JP2000083363A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lightweight inner rotor type stepping motor, having enhanced motor performance suitable for use over a wide temperature range. SOLUTION: A stator core 12 has a pole 12a arranged at the opposite ends thereof, with housing fitting parts 14 which are fitted with stator fitting parts 18 thus fixing a bearing housing 16 to the core 12. The core 12 and the housing 16 are formed of materials having identical coefficient of linear expansion. A frame 19 which supports the housing 16 is formed of a material lighter than the materials of the core 12 and the housing 16. Outer circumferential wall 19b of the frame 19 is fitted to the frame fitting part 15 at the end of the core 16, and the inner circumferential wall 19a thereof is fitted to the outer circumference of the housing 16 and both frames 19 are clamped at the opposite ends of the stator 11 and is secured in place by means of fixing with screw. According to the structure, a fixed air gap g can be kept, despite a wide range of temperature fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor such as an inner rotor type stepping motor, and more particularly to a motor suitable for being mounted on equipment having a wide operating temperature range.

[0002]

2. Description of the Related Art FIG. 2 is a partially sectional side view showing the structure of a conventional inner rotor type stepping motor, in which 1 is a stator, 2 is a rotor, 3 is a frame, and 4 is a bearing. is there.

[0003] The cylindrical stator 1 has a stator core 1
a is formed by winding a stator winding 1c around each of a plurality of magnetic poles 1b (only one is shown) of a.
At both ends, annular frame fitting portions 1d are provided. The pair of frames 3 are respectively screwed to both ends of the stator 1. Each of these frames 3 has an annular stator fitting portion 3a provided on the outer peripheral portion thereof.
By fitting to the outer periphery of d, it is positioned in the radial direction and the axial direction.

[0004] Bearings 4 are fitted and supported in recesses formed inside the frame 3, respectively, and these bearings 4 are mounted on the rotor 2 disposed inside the stator 1.
Is rotatably supported. The rotor 2 is a magnet 2a
And an air gap G is formed between the outer peripheral surface of the rotor 2 and the front end surface of the magnetic pole 1b. The pair of frames 3 are formed of an aluminum alloy different from the stator core 1a usually made of an iron-based material in order to reduce the weight of the entire motor.

A stepping motor having such a configuration is
Since it is lightweight and the frame 3 also serves as a bearing housing for supporting the bearing 4, the number of parts is small,
It is excellent in that the structure is simple.

[0006]

In the conventional configuration, the rotor 2 is positioned in the radial direction at the fitting portion between the stator fitting portion 3a of the frame 3 and the frame fitting portion 1d of the stator core 1a. However, in the conventional stepping motor, the materials of the stator core 1a and the frame 3 are different for weight reduction, and the linear expansion coefficients thereof are largely different, so that the operating temperature range is wide (for example, −40 ° C. to +
In the case of 100 ° C.), a gap is easily generated between the two fitting portions 1d and 3a due to radial expansion according to a temperature change.

The occurrence of such a gap impairs the positioning performance of the rotor 2 in the radial direction and causes the rotor 2 to be offset in the radial direction, so that the air gap G in the offset direction becomes narrow. However, it is necessary to consider the design so as to function normally even if such a change in the gap G occurs.
Must be set large, and therefore the stator 1
There is a problem that the magnetic resistance between the motor and the rotor 2 increases, which causes a decrease in motor performance.

The above problem can be solved by making the materials of the stator core 1a and the frame 3 the same and making the coefficients of linear expansion coincide with each other. I have no choice.
Therefore, there is a problem that the weight increases and the whole motor becomes heavy.

Accordingly, a first object of the present invention is to provide a lightweight motor which can improve the motor performance and is suitable for use in a wide temperature range.

Further, a second object of the present invention is to provide a motor in which the rattling based on temperature change is prevented from occurring in the axial direction in solving the first object. .

[0011]

SUMMARY OF THE INVENTION The present invention comprises a stator,
Bearing housings respectively attached to both ends of the stator, bearings respectively supported in these housings,
A motor provided with a rotor rotatably supported by these bearings and arranged inside the stator is assumed.

According to a first aspect of the present invention, a housing fitting portion is provided at each of both ends of a magnetic pole of a stator core of the stator, and the housing is fitted inside the fitting portion. And connecting the bearing housing to the stator core, and forming the stator core and the bearing housing with materials having similar linear expansion coefficients,
The outer peripheral wall of the frame supporting the bearing housing,
Fitting the outer periphery of the end of the stator core, fitting the inner peripheral wall of the frame to the outer periphery of the bearing housing, attaching the frame to both ends of the stator, and attaching the frame to the stator core and the bearing. It is characterized by being formed of a material lighter than the housing.

According to the first aspect of the present invention, the bearing housing supporting the bearing and the stator core of the stator have the same linear expansion coefficient. No gap is generated between the fitting portions, and accordingly, the air gap between the rotor supported by the bearing and the magnetic pole of the stator core can be maintained at a predetermined size. Therefore, there is no need to design a large air gap in anticipation of a change in the air gap due to a wide temperature change. Also, since the bearing housing is fitted and mounted inside the housing fitting portion of the magnetic pole, the shape of the bearing housing, which is heavy because it has the same linear expansion coefficient as the stator core, can be reduced in size and weight. In addition, since the frame connected to the stator and supporting the bearing housing is formed of a lightweight material, the weight of the entire motor can be reduced.

In order to solve the second problem, the invention according to claim 2 is dependent on the invention according to claim 1, wherein the outer peripheral wall and the inner peripheral wall of the frame along the axial direction have the same length. It is a feature.

Since the second aspect of the invention is dependent on the first aspect of the invention, in addition to the effects of the first aspect of the invention, the extension of the inner and outer peripheral walls of the frame along the motor axial direction due to a wide range of temperature changes. Since the shrinkage can be made the same, there is no possibility that a gap is generated at the joint in the axial direction where the frame faces regardless of a wide temperature change.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a side view showing a partial cross section of the configuration of the inner rotor type stepping motor according to the first embodiment, and the operating environment temperature of this motor is in a wide range from −40 ° C. to + 100 ° C.

In FIG. 1, reference numeral 11 denotes a relatively short cylindrical stator, which has a plurality (only one shown) integrally protruding from an inner surface of a stator core 12 made of an iron-based material as a magnetic material. The stator winding 1 is connected to each of the magnetic poles 12a.
3 is wound. At both ends of each magnetic pole 12a, a housing fitting portion 14 is provided integrally extending in the axial direction of the stator core 12 respectively. These fitting portions 14
Are located on a circle (not shown) drawn with the same radius,
Each has an arcuate fitting surface. At both ends in the axial direction of the outer periphery of the stator core 12, stepped frame fitting portions 15 are provided, respectively, and are formed continuously in the circumferential direction of the stator core 12.

A pair of bearing housings 16 are arranged inside the stator 11, respectively. These housings 1
6 has a bearing fitting recess 16a and integrally has an annular projection 17 that is continuous in the circumferential direction on the outer surface of the peripheral wall.
An opening edge of the peripheral wall on the tip side from the annular projection 17 is used as a stator fitting portion 18, and the fitting portion 18 is fitted to an inner side surface (the fitting surface) of the housing fitting portion 14. Thereby, both bearing housings 16 are connected to stator 11. In this connection state, the housing fitting portion 14 and the annular projection 17 are in contact with each other, whereby the fitting depth of the fitting portions 14 and 18 is regulated.

The pair of bearing housings 16 and the stator core 12 are formed of materials having similar linear expansion coefficients. Therefore, in the present embodiment, the stator core 12
The bearing housing 16 is formed of the same iron-based metal material as that described above. Alternatively, the bearing housing 16 may be formed of a material having a similar linear expansion coefficient such as titanium.

The bearing housings 16 are supported via a pair of frames 19 made of different kinds of lightweight materials so as not to come off the stator 11. The frame 19 is formed in a ring shape from aluminum or its alloy, or a synthetic resin having a wide operating temperature range, and has an inner peripheral wall 19a and an outer peripheral wall 19b having the same length.
And The pair of frames 19 are fitted in such a manner that the inner surface of the inner peripheral wall 19a is fitted to the outer surface of the peripheral wall of the bearing housing 16 and the distal end of the outer peripheral wall 19b is fitted to the frame fitting portion 15.
And is connected to the stator 11 through a plurality of screws (not shown) screwed into the stator 11.

By this connection, the tip of the inner peripheral wall 19a comes into contact with the annular projection 17, and the projection 17 is sandwiched between the housing fitting portion 14 and the bearing housing 16 is fixed. A screw hole (not shown) is formed at an appropriate position of the frame 19, and the entire motor is fixed by using this hole. The protrusion 17 and the stator fitting portion 15 against which the outer peripheral wall 19b abuts
It is set at the same position in the axial direction of the rotor described later.

A pair of frames 19 sandwiching the stator 11
The bearings 20 such as ball bearings are accommodated in the bearing fitting recesses 16a of the two bearing housings 16 positioned in the radial direction and the axial direction, respectively. These bearings 20 rotatably support a rotor 21 disposed inside the stator 11.
A predetermined air gap g is formed between the outer peripheral surface facing the magnetic pole 1 and the magnetic pole 12a. The rotor 21
A rotor magnet 21c, which is magnetized in the thickness direction on the outer periphery of a rotor shaft 21b that penetrates the bearing 20 and is supported by these via a sleeve 21a,
1c and the rotor core 21d on the N pole side / S pole side are attached.

In the stepping motor having the above structure,
A pair of bearing housings 16 for supporting the bearings 20
And the stator core 12 of the stator 11 are formed of an iron-based metal material having a linear expansion coefficient equivalent to each other, and are fitted together and assembled. Therefore, even in an operating environment ranging from −40 ° C. to + 100 ° C., these bearing housings 16
Since there is no difference in expansion and contraction in the radial direction between the stator core 12 and the stator core 12, a gap is generated in the fitting part between the housing fitting part 14 and the stator fitting part 18, and the rotor 21 There is no approach.

Therefore, regardless of the influence of the radial expansion and contraction caused by the wide temperature change as described above, the distance between the rotor 21 supported by the bearing 20 in the bearing housing 16 and the magnetic pole 12a of the stator core 12 is maintained. Air gap g
Can be held at a constant narrow size. Therefore, when designing this motor, the air gap g
It is not necessary to make a large air gap in anticipation of the change in the air gap. Thereby, the problem of widening the air gap g, that is, the magnetic resistance between the stator 11 and the rotor 21 does not increase and the driving torque does not decrease, so that the motor performance can be improved.

In addition, as described above, the stator fitting portion 18
Is fitted inside the housing fitting portion 14 of the magnetic pole 12a, since the distance from these fitting portions to the central axis of the motor is short, machining accuracy is easily obtained, and the stator It is easy to obtain the concentricity of the rotor 21 with respect to the rotor 11. Therefore, a narrow air gap g can be provided with high precision, and this is also advantageous in improving motor performance.

Further, since it is not necessary to increase the air gap g in consideration of the effect of thermal expansion as described above, the inner and outer diameters of the stator 11 can be reduced accordingly. And can be.

Further, as described above, in the stepping motor having the above-described structure, the stator fitting portion 18 of the bearing housing 16 is fitted and mounted inside the housing fitting portion 14 of the magnetic pole 12a. The shape of the bearing housing 16, which is heavy due to the same expansion coefficient, can be reduced in size.
Weight can be reduced. In addition, in order to support the bearing housing 16, the stator 11
Since the frame 19 connected to the motor is formed of a lightweight material such as aluminum, the weight of the entire motor can be reduced.

As described above, the stepping motor having the above-described structure is constituted by the outer peripheral wall 19 b and the inner peripheral wall 19 of the frame 19.
Since the length "a" is the same, the expansion and contraction of the inner and outer peripheral walls 19a and 19b along the motor axis direction due to a wide temperature change can be made the same. Therefore, there is no possibility that a gap is generated between the joints in the axial direction facing the frame 11 regardless of a wide temperature change.

Therefore, the stepping motor according to the present embodiment is used for a wide range of temperature changes.
Since the characteristics of the motor can be improved and the size and weight can be reduced, it is suitable for the use conditions as described above.

An annular projection 17 is provided on the bearing housing 16.
Is provided, and the projection 17 is sandwiched between the housing fitting portion 14 and the inner peripheral wall 19a of the frame 19, so that the bearing housing 16 is fitted to the housing fitting portion 14, Frames 19 on both sides of stator 11
Through this, the bearing housing 16 can be securely mounted. In addition, since the stator fitting portion 18 of the bearing housing 16 does not need to have a thickness including the size of the protrusion of the annular projection 17, a large-diameter bearing 20, and therefore a low-cost bearing 20, can be used. The service life and, consequently, the motor life can be improved.

Although the present invention is particularly suitable for use in an environment where the operating temperature range is wide, it can be used as a general-purpose motor without being limited by these operating conditions.

[0032]

The present invention is embodied in the form described above and has the following effects.

According to the first aspect of the present invention, the air gap between the rotor and the magnetic pole of the stator core can be maintained at a predetermined size even in an environment where the temperature changes over a wide range. As a result, the frame is formed of a lightweight material in combination with being able to be used in a wide temperature range and the shape of the bearing housing can be reduced, so that a light motor can be provided.

According to the second aspect of the present invention, in addition to the effects of the first aspect, expansion and contraction of the inner and outer peripheral walls of the frame along the motor axial direction due to a temperature change. Can be made the same, so that rattling based on a wide temperature change can be prevented from occurring in the axial direction.

[Brief description of the drawings]

FIG. 1 is a side view showing a partial cross section of a configuration of an inner rotor type stepping motor according to a first embodiment of the present invention.

FIG. 2 is a side view showing a partial cross section of a configuration of an inner rotor type stepping motor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Stator, 12 ... Stator core, 12a ... Magnetic pole, 14 ... Housing fitting part, 15 ... Frame fitting part, 16 ... Bearing housing, 18 ... Stator fitting part, 19 ... Frame, 19a ... Inner peripheral wall of frame, 19b ... the outer peripheral wall of the frame, 20 ... bearing, 21 ... rotor, g ... air gap.

Claims (2)

[Claims] 1. A stator, bearing housings respectively mounted on both ends of the stator, bearings supported in the housings, and a rotor rotatably supported by the bearings and arranged inside the stator. In the motor comprising: a housing fitting portion is provided at each of both ends of the magnetic poles of the stator core of the stator, and the bearing housing is connected to the inside of the fitting portion to connect the bearing housing to the stator core. The bearing housing is formed of a material having a similar coefficient of linear expansion, an outer peripheral wall of a frame supporting the bearing housing is fitted to an outer periphery of an end portion of the stator core, and an inner peripheral wall of the frame is attached to an outer periphery of the bearing housing. And the frames are attached to both ends of the stator, respectively, and A motor, wherein the frame is formed of a material that is lighter than the stator core and the bearing housing. 2. The motor according to claim 1, wherein the outer peripheral wall and the inner peripheral wall of the frame along the axial direction have the same length.