JPH0440581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a brake control circuit for a hydraulic motor equipped with a negative mechanical brake.

(Conventional Control Circuit) The conventional control circuit shown in FIG. 1 guides the pressure of the pump 1 to the mechanical brake 2 so that the mechanical brake maintains a released state when the motor 3 is driven.

That is, if the directional control valve 4 is switched from the illustrated state to either the left or right position, for example, to the left side position in the drawing, the pressure oil from the pump 1 acts on the counterbalance valve 5 as pilot pressure, causing the counterbalance valve 5 to move as shown in the drawing. Switch to left position.

When the counterbalance valve 5 is switched as described above, oil from the pump flows into the motor 3 through one of the main passages 6, and also flows into the mechanical brake 2 through the brake passage 7, and the oil flows into the mechanical brake 2 through the brake passage 7. 2 is maintained in the released state.

At the same time, the return oil from the motor 3 returns to the tank 9 through the other main passage 8, so the motor 3 is driven.

When the directional control valve 4 is switched from the above state to the neutral position shown, communication between the main passages 6, 8 and the directional control valve 4 is cut off. At this time, since the motor 3 acts as a pump due to inertia, the return side, that is, the main passage 8 side, becomes high pressure.

This high-pressure oil is flowed into the main passage 6 through the relief valve 11, which converts the inertial energy of the motor into thermal energy and applies a brake to the motor.

The brake is applied to the motor as described above, but the mechanical brake 2 is also brought into communication with the tank 10 at the same time as the counterbalance valve is returned to the neutral position.

When the mechanical brake communicates with the tank as described above, the force of the spring 12 acts on the mechanical brake.

(Problems to be Solved by the Invention) In the conventional control circuit described above, the mechanical brake also operates at the same time as the relief operation of the brake valve.

If the mechanical brake is activated at the same time as the relief operation, the motor will not stop smoothly, such as when the inertial load on the motor is large, resulting in a poor feeling for the operator.

In addition to the problem of feeling, there were also problems such as impairing the durability of the mechanical brake.

The object of the present invention is to provide a control circuit that eliminates the above-mentioned conventional drawbacks by preventing the mechanical brake from operating during the relief operation.

(Means for Solving the Problems) The present invention includes: a directional switching valve that switches the flow path of oil discharged from a pump; a counterbalance valve that communicates with the directional switching valve via a first main passage;
a motor that communicates with the counterbalance valve via a second main passage; a crossover main relief valve that short-circuits the second main passage;
This is based on a brake control circuit for a hydraulic motor equipped with a mechanical brake that applies a brake when the motor is stopped.

A brake passage that communicates with the mechanical brake, a first branch passage that communicates the upstream side of the counterbalance valve with the brake passage, and a first branch passage that allows only flow from the first main passage to the brake passage. check valve and
A second branch passage connecting the downstream side of the counterbalance valve and the brake passage, and a second branch passage provided in this second branch passage, and when the pressure in the second branch passage exceeds the set pressure, the pressure oil is directed to the brake passage side. The brake control valve is characterized in that it includes a sub-relief valve that allows water to flow out, and a brake control valve that is connected to the brake passage and connects the brake passage to the tank when the pressure in the brake passage becomes below a certain level.

(Operation of the present invention) Since the present invention is configured as described above, when the directional control valve is switched to drive the motor, the counterbalance valve is also switched to supply pressure oil to the motor. At this time, pressure oil is also supplied to the mechanical brake, and the brake is released.

When the directional control valve is returned to the neutral position from this state, the counterbalance valve also returns to the neutral position, and the inertial energy of the motor is converted into thermal energy by the action of the main relief valve, and the brake is applied.

When the pressure in the second main passage when the brake is activated is equal to or higher than the set pressure of the sub-relief valve, the pressure oil in the passage is supplied to the mechanical brake, so the brake remains open.
Then, when the pressure in the second main passage becomes equal to or lower than the set pressure of the sub-relief valve, the sub-relief valve is closed, the brake control valve is switched, and the mechanical brake is opened to the tank.

(Effects of the Present Invention) According to the control circuit of the present invention, the mechanical brake does not operate unless the circuit pressure becomes equal to or lower than the set pressure of the sub-relief valve as described above. In other words, the mechanical brake will not operate unless the motor is braked to a certain extent, which solves problems such as poor feeling for the operator.

Moreover, since the pressure oil supplied to the mechanical brake is controlled by the sub-relief valve, its pressure becomes stable.

Moreover, the durability of the mechanical brake is not impaired.

(Embodiment of the present invention) The embodiment shown in FIG. 2 includes a directional control valve 13, a counterbalance valve 14, crossover type main relief valves 15 and 16, and a mechanical brake 17. Same as before.

A first main passage 18, 1 connects the directional control valve 13 and the counterbalance valve 14.
9 is provided with first branch passages 23 and 24 that communicate with the brake passage 22 via check valves 20 and 21, and also has a counter balance valve and a motor 25.
Second branch passages 28 and 29 are connected to second main passages 26 and 27 that connect the two main passages.

The second branch passages 28 and 29 are the brake passages 2
2, sub-relief valves 30 and 31 are provided in the passageway thereof.

A brake control valve 32 is connected to the brake passage 22 that connects each branch passage as described above, and this control valve 32 has two positions.
3, the position where the brake passage 22 is communicated with the tank 34 is maintained.

When the pressure in the brake passage 22 increases,
The pressure acts on the brake control valve 32 through the pilot passage 35 to switch the control valve.

When the brake control valve is switched, communication between the brake passage 22 and the tank 34 is cut off.

Thus, when the directional control valve 13 is switched, for example, to the left-hand position, oil from the pump 36 acts on the counterbalance valve 14, thereby switching the counterbalance valve 14 to the left-hand position.

When the counterbalance valve 14 is switched to the left position, the oil from the pump 36 is transferred to the first main passage 1.
8 and the second main passage 26 into the motor 25 . Also, the return oil from the motor 25 is
Since the motor returns to the tank 37 through the second main passage 27 and the first main passage 19, the motor rotates in a predetermined direction.

At the same time as the counterbalance valve 14 is switched as described above, the oil from the pump is transferred to the first branch passage 2.
3 also flows into the brake passage 22, passes through the pilot passage 35, acts on the brake control valve 32, and switches the control valve 32.

When the brake control valve 32 is switched, communication between the brake passage 22 and the tank 34 is cut off.
The oil from the pump 36 flows into the mechanical brake 17 and releases the brake.

When the directional control valve 13 is returned to the neutral position from the above state, the counterbalance valve 14 is also returned to the neutral position shown. At this time, the motor 25 performs a pumping action using its inertial energy, and the inertial energy is converted into thermal energy by the main relief valve 15.

When the brake is activated as described above,
When the pressure in the circuit is higher than the set pressure of the sub-relief valve 31, the pressure oil in the circuit flows into the brake passage 2.
2 to the pilot passage and brake control valve 3.
2 in a closed state, and continues to supply pressure oil to the mechanical brake 17.

Since the pressure oil is continuously supplied to the mechanical brake, the mechanical brake maintains the brake release state.

When the circuit pressure becomes lower than the set pressure of the sub-relief valve 31, the supply of pressure oil to the brake passage 22 is cut off. For this purpose, the brake control valve 32 returns to the illustrated position, returns the oil in the mechanical brake 17 to the tank 34, and operates the brake.

In other words, the mechanical brake 17 does not act simultaneously with the relief operation of the main relief valve, but acts when the pressure in the circuit becomes low, that is, when the motor 25 has been braked to some extent. Become.

According to the control circuit of the embodiment described above, the mechanical brake does not operate unless the circuit pressure becomes equal to or lower than the set pressure of the sub-relief valve as described above. In other words, the mechanical brake will not operate unless the motor is braked to a certain extent, which solves problems such as poor feeling for the operator.

Moreover, since the pressure oil supplied to the mechanical brake is controlled by the sub-relief valve, its pressure becomes stable.

Moreover, the durability of the mechanical brake is not impaired.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, and FIG. 2 is a circuit diagram of the present invention. 14... Counter balance valve, 15, 16...
Main relief valve, 17... Mechanical brake, 18, 19... First main passage, 20, 21
...Check valve, 22...Brake passage, 23,
24...first branch passage, 25...motor, 26,
27... Second main passage, 28, 29... Second branch passage, 30, 31... Sub-relief valve, 32...
...Brake control valve, 34...Tank.

Claims (1)

[Claims] 1. A directional switching valve that switches the flow path of oil discharged from the pump, a counterbalance valve communicating with the directional switching valve via a first main passage, and a motor communicating with the counterbalance valve via a second main passage. a brake passage communicating with the mechanical brake; , a first branch passage that communicates the upstream side of the counterbalance valve with the brake passage;
A check valve provided in the branch passage and allowing flow only from the first main passage to the brake passage; a second branch passage connecting the downstream side of the counterbalance valve and the brake passage; and a check valve provided in the second branch passage; A sub-relief valve that allows the pressure oil to flow out to the brake passage when the pressure in the second branch passage exceeds the set pressure, and a sub-relief valve that is connected to the brake passage and is connected to the brake passage when the pressure in the brake passage falls below a certain level. A brake control circuit for a hydraulic motor includes a brake control valve that communicates a brake passage with a tank.