JPH076371B2 - SOHC internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention relates to an SOHC internal combustion engine, and in particular to an intake valve that opens and closes an intake port and an exhaust port that open to a combustion chamber of a cylinder head, respectively. Exhaust valves are arranged on both sides of the cylinder axis, and one cam shaft is provided between the intake and exhaust valves, and the intake and exhaust rocker arms that interlock between the cam shaft and the intake and exhaust valves are pivotally supported. An intake / exhaust rocker shaft and an ignition plug that faces the electrode in the center of the ceiling surface of the combustion chamber are installed.The cam shaft is opposite to the ignition plug from the cylinder axis in order to bring the ignition plug close to the cylinder axis. The camshaft is supported by a bearing formed between the bearing wall integrally formed on the cylinder head and the holder fixed to the cylinder head, and the intake and exhaust rocker shafts are mounted on the holder. Bearing the internal combustion engine Regarding the improvement of Seki.

(2) Conventional Technology An internal combustion engine of this kind is disclosed in Japanese Patent Laid-Open No. 167805/56.

(3) Problems to be Solved by the Invention In the internal combustion engine disclosed in the above publication, the three axes of the cam shaft, the intake rocker shaft, and the exhaust rocker shaft are sucked, and the exhaust valves are dispersedly arranged in the arrangement direction. Since the valve operating mechanism spreads in the arrangement direction of the intake valve and the exhaust valve, the intake valve and the exhaust valve must be spaced apart from each other, which leads to an increase in the size of the engine head.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide the internal combustion engine in which a valve operating mechanism can be easily arranged even between intake and exhaust valves with a narrow interval.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention arranges one of the intake and exhaust rocker shafts substantially directly above the cam shaft, and at the same time, arranges one of the rocker shafts. The holder is fixed to the bearing wall by at least two bolts adjacent to both sides of the shaft and the cam shaft, and the rocker arm pivotally supporting one of the rocker shafts is formed in a bell crank shape.

(2) Action Since the intake rocker shaft or the exhaust rocker shaft is arranged almost directly above the cam shaft, the valve mechanism becomes compact, and the valve mechanism can be easily arranged even between intake and exhaust valves with a narrow interval.

Moreover, since the rocker arm pivotally supported on the rocker shaft directly above the cam shaft has a bell crank shape, the intake valve or the exhaust valve connected to the rocker arm can be driven without any trouble.

Further, when the camshaft drives a bell crank-shaped rocker arm, a large upward reaction force acts on the holder from the camshaft, but at least two bolts adjacent to both sides of the camshaft and the rocker shaft immediately above it act as the reaction force. The camshaft is always supported stably by holding the holder evenly while holding the holder evenly.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3, a plurality of cylinders 1,
The cylinder head 3 is attached to the upper surface of the cylinder block 2 having 1 ... A piston 5 is slidably fitted into each cylinder 1, and a combustion chamber 6 is provided in a bottom surface of a cylinder head 3 facing the piston 5.

The ceiling surface 7 of each combustion chamber 6 is formed in a mountain shape from two slopes 7a and 7b that descend toward both sides from a ridge line L (FIG. 3) extending in the arrangement direction of the plurality of cylinders 1, 1. Slope 7
a has one end of a pair of intake ports 8,8 and the other slope 7
Similarly, one ends of a pair of exhaust ports 9 and 9 are opened in b and 7b side by side along the ridge line L, respectively. A pair of intake ports 8,8
The other end of the cylinder head 3 merges into one inside the cylinder head 3 and opens to one outside surface of the cylinder head 3, to which an intake manifold (not shown) is connected. Also a pair of exhaust ports
The other end sides of 9, 9 merge into one in the cylinder head 3 and open to the other outer side surface of the cylinder head 3, to which an exhaust manifold (not shown) is connected.

The pair of intake valves 10, 10 and the exhaust valves 11, 11 for opening and closing the pair of intake ports 8, 8 and the exhaust ports 9, 9 are valve guides 12, 12 and 13 fitted to the cylinder head 3. , 13 are slidably supported respectively. At that time, the intake and exhaust valves 10 and 11 facing each other are arranged in a V shape so that the valve heads thereof are separated from each other on both sides of the axis Y of the cylinder 1.

The intake and exhaust valves 10 and 11 are equipped with valve springs 14 and 15 for biasing them in the valve closing direction.

Between the intake valve 10, 10 group and the exhaust valve 11, 11 group, one cam shaft 16 extending in the arrangement direction of the plurality of cylinders 1, 1 is biased from the cylinder axis Y to the exhaust valve 11 side. It is arranged as a place.

An intake rocker shaft parallel to the cam shaft 16 is provided directly above the cam shaft 16.
18 is arranged, and an intake rocker shaft 17 parallel to the exhaust rocker shaft 18 is arranged between the exhaust rocker shaft 18 and the intake valves 10, 10.

The cam shaft 16 corresponds to each cylinder 1 and has one journal 19 and a pair of exhaust cams 21 and 21 adjacent on both sides thereof.
It has a pair of intake cams 20, 20 adjacent to each other on both sides.

A pair of intake rocker arms 22, 22 are pivotally supported on the intake rocker shaft 17 so as to correspond to each cylinder 1, one end of which is provided with the intake cams 20, 20 and the other end thereof is provided with adjusting bolts 24, 24. The heads of the intake valves 10 and 10 are engaged with each other.

A pair of exhaust rocker arms 23, 23 corresponding to each cylinder 1 are swingably supported on the exhaust rocker shaft 18, one end of which is connected to the exhaust cams 21, 21, and the other end thereof is adjusted bolts 25, 25.
Are engaged with the head portions of the exhaust valves 11 and 11 via the. In this case, the exhaust rocker arm 23 is formed in a bell crank shape because of the vertical arrangement of the exhaust rocker shaft 18 and the cam shaft 16.

The journal 19 includes a bearing wall 26 formed integrally with the cylinder head 3 so as to cross the cylinder axis Y, and a bearing wall 26 formed on the bearing wall 26.
Is rotatably supported by a bearing 31 formed between joint surfaces of a holder 30 (see FIGS. 4 to 6) fixed by bolts 27, 28, 29 of the book, and the rocker shafts 17, 18 are holders. It is supported by bosses 32 and 33 formed integrally with 30.

Of the bolts 27, 28, 29, two bolts 27, 28 are arranged adjacent to each other so as to sandwich the cam shaft 16 and the exhaust rocker shaft 18 immediately above it, and the remaining one bolt 29 is a plug described later. It is arranged on the opposite side of the bolt 28 with the accommodation hole 38 interposed therebetween.

The cylinder head 3 is provided with a plug mounting hole 37 that opens at the center of the ceiling surface 7 of each combustion chamber 6 as a screw hole, and an ignition plug 39 is screwed into this hole 37. Thus spark plug
The 39 electrodes face the center of the ceiling surface 7.

The spark plug 39 is arranged so as to pass between the cylinder axis Y and the intake valves 10 and 10. In order to bring the spark plug 39 close to the cylinder axis Y as much as possible, the cam shaft 16 moves from the cylinder axis Y to the spark plug. It is arranged so as to be offset from the side opposite to 39, that is, toward the exhaust valve 11 side.

Each of the bearing walls 26 and the holder 30 is provided with a series of plug accommodating holes 38 connected to the plug mounting holes 37 and accommodating the ignition plug 39, and a seal member 40 is provided between the joint surfaces of the bearing wall 26 and the holder 30. Is installed.

In this case, in order to bring the plug housing hole 38 as close as possible to the cylinder axis Y without interfering with the intake rocker shaft 17, the intake rocker shaft 17 is divided at the portion where the plug housing hole 38 passes.

As shown in FIG. 2, the cam shaft 16 also has a journal 19 'at its end, and the journal 19' is fixed to both end walls of the cylinder head 3 and two bolts 41 and 42. Is rotatably supported by a bearing 44 formed between the joint surface with the holder 43, and the holder 43 sucks and exhausts the rocker shaft.
17,18 ends are supported.

The intake rocker shaft 17 is equipped with a wave washer 45 interposed between the adjacent intake rocker arms 22 and 22, and a wave washer 45 'interposed between the intake rocker arm 22 and the holder 43 at the outer position, By these, each intake rocker arm 22 is elastically held by the adjacent holder 30.

In addition, the exhaust rocker shaft 23 has two adjacent exhaust rocker arms 23, 2
The coil springs 46 interposed between the exhaust rocker arms 23 and the holders 43 are mounted between the coil springs 46, and the exhaust rocker arms 23 and the holder 43 at the outer position. Retained.

As shown in FIG. 1, a head cover 47 for covering the valve operating mechanism including the cam shaft 16, the rocker shafts 17, 18 and the rocker arms 22, 23 is joined to the upper end of the cylinder head 3 via a seal member 48. It The head cover 47 is provided with a plug insertion port 49 communicating with the plug accommodating hole 38, and a seal member 50 is provided so as to surround the plug insertion port 49.
And the bearing wall 26 are opposed to each other.

The plug accommodating hole 38 accommodates a plug cap 52 which is attached to the plug 51 so as to connect a high-voltage cord 51 connected to an ignition coil (not shown) to the ignition plug 39, and the upper end of the cap 52 has a plug insertion port 49. Is fitted airtightly.

Next, the operation of this embodiment will be described. During operation of the engine, the cam shaft 16 is rotationally driven from the crank shaft via a timing transmission device (not shown). When the intake stroke is started in each cylinder 1, the intake cams 20, 20 exert a lift action to swing the intake rocker arms 22, 22 in the opening direction of the intake valves 10, 10, so that the intake valves 10, The valve 10 is opened against the force of the valve springs 14 and 14, and the air-fuel mixture generated by the air-fuel mixture generating device such as a vaporizer (not shown) is sucked into the cylinder 1 through the intake ports 8 and 8.

When the intake cams 20,20 release the intake rocker arms 22,22,
The intake valves 10 and 10 are closed by the force of the valve springs 14 and 14, and the engine shifts to the compression stroke.

At the end of the compression stroke, the spark discharge of the spark plug 39 ignites the compressed gas in the combustion chamber 6 and advances to the expansion stroke. At this time, since the ignition plug 39 is close to the cylinder axis Y and the electrode is located at the center of the ceiling surface 7 of the combustion chamber 6, the flame propagation distance from the ignition point to the peripheral edge of the combustion chamber 6 is substantially. Equal, and therefore the burning time is minimal, so
It is possible to obtain a good combustion state that is advantageous for exhibiting high output.

Next, when the exhaust stroke is started, the exhaust cams 21, 21 exert a lift action to swing the exhaust rocker arms 23, 23 in the opening direction of the exhaust valves 11, 11, so that the exhaust valves 11, 11 are Spring 15,15
The exhaust valve exhausts exhaust gas from the combustion chamber 6 by opening the valve against the force of
Discharge to 9,9. Exhaust cams 21,21 are exhaust rocker arms 23,2
When 3 is released, the exhaust valves 11 and 11 are closed by the force of the valve springs 15 and 15.

In such an internal combustion engine, the camshaft 16 of the exhaust rocker shaft 18 is displaced despite the cam shaft 16 being displaced from the cylinder axis Y to the side opposite to the spark plug 39 in order to bring the spark plug 39 close to the cylinder axis Y. The valve mechanism is made compact due to the arrangement directly above 16, and even if the gap between the intake and exhaust valves 10 and 11 is narrow,
In the meantime, the valve gear can be easily arranged.

Also, because the exhaust rocker shaft 18 is placed directly above the cam shaft 16,
When the exhaust rocker arm 22 is driven by the exhaust cam 21, a large upward reaction force acts on the holder 30 from the cam shaft 16,
The two bolts 27, 28 arranged adjacent to both sides of the exhaust rocker shaft 18 and the cam shaft 16 evenly bear the above reaction force to firmly fix the holder 30 and increase the rigidity of the bearing 31. The support for the journal 19 can always be stabilized.

C. Effects of the Invention As described above, according to the present invention, one of the intake and exhaust rocker shafts is arranged substantially directly above the cam shaft, and at least two adjacent rocker shafts and both sides of the cam shaft are provided. Since the holder is fixed to the bearing wall by the bolt and the rocker arm pivotally supported by the one rocker shaft is formed in a bell crank shape,
Even if the space between the intake and exhaust valves is not large, the valve mechanism can be compactly arranged between them, which contributes to downsizing of the engine, and the holder is firmly fixed and the cam A stable supporting state of the shaft is always obtained.

[Brief description of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a vertical sectional side view of an SOHC type internal combustion engine, Fig. 2 is a view taken along the line II-II in Fig. 1, and Fig. 3 is III in Fig. 1. -III line arrow view, FIG. 4, FIG.
6 and 6 are side views of the holder in the internal combustion engine,
It is a top view and a bottom view. Y ... Cylinder axis line, 3 ... Cylinder head, 6 ... Combustion chamber, 7 ... Ceiling surface,
8 ... intake port, 9 ... exhaust port, 10 ... intake valve,
11 …… Exhaust valve, 16 …… Cam shaft, 17 …… Intake rocker shaft, 18
...... Exhaust rocker shaft, 19 …… Journal, 20 …… Intake cam, 21 …… Exhaust cam, 22 …… Intake rocker arm, 23 ……
Exhaust rocker arm, 26 ... Bearing wall, 30 ... Holder, 31 ...
…bearing

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02P 13/00 301 B

Claims (1)

[Claims] Claims: 1. An intake valve and an exhaust valve for opening and closing an intake port and an exhaust port opened in a combustion chamber of a cylinder head are arranged on both sides of an axis of a cylinder, and one camshaft is provided between the intake and exhaust valves. And the intake and exhaust rocker shafts that pivotally support the exhaust rocker arms, and the spark plug that exposes the electrode to the center of the ceiling surface of the combustion chamber. In order to bring this ignition plug close to the axis of the cylinder, the cam shaft is arranged offset from the axis of the cylinder on the side opposite to the ignition plug, and the bearing wall integrally formed with the cylinder head and the holder fixed to it are provided. In the SOHC type internal combustion engine in which the cam shaft is supported by the bearing formed between the joint surfaces of the SOHC, and the holder and the intake and exhaust rocker shafts are supported, one of the intake and exhaust rocker shafts is arranged almost directly above the cam shaft. With The holder is fixed to the bearing wall by at least two bolts adjacent to both sides of the one rocker shaft and the cam shaft, and the rocker arm pivotally supported by the one rocker shaft is formed in a bell crank shape. SOHC
Type internal combustion engine.