JP5453657B2 - Stepping motor - Google Patents

Description

  The present invention relates to a PM (permanent magnet) type stepping motor.

  The stepping motor is used, for example, for driving a pickup lens or a magnetic head included in a media-related device (optical disk device or magnetic recording device), driving a camera lens, or the like. For example, Patent Document 1 discloses a stepping motor in such a field.

The stepping motor described in Patent Document 1 has a magnet (rotor) provided on the outer periphery of a lead screw shaft (rotating shaft), and a stator is disposed so as to face the outer peripheral surface of the magnet. A frame extending in the axial direction of the lead screw shaft is fixed to the front end portion of the stator, a ball bearing is fixed to the front end of the frame, and an opening that allows insertion of a thrust bearing is formed at the rear end of the frame. Has been. Furthermore, the rear end portion of the rotating shaft is urged by a preload mechanism using a leaf spring, the front end of the rotating shaft is supported by a ball bearing, and the approximate center of the rotating shaft is supported by a thrust bearing fixed to the housing and the frame. It is supported. Therefore, by preloading the rotating shaft in the axial direction by the leaf spring, the axial play of the rotating shaft is suppressed.
Japanese Patent Application Laid-Open No. 7-241065

  In the conventional stepping motor described above, when the frame is attached to the motor body, the frame needs an opening larger than the diameter of the lead screw. However, in the stepping motor in which the worm gear is fixed to the rotating shaft instead of the lead screw, the diameter of the worm gear needs to be smaller than the diameter of the opening of the frame. Furthermore, today, the housing has become smaller with the miniaturization of the motor, but in reality, the diameter of the worm gear cannot be made smaller than necessary due to the relationship between the module and the thickness of the resin. Therefore, in consideration of the assembly work of the stepping motor, there is a problem that it is difficult to employ a large diameter (large) screw portion in a motor having a frame.

  An object of the present invention is to provide a stepping motor that facilitates the use of a large screw part.

The present invention relates to a stepping motor having a rotating shaft, a rotor made of a permanent magnet, a stator, and a housing that houses the rotor and the stator.
A screw part fixed to the rotating shaft protruding from the housing and larger than the diameter of the rotating shaft;
A frame fixed to the housing and supporting the screw part;
The frame is provided with a housing attachment portion attached to the front end portion of the housing, a shaft support portion that supports the tip of the rotating shaft, and a base portion that connects the housing attachment portion and the shaft support portion.
The housing mounting portion is larger than the diameter of a part of the rotating shaft exposed from between the rear end of the screw portion and the front end of the housing and is larger than the diameter of the screw portion so that the rotating shaft can be inserted. There is a small slit,
A convex portion that protrudes in the axial direction is formed at the front end portion of the housing, and an opening portion that fits the convex portion is formed at the housing mounting portion, and the diameter of the opening portion is smaller than the diameter of the screw portion. A slit formed with a width smaller than the diameter of the part extends to the opening,
The housing is attached to the frame in a state where the housing is positioned with respect to the frame by press fitting the convex portion into the opening.

  Today's stepping motors are being further downsized to be incorporated into media-related equipment and cameras, but the screw part may need to be downsized or upsized depending on the application. . Therefore, in order to correspond to the screw portions of various diameters, the frame mounting portion of the frame provided in the stepping motor according to the present invention is larger than the diameter of the rotating shaft so that the rotating shaft can be inserted and the screw. A slit smaller than the diameter of the part is provided. With such a frame configuration, the rotating shaft exposed from the gap between the rear end of the screw portion and the front end of the housing can be easily inserted into the slit of the housing mounting portion. The assembly work of the frame can be easily performed regardless of the size. This is particularly effective for a stepping motor that is miniaturized in consideration of incorporation into equipment.

  Furthermore, a convex portion that protrudes in the axial direction is formed at the front end portion of the housing, an opening that fits the convex portion is formed at the housing mounting portion, and the slit extends to the opening. In this case, the positioning and assembling work of the frame with respect to the housing becomes extremely easy by fitting the convex portion into the opening.

  According to the present invention, the adoption of a large screw part is facilitated.

It is sectional drawing which shows one Embodiment of the stepping motor which concerns on this invention. It is a perspective view which shows the external appearance of the stepping motor shown in FIG. It is a perspective view which shows a flame | frame.

  Hereinafter, preferred embodiments of a stepping motor according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the stepping motor 1 is used for driving a pickup lens, a magnetic head, etc. of a media-related device (optical disk device or magnetic recording device), a lens driving of a camera, etc., and has a diameter of about 3 to 5 mm. The size is reduced. The stepping motor 1 has a rotating shaft 3, and a rotor 5 as a permanent magnet formed by alternately magnetizing N and S poles is fixed to the outer periphery of the rotating shaft 3. A concave portion 5b that is recessed in the direction of the axis L of the rotary shaft 3 is formed in the rear end portion 5a of the rotor 5, and the rear end portion 3a of the rotary shaft 3 is located in the concave portion 5b.

  Before and after the rotor 5, a pair of stators 7 and 9 are arranged as a magnetic circuit for applying a rotational force to the rotor 5. In this way, the stepping motor 1 is reduced in the radial direction by arranging the stators 7 and 9 in parallel with the rotor 5 in the direction of the axis L.

  The front stator 7 includes a coil bobbin 13 around which a coil 11 that generates a magnetic field is wound, and a yoke 15 that is made of a magnetic material and accommodates the coil bobbin 13. The yoke 15 is obtained by connecting an outer yoke part 19 to an inner yoke part 17.

  The inner yoke part 17 has a tubular sleeve portion 17a that extends in the direction of the axis L and is arranged around the axis L. A disc-shaped connecting portion 17b orthogonal to the axis L is provided at the rear end portion of the sleeve portion 17a, and a plurality of first magnetic pole teeth 17c are provided at equal intervals on the outer peripheral end portion of the connecting portion 17b. It has been. Each first magnetic pole tooth 17c extends from the connecting portion 17b to a position facing the outer peripheral surface of the rotor 5 in the axis L direction.

  An outer yoke component 19 is joined to the front end portion of the sleeve portion 17a. The outer yoke part 19 has a disk-like base part 19a orthogonal to the axis L, and the base part 19a is fixed to the inner yoke part 17 through a through hole formed in the center part thereof.

  The same number of second magnetic pole teeth 19b as the first magnetic pole teeth 17c are provided at equal intervals on the outer peripheral end of the base portion 19a. Each of the second magnetic pole teeth 19b extends to a position facing the outer peripheral surface of the rotor 5, and each enters between the first magnetic pole teeth 17c so as not to contact the first magnetic pole teeth 17c. As a result, the first magnetic pole teeth 17 c and the second magnetic pole teeth 19 b are alternately arranged on the outer peripheral surface of the rotor 5.

  And the coil bobbin 13 shape | molded by the heat resistant resin is arrange | positioned in the space enclosed by the connection part 17b, the base part 19a, the 2nd magnetic pole tooth 19b, and the sleeve part 17a. A part of the coil bobbin 13 is formed with a terminal block 13a that is exposed to the outside from between the adjacent second magnetic pole teeth 19b. The coil 11 is electrically connected to a terminal 21 that is press-fitted and fixed to the terminal block 13a. It is connected. As a result, the coil 11 can be energized via the terminal 21.

  Similarly to the stator 7, the rear stator 9 includes a coil bobbin 25 around which a coil 23 for generating a magnetic field is wound, and a yoke 27 formed of a magnetic body that houses the coil bobbin 25. The yoke 27 has an inner yoke 29 and an outer yoke 31. The yoke 27 is connected to the inner yoke 29 and the outer yoke 31 by a tubular guide member 47 constituting a part of a preload mechanism 43 described later. Has been configured.

  The guide member 47 is made of a magnetic material and extends in the direction of the axis L with the axis L as a center. The outer diameter and inner diameter of the guide member 47 are enlarged on the front end 47 a side of the guide member 47. An inner yoke 29 is provided on the guide member 47 so as to come into contact with a step on the outer wall surface caused by the expansion of the outer diameter.

  The inner yoke 29 has a disk-shaped base portion 29a orthogonal to the axis L, and the base portion 29a is fixed to the guide member 47 through a through hole formed in the center portion thereof. A plurality of first magnetic pole teeth 29b are provided at the outer peripheral end of the base portion 29a, and each first magnetic pole tooth 29b extends from the base portion 29a to a position facing the outer peripheral surface of the rotor 5 in the axis L direction. .

  The outer yoke 31 is joined to the rear end portion 47 b of the guide member 47. The outer yoke 31 has a disk-like base portion 31a orthogonal to the axis L, and the base portion 31a is fixed to the guide member 47 through a through hole formed in the central portion thereof.

  The same number of second magnetic pole teeth 31b as the first magnetic pole teeth 29b are provided at equal intervals on the outer peripheral end of the base portion 31a. Each of the second magnetic pole teeth 31b extends from the base 31a to the position facing the outer peripheral surface of the rotor 5 in the direction of the axis L, and each enters between the first magnetic pole teeth 29b so as not to contact the first magnetic pole teeth 29b. Yes. As a result, on the outer peripheral surface of the rotor 5, the first magnetic pole teeth 29b and the second magnetic pole teeth 31b are alternately arranged opposite to each other.

  In the space surrounded by the base portions 29a and 31a, the second magnetic pole teeth 31b, and the guide member 47, the coil bobbin 25 formed of heat resistant resin is disposed. A part of the coil bobbin 25 is formed with a terminal block 25a exposed to the outside from between the adjacent second magnetic pole teeth 31b. The coil 23 is electrically connected to a terminal 33 press-fitted and fixed to the terminal block 25a. It is connected. As a result, the coil 23 can be energized via the terminal 33.

  The stepping motor 1 has a non-magnetic housing 35 formed of brass or stainless steel that accommodates the rotor 5 and the stators 7 and 9. The casing 35 has a cylindrical cover 35B joined to a rear end portion of a cylindrical casing main body 35A by welding W (see FIG. 2).

  The inner diameter of the casing 35 is equal to the outer diameter of the stators 7 and 9, and the outer surfaces of the first magnetic pole teeth 17 c and 29 b and the second magnetic pole teeth 19 b and 31 b are in contact with the casing 35. As a result, by accommodating the stators 7 and 9 in the casing 35, the centers of the sleeve portion 17a and the guide member 47 coincide.

  The stators 7 and 9 are guided by the housing main body 35A so that the first magnetic pole teeth 29b and the second magnetic pole teeth 31b are displaced at a predetermined interval with respect to the first magnetic pole teeth 17c and the second magnetic pole teeth 19b. However, it is accommodated in the housing body 35A. As a result, the first magnetic pole teeth 17 c and 29 b and the second magnetic pole teeth 19 b and 31 b surround the rotor 5.

  Therefore, when the coils 11 and 23 are energized through the terminals 21 and 33 of the terminal blocks 13a and 25a protruding from a part of the housing main body 35A, the magnetic fields generated by the coils 11 and 23 cause the yokes 15 and 27 to pass through. To the periphery of the rotor 5. As a result, a rotational force is generated in the rotor 5 and the rotary shaft 3 rotates.

  Further, the front end portion 3b of the rotating shaft 3 protrudes forward from an opening formed in the front end portion of the housing body 35A, and a screw portion 41 made of a resin worm gear is press-fitted into the protruding portion of the rotating shaft 3. Has been. In order to pivotally support the front end portion 3b of the rotating shaft 3, a metal frame 37 is attached to the front end portion of the housing body 35A.

  As shown in FIGS. 1 to 3, the frame 37 has a plate-like base piece (base portion) 37 a extending in the direction of the axis L, and the tip of the rotating shaft 3 is attached to the front end portion of the base portion 37 a. A supporting shaft supporting piece (shaft supporting portion) 37b is erected, and a housing attaching piece (housing attaching portion) 37c attached to the housing 35 is erected at the rear end of the base piece 37a. The housing attachment piece 37c and the shaft support piece 37b are connected by the piece 37a. The base piece 37a has a fixing screw hole (not shown).

  Further, the front end portion 3b of the rotary shaft 3 is rotatably held by a pivot bearing 39 that is press-fitted and fixed in a through hole 37d of the shaft support piece 37b. An annular protrusion 35b is formed at the front end of the housing body 35A, and an opening 37e is formed in the housing attachment piece 37c. The protrusion 35b of the housing 35 is press-fitted into the opening 37e. As a result, the frame 37 is firmly connected to the housing 35. Further, the frame 37 is fixed to the housing 35 by welding W. As described above, by adopting the configuration in which the opening 37e and the convex portion 35b are fitted, the positioning and assembling work of the frame 37 with respect to the housing 35 becomes extremely easy.

  By the way, today's stepping motor 1 has been further reduced in size (3 to 5 mm in diameter), and along with this, the screw portion 41 needs to be reduced in size and increased in size depending on the application. There are some cases. In particular, when a worm gear is used for the screw portion 41, the diameter of the screw portion 41 is very close to or larger than the diameter of the housing body 35A of the stepping motor 1.

  Therefore, a slit 50 larger than the diameter of the rotating shaft 3 and smaller than the diameter of the screw portion 41 is provided in the housing mounting piece 37c of the frame 37 so as to correspond to a large screw portion 41 such as a worm gear. ing. The slit 50 extends to the opening 37e. Further, the thickness dimension A of the housing attachment piece 37 c of the frame 37 is smaller than the gap dimension B between the rear end of the screw portion 41 and the front end of the housing 35.

  By adopting such a frame 37, a part 3c of the rotating shaft 3 exposed from the gap S between the rear end of the screw portion 41 and the front end of the housing 35 is inserted into the slit 50 of the housing mounting portion 37c. Such assembling work can be performed. By adopting such a slit 50, the assembly work of the frame 27 can be easily performed regardless of the diameter of the screw portion 41. When the frame 37 is fixed to the housing 35, the projection 35b is press-fitted into the opening 37e, and at the same time, the front end 3b of the rotary shaft 3 is inserted into the recess 39a of the pivot bearing 39.

  Further, when the driven member is driven using the screw portion 41, the rotating shaft 3 receives a thrust force as a reaction from the screw portion 41. When rotating in the forward and reverse directions, a force acts on the rotating shaft 3 in a direction in which it is pushed or protruded by the worm gear 41, and it is necessary to apply a preload in one direction so as to hold down the thrust movement amount generated at this time. Therefore, the stepping motor 1 has a preload mechanism 43 that applies a preload in the direction of the axis L to the rotation shaft 3 in the housing 35 behind the rotation shaft 3.

  The preload mechanism 43 includes a resin-made pivot bearing 45 that holds the rear end portion 3a of the rotary shaft 3, a guide member 47 that slidably holds the pivot bearing 45, and a preload that urges the pivot bearing 45 in the direction of the axis L. And a spring 49. The pivot bearing 45 is located on the front end portion 45a side of the pivot bearing 45, and has a shaft holding portion 45c having a recess 45b for supporting the rear end portion 3a of the rotary shaft 3, and a rear end portion of the shaft holding portion 45c. And a spring winding portion 45d extending in the axis L direction.

  The shaft holding portion 45 c is in sliding contact with the inner wall surface 47 c of the guide member 47, and the guide member 47 is joined to the outer yoke 31 and the inner yoke 29, so that the center of the guide member 47 is the axis of the rotary shaft 3. It is consistent with L. Therefore, the pivot bearing 45 is reliably positioned on the axis L, is guided by the guide member 47, and slides in the axis L direction. Further, the guide member 47 is arranged so that the front end portion 47 a enters the recess 5 b, and the front end portion 45 a of the pivot bearing 45 enters the recess 5 b of the rotor 5 while being guided by the guide member 47. . As a result, the pivot bearing 45 holds the rear end 3a of the rotary shaft 3 in the recess 5b.

  The outer diameter of the spring winding portion 45d extending from the rear end portion of the shaft holding portion 45c is smaller than the outer diameter of the rear end portion of the shaft holding portion 45c, and the spiral spring 49 is wound around the side surface 45e of the spring winding portion 45d. Has been. Thus, the preload spring 49 is positioned on the axis L and is disposed between the side surface 45e of the pivot bearing 45 and the inner wall surface 47c of the guide member 47.

  Further, the front end portion of the preload spring 49 contacts the rear end portion of the shaft holding portion 45c, and the rear end portion of the preload spring 49 contacts the inner wall surface 35a of the casing 35 (more specifically, the cover 35B). Therefore, the pivot bearing 45 is urged in the direction of the axis L by the preload spring 49.

  Accordingly, the concave portion 45b of the pivot bearing 45 is reliably pressed against the rear end portion 3a of the rotary shaft 3 in the concave portion 5b and is brought into contact with the rear end portion 3a of the rotary shaft 3 so that the rotary shaft 3 can be freely rotated. Hold. Accordingly, the preload mechanism 43 applies a preload to the rotary shaft 3 in the direction of the axis L via the pivot bearing 45.

  DESCRIPTION OF SYMBOLS 1 ... Stepping motor, 3 ... Rotating shaft, 5 ... Rotor, 7, 9 ... Stator, 35b ... Convex part, 35 ... Housing, 37 ... Frame, 37a ... Base piece (base part), 37b ... Shaft support piece (shaft) Support part), 37c ... Case attachment piece (Case attachment part), 37e ... Opening part, 41 ... Screw part (worm gear), 50 ... Slit, L ... Axis, S ... Gap.

Claims (1)

In a stepping motor having a rotating shaft, a rotor made of a permanent magnet, a stator, and a housing that houses the rotor and the stator,
A screw portion fixed to the rotating shaft protruding from the housing and larger than the diameter of the rotating shaft;
A frame fixed to the housing and supporting the screw part;
The frame includes a housing attachment portion attached to a front end portion of the housing, a shaft support portion that supports a tip end of the rotating shaft, and a base portion that connects the housing attachment portion and the shaft support portion. And
The housing mounting portion is larger than a diameter of a part of the rotating shaft exposed from between a rear end of the screw portion and a front end of the housing so that the rotating shaft can be inserted. A slit smaller than the diameter of the screw part is provided,
A convex portion protruding in the axial direction is formed at the front end portion of the casing, and an opening portion that fits the convex portion is formed at the casing mounting portion, and the diameter of the opening portion is that of the screw portion. The slit formed with a width smaller than the diameter and smaller than the diameter of the opening extends to the opening,
The stepping motor is characterized in that the casing is attached to the frame in a state where the casing is positioned with respect to the frame by the press-fitting of the convex portion into the opening.

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