JPS5841211A - Cam shaft - Google Patents

Abstract

PURPOSE:To improve wear resistance, strength and bonding strength of a cam shaft, by making the cam lobe of a cam shaft with sintered metals and a sleeve. CONSTITUTION:A cam lobe 3 is made by bonding a first and a second sintered alloys 4, 5 to a sleeve 2. Since coupling of the cam lobe 3 and a stem is achieved by coupling a steel sleeve to the stem also made of steel and they are made of the same material, they can be coupled together securely by way of welding or soldering. Further, since the cam lobe is reinforced by the sleeve and a rather great bonding strength can be obtained also by press fitting and quenching, a cam shaft thus manufactured can be used with no trouble in an engine having a relatively low duty. Thus, it is enabled to manufacture a cam shaft having an excellent wear resistance, strength and bonding strength at a high productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camshaft for opening and closing valves of an internal combustion engine, and relates to a composite camshaft made of a composite of different materials.

Conventionally, camshafts for internal combustion engines have been made of cast iron or steel, but in recent years, composite camshafts made of various materials have been attracting attention.

The reason for this is the demand for higher speed, higher output, and lighter weight of internal combustion engines. That is, in response to higher speeds, the cam surface, which is the sliding surface with the cam follower, needs to have wear resistance, but materials with sufficient wear resistance can only be obtained from chilled or hardened cast iron. On the other hand, when trying to reduce weight, it is necessary to use steel, which has excellent strength.

Therefore, the cam lobe, which requires wear resistance, and the stem, which requires strength, are made of materials appropriate for the purpose, and these are assembled into a composite camshaft, for example, a stem made of steel pipe as shown in Japanese Utility Model Publication No. 51-7367. A camshaft with a cam lobe made of bonded metal has been proposed. The camshaft using this sintered metal cam lobe has a problem in the connection between the cam lobe and the stem, and although various ideas have been made, each has its own drawbacks.

For example, as in JP-A No. 54-102209, there is a method in which a compacted powder or pre-sintered cam lobe is assembled to a stem, and this is liquid-phase sintered to utilize shrinkage and diffusion of the sintered alloy to bond the stem. However, although this method provides a strong bond between the cam lobe and the stem, the entire camshaft must be passed through the sintering furnace, which not only lowers production efficiency, but also reduces the production efficiency at a temperature of usually 1250°C.
Because the front and rear parts are sintered, large camshafts tend to bend or distort the stem due to heat. On the other hand, when trying to braze or weld a sintered cam lobe, it is difficult to obtain sufficient bonding strength due to poor weldability and brazing properties because the sintered alloy and the steel stem are different materials. Not only,
The fitting part with the stem is made of a sintered alloy that is porous and highly hard and has poor rigidity, so the productivity is poor.

The present invention solves these problems with conventional camshafts, and by making the reel and cam lobe made of a three-layer composite material, the wear resistance and strength of the cam lobe are improved, and the productivity of the camshaft assembly is improved. The present invention will be described in detail below.

First, the gist of the present invention resides in a camshaft having the following four configurations as described in the claims.

(1) The first sintered metal material 4 is arranged on the outer circumferential side of the cam lobe 3.

(2) The steel sleeve 2 is disposed on the inner circumferential side of the cam lobe 3.

(3) Arranging the second sintered metal material 5 between the first sintered metal material 4 and the sleeve 2.

(4) Sleeve 2 and stem 1 are combined.

The camshaft of the present invention is used in the first embodiment of the present invention.
The explanation will be made with reference to the drawings and FIG. 2, which is a cross section taken along the line A in FIG. 1.

The rotation of the camshaft is transmitted by attaching a belt pulley 8 to a bushing 11 connected to the shaft end of the stem 1. The other shaft end of the stem 1 is closed with a cap 12, and the inside of the stem 1 is made hollow. On the other hand, journal 6, gear 7, cam lobe 3
is assembled to the stem 1 to form a camshaft.

At this time, the cam lobe 3 is formed as a single cam lobe by joining the first and second sintered alloys and the sleeve in advance, and is formed by the same means as the journal 6 and gear 7, such as press fitting, shrink fitting, welding, or brazing. Assembled to the stem. This is made possible in the present invention by connecting the sleeve 2 of the cam lobe 3 to the stem 1. That is, even if an attempt was made to directly weld or braze the sintered alloy and the steel, it was difficult to achieve a sufficient bond due to the restriction of joining dissimilar materials, whereas in the present invention, the cam lobe and the stem This is achieved by joining the steel sleeve and stem, and such similar materials have excellent weldability and brazeability, making it possible to achieve a sufficient joint. In addition, it has been difficult to bond sintered alloys with poor toughness by press-fitting or quenching, but in the present invention, since the cam lobe is reinforced with a sleeve, a certain degree of bonding force can be obtained even by press-fitting or quenching, and it can be used in relatively light-load engines. can be fully used.

On the other hand, Kamrop is pre-assembled before the camshaft,
This utilizes bonding caused by contraction and diffusion of the sintered alloy.

Specifically, complete bonding is achieved by assembling the green compacts of the first sintered alloy and the second sintered alloy and the sleeve and sintering them together in a sintering furnace. This is due to the presence of the second sintered alloy between the sleeve and the first sintered alloy. In other words, when a single sintered alloy compact and sleeve are sintered together, the compact The unavoidable assembly with the sleeve is to prevent the risk that clearances will remain after sintering has been completed.

The reason why the bonding caused by sintering is insufficient is that Cr+Mo is added to the sintered alloy, which requires wear resistance.
w Due to the effects of Ni, V*Wl, etc., the wettability of the sintered alloy itself decreases, making it difficult to bond with the sleeve, and the sintered alloy starts diffusion bonding with the sleeve when a liquid phase occurs, resulting in local sintering. This is because when the bonding metal and the sleeve start to bond, a clearance remains in a certain part.

In contrast, in the present invention, a second sintered alloy whose liquid phase generation temperature is lower than that of the first sintered alloy material is interposed between the first sintered alloy material that requires wear resistance and the sleeve. Before the sintered alloy generates a liquid phase and shrinks significantly, the second sintered alloy material generates a liquid phase and acts as a brazing agent between the sleeve and the first sintered alloy. Furthermore, since the second sintered alloy naturally stays in a liquid phase for a longer period of time than the first sintered alloy, bonding by diffusion to the sleeve and the first sintered alloy progresses more, and strict sintering temperature and time constraints are required. It becomes possible to achieve a bond greater than that of the first sintered alloy that is received.

Such a second sintered alloy must first have excellent wettability and a low liquid phase generation temperature, and since the sintering conditions are the same as those for the first sintered alloy, it must have strength under these conditions. . Therefore, specifically, C1.0 to 4.5 in weight%, (
The desired oC content is a sintered alloy consisting of a total of 1.0 to 5.0% of one or more of P-% B% Si, Cu 1.5 to 5.0%, and the remainder substantially Fe. In order to prevent the formation of ferrite in the base structure, a value of 1.0 or more is selected, and conversely, to prevent excessive cementite formation, a value of 4.5 or less is selected.
BM St) has the effect of lowering the liquid phase generation temperature when added in a small amount, but if it is less than 1.0, the effect is insufficient, and if it exceeds 5.0, embrittlement is significant. Cu also has the effect of lowering the liquid phase generation temperature, but it is added to improve wettability and adjust the sintering shrinkage rate, and if it is less than 1.01, it is not effective (if it is more than 5.0, it will become brittle). Further, for the purpose of improving base strength, it is also possible to add 0.5 to 2.0% of one or more of (Ni, Cr, Mo).

On the other hand, the first sintered alloy material was previously proposed by the applicant in JP-A No. 5
C005 to 4.0% by weight, such as No. 4-62108
, Cr8, O~30.0%, (PN B% st) or two or more 0.1~5%. Ol, Mo 20%
The liquid phase sintered alloys listed below are suitable.The first sintered alloy forms a liquid phase at around 1240°C and shrinks by about 6 inches, while the second sintered alloy forms a liquid phase at around 1220°C.

Although the first sintered alloy and the second sintered alloy may be powder-formed separately, they are preferably molded as one body as shown in FIG. First, as shown in the third section, the die B1, the second lower bunch D1, and the core lot F are raised and filled with powder J of the first sintered alloy. This can also be achieved by lowering the first lower punch C, but since the lower punch of a press machine is generally fixed and supported on a base, the lower punch will be described as fixed below.

Next, as shown in FIG. 3(b)K, the first upper punch G is lowered, and the die B1, second lower punch D, and core iron F are lowered by about half the amount of descent of the first upper bunch G. Therefore, the powder J is relatively compressed from both the first upper punch G and the lower punch C, and a green compact having a uniform density in the compression direction is obtained. The second lower punch D is shown in Figure 3 (A).
In this case, it is raised by a cylinder, and is lowered by a second upper punch H which is lowered with a phase shift from the first upper bunch C, as shown in FIG. 3(B).

Next, as shown in FIG. 3(C), the first lower bunch C is raised by a cylinder, and the core rod F1 and the die B are also raised so that the upper surfaces of the powder J and the die B are at the same height. On the other hand, the second lower punch D is lowered by the cylinder and at the same time, the second sintered alloy powder K is filled. It is desirable to suck and fill the powder K in this way, but since the second lower punch D has been lowered to a certain extent by the second upper punch H from the state shown in FIG.
You may also fill it with

Next, as shown in FIG. 3), the second lower bunch D remains as it is, and the first lower punch C and powder J are lowered by the first upper punch G. In this case, the first lower bunch C is floated by the cylinder, and the powder J is not compressed by the first upper and lower punches G and C. From the state shown in Figure 3), the first upper bunch C
At the same time as the second upper punch H, which has a more developed phase difference, starts compressing into powder, the die B1 core rod F1 is lowered at the same speed. Therefore, the first and second upper punches, the die, and the first lower punch descend at the same speed, and the powder is relatively compacted by the second lower punch D. Next, the movement of the die and core rod is stopped at the lowering limit of the second upper punch G.
The powder is compacted using a chisel, resulting in the state shown in Figure 3 (E). By this compaction, the powder is compacted in the same amount from above and below, and a uniform density is obtained. Next, as shown in FIG. 3(f), the first and second upper punches are raised, and the core rod F of the die B1 is pulled down to take out the compacted powder body.

According to this manufacturing method, a green compact made of two materials with a thin wall thickness and a relatively high compression direction can be easily formed, and furthermore, during compaction, the second and second lower punches are at the lowest position. Since it is only necessary to provide two upper punches that are shifted in phase by one crank, there is no mechanical structural unreasonableness.

The camshaft of the present invention described above has excellent wear resistance, strength, and bonding strength because the cam lobe is formed of the first and second sintered metal materials and the sleeve. The main effect of the sintered alloy is to improve the bonding strength between the first sintered alloy and the sleeve, but it can also have an economical effect by reducing the amount of the expensive first sintered alloy, which contains many additive elements. However, the distribution of the first and second sintered alloys is determined by the limit of compaction of each, and usually a wall thickness of 0.5zi+ or more is required.

It goes without saying that oil fillers, gears, cam lobes, journal stopper pins, etc., which are provided on a normal camshaft, are also provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the camshaft of the present invention. Figure 2: Cross-sectional view taken along the line A-A in Figure 1 and Figure 3: Cross-sectional view showing the manufacturing process of the present invention. Explanation of numbers 1, stem 2. Sleeve 3, cam lobe body 4. First sintered alloy material 5, second sintered alloy material

Claims (2)

[Claims] (1) In a camshaft consisting of a stem 1 made of a steel pipe and a cam lobe 3 made of a sintered metal, the cam lobe 3
A first sintered metal material 4 is arranged on the outer circumference side, a steel sleeve 2 is arranged on the inner circumference side, and a second sintered metal material 4 is arranged between the steel sleeve 2 and the first sintered metal material 4. A camshaft is formed by joining the sleeve 2 and the stem 1 to form a cam lobe 3. (2) The first sintered alloy material is a liquid phase sintered alloy, the second sintered alloy material is a liquid phase sintered alloy whose liquid phase generation temperature is relatively low, and the sleeve 2 and the first sintered alloy material are liquid phase sintered alloys. The camshaft 0 described in the first paragraph of the patent encirclement, characterized in that the alloy material 4 and the second sintered alloy material 5 are bonded by sintering shrinkage and diffusion.