JPS6140861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit for a rotating body brake in a construction machine such as a hydraulic excavator.

2. Description of the Related Art Conventionally, there is a hydraulic circuit shown in FIG. 1, for example, as a hydraulic circuit used in a parking brake of a hydraulic excavator or the like.

In FIG. 1, reference numeral 1 denotes a rotation body driven by a hydraulic motor 2, and the hydraulic motor 2 is provided with a brake cylinder 3.
The braking of the parking brake 3a is released by supplying pressure oil to the brake cylinder 3, and the braking of the parking brake 3a is applied by the action of the built-in spring by discharging the pressure oil from the brake cylinder 3.

The hydraulic motor 2 is connected to a directional switching valve 6 via a brake valve 4 and a counterbalance valve 5, and the directional switching valve 6 is connected to a hydraulic power source 7 and an oil tank 8. This directional control valve 6 has ports A and B in the neutral position.
The directional control valve 6 and the counterbalance valve 5 are connected to a shuttle valve 11, and a passage 11c from the shuttle valve 11 is connected to the brake cylinder 3.

The operation of the hydraulic circuit shown in FIG. 1 is such that, for example, when the directional control valve 6 is switched to the left position, the hydraulic motor 2 is operated via the counterbalance valve 5 and the brake valve 4 to the hydraulic power source 7 of the directional control valve 6. It is communicated with the oil tank 8, and pressurized oil is supplied to the left side of the hydraulic motor 2 to start it.

At this time, the pressure oil from the directional control valve 6 is simultaneously supplied to the brake cylinder 3 via the shuttle valve 11, and the braking is released at the same time as the hydraulic motor 2 is started. On the other hand, if the directional control valve 6 is returned to the neutral position in order to stop the hydraulic motor 2 during rotation, the supply of pressure oil to the hydraulic motor 2 is cut off, but due to the inertial rotation of the hydraulic motor 2, the right side Pressure oil is discharged from the port and is gradually discharged into the oil tank 8 through the throttle 9 of the directional control valve 6, and the pressure generated on the upstream side of the throttle 9 causes the shuttle valve 11 to be closed.
Pressure oil is supplied to the brake cylinder 3 through the brake cylinder 3 to release braking during inertial rotation, and when the hydraulic motor 2 finally stops, the pressure oil in the brake cylinder 3 is supplied through the shuttle valve 11 and the directional control valve 6. The hydraulic motor 2 is braked by discharging it into the tank 8.

However, in the conventional circuit shown in FIG. 1, the delay time during the inertial rotation of the hydraulic motor 2 from when the directional control valve 6 is returned to neutral until braking is performed depends on the size of the throttle 9 provided in the directional control valve 6. The size of the orifice 9 must be determined experimentally based on the size of the winding body 1, the speed, the length of the pipe, etc., and each time these conditions change, I have to change the aperture size.

Therefore, it is difficult to select an appropriate orifice size. For example, if the orifice is small, it will take a long time for the pressure oil in the brake cylinder 3 to be discharged, delaying braking, and the A situation occurs where the brake is not released due to a delay in the supply of pressure oil. On the other hand, when the throttle is large, the braking delay time is short, so the hydraulic motor 2
Braking is applied during the inertial rotation of the brake, and the brake is used as a dynamic brake, which causes heat generation, abnormal noise (squeal), and increased wear.

In addition, as shown by the broken line in FIG. 1, a throttle 12 is also provided in the passage 11c between the brake cylinder 3 and the shuttle valve 11, making it easier to select the braking delay time. This is causing similar problems.

On the other hand, in order to solve the problem with the hydraulic circuit shown in Figure 1, a hydraulic circuit has been proposed in which the main pipe of the hydraulic motor is provided with a restriction instead of the directional control valve as shown in Figure 2. There is.

That is, in the hydraulic circuit shown in FIG. 2, the hydraulic motor 2 is connected to the directional control valve 6 via the brake valve 4 and the counterbalance valve 5, and shuttle valves 13 and 1 are provided upstream of the brake valve 4 and the directional control valve 6, respectively.
4 is connected to the directional control valve 6, and a hydraulic power source 7 and an oil tank 8 are connected to the directional control valve 6. Furthermore, a throttle 15 is provided in the main pipe of the hydraulic motor 2, and the differential pressure generated across the throttle 15 is applied to a switching valve 16 that switches the output of the shuttle valve 13, and also between the output of the shuttle valve 14 and the output of the switching valve 16. A switching valve 18 is provided with a throttle 17 that operates to switch the brake cylinder 3 to the pressure oil side and the oil tank 8.

The action of this hydraulic circuit in FIG. 2 is as follows:
For example, if the switch is switched to the left side, the shuttle valve 1
4, the switching valve 18 switches to the right side, supplies pressure oil from the shuttle valve 14 to the brake cylinder 3, releases braking, and starts the hydraulic motor 2. On the other hand, when the directional switching valve 6 is returned to the neutral position, pressure oil due to the inertial rotation of the hydraulic motor 2 flows into the throttle 15 and creates a differential pressure. An output is applied to the directional switching valve 18 to switch it to the left side, and pressure oil from the shuttle valve 13 is supplied to the brake cylinder 3 to maintain the brake release state during inertial rotation. Subsequently, when the hydraulic motor 2 stops, the differential pressure across the throttle 15 disappears, so the switching valve 18 returns to neutral, and the brake cylinder 3 is communicated with the oil tank 8, thereby applying braking to the hydraulic motor 2.

However, in the circuit shown in FIG. 2, since the throttle 15 is provided in the main conduit of the hydraulic motor 2, there is a problem in that the pressure loss due to the throttle 15 is large.

Furthermore, in order to eliminate the loss caused by such throttling, an overload relief valve consisting of a combination of a directional control valve and a relief valve is provided between the hydraulic motor and the counterbalance valve, as shown in Japanese Patent Application Laid-Open No. 56-167903. A circuit has also been proposed in which the overload relief valve is operated by the pressure oil generated by the inertial rotation of the hydraulic pump, and the pressure oil generated by the inertial rotation is supplied to the brake cylinder through the switching operation of the directional control valve. However, in this circuit, the switching operation to supply pressure oil to the brake cylinder due to inertial rotation is performed only after the relief operation of the overload relief valve is performed, so there is a corresponding delay in response to the inertial oil pressure of the hydraulic motor. Moreover, since two sets of a relief valve and a switching valve (with a throttle) are used as the overload relief valve, there is a problem that the circuit configuration becomes complicated.

The present invention has been made in view of these conventional problems, and includes a sequence valve that releases the brake by supplying pressure oil to the brake cylinder of a hydraulic motor and performs braking by discharging the pressure oil. By directly introducing the main line pressure of the hydraulic motor as the operating pilot pressure, the brake can be released in direct response to the pressure oil supplied from the hydraulic source and the pressure oil generated by the inertial rotation of the hydraulic motor while the hydraulic motor is operating. However, when stopping the hydraulic motor, the parking brake is applied without causing a timing lag, and the throttle that switches to release the brake by inertial pressure oil without depending on the operation of the overload relief valve is installed not only in the main pipe but also in the pilot pipe. It is an object of the present invention to provide a hydraulic circuit for a power body brake which has excellent responsiveness and has a simple circuit configuration since it is not necessary to provide a hydraulic circuit in either a passageway or a switching valve.

FIG. 3 is a hydraulic circuit diagram showing an embodiment of the present invention.

First, to explain the configuration, reference numeral 1 denotes a rotating body such as a hydraulic excavator, and between a directional switching valve 6 connected to a hydraulic power source 7 and an oil tank 8 and the rotating body 1, there is a hydraulic motor section 20, a sequence valve, etc. A hydraulic circuit is provided which includes a section 30, an overload relief valve 40, and a counterbalance valve section 50.

First, the motor section 20 is provided with a hydraulic motor 2 that rotationally drives the rotation body 1, a brake cylinder 3 is provided on the rotation axis of the hydraulic motor via a parking brake 22, and a spring 24 is installed in the brake cylinder 3. The hydraulic motor 2 is braked by the parking brake 22 with the pressing force of the spring by discharging the parking brake 22 by supplying pressure oil to the brake cylinder 3 and discharging the pressure oil from the brake cylinder 3. There is.

Furthermore, the main pipes 20a and 20b of the hydraulic motor 2 are connected to the directional control valve 6 via a sequence valve section 30, an overload relief valve section 40, and a counterbalance valve section 50.

Next, the sequence valve section 30 has a sequence valve 32.
Main pipe lines 20a and 20b of the hydraulic motor 2 are branch-connected to ports A and C of the sequence valve 32, respectively, and an output C of the shuttle valve 34 is connected to the central port B. Port D, which is connected and becomes the outflow side, is connected to the hydraulic motor section 20
It is connected to the brake cylinder 3 of.

Furthermore, the pilot pressure of the sequence valve 32 is directly introduced into the main pipes 20a to 20b of the hydraulic motor 2, and therefore the sequence valve 32 is directly introduced into the main pipes 20a to 20b of the hydraulic motor 2.
The switching operation is performed by directly sensing the pressures of a and 20b. Furthermore, port A of the shuttle valve 34,
Pilot pipes 60a and 60b branched from the main pipes 20a and 20b and shown by broken lines are connected to B.

The setting springs 36a and 36b of the sequence valve 32 are each made of a spring stronger than the setting spring of a normal directional control valve.

Next, to explain the overload relief valve section 40, the overload relief valve section 40 is provided with overload relief valves 40a and 40b, and the overload relief valve 40a maintains the pressure oil in the main pipe 20a at a specified pressure. Also, overload relief valve 4
0b is connected to maintain the pressure oil in the main pipe 20b at a specified pressure.

Further, each of the overload relief valves 40a and 40b is operated by pressure oil generated by inertial rotation of the hydraulic motor 2 when the directional control valve 6 is returned to the neutral position, and prevents cross flow between the main pipes 20a and 20b. It also functions as a brake valve.

Furthermore, the main pipe 20 is connected to the counterbalance valve section 50.
A counterbalance valve 52 that operates by supplying pressure oil to ports a and 20b is provided, and ports A and B on the inflow side of the counterbalance valve 52 are connected to ports A and B of the directional control valve 6, while ports on the outflow side Ports C and D are connected to main pipes 20a and 20b, respectively, with check valves 54a and 54b interposed therebetween.

Next, the operation of the hydraulic circuit of the present invention will be explained.

First, when the directional control valve 6 is in the neutral position as shown in the figure, there is no supply of pressure oil to the brake cylinder 3, so the parking brake 22 is actuated by the spring 24 to stop the hydraulic motor 2.

In this state, if the directional control valve 6 is switched to the left position, for example, the pressure oil from the hydraulic source 7 is transferred from the port A of the directional control valve 6 to the counterbalance valve 52.
The counterbalance valve 52 is switched to the left position, and at the same time, part of the pressure oil supplied to the main pipe 20a is supplied to the sequence valve section 30 via the pilot pipe 60a. It flows to the shuttle valve 34. Here, the setting springs 36a and 36b of the sequence valve 32 are set to be lower than the cracking pressure of the overload relief valves 40a and 40b, and when the pressure is below the set pressure, the sequence valve 32 is in the neutral position shown in the figure.
Pressure oil from the shuttle valve 34 is supplied to the brake cylinder 3 from port D, and the parking brake 22
Release the brake. This parking brake 22
When the brake is released, the hydraulic motor starts rotating, and the oil discharged from the hydraulic motor 2 returns to the oil tank 8 via the main pipe 20b, the counterbalance valve 52, and the directional control valve 6.

On the other hand, at the time of startup, the inertial load applied to the hydraulic motor 2 is large, so the pressure in the main pipe 20a increases, and therefore the overload relief valve 40a cracks and enters the relief state.

At this time, the setting spring 3 of the sequence valve 32
Since the pressure setting by 6a and 36b is set lower than the cracking pressure of the overload relief valves 40a and 40b (about 80% of the cracking pressure), the sequence valve 32 is switched to the left position due to the pressure increase in the main pipe 20a. However, port A,
Pressure oil from the main pipe 20a is directly supplied to the brake cylinder 3 via D to maintain the brake released state.

Subsequently, the hydraulic motor 2 accelerates and the suction oil amount approaches the discharge oil amount, the pressure in the main pipe 20a decreases, the relief operation of the overload relief valve 40a stops, and the main pipe acting on the left side of the sequence valve 32 When the pilot pressure from the passage 20a falls below the set pressure, the sequence valve 32 returns to the neutral position shown in the figure again, and pressurized oil from the shuttle valve 34 is supplied to the brake cylinder 3 to release the brake while the hydraulic motor 2 is being driven. hold.

Next, as described above, when the directional control valve 6 is switched from the left position to the neutral position shown in the figure, the supply of pressure oil from the hydraulic source 7 is cut off, and the counterbalance valve 52 is also switched to the shown neutral position. The hydraulic motor 2 returns to the neutral position, and at this time, the hydraulic motor 2 is inertially rotated by the inertial force of the rotation body 1 and operates as a hydraulic pump, and the pressure on the main pipe 20b side increases.

Therefore, the overload relief valve 40b enters the relief state due to the pressure oil in the main pipe 20b.
Furthermore, the sequence valve 32 is switched from the neutral position to the right position by the pressure oil generated by the inertial rotation of the main line 20b, and the pressure oil in the main line 20b is supplied to the brake cylinder 3 via ports C and D, and the hydraulic motor 2 is switched from the neutral position to the right position. The brake release state of the parking brake 22 is maintained even during inertial rotation.

Next, if the inertial rotation of the hydraulic motor 2 decreases and the relief state of the overload relief valve 40b is released, and the hydraulic motor 2 is completely stopped, the pressure in the main pipe 20b disappears, so the sequence valve 32 is not shown. The brake cylinder 3 returns to the neutral position of the sequence valve 32 and the shuttle valve 3.
4 and a pilot pipe 60b to the oil tank 8, the pressure oil in the brake cylinder 3 is discharged, and the parking brake of the swing body 1 is applied by actuation of the parking brake 22 by the spring 24.

Of course, the same effect as described above is performed when the directional switching valve 6 is switched to the right side to rotate the hydraulic motor 2 in the reverse direction, and then the directional switching valve 6 is returned to the neutral position and stopped.

As described above, the present invention includes a hydraulic motor that drives a rotating body such as a hydraulic shovel or a winch, and releases the braking of the hydraulic motor by supplying pressure oil to the brake cylinder. As a hydraulic circuit for a rotating body brake that performs braking by discharging pressure oil from A sequence valve connected to the switching valve and connected to the pressure in the main pipeline to the hydraulic motor as pilot pressure is arranged, and the pressure oil applied to the hydraulic motor main pipeline when the directional switching valve is switched to the left or right is supplied to the brake cylinder. When the parking brake is released and the directional control valve is returned to the neutral position after this switching, the sequence valve is switched using the pressure oil generated by the inertial rotation of the hydraulic motor, and the inertial pressure oil is supplied to the brake cylinder. Maintains the brake release state during inertial rotation,
When the relief operation of the overload relief valve stops due to a drop in inertial pressure oil and the hydraulic motor stops, the sequence valve returns to the neutral position and discharges the pressure oil from the brake cylinder into the tank. By directly detecting the pressure, the brake can be released by supplying pressure oil to the brake cylinder, and the brake can be applied by discharging the pressure oil from the brake cylinder, so parking brake can be applied directly in response to pressure changes from inertial rotation of the hydraulic motor to standstill. The control response is high because it can achieve control of There is no reduction in the efficiency of the hydraulic motor due to loss, and the hydraulic circuit configuration is simple because the parking brake release and braking are achieved by a combination of a sequence valve and a shuttle valve operated by the pressure in the main pipe. This makes it easier to connect piping and incorporate the hydraulic circuit into the hydraulic motor, and because the piping can be shortened, response can be improved and piping losses can be reduced. Furthermore, the pilot set pressure of the sequence valve can be reduced. Since the pressure is set lower than the cracking pressure of the overload relief valve, the pressure of the hydraulic motor is sufficiently high compared to the conventional circuit that switches the pressure oil supply and pressure oil discharge to the brake cylinder based on the cracking operation of the overload relief valve. Responsiveness of braking control to inertial rotation and standstill can be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 are hydraulic circuit diagrams showing conventional examples;
The figure is a hydraulic circuit diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Exertion body, 2... Hydraulic motor, 3... Brake cylinder, 6... Directional switching valve, 7... Hydraulic pressure source, 8... Oil tank, 20... Hydraulic motor section, 2
0a, 20b... Main pipe line, 22... Parking brake, 24... Spring, 30... Sequence valve section, 32... Sequence valve, 34... Shuttle valve, 36a, 36b... Setting spring, 40
...Overload relief valve section, 40a, 40b
... Overload relief valve, 50 ... Counterbalance valve section, 52 ... Counterbalance valve, 5
4a, 54b...Check valve, 60a, 60b...
...Pilot conduit.

Claims (1)

[Claims] 1. A hydraulic motor that drives a rotating body such as a hydraulic shovel or a winch, releases the braking of the hydraulic motor by supplying pressure oil to a brake cylinder, and releases pressure oil from the brake cylinder. In a hydraulic circuit for a power brake that applies braking by discharge, the hydraulic motor is connected to a counterbalance valve via an overload relief valve, and the counterbalance valve is connected to a hydraulic source and a tank. a sequence valve connected to the main pipe line of the hydraulic motor as a pilot pressure, and supplying pressure oil applied to the hydraulic motor main pipe line to the brake cylinder when the directional switching valve is switched to the left or right, When the directional control valve is returned to neutral after the switching, the sequence valve is switched in the opposite direction by the inertia pressure oil of the hydraulic motor to supply inertia pressure oil to the brake cylinder, and the inertia pressure oil is cut off. A hydraulic circuit for a rotating body brake, characterized in that the sequence valve returns to a neutral position and provides a circuit connection for communicating the brake cylinder with a tank.