JP2002176739A - Motor with built-in permanent magnet and injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor with a built-in permanent magnet which can assure a sufficient internal diameter of a rotor without increase of an external diameter of the rotor, while maintaining a large output torque and also provide an injection molding machine provided with the motor with built-in permanent magnet. SOLUTION: The motor 2 with built-in permanent magnet 2 comprises a mother material 8 which is formed by integrally tightening a plurality of laminated annular steel plates 4 with non-magnetic material bolts 6 provided through the axial line direction, and magnetic belts 10 formed of a plurality of permanent magnets provided along the circumference at the area near the external circumference of this mother material 8. In this motor, an N magnetic belt 10a which is formed of a permanent magnet directed to the axial center side and is extended in the axial line direction, and an S magnetic belt 10b which is formed of a permanent magnet directed to the axial center side and is extended in the axial line direction, are alternately disposed with a gap kept in the circumferential direction, and the positions of the non-magnetic material bolts 6 are identified at the area near the magnetic belts on the shortest route connecting between the center of the circumferential direction of the magnetic belts 10 and the axial center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor with a built-in permanent magnet suitable for use as a drive source of, for example, an injection molding machine and a stirrer, and an injection molding machine using this motor.

[0002]

2. Description of the Related Art Conventionally, as a driving source for an injection molding machine, a stirrer or the like, as shown in FIG. 5, a nonmagnetic material such as a plurality of stacked iron-like ring-shaped magnetic material plates 102a is axially penetrated. Base material 10 integrally fastened with bolts 104
2 and a plurality of permanent magnets 106 provided along the circumferential direction (in the longitudinal section) near the outer peripheral portion of the base material 102.
And a motor 110 with a built-in permanent magnet provided with a rotor 108 including the following.

As described above, the bolts 104 penetrate the plurality of ring-shaped magnetic plates 102a in the axial direction, and by fastening these ring-shaped magnetic plates 102a together, they have sufficient strength against a large torque. A rotor 108 is implemented.

Further, the bolt 104 is made of a non-magnetic material such as stainless steel to prevent polarization (magnetization) of the magnetic pole in the axial direction so as to improve the efficiency of the motor when using a magnetic bolt. Have been.

As shown in FIG. 6, a permanent magnet generally has a magnetic pole oriented in the axial center (in a longitudinal section) N, N, S, S, N, N, S, S in a circumferential direction. .. Are held in the magnet insertion holes 102b arranged with a slight gap in the base material 102 so as to be arranged in the order of.

An air hole 102C is provided between the permanent magnet 106a and the adjacent permanent magnet 106b. This air hole 102C is provided between adjacent permanent magnets 106.
The lines of magnetic force are prevented from leaking outside (the side away from the axis) from between the opposite ends of the a and 106b, and the lines of magnetic force are directed to the inside of the base material 102 to magnetize the base material 102 more strongly. It is provided for.

In recent years, there has been an increasing demand for compact injection molding machines and agitators. For example, as in an injection molding machine 120 schematically shown in FIG. 7, a ball nut 122 for injecting resin, a ball screw There is a demand for downsizing by housing the rotor 124 and the hollow shaft 126 containing the ball nut 122 and the ball screw 124 in the rotor 128.

[0008]

As described above, the rotor 1
In order to store other components such as the ball nut 122 in the rotor 28, it is necessary to make the rotor 128 hollow and increase the inner diameter 128a of the center hole thereof. In this case, FIG.
The inner diameter 128a of the center hole of the rotor 128 as shown in FIG.
Is simply increased, the center hole and the non-magnetic bolt 10
4 approach and the strength near the center hole of the rotor 128 is insufficient.

Of course, by increasing the outer diameter 128b of the rotor 128, a sufficient space is secured between the center hole and the outer peripheral portion of the rotor 128, and the nonmagnetic bolt 104 is separated from the center hole. If installed, the strength near the center hole of the rotor 128 can be ensured.

However, increasing the outer diameter 128b of the rotor 128 increases the size of the injection molding machine 120 in the radial direction, which is contrary to the demand for compactness.

Further, without providing the bolt 104, a plurality of ring-shaped magnetic plates 10 may be provided by caulking or other means.
The above problem does not occur if 2a is integrated, but the rotor in which a plurality of ring-shaped magnetic plates 102a are integrated by other means such as caulking has insufficient strength as compared with a bolted rotor. However, especially when used for applications such as screw drive of an injection molding machine, it cannot withstand the large output torque.

In view of the above circumstances, the present invention provides a motor with a built-in permanent magnet which can secure a sufficient inner diameter of the rotor without increasing the outer diameter of the rotor and maintaining a large output torque. An object of the present invention is to provide an injection molding machine including a motor with a built-in permanent magnet.

[0013]

According to a first aspect of the present invention, there is provided a base material formed by integrally fastening a plurality of stacked ring-shaped magnetic plates with non-magnetic bolts penetrating in the axial direction. A permanent magnet provided in the vicinity of an outer peripheral portion of the material along a circumferential direction in a longitudinal section, wherein the permanent magnet includes a rotor having an N pole directed toward an axial center. A magnet or one of two or more permanent magnets arranged without any gap in the circumferential direction with the N pole facing the center of the axis, and an N magnetic band extending in the axial direction, and an S pole. It consists of one of the permanent magnets directed toward the axis center or two or more of the permanent magnets arranged with no gap in the circumferential direction with the S pole directed toward the axis center, and extends in the axial direction. With a gap in the circumferential direction in the longitudinal section In addition to each other, the position where the bolt of the non-magnetic material penetrates is located on the shortest path connecting the circumferential center of each magnetic zone and the axis center in the longitudinal section, and near each magnetic zone. Thus, the above problem has been solved.

According to the present invention, since the penetrating position of the non-magnetic material bolt is specified near each magnetic zone, the non-magnetic material bolt can be separated from the center hole of the rotor.
As a result, the inner diameter of the rotor can be increased without increasing the outer diameter of the rotor and maintaining the strength of the rotor, and larger components can be stored in the rotor.

Each of the N and S magnetic bands has an N pole and an S pole, respectively.
One of the permanent magnets with the poles facing the axis center, or N
Since one or more of the permanent magnets are arranged without any gap in the circumferential direction with their poles and south poles facing the center of the shaft, the permanent magnet can solve the problem of reduction in generated torque described below. it can.

The reduction in the generated torque has been confirmed in the course of trial and error in specifying the penetration position of the non-magnetic bolt for solving the above-mentioned problem.

First, the inventor prototyped a rotor 140 shown in FIG. 9 in order to solve the problem of insufficient strength near the center hole of the rotor 128.

The rotor 140 specifies the penetrating position of the non-magnetic material bolt 104 near the permanent magnet 106, and separates the non-magnetic material bolt 104 from the center hole, thereby
It is intended to solve the problem of insufficient strength near the center hole.

When the motor equipped with the rotor 140 was installed in an injection molding machine and various performances were confirmed by experiments, the extrusion force for injecting the resin was lower than in the conventional case. That is, the output torque of the motor was reduced.

As a result of intensive studies on the cause of the decrease in the output torque of the motor, the inventor has found that the non-magnetic bolt 1
It has been found out that the positional relationship between the permanent magnet 106 and the permanent magnet 106 affects the magnitude of the output torque.

As shown in FIG. 9, when a non-magnetic bolt 104 is installed near the end of the permanent magnet 106 adjacent to and opposite to the permanent magnet 106 with the same pole toward the center of the axis, the end is generated at the end. It interfered with the leakage of the magnetic flux and caused disturbance of the magnetic flux, and as a result, adversely affected the performance of the motor (the injection performance when used in an injection molding machine).

When the non-magnetic bolts 104 are installed adjacent to each other and separated from the opposite end of the permanent magnet 106 with the same pole toward the center of the shaft, the non-magnetic bolts 104 The magnetization of the base material 102 was reduced by hindering the lines of magnetic force, and the generated torque of the motor with a built-in permanent magnet was reduced.

Further, when the non-magnetic bolt 104 is installed outside the permanent magnet 106 (on the side away from the axis),
As a result, the permanent magnet 106 is separated from the outer peripheral portion of the rotor 128 to the inside (toward the center of the shaft), and the torque generated by the motor with a built-in permanent magnet is rather reduced.

That is, even if the installation position of the bolt 104 is variously changed in the vicinity of the permanent magnet 106, the output torque of the motor is still reduced in any case, and the bolt 104 and the permanent magnet 106 come close to each other. This arrangement causes a decrease in the output torque of the motor.

The present inventor has proposed a bolt 1
04 and the permanent magnet 106 are arranged close to each other,
As a result of further trial and error focusing on the shape and arrangement of the permanent magnet 106 in order to generate a conventional output torque, the present invention was completed.

In the present invention, since there is no gap between the permanent magnets adjacent to each other and having the same pole toward the center of the shaft, the lines of magnetic force do not leak from the gap. As a result, the magnetic field lines are not disturbed due to the interference between the magnetic field lines and the non-magnetic bolts 104, so that the torque generated by the permanent magnet built-in motor does not decrease.

Further, since the magnetic flux flows along the periphery of the non-magnetic bolt, the magnetization of the inside of the base metal near the center in the circumferential direction of each permanent magnet is promoted.

As a result, the motor with a built-in permanent magnet according to the present invention can output a torque of the same magnitude as the conventional one.

According to a second aspect of the present invention, in the first aspect, an air hole penetrating in the axial direction is formed in a gap between the N magnetic band and the S magnetic band.

By doing so, the base material is magnetized further inward in the vicinity of the end on the opposite side of the permanent magnet of the opposite polarity, and in addition to the above-mentioned invention, the output torque of the motor is further increased. can do.

According to a third aspect of the present invention, there is provided the motor with a built-in permanent magnet according to the first or second aspect, wherein the motor is coaxially inserted into the rotor and connected to the rotor to be integrated with the rotor. The object has been solved by an injection molding machine provided with a rotating ball screw and a ball nut screwed with the ball screw.

By inserting the ball nut and the ball screw into the rotor and integrating with the motor with a built-in permanent magnet in this way, the injection molding machine is compact and has the same pushing force for resin injection as before. Can be realized.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a motor 2 with a built-in permanent magnet according to an embodiment of the present invention. The motor 2 with a built-in permanent magnet has a plurality of laminated steel plates (magnetic plates) 4 arranged in the axial direction. A base material 8 integrally fastened with a stainless steel (non-magnetic material) bolt 6 penetrating therethrough, and a magnetic zone 10 formed of a plurality of permanent magnets provided in the vicinity of the outer periphery of the base material 8 along the circumferential direction. , And a stator 14, and a center hole 12 b having an inner diameter 12 a is formed in the rotor 12.

FIG. 2 is a longitudinal sectional view in the direction perpendicular to the axis of the rotor 12 in FIG.

The ring-shaped steel plate 4 has insulating layers formed on both sides. As a result, the base material 8 has magnetism and generation of eddy current in the axial direction is restricted.

In the vicinity of the outer peripheral portion of the ring-shaped steel plate 4, a plurality of (eight in the present embodiment) substantially rectangular magnetic band insertion holes 4a are polygonally shaped (octagonal in the present embodiment). ) Is formed.

Each of the magnetic band insertion holes 4a holds a plate-like magnetic band 10. The magnetic zone 10 is composed of one permanent magnet with its N pole facing the center of the axis and extending in the axial direction, and one permanent magnet with its S pole facing the center of the shaft. An N magnetic band 10a and an S magnetic band 10b are arranged alternately with a gap in the circumferential direction in the longitudinal section.

The bolt insertion hole 46 is formed on the shortest path L connecting the center of each magnetic band 10 in the circumferential direction and the center of the axis, and in the vicinity of each magnetic band 10.

As shown in FIG. 1, the bolt 6 penetrates through the bolt insertion hole 4b and a pair of end plates 16a, 1 which sandwich the ring-shaped steel plate 4 from both sides in the axial direction.
6b penetrates one end plate 16a and is screwed with the other end plate 16b. Thus, the stacked ring-shaped steel plates 4 are integrally fastened.

The reason why the bolt 6 is made of a non-magnetic material is to prevent the polarization (magnetization) of the magnetic pole in the axial direction of the bolt 6 and to improve the efficiency of the motor.

A substantially triangular air hole 4c penetrating in the axial direction is formed in the gap between the N magnetic band 10a and the S magnetic band 10b.

Next, the operation of the permanent magnet built-in motor 2 will be described.

In the motor 2 with a built-in permanent magnet, the bolt 6 and the magnetic zone 10 are provided close to each other. Therefore, even if the inner diameter 12a of the center hole 12b of the rotor 12 is increased, the bolt 6 is moved from the center hole 12b. Parts such as a ball nut and a ball screw can be housed in the rotor 12 while securing the strength of the rotor 12.

As described above, by inserting the ball nut and the ball screw into the rotor 12 and integrating the ball nut and the ball screw with the motor 2 with a built-in permanent magnet, it is possible to realize a compact injection molding machine as described later.

That is, the size of the injection molding machine and the like can be reduced with respect to the injection molding machine and the like in which the permanent magnet built-in motor and the ball screw and the like are arranged in the axial direction or the radial direction.

Further, since each magnetic zone 10 is constituted by one permanent magnet, there is no gap between the permanent magnets having the same pole toward the center of the shaft as in the prior art. The lines of magnetic force do not leak outward from the gap between the magnets. As a result, there is no possibility that the magnetic field lines leaking to the outside and the non-magnetic bolt 6 interfere with each other to cause disturbance of the magnetic field lines. That is, the generated torque of the motor 2 with a built-in permanent magnet does not decrease.

Further, since the magnetic field lines flow along the periphery of the non-magnetic bolt 6, the magnetization inside the base material 8 near the center in the circumferential direction of each magnetic zone 10 is promoted.

A plurality of magnetic band insertion holes 4a for holding the magnetic band 10 are provided in the base material 8, and the N magnetic band 10a and the S magnetic band 10b held in the magnetic band insertion holes 4a are connected to each other. Since the air hole 4c is provided between the N magnetic bands 10
The lines of magnetic force do not leak outward from between the magnetic field a and the S magnetic band 10b. That is, the base material 8 can be more strongly magnetized.

Since the rotor 12 is strongly magnetized, the motor 2 with a built-in permanent magnet can output a large torque.

In the embodiment of the present invention,
In order to fasten the ring-shaped steel plate 4 integrally, the material of the bolt 6 is a non-magnetic stainless steel. However, the present invention is not limited to this, and the material of the bolt 6 is, for example, copper or the like. Other non-magnetic materials may be used.

In the embodiment of the present invention, N
The magnetic band 10a is configured by one permanent magnet with the N pole facing the center of the axis, but the present invention is not limited to this. It may be an N magnetic band composed of a plurality of permanent magnets arranged without gaps.
The same applies to the S magnetic band 10b.

Further, in the embodiment of the present invention,
Although eight plate-shaped magnetic zones 10 are provided in the base material 8 in an octagonal shape, the present invention is not limited to this, and for example, six or ten plate-shaped magnetic zones are provided. Hexagonal shape on rotor,
Alternatively, it may be provided in a decagonal shape.

Furthermore, in the embodiment of the present invention, the cross-sectional shape of the magnetic zone 10 is substantially rectangular, but the present invention is not limited to this. It may be a magnetic zone having a substantially arc-shaped cross-sectional shape along the same. This may allow a larger center hole to be drilled.

Next, an injection molding machine 20 equipped with the permanent magnet built-in motor 2 according to the embodiment of the present invention will be described.

FIG. 3 is a cross-sectional view showing the entire structure of the injection molding machine 20, and FIG. 4 is an enlarged cross-sectional view showing the structure around the permanent magnet built-in motor 2 in the injection molding machine.

The injection molding machine 20 includes an injection screw 22
A metering motor 26 capable of rotating the injection screw 22 to introduce a predetermined amount of raw material chips 25 from a raw material supply port 24 on the base end side of the injection screw 22 to the distal end side of the injection screw 22; A heating cylinder 28 which includes the injection screw 22 and is capable of heating and melting the raw material chip 25 is provided.

The permanent magnet built-in motor 2, the weighing motor 2
6, the injection screw 22 is arranged coaxially in this order,
The motor 2 with a built-in permanent magnet is a rotor 26a of the weighing motor 26.
At the same time, by driving the injection screw 22 to the tip side in the axial direction, the molten resin in the heating cylinder 28 is injected from the tip nozzle 28a of the heating cylinder 28.

The rotor 12 of the motor 2 with built-in permanent magnets has a hollow shaft 32 through a key 30 in the center hole 12b.
Is fitted. An end plate 34 is fastened to one end of the hollow shaft 32 on the side away from the weighing motor 26 in the axial direction by bolts 35.
, A ball screw 36 is fixed.

The ball screw 36 is coaxially inserted through the hollow shaft 32 and is screwed with a ball nut 38. The ball nut 38 is slidable in the axial direction, and
The ball screw 36 is supported in the injection molding machine 20 so as not to rotate around the axis, and moves in the axial direction in conjunction with the rotation of the ball screw 36.

The ball nut 38 is engaged with the rotor 26a of the metering motor 26, and moves in the axial direction integrally with the rotor 26a and the injection screw 22.

The injection molding machine 20 includes a motor 2 with a built-in permanent magnet.
Is converted into a large pushing force in the axial direction by the ball screw 36 and the ball nut 38, and the large pushing force drives the injection screw 22 in the distal direction to inject the molten resin strongly from the distal nozzle 28a. be able to.

In the injection molding machine 20, the ball nut 38 and the like are housed in the large center hole 12b of the rotor 12 in the motor 2 with a built-in permanent magnet, so that the outer diameter and the length in the axial direction can be kept small. I have.

[0064]

As described above, according to the present invention,
The inner diameter of the motor with a built-in permanent magnet can be increased without increasing the outer diameter of the rotor and maintaining the generated torque.

[Brief description of the drawings]

FIG. 1 is a sectional view of a motor with a built-in permanent magnet according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a cross-sectional view of the injection molding machine according to the embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view showing a periphery of a motor with a built-in permanent magnet of the injection molding machine.

FIG. 5 is a sectional view showing an outline of the entire structure of a conventional motor with a built-in permanent magnet.

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5;

FIG. 7 is a sectional view showing an outline of the entire structure of a conventional injection molding machine.

FIG. 8 is a sectional view showing the structure of a motor with a built-in permanent magnet of the injection molding machine.

FIG. 9 is a cross-sectional view showing a structure of a motor with a built-in permanent magnet in a development process of the present invention.

[Explanation of symbols]

 2, 110: motor with built-in permanent magnet 4, 102a: ring-shaped steel plate (magnetic plate) 4C: air hole 6, 104: bolt (of nonmagnetic material) 8, 102: base material 10: magnetic band 10a: N magnetic band 10b S magnetic band 12 Rotor 20 Injection molding machine 36 Ball screw 38 Ball nut 106 Permanent magnet

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (reference) H02K 21/14 H02K 21/14 M F term (reference) 4F206 AJ11 JA07 JL02 JT02 JT32 JT38 JT40 5H607 AA12 BB01 BB09 BB14 BB21 BB22 BB23 BB26 CC01 CC03 CC05 DD02 DD03 DD19 EE31 EE53 EE56 FF12 HH07 5H621 GA01 HH01 JK02 JK05 JK15 JK17 PP02 PP03 PP08 5H622 CA02 CA07 CA14 CB05 PP11 PP14 PP16

Claims (3)

[Claims] 1. A base material formed by integrally fastening a plurality of stacked ring-shaped magnetic plates with non-magnetic bolts penetrating in the axial direction, and a circumference in a longitudinal section near an outer peripheral portion of the base material. A permanent magnet provided with a plurality of permanent magnets provided along the direction, wherein one permanent magnet or N
2 with no gaps in the circumferential direction with the poles facing the shaft center
One or more of the permanent magnets, the N magnetic band extending in the axial direction, and one permanent magnet with the S pole facing the center of the axis, or the S pole facing the center of the shaft. And an S magnetic band, which is made of one of the two or more permanent magnets arranged in the circumferential direction without any gap and extends in the axial direction,
In the longitudinal section, the gaps are arranged alternately in the circumferential direction with a gap therebetween, and the shortest path connecting the circumferential center of each magnetic zone and the axis center in the longitudinal section with the penetration position of the bolt of the nonmagnetic material in the longitudinal section A motor with a built-in permanent magnet, which is specified above and near each magnetic zone. 2. The motor with a built-in permanent magnet according to claim 1, wherein an air hole penetrating in the axial direction is formed in the gap between the N magnetic band and the S magnetic band. 3. A ball screw comprising the motor with a built-in permanent magnet according to claim 1 and being coaxially inserted into the rotor, coupled to the rotor and rotating integrally with the rotor. An injection molding machine comprising: a ball nut to be screwed with the ball screw; and movement of the ball nut drives an injection screw.