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Rotation shaft, feeding device, motor and manufacturing method for rotation shaftRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Reciprocating Rigid Pumping MemberRotation shaft, feeding device, motor and manufacturing method for rotation shaft description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060110270, Rotation shaft, feeding device, motor and manufacturing method for rotation shaft. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to Japanese Application No. 2004-335950 filed Nov. 19, 2004, which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to a rotation shaft where a spiral groove is formed on its outer peripheral face, a feeding device and a motor provided with the rotation shaft and a manufacturing method for the rotation shaft. BACKGROUND OF THE INVENTION [0003] In an optical disk reproduction/recording device which performs reproduction or recording information from or on an optical recording disk such as a CD, an optical head device on which an objective lens and various optical elements are mounted is moved by using a feeding device in a radial direction of the optical recording disk. A stepping motor which is provided with a rotation output shaft where a spiral groove is formed on its outer peripheral face is used in the feeding device. A rack part provided in the optical head device is engaged with the spiral groove of the rotation output shaft to linearly drive the optical head device along the axial direction of the rotation output shaft. [0004] The spiral groove of the rotation output shaft is formed by mechanical working such as rolling, cutting, grinding or the like, and the flank surface is formed in a substantially smooth surface (see, for example, Japanese Patent Laid-Open No. Hei 8-340668). [0005] In the feeding device constructed as described above, lubricant such as grease or oil is coated in the spiral groove to reduce friction between the rack part and the spiral groove and thus wear of the rack part and the spiral groove is prevented. However, since the flank surface of a conventional spiral groove is commonly formed in a mirror surface, it is difficult for the lubricant to be held and retained on the spiral groove. Therefore, in the conventional feeding device, when feeding operation is repeatedly performed, grease shortage occurs on the flank surface of the spiral groove. In the case that the rotation output shaft is formed of brass, when lubricant shortage described above occurs, the lubricant discolors black due to wear powder and the appearance of the rotation output shaft is significantly deteriorated. In addition, when the rack part is formed of resin, the rack part wears easily causing hindrance in the feeding operation. Further, when wear occurs as described above, noise is generated between the rack part and the spiral groove of the rotation output shaft to give a discomfort feeling to a user. SUMMARY OF THE INVENTION [0006] In view of the problems described above, it is an object and advantage of the present invention to provide a rotation shaft which is capable of preventing wear by enhancing holding power of lubricant on a spiral groove for feeding, and a feeding device, a motor and a manufacturing method for the rotation shaft. [0007] In order to achieve the above object and advantage, according to an embodiment of the present invention, there is provided a rotation shaft including a spiral groove for feeding which is formed on an outer peripheral face of the rotation shaft, and a plurality of fine recessed parts which is formed on a flank surface in the spiral groove. [0008] In accordance with an embodiment of the present invention, the flank surface of a spiral groove formed on the outer peripheral face of a rotation shaft which is used in a feeding device is formed with a plurality of fine recessed parts in a dispersed state. Therefore, when lubricant such as grease or oil is coated on the spiral groove, a high degree of holding power of the lubricant on the spiral groove can be attained. Further, when a feeding device is constructed in which the rack part of a movable body is engaged with the spiral groove of the rotation shaft, the lubricant is held on the spiral groove all the time even when feed operations are performed repeatedly. Accordingly, even when the rotation output shaft is formed of brass, the situation can be prevented in which the lubricant discolors black due to wear powder to cause the appearance of the rotation output shaft to deteriorate. Further, even when the rack part is formed of resin, since wear of the rack part can be prevented, the feeding operation can be stably performed over a long time period. In addition, the occurrence of noise between the rack part and the spiral groove of the rotation output shaft can be prevented. [0009] This invention is effectively applied to a rotation shaft whose raw material is nonferrous metal such as copper alloy or aluminum. In other words, when shortage of lubricant occurs in the case that raw material of the rotation shaft is nonferrous metal such as copper alloy or aluminum, the lubricant is easy to discolor black due to wear powder. However, according to an embodiment of the present invention, this problem can be effectively prevented. [0010] According to an embodiment of the present invention, there is provided a feeding device including a rotation shaft which is formed with a spiral groove for feeding on an outer peripheral face of the rotation shaft and the spiral groove of the rotation shaft is provided with a plurality of fine recessed parts which is formed on a flank surface of the spiral groove. The feeding device also includes a rack part which engages with the rotation shaft, a movable body which is linearly driven in an axial direction by rotation around the axial line of the rotation shaft, and lubricant which is coated on the spiral groove of the rotation shaft. [0011] This invention is effectively applied to a feeding device which is provided with a rack part made of resin. In other words, when shortage of lubricant occurs in the case that the rack part is made of resin, the rack part is easy to be worn to cause a problem to occur in feeding operations. However, according to an embodiment of the present invention, this problem can be effectively prevented. [0012] The rotation shaft in accordance with an embodiment of the present invention can be used as the rotation output shaft of a motor. In this case, the motor includes a main motor body in which the rotation output shaft is rotated around its axial line. [0013] According to an embodiment of the present invention, there is provided a manufacturing method for a rotation shaft including a spiral groove forming step which forms a spiral groove on the outer peripheral face of the rotation shaft, and a roughening step which forms a plurality of fine recessed parts on the flank surface of the spiral groove by using a first abrasive medium whose size is set to be capable of reaching to the flank surface. According to an embodiment of the present invention, a plurality of fine recessed parts can be easily formed on the flank surface of the spiral groove formed on the outer peripheral face of the rotation shaft and a large quantity of rotation shafts can be efficiently processed. [0014] This invention is effectively applied to a rotation shaft whose raw material is nonferrous metal. [0015] In accordance with an embodiment of the present invention, it is preferable that the roughening step uses mixed media of the first abrasive medium and a second abrasive medium whose size is larger than the size of the first abrasive medium. According to the manufacturing method for the rotation shaft described above, roughening of the flank surface of the spiral groove and deburring can be simultaneously performed and thus productivity of the rotation shaft can be improved. [0016] In accordance with an embodiment of the present invention, roughening step and deburring step, which removes burr from the rotation shaft by using a second abrasive medium whose size is larger than the size of the first abrasive medium, may be performed separately. [0017] Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIG. 1(a) is a schematic plan view showing an optical disk reproduction/recording device in which a feeding device in accordance with an embodiment of the present invention is provided and FIG. 1(b) is a side view showing the essential portion of the feeding device. [0019] FIG. 2(a) is an enlarged side view showing a rotation shaft in accordance with an embodiment of the present invention and FIG. 2(b) is an enlarged cross-sectional view showing a spiral groove. Continue reading about Rotation shaft, feeding device, motor and manufacturing method for rotation shaft... 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