JPS6244086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve seat attachment device to a cylinder head, which increases the degree of adhesion of the valve seat to the cylinder head, improves the thermal conductivity of this part, and reduces the heat of the valve seat. This is to suppress the occurrence of distortion due to

In a four-stroke engine, intake and exhaust into the combustion chamber are controlled by valves. This valve is generally called a mushroom valve, and has an intake hole (or exhaust hole) in the cylinder head.
The back part is brought into contact with and separated from the combustion chamber side to open and close the intake hole (exhaust hole). A concave-shaped seat hole is formed in the valve abutting portion of the cylinder head, and an annular valve seat is fitted into this seat hole to increase the ease with which the valve is seated and to improve airtightness.

This valve seat is usually press-fitted into the seat hole of the cylinder head by a method called cold fitting, but this method creates a space between the bottom surface of the valve seat (the surface where it seats on the cylinder head) and the cylinder head. This space can easily cause the valve seat to sink as the engine operates.
When this happens, there is a problem that the contact between the valve and the valve seat becomes poor.

To prevent this, it has been devised to improve the adhesion of the valve seat to the cylinder head by applying copper plating to the valve seat, but this method requires many work steps and is expensive. A problem arose. Furthermore, the conventional valve seat mounting structure has the problem of deformation of the valve due to poor heat dissipation due to the accuracy of the seat hole, distortion during press-fitting, and poor adhesion between the valve seat and the seat hole.

The present invention provides a valve seat attachment device to a cylinder head that solves these problems.

An embodiment of the present invention will be explained with reference to FIG. 1. 1 is a cylinder head, 2 is a valve seat, 3 is an intake hole (the exhaust hole has the same structure), 4 is a seat hole, and 5 is a guide pipe for the valve rod. . The bottom portion of the seat hole 4 is formed into a wedge-shaped cross section that increases in depth toward the outer periphery.
Note that although this figure is drawn with the intake hole 3 open upward for convenience, in actual use it is usually the opposite.

When the valve seat 2 is cold-fitted into the seat hole 4 of the cylinder head 1, as shown in FIG. Apply 6. In this example, the filler 6 used was the product name "Thermotite". The filler 6 is desirably one that is heat resistant, has good thermal conductivity, does not change over time, and has vibration resistance. As shown in FIG. 2, the bottom surface of the seat hole 4 of the cylinder head 1 is inclined at an angle Θ with respect to the horizontal plane (it becomes deeper toward the outer circumference), so that the filler 6 cannot flow there. As a result, the valve seat 2 can be press-fitted smoothly. Furthermore, since the filler 6 flows into the seat hole 4 in this manner, even if the amount is somewhat large, it will not interfere with the press-fitting of the valve seat 2.

Since the present invention is constructed as described above, there is an advantage that the press-fitting property when cold-fitting the valve seat into the cylinder head is improved, and the degree of tightness between the valve seat and the cylinder head is perfect. Further, in connection with this, since thermal conductivity is improved, there is also the advantage that generation of distortion due to heat in the valve seat can be suppressed. Furthermore, these effects are
The same result can be obtained by applying the filler to the valve seat side and then fitting it into the seat hole, contrary to the above embodiment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a sectional view showing the assembled state of the device shown in FIG. 1... Cylinder head, 2... Valve seat, 3... Intake hole, 4... Seat hole, 6... Filler.

Claims (1)

[Claims] 1. In an engine in which a seat hole is formed in the valve seat mounting part of the cylinder head and the valve seat is press-fitted into the seat hole and installed, the bottom part of the seat hole of the cylinder head is deepened toward the outer periphery. The valve seat is formed into a wedge-shaped cross section with increasing thickness, and a filler is interposed on the outer periphery of the valve seat or the inner wall of the cylinder head into which the valve seat is press-fitted, and the filler increases the degree of adhesion of the valve seat to the cylinder head. Valve seat attachment device to the cylinder head.