JP5141861B2 - Stepping motor - Google Patents

Description

  The present invention relates to a stepping motor, and more particularly to a PM (permanent magnet) type stepping motor.

  10 and 11 show a conventional PM (permanent magnet) type stepping motor 30. FIG. In the stepping motor 30, a coil 34a is wound around a bobbin 33a, the outer periphery of the bobbin 33a is covered with an outer yoke 31a and an inner yoke 32a, and a first stator portion is configured. Further, the coil 34b is wound around the bobbin 33b, and the outer periphery of the bobbin 33b is covered with the outer yoke 31b and the inner yoke 32b to constitute the second stator portion. Furthermore, the stator portion is configured by fixing the first stator portion and the second stator portion.

  Further, a rotor portion is constituted by a magnet (permanent magnet) 38, a shaft 39, and a rotor sleeve 37 that are multipolarly magnetized on the outer periphery. On the other hand, the front plate 20 is fixed to the outer side in the axial direction of the outer yoke 31a, and a bearing 35a for supporting the rotor shaft 39 is fixed to the front plate 20. Similarly, the end plate 21 is fixed to the outer side of the outer yoke 31b in the axial direction, and a bearing 35b that supports the shaft 39 is fixed to the end plate 21. Then, the shaft 39 of the rotor portion is pivotally supported by the bearings 35a and 35b, so that the rotor portion rotates in a cylindrical space formed at the center of the stator portion. In addition, the part shown with the codes | symbols 36a and 36b is a spacer which has slidability.

  The first stator portion and the second stator portion are each provided with a plurality of pole teeth that are close to and opposed to the outer periphery of the magnet 38 so as to alternately mesh with each yoke. In the stepping motor 30 shown in FIGS. 10 and 11, a magnetic field is applied to the pole teeth of the outer yoke 31a and the inner yoke 32a and the outer yoke 31b and the inner yoke 32b by the pulse voltage applied to the coils 34a and 34b. A driving force is generated by the generated magnetic field and the magnetic field of the magnetized magnet 38, and as a result, the rotor unit rotates.

  However, since the conventional stepping motor 30 shown in FIGS. 10 and 11 has a configuration in which the bearing 35a is fixed to the front plate 20 and the bearing 35b is fixed to the end plate 21, the front plate 20 and the end plate The total length of the motor is increased by the thickness of 21. For this reason, when the full length of the stepping motor 30 is regulated, there is a problem that the ratio of the occupied volume of the coils 34a and 34b to the full length of the motor becomes small and an increase in output torque cannot be expected. Although the front plate 20 functions as a motor mounting plate, the motor mounting plate has a different shape depending on the customer. As a result, the stepping motor 30 is completed with the front plate 20 mounted. Therefore, there is a problem that it is difficult to standardize the manufacturing process, and thus to standardize the motor structure.

  As a countermeasure for such a problem, there has been proposed a stepping motor having a configuration in which the bearings 35a and 35b are directly attached to the inner circumferences of the outer yokes 31a and 31b without using the front plate 20 and the end plate 21 ( For example, see Patent Document 1.)

  FIG. 12 shows an exploded perspective view of the stepping motor 40 with the front plate and end plate removed. The stepping motor 40 includes a rotor magnet 41, a shaft 42, a plurality of pole teeth 43a, 44a alternately arranged in the circumferential direction, inner yokes 43, 44 made of a soft magnetic material, excitation coils 45, 46, circumferential direction. Are provided with outer yokes 47 and 48 made of a soft magnetic material having a plurality of pole teeth 47a and 48a arranged alternately. The stators 49 and 50 are constituted by these components. The bearings 51 and 52 that support the shaft 42 are sintered oil-impregnated bearings fixed to the outer yokes 47 and 48, respectively.

  As is clear from FIG. 12, the sintered oil-impregnated bearing 51 has a two-stage shape having a large-diameter portion 51a and a small-diameter portion 51b (the same applies to the sintered oil-impregnated bearing 52). The small diameter portions of the sintered oil-impregnated bearings 51 and 52 are fitted and inserted into the inner circumferences of the outer yokes 47 and 48, respectively, so that they are fixed to the outer yokes 47 and 48, respectively, and the large diameter portion is the outer yoke. The bearings 51 and 52 are positioned in the axial direction by contacting the outer surfaces of the 47 and 48 in the axial direction.

JP 2006-254557 A (page 3, FIG. 1)

  However, in the configuration of the conventional stepping motor 40 described above, the bearings 51 and 52 may fall off the outer yokes 47 and 48 when an axial load is applied to the shaft 42 or when an external impact is applied. . Even when the small-diameter portions of the sintered oil-impregnated bearings 51 and 52 are fitted to the inner circumferences of the outer yokes 47 and 48 and are fixed to the outer yokes 47 and 48 with an adhesive, respectively, temperature changes and changes with time As a result, the adhesive deteriorates, and the bearings 51 and 52 may fall off the outer yokes 47 and 48 depending on the degree of deterioration.

  On the other hand, when the sintered oil-impregnated bearings 51 and 52 are composed of iron-based sintered oil-impregnated bearings, and the small diameter portion is fitted to the inner periphery of the outer yokes 47 and 48 and fixed to the outer yokes 47 and 48 by welding, respectively. There is no possibility that the above-mentioned drop-off problem will occur. However, the bearing 51 (52) has a two-stage shaft structure including a large-diameter portion 51a and a small-diameter portion 51b, and the large-diameter portion 51a abuts against the axially outer surfaces of the outer yokes 47 and 48. The bearing 51 (52) protrudes outward in the axial direction of the outer yokes 47 and 48 by the thickness of the large diameter portion 51a of (52), and the total length of the stepping motor 40 is increased. As the outer diameter of the stepping motor 40 becomes smaller, the ratio of the outer diameter of the large diameter portion 51a of the bearing 51 to the outer diameter of the stepping motor 40 becomes larger. Similar to the examples of FIGS. 10 and 11, the ratio of the coil occupation volume to the total motor length is reduced, and it is difficult to increase the motor torque.

  The present invention has been made in view of the above problems, and the object of the present invention is to increase the ratio of coil occupied volume in a stepping motor even when the total length of the motor is restricted. The aim is to improve the motor torque as much as possible.

In order to solve the above-described problems, the stepping motor of the present invention stores an outer yoke having a plurality of pole teeth alternately arranged on the same circumference and a coil wound around a bobbin inside the inner yoke. The rotor is provided with a flange so as to be fitted with the notch formed in the bottom plate of the outer yoke of the stator, and the bearing is fixed to the outer yoke by fitting the flange into the notch. Is. With such a configuration, the positioning and fixing of the bearing with respect to the outer yoke are reliably performed, and the protrusions from the bottom plate of the outer yoke to the outside in the axial direction are eliminated, thereby avoiding an increase in the total length of the motor.
Therefore, even when the total length of the motor is restricted, it is possible to increase the ratio of the coil occupation volume and improve the motor torque as much as possible.
(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each item does not limit the technical scope of the present invention. Therefore, the technical aspects of the present invention also apply to those in which some of the constituent elements in each section are replaced, deleted, or other constituent elements are added while referring to the best mode for carrying out the invention. It can be included in the range.

(1) A cylindrical outer peripheral frame and a bottom plate that closes one end of the outer peripheral frame, an opening is formed at the center of the bottom plate, and a plurality of poles provided parallel to the outer peripheral frame along the periphery of the opening An annular space is formed by the outer yoke having teeth and the inner yoke having a plurality of pole teeth alternately arranged on the same circumference as the plurality of pole teeth of the outer yoke. A stator in which a coil wound around a bobbin is stored;
A rotor composed of a shaft and a magnet fixed to the shaft, and rotatably disposed in a cylindrical space surrounded by a plurality of pole teeth of the stator;
A pair of bearings that pivotally attach the shaft of the rotor to the outer yoke of the stator across the magnet;
A notch is formed between the pole teeth of the bottom plate of the outer yoke, extending further outward in the radial direction from the periphery of the opening of the bottom plate,
The bearing includes: a boss portion made of a hollow cylindrical sintered oil-impregnated alloy ; and a flange portion that protrudes from an outer periphery of the boss portion and fits into a notch of the bottom plate of the outer yoke, and the boss portion and the flange portion stepping motor is formed by separate parts, and that the flange portion is the bottom plate notch in fitted with bearings of the outer yoke is mounted.

  In the stepping motor described in this section, the rotation of the bearing relative to the outer yoke is prevented by fitting the flange portion of the bearing into the notch in the bottom plate of the outer yoke. In addition, the flange portion of the bearing fitted into the notch of the bottom plate of the outer yoke comes into contact with the bobbin stored in the annular space formed by the outer yoke and the inner yoke, so that the bearing with respect to the outer yoke is The axial position is also accurately positioned.

(2) In the above item (1), a plurality of notches extending from the peripheral edge of the opening of the bottom plate to the outside in the radial direction are formed between the pole teeth of the bottom plate of the outer yoke, A stepping motor comprising a plurality of flange portions protruding from the outer periphery of the portion and fitted into notches in the bottom plate of the outer yoke (claim 1).
In the stepping motor described in this section, the plurality of flange portions of the bearing are fitted into the plurality of notches of the bottom plate of the outer yoke, so that the rotation of the bearing with respect to the outer yoke is performed at a plurality of positions on the outer periphery of the boss portion. It is blocked more reliably. Further, the plurality of flange portions of the bearing fitted into the plurality of notches on the bottom plate of the outer yoke abut on the bobbin stored in the annular space formed by the outer yoke and the inner yoke, so that the outer yoke The position of the bearing in the axial direction is also more reliably positioned at a plurality of positions on the outer periphery of the boss portion.

Further, since the boss portion is made of a hollow cylindrical sintered oil-impregnated alloy, it is possible to ensure necessary lubricity when the rotor shaft rotates. In addition, by using a copper-based sintered oil-impregnated alloy as the sintered oil-impregnated alloy, it is possible to reduce the sliding noise of the shaft as compared with the case of using an iron-based sintered oil-impregnated alloy.
  In addition, since the boss portion and the flange portion of the bearing are separately formed in the stepping motor described in this section, it is easy to use a manufacturing method and material suitable for each of the boss portion and the flange portion. Become.

(3) The boss portion of the bearing is formed to have an outer diameter that is fitted and inserted into the inner peripheral surface of the pole teeth of the outer yoke, and the flange portion of the bearing has a thickness equal to or less than the thickness of the bottom plate of the outer yoke. The boss is fitted in a notch in the bottom plate of the outer yoke and is in contact with a bobbin of the coil stored in an annular space formed by the outer yoke and the inner yoke. A stepping motor in which one end face in the axial direction of the portion is formed at a position where it does not protrude outward in the axial direction from the bottom plate.
In the stepping motor described in this section, the bearing is stably held with respect to the outer yoke by fitting and inserting the boss portion of the bearing into the inner peripheral surface of the pole teeth of the outer yoke. In addition, the bearing flange portion is fitted into the notch of the bottom plate of the outer yoke, the bearing is prevented from rotating with respect to the outer yoke, and the axial position is positioned. Also, it does not protrude outward in the axial direction from the bottom plate of the outer yoke.

(4) The boss portion of the bearing is formed to have an outer diameter that is fitted and inserted into the inner peripheral surface of the pole teeth of the outer yoke, and the flange portion of the bearing is equal to or less than the bottom plate of the outer yoke. A stepping motor having a thickness and being flush with one axial end surface of the boss portion so as not to protrude axially outward from the bottom plate of the outer yoke (claim 2).
In the stepping motor described in this section, the bearing is stably held with respect to the outer yoke by fitting and inserting the boss portion of the bearing into the inner peripheral surface of the pole teeth of the outer yoke. The axial direction of the bottom plate of the outer yoke is such that the flange portion of the bearing fits into the notch of the bottom plate of the outer yoke, prevents rotation of the bearing relative to the outer yoke, and is positioned in the axial direction. The outer surface and the axially outer surface of the bearing are flush (flat), and neither the boss portion nor the flange portion protrudes axially outward from the bottom plate of the outer yoke. As a result, the total length of the annular space formed by the outer yoke and the inner yoke is increased, and the ratio of the occupied volume of the coil stored in the space can be increased, so that the magnetomotive force can be increased. As a result, the motor torque can be increased.

( 5 ) A stepping motor in which the boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, and the flange portion is made of a metal material having an annular portion fitted to the outer periphery of the boss portion. Item 3).
In the stepping motor described in this section, since the boss part and the flange part of the bearing are formed separately, the parts are manufactured separately by the manufacturing method suitable for each of the boss part and the flange part. By making them easy and fixing them, the bearing can be configured. Here, since the boss portion is made of a hollow cylindrical sintered oil-impregnated alloy, it is possible to ensure necessary lubricity when the rotor shaft rotates. Moreover, as the oil-impregnated sintered alloy, by the use of the oil-impregnated sintered alloy of copper, compared with the case of using the oil-impregnated sintered alloy iron-based, it is possible to reduce the sliding noise of the shaft. On the other hand, a flange part consists of a metal material provided with the annular part fitted to the outer periphery of a boss | hub part, for example, is formed by punching a board | plate material. Also, by using ferrous metal as the metal material, when fixing the bearing to the outer yoke formed of ferrous metal, it is easy and reliable to fix both by welding. It becomes. The fixing of the boss portion and the flange portion of the bearing is divided line by fitting an annular portion provided on the flange portion on the outer periphery of the boss portion.

( 6 ) A stepping motor in which the boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, and the flange portion is made of a resin material having an annular portion fitted to the outer periphery of the boss portion. Item 4 ).
In the stepping motor described in this section, the boss portion of the bearing and the flange portion are formed separately, and the boss portion is made of a hollow cylindrical copper-based sintered oil-impregnated alloy. It is possible to ensure the necessary lubricity. In addition, by using a copper-based sintered oil-impregnated alloy as the sintered oil-impregnated alloy, it is possible to reduce the sliding noise of the shaft as compared with the case where an iron-based sintered oil-impregnated alloy is used. On the other hand, a flange part consists of a resin material provided with the annular part fitted to the outer periphery of a boss | hub part, and the variation in a shape can be reduced by integrally forming a flange part with a resin mold. Also, since the bearing flange is made of resin, the notch on the bottom plate of the outer yoke is completely blocked by the bearing flange, which reliably prevents foreign matter and other foreign matter from entering the stator. Is done.
( 7 ) A stepping wherein the boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, and the flange portion is made of a spring-like thin metal plate having an annular portion fitted to the outer periphery of the boss portion. A motor (Claim 5 ).
In the stepping motor described in this section, the boss portion of the bearing and the flange portion are formed separately, and the boss portion is made of a hollow cylindrical copper-based sintered oil-impregnated alloy. It is possible to ensure the necessary lubricity. In addition, by using a copper-based sintered oil-impregnated alloy as the sintered oil-impregnated alloy, it is possible to reduce the sliding noise of the shaft as compared with the case where an iron-based sintered oil-impregnated alloy is used. On the other hand, since the flange portion is formed from a spring-like thin metal plate having an annular portion fitted to the outer periphery of the boss portion, the bearing can be attached to the outer yoke without using welding.

(8) wherein the circle connecting tips of flange diameter, the outer yoke of the bottom plate of the notches stepping motor is formed so as to slightly exceed the diameter of a circle connecting base (claim 6).
In the stepping motor described in this section, for example, the notch of the outer yoke is connected so that the diameter of the circle connecting the tips of the flange portions is slightly larger than the diameter of the circle connecting the base end of the notch of the bottom plate of the outer yoke. It is formed in an interference fit state such as being set to be about 0.1 mm larger than the diameter of the circle. Therefore, when the bearing is mounted on the outer yoke, the outer periphery of the flange portion is deformed and pushed into the notch of the outer yoke. As a result, when an outward force is applied to the bearing in the axial direction, the deformed flange portion becomes a snapping state (elastically deformed state), thereby preventing the bearing from coming off from the outer yoke.
( 9 ) A stepping motor in which the outer shape of the flange portion of the bearing has the same shape as the notch of the bottom plate of the outer yoke (Claim 7 ).
In the stepping motor described in this section, the notch of the bottom plate of the outer yoke is blocked by the flange portion of the bearing while the flange portion of the bearing is fitted in the notch of the bottom plate of the outer yoke. Intrusion of foreign matter into the stator is reliably prevented.

( 10 ) A stepping motor in which at least one flange portion of the pair of bearings is welded to a bottom plate of the outer yoke (claim 8 ).
The stepping motor described in this section can reliably prevent the bearing from falling off the outer yoke.

  Since the present invention is configured as described above, in the stepping motor, even when the total length of the motor is restricted, it is possible to increase the ratio of the coil occupied volume and improve the motor torque as much as possible. Become.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the stepping motor 1 according to the embodiment of the present invention is provided with a plurality of pole teeth 2a and 3a on each of the outer yoke 2 and the inner yoke 3, and each pole tooth 2a. An annular space is formed by combining the outer yoke 2 and the inner yoke 3 so as to alternately mesh with 3a. And the stator 6 is comprised in the annular space. In the stator 6, the stators 6A and 6B (that is, the stators 6A and 6B have the same structure) in which the coil 5 wound around the bobbin 4 is housed have a phase difference of 90 degrees in electrical angle. Thus, a two-phase magnetic field is formed by abutting back to back with each other.

The rotor 9 is constituted by the shaft 8 and the rotor magnets 7A and 7B fixed to the shaft 8.
The outer peripheral surfaces of the rotor magnets 7A and 7B are each multi-polarized in the circumferential direction. The rotor 9 is arranged in a cylindrical space surrounded by the plurality of pole teeth 2a and 3a of the stators 6A and 6B. The pole teeth 2a and 3a of the stator 6A and the pole teeth 2a and 3a of the stator 6B are The rotor magnets 7A and 7B are arranged to face each other with a predetermined gap (gap) therebetween on the outer peripheral surfaces. The shaft 8 is rotatably supported by a bearing 10A attached to the outer yoke 2 of the stator 6A and a bearing 10A attached to the outer yoke 2 of the stator 6B.

The outer yoke 2 and the inner yoke 3 of the stator 6A, and the outer yoke 2 and the inner yoke 3 of the stator 6B are all made of the same material, and all are soft magnetic plates (for example, electromagnetic steel plates, silicon steel plates, pure steel plates, etc.). An iron plate or the like is formed into a predetermined shape by drawing or pressing, and the pole tooth portion is bent in the axial direction.
On the other hand, the bobbin 4 is made of a synthetic resin (for example, liquid crystal polymer), and a magnet wire is wound around the core part of the bobbin 4 with a predetermined number of turns to constitute the coil 5. A flange 4c is integrally formed at both ends of the core part of the bobbin 4, and a terminal 4a in which a terminal pin 4b is implanted is formed integrally with the flange at one end. It is entangled with each terminal pin 4b. Further, the terminals 4a are drawn out from the notches 2d formed in the outer peripheral frame of the outer yoke 2, respectively.

FIG. 3 shows an exploded perspective view of the outer yoke 2 of the stator 6B and the bearing 10A attached to the outer yoke 2. Since the stator 6A has the same structure as the stator 6B, detailed description thereof is omitted.
The outer yoke 2 has a cup shape including a cylindrical outer peripheral frame 2f and a bottom plate 2c that closes one end of the outer peripheral frame 2f. An opening 2e is formed in the center of the bottom plate 2c, and the outer peripheral frame extends along the periphery of the opening 2e. A plurality of pole teeth 2a provided in parallel with 2f are provided. In addition, a plurality of notches 2b are formed between the pole teeth 2a of the bottom plate 2c of the outer yoke 2 in consideration of the strength of the outer yoke 2 and extending further outward in the radial direction from the periphery of the opening of the bottom plate 2c. Yes.
Further, a terminal cutout portion 2d is formed in the outer peripheral frame 2f, and the terminal 4b of the bobbin 4 is drawn out through the cutout portion 2d.

The bearing 10 </ b> A includes a hollow cylindrical boss portion 11 and a plurality of flange portions 12 a that protrude from the outer periphery of the boss portion 11 and fit into the notches 2 b of the bottom plate 2 c of the outer yoke 2. Here, the boss portion 11 is formed to have an outer diameter that is fitted and inserted into the inner peripheral surface of the pole tooth 2 a of the outer yoke 2. Then, the boss 11 of the bearing 10A is fitted and inserted into the inner peripheral surface (opening 2e) of the pole teeth of the outer yoke 2. At the same time, the flange portion 12a is fitted into the notch portion 2b formed between the pole teeth 2a of the outer yoke 2, and the bearing 10A is externally welded by spot welding between the flange portion 12a and the bottom plate 2c of the outer yoke 2. Fixed to the yoke 2. The bearings 10A attached to the stators 6A and 6B have the same structure.
Here, the outer shape of the flange portion 12a of the bearing 10A is from the viewpoint of preventing dust from entering the stator 6 from the notch portion 2b formed between the pole teeth 2a of the outer yoke 2. It is preferable to match the shape of the notch 2b formed between the pole teeth 2a.

Further, FIG. 4 is a perspective view of the bearing 10A, and FIG. 5 is a sectional view taken along line AA of the bearing 10A shown in FIG. The bearing 10 </ b> A has a separate structure including a hollow cylindrical boss portion 11 having a small diameter portion and a large diameter portion, and a flange forming portion 12 fitted to the outer periphery of the small diameter portion of the boss portion 11. The boss portion 11 is formed from a copper-based sintered oil-impregnated alloy, and the flange forming portion 12 is formed from an iron-based metal material.
The flange portion 12a is formed by the outer yoke 2 and the inner yoke 3 having a thickness equal to or less than the thickness of the bottom plate 2c of the outer yoke 2 and fitted into the notch 2b of the bottom plate 2c of the outer yoke 2. The axially one side end surface of the boss portion 11 is formed at a position that does not protrude outwardly in the axial direction from the bottom plate 2c while being in contact with the flange 4c of the bobbin 4 of the coil 5 stored in the annular space. Yes.

Specifically, the flange formation part 12 is a structure provided with the some flange part 12a which protrudes radially from the outer periphery of the annular ring part 12b. The flange portion 12a has the same thickness as the bottom plate 2c of the outer yoke 2 or less. And as FIG. 5 shows, the edge 11a for caulking is provided in the outer periphery of the small diameter part of the boss | hub part 11, and the inner periphery 12c of the annular part 12b is a small diameter part of the boss | hub part 11. Then, the boss portion 11 is fixed to the inner periphery of the annular portion 12b by caulking the caulking edge portion 11a using a jig (not shown). Moreover, both are fixed so that the boss portion 11 does not protrude from the flange forming portion 12, that is, the flange portion 12 a is flush with the one axial end surface of the boss portion 11. The central hole 11 b of the boss portion 11 is a hole for inserting the shaft 8.
In the present embodiment, the flange forming portion 12 is formed of an iron-based metal material. However, instead of the iron-based metal material, a resin material (for example, PBT (polybutylene terephthalate), PPS (polyphenylene) is used. In the case where the flange forming portion 12 is formed of a resin material, it can be integrally formed with the boss portion 11 by a resin mold.

Here, the assembly procedure of the stepping motor 1 will be described.
First, the inner circumference of the pole tooth 2a of the outer yoke 2 of the stator 6B is inserted through a jig (not shown) manufactured on the basis of the stator inner diameter, and the bobbin 4 around which the coil 5 is wound is inserted into the outer yoke 2. Accommodate. At this time, the terminal 4b of the bobbin 4 is pulled out from the terminal notch 2d formed in the outer peripheral frame 2f. Then, by inserting the inner circumference of the pole teeth 3a of the inner yoke 3 of the stator 6B through a jig (not shown), the pole teeth 2a of the outer yoke 2 and the pole teeth 3a of the inner yoke 3 can have the same circumference. The outer yoke 2 and the inner yoke 3 are combined so as to alternately mesh with each other. At this time, the pole teeth 2a of the outer yoke 2 and the pole teeth 3a of the inner yoke 3 are positioned so as to have a phase difference of 180 degrees in electrical angle.

  Next, the inner circumference of the pole teeth 3a of the inner yoke 3 of the stator 6A is inserted through a jig (not shown), and the bobbin 4 around which the coil 5 is wound is accommodated in the inner yoke 3. Then, by inserting the inner circumference of the pole teeth 2a of the outer yoke 2 of the stator 6A through a jig (not shown), the pole teeth 3a of the inner yoke 3 and the pole teeth 2a of the outer yoke 2 are on the same circumference. The outer yoke 2 and the inner yoke 3 are combined so as to engage with each other alternately. At this time, the pole teeth 2a of the outer yoke 2 and the pole teeth 3a of the inner yoke 3 are positioned so as to have a phase difference of 180 degrees in electrical angle. Similarly to the stator 6B, the terminal 4b of the bobbin 4 is pulled out from a terminal notch 2d formed in the outer peripheral frame. The stator 6A and the stator 6B are stacked and positioned back to back so that the phase difference is 90 degrees in electrical angle, and the outer peripheral frame 2f of the outer yoke 2 of the stator 6A and the outer peripheral frame of the outer yoke 2 of the stator 6B. The stator 6 consisting of two phases is obtained by welding between the two and fixing them together. As described above, the stator 6A and the stator 6B are formed coaxially.

Next, the bearing 10A is mounted on the outer yoke 2 of the stator 6B. At this time, the large-diameter portion of the boss portion 11 of the bearing 10A shown in FIG. 3 is fitted and inserted into the inner peripheral surface (opening 2e) of the pole tooth 2a of the outer yoke 2, and the flange portion 12a of the bearing 10A. Is fitted into a notch 2b formed between the pole teeth 2a of the outer yoke 2. At this time, the boss 11 of the bearing 10A contacts the flange 4c of the bobbin 4, so that the flange 4c functions as an axial stopper of the bearing 10A and restricts the movement of the bearing 10A.
Further, the bearing 10 </ b> A is fixed to the outer yoke 2 by welding between the flange portion 12 a and the bottom plate 2 c of the outer yoke 2.

Next, the rotor magnets 7A and 7B are fixed to the intermediate portion of the shaft 8, and multipolar magnetization is applied to the outer periphery. The rotor shaft 8 is inserted into the inner peripheral surface (opening 2e) of the pole teeth 2a of the outer yoke 2 of the stator 6A, one end of the shaft 8 is inserted into the bearing 10A, and the rotor 9 is inserted into the stators 6A and 6B. In a cylindrical space surrounded by a plurality of pole teeth 2a and 3a.
Further, after the other bearing 10A is inserted into the other end of the shaft 8, the boss portion 11 of the bearing 10A is fitted and inserted into the inner peripheral surface (opening 2e) of the pole tooth 2a of the outer yoke 2, as shown in FIG. The flange portion 12a of the bearing 10A is fitted into a notch 2b formed between the pole teeth 2a of the outer yoke 2, and the bearing 10A is mounted on the outer yoke 2 of the stator 6A. Also at this time, the boss 11 of the bearing 10A abuts on the flange 4c of the bobbin 4, so that the flange 4c functions as an axial stopper and restricts the movement of the bearing 10A. In the illustrated example, the two rotor magnets 7A and 7B are used.

For the case of the stator 6 B may be secured by welding between the flange portion 12a and the bottom plate 2c of the outer yoke 2 of the bearing 10A. On the other hand, when a front plate (not shown) as a motor mounting plate is fixed on the bottom plate 2c of the outer yoke 2 of the stator 6A, the bearing 10A on the stator 6A side is pressed by the front plate. There is no need to weld between the flange portion 12a of the bearing 10A and the bottom plate 2c of the outer yoke 2.
Through the above steps, the assembly of the stepping motor 1 is completed. Thus, the pole teeth 2a and 3a of the stator 6 are arranged to face the outer peripheral surfaces of the rotor magnets 7A and 7B via the rotor magnets 7A and 7B and a predetermined gap (gap).

According to the embodiment of the present invention configured as described above, the following operational effects can be obtained.
First, the flange portion 12a of the bearing 10A is fitted into the notch 2b of the bottom plate 2c of the outer yoke 2, whereby the rotation of the bearing 10A with respect to the outer yoke 2 is prevented. Further, the flange 4c of the bobbin 4 in which the flange portion 12a of the bearing 10A fitted into the notch 2b of the bottom plate 2c of the outer yoke 2 is stored in an annular space formed by the outer yoke 2 and the inner yoke 3 is provided. , The axial position of the bearing 10A with respect to the outer yoke 2 is also accurately positioned. Moreover, in the bearing 10A, the flange portion 12a is fitted in the notch 2b of the bottom plate 2c of the outer yoke 2, and the boss portion 11 and the flange portion 12a are both axially outward from the bottom plate 2c of the outer yoke 2. Since it is formed in a shape that does not protrude, the axially outer surfaces of the bottom plate 2c of the outer yoke 2 are arranged at both end positions in the axial direction of the allowable total length of the motor even when the total length of the motor is restricted. It becomes possible. As a result, the total length of the annular space formed by the outer yoke 2 and the inner yoke 3 is increased, and the ratio of the occupied volume of the coil 4 stored in the space is increased.

  In addition, the plurality of flange portions 12a of the bearing 10A are fitted into the plurality of notches 2b of the bottom plate 2c of the outer yoke 2, so that the rotation of the bearing 10A relative to the outer yoke 2 is performed at a plurality of positions on the outer periphery of the boss portion 11. This is reliably prevented by the fitting of the flange portion 12a and the notch 2b. A bobbin in which a plurality of flange portions 12a of the bearing 10A fitted in a plurality of notches 2b of the bottom plate 2c of the outer yoke 2 are stored in an annular space formed by the outer yoke 2 and the inner yoke 3 is provided. 4, the axial position of the bearing 10 </ b> A relative to the outer yoke 2 is also reliably positioned by the contact between the flange portion 12 a and the flange 4 c at a plurality of positions on the outer periphery of the boss portion 11. It will be.

  Further, the boss 11 of the bearing 10 </ b> A is fitted and inserted into the inner peripheral surface (opening 2 e) of the pole tooth 2 a of the outer yoke 2, so that the bearing 10 </ b> A is stably held with respect to the outer yoke 2. Further, the flange portion 12a of the bearing 10A is fitted into the notch 2b of the bottom plate 2c of the outer yoke 1, the rotation of the bearing 10A with respect to the outer yoke 2 is prevented, and the axial position is positioned. Neither the boss portion 11 nor the flange portion 12a protrudes from the bottom plate 2c of the outer yoke 2 outward in the axial direction.

  More specifically, the flange portion 12a of the bearing 10A has the same thickness as the bottom plate 2c of the outer yoke 2, and is formed flush with one end surface in the axial direction of the boss portion 11. As shown, the axially outer surface of the bottom plate 2c of the outer yoke 2 and the axially outer surface of the bearing 10A are flush (flat), and both the boss portion 11 and the flange forming portion 12 (flange portion 12a). The outer yoke 2 does not protrude outward in the axial direction from the bottom plate 2c.

Further, since the boss portion 11 and the flange portion 12a of the bearing 10A are formed separately, the boss portion 11 and the flange portion 12a are separately manufactured by a manufacturing method suitable for each of the boss portion 11 and the flange portion 12a, so that each part can be easily manufactured It can be. And 10A of bearings can be comprised by fixing each part mutually. Here, since the boss part 11 is made of a hollow cylindrical sintered oil-impregnated alloy, it is possible to ensure necessary lubricity when the shaft 8 of the rotor 9 rotates. In addition, by using a copper-based sintered oil-impregnated alloy, the sliding noise of the shaft 8 can be suppressed smaller than when using an iron-based sintered oil-impregnated alloy.
On the other hand, when the flange portion 12a is made of an iron-based metal material having an annular portion 12b fitted to the outer periphery of the boss portion 11, the bearing 10A is fixed to the outer yoke 2 formed of an iron-based metal. In addition, the work of fixing both by welding is easy and surely fixed.

  Further, since the outer shape of the flange portion 12a of the bearing 10A has the same shape as the notch 2b of the bottom plate 2c of the outer yoke 2, the flange portion 12a of the bearing 10A is notched 2b of the bottom plate 2c of the outer yoke 2. In this state, the notch 2b of the bottom plate 2c of the outer yoke 2 is blocked by the flange portion 12a of the bearing 10A, so that foreign matter such as dust can be prevented from entering the stator. It should be noted that the outer shape of the flange portion 12a of the bearing 10A does not have to be the same shape as the notch 2b of the bottom plate 2c of the outer yoke 2 if the foreign matter is prevented from entering by other means.

  Furthermore, since at least one flange portion 12a of the pair of bearings 10A is welded to the bottom plate 2c of the outer yoke 2, it is possible to reliably prevent the bearing 10A from falling off the outer yoke 2.

  In the present embodiment, the flange forming portion 12 of the bearing 10A is formed of an iron-based metal material. However, instead of the iron-based metal material, a resin material (for example, PBT (polybutylene terephthalate), It may be formed from PPS (polyphenylene sulfide) or the like. When the flange forming portion 12 is formed of a resin material, it can be integrally formed with the boss portion 11 by a resin mold. When the flange forming portion 12 is formed of a resin material, the mounting to the outer yoke 2 is performed by fitting the flange portion 12a of the bearing 10A into the notch 2b of the bottom plate 2c of the outer yoke 2 and heating and pressing the flange portion 12a. By deforming the flange portion 12a, the notch 2b can be completely closed and the bearing 10A can be firmly attached.

  6 shows a bearing 10C different from the bearing 10A according to the embodiment of the present invention, and FIG. 7 is a partial sectional view showing the stepping motor with the bearing 10C attached thereto. The boss portion 11 of the bearing 10C has the same structure as the bearing 10A, and a small diameter portion is caulked and fixed to the flange forming portion 12. On the other hand, the flange forming portion 12 has substantially the same shape as the flange forming portion 12 in the bearing 10A, is formed of a thin metal plate such as a stainless steel plate having a spring thickness of about 0.1 mm, and the outer yoke 2 The diameter of the notch 2b is set to be about 0.1 mm larger. When the bearing 10C is mounted on the outer yoke 2, the outer periphery of the flange portion 12a is deformed and pushed into the notch 2b of the outer yoke 2. For this reason, when an outward force is applied to the bearing 10C in the axial direction, the deformed flange portion 12a is brought into a slippery state, and the effect of preventing the bearing 10C from coming off is exhibited.

8 and 9 show a bearing 10B according to a reference example of the present invention having a structure different from that of the bearing 10A.
The bearing 10B has a configuration provided with a hollow cylindrical boss portion 10a and a plurality of flange portions 10b protruding radially on one side of the boss portion 10a. The central hole 10c is a hole through which the shaft 8 is inserted. In this bearing 10B, the boss portion 10a and the flange portion 10b are an integral structure, and are formed of an iron-based sintered oil-impregnated alloy. Similarly to the bearing 10A, the boss portion 10a is fitted and inserted into the inner periphery (opening 2e) of the pole tooth 2a of the outer yoke 2, and the flange portion 10b is formed between the pole teeth 2a of the outer yoke 2. The bearing 10B is fixed to the outer yoke 2 by being fitted to 2b and welding between the flange portion 10b and the bottom plate 2c of the outer yoke 2.

  Thus, since the bearing 10B has the boss portion 10a and the flange portion 10b formed of an iron-based sintered oil-impregnated alloy in an integral structure, the number of parts can be reduced. Further, when the bearing 10B is fixed to the outer yoke 2 formed of an iron-based metal, the work of fixing both by welding is easily and reliably fixed.

When a motor mounting plate (not shown) for attaching the stepping motor to the housing is attached to the stepping motor, a jig (not shown) is attached to the shaft 8, and the upper surface ( After mounting the motor mounting plate on the upper surface of the bottom plate 2c of the outer yoke 2, it is fixed to the outer yoke 2 by welding. Therefore, since the motor mounting plate is mounted after the stepping motor is completed, the manufacturing process can be standardized and the motor structure can be standardized even if the motor mounting plate has a different shape.
Although the stepping motor of the present invention has been described above, it is understood that the present invention is not limited to the above-described embodiment and can be modified within the scope of the gist of the present invention.

1 is a cross-sectional view of a stepping motor according to a first embodiment of the present invention. FIG. 2 is a plan view of the stepping motor shown in FIG. 1. FIG. 2 is an exploded perspective view showing an outer yoke and a bearing of the stepping motor shown in FIG. 1. FIG. 2 is a perspective view of a bearing of the stepping motor shown in FIG. 1. It is AA sectional drawing of FIG. It is sectional drawing of the bearing of another structure of the stepping motor shown by FIG. FIG. 7 is a partial cross-sectional view of a stepping motor using the bearing shown in FIG. 6. It is a perspective view of the bearing of another structure of the stepping motor shown in FIG. It is BB sectional drawing of FIG. It is a partial section perspective view of the conventional stepping motor. It is sectional drawing of the stepping motor shown by FIG. It is a disassembled perspective view of the other conventional stepping motor.

Explanation of symbols

  1: stepping motor, 2: outer yoke, 2a: pole tooth, 2b: notch, 2c: bottom plate, 2e: opening, 2f: outer frame, 3: inner yoke, 3a: pole tooth, 4: bobbin, 4c: Flange, 5: Coil, 6, 6A, 6B: Stator, 7A, 7B: Rotor magnet, 8: Shaft, 9: Rotor, 10A, 10B, 10C: Bearing, 10a: Boss part, 10b: Flange part, 11: Boss Part, 12a: flange part, 12b: ring part

Claims (8)

A cylindrical outer peripheral frame and a bottom plate that closes one end of the outer peripheral frame are provided, an opening is formed in the center of the bottom plate, and a plurality of pole teeth are provided along the periphery of the opening and in parallel with the outer peripheral frame. An annular space is formed by the outer yoke and the inner yoke having a plurality of pole teeth arranged alternately on the same circumference as the plurality of pole teeth of the outer yoke, and the bobbin is formed in the annular space. A stator in which a wound coil is stored;
A rotor composed of a shaft and a magnet fixed to the shaft, and rotatably disposed in a cylindrical space surrounded by a plurality of pole teeth of the stator;
A pair of bearings that pivotally attach the shaft of the rotor to the outer yoke of the stator across the magnet;
A plurality of notches are formed between the pole teeth of the bottom plate of the outer yoke, extending further outward in the radial direction from the periphery of the opening of the bottom plate,
The bearing includes a boss portion made of a hollow cylindrical sintered oil-impregnated alloy , and a plurality of flange portions that protrude from the outer periphery of the boss portion and fit into notches in the bottom plate of the outer yoke, and the boss portion and the A stepping motor characterized in that the flange portion is formed as a separate part, and the plurality of flange portions are fitted into notches in the bottom plate of the outer yoke. The boss portion of the bearing is formed with an outer diameter that is fitted and inserted into the inner peripheral surface of the pole teeth of the outer yoke,
The flange portion of the bearing has a thickness equal to or less than that of the bottom plate of the outer yoke, and faces the one end surface in the axial direction of the boss portion so as not to protrude axially outward from the bottom plate of the outer yoke. The stepping motor according to claim 1, wherein the stepping motor is formed as a single unit. The boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, and the flange portion is made of a metal material having an annular portion fitted to the outer periphery of the boss portion. The stepping motor according to 1 or 2. The boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, the flange portion is made of a resin material having an annular portion fitted to the outer periphery of the boss portion, and the flange portion is a resin mold. The stepping motor according to claim 1, wherein the stepping motor is integrally formed on the outer periphery of the boss portion. The boss portion of the bearing is made of a hollow cylindrical copper-based sintered oil-impregnated alloy, and the flange portion is made of a spring-like thin metal plate having an annular portion fitted to the outer periphery of the boss portion. The stepping motor according to claim 1 or 2. 6. The stepping motor according to claim 5 , wherein a diameter of a circle connecting the leading ends of the flange portions is formed so as to be slightly larger than a diameter of a circle connecting the base ends of the notches of the bottom plate of the outer yoke. The stepping motor according to any one of claims 1 to 6, wherein an outer shape of a flange portion of the bearing has the same shape as a notch of a bottom plate of the outer yoke. Wherein at least one flange portion of the pair of bearings, any one stepping motor according to claim 1 to 7, characterized in that it is welded to the bottom plate of the outer yoke.

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