JPH0233543B2 - YUATSUHEIKAIRONONEGATEIBUBUREEKISOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic closed circuit negative brake device for hydraulic excavators, hydraulic cranes, etc.

FIG. 1 is a diagram showing a hydraulic closed circuit having a conventional negative brake device. In the figure, 1 is a double tilting variable displacement hydraulic pump, 2 is a tilting actuator that controls the amount of tilting of the hydraulic pump 1, 3 is a servo valve connected to the tilting actuator 2, and 4 is a servo valve that operates the servo valve 3. 5 is a hydraulic pressure source, 6 is a pressure cut-off switching valve provided between the hydraulic source 5 and the servo valve 3, and when the switching valve 6 is in the A position, the pressure oil from the hydraulic source 5 is transferred to the servo valve 3. and is not supplied at the B position. 7 is a hydraulic motor operated by the pressure oil of the hydraulic pump 1; 8 is a load driven by the hydraulic motor 7; 9 is a brake drum fixed to the output shaft of the hydraulic motor 7;
10 is a brake cylinder, 11 is a spring of the brake cylinder 10, and 12 is a brake shoe fixed to the piston rod of the brake cylinder 10. The brake shoe 12 is provided at a position where it should come into contact with the brake drum 9. 13 and 14 are pipes connecting the hydraulic pump 1 and the hydraulic motor 7, 15 is a hydraulic power source, and 16 and 17 are the hydraulic power source 15 and the pipes 13 and 14.
A check valve installed in a conduit connecting the
8 and 19 are relief valves provided between the pipes 13 and 14, 20 is a shuttle valve provided between the pipes 13 and 14, 21 is a relief valve connected to the outlet port of the shuttle valve 20, and 22 is a pipe. A shuttle valve is provided between the passages 13 and 14, and the outlet port of the shuttle valve 22 is connected to the pilot port of the switching valve 6 and the brake cylinder 10. 24 is a tank.

In this hydraulic closed circuit, when the operating lever 4 is in the neutral position, the piston 2a of the tilting actuator 2 is in the neutral position, so the amount of tilting of the hydraulic pump 1 is zero, and pressure oil flows into the pipes 13 and 14. Since no oil is supplied, the hydraulic motor 7 is stopped, and no pressure oil is supplied to the brake cylinder 10 from the pipes 13 and 14, so the brake shoe 12 is pressed against the brake drum 9 by the spring 11, and the brake is not activated. It is in an active state. When the operating lever 4 is moved to the operating position, for example, to the right position, the servo valve 3 becomes the A position, and pressure oil from the hydraulic source 5 is supplied to the tilting actuator 2.
When the piston 2a moves to the right and the piston 2a moves by an amount corresponding to the amount of operation of the operating lever 4, the servo valve 3 becomes the N position, and the pressure oil from the hydraulic source 5 is no longer supplied to the tilting actuator 2. , the piston 2a stops at that position, and the amount of tilting of the hydraulic pump 1 becomes a value corresponding to the amount of operation of the operating lever 4. In this case, the pressure oil of the hydraulic pump 1 is
3, the hydraulic motor 7 is operated,
Further, since the pressure oil in the pipe line 13 is supplied to the brake cylinder 10 via the shuttle valve 22, the piston of the brake cylinder 10 moves to the left against the spring 11, so that the brake shoe 12 is moved to the brake drum 9. The brake is released.
When the operating lever 4 is returned to the neutral position from this state, the servo valve 3 is placed in the B position, pressure oil from the hydraulic source 5 is supplied to the tilting actuator 2, and the piston 2
Since a moves to the left and the amount of tilting of the hydraulic pump 1 becomes smaller, the discharge amount of the hydraulic pump 1 decreases.
At this time, since the hydraulic motor 7 is rotated by the inertial force of the load 8, the pressure in the pipe line 14 increases, and when the pressure in the pipe line 14 exceeds the set pressure of the switching valve 6,
Since the switching valve 6 is switched to the B position by the pressure in the pipe line 14 via the shuttle valve 22, pressure oil from the hydraulic source 5 is no longer supplied to the tilting actuator 2, so the piston 2a stops and the hydraulic pump 1 is turned off. The amount of tilting (discharge amount) is maintained at a predetermined value. and,
As the inertia of the load 8 decreases, the hydraulic motor 7
The rotational speed of is reduced, the pressure in the pipe line 14 is reduced,
When the pressure in the pipe line 14 becomes lower than the set pressure of the switching valve 6, the switching valve 6 becomes the A position, the piston 2a moves to the left, the amount of tilting of the hydraulic pump 1 decreases, and the pressure in the pipe line 14 decreases. The switching valve 6 becomes the B position, the piston 2a stops, and the amount of tilting of the hydraulic pump 1 is maintained at a predetermined value. In this way, the amount of tilting of the hydraulic pump 1 gradually decreases as the rotational speed of the hydraulic motor 7 decreases, but at this time, pressure is generated in the pipe line 14, and this pressure is applied to the shuttle valve. 22 to the brake cylinder 10, the brake is held in the released state. When the hydraulic motor 7 stops and the piston 2a returns to the neutral position, the servo valve 3 goes to the N position and pressure oil from the hydraulic source 5 is no longer supplied to the tilting actuator 2, so the piston 2a returns to the neutral position. hold. In this case, since the amount of tilting of the hydraulic pump 1 becomes zero and the hydraulic motor 7 also stops, pressure oil is not supplied to the brake cylinder 10 and the brake is activated. Thus, when the hydraulic motor 7 is rotating, the brake is in the released state, and when the hydraulic motor 7 stops, the brake is in the applied state.

However, in the conventional negative brake device, when the hydraulic motor 7 is stopped, an external force acts on the load 8 and the brake drum 9
If the brake shoe 12 slips even slightly, high pressure will be generated in the pipe 13 or 14, and this pressure will be supplied to the brake cylinder 10 via the shuttle valve 22, resulting in a decrease in braking force.
This is equivalent to stopping on a steep slope with a traveling device, and equivalent to stopping with a heavy load suspended on a hydraulic winch, etc., so when the brake must be applied reliably, There is a danger that the power will be reduced.

As a way to solve this problem, the shuttle valve 2
A switching valve interlocked with the operating lever 4 is provided between the operating lever 2 and the brake cylinder 10, so that when the operating lever 4 is in the neutral position, the brake cylinder 10 is connected to the tank 24, and when the operating lever 4 is in the operating position, the brake cylinder 10 is connected to the tank 24. The cylinder 10 is connected to the shuttle valve 22
It is possible that it communicates with However, in this method, when the operating lever 4 is returned from the operating position to the intermediate position, the hydraulic motor 7 continues to rotate for a while due to the inertia of the load 8, whereas the brake immediately enters the operating state. Therefore, a sudden shock occurs when the vehicle stops, and the brake drum 9 and the brake shoe 12 slip when the vehicle stops, so it is necessary to increase the size of the brake device and the durability of the brake device decreases.

This invention was made to solve the above-mentioned problems, and even if an external force is applied to the load while the hydraulic motor is stopped, the braking force will not decrease, and the hydraulic motor will not decrease when stopped. It is an object of the present invention to provide a hydraulic closed circuit negative brake device in which the brake is activated after the vehicle has stopped.

In order to achieve this object, the present invention provides a hydraulic pump having a variable displacement hydraulic pump having a tilting actuator, and a hydraulic motor connected to the variable displacement hydraulic pump by two pipes and driving a load. In the negative brake system of the circuit, a shuttle valve provided between the two pipes connects the brake cylinder and the tank when the tilting actuator is in the neutral position, and connects the brake cylinder and the tank when the tilting actuator is in the operating position. A switching valve is provided to connect the output port of the shuttle valve and the brake cylinder.

FIG. 2 is a diagram showing a hydraulic closed circuit having a negative brake according to the present invention. In the figure 2
3 is a switching valve that is switched in conjunction with the tilting actuator 2 of the variable displacement hydraulic pump 1, and when the piston 2a of the tilting actuator 2 is in the neutral position,
The switching valve 23 connects the brake cylinder 10 and the tank 24.
When the piston 2a is in the operating position, the switching valve 23 communicates the shuttle valve 22 with the brake cylinder 10.

In this hydraulic closed circuit, when the operating lever 4 is in the neutral position, the piston 2a is in the neutral position and the amount of tilting of the hydraulic pump 1 is zero, so the hydraulic motor 7 is stopped and the switching valve 23 is in the neutral position. Since the brake cylinder 10 is in communication with the tank 24 by the brake cylinder 10, the brake is in an applied state. At this time, an external force acts on the load 8 and the brake drum 9
Because brake shoe 12 and brake shoe 12 slipped, conduit 1
Even if high pressure is generated in the brake cylinder 3 or the pipe 14, this pressure is not supplied to the brake cylinder 10 via the shuttle valve 22, so the braking force will not be reduced. When the operating lever 4 is set to the operating position, the piston 2a moves to a position corresponding to the operating amount of the operating lever 4, and the amount of tilting of the hydraulic pump 1 becomes a value corresponding to the operating amount of the operating lever 4. Since the hydraulic motor 7 is operated and the switching valve 23 communicates the shuttle valve 22 and the brake cylinder 10, pressure oil from the hydraulic pump 1 is supplied to the brake cylinder 10 via the shuttle valve 22 and the switching valve 23. As a result, the brake is released. When the operating lever 4 is returned to the neutral position from this state, the piston 2a approaches the neutral position as the rotational speed of the hydraulic motor 7 decreases, but as long as the hydraulic motor 7 is rotating, the piston 2a remains in the neutral position. Since the position is not the same, the switching valve 23
Shuttle valve 22 and brake cylinder 10 by
Since the brake cylinder 10 is in communication with the tank 24, the brake is held in the released state, and when the hydraulic motor 7 stops, the piston 2a is in the neutral position. state.

As explained above, in the hydraulic closed circuit negative brake device according to the present invention, even if an external force is applied to the load while the hydraulic motor is stopped, the braking force does not decrease, so for example, when driving It is safe because the brake can be applied reliably when the equipment is stopped on a steep slope or when the hydraulic winch is suspended with a heavy load. In addition, when stopping the hydraulic motor, the brake is activated after the hydraulic motor has stopped, so there is no sudden shock when stopping, and there is no need to increase the size of the brake device. The durability of the brake device does not deteriorate. In this way, the effects of this invention are significant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a hydraulic closed circuit having a conventional negative brake device, and FIG. 2 is a diagram showing a hydraulic closed circuit having a negative brake device according to the present invention. DESCRIPTION OF SYMBOLS 1... Double tilting variable displacement hydraulic pump, 2... Tilt actuator, 2a... Piston, 3... Servo valve, 4... Operating lever, 6... Pressure cut-off switching valve, 7... Hydraulic motor, 8...Load, 9...
...Brake drum, 10...Brake cylinder,
11... Spring, 12... Brake shoe, 22...
...Shuttle valve, 23...Switching valve.

Claims (1)

[Claims] 1. In a hydraulic closed circuit negative brake device comprising a variable displacement hydraulic pump having a tilting actuator and a hydraulic motor connected to the variable displacement hydraulic pump by two pipes and driving a load, the two A shuttle valve provided between the pipelines and the brake cylinder are connected to the tank when the tilting actuator is in a neutral position, and an output port of the shuttle valve is connected to the brake cylinder when the tilting actuator is in the operating position. A hydraulic closed circuit negative brake device characterized by comprising a switching valve for connecting.