JP3056220B2 - Hydraulic drive - Google Patents

Description

The present invention relates to a hydraulic drive device for a hydraulic machine such as a hydraulic excavator, and particularly for controlling the operation of a hydraulic actuator in a gravitational direction, such as an arm cloud and a boom lowering. The present invention relates to a hydraulic drive device suitable for the present invention.

[Conventional technology]

As shown in FIG. 12, a conventional hydraulic drive device of a hydraulic shovel, for example, includes a hydraulic pump 10, a hydraulic actuator, for example, a boom cylinder 2 for driving a boom 1, an arm cylinder 4 for driving an arm 3, and hydraulic actuators 2, 4. It has direction switching valves 11 and 100 connected to each.
The direction switching valve 100 on the arm cylinder 4 side is a flow control valve 10
1. A pressure compensating valve 14 and a check valve 15. The flow control valve 101 is moved by the pilot pressure from a pilot valve (not shown) being pressurized in the A or B direction, and the driving of the arm cylinder 4 is switched. I do. The direction switching valve 11 on the boom cylinder 2 side is similarly configured.

In the cloud operation of the arm cylinder 4, during excavation under meter-in control, the pilot pressure is increased in the direction A of the flow control valve 101, and the metered-in variable throttle is opened.
The pressure compensating valve 14 is operated so that the pressure difference before and after 18 is substantially constant. As a result, the passing flow rate Q18 of the flow control valve 101 is not affected by the pressure fluctuation of the pressure oil, and a flow rate proportional to the variable throttle opening is supplied to the bottom chamber 4a of the arm cylinder 4.

The hydraulic pump 10 also has a pump regulator 24 that controls the pump discharge amount so that the pump discharge pressure is higher than the maximum load pressure of the hydraulic actuators 2 and 4 by a certain differential pressure.
And so-called load sensing control is performed. For this reason, for example, when the discharge amount of the hydraulic pump 10 is not saturated, for example, when the arm is alone, the hydraulic pump 10
The flow rate Qp almost equal to Q18 is discharged.

On the other hand, in the cloud operation of the same arm cylinder 4, at the time of free fall as meter-out control, the return oil from the rod chamber 4 b of the arm cylinder 4 discharged by its own weight is discharged by the meter-out variable throttle 102 in the flow control valve. By controlling the flow rate to the reservoir 16, the speed of the arm cylinder 4 is controlled. That is, the speed control method differs between excavation and free fall.

Here, the throttle amount characteristic of the variable throttle 102 compares the flow rate Q82 discharged from the rod chamber 4b of the arm cylinder with the flow rate Q18 supplied to the bottom chamber 4a so that cavitation does not occur in the bottom chamber 4a. It is determined in advance. This is because the occurrence of cavitation causes a breathing phenomenon of the arm and significantly impairs the workability of the excavator.

Further, in the case of a hydraulic shovel, there is a case where the hydraulic pump 10 is operated with a reduced rotation speed of a prime mover (not shown) for driving the hydraulic pump 10 due to a problem such as noise. In this case, the discharge amount of the hydraulic pump is also reduced. It is necessary to prevent the above-mentioned breathing phenomenon from occurring even in the free fall in such a driving state.
The aperture amount of 2 is set based on this case. Therefore, in a normal operation in which the rotation speed of the prime mover is high, the discharge amount of the hydraulic pump 10 is also large, and the back pressure generated in the meter-out variable throttle 102 becomes a resistance, and energy loss occurs during excavation. The hydraulic horsepower at this time is Pp × Qp = Pp × Q18, where Pp is the pump discharge pressure.

When the arm cloud is operated by a combined operation with the boom raising, the load pressure of the boom cylinder 2 is higher than the load pressure of the arm cloud, so that the discharge flow rate of the hydraulic pump 10 is given priority over the arm cylinder 4 on the low pressure side. Flows to For this reason, when the rotation speed of the prime mover decreases and the pump discharge amount Qp decreases, it is not possible to secure sufficient pressure oil to be supplied to the boom cylinder 2. That is, the discharge amount of the hydraulic pump 10 is saturated. This is called saturation, and is one of the issues in load sensing control.

To cope with the above problems, Japanese Patent Application Laid-Open No. 63-83808 discloses that the rod chamber 4b
It has been proposed to supply a part of the return oil from the cylinder to the arm cylinder again to reduce the energy loss and the saturation. That is, a regeneration circuit is provided in which the rod chamber 4b of the arm cylinder 4 and the flow control valve 101 are connected between the pressure compensating valve 14 and the flow control valve 101 via a check valve and a throttle member. At the time of arm cloud,
Due to the back pressure between the arm cylinder rod chamber 4b and the flow control valve 101, a part of the return oil from the arm cylinder rod chamber 4b is released through the check valve and the throttle member of the regeneration circuit.
It flows between 14 and the flow control valve 101, and is supplied again through the flow control valve to the arm cylinder bottom chamber 4a. As a result, the flow rate supplied from the hydraulic pump 10 to the arm cylinder is reduced by the amount of the regenerated pressure oil, energy loss is reduced, and the hydraulic pump 10 is hardly saturated.

[Problems to be solved by the invention]

However, in the prior art described in JP-A-63-83808, as a result of the provision of the regeneration circuit, the supply port of the flow control valve 101 on the pressure compensating valve 14 side communicates with the rod chamber 4b of the arm cylinder 4 through the regeneration circuit. It is possible. For this reason, after the heavy object is lifted by the arm 3, the flow control valve 101
When the load is returned to the neutral position and the heavy object is held at the lifted height, the load pressure in the arm cylinder rod chamber 4b is increased by the work port connected to the rod chamber 4b of the flow control valve 101 and the supply port. Port and flow control valve 101
Therefore, there is a problem that the amount of leakage in the flow control valve increases, and the movement of the arm 3 makes it difficult to hold a heavy object at a desired height.

Further, the conventional apparatus shown in FIG.
In the conventional device described in the above item, at the time of free fall as meter-out control, the flow rate of return oil from the arm cylinder 4 to the reservoir 16 is controlled by the meter-out variable throttle 102 in the flow rate control valve as described above, The speed of the arm cylinder 4 is controlled.
Is configured to function as it is during excavation, which is meter-in control, and there has been a problem that during excavation, the return oil from the arm cylinder 4 is throttled, and energy loss occurs.

A first object of the present invention is to return a part of the return oil from the hydraulic actuator to the supply side at the time of meter-out control, to reduce the energy loss and the saturation of the pump discharge amount, and to set the flow control valve in the neutral position. It is an object of the present invention to provide a hydraulic drive device that does not cause an increase in the amount of leakage when the hydraulic drive device is located at

A second object of the present invention is to return a part of the return oil from the hydraulic actuator to the supply side during the meter-out control to reduce the energy loss and the saturation of the pump discharge amount. To provide a hydraulic drive device capable of reducing the pressure.

[Means for solving the problem]

The first and second objects are to provide a hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply. A hydraulic oil supply source for controlling the supply of pressure oil to the hydraulic actuator and the discharge of pressure oil from the hydraulic actuator to the reservoir, and a flow control valve for controlling the drive direction and drive speed of the hydraulic actuator; A hydraulic drive device for controlling the discharge amount of the hydraulic pump such that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a constant differential pressure, wherein a metering-out variable throttle and a reservoir of the flow control valve are provided; A pressure generating means is provided in a discharge line between the pressure generating means and a portion between the metering-out variable throttle of a flow control valve of the discharge line and the pressure generating means. A regeneration circuit connected to a supply line between the pressure oil supply source and the flow control valve via a check valve; the pressure generation means comprising a variable restriction member; This is achieved by guiding the load pressure of the hydraulic actuator to a member and changing the throttle characteristic according to the load pressure.

The first and second objects are to provide a pressure oil supply source having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply source, A hydraulic oil supply from the source to the hydraulic actuator and a flow control valve for controlling the driving direction and the driving speed of the hydraulic actuator by controlling the discharge of the hydraulic oil from the hydraulic actuator to the reservoir, respectively. In the hydraulic drive device for controlling the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a constant differential pressure, the variable throttle of meter-out of the flow control valve is provided. Pressure generating means is provided in the discharge line between the
A portion between the metering variable throttle of the flow control valve of the discharge line and the pressure generating means is connected to a supply line between the pressure oil supply source and the flow control valve via a check valve. Providing a connected regeneration circuit; further comprising a pressure compensating valve provided in a supply pipe line between the pressure oil supply source and the flow control valve, for maintaining a differential pressure across the flow control valve constant. The pressure generating means comprises a variable throttle member, which guides the pressure between the pressure compensating valve and the flow control valve to the variable throttle member, and changes the throttle characteristic according to the pressure.

The first and second objects are to provide a pressure oil supply source having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply source, A hydraulic oil supply from the source to the hydraulic actuator and a flow control valve for controlling the driving direction and the driving speed of the hydraulic actuator by controlling the discharge of the hydraulic oil from the hydraulic actuator to the reservoir, respectively. In the hydraulic drive device for controlling the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a constant differential pressure, the variable throttle of meter-out of the flow control valve is provided. Pressure generating means is provided in the discharge line between the
A portion between the metering variable throttle of the flow control valve of the discharge line and the pressure generating means is connected to a supply line between the pressure oil supply source and the flow control valve via a check valve. A regeneration circuit connected thereto is provided; wherein the pressure generating means comprises a variable relief valve, and the load pressure of the hydraulic actuator is guided to the variable relief valve, and the relief characteristic is changed according to the load pressure. You.

Further, the first and second objects are to provide a hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply. A hydraulic oil supply from the source to the hydraulic actuator and a flow control valve for controlling the driving direction and the driving speed of the hydraulic actuator by controlling the discharge of the hydraulic oil from the hydraulic actuator to the reservoir, respectively. In the hydraulic drive device for controlling the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a constant differential pressure, the variable throttle of meter-out of the flow control valve is provided. Pressure generating means is provided in the discharge line between the
A portion between the metering variable throttle of the flow control valve of the discharge line and the pressure generating means is connected to a supply line between the pressure oil supply source and the flow control valve via a check valve. Providing a connected regeneration circuit; further comprising a pressure compensating valve provided in a supply pipe line between the pressure oil supply source and the flow control valve, for maintaining a differential pressure across the flow control valve constant. The pressure generating means comprises a variable relief valve, which guides the pressure between the pressure compensating valve and the flow control valve to the variable relief valve, and changes the relief characteristic according to the pressure.

Further, the first object is to provide a pressure oil supply source having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply source, and Each of which controls the supply of pressure oil to a hydraulic actuator and the discharge of pressure oil from the hydraulic actuator to a reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes: In a hydraulic drive device that controls the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a certain differential pressure, a metering-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in the discharge line between the pressure control means and the flow control valve of the discharge line. A regeneration circuit connected to a supply line between the pressure oil supply source and the flow control valve via a check valve is provided; an adjustment means for changing the characteristic of the pressure generation means is provided; This is achieved by operating the adjusting means according to the target rotation speed or the actual rotation speed of the prime mover that drives the hydraulic pump, and changing the characteristics of the pressure generating means.

Further, the first object is to provide a pressure oil supply source having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply source, and Each of which controls the supply of pressure oil to a hydraulic actuator and the discharge of pressure oil from the hydraulic actuator to a reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes: In a hydraulic drive device that controls the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a certain differential pressure, a metering-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in the discharge line between the pressure control means and the flow control valve of the discharge line. A regeneration circuit connected to a supply line between the pressure oil supply source and the flow control valve via a check valve; a supply pipe between the pressure oil supply source and the flow control valve Further comprising a pressure compensating valve provided in the passage for maintaining the differential pressure across the flow control valve constant, wherein the regeneration circuit is connected to a supply line between the pressure compensating valve and the flow control valve. Is done.

Further, the first object is to provide a pressure oil supply source having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply source, and Each of which controls the supply of pressure oil to a hydraulic actuator and the discharge of pressure oil from the hydraulic actuator to a reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes: In a hydraulic drive device that controls the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a certain differential pressure, a metering-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in the discharge line between the pressure control means and the flow control valve of the discharge line. A regeneration circuit connected to a supply line between the pressure oil supply source and the flow control valve via a check valve; a supply pipe between the pressure oil supply source and the flow control valve A pressure compensating valve provided in the passage, the pressure compensating valve maintaining the differential pressure across the flow control valve constant, wherein the regeneration circuit is connected to a supply line between the pressure oil supply source and the pressure compensating valve. Achieved.

Further, the first object is to provide a pressure oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by pressure oil supplied from the pressure oil supply, and Each of which controls the supply of pressure oil to a hydraulic actuator and the discharge of pressure oil from the hydraulic actuator to a reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes: In a hydraulic drive device that controls the discharge amount of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the load pressure of the hydraulic actuator by a certain differential pressure, a metering-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in the discharge line between the pressure control means and the flow control valve of the discharge line. A regeneration circuit connected to a supply line between the pressure oil supply source and the flow control valve via a check valve; a supply pipe between the pressure oil supply source and the flow control valve This is achieved by further comprising a check valve provided in the passage for preventing the backflow of the pressure oil, wherein the regeneration circuit is connected to a supply line between the check valve and the flow control valve.

[Action]

In the present invention configured as described above, during meter-out control such as free fall, between the meter-out variable restrictor of the flow control valve and the reservoir (hereinafter simply referred to as "between the flow control valve and the reservoir"). The pressure generating means provided at the function as a base of the meter-out variable throttle, and a part of the return oil from the hydraulic actuator passes through the regeneration circuit between the flow control valve and the pressure generating means to the supply side downstream of the flow control valve. And flows back through the flow control valve to the hydraulic actuator. Therefore, the flow rate supplied from the hydraulic pump to the hydraulic actuator is reduced by an amount corresponding to the regeneration flow rate. As a result, the energy loss is reduced, and the pump discharge amount is hardly saturated,
Complex operability is improved.

Further, since the regeneration circuit is configured to guide return oil from downstream of the flow control valve, the regeneration circuit is shut off from the hydraulic actuator by the flow control valve at the neutral position of the flow control valve. Therefore, after lifting a heavy object by the hydraulic actuator, when the flow control valve is returned to the neutral position and the heavy object is to be held at the lifted position, the load pressure of the hydraulic actuator is supplied to the supply port of the flow control valve and the built-in port. It does not affect road checks. For this reason, the leak amount does not increase in the flow control valve unlike the related art,
It is easy to hold heavy objects.

Further, in the present invention, the pressure generating means provided between the flow control valve and the reservoir functions as a base of the meter-out variable throttle, so that the meter-out variable throttle in the flow control valve is weakened by the base. can do. That is, the combination of the meter-out variable throttle in the flow control valve and the pressure generating means constitutes a substantial meter-out variable throttle. The variable throttle in the flow control valve is such that it hardly functions as a throttle during meter-in control such as when excavating with an arm.

Therefore, when the pressure generating means is constituted by a variable throttle member or a variable relief valve, the load pressure of the hydraulic actuator is guided to the variable throttle member or the variable relief valve, and the throttle characteristic or the relief characteristic is changed according to the load pressure. In meter-in control, the variable throttle member or the relief valve is opened by the load pressure of the hydraulic actuator, and the return oil from the hydraulic actuator is throttled or relieved, so that energy loss during excavation does not occur or is significantly reduced. When a pressure compensating valve is provided, the pressure between the pressure compensating valve and the flow control valve changes in proportion to the load pressure, so instead of guiding the load pressure of the hydraulic actuator to the variable throttle member or the variable relief valve, The same applies when the pressure between the pressure compensating valve and the flow control valve is derived.

Further, when the pressure generating means is provided with an adjusting means for changing its characteristic, and when the adjusting means is operated according to the target rotation speed or the actual rotation speed of the prime mover for driving the hydraulic pump, the target rotation speed of the prime mover is provided. Alternatively, the characteristic of the pressure generating means is adjusted so that the setting of the throttle amount or the relief pressure is weakened when the actual rotation speed is high, and the setting of the throttle amount or the relief pressure is increased when the rotation speed decreases. Thus, even when the rotation speed of the prime mover changes, the back pressure generated by the pressure generating means during the meter-out control is adjusted according to the rotation speed so that the breathing phenomenon does not occur and excessive energy loss does not occur. As a result, operability is improved and further energy saving can be achieved.

Further, in the case where the pressure oil supply source and the flow control valve are further provided with a pressure compensating valve which is provided in a supply pipe between the flow control valve and the pressure differential valve before and after the flow control valve to maintain a constant pressure difference, As a method, there are a case where the supply line is connected between the pressure compensating valve and the flow control valve, and a case where the supply line is connected between the pressure oil supply source and the pressure compensating valve. However, since the regeneration circuit is configured to guide the return oil from downstream of the flow control valve, the regeneration circuit is shut off from the hydraulic actuator by the flow control valve when the flow control valve is in the neutral position, not only in the former case but also in the latter case. , Heavy objects can be held. In the latter case, at the time of meter-out control, the return oil from the hydraulic actuator can be distributed to other hydraulic actuators.

If the supply line between the pressure oil supply source and the flow control valve is further provided with a check valve for preventing backflow of the pressure oil, the regeneration circuit is supplied between the check valve and the flow control valve. By connecting to the pipeline, the entire amount of return oil from the actuator can be reliably returned to the actuator and regenerated.

〔Example〕

 Hereinafter, one embodiment of the present invention will be described with reference to FIG.

In FIG. 1, the hydraulic drive device of the present embodiment is shown as an example applied to a hydraulic shovel, and serves as a hydraulic actuator for driving a boom cylinder 2 and an arm 3 for driving a boom 1 of the hydraulic shovel. Arm cylinder 4. The hydraulic drive device has a variable displacement hydraulic pump 10, and the boom cylinder 2 and the arm cylinder 4 are driven by pressure oil supplied from the hydraulic pump 10. The hydraulic pump 10 is driven by a motor (not shown). Directional switching valves 11 and 12 are arranged between the hydraulic pump 10 and the boom cylinder 2 and the arm cylinder 4, respectively.

The directional control valve 12 includes a flow control valve 13, a pressure compensating valve 14, and a check valve 15. The flow control valve 13 moves when a pilot pressure from a pilot valve (not shown) is increased in the A or B direction. Then, the supply of the pressure oil from the hydraulic pump 10 to the arm cylinder 4 and the discharge of the pressure oil from the arm cylinder 4 to the reservoir 16 are controlled, and the driving direction and the driving speed of the arm cylinder 4 are controlled. That is, the flow control valve 13
At the position on the right side in the figure when pressurized in the direction, the pressure oil supply line 17 of the hydraulic pump 10 is connected to the line 19 connected to the bottom chamber 4a of the arm cylinder 4 via the internal variable throttle 18. In addition to forming a meter-in circuit, the pipe 20 connected to the rod chamber 4b of the arm cylinder 4 is connected to the first discharge pipe 21 via a flow path 33 described later therein, thereby forming a meter-out circuit. I do. In addition, at the position on the left side of the drawing when pressurized in the B direction, the pressure oil supply pipe 17 is connected to an internal variable throttle.
The line 20 is connected to the line 20 to form a meter-in circuit, and the line 19 is connected to the second discharge line 23 to form a meter-out circuit. Therefore, at the position on the right side in the figure, the pressure oil from the hydraulic pump 10 is supplied to the bottom chamber 4a of the arm cylinder 4
And the arm cylinder 4 is driven in the extension direction at a speed corresponding to the amount of throttle of the variable throttle 18, and at the position on the left side of the drawing, pressure oil from the hydraulic pump 10 is supplied to the rod chamber 4 b of the arm cylinder 4, The arm cylinder 4 is driven in a contraction direction at a speed corresponding to the amount of the stop of the variable stop 22.

The pressure compensating valve 14 is provided in a supply line 17 constituting a meter-in circuit between the hydraulic pump 10 and the flow rate control valve 13. When the arm cylinder 4 is driven, the pressure compensating valve 14 is positioned before and after the opened meter-in variable throttle 18 or 22. It operates so that the differential pressure becomes almost constant. As a result, the passing flow rate Q18 of the flow control valve 18 becomes a flow rate proportional to the variable throttle opening without being affected by the fluctuation of the discharge pressure of the hydraulic pump 10 and the load pressure of the arm cylinder 4. Speed control becomes possible. The check valve 15 is provided between the pressure compensating valve 14 and the flow control valve 13, and prevents the backflow of the pressure oil.

The direction switching valve 11 on the side of the boom cylinder 2 is similarly configured.

The hydraulic pump 10 is provided with a pump regulator 24 for controlling the discharge amount so that the discharge pressure becomes higher than the load pressure on the high pressure side of the boom cylinder 2 and the arm cylinder 4, that is, the maximum load pressure by a certain differential pressure. Performing sensing control. For this reason, in the work in which the discharge amount of the hydraulic pump 10 is not saturated, for example, in the independent operation of the arm 3 when the prime mover is at a high rotation speed, the hydraulic pump 10 discharges a flow rate substantially equal to the passing flow rate Q18.

The load pressure of the arm cylinder 4 is taken out from the inside of the flow control valve 13 by the load line 25, and the load pressure of the boom cylinder 2 is likewise taken out by the load line 26. The maximum pressure of both is selected by the selection valve 27, Retrieved on line 28. The load pressure taken out by the load line 25 is led as an outlet pressure of the flow control valve 13 to act on the pressure compensating valve 14 so as to oppose the inlet pressure of the flow control valve 13;
The above-described pressure compensation control is performed. At this time, the flow control valve 13
Is determined by the strength of the spring 29. Load line 26
The same applies to the side. The maximum load pressure taken out by the load line 28 is supplied to the pump regulator 24 by the hydraulic pump.
It is guided so as to oppose the discharge pressure of 10 and performs the above-described load sensing control.

As a feature of the present embodiment, a throttle 30 is provided as a pressure generating means at a portion between the flow control valve 13 and the reservoir 16 of the first discharge line 21, and between the flow control valve 13 and the throttle 30,
A regeneration line between the check valve 15 and the flow control valve 13 of the supply line 17
The regeneration line 31 is provided with a check valve 32 that allows only the flow of the pressure oil from the discharge line 21 to the supply line 17.

The aperture 30 functions as a base of a meter-out variable aperture during arm-cloud control for meter-out control described later. That is, in this embodiment, the meter-out variable throttle is configured by combining the variable throttle in the meter-out flow path 33 in the flow control valve 12 and the throttle 30. For this reason, the variable throttle in the meter-out channel 33 in the flow control valve 12 is weakened by the amount corresponding to the base of the throttle 30. The degree of this throttle is such that it hardly functions as a throttle during excavation, which is meter-in control described later. In this sense, FIG.
The meter-out channel 33 of the flow control valve 13 does not show a throttle symbol.

Next, the operation of this embodiment will be described. First, the concept of meter-in control and meter-out control related to the description of the operation of the present embodiment will be described with reference to FIGS.

2 and 3, the hydraulic excavator includes, as a front attachment, a boom 1 driven by the boom cylinder 2 and an arm 3 driven by an arm cylinder 4, and a bucket 5 driven by a bucket cylinder 6. Have.

In FIG. 2, the arm 3 is about to freely fall in the direction of gravity in the cloud operation, and at this time, the flow control valve 13 of the directional control valve 12 connected to the arm cylinder 4 is acted on by pilot pressure in the A direction. The position is switched to the right position. At this position, the free fall speed of the arm 3 is controlled by appropriately controlling the discharge of the return oil from the rod chamber 4b of the arm cylinder 4 to the reservoir 16. This control during free fall is called meter-out control.

On the other hand, FIG. 3 shows a state at the time of excavation, and the flow control valve 13 of the directional control valve 12 connected to the arm cylinder 4 is also at the right position in the drawing, and the hydraulic oil from the hydraulic pump 10 The driving speed of the arm cylinder 4 is controlled by appropriately controlling the supply of the arm cylinder 4 to the bottom chamber 4a. This control during excavation is called meter-in control.

In this embodiment, the control at the time of excavation, which is the meter-in control, is the same as the conventional one. That is, at the time of meter-in control,
Since the meter-in circuit pressure is greater than the meter-out circuit pressure, the check valve 32 of the regeneration circuit is closed, and the differential pressure across the meter-in variable throttle 18 that is opened by the pilot pressure acting in the direction A of the flow control valve 13 substantially decreases. The pressure compensating valve 14 operates so as to be constant. Here, the opening area of the variable diaphragm 18 is
A18, if the differential pressure before and after is ΔPA, meter-in variable throttle
The flow rate Q18 passing through 18 is The flow rate Q18 is proportional to the variable throttle opening A18. That is, the arm cylinder 4 is driven in the extension direction at a speed corresponding to the amount of aperture of the variable aperture 18.

Further, at this time, since the pump regulator 24 is provided and the load sensing control is performed, the hydraulic pump 10 is not used for the operation in which the discharge amount of the hydraulic pump 10 is not saturated, for example, the operation of the arm 3 alone when the prime mover is at a high rotation speed. Numeral 10 discharges a flow rate substantially equal to the passing flow rate Q18. That is,
Assuming that the pump discharge amount is Qp, control is performed so that Qp = Q18.

During free fall, which is meter-out control, the pressure oil in the bottom chamber 4b is discharged by its own weight, and the flow rate in the flow rate control valve 13 is reduced.
The combination of the variable throttle at 33 and the throttle 30 at the discharge line 21 increases the pressure in the meter-out circuit, and controls the discharge of return oil from the rod chamber 4b of the arm cylinder 4 to control the speed of the arm cylinder 4, i. Controls the speed of the fall. At this time, the meter-out pressure is greater than the meter-in pressure due to the area ratio between the rod chamber 4a of the arm cylinder 4 and the bottom chamber 4b. In the present embodiment, the pressure of the meter-out circuit in the discharge line 21 between the flow control valve 13 and the throttle 30 also becomes larger than the pressure of the meter-in circuit, and the return from the arm cylinder 4 passing through the flow control valve 13 Part of the oil flows into the supply line 17 downstream of the flow control valve via the regeneration circuit including the regeneration line 31 and the check valve 32, and is supplied again to the bottom chamber 4a of the arm cylinder 4 through the flow control valve 13. Is done. Therefore, the flow rate supplied from the hydraulic pump 10 to the arm cylinder 4 is reduced by an amount corresponding to the regeneration flow rate. That is, assuming that the flow rate flowing into the meter-in circuit after passing through the regeneration circuits 31 and 32 is Q30, the pump flow rate Qp required to generate a differential pressure of ΔPA across the flow rate control valve 13 is Qp = Q18−Q30. Become. Therefore, the hydraulic horsepower at this time is Pp Qp = Pp (Q18−Q30) <Pp Q18, and the energy consumption is reduced by Pp Q30 compared to the conventional hydraulic horsepower Pp Q18. In addition, since the discharge amount of the hydraulic pump 10 supplied to the arm cylinder 4 is reduced, when performing the arm cloud by a combined operation with raising the boom 1,
Although the load pressure on the boom cylinder 2 is higher than the load pressure on the arm cloud side, a sufficient flow of pressure oil can be supplied to the boom cylinder 2 as well. Therefore, the discharge amount of the hydraulic pump 1 is hardly saturated, and the composite operability is improved. That is, it is a measure against saturation, which is one of the problems of the load sensing control.

Further, in the present embodiment, since the regeneration circuits 31 and 32 are configured to guide the return oil from the discharge pipe 21 downstream of the flow control valve 13, when the flow control valve 13 is at the neutral position,
Reference numerals 1 and 32 are isolated from the rod chamber 4b of the arm cylinder 4. Therefore, after the arm cylinder 4 is contracted and the heavy object is lifted, when the flow control valve 13 is returned to the neutral position to keep the heavy object at the raised height, the load pressure of the arm cylinder rod chamber 4b is regenerated. A situation does not occur that acts on the supply port of the flow control valve 13 via the circuits 31, 32. This is the same as disclosed in Japanese Patent Application Laid-Open No. 63-8380
No. 8 is in contrast to applying the load pressure of the arm cylinder rod chamber 4b to the supply port of the flow control valve. Therefore, in the present embodiment, while regenerating the flow rate as described above, it is possible to reduce the energy loss,
At the neutral position of the flow control valve, there is no problem that the amount of leak increases in the flow control valve as in the conventional example, and it becomes easy to hold heavy objects.

Another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the configuration of the throttle provided in the discharge conduit is changed, and the other configuration is the same as that of the first embodiment.

That is, in FIG.
The variable throttle member 40 is provided at one side with a spring 41 acting in the throttle setting direction. On the opposite side of the spring 41, the load pressure of the arm cylinder 4 is applied to a branch line 42 connected to the load line 25. The throttle characteristic is guided in the throttle release direction via the throttle valve, and the throttle characteristic changes according to the load pressure.

In the first embodiment, the throttle 30 works well for collecting the pressurized oil as described above at the time of free fall as the meter-out control, but at the time of excavation as the meter-in control, the meter-in circuit pressure> the meter-out circuit pressure. As a result, the flow rate Q30 passing through the regeneration circuits 31 and 32 becomes zero, and the entire amount of the return oil from the rod chamber 4b of the arm cylinder 4 passes through the throttle 30, resulting in an energy loss corresponding to the pressure generated by the throttle. . This energy loss also occurs in the conventional example shown in FIG. 10 and the conventional example of Japanese Patent Application Laid-Open No. 63-83808 in the meter-out variable restrictor in the flow control valve.
Is not inferior to the conventional example. However, it goes without saying that it is preferable from the viewpoint of energy saving if this energy loss can be eliminated or reduced.

In the present embodiment, by providing the above-described variable throttle member 40, at the time of free fall with a low load pressure, the variable throttle 40 functions similarly to the throttle 30 of the first embodiment, and will be described in the first embodiment. With such an effect, the amount of restriction is reduced in accordance with the load pressure during excavation with a high load pressure, and the restriction function is released. On the other hand, as described above, the meter-out variable throttle in the flow control valve is set to such a degree that it hardly functions as a throttle during meter-in control. Therefore, the energy loss due to the restriction on the meter-out side during excavation is greatly reduced, and further energy saving can be achieved.

FIG. 5 shows a modification of the embodiment of FIG. In this embodiment, the pressure between the pressure compensating valve 14 and the flow control valve 13 is guided by the branch line 43 instead of guiding the load pressure to the variable throttle member 40. The differential pressure ΔPA before and after the meter-in flow path of the flow control valve 13 is kept constant by the pressure compensating valve 14. Accordingly, since the pressure between the pressure compensating valve 14 and the flow control valve 13 is higher than the load pressure by the constant differential pressure ΔPA, even if the pressure is derived instead of the load pressure, the same The effect can be obtained.

In the embodiment shown in FIGS. 4 and 5, the load pressure or a substitute pressure is directly guided to the variable restrictor member to control the variable restrictor member hydraulically. However, the load pressure or the substitute pressure is electrically detected. Then, the variable aperture member may be electrically controlled.

Still another embodiment of the present invention will be described with reference to FIGS. The above embodiment is an example in which a throttle is used as a pressure generating member provided in a discharge pipe. In this embodiment, a relief valve is used as a pressure generating member.

That is, FIG. 6 corresponds to the embodiment of FIG. 1 in which the fixed throttle 30 is provided.
A relief valve 50 is provided. The same effect can be obtained by controlling the discharge of the return oil at the time of meter-out control also by the relief valve 50 as in the first embodiment.

7 and 8 show the variable throttle member 40, respectively.
4 and 5 in which a variable relief valve 51 is provided in place of the variable throttle 40, and the relief valve 51 includes a load pressure or pressure compensating valve and a flow control valve. The pressure between them is guided, and the setting of the relief pressure is changed. Also in this embodiment, as in the embodiment of FIGS. 4 and 5, the relief pressure setting is released during meter-in control, and the same effect can be obtained.

Another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the characteristics of the pressure generating means provided in the discharge line 21 are to be further changed depending on the rotation speed of the prime mover.

That is, in FIG. 9, reference numeral 60 denotes a prime mover for driving the hydraulic pump 10. In the prime mover 60, the governor lever 62 is operated by operating the operation lever 61, and the target rotation speed is set.
The target rotation speed is detected by the detector 63, and the detection signal is amplified by the amplifier 64. On the other hand, a variable throttle member 65 is provided in the discharge line 21 of the meter-out circuit.
The load pressure or the pressure between the pressure compensating valve and the flow control valve is guided to the side facing the spring 66 by the branch line 42 or 43 as in the embodiment of FIGS. Further, on this side of the variable throttle member 65, a solenoid 67 that acts in the direction of releasing the aperture of the variable throttle member 65 is provided, and an amplified current from the amplifier 64 is applied to the solenoid 67.

The discharge amount of the hydraulic pump 10 is represented by the product of the swash plate inclination angle and the rotation speed, and the maximum discharge amount is determined by the rotation speed. on the other hand,
At the time of free fall, that is, at the time of arm cloud, which is the meter-out control of the arm cylinder 4, the flow rate of the return oil of the arm cylinder 4 to the reservoir 16 is controlled by combining the metering-out variable throttle and the variable throttle 65 in the flow control valve. Thus, the speed of the arm cylinder 4 is controlled.

Here, the throttle amount of the variable throttle 65 is determined such that cavitation is not generated in the bottom chamber 4a by comparing the flow rate Q82 discharged from the rod chamber 4b of the arm cylinder with the flow rate Q18 supplied to the bottom chamber 4a. Is done. This is because the occurrence of cavitation causes a breathing phenomenon of the arm and significantly impairs the workability of the excavator.

Also, in the case of a hydraulic shovel, there is a case where the operation is performed with the rotation speed of the prime mover 60 for driving the hydraulic pump 10 reduced due to a problem such as noise, and in this case, the maximum discharge amount of the hydraulic pump 10 also decreases. It is necessary to prevent the above-mentioned breathing phenomenon from occurring even in such an operation state, and the aperture amount of the variable aperture 65 is set based on this case. Therefore, even if the rotation speed of the motor 60 changes, the variable
In the normal operation in which the rotation speed of the hydraulic pump 10 is high, the maximum discharge amount of the hydraulic pump 10 is also large, and the back pressure generated in the meter-out variable throttle 82 becomes a resistance, resulting in energy loss.

In the above-described embodiment, the provision of the regenerating circuits 31 and 32 has the meaning of reducing the back pressure in this part in the form of regenerating the return oil and reducing the energy roll.

In the present embodiment, by further providing the above configuration,
When the rotation speed of the prime mover 60 decreases, the solenoid 67 is applied with an amplified current corresponding to the rotation speed, and the aperture of the variable aperture 65 is increased. As a result, it is possible to always obtain an optimum throttle amount that does not cause a breathing phenomenon and does not cause excessive energy loss regardless of a change in the number of revolutions, thereby improving operability and further reducing energy loss. Can be.

Although the target rotation speed of the prime mover 60 is detected in the above embodiment, the same effect can be obtained by detecting the actual rotation speed. Although the variable throttle member 65 is used, a variable relief valve may be used as in the embodiment shown in FIGS.

Still another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the connection position of the regeneration circuit to the pressure oil supply line is changed, and the other configuration is the same as that of the first embodiment.

That is, in FIG. 10, the regeneration line 70 connects the discharge line 21 to the supply line 17 between the hydraulic pump 10 and the pressure compensating valve 14.

Also in the present embodiment, at the time of meter-out control such as free fall, a part of the return oil from the arm cylinder 4 that has passed through the flow control valve 13 communicates with the hydraulic pump 10 through the regeneration line 70 and the check valve 32. The return oil flows into the supply line 17 between the pressure compensating valves 14, and when the arm 3 is operated alone, this return oil is supplied again to the bottom side of the arm cylinder 4 through the pressure compensating valve 14 and the flow control valve 13. Further, when the arm 3 and the boom 1 are combined, the return oil is also distributed to the boom cylinder 2 because the meter-out circuit pressure generated at the throttle 30 is high, so that a sufficient amount of pressure oil can be supplied to the boom cylinder 2. That is, the regeneration pressure oil can be used in another hydraulic actuator.

When the flow control valve 13 is in the neutral position, the regeneration circuit 70 is configured to guide the return oil from downstream of the flow control valve 13, so that the regeneration circuit 70 is shut off from the arm cylinder 4 by the flow control valve 13. Therefore, even if the regeneration circuit 70 is connected between the hydraulic pump 10 and the pressure compensating valve 14 as in the present embodiment, the pressure oil in the rod chamber 4b of the arm cylinder 4 does not flow into the supply line 17, It is possible to hold heavy objects in position. This is the same as disclosed in Japanese Patent Application Laid-Open No. 63-83808
Since the regeneration circuit of the signal guides the return oil from the upstream side of the flow control valve, when the regeneration circuit is connected between the hydraulic pump 10 and the pressure compensating valve 14 as in this embodiment, the flow control valve However, even in the neutral position, the return oil flows into the supply pipe line, which is in contrast to the fact that heavy objects cannot be held, and as a result, in the conventional example, the connection configuration as in the present embodiment cannot be adopted.
Regenerated pressure oil cannot be used in other hydraulic actuators.

The embodiment of FIG. 10 uses a fixed throttle as the pressure generating means.
Although 30 is employed, it goes without saying that other pressure generating means such as a variable throttle and a relief valve can be employed as in the embodiment of FIGS. 4 to 9 described above.

Still another embodiment of the present invention will be described with reference to FIG. This embodiment is different from the above-described embodiment in the point of the configuration of the flow control valve and the pressure compensating valve of the direction switching valve and the point of the combination of the driven pressure actuator.

That is, in FIG. 11, the pressure oil supplied from the hydraulic pump 10 is supplied to the boom cylinder 2 and the swing motor 73, which are hydraulic actuators, via the direction switching valves 71 and 72, respectively. At this time, the discharge amount of the hydraulic pump 10 is controlled by the pump regulator 24 so that the differential pressure between the maximum load pressure and the discharge pressure is kept constant. In the hydraulic circuit, a supply line 74 and first and second discharge lines 75 and 76 are provided for the direction switching valve 71, and the supply line 77 and the First and second discharge lines 78, 79 are provided.

The directional control valve 71 comprises a flow control valve 80 and a pressure compensating valve 81. The inside of the flow control valve 80 is pressurized in the A direction when the boom is lowered and moves to the right side position in the figure, when the rod chamber of the boom cylinder 2 is moved. A meter-in variable throttle 82 for controlling the flow rate of the pressure oil supplied to the bottom chamber 2a and a meter-out variable throttle 83 for controlling the discharge of return oil from the bottom chamber 2a are provided, and are pressurized in the B direction when the boom is raised. The meter-in variable throttle 84 controls the flow rate of the pressure oil supplied to the bottom chamber 2a of the boom cylinder 2 when it moves to the left position in the figure, and the meter-out controls the discharge of the pressure oil from the rod chamber 2b. A variable aperture 85 is provided.

The pressure compensating valve 81 is connected downstream of the meter-in variable throttles 82 and 84, and the pressure compensating valve 81 is further connected to meter-in flow paths 86 and 87 in the flow control valve 81. Accordingly, the pressure oil that has passed through the meter-in variable throttles 82 and 84 passes through the pressure compensating valve 81, is returned to the flow control valve 80, and is thereafter supplied to the boom cylinder 2. A load line 88 for guiding the load pressure of the boom cylinder 2 is connected to the pressure compensating valve 81. The maximum pressure of this load pressure and a load pressure guided by a similar load line 89 on the swing motor 73 side is determined by the selection valve 27. Selected by
It is taken out to the load line 28.

A maximum load pressure is guided to one end of the pressure compensating valve 81 via a pilot line 90 connected to the load line 28, and urges the valve body in a valve closing direction. as a result,
Flow control valve variable throttle that urges the valve element at the other end in the valve opening direction
The pressure downstream of 82 and 84 is controlled to a value corresponding to the maximum load pressure. On the other hand, the pressure upstream of the variable throttles 82 and 84 is
The discharge pressure is 0. Therefore, since the differential pressure across the variable throttles 82 and 84 is always the difference between the discharge pressure of the hydraulic pump 10 and the maximum load pressure, the meter-in supply flow rate proportional to the opening area of the variable throttles 82 and 84 is determined. The pressure compensating valve 81
Is based on the concept of a composite valve described in JP-B-58-31486.

 The direction switching valve 72 is similarly configured.

Also in this embodiment, similarly to the embodiment shown in FIG. 4, the variable throttle member 40 as the pressure generating means is provided in the first discharge line 75, and the flow control valve 80 and the variable throttle member 40 are provided.
Is connected to the supply line 74 between the hydraulic pump 10 and the flow control valve 80 via the regeneration circuit 31 including the check valve 32. As a result, when the boom is free-falling, which is the meter-in control of the boom cylinder 2, the return oil from the bottom chamber 2a is returned to the supply line 74 via the regeneration circuit 31, and the energy loss is reduced. The same effect as that of the embodiment can be obtained.

Instead of the variable throttle member 40, other pressure generating means such as a fixed throttle and a relief valve shown in FIG. 1 or FIGS. 5 to 9 can be used.

〔The invention's effect〕

According to the present invention, a part of the return oil from the hydraulic actuator is returned to the supply side on the vortex side of the flow control valve during the meter-out control, so that energy loss can be reduced and saturation measures can be taken, and the flow control valve can be moved to the neutral position. , The increase in the amount of leak does not occur, and the holding of heavy objects becomes easy.

Further, according to the present invention, since the variable pressure generating means is used, even at the time of the meter-in control, the energy loss due to restricting the return oil from the hydraulic actuator is reduced, and the energy is saved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive device according to one embodiment of the present invention, and FIGS. 2 and 3 illustrate the operation of a hydraulic excavator to which the present invention is applied by meter-out control and meter-in control. FIG. 4 is a hydraulic circuit diagram of a hydraulic drive device according to another embodiment of the present invention, and FIG. 5 is a circuit diagram of a hydraulic drive device according to still another embodiment of the present invention. FIG. 6, FIG. 7, and FIG. 8 are main part circuit diagrams corresponding to the embodiments of FIG. 1, FIG. 4, and FIG. 5, respectively, when a relief valve is used as the pressure generating means. FIG. 9 is a schematic diagram showing a main part of a hydraulic drive device according to still another embodiment of the present invention, and FIG. 10 is a hydraulic circuit showing a hydraulic drive device according to still another embodiment of the present invention. FIG. 11 is a hydraulic drive device according to still another embodiment of the present invention. FIG. 12 is a hydraulic circuit diagram showing a conventional hydraulic drive device. Description of symbols 4… Arm (hydraulic actuator) 10… Hydraulic pump 12… Directional switching valve 13… Flow control valve 14… Pressure compensating valve 16… Reverser 21 …… Discharge line 24 …… Pump regulator 30 ... throttle (pressure generating means) 31 ... regeneration line 32 ... check valve 40 ... variable throttle member 50 ... relief valve (pressure generating means) 51 ... variable relief valve 60 ... prime mover 63 ... rotation Number detector 65 Variable aperture member 67 Solenoid (adjustment means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-83808 (JP, A) JP-B-46-15059 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F15B 11/00-11/22

Claims (8)

(57) [Claims] 1. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line between the two via a check valve; the pressure generating means comprises a variable throttle member, which guides the load pressure of the hydraulic actuator to the variable throttle member, A hydraulic drive device that changes the throttle characteristic according to pressure. 2. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line via a check valve; provided in a supply line between the pressure oil supply source and the flow control valve, before and after the flow control valve A pressure compensating valve for keeping the differential pressure constant, wherein the pressure generating means comprises a variable throttle member, and guides the pressure between the pressure compensating valve and the flow control valve to the variable throttle member, Characteristic of changing aperture characteristics Hydraulic drive system for. 3. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line between the two via a check valve; the pressure generating means comprises a variable relief valve, which guides the load pressure of the hydraulic actuator to the variable relief valve, A hydraulic drive device that changes a relief characteristic according to a pressure. 4. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line via a check valve; provided in a supply line between the pressure oil supply source and the flow control valve, before and after the flow control valve A pressure compensating valve for keeping the differential pressure constant, wherein the pressure generating means comprises a variable relief valve, and guides the pressure between the pressure compensating valve and the flow control valve to the variable relief valve; To change the relief characteristics. Hydraulic drive system according to claim. 5. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line between the two via a check valve; an adjusting means for changing the characteristic of the pressure generating means, and a motor for driving the hydraulic pump with the adjusting means A hydraulic drive device that operates according to the target rotation speed or the actual rotation speed to change the characteristics of the pressure generating means. 6. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line via a check valve; provided in a supply line between the pressure oil supply source and the flow control valve, before and after the flow control valve A hydraulic drive device further comprising a pressure compensating valve for keeping the differential pressure constant, wherein the regeneration circuit is connected to a supply line between the pressure compensating valve and the flow control valve. 7. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line via a check valve; provided in a supply line between the pressure oil supply source and the flow control valve, before and after the flow control valve A hydraulic drive device further comprising a pressure compensating valve for maintaining a constant differential pressure, wherein the regeneration circuit is connected to a supply line between the pressure oil supply source and the pressure compensating valve. 8. A hydraulic oil supply having at least one hydraulic pump, at least one hydraulic actuator driven by hydraulic oil supplied from the hydraulic oil supply, and a hydraulic oil supply from the hydraulic oil supply to the hydraulic actuator. Each of which controls the supply of the pressure oil and the discharge of the pressure oil from the hydraulic actuator to the reservoir, and includes a flow control valve for controlling a driving direction and a driving speed of the hydraulic actuator, and the pressure oil supply source includes:
In a hydraulic drive device for controlling a discharge amount of the hydraulic pump so that a discharge pressure of the hydraulic pump is higher than a load pressure of the hydraulic actuator by a constant differential pressure, a meter-out variable throttle and a reservoir of the flow control valve are provided. A pressure generating means is provided in a discharge line between the two, and a portion between the metering-out variable throttle of the flow control valve of the discharge line and the pressure generating means is provided by the pressure oil supply source and the flow control valve. A regenerative circuit connected to the supply line between the two via a check valve; provided in the supply line between the pressure oil supply source and the flow control valve to prevent backflow of pressure oil A hydraulic drive device, further comprising a check valve, wherein the regeneration circuit is connected to a supply line between the check valve and the flow control valve.