JPH01234603A - Cushion control device of working cylinder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a cushion control device in an actuating cylinder, such as a boom cylinder of an excavating and loading vehicle.

[Conventional technology]

Conventionally, when an operating cylinder such as a boom cylinder approaches a cylinder end, the cylinder return passage is throttled and hydraulic pressure is built up to slow the cylinder speed and reduce cylinder end shock.

[Problem to be solved by the invention]

In the above-mentioned shock control, the amount of reduction in cylinder speed is determined by the problem of cylinder withstand pressure, and therefore a shock reduction effect sufficient to keep up with the increase in cylinder speed could not be obtained.

The present invention has been made in view of the above circumstances, and its purpose is to reduce the cylinder speed of the operating cylinder by controlling the stroke of the operating valve, thereby reducing the cylinder end shock. An object of the present invention is to provide a cushion control device for an operating cylinder that can exhibit a shock reducing effect.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a pilot pressure control circuit that supplies pilot pressure to a pilot port of an operating valve that operates an operating cylinder, which operates near the end of the cylinder stroke of the operating cylinder to reduce the pilot pressure. The structure includes a pilot pressure control means for controlling the pressure.

[For production]

When the actuating cylinder is actuated and near the end of its cylinder stroke, the pilot pressure control means is actuated to reduce the pilot pressure and restore the spool of the operating valve, thereby reducing the cylinder speed of the actuating cylinder.

In this way, by controlling the operating valve stroke, the cylinder speed of the operating cylinder is reduced to reduce cylinder end shock.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In the drawing, numeral 1 is a working cylinder operating circuit, and numeral 2 is a pilot pressure control circuit.

The operating cylinder operating circuit 1 includes a boom cylinder 3 as an operating cylinder, a boom high-speed operation valve 4, and a boom low-speed operation valve 5.
The pump ports 4a and 4b of the boom high-speed operation valve 4 are connected to the discharge side of the pump 6 through pipes 8 and 9, and a check valve is connected to the pipe 8. 10 is the default.

The tank port 4C of the boom high speed operation valve 4 is connected to the tank 1.
1, and the port 4d of the boom high-speed operation valve 4 is connected to the bottom side 3a of the boom cylinder 3 via a pipe line 12, and a check valve 13 is provided in this pipe line 12.

Pump port 5a of the boom low speed operation valve 5.

5b is connected to the discharge side of the pump 7 through conduits 14 and 15, and the conduit 14 is provided with a check valve 16.

The tank port 5C of the boom low speed operation valve 5 is connected to the tank 1.
1 and ports 5d, 5 of the boom low speed operation valve 5.
e is connected to the bottom side Bas rod side 3b of the boom cylinder 3 via pipes 17 and 18.

The pilot pressure control circuit 2 includes one fixed-capacity control pump, a proportional control valve 20, and a switching valve 21. The proportional control valve 20 is provided on the discharge side of the control pump 19, and the boom operation lever 22 It outputs pilot pressure according to the amount of operation.

The output side of this proportional control valve 20 is a pilot pipe 23.2.
4 to the port 20a of the switching valve 20.

20b, and a throttle 25 is connected to the pilot pipe 24.
and check valve 26 are provided in parallel.

Further, the port 20c of the switching valve 20 is connected to the pilot pipe 2.
The pilot ports 4e and 1 of the boom high-speed operation valve 4 are connected to the pilot port 5f of the boom low-speed operation valve 5 through 7.28, respectively. Further, the switching valve 2
The 0 port 20d communicates with the tank 11 via a pilot line 29, and this pilot line 29 is provided with a back pressure compensation valve 30 and a throttle 31.

A boom angle detection sensor (not shown) is incorporated into the electrical circuit of the solenoid 32 of the switching valve 20. This boom angle detection sensor operates 100 to 150 mm before the cylinder stroke of the boom cylinder 3.

The throttle 25, the switching valve 21, the back pressure compensation valve 30, and the throttle 31 constitute a pilot pressure control means A.

Next, the operation will be explained.

When the boom angle detection sensor is not operating, the output pressure of the proportional control valve 20 is transferred to the position I of the switching valve 21, the pilot port 4e of the boom high speed operation valve 4 and the boom low speed operation valve via the pilot pipes 27 and 28. 5 is introduced into the pilot port 5f of No. 5 as it is.

When the boom cylinder 3 is actuated 100 to 150+ nm before the cylinder stroke, the boom angle detection sensor is actuated, the solenoid 32 is energized, the switching valve 20 is switched, and the position opening is located on the port side. For this reason, the output pressure of the proportional control valve 20 is
5. In order to flow to the tank 11 via the position port of the switching valve 20, the back pressure compensation valve 30, and the throttle 31, the boom height and low speed operation valves 4 and 5 pilot ports 4 e s 5 f
The output pressure acting on the boom height and low speed operation valve 4,
5 is returned by the force of the springs 33 and 34, resulting in a reduction in the speed of the boom cylinder 3 and a reduction in cylinder end shock.

In reality, the speed reduction amount of boom cylinder 3 is 20% to 40%.
%, and in this case, the boom height and spool stroke of the low-speed operating valves 4 and 5 are 3.5 mm to 4.2 mm, as shown in Figure 2, and the pilot pressure P at this spool stroke is As shown in Figure 3, it is 14.3 kg/ca-16, 6 kg/cJ.

Therefore, by adjusting the throttle 25.31 and the back pressure compensation valve 30, the pilot pressure P is 14.3 kg/ca ~ 1
6, set at 6 kg/cJ.

〔Effect of the invention〕

As described in detail above, the operating cylinder cushion control device according to the present invention provides a pilot pressure control circuit that supplies pilot pressure to the pilot port of the operating valve that operates the operating cylinder at the end of the cylinder stroke of the operating cylinder. The present invention is characterized in that it is provided with a pilot pressure control means that operates at a low temperature to lower the pilot pressure.

Therefore, when the actuating cylinder is actuated and near the end of its cylinder stroke, the pilot pressure control means is actuated to reduce the pilot pressure and return the spool of the operating valve.
As a result, the cylinder speed of the working cylinder is reduced.

In this way, by controlling the operation valve stroke, the cylinder speed of the operating cylinder can be reduced to reduce cylinder end shock, and a sufficient shock reduction effect can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram of an embodiment of the present invention, FIG. 2 is a spool stroke/flow diagram of the operating valve, and FIG. 3 is a spool stroke/pressure diagram of the operating valve. 3 is a boom cylinder, 21 is a switching valve, 25°31 is a throttle, 30 is a back pressure compensation valve, and A is a pilot pressure control means.

Claims (1)

[Claims] A pilot pressure control circuit that supplies pilot pressure to a pilot port of an operating valve that operates an operating cylinder is provided with a pilot pressure control means that operates near the end of the cylinder stroke of the operating cylinder to reduce the pilot pressure. Cushion control device for the actuating cylinder.