JPH0960605A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control speed smoothly at the time of load reverse or deceleration of an actuator. SOLUTION: A device is provided with a means for instructing the feed flow rate to a hydraulic actuator, a means for controlling an opening degree of a flow rate control valve 11 in a supplying circuit 1 corresponding to a flow rate instructing value, a means for calculating the control flow rate from a valve opening degree and a pressure difference between the front and rear pressure thereof, and a means for feed back-controlling the opening degree of the flow rate control valve 11 so as to match the instructing flow rate with a real flow rate. And also it is provided with a means for feed back-controlling pressure of a return side to a prescribed value through the pressure control valve 12 of a return circuit 2 when the instructing flow rate is larger than the real flow rate, and for feed back controlling pressure of the return side to a pressure value according to a flow rate deviation value when a feed flow rate is larger than the instruction flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control apparatus which is optimal for flow rate control even when a load reverses during operation, such as a swing motor of a hydraulically driven power shovel.

[0002]

2. Description of the Related Art For example, when controlling a hydraulically driven swing motor for a power shovel on a sloping ground, the load of the motor may reverse from a positive load to a negative load during the swing. When a positive load is applied to the swing motor, the motor rotation speed can be controlled by controlling the flow rate of the hydraulic oil sent to the motor.However, when the negative load is switched on the way, the motor rotates due to the load. You may be forced to run out of control.

Therefore, the applicant of the present invention has filed a Japanese Patent Application Laid-Open No. 6-21.
As No. 3208, when the load is reversed, the pressure on the hydraulic oil supply side becomes lower than the pressure on the discharge side. Therefore, when this is detected, the flow rate on the meter-out side, which is the discharge side, is reduced to reduce the resistance. There has been proposed a hydraulic control device that applies a braking force to prevent the swing motor from running out of control.

In this case, the meter-in side, which is the supply side,
A flow rate pressure control valve is provided on each of the discharge side, that is, the meter-out side, and when the load pressure on the meter-in side falls below a certain fixed value, the meter-out side pressure is maintained so that the meter-in side pressure is kept constant. The opening of the flow rate pressure control valve is reduced so that the rotation of the swing motor does not suddenly increase even if the load reverses.

[0005]

However, the load pressure on the meter-in side is compared with a constant value in this way, and when it becomes lower than that, the meter-in side pressure is restored so as to recover the pressure on the meter-in side to a constant value. In the method of narrowing down and applying resistance, there is a problem that the control on the meter-out side is likely to be turned on and off, and hunting and rapid braking are likely to be applied.

This is because the opening on the meter-out side is controlled to be turned on and off in order to keep the pressure on the meter-in side at a constant value. When the state is sharply throttled, the pressure on the meter-out side suddenly rises, the turning operation of the motor is suddenly braked, the turning speed of the turning motor is jerky, and the operability is deteriorated.

Such a phenomenon may also occur transiently, for example, when the supply flow rate is reduced in order to reduce the rotation speed of the motor. This is because if the speed is reduced during turning, the motor is rotated in the same direction due to the inertial force that tries to continue turning, and the pressure on the meter-in side is temporarily reduced by reducing the flow rate on the meter-in side. This is because the pressure may drop below a certain level.

The present invention solves such a problem.
An object of the present invention is to provide a hydraulic control device that can perform smooth speed control even when the actuator load reverses or decelerates.

[0009]

According to a first aspect of the present invention, a hydraulic actuator for driving a load, a flow control valve provided in a hydraulic oil supply circuit for the hydraulic actuator, and a hydraulic oil return circuit are also provided. In a hydraulic control device provided with a pressure control valve, means for detecting the pressure of the supply circuit,
Means for detecting the pressure of the return circuit, means for detecting the opening of the flow control valve, means for instructing the flow rate supplied to the hydraulic actuator, and means for controlling the opening of the flow control valve according to the flow command value. , A means for calculating the actual supply flow rate from the opening of the flow control valve and the pressure difference across the flow control valve, a means for feedback-correcting the opening of the flow control valve so that the command flow rate and the actual flow rate match, and a command flow rate Is larger than the actual flow rate, the opening of the pressure control valve is feedback-corrected so that the return side pressure matches the predetermined value, and when the supply flow rate is larger than the command flow rate, the return side pressure is adjusted to the predetermined value. And a control means for feedback-correcting the opening degree of the pressure control valve so as to match the pressure value according to the flow rate deviation.
A first flow rate pressure control valve provided in a hydraulic oil supply circuit for the hydraulic actuator, a second flow rate pressure control valve also provided in a hydraulic oil return circuit, and the first and second flow rate pressure valves. In a hydraulic control device provided with a hydraulic source connected to a control valve, a means for detecting the pressure of a supply circuit, a means for detecting the pressure of a return circuit, and an opening degree of the first and second flow rate pressure control valves are set. Detecting means, means for instructing a flow rate to be supplied to the hydraulic actuator, means for controlling the opening degree of the first flow rate pressure control valve according to the flow rate command value, and opening degree of the first flow rate pressure control valve and its A means for calculating the actual supply flow rate from the front-back pressure difference, a means for feedback-correcting the opening of the first flow rate pressure control valve so that the command flow rate and the actual flow rate match, and the command flow rate is lower than the actual flow rate. Is too large, the pressure on the return side Is corrected by feedback so that the opening degree of the second flow rate pressure control valve becomes equal to a predetermined value, and when the supply flow rate is larger than the command flow rate, the pressure on the return side is higher than the predetermined value and according to the flow rate deviation. And a control means for feedback-correcting the opening degree of the second flow rate pressure control valve so as to coincide with the pressure value.

According to a third aspect of the invention, in the first or second aspect of the invention, when the supply flow rate Qid is larger than the command flow rate Qcom, the means for controlling the pressure on the return side to a pressure value Pcom corresponding to these flow rate deviations is provided. , Pcom = Pmax × (Qid−Qcom) / Qid However, Pmax sets the control pressure value Pcom so that it becomes a predetermined maximum pressure value.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, when the supply flow rate Qid is larger than the command flow rate Qcom, the means for controlling the pressure on the return side to a pressure value Pcom according to these flow rate deviations is provided. , Pcom = Pmax × {(Qid−Qcom) / Qi
d} ² However, the control pressure value Pcom is set so that Pmax becomes a predetermined maximum pressure value.

[0012]

In the first aspect of the invention, the opening degree of the flow control valve is controlled according to the command value of the flow rate, the hydraulic oil is supplied from the hydraulic source to the hydraulic actuator, and the hydraulic actuator is operated according to the supplied flow rate. The speed of is controlled.

A pressure control valve is provided on the return side from the hydraulic actuator to control the pressure.

Now, when the actual supply flow rate is smaller than the command flow rate for the hydraulic actuator, it is necessary to increase the opening of the flow control valve to increase the flow rate for the hydraulic actuator. It is preferable that the return pressure from the hydraulic actuator is low and the outflow resistance is small. At the time of this increase request, the opening of the pressure control valve is controlled so that the return side pressure becomes a certain low predetermined value (for example, zero pressure), and a quick increase is achieved.

On the other hand, when the actual supply flow rate is larger than the command flow rate of the hydraulic actuator, it is necessary to reduce the opening degree of the flow rate control valve to reduce the supply flow rate to the hydraulic actuator. In order to stably reduce the amount, it is advisable to raise the pressure on the return side and brake the hydraulic actuator.

Therefore, at the time of this reduction request, the pressure control valve controls the pressure on the return side according to the deviation between the command flow rate and the actual flow rate such that the larger the deviation is, the higher the pressure value becomes. As a result, the discharge resistance from the hydraulic actuator increases, the brake is applied, and the operating speed of the hydraulic actuator is reduced.

In this case, the reduction request is greater as the deviation between the command flow rate and the actual flow rate is larger, and when the deviation is small, the reduction amount may be small. Therefore, by increasing the pressure resistance on the return side of the hydraulic actuator as the deviation increases, the pressure resistance can be quickly reduced with good response.

By the way, such a reduction is required because, for example, the load applied to the hydraulic actuator is reversed during the operation of the hydraulic actuator, and the positive load to the negative load up to that point, that is, the hydraulic actuator is driven by the load. In this case, even if the opening of the first flow rate pressure control valve does not change, the load side pressure decreases and the flow rate increases above the command flow rate. Also occurs when the operating speed is reduced by reducing the command flow rate.

In such a case, by imparting resistance to the flow on the discharge side from the hydraulic actuator and applying an appropriate brake to its operation as described above, rapid and stable deceleration is possible. is there.

Since the pressure control of the return circuit is performed according to the deviation between the commanded flow rate and the actual flow rate, the pressure does not change stepwise and stable control is possible, and the deviation is small. At times such as when the pressure loss becomes excessively large or the deviation is large, the brake pressure does not become insufficient.

Even for minute flow rate fluctuations within the range of normal feedback control, if the actual flow rate exceeds the command flow rate, the pressure in the return circuit will rise, but this pressure depends on the flow rate deviation. Therefore, for a minute deviation, a substantial pressure change hardly occurs.

According to the second aspect of the present invention, bidirectional control can be performed in the same manner for a hydraulic actuator that operates reversibly. That is, since the supply circuit is provided with the first flow rate pressure control valve and the return circuit is provided with the second flow rate pressure control valve, even if the supply direction of the hydraulic fluid to the hydraulic actuator is reversed, The second flow rate pressure control valve is used to control the flow rate on the inflow side of the hydraulic actuator.
The pressure control on the discharge side can be performed by the flow rate pressure control valve, and by this, the control similar to that of the first invention can be realized in any operation direction of the hydraulic actuator.

In the third aspect of the invention, the pressure value Pcom corresponding to the flow rate deviation is Pcom = Pmax × (Qid-Qco
Since it is controlled as m) / Qid, the pressure value on the return side can be appropriately controlled according to the magnitude of the flow rate deviation, and stable flow rate control can be performed without causing sudden pressure fluctuations.

In the fourth aspect of the invention, the pressure value Pcom corresponding to the flow rate deviation is Pcom = Pmax × {(Qid-Qco
m) / Qid} ² , so that Pcom can be made very small when the deviation is small, and for flow rate fluctuations such as within the range of feedback control, by eliminating almost no pressure change on the return side, stable without hunting. It is possible to control the flow rate.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a hydraulic motor M is provided as a hydraulic actuator that operates by receiving the supply of hydraulic oil from a pump P, and a hydraulic oil supply circuit 1 for this hydraulic motor M In the oil return circuit 2, a first flow rate pressure control valve 11 and a second flow rate pressure control valve 12 are provided, respectively.

The first and second flow rate pressure control valves 11 and 12 are constructed in the same manner. Therefore, to describe only one of them, a flange 16 is formed on a part of the spool 15.
The flange 16 defines a small pressure receiving area chamber 17 and a large pressure receiving area chamber 18. The discharge pressure from the pump P is directly transmitted to the small pressure receiving area chamber 17, while the adjusting pressure obtained by adjusting the discharge pressure via the pilot valve 20 is transmitted to the large pressure receiving area chamber 18. The spool 15 is displaced in accordance with the balance between the force due to the pressure and the acting force of the spring 21.

Depending on its position, the spool 15 selectively connects the operation port 23 communicating with the hydraulic motor M to the pump port 24 communicating with the pump P or the tank port 25 communicating with the tank T.

A first pressure sensor 31 is provided to detect the discharge pressure of the pump P, and a second pressure sensor 32 is provided to detect the load pressure of the hydraulic motor M. Further, a stroke sensor 33 is provided to detect the opening degree of the spool 15.

Each of these detection signals is input to a pilot valve drive circuit 41 for driving the pilot valve 20, and the drive circuit 41 further includes a controller 42.
The flow control command signal from is input. A flow rate command signal and a pressure control command signal from the operation unit 43 are input to the controller 42.

As a result, for example, in the first flow rate pressure control valve 11, the pilot valve 20 adjusts the pressure in the large pressure-receiving area chamber 18 so that the flow rate commanded by the controller 42 can be obtained. Spool 1
5 is displaced, the opening of the spool 15 and the pressures upstream and downstream thereof are detected, and the actual flow rate is identified (calculated) by these feedback signals so that the command flow rate and the actual flow rate match. In addition, the displacement of the spool 15 is finally feedback-controlled via the pilot valve 20. The controlled flow rate is determined by the valve opening of the spool 15 and the pressure difference before and after the valve opening. Therefore, the flow rate may be calculated from these detected values, and the position of the spool 15 may be controlled so that it matches the commanded flow rate.

Further, the first flow rate pressure control valve 11 is not limited to flow rate control, and when pressure control is instructed by the controller 42, for example, the spool 15 is arranged so that the load pressure downstream thereof matches the instructed pressure. Is feedback-controlled, whereby the load pressure of the supply circuit 1 can be controlled to the command pressure.

The second flow rate pressure control valve 12 also operates in exactly the same manner in response to a signal from the controller 42 to perform flow rate control or pressure control of the return circuit 2.

The structure of the first and second flow rate pressure control valves 11 and 12 has already been described in JP-A-6-2.
It is known from Japanese Patent No. 13208.

Further, operating check valves 51 and 52 are provided in the supply circuit 1 and the return circuit 2, and the operating check valves 51 and 52 are operated by the operating check valve drive circuit 44.
Switching operation is performed by the signal from. Operate check valves 51 and 52 are OFF when the operation device 43 is not operated
The check function holds the load pressure and prevents the hydraulic motor M from running away. When operating the operating device 43,
The meter-in side remains off, maintaining the check function,
Reverse rotation due to load pressure during leaning and turning is prevented, and the meter-out side is turned on to form a return flow path that can freely flow.

Next, the controller 42 compares the commanded flow rate with the actual flow rate, and when the commanded flow rate is larger, the opening degree of the first flow rate pressure control valve 11 is increased to change the supply flow rate. At this time, the pressure in the return circuit 2 is maintained at a constant low pressure (for example, zero pressure) via the second flow rate pressure control valve 12 to prevent pressure loss, and the command is issued. When the actual flow rate is larger than the flow rate, it is time to reduce the control flow rate, but in order to reduce the opening degree of the first flow rate pressure control valve 11 and brake the rotation of the hydraulic motor M, the command flow rate and the actual flow rate are set. According to the deviation from the flow rate, that is, as the deviation increases, the opening degree of the second flow rate pressure control valve 12 is narrowed and the pressure in the return circuit 2 is increased.

In this way, for example, when the direction of the load applied to the hydraulic motor M is reversed midway, and there occurs a positive load to a negative load up to that point, that is, a state in which the hydraulic motor M is rotationally driven by the load. , The first flow pressure control valve 1
Even if the opening of No. 1 does not change, the load side pressure decreases, the flow rate increases more than the command flow rate, and when the command flow rate is reduced and the operating speed is reduced while the hydraulic motor M is rotating, the hydraulic motor remains unchanged. Although the actual flow rate increases for a while due to the inertial force that attempts to rotate M, in response to such a phenomenon, the pressure in the return circuit 2 is increased according to the deviation between the command flow rate and the actual flow rate, and the brake is applied. By effectively applying the above, the hydraulic motor M is quickly decelerated and stable flow rate control is realized.

Now, the control operation executed by the controller 42 will be described in more detail with reference to the flowchart of FIG.

In step 1, the flow rate command value S and the supply circuit 1
Pump pressure P1a, load pressure P1b, spool displacement amount (valve opening) X1 of the first flow rate pressure control valve 11, return circuit 2
When the load pressure P2b and the spool displacement amount X2 of the second flow rate pressure control valve 12 are read, first, in step 2, the rotational direction of the hydraulic motor M is determined based on whether the flow rate command value S is positive or negative.

If S> 0, the hydraulic motor M rotates to the right, otherwise it rotates to the left. During clockwise rotation, the flow rate sent from the first flow rate pressure control valve 11 to the supply circuit 1 is meter-in (M / I) controlled, and the second flow rate pressure control valve 12 meters the load pressure of the return circuit 2 meter-out (M / O). )Control. When turning counterclockwise, the second
The first flow rate pressure control valve 11 controls the flow rate sent from the flow rate pressure control valve 12 to the return circuit 2 by meter-in control.
The return pressure is controlled to be metered out (however, at this time, the return circuit 2 functions as a supply circuit and the supply circuit 1 functions as a return circuit).

When the hydraulic motor M is in the right rotation control, the routine proceeds to step 3 and step 8, where the first flow rate pressure control valve (valve 1) is metered in and the second flow rate pressure control valve (valve 2) is metered out. Control.

First, the meter-in control will be described. In step 4, the flow rate passing through the valve 1 is calculated from X1 and P1a and P1b as the identified flow rate Qid. Further, in step 5, the command flow rate Qcom is set from the flow rate command value S described above. Then, in step 6, the valve opening degree of the valve 1 required to match Qid with Qcom is calculated based on these Qcom and Qid, and in step 7, this correction amount Xq1 is output. If Qid is smaller than Qcom, the valve opening is increased to increase the actual flow rate, and conversely, if Qid is larger than Qcom, the valve opening is reduced.

Explaining the meter-out control in step 8, first, the identified (actual) flow rate Qid calculated on the meter-in side in step 9 is compared with the commanded flow rate Qcom, and when Qid> Qcom, that is, the flow rate is reduced. When it is necessary, the process proceeds to step 10, and the pressure command Pcom is set by function calculation in order to control the pressure in the return circuit 2 to a pressure that increases according to this flow rate deviation.

Then, in step 11, the opening of the second flow rate pressure control valve 12 (valve 2) is calculated so that the actual pressure P2b of the return circuit 2 becomes the set Pcom, and in step 12 The correction amount Xp2 for this is output.

Here, the command pressure Pcom is calculated by the function calculation as follows, for example. That is, Pcom = Pmax × (Qid−Qcom) / Qid (1) However, Pmax is a pressure value of a characteristic that linearly decreases as the operation command value S increases as shown in FIG. FIG. 4 shows Pcom as a function corresponding to the deviation between the commanded flow rate Qcom and the actual flow rate Qid.

When the deviation between Qid and Qcom is small, Pcom also has a small value. However, when the deviation becomes large, Pcom also becomes larger, and therefore when the actual flow rate exceeds the command flow rate, the valve 2 Is greatly narrowed down, and the pressure in the return circuit 2 rises. As a result, the pressure loss on the return side from the hydraulic motor M is increased, the brake is applied, and the valve 1 reduces the flow rate and the hydraulic motor M The supply flow rate will be reduced responsively.

This Pcom is the commanded flow rate Qcom.
Is set according to the deviation between the actual flow rate Qid and the actual flow rate Qid. Therefore, when the deviation is small and a large brake (pressure loss) is not required, the pressure increase width is controlled to be small.

The control function of Pcom can be calculated as a quadratic function as follows.

Pcom = Pmax × {(Qid−Qcom) / Qid} ² (2) In this case, as shown in FIG. 5, Pcom is small when the deviation is small and increases as the deviation increases. Since it rises secondarily, when the deviation between the command flow rate and the actual flow rate is very small within the normal feedback control range, there is almost no pressure increase in the return circuit 2, reducing control hunting and improving stability. To be

In step 9, Qid ≦ Qco
When it is determined that the value is m, the process proceeds to step 13. In this case, the actual flow rate is less than the command flow rate, and the flow rate needs to be increased. In the return circuit 2, it is preferable that the pressure loss is as small as possible, so that Pcom =
0 is set, and the actual circuit pressure P2b is set to this set pressure P
com, the opening degree of the valve 2 required to make it coincide with com is calculated, and in step 15, a correction amount Xp2 for this is output.

When the actual flow rate is less than the command flow rate, it is necessary to increase the flow rate in a responsive manner. In this case, the pressure loss on the return side should be as small as possible. Therefore, Pcom = 0 is set. The valve 2 is controlled to the maximum opening.

Next, in step 2, when the hydraulic motor M is not rotating to the right from the sign of the flow rate command value S,
Proceeding to the routine of steps 23 to 35, the flow rate control for the left rotation of the hydraulic motor M is performed.

In this case, the second flow rate pressure control valve 12 controls the meter-in flow rate and the first flow rate pressure control valve 11 controls the meter-out pressure. Except for the difference in the flow direction of the hydraulic oil with respect to the motor M, the above steps 3 to
Since the control up to 15 is substantially the same, the detailed description is omitted.

With the above construction, the overall operation will be described.

However, here, a hydraulic motor M for sending hydraulic oil to the supply circuit 1 and discharging hydraulic oil from the return circuit 2
The right rotation control will be described as an example.

The opening of the first flow rate pressure control valve 11 is set in accordance with the flow rate command value S, whereby the hydraulic oil is sent to the supply circuit 1. Actual flow rate Qid at this time
Is calculated based on the valve opening degree and the pressure difference before and after the valve opening degree, and this Qid is compared with the command flow rate Qcom.

If Qid is smaller than Qcom, the first flow rate pressure control valve 11 is used to increase the supply flow rate.
The opening degree of is corrected to be increased. At this time, the second flow rate pressure control valve 12 that controls the pressure of the return circuit 2 is set to zero as the command pressure in order to minimize the pressure loss on the return side. In this way, when it is necessary to increase the amount, the flow rate quickly increases without increasing the pressure in the return circuit 2.

The increase of the flow rate is required when it is desired to increase the rotational speed of the hydraulic motor M from the middle, and the command value S is set to a larger value S2 from the previous value S1.
It was when I changed it to. However, since the first flow rate pressure control valve 11 performs feedback control while detecting the actual flow rate, there is a slight flow rate variation within the range of this feedback control. If is smaller than the command flow rate, such control is performed.

On the other hand, when Qcom is larger than Qid, that is, when the actual flow rate is greater than or equal to the command flow rate and it is necessary to reduce the flow rate, the opening degree of the first flow rate pressure control valve 11 is corrected in the reducing direction. While the flow rate is throttled, the second flow rate pressure control valve 12 sets the pressure in the return circuit 2 to a target value that is a pressure that changes according to the deviation between Qid and Qcom from the constant value Pcom = 0. Control.

This pressure Pcom is set so as to increase as the deviation between Qcom and Qid increases, as shown in the above equation (1). Therefore, the opening of the second flow rate pressure control valve 12 increases as the deviation increases. To increase the pressure loss in the return circuit 2 and increase the braking force for the rotation of the hydraulic motor M. As a result, the rotation speed of the hydraulic motor M rapidly decreases.

Such a state occurs when, for example, the direction of the load applied to the hydraulic motor M reverses midway and the positive load to the negative load up to that point, that is, the hydraulic motor M is about to be rotationally driven by the load. Alternatively, even if the speed of the hydraulic motor M is decelerated while the hydraulic motor M is rotating, the inertial load applied to the hydraulic motor M forces the hydraulic motor M to rotate. Accordingly, the pressure of the return circuit 2 is increased and the brake is applied, so that the hydraulic motor M is quickly decelerated and stable flow rate (speed) control is possible.

By the way, since the pressure control of the return circuit 2 is performed according to the deviation between the commanded flow rate and the actual flow rate, the pressure does not change stepwise and stable control is possible, and the deviation It does not occur that the pressure loss becomes excessively large when it is small, or the brake pressure becomes insufficient when the deviation is large.

Even for minute flow rate fluctuations within the range of normal feedback control, if the actual flow rate exceeds the command flow rate, the pressure in the return circuit will rise, but this pressure depends on the flow rate deviation. Since a slight deviation hardly causes a substantial pressure change, hunting is unlikely to occur and the control stability is good.

In the above description, the first and
The second flow rate pressure control valves 11 and 12 are connected to the supply circuit 1 respectively.
Since it is interposed in the return circuit 2, the supply direction of the hydraulic oil to the hydraulic motor M can be reversed and reversibly rotated, but the present invention is not necessarily limited to such a configuration.

That is, at least a flow control valve capable of feedback control for the supply circuit 1 and a pressure control valve also capable of feedback control for the return circuit 2 may be used. In this case, the rotation of the hydraulic motor M does not occur. Although limited to one direction, similar effects can be exhibited in this case as well.

Alternatively, the first and second flow rate pressure control valves 1
Similar control can be performed by arranging two two-way flow pressure control valves in series in each of the circuits 1 and 2 instead of 1, 12.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the control contents of the same.

FIG. 3 is an explanatory diagram showing a relationship between an operation command and maximum pressure for pressure setting.

FIG. 4 is an explanatory diagram showing functional characteristics for pressure setting.

FIG. 5 is an explanatory diagram showing another example of relational characteristics for pressure setting.

[Explanation of symbols]

 1 Supply Circuit 2 Return Circuit 11 First Flow Rate Pressure Control Valve 12 Second Flow Rate Pressure Control Valve 31 Pressure Sensor 32 Pressure Sensor 33 Straw Sensor 42 Controller M Hydraulic Motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Haruki Ikata Inventor Haruki 2-4-1 Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Industry Co., Ltd. (72) Inventor Takahashi Yoneaki Hamamatsu-cho, Minato-ku, Tokyo 2-4-1 World Trade Center Building Kayaba Industry Co., Ltd.

Claims (4)

[Claims] 1. A hydraulic control device comprising a hydraulic actuator for driving a load, a flow control valve provided in a hydraulic oil supply circuit for the hydraulic actuator, and a pressure control valve also provided in a hydraulic oil return circuit. In, the means for detecting the pressure in the supply circuit, the means for detecting the pressure in the return circuit, the means for detecting the opening of the flow control valve, the means for instructing the supply flow rate to the hydraulic actuator, and the flow rate command value Therefore, the means for controlling the opening of the flow control valve, the means for calculating the actual supply flow from the opening of the flow control valve and the pressure difference across it, and the flow control valve so that the command flow and the actual flow match Feedback correction of the opening of the pressure control valve and feedback correction of the opening of the pressure control valve so that the pressure on the return side matches the specified value when the command flow rate is larger than the actual flow rate. And a control means for feedback-correcting the opening of the pressure control valve so that the pressure on the return side is higher than the predetermined value and matches the pressure value according to the flow rate deviation when the supply flow rate is larger than the prescribed flow rate. A hydraulic control device characterized by. 2. A hydraulic actuator for driving a load, a first flow rate pressure control valve provided in a hydraulic oil supply circuit for the hydraulic actuator, and a second flow rate pressure valve also provided in a hydraulic oil return circuit. In a hydraulic control device including a control valve and a hydraulic pressure source connected to the first and second flow rate pressure control valves, a means for detecting a pressure in a supply circuit, a means for detecting a pressure in a return circuit, and 1, means for detecting the opening of the second flow rate pressure control valve, means for instructing the supply flow rate to the hydraulic actuator, and means for controlling the opening of the first flow rate pressure control valve according to the flow rate command value The means for calculating the actual supply flow rate from the opening of the first flow rate pressure control valve and the pressure difference across the first flow rate control valve and the opening degree of the first flow rate pressure control valve so that the command flow rate and the actual flow rate match. Feedback correction hand When the command flow rate is larger than the actual flow rate, the opening of the second flow rate pressure control valve is feedback-corrected so that the pressure on the return side matches the predetermined value, and when the supply flow rate is larger than the command flow rate. Is equipped with control means for feedback-correcting the opening of the second flow rate pressure control valve so that the pressure on the return side is higher than the predetermined value and matches the pressure value according to the flow rate deviation. Control device. 3. A means for controlling the pressure on the return side to a pressure value Pcom according to these flow rate deviations when the supply flow rate Qid is larger than the command flow rate Qcom, Pcom = Pmax × (Qid−Qcom) / Qid , Pmax sets the control pressure value Pcom so that the maximum pressure value becomes a predetermined maximum pressure value. 4. A means for controlling the pressure on the return side to a pressure value Pcom according to these flow rate deviations when the supply flow rate Qid is larger than the command flow rate Qcom, Pcom = Pmax × {(Qid-Qcom) / Qi
d} ² However, the hydraulic control device according to claim 1 or 2, wherein the control pressure value Pcom is set so that Pmax becomes a predetermined maximum pressure value.