JP3083152B2 - Hydraulic drive for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a hydraulic drive device that controls a drive speed of a hydraulic actuator provided in a construction machine such as a hydraulic shovel or a crane.

[0002]

[Prior art]

FIG. 3 is a hydraulic circuit diagram showing a hydraulic circuit of a conventional hydraulic drive device of a construction machine. Here, a hydraulic circuit having two hydraulic actuators is shown for convenience of explanation.

A conventional hydraulic drive device is provided with a variable displacement hydraulic pump 2 having a regulator 1 for changing the displacement as a hydraulic source, and is connected to the hydraulic pump 2 so as to branch in parallel. Hydraulic actuators 7, 8 via directional control valves 3, 4, which can be opened and closed by the operator, and check valves 5, 6, respectively, are sequentially connected to the downstream pipelines. Pressure compensating valves 9 and 10 to be described later are connected between the upstream pipes and the downstream pipes of the respective directional control valves 3 and 4. Further, downstream pipes of the direction switching valves 3 and 4 are connected to the regulator 1 via other check valves 11 and 12.

FIG. 4 is a partially broken sectional view showing the internal structure of the pressure compensating valve 9.

The pressure compensating valve 9 is connected to a cylindrical spool chamber 11 in a sleeve 10 forming an outer wall, and is connected to the spool chamber 11.
A pressure chamber 12 having a diameter larger than that of the spool chamber 11 is formed, and a spool 13 is slidably housed in the spool chamber 11.

The spool chamber 11 has an inlet port 14 through which the discharge pressure of the hydraulic pump 2 is led and an outlet port 15 connected to the upstream side of the direction switching valve 3. 1
A conduit 16 is formed to communicate with the downstream side of the direction switching valve 3 connected to the hydraulic actuator 7 via the check valve 5 shown in the figure. The load pressure is supplied to the pressure chamber via the downstream side of the directional control valve 3.
It is led to 12 and further to regulator 1.

On the other hand, a fixed stop 17 and a variable stop 18
A wide-diameter spring receiving portion 19 is formed integrally with the end of the spool 13 so as to be slidable in the pressure chamber 12. A spring 20 supported on the end face of the pressure chamber 12 is in contact with the spring receiving portion 19.

Although the description is omitted, the pressure compensating valve 10 has the same configuration.

When the directional control valve 3 is opened in the hydraulic drive device configured as described above, the pressure oil from the hydraulic pump 2
With the differential pressure across the directional control valve 3 kept constant through the pressure compensating valve 9, the directional control valve 3 and the check valve 5 flow, and further flow to the hydraulic actuator 7 to drive the hydraulic actuator 7 I do. And the hydraulic actuator 7
Is supplied to the regulator 1 through the pilot circuit 21. Thus, the discharge pressure of the hydraulic pump 2 is controlled so that the difference from the self-pressure of the hydraulic pump 2 is kept constant.

When the directional control valves 3 and 4 are simultaneously operated simultaneously,
If the operation amounts of these directional control valves 3 and 4 are kept constant, the operation of the pressure compensating valves 9 and 10 causes these hydraulic actuators 7 and 8 to receive no change in the load pressure of the other hydraulic actuators. Flows at a constant flow rate, and the hydraulic actuators 7 and 8 are driven at a constant speed.

When it is desired to drive the hydraulic actuators 7 and 8 at high speed, for example, by adjusting the size of the fixed throttle 17 of the spool 13 of the pressure compensating valve 9, the hydraulic pressure can be adjusted with a flow rate characteristic as shown in FIG. The speed of the actuator 7 can be increased. In FIG. 2, II represents a flow rate characteristic obtained when the fixed throttle 17 is not provided.

[0012]

[Problems to be solved by the invention]

When a conventional hydraulic drive device having the above-described pressure compensating valves 9 and 10 is used in a low flow rate region, as shown in FIG.
Compared to IV flow characteristics without fixed throttle 17, fixed throttle 17
, The speed of the hydraulic actuators 7 and 8 changes when the pressure difference ΔP across the directional control valves 3 and 4 changes with a change in load. In the flow rate range, the hydraulic actuators 7 and 8 cannot be driven at a constant speed, and there is a problem that it is difficult to realize a work by a low speed operation.

The present invention has been made in view of such circumstances, and an object thereof is to allow a constant flow rate to flow in a low flow region regardless of an increase in the discharge pressure of a hydraulic pump. An object of the present invention is to provide a hydraulic drive device capable of increasing a flow rate in proportion to an increase in the discharge pressure of a hydraulic pump in a flow rate range.

[0014]

[Means for Solving the Problems]

In order to achieve the above object, a pressure compensating valve for controlling a differential pressure between upstream and downstream of a direction switching valve for controlling a flow of pressure oil supplied from a hydraulic source to a hydraulic actuator is provided. A hydraulic drive device for a construction machine, wherein the drive speed of the hydraulic actuator is controlled by operating the directional control valve, wherein a predetermined reference flow rate is set between an inflow side and an outflow side of the pressure compensating valve. A throttle means which opens in a high flow rate range of the pressure oil discharged from the hydraulic pressure source and closes in a low flow rate range is provided, and the pressure compensating valve controls the front-rear differential pressure regardless of opening and closing of the throttle means. .

[Operation] Since the present invention has the above-described configuration, when the flow rate of the hydraulic oil from the hydraulic pump increases and the high-pressure region is established, and the throttle device is opened, the direction switching is performed. The differential pressure across the valve increases, and control can be performed to increase the flow rate to the corresponding actuator. Conversely, when the flow rate of the hydraulic oil from the hydraulic pump decreases to a low flow rate region and the throttle means is closed, the differential pressure across the directional control valve becomes constant, and the flow rate to the corresponding hydraulic actuator is reduced. Constant control can be performed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partially broken cross-sectional view of the pressure compensating valve of the present embodiment, and the same parts as those of FIG.

It should be noted that the hydraulic pump 2, the direction switching valves 3, 4, the check valve 5,
6, hydraulic actuators 7, 8 and check valves 11, 12 are not shown, but they are provided with the same ones as the conventional hydraulic drive shown in FIG. The connection of the pressure compensating valve described later provided in the embodiment may be considered to be the same as the case of FIG. 3 already described.

As shown in FIG. 1, the pressure compensating valve provided in the present embodiment includes a spool chamber 11 and a pressure chamber 12 formed in a sleeve 10 having an inlet port 14 and an outlet port 15. As in the conventional case, the spool 13 in which the spring receiving portion 19 is integrally formed is housed at the end, and the spring 20 is disposed between the spring receiving portion 19 and the end face of the pressure chamber 12. However, a point different from the conventional one is that only the variable aperture 18 is provided without providing the fixed aperture.

Further, in the vicinity of the pressure compensating valve of the present embodiment, a pipe 22 is provided between the inlet port 14 and the outlet port 15, and a throttle 24 which is opened and closed by an on-off valve 23 is provided in the pipe 22. is there.
The on-off valve 23 receives detection signals from a flow rate detector of the hydraulic pump 2 (not shown) and front and rear differential pressure detectors of the directional switching valves 3 and 4 (not shown), and is driven to open and close by a controller (not shown) for performing logical judgment. Has become. The above-described controller stores a reference flow rate corresponding to a low flow rate region in advance. In addition, a throttle means that opens and closes in accordance with the magnitude of the flow rate of the hydraulic oil discharged from the hydraulic pump 2 by the above-described pipeline 22, the on-off valve 23, and the throttle 24 is configured.

In the present embodiment configured as described above, when the hydraulic actuator 7 drives, for example, a high-load side working machine member, and the hydraulic actuator 8 drives a low-load side working machine member, Each of the detectors detects the pump discharge flow rate and the magnitude of the differential pressure between the direction switching valves 3 and 4, and the on / off valve 23 is opened and closed by a drive signal output from a controller in response to each detection signal. That is, when the controller determines that the pump discharge flow rate detected by the flow rate detector is higher than the reference flow rate and is in a high flow rate range, a drive signal is output from the controller so that the on-off valve 23 is opened. Then, the hydraulic oil is merged upstream of the directional control valves 3 and 4 via the pipeline 22, the on-off valve 23 and the throttle 24, and the flow rate increases with an increase in the differential pressure across the directional control valves 3 and 4. 2 It is possible to obtain the flow characteristics shown in FIG. 1, that is, the same flow characteristics as those of the conventional pressure compensating valves 3 and 4 provided with the fixed throttle.

For this reason, when the load pressure increases and the discharge pressure of the hydraulic pump 2 increases accordingly, the flow rate flowing through the directional control valves 3 and 4 increases in proportion to the discharge pressure. Can be driven as fast as possible.

When it is desired to drive the work implement member at a low speed, the signal output from the flow rate detector is determined by the controller to be a signal corresponding to the reference flow rate, and the on / off valve 23 is closed by the controller. A drive signal is output, and control is performed such that the on-off valve 23 closes and pressure oil does not flow from the throttle 24. As a result, only the variable aperture 18 of the spool 13 works,
The differential pressure between the directional control valves 3 and 4 becomes constant, and a constant flow characteristic as shown in FIG. 2 IV is obtained. This makes it possible to easily realize the work by the fine speed operation.

[0024]

【The invention's effect】

According to the present invention, the throttle means is provided between the inflow side and the outflow side of the spool of the pressure compensating valve according to the magnitude of the flow rate of the pressure oil discharged from the hydraulic pressure source. A flow rate that increases in proportion to an increase in the discharge pressure of the hydraulic pump can flow, and in a low flow rate region, a constant flow rate can flow regardless of the increase in the discharge pressure of the hydraulic pump. The operation by the operation can be easily realized.

[Brief description of the drawings]

FIG. 1 is a partially broken sectional view showing a configuration of a pressure compensating valve provided in an embodiment of a hydraulic drive device for a construction machine according to the present invention.

FIG. 2 is a characteristic diagram showing flow characteristics of a pressure compensating valve provided in an embodiment of the present invention and a conventional hydraulic drive device.

FIG. 3 is a hydraulic circuit diagram showing a configuration of a conventional hydraulic drive device.

FIG. 4 is a partially broken sectional view showing a configuration of a pressure compensating valve provided in the hydraulic drive device shown in FIG.

[Explanation of symbols]

 2 ... Hydraulic pump 3,4 ... Direction switching valve 7,8 ... Hydraulic actuator 9,10 ... Pressure compensation valve 22 ... Pipe line 23 ... On / off valve 24 ... Throttle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-247805 (JP, A) JP-A-57-86602 (JP, A) JP-A-50-28926 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) F15B 11/00-11/22

Claims (2)

(57) [Claims] A pressure compensating valve for controlling a differential pressure between upstream and downstream of a direction switching valve for controlling a flow of pressure oil supplied from a hydraulic source to a hydraulic actuator;
A hydraulic drive system for a construction machine, wherein the drive speed of the hydraulic actuator is controlled by operating the directional control valve, wherein a hydraulic pressure source is provided between an inflow side and an outflow side of the pressure compensating valve from a predetermined reference flow rate. A throttle device that opens in a high flow rate range of the pressure oil discharged from the engine and closes in a low flow rate range, and controls the pressure difference between the front and rear by the pressure compensating valve regardless of the opening and closing of the throttle means. Hydraulic drive. A pressure compensating valve for controlling a differential pressure between upstream and downstream of a direction switching valve for controlling a flow of pressure oil supplied from a hydraulic source to a hydraulic actuator;
In a hydraulic drive device for a construction machine that controls a drive speed of the hydraulic actuator by operating the direction switching valve, a flow rate detector that detects a flow rate of pressure oil discharged from the hydraulic pressure source, a predetermined low flow rate Storing a corresponding reference flow rate, comparing the flow rate detected by the flow rate detector with the reference flow rate, and outputting a first drive signal when the detected flow rate is larger than the reference flow rate; A controller that outputs a second drive signal when the flow rate is smaller than the reference flow rate, and a throttle unit that opens when a first drive signal is input from the controller and closes when a second drive signal is input. A hydraulic drive device for a construction machine, wherein the pressure compensating valve controls the front-rear pressure difference regardless of opening / closing of the throttle means. "