JPH0744399Y2 - Die cushion preliminary lowering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a preliminary lowering device for a die cushion provided in a press.

[Conventional technology]

A die cushion conventionally provided in a press has a structure that elastically supports a lower die cushion pad provided in the vicinity of a lower die via a plurality of die cushion pins,
When the upper mold that descends along with the slide comes into contact with the lower mold cushion pad and a press load is applied to the lower mold cushion pad, the pressure in the cushion cylinder that supports the die cushion pad from below is discharged, and the upper mold and lower mold cushion pad are discharged. The pad also descends by the cushion stroke.

[Problems to be solved by the device]

However, when performing press molding using the above die cushion, when the upper mold that descends with the slide collides with the lower mold cushion pad, the lower mold cushion pad and the die cushion pin collide, and a large pin touch noise is generated, which causes noise. There was a problem that caused In order to improve such a problem, for example, in Japanese Patent Laid-Open No. 63-63536, a pin detector position is detected by a position detector such as a limit switch, and pressure oil is supplied to an upper oil chamber of a hydraulic cushion cylinder by a signal from the detector. A die cushion device has been proposed which is supplied to push down the cushion pad.

However, the die cushion device of the above publication has a problem that the position of the position detector must be adjusted each time the mold is replaced and the pin-touch position changes, which makes the work complicated.

Further, in the above-mentioned publication, since the lower hydraulic pressure of the hydraulic cushion cylinder is released by the relief valve, the cushioning ability is constant, and as a result, surge pressure is generated immediately after the die comes into contact with the material, and an indentation is formed on the molded product. There are also defects such as scratches and the like, which lowers the quality of the molded product.

The present invention has been made in order to improve the above-mentioned problems, and a preliminary lowering device for a die cushion that reduces the noise during impact by lowering the lower cushion pad immediately before the upper mold collides with the lower cushion pad. Is to provide.

[Means and Actions for Solving the Problems]

In order to achieve the above-mentioned object, the present invention is one in which a lower mold cushion pad provided in the vicinity of a lower mold installed on a bolster of a press body is elastically supported by a die cushion via a die cushion pin. Detects the slide speed and slide acceleration at the pin touch position where the upper die, which descends with the slide that is vertically movable on the main body, collides with the lower die cushion pad, and calculates the flow rate required for preliminary lowering from the slide speed. And controls the discharge flow rate of a variable displacement pump that supplies hydraulic pressure to the upper chamber of the locking device provided under the cushion cylinder of the die cushion, and according to the cushioning capacity calculated from the slide acceleration, the locking device The lower cushion pad is controlled by controlling the servo valve connected to the lower chamber. Which it was so as to control the acceleration, since the lower mold cushion pad just before the upper die collides with the lower mold cushion pad is preliminarily lowered, can be reduced in noise by Pintatchi sound.

In addition, by controlling the cushioning ability according to the slide acceleration at the pin touch position, surge pressure that causes indentations or scratches on the molded product does not occur in the lower chamber of the locking device.

〔Example〕

 An embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, reference numeral 1 is a press body, and a lower mold 2 is placed on a bolster 1a, and a lower mold cushion pad 2a provided around the lower mold 2 is a plurality of die cushions provided in the bolster 1a. It is elastically supported by the die cushion 4 via the pin 3.

The die cushion 4 is composed of a die cushion pad 5 that supports the die cushion pins 3 from below and a cushion cylinder 6 that supports the die cushion pad 5. Below the cushion cylinder 6, the cushion speed is controlled by NC control. A locking device 8 is provided.

The locking device 8 has three chambers 8 ₁ , 8 ₂ and 8 ₃ divided by pistons 8 a and 8 b, and each chamber 8 ₁ to 8 ₃ is an NC die cushion tank unit by a pipe line 9.
Connected to 10.

A preliminary lowering device 11 of the present invention is connected in the middle of the conduit 9.

The preliminary lowering device 11 has a variable displacement pump 13 whose swash plate angle is controlled by a control device 12, and the discharge pressure of this pump 13 is passed through a locking valve 14 to the upper chamber of the locking device 8.
8 ₁ is supplied to the die cushion 4, and the die cushion 4 is preliminarily lowered as follows.

The operation will be described below with reference to the flow chart shown in FIG. 2. The pressures of the upper chamber 8 ₁ and the lower chamber 8 ₃ are detected by the two pressure detectors 15 and 16 and input to the control device 12, respectively. Further, a crank angle is input from an electronic rotary cam 17 provided in a slide drive mechanism (not shown) of the press body 1, and a rotation speed of the main motor is input from a rotation detector 18.

Now, from the slide top dead center, when the upper die 21 attached to the slide 20 starts descending together with the slide 20, the control device
The reference numeral 12 designates the position of the slide 20 based on the signal input from the electronic rotary cam 17, the press speed based on the signal input from the rotation detector 18, and the pull-down force FA based on the signals input from the pressure detectors 15 and 16. , NC die cushion capacity FB
Is calculated, and the slide acceleration a and the slide speed V at the pin touch position are calculated from the preset pin touch position press speed.

Then, by correcting these by the slide position, the NC die cushion capacity f which becomes the above-mentioned slide acceleration a at the pin touch position and the flow rate q which becomes the slide speed V are calculated respectively, and the pull down force FA and the NC die cushion capacity FB are calculated. The calculated pad pull-down force F (F = FA-FB) is compared with the NC die cushion capability f that is the slide acceleration a at the pin touch position (ΔF = F-f), and the pressure B required for the cushion action is calculated, NC die cushion tank unit 10
The servo valve 22 provided inside is set to this value B.

At the same time, the required flow rate A is calculated from the flow rate q for achieving the slide speed V at the pin touch position, and the variable displacement pump
The swash plate angle is controlled by the servo mechanism 13a so that the discharge flow rate of 13 becomes A.

As a result, immediately before the upper mold 21 descending together with the slide 20 collides with the lower mold cushion pad 2a, the variable displacement pump 13
Die cushion 4 by the flow rate A supplied to the upper chamber 8 ₁
Is lowered, the pin touch sound generated when the upper die 21 and the lower die cushion pad 2a collide with each other is reduced.

After that, the hydraulic pressure released from the lower chamber 8 ₃ is controlled by the servo valve 22 provided in the NC die cushion tank unit 10 to control the descending speed of the die cushion 4.
By properly controlling the servo valve 22 by this,
The acceleration of the die cushion pad 5 can be freely changed.

[Effect of device]

As described in detail above, this invention detects the slide speed and the slide acceleration at the pin touch position, calculates the flow rate to be supplied to the upper chamber of the locking device from the slide speed, and obtains the obtained flow rate. Since the lower cushion pad is preliminarily lowered at the same speed as the slide lowering speed,
It is possible to significantly reduce the noise due to the pin touch sound generated when the upper mold collides with the lower mold cushion pad, and it is not necessary to detect the pin touch position with a position detector such as a limit switch. Even if the position changes, the troublesome work of adjusting the position detector each time is not required.

In addition, since only the required flow rate is supplied from the variable displacement pump to the upper chamber of the locking device, energy is not wasted and the cushioning capacity is controlled by the slide acceleration at the pin touch position. The cushioning force can be freely controlled by this, so that so-called surge pressure that temporarily raises the hydraulic pressure in the lower chamber of the locking device does not occur, so it is possible to obtain a good quality product with no indentations or scratches on the molded product. Will be available.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a circuit diagram, and FIG. 1 is a press body, 1a is a bolster, 2 is a lower die, 2a is a lower die cushion pad, 3 is a die cushion pin, 4 is a die cushion, 5 is a die cushion pad, 6 is a cushion cylinder, 8 is a locking device, and 13 is Variable displacement pump,
20 is a slide and 21 is an upper mold.

Claims (1)

[Scope of utility model registration request] 1. A press body comprising a lower die cushion pad 2a provided in the vicinity of a lower die 2 installed on a bolster 1a of a press body 1 and elastically supported by a die cushion 4 via a die cushion pin 3. The upper mold 21 that descends together with the slide 20 that is vertically movable on the main body 1 detects the slide speed and slide acceleration at the pin touch position where the upper mold 21 collides with the lower mold cushion pad 2a, and is necessary for preliminary lowering from the above-mentioned slide speed. and calculate the flow rate, controls the discharge flow rate of the supplied variable displacement pump 13 to the hydraulic into the upper chamber 8 ₁ of the die cushion 4 of the cushion cylinder 6 locking device 8 provided on the lower was calculated from the slide acceleration depending on the cushion ability, by controlling the servo valve 22 connected to the lower chamber 8 ₃ above locking device 8, the lower mold succumbed Preliminary lowering device of the die cushion is formed by to control the acceleration of the Npaddo 5.