JP4153466B2 - Injection device for electric injection molding machine - Google Patents

Description

  The present invention relates to an injection apparatus for an electric injection molding machine that forms a molded product by injecting a molten material in a cylinder into a cavity in a mold by advancing a screw by driving an electric motor (injection servo motor). It is about.

  Injection molding in an electric injection molding machine generally includes a process for closing a mold, a mold clamping process for clamping the mold, a nozzle touch process for pressing the nozzle against the mold sprue, and a ball screw connected to the screw by an electric motor. Rotate the screw in the cylinder to advance, and inject the molten material collected in front of the screw into the mold cavity, and then maintain the holding pressure to suppress the generation of bubbles and sink marks for a while. For the next cycle between the pressure holding step and the molten material filled in the mold cavity is cooled and solidified, the screw is rotated and retracted, and the resin is melted and stored in front of the cylinder. Opening the mold and extruding the molded product with the ejector pin provided on the mold in order to remove the solidified molded product from the mold Consisting of the form product ejection process.

  FIG. 4 is a diagram showing the schematic configuration of a conventional injection apparatus, FIG. 5 is a diagram showing details of the nut portion (A), and FIG. 6 is a diagram showing injection maintenance from the conventional injection process to the pressure holding process. It is a graph showing the relationship between the injection speed V and the injection pressure P with respect to the pressure time t.

  In FIG. 4, 1 is a connecting member, 3 is a screw, 4 is a cylinder, 7 is a front plate, 8 is an intermediate plate, 9 is a load cell, 10 is a rear plate, 11 is a ball screw, 12 is a timing belt, and 13 is an electric motor ( Injection servo motor), 14 is a nut, 15 is a controller, 16 is a tachometer, 17 is a rotary servo motor, and 19 is an encoder. These details will be described later with reference to FIG. 1, but only those necessary for the description of the prior art will be described below.

  In general, the injection device of the electric injection molding machine advances the screw 3 in the cylinder 4 by rotating the ball screw 11 connected to the screw 3 by the electric motor 13, so that the molten material collected in front of the screw 3 is collected. A reaction force generated during an injection process for injection into a mold cavity (not shown) is received by the connecting member 1 that connects the front plate 7 and the rear plate 10 and the nut 14.

  In the control of the electric motor 13 in the injection process, first, when the screw 3 is advanced at a set speed by speed control, the filling amount of the molten material into the mold cavity increases with the injection time. The injection pressure P increases. Then, a method is adopted in which the pressure control is switched from the speed control to the pressure control at the holding pressure switching position before the molten material filled in the mold cavity becomes a full pack, and then the holding pressure is applied for a while.

  In this case, the operator generally sets the injection speed and the injection limit pressure so that the injection pressure P does not exceed the injection limit pressure Pa during the speed-controlled injection process.

  However, abnormal conditions during the injection process, for example, when the mold cavity is fully packed, it does not reach the holding pressure switching position, and if injection is performed under the wrong molding condition of maintaining high speed, or during filling In the case where clogging of the molten material occurs in the narrowed flow path portion such as the nozzle or the mold gate, the pressure suddenly rises and the injection pressure P reaches the injection limit pressure Pa as shown in FIG. There can be.

Thus, in the control method of the conventional apparatus, when the injection pressure P reaches the injection limit pressure Pa, the injection speed V is braked to limit the rise of the injection pressure P, and the injection limit pressure Pa is set. Maintaining pressure control is generally employed. That is, in the conventional apparatus, the pressure increase in the cylinder is suppressed by controlling the electric motor (see, for example, Patent Document 1).
JP 2003-300236 A

  However, in the conventional electric injection molding machine, when the pressure P during injection approaches the injection limit pressure Pa, the above-described abnormal state occurs, and the injection pressure P increases rapidly to reach the injection limit pressure Pa. If a situation such as this occurs, suddenly braking the electric motor by the above-described control to suddenly decelerate the injection speed V and stop the pressure rise will cause the rotor and screw of the electric motor to have their axes aligned. There is little inertia during deceleration because of the inertia of the drive system such as the bearing part that is rotatably supported in the center, the ball screw mechanism part assembled in the bearing part, and the timing belt, pulley, and screw that transmits the power of the electric motor to the ball screw mechanism. However, the screw moves forward. In other words, inertial flow cannot be avoided.

  At this time, for example, when nozzle clogging occurs, the molten material from the screw tip to the nozzle tip is compressed, causing a pressure increase, the injection pressure P exceeds the injection limit pressure Pa, and the injection device and the mold are not damaged. The abnormal pressure Pb may be reached beyond the limit pressure PL.

  In particular, when the injection speed is high, the pressure increase becomes an extremely large pressure, and as a result, the injection device and the mold may be damaged. The injection limit pressure Pa is a limit pressure that does not damage the mold against a pressure that repeatedly acts, or a limit pressure on molding quality such that the dimension of the molded product deviates from the allowable dimension. The limit pressure PL is This is a single limit pressure that does not damage the injection device or mold in the event of an abnormality.

  Accordingly, the present invention provides a highly reliable injection apparatus for an electric injection molding machine in which the injection pressure does not exceed the limit pressure due to abnormal molding conditions or abnormal pressure rise caused by clogging of the molten material. With the goal.

  In order to solve the above-described problems, the present invention provides an injection molding having support structures (1, 7, 8, 10) for supporting a cylinder (4) and a screw (3) provided in the cylinder (4), respectively. In the injection device of the machine, when the screw (3) receives a force greater than a predetermined magnitude acting on the rear side thereof, the screw support (1, 8, 10) is applied to the cylinder support (7). On the other hand, the cylinder support part and the screw support part are connected via a displacement mechanism (2, 5) that is displaced rearward by a predetermined amount.

  Moreover, the injection device of the electric injection molding machine of the present invention includes a plate (7, 10) between a front plate (7) for attaching the cylinder (4) and a rear plate (10) for supporting the screw (3). In the injection apparatus for an injection molding machine, provided with an intermediate plate (8) for supporting a screw (3) so that the connecting member (1) is connected, and the connecting member (1) is used as a guide, the front plate (7) and the connecting member (1), the connecting member (1) is applied to the front plate (7) when the screw (3) receives a force of a predetermined magnitude or more acting behind the screw (3). Is mounted via a displacement mechanism (2, 5) that is displaced backward by a predetermined amount.

  The displacement mechanism is constituted by a spring mechanism (2).

  Furthermore, the spring mechanism (2) is inserted between the front end side of the connecting member (1) and the front plate (7), and one end thereof is attached to the front end side of the connecting member (1), The other end is constituted by a spring (2a) attached to the front plate (7).

  According to such a configuration, when the injection pressure becomes equal to or higher than the limit pressure, the spring mechanism (2) is compressed, so that the screw (3) can be prevented from moving forward and the pressure increase in the cylinder (4) can be suppressed.

  In the injection device for an injection molding machine according to the present invention, the displacement mechanism is constituted by a liquid pressure mechanism (5). The fluid pressure mechanism (5) is provided with a fluid pressure cylinder (21) at the tip of the connecting member (1), and the front plate (7) is attached to the cylinder and the piston rod (22a) is connected to the fluid pressure mechanism (5). When the tip of the member (1) is attached and a predetermined force is received, the piston (22) in the cylinder (21) releases the liquid (6) by the liquid pressure device (18), and the cylinder (21) Is capable of being displaced from the front side to the rear side.

  According to such a configuration, when the injection pressure exceeds the limit pressure, the liquid (6) in the liquid pressure mechanism (5) is relieved to stop the screw (3) from moving forward and the pressure in the cylinder (4) increases. Can be suppressed.

  In the embodiment, based on the screw advance speed in the cylinder 4 and the injection pressure, the rotation speed of the injection servo motor 13 that moves the screw 3 via the ball screw 11 is controlled to melt the mold into the cavity. In an injection device of an electric injection molding machine that controls material injection, an inertial flow amount during deceleration from when a braking signal is transmitted from the controller 15 to the injection servo motor 13 until the speed of the screw 3 becomes zero is obtained in advance. In addition, a spring mechanism or a fluid pressure mechanism that has a compression amount that is equal to or greater than the flow amount and that does not compress below the limit pressure is provided.

  As described above in detail, according to the present invention, when an abnormal state in which injection cannot be performed occurs during injection, the spring mechanism (2) is compressed, so that the advance of the screw (3) is stopped. In addition, an increase in injection pressure due to inertial flow can be suppressed. Therefore, even if an abnormal state that prevents injection occurs, pressure exceeding the limit pressure PL is not applied to the injection molding machine or mold, and damage to the injection molding machine or mold can be prevented. An injection apparatus for an injection molding machine that can improve reliability and safety can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an injection device of an electric injection molding machine according to an embodiment of the present invention, and FIG. 2 is a detailed diagram showing a configuration of a spring mechanism 2 of a nut portion (A).

  The injection device of the electric injection molding machine in the embodiment of the present invention includes a cylinder 4 attached to the front plate 7, a screw 3 inserted into the cylinder 4 so as to be able to rotate and move forward and backward, and attached to the intermediate plate 8, A load cell 9 that measures the distortion due to the reaction force of the screw 3 at the time of injection as an injection pressure at the rear end of the screw 3, a ball screw 11 that is attached to the intermediate plate 8 and moves the screw 3 in the axial direction, and a ball screw via a timing belt 12 11 has an injection servo motor (electric motor) 13 that rotates 11.

  The front plate 7 and the rear plate 10 are connected by the connecting member 1 and the nut 14, and the intermediate plate 8 to which the screw 3 is attached is attached so as to be movable using the connecting member 1 as a guide. The controller 15 also controls the injection servo motor 13 based on the signal from the load cell 9 and the signal from the encoder 19 provided in the injection servo motor 13.

  Further, the intermediate plate 8 has a rotary servo motor 17 provided with a tachometer 16 for rotating the screw 3 while melting the resin supplied into the cylinder 4 and plasticizing it while feeding it forward.

Between the connecting member 1 on the front plate 7 side and the nut 14, a spring mechanism 2 having a compression amount Y (Y ≧ X) equal to or greater than the flow amount X and not compressing below a limit pressure is provided. The spring mechanism 2 is configured by a spring 2 a inserted between the front end side of the connecting member 1 and the front plate 7, one end of which is attached to the front end side of the connecting member 1, and the other end attached to the front plate 7. Next, the operation when an abnormal state occurs during injection in the electric injection molding machine of the present embodiment having the above-described configuration will be described.

  First, a signal is transmitted from the controller 15 to the injection servo motor 13 so that the screw 3 moves forward at a set speed, and the molten material is injected into the mold cavity. At this time, injection is performed while constantly measuring the injection speed V and the injection pressure P.

  Furthermore, at this time, an abnormal state during injection, for example, the holding pressure switching position is not reached even though the inside of the mold cavity is fully packed, and thus an incorrect error that maintains high speed. As shown in FIG. 6, when the injection is performed under molding conditions, or when clogging of the molten material occurs in the narrowed flow path portion such as the nozzle and the mold gate during filling, the pressure rapidly increases as shown in FIG. Even if the injection pressure P exceeds the injection limit pressure Pa and the operation is stopped by applying sudden braking to the injection servo motor 13 by motor control, the limit pressure PL is exceeded by the inertial flow.

The reaction force generated at that time is transmitted from the screw 3 to the spring mechanism 2 through the intermediate plate 8, the ball screw 9, the rear plate 10, and the connecting member 1. As a result, when the spring mechanism 2 is compressed by the compression amount Y, the screw 3, the intermediate plate 8, the ball screw 9, the rear plate 10, and the connecting member 1 retreat, and therefore the advancement of the screw 3 relative to the cylinder 4 is suppressed or stopped. An increase in injection pressure due to inertial flow X can be suppressed. Therefore, even when an abnormal state occurs in which injection cannot be performed, pressure exceeding the limit pressure PL is not applied to the injection molding machine or the mold.
Embodiment 2. FIG.
FIG. 3 is a detailed view showing the configuration of the fluid pressure mechanism 5 of the nut portion A of the injection device of the electric injection molding machine according to another embodiment of the present invention. The structure other than the nut portion A is the same as that shown in FIG. 2, and has a compression amount Y greater than the flow amount X between the connecting member 1 on the front plate 7 side and the nut 14 and does not stroke below the limit pressure. The pressure mechanism 5 and the liquid pressure device 18 are provided so that the liquid 6 of the liquid pressure mechanism 5 is relieved by the liquid pressure device 18 when an abnormal state occurs during injection as in the above-described embodiment.

  That is, the liquid pressure mechanism 5 is provided with a hydraulic cylinder 21 at the distal end of the connecting member 1, the front plate 7 is attached to the cylinder, the distal end of the connecting member 1 is attached to the piston rod 22 a, and a predetermined force (corresponding to the limit pressure). The piston 22 in the cylinder 21 releases the liquid 6 by the liquid pressure device 18 when the force is applied, and the cylinder 21 can be displaced from the front side to the rear side.

  Even with such a configuration, when the reaction force described above is generated when the injection process is abnormal, the screw 3, the intermediate plate 8, the ball screw 9, the rear plate 10, and the connecting member 1 are retracted, and the advancement of the screw 3 with respect to the cylinder 4 is stopped. Therefore, an increase in injection pressure due to inertial flow X can be suppressed. For this reason, even when an abnormal state occurs in which injection is impossible, no pressure exceeding the limit pressure PL is applied to the injection molding machine or the mold. Here, oil, water, grease or the like can be applied to the liquid 6.

It is a side view which shows the structure of the injection apparatus of the electric injection molding machine in Embodiment 1 of this invention. FIG. 3 is a configuration diagram illustrating details of a nut portion in the first embodiment. FIG. 6 is a configuration diagram showing details of a nut portion in a second embodiment. It is a figure which shows this schematic structure of the conventional injection apparatus. It is a figure which shows the detail of a nut part (A). It is a graph showing the relationship between the injection speed V and the injection pressure P with respect to the injection pressure holding time t from the conventional injection process to the pressure holding process. It is a graph showing the case where a pressure rises rapidly as a conventional problem, and injection pressure P may reach injection limit pressure Pa.

Explanation of symbols

  1 connecting member, 2 spring mechanism, 2a spring, 3 screw, 4 cylinder, 5 fluid pressure mechanism, 6 liquid (oil, water, grease), 7 front plate, 8 intermediate plate, 9 load cell, 10 rear plate, 11 ball screw, 12 timing belt, 13 electric motor (injection servo motor), 14 nut, 15 controller, 16 tachometer, 17 rotation servo motor, 18 fluid pressure device, 19 encoder, 21 cylinder, 22 piston, 22a piston rod.

Claims (6)

In an injection apparatus for an injection molding machine having a support structure for supporting a cylinder and a screw provided in the cylinder,
When the screw receives a force greater than a predetermined magnitude acting on the rear side thereof, the screw support portion and the cylinder support portion are displaced via a displacement mechanism that is displaced rearward by a predetermined amount with respect to the cylinder support portion. An injection apparatus for an injection molding machine, wherein the screw support portion is connected. An injection molding machine in which a connecting member for connecting these plates is provided between a front plate for mounting a cylinder and a rear plate for supporting a screw, and an intermediate plate for supporting the screw is provided so that the connecting member serves as a guide. In the injection device,
Through a displacement mechanism that causes the front plate and the connecting member to be displaced rearward by a predetermined amount with respect to the front plate by receiving a force of a predetermined magnitude or more that acts on the rear of the screw. An injection device for an injection molding machine, characterized by being attached. In the injection apparatus of the injection molding machine according to claim 1 or 2,
2. The injection apparatus of an injection molding machine, wherein the displacement mechanism is constituted by a spring mechanism. In the injection apparatus of the injection molding machine according to claim 3,
The spring mechanism is configured by a spring inserted between the front end side of the connecting member and the front plate, one end of which is attached to the front end side of the connecting member, and the other end attached to the front plate. An injection apparatus for an injection molding machine. In the injection apparatus of the injection molding machine according to claim 1 or 2,
An injection apparatus for an injection molding machine, wherein the displacement mechanism is constituted by a liquid pressure mechanism. In the injection apparatus of the injection molding machine according to claim 5,
The fluid pressure mechanism is provided with a fluid pressure cylinder at the tip of the connecting member, the front plate is attached to the cylinder, the tip of the connecting member is attached to the piston rod, and when a predetermined force is received, An injection apparatus for an injection molding machine, characterized in that a piston is displaceable from the front side to the rear side by releasing the liquid by a liquid pressure device.

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