JPH0821444A - Bearing device for motor - Google Patents

Abstract

PURPOSE:To provide a motor bearing device which can suppress the shaft deflection of a rotary shaft to the exceedingly small value with the simple structure, can reduce the number of parts, in an inexpensive manner. CONSTITUTION:As for a motor bearing device which has a shaft insertion hole 2 for the insertion of the rotary shaft of a motor at the center and uses a cylindrical shaped slide bearing 1 impregnated or coated with a lubricating agent, bearing surface parts 3 and 5 which support a rotary shaft in the vicinity of both the end parts of a shaft insertion hole are provided, and a large diameter part 7 having the larger diameter than that of a bearing surface part is provided between the bearing surface parts, and on one or both the bearing surface parts, pressure deflecting means 9 and 10 for deflecting the pressure of an oil film formed between the rotary shaft and the bearing surface part in the circumferential direction during the revolution of the rotary shaft are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor bearing device, and more particularly to a motor bearing device using a cylindrical plain bearing impregnated or coated with lubricating oil.

[0002]

2. Description of the Related Art Conventionally, as a bearing device for a motor, a pair of bearing members are coaxially held at intervals with a cylindrical bearing holding member, and the rotating shaft of the motor is supported by the pair of bearing members. It is generally configured to rotatably support. As the bearing members, there are roughly classified slide bearings and rolling bearings, which are used in various combinations depending on the application and performance of the motor. Further, various structures of so-called dynamic pressure groove bearings have been proposed, which include one cylindrical bearing member and a rotary shaft having a groove for generating dynamic pressure on the outer peripheral surface.

For rolling bearings such as ball bearings, by using an appropriate preloading means, the runout of the rotary shaft can be made highly accurate within a few micrometers.
Further, generally, the groove bearing has characteristics such as high rigidity, and since the rotating shaft can be supported in a non-contact state with respect to the bearing member, noise is small and the service life is long even at high speeds exceeding 10,000 rpm. There are features.

On the other hand, sliding bearings such as oilless metal are
The structure is simple and inexpensive, and as shown in FIG. 4, a structure in which a single component can support a rotary shaft at two locations in the axial direction,
That is, the hollow cylindrical bearing member (30) has two bearing surface portions (32) and (33) for rotatably supporting the rotary shaft (31) in the vicinity of both end surface portions thereof, and the bearing surface portion (32) between them. , (33) with a larger diameter portion (34) than the diameter of (33).

[0005]

However, although the groove bearing is generally suitable for a bearing device of a motor having a constant rotation direction, it is not suitable for a motor having a two-direction operation mode of forward rotation and reverse rotation. is there. Further, there is a drawback that the groove for generating the dynamic pressure is complicated and becomes an expensive part. Further, it is necessary to use two ball bearings in a pair or in combination with a slide bearing, which increases the number of parts and requires a separate preloading means.
There is a drawback that the bearing structure becomes complicated. Further, since the ball bearing itself is composed of a large number of parts such as an outer ring, an inner ring, balls, and a retainer, there is a drawback that noise and vibration are generated by the rolling of them, which is expensive.

Since the slide bearing has a structure in which the rotary shaft and the bearing member are supported while sliding, it is necessary to provide an appropriate gap (clearance) between the bearing member and the rotary shaft. . In order to reduce the runout of the rotating shaft, the smaller the clearance, the better. However, there are variations in the dimensions of the inner peripheral surface (bearing surface) of the bearing member and the outer peripheral surface of the rotating shaft, and changes in shape and dimensions due to temperature changes. In consideration of workability when inserting the rotary shaft into the bearing member, it is usually 2 to 10
It is set to about micrometer. However, when the clearance between the bearing surface portions (32) and (33) and the rotary shaft (31) is set to about 5 μm using the bearing member (30) as shown in FIG.
However, when the precession movement indicated by the alternate long and short dash line is performed, there is a drawback that the runout becomes about 10 to 20 micrometers in the vicinity of the tip of the rotary shaft (31) protruding from the bearing member (30).

The present invention has been made under such circumstances, and has a simple structure that suppresses the shaft runout of the rotary shaft, and has good workability and a small number of parts. Is provided.

[0008]

In order to solve the above-mentioned problems, the motor bearing device of the present invention is a cylinder provided with a lubricating oil at the center thereof and having a shaft insertion hole through which the rotation shaft of the motor is inserted. A bearing device using a sliding bearing, having bearing surface portions rotatably supporting a rotating shaft near both end surface portions of the shaft insertion hole, and having a diameter between the two bearing surface portions rather than the bearing surface portions. And a large-diameter portion of the bearing surface portion, and also on one or both of the bearing surface portions, a biasing means for unevenly distributing the pressure of the oil film formed between the rotating shaft and the bearing surface portion in the circumferential direction when the rotating shaft rotates. Is configured.

The plain bearing may be formed of a sintered oil-impregnated alloy, or the two bearing surface portions may have different axial lengths.

The biasing means may be a groove formed in the bearing surface in the axial direction.

[0011]

The bearing device for a motor according to the present invention, which is provided with such means, has a bearing surface portion on which the rotation shaft of the motor is rotatably supported.
Since the pressure of the oil film formed between the rotating shaft and the bearing surface portion at the time of rotation is locally low or high in the circumferential direction, the rotating shaft is slipped due to the unevenly distributed pressure. It is constrained to a fixed position in the bearing and does not cause precession.

Further, when the sliding bearing is made of a sintered alloy impregnated with lubricating oil, a good oil film is formed on the sliding portion between the rotating shaft and the bearing surface portion, and smooth rotation can be obtained.

Further, if the axial lengths of the two bearing surface portions are adjusted by the position of the center of gravity of the entire rotor including the rotating shaft,
Friction loss can be reduced while more effectively suppressing shaft runout.

If the pressure biasing means is a groove formed in the bearing surface portion, a portion having a relatively low pressure of the oil film in the circumferential direction can be formed with a simple shape.

[0015]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a partially broken perspective view showing an embodiment of a slide bearing used in the present invention, FIG. 2 is a longitudinal sectional view showing an embodiment of a bearing device of the present invention together with a motor, and FIG. 3 is an operation of the present invention. 4A and 4B are a vertical cross-sectional view and a plan view for explaining FIG.

In FIG. 1, reference numeral (1) is an example of a sliding bearing used in the present invention, which is formed porous by, for example, sintering a copper-based alloy powder. The sliding bearing (1) is impregnated with lubricating oil and is a so-called oil-free bearing (oilless metal). This sliding bearing (1)
A shaft insertion hole (2) through which a rotation shaft (11) of a motor to be described later is inserted is formed at the center of the shaft insertion hole (2), and the bearing surface portion (3) is provided in the vicinity of both end surface portions of the shaft insertion hole (2). And (5) are formed with high dimensional accuracy. A large diameter portion (7) having a larger diameter than the bearing surface portions (3) and (5) is formed between these two bearing surface portions (3) and (5). Further, the bearing surface portions (3) and (5) are formed with shallow recessed grooves (9) and (10) extending in the axial direction as a biasing means to form a slide bearing (1).

FIG. 2 is a vertical cross-sectional view showing an example of a bearing device for a motor according to the present invention used in an external rotor type brushless motor. In the figure, a rotary shaft (11) is attached to the center of a cup-shaped rotor hub (13), and a ring-shaped rotor drive (13) is provided on the inner peripheral surface of the side wall of the rotor hub (13). The field magnet (15) is fixed to form the rotor of the motor.

On the stator side, a housing bracket having a through hole for holding the slide bearing (1) and the shaft sealing device (28) in the center and a bottom plate portion for accommodating the circuit board (26) on the outer peripheral portion thereof. A drive coil (24) on the outer periphery of (20)
The wound armature core (22) is attached and configured.

The rotating shaft (11) has two bearing surface portions (3) and (5) of a cylindrical plain bearing (1) as shown in FIG.
Is rotatably supported by. Here, the axial length of the bearing surface portion (3) or (5) will be described.
First, in order to suppress the axial runout of the rotating shaft (11), it is preferable to increase the axial length of the bearing surface portions (3) and (5). However, when the axial length of the bearing surface portions (3) and (5) is increased, friction loss due to sliding between the bearing surface portions (3) and (5) and the rotating shaft (11) increases, and the driving current of the motor increases. Therefore, there is a problem that power consumption increases. Therefore, it is necessary to determine the dimensions in consideration of these relationships.

When the rotating shaft (11) makes a precession movement, it makes a conical rotation centering on the center of gravity, so the shake near the center of gravity is small, and the farther from the center of gravity the larger the shake.
In the example shown in FIG. 2, the center of gravity of the entire rotor is the rotation axis (1
It is near the central portion in the axial direction of 1). Therefore, the rotation axis (1
The runout near the center of 1) is relatively small, and the rotation axis (1
The runout increases at both ends of 1). Therefore, in the illustrated example, the two bearing surface portions (3) and (5) of the plain bearing (1) are included.
Bearing surface part (3) close to the central part of the rotating shaft (11)
And the axial length of the bearing surface portion (5) that supports the end of the rotary shaft (11) is set to be relatively long so that friction loss does not become a problem.

Next, the operation of the biasing means will be described with reference to FIG. FIG. 3 (a) is a vertical sectional view showing the relationship between the sliding bearing (1) and the rotating shaft (11) used in the motor bearing device of the present invention, and FIG. 3 (b) is a plan view thereof.
FIG. 3A is a cross section taken along the line AA of FIG.

The rotating shaft (1) supported by the plain bearing (1)
When 1) rotates, the lubricating oil (not shown) with which the plain bearing (1) is impregnated forms a seepage oil film on the bearing surface portions (3) and (5) by its pumping action. Therefore,
The rotating shaft (11) is supported by the bearing surface portions (3) and (5) through the oil film. Here, since the bearing grooves (3) and (5) are formed with the concave grooves (9) and (10) as the biasing means, respectively, the rotating shaft (11) and the bearing surface (3) ( 5), the pressure of the oil film in the concave grooves (9) and (10) becomes low, and a pressure difference occurs in the circumferential direction. As a result, the rotating shaft (11) has concave grooves (9) (1
A force that pushes it toward 0) acts, and the position of the rotating shaft (11) is stabilized.

In the drawings, the clearance between the rotary shaft (11) and the bearing surface portions (3) and (5) and the depths of the concave grooves (9) and (10) are exaggerated in order to facilitate understanding. And illustrated. Actually, the design value of the clearance between the bearing surface portions (3) and (5) and the rotating shaft (11) (the difference between the radius of the bearing surface portions (3) and (5) and the radius of the rotating shaft (11)) is 5 It is of the order of micrometers, at which time the groove (9)
The depth of (10) is not less than twice the clearance, for example, about 10 to 50 micrometers.

[0024]

As described above, the bearing device for a motor of the present invention is provided with the biasing means for unevenly distributing the pressure of the oil film in the circumferential direction on the bearing surface portion that rotatably supports the rotary shaft. The uneven pressure stabilizes the position of the rotary shaft, and the shake of the shaft can be suppressed to an extremely small value. Further, since the ball bearing, the groove shaft and the like are not used, the structure of the bearing device is simple and inexpensive, and the present invention can be applied to the forward and reverse rotation type motors.

Further, considering the position of the center of gravity of the rotor, 2
By setting the axial lengths of the two bearing surface portions, shaft runout can be suppressed more effectively, and power consumption due to friction loss can be reduced.

[Brief description of drawings]

FIG. 1 is a partially broken perspective view showing an example of a slide bearing used in a bearing device for a motor of the present invention.

FIG. 2 is a longitudinal sectional view showing an embodiment of a motor bearing device of the present invention together with the motor.

3A and 3B are views for explaining the action of the bearing device for a motor of the present invention, FIG. 3A is a vertical cross-sectional view showing the relationship between a rotary shaft and a slide bearing, and FIG. 3B is a plan view thereof. Is.

FIG. 4 is a vertical sectional view showing an example of a conventional motor bearing device.

[Explanation of symbols]

 (1) (30) Slide bearing (2) Shaft insertion hole (3) (5) (32) (33) Bearing surface portion (7) (34) Large diameter portion (9) (10) Recessed groove (biasing means) (11) (31) Rotating shaft (13) Rotor hub (15) Field magnet (20) Housing bracket (22) Armature core (24) Drive coil (26) Circuit board (28) Shaft sealing device

Front page continued (72) Inventor Riki Akimoto 2-122, Mampei-cho, Kumagaya-shi, Saitama Kumagai Seimitsu Co., Ltd.

Claims (4)

[Claims] 1. A motor bearing device using a cylindrical plain bearing having a lubricating oil, the shaft inserting hole having a shaft inserting hole through which a rotary shaft of the motor is inserted, the shaft inserting hole being near both end surfaces thereof. Each of which has a bearing surface portion that rotatably supports the rotating shaft, and a large diameter portion having a diameter larger than the bearing surface portions is provided between the bearing surface portions, and the rotating shaft is provided on both or one of the bearing surface portions. A bearing device for a motor, comprising: a biasing means for biasing a pressure of an oil film formed between the rotary shaft and the bearing surface portion in a circumferential direction when the rotor rotates. 2. The motor bearing device according to claim 1, wherein the plain bearing is made of a sintered oil-impregnated alloy. 3. The motor bearing device according to claim 1, wherein the two bearing surface portions provided in the vicinity of both end surface portions of the shaft insertion hole are formed so as to have different axial lengths. 4. The motor bearing device according to claim 1, wherein the biasing means is a concave groove formed in the bearing surface portion in the axial direction.