JP3620817B2 - Sintered oil-impregnated bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sintered oil impregnated bearing suitable for use in supporting a shaft rotating at a relatively high speed, such as a spindle motor bearing, with high accuracy.
[0002]
[Prior art]
Sintered oil-impregnated bearings reduce the frictional resistance and suppress noise and vibration by forming an oil film by oozing out the contained lubricating oil to the inner peripheral surface of the shaft hole, which is the sliding surface with the rotating shaft. It has the characteristic that it is. In addition, as a sintered oil-impregnated bearing that further enhances the effect of suppressing vibration and noise, a clearance gap (hereinafter referred to as a middle bulge portion) that does not contact the rotating shaft is formed at the axial center of the inner peripheral surface of the shaft hole. In some cases, the portion where the rotating shaft slides is limited to both ends, and the reduction of the frictional resistance is improved.
[0003]
[Problems to be solved by the invention]
By the way, in a spindle motor bearing, such as for a CD-ROM driver, in which the rotating shaft is standing, the load on the rotating shaft is not normally biased to one place in the circumferential direction unlike when the rotating shaft is turned sideways. In addition, the dynamic pressure effect generated by the increase in the pressure of the lubricating oil is not expected, and since it rotates at a high speed of about 10,000 / rpm, even a bearing having the above-described middle bulge portion can obtain a sufficient lubricating action. Was difficult. For example, a phenomenon in which the frictional resistance increases or the rotational speed fluctuates with the lapse of operating time occurs, and the middle swelling portion of such a bearing has a sludge-like shape particularly at one end in the axial direction where the load is large. In some cases, material was observed. This was assumed to be caused by insufficient supply of the lubricating oil to the sliding surface or deterioration of the lubricating oil due to heat generation of the bearing.
[0004]
Therefore, according to the present invention, even when the supporting rotating shaft rotates at a relatively high speed and the load received from the rotating shaft is biased in the axial direction, the lubricating action by the oil impregnation is sufficiently performed and high bearing performance is achieved. An object of the present invention is to provide a sintered oil-impregnated bearing that exhibits the following.
[0005]
[Means for Solving the Problems]
In the present invention, a bearing portion in which a rotating shaft slides is formed at both axial end portions of the inner peripheral surface of the shaft hole, and an intermediate bulge portion that does not contact the rotating shaft is formed between these bearing portions. The oil-impregnated bearing is characterized in that a plurality of grooves formed so as not to open at the end face of the bearing are arranged in the circumferential direction from at least one bearing portion to the middle swelling portion.
[0006]
According to the present invention, a large amount of lubricating oil in the bearing flows into the bearing portion through the groove from the gap between the rotating shaft and the middle bulge portion, and a dynamic pressure effect is caused between the groove in the bearing portion. As a result, the bearing performance is improved.
[0007]
If the groove penetrates the bearing portion and opens at the end face, the lubricating oil leaks out and the circulating action of the lubricating oil is not ensured. Therefore, in this invention, it is set as the preferable aspect that the length of the groove | channel formed in a bearing part shall be 10 to 80% of the length of a bearing part. In addition, if there is a difference in the load on the rotating shaft applied to the bearing portions at both ends in the axial direction, that is, if the load is biased in the axial direction, a groove should be formed on the side of the bearing portion with the larger load. Good. However, this is the simplest configuration of the present invention, and it is desirable to form grooves respectively from the bearing portions at both ends in the axial direction to the middle swelling portion.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(1) One embodiment Fig. 1 shows a spindle motor for a CD-ROM driver to which a cylindrical sintered oil-impregnated bearing (hereinafter abbreviated as a bearing) 10 according to an embodiment of the present invention is applied. 1 is shown. The motor 1 is an outer rotor type including a housing 2, a drive coil 3, and a magnet rotor 4. The magnet rotor 4 rotates at a high speed of about 10,000 / rpm. The bearing 10 is press-fitted into the core 2 a of the housing 2, and the rotary shaft 5 is rotatably inserted into the bearing 10. The motor 1 is incorporated in a device with the magnet rotor 4 disposed on the upper side and the rotating shaft 5 standing. The thrust load of the rotating shaft 5 is supported by the receiving plate 6 fixed to the bottom of the housing 2, and the radial load is supported by the bearing 10. The rotating shaft 5 protrudes upward from the bearing 10, and the protruding end is press-fitted into the boss 4 a of the magnet rotor 4. A disc chuck 7 for attaching and detaching a CD-ROM (not shown) to the magnet rotor 4 is mounted on the boss 4a of the magnet rotor 4. The bearing 10 is a porous sintered body obtained by compressing and sintering metal powder, and is an oil-impregnated sintered bearing after being immersed in lubricating oil.
[0009]
As shown in FIG. 2A, the bearing 10 is formed with a shaft hole 11 into which the rotary shaft 5 is rotatably inserted, but the inner diameter of the shaft hole 11 is not uniform over the entire length. . That is, bearing portions 12 that substantially support the rotating shaft 5 are formed at both axial ends of the inner peripheral surface, and the rotating shaft 5 has a larger diameter than the bearing portion 12 and contacts between the bearing portions 12. A middle bulge portion 13 that is not formed is formed coaxially with the bearing portion 12. The opening edge of each bearing part 12 and each step part 12a and 13a which transfers to the middle swelling part 13 from the bearing part 12 are chamfered, and are formed in the taper shape.
[0010]
On the inner peripheral surface of the shaft hole 11, a plurality of (for example, three) grooves 14 are arranged at equal intervals in the circumferential direction from one bearing portion 12 (upper side in FIG. 2A) to the middle swelling portion 13. ing. These grooves 14 are semi-elliptical as shown in FIG. 2B, and are formed from the end edge of the middle bulge portion 13 to the bearing portion 12, and the bottom surface thereof is more gently tapered than the step portion 13a. It is a surface. The length of the portion formed in the bearing portion 12 of the groove 14 is in the range of 10 to 80% of the length of the bearing portion 12. The bearing 12 is press-fitted into the housing 2 of the motor 1 shown in FIG. 1 with the bearing portion 12 having a groove 14 formed on the upper side.
[0011]
Next, an example of a method for manufacturing the bearing 10 will be described.
First, as shown in FIG. 3A, the lower punch 21b and the core rod 22 are inserted into the mold hole of the die 20, and the raw material powder P is filled into the cavity 23 formed by these. As shown in FIG. 4, the core rod 22 is used in which a large-diameter portion 22 b and a protrusion 22 c for forming the middle swelling portion 13 and the groove 14 are formed in the middle of the rod 22 a forming the bearing portion 12. Next, as shown in FIG. 3 (b), the powder P is compression-molded by the upper and lower punches 21a and 21b, and thereafter, as shown in FIG. 3 (c), the core rod 22 and the lower punch 21b are moved upward. Thus, the green compact P1 is extracted from the die 20, and a spring bag is formed on the green compact P1 and is extracted from the core rod 22. Next, the green compact P1 is sintered, and the sintered body is set in the die 30 through the cylindrical core rod 32 in the shaft hole as shown in FIG. 5 (a), and the upper and lower punches 31a and 31b. The sintered body is compressed and subjected to sizing, the middle bulge portion 13 and the groove 14 are expanded, and the bearing 10 is formed. In this sizing, as shown in FIG. 5 (b), the central portion of the sintered body is expanded using the upper and lower dies 30a and 30b having stepped mold holes, and the middle swelling portion 13 and the groove 14 are expanded. It is also possible to take measures that make it easier to do.
[0012]
In the bearing 10, when the motor 1 is operated, the impregnated lubricating oil flows into the groove 14 from the gap between the rotating shaft 5 and the middle bulging portion 13, thereby lubricating the upper bearing portion 12. The oil supply is particularly increased. Further, in the upper bearing portion 12, a dynamic pressure effect by the lubricating oil is generated between the grooves 14 adjacent to each other in the circumferential direction. Here, since the load (radial load) applied to the bearing 10 from the rotating shaft 5 is greatly applied to the upper bearing portion 12 on the magnet rotor 4 side, supply of lubricating oil to the upper bearing portion 12 and shaft support are performed. However, in the present embodiment, the lubrication of the upper bearing portion 12 and the rigidity for supporting the shaft due to the generation of dynamic pressure are improved by the action of the groove 14, so that the bearing performance is greatly improved. To improve. Further, since the groove 14 does not pass through the bearing portion 12 and is not opened at the end surface, and the length of the bearing portion 12 is in the range of 10 to 80% of the bearing portion 12, the lubricating oil from the groove 14 Leakage is prevented and the circulation of lubricating oil is ensured.
[0013]
(2) Form of bearing Next, various forms of the bearing will be exemplified.
{Circle around (1)} As shown in FIG. 6, the groove 14 shown in the above embodiment is formed in a vertically symmetrical state from the bearing portion 12 at both ends to the middle bulge portion 13.
(2) As shown in FIG. 7, the bearing divided body 10A in which the bearing portion 12 is formed on one end side and the bulging portion 13A having a larger diameter than the bearing portion 12 is formed on the other end side faces the bulging portions 13A. Together, they are press-fitted into the housing 15, and the middle bulge portion 13 is formed by combining the bulge portions 13 </ b> A. A plurality of grooves 14 are formed in each bearing divided body 10A from the bearing portion 12 to the bulging portion 13A.
{Circle around (3)} As shown in FIGS. 8A and 8B, a linear groove 14 a connecting a pair of grooves 14 arranged in the axial direction is formed on the inner peripheral surface of the middle bulge portion 13.
{Circle around (4)} As shown in FIG. 9, the boundary between the groove 14, the bearing portion 12, and the middle swelling portion 13 is chamfered and is not clear. A large number of lines L extending in the axial direction in FIG. 9 are equal width lines for clarifying the shape of the groove 14 and do not actually exist.
[0014]
(3) Form of groove shape Next, various forms of the shape of the groove 14 formed between the bearing portion 12 and the middle bulge portion 13 will be illustrated.
(1) As shown in FIG. 10 (a), it is semi-elliptical and has a step on the bottom.
{Circle around (2)} As shown in FIG.
(3) As shown in FIG. 10 (c), it is a right triangle.
(4) As shown in FIG. 10 (d), it is an isosceles triangle.
[0015]
(4) Form of groove in side view shape Next, various forms of groove 14 formed in side view shape between the bearing portion 12 and the middle bulge portion 13 will be described.
(1) As shown in FIG. 11 (a), it has a triangular shape.
{Circle over (2)} As shown in FIG.
(3) As shown in FIG. 11 (c), the bottom surface has a gentle triangular shape.
[0016]
(5) Form of manufacturing method of bearing Next, various forms of the manufacturing method of the bearing 10 will be illustrated.
(1) As shown in FIG. 12A, the powder P is compressed by the die 20, the upper and lower punches 21a, 21b and the core rod 40. The core rod 40 that forms the shaft hole has a triangular prism shape as shown in FIG. The shaft hole of the green compact in which the powder P is compression-molded has a triangular cross-section corresponding to the core rod, and the three corners are grooves. After compacting and sintering the green compact, the sintered body is compressed in the axial direction to perform sizing. By this sizing, the central portion of the groove is expanded to form a middle bulge portion, and the opening on the end face side of the groove is formed. Close the end.
[0017]
(2) The core rod for forming the shaft hole is formed into a columnar shape, and the green compact is made into a simple cylindrical shape. After the green compact is sintered, as shown in FIG. Sizing is performed using the core rod 22 that forms the shape and is taken out by springback. The shaft hole of the green compact has a diameter into which the large diameter portion 22b of the core rod 22 can be inserted.
[0018]
(3) The triangular cylindrical core rod 40 shown in FIG. 12B is press-fitted into a shaft hole of a simple cylindrical sintered body, and three grooves are formed on the inner peripheral surface of the shaft hole by coining. Next, the sintered body is sized by the method shown in FIG.
[0019]
(4) As shown in FIG. 13A, the powder P is compression-molded by the die 20, the upper and lower punches 21a, 21b and the core rod 50. The core rod 50 that forms the shaft hole is a columnar member in which a small diameter portion 50b that forms the bearing portion 12 is formed at one end of the large diameter portion 50a that forms the middle bulge portion 13, and the large diameter portion 50a and the large diameter portion 50a. A protrusion 51 is formed on the outer peripheral surface of the portion extending from the portion 50a to the small diameter portion 50b. Grooves 14 corresponding to the protrusions 51 are formed on the inner peripheral surface of the shaft hole of the green compact in which the powder P is compression-molded. After the green compact is formed and sintered, as shown in FIG. 13B, the die 60 having stepped mold holes, the upper and lower punches 61a and 61b, and the cylindrical core rod 62 narrower than the core rod 50 are used for firing. The sizing is performed by compressing the ligated body in the axial direction, and by this sizing, the middle bulge portion 13 is expanded and the middle bulge portion 13 is expanded, and both ends of the groove 14 are closed to form the bearing 10. FIG. 13 (a) shows the green compact molding process for compressing powder, but the core rod 50 is press-fitted into the axial hole of the cylindrical sintered body to form the groove 14 by coining. ) Sizing may be used.
[0020]
(5) As shown in FIG. 14A, the powder P is compression-molded by the die 20, the upper and lower punches 21a, 21b and the core rod 70. The core rod 70 that forms the shaft hole is a cylindrical shape in which a small diameter portion 70b that forms the bearing portion 12 is formed at one end of the large diameter portion 70a that forms the middle bulge portion 13, and from the large diameter portion 70a to the small diameter portion 70b. A plurality of protrusions 70c for forming the grooves 14 are formed on the outer peripheral surface of the extending portion. Grooves 14 corresponding to the projections 70c are formed on the inner peripheral surface of the shaft hole of the green compact in which the powder P is compression-molded. After forming and sintering the green compact, the sintered body is axially compressed by the die 60, the upper and lower punches 61a and 61b, and the cylindrical core rod 62 similar to FIG. By sizing, the middle bulge portion 13 and the groove 14 are expanded and the bearing 10 is molded. FIG. 14 (a) shows the green compact molding process for compressing powder, but the core rod 70 is press-fitted into the axial hole of the cylindrical sintered body to form the groove 14 by coining. ) Sizing may be used.
[0021]
(6) As shown in FIG. 15 (a), after obtaining a sintered body having a bearing portion 12 on one end side and a bulging portion 13A on the other end side, this sintered body is shown in FIG. 15 (b). As described above, sizing is performed by the core rod 81 having the die 60, the upper and lower punches 61a and 61b, and the plurality of protrusions 80 for forming the groove 14, and the bearing divided body 10A having the groove 14 is obtained. As shown in FIG. 7, two of the bearing divided bodies 10A are incorporated in the housing 15 to constitute a bearing.
[0022]
【The invention's effect】
As described above, according to the present invention, since the impregnated lubricating oil flows into the groove from the gap between the rotating shaft and the middle bulge portion, the supply amount of the lubricating oil to the bearing portion increases. Since the dynamic pressure effect by the lubricating oil is generated between the grooves adjacent in the circumferential direction, the lubricity of the bearing portion and the rigidity for supporting the shaft are improved, and the bearing performance is greatly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a spindle motor to which a bearing according to an embodiment of the present invention is applied.
2A is a longitudinal sectional view of a bearing according to an embodiment of the present invention, and FIG. 2B is a partial perspective view of an inner peripheral surface thereof.
FIG. 3 is a view showing an example of a bearing manufacturing method according to an embodiment of the present invention, and is a cross-sectional view showing a powder compression step in the order of (a) to (c).
FIG. 4 is a partial perspective view of a core rod used in the same process.
FIG. 5 is an example of a bearing manufacturing method according to an embodiment of the present invention, and is a cross-sectional view showing a sintered body sizing step in the order of (a) and (b).
FIG. 6 is a longitudinal sectional view showing a form example of a bearing according to the present invention.
FIG. 7 is a longitudinal sectional view showing a form example of a bearing according to the present invention.
8A is a longitudinal sectional view showing an example of a bearing according to the present invention, and FIG. 8B is a partial perspective view of an inner peripheral surface.
FIG. 9 is a partial perspective view of an inner peripheral surface showing a form example of a bearing according to the present invention.
FIGS. 10A to 10D are front views showing an example of the shape of the bearing according to the present invention. FIGS.
11A to 11C are cross-sectional views showing examples of the shape of the bearing according to the present invention in a side view.
12A and 12B are views showing an example of a manufacturing method of a bearing according to the present invention, in which FIG. 12A is a cross-sectional view of a powder compression step, and FIG. 12B is a partial perspective view of a core rod used in the step.
13A and 13B are views showing an example of a manufacturing method of a bearing according to the present invention, in which FIG. 13A is a cross-sectional view of a powder compression step, and FIG. 13B is a cross-sectional view of a sintered body sizing step.
14A and 14B are diagrams showing an example of a manufacturing method of a bearing according to the present invention, in which FIG. 14A is a cross-sectional view of a powder compression step, and FIG. 14B is a cross-sectional view of a sintered body sizing step.
FIGS. 15A and 15B are diagrams showing an example of a manufacturing method of a bearing according to the present invention, in which FIG. 15A is a cross-sectional view of a powder compression process, and FIG.
[Explanation of symbols]
5 ... Rotating shaft, 10 ... Sintered oil-impregnated bearing, 11 ... Shaft hole, 12 ... Bearing part,
13 ... middle bulge part, 14 ... groove.

Claims (3)

In a sintered oil-impregnated bearing in which bearing portions on which the rotating shaft slides are formed at both ends in the axial direction of the inner peripheral surface of the shaft hole, and an intermediate bulge portion that does not contact the rotating shaft is formed between these bearing portions,
A sintered oil-impregnated bearing characterized in that a plurality of grooves formed so as not to open at the end face of the bearing are arranged in the circumferential direction from at least one of the bearing portions to the middle swelling portion. The length of the part formed in the said bearing part of the said groove | channel is 10 to 80% of the length of this bearing part, The sintered oil-impregnated bearing of Claim 1 characterized by the above-mentioned. 3. The sintered oil-impregnated bearing according to claim 1, wherein there is a difference in the load of the rotating shaft applied to each of the bearing portions, and the groove is formed on the bearing portion side where the load is large.

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