JP2003225924A - Voice coil type linear motor and injection molding machine using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voice coil type linear motor excellent in precision and rigidity and an injection molding machine using the linear motor as the driving source of a linear movement part. <P>SOLUTION: Four coils 1 are arranged in parallel to each other around a central axis 30. A through hole 22a penetrated by a coil 22 is formed in each magnet 22. The magnets 22 are fitted to the front and back of a spacer 23 made of a non-magnetic substance so that two magnets forms a pair. A movable body 24 is composed of the spacer 23 and the eight magnets 22. The four magnets 22 are arranged on the front and other four magnets 22 are arranged on the back of the spacer 23 symmetrically around the central axis 30. In each of the magnets fitted to the front of the spacer 23, a notch 22b is formed in each angular part adjoining the central axis 30. An output shaft 25 passes on the central axis 30 to penetrate the notch 22b, and the rear end of the output shaft 25 is connected directly with the front of the spacer 23. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a voice coil type linear motor used as a drive source in an injection unit and other linear motion parts in an injection molding machine.

[0002]

2. Description of the Related Art An injection molding machine for manufacturing a molded product by injecting a resin or metal melt into a mold has an injection shaft for axially driving a screw or a plunger, and a mold clamping for opening and closing the mold. Many linear motion parts such as a shaft and an extrusion shaft that pushes out a product from a mold using an ejector pin are provided.

When the linear drive is performed electrically, a mechanism for converting the rotational movement of the electric motor into a linear movement using a ball screw or the like is general. On the other hand, in recent years, a mechanism for directly driving a linear motion section using a voice coil type DC linear motor has been developed.

FIG. 3 shows an example of a conventional voice coil type linear motor.

This voice coil type linear motor is constructed by combining four (two pairs) of magnets 22 with two coils 21. The two coils 21 are arranged in parallel with each other. Each pair of magnets 22 is attached to the front surface and the back surface of the magnet 22 with a spacer 23 made of a non-magnetic material sandwiched therebetween. The mover 24 is composed of the spacer 23 made of non-magnetic material and the four magnets 22. A through hole through which the coil 21 penetrates is formed in the spacer 23 and each magnet 22.

As shown in FIG. 3, the four magnets 22 form a closed loop magnetic circuit 29 connecting the magnets. The magnetic field generated by the magnetic circuit 29 is applied to the coil 21.
When the electric current flowing inside traverses, a force is generated between the magnet 22 and the coil 21, and the mover 24 is driven along the axis of the coil 21.

(Problems of the conventional drive mechanism using the voice coil type linear motor) When the voice coil type linear motor is used as a drive source for the linear motion part, the output shaft is attached to the mover to move the mover. It is necessary to transmit the movement of the above to the driven member via the output shaft. However, since the magnet is fragile in material and it is not easy to secure dimensional accuracy, it is not suitable as a surface for mounting the output shaft. Therefore, the output shaft is attached to the non-magnetic spacer.

However, as shown in FIG. 4, when the output shaft 25 is directly attached to the side surface of the spacer 23, the output shaft 25 is in a state of being offset with respect to the central shaft 30 of the thrust of the linear motor. A bending moment will be generated at.

On the other hand, as shown in FIG. 5, connecting members 27 having a symmetrical shape with respect to the central axis 30 of thrust are fixed to both side surfaces of the spacer 23, and the output shaft is attached to the other end of the connecting member 27. If 25 is attached, the above offset can be avoided. However, in this case, since the structure becomes complicated, the size of the device is increased and the rigidity is structurally lowered.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in an injection molding machine using a voice coil type linear motor as a drive source for a linear motion section. Is to provide a voice coil type linear motor excellent in accuracy and rigidity. Another object of the present invention is to provide an injection molding machine using such a voice coil type linear motor.

[0011]

A voice coil type linear motor of the present invention comprises a plurality of coils having an axis parallel to the central axis, a spacer made of a non-magnetic material, and a front surface and a back surface of the spacer. A mover composed of a plurality of pairs of magnets attached to form a pair, an output shaft connected to the mover and driven along the coil,
In a voice coil type linear motor including: the plurality of coils arranged axially symmetrically around the central axis, the mover has an axially symmetrical shape with respect to the central axis, and the output shaft is , Arranged on the central axis and directly connected to the front surface of the spacer at its rear end.

In the voice coil type linear motor of the present invention, the mover is moved along the coil by the interaction between the magnetic field generated by the magnets attached to the front and back surfaces of the mover and the direct current flowing through the coil. The driving thrust is generated.

According to the voice coil type linear motor of the present invention, since the output shaft coincides with the central axis of the thrust of the linear motor, no bending moment acts on the output shaft. Further, by directly connecting the rear end portion of the output shaft to the front surface of the spacer, avoiding a complicated structure,
High rigidity can be secured.

Preferably, the linear motor is composed of four coils and four pairs of magnets. In that case, the four coils are arranged in axial symmetry around the central axis, the mover includes four pairs of magnets arranged in axial symmetry around the central axis, and each coil is , Through the through holes formed in each magnet.

Alternatively, the linear motor may be composed of two coils and two pairs of magnets. In that case,
The two coils are arranged in an axially symmetrical manner about the central axis, the mover includes two pairs of magnets arranged in an axially symmetrical manner about the central axis, and each coil has each magnet. Penetrate through the through hole formed in.

Preferably, each magnet mounted on the front surface side of the spacer is formed with a cutout portion through which the output shaft passes on the central axis, and the rear end portion of the output shaft is made of the non-magnetic material. Directly connect to the spacer made of.

By using the above-mentioned voice coil type linear motor as a drive source for the linear motion part of the injection molding machine, the structure of the device can be simplified and the total length of the device can be shortened.

[0018]

FIG. 1 shows an example of a voice coil type linear motor according to the present invention. In the figure, 21 is a coil, 22 is a magnet, 23 is a spacer made of non-magnetic material, 24 is a mover, and 25 is an output shaft.

In this example, four coils (2
A combination of the magnets 22 of (pair) is regarded as one unit, and two driving units are formed by combining the two units.

The four coils 21 are arranged parallel to each other around the central axis 30. Each magnet 22 has a substantially square planar shape, and a through hole 2 through which the coil 21 penetrates in the center.
2a is formed. The magnets 22 are attached to the front surface and the back surface of the magnet 22 with a spacer 23 made of a non-magnetic material interposed therebetween so that the two magnets form a pair. Spacer 23
Has four through holes through which the coil 21 penetrates. The non-magnetic spacer 23 and the eight magnets 2
The movable element 24 is constituted by 2.

Four magnets 22 are arranged on each of the front surface and the back surface of the spacer 23 so as to surround the center axis 30 in an axially symmetrical manner. Further, each magnet 22 attached to the front surface side of the spacer 23 is formed with a notch 22b at each corner adjacent to the central axis 30. The output shaft 25 passes over the center shaft 30 and penetrates through the notch 22b, and the rear end of the output shaft 25 is directly connected to the front surface (left side in the figure) of the spacer 23 made of a non-magnetic material. .

FIG. 2 shows an example in which the above voice coil type linear motor is applied to an injection shaft of an injection unit of an injection molding machine.

The barrel 1 is connected to the back surface of a mold (not shown) through a nozzle at the tip side (left side in the figure).
The tip side of the screw 2 is housed inside the barrel 1. The rear end of the barrel 1 is supported at the center of the front plate 3. A rear plate 4 is disposed behind the front plate 3 so as to face the front plate 3. Between the front plate 3 and the rear plate 4, 4
The guide bars 5 of the book are bridged, and the two are connected to each other through the guide bars 5.

An intermediate plate 6 is arranged between the front plate 3 and the rear plate 4. Intermediate plate 6
Through holes are provided at four corners of the peripheral edge of the guide bar 5, and the guide bar 5 passes through the through holes. The intermediate plate 6 is guided by the guide bar 5 and can move in the front-rear direction (left-right direction in the drawing).

A bearing 7 is incorporated in the center of the intermediate plate 6, and the rear end of the screw 2 is rotatably supported by the bearing 7. A servomotor 8 for measurement is mounted on the intermediate plate 6. The shaft of the servomotor 8 is connected to the vicinity of the rear end of the screw 2 via a pulley and a timing belt 9.

The intermediate plate 6 is fixed to the output shaft 25 of the voice coil type linear motor 20 via the load cell 10. The rear end of the output shaft 25 is directly connected to the nonmagnetic spacer 23 of the mover 24. The coil 21 of the voice coil type linear motor 20 is fixed to the rear surface of the rear plate 4.

In the above example, the case where the voice coil type linear motor is used as the drive source of the injection shaft of the injection unit in the injection molding machine has been described, but the voice coil type linear motor of the present invention opens and closes the mold. Also, the present invention can be applied to a drive source of another linear drive unit in an injection molding machine, such as a drive source of a movable platen of a mold clamping device that performs mold clamping, and a drive source of an ejector pin that pushes a product from a mold surface.

[0028]

According to the voice coil type linear motor of the present invention, since the output shaft coincides with the central axis of the thrust of the linear motor, no bending moment acts on the output shaft. Further, by directly connecting the rear end portion of the output shaft to the front surface of the spacer, it is possible to prevent the structure from becoming complicated and ensure high rigidity.

The voice coil type linear motor of the present invention is
By using it as the drive source of the linear motion part of the injection molding machine, the structure of the device can be simplified and the total length of the device can be shortened.

[Brief description of drawings]

1A and 1B are views showing a schematic structure of a voice coil type linear motor of the present invention, FIG. 1A is a sectional view in a direction parallel to a central axis, and FIG.

FIG. 2 is a diagram showing an example of an injection molding machine in which the voice coil type linear motor of the present invention is used as a drive source of an injection shaft of an injection unit.

3A and 3B are views showing a structure of a voice coil type linear motor in which two coils are combined with four magnets, FIG. 3A is a top view, FIG. 3B is a front view, and FIG. Fig.

FIG. 4 is a diagram illustrating an example in which an output shaft is connected to a non-magnetic spacer of a voice coil linear motor.

FIG. 5 is a diagram illustrating another example in which an output shaft is connected to a non-magnetic spacer of a voice coil type linear motor.

[Explanation of symbols]

1 ... barrel, 2 ... screw, 3 ... front plate, 4 ... rear plate, 5 ... Guide bar, 6 ... Intermediate plate, 7 ... Bearing, 8 ... Servo motor for weighing, 9 ... Timing belt, 10 ... load cell, 20 ... Voice coil type linear motor, 21 ... coil, 22 ... Magnet, 22a ... through-hole, 22b ... notch, 23 ... Spacer made of non-magnetic material, 24 ... mover, 25 ... Output shaft, 27 ... connecting member, 29 ... Magnetic circuit, 30 ... central axis.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhito Ogura             2068 Ooka, Numazu City, Shizuoka Prefecture Toshiba Machine Co., Ltd.             In the company (72) Inventor Katsuyoshi Kido             2068 Ooka, Numazu City, Shizuoka Prefecture Toshiba Machine Co., Ltd.             In the company (72) Inventor Hiroyuki Onuma             2068 Ooka, Numazu City, Shizuoka Prefecture Toshiba Machine Co., Ltd.             In the company F-term (reference) 4F206 JA07 JD03 JL02 JM01 JM04                       JN03 JN11 JT02 JT33                 5H633 BB09 BB10 GG03 GG09 GG13                       HH02 HH05 HH13 HH26 JA05                       JA06 JA10                 5H641 BB10 GG03 GG10 HH02 HH14                       HH18 JA02 JA09 JA10 JA11                       JA20

Claims (8)

[Claims] 1. A plurality of coils each having an axis parallel to the central axis, a spacer made of a non-magnetic material, and a plurality of pairs of magnets attached to the front surface and the back surface of the spacer so as to be paired with each other. A voice coil type linear motor comprising: a movable element which is driven by the movable element; and an output shaft which is connected to the movable element and is driven along the coil, wherein the plurality of coils are axisymmetrical about the central axis. The mover has a shape that is axisymmetric with respect to the central axis, the output shaft is disposed on the central axis, and the rear end is directly connected to the front surface of the spacer. Characteristic voice coil type linear motor. 2. Four coils are arranged in axial symmetry around the central axis, and the mover includes four pairs of magnets arranged in axial symmetry around the central axis, The voice coil type linear motor according to claim 1, wherein each coil penetrates through a through hole formed in each magnet. 3. Two coils are arranged in axial symmetry about the central axis, and the mover includes two pairs of magnets arranged in axial symmetry around the central axis, The voice coil type linear motor according to claim 1, wherein each coil penetrates through a through hole formed in each magnet. 4. A notch formed in each magnet attached to the front surface side of the spacer so that the output shaft passes through the central axis and penetrates therethrough. The described voice coil type linear motor. 5. An injection molding machine using a voice coil type linear motor as a drive source for a linear motion part, wherein the linear motor has an axis parallel to a central axis, and the linear motor is provided around the central axis. It is composed of a plurality of coils arranged in axial symmetry, a spacer made of a non-magnetic material, and a plurality of pairs of magnets attached to the front surface and the back surface of the spacer so as to be paired with each other. A mover having a symmetrical shape, and an output shaft arranged on the central axis, directly connected to a front surface of the spacer at a rear end thereof, and driven along the coil. Injection molding machine. 6. Four coils are arranged in axial symmetry around the central axis, and the mover includes four pairs of magnets arranged in axial symmetry around the central axis, The injection molding machine according to claim 5, wherein each coil penetrates through a through hole formed in each of the magnets. 7. The two coils are arranged in axial symmetry about the central axis, and the mover includes two pairs of magnets arranged in axial symmetry about the central axis, The injection molding machine according to claim 5, wherein each coil penetrates through a through hole formed in each of the magnets. 8. The notch portion through which the output shaft passes through on the central axis is formed in each magnet attached to the front surface side of the spacer, according to claim 6 or 7. The described injection molding machine.