JPH02539B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention has one overhead camshaft that traverses near the upper center of the combustion chamber, and has four rocker arms for each cylinder. This invention relates to a single overhead camshaft engine in which two intake valves and two exhaust valves are opened and closed.

(Background of the Invention) In this type of engine, an overhead camshaft and a rocker arm shaft have conventionally been mounted on the cylinder head side, and a head cover has been placed over the top of this assembly. That is, the overhead camshaft or rocker arm shaft was inserted from the side or held between the cylinder head and a bearing cap fixed to its upper surface, and then a head cover was attached to cover them. This resulted in problems such as the engine becoming larger and the number of parts increasing.

Therefore, it is conceivable to hold the rocker arm shaft on the head cover side and hold the camshaft between the mating surfaces of the cylinder head and the head cover. However, in this case, a large reaction force from the rocker arm is applied to the head cover, resulting in problems such as insufficient rigidity and increased weight.

On the other hand, when using a single camshaft and opening and closing multiple intake and exhaust valves for each cylinder via rocker arms, it is difficult to reasonably arrange the spark plug so that it faces near the center of the combustion chamber. It was hot.

(Purpose of the Invention) The present invention was made in view of the above circumstances, and is designed to hold one camshaft between the mating surfaces of the cylinder head and the head cover, and to provide four cylinders for one cylinder.
While opening and closing multiple intake and exhaust valves through each rocker arm, when holding the rocker arm shaft in the head cover, the strength of the cylinder head is used to supplement the rigidity of the head cover, making the head cover lighter and more compact. It is an object of the present invention to provide a single overhead camshaft type engine in which a spark plug facing near the center of a combustion chamber can be arranged without difficulty.

(Structure of the Invention) According to the present invention, the purpose is to provide one camshaft that crosses the upper part near the center of the combustion chamber, and two intake and two exhaust gases that engage with this camshaft for each cylinder. It is equipped with a rocker arm and a plurality of intake and exhaust valves that are opened and closed by these rocker arms, and the camshaft is held between the mating surfaces of the cylinder head and the head cover, and the rocker arm shaft that holds the rocker arm is placed on the head cover side. In a single overhead camshaft engine, the valve train including the camshaft and the rocker arm is housed in a valve train chamber formed between the cylinder head and the head cover. The ignition plug is placed in a position surrounded by two rocker arms, with its ignition part facing near the center of the combustion chamber, while the camshaft is sandwiched between a plurality of cams on the camshaft on the opposite side of the ignition plug. This is achieved by a single overhead camshaft engine characterized in that a protrusion that protrudes from the cylinder head and comes into contact with the cylinder head is formed on the head cover, and the protrusion is bolted to the cylinder head.

(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 . A valve operating chamber is formed between the cylinder head 32 and the head cover 34, and this valve operating chamber is fluid-tightly closed at the joint surface between the cylinder head 32 and the head cover 34.
This valve operating chamber accommodates a valve operating system including four rocker arms 104, 104, 116, and 116, which will be described later, together with the camshaft 36.

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 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 central bearing 80 is a protrusion that brings the cylinder head into contact with the vicinity of the center of the head cover. The sprocket 38 is fixed to one end (upper side in FIG. 3) of this camshaft 36, and a gear mechanism (not shown) for detecting rotational speed is connected to the other end (lower side in FIG. 3). Cylinder head 32 and head cover 3
4, a cooling air passage 82 is formed as shown in FIGS. 2 and 3. That is, the exhaust valves 60, 60
A vertically elongated gap is formed between them that opens toward the front and above of the engine 18, and in this embodiment, this gap further opens from below the central bearing 80 to the rear through between the intake valves 50, 50. ing.
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 a spark 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, reference numeral 86 denotes an ignition plug disposed close to the bearing 80, and the ignition portion of the ignition plug 86 is located near the center of the combustion chamber 44.

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),
Although this wall is far from the center of the camshaft 36, according to the present application, there is no cam at this position but a bearing 80, and the bearing surface has a smaller diameter than the maximum diameter of the cams 72 and 74, so the wall of the valve train chamber is It can be brought close 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
8 is formed with an oil passage 992 (FIG. 2), and this oil passage 92 is connected to the exhaust valve 60 located below in FIG.
The lubricating oil after lubricating the exhaust valve 60 is guided to the sprocket 38 housing chamber 94 (FIG. 3) through the loading chamber of the valve spring 64 of the exhaust valve 60 located at the upper side of the figure.

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.

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 from above, and the other arm 110,1
10 presses the shaft end 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 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 relative to the combustion chamber 44, the outer rocker arms 116, 116 are arranged relative to the third and fourth
As shown in the figure, the arm 120, 120 side is the arm 12.
2, 122, the distance between the two rocker arm shafts 118, 118 can be widened, and as a result, the spark plug attachment/removal hole 84 can be expanded.
can be expanded sufficiently. It goes without saying that the fact that the exhaust valves 60, 60 are provided at an angle so that the gap between their upper parts gradually widens as described above also 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 provides a cylinder head located near the center of the valve chamber between two rocker arms located on one side of the camshaft, that is, between a plurality of cams formed on the camshaft. Since a contacting protrusion is formed and this protrusion is bolted to the cylinder head, even if the head cover alone lacks rigidity, its strength is sufficiently increased when assembled to the cylinder head. This allows the head cover and engine to be made lighter and smaller. Further, the ignition plug is placed at a position surrounded by the camshaft and two rocker arms located on one side of the camshaft, and the protrusion is positioned at a position surrounded by the camshaft and two rocker arms located on the other side. Therefore, the ignition plug can be easily positioned near the center of the combustion chamber.

[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, 50...
Intake valve, 60... Exhaust valve, 72, 74... Cam,
76, 78...Bearing, 80...Central bearing, 82
...Cooling air passage, 84...Ignition plug attachment/removal hole, 86...
...Spark plug, 104...Inner lock arm, 116
...Outer rotuka arm.

Claims (1)

[Claims] 1. One camshaft that crosses above the center of the combustion chamber, two rocker arms each for intake and exhaust for one cylinder that engage with this camshaft, and these rocker arms. It is equipped with a plurality of intake and exhaust valves that are opened and closed, the camshaft is held between the mating surfaces of the cylinder head and the head cover, and the rocker arm shaft that holds the rocker arm is held on the head cover side, and the camshaft is and a single overhead camshaft engine in which a valve train including a rocker arm is housed in a valve train chamber formed between the cylinder head and the head cover, the camshaft being surrounded by two rocker arms located on one side thereof. The ignition plug is placed in a position where the ignition part faces near the center of the combustion chamber, while the camshaft is held between the plurality of cams on the camshaft and protrudes to the opposite side of the ignition plug to the cylinder head. 1. A single overhead camshaft engine, characterized in that a contacting protrusion is formed on the head cover, and the protrusion is bolted to the cylinder head.