JPH04175403A - Cam shaft for engine - Google Patents

Abstract

PURPOSE:To ease stress accompanying shrinkage fit of a cam piece to a shaft member by forming the cam piece of a sintered body of an antiwear alloy powder material, and inserting a film-like stress easing member between the shaft member and the cam piece. CONSTITUTION:A cam shaft CA is composed of a hollow shaft member 1 having a journal member 2 in the central part, a pair of cam pieces 3 corresponding to each cylinder of an engine provided in four predetermined positions of the cam shaft member 1, an aluminum foil 4A as a stress easing member inserted between each cam piece 3 and the shaft member 1, journal members 5 attached to both ends of the shaft member 1 and others. The respective cam pieces 3 are powder molded by the use of antiwear alloy powder material and then produced as a sintered body subjected to a sintering process. Then, since the aluminum foil 4A is inserted between the shaft member 1 and cam piece 3, hoop stress generated in the cam piece 3 is eased and evened when each cam piece 3 is cooled and contracted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a camshaft for an engine, and particularly to one in which a cam piece is shrink-fitted to a shaft member.

[Prior art]

BACKGROUND ART In recent years, as automobile engines have become more powerful and have lower fuel consumption, there has been a demand for lighter camshafts and improved wear resistance in engine valve systems.

Therefore, technology to make the camshaft hollow and lightweight,
BACKGROUND ART A technique for manufacturing a camshaft by combining a hollow shaft member and a cam piece is becoming popular. As the shaft member of the above camshaft, it is possible to adopt a shaft member made of lightweight aluminum alloy, and the cam piece, which is the frictional sliding part of the camshaft, is made by cutting a wear-resistant alloy material such as chromium molybdenum steel. A cam piece made of

The above-mentioned cam piece was integrally joined by casting when casting the shaft member, but recently it has been
As described in Japanese Patent No. 30509, a method of shrink-fitting a cam piece to a shaft member to join them is also known.

[Problem to be solved by the invention]

However, the cam piece has a specially shaped cam surface,
Since the cam surface must be machined with high precision, if the cam surface is manufactured by cutting a wear-resistant alloy material, there is a problem in that the cutting cost increases.

Therefore, it is conceivable to manufacture the cam piece by powder-molding the cam piece using a wear-resistant alloy powder material and sintering it. However, when this cam heath is shrink-fitted to the shaft member, a large hoop stress (circumferential tensile stress) is generated in the cam piece when the cam piece contracts, and the inner peripheral surface of the through hole through which the shaft member is inserted, or the shaft. As the hoop stress increases locally due to minute irregularities on the outer circumferential surface of the member, cranks are likely to occur in the cam piece, which has relatively low toughness, and there is a problem that it is impossible to manufacture a highly reliable camshaft. .

An object of the present invention is to provide a camshaft for an engine in which a cam piece made of a sintered alloy is shrink-fitted to a shaft member made of an aluminum alloy, and stress caused by the shrink-fitting is alleviated.

[Means to solve the problem]

The camshaft for an engine according to the present invention is a camshaft for an engine in which a cam piece is shrink-fitted to a shaft member made of an aluminum alloy.
It is composed of a sintered body made of a wear-resistant alloy powder material, and a thin film stress relaxation member is sandwiched between the shaft member and the cam piece.

[Function] In the engine camshaft according to the present invention, the cam piece made of a sintered body obtained by sintering a wear-resistant alloy powder material has an F [shaped stress relaxation member sandwiched between it and the shaft member. Because the cam piece is shrink-fitted, even if there are minute irregularities on the inner peripheral surface of the through hole and the outer peripheral surface of the shaft member, the stress relaxation member uniformly smooths out the irregularities. Since the cam piece undergoes plastic deformation, the hoop stress generated in the cam piece is uniformized, and no cracks occur in the cam piece.

This camshaft is composed of a shaft member made of an aluminum alloy and a cam piece made of a sintered body of a wear-resistant alloy powder material, so it is lightweight and has excellent wear resistance.

〔Effect of the invention〕

According to the engine camshaft according to the present invention, the above [
As explained in the ``Function'' section, the cam piece is shrink-fitted with the stress-relaxing member sandwiched between it and the shaft member, so the hoop stress generated in the cam piece is alleviated and cracks do not occur in the cam piece. There is no credibility.
The camshaft is made of an aluminum alloy shaft member and a sintered alloy cam piece that is shrink-fitted to the shaft member, making it a lightweight camshaft with excellent wear resistance. Effects such as this can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> In this embodiment, the present invention is applied to a camshaft CA for a four-cylinder automobile engine, as shown in FIG.

The camshaft CA includes a hollow shaft member l having a journal member 2 in the center thereof, a pair of cam pieces 3 provided at each of four predetermined portions of the shaft member 1 corresponding to each cylinder of the engine, It consists of an aluminum foil 4A as a stress relaxation member fixed between each cam piece 3 and the shaft member 1, and journal members 5 attached to both ends of the shaft member 1, respectively.

Next, a method for manufacturing the camshaft CA will be explained with reference to FIGS. 2 and 3.

First, the shaft member 1 was manufactured, and in parallel with the manufacturing of the shaft member 1, each cam piece 3 was manufactured.

The shaft member 1 was manufactured by cutting an aluminum alloy 7075-T6 round piece. At the 10th axis of the shaft member,
An oil passage la for circulating lubricating oil was formed, and a journal member 2 made of chromium molybdenum steel was externally fitted and fixed to a predetermined portion of the shaft member 1 by shrink fitting. The outer diameter of the portion of the shaft member l into which the cam piece 3 is shrink-fitted is machined to 26.35 m, and then those portions are machined to a thickness of 0.
゜2 cabinets, width 17cm, length 81m+ aluminum foil 4A
wrapped around each.

On the other hand, each of the cam pieces 3 was manufactured as a sintered body by powder-molding a wear-resistant alloy powder material and then performing a sintering process. And the through holes 3a of those cam pieces 3
The inner diameter was processed to 26.50mm. The composition of the wear-resistant alloy powder material is shown in Table 1.

Next, each cam piece 3 is heated to 500°C, and as shown in FIG. 2, each cam piece 3 is inserted from the end of the shaft member l, and held at a predetermined position where aluminum foil 4A is wrapped, and in a predetermined posture. In that state, shrink fit allowance 5
The cam piece 3 was shrink-fitted to the shaft member 1 at 0 μm.

When each of the cam pieces 3 cools and contracts, the aluminum foil 4A is plastically deformed so as to uniformly smooth out minute irregularities on the inner peripheral surface of the through hole 3a of the cam piece 3 and the outer peripheral surface of the shaft member 1. Since the cam piece 3 is sandwiched between the shaft member 1 and the cam piece 3, the hoop stress generated in the cam piece 3 is relaxed and the hoop stress is made uniform, and the cam piece 3 is fixed to the shaft member 1 in this state.

After shrink fitting, the surface of the cam piece 3 was observed visually and by fluorescent flaw detection, and no cranking was found.

Next, after shrink-fitting the cam piece 3, journal members 5 made of chromium-molybdenum steel are externally fixed to both ends of the shaft member 1 by shrink-fitting, and then finishing processing such as polishing is performed to obtain the camshaft CA. Ta.

The camshaft CA manufactured in this manner is composed of the shaft member 1 made of aluminum alloy and the cam piece 3 made of a sintered body of wear-resistant alloy powder material, so it is lightweight and has excellent wear resistance. becomes.

Next, second to fifth embodiments of the present invention will be described below. However, since the camshaft of each embodiment has basically the same structure as the camshaft CA of the above embodiment except for the stress relaxation member, only the method of shrink fitting the stress relaxation member and the cam piece 3 will be described.

<Second Example> The camshaft CB of this example is manufactured using copper foil 4B as a stress relaxation member, as shown in FIGS. 4 and 5.

In the part of the shaft member 1 where the cam piece 3 is shrink-fitted,
A copper foil 4B having a thickness of 0.2 cm, a width of 17 cm, a length of 81 cm and a plurality of holes 4b with a diameter of 3.0 cm is wrapped, and then the cam piece 3 is attached to the shaft under the same conditions as in the first embodiment. Shrink-fit to member 1.

At this time, the plurality of holes 4b' formed in the copper foil 4B promote plastic deformation of the copper foil 4B in the same way as the aluminum foil 4A, so the hoop stress generated in the cam piece 3 is uniformly relaxed. .

After shrink fitting, the surface of the cam piece 3 was observed visually and by fluorescent flaw detection, and no cracks were found.

<Third Example> The camshaft CC of this example is manufactured using an aluminum oxide film 4C as a stress relaxation member, as shown in FIGS. 6 to 8.

After processing the outer diameter of the part of the shaft member 1 into which the cam piece 3 is shrink-fitted to 26.35 mm, that part is subjected to alumite treatment to form an aluminum oxide film 4C with a thickness of approximately 15 μm, and then that part is By heating to 100'C and cooling with water, minute cracks 4C (see FIG. 8) were formed in the aluminum oxide film 4C.

On the other hand, the inner diameter of the through hole 3a of the cam piece 3 is set to 26°305
Then heat the cam piece 3 to 500"C,
It was shrink-fitted to the shaft member 1 with a shrink-fitting allowance of 60 m.

At this time, the aluminum oxide film 4C is deformed by the cracks 4C formed in the aluminum oxide film 4C, and the hoop stress of the cam piece 3 is uniformly relaxed, and the cam piece 3 is fixed to the shaft member 1 in this state.

After shrink fitting, the surface of the cam piece 3 was observed visually and by fluorescent flaw detection, and no cracks were found.

<Fourth Example> The camshaft CD of this example was manufactured using a plating layer 4D made of low melting point solder for aluminum as a stress relaxation member, as shown in FIGS. 9 and 1O. .

The outer diameter of the portion of the shaft member 1 into which the cam piece 3 is shrink-fitted is processed to 26.156 to 27.050 mm, and then a low melting point solder for aluminum having a composition of Sn91-Zn9 is used to process the outer diameter of the portion to a thickness of 10 to 20 μm. A plating layer 4D was formed.

On the other hand, the inner diameter of the through hole 3a of the cam piece 3 is set to 26°115.
~26.795+a+, then heated to 530"C, and then shrink-fitted to the shaft member 1 with a shrink-fitting allowance of 41-611!m.

At this time, the plating layer 4D heated by the cam piece 3
is melted, the cam piece 3 becomes brazed to the shaft member 1, and the hoop stress is uniformly relieved.

After shrink fitting, the surface of the cam piece 3 was observed visually and by fluorescent flaw detection, and no cranking was found. Further, the cam piece 3 was strongly brazed to the shaft member I by a plating layer 4D.

<Fifth Example> The cam shirt CE of this example was manufactured using a plating layer 4E made of general solder as a stress relaxation member, as shown in FIGS. 11 and 12.

The outer diameter of the portion of the shaft member 1 into which the cam piece 3 is shrink-fitted was machined to 26.35 am. Next, add a thickness of 20 mm to that part.
A Fe thermal spray layer 4e of μm thickness is formed, and then Pb5O-3n
A plating layer 4E having a thickness of 10 to 20 t1m was formed using solder having a composition of 50.

On the other hand, the inner diameter of the through hole 3a of the cam piece 3 is set to 26°335.
mm, and then heated to 530″C and shrink-fitted to the shaft member 1.

At this time, like the plating layer 4D, the plating layer 4E is melted, and the hoop stress of the cam piece 3 is uniformly relaxed.

After shrink fitting, the surface of the cam piece 3 was observed visually and by fluorescent flaw detection, and no cracks were found. The cam piece 3 was strongly brazed to the shaft member 1 with a plating layer 4E.

[Comparative example]

Next, the camshaft CF of the comparative example will be explained.
As shown in FIG. 13, this camshaft CF has a cam piece 3 similar to that described above directly shrink-fitted to a shaft member 1 similar to that described above without using a stress relaxation member.

The outer diameter of the portion of the shaft member 1 into which the cam piece 3 is shrink-fitted is processed to 26.35mm, and the through hole 3a of the cam piece 3 is
The inner diameter was processed to 26.305 mm. Next, the cam piece 3 was heated to 500° C. and shrink-fitted to the shaft member 1 with a shrink-fitting allowance of 45 μm.

After shrink-fitting, cracks 6 caused by locally generated large hoop stress as shown in Fig. 13 were visually confirmed on the surface of the cam piece 3, and it was not possible to manufacture a camshaft of quality that could withstand practical use. .

As explained in the first to fifth embodiments, stress relaxation members 4A to 4E are provided between the cam piece 3 and the shaft member 1.
By sandwiching the cam piece 3, the hoop stress generated in the cam piece 3 can be alleviated, cracks and cranks can be prevented from occurring, and the cam piece 3 can be strongly fixed to the shaft member 1.

The camshaft CA-CE is lightweight and has a cam piece 3 with excellent wear resistance.

Note that the wear-resistant alloy powder is not limited to the one having the above composition, but it is also possible to use wear-resistant alloy powders having various other compositions.

[Brief explanation of the drawing]

1 to 12 show embodiments of the present invention.
The figure is a perspective view of the camshaft, Figure 2 is a partial perspective view of the camshaft of the first embodiment, Figure 3 is a sectional view of the camshaft, and Figure 4 is a partial perspective view of the camshaft of the second embodiment. Figure 5 is a sectional view of the camshaft, Figure 6 is a partial perspective view of the camshaft of the third embodiment, Figure 7 is a sectional view of the camshaft, and Figure 8 is the main part of Figure 7. Partial enlarged view, No. 9
The figure is a partial perspective view of the camshaft of the fourth embodiment, Figure 10 is a cross-sectional view of the same camshaft, Figure 11 is a partial perspective view of the camshaft of the fifth embodiment, and Figure 12 is a cross-sectional view of the same camshaft. , FIG. 13 is a partial perspective view of a camshaft of a comparative example. CA-CB-CC-CD-CE-CF...Camshaft, 1...Shaft member, 3...Cam piece, 4
A: Aluminum foil, 4B: Copper foil, 4C: Aluminum oxide film, 4D, 4E: Plating layer. Patent applicant Mazda Motor Corporation Hiroshima Aluminum Industry Co., Ltd. Figure 1 CA 1: Nyanotodai Attached 53:
Cam piece Fig. 2 Fig. 3 Fig. 4A Ni aluminum foil 415: Sae i Fig. 9 Fig. 10 Fig. 11
Figure 12 Figure 13 F 1a CF/Camshaft November 13, 1991

Claims (1)

[Claims] (1) In an engine camshaft in which a cam piece is shrink-fitted to an aluminum alloy shaft member, the cam piece is composed of a sintered body made of a wear-resistant alloy powder material, and the shaft member and the cam piece are A camshaft for an engine, characterized in that a thin film-like stress relaxation member is sandwiched between the camshafts.