JPH0240867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a single overhead camshaft engine having one overhead camshaft that traverses near the upper center of the combustion chamber.

(Background of the Invention) When this type of engine has one spark plug, it is difficult to arrange the spark plug near the center of the combustion chamber because the spark plug interferes with the camshaft. Further, when the camshaft bearing is provided above the center of the combustion chamber, it becomes even more difficult to arrange the ignition plug and the bearing. For this reason, there were problems in that the ignition part of the ignition plug could not be placed near the center of the combustion chamber, or the ignition part had to be arranged at a large angle. In addition, it is necessary to provide an opening in the head cover for attaching and removing the spark plug, but if the opening is complicated or the camshaft bearing is integrated with the head cover, the head cover and cylinder head may be separated. There was a problem in that sealing between the mating surfaces became difficult and the reliability of the seal decreased. Spark plugs are also required to be easy to install and remove, and have good cooling performance.

On the other hand, when an engine is mounted on a vehicle such as a motorcycle, the upper part of the cylinder is sometimes supported on the vehicle body, but in the past, the head cover did not have sufficient rigidity, so the upper surface of the head cover was not fixed to the vehicle body. It was fixed to the vehicle body via a bracket etc. For this reason, there was a problem that the engine was not easily mounted on the vehicle body.

(Object of the Invention) The present invention was made in view of the above circumstances, and the camshaft is arranged so as to cross the upper part of the center of the combustion chamber, and the ignition plug is arranged so that its ignition part is located near the center of the combustion chamber. When placed in the ideal position, the camshaft bearing can be placed above the center of the combustion chamber while the camshaft can be placed in a preferable position near the center of the combustion chamber, creating a seal between the mating surfaces of the head cover and cylinder head. An object of the present invention is to provide a single overhead camshaft engine capable of improving the performance, the ease of attaching and removing a spark plug, and the cooling performance thereof.

(Structure of the Invention) According to the present invention, this purpose is to provide one overhead camshaft for one cylinder that crosses near the upper part of the center of the combustion chamber, and two overhead camshafts disposed on one side of this camshaft. In a single overhead camshaft engine having two exhaust valves and one spark plug with an ignition part facing near the center of the combustion chamber, the head cover covering the upper part of the cylinder head is formed into a substantially U-shape in plan view between the two exhaust valves. A slit is formed at the top of the combustion chamber and substantially orthogonal to the overhead camshaft, and the spark plug is disposed within the slit, while a bearing for the camshaft located above near the center of the combustion chamber is connected to the head cover and the cylinder head. One overhead camshaft type engine, characterized in that two of the bolts formed between the joint faces and fixing the head cover to the cylinder head on both sides of the bearing are provided at positions sandwiching the spark plug on the inner wall of the slit. This is achieved by

(Embodiment) Fig. 1 is a partially sectional side view of an embodiment of the present invention applied to a motorcycle, Fig. 2 is a central vertical sectional view showing the main parts of the engine, and Fig. 3 is the same as Fig. 2. FIG. 4 is a plan view showing the valve operating mechanism with the cylinder head cover removed, and FIG. 4 is a partially sectional plan view of the cylinder head cover to show how each rocker arm is attached.

In FIG. 1, numeral 10 is the main frame, 1
2 is a front fork supporting the front wheel 14; 16;
is the rear wheel. 18 is 4 valves 1 overhead camshaft type 1
The engine is a cylinder engine and is mounted on a main frame 10 so that its intake passage 20 and exhaust passage 22 point toward the rear of the vehicle body and toward the front of the vehicle body, respectively. 24 is a carburetor that supplies air-fuel mixture to the intake passage 20; 26 is an exhaust pipe;
6 is bent so as to guide the exhaust gas discharged from the exhaust passage 22 from the front of the engine 10 to the rear through the lower part of the engine 10.

28 is a crankcase, 30 is a cylinder, 32
34 is a cylinder head, and 34 is a cylinder head cover (hereinafter referred to as a head cover). A camshaft 36 is laterally supported between the joint surfaces of the cylinder head 32 and the head cover 34, and a sprocket 38 fixed to one end of the camshaft 36 is connected to the crankshaft 4.
The timing chain 42 that runs between
The crankshaft 40 is rotated at half the speed of the crankshaft 40. This camshaft 36 crosses the vicinity above the center of the combustion chamber 44 .

Two intake ports 46, 46 (FIGS. 2 and 3) that open into the combustion chamber 44 and two exhaust ports 48, 48 are formed in the cylinder head 32, and each intake port 46,
46 communicates with the two intake passages 20, 20, and each exhaust port 48, 48 communicates with the two exhaust passages 22, 22. In this embodiment, two exhaust pipes 26 (only one of which is shown in FIG. 1) are provided, and exhaust gas from each exhaust passage 22, 22 is separately discharged through these two exhaust pipes 26. .

Reference numerals 50 and 50 indicate intake valves, and as is clear from FIG. The ports 46, 46 are biased closed. In FIG. 3, reference numerals 58, 58 indicate the axes of the intake valves 50, 50, and as is clear from this figure, the axes 58, 58 are perpendicular to the camshaft 36.

Reference numerals 60 and 60 are exhaust valves, and as is clear from FIG. The exhaust ports 48, 48 are biased to close. 68,6 in Figure 3
Reference numeral 8 indicates the axes of the exhaust valves 60, 60, and as is clear from this figure, the exhaust valves 60, 60 are supported such that their upper portions are gradually separated from each other.

The cylinder head 32 has each valve 50, 50, 60,
After assembling 60 and each valve spring 54, 54, 64, 64, it is fixed to the cylinder 30 (FIG. 1) by four bottles 70 shown in FIG.

As shown in FIG. 3, the camshaft 36 is formed with two intake-side cams 72, 72 located on the inside and two exhaust-side cams 74, 74 located on the outside. and 74 are close to each other, while the inner cams 72 and 72 are spaced apart. The camshaft 36 is pivotally supported at both ends and the center by three slide bearings 76, 78, and 80 formed between the joint surfaces of the cylinder head 32 and the head cover 34. That is, the inner cam 72,
72 is pivotally supported by a central bearing 80 located near above the center of the combustion chamber 44. The bearing surface of this bearing 80 has a diameter smaller than the maximum diameter of each cam 72, 74, and in this embodiment, the diameter is even smaller than the minimum diameter portion of each cam 72, 74. This camshaft 36
At one end (upper side in Fig. 3) is the sprocket 3.
8 is fixed, and a rotational speed detection gear mechanism (not shown) is connected to the other end (lower side in FIG. 3). Cylinder head 32 and head cover 34
As shown in FIGS. 2 and 3, a cooling air passage 82 is formed therein. That is, a vertically elongated gap is formed between the exhaust valves 60, 60 that opens toward the front and upward of the engine 18, and in this embodiment, this gap extends from below the central bearing 80 to between the intake valves 50, 50. It opens to the rear through. The cooling air passage 82 has a substantially cylindrical space between the two exhaust valves 60 and 60 near the bearing 80, and this space serves as an ignition plug attachment/removal hole 84. That is, the wall forming the attachment/detachment hole 84 is integrated with the bearing 80. In FIGS. 2 and 3, 86 is an ignition plug disposed close to the bearing 80, and the ignition part of the ignition plug 86 is located near the center of the combustion chamber 44. In this way, the head cover 34 is formed with a slit that opens toward the front, and as a result, the head cover 34 is approximately U in plan view.
It becomes a character shape.

Since the bearing surface of the bearing 80 has a smaller diameter than the maximum diameter of the cams 72 and 74, the spark plug 86 is even closer to the cam shaft 36.
It can be placed close to the In other words, if there is a cam near the center of the camshaft 36, that is, above the center of the combustion chamber 44, the wall of the valve chamber that houses the valve mechanism (this wall is the ignition plug It is necessary to provide a hole (which also serves as the attachment/detachment hole 84),
While this wall is far from the center of the camshaft 36, according to the present application there is no cam at this position and the bearing 8
0, and its bearing surface has a diameter smaller than the maximum diameter of the cams 72 and 74, so that the wall of the valve chamber can be brought closer to the center of the camshaft 36. Therefore, the ignition plug 86 can be disposed at an angle closest to vertical without greatly tilting the engine while keeping the overall height of the engine low, which is a preferable position for obtaining good combustion.

The cylinder head 32 and head cover 34 are provided with auxiliary ribs 88 and 90 on the cooling air inflow side. In particular, the rib 8 of the cylinder head 32
An oil passage 92 (FIG. 2) is formed in 8, and this oil passage 92 supplies lubricating oil after lubricating the exhaust valve 60 located below in FIG. 3 to the exhaust valve located above in FIG. The sprocket 38 is guided through the loading chamber of the valve spring 64 into the sprocket receiving chamber 94 (FIG. 3).

On the other hand, since both exhaust valves 60, 60 are expanded so that their upper parts are separated from each other, a large area can be secured on the inflow side of the cooling air passage 80 and the ignition plug attachment/removal hole 84.
The cooling performance and detachability of the spark plug 86 are further improved.

Note that the cylinder head 32 and head cover 3
The wall of the spark plug attachment/removal hole 84 formed in the cylinder head 4 functions as a kind of pillar, and since the bearing 80 is formed integrally with this wall, the rigidity of the cylinder head 32 and the head cover 34 is also improved.

As shown in FIG.
It is fixed at 2. That is, bearings 76, 78 are connected to bolts 96, 96, 98, 98, and central bearing 8 is connected to bolts 96, 96, 98, 98.
0 is tightened with three bolts 100, and the outer periphery of the joint surface is further tightened with a large number of bolts 102, respectively.

Of these bolts, the two bolts on the inside of the slit are positioned so as to sandwich the ignition plug 86, so that the ignition plug 86 can be disposed close to the camshaft. As a result, the ignition plug 86 can be placed at an angle close to vertical, and the head cover 3
The sealing performance between the mating surfaces of the cylinder head 36 and the cylinder head 36 is also ensured. Also, the ignition plug 86 is inserted between the camshaft 36 and the ignition plug 86.
A boss portion for suspending the engine is integrally formed on the upper surface of the head cover in the vicinity of the area surrounded by the bolt on the opposite side of the spark plug and the bolts on both sides of the spark plug in the slit.

Reference numerals 104 and 104 designate inner rocker arms that slide and swing from above on the inner cams 72 and 72, respectively. The inner rocker arms 104, 104 are pivotally supported by a rocker arm shaft 106 inserted into the inner surface of the head cover 34 so as to be parallel to the cam shaft 36 (FIG. 4). This Rotsuka arm 104,
104, each one arm 108, 108 is the inner cam 7
2,72 sliding contact from above, local arm 110,1
10 presses the axis of each intake valve 50, 50. In FIG. 4, reference numeral 112 denotes a positioning bolt screwed into the head cover 34 from the inner surface so as to pass through the rocker arm shaft 106. That is, two bolts 98, 100 of the large number of bolts 96 to 102 are attached to this rocker arm shaft 106.
(Fig. 4) Recesses 114, 114
are formed, so these recesses 114, 114
The positioning bolt 112 is required to fix the position of the cylinder head 32 and to facilitate the insertion of the bolts 98, 100 when attaching the head cover 34 to the cylinder head 32.

Reference numerals 116 and 116 designate outer rocker arms that slide into contact with the outer cams 74 and 74 from above. These rocker arms 116, 116 are pivotally supported by two rocker arm shafts 118, 118 held by the head cover 34 so as to be parallel to the cam shaft. One arm 120, 120 of the rocker arms 116, 116 slides into contact with the outer cams 74, 74 from above, and the other arm 122, 122 presses the shaft end of each of the exhaust valves 60, 60. Furthermore, 124,1
24 is a positioning bolt that passes through each rocker arm shaft 118, 118, and 126, 126 is a bolt 1.
This is a recessed portion to avoid interference with 00. Note that the cam shaft 36 is connected to each rocker arm shaft 106, 118.
placed at a lower position. In this embodiment, the rocker arms 116, 1 on the exhaust side are
16 is disposed outside the combustion chamber 44, and the outer rocker arms 116, 116 are formed so that the arms 120, 120 side thereof are wider than the arms 122, 122, as shown in FIGS. Since there are two rocker arm shafts 118, 118
As a result, the ignition plug attachment/detachment hole 84 can be sufficiently enlarged. The point here is that the exhaust valves 60, 60 are provided in an inclined manner so that the gap between their upper parts gradually widens as described above.
Of course, this contributes to the enlargement of the spark plug attachment/removal hole 84.

The rocker arm 104,1 is attached to the head cover 34.
04, 116, 116, Rocker arm shaft 106,
118, 118 are assembled in advance, and each recess 1 is further assembled with positioning bolts 112, 124, 124
14, 126, and 126 are positioned as shown in FIG. 4, they are mounted on the cylinder head 32 and tightened with the respective bolts 96 to 102.

During operation of the engine 18, the camshaft 26 rotates, and the cams 72, 72, 74, 74 swing the rocker arms 104, 104, 116, 116 to move the intake valves 50, 50 and exhaust valves 60, 60 to predetermined positions. Opens and closes according to intake and exhaust timing. While the vehicle is running, running air flows into the cooling air passage 82 formed between the exhaust valves 60, 60, and particularly sufficiently cools the area around the threaded portion of the ignition plug 86. A portion of the cooling air passes between the intake valves 50 and 50 to the rear of the engine 18, and the other portion flows out from the spark plug attachment/removal hole 84 to the upper side of the engine 18.

(Effects of the Invention) As described above, the present invention forms the head cover into a substantially U-shape in plan view, forms a slit located between two exhaust valves on the inner wall of this U-shape, and forms a slit in the slit. The ignition plug is arranged, a bearing of the camshaft located above near the center of the combustion chamber is formed between the joint surface of the head cover and the cylinder head, and one of the bolts that fixes the head cover to the cylinder head on both sides of this bearing. Since the two spark plugs are placed in a position sandwiching the spark plug in the slit, the spark plug can be placed close to the bearing of the camshaft, the spark plug can be placed in a more favorable position, and the head cover and cylinder head can be placed close together. The sealing performance between the mating surfaces is also improved. Furthermore, since the slit opens on the side of the engine, the ease of attaching and detaching the spark plug and the cooling efficiency are improved.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a motorcycle to which an embodiment of the present invention is applied, FIG. 2 is a central longitudinal sectional side view of the main parts thereof, and FIG. 3 is a plan view showing the state in which the head cover is removed in FIG. 2. FIG. 4 is a partially sectional plan view of the head cover. 18...Engine, 36...Camshaft, 60...
Exhaust valve, 84...Ignition plug attachment/removal hole, 86...Ignition plug, bolt...100.

Claims (1)

[Claims] 1. For one cylinder, one overhead camshaft that crosses near the upper center of the combustion chamber, two exhaust valves disposed on one side of this camshaft, and an ignition section. In a single overhead camshaft engine having one spark plug facing near the center of the combustion chamber, the head cover covering the upper part of the cylinder head is approximately U-shaped in plan view and is located between the two exhaust valves, and the head cover covers the upper part of the cylinder head. A slit is formed substantially perpendicular to the shaft, and the spark plug is disposed within the slit, while a bearing for the camshaft located above near the center of the combustion chamber is formed between the joint surface of the head cover and the cylinder head. A single overhead camshaft engine, characterized in that two of the bolts for fixing the head cover to the cylinder head on both sides of the bearing are provided at positions sandwiching the spark plug on the inner wall of the slit.