JP4089738B2 - Hydraulic drive device - Google Patents

Description

  The present invention relates to a hydraulic drive apparatus suitable for use in, for example, injection molding machines, machine tools, construction machines, and the like.

  Conventionally, as a hydraulic drive device, one fixed displacement hydraulic pump is driven by a servo motor, and the servo motor is controlled by a controller based on a pressure detection value, a flow detection value, a pressure command value, and a flow command value. There is what is controlled (Patent Document 1: Japanese Patent Laid-Open No. 2000-320466).

  By the way, in the conventional hydraulic pressure driving device, since one fixed displacement hydraulic pump is driven by a servo motor, the shaft torque required by the servo motor is proportional to the load pressure and the capacity of the fixed displacement hydraulic pump. Will do. Therefore, when a large capacity fixed displacement hydraulic pump is used when a large flow rate is required, if the load pressure increases, the required shaft torque and drive current of the servo motor become extremely large. The motor and controller become very large and expensive.

  On the other hand, when high pressure is required, if the shaft torque required by the servo motor is reduced using a small capacity fixed displacement hydraulic pump, the demand cannot be met when a large flow rate is required.

As described above, the conventional hydraulic drive apparatus has a problem that it is impossible to achieve both high pressure control and large flow rate control with a small and inexpensive structure.
JP 2000-320466 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic drive device capable of achieving both high pressure control and large flow rate control with a small and inexpensive structure.

In order to solve the above problems, the hydraulic drive device of the present invention is
Two series of medium-capacity first fixed displacement hydraulic pumps whose shafts are connected to each other and a small second fixed displacement hydraulic pump;
A first input port connected to the discharge port of the first fixed displacement hydraulic pump, a second input port connected to the discharge port of the second fixed displacement hydraulic pump, and a load line A first position having an output port and a return port connected to the tank, wherein the first and second input ports communicate with the output port, while the return port is closed; and the first input port A second position where the second input port communicates with the return port, and a third position where the first input port communicates with the return port while the second input port communicates with the output port. A four-port three-position electromagnetic switching valve having a position;
A servo motor for driving the first fixed displacement hydraulic pump and the second fixed displacement hydraulic pump;
A pressure sensor for directly or indirectly detecting the pressure of the load line;
A flow rate detection sensor for detecting the rotational position or speed of the servo motor;
While receiving the output of the pressure sensor and the flow rate detection sensor, and receiving the pressure command and the flow rate command, the pressure and the flow rate of the load line become the pressure and the flow rate according to the pressure command and the flow rate command. A controller for controlling the servo motor ,
The flow toward the load line is forward between the discharge port of the first fixed displacement hydraulic pump and the first input port of the electromagnetic switching valve and the load line. A connected first check valve;
The flow toward the load line is forward between the discharge port of the second fixed displacement hydraulic pump and the second input port of the electromagnetic switching valve and the load line. And a second check valve connected thereto .

  According to the hydraulic drive apparatus having the above-described configuration, the controller positions the four-port three-position electromagnetic switching valve at the first position when controlling the low pressure and large flow rate.

  Then, the medium flow rate liquid flowing into the first input port of the electromagnetic switching valve from the medium capacity first fixed displacement type hydraulic pump and the second capacity of the electromagnetic switching valve from the small capacity second fixed displacement type hydraulic pump. The small flow rate liquid flowing into the input port merges, and the large flow rate liquid is supplied from the output port to the load line.

  At this time, the controller controls the load line pressure and flow rate based on the pressure command indicating low pressure, the flow rate command indicating large flow rate, the signal from the pressure sensor, and the signal from the flow rate detection sensor. And the rotational speed of the servo motor is controlled so that the flow rate becomes large.

  As described above, when the electromagnetic switching valve is located at the first position, the load line is controlled with a low pressure and a large flow rate.

  On the other hand, when controlling the medium pressure / medium flow rate, the controller positions the electromagnetic switching valve at the second position.

  Then, a small flow rate of liquid flowing into the second input port of the electromagnetic switching valve from the small fixed second fixed displacement hydraulic pump is discharged from the return port to the tank, and the second fixed displacement hydraulic pump is Unload. However, the medium flow rate liquid flowing into the first input port of the electromagnetic switching valve from the first fixed displacement hydraulic pump is supplied from the output port to the load line.

  At this time, the controller controls the load line pressure and flow rate based on the pressure command indicating the intermediate pressure, the flow rate command indicating the intermediate flow rate, the signal from the pressure sensor, and the signal from the flow rate detection sensor. The rotation speed of the servo motor is controlled so that the medium pressure and the medium flow rate are obtained.

  As described above, when the electromagnetic switching valve is located at the second position, the medium pressure flow is controlled with respect to the load line.

  Further, at the time of controlling the high pressure and the small flow rate, the controller positions the electromagnetic switching valve at the third position.

  Then, the medium flow rate liquid flowing into the first input port of the electromagnetic switching valve from the medium capacity first fixed displacement type hydraulic pump is discharged from the return port to the tank, and the first fixed displacement type hydraulic pump is Unload. However, a small amount of liquid flowing from the second fixed displacement hydraulic pump into the second input port of the electromagnetic switching valve is supplied from the output port to the load line.

  At this time, the controller controls the load line pressure and flow rate based on the pressure command indicating high pressure, the flow rate command indicating small flow rate, the signal from the pressure sensor, and the signal from the flow rate detection sensor. And the rotational speed of the servo motor is controlled so that the flow rate is small.

  Thus, when the electromagnetic switching valve is located at the third position, the high pressure and small flow rate is controlled with respect to the load line.

  In this way, just by using one 4-port 3-position type electromagnetic switching valve and the above-mentioned connection structure, the three-stage operation mode of low pressure / high flow rate, medium pressure / medium flow rate, and high pressure / low flow rate can be selected, and the servo The shaft torque required for the motor can be reduced.

  Therefore, according to the present invention, it is possible to achieve both high pressure control and large flow rate control, and it is possible to reduce the current value required by the servo motor and the controller, thereby making the servo motor and the controller small and inexpensive. Can do.

  Furthermore, for example, in a hydraulic drive device of an injection molding machine or a press machine, there has been a request to maintain a high pressure for a long time, but conventionally, a servo motor or a controller generates a large amount of heat due to a large current. There was a problem that this request could not be met. However, in the hydraulic drive apparatus having the above configuration, since the current value is small, the pressure can be maintained at a high pressure for a long time.

In addition, if the electromagnetic switching valve is locked with, for example, dust and the like, it stops between the first position and the second position, or between the first position and the third position, and the first Even if the space between the input port or the second input port and the output port is closed, the first check valve or the first check valve or the liquid from the first and second fixed displacement hydraulic pumps bypasses the electromagnetic switching valve. The load line can be supplied through the second check valve. As described above, when the electromagnetic switching valve fails, the electromagnetic switching valve is bypassed by the first check valve and the second check valve, so that damage to the piping and hydraulic equipment can be prevented.

Moreover, the hydraulic drive device of one embodiment is
A relief valve connected to the load line;

  According to the embodiment, even if the pressure of the load line is excessive due to the liquid supplied from the first and second check valves by the relief valve, the pressure is excessively released by releasing the liquid to the tank. It is possible to prevent the device from being damaged.

Moreover, in the hydraulic drive device of one embodiment,
The above controller
A pressure control unit that receives the pressure command and a pressure detection signal from the pressure sensor, and outputs a pressure control signal based on a deviation between the pressure command and the pressure detection signal;
A limit unit that receives a pressure control signal and a flow rate command from the pressure control unit, and outputs a limit control signal generated by adding a limit according to the flow rate command to the pressure control signal; and
Based on the restriction control signal from the restriction unit and the flow rate detection signal from the flow rate detection sensor, the pressure and flow rate of the load line are set to the pressure and flow rate according to the pressure command and the flow rate command. A rotation speed control unit that generates a rotation speed control signal for control and outputs the signal to the servo motor.

  According to the above-described embodiment, the restriction unit adds a restriction corresponding to the flow rate command to the pressure control signal based on the deviation between the pressure command and the pressure detection signal (limiter control). To generate a limit control signal. Based on the restriction control signal and the flow rate detection signal from the flow rate detection sensor, the rotation speed control unit changes the pressure and flow rate of the load line to the pressure and flow rate according to the pressure command and the flow rate command. A rotation speed control signal for controlling the motor is generated and output to the servo motor.

  In this way, a restriction control signal is created by adding a restriction according to the flow rate command to the pressure control signal, and the pressure and flow rate are controlled based on this restriction control signal. Can be made accurately and smoothly.

  According to the present invention, it is possible to provide a hydraulic drive device that can achieve both high-pressure control and high-flow rate control with a small and inexpensive structure, with a small motor shaft torque and controller output current. .

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  As shown in FIG. 1, this hydraulic drive unit includes a first fixed displacement hydraulic pump 1 and a second fixed displacement hydraulic pump 2 that have shafts connected to each other, and the first and second fixed displacements. Servo motor 3 for driving the hydraulic pumps 1 and 2, a four-port three-position electromagnetic switching valve 5 for controlling the hydraulic oil from the first and second fixed displacement hydraulic pumps 1 and 2, and the servo motor 3 is provided.

  The first and second fixed displacement hydraulic pumps 1 and 2 are examples of first and second fixed displacement hydraulic pumps.

  The first fixed displacement hydraulic pump 1 has a medium capacity, and the second fixed displacement hydraulic pump 2 has a small capacity smaller than the medium capacity of the first fixed displacement hydraulic pump 1.

  The electromagnetic switching valve 5 has a first input port P1, a second input port P2, an output port A, and a return port R.

  The electromagnetic switching valve 5 includes a first position S1 in which the first and second input ports P1 and P2 communicate with the output port A, while a return port R is closed, and an output from the first input port P1. The second input port P1 communicates with the return port R while the second input port P1 communicates with the return port R, and the first input port P1 communicates with the return port R while the second input port P2 communicates with the output port A. And a third position S3 communicating with.

  Further, the electromagnetic switching valve 5 has solenoids a and b. When the solenoids a and b are demagnetized, the solenoid switching valve 5 is located at the neutral position, that is, the first position S1, and when only the solenoid a is excited, If it is located at the position S2 and only the solenoid b is excited, it is located at the third position S3.

  The discharge port of the first fixed displacement hydraulic pump 1 is connected to the first input port P1 of the electromagnetic switching valve 3 via the first discharge line 11, and the discharge port of the second fixed displacement hydraulic pump 2 Is connected to the second input port P <b> 2 of the electromagnetic switching valve 3 via the second discharge line 12. Further, the output port A of the electromagnetic switching valve 5 is connected to a load line 15, and the load line 15 communicates with a main machine hydraulic circuit 16. The return port R of the electromagnetic switching valve 5 is connected to the tank T.

  A first check valve 21 is connected between the first discharge line 11 and the load line 15 so that the flow toward the load line 15 is forward. Further, a second check valve 22 is connected between the second discharge line 12 and the load line 15 so that the flow toward the load line 15 is forward. Furthermore, a relief valve 23 is connected to the load line 15.

  Further, a pressure sensor 25 is connected to the load line 15, and the pressure of the load line 15 is directly detected by the pressure sensor 25.

  On the other hand, the servo motor 3 is provided with a position detector 26 comprising an encoder for detecting the rotational position of the servo motor 3. The position detector 26 is an example of a flow rate detection sensor for indirectly detecting the flow rates of the two first and second fixed displacement hydraulic pumps 1 and 2.

  The controller 6 receives outputs from the pressure sensor 25 and the position detector 26, and also receives a pressure command and a flow rate command, so that the pressure and flow rate of the load line 15 correspond to the pressure command and the flow rate command. The servo motor 3 is controlled so that the pressure and flow rate are achieved.

  Specifically, the controller 6 includes a pressure control unit 31, a limiting unit 32, and a rotation speed control unit 33. The pressure control unit 31, the limiting unit 32, and the rotation speed control unit 33 are constituted by microcomputer software, hardware, and the like.

  The pressure control unit 31 receives the pressure command and the pressure detection signal Pf from the pressure sensor 25, and outputs a pressure control signal Vp based on a deviation between the pressure command and the pressure detection signal Pf. The pressure control unit 31 converts the pressure deviation into a pressure control signal by so-called PID (proportional / integral / derivative) control.

  The limiting unit 32 has the same function as the limiter circuit, receives the pressure control signal Vp and the flow rate command from the pressure control unit 31, and the pressure control signal Vp has a predetermined value corresponding to the flow rate command. When the value is larger than the limit, a limit corresponding to the flow rate command is added, and a limit control signal VL corresponding to a desired rotation speed is generated and output.

  Although not shown, the controller 6 determines whether the flow rate command represents a large flow rate, a medium flow rate, or a small flow rate according to a predetermined standard, and the determined large flow rate, medium flow rate, and small flow rate. Accordingly, a control signal for positioning the electromagnetic switching valve 5 at the first, second and third positions S1, S2, S3 is output to the solenoids a, b.

  Further, the rotational speed control unit 33, for example, the number of detection signals received from the position detector 26 per unit time, that is, the rotational speed of the servo motor 3 and the position S1 of the electromagnetic switching valve 5 determined by the control signal. , S2 or S3, that is, based on the amount of hydraulic oil supplied to the load line 15 per fixed rotation angle of the servo motor 3, the flow rate is detected.

  Further, the rotation speed control unit 33 generates a rotation speed control signal corresponding to the deviation between the restriction control signal VL from the restriction unit 32 corresponding to the desired flow rate and the detected flow rate, and outputs the rotation speed control signal to the servo motor 3. Then, the pressure and flow rate of the load line 15 are controlled to be the pressure and flow rate corresponding to the pressure command and the flow rate command. The rotation speed control unit 33 functions as a driver, and the rotation speed control signal is an AC motor control current.

  The hydraulic drive device having the above configuration operates as follows.

  Now, it is assumed that the low pressure and large flow rate is controlled by the pressure command and the flow rate command. At this time, the controller 6 places the 4-port 3-position electromagnetic switching valve 5 in the first position S1.

  Then, the medium flow rate hydraulic oil flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 and the small capacity second fixed displacement hydraulic pump 2 to the electromagnetic switching valve 5 are provided. The small amount of hydraulic fluid flowing into the second input port P2 joins, and a large amount of liquid is supplied from the output port A to the load line 15.

  At this time, the controller 6 determines the pressure and flow rate of the load line 15 based on the pressure command indicating low pressure, the flow rate command indicating large flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. Controls the rotation speed of the servo motor 3 so that the pressure is low and the flow rate is large.

  Thus, when the electromagnetic switching valve 5 is located at the first position S1, the load line 15 is controlled with a low pressure and a large flow rate.

  Specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and a restriction corresponding to the flow rate command is added by the restriction unit 32 to the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal. A limit control signal VL is generated. Then, based on the restriction control signal VL, the flow rate calculated from the signal from the position detector 26 and the control signal representing the first position S1, the rotational speed control unit 33 determines the pressure of the load line 15. And a rotation speed control signal for controlling the flow rate so that the pressure command and the flow rate correspond to the pressure command and the flow rate command are generated and output to the servo motor 3.

  In this manner, the restriction unit 32 creates a restriction control signal VL by adding a restriction corresponding to the flow rate command to the pressure control signal Vp, and controls the pressure and flow rate based on the restriction control signal VL. Control and flow control can be performed accurately and smoothly.

  Next, it is assumed that the medium pressure / medium flow rate is controlled by the pressure command and the flow rate command.

  At this time, the controller 6 places the 4-port 3-position electromagnetic switching valve 5 in the second position S2.

  Then, the medium flow rate hydraulic fluid flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 is supplied from the output port A to the load line 15, while the small capacity first oil is supplied. 2 The small amount of hydraulic fluid flowing from the fixed displacement hydraulic pump 2 to the second input port P2 of the electromagnetic switching valve 5 is discharged from the return port R to the tank T, and the second fixed displacement hydraulic pump 2 is unloaded. .

  At this time, the controller 6 determines the pressure of the load line 15 based on the pressure command indicating the intermediate pressure, the flow command indicating the intermediate flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. The rotational speed of the servo motor 3 is controlled so that the flow rate becomes the intermediate pressure and the intermediate flow rate.

  As described above, when the electromagnetic switching valve 5 is located at the second position S <b> 2, the medium pressure flow is controlled with respect to the load line 15.

  Specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and a restriction corresponding to the flow rate command is added by the restriction unit 32 to the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal. A limit control signal VL is generated. Then, based on the restriction control signal VL, the flow rate calculated by the signal from the position detector 26 and the control signal representing the second position S2, the rotational speed control unit 33 determines the pressure of the load line 15. And a rotational speed control signal for controlling the flow rate so as to become a medium pressure and a medium flow rate according to the pressure command and the flow rate command, and outputs the rotation speed control signal to the servo motor 3.

  In this manner, the restriction unit 32 creates a restriction control signal VL by adding a restriction corresponding to the flow rate command to the pressure control signal Vp, and controls the pressure and flow rate based on the restriction control signal VL. Control and flow control can be performed accurately and smoothly.

  Next, it is assumed that high pressure and small flow rate are controlled by a pressure command and a flow rate command.

  At this time, the controller 6 positions the 4-port 3-position electromagnetic switching valve 5 at the third position S3.

  Then, the medium flow rate hydraulic fluid flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 is discharged from the return port R to the tank T, and the first fixed displacement hydraulic pump is discharged. While the pump 1 is unloaded, a small amount of hydraulic fluid flowing from the small-capacity second fixed displacement hydraulic pump 2 to the second input port P2 of the electromagnetic switching valve 5 is supplied from the output port A to the load line 15. .

  At this time, the controller 6 determines the pressure and flow rate of the load line 15 based on the pressure command indicating high pressure, the flow rate command indicating small flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. The rotational speed of the servo motor 3 is controlled so that the pressure becomes the high pressure and the small flow rate.

  Thus, when the electromagnetic switching valve 5 is located at the third position S3, the load line 15 is controlled with a high pressure and a small flow rate.

  Specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and a restriction corresponding to the flow rate command is added by the restriction unit 32 to the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal. A limit control signal VL is generated. Then, based on the restriction control signal VL, the flow rate calculated from the signal from the position detector 26 and the control signal representing the third position S3, the rotation speed control unit 33 determines the pressure of the load line 15. And a rotational speed control signal for controlling the flow rate so as to be a high pressure and a small flow rate according to the pressure command and the flow rate command, and output the generated rotational speed control signal to the servo motor 3.

  In this manner, the restriction unit 32 creates a restriction control signal VL by adding a restriction corresponding to the flow rate command to the pressure control signal Vp, and controls the pressure and flow rate based on the restriction control signal VL. Control and flow control can be performed accurately and smoothly.

  In this way, by using only one 4-port 3-position electromagnetic switching valve 5 and the above-described connection structure, a three-stage operation mode of low pressure / high flow rate, medium pressure / medium flow rate, and high pressure / small flow rate is selected, By appropriately unloading and merging the two pumps, the shaft torque required for the servo motor 3 can be reduced.

  Therefore, according to this hydraulic pressure drive device, it is possible to achieve both high pressure control and large flow rate control, and the current value required by the servo motor 3 and the controller 6 can be reduced. Small and inexpensive.

  Further, since the current value is small in the above hydraulic pressure driving device, if high pressure and small capacity control is selected, the pressure can be maintained at a high pressure for a long time.

  Next, the electromagnetic switching valve 5 is locked with, for example, dust, and stopped between the first position S1 and the second position S2 or between the first position S1 and the third position S3. Assume that the space between the first input port P1 and the second input port P2 and the output port A and the return port R is closed.

  At this time, the pressure in the discharge lines 11 and 12 tends to rise, but the first check valve 21 and the second check valve 22 are opened, and the hydraulic oil from the first and second fixed displacement hydraulic pumps 1 and 2 is opened. However, the electromagnetic switching valve 5 is bypassed and supplied to the load line 15. Thus, when the electromagnetic switching valve 5 fails, the hydraulic oil bypasses the electromagnetic switching valve 5 with the first check valve 21 and the second check valve 22, thereby preventing damage to piping, hydraulic equipment, and the like. be able to.

  Further, when the pressure of the load line 15 is going to be excessive due to the hydraulic oil supplied from the first and second check valves 21 and 22, the hydraulic oil is released to the tank T by the relief valve 23, and the pressure is increased. Can be prevented, and damage to the equipment can be prevented.

  In the above embodiment, the pressure of the load line 15 is directly detected by the pressure sensor 25. However, the current value flowing through the servo motor 3 may be detected by the current sensor, and the pressure may be indirectly detected based on the current value. .

  In the above embodiment, the position detector is used as an example of the flow rate detection sensor, and the flow rate is detected based on the rotation position and time of the servo motor 3, but the rotation speed of the servo motor 3 is directly detected. The flow rate may be detected.

  Further, the controller used in the present invention is not limited to the controller 6 of the above-described embodiment. For example, a controller having a difference selection unit as shown in FIG. Any device may be used as long as the pressure and the flow rate are controlled according to the command.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st fixed displacement type hydraulic pump 2 2nd fixed displacement type hydraulic pump 3 Servo motor 5 Electromagnetic switching valve 6 Controller 21, 22 Check valve 23 Relief valve 25 Pressure sensor 26 Position detector

Claims (3)

Two series of medium-capacity first fixed displacement hydraulic pumps (1) and small-capacity second fixed displacement hydraulic pumps (2) having shafts connected to each other;
A first input port (P1) connected to the discharge port of the first fixed displacement hydraulic pump (1) and a second input connected to the discharge port of the second fixed displacement hydraulic pump (2) The first and second input ports having a port (P2), an output port (A) connected to the load line (15), and a return port (R) connected to the tank (T) (P1, P2) communicates with the output port (A), while the return port (R) is closed and the first input port (P1) communicates with the output port (A). On the other hand, the second input port (P2) communicates with the return port (R) at a second position (S2), and the first input port (P1) communicates with the return port (R) while the second input port. (P2) has a third position (S3) that communicates with the output port (A) 4 And over preparative 3-position type solenoid valve (5),
A servo motor (3) for driving the first fixed displacement hydraulic pump (1) and the second fixed displacement hydraulic pump (2);
A pressure sensor (25) for directly or indirectly detecting the pressure of the load line (15);
A flow rate detection sensor (26) for detecting the rotational position or speed of the servo motor (3);
In addition to receiving outputs from the pressure sensor (25) and the flow rate detecting sensor (26), the pressure command and the flow rate command are received, and the pressure and flow rate of the load line (15) are in accordance with the pressure command and the flow rate command. A controller (6) for controlling the servo motor (3) so that the pressure and flow rate are as follows .
The load line between the discharge port of the first fixed displacement hydraulic pump (1) and the first input port (P1) of the electromagnetic switching valve (5) and between the load line (15). A first check valve (21) connected so that the flow toward (15) is forward;
The load line between the discharge port of the second fixed displacement hydraulic pump (2) and the second input port (P2) of the electromagnetic switching valve (5) and between the load line (15). A second check valve (22) connected so that the flow toward (15) is forward;
Hydraulic drive apparatus according to claim Rukoto equipped with. The hydraulic drive device according to claim 1 ,
A hydraulic drive device comprising a relief valve (23) connected to the load line (15). In the hydraulic drive unit according to claim 1 or 2 ,
The controller (6)
A pressure control unit (31) that receives the pressure command and a pressure detection signal from the pressure sensor and outputs a pressure control signal (Vp) based on a deviation between the pressure command and the pressure detection signal;
In response to the pressure control signal and the flow rate command from the pressure control unit (31), the limit unit (32) outputs a limit control signal (VL) generated by adding a limit corresponding to the flow rate command to the pressure control signal. )When,
Based on the restriction control signal from the restriction unit (32) and the flow rate detection signal from the flow rate detection sensor (26), the pressure and flow rate of the load line (15) are changed to the pressure command and flow rate command. A hydraulic pressure drive device comprising: a rotation speed control unit (33) that generates a rotation speed control signal for controlling the pressure and the flow rate to correspond to each other and outputs the signal to the servo motor (3).

Images