JPS614809A - Method of securing sintered part by securing engagement - Google Patents

Abstract

PURPOSE:To temporarily secure a shaft member, inserted into a through-hole, by means of the deforming stress of a projection and to improve productivity of engaging securing, by a method wherein a projection is provided on the inner peripheral surface of a through-hole in a sintered part under a preliminarily- sintered condition, and an escape hole is formed behind the projection. CONSTITUTION:A through-hole 2 with a given radius D is formed around the center of a base circle in a sintered part, in which metallic powder is sintered, such as a cam 1, and a projection 3, protruded toward the inner periphery side, is formed on the spot, where a thickness wall in a radial direction is thickermost, of the inner periphery of the through-hole 2. Further, an escape hole 4 is provided in a cam 1 in a position where the projection 3 is nipped between the through-hole 2 and the escape hole. With a shaft 5 pressed in the through-hole 2, the projection 3 forms a press-in margin C proportioning a projecting distance of the projection, and since the escape hole 4 is formed behind the projection 3, the projection 3 is resiliently deformed and simultaneously deforms the escape hole 4. This enables the cam 1 and the shaft 5 to be temporarily secured by means of the deforming stress of the projection 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for fitting and fixing a sintered part such as a cam in an engine camshaft to a shaft member such as a shaft, and relates to a method for fitting and fixing a sintered part such as a cam in an engine camshaft. It can be used in the field of parts manufacturing.

BACKGROUND OF THE INVENTION It is well known that sintered parts are increasingly being used as parts of automobile engines that require strong wear resistance, such as cams in valve train mechanisms. This type of cam is installed in the engine by being attached to a shaft that rotates in synchronization with the crankshaft.
Since the cam is a sintered part, there are problems when attaching it to the shaft as described below.

In other words, the cam is generally attached to the shaft by inserting the shaft into its through hole, but in order to time the opening and closing of the engine pulp, it is necessary to accurately position the cam in the circumferential direction (so-called phase) with respect to the shaft. Conventionally, a groove along the axial direction is formed on the outer surface of the shaft, and a protrusion is formed on the inner surface of the through hole in the cam, and these V grooves and the protrusion are engaged. A method has been adopted in which the phase is determined and the shaft is fixed in the circumferential direction, and the shaft is fixed in the axial direction by caulking a part of the shaft. However, with this method, play occurs in both the circumferential direction and the axial direction, resulting in poor installation accuracy in many cases.Moreover, the above-mentioned grooves need to be machined, resulting in high costs. There's a problem.

On the other hand, there is a method of attaching the cam to the shaft by press-fitting the shaft into a through-hole formed in the cam.With this method, the cam and the shaft can be easily fixed without causing play. can do.

However, when fitting and fixing the cam and shaft,
Normally, the cam is pre-sintered before it is fitted onto the shaft, and then the main sintering process is carried out.At the time of fitting, the cam has poor dimensional accuracy and is insufficient in strength. There is a problem in that the cam may crack due to the stress caused by press-fitting the shaft, or conversely, the inner diameter of the through hole into which the shaft is inserted is too large and the cam and jab cannot be fixed to each other.

Therefore, the applicant filed a patent application filed prior to the filing of the present application.
In Japanese Patent Application No. 246255 and Japanese Patent Application No. 11759/1984, a method of fitting and fixing sintered parts was proposed which can solve the above-mentioned conventional problems. Fig. 5 shows a cam which is a sintered part used in the method proposed in Japanese Patent Application No. 58-246255, and a protrusion 3a made of a hollow bottle is attached to the inner periphery of the through hole 2a of the cam 1a. , the shaft is temporarily fixed to the cam 1a by the projection 3a. Therefore, in the method proposed above, the shaft member and the mating member can be connected without applying an excessive load to the mating member and without causing cracks in the mating member or play in the mating part. This provides an excellent effect of being able to fit and fix the parts.

However, in any case, the methods proposed in the above applications require a process of assembling the protrusions to the fitting member, for example, either molding each separately and then assembling them, or combining them in the same process. In this respect, there was room for improvement to increase productivity.

Purpose of the Invention The present invention has been made in view of the above circumstances, and it is possible to manufacture sintered parts into shaft members in a simple process and with high precision without causing any inconvenience such as breakage of sintered parts such as cams. It is an object of the present invention to provide a method that allows for good fitting and fixing.

Structure of the Invention This invention involves inserting a shaft member into a through hole in a sintered part in a pre-sintered state, and performing main sintering in that state to join the two by diffusion bonding. The inner diameter of the shaft member is formed to be slightly larger than the outer diameter of the shaft member, and a protrusion integral with the sintered part is formed on the inner circumferential side of the through hole, and the sintered part is further formed with a projection part that is integral with the through hole. By providing a relief hole at a position where the protrusion is sandwiched between the two holes, and inserting the shaft member into the through hole while deforming the protrusion, the shaft member is moved against the sintered part by the deformation stress of the protrusion. It is characterized in that it is temporarily fixed by using.

EXAMPLES The present invention will be described below by taking as an example a case in which a cam, which is a sintered part, is fitted and fixed to a shaft. Figures 1 and 2 show a cam 1 as an intermediate product obtained by compression molding powder raw materials and pre-sintering. A hole 2 is formed.

A protrusion 3 is provided at a portion of the inner periphery of the through hole 2 having the thickest wall thickness in the radial direction so as to protrude toward the inner periphery of the through hole 2. The protrusion 3 is formed when the cam 1 is manufactured by compression molding and pre-sintering the powder raw material.
It is molded simultaneously with the cam 1 from the same raw material.

Since the protrusion 3 is formed as described above, the actual inner diameter of the through hole 2 is locally slightly reduced by the protrusion 3.

Furthermore, the cam 1 is located at a position where the protrusion 3 is sandwiched between the through hole 2 and the protrusion 3, in other words, when the protrusion direction of the protrusion 3 toward the center of the through hole 2 is the front side. , an escape hole 4 is formed at a rear position of the protrusion 3. It is desirable that the diameter of the relief hole 4 be as small as possible within a range that allows elastic deformation of the protrusion 3. Further, the planar shape of the relief hole 4 is not limited to a circular shape, but can be a semicircular shape or other flat shape.

On the other hand, the shaft 5 to which the cam 1 is attached is, for example, a W4 tube shaft, and its outer diameter d is slightly smaller than the inner diameter of the through hole 2 and larger than the radial dimension at the location where the protrusion 3 is provided. Therefore, the projection 3 forms a press-fitting allowance C. Here, the dimensional difference (0, -d) between the outer diameter d of the shaft 5 and the inner diameter of the through hole 2 is set to an extent that can be absorbed by contraction of the cam 1 during main sintering.

In order to assemble the cam 1 formed as described above and the shaft 5, first, the phases of the two, that is, the relative positions in the circumferential direction are determined, and they are arranged on substantially the same axis, and in this state, the shaft 5 is inserted through the shaft 5. Press fit into hole 2. In that case, the protrusion 3
forms a press-fitting allowance C corresponding to its protrusion maximum, and since a relief hole 4 is formed at the rear of the protrusion 3, by inserting the shaft 5 into the through hole 2 of the cam 1, the protrusion 3 is elastically deformed as shown in FIG. 3, and the relief hole 4 is also deformed at a portion indicated by 48 in the figure. As a result, the cam 1 and the shaft 5 are temporarily fixed to each other due to the deformation stress of the protrusion 3. When the temporarily fixed state is heated for the main sintering process, diffusion bonding begins between the cam 1 and the protrusion 3 and the shaft 5 as the temperature rises, and during the diffusion bonding process, the cam 1 and the shaft 5 are heated. There is no change in the relative position with respect to the shaft 5, and the diffusion bonding continues at the initially set relative position. As diffusion bonding progresses, cam 1
contracts, the inner diameter of the through hole 2 becomes smaller, and eventually the entire inner circumferential surface of the through hole 2 comes into close contact with the outer circumferential surface of the shaft 5, as shown in FIG. 4, and in this state, both are diffused. Joined by bonding.

Therefore, in the above method, by forming the protrusion 3, the cam 1 is prevented from breaking and other inconveniences occur.
Furthermore, regardless of the dimensional accuracy of the cam 1 or the shaft 5, the cam 1 and the shaft 5 can be fitted and fixed without creating a gap.

Note that the present invention is not limited to the case where the cam 1 and the shaft 5 are fitted and fixed, but can also be applied to the case where other shaft members and appropriate sintered parts to be fitted thereon are fitted and fixed. can.

Effects of the Invention As is clear from the above description, the method of the present invention includes inserting a shaft member into a through hole in a sintered part in a pre-sintered state,
Before joining these two by diffusion bonding by performing main sintering in this state, the inner diameter of the through hole is formed to be slightly larger than the outer diameter of the shaft member, and the inner diameter of the through hole is By providing a protrusion, forming a relief hole behind the protrusion, and inserting the shaft member into the through hole while deforming the protrusion and the relief hole, the shaft member is free from the deformation stress of the protrusion. The sintered part was temporarily fixed to the sintered part by the process, and then the final sintering was performed to bond the sintered part and the shaft member to each other by diffusion bonding. This prevents excessive loads from being applied to the sintered parts, and the protrusions absorb variations in the dimensional accuracy of the sintered parts and shaft members as deformation. In particular, by diffusion bonding the protrusion itself with the shaft member, the sintered part and the shaft member come into close contact with each other. Parts can be firmly fitted and fixed. That is, according to the method of the present invention: The fixing accuracy in the axial direction and the circumferential direction is improved, the machining allowance during finishing machining is accordingly reduced, and the material yield and machining efficiency are improved. In addition, in this invention, since the position in the circumferential direction, that is, the phase, can be changed steplessly, when the cam and the shaft are fixed together, it is easy to change the phase of the cam, and as a result, when the cam is installed, It is possible to improve the performance of the device.

Furthermore, particularly in the method of the present invention, the protrusion formed in the through hole of the sintered part is formed integrally with the sintered part using the same raw material powder as the sintered part during pre-forming of the sintered part. Since the protrusions are formed simultaneously with the sintered parts, there is no need to assemble or combine the protrusions with the sintered parts, compared to the case where the protrusions are made of a different material from the sintered parts, which has the advantage of high productivity.

[Brief explanation of the drawing]

1 to 4 are for showing an embodiment of the present invention, in which FIG. 1 is a front view of a sintered part of the cam, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is a cam. 4 is a front view showing the state during the main sintering process, and FIG. 5 is a front view of the cam used in another method proposed by the applicant. It is a front view. 1...Cam, 2...Through hole, 3...Protrusion,
4...Escape hole, 5...Shaft, C...
Press fit allowance, D...inner diameter of through hole, d...outer diameter of shaft. Applicant Toyota Motor Corporation Agent Patent Attorney Yutaka 1) Hisashi Take (and 1 other person) Figure I Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A through-hole is formed at a predetermined location in a sintered part made by pre-sintering metal powder, and the shaft member is inserted into the through-hole and main sintering is performed to connect the sintered part and the shaft member. When joining by diffusion bonding, the inner diameter of the through hole is formed to be slightly larger than the outer diameter of the shaft member, and a protrusion is formed integrally with the sintered part on the inner peripheral surface of the through hole. Furthermore, an escape hole is provided in the sintered part at a position sandwiching the protrusion between the through hole and the shaft member is press-fitted into the through hole while deforming the protrusion. A method for fitting and fixing sintered parts, characterized in that the sintered parts are temporarily fixed to the sintered parts by the deformation stress of the projections.