JPH08169038A - Pressure detecting device for injection molding machine - Google Patents

Abstract

PURPOSE: To detect pressure with a high precision in injection molding by providing a strain sensor for detecting extension quantity of a guide bar in the guide bar which guides movement of a moving body to be moved back and forth integrally with a screw in a heating cylinder, in an in-line screw type injection molding machine. CONSTITUTION: In a process of injection charging, a ball screw axis 13 is rotated so as to advance a screw 4 together with a moving body 8 and injection charging of a melting resin into a mold from a nozzle 3 is performed. A guide bar 6 in which the moving body 8 is slidably inserted and whose both ends are supported by holding blocks 1 and 5 has a housing hole 6a punched from an end part in the axial direction. Into the back of the housing hole 6a, a sensor 20a of a strain sensor unit 20 is screwed. The holding block 5 receives a force F' in the opposite direction by a reaction at the time that the moving body 8 receives a motive force F in the axial direction. When the guide bar 6 is extended, the strain sensor unit 20 detects an extension quantity of the guide bar 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device in an inline screw type injection molding machine using an electric servomotor as a drive source for injection.

[0002]

2. Description of the Related Art An in-line screw type injection molding machine using an electric servo motor as a drive source of an injection system mechanism is known, and compared with an in-line screw type injection molding machine using a hydraulic drive source such as an injection hydraulic cylinder. Since it can precisely control feedback of speed and pressure, it has been adopted in many models recently.

In an injection molding machine, the speed and pressure of the injection stroke (the primary injection stroke and the subsequent pressure-holding stroke) are important control factors for molding a good product. Must be monitored and for this reason
A sensor for detecting the injection speed and the injection pressure is provided. By the way, in an injection molding machine using a hydraulic cylinder as an injection drive source, the injection pressure (injection resin pressure) can be detected by detecting the hydraulic pressure, so that the pressure can be easily detected by a relatively inexpensive hydraulic sensor. But
In an injection molding machine that uses an electric servomotor as an injection drive source, there is a rotation-> linear motion conversion mechanism. Therefore, conventionally, the injection pressure (injection resin pressure) is detected by detecting the compression force generated by the linear motion. I was trying to detect.

FIG. 5 is a diagram showing a main structure of an injection system mechanism of such a conventional electric injection molding machine. In the figure, 1 is a holding block (tailstock) fixedly arranged, 2 is a heating cylinder whose rear end is held by the holding block 1, 3 is a nozzle attached to the tip of the heating cylinder 2, and 4 is a nozzle. A screw (only the rear end of the screw is shown in the figure) built in the heating cylinder 2 so as to be rotatable and movable back and forth, 5 is a holding block fixedly arranged, and 6 is a holding block. A plurality of guide bars stretched between the holding blocks 1 and 5, 7 is a mounting nut fastened to the end of the guide bar 6, and 8 is inserted into the guide bar 6 and slides along the guide bar 6 (forward and backward movement). ) A movable body that can be integrated with the movable body 8 and the screw 4
Is moving back and forth.

Reference numeral 9 denotes an injection electric servomotor properly mounted on a fixed base (hereinafter referred to as injection motor 9).
The output pulley 10 is fixed to the rotary shaft.
A pulley 11 is rotatably held by the holding block 5, and a timing belt 12 is provided between the pulley 11 and the output pulley 10.
Have been passed over. A ball screw shaft 13 is rotatably held by the holding block 5 and is connected to the pulley 11 so as to rotate integrally therewith. Reference numeral 14 denotes a nut body screwed to the ball screw shaft 13, which is non-rotatably attached to the moving body 8. When the nut body 14 moves in the axial direction as the ball screw shaft 13 rotates, it becomes integral with the nut body 14. The moving body 8 is moved back and forth.

Reference numeral 15 denotes an electric servomotor for plasticizing / measuring (hereinafter referred to as a metering motor 15) which is mounted on a fixed base as appropriate, and an output pulley 16 is fixed to its rotary shaft. Reference numeral 17 denotes a pulley which is appropriately rotatably held on a fixed base, and a timing belt 18 is stretched between the output pulley 16 and the pulley. The pulley 17 and the rear end of the screw 4 are connected to each other in the moving body 8 via a spline shaft coupling mechanism (not shown) (for example, a spline shaft integrated with the pulley 17 is provided in the moving body 8). The rotating body is spline-shaft-coupled, and the rotating body and the rear end of the screw 4 are connected to each other through an appropriate member so as to integrally rotate.) The rotation of the pulley 17 causes the screw 4 to move back and forth (that is, move). The screw 4 is rotationally driven regardless of the longitudinal movement position of the body 8.

Reference numeral 19 denotes a strain sensor for detecting the amount of compression, which is held by being sandwiched between the nut body 14 and the main body of the moving body 8 so as to be concentric with the ball screw shaft 13. The rotation of the ball screw shaft 13 detects the axial propulsive force received by the nut body 14, and thereby the injection pressure corresponding to the resin pressure is detected.

In the above structure, during the plasticizing / measuring process, the measuring motor 15 is rotated in a predetermined direction,
Output pulley 16, timing belt 18, pulley 17,
Also, the screw 4 is rotationally driven in a predetermined direction via the spline shaft coupling mechanism (not shown). This screw 4
Rotation causes the resin material to be kneaded and plasticized and transferred forward, and as the molten resin is stored in the front side of the screw 4, the screw 4 receives a reaction force from the molten resin and receives a backward force. Further, during the plasticizing / measuring process, the injection motor 9 is also rotationally driven at a low speed in a direction opposite to that at the time of the injection filling process, which will be described later, so that the moving body 8 (screw 4) is driven backward at a low speed and the screw 4 Apply back pressure to.

During the injection filling process, only the injection motor 9 is rotated in a predetermined direction, and the ball screw shaft 13 is rotated via the output pulley 10, the timing belt 12 and the pulley 11. As a result, the nut body 14 advances along the ball screw shaft 13, and the moving body 8 moves toward the nut body 1.
Move forward together with 4. Therefore, the screw 4 that moves in the axial direction together with the moving body 8 advances, and the molten resin is injected and filled from the nozzle 3 into the mold.

When the moving body 8 is moved,
Axial thrust force received by the nut body 14 is applied to the strain sensor 1
9 detects and sends this detection information to a system controller (not shown).

[0011]

As described above, in the conventional injection molding machine using the electric servomotor as the injection drive source, the distortion caused by the injection pressure, that is, the injection resin pressure is a compression force. The sensor 19 is sandwiched by a member that receives an axial driving force to detect the amount of compression. However, if the strain sensor 19 for compression detection having such a configuration is adopted, there are the following problems.

Since the strain sensor 19 is held, if excessive pressure is applied to the strain sensor 19 due to a malfunction due to a sensing error or the like, there is no escape area and the strain sensor 19 is damaged due to impact. When the strain sensor 19 is damaged as described above, it is necessary to replace the strain sensor 19, but it is necessary to disassemble the device including the ball screw transmission mechanism and the like, and the removal / reattachment is complicated and it takes a lot of time. Takes time and effort. Since the strain sensor 19 is located concentrically with the ball screw shaft 13, the strain sensor 19 is affected by the vibration due to the rotation and a detection error is likely to occur. The strain sensor 19 for detecting compression is relatively expensive in the first place.

Therefore, the technical problem to be solved by the present invention is to eliminate the above-mentioned problems of the prior art. The purpose of the invention is to provide an injection molding machine using an electric servomotor as an injection drive source. In order to provide a pressure detecting device, there is almost no risk of damaging the pressure detecting sensor, the sensor can be easily attached / removed, and the pressure can be detected with high accuracy without being adversely affected by vibration. It is in.

[0014]

In order to achieve the above-mentioned object, the present invention receives an axial propulsion force by a rotation → linear motion conversion mechanism for converting the rotational force of an injection electric servomotor into a linear motion, and a heating cylinder. In an in-line screw type injection molding machine that performs injection filling of molten resin into the mold by advancing the moving body that moves back and forth integrally with the screw inside, the moving body is slidably inserted, and both ends Is equipped with a strain sensor that detects the amount of extension of the guide bar supported by the holding block, and detects the pressure by detecting the extension of the guide bar due to the reaction when the moving body receives an axial propulsion force. Is configured.

The strain sensor is built in a hole axially formed from one end of the guide bar or wound around the outer circumference of the guide bar.

[0016]

When the moving body is driven back and forth by the axial thrust, one of the holding blocks receives a force in the opposite direction to the above axial thrust through the ball screw shaft by its reaction. The guide bar is stretched. The strain sensor inserted into or installed on the guide bar detects the amount of extension of the guide bar, and this detection information is sent to the system controller.

Therefore, rather than detecting compression directly,
Since the pressure is detected by detecting the extension of the guide bar, there is almost no risk of the strain sensor being damaged, and since it is not affected by the vibration of the rotary drive system, accurate pressure detection without error is possible. . Further, since the strain sensor is attached by inserting it from one end of the guide bar into a hole bored in the axial direction or is wound around the outer periphery of the guide bar, the strain sensor can be strained without disassembling other members. Since only the sensor can be attached / detached, workability is significantly improved. Further, the strain sensor for detecting elongation is relatively inexpensive as compared with the conventional strain sensor for compression detection, and the cost of the sensor can be reduced to 2/3 to 1/2.

[0018]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is an explanatory diagram showing a main configuration of an injection system mechanism of an electric injection molding machine according to a first embodiment of the present invention. In the figure, 1 is a holding block (tailstock), 2 is a heating cylinder, 3 is a nozzle, 4 is a screw, 5 is a holding block, 6 is a guide bar, 7 is a mounting nut, 8 is a moving body, and 9 is for injection. Motor (electric servo motor for injection), 10 is an output pulley, 11 is a pulley, 12
Is a timing belt, 13 is a ball screw shaft, 14 is a nut body, 15 is a metering motor (plasticizing / measuring electric servomotor), 16 is an output pulley, 17 is a pulley, and 18 is a timing belt. 1 to 18 are all equivalent to the constituent elements shown in FIG. 5, and the operation of the injection system mechanism by these constituent elements 1 to 18 is also the same as the operation described above. The description thereof is omitted to avoid it (this also applies to the second embodiment of the present invention described later). Although the holding block 5 is described as being fixed in the above description, the holding block 5 is actually semi-fixed so that it can slide about several mm depending on the expansion and contraction of the guide bar 5. Has been supported.

In FIG. 1, a strain sensor unit 20 is built in one of the guide bars 6. The guide bar 6 incorporating the strain sensor unit 20 is provided with a storage hole that is bored in the axial direction from the end on the holding block 5 side, and the strain sensor unit 20 is inserted and mounted in this storage hole. It is like this.

FIG. 2 is a cross-sectional view of an essential part showing a state where the strain sensor unit 20 is housed. As shown in the figure,
The guide bar 6 has a storage hole 6 formed axially from the end thereof.
a is provided, and the sensor portion 20 of the strain sensor unit 20 having the measuring pin is provided in the inner portion of the storage hole 6a.
The sensor part 20 in which a is screwed in and is in close contact with the guide bar 6
The extension amount of the guide bar 6 is detected by a. The sensor unit 20a is connected to the small charge amplifier unit 20 of the strain sensor unit 20 via the cord 20c.
The small charge amplifier section 20b is attached to the inlet side of the storage hole 6a by the lid 20d. Although not shown, the detection signal of the sensor unit 20a is amplified from the small charge amplifier unit 20b,
It is sent to a system controller (not shown).

In the above structure, the moving body 8 rotates →
When it is driven forward by receiving the axial propulsive force F shown in FIG. 1 by the linear motion conversion mechanism, the holding block 5 moves in the opposite direction to the axial propulsive force F via the ball screw shaft 13 by its reaction. The force F ′ is received, which causes the guide bar 6 to be stretched. The strain sensor unit 20 inserted in the guide bar 6 is
Is detected, and the detection information is sent to the system controller as injection pressure information.

FIG. 3 is an explanatory view showing the essential structure of the injection system mechanism of the electric injection molding machine according to the second embodiment of the present invention. In the figure, reference numeral 21 denotes a strain sensor unit. In this embodiment, the strain sensor unit 21 is wound around the outer circumference of the guide bar 6 to detect the extension amount of the guide bar 6 as in the first embodiment. However, pressure information is obtained.

FIG. 4 is a perspective view showing a state in which the strain sensor unit 21 is wound around the outer circumference of the guide bar 6. In the mounted state shown in the figure, a sensor portion (not shown) on the inner surface of the strain sensor unit 21 is in close contact with the guide bar 6, and the amount of extension of the guide bar 6 is detected by this sensor portion. Information detected by the sensor unit is appropriately amplified by an amplifier unit (not shown) in the strain sensor unit 21 and taken out from the connector unit 21a of the strain sensor unit 21. The strain sensor unit 21 of the present embodiment can be detached in a split-split manner at the separating portion 21c by removing the mounting screw 21b. When the mounting screw 21b is removed, the strain sensor unit 21 is distorted by using the connection support portion 21d as a pivot fulcrum. The sensor unit 21 can be separated into halves in a split-split manner.

The operation of detecting the amount of extension of the guide bar 6 in the second embodiment having such a configuration is the same as in the first embodiment.

As described above, the first and second aspects of the present invention
In the embodiment, the pressure is detected by detecting the extension of the guide bar 6 instead of directly detecting the compression as in the conventional case. Therefore, there is almost no possibility that the strain sensor will be damaged, and the vibration of the rotary drive system is reduced. Since it is not affected by, it is possible to perform accurate pressure detection without error. Further, since the strain sensor is attached by inserting it from one end of the guide bar 6 into a hole bored in the axial direction, or is wound around the outer periphery of the guide bar 6, without disassembling other members. Since only the strain sensor can be attached / detached, workability is remarkably improved. Furthermore, the strain sensor that detects elongation is
The strain sensor is relatively inexpensive compared to the conventional strain sensor for compression detection, and the cost of the sensor can be reduced to 2/3 to 1/2.

[0026]

As described above, according to the present invention, in an injection molding machine using an electric servomotor as an injection drive source, there is almost no risk of damaging a sensor for pressure detection, and mounting / removal of the sensor. It is possible to provide a pressure detection device that is easy and reliable, and is capable of highly accurate pressure detection without being adversely affected by vibration, and its value is great.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main configuration of an injection mechanism in an injection molding machine according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an essential part showing a mounted state of a strain sensor unit in the injection molding machine according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a main configuration of an injection mechanism in an injection molding machine according to a second embodiment of the present invention.

FIG. 4 is a perspective view of essential parts showing a mounted state of a strain sensor unit in an injection molding machine according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a main configuration of an injection mechanism in an injection molding machine according to a conventional technique.

[Explanation of symbols]

1 Holding Block (Tail Stock) 2 Heating Cylinder 3 Nozzle 4 Screw 5 Holding Block 6 Guide Bar 6a Storage Hole 7 Mounting Nut 8 Moving Body 9 Injection Electric Servo Motor (Injection Motor) 10 Output Pulley 11 Pulley 12 Timing Belt 13 Ball Screw Shaft 14 Nut body 15 Plasticizing / measuring electric servomotor (measuring motor) 16 Output pulley 17 Pulley 18 Timing belt 20 Strain sensor unit 20a Sensor part 20b Small charge amplifier part 20c Code 21 Strain sensor unit 21a Connector part 21b Mounting screw 21c Separation part 21d Connection support part

Claims (3)

[Claims] 1. A moving body that moves forward and backward together with a screw in a heating cylinder is moved forward by receiving a thrust force in the axial direction by a rotation → linear motion conversion mechanism that converts the rotational force of an injection electric servomotor into a linear motion. In this way, in an in-line screw type injection molding machine that performs injection filling of molten resin into the mold, the movable body is slidably inserted, and the extension amount of the guide bar supported at both ends by the holding block is detected. The pressure of the injection molding machine is characterized in that the pressure is detected by providing a strain sensor for detecting the extension of the guide bar due to the reaction when the moving body receives an axial thrust force. Detection device. 2. The pressure detecting device for an injection molding machine according to claim 1, wherein the strain sensor is built in a hole axially formed from one end of the guide bar. 3. The pressure detection device for an injection molding machine according to claim 1, wherein the strain sensor is wound around an outer circumference of the guide bar.