JPS63235666A - Single overhead cam engine - Google Patents

Abstract

PURPOSE:To aim at improvements in the ideal arrangement of a spark plug and its detachability, by forming a head cover covering the upper part of a cylinder head into almost U-shaped form in plane view, forming a slit almost orthogonal with an overhead camshaft, and setting up the spark plug in this slit. CONSTITUTION:In an interspace between joined surfaces of a cylinder head 32 and a head cover 34, a camshaft 36 is pivotally supported in lateral, while this camshaft 36 is set up in and around the central upper part of a combustion chamber. On the other hand, each cooling air passage 82 is formed in the cylinder head 32 and the head cover 34. In addition, in this cooling air passage 82, a part to be approached to a bearing 80 of the camshaft 36 between exhaust valves 64 is formed into a cylindrical space, setting this space to a spark plug detachable hole 84. And a spark plug 86 is set up so as to make it come nearer to the bearing 80 with this spark plug detachable hole 84, and an ignition part of the spark plug 86 is set up an and around the center of the combustion chamber. With this constitution, the ignition part of the spark plug 86 is adjoingly installed in an ideal position in and around the center of the combustion chamber, while the detachability and coolability of the spark plug 86 are both improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an IrA upper 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. There was a problem that the cooling performance of the ignition plug was poor.

On the other hand, it is desirable for the head force bar 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. When placed in an ideal position, it is possible to improve the ease of attaching and detaching the ignition plug, and also improve the cooling performance.
The purpose of the present invention is to provide a single overhead camshaft engine that is suitable for making the head cover thinner and lighter.

(Structure of the Invention) According to the present invention, this object is achieved by one overhead camshaft having 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 the engine, the head cover covering the upper part of the cylinder head is substantially U-shaped in plan view, and has a slit substantially orthogonal to the overhead camshaft, and the spark plug is located within the slit. Achieved by a camshaft engine.

(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 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, reference numeral 10 is a main frame, 12 is a front fork that supports a front wheel 14, and 16 is a rear wheel.

Reference numeral 18 denotes a four-valve, one-head camshaft, one-cylinder engine, which is mounted on the main frame 10 so that its intake passage 20 points toward the rear of the vehicle, and its exhaust passage 22 points toward the front of the vehicle. 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 is a cylinder head, 34 is a cylinder, and a head force bar (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 is fixed to one end of the camshaft 36.
is rotated at half the speed of the crankshaft 40 by a timing chain 42 which is connected to the crankshaft 4o. This camshaft 36 crosses the vicinity above the center of the combustion chamber 44 .

The cylinder head 32 has two intake ports 4s, 4s (Fig. 2.3) that open into the combustion chamber 44, and two exhaust ports 48.
48 are formed, each intake port 46.46 communicates with two said intake passages 20.20, and each exhaust port 48.48 communicates with two said 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 numeral 50.50 denotes an intake valve, and as is clear from FIG. 2, its valve shaft 52.52 is supported so as to be inclined rearward, and its entire valve 56.56 is connected to the intake port 46.50 by a valve spring 54.54. 46 is biased to close. In FIG. 3, reference numeral 58.58 indicates the axis of this intake valve 50.50, and as is clear from this figure, this axis 58.58 is perpendicular to the camshaft 36.

Reference numeral 60.60 denotes an exhaust valve, and as is clear from FIG. 48.48 is biased to close. Third
In the figure, 68°68 indicates the axis of this exhaust valve 60.60, and as is clear from this figure, this exhaust valve 60.60
are supported such that their upper parts gradually move away from each other.

The cylinder head 32 has each valve 50, 50, 60.

60 and each valve spring 54, 54, 64, 64 are fixed to the cylinder 30 (FIG. 1) by four bottles 70 shown in FIG.

As shown in FIG.
intake side cams 72.72 and two outer exhaust side cams 74.74 are formed, each one of the cams 72 and 74 are close to each other, while the inner cams 72.72 are spaced apart. ing. Both ends and the center of the camshaft 36 are supported 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 center bearing 80 is located between the inner cams 72 and 72 near the upper part of the center of the combustion chamber 44.
It is pivoted. The bearing surface of this bearing 80 is connected to each cam 72.
The diameter is smaller than the maximum diameter of cam 74, and in this embodiment, each cam 72
．． The diameter is even smaller than the minimum diameter portion of 74. The sprocket 38 is fixed to one end (upper side in FIG. 3) of the camshaft 36, and a gear mechanism (not shown) for detecting rotational speed is connected to the other end (lower side in FIG. 3).

The cylinder head 32 and the head cover 34 have a second
As shown in FIG. 3, a cooling air passage 82 is formed. That is, a vertically elongated gap is formed between the exhaust valves 60, 60, which opens toward the front and above 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 re-exhaust valves 60 and 60 and close to 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. 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 cam 72, 74, the spark plug 86 can be disposed closer to the camshaft 36. That is, the center of the camshaft 36, that is, the combustion chamber 4
4. If there is a cam near the top of the center, a wall of the valve chamber housing the valve mechanism (this wall also serves as the ignition plug attachment/removal hole 84) must be provided to avoid interference with the maximum diameter part of the cam. However, according to the present application, there is no cam at this position and there is a bearing 8o, and the bearing surface has a smaller diameter than the maximum diameter of the cams 72 and 74, so the valve drive The wall of the 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 flow side.

In particular, within the rib 88 of the cylinder head 32 is an oil passage 992 (
2), and this oil passage 92 supplies the lubricating oil after lubricating the exhaust valve 60 located below in FIG. 3 to the loading chamber of the valve spring 64 of the exhaust valve 60 located above in the same figure. The sprocket 38 is guided through the sprocket 38 into the housing chamber 94 (FIG. 3).

On the other hand, since the upper parts of the re-exhaust valves 60 and 60 are widened apart from each other, a large area can be secured on the inflow side of the cooling air passage 80 and the ignition plug attachment/detachment hole 84, and the cooling performance and attachment/detachment of the ignition plug 86 are improved. Improve further.

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

The head cover 34 is fixed to the cylinder head 32 by a large number of bolts 96-102, as shown in FIG. That is, the bearing 76.78 is the bolt 96.96.98.
98, the central bearing 80 is tightened with three bolts 100, and the outer periphery of the joint surface is further tightened with a number of bolts 102, respectively.

Reference numeral 104.104 denotes an inner rocker arm that slides into sliding contact with the inner cam 72.72 from above and swings. These 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). 108, 108 slide into inner cam 72.72 from above, and the local arm 110°1
10 presses against 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. In other words, this rocker arm shaft 1
06, a recess 11 is provided at a position where two of the bolts 96 to 102 (7) interfere with each other (see FIG. 4).
4,114 is formed, this recess 114,1
When installing the head cover 34 to the cylinder head 32 while fixing the position of the bolt 98. In order to make it easier to insert the lOO, a positioning pole 112 is required.

116.116 is an outer rocker arm that slides into contact with the outer cam 74.74 from above. These rocker arms 1
16, 116 are two rocker arm shafts 118, 11 held by the head cover 34 so as to be parallel to the cam shaft.
It is pivoted on 8. This rocker arm 116, 116
One arm 120, 120 slides into contact with the six outer valves 74, 74 from above, and the other arm 122, 122 presses the shaft end of each exhaust valve 60, 60. Note that 124° 124 is a positioning bolt passing through each rocker arm shaft 118, 118, and 126, 126 is a recessed portion to avoid interference with the bolt 100. Note that the cam shaft 36 is located at a position lower than each rocker arm shaft 106°118. In this embodiment, the rocker arm 116 on the exhaust side is
．． In addition to locating the outer rocker arm 116 outwardly with respect to the combustion chamber 44, the outer rocker arm 116 is located outside the arm 12o as shown in FIGS.

Since the 120 side is formed to be wider than the arms 122, 122, the distance between the two rocker arm shafts 118 and 118 can be increased, and as a result, the spark plug attachment/removal hole 84 can be expanded.
can be expanded sufficiently. Exhaust valve 60 here
．． Needless to say, the fact that the spark plug 60 is inclined so that the distance between the upper parts of the spark plug 60 gradually widens as described above also contributes to the enlargement of the spark plug attachment/removal hole 84.

The head cover 34 has a rocker arm 104°104,
116, l l 6, rocker arm shaft 106.11
8 and 118 in advance, and then the positioning bolt 11
2,124,124 each four parts 114,126.1
26 in Figure 4. After positioning, the cylinder head 32 is crowned 1. , tighten each bolt 96-102.

During operation of this engine 18, the camshaft 26 rotates and the cams 72, 72, 74, 74 move to the rocker arms 104, 104.
, 116, and 116 to open and close the intake valve 50.50 and the exhaust valve 60.60 according to predetermined intake/exhaust timing. While the vehicle is running, running air flows into the cooling air passage 82 formed between the exhaust valves 60 and 60, and the ignition plug 86
In particular, sufficiently cool the area around the screwed part. 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, in the present invention, the head cover is formed into a substantially U-shape in plan view, and the ignition plug is disposed within the slit formed by the inner wall of this U-shape. By attaching and detaching the spark plug obliquely, the ignition part can be exposed to an ideal position near the center of the combustion chamber, improving the ease of attaching and detaching the ignition plug and its cooling performance. In addition, since the wall that is approximately U-shaped in plan view formed by the inner wall of the slit and the approximately U-shaped wall in plan view that is formed by the outer wall of the head cover are closely opposed to each other, the rigidity of the head cover is increased and its thickness is reduced. This has the effect of reducing weight.

[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 vertical 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 (2)

[Claims] (1) A head cover that covers the top of the cylinder head in 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. Planar view abbreviation U
1. A single overhead camshaft type engine, characterized in that a slit is formed in a shape substantially orthogonal to the overhead camshaft, and the spark plug is positioned within the slit. (2) A boss portion for suspending the engine is formed near the innermost part of the slit and near a portion of the slit that crosses the head cover in the length direction of the slit. 1 Overhead camshaft engine.