JPH0712734Y2 - Hydrodynamic bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a hydrodynamic bearing device having a radial bearing provided with grooves for generating dynamic pressure at two axially separated locations.

[Conventional technology]

Conventionally, in order to solve the contradictory problems of decreasing the friction torque and increasing the radial stiffness of a dynamic pressure type radial bearing, the bearing width of either one of the pair of opposing receiving surfaces is roughly A bearing having a small bearing clearance in the central portion and a large bearing clearance in both sides of the bearing width is disclosed in Japanese Utility Model Publication No. 63-18827.

In the dynamic pressure type radial bearing of the publication, the bearing portion is provided at one place, but in an apparatus incorporating this type of bearing, the bearing portion is provided at two places axially separated from each other. Since it is widely used, the configuration of the publication is applied in this case as shown in FIG.

A support member 10 in which a thrust receiver 11 made of a spherical body is press-fitted and fixed to one end is fitted around a shaft member 20,
The outer diameter surface of 20 is provided with cylindrical radial receiving surfaces 22a, 22b in which herringbone-shaped grooves 21a, 21b for generating dynamic pressure are formed at two locations spaced apart in the axial direction. Cylindrical radial bearing surfaces 12a, 12b facing the radial receiving surfaces 22a, 22b are provided on the inner diameter surface of the. The radial receiving surfaces 22a, 22b and the radial bearing surfaces 12a, 12b constitute a dynamic pressure type radial bearing.

Further, the thrust bearing surface 13 of the thrust receiver 11 fixed to the supporting member 10 and the thrust bearing surface 23 of the shaft member 20 facing the thrust bearing surface 13 constitute a pivot type thrust bearing.

The inner surface of the support member 10 is axially provided with an air vent groove 14 which communicates with the outside from a location between the thrust receiving surface 23 and the thrust bearing surface 13, and two radial bearing surfaces 12a, 12b.
A clearance portion 15 having a diameter larger than that of the radial bearing surfaces 12a and 12b is provided at a position between them.

The two radial bearing surfaces 12a, 12b of the above-mentioned support member 10 have a radial bearing surface with a width smaller than the bearing width in the approximate center.
The flange portions 16a, 16b having a smaller diameter than the axial end portions of the 12a, 12b are provided, and the radial clearance ΔR between the flange portions 16a, 16b and the radial receiving surfaces 22a, 22b is the axis of the radial bearing surfaces 12a, 12b. Radial clearance Δr between both ends in the radial direction and the radial receiving surfaces 22a, 22b
Is smaller than.

[Problems to be solved by the device]

In the hydrodynamic bearing device having the dynamic pressure type radial bearing of the configuration shown in FIG. 2, as described above, in each bearing portion, the radial clearance ΔR at the approximate center in the axial direction is the radial clearance Δr on both sides.
Since it is smaller than the above, the friction torque of each bearing part can be reduced and the radial rigidity can be increased, but the grooves 21a and 21b for generating dynamic pressure of each bearing part have the load acting point Pa which is the top edge thereof. , Pb are provided at equal lengths on both sides in the axial direction and have a herringbone shape symmetrical with respect to the load acting points Pa, Pb, and between the load acting points Pa, Pb of the two bearing parts. Since the axial length (bearing interval) L ₁ is narrow, there is a drawback that the moment rigidity of the entire device is reduced.

This invention has been made for the purpose of solving the above problems.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, the dynamic pressure generating groove provided in at least one of the radial bearing surface and the radial receiving surface in each of the two axially distant bearing portions has a dynamic pressure generating groove. The length of the groove formed on the inner side in the axial direction around the load acting point of the groove for use is longer than the length of the groove formed on the outer side in the axial direction, and the radial bearing surface and the radial receiving surface of each bearing portion are The radial clearance between the two is smaller than the radial clearance at the axially inner end of the groove for dynamic pressure generation, which is outside the axial direction of the groove for dynamic pressure generation. It is set.

[Action]

In the hydrodynamic bearing device of the present invention, the inner length in the axial direction centering on the load acting point of the groove for generating dynamic pressure of each bearing portion is formed longer than the outer length in the axial direction, and On the other hand, since it has an asymmetrical herringbone shape, each bearing width is the same as that of a symmetrical herringbone-shaped groove for dynamic pressure generation provided at two locations. The bearing spacing between the load acting points of the bearing portion becomes longer.

In addition, in the bearing width of each bearing portion, radial rigidity is ensured as a bearing in the portion with a small radial clearance, and the portion with a large radial clearance has both a function as a lubricant reservoir and pumping action. There is.

〔Example〕

FIG. 1 shows an embodiment in which the present invention is applied to a bearing of the type shown in FIG.

Herringbone-shaped grooves 21a, 21b for generating dynamic pressure, which are formed at two locations on the outer diameter surface of the shaft member 20 at intervals in the axial direction.
Is asymmetric with respect to the load acting points Pa and Pb, with the length of the groove on the inner side in the axial direction being longer than the length of the groove on the outer side in the axial direction around the respective load acting points Pa and Pb.

In addition, the two radial bearing surfaces 12a, 12b of the support member 10 have axially outer portions of the bearing device, that is, load application points.
Collar portions 16a, 16b having a smaller diameter than the axially inner portion of the bearing device are provided at the locations corresponding to the substantially symmetrical portions on both sides in the axial direction of the dynamic pressure generating grooves 21a, 21b centered on Pa, Pb. is there.

The hydrodynamic bearing device with the above configuration is
Since b shifts axially outward from the position shown in FIG. 2, the bearing spacing L ₂ between the load acting points Pa and Pb is wider than the bearing spacing L _{1 in} the case of FIG.

Further, the radial clearance formed between the radial bearing surfaces 12a, 12b and the radial receiving surfaces 22a, 22b of each bearing portion is such that the radial clearance ΔR in the collar portions 16a, 16b is
It is smaller than the radial clearance Δr in the axially inner part than 6b. That is, the radial clearance between the radial bearing surfaces 12a, 12b and the radial receiving surfaces 22a, 22b in each bearing is determined by the dynamic pressure generating groove 21 including the load acting points Pa, Pb.
The radial clearances at the axially outer portions of a and 21b are set smaller than the radial clearances at the axially inner ends of the dynamic pressure generating grooves 21a and 21b.

Further, in the brim portions 16a, 16b, the axial lengths 30, 31 of the portions axially outside from the load acting points Pa, Pb are more than the lengths 32, 33 of portions axially inner than the load acting points Pa, Pb. The length is slightly longer. Since pressure is generated in the fluid in the bearing clearance at the axially inner ends of the grooves 21a, 21b for generating dynamic pressure, the fluid in the bearing clearance on both sides in the axial direction around the load acting points Pa, Pb is generated. The pressures generated are balanced.

Since the configuration other than the above is the same as that in FIG. 2,
Only corresponding parts are given the same reference numerals.

By configuring as above, the bearing spacing of each bearing
Since L ₂ is widened, the moment rigidity of the entire device does not decrease, and the radial rigidity as a bearing is secured in the flange portions 16a, 16b of the radial clearance ΔR of each bearing portion, and the flange portions 16a, 16b are secured. The portion having the radial clearance Δr on the inner side in the axial direction performs a function as a lubricant reservoir for holding the lubricant and a pumping action for replenishing the lubricant.

That is, of the bearing width of each bearing portion, the bearing width of the portion with a small radial clearance that contributes to friction torque is short,
The friction torque of the entire device becomes small.

In the embodiment, the dynamic pressure generating grooves 21a and 21b provided on the outer diameter surface of the shaft member 20 may be provided on the inner diameter surface of the support member 10, and the outer diameter surface of the shaft member 20 and the support member 10 may be formed. It may be provided on both the inner diameter surface.

Further, in the above embodiment, the radial bearing surface 12 of the support member 10 is
The case where the flange portions 16a, 16b are provided on the a, 12b has been described, but instead of this, the radial receiving surfaces 22a, 22b of the shaft member 20 have a larger diameter than the axially inner portion at the axially outer portion. A brim portion may be provided.

[Effect of device]

As described above, according to the present invention, the contradictory problems of reduction of friction torque and increase of radial rigidity are solved in a hydrodynamic bearing device in which dynamic pressure type radial bearings are provided at two axially separated locations. Not only can this be achieved, but also the moment rigidity of the entire device can be secured, so the stability and reliability of the performance of this type of hydrodynamic bearing device can be greatly improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of the present invention, and FIG. 2 is a vertical sectional side view showing a hydrodynamic bearing device to which a conventional structure is applied. In the figure, 10 is a supporting member, 12a and 12b are radial bearing surfaces, 20 is a shaft member, 21a and 21b are grooves for generating dynamic pressure, 22a and 22b are radial receiving surfaces, Pa and Pb are load acting points, ΔR, Δr has a radial clearance.

Claims (1)

[Scope of utility model registration request] At least a radial bearing surface formed at two axially distant positions on an inner diameter surface of a support member, and a radial receiving surface formed on an outer diameter surface of the shaft member facing the radial bearing surface. In a hydrodynamic bearing device having a herringbone-shaped groove for dynamic pressure generation on one side, each of the two dynamic pressure generation grooves is axially inward with respect to the load acting point of the dynamic pressure generation groove. Is longer than the length of the groove on the outer side in the axial direction, the radial clearance between the two radial bearing surfaces and the radial receiving surface is defined by the axis of the groove for dynamic pressure generation including the load acting point. A hydrodynamic bearing device characterized in that a radial clearance at an outer side portion in the direction is set to be smaller than a radial clearance at an axially inner end portion of a groove for generating a dynamic pressure.