JP2542539Y2 - Ceramic valve - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake and exhaust valve made of ceramics for an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, in particular, in a diesel engine, the most effective means for improving thermal efficiency is to increase the combustion temperature and recover exhaust heat by using a combustion chamber having an insulated structure.

However, when the thermal efficiency is to be improved by the above-described means, a higher heat load than before is applied to the intake and exhaust valves due to the heat insulation of the combustion chamber. Therefore, a heat-resistant alloy is usually used for the intake / exhaust valve. However, at such a high temperature, even though the heat-resistant alloy is used, oxidative corrosion is severe and the valve function is deteriorated in a short period of time.

In addition, the intake / exhaust valve made of a heat-resistant alloy has a large number of drawbacks, such as a large weight, a large inertial force of movement, and difficulty in following the high-speed rotation of the engine.

Therefore, in recent years, intake and exhaust valves for internal combustion engines used under high temperature load conditions for high rotation and high output have been made of ceramics having excellent heat resistance, corrosion resistance, heat insulation properties, wear resistance and the like. Various attempts have been made to form and improve the durability and weight of the valve, thereby improving the response performance and contributing to the improvement of the performance of the internal combustion engine.

Generally, in a valve operating mechanism of an intake / exhaust valve for an internal combustion engine, a cotter 12 is fitted in an annular cotter groove 5 provided on an outer periphery of a stem 2 near a stem end 3 as shown in FIG. To fix the retainer 13,
The valve 1 which is constantly pulled in the closing direction by a valve spring 14 held by a locker arm 3, a rocker arm 11 having a metal adjusting bolt 9 for adjusting a valve clearance at a stem end 3, and a rotating cam. 10, the rotation of the cam 10
The rocker arm 11 slidably in contact with one end swings and moves the adjusting bolt 9 up and down, and the stem 2 abutting on the adjusting bolt 9 is pushed against the urging force of the valve spring 14 to open the valve 1. This opening and closing is performed continuously and at a high speed, and the valve operating mechanism is driven.

However, the top surface 4 of the valve 1 is shown in FIG.
As shown in FIG. 5, the adjusting bolt 9 is generally processed into a flat shape, and the adjusting bolt 9 in contact with the flat surface 15 moves up and down while moving on the flat surface 15 by the rotation of the cam 10. Due to the brittleness of ceramic valves, the impact load generated by the adjustment bolt and the bounce of the stem end coming and going when the internal combustion engine rotates at high speed causes chipping not only on the ceramic valve seat surface but also on the cotter. There is a problem that the ceramic valve is cut off from the groove 5 portion.

Therefore, the cotter groove of the ceramic valve is polished or the rotation of the cam is changed up and down via a direct-acting valve lifter so that the top surface of the valve lifter and the stem end are in point contact. (Japanese Patent Laid-Open No. 2-104907, Japanese Utility Model Application Laid-Open No. 2-12)
No. 2103).

[0009]

However, if the cotter grooves are polished to the degree of polishing, they cannot withstand the impact load due to bounce generated during high-speed rotation, and the ceramic valve is cut off from the cotter grooves of the stem.

In addition, simply applying the formation of the valve lifter so that the top surface of the stem end is in point contact with the ceramic valve that moves up and down by the rocking of the rocker arm by applying the rotation of the cam to the internal combustion engine is not sufficient. If the rotation speed is below the rotation speed at which bounce occurs, the ceramic valve will not be damaged and abnormal wear of the valve guide will not occur.However, if the characteristics of the ceramic valve are rotated at high speed, the impact load due to the bounce generated will not be enough. Unbearable,
Again, the problem of the ceramic valve being cut from the cotter groove of the stem could not be solved.

[0011]

[Purpose of the Invention] The present invention has been devised in view of the above-mentioned disadvantages. The purpose of the present invention is to ensure that even if bounce occurs due to high-speed rotation at a high temperature, the cotter groove is not cut off, and that durability and reliability are improved. An object of the present invention is to provide an excellent ceramic valve.

[0012]

According to the ceramic valve of the present invention, the shape of the top surface of the stem end which moves up and down when an adjustment bolt provided at one end of a rocker arm which swings by rotation of a cam comes into contact with the rocker arm is adjusted. A spherical shape having a radius of curvature r equal to or greater than a distance l from the center of the circular cotter groove provided on the outer periphery of the stem to the axis of the cotter groove.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a ceramic valve according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a fragmentary cutaway view showing the structure of the ceramic valve of the present invention.

In FIG. 1, reference numeral 1 denotes a distance 8 between the top surface 4 of the stem end 3 and the center 1 of the annular cotter groove 5 provided on the outer periphery of the stem 2 from the top surface 4 to a distance 1 indicated by 7 or more. Is a spherical ceramic valve having a radius of curvature r indicated by.

As shown in FIG. 2 in which the main part is enlarged, when a bounce is generated by high-speed rotation, the top surface 4 of the stem end 3 collides with the adjustment bolt 9, and the eccentric load F acts on the stem end 3. I will be.

However, the shape of the top surface 4 of the stem end 3 is changed to a spherical shape having a radius of curvature r which is equal to or greater than the distance 1 from the top surface 4 to the axial center 6 of the annular cotter groove 5 provided on the outer periphery of the stem 2. Therefore, the eccentric load F is a component force F
In FIG. 2, for example, in FIG. 2, a component force Fa acts on the cotter groove 5 on the A side below the axial center 6 of the cotter groove 5, and the tensile stress generated on the A side is reduced.

That is, when the radius of curvature r is smaller than the distance 1 indicated by 7 in the drawing, the component force Fa of the eccentric load F acts above the axial center 6 of the cotter groove 5, and a tensile stress acts on the B side. Then, the cotter groove 5 on the B side is broken.

In order to measure the stress generated in the cotter groove and the opening amount of the ceramic valve from the relationship between the radius of curvature r and the distance l, strain gauges are attached to both sides A and B of the cotter groove, and the ceramic valve is attached. A conductive material such as aluminum foil is attached to the bottom surface of the, and using the eddy current type non-contact displacement meter, the tensile and compressive stresses σ _A and σ _B on the A and B sides during bounce and opening of the valve The amount was measured.

FIG. 3 shows the results. As is clear from the figure, when r <l or when the conventional top surface is flat,
While the tensile and compressive stresses σ _A and σ _B are large, it can be seen that the present invention in which r ≧ 1 is extremely effective in preventing cutting from the cotter groove.

Further, based on the relationship between the radius of curvature r and the distance l, the same three types of ceramic valves were assembled in a four-cylinder cylinder head, and a motoring test was performed at a rotational speed at which bounce occurred. In the case of a ceramic valve having a flat surface, all of the ceramic valves break from the cotter groove in a maximum of 10 hours, and in the case of a ceramic valve of r <l, the same breaks in a maximum of 35 hours. None of the 1 ceramic valves failed in the 200 hour motoring test.

[0021]

As described above, in the ceramic valve of the present invention, the shape of the top surface of the stem end is determined by changing the shape of the radius of curvature of not less than 1 from the top surface to the axial center of the annular cotter groove provided on the outer periphery of the stem. Due to the spherical shape having r, even if bounce occurs due to high-speed rotation at a high temperature, a ceramic valve excellent in durability and reliability, which does not break from the cotter groove portion, can be provided.

[Brief description of the drawings]

FIG. 1 is a fragmentary cutaway view showing the structure of the ceramic valve of the present invention.

FIG. 2 is an enlarged view of a main part of the ceramic valve of the present invention.

FIG. 3 shows tensile and compressive stresses σ _A , σ on the A side and the B side during bounce in the ceramic valve of the present invention and the conventional example.
It is a recording diagram which measured _B and the opening amount of the valve.

FIG. 4 is a fragmentary sectional view for explaining a valve operating mechanism of an intake / exhaust valve for an internal combustion engine.

FIG. 5 is a partially cutaway view showing a main part of a conventional ceramic valve.

[Explanation of symbols]

 Reference Signs List 1 ceramic valve 2 stem 3 stem end 4 top surface 5 cotter groove 6 axis center 7 distance l 8 radius of curvature r 9 adjusting bolt 10 cam 11 rocker arm

Claims (1)

(57) [Scope of request for utility model registration] 1. A ceramic valve in which the rotation of a cam moves up and down by swinging of a rocker arm, the shape of a top surface of a stem end to which an adjustment bolt provided at one end of the rocker arm abuts is changed from the top surface to the outer periphery of the stem. A ceramic valve having a spherical shape having a radius of curvature r equal to or greater than a distance l from an axial center of an annular cotter groove provided.