JP2003065013A - Hollow stem valve for fourcycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow stem valve, capable of maintaining high strength even at a high temperature, in the poppet valve of which stem is hollowed. SOLUTION: The valve is made in such a way that a parent material with a comparatively thick wall is elongated and squeezed by pressing and deep- drawing to form the long and slender stem, an umbrella shaped part having a sudden change in its diameter is formed at the open end by plastic working, and the boundary part between the parent material and the umbrella shaped part is conically machined to form the valve disc part after the larger diameter end of the umbrella shape part is cut off with some length of the parent material being left.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake / exhaust valve suitable for a high-performance four-stroke engine for vehicles such as motorcycles and passenger cars, and more particularly to a hollow valve whose inner surface is hollow from the stem portion to the valve portion. It concerns poppet valves.

[0002]

2. Description of the Related Art Generally, it is known that reducing the weight of a poppet valve used as an intake / exhaust valve greatly contributes to improvement of output and efficiency of a four-stroke engine. Therefore, conventionally, as shown in FIG. 5 (a), the stem 91 of the poppet valve 90, which is an intake / exhaust valve, is made hollow and sodium 9
2 which is filled with 2 and closed by a plug 93 (for example, Japanese Patent Laid-Open No. 6-10628), or as shown in FIG. 6B, the stem 91 and the umbrella portion 94 are drawn using a thin plate material as a material, Alternatively, it is known that the stem cap 95 is welded to the open end of the stem 91 (for example, JP-A-8-210112).

On the other hand, for the purpose of reducing the weight of the poppet valve, the inventor first proposed a poppet valve (Japanese Unexamined Patent Publication No. 2000-45730) in which a stem and an umbrella portion are integrally formed by plastically working a steel plate. Proposed. There, a steel plate, which is the raw material, is squeezed to make a cup-shaped semi-finished product, and the sides of this semi-finished product are handled little by little from the bottom to form a thin and thin stem, and a relatively thick umbrella and a valve that sits on the valve seat. is doing.

[0004]

Therefore, the wall thickness of the stem portion is reduced to reduce the wall thickness of the stem, and the rigidity of the conical portion forming the valve portion cannot be obtained. Further, in a product manufactured by processing such a plate material, there is a problem that the wall thickness becomes excessively thin when the valve portion is ground to remove the black skin and finish processing. Therefore, although stellite and other heat-resistant metals were built up in advance to make them thick and then polished, the manufacturing cost increased. Further, when the plate thickness of the material is made thick enough not to require the build-up step, the effect of reducing the weight is drastically reduced.

[0005]

[Means for Solving the Problems] The above problem is that an umbrella portion in which a relatively thick base material is pressed and deep-drawn to squeeze to form an elongated stem, and the diameter of which changes sharply at the open end by plastic working And the large-diameter end of the umbrella portion is cut away leaving a little end of the base material, and the boundary portion between the base material and the umbrella portion is removed in a conical shape to form the valve portion. . There, it is preferable to weld a lid member having a spherical surface with a small diameter to the inside of the umbrella portion as it bulges toward the opening end. Further, it is more preferable that the lid member is provided with a small-diameter vent hole that penetrates the front and back.

[0006]

[Function] In the hollow valve, the outer edge of the umbrella portion is formed by the cylindrical stem obtained by plastic working and the relatively thick base material, and at the same time, the inclined umbrella portion with gradually decreasing thickness is continuously formed. The thin stem is axially ironed from its inner end. Therefore, the thickness of the corner portion where the outer edge of the umbrella portion and the umbrella portion are continuous is increased, so that even if the outer surface of this connecting portion is removed in a conical shape, the thickness is sufficient to withstand use. Inside the umbrella portion, a cover material consisting of a small-diameter spherical surface is welded as it bulges toward the opening end, thereby forming a box-shaped vacant chamber inside the umbrella portion. Further, the lid member is provided with a small-diameter vent hole penetrating through the front and back surfaces to reduce the pressure difference between the inside and outside of the chamber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. In FIG. 1, 10 is a hollow valve according to the present invention, which is a poppet valve used in an engine or a compressor. The hollow valve 10 is slidably supported by a stem 11 by being fitted into a valve guide of an engine (not shown). The stem 11 is made of a thin-walled stainless steel tube, and has an umbrella portion 12 that expands in a conical shape is formed at one end, and an end member 14 having a cotter groove 13 is friction-welded and integrally attached to the other end. ing.

As shown in FIG. 2, the hollow valve 10 is formed by first pressing and drawing a stainless steel plate S as a base material shown in (a) to bulge the stem 11 shown in (b).
11a is a small diameter part formed at the end of the stem 11,
It is provided to attach the end member 14.

Further, leaving a small portion of the outer edge 16 of the umbrella portion, the umbrella edge 12 is cut by cutting in a direction perpendicular to the axis 17.
Is shaped and the boundary portion between the umbrella portion 12 and the outer edge 16 of the umbrella portion is removed in a conical shape to form the seating surface 18 of the hollow valve 10.

As shown in FIG. 3, a lid member 20 is welded to the back surface of the seating surface 18, that is, the inside of the umbrella portion 12, and the inner surface from the umbrella portion 12 to the stem 11 is closed. The lid member 20 is formed by pressing a stainless plate, and has a dish-like spherical surface that bulges outward toward the opening end. Then, the circular outer edge portion is metallurgically integrated with the back surface of the umbrella portion 12 by welding. Thus,
The inner surface from the stem 11 to the umbrella portion 12 is closed by the lid member 20, and the inner surface of the umbrella portion 12 is a convex lens box having high rigidity. Reference numeral 21 denotes a ventilation hole provided in the central portion of the lid member 20, and the space formed on the inner surface of the umbrella portion 12 is communicated with the outer surface by the ventilation hole 21.

As described above, the stem 11 and the end member 14 are connected by friction welding. As shown in FIG. 4, the end member 14 includes a round shaft portion 23 having the cotter groove 13 at one end and a taper shaft portion 24 formed at the other end. In order to reduce the weight, the shaft core has a lightening hole 14a.

The taper shaft portion 24 thus formed
Is friction welded to the small diameter portion 11a formed at the end of the stem 11. Friction welding starts when the small diameter end of the tapered shaft portion 24 is pushed into the straight tubular portion while the end member 14 is rotated at a high speed, and red heat is generated by frictional heat. The small-diameter portion 11a is expanded by the end member 14 and changes into a tapered tube along the taper shaft portion 24. The portion where the small diameter portion 11a and the end member 14 are rubbed is melted by frictional heat and is removed to the outside even if an oxide film and other impurities are present between them, so that the end member 14
When the rotation reaches the predetermined position, the rotation is stopped, and the contact surfaces of the two are tightly coupled.

Although the above-mentioned friction welding technique itself is a well-known technique, the end portion of the stem 11 is processed into a step with a small diameter in advance, and the end member 14 to be welded thereto has a tapered shaft. A relatively large friction surface is formed by providing the portion 24, and friction welding can be efficiently and reliably performed, and it is not yet known that the stem 11 and the end member 14 are reliably coupled. .

The poppet valve thus constructed has a hollow interior formed by a thin-walled pipe, and can be reduced to about half the weight of the conventional solid one. Further, although the hollow valve is made of a material having a relatively thin plate thickness, it is reinforced by the lid member 20, so that the umbrella portion 14 has high rigidity and receives a strong combustion pressure in the combustion chamber. The distortion does not impair the hermeticity.
Further, since the hollow on the inner surface of the umbrella portion is shallowed by the lid member 20, even if the intake / exhaust valve of the engine is replaced with a hollow valve, the space volume of the upper surface of the piston is not increased, so that the compression ratio of the engine can be kept high. it can.

It is preferable that the peripheral edge of the lid member 20 is welded to the inner surface of the umbrella portion 12 and to a position closer to the stem 11 than the valve portion 18, whereby the central portion of the lid member 20 projects toward the combustion chamber side. Despite the shape, the lid member 20 can be prevented from protruding from the umbrella portion 12 toward the combustion chamber and interfering with a piston (not shown).

Further, even though the inner surface of the lid member 20 is made hollow, the inside is communicated to the combustion chamber side by the vent hole 21, so that the hollow valve 10 is prevented from being deformed by the pressure difference between the inside and the outside. Can be prevented.

[0017]

According to the first aspect of the present invention, by increasing the wall thickness of the umbrella portion that receives the combustion pressure, the rigidity is high, and the strong strength is maintained even in a high temperature state. It is possible to obtain a hollow valve that is not lightweight. According to the second aspect of the present invention, the cap portion that receives a strong combustion pressure is reinforced by the lid member, so that the cap portion can retain high rigidity without increasing the wall thickness. According to the invention of claim 3, even if the rigidity of the umbrella portion is improved by providing the lid member, the pressure difference between the inside and outside of the lid member can be suppressed to a low level, so that the hollow valve is damaged by the action of the high temperature combustion gas. There is nothing to do. And so on.

[Brief description of drawings]

FIG. 1 is a half-sectional side view of a hollow valve showing an embodiment of the present invention.

FIG. 2 is a process drawing showing a manufacturing process of a hollow valve.

FIG. 3 is an enlarged cross-sectional view of a main part of FIG.

FIG. 4 is a partial cross-sectional view of the hollow valve showing deformation of the stem in the manufacturing process.

FIG. 5 is a sectional view showing a conventional poppet valve.

[Explanation of symbols]

10 ... Hollow valve 11 ... Stem 11a ... small diameter part 12 ... ・ Umbrella part 13 ... Cotta groove 14 ... End member 14a ... meat removal hole 16 ... Outer edge of umbrella section 17 ... ・ Axis 18 ... Seat surface 20 ... Lid 21 ... Vents 23 ... Round shaft 24 ... Taper shaft part

Claims (3)

[Claims] 1. A relatively thick base material is pressed and deep-drawn to form an elongated stem by squeezing, and an umbrella portion whose diameter changes abruptly by plastic working is formed at the open end. A hollow valve for a four-stroke engine in which a large-diameter end is cut off while leaving the end part of the base material slightly, and the boundary part between the base material and the umbrella part is deleted in a conical shape to form a valve part. 2. A hollow valve for a four-stroke engine according to claim 1, wherein a cover member formed of a spherical surface having a small diameter is welded to the inside of the umbrella portion and bulges toward the opening end. 3. A hollow valve for a four-stroke engine according to claim 2, wherein the lid member is provided with small-diameter vent holes penetrating through the front and back.