JPH0561444B2 - - 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, a protrusion p (bead) having a semicircular cross section is formed on the inner circumferential surface of the cotter c, and the protrusion p is fitted into an annular groove g provided in 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, so the protrusion of the tip c, which has a narrow area, is particularly The portion p comes into intensive contact with the bottom surface of the groove g of the stem s. For this reason, the protruding portion g causes a concentrated load to be applied to the stem s, resulting in the inconvenience that the stem s may crack or be damaged.

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 has a ceramic valve for intake and exhaust air in an engine combustion chamber, and is provided with a retainer attached to a stem via a clasp to support the valve. An annular groove is formed in the stem of the valve, and a protrusion that fits into the groove is provided on the valve stem, and the contact length of the valve stem with respect to the valve stem is determined by the length of contact of the valve stem with the valve stem. It adopts a configuration characterized in that it is set within a range of 0.6 times or more and 1.1 times or more of the outer diameter dimension.

[Operations and Effects] According to the invention configured as described above, only the edge portion of the spigot does not come into intensive contact with the stem of the valve, and the inner circumferential surface of the spigot is substantially even with the outer circumferential surface of the stem. Since the valve comes into contact with the valve, load concentration is avoided, and cracks do not occur in the valve, contributing to a longer life.
Moreover, in order to realize this, the contact length of the valve stem with respect to the valve stem must be 0.6 of the outer diameter of the stem.
Since it is only necessary to set the value within the range of 1.1 times or more, a simple structure is required, and it is also advantageous in terms of cost.

[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, reference numeral 1 denotes an exhaust valve in the engine combustion chamber, 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, as can be seen in Fig. 2, has a two-part outer housing and is cylindrical overall. 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 upper and lower length L of the cotter 3 is the outer diameter d of the stem 1b.
It is set to be 1.4 times. At this time, the vertical length L of the cotter 3 is the stem 1b.
It is sufficient that the length of contact between the valve stem and the valve stem is substantially 0.6 times or more and 1.1 times or less of the outer diameter of the stem 1b. It is set to be within the range. The reason for setting such a dimensional relationship is that if the kotta is smaller than the lower limit of the above range, it will lose its own function, and if it exceeds the upper limit of the above range, it will not be easy to wear and the whole will become heavy. It's inconvenient.

As shown in FIG. 3, 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 cotter 3, which is an annular portion 4a.
and a collar portion 4b, and the inner peripheral surface of the annular portion 4a is tapered in a direction opposite to that of the cotter 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, and the valve body 1a, which is biased upward in the axial direction of the valve 1, moves through the exhaust passage 8 via the valve seat 7. It is closed airtight. 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 exhaust passage 8 is alternately opened and closed by repeatedly engaging and disengaging the exhaust passage 8. As the valve 1 is displaced in the vertical direction, the rod 3 firmly contacts the stem 1b due to the wedge effect with the retainer 4. In this embodiment, the vertical length L of the rod 3 is set to the stem 1b. Since the outer diameter is set to 1.4 times the outer diameter d, unlike the conventional technology in which the protruding ridges (beads) of the kobuta strongly bite locally into the grooves of the stem, the inner circumferential surface of the kobuta 3 is aligned with the outer circumferential surface of the stem 1b. The contact is made evenly throughout, and the contact force against the stem 1b is dispersed without being locally concentrated. As a result, the protruding ridges of the kotta prevent the load from being concentrated on the valve stem, preventing the stem 1b from cracking or breaking, which extends the usable period and contributes to a longer service life. It is something.

In order to prevent cracks in the stem 1b while producing such valuable effects, the vertical length L of the cotter 3 can be adjusted as in the above embodiment.
Since it is only necessary to set the outer diameter dimension d to 1.4 times, a slight change is required and the overall structure does not become larger in any way, and the structure remains simple, while at the same time reducing cost. In addition to being inexpensive, it is also advantageous from an industrial standpoint.

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, and 24 is a piston for moving up and down within the cylinder block 23.

By the way, the outer diameter d of the stem 1b is 5.5 mm, the length L of the stopper 3 is 7.8 mm, and the contact length between the stem 1b and the stopper 3 is 6 mm, and the valve is made of ceramic, for example, Si ₃ N ₄ and has a protrusion. When the strip 3a is provided at the upper end of the cotter 3, it is possible to
As a result of experiments under the conditions of idling at 10,000 rpm and from idling to 12,000 rpm, it was found that no cracks were found in valve 1 and there was no problem.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6.

In the first embodiment described above, the taper of the retainer 3 and the taper of the retainer 4 were set to be at the same angle, but in the second embodiment of the present invention, the taper y of the retainer 3 is set to be the same as the taper x of the retainer 4. It is set to be smaller by, for example, 0.5 degrees.

With this configuration, as shown in FIG. 6, the lower end of the retainer 4 comes into strong contact with the lower end of the cotter 3, thereby avoiding load concentration on the groove of the stem due to the protruding ridges, and the lower end of the cotter 3. The entire inner circumferential surface comes into contact with the outer circumferential surface of the stem 1b approximately evenly. 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.

In the case of this second embodiment, the taper y of the cutter 3 is
When the maximum angle is greater than the taper x of the retainer 4, it can be set to be smaller with an angular difference of 0.7 degrees. The reason for setting such an angle is that if the above-mentioned angular difference exceeds 0.7, there is a risk that the wedge effect inherent between the cotter and the retainer will be lost.

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.

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

[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 are an exploded cross-sectional view and a cross-sectional view of essential parts showing second and third embodiments of the present invention, respectively, and FIG. 7 is a view showing a conventional cotter. In the figure, 1...Ceramic valve, 1b...Stem, 1a...Valve body, 2...Groove, 3...Kotta, 3
a... Protrusion portion, 4... Retainer, 8... Exhaust path,
15...Intake path.

Claims (1)

[Scope of Claims] 1. An engine having a ceramic valve for inhaling or exhausting air into an engine combustion chamber, and provided with a retainer attached to the stem via a clasp to support the valve, the stem of the valve having: is formed with an annular groove, and the tip is provided with a protrusion that fits into the groove, and the contact length of the tip with the valve stem is at least 0.6 times the outer diameter of the stem. A ceramic valve holding structure characterized by being set within a range of 1.1 times or less. 2. The ceramic valve according to claim 1, wherein the vertical length of the shank is set within a range of 1.1 times or more and 1.5 times or less of the outer diameter of the valve stem. holding structure. 3. The ceramic valve holding structure according to claim 1, wherein the protrusion of the cotter is formed at the upper end of the cotter. 4. Claim 1, wherein the taper of the retainer and the taper of the retainer are set to have an angular difference such that the taper angle of the retainer is equal to or at most 0.7 degrees larger.
Ceramic valve holding structure as described in section.