JPH0561443B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a structure that supports an intake and exhaust valve formed of ceramic through a holder.
In particular, the present invention relates to a valve holding structure that is an improved version of this structure.

[Prior Art] In recent years, intake and exhaust valves for the combustion chamber of an engine have been proposed to be made of heat-resistant ceramic. In this case, valve b
As shown in FIG. 7, the stem s is supported by a retainer r via an externally-containing clasp c. At this time, the inner diameter of the retainer r is made to match the outer diameter of the stem s so that the retainer r is in close contact with the stem s.

[Problems to be Solved by the Invention] However, as the valve b operates, the tip c is more firmly wedged into the stem s due to its own wedge effect. comes into strong contact with the stem s. For this reason, the edge portion e causes a concentrated load on the stem s, causing the stem s to crack x or break.

This invention was made to solve these problems, and even though the valve is made of ceramic and is supported by a member such as a clasp, concentrated loads can be avoided and the life of the valve can be extended. The purpose of the present invention is to provide an excellent ceramic valve holding structure that can contribute to the manufacturing process and has such valuable effects while having an extremely simple structure without complicating the structure and being advantageous in terms of cost. .

[Means for Solving the Problems] The present invention provides a ceramic valve for intake or exhaust air in an engine combustion chamber, which is provided with a retainer attached to a stem via a retainer to support the valve, and a retainer attached to the stem via a retainer. A configuration is adopted in which the diameter is set to be relatively larger than the diameter of the stem with a slight difference.

[Function] According to the present invention configured as described above, only the edge portion of the plug is prevented from intensively contacting the stem of the valve, and the inner circumferential surface of the plug is substantially evenly contacted with the outer peripheral surface of the stem. Since they are in contact with each other, the occurrence of weight concentration is avoided. In addition, to realize this, it is only necessary to set the diameter of the stem so that it is relatively larger than the diameter of the stem by a slight difference, resulting in a simple structure.

[Embodiments] Each embodiment of the present invention will be described below with reference to the drawings.

First, in the first embodiment shown in FIG. 1, 1 is a valve for exhausting the combustion chamber of the engine, which will be described later, and this valve 1 is made of ceramic.
It consists of a valve body 1a and a cylindrical stem 1b. A stem 1b of this valve 1 is formed with an annular groove 2 located at its upper end. 3 is a metal kotsuta, which is divided into two halves and has a cylindrical shape as a whole, as seen in Fig. 2. Such a tipper 3 is attached to the stem 1b of the valve 1, and a protrusion 3a having a semicircular cross section and located within the groove 2 is integrally formed on the inner peripheral surface along the circumferential direction. In this case, the diameter of the inner circumferential surface of the cotter 3 is set to be slightly larger than the outer diameter of the stem 1b, for example, by about 0.08 mm. As shown in FIG. 2, the outer circumferential surface of the cotter 3 is tapered so that the diameter gradually decreases from the top to the bottom. Reference numeral 4 denotes a retainer fitted to the outer circumferential surface of the kettle 3, which is composed of an annular portion 4a and a flange portion 4b, and the inner circumferential surface of the annular portion 4a is tapered in a direction opposite to that of the kettle 3. Such a valve 1 is attached to a cylinder head 5 of an engine as shown in FIG. A valve spring 6 is provided between the valve 1 and the cylinder head 5. The spring 6 urges the valve 1 upward in the axial direction, and the valve element 1a seals the exhaust passage 8 through the valve seat 7. It is closed to. At this time, depending on the state of the biasing state of the valve spring 6 in the above-mentioned direction, the taper of the retainer 4 causes the stopper 3 to firmly abut against the outer circumferential surface of the stem 1b with a so-called wedge effect.

Therefore, when the engine is operating, the valve 1 is displaced vertically in the axial direction, and the valve seat 7 of the valve body 1a is
The intake passage 8 is alternately opened and closed by repeatedly engaging and disengaging the intake passage. As the valve 1 is displaced in the vertical direction, the rod 3 comes into firm contact with the stem 1b due to the wedge effect with the retainer 4. In this embodiment, the diameter of the inner circumferential surface of the rod 3 is set to the stem 1b. The diameter is set to be slightly larger, for example, by 0.08 mm, than the outer diameter of the stem 1b, unlike the conventional case in which only the edge portion of the kotsuta 3 is locally firmly wedged into the stem 1b, and the inner circumferential surface of the kotsuta 3 is It comes into contact with the outer peripheral surface of the stem 1b evenly as a whole, so that the contact force against the stem 1b is not concentrated locally but is dispersed. As a result, concentrated loads are not applied to the valve stem due to the edge of the kotta, and the stem 1b is prevented from cracking or being damaged, which extends the usable period and contributes to a longer service life. It is what it is.

In order to prevent cracks in the stem 1b while producing such valuable effects, the diameter of the inner circumferential surface of the rod 3 is set to be slightly larger than the outer diameter of the stem 1b. Since only one piece is required, the overall structure does not need to be enlarged and the structure remains simple, and the cost is also low, which is advantageous from an industrial point of view. .

Here, a supplementary explanation will be given schematically regarding the structure of an engine to which the ceramic valve 1 is applied.

9 is a tubular valve guide inserted through the stem 1b of the valve 1; 10 is a cam connected to the shaft 11; 12 is a swing arm to which the cam 10 abuts from above; one end of this swing arm abuts the upper end of the stem 1b; The end is supported by a spherical fulcrum 13. 14
1 is an intake valve, which has a function of opening and closing the intake passage 15 via a valve seat 16, and is configured similarly to the exhaust valve 1. 17 is a valve guide, 18 is a valve spring, and 19 is a swing arm, one end of which abuts the upper end of the valve 14 and the other end supported by a spherical fulcrum 20. A cam 21 is connected to the shaft 22 and is in contact with the swing arm 19. 23 is a cylinder block, 24 is a cylinder block 23
It is a piston that moves up and down inside.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment of the present invention, the diameter of the valve 3 is set to be larger than that of the stem 1b in the first embodiment.
The stem 31 of is slimmed in the radial direction to 0.01 to 0.08 mm.
The diameter is set to be smaller than that of the cotter 32 by a certain extent.
With this configuration, the diameter of the stem 32 of the valve 30 is relatively larger than that of the stem 31 of the valve 30. Even with this configuration, the same effects as in the first embodiment can be obtained. In the second embodiment, the same parts as in the first embodiment are given the same reference numerals, and only the different parts will be explained.

Next, a third embodiment of the present invention will be described with reference to FIG.

Whereas in the first embodiment, the protrusion 3a of the retainer 4 is formed at the uppermost end, in the third embodiment of the present invention, the protrusion 33a of the retainer 33 is formed from the upper end of the retainer 33 toward the center. It is positioned in a position where it descends.

In each of the embodiments described above, the protruding portion of the retainer is formed to have a semicircular cross section, but it is not limited to this shape and may be formed, for example, in a rectangular shape. In this case, it goes without saying that the cross-sectional shape of the groove in the valve stem also corresponds to the protrusion.

Also, the dimensional difference between the kotsuta and the stem should be in the range of 0.01 and 0.08 mm, not just 0.08 mm.

In addition, various changes may be made without departing from the gist of the present invention in concrete and practical implementation.

[Effects of the Invention] As described above, according to the present invention, the main feature is that the diameter of the valve stem is set to be relatively larger than the diameter of the valve stem with a slight difference. This feature makes it possible to avoid applying a concentrated load to the ceramic valve due to the edge of the cotter, effectively suppressing the occurrence of cracks in the valve, contributing to a long and durable life. At the same time, it is possible to provide a ceramic valve holding structure which has excellent effects such as a simple structure without complicating the overall structure and being advantageous in terms of cost.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention, FIG. 1 is a front view of the whole body, FIG. Longitudinal cross-sectional views applied to Figures 5 and 6
The figures show second and third embodiments of the present invention and show cross-sectional views of essential parts, and FIG. 7 is a diagram showing a conventional cotter. In the figure, 1...ceramic valve, 3...knotter, 4...retainer, 8...exhaust path, 15...intake path.

Claims (1)

[Scope of Claims] 1. A device having a ceramic valve for intake or exhaust air in an engine combustion chamber, and provided with a retainer attached to a stem via a cotter to support the valve, the diameter dimension of the cotter. A valve holding structure made of ceramic, characterized in that the diameter is set to be relatively larger than the diameter of the stem with a slight difference. 2 The difference in diameter between the stem and the stub is 0.01.
The ceramic valve holding structure according to claim 1, characterized in that the diameter is within the range of 0.08 mm.