JP3448496B2 - Screw feed motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw feed motor used in a head / seek mechanism such as a floppy disk drive, a zoom mechanism of a still camera and a video camera, and more particularly to a screw feed motor in which the motor shaft is a screw shaft. Regarding motors.

[0002]

2. Description of the Related Art Conventionally, a small screw feed stepping motor used in a head seek mechanism of a floppy disk drive has one end inserted into a cylindrical hole of a PM type (permanent magnet type) inner rotor 1 as shown in FIG. The screw shaft 2 is fixed and has the other end portion projecting to the outside of the motor main body as a male screw portion 2a. A tapered ball receiving hole 2b is formed on one end surface of the screw shaft 2, and a tapered ball receiving hole 2c is formed on the tip surface of the male screw portion 2a. A leaf spring 4 is provided on the bottom surface of the cup-shaped outer yoke 5 which also serves as a case, which constantly elastically urges the steel ball 3 housed in the ball receiving hole 2b from one end side to the other end side of the screw shaft 2. The backlash in the axial direction of the screw shaft 2 (backlash of the screw) is prevented. Here, steel ball 3
The reason for using is to reduce the sliding loss due to the leaf spring 4. A lid-shaped outer yoke 7 that closes the opening of the cup-shaped outer yoke 5 is fitted to the bearing metal 6 that slides along the midway peripheral surface of the screw shaft 2. On the motor body side, the bearing metal 6 is fitted into the mounting hole of the upright piece 20a of the frame of the floppy disk drive, and the flange 5a of the cup-shaped outer yoke 5 is screwed on. Male screw part 2a
The side is formed by abutting the ball receiving hole 2c on the steel ball 23 of the bearing 21 fitted in the mounting hole of the cut-and-raised piece 20b. The head carriage 22 having a female screw portion 22a that is screwed with the screw shaft 2 is reciprocally screwed in the axial direction.

[0003]

However, the screw feeding motor described above has the following problems.

Although it is necessary to form ball receiving holes 2b and 2c on both end surfaces of the screw shaft 2 used for the screw feeding motor, since these ball receiving holes 2b and 2c are formed by cutting, they are fine. This has been an obstacle to the formation of a diameter shaft and cost reduction.

Further, since the axial center of the screw shaft 2 is held by using the slide bearing metal 6, sliding loss occurs due to the metal 6, which causes a torque loss.

In view of the above problems, the first aspect of the present invention
An object of the present invention is to provide a screw feeding motor that can use a small-diameter screw shaft and can realize cost reduction.

A second object of the present invention is to provide a screw feed motor capable of holding the axial center of a screw shaft without using a radial slide bearing and reducing sliding loss. .

[0008]

In order to solve the first problem, one end side is inserted and fixed in a cylindrical hole of a PM type rotor magnet , and a male screw portion is formed at least on the other end side portion protruding outside the motor body. In a screw feeding motor including a screw shaft having a shaft, the PM rotor magnet is a bottomed cylindrical body, and the PM center rotor magnet is axially regulated by aligning the center of rotation of the bottom outer surface of the PM rotor magnet . Ru formed a resilient thrust bearing means for energizing.

Originally, at the time of mounting the screw feed motor, the tip end side of the screw shaft is supported by the thrust bearing. Therefore, as in the present invention, the base end side of the screw shaft, that is, the PM type rotor magnet. The axial center can be maintained even in the structure in which the bottomed tubular body is thrust-supported by the elastic thrust bearing means. Instead of supporting the base end of the screw shaft by elastic thrust bearing means as in the conventional art,
Since the bottom of the bottomed cylindrical body of the PM type rotor magnet is supported, it is not necessary to form a ball receiving hole on the end surface of the screw shaft itself by cutting, and the bottomed cylindrical shape is thicker than the diameter of the screw shaft. A structure such as a ball receiving hole for aligning regulation can be provided at the bottom of the body. The cost can be reduced because the cutting process on the base end side of the shaft can be eliminated.

Since a screw shaft having a small diameter unsuitable for cutting can be used, it contributes to downsizing of the motor.

As the elastic thrust bearing means, a PM type rotor magnet is provided by applying an aligning ball to the center on the outer surface side of the bottom portion.
The thrust bearing means for thrust-supporting the rotor and the elastic urging means for constantly elastically urging the PM type rotor magnet in the axial direction via the thrust bearing means.

The thrust bearing means has a substantially tapered ball receiving hole formed at the center of the outer surface of the bottom, an aligning ball housed in the ball receiving hole, and an axial ball for pressing the aligning ball. And a ball retainer having a substantially tapered ball pushing hole. P
The M-shaped rotor magnet, that is, the function of holding the axial center of the screw shaft (alignment regulation) is exerted.

In the above thrust bearing means, it is preferable that the solid angle of the ball receiving hole on the PM rotor magnet side is larger than the solid angle of the ball pushing hole. In such a case, the contact circle between the aligning ball and the ball receiving hole is larger than the contact circle between the aligning ball and the ball pushing hole. It is immovable and the aligning ball slides over the ball pushing hole. Since the aligning ball does not move with respect to the PM type rotor magnet, it is difficult for the magnet to wear. In particular, when the PM type rotor magnet uses a plastic magnet, the friction coefficient becomes large, and accordingly, it becomes difficult for the aligning ball and the PM type rotor magnet to slide. Also, if the ball pushing hole side is molded with slippery plastic,
Furthermore, the alignment ball does not move with respect to the PM type rotor magnet.

It is preferable that the PM type rotor magnet has a penetrating portion that axially connects the ball receiving hole and the inner side of the cylindrical hole. This penetrating portion can be used as an oil supply hole (grease reservoir). Since the aligning ball adheres to the grease in the penetrating portion, it becomes even more difficult for the aligning ball to move with respect to the PM rotor magnet.

In order to solve the second problem, in addition to the above structure, the screw shaft freely penetrates through the end portion of the motor body with a clearance so that the first support member outside the machine can be installed. According to the configuration including the motor holding portion that is fitted and positioned in the mounting hole, the motor holding portion is not in contact with the peripheral surface of the screw shaft, so that sliding loss can be reduced and the output torque can be improved. To do. Further, not only the case where only the other end side portion of the screw shaft protruding to the outside of the motor body is the male screw portion, the entire shaft length may be the male screw portion. In such a case, since it is possible to use a rolled screw shaft obtained by cutting a rolled screw rod material to a predetermined size, it is possible to eliminate cutting screw processing and realize a significant cost reduction. In particular, since the length of the protruding male screw portion can be changed by changing the depth of press-fitting the screw shaft into the PM type rotor magnet, cost reduction can be realized by sharing the screw shaft.

As described above, since the tip end side of the screw shaft is supported by the thrust bearing when the screw feeding motor is mounted, the bottomed cylindrical body of the PM type rotor magnet is elastically thrust bearing means. It is possible to maintain the axial center even with the structure of thrust support.

If the motor holding portion is integrally formed with the mold resin material of the yokes integrated by insert molding at the same time, it contributes to reduction of the number of parts and further cost reduction. realizable.

Further, a crown body integrally protruding with a bearing surface of a second support outside the machine and a spherical journal portion which should constitute a pivot bearing is fitted to a tip end portion on the other end side of the screw shaft. Preferably. Not only can the machining of the ball receiving hole at the other end of the screw shaft be eliminated, but the crown body itself also has a spherical journal part, which contributes to the reduction of the number of parts and cost reduction. realizable.

It is preferable that the crown body is formed of a slippery plastic material. It contributes to the reduction of friction in the spherical journal.

As the elastic force urging means, a plurality of radial leaf spring pieces whose tip portions are in pressure contact with each other at substantially equal intervals around the central area of the surface of the ball retainer opposite to the ball pushing hole are integrated toward the center. It is a ring plate that you have. Since a plurality of radial leaf spring pieces are applied to the periphery of the central area of the presser foot with an even biasing force, the attitude of the presser foot can be unified with the axis line, so that highly accurate axis centering can be realized.

A screw feeding mechanism having a screw feeding motor as described above and a driven member which is screwed to the screw shaft thereof and axially screw-fed by the rotation thereof is used as a screw feeding mechanism for a floppy disk drive, a still camera and a video camera. Suitable for use in electric devices such as cameras.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 8 is a vertical cross-sectional side view showing a screw feeding mechanism using the screw feeding motor according to the first embodiment. The same parts as those shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

The screw feed motor (small stepping motor) of this embodiment is a cylindrical hole 30a of the PM type inner rotor 30.
And a screw shaft 31 having a male screw portion 31a over its entire length. The screw shaft 31 is a rolled screw shaft which is used by cutting a rolled screw rod material to a predetermined size. Further, the PM type inner rotor 30 is a plastic magnet molded product such as neodymium or samarium iron chisso and has a bottomed cylindrical body. Then, the thrust bearing mechanism 40 that regulates the center of rotation of the outer surface of the bottom portion 30b of the bottomed tubular body, and the PM type inner rotor 30 in the axial direction (the tip direction of the screw shaft 31) via this thrust bearing mechanism 40. It has a ring plate 50 which is a resilient biasing means for constantly biasing.

In the thrust bearing mechanism 40, a centering ball (steel ball) 3 is applied to the center of the outer surface side of the bottom portion 30b to support the thrust of the PM type inner rotor 30, and the bottom portion 30b is used.
Taper-shaped ball receiving hole 30c formed in the central area of the outer surface of
And an aligning ball 3 housed in the ball receiving hole 30c, and a substantially tapered ball pushing hole 32a for pressing the aligning ball 3 in the axial direction.
And a ball retainer 32 having

Here, the solid angle (about 120 °) of the ball pressing hole 32a of the ball pressing member 32 is the ball of the PM type inner rotor 30.
It is larger than the solid angle (about 60 °) of the receiving hole 30c . Further, in the PM type inner rotor 30, the penetrating portion 3 that axially connects the ball receiving hole 30c and the inside of the cylindrical hole 30a.
0d is formed. The penetrating portion 30d is used as a grease reservoir. The ball retainer 32 is a molded product made of a slippery plastic material.

The ball retainer 32 includes a fitting portion 32b which is axially movably inserted into a cylindrical hole of a throttle cylindrical portion 5a projecting from the bottom surface of the cup-shaped outer yoke 5 which also serves as a case, and a flange portion 32c which prevents the same from coming off. It is an integrally molded product. 2A and 3
As shown in FIG. 5, the fitting portion 32b is formed with positioning grooves 32d corresponding to the plurality of radial leaf spring pieces 50a of the ring plate 50. The ring plate 50 is the cup-shaped outer yoke 5.
A plurality of radiations are positioned by the five pole claws (cropoles) 5b cut and raised inward from the bottom surface of the base plate, are fitted in the positioning groove 32d, and the tips are pressed against each other around the central region of the collar-shaped portion 32c at substantially equal intervals. The plate spring piece 50a is integrally provided toward the center.

The outer stator of the motor body closes the opening of the cup-shaped outer yoke 5 and the opening of the cup-shaped outer yoke 5, and as shown in FIG. A lid-shaped outer yoke 7 having a claw (cropole) 7a, a crown-shaped first inner yoke 8 in which a polar claw 8a is positioned between the polar claws 5b in the cup-shaped outer yoke 5, and a cup-shaped outer yoke 5. A second crown-shaped inner yoke 9 in which the polar claw 9a is positioned between the polar claws 7a of the lid-shaped outer yoke 7, a winding coil 11 forming the A phase, and a winding coil 12 forming the B phase.
And have. The first inner yoke 8 and the second inner yoke 9 are integrated by a molding resin 13 by insert molding, and the molding resin 13 also serves as an insulating layer. Further, at the time of insert molding, the terminal block 14 and the motor holding portion 60 are simultaneously formed of the molding resin 13. Terminal pins 14 a are erected on the terminal block 14.

In this motor holding portion 60 made of resin, the screw shaft 31 freely penetrates at the end portion of the motor body with a clearance 60a, and is fitted and positioned in the mounting hole of the standing piece 20a of the frame. . Motor holding unit 60
Has a positioning protrusion 60b fitted between the pole claws 7a of the lid-shaped outer yoke 7.

FIG. 1 shows a screw feeding motor having such a structure.
When used in the screw feeding mechanism shown in (1), since the tip end side of the screw shaft 31 is thrust supported by the ball receiving hole 2c, the steel ball 23 and the bearing 21, only the thrust bearing mechanism 40 is provided on the base end side as in this example. However, the conventional metal bearing 6 is not provided. The number of parts can be reduced. In this example, the bottom portion 3 of the bottomed tubular body of the PM rotor magnet 30 is used.
Since the structure supports 0b, the screw shaft 3
Since it is not necessary to form a ball receiving hole in the base end surface of 1 itself by cutting and an inexpensive rolling screw shaft can be used, cost reduction can be realized. The bottom portion 30b of the bottomed tubular body having a diameter larger than that of the screw shaft 31.
Further, it is possible to reduce the manufacturing cost by forming the ball receiving hole 30c for alignment regulation by resin molding. It also contributes to downsizing of the motor.

The solid angle of the ball pressing hole 32a of the ball pressing member 32 is P.
Since that is larger than the solid angle of the M-shaped rotor magnet 30 side of the ball reception hole 30c, so towards the contact circle of the ball receiving hole 30c side is larger than the contact circle of the ball pushing holes 32a, Chokokorodama 3
And the ball pushing hole 32a slips. Therefore, PM
Since the aligning ball 3 does not move with respect to the shaped rotor magnet 30, abrasion of the magnet 30 is unlikely to occur. In particular, since the PM rotor magnet 30 is a plastic magnet such as Neody, the friction coefficient is large, and the aligning ball 3 is accordingly increased.
This makes it difficult for the PM-shaped rotor magnet 30 to slide, which is convenient. In addition to this, since the ball retainer 32 is made of slippery plastic, sliding is less likely to occur between the PM rotor magnet 30 and the aligning ball 3. Further, since the penetrating portion 30d is used as an oil supply hole (a grease reservoir), it adheres to the aligning ball 3 on the grease, so that the aligning ball is even more important.
Becomes difficult to move with respect to the PM type rotor magnet. Since the motor holding portion 60 is not in contact with the peripheral surface of the screw shaft 31, the sliding loss can be reduced and the output torque can be improved. Further, since the screw shaft 31 is not in contact, the rolled screw shaft 31 having the male screw portion as the entire shaft length can be used, and further cost reduction can be realized. In particular, since the length of the protruding male screw portion 31a can be changed by changing the depth of press-fitting the screw shaft 31 into the PM type rotor magnet 30, it is possible to use a screw feed motor having a different male screw portion 31a length. As a result, the screw shaft 31 can be shared, and cost reduction can be realized.

The motor holding portion 60 is integrally formed with the molding resin materials of the yokes 8 and 9 integrated by insert molding at the same time. Therefore, it contributes to the reduction of the number of parts and the like, and further cost reduction can be realized. The lid-shaped outer yoke 7 may be integrated at the same time by the insert molding. Contributes to the reduction of assembly man-hours.

The ring plate 50 is a collar-shaped portion 32c of the ball retainer 32.
A plurality of radiating leaf spring pieces 50a, whose tip portions are in pressure contact with each other at substantially equal intervals, are integrally provided around the central region of the opposite surface toward the center. Since the plurality of radial leaf spring pieces 50a are applied to the periphery of the central region of the ball retainer 32 with an even biasing force, the posture itself of the ball retainer 32 can be made uniform with the axis.
Achieves highly accurate axis centering.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
FIG. 8 is a vertical cross-sectional side view showing a screw feeding mechanism using the screw feeding motor according to the first embodiment. The same parts as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

A feature of the present embodiment is that a crown body 70 in which a bearing 23 fitted in a mounting hole of the cut-and-raised piece 20b and a spherical journal portion 71 which constitutes a pivot bearing are integrally projected at the tip portion of the screw shaft 31. It is a place where it is fitted. The crown 70 is a molded product made of a slippery plastic material. When such a crown 70 is used, cutting work on the tip side of the screw shaft 31 can be eliminated, and the steel ball 23 is also unnecessary, so that further cost reduction can be realized. Further, since the slippery plastic material is used, it contributes to the reduction of friction. Other operational effects of this example are similar to those of the first embodiment.

The screw feeding mechanism using the screw feeding motor described above is a floppy disk drive,
It is suitable for use in electric devices such as still cameras and video cameras.

[0037]

As described above, according to the present invention, the bottom end of the bottomed cylindrical body of the PM type inner rotor into which the screw shaft is inserted is not supported by the elastic thrust bearing means at the base end of the screw shaft. Since it is characterized in that it is supported by the elastic thrust bearing means, it has the following effects.

Since it is not necessary to form a ball receiving hole on the end surface of the screw shaft itself by cutting, cost reduction can be realized. Further, a screw shaft having a small diameter unsuitable for cutting can be used, which contributes to downsizing of the motor.

In the thrust bearing means, when the solid angle of the ball pushing hole is larger than the solid angle of the ball receiving hole on the PM rotor magnet side , the aligning ball does not move with respect to the PM rotor magnet. , It is hard to wear the magnet. In particular, when the PM type rotor magnet uses a plastic magnet, the friction coefficient becomes large, and the aligning ball and P
Sliding with the M-shaped rotor magnet becomes difficult. Moreover, if the ball pushing hole side is molded with slippery plastic, the aligning ball does not move with respect to the PM type rotor magnet.

When the ball receiving hole and the inner side of the cylindrical hole are provided with a penetrating portion that communicates with each other in the axial direction, this penetrating portion can be used as an oil supply hole (grease reservoir). Since the aligning ball adheres to the grease in the penetrating portion, it becomes even more difficult for the aligning ball to move with respect to the PM rotor magnet.

According to the configuration of the present invention, at the end of the motor main body, the motor shaft is provided with the motor shaft holding the screw shaft with a play clearance and fitted and positioned in the mounting hole of the first support outside the machine. Since the motor holding portion is not in contact with the peripheral surface of the screw shaft, sliding loss can be reduced and the output torque can be improved. It is not limited to the case where only the other end side portion of the screw shaft projecting outside the motor body is the male screw portion, and the entire shaft length may be the male screw portion.
In such a case, since it is possible to use a rolled screw shaft obtained by cutting a rolled screw rod material to a predetermined size, it is possible to eliminate cutting screw processing and realize a significant cost reduction.

In particular, since the length of the protruding male screw portion can be changed by changing the depth at which the screw shaft is press-fitted into the PM type rotor magnet, cost reduction can be realized by sharing the screw shaft.

When the motor holding portion is integrally formed with the mold resin material of the yokes integrated by insert molding at the same time, it contributes to the reduction of the number of parts and further cost reduction can be realized.

In the case where a crown body integrally protruding with a bearing surface of a second support outside the machine and a spherical journal portion which should constitute a pivot bearing is fitted to the tip end of the screw shaft, Not only can the cutting process of the ball receiving hole on the tip side be eliminated, but the number of parts can be reduced and the cost can be reduced.

When this crown is formed of a slippery plastic material, it contributes to the reduction of friction of the spherical journal portion.

As the elastic force urging means, a plurality of radial leaf spring pieces whose tip portions are in pressure contact with each other at substantially equal intervals around the central area of the surface of the ball retainer opposite to the ball pushing hole are integrally united toward the center. In the case of a ring plate that has, since a plurality of radial leaf spring pieces are applied to the periphery of the central area of the ball retainer with an even biasing force, the posture of the ball retainer can be made uniform with the axis line, so a highly accurate axis center Hold can be realized.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a screw feed mechanism using a screw feed motor according to a first embodiment of the present invention.

FIG. 2A is a rear view showing the screw feeding motor.
FIG. 3B is a plan view showing the screw feeding motor.

FIG. 3 is a cutting plane surface showing a relationship between a ring plate and a ball retainer in the screw feeding motor.

FIG. 4 is a vertical sectional side view showing a screw feeding mechanism using a screw feeding motor according to a second embodiment of the present invention.

FIG. 5 is a vertical cross-sectional side view showing a screw feeding mechanism using a conventional screw feeding motor.

[Explanation of symbols]

1,30 ... PM type (permanent magnet type) inner rotor 2, 31 ... Screw shaft 2a, 31a ... Male screw part 2b, 2c, 30c ... Ball receiving hole 3,23 ... Steel balls (aligning balls) 4 ... Leaf spring 5 ... Cup-shaped outer yoke 5 5b, 7a, 8a, 9b ... Polar claws 6 ... Bearing metal 7 ... Lid-shaped outer yoke 8 ... 1st inner yoke 9 ... Second inner yoke 11, 12 ... Winding coil 13 ... Mold resin 14 ... Terminal block 14a ... Terminal pin 20a ... Standing piece of frame 20b ... raised piece 22 ... Head carriage 22a ... Female thread portion 30a ... Cylindrical hole 30b ... bottom 30d ... Penetration part 32 ... Ball retainer 32a ... push hole 32b ... Fitting part 32c ... collar part 32d ... positioning groove 40 ... Thrust bearing mechanism 50 ... Ring plate 50a ... Radial leaf spring piece 60 ... Motor holding section 60a: Yukan clearance 60b ... positioning protrusion 70 ... Crown 71 ... Spherical journal section.

Continuation of the front page (56) Reference JP-A-9-154271 (JP, A) JP-A-9-219946 (JP, A) JP-A-10-217993 (JP, A) JP-A-5-176518 (JP , A) Actual Kaihei 5-62172 (JP, U) Actual Kaihei 7-27287 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02K 37/00 H02K 5/00 H02K 7/00

Claims (5)

(57) [Claims] 1. A screw feeding motor having a screw shaft having a male screw portion at least on the other end side which is inserted into and fixed to a cylindrical hole of a PM type inner rotor, and which protrudes out of the motor body. forms the inner rotor is a bottomed cylindrical body, have a resilient thrust bearing means for elastically urged in the axial direction of the rotational center by aligning regulating the PM type inner rotor of the outer bottom surface, said resilient thrust bearing Means, on the outer surface side of the bottom
Align the PM type inner rotor with a centering ball at the center and slide it.
Thrust bearing means for supporting the thrust and this thrust bearing hand.
The PM type inner rotor in the axial direction through a step.
Elastic thrusting means for elastically biasing when the thrust shaft
The receiving means is a substantially tapered shape formed at the center of the outer surface of the bottom.
Ball receiving hole, the aligning ball housed in the ball receiving hole, and the aligning ball
Equipped with a substantially tapered ball pushing hole for pushing the ball in the axial direction
The PM type inner rotor has the
Has a penetrating part that axially connects the ball receiving hole and the inside of the cylindrical hole.
And, the solid angle of the ball pushing hole size than the solid angle of the ball receiving hole
The screw feed motor is characterized in that the through portion is used as a grease reservoir . 2. The screw feeding motor according to claim 1 , wherein the ball retainer is formed of a slippery plastic material. 3. The method of claim 1, the distal end portion of the other end of the screw shaft, the spherical journal portion for constituting a bearing surface and the pivot bearing of the second support outside protrudes integrally A screw feeding motor characterized by being fitted with a crown. 4. The screw feeding motor according to claim 3 , wherein the crown is formed of a slippery plastic material. 5. A screw having a screw feed motor defined in any one of claims 1 to 4 , and a driven member screwed into the screw shaft and screw-fed axially by rotation of the screw shaft. An electric device comprising a feeding mechanism.