JP2008030267A - Electric injection unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly measure injection pressure and back pressure from the quantity of distortion of a steel sheet even when an apparatus is miniaturized by adopting a lengthy steel sheet for connecting the front and rear plates of an electric injection unit and making the steel sheet a distortion member for detecting pressure. <P>SOLUTION: An injection plate holding the rear end of a screw in an injection heating cylinder rotatably is set forward/backward movably between the front plate having the injection heating cylinder and the rear plate having an electric motor for injecting/driving. The plates are fixed to the sliding stand of a guide means placed on the upper surface of a base to be set movably on the base. The front and rear plates are separated from the injection plate and connected to each other by lengthy steel sheets set on both sides of the plate. At least one of the steel sheets is fitted with a distortion detector on the side to be the distortion member for detecting pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric injection apparatus that uses an electric motor to drive an injection of a screw in an injection heating cylinder.

In the electric injection device, an intermediate plate (rotatably holding a rear end of a screw in the injection heating cylinder between a front plate having an injection heating cylinder and a rear plate having an electric motor for driving the injection ( The injection plate is connected to the front and rear plates by a tie bar made of a steel rod that penetrates the intermediate plate, and the rotation of the electric motor is converted into a linear motion. Provided. As a means for measuring the injection pressure, a load cell is provided between the tip of the ball screw shaft of the injection driving means and the center of the back surface of the intermediate plate, or a strain detector is attached to the tie bar.
JP 2003-80559 A

  In the detection of the injection pressure by the load cell, a load cell is disposed on the central axis of the ball screw shaft to prevent detection errors due to uneven loads. For this reason, it is necessary to provide a load cell accommodating portion in the intermediate plate, and the internal structure of the intermediate plate becomes complicated accordingly. Therefore, there is a problem that it is difficult to adopt as the electric injection device is downsized.

  In addition, detection of injection pressure due to tie bar distortion requires only a strain detector attached to the tie bar, which is easier than with a load cell. However, the tie bar penetrates the intermediate plate and is installed on the front and rear plates. For this reason, the detection accuracy of the injection pressure is likely to be lowered by bending due to the load of the intermediate plate or by receiving frictional resistance during movement. In addition, the length of the tie bar is limited by the distance between the front and rear plates, and the amount of distortion due to the elongation is proportional to the length. Therefore, it is necessary to cause elongation corresponding to the injection pressure. However, it is difficult to reduce the size of a standard strain detector so as to be compatible with a small-diameter tie bar in terms of detection accuracy, and it may be difficult in terms of mounting accuracy.

  An object of the present invention is to reduce the size of an electric injection molding machine (for example, a clamping force of 5 t or less) by adopting a long steel plate to connect the front and rear plates and using the steel plate as a strain member for pressure detection. In addition, it is possible to use standard strain detectors that are normally used in the miniaturization of the injection device, and the injection pressure and back pressure can be reduced without receiving interference from the injection plate between the front and rear plates. It is an object of the present invention to provide a new electric injection device that can accurately measure the amount of distortion.

  According to the above-mentioned object, the present invention provides a front plate having an injection heating cylinder, a rear plate having an electric motor for driving an injection, and a rear end of a screw in the injection heating cylinder, which is positioned between the two plates so as to freely advance and retract. It consists of an injection plate that is rotatably held, and an injection drive means that moves the injection plate forward by converting the rotation of the electric motor into a linear motion. The front plate and the rear plate are separated from the injection plate and connected by long steel plates installed on both sides of the plate, and at least one of the steel plates is distorted on the side surface. A detector is provided as a strain member for pressure detection.

  Further, the injection driving means includes a pair of rotatable ball screw shafts that pass through the injection plate and are supported in parallel on both in-plane sides of the front plate and the rear plate, and in a penetration portion of each ball screw shaft of the injection plate. It consists of a pair of ball nut members that are screwed together with a ball screw, and the long steel plates are installed on both sides of the front plate and the rear plate in parallel with the ball screw shaft.

  The guide means includes a linear guide rail laid on both sides of the upper surface of the machine base, a linear guide member slidably fitted to the linear guide rail, and the linear guide member attached to the lower surface. It consists of the above-mentioned sliding table.

  In the above configuration, since the long steel plates connecting the front and rear plates are separated from the injection plate, they are not affected by the deflection caused by the load of the injection plate or the frictional resistance accompanying the movement, and the front and rear plates are injected. Since the friction resistance at the support part at the bottom of the plate is reduced by supporting the plate with the guide means on the upper surface of the machine base, even if pressure detection is performed using a steel plate as a strain member, the injection pressure is determined from the amount of strain in the steel plate. Both back pressure and back pressure can be measured accurately.

  In addition, because the strain member is a steel plate, the attachment to the front and rear plates is performed by contacting the plate side with the plate surface as the back, so that even if the steel plate is installed on the front and rear plates, it bends by its own weight. In addition, since the mounting surface of the strain detector is secured by the plate surface, even if the distance between the front and rear plates of the injection device is extremely short (for example, a clamping force of 10 KN or less), the injection pressure and the back pressure Can be accurately detected.

  In the figure, 1 is a front plate, 2 is a rear plate, and 3 is an injection plate, which are individually installed on a sliding table 6 provided on guide means 5 laid on both sides of the upper surface of the machine base 4. The guide means 5 comprises a linear guide rail 5a and a linear guide member 5b which is attached in the lower part of each slide base 6 and is slidably fitted to the rail.

  The front plate 1 includes an injection heating cylinder 8 in which an injection screw 7 is rotatably and reciprocally mounted at the front center, and the rear plate 2 is provided with an electric motor 9 for injection driving by a servo motor. The injection plate 3 is positioned between the front and rear plates 1 and 2 so as to freely move back and forth, and a rotary shaft 7a provided with a rear end of the screw 7 protruding from the rear portion of the injection heating cylinder 8 of the front plate 1 in the center portion. And the screw 7 is rotatably held. A pulley 10 for transmitting the rotation of a metering electric motor (not shown) is attached to the front end of the rotating shaft 7a.

  A pair of rotatable ball screw shafts 11, 11 are mounted in parallel on both sides of the front plate 1 and the rear plate 2 in a diagonal line so as to penetrate the injection plate 3. A pair of ball nut members 12, 12 are screwed into the ball screw shafts 11, 11 in the portions of the injection plate 3 through which the ball screw shafts 11, 11 pass. 12, the rotation of the ball screw shafts 11 and 11 is converted into a linear movement of the injection plate 3, and the injection plate 3 moves forward together with the screw 7 and is driven for injection. The rotation of the ball screw shafts 11 and 11 by the electric motor 9 is caused by a drive belt 15 provided over the pulleys 13 and 13 at the shaft end protruding from the rear surface of the rear plate 2 and the pulley 14 at the drive shaft end of the electric motor 9. Is done through.

  The front plate 1 and the rear plate 2 are connected to each other by long steel plates 16 'and 16 "installed on the upper and lower positions on both sides. The steel plates 16' and 16" have a rectangular cross section and the same cross section. The cross-sectional area is set so as to have a necessary cross-sectional area in consideration of the strain amount necessary for detecting the injection pressure and the steel plate material. Further, the steel plates 16 'and 16 "are separated from the injection plate 3 in parallel with the ball screw shafts 11 and 11, and both ends formed wide are attached to the side surfaces of both plates with the plate surface as the back, and are attached to the upper steel plate 16'. A strain detector 17 (tie bar sensor manufactured by Minebea Co., Ltd .: UX010) is fastened with bolts and attached to both side surfaces, whereby the upper steel plate 16 'is used as a strain member for pressure detection, and the amount of strain of the steel plate 16'. The injection pressure and back pressure can be measured.

  Reference numeral 18 denotes a nozzle touch means. A ball shaft having a tip end portion inserted through the lower center of the rear plate 2 and the injection plate 3 through a rotating shaft 15a having a ball screw shaft and a ball screw portion provided in the lower center of the front plate 1 A nozzle touch force generator 18c having a normal structure with a spring is disposed between a shaft tip screwed into the nut member 15b and protruding from the front plate 1 and the fixing plate 19 of the mold clamping device.

  In this nozzle touch means 18, the rear end of the rotating shaft 18a is connected to an electric motor 20 with a brake installed at the center of the upper surface of the machine base 4, so that the rotating shaft 18a can be rotated forward and backward by the electric motor. In the forward rotation (left rotation), the rear plate 2 and the injection plate 3 move forward together with the front plate 1, and the nozzle at the tip of the injection heating cylinder 8 touches the mold 19a and the nozzle touch as shown in the figure. The force generator 18c is repelled. In reverse rotation (right rotation), the nozzle moves backward and moves away from the mold 19a.

  In the above configuration, in the nozzle touch state shown in FIG. 1, when the ball screw shafts 11, 11 rotate forward (rotate counterclockwise), the injection plate 3 moves forward together with the injection screw 7 and is metered into the tip of the injection heating cylinder 8. The injection screw 7 pressurizes the molten resin, and the molten resin is injected from the nozzle into the mold 19a. The reaction force against the injection pressure acts on the rear plate 2 via the ball screw shafts 11 and 11. Since the rear plate 3 is not fixed on the machine base but is supported by the linear guide rail 5a together with the front plate 1, and is connected to the front plate 1 by the steel plates 16 ', 16 "on both sides, the reaction force is the steel plate 16 ′, 16 ″ concentrates as a tensile force, and the steel plates 16 ′, 16 ″ extend to generate distortion.

  Further, when plasticizing and weighing the resin by the rotation of the injection screw 7, the backward movement of the injection plate 3 is controlled by the rotation control (right rotation) of the ball screw shafts 11 and 11, and the back pressure corresponding to the resin pressure is generated. Therefore, the reaction force of the back pressure acts on the rear plate 3. As a result, the steel plates 16 'and 16 "are pulled and strained as in the injection.

  The strain amount of the steel plates 16 'and 16 "is detected by a strain detector 17 on the side surface of the steel plate 16'. Since the strain amount due to tension differs depending on the injection pressure and back pressure, the detected steel plate 16 'is detected there. The injection pressure and the back pressure can be measured from the amount of distortion of the steel plate.In addition, the steel plates 16 'and 16 "having a rectangular cross section are brought into contact with the side surfaces of the front and rear plates with the plate surface as the back without passing through the injection plate 3. Since the two plates are connected, there is no bending of the steel plates 16 'and 16 "due to the interference of the load of the injection plate 3, and even if the plate body is installed on the front and rear plates, it will not be bent by its own weight. Therefore, a back pressure significantly lower than the injection pressure can be accurately measured from the strain amount of the steel plate 16 '.

  Although not shown, the strain detector 17 may be attached to both of the steel plates 16 'and 16 ". In this case, the average value of the strain amount detected from both can be used as the detected value. The accuracy of pressure measurement is further improved.

It is a side view of the electric injection device concerning this invention. It is a top view same as the above. It is the sectional view on the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front plate 2 Rear plate 3 Injection plate 4 Machine stand 5 Guide means 5a Linear guide rail 5b Linear guide member 6 Slide stand 7 Injection screw 8 Injection heating cylinder 9 Electric motor 11 for injection drive Ball screw shaft 12 Ball nut member 16 '16 "Steel plate 17 Strain detector

Claims (3)

  A front plate having an injection heating cylinder, a rear plate having an electric motor for driving the injection, and an injection plate which is positioned between the two plates so as to freely move forward and backward and rotatably holds the rear end of the screw in the injection heating cylinder. And an injection drive means for converting the rotation of the electric motor into a linear motion to move the injection plate forward, and these plates are fixed on the slide base of the guide means laid on the top surface of the machine base. The front plate and the rear plate are separated from the injection plate and connected by a long steel plate installed on both sides of the plate. At least one of the steel plates is attached with a strain detector on the side surface. An electric injection device characterized by being a strain member for pressure detection.   The injection drive means includes a pair of rotatable ball screw shafts that pass through the injection plate and are supported in parallel on both in-plane sides of the front plate and the rear plate, and a ball in a penetration portion of each ball screw shaft of the injection plate. 2. A pair of ball nut members screwed to a screw, wherein the long steel plate is installed on both sides of a front plate and a rear plate in parallel with the ball screw shaft. The electric injection device described.   The guide means includes a linear guide rail laid on both sides of the upper surface of the machine base, a linear guide member slidably fitted to the linear guide rail, and the linear guide member attached to the lower surface and provided on the linear guide rail. The electric injection device according to claim 1, comprising the sliding table.

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