JPH09291903A - Hydraulic controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic controller which is capable of operating an actuator of a construction machine or the like with good operability and without response delay. SOLUTION: The controller coprises an oil pressure control circuit for supplying and exhausting pressure oil from a variable volume pump 12 having an exhaust flow rate adjustment means 10 to each of the actuators 20A and 20B via respective open center-type direction change-over valves 18a and 18b. Then the oil pressure control circuit has respective pilot valve means 22A and 22B operating the direction change-over valve, a variable pressure reducing valve 44 attached to pressure generation means 40 provided on a tank line 36 of a center bypass 16 of the direction change-over valve, the valve 44 decreasing the respective secondary pressure in accordance with the scale of the pressure of the pressure generation means, wherein the maximum pressure P1 out of the operation pressure of respective pilot means and the high pressure side pressure with the secondary pressure P2 of the variable pressure reducing valve are applied to the exhaust flow rate adjustment means 10 as an exhaust flow rate control pressure P3 of the variable volume pump 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a construction machine or the like, and more particularly to a hydraulic control device having improved operability and operation responsiveness in such a control device.

[0002]

2. Description of the Related Art Generally, a hydraulic control device of this type is shown in FIG.
As shown in FIG. 9, pressure oil from the variable displacement pump 12 having the discharge flow rate adjusting means 10 is discharged from the discharge line 14 through the open center type directional control valve 18 having the center bypass line 16 to a hydraulic excavator or the like. Is configured to be supplied to and discharged from the actuator 20. Normally, the operating pressure between the signal lines 24 and 26 of the pilot valve 22 for operating the directional control valve 18 is selected to be high by the shuttle valve 28, and then the discharge flow rate adjusting means 10 is supplied via the signal line 30. Is configured to be applied to.

That is, for example, the pilot valve 22 is operated to the left side L in the figure to operate the operating pressure oil from the hydraulic pump 32 from the signal line 24 to the hydraulic chamber 18b of the directional control valve 18.
When applied to the discharge line 14, the spool 18c moves to the left side in the drawing in the housing 18d.
A part of the pump discharge pressure oil from the throttle opening 18
Center bypass line 16 and tank line 3 via e
4, discharged to the tank 36. Note that FIG. 7 (hydraulic symbol) and FIG. 8 (cross-sectional structure) show a state during the stroke of the spool.

On the other hand, another part of the pump discharge pressure oil from the discharge line 14 is supplied to and discharged from the actuator 20 through the throttle opening 18f and the like, and drives this. In addition, during this period, the pump 12 has its adjusting means 10
The operating pressure in the signal line 24 (operating pressure on the high pressure side)
The discharge flow rate is adjusted by applying.

Therefore, according to such a hydraulic control device, the actuator can be driven to a desired state in response to the operation of the pilot valve means.

[0006]

However, the above-mentioned conventional hydraulic control device still has problems to be improved, especially regarding its operability and responsiveness.

That is, in the hydraulic circuit of the conventional control device, the variable displacement pump controls the discharge flow rate of the operating pilot valve of the operating directional control valve of the actuator as described above when the actuator in the circuit is driven. It is adjusted in accordance with the manipulated variable, in other words, regardless of the manipulated variable of the directional control valve.

However, the connection opening portions 18e and 18f (FIG. 8) for the center bypass line or the actuator line of the directional control valve at the start of operation (when the spool stroke starts) have an extremely small area at the start, Therefore, variations depending on the mutual machining accuracy of the spool and the housing are likely to occur. For this reason,
Actually, the matching between the opening areas 18e and 18f and the pump discharge adjustment flow rate is lost, which causes a difficulty (decrease in operability) such as a shock when the actuator is operated (started).

Here, as a technique for overcoming the above-mentioned difficulties, a new technique has been proposed by the present applicant (Japanese Patent Publication No.
-11881 gazette). That is, this technique will be briefly described. As shown in FIG. 10, the pressure oil from the variable displacement pump 12 having the discharge flow rate adjusting means 10 is discharged from the discharge line 14 to the open center type direction having the center bypass line 16. In a hydraulic circuit for supplying / discharging to / from the actuator 20 via the switching valve 18, the pilot valve 22 means for operating the direction switching valve 18 and the tank line 36 of the center bypass of the direction switching valve 18 are provided in this circuit. The variable pressure reducing valve 44 attached to the pressure generating means 40 via a signal line 42 is provided.

The variable pressure reducing valve 44 is constructed so as to reduce the secondary pressure from the hydraulic pump 32 in accordance with the magnitude of the pressure of the pressure generating means 40.
This secondary pressure is applied to the discharge flow rate adjusting means 10 of the variable displacement pump 12.

Therefore, according to the new technology, unlike the prior art, the variable displacement pump has its discharge flow rate adjusted directly in relation to the operation of the directional control valve. Therefore,
It is obvious that the above-mentioned difficulties (reduction in operability) can be solved.

However, the discharge flow rate adjusting action of the pump according to this new technique is that after the various steps, that is, the pilot valve 22 is operated and the direction switching valve 18 is operated, whereby the center bypass line 16 is operated. The pressure decreases, the pressure in the signal line 42 decreases, the pressure in the signal line 46 increases (that is, is reduced according to the decreased pressure), and as a result, the discharge flow rate adjusting means 1
It is achieved by operating 0.

Therefore, in this new technique, a response delay occurs between the operation of the pilot valve and the resulting pump discharge flow rate adjusting action. That is, another drawback is that the actuator does not operate quickly. By the way, the above-mentioned new technology is originally intended mainly to control the hydraulic control device regardless of the type of the variable displacement pump.

Therefore, an object of the present invention is to provide a hydraulic control device capable of operating an actuator of a construction machine or the like with good operability and without delay in response.

[0015]

In order to achieve the above object, a hydraulic control device according to the present invention allows pressure oil from a variable displacement pump having a discharge flow rate adjusting means to be passed through respective open center type directional control valves. Hydraulic pressure control circuit for supplying / discharging to / from each actuator. The hydraulic control circuit is attached to each pilot valve means for operating the directional control valve and the pressure generating means provided on the tank line of the center bypass of the directional control valve. A variable pressure reducing valve for reducing the secondary pressure according to the magnitude of the pressure of the pressure generating means, the maximum pressure among the operating pressures of the pilot valve means, and The high pressure side pressure between the secondary pressure of the variable pressure reducing valve and the secondary pressure of the variable pressure reducing valve is applied to the discharge flow rate adjusting means as the discharge flow rate control pressure of the variable displacement pump.

In this case, the secondary pressure of the variable pressure reducing valve is
It can be configured to be higher than the maximum operating pressure of the pilot valve means over a part and / or the entire range of the discharge flow rate adjustment of the variable displacement pump.

Further, a pressure adjusting means for further adjusting the control pressure by an external signal can be provided in the application line of the pump discharge flow rate control pressure.

Further, the pump discharge flow rate control pressure application line may be provided with pressure adjusting means for adjusting the control pressure by an external signal so that the pressure is selected as a high pressure.

In the hydraulic control system of the present invention, the control pressure of the pump discharge flow rate is the maximum pressure among the operating pressures of the pilot valve means for operating the directional control valve and the variable pressure reducing valve.
It is selected from the secondary pressure, that is, the high pressure side pressure between the working pressure which is directly communicated with the direction switching valve via the signal line connected to the variable pressure reducing valve and the center bypass line connected to the pressure generating means, and Both pressures are configured so that the secondary pressure of the latter variable pressure reducing valve is higher than the maximum operating pressure of the former pilot valve over a part and / or the entire range of the pump discharge flow rate adjustment range.

Therefore, according to the present invention, it is obvious that the operability of the actuator is improved since the discharge flow rate of the variable displacement pump can be adjusted directly in relation to the operation (amount) of the directional control valve. . Moreover, in this case, the adjusting action of the variable displacement pump is performed at the same operation pilot pressure as that of the directional switching valve itself at least when the operation of the directional switching valve is started (when the actuator is started). It is also possible to eliminate the response delay of the actuator regarding the operation.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a hydraulic control device according to the present invention will be described below in detail with reference to the accompanying drawings. For the sake of convenience of explanation, the same components as those of the conventional and general structures shown in FIGS. 7 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, first, the basic construction of the hydraulic control device according to the present invention is the same as that of the conventional one (particularly shown in FIG. 10).
The configuration is the same as Therefore, although partially overlapped, in order to make it easy to understand, the basic configuration is the variable displacement pump 12 having the discharge flow rate adjusting means 10.
Pressure oil from the discharge line 14 to the center bypass 1
In the hydraulic control circuit for supplying / discharging to / from each actuator 20A, 20B through each (two in the illustrated example) open center type directional control valves 18A, 18B having 6
In the control circuit, signals are sent to the pilot valve 22A, 22B means for operating the direction switching valves 18A, 18B and the pressure generating means 40 provided on the tank line 36 of the center bypass 16 of the direction switching valves 18A, 18B. A variable pressure reducing valve 44 attached via a line 42 is provided.

The variable pressure reducing valve 44 is configured to reduce the secondary pressure P2 (generated on the signal line 50) from the hydraulic pump 32 according to the magnitude of the pressure of the pressure generating means 40. This secondary pressure P2
And the maximum pressure P1 (generated on the signal line 54 via the shuttle valves 52A, 52B and 52C) among the operating pressures of the pilot valves 22A and 22B, the high pressure side pressure P3 (the shuttle valve 52D is Is generated on the signal line 46 via the) as the discharge flow rate control pressure P3 of the variable displacement pump 12 to the discharge flow rate adjusting means 10.

In this case, if the relationship between the maximum operating pressure P1 and the secondary pressure P2 is set as shown in FIG.
If the maximum operating pressure P1 system pressure is set to P11 and the secondary pressure P2 system pressure is set to P21 with respect to the strokes of the directional control valves 18A and 18B, the above-mentioned direction is set. When the switching valves 18A, 18B are suddenly operated, even if there is a response delay in the secondary pressure P2 system, at least the maximum operation pressure P with a small response delay
From the system 1, a signal of the level of pressure P11 is applied to the discharge flow rate adjusting means 10. Therefore, the difference in discharge flow rate (P21-P
11), but each actuator 20A, 20B
Can be reliably started by the discharge flow rate based on the pressure P11, and the responsiveness can be greatly improved.

Moreover, the high-pressure side pressure P3 between the secondary pressure P2 and the maximum pressure P1 of the operating pressures of the pilot valves 22A and 22B is, as shown in FIG. Since the secondary pressure P2, which is the level as a result of the movement of the spools of the switching valves 18A and 18B, is set, the bypass flow rate is determined by the opening area of the center bypass itself even when this is a half operation St1 (see FIG. 2). . As a result, the pressure of the signal line 42 is determined, and the secondary pressure P2 is further determined.
The unbalance of the discharge flow rate with respect to the opening area due to the processing accuracy of the housing and spool of B is significantly large as compared with the conventional method in which the pump discharge flow rate is uniquely determined by the signal pressure of the signal line 30, as shown in FIG. To be improved.

Therefore, according to this embodiment, the discharge flow rate Q of the variable displacement pump 12 is, as shown in FIG. 4, proportional to the control pressure P3 along the high pressure side of the both pressures P2 and P1, the so-called positive type. Is composed of.

Therefore, according to the hydraulic control system of the present invention having such a configuration, the pilot valves 22A, 22B are provided.
It is obvious that the actuators 20A and 20B can be driven to desired states in accordance with the operation amount by operating the.

Further, in the present invention, in the above-described driving, the pilot flow rate is adjusted so that the discharge flow rate of the variable displacement pump is adjusted when the directional control valve is half-operated (when the actuator is started). It is controlled by the maximum operating pressure P1 of. Further, during the full operation of the directional control valve (when the actuator is steadily driven), the secondary pressure P2 of the variable pressure reducing valve which is directly related to the operation amount of the directional control valve (delayed when operating the directional control valve). Since it is configured to be controlled by the above, it is possible to improve the operability of the hydraulic control device and at the same time eliminate the operation delay of the actuator.

Further, the hydraulic circuit of the present invention has the advantages that it can have a relatively simple structure and can be operated easily.

Further, in the present invention, in the above structure, the pressure adjusting means 60 (FIG. 5) for further adjusting the control pressure P3 on the signal line L on the signal line 46 by the external signal 60a.
Is provided (see FIG. 5) or the pressure adjusting means 62 is adjusted by the external signal 62a with respect to the control signal pressure P3.
Can be provided such that its pressure is selected to be high pressure (62b) (see FIG. 6).

With this configuration, the control signal pressure P3 can be optimally matched to the applied device, and thus the above-mentioned effects of the present invention can be further improved.

If a pressure reverse conversion means is provided instead of the pressure adjustment means, the variable displacement pump can be changed from the positive type to the negative type.

While the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and many design changes can be made without departing from the spirit of the present invention.

[0034]

As described above, the hydraulic control device according to the present invention supplies the pressure oil from the variable displacement pump having the discharge flow rate adjusting means to each actuator via each open center type directional control valve. The hydraulic control circuit comprises a pilot pressure control valve for operating the directional control valve and a variable pressure reducing valve attached to the pressure generating means provided on the tank line of the center bypass of the directional control valve. And a variable pressure reducing valve for reducing the secondary pressure according to the magnitude of the pressure of the pressure generating means, the maximum pressure among the operating pressures of the pilot valve means, and the variable pressure reducing valve A high-pressure side pressure between the next pressure and the next pressure is applied to the discharge flow rate adjusting means as the discharge flow rate control pressure of the variable displacement pump, so that the open center type directional control valve is provided. In a hydraulic control device that drives an actuator by adjusting the discharge flow rate of a variable displacement pump, the maximum operating pressure of the pilot valve that is almost followed by the operation of the directional control valve when the directional control valve is half-operated (when the actuator is started). It is possible to control via the secondary pressure of the variable pressure reducing valve which is directly related to the operation amount of the directional control valve when the one-way directional control valve is fully operated (when the actuator is steadily driven). Thus, the operability of the hydraulic control device can be improved, and at the same time, the operation delay of the actuator can be eliminated. Further, the hydraulic control device of the present invention has a relatively simple structure and has an advantage that it can be easily operated.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic control device according to the present invention.

2 is a graph showing the relationship between the maximum operating pressure P1 of the pilot valve, the secondary pressure P2 of the variable pressure reducing valve, and the spool stroke of the directional control valve in the hydraulic circuit shown in FIG.

3 is a graph showing the relationship between the maximum operating pressure P1 of the pilot valve, the secondary pressure P2 of the variable pressure reducing valve, and the control pressure P3 of the pump discharge flow rate in the hydraulic circuit shown in FIG.

4 is a graph showing the relationship between pump control pressure P3 and pump discharge flow rate Q of the variable displacement pump in the hydraulic circuit shown in FIG.

5 is a schematic configuration diagram of a pressure adjusting means provided on a pump signal line 46 of the hydraulic circuit shown in FIG.

6 is a schematic configuration diagram of another pressure adjusting means different from that of FIG. 5 provided on the pump signal line 46 of the hydraulic circuit shown in FIG.

FIG. 7 is a hydraulic symbol diagram of a general open center type directional control valve.

8 is a partial cross-sectional view of the open center type directional control valve shown in FIG.

FIG. 9 is a hydraulic circuit diagram showing a configuration of a conventional hydraulic control device.

FIG. 10 is a hydraulic circuit diagram showing a configuration of another conventional hydraulic control device different from that of FIG.

[Explanation of symbols]

 10 Discharge flow rate adjusting means 12 Variable displacement pump 14 Discharge line 16 Center bypass (line) 18A, 18B Directional switching valve 20A, 20B Actuator 22A, 22B Pilot valve 32 Hydraulic pump 34 Tank 36 Tank line 40 Pressure generating means 42, 46, 50 , 54 Signal line 44 Variable pressure reducing valve 52A, 52B, 52C, 52D Shuttle valve 60, 62 Pressure adjusting means

Claims (4)

[Claims] 1. A hydraulic control circuit for supplying / discharging pressure oil from a variable displacement pump having a discharge flow rate adjusting means to / from each actuator via each open center type directional control valve, wherein the hydraulic control circuit comprises a directional control circuit. A variable pressure reducing valve attached to each pilot valve means for operating the switching valve and the pressure generating means provided on the tank line of the center bypass of the directional switching valve, the variable pressure reducing valve depending on the magnitude of the pressure of the pressure generating means. A variable pressure reducing valve for reducing the secondary pressure, the maximum pressure among the operating pressures of the pilot valve means,
A hydraulic control device configured to apply a high-pressure side pressure between the secondary pressure of the variable pressure reducing valve and the secondary flow rate as a discharge flow rate control pressure of a variable displacement pump to the discharge flow rate adjusting means. 2. The secondary pressure of the variable pressure reducing valve is configured to be higher than the maximum operating pressure of the pilot valve means over a part and / or the whole of the discharge flow rate adjusting range of the variable displacement pump. Item 2. The hydraulic control device according to item 1. 3. The hydraulic control device according to claim 1, wherein the pump discharge flow rate control pressure application line is provided with pressure adjusting means for further adjusting the control pressure by an external signal. 4. The hydraulic control according to claim 1, wherein the pump discharge flow rate control pressure application line is provided with pressure adjusting means for adjusting the control pressure by an external signal so that the pressure is selected as a high pressure. apparatus.