JPH0160673B2 - - 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. Therefore, there was a problem in that the ignition part of the spark plug could not be placed near the center of the combustion chamber.
Furthermore, even if the ignition plug can be placed in the desired position by offsetting the camshaft to avoid interference with the camshaft, the ignition plug is usually installed above the engine, making it difficult to attach and remove it. I had a problem with it getting worse. This problem has become particularly important in engines having three or more intake and exhaust valves.

Additionally, supporting the camshaft above the center of the combustion chamber is suitable for reducing the diameter and weight of the camshaft, but installing a bearing in this position is extremely difficult due to interference with the spark plug. It was hot.

On the other hand, it is desirable for the head cover to have a structure that can easily increase its rigidity so that it can be made thinner and lighter.

(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. A single overhead camshaft type that makes it easy to attach and detach the spark plug when placed in the ideal position, and is especially suitable for cases with three or more intake/exhaust valves, and is also suitable for thinning and lightweighting the head cover. The primary purpose is to provide an engine.

A second objective is to provide a single overhead camshaft engine that allows the camshaft bearing to be placed in an ideal position above the center of the combustion chamber without being subject to any major restrictions on the placement of the spark plug. do.

(Structure of the Invention) According to the present invention, the first object is to provide a combustion engine which has one overhead camshaft that crosses near the upper part of the center of the combustion chamber, and one spark plug whose ignition part faces near the center of the combustion chamber. In an overhead camshaft engine, an ignition plug is disposed on a plane perpendicular to the camshaft, and a pair of rocker arms are disposed on both sides of the spark plug, and one of the two rocker arm shafts that pivotally supports these rocker arms. This is achieved by a single overhead camshaft engine characterized in that its end is supported on a wall forming a spark plug attachment/removal hole.

The second object is to provide a single overhead camshaft engine that has one overhead camshaft that crosses above the center of the combustion chamber and one spark plug whose ignition part faces near the center of the combustion chamber. An ignition plug and a camshaft bearing are arranged on a plane perpendicular to the shaft, and a pair of rocker arms are arranged on both sides of the spark plug, and the inner ends of the two rocker arm shafts that pivotally support these rocker arms are used for ignition. This is achieved by a single overhead camshaft engine, which is supported on a wall forming a plug attachment/removal hole, and the cap of the bearing is integrated into this wall.

(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 correspond to the camshaft 3.
Orthogonal to 6.

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) with four bolts 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 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).

A cooling air passage 82 is formed in the cylinder head 32 and the head cover 34, as shown in FIGS. That is, a vertically elongated gap is formed between the exhaust valves 60, 60 that opens forward 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 a spark plug attachment/removal hole 84. That is, the wall forming the attachment/detachment hole 84 is integrated with the cap portion, which is the half of the bearing 80 on the head cover 34 side. In FIGS. 2 and 3, reference numeral 86 indicates 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. is located on a plane perpendicular to the camshaft 36. 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 has a substantially U-shape in plan view.

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 housing the valve mechanism (this wall is It is necessary to provide a plug attachment/removal 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.

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 are outer rocker arms that slide into contact with the outer cams 74 and 74 from above, and are located on both sides of the spark plug 86. These rotuka arms 1
16, 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. The inner ends of the rocker arm shafts 118, 118 are connected to the ignition plug attachment/removal hole 8.
It is supported by walls forming 4. 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. Note that 124 and 124 are positioning bolts that pass through each rocker arm shaft 118 and 118, and 126 and 126 are recessed portions to avoid interference with the bolt 100. Note that the cam shaft 36 is disposed at a lower position than each rocker arm shaft 106, 118. In this embodiment, the rocker arms 116, 116 on the exhaust side are not only disposed on the outside with respect to the combustion chamber 44, but also the outer rocker arms 116, 116 are disposed outside the arms 120, 120 as shown in FIGS. Since the sides are formed to be wider than the arms 122, 122, the distance between the two rocker arm shafts 118, 118 can be increased, and as a result, the spark plug attachment/removal hole 84 can be sufficiently enlarged. . 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.

(Effect of the invention) As described above, the first invention arranges the ignition plug on a plane perpendicular to the camshaft, and a pair of rocker arms are arranged on both sides of the ignition plug, making the ignition plug ideal. Three or more intake/exhaust valves can be arranged without difficulty while arranging them in different positions, and the ignition plug can be easily attached and detached. In addition, since the inner end of the locker arm shaft at the position sandwiching the ignition plug is supported by the wall that forms the ignition plug removable hole, the locker arm shaft can be held using the rigidity of the ignition plug removable hole. Since it is also supported from below, the head cover can be made thinner and lighter.

Further, according to the second invention, since the head cover side cap of the camshaft bearing is integrated into the wall forming the ignition plug attachment/removal hole, there is no need to sacrifice the installation position or angle of the ignition plug. It becomes possible to provide the bearing above the center of the combustion chamber, thereby increasing the rigidity of this cap and making it possible to securely fix it.

[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.

Claims (1)

[Scope of Claims] 1. In a single overhead camshaft engine having one overhead camshaft that crosses the vicinity above the center of the combustion chamber and one spark plug whose ignition part faces the vicinity of the center of the combustion chamber, the camshaft includes: An ignition plug is arranged on a plane perpendicular to the ignition plug, and a pair of rocker arms are arranged on both sides of the spark plug, and the inner ends of the two rocker arm shafts that pivotally support these rocker arms form a spark plug attachment/removal hole. A single overhead camshaft engine characterized by being supported on a wall. 2. In a single overhead camshaft engine that has one overhead camshaft that crosses near the upper part of the center of the combustion chamber and one spark plug whose ignition part faces near the center of the combustion chamber, on a plane perpendicular to the camshaft. A spark plug and a camshaft bearing are provided, and a pair of rocker arms are provided on both sides of the spark plug, and the inner ends of the two rocker arm shafts that pivotally support these rocker arms are connected to a wall that forms a spark plug attachment/removal hole. 1. A single overhead camshaft engine, characterized in that the engine is supported by a wall, and a cap of the bearing is integrated into the wall.