JPS60121308A - Dynamic pressure type composite bearing device - Google Patents

Abstract

PURPOSE:To maintain a thrust load capacity and simultaneously reduce torque of a radial bearing portion, by sealing a lubricant having viscosity lower than that of a lubricant for a thrust bearing portion in the radial bearing portion. CONSTITUTION:An outer sleeve 1 has a circular hole 11 where a shaft member 2 is inserted, and also has radial inner surface 111 and 112 forming a radial bearing portion between the circular hole 11 and an outer circumferential surface of the shaft member 2. There is retained at an end of the circular hole 11 a thrust receiving member 12 having a semispherically recessed thrust receiving surface 121. The shaft member 2 is provided with radial outer surfaces 22 and 23 having dynamic pressure generating grooves 21, and with a thrust receiving surface 24 at an end thereof. A lubricant having viscosity lower than that of a lubricant for the thrust bearing portion is sealed in the ratial bearing portion for purpose of reduction in torque.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dynamic pressure type compound bearing device consisting of an outer cylinder and a shaft body, one of which rotates. A dynamic pressure type composite bearing device that is effective for supporting rotating bodies that require high-precision rotation transmission, such as micro motors and audio equipment, which require low torque and low torque. It is related to.

[Conventional technology]

Among conventionally known rotating devices of this type, a rotating device that employs a composite hydrodynamic bearing that integrally includes a radial bearing and a thrust bearing in the bearing portion that supports the rotating body is well known. . -For example, JP-A-55-54
As disclosed in Japanese Patent No. 718, a cylindrical shaft body has a radial inner surface for forming a radial bearing portion on the inner peripheral surface of a circular hole into which it is inserted, and a thrust member is provided at one end side of the circular hole. an outer cylinder provided with a thrust bearing member forming one thrust bearing surface for forming a bearing portion; an outer peripheral surface at a position facing the radial inner surface being a radial outer surface; and a thrust bearing member of the outer cylinder at the shaft end; It has a structure in which a thrust receiving surface for external force is provided opposite to the receiving surface, and a lubricant such as oil or grease is provided in both the bearing parts.

However, in the above-mentioned conventional bearing device, different lubricants with the same viscosity are used in the radial bearing part and the thrust bearing part, so the torque of the radial bearing part is large compared to that of the thrust bearing part, and the radial load capacity is also large. Hey.

Therefore, in the above-mentioned conventional bearing structure, when this is used in a vertical type, for example, the weight is very small compared to the weight of the bearing portion of the rotating body.

In this way, as a bearing device for a rotating body under usage conditions where the vertical load is very small relative to the thrust load,
The radial load capacity of the shank that ensures only the necessary thrust load capacity may be small, but rather, as a rotating body, it is an important challenge to reduce the torque of the entire bearing even if it sacrifices the radial load capacity.

In general, in a bearing device in which a lubricant of the same viscosity is used in the radial bearing part and the thrust bearing part, the R bending torque of the radial bearing part in the whole is, for example, as shown in FIG. 2 of the present invention described later. In the case of the second embodiment, it is about 90%. Therefore, if the torque of the radial bearing section is reduced without reducing the thrust load capacity: + -"--'
+7-m is desirable.

[Problem that the invention seeks to solve]

The present invention relates to a hydrodynamic type composite bearing having both a radial bearing section and a thrust bearing section as described above, which can reduce the load capacity of the radial bearing section without sacrificing the thrust load capacity. In particular, it is possible to reduce the torque of the radial bearing portion and thereby obtain a bearing device with low torque and high-speed performance.

[Means for resolving gaps]

That is, the present invention provides a hydrodynamic type composite bearing device as described above for supporting a rotating body, in which a lubricant is included in the radial bearing part, especially in the thrust bearing part, among the lubricants sealed in both the bearing parts. The structure includes a lubricant that is effective in reducing torque and has a lower viscosity than other lubricants.

[For production]

Thus, in the bearing device of the present invention, the torque of the radial bearing portion can be reduced while maintaining the necessary thrust load capacity without sacrificing the thrust load capacity due to the relationship with the viscosity of the lubricant. , low torque of the entire bearing device can be achieved.

〔Example〕

Next, this invention will be explained with reference to the typical embodiments shown in FIGS. 1 to 4. 1 is an outer cylinder, 2 is a shaft body, 3 is a rotational drive mechanism for the shaft body 2, and 4 is a mechanism held by the outer cylinder. The stator 5 is a body that holds the rotor 6, and 14 is an elastic O-ring that elastically supports the thrust receiving member 12 and seals between it and the other member.

Introduction In the first embodiment of the composite bearing device for the rotating part of a circumferentially opposed type motor shown in FIG. The side has radial inner surfaces 111 and 112 that form a radial bearing part between it and the outer surface of the shaft body, which will be described later.
A thrust receiving member 12 having a hemispherically concave thrust receiving surface 121 is held at one end of the circular hole 11 (lower side when viewed from the drawing) via a presser plate 13. . The radial clearance b between the radial inner surface 111 and the radial inner surface 112 in the circular hole of the outer cylinder l can be changed by increasing the inner diameter between the two radial inner surfaces to the clearance tz of the radial bearing part. It is formed larger than.

Also, the radial inner surface ill, 11 with the clearance tl.
Both of the axial lengths of 2 are longer than the axial lengths of dynamic pressure generating grooves 21 formed on the outer cylindrical surface of the shaft body, which will be described later.

The shaft body 2 has a plurality of herringbone-shaped dynamic pressure generating grooves 21 on two outer cylinder surfaces facing the radial inner surface of the outer cylinder.
A radial outer surface 22 having a
Thrust receiving member side) K is formed with a convex receiving part (thrust receiving surface) 24 having a hemispherical convex receiving surface having a plurality of spiral grooves 241.

The radial bearing portion and the thrust bearing portion are filled with a lubricant necessary for forming a pressure fluid layer. In order to reduce the torque of the thrust bearing, a lubricant with a lower viscosity than that of the thrust bearing is included.

In the above embodiment, in creating the relationship b) tz, the inner diameter of the outer cylinder between the radial inner surface Ill and 112 was formed as a large diameter, but the shaft diameter between the radial outer surface 22.5 of the shaft body was formed as a small diameter. In some cases, a relationship of H)t+ is created and implemented.

FIG. 2 shows a second embodiment. In particular, in this embodiment, the circular hole 11 of the outer cylinder l that cooperates with the shaft body 2 is not directly formed in the outer cylinder. Separately from this, a seal body, for example, a magnetic fluid seal S, is added to the end of the outer cylinder on the side opposite to the thrust receiving member to prevent leakage of the lubricant, which is formed through a sleeve 15 formed separately. In addition, instead of the spherical thrust bearing shown in the first embodiment, the thrust bearing has a planar shape between the end surface 24a of the shaft body and the upper surface L21a of the thrust bearing member 12a facing thereto. This shows an example in which a thrust bearing part is formed, and the other structure is the same as that of the first embodiment. In particular, the thrust bearing part in the second embodiment is
In the example of multiple spirals for generating dynamic pressure on the upper surface L21a (the surface facing the shaft end surface 24a), a ball 122 is embedded in the center of the thrust receiving member in order to further reduce the torque at the time of starting and stopping. The structure is such that a convex portion is formed and the top of the convex portion contacts the thrust receiving surface 24a on the shaft body side, but the formation of the convex portion is not necessarily necessary. Naturally, in this example,
When the rotational speed of the spindle reaches a certain range, the thrust bearing surface 24a and the convex portion no longer come into contact with each other (and the bearing operates as a complete hydrodynamic thrust bearing).

When the sleeve 15 is used as in the second embodiment, the sleeve may be made of an oil-impregnated porous member such as metal or plastic impregnated with oil.

FIG. 3 shows a third embodiment, in particular, in this embodiment, the radial bearing part on the thrust bearing part side in the first embodiment is omitted, and there is only one radial bearing part, and the thrust This figure shows an example in which a sealing body, such as a magnetic fluid seal, is attached to the upper part of the receiving part.

Three members 151. 152 and 153, and an air vent hole 16 is provided between the radial bearing portions, which communicates with the inside and outside of the bearing.In particular, the air vent hole 16 allows the air between the outer cylinder and the shaft body to be used. This helps prevent the lubricant from leaking due to expansion due to temperature changes in the surrounding air.

〔Effect of the invention〕

As described above, in the dynamic pressure type composite bearing device of the present invention, a lubricant as a medium is sealed in the radial bearing portion and the thrust bearing portion formed between the outer cylinder and the shaft body. Rather than using a lubricant with the same viscosity, we used the thrust bearing as a reference, and the radial bearing used a lubricant with a lower viscosity than that of the thrust bearing, so it can be used under the same specifications as conventional products. If so, the torque of the radial bearing can be reduced without reducing the thrust load capacity, and as a result,
Of course, it is possible to reduce the torque of the bearing device as a whole and achieve a significant performance improvement. Alternatively, it is particularly effective as a bearing device for a rotating body driven by a planar opposed motor that exerts a large suction force in the axial direction.

Furthermore, as shown in the examples, among the radial clearances between the inner circumferential surface of the circular hole of the outer cylinder and the outer circumferential surface of the shaft body, between the same surfaces excluding the radial bearing portion, for example, between the radial bearing portion and the radial If the radial clearance tl between the bearing (first embodiment) and between the radial bearing part and the thrust bearing part (third embodiment) is made larger than the radial clearance t2 of the radial bearing part, the rotation In order to significantly reduce the viscous resistance of the lubricant inside and further reduce or eliminate the frictional torque of the bearing device as a whole, the lubricant should be sealed to prevent it from getting around the gap 11, and the bearing should be sealed. It is effective to add a lubricant such as oil with high surface tension. Particularly when a seal body is not used, it is desirable to use oil with high surface tension to improve oil retention in the bearing.

In addition, in the embodiment, an example was explained in which the hydrodynamic pressure generating groove was mainly provided on the shaft body side, but it may also be provided on the outer cylinder side.
It may also be provided on both sides.

Furthermore, the detailed structure of each bearing, the bearing type, the shape of the dynamic pressure generation groove, the design specifications of the bearing, the presence or absence of a seal, the presence or absence of an air vent hole, the position where it will be used, the lubricant to be used, etc. It goes without saying that the present invention is not limited to the examples, and may be implemented with appropriate modifications within the scope of the claims.

[Brief explanation of drawings]

1 to 4 are longitudinal sectional views showing a hydrodynamic type composite bearing device of the present invention, in which FIG. 1 shows the first embodiment, FIG. 2 shows the second embodiment, and the third embodiment. The figure is 1.22, O is the radial outer surface, U is the radial clearance between the inner circumferential surface of the circular hole and the outer circumferential surface of the shaft that is not the radial bearing part, t2 is the radial clearance of the radial bearing part, and S is the radial clearance of the radial bearing part. It is a magnetic fluid seal. Patent applicant: NSK Ltd. 3 times

Claims (1)

[Scope of Claims] (1) It has a circular hole into which the shaft body is inserted, and has a radial inner surface forming a radial bearing portion on the inner peripheral surface of the circular hole, and a thrust bearing at one end side of the circular hole. an outer cylinder having a thrust receiving member having one thrust receiving surface forming a part, and a radial outer surface on an outer surface facing the radial inner surface with a slight clearance, and a thrust bearing member of the outer cylinder at the shaft end. The shaft body has a thrust bearing surface facing the bearing surface, and a dynamic pressure generating groove is provided in one or both of the mutually facing bearing surfaces, and the bearing part is provided with moisture. A dynamic pressure type composite bearing device having a lubricating agent, wherein the radial bearing portion is lubricated with a lubricant having a lower viscosity than the thrust bearing portion. . (2. Claim 1, wherein the thrust bearing portion is a flat bearing or spherical bearing having a hydrodynamic groove. (3) Claim 1. In item 1 or 2, the radial clearance tl in the radial clearance between the inner circumferential surface of the outer cylinder and the outer circumferential surface of the shaft body, excluding the radial bearing part, is equal to A dynamic pressure type composite bearing device in which the clearance is larger than the clearance tl. (4) In claim 3, the radial clearance t- is larger than the radial clearance tl of the radial bearing portion.
A dynamic pressure type composite bearing device (5) in which the portion communicates with the outside through an air vent hole provided in the outer cylinder. A dynamic pressure type composite bearing device in which the radial inner surface of the hole is longer than the axial length of the dynamic pressure generation groove provided on the radial outer surface of the shaft body.