JPS6316109A - Valve gear for four-stroke internal combustion engines - Google Patents

Abstract

PURPOSE:To reduce the number of parts by fixing a cam holder block for rotatably supporting a valve system cam shaft on a cylinder head and providing a adjustable bolt which supports rocker arm on its swing center to this cam holder block. CONSTITUTION:A cam holder block 15 is fixed with bolts 16 on a cylinder head 2. An adjustable bolt 24 is provided on upper side members 21, 22 provided on the cam holder block 15. The tip of the adjustable bolt 24 forms a ball pivot 25, and is fitted in a supporting hole 29 formed in the back central part of an intake side rocker arm 28 and a exhaust side rocker arm 32. When being driven by cams 19, 20, rocker arms 28, 32 swing around the pivot 25 as center to open and close valves.

Description

DETAILED DESCRIPTION OF THE INVENTION A1 Object of the Invention (11) Field of Industrial Application The present invention relates to an improvement of a valve train for a four-stroke internal combustion engine.

(2) Conventional technology As an S OHC type valve train for a conventional internal combustion engine, a rocker arm shaft is provided on a cam holder fixed on the cylinder head, and the rocker arm is swingably supported on the shaft, and one end of the rocker arm is It is known that a valve operating cam is connected to one end, and an on-off valve (an intake valve or an exhaust valve) is connected to the other end via an adjuster for adjusting a valve gap (see Japanese Patent Laid-Open No. 172409/1983).

(3) Problems to be Solved by the Invention However, in the conventional valve train, a rocker shaft for supporting the rocker arm, a coil spring for positioning the arm, etc. are required, which increases the number of parts. At the same time, the structure becomes complicated, leading to an increase in the size and weight of the entire valve train. Also, since the adjuster for adjusting the valve gap is provided at the end of the rocker arm, the mass of the moving parts of the valve train becomes large, making the valve train difficult to operate. There is a problem that the high-speed followability of the mechanism is poor.

Therefore, the present invention provides a valve train for a four-stroke internal combustion engine with a simple configuration, which solves the above-mentioned problems at once by eliminating the rocker shaft from the valve train and removing the valve gap adjustment adjuster from the movable parts of the valve train. The purpose is to

B9 Structure of the Invention fll Means for Solving the Problems According to the present invention, a cam holder block for supporting a valve drive camshaft is fixed on the cylinder head of an engine body, and an adjuster is attached to this cam holder block. A bolt is screwed in such a way that its vertical position can be adjusted, and a rocker arm is swingably suspended from a pivot portion integrally provided at the lower end of the adjustment bolt, and the base end of the rocker arm is attached to a pivot portion on the valve drive camshaft. It is characterized by being interlocked with the valve cam, and its tip is directly connected to the upper end of the opening/closing valve.

(2) Operation When the valve camshaft rotates, the rocker arm swings around the pivot part of the adjustment bolt screwed into the cam holder block, and the opening/closing valve (intake valve or exhaust valve).

(3) Example A first example of the present invention will be described below with reference to FIGS. 1 to 5. This embodiment is a case in which the present invention is implemented in an S, OHC type valve train of a 4-valve, 2-cycle, 4-cylinder internal combustion engine equipped with two intake valves and two exhaust valves. The intake valve or exhaust valve in the explanation of the example is referred to as an on-off valve in the present invention, and the intake cam or exhaust cam in the above embodiment is referred to as a valve operating cam in the present invention.

The engine body E of a 5OHC type four-valve internal combustion engine includes a cylinder block 1 and a cylinder head 2 which is superimposed and connected thereon by a plurality of connecting bolts 10 via a gasket 3. A piston 5 is slidably fitted into each cylinder 4. Further, a combustion chamber 6 facing the upper surface of the piston 5 is formed on the inner surface of the cylinder head 2, and a roof surface 7 of each combustion chamber 6 is formed in the shape of a roof having sloped surfaces facing each other. Each combustion chamber 6
Two intake valve ports 8 of the same diameter are opened in parallel on one side of the roof surface 7, and two exhaust valve ports 12 with a diameter slightly smaller than the intake valve ports 8 are opened in parallel on the other side. It is perforated. □Thus, the two intake valve ports 8 are opposed to the two exhaust valve ports 12, respectively.

Intake boats 9 formed in the cylinder head 2 are communicated with the two intake valve ports 8, and these intake boats 9 are gathered into one in the cylinder head 2 and open on one side of the cylinder head 2. and communicates with a fuel supply device, such as a carburetor, through an intake manifold. Further, the two exhaust valve ports 12 are communicated with an exhaust port 13 formed in the cylinder head 2, and these exhaust ports 13 are gathered into one in the cylinder head 2 and opened on the other side of the cylinder head 2. It is connected to the exhaust system via an exhaust manifold.

A pair of intake valves 11 that open and close the two intake valve ports 8 and a pair of exhaust valves 14 that open and close the two exhaust valve ports 12 are supported on the cylinder head 2 so as to be slidable up and down, respectively. The pair of intake valves 11 and the pair of exhaust valves 14 are arranged on both sides of the central axis LL of the cylinder 4 so that their upper ends are inclined away from each other. The pair of intake valves 11 and exhaust valves 14 are urged in the valve closing direction by valve springs 40 and 41, respectively.

A cam holder block 15 is fixed to the upper surface of the cylinder head 2 by a plurality of connecting bolts 16 . A bearing hole 17 is formed between the joint surface of the cylinder head 2 and the cam holder block 15 so as to be closer to the exhaust valve 11 side than the vertical axis LL of the cylinder 4, and the valve drive camshaft 18 is inserted into this bearing hole 17. This valve train camshaft 18 is rotatably supported.
A valve operating cam, that is, an intake cam 19 and an exhaust cam 20 are integrally formed.

The cam holder block 15 includes a plurality of intake-side and exhaust-side upper wall portions 21 and 22 along the direction in which the intake valves 11 and the exhaust valves 14 are arranged in parallel. Two female threaded holes 23 are bored per cylinder 4 in the intake side upper wall portion 21, and a tool insertion 12 is inserted into each of the female threaded holes 23 on the upper surface.
4. An adjustment bolt 24 having a diameter is screwed so that the vertical position can be adjusted, and a spherical pivot portion 25 is integrally formed at the lower end of the adjustment bolt 24.

Also, a lock nut 26 is attached to the upper end of the adjustment bolt 24.
The lower surface of the lock nut 26 is engaged with the upper surface of the intake side upper wall portion 21, and the adjustment bolt 24 is locked to the intake side upper wall portion 21.

An intake side port hook arm 28 is suspended from the spherical pivot portion 25 of the adjustment bolt 24 with a snap ring 27 so as to be movable up and down. That is, the rocker arm 2
A support hole 29 with an open top and a hemispherical concave surface 30 on the bottom is formed in the center of the 8, and the spherical pivot portion 25 is fitted into the support hole 29, and the lower hemisphere of the pivot portion 25 is The hemispherical concave surface 30 is slidably contacted. As shown in FIGS. 4 and 5, the snap ring 27 is constructed by winding a wire such as a steel wire, and includes a coil portion 271 and a coil portion 27. As shown in FIG.
The hook portion 27□ is tightly wound around the upper hemisphere due to its elastic force, and the hook portion 27□ straddles the center of the suction side opening hook arm 28, with the tip of the image forming a locking hole bored on both sides of the center of the rocker arm. 31. Rotatably fit into 31.

As described above, the intake side port hook arm 28 is swingably suspended from the adjustment bolt 24 via the snap ring 27. The base end of the intake side rocker arm 28 is connected to the intake cam 19 of the valve train camshaft 18, and the tip thereof is
It is directly connected to the upper end of the intake valve 11.

In addition, two female screw holes 23 are drilled in the exhaust side upper wall portion 22 for each cylinder 4, and adjustment bolts 24 are screwed into each of these female screw holes 23 so that the vertical position can be adjusted. A lock nut 26 is screwed onto the upper end of 24, and the lower surface of the nut 26 is engaged with the upper surface of the exhaust side upper wall portion 22. The intake side rocker arm 28 and the exhaust side rocker arm 32 are swingably suspended from the spherical pivot portion 25 of the adjustment bolt 24 via a snap ring 27. is the exhaust cam 2 of the valve train camshaft 18
0, and its tip is directly connected to the upper end of the exhaust valve 14.

As shown in Fig. 1.2, above the combustion chamber 6, a plug storage hole 33 is diagonally bored in the cylinder head 2 from the intake valve 11 side toward the center of the combustion chamber 6, and a cam holder block 15, a plug insertion hole 34 that coincides with the plug storage hole 33 is obliquely bored. On the joint surface between the cylinder head 2 and this cam holder block 15, a hole is provided surrounding the plug storage hole 33 and the plug insertion hole 34.
A ring 35 is interposed. The ignition plug 36 accommodated in the plug storage hole 33 through the plug insertion hole 34 is screwed onto the wall of the combustion chamber 6, and its electrode 36a faces the center of the combustion chamber 6.

A head cover 37 covering the valve train is superimposed on the circumference of the cylinder head 2 via a seal ring 38, and the head cover 37 is fixed to the cylinder head 2.

Next, the operation of this first embodiment will be explained.

When the valve drive camshaft 18 is rotated by engine operation, each pair of intake and exhaust side port hook arms 28 per cylinder 4
, and 32 respectively swing around the pivot portion 25 of the adjustment bolt 24, and cooperate with the valve springs 40, 41 to open and close the pair of intake valves 11 and exhaust valves 14 at predetermined timing.

By the way, the valve gap of the intake valve 11 or the exhaust valve 14 (the gap between the upper end of the intake valve 11 and the tip of the intake side opening arm 28,
Alternatively, to adjust the gap between the upper end of the exhaust valve 14 and the tip of the exhaust side opening lock arm 32, rotate the lock nut 26 in the loosening direction, and then turn the adjustment nut 24 to adjust it up and down. Alternatively, the center of swing of the exhaust side port hook arm 32 can be adjusted vertically to adjust the valve gap.

A second embodiment of the invention is shown in Figure 6.7.

This embodiment is a modification of the suspension means of the intake and exhaust side ports 7 and the arms 28 and 32 using the adjustment bolts 24, and the inner wall of the support hole 29 of the intake and exhaust side rocker arms 28 and 32 has a substantially horizontal surface. An annular groove 50 is formed, and this annular groove 5
0, a snap ring 27' having a notch 51 is fitted therein. This snap ring 27' is resiliently engaged with the upper hemisphere of the spherical pivot portion 25 of the adjustment bolt 24. Therefore, the intake side port hook arm 28 or the exhaust side port hook arm 32 is swingably suspended from the pivot portion 25 via the snap ring 27'.

C0 Effects of the Invention As is clear from the above examples, according to the present invention, 2.
On the cam holder block fixed on the cylinder head,
An adjustment bolt is screwed so that its vertical position can be adjusted, a rocker arm is swingably suspended from a pivot portion integrally provided at the lower end of the adjustment bolt, and the base end of the rocker arm is placed on the valve drive camshaft. It is linked to the valve operating cam, and its tip is directly connected to the upper end of the opening/closing valve, making it possible to
To eliminate the need for a rocker shaft for supporting an exhaust rocker arm, a coil spring for positioning the rocker arms, etc., thereby reducing the number of parts in a valve operating device, simplifying its structure, and making the device smaller and lighter. Can be done. In addition, by providing the valve gap adjustment mechanism of the valve train in the cam holder block, the mass of the moving parts of the valve train can be reduced, and the valve train has excellent followability when the valve train camshaft rotates at high speed. , can contribute to improving the high-speed performance of the engine.

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional side view of the head of an engine equipped with the device of the present invention taken along the line 1-1 in FIG. 3 is a partial bottom view of the cylinder throat taken along the line m-■ in FIG. 1, FIG. 4 is an exploded perspective view of the rocker arm support, and FIG. 5 is a plan view of the engine excluding the head cover. 6 is an assembled perspective view of the support portion.
Figure 7 shows a second embodiment of the present invention, Figure 6 is an assembled perspective view of the rocker arm support part, and Figure 7 shows Figures 6 - ■.
FIG. 3 is an enlarged partial cross-sectional view taken along the line. E... Engine body 2... Cylinder head, 11... Intake valve as an on-off valve, 14... Exhaust valve as an on-off valve, 15... Cam holder block, 18... Valve drive cam Axis, 19...
Intake cam as a valve train cam, 20... Exhaust cam as a valve train cam, 24... Adjustment bolt, 25...
Pivot part, 28...Intake side mouth hook arm, 29...
・Exhaust side rocker arm

Claims (1)

[Claims] A cam holder block for supporting the valve camshaft is fixed onto the cylinder head of the engine body, and an adjustment bolt is screwed onto the cam holder block so that the vertical position can be adjusted. A rocker arm is swingably suspended from an integrally provided pivot part, the base end of the rocker arm is interlocked with the valve drive cam on the valve drive cam shaft, and the tip thereof is directly connected to the upper end of the opening/closing valve. A valve train for a four-stroke internal combustion engine featuring: