JP2001025202A - Dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure service life of a sliding bearing by preventing inclination of a shaft effectively, without complicating the constitution. SOLUTION: By a bearing holder 4 fitted to a bracket 2, a shaft 9 having a rotation transmitting to the part 18 at its one end part is supported freely/ rotatably through a plurality of sleeve bearings 7, 8. For a rotor bush 21 to be fitted freely/slidably to the sleeve bearing 7 integrated with a rotor 10 and arranged on the other end side of the shaft 9, a holding part 21b which covers the corner part of the peripheral end of the sleeve bearing 7, and a support surface 21c which slides on the peripheral surface of the end part of the sleeve bearing 7 in the holding part 21b are formed integrally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor suitable as a drive source of a paper feed mechanism in a laser beam printer, a copying machine, or the like.

[0002]

2. Description of the Related Art A DC brushless motor used for this type of application generally includes a motor section and a motor circuit board, and the motor section has a configuration as shown in FIG. That is, the motor unit 1 is provided with a bracket 2 serving as a base for attaching to a required portion of an applied device such as the above-described laser beam printer or copier.
A base portion of a cylindrical bearing holder 4 is fixedly penetrated through the mounting hole 3. A shaft 9 is rotatably supported inside the bearing holder 4 via a pair of upper and lower cylindrical oil-impregnated sleeve bearings 7, 8. Have been. The bracket 2 and the bearing holder 4
Thus, a fixing member is configured.

A cup-shaped rotor 10 is fixed to the upper end of the shaft 9 extending from the upper end of the bearing holder 4 by press-fitting means or the like, so that the rotor 10 rotates integrally with the shaft 9. This rotor 1
An annular rotor magnet 11 is internally fitted and fixed to the inner peripheral surface of the reference numeral 0. On the other hand, a stator 12 is fitted on the outer peripheral surface of the bearing holder 4 so as to face the rotor magnet 11 with a small gap, and is fixed by screws 13. A rotor bush 14 fixed to the rotor 10 is interposed between the rotor 10 and the upper surface of the upper sleeve bearing 7. And holds the rotating rotor 10 in sliding contact with the rotor. Also, the bearing holder 4
A circuit board 17 on which necessary electronic components are mounted and on which a rotation drive circuit for the rotor 10 and a coil current control circuit for the stator 12 are formed is fixed.

A screw tooth 18 is formed at a lower end portion of the shaft 9 derived from the bearing holder 4. When the DC brushless motor is attached to an electronic device or the like, a transmission gear 19 such as a speed reduction mechanism of the electronic device is engaged with the screw teeth 18 and connected thereto.
The DC brushless motor is connected to an external drive power supply via a control circuit of the circuit board 17 to control the stator 12.
When a drive current (excitation current) is supplied to the phase stator coil, a rotational force is generated in the rotor 10 by magnetic interaction between the stator 12 and the rotor magnet 11, and the rotational force of the rotor 10 is applied to the screw of the shaft 9. Tooth 18
And transmitted to the drive load of the applied electronic device through the transmission gear 19.

[0005]

In the DC brushless motor used for the above-mentioned applications, the shaft 9 is rotatable by sleeve bearings 7 and 8 which are inexpensive sliding bearings compared to ball bearings and the like. It has a supporting structure, and there is necessarily a slight gap between the sleeve bearings 7, 8 and the shaft 9 due to its structure. On the other hand, the transmission gear 19 is meshed from one side with the screw teeth 18 at the lower end portion, which is the output portion of the rotational force of the shaft 9, so that the screw teeth 18 and the transmission gear 19 An unbalanced load is applied in one direction indicated by the arrow A due to the engagement. For this reason, a force is exerted on the shaft 9 to tilt the shaft 9 in the direction of the arrow B due to the gap between the sleeve bearings 7 and 8.

Due to the generation of the force for tilting the shaft 9, a high load is applied to the lower sleeve bearing 8 and a low load is applied to the upper sleeve bearing 7. Therefore, the lower sleeve bearing 8 has a problem that the surface pressure received from the shaft 9 increases with the application of a high load, and the life of the lower sleeve bearing 8 is shortened. In addition, if the shaft 9 is tilted, the rotation of the shaft 9 is not obtained smoothly. In addition, even if the rotor 10 that rotates integrally with the shaft 9 is slightly tilted, the life of the motor itself is reduced. Will also be shortened.

In view of the above, the present invention has been made in view of the above-mentioned conventional problems, and effectively prevents the shaft from being tilted without complicating the structure, thereby enabling smooth sliding between the shaft and the sleeve bearing. It is an object of the present invention to provide a DC brushless motor that can secure the life of a slide bearing by holding the motor.

[0008]

In order to achieve the above-mentioned object, a DC brushless motor according to the present invention comprises a fixed member having a cylindrical bearing holder, and a rotatable member mounted on the bearing holder via a plurality of sleeve bearings. A shaft to which rotational force is transmitted from one end derived from the bearing holder, a rotor having a rotor magnet and fixed to the other end of the shaft, and a shaft facing the rotor magnet. The rotor includes a stator mounted on a fixed member, and a rotor bush integrated with the rotor and slidably provided with respect to the sleeve bearing disposed on the other end of the shaft. A holding portion that covers the peripheral edge of the sleeve bearing facing the bush, and a receiving surface that slides on the outer peripheral surface of the end of the sleeve bearing in the holding portion are integrated. It has been made.

In this DC brushless motor, the shaft of the device to which the gear is applied is inclined by the load caused by the gear meshing with the teeth of the shaft from one side.
While effectively preventing the bearing surface of the rotor bush from sliding on the sleeve bearing, the load applied to the shaft is
Since the sleeve bearing arranged on the side opposite to the one end for transmitting the rotational force in the shaft is shared and received,
Unlike a conventional motor, a load applied to a shaft does not concentrate on a sleeve bearing at one end. Therefore, the load attributable to the tilt force applied to the shaft is reduced in the sleeve bearing on one end side compared to the conventional motor, and the surface pressure received from the shaft is reduced, so that the life can be sufficiently ensured. Further, this motor has a simple configuration in which the holding portion having the receiving surface is formed integrally with the rotor bush, and the number of parts does not increase compared to the rotor bush of the conventional motor, so that no cost increase is caused. .

In the above invention, the sleeve bearing at the other end of the shaft abuts on a supported piece extending radially outward from the end of the sleeve bearing, and abuts on a peripheral end corner of the bearing holder in the supported piece. The supported surface supported is integrally formed,
It is preferable that the rotor bush has a configuration in which the receiving surface is provided so as to slide on the outer peripheral surface of the supported piece.

[0011] This makes it possible to effectively prevent the shaft from tilting by the receiving surface of the rotor bush, and furthermore, the sleeve bearing is supported by the bearing holder via the supported surface. Therefore, the load applied to the shaft can be effectively received by the sleeve bearing 7 on the side opposite to the one end portion. Therefore, the load attributable to the tilting force applied to the shaft is further reduced in the sleeve bearing on one end side, so that the service life can be kept longer. Further, in this DC brushless motor, a supported piece having a supported surface is integrally formed with a sleeve bearing,
This is a simple configuration in which the holding portion having the receiving surface is formed integrally with the rotor bush, and the number of components does not increase as compared with the conventional motor, so that the cost does not increase.

In the above invention, it is more preferable that the rotor bush is formed integrally with the rotor. Thereby, there is an advantage that the number of parts is reduced and the cost can be reduced due to the simplification of the configuration.

[0013]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a motor unit 20 in a DC brushless motor according to one embodiment of the present invention.
The same or equivalent components are denoted by the same reference numerals and description thereof will be omitted. The only difference between the motor unit 20 and the motor unit 1 shown in FIG. 5 is that the shape of the rotor bush 21 is different. That is, the rotor bush 21
5 has an end receiving surface 21 that slides on the upper end surface of the upper sleeve bearing 7 similarly to the rotor bush 14 in FIG.
Are integrally formed so as to protrude outward in the radial direction, and have a shape in which the holding portion 21b has a side receiving surface 21c that is in sliding contact with the outer peripheral surface of the upper end of the upper sleeve bearing 7. The rotor bush 21 is fixed to the rotor 10 as in FIG.

Next, a supplementary description of the motor unit 20 will be given. The lower sleeve bearing 8 has a slightly larger diameter than the upper sleeve bearing 7, and accordingly, the bearing holder 4
A concave portion 4a into which the peripheral end portion of the lower sleeve bearing 8 is fitted is formed. The lower end of the lower sleeve bearing 8 is fitted into the concave portion 4 a, the upper peripheral surface is applied to the holding surface 4 b which is the upper surface of the concave portion 4 a, and the lower end surface is fitted by the washer 22 fitted to the shaft 9. It is supported in a retaining state. The supporting structure of the lower sleeve bearing 8 is the same in the motor portion 1 of the conventional motor shown in FIG. 5, and also in the conventional motor portion 1, the lower sleeve bearing 8 has the above-described supporting structure. As a result, a larger load was applied to the inclination of the shaft 9 than to the upper sleeve bearing 7. The circuit board 17 is provided with a rotational position detector 23 composed of a Hall element or a Hall IC, and the like.
1 is mounted in an arrangement facing and close to 1.

FIG. 2 is a plan view showing the entire DC brushless motor of this embodiment, and FIG. 3 is a side view showing the entire motor. In these figures, the same parts as those in FIG. The code is attached. This motor is composed of a motor section 20 and a circuit board 17, and at the four corners of the bracket 2, as shown in FIG. 2, mounting pieces 27 having screw insertion holes 24 are bent one step lower as shown in FIG. Is formed. The motor is adapted to be attached to an applicable electronic device using the four attachment pieces 27. As shown in FIG. 3, the bracket 2 integrally has a connection piece 28 formed by bending a part thereof one step higher. The connection piece 28 is electrically connected to the ground of the circuit board 17. You.

This DC brushless motor uses a rotor bush 21 to incline the shaft 9 by a load caused by the transmission gear 17 of the applicable device shown in FIG. 5 meshing with the screw teeth 18 of the shaft 9 from one side. In addition to the end receiving surfaces 21a, the side receiving surfaces 21c effectively prevent sliding while sliding on the upper sleeve bearing 7, and at the same time, the upper sleeve bearing 7 shares and receives the load force applied to the shaft 9. Therefore, unlike the conventional motor, the load applied to the shaft 9 does not act intensively on the lower sleeve bearing 8. Therefore, the lower sleeve bearing 8
In the first embodiment, the load caused by the tilt force applied to the shaft 9 is reduced as compared with the conventional motor. Since the sleeve bearings 7 and 8 have a characteristic that the life becomes longer as the surface pressure received from the shaft 9 is smaller, the life of the lower sleeve bearing 8 can be sufficiently ensured.

This motor has a simple structure in which a holding portion 21b having a side receiving surface 21c is formed integrally with the rotor bush 21, and the shape of the rotor bush 21 is different from that of the rotor bush 14 of the conventional motor. Since only the change is made, there is no increase in cost because the number of parts does not increase.

FIG. 4 shows a DC according to another embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing a motor unit 29 of the brushless motor. In this figure, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.
Only the configuration different from the above will be described. This motor part 2
9 is different from the motor section 20 of FIG. 1 in that the upper sleeve bearing 30 is integrally formed with a supported piece 30a extending radially outward from an upper end portion thereof.
Are supported by the supported surface 30b, which is the lower surface of the supported piece 30a, sliding on the upper end surface of the bearing holder 4, and further, the rotor bush 31 slides against the upper end surface of the upper sleeve bearing 7. A holding portion 31b having a surface 31a and covering the supported piece 30a of the upper sleeve bearing 7 is integrally protruded from the peripheral end portion, and the holding portion 3b is provided.
1b has only a configuration having a side receiving surface 31c that slides on the outer surface of the supported piece 30a of the upper sleeve bearing 7. Note that this rotor bush 31 is similar to that shown in FIG.
Similarly to the above, it is fixed to the rotor 10.

In this DC brushless motor, the transmission gear 19 of the applicable device is such that the screw teeth 18 of the shaft 9 are
The inclination force that the shaft 9 receives by meshing with
In addition to being able to be effectively prevented not only by the end receiving surface 31a of the rotor bush 31 but also by the side receiving surface 31c, the upper sleeve bearing 30 is inclined to the bearing holder 4 via the supported surface 30b. Since the upper sleeve bearing 7 is supported so as to prevent the load, the upper sleeve bearing 7 can more reliably share and receive the load applied to the shaft 9. for that reason,
In the lower sleeve bearing 8, since the load applied by the tilting force applied to the shaft 9 is further reduced as compared with the case of the embodiment, the life of the lower sleeve bearing 8 can be kept longer.

In this DC brushless motor, a supported piece 30a having a supported surface 30b is formed integrally with the upper sleeve bearing 30, and a holding portion 31b having a side receiving surface 31c is formed integrally with the rotor bush 31. 5 as in the first embodiment.
Since the number of parts is not increased as compared with the conventional motor, no cost increase is caused.

In each of the above embodiments, the rotor 1
0, the rotor bushes 21 and 31 provided separately are fixed to the rotor 10.
Even if the ring-shaped rotor bush portion having the same shape as that of the rotor bush 1 or 31 is formed integrally with the rotor 10, the same effect as described above can be obtained. There is an advantage that the cost can be reduced.

[0022]

As described above, according to the DC brushless motor of the present invention, the rotor bush which is integrated with the rotor and is slidably provided on the sleeve bearing covers the peripheral edge of the sleeve bearing. And the receiving surface that slides on the outer peripheral surface of the end of the sleeve bearing in the holding portion is integrally formed, so that the applicable device is connected to one end of the shaft for transmitting the rotational force. The bearing surface of the rotor bush effectively prevents the bearing surface of the rotor bush from sliding against the sleeve bearing, and the load applied to the shaft is arranged on the side opposite to one end of the shaft. Since the sleeve bearing is shared and received, the load applied to the shaft unlike the conventional motor does not act intensively on the sleeve bearing at one end. Therefore, the load attributable to the tilt force applied to the shaft is reduced in the sleeve bearing on one end side compared to the conventional motor, and the surface pressure received from the shaft is reduced, so that the life can be sufficiently ensured. Further, this motor has a simple configuration in which the holding portion having the receiving surface is formed integrally with the rotor bush, and the number of parts does not increase compared to the rotor bush of the conventional motor, so that no cost increase is caused. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a motor unit in a DC brushless motor according to one embodiment of the present invention.

FIG. 2 is a plan view showing the whole of the motor.

FIG. 3 is a side view showing the whole of the motor.

FIG. 4 is a longitudinal sectional view showing a motor unit in a DC brushless motor according to another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a motor unit in a conventional DC brushless motor.

[Explanation of symbols]

 2 Bracket 4 Bearing holder 7, 8, 30 Sleeve bearing 9 Shaft 10 Rotor 11 Rotor magnet 12 Stator 18 Screw tooth (teeth portion) 21, 31 Rotor bush 21b, 31b Holding portion 21c, 31c End receiving surface (receiving surface) 30a Supported piece 30b Supported surface

Claims (3)

[Claims] A fixing member having a cylindrical bearing holder;
A shaft rotatably supported by the bearing holder via a plurality of sleeve bearings, and having a rotational force transmitted from one end derived from the bearing holder; and a rotor magnet fixed to the other end of the shaft. A stator mounted on the fixed member facing the rotor magnet, and slidably provided on the sleeve bearing integrated with the rotor and disposed on the other end side of the shaft. A holding portion that covers a peripheral edge of the sleeve bearing facing the rotor bush, and a receiving surface that slides on an outer peripheral surface of an end of the sleeve bearing in the holding portion. Wherein the DC brushless motor is integrally formed. 2. A supported piece extending radially outward from an end of the sleeve bearing on the other end side of the shaft, and abutment supported on a peripheral edge of an end face of the bearing holder in the supported piece. 2. The D according to claim 1, wherein the supported surface is integrally formed, and the rotor bush is disposed such that the receiving surface is in sliding contact with an outer peripheral surface of the supported piece. 3.
C brushless motor. 3. The DC brushless motor according to claim 1, wherein the rotor bush is formed integrally with the rotor.