JP2006077867A - Bearing sleeve and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability and heat resistance of a bearing by forming a number of fine vertical grooves approximately perpendicular to the rotating direction, in the inner face of a journal bearing. <P>SOLUTION: Blanking work for a bearing sleeve 1 is followed by wiring work. Herein, with a wire 2 passing through a blank inner face 1a, the bearing sleeve 1 is slid once or several times in the axial direction. At this time, paste 3 containing diamond grains having grain sizes of 10 μm or smaller is previously applied to the wire 2 to give no rotation to both the bearing sleeve 1 and the wire 2. Thus, the number of fine vertical grooves 1b approximately perpendicular to the rotating direction are formed in the inner face 1a of the journal bearing to serve as lubricating oil reservoirs. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing sleeve used for a cooling fan bearing and the like and a method of manufacturing the same.

  Conventionally, as a method of forming a vertical groove or an oil reservoir of a concave portion on the inner surface of the bearing, a method of processing a groove pattern by etching (for example, see Patent Document 1), a method by mold processing (for example, see Patent Document 2) , A method of forming a spiral groove on the inner surface of the sleeve by cutting, plastic working or turning (see, for example, Patent Document 3), a blasting method using abrasive grains (for example, see Patent Document 4), and an eyeball. Various methods are known, such as a method for jetting a shaped shot (for example, see Patent Document 5) and a method using a diamond film forming technique (for example, see Patent Document 6).

Ceramics are superior to metal materials in terms of heat resistance and wear resistance, and are widely applied to cutting tools and the like. Further, since ceramics having a high density do not have a function of impregnating with oil, the use thereof is limited to bearings using water or oil (submersible pump, blood pump, mechanical seal, etc.). However, since ceramics have strong covalent bonds and ionic bonds, it is known that very small amounts of water and oil act as lubricants. In recent years, it has attracted attention as a bearing material for cooling fans that employs sliding friction, which is an intermediate between a fluid bearing and a ball bearing, and has been put into practical use.
JP-A-6-10148 (2nd page, FIG. 6) JP-A-10-249464 (page 2-3, FIG. 1 to FIG. 7) JP 2002-36004 A (page 2-3, FIG. 1) JP 2002-193893 A (page 2-3, FIG. 1 to FIG. 2) JP 7-188738 A (page 3-4, FIG. 1) JP 2004-116770 A (page 3-4, FIGS. 1 to 6)

  However, none of the above known methods can be used to form a vertical groove or a reservoir of oil in the concave portion on the inner surface of a ceramic small journal bearing (φ0.1 to φ20). This is because ceramics are poor in terms of workability, dimensional accuracy, and surface roughness accuracy, and there is a problem that galling, looseness, and the like are generated as a bearing. In addition, if the surface is rough, grain boundary detachment occurs and the mating material is worn, and when it is mirror-finished, there is a problem that a stick-slip phenomenon occurs between the interfaces.

  The present invention has been made to solve such a conventional problem, and is a method of forming a longitudinal groove having a depth of 1 μm or less on the inner surface of a ceramic small journal bearing. The object is to provide a bearing sleeve that can improve the durability by taking advantage of ceramics, and a method of manufacturing the same.

  The means of the present invention for achieving the above-described object is characterized in that a large number of fine vertical grooves substantially perpendicular to the rotation direction are provided on the inner surface of the journal bearing.

  The material of the bearing sleeve is ceramics.

  According to another aspect of the present invention for achieving the above-mentioned object, in the method of manufacturing the bearing sleeve according to claim 1 or 2, the longitudinal groove is inserted through a shaft hole of a plurality of bearing sleeves stacked. And processing.

  The wire used in the wire processing is characterized in that diamond grains having a particle diameter of φ10 μm or less are deposited.

  The particle size is more preferably φ2 to φ4 μm.

  According to the present invention, a large number of fine vertical grooves that are substantially orthogonal to the rotation direction are provided on the inner surface of the journal bearing, and these vertical grooves are formed by inserting a wire through the shaft hole of the bearing sleeve. The obtained vertical groove becomes an oil pool of the lubricating oil, and a micropool phenomenon occurs, so that a significant reduction (about μ = 0.001) of the dynamic friction coefficient (usually μ = 0.1) can be expected. According to the present invention, high-precision machining with a roundness of 1.0 μm or less and a cylindricity of 1.0 μm or less is possible, so that the clearance between the bearing and the shaft can be designed to be small. At the same time, the surface of the groove was mirror-finished by wire processing, and the surface roughness was about 0.1 μm Ra and about 0.5 μm Ry when measured using a non-contact surface roughness meter (X (axis of FIG. 3 Direction) See Profile). This can be expected to improve the durability of the bearing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a central longitudinal sectional view of a bearing sleeve according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a bearing sleeve made of alumina, and a large number of longitudinal grooves 1b having a depth of about 1 μm are formed on the inner surface 1a of the shaft hole in a substantially central axis direction. The direction of the longitudinal groove 1b is formed to be 90 ° ± 30 ° or less as an inclination angle α with respect to the rotation direction of the bearing.

  Next, a method for manufacturing the bearing sleeve 1 will be described. First, a blank of the bearing sleeve 1 as shown in FIG. 1 is formed in advance from an alumina material by press molding. FIG. 2 is a schematic view showing a groove processing method. In FIG. 2, 2 is a wire made of a piano wire having a diameter slightly smaller than the inner diameter of the bearing sleeve 1, and 3 is a diamond particle having a particle diameter of φ10 μm or less (preferably φ2 to φ4 μm). The paste is applied by applying the paste to the wire 2. Shift to wire processing following blank processing. Here, the wire 2 coated with the diamond paste 3 is inserted into the shaft inner surface 1a of the blank of a large number of bearing sleeves 1 which are overlapped and fixed. The wire 2 is slid back and forth once or several times in the central axis direction with respect to the bearing sleeve 1.

  A slight relative rotational movement between the bearing sleeve 1 and the wire 2 occurs during wire processing. In this case, the inclination α of the longitudinal groove 1b slightly deviates from 90 °, but if it is within ± 30 °, the lubricating oil is retained. Will not be affected. When this operation is finished and washed, the bearing sleeve 1 is completed. By the above method, a large number of longitudinal grooves having a depth of 1 μm or less can be formed on the inner surface 1 a of the bearing sleeve 1.

  Instead of the wire 2, an electrodeposited wire in which diamond grains are deposited on the wire surface by electrodeposition may be used. This processing can be performed with all wire-processable ceramics having a cylindrical bearing sleeve, and with materials such as metal, carbon, and diamond.

  Next, effects of the embodiment of the present invention will be described. When the minimum thickness of the lubricating oil film formed between the two surfaces of the bearing and the shaft manufactured using the method of the present invention is hmin and the square root roughness of the roughness of the two surfaces is Rarms1 and Rarms2, respectively, The oil film parameter e, which is a guideline of the lubrication state on the sliding surface, is expressed by e = hmin / (Rarms1 + Rarms2) (refer to NIPPON VALQUA INDUSTRIES.LTD HP). It is considered that a lubrication mechanism has occurred.

By using fine ceramics such as Al ₂ O ₃ , ZrO ₂ , Si ₃ N ₄ , and SiC as materials, rust generation, corrosion, and seizure can be prevented. Since the ceramic has a hardness of Hv1000 or more, it has excellent wear resistance and the groove shape is easily maintained. Therefore, improvement in durability and improvement in heat resistance can be expected. Moreover, since the thermal expansion coefficient of ceramics is small, there is an advantage that there is little shape change at the time of temperature rise.

  Although the clearance between the bearing sleeve 1 and the shaft can be designed to be small, the depth of the longitudinal groove 1b is preferably equal to or less than the clearance. In particular, when the occurrence of internal cracks is suppressed and the crystal grain boundary is prevented from falling off, the groove depth is desirably 1 μm or less, which is possible by using the method of the present invention (FIG. 3). Y (perpendicular to axis) Profile). The surface roughness was about 0.1 μm Ra and about 0.5 μm Ry when measured using a non-contact type surface roughness meter, as shown in the graph for measuring the surface roughness of the inner surface of the bearing inner diameter in FIG. Even if the oil film is 1 μm, the oil reservoir effect is exhibited and a fluid lubrication mechanism is generated. Lubrication is also possible for oil mist level thin films.

  The bearing sleeve and the manufacturing method thereof according to the present invention can be widely applied to small journal bearings in general.

It is a center longitudinal cross-sectional view of the bearing sleeve which is embodiment of this invention. It is sectional drawing which shows the wire processing method of this invention. It is the graph which measured the bearing inner surface processing surface surface roughness and groove depth of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing sleeve 1a Inner surface 1b Longitudinal groove 2 Wire 3 Diamond paste

Claims (5)

  A bearing sleeve having a large number of fine vertical grooves substantially orthogonal to the rotation direction on the inner surface of a journal bearing.   The bearing sleeve according to claim 1, wherein a material of the bearing sleeve is ceramic.   3. The method of manufacturing a bearing sleeve according to claim 1, wherein the longitudinal grooves are processed by inserting wires into shaft holes of a plurality of stacked bearing sleeves.   4. The method of manufacturing a bearing sleeve according to claim 3, wherein the wire used in the wire processing is coated with diamond grains having a particle diameter of 10 [mu] m or less. The method for manufacturing a bearing sleeve according to claim 4, wherein the particle diameter is more preferably φ2 to φ4 μm.