JP2008030379A - Hydraulic circuit for injection apparatus and back pressure controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the back pressure in the neighborhood of non-back pressure (OMPa) in an injection apparatus by adopting a hydraulic motor for controlling the back pressure and adopting a bi-directional hydraulic pump for pressure-conveying and feeding a pressure oil to an injection cylinder. <P>SOLUTION: A hydraulic path of a front room side of the injection cylinder and a hydraulic path of a back room side thereof are connected by a hydraulic pump circuit. The bi-directional hydraulic pump rotating regularly and reversely by an electrically driven servo motor is provided in the hydraulic pump circuit. A check valves are provided in the hydraulic paths on the tank side of the front room side hydraulic path and the back room side hydraulic path. An electromagnetic switching valve is provided and a hydraulic motor for controlling the back pressure rotating regularly and reversely by the electrically driven servo motor is provided in a discharging oil path provided in parallel to the hydraulic path on the back room side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic circuit of an injection device and a back pressure control method capable of performing back pressure control of an injection piston by a hydraulic motor during plasticization measurement of resin.

In a hydraulic injection device in which an injection screw in a heating cylinder is connected to a piston of an injection cylinder, and the resin plasticized and measured by the rotation of the injection screw is moved forward by the injection piston by hydraulic pressure, the mold is injected and filled. The speed of the injection piston retreating by the resin pressure during chemical weighing is controlled by applying a back pressure by hydraulic pressure to the injection piston, and the control is performed by a relief valve.
JP-A-1-281913 JP 7-276449 A

  In the conventional back pressure control, the valve body is biased by a spring even when the back pressure by hydraulic pressure is set to 0 so that no pressure is generated in the oil discharged by setting the relief valve to fully open. Therefore, a pressure is generated in the oil in the cylinder rear chamber that is pressurized by the retreating force of the injection piston, and acts as a back pressure of the injection piston while being low in pressure. For this reason, it is considered that back pressure control near no back pressure (0 MPa) is difficult by back pressure control using only a relief valve, and a back pressure electromagnetic switching valve and a back pressure control logic valve are used in combination.

  However, the back pressure acting on the injection piston is not only the oil pressure, but also the reverse resistance due to the weight of the injection piston (piston + screw) and the frictional resistance of the piston ring acts as a mechanical back pressure. This also contributes to the difficulty of back pressure control near no back pressure.

  The present invention has been conceived from the above circumstances, and its purpose is to employ a hydraulic motor for back pressure control and a bidirectional hydraulic pump for pressure supply of pressure oil to the injection cylinder. An object of the present invention is to provide a hydraulic circuit of an injection device and a back pressure control method that enable back pressure control near no back pressure (0 MPa).

  The hydraulic circuit of the present invention according to the above object includes a hydraulic pump circuit connected over both the front chamber side hydraulic path and the rear chamber side hydraulic path of the injection cylinder, a bidirectional hydraulic pump provided in the hydraulic pump circuit, and the bidirectional circuit thereof. An electric servo motor that rotates the hydraulic pump in the forward and reverse directions, a check valve provided in the tank side hydraulic path of the front chamber side hydraulic path and the rear chamber side hydraulic path, and an electromagnetic switching valve are provided in parallel with the rear chamber side hydraulic path. It comprises a drain oil passage provided, a hydraulic motor for back pressure control provided in the drain oil passage, and an electric servo motor that rotates the hydraulic motor forward and backward.

  Further, the back pressure control by the hydraulic circuit according to the present invention switches the rear chamber side hydraulic path of the injection cylinder to the discharge oil path when plasticizing and metering resin, and discharges oil from the injection cylinder by retreating the injection piston by resin pressure. The pressure oil discharged to the road is controlled by forward / reverse rotation of a hydraulic motor by an electric servo motor to perform back pressure control on the injection piston, and in both directions in synchronization with the backward movement of the injection piston The hydraulic pump is reversely rotated by an electric servo motor, and pressure oil at a flow rate that applies an oil pressure corresponding to the reverse resistance force on the injection piston side to the injection piston is supplied to the front chamber of the injection cylinder. .

  In the above configuration, since it is only necessary to provide a hydraulic motor in the discharge oil passage instead of the relief valve, the configuration of the discharge oil passage is not particularly complicated, and the rotation direction and rotation speed of the hydraulic motor are controlled by an electric servo. Since the back pressure can be controlled by the motor, the back pressure can be easily controlled according to the reverse speed of the injection piston. In addition, oil can be discharged according to the reverse speed so that no pressure is generated in the oil in the rear chamber of the injection cylinder due to the positive rotation of the hydraulic motor, so back pressure control near no back pressure can be easily performed. .

  In addition, both the front chamber side hydraulic path and the rear chamber side hydraulic path of the injection cylinder are connected to a hydraulic pump circuit provided with a bidirectional hydraulic pump, and the rotational direction and rotational speed of the bidirectional hydraulic pump are controlled by an electric servo motor. Thus, since the pressure oil of the tank can be pumped and supplied to both the front chamber and the rear chamber of the injection cylinder, a switching valve for alternately switching the front chamber side hydraulic path and the rear chamber side hydraulic path becomes unnecessary. In the bidirectional hydraulic pump, when the injection piston moves forward, the oil in the front chamber can be pumped and supplied to the rear chamber together with the pressure oil from the tank, thereby reducing the amount of oil used and reducing the size of the tank. .

  Furthermore, in the bidirectional hydraulic pump, when the injection piston moves backward, the pressure oil in the tank can be pumped and supplied to the front chamber of the injection cylinder, so that the injection piston moving backward with resin pressure is pressurized by the oil pressure in the front chamber, Mechanical back pressure due to reverse resistance can be removed, and back pressure control near no back pressure (0 MPa) can be easily performed in combination with back pressure control by the hydraulic motor.

  In the figure, reference numeral 1 denotes an injection cylinder of an injection device, which is provided with an injection piston 2 that can rotate and advance and retract. The cylinder 2 is divided into a front chamber 1a and a rear chamber 1b by a head 2a of the injection piston 2. Although not shown in the figure, an injection screw in the heating cylinder is connected to the tip of the injection piston 2. A metering motor 3 is an electric (AC) servo motor. A drive shaft is inserted into the injection piston so that an injection screw (not shown) can be rotated together with the injection piston 2.

  Reference numeral 10 denotes a hydraulic circuit, a front chamber side hydraulic passage 12 provided between the front chamber 1a and the tank 11, a rear chamber side hydraulic passage 13 provided between the rear chamber 1b and the tank 11, and a front chamber side hydraulic passage 12 thereof. The hydraulic pump circuit 14 connected over both the rear chamber side hydraulic path 13 and the discharge oil path 16 provided with the electromagnetic switching valve 15 in parallel with the rear chamber side hydraulic path 13.

  The hydraulic pump circuit 14 is provided with a bidirectional hydraulic pump 18 that rotates forward and backward by an electric (AC) servo motor 17. By connecting the hydraulic pump circuit 14, in the front chamber side hydraulic path 12 and the rear chamber side hydraulic path 13, the suction of the pressure oil from the tank 11 due to the rotation of the bidirectional hydraulic pump 18 is caused by the rotation direction of the tank side oil path 12a. , 13a are switched, and the pressure oil passes through the hydraulic pump circuit 14. Pilot check valves 19 and 20 are provided in the tank side oil passages 12a and 13a. The check valve 20 of the tank side oil passage 12a is caused by the circuit pressure of the tank side oil passage 13a. The valve is opened by the circuit pressure of the tank side oil passage 12a.

  The drain oil passage 16 is provided with a back pressure control hydraulic motor 22 that rotates forward and backward using an electric (AC) servo motor 21 as a drive source. The pressure oil discharged from the rear chamber 1b to the discharge oil passage 16 is controlled by the rotation direction of the hydraulic motor 22 so that back pressure control can be performed on the injection piston 2 that moves backward by the resin pressure during plasticization measurement. is there. Sensors 23, 24, and 25 for detecting circuit pressure are attached to the front chamber side hydraulic path 12, the rear chamber side hydraulic path 13, and the discharge oil path 16, respectively.

  In the hydraulic circuit 10 having the above-described configuration, as shown in FIG. 1, the rear chamber 1 b and the discharge oil passage 16 are shut off by the electromagnetic switching valve 15, and the rear chamber 1 b is connected to the rear chamber side hydraulic passage 13. 17, when the bidirectional hydraulic pump 18 is rotated forward (in the direction of the arrow), the front chamber side hydraulic path 12 side of the hydraulic pump circuit 14 becomes negative pressure, the check valve 20 is opened, and the pressure oil in the tank 11 is transferred to the tank side. It is sucked up into the oil passage 12a. The pressure oil is pumped from the hydraulic pump circuit 14 to the rear chamber 1b through the rear chamber side hydraulic passage 13 as indicated by the solid line arrow. As a result, the injection piston 2 starts moving forward, and starts injection filling of the resin mold plasticized and measured in the heating cylinder at the tip of the injection screw (not shown).

  In the front chamber 1 a, the pressure oil is pressurized by the forward movement of the injection piston 2, so that the pressure oil flows out to the front chamber side hydraulic path 12 as indicated by the dotted arrow, and further, the tank 11 is rotated by the rotation of the bidirectional hydraulic pump 18. From the rear chamber side hydraulic passage 13 to the rear chamber 1b. As a result, the amount of pressure oil pressure-fed and supplied from the tank 11 to the rear chamber 1b can be reduced by the amount flowing from the front chamber 1a.

  Next, when the operation process in the injection apparatus shifts from the resin injection filling process to the plasticization metering, the forward rotation of the bidirectional hydraulic pump 18 by the electric servo motor 17 is stopped, and as shown in FIG. After the hydraulic path is switched from the rear chamber side hydraulic path 13 to the discharge oil path 16 by the electromagnetic switching valve 15, the metering motor 3 starts and rotates the injection piston 2 together with the injection screw at the tip (not shown), and the heating cylinder Start plasticizing metering of resin inside.

  The injection piston 2 moves backward while discharging the pressure oil in the rear chamber 1b by the pressure of the resin sent into the tip of the heating cylinder by the screw rotation and measured. Further, since the front chamber 1a expanded as the injection piston 2 moves backward becomes negative pressure, the check valve 20 of the tank side oil passage 12a is opened, and the hydraulic pressure of the tank 11 is transferred to the front chamber 1a. Suction supply is carried out through 12.

  The pressure oil discharged from the rear chamber 1 b by the backward movement of the injection piston 2 passes through the hydraulic motor 22 provided in the discharge oil passage 16 and returns to the tank 11. At this time, the hydraulic motor 22 is rotated by the pressure oil in the discharge oil passage 16 and supplies power to the electric servomotor 21. This power is consumed as regenerative electric power of the electric servo motor 21, and the consumed energy is converted into heat by the countercurrent resistance.

  When the hydraulic motor 22 is rotated forward (discharge direction) by the electric servo motor 21, oil is actively discharged from the discharge oil passage 16 to the tank 11, and the flow rate is only the pressurization of the injection piston. And the pressure in the oil in the rear chamber 1b is less likely to stand. Further, since the discharge flow rate varies depending on the rotation speed of the hydraulic motor 22, the back pressure control corresponding to the reverse speed of the injection piston 2 can be performed by the rotation control of the hydraulic motor 22 by the electric servomotor 21.

  When the bidirectional hydraulic pump 18 is reversely rotated by the electric servomotor 17 in synchronization with the forward rotation of the metering motor 3 and the hydraulic motor 22, as shown by the solid line arrow, the pressure oil in the tank 11 is discharged. The oil is sucked up from the tank-side oil passage 13a to the hydraulic pump circuit 14, and is pressurized and supplied from the front chamber-side hydraulic passage 12 to the front chamber 1a, and pressure is applied to the oil in the front chamber 1a. As a result, oil pressure is further applied to the injection piston 2 that moves backward by the resin pressure.

  Since this oil pressure is applied to the injection piston 2 as a pressure against the reverse resistance force, there is no excessive back pressure due to the reverse resistance force on the injection piston side, and the positive oil in the discharge oil passage 16 by the hydraulic motor 22 is eliminated. The back pressure control in the back pressure range of 0 to 2 MPa is facilitated by the discharge. As a result, injection molding of a low-viscosity resin such as a liquid crystal polymer can be performed with high accuracy by back pressure control in the vicinity of no back pressure (0 MPa).

  Further, when the hydraulic motor 22 is rotated in reverse, the hydraulic oil 22 is operated so as to block the flow of the pressure oil, the flow rate of the discharge oil passage 16 is reduced, and the oil pressure rises in the rear chamber 1b and becomes the back pressure of the injection piston 2. When the back pressure reaches the set value and the oil pressure is applied to the hydraulic motor 22, the electric servo motor 21 operates as a brake to keep the back pressure at the set value.

  In the back pressure control, as shown in FIG. 3, the circuit pressure of the drain oil passage 16 is detected by the sensor 25, and the rotational speed of the electric servo motor 21 is detected by the rotational speed detector 26, and the detected value and The shaft torque of the hydraulic motor 22 can be controlled by the electric servo motor 21 in comparison with the set value.

It is a hydraulic circuit diagram at the time of the start of injection of the injection device concerning this invention. It is the hydraulic circuit figure at the time of back pressure control similarly. It is a back pressure control diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection cylinder 1a Front chamber 1b Rear chamber 2 Injection plunger 3 Metering motor 10 Hydraulic circuit 11 Tank 12 Rear chamber side hydraulic path 13 Front chamber side hydraulic path 13a Tank side oil path 14 Hydraulic pump circuit 14a Tank side oil path 15 Electromagnetic switching Valve 16 Drain oil passage 17 Electric servo motor 18 Bidirectional hydraulic pump 19, 20 Pilot check valve 21 Electric servo motor 22 Hydraulic motor for back pressure control

Claims (3)

  A hydraulic pump circuit connected across both the front chamber side hydraulic path and the rear chamber side hydraulic path of the injection cylinder, a bidirectional hydraulic pump provided in the hydraulic pump circuit, and an electric servo motor that rotates the bidirectional hydraulic pump forward and backward A check valve provided in the tank side hydraulic path of the front chamber side hydraulic path and the rear chamber side hydraulic path, a discharge oil path provided in parallel with the rear chamber side hydraulic path by providing an electromagnetic switching valve, and the discharged oil A hydraulic circuit for an injection device, comprising a hydraulic motor for back pressure control provided on a road, and an electric servo motor that rotates the hydraulic motor forward and backward.   2. The hydraulic circuit according to claim 1, wherein a rear chamber side hydraulic path of the injection cylinder is switched to the discharge oil path when plasticizing and metering resin, and the injection cylinder is moved from the injection cylinder to the discharge oil path by retreating the injection piston due to resin pressure. A back pressure control method, wherein the discharged pressure oil is controlled by forward / reverse rotation of the hydraulic motor by an electric servo motor to perform back pressure control on the injection piston.   3. The back pressure control according to claim 2, wherein the bidirectional hydraulic pump is reversely rotated by the electric servomotor in synchronization with the backward movement of the injection piston, and the oil corresponding to the reverse resistance force on the injection piston side is applied to the injection piston. A back pressure control method characterized by supplying pressure oil at a flow rate for applying pressure to the front chamber of the injection cylinder.

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