JPH055406A - Valve system of 4 stroke engine - Google Patents

Abstract

PURPOSE:To stabilize combustion in a low speed range when the bore diameter of a cylinder is large and intake valves on both sides are apt to separate from the intermediate intake valve. CONSTITUTION:Axis centers of intake valves 2 on both sides are deviated to the intermediate intake valve 2 side against axis centers of respective valve lifters 9L, 9R installed thereto by dimension (e). Intake valves 2 on both sides can be positioned towards the intermediate intake valves 2 without making neighboring valve lifters 9 approach each other beyond requirement. Mutual interference between adjacent valve lifters can be avoided, and it is possible to gather mixture around the ignition plug as making it possible to use valve lifters relatively large in diameters.

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 a four-stroke engine, and in particular, a plurality of intake valves closed by valve springs are provided in a combustion chamber and are constructed so as to be opened and closed by a common cam shaft. The present invention relates to a valve train.

[0002]

2. Description of the Related Art Conventionally, in engines of motorcycles and passenger cars, two or three intake valves are provided for each cylinder in order to obtain high performance, and they are directly opened and closed by a valve cam via a valve lifter. (For example, Japanese Patent Laid-Open No. Sho 5
7-176311).

[0003]

However, such a structure has a problem that the adjacent valve lifters interfere with each other and the design becomes difficult.

That is, if it is attempted to prevent the adjacent valve lifters from interfering with each other, the intake valve will be separated from the spark plug, and combustion will become unstable particularly in the low engine speed range.

[0005]

A valve train for a four-stroke engine according to the present invention is provided with an ignition plug at substantially the center of a combustion chamber.
Each cylinder is equipped with three intake valves and multiple exhaust valves, and these valves are distributed to one side and the other side of the center line that passes through the center of the combustion chamber and is parallel to the cam axis, and the intermediate intake valves are installed on both sides. The valve is located outside the spark plug and outside the cylinder with respect to the center line with respect to the valve, while the inclination of the intermediate intake valve with respect to the cylinder axis is smaller than that of the intake valves on both sides, and when viewed in the cam axis direction. The extension lines of the intermediate intake valve and the intake valves on both sides intersect above the combustion chamber, the upper end of each intake valve faces the bottom surface of the valve lifter, and the crown surfaces of these valve lifters contact the common intake cam shaft. In this four-stroke engine, the axial centers of the intake valves on both sides are deviated to the intermediate intake valve side with respect to the axial centers of the valve lifters attached to them.

[0006]

[Function] The intake valves on both sides are positioned closer to the intermediate intake valve without bringing the valve lifters closer to each other than necessary.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a sectional view showing a valve operating system for a four-stroke engine according to the present invention, FIG. 2 is a bottom view of a combustion chamber of a four-stroke engine equipped with the valve operating according to the present invention, and FIG.
4 is a plan view showing a valve train for a four-stroke engine according to the present invention, and FIG. 4 is a sectional view taken along line IV-IV in FIG.

In these drawings, reference numeral 1 denotes a four-stroke engine, which has three intake valves 2 for each cylinder and an intake passage 21 connected to the combustion chamber 3 via the intake valves 2. Reference numeral 4 denotes an exhaust valve provided for each cylinder, which opens and closes an exhaust passage 41 connected to the combustion chamber 3.

Reference numeral 5 denotes a cylinder head forming the combustion chamber 3,
Reference numeral 3a is an electrode of the spark plug, and the electrode 3a faces substantially the center of the combustion chamber 3.

As shown in FIG. 2, the intake valve 2 and the exhaust valve 4 are distributed to one side and the other side of a center line which passes through the center of the combustion chamber 3 and is parallel to a cam shaft described later. Each intake valve 2 is slidably fitted into the valve guide 6 and attached to the valve seat of the cylinder head 5 by the valve spring 7 and the retainer 8.

The intermediate intake valve 2 among the three intake valves 2 is disposed at a position outside the cylinder with respect to the center line with respect to the intake valves 2 on both sides (closer to the inner peripheral wall of the cylinder), and has a spark plug. Is set to a position on the outside (just beside the electrode 3a of the spark plug). Further, the intake valves 2 on both sides are located at positions on both sides of the spark plug electrode 3a in the axial direction of the cam shaft.

The intermediate intake valve 2 is mounted so as to be inclined such that the inclination angle with respect to the cylinder axis is smaller than that of the intake valves 2 on both sides, and the valve rod 2a of the intermediate intake valve 2 is extended. The line and the extension line of the valve rods 2a of the intake valves 2 on both sides intersect above the combustion chamber 3 when viewed in the cam axis direction.

Reference numeral 8a designates a split-type valve cotter. As is well known, the inner surface is engaged with an outer peripheral groove provided on the valve rod 2a, and the outer surface is retained in a conical hole of the retainer 8.
9 is a steel valve lifter formed in an inverted cup shape,
A cylindrical portion 9a slidably fitted to the guide surface 5a of the cylinder head 5, and a top portion 9b which forms a crown surface thereof and is interposed between the intake cam shaft 11 and the valve rod 2a of the intake valve 2. It consists of

Reference numeral 12 denotes a steel pad hardened by heat treatment, which is interposed between the back surface of the top portion 9b and the valve rod 2a and positioned by the outer surface of the top portion of the valve rod 2a. Adjust the size of the valve gap.

In the present invention, as shown in FIG. 4, the intermediate valve lifter 9 is arranged coaxially with the intermediate intake valve 2, and the two valve lifters 9L and 9R arranged outside thereof correspond to each other. The intake valve 2 is provided so as to be offset from the axis of the intake valve 2 by a dimension e.

In other words, the axial centers of the intake valves 2 on both sides are deviated toward the intermediate intake valve 2 side with respect to the axial centers of the respective valve lifters 9L and 9R. As a result, the valve lifters 9L, 9
Since the outer periphery of the valve spring 7 may come into contact with the inner surface of R, the valve rod 2a is extended from the engaging portion (the retainer 8 mounting portion) of the valve spring 7 to the top portion 9b side of the valve lifter 9. It faces the bottom of the lifter 9.

That is, only the portion of the valve rod 2a above the valve spring 7 is inserted into the inner surface hole of each valve lifter 9, and the valve spring 7 and the retainer 8 are prevented from entering, so that the valve spring 7 is closed.
It is possible to prevent contact with.

The cam body 11a of the intake camshaft 11 is
As shown in FIG. 4, the formation position is set so that the center of the cam surface in the width direction (center of the cam surface) is positioned on the axial center of the intake valve 2.

Therefore, according to the present invention, the valve lifter 9
Intake valves 2 on both sides without bringing them closer than necessary
Will be positioned closer to the intermediate intake valve 2.

Further, as shown in this embodiment, the intake valve 2
When the valve rod 2a of the valve spring 7 is extended from the engaging portion of the valve spring 7 toward the end side and faces the bottom of the valve lifter 9, the valve spring 7 is
Even if the valve lifter 9 is displaced with respect to the valve rod 2a without entering the inside of the back surface of the valve, the diameter of the valve spring 7 is not limited.

In this embodiment, only the valve lifter 9 is biased to one side, but the cam body of the intake cam shaft can also be biased as shown in FIG. FIG. 5 is a sectional view showing another embodiment in which the cam body of the intake cam shaft is also displaced. In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 5, the cam body 11 a of the cam shaft 11 has its cam surface centered on the axial center of the valve lifter 9. That is, the cam body 11a is also displaced by the dimension e with respect to the axis of the intake valve 2.

Further, in the present embodiment, an example in which an inverted cup type having a pad 12 interposed between the valve lifter 2a and the valve rod 2a is used as the valve lifter 9, but as shown in FIG. A lash adjuster type can also be used.

FIG. 6 is a sectional view showing a modification of the valve lifter.
In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are designated by the same reference numerals, and detailed description thereof will be omitted. A valve lifter 9 indicated by reference numeral 9 in FIG. 6 is of a lash adjuster type.

[0024]

As described above, the valve operating system for a four-stroke engine according to the present invention is provided with an ignition plug at approximately the center of the combustion chamber, and is provided with three intake valves and a plurality of exhaust valves per cylinder.
These valves are distributed to one side and the other side of the center line that passes through the center of the combustion chamber and is parallel to the camshaft, and the intermediate intake valves are ignited outside the cylinders with respect to the center lines rather than the intake valves on both sides. While being located outside the plug, the inclination of the intermediate intake valve with respect to the cylinder axis is smaller than that of the intake valves on both sides, and the extension lines of the intermediate intake valve and the intake valves on both sides when viewed in the cam axis direction are set to the combustion chamber. In the four stroke engine in which the upper end of each intake valve faces the bottom surface of the valve lifter and the crown surfaces of these valve lifters are brought into contact with a common intake cam shaft, Is displaced toward the intermediate intake valve side with respect to the axis of each valve lifter attached to them, so that the intake valves on both sides are positioned closer to the intermediate intake valve without bringing the valve lifters closer together than necessary. Be done.

Therefore, it is possible to prevent the adjacent valve lifters from interfering with each other, and it is possible to collect the air-fuel mixture around the spark plug while enabling the use of a valve lifter having a relatively large diameter.

Therefore, if the present invention is applied to an engine in which the bore diameter of the cylinder is large and the intake valves on both sides tend to be separated from the intermediate intake valve, combustion becomes stable even in the low speed range.

[Brief description of drawings]

FIG. 1 is a sectional view showing a valve train of a four-stroke engine according to the present invention.

FIG. 2 is a bottom view of a combustion chamber of a four-stroke engine equipped with the valve gear according to the present invention.

FIG. 3 is a plan view showing a valve train for a four-stroke engine according to the present invention.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a sectional view showing another embodiment in which the cam body of the intake camshaft is also displaced.

FIG. 6 is a cross-sectional view showing a modified example of the valve lifter.

[Explanation of symbols]

 2 intake valve 7 valve spring 8 retainer 8a valve cotter 9 valve lifter 9a cylinder part 9b top part 11 intake camshaft 11a cam body 12 pad

Claims (1)

Claim: What is claimed is: 1. A spark plug is provided substantially in the center of a combustion chamber, and three intake valves and a plurality of exhaust valves are provided for each cylinder, and these valves pass through the center of the combustion chamber and a camshaft. The center intake valve is divided into one side and the other side, and the intermediate intake valve is positioned outside the cylinder and outside the spark plug with respect to the intake valves on both sides, while the intermediate intake valve Of the intake valve is smaller than that of the intake valves on both sides, and the extension lines of the intermediate intake valve and the intake valves on both sides when viewed in the cam axis direction intersect above the combustion chamber, and the upper end of each intake valve is In a four-stroke engine in which the crown faces of the valve lifters are opposed to each other and the crown faces of these valve lifters are brought into contact with a common intake cam shaft, the axial centers of the intake valves on both sides are set to the axes of the valve lifters attached to them. Characterized by being displaced toward the middle intake valve side with respect to the heart The valve operating system of the four-stroke engine.