JPH1086204A - Hydraulic drive device for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic drive device for injection molding machine having excellent pressure control properties in dwelling process and measuring process, which provides high energy efficiency. SOLUTION: A hydraulic drive device comprises a main pressure reducing valve 6 which is arranged between a proportional direction flow rate control valve 3' for controlling a driving speed of an injection cylinder 1 and an injection cylinder 1, and is controlled by a pilot pressure. As for the pilot pressure for the main pressure reducing valve 6, a pilot pressure for a main relief valve 7 obtainable from a proportional pressure control valve 8 is used in common. In both of dwelling process and measuring process, hydraulic oil is supplied to the main pressure reducing valve 6 from the proportional direction flow rate control valve 3'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive for an injection molding machine for driving an injection cylinder.

[0002]

2. Description of the Related Art A hydraulic drive of an injection molding machine of this kind is
Usually, it has a hydraulic pump, an electric motor, an accumulator and the like. Further, it has a hydraulic source for supplying pressure oil of a constant pressure irrespective of fluctuations in the use flow rate, and a control valve for controlling the pressure oil supplied from the hydraulic source.

As a control valve, specifically, a servo valve and an electromagnetic proportional valve are known. Of these, the servo valve is expensive because of its structure, which may impede operation due to dust entering the inside thereof.

On the other hand, an electromagnetic proportional valve generally has only one of a flow control function and a pressure control function. By the way, an injection molding machine repeats a cycle including a measuring step, an injection step, and a pressure-holding step as its injection operation, and performs flow control, pressure control, and the like for each step.
Different control characteristics are required. Therefore, when an electromagnetic proportional valve is used, necessary functions are realized by using a plurality of valves in combination.

FIG. 2 shows a conventional hydraulic drive of an injection molding machine using an electromagnetic proportional valve. In FIG. 2, a solid line indicates a portion of the pipeline in which the pressure oil flows at a large flow rate, and a broken line indicates a pilot pressure portion for transmitting pressure.

Hereinafter, the hydraulic drive device will be described with reference to FIG. This hydraulic drive device operates as follows during each step of the injection molding machine.

During the metering process, the flow rate of the hydraulic oil supplied from the hydraulic source 10 is controlled so as to control the rotation speed of the screw rotation hydraulic motor 2. At this time, the pressure of the injection cylinder 1 is simultaneously controlled. That is, during the metering process, the solenoid b of the proportional directional flow control valve 3 is energized to control the supply flow rate of hydraulic oil to the screw rotation hydraulic motor 2. In addition, the rotation of the screw causes the injection cylinder 1 to move backward. At this time, the hydraulic oil returning from the injection cylinder 1 to the tank 9 is controlled by the main relief valve 7 controlled by the proportional pressure control valve 8. And the pressure (back pressure) of the injection cylinder 1 is controlled. The proportional pressure control valve 8 receives supply of pressure oil from the hydraulic pressure source 10 through the flow control valve 11, and generates a pilot pressure according to a given electric signal.

[0008] During the injection process, the flow rate of the hydraulic oil supplied from the hydraulic pressure source 10 is controlled so as to control the speed of the injection cylinder 1. At this time, the screw rotation hydraulic motor 2 is stopped. That is, during the injection process, the flow rate of the working oil supplied to the injection cylinder 1 is controlled by the current flowing through the solenoid a of the proportional direction flow control valve 3. At the same time, the compensating pressure switching valve 5 is also energized to guide the load pressure of the injection cylinder 1 to the load pressure compensating valve 4. Thus, the speed of the injection cylinder 1 can be controlled without being affected by the load pressure.

During the pressure holding step, the pressure of the injection cylinder 1 is controlled. The screw rotation hydraulic motor 2 is stopped.
That is, during the pressure-holding step, the pressure of the injection cylinder 1 is controlled by supplying a constant flow of hydraulic oil by the proportional directional flow control valve 3 and releasing excess hydraulic oil from the main relief valve 7 to the tank 9.

[0010]

However, the conventional hydraulic drive for an injection molding machine shown in FIG. 2 has the following problems.

In the measuring step, since the pressure is controlled by the main relief valve 7 using only the return oil due to the retreat of the injection cylinder 1, it is easily affected by the retreat speed of the injection cylinder 1, and especially when the retreat speed is low, Pressure control may not be performed.

In the pressure holding step, there is a case where it is desired to rapidly increase the pressure in the injection cylinder 1. At this time, if the flow rate of the working oil supplied from the proportional directional flow control valve 3 is not sufficient, No high boosting characteristics can be obtained. On the other hand, if the supply flow rate from the proportional direction flow control valve 3 is too large, the flow rate lost from the main relief valve 7 increases, and the energy efficiency decreases.

An object of the present invention is to provide a hydraulic drive device for an injection molding machine which has excellent pressure control characteristics in each of a measuring step and a pressure-holding step and has high energy efficiency.

[0014]

According to the present invention, there is provided a hydraulic drive for an injection molding machine for driving an injection cylinder.
A main pressure reducing valve provided between the proportional directional flow control valve for controlling the driving speed of the injection cylinder and the injection cylinder and controlled by a pilot pressure, and a proportional pressure as the pilot pressure for the main pressure reducing valve; The pilot pressure for the main relief valve obtained from the control valve is shared.

[0015] Further, with this apparatus, when controlling the pressure of the injection cylinder in the injection molding measuring step and the pressure holding step, both the main pressure reducing valve and the main relief valve are used, and the proportional directional flow rate is controlled. The control valve supplies a flow rate to the main pressure reducing valve in any of the measuring step and the pressure holding step. Thereby, excellent pressure control characteristics and high energy efficiency are realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hydraulic drive for an injection molding machine according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a hydraulic drive device of an injection molding machine according to one embodiment of the present invention. In FIG. 1, the same or similar parts as in the conventional example are denoted by the same reference numerals as in FIG. 2, and description thereof will be omitted.

Referring to FIG. 1, the present hydraulic drive device is a hydraulic drive device for an injection molding machine that drives an injection cylinder 1 and includes a proportional directional flow control valve 3 for controlling the drive speed of the injection cylinder 1. ′ And the injection cylinder 1,
It has a main pressure reducing valve 6 controlled by pilot pressure. As the pilot pressure for the main pressure reducing valve 6, the pilot pressure for the main main relief valve 7 obtained from the proportional pressure control valve 8 is shared.

The hydraulic drive apparatus uses both the main main pressure reducing valve 6 and the main main relief valve 7 when controlling the pressure of the injection cylinder 1 in the injection molding measuring step and the pressure holding step. Proportional flow control valve 3 '
Supplies the flow rate to the main pressure reducing valve 6 in both the measuring step and the pressure maintaining step.

The hydraulic drive device operates as follows during each step of the injection molding machine.

During the metering process, the control of the supply flow rate of the working oil to the screw rotation hydraulic motor 2 is the same as in the conventional example shown in FIG. When controlling the supply flow rate of hydraulic oil to the screw rotation hydraulic motor 2, the proportional directional flow control valve 3 '
Thus, the flow rate is supplied to the main pressure reducing valve 6. Thus, the pressure control of the injection cylinder 1 is performed using the main main pressure reducing valve 6 and the main main relief valve 7.

During the pressure holding step, the pressure of the injection cylinder 1 is controlled by the main main pressure reducing valve 6 and the main main relief valve 7 based on the pressure command given to the proportional pressure control valve 8. The hydraulic oil is supplied from the main pressure reducing valve 6 at the time of pressure increase, while the main main relief valve 7 is supplied at the time of pressure decrease.
To release pressure.

During the injection process, the operation is basically the same as that of the conventional example shown in FIG. However, the present hydraulic drive system is configured to fully close the main main relief valve 7 and fully open the main main pressure reducing valve 6 by inputting a sufficiently large command to the proportional pressure control valve 8, and thereby to set the main pressure reducing valve 6. Prevents the speed control from adversely affecting the speed control.

[0024]

The hydraulic drive system for an injection molding machine according to the present invention is provided between a proportional directional flow control valve for controlling the drive speed of an injection cylinder and an injection cylinder and is controlled by a pilot pressure. The pilot pressure for the main pressure reducing valve is shared with the pilot pressure for the main relief valve obtained from the proportional pressure control valve. Since the flow rate is supplied, the pressure control characteristics in each of the measuring step and the dwelling step are excellent, and the energy efficiency is high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hydraulic drive device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a hydraulic drive device of an injection molding machine according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 injection cylinder 2 screw rotation hydraulic motor 3, 3 'proportional directional flow control valve 4 load pressure compensation valve 5 compensation pressure switching valve 6 main main pressure reducing valve 7 main main relief valve 8 proportional pressure control valve 9 tank 10 hydraulic pressure source 11 flow rate Control valve

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinji Terada 731-1, Naganumahara-cho, Inage-ku, Chiba-shi, Chiba Sumitomo Heavy Industries, Ltd. Chiba Works

Claims (2)

[Claims] 1. A hydraulic drive device for an injection molding machine for driving an injection cylinder, wherein the hydraulic pressure control valve is provided between a proportional directional flow control valve for controlling a drive speed of the injection cylinder and the injection cylinder, and is controlled by a proportional pressure control valve. A hydraulic drive device for an injection molding machine, comprising: a main pressure reducing valve and a main relief valve controlled by a pilot pressure to be applied. 2. In the filling step of injection molding, the main pressure reducing valve is fully opened and the main relief valve is fully closed by increasing the pilot pressure to a predetermined value or more by the proportional pressure control valve. The directional flow control valve controls the flow rate, thereby controlling the speed of the injection cylinder.In the pressure holding step, the proportional directional flow control valve is fully opened, and the pilot pressure is controlled by the proportional pressure control valve. The pressure of the injection cylinder is controlled by the main pressure reducing valve and the main relief valve, and in the measuring step, hydraulic oil is supplied to the main pressure reducing valve by the proportional directional flow control valve, and the pressure control of the injection cylinder is controlled by the proportional pressure control valve. The hydraulic drive device for an injection molding machine according to claim 1, wherein: