JP2003264972A - Stepping motor and magnet rotor thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet rotor of which the dies are resistant to damage, in the magnet motor provided with a magnet formed by pressing a powdery magnetic body with the dies. <P>SOLUTION: This magnet rotor R is formed, by inserting a resin rotor body Ra so as to be integrally and coaxially fitted into the inner periphery of a cylindrical magnet Rb formed by pressing the powdery magnet body with the dies 70, 71, 72. In the magnet rotor R, there is provided a groove 540 for stopping rotation which functions as a rotation stopper of the rotor body Ra and the magnet Rb on upper and lower end portions 54a, 54b of the inner periphery of the magnet Rb, and the groove 540 for stopping rotation is formed so as to be a circular-arc shape protruding in the radial direction of the magnet Rb. Thus, from an outer periphery 72d of a portion 71a, corresponding to the groove 540 for stopping rotation of the movable dies 71, 72, an angle portion 81b in the conventional magnet Rb, can be eliminated and resistance to damages to the movable dies 71, 72 can be attained. <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 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.
Generally, in such a step motor, the magnet rotor is configured by integrally forming an annular magnet on the outer peripheral portion of the resin rotor body by insert molding.

At the end of the inner peripheral surface of the magnet Rb, a polygonal enlarged portion 541 having an enlarged inner diameter is formed as shown in FIGS. 7 (a) and 7 (b). The enlarged portion 541 prevents the rotor body and the magnet Rb from rotating.

[0004]

Here, the method of molding the magnet Rb will be described with reference to FIG. 8. The magnetic material of powder filled in the fixed mold 80 is pressed by the movable mold 81 to be solidified. After that, the magnet Rb is molded by sintering or the like.

However, in the above-mentioned conventional magnet Rb, since the enlarged portion 541 is formed at the end 54a of the inner peripheral surface thereof, the portion 8 of the movable die 81 corresponding to the enlarged portion 541 is formed.
Since 1a is thin as indicated by the symbol t in FIG. 8 and has a long protrusion length as indicated by the symbol L, damage such as cracking and chipping easily occurs.

Moreover, since the enlarged portion 541 is formed in a polygonal shape, the outer peripheral surface 81b of the enlarged portion corresponding portion 81a must also be formed in a polygonal shape. Therefore, the damage is more likely to occur at the polygonal corner portion 81b of the enlarged portion corresponding portion 81a.

In view of the above points, the present invention provides a magnet rotor for a step motor, which is provided with a magnet formed by pressing a powder magnetic material with a die, in which the die is less likely to be damaged. To aim.

[0008]

In order to achieve the above object, in the invention described in claim 1, a cylindrical magnet formed by pressing a powder magnetic material with a die (70, 71, 72). (Rb) and a resin rotor body (Ra), and the rotor body (R) is attached to the inner peripheral surface of the magnet (Rb).
In a step motor magnet rotor formed by insert molding so that (a) is integrally and coaxially fitted, end portions (54a, 54a) of the inner peripheral surface of the magnet (Rb).
b) is provided with a detent groove portion (540) that functions as a detent for the rotor body (Ra) and the magnet (Rb), and the detent groove portion (540) is provided in the magnet (Rb).
It is characterized in that it is formed in an arc shape that is convex in the radial direction.

According to this, the rotation preventing groove portion (540)
Is formed in an arc shape that is convex in the radial direction of the magnet (Rb), so that the outer peripheral surface of the portion of the mold (71, 72) corresponding to the rotation-preventing groove portion (540) has no corner portion. Therefore, the molds (71, 72) are less likely to be damaged.

By the way, when the rotor body (Ra) is insert-molded on the magnet (Rb), the rotor body (R) is
Due to the heat shrinkage of a), a gap is likely to be formed between the facing surfaces of the magnet (Rb) and the rotor body (Ra).

On the other hand, in the invention described in claim 2,
Since the bottom surface (540b) of the anti-rotation groove portion (540) is formed in a taper shape, even if the above-mentioned gap occurs, the magnet (Rb) is formed in the anti-rotation groove portion (540).
And the rotor body (Ra) are in close contact with each other. Therefore, it is possible to prevent a problem in which the magnet (Rb) and the rotor body (Ra) are misaligned due to the gap, and it is difficult for the magnet rotor to smoothly rotate.

Further, as in the invention described in claim 3, a step motor comprising a stator (S) and a magnet rotor (R) rotatably supported in the stator (S) is provided. It is preferable to use the magnet rotor described in 1 or 2.

The reference numerals in the parentheses of the above means are examples showing the correspondence with the concrete means described in the embodiments described later.

[0014]

1 and 2 show an embodiment of an indicating instrument for a passenger vehicle to which the present invention is applied. The indicating instrument is a speedometer on an instrument panel in a passenger compartment of the passenger vehicle. Is arranged as.

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 a casing C, and the reduction gear train G includes four spur gears 52,
The rotation of the step motor M is decelerated and transmitted to the pointer shaft 60 by 52a, 52b, and 52c.

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, 52a, 52b, 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 one 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 hollow portion 54 is formed in the magnet Rb and a shaft of the magnet Rb. Concentrically formed, the rotor body R
It is coaxially fitted in the recess 53 of a.

Here, the structure of the hollow portion 54 of the magnet Rb will be described in detail with reference to FIGS. 4 and 5 in relation to the annular recess 53 of the rotor body Ra. 4 is a plan view showing only the magnet Rb, and FIG. 5 is a sectional view taken along line YY of FIG.

As shown in FIG. 4, the rotor body R is attached to the inner peripheral end portions 54a and 54b of the hollow portion 54 of the magnet Rb.
A detent groove 540 that functions as a detent between the a and the magnet Rb is provided.

The detent groove 540 is preferably provided at a plurality of locations on the same end of the hollow portion 54,
In this embodiment, the rotation preventing groove portions 5 are provided at three locations on the same end portion.
40 is provided. Further, in this embodiment, the hollow portion 54
The upper and lower end portions 54a and 54b are provided with rotation preventing groove portions 540 both above and below the upper and lower end portions 54a and 54b.
A total of 6 places including a and 54b, and a groove portion 540 for preventing rotation.
Is provided.

Further, the anti-rotation groove portion 540 is formed in an arc shape which is convex in the radial direction of the magnet Rb. In other words, the reference numeral 54 in the detent groove portion 540
The portion indicated by 0a is formed in an arc shape.

Further, as shown in FIG. 5, the bottom surface 540b of the anti-rotation groove portion 540 is formed in a tapered shape. The tapered bottom surface 540b is also formed as an arc surface following the arc of reference numeral 540a.

Further, the inner peripheral surface upper end 54a of the hollow portion 54 is
And the tapered surface 54c over the entire circumference of the lower end 54b.
Are formed. Further, tapered surfaces 54d are formed on both upper and lower ends of the outer peripheral surface of the magnet Rb.

Here, the method of molding the magnet Rb will be described with reference to FIG.
To explain with reference to FIG.
A through hole 70a having a shape corresponding to the cylindrical shape is formed. The hollow portion 54 is provided below the through hole 70a.
The lower movable mold 71 having a shape corresponding to the lower end portion 54b of is positioned.

After that, after filling the through hole 70a with a powder magnetic material, an upper movable mold 72 having a shape corresponding to the upper end 54a of the hollow portion 54 is pressed against the magnetic material from above the through hole 70a. By doing so, the magnetic substance is hardened.
Then, after the hardened magnetic body is sintered, the inner peripheral surface upper and lower end portions 5
The magnet Rb is molded by polishing 4a, 54b and the upper and lower ends of the outer peripheral surface.

Incidentally, reference numerals 71a and 72a in FIG.
Reference numeral 71 is a portion corresponding to the rotation preventing groove portion 540.
d and 72d are tapered bottom surfaces 5 of the rotation preventing groove portion 540.
This is a portion corresponding to 40b. Further, reference numeral 71 in FIG.
Reference numerals 71c and 72c denote magnets Rb, b and 72b corresponding to tapered surfaces 54c formed at the upper end 54a and the lower end 54b of the inner peripheral surface of the hollow portion 54.
Is a portion corresponding to the tapered surfaces 54d formed at the upper and lower ends of the outer peripheral surface of the.

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, the magnet Rb has the hollow portion 5
At step 4, the two mold parts of the mold are combined with each other through the magnet Rb so that the mold parts fit in the opening part of the mold. After that, the thermoplastic synthetic resin material is injected into the mold in a liquid state and then cured to fix the rotor body Ra to the spur gear 52.
And the magnet Rb 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 present embodiment thus constituted, the rotor main body Ra is made of the thermoplastic synthetic resin material when the magnet rotor R is insert-molded as described above, so that the rotor main body Ra is It contracts due to its curing. 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.

Then, in the annular recess 53 of the rotor body Ra, a surface indicated by reference sign g in FIG. 3 facing the hollow portion 54 of the magnet Rb has a gap g due to contraction in the radial direction. On the other hand, as described above, the rotor body Ra
Since the rotor main body Ra contracts along the axis of the rotor main body Ra toward the center in the axial direction from both end faces of the rotor in the axial direction as illustrated by each arrow B, the taper of the rotation preventing groove portion 540 is reduced. The bottom surface 540b and the surface of the rotor body Ra that faces the bottom surface 540b come into close contact with each other.

That is, during the insert molding, although the outer dimensions of the magnet Rb do not change, the rotor body Ra contracts due to hardening, but the tapered bottom surface 540b and the rotor body Ra of the rotor Ra as described above. Of which, the bottom surface 540
The tight engagement between the surface facing b is maintained as it is. Therefore, the relative position of the rotor body Ra to the magnet Rb is maintained unchanged regardless of the contraction of the rotor body Ra at the time of the insert molding, which causes the rotor body Ra to be displaced relative to the magnet Rb. There is no. Therefore, the step motor M using the magnet rotor R thus insert-molded can smoothly rotate. As a result, under such smooth rotation of the step motor M, the pointer 30 can smoothly rotate by the reduction gear train G.

Further, according to the present embodiment, since the anti-rotation groove portion 540 is formed in an arc shape which is convex in the radial direction of the magnet Rb, the anti-rotation groove portion 540 of the movable molds 71 and 72. Outer peripheral surface 72d of the portion 71a corresponding to
Has a corner portion 81 as seen in the conventional magnet Rb.
b can be eliminated, and the movable dies 71 and 72 are less likely to be damaged.

(Other Embodiments) In the above embodiment, the bottom surface 540b of the anti-rotation groove portion 540 is formed in a tapered shape, but in implementing the present invention, the tapering of the bottom surface 540b is omitted. Also, for example, the bottom surface 540b
Even if is formed on the surface extending in parallel to the radial direction, the effect that the movable dies 71 and 72 are less likely to be damaged can be similarly exhibited.

In the above embodiment, the magnet Rb is used.
Although the anti-rotation groove portions 540 are provided on both upper and lower sides of the upper end portion 54a and the lower end portion 54b of the hollow portion 54 of FIG. The groove portion 540 may be provided.

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 may be a general industrial instrument. 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 an embodiment of an indicating instrument for a passenger car according to the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

3 is an enlarged cross-sectional view of the magnet rotor shown in FIG.

FIG. 4 is a plan view of the magnet shown in FIG.

5 is a cross-sectional view taken along line YY of FIG.

6 is a cross-sectional view of a mold for molding the magnet shown in FIG.

FIG. 7A is a plan view showing a conventional magnet, and FIG. 7B is a ZZ sectional view.

8 is a cross-sectional view of a mold for molding the conventional magnet shown in FIG.

[Explanation of symbols]

54a ... Upper end of hollow part, 54b ... Lower end of hollow part, 70 ... Fixed mold, 71 ... Lower movable mold, 72 ... Upper movable mold, 540 ... Rotation stop groove part, R ... Magnet Rotor, Ra ... Rotor body, Rb ... Magnet.

Claims (3)

[Claims] 1. A powder magnetic material is applied to a mold (70, 71, 7).
2) Cylindrical magnet (R
b) and a rotor body (Ra) made of resin, and the rotor body (Ra) is provided on the inner peripheral surface of the magnet (Rb).
In a step motor magnet rotor formed by insert molding so as to be integrally and coaxially fitted, end portions (54a, 54a) of the inner peripheral surface of the magnet (Rb).
b), the rotor body (Ra) and the magnet (R)
b) Detent groove (54) that functions as a detent against
0) is provided, and the rotation preventing groove portion (540) is connected to the magnet (R).
A magnet rotor for a step motor, wherein the magnet rotor is formed in an arc shape which is convex in the radial direction of b). 2. The step motor magnet rotor according to claim 1, wherein a bottom surface (540b) of the rotation preventing groove portion (540) is formed in a tapered shape. 3. A stator (S) and this stator (S)
A step motor comprising a magnet rotor (R) rotatably supported therein, wherein the magnet rotor (R) is the magnet rotor according to claim 1 or 2.