JP2011147948A - Hydraulic press, and method for controlling hydraulic press - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic press in which a pressurization rate can be improved, and further, energy saving can be achieved, and a method for controlling a hydraulic press. <P>SOLUTION: The hydraulic press is composed of a plurality of pressurizing cylinders CC, CR, CL, and, when the oil pressure Pc in the switching source pressurizing cylinder CC fed with hydraulic oil exceeds set pressure P1, a cylinder control block 20 switches the feeding place of the hydraulic oil to the switching place pressurizing cylinders CR, CL as a combination at which pressurizing capacity increases. The pressurizing capacity mode can be changed during the molding step. The driving can be performed at a pressurizing capacity mode at which the load is lower than the maximum load applied to the molding of a workpiece in the initial stage of the molding step, and the pressurizing rate increases. The molding time is made short, and the increase of deformation resistance caused by the reduction in the temperature of the workpiece during the molding in hot working can be prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic press and a control method of a hydraulic press. More specifically, the present invention relates to a hydraulic press capable of improving the pressurization speed and saving energy, and a control method of the hydraulic press.

  In large hydraulic presses, energy saving is an especially important issue, and the number of hydraulic oils is reduced by reducing the number of pumps. In addition, the press speed is slower and the molding time is longer than that of a mechanical press, so when using a hydraulic press for hot working, the hydraulic press must be pressed so that the temperature of the workpiece during molding does not drop significantly. There is a need to improve the pressure speed and shorten the one-cycle operation time. However, generally, since it is necessary to increase the amount of hydraulic oil in order to improve the pressurization speed, it is difficult to achieve both energy saving and improvement in pressurization speed by reducing the number of pumps.

In general, a large hydraulic press is composed of a plurality of pressure cylinders due to manufacturing and manufacturing problems. And the number of the pressurization cylinders which supply hydraulic oil according to the pressurization force required for shaping | molding of a workpiece | work is selected (refer patent document 1).
For example, in the case of a 9000 ton hydraulic press that is composed of three pressurizing cylinders having a pressurizing capacity of 3000 tons, the following three pressurizing capacity modes are provided.
・ 3000ton mode: Supply hydraulic fluid to one central pressure cylinder ・ 6000ton mode: Supply hydraulic fluid to two pressure cylinders on both sides ・ 9000ton mode: Supply hydraulic fluid to all three pressure cylinders

Here, in general, since the amount of hydraulic oil supplied from the pump is constant in any pressurizing capacity mode, the higher the pressurizing speed mode is, the higher the pressurizing capacity mode is. Becomes slower. For example, when the pressurization speed in the 3000 ton mode is 100 mm / sec, the pressurization speed in the 6000 ton mode is 50 mm / sec, and the pressurization speed in the 9000 ton mode is 33 mm / sec.
Therefore, among these three pressurization capability modes, a mode exceeding the maximum load required for forming the workpiece is selected to ensure the pressurization capability, and the pressurization speed is controlled by not selecting a pressurization capability mode higher than necessary. Decline can be prevented.

By the way, as shown in FIG. 4, generally, the load applied to the forming of the workpiece increases according to the stroke and rapidly increases in the vicinity of the lower limit position.
In the conventional method for selecting the pressurizing capacity mode as described above, it is necessary to select a pressurizing capacity mode that exceeds the maximum load required for forming the workpiece. For example, when the maximum load is 5000 tons, it is necessary to select the 6000 ton mode, and the pressurization speed at this time is 50 mm / sec.

However, even though most of the molding process is sufficiently lower than the maximum load, it is necessary to operate in the pressurization capacity mode exceeding the maximum load in all molding processes, so it is more than necessary except near the lower limit position. Therefore, there is a problem in that the molding speed is reduced by that amount.
Here, the forming step refers to a step in which the workpiece is formed by lowering the slide.

Japanese Patent Laid-Open No. 2002-172500

  In view of the above circumstances, an object of the present invention is to provide a hydraulic press and a control method of the hydraulic press that can improve the molding speed and save energy.

The hydraulic press of the first invention is a hydraulic press composed of a plurality of pressurizing cylinders, and includes a cylinder control block that switches a supply destination of hydraulic oil, and the cylinder control block is supplied with hydraulic oil. When the hydraulic pressure in the switching source pressurizing cylinder exceeds the set pressure, the supply destination of the hydraulic oil is switched to the switching destination pressurizing cylinder which is a combination in which the pressurizing capacity is increased.
The hydraulic press according to a second aspect of the present invention is the hydraulic press according to the first aspect, wherein a pressure release valve is connected to each of the pressure cylinders, and the pressure release valve connected to the switching source pressure cylinder is the switching source. It is characterized in that it is opened just before the hydraulic pressure in the pressure cylinder becomes negative.
The hydraulic press according to a third aspect of the present invention is the hydraulic press according to the second aspect, wherein the pressurizing cylinders are respectively connected via communication valves, and the communication valve for connecting the switching source pressurizing cylinder and the switching destination pressurizing cylinder is The cylinder control block is opened simultaneously with the switching of the cylinder control block.
In the hydraulic press control method according to the fourth aspect of the present invention, in the hydraulic press constituted by a plurality of pressurizing cylinders, when the hydraulic pressure in the switching source pressurizing cylinder to which the hydraulic oil is supplied exceeds the set pressure The supply destination of the hydraulic oil is switched to a switching destination pressurizing cylinder which is a combination in which the pressurizing capacity is increased.
According to a fifth aspect of the present invention, there is provided the hydraulic press control method according to the fourth aspect, wherein the switching source pressurizing cylinder is depressurized immediately before the hydraulic pressure in the switching source pressurizing cylinder becomes negative. .
The hydraulic press control method according to a sixth aspect of the present invention is the method of controlling the hydraulic press according to the fifth aspect, wherein the hydraulic oil in the switching source pressurizing cylinder is supplied into the switching destination pressurizing cylinder at the same time as the hydraulic oil supply destination is switched. It is characterized by.

According to the first aspect of the invention, the cylinder control block supplies the hydraulic oil to the switching destination pressurizing cylinder which is a combination in which the pressurizing capacity is increased when the hydraulic pressure in the switching source pressurizing cylinder to which the hydraulic oil is supplied exceeds the set pressure. Since the supply destination is switched, the pressure capability mode can be changed during the molding process. Therefore, it is possible to operate in the pressurizing capacity mode that is lower than the maximum load required for forming the workpiece in the initial stage of the forming process, and the pressurizing speed is increased. As a result, the molding time is shortened, and an increase in deformation resistance due to a decrease in the temperature of the workpiece being molded during hot working can be prevented. Also, depending on the workpiece, the high pressurization capability mode may not be required. In this case, the molding process can be completed without going through the high pressurization capability mode, and the pressurization speed is increased accordingly. . Furthermore, even if the number of pumps is reduced, the pressurization speed can be maintained, so that energy saving and the installation space of the press device can be reduced.
According to the second aspect of the present invention, the pressure release valve is opened immediately before the hydraulic pressure in the switching source pressurizing cylinder becomes negative pressure, so that the hydraulic pressure in the switching source pressurizing cylinder becomes negative pressure as the slide advances. Can be prevented. In addition, there is a time lag from switching the cylinder control block to opening the pressure release valve, so the compression of hydraulic oil in the switching source pressurizing cylinder is canceled by the advance of the slide, and the pressure release valve is opened. Occurrence of impact at the time can be prevented.
According to the third invention, since the communication valve is opened simultaneously with the switching of the cylinder control block, the hydraulic oil compressed in the switching source pressurizing cylinder is supplied into the switching destination pressurizing cylinder, Since the decrease in the hydraulic pressure in the pressure cylinder and the increase in the hydraulic pressure in the switching destination pressurization cylinder are performed quickly, the time during which the slide stops can be shortened by changing the pressurization capability mode. As a result, it is possible to prevent an increase in deformation resistance due to a decrease in the temperature of the workpiece being formed during hot working. In addition, the energy accumulated by compressing the hydraulic oil in the switching source pressurizing cylinder is transmitted to the hydraulic oil in the switching destination pressurizing cylinder, and the energy can be effectively used. Furthermore, since the hydraulic pressure in the switching source pressurization cylinder is quickly lowered, the time lag from switching the cylinder control block to opening the pressure relief valve is shortened, and the pressurization capacity mode is changed quickly. Is called.
According to the fourth aspect of the present invention, the supply destination of the hydraulic oil to the switching destination pressurization cylinder which is a combination in which the pressurization capacity is increased when the hydraulic pressure in the switching source pressurization cylinder to which the hydraulic oil is supplied exceeds the set pressure. Since switching is performed, the pressure capability mode can be changed during the molding process. Therefore, it is possible to operate in the pressurizing capacity mode that is lower than the maximum load required for forming the workpiece in the initial stage of the forming process, and the pressurizing speed is increased. As a result, the molding time is shortened, and an increase in deformation resistance due to a decrease in the temperature of the workpiece being molded during hot working can be prevented. Also, depending on the workpiece, the high pressurization capability mode may not be required. In this case, the molding process can be completed without going through the high pressurization capability mode, and the pressurization speed is increased accordingly. . Furthermore, even if the number of pumps is reduced, the pressurization speed can be maintained, so that energy saving and the installation space of the press device can be reduced.
According to the fifth aspect of the present invention, since the pressure release is performed immediately before the hydraulic pressure in the switching source pressurizing cylinder becomes negative pressure, it is possible to prevent the hydraulic pressure in the switching source pressurizing cylinder from becoming negative pressure due to the advance of the slide. it can. In addition, since there is a time lag from switching of the hydraulic oil supply destination to depressurization, the compression of the hydraulic oil in the switching source pressurizing cylinder is eliminated by the advance of the slide, and the occurrence of an impact when depressurizing is prevented. Can do.
According to the sixth aspect of the present invention, the hydraulic oil in the switching source pressurizing cylinder is supplied to the switching source pressurizing cylinder at the same time as the hydraulic oil supply destination is switched. Since the lowering of the pressure and the increase of the hydraulic pressure in the switching destination pressurizing cylinder are performed quickly, the time during which the slide stops can be shortened by changing the pressurizing capacity mode. As a result, it is possible to prevent an increase in deformation resistance due to a decrease in the temperature of the workpiece being formed during hot working. In addition, the energy accumulated by compressing the hydraulic oil in the switching source pressurizing cylinder is transmitted to the hydraulic oil in the switching destination pressurizing cylinder, and the energy can be effectively used. Furthermore, since the hydraulic pressure in the switching source pressurizing cylinder is quickly lowered, the time lag from switching of the hydraulic oil supply destination to depressurization is shortened, and the pressurization capacity mode is quickly changed.

1 is a hydraulic circuit diagram of a hydraulic press 1 according to a first embodiment of the present invention. It is a hydraulic-circuit figure of the hydraulic press 2 which concerns on 2nd Embodiment of this invention. It is the graph which showed the relationship of the pressurization speed with respect to time in a formation process, and the hydraulic pressure in a cylinder, (A) shows the case of 1st Embodiment, (B) shows the case of 2nd Embodiment. It is a graph which shows the general relationship of the load concerning shaping | molding of the workpiece | work with respect to a stroke.

Next, an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the hydraulic press 1 according to the first embodiment of the present invention has three pressure cylinders CC, CR, CL arranged side by side on a crown (not shown), and each pressure cylinder CC. , CR and CL rams are connected to a common slide (not shown). Therefore, if the pressurizing capacity of each pressurizing cylinder CC, CR, CL is 3000 tons, the hydraulic press 1 has a pressurizing capacity of 9000 tons at the maximum. And the following three pressurization capability modes are realizable by selecting the pressurization cylinders CC, CR, and CL which supply hydraulic fluid.
・ 3000ton mode: Supply hydraulic oil to the central pressure cylinder CC ・ 6000ton mode: Supply hydraulic oil to the right pressure cylinder CR and left pressure cylinder CL ・ 9000ton mode: Central pressure cylinder CC, right pressure cylinder CR, Supply hydraulic fluid to all left pressure cylinders CL

Next, the hydraulic circuit of the hydraulic press 1 will be described.
The pump P driven by the motor M sucks and discharges the hydraulic oil stored in the tank T, and supplies the hydraulic oil to the pressure cylinders CC, CR, and CL. The discharge port of the pump P is connected to the cylinder control block 20 via the control valve 11 and the check valve 12.
The control valve 11 is a solenoid valve that is closed when the solenoid is ON and open when the solenoid is OFF. The control valve 11 controls the hydraulic oil supplied from the pump P to be returned to the tank T when in the open state and guided to the cylinder control block 20 when in the closed state.

The cylinder control block 20 plays a role of switching the supply destination of the hydraulic oil supplied from the pump P. The cylinder control block 20 includes a control valve 21 and a control valve 22. The control valves 21 and 22 are solenoid valves that are opened when the solenoid is ON and closed when the solenoid is OFF. Both are supplied with hydraulic oil from the pump P in parallel. The control valve 21 is connected to the oil chamber of the central pressurization cylinder CC via the check valve 13, and the control valve 22 is connected to the oil chambers of the right pressurization cylinder CR and the left pressurization cylinder CL via the check valve 14. It is connected to the.
Therefore, by switching between the open and closed states of the control valve 21 and the control valve 22, a pressurizing cylinder that supplies hydraulic oil can be selected and the pressurization capability mode can be changed.

  The hydraulic press 1 includes a prefill tank PT. The prefill tank PT is connected to an oil chamber of a central pressurizing cylinder CC via a prefill valve 31, and is connected to a right pressurizing cylinder via a prefill valve 32. It is connected to the oil chamber of CR and the left pressure cylinder CL. The prefill valves 31 and 32 are solenoid valves that are closed when the solenoid is ON and open when the solenoid is OFF.

  The prefill valve 31 is opened when hydraulic oil is not supplied to the central pressurizing cylinder CC and hydraulic oil is supplied to the right pressurizing cylinder CR and the left pressurizing cylinder CL (6000 ton mode). It plays a role of sucking hydraulic oil into the cylinder CC. On the other hand, the prefill valve 32 is opened when hydraulic oil is supplied to the central pressure cylinder CC and hydraulic oil is not supplied to the right pressure cylinder CR and the left pressure cylinder CL (3000 ton mode). The cylinder CR and the left pressure cylinder CL play a role of sucking hydraulic oil.

  The oil chamber of the central pressurizing cylinder CC is connected to the tank T via the pressure relief valve 41, and the oil chambers of the right pressure cylinder CR and the left pressure cylinder CL are connected to the tank T via the pressure relief valve 42. Has been. The pressure relief valves 41 and 42 are solenoid valves that are closed when the solenoid is ON and open when the solenoid is OFF.

A pressure detector PH1 for detecting the hydraulic pressure Pc in the central pressure cylinder CC is installed between the central pressure cylinder CC and the pressure release valve 41, and the right pressure cylinder CR and the left pressure cylinder CL. And a pressure release valve 42 is provided with a pressure detector PH2 for detecting the hydraulic pressure Plr in the right pressure cylinder CR and the left pressure cylinder CL. The pressure detector PH1 and the pressure detector PH2 are connected to the control device CTL, and the respective pressure detection results are sent to the control device CTL.
The control device CTL is also connected to the control valves 11, 21, 22, prefill valves 31, 32, and pressure relief valves 41, 42, and functions to control ON / OFF of the solenoid of each valve according to a predetermined condition. Have

The above-mentioned three pressurization capacity modes can be realized by controlling the above hydraulic circuit as follows.
That is, with the control valve 11 in the closed state and the hydraulic oil being supplied from the tank T to the cylinder control block 20, the 3000 ton mode: the control valve 21 is opened, the control valve 22 is closed, and the prefill valve 31 is With the prefill valve 32 opened and the pressure relief valve 41 closed, hydraulic oil is supplied to the central pressurizing cylinder CC. The pressure relief valve 42 may be closed or open.

6000 ton mode: the control valve 21 is closed, the control valve 22 is opened, the prefill valve 31 is opened, the prefill valve 32 is closed, and the pressure release valve 42 is closed, and the left pressurization cylinder CR and the left addition Supply hydraulic fluid to the pressure cylinder CL. The pressure relief valve 41 may be closed or open.

9000 ton mode: the control valve 21 is open, the control valve 22 is open, the prefill valve 31 is closed, the prefill valve 32 is closed, the pressure release valve 41 is closed, and the pressure release valve 42 is closed Hydraulic fluid is supplied to all of the central pressure cylinder CC, the right pressure cylinder CR, and the left pressure cylinder CL.

Next, a method for switching the pressure capability mode will be described.
(1) Switching from 3000 ton mode to 6000 ton mode As shown in FIG. 3 (A), in the initial stage of the molding process, the operation is performed in the 3000 ton mode with the lowest pressurizing capacity. The pressurization speed at this time is V1, which is the fastest speed. In the 3000 ton mode, the hydraulic pressure Pc in the central pressurizing cylinder CC increases with time (cylinder advance). The hydraulic pressure Pc is detected by the pressure detector PH1, and the detection result is sent to the control device CTL.

When the hydraulic pressure Pc exceeds the set pressure P1, the control device CTL changes the control valve 21 from the open state to the closed state, the control valve 22 from the closed state to the open state, and the prefill valve 32 from the open state to the closed state. When the extraction valve 42 is in an open state, an operation (switching 1) is performed to make it close. That is, the hydraulic oil supply destination is switched from the central pressure cylinder CC to the right pressure cylinder CR and the left pressure cylinder CL.
In switching 1, the prefill valve 31 and the pressure relief valve 41 remain closed. Further, the set pressure P1 is set to a pressure slightly lower than the pressurizing capacity in the 3000 ton mode, so that the load applied to the molding of the workpiece does not exceed the pressurizing capacity.

  Here, in the switching 1, the central pressure cylinder CC corresponds to the “switching source pressure cylinder supplied with hydraulic oil” described in the claims, and the right pressure cylinder CR and the left pressure cylinder CL. Corresponds to “a switching destination pressurizing cylinder that is a combination that increases the pressurizing ability” described in the claims. That is, in the switching of the pressurizing capacity mode, the pressurizing cylinder to which the operating oil was supplied in the pressurizing capacity mode before the switching is the “switching source pressurizing cylinder”, and the operating oil is switched in the pressurizing capacity mode after the switching. The pressure cylinder supplied is the “switching destination pressure cylinder”.

  As in this embodiment, when a plurality of pressurizing cylinders having the same pressurizing capacity are provided, the number of pressurizing cylinders for supplying hydraulic oil increases in accordance with the high pressurizing capacity mode. When a plurality of pressure cylinders having different pressure capacities are provided, there may be one switching destination pressure cylinder. Thus, the “combination that increases the pressurizing ability” described in the claims is a concept including the case of a single pressurizing cylinder.

  When switching 1 is performed, hydraulic oil from the pump P is supplied to the right pressurization cylinder CR and the left pressurization cylinder CL, and the hydraulic pressure Plr is increased, while the hydraulic pressure Pc in the central pressurization cylinder CC is The compression of the hydraulic fluid inside is canceled by the advance of the slide and descends.

  When the control device CTL drops below the set pressure P2 immediately before the hydraulic pressure Pc becomes negative, the operation to switch the pressure relief valve 41 from the closed state to the open state and the prefill valve 31 from the closed state to the open state (switching 2). I do.

  By switching 2, it is possible to prevent the hydraulic pressure Pc in the central pressurizing cylinder CC from becoming negative due to the subsequent advance of the slide. Further, in the time lag from switching 1 to switching 2, the compression of the hydraulic oil in the central pressurizing cylinder CC is canceled by the advance of the slide, so the impact due to the hydraulic oil jetting when the pressure release valve 41 is opened. Can be prevented.

  It should be noted that a time zone (hereinafter referred to as “dead zone”) in which the pressurization speed is approximately zero occurs between the switching 1 and the switching 2. The length of the dead zone is determined by the compression volume of the pressure cylinder, the amount of extension of the press frame, and the like. Here, the compression volume is an amount determined by the volume of the oil chamber of the pressure cylinder and the pressure difference, and is generated by the compressibility of the hydraulic oil. Since hydraulic oil is compressible, it takes time to increase the pressure even if hydraulic oil is supplied from the pump to the pressure cylinder, and the press frame extends as the pressure exerted by the pressure cylinder increases. A dead zone occurs.

  As shown in FIG. 3 (A), switching 2 changes to the 6000 ton mode, and the pressurization speed drops to a speed V2 that is approximately half of the pressurization speed V1 in the 3000 ton mode, but the pressurization capability increases and the workpiece can be molded. It becomes.

(2) Switching from 6000ton mode to 9000ton mode
Even in the 6000 ton mode, the hydraulic pressure Plr increases with time (cylinder advance). The hydraulic pressure Plr is detected by the pressure detector PH2, and the detection result is sent to the control device CTL.
When the hydraulic pressure Plr exceeds a set pressure that is slightly lower than the pressurizing capacity in the 6000 ton mode, the control device CTL changes the control valve 21 from the closed state to the open state, changes the prefill valve 31 from the open state to the closed state, and releases the pressure release valve 41. If is in an open state, an operation for closing is performed. That is, in addition to the right pressurization cylinder CR and the left pressurization cylinder CL, switching is performed so as to supply hydraulic oil to the central pressurization cylinder CC.

  Switching from 6000 ton mode to 9000 ton mode does not have a pressurizing cylinder that stops the supply of hydraulic oil from pump P, so there are two stages, switching 1 and switching 2 as in switching from 3000 ton mode to 6000 ton mode. There is no need, and no dead zone occurs.

  Here, in switching from the 6000 ton mode to the 9000 ton mode, the right pressurizing cylinder CR and the left pressurizing cylinder CL correspond to the “switching source pressurizing cylinder” recited in the claims, The right pressure cylinder CR and the left pressure cylinder CL correspond to the “switching destination pressure cylinder” recited in the claims. In other words, the switching source pressurizing cylinder and the switching destination pressurizing cylinder may include a common pressurizing cylinder.

  By controlling the hydraulic circuit as described above, the pressurization capacity mode can be changed during the molding process. Therefore, it is possible to operate in the pressurizing capacity mode that is lower than the maximum load required for forming the workpiece in the initial stage of the forming process, and the pressurizing speed is increased. As a result, the molding time is shortened, and an increase in deformation resistance due to a decrease in the temperature of the workpiece being molded during hot working can be prevented. Also, depending on the workpiece, the high pressurization capability mode may not be required. In this case, the molding process can be completed without going through the high pressurization capability mode, and the pressurization speed is increased accordingly. . Furthermore, even if the number of pumps is reduced, the pressurization speed can be maintained, so that energy saving and the installation space of the press device can be reduced.

  Although not shown in FIG. 1, the hydraulic press 1 is separately provided with a cylinder and a hydraulic circuit for pulling up the slide after forming the workpiece.

(Second Embodiment)
As shown in FIG. 2, the hydraulic press 2 according to the second embodiment of the present invention has a hydraulic circuit whose hydraulic circuit is the same as that of the central press cylinder CC in the hydraulic circuit of the hydraulic press 1 according to the first embodiment. An oil passage 51 between the valve 41 and an oil passage 52 between the right pressure cylinder CR and the left pressure cylinder CL and the pressure relief valve 42 are connected via a communication valve 53 and a check valve 54. It has a configuration. The communication valve 53 is a solenoid valve that opens when the solenoid is ON and closes when the solenoid is OFF. The check valve 54 allows the hydraulic oil to flow only from the oil passage 51 to the oil passage 52.
Since the rest of the configuration is the same as that of the hydraulic press 1, the same reference numerals are assigned to the same members and the description thereof is omitted.

  Also in the present embodiment, the same three pressurization capacity modes as in the first embodiment can be realized. In each pressurization capacity mode, the control valves 11, 21, 22, prefill valves 31, 32, pressure release The states of the valves 41 and 42 are the same as in the first embodiment. The communication valve 53 is controlled to be closed in the 3000 ton mode, but may be closed or opened in the 6000 ton mode and the 9000 ton mode.

Next, a method for switching the pressure capability mode will be described.
(1) Switching from 3000 ton mode to 6000 ton mode As shown in FIG. 3B, in the initial stage of the molding process, the operation is performed in the 3000 ton mode with the lowest pressurizing capacity. When the hydraulic pressure Pc exceeds the set pressure P1, the control device CTL changes the control valve 21 from the open state to the closed state, changes the control valve 22 from the closed state to the open state, and changes the prefill valve 32 from the open state to the closed state. When the pressure release valve 42 is in the open state, the operation is switched to the closed state, and the communication valve 53 is changed from the closed state to the open state (switch 1). That is, the hydraulic oil supply destination is switched from the central pressure cylinder CC to the right pressure cylinder CR and the left pressure cylinder CL, and the oil chamber of the central pressure cylinder CC, the right pressure cylinder CR, and the left pressure cylinder CL. It communicates with the oil chamber.
In switching 1, the prefill valve 31 and the pressure relief valve 41 remain closed.

  When switching 1 is performed, the hydraulic oil from the pump P is supplied to the right pressure cylinder CR and the left pressure cylinder CL, and the hydraulic oil compressed in the central pressure cylinder CC is also supplied through the communication valve 53. Is done. Therefore, the lowering of the hydraulic pressure Pc in the central pressurizing cylinder CC and the rising of the hydraulic pressure Plr in the right pressurizing cylinder CR and the left pressurizing cylinder CL are performed more quickly than in the first embodiment.

As described above, a dead zone occurs when switching from 3000 ton mode to 6000 ton mode. In this dead zone, the work is stopped with the upper and lower molds held down, so if hot forging, the heat of the work is taken away by the mold side, the temperature decreases, and the deformation resistance increases. Cause. However, in this embodiment, since the dead zone can be shortened, an increase in change resistance can be prevented.
Further, the energy accumulated by compressing the hydraulic oil in the central pressure cylinder CC is transmitted to the hydraulic oil in the right pressure cylinder CR and the left pressure cylinder CL, so that the energy can be effectively used.

When the control device CTL drops below the set pressure P2 immediately before the hydraulic pressure Pc becomes negative, the operation to switch the pressure relief valve 41 from the closed state to the open state and the prefill valve 31 from the closed state to the open state (switching 2). I do. By this switching 2, it becomes 6000ton mode.
As described above, since the hydraulic pressure in the central pressurizing cylinder CC is lowered quickly, the time lag from switching 1 to switching 2 is shortened, and the change of the pressurizing capacity mode is quicker than in the first embodiment. Done.

(2) Switching from 6000ton mode to 9000ton mode
Switching from the 6000 ton mode to the 9000 ton mode is the same as in the first embodiment. Note that switching from the 6000 ton mode to the 9000 ton mode does not require control of the communication valve 53 because there is no pressurizing cylinder that stops supplying hydraulic oil from the pump P.

  Although the above embodiment is a hydraulic press provided with three pressure cylinders, it goes without saying that the present invention can be applied to a hydraulic press provided with a plurality of pressure cylinders.

CC, CR, CL Pressure cylinder 20 Cylinder control block 21, 22 Control valve 31, 32 Prefill valve 41, 42 Pressure release valve 53 Communication valve

Claims (6)

A hydraulic press composed of a plurality of pressure cylinders,
It has a cylinder control block that switches the supply destination of hydraulic oil,
The cylinder control block controls the supply destination of hydraulic oil to the switching destination pressurization cylinder, which is a combination in which the pressurization capacity is increased when the hydraulic pressure in the switching source pressurization cylinder to which the hydraulic oil is supplied exceeds a set pressure. Hydraulic press characterized by switching. A pressure relief valve is connected to each of the pressure cylinders,
The hydraulic press according to claim 1, wherein the pressure release valve connected to the switching source pressurizing cylinder is opened immediately before the hydraulic pressure in the switching source pressurizing cylinder becomes negative. Each of the pressure cylinders is connected via a communication valve;
The hydraulic press according to claim 2, wherein the communication valve that connects the switching source pressurizing cylinder and the switching destination pressurizing cylinder is opened simultaneously with the switching of the cylinder control block. In a hydraulic press composed of multiple pressure cylinders,
When the hydraulic pressure in the switching source pressurizing cylinder to which the hydraulic oil is supplied exceeds the set pressure, the hydraulic oil supply destination is switched to the switching destination pressurizing cylinder that is a combination in which the pressurizing capacity is increased. Control method of hydraulic press. 5. The hydraulic press control method according to claim 4, wherein the pressure of the switching source pressurizing cylinder is released immediately before the hydraulic pressure in the switching source pressurizing cylinder becomes negative. 6. The method of controlling a hydraulic press according to claim 5, wherein the hydraulic oil in the switching source pressurizing cylinder is supplied into the switching destination pressurizing cylinder simultaneously with switching the supply destination of the hydraulic oil.

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