JPS644047B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to intake and exhaust valves used in various internal combustion engines such as automobiles, ships, construction machinery, and agricultural machinery. This relates to a hollow intake/exhaust valve whose interior is hollow and metal sodium is sealed therein for the purpose of increasing the

(Prior Art) In general, the intake and exhaust valves of the above-mentioned internal combustion engine are directly exposed to high temperature and high pressure gas caused by combustion within the cylinder. Further, the sealing surface of the head portion of the valve body that contacts the cylinder-side valve seat is subjected to mechanical shocks due to the opening and closing operations of the valve. It should be noted that a mechanical shock also occurs at the stem end of the valve body between it and the tappet or rocker arm due to the opening/closing operation of the valve.

Therefore, in order to cope with high temperature and high pressure gas, the valve body is made of austenitic or martensitic heat-resistant steel, and in order to increase its strength against mechanical shock, the entire valve body or Heat treatment or surface hardening treatment is applied to the necessary parts.

The mechanical strength of the austenitic heat-resistant steel is not significantly improved by heat treatment or surface hardening treatment. To deal with this, conventionally, the valve body 50 is made of austenitic heat-resistant steel as shown in FIG. 54 is constructed by welding martensitic heat-resistant steel, carbon steel, etc., which have excellent mechanical strength improved through heat treatment.

Furthermore, as internal combustion engines have become faster and more powerful in recent years, martensitic heat-resistant steel has insufficient heat resistance, so the valve body 50 can be formed primarily of austenitic heat-resistant steel. However,
This austenitic heat-resistant steel also has poor thermal conductivity, which causes the temperature of the valve body 50 to rise, causing a lack of lubricating oil between the stem 53 and the valve guide of the cylinder (not shown). Cheap. As a result, problems such as a seizure phenomenon between the stem 53 and the valve guide and a reduction in the knock resistance of the internal combustion engine occur even if a localized high temperature area (hot spot) occurs within the cylinder head.

As a countermeasure to this problem, as shown in FIG. 1, a hollow part 55 is formed which communicates from the stem 53 of the valve body 50 to the inside of the umbrella part 51, and a metal sodium 56 is sealed in the hollow part 55. This metal sodium 56 liquefies during the operating state of the internal combustion engine, and transmits heat from the umbrella portion 51 as the valve body 50 opens and closes, thereby suppressing a rise in temperature of the valve body 50.

The heat transfer effect can be enhanced by enclosing a sufficient amount of the metal sodium 56. Therefore, in order to increase the volume of the hollow part 55, an opening 57 is formed in the end face of the umbrella part 51 of the valve body 50, as shown in FIG. Process. After that, this blank space 5
Metal sodium 56 is put into the hollow part 55 including 5a, and a heat-resistant steel cover body 58 formed in a separate process is welded to the valve body 50 by friction welding or the like to close the opening 57. As a result, in the conventional example shown in FIG. 2, the volume of the hollow portion 55 is increased compared to that shown in FIG. 1, and the amount of metal sodium 56 enclosed is also increased. In addition, in this FIG. 2, the end 54 of the stem 53 is plated (welded) with steel with high mechanical strength in order to cope with the impact with the tappet etc.
At the same time, this closes the degassing hole 59 when the metal sodium 56 is sealed in the hollow part 55.

By the way, in the case of the conventional example shown in FIG.
The welded portion of the cover body 58 that closed the cover body 58 is close to the welded portion of the cover body 58. For this reason, cracks around the weld, called "second weld cracks," are likely to occur where the heat-affected areas from both welds are close to each other. Furthermore, when friction welding the cover body 58 to the end of the umbrella part 51 of the valve body 50 as shown in FIG. Requires space. For these reasons, both of the above-mentioned welded parts must have an appropriate distance between them, and as a result, even in the example of FIG. 2, it is difficult to retain a sufficient amount of metal sodium 56, and This has hindered efforts to reduce the weight of the valve body 50.

(Object of the Invention) The object of the present invention is to provide a hollow intake/exhaust valve of the type in which an opening is formed in the end face of the umbrella portion of the valve body and the opening is closed with a cover body, and cracks around the weld (second weld crack) A hollow intake and exhaust system for an internal combustion engine that can prevent this from occurring, secure enough space for holding metal sodium, support higher speeds and higher outputs due to lighter weight, and shorten the manufacturing process. The purpose is to provide a valve.

(Structure of the Invention) In order to achieve the above object, the present invention is structured as follows.

That is, a hollow portion is formed inside the valve body made of heat-resistant steel, which communicates from an opening formed in the end face of the cap portion to the inside of the stem. Metal sodium is sealed in this hollow part, and the opening is closed with a cover body made of heat-resistant steel.

The sealing surface of the umbrella part that contacts the cylinder-side valve seat is made of a metal with high mechanical strength and wear resistance, and the cover body and the valve body are connected to each other at this sealing surface. Note that the above valve body may be formed of austenitic heat-resistant steel. Furthermore, the stem end of the valve body has high mechanical strength to withstand impact from tappets, etc.
Constructed of wear-resistant metal.

(Example) Hereinafter, the above configuration of the present invention will be explained in more detail according to the example shown in FIGS. 3 to 6 A to E.

First, in FIG. 3 showing a cross section of a hollow intake and exhaust valve of an internal combustion engine, and FIG. 4 showing a partially enlarged view of FIG. 3, the valve body 10 is made of, for example, austenitic heat-resistant steel. , handles stress against external forces associated with well-known valve opening and closing operations, and
The stem 12 has wear resistance against a valve guide on the cylinder side (not shown). This valve body 1
The inside of the valve body 10 is a hollow part 13, and this central part 13 communicates from an opening 14 at the end face of the umbrella part 11 in the valve body 10 to the end face of the stem 12. This opening 14 is closed with a disk-shaped cover body 15 that is separately formed of heat-resistant steel (for example, austenitic heat-resistant steel) having the same characteristics as the valve body 10. By adopting a configuration in which the opening 14 is formed in this way and the opening is closed with the cover body 15, a space 13a having a shape substantially similar to the outer shape of the umbrella 11 is formed inside the umbrella 11. is configured,
As a result, the above-mentioned hollow part 1 including this cavity 13a
3 can be sufficiently secured.

On the outer periphery of the umbrella portion 11, the sealing surface 16, which repeatedly comes into contact with the cylinder-side valve seat (not shown), is made of heat-resistant martensitic steel, carbon steel, etc. whose mechanical strength is significantly improved by heat treatment, etc. Welding). and,
This sealing surface 16 is formed on the valve body 10 at the same time as its molding.
It serves the function of connecting the umbrella part 11 and the cover body 15 (see Fig. 4).

Metal sodium 18, which occupies approximately two-thirds of the volume of the hollow portion 13, is sealed inside the hollow portion 13. This metal sodium 18 becomes liquid during operation of the internal combustion engine, and functions to transfer the heat of the umbrella portion 11 to the stem 12 side as the valve body 10 reciprocates. In addition, this metal sodium 18
has a specific gravity of 0.97, which is very small compared to the specific gravity of heat-resistant steel, 7.8. Therefore, by filling the hollow portion 13 of the valve body 10 with this metal sodium 18, the weight of the intake and exhaust valve can be reduced.

The stem end portion 17 is separately formed of an alloy having high mechanical strength, similar to the alloy used for the sealing surface 16, and is welded to the end surface of the stem 12. As a result, the hollow portion 13 of the valve body 10 is sealed, and the stem end can withstand shocks received from a not-shown tappet or rocker arm.

In the embodiment shown in FIG. 5, an uneven portion 19 for centering is formed between the opening 14 of the valve body 10 and the cover body 15. According to this configuration, the valve body 10 and the cover body 15 are As described above, when the sealing surfaces 16 are formed and bonded together at the same time, there is an advantage that a jig for mutual centering is not required.

The manufacturing procedure of the hollow intake/exhaust valve shown in FIG. 5 will be explained with reference to FIGS. 6A to 6E. First, Figure 6A
As shown in , a hollow valve body 10 is molded by means such as upset molding or extrusion molding. In the case of austenitic heat-resistant steel, the shape shown in FIG. 6B can be formed by cold plastic working because its characteristics are that plastic working is easy. FIG. 6C shows an intermediate product obtained by processing predetermined portions of the valve body 10 molded in this way by cutting, grinding, etc. For those that require liquefaction treatment, a predetermined treatment is performed after this.

Next, a cover body 15 formed separately from the valve body 10
are centered and fitted into the opening 14 of the valve body 10 by the mutual centering concave and convex portions 19, and in this state, the sealing surface 16 is welded.
The valve body 10 is formed by molding as shown in FIG. 6D.
and the cover body 15 are connected. According to this coupling means, there is little extra thickness or space for obtaining the coupling strength between the valve body 10 and the cover body 15, and the umbrella part 1
The space 13a within the space 1 can be made larger. For those requiring surface hardening treatment such as nitriding treatment, this is performed after this. After that, metal sodium 1 is added to the hollow part 13 of the valve body 10 as shown in FIG. 6E.
8, and insert the hollow part 13 from the open end of the stem 12.
A metal plug 20 is driven into the stem 12, and a mechanically strong stem end 17 is fixed to the end of the stem 12 by friction welding or flash butt welding.

In the embodiment of the present invention, the stem end 17 can be replaced with a structure as shown in the conventional example shown in FIG.

(Effects of the Invention) As described above, the present invention is characterized by the coupling of a cover body that closes an opening formed on the end face of a cap portion of a valve body, and the sealing surface formed with mechanical strength on the outer periphery of this cap portion. Because it is configured to perform both forming and forming by the same means, it is possible to prevent cracking around the welded area (second weld cracking) that occurs due to welding at two or more locations, and compared to a case where the cover body is friction welded. This makes it possible to secure sufficient storage space for metal sodium, reduce the weight of the valve body, and support higher speed and higher output machines. Moreover,
According to this invention, since the coupling of the cover body and the molding of the sealing surface can be performed simultaneously, the manufacturing process can be shortened.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional hollow intake and exhaust valve.
FIG. 2 is a sectional view showing a further different conventional hollow intake and exhaust valve, FIGS. 3 to 6 A to E show embodiments of the present invention, and FIG. 3 is a sectional view of the hollow intake and exhaust valve. Figure 4 is an enlarged sectional view of a part of Figure 3, Figure 5 is a sectional view of a different embodiment corresponding to Figure 4, and Figure 6A is a rough-shaped valve body. 6B is a sectional view thereof, and FIGS. 6C to 6E are partial sectional views sequentially showing the finishing procedure of the valve. DESCRIPTION OF SYMBOLS 10... Valve body, 11... Umbrella part, 12... Stem, 13... Hollow part, 14... Opening part, 15...
Cover body, 16...Sealing surface, 18...Metal sodium.

Claims (1)

[Scope of Claims] 1. A hollow part is formed inside the valve body made of heat-resistant steel, which communicates from the opening of the end face of the cap to the stem,
This hollow intake/exhaust valve for an internal combustion engine is formed by enclosing metal sodium in the hollow part and closing the opening at the end face of the cap part with a cover body made of heat-resistant steel. The sealing surface that comes into contact with the valve seat is made of metal with high mechanical strength and wear resistance.
A hollow intake/exhaust valve for an internal combustion engine, characterized in that the cover body and the valve body are connected to each other at the sealing surface. 2. The hollow intake and exhaust valve for an internal combustion engine according to claim 1, wherein the valve body is made of austenitic heat-resistant steel. 3. The hollow intake and exhaust valve for an internal combustion engine according to claim 1 or 2, wherein the stem end of the valve body is made of a metal having high mechanical strength and wear resistance.