JPS6318104A - Sohc type internal combustion engine - Google Patents

Abstract

PURPOSE:To shorten a space between an intake and an exhaust valve to make an engine compact by arranging one of an intake and an exhaust rocker shaft about right above a cam shaft, and forming a rocker arm pivotally supported on said one of the rocker shafts into a bell crank shape. CONSTITUTION:An intake and an exhaust valve 10, 11 are opened and closed by the rotation of one camshaft 16 through an intake and an exhaust rocker arm 22, 23 whose middle parts are rotatably supported on an intake and an exhaust rocker shafts 17, 18 borne in parallel with a cylinder axis Y, and one of said rocker shafts 17, 18 (the exhaust rocker shaft 18 in a figure) is arranged right above the cam shaft 16. A holder 30 supporting each of the rocker shafts 17, 18 is fixed to a bearing wall 26 uniting with a cylinder head 3 through at least two bolts 27, 28 being adjacent to both sides of the rocker shaft 18 and the cam shaft 16. In addition to that, the exhaust rocker arm 23 pivotally supported on the exhaust rocker shaft 18 is formed into a bell crank shape.

Description

Detailed Description of the Invention A4 Purpose of the Invention (1) Field of Industrial Application The major invention is an SOH'C internal combustion engine, particularly an intake valve that opens and closes an intake boat and an exhaust port that open into the combustion chamber of a cylinder head. and exhaust valves are arranged on both sides of the axis of the cylinder, and a single camshaft is placed between these intake and exhaust valves, and intake and exhaust rocker arms that interlock each other between this camshaft and the intake and exhaust valves are pivoted. A supporting intake and exhaust rocker shaft and a spark plug with an electrode facing the center of the ceiling of the combustion chamber are arranged.
In order to bring the spark plug closer to the axis of the cylinder, the camshaft is disposed so as to be offset from the axis of the cylinder to the side opposite to the spark plug, and the bearing wall integrally formed on the cylinder head and the holder fixed thereto are connected. The present invention relates to an improvement in an internal combustion engine in which a camshaft is supported by a bearing formed between surfaces, and intake and exhaust rocker shafts are supported in the holder.

(2) Prior Art This type of internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. 167805/1983.

(3) Problems to be Solved by the Invention In the internal combustion engine disclosed in the above-mentioned publication, three shafts, a camshaft, an intake rocker shaft, and an exhaust rocker shaft, are distributed in the arrangement direction between the intake and exhaust valves. As a result, the valve mechanism expands in the direction in which the suction and exhaust valves are arranged, which forces the suction and exhaust valves to be spaced apart from each other, leading to an increase in the size of the engine head.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide the above-mentioned internal combustion engine that enables easy arrangement of a valve operating mechanism even between intake and exhaust valves that are closely spaced.

B0 Structure of the Invention (1) Means for Solving Problems In order to achieve the above object, the present invention disposes one of the intake and exhaust rocker shafts substantially directly above the camshaft, and also provides a means for solving the problems. The holder is fixed to the bearing wall by at least two bolts adjacent to both sides of the camshaft, and the rocker arm pivotally supported by the one rocker shaft is formed in the shape of a bell crank.

(2) Function Since the intake rocker shaft or exhaust rocker shaft is placed almost directly above the camshaft, the valve mechanism becomes compact, and the valve mechanism can be easily installed even between intake and exhaust valves that are closely spaced. .

Moreover, since the rocker arm pivotally supported by the rocker shaft directly above the camshaft has a bell crank shape, it is guaranteed that the intake valve or the exhaust valve connected to the rocker arm can be driven without any problem.

Also, when driving a camshaft or a bell crank-shaped rocker arm, a large upward reaction force acts on the holder from the camshaft, but the small (two bolts) adjacent to both sides of the camshaft and the rocker shaft directly above it act on the holder. Since the holder is strongly held by bearing the reaction force evenly, the support of the camshaft is always stable.

(3) Embodiment Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. In FIGS. 1 to 3, a plurality of cylinders 1.
A cylinder head 3 is connected to the upper surface of a cylinder block 2 having gaskets 4 through gaskets 4. A piston 5 is slidably fitted into each cylinder 1, and a combustion chamber 6 is recessed in the bottom surface of the cylinder head 3 facing the piston 5.

The ceiling surface 7 of each combustion chamber 6 has a plurality of cylinders 1°1...
・Two slopes descending from the ridge extending in the arrangement direction & 1lL (Fig. 3) towards both sides? A and 7b are formed in a mountain shape, and one end of a pair of intake boats 8, 8 is on one slope 7a, and one end of a pair of exhaust ports 9, 9 is on the other slope 7b, 7b, respectively. The openings are lined up along the ridge. The other ends of the pair of intake ports 8, 8 merge into one in the cylinder head 3 and open into the cylinder on one outer surface of the cylinder 3, to which an intake manifold (not shown) is connected. Further, the other ends of the pair of exhaust ports 9, 9 merge into one in the cylinder head 3 and open on the other outer surface of the cylinder head 3, to which an exhaust manifold (not shown) is connected.

Each pair of intake valves 10.10 and exhaust valves 11.9 for opening and closing each pair of intake ports 8.8 and exhaust ports 9.9.
11 is a valve guide 12 fitted into the cylinder head 3.
12 and 13.13, respectively.

In this case, the opposing intake and exhaust valves 10, 11 are arranged in a figure 7 shape on both sides of the axis MAY of the cylinder 1 so that the valve heads are spaced apart from each other.

These intake and exhaust valves 10.11 are each equipped with a valve spring 14.15 that biases them in the valve closing direction.

Between the intake valve 10.10... group and the exhaust valve 11.11... group, a single camshaft 16 extending in the arrangement direction of the plurality of cylinders 1.1... is connected from the cylinder axis Y. Exhaust valve 1
It is arranged offset to the 1 side.

An exhaust rocker shaft 18 parallel to the shaft 16 is disposed approximately directly above the camshaft 16, and the exhaust rocker shaft 18 and the intake valve 1
An intake rocker shaft 17 parallel to the exhaust rocker shaft 18 is disposed midway between 0.10 and 0.10.

The camshaft 16 has one journal 19 corresponding to each cylinder 1 and a pair of exhaust cams 21 .
21, and a pair of intake cams 20.
20.

A pair of intake rocker arms 22.22 are swingably supported on the intake rocker shaft 17 in correspondence with each cylinder 1, one end of which is connected to the intake cams 20, 20, and the other end is connected to an adjustment bolt 24.24. via the intake valve 10. It) is respectively engaged with the head of.

Further, a pair of exhaust rocker arms 23, 23 are pivotally supported on the exhaust rocker shaft 18 in correspondence with each cylinder 1, and
One end of these is engaged with the exhaust cam 21.21, and the other end is engaged with the head of the exhaust valve 11.11 via an adjustment pole (25.25).

In this case, the exhaust rocker arm 23 is formed in a bell crank shape due to the vertical arrangement of the exhaust rocker shaft 18 and the camshaft 16.

The journal 19 includes a bearing wall 26 that is integrally formed on the cylinder head 3 so as to cross the cylinder axis Y, and a holder 3 that is fixed to this with three bolts 27, 28, and 29.
The rocker shaft 17.
18 is supported on bosses 32, 33 formed integrally with the holder 30.

Among the bolts 27, 28, and 29, two bolts 27
．． The bolts 28 are arranged adjacent to each other on both sides of the camshaft 16 and the exhaust rocker shaft 18 immediately above the camshaft 16 so as to sandwich the same, and the remaining bolt 29 is arranged on the opposite side of the bolt 28 with a plug accommodation hole 38 to be described later in between.

A plug receiving hole 37 opening at the center of the ceiling surface 7 of each combustion chamber 6 is formed as a screw hole in the cylinder 7 door 3, and a spark plug 39 is screwed into this hole 37. In this way, the electrode of the spark plug 39 faces the center of the ceiling surface 7.

The spark plug 39 is connected to the cylinder axis Y and the intake valve 10, lO
However, in order to bring the camshaft 16 as close as possible to the cylinder axis Y, the camshaft 16 is offset from the cylinder axis Y to the side opposite to the spark plug 39, that is, to the exhaust valve 11 side. It is arranged in such a way that

A plug mounting hole 3 is provided in each of the bearing walls 26 and the holder 30.
A series of plug accommodating holes 38 are provided to accommodate the ignition plug 39, and a seal member 40 is interposed between the joint surface of the bearing wall 26 and the holder 30.

In this case, in order to make the plug housing hole 38 as close as possible to the cylinder axis dY without being interfered with by the suction port 7 force axis 17, the suction port 7 force axis 17 is divided at a portion where the plug housing hole 38 passes.

As shown in FIG. 2, the camshaft 16 also has a journal 19' at its end, and this journal 19' is fixed to both end walls of the cylinder head 3 with two bolts 41 and 42. The bearing 4 formed between the joint surfaces with the holder 43
The holder 43 is rotatably supported by the holder 43, and the ends of the intake and exhaust rocker shafts 17 and 18 are supported by the holder 43.

The intake rocker shaft 17 has adjacent intake rocker arms 22 .
A wave washer 45 is interposed between the intake rocker arm 22 and the wave washer 45' which is interposed between the intake rocker arm 22 and the holder 43 at the outer position. The bullet is retained.

Further, the exhaust rocker shaft 18 has adjacent exhaust rocker arms 2.
3. A coil spring 46 interposed between the exhaust port 7 and the holder 43 is installed, and a coil spring 46' is installed between the exhaust port 7 arm 23 and the holder 43 at the outer position. The bullet is held at 30.

As shown in FIG.
A head cover 47 that covers the valve mechanism made of 2.23, etc. is joined via a seal member 48. This head cover 47 has a plug insertion opening 49 that communicates with the plug accommodation hole 38.
A sealing member 50 is interposed between the opposing surfaces of the head cover 47 and the bearing wall 26 so as to surround the plug insertion opening 49 .

A plug cap 52 that is attached to the spark plug 39 in order to connect a high voltage cord 51 connected to an ignition coil (not shown) to the spark plug 39 is housed in the plug housing hole 38 , and the upper end of the cap 52 is connected to the plug insertion opening 49 . is hermetically fitted.

Next, the operation of this embodiment will be explained. During operation of the engine, the camshaft 16 is rotationally driven by the crankshaft via a timing transmission device (not shown). When the intake stroke starts in each cylinder 1, the intake cam 20.20 exerts a lifting action to move the intake rocker arm 22.22 to the intake valve 10.
Since the intake valve 10.10 is swung in the opening direction of the valve 10, the intake valve 10.10 is opened against the force of the valve spring 14.14, and the air-fuel mixture generated by an air-fuel mixture generating device such as a carburetor (not shown) is transferred to the intake port. 8, 8 into the cylinder 1.

When the intake cam 20.20 releases the intake rocker arm 22.22, the intake valve 10.10 closes under the force of the valve spring 14.14 and the engine moves into the compression stroke.

At the end of the compression stroke, the compressed gas in the combustion chamber 6 is ignited by a spark discharge from the spark plug 39, and the engine advances to the expansion stroke. At this time, since the spark 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 periphery of the combustion chamber 6 is substantially equal. , so the combustion time is minimized, so
A good combustion condition that is advantageous for producing high output can be obtained.

Next, when the compression stroke is started, the exhaust cam 21.21 exerts a lifting action and swings the exhaust rocker arm 23.23 in the opening direction of the exhaust valve 11.11.
．． 11 opens against the force of valve springs 15 and 15 to discharge exhaust gas from the combustion chamber 6 to exhaust ports 9, 9. When the exhaust cam 21.21 releases the exhaust rocker arm 23.23, the exhaust valve 11.11 closes under the force of the valve springs 15,15.

In such an internal combustion engine, although the camshaft 16 is deviated 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 camshaft of the exhaust rocker shaft 18 The arrangement directly above the valve 10 and 16 makes the valve train compact, and even if the distance between the intake and exhaust valves 10 and 11 is narrow, the valve train can be easily disposed between them.

Furthermore, since the exhaust rocker shaft 18 is disposed directly above the camshaft 16, a large upward reaction force acts on the holder 30 from the camshaft 16 when the exhaust port 7 and the arm 22 are driven by the exhaust cam 21. The two bolts 27 and 28 disposed adjacent to each other on both sides of the camshaft 16 equally bear the above reaction force, firmly fixing the holder 30 and increasing the rigidity of the bearing 31, so that the camshaft 16 is tightened against the journal 19. Support can be kept stable at all times.

C0 Effects of the Invention As described above, according to the present invention, one of the intake and exhaust rocker shafts is disposed almost directly above the camshaft, and two (two in total) adjacent to both sides of the one rocker shaft and the camshaft are arranged. The holder is fixed to the bearing wall with the bolt, and the rocker arm that is pivotally supported by the one rocker shaft is formed in the shape of a bell crank.
The valve mechanism can be arranged compactly between the intake and exhaust valves without requiring a large distance between them, contributing to the downsizing of the engine.Moreover, the holder is firmly fixed, and the cam A stable support can be obtained for the shaft at all times.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 shows an SOH
A vertical side view of the C-type internal combustion engine, FIG. 2 is a view taken along the nn arrow in FIG. 1, FIG. 3 is a view taken along the mm line in FIG. 1, FIGS.
and FIG. 6 are side views of the holder in the internal combustion engine,
They are a top view and a bottom view. Y... Cylinder axis, 3... Cylinder head, 6... Combustion chamber, 7... Ceiling surface, 8... Intake port, 9... Exhaust port, 10
...Intake valve, 11...Exhaust valve, 16...Camshaft,
17...Intake rocker shaft, 18...Exhaust rocker shaft, 1
9... Journal, 20... Intake cam, 21...
Exhaust cam, 22... Intake rocker arm, 23... Exhaust rocker arm, 26... Bearing wall, 30... Holder, 31... Bearing Fig. 4 Fig. 3 Fig. 2

Claims (1)

[Claims] Intake and exhaust valves that open and close the intake and exhaust ports that open into the combustion chamber of the cylinder head are arranged on both sides of the axis of the cylinder, and a camshaft is connected between these intake and exhaust valves. The ignition system includes suction and exhaust rocker shafts that pivot the suction and exhaust rocker arms that interlock the suction and exhaust valves, and a spark plug that has an electrode facing the center of the ceiling of the combustion chamber. In order to bring the plug close to the cylinder axis, the camshaft is offset from the cylinder axis to the side opposite to the spark plug, and the camshaft is placed between the joint surface between the bearing wall integrally molded in the cylinder head and the holder fixed to it. In an SOHC type internal combustion engine in which a camshaft is supported by a formed bearing and an intake and exhaust rocker shaft is supported in the holder, one of the intake and exhaust rocker shafts is disposed approximately directly above the camshaft, and one of the intake and exhaust rocker shafts is disposed approximately directly above the camshaft. A SOHC type internal combustion engine characterized in that a holder is fixed to a bearing wall by at least two bolts adjacent to both sides of a rocker shaft and a camshaft, and a rocker arm pivotally supported by one of the rocker shafts is formed in a bell crank shape. institution.