JPH0295707A - Intake/discharge valve for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent generation of fine cracks on a ceramic intake/discharge valve by keeping at least a part of a small diameter part, to which stress is concentrated by the engagement of cotters, unprocessed from the time of final sintering. CONSTITUTION:An intake/discharge valve formed of ceramic is composed of bevel part 2 and a shaft 3. The shaft 3 is formed of a sliding contact part 5 which slidingly contact with an inner face of a valve guide 4 and a small diameter part 6 provided continuously and co-axially to the tip of the part 5. A circular groove 8 which engages with a bead 7a formed on an inner faces of a pair of substantially semi-cylindrical cotters 7 is formed on the intermediate part of the small diameter part 6. Outer peripheral faces of the cotters 7 have tapered shape which widen in diameter upwardly, and engage with a taper hole 10 of spring bearing 9 which are widened in diameter upward. The outer circumferencial surface of the sliding contact part 5 of the shaft 3 is a polished surface, while all of the outer circumferencial surface of the small diameter part 6, including a surface 11 contact to a half-shaft hole part 7b except for the beads 7a of the cotters 7 and the circular groove 8, remains unprocessed from the time of final sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ceramic intake and exhaust valve for an internal combustion engine.

[Conventional technology]

The production of intake and exhaust valves for internal combustion engines from ceramic materials is already practiced.

[Problem to be solved by the invention]

Ceramic materials have excellent heat resistance and are lightweight.

Although it has advantages such as relatively high strength, it tends to cause minute cracks on the machined surface during machining such as grinding and polishing, and these cracks are the cause.

There is a problem that the strength of the product decreases.

In particular, in intake and exhaust valves for internal combustion engines, high stress is concentrated at the fitting part of the plug, so if there is a minute crack like the one mentioned above in this part, it is more likely to break than this part, and the strength will be lowered. This results in a lack of reliability.

Furthermore, the portion of the intake/exhaust valve shaft that makes sliding contact with the valve guide requires highly accurate machining in order to ensure correct movement of the shaft, that is, to minimize fitting tolerances with the valve guide.

The present invention solves various problems when manufacturing intake and exhaust valves for internal combustion engines using ceramic materials.
The aim is to enable the practical application of ceramic valves.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an intake and exhaust valve for an internal combustion engine, which is made of a ceramic material, and includes an annular groove in which a cotter for locking a spring receiver is fitted in a part of the shaft.
In an intake/exhaust valve for an internal combustion engine in which a shaft is slidably guided at a proper position by a valve guide, of the shaft:
A portion including the annular groove is a small diameter portion smaller in diameter than a sliding contact portion that makes sliding contact with the valve guide, and an outer circumferential surface of the sliding contact portion is a polished surface, and at least a portion of the outer circumferential surface of the small diameter portion. It is characterized by having an unprocessed surface as it is after final sintering.

The portion of the small diameter portion of the shaft that remains unprocessed after final sintering may be only the inner surface of the groove, only the outer circumferential surface of the small diameter portion other than the groove, or both, or a local portion such as only a part of the inner surface of the groove. etc.

[For production]

According to the present invention, by making at least a part of the small diameter part where stress is concentrated when the kotsuta is fitted into an unprocessed surface as it is after final sintering, the occurrence of minute cracks in that part is prevented. Ru.

Further, by using a polished surface for the sliding contact portion, which requires precision rather than strength, the precision of that portion is improved. In addition, by making the fitting tolerance with the valve guide small, the shaft is guided by the valve guide and accurately reciprocates along a desired trajectory.

〔Example〕

FIG. 1 shows a first embodiment of the invention.

Reference numeral (1) is an intake and exhaust valve (hereinafter referred to as valve) made of a ceramic material for internal combustion engines, and is composed of a head portion (2) and a shaft (3).

The shaft (3) has a sliding contact portion (5) that slidingly contacts the inner surface of the valve guide (4), and a small diameter portion (6) that is coaxially connected to the tip of the sliding contact portion (5).
).

An annular groove (8) into which bead portions (7a) provided on the inner surfaces of a pair of semi-cylindrical cotters (7) can fit is provided in the middle portion of the small diameter portion (6). There is.

The outer circumferential surface of the cotter (7) has a tapered shape whose diameter increases upward in FIG. By fitting together, the spring receiver (9) is prevented from being pulled out above the shaft (3).

In the first embodiment, the sliding contact portion (5) on the shaft (3)
The outer circumferential surface of the cotter (7) is the polished surface, and the entire outer circumferential surface of the small diameter portion (6), that is, the annular groove (8) and the semi-axial hole portion (7b) excluding the bead portion (7a) of the cotter (7). Contact surface (1
The entire outer peripheral surface of the small diameter portion (6), including 1), is an unprocessed surface as it is after final sintering.

With this configuration, no minute cracks will occur due to machining in the annular groove (8) and the contact surface (11), where stress is concentrated, and reliability in terms of strength can be increased. .

In addition, the precision of the outer circumferential surface of the sliding contact portion (5) for smooth sliding with the valve guide (4) has been increased, and the valve guide (4) has been improved in accuracy.
4), and the shaft (3) can be accurately guided and reciprocated.

Furthermore, since the sliding contact portion (5) is larger in diameter than the small diameter portion (6), it is convenient for polishing the sliding contact portion (5), and the shaft (3) is attached to the valve guide (4). Easy to insert.

In the first embodiment, the entire outer circumferential surface of the small diameter portion (6) is an unprocessed surface, but the unprocessed range may be, for example, only the circumferential surface of the annular groove (8) or only the contact surface (11). , ring groove (8)
and the contact surface (11) only, or the annular groove (8
) may be locally limited, such as only a part of the area.

In addition, as in the second embodiment shown in FIG.
) is fitted in its entirety into the annular groove (13), in the so-called internal type, only the circumferential surface of the annular groove (13), or only its upper and lower end surfaces (13a) (13b), Alternatively, only the intermediate groove bottom (13c) may be left unprocessed.

In FIG. 2, (14,) is a small diameter portion of the valve shaft, and (15) is a spring receiver, and these and other structures are the same as those of the first embodiment.

〔Effect of the invention〕

According to the present invention, since at least a part of the small diameter part where stress is concentrated is made into an unprocessed surface as it is after final sintering, the occurrence of minute cracks in that part can be prevented and the reliability of strength can be improved. can.

Furthermore, since the sliding contact portion, which requires precision rather than strength, is a polished surface, the precision of that portion is improved, and the shaft can reciprocate smoothly and accurately along the valve guide.

Furthermore, since the diameter of the m-contact part is smaller than that of the small-diameter part, it is convenient for polishing the sliding contact part and inserting the shaft into the valve guide.

[Brief explanation of drawings]

FIG. 1 is a front view of a first embodiment of the present invention. FIG. 2 is a front view of main parts of a second embodiment of the present invention. (12) Kotta (13a) (+3b) End face (14) Small diameter section (13) Ring groove (13c) Groove bottom (15) Spring receiver (1) Intake and exhaust valves for internal combustion engines (valves)

Claims (1)

[Claims] For internal combustion engines, it is made of ceramic material and has an annular groove on a part of the shaft for fitting a cotter for locking the spring receiver, and the shaft is slidably guided in the appropriate position by a valve guide. In the intake/exhaust valve, a portion of the shaft that includes the annular groove is a small diameter portion that is smaller in diameter than a sliding contact portion that slides in contact with the valve guide, and an outer peripheral surface of the sliding contact portion is a polished surface; An intake and exhaust valve for an internal combustion engine, characterized in that at least a part of the outer circumferential surface of the small diameter portion is an unprocessed surface that is left as it is after final sintering.