KR19990036376A - Stepping motor and method for assembling the same - Google Patents

Abstract

This invention is a simple structure, It aims at preventing the position shift of an inner yoke and an outer yoke, and improving all the characteristics of a stepping motor. For this purpose, the stepping motor 1 is a stator 2, a bottom plate 7 and a mounting plate fixed to both ends of the stator 2, a holder 9a and 9b and a holder fixed to the mounting plate 8, respectively. 10 and a lead screw 14 provided on the rotating shaft 61 of the rotor 6. The stator 2 prepares one set of the inner yoke 3, the outer yoke 4, and two sets of coils 5 provided therebetween, and the bases 31 of the inner yoke 3 are bonded to each other. It is stuck as much as possible. The inner yoke 3 and the outer yoke 4 have the base 31 of the inner yoke 3 abutting the end 421 of the outer circumferential portion 42 of the outer yoke 4, and the outer circumferential edge of the base 31. The part 32 is joined so that it may expose to the outer peripheral surface part of the outer yoke 4.

Description

How to Assemble Stepping Motors and Stepping Motors

A small stepping motor in which a lead screw is provided on the rotating shaft is used to drive a lens for focusing or zooming a camera or a video camera. This type of stepping motor has a low power consumption, a predetermined torque required to drive the lens at the lowest input value (current) as possible, and can be rotated to a high frequency region for the high speed driving of the lens. Characteristics, such as a good angular precision, are required.

12 and 13 show the structure of a conventional stepping motor. The conventional stepping motor 100 shown in these figures is provided with the stator 120 and the rotor 160 rotatably inserted in the inside of the stator 120. The stator 120 prepares one set of the inner yoke 130, the outer yoke 140, and two sets of coils 50 provided therebetween, and the bases 131 of the inner yoke 130 Is fixed so that is bonded.

A plurality of magnetic poles 134 and 144 are formed in the inner yoke 130 and the outer yoke 140, respectively, and the cylindrical poles in which the magnetic poles 134 and 144 of the yokes 130 and 140 are fixed to the rotation shaft 161 of the rotor 160. Alternatingly along the outer circumferential surface of the permanent magnet 162, it is arrange | positioned noncontact with each other. In addition, each magnetic pole of the inner yoke 130 and the outer yoke 140 faces the outer circumferential surface of the permanent magnet 162 of the rotor 160 with a predetermined gap 170 therebetween.

In the stator 120 of the conventional stepping motor 100, the inner yoke 130 and the outer yoke 140 can be aligned by their own shape.

That is, as shown in FIG. 13, the step part 145 is formed in the inside of the edge part (the side of the contact surface 139 of the inner yoke 130 comrades) of the outer yoke 140, and the The outer circumferential edge portion 132 of the base 131 is engaged with the stepped portion 145, and the inner yoke 130 is coupled to the outer yoke 140, thereby positioning the yokes 130 and 140. Therefore, as shown in FIG. 12, the outer peripheral edge part 131 of the inner yoke 130 is not exposed in the vicinity of the mating surface 139 of the outer peripheral surface of the stepping motor 100. As shown in FIG. However, as such a structure, since the outer circumferential edge portion 132 of the inner yoke 130 is engaged with the stepped portion 145 of the outer yoke 140, there is a size error between the inner yoke 130 and the outer yoke 140. If there is (an error of the inner diameter of the engaging portion, the size error of the outer diameter, etc.), the errors are all caused by the displacement of the inner yoke 130 and the outer yoke 140 in the inner space of the stator 120. That is, the sizes (gap lengths) of the magnetic poles 134 and 144 of the inner yoke 130 and the outer yoke 140 and the gap 170 of the outer circumferential surface of the permanent magnet 162 become uneven.

In addition, when the outer diameter of the base 131 of the inner yoke 130 is shorter than the designed value, or, if the inner diameter of the car part 145 exceeds the designed value, the inner circumferential surface of the outer peripheral edge 132 and the stepped part 145 A gap is formed between the inner yoke 130 and the outer yoke 140 so that the coupling and fixing of the inner yoke 130 cannot be accurately performed. Moreover, magnetic leakage occurs from this gap, which adversely affects the magnetic performance.

Therefore, in the stepping motor 100 according to the related art, the driving speed torque characteristic of the stepping motor is deteriorated due to the size error of the inner yoke 130 and the outer yoke 140 or the positional shift based thereon, Since the increase of coins and the angular precision also fall, there existed a problem that the above-mentioned requirements cannot be fully satisfied.

If the size of the outer diameter of the base 131, the size of the inner diameter of the stepped portion 145, and the positional accuracy of each of the magnetic poles 134 and 144 are all according to the design value, the above problem does not occur. In addition, it is difficult to perform such precision processing, which leads to complexity of the manufacturing process and a significant increase in the manufacturing cost, resulting in a lack of practicality.

An object of the present invention is a simple structure, it is possible to prevent the positional displacement of the inner yoke and the outer yoke at the time of assembly, thereby to facilitate the stepping motor and such a stepping motor that can improve various characteristics of the stepping motor It is providing the assembly method of the stepping motor which can be assembled.

The present invention relates to a stepping motor, in particular, a stepping motor used for driving a lens for focusing or zooming in an optical device such as a camera or a video camera.

1 is a plan view showing an embodiment of the stepping motor of the present invention.

FIG. 2 is a cross-sectional view taken along line Il-II in FIG. 1. FIG.

3 is an exploded perspective view showing the configuration of the inner yoke and the outer yoke.

4 is a plan view showing the configuration of the outer yoke;

5 is a cross-sectional view taken along the line V-V in FIG. 4 (sectional view).

6 is a plan view showing the configuration of the inner yoke;

FIG. 7 is a cross-sectional view (sectional view) taken along the line VII-VII of FIG. 6. FIG.

8 is a partial cross-sectional side view showing a method for assembling the stepping motor of the present invention.

9 is a partial cross-sectional side view showing a method for assembling the stepping motor of the present invention. 10 is a diagram illustrating a relationship between a drive speed and a torque of a stepping motor.

11 is a diagram showing a relationship between a drive speed of a stepping motor and a magnetic dynamic current. 12 is a plan view showing the structure of a conventional stepping motor.

13 is a cross-sectional view taken along the line XIII-XIII in FIG. 12.

* Explanation of symbols for the main parts of the drawings

1: stepping motor 2: stator

3,3 ': My York 31,31': Donation

32: outer edge 33: opening

34: Stimulation 35, 36: Notch

37,37 ': projection 38,38': hole

39: butt 4: outer yoke

41: bottom part 42: outer periphery

421: end 43: opening

44: stimulation 45,46: notch

5: coil 51: bobbin

52: winding 53: terminal portion

531,532: terminal 54: projection for positioning

6: rotor 60: axis

61: rotating shaft 62: permanent magnet

63: home 7: bottom plate

71: lead thrust spring 72: leaf spring

8: mounting plate 9a, 9b: bearing

91,92: circular opening 10: holder

11, 12: support portion 13: mounting hole

14: lead screw 15: gap

20: Jig 21: Circumference for Positioning

22: jig 23: cylindrical portion for positioning

24, 25: side hole 26: bottom opening

100: stepping motor 120: stator

130: My York 131: donation

132: outer edge 134: magnetic pole

139: butt 140: outer yoke

144: stimulus 145: step

150: coil 160: rotor

161: rotating shaft 162: permanent magnet

170: gap

(1) The present invention has a stator having at least one inner yoke, an outer yoke and a coil provided therebetween, and a rotor rotatably inserted in the inner side of the stator, the plurality of magnetic poles formed on the inner yoke. And a stepping motor in which a plurality of magnetic poles formed in the outer yoke are alternately arranged along the outer circumferential surface of the rotor, wherein the inner yoke has a disk-shaped base whose outer diameter is substantially the same as the outer diameter of the outer yoke, and the outer circumference of the base The edge portion is exposed near the outer circumferential surface of the outer yoke.

(2) The stator is preferably configured by fixing two sets of inner yokes, outer yokes and coils provided therebetween such that the bases of the respective inner yokes are joined.

(3) It is preferable that each magnetic pole of the said inner yoke and an outer yoke is non-contact with the outer peripheral surface of the said rotor, and is provided in the equidistant position from the rotation center of the said rotor.

(4) It is preferable that the rotor has a permanent magnet, and the outer diameter near the base of the permanent magnet is decreasing.

(5) It is preferable that the lead screw is provided in the rotating shaft of the said rotor.

(6) Furthermore, as a method of assembling a stepping motor for assembling the stepping motor described above,

A first step of inserting a coil between the inner yoke and the outer yoke, aligning the positions of the inner yoke and the outer yoke, and assembling them to assemble the stator;

And a second step of inserting the rotor inside the stator,

The alignment of the inner yoke and the outer yoke in the first step is performed based on the inner diameter of the stator.

(7) Preferably, the positioning is performed by inserting a jig into the internal space of the stator.

(8) Furthermore, as a method of assembling a stepping motor for assembling the stepping motor described above,

A first step of inserting a coil between the inner yoke and the outer yoke, aligning the positions of the inner yoke and the outer yoke, and assembling them to assemble the stator;

And a second step of inserting the rotor inside the stator,

Positioning of the inner yoke and the outer yoke in the first step is performed based on the outer diameter of the stator.

(9) Preferably, the positioning is performed by inserting the stator into the inner space of the jig.

(10) The coupling of the inner yoke and the outer yoke is preferably performed through a hole formed in the jig.

(11) Moreover, it has the stator which has an inner yoke, an outer yoke, and a coil provided between it, and a rotor, and the said inner yoke and an outer yoke assemble a stepping motor which cannot be aligned by its shape. As a method of assembling a stepping motor

Inserting the coil between the inner yoke and the outer yoke, aligning the positions of the inner yoke and the outer yoke using a jig, and combining them to assemble the stator;

And a second step of inserting the rotor inside the stator,

Positioning of the inner yoke and the outer yoke in the first step is characterized in that it is performed based on the inner or outer diameter of the stator.

EMBODIMENT OF THE INVENTION Hereinafter, the stepping motor of this invention and the assembly method of a stepping motor are demonstrated in detail based on the optimal embodiment shown in an accompanying drawing.

1 is a plan view showing an embodiment of the stepping motor of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is an exploded perspective view showing the configuration of the inner yoke and the outer yoke, and FIG. 4 is a configuration of the outer yoke. FIG. 5 is a sectional view taken along the line VV in FIG. 4 (cross section), FIG. 6 is a plan view showing the structure of the inner yoke, and FIG. 7 is a sectional view taken along the line VII-VII in FIG. In addition, in the following description, the right side in FIG. 1 and FIG. 2 is called "base", and the left side is called "tip".

As shown in Fig. 1 and Fig. 2, the stepping motor 1 of the present embodiment is a stepping motor of the PM type, and mainly includes a stator 2 and a rotor rotatably inserted inside the stator 2. 6), a bottom plate (cover) 7 fixed to the base end of the stator 2, a mounting plate 8 fixed to the tip of the stator 2, bearings 9a and 9b, and a mounting plate ( It consists of the holder 10 fixed to 8) and the lead screw 14 provided in the rotating shaft 61 of the rotor 6. As shown in FIG.

The stator 2 prepares two sets of units composed of one set of the inner yoke 3, the outer yoke 4, and the coil 5 provided therebetween, and this is the base 31 of both inner yoke 3. It is configured to be bonded to each other to be bonded. Since both units have almost the same structure, one unit (base end side) of the unit will be described below.

As shown in FIGS. 2-5, the outer yoke 4 is a normal member which has a bottom part comprised from a soft magnetic material, and the bottom part 41 and the cylindrical outer peripheral part 42 built in from the bottom part 41 are shown. ), And a plurality of magnetic poles 44 placed in the same direction as the outer circumferential portion 42 from the edge of the opening 43 formed in the central portion of the bottom surface portion 41.

The outer circumferential portion 42 is provided with notches 45 and 46 at positions facing each other with the opening 43 therebetween. The notch 45 is inserted with a terminal portion 53 formed in the bobbin 51, which will be described later, to protrude outward, and the notch 46 is coupled with a positioning protrusion 54 formed in the bobbin 51, whereby Positioning with respect to the outer yoke 4 of the bobbin 51 is made.

In the present embodiment, the number of magnetic poles 44 is five, and each magnetic pole 44 is equidistant from the center of rotation (axis 60) of the rotor 6, i.e., at equiangular intervals on concentric circles. It is arranged. In addition, the width of each magnetic pole 44 is gradually decreasing toward the direction away from the bottom face 41.

Between the adjacent magnetic poles 44, the magnetic pole 34 of the inner yoke 3 mentioned later is inserted non-contact. In this case, the magnetic pole 34 and the magnetic pole 44 face in opposite directions to each other.

As shown in FIG. 2, FIG. 3, FIG. 6, and FIG. 7, the inner yoke 3 is a member comprised of a soft magnetic material, and is located in the central part of the disk-shaped base (ring plate shape) and the base part 31. As shown in FIG. It is composed of a plurality of magnetic poles 34 which are entered from the edge of the formed opening 33.

The outer diameter of the base 31 is substantially the same as the outer diameter of the outer yoke 4 (more specifically, the outer diameter near the end 421 of the outer circumferential portion 42).

In addition, notches 35 and 36 are formed in the outer circumferential portion of the base 31 so as to face each other with the opening 33 interposed therebetween. The notch 35 is inserted into the terminal portion 53 formed in the bobbin 51 and protrudes outward, and the notch 36 is coupled to the positioning projection 54 formed in the bobbin 51, thereby the bobbin ( The positioning with respect to the inner yoke 3 of 51) is made.

The base 31 is provided with a protrusion 37 and a hole 38 at positions facing each other with the opening 33 interposed therebetween. The protrusions 37 and the holes 38 respectively engage with the holes 38 'and the protrusions 37' of the other inner yoke 3 'indicated by the dotted lines in Fig. 7, respectively, and the inner yokes 3 and 3'. ) Positioning of each other, that is, positioning of units.

In this embodiment, the number of magnetic poles 34 is five equal to the magnetic poles 44, and each magnetic pole 34 is equidistant from the axis 60, i.e., concentrically, like the magnetic poles 44. Are arranged at equiangular intervals. In addition, the width of each magnetic pole 34 is gradually decreasing from the base 31 toward the lower side in FIG.

The inner yoke 3 and the outer yoke 4 are different from the inner yoke 130 and the outer yoke 140 in the conventional stepping motor 100, and themselves have means for positioning (stepped portions). (145) is not installed. Therefore, when assembling the stator 2, the inner yoke 3 and the outer yoke 4 are aligned by using the jig 20 or 22, for example, as described later.

In the state in which the outer yoke 4 and the inner yoke 3 are assembled, the five magnetic poles 44 and the five magnetic poles 34 are alternately arranged on the concentric circles and non-contacted with each other, and a total of ten poles are provided. Is formed. In this state, the base 31 of the inner yoke 3 is in contact with the end portion 421 of the outer circumferential portion 42, and the outer circumferential edge portion 32 of the base 31 is near the outer circumferential surface of the outer yoke 4. Exposed.

As described above, in the present invention, since the outer circumferential edge portion 32 of the base 31 does not contact the outer circumferential portion 42, for example, the outer diameter and the size of the outer diameter of the base 31 and the vicinity of the end portion 421 of the outer circumferential portion 42. Even if there is an error, the magnitude error is only absorbed by the deviation of the outer circumferential edge portion 32 and the outer circumferential surface near the end portion 421 of the outer circumferential portion 42, and the magnetic pole 34 and the magnetic pole inside the stator 2 are absorbed. It does not affect the positional relationship of (44). Therefore, the size precision of the gap 15 is extremely high.

Moreover, in the state which combined the outer yoke 4 and the inner yoke 3, the coil 5 is inserted in the annular space formed between the outer peripheral part 42 and each magnetic pole 34,44. The coil 5 is comprised by providing the winding 52 to the bobbin 51 which consists of insulating materials, such as a synthetic resin. The terminal portion 53 formed on the bobbin 51 is constructed by embedding a pair of terminals 531 and 532 in a non-contact manner in a constituent material (synthetic resin) of the bobbin 51. Both ends of the winding 52 are electrically connected to terminals 531 and 532 of the terminal portion 53, respectively.

When a pulse signal is applied to the windings 52 through these terminals 531 and 532 by a driving circuit (not shown) of the stepping motor 1, the coil 5 is excited to rotate and drive the rotor 6 in rotation. Torque is generated. Then, the rotor 6 rotates by a predetermined number of steps, that is, by a predetermined angle, in accordance with the number of pulses of the input pulse signal.

The unit as described above is fixed by, for example, welding so that the bases 31 and 31 'of the inner yokes 3 and 3' are joined to each other. The abutment surfaces 39 between the bases 31 and 31 'are preferably joined as tightly as possible, that is, in close contact.

In this case, both units are fixed in a positional relationship in which the respective magnetic poles 34 and 44 in one unit and the magnetic poles in the other unit are shifted by half poles in the circumferential direction. Therefore, the protrusion 37 and the hole 38, and the hole 38 'and the protrusion 37' are formed at the position where both units become such a positional relationship. With this structure, the number of steps of the stepping motor 1 is 20 steps in total. Moreover, you may perform micro step driving by the said drive circuit of the stepping motor 1 further.

In addition, of course, in this invention, the number of magnetic poles and the number of steps are not limited to what was illustrated in the present Example.

The rotor 6 is comprised from the rotating shaft 61 and the cylindrical permanent magnet 62 provided in the outer periphery of the rotating shaft 61. As shown in FIG. In this case, the rotary shaft 61 and the permanent magnet 62 press the rotary shaft 61 into the internal space (axial hole) of the permanent magnet 62, or the rotary shaft 61 into the internal space of the permanent magnet 62. It is fixed by inserting (inserting) and adhering these with an adhesive agent.

The permanent magnet 62 is a multipolar magnet (10 poles) in the radial direction. In addition, a groove 63 is formed along the outer periphery of the center portion of the permanent magnet 62 in the longitudinal direction, that is, near the base 31 of the inner yoke 3, and the outer diameter of the permanent magnet 62 is different. It is decreasing in comparison with. By such a configuration, the magnetic dynamic current can be improved, and the effect of improving the papermaking ability of the stepping motor described later becomes more remarkable.

As the permanent magnet 62, one having excellent magnetic properties is used. For example, a rare earth magnet having a rare earth element and a transition metal as a base component, or a rare earth magnet having a rare earth element, a transition metal and a boron as a base component is preferred. Used. In addition, the form (type) of the permanent magnet 62 may be anything, such as a bonded magnet and a sintered magnet, for example.

In the state where the rotor 6 is inserted into the inner space (inner hole) of the stator 2, the magnetic poles 34 and 44 are not in contact with the outer circumferential surface of the portion other than the groove 63 of the permanent magnet 62. Face to face. In this case, a gap 15 is preferably formed between the outer circumferential surface of the permanent magnet 62 and the magnetic poles 34 and 44, preferably about 0.05 to 0.25 mm, more preferably about 0.10 to 0.20 mm.

The bottom plate 7 is fixed to the base end of the stator 2 via a lead thrust spring 71 so as to shield the internal space of the stator 2. The lead thrust spring 71 has a leaf spring 72 at the center of the member on the thin plate ring, and presses the rotating shaft 61 in the tip direction by the leaf spring 72 (preload).

In addition, the mounting plate 8 is fixed to the tip of the stator 2, and the holder 10 is fixed to the support 11 of the tip. The fixing of the stator 2 and the mounting plate 8 is preferably performed by welding such as plasma welding.

In addition, the fixing of the holder support 11 and the mounting plate 8 is preferably performed by welding such as plasma welding or by screwing.

The holder 10 is a plate-shaped member, and has the support parts 11 and 12 formed in the base end side and the front end side, respectively, and are bent in the perpendicular direction. The circular opening 91 is formed in the support part 11 and the mounting plate 8, The bearing 9a is press-fitted in this circular opening 91. FIG. Moreover, the circular opening 92 is formed in the support part 12, and the bearing 9b is press-fitted in this circular opening 92. As shown in FIG.

Moreover, the holder 10 is provided with the installation hole 13 for attaching the holder 10 to a predetermined site | part.

The rotating shaft 61 is extended to the support part 12 vicinity in the front-end direction, and is rotatably supported by the bearings 9a and 9b. In addition, in this embodiment, although the bearings 9a and 9b use the sliding bearing which consists of a sintered compact, it may be a sliding bearing or rolling bearing by a resin molding.

The lead screw 14 is provided in the position between the bearings 9a and 9b of the rotating shaft 61. When the lead screw 14 rotates by the rotation of the rotor 6, the moving body (not shown) which has the engagement part which engages with the screw of the lead screw 14 turns a lead screw (in the longitudinal direction of the rotating shaft 61). The distance moves according to the rotation amount of 14). The movement of the movable body can be used for lens driving for focusing and zooming of optical systems in various optical devices such as cameras, video cameras, and copiers, for example.

The yoke 3 and the outer yoke 4 may be made of a metal material such as a galvanized steel sheet or a Fe-Cr alloy, in addition to a soft magnetic material such as pure iron.

Next, an example of the assembling method of the stepping motor 1 is demonstrated.

Fig. 8 is a partial cross-sectional side view showing the first assembling method of the stepping motor of the present invention.

The first assembling method is characterized in that the alignment of the inner yoke 3 and the outer yoke 4 is performed based on the inner diameter of the stator 2 (inner diameter of the inner space of the stator 2). In detail below, first, the winding 52 is attached to the bobbin 51 to assemble the coil 5, and the coil 5 is placed between the inner yoke 3 and the outer yoke 4, that is, the outer circumferential portion 42. ) And an annular space formed between the magnetic poles 34 and 44. At this time, the terminal portion 53 and the positioning projection 54 of the bobbin 51 are inserted into corresponding notches 35, 36, 45, 46, respectively. This operation is performed on two sets of units composed of one set of inner yoke 3, outer yoke 4, and coil 5.

Next, the protrusions 31 and 31 'of the inner yokes 3 and 3' of both units are joined so that the protrusions 37 and the holes 38 'and the holes 38 and the protrusions 37' are respectively engaged. Joining is carried out while positioning, and the positioning circumferential part 21 of the jig 20 is inserted in the internal space of the stator 2. At this time, since the outer circumferential edge portions 32 of the bases 31 and 31 'of the inner yoke 3 and 3' are exposed near the outer circumferential surface of the outer yoke 4, the outer portion of the inner yoke 3 and 3 'is exposed. Movement to the yoke 4 is possible. Accordingly, the inner yoke 3 and the outer yoke 4 of both units are aligned so that each magnetic pole 34, 44 is equidistant from the axis 60, that is, concentrically.

In addition, the mounting plate 8 is inserted in advance in the positioning circumferential portion 21 of the jig 20, and the alignment of the stator 2 and the mounting plate 8 is simultaneously performed.

Next, a pressing force in the direction of the axis line 60 is applied to the stator 2 to make the gap of the butt face 39 as small as possible. In this state, the vicinity of the outer circumference of the butt face 39, the base 31 and the outer circumference portion ( The boundary portion (outer boundary portion) of 42 and the boundary portion (outer portion boundary portion) of the outer yoke 4 and the mounting plate 8 are respectively welded by plasma welding, for example, and fixed (bonded). Further, the bottom plate 7 is placed on the side opposite to the mounting plate 8 of the stator 2, and the stator 2 and the bottom plate 7 are fixed in the same manner. As described above, the first step of assembling the stator 2 is completed.

Next, the stator 2 is removed from the jig 20, and the rotor 6, which is assembled in advance, is inserted into the internal space of the stator 2 (second step). In addition, the bearings 9a and 9b are fixed to the support portions 11 and 12 of the holder 10.

In a state where the bearing 9a is coupled to the mounting plate 8, the mounting plate 8 and the support 11 of the holder 10 are fixed by, for example, welding or screwing. Thereby, the stepping motor 1 of this invention is completed.

9 is a partial cross-sectional side view showing a second assembling method of the stepping motor of the present invention. Hereinafter, although this 2nd assembling method is demonstrated, the description about the same matter as the said 1st assembling method is abbreviate | omitted.

As for the second assembling method, the positioning of the inner yoke 3 and the outer yoke 4 is performed based on the outer diameter of the stator 2.

First, as described above, two sets of units in which the coil 5 is inserted between the inner yoke 3 and the outer yoke 4 are prepared.

Next, the bases 31 and 31 'of the inner yokes 3 and 3' of both units are positioned so as to engage the protrusions 37 and the holes 38 'and the holes 38 and the protrusions 37', respectively. The stator 2 is inserted into the inner space of the cylindrical portion 23 for positioning of the jig 22 while joining while determining. Thereby, the inner yoke 3 and the outer yoke 4 of both units are aligned so that each magnetic pole 34, 44 is disposed equidistant from the axis 60, that is, on a concentric circle.

In addition, the mounting plate 8 is inserted into the cylindrical portion 23 for positioning of the jig 20 in advance, and the stator 2 and the mounting plate 8 are aligned at the same time.

Next, a pressing force in the direction of the axis line 60 is applied to the stator 2 to make the gap of the butt face 39 as small as possible. In this state, the vicinity of the outer circumference of the butt face 39, the base 31 and the outer circumference portion ( Side hole (hole part) formed in the cylindrical part 23 for positioning of the jig 22 by the boundary part (outer periphery boundary part) of 42, and the boundary part (outer periphery boundary part) of the outer yoke 4 and the mounting plate 8, respectively. (24) and (25), for example, by welding by plasma, and fixing (bonding) them. Further, the bottom plate 7 is placed on the side opposite to the mounting plate 8 of the stator 2, and the stator 2 and the bottom plate 7 are fixed in the same manner. As described above, the first step of assembling the stator 2 is completed.

Next, the stator 2 is removed from the jig 22, and the rotor 6 is inserted into the inner space of the stator 2 as described above (second step), and the mounting plate 8 and the holder are The support 11 of 10 is fixed by, for example, welding or screwing. Thereby, the stepping motor 1 of this invention is completed.

In addition, the insertion of the rotor 6 into the internal space of the stator 2 may be performed through the bottom opening 26 of the jig 22 as it is with the stator 2 mounted on the jig 22. .

In order to confirm the effects of the stepping motor 1 of the present invention as described above, the relationship between the drive speed and torque of the stepping motor and the drive speed and the self starting current of the stepping motor was investigated. In addition, as a comparative example, the same characteristic was investigated also about the conventional stepping motor 100 shown to FIG. 12 and FIG. These results are shown in the graph of FIG. 10 and FIG.

In addition, all conditions and measurement conditions with respect to each stepping motor 1,100 are as follows. Outer diameter of stator: 10 mm

Inner diameter of the stator (invention): 4.3 mm (design value)

Stator inner diameter (comparative example): 5.3 mm (design value)

Height of the stator: 10 mm

Gap spacing: 0.15 mm (design value)

Gap spacing error (invention): within ± 0.05 mnm

Gap gap error (comparative example): within ± 0.11 mm

Permanent Magnet: Bond Magnet by Sm-Co Magnetic Powder

Number of poles: 10 poles x 2 (total 20 steps)

Coil Specification: 45Ω

Specified voltage: 5.2 V

Driving method: bipolar 2W1-2 phaseClick here

As mentioned above, compared with the comparative example, the stepping motor of this invention has a small error of the space | interval of a gap, and its magnitude | size precision is high.

As shown in Fig. 10, the stepping motor of the present invention has a higher pull-in torque and pull-out torque in the high speed region than in the comparative example. In particular, while the maximum magnetic dynamic frequency of the stepping motor of the comparative example is about 6140 Hz at the CK input, the maximum magnetic dynamic frequency of the stepping motor of the present invention is about 7680 Hz at the CK input, and the maximum magnetic dynamic frequency is improving. . In addition, while the maximum continuous response frequency of the stepping motor of the comparative example is about 16130 Hz with the CK input, the maximum continuous response frequency of the stepping motor of the present invention achieves 17280 Hz or more with the CK input, and the maximum continuous response frequency is improved. Doing.

11, the stepping motor of the present invention has a lower magnetic dynamic current (voltage) in the high speed region than in the comparative example. In particular, while the magnetizing current of the stepping motor of the present invention at 4000 Hz at the CK input is about 21 mA, the magnetizing current of the stepping motor of the comparative example at the frequency is 28 mA or more. The magnetic dynamic current is reduced by 25% or more.

As mentioned above, although the stepping motor and the assembly method of the stepping motor of this invention were demonstrated according to the Example which showed, this invention is not limited to this, In particular, each component which comprises a stepping motor can produce the same function. Any may be appropriately substituted.

In the above embodiment, two sets of units are used as the stator 2 in order to improve the stability (balance) of the structure and the magnetic circuit, but one set or three or more sets of units may be used.

In addition, the use of the stepping motor is not limited to the lens driving for focusing and zooming of the optical system in the above-mentioned various optical devices, and any may be used.

In addition, although the PM type stepping motor was demonstrated in the Example shown, this invention is not limited to this, A VR type or a hybrid type stepping motor is possible.

As described above, according to the stepping motor of the present invention, the inner circumferential edge portion of the inner yoke is exposed to the vicinity of the outer circumferential surface of the outer yoke, whereby the inner yoke and the outer yoke can be aligned, for example, based on the inner diameter. . This improves the size accuracy of the gap between each magnetic pole of the stator and the rotor, and also prevents magnetic leakage, thus improving all the characteristics of the stepping motor.

In particular, since a predetermined torque is obtained at a lower input value (current), power consumption can be saved, and a battery can be extended, and the rotation can be made to a higher frequency region, thereby speeding up driving. In addition, angular accuracy is also improved.

Further, according to the stepping motor of the present invention, it is not necessary to provide a means for aligning itself in the inner yoke and the outer yoke, such as the stepped portion, and also does not require a special machining process such as precision machining. Therefore, manufacture (processing) of these parts is easy and can be manufactured in low cost.

Further, according to the assembling method of the stepping motor of the present invention, the stepping motor having the above excellent characteristics can be manufactured easily and reliably without causing complicated manufacturing processes, and can cope with mass production.

Since the stepping motor of the present invention can be used for driving a lens such as focusing or zooming, it is suitable for mounting on an optical device such as a camera or a video camera.

Claims (15)

A stator having at least one set of inner yoke, outer yoke and a coil provided therebetween, and a rotor rotatably inserted inside the stator, the plurality of magnetic poles formed in the inner yoke and the outer yoke In a stepping motor in which a plurality of formed magnetic poles are alternately arranged along the outer circumferential surface of the rotor, The inner yoke has a disk-like base having an outer diameter substantially the same as the outer diameter of the outer yoke, and the outer peripheral edge portion of the inner yoke is exposed near the outer circumferential surface of the outer yoke. The stepping motor according to claim 1, wherein the stator is configured by fixing two sets of inner yokes, outer yokes, and coils provided therebetween so that the bases of the respective inner yokes are joined. The stepping motor according to claim 1 or 2, wherein each of the magnetic poles of the inner yoke and the outer yoke is in contact with the outer circumferential surface of the rotor and is provided at an equidistant position from the center of rotation of the rotor. . The stepping motor according to claim 1 or 2, wherein the rotor has a permanent magnet, and the outer diameter of the base portion of the permanent magnet is decreasing. 4. The stepping motor according to claim 3, wherein the rotor has a permanent magnet, and the outer diameter near the base of the permanent magnet is decreasing. The stepping motor according to claim 1 or 2, wherein a lead screw is provided on the rotating shaft of the rotor. 4. The stepping motor according to claim 3, wherein a lead screw is provided on the rotating shaft of the rotor. The stepping motor according to claim 4, wherein a lead screw is provided on a rotation shaft of the rotor. The stepping motor according to claim 5, wherein a lead screw is provided on a rotation shaft of the rotor. An assembling method of a stepping motor for assembling the stepping motor according to any one of claims 1 to 9, A first step of inserting a coil between the inner yoke and the outer yoke and aligning the stator while assembling the inner yoke and the outer yoke; And a second step of inserting the rotor inside the stator, Positioning of the inner yoke and the outer yoke in the first step is performed based on the inner diameter of the stator. 11. The method of assembling a stepping motor according to claim 10, wherein the positioning is performed by inserting a jig into the inner space of the stator. An assembling method of a stepping motor for assembling the stepping motor according to any one of claims 1 to 5, A first step of inserting a coil between the inner yoke and the outer yoke and aligning the stator by assembling the inner yoke and the outer yoke; And a second step of inserting the rotor inside the stator, Positioning of the inner yoke and the outer yoke in the first step is performed based on the outer diameter of the stator. 13. The method of assembling a stepping motor according to claim 12, wherein the positioning is performed by inserting the stator into the inner space of the jig. The method of assembling a stepping motor according to claim 13, wherein the coupling of the inner yoke and the outer yoke is performed through a hole formed in the jig. Assembly of a stepping motor having a stator having an inner yoke, an outer yoke and a coil installed therebetween, and a rotor, the assembling stepping motor being unable to be aligned by its own shape. As a method, A first step of inserting the coil between the inner yoke and the outer yoke and aligning the stator by assembling the inner yoke and the outer yoke by using a jig; And a second step of inserting the rotor inside the stator, Positioning of said inner yoke and said outer yoke in said 1st process is performed based on the inner diameter or outer diameter of a stator, The assembly method of the stepping motor characterized by the above-mentioned.