JPH10267121A - Brake device for hydraulic travel device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of excessively large braking torque by mitigating the effectiveness of a mechanical brake upon braking in the low speed side of a hydraulic motor. SOLUTION: A mechanical brake 11 is provided for braking the rotation of a hydraulic motor 2. A brake valve 10 for controlling the supply and discharge of hydraulic pressure is provided in a brake cancel cylinder 12 interlocking with the mechanical brake 11 to release the hydraulic pressure of the brake cancel cylinder 12 upon braking and generate a braking force. A mechanical brake control valve 16 is provided in a passage 15 for connecting the brake valve 10 to the brake cancel cylinder 12. The mechanical brake control valve 16 is switched interlocking with a high and low speed selector valve 6 so that the passage 15 is more restricted in the low speed side of the hydraulic motor 2 than in the high speed side and the effectiveness of the mechanical brake 11 is mitigated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a brake device of a hydraulic traveling device which travels and rotates by a hydraulic motor.

[0002]

2. Description of the Related Art Conventionally, a hydraulic traveling device driven by a hydraulic motor, for example, a brake device of an industrial vehicle such as a hydraulic traveling tractor is configured as shown in FIG.

[0003] Reference numeral 1 denotes a hydraulic pump that is driven to rotate by a motor M such as an engine. Reference numeral 2 denotes a hydraulic motor that rotates by receiving a supply of hydraulic oil from the hydraulic pump 1, and both are connected by closed loop closed circuits 3a and 3b. You. The hydraulic motor 2
Is decelerated by a speed reducer and transmitted to vehicle drive wheels and the like.

The forward, reverse, and stop of the hydraulic pump 1 and the increase and decrease of the discharge amount are controlled by operating a regulator 4. The regulator 4 includes a cylinder 4a,
The left and right chambers of the piston 4b are provided with a charge pump 1a.
From the left and right chambers is controlled by a manually operated control valve 4c, whereby the piston 4b moves left and right, and interlocks with it. The swash plate tilt angle of the hydraulic pump 1 changes to change the discharge amount. The displacement of the piston 4b is fed back to the control valve 4c to maintain a tilt angle according to the operation amount of the control valve 4c.

[0005] The hydraulic motor 2 rotates reversibly according to the pump discharge amount and its supply direction, and the rotational speed increases as the pump discharge amount increases. A high / low switching valve 6 is provided for relatively switching the rotation speed of the hydraulic motor 2, and when the hydraulic pressure is switched by this, hydraulic cylinders 7a, 7b for switching the swash plate tilt angle of the hydraulic motor 2 in two stages. Operates. In addition, even if the rotation direction of the hydraulic motor 2 is reversed, the high pressure is always guided to one of the hydraulic cylinders 7a and 7b.

The high / low speed switching valve 6 is supplied with pilot pressure from a charge pump 1a via a high / low speed selection valve 8.
Thus, the switching is performed.

A switching valve 9 switches according to the pressure difference between the closed circuits 3a and 3b.
And a part of the hydraulic oil in the circuit is flushed by relief.

To apply a brake to the rotation of the hydraulic motor 2, a mechanical brake 11 is provided. During normal running, hydraulic pressure is supplied to the brake release cylinder 12 via the position of the brake valve 10, and the brake is released.

When temporarily stopping the running of the vehicle, for example,
By switching to the position or, the drive pressure for the regulator 4 is released to the tank T, the discharge amount of the hydraulic pump 1 is set to zero, and the hydraulic brake by the hydraulic motor 2 is applied. In the case of a position,
Since hydraulic pressure is supplied or held to the brake release cylinder 12, the mechanical brake 11 does not operate.

On the other hand, at the time of sudden braking, for example, when the traveling is stopped urgently, the brake valve 10 is switched to the position, and the hydraulic pressure of the brake release cylinder 12 is also released.
This allows the mechanical brake 1
1 is operated by the return spring, and a large braking force is obtained.

[0011]

When the high / low speed switching valve 6 is on the low speed side and the hydraulic motor 2 is operating at a relatively low speed, the generated torque is large because the hydraulic motor 2 has a large capacity. At the time of braking, an effective brake operation can be obtained only by the hydraulic brake by reducing the pump discharge amount.
On the low-speed side of the hydraulic motor 2, if the mechanical brake 11 is suddenly applied together with the hydraulic brake, the brake will be applied too much, generating excessive braking torque and causing insufficient durability of the hydraulic motor 2 and the reducer. There is.

On the other hand, when the hydraulic motor 2 is on the high-speed side, the torque generated by the hydraulic motor 2 is small. Therefore, even if the mechanical brake 11 is activated at the same time, a large braking torque is not generated.

Therefore, even if the problem does not occur on the high speed side, in order to cope with the large braking torque generated on the low speed side, it is necessary to increase the strength of each component of the hydraulic motor 2 and the speed reducer. The increase in size and the accompanying cost were inevitable.

In order to solve such a problem, the present invention reduces the effect of the mechanical brake during braking on the low speed side, thereby preventing the generation of excessive braking torque and ensuring the durability of a hydraulic motor, a speed reducer, and the like. The purpose is to do.

[0015]

According to the present invention, a hydraulic pump and a hydraulic motor are connected in a closed circuit, a regulator for controlling the discharge amount of the hydraulic pump is provided, and the capacity of the hydraulic motor is controlled at least via a hydraulic cylinder. The hydraulic cylinder is configured to be switchable in two stages. The hydraulic pressure to the hydraulic cylinder is switched via a high / low speed switching valve, and a mechanical brake for braking the rotation of the hydraulic motor is provided. In a hydraulic traveling device having a brake valve for controlling supply and discharge and releasing a hydraulic pressure of a brake release cylinder during braking to generate a braking force, a mechanical brake control is provided in a flow path connecting the brake valve and the brake release cylinder. A valve is provided, and this mechanical brake control valve is switched in conjunction with the high / low speed switching valve. Both are configured to narrow the flow path when compared to the high speed side of the hydraulic motor low-speed side.

In the second invention, the high / low speed switching valve is switched in accordance with a pilot pressure supplied through a high / low speed selection valve, and the hydraulic pressure from the closed circuit is selectively introduced into a hydraulic cylinder. The mechanical brake control valve is configured to perform a switching operation according to the pilot pressure.

In the third invention, the high / low speed switching valve is switched in accordance with a pilot pressure supplied via a high / low speed selection valve, and the hydraulic pressure from the closed circuit is selectively introduced into a hydraulic cylinder. The high / low speed selection valve and the mechanical brake control valve are constituted by electromagnetic switching valves, and when the high / low speed selection valve is on the low speed side, switching is performed in synchronization with each other so that the mechanical brake control valve is in a position to narrow the flow path.

[0018]

In the present invention, when the hydraulic motor brakes on the low speed side with a large capacity, the holding pressure of the mechanical brake is released through the throttle of the mechanical brake control valve, so that the brake is gradually applied. Since the hydraulic motor has a large capacity, a large hydraulic brake torque is generated, and even if the mechanical brake has a moderate braking force, the required braking characteristics are secured in both cases. By weakening the mechanical brake in this way, the overall braking torque does not become excessive,
The durability of the hydraulic motor and the speed reducer is ensured.

On the other hand, at the time of braking on the high-speed side of the hydraulic motor, the holding pressure of the mechanical brake is suddenly released, and the mechanical brake is quickly operated. On the high-speed side, the capacity of the hydraulic motor is small and the application of the hydraulic brake is weak, so this is compensated for by the mechanical brake to ensure reliable braking characteristics.

[0020]

FIG. 1 shows an embodiment of the present invention.

As shown in the figure, a mechanical brake control valve 1 is provided in the middle of an oil passage 15 connecting a brake valve 10 and a brake release cylinder 12 of a mechanical brake 11.
6 are interposed. The mechanical brake control valve 16 is switched in conjunction with the high / low speed switching valve 6 so that the hydraulic motor 2 is at the a position on the high speed side and has a large flow rate, and the hydraulic motor 2 is at the b position on the low speed side and has a small flow rate via the orifice 16a. To narrow the oil passage 15.

The mechanical brake control valve 16 switches according to the pilot pressure supplied to the high / low speed switching valve 6 via the high / low speed selection valve 8, and the b position is selected when the high / low speed switching valve 6 is on the low speed side. Is done.

The same components as those shown in FIG. 3 are denoted by the same reference numerals, and the operation will be described below.

When the high / low speed selection valve 8 is switched so that the hydraulic motor 2 rotates on the low speed side, the mechanical pressure of the mechanical brake control valve 16 is reduced by the pilot pressure.
A position has been selected.

In this state, when the brake valve 10 is switched to the position to apply sudden braking to the vehicle, the discharge amount of the hydraulic pump 1 is reduced, and the hydraulic pressure of the brake release cylinder 12 of the mechanical brake 11 is reduced by the mechanical brake. The control valve 16 is gradually released while being throttled by the orifice at the position b.

As a result, the hydraulic brake by the hydraulic motor 2 operates and the mechanical brake 11 operates slowly. Since the hydraulic motor 2 has a large capacity, the effect of the hydraulic brake is good, and even if the effect of the mechanical brake 11 is weak, the characteristic becomes necessary and sufficient as the total braking torque, and excessive braking torque is applied to the hydraulic motor 2 and the reduction gear. It does not work.

On the other hand, when the high / low speed selection valve 8 is switched so that the hydraulic motor 2 rotates on the high speed side, the mechanical brake control valve 16 is also moved to the high speed side by the pilot pressure.
The position has been switched.

In this state, when the brake valve 10 is switched to the position, for example, when the vehicle is suddenly braked, the discharge amount of the hydraulic pump 1 is reduced, and the hydraulic pressure of the brake release cylinder 12 of the mechanical brake 11 is reduced by the mechanical pressure. It is quickly released via the a position of the brake control valve 16.

As a result, the hydraulic brake operates and
The mechanical brake 11 operates immediately and a good braking force is obtained. However, in this case, since the hydraulic motor 2 has a small capacity on the high-speed side, the braking torque does not become excessive even when the mechanical brake 11 operates simultaneously.

When the brake valve 10 is in a position other than the position, only the hydraulic brake is used, so that the braking torque does not become excessive as in the related art.

FIG. 2 shows another embodiment in which the mechanical brake control valve 16 is constituted by an electromagnetic switching valve, and the switching operation is performed in synchronization with the high / low speed selection valve 8 also constituted by an electromagnetic switching valve. It is like that.

When the high / low speed selection valve 8 is switched to the low speed side, the mechanical brake control valve 16 is synchronized with this.
Becomes the b position, and the oil passage 15 is narrowed.

Accordingly, also in this case, when the hydraulic motor 2 is rotating on the low speed side as described above, when the mechanical brake 11 is activated, the release of the hydraulic pressure of the brake release cylinder 12 is controlled by the mechanical brake control valve 16. The throttle is throttled, the operation of the mechanical brake 11 becomes gentle, and generation of excessive braking torque can be prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing another embodiment.

FIG. 3 is a hydraulic circuit diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Hydraulic motor 3 Closed circuit 8 High / low speed selection valve 10 Brake valve 11 Mechanical brake 12 Brake release cylinder 15 Oil passage 16 Mechanical brake control valve

Claims (3)

[Claims] A hydraulic pump and a hydraulic motor are connected in a closed circuit, a regulator for controlling a discharge amount of the hydraulic pump is provided, and a capacity of the hydraulic motor can be switched to at least two stages via a hydraulic cylinder. While switching the hydraulic pressure to the hydraulic cylinder via a high / low speed switching valve, a mechanical brake for braking the rotation of the hydraulic motor is provided, and a brake valve for controlling the supply and discharge of the hydraulic pressure to a brake release cylinder interlocked with the mechanical brake is provided. In the hydraulic traveling device, wherein a hydraulic pressure of a brake release cylinder is released during braking to generate a braking force, a mechanical brake control valve is provided in a flow path connecting the brake valve and the brake release cylinder, The valve is switched in conjunction with the high / low speed switching valve and is connected to the high speed side of the hydraulic motor. Compare to the brake device of hydraulic traveling apparatus characterized by being configured to narrow the flow path at the time of the low speed side. 2. The high / low speed switching valve is switched in accordance with a pilot pressure supplied through a high / low speed selection valve to selectively introduce hydraulic pressure from the closed circuit to a hydraulic cylinder while controlling the mechanical brake control. The brake device according to claim 1, wherein the valve is configured to perform a switching operation in accordance with the pilot pressure. 3. The high / low speed switching valve is switched in accordance with a pilot pressure supplied through a high / low speed selection valve to selectively introduce the hydraulic pressure from the closed circuit to a hydraulic cylinder, while selecting the high / low speed selection valve. 2. The valve according to claim 1, wherein the valve and the mechanical brake control valve are constituted by electromagnetic switching valves, and when the high / low speed selection valve is on the low speed side, the mechanical brake control valves are switched in synchronization with each other so as to be in a position to narrow the flow path. Hydraulic traveling equipment brake device.