JP3519569B2 - Method of manufacturing rotary bearing having dynamic pressure generating groove for small motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a rotary bearing structure of a small motor, and more particularly to a method of forming a rotary bearing portion of a small motor having a dynamic pressure bearing function. . 2. Description of the Related Art Hitherto, various configurations having a dynamic pressure bearing function as a rotary bearing structure of a small motor have been proposed.
For example, there is one described in JP-A-5-313213. [0003] However, in the conventional dynamic pressure bearing structure, it is difficult to form a groove such as a herringbone for generating the dynamic pressure, which requires advanced technology and expensive equipment. Therefore, the result was very expensive. [0004] Further, in conventional hydrodynamic bearing structures by etching, grooves in a herringbone or the like for generating a dynamic pressure are limited in the inner diameter of the bearing to be processed, and are stable in those having a small rotating shaft support. There was a drawback that it was not possible to perform the processing. [0005] In the groove forming method by rolling using a hard sphere, a bulge is formed on both sides of the groove and a projection is formed on the inner peripheral surface, so that finishing such as ball sizing is required. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method of forming a rotary bearing of a rotary motor of a small motor having a simple structure and an inexpensive dynamic pressure bearing function. . SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method for forming a rotary bearing portion of a small motor according to the present invention is to form a clearance between an inner peripheral surface of a rotary shaft bearing portion to be machined at a tip and a clearance. A mandrel with a small guide and a protrusion on the outer peripheral surface that has the same number of grooves as the groove to be machined and a predetermined number is attached to a processing machine that can perform feed motion simultaneously with forward and reverse rotation. A groove, such as a concave herringbone for generating a dynamic pressure, is manufactured by cutting in a rotary bearing portion which is a work fixed and held on the processing machine table side. According to the above-mentioned method, the mandrel having a projection for forming a groove by the guide portion at the tip is 1-2 μm.
Is accurately guided without causing any misalignment of the rotation bearing part (work) due to the gap of, the feed motion is performed while rotating by a predetermined angle, and after performing the predetermined feed, it is reversed with a negative angle with the above The mandrel protrudes, and a predetermined groove shape is cut and formed on the inner peripheral surface of the rotary support (work) by the protrusion of the mandrel. After the predetermined groove is formed, the mandrel is separated from the workpiece by repeating the forward and reverse rotations and the feed motion in the reverse order. At this time, the feed speed and the rotation speed are completely synchronized. According to this manufacturing method, the load at the time of grooving is applied along the axial direction of the mandrel. Therefore, even if the rotary bearing (work) is small, a sufficient load sufficient to form grooving is applied. By making the protrusions on the surface of the mandrel into a sharp rectangular shape and finishing the entire mandrel with a super-steel, cutting can be performed, and bulges at both ends of the groove, which occur in the rolling process, do not occur. FIG. 1 is a partially enlarged view of a groove processing mandrel according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a rotary bearing processing step according to an embodiment of the present invention. FIG. 1A shows a blank 1 serving as a rotary bearing and a mandrel 2 having projections 3 of the same number as a predetermined number of grooves on the outer periphery for forming grooves on the inner peripheral surface thereof. FIG. 1B shows a state in which the grooved mandrel 2 is slid clockwise with a predetermined low-speed rotational movement and guided to the inner peripheral surface of the blank material 1 by the guide portion 4 at the tip of the mandrel. FIG. 1 (c) shows groove processing. The groove processing mandrel 2 guided to the inner peripheral surface of the blank material 1 by the guide portion 4 is rotated clockwise at a low speed and slid in the direction of the arrow to form the blank material. A spiral groove 5 formed by the projections 3 is formed on the inner peripheral surface of the blank 1. After sliding a predetermined distance, the groove machining mandrel 2 rotates counterclockwise while keeping the slide feed speed unchanged. The groove shape of the dynamic pressure type rotary bearing is formed on the peripheral surface. FIG. 1D shows the state after the protrusion 3 of the grooved mandrel 2 has passed through the inner peripheral surface of the blank material. The grooved mandrel 2 is again turned clockwise, starts sliding in the opposite direction, and slides in the rotational direction. The direction is reversed and the groove processing is completed. At this time, the blank material is held without slipping, and the sliding (feeding) speed of the grooved mandrel 2 and the timing of rotation are completely synchronized, so that the protrusion 3 follows the formed groove shape 5 accurately. ,
Once formed, the groove shape is not damaged or deformed. The present invention does not require expensive equipment as described above, and is small, simple and inexpensive, and has a small amount of shaft runout.
A rotary bearing having a groove for generating dynamic pressure can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged view of a grooved mandrel. FIG. 2 is a view showing a method and a step of forming a groove according to an embodiment of the present invention. [Explanation of Signs] 1 {Blank material 2} Grooving mandrel 3} Protrusion 4} Sleeve 5} Groove 6} Rotating shaft

Claims (1)

(1) A method of manufacturing a rotary bearing of a small motor, comprising a dynamic pressure generating groove (5), wherein a rib corresponding to the dynamic pressure generating groove is provided. A mandrel (2) formed in a convex shape on the surface and rotatably held by a chuck of a cutting machine such as an NC lathe, and a diameter of an inner peripheral portion of a rotary support portion to be machined at the tip of the mandrel. Also 1-2
A guide portion having a gap of μm is arranged, and the mandrel is guided by this guide portion, and within a rotary bearing surface of a blank material fixed and held on a table side of a cutting machine such as the NC lathe, A rotary feed motion is performed at a predetermined feed speed and an angle in the rotary bearing portion, and after a predetermined length is processed, a rotary feed motion is performed in a direction opposite to the above-mentioned rotation direction, and the motion of a small motor formed by processing a continuous herringbone. A method for manufacturing a rotary bearing having a pressure generating groove.