JP2653898B2 - Yoke for stepping motor and insert molding method of the yoke - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a yoke for a stepping motor and an insert molding method for the yoke.

[Conventional technology]

Generally, a stator of a stepping motor has a yoke in which a plurality of yoke elements are combined, and the yoke is formed integrally with a bobbin. In order to integrate the yoke and the bobbin, a method is employed in which a plurality of yoke elements are sequentially incorporated into a molding die and molded.

That is, as shown in FIGS. 7A to 7C, a molding die used for molding the yoke is composed of a core 1, a lower die 2, and a horizontal die 3. And a pair of split molds 5a and 5b which are overlapped on the split molds 4a and 4b and which are split into left and right. These split molds 4a,
On the inner surface of 5a, there is provided a projection 8 which enters into a notch 7 for positioning formed in each of the yoke elements 6a, 6b, 6c, 6d, and the engagement between the notch 7 and the projection 8 is provided. Thereby, positioning of the yoke elements 6a, 6b, 6c, 6d is performed.

Further, each yoke element 6a, 6b, 6c, 6d
1 has a ring portion 9a as shown in FIG. 1, and a plurality of yoke teeth portions 9b projecting in a direction perpendicular to the surface of the ring portion 9a at predetermined intervals on an inner edge of the ring portion 9a. Is provided. The yoke teeth 9b enter between the yoke teeth 9b of the other yoke elements 6a, 6b, 6c, 6d when the yoke elements 6a, 6b, 6c, 6d are incorporated into the molding die, and the adjacent yoke teeth 9b. 9b are arranged at predetermined intervals.

Next, a mold assembling procedure for forming the stator will be described.

First, as shown in FIG. 7A, the split molds 4a, 4b,
Retract a and 5b to the side. In this state, the first yoke element 6a is inserted into the metal core 1, and its ring portion 9a is abutted against the surface of the lower die 2.

Next, as shown in FIG. 7B, the pair of lower left and right split dies 4a, 4b is advanced toward the core 1 and the split dies 4a, 4b are closed. Thereafter, the second yoke element 6b is inserted into the cored bar 1 with the ring 9a facing upward, and the ring 9a is placed on the lower split molds 4a, 4b. Therefore, the directions of the first yoke element 6a and the second yoke element 6b are opposite, and the yoke teeth 9b of these yoke elements 6a, 6b are alternately positioned so as to mesh with each other. At this time, the lower split molds 4a and 4b form a molding cavity 10a between the cored bar 1, the first yoke element 6a and the second yoke element 6b.

Next, as shown in FIG. 7B, the third yoke element 6c is inserted into the mandrel 1 with the ring portion 9a facing downward, and the yoke element 6c is mounted on the second yoke element 6b. Place.

Then, as shown in FIG.
a, 5b is advanced to the cored bar 1 side, and after the split molds 5a, 5b are closed, the fourth yoke element 6d is inserted into the cored bar 1 with the ring portion 9a facing upward. These yoke elements 6c, 6d
Of the upper split mold 5a, 5
b forms a molding cavity 10b between the cored bar 1, the third yoke element 6c, and the fourth yoke element 6d.

Finally, resin is injected into the cavities 10a, 10b, and the yoke elements 6a, 6b, 6c, 6d and the bobbin are integrally insert-molded, thereby forming an integral stator assembly.

By the way, as shown in FIGS. 10 and 11, a plurality of yoke teeth 9b are provided at predetermined intervals in each of the yoke elements 6a, 6b, 6c, 6d. These yoke teeth 9b are adapted to enter between the yoke teeth 9b of the corresponding other yoke elements 6a, 6b, 6c, 6d when incorporated in the molding die as described above. The elements 6a, 6b, 6c, and 6d must determine the positional relationship so that the angle between the adjacent yoke teeth 9b is θ.

For this reason, conventionally, a notch 7 is provided in the ring portion 9a of each yoke element 6a, 6b, 6c, 6d, and the corresponding horizontal die 3 is provided.
On the inner surface of the split molds 5a and 5c, there are formed convex portions 8 which enter the notches 7 and position the respective yoke elements 6a, 6b, 6c and 6d. Then, as shown in FIG. 7A, the protruding portions 8 are linearly arranged along the metal core 1 with respect to each of the split dies 4a, 4b, 5a, 5b.

Further, when performing the positioning of the yoke elements 6a, 6b, 6c, 6d, the positional relationship of the yoke tooth portions 9b which enter each other is the same as the adjacent ones over the entire circumference at the same angle θ.
It is necessary to arrange these yoke elements 6a, 6b, 6c, 6d.

In order to obtain this relationship, as shown in FIG. 12, the position of the notch 7 of each of the yoke elements 6a, 6b, 6c, 6d is determined by the reference position 1st yoke element 6a and 4th yoke element
6d, the second yoke element 6b and 3
The second yoke element 6c needs to be provided at a position of θ + θ / 2. That is, two types of yoke elements are inevitably required.

Note that in order for each yoke element 6a, 6b, 6c, 6d to be of one type, a common yoke element requires the position of θ / 2 and the position of θ / 2.
It is preferable to provide cutouts 7 having the same shape at two positions at + θ / 2.

However, since the notch 7 having the same shape must be reliably selected and incorporated into a molding die, careful and troublesome assembling work is required. Also, if the assembling is performed by mistake using another notch 7, each of the yoke elements 6a, 6b, 6
The angle between the yoke teeth 9b of c and 6d does not become the predetermined angle θ.

Therefore, conventionally, in order to prevent this assembling error, two types of yoke elements having different positions of the notch 7 are prepared and used.

[Problems to be solved by the invention]

As described above, in the conventional yoke, at least two types of yoke elements are prepared to prevent an assembly error. Therefore, the number of types of yoke elements has increased, and common use of components has not been achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a yoke for a stepping motor and an insert for the yoke, which can share a yoke element and prevent an assembly error during insert molding. It is to provide a molding method.

[Means and actions for solving the problem]

In order to achieve the above object, the present invention comprises two yoke elements each having a ring portion and a plurality of yoke teeth portions arranged at intervals in a circumferential direction on an inner peripheral portion of the ring portion. The two yoke elements are positioned using a molding die so that the yoke teeth of the yoke element enter between the yoke teeth of the other yoke element to form a substantially cylindrical yoke body. In a yoke for a stepping motor in which a main body is overlapped in at least two axial directions and integrally formed with a bobbin, the molding die has a plurality of projections for positioning these yoke elements at positions corresponding to the yoke elements. The convex portions are arranged in a line on the same straight line along the axial direction of the yoke main body, and the ring portion of the yoke element is predetermined. The first and the second cutout portions having different distances from the reference position are provided at two places with the reference position as a boundary.
The second notch portion is characterized in that its depth and width are defined to be different from each other, and each is formed in a shape capable of engaging with the corresponding convex portion of the molding die.

Further, in order to achieve the above object, the present invention provides a first to fourth yokes each having a ring portion and a plurality of yoke teeth portions arranged at intervals in a circumferential direction on an inner peripheral portion of the ring portion. A stepping motor yoke for insert-molding integrally with the bobbin in a state where these four yoke elements are positioned by using a molding die, wherein the ring portion of the first to fourth yoke elements comprises: At two places with a predetermined reference position as a boundary, first and second notches having different distances and shapes from the reference position are provided, and the molding die corresponds to the yoke element. A plurality of projections for positioning these yoke elements at the set positions, and these projections are arranged in a line on the same straight line along the axial direction of the yoke main body, and Has a shape that can be engaged with the corresponding first and second notches, and inserts the first yoke element into the mold so that the first notch is convex. After the second yoke element is engaged with the first yoke element, the second yoke element is inserted into the mold in a direction opposite to the first yoke element, and the second yoke element is inserted between the yoke teeth of the first yoke element. And the second notch of the second yoke element is engaged with the projection of the molding die. Next, the third yoke element is connected to the first yoke element. By inserting the second notch portion into the convex portion by inserting the second yoke element into the molding die in the same direction, the fourth yoke element is inserted into the molding die in a direction opposite to that of the third yoke element. And inserting the yoke teeth of the fourth yoke element between the yoke teeth of the third yoke element. Ri causes written, has a first notch portion of the fourth yoke elements characterized in that so as to engage the convex portion of the mold.

Thus, according to the above configuration, the yoke can be assembled using a plurality of yoke elements having the same structure, and the yoke elements can be shared. In addition, when assembling the yoke elements into the mold, the assembling work of these yoke elements can be performed reliably and easily without inducing an error in assembling the yoke elements.

〔Example〕

Hereinafter, the present invention will be described based on an embodiment shown in FIGS. 1 to 6. As shown in FIGS. 1 and 2, the motor frame 11 includes a cup frame 11a and a base frame 11b. Cup frame 11a
Is formed into a low cylinder shape by pressing a sheet metal, and a mounting hole 13 is formed in the center of the bottom of the cup frame 11a. On the peripheral wall of the cup frame 11a, a lead wire lead-out groove 14 is formed in a cutout shape.
The stator 20 and the rotor 40 are housed in the cup frame 11a.

The stator 20 has two yoke bodies separated in the axial direction.
21 and 22, and a bobbin 23 made of an insulator such as a synthetic resin surrounding the outer periphery of the yoke bodies 21 and 22.
The bobbin 23 has winding drum portions 24 and 25 covering the periphery of the yoke main bodies 21 and 22. These winding drum parts 24 and 25 have windings
26,27 are wound.

The bobbin 23 made of the above insulator has
28 and 29 are formed to protrude. Terminal pin mounting part 28,
Terminal pins 30 are implanted in the respective 29, and these terminal pins 30 are connected to the terminals of the windings 26 and 27, respectively. Further, lead wires 31 are connected to the terminal pins 30, respectively. These lead wires 31 are led out of the motor and connected to a printed wiring board (not shown) for supplying a pulse signal, for example.

In this case, the terminal pin mounting portions 28 and 29 are exposed to the outside from the lead wire lead-out groove 14 on the peripheral wall of the cup frame 11a. Therefore, the lead wire 31 is substantially drawn out from the lead wire drawing groove 14.

The bobbin 23 is located at one end of one yoke main body 21 and integrally has a flange portion 32, and is located at the other end of the other yoke main body 22, and is a bearing holder serving also as a closing plate. 33 are integrated. Therefore, the pair of yoke bodies 21 and 22 separated in the axial direction by the flange portion 32 and the bearing holder 33 are integrally held and assembled.

The bearing holder 33 is fitted into a mounting hole 13 formed in the center of the bottom of the cup frame 11a, and substantially closes the mounting hole 13. The bearing holder 33 has a bearing 34 at the center, and the bearing 34 has a mounting hole.
It is located in the center of thirteen. The other flange portion 32 is formed with, for example, three locking recesses 35 which are located on the end surface facing the base frame 11b and are spaced apart in the circumferential direction.

The rotor 40 is housed in the stator 20 thus formed. The rotor 40 has a permanent magnet 41 having a cylindrical shape.
The motor shaft 15 penetrates and is mounted via the mold resin. In the magnet 41, a large number of S poles and N poles along the axial direction are alternately magnetized along the circumferential direction.

One end of the motor shaft 15 is rotatably supported by the bearing. The other end of the motor shaft 15 is rotatably supported by another bearing 16 mounted on the base frame 11b.

The base frame 11b is formed by press-molding a sheet metal, and has a substantially disk shape that fits into the opening of the cup frame 11a. The bearing 16 is attached to the center of the base frame 11b.

The motor shaft 15 of the rotor 40 passes through the bearing 16. Therefore, the motor shaft 15 is rotatably supported by the bearing 34 attached to the bearing holder 33 and the bearing 16 attached to the base frame 11b. For this reason, the rotor 40 is supported concentrically with respect to the stator 20.

 Reference numerals 37 and 38 in the figure denote spacers.

The base frame 11b has a pair of mounting portions 17, 17 extending in the radial direction. Fixing holes 18, 18 are formed in the mounting portions 17, 17, respectively. These mounting parts 17,
17 extends in the outer diameter direction from the peripheral surface of the cup frame 11a, and a fixing tool such as a screw is inserted into the fixing holes 18, 18 of these mounting portions 17, 17, and this is fixed to the motor fixing portion of the device. By doing so, the motor is fixed to the device.

Further, on the base frame 11b, a plurality of positioning projections 19 that are located around the bearing 16 and are depressed inward are formed on the same circumference. These positioning projections 19 are
At the opening of the flange portion 32,
By this fitting, the base frame 11
b is centered. At the same time, the base frame 11b is engaged with the stator 20 so as to be immovable in the radial direction.

A locking projection 36 is formed on the base frame 11b. The locking projection 36 is provided with the locking recess 35 of the flange 32.
And is selectively fitted into one of these locking recesses 35. Therefore, the base frame 11b is prevented from rotating in the circumferential direction with respect to the stator 20.

On the other hand, the yoke bodies 21 and 22 are similar to those shown in FIGS.
The yoke element 50 is configured by combining two yoke elements 50 having the same dimensions and shape as shown in the figure.

That is, the yoke element 50 has a plate-shaped ring portion 51 forming an outer peripheral portion, and a plurality of yoke teeth portions 52 are provided on an inner edge of the ring portion 51. The yoke teeth 52
The ring portions 51 extend at right angles in the same direction from the plate surface and are arranged at equal intervals in the circumferential direction of the ring portion 51, and have a comb-like shape as a whole. And
The yoke element 50 constitutes a comb-shaped protruding stator electrode by arranging the yoke teeth 52 facing each other and facing each other, similarly to the conventional one.

Each of the electrode portions projecting in a comb shape has a step angle θ in the circumferential direction inside the winding drum portions 24 and 25 of the bobbin 23.
Are arranged at a predetermined interval corresponding to.

As shown in FIG. 3, the ring portion 51 of each yoke element 50
Is a first notch 53 disposed at a position at an angle θ / 2 from the reference position l, and an angle θ + θ / 2 from the reference position l.
And a second cutout portion 54 disposed only at a position apart from the second cutout portion. These first and second notches 53, 54
Is opened at the outer peripheral edge of the ring portion 51. The width and depth of the first cutout 53 and the second cutout 54 are different from each other, and the width of the first cutout 53 is W1 and the depth is H1. The width of the second notch 54 is W2 and the depth is H2. And the width W1 is greater than the width W2 and the depth
H1 is set smaller than H2. However, the relationship between the size of the width and the depth may be reversed.

On the other hand, the insert molding die incorporating the yoke element 50 has a first notch 53 and a second notch.
Protrusions 55, 56, 57, 58 that determine the mounting position of each yoke element 50 by using 54 are provided.

That is, this mold is similar to the above-mentioned conventional mold,
The core is composed of a metal core, a lower mold, and a horizontal mold. It is composed of split molds 65,65. As shown in FIG. 5 and FIG. 6, the first notch 53 and the second notch 53 of the yoke element 50 to be inserted in the corresponding directions are provided on the inner surfaces of the split molds 64 and 65. Protrusions 55, 56, 57, 58 are provided to engage with and engage one of the parts 54.

In other words, the inner surface of the lower split mold 64 has 1
When the second yoke element 50 is inserted, a projection 55 corresponding to the first cutout 53 is formed. The width of the projection 55 is W1, and the height is H1. For this reason, the convex part
Only the first notch 53 is engaged with 55.

In addition, the inner surface of the lower split mold 64 has two
When the second yoke element 50 is inserted, a projection 56 corresponding to the second cutout 54 is formed. The width of the projection 56 is W2 and the height is H2. Therefore, only the second cutout 54 is engaged with the projection 56.

On the inner surface of the upper split mold 65, a convex portion 57 corresponding to the second cutout portion 54 is formed when the third yoke element 50 is inserted in a normal direction. The width of the projection 57 is W2 and the height is H2. For this reason, the convex part
Only the second cutout 54 is engaged with 57.

In addition, the inner surface of the upper split mold 65 has 4
When the second yoke element 50 is inserted, a convex portion 58 is formed corresponding to the first notch portion 53, and the width of the convex portion 58 is W1, and the height is H1. Therefore, only the first cutout 53 is engaged with the projection 58.

Thus, in the above configuration, the procedure for performing the insert molding by assembling the four yoke elements 50 is performed as described above.

That is, first, with the horizontal split molds 64 and 65 retracted to the side, the first yoke element 50 is inserted into the mandrel, and the ring portion 51 is pressed against the surface of the lower mold, and The notch 53 is engaged with the projection 55. In this state, only the first cutout portion 53 engages with the projection 55, so that the incorporation of the yoke element 50 in a wrong alignment is prevented.

Next, the second yoke element 50 and the third yoke element
50 is inserted into the core of the molding die in the same procedure as described above. At this time, the second yoke element 50 and the third yoke element 50 are opposed to each other, and the second notch 54 is engaged with the corresponding projection 56, 57 of the split mold 64, 65. Combine. Also, since the first notch 53 cannot fit into the protrusions 56 and 57, the first notch 53 is mistakenly inserted into the protrusions 56 and 57.
To prevent misalignment.

Next, the fourth yoke element 50 is inserted into the core of the forming die, and the first cutout 53 is engaged with the corresponding convex portion 58 of the split die 65. Since only the first notch 53 can be fitted into the projection 58, the second notch 54 is erroneously locked and the yoke element 50 in the wrong alignment is locked.
Is prevented from being incorporated.

Finally, a resin is injected into the cavity, and each yoke element 50 and the bobbin are integrally insert-molded to form an integral stator assembly.

According to the present invention, the four yoke elements 50 having the same structure can be definitely positioned in the molding die and the insert molding can be performed. Thus, even if one type of yoke element 50 is used, an assembly error can be prevented beforehand, and there is no need to prepare two types of yokes.

Note that the stepping motor of the present invention is not limited to a stepping motor for feeding a magnetic head, and can be applied to various fields such as OA equipment and FA equipment. In addition, the present invention can be variously modified within the scope of the gist described in the claims.

〔The invention's effect〕

As described above, according to the present invention, a yoke body can be formed by combining a plurality of yoke elements having the same structure, and it is not necessary to prepare a plurality of yoke elements having different structures. Therefore, the yoke elements can be shared, and accordingly, the number of parts can be reduced, and the manufacturing cost of the yoke can be reduced. Moreover, despite the fact that the common yoke element is housed in the mold and insert molded, it is possible to prevent erroneous incorporation of the yoke element into the mold.
The operation of assembling the yoke can be performed reliably and easily.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 is an exploded perspective view of a stepping motor, FIG. 2 is a longitudinal sectional view of the stepping motor, and FIG. 3 is a perspective view of a yoke. 4 is a plan view of the yoke, FIG. 5 is a front view of a main part of the molding die, and FIG. 6 is a perspective view of a main part of the molding die. 7A to 7C to FIG. 12 show a conventional one, FIGS. 7A to 7C are explanatory views showing a procedure for assembling the yoke element, FIG. 8 is a cross-sectional view of a split mold, FIG. 9 is a partial front view of the molding die, FIGS. 10 and 11 are perspective views of the yokes, and FIG. 12 is an explanatory view showing the assembled state of each yoke. 21,22 ... yoke body, 50 ... yoke element, 51 ... ring part, 52 ... yoke tooth part, 53 ... first notch part, 54 ... second notch part, 55, 56 , 57,58 …… Protrusion, 64,65 …… Split mold (molding mold).

Claims (2)

(57) [Claims] A first yoke element having a ring portion and a plurality of yoke teeth arranged on an inner peripheral portion of the ring portion at an interval in a circumferential direction; The two yoke elements are positioned using a mold so that the part enters between the yoke teeth of the other yoke element to form a substantially cylindrical yoke body. In a yoke for a stepping motor which is formed so as to be integrally formed with a bobbin by being superposed in the axial direction, the molding die has a plurality of convex portions for positioning these yoke elements at positions corresponding to the yoke elements,
These projections are arranged in a line on the same straight line along the axial direction of the yoke main body, and the ring portion of the yoke element has two reference positions at a predetermined reference position boundary. And first and second notches having different distances from each other. The first and second notches have depths and widths that are defined to be different from each other, and correspond to the above-described respective notches. A yoke for a stepping motor, wherein the yoke is formed in a shape engageable with a convex portion of a molding die. 2. The apparatus according to claim 1, further comprising a first to a fourth yoke element having a ring portion and a plurality of yoke teeth circumferentially arranged at an inner peripheral portion of the ring portion at intervals. In the insert molding method for a yoke for a stepping motor, in which the yoke element is inserted and molded integrally with a bobbin in a state where the yoke element is positioned by using a molding die, the ring portion of the first to fourth yoke elements may have a predetermined reference position. The first and second cutouts have different distances and shapes from the reference position at two locations as boundaries, and the molding die has a yoke element at a position corresponding to the yoke element. And a plurality of projections for positioning the first and second projections. The projections are arranged in a line on the same straight line along the axial direction of the yoke main body, and the first and second projections correspond to the respective projections. It has a shape that can be engaged with the second notch, and after inserting the first yoke element into the molding die and engaging the first notch with the projection, Inserting the second yoke element into the molding die in a posture opposite to the first yoke element, and inserting the yoke teeth of the second yoke element between the yoke teeth of the first yoke element; The second notch of the second yoke element is engaged with the projection of the mold, and then the third yoke element is inserted into the mold in the same direction as the first yoke element. Then, the second notch portion is engaged with the convex portion. Next, the fourth yoke element is inserted into the molding die in a posture opposite to the third yoke element, and the third yoke element is The yoke teeth of the fourth yoke element are inserted between the yoke teeth. 4. A method for insert-molding a yoke for a stepping motor, wherein the first notch of the yoke element of No. 4 is engaged with the projection of the molding die.