JP2740439B2 - Fixed structure of sintered oil-impregnated bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing applicable to, for example, a motor.

[0002]

2. Description of the Related Art When a sintered oil-impregnated bearing is used as a bearing for rotatably supporting a spindle or other shaft in various motors, for example, a spindle motor for a floppy disk drive, the sintered oil-impregnated bearing is pressed into a bearing housing. .

[0003]

According to the conventional bearing structure in which the sintered oil-impregnated bearing is press-fitted into the housing, the dimensions of the housing are not always accurate. However, there is a drawback that the accuracy is deteriorated depending on the dimensional accuracy of the housing, and if the housing is to be machined with high accuracy, the cost will increase, and the housing itself is also made of die-cast or brass, which is expensive, There is a drawback that the operation for press-fitting the sintered oil-impregnated bearing is required, so that the assembly cost is increased. Therefore, for example, in the case of a motor, it is conceivable to press-fit a sintered oil-impregnated bearing directly into the inner periphery of a stator core without using a housing. Insufficient lubricating oil may cause seizure, or may cause other parts such as the stator core to adhere to the lubricating oil and become dirty.

The present invention has been made in view of such problems of the prior art, and eliminates the need for a housing by preventing the outflow of lubricating oil without using a bearing housing.
Thus, a highly accurate sintered oil-impregnated bearing can be obtained without being affected by the dimensional accuracy of the housing, and the cost of the housing itself and the press-fitting cost of the bearing can be reduced to achieve a significant cost reduction. It is an object of the present invention to provide an oil-impregnated bearing.

[0005]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 provides a rotary shaft and a support for the rotary shaft.
As well as the outer peripheral surface is 5% or less in area ratio
Sintered oil-impregnated bearing formed on
Stator core arranged radially outward with a gap
And a substrate supporting the sintered oil-impregnated bearing, and a head on one end side
And penetrate the stator core, and the other end is
The stator core is fixed by being screwed to the board
Between the screw head and the stator core.
Holding member, and a part of the holding member includes a sintered member.
Engages with the axial end surface of the oil bearing and applies the biasing force
The sintered oil-impregnated bearing is pressed and fixed to the substrate by
It is characterized by that. The invention according to claim 2 is characterized in that the pressing
Fixing the stator core to the substrate without using
Part of the above screw engages the axial end face of the sintered oil-impregnated bearing
Then, the sintered oil-impregnated bearing is attached to the substrate by the tightening force of these screws.
It is characterized by being pressed and fixed.

[0006]

By setting the porosity of the outer peripheral surface of the sintered oil-impregnated bearing to 5% or less in area ratio, there is almost no outflow of lubricating oil from the outer peripheral surface even if the sintered oil-impregnated bearing is not pressed into the bearing housing. Oil-impregnated sintered bearing, the pressing by Rukoto by the biasing force of <br/> pressing member that axial end face pressed or,
Some of the screws that fix the stator core are made of sintered oil-impregnated bearings.
Direction, and pressed by the tightening force of the screw
Thus , the spindle and the shaft can be rotatably supported by the sintered oil-impregnated bearing.

[0007]

Hereinafter, an embodiment of a fixed structure of a sintered oil-impregnated bearing according to the present invention will be described with reference to the drawings. The fixing structure of the sintered oil-impregnated bearing according to the present invention can be applied to various motors, rotary encoders, and the like that rotatably support a spindle or a shaft.
The example shown in FIG. 1 is an example of a floppy disk drive motor. In FIG. 1, a stator core 14 is fixed on a substrate 10 with mounting screws 18 with a ring-shaped spacer 12 interposed therebetween. A ring-shaped sintered oil-impregnated bearing 22 is arranged on the inner peripheral side of the spacer 12 and the stator core 14 with its central axis oriented in a direction orthogonal to the substrate 10 , arranged on the stator core 14 and fixed with set screws 18. The upper end surface 34 in the axial direction of the sintered oil-impregnated bearing 22 is pressed by the inner peripheral edge of the pressing member 16. Yo
More specifically, a screw 18 having a head on one end side
Penetrates the member 16, the stator core 14, and the spacer 12
At the same time, the other end of the screw 18 is screwed into the substrate 10.
As a result, the stator core 14 is fixed to the substrate 10,
Pressing between the head of screw 18 and stator core 14
The member 16 is interposed. Axial direction of sintered oil-impregnated bearing 22
A part of the holding member 16 is engaged with the end face, and the holding member 16
The sintered oil-impregnated bearing 22 is pressed against the substrate 10 by the urging force of
It has been fixed Te. A gap 25 is provided between the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 and the inner peripheral surface of the stator core 14. That is, the radially outer side than the sintered oil-impregnated bearing 22
The stator core 14 is disposed with a gap 25 on the side.
You.

The stator core 14 has an appropriate number of salient poles,
A drive coil 20 is wound around each salient pole. A spindle 26 as a rotating shaft is rotatably fitted on the inner peripheral side of the sintered oil-impregnated bearing 22. The lower end of the spindle 26 is in contact with the thrust receiver 24 attached to the substrate 10 on the inner peripheral side of the sintered oil-impregnated bearing 22. Sintered oil-impregnated bearing 2
The center boss of the cup-shaped rotor case 28 is fixed to the upper end of the spindle 26 protruding from the upper end of the spindle 2 by press fitting or the like. A ring-shaped rotor magnet 30 alternately magnetized in the circumferential direction is fixed to the inner peripheral surface of the peripheral wall of the rotor case 28. The inner peripheral surface of the magnet 30 faces the end surface of each salient pole of the stator core 14 with an appropriate gap. As is well known, the rotor is rotationally driven by controlling the energization of each drive coil 20.

The sintered oil-impregnated bearing 22 has a myriad of porosity, and the porosity appears on both the inner peripheral surface 31 and the outer peripheral surface 32 shown in FIG. The area ratio of the porous surface appearing on the inner peripheral surface and the outer peripheral surface of the conventional general oil-impregnated bearing varies, but is usually 10% or more. In contrast, in the sintered oil-impregnated bearing 22 according to the embodiment of the present invention, the outer peripheral surface 3
The area ratio of the porous body 2 is set to 5% or less, and the area ratio of the porous area of the inner peripheral surface 31 is a normal area ratio.

As described above, by setting the porous area ratio of the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 to 5% or less,
There is almost no outflow of lubricating oil from the outer peripheral surface 32 of the sintered oil-impregnated bearing 22. Therefore, it is not necessary to use a bearing housing as in the embodiment shown in FIG. 1, so that a highly accurate sintered oil-impregnated bearing can be obtained without being affected by the dimensional accuracy of the housing, and the cost of the housing itself can be reduced. In addition, it has become possible to significantly reduce costs by reducing the press-fitting cost of the bearing. Further, since the lubricating oil does not flow out from the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 without using the bearing housing, the periphery is not contaminated with the lubricating oil. Since the inner peripheral surface 31 of the sintered oil-impregnated bearing 22 has a normal area ratio, the space between the inner peripheral surface 31 and the spindle 26 is normally lubricated.

The following method is used to reduce the area ratio of the porous surface 32 of the sintered oil-impregnated bearing 22 to 5% or less.
Sintered oil-impregnated bearings have a sizing step in order to obtain dimensional accuracy after molding and sintering a powdery raw material into a predetermined shape. In this sizing step, the sizing margin on the outer diameter side is, for example, 20 μm. As described above, one method is to take more than usual. The sizing process is a type of plastic working in which compression is performed using a mold. However, by increasing the sizing allowance on the outer diameter side, the sintered oil-impregnated bearing 22 is formed.
Of the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 can be reduced to 5% or less as described above. Another method is to make the surface roughness of a die (die) used in the forming step and the sizing step of the sintered oil-impregnated bearing to, for example, about 1S . Also in this case, the amount of the porous material appearing on the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 is crushed and decreased, and the area ratio of the porous surface 32 of the sintered oil-impregnated bearing 22 can be reduced to 5% or less.

In the embodiment shown in FIG. 1, a spacer may be interposed in the gap 25 between the outer peripheral surface 32 of the sintered oil-impregnated bearing 22 and the inner peripheral surface of the stator core 14. This spacer is different from the bearing holder because it does not hold the sintered oil-impregnated bearing 22.

Next, various modifications of the holding structure for the sintered oil-impregnated bearing shown in FIGS. 3 and 4 will be described. The example in FIG.
The other end 34 in the axial direction of the sintered oil-impregnated bearing 22, which is positioned by placing one end in the axial direction on the substrate 10, is connected to the head 38 of a suitable number of screws 36 screwed into the screw holes of the substrate 10 and the body. The sintered oil-impregnated bearing 22 is fixed by a jaw and tightened by a screw 36 . In the example of FIG. 4, an appropriate number of screws 40 having a dish-shaped head 42 are screwed into the substrate 10,
The outer peripheral edge of the other end 34 in the axial direction of the sintered oil-impregnated bearing 22 positioned with one end in the axial direction placed on the substrate 10 is
Pressing a conical surface of the head 42, Ru der that secure the <br/> sintered oil-impregnated bearing 22 in the tightening force of the screw 40.

[0014]

According to the present invention, since the area ratio of the porosity of the outer peripheral surface of the sintered oil-impregnated bearing is set to 5% or less, almost no lubricating oil flows out of the outer peripheral surface of the sintered oil-impregnated bearing.
There is no longer any need to use a bearing housing. As a result, a highly accurate sintered oil-impregnated bearing can be obtained without being affected by the dimensional accuracy of the bearing housing, and the cost of the bearing housing itself and the cost of press-fitting the bearing can be reduced to achieve a significant cost reduction. It is now possible. Further, since the lubricating oil does not flow out from the outer peripheral surface of the sintered oil-impregnated bearing, the periphery is not contaminated with the lubricating oil. And
Press the sintered oil-impregnated bearing with a holding member or with screws.
If the lubricating oil in the sintered oil-impregnated bearing oozes out
However, there is a gap outside the sintered oil-impregnated bearing in the radial direction.
Since the data core is provided,
Therefore, lubricating oil does not permeate into the stator core.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a motor having a sintered oil-impregnated bearing according to the present invention.

FIG. 2 is a sectional view showing an embodiment of the sintered oil-impregnated bearing according to the present invention.

FIG. 3 is a cross-sectional view showing a modified example of the mounting structure of the sintered oil-impregnated bearing according to the present invention.

FIG. 4 is a sectional view showing another modified example of the mounting structure of the sintered oil-impregnated bearing according to the present invention.

DESCRIPTION OF SYMBOLS 10 Substrate 14 Stator core 16 Holding member 18 Screw 22 Sintered oil-impregnated bearing 25 Gap 26 Rotation shaft 32 Outer peripheral surface 36 of sintered oil-impregnated bearing Screw 40 Screw

Claims (2)

(57) [Claims] (1)A rotation axis, While supporting this rotating shaft, the outer surface of the porous
A sintered oil-impregnated bearing formed at a volume ratio of 5% or less; It is arranged with a gap radially outside of this sintered oil-impregnated bearing.
Installed stator core, A substrate supporting the sintered oil-impregnated bearing, It has a head at one end and penetrates the stator core
In addition, the other end is screwed into the substrate, so that
Screw to fix the data core, Interposed between the head of this screw and the stator core
With a holding member, A part of the holding member is an axial end face of the sintered oil-impregnated bearing.
And the pressing oil of the holding member
The bearing is pressed and fixed to the substrate.
Fixed structure of sintered oil-impregnated bearing. 2. A rotary shaft, thereby supporting the rotary shaft, porous is the surface of the outer peripheral surface
A sintered oil-impregnated bearing formed at a volume ratio of 5% or less and a radially outer side of the sintered oil-impregnated bearing with a gap therebetween.
A stator core provided, a substrate supporting the sintered oil-impregnated bearing , a head at one end, and the other end screwed to the substrate.
And a screw for fixing the stator core, and a part of the screw is engaged with the axial end face of the sintered oil-impregnated bearing.
Then, the sintered oil-impregnated bearing is raised by the tightening force of this screw.
Sintering characterized by being pressed and fixed to the substrate
Fixed structure for oil-impregnated bearings.