JPH0363926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toggle type mold clamping device for an injection molding machine.

(Prior art) Conventionally, in a toggle type mold clamping device, the
As shown in the figure, the mold clamping force adjustment nut 1 locked to the toggle support 4 is screwed onto the toggle support side end of the tie bar 3, and the toggle support 4
The mold clamping cylinder 16 is connected between the movable platen 15 and the movable platen 15.
The crosshead 18 is connected via two sets of links 17 that are symmetrically connected to each other with the mold clamping cylinder 16 in between, and the crosshead 18 is attached to the tip of the rod of the clamping cylinder 16 and one link 17 of the two sets of links is connected. The platen 1 is connected via a link 19, and is movable along the tie bar 3 by the rod extension operation of the mold clamping cylinder 16.
5, and at the forward end position, the toggle mechanism 17~
The mold clamping force is adjusted by rotationally adjusting the mold clamping force adjusting nut 1 via the gear 20 so that when the tie bar 3 is extended by the cylinder force expanded by the cylinder force 19, a predetermined mold clamping force is obtained as a reaction force. It was set. Furthermore, in Japanese Patent Application Laid-open No. 60-199560, an annular groove is provided in the adjustment nut, an annular member on the cylinder platen side is slidably fitted into the annular groove, and the bottom surface of the annular groove and the end surface of the annular member are A mold clamping force adjusting device is disclosed in which pressure oil whose pressure is regulated by a relief valve is introduced between the mold clamping force and hydraulic pressure is also used.

(Problem to be solved by the invention) However, with this conventional device, the toggle components expand and contract due to changes in the heat balance during the operation of the molding machine, and the mold clamping force changes slightly with each tie bar. A constant mold clamping force no longer acts uniformly on the entire mold. Therefore, problems may arise when molding ultra-precision products such as disks, which require extremely high dimensional accuracy. In addition, the above-mentioned Japanese Patent Publication No.
The hydraulic system seen in Publication No. 60-199560 is a step forward compared to the system using only an adjustment nut, but this system uses a relief valve to regulate the pressure, so the injection pressure when injecting the resin into the mold is used. When the oil pressure in the relief circuit rises above the set pressure of the relief valve, the relief valve operates and the oil flows out and lowers the pressure to adjust the mold clamping force, but on the other hand, the resin pressure decreases as the injected resin contracts. However, even if the pressure falls below the initial set pressure of the relief valve and the mold clamping force decreases, it cannot cope with this, so it is not suitable for ultra-precision molding such as disk molding in which information is transferred and recorded from a stamper.

The present invention was made in order to solve the above-mentioned conventional problems, and an object of the present invention is to enable the necessary mold clamping force to be applied uniformly to the entire mold.

(Means for Solving the Problems) A toggle type mold clamping device of the present invention is a toggle type mold clamping device in which a clamping force adjusting nut is screwed onto an end of a tie bar. An adjustment cylinder is formed between the cylinder and the toggle support, a hydraulic circuit for controlling the cylinder is configured via an oil passage bored in the toggle support, and the hydraulic circuit includes a pressure adjustment valve for adjusting the internal pressure of the cylinder and a cylinder. a pressure detector for detecting the internal pressure of the detector, a setting device for setting the mold clamping force, and a comparator for comparing the set value from the setting device and the detected value from the detector, The pressure regulating valve is controlled by an output signal from the device, and the regulating cylinder is capable of absorbing minute changes in mold clamping force due to heat.

(Example) An example of the present invention will be described below with reference to FIG.

In the figure, 1 is a mold clamping force adjusting nut, and a locking collar 2 is provided around the middle of the nut 1. This nut 1
The tie bar 3 is screwed onto the end of the tie bar 3 and is attached to the toggle support 4 by a locking tool 5.
It is rotatably attached to prevent it from coming off in the outward direction.

Reference numeral 6 denotes a cylinder chamber, which is recessed concentrically around the mold clamping force adjusting nut 1. A ring-shaped piston 7 (the locking collar 2 may also be a piston) is slidably fitted into the mold clamping force adjusting nut 1 into the cylinder chamber 6, and the adjusting cylinder 8 is formed.

Reference numeral 9 denotes a hydraulic circuit, which connects the adjustment cylinder 8 and the hydraulic pump 10. By pressing the piston 7 in the direction of expanding and contracting the tie bar 3 with the hydraulic pressure supplied from the hydraulic pump 10, the mold clamping force adjustment nut 1 is connected.
The tensile force (mold clamping force) applied to the tie bar 3 is adjusted through the tie bar 3.

11 is a pressure detector provided in the hydraulic circuit 9, which is connected to the comparator 12;
1 detects the pressure inside the regulating cylinder 8 and inputs it to the comparator 12.

13 is a pressure regulating valve such as a servo valve provided in the hydraulic circuit 9, which is connected to the comparator 12;
The comparator 12 compares the actual value of the mold clamping force input from the pressure detector 11 with the set value of the mold clamping force input from the setting device 14, and determines whether the actual value is less than the allowable range of the set value. The pressure regulating valve 13 is controlled so that

Note that one pressure detector 11 and one pressure adjustment valve 13 may be provided for each adjustment cylinder 8, but the same effect can be obtained by providing one each common to all adjustment cylinders 8 and setting the mold clamping force. It is.

(Function) When the required mold clamping force at each stage during the mold clamping and mold opening strokes is set using the setter 14, the output signal from the comparator 12 at each interval is detected while the movable platen position is detected by the LS or encoder. The pressure regulating valve 13 can be controlled by this, and the same necessary internal pressure can be given to all regulating cylinders 8. Therefore, each tie bar 3 is expanded and contracted by the adjustment cylinder 8, and the tensile force (mold clamping force) applied to the tie bar 3 becomes constant.

(Effects of the Invention) As described above, the present invention utilizes the adjustment cylinder formed between the mold clamping force adjustment nut and the toggle support to perform feedback control so that the mold clamping force applied to each tie bar is constant. It is possible to obtain a constant mold clamping force by absorbing minute changes in mold clamping force caused by such factors. Therefore, it goes without saying that products that require ultra-precision molding such as disks can be produced reliably and easily, which is a remarkable effect. Since the oil passage is constructed through an oil passage drilled into the toggle support, which is a fixed part, there is no rotating part in the hydraulic circuit, so there is no need to install a rotating valve, and there is no need to take special precautions against oil leakage, making it easy to control. It also has the advantage of being reliable and providing the device at a low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention. FIG. 2 is an overall view of a conventional toggle type mold clamping device, and FIG. 3 is a sectional view of a main part of the device corresponding to FIG. 1. 1... Mold clamping force adjustment nut, 2... Locking collar, 3...
...Tie bar, 4...Toggle support, 6...Cylinder chamber, 7...Piston, 8...Adjustment cylinder,
9...Hydraulic circuit, 10...Hydraulic pump, 11...
Pressure detector, 12... comparator, 13... pressure regulating valve, 14... setting device.

Claims (1)

[Claims] 1. In a toggle type mold clamping device in which a mold clamping force adjustment nut, which is locked to a toggle support, is screwed onto the end of a tie bar, an adjustment cylinder is formed between the nut and the toggle support, and the cylinder is controlled. A hydraulic circuit is configured through an oil path bored in the toggle support, and the hydraulic circuit is equipped with a pressure regulating valve that adjusts the internal pressure of the cylinder and a pressure detector that detects the internal pressure of the cylinder, as well as a mold clamping force. It is characterized by comprising a setting device for setting, and a comparator for comparing a setting value from the setting device and a detected value from the detector, and controlling the pressure regulating valve by an output signal from the comparator. Toggle type mold clamping device.