JPH0888952A - Bearing structure of small-sized motor - Google Patents

Abstract

PURPOSE: To provide a bearing structure of a small-sized motor which can stabilize the performance of itself for a long period and can elongate the life. CONSTITUTION: In the bearing structure of a small-sized motor which is constituted by bearing the middle section of a rotor shaft 20, where a feed screw part 20a is made at on end and also the small-sized motor body is installed at the other end, rotatably with the oil-containing slide bearing 30 attached to the stator, a screw part 20b is made up to the position leading to the slide part 20d with the slide bearing 30 continuously from the feed screw part 20a, at the rotor shaft 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a small motor used as a motor for driving an autofocus of a camera.

[0002]

2. Description of the Related Art In recent years, with downsizing and cost reduction of devices such as cameras with automatic focusing function and FDD, downsizing and cost reduction of small motors used in these devices are also required. FIG. 5 shows a structure of a stepping motor with a feed screw, which is a typical small motor used for autofocus driving of a camera. In FIG.
The stator 1 is composed of two claw pole type yoke units 5 and 6, and a cylindrical permanent magnet 2a fixed to a rotor shaft 2 is rotatably arranged on the inner peripheral portion of the stator 1. The permanent magnet 2a is attached to one end side of the long rotor shaft 2, that is, the right end side in the illustrated case, and the feed screw portion 2b is formed on the other end side of the rotor shaft 2, that is, the left end side in the illustrated case. There is. A drive unit for autofocus of a video camera is screwed into the feed screw portion 2b,
By driving the stepping motor, it moves to the left and right in the figure along the feed screw portion 2b.

A leaf spring component 7 is arranged on the right end surface of the right yoke unit 6 in FIG. 5, and is fixed to the yoke unit 6 by welding. The central portion of the leaf spring component 7 abuts the steel ball 8 (thrust bearing) on the right end surface of the rotor shaft 2 to constantly push the rotor shaft 2 to the left.
A front plate 4 is attached to the left end surface of the left yoke unit 5, and a support frame 3 having a substantially U-shaped cross section is fixed to the front plate 4. A cylindrical plain bearing 3a is provided penetrating the right vertical wall of the support frame 3 and the front plate 4, and a concave bearing 3b is attached to the left vertical wall of the support frame 3 and these bearings 3a are provided. , 3b rotatably support the middle portion and the tip portion of the long rotor shaft 2.

The cylindrical plain bearing 3a is made of an oil-impregnated sintered metal alloy, and the inner diameter thereof is formed to be slightly larger than the diameter of the rotor shaft 2, so that the rotor shaft 2 has the plain bearing 3a.
It is inserted into and is rotatably supported. At this time, the lubricating oil contained in the plain bearing 3a exudes and an oil film is formed on the inner peripheral surface thereof, so that the rotor shaft 2 can be smoothly rotated.

In this rotor shaft 2, when the drive part of the external equipment screwed to the feed screw part 2b is moved, it is natural to screw the drive part to the sliding part with the slide bearing 3a. However, it is impossible because the slide bearing 3a hinders the movement. Therefore, the feed screw portion 2b
Is finished at a position before the sliding portion with the slide bearing 3a.

[0006]

However, in the bearing structure of the small motor as described above, the sliding bearing 3a is also small because the motor itself is small. Therefore, the amount of the lubricating oil impregnated in the sliding bearing 3a becomes small, and as the lubricating oil in the sliding bearing 3a becomes smaller, the running out of lubricating oil easily occurs, the bearing friction increases, and the friction loss increases. Therefore, there is a problem that the motor performance is deteriorated and the life is shortened.

Particularly, in a small motor having a rotor shaft diameter of about 10 mm, which is used for autofocusing of a video camera, the theoretical output torque is 10 gf · cm or less, but the bearing loss is 1 to 10. 3 gf · cm
Then, 10 to 30% or more of the output torque is wasted as bearing loss, and there is a problem that this bearing loss becomes a major obstacle to improvement of motor performance.

In order to reduce the bearing loss, it is conceivable to reduce the sliding area by increasing the gap between the inner diameter of the slide bearing 3a and the diameter of the rotor shaft 2 in order to reduce the bearing loss. It cannot be used because the gap causes play and vibration or noise is generated when the rotor shaft 2 rotates.

Further, it has been proposed that low friction coefficient material such as molybdenum disulfide is used as the material of the slide bearing 3a, but the low friction coefficient material such as molybdenum disulfide is expensive. Therefore, it cannot be adopted because it hinders the price reduction of small motors.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a bearing structure for a small motor capable of stabilizing motor performance for a long period of time and prolonging its service life.

[0011]

In order to achieve the above object, according to the present invention, the intermediate portion of the rotor shaft having the feed screw portion formed on one end side and the small motor body mounted on the other end side is fixed to the stator. In a bearing structure of a small motor that is rotatably supported by a slide bearing attached to the rotor shaft, a threaded portion is formed on the rotor shaft up to a position continuous with the feed screw portion and reaching a sliding portion with the slide bearing. It has been done.

Preferably, the slide bearing is an oil-impregnated bearing.

[0013]

Since the threaded portion is formed on the rotor shaft continuously to the feed screw portion up to the position where it slides with the slide bearing, lubricating oil is replenished to the feed screw portion or the threaded portion. As a result, when the rotor shaft rotates, the lubricating oil reaches the sliding portion with the slide bearing by using the screw portion formed continuously with the feed screw portion as a transmission path, and it is possible to prevent the occurrence of lubricating oil shortage.

Further, since the threaded portion is formed on the rotor shaft up to the position where it slides with the slide bearing,
The sliding area (the contact area between the outer periphery of the screw portion and the inner peripheral surface of the sliding bearing) is reduced, and the bearing loss can be reduced.

When the sliding bearing is an oil-impregnated bearing, the sliding bearing can be impregnated with the lubricating oil and held, so that the frequency of lubricating oil supply can be reduced.

[0016]

1 to 3 show a bearing structure of a stepping motor with a feed screw according to a preferred embodiment of the present invention,
FIG. 4 shows the entire stepping motor with a feed screw having the bearing structure of FIG. In the present embodiment, the parts other than the bearing structure of FIGS. 1 to 3 are basically the same as the conventional stepping motor of FIG. 5, and the same parts are denoted by the same reference numerals and the description thereof will be omitted.

As shown in FIGS. 1 to 4, a feed screw portion 20a is formed on one end side of the rotor shaft 20, and a small motor body is mounted on the other end side of the rotor shaft 20. Is rotatably supported by a slide bearing 30 attached to the stator 1.

The rotor shaft 20 has a feed screw portion 20a.
The threaded portion 20b is formed continuously up to the position where the threaded portion 20d with the slide bearing 30 is reached.
In b, the thread groove is gradually shallowed as it approaches the small motor main body side, and the terminal end portion of the screw formed so that the thread formation is finally completed is formed.
This terminal portion is referred to as an incomplete screw portion 20c.

A groove 30a having a cylindrical shape concentric with the rotor shaft 20 is cut out at an end of the slide bearing 30 on the side of the small motor body (hereinafter, this groove is referred to as an escape groove 30a). Thus, the frictional loss is reduced by reducing the sliding area with the rotor shaft 20 in a state where sufficient strength is secured without narrowing the width of the bearing 20 in the axial direction.

In the embodiment shown in FIG. 1, the state in which the incomplete screw portion 20c is formed from a position before reaching the sliding portion 20d with the sliding bearing 30 and enters the sliding portion 20d with the sliding bearing 30. The formation is completed at.

In the embodiment shown in FIG. 2, the incomplete thread portion 20c is entirely formed in the sliding portion 20d with the sliding bearing 30, and the sliding area with the sliding bearing 30 is larger than that in the case of FIG. (Contact area between the outer circumference of the screw part and the inner peripheral surface of the slide bearing) is reduced, and friction loss can be reduced.

In the embodiment shown in FIG. 3, the screw portion 20
b is formed up to the side of the small motor main body beyond the sliding portion 20d with the sliding bearing 30, and the sliding area with the sliding bearing 30 is further reduced, and the friction loss can be further reduced, as compared with the case of FIG. Further, the screw portion 20c is the permanent magnet 2a.
In the case where it is formed up to the position where it reaches the fixing portion, the thread and the thread groove become uneven and become a rough surface at the connection surface with the permanent magnet 2a, so that the rotor shaft 20 and the permanent magnet 2a When the integration is performed with an adhesive or the like, the adhesive strength can be improved.

In the above structure, when the rotor shaft 20 rotates by replenishing the feed screw portion 20a or the screw portion 20b with lubricating oil, the feed screw portion 20a and the screw portion 20b formed continuously thereto are transmitted. Since the lubricating oil reaches the sliding portion 20b with the slide bearing 30 as a path, the motor shaft 20 rotates smoothly without running out of the lubricating oil.

Further, since the screw portion 20b is formed,
Since the area of the sliding portion 20d of the rotor shaft 20 with respect to the slide bearing 30 is reduced, the bearing loss can be reduced.

Furthermore, the sliding portion 20 with the slide bearing 30
Since the lubricating oil can be supplied to d, the sliding bearing 30 need not be oil-impregnated, but is preferably an oil-impregnated bearing. In this case, since the plain bearing 30 can be impregnated with the lubricating oil and held, the frequency of lubricating oil supply can be reduced.

The screw portion 20b is the feed screw portion 20a.
It is not necessary to use the same screw specifications as those of the above, but the shape and dimensional specifications such as thread, thread groove, pitch, etc. are appropriately set according to the purpose of transmission of lubricating oil and reduction of bearing loss. Here, if the width of the thread groove formed in the threaded portion 20b in the axial direction of the outermost diameter is made smaller than the axial length of the sliding portion 20d with the slide bearing 30, the biting phenomenon can be reliably prevented.

Further, since lubricating oil can be supplied to the slide bearing 30 to ensure the smooth rotation of the rotor shaft 20, the radial gap between the rotor shaft 20 and the slide bearing 30 is increased for the purpose of reducing bearing loss. There is no need. Therefore, vibration and noise due to the play due to this gap will not occur.

Further, the lubricating oil is applied to the bearing 30 of the rotor shaft 20.
Since the sliding portion 20d can be replenished, the bearing loss can be reduced without using an expensive low friction coefficient material such as molybdenum disulfide as the material of the bearing 30, and the cost increase can be suppressed.

[0029]

By supplying lubricating oil to the feed screw portion or the screw portion of the rotor shaft, it is possible to prevent running out of lubricating oil in the sliding portion of the screw portion with the bearing. Therefore, bearing loss due to running out of lubricating oil can be suppressed and smooth rotation of the motor shaft can always be ensured, and long-term stabilization of the motor performance and long life can be achieved.

Further, since the threaded portion is formed on the rotor shaft up to the position where it slides with the slide bearing, the sliding area is reduced and the bearing loss can be reduced. Therefore, the performance of the motor can be improved and the life of the motor can be extended.

Further, when the sliding bearing is an oil-impregnated bearing, the sliding bearing can be impregnated with the lubricating oil and held, so that the frequency of lubricating oil supply can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a bearing structure of a small motor according to the present invention.

FIG. 2 is a sectional view showing a bearing structure of a small-sized motor according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a bearing structure of a small-sized motor according to still another embodiment of the present invention.

FIG. 4 is a sectional view showing a small motor provided with a bearing structure according to the present invention.

FIG. 5 is a sectional view showing a small motor having a conventional bearing structure.

[Explanation of symbols]

1 Stator 20 Rotor shaft 2a Permanent magnet 20a Feed screw part 3 Support frame 20b Screw part 3b Concave bearing 20c Incomplete screw part 3c Steel ball 20d Sliding part 4 Front plate 30 Sliding bearing 5, 6 Yoke unit 30a Escape groove 7 Leaf spring Parts 8 Steel ball

Claims (2)

[Claims] Claims: 1. A small size in which a middle portion of a rotor shaft having a feed screw portion formed on one end side and a small motor main body mounted on the other end side is rotatably supported by a slide bearing attached to a stator. In the bearing structure of the motor, a threaded portion is formed on the rotor shaft so as to be continuous with the feed screw portion and reach a position where it slides with the slide bearing. 2. The bearing structure for a small motor according to claim 1, wherein the slide bearing is an oil-impregnated bearing.