JP2001315177A - Clamping hydraulic apparatus for injection holding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem wherein pressure control can not be linearly performed and accurate clamping pressure control can not be performed in a pressure control valve provided in a mold clamping side pipeline in a hydraulic circuit. SOLUTION: In a mold clamping apparatus for performing opening and closing a mold and clamping the mold by feeding a hydraulic oil from a hydraulic source into the mold clamping apparatus, a pressure difference control valve provided in a pipeline for feeding the hydraulic oil into a mold clamping cylinder forwarding room, a normal open cartridge valve connected with the pressure difference of the pressure difference control valve and for separately making the hydraulic oil in the mold clamping cylinder forwarding room flow into a tank and the pressure control valve for controlling the hydraulic pressure on the inlet side of the pressure difference control valve and generating control pressure of the cartridge valve are provided. In addition, the pressure difference in the pressure difference control valve is set in such a way that a puppet valve in the cartridge valve balances with a spring force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device for controlling a mold clamping pressure in an injection molding machine, and more particularly to a hydraulic device for controlling a mold clamping pressure by a low pressure.

[0002]

2. Description of the Related Art Control of a mold clamping pressure in an injection molding machine is performed by:
By switching the solenoid of the directional control valve, the hydraulic oil from the hydraulic source flows through the mold-clamping cylinder advance chamber, and the mold-clamping pressure is increased after the mold-closing is completed. The pressure for tightening is controlled by a pressure control valve.

FIG. 2 shows a conventional clamping hydraulic device based on a hydraulic circuit, in which pressure oil is sent from a hydraulic source 5 to a clamping cylinder advance chamber 3 via a directional control valve 6, and the hydraulic source 5 and the directional control are controlled. A safety valve 10 is provided in a pipe branched from a pipe between the valves 6, a pressure oil from a hydraulic source 5 is detected by a pressure detector 14, and a mold clamping pressure by a hydraulic pressure of the hydraulic source 5 is detected by an electromagnetic relief valve 13. Is controlled by However, the electromagnetic relief valve 13 that controls the mold clamping pressure cannot perform low-pressure mold clamping control due to the characteristics of the electromagnetic relief valve 13 and cannot perform linear pressure control in a low-pressure region.

[0004]

As described above, in the electromagnetic relief valve (pressure control valve) provided in the mold-clamping side line of the hydraulic circuit having the above-described structure, the pressure of the electromagnetic relief valve is determined by the characteristics of the low pressure region. Even if the control output value is set to 0 MPa, the minimum control value will be 0.5 to 1 MPa. Therefore, the problem is that the pressure control in the low pressure region of the pressure control valve cannot be performed linearly, and accurate mold clamping pressure control in the setting range of 0 to 1 MPa cannot be performed.

[0005]

According to the present invention, there is provided a mold clamping apparatus for opening and closing a mold by supplying pressure oil from a hydraulic pressure source to a mold clamping cylinder. In the device, a differential pressure control valve provided in a pipeline for supplying pressure oil to the mold clamping cylinder advance chamber, and a normal open in which the differential pressure of the differential pressure control valve is connected to divide the pressure oil in the mold clamp cylinder advance chamber to the tank And a pressure control valve for controlling the oil pressure on the inlet side of the differential pressure control valve to generate a control pressure for the cartridge valve. Then, the differential pressure of the differential pressure control valve is set so that the poppet valve inside the cartridge valve balances the spring force.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a mold clamping hydraulic device based on a hydraulic circuit that controls a mold clamping pressure, which is an embodiment of the present invention. Reference numeral 1 denotes a mold clamping cylinder, which has a mold clamping piston 2 that slides in the mold clamping cylinder 1, and connects the mold clamping piston 2 to a movable plate (not shown) to fix a position (not shown). The mold is opened and closed by moving the movable plate close to and away from the fixed plate.

A hydraulic device for opening / closing the mold and for clamping the mold is configured such that the solenoid a or the solenoid b of the directional control valve 6 is excited in the mold clamping cylinder forward chamber 3 or the mold clamping cylinder retreat chamber 4, and the hydraulic pressure is applied to the mold clamping cylinder 1. It becomes a hydraulic circuit for supplying the pressure oil from the source 5. Therefore, the mold-clamping hydraulic device of the present invention provides a differential pressure control valve
And the differential pressure generated by the differential pressure control valve 7 is connected to the cartridge valve 8. The cartridge valve 8 controls the oil pressure in the mold clamping cylinder advance chamber 3 by shunting the pressure oil in the mold clamping cylinder advance chamber 3 to the tank.

The differential pressure control valve 7 adjusts the opening / closing degree of the throttle by replacing it with a flow control valve using an adjustable throttle or a simple fixed throttle. Then, the differential pressure between the inlet side and the outlet side of the differential pressure control valve 7 due to the pressure oil from the hydraulic pressure source 5 is
The poppet valve 8B inside the cartridge valve 8
It is set in advance so as to balance with the spring force of A. In the present embodiment, the differential pressure is adjusted so that the pressure difference between the inlet side and the outlet side of the differential pressure control valve 7 is 1 to 1.5 MPa.

The cartridge valve 8 has an internal poppet valve 8.
B is a normally open check valve that biases B in the opening direction by a spring 8A. When the control pressure of the hydraulic pressure for pressing the poppet valve 8B inside the cartridge valve 8 is not supplied, the spring force by the spring 8A works, the poppet valve 8B is opened, and the pressurized oil in the mold clamping cylinder advance chamber 3 is circulated through the tank. I have. Also,
When hydraulic pressure for pressing the poppet valve 8B is supplied and control of the control pressure by the pressure control valve 9 is performed, the poppet valve 8B inside the cartridge valve 8 that circulates the pressurized oil in the mold clamping cylinder advance chamber 3 to the tank is changed. The state is controlled by opening and closing, and the hydraulic pressure is supplied to the mold clamping cylinder advance chamber 3 so that the mold clamping pressure can be generated. As described above, the hydraulic control by only the electromagnetic relief valve performed in the conventional mold clamping hydraulic circuit is replaced by the control of the cartridge valve 8 by the control of the control pressure by the pressure control valve 9.

The pressure control valve 9 adjusts the oil pressure on the inlet side of the differential pressure control valve 7 by means of a throttle 11 so that the flow becomes necessary for opening and closing the poppet valve 8B inside the cartridge valve 8.
The control pressure is controlled with the flow rate kept constant. And the other throttle 12 is the cartridge valve 8
The peak pressure of the pressure fluctuation of the pressure control valve 9 that generates the control pressure is cut off, and the control of the control pressure by the pressure control valve 9 is stabilized. As described above, the pressure control valve 9 may be a relief valve and may be a manually adjustable type, but is preferably an electromagnetic proportional valve type. In the embodiment, an electromagnetic relief valve for a small flow rate (controlling about 1 L / min) is used.

As for the mold clamping pressure, the pressure oil in the mold clamping cylinder advance chamber 3 is detected by a pressure detector 14. In controlling the mold clamping pressure, a pressure command signal corresponding to the pressure command value was calculated by a control device (not shown), and the output signal of the pressure command value was generated by the differential pressure control valve 7 to generate a differential pressure. The control pressure is controlled by the pressure control valve 9 in the state. The pressure of 0 to 1 MPa, which is a characteristic of the pressure control valve 9 and is in a pressure uncontrollable range, is applied to the differential pressure (
The control pressure is controlled from the pressure range above the set pressure of 1.5 MPa), so that the clamping pressure can be controlled by setting the low pressure from 0 to 1 MPa, and the area from the minimum pressure to the maximum pressure can be controlled almost linearly. Can be.

In the conventional hydraulic circuit, when controlling the mold clamping pressure by a low pressure of a spring built-in mold or the like, the mold cannot be opened and closed smoothly. Depending on the relationship with the spring force built into the mold, the mold clamping force due to the mold clamping pressure cannot open against the mold spring force and the mold opens, resulting in stable opening and closing of the mold. The operation could not be performed. However, the hydraulic device of the present invention can control the pressure control range from the minimum pressure to the maximum pressure almost linearly, so that the mold closing / clamping pressure increasing control for closing the mold from the mold open state and the mold can be performed. In opening depressurization and mold opening control, the mold clamping force based on the control value of the mold clamping pressure is opposed to the spring force built into the mold, enabling smooth mold opening and closing operations, and the molding that occurs when the molded product is released. It is possible to reduce improper molding of products.

In addition, a movable mold and a fixed mold attached to a movable plate (not shown) and a fixed plate according to another embodiment are positioned close to each other.
In the separating device, the mold is opened by injecting and filling a molten resin from an injection device (not shown) from the closed state of the mold, and then the mold is opened. With the use of a hydraulic device, the control of the mold clamping pressure can be controlled almost linearly from the minimum pressure to the maximum pressure, and in particular, excessive pressure generated in a low pressure region due to a pressure control impossible range which is a characteristic of the pressure control valve. The internal distortion of the molded article can be removed without applying a mold clamping force due to a large mold clamping pressure to the molded article.

[0014]

The mold clamping hydraulic device according to the present invention enables the mold clamping pressure to be controlled particularly at a low pressure, and the pressure from the minimum pressure to the maximum pressure can be controlled almost linearly, thereby improving the quality of the molded product. Defects can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mold clamping hydraulic device based on a hydraulic circuit that controls a mold clamping pressure for implementing the present invention.

FIG. 2 is a view showing a conventional mold clamping hydraulic device based on a hydraulic circuit.

[Explanation of symbols]

 1 ‥‥‥ Clamping cylinder 2 ‥‥‥ Clamping piston 3 ‥‥‥ Clamping cylinder advance chamber 4 ‥‥‥ Clamping cylinder retreat chamber 5 ‥‥‥ Hydraulic power source 6 ‥‥‥ Directional control valve 7 差 Difference Pressure control valve 8 ‥‥‥ Cartridge valve 8A ‥‥‥ Spring 8B ‥‥‥ Poppet valve 9 ‥‥‥ Pressure control valve 10 ‥‥‥ Safety valve 11 絞 り Restrictor 12 ‥‥‥ Restrictor 13 ‥‥‥ Electromagnetic relief valve 14 ‥‥‥ Pressure detector

Claims (2)

[Claims] 1. A mold clamping device for opening and closing and clamping a mold by supplying pressurized oil from a hydraulic pressure source to a mold clamping cylinder. A pressure control valve, a normally open cartridge valve to which the differential pressure of the differential pressure control valve is connected to divert the pressure oil of the mold clamping cylinder advance chamber to the tank, and a cartridge valve which controls the hydraulic pressure at the inlet side of the differential pressure control valve. And a pressure control valve for generating a control pressure of the mold. 2. The mold clamping hydraulic device for an injection molding machine according to claim 1, wherein the differential pressure of the differential pressure control valve is set so that the poppet valve inside the cartridge valve balances the spring force.