JPH04269521A - Injection device for injection molding machine - Google Patents

Abstract

PURPOSE:To provide the adequate molding condition by setting the injection speed and dwell pressure independent in the filling process and the dwelling process in the injection molding. CONSTITUTION:A servo valve 13 is connected with an injection cylinder 8 which is connected with a screw 7 of an injection molding machine. A hydraulic source 18 is connected with the servo valve 13, and an electromagnetic relief valve 20 is installed between the servo valve 13 and the hydraulic source 18. Adequate injection speed and dwell pressure can be provided by adjusting independently the servo valve 13 and the electromagnetic relief valve 20 respectively corresponding to the load to be applied to the screw 7 during the dwelling process by means of either flow rate or pressure for respective set dwell pressure preliminarily.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device for an injection molding machine for reciprocating a screw in a heating cylinder according to molding conditions.

0002

[Prior Art] In injection molding, when the molding material that has been plasticized in the heated cylinder is injected under pressure into the mold cavity using a screw, the molding conditions such as material temperature, injection pressure, and injection speed are It has a big impact on quality.

Focusing on injection pressure and injection speed, when filling a mold cavity with plasticized molding material, generally speaking, the faster the injection speed (primary injection speed), the better the molding quality. Injection pressure (
It is necessary to increase the primary injection pressure. Further, after filling the plasticized material, a holding pressure (secondary injection pressure, tertiary injection pressure) is required in order to further replenish the material and prevent volumetric contraction. The holding pressure needs to be high in order to increase the density when high dimensional accuracy is required, but it is better to use a low pressure in order to reduce residual stress and distortion.

Conventionally, there has been known an injection device for an injection molding machine in which the injection filling speed and holding pressure can be adjusted appropriately depending on the molded product using a servo valve. This is, for example,
As shown in FIG. 3, an injection cylinder 2 connected to a screw 1 is connected to a hydraulic source 4 via a servo valve 3, and a control device (not shown) controls the servo valve 3 to inject from the hydraulic source 4. By adjusting the amount of oil supplied to the cylinder 2, that is, the oil pressure, the injection pressure and injection speed can be adjusted. In the figure, 5 is a reserve tank, and 6 is a pilot pressure introduction path.

With this configuration, by controlling the servo valve 3 according to the molded product, as shown in FIG. 4, in the filling process (primary injection pressure process), the injection pressure is maximized and the injection speed (primary injection speed ), and in the holding pressure stroke (secondary and tertiary injection pressure stroke), only the injection pressure is adjusted without adjusting the injection speed.

[0006]

However, in the conventional example described above, the injection pressure and the injection speed are adjusted only by the servo valve 3, so the injection pressure and the injection speed cannot be adjusted independently. Therefore, when molding products that have thin walls, large projected areas, and require high dimensional accuracy, such as optical disk substrates, it is difficult to obtain sufficient molding conditions, and warpage and distortion due to residual stress are likely to occur. There's a problem.

The present invention has been made in view of the above points, and it is possible to independently set the injection pressure and the injection speed in the pressure holding process, so that appropriate molding conditions can be obtained, thereby improving the molding quality. The purpose is to improve

[0008]

[Means for Solving the Problems] In order to solve the above problems, the injection device of the injection molding machine of the present invention advances the screw in the heating cylinder to fill the mold cavity with the molding material, and maintains the molding material. an injection cylinder for pressurizing the injection cylinder, a hydraulic source for supplying oil to the injection cylinder, a flow control valve interposed between the oil pressure source and the injection cylinder to control the flow rate of the oil, and the flow control valve. a pressure control valve provided between a valve and the hydraulic pressure source to control hydraulic pressure; a screw position setting means for setting a screw position for switching from a filling stroke to a pressure holding stroke; and a screw position setting means for setting a screw position for switching from a filling stroke to a pressure holding stroke; During the pressure holding process, which is switched from the filling process, the flow rate and pressure of the oil supplied to the injection cylinder for holding pressure are set in advance, depending on the load applied to the screw. The present invention is characterized by comprising a control device capable of independently controlling a flow rate control valve and a pressure control valve.

[0009]

[Operation] With this configuration, the pressure of the oil supplied from the hydraulic source to the injection cylinder is adjusted by the pressure control valve, the flow rate is adjusted by the flow control valve, and the load applied to the screw is reduced during the pressure holding stroke. Since the injection speed and holding pressure can be adjusted independently according to at least one of the flow rate and pressure for holding pressure, which are respectively set in advance, appropriate molding conditions can be obtained. .

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, in the injection device of the present invention, a piston rod 9 of an injection cylinder 8 is connected to a screw 7 that is fitted into a heating cylinder (not shown) of an injection molding machine. The injection cylinder 8 is a double-acting cylinder, and ports 11 and 12 provided on both sides of the piston 10 are respectively connected to two ports 14 and 15 of a servo valve 13 (4-port 3-position switching valve). The other two ports 16 and 17 of the servo valve 13 are connected to a hydraulic power source 18 and a reserve tank 19, respectively. Further, an electromagnetic relief valve 20 is provided between the servo valve 13 and the hydraulic power source 18. In the figure, 21 is a pilot pressure introduction path.

The servo valve 13 receives a control signal from a control device (not shown), operates a solenoid valve, adjusts the pilot pressure, and controls the flow rate of the oil supplied to the ports 11 and 12 of the injection cylinder 8. It is a flow control valve that controls the flow rate.

The electromagnetic relief valve 20 is a pressure control valve for maintaining the hydraulic pressure supplied from the hydraulic power source 18 to the servo valve 13 at a predetermined pressure in response to a control signal from a control device (not shown). It is.

[0013] Furthermore, when the screw 7 reaches the screw position set by the screw position setting means (not shown), this control device thereafter adjusts the holding pressure set in advance according to the load applied to the screw 7. Therefore, the servo valve 13 and the electromagnetic relief valve 20 are each independently controlled so that the flow rate and pressure of the oil supplied to the injection cylinder 8 are controlled by at least one of the flow rate and the pressure.

The operation of this embodiment constructed as above will be explained next. By independently controlling the servo valve 13 and the electromagnetic relief valve 20, the pressure and flow rate of the oil supplied to the injection cylinder 8 can be adjusted independently, and the pressure and flow rate acting on the screw 7 can be adjusted independently. The movement speed can be adjusted independently. That is, the injection pressure and injection speed of the injection device can be adjusted independently.

Therefore, as shown in FIG. 2, for example, the primary injection pressure, the secondary injection pressure, and the tertiary injection pressure are set, and the primary injection speed, the secondary injection speed, and the tertiary injection speed are set with respect to these pressures. Can be done.

The hydraulic pressure generated by the hydraulic power source 18 is adjusted to a predetermined pressure by an electromagnetic relief valve 20 and supplied to the servo valve 13, and the servo valve 13 supplies a predetermined flow rate to the injection cylinder 8. Then, the piston rod 9 expands and contracts at a speed corresponding to the flow rate of the oil supplied to the injection cylinder 8 to move the screw 7.

When the screw reaches the screw position set by the screw position setting means (not shown), the flow rate and pressure of the oil supplied from the hydraulic source 18 to the injection cylinder 8 are controlled by the servo valve 13 and the electromagnetic relief valve. 20 adjusts the flow rate and pressure for pressure holding. At this time, the injection speed and holding pressure will change depending on the load applied to the screw 7, but the flow rate and pressure are controlled by at least one of the flow rate and pressure for holding pressure, which are respectively set in advance. By independently controlling the servo valve 13 and the electromagnetic relief valve 20, it is possible to obtain an appropriate injection speed and holding pressure for holding pressure.

In this way, by improving the molding conditions of the holding process and packing the material into the mold cavity well, it is possible to prevent warpage, distortion, etc. due to residual stress. Therefore, good molding quality can be achieved when molding products such as optical disc substrates that have thin walls, large projected areas, and require advanced optical properties, highly accurate pit transferability, and high dimensional accuracy. can be obtained stably.

[0019]

[Effects of the Invention] The injection device of the injection molding machine of the present invention is configured as described in detail above, so that the pressure of the oil supplied from the hydraulic source to the injection cylinder is adjusted by the pressure control valve.
The flow rate is adjusted with a flow control valve, and the injection speed and holding pressure are independently controlled by at least one of the preset flow rate and pressure for holding pressure, depending on the load applied to the screw during the holding stroke. Therefore, appropriate molding conditions can be obtained. As a result, by improving the molding conditions of the holding pressure stroke and packing the material into the mold cavity well, it is possible to prevent warpage, distortion, etc. due to residual stress. Therefore, good molding quality can be achieved when molding products such as optical disc substrates that have thin walls, large projected areas, and require advanced optical properties, highly accurate pit transferability, and high dimensional accuracy. It has an excellent effect of being able to be obtained stably.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an example of molding conditions when the apparatus of FIG. 1 is used.

FIG. 3 is a hydraulic circuit diagram of an injection device of a conventional injection molding machine.

FIG. 4 is a diagram showing an example of molding conditions when the apparatus of FIG. 3 is used.

[Explanation of sign]

7...Screw 8...Injection cylinder 13...Servo valve (flow control valve) 18...Hydraulic power source

Claims (1)

[Claims] Claims: 1. An injection cylinder for advancing a screw in a heating cylinder to fill a mold cavity with molding material and maintaining pressure; a hydraulic source for supplying oil to the injection cylinder; a flow rate control valve interposed between the injection cylinder and controlling the flow rate of the oil; a pressure control valve installed between the flow rate control valve and the hydraulic pressure source and controlling the hydraulic pressure; a screw position setting means for setting a screw position for switching to a pressure holding stroke; and a screw position setting means for setting a screw position for switching to a pressure holding stroke; A control device capable of independently controlling either the flow rate control valve or the pressure control valve according to either the flow rate or pressure of the oil liquid supplied to the injection cylinder for pressure holding, respectively set. An injection device for an injection molding machine characterized by: