JPH045685Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an on-off valve for an internal combustion engine that uses ceramics.

[Prior Art] In conventional on-off valves for internal combustion engines made of metal, an annular groove with a semicircular arc cross section is provided at the upper end of the stem, as disclosed in, for example, Japanese Utility Model Application Publication No. 58-27509. A protrusion provided on the cylindrical surface of the rotator is engaged with the annular groove, and the conical outer peripheral surface of the rotator is fitted into the conical hole of the rotator, thereby connecting the rotator to the stem. The on-off valve is pressed against the intake and exhaust ports by a spring interposed between the spring seat attached to the rotator and the cylinder head.

Incidentally, many attempts have already been made to utilize the heat insulating properties of ceramics to obtain internal combustion engines with high thermal efficiency. In such an internal combustion engine, it is desirable to mold the on-off valves, that is, the intake and exhaust valves, from ceramics, but in the case of ceramics, it is preferable to form an annular groove in the stem into which the above-mentioned clasp engages. It is difficult to adopt this method because the strength of that part will be impaired. Therefore, it is required that the inner surface of the rotator be made into a cylindrical surface and that the rotator be coupled by frictional engagement between the cylindrical surface and the stem.

However, ceramics generally have a very smooth surface roughness of about 1 μm after firing. If the surface roughness of ceramics is intentionally made rougher, there will be problems in terms of strength, such as cracks occurring in these areas during firing. It is also conceivable to mechanically process the surface roughness of the ceramic after firing, but this may also lead to cracks and cracks.

[Problems to be solved by the invention] Therefore, in view of the above-mentioned problems, the purpose of the invention is to provide the surface of the stem made of fired ceramics with
To provide an on-off valve for an internal combustion engine, which can obtain sufficient frictional engagement with the cylindrical surface of a plug by simple surface processing without impairing strength.

[Means for Solving the Problems] In order to achieve the above object, the structure of the present invention is to form a metallized layer on the contact engagement surface of the stem made of ceramics, and to apply a predetermined surface roughness to the outer periphery of the metallized layer. A metal coating layer having the following properties is formed.

[Function] In order to form a suitable rough surface on the engagement surface 4 that engages with the connector 2 of the stem 1 made of ceramics,
By forming the metallized layer 7 on the surface of the stem 1 fired from ceramics, a metal coating layer 8 having a desired surface roughness can be formed on this surface. This coating layer 8 provides reliable frictional engagement with the cylindrical surface 14 of the blade 2.

[Example of the invention] The invention will be explained based on an example. As shown in FIG. 2, first, the on-off valve 10 has a mushroom-shaped valve body 15 formed at the lower end of a stem 1, and a splitter 2, which is a split body, frictionally engaged with the upper end. The rotator 12 is connected to the stem 1 by firmly fitting into the conical hole 13 of the rotator 12. A cam follower slidingly contacts a known cam on the upper surface of the rotator 12, and a valve body 15 on the lower surface.
Valve springs pressing against the exhaust ports are respectively engaged via spring seats.

A cylindrical surface 14 into which the stem 1 is fitted is formed on the shank 2. The shank 2 is made of a normal metal, and the cylindrical surface 14 has a normal surface roughness of about 10 μm.

According to the present invention, in order to form an appropriate roughness on the engagement surface 4 of the stem 1 made of ceramics, which engages with the connector 2, as shown in FIG.
After pre-forming and firing a slightly gently constricted surface 1a on the part that engages with the kotsuta 2,
As shown in FIG. 4, a metallized layer 7 is formed on the constricted surface 1a of the stem 1. This metallized layer 7 is for metallizing the surface of the ceramic, thereby making it possible to coat it with a desired metal.

The method for forming the metallized layer 7 includes Pi, Nb,
Active metals such as Zr, noble metals such as Au, Ab, Pd,
It is formed using a high melting point metal such as Mo or W by a welding method. Alternatively, a paste containing metal powder such as Mo or Mn may be applied to the surface of the stem 1 and fired. Furthermore, metal powder such as Mo or Mn may be thermally sprayed onto the surface of the stem 1.

After forming the thin metallized layer 7 on the surface of the stem 1 in this manner, the surface of the metallized layer 7 is coated (brazed or welded) with a predetermined metal, as shown in FIGS. 1 and 4. Finally, the surface of the metal coating layer 8 is polished to a predetermined size to have a surface roughness of about 10 μm. A thickness of about 0.5 mm is sufficient for the metal coating layer 8.

The constricted surface 1a of the stem 1 is shaped into a gentle arc, and the strength of the stem 1 is not impaired because the finish (outer diameter) after metal coating is such that it does not interfere with the cylinder head of the on-off valve. This is to ensure that the outer diameter is equal to that of other parts for ease of assembly.

By configuring the present invention as described above, the engaging surface 4 having a predetermined surface roughness can be formed on the surface without any adverse effect on the strength of the stem 1 made of ceramics. , engage the cylindrical surface 14 of the rotator 2 so as to sandwich this engagement surface 4, and insert the rotator 2 into the conical hole 13 of the rotator 12.
By tightly taperingly fitting into the stem 1, the shaft 2 is firmly frictionally engaged with the stem 1 without slipping in the axial direction. As a result, the stem 1 and the rotator 12 are coupled, and the motion of the rotator 12, which receives the driving force of the cam, is integrally transmitted to the stem 1.

[Effects of the invention] As described above, the present invention forms a metal coating layer 8 with an appropriate surface roughness on the surface of the stem 1 of an on-off valve, which is usually formed from ceramics. Sufficient frictional engagement can be obtained with the rotator 12, which supports the valve spring and cam followers, and the assembly interval between the cylinder head and the rotator 12 can be maintained at a predetermined dimension, thereby ensuring normal operation of the on-off valve. I can do it. Since the coating layer 8 is formed via the metallized layer 7 on the surface of the stem 1 molded from ceramics using a normal method, the strength of the ceramics is not impaired and the heat insulating properties of the ceramics are maintained. An excellent on-off valve for internal combustion engines can be provided at low cost.

[Brief explanation of the drawing]

Fig. 1 is a plan sectional view showing the main parts of the on-off valve for an internal combustion engine according to the present invention, Fig. 2 is a side view of the on-off valve for an internal combustion engine, and Figs. FIG. 3 is a side sectional view showing the manufacturing process of the engine on-off valve. DESCRIPTION OF SYMBOLS 1... Stem, 2... Kotsuta, 4... Kotsuta engaging surface, 7... Metallized layer, 8... Metal coating layer, 10... Opening/closing valve, 12... Rotator,
13... Conical hole, 14... Cylindrical surface.

Claims (1)

[Scope of utility model registration request] 1. An on-off valve for an internal combustion engine, characterized in that a metallized layer is formed on the contact engagement surface of a stem made of ceramics, and a metal coating layer having a predetermined surface roughness is formed on the outer periphery of the metallized layer.