JPH0893705A - Hydraulic driving circuit - Google Patents

Abstract

PURPOSE: To provide a hydraulic driving circuit by which a starting shock can be effectively reduced even when a large inertial load is suddenly operated by arranging a flow rate regulating means on a pump control signal line. CONSTITUTION: A flow rate regulating means 50 to regulate a flow of control pressure oil in a line 46 is arranged on the pump control signal line 46. The flow rate regulating means 50 is composed of a flow regulating valve 50 enclosing a throttle function 50a, and is operated through an external operation signal line 52 applied even to directional control valves 20 and 22. As a result that a flow of control pressure oil in the pump control signal line 46 is regulated through the flow regulating valve 50, the control time equivalent to an increase in a pump delivery flow rate is set without having direct relation to the operation time of the directional control valves, and a starting shock of a hydraulic driving circuit is reduced. A sudden flow of the control pressure oil in the pump control signal line 46 is properly restricted when the flow rate regulating means 50 is actuated in synchronism with sudden operation of the directional control valve 20 through the external operation signal line 52. That is, the pump delivery flow rate is gently increased, and the starting shock is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive circuit for an actuator for a construction machine or the like, and more particularly to a hydraulic drive circuit configured to reduce a shock at the time of starting the actuator in the hydraulic drive circuit of this type. It is about.

[0002]

2. Description of the Related Art Generally, since a hydraulic drive circuit of this type operates a plurality of actuators having different loads at the same time,
Preferably, it is configured as a load sensing control type hydraulic drive circuit having excellent so-called combined operability.

That is, a load sensing control type hydraulic drive circuit (hereinafter simply referred to as a conventional hydraulic drive circuit)
In FIG. 6, as the applied pressure increases or decreases,
A plurality of (two in the illustrated embodiment) are provided on the respective branch discharge lines 16 and 18 of the discharge line 14 of the variable displacement pump 12 provided with the negative flow rate control type discharge flow rate control means 10 for decreasing or increasing the discharge flow rate. The closed center type switching valves 20 and 22 are connected in parallel. The switching valves 20 and 22 are connected to the actuators 24 and 26 via actuator lines 24a, 24b, 26a and 26b, respectively.
The actuators 24 and 26 for operating the actuators 24 and 26 individually or simultaneously by operating 0 and 22
Of the individual and / or maximum load pressures are respectively detected via the load detection lines 28, 30, the high pressure selection means 32 and the maximum load signal line 34.
Further, the maximum load pressure of the maximum load signal line 34 is applied to a flow control valve with pressure compensation 38 provided on a bypass line 36 of the variable displacement pump discharge line 14, and
The bypass line 36 is provided with pressure generating means 40 downstream of the pressure-compensated flow rate control valve 38 to release it to the tank 42, and the pressure of the upstream line 44 of the pressure generating means 40 is changed via the pump control signal line 46 to a variable capacity. It is configured to apply the discharge flow rate control means 10 of the pump 12.

Therefore, in the hydraulic drive circuit configured as described above, the amount of oil supplied to the low load side actuator is limited and the pump discharge pressure drives the high load side actuator during complex operation of actuators having different loads. Since the pressure automatically rises, good composite operability can be achieved without causing obstacles such as cavitation.

[0005]

However, the conventional hydraulic drive circuit described above still has the following drawbacks.

That is, for example, when the actuator 24 has a large inertia load, the switching valve 20 is activated to start it.
Is assumed to be operated to the left (particularly, a sudden operation) in FIG. 6, the branch discharge line 16 is connected to the actuator line 24b and the load detection line 28 via the in-switch valve passage 20a, and The load detection line 28 further includes a high voltage selection means 32 and a load signal line 34.
Is connected so as to act on the flow control valve 38 with pressure compensation via.

However, at this time, if the inertia of the actuator 24 is large as described above, even if the branch discharge line 16 is connected to the actuator line 24b as described above, immediately after the operation of the switching valve, the passage 20a is connected to the passage 20a. No pressure difference is generated before and after the oil passage, and almost no pressure oil flows. On the other hand, pressure oil acts on the load signal line 34 from the load detection line 28 through the high pressure selection means 32. Therefore, the pressure-compensated flow control valve 38 is closed because the differential pressure between the pressure of the load signal line 34 and the bypass line pressure 36a becomes smaller than the spring pressure 38a.

As a result, the pressure oil does not flow to the pressure generating means 40, so that the pressure in the upstream line 44 suddenly drops, and as a result, the variable displacement pump 12 receives the control pressure oil in the pump control signal line 46. The rapid flow to the upstream line 44 causes the discharge flow rate to rapidly increase via the discharge flow rate control means 10.

FIGS. 7A and 7B show this state, that is, the stroke amount St of the switching valve at the time of activation of the large inertia actuator, its operation time Δt1, and the increment Q of the variable displacement pump discharge flow rate. The relationship with the control time Δt2 is shown. Therefore, as is clear from FIG. 7, it is clear that the increase amount Q of the variable displacement pump discharge flow rate can rapidly increase. In the figure, the dotted line shows the amount of pressure oil supplied to the actuator, and both times Δt
It is shown that 1 and Δt2 substantially correspond to each other.

That is, in the conventional hydraulic drive circuit described above, when the large inertia actuator is started, the pressure oil is not immediately supplied to the actuator, but the pump discharge flow rate is about to increase immediately. It had the basic difficulty of occurring.

Therefore, an object of the present invention is to provide a hydraulic drive circuit capable of effectively reducing a start shock even when a large inertia load is suddenly operated to start.

[0012]

In order to achieve the above object, the hydraulic drive circuit according to the present invention is a negative flow rate control type discharge flow rate control means for decreasing or increasing the discharge flow rate with increase or decrease of applied pressure. A plurality of closed center type switching valves are connected in parallel to the discharge line of a variable displacement pump equipped with, and actuators are connected to these switching valves, and these switching valves are operated to drive the actuators individually or simultaneously. When detecting the individual and / or maximum load pressure of the actuator, the maximum load pressure is applied to a flow control valve with pressure compensation provided on the bypass line of the variable displacement pump discharge line, and the bypass line is A pressure generating means is provided on the downstream side of the flow control valve with pressure compensation to release it to the tank to generate the pressure. In a hydraulic drive circuit configured to apply the upstream pressure of the stage to the discharge flow rate control means of the variable displacement pump via a pump control signal line, on the pump control signal line, control pressure oil in the line is supplied. It is characterized in that a flow rate adjusting means for adjusting the flow is provided.

In this case, the flow rate adjusting means is a flow rate adjusting valve operated by an external signal (preferably a switching valve operation signal can be used) or a flow rate adjusting valve with pressure compensation which operates by itself. Can be configured.

[0014]

According to the present invention, by adjusting (for example, limiting) the flow of the control pressure oil in the pump control signal line via the flow rate adjusting means, the control time for the pump discharge flow rate increase is controlled by the operation of the switching valve. It is possible to set (for example, extend) regardless of time. In other words, even when the large inertia actuator is suddenly operated to start up, it is possible to prevent the sudden increase in the pump discharge flow rate at this time,
The starting shock can be effectively reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive circuit according to the present invention will be described in detail below with reference to the accompanying drawings.
For convenience of explanation, the same components as those of the conventional structure shown in FIGS. 6 and 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the basic construction of the hydraulic drive circuit according to the present invention is the same as the conventional one (FIG. 6).
Therefore, in order to make it easy to understand though it is redundant, the hydraulic drive circuit is basically arranged on the discharge line 14 of the variable displacement pump 12 provided with the negative flow rate control type discharge flow rate control means 10. , A plurality of (two) closed center type switching valves 20, 22 are connected in parallel, and actuators 24, 26 are connected to these switching valves 20, 22, respectively, and the switching valves 20, 2 are also connected.
The individual and / or maximum load pressures of the actuators 24 and 26 when operating the actuators 24 and 26 individually or simultaneously by operating the load detection lines 28 and 30, the high voltage selecting means 32 and the maximum load signal line 34, respectively. It is configured to be detected through. Then, the maximum load pressure of the maximum load signal line 34 is set to the discharge line 14
The pressure is applied to the flow control valve with pressure compensation 38 provided on the bypass line 36 of the above, and the bypass line 36 is provided with the pressure generating means 40 downstream of the flow control valve with pressure compensation 38 to release it to the tank 42 to generate the pressure. The pressure of the upstream line 44 of the means 40 is configured to be applied to the discharge flow rate control means 10 via the pump control signal line 46.

However, in the present invention, in the above-mentioned structure, the line 4 is provided on the pump control signal line 46.
6. A flow rate adjusting means 50 for adjusting the flow of the internal control pressure oil is provided. In this embodiment, the flow rate adjusting means 50
Is formed by a flow rate adjusting valve 50 having a throttle function 50a incorporated therein, and the flow rate adjusting valve 50 is operated via an external operation signal line 52 which is also applied to the operation of the switching valves 20 and 22. .

Therefore, according to the present invention, as described in detail below, the flow of the control pressure oil in the pump control signal line 46 is adjusted through the flow rate adjusting valve 50, and as a result, the pump discharge flow rate increase amount is increased. The control time is set irrespective of the operating time of the switching valve, which reduces the starting shock of the hydraulic drive circuit.

That is, as in the case of the conventional example (FIG. 6), when the actuator 24 has a large inertia load,
Assuming that the switching valve 20 is suddenly operated to activate it, the branch discharge line 16 is connected to the actuator 24 and the load detection line 28 acts on the pressure-compensated flow control valve 38 as described above. Therefore, in the conventional example, although the pressure oil is not immediately supplied to the actuator, the variable displacement pump 12 immediately changes the pump discharge flow rate due to the rapid flow of the control pressure oil in the pump control signal line 46. Attempting to increase suddenly, a starting shock occurs.

In the present invention, however, the rapid flow of the control pressure oil in the pump control signal line 46 is controlled by the flow rate adjusting means 50 via the external operation signal line 52.
By operating in synchronization with the sudden operation of 0, the limitation is appropriately made. That is, the pump discharge flow rate gradually increases and the start shock is reduced. 2A and 2B
7 shows this state in comparison with the conventional example [(a) and (b) of FIG. 7]. That is, (a) and (b) of FIG.
At the same stroke length St, operation time Δt1 and discharge flow rate increase Q of the switching valve and the variable displacement pump, the pump control time is changed from the conventional Δt2 to the Δ of the present invention.
It is shown to be significantly extended to t2 '. Incidentally, the negative flow rate control type discharge flow rate control means 1
As shown in FIG. 3, for example, 0 normally includes a servo valve 10a, an operating piston 10b, etc., and holds a considerable amount of control pressure oil, and this control pressure oil is used as a switching valve 20, 22.
During the operation of, the signal line 46 flows to the upstream side 44.

As described above, according to the present invention, by adjusting the flow of the control pressure oil in the pump control signal line via the flow rate adjusting means, the control time for the pump discharge flow rate increase can be changed to the operation time of the switching valve. Can be set (extended) regardless of. Therefore, even when the large inertia actuator is suddenly operated to start, the start shock can be effectively reduced. In the present invention, the control time can be shortened contrary to the above,
On the contrary, the small inertia actuator or the like may be rapidly operated depending on the situation. Further, by appropriately operating the flow rate adjusting means, it is possible to prevent the operability from changing due to a change in pressure oil viscosity due to temperature, for example.

FIG. 4 and FIG. 5 show another embodiment of the flow rate adjusting means according to the present invention. First, the flow rate adjusting means 54 shown in FIG. 4 is formed by a flow rate adjusting valve 54 having a pressure compensating flow rate controlling function 54a, and is operated via an external signal line 52 as in the case of the flow rate adjusting valve 50 described above. It is configured as follows. On the other hand, the flow rate adjusting means 56 shown in FIG. 5 is formed by the pressure compensating flow rate control valve 56, and is configured to operate by itself through the pressure fluctuation in the pump control signal line 46. It should be noted that, in any of the embodiments, it is clear that almost the same operation as in the above-mentioned embodiments can be achieved, and therefore detailed description thereof will be omitted.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit of the present invention.

[0024]

As described above, in the hydraulic drive circuit according to the present invention, a plurality of closed center type switching valves are connected in parallel to the discharge line of the variable displacement pump having the negative flow rate control type discharge flow rate control means. However, an actuator is connected to each of these switching valves, and individual and / or maximum load pressures of these actuators are detected, and this maximum load pressure is provided on the bypass line of the variable displacement pump discharge line with a pressure-compensated flow rate. In addition to being applied to the control valve, the bypass line is provided with pressure generating means on the downstream side of the flow control valve with pressure compensation to release it to the tank, and the pressure on the upstream side of the pressure generating means is passed through the pump control signal line. In the load sensing control type hydraulic drive circuit for applying to the discharge flow rate control means, on the pump control signal line, By adopting the configuration in which the flow rate adjusting means for adjusting the flow of the control pressure oil in the line is provided, the flow of the control pressure oil in the pump control signal line is adjusted through the flow rate adjusting means to increase the pump discharge flow rate. The control time can be set (extended) regardless of the operation time of the switching valve.

Therefore, according to the hydraulic drive circuit of the present invention,
Even when the large inertia actuator is suddenly operated to start, the starting shock can be effectively reduced.
In the present invention, for example, it is possible to reversely operate the small inertia actuator or the like rapidly depending on the situation, and to prevent the operability from changing due to the change in pressure oil viscosity due to temperature, for example. It is also possible to achieve the advantages such as being able to do so.

[Brief description of drawings]

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

2A and 2B show operating characteristics of the hydraulic drive circuit shown in FIG. 1, in which FIG. 2A is a characteristic diagram of switching valve operation time, and FIG.
FIG. 4 is a characteristic diagram of pump control time.

FIG. 3 is a hydraulic circuit diagram showing a discharge flow rate control means in the hydraulic drive circuit shown in FIG.

4 is a symbol diagram showing another embodiment of the flow rate adjusting means in the hydraulic drive circuit shown in FIG.

5 is a symbol diagram showing still another embodiment of the flow rate adjusting means in the hydraulic drive circuit shown in FIG.

FIG. 6 is a hydraulic circuit diagram showing a conventional hydraulic drive circuit.

7A and 7B show operational characteristics of the hydraulic drive circuit shown in FIG. 6, in which FIG. 7A is a characteristic diagram of switching valve operation time, and FIG.
FIG. 4 is a characteristic diagram of pump control time.

[Explanation of symbols]

 10 Discharge Flow Rate Control Means 12 Variable Displacement Pump 14 Discharge Lines 16, 18 Branch Discharge Lines 20, 22 Switching Valves 24, 26 Actuators 28, 30 Load Detection Lines 32 High Pressure Selection Means 34 High Pressure Load Signal Lines 38 Pressure Compensated Flow Control Valves 40 Pressure generating means 42 Tank 44 Upstream line 46 Pump control signal lines 50, 54, 56 Flow rate adjusting means

Claims (4)

[Claims] 1. A plurality of closed center type switching valves are connected in parallel to a discharge line of a variable displacement pump equipped with a negative flow rate control type discharge flow rate control means for decreasing or increasing a discharge flow rate with an increase or decrease in applied pressure. However, actuators are connected to these switching valves, and the individual and / or maximum load pressures of the actuators when operating these switching valves to drive the actuators individually or simultaneously, the maximum load pressures are detected. While applying to the pressure compensating flow rate control valve provided on the bypass line of the variable capacity pump discharge line, the bypass line is provided with pressure generating means downstream of the pressure compensating flow rate control valve to release to the tank, The pressure on the upstream side of the pressure generating means is supplied to the variable displacement pump through a pump control signal line. A hydraulic drive circuit configured to apply the discharge flow rate control means, wherein a flow rate adjusting means for adjusting a flow of control pressure oil in the line is provided on the pump control signal line. 2. The hydraulic drive circuit according to claim 1, wherein the flow rate adjusting means comprises a flow rate adjusting valve operated by an external signal. 3. The hydraulic drive circuit according to claim 2, wherein the external signal comprises a switching valve operation signal. 4. The hydraulic drive circuit according to claim 1, wherein the flow rate adjusting means comprises a flow rate adjusting valve with pressure compensation capable of operating by itself.