JPH0531779A - Injection device and injection controlling method of injection molding machine - Google Patents

Abstract

PURPOSE:To enhance an infection controlling property by setting the discharge quantity of a variable discharge-type pump from the injection speed of a screw plunger that is determined by a sort of molding materials and the like, and providing a controller for setting the relief pressure of a relief valve by calculating the maximum discharge pressure the correlation between the set discharge quantity and the capacity of an electric motor. CONSTITUTION:A hydraulic pump 36 is of the type of a variable discharge-type pump capable of being driven by a constant speed electric motor, and the relief valve 46 serves to make the set pressure variable. Subsequently, the maximum discharge pressure is calculated by a controller 48 from the correlation between the pump discharge quantity calculated from the set injection speed of a screw plunger 18 and the capacity of the electric motor, and then injection driving is effected by adjustment-controlling the pump discharge quantity and discharge pressure within the range of these pump discharge quantity and maximum discharge pressure. In this manner, the high pressure- low speed infection and constant pressure-high speed infection can be set arbitrarily, to thereby improve the infection controlling property, and thus the most suitable injection requirements can be set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device and an injection control method for an injection molding machine, and more particularly to performing injection over a wide range from high pressure low speed injection to low pressure high speed injection according to changes in injection molding materials and the like. The present invention relates to a preferable injection device of an injection molding machine and a control method thereof.

[0002]

2. Description of the Related Art As shown in FIG. 3, a general injection device in an injection molding machine includes a hydraulic pump 2 for supplying a working hydraulic pressure to an injection cylinder 1. Pump 2 is electric motor 3
It is driven by, and is usually composed of a constant discharge pump. An electromagnetic opening / closing valve 4 and a flow rate control valve 6 are provided in the middle of a hydraulic pressure supply path from the pump 2 to the injection cylinder 1. The opening operation of the opening / closing valve 4 supplies pressure oil to the cylinder 1 during injection to control the flow rate. While controlling the amount of pressure oil, that is, the injection speed by the valve 6, the cylinder 1 is driven,
An injection operation is given to the screw plunger that is interlocked with the cylinder 1. Further, in order to manage the discharge pressure of the pump 2, that is, the injection pressure, a relief valve 5 is provided in the hydraulic pressure supply passage on the discharge side of the pump 2, and when the pressure is equal to or higher than the set pipeline pressure, the pressure is stored in the tank. I'm trying to miss it.

In a conventional injection molding machine, the injection speed and injection pressure required for each molded product are determined by the type of molding material, the gate, the shape of the molded product, and the like.
Therefore, in the conventional machine, the discharge amount of the flow control valve 6 is set by the speed at which the injection cylinder 1 is driven, and the relief pressure is set by the required discharge pressure. Then, the capacity of the electric motor for driving the pump is determined by the maximum capacity determined by the discharge amount and the relief pressure.

However, in the injection device manufactured after the specifications such as those of the conventional machine are manufactured, when the injection material is changed or the cavity shape is changed, the injection condition is changed, and sometimes the injection device itself is changed. It may be necessary to change the specifications, that is, the maximum discharge pressure and the maximum discharge amount. In order to eliminate the complexity of changing the injection device according to this injection condition correspondence, as shown in FIG. 4, the injection cylinder 1A has a tandem structure configured to have different pressure receiving areas, and the injection cylinder 1A has a tandem structure. An injection device has been proposed in which pressure oil is supplied from the hydraulic pump 2 via a branch line. In this injection device, electromagnetic on-off valves 4A and 4B are provided in each of the branch lines, and the cylinder chamber to be used is changed by switching operation of the on-off valves 4A and 4B so that the screw plunger is driven at low pressure high speed or high pressure low speed. It is switched to and used. Further, there is also known an injection device of the same type as that in which an injection cylinder has a parallel structure (Japanese Patent Publication No. 62-27651).

[0005]

However, in the above-mentioned conventional injection device, the relationship between the injection pressure and the injection speed becomes the characteristic line X in FIG. 2B in the case of the single cylinder structure shown in FIG. The tandem cylinder structure shown in FIG. 4 has a stepwise characteristic as shown by characteristic lines Y and Z in FIG. 2B, and the pressure and speed can be arbitrarily set only within the range of the characteristic line. There was a defect (Fig. 3 (2), Fig. 4
(2) Hatching part cannot be set). Moreover, there is a problem that the structure becomes complicated when the injection cylinder having the tandem structure or the parallel structure is adopted.

Focusing on the above-mentioned conventional problems, the present invention makes it possible to arbitrarily set high-pressure low-speed injection and constant-pressure high-speed injection, improve injection controllability, and set an optimum injection condition. It is an object of the present invention to provide an injection device and a control method.

[0007]

In order to achieve the above object, an injection device of an injection molding machine according to the present invention includes a hydraulic pump connected to an oil supply port of an injection cylinder of the injection molding machine via an opening / closing valve. An injection device provided with a relief valve interposed in the oil supply passage of the hydraulic pump and driving the piston of the injection cylinder by the oil supply from the hydraulic pump to give an injection operation to the screw plunger. A variable discharge pump driven by a rotating electric motor, the relief valve is configured as a variable relief valve, and the discharge amount of the variable discharge pump is determined from the injection speed of the screw plunger determined by the type of molding material. The maximum discharge pressure is calculated from the relationship between the set discharge amount and the displacement of the electric motor while setting the relief valve. Is obtained by a configuration in which a controller for setting a leaf pressure.

Further, the injection control method according to the present invention includes a hydraulic pump connected to an oil supply port of an injection cylinder of an injection molding machine via an opening / closing valve, and a relief valve provided in an oil supply passage of the hydraulic pump. In the injection control method for driving the piston of the injection cylinder by supplying oil from the hydraulic pump to give an injection operation to the screw plunger, the hydraulic pump is a variable discharge pump that can be driven by an electric motor rotating at a constant speed. At the same time, the relief valve has a variable set pressure, the maximum discharge pressure is calculated from the relationship between the pump discharge amount calculated from the set injection speed of the screw plunger and the capacity of the electric motor, and the pump discharge amount and the maximum discharge pressure are calculated. Within this range, the pump discharge amount and discharge pressure are adjusted to adjust the injection drive.

[0009]

According to the above structure, the injection operation of the screw plunger in the injection device is supplied by the variable discharge hydraulic pump driven by the constant-speed electric motor.
When the injection speed is set by determining the molding material, shape of the molded product, etc., the pump discharge rate can be determined based on this.
It is set by the discharge amount adjusting means of the pump. On the other hand, the rated capacity of the electric motor that drives the pump is constant, which is proportional to the product of the pump discharge amount and the discharge pressure, so that the maximum discharge pressure can be determined by the relationship between the capacity of the electric motor and the pump discharge amount. Therefore, the maximum injection pressure can be automatically set by adjusting the set pressure of the relief valve by the controller so as to correspond to the maximum discharge pressure.

In the above structure, the injection speed can be arbitrarily set by adjusting the discharge amount of the variable discharge pump,
The injection pressure can be arbitrarily set by adjusting the relief pressure within the range of the maximum set pressure. Therefore, normally, a pump that can obtain the maximum discharge amount at the maximum rated capacity of the electric motor is selected, but since the relief pressure can be arbitrarily adjusted, it is possible to select a hydraulic pump whose pump capacity is equal to or larger than the electric motor capacity. . As a result, while adopting a constant-speed rotary motor, it becomes possible to perform injection control that changes linearly in the range from high-pressure low-speed injection to low-pressure high-speed injection, so-called stepless injection control is possible, and controllability is greatly improved. is there.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of an injection device and an injection control method for an injection molding machine according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an injection device of an injection molding machine according to an embodiment. As shown in this figure, the injection device includes a heating cylinder 16 provided with a nozzle 14 connected to a gate 12 of a mold 10, and a screw plunger 18 is incorporated in the cylinder 16. A material supply hopper 20 is attached to the heating cylinder 16, and the material from the hopper 20 falls into the heating cylinder 16 by its own weight and is sent to the tip of the cylinder 16 while being kneaded by the rotation of the screw plunger 18. It is like this. In order to drive the screw plunger 18 to rotate, a screw rotation drive unit 22 is attached to the rear end of the screw plunger 18. When the tip of the heating cylinder 16 is filled with the molten material, the screw plunger 18 moves backward due to the reaction force of the material, and the backward movement amount is restricted by a limit switch (not shown) or the like, and the rotation of the screw plunger 18 is stopped. We try to measure by doing so.

After the above-mentioned measurement, the screw plunger 18 is advanced to perform injection. Due to this injection operation,
An injection cylinder 24 is provided. In this embodiment, the injection cylinder 24 is installed parallel to the screw plunger 18, and its rod 26 is connected to a mounting plate 28 of the screw rotation drive unit 22 so that the screw plunger 18 can be axially driven. A piston 3 connected to the rod 26 is provided inside the injection cylinder 24.
No. 0 is slidably mounted, and an injection operation is given by supplying hydraulic oil to one of the cylinder chambers 32A and 32B, which is partitioned by 0.

In such a structure, hydraulic oil is supplied to the cylinder chamber 32B for driving the injection cylinder 24 from a hydraulic pump 36 driven by a constant speed rotary electric motor 34. This hydraulic pump 36
Is configured as a variable discharge type piston pump.

An electromagnetic opening / closing valve 40 is provided in the middle of the hydraulic pressure supply line 38 extending from the variable discharge hydraulic pump 36 to the injection cylinder 24, and connects the pump 36 and the injection side cylinder chamber 32B during injection. When connecting and communicating and filling the heating cylinder with material, the pump 36 and the cylinder chamber 32
The connection with B is cut off.

Further, a branch pipe line 44 is provided between the hydraulic pump 36 and the opening / closing valve 40, which branches from the hydraulic pressure supply pipe line 38 to reach the tank 42, and a relief valve 46 is interposed in the branch pipe line 44. The relief valve 46 is activated when the line pressure reaches or exceeds a predetermined value, returns the pump pressure to the tank 42, and allows the injection pressure to be set. In this embodiment, the relief valve 46 has a variable set pressure structure so that the injection pressure can be set arbitrarily.

The variable discharge hydraulic pump 36 described above is also used.
A controller 48 is provided in the injection device so that the set values of the variable relief valve 46 and the variable relief valve 46 can be adjusted. In the controller 48, the injection speed v is set according to specifications such as the type of molding material, the gate size, and the product shape as described above. The required discharge amount Q from the pump 36 is calculated in accordance with the injection speed v. , Also electric motor 3
The maximum value of the injection pressure is calculated from the rated output of No. 4, and the set output is made to the pump 36 and the relief valve 46 based on these performance results. That is, when the injection speed v of the screw plunger 18 is set, the pressure receiving area A of the piston 30 in the cylinder chamber 32B of the injection cylinder 24 is known, so the required discharge amount Q is calculated by the following equation.

[0018]

[Equation 1] Q = Av

Therefore, it is assumed that the controller 48 sets and outputs to the pump 36 so that the discharge amount Q is obtained.

It is known that the output N (kw) of the electric motor 34 is proportional to the product of the discharge pressure p and the discharge amount Q,
The following equation holds. However, α is a constant.

[0021]

(2) N = αpQ

Therefore, the discharge pressure p can be easily calculated by the known rated output N and the calculated discharge amount Q. The calculation result is output from the controller 48 to the variable relief valve 46, and the relief pressure is set to p. This set pressure p is the electric motor 34
The maximum value within the capacity of.

In this way, the discharge amount Q of the variable discharge pump 36 is calculated, and from this, the relief pressure p of the variable relief valve 46 is set by the controller 48, and the injection condition is set. In this case, the following equation is established from the above equations 1 and 2.

[0024]

## EQU00003 ## pv = N / .alpha.A = const.

Therefore, the relationship between the discharge pressure p and the injection speed v by this injection device shows a characteristic line A as shown in FIG. However, the discharge pressure p has a pump capacity of 1 in practice.
Since it is 40 to 210 Kg / cm ² , the upper limit of the maximum discharge pressure is actually set to 140 to 210 Kg / cm ² in FIG.
The characteristic line B shown in (2) is obtained. The discharge pressure and the injection pressure are proportional.

From the above, in the injection apparatus using the constant speed rotary motor 34 according to the embodiment, the maximum discharge pressure p is automatically set by setting the injection speed v, and therefore the high speed is achieved. Injection control is performed linearly over the range from low-pressure injection to low-speed high-pressure injection, and injection that meets the injection conditions at that time can be performed. As a result,
The complicated work of changing the specifications of the injection device having different pumping capacity and relief pressure by changing the injection conditions becomes unnecessary. Further, there is no inconvenience that a control region that cannot be adjusted by the tandem injection cylinder structure is generated. Therefore, precise injection control is possible.

Further, in the above-mentioned structure, since pv = constant, the discharge pressure p, that is, the injection pressure can be controlled, and the injection control can be performed mainly by the injection pressure. Further, the hydraulic pump 36 is generally selected to have a capacity that matches the capacity of the electric motor 34, but a pump capacity greater than the capacity of the electric motor 34 can be adopted by controlling the injection pressure. In other words, even if the capacity of the electric motor 34 is small, it is possible to provide a higher injection capacity.

[0028]

As described above, according to the present invention,
The hydraulic pump is a variable discharge type pump driven by a constant speed electric motor, and the relief valve is configured as a variable relief valve, and the variable discharge type is determined from the injection speed of the screw plunger determined by the type of molding material. A range of pump discharge amount and maximum discharge pressure is provided with a controller that sets the discharge amount of the pump and calculates the maximum discharge pressure from the relationship between the set discharge amount and the capacity of the electric motor to set the relief valve. Since it is configured to adjust the pump discharge amount and discharge pressure to drive the injection inside, high pressure low speed injection and constant pressure high speed injection can be set arbitrarily, and injection controllability can be improved and optimum injection conditions can be set. The effect is obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an injection device according to an embodiment.

FIG. 2 is a diagram showing characteristics of an injection pressure and an injection speed by the device.

FIG. 3 is a configuration diagram of a conventional general injection apparatus and a characteristic diagram thereof.

FIG. 4 is a configuration diagram of an injection device according to another conventional example and a characteristic diagram thereof.

[Explanation of symbols]

10 mold 12 gates 14 nozzles 16 heating cylinder 18 Screw Plunger 22 Screw rotation drive 24 injection cylinder 34 constant speed rotary motor 36 Variable discharge hydraulic pump 40 solenoid valve 46 Variable relief valve 48 controller

Claims (2)

[Claims] 1. A hydraulic pump connected to an oil supply port of an injection cylinder of an injection molding machine via an opening / closing valve, and a relief valve installed in an oil supply passage of the hydraulic pump,
In the injection device that drives the piston of the injection cylinder by the oil supply from the hydraulic pump to perform the injection operation to the screw plunger, the hydraulic pump is a variable discharge type pump driven by a constant speed electric motor, and the relief valve is used. Is configured as a variable relief valve, the discharge amount of the variable discharge pump is set from the injection speed of the screw plunger determined by the type of molding material, and the maximum discharge is set based on the relationship between the set discharge amount and the capacity of the electric motor. An injection device for an injection molding machine, comprising a controller for calculating a pressure and setting a relief pressure of the relief valve. 2. A hydraulic pump connected to an oil supply port of an injection cylinder of an injection molding machine via an opening / closing valve, and a relief valve installed in an oil supply passage of the hydraulic pump,
In the injection control method of driving the piston of the injection cylinder by the oil supply from the hydraulic pump to perform the injection operation to the screw plunger, the hydraulic pump is a variable discharge type pump that can be driven by a constant speed electric motor, and The relief valve has a variable set pressure, the maximum discharge pressure is calculated from the relationship between the pump discharge amount calculated from the set injection speed of the screw plunger and the capacity of the electric motor, and within the range of these pump discharge amount and maximum discharge pressure. An injection control method for an injection molding machine, characterized in that the pump discharge amount and discharge pressure are adjusted to adjust the injection drive.