JPH0321722B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) This invention provides a method for connecting the intake and exhaust valves using a single camshaft when each cylinder has a plurality of intake valves and a plurality of exhaust valves. The present invention relates to a single overhead camshaft type engine that is driven to open and close.

(Background of the Invention) Conventionally, there has been a so-called overhead camshaft (hereinafter referred to as OHC) engine in which a camshaft is disposed in the engine head and adapted to high-speed rotation. Also 1
Engines that pursue high output by providing a plurality of intake valves and a plurality of exhaust valves in each combustion chamber to increase intake and exhaust efficiency are already known.

When constructing an OHC engine with multiple intake and exhaust valves, conventionally, separate camshafts were provided for each intake and exhaust valve, and a double overhead cam (DOHC) configuration was used. A spark plug was placed between the shafts. But this
DOHC configurations had the problem of increasing the number of parts and making the engine larger. Therefore, a configuration in which all the intake and exhaust valves are opened and closed by a single camshaft has been considered, but in this case, the layout especially around the cylinder head becomes a problem. In other words, it is desirable to arrange the spark plug so that the electrode, which is the ignition part, faces approximately the center of the combustion chamber, but if the camshaft is located above the center of the combustion chamber, the valve mechanism such as the camshaft may This is because the ignition plugs are close together, making it particularly difficult to secure a space (attachment/detachment hole) for attaching and detaching the ignition plug. As a result, there was a problem in that the cylinder head became larger.

Further, when each intake/exhaust valve is opened and closed by a rocker arm, it is desirable to consider the relationship with the rocker arm and to enable a rational arrangement that is suitable for downsizing and has excellent workability.

(Purpose of the Invention) This invention was made in view of the above circumstances, and when a plurality of intake valves and exhaust valves are driven to open and close by a single camshaft, the ignition plug is positioned near the center of the combustion chamber. To provide a single overhead camshaft type engine which can easily secure a mounting/detaching hole while increasing the size of the engine, is suitable for miniaturization of the engine, and can be rationally arranged with excellent workability.

(Structure of the Invention) According to the present invention, one camshaft is located within a substantially V-shaped angle formed by a plurality of intake valves and a plurality of exhaust valves mounted on a cylinder head. and the intake side and exhaust side rocker arm shafts located above the camshaft are installed horizontally so that they form an almost inverted triangle when viewed from the side, and the center of the camshaft is centered on the intake and exhaust sides.
Position it below the line connecting the valve stem ends of the exhaust valve, and connect either the intake side or exhaust side rocker arm to 2.
An ignition plug is arranged between the cylinder heads so that its ignition part faces near the center of the combustion chamber, and the bearing split surface of the camshaft is positioned on the same plane as the upper surface of the cylinder head. Achieved by an overhead camshaft engine.

If the camshaft is deviated to one side with respect to the cylinder centerline and the ignition plug is tilted to the other side, the ignition plug attachment/detachment hole can be more easily secured to a larger size.

(Example) The present invention will be explained in detail below based on the drawings.

FIG. 1 is a partially sectional side view of a motorcycle equipped with an engine that is an embodiment of the present invention;
FIG. 2 is a longitudinal sectional view of the main part thereof, and FIGS. 3 and 4 are sectional views taken along the - line and - line in FIG. 2.

In FIG. 1, numeral 1 is a cradle type main frame, 2 is a front wheel fork, 3 is a front wheel, and 4 is a rear wheel. Numeral 5 is a steering head pipe constituting the main frame 1, and 6 is a main pipe whose front end is welded to the head pipe 5 and extends rearward approximately horizontally. Reference numeral 7 designates a down tube which also constitutes the main frame 1, and whose side surfaces are bent into a substantially inverted trapezoid shape, and whose front end is welded to the head pipe 5 and its rear end to the main pipe 6, respectively. Further, 8 is a tank rail, and 9 is a reinforcing stay. The front wheel fork 2 is rotatably supported by a head pipe 5 of the main frame 1. Reference numeral 10 denotes a rear arm that pivotally supports the rear wheel 4. Its front end is pivoted to the main frame 1 so as to be able to swing vertically, and a spring 11 with a damper is installed between the rear end and the main pipe 6. has been done.

Reference numeral 12 designates a single overhead camshaft type single cylinder engine having one camshaft 13, which is located below and rearward of the head pipe 5. The upper and lower parts of this engine 12 are held by the main pipe 6 and down tube 7, respectively. Two exhaust valves 14 are provided near the front of the combustion chamber 15, and the shafts of these valves are arranged in parallel in the direction of the camshaft 13 on a plane perpendicular to the camshaft 13. The exhaust passage 16 opens in the direction in which the engine 12 travels in the vehicle, and exhaust gas exiting from the exhaust passage 16 is guided to the rear of the vehicle by an exhaust pipe 17. 18 is an intake valve, and combustion chamber 15
Two valve shafts are provided near the rear of the camshaft 13, and these valve shafts are on a plane perpendicular to the camshaft 13.
are arranged in parallel in the direction. The intake passage 19 opens toward the rear of the engine 12, and a carburetor 20 is connected thereto. The center of the camshaft 13 is located at the suction/
It is located below the line connecting the valve shaft ends of the exhaust valves 14 and 18. The exhaust valve 14 and the intake valve 18 are connected to the cylinder head 2 connected above the cylinder block 21.
A cylinder head cover 23 is mounted above the cylinder head 22.
These cylinder head 22 and cylinder head cover 23 form a valve operating chamber, and this valve operating chamber accommodates a valve operating mechanism such as rocker arms 32, 33, 36, rocker arm shafts 34, 35, 37, valve springs 27, 28, etc. be done. In addition, 24 in the figure is the camshaft 1.
A timing chain 26 is spanned between this sprocket 24 and a sprocket 25 provided on the crankshaft, so that when the crankshaft rotates twice, the camshaft 13 rotates once. Rotate.

Next, the cylinder head 22 is
Describe the area. The two exhaust valves 14 are arranged side by side on the cylinder head 22 so as to be tilted forward, and a valve spring 27 is attached to the upper protrusion of the shaft portion 14a, and this valve spring 27 moves in the direction of closing the exhaust valve 14. It is energizing. Two intake valves 18 are arranged in parallel near the rear of the combustion chamber 15. The intake valve 18 is provided so as to be inclined rearward, and a valve spring 28 is attached to the upper protrusion of the shaft portion 18a, urging the intake valve 18 in the closing direction. Here, the valve shafts of the intake valve 18 and the exhaust valve 14 are located on a plane perpendicular to the camshaft 13. A camshaft 13 is laterally supported between the mating surfaces of the cylinder head 22 and the head cover 23 in a space within a generally V-shaped angle formed by the exhaust valve 14 and the intake valve 18. ing.
The center of the camshaft is the intake valve 18 and the exhaust valve 14.
It is located below the line connecting the ends of the valve stem. Further, as is clear from FIGS. 2 and 3, this camshaft 13 is offset toward the intake valve 18 side with respect to the center of the cylinder. One intake cam 29 for opening and closing the intake valve 18 is formed approximately in the center of the camshaft 13, and two exhaust cams 30, 31 sandwich this cam 29.
is formed. The sprocket 24 is fixed to one end of the camshaft 13.

Reference numerals 32 and 33 denote a pair of left and right exhaust rocker arms that are made separately, and these are connected to a pair of left and right rocker arm shafts 34 and 3 located above the camshaft 13.
5 so as to be able to swing independently, one end of which is in sliding contact with the cams 30 and 31, and the other end of which is opposed to the shaft end of each of the exhaust valves 14. The rocker arm shafts 34 and 35 are disposed coaxially, and a gap is formed between the two shafts through which an attachment/detachment hole 40 for a spark plug 38 (to be described later) passes. Reference numeral 36 denotes an intake rocker arm, which is rotatably supported by a single rocker arm shaft 37 located above the camshaft 13. The rocker arm shaft 37 is positioned so as to form a substantially inverted triangle in side view together with the rocker arm shafts 34 and 35 on the exhaust side and the camshaft 13. One end of the rocker arm 36 is in sliding contact with the cam 29, and the other end is bifurcated and faces the shaft ends of the two intake valves 18, respectively.

Reference numeral 38 denotes an ignition plug, and an electrode 39 which is the ignition part at the tip faces approximately the center of the combustion chamber 15 from a position surrounded by each exhaust valve 14 and intake valve 18, and is located between the two exhaust valves 14. It is attached so as to be substantially parallel to the exhaust valve 14. That is, the spark plug 38 is on a plane perpendicular to the camshaft 13,
It can be attached and detached from between the two rocker arm shafts 34 and 35 on the exhaust side. An attachment/detachment hole 40 is formed in the cylinder head 22 and head cover 23 for attaching and detaching the spark plug 38. In other words, the cap member that holds the bearing of the camshaft 13 from above is also used as the head cover 23.
This head cover 23 is integrally formed with an attachment/detachment hole 40 that closely contacts the cylinder head 22 side and communicates with the cylinder head 22.

This attachment/detachment hole 40 opens obliquely toward the front and upper side of the engine 12. Therefore, the ignition plug 38 can be attached and removed from the upper front of the engine 12, that is, from the lower rear of the head pipe 5.

41 is a cooling air passage formed in the cylinder head 22, and its front opening 42 is connected to two exhaust valves 1.
The rear opening 43 passes between the two intake valves 18, 18 and is oriented toward the front of the engine 12.
It passes through the gap and points toward the rear of the engine 12.
This cooling air passage 41 merges with the attachment/detachment hole 40 near the spark plug 38, and also joins the camshaft 13.
It is formed to pass under the In this embodiment, as is clear from FIGS. 3 and 4, the camshaft 1
A horizontal cooling air passage 44 is formed in the cylinder head 23, passing below the spark plug 38 and merging with the first cooling air passage 41 near the spark plug 38. The cooling air passage heat radiation passage 44 has a side surface opposite to the sprocket 24 that opens laterally.

In the above embodiment, the attachment/detachment hole 40 of the spark plug 38 is inclined toward the exhaust valve 14 side, and the camshaft 13 is connected to the intake valve 14 side.
Although the spark plug 38 is tilted toward the intake valve 18 side, it is also possible to tilt the camshaft 13 toward the opposite side. In this case, two intake rocker arms 36 may be provided and the spark plug 38 may be placed between them.

(Effect of the invention) As described above, the present invention has a plurality of suction and
One camshaft and the rocker arm shafts on the intake side and exhaust side located above the camshaft are arranged so as to form an almost inverted triangle when viewed from the side, within an included angle surrounded by the exhaust valve on the V side when viewed from the side. Since the center of the camshaft is located below the line connecting the ends of each valve shaft, these can be compactly housed in parallel and at a low position within the included angle of the V-shape.

In addition, the ignition plug is placed so that its ignition part faces near the center of the combustion chamber and is located between the two rocker arms on the intake side or the exhaust side.
Since the spark plug can be attached and detached from between the two rocker arms, it is possible to arrange the spark plug in an ideal position while also securing a hole for attaching and detaching the spark plug.

Furthermore, since the camshaft is located on the same plane as the top surface of the cylinder head, that is, the surface where it meets the cylinder head cover, machining of the split surface of the camshaft bearing can be done at the same time as machining the top surface of the cylinder head, reducing machining man-hours. is reduced, resulting in better workability.

Further, by shifting the camshaft to one side with respect to the cylinder center and tilting the spark plug to the other side, it is possible to secure an even larger spark plug attachment/removal hole.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view of a motorcycle equipped with an engine that is an embodiment of the present invention;
FIG. 2 is a longitudinal sectional view of the main part thereof, and FIGS. 3 and 4 are sectional views taken along the - line and - line in FIG. 2. 12...Overhead camshaft engine, 13...Camshaft, 14...Exhaust valve, 15...Combustion chamber, 18...
Intake valve, 34, 35... Rotsuka arm shaft, 38...
...Spark plug, 39...Electrode as ignition part, 40...
...Detachment hole.

Claims (1)

[Scope of Claims] 1. A camshaft and an intake valve located above the camshaft within a generally V-shaped angle formed by a plurality of intake valves and a plurality of exhaust valves mounted on the cylinder head. The rocker arm shafts on the side and exhaust sides are installed horizontally so that they form an approximately inverted triangle when viewed from the side, and the center of the camshaft is located below the line connecting the valve shaft ends of the intake and exhaust valves. and two rocker arms on the exhaust side, and an ignition plug is arranged between them so that its ignition part faces near the center of the combustion chamber, while the bearing split surface of the camshaft is on the same plane as the top surface of the cylinder head. A single overhead camshaft type engine characterized by being located at. 2. Claim 1, wherein the camshaft is arranged offset to one side with respect to the cylinder centerline, and the ignition plug is inclined toward the other side.
Single overhead camshaft engine as described in Section 1.