JPS63235645A - Single over head cam engine - Google Patents

Abstract

PURPOSE:To improve the rigidity of a head cover after assembling, by forming a projection in and around the center of the head cover, and bolting this projection to a cylinder head, in case of an engine which has one camshaft traversing an upper part in and around the center of a combustion chamber. CONSTITUTION:In a 4-valve single overhead camshaft type one-cylinder engine 18, a camshaft 36 is pivotally supported laterally by a bearing 80 between joined surfaces of a cylinder head 32 and a cylinder head cover 34. And, with rotation of this camshaft 36, rocker arms 104 and 116 at both suction and exhaust sides supported, free of rock motion, by each of rocker arm shafts 106 and 118 are rocked by cams 72 and 74 at both suction and exhaust sides unitized with the camshaft 36, thereby opening or closing both suction and exhaust valves 50 and 60. In this case, the bearing 80 is projectingly installed in and around the center of the cylinder head cover 34 at a position corresponding to the upper vicinity of the center of a combustion chamber 44, setting it down to a projection, and it is clamped to the cylinder head 32 by a bolt 100 upon making this projection contact with the cylinder head 32.

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) 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 is inserted from the side or held between the cylinder head and a bearing cap fixed to the top surface of the cylinder head, and then a head cover is attached to cover them. As a result, there were problems in that the engine became larger and the number of parts increased.

Therefore, it is conceivable to hold the rocker arm shaft on the head cover side and hold the camshaft between the cylinder head and the base of 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.

(Object of the Invention) The present invention has been made in view of the above circumstances, and when the camshaft is held between the pedestals of the cylinder head and the head cover, and the rocker arm shaft is held on the head cover,
To provide a single overhead camshaft engine which uses the strength of a cylinder head to supplement the rigidity of a head cover, thereby making it possible to reduce the weight and size of the head cover.

(Structure of the Invention) According to the present invention, the object is to include one camshaft that crosses above the center of the combustion chamber, and intake/exhaust rocker arms that engage with this camshaft. In a single overhead camshaft engine that engages between the base surfaces of a cylinder head and a head cover, and also holds a rocker arm shaft that holds the rocker arm on the head cover side, a protrusion that abuts the cylinder head is formed near the center of the head cover. However, this is achieved by a single overhead camshaft engine characterized by bolting this protrusion 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 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. Er51, reference numeral 10 is a main frame, 12 is a front fork that supports the front wheel 14, and 16 is a rear wheel. Reference numeral 18 is a 4-valve, 1-head camshaft, 1-cylinder engine, in which an intake passage 20 extends from the rear of the vehicle body to an exhaust passage 22.
Main frame 1 so that each point points toward the front of the vehicle.
It is attached to 0. 24 is a carburetor that supplies air-fuel mixture to the intake passage 20; 26 is an exhaust pipe; this exhaust pipe 26 carries the exhaust gas discharged from the exhaust passage 22 to the engine 1;
It is bent so as to pass from the front of the engine 10 to the rear of the engine 10.

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

The cylinder head 32 has two intake ports 46, 46 (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, the exhaust pipe 26 (one of which is shown in FIG. 1) is provided with two pipes, and the 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. .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 six valves 50, 50, and 60.

After assembling the 60 and 6 valve springs 54, 54, 64, 64, they 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, one cam 72 and 74 are close to each other, and the inner cams 72.72 are spaced apart. are doing. 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 8o 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. This central bearing 80 serves as a protrusion that brings the cylinder head into contact with the vicinity of the center of the head cover. This camshaft 3
The sprocket 38 is fixed to one end (upper side in FIG. 3) of 6, 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 bed cover 34, as shown in FIG. 2.3. That is, a vertical gap is formed between the exhaust valves 60 and 60, opening 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 and 50. It opens to the rear through. This cooling air passage 82 is located between the re-exhaust valves 60, 60 and the bearing 8.
The portion close to 0 is a substantially cylindrical space, which serves as the ignition plug attachment/detachment hole 84. That is, the wall forming the attachment/detachment hole 84 is integrated with the bearing 80. Second
, 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.

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 80, and the bearing surface has a smaller diameter than the maximum diameter of the cams 72 and 74, so the valve drive The walls of the chamber can be brought closer to the center of the camshaft 36. Therefore, the spark plug 86 can be placed at the angle closest to vertical without greatly tilting while keeping the overall height of the engine low.
This is a favorable 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, there 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 spark 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.
The rigidity of the cylinder head 32 and head cover 34 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 bearings 76, 78 are connected to the bolts 96, 96, 98.
At 98, the central bearing 80 is tightened with three bolts 100, and the outer periphery of the joint surface is tightened with a large 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. 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 rocker arm 104° 104 has one arm 108, 108 in sliding contact with the inner cam 72, 72 from above, and a 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 side so as to pass through the rocker arm shaft 106. In other words, this rocker arm shaft 1
06, a recess 11 is formed at a position where two of the bolts 96 to 102 (FIG. 4) interfere.
4,114 is formed, this recess 114,1
The positioning bolt 112 is required in order to fix the position of 14 and make it easier to insert the poles 98 and 100 when attaching the head cover 34 to the cylinder head 32.

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 116,1
16 is one arm 120.120 is the outer cam 74.74
The other arm 122, 122 presses the shaft end of each exhaust valve 60, 60. In addition, 124°124
126 and 126 are recessed portions 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, not only the exhaust side rocker arm 116.116 is disposed on the outside with respect to the combustion chamber 44, but also the outer rocker arm 116.
As shown in Figure 4, the arm 120°120 side is the arm 122.
Since it is formed to be wider than the rocker arm shaft 122, the interval between the two rocker arm shafts 118 and 118 can be increased, and as a result, the ignition plug attachment/removal hole 84 can be sufficiently enlarged. It goes without saying that the fact that the exhaust valves 60 and 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 head cover 34 has a rocker arm 104°104.1
16, 116, rocker arm shaft 106, 118, 118
are assembled in advance, and the positioning bolts 112, 124 are
, 124, each recess 114, 126, 126 is
After positioning the cylinder in the position shown in the figure, the cylinder is fitted onto the rod 32, and each bolt 96 to 102 is tightened.

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. ．． 116 to open and close the intake valves 50.50 and exhaust valves 60.60 according to predetermined intake/exhaust timings. While the vehicle is running, air flows into the cooling air passage 828 formed between the exhaust valves 60 and 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, in the present invention, a protrusion that contacts the cylinder head is formed near the center of the head cover, and this protrusion is bolted to the cylinder head, so that the rigidity of the head cover alone is reduced. Even if it is insufficient, its strength will be sufficiently increased when assembled to the cylinder head. Therefore, the head cover and the engine can be made lighter and smaller.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a motorcycle to which a first embodiment of the present invention is applied, FIG.
This figure is a plan view showing a state in which the head cover is removed in FIG. 2, and 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...center bearing, 82...
Cooling air passage. 84... Spark plug attachment/removal hole, 86... Spark plug, 104...
...Inner rocker arm. 116...Outside rocker arm. Patent applicant Yamaha Motor Co., Ltd. Agent Patent attorney Fumio Yamada (and one other person)

Claims (1)

[Claims] (1) It is equipped with one camshaft that crosses above the center of the combustion chamber, and each rocker arm for intake and exhaust that engages with this camshaft, and the camshaft is engaged between the joint surface of the cylinder head and the head cover. In a single overhead camshaft engine in which a rocker arm shaft that holds the rocker arm is held on the head cover side, a protrusion that abuts the cylinder head is formed near the center of the head cover, and this protrusion is bolted to the cylinder head. One overhead camshaft engine characterized by a stop.