JPH09331647A - Bearing equipment for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent oil from vaporizing and scattering and enable always stable oil supply, by forming a dynamic pressure generating trench in a rotary shaft or a sleeve as dynamic pressure bearing structure, and arranging a sintered oil retaining bearing on the outer peripheral of the sleeve. SOLUTION: A sintered oil retaining bearing 11 wherein porous parts are formed is forcibly inserted in the inner peripheral surface of a bearing holder 1a. A sleeve 12 is forcibly inserted in the inner peripheral of the sintered oil retaining bearing 11 and held. When the rotary shaft 6 begins to rotate, the temperature of the bearing part rises, and oil in the bearing 11 flows out. The oil enters a dynamic pressure generating trench (2), and acts as a dynamic pressure bearing. When the rotation of the rotary shaft 6 stops in an arrow mark (3), the temperature of the bearing pat decreases, the oil which has flown out from (1) returns the porous part of the bearing 11. By the effect of this circulation, oil does not vaporize and scatter but stable oil supply is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device for a motor, and more particularly to improvement of a hydrodynamic bearing structure.

[0002]

2. Description of the Related Art Conventionally, various types of bearings for a motor such as a small motor using a hydrodynamic bearing structure have been proposed. For example, JP-A-7-170740 and JP-A-8-9587. There was one described in.

In the above, the inner diameter of the rotary shaft, the dynamic pressure generating groove formed on the inner peripheral surface of the sleeve, and the inner peripheral surface of the sleeve on both sides of the radial bearing made of oil is made larger than that of the dynamic pressure generating groove. An oil sump is provided, and projections smaller than the inner diameter of the oil sump are provided at both ends of the inner peripheral surface of the sleeve. With this configuration, the protrusions provided at both ends of the inner peripheral surface of the sleeve prevent dust and dirt from entering, and suppress evaporation and scattering of oil.

[0004]

However, since the rotary shaft is generally made of stainless steel and the sleeve is made of brass, it is difficult to retain oil. Even with the dynamic pressure bearing structure as described above, it is impossible to prevent evaporation and scattering of oil, and it has been impossible to supply oil for a long period of time. As a result, the dynamic pressure effect becomes weaker over time, causing shaft runout, and problems such as seizure occur due to contact with the sleeve, which adversely affects durability.

Therefore, the present invention solves the above problems and prevents the evaporation and scattering of oil in the dynamic pressure bearing structure so that the oil can be supplied for a long period of time and has a long life and excellent reliability. It is intended to provide a bearing device for a motor.

[0006]

According to the present invention, as a dynamic pressure bearing structure, a dynamic pressure generating groove is formed in either one of a rotary shaft and a sleeve, and a sintered oil-impregnated bearing is arranged on the outer circumference of the sleeve to form an oil. It is possible to prevent the evaporation and scattering of the oil, and to realize a stable oil supply at all times, thereby greatly improving the durability.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A motor bearing device of the present invention comprises a rotary shaft and a sleeve, and a dynamic pressure generating groove is formed on either the outer peripheral surface of the rotary shaft or the inner peripheral surface of the sleeve. In this motor bearing device, a sintered oil-impregnated bearing is arranged on the outer circumference of the sleeve. Further, it is effective that the axial length of the sintered oil-impregnated bearing is larger than the axial length of the sleeve. Further, the sintered oil-impregnated bearing,
It is preferable that the sleeve has a first diameter into which the sleeve is press-fitted and a second diameter smaller than the first diameter.

[0008]

[First Embodiment] FIG. 1 is a sectional view of a main portion of a brushless motor according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a bearing portion in FIG. In FIG. 1, reference numeral 1 denotes a bearing housing made of aluminum die-casting, which also serves as a bracket, and is fixed to the opening edge of the outer casing 2. A bearing holder 1a is formed in the center of the bearing housing 1, and a stator core 3 is fixed to the outer circumference.

Further, a magnet case 8 having a field magnet 7 facing the outer periphery of the stator core 3 is fixed to the rotary shaft 6 so that the thrust bearing plate 2a provided on the outer casing 2 can pivotally support it. It has become.

As shown in FIG. 2, a sintered oil-impregnated bearing 11 having a large number of pores is press-fitted into the inner peripheral surface of the bearing holder 1a, and the sintered oil-impregnated bearing 11 is further inserted.
A sleeve 12 is press-fitted and held on the inner peripheral surface of the. The sleeve 12 and the sintered oil-impregnated bearing 11 configured to have a length greater than the axial length of the sleeve 12 are arranged at two axial positions as an integral bearing portion to hold the rotary shaft 6 in which the dynamic pressure generating groove is formed. are doing.

Next, the principle of oil supply of the motor bearing device constructed as described above will be described. As shown in FIG. 2, when the rotary shaft 6 starts to rotate, the oil in the sintered oil-impregnated bearing 11 starts to flow out due to the temperature rise of the bearing portion as shown by the arrow. The oil that has flowed out enters the dynamic pressure generating groove portion of the rotary shaft 6 and acts as a dynamic pressure bearing. Then, when the rotation of the rotary shaft 6 is stopped as indicated by an arrow, the oil that has flowed out further due to the temperature decrease of the bearing portion is the original sintered oil-impregnated bearing 11 this time.
Return to the porus. Due to this circulation action, oil does not evaporate or scatter, and a stable oil supply can always be realized.

If the axial length of the sintered oil-impregnated bearing 11 is made larger than the axial length of the sleeve 12 and the sleeve 12 is arranged substantially at the center of the sintered oil-impregnated bearing 11 in the axial direction. Since the oil in the sintered oil-impregnated bearing 11 is more easily circulated, the dynamic pressure effect can be easily improved, and smooth rotation can be realized while preventing shaft runout of the rotary shaft 6.

[0013]

[Second Embodiment] FIG. 3 is a cross-sectional view of a main portion showing a bearing portion according to another embodiment of the present invention. In the figure, the sintered oil-impregnated bearing 21 has a first diameter A into which the sleeve 12 is press-fitted on the inner peripheral surface thereof and a second diameter A smaller than the first diameter A.
And a diameter B of. By doing so, the sleeve 12 press-fitted into the first diameter A of the sintered oil-impregnated bearing 21 becomes
The axial position is determined by the stepped portion 21a formed from the diameter A to the second diameter B, so that the sleeve 12 can be easily positioned.

Further, since the sintered oil-impregnated bearing 21 is provided with the second diameter B smaller than the first diameter A as described above, it is easy to draw in oil. That is, since the gap between the rotary shaft 6 and the rotating shaft 6 is narrowed by the second diameter B, the oil flowing out from the sintered oil-impregnated bearing 21 can be easily pulled back into the original sintered oil-impregnated bearing 21 as the temperature rises, and the oil circulation. Becomes smoother. Further, if the sleeve 12 is press-fitted into the sintered oil-impregnated bearing 21 and then the portion on the side opposite to the stepped portion 21a is deformed under pressure, the sleeve 12 will not be displaced in the axial direction, and it will be extremely easy to handle.

[0015]

[Third Embodiment] FIG. 4 is a cross-sectional view of a main portion showing a bearing portion according to another embodiment of the present invention. In each of the above-described embodiments, the sintered oil-impregnated bearings are arranged at two locations in the axial direction on the inner peripheral surface of the bearing holder 1a, whereas in the present embodiment, a cylindrical burnt formed long in the axial direction is formed. The oil-impregnated bearing 31 is used. By doing so, since only one sintered oil-impregnated bearing is press-fitted into the bearing holder 1a, the assembly becomes simple and the workability can be greatly improved.

The present invention is not limited to the above-described embodiments, but can be variously modified and implemented without departing from the gist of the present invention. For example, although the brushless motor is described in detail in each of the above embodiments, a brush motor may be used without any problem. Further, it goes without saying that the dynamic pressure generating groove may be formed on the sleeve instead of the rotating shaft, and the shape thereof can be changed in addition to the above-mentioned respective embodiments.

[0017]

As described above, according to the present invention, the rotary shaft and the sleeve are provided, and the dynamic pressure generating groove is formed on either the outer peripheral surface of the rotary shaft or the inner peripheral surface of the sleeve. Since the sintered oil-impregnated bearing is arranged on the outer circumference of the sleeve,
It is possible to realize stable oil supply by preventing evaporation and scattering of oil, and to significantly improve the service life of the oil, and to provide a highly reliable motor bearing device.

If the axial length of the sintered oil-impregnated bearing is set to be larger than the axial length of the sleeve, the oil can more easily circulate, and the dynamic pressure effect can be easily improved. Therefore, it is possible to realize smooth rotation while preventing shaft runout of the rotary shaft.

Further, since the sintered oil-impregnated bearing has the first diameter into which the sleeve is press-fitted and the second diameter smaller than the first diameter, the sleeve can be easily positioned. The oil can be drawn in easily and its circulation can be smoothed.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a brushless motor according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a bearing section in FIG.

FIG. 3 is a cross-sectional view of a main portion showing a bearing portion according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main portion showing a bearing portion according to another embodiment of the present invention.

[Explanation of symbols]

 1 ... Bearing housing 1a ... Bearing holder 6 ... Rotating shafts 11, 21, 31 ... Sintered oil-impregnated bearing 12 ... Sleeve

Claims (3)

[Claims] 1. A motor bearing device comprising a rotary shaft and a sleeve, wherein a dynamic pressure generating groove is formed on either the outer peripheral surface of the rotary shaft or the inner peripheral surface of the sleeve. A bearing device for a motor, characterized in that a sintered oil-impregnated bearing is arranged in the. 2. The bearing device for a motor according to claim 1, wherein an axial length of the sintered oil-impregnated bearing is larger than an axial length of the sleeve. 3. The bearing device for a motor according to claim 1, wherein the sintered oil-impregnated bearing has a first diameter into which the sleeve is press-fitted and a second diameter smaller than the first diameter.