JPH0447443Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a bearing device used in rotating cylinders of audio/visual equipment, office equipment, etc.

[Conventional technology]

2. Description of the Related Art Conventionally, a video tape recorder shown in FIG. 3, for example, is known as a device using a rotary cylinder with a bearing device of this type. In this bearing device, the lower end of a shaft 10 is fixed to a lower cylinder (fixing member) 1 by press fitting or the like, and a sleeve 20 fixed to an upper cylinder 3 equipped with a magnetic head 2 is rotatably attached to the shaft 10. Sleeve 2
The lower end surface of a cylindrical thrust receiver 23 fixed to the upper end of the shaft body 10 by press fitting or the like faces the upper end surface of the shaft body 10 in a plane.

On the outer circumferential surface of the shaft body 10, herringbone-shaped grooves 11a and 1 for generating dynamic pressure are provided at two locations spaced apart in the axial direction on the fixed end side and the non-fixed end side (free end side).
A cylindrical radial receiving surface 12a on which 1b is formed,
12b, and radial bearing surfaces 22a, 2 are provided on the inner diameter surface of the sleeve 20, facing the radial bearing surfaces 12a, 12b of the shaft body 10 with a radial clearance therebetween.
2b, and these radial receiving surfaces 12a, 12
b and the radial bearing surfaces 22a and 22b constitute a dynamic pressure type radial fluid bearing that supports the sleeve 20 in the radial direction with respect to the shaft body 10.

Further, a thrust bearing surface 25 in which a spiral groove for generating dynamic pressure is formed is provided on the lower end surface of the thrust receiver 23.
and the thrust bearing surface 15 provided on the upper end surface of the shaft body 10 constitute a dynamic pressure type thrust fluid bearing that supports the sleeve 20 in the axial direction with respect to the shaft body 10.

A relief portion 26 having a larger diameter than the radial bearing surfaces 22a, 22b is provided on the inner diameter surface of the sleeve 20 at a location between the radial bearing surfaces 22a, 22b separated in the axial direction. An air vent hole 27 communicating with the outside of the bearing is provided in the radial direction. Furthermore, an air vent groove 28 is provided in the press-fitting surface of the thrust receiver 23 of the sleeve 20 in the axial direction, which communicates with the outside of the bearing from between the radial bearing surface 22a on the opposite side of the fixed end and the thrust bearing surface 25.

Further, a cylindrical rotary transformer 30 is attached to a mounting portion 29 provided on the sleeve 20, and a mounting portion 1a provided on the lower cylinder 1 faces the rotating rotary transformer 30 with a radial clearance therebetween. Fixed side rotary transformer 31
is installed. With these rotary transformer mechanisms, a signal taken out from the magnetic head 2 attached to the upper cylinder 3 is transmitted through the rotary transformer 30 on the rotating side to the rotary transformer 31 on the fixed side.
It has come to be transmitted to

As a rotational drive mechanism of the bearing device, an annular rotor magnet 34 is connected to the mounting portion 29 of the sleeve 20 via a mounting ring 35 and a yoke 36.
An annular stator coil 37 attached to the lower cylinder 1 is axially opposed to the rotor magnet 34.

The bearing device configured as described above generates rotational force in the rotor magnet 34 by energizing the stator coil 37, and the sleeve 20 and the upper cylinder 3 and other attached parts fixed to the sleeve 20 become an integrated rotating body. When rotated, the radial bearing surface 22
A groove 11 for generating dynamic pressure in the shaft body 10 is provided in the bearing clearance between a and 33b and the radial bearing surfaces 12a and 12b.
Dynamic pressure is generated by a and 11b, and a fluid film is generated by the lubricant such as oil and grease filled in the bearing clearance, and the pressure of this fluid film causes the sleeve 20 and its attached parts to It is supported in the radial direction in a non-contact state with respect to the shaft body 10, and dynamic pressure is generated by the groove 24 for generating dynamic pressure in the thrust receiver 23 in the bearing clearance between the thrust bearing surface 25 and the thrust bearing surface 15. A fluid film is generated by the lubricant such as oil and grease filled in this bearing clearance, and the pressure of this fluid film causes the sleeve 20 and its attached parts to come into contact with the shaft body 10. It is supported in the axial direction and rotates.

[Problem to be solved by the invention] Generally, the outer circumferential surface of the shaft body 10 of this type of bearing device has grooves 11a for generating dynamic pressure at two locations on the fixed end side and the non-fixed end side, as described above. 11b is provided to prevent rotating bodies such as the sleeve 20 supported in the radial direction with respect to the shaft body 10 and the cylinder 3 from rotating at an angle with respect to the lower cylinder 1 due to side pressure. In the conventional bearing device, by making the width (length in the axial direction) of the groove 11a for generating dynamic pressure on the side opposite to the fixed end larger than the width of the groove 11b for generating dynamic pressure on the fixed end side, The radial rigidity of the hydrodynamic bearing on the non-fixed end side is made higher than that of the hydrodynamic bearing on the fixed end side, so that it can support a large load.

However, if the width of the groove 11a for dynamic pressure generation on the non-fixed end side is made larger than the width of the groove 11b for dynamic pressure generation on the fixed end side, the axis of the shaft body 10 and the sleeve 20 will change accordingly. As the length in the direction becomes longer, the overall height of the bearing device becomes larger, which is a factor that hinders miniaturization of this type of equipment.

This invention solves the above problems and provides a bearing device in which the radial rigidity of the hydrodynamic bearing on the opposite fixed end side is higher than that of the hydrodynamic bearing on the fixed end side, and the overall height dimension can be reduced. The purpose is to

[Means to solve the problem]

In this invention, either the sleeve or the shaft body fitted into the sleeve has one axial end fixed to a fixed member, and is formed on the fixed end side and the opposite fixed end side of the inner diameter surface of the sleeve. The groove for generating dynamic pressure is provided in at least one of the cylindrical radial bearing surface and the radial bearing surface formed on the outer diameter surface of the shaft body with a radial clearance from the radial bearing surface of the sleeve. In a bearing device configured to support either a sleeve or a shaft body in the radial direction at two locations axially apart from the other, the radial bearing surface and the radial bearing surface on the non-fixed end side. The radial clearance between the fixed end side radial bearing surface and the radial bearing surface is set to be smaller than the radial clearance between the fixed end side radial bearing surface and the radial bearing surface.

The depth of the groove for generating dynamic pressure provided on the side opposite to the fixed end is preferably the same as or deeper than the groove for generating dynamic pressure provided on the fixed end side.

〔Example〕

FIG. 1 shows an embodiment in which this invention is applied to the bearing device shown in FIG. 3.

The width of the groove 11a for generating dynamic pressure provided in the radial receiving surface 12a on the side opposite to the fixed end of the shaft body 10 is the same as the width of the groove 11b for generating dynamic pressure provided in the radial receiving surface 12b on the fixed end side. Although the settings are the same,
The radial clearance t _a between the radial bearing surface 22 a and the radial bearing surface 12 a on the opposite fixed end side is smaller than the radial clearance t _b between the radial bearing surface 22 b and the radial bearing surface 12 b on the fixed end side. It is set.

Since the configuration other than the above-mentioned configuration is the same as that in FIG. 3, the main components are indicated by the same reference numerals, and repeated explanation will be omitted.

In this way, when the radial clearance between the opposite fixed end side and the fixed end side is different, it is difficult to perform centerless grinding on the outer diameter surface of the shaft body 10 to produce different diameters. Since it is relatively easy to cut the inner diameter surface of the sleeve 20 to have different diameters, the radial bearing surfaces 12a and 12b of the shaft body 10 are machined to have the same diameter, and the radial bearing surface 22a on the side opposite to the fixed end of the sleeve 20 is machined to have the same diameter. It is preferable to set the diameter to be smaller than that of the radial bearing surface 22b on the fixed end side.

With the above configuration, the radial rigidity of the fluid bearing on the opposite fixed end side is higher than the radial rigidity of the fluid bearing on the fixed end side, so the load capacity of the fluid bearing on the opposite fixed end side is higher than that of the fluid bearing on the opposite fixed end side. This is larger than the load capacity of a hydrodynamic bearing, so even if the rotating body receives lateral pressure, it will not rotate tilted.

Note that the depths of the groove 11a for generating dynamic pressure on the side opposite to the fixed end of the shaft body 10 and the groove 11b for generating dynamic pressure on the fixed end side may be set to the same depth. , Groove 11 for generating dynamic pressure on the opposite fixed end side
From the viewpoint of processing, it is preferable to set the depth of a to be deeper than the dynamic pressure generating groove 11b on the fixed end side within a predetermined limit. By making the depths of the grooves 11a and 11b different in this manner, the radial rigidity of the hydrodynamic bearing on the non-fixed end side can be made higher than the radial rigidity of the hydrodynamic bearing on the fixed end side.

In the above embodiment, the radial bearing surface 1 of the shaft body 10
Grooves 11a for generating dynamic pressure provided in 1a and 11b,
11b is the radial bearing surface 22 of the sleeve 20
a, 22b, or may be provided on both the radial bearing surfaces 12a, 12b of the shaft body 10 and the radial bearing surfaces 22a, 22b of the sleeve 20.

FIG. 2 shows a case in which the diameter D _a of the radial bearing surface 22a on the side opposite to the fixed end of the sleeve 20 is set to be smaller than the diameter D _b of the radial bearing surface 22b on the fixed end side.
This figure shows a state in which a groove 21a for generating dynamic pressure (the groove on the fixed end side is not shown) is plastically worked using a jig 40 for forming grooves by ball rolling.

When performing groove machining using the balls 41 of the groove machining jig 40 in this way, the groove machining jig 40
It is difficult to machine the grooves on the fixed end side and the non-fixed end side to the same depth by changing the amount of protrusion of the ball 41 from the outer circumferential surface of the ball 41 during processing.
It is better to perform groove processing without changing the amount of protrusion of the groove, and make the depth g _a of the groove on the non-fixed end side deeper than the depth g _b of the groove on the fixed end side.

Now, the radial clearance t _a between the radial bearing surface on the non-fixed end side is t compared to the radial clearance t _b between the radial bearing surface on the fixed end side. Considering the case where _a = (0.5 to 0.9) t _b , on the fixed end side, the depth g _b of the groove for generating dynamic pressure with respect to the radial clearance t _b , generally g _b ≒ Since the design is made so that the relationship t _b holds, the depth g _a of the groove for generating dynamic pressure on the non _- fixed end side is given by g _a = g _b + (t _b − Since t _a )≈(1 to 3) t _a , it can be seen that there is no problem in terms of bearing performance and that the radial rigidity is within the optimum range.

In the above embodiment, a bearing device is described in which a rotating body consisting of the sleeve 20 and its attached parts rotates around the shaft body 10, but on the contrary, the sleeve 20 is fixed to the lower cylinder 1,
This invention can also be applied to a bearing device having a structure in which a rotating body consisting of a shaft body 10 fixed to an upper cylinder 3 and its attached parts is supported by a sleeve 20 and rotates.

Furthermore, in the above embodiment, the thrust bearing surface 25 of the cylindrical thrust bearing 23 press-fitted and fixed into the sleeve 20 and the thrust bearing surface 15 of the shaft body 10 face each other in a plane to form a dynamic pressure type thrust fluid bearing. The structure is a pivot type in which a spherical thrust bearing is press-fitted into the sleeve 20 and fixed, and the convex spherical thrust bearing surface of the thrust bearing makes point contact with the flat thrust bearing surface 15 of the shaft body 10. It may also be configured as a thrust sliding bearing.

Further, in the above embodiment, the sleeve 20 and the upper cylinder 3 are constructed as separate bodies, but they can also be constructed as one piece.

[Effect of idea]

As explained above, in this invention, either the sleeve or the shaft body is radially supported relative to the other by dynamic pressure type radial fluid bearings provided on the fixed end side and the non-fixed end side. In bearing devices,
The radial clearance between the radial bearing surface on the non-fixed end side is set smaller than the radial clearance between the radial bearing surface on the fixed end side. Even if the width of the groove for generating dynamic pressure in the hydrodynamic bearing on the side is the same as the width of the groove for generating dynamic pressure in the hydrodynamic bearing on the fixed end side, the radial rigidity of the hydrodynamic bearing on the opposite fixed end side is the same as that of the hydrodynamic bearing on the fixed end side. This means that it can support a larger load than a hydrodynamic bearing. Therefore, according to this invention, even if the rotating body such as the upper cylinder that is integrated with the sleeve or the shaft body is subjected to side pressure, it will not tilt and rotate, and the axial length between the sleeve and the shaft body will be Since the bearing device can be designed to have the minimum necessary dimensions, it is possible to obtain a bearing device with a reduced height and compact size and high precision performance.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional side view showing an embodiment of this invention;
FIG. 2 is a cross-sectional view showing a state in which grooves are formed on the inner diameter surface of the sleeve, and FIG. 3 is a longitudinal cross-sectional side view showing an example of a conventional bearing device. In the figure, 1 is the lower cylinder (fixed member), 10 is the shaft body, 11a and 11b are grooves for generating dynamic pressure on the opposite fixed end side and the fixed end side of the shaft body, respectively.
2b is a radial receiving surface on the opposite fixed end side and the fixed end side of the shaft, 20 is a sleeve, 22a, 22b
are the radial bearing surfaces on the non-fixed end side and fixed end side of the sleeve, t _a is the radial clearance between the radial bearing surface on the non-fixed end side, and t _b is the radial bearing surface on the fixed end side, respectively. There is a radial clearance between the surface and the radial receiving surface.

Claims (1)

[Claims for Utility Model Registration] (1) One axial end of the sleeve and the shaft fitted to the sleeve is fixed to a fixed member, and the fixed end side of the inner diameter surface of the sleeve A movement provided on at least one of a cylindrical radial bearing surface formed on the non-fixed end side and a radial bearing surface formed on the outer diameter surface of the shaft body with a radial clearance from the radial bearing surface of the sleeve. In a bearing device in which radial bearings are configured in two locations separated in the axial direction, one of the sleeve and the shaft body is supported radially with respect to the other by a groove for generating pressure, A bearing device characterized in that the radial clearance between the radial bearing surfaces is set smaller than the radial clearance between the radial bearing surfaces on the fixed end side. (2) A claim in which the depth of the groove for generating dynamic pressure provided on the side opposite to the fixed end is set to be equal to or deeper than the depth of the groove for generating dynamic pressure provided on the fixed end side. (1) Bearing device described.