JPH0316505B2 - - 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, a so-called overhead camshaft (overhead camshaft), in which a camshaft is disposed in the engine head and a valve train including the camshaft and a rocker arm shaft is accommodated in a valve train chamber, is adapted to high-speed rotation. There is an engine (hereinafter referred to as OHC). Furthermore, an engine is already known in which a plurality of intake valves and a plurality of exhaust valves are provided in each combustion chamber to improve intake and exhaust efficiency, thereby achieving high output.

When constructing an OHC engine with multiple intake and exhaust valves, conventionally, separate camshafts were provided for each intake and exhaust valve, resulting in a double overhead cam (DOHC) configuration.
An ignition plug attachment/removal hole was formed between both camshafts so as to penetrate upward through the valve train chamber. 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 using one camshaft and a plurality of rocker arms can be 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. For this reason, the camshaft had to be placed high, resulting in the problem of an increase in the size of the cylinder head. In addition, in order to secure the ignition plug attachment/removal hole, it is possible to deviate the camshaft to one side or make the rocker arm asymmetric between the intake side and the exhaust side, but in this case, there are problems caused by thermal imbalance. It is possible that this may occur.

(Object 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 via a rocker arm, the ignition plug is connected to the combustion chamber. An object of the present invention is to provide a single overhead camshaft type engine which can face near the center and easily secure its attachment/detachment hole, is suitable for downsizing the engine, and is capable of reducing adverse effects caused by thermal imbalance. .

(Structure of the Invention) According to the present invention, the object is to provide one camshaft within a substantially V-shaped included angle in side view formed by a plurality of intake valves and a plurality of exhaust valves. One spark plug is located on a vertical plane and its ignition part faces near the center of the combustion chamber, and a plurality of rocker arms that open and close intake and exhaust valves by means of a camshaft are provided. In one overhead camshaft type engine, the engine has a single overhead camshaft type engine in which a valve train including a valve train is housed in a valve train chamber, and an ignition plug attachment/removal hole is formed so as to pass through the valve train chamber and open upward. A single overhead camshaft engine characterized by having two intake-side rocker arms that are longer than the exhaust-side rocker arms, and an ignition plug attachment/removal hole arranged between these intake-side rocker arms. This is achieved by

(Embodiment) FIG. 1 is a vertical sectional view of a main part of an engine which is an embodiment of the present invention, and FIGS. 2 and 3 are sectional views taken along the - line and - line.

In FIG. 1, the reference numeral 12 designates a single-cylinder engine with a single overhead camshaft having one camshaft 13. As shown in FIG. 14
are intake valves, two of which are provided near one side of the combustion chamber 15. 16 is an intake passage, and a carburetor is connected to this intake passage 16. Reference numeral 18 designates exhaust valves, two of which are provided near the other side of the combustion chamber 15. An exhaust pipe is connected to the exhaust passage 19. The intake valve 14 and the exhaust valve 18 are provided in a cylinder head 22 joined above the cylinder block, and a cylinder head cover 23 is mounted above the cylinder head 22. A valve train chamber is formed by these cylinder head 22 and cylinder head cover 23, and this valve train chamber includes rocker arms 32, 33, 36, rocker arm shafts 34, 3.
5, 37, valve springs 27, 28, and other valve operating functions are accommodated. 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 provided on the crankshaft. When rotated, the camshaft 13 rotates once.

The camshaft 13 crosses above the combustion chamber 15, the two intake valves 14 are arranged in parallel to be orthogonal to one side of the camshaft 13, and a valve spring 27 is attached to the upper protrusion of the shaft portion 14a. is installed, and this valve spring 27
biases the intake valve 14 in the direction of closing. Two exhaust valves 18 are arranged in parallel on the other side of the camshaft 13 so as to be perpendicular to the camshaft 13. A valve spring 28 is attached to the upper protrusion of the shaft portion 18a of the exhaust valve 18, and biases the exhaust valve 18 in the closing direction. One camshaft 13 is located in the space within the angle formed by the intake valve 14 and the exhaust valve 18 that is approximately V-shaped in side view.
is pivotally supported between the mating surfaces of the cylinder head 22 and head cover 23. One exhaust cam 29 for opening and closing the exhaust valve 18 is formed approximately in the center of the camshaft 13, and two intake cams 30 and 31 are formed sandwiching this cam 29. The sprocket 24 is fixed to one end of the camshaft 13.

Reference numerals 32 and 33 denote a pair of left and right intake rocker arms that are divided into two, and these are connected to a pair of left and right rocker arm shafts 34 located above the camshaft 13;
35 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 intake valve 14. Note that the rocker arm shafts 34 and 35 are arranged between the camshaft 13 and the intake valve 14 so as to be parallel to the camshaft 13, but between these divided rocker arm shafts 34 and 35 there is an ignition valve which will be described later. A gap is formed through which the attachment/detachment hole 40 of the plug 38 passes. Reference numeral 36 denotes an exhaust 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 arms 34 and 35 on the intake side and the camshaft 13. One end of this 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 exhaust valves 18, respectively.

38 is a spark plug. An electrode 39 serving as an ignition portion at its tip faces approximately the center of the combustion chamber 15, and is installed between the two intake valves 14 so as to be approximately parallel to the intake valves 14. That is, the spark plug 38 is on a plane perpendicular to the camshaft 13,
Two divided intake side rocker arms 34, 3
It can be attached and detached from between 5. An attachment/detachment hole 40 is formed in the cylinder head 22 and head cover 23 for attaching and detaching the spark plug 38. That is, the cap member for holding the bearing of the camshaft 13 from above is also used by the head cover 23, and the 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 4
0 passes through the valve train chamber and opens toward the upper side of the engine 12. Therefore, the ignition plug 38 can be attached and detached from above the engine 12.

Here, the camshaft 13 is deviated toward the exhaust side, and the interval between the rocker arms 32 and 33 on the intake side is widened and set longer than the rocker arm 36 on the exhaust side. For this reason, the intake side rocker arm 3
A large ignition plug attachment/removal hole 40 is formed between 2 and 33.

41 is a cooling air passage formed in the cylinder head 22, and the opening 42 is connected to the two intake valves 14,
The other opening 43 passes between the two exhaust valves 18 and 18 and points toward the other side of the engine 12 . This cooling air passage 41 merges with the attachment/detachment hole 40 near the ignition plug 38 and is formed to pass below the camshaft 13. In this embodiment, as is clear from FIGS. 2 and 3, the cooling air passage 4 passes below the camshaft 13 and near the spark plug 38.
A lateral cooling air passage 44 is formed in the cylinder head 23, which joins the cylinder head 23. This cooling air passage 4
4 has an opening in the lateral direction on the side opposite to the sprocket 24.

(Effect of the invention) As described above, the present invention has a plurality of suction and
One camshaft, one spark plug, and a plurality of rocker arms that open and close the intake and exhaust valves are arranged within the included angle on the V side when viewed from the side surrounded by the intake valve, and the camshaft is used to exhaust air. The locker arms on the intake side are made into two pieces, the distance between them is widened, and the locker arms on the exhaust side are made longer than the locker arms on the exhaust side.The locker arm shafts of these locker arms on the intake side are divided into two, and the spark plug is installed between the divided locker arm shafts. The camshaft can be lowered to make the engine more compact. Further, since the rocker arm on the exhaust side, which becomes hot due to exhaust heat, is shorter than the rocker arm on the intake side, which has a lower temperature, it is possible to make the amount of thermal deformation of the rocker arms on the intake side and the exhaust side almost equal. As a result, the gap between the rocker arm and the cam surface of the camshaft, which is the gap between the end of the intake and exhaust valve shafts, can be adjusted against changes in engine temperature, and the negative effects caused by asymmetrical arrangement of the valve mechanism and cylinder head can be avoided. It can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a main part of an engine according to an embodiment of the present invention, and FIGS. 2 and 3 are sectional views taken along the - line and - line. 12...Overhead camshaft engine, 13...Camshaft, 14...Intake valve, 15...Combustion chamber, 18...
Exhaust valve, 32, 33...Intake side rocker arm, 3
4, 35... Rocker arm shaft, 36... Exhaust side rocker arm, 38... Ignition plug, 39... Electrode as ignition part, 40... Attachment/removal hole.

Claims (1)

[Claims] 1. A camshaft located within a substantially V-shaped angle formed by a plurality of intake valves and a plurality of exhaust valves in a side view, and a plane perpendicular to the camshaft. A spark plug, whose ignition part faces near the center of the combustion chamber, and a plurality of rocker arms that open and close intake and exhaust valves using a camshaft are provided, and a valve operating mechanism including the camshaft and rocker arms is provided. In a single overhead camshaft type engine which is housed in a valve train chamber and has an ignition plug attachment/removal hole formed so as to pass through the valve train chamber and open upward, the camshaft is deviated toward the exhaust valve side and the intake air is removed. A single overhead camshaft type engine characterized in that there are two side rocker arms, each of which is longer than an exhaust side rocker arm, and a spark plug attachment/removal hole is arranged between these intake side rocker arms.