JPS5850355A - Cam shaft - Google Patents

Abstract

PURPOSE:Improve anti-wear property, stem strength and cam lobe strength by adding sintered alloy to a cam lobe with which is combined a pipe to be cast in a stem. CONSTITUTION:A cam shaft is formed with cam lobes 3, journals 4, a gear 5 and cam gear 6 all cast in a stem 1. On an end of the stem 1 is mounted a belt wheel 9 rotated by a crank shaft which receives rotation from a crank shaft. The cam lobes 3 are attached to a pipe 2 under the condition of pressed powder and completely metallurgically combined with the pipe 2 by liquid state sintering to progress the contraction and diffusion of the cam lobe 3.

Description

[Detailed Description of the Invention] The present invention relates to a camshaft for an internal combustion engine,
In particular, it relates to a multi-force gusset using different materials for component parts such as cam lobes, journals, and stems.

Chilled castings, hardened steel, or carburized steel have been used for the camshaft, but these do not satisfy the demands of modern internal combustion engines. In other words, as internal combustion engines are required to be faster, have higher output, and are lighter in weight, cast iron camshafts not only do not reduce weight, but also prevent bending and distortion in large camshafts, while steel camshafts cannot. Therefore, composite camshafts are attracting attention, in which components such as cam lobes, journals, and stems that make up the camshaft are assembled using materials appropriate for their intended use.

This composite camshaft has a stem with a steel plate and a stem,
An assembled composite force shaft in which a cam lobe or journal is welded, brazed, or sintered to the stem by diffusion bonding, or the cam lobe or journal is wrapped separately in the molten metal that makes up the stem, or the stem is made up of the cam lobe or journal. There is a separately wrapped composite camshaft that is wrapped separately in molten metal.

On the other hand, sintered alloys are used for cam lobes from the viewpoint of formability and wear resistance, but for sliding parts such as camshafts that are subject to high blood pressure, it is necessary to use high-density sintered alloys to increase the blood pressure strength. . Therefore, because the cam lobe made of liquid phase sintered alloy is a sintered alloy, there are various restrictions when using it in a composite camshaft. 1. Because the sintered alloy is formed from a powder compact, there is a limit to its minimum wall thickness.In an assembled composite camshaft in which a steel pipe is installed in the hole in the center of the cam lobe, the outer diameter of the stem is equal to the thickness of the cam lobe. If the cam lobe becomes smaller, the stem wall thickness must be increased for strength reasons, which not only reduces the effect of weight reduction, but also causes the cam lobe itself to easily crack due to twisting, so either strengthen the bonding force with the stem or increase the cam lobe wall thickness. There is only one way to go.

On the other hand, when trying to wrap a cam lobe made of sintered alloy separately in molten metal, the oxide film existing in the sintered alloy pores not only inhibits metallurgical bonding but also prevents eaves swelling.
When wrapped by gold alloy, the cam lobe made of a sintered alloy, which is an iron-based alloy, and the stem are not metallurgically bonded at all, and the bonding strength is extremely weak. Therefore, for example, as shown in JP-A No. 50-7961.6, a hot water passage and a core fitting hole are provided to provide a rotating size and a υ1 wrapper. Providing a core fitting hole is difficult because of the limitations on wall thickness for powder compaction of sintered alloys as mentioned above, and the poor machinability of sintered alloys that are generally dense and have voids. It is difficult to put it into practical use due to the difficulty of the process and the problem of the strength of the sintered alloy. Furthermore, in the force 13 shaft, the cam lobe MB
K and T# are also subjected to rotational torsional stress and bending stress, so although stem strength is required at this part, the disadvantage of a separately wrapped composite camshaft is that this separately wrapped part is the weakest in terms of strength. There is.

The present invention solves the drawbacks of such conventional camshafts, especially cast-in type composite camshafts, and improves surface 1 wear resistance,
The present invention is intended to provide a camshaft which has sufficient stem strength and stem-cam lobe joint strength, is lightweight, and has excellent productivity.The present invention will be described in detail below.

First, the gist of the present invention lies in a camshaft that depends on the following four constituent elements, as described in the claims.

(1) A sintered metal cam lobe is separately wrapped in molten metal that forms the stem.

(2) The sintered metal cam lobe has a hollow hole passing through it in the axial direction, and a steel pipe is fitted into the hollow hole.

(3) The steel pipe should protrude in the axial direction from the cam lobe.

(4) The steel pipe is separately wrapped by the molten metal that forms the stem.

The camshaft of the present invention will be described with reference to FIG. 1 which is an embodiment, FIG. 2 which is a cross section taken along the line A-A in FIG. 1, and FIG. 3 which is an enlarged view of the main part of FIG. 1.

5- The camshaft has cam lobe 3, journal 4, and gear 5.
, the cam gear 6 is formed around the stem 1, and a belt pulley 9 to which rotation is transmitted from the crankshaft is attached to the shaft end of the stem 1.

The cam lobe 3 is provided with a hollow hole 30, and the steel pipe 2 is connected to the hollow hole 30. The cam lobe 3 and the pipe 2 are assembled into the pipe 2 in the form of a powder compact, and are completely metallurgically connected by liquid-phase sintering, which allows the cam lobe 3 to shrink and diffuse. There is. pipe 2
has a protruding shaft end portion 23 that protrudes from the cam lobe 3 in the axial direction.

The camshaft is made by casting the cam lobe 3, journal 4, etc. into a mold, and after pouring, the molten metal that forms the stem 1, specifically the lightweight and strong molten Ae alloy, is cast. An oil passage 13 is formed on the inner circumferential side of the pipe, and a separately wrapped protrusion 12 is formed on the outer circumferential side of the pipe. Therefore, the pipe 2 is completely encased in A6 alloy from the inner and outer circumferential sides, thereby achieving a strong connection with the stem 1. In particular, when wrapping the tube with A1 alloy, which has a large amount of shrinkage, the outer circumferential side of the pipe will be strongly bonded. Furthermore, by providing relatively deep rifling marks 27 on the outer circumferential side and/or the inner circumferential side 1 of the pipe as shown in FIG. achieved. Of course, this rotational alignment can also be achieved by providing grooves or protrusions in addition to the rifling marks 27.

On the other hand, the journal 4 and gear 5 are made of steel because they do not require special wear resistance, but
Since the bending stress is also relatively small compared to the cam lobe, it is possible to provide a cast-in groove 41 in the journal 4 as shown in FIG. 1, or to provide an eccentric annular cast-in groove 51 in the gear 5 as shown in FIG. The connection with the stem 1 can be achieved by means such as providing a bridge.

Furthermore, the cam gear 6 is required to have the same wear resistance as the cam lobe, and therefore it is preferable to use a sintered alloy, but it is common for the axial position of the cam lobe 3 and the cam gear 6 to be close to each other as shown in FIG. Alternatively, a plurality of cam lobes 3 and cam gears 6 may be assembled into one pipe 2 as shown in FIG. 5. In this case, in order to form a cast-in protrusion 12 on the pipe 2 of the stem 1 shown by a dashed line, it is necessary to provide a hot water passage 29 in the pipe 2. However, if the axial distance between the cam lobe 3 and the cam gear 6 is wide to some extent, it is preferable to provide each cam lobe 3 and the cam gear 6 with separate pipes 2.

In this way, in the present invention, a steel pipe having a longer axial length is connected to the cam lobe, and this is cast into the stem, so the pipe is firmly cast into the stem, and the bonding strength with the stem is excellent. However, the steel pipe has no effect in reinforcing stem 1. In other words, a steel pipe with a relatively large diameter and long in the axial direction is cast into the stem of the cam lobe, which is subjected to the most bending and twisting.
A reinforcing effect can be obtained in which the torsional force is supported by the pipe.

On the other hand, the thicker the cast-in projection 2 provided on the stem 1, the greater the cast-in strength and stem strength, but at the same time, the minimum wall thickness of the cam lobe 3 can be made larger, Stem 1 and cam lobe 3 can be made thick enough and have a large outer diameter for stem 1.
The strength of each of these is also improved. However, in order for the pipe 2 to exert its reinforcing effect on the stem, a certain degree of outer diameter and wall thickness are required.
In addition, since it is preferable that the outer diameter of the hot water passage 13 formed on the inner periphery of the vibrator be larger in order to improve castability, the diameter and wall thickness of the pipe 2 are selected based on the balance between these.

Examples will be shown below to further improve the effects of the present invention.

In order to prevent the stem 1 and the pipe 2 from rotating in the rotational direction, for example, as shown in FIG. It is done to eccentricize the center of. By arranging such an eccentric pipe 2, the oil passage 13 transmits the rotation of the stem 1 to the pipe 2 without the crank action, and no special anti-rotation means is required.

Further, as shown in FIG. 7, by slanting the shaft end of the pipe 2 in the axial direction, it is possible to provide a sufficient rotation prevention means, and furthermore, machining is extremely easy.

The pipe 2 can be obtained by cutting a steel pipe, but it is also possible to use a pipe 2 whose cross section is a non-perfect circular ring, the thickness of which varies in the circumferential direction, as shown in FIG. By using the bendable pipe 2, the inner and outer circumferences of the pipe 2 respectively perform a cranking action and at the same time act as a rotation prevention means.

Furthermore, a camshaft as shown in FIG. 9 is also possible, in which the hollow hole 3o of the cam lobe 3 is formed with a corrugated shape in a wide range where the cam lobe wall thickness is extremely small. In the Gagaru Kamunya Futo, the pipe 2 is also machined to have the same cross section as the corrugated hollow hole 3o, which is highly effective in preventing rotation.

As mentioned above, the connection between the cam lobe 3 and the pipe 2 is achieved by assembling the cam lobe 3 with the pipe 2 in the form of powder compact and performing liquid phase sintering. As shown in FIG. 10, it is preferable to provide a radial protrusion 25 extending from the tube 10 so that the protrusion 23 at the shaft end gradually expands toward the axial end. This huffing is due to the fact that the pipe 2 is strengthened in the axial direction by the cast-in part 12 of the stem that encloses the hollow protrusion 23, and the productivity of the cam lobe is improved. That is, in order for the radial protrusion 25 to support the cam lobe 3 of the powder compact, the cam lobe 3 and the pipe 2 are connected to each other by a silk wire, as shown in FIG.
The assembly is manufactured by laminating the bodies and sintering them, which significantly improves productivity. Note that this radial protrusion 25
It is not necessary to provide them all around the pipe 2, but they may be provided in a wave shape as shown in FIG. 9, or they may be provided at both ends of the pipe 2. In addition, when the shaft end of the pipe 2 is expanded as shown in Fig. 10, the other end may be squeezed, but in order to obtain the cast-in strength due to the cast-in protrusions of the stems 1 and 2, the method shown in Fig. 12 is used. As shown, it is preferable to provide radial protrusions 25 at both ends 23 of the pipe 2. In this case, one radial projection 25 has to be machined after sintering.

The molten metal forming the stem 1 is selected from light metals for the purpose of weight reduction, and specifically, AI or A/? Alloy, good.”
・Sh< is a hypoeutectic or hypereutectic A/! based on strength and castability.
If -81 alloy is used, it is desirable that the casting method be Deitznost.

In addition, in order to improve the uj wrapping property with such A6 alloy, each component is subjected to Japanese surface treatment and aluminization treatment, and the sintered alloy is subjected to a sealing treatment,
Stem 1 has also been subjected to strengthening treatments such as non-toplast processing, and has been put into practical use.

As described above, the shaft of the present invention is achieved by arranging a sintered alloy in the cam lobe, and improves the strength of the stem by connecting the pipe to the cam lobe and casting the pipe into the stem. ''- is not only achieved, but also the effect of reinforcing the pipe is obtained.Furthermore, not only no processing is required for the sintered alloy, but the connection with the pipe is easy and strong, and productivity is excellent.

[Brief explanation of drawings]

FIG. 1: Cross-sectional view of the first embodiment of the present invention. Figure 2: Cross-sectional view taken along line A-A in Figure 1. Figure 3: Enlarged cross-sectional view of the wave portion in Figure 1. FIGS. 4 to 11 are cross-sectional views illustrating details of the present invention. 12th N: Cross-sectional view of another embodiment of the present invention. Explanation of the number 1: Stem 2: Pipe 3: Cam lobe 4: Journal 5: Gear
6: Cam gear 23: Projecting part 30: Hollow part Patent applicant Nippon Piston Ring Co., Ltd. 13- JP-A-58-50355 (5)・Indication of the incident 1981 Special Y [Section No. 145605 No. 2,
Title of the invention: Camshaft 3. Patent related to the person making the amendment. Applicant (〒102) Address: 2-6-4, Kudankita 4-chome, Chiyoda-ku, Tokyo, 102, Subject of the amendment: Detailed Description of the Invention Column 5, Daily Edition of the Order for Amendment, January 5, 1982, 6, Details of the Amendment, Page 2, Line 2 [3, Detailed Description of the Invention]
``Detailed description of the invention.'' ~ 2 ~

Claims (4)

[Claims] (1) A cam shaft made of a sintered metal cam lobe 3 wrapped around a molten metal forming the stem 1,
The cam lobe 3 made of I sintered alloy has a hollow hole 30 passing through in the axial direction, and the steel vibrator 2 is fitted into the hollow hole 30 and connected to the cam lobe 3 without protruding in the axial direction. A camshaft characterized in that the steel pipe 2 forming the stem 1 is cast into molten metal. (2) The camshaft according to item 1 of the patent scope, characterized in that the center of the vibrator 2 is eccentric with respect to the stem 1. (3) The camshaft according to claim 1, wherein the pipe 2 has a radial protrusion 25 that is gradually expanded toward its axial end. (4) Kano-Jandt 0 according to claim 1, wherein the stem 1 is made of Ae or Al alloy.