JPS59205473A - Preparation of cam shaft - Google Patents

Abstract

PURPOSE:To fabricate a cam shaft excellent in durability in good yield, in fabricating the cam shaft, by molding a substrate material into a predetermined profile while vapor depositing a hard metal compound to the cam part of the molded one by a chemical vapor deposition method. CONSTITUTION:A cam shaft substrate material to which a fundamental shape is imparted by casting and the other mechanical processing is preformed precisely so as to obtain a predetermined cam profile. In the next step, the molded one is put in a reaction furnace for chemical vapor deposition and heated to 1,000- 1,200 deg.C. On the other hand, TiCl4 is gasified by heating the same to 20-80 deg.C and sent into the reaction furnace along with CH4 and H2 being carrier gases. TiCl4 and the carrier gases are chemically reacted on the surface of the cam shaft substrate material in the furnace to form TiC and HCl while TiC among them is precipitated to the surface of the cam shaft substrate material to form a hard TiC vapor deposition layer. Because the largest load is especially applied to a cam nose part Cn, the life of a cam is prolonged by the enhancement of the abrasion resistance of said part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a camshaft used in a reciprocating engine or the like.

Cams and camshafts are widely used in various mechanical devices, but camshafts used in the valve mechanism of reciprocating engines in particular open and close intake and exhaust valves thousands of times per minute under harsh conditions. A high degree of durability is required to carry the engine, and the cam profile greatly affects engine performance, so even the 11-degree shape requires sufficient ventilation (
You have to pull it.

Therefore, as a manufacturing method for camshafts that meet these demands, conventional methods have been adopted in which the camshaft material is formed by die casting, and the cam part and journal part are precisely polished and finished (Incorporated Association) Society of Automotive Engineers of Japan June 1, 1975
Japanese Automotive Engineering Handbook Volume 2 P, 1-86>. In other words, the surface of the material is rapidly cooled (chilled) by contact with a mold with good thermal conductivity to form a hardened layer, which is then polished into a predetermined shape.
By adopting this process, we can solve the problem of deformation of the material when heat-treated after casting, and obtain a camshaft with excellent durability and precision.

However, such conventional manufacturing methods require many steps to fabricate the mold for mold casting, and also have to be polished because the hardened layer formed during chilling is polished. There were inconveniences in production and product management, such as defective products in which the hardened layer was partially lost and yields deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to solve these conventional problems and to provide a camshaft that is more durable and can be made smaller and lighter.

To this end, in the present invention, first, the cam part is precisely machined to a predetermined profile to form an Ic camshaft material, and then a hard coating is formed by depositing a metal compound on the cam part using chemical vapor deposition. I did it like that.

The chemical vapor deposition method is a type of plating method in which a J-type compound (vapor deposition substance), which has a relatively low temperature and high vapor pressure, is sent into a reaction furnace together with Kyrelia gas and deposited as a solid on the surface of the material. C11emical Vapo
rDeposition) method.

Now, to explain the case of emulsifying a cam shaft by depositing TiC on cam axle material using the CVD method, first, prior to the CVD process, the cam axle material is given a basic shape by casting or other machining. (Cam part) is precisely molded in advance to have a predetermined cam profile.

This shaped cam axon material is inserted into a CVD reactor and heated to iooo to 1200°C.

On the other hand, Ti C1f, A is heated at 20 to 80° C. to gasify it, and this is sent to the above-mentioned reactor together with CH and H2 as a carrier cass.

Then, on the surface of the camshaft material in the reactor, TiC/,
A chemical reaction occurs between the carrier gas and TiC to produce TiC and HC, of which TiC precipitates on the surface of the material to form a hard vapor deposited layer.

The TiC coating formed on the cam surface in this way has a hardness of HV? 500, the hardness is extremely high at 1-1v = 3800 to 4000, and therefore a camshaft with extremely high durability can be obtained.

In addition, in the engine camshaft, the cam nose part Cn provides lift to the tappet side against the tension of the valve spring.
The area (see drawing) is subject to the heaviest load, and the wear resistance of this area determines the lifespan of the cam. Therefore, the above CV
The hard coating D may be applied locally only to this cam nose portion Cn. As a method for performing such local vapor deposition, a method has been developed in which the area to be vapor deposited is locally heated using a laser, an electron beam, or the like.

In addition, when using a material that deforms under high temperatures and tends to reduce cutting accuracy as the camshaft material, the above-mentioned CVD method using local heating is effective. Low-temperature CVD methods for obtaining a deposited plating layer at a temperature of 400° C. or lower have been developed, such as MOCVD using chemical compounds and LPGVD performing treatment v11 under low pressure.

Furthermore, dozens of other vapor deposition materials have been developed in addition to the above-mentioned TiC, and among them, those suitable for camshafts include, for example, T1CN, Af20. and so on. 1-iCN is 1”■-2000~3000T
Although it is inferior to iC in terms of hardness, it is considerably superior in toughness, so it is advantageous in terms of fatigue strength under repeated loads. Also, Aヱ203 is]”\l-230
It has the characteristic of being strong against thermal loads, although it is about 0. In this way, each vapor deposition substance has its own characteristics, so
By simply selecting the appropriate camshaft, you can create 11 camshafts for various purposes and uses. can be provided. (For more information about CVD, see ['Current situation and prospects of recent surface treatment technology CVD' Abstracts of the 49th Special Lecture of the Japan Society of Mechanical Engineers ff?' J (published October 1982).) By the way, the CVD method As mentioned above, the coating formed by
Therefore, a camshaft with excellent wear resistance and scuff resistance can be obtained, but in practice, the only way to improve this durability is to increase the surface pressure between the tappet or follower, that is, to increase the cam width. This allows the camshaft to be made smaller and lighter.

Furthermore, if we focus on lubricity, it is known that under conditions where a boundary lubrication state occurs, such as in the case of a cam nose, it is preferable to provide a certain degree of large surface roughness to improve oil retention (for example, , “Lubrication” Vol. 23 No. 9 (19
78), pp. 654-662), whereas C.
The coating formed by the VD method has a thickness of 1 to 1, depending on its thickness.
Since it has a surface roughness of 5 μnl, it is advantageous in this respect as well compared to conventional polished cam surfaces.

In summary, the present invention provides a predetermined cam shape in advance and then calculates r* c, rt CN, Δ220. The camshaft is finished by applying a hard coating to the cam by chemical vapor deposition of metal compounds such as There is no need to prepare a complicated mold for forming a hardened layer on the camshaft material by chilling, and therefore, the retention is improved and productivity is significantly improved.

In addition, the camshaft manufactured according to the present invention has an extremely hard metal compound coating formed on the cam surface and has excellent lubricity, so it has significantly higher durability than conventional camshafts, and can therefore be made smaller and lighter. .

[Brief explanation of the drawing]

The figure is a side view for explaining the cam nose portion On of the camshaft.

Claims (1)

[Claims] A method for manufacturing a camshaft, which comprises forming a cam portion of a camshaft material in advance into a predetermined profile, and then coating a small portion of the cam portion (in particular, the cam nose portion) with a metal compound by chemical vapor deposition.