JP2003092847A - Stepping motor and its magnet rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor and its magnet rotor which can eliminate a position discrepancy between an annular magnet constituting the magnet rotor and a rotor body made of thermoplastic synthetic resin, even if a gap is produced between the magnet and the rotor body by the contraction of the rotor body which is caused by the insert molding of the rotor body together with the magnet by devising the shape of the annular magnet. SOLUTION: A large diameter part 54a and a small diameter part 54b of a stepped hollow part 54 of a magnet Rb are coupled coaxially and integrally with a large diameter wall 53a and a small diameter wall 53b of a recessed part 53 of a rotor main part Ra. The wall part 53c with a V-shaped cross-section of the rotor body Ra is tightly engaged with the inside of the wall part 54c with a V-shaped cross-section of the magnet Rb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor and its magnet rotor.

[0002]

2. Description of the Related Art Conventionally, for example, in some passenger car indicating instruments, a step motor is adopted as a drive source of the pointer. This step motor is configured to rotatably support a magnet rotor in a stator.

[0003]

By the way, in the above step motor, the magnet rotor is constructed by integrally forming an annular magnet by insert molding on the outer peripheral portion of the rotor body made of a thermoplastic synthetic resin material.

However, when the magnet rotor is formed by insert molding as described above, the rotor body shrinks, so that a gap is created between the facing surfaces of the magnet and the rotor body. As a result, a positional deviation occurs between the magnet and the rotor body. Therefore, in a step motor using such a magnet rotor, the magnet rotor is difficult to rotate smoothly due to the positional deviation between the magnet and the rotor body as described above.

In order to cope with the above, the present invention devises the shape of the annular magnet which constitutes the magnet rotor, and inserts the magnet into the rotor main body made of the thermoplastic synthetic resin material. An object of the present invention is to provide a step motor and a magnet rotor for the step motor, which prevent misalignment between the magnet and the rotor body even if a gap is generated between the magnet and the rotor body due to the contraction of the rotor body. .

[0006]

In order to solve the above-mentioned problems, a magnet rotor for a step motor according to the invention described in claim 1 has a hollow portion (5) of an annular magnet (Rb).
4) Inside the rotor body (R
The magnet and the rotor body are insert-molded so that (a) is integrally and coaxially fitted.

In the magnet rotor, the hollow portion of the magnet is formed at the small diameter portion (54b) and the large diameter portion (54a) coaxial with each other and the boundary between the small diameter portion and the large diameter portion, and is accompanied by insert molding. At the time of contraction of the rotor body, an annular wall portion (53
c, 53d), the magnet rotor has an annular wall portion (54c, 54d) having a shape capable of preventing the positional displacement, and the rotor main body is integrally formed by inserting the rotor main body into the hollow portion of the magnet via the annular wall portion of the hollow portion. And to fit coaxially,
The magnet is insert-molded together with the rotor body.

According to this, at the time of insert molding of the magnet rotor, the rotor main body is made of the thermoplastic synthetic resin material, and therefore contracts due to hardening thereof. However, the annular wall portion of the hollow portion of the magnet has a shape capable of preventing the annular wall portion of the rotor body from being displaced. Therefore, during the contraction, the annular wall portion of the rotor body is maintained at the same position by the annular wall portion of the magnet without displacement. In other words, the relative position of the rotor body with respect to the magnet is maintained unchanged regardless of the contraction of the rotor body during the insert molding, so that the rotor body is not displaced with respect to the magnet. Therefore, the step motor using the magnet rotor insert-molded in this way can rotate smoothly.

Further, according to the invention described in claim 2, in the invention described in claim 1, the annular wall portion of the magnet is sectioned from the small diameter portion side to the large diameter portion side along the axial direction of the magnet. The rotor body is formed in a V shape, and the annular wall portion of the rotor body is formed in a V shape in cross section in the annular wall portion having a V shape in cross section with the insert molding.

As a result, each contracting force of the rotor body generated along the axial direction and the radial direction of the magnet during the insert molding also acts on the annular wall portion having a V-shaped cross section of the magnet, but in the axial direction. The contracting force generated along the vector acts by being vector-divided in each normal direction of both surface portions of the annular wall portion of the magnet due to the V-shaped cross section. For this reason, the V-shaped annular wall portion of the rotor body comes into close contact with the V-shaped wall portion of the magnet. Therefore, even if the contracting force along the radial direction acts on the annular wall portion having a V-shaped cross section, the magnet is not displaced in the radial direction of the rotor body.
Therefore, the function and effect of the invention described in claim 1 can be achieved more reliably.

A step motor according to a third aspect of the present invention includes a stator (S) and a magnet rotor (R) rotatably supported in the stator.
In the step motor, the magnet rotor is the magnet rotor according to claim 1 or 2.

As a result, it is possible to provide a step motor capable of achieving the effects of the magnet rotor according to the first or second aspect.

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments described later.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 and 2 show a first embodiment of an indicating instrument for a passenger vehicle to which the present invention is applied. The indicating instrument is an instrument panel in the passenger compartment of the passenger vehicle. Is installed as a speedometer.

The indicating instrument comprises a scale board 10 and a wiring board 2.
0, pointer 30, and rotating inner unit D are provided, and the scale plate 1
0 is installed side by side in the opening 41a of the bottom wall 41 of the ring-shaped dial plate 40 from the back side thereof. Wiring board 20 is arranged on the back surface side along scale board 10.

As shown in FIG. 2, the rotating internal unit D is assembled to the wiring board 20 from the rear surface side thereof at a position corresponding to the scale 10. The rotating inner unit D includes an inner unit body 50 and a pointer shaft 60. The internal machine body 50 is
The casing C is provided, and the casing C is attached to the wiring board 20 from the back surface side by one side wall 51a thereof.

As shown in FIG. 2, the inner unit main body 50 is provided with a reduction gear train G and a step motor M. The reduction gear train G is assembled in the casing C. The reduction gear train G uses four spur gears 52 to 52c to reduce the rotation of the step motor M and transmit it to the pointer shaft 60. It has become.

The spur gear 52 is a step motor M which will be described later.
Which is integrally formed with the magnet rotor R of
The spur gear 52, together with the magnet rotor R, is coaxially supported by a rotating shaft 52d that is rotatably supported between one side wall 51a of the casing C and the other side wall 51b facing the side wall 51a. Further, the spur gear 52c is coaxially supported at an intermediate portion of a pointer shaft 60 rotatably supported by both side walls 51a and 51b so as to mesh with the spur gear 52b.
Both spur gears 52a and 52b are the one side wall 51 of the casing C.
It is rotatably supported between a and the other side wall 51b, and the spur gear 52a meshes with the spur gear 52. The spur gears 52 to 52c are made of a soft synthetic resin material.

The pointer shaft 60 is rotatably supported by the other side wall 51b of the casing C at the base end portion thereof, and the pointer shaft 60 extends from the base end portion of the side wall 5 of the casing C.
It extends rotatably through 1a, the wiring board 20, and the scale board 10. The pointer 30 is supported by the tip end portion of the pointer shaft 60 by the rotation base portion 31, and extends from the rotation base portion 31 along the surface of the dial 10.

As shown in FIG. 2, the step motor M is mounted in a casing C, and the step motor M is composed of a stator S and a magnet rotor R. The stator S is attached to one side wall 51a of the casing C as shown in FIG. As shown in FIG. 2, the magnet rotor R is coaxially supported together with the spur gear 52 on the rotating shaft 52d in the stator S, and the magnet rotor R is made of a thermoplastic synthetic resin material. 3, a rotor body Ra formed integrally with the spur gear 52 coaxially,
It is composed of a magnet Rb formed of a metal magnetic material in an annular shape.

An annular recess 53 is formed coaxially with the rotor body Ra at an intermediate portion of the outer peripheral wall of the rotor body Ra, while a stepped hollow portion 54 is formed on the magnet Rb.
Is formed concentrically with the shaft of the magnet Rb and is coaxially fitted in the recess 53 of the rotor body Ra.

Here, the stepped hollow portion 5 of the magnet Rb
4 will be described in detail in relation to the annular recess 53 of the rotor body Ra. As shown in FIGS. 3 and 4, the stepped hollow portion 54 of the magnet Rb is configured by coaxially forming a small diameter portion 54b immediately below the large diameter portion 54a, and the large diameter portion 54a and the small diameter portion 54b. The annular wall portion formed in the radial direction at the boundary with is cut out in a V-shaped cross section in the direction along the axis of the magnet Rb from the surface side to the inside.
It is formed as an annular V-shaped wall 54c in cross section.

On the other hand, the bottom wall of the recess 53 of the rotor body Ra is formed by coaxially forming a small diameter wall portion 53b immediately below the large diameter wall portion 53a, as shown in FIGS. The annular wall portion formed in the radial direction at the boundary between the large diameter wall portion 53a and the small diameter wall portion 53b is bulged outward from the surface side thereof in a V-shaped cross section in the direction along the axis of the rotor body Ra. And is formed as an annular V-shaped wall portion 53c.

However, in the state where the magnet Rb is coaxially and integrally fitted to the rotor body Ra as described above, the stepped hollow portion 54 of the magnet Rb has a large diameter portion 54a and a small diameter portion 54b. At the cross section V of the rotor body Ra, the rotor body Ra is coaxially and integrally fitted to the large diameter wall portion 54a and the small diameter wall portion 54b of the recess 54, respectively.
The V-shaped wall portion 53c is a V-shaped wall portion 5 having a cross section of the magnet Rb.
It is tightly engaged with the inside of 4c.

The magnet rotor R has a spur gear 52.
In addition, insert molding is performed as follows. That is, the magnet Rb having the above-described structure is prepared, and the insert molding die having a cavity corresponding to the outer shape of the integral structure of the spur gear 52 and the rotor body Ra shown in FIG. 3 is prepared. On the outer peripheral wall of the mold, an opening corresponding to the opening surface of the recess 53 of the rotor body Ra is formed. In addition, the said metal mold | die consists of two metal mold | die parts divided into the axial direction, and these metal mold | die parts are combined coaxially and the said opening part is formed.

Then, both mold parts of the mold are combined with each other through the magnet Rb so that the magnet Rb fits in the opening of the mold in the stepped hollow portion 54. After that, the thermoplastic synthetic resin material is poured into the mold in a liquid state and then cured to integrally mold the rotor body Ra coaxially with the spur gear 52, and the magnet R.
b and the rotor body Ra are coaxially insert-molded.
Thereby, the magnet Rb is integrally formed by insert molding so as to be coaxially fitted to the rotor body Ra as described above.

In the first embodiment constructed as described above, since the forming material of the rotor body Ra is the thermoplastic synthetic resin material during the insert molding of the magnet rotor R as described above, the rotor body is concerned. Ra contracts due to its hardening. This contraction occurs toward the axis of the rotor body Ra along the radial direction from the outer peripheral surface side of the rotor body Ra as illustrated by each arrow A in FIG. 4, and as shown by each arrow B. It is generated from both axial end faces of Ra along the axis of the rotor body Ra toward the center in the axial direction.

Therefore, as illustrated in FIG. 4, the large-diameter wall portion 53a of the bottom wall of the recess 53 of the rotor body Ra extends radially from the large-diameter portion 54a of the stepped hollow portion 54 of the magnet Rb. While contracting to form the gap g, the small-diameter wall portion 53b of the bottom wall of the recess 53 contracts radially from the small-diameter portion 54b of the stepped hollow portion 54 to form the gap g.

On the other hand, as described above, the rotor main body Ra contracts from both axial end faces of the rotor main body Ra along the axis of the rotor main body Ra toward the center in the axial direction as illustrated by each arrow B. Therefore, between the upper inner wall shown in FIG. 4 of the recess 53 of the rotor body Ra and the upper end surface of the magnet Rb shown in FIG. 4, and between the lower inner wall of the recess 53 and the magnet Rb.
No gap is formed between the lower end face and the lower end face.

Further, as described above, in the magnet Rb, the large diameter portion 54a and the small diameter portion 54 of the stepped hollow portion 54.
A wall having a V-shaped cross section 54c is previously formed in an annular shape at the boundary with b. Therefore, at the time of the insert molding, the liquid thermoplastic synthetic resin material to be injected into the mold is also filled in the V-shaped cross-section wall portion 54c to form the V-shaped cross-section wall portion 53c.

As described above, the rotor main body Ra contracts from both axial end faces of the rotor main body Ra along the axis of the rotor main body Ra toward the center in the axial direction as illustrated by each arrow B. Therefore, the contracting force indicated by the arrow B is in each direction indicated by the double-headed arrow B1 by the V-shaped wall portion 54c of the magnet Rb (each normal direction to the one side surface portion a and the other side surface portion b of the wall portion 54c). And is applied to the V-shaped wall 54c in cross section. Therefore, the V-shaped cross-section wall portion 53c is in close contact with the one side surface portion and the other side surface portion of the cross-section V-shaped wall portion 54c at the one side surface portion and the other side surface portion, respectively. The wall portion 54c is tightly engaged with the wall portion 54c. Therefore, the contracting force of the rotor body Ra that is generated toward the axis of the rotor body Ra as illustrated by each arrow A as described above also acts on the annular V-shaped cross-section wall portion 54c. Is absorbed by the close engagement of the V-shaped wall section 53c with the V-shaped wall section 54c as described above, and the radial relative of the V-shaped wall section 53c with respect to the V-shaped wall section 54c. No positional deviation occurs, and as a result, no gap occurs between the V-shaped cross-section wall portion 53c of the rotor body Ra and the V-shaped cross-section wall portion 54c of the magnet Rb.

That is, during the insert molding, the outer dimensions of the magnet Rb do not change, but the rotor body Ra contracts due to hardening.
The close engagement between the V-shaped wall portion 53c and the V-shaped cross-section wall portion 54c is maintained. Therefore, the relative position of the V-shaped cross-section wall portion 53c to the V-shaped cross-section wall portion 54c,
In other words, the relative position of the rotor body Ra with respect to the magnet Rb is determined by the rotor body R during the insert molding.
Since it is maintained unchanged regardless of the contraction of a, the rotor body Ra will not be displaced relative to the magnet Rb. Therefore, the step motor M using the magnet rotor R thus insert-molded can smoothly rotate. As a result, under such a smooth rotation of the step motor M, the pointer 30 moves with the reduction gear train G,
It can rotate smoothly.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention. In the second embodiment, the first
The magnet R of the magnet rotor R described in the embodiment
In b, instead of the annular V-shaped wall section 54c in section, an annular wall section 54d having an inclined section is adopted. The slanted wall section 54d is inclined downward in the radial direction as shown in FIG. 5 from the large diameter section 54a to the small diameter section 54b at the boundary between the large diameter section 54a and the small diameter section 54b of the magnet Rb. Is formed in.

Along with this, in the second embodiment, in the rotor body Ra of the magnet rotor R described in the first embodiment, instead of the annular V-shaped cross-section wall portion 53c,
The configuration is such that an annular slanted wall portion 53d is adopted. The slanted wall portion 53d has a radial direction as shown in FIG. 5 from the large diameter wall portion 53a to the small diameter wall portion 53b at the boundary between the small diameter wall portion 53b and the large diameter wall portion 53a of the rotor body Ra. And is formed so as to incline downward.

However, in the state where the magnet Rb is coaxially and integrally fitted to the rotor body Ra as described in the first embodiment, the inclined wall section 53d of the rotor body Ra has Wall 54 with inclined section of magnet Rb
It is tightly engaged with d.

The insert molding of the magnet rotor R is performed as follows. That is, the magnet Rb having the above-mentioned configuration according to the second embodiment is prepared, and the external shape of the spur gear 52 shown in FIG. 3 and the integral structure of the rotor body Ra having the configuration according to the second embodiment are equivalent. An insert molding die having a void is prepared. It should be noted that this mold is different from the mold described in the first embodiment only in the shape part of the cross-sectional shape of the rotor body Ra different from that in the first embodiment.

Therefore, using the mold of the second embodiment, the magnet Rb referred to in the second embodiment is injected and cured by injection of the liquid thermoplastic synthetic resin material as in the first embodiment. Is integrally formed by insert molding so as to be coaxially fitted to the rotor body Ra. Other configurations are the same as those in the first embodiment.

In the second embodiment thus constructed, the rotor body Ra is hardened at the time of insert molding of the magnet rotor R, so that each arrow of FIG. It contracts in the directions illustrated by A and each arrow B.

Therefore, the gaps g described in the first embodiment are formed in the same manner as in the first embodiment. on the other hand,
As described above, in the magnet Rb, an inclined cross-section wall portion 54d is formed in advance at the boundary between the large diameter portion 54a and the small diameter portion 54b of the stepped hollow portion 54. Therefore, when the insert molding is performed, the liquid thermoplastic synthetic resin material to be injected into the mold is the wall portion 54 having the inclined cross section.
A wall portion 53d having an inclined cross section is formed in an annular shape over the surface of d. Further, as described in the first embodiment, the rotor main body Ra is oriented from the axial end surfaces of the rotor main body Ra toward the center in the axial direction along the axis of the rotor main body Ra as illustrated by each arrow B. The contraction force indicated by the arrow B is vector-changed in the direction indicated by the arrow B2 (the normal direction to the surface of the wall portion 54d) by the sectional slanted wall portion 54d of the magnet Rb, so that the cross section is reduced. It acts on the inclined wall portion 54d. Therefore, the slanted wall section 53d is in close contact with the surface of the slanted wall section 54d at its surface, and is in close contact with the slanted wall section 54d. Therefore, the contracting force of the rotor body Ra generated toward the axis of the rotor body Ra as illustrated by the arrows A as described above also acts on the annular cross-section inclined wall portion 53d, but the contracting force is The wall portion 54 having the inclined section as described above
It is absorbed by the close engagement of the slanted wall section 53d with respect to d, and the relative displacement of the slanted wall section 53d with respect to the slanted wall section 54d in the radial direction does not occur. As a result, the rotor body Ra A gap does not occur between the slanted wall portion 53d having the slanted cross section and the wall portion 54d having the slanted cross section of the magnet Rb.

That is, in the second embodiment, as in the first embodiment, the outer dimensions of the magnet Rb do not change during the insert molding, but the rotor body Ra does not change.
Although shrinkage occurs due to hardening, the engagement due to the close contact between the slanted wall section 53d and the slanted wall section 54d as described above is maintained as it is. Therefore, the wall section 5 having an inclined cross section
The relative position of 3d with respect to the inclined wall section 54d, in other words, the relative position of the rotor body Ra with respect to the magnet Rb is maintained unchanged regardless of the contraction of the rotor body Ra during the insert molding. Therefore, the rotor body Ra will not be displaced with respect to the magnet Rb. Therefore, the step motor M using the magnet rotor R thus insert-molded can smoothly rotate. As a result, also in the second embodiment, the pointer 30 can be smoothly rotated by the reduction gear train G under such smooth rotation of the step motor M.

In implementing the present invention, the magnet Rb of the magnet rotor R described in the first embodiment is used.
Even if the annular V-shaped cross-section wall portion 54c is generally an annular concave wall portion, it is possible to achieve substantially the same effects as the first embodiment. In this case, an annular V-shaped wall portion 53c formed on the rotor body Ra
May be an annular convex wall portion having an annular cross section that engages with the annular concave wall portion.

In implementing the present invention, the magnet Rb of the magnet rotor R described in the second embodiment is also used.
Unlike the second embodiment, the annular wall 54d having a slanted section in cross section may be formed so as to incline upward in the radial direction shown in FIG. 5 from the small diameter portion 54b to the large diameter portion 54a. It is possible to achieve substantially the same effects as the second embodiment.

Further, in carrying out the present invention, the step motor M is not limited to a speedometer, but may be a tachometer or other various indicator instruments, and is not limited to an indicator instrument, and is not limited to general industrial equipment. It may be a step motor used as a drive source of the.

Further, in carrying out the present invention, the present invention is not limited to the indicating instrument for a passenger car, but the present invention may be applied to an indicating instrument generally adopted in an automobile or other vehicle.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of an indicating instrument for passenger cars according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 in FIG.

FIG. 3 is an enlarged cross-sectional view of the magnet rotor according to the first embodiment.

FIG. 4 is a partially enlarged sectional view of the magnet rotor of FIG.

FIG. 5 is an enlarged sectional view of an essential part showing a second embodiment of the present invention.

[Explanation of symbols]

R ... Magnet rotor, Ra ... Rotor body, Rb ... Magnet, S ... Stator, 54 ... Hollow part, 54a ... Large diameter part, 54b ... Small diameter part, 53c, 54c ... Annular wall part, 53
d, 54d ... Inclined wall portion.

Claims (3)

[Claims] 1. A hollow portion (5) of an annular magnet (Rb).
4) Inside the rotor body (R
In a magnet rotor for a step motor, in which the magnet and the rotor body are insert-molded so that (a) is integrally and coaxially fitted, a hollow portion of the magnet has a small diameter portion (5) that is coaxial with each other.
4b) and a large-diameter portion (54a), and an annular shape formed at the boundary between the small-diameter portion and the large-diameter portion and corresponding to the boundary of the outer peripheral wall of the rotor body when the rotor body contracts due to the insert molding. Annular wall portions (54c, 54d) having a shape capable of preventing displacement of the wall portions (53c, 53d)
The magnet is insert-molded together with the rotor body so that the rotor body is integrally and coaxially fitted into the hollow portion of the magnet via the annular wall portion of the hollow portion. A magnet rotor for a step motor. 2. The annular wall portion of the magnet is formed in a V-shaped cross section along the axial direction of the magnet from the small diameter portion side toward the large diameter portion side, and the annular wall portion of the rotor body is The magnet rotor for a step motor according to claim 1, wherein the magnet rotor is formed in a V-shaped cross section in the annular wall portion having a V-shaped cross section along with the insert molding. 3. A step motor comprising a stator (S) and a magnet rotor (R) rotatably supported in the stator, wherein the magnet rotor is the magnet rotor according to claim 1 or 2. A step motor characterized by being present.