Rotating body, rotating body material, and method of manufacturing rotating body

Abstract

A novel rotating body, its material, and manufacturing method thereof, shortening a distance for cutting a bore surface in its axial direction, reducing processing costs, enabling lower-cost manufacture of inner rotor. A metallic rotating body 11 has a bore surface 12 for press-fitting a shaft thereinto, including a cutting-processed portion 13 at first end and an unprocessed portion 14 at second end. The processed portion 13 has an inner diameter formed smaller than the unprocessed portion 14. A chamfer 15 at first end of the bore surface 12 is cut, while a chamfer 6 at the second end not. A bore surface 2 of material 1 processed into the rotating body 11 includes a small-diameter portion 3 at first end and a large-diameter portion 4 at second end. A step 5 is formed between the small- and large-diameter portions 3, 4, with the chamfer 6 formed at second end.

Claims

1. A rotating body made of metal into which a shaft can be press-fit, comprising: a bore surface including a processed portion at a first end that has undergone a cutting process such that it is straight and linear so as to accommodate press-fitting of the shaft and an unprocessed portion provided at a second end, wherein the processed portion has an inner diameter smaller than an inner diameter of the unprocessed portion, and the difference in an inner diameter between the processed portion and the unprocessed portion is in a range from 0.01 to 0.02 mm.

2. The rotating body according to claim 1, further comprising a chamfered portion on each of the first and second ends the bore surface, wherein the chamfered portion at the first end is formed during the cutting processing, while the chamfered portion at the second end has not undergone a cutting processing.

3. The rotating body according to claim 1, wherein the rotating body is an inner rotor for an internal gear oil pump.

4. The rotating body according to claim 1, wherein, the processed portion occupies to of the area of the bore surface in a bore axis direction.

5. The rotating body according to claim 4, further comprising a chamfered portion on each of the first and second ends the bore surface, wherein the chamfered portion at the first end is formed during the cutting processing, while the chamfered portion at the second end has not undergone a cutting processing.

6. The rotating body according to claim 4, wherein the rotating body is an inner rotor for an internal gear oil pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein like designations denote like elements in the various views, and wherein:

(2) FIG. 1 is an explanatory diagram illustrating an embodiment of a method of manufacturing a rotating body according to the present invention.

(3) FIG. 2 is an explanatory diagram illustrating a conventional method of manufacturing a rotating body.

DETAILED DESCRIPTION OF THE INVENTION

(4) Next is a description of a rotating body, a rotating body material, and a method of manufacturing the rotating body according to an embodiment of the present invention, with reference to the drawings.

Embodiment 1

(5) The rotating body according to the present embodiment is an inner rotor for an internal gear oil pump made of a ferrous metal. In FIG. 1 showing a method of manufacturing a rotating body of the present embodiment, there are illustrated a material 1 as a rotating body material at the left side thereof, and a rotating body 11, obtained by allowing the rotating body material to be subjected to a cutting processing, at the right side thereof. It is to be noted herein that FIG. 1 is only an explanatory diagram schematically and mainly showing a bore surface into which a shaft (not shown) is press-fitted, and not intended to show the actual shape of the inner rotor, etc.

(6) At the left side of FIG. 1, the material 1 is the one obtained by powder metallurgy in which a metal powder is molded and then baked, including a bore surface 2 of a substantially cylindrical shape. The bore surface 2 includes a small-diameter portion 3 at a first end and a large-diameter portion 4 at a second end such that the small-diameter portion 3 and the large-diameter portion 4 extend in a linear manner, each defining a constant inner diameter. Since the small-diameter portion 3 is to be subjected to a cutting processing described later, its inner diameter is set smaller than that of the large-diameter portion 4 to ensure a processing margin, while there is formed a step 5 between the small-diameter portion 3 and the large-diameter portion 4. Also, a chamfered portion 6 is formed at the second end. Meanwhile, a step 7 between the chamfered portion 6 and the large-diameter portion 4 is the one formed for convenience of molding in powder metallurgy.

(7) On the other hand, at the right side in FIG. 1, there is illustrated the rotating body 11 that is formed by allowing only the small-diameter portion 3 of the material 1 to be subjected to the cutting processing. That is, the inner bore surface 12 of the rotating body 11 includes a processed portion 13 that has undergone a cutting processing at a first end, and an unprocessed portion 14 that has not undergone a cutting processing at a second end. Accordingly, the large-diameter portion 4 of the material 1 is identical to the unprocessed portion 14 of the rotating body 11. In this way, in the inner bore surface 12 of the rotating body 11, only the processed portion 13 that defines a range in which the shaft is press-fitted is formed by the cutting processing, and thus the cutting distance of the inner bore surface 12 in the bore axis direction is shortened, so that the processing cost of the bore surface is reduced. According to the present embodiment, the processed portion 13 occupies to area of the bore surface 12 in the bore axis direction, thereby enabling the reduction of the processing cost in the remaining to area. Moreover, the resultant decreased cutting distance leads to a prolonged life of a cutting tool used for the cutting processing, resulting in the reduction of costs incurred by the cutting tool.

(8) Here, since the unprocessed portion 14, which defines a range in which the shaft is not press-fitted, may serve to guide the shaft when press-fitting the shaft, the difference in inner diameter between the processed portion 13 and the unprocessed portion 14 should preferably be as small as possible. On the other hand, in order to efficiently process only the processed portion 13 without the unprocessed portion 14 being hit by the cutting tool such as turning tool during the cutting processing, the inner diameter of the unprocessed portion 14 should desirably be set larger than the inner diameter of the processed portion 13. For this reason, the inner diameter of the processed portion 13 is formed so slightly smaller than the inner diameter of the unprocessed portion 14 that the bore surface 12 thereof defines a shape close to a straight and linear shape in the conventional inner rotors. Incidentally, the difference in inner diameter between the processed portion 13 and the processed portion 14 is in the order of 0.01 to 0.02 mm, for example.

(9) Also, the bore surface 12 is provided with a chamfered portion 15 at its distal end on the first end side that is formed by performing a cutting processing. Note that the chamfered portion 6 at the opposite end portion on the second end side is not subjected to a cutting processing, and hence it remains the same as it was in the material 1. In this manner, forming in advance the chamfered portion 6 at the end portion on the second end side in the material 1 can eliminate the need for the step of forming the chamfered portion 6 by a cutting processing, thereby enabling the reduction of the processing cost.

(10) As discussed above, the rotating body according to the present embodiment is the metallic rotating body 11 into which a shaft is press-fitted, wherein the bore surface 12 into which the shaft is press-fitted includes the processed portion 13 that has undergone a cutting processing at the first end, and the unprocessed portion 14 that has not undergone a cutting processing at the second end, and the processed portion 13 is formed to have an inner diameter smaller than an inner diameter of the unprocessed portion 14. Also, the chamfered portion is provided on both ends of the bore surface 12, wherein the chamfered portion 15 at the first end is the one subjected to a cutting processing, while the chamfered portion at the second end is not the one subjected to a cutting processing.

(11) Also, the rotating body material according to the present embodiment is the material 1 serving as a rotating body material that is to be processed into the metallic rotating body 11 into which a shaft is press-fitted, including:

(12) the bore surface 2 including the comparatively small-diameter portion 3 at the first end, and the comparatively large-diameter portion 4 at the second end, the comparatively large-diameter portion 4 having a larger diameter than the comparatively small-diameter portion 3, wherein the step 5 is formed between the comparatively small-diameter portion 3 and the comparatively large-diameter portion 4, while the chamfered portion 6 is formed at the second end.

(13) Still also, the method of manufacturing a rotating body according to the present invention is the method of manufacturing the metallic rotating body 11 into which a shaft is press-fitted, including:

(14) a material-forming step of forming the material 1; and

(15) a cutting-processing step of allowing the material 1 to undergo a cutting processing,

(16) wherein the bore surface 2 of the material 1 formed at the material-forming step includes the comparatively small-diameter portion 3 at the first end, and the comparatively large-diameter portion 4 at the second end, the comparatively large-diameter portion 4 having a larger diameter than the comparatively small-diameter portion 3,

(17) wherein the step 5 is formed between the comparatively small-diameter portion 3 and the comparatively large-diameter portion 4, while the chamfered portion 6 is formed at the second end, and

(18) wherein only the comparatively small-diameter portion 3 is subjected to a cutting processing at the cutting processing step.

(19) Accordingly, the cutting distance of the bore surface 12 in the bore axis direction is shortened, thereby reducing the processing cost of the bore surface. Moreover, the resultant decreased cutting distance leads to a prolonged life of a cutting tool used for the cutting processing, resulting in the reduction of costs incurred by the cutting tool.

(20) In the meantime, the present invention is not limited to the foregoing embodiment. For example, the material is not limited to the one formed by powder metallurgy, but may be one formed by casting or forging. Also, the rotating body is not limited to an inner rotor for an internal gear oil pump.

DESCRIPTION OF SYMBOLS

(21) 1 material (rotating body material) 2 bore surface 3 small-diameter portion 4 large-diameter portion 5 step 6 chamfered portion 11 rotating body 12 bore surface 13 processed portion 14 unprocessed portion 15 chamfered portion