JPS6043405A - Production of cam shaft consisting of sintered alloy - Google Patents

Abstract

PURPOSE:To produce easily a cam shaft consisting of a sintered alloy having high joint reliability by assembling a green compact molding for a cam part consisting of an outside layer formed of a wear resistant material having large shrinkability and an inside layer formed of a material having small shrinkability to a shaft part and sintering the assembly. CONSTITUTION:Wear resistant sintering material powder with which >=2% shrinkage change arises when sintered is packed between a curved partition plate 6 and the inside circumferential surface of a die 4 of a green compact molding device 7 formed by disposing a core rod 5 to the center of the die 4 and said plate 6 around the same. Sintering material powder with which <=2% shrinkage change arises when sintered is packed between the plate 6 and the rod 5. The plate 6 is thereafter removed and the powders are compressed from above and below by using punches, by which a green compact molding 1 for the cam part consisting of the outside layer 2 and the inside layer 3 is obtd. The molding 1 is temporarily sintered according to need and thereafter the molding is assembled to a shaft part (not shown in figure) and is heated at a prescribed temp. to sinter the above-mentioned inside and outside layers 2, 3 and at the same time to accomplish simultaneously joining and fixing of both layers as well as the cam part and the shaft part, by which the sintered alloy cam shaft is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a camshaft for an internal combustion engine, etc., in which a shaft portion and a cam portion are separated, the cam portion is made of a sintered body, and the cam portion is fitted into the shaft portion. This relates to a camshaft that is fixed together.

BACKGROUND ART Recently, sintered camshafts, which have been developed for the purpose of improving wear resistance, high temperature resistance, workability, etc., have been frequently used in camshafts for internal combustion engines and the like. This camshaft has a cam portion made of a sintered body made of metal powder, which is fitted and fixed onto the outer periphery of a shaft portion made of, for example, chromium molybdenum steel.

In the camshaft having the above configuration, the cam part is fixed to the shaft part by (i) press-fitting the cam part into the shaft part and fixing it; or (Ol) fitting the cam part into the shaft part and brazing the fitting contact part. How to attach and fix (iii
) A method of fitting the cam part to the shaft part and fixing the fitted part by caulking, (Gy) A method of mechanically fixing it with screws, (V) A method of fI as the shaft part! For fixing when using an i-tube, the part of the shaft corresponding to the cam part is bulged out, and the bulged part is pressed against the inner periphery of the cam part to fix it, which is the so-called bulge process. It's being done well. In all of these fixing methods, it is necessary to fit the cam part to the outer periphery of the shaft part, and therefore, the dimensional accuracy of each component, especially the fitting part of the cam part, before fitting is required. It is required to be good, and as a result,
Requires a dimensioning process that requires man-hours such as cutting.
was.

In response, we have also proposed a method in which the cam part and journal are formed from a wear-resistant sintered alloy material that generates a liquid phase during sintering, and the cam part and journal are firmly fixed to the shaft part by diffusion bonding. has been done. However, since this method generates a liquid phase during sintering, the amount of shrinkage of the cam part and journal due to sintering is extremely large, and the shrinkage does not occur uniformly, resulting in the shaft of the cam part and journal Misalignment was likely to occur in the positioning of the parts. Furthermore, the shrinkage caused by sintering occurs not only in the radial direction but also in the axial direction, resulting in non-uniform shrinkage, so it is impossible to avoid the formation of gaps at both ends of the cam part and journal. However, the bonding strength was sometimes insufficient, and the reliability was not satisfactory.

The present inventors have found that the cam part is firmly fixed to the shaft part, there is little dimensional change in the cam part, positioning for assembly can be performed easily and accurately without requiring man-hours, and the joint reliability is high. As a result of extensive research aimed at developing a manufacturing method that can produce sintered metal camshafts, we have come to the following knowledge.

That is, the cam part before sintering is divided into an outer layer and an inner layer, the outer layer is made of a sintered alloy material with high wear resistance and a large amount of shrinkage, and the inner layer is made of a sintered alloy material with a small amount of shrinkage, If this cam part is assembled to the shaft part and then sintered, the inner layer will absorb the large shrinkage change of the outer layer, providing dimensional stability and making it possible to set the interference with the shaft to an appropriate value. It turned out to be possible. Furthermore, it has been found that good bonding can be obtained when the amount of shrinkage of the outer layer is 2% or more and the amount of shrinkage of the inner layer is less than 2%.

In this case, the amount of contraction of the inner diameter part of the entire cam part is 1%.
It is preferably within 4%.

The present invention has been made based on the above findings. That is, in the present invention, the powder compact or temporary sintered body of the cam part is composed of an outer layer and an inner layer, and the outer layer is composed of a wear-resistant sintered material that undergoes a shrinkage change of 2% or more during sintering. , the inner layer is composed of a compacted material that exhibits a shrinkage change of less than 2% during sintering, the compacted compact or temporary sintered compact of the cam section is assembled to the shaft section, and then heated at a predetermined temperature to form the above-mentioned This is a method of manufacturing a sintered alloy camshaft by simultaneously performing the assembly and joining of the inner and outer layers and the fixing of the cam part to the shaft part.

The present invention will be explained in detail below. According to the present invention)g! The outer layer of the cam part to be manufactured is, for example, Fe-15Cr-I
As shown in Mo-0,5Mn-0,5Nb--α3p-2,6C, it has components that form a liquid phase at relatively low temperatures, exhibits high wear resistance after sintering, and Constructed from a wear-resistant sintered material that exhibits a shrinkage change of 2% or more.

Moreover, the inner layer of the cam part is made of, for example, Fe 3Ni IC
As shown in Figure 2, the wear resistance is not very high, but it is constructed from a sintered material that exhibits a shrinkage change of less than 2% during sintering.

As shown in FIG. 1, the powder compact 1 of the cam portion is composed of the outer layer 2 and the inner layer M53 as described above.
The compacted product 1 is made of a mold 4 with a core rod 5 in the center of the mold 4.
and the inner peripheral surface of the mold 4 and the core rod 5.
A partition curved plate 6 forming a boundary between the outer layer 2 and the inner layer 3 is disposed between the partition curved plate 6 and the inner peripheral surface of the mold 4, and a punch having the projected shape of the outer layer 2 is disposed between the partition curved plate 6 and the inner peripheral surface of the mold 4. The molding is performed by a powder compacting machine 7 which is designed so that a punch having a projected shape of the inner layer 3 can be inserted and removed between the partition curved plate 6 and the core rod 5. In the powder compacting machine 7, the partition curved plate 6. The mixed powder constituting the outer layer 2 is filled between the inner peripheral surface of the mold 4 and the mixed powder constituting the inner layer 3 between the partition curved plate 6 and the core rod 5. When the plate 6 is removed and compressed from above and below in this state, a powder compact 1 as shown in FIG. 1 is formed. In this powder compact 1, the outer layer 2 is, for example, Fe-1Fe-15Cr-f, 5Mh-a5Nb-[
13P-26C and the inner layer 3 is made of, for example, Fe-3NtIC (Example 1, described below), the apparent density of the outer N2 before final compression is 2-89/c.
It became quiet and the apparent density of inner N3 was 2.71! /ca, the apparent densities of both powders are approximately the same value.

Since the compressibility of both powders (the density of the green compact obtained with a compression force of 5 myo/c1d was 12 g/cnl) is almost the same, The density of the outer layer 2 and the inner layer 3 is almost the same. Also,
Due to the above structure, at the interface between the outer layer 2 and the inner layer 3 after compression molding, the powders of both layers are intertwined with each other due to minute irregularities, which allows for smoother diffusion during sintering. - The bonding strength between the inner layers 3 is good and strong. In FIG. 1, the reference numeral 3a is a convex portion for more firmly fitting the outer layer 2 and the inner layer 3, and 3b is a convex portion.
...This is a convex portion for more firmly fitting the inner layer 3 and the pipe shaft 8 (Fig. 3), but as mentioned above, the joint is made with sufficient strength, so it is not necessary to provide it. do not have.

The compacted compact 1 formed by pressing as described above may be used as it is, or
Alternatively, after being pre-sintered, it is connected to a pipe shaft (shaft portion) 8 as shown in FIG.

The alignment in the axial direction at this time is performed by fitting a bottle 9 shown in FIG. 4 into the hole 8a. Further, the journal 10 (Fig. 5) is also made of powder sintered material (for example, Fe-5Ni-
IC), and its axial alignment is performed using the bin 9 as described above.

- As described above, the powder compact 1 of the cam portion or its temporary sintered body and the journal 1o are attached to the pipe shaft 8 and heated at 1150° C. for 60 minutes in a vacuum atmosphere.

By this heating, the outer Wj2 and the inner layer 3 are sintered and joined,
The inner layer 3 and the pipe shaft 8 are the outer layer 2 produced by sintering.
The inner layer 3 is then tightly fitted by shrinking. In the case of the above powder composition, the outer layer 2 has a shrinkage rate of 7%, and the inner layer 3 has a shrinkage rate of 1.
．． Since it has a shrinkage rate of 0%, the shrinkage of the outer layer 2 (as well as the inner layer 3) is relaxed, resulting in an overall shrinkage rate of 1.8% suitable for fitting.

In this way, in the present invention, the inner layer 3 with a small shrinkage rate exists in the middle part, and since this inner layer 3 has high abrasion resistance, it plays the role of a cushion that absorbs and alleviates the large shrinkage rate of the outer N2. The cam portion contracts uniformly, and variations in dimensions due to the contraction are reduced. In addition, in the present invention, a powder compact or a temporary sintered body, which has better dimensional accuracy than the actual sintered body, is directly fitted onto the pipe shaft, and then the final sintering is performed, so variations in tightness are reduced. It is smaller, and the variation in dimensions in the finished product (camshaft) is also 1-1
The variation in degree can also be reduced.

Furthermore, in the present invention, if a brazing material (for example, Cu-2ONi) is interposed between the cam part and the pipe shaft, and then the main sintering process is performed, the cam part can be fixed to the shaft. It can be made stronger.

In addition, the shrinkage rate of the inner layer in the present invention is less than 2%,
The numerical limitation of the shrinkage rate of the outer layer to 2% or more means that the shrinkage rate of the inner layer is 2% or more and the outer layer's shrinkage rate is less than 2%.
This is because it was confirmed that problems such as a gap was created between the cam part and the pipe shaft, and positional deviation occurred. Furthermore, as described above, the amount of inner diameter contraction of the entire cam portion is preferably in the range of 1% to 4%.

In addition, the above-mentioned brazing filler metal plays the role of making the joint strength between the cam part and the shaft j stronger, more complete, and more stable by its diffusion. ．． Cu-N1 (20%), Cu-
P (8J%), Cu-Zn (40%), Cu-3n (1
1%)% Cu-Ag Zn(Ag; 20%, Zn
; 65%), Cu-Ag Zn (Ag; 40%, Zn;
20%), Cu-Fe (Fe; 30%), Cu-
Zn-Ni (Ni: 20%, Zn: 20%) etc. can be considered.

Furthermore, in the present invention, liquid phase sintering is carried out in order to give this outer layer high wear resistance and to obtain a high shrinkage rate necessary for fitting and joining. This is the surest and easiest method. By this liquid phase sintering, the liquid phase generated from the outer layer reaches the inner layer and causes diffusion bonding with the constituent particles of the inner layer, so that the bonding strength between the inner and outer layers can be further improved.

As explained above, the present invention consists of a compacted powder body or a temporarily sintered body of a cam part consisting of an outer layer and an inner layer, and the outer layer undergoes a shrinkage change of 2% or more during sintering, resulting in a wear-resistant sintered body. The inner layer is made of a sintered material that undergoes a shrinkage change of less than 2% during sintering, and the powder compact or temporary sintered body of this cam part is assembled into the shirt) [1], and then Since the cam is heated at a predetermined temperature to sinter and bond the inner and outer layers and fix the cam part to the shaft part at the same time, the cam part is firmly fixed to the shaft part, and there is little dimensional change in the cam part. It is possible to easily and accurately position the camshaft for assembly without requiring any man-hours, and to obtain a sintered alloy camshaft with high bonding reliability.

In the above description of the present invention, the compacted body or temporary sintered body of the cam part was assumed to be one in which the inner layer and the outer layer were integrally compression-molded, but the inner layer and the outer layer were molded separately, and these may be combined when assembling the camshaft. Although positioning is provided in the explanation for the countertail shape, this is not limited to this.

The present invention will now be described in further detail with reference to Examples.

〔Example〕

Using the outer layer and inner layer powder materials having the configurations shown in Tables 1 to 4 below, a compacted body is formed based on the method of the present invention, and this is assembled on a chrome-molybdenum steel pipe shaft, As mentioned above, it was heated at 1150°C for 60 minutes in a vacuum atmosphere. In Example 31C,
A brazing filler metal (Cu-2ONi) was interposed between the cam part and the pipe shaft.

Further, in Example 5, a pre-sintered body was constructed by pre-sintering at 950° C. using the same constituent materials as in Example 4, and this was assembled into a pipe shaft.

For the above Examples 1 to 5, Table 1, (1
With the powder having the composition shown in the figure, the shrinkage rate of the inner and outer layers is both +c2.
% of the cam part is formed, and the rest is carried out in Examples 1 to 3.
A camshaft was manufactured in the same manner as in 4.

When we checked the appearance of the bonded state and positional deviation of each of Examples 1 to 5 and Comparative Example 1111, as shown in the table, in Comparative Example 1, a slight gap and positional deviation occurred, and as shown in the table, Comparative Example 1 In contrast to Examples 1 to 5, the bonded state was good and no positional deviation occurred. In particular, the bonding in Example 3 using No. 1 brazing material was strong.

[Brief explanation of drawings]

Figures 1 to 5 are for explaining the present invention. Figure 1 is a perspective view of the compacted product of the cam section, Figure 2 is a perspective view of the compaction machine, and Figure 6 is FIG. 4 is a perspective view of the pipe shaft, FIG. 4 is a perspective view of the positioning pin, and FIG. 5 is a perspective view of the journal. 1...Powder compact of cam part, 2...Outer layer,
3... Inner layer, 4... Mold, 5... Core rod, 6... Partition curved plate, End... Pipe shaft [shaft part], 9 ...Pin, 10...
···journal. Figure 1 h

Claims (3)

[Claims] (1) Shirt) [In a method of manufacturing a sintered alloy camshaft in which a cam part made of a sintered material is fitted and fixed on the outer periphery of H, It is composed of an outer layer having a surface and an inner layer that fits into the shaft part, the outer layer is made of a wear-resistant sintered material that undergoes a shrinkage change of 2% or more when sintered, and the inner layer The compacted powder body or temporary sintered body of the cam part is assembled to the shaft part, and then heated at a predetermined temperature to sinter the inner and outer layers. A method of manufacturing a sintered metal camshaft, characterized in that joining and fixing the cam portion to the shaft portion are performed at the same time. (2) When assembling the cam part to the shaft part, by heating the cam part and the shaft part to a predetermined temperature with fR or copper alloy! 7. The method of manufacturing a sintered alloy camshaft according to claim 1, wherein the sintered alloy camshaft is bonded and fixed. (3) During heating after the cam part is assembled to the shaft part, a liquid phase is generated in the wear-resistant sintered material that makes up the outer layer.
3. A method for manufacturing a sintered alloy camshaft according to claim 1 or 2, characterized in that at least the inner layer and the outer layer are bonded and fixed together in a liquid phase.