JPH07119422A - Valve structure for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a valve structure capable of simultaneously attaining improvement in working responsiveness and reduction in flow resistance. CONSTITUTION:A suction valve 20 has a shaft part and a shade part 20b integrally formed on its lower end, and a valve guide 24 is fitted to the shaft part. The shade part 20b is formed of a combusting face 20c situated on a combusting chamber side; a neck part 20d provided on the back surface side; a shade part round face 20e; and a sitting face 20f continued to the shade part round face 20e. The whole body of the shade part 20b is thinly formed, and the shade part round face 20e is formed into a sharply curved face sharply contracted in diameter from the outer circumference to the neck part 20d side. A thin cap 38 is provided on the upper part side of the shade part round face 20e formed into the sharply curved face with a prescribed space part 36 to cover the whole circumference. The cap 38 is formed from, for example, an iron good heat conductive material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve structure for an internal combustion engine.

[0002]

2. Description of the Related Art As a valve structure for opening and closing a combustion chamber of an internal combustion engine, for example, a gasoline engine, a shaft portion slidably supported and an umbrella portion integrally formed on one end side of the shaft portion are provided. Known poppet valves. FIG. 3 shows a typical valve structure of this type which has been conventionally used. The valve structure shown in FIG. 1A has a shaft portion 1 and an umbrella portion 2 provided on one end side of the shaft portion 1, and a neck portion 3 and an umbrella portion R are provided on the back side of the umbrella portion 2. The surface 4 is formed.

The umbrella portion 2 is formed in a thin shape, and the umbrella portion rounded surface 4 has a sharp curved surface whose diameter is sharply reduced from the outer circumference toward the neck portion 3 side. The member indicated by reference numeral 5 in FIG.
The valve guide is slidably fitted to the shaft portion 1. Further, the valve structure shown in FIG. 1B has a shaft portion 1 and an umbrella portion 2 provided on one end side of the shaft portion 1, and a neck portion 3 and an umbrella portion are provided on the back side of the umbrella portion 2. The rounded surface 4 is formed, and the umbrella portion 2 is formed.
Is formed in a thick shape, and the rounded surface 4 of the umbrella portion is a gentle curved surface whose diameter is gradually reduced from the outer circumference to the neck portion 3 side.

However, the technical problems described below have been pointed out in all of the conventional valve structures.

[0005]

That is, FIG. 3 (A)
In the valve structure shown in (1), since the umbrella portion 2 is formed in a thin shape, the inertial weight of the entire valve is small and the operation response is excellent, but the umbrella portion rounded surface 4 extends from the outer circumference to the neck portion 3 side. Since it has a sharp curved surface that sharply reduces its diameter, especially when this structure is adopted for an intake valve of an internal combustion engine, the shaft portion 1 side to the umbrella portion 2
There was a problem that the flow resistance of the air-fuel mixture flowing to the side increased.

On the other hand, in the valve structure shown in FIG. 3 (B), since the rounded surface 4 of the umbrella portion is a gentle curved surface whose diameter is gradually reduced from the outer circumference to the neck 3 side, this is adopted for the intake valve. However, since the flow resistance of the air-fuel mixture is small, the air-fuel mixture can be smoothly supplied to the combustion chamber, but the umbrella portion 2 is formed in a thick wall shape, and the umbrella portion rounded surface 4 becomes a gentle curved surface. Because
There is a problem that the inertial weight of the entire valve is large and the operation response is poor.

That is, in the conventional valve structure, the improvement of the operation response and the problem of the flow resistance are contradictory to each other, and a valve structure satisfying both of them cannot be obtained at the same time. The present invention has been made in view of the above conventional problems, and an object of the present invention is to improve the operation responsiveness and at the same time solve the problem of flow resistance. It is to provide a valve structure.

[0008]

To achieve the above object, the present invention comprises a shaft portion slidably supported and an umbrella portion integrally formed at one end side of the shaft portion. A valve structure for opening and closing the combustion chamber, which is provided between the intake and exhaust passages of the internal combustion engine and the combustion chamber, has a neck portion and a umbrella portion rounded surface on the back side of the umbrella portion, and makes the umbrella portion thin. In addition to forming, the umbrella portion rounded surface is formed into a sharp curved surface that sharply reduces in diameter from the outer periphery to the neck side, and a thin-walled cap having a gentle curved surface is provided on this umbrella portion rounded surface with a space. Is characterized by.

The cap may be composed of a small-diameter portion fixed to the neck portion and a large-diameter portion that abuts on the rounded surface of the umbrella portion. Further, the cap can be made of a metal material having good thermal conductivity such as iron or amiminium.

[0010]

According to the valve structure having the above structure, the umbrella portion is formed in a thin shape, and the curved surface of the curved portion of the umbrella portion is formed into a sharp curved surface that is sharply reduced in diameter from the outer periphery to the neck side. Since the thin-walled cap is provided, the inertial weight of the entire valve can be reduced. Further, since a thin-walled cap having a gentle curved surface is provided on the curved surface of the umbrella portion with a space therebetween, the flow resistance of the air-fuel mixture or exhaust gas flowing between the intake and exhaust passages and the combustion chamber does not increase. .

Further, according to the second aspect of the invention, there is a small diameter portion fixed to the neck portion and a large diameter portion abutting on the rounded surface of the umbrella portion, and only the small diameter portion is fixed. It is possible to prevent the cap from being detached when thermal stress is generated due to a difference in thermal expansion coefficient between the cap portion and the cap, or when a tensile force is applied by the operation of the intake valve. Further, according to the configuration of claim 3, when the cap is made of a metal material having good thermal conductivity such as iron or aluminum, when the fuel is injected by the fuel injection valve in the fuel injection type internal combustion engine,
When the injected fuel adheres to the cap and the fuel adhering to the cap vaporizes, heat is taken from the cap with good thermal conductivity, and because the cap is thin, its heat capacity is also small. It is expected that the temperature is lowered to prevent fuel residue and sludge formation on the rounded surface of the umbrella portion due to the flow down of the lubricating oil supplied to the sliding portion of the shaft portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 show an embodiment of a valve structure for an internal combustion engine according to the present invention. The valve structure shown in the same figure is one in which the present invention is applied to a fuel injection type gasoline engine, and in the figure, 10 is a cylinder head of the engine.
A cylinder block (not shown) is arranged below 0, and a combustion chamber 12 is formed between the cylinder block and the cylinder head 10.

The cylinder head 10 is divided into an intake passage 14 for supplying air-fuel mixture to the combustion chamber 12 and an exhaust passage 16 for discharging exhaust gas from the combustion chamber 12 to the outside.
One end of each of these passages 14 and 16 is connected to the combustion chamber 1 respectively.
It opens at the upper end of 2. A ring-shaped valve seat 18 is fixedly provided on the cylinder head 10 side at the opening where the passages 14 and 16 communicate with the combustion chamber 12.

Further, the intake passage 14 and the combustion chamber 1 are provided at the opening where these passages 14 and 16 communicate with the combustion chamber 12.
An intake valve 20 that opens and closes the exhaust passage 16 and the exhaust valve 22 that opens and closes the exhaust passage 16 and the combustion chamber 12 are arranged. The intake and exhaust valves 20 and 22 include the shaft portion 20.
a, 22a and umbrella portions 20b, 22b integrally formed at the lower ends of the shaft portions 20a, 22a.
The valve guides 24 are fitted to the a and 22a, respectively, and the stem seal 2 is attached to the upper end of each valve guide 24.
5 is fitted.

Each of the valve guides 24 is a cylinder head 1.
0 is fixed to each shaft portion 20a, 22a by this configuration.
Are respectively supported by the thin head 10 so as to be slidably movable along the longitudinal axis direction, and a small amount of lubrication is applied from the upper side to the portions where the shaft portions 20a, 22a and the inner peripheral surface of the valve guide 24 are in sliding contact. The oil is constantly supplied, and the supplied lubricating oil flows down along the shaft portions 20a and 22a, travels along the back surface of the umbrella portion 20b and enters the combustion chamber 12, and the combustion chamber 12
Burns inside.

At the upper ends of the shaft portions 20a and 22a of the intake and exhaust valves 20 and 22, return springs 26 for biasing the valves 20 and 22 in the valve closing direction and a lash adjuster 28 are provided.
And the lash adjuster 28, the camshaft 3
The cam 32 provided at 0 contacts the intake and exhaust valves 20 and 22 at a predetermined timing. Further, a fuel injection nozzle 34 for injecting fuel in a mist state is arranged in the intake passage 14. The fuel injection nozzle 34 is configured such that the direction of fuel injection is such that the umbrella portion 20 of the intake valve 20.
The cylinder head 1 is oriented so that it faces the rear direction of b.
It is fixed at 0.

The basic construction of such a gasoline engine is the same as the conventional construction of this kind, but in the case of the present embodiment, the construction of the intake valve 20 is remarkable, as will be described below. There are various characteristics. That is, the intake valve 20 of the present embodiment
As shown in detail in FIG. 2, the umbrella portion 20b includes a combustion surface 20c located on the combustion chamber 12 side, a neck portion 20d provided on the back side thereof, an umbrella portion rounded surface 20e, and this umbrella portion rounded. The seating surface 20f is continuous with the surface 20e.

Further, in this embodiment, the entire umbrella portion 20b is formed in a thin shape and the umbrella portion rounded surface 20e is formed into a sharp curved surface which is sharply reduced in diameter from the outer circumference toward the neck portion 20d. . A thin-walled cap 38 is provided on the upper side of the umbrella portion rounded surface 20e formed in such a sharp curved surface so as to cover the entire circumference thereof with a predetermined space 36 therebetween.

The cap 38 is composed of a small diameter portion 38a, a large diameter portion 38b, and a curved surface portion 38c. For example, a heat resistant plastic material or the like can be adopted, but it is economical and easy to process. Considering this, an iron-based material having good heat conductivity is desirable, and its wall thickness is 0.
5 mm or less is more desirable. The cap 38 has a length from the upper end of the neck portion 20d to the lower end of the umbrella portion rounded surface 20e and does not reach the seating surface 20f, and the curved surface portion 38c on the outer periphery of the cap 38 has the umbrella portion rounded surface 20e. It is a gentle curved surface that is gentler than the sharp curved surface.

Further, in the cap 38, only the small diameter portion 38b is fixed to the umbrella portion 20b, and the large diameter portion 38b is in contact with the umbrella portion rounded surface 20e. That is, FIG. 2 (A) shows an example in which only the small diameter portion 38a is caulked and fixed to the neck portion 20d.
Further, FIG. 2B shows an example in which only the small diameter portion 38a is brazed and fixed to the neck portion 20d. When such a mounting structure of the cap 38 is adopted, the cap 38 is used when thermal stress is generated due to a difference in thermal expansion coefficient between the cap portion 20b and the cap 38, or when a tensile force is applied by the operation of the intake valve 20. Can be effectively prevented.

Now, the intake valve 20 constructed as described above.
Then, while forming the entire umbrella portion 20b into a thin shape,
Since the umbrella portion rounded surface 20e is formed into a sharp curved surface that sharply reduces in diameter from the outer periphery to the neck portion 20d side, and the thin cap 38 is provided on the umbrella portion rounded surface 20e, the inertial weight of the entire valve is reduced. Therefore, the operation response of the intake valve 20 can be greatly improved.

Further, since the thin cap 38 having a gentle curved surface is provided on the umbrella portion rounded surface 20e with a space therebetween, the flow resistance of the air-fuel mixture flowing between the intake passage 14 and the combustion chamber 12 is prevented. Can be reduced. Further, when the cap 38 is made of an iron-based material having good thermal conductivity, the following operational effects can be obtained. That is, in the engine shown in this embodiment, as described above, in order to ensure the smoothness of the sliding movement of the intake valve 20, the portions where the shaft portions 20a, 22a and the inner peripheral surface of the valve guide 24 are in sliding contact. A small amount of lubricating oil is constantly supplied to the combustion chamber 12 from the upper side thereof, and the supplied lubricating oil flows down along the shaft portions 20a and 22a and travels along the surface of the umbrella portion rounded surface 20e to the combustion chamber 12. Enter, combustion chamber 1
It is designed to burn within 2.

However, when such a lubricating oil is supplied, the temperature of the intake valve 20 also rises with the combustion of the engine, and the lubricating oil flowing along the umbrella rounded surface 20e of the valve 20 has a specific temperature. It is known that under the conditions, it becomes sludge to increase flow resistance or adversely affect engine performance. To cope with such a problem, in the valve structure of the present embodiment, when the cap 38 is made of a material having good thermal conductivity, when the fuel is injected by the fuel injection nozzle 34 valve, the injected fuel is the cap 38. When the fuel adhering to the surface and vaporizing to the cap 38 is vaporized, heat is taken from the cap 38 having good thermal conductivity, and the heat capacity is small because the cap 38 is thin. The temperature of the cap 38 lowers, the lubricating oil supplied to the sliding portion of the shaft portion 20a (between the shaft portion 20a and the valve guide 24) flows down, and the umbrella portion radius surface 20.
Sludge formation on e is prevented.

In addition, in such an operation effect, since the space portion 36 is formed between the cap 38 and the umbrella portion rounded surface 20e, the heat insulation effect of the space portion 36 causes
Heat is also prevented from being transferred from the umbrella rounded surface 20e to the cap 38. Further, in the above embodiment, the case where the present invention is adopted as the intake valve of the fuel injection type gasoline engine is illustrated, but the implementation of the present invention is not limited to this, and for example, the intake air of another type of engine It can also be used as a valve or as an exhaust valve of an engine of the same type or another type.

[0025]

As described above in detail in the embodiments,
According to the valve structure for an internal combustion engine of the present invention, improvement in actuation response and reduction in flow resistance can be achieved at the same time.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an example of an internal combustion engine to which a valve structure of the present invention is applied.

FIG. 2 is a half sectional view showing an embodiment of the valve structure of the present invention.

FIG. 3 is a front view showing two examples of a conventional valve structure.

[Explanation of symbols]

 10 Cylinder Head 12 Combustion Chamber 14 Intake Passage 16 Exhaust Passage 20 Intake Valve 20a Shaft 20b Umbrella 20c Combustion Surface 20d Neck 20e Umbrella Rough Surface 20f Seating Surface 24 Valve Guide 36 Space 38

Claims (3)

[Claims] 1. A shaft portion slidably supported and an umbrella portion integrally formed at one end side of the shaft portion, wherein a neck portion and a rounded surface of the umbrella portion are provided on the back side of the umbrella portion. Then, in the valve structure which is installed between the intake and exhaust passages of the internal combustion engine and the combustion chamber and opens and closes the combustion chamber, the umbrella portion is formed in a thin shape, and the umbrella portion rounded surface is sharply cut from the outer periphery. A valve structure for an internal combustion engine, characterized in that a thin-walled cap having a gentle curved surface is formed on the rounded surface of the umbrella portion, which is formed into a sharp curved surface having a reduced diameter on the neck side. 2. The valve structure for an internal combustion engine according to claim 1, wherein the cap has a small-diameter portion fixed to the neck portion and a large-diameter portion that abuts the rounded surface of the umbrella portion. 3. The valve structure for an internal combustion engine according to claim 1, wherein the cap is made of a metal material having good heat conductivity such as iron or aluminum.