JP2852695B2 - Method of manufacturing engine valve lifter - Google Patents

Description

The present invention relates to a method for manufacturing a valve lifter interposed between a valve driving cam and a valve stem in a valve train of a reciprocating engine.

(Prior art) Conventionally, as this type of valve lifter, one made of hardened steel or cast iron has been mainly used, but in order to reduce the inertial mass of the valve operating system, to achieve high output and low fuel consumption, It is considered that the valve lifter is made of a light alloy such as an aluminum alloy. And in that case, when the entire valve lifter is made of aluminum alloy, abrasion occurs on the sliding surface with the cam and the contact surface with the valve stem,
For example, as disclosed in Japanese Utility Model Application Laid-Open No. 62-16703, a hard surface made of, for example, a ceramic having a contact surface for the cam on the upper surface and a contact surface for the valve stem on the lower surface, as disclosed in Japanese Utility Model Application Laid-Open No. 62-16703. A valve lifter in which a wear-resistant top plate is coupled to the upper end of a cylindrical aluminum alloy skirt by, for example, plastic flow of the skirt has been proposed.

By the way, when the skirt portion of the valve lifter is made of an aluminum alloy, the skirt portion is deformed by heat and stress when the engine rotates at a high speed, and there is a possibility of causing local wear. Therefore, a high-strength aluminum alloy is used for the skirt portion. There is a need. When the aluminum alloy is plastically flow-engaged to the ceramic top plate, if the shape of the joint is fixed, the joint strength of the joint is determined by the material of the skirt, so the joint strength is increased. Therefore, it is necessary to use a high-strength aluminum alloy for the skirt.

However, since a high-strength aluminum alloy has a high deformation resistance, a large load is required to cause plastic flow in the high-strength aluminum alloy, and there is a possibility that a top plate made of ceramic, which is a brittle material, may be broken at the time of bonding.

Therefore, as an aluminum alloy constituting the skirt portion, it is also considered to use a material having a low deformation resistance at the time of bonding with the ceramic top plate to bond the top plate to the top plate, and then to perform a heat treatment for hardening the low-strength aluminum alloy material. But
There is a problem that the compressive residual stress obtained in the plastic flow joint is lost due to the thermal expansion of the aluminum alloy material during the heat treatment, and the joint strength of the joint decreases.

(Objects of the Invention) In view of the circumstances described above, the present invention provides a hard wear-resistant top plate such as ceramic having a sliding contact surface with a cam.
It is an object of the present invention to provide a method of manufacturing a valve lifter capable of suppressing a fracture of a top plate and a decrease in a bonding strength of a plastic flow joint when a light alloy skirt portion is joined by plastic flow to produce a valve lifter. .

(Structure of the Invention) In the method for manufacturing a valve lifter according to the present invention, after the wear-resistant top plate and the light alloy skirt portion are plastically flow-coupled, an iron-based cylindrical member is fitted at least on the outer periphery of the skirt portion.
Next, a heat treatment for hardening the skirt portion is performed to obtain a valve lifter in which the iron-based tubular member is fitted.

(Effect of the Invention) In the method of the present invention, an iron-based tubular member having a lower coefficient of thermal expansion than an aluminum alloy is fitted around the outer periphery of a skirt made of a light alloy such as an aluminum alloy. Since the thermosetting treatment is performed, the thermal expansion of the skirt portion during the thermosetting treatment is suppressed by the iron-based cylindrical member, and as a result, the compressive residual stress obtained in the plastic flow joint is hardened by the heat treatment. Thus, the possibility that the bonding strength is reduced due to the loss is eliminated. Further, since the iron-based tubular member is fitted around the completed valve lifter skirt, wear of the skirt is prevented, and the skirt is formed of an aluminum alloy material having low deformation resistance. Therefore, even when ceramic is used for the top plate, it is possible to prevent the top plate from breaking during plastic flow coupling.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a valve lifter obtained by the manufacturing method of the present invention. The valve lifter 1 has a top plate 2 made of ceramic and a cylindrical skirt portion made of an aluminum alloy plastically flow-coupled to the top plate 2. 3 and a foil-like iron-based tubular member 4 fitted over the outer periphery of the skirt portion 3 and a part of the outer periphery of the top plate 2.

The top plate 2 is made of ceramic such as Si ₃ N _{4 and has} a diameter of about 30 mm.
The upper surface thereof is a sliding contact surface 2a of the valve driving cam. In the center of the lower surface of the top plate 2, a contact surface 2b of the valve stem is formed. As is particularly clear from FIG. 2, the skirt portion 3 can be fitted around the contact surface 2b of the valve stem. The wall 2c is annularly projected. Wall 2c
A V-shaped groove 2d is formed on the outer peripheral surface of the.

As shown in FIG. 2, the skirt 3 is an integrally molded product of a cylindrical sleeve 3a and a pedestal 3b extending radially inward from the upper end of the sleeve 3a. Has a coaxial hole 3c that can be fitted into the annular wall 2c of the top plate 2. The skirt portion 3 is made of, for example, silicon having extremely low deformation resistance during plastic flow coupling.
It is formed by extruded aluminum alloy containing 12%.

The iron-based tubular member fitted to the outer periphery of the skirt portion 3 is made of a thin steel material such as carburized SCR420, and has a thickness of 0.4 mm.

The manufacturing method of the valve lifter 1 having the above configuration is as follows. First, insert the skirt 3 into the hole 3c
By fitting the annular wall portion 2c of the top plate 2 to the top plate 2 and then applying a load to the skirt portion 3 at a position indicated by an arrow F in FIG. The peripheral wall material 3d of the hole c of 3 is caused to flow into the V-shaped groove 2d of the top plate 2, thereby connecting the top plate 2 and the skirt portion 3. Next, an iron-based tubular member 4 is fitted around the outer periphery of the skirt portion 3 and heated at a temperature of 495 ° C. for 1 hour to shrink the tubular member 4 around the skirt portion 3 and, after cooling with water, at 175 ° C. Age hardening treatment was performed at the temperature for 8 hours. By this heat treatment, the bonding load of the plastic flow joint was 2300 kgf before the treatment, but increased to 5200 kgf after the treatment. Next, the desired valve lifter 1 was obtained by grinding the outer periphery of the iron-based cylindrical member 4.

In the above embodiment, an aluminum alloy is used as the material of the skirt portion 3. However, a magnesium alloy or an aluminum / lithium alloy or the like can be used instead of the aluminum alloy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a valve lifter manufactured by the manufacturing method of the present invention, and FIG. 2 is a cross-sectional view showing a part of a manufacturing process. DESCRIPTION OF SYMBOLS 1 ... Valve lifter 2 ... Top plate 3 ... Skirt part 4 ... Iron-based cylindrical member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01L 1/14

Claims (1)

(57) [Claims] After a hard wear-resistant top plate having a sliding contact surface with a valve driving cam and a cylindrical light alloy skirt portion are plastically flow-coupled to each other, an iron-based cylinder is provided on at least the outer periphery of the skirt portion. A method of manufacturing a valve lifter for an engine, wherein a valve lifter to which the iron-based tubular member is fitted is obtained by performing a heat treatment for fitting the cylindrical member and then hardening the skirt portion.