JP2534872Y2 - Hydrodynamic 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 dynamic pressure bearing using grease or the like as a lubricant.

[0002]

2. Description of the Related Art Conventionally, there is a dynamic pressure bearing as shown in FIGS. This dynamic pressure bearing comprises a shaft 1 and a sleeve 2. The shaft 1 has a dynamic pressure generating portion 5 provided with a V-shaped groove 3 for generating dynamic pressure.
Is provided with a cylindrical surface 6 serving as a bearing surface and conical chamfers 7 connected to both ends thereof. The axial dimension a of the dynamic pressure generating part 5 is the same as the axial dimension b of the cylindrical surface 6. Grease 8 is filled between the sleeve 2 and the shaft 1 including the chamfer 7.

[0003]

As shown in FIG. 5, when the shaft 1 is displaced to the right in the axial direction with respect to the sleeve 2 in the above dynamic pressure bearing, grease is generated due to imbalance in dynamic pressure. The grease 8 is discharged to the right side, and the grease 8 exists in the regions c and d, but the grease 8 does not exist in the region e, and the oil film breaks.

The grease 8 at the left chamfer 7 is initially supplied to the area e from near the inner peripheral surface 6, but the grease 8 at the chamfer 7 at a distance from the inner peripheral surface 6 is generated by dynamic pressure. Since the influence of the suction force is small, the suction force remains at that location and is not supplied to the area e.

The axial dimension a of the dynamic pressure generating portion 5
Is the same as the axial dimension b of the cylindrical surface 6, so that even if the shaft 1 is slightly displaced in the axial direction, the dynamic pressure generating part 5 and the chamfer 7 are no longer overlapped and are located at the chamfer. The force exerted on the grease 8 becomes weaker.

Therefore, in the above dynamic pressure bearing, the shaft 1
There is a problem that the oil film breaks at an early stage when is moved relative to the sleeve 2 in the axial direction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic pressure bearing in which an oil film does not easily break even when the shaft is displaced in the axial direction with respect to the sleeve.

[0008]

According to a first aspect of the present invention, there is provided a hydrodynamic bearing having a small-diameter cylindrical surface at an inner peripheral center and a large-diameter cylindrical surface provided at an inner peripheral end. A shaft having a dynamic pressure generating portion which is inserted into a small-diameter cylindrical surface and a large-diameter cylindrical surface of the sleeve, and has a groove for generating dynamic pressure uniformly provided on the entire surface; A lubricant filled between the small-diameter cylindrical surface and the large-diameter cylindrical surface of the sleeve and the shaft, and the axial length of the dynamic pressure generating portion of the shaft is set to the axial length of the small-diameter cylindrical surface of the sleeve. In this case, even if the shaft moves by a predetermined length with respect to the sleeve, the entire small-diameter cylindrical surface of the sleeve overlaps the dynamic pressure generating portion of the shaft. The dynamic pressure bearing according to the second aspect of the present invention is the dynamic pressure bearing according to the first aspect, wherein the diameter of the large-diameter cylindrical surface is 0.1 to 0.1 than the diameter of the small-diameter single cylindrical surface.
It is characterized by being 2mm larger.

[0009]

According to the first aspect of the present invention, the distance between the large-diameter cylindrical surface and the outer peripheral surface of the shaft in the open-ended sleeve is constant. The suction force by the dynamic pressure acts on the filled lubricant effectively. Therefore, even if the shaft is displaced in the axial direction with respect to the sleeve and a portion where the lubricant is insufficient due to imbalance of the dynamic pressure occurs, the lubricant in the large-diameter cylindrical surface is applied to the portion where the lubricant is insufficient. Supplied.
Thus, the oil film is less likely to break. Further, the axial length of the dynamic pressure generating portion of the shaft is longer than the length of the small-diameter cylindrical surface of the open-ended sleeve, and even if the shaft moves by a predetermined length with respect to the sleeve, The entire small-diameter cylindrical surface of the sleeve overlaps the dynamic pressure generating portion of the shaft. Therefore, even if the shaft is displaced in the axial direction with respect to the sleeve, the dynamic pressure generating portion and the large-diameter cylindrical surface easily overlap,
Even if they do not overlap, the distance between them is reduced.
Thus, the lubricant inside the large-diameter cylindrical surface is easily supplied to the dynamic pressure generating section.

Further, in the invention according to claim 2, the diameter of the large-diameter cylindrical surface is 0.1 to 0.2 mm larger than the diameter of the small-diameter cylindrical surface.
Since the diameter is increased, the suction force due to the dynamic pressure acts uniformly on the lubricant filled inside the large-diameter inner peripheral surface.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

In FIG. 1, 1 is a shaft, and 12 is a sleeve. The shaft 1 has exactly the same structure as the shaft 1 of the conventional example shown in FIGS. The above sleeve 12
Is an open-end type, has a small-diameter cylindrical surface 16 at the center of the inner periphery, and large-diameter cylindrical surfaces 17, 17 at both ends of the inner periphery. The dimension of the step between the large-diameter cylindrical surface 17 and the small-diameter cylindrical surface 16 is
It is set to 0.1 to 0.2 mm. The axial dimension f of the small diameter cylindrical surface 16 is smaller than the axial dimension a of the dynamic pressure generating portion 5 of the shaft 1. Grease 8 is filled between the large-diameter cylindrical surface 17 and the small-diameter cylindrical surface 16 of the sleeve 12 and the dynamic pressure generating portion 5 of the shaft 1.

In the above configuration, it is assumed that the shaft 1 is shifted to the right in the axial direction with respect to the sleeve 12, as shown in FIG. Then, with respect to the small-diameter cylindrical surface 16 of the sleeve 12, the dimension n of the right overlapping portion from the axial center of the dynamic pressure generating portion 5 is larger than the dimension (m +
1), and the grease 8 is discharged to the right side due to the axial imbalance of the dynamic pressure. Therefore, the grease 8 exists in the area n, m (n = m) of the small-diameter cylindrical surface 16 due to the balance of the dynamic pressure in the axial direction, but the grease 8 tends to be insufficient in the area l. However, since the distance between the large-diameter cylindrical surface 17 of the sleeve 12 and the outer peripheral surface of the shaft 1 is constant and as small as 0.1 to 0.2 mm, the grease pool inside the large-diameter inner peripheral surface 17 on the left side. The suction force due to the dynamic pressure acts uniformly and effectively on the grease 8 filled in the space. Therefore, grease 8
The oil is supplied between the small-diameter cylindrical surface 16 in the region 1 and the dynamic pressure generating section 5 so that the oil film is hardly broken.

The axial dimension a of the dynamic pressure generating portion 5 of the shaft 1 is determined by the dimension f of the small-diameter cylindrical surface 16 of the sleeve 12.
The shaft 1 is longer than the sleeve 1
Even if it is displaced in the axial direction with respect to 2, the dynamic pressure generating portion 5 and the large-diameter cylindrical surface 17 are likely to overlap, and even if they do not overlap, the distance between them becomes short. Therefore, the grease 8 inside the large-diameter cylindrical surface 17 is easily supplied to the dynamic pressure generating unit 5. Therefore, oil film breakage is less likely to occur.

FIG. 3 shows another embodiment.
The shaft 21 is provided with two dynamic pressure generating portions 25, 25, and large-diameter cylindrical surfaces 27, 2
7 and 27, and the small-diameter cylindrical surfaces 26 and 26 are
5, 25. The dimension g of the step between the large-diameter cylindrical surface 27 and the small-diameter cylindrical surface 26 is 0.1 to 0.2 mm. The axial dimension of the dynamic pressure generating section 25 is longer than the axial dimension of the small-diameter cylindrical surface 26.

Also in this case, as in the previous embodiment, grease is effectively supplied from the grease pool inside the large-diameter cylindrical surface 27 to the dynamic pressure generating section 25, thereby preventing the oil film from being cut.

[0017]

As is apparent from the above description, according to the first aspect of the present invention, a small-diameter cylindrical surface is provided at the center of the inner periphery of the open-ended sleeve, and a lubricant pool is formed at the inner peripheral end. Since the large-diameter cylindrical surface is provided, the distance between the large-diameter cylindrical surface of the sleeve and the outer peripheral surface of the shaft is constant, and the lubricant filled inside the large-diameter cylindrical surface causes the shaft to move with respect to the sleeve. In the case of moving in the axial direction, the suction force due to the dynamic pressure is effectively received, and the oil is supplied between the small-diameter cylindrical surface and the dynamic pressure generating portion, so that the oil film is less likely to break. Further, even if the axial dimension of the dynamic pressure generating portion of the shaft is longer than the dimension of the small-diameter cylindrical surface of the open-ended sleeve, even if the shaft moves by a predetermined length with respect to the sleeve,
Since the entire small-diameter cylindrical surface of the sleeve overlaps with the dynamic pressure generating portion of the shaft, even if the shaft is axially displaced with respect to the sleeve, the dynamic pressure generating portion and the large-diameter cylindrical surface are displaced. Are easy to overlap, and even when they do not overlap, the distance between them is short, and therefore, the lubricant inside the large-diameter cylindrical surface is easily supplied to the dynamic pressure generating portion, and the oil film is less likely to break.

According to the second aspect of the present invention, the diameter of the large-diameter cylindrical surface is set to be 0.1 to 0.1 larger than the diameter of the small-diameter cylindrical surface.
Since the diameter is increased by 2 mm, suction force due to dynamic pressure acts uniformly on the lubricant filled inside the large-diameter inner peripheral surface. Therefore, the lubricant inside the large-diameter cylindrical surface is more easily supplied to the dynamic pressure generating portion, and the oil film is less likely to break.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hydrodynamic bearing according to an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is a cross-sectional view of another embodiment.

FIG. 4 is a sectional view of a conventional example.

FIG. 5 is an operation explanatory diagram of the conventional example.

[Explanation of symbols]

1,21 ... shaft, 2,22 ... sleeve, 5,25 ...
Dynamic pressure generating section, 16, 26: small-diameter cylindrical surface, 17, 27: large-diameter cylindrical surface.

Continuing from the front page (72) Inventor Yasuo Takamura 3-5-8 Minamisenba, Chuo-ku, Osaka City, Osaka Prefecture Inside Koyo Seiko Co., Ltd. (56) References JP-A-55-97520 (JP, A) 84421 (JP, U)

Claims (2)

(57) [Scope of request for utility model registration] 1. An open-ended sleeve comprising a small-diameter cylindrical surface at the center of the inner periphery and a large-diameter cylindrical surface provided at the inner periphery end, and inserted into the small-diameter cylindrical surface and the large-diameter cylindrical surface of the sleeve. And a shaft having a dynamic pressure generating portion in which grooves for generating dynamic pressure are uniformly provided on the entire surface; and a lubricant filled between the small-diameter cylindrical surface and the large-diameter cylindrical surface of the sleeve and the shaft. Wherein the axial length of the dynamic pressure generating portion of the shaft is longer than the axial length of the small diameter cylindrical surface of the sleeve, so that the sleeve moves even if the shaft moves by a predetermined length with respect to the sleeve. Wherein the entirety of the small-diameter cylindrical surface overlaps the dynamic pressure generating portion of the shaft. 2. The dynamic pressure bearing according to claim 1, wherein the diameter of the large-diameter cylindrical surface is 0.1 to 0.2 mm larger than the diameter of the small-diameter single cylindrical surface. .