JP2000035005A - Controller for hydraulically-operated machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a setting property at all times no matter which spool stroke position a flow control valve is displaced to in a hydraulically-operated machine. SOLUTION: A controller for a hydraulically-operated machine is provided with a bleed-off circuit 15 discharging a pressure oil supplied to a hydraulic actuator from a hydraulic pump 1. The bleed-off circuit 15 is provided with a variable bleed valve 13 which changes a flow rate of the pressure oil discharging from a flow control valve 5 through a line 11. The variable bleed valve 13 is controlled such that a flow rate of discharged oil becomes higher when a discharged Pp of the hydraulic pump 1 becomes higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a hydraulic drive machine, and more particularly to a device capable of improving the stability of vibration of a load speed of a hydraulic drive machine when the load speed changes.

[0002]

2. Description of the Related Art Generally, in a hydraulic system that drives a large inertia, the speed of a load is approximately a secondary vibration system due to the elasticity of oil.

Therefore, in a hydraulically driven machine such as a construction machine for driving a work machine with a large inertia, the damping characteristic, that is, the settling property is improved in such a secondary vibration system, and the vibration of the speed of the blade edge of the work machine is reduced. It is important to control.

FIG. 14 conceptually shows the construction of a hydraulic circuit of a construction machine in which a hydraulic pump 1 is controlled by a so-called negative control (negative control) and a flow control valve 5 is provided with a center bypass circuit (open center). It is shown.

FIG. 15 shows an inflow flow rate Q of the hydraulic actuator in response to an input (step input) of the operation lever 6.
And the response (step response) of the speed of the cutting edge of the working machine.

In the control by the negative control and the open center, as shown in FIG. 15, a neutral circuit 15 is provided as a bleed-off circuit for discharging the pressure oil supplied from the hydraulic pump 1 to the hydraulic actuator to the tank 12.

FIG. 8 shows the relationship between the spool stroke of the flow control valve 5, the opening area (meter-in) to the hydraulic actuator, and the opening area to the neutral circuit 15.

Therefore, the flow control valve 5 is controlled by the operation lever 6.
8, the inflow opening of the flow control valve 5 is closed and the amount of outflow to the neutral circuit 15 (bleed-off flow rate) is obtained from the relationship shown in FIG.
Increase.

Then, the pressure oil passing through the neutral circuit 15 passes through the throttle 18 in front of the tank 12. here,
In the control by the negative control, the displacement volume q (cc / r) of the variable displacement pump 1 is adjusted according to the pressure difference around the throttle 18.
ev) is changed. This is performed by changing the swash plate 1a of the pump 1 by the pump swash plate control mechanism 3. That is, as shown in FIG. 10, the pump displacement volume q decreases as the differential pressure across the throttle 18 increases.

[0010] Therefore, when the inflow opening is closed, the neutral opening is opened. As a result, a large amount of pressure oil flows through the throttle, so that the differential pressure across the throttle increases, and as a result, the pump displacement volume q Decrease. Further, since the neutral opening is opened, the pressure oil escapes from the pump 1 to the tank 12, and the pressure decreases.

Therefore, if the speed of the cutting edge of the working machine driven by the hydraulic actuator overshoots, the outflow to the neutral circuit 15 increases, and the inflow to the hydraulic actuator decreases. Further, as the pump displacement volume q is reduced, the pump discharge amount itself is reduced.

For this reason, the vibration of the cutting edge speed of the working machine is rapidly attenuated. That is, the control by the negative control and the open center has an advantage that the stabilization of the working machine cutting edge speed is excellent as shown in FIG.

On the other hand, instead of the negative control, the pump 1
The hydraulic circuit shown in FIG. 12 which employs a closed center flow control valve 5 that does not have a center bypass circuit and which has no center bypass circuit, is not excellent in stabilization.

That is, in such a closed center type load sensing hydraulic system, even when one hydraulic pump 1 simultaneously controls a plurality of hydraulic actuators having different load pressures, the load pressure can be controlled independently of the engine speed. Independently, the speed of the hydraulic actuator can be adjusted only by the operation amount of the operation lever 6, so that there is an advantage that the operability is good, but the flow rate corresponding to the input of the operation lever 6 is reduced. Therefore, there is a problem that the working machine cutting edge speed oscillates due to the inertia of the working machine, the compression of the pressure oil, and the like, and the settability is poor (see FIG. 13).

Therefore, in such a closed center type load sensing hydraulic system, it is desired to improve the stabilization of the vibration of the working machine cutting edge speed.

For this purpose, as in the case of the open center type negative control hydraulic system shown in FIG. 14, it is considered that the vibration can be suppressed by increasing the bleed-off flow rate when the working machine blade edge speed fluctuates.

Here, as a technique for changing the bleed-off flow rate, there is a technique described in JP-A-8-239865.

In this publication, the relationship between the spool stroke of the flow control valve and the bleed-off flow rate is set as shown by the solid line in FIG. 8, and the spool stroke of the flow control valve (the operation amount of the operation lever) increases. It is described that the bleed-off flow rate is changed so as to be small according to the flow rate.

However, when the relationship between the spool stroke of the flow control valve and the bleed-off flow rate is set as described above, the bleed-off flow rate becomes too large when the operation lever is operated in the fine control range, and a large load is applied. This causes a problem that the load does not move during driving. In the range where the operation amount of the operation lever is large,
The bleed-off flow rate becomes small, resulting in insufficient stabilization. Further, when the operation lever is operated to the full stroke, the bleed-off flow rate decreases to near zero, and the effect of improving the stabilization is hardly obtained.

As described above, in the prior art, since the bleed-off flow rate is changed by the spool stroke of the flow control valve (the operation amount of the operation lever), the spool stroke position of the flow control valve (the operation amount of the operation lever) is changed. It is conceivable that the effect of improving the settability may or may not be obtained.

The present invention has been made in view of such circumstances, and in a hydraulically driven machine, even if the flow rate control valve is operated at any spool stroke position, the effect of improving the settling property is always obtained. Is to solve the problem.

[0022]

SUMMARY OF THE INVENTION According to the present invention, a load is controlled by increasing or decreasing a bleed-off flow rate and a pump discharge rate in accordance with a change in load speed, regardless of the operation amount of an operation lever. This is to improve the stabilization of the speed vibration. That is, when the speed is excessive, the bleed-off flow rate is increased and the pump discharge amount is reduced. When the speed is insufficient, control is performed to decrease the bleed-off flow rate and increase the pump discharge amount.

In order to realize this, theoretical analysis was performed on the secondary vibration system of the hydraulic system, and the following was found.

That is, in the secondary vibration system of the hydraulic system,
The coefficient of the damping term is -∂Q / ∂P, where P is the load pressure of the hydraulic actuator (discharge pressure of the hydraulic pump) and Q is the flow rate flowing into the hydraulic actuator. Therefore, as shown in the following equation (1), if ∂Q / ∂P is a negative value and the absolute value is increased, the attenuation term is increased, and the settling property is improved.

∂Q / ∂P <0 (1) Therefore, as the pump discharge pressure P increases, the bleed-off flow rate is increased, the pump discharge rate is reduced, and the flow rate Q flowing into the hydraulic actuator is reduced. (1) The relationship of the expression is maintained to improve the settling property.

That is, according to the first aspect of the present invention, in order to achieve the above-mentioned solution, a hydraulic pump, and a flow control valve for supplying discharge hydraulic oil of the hydraulic pump to the hydraulic actuator by a flow rate corresponding to an operation amount are provided. A bleed-off circuit for discharging pressure oil supplied from the hydraulic pump to the hydraulic actuator, and a bleed-off circuit provided in the bleed-off circuit for changing a flow rate of the discharged pressure oil. A variable bleed valve and variable bleed valve control means for controlling the variable bleed valve such that the larger the discharge pressure of the hydraulic pump is, the larger the flow rate of the discharged hydraulic oil is.

According to the configuration of the first aspect of the present invention, as shown in FIG. 1, a bleed-off circuit 15 for discharging the pressure oil supplied from the hydraulic pump 1 to the hydraulic actuator is provided. The bleed-off circuit 15 is provided with a variable bleed valve 13 for changing the flow rate of the pressure oil discharged from the flow control valve 5 through the pipe 11.

Therefore, the variable bleed valve 13 is controlled such that as the discharge pressure Pp of the hydraulic pump 1 increases, the flow rate of the discharged hydraulic oil increases.

That is, regardless of the spool stroke of the flow control valve 5 (the operation amount of the operation lever 6), as the discharge pressure Pp of the hydraulic pump 1 increases, the flow rate Q flowing into the hydraulic actuator decreases. Thus, the above (1)
Is maintained, and the stabilization of the vibration of the speed of the cutting edge of the working machine is stable, regardless of the position of the spool stroke (the operation amount of the operation lever 6) of the flow control valve 5, as shown in FIG. , Will always improve.

According to a second aspect of the present invention, there is provided a control device for a hydraulic drive machine comprising a hydraulic pump and a flow control valve for supplying discharge hydraulic oil of the hydraulic pump to a hydraulic actuator by a flow rate corresponding to an operation amount. A bleed-off circuit for discharging pressure oil supplied from the hydraulic pump to the hydraulic actuator, a variable bleed valve provided in the bleed-off circuit for changing a flow rate of the discharged pressure oil, and a discharge pressure of the hydraulic pump Variable bleed valve control means for controlling the variable bleed valve is provided such that the larger the amount of change, the larger the flow rate of the discharged pressure oil.

In the second invention, unlike the first invention, the discharge pressure change amount ΔPp of the hydraulic pump 1 is used in place of the discharge pressure Pp of the hydraulic pump 1, and as the discharge pressure change amount ΔPp of the hydraulic pump 1 increases, By reducing the flow rate Q flowing into the hydraulic actuator, the relationship of the above equation (1) is maintained so that the position of the spool stroke (the operation amount of the operation lever 6) of the flow control valve 5 is , The effect of improving the settability is always obtained.

In the third aspect of the present invention, the variable displacement hydraulic pump, a flow control valve for supplying a discharge pressure oil of the hydraulic pump to the hydraulic actuator by a flow rate corresponding to an operation amount, and a discharge pressure of the hydraulic pump In a control device for a hydraulic drive machine, comprising: a load sensing control means for controlling a displacement volume of the hydraulic pump so that a differential pressure of a load pressure of the hydraulic actuator becomes a set value. A bleed-off circuit for discharging the pressurized oil to be discharged, a variable bleed valve provided in the bleed-off circuit for changing the flow rate of the discharged pressure oil, and the discharge pressure as the discharge pressure of the hydraulic pump increases. Variable bleed valve control means for controlling the variable bleed valve so as to increase the flow rate of oil is provided.

According to the third invention, as shown in FIG. 1, as in the first invention, as the discharge pressure Pp of the hydraulic pump 1 increases, the pressure discharged from the flow control valve 5 through the pipe 11 increases. The variable bleed valve 13 is controlled so that the oil flow rate is increased.

Further, in the third aspect, as the discharge pressure Pp of the hydraulic pump 1 increases, the displacement q of the hydraulic pump 1 decreases, and the discharge amount of the hydraulic pump 1 decreases.

That is, as the bleed-off flow rate discharged from the flow rate control valve 5 via the pipe line 11 increases, the amount of pressure oil flowing into the hydraulic actuator decreases.

As a result, the inflow pressure (highest load pressure) PL to the hydraulic actuator decreases in reverse, so that the differential pressure between the pump discharge pressure Pp and the hydraulic actuator inflow pressure PL increases. Here, in the load sensing control means 3, the pressure difference Δ between the pump discharge pressure and the inflow pressure of the hydraulic actuator is determined.
Control is performed to hold P at the set value ΔPLS. For this reason, as shown in FIG. 9, when the bleed-off flow rate increases, the pressure difference ΔP increases, and the load sensing control means 3 pushes and removes the pump 1 so as to maintain the large pressure difference ΔP at a set value. Control is performed to reduce (squeeze) the volume q.

Therefore, the discharge amount of the hydraulic pump 1 is reduced, and the flow rate flowing into the hydraulic actuator is further reduced.

As described above, according to the third aspect of the present invention, as the pump discharge pressure P increases, the bleed-off flow rate is increased and the pump discharge rate is further reduced, thereby reducing the flow rate Q flowing into the hydraulic actuator. Like that. For this reason, the relationship of the above equation (1) is maintained, and the settability is improved.

Further, in the fourth invention, a variable displacement hydraulic pump, a flow control valve for supplying a discharge pressure oil of the hydraulic pump to the hydraulic actuator by a flow rate corresponding to an operation amount, and a discharge pressure of the hydraulic pump In a control device for a hydraulic drive machine, comprising: a load sensing control means for controlling a displacement volume of the hydraulic pump so that a differential pressure of a load pressure of the hydraulic actuator becomes a set value. A bleed-off circuit that discharges the pressure oil to be discharged, a variable bleed valve provided in the bleed-off circuit to change the flow rate of the discharged pressure oil, and as the discharge pressure change amount of the hydraulic pump increases,
Variable bleed valve control means for controlling the variable bleed valve so as to increase the flow rate of the discharged pressure oil.

In the fourth invention, instead of the "hydraulic pump discharge pressure Pp" of the third invention, "hydraulic pump discharge pressure change amount ΔPp"
Is used.

In a fifth aspect based on the first to fourth aspects, the variable bleed valve control means controls the variable bleed valve by supplying an electric signal to the variable bleed valve. And

In the sixth invention, the first invention or the third invention
In the present invention, the variable bleed valve control means controls the variable bleed valve by supplying a pilot pressure signal indicating a discharge pressure of the hydraulic pump to the variable bleed valve via a pilot pressure oil pipeline. There is.

In the seventh invention, the first invention or the third invention
In the invention, discharge pressure detecting means for detecting the discharge pressure of the hydraulic pump, and setting means for setting a correspondence relationship between the discharge pressure of the hydraulic pump and the opening amount of the variable bleed valve,
Further, the variable bleed valve control means obtains the opening amount of the variable bleed valve corresponding to the current discharge pressure detected by the discharge pressure detecting means in accordance with the set correspondence, and calculates the obtained opening amount. The variable bleed valve is controlled so as to obtain the following.

In the eighth invention, the second invention or the fourth invention
In the invention, discharge pressure change amount detection means for detecting a discharge pressure change amount of the hydraulic pump, and setting means for setting a correspondence relationship between the discharge pressure change amount of the hydraulic pump and the opening amount of the variable bleed valve, Further, the variable bleed valve control means, the opening amount of the variable bleed valve corresponding to the current discharge pressure change amount detected by the discharge pressure change amount detection means,
The variable bleed valve is controlled according to the set correspondence, and the variable bleed valve is controlled so as to obtain the determined opening amount.

In the ninth invention, the first invention or the third invention
In the invention, a discharge pressure detecting means for detecting a discharge pressure of the hydraulic pump, an operation amount detecting means for detecting an operation amount at which the flow control valve is operated, a discharge pressure of the hydraulic pump and an opening of the variable bleed valve First to set the correspondence with quantity
Setting means, and the second setting means for setting the correspondence between the operation amount and the opening amount, wherein the opening amount of the variable bleed valve decreases as the operation amount of the flow control valve increases, The variable bleed valve control means obtains the opening amount of the variable bleed valve corresponding to the current discharge pressure detected by the discharge pressure detection means in accordance with the set first correspondence, and detects the operation amount. The opening amount of the variable bleed valve corresponding to the current operation amount detected by the means is obtained according to the set second correspondence relationship, and among the obtained opening amounts of the variable bleed valve,
The variable bleed valve is controlled so as to obtain a smaller opening amount.

[0046]

Embodiments of the present invention will be described below.

FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive control device for a construction machine assumed in this embodiment.

That is, as shown in FIG. 1, the hydraulic drive control device is driven by an engine 2, a variable displacement hydraulic pump 1 driven by the engine 2, and a flow of pressurized oil. A hydraulic actuator (not shown) and a flow control valve 5 that changes the opening area according to the spool stroke position to control the flow rate of the hydraulic oil discharged from the hydraulic pump 1 and supply the hydraulic oil to the hydraulic actuator A pressure sensor 8 for detecting the discharge pressure Pp of the hydraulic pump 1, and an operation lever 6 as an electric lever for operating the spool stroke position of the flow control valve 5.
, And the displacement volume q (cc / re) of the hydraulic pump 1 so that the pressure difference ΔP between the discharge pressure Pp of the hydraulic pump 1 and the load pressure PL of the hydraulic actuator becomes the set value ΔPLS.
v) a swash plate control mechanism as load sensing control means for controlling v), a bleed-off circuit 15 for discharging pressure oil to be supplied from the hydraulic pump 1 to the hydraulic actuator via the pipe line 4, and a bleed-off circuit And a variable bleed valve 13 for changing the flow rate of pressure oil discharged from the flow control valve 5 to the tank 12 through the pipe 11
And a controller 7 for controlling the variable bleed valve 13 so that the flow rate of the pressure oil discharged from the bleed-off circuit 15 increases as the discharge pressure Pp of the hydraulic pump 1 increases, as described later. I have. The hydraulic actuator is connected to a predetermined work machine (for example, a boom) (not shown), and the work machine (boom) is driven in accordance with the drive (extension / contraction drive) of the hydraulic actuator (for example, a hydraulic cylinder). Is done. In an actual apparatus, the hydraulic actuator and the flow control valve 5 are provided for each working machine such as a boom, an arm, and a bucket of a construction machine. In the present embodiment, the stabilization of the vibration of the speed of the working machine cutting edge (bucket cutting edge) of such a construction machine is improved.

More specifically, a signal indicating the operation amount of the electric lever 6 is input to the controller 7,
The current is converted into a command current for the flow control valve 5, and is applied to the electromagnetic proportional control valve 17. In the electromagnetic proportional control valve 17, the command current is converted into a pilot pressure, which is applied to the flow control valve 5, so that the flow control valve 5 is driven.

In the load sensing control, the pressure difference ΔP between the discharge pressure Pp of the hydraulic pump 1 and the maximum load pressure PL among the load pressures of the respective hydraulic actuators is set to a set value Δ
The displacement volume q (cc) of the hydraulic pump 1 is set to PLS.
/ rev) is controlled, but in this embodiment, for convenience of explanation, it is assumed that the load pressure of the hydraulic actuator corresponding to the flow control valve 5 shown in FIG. 1 is the maximum load pressure PL.

A pilot pressure signal indicating the discharge pressure Pp of the hydraulic pump 1 is input to the pump swash plate control mechanism 3 through the pilot line 9. On the other hand, the pilot pressure signal indicating the load pressure PL of the hydraulic actuator is transmitted to the pilot line 1
0 is input to the pump swash plate control mechanism 3.

In the pump swash plate control mechanism 3, the pressure difference ΔP (= Pp−PL) between these inputted pressures Pp and PL is set to a set value Δ
The swash plate 1a of the variable displacement hydraulic pump 1 is changed so as to be held by the PLS. That is, the differential pressure ΔP is equal to the set value ΔP
When it is larger than LS, the tilt angle of the swash plate 1a of the hydraulic pump 1 is reduced, and the displacement q of the hydraulic pump 1 is reduced. That is, the flow rate discharged from the hydraulic pump 1 is reduced. On the other hand, when the differential pressure ΔP is smaller than the set value ΔPLS, the tilt angle of the swash plate 1a of the hydraulic pump 1 is increased, and the displacement q of the hydraulic pump 1 is increased. That is, the flow rate discharged from the hydraulic pump 1 is increased.

The bleed-off circuit 15 has a line 11 branched from the pressure oil supply line 4 from the flow control valve 5 to the hydraulic actuator. The pipe 11 is a branch pipe of the pipe 4 from the flow control valve 5 to the hydraulic actuator, and discharges the pressure oil flowing out of the flow control valve 5 to the tank 12. Further, a variable bleed valve 13 for adjusting the flow rate of the discharged pressure oil is provided on the pipeline 11.

From the controller 7, as described later,
A command current i corresponding to the opening amount (opening area) A of the variable bleed valve 13 is generated.
4, the electromagnetic solenoid 13a of the variable bleed valve 13
Is added to The variable bleed valve 13 has a spring 13b
For example, as shown in FIG. 11, when the command current i decreases, the opening amount A increases, and when the command current i increases, the opening amount A increases.

In a predetermined memory of the controller 7, FIG.
As shown in (1), the correspondence between the discharge pressure Pp of the hydraulic pump 1 and the opening amount (opening area) A of the variable bleed valve 13 is stored as a storage table. That is, the hydraulic pump 1
When the discharge pressure Pp is given, the opening amount A of the variable bleed valve 13 corresponding to the given discharge pressure Pp can be read out according to the correspondence shown in FIG.
Data of each opening amount A corresponding to each discharge pressure Pp is stored.

When the discharge pressure Pp of the hydraulic pump 1 is given, the opening amount A of the variable bleed valve 13 corresponding to the discharge pressure Pp is given.
May be obtained by calculation.

Therefore, the controller 7 receives the detection pressure Pp output from the pressure sensor 8 and reads the opening amount A of the variable bleed valve 13 corresponding to the detection pressure Pp from the storage table of the controller 7. Then, a corresponding command current i is output to the variable bleed valve 13 in accordance with the characteristics of FIG. 11 so that the read opening amount A is obtained.

Therefore, the opening area A of the variable bleed valve 13 is changed according to the current pump discharge pressure Pp according to the correspondence shown in FIG. That is, as shown in FIG. 5, the variable bleed valve 13 is controlled such that the flow rate of the pressure oil discharged from the flow control valve 5 to the tank 12 increases as the discharge pressure Pp of the hydraulic pump 1 increases.

As described above, regardless of the spool stroke of the flow control valve 5 (the operation amount of the operation lever 6), as the discharge pressure Pp of the hydraulic pump 1 increases, the flow rate Q flowing into the hydraulic actuator decreases. As a result, the relationship (1), ∂Q / ∂P <0, is maintained.

For this reason, as shown in FIG. 2, the stabilization of the vibration of the speed of the cutting edge of the working machine can be maintained regardless of the position of the spool stroke of the flow control valve 5 (the operation amount of the operation lever 6). , Will always improve.

In particular, in the present embodiment, since the control shown in FIG. 5 is employed in the hydraulic circuit employing the load sensing control, the following effects can be obtained.

That is, in this embodiment, as shown in FIG. 5, as the discharge pressure Pp of the hydraulic pump 1 increases, the flow rate of the pressure oil discharged from the flow control valve 5 via the pipe 11 increases. Next, the variable bleed valve 13 is controlled.

At this time, as the bleed-off flow rate discharged from the flow rate control valve 5 through the pipe line 11 increases, the amount of hydraulic oil flowing into the hydraulic actuator decreases.

As a result, the inflow pressure (highest load pressure) PL to the hydraulic actuator drops in reverse, so that the differential pressure between the pump discharge pressure Pp and the hydraulic actuator inflow pressure PL increases. Here, in the pump swash plate control mechanism 3, as described above, the pump discharge pressure Pp and the inflow pressure PL of the hydraulic actuator
Is maintained at a set value ΔPLS. Therefore, as shown in FIG. 9, when the bleed-off flow rate increases, the differential pressure ΔP increases, and the pump swash plate control mechanism 3 controls the pump 1 so that the large differential pressure ΔP is maintained at the set value ΔPLS. Is controlled so that the swash plate 1a is made smaller and the displacement volume q is made smaller.

For this reason, the discharge amount of the hydraulic pump 1 is reduced, and the flow rate Q flowing into the hydraulic actuator is further reduced.

As described above, according to this embodiment, as the pump discharge pressure P increases, the bleed-off flow rate is increased, and the pump discharge rate is also reduced, so that the flow rate Q flowing into the hydraulic actuator is reduced. Like that. For this reason, the relationship of the above equation (1) is maintained, and the settability is improved.

It should be noted that implementations in which various modifications are made to the above-described embodiment are also possible.

That is, in the hydraulic circuit shown in FIG. 1, a branch pipe 11 is provided in the pressure oil supply pipe 4 from the flow control valve 5 to the hydraulic actuator. The hydraulic oil is discharged from the hydraulic pump 1 as shown in FIG.
A branch line 11 may be provided in the pressure oil supply line 4 through which the pressure oil supplied from the hydraulic pump 1 to the hydraulic actuator may be discharged. In short, as long as the bleed-off circuit 15 discharges the pressure oil supplied from the hydraulic pump 1 to the hydraulic actuator, the branch pipe line 11 can be set at any position.

In the present embodiment, the controller 5
As shown in FIG. 5, a correspondence relationship between the discharge pressure Pp of the hydraulic pump 1 and the opening amount A of the variable bleed valve 13 is set in advance and corresponds to the current discharge pressure Pp detected by the pressure sensor 8. The opening amount A of the variable bleed valve 13 is obtained in accordance with the set correspondence, and the command current i is output to the variable bleed valve 13 so as to obtain the obtained opening amount A. As shown in FIG. 4, it is possible to omit the arrangement of the pressure sensor 8 and the controller 7.

In the hydraulic circuit shown in FIG. 4, a pilot pressure signal indicating the discharge pressure Pp of the hydraulic pump 1 is applied to the pilot port 13c of the variable bleed valve 13 via the pilot pressure oil line 16. This variable bleed valve 13
The opening amount A is assumed to have such a characteristic that the opening amount A increases as the pilot pressure applied to the pilot port 13c increases. Therefore, as the discharge pressure Pp of the hydraulic pump 1 increases, the opening amount A of the variable bleed valve 13 increases, so that the same relationship as shown in FIG. 5 is obtained, and the controller 7 shown in FIGS. The same effect as the device having the pressure sensor 8 can be obtained.

In the above description, the opening area A of the variable bleed valve 13 is increased as the discharge pressure Pp of the hydraulic pump 1 is increased. The quantity ΔPp may be used.

For example, as shown in FIG. 6, a correspondence relationship is set in which the larger the change amount ΔPp of the discharge pressure Pp of the hydraulic pump 1 is, the larger the opening amount A of the variable bleed valve 13 is, and the current discharge pressure is set. The opening amount A of the variable bleed valve 13 corresponding to the change amount ΔPp may be obtained according to the set correspondence, and the variable bleed valve 13 may be controlled so as to obtain the obtained opening amount A.

Also in this case, regardless of the spool stroke of the flow control valve 5 (the operation amount of the operation lever 6), the larger the discharge pressure change amount ΔPp of the hydraulic pump 1, the smaller the flow rate Q flowing into the hydraulic actuator. It is. As a result, the relationship (1), ∂Q / ∂P <0, is maintained.
The same effect as when the corresponding relationship is adopted can be obtained.

Note that the discharge pressure change amount ΔPp of the hydraulic pump 1
May be obtained from the detection result of the pressure sensor 8 (for example, the difference between the previous sampling data and the current sampling data may be used to calculate the discharge pressure change amount ΔPp), and the discharge pressure change amount ΔPp May be provided.

As shown in FIG. 8, the flow control valve 5
As the spool stroke (the operation amount S of the operation lever 6) becomes larger, it is also possible to take into consideration the characteristic of reducing the bleed-off flow rate.

In this embodiment, in addition to the correspondence shown in FIG. 5, as shown in FIG. 7, as the spool stroke of the flow control valve 5 (the operation amount S of the operation lever 6) increases, the variable bleed valve 13 A correspondence relationship that the opening amount A becomes smaller is set.

Therefore, the hydraulic pump 1 is controlled by the pressure sensor 8.
Is detected, the detected discharge pressure Pp is detected.
Is determined in accordance with the correspondence shown in FIG.

On the other hand, the spool stroke position of the flow control valve 5 is detected by predetermined detecting means, specifically, detecting means for detecting the operation amount S of the operating lever 6. For example, if the operation lever 6 is an electric lever, the operation amount can be extracted as an electric signal by a potentiometer provided on the electric lever.

Then, the current detected spool stroke position of the flow control valve 5 (the operation amount of the operation lever 6)
Is determined according to the correspondence shown in FIG.

Therefore, the smaller one of the opening amount A of the variable bleed valve 13 obtained from the correspondence shown in FIG. 5 and the opening A of the variable bleed valve 13 obtained from the correspondence shown in FIG. The opening amount A is selected. Then, the variable bleed valve 13 is controlled so that the selected smaller opening amount A is obtained.

As described above, according to the present embodiment, in the closed center type load sensing hydraulic system, the stabilization of the vibration of the speed of the cutting edge of the working machine can be improved.

In this embodiment, it is assumed that the present invention is applied to a hydraulically driven machine that performs load sensing control.
The method of controlling the hydraulic pump 1 is arbitrary.

The present invention is also applicable to a hydraulic drive machine employing a positive control system for controlling the discharge amount of the hydraulic pump 1 according to the operation amount of the operation lever 6.

In short, if the present invention is applied to a closed-center type hydraulic drive machine in which the effect of the stabilization has not been obtained conventionally, the effect of the stabilization can be drastically obtained.

Of course, the present invention may be applied to an open center type hydraulic drive machine.

In this embodiment, the boom, the arm,
Although a construction machine equipped with a bucket or the like is assumed, the invention is not limited to this, and any hydraulic drive machine in which stabilization of vibration of load speed is a problem can be applied.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a response of a flow rate to a hydraulic actuator corresponding to a lever input and a cutting edge speed of a work machine in the hydraulic drive machine shown in FIG. 1;

FIG. 3 is a diagram showing a modification of the hydraulic circuit diagram of FIG. 1;

FIG. 4 is a diagram showing a modification of the hydraulic circuit diagram of FIG. 1;

FIG. 5 is a graph showing a correspondence relationship between a discharge pressure of a hydraulic pump and an opening amount of a variable bleed valve.

FIG. 6 is a graph showing a correspondence relationship between a discharge pressure change amount of a hydraulic pump and an opening amount of a variable bleed valve.

FIG. 7 is a graph showing a correspondence relationship between a spool stroke (operation amount of an operation lever) of a flow control valve and an opening amount of a variable bleed valve.

FIG. 8 is a diagram used to explain a conventional technique;
5 is a graph illustrating a characteristic in which a bleed-off flow rate changes according to a spool stroke position of a flow control valve.

FIG. 9 is a graph showing a relationship between a pump discharge pressure and a differential pressure between the maximum load pressure of the hydraulic actuator and a pump displacement volume.

FIG. 10 is a graph used to explain negative control, and is a graph showing the relationship between the differential pressure across the throttle in a neutral circuit and the pump displacement volume.

FIG. 11 is a graph showing a correspondence relationship between an opening amount of a variable bleed valve and a command current.

FIG. 12 is a hydraulic circuit diagram conceptually showing a closed center type load sensing hydraulic system.

FIG. 13 is a graph showing a response of a flow rate to a hydraulic actuator corresponding to a lever input and a work implement cutting edge speed in the hydraulic drive machine shown in FIG. 12;

FIG. 14 is a hydraulic circuit diagram conceptually showing a hydraulic system adopting an open center type negative control system.

FIG. 15 is a graph showing a response of a flow rate to a hydraulic actuator and a work implement cutting edge speed corresponding to a lever input in the hydraulic drive machine shown in FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 2 Engine 3 Pump swash plate control mechanism 5 Flow control valve 6 Operating lever 7 Controller 8 Pressure sensor 12 Tank 13 Variable bleed valve 15 Bleed-off circuit

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) 2D003 AB05 BB02 CA06 DA03 DA04 DB02 DB04 DB05 EA01 3H045 AA04 AA10 AA13 AA24 AA33 BA19 BA28 CA03 DA16 3H089 AA24 AA27 AA60 BB10 DA03 DA13 DB12 EE31 EE34 FF05 FF07 FF07

Claims (9)

[Claims] 1. A control device for a hydraulic drive machine, comprising: a hydraulic pump; and a flow control valve for supplying a discharge pressure oil of the hydraulic pump to a hydraulic actuator by a flow rate corresponding to an operation amount. A bleed-off circuit for discharging pressure oil supplied to a hydraulic actuator; a variable bleed valve provided in the bleed-off circuit for changing a flow rate of the discharged pressure oil; and A control device for a hydraulically driven machine, comprising: a variable bleed valve control means for controlling the variable bleed valve so as to increase the flow rate of discharged hydraulic oil. 2. A control device for a hydraulic drive machine comprising: a hydraulic pump; and a flow control valve for supplying a discharge pressure oil of the hydraulic pump to a hydraulic actuator by a flow rate corresponding to an operation amount. A bleed-off circuit for discharging the pressure oil supplied to the hydraulic actuator; a variable bleed valve provided in the bleed-off circuit for changing the flow rate of the discharged pressure oil; and a change in the discharge pressure of the hydraulic pump increases. And a variable bleed valve control means for controlling the variable bleed valve so as to increase the flow rate of the discharged pressure oil. 3. A variable displacement hydraulic pump, a flow control valve for supplying a discharge pressure oil of the hydraulic pump to a hydraulic actuator by a flow rate corresponding to an operation amount, a discharge pressure of the hydraulic pump and a load of the hydraulic actuator. The pressure differential is
A control device for a hydraulically driven machine comprising: a load sensing control unit that controls a displacement volume of the hydraulic pump so as to be a set value.A bleed-off circuit that discharges pressure oil supplied from the hydraulic pump to the hydraulic actuator. A variable bleed valve provided in the bleed-off circuit and configured to change a flow rate of discharged hydraulic oil; and the variable bleed valve is configured such that as the discharge pressure of the hydraulic pump increases, the flow rate of the discharged hydraulic oil increases. A control device for a hydraulically driven machine comprising variable bleed valve control means for controlling a bleed valve. 4. A variable displacement hydraulic pump, a flow control valve for supplying a discharge pressure oil of the hydraulic pump to a hydraulic actuator by a flow rate corresponding to an operation amount, a discharge pressure of the hydraulic pump, and a load of the hydraulic actuator. The pressure differential is
A control device for a hydraulically driven machine comprising: a load sensing control unit that controls a displacement volume of the hydraulic pump so as to be a set value.A bleed-off circuit that discharges pressure oil supplied from the hydraulic pump to the hydraulic actuator. A variable bleed valve provided in the bleed-off circuit, for changing the flow rate of the discharged pressure oil, and as the discharge pressure change amount of the hydraulic pump increases, the flow rate of the discharged pressure oil increases. A control device for a hydraulically driven machine, comprising a variable bleed valve control means for controlling the variable bleed valve. 5. The hydraulic drive according to claim 1, wherein the variable bleed valve control means controls the variable bleed valve by supplying an electric signal to the variable bleed valve. Machine control device. 6. The variable bleed valve control means controls the variable bleed valve by supplying a pilot pressure signal indicating a discharge pressure of the hydraulic pump to the variable bleed valve via a pilot pressure oil pipeline. The control device for a hydraulically driven machine according to claim 1 or 3, wherein 7. A discharge pressure detecting means for detecting a discharge pressure of the hydraulic pump, and a setting means for setting a correspondence relationship between a discharge pressure of the hydraulic pump and an opening amount of the variable bleed valve. The variable bleed valve control means obtains the opening amount of the variable bleed valve corresponding to the current discharge pressure detected by the discharge pressure detecting means according to the set correspondence, and obtains the obtained opening amount. The control device for a hydraulically driven machine according to claim 1, wherein the control device controls the variable bleed valve. 8. A discharge pressure change amount detecting means for detecting a discharge pressure change amount of the hydraulic pump, and a setting means for setting a correspondence relationship between a discharge pressure change amount of the hydraulic pump and an opening amount of the variable bleed valve. The variable bleed valve control means obtains the opening amount of the variable bleed valve corresponding to the current discharge pressure change amount detected by the discharge pressure change amount detection means in accordance with the set correspondence. 5. The control device for a hydraulically driven machine according to claim 2, wherein the variable bleed valve is controlled so that the obtained opening amount is obtained. 9. A discharge pressure detecting means for detecting a discharge pressure of the hydraulic pump, an operation amount detecting means for detecting an operation amount of the operated flow control valve, a discharge pressure of the hydraulic pump and the variable bleed valve. A first setting means for setting a correspondence relationship with the opening amount of the variable bleed valve, wherein the opening amount of the variable bleed valve decreases as the operation amount of the flow control valve increases. The variable bleed valve control means, wherein the variable bleed valve control means sets the opening amount of the variable bleed valve corresponding to the current discharge pressure detected by the discharge pressure detection means to the first set value. And the opening amount of the variable bleed valve corresponding to the current operation amount detected by the operation amount detecting means is obtained according to the set second correspondence relationship. Of the amount of opening of the variable bleed valves,
The control device for a hydraulically driven machine according to claim 1 or 3, wherein the variable bleed valve is controlled so that a smaller opening amount is obtained.