JPH0525921B2 - - Google Patents

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. It can be used in the field of manufacturing.

BACKGROUND OF THE INVENTION It is well known that sintered parts are increasingly being used as parts of automobile engines that are strongly required to be wear-resistant, and one example of this is the cam in a valve mechanism. This type of cam is installed in the engine by being attached to a shaft that rotates in synchronization with the crankshaft, but because the cam is a sintered part, there are problems when attaching it to the shaft, as described below. It was hot.

In other words, the cam is generally attached to the shaft by inserting the shaft into its through hole, but in order to adjust the opening and closing timing of the engine's valves, it is necessary to accurately position the cam in the circumferential direction (so-called phase) relative to the shaft. Therefore, conventionally, a V 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 fixed in the circumferential direction, and fixed in the axial direction by caulking a part of the shaft. However, with this method, play often occurs in both the circumferential and axial directions, resulting in poor installation accuracy.
Moreover, since it is necessary to process the V-groove, there is a problem of high cost.

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. According to this method, the cam and the shaft can be easily fixed without causing play. can do. However, when fitting and fixing a cam and a shaft, the cam is usually pre-sintered before being fitted onto the shaft, and then the main sintering process is performed. Due to poor dimensional accuracy and insufficient strength, the cam may crack due to stress from 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 shaft cannot be fixed to each other. There was a problem that sometimes occurred.

Purpose of the Invention The present invention has been made in view of the above circumstances, and it is an object of the present invention to easily and precisely fit and fix a sintered part to a shaft member without causing any inconvenience such as breakage of the sintered part such as a cam. The purpose is to provide a method that allows for

Composition 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, thereby allowing the above-mentioned The inner diameter of the through hole is formed to be slightly larger than the outer diameter of the shaft member, and a hole is formed on either the inner peripheral surface of the through hole or the outer peripheral surface of the shaft member by the outer peripheral surface or inner peripheral surface of the other. By providing a protrusion made of a soft material that is easily deformed when pressed and whose melting point is lower than the temperature during main sintering, and inserting the shaft member into the through hole while deforming the protrusion, the shaft member is is temporarily fixed to the sintered part by the deformation stress of the protrusion, and then the protrusion is melted by performing main sintering.

Embodiments 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. 1st
Figures 1 and 2 show a cam 1 as an intermediate product obtained by compression molding and pre-sintering powder raw materials, and the cam 1 has a through hole 2 with a predetermined radius D centered on the center of the base circle. is formed, and a protrusion 3 is provided at a portion of the inner periphery of the through hole 2 that is thickest in the radial direction. That is, a pin 4 made of a soft material is embedded in the cam 1 toward the axial direction of the through hole 2, and a part of its outer circumferential surface protrudes toward the inner circumferential side of the through hole 2, and the protruding portion is a protrusion. It forms part 3. Therefore, the substantial inner diameter of the through hole 2 is locally slightly reduced by the protrusion 3.

Here, the protrusion 3 temporarily fixes the cam 1 and the shaft 5 inserted into its through hole 2 by its deformation stress, and the pin 4 forming the protrusion 3 is in a pre-sintered state. The cam 1 is made of a soft material that can be easily deformed without breaking and has a melting point lower than the temperature during main sintering. Specifically, the soft materials include pure copper (melting point 1083℃) and brass (melting point 950℃).
℃), silver brazing filler metal (melting point 620-780℃), etc.
A soft material with a melting point similar to that of silver braze may melt before diffusion bonding occurs between the cam 1 and the shaft 5 during final sintering, making it useless for temporary fixing. Pure copper, brass, or a material having a melting point similar to these is preferable. The pin 4 can be attached to the cam 1 by arranging the pin 4 in the mold when compression molding the powder raw material, or by assembling the pin 4 into the powder compact and pre-sintering it. It may be fixed by any method.

On the other hand, the shaft 5 to which the cam 1 is attached is, for example, a steel pipe shaft, and its outer diameter d is slightly smaller than the inner diameter D of the through hole 2 and larger than the radial dimension at the location where the projection 3 is provided. Therefore, the projection 3 forms a press-fitting allowance C. Here, the dimensional difference (D-d) between the outer diameter d of the shaft 5 and the inner diameter D 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 substantially on the same axis, and in that state, the shaft 5 is inserted through the Press fit into hole 2. In this case, since the protrusion 3 forms a press-fitting allowance C corresponding to the amount of protrusion, and the protrusion 3 is formed by the pin 4 made of a soft material,
By inserting the shaft 5 into the through hole 2 of the cam 1, the projection 3 is deformed as shown in FIGS. 3 and 4. As a result, the cam 1 and the shaft 5 are temporarily fixed to each other by the deformation stress of the protrusion 3. When the pins 4 are heated for the main sintering process while temporarily fixed in this way, diffusion bonding begins between the cam 1 and the shaft 5 as the temperature rises, if the pin 4 is made of pure copper, for example. Pin 4 then melts. In this case, since partial diffusion bonding has started, even if the pin 4 melts, the relative position between the cam 1 and the shaft 5 will not change, and the diffusion bonding will continue at the initially set relative position. do. As the diffusion bonding progresses, the cam 1 contracts, and the inner diameter D of the through hole 2 becomes smaller, and eventually the entire inner circumferential surface of the through hole 2 becomes the outer circumferential surface of the shaft 5, as shown in FIG. They are brought into close contact with each other, and in this state, both are bonded by diffusion bonding.

Therefore, in the above method, the material, wall thickness, and protrusion amount of the pin 4 that forms the protrusion 3 are appropriately set to reduce the load required for deformation to less than the load that would cause the cam 1 to break before the main sintering process. By setting cam 1
cam 1 without any inconvenience such as cracking, regardless of the dimensional accuracy of cam 1 or shaft 5, and without creating any gaps.
and the shaft 5 can be fitted and fixed.

In carrying out the method of the present invention, the protrusion 3 formed on the inner peripheral side of the through hole 2 in the cam 1 is not based on the pin 4 in the above-mentioned embodiment.
It may also be formed by a suitable hollow pin. Further, the present invention can be applied not only to the case of fitting and fixing the cam 1 and the shaft 5, but also to the case of fitting and fixing other shaft members and appropriate sintered parts to be fitted thereto. . Furthermore, since the present invention temporarily fixes the shaft member and the sintered component by the deformation force of the projection, the projection is provided on the outer periphery of the shaft member instead of being provided on the inner periphery of the through hole in the sintered component. It may be provided in the section.

Effects of the Invention As is clear from the above description, the method of the present 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 diffusion bond these two parts. Prior to joining by, the inner diameter of the through hole is formed to be slightly larger than the outer diameter of the shaft member, and on either the inner circumferential surface side of the through hole or the outer circumferential surface side of the shaft member,
A protrusion made of a soft material that is easily deformed when pressed by the other outer or inner circumferential surface and whose melting point is lower than the temperature during main sintering is provided, and the shaft member is deformed while the protrusion is deformed. By inserting the shaft member into the through hole, the shaft member is temporarily fixed to the sintered part by the deformation stress of the protrusion, and then the protrusion is melted by performing main sintering. By setting the deformation stress appropriately, excessive loads are not applied to the sintered parts, and variations in the dimensional accuracy of the sintered parts and shaft members are absorbed by the protrusions as deformation, and the final Specifically, the protrusion is heated and melted, and the sintered part and the shaft member come into close contact with each other. Therefore, the shaft member and the sintered part are not cracked or rattled at the fitting part, and the sintered part and the shaft member are bonded together. 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, and accordingly, the machining allowance during finishing machining is reduced, and the material yield and machining efficiency are improved. Also, in this invention,
Since the position in the circumferential direction, that is, the phase, can be changed steplessly, when the cam and shaft are fitted and fixed, it is easy to change the phase of the cam, and as a result, the performance of the equipment in which the cam is installed is improved. You can improve your performance.

[Brief explanation of the drawing]

The figures are for showing an embodiment of the present invention, and FIG. 1 is a front view of a cam, which is a sintered part, and FIG.
The figure is a longitudinal cross-sectional view, Figure 3 is a front view of the cam and the shaft that is temporarily fixed, Figure 4 is an enlarged view of the part shown in Figure 3, and Figure 5 is the main sintering process. FIG. 1...Cam, 2...Through hole, 3...Protrusion, 5
...Shaft, C...Press-fitting allowance, D...Inner diameter of through hole, d...Outer diameter of shaft.

Claims (1)

[Claims] 1. A through hole is formed at a predetermined location of a sintered part made by pre-sintering metal powder, and a shaft member is inserted into the through hole and main sintering is performed, whereby the sintered part and shaft member are bonded. When joining by diffusion bonding, the inner diameter of the through hole is formed slightly larger than the outer diameter of the shaft member, and on either the inner peripheral surface side of the through hole or the outer peripheral surface side of the shaft member, A protrusion made of a soft material that is easily deformed when pressed by the other outer or inner circumferential surface and whose melting point is lower than the main sintering temperature is provided, and the shaft member is deformed while the protrusion is deformed. is press-fitted into the through hole, the shaft member is temporarily fixed to the sintered part by the deformation stress of the protrusion, and then main sintering is performed to melt the protrusion. How to fit and fix sintered parts.