JP2020040107A - Hydraulic press and operation method thereof - Google Patents

Abstract

To provide a hydraulic press where a cycle time is shortened, thereby enabling improvement in productivity, and an operation method thereof.SOLUTION: A hydraulic press comprises: a main hydraulic cylinder 1 which lowers a slide 4; a hydraulic pump 21 and an accumulator 13 as hydraulic power source for the main hydraulic cylinder 1; a pump circuit 20 provided between the main hydraulic cylinder 1 and the hydraulic pump 21; a main control valve 11 interposed in the pump circuit 20; a pressure oil replenishment pipe 55 for replenishing a high pressure hydraulic oil in the accumulator 13 to the main hydraulic cylinder 1; and an auxiliary control valve 56 interposed in the pressure oil replenishment pipe 55. Since the accumulated pressure oil in the accumulator 13 can be supplied to the main hydraulic cylinder 1 when the auxiliary control valve 56 is opened, repression energy of mechanical system, a compressed volume of the hydraulic oil in the cylinder and so on can be absorbed in a first half boosting section of a second process. Therefore, press work productivity can be improved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic press and a method of operating the same. More specifically, the present invention relates to a hydraulic press for forming a same work a plurality of times and a method of operating the same.

There are three types of supply sources of hydraulic oil for driving hydraulic presses.
The first is a type of Patent Document 1 in which hydraulic oil for driving a hydraulic cylinder is supplied only by a hydraulic pump. In this type, high-pressure hydraulic oil from a hydraulic pump is used for all operations in a series of steps including lowering, pressing, and raising the slide. Therefore, a large-sized hydraulic pump having a sufficient capacity is provided.

  The second is a type of Patent Documents 2 and 3 in which hydraulic oil for driving a hydraulic cylinder is supplied by an accumulator. In this type, high-pressure hydraulic oil from an accumulator is used for all operations in a series of steps including lowering, pressing, and raising the slide. For this reason, an accumulator having a sufficiently large capacity and capable of supplying high-pressure hydraulic oil is provided, and a hydraulic pump having a small capacity sufficient to replenish the accumulator with hydraulic oil is used.

  The third type is a patent document 4 in which an accumulator is used as an auxiliary while supplying hydraulic oil to a hydraulic cylinder mainly by a hydraulic pump. The use of the accumulator in this type is used to increase the speed when the slide is raised. In other words, the accumulator is used when the hydraulic oil is sufficient at a low pressure, and the accumulator has not been used for the original molding process that requires the high-pressure hydraulic oil. Therefore, a small accumulator for normal pressure has been used.

  By the way, in pressure molding by a hydraulic press, (a) improvement in lubricity of a pair of upper and lower dies, (a) relaxation of distortion at a contact portion between the dies and the material, and (c) low-speed molding and during molding of the material For the purpose of suppressing the temperature drop, molding is performed in a plurality of times instead of molding with one press.

In the case of molding a plurality of times as described above, generally, a pair of upper and lower molds are installed on a press so that an eccentric load is not applied, and molding is performed such that a strain rate is reduced.
In such a hydraulic press that performs molding a plurality of times, it is necessary to keep the molding speed of the press low (generally, the mold is heated in order to prevent the temperature of the work from lowering). (Capacity according to speed).

Referring to FIG. 6, a cycle diagram in the case where the conventional hydraulic press is formed by dividing into two times will be described.
The conventional press cycle shown in the figure is as follows, wherein (1) to (6) are the first pressing step, and (7) to (10) are the second pressing step. The thin line shows the stroke of the slide and the upper mold, and the thick line shows the press load.

(First process)
(1) The work is set on the lower mold.
(2) The slide is idled down from the stop position, and the upper mold is lowered.
(3) After the upper mold comes into contact with the work, the work is formed at a pressure lowering speed required for the work. During this step, the press load gradually increases.
(4) When the first molding completion point is reached, pressurization is completed and pressure is released. This reduces the pressing load rapidly. The lower limit of the first pressurization is indicated by reference symbol LL1.
(5) Raise the slide and the upper mold.
(6) The slide is stopped at a preset position for a preset time, and a measure necessary for the molding process (such as lubrication of a mold) is performed.

(2nd process)
(7) The slide and the upper mold are moved downward from the stop position, and the upper mold is lowered.
(8) Lower the pressure for the second molding.
During this step, the press load gradually increases.
During the second machining descent (8), the pressurizing section until the first molding completion point (up to the pressurization lower limit LL1) (work is hardly formed during this period, and the elastic pressure energy of the mechanical system and the operation in the cylinder are reduced. (The oil is absorbed by the compressed volume of oil, etc.), and there is an original second molding section thereafter.
(9) Immediately before the completion of the second molding, the press load sharply increases, and the pressing is completed when the molding completion point is reached. Immediately after that, release the pressure. The lower limit of the second pressurization is indicated by reference symbol LL2.
(10) Raise the slide and the upper mold and stop at a preset position. Then, the operation is stopped until the next work is supplied onto the lower mold.

The phenomenon that occurs in the two-time pressure molding will be described in detail. The case where the workpiece is not reheated and the case where the workpiece is not reheated will be described separately.
(I) In the case where the same workpiece is molded a plurality of times without reheating with the same mold, the molding load is once unloaded in the middle of the molding process (stop (6) between the first and second processes). The upper mold is raised to provide a space between the mold and the raw material, and measures necessary for the molding process (for example, lubrication of the mold) are performed.
In the second molding after the first molding, molding is performed from the lower pressure limit LL1 of the first molding to the target value (lower pressure LL2) of the second molding.
In the second and subsequent moldings, the molding hardly proceeds even if the pressure is raised to the point of completion of the previous molding (LL1), and is absorbed only by the elastic energy of the mechanical system and the compression volume of the hydraulic oil in the cylinder. The molding proceeds only when the pressure is increased beyond the molding completion time (LL1).

(Ii) When reheating after completion of the first molding, and performing the second and subsequent moldings again with the same mold. In this case, the first molding is performed in units of one lot, and after completion, the one lot is reused. The work is heated and the second molding is performed on the work of this one lot (when the third molding is necessary, the molding is performed after reheating similarly to the second molding).
In this case as well, in the second and subsequent moldings, the molding hardly proceeds even if the pressure is raised to the point of completion of the previous molding (LL1), and is merely absorbed by the repulsive energy of the mechanical system or the compression volume of the hydraulic oil in the cylinder. When the pressure is increased to a value equal to or higher than the pressure at the time of completion of the previous molding (LL1), molding proceeds only when the pressure is increased.

A large hydraulic press generally has a large stroke (for example, 1000 mm or more), and requires a large driving power (pump discharge amount) for short-time pressure rise of the hydraulic cylinder because the pressing force is controlled by the hydraulic cylinder. Becomes
However, in a press that requires a low molding speed, a press having a small power is generally used from the viewpoint of economy. In this case, with a hydraulic power source having a small power, the pressure cannot be increased in a short time due to the compressibility of the hydraulic oil in the cylinder or the elongation of the mechanical system, so that the cycle time has been long.

  As described above, in the above-described related art, the second and subsequent molding operations include a cycle that does not directly contribute to molding, and therefore the processing time is long. This is because, as described above, in the second and subsequent moldings, the pressurization up to the completion of the previous molding is absorbed by the elastic energy of the mechanical system and the compression volume of the hydraulic oil in the cylinder.

JP 2016-112596 A JP-A-7-155999 JP-T-2015-522419A Japanese Patent No. 4192206

The present inventor has found that the cycle time can be reduced and the productivity can be increased by reducing the pressurizing time of the second and subsequent molding operations.
Therefore, an object of the present invention is to provide a hydraulic press and a method of operating the hydraulic press, which can shorten the pressurizing time of the second and subsequent molding operations, shorten the cycle time, and increase the productivity.

A hydraulic press according to a first aspect of the present invention is a hydraulic press for performing a molding operation by lowering and raising a slide having an upper mold attached to a lower mold on a bed, wherein the main hydraulic cylinder for lowering the slide and the main hydraulic cylinder are provided. A hydraulic pump and an accumulator as a hydraulic pressure source for a hydraulic cylinder, a pump circuit disposed between the main hydraulic cylinder and the hydraulic pump, and a main circuit interposed between the hydraulic pump and the main hydraulic cylinder. A control valve, a pressure oil supply pipe disposed between the accumulator and the main hydraulic cylinder, the pressure oil supply pipe configured to supply accumulated pressure oil in the accumulator to the main hydraulic cylinder, and a pressure oil supply pipe interposed in the pressure oil supply pipe. And a supplementary control valve for controlling the supplied pressure oil supply.
The hydraulic press according to a second aspect of the present invention is the hydraulic press according to the first aspect, further comprising a control unit for controlling the opening and closing of the auxiliary control valve. In the first half pressure rising section at the time of descending, the auxiliary control valve is controlled to open so as to supply the accumulator oil in the accumulator to the main hydraulic cylinder.
A method of operating a hydraulic press according to a third aspect of the present invention is a method of operating a hydraulic press, comprising: a main hydraulic cylinder for lowering a slide on which an upper die is attached to a lower die on a bed; A method of operating a hydraulic press including a hydraulic pump and an accumulator as a hydraulic pressure source for a hydraulic cylinder, wherein a molding operation performed using the hydraulic press includes a first step of performing primary molding and a secondary molding and subsequent steps. And the second and subsequent steps to be performed. The first step is performed using hydraulic oil supplied by the hydraulic pump, and in the second and subsequent steps, the accumulator is operated in the first half pressure increasing section at the time of pressurizing and lowering. The present invention is characterized in that the operation is performed using the supplied hydraulic oil, and using the hydraulic oil supplied from the hydraulic pump in the latter half pressure rising section at the time of pressurizing and lowering.
A method for operating a hydraulic press according to a fourth invention is characterized in that, in the third invention, the molding operation is a multi-step molding operation in which the same work is divided into a plurality of times with the same mold without reheating. I do.
A method for operating a hydraulic press according to a fifth invention is characterized in that, in the third invention, the molding operation is a multi-step molding operation in which a heated work is molded, reheated, and molded again with the same mold. And
A method of operating a hydraulic press according to a sixth aspect of the present invention is the method according to the third aspect, wherein the hydraulic oil is supplied to the accumulator from a hydraulic pump or from a main hydraulic cylinder when the main hydraulic cylinder is depressurized. I do.

According to the first invention, when the auxiliary control valve is opened, the high-pressure hydraulic oil in the accumulator can be supplied to the main hydraulic cylinder. In this case, the replenished hydraulic oil absorbs the elastic energy of the machine and the compression volume of the hydraulic oil, so that the pressure can be increased quickly. For this reason, the second and subsequent pressing steps can be shortened, and the productivity of press working can be improved.
According to the second invention, when the control unit controls the opening of the supplementary control valve in the first half boosting section at the time of pressurizing and lowering in the second and subsequent steps, the hydraulic oil to the main hydraulic cylinder in the first half boosting section in the second and subsequent steps Since the supply is performed from the accumulator, the pressure is accelerated by absorbing the elastic energy of the machine and the compression volume of the working oil, and the time of the first half pressure increase section in the second and subsequent steps can be shortened.
According to the third aspect of the present invention, the supply of hydraulic oil to the main hydraulic cylinder in the first half boosting section after the second step is supplied from the accumulator, thereby absorbing the elastic energy of the machine and the compression volume of the hydraulic oil to speed up the boosting. Secondly, the time of the first half boosting section in the second and subsequent steps can be shortened. For this reason, the productivity of press working can be improved.
According to the fourth aspect, in a molding operation in which the same workpiece is molded a plurality of times with the same mold without reheating, it is possible to shorten the time of the first-half pressure step in the second and subsequent steps.
According to the fifth aspect of the invention, in a molding operation in which the heated workpiece is molded, then reheated, and then molded again with the same mold, the time of the first half pressure step in the second and subsequent steps can be reduced.
According to the sixth aspect, the hydraulic oil is introduced into the accumulator not only from the hydraulic pump but also when the main hydraulic cylinder is depressurized, so that the high-pressure hydraulic oil can be efficiently supplied to the accumulator.

It is a hydraulic circuit diagram of a hydraulic press concerning one embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram during a first pressurizing step in the hydraulic press of FIG. 1. FIG. 2 is a hydraulic circuit diagram during a second pressurizing step in the hydraulic press of FIG. 1. It is explanatory drawing of the operating method of the hydraulic press which concerns on this invention. It is explanatory drawing of the driving method which showed this invention and the prior art in comparison. It is explanatory drawing of the operating method of the conventional hydraulic press.

Next, an embodiment of the present invention will be described with reference to the drawings.
A configuration of a hydraulic press according to an embodiment of the present invention will be described with reference to FIG.
1 is a main hydraulic cylinder, 2 is its cylinder body, and 3 is a ram. A slide 4 is attached to a lower end of the ram 3. A bed 5 is arranged below the slide 4. An upper mold 6 constituting a pair of molds is attached to the lower surface of the slide 4, and a lower mold 7 is arranged on the upper surface of the bed 5.

The cylinder body 2 of the main hydraulic cylinder 1 is fixed to a crown (not shown), and the crown and the bed 5 are connected to each other by an applied (not shown). A retraction cylinder 8 is connected to the slide 4, and the retraction cylinder 8 is fixed to a crown (not shown).
Such a mechanical configuration is the same as that of a known hydraulic press.

When hydraulic oil is supplied to the oil chamber 1a of the main hydraulic cylinder 1, the ram 3 descends, the slide 4 descends, the upper mold 6 approaches the lower mold 7, and the work can be formed under pressure. .
When hydraulic oil is supplied to the oil chamber 8a of the pull-back cylinder 8, the slide 4 is raised by the pull-back cylinder 8.
The slide 4 is moved up and down by the expansion and contraction of the main hydraulic cylinder 1 and the pull-back cylinder 8, and the upper and lower dies 6, 7 are separated from each other, so that the molding operation can be performed.

First, a basic configuration of a hydraulic circuit for operating the above hydraulic press will be described.
The main hydraulic cylinder 1 and the retraction cylinder 8 are connected to a main hydraulic oil supply circuit. The main hydraulic oil supply circuit includes a pump circuit 20, a first supply circuit 30, and a second supply circuit 40. The main control valve 11 is interposed between the pump circuit 20 and the first supply circuit 30 and the second supply circuit 40.

  The pump circuit 20 mainly includes a pump 21 driven by a motor and a discharge pipe 22. The pump 21 is a known hydraulic pump. The discharge pipe 22 is provided with a check valve 23 that allows only the flow in the discharge direction and prevents the reverse flow.

The first supply circuit 30 includes a supply pipe 31 and a pressure sensor 32. The supply pipe 31 is provided between the main control valve 11 and the oil chamber 1 a of the main hydraulic cylinder 1.
The second supply circuit 40 includes a supply pipe 41 and a check valve 42. The supply pipe 41 is disposed between the main control valve 11 and the oil chambers 8a of the two retraction cylinders 8. The check valve 42 is provided so as to allow only the supply of the hydraulic oil and prevent the backflow.

The main control valve 11 may be any control valve as long as it can change the supply / discharge direction of the hydraulic oil. The illustrated main control valve 11 is a three-position four-port electromagnetically operated directional control valve. The pump side port is connected to the pump circuit 20, and the tank side port is connected to the tank 12.
The main control valve 11 has all four ports closed in the neutral position. At the position I, the pump circuit 20 communicates with the first supply circuit 30 and the second supply circuit 40 communicates with the tank 12. In the II position, the pump circuit 20 communicates with the second supply circuit 40 and the first supply circuit 30 communicates with the tank 12.

  Reference numeral 13 denotes an accumulator. The accumulator used in the present invention is a known fluid device called an accumulator, which can store pressure oil and discharge it appropriately. The accumulator 13 has a capacity large enough to supply hydraulic oil to the main hydraulic cylinder 1 in a short time.

  An auxiliary supply circuit 51 is connected between the accumulator 13 and the pump-side port of the main control valve 11. The auxiliary supply circuit 51 is provided with an on-off valve 52. This open / close valve 52 may be any control valve as long as it is a control valve capable of permitting or preventing the supply of hydraulic oil. The illustrated on-off valve 52 is a two-position on-off valve, and when switching between on and off by electromagnetic operation, the pressure oil supplied from the pump circuit 20 can be supplied to the accumulator 13 to accumulate the pressure or stop the supply.

  A pressure oil supply pipe 55 is connected between the accumulator 13 and the supply pipe 31 of the first supply circuit 30. By this circuit, the oil chamber 1a in the main hydraulic cylinder 1 and the accumulator 13 are communicated. An auxiliary control valve 56 is interposed in the pressure oil supply pipe 55. The auxiliary control valve 56 is a two-position on-off valve controlled by electromagnetic operation. When the auxiliary control valve 56 is switched between open and closed by electromagnetic operation, the accumulator oil in the accumulator 13 can be supplied to the oil chamber 1 a in the main hydraulic cylinder 1. . Further, the pressure oil in the oil chamber 1a of the main hydraulic cylinder 1 can be introduced into the accumulator 13 to accumulate the pressure.

Further, details of the hydraulic circuit will be described.
A discharge pipe 24 is connected to a discharge pipe 22 of the pump circuit 20 and extends to the tank 12. An open / close valve 25 is interposed in the discharge pipe 24, and is always open and is switched to close by electromagnetic operation. The discharge pipe 24 is provided in order to return the hydraulic oil to the tank 12 when the pump 21 is unloaded so as not to apply an unnecessary load.

A discharge pipe 44 is connected to the supply pipe 41 of the second supply circuit 40, and the discharge pipe 44 extends to the tank 12. An open / close valve 45 is interposed in the discharge pipe 44, is normally closed, and is opened by electromagnetic operation. When the main hydraulic cylinder 1 is idled and lowered, the on-off valve 45 is opened to allow the hydraulic oil in the retraction cylinder 8 to escape into the tank.
Further, a pressure regulating valve 46 is interposed between the supply pipe 41 and the discharge pipe 44, and when the main hydraulic cylinder 1 is pressurized and lowered, the hydraulic oil is released to the tank 12 while applying a counter pressure. I have.

  A supply oil tank 15 is provided above the main oil cylinder 1, and the supply oil tank 15 is connected to an oil chamber 1 a of the main hydraulic cylinder 1 via a prefill valve 16. Therefore, hydraulic oil can be supplied to the oil chamber 1a of the main oil chamber cylinder 1 when the slide 4 idles and descends.

An arbitrary type of position sensor 18 for detecting the slide position is attached to the slide 4 so that the slide position can be detected. Further, it is possible to determine whether the process is the first process or the second and subsequent processes from the detection signal of the position sensor 18.
The pressure sensor 32 interposed in the supply pipe 31 is provided to detect the pressure in the oil chamber 1a of the main hydraulic cylinder 1.

The hydraulic press according to the present embodiment is provided with a control unit configured by a computer or the like. The control unit controls opening and closing of the main control valve 11, the auxiliary control valve 56, and other control valves in order to control the operation of the hydraulic press. At the time of this opening / closing control, the descending position of each step of the slide 4 is grasped by a detection signal of the position sensor 18.
Further, the control unit opens the auxiliary control valve 56 to supply the pressure accumulating oil in the accumulator 13 to the main hydraulic cylinder 1 in the first half pressurizing section at the time of pressurizing and lowering in the second and subsequent steps of performing the secondary forming and the subsequent for the same work. Control.

  When the control unit controls the auxiliary control valve 56 to open in the first half pressure increasing section at the time of pressurizing and lowering in the second and subsequent steps, the hydraulic oil supply to the main hydraulic cylinder 1 in the first half pressure increasing section in the second and subsequent steps is performed by the accumulator 13. Since it can be performed, the pressure can be accelerated by absorbing the elastic energy of the machine and the compression volume of the working oil, and the time of the first half pressure rising section in the second and subsequent steps can be reduced.

Next, a press operation by the hydraulic circuit will be described.
As shown in FIG. 2, when the main control valve 11 is switched to the position I, the hydraulic oil discharged from the pump 21 is supplied to the oil chamber 1a of the main hydraulic cylinder 1 through the pump circuit 20 and the first supply circuit 30. As a result, the ram 3 is lowered, and the slide 4 and the upper die 6 are lowered accordingly, so that the molding operation can be performed.
The hydraulic oil in the retraction cylinder 8 is returned to the tank 12 through the second supply circuit 40, the pressure adjustment valve 46, and the discharge pipe 44.

  As shown in FIG. 3, when the auxiliary control valve 56 is opened, the high-pressure accumulated oil in the accumulator 13 is discharged to the hydraulic oil supply pipe 55 and supplied to the oil chamber 1 a of the main hydraulic cylinder 1 through the first supply circuit 30. Is done. Thereby, hydraulic oil can be supplied to the oil chamber 1a of the main hydraulic cylinder 1 in a short time.

Although not shown, when the main control valve 11 in FIG. 1 is switched to the II position, the hydraulic oil discharged from the pump 21 is supplied to the oil chamber 8a of the pullback cylinder 8 through the pump circuit 20 and the second supply circuit 40. . As a result, the ram 3 rises, and accordingly, the slide 4 and the upper mold 6 rise.
The working oil in the oil chamber 1a of the main cylinder 1 is returned to the oil tank 15 through the prefill valve 16 that is opened.

  In the operating method of the present invention, the accumulated pressure in the accumulator 13 may be supplied from the pump 21 by opening the on-off valve 52 with the main control valve 11 in the neutral position and supplying the auxiliary control valve 56 when the main hydraulic cylinder 1 is depressurized. It may be opened and the compressed volume in the main hydraulic cylinder 1 may be supplied to the accumulator 13.

  The operating position of the slide 4 can be grasped by the position sensor 18, and the hydraulic oil pressure in the main hydraulic cylinder 1 can be grasped by the pressure sensor 32. The timing may be determined.

Next, a method of operating the hydraulic press according to the present invention will be described with reference to FIG.
The thin lines indicate the strokes of the slide 4 and the upper mold 6. The thick solid line indicates the press load in the first step, and the thick dotted line indicates the press load in the second step. The following describes the case of (i) a molding method that does not reheat the same work using the same mold.

(First pressurization step)
The first pressurization step is substantially the same as the conventional operation method shown in FIG. 6, but is as follows.
(1) The work is set on the lower mold 7.
(2) The slide 4 is idled down from the stop position, and the upper mold 6 is lowered.
(3) After the upper mold 6 comes into contact with the work, the work is formed at a pressure lowering speed required for the work. During this step, the pressing load increases.
(4) When the first molding completion point is reached, pressurization is completed and pressure is released. This reduces the pressing load rapidly. The lower limit of the first pressurization is indicated by reference symbol LL1.
(5) Raise the slide 4 and the upper mold 6.
(6) The slide is stopped at a preset position for a preset time, and measures necessary for the molding process (such as lubrication of a mold) are performed.

(2nd pressurization process)
(7) The slide 4 and the upper mold 6 are idled and lowered from the stop position, and the upper mold 6 is lowered.
(8) Lower the pressure for the second molding.
In the second molding step, there are a first-half pressurizing section 81 up to the first molding completion point (up to the pressure lower limit LL1) and a second-half molding section 82 thereafter. In FIG. 4, the first and second half boosting sections are indicated by thick dotted lines.

(8-1) The first-half pressurizing section 81 is a section in which the work is hardly formed, and the elastic pressure energy of the mechanical system, the compression volume of the hydraulic oil in the cylinder, and the like are absorbed. In the first half pressure rising section, the hydraulic oil is supplied to the main hydraulic cylinder 1 from the accumulator 13 to perform the rapid supply. This makes it possible to reduce the time required for the first half of the pressure molding.

(8-2) The hydraulic pump 21 supplies hydraulic oil to the main hydraulic cylinder 1 from the first molding completion point (pressurization lower limit LL1) to the second molding completion point (indicated by pressurization lower limit LL2). This latter half pressure rising section is the same as the conventional press operation method.
(9) In the second molding, the press load sharply increases, and the pressing is completed when the molding completion point is reached. Thereafter, the pressure is released. The lower limit of the second pressurization is indicated by reference symbol LL2.
(10) The slide 4 and the upper die 6 are raised, stopped at a preset position, and the work is removed. Then, the operation is stopped until the next work is supplied onto the lower mold.

  In the above operation method, the hydraulic oil replenishment from the accumulator 13 in the above (8-1) may be performed only by the accumulator 13 as described above, or the hydraulic oil replenishment from the pump 21 may be performed simultaneously. Good.

The operation method of the present invention and the conventional operation method are shown in comparison with FIG. The thick dotted line shows the cycle diagram of the second step in the present invention, and the thick solid line shows the cycle diagram in the prior art.
As shown in the figure, in the pressurizing and lowering 8A according to the present invention, since the hydraulic oil is supplied from the accumulator 13 in the first half pressurizing section 81, the rise of the press load becomes steep, and the pressurizing and lowering step 8 in the conventional method is performed. Pressurization is completed earlier than before. For this reason, the press can improve productivity.
In FIG. 5, this cycle shortening time is shown as the difference between the thick dotted line (the present invention) and the thick solid line (the prior art).

  The above effect is achieved by rapidly filling the portion absorbed by the resilient pressure energy of the mechanical system or the compression volume of the hydraulic oil in the cylinder by the supply of the hydraulic oil from the accumulator 13, and the pressurization up to the previous molding completion time is rapidly performed. It is caused by things.

  The replenishment of the hydraulic oil to the main hydraulic cylinder 1 by the accumulator 13 in the present invention does not need to be strictly coincident with the first-half pressurizing section 81, and may be performed in most of the first-half pressurizing section 81. Further, the operation may be performed slightly beyond the first-half boosting section 81 to the beginning of the second-half boosting section. Even in that case, the above effects can be achieved.

  In the subsequent latter pressure rising section, the original second molding is performed by the hydraulic oil supplied by the hydraulic pump 21. That is, the work is pressed from the first lowering lower limit LL1 to the second lowering lower limit LL2. Thereby, molding is completed.

In the above pressure molding, (i) also in the case of the molding method in which the same work is not reheated using the same mold, (ii) after completion of the first molding, reheating is performed, and the second and subsequent times are performed again with the same mold. The same applies to the case where the molding is performed.
In the case of the latter (ii), the first molding is performed in units of one lot, and after completion, the one lot is reheated, and the second molding is performed on the work of this one lot. In this case as well, at the time of the second molding, as in the above, the hydraulic pressure from the accumulator 13 can be used to quickly increase the pressure in the first-half pressurization section of the second process, thereby shortening the press molding time.

(Other embodiments)
The operation method of supplying hydraulic oil to the main hydraulic cylinder 1 by the accumulator in the second and subsequent steps has been described above. However, even in the forming operation including the third step and thereafter, the operation from the accumulator to the main hydraulic cylinder 1 is performed in the same manner as described above. , The press molding time can be reduced.

1 Main Hydraulic Cylinder 4 Slide 5 Bed 6 Upper Die 7 Lower Die 8 Retraction Cylinder 11 Main Control Valve 13 Accumulator 20 Pump Circuit 21 Pump 22 Discharge Pipe 30 First Supply Circuit 31 Supply Pipe 40 Second Supply Circuit 41 Supply Pipe 51 Auxiliary supply circuit 52 On-off valve 55 Pressure oil supply pipe 56 Auxiliary control valve

Claims (6)

A hydraulic press that performs a molding operation by lowering and raising a slide on which an upper mold is attached to a lower mold on a bed,
A main hydraulic cylinder for lowering the slide,
A hydraulic pump and an accumulator as a hydraulic source for the main hydraulic cylinder,
A pump circuit disposed between the main hydraulic cylinder and the hydraulic pump,
A main control valve interposed between the hydraulic pump and the main hydraulic cylinder,
A pressure oil supply pipe disposed between the accumulator and the main hydraulic cylinder, for supplying pressurized oil in the accumulator to the main hydraulic cylinder, and a pressure oil interposed in the pressure oil supply pipe A hydraulic press comprising an auxiliary control valve for controlling replenishment. A control unit for controlling the opening and closing of the auxiliary control valve is provided. The control unit is configured to perform the second forming and the subsequent steps on the same workpiece in the second and subsequent steps. 2. The hydraulic press according to claim 1, wherein the auxiliary control valve is controlled to open so as to supply pressure to the main hydraulic cylinder. A main hydraulic cylinder for lowering the slide for lowering the slide on which the upper die is attached to the lower die on the bed to perform the molding operation, and a hydraulic pump and an accumulator as a hydraulic source for the main hydraulic cylinder A hydraulic press operating method comprising:
The molding operation performed using the hydraulic press,
It includes a first step of performing primary molding and a second and subsequent steps of performing secondary molding and thereafter.
The first step is performed using hydraulic oil supplied by the hydraulic pump,
In the second and subsequent steps, the operation is performed using hydraulic oil supplied by an accumulator in the first half pressure rising section at the time of pressurizing and descending, and using hydraulic oil supplied by the hydraulic pump in the second half pressure rising section at the time of pressurizing and falling. Operating method of hydraulic press. 4. The hydraulic press operating method according to claim 3, wherein the forming operation is a multi-step forming operation in which the same work is formed in a plurality of times with the same mold without reheating. The method of operating a hydraulic press according to claim 3, wherein the forming operation is a multi-step forming operation of forming a heated work, reheating the formed work, and forming the work again with the same mold. 4. The method according to claim 3, wherein the hydraulic oil is supplied to the accumulator from a hydraulic pump or from a main hydraulic cylinder when the main hydraulic cylinder is depressurized.

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