JPH10156600A - Pressurizing force controlling device for hydraulic press and controlling method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To machine a small size machining object for requiring a smaller pressing force than an adding weight with a large size hydraulic press by throttling a meter outside circuit, regulating a meter inside circuit and controlling it in a suitable pressurizing force in a case of a set pressurizing force being small against the adding weight of a die and a slide. SOLUTION: When the pressurizing force from a pressurizing force setting switch 41 is smaller or some larger against the adding weight of a slide 2 and a die 3, the pressure of a meter outside circuit is controlled with a controller 40 so as to throttle to a prescribed return pressure with a solenoid proportional throttling valve 13. Further, the meter inside pressure is controlled with the controller 40 so as to definitely make the pressing force with the controller 40. Therefore, the adding weight of the slide 2 and the die 3 is held with the throttled pressure, made without adding to the pressurizing force and the pressurizing force being made suitable to a small size shape is supplied with a variable capacity type hydraulic pump 11. Therefore, the necessity for installing a small size hydraulic press side by side like the convention is eliminated, and the equipment expenditure is not increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurizing force control device for a hydraulic press and a control method therefor, and more particularly to a pressurizing force control device and a control method for processing a small press with a large hydraulic press.

[0002]

2. Description of the Related Art Conventionally, a press machine includes a mechanical press for processing a workpiece by raising and lowering a slide by a crank mechanism and a link mechanism, and a hydraulic press for processing a workpiece by raising and lowering a slide by hydraulic pressure. The hydraulic press has the advantage that the pressure can be easily varied by adjusting the hydraulic pressure, and the slide motion can be freely varied by adjusting the pressure and flow rate according to the pressurizing condition. Various methods and apparatuses have been proposed as methods for controlling the slide motion of the hydraulic press. For example, in Japanese Utility Model Publication No. 3-53829, in the pressurizing step, it is determined whether or not the descending speed of the slide is equal to or less than a predetermined reference speed for slide stop determination, and the descending speed of the slide is equal to or less than the reference speed. From the point in time when it is determined that the pressure has risen, the predetermined pressurization rise time is measured by the timer, and the slide stop determination reference speed is set to a value close to zero. There has been proposed a hydraulic press pressing process completion detecting device that can accurately detect the completion of the working process by setting the time required until the pressing force reaches the set pressure from the time when the pressure becomes substantially zero.

[0003] The present applicant has disclosed in Japanese Patent Application Laid-Open No. 8-150500.
(Japanese Patent Application No. 6-294351).
According to the publication, the slide is lowered from the descending region to the forming region while controlling the position of the slide based on the position signal detected by the slide position detecting means for detecting the position of the slide, and the pressing force of the slide is detected in the forming region. The pressurizing signal from the pressurizing force detecting means is compared with the set ability set in advance according to the processing conditions. If the pressurizing force does not reach the set ability, slide to bottom dead center while continuing position control. Is lowered to hold the position for a set time, and when the applied pressure in the molding area reaches a set capacity, the pressure is switched from position control to pressure control to hold the pressure for the set time.

[0004]

However, in both of these publications, the pressing force is controlled in accordance with the descending speed or position of the slide, but in both cases, the pressing force for processing the workpiece is the addition of the slide and the die. Much larger than the weight
The pressurization is performed only by controlling the pressurization of the hydraulic cylinder of the hydraulic press. This slide control method
This is a good control when processing a workpiece according to the size of the hydraulic press. In recent years, as the control of the hydraulic press has been developed and the accuracy has been improved, the processing of a large workpiece with a large hydraulic press has been increasing. With this large-sized hydraulic press, it is not possible to process a workpiece with a pressing force smaller than the added weight of the slide and the mold. For example, it is impossible to perform processing at a pressure Pm or less indicated by a dashed line in FIG. For this reason, it is necessary for the press working company to install a large-sized hydraulic press and a small hydraulic press corresponding to a small workpiece, and thus there is a problem that an installation place is increased and equipment cost is increased.

The present invention has been made in view of the above-mentioned conventional problems, and relates to a pressure control device and a control method thereof for a hydraulic press, and more particularly to a pressure control device having a pressure smaller than the added weight of a slide and a mold. It is an object of the present invention to provide a pressure control device and a control method for a large hydraulic press for processing a small-sized workpiece.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the invention of a pressure control device for a hydraulic press according to the present invention is directed to a hydraulic pressure control device for a small-diameter single-acting hydraulic cylinder through a control valve. Supplying to one side, the mold attached to the slide is raised or held at high speed, and pressure oil from the hydraulic pump is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve. A large hydraulic pressure that raises or holds the mold attached to the slide at a low speed, supplies controlled pressure oil to the other side of the double-acting hydraulic cylinder, and processes the workpiece with the pressing force of the pressure oil. In the pressurizing force control device of the press, a pressurizing force setting means for inputting and setting a pressurizing force, an ascending side pressure sensor for detecting a pressure on one side of a double-acting hydraulic cylinder for ascending the die, and processing the workpiece To detect the pressure on the other side of the double acting hydraulic cylinder The sum of the weight of the slide and the mold is calculated based on the signal from the pressure sensor and the signal from the rising side pressure sensor, and is compared with the set pressing force, and the pressing force is substantially close to the added weight of the slide and the mold. When the force is smaller than the force, the command to reduce the oil in the meter-out circuit returning to the tank from the double-acting hydraulic cylinder and the single-acting hydraulic cylinder to the measured pressure near one side of the large-diameter double-acting hydraulic cylinder, and Control means for outputting a command for adjusting the pressure of the meter-in circuit supplied to the other side of the dynamic hydraulic cylinder to a pressure at which pressure is applied, and a control valve for reducing oil in the meter-out circuit in response to a command from the control means And a pressure regulating valve or a control valve for regulating the pressure oil of the meter-in side circuit to a pressure at which a pressurizing force is generated in accordance with a command from the control means. According to the above configuration, the oil in the meter-out side circuit returning from the double-acting hydraulic cylinder and the single-acting hydraulic cylinder to the tank is throttled by the control valve, and the throttled pressure is double-acting due to the added weight of the slide and the mold. Since the pressure is near the measured pressure on the rising side of the hydraulic cylinder, the weight of the slide and the mold is maintained by the reduced pressure, and is not added to the pressing force for processing the workpiece. Further, the pressure for processing the workpiece is controlled by a pressure supplied from the hydraulic pump to the other pressurizing side of the double-acting hydraulic cylinder so that a small pressure suitable for a small-sized shape is generated. As described above, the oil returning to the tank is controlled to be in the vicinity of the pressure generated by the added weight of the slide and the mold, and the small pressure and the position of the slide are controlled by the pressure and the discharge amount supplied from the pump. The accuracy of the pressure and the pressure rate can be improved. With this, the press processing company can process the workpiece with a pressing force smaller than the added weight of the slide and the mold by using a large hydraulic press, and there is no need to provide a small hydraulic press together, and In addition, there is no need to increase the installation location, and the equipment cost does not increase.

[0007] The pressure regulation of the pressure generating the meter-in side circuit of the double-acting hydraulic cylinder is performed by detecting the return pressure of the meter-out side circuit by an ascending side pressure sensor and responding from the control means in accordance with the return pressure. The pressure oil of the meter-in side circuit is controlled by a pressure regulating valve or a control valve according to a command. According to the above configuration, the pressing force is controlled to be in the vicinity of a pressure at which the oil returning to the tank is generated by the added weight of the slide and the mold, and the controlled return pressure is detected, and supplied from the pump in accordance with the returned pressure. Since the pressure of the pressurized oil is controlled, the accuracy of the pressurized pressure is improved. As a result, the accuracy of the pressurizing force and pressurizing speed of the hydraulic pump can be further improved, and a large hydraulic press can accurately process the workpiece with a pressurizing force smaller than the added weight of the slide and the mold. can do.

Further, the control valve for reducing the oil in the meter-out side circuit and the control valve for regulating the pressure oil in the meter-in side circuit to a pressure at which a pressurizing force is applied are the same. With the above configuration, the oil in the meter-out circuit returning from the double-acting hydraulic cylinder and the single-acting hydraulic cylinder to the tank is throttled by the same control valve, and the pressure that causes the pressurizing force in the meter-in circuit is adjusted by the same control valve. Have been. This allows
The structure is simple and the cost can be reduced.

The invention of a pressure control method for a hydraulic press according to the present invention is directed to a mold in which pressure oil from a hydraulic pump is supplied to one side of a small-diameter single-acting hydraulic cylinder via a control valve and attached to a slide. At a high speed, and pressurized oil from a hydraulic pump is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve to raise the mold attached to the slide at a low speed. Or while holding and supplying a controlled pressure oil to the other side of the double-acting hydraulic cylinder, in a pressure control method of a large hydraulic press for processing a workpiece with the pressure by the pressure oil, a double-acting hydraulic cylinder and By squeezing the return oil from the single-acting hydraulic cylinder, a small pressing force corresponding to a pressure equal to or lower than the pressure for raising the slide and the mold is generated in the double-acting hydraulic cylinder of a large hydraulic press that generates a large pressing force. , Small Jo of which a control method for machining a workpiece. According to the above-described method, the same operation and effect as those of the pressure control device of the hydraulic press can be obtained.

Another method is to supply pressurized oil from a hydraulic pump to one side of a small-diameter single-acting hydraulic cylinder via a control valve to raise or hold a mold attached to a slide at high speed, In addition, the pressurized oil from the hydraulic pump is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve, and the mold attached to the slide is raised or held at a low speed. In the pressure control method of a large hydraulic press that supplies the controlled pressure oil to the other side of the cylinder and processes the workpiece with the pressure by the pressure oil, the slide is performed by the pressure measured on one side of the double-acting hydraulic cylinder. And the added weight of the mold and the input pressure for processing the workpiece, and when the applied pressure is smaller than the force almost in the vicinity of the added weight of the slide and the mold, the Tank from dynamic hydraulic cylinder Return The pressure of the oil in the meter-out side circuit is controlled to be close to the measured pressure on one side of the double-acting hydraulic cylinder, and the pressure of the meter-in side circuit supplied from the hydraulic pump to the other side of the double-acting hydraulic cylinder is measured. The control method is such that control is performed in accordance with the oil pressure of the out-side circuit to generate the input pressure. In the other methods described above, the same functions and effects as described above can be obtained.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a hydraulic press control apparatus and a control method for a hydraulic press according to the present invention. FIG. 1 is a circuit diagram of a pressure control device 1 for a large hydraulic press. In FIG. 1, a mold 3 is attached to a slide 2 of a hydraulic press, and the mold 3 descends to perform processing such as pressure molding or cutting of a workpiece 4. The slide 2 is moved up and down by a double-acting cylinder 5 or a single-acting cylinder 6. The double-acting cylinder 5 includes a piston 5a, a lower piston rod 5b, an upper piston rod 5c, and a tube 5d. The piston 5a is slidably and pivotally inserted into the tube 5d. The lower piston rod 5b
One end is fixed to the slide 2 and the other end is fixed to the piston 5a,
It is slidably and pivotally inserted into the tube 5d below in the figure. The upper piston rod 5c has one end fixed to the piston 5a and the other end fixed to a piston 6a of a single-acting cylinder 6, which will be described later.

The single-acting cylinder 6 is disposed above the double-acting cylinder 5 in the drawing and concentrically opposed to the double-acting cylinder 5. The single-action cylinder 6 includes a piston 6a, a piston rod 5c, and a tube 6b. The piston 6a is slidably and pivotally inserted into the tube 6b. An upper piston rod 5c of the double acting cylinder 5 is fixed to the piston 6a. In this embodiment, in the present embodiment, the double-acting cylinder 5 is configured such that the diameter of the lower piston rod 5b is larger than the diameter of the upper piston rod 5c, and the lower cross-sectional area Ae of the lower cylinder chamber 5e.
Is larger than the upper cross-sectional area Af of the upper cylinder chamber 5f. The single-acting cylinder 6 has a lower cylinder chamber 6c and an upper cylinder chamber 6d, and the lower cross-sectional area ac of the lower cylinder chamber 6c is
(Lower cross-sectional area ac = upper cross-sectional area Af−lower cross-sectional area Ae). Further, the diameter of the piston 5a of the double-acting cylinder 5 is formed larger than the diameter of the piston 6a of the single-acting cylinder 6. Also, the upper cylinder chamber 6d
Are open to the atmosphere via a filter or the like (not shown). The lower cylinder chamber 5e of the double-acting cylinder 5 raises the slide 2 and the mold 3 at a low speed. In the upper cylinder chamber 5f of the double-acting cylinder 5, the slide 2 and the mold 3 are lowered at a low speed, and the workpiece 4 is processed by pressure molding or cutting. The cylinder chamber 6c below the single-acting cylinder 6 raises the slide 2 and the mold 3 at a high speed.

The variable displacement hydraulic pump 11 (hereinafter referred to as the hydraulic pump 11) has a suction-side port connected to a suction-side pipe 11a.
To the oil tank 12, and the discharge side port is connected to the P port of the electromagnetic proportional control valve 13 by the discharge side pipe 11b. The hydraulic pump 11 receives an instruction from the control unit 40 and changes the discharge amount from the hydraulic pump 11. The electromagnetic proportional control valve 13 has four ports and three positions,
Also, it receives a command from the control unit 40 described later. The A port of the electromagnetic proportional control valve 13 is connected to the lower cylinder chamber 6 c of the single-acting cylinder 6 via the first pipe 14.
The first pipe 14 is branched from the second pipe 14a, and the second pipe 1
4a is connected to the first logic valve 15. The B port of the electromagnetic proportional control valve 13 is connected to the upper cylinder chamber 5 f of the double-acting cylinder 5 via the third pipe 16. Third
A second logic valve 17 is provided on the pipe 16. The first logic valve 15 and the second logic valve 17 are connected by a fourth pipe 18. One end of a fifth pipe 19 is connected to the fourth pipe 18, and the other end of the fifth pipe 19 is connected to the lower cylinder chamber 5 e of the double-acting cylinder 5. The T port of the electromagnetic proportional control valve 13 is connected to the oil tank 12 via the sixth pipe 20. In the discharge side pipe 11b,
A relief valve 21, an unload valve 22, and an accumulator 23 are provided. The unload valve 22 changes the discharge pressure from the hydraulic pump 11 in response to a command from the control unit 40 described later.

A first pilot solenoid valve 24 for control is connected to the first logic valve 15, and a second solenoid valve 25 for pilot is connected to the second logic valve 17. The first pilot solenoid valve 24 and the second pilot solenoid valve 25 are connected to the accumulator 23,
Along with receiving the pilot pressure oil, it is also connected to a control unit 40 described later and receives a command. A rising side pressure sensor 31 for detecting a pressure for raising the slide 2 and the mold 3 is disposed in the lower cylinder chamber 5 e of the double-acting cylinder 5. Further, the upper cylinder chamber 5f of the double acting cylinder 5
Is provided with a processing-side pressure sensor 32 for detecting the pressure of a double-acting hydraulic cylinder for processing a workpiece. The slide 2 is provided with a position sensor 33 for detecting the position. Further, the accumulator 23 is provided with an accumulator pressure sensor 34 for measuring the pressure. Each sensor is connected to a control unit 40 described later, and transmits the detected signal. An electromagnetic valve 26 is provided between the accumulator 23 and the discharge-side pipe 11b, and the electromagnetic valve 26 is connected to a control unit 40 described later. When the pilot pressure of the accumulator 23 decreases, the solenoid valve 26 operates according to a command from the control unit 40 that has received a signal from the accumulator pressure sensor 34, and supplies pressure oil from the hydraulic pump 11 to the accumulator 23.
Has been replenished.

The control unit 40 includes a controller and the like. The control unit 40 receives signals detected from the respective sensors and calculates by receiving an external command. The hydraulic pump 11, the electromagnetic proportional control valve 13, the unload valve 22, the pilot Signals for respective commands, which will be described later, are output to the first solenoid valve for use 24 and the second solenoid valve for pilot 25. Control unit 40
Is a pressure setting switch 4 for inputting and setting the pressure.
1. When the mold is activated, the mold is raised and lowered at the same time to raise and lower the die (high-speed raising), lowering the rapid-feeding (high-speed lowering), slowly raising (low-speed raising), or pressing (low-speed) An upper descent speed selection switch 42 for selecting descent or the like of descent is provided.

Next, the operation of the above configuration will be described. First, the worker attaches the mold 3 to be processed to the slide 2. The control unit 40 receives the pressure signal Ps from the rising pressure sensor 31 of the double-acting cylinder 5 and adds the weight Ws of the slide 2 and the weight Wk of the mold 3 to the added weight Wz.
(Wz = Ws + Wk = Ps × Ae) is obtained. In addition, the control unit 40 increases the raising pressure Pu (Pu = Wz / P) of the single-acting cylinder 6 for raising the slide 2 and the mold 3 at rapid traverse.
Ac). In the above, the double-acting cylinder 5
Is measured, the additional weight Wz may be obtained by measuring the raising pressure of the single-acting cylinder 6, or the additional weight Wz of the weight Ws of the slide 2 and the weight Wk of the mold 3 may be obtained in advance. , May be input to the control unit 40. By the above,
The control unit 40 stores the added weight Wz of the weight Ws of the slide 2 and the weight Wk of the mold 3 and also stores the accompanying rising pressure Ps of the double-acting cylinder 5. next,
The (a) high-speed rise, (b) high-speed fall, (c) low-speed rise, and (d) low-speed fall of the mold selected by the up / down speed selection switch 42 will be described individually.
2A and 2B are diagrams for explaining the operating speed and the pressing force of the slide 2, FIG. 2A shows the relationship between the position of the slide 2 and time, and FIG. 2 shows the relationship between the pressing force and time. Further, WA in the drawing indicates a position control range, and WB in the drawing indicates a pressure control range.

(1) High-speed ascent First, as shown in FIG. 3, the operator switches the up / down speed selection switch 42 to the high-speed ascent position. The control unit 40 receives the signal of the high speed rise from the up / down speed selection switch 42 and outputs a command to the electromagnetic proportional control valve 13, the hydraulic pump 11, the unload valve 22, and the pilot second solenoid valve 25. As a result, the hydraulic pump 11 increases the discharge amount to a predetermined value of the rapid traverse, and the unload valve 22 increases the set pressure equal to or higher than the raising pressure Pu of the single-acting cylinder 6 for raising the slide 2 and the mold 3 at the rapid traverse. Is set. The electromagnetic proportional control valve 13 switches to the raised position Up.
Further, the second solenoid valve for pilot 25 is switched to the return position Td to the oil tank 12, and the second logic valve 17 is operated. Thus, the pressure oil from the hydraulic pump 11 reaches the lower cylinder chamber 6c of the single-acting cylinder 6 through the discharge-side pipe 11b, the raising position Up of the electromagnetic proportional control valve 13, and the first pipe 14 in order. The slide 2 and the mold 3 are raised at a rapid traverse. At this time, the air in the upper cylinder chamber 6d of the single-acting cylinder 6 is released to the atmosphere via a filter (not shown). Further, as the single-acting cylinder 6 rises, the oil in the cylinder chamber 5f above the double-acting cylinder 5
The second logic valve 17 is opened from, and most of the oil is supplied from the fourth pipe 18 and the fifth pipe 19 to the lower cylinder chamber 5 e of the double-acting cylinder 5, and surplus oil due to the difference in the area of the double-acting cylinder 5 The third pipe 16 returns to the oil tank 12 via the raising position Up of the electromagnetic proportional control valve 13 and the sixth pipe 20. As a result, even when the single-acting cylinder 6 rises at a high speed, the double-acting cylinder 5 follows without a negative pressure.

(2) Low speed rise As shown in FIG. 4, the operator switches the up / down speed selection switch 42 to the low speed rise position. The control unit 40 receives a low-speed signal from the up-down speed selection switch 42 and outputs a command to the electromagnetic proportional control valve 13, the hydraulic pump 11, the unload valve 22, and the first pilot solenoid valve 24. As a result, the hydraulic pump 11 increases to a predetermined low-speed discharge amount, and the unload valve 22 sets the pressure higher than the raising pressure Ps of the double-acting cylinder 5 for raising the slide 2 and the mold 3 at low speed. Is set to The electromagnetic proportional control valve 13 switches to the raised position Up. Further, the first solenoid valve for pilot 24 is switched to the return position Td to the oil tank 12, and the first logic valve 15 is operated.
Thereby, the pressure oil from the hydraulic pump 11 reaches the lower cylinder chamber 6c of the single-acting cylinder 6 through the discharge pipe 11b, the raising position Up of the electromagnetic proportional control valve 13, and the first pipe 14 in order. And the branched second pipe 14
a through the first logic valve 15, the fourth pipe 18, and the fifth pipe 19, the lower cylinder chamber 5e of the double-acting cylinder 5.
And raise the slide 2 and the mold 3 at a low speed. At this time, the air in the upper cylinder chamber 6d of the single-acting cylinder 6 is released to the atmosphere via a filter (not shown). or,
The oil in the cylinder chamber 5f on the upper side of the double-acting cylinder 5 returns from the third pipe 16 to the oil tank 12 via the raising position Up of the electromagnetic proportional control valve 13 and the sixth pipe 20.

(3) High-speed descent As shown in FIG. 5, the operator switches the up-down speed selection switch 42 to the high-speed down position. The control unit 40 receives a high-speed descent signal from the up / down speed selection switch 42 and outputs a command to the electromagnetic proportional control valve 13, the hydraulic pump 11, and the pilot second electromagnetic valve 25. As a result, the hydraulic pump 11 increases to a predetermined discharge amount at the rapid traverse. The electromagnetic proportional control valve 13 switches to the lower position Ud.
Further, the second solenoid valve for pilot 25 is switched to the return position Td to the oil tank 12, and the second logic valve 17 is operated. As a result, the oil from the hydraulic pump 11 sequentially passes through the discharge side pipe 11b, the lowered position Ud of the electromagnetic proportional control valve 13, and the third pipe 16, reaches the cylinder chamber 5f above the double acting cylinder 5, and The return oil from the lower cylinder chamber 5e of the dynamic cylinder 5 also opens the second logic valve 17 from the fifth pipe 19 and the fourth pipe 18, and the third pipe 1
6, the cylinder 2 reaches the upper cylinder chamber 5f of the double-acting cylinder 5, and the slide 2 and the mold 3 are lowered by rapid traverse. At this time, the amount of oil discharged from the hydraulic pump 11 is discharged only to supplement the shortage due to the difference in the area of the double-acting cylinder 5. Also, the cylinder chamber 6 below the single-acting cylinder 6
c returns from the first pipe 14 to the oil tank 12 via the lowered position Ud of the electromagnetic proportional control valve 13 and the sixth pipe 20. Alternatively, as another method, a command is also output to the first pilot solenoid valve 24 without switching the electromagnetic proportional control valve 13 so that the oil in the cylinder chamber 6 c below the single-acting cylinder 6
The first logic valve 15 is also opened from the ninth and fourth pipes 18 and supplied to the upper cylinder chamber 5f of the double-acting cylinder 5,
The missing part due to the difference in the area of the double acting cylinder 5 may be supplemented.

(4) Lowering at Low Speed (Pressing) The operator inputs and sets the pressing force Fp for processing the workpiece 4 from the pressing force setting switch 41. Further, as shown in FIG. 6, the operator switches the up / down speed selection switch 42 to the low speed down position. The control unit 40 receives the signal of the low speed descent from the up / down speed selection switch 42, and receives the electromagnetic proportional control valve 13, the hydraulic pump 11, the unload valve 22,
Then, a command is output to the first pilot solenoid valve 24. In response to this command, the unload valve 22 causes the pressure oil supplied to the upper cylinder chamber 5f of the double-acting cylinder 5 to the pressure F
The pressure is controlled to the pressure Pp for generating p. Further, the hydraulic pump 11 discharges the pressure oil at the pressurized pressure Pp and increases the discharge amount to a predetermined low-speed discharge amount. The electromagnetic proportional control valve 13 switches to the lower position Ud. Further, the first solenoid valve for pilot 24 is switched to the return position Td to the oil tank 12, and
The first logic valve 15 is operated. Thereby, the pressure oil from the hydraulic pump 11 controlled to the pressurization pressure Pp passes through the discharge side pipe 11 b, the lowered position Ud of the electromagnetic proportional control valve 13, and the third pipe 16 in order, and is moved to the upper side of the double-acting cylinder 5. , And a predetermined pressure Fp is obtained. Return oil from the lower cylinder chamber 5e of the double-acting cylinder 5 flows from the fifth pipe 19 and the fourth pipe 18 to the first logic valve 15e.
To return to the oil tank 12 through the second pipe 14a, the first pipe 14, the lowered position Ud of the electromagnetic proportional control valve 13 and the sixth pipe 20 in that order. Further, after the lower cylinder chamber 6c of the single-acting cylinder 6 joins the return oil from the lower cylinder chamber 5e of the double-acting cylinder 5 with the first pipe 14, the lower position Ud of the electromagnetic proportional control valve 13 and It returns to the oil tank 12 via the sixth pipe 20.

In the above, according to the present invention, the pressing force Fp is smaller than the additional weight Wz or the additional weight Wz.
When it is slightly larger, the following control is further performed.
The control unit 40 applies the pressure Fp from the pressure setting switch 41.
Then, the weight Ws of the slide 2 and the weight Wk of the mold 3 stored in the control unit 40 are compared with the added weight Wz. At this time, when the pressing force Fp is smaller than the added weight Wz or slightly larger than the added weight Wz, the fifth cylinder chamber 5e on the lower side of the double-acting cylinder 5
The first logic valve 15 is opened via the pipe 19 and the fourth pipe 18, and further, the oil tank 12 is sequentially passed through the second pipe 14 a, the first pipe 14, the lowered position Ud of the electromagnetic proportional control valve 13 and the sixth pipe 20. The return circuit, that is, the pressure of the meter-out side circuit is set to a predetermined return pressure P by the electromagnetic proportional control valve 13.
to b. The predetermined return pressure Pb is reduced by a rising side pressure sensor 31 which detects a pressure for raising the slide 2 and the mold 3, in the lower cylinder chamber 5 e of the double-acting cylinder 5.
Is measured, and the return pressure Pb is reduced to a predetermined value by the electromagnetic proportional control valve 13 so that the pressure becomes substantially close to the raising pressure Ps for raising the slide 2 and the mold 3. Thereby, the lower cylinder chamber 5 of the double-acting cylinder 5
When the predetermined return pressure Pb of e is higher than the raising pressure Ps, the slide 2 and the mold 3 are held at that position.
When the predetermined return pressure Pb is slightly lower than the raising pressure Ps, the slide 2 and the mold 3 are lowered at a low speed.

At this time, in the range of the position control of the lowering of the mold 3 shown in FIG. 2, the predetermined return pressure Pb is higher than the raising pressure Ps to hold the slide 2 and the mold 3. Desirably, the descending position control is controlled by the discharge amount of the pressure oil discharged from the hydraulic pump 11. The position control at this time is performed by the control unit 40 receiving a position signal from the position sensor 33 attached to the slide 2 outputting a command to the hydraulic pump 11 to control the discharge amount of the pressure oil. Or, the predetermined return pressure Pb is equal to the rising pressure P
When the slide 2 and the mold 3 are lowered at a slow speed slightly lower than s, the slow speed is detected by the position sensor 33 attached to the slide 2 and the control unit 40 considers the slow speed. It is also performed by outputting a command to the hydraulic pump 11 to adjust and control the discharge amount of the pressure oil. As described above, when the pressing force Fp on the workpiece 4 is small and the accuracy of the drawing speed is required, the discharge amount of the hydraulic pump 11 is adjusted by the signal from the position sensor 33 to adjust the slide amount. By controlling the positions of the mold 2 and the mold 3, the descent is performed at a constant speed.

In the range of the pressure control for lowering the mold 3 shown in FIG. 2, as described above, the pressure of the meter-out side circuit from the lower cylinder chamber 5e of the double-acting cylinder 5 is adjusted to a predetermined value. While controlling the return pressure Pb, the double-acting cylinder 5
The pressure of the circuit on the meter-in side to the upper cylinder chamber 5f is controlled to a pressurizing pressure Px for obtaining a predetermined pressing force Fp. That is, the pressurized pressure Px of the meter-in side circuit is
In addition to the predetermined return pressure Pb of the meter-out side circuit,
The pressure obtained by adding the pressurizing pressure Pp of the upper cylinder chamber 5f of the double-acting cylinder 5 for obtaining the pressing force Fp is applied to the meter-in side circuit. This pressure Px is applied to the double-acting cylinder 5
Is detected by the processing-side pressure sensor 32 of the upper cylinder chamber 5f and sent to the controller 40. The controller 40 unloads the unload valve so that the upper cylinder chamber 5f of the double-acting cylinder 5 has a predetermined pressurizing pressure Px. 22 is controlled. That is, the control unit 40 controls the processing side pressure sensor 32 of the meter-in side circuit.
And receives the pressurizing signal of the pressurizing pressure Px from the controller and the return pressure signal of the predetermined return pressure Pb from the ascending side pressure sensor 31 of the circuit on the meter-out side, and controls the unload valve 22. The difference between the pressure Px and the return pressure Pb is the pressing force Fp.
Is controlled so that the pressure Pp of the cylinder chamber 5f on the upper side of the double-acting cylinder 5 is obtained. in this way,
When a constant value such as a stamp is required, the pressing force F
In order to keep p constant, the pressure of the meter-in side circuit and the meter-out side circuit are detected, and the pressure of the meter-in side circuit is controlled in accordance with the pressure of the meter-out side circuit.

Another method of controlling this is to adjust the discharge pressure of the hydraulic pump 11 by the relief valve 21 without using the unload valve 22 and to control the discharge pressure of the hydraulic pump 11 by a command from the control unit 40. Thus, the circuit on the meter-in side of the electromagnetic proportional control valve 13 may be throttled so that the cylinder chamber 5f on the upper side of the double-acting cylinder 5 has a predetermined pressurizing pressure Px. Thus, with one electromagnetic proportional control valve 13, the return oil from the double-acting cylinder 5 and the single-acting cylinder 6 can be controlled, and the pressurizing pressure supplied from the hydraulic pump 11 to the double-acting cylinder 5 can be controlled. Can be simplified and inexpensive. With the above control, the pressing force Fp of the workpiece 4 is increased by the weight Ws of the slide 2 and the weight Wk of the mold 3.
Even when it is smaller than z, accurate position control and / or pressure control can be performed. In the above embodiment, a variable displacement hydraulic pump is used. However, a fixed pump may be used. In addition, the pressure is adjusted by making the unload valve 22 variable. May be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a pressure control device for a hydraulic press according to the present invention.

FIG. 2 is a diagram showing position control and pressure control of a hydraulic press.

FIG. 3 is an operation circuit diagram when the slide of the hydraulic press is raised at a high speed.

FIG. 4 is an operation circuit diagram when the slide of the hydraulic press is raised at a low speed.

FIG. 5 is an operation circuit diagram when the slide of the hydraulic press is lowered at high speed.

FIG. 6 is an operation circuit diagram when the slide of the hydraulic press is lowered at a low speed (during press working).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit of pressure control device of hydraulic press, 2 ... Slide, 3 ... Mold, 4 ... Workpiece, 5 ... Double acting cylinder, 6 ...
Single-acting cylinder, 11: variable displacement hydraulic pump, 12: oil tank, 13: electromagnetic proportional control valve, 15: first logic valve, 17: second logic valve, 21: relief valve, 22 ...
Unload valve, 23: accumulator, 24: first solenoid valve for pilot, 25: second solenoid valve for pilot, 31
... Ascent pressure sensor, 32 ... Processing pressure sensor, 33 ...
Position sensor, 33 ... pressure sensor for accumulator, 40
... Control unit, 41 ... Pressure setting switch, 42 ... Up / down speed selection switch.

Claims (5)

[Claims] 1. A pressure oil from a hydraulic pump is supplied to one side of a small-diameter single-acting hydraulic cylinder via a control valve to raise or hold a mold attached to a slide at a high speed. The pressure oil is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve to raise or hold the mold attached to the slide at a low speed, and to the other side of the double-acting hydraulic cylinder. In a pressure control device of a hydraulic press for supplying a controlled pressure oil and processing a workpiece with the pressure by the pressure oil, a pressure setting means for inputting and setting a pressure, and a pressurizing device for raising a mold. A rising pressure sensor that detects the pressure on one side of the dynamic hydraulic cylinder, a processing pressure sensor that detects the pressure on the other side of the double-acting hydraulic cylinder that processes the workpiece, and slides using signals from the rising pressure sensor Calculate the added weight of the mold and Compared with the set pressing force, when the pressing force is smaller than the force that is substantially close to the added weight of the slide and the mold, the oil in the meter-out side circuit that returns to the tank from the double-acting hydraulic cylinder and the single-acting hydraulic cylinder And a command to adjust the pressure of the meter-in side circuit supplied from the hydraulic pump to the other side of the double-acting hydraulic cylinder to a pressure that produces a pressing force. Control means for outputting, a control valve for reducing oil in the meter-out side circuit in response to a command from the control means, and pressure oil in the meter-in side circuit adjusted to a pressure at which pressurizing force is applied in response to a command from the control means. A pressure control device for a hydraulic press, comprising a pressure control valve or a control valve for pressing. 2. The pressurizing force control device for a hydraulic press according to claim 1, wherein the pressure for generating the pressurizing force of the meter-in side circuit of the double-acting hydraulic cylinder is controlled by the return pressure of the meter-out side circuit by an ascending side pressure sensor. A pressure control device for a hydraulic press, wherein a pressure oil of a meter-in side circuit is detected and controlled by a pressure regulating valve or a control valve in accordance with a command from a control means in accordance with the detected return pressure. 3. A pressure control device for a hydraulic press according to claim 1, wherein the control valve throttles oil in the meter-out side circuit, and controls the pressure of the meter-in side circuit to a pressure at which pressure is generated. A pressure control device for a hydraulic press, characterized in that the valve is the same as the valve. 4. A pressurized oil from a hydraulic pump is supplied to one side of a small-diameter single-acting hydraulic cylinder via a control valve to raise or hold a mold attached to a slide at a high speed. The pressure oil is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve to raise or hold the mold attached to the slide at a low speed, and to the other side of the double-acting hydraulic cylinder. In a pressure control method of a hydraulic press that supplies a controlled pressure oil and processes a workpiece with the pressure by the pressure oil, a large pressure is applied by squeezing return oil from a double-acting hydraulic cylinder and a single-acting hydraulic cylinder. A small-sized workpiece is machined by generating a small pressing force corresponding to a pressure equal to or less than a pressure for raising a slide and a mold in a double-acting hydraulic cylinder of a large hydraulic press that generates pressure. Addition of hydraulic press Pressure control method. 5. A pressurized oil from a hydraulic pump is supplied to one side of a small-diameter single-acting hydraulic cylinder via a control valve to raise or hold a mold attached to a slide at a high speed. The pressure oil is supplied to one side of a large-diameter double-acting hydraulic cylinder via a control valve to raise or hold the mold attached to the slide at a low speed, and to the other side of the double-acting hydraulic cylinder. In a pressure control method of a hydraulic press that supplies a controlled pressure oil and processes a workpiece with the pressure by the pressure oil, the added weight of a slide and a mold is measured by a pressure measured on one side of a double-acting hydraulic cylinder. And when the applied pressure is smaller than the force which is substantially close to the added weight of the slide and the mold when compared with the input applied pressure for processing the workpiece, the double-acting hydraulic cylinder returns to the tank. Meter-out side rotation While controlling the pressure of the oil in the road to be close to the pressure measured on one side of the double-acting hydraulic cylinder,
A pressure of a hydraulic press, wherein the pressure of a meter-in side circuit supplied to the other side of a double-acting hydraulic cylinder from a hydraulic pump is controlled in accordance with an oil pressure of a meter-out side circuit to generate an input pressure. Control method.