JPS621083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a valve for an internal combustion engine, which has a sheathing on the valve material in the area of the outer valve seat.

Valves of this type with a jacket are known. In this case, the valve is laminated with a workpiece material whose heat-resistant strength and hardness are higher than the values of the valve workpiece material due to the high mechanical and thermal alternating stresses in the valve seat area. The composition of these materials is structured differently than the valve material and often has a different behavior with respect to expansion and contraction upon temperature changes.

In these valves, to avoid crack formation,
Although it is known to control the effects of thermal expansion in the sheathing layer and in the valve workpiece during the welding process by appropriate preheating, residual stresses may occur due to the difference in expansion coefficients upon cooling after such a process. A condition arises.

The problem with manufacturing this type of valve is that the residual stress that occurs is mostly tensile stress in the sheath, and this tensile stress can lead to cracking at critical stress periods and failure of the valve with serious injury. It's all over the place.

The object of the invention is to create a method for manufacturing a valve that eliminates in a simple manner the tensile stresses occurring in the sheath, thereby ensuring that the occurrence of cracks is avoided.

This problem is solved according to the invention by heating part of the valve material at the base of the valve head in a block-like manner above the thermal yield point, except for the circularly surrounding edge area;
This is followed by rapid cooling, in which case the edge area is deformed by the action of forces that occur during the shrinkage process of the heat-treated subarea;
This problem can be solved by having a size that reduces the outer diameter of the valve.

By this processing step for carrying out the shrinkage process,
The advantage arises that within the confines of the sheath, existing tensile stresses are converted into compressive stresses.

The partial areas for heating and cooling are designed in the form of a ring, so that the heating is essentially limited to the desired partial area.

A simple device for local heating is obtained by arranging an induction coil for the generation of heat.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

The illustrated valve consists of a valve stem 1 and a valve head 2 . The valve head 2 is provided with a jacket 3 in the region of the valve seat, which is accommodated in a corresponding boat-shaped recess 4.

When applying the method according to the invention, the valve material is heated in blocks starting from the base 5 of the valve head in partial areas 6. In this case, block-like means that the heating should take place to a certain depth and that a certain spatial area is heated. Heating takes place via an induction coil, not shown. The arrangement of the partial areas 6 is configured as a ring in this embodiment. Therefore, the circularly surrounding edge range 7 must always be maintained,
This edge region 7 is of such a size that it can be contracted by heating the partial region 6 above the thermal yield point of the valve material and by subsequent rapid cooling. Due to this contraction process, the valve outer diameter 8 decreases.

In this method, it is important that only the partial areas 6 are heated to a high degree, so that the edge areas 7, which are not subjected to thermal action, are contracted after cooling.

During rapid cooling of the heated partial region 6, a conversion of the tensile stresses in the housing 3 into compressive stresses takes place by a contraction process accompanied by a reduction in the outer valve diameter 8.

The embodiments of the present invention are as follows.

Device for carrying out the method according to claims 1 and 2, characterized in that an induction coil is provided for the generation of heat.

[Brief explanation of the drawing]

The drawing shows a partial sectional view of a valve with a jacket, in which the formation of the valve by application of the method of the invention is indicated by dashed lines. 5... Valve head range, 6... Partial range, 7... Edge range, 8... Valve outer diameter.

Claims (1)

[Claims] 1. A method for manufacturing a valve for an internal combustion engine in which the valve material within the valve seat area on the outside has an exterior, in which the valve material of the valve head bottom 5 is connected in a circular manner. The subarea 6, excluding the edge area 7, is heated block-wise beyond its thermal yield point and then cooled rapidly, the edge area 7 occurring during the shrinkage process of the heat-treated subarea 6. A method characterized in that the deformation of the edge region 7 is carried out by the action of a force and has such a magnitude that the valve outer diameter 8 decreases. 2. A method according to claim 1, characterized in that the partial region 6 subjected to heating and cooling is formed in the form of a ring.