JPS63235610A - One-overhead camshaft type engine - Google Patents

Abstract

PURPOSE:To enable a comparatively large sparking plug installation hole to be secured by providing cams for intake and exhaust valves on each side of a bearing which supports a cam shaft at a position near by the upper portion of the middle of a combustion chamber on the am shaft provided in such a way to cross the above the middle of combustion chamber. CONSTITUTION:In a 4-valve/1-overhead camshaft type 1-cylinder engine, a cam shaft 36 is rotatably supported sideways by bearing 80 in a space between contact surfaces of a cylinder head 32 to a cylinder head cover 34. By the rotation of the cam shaft 36, intake and exhaust sides rocker arms 104, 116 supporter oscillatably by a rocker arm shaft are made to oscillate through intake and exhaust sides cams 72, 74 so as to make intake and exhaust valves 50, 60 open close. In this case, at a position corresponding to the upper portion of a combustion chamber 44, a bearing 80 projectedly provided near by the middle of the head cover 34 is put between the intake and exhaust sides cams 72, 74 which are provided on both sides of the bearing respectively, and the exhaust side cams 74 are arranged at positions far from the bearing 80. With this arrangement, a comparatively large sparking plug mounting/demounting 84 can be secured.

Description

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

(Background of the Invention) Some engines of this type have one spark plug disposed between two exhaust valves, but when the camshaft bearing is disposed near the upper center of the combustion chamber, this bearing Therefore, there was a problem in that the hole for installing and removing the ignition plug became narrow. In other words, if the cam of the camshaft is not located near the upper part of the center of the combustion chamber, or if a bearing is not installed here, a relatively large spark plug installation/removal hole can be secured by placing the spark plug installation/removal hole close to this camshaft. However, if there is a bearing near the center, a problem arises in that the ignition plug attachment/removal hole must be made smaller.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it is an object of the present invention to secure a relatively large ignition plug attachment/removal hole even though the camshaft bearing is located near the upper center of the combustion chamber. An object of the present invention is to provide an overhead camshaft engine capable of improving the workability of attaching and detaching a spark plug.

(Structure of the Invention) According to the present invention, this object includes: an overhead camshaft that crosses the vicinity above the center of the combustion chamber; a bearing that supports this camshaft above the center of the combustion chamber; In a single overhead camshaft engine comprising a plurality of intake valves and two exhaust valves that are opened and closed, and one spark plug disposed between the two exhaust valves so that the ignition part faces near the center of the combustion chamber, the cam At least one intake valve cam and one exhaust valve cam are provided on each shaft with the bearing in between, and at least one of the exhaust valve cams is disposed at a position far from the bearing. This is achieved by a single overhead 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 indicates a main frame, 12 a front fork that supports a front wheel 14, and 16 a rear wheel.

Reference numeral 18 denotes a four-valve, one-head camshaft, one-cylinder engine, which is attached to the main frame IO so that its intake passage 20 points toward the rear of the vehicle body, and its exhaust passage 22 points toward the front of the vehicle body. 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 exhaust gas discharged from the exhaust passage 22 from the front of the engine 10 to the rear through below 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 near one side of the center of the combustion chamber 44 .

The cylinder head 32 has two intake ports 46, 46 (FIGS. 2 and 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. .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 so that their upper parts gradually move away from each other (9)
Ru.

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

60 and each valve spring 54, 54, 64, 84 is fixed to the cylinder 30 (FIG. 1) by a four-piece bottle 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. The camshaft 36 is pivotally supported at both ends and the center by three sliding 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 head cover 34 have a
As shown in the figure, a cooling air passage 82 is formed. 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 the.

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, 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 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, 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 both 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 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. 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 suppresses 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
In 06, two of the numerous portos 96-102 98. Zo.

Since the four parts 114, 114 are formed at the positions where the concave parts 114 and 114 interfere (Fig. 4), when fixing the positions of these concave parts 114 and 114 and attaching the head cover 34 to the cylinder and the rad 32, insert the poles 98 and 100. In order to facilitate this, 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 outer cam 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 that passes through each rocker arm shaft 118, 118, and 126, 126 is a recessed portion to avoid interference with the port 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 on the outside with respect to the combustion chamber 44, the outer rocker arm 116 is arranged so that its arm 120, 120 side is located on the arm 122, 122 as shown in FIG.
Since it is formed to be wider than that of the rocker arm shaft 118, the distance between the two rocker arm shafts 118, 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.

Head cover 34mm is 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 to make each recess 114, 126, 126 a fourth
After positioning in the position shown in the figure, cover the cylinder with the rod 32 and tighten with each port 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, 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, the cooling air passage 828 formed between the exhaust valves 60 and 60 flows into the cooling air passage 82, and the vicinity of the threaded portion of the ignition plug 86 is particularly sufficiently cooled. 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.

According to the above embodiment, since the upper portions of both exhaust valves are widened, the ignition plug attachment/removal hole can be made even larger.

(Effects of the Invention) As described above, in the present invention, since at least one exhaust valve cam is disposed at a position far from the bearing near the upper center of the combustion chamber, A large space can be secured and the ignition plug attachment/removal hole can be enlarged. This improves the workability of attaching and detaching the spark plug. Furthermore, by arranging both the two exhaust valve cams at positions far from the bearing, the ignition plug attachment/removal hole can be made even larger.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a motorcycle IP to which an 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...Ignition plug attachment/removal hole, 86...Ignition plug, 104...Inner rocker arm, 116...Outer rocker arm. Patent applicant Yamaha Motor Co., Ltd. Agent Patent attorney Fumio Yamada (and one other person)

Claims (2)

[Claims] (1) One overhead camshaft that crosses near the upper center of the combustion chamber, a bearing that supports this camshaft near the upper center of the combustion chamber, multiple intake valves and two exhaust valves that are opened and closed by the camshaft. In a single overhead camshaft engine equipped with a valve and an ignition plug disposed between both exhaust valves so that an ignition part faces near the center of a combustion chamber, the camshaft has a valve on each side with the bearing in between. 1. A single overhead camshaft engine, characterized in that at least one cam for an intake valve and at least one cam for an exhaust valve are provided, and at least one of the cams for the exhaust valve is disposed at a position far from the bearing. (2) 1 as set forth in claim 1, characterized in that two intake valves and two intake valve cams are provided, and two exhaust valve cams are both provided at positions far from the bearings.
Overhead camshaft engine.