JPH0455099A - Hydraulic press device and method for controlling pressurizing force - Google Patents

Abstract

PURPOSE:To prevent a molding defect with the hydraulic press device by arranging two pieces of cylinders which vary in diameter in a series state and controlling die clamping force and pressurizing force. CONSTITUTION:The cylinder 10 of the hydraulic press device which obtains the pressurizing force by driving the cylinder 10 with the oil pressure from a hydraulic source 20 is constituted by arranging two pieces of the 1st and 2nd cylinders 11 and 12 having different diameter in series. The die clamping is executed by the 1st cylinder 11 of a small diameter and the molding is executed by controlling the pressurizing force with the 2nd cylinder 12 of a large diameter. The overrun of the pressurizing force from the die clamping to the molding pressurization is extremely lessened in this way and the molding defect is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a hydraulic press device that obtains pressurizing force by driving a hydraulic cylinder from a hydraulic source, and a pressurizing force control method thereof.

[Prior Art] Conventionally, the process of pressing using a thermoforming press machine, such as thermoforming or lamination molding, in which a heated and softened resin sheet is compressed and drawn with a curved mold, is performed using a hot plate. After inserting (molding) the pressurized object (molding material) in between, the mold is clamped,
After that, it is pressurized and heated at a predetermined molding force for a predetermined period of time.

In a hydraulic press device that obtains pressurizing force by driving a cylinder using hydraulic pressure from a hydraulic source, the pressurizing force is controlled by adjusting the hydraulic pressure supplied to the cylinder.

For example, based on information from a pressure sensor that detects the oil pressure acting on a cylinder, the operation of an electromagnetic relief valve that continuously adjusts the set pressure provided in the hydraulic path from the oil pressure source to the cylinder may be controlled. It controls the operation (ON, OFF) of the pump, which is the hydraulic pressure source, to control the hydraulic pressure acting on the cylinder.

By the way, it is desirable to close the mold as quickly as possible from the point of view of work efficiency after putting the pressurized object into the mold, and for that purpose it is necessary to have a hydraulic source (hydraulic pump) with a large discharge volume. .

If we try to cover everything from mold clamping to molding pressure using the hydraulic pressure from a hydraulic pump, it is necessary to have a large capacity in order to satisfy the above-mentioned requirements for rapid mold clamping and high output pressure. A separate hydraulic pump is required, which also increases the size of the hydraulically controlled valve, increasing equipment costs and running costs. Therefore, separate pumps are provided for pressurization and mold clamping. Configuring is being done.

In this case, the hydraulic pressure from the pump dedicated to mold clamping is set to the set pressure or 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.

[Problem to be solved by the invention] However, as described above, the hydraulic control configuration in which the mold clamping hydraulic pressure is controlled by the unload valve has problems such as surge pressure (and control response delay) that occurs when the unload valve is activated. For some reasons, the pressure exceeds the force required for mold clamping (overrun), resulting in molding defects. Such molding defects often occur particularly when molding is performed using a pressure close to the mold clamping pressure.

[Object of the Invention] An object of the present invention is to provide a hydraulic press device and a method for controlling the pressure force thereof, which prevent overrun of mold clamping force and enable molding with an appropriate pressure force.

[Structure of the Invention] In order to achieve the above-mentioned object, in the present invention, at least two cylinders with different diameters are arranged in series as drive cylinders, and as a control method, /JS diameter Hydraulic pressure is supplied to the cylinder to perform mold clamping with a predetermined pressurizing force, and then hydraulic pressure is supplied to the large diameter cylinder and the pressurizing force is controlled by controlling this oil pressure.

In addition, at least two cylinders with different diameters are arranged in series, and a first hydraulic path supplies hydraulic pressure from a hydraulic source to a small-diameter cylinder, and a first hydraulic path branches out from the first hydraulic path to supply a predetermined set pressure. a second hydraulic path that supplies hydraulic pressure to the large-diameter cylinder through the sequence valve, and the second hydraulic path includes a pressure control valve that controls the hydraulic pressure of the second hydraulic path; A relief valve is provided on the cylinder side of the pressure control valve and is capable of setting a pressure higher than the maximum insensitive pressure of the pressure control valve.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described 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 pressurizing force control method of the present invention are applied.

The cylinder lO that operates and drives the hydraulic press device includes a first cylinder 11 as a ram and a second cylinder 12 as shown in the figure.
It has a double structure, with the first cylinder 11
It functions in the same way as when the second cylinder 12 and the second cylinder 12 are connected in series.

The pressure receiving area of the ram of the first cylinder 11 is the second cylinder I
Therefore, for the same amount of pressure oil supplied, the second cylinder 12 operates faster than the first cylinder 11, and when the same hydraulic pressure is applied, the second cylinder 12 has a larger driving force (applied force). pressure).

Note that the setting of the pressure receiving area of the ram of the first cylinder 11 will be described in detail later.

The first cylinder 11 is connected to a hydraulic power source 20 and a first pipe line 21 so that hydraulic pressure is supplied thereto, and the second cylinder 12 is connected to a hydraulic power source 20 of the first pipe line 21 and supplied with hydraulic pressure.
A second pipe line 22 branched from the vicinity is connected to supply hydraulic pressure.

A check valve 31 is provided on the side of the hydraulic power source 20 from the branching position of the first pipe line 21 and the second pipe line 22 to prevent backflow of hydraulic oil.
or installed.

The first pipe line 21 is provided with a descending valve 32, which is a two-bottom, two-position switching valve, in the middle thereof, and by switching the descending valve 32, the flow in the first pipe line 21 is The hydraulic oil can be discharged to the outside to lower the oil pressure in the first pipe line 21.

The second pipe line 22 includes a sequence valve 33 and a relief valve 3.
4 or 4 are interposed in series with the sequence valve 33 facing the hydraulic power source 20 and the respective discharge ports (tank boat) facing the second syringe 12.

A pipe line 22A on the second cylinder 12 side from the relief valve 34 and a pipe line 22B on the hydraulic source 20 side from the relief valve 34 are connected by a pipe line 22C that bypasses the relief valve 34, and a check valve is provided in the pipe line 22C. 35 installed, pipe 22A
If the pressure is higher than that of pipe 22B, the hydraulic oil is
It is released to the B side, and the pressure of the pipe 22B is constantly released to the pipe 22A.
It is constructed so that the pressure can be controlled.

Moreover, the pipe line 22 between the sequence valve 33 and the relief valve 34
B branches into a conduit 23, and the conduit 23 is equipped with a filter 36.
An electromagnetic relief valve 37 is installed via the.

The pressure setting of the electromagnetic relief valve 37 (different from the pressure of the second cylinder 12) is determined by the controller 40 sending a predetermined signal to the electromagnetic relief valve 37 based on a control signal from a control device (not shown) that controls the entire device. This is done by sending. The control device may be programmed to automatically change the pressure as the entire device operates, or may be configured to be adjustable manually.

Also, the pipe line 22 on the second cylinder 12 side from the relief valve 34
Pipe line 2 detected by pressure sensor 41 provided at A
2A (=hydraulic pressure of the second cylinder 12) is input to the controller 40, and the controller 40 is configured to compare this detected pressure with a set pressure and perform feedback control.

Generally, the electromagnetic relief valve 37 has a dead area (i.e., a range where pressure cannot be controlled) in the low pressure area due to its mechanical structure, or the electromagnetic relief valve 37 has a dead area (i.e., an area where pressure cannot be controlled) in the low pressure area, or the Due to the configuration, the hydraulic pressure supplied to the second cylinder 12 can be controlled in the range from O to the maximum output.

In other words, 1, for example, the maximum dead area pressure of the electromagnetic relief valve 37
OK kg/c■2, the set pressure of the relief valve 34 is set to 10 kg/cm" (more than the maximum insensitive pressure of the electromagnetic relief valve 37), and the set pressure of the electromagnetic relief valve 37 and the setting of the relief valve 34 are Set the pressure of the electromagnetic relief valve 37 so that the pressure is the same as the desired pressure.In other words, if you want a pressure of 1 kg/c 2, set the pressure of the electromagnetic relief valve 37 to 11 kg/c 2. Good.

With this setting, the hydraulic fluid discharged from the hydraulic source 20 will not flow to the second cylinder 12 unless the pressure reaches 10 kg/c2 or more (in this state, the pressure sensor 41 does not detect the hydraulic pressure). , the electromagnetic relief valve 37 is in a closed state.) When the pressure in the pipe line 22B on the side of the hydraulic source 20 reaches 11 kg/c or more, the electromagnetic relief valve 37 operates and the hydraulic source 20
The pressure in the side pipe line 22B is maintained at 11 kg/cm". As a result, the pressure in the cylinder side pipe line 22A via the relief valve 34, that is, the pressure in the second syringe 12, is 1 kg/cm".
It will be held at c■2.

In other words, the set pressure of the electromagnetic relief valve 37 is
By arbitrarily setting the pressure to the second cylinder 12 above the set pressure of 4, it is possible to arbitrarily control the pressure to the second cylinder 12 from 0 to the maximum output (=maximum set pressure of the electromagnetic relief valve 37, set pressure of the car relief valve 34). It is something. In addition, the pressure acting on the second cylinder 12 is the value obtained by subtracting the set pressure of the relief valve 34 from the set pressure of the electromagnetic relief valve 37, or
The controller 40 does not need to have a control configuration that performs such calculations, and can be controlled by normal feedback control based on oil pressure information from the pressure sensor 41.

In addition, the types of the electromagnetic relief valve 37 and the relief valve 34,
The structure is not particularly limited, and it is preferable to use a balanced piston type relief valve from the viewpoint that any known one can be used or that it has excellent override pressure characteristics.

According to the hydraulic circuit of the hydraulic press device as described above, mold clamping is performed quickly by the first cylinder 11 having a small pressure receiving area and without overrunning the pressurizing force or molding pressurizing force, and then the controller 40 Molding pressure can be applied by the second cylinder 12, which has a large pressure-receiving area and is supplied with hydraulic pressure controlled by an electromagnetic relief valve 37.

In other words, below the set pressure of the sequence valve 33, the hydraulic pressure does not act on the second pipe line 22 and acts only on the first cylinder 11 via the first pipe line 21, so that the set pressure of the sequence valve 33 If set to a hydraulic pressure that generates mold clamping pressure in the first cylinder 11, only the first cylinder 11 will be driven after the hydraulic power source 20 starts driving, and mold clamping will be completed with a predetermined pressure applied by the first cylinder 11. do.

Here, the first cylinder 11 is caused by the surge pressure generated when the sequence valve 33 is activated, or by the pressure applied when the sequence valve 33 is activated.
The pressure receiving area is set so as to be smaller than the minimum molding pressure (by the second cylinder 12). This prevents molding defects from occurring due to overrun of the pressurizing force after the first silicitor 11 completes mold clamping. Also, if the pressure oil supply amount is constant, the operating speed of the hydraulic cylinder is inversely proportional to the pressure receiving area, so if the first cylinder 11 has a small pressure receiving area.
The mold can be tightened extremely quickly. It goes without saying that the pressure receiving area of the second cylinder 12 is set so that a desired maximum pressing force can be obtained by the hydraulic pressure controlled by the electromagnetic relief valve 37.

After the mold clamping is completed as described above, when the sequence valve 33 is opened at a pressure higher than the set pressure and the same hydraulic pressure is applied to the first pipe line 21 and the second pipe line 22, the electromagnetic relief valve 37 is opened as described above.
By controlling the hydraulic pressure acting on the second cylinder 12, the molding pressure can be set.

At the initial stage of operation of this second cylinder 12, the first cylinder 1
1 and the pressure force of the second cylinder 12 are balanced, the pressure force of the second cylinder 12 presses the first cylinder 11, and the oil in the first cylinder 11 flows through the first pipe line 21 to the second pipe line. 22, the first cylinder 11 contracts, and the second cylinder 12 takes over the mold clamping pressure from the first cylinder 11, and molding pressure starts.

In other words, when the hydraulic pressure from the hydraulic source 20 is equal to or higher than the set pressure of the sequence valve 33, the pressurizing force of the second cylinder 12 controlled by the electromagnetic relief valve 37 becomes the pressurizing force of the press device (including the tightening pressurizing force!), A desired molding force 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 pipe line 21 is opened, and the set pressure of the electromagnetic relief valve 37 is set to 0, thereby reducing the pressure inside the first pipe line 21 and the second pipe line 22. Reduce oil pressure.

In the above embodiment, the cylinder lO may be configured as a double structure, or two independent cylinders may be arranged in series, and the pattern of the hydraulic circuit may also be similar to that shown in FIG. It is not limited to what is shown in , but can be changed as appropriate.

[Effects of the Invention] According to the hydraulic press device and its pressurizing force control method according to the present invention, two cylinders with different diameters are arranged in series and driven, and mold clamping is performed by the small diameter cylinder. In addition, by controlling the pressure force by controlling the hydraulic pressure supplied to the large-diameter cylinder, it is possible to extremely minimize the overrun of the pressure force from mold clamping to molding pressure. Even when the pressurizing force is close to the mold clamping pressure, it is possible to prevent molding defects due to the pressurizing force overrunning the molding pressurizing force.

In addition, mold clamping can be performed quickly by using a small diameter cylinder, and since the molding pressure is obtained using a large diameter cylinder, an excessive hydraulic pump capacity is not required, reducing equipment costs. and can contribute to reducing running costs.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic press device to which the hydraulic press device and pressurizing force control method of the present invention are applied. lO...Cylinder 11...First cylinder (small diameter cylinder) 12...
Second cylinder (large diameter cylinder) 20... Hydraulic source 21... First pipe line (first hydraulic path) 22... Second pipe line (second hydraulic path) 33... Sequence valve 34...relief valve

Claims (3)

[Claims] (1) A hydraulic press device that obtains pressurizing force by driving a cylinder with hydraulic pressure from a hydraulic source, and is constructed by arranging at least two cylinders with different diameters in series. . (2) Hydraulic pressure is supplied to a small-diameter cylinder to perform mold clamping with a predetermined pressure, and then hydraulic pressure is supplied to a large-diameter cylinder and the pressure is controlled by controlling this hydraulic pressure. A pressurizing force control method for a hydraulic press device according to claim (1). (3) A pressurizing force is obtained by driving a cylinder with hydraulic pressure from a hydraulic source, and at least two cylinders with different diameters are arranged in series, and hydraulic pressure is applied from the hydraulic source to a cylinder with a small diameter. A first hydraulic path for supplying hydraulic pressure, and a second hydraulic path branching from the first hydraulic path and supplying hydraulic pressure to a large diameter cylinder via a sequence valve having a predetermined set pressure, The second hydraulic path includes a pressure control valve that controls the hydraulic pressure of the second hydraulic path, and a relief valve that can be set to a maximum insensitive pressure of the pressure control valve or more on the cylinder side of the pressure control valve. A hydraulic press device characterized by: