JPH0382350A - Electric motor field rotor and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the cost of machining with an assembly process of each part eliminated by integrally molding the permanent magnet in a field part and an output shaft through a plastic supporting part. CONSTITUTION:An output shaft 1 is set to the center part of a fixed metal mold 11, and a cylindrical core 13 is extruded, till it is brought into contact with the end face of a movable metal mold 12, by a hydraulic actuator 14. Under this condition, the first material for forming a field part 2 is injected from a runner 15, and the melted material is injected into a cavity part A for molding the field part 2 through a spool 16 and a gate 17. After the field part 2 is molded, the core 13 is retracted by the actuator 14, and the second material for a supporting part 3 is injected from a runner 18 with the material injected into a cavity part 8 through a spool 19 and a gate 20. In this way, the output shaft 1 and the field part 2 are integrally connected by the supporting part, when the mold is released, a rotor, in which the three of these output shaft 1, field part 2 and supporting part 3 are integrally formed, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a field rotor used for driving and position detection of an electric motor, and a method for manufacturing the same.

[Conventional technology]

In recent AC servo motors, DC servo motors, step motors, etc., permanent magnets are used as rotating fields to avoid wear of brushes and slip rings and the problems of mechanical and electrical noise caused by these. A technology is applied in which the current flowing through the child winding is controlled by a semiconductor switching element ("Control Motor Technology Utilization Manual", General Electronics Publishing Co., Ltd., pp. 143-157, 1932).
(3rd edition published on November 1, 2013) In such electric motors, the rotating field that receives rotational force and the output shaft are of course mechanically coupled, but in order to increase the output (torque), It is necessary to minimize the fluctuation of the field during rotation with respect to the size of the magnetic gap between the fixed armature and the fixed armature, which is set as narrow as possible.

Conventionally, a permanent magnet that forms a rotating field has been bonded to the inner circumference of a cup-shaped iron plate case, and the case has been fixed to the output shaft by caulking or bonding.

[Problem to be solved by the invention]

However, in this conventional rotor structure, dimensional errors occur between the output shaft and the case, and between the case and the permanent magnets, so the errors accumulate and the rotational wobbling of the permanent magnets becomes large. It was also difficult to control the width of the blur. If the vibration becomes large, the permanent magnet will come into contact with the fixed armature if a narrow magnetic gap is set.

Furthermore, if the permanent magnet is fixed to the output shaft through the case, the inertial mass of the rotating part increases by the amount of the case, which also causes the disadvantage that the response speed of the servo motor etc. decreases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the wobbling of the permanent magnets in the rotating field section, reduce the inertial mass of the rotating section, and improve the characteristics required of a servo motor or the like.

[Means to solve the problem]

In order to achieve this object, the electric motor field rotor of the present invention is characterized in that the permanent magnet field part and the output shaft are integrally connected by a plastic support part.

In this case, the magnetic material constituting the permanent magnet field section can be a plastic magnet material.

Further, the plastic support portion may be formed of a plastic magnet material having a small magnet particle diameter, and the plastic support portion may be magnetized for rotational position detection.

The method of the present invention for manufacturing this electric motor field rotor includes arranging an output shaft and a permanent magnet field part concentrically with respect to the output shaft in a mold, and forming a permanent magnet field part between the output shaft and the permanent magnet field part. The rotor is manufactured by integrating the permanent magnet field part and the output shaft by filling a cavity region of a mold that connects them with a plastic material.

When forming the permanent magnet field part with a plastic magnet, the output shaft is placed in the molding die, and the output shaft is placed in the cavity part for forming the field part and the cavity part for forming the plastic support part shaped in the mold. A rotor is manufactured by filling different plastic materials and integrating the output shaft, permanent magnet field part, and plastic support part.

〔Example〕

Hereinafter, the present invention will be specifically explained based on Examples.

11th! I(a) is a sectional view showing an embodiment of a motor field rotor according to the present invention, and I(b) is a right side view thereof.

In the figure, 1 is an output shaft, 2 is a cylindrical permanent magnet field part, and 3 is a plastic support part that integrates the output shaft l and the field part 2. As the field part 2, in addition to alloy magnets such as alnico, ferrite magnets are used.

A magnetic material with a high energy product such as a rare earth magnet can be used, but in order to particularly reduce the inertial mass, the bottom shape is formed by mixing the above-mentioned ferrite powder or rare earth cobalt magnet material, such as alloy powder of samarium cobalt, with plastic. be able to.

FIG. 2(a) shows an example in which the plastic support portion 3 is made of plastic magnet material, and radial NS magnetized portions are formed at a predetermined pitch on the end face as shown in FIG. 2(b). There is. In this embodiment, a magnetic sensor 4 such as a magnetic coil or a Hall element is installed close to the magnetized portion to detect the rotational position of the rotor. Conventionally,
Such rotational position detection has been performed by separately preparing a rotational position detector such as a pulse encoder and connecting it to the output shaft l using a coupling or the like. By performing this role with the magnetized portion and magnetic sensor formed on the plastic support B3, there is no need to provide a separate detector.

It is preferable that the magnetic material of the plastic support [3] used for this position detection has a large number of poles in order to improve the position detection accuracy, but in order to increase the number of poles, it is necessary to reduce the magnetization pitch. Therefore, in contrast to the field part 2 which is formed of a magnetic material with a large magnet particle size but a high energy product, the plastic support part 3 is made of ferrite magnetic powder which has a low energy product but a relatively small magnet particle size. Form. For example, as the field part 2, the particle size is 75 to 250.
When using a material with an energy product of 4 to 13 MGOe, the plastic support part 3 has a particle size of 1, 0 to 13 MGOe.
1.2 p m, energy product 1.7 M GOe
You can use a 7g light. In this way, by using a magnet material with small magnet particles, it becomes possible to perform magnetization with a large number of poles with a narrow pitch, and a fine position detection function can be easily obtained.

Furthermore, the position detector can be realized using inexpensive materials.

FIG. 3 shows an example in which a yoke 5 for forming a magnetic closed circuit is integrally molded on the outer periphery of the field [2, that is, on the opposite side from the fixed armature 6. By providing this yoke 5, the magnetic flux passes through the yoke 5 as shown in Fig. 4, the leakage magnetic flux of the magnet of the field section 3 is reduced, the magnetic resistance is reduced, and the magnetic flux density is reduced. It can be prevented. This yoke 5 can be made of a magnetic material such as pure iron, carbon steel, permalloy, or the like.

Next, a method of manufacturing a motor field rotor according to the present invention will be explained.

FIG. 5 shows an embodiment of a manufacturing apparatus using injection molding. In the figure, 11 is a fixed mold, and 12 is a movable mold. First, as shown in FIG. 5(a), the output shaft 1 is set in the center of the fixed mold 11, and the cylindrical core 13 is
is pushed out by the hydraulic actuator 14 until it comes into contact with the end surface of the movable mold 12.

In this state, from the runner 15, the first
Inject the material of sprue 16. The molten material is injected into the field 112 molding cavity BA through the gate 17. At this time, the core 13 serves to prevent the first material from entering the cavity part B for forming the support part 3.

After the field portion 2 is formed, the hydraulic actuator 14 is driven to retract the core 13 as shown in FIG. 5(b), and the runner 1 is
8 to inject a second material for forming the support part 3,
Sprue 19. Material is injected into the cavity flBB for the support part 3 through the gate 20. Thereby, the support part 3 integrally connects the output shaft l and the field part 2, and when the mold is released, a rotor in which the three parts are integrated can be obtained.

Furthermore, as shown in FIG. 3, a yoke 5 is provided on the outer circumference of the field section 2
When integrally molding, a mold structure may be used in which a third material is further injection molded.

In addition, in consideration of productivity, it is also possible to manufacture a part in advance on a separate line and set it in the mold.

For example, the yoke and field part may be joined together in advance, and the output shaft may be placed in a mold and integrated using the method described above, or the yoke and output shaft may be placed in the mold and then integrated using the same method. It is practical to integrate them.

FIG. 6 shows an embodiment in which a rotary mold is used without using a core. This example has a rotary mold 31 that advances and retreats every half rotation, a movable mold 32, a fixed mold 33, and material supply paths 34 and 35. At the top of the drawing,
The second material injected from the material supply path 34 is injected into the cavity part B, and the support part 3 is formed. Next, the rotary mold 31 is retreated and rotated for half a rotation, and then advanced to the lower mold, and the first material injected from the material supply path 35 is injected into the cavity 11A to form the field part 2. do. In this way, a rotor product in which the output shaft 1 and the field part 2 are integrated by the support part 3 can be manufactured.

〔Effect of the invention〕

As described above, in the present invention, the permanent magnet of the field section and the output shaft are integrally molded using a plastic support section. Thereby, the assembly process of each part can be omitted, and processing costs can be reduced. Also,
The assembly accuracy is high because the positional relationship of each part is precisely determined by the mold etc. In particular, since the vibration of the field portion is significantly reduced, the magnetic gap with the fixed armature can be narrowed, and the magnetic flux density can be increased, making it possible to realize a high-torque, high-output electric motor.

In addition, by forming the support part from a magnetic material and magnetizing it, the position detector can be integrated with the rotor in combination with the sensor, and it is possible to achieve downsizing and cost reduction.

Furthermore, by forming the bottoms of the field part and the position detection part with different magnetic materials, the detection part can be finely magnetized, and the position detection accuracy is improved.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view showing an embodiment of the present invention;
c) is a side view thereof, Fig. 2(a) is a sectional view showing another embodiment of the present invention, Fig. 2(a) is an explanatory view showing the state of magnetization,
FIG. 3 is a sectional view showing another embodiment of the present invention, FIG. 4 is an explanatory diagram showing the effect of magnetic flux by the yoke, and FIGS. 5 and 6 are molds for manufacturing the rotor of the present invention, respectively. It is an explanatory view showing an example. 1: Output shaft 3: Support part 5: Yoke 11: Fixed mold 13: Core 15.18: Runway 17, 20: Gate 31: Rotating mold 33: Fixed mold 2: Field part 4: Sensor 6 : Fixed armature 12 : Movable mold 14 : Hydraulic actuator 16.19 Varnish blue 32 : Movable mold 34, 35 : Material supply path

Claims (1)

[Scope of Claims] 1. An electric motor field rotor characterized in that a permanent magnet field part and an output shaft are integrally connected by a plastic support part. 2. The electric motor field rotor according to claim 1, wherein the magnetic material constituting the permanent magnet field portion is a plastic magnet material. 3. The electric motor field according to claim 1 or 2, wherein the plastic support part is made of a plastic magnet material having a small magnet particle diameter, and the plastic support part is magnetized for detecting rotational position. magnetic rotor. 4. An output shaft and a permanent magnet field part are arranged concentrically with respect to the output shaft in a molding die, and a plastic is placed in the cavity area of the mold that connects the output shaft and the permanent magnet field part. A method of manufacturing an electric motor field rotor, characterized in that the rotor is manufactured by filling a material and integrating a permanent magnet field part and an output shaft. 5. Arrange the output shaft in a mold for molding, fill the cavity for forming the field part and the cavity for forming the plastic support part formed in the mold with different plastic materials, and connect the output shaft and the permanent magnet. A method of manufacturing a field rotor for an electric motor, characterized in that the rotor is manufactured by integrating a field part and a plastic support part.