Process for obtaining a valve seat

Abstract

 The invention concerns a process for obtaining a valve seat (3) in an intake duct of an internal combustion engine in which the finishing milling of the duct is eliminated, thus obtaining improvements in engine performance.

Description

[0001] This invention concerns a process for obtaining a valve seat in an intake duct of an internal combustion engine.

[0002] The current process for obtaining a valve seat in an intake duct of an internal combustion engine consists in the following stages:

a. milling of the cylinder head to obtain a valve seat housing in cast iron or other suitable material;

b. driving of valve seat;

c. milling of the junction point between driven valve seat and housing edge on the intake duct in order to eliminate any diameter differences;

d. machining of the valve rest chamfer on the cast iron valve seat.

[0003] The purpose of the invention is to make this operation less expensive, while maintaining at least the same engine performance, but eliminat­ing the stage c. of the known process which is the most difficult to perform in as far as edges could remain due to the machining itself.

[0004] This purpose is achieved by a process for obtaining a valve seat in an intake duct of an internal combustion engine, characterized in that the process consists in the following machining stages:

a. milling of the cylinder head to obtain the housing for a valve seat ring in cat iron or other suitable material;

b. driving in the housing thus obtained of a valve seat with inside diameter equal to the intake duct diameter and equipped with bilateral chamfer;

c. milling of the valve rest chamfer.

[0005] Further characteristics and advantages will become clear from the following description, referred to the attached figures, provided merely by way of non-limitative example, of which:

- Fig. 1 is a cross section of the object obtained with the process of the invention;

- Fig. 2 is an enlargement of a detail in Fig. 1.

[0006] With reference to the figures, 1 indicates a part of a light alloy cylinder head of an internal combustion engine cut away in correspon­dence of one of the intake ducts.

[0007] In it, a housing 2 has been obtained, by milling or other suitable machining, at the exit of the feed duct, capable of receiving a valve seat 3 made for example from cast iron, which is put in place by driving.

[0008] The above valve seat has an inside diameter hole 4, substantially equal to the inside diameter of the intake duct at the point where the housing 2 is obtained. In addition, it is equipped, at the time of driving it in, with a bilateral chamfer 5.

[0009] After the valve seat has been driven in place, the valve rest chamfer 6 is made, which has an inclination generally of 45 degrees and whose axis is coaxial with that of the valve guide 7.

[0010] The duct thus obtained, eliminating the finishing operation on the junction point between valve seat and the duct itself, has a step 8 due to the difference between the two diameters resulting from the chamfer.

[0011] However, the above step being favourable to the direction of the feeding mixture flow, it does not hinder in any way the engine perfor­mance and at the same time prevents the formation, either by mere chance or as a result of poor machining, of adverse steps which, as it can be easily inferred, would be a hindrance to the free passage of the flow itself.

Claims

1. Process for obtaining a valve seat in an intake duct of an internal combustion engine, characterized in that the process consists in the following machining stages:

a. milling of the cylinder head to obtain the housing for a valve seat ring in cast iron or other suitable material;

b. driving in the housing thus obtained of a valve seat with inside diameter equal to the intake duct diameter and equipped with bilateral chamfer;

c. milling of the valve rest chamfer.

Drawing