control valve, 18..
Constant horsepower control valve, 19... Spool, 22... Volume control cylinder, 30... Spring.

Claims (1)

[Claims] In a displacement control device for a variable displacement motor in which the displacement control cylinder of the variable displacement motor is controlled by a constant horsepower control valve, the constant horsepower control valve controls the spring and motor supply pressure and the pilot pressure from the remote control valve. In addition to opposing each other via the spool, the displacement volume per rotation of the motor decreases when the pilot pressure overcomes the spring and motor supply pressure, increases when the pilot pressure overpowers the spring and motor supply pressure, and maintains a constant volume when balanced. A displacement control device for a variable displacement motor, characterized in that it controls a control cylinder.