JP2002213435A - Dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing, capable of preventing leakage of a lubricating fluid and a shaft directional abnormal movement of a rotating body by restraining generation of a shaft directional flow of the lubricating fluid in a dynamic pressure shaft for forming herringbone-type dynamic pressure grooves on an inner peripheral surface of a cylindrical body or an outer peripheral surface of the shaft inserted on the inside. SOLUTION: A difference |L1-L2| between dimensions L1 and L2 on both sides by sandwiching the center line C of the dynamic pressure grooves 3a and 3b is set to 1% or less of the total length (L1+L2), so as to restrain generation of the shaft directional flow of the lubricating fluid caused by shaft directional asymmetry of herringbone pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dynamic pressure bearing, and more particularly to a radial dynamic pressure bearing having a herringbone type dynamic pressure groove.

[0002]

2. Description of the Related Art In a radial dynamic pressure bearing having a herringbone type dynamic pressure groove, a shaft is generally inserted into a cylindrical body, and a herringbone is provided on an inner peripheral surface of the cylindrical body or an outer peripheral surface of the shaft. A configuration in which a shaped dynamic pressure groove is formed and a lubricating fluid is supplied between the cylindrical body and the shaft is adopted.

[0003] In such a configuration, when the cylinder and the shaft rotate relative to each other, a film pressure of the lubricating fluid is generated at the portion where the cylinder and the shaft are formed due to the action of the dynamic pressure groove, so that the cylinder and the shaft are not in contact with each other. And relative rotation.

[0004]

By the way, in the above-mentioned radial dynamic pressure bearing having a herringbone type dynamic pressure groove formed therein, when the cylindrical body and the shaft rotate relative to each other, the lubrication between them occurs. The fluid flows in the axial direction, causing the lubricating fluid to leak out of the bearing device, or in a bearing device in which one end of the shaft is sealed, the flow of the lubricating fluid causes the pressure rise or pressure drop in the sealed portion. This may cause a problem that the rotating body (the rotating body of the cylinder or the shaft) abnormally moves in the axial direction.

The present invention has been made in view of such circumstances, and suppresses the generation of the flow of the lubricating fluid during the relative rotation of the cylinder and the shaft, thereby preventing the leakage of the lubricating fluid and the axial direction of the rotating body. It is an object of the present invention to provide a dynamic pressure bearing capable of preventing abnormal movement.

[0006]

In order to achieve the above object, a hydrodynamic bearing according to the first aspect of the present invention is a hydrodynamic bearing comprising: an inner peripheral surface of a cylindrical body or an outer peripheral surface of a shaft inserted into the cylindrical body.
A herringbone type dynamic pressure groove is formed on at least one of the surfaces, and by applying the lubricating film pressure to the lubricating fluid between the cylinder and the shaft by the dynamic pressure groove during relative rotation of the shaft, the cylindrical body and in the dynamic pressure bearing for lubrication between the shaft, the dynamic differences in dimensions L ₁ and L ₂ to both sides of the axial center of the herringbone pattern of grooves | L ₁ -L ₂ | is,
It is characterized by satisfying the following expression (1). | L ₁ −L ₂ | ≦ 0.01 (L ₁ + L ₂ ) (1)

Further, in order to achieve the same object, a second aspect of the present invention is provided.
The dynamic pressure bearing of the invention according to the present invention forms a herringbone type dynamic pressure groove on at least one of the inner peripheral surface of the cylindrical body or the outer peripheral surface of the shaft inserted into the cylindrical body. In a dynamic pressure bearing for lubricating between a cylindrical body and a shaft by applying a lubricating film pressure to a lubricating fluid between the cylindrical body and the shaft during relative rotation of the cylindrical body and the shaft, the herringbone type dynamic pressure groove Radial gaps δ ₁ and δ between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the shaft at both ends in the axial direction of
₂ of the difference | δ ₁ -δ ₂ | is characterized by that it meets the following expression (2).

| Δ₁−δ_Two| ≦ 0.45 ｛(δ₁+ Δ_Two) / 2｝^1/2 ..... (2) In order to further achieve the same object, the operation of the invention according to claim 3
The pressure bearing is inserted into the inner peripheral surface of the cylinder or into the cylinder.
At least one of the outer peripheral surfaces of the shaft
Two sets of herringbones at a predetermined distance in the axial direction
Type dynamic pressure grooves, and each dynamic pressure groove
When the body and shaft rotate relative to each other, the lubricating fluid
Applying force to lubricate between the cylinder and shaft
The gap between the cylinder and the shaft between the two sets of dynamic pressure grooves is
Make the lubricating fluid reservoir larger than the gap at the position where the dynamic pressure groove is formed.
Of the lubricating fluid reservoir,
Between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the shaft at both ends in the axial direction
Radial gap Δ₁And Δ_TwoDifference | Δ ₁−Δ_Two|
It is characterized by satisfying the expression (3). | Δ₁−Δ_Two| ≦ 0.45 ｛(Δ₁+ Δ_Two) / 2｝^1/2 ... (3)

According to the present invention, there is provided a dynamic pressure bearing according to the first aspect of the present invention, which has the features of the second aspect of the present invention (claim 4), and the invention according to the fourth aspect. In the dynamic pressure bearing of the present invention, a configuration (claim 5) further combining the features of the invention according to claim 3 can be suitably adopted.

The present inventors have conducted intensive studies on the behavior of a radial dynamic pressure bearing having a herringbone type dynamic pressure groove during rotation. As a result, in this type of dynamic pressure bearing, the dynamic pressure Symmetry, uniformity in the axial direction of the radial gap between the cylindrical body and the shaft at the location of the dynamic pressure groove,
Further, in the case where two sets of dynamic pressure grooves are formed in the axial direction and the lubricating fluid reservoir is formed therebetween, the uniformity of the radial gap of the lubricating fluid reservoir in the axial direction is determined by the lubricating fluid. It has been found that this has a significant effect on the generation of the flow, which has led to the present invention.

That is, as shown in FIG.
(3b) The greater the difference | L ₂ −L ₂ | between the dimensions L ₁ and L ₂ on both sides of the center C of the herringbone pattern in the axial direction of the herringbone pattern, the greater the lubrication due to the axial asymmetry of the herringbone pattern. The axial flow of the fluid increases. The difference | L ₂ −L ₂ | is expressed by the total length (L ₁ + L ₂ ) of the herringbone pattern as shown in the above equation (1).
By setting the difference to 1% or less (claim 1), the difference | L
It was confirmed that can suppress the occurrence of flow in the axial direction of the lubricating fluid resulting from | ₁ -L _2.

As shown in FIG. 3, the dynamic pressure grooves 3a (3
b) the inner peripheral surface of the cylindrical body 1 at both ends in the axial direction and the shaft 2
Radial gap δ between outer peripheral surfaces₁And δ_TwoDifference | δ₁−δ_Two| Is large
The more it becomes, the more the dynamic pressure grooves 3a (3b) are formed
Pressure distribution in the axial direction of the lubricating fluid in the
Axial flow increases. This difference | δ₁−δ_Two|
As shown in the expression (2), the shape of the dynamic pressure grooves 3a (3b)
Not more than 45% of the square root of the average radius gap at the formation site
(Claim 2), the difference | δ₁−δ _Two|
The flow of lubricating fluid in the axial direction
Was confirmed.

Further, as shown in FIG. 4, two sets of dynamic pressure grooves 3a and 3b are formed in the axial direction, and the cylindrical body 1 and the shaft 2 between them are formed.
Clearance dynamic pressure grooves 3a between, in the dynamic pressure bearing in which a lubricating fluid reservoir 4 is set larger than the gap in the formation site of 3b, a radial gap delta ₁ in the axial ends of the lubricant reservoir 4 difference Δ ₂ | Δ ₁ -Δ ₂ | is the greater, the pressure difference in the axial direction of the fluid pressure is generated in the lubricating fluid reservoir 4, the axial flow of the lubricating fluid is increased. By setting the difference | Δ ₁ −Δ ₂ | to 45% or less of the square root of the average radial gap in the lubricating fluid reservoir 4 as shown in the above equation (3), the difference | It has been confirmed that the generation of the axial flow of the lubricating fluid due to Δ ₁ −Δ ₂ | can be suppressed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of the embodiment of the present invention.

In this example, two sets of herringbone type dynamic pressure grooves 3a and 3b are formed on the outer peripheral surface of the shaft 2 inserted into the cylindrical body 1 at predetermined intervals in the axial direction. At the same time, between the respective dynamic pressure grooves 3a and 3b, the cylindrical body 1 at the portion where the respective dynamic pressure grooves 3a and 3b are formed.
The lubricating fluid reservoir 4 is formed by forming a gap larger than the gap between the shaft and the shaft 2. The space between the cylinder 1 and the shaft 2 is filled with a lubricating fluid such as oil.

In the above configuration, when the cylinder 1 and the shaft 2 rotate relative to each other, a film pressure of the lubricating fluid is generated at the positions where the dynamic pressure grooves 3a and 3b are formed, whereby the cylinder 1 and the shaft 2 are moved in the radial direction. Rotate relative to each other without contact with each other. The cylindrical body 1 and the shaft 2 also have a pumping action during relative rotation of a thrust dynamic pressure bearing (not shown) having, for example, a spiral dynamic pressure groove provided between them in the thrust direction. Thereby, it is possible to rotate while maintaining a non-contact state with each other.

As shown schematically in FIG. 2, the herringbone pattern of each of the dynamic pressure grooves 3a and 3b has the axial dimensions L ₁ and L _{2 on} both sides of the axial center C thereof.
The difference | L ₁ -L ₂ | is _{1 of the} total axial length (L ₁ + L ₂ ).
% Or less. That is, the above expression (1) is satisfied.

As shown schematically in FIG. 3, the difference | δ ₁ between the radial gaps δ ₁ and δ ₂ between the cylindrical body 1 and the shaft 2 at both axial ends of each of the dynamic pressure grooves 3a and 3b. −δ ₂ | satisfies the expression (2).

Further, as schematically shown in FIG. 4, the difference | Δ ₁ −Δ between the radial gaps Δ ₁ and Δ ₂ between the cylindrical body and the shaft 2 at both axial ends of the lubricating fluid reservoir 4. ₂ | satisfies the expression (3).

According to the above embodiment of the present invention, when the cylindrical body 1 and the shaft 2 rotate relative to each other, the lubricating fluid between them does not flow in the axial direction, so that the lubricating fluid leaks out of the bearing device. There is no problem that the cylinder 1 and the shaft 2 move abnormally in the axial direction relatively to each other.

Next, the aforementioned | L ₁ −L ₂ |, | δ ₁ −
An experimental result of measuring the flow of the lubricating fluid between the dynamic pressure grooves 3a or 3b while changing δ ₂ | and | Δ ₁ −Δ ₂ | variously will be described.

In this experiment, as shown in FIG.
With the lubricating fluid being supplied to the portion where the dynamic pressure groove 3a or 3b was formed, the amount of movement of the liquid surface in the axial direction at both axial ends was measured.

First, as for | L ₁ -L ₂ |, α = | L ₁ -L ₂ | / (L ₁ + L ₂ ) × 100 (%) (4) and α is 0.2 What changed variously between 10% and 10% was prepared, and the movement amount of the liquid level was measured. At this time, β and γ were each set to 45%. The measurement results are shown in [Table 1].

[0024]

[Table 1]

For | δ ₁ −δ ₂ |, β = | δ ₁ −δ ₂ | / ｛(δ ₁ + δ ₂ ) / 2｝ ^1/2 × 100 (%) (5) The values of β were variously changed between 15 and 75%, and the amount of movement of the liquid surface was measured. At this time, α is 1
% And γ were set to 45%. The measurement results are shown in [Table 2].

[0026]

[Table 2]

Further, as for | Δ ₁ −Δ ₂ |, γ = | Δ ₁ −Δ ₂ | / ｛(Δ ₁ + Δ ₂ ) / 2｝ ^1/2 × 100 (%) (6) Were prepared by varying the value of γ between 15% and 75%, and the amount of movement of the liquid surface was measured. Here, the lubricating fluid was supplied to the two sets of dynamic pressure grooves 3a and 3b and the lubricating fluid reservoir 4 between them. At this time, α was set to 1%, and β was set to 45%. The measurement results are shown in [Table 3].

[0028]

[Table 3]

As is apparent from the above measurement results, | L
_{As the} values of ₁₋ L ₂ |, | δ ₁ −δ ₂ | and | Δ ₁ −Δ ₂ | increase, the amount of movement of the liquid surface in the axial direction increases, and α is 1% or less, and β and γ Is set to 45% or less, the liquid level does not move, that is, the axial flow of the lubricating fluid does not occur, the lubricating fluid leaks out, or the cylinder 1 and the shaft 2 are relatively moved. It was confirmed that the problem of large movement in the axial direction could be prevented.

When α is set to 1% or less, even if β and γ are as large as 75%, the lubricating fluid leaks or the cylinder 1 and the shaft 2 are displaced abnormally in the axial direction relative to each other. Does not occur, and when β is set to 45% or less,
Even if α exceeds 1% and γ is as large as about 75%,
Similarly, there is no flow in which the lubricating fluid leaks or the cylinder 1 and the shaft 2 are displaced abnormally in the axial direction relative to each other. Further, when γ is set to 45% or less, α becomes 1%. Even if β exceeds 75%, it is also confirmed that there is no flow of lubricating fluid that leaks or that the cylinder 1 and the shaft 2 are displaced abnormally in the axial direction relative to each other. did it.
By setting α to 1% or less and β to 45% or less, even if γ is large, the flow of the lubricating fluid in the axial direction hardly occurs, and in addition, the value of γ is set to 45% or less. By doing so, the flow can be almost completely eliminated.

In the above embodiment, the shaft 2
An example is shown in which the herringbone type dynamic pressure grooves 3a, 3b are formed on the outer peripheral surface.
Even if it is formed on the inner peripheral surface of the cylindrical body 1, the same result as described above can be obtained.

[0032]

As described above, according to the first aspect of the present invention, in a radial dynamic pressure bearing having a herringbone type dynamic pressure groove, the dimensional difference between both sides of the herringbone pattern with respect to the axial center thereof is reduced. By setting the length of the pattern to 1% or less of the total length in the axial direction, the generation of the flow of the lubricating fluid in the axial direction can be suppressed, whereby the lubricating fluid leaks out of the bearing device, or It is possible to prevent the body and the shaft from moving relatively largely in the axial direction.

According to the second aspect of the present invention, the difference in the radial gap between the cylindrical body and the shaft at both ends in the axial direction of the herringbone type dynamic pressure groove is also calculated as 45% of the square root of the average radial gap. % Or less, the generation of the flow of the lubricating fluid in the axial direction can be similarly suppressed, and the lubricating fluid leaks out of the bearing device or the cylinder and the shaft move relative to each other as described above. A large movement in the axial direction can be prevented.

Further, according to the third aspect of the present invention, the radial gap between the cylindrical body and the shaft at both ends in the axial direction of the lubricating fluid reservoir formed between the two sets of herringbone type dynamic pressure grooves. By making the difference 45% or less of the square root of the average radial gap, it is possible to suppress the generation of the flow of the lubricating fluid in the axial direction. Relative movement of the shaft and the shaft in the axial direction can be prevented.

Still further, as in the invention according to claim 4,
By having the features of the invention according to claim 1 and the features of the invention according to claim 2 together, the above-mentioned effect is further ensured, and as in the invention according to claim 5,
By adding the features of the invention according to claim 3 in addition to these, the above-mentioned effects are further ensured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 shows each dynamic pressure groove 3a, 3b in the embodiment of FIG.
FIG. 4 is a schematic diagram for explaining the axial symmetry of the herringbone pattern of FIG.

FIG. 3 shows each dynamic pressure groove 3a, 3b in the embodiment of FIG.
FIG. 4 is a schematic diagram for explaining a difference in a gap between a cylindrical body 1 and a shaft 2 at both axial end portions of FIG.

FIG. 4 is a diagram illustrating a lubricating fluid reservoir 4 according to the embodiment of FIG.
FIG. 4 is a schematic diagram for explaining a difference in a gap between a cylindrical body 1 and a shaft 2 at both axial end portions of FIG.

FIG. 5 shows a dynamic pressure groove 3a (3) according to an embodiment of the present invention.
By varying the values of | L ₁ -L ₂ | and | δ ₁ -δ ₂ | of b) and | Δ ₁ -Δ ₂ | of the lubricating fluid reservoir 4, the lubrication at the portions where the dynamic pressure grooves 3 a and 3 b are formed is changed. It is explanatory drawing of the experiment which measured the flow of the fluid.

[Explanation of symbols]

 Reference Signs List 1 cylindrical body 2 shaft 3a, 3b dynamic pressure groove 4 lubricating fluid reservoir

Claims (5)

[Claims] 1. A herringbone-type dynamic pressure groove is formed on at least one of an inner peripheral surface of a cylindrical body and an outer peripheral surface of a shaft inserted into the cylindrical body, and the dynamic pressure groove defines the herringbone type dynamic pressure groove. In a hydrodynamic bearing for applying lubricating film pressure to a lubricating fluid between the cylindrical body and the shaft during relative rotation of the shaft and lubricating between the cylindrical body and the shaft, the axial center of the herringbone pattern of the dynamic pressure groove is sandwiched therebetween difference dimensions L ₁ and L ₂ to both sides | L ₁ -L ₂ |
Satisfies the following expression (1). | L ₁ −L ₂ | ≦ 0.01 (L ₁ + L ₂ ) (1) 2. A herringbone-type dynamic pressure groove is formed on at least one of an inner peripheral surface of a cylindrical body and an outer peripheral surface of a shaft inserted into the cylindrical body. In a hydrodynamic bearing for applying a lubricating film pressure to a lubricating fluid between the cylindrical body and the shaft during relative rotation of the shaft and lubricating between the cylindrical body and the shaft, both ends in the axial direction of the herringbone type dynamic pressure groove The radial gap δ ₁ between the inner peripheral surface of the cylindrical body and the outer peripheral surface of the shaft at
And a difference | δ ₁ −δ ₂ | between them and δ ₂ satisfies the following expression (2). | Δ ₁ −δ ₂ | ≦ 0.45 ｛(δ ₁ + δ ₂ ) / 2｝ ^1/2 (2) 3. A herringbone type of two sets with a predetermined axial distance between at least one of the inner peripheral surface of the cylindrical body and the outer peripheral surface of the shaft inserted into the cylindrical body. Forming a dynamic pressure groove, applying lubricating film pressure to a lubricating fluid between the cylindrical body and the shaft during relative rotation of the cylindrical body and the shaft by each of the dynamic pressure grooves to lubricate between the cylindrical body and the shaft, In a dynamic pressure bearing in which a gap between a cylindrical body and a shaft between two sets of dynamic pressure grooves is made larger than a gap at a position where a dynamic pressure groove is formed, a lubricating fluid reservoir is provided. radial gap delta ₁ and delta ₂ of the difference between the outer peripheral surface of the inner peripheral surface and the axis of the cylindrical body in part | delta ₁
−Δ ₂ | satisfies the following expression (3). | Δ ₁ −Δ ₂ | ≦ 0.45 ｛(Δ ₁ + Δ ₂ ) / 2｝ ^1/2 (3) 4. The dynamic pressure bearing according to claim 1, wherein | δ ₁ −δ ₂ | satisfies the expression (2). 5. The dynamic pressure bearing according to claim 4, wherein | Δ ₁ −Δ ₂ | satisfies the expression (3).