JP3201889B2 - Hydraulic press equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic press device for obtaining a pressing force by driving a cylinder with hydraulic pressure from a hydraulic pressure source.

[0002]

2. Description of the Related Art Conventionally, for example, a pressing process using a hot press forming apparatus such as thermoforming or laminating, in which a heated and softened resin sheet is pressed with a curved mold and drawn, is used.
After the object to be pressed (molding material) is inserted (molded) between the hot plates, the mold is clamped, and then pressurizing and heating are performed at a predetermined molding pressure for a predetermined time. In a hydraulic press device that obtains a pressurizing force by driving a cylinder with a hydraulic pressure from a hydraulic pressure source, control of the pressurizing force is performed by adjusting a hydraulic pressure supplied to the cylinder.

For example, based on information from a pressure sensor that detects a hydraulic pressure acting on a cylinder, an electromagnetic relief valve that can continuously adjust a set pressure provided in a hydraulic path from a hydraulic source to the cylinder is operated and controlled. In addition, the hydraulic pressure acting on the cylinder is controlled by controlling (ON, OFF) the operation of a pump as a hydraulic pressure source. By the way, it is desirable that the clamping after the pressurized object is put into the mold is performed as quickly as possible from the viewpoint of work efficiency. For that purpose, it is necessary to provide a hydraulic source (hydraulic pump) having a large discharge amount. Here, if it is intended to cover all of the mold pressing and molding pressurization with the hydraulic pressure from one hydraulic pump, a large capacity is required to satisfy the above-mentioned demands for faster mold clamping and high output pressurization. Hydraulic pump is required, and the valve size of the hydraulic control is also increased, which increases both equipment cost and running cost. Therefore, dedicated pumps are provided for pressurization and mold clamping respectively. Is being done. In this case, the hydraulic pressure from the pump for exclusive use of mold clamping is set so that the set pressure becomes a predetermined mold clamping pressure (or is feedback-controlled based on information from a pressure sensor that detects the hydraulic pressure acting on the cylinder). Controlled by an unload valve.

[0004]

However, in the hydraulic control structure for controlling the mold clamping oil pressure by the unload valve as described above, the mold clamping is caused by factors such as a surge pressure (and a control response delay) generated when the unload valve operates. Pressurization (overrun) with a force higher than the force required for molding, and there is a problem that molding failure occurs. The occurrence of such molding defects often occurs particularly when molding is performed with a pressing force close to the mold clamping pressure.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic press apparatus which prevents overrun of a mold clamping force and enables forming with an appropriate pressing force, and a method of controlling the pressing force.

In order to achieve the above object, in the press apparatus of the present invention, preferably, at least two small-diameter and large-diameter cylinders are arranged in series, and the hydraulic source and the small-diameter cylinder are connected to the first cylinder. To supply the pressurized oil from the hydraulic pressure source to the small-diameter cylinder so that the small-diameter cylinder can be moved.
When the hydraulic pressure supplied to the small-diameter cylinder becomes equal to or higher than the set pressure, the sequence valve opens to supply the pressurized oil to the large-diameter cylinder via the second pipeline branched from the first pipeline to press the small-diameter cylinder. enable. In the small-diameter cylinder, the pressure receiving area is set to a size such that the pressing force due to the surge pressure generated when the sequence valve is opened is smaller than the minimum forming pressure. Pressure oil is supplied from the first pipeline. Further, the set pressure of the sequence valve is set to a pressure equal to or higher than the mold clamping pressure by the small diameter cylinder, so that the supply of the pressurized oil from the second pipeline to the large diameter cylinder is performed after the mold clamping is completed. The second pipe is provided with a relief valve in the middle thereof to reduce the pressure oil flowing out of the sequence valve, and supplies the reduced pressure oil to the large-diameter cylinder. In the above-mentioned hydraulic press device, when a workpiece is inserted, first, pressurized oil is supplied from the first conduit to the small-diameter cylinder, and the small-diameter cylinder is advanced toward the workpiece, abutted, and clamped. During this process,
Since the pressure receiving area of the small-diameter cylinder is small, the operation is performed quickly. On the other hand, during this time, no pressure oil is supplied to the large-diameter cylinder. When the mold clamping is completed, the pressure in the first line increases, and the sequence valve in the second line branched from the first line opens. At this time, a surge pressure is generated. However, since the pressure receiving area of the small-diameter piston is set so as not to be the minimum molding pressure even when the surge pressure is received, the workpiece does not have molding failure. When the sequence valve opens, the pressure oil depressurized by the relief valve acts on the large pressure receiving area of the large-diameter cylinder via the second conduit, and presses the small-diameter cylinder against the workpiece with the pressure applied by the above clamping pressure. , Press molding. After the molding is completed, the first and second conduits are drained, and the cylinder returns to the non-pressurized position due to the weight of the cylinder. More preferably, the relief valve is an electromagnetic relief valve controlled by a controller based on a signal from a pressure sensor that detects a pressure in the second conduit. Thereby, while feeding back the pressure of the second conduit,
Produces optimal pressure oil for large diameter cylinders. Preferably, a relief valve for adjustment set to be equal to or higher than the maximum dead pressure of the electromagnetic relief valve is provided between the sequence valve and the pressure sensor. As a result, even if an electromagnetic relief valve having insensitivity in the low pressure range is used, the relief valve for adjustment reduces the insensitive pressure component. Supply.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a hydraulic circuit diagram of a hydraulic press device to which the hydraulic press device and the pressurizing force control method of the present invention are applied. As shown in the drawing, the cylinder 10 that drives the hydraulic press device has a double structure in which the first cylinder 11 is a ram and the second cylinder 12 is formed, and the first cylinder 11 and the second cylinder 12 are connected in series. It functions in the same way as when connected.

The pressure receiving area of the ram of the first cylinder 11 is smaller than the pressure receiving area of the ram of the second cylinder 12,
With the same oil supply amount, the first cylinder 11 operates faster, and when the same oil pressure acts, the second cylinder 12 can obtain a larger driving force (pressurizing force). The setting of the pressure receiving area of the ram of the first cylinder 11 will be described later in detail. The first cylinder 11 is connected to a hydraulic pressure source 20 by a first conduit 21 so as to be supplied with hydraulic pressure.
A second pipeline 22 branched from the vicinity of the hydraulic pressure source 20 of the first pipeline 21 is connected to supply hydraulic pressure.

A check valve 31 for preventing a backflow of hydraulic oil is provided on the hydraulic power source 20 side from a branch position of the first pipe line 21 and the second pipe line 22. In the first conduit 21,
On the way, the lowering valve 3 which is a 2-port 2-position switching valve
2 is provided, and by switching the descending valve 32, the hydraulic oil in the first pipeline 21 is discharged to the outside, so that the hydraulic pressure in the first pipeline 21 can be reduced. It has become. In the second pipeline 22, a sequence valve 33 and a relief valve 34 are provided in series with the sequence valve 33 on the hydraulic pressure source 20 side and a discharge port (tank port) on the second cylinder 12 side, respectively.

The pipeline 22A on the second cylinder 12 side from the relief valve 34 and the pipeline 2 on the hydraulic pressure source 20 side from the relief valve 34
2B is connected by a pipe 22C bypassing the relief valve 34, and a check valve 35 is installed in the pipe 22C. When the pressure of the pipe 22A is higher than that of the pipe 22B, the operating oil is supplied to the pipe 22C. The pressure is released to the side 22B, and the pressure in the line 22A can always be controlled by the pressure in the line 22B. The pipe 22B between the sequence valve 33 and the relief valve 34 branches to the pipe 23, and the pipe 23 is provided with an electromagnetic relief valve 37 via a filter 36. Pressure setting of the electromagnetic relief valve 37 (second cylinder 12
Is different from the pressure of the controller 4 based on a control signal from a control device (not shown) for controlling the entire apparatus.
0 is performed by sending a predetermined signal to the electromagnetic relief valve 37. The control device is programmed to automatically change the pressure with the operation of the entire device, or is configured to be adjustable by manual operation.

The second cylinder 12 is controlled by a relief valve 34.
The hydraulic pressure in the pipeline 22A (= the hydraulic pressure of the second cylinder 12) detected by the pressure sensor 41 provided in the side pipeline 22A is configured to be input to the controller 40. It is configured to perform feedback control by comparing with a set pressure. Here, the electromagnetic relief valve 37 generally has an insensitive range (that is, a range in which pressure cannot be controlled) in a low pressure range due to a mechanical structural factor. With this configuration, the hydraulic pressure supplied to the second cylinder 12 can be controlled in a range from 0 to the maximum output.

That is, for example, when the maximum dead pressure of the electromagnetic relief valve 37 is 10 kg / cm ² , the set pressure of the relief valve 34 is set to 10 kg / cm ² (more than the maximum dead pressure of the electromagnetic relief valve 37) and The pressure of the electromagnetic relief valve 37 is set so that the difference between the set pressure of the electromagnetic relief valve 37 and the set pressure of the relief valve 34 becomes a desired pressure. That is, 1
When a pressure of kg / cm ² is desired, the set pressure of the electromagnetic relief valve 37 may be set to 11 kg / cm ² . By setting in this manner, the hydraulic oil discharged from the hydraulic power source 20 has a pressure of 1
If it does not exceed 0 kg / cm ² , it will not flow to the second cylinder 12. (In this state, since the pressure sensor 41 does not detect the oil pressure, the electromagnetic relief valve 37 is in the closed state.) The hydraulic pressure source 20
When the pressure in the pipeline 22B on the side becomes 11 kg / cm ² or more, the electromagnetic relief valve 37 operates to maintain the pressure in the pipeline 22B on the hydraulic power source 20 side at 11 kg / cm ² . As a result, the pressure of the cylinder side pipe line 22A via the relief valve 34, that is, the pressure of the second cylinder 12, is maintained at 1 kg / cm ² .
That is, by setting the set pressure of the electromagnetic relief valve 37 arbitrarily to a value equal to or higher than the set pressure of the relief valve 34, the pressure on the second cylinder 12 is reduced from 0 to the maximum output (= the maximum set pressure of the electromagnetic relief valve 37 −the relief valve). (Set pressure of 34). The pressure acting on the second cylinder 12 is a value obtained by subtracting the set pressure of the relief valve 34 from the set pressure of the electromagnetic relief valve 37. However, the controller 40 does not need to have a control configuration for performing such calculation. It can be controlled by ordinary feedback control based on the oil pressure information from the pressure sensor 41.

The type and structure of the electromagnetic relief valve 37 and the relief valve 34 are not particularly limited, and any known type can be used. However, from the viewpoint of excellent override pressure characteristics, a balanced piston type relief valve is preferred. It is preferable to use Thus, according to the hydraulic circuit of the hydraulic press device as described above, the first cylinder 11 having a small pressure receiving area quickly performs mold clamping so that the pressing force does not overrun beyond the forming pressure, and then the controller 40
The forming pressure can be increased by the second cylinder 12 having a large pressure receiving area to which the hydraulic pressure controlled by the (electromagnetic relief valve 37) is supplied. That is, when the pressure is equal to or less than the set pressure of the sequence valve 33, the hydraulic pressure does not act on the second pipe 22, but acts only on the first cylinder 11 via the first pipe 21. If the first cylinder 11 is set to a hydraulic pressure that generates a mold clamping pressure, the hydraulic pressure source 20
After the start of driving, only the first cylinder 11 is driven, and the first cylinder 11 completes mold clamping with a predetermined pressing force.

Here, the first cylinder 11 receives its pressure so that the pressure applied when a surge pressure generated when the sequence valve 33 operates is smaller than the minimum forming pressure (by the second cylinder 12). Set the area. As a result, it is possible to prevent occurrence of molding failure due to overrun of the pressing force after the completion of the mold clamping by the first cylinder 11. In addition, when the pressure oil supply amount is constant, the operating speed of the hydraulic cylinder is inversely proportional to the pressure receiving area, so that the first cylinder 11 having a small pressure receiving area can clamp the mold very quickly. Needless to say, the pressure receiving area of the second cylinder 12 is set such that a desired maximum pressure is obtained by the hydraulic pressure controlled by the electromagnetic relief valve 37.

After completion of mold clamping as described above, when the sequence valve 33 is opened at a pressure equal to or higher than the set pressure and the same hydraulic pressure acts on the first conduit 21 and the second conduit 22, the electromagnetic relief valve 37 is operated as described above. Thus, the hydraulic pressure acting on the second cylinder 12 can be controlled to set the molding pressure. In the early stage of the operation of the second cylinder 12, the pressing forces of the first cylinder 11 and the second cylinder 12 are balanced, and the second cylinder 1
The first cylinder 11 is pressed by the pressing force of 2,
The oil in the first cylinder 11 escapes (is supplied) to the second pipe 22 via the first pipe 21, and the first cylinder 11 contracts, and the first cylinder 11 clamps the mold. The molding pressure is started from the state where the second cylinder 12 takes over the pressure. That is, when the hydraulic pressure from the hydraulic pressure source 20 is equal to or higher than the set pressure of the sequence valve 33, the pressing force of the second cylinder 12 controlled by the electromagnetic relief valve 37 becomes the pressing force (including the mold clamping pressure) of the press device, A desired molding pressure can be set by controlling the hydraulic pressure acting on the second cylinder 12 as described above.

After the molding is completed, the lowering valve 32 of the first conduit 21 is opened, and the set pressure of the electromagnetic relief valve 37 is reduced to zero.
By doing so, the oil pressure in the first pipeline 21 and the second pipeline 22 is reduced. In the above embodiment, the cylinder 10
Is configured as a double structure, but may be configured by arranging two independent cylinders in series, and the pattern of the hydraulic circuit is not limited to that shown in FIG.
It can be changed as appropriate.

[0017]

According to the press apparatus according to the present invention, the pressurized oil is supplied to the small-diameter cylinder having a small pressure receiving area to quickly move the small-diameter cylinder toward the workpiece and mold clamping, and after the mold clamping, the large cylinder is moved to a large diameter. By supplying the decompressed oil to the large-diameter cylinder of the pressure receiving area, the pressure of this large-diameter cylinder is added, and the small-diameter cylinder is pressed, thereby reliably forming without requiring an excessive hydraulic pump capacity. can do. In addition, in this process, even after the mold is clamped and the sequence valve is opened and a surge pressure is generated, the pressure receiving area of the small-diameter cylinder becomes smaller than the minimum forming pressure by the large-diameter cylinder operation even if the surge pressure acts. Because of the size, even when the molding pressure is close to the mold clamping pressure, the molding pressure does not overrun the molding pressure or more, so that there is no occurrence of molding failure of the workpiece.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic press device to which a hydraulic press device and a pressing force control method thereof according to the present invention are applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cylinder 11 ... 1st cylinder (small diameter cylinder) 12 ... 2nd cylinder (large diameter cylinder) 20 ... Hydraulic power source 21 ... 1st pipeline (1st hydraulic path) 22 ... 2nd pipeline ( (Second hydraulic path) 33 ... sequence valve 34 ... relief valve 37 ... electromagnetic relief valve (pressure control valve)

Claims (3)

(57) [Claims] At least two small-diameter and large-diameter cylinders are arranged in series, and a hydraulic pressure source and the small-diameter cylinder are connected to a first cylinder.
Connected via the pipeline, supplies pressure oil from the hydraulic pressure source to the small-diameter cylinder to allow the small-diameter cylinder to move, and when the supply hydraulic pressure to the small-diameter cylinder becomes equal to or higher than a set pressure, the sequence valve opens. In a hydraulic press device capable of supplying pressure oil to the large-diameter cylinder through a second pipeline branched from the first pipeline and pressing the small-diameter cylinder, the small-diameter cylinder has a pressure-receiving area. The pressure by the surge pressure generated when the sequence valve is opened is set to be smaller than the minimum molding pressure, and the pressure from the first pipe line is set during the period from the movement of the small-diameter cylinder to the molding. Oil is supplied, and the sequence valve sets the set pressure to a pressure equal to or higher than the mold clamping pressure by the small-diameter cylinder, and supplies the pressurized oil from the second pipeline to the large-diameter cylinder. After the mold clamping is completed, the second pipeline has a relief valve to reduce the pressure oil flowing out of the sequence valve and supply the reduced pressure oil to the large-diameter cylinder. A hydraulic press device, characterized in that: 2. The relief valve according to claim 1, wherein the relief valve is an electromagnetic relief valve controlled by a controller based on a signal from a pressure sensor for detecting a pressure in the second conduit. Hydraulic press equipment. 3. The relief valve according to claim 2, further comprising an adjustment relief valve set between the sequence valve and the pressure sensor, the adjustment relief valve being set to a maximum inoperative pressure of the electromagnetic relief valve. Hydraulic press device.