JPH08270417A - Engine valve - Google Patents

Abstract

PURPOSE: To prevent the outer diameter part side of a valve face part from locally wearing by making a convex surface bulging toward a seat surface of a valve face part in a bevel part which will abut against the seat surface of a valve seat. CONSTITUTION: A face part 2 of an engine valve 1 is bulged toward a seat surface of a valve seat 4 to form an arcuate convex surface 9 with a large radius of curvature having the center on a line approximately disecting the width of the valve face part. Thus, when the valve face part is made of the convex surface 9, the central part of the convex surface 9 will contact with the seat surface 5 to prevent the outer diameter part side of the valve face part 2 from locally wearing even if a taper angle of the seat surface 5 of the valve seat 4 have some errors and the center axis of a valve guide and the valve seat 4 or the valve seat 4 and engine valve 1 is somewhat inclined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine valve having a modified valve face portion.

[0002]

2. Description of the Related Art As shown in FIG. 3, a valve face portion (02) of an umbrella portion in a conventional engine valve (01) is formed into a flat taper surface and is press-fitted into a cylinder head (03). By contacting the tapered seat surface (05) of (04), the airtightness of the cylinder is maintained.

[0003]

The above-mentioned conventional engine valve (01) includes the valve face portion (02) and the valve seat (04).
Since the sheet surface (05) of (1) contacts a wide surface, high airtightness can be obtained when the entire contact surface is in uniform contact.
However, if there is an error in the taper angle of the contact surfaces, or if the center axes of the valve guide (not shown) that guides the engine valve (01) and the valve seat (04) are tilted due to processing errors, etc. The contact surface may not come into contact with the surface, but may come into contact with the inner diameter or the outer shape portion side.

As shown in an enlarged view in FIG. 4, should the outer diameter side contact with the outer diameter side, the outer diameter side of the valve face portion (02) is intensively worn, as shown by the imaginary line in the figure. , The thickness of the umbrella part in that part becomes thin. In this case, due to stress concentration, a part of the umbrella part causes fatigue fracture and is damaged,
Airtightness is impaired, gas leaks occur, and durability and reliability are significantly reduced.

Further, in an engine valve in which a hard alloy such as stellite having wear resistance is plated on the valve face portion (02), normally, as shown in FIG.
In 2), after forming an annular groove (06) with an arcuate cross section,
Since the deposit (07) is applied, the deposit thickness of the outer diameter portion of the valve face portion (02) is thinner than that of the central portion.

Therefore, as described above, the valve face portion (0
2) and the taper angle of the seat surface (05) causes an uneven contact on the inner diameter or outer diameter side, and if the inner and outer diameter side is worn out intensively, The boundary layer (08) with the base material is easily exposed.

In this case, since the boundary layer (08) is an accelerated wear region having a low hardness, the progress of wear is rapid, which causes a loss of the umbrella portion and gas leakage.

The present invention has been made to solve the above-mentioned problems, and prevents the valve face portion from being worn out intensively on the outer diameter portion side, whereby the umbrella portion is damaged or gas leaks. The purpose is to provide a durable and reliable engine valve that does not generate

[0009]

According to the present invention, the above problems can be solved as follows. (1) The valve face portion of the umbrella portion that comes into contact with the seat surface of the valve seat has a convex curved surface that bulges toward the seat surface.

(2) In the above item (1), a hard alloy having wear resistance is plated on the valve face portion, and the surface thereof is a convex curved surface bulging toward the seat surface.

[0011]

[Function] Even if an error occurs in the taper angle of the seat surface of the valve seat or the central axis of the valve seat and the engine valve is slightly inclined, the central portion of the convex curved surface of the valve face portion comes into contact with the seat surface. Therefore, unlike the conventional case, the inner and outer diameter portions of the valve face portion are not abraded in a concentrated manner.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the same members as those of the above-described conventional example are denoted by the reference numerals excluding the leading "0", and the detailed description thereof will be omitted.

FIG. 1 shows a first embodiment of the present invention in which a valve face portion (2) of an engine valve (1) bulges toward a seat surface (5) of a valve seat (4). In addition, an arc-shaped convex curved surface having a relatively large radius of curvature (for example, a radius of about 20 to 50 mm) having a center on a line that bisects its width.
It is as (9). With such a large radius of curvature,
There is an advantage that the surface pressure of the contact portions is reduced and the wear of the mutual contact surfaces can be suppressed.

In this way, the valve face (2) is formed into a convex curved surface.
In case of (9), an error may occur in the taper angle of the seat surface (5) of the valve seat (4), or the valve guide and the valve seat.
(4) Or even if the central axes of the valve seat (4) and the engine valve (1) are slightly inclined, the substantially central portion of the convex curved surface (9) comes into contact with the seat surface (5).

Therefore, by operating the engine for a long time,
Even though the mutual contact surfaces may wear, the outer diameter side of the valve face (2) does not wear intensively as in the conventional case, but the outer diameter side wears intensively. In this case, it is possible to prevent the accidental loss of the umbrella portion and the occurrence of gas leakage.

Further, the processing accuracy of the valve guide (not shown) for guiding the engine valve and the valve seat (4) depends on the valve face portion (2) of the engine valve and the seat surface (4) of the valve seat (4). Since it greatly affects uneven wear of 5), gas leakage, etc., normally, the reaming of the valve guide and the seat surface (5) of the valve seat (4) are performed simultaneously by one machine, and Although the axes are matched, if the convex curved surface (9) as in the above embodiment is used,
Since such high processing accuracy is not required, the troublesome simultaneous processing can be omitted, and it is not necessary to install an expensive processing machine.

Further, when the valve face portion (2) is formed into the convex curved surface (9), the corner portion unlike the conventional tapered surface is not formed, so that the flow resistance of the mixed gas or the exhaust gas becomes small,
Intake and exhaust efficiency is improved.

FIG. 2 shows a second embodiment of the present invention. In the second embodiment, as in the conventional case, the annular groove (6) formed in the valve face portion (2) is plated with stellite (7) and the surface thereof is the same as in the first embodiment. Is a convex curved surface (9).

Also in the second embodiment, the same operational effects as those of the above-mentioned first embodiment can be obtained. Further, since the thickness of the metal deposit (7) at the center of the valve face portion (2) is sufficiently larger than that of the outer diameter portion, it reaches the boundary layer (8) which is the accelerated wear region. Then, it takes a considerable time to expose it, and the durability is greatly improved. Therefore, it is particularly effective as an engine valve for a diesel engine that is required to have a long life under severe operating conditions.

Further, since the surface of the heap metal (7) is the convex curved surface (9), there are the following processing merits. That is, normally, the heap metal (7) is bulged in a convex shape to be overlaid, and therefore the cutting allowance of the portion having high hardness is smaller than that in the case of the conventional tapered processing. Not only the time is shortened and productivity is increased, but also the life of cutting tools such as grinding wheels is greatly extended.

The present invention is not limited to the above embodiment, but the convex curved surface (9) may be an elliptic curved surface, for example.

[0022]

According to the present invention, the following effects can be obtained. (a) Since the outer diameter side of the valve face part is prevented from being worn intensively, there is no risk of the umbrella part being damaged or gas leaks occurring, and durability and reliability are improved. A high engine valve can be obtained.

(B) According to the second aspect, it takes a long time to reach the accelerated wear region, which is the boundary layer between the deposit and the base material, and the durability is greatly improved.

[Brief description of drawings]

FIG. 1 is an enlarged vertical sectional front view of a main part showing a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional front view of a main part of the second embodiment.

FIG. 3 is a vertical cross-sectional front view of essential parts showing a contact state between a conventional engine valve and a valve seat.

FIG. 4 is an enlarged explanatory view of a main portion showing a state in which the valve face portion is eccentrically contacted on the outer diameter portion side.

FIG. 5 is an explanatory diagram of a main part showing a state in which the heap portion is also unevenly contacted on the outer diameter side.

[Explanation of symbols]

 (1) Engine valve (2) Valve face part (4) Valve seat (5) Seat surface (6) Annular groove (7) Fill metal (8) Boundary layer (9) Convex curved surface

Claims (2)

[Claims] 1. An engine valve, wherein a valve face portion of an umbrella portion adapted to come into contact with a seat surface of a valve seat has a convex curved surface that bulges toward the seat surface. 2. The engine valve according to claim 1, wherein a hard alloy having wear resistance is plated on the valve face portion, and the surface thereof has a convex curved surface that bulges toward the seat surface.