JPH04365907A - Manufacture for cam shaft - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing cam shaft suitable for manufacturing an assembly cam shaft for a vehicle especially, having high accuracy after assembly, and not requiring high accuracy work form a single unit of each kind of part such as a cam or the like on an assembled side so as the enable manufacture at a low cost. CONSTITUTION:In the case of arranging several kinds of a signal unit work part including a cam 21 in longitudinal axial direction of a main shaft 20 and joining them to an outer circumference surface, firstly the longitudinal sectional surface of main shaft 20 is formed in a shape other than a circular shape. A part 21 is formed with provision of a coupling hole 22 which is formed in a similar shape larger than the longitudinal sectional surface shape of the main shaft 20. The part 21 is set in the prescribed position of the main shaft 20 through the coupling hole 22. The main shaft 20 and the parts 21 and turned relatively, and a part of the main shaft 20 is forced to abut on a part of the coupling hole 22 of the part so as to make pressure-contact with each other.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method of manufacturing a camshaft that drives intake and exhaust valves of an internal combustion engine, and more specifically, the present invention relates to a method of manufacturing a camshaft that drives intake and exhaust valves of an internal combustion engine. This invention relates to a manufacturing method for arranging and assembling various parts such as cam lobes, journals, and gears.

0002

2. Description of the Related Art Conventionally, the following methods of manufacturing camshafts using an assembly structure have been known. That is, ■
A method in which the main body shaft is prepared as a hollow shaft, parts such as a cam are positioned at predetermined positions on the outer circumference of the main body shaft, and the parts are caulked and fitted by expanding or expanding the main body shaft. ■ A concave groove extending in the axial direction is provided on the outer circumference of the main body shaft, and a rib-like convex line is provided on the inner circumferential surface of the coupling hole of a component such as a cam, so that the convex line is fitted into the concave groove and the outer circumference of the main body shaft is Assemble the parts. After this, the joint surface between the main body shaft and the parts is filled with brazing agent to strengthen the joint. (2) A plurality of protrusions are provided to protrude along the circumference at the component assembly position of the main body shaft, and a plurality of protrusions extending in the axial direction are also provided on the inner peripheral surface of the coupling hole of the component. There is a method of press-fitting the protrusions on both sides alternately.

0003

[Problem to be Solved by the Invention] However, in the case of method (2), since the coupling method utilizes deformation by expanding the main body shaft, the position of parts such as cams may shift after assembly, resulting in poor accuracy. There is a problem in that the main body shaft may be bent or otherwise distorted or deformed. Also. In the method (2), there is a problem in that hard machining is required for the fitting accuracy of the concave groove and the convex strip, and the machining cost increases. Furthermore, in the case of method (2), it is necessary to form a protrusion on the inner circumferential surface of the coupling hole for each component such as a cam, which does not improve productivity. Furthermore, there is the problem that the main body shaft is likely to bend during press-fitting, similar to method (2). Therefore, it is an object of the present invention to be particularly suitable for manufacturing assembled camshafts for automobiles, to have high precision after assembly,
Moreover, it is an object of the present invention to provide a method of manufacturing a camshaft that does not require high-precision machining in the single-unit molding of various parts such as a cam to be assembled, and can be manufactured at low cost as a result.

0004

[Means for Solving the Problems] A method for manufacturing a camshaft according to the present invention is to arrange several types of single machined parts including a cam in the longitudinal axis direction of the main body shaft and connect them to the outer circumferential surface of the main body shaft. The process of forming a vertical cross-section into a shape other than a perfect circle, the process of molding a part with a connecting hole of a similar shape that is larger than the vertical cross-sectional shape of the main body shaft, and the process of positioning the part at a predetermined position on the main body shaft by passing it through the connecting hole. and a joining step of rotating the main body shaft and the component relative to each other and bringing a part of the main shaft into contact with a part of the joining hole of the part to press the part. Further, in the case of the present invention, the component is a sintered cam, and a plurality of cams can be arranged in the longitudinal direction of the main body shaft and connected at different angles about the central axis of the main body shaft.

[0005]

[Operation] The main body shaft is formed into a desired vertical cross-sectional shape, and a large coupling hole similar to the vertical cross-sectional shape of the main body shaft is provided in a part such as a cam. Parts such as cams are arranged and positioned in the longitudinal direction of the outer circumference of the main body shaft through the coupling holes. The main body shaft and the component are rotated relative to each other, and a part of the main body shaft is brought into contact with a part of the coupling hole of the component and crimped. The crimping part has a wide degree of freedom in terms of area. Therefore, there is no need to process the cam with high precision, and since the accuracy of the cam is generally sufficient as a sintered product, post-processing after the single unit processing by sintering is not required.

[0006]

[Embodiment] A method of manufacturing a camshaft according to the present invention will be explained below. FIG. 1 is a partially sectional side view of an example of an automobile camshaft manufactured by the manufacturing method of the present invention. The camshaft 10 has a structure in which a plurality of parts such as a cam 12, a journal 13, a gear 14, etc. are arranged around the longitudinal outer circumference of a main body shaft 11 made of metal. In particular, the cam 12 is generally a single sintered body. The journal 13 and gear 14 are also individually molded into a desired shape in preparation for assembly. Example camshaft 1
0 shows a solid shaft, but the main shaft 11
The present invention is also applicable to a hollow shaft having a long cavity along the central axis of the shaft.

FIGS. 2 to 4 are cross-sectional views of a manner in which a main shaft 20 of a camshaft having a cross-sectional shape as shown and a cam 21, which is one of the assembled parts, are connected as a first embodiment of the present invention. It is a diagram. As shown in FIGS. 2 and 3, the main body shaft 20 has an elliptical cross section with a major axis D1 and a minor axis D2. The cam 21 is provided with a coupling hole 22 having a similar oval shape larger than the cross-sectional shape of the main body shaft 20. The connecting hole 22 of the cam 21 is set within a range in which the short diameter d2 thereof is not larger than the long diameter D1 of the main shaft 20 so that the main shaft 20 can be inserted therethrough. However, although the main body shaft 20 is shown as having an elliptical cross section to facilitate understanding, in reality, the dimensional difference between the major axis and the minor axis is about 0.1 mm.

In relation to these cross-sectional dimensions, the cam 21 is assembled at a predetermined position on the main body shaft 20 by passing the cam 21 through the coupling hole 22 and positioning the cam 21 at a predetermined position on the main body shaft 20 . From this, as shown in FIGS. 3 and 4, either the main body shaft 20 or the cam 21 is rotated around the central axis of the other. Or the main shaft 20
and cam 21 are rotated in relative directions around the same central axis. As a result, the major axis D of the main body shaft 20
1 comes into contact with a portion of the cam 21 that is close to the major axis d1 of the coupling hole 22 (the abutting portion is indicated by reference numeral 23). By relatively rotating with the required rotational force, the main body shaft 20
And the cam 21 is crimped at the two abutting portions 23, 23. If both the main body shaft 20 and the cam 21 are rotated relative to each other at the same time, the coupling force can be increased.

When assembling the cam 21, since the cross-sectional shape of the main body shaft 20 is similar and smaller than the coupling hole 22 of the cam 21, it is easy to insert the cam 21 into a predetermined position of the main body shaft 20. Therefore, no large force is applied to the main body shaft 20 during insertion, so there is no deformation. In addition, in the case of a structure in which a plurality of cams 21 of the same shape are arranged and assembled in the longitudinal direction of the main body shaft 20, the assembly method is based on relative rotation with the main body shaft 20.
It is possible to assemble a plurality of cams 21 at the same time, and productivity can be increased. However, since the plurality of cams 21 have different mounting angles around the shaft axis in correspondence with the intake and exhaust valves, it is necessary to pay attention to the rotation angle with respect to the main body shaft 20. Furthermore, by applying welding or brazing to the crimped portion, the bonding strength is increased and a camshaft capable of carrying a higher load can be obtained.

On the other hand, FIGS. 5 and 6 show second and third embodiments in which the shapes of the coupling portions are different. The main body shaft 30 according to the second embodiment shown in FIG. 5 has a cross-sectional shape in which a perfect cylinder having a predetermined diameter is formed, and a part of the circumference is cut out in an arc shape to provide a flat part 31. On the other hand, the cam 32 is provided with a coupling hole 33 through which the main body shaft 30 can be inserted. The coupling hole 33 has a similar shape to the main body shaft 30 and has a large inner diameter, and the coupling hole 33 is provided with a flat portion 34 in which a part of the inner circumference is cut out in an arc shape.

Therefore, in the second embodiment shown in FIG. 5, when assembling, the flat part 34 of the coupling hole 33 of the cam 32 is aligned with the flat part 31 of the main body shaft 30, and the cam 32 is inserted to a predetermined position on the main body shaft 30. position. As in the case of the first embodiment, either one of the main body shaft 30 or the cam 32 is rotated around the central axis of the other, or both the main body shaft 30 and the cam 32 are simultaneously rotated in relative directions. let As a result, the main body shaft 30
The corner end of the flat part 31 becomes the abutting part 35 and the cam coupling hole 3
Press to the flat part 34 of No. 3. At this time, at a position facing the contact portion 35, the inner circumferential surface of the coupling hole 33 of the cam 32 is in close contact with the outer circumferential surface of the main body shaft 30 at a portion 36.

Further, in the case of the third embodiment shown in FIG. 6, the main body shaft 40 is shaped like a rice ball with a triangular cross section formed by three gently curved sides 41 and three tops 42. On the other hand, the cam 43 is provided with a similar triangular coupling hole 44 that is larger than the cross-sectional shape of the main body shaft 40 . Also in the case of this third embodiment, the main body shaft 40
Due to the relative rotation between the cam 43 and the cam 43, the three tops 42 of the main body shaft 40 come into contact with three sides of the coupling hole 44 of the cam 43 and are pressed together, as shown in FIG. In the second and third embodiments shown in FIGS. 5 and 6, the first point is that the joint strength is increased by welding or applying brazing to the joint.
This is the same as in the embodiment.

[0013] As is clear from the first to third embodiments described above, the connection portion by pressure bonding between the main body shaft and parts such as the cam can be provided over a wide area range. That is, the contact part 23 of the first embodiment, the contact part 35 (circumferential contact part 36) of the second embodiment
) and the contact portion 42 of the third embodiment, there is a wide degree of freedom in the crimping region. Therefore, it is not necessary to machine the cam with high precision as in the past, and since the precision of a sintered product is generally sufficient for the cam, there is no need for post-processing after single-piece processing by sintering. Furthermore, since there is no need to provide a special rib-like protrusion on the inner circumferential surface of the coupling hole of the cam as in the past, stress concentration does not act on the cam during and after crimping. As a result, no special high strength materials are required.

[0014]

Effects of the Invention As explained above, the method for manufacturing a camshaft according to the present invention is particularly suitable for automobile camshafts. It is not necessary to process the cam with high precision as in the past, and since the accuracy of the cam is generally sufficient as a sintered product, there is no need for post-processing after single-piece processing by sintering. Furthermore, unlike in the past, there is no need to provide a special rib-like protrusion on the inner circumferential surface of the cam's coupling hole, so there is no stress concentration on the cam during or after crimping, making it possible to use specially designed high-strength materials. does not require. As a result, manufacturing at low cost is possible.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional assembly diagram of an automobile camshaft obtained by the camshaft manufacturing method of the present invention.

FIG. 2 is a cross-sectional view of the first embodiment of the cross-sectional shape of the joint between the main body shaft and the assembled parts.

FIG. 3 is a cross-sectional view of the manner in which the main shaft and the assembly parts are connected in the first embodiment.

4 is a sectional view taken along the arrow A-A line in FIG. 3. FIG.

FIG. 5 is a cross-sectional view of a second embodiment of the cross-sectional shape of the joint between the main body shaft and the assembly part.

FIG. 6 is a cross-sectional view of a third embodiment of the cross-sectional shape of the joint between the main body shaft and the assembly component.

[Explanation of symbols]

10 (20, 30, 40). ．． Main body shaft, 11
(21, 32, 43). ．． Cam (parts), 22 (3
3, 44). ．． Binding hole, 23 (35, 42). ．． Contact part to be crimped

Claims (2)

[Claims] Claim 1: A method for manufacturing a camshaft in which several types of single machined parts, including a cam, are arranged in the longitudinal axis direction of a main body shaft and connected to the outer circumferential surface of the main body shaft. a process of molding, a process of molding a part with a coupling hole of a similar shape larger than the vertical cross-sectional shape of the main body shaft, a process of positioning the part at a predetermined position on the main body shaft by passing it through the coupling hole, a process of moving the main body shaft and the part relative to each other. A method for manufacturing a camshaft, comprising a joining step of rotating a part of the main body shaft to abut and press a part of a joining hole of a component. Claim 2: The component is a sintered cam, and a plurality of cams are arranged in the longitudinal direction of the main body shaft and connected at different angles about the central axis of the main body shaft.
A method for manufacturing a camshaft according to claim 1.