JPH0453721A - Mold clamping hydraulic circuit for injection molder - Google Patents

Abstract

PURPOSE:To reduce the leakage of a proportional pressure reducing valve and downsize an accumulator, a pump and an oil source by a method wherein a means, which closes a first and a second logic valves by detecting pressure with a pressure detector. CONSTITUTION:In mold clamping process, the solenoid (b) of a changeover valve 14 is excited so as to open both a first and second logic valves 10 and 12 in order to flow the pressure oil accumulated in an accumulator 5 in a mold clamping cylinder 34 for generating pressure. Next, in dwelling process, when pressure is raised up to the predetermined one, the pressure information is inputted through a pressure detector 15 and an amplifier 16 to a controller 17, which turns off the solenoids (a) and (b) upon the receipt of the pressure information. As a result, both the first and the second logic valves 10 and 12 are closed, resulting in holding the inner pressure of the cylinder by the second and third logic valves 12 and l3. Further, the pressure oil in the accumulator 5 is blocked by the first logic valve 10, resulting in preventing the pressure oil from flowing in a proportional pressure reducing valve 11 and allowing to prevent the leak of the proportional pressure reducing valve 11 from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold clamping hydraulic circuit for an injection molding machine for driving a mold clamping device in the injection molding machine.

(Prior Art) Conventionally, in an injection molding machine, a molding material heated and fluidized in a heating cylinder is injected into a mold under high pressure.
The molded product is cooled or hardened in the mold, and then the mold is opened and the molded product is taken out.

FIG. 3 is a mold clamping hydraulic circuit diagram for a conventional injection molding machine.

The injection molding machine includes a mold clamping device 31 and an injection device (not shown) that is disposed opposite to the mold clamping device 31 so as to be able to move toward and away from the mold clamping device 31.

The mold clamping device 31 includes a fixed platen 32 and a movable platen 33, and when the mold clamping cylinder 34 reciprocates the movable platen 33 along the tie bars 35, the fixed mold 3
7 and the movable mold 38 are separated by tI.

The injection device is also equipped with a reciprocating nozzle that heats and melts the resin and injects it.
Molten resin is injected into 8.

In the above-mentioned injection molding machine, the movable mold 38 reciprocates for each molding cycle and comes into contact with and separates from the opposing fixed mold 37, so the movable mold 38 is reciprocated at high speed. This is important for improving molding efficiency.

Therefore, a mold clamping cylinder 34 is provided in order to reciprocate the movable mold 38 and increase the force with which it presses against the fixed mold 37, that is, the mold clamping force.

The mold clamping cylinder 34 has a cylinder chamber 41 formed in a toggle support 40 and a piston 42 fixed to a tie bar 35 in the cylinder chamber 41, and oil chambers 43 on both sides of the piston 42. Form 44. By supplying and discharging oil to the core oil chambers 43 and 44, the toggle support 40 can be moved along the tie bars 35 to perform mold clamping.

Therefore, a port 45 is formed in the toggle support 40 for supplying and discharging oil into the oil chamber 44 of the mold clamping cylinder 34. A proportional pressure reducing valve 53 with a check valve and a switching valve 54 are connected to the port 45.
By switching the switching valve 54, oil is supplied and discharged from the oil chamber 44.

Further, 55 is an accumulator, 56 is a check valve, and 57
58 is a pump, 58 is a switching valve for discharging excess oil when oil exceeding the oil pressure set by the accumulator 55 is supplied, and 59 is a reservoir.

In the mold clamping hydraulic circuit for an injection molding machine having the above structure, the mold clamping force is adjusted by controlling the pressure using the proportional pressure reducing valve 53 with a check valve.

(Issues to be solved by the invention!) However, in the mold clamping hydraulic circuit for an injection molding machine having the above configuration, the proportional pressure reducing valve 53 with a check valve discharges excess oil in order to maintain the hydraulic pressure at a predetermined value. Because of the structure, leakage of about 1 to 22/inch usually occurs.

Therefore, the accumulator 55 and pump 57, which serve as hydraulic pressure sources, need to be designed to a size that compensates for the amount of leakage.

In particular, when injection, metering, and mold clamping feed are performed by drive means other than hydraulics, and only the mold clamping force is generated by hydraulics, the oil source is small, so there is a risk of leakage in relation to the oil source discharge amount. The ratio of quantity will be very high.

The present invention solves the problems of the conventional mold clamping hydraulic circuit for an injection molding machine, and provides a hydraulic circuit for driving a mold clamping device.
It is an object of the present invention to provide a mold clamping hydraulic circuit for an injection molding machine that can reduce the amount of leakage from a proportional pressure reducing valve and downsize an accumulator, a pump, and an oil source.

(Means for Solving the Problems) For this purpose, the present invention provides a mold clamping hydraulic circuit for an injection molding machine that supplies oil pressure-fed by a pump to a mold clamping cylinder via a proportional pressure reducing valve, on the upstream side of the proportional pressure reducing valve. a first logic valve that is disposed adjacent to the proportional pressure reducing valve and selectively opens and closes the oil passage; and a second logic valve that is disposed adjacent to the downstream side of the proportional pressure reducing valve and selectively opens and closes the oil passage. have

A pressure detector is disposed in the oil passage between the second logic valve and the mold clamping cylinder and detects the pressure in the oil passage, and the first and second logic valves are activated by the pressure detection of the pressure detector. We are trying to have a means to close it.

(Function) According to the present invention, in a mold clamping hydraulic circuit for an injection molding machine that supplies oil pressure-fed by a pump to a mold clamping cylinder via a proportional pressure reducing valve, the hydraulic circuit is arranged adjacent to the upstream side of the proportional pressure reducing valve. It has a first logic valve that selectively opens and closes the oil passage, and a second logic valve that is disposed adjacent to the downstream side of the proportional pressure reducing valve and selectively opens and closes the oil passage.

A pressure detector is disposed in the oil passage between the second logic valve and the mold clamping cylinder and detects the pressure in the oil passage, and the first and second logic valves are activated by the pressure detection of the pressure detector. We are trying to have a means to close it.

Therefore, the proportional pressure reducing valve closes the first and second logic valves disposed upstream and downstream when not in use.
Since the proportional pressure reducing valve is completely enclosed, there is no leakage from the proportional pressure reducing valve.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a mold clamping hydraulic circuit diagram for an injection molding machine according to the present invention.

In the figure, 5 is an accumulator, 6 is a check valve connected to a pump (not shown), 10 is a first logic valve connected to the downstream side of the check valve 6, and 11 is a proportional pressure reduction connected to the first logic valve. The valve 12 is the proportional pressure reducing valve 11
This is a second logic valve disposed between the mold clamping cylinder 34 and the mold clamping cylinder 34.

The first and twentieth sick valves 10.12 are disposed to surround the proportional pressure reducing valve 11, and are structured to take two positions, a position where the oil passage is communicated and a position where the oil passage is closed.

Further, 13 is an oil passage 2 on the downstream side of the second logic valve 12.
This is a third logic valve disposed in an oil passage 22 branched from 1. and the first, second, and 30th sick valves 10.
12 and 13 can be switched by a switching valve 14. The switching valve 14 is switched by solenoids a and b to take three positions, the first, second and third positions.
0 Zinc valves 10, 12, and 13 are operated respectively.

Further, 15 is a pressure detector that detects the oil pressure in the oil passage 21;
16 is an amplifier, and 17 is a controller.

In the mold clamping hydraulic circuit for an injection molding machine having the above configuration, in order to suppress leakage from the proportional pressure reducing valve 11, first and twentieth sick valves 10, 12 are provided, and the proportional pressure reducing valve 11 is connected to the upstream side,
Surround from downstream. Also, in order to release the mold clamping pressure, a third
0 Tsukuji valve 13 is provided. The switching valve 14 is the logic valve 1
0.12.13 Regulates the pilot pressure for opening and closing.

In addition, the pressure during mold clamping is detected by the pressure detector 15 and the amplifier 16, and the controller 1 uses this pressure information.
7 drives the solenoids a and b of the switching valve 14, and opens and closes the logic valves 10, 12, and 13 to generate, maintain, and release mold clamping pressure.

FIG. 2 is a diagram showing the on/off state of the solenoid and the open/closed state of the logic valve in each process.

In the mold clamping process, the solenoid b of the switching valve 14 is energized, the first and 20th thick valves 10.12 are opened, and the pressure oil accumulated in the accumulator 5 flows into the mold clamping cylinder 34 to generate pressure.

Next, in the pressure holding step, when the pressure rises to a predetermined pressure, pressure information is input to the controller 17 through the pressure detector 15 and amplifier 16, and the controller 17 that receives the information turns off solenoids a and b. . As a result, the first and 20th thick valves 10.12 are closed, the cylinder internal pressure is maintained by the second and 30th thick valves 12.13, and the pressure oil in the accumulator 5 is blocked by the first logic valve 10, resulting in proportional pressure reduction. Inflow into the valve 11 can be prevented, and leakage from the proportional pressure reducing valve 11 can be prevented.

When the pressure is released, the solenoid a of the switching valve 14 is energized to open the third logic valve 13, allowing high-pressure oil to escape to the reservoir and releasing the pressure.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

For example, it can be employed in mechanical devices that require pressure maintenance, such as a hydraulic press.

(Effects of the Invention) As explained in detail above, in the mold clamping hydraulic circuit for an injection molding machine of the present invention, the oil pumped by the pump is supplied to the mold clamping cylinder via the proportional pressure reducing valve. In the tightening hydraulic circuit, a first logic valve is arranged adjacent to the upstream side of the proportional pressure reducing valve and selectively opens and closes the oil passage, and a first logic valve arranged adjacent to the downstream side of the proportional pressure reducing valve and selectively It has a second logic valve that automatically opens and closes the oil passage.

A pressure detector is disposed in the oil passage between the second logic valve and the mold clamping cylinder and detects the pressure in the oil passage, and the first and 20th zinc valves are activated by the pressure detection of the pressure detector. We are trying to have a means to close it.

Therefore, the proportional pressure reducing valve closes the first and second logic valves disposed upstream and downstream when not in use.
Since both the oil supplied from the oil source and the oil discharged from the mold clamping cylinder are completely cut off from the proportional pressure reducing valve, there is no leakage from the proportional pressure reducing valve.

In addition, since the amount of leakage is reduced, the capacity of pumps, accumulators, etc. can be reduced, and
Heat generation in the hydraulic circuit can be reduced. Therefore, it is also possible to reduce the cooler capacity or eliminate the cooler.

[Brief explanation of drawings]

Fig. 1 is a mold clamping hydraulic circuit diagram for an injection molding machine of the present invention, Fig. 2 is a diagram showing the on/off status of solenoid I and the open/close state of a logic valve in each process, and Fig. 3 is a diagram of a conventional mold clamping system for an injection molding machine. It is a hydraulic circuit diagram. 10... First logic valve, 11... Proportional pressure reducing valve, 1
2...2nd logic valve, 13...30th zinc valve,
14...Switching valve, 15...Pressure detector, 16...
Amplifier, 17...controller, 34...mold clamping cylinder.

Claims (1)

[Scope of Claims] In a mold clamping hydraulic circuit for an injection molding machine that supplies oil pressure-fed by a pump to a mold clamping cylinder via a proportional pressure reducing valve, (a) disposed adjacent to the upstream side of the proportional pressure reducing valve; a first logic valve that selectively opens and closes the oil passage; (b) a second logic valve that is disposed adjacent to the downstream side of the proportional pressure reducing valve and selectively opens and closes the oil passage; ) a pressure detector disposed in the oil passage between the second logic valve and the mold clamping cylinder to detect the pressure in the oil passage;
A mold clamping hydraulic circuit for an injection molding machine, comprising means for closing a logic valve.