JPS6253686B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is mounted on a small vehicle having one steering front wheel, and has two intake valves and two exhaust valves per combustion chamber, and one This invention relates to an overhead camshaft engine equipped with a double camshaft.

(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 is adapted to high-speed rotation. Also 1
A so-called four-valve engine is already known, in which two intake valves and two exhaust valves are provided for each combustion chamber, and high output is pursued by increasing intake and exhaust efficiency. OHC engines have a so-called single camshaft between the intake and exhaust valves.
There is an OHC (hereinafter referred to as SOHC) engine,
When this is combined with the four-valve engine, the layout around the cylinder head becomes a problem. In other words, in the case of a 4-valve engine, the spark plug should be placed so that its electrode faces approximately the center of the combustion chamber.
Because the valve mechanism such as the camshaft installed between the intake and exhaust valves is placed in a position sandwiched between the intake and exhaust valves, the ignition plug is in close proximity, especially when installing and removing the ignition plug. This is because it becomes difficult to secure a space (attachment/detachment hole).

In small vehicles such as motorcycles, which have a single steerable front wheel and a fuel tank, etc. located above the engine, the ignition plug was previously installed and removed from the side of the vehicle; In the case of an OHC four-valve engine, the ease of attaching and detaching the spark plug becomes a problem, and especially in air-cooled motorcycle engines with three or more cylinders, this problem becomes even more important in the middle cylinders. I'm getting old.

(Objective of the Invention) This invention was made in view of the above circumstances, and consists of arranging two exhaust valves and two intake valves one behind the other, and arranging the ignition plug so that the electrode is located in the center of the combustion chamber. When applying an engine with one overhead camshaft between the intake and exhaust valves to a small vehicle such as a motorcycle with one front wheel, it is possible to secure a sufficient hole for installing and removing the spark plug, and the layout of each part can be adjusted. The purpose of the present invention is to provide an overhead camshaft engine that can be operated easily.

(Structure of the Invention) According to the present invention, the object is to provide a small vehicle equipped with one steering front wheel held by a steering head pipe and an engine located diagonally below and rearward of the steering head pipe. Two exhaust valves are arranged in the front and two intake valves are arranged in the rear of the combustion chamber, one camshaft is disposed laterally between the exhaust valve and the intake valve, and The rocker arm shaft on the exhaust valve side is divided into left and right parts, and the rocker arm shaft on the exhaust valve side is divided into left and right parts to form both rocker arm shafts. This is achieved by an overhead camshaft engine for a small vehicle, characterized in that the attachment/detachment hole is located near the center of the engine.

In other words, the rocker arm shaft on the exhaust valve side is divided into left and right parts to avoid interference between the mounting/removal hole and the rocker arm shaft, and the mounting/removal hole is opened diagonally forward and upward, allowing for the installation and removal of the ignition plug from the rear under the steering shaft cylinder. This made it possible.

(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, and FIGS. 3 and 4 are sectional views taken along the - line and - line.

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 pivotally attached 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 an 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 the main pipe 6 and the down tube 7, respectively.
is held in Reference numeral 14 designates exhaust valves, two of which are provided near the front of the combustion chamber 15. The exhaust passage 16 opens in the vehicle traveling direction of the engine 12, and the exhaust gas exiting from the exhaust passage 16 is guided to the rear of the vehicle by an exhaust pipe 17. Reference numeral 18 denotes intake valves, two of which are provided near the rear of the combustion chamber 15. The intake passage 19 opens toward the rear of the engine 12, and a carburetor 20 is connected thereto. Exhaust valve 14
The intake valve 18 is provided in a cylinder head 22 joined above the cylinder block 21, and a cylinder head cover 23 is mounted above the cylinder head 22. In addition, 24 in the figure is a sprocket provided integrally with the camshaft 13, and a timing chain 26 is spanned between this sprocket 24 and a sprocket 25 provided on the crankshaft. When the camshaft 13 rotates twice, the camshaft 13 rotates once.

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. 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. Exhaust valve 14 and intake valve 1
In the approximately V-shaped space formed by 8, there is 1 horizontally.
A camshaft 13 is supported between mating surfaces of a cylinder head 22 and a head cover 23. One intake cam 29 for driving the intake valve 18 to open and close is formed approximately in the center of the camshaft 13.
Two exhaust cams 30 and 31 are formed with 9 in between. The sprocket 24 is fixed to one end of the camshaft 13.

Reference numerals 32 and 33 designate a pair of left and right exhaust rocker arms that are made separately, and these are rotatably supported by a pair of left and right rocker arm shafts 34 and 35, respectively, and one end thereof is connected to the cams 30 and 3, respectively.
1, and the other end faces the shaft end of each exhaust valve 14. Although the rocker arm shafts 34 and 35 are arranged coaxially, 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 pivotally supported by one rocker arm shaft 37 so as to be swingable. This rocker arm 36 has one end connected to the cam 29.
The other end is bifurcated and faces the shaft ends of the two intake valves 18 described above. 38 is an ignition plug, and the electrode 39 at its tip faces approximately the center of the combustion chamber 15 from a position surrounded by each exhaust valve 14 and intake valve 18, and
The exhaust valve 14 is located between the exhaust valves 14 and 14, and is mounted so as to be substantially parallel to the exhaust valve 14. The cylinder head 22 and the head cover 23 are formed with an attachment/detachment hole 40 for attaching/detaching the spark plug 38.
is opened diagonally upward and in front 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 ignition plug 3
At 8, a lateral heat dissipation passage 44 perpendicular to the cooling air passage 41 is formed in the cylinder head 23. The heat radiation path 44 has a side surface opposite to the sprocket 24 that opens laterally.

In the engine 12 configured as described above, when a motorcycle equipped with this engine 12 runs, the running air flows in from the front opening 42 of the cooling air passage 41 and hits the ignition plug 38, causing the ignition plug 38 is sufficiently cooled. After cooling the spark plug 38, the cooling air exits rearward through the rear opening 43. When the cooling air hits the ignition plug 38, it also sufficiently hits the mounting surface of the ignition plug 38. Since a heat radiation path 44 is formed in this cylinder head 23, the cooling air that enters from the front opening 42 is directed to the ignition plug 3.
8, the flow is disturbed and a turbulent flow is generated in the heat radiation path 44. Therefore, cooling of the cylinder head 22 is further promoted. Note that the cooling air passage 41 communicates with the attachment/detachment hole 40 for the ignition plug 38, but since a negative pressure is generated near the upper opening due to the running wind, the cooling air near the ignition plug 38 is It is also sucked out from the hole 40. Therefore, the inflow of cooling air from the front opening 42 is further promoted, increasing the cooling effect.

When attaching and detaching the spark plug 38, a tool may be inserted into the attachment/detachment hole 40 from the rear of the head pipe 5. There is a relatively large space at the bottom and rear of the head pipe, so workability is good.

Further, in the embodiment, the attachment/detachment hole 40 for the spark plug 38 is
is located between the divided locker arms 34 and 35 on the exhaust side as shown in FIG. 2, but the present invention is not limited thereto. It includes everything that has been done. That is, it includes those in which the attachment/detachment hole is completely inserted between the divided rocker arm shafts, those in which a wall forming the attachment/detachment hole is inserted, and furthermore, the wall is located close to the divided portions of the rocker arm shaft.

(Effects of the Invention) As described above, the present invention locates the two exhaust valves of the single overhead camshaft 4-valve type engine in the front, which is mounted diagonally below and behind the steering head pipe.
Divide the rocker arm shaft on the exhaust valve side into left and right,
Since the ignition plug attachment hole is opened diagonally forward and upward, it is possible to avoid interference between the ignition plug attachment hole and the rocker arm shaft, and to secure sufficient space for the attachment and detachment hole, and also to prevent the ignition plug attachment hole from interfering with the rocker arm shaft. The space near the rear and lower part can be used as a space for attaching and detaching the ignition plug, making it possible to arrange each member of the cylinder head without strain and to improve the ease of attaching and detaching the ignition plug.

[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, and FIGS. 3 and 4 are sectional views taken along the - line and - line. 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, 40...Removal hole.

Claims (1)

[Claims] 1. In a small vehicle equipped with one steerable front wheel held by a steering head pipe and an engine located diagonally below and behind the steering head pipe, two wheels are provided for each combustion chamber. An exhaust valve arranged at the front, an intake valve arranged at the rear, one camshaft arranged laterally between the exhaust valve and the intake valve, and an electrode facing approximately the center of the combustion chamber. and an attachment/detachment hole for the ignition plug that opens diagonally forward and upward, and the rocker arm shaft on the exhaust valve side is divided into left and right parts, and the attachment/detachment hole is provided near between the two rocker arm axes. An overhead camshaft engine for small vehicles that is characterized by its central position.