JPS5920882B2 - Hydraulic drive vehicle control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a control system for a hydraulically driven vehicle that rotates a hydraulic motor and has a brake circuit that hydraulically brakes the hydraulic motor and a shaft brake that mechanically brakes the hydraulic motor. Regarding circuit improvement.

A conventional control circuit for a hydraulically driven vehicle is configured as shown in FIG. 1, for example.

That is, hydraulic pressure discharged from a hydraulic pump a is supplied to a hydraulic motor d via an electromagnetic operation valve (a manual one may also be used) and a counterbalance valve C to drive the hydraulic motor d to rotate. Between the balance valve C and the hydraulic motor d, a brake relief valve e is provided in parallel with the hydraulic motor d, which hydraulically brakes the hydraulic motor d when the counterbalance valve C is neutral, that is, during braking.

In addition, a pipe branched from the circuit connecting the operation valve and the counterbalance valve C is connected to the brake cylinder g via the shuttle valve f, so that the inertial body rotated by the hydraulic motor d can be braked. It has become.

The brake circuit of the conventional control circuit is shown in FIG.

In other words, when the operating valve is set to the braking position to brake the hydraulic motor d which is currently rotating at the rotational speed N, there is no pressure difference between the circuit connecting the operating valve and the counterbalance valve C, and the counterbalance valve C is in the neutral position and closes the circuit of hydraulic motor d.

At this time, since the hydraulic motor d is rotated by coasting of the inertial body, the flow rate of the hydraulic pressure discharged from the hydraulic motor d is controlled by the brake relief valve e, and acts as a retarder.

At the same time, the shuttle valve f also becomes the neutral position, and the hydraulic pressure in the brake cylinder g is gradually drained through the throttle in the shuttle valve f, so that the piston rod in the brake cylinder g is protruded by the compression spring and the inertial body Acts as a shaft brake that mechanically brakes the

However, in the conventional control circuit described above, the timing of the shaft brake changes depending on the throttle ratio of the throttle installed in the shuttle valve and the oil temperature, so the shaft brake operates before the rotation of the hydraulic motor has sufficiently decreased and the brake shoe is activated. There was a risk that it would wear out prematurely.

This invention was made for the purpose of solving this problem.

The present invention will be described in detail below with reference to an embodiment shown in FIG. 3 and subsequent figures.

In the figure, reference numeral 1 denotes a hydraulic motor, and hydraulic pressure discharged from the hydraulic motor 1 is supplied to a hydraulic motor 4 via an operating valve 2 and a counterbalance valve 3 to drive the motor to rotate.

Between the pipes 5 and 6 connecting the counterbalance valve 3 and the hydraulic motor 4, there is a throttle 7 and a check valve 8 on the outlet side.
A pair of brake IJ valves connected in series.
and 10 are interposed in opposite directions, and a pipe line 11 is branched from between the outlet side of these relief valves 9 and 10 and the throttle I.

These pipes 11 are connected to the inlet side of the shuttle valve 12 via a check valve 13, and a portion is introduced into the shuttle valve 12 as pilot pressure via a pilot circuit 22. .

On the other hand, the shuttle valve 12 is composed of the operation valve 2 and the counterbalance valve 3.
A pipe line 14 branched from pipe lines 14 and 15 connecting between
a.

The inlet side is connected to 15a via check valves 16 and 17, and the outlet side is connected to a brake cylinder 18.

The brake cylinder 18 has a piston 18a biased by a compression spring 19, and a piston rod 18b that protrudes from the piston 18a has a brake at the tip thereof for braking the inertial body 20 rotated by the hydraulic motor 4. body 21
is installed.

The operation during running is the same as that of the conventional one, but when the operation valve 2 is now operated to the braking position, the pipes 14 and 15 connecting between the operation valve 2 and the counterbalance valve 3 are activated. Since the differential pressure between the two ends disappears, the counterbalance valve 3 returns to the neutral position and closes the circuit of the hydraulic motor 4.

Thereafter, the hydraulic motor 4 is rotated by coasting of the inertial body 20,
The pressure discharged from the hydraulic motor 4 is applied to the brake IJ.
The fluid resistance through the IJ-F valve 9 or 10 causes the hydraulic motor 4 to act as a retarder.

On the other hand, the pressure exiting the relief valve 9 or 10 is generated by the throttle 7 provided on the outlet side, and a portion is supplied to the inlet side of the shuttle valve 12 and the pilot circuit 22 via the conduit 11.

As a result, even if the pressure difference between the pipes 14 and 15 disappears, the shuttle valve 12 is maintained at the communication position a, and a portion of the hydraulic pressure that has exited the relief valve 9 or 10 flows into the brake cylinder 18, and the shaft brake is activated. Open so that it does not operate.

This opening continues while the hydraulic motor 4 is rotating due to coasting, and when the rotation stops and the shuttle valve 12 is returned by the spring, the hydraulic pressure in the brake cylinder 18 is drained through the shutoff position b of the shuttle valve 12. The shaft brake starts to work, and the waveforms at various parts during braking are as shown in Figure 4.

Note that the check valves 16 and 17 provided between the pipes 14 and 15 and the shuttle valve 12 are for quickly releasing the starting standby brake, and are also provided in series with the IJ IJ-F valves 9 and 10. The check valve 8 is provided to prevent the shaft brake from being released even if the pressure in the circuit increases due to the vehicle body load applied to the hydraulic motor 4 when parking on a slope.

As detailed above, this invention prevents the shaft brake from acting while the hydraulic motor is rotating due to inertia, thereby preventing unnecessary wear and heat generation of the brake shoes of the shaft brake. This has the advantage that it can be easily and inexpensively implemented since it is only necessary to provide a check valve and a throttle to the existing circuit.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of a conventional control circuit, FIG. 3 is a circuit diagram of a control circuit according to an embodiment of the present invention, and FIG. 4 is a waveform diagram during braking. 1 is a hydraulic pump, 2 is an operating valve, 3 is a counterbalance valve, 4 is a hydraulic motor, 7 is a throttle, 8 is a check valve, 9 and 10
is the brake IJ IJ-fu valve, 12 is the shuttle valve, 1
4 and 15 are pipes, 16 and 17 are check valves, and 18 is a brake cylinder.

Claims (1)

[Claims] 1. Hydraulic pressure discharged from the hydraulic pump 1 is supplied to the hydraulic motor 4 via the operating valve 2 and the counterbalance valve 3 to drive it to rotate, and a portion is supplied to the brake cylinder 18 that constitutes the shaft brake. , a brake relief valve 9.10 provided in parallel with the hydraulic motor 4.
A throttle 7 and a check valve 8 are provided in series on the outlet side of the control valve 2 and the counterbalance valve 8 to generate pressure on the outlet side of the relief valve 9 or the relief valve 10 during braking. The inlet side of the shuttle valve 12 connected to the pipe line 14-15 connecting between 3 and 3 via check valves 16 and 17, and the outlet of each relief valve 9, 10 so as to be introduced as pilot pressure at communication position a, respectively. The inlet side of the shuttle valve 12 is connected to the side, and the shuttle valve 12
A control circuit for a hydraulically driven vehicle in which the outlet side of the brake cylinder 18 is connected to the brake cylinder 18.