JP2003328711A - Valve system for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of large frictional resistance besides complicated structure caused by an oil seal provided between a valve guide and a poppet valve inserted through the valve guide, and the problem of being subject to thermal damage by heat in a combustion chamber in the case of forming the poppet valve as a hollow valve. <P>SOLUTION: In an engine wherein a stem of the poppet valve for opening/ closing a valve port leading to a combustion chamber is supported to a cylinder head by a valve guide, the valve guide is provided with a guide hole formed slightly larger in diameter than the stem, and peripheral grooves further larger in diameter than the guide hole are provided at both ends of the guide hole. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for driving an intake valve and an exhaust valve of an engine, and more particularly to improvement of a structure including a valve guide for slidably supporting them.

[0002]

2. Description of the Related Art Conventionally, in a high-speed four-stroke engine used for automobiles and motorcycles, as is well known, an intake air opening and closing a combustion chamber provided in a cylinder head and an intake passage and an exhaust passage leading to the combustion chamber. Two sets of poppet valves, a valve and an exhaust valve, are slidably supported by a valve guide. An oil seal is provided between the intake valve and the exhaust valve and the valve guide to prevent the lubricating oil in the cam chamber from leaking into the intake passage or the exhaust passage through the gap between them, so-called oil drop.

[0003]

However, the conventional seal structure causes a large frictional resistance between the oil seal and the intake valve or the exhaust valve, which lowers the efficiency of the engine and complicates the assembly process. It was degrading engine productivity. If the valve body and the stem are made hollow to reduce weight, the hot burned gas in the combustion chamber may flow into the stem and become even hotter. There was something to do. According to the present invention, an annular groove is provided in the gap between the intake valve or the exhaust valve and the valve guide, and a so-called labyrinth seal is provided, so that a conventional oil seal is omitted, and oil falling is effectively prevented without giving frictional resistance. This is the purpose.

[0004]

In the engine of the type in which the stem of the poppet valve that opens and closes the valve opening leading to the combustion chamber is supported on the cylinder head by the valve guide, the valve guide is slightly larger than the stem. The problem is solved by providing the guide hole formed in the diameter and providing the peripheral grooves located at both ends of the guide hole and having a diameter larger than that of the guide hole. There, two peripheral grooves are provided at the end facing the valve opening of the valve guide and one at the end facing the cam chamber, and there are comparisons between the peripheral grooves provided at both ends. It is preferable to form a circular guide surface that is long.

[0005]

[Operation] When the stem is inserted into the guide hole, the two ends of the valve guide communicate with each other through the gap between the guide hole and the stem.
Lubricating oil intervenes there, and the gap in which the lubricating oil intervenes expands in the circumferential groove portion. A large pressure difference generated between both ends of the valve guide due to opening and closing of the intake valve or the exhaust valve is mitigated by the labyrinth effect of the narrow space partially expanded by the circumferential groove.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. In FIG. 1, 10 is an overhead camshaft type cylinder head of a four-stroke engine embodying the present invention. The cylinder head 10 is made by casting aluminum,
A combustion chamber recess 11 is formed on the lower surface thereof. An intake port 12 and an exhaust port 13 are led out from the combustion chamber recess 11, and the other ends thereof are open to the side surface of the cylinder head 10. The cylinder head 10 rotatably supports a cam shaft 16 in a cam chamber 15 formed above a wall surface of the combustion chamber recess 11, and the cam shaft 16 is a rocker arm 1.
The intake valve 18 and the exhaust valve 19 are driven via 7. It should be noted that the above engine configuration is not much different from the conventionally known configuration.

The intake valve 18 and the exhaust valve 19 include a stem 21,
2 has a valve body 22, 22 at one end and a cotter groove 24 at the other end, which is not much different from the conventional one.
As is apparent from the above, the stem 2 is
The area between the first cotter groove 24 and the vicinity thereof is hollowed out for weight reduction. Due to this thinning, a high temperature burned gas generated in the combustion chamber is pushed into the stem 21 during the combustion stroke of the engine. Further, by allowing burnt gas to flow into the narrow holes provided in such a stem, it is possible to mitigate the instantaneous pressure increase due to detonation and suppress the occurrence of knocking.

A valve guide 25 is shrink-fitted to the cylinder head 10. The valve guide 25 is made of cast iron or a sintered alloy in a tubular shape, and its inner surface is smoothly finished to form a guide hole 25a. 25b is a guide hole 25
It is a circumferential groove provided near the end of a. In this embodiment, one circumferential groove 25b is provided at the end portion on the cam chamber 15 side, and two circumferential grooves 25b are provided close to the end portions on the ports 12 and 13 side where the pressure change is large. I am sure of.

Between the valve guide 25 and the stems 21 of the intake valve 18 and the exhaust valve 19 inserted through the valve guide 25, a stem 21 is provided.
Has a minimum clearance required for sliding, and the inside of the cam chamber 15 and the ports 12 and 13 are communicated with each other through this clearance, and lubrication is performed by the lubricating oil flowing from the cam chamber 15. Has been done.

Since the inner peripheral surface of the valve guide 25 is provided with the peripheral groove 25b, the peripheral groove 25b is provided in the area of the gap for communicating the inside of the cam chamber 15 with the ports 12 and 13. There is a so-called labyrinth effect, in which there is a large change between the part and the part that does not, and the pressure fluctuation between them is eliminated. Therefore, the inside of the cam chamber 15 and the port 12,
Even if there is a large pressure difference with 13, it is possible to prevent the lubricating oil from leaking out.

[0011]

According to the invention of claim 1, the oil seal conventionally provided between the cam chamber and the valve guide is omitted by the simple structure in which the circumferential groove is provided on the inner circumferential surface of the valve guide. As a result, the power loss of the engine can be reduced, the assembling work can be facilitated, and the durability can be improved. According to the second aspect of the present invention, the valve guide can be easily processed by providing the circumferential grooves on both ends of the valve guide. And so on.

[Brief description of drawings]

FIG. 1 is a sectional view of an engine showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a main part thereof taken out.

[Explanation of symbols]

10 ... Cylinder head 11 ... Combustion chamber recess 12 ... Intake port 13 ... Exhaust port 15 ... Cam room 16 ... Cam shaft 17 ... Rocker arm 18 ... Intake valve 19 ... Exhaust valve 21 ... Stem 22 ... Valve 24 ... Cotta groove 25 ... Valve guide 25a ... Guide hole 25b ... circumferential groove

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinji Noguchi             202, Higashiwaki, Nishiyuki-cho, Toyohashi-shi, Aichi Stock             Company Noguchi Factory (72) Inventor Isao Shirayanagi             3329 Kiga, Hosoe-cho, Inasa-gun, Shizuoka Prefecture

Claims (2)

[Claims] 1. An engine of a type in which a stem of a poppet valve for opening and closing a valve opening leading to a combustion chamber is supported on a cylinder head by a valve guide, and the valve guide is provided with a guide hole having a diameter slightly larger than that of the stem. At the same time, an engine valve operating device is provided at both ends of the guide hole, the peripheral groove having a diameter larger than that of the guide hole. 2. The peripheral groove according to claim 1, wherein two peripheral grooves are provided at an end portion facing the valve opening of the valve guide and one at the end portion facing the cam chamber. A valve train for an engine in which a relatively long circular guide surface is formed between the circumferential grooves.