JP2503969B2 - Ceramic bearing and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a plain bearing made of ceramics. The present invention also includes a method of manufacturing such a ceramic bearing.

[Prior art]

The new ceramic materials, which have become available with the progress of fine ceramics technology in recent years, take advantage of the characteristics of conventional ceramics such as heat resistance and chemical resistance as well as the advantages of low wear resistance and small friction coefficient. It is used for skid rails in heating furnaces. On the other hand, with the miniaturization and high performance of various industries and consumer machinery, it is required that the bearings that support the rotating shaft be smaller and lighter and endure high load and high rotation. Improvements in special steels used as bearing materials and advances in processing technology continue to meet these demands, but they are still not fully satisfactory.

[Problems to be Solved by the Invention]

It is an object of the present invention to take the current state of the art one step further and provide a bearing made of ceramics and having better performance than conventional steel bearings. Providing a method for manufacturing such a ceramic bearing is also included in the object of the present invention.

[Means for Solving the Problems]

Referring to the drawings, the ceramic bearing of the present invention has an outwardly convex or concave cross section, that is, V in the illustrated example.
An integrally formed ceramic inner member 1 having a shape obtained by rotating a V-shaped concave cross section around an axis A.
And surrounding it, corresponding to the outer surface shape of the inner member 1,
In the illustrated example, a curved line, which also has an inner surface shape obtained by rotating a part of a substantially circular arc, is composed of a ceramic outer member 2 integrally formed of sintered ceramics, and has a maximum diameter D of the inner member. The minimum diameter of the outer member formed by sintering _I
It is characterized in that it is larger than D ₀ . The difference between the maximum diameter D _I of the inner member and the minimum diameter D ₀ of the outer member is
It suffices that both are above the limit capable of maintaining the structure as a bearing against the thrust in the axial direction. Usually at least 2μ
m is sufficient, and 10 μm or more is safe. This ceramic bearing generally does not require lubrication,
It is of course possible to lubricate depending on the application, and in that case, it is advisable to provide the outer member with the lubrication hole 5 as shown in FIG. The ceramic bearing of the present invention can have various modes. For example, in the example shown in FIG. 1, the outer surface of the inner member is concave and the inner surface of the outer member is convex, but as shown in FIG. 2, the relationship may be reversed. The shaft 3 is also made of a material different from that of the inner member, such as steel in the example of FIG. 1, and is integrated by means such as press fitting, cold fitting, and adhesion, but as shown in FIG. In addition, the inner member 1 and the shaft 3 can be originally manufactured integrally. As shown in FIG. 3, the method for manufacturing a ceramic bearing according to the present invention has a shape obtained by rotating an outwardly convex or concave cross section, in the illustrated example, a V-shaped concave cross section around the axis A. Preparing an inner member made of ceramics having an inner surface shape corresponding to the outer surface shape of the inner member, but having a minimum diameter d ₀ larger than the maximum diameter D _{I of the} inner member, forming a ceramic material by firing. 2A, for example, by surrounding the powder with a binder and molding it and holding the whole at the required temperature for the required time and firing,
Is made into ceramics, and its minimum diameter is made smaller than the maximum diameter of the inner member as shown in FIG. As ceramics, fine ceramics such as alumina, zirconia, silicon nitride and the like are suitable, and may be selected according to the use of the bearing as a product. It is preferable to polish the outer surface of the inner member so that the core is exposed and smoothed.

[Work]

Since the formation of ceramics by sintering involves shrinkage,
The material 2A of the outer member has a smaller minimum diameter and is easily smaller than the maximum diameter of the inner member. As a result, the two members, the inner and outer members, no longer come off in the axial direction. If the degree of contraction is limited to the extent that the outer member tightens the inner member, the rotation is free. Well-tightened and dense ceramic smooth surfaces have surprisingly low friction coefficient and high performance as a bearing. Therefore, although it is a kind of slide bearing, it can be used for both thrust bearings and radial bearings. Needless to say, it has excellent wear resistance and can withstand long-term use.

【Example】

An inner member having the maximum diameter D _I = 7 mm having the shape shown in FIG. 3 was manufactured by molding and sintering alumina powder, and the surface thereof was polished. The same alumina powder was molded, and a material for the outer member having a shape shown in FIG. 3 and a minimum diameter d ₀ = 8 mm was prepared. A ceramic bearing having a cross-sectional shape shown in FIG. 4 was obtained by placing the inner member 1 in the material 2A in a furnace and sintering it. The shrinkage due to sintering of the material is about 22% in view of the degree of reduction of the outside diameter. A steel shaft was press-fitted into the ceramic bearing, the outer member was fixed, and a load of 300 g was applied to the bearing, and one end of the shaft was driven at a rotation speed of about 6000 rpm.
The bearing maintained its performance after 210 consecutive days of use. Steel miniature bearings of approximately the same size, tested under the same conditions for comparison, were worn and lost function after 150 days of operation.

【The invention's effect】

The ceramic bearings of the present invention are significantly more durable than conventional steel bearings. Therefore, it is suitable for equipment that requires continuous operation for a long period of time and for applications where maintenance is difficult. It also has properties such as chemical resistance, acid resistance, and salt water resistance that are unique to ceramics, making it useful for various chemical plants and ships. Needless to say, it has heat resistance, so it is useful as a bearing used at a temperature at which lubricating oil cannot be used or at a higher temperature. The advantage of low wear means that it can also be used for applications such as casters for use in clean rooms for IC manufacturing. The inner member and the outer member that make up the bearing are made of ceramics that are integrally formed, and have a simple structure,
It can be used as it is for both thrust bearings and radial bearings without slipping out in the axial direction due to the difference in inner and outer diameters of both.

[Brief description of drawings]

1 and 2 are sectional views showing examples of the ceramic bearing of the present invention. 3 and 4 are schematic cross-sectional views for explaining the method for manufacturing a ceramic bearing according to the present invention.
The figure shows the state before sintering, and FIG. 4 shows the state after sintering. 1 …… Inner member 2 …… Outer member, 2A …… Outer member material 3 …… Shaft D _I …… Maximum diameter of inner member D ₀ …… Minimum diameter of outer member d ₀ …… Minimum diameter of material

Claims (6)

(57) [Claims] 1. An inner member made of ceramics, which is integrally formed and has a shape obtained by rotating a cross section of a convex or concave toward the outside around an axis, and an outer surface of the inner member surrounding the inner member. It has an inner surface shape corresponding to the shape and is composed of an outer member integrally formed of sintered ceramics, wherein the maximum diameter of the inner member is larger than the minimum diameter formed by sintering of the outer member. Ceramic bearing. 2. The ceramic bearing according to claim 1, wherein the difference between the maximum diameter of the inner member and the minimum diameter of the outer member is 2 μm or more. 3. The ceramic bearing according to claim 1, wherein the outer member is provided with a radial oil filling hole. 4. A ceramic bearing according to claim 1, wherein the ceramic is selected from fine ceramics such as alumina, zirconia, silicon nitride and the like. 5. An inner member made of ceramics having a shape obtained by rotating a convex or concave cross section toward the outside around an axis is prepared, and the periphery thereof is an inner surface shape corresponding to the outer surface shape of the inner member. But has a minimum diameter larger than the maximum diameter of the inner member, surrounded by a material that forms ceramics by firing,
A method of manufacturing a ceramic bearing, characterized in that the material of the outer member is made into ceramic by firing and the minimum diameter is made smaller than the maximum diameter of the inner member so that the inner member does not come off from the outer member. 6. The method of manufacturing a ceramic bearing according to claim 5, which is carried out by polishing the surface of the inner member in advance.