JPH11229822A - Overhead valve engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the blowby of intake air from the exhaust valve opening even during valve overlap. SOLUTION: In this overhead valve engine, a valve shaft of an intake valve 5 is inclined so as to stick out toward an intake port 1. In this case, the valve shaft of an exhaust valve 6 is made to face in a direction substantially parallel with a cylinder center shaft line 7. A valve camshaft 9, tappets 10, 10, and push rods 11, 11 are arranged left and right on one side of a cylinder block 12, and rocker arms 40, 41 are provided to a cylinder head 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an overhead valve engine.

[0002]

2. Description of the Related Art As a prior art of an overhead valve engine, an intake port and an exhaust port are led out of an intake valve port and an exhaust valve port in mutually opposite directions, and a valve shaft of the intake valve is inclined in a direction in which the intake port is drawn out. There is something. This type of engine has the advantage that it is possible to provide a large intake valve and to reduce the bending of the intake port, thereby increasing the intake efficiency.

In the above prior art, the valve shaft of the exhaust valve is also inclined in the direction in which the exhaust port is drawn out, and the intake and exhaust valves are arranged in a V-shape. Therefore, a so-called overhead cam type valve operating mechanism is employed. In this valve operating mechanism, a wrapping transmission is provided in front of a cylinder block with the direction of the central axis of the crankshaft as the front-rear direction, and a valve operating camshaft and a tappet are provided in a cylinder head.

[0004]

The above prior art has the following problems. A wrapping transmission is provided in front of the cylinder block, and is composed of relatively large parts such as a drive wheel, a driven wheel, a wrapping transmission band, a tension, and a transmission cover that integrally covers these. I have. For this reason, the size of the engine in the front-rear direction becomes longer.

[0005] Since the wrapping transmission is provided in front of the cylinder block, when performing a series of maintenance from the wrapping transmission to the intake and exhaust valves, a transmission cover in front of the cylinder block and a head cover of the cylinder head are provided. It is necessary to remove both, and to perform maintenance from two directions, the work becomes complicated. In addition, maintenance conditions become severe, and the types of devices to be mounted are greatly restricted.

[0006] Since the valve head camshaft and the tappet are provided on the cylinder head, the dimension in the cylinder axis direction becomes longer.

[0007] Since the intake and exhaust valves are arranged in a V-shape, the intake air easily flows through the exhaust valve port when the valves overlap.

[0008]

The main structure of the invention of claim 1 is as follows (see FIGS. 1 and 2). The intake port (1) and the exhaust port (2) are the intake valve port (3) and the exhaust valve port
In an overhead valve engine derived in the opposite direction from (4) and the valve shaft of the intake valve (5) is tilted in the direction in which the intake port (1) extends, when viewed in a direction parallel to the cylinder center axis (7). ,
The direction of the crankshaft center axis (8) is the front-rear direction, and the direction orthogonal to the crankshaft center axis (8) is the left-right direction, and the valve shaft of the valve operating cam shaft (9) and the valve shaft of the intake valve (5) and each port (1). ) And (2) are oriented long in the front-rear direction, and the cylinder center axis is
When viewed in a direction parallel to the direction orthogonal to (7) and the crankshaft central axis (8), the valve axis of the exhaust valve (6) is the cylinder central axis.
(7) oriented substantially parallel to the valve cam shaft
(9) Tappet (10) (10) and push rod (11)
(11) are disposed on the left and right sides of the cylinder block (12), and the rocker arms (40) (4) are attached to the cylinder head (14).
Those provided with 1).

[0009]

Operation and effect of the present invention (invention of claim 1) The following operation and effect can be obtained (see FIGS. 1 and 2). Since a valve operating mechanism is used in which the valve operating cam shaft (9), tappets (10) (10), and push rods (11) (11) are disposed on one side of the cylinder block (12), the cylinder block Compared to an overhead cam type valve train that requires a wrapping transmission in front of the
The size of the engine in the front-rear direction can be shortened. Further, since the valve train can be made more compact than the wrapping transmission, the size of the engine in the left-right direction is not so large.

When performing a series of maintenance from the push rod (11) to the valves (5) and (6), the head cover (20) of the cylinder head (14) may be removed and maintenance may be performed from one direction. , Its work is simplified. In addition, since the maintenance conditions are mild, there are few restrictions on the models to be mounted.

A rocker arm is mounted on the cylinder head (14).
Although (40) and (41) are provided, the size of the engine in the direction of the cylinder center axis (7) can be shortened as compared with the overhead cam type in which the valve head cam shaft and the tappet are provided on the cylinder head.

When viewed in a direction parallel to a direction perpendicular to the cylinder center axis (7) and the crankshaft center axis (8), the exhaust valve
Since (6) is oriented in a direction substantially parallel to the cylinder center axis (7), even when the valve overlaps, the intake air hardly flows through the exhaust valve port (4).

(Invention of claim 2) In addition to the effect of claim 1, the following effect is obtained (see FIG. 1 (A)). One intake valve (5) and one exhaust valve (6) are provided for one combustion chamber (17), and each valve (5) (6) is viewed in a direction parallel to the cylinder center axis (7). Is arranged closer to the push rods (11) and (11) than the crankshaft center axis (8), the rocker arms (40) and (41) can be formed shorter, and the deformation thereof can be reduced. Timing accuracy is improved.

(Invention of claim 3) In addition to the effect of claim 1 or 2, the following effect is obtained (see FIG. 1C). On the piston facing surface (39) of the cylinder head (14), a cavity (37) is formed in a region including each of the valve ports (3) and (4) and the spark plug insertion port (22), and other regions are formed. Since the squish area (38) is used, a squish flow is introduced into the cavity (37),
The flame propagation in 7) is promoted, and the combustion performance is enhanced.

(Invention of claim 4) One intake valve (3) and one exhaust valve (4) are provided for one combustion chamber (17), and viewed in a direction parallel to the cylinder center axis (7). , Each valve port (3) (4)
Of the crankshaft is located at one side to the left and right from the crankshaft center axis line (8), and the spark plug insertion port (22) is located between the valve ports.
The squish area is wide around the spark plug insertion port (22) because it is located to the left and right and the other side from (18).
(38) is formed, and the flame generated by the ignition plug (21) propagates in the cavity (37) at a high speed by a strong squish flow, so that the combustion performance is enhanced.

(Invention of claim 5) In addition to the function and effect of claim 3 or 4, the following function and effect can be obtained (FIG. 1).
(A)). Since the periphery of each of the valve ports (3) and (4) and the periphery of the spark plug insertion port (22) are partially spherical, the cavity (37) can be formed as a multi-spherical combustion chamber.
Combustion performance increases.

(Invention of claim 6) In addition to the function and effect of any one of claims 1 to 5, the following function and effect can be obtained (see FIG. 2). Of the rocker arm pivots (13) (33), the intake valve
The rocker arm pivot portion (33) for (5) is oriented long in the left-right direction, and a rocker arm output portion (15) is led out from one end of the rocker arm pivot portion (13) to the side opposite to the exhaust valve (6). From the other end of the rocker arm pivot (33), a rocker arm input (16) is connected to a rocker arm for the exhaust valve (6).
Since it is led to the (41) side, the rocker arm (40) for the intake valve (5) can have a simple structure.

(Invention of Claim 7) In addition to the functions and effects of the inventions of Claims 1 to 6, the following effects are obtained (see FIG. 2).

Of the rocker arm pivots (13) (33),
A rocker arm (41) for the exhaust valve (6) is formed of sheet metal,
Since the rocker arm pivot portion (33) is of a pivot type, the rocker arm (41) can be manufactured at low cost.

(Invention of Claim 8) In addition to the effect of any one of the inventions of Claims 1 to 7, the following effect is obtained (see FIG. 2). When viewed in a direction parallel to the central axis (8) of the crankshaft, the cylinder (19) is inclined to
Since the valve operating camshaft (9), tappets (10) (10) and push rods (11) (11) are arranged on the lower side of the left and right sides of (12), the height of the engine Dimensions can be shortened.

[0021]

Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are diagrams for explaining an embodiment of the present invention. In this embodiment, an air-cooled single-cylinder spark ignition tilt engine is used.

The configuration of this engine is as follows. As shown in FIG. 2, the crankcase (42) and the cylinder (1
9) and a cylinder block (12) is formed.
A cylinder head (14) is mounted on the top dead center side of (19), and a head cover (20) is mounted on the cylinder head (14).

The crankcase (42) has a crankshaft (2).
3) and the valve operating cam shaft (9) are installed in parallel. The piston (25) is fitted inside the cylinder (19), and the crankshaft (2)
3) and the piston (25) are connected by a connecting rod (24). The valve gear cam gear (26) meshes with the crank gear (34), and the valve gear cam shaft (9) is driven by the crank shaft (23). The idle gear (27) meshes with the crank gear (34), the governor gear (28) meshes with the idle gear (27), and the governor (32) is driven by the crank shaft (23).

The construction of the cylinder head (14) and the valve train is as follows. As shown in FIG. 1 (C), the intake port
(1) and the exhaust port (2) are the intake valve port (3) and the exhaust valve port (4)
And the valve shaft of the intake valve (5) is tilted in the direction in which the intake port (1) extends.

As shown in FIG. 1A, when viewed in a direction parallel to the cylinder center axis (7), the direction of the crankshaft center axis (8) is the front-rear direction, and is orthogonal to the crankshaft center axis (8). The direction of the valve cam shaft (9), the valve shaft of the intake valve (5), and each of the ports (1) and (2) are long in the front-rear direction, and the cylinder center axis (7) and When viewed in a direction parallel to the direction orthogonal to the crankshaft center axis line (8), the exhaust valve (6)
Are oriented in a direction substantially parallel to the cylinder center axis (7). The valve cam shaft (9) is oriented parallel to the crankshaft center axis (8). Cylinder center axis
Looking in the direction parallel to (7), the valve shaft and each port of the intake valve (5)
(1) and (2) are oriented along the direction of the crankshaft center axis (8). The valve axis of the exhaust valve (6) is the cylinder center axis.
It is oriented in a direction substantially parallel to (7).

The valve operating cam shaft (9), tappets (10) and (10) and push rods (11) and (11) are connected to the cylinder block (1).
The rocker arms (40) and (41) are provided on the left and right sides of 2), and are provided on the cylinder head (14).

An intake valve (5) and an exhaust valve (6) are provided for each combustion chamber (17), and a cylinder center axis (7) is provided.
When viewed in a direction parallel to, the valve shafts of the valves (5) and (6) are arranged closer to the push rods (11) and (11) than the crankshaft center axis (8), and the rocker arm output is provided at each valve shaft end. Department (15) (35)
Has been contacted.

As shown in FIG. 1B, the cylinder head
Of the piston facing surface (39) of (14), each valve port (3) (4)
And a cavity in an area including the spark plug insertion port (22).
(37) is formed, and other areas are squish areas
(38). An ignition plug (21) is inserted into the ignition plug (22), and its electrode part is connected to the combustion chamber (17).
It is located in the center.

One combustion chamber (17) is provided with one intake valve port (3) and one exhaust valve port (4), and as shown in FIG. 1B, is parallel to the cylinder center axis (7). When viewed in a suitable direction, the center of each of the valve ports (3) and (4) is disposed to be separated from the crankshaft center axis (8) to one side on the left and right sides, and the ignition plug insertion port (22) is located between the valve ports ( 18) and left and right side apart from each other. As shown in FIG. 1 (C), the peripheral portions of the valve ports (3) and (4) and the peripheral portion of the spark plug insertion port (22) are partially spherical. A virtual sphere obtained by extending each partial sphere is shown in the figure.

As shown in FIG. 1A, of the rocker arm pivots (13) (33), the rocker arm pivot (13) for the intake valve (5) is oriented long in the left-right direction. A rocker arm output section (15) is led out from one end of the support section (13) to the side opposite to the exhaust valve (6), and a rocker arm input section (1) is connected to the other end of the rocker arm pivot support section (13).
6) is led out to the rocker arm (41) side for the exhaust valve (6). The rocker arm pivot portion (13) for the intake valve (5) is oriented along a direction perpendicular to the crankshaft central axis (8) when viewed in a direction parallel to the cylinder central axis (7). The rocker arm pivot portion (13) for the intake valve (5) is formed by fitting a boss of the rocker arm (40) to a pivot that is long in the left-right direction.

As shown in FIGS. 1 (A) and 2, the rocker arm (41) for the exhaust valve (6) of the rocker arm pivots (13) (33) is formed of sheet metal, and the rocker arm pivots.
(33) is a pivot type. Each rocker arm input section (16) (36) is in contact with the output end of each push rod (11) (11), and each rocker arm output section (15) (15) is connected to each valve (5) (6). It is in contact with the valve shaft end.

As shown in FIG. 2, the center axis of the crankshaft
When viewed in a direction parallel to (8), the cylinder (19) is inclined,
On the lower side of the left and right sides of the cylinder block (12), the valve operating camshaft (9), tappets (10) and (10) and the push rod
(11) and (11) are arranged. The valve operating cam shaft (9) is disposed on the lower side of the crankcase (42), and the governor (32)
Are located on the higher side of the crankcase (42). A fuel tank (29) is disposed above the crankcase (42), and an air cleaner is disposed above the cylinder head (14).
(30) and an exhaust muffler (not shown) are arranged.

In this engine, the intake port (1) is drawn forward, and the exhaust port (2) is drawn rearward, with the cooling fan (not shown) facing forward and the valve camshaft (9) side facing left. The rocker arm (40) for the intake valve (5) is located at the front, and the rocker arm (41) for the exhaust valve (6) is located at the rear.

[Brief description of the drawings]

FIG. 1 is a view for explaining an engine according to an embodiment of the present invention. FIG. 1 (A) is a plan view of a cylinder head, and FIG. 1 (B).
FIG. 1 is a view of a piston facing surface of a cylinder head viewed from a piston side, and FIG. 1C is a longitudinal sectional side view of a main part of an engine in which a cylinder head and a cylinder block are vertically cut at different positions.

FIG. 2 is a longitudinal rear view of the engine of FIG. 1;

[Explanation of symbols]

(1) ... intake port, (2) ... exhaust port, (3) ... intake valve port, (4) ... exhaust valve port, (5) ... intake valve, (6) ... exhaust valve,
(7)… Cylinder center axis, (8)… Crankshaft center axis,
(9) Valve camshaft, (10) Tappet, (11) Push rod, (12) Cylinder block, (13) Rocker arm pivot, (14) Cylinder head, (15) Rocker arm output section , (16) ... rocker arm input section, (17) ...
Combustion chamber, (18) ... between valve openings, (19) ... cylinder, (2
2) spark plug insertion opening, (33) rocker arm pivot, (35) rocker arm output, (37) cavity, (38) squish area, (39) piston facing surface, (40) (41) ) ... Rocker arm.

Claims (8)

[Claims] An intake port (1) and an exhaust port (2) are led out of an intake valve port (3) and an exhaust valve port (4) in opposite directions, and a valve shaft of the intake valve (5) is connected to the intake port. In the overhead valve engine tilted in the lead-out direction of (1), when viewed in a direction parallel to the cylinder center axis (7), the direction of the crankshaft center axis (8) is the front-rear direction, and the crankshaft center axis is
The valve operating camshaft (9), with the direction orthogonal to (8) as the left-right direction.
And the valve shaft of the intake valve (5) and each of the ports (1) and (2) are long in the front-rear direction, and are parallel to the direction orthogonal to the cylinder center axis (7) and the crankshaft center axis (8). When viewed in a different direction, the valve shaft of the exhaust valve (6) is oriented in a direction substantially parallel to the cylinder center axis (7), and the valve cam shaft (9), the tappet (10) (10) and the push Rods (11) and (11) are arranged on one side of the left and right sides of the cylinder block (12), and rocker arms (40) and (41) are provided on the cylinder head (14). 2. The overhead valve engine according to claim 1, wherein one intake valve (5) and one exhaust valve (6) are provided for one combustion chamber (17), respectively, and are parallel to the cylinder center axis (7). The valve shaft of each of the valves (5) and (6) is arranged closer to the push rods (11) and (11) than the crankshaft center axis line (8) when viewed in a suitable direction. 3. The overhead valve engine according to claim 1, wherein each of the valve ports (3) and (4) and the spark plug insertion port (22) of the piston facing surface (39) of the cylinder head (14) are connected. A cavity (37) is formed in a region including the squish area (38). 4. An overhead valve engine according to claim 3, wherein one intake valve port (3) and one exhaust valve port (4) are provided for each combustion chamber (17), and the cylinder center axis (7) is When viewed in a parallel direction, the center of each valve port (3) (4) is the center axis of the crankshaft.
(8) The ignition plug insertion port (22) is disposed to be separated from the inter-valve portion (18) to the left and right side and the other side. 5. The overhead valve engine according to claim 3, wherein a peripheral portion of each of the valve ports (3) and (4) and a spark plug insertion port (2) are provided.
2. The peripheral part of 2) is a partial spherical surface. 6. The overhead valve engine according to claim 1, wherein, among the rocker arm pivot portions (13) and (33), the rocker arm pivot portion (13) for the intake valve (5) extends in the left-right direction. This rocker arm pivot (13)
Rocker arm output from one end to the side opposite to exhaust valve (6)
(15) is drawn out, and a rocker arm input portion (16) is led out to the rocker arm (41) side for the exhaust valve (6) from the other end of the rocker arm pivot portion (13). 7. The overhead valve engine according to claim 1, wherein the rocker arm (41) for the exhaust valve (6) of the rocker arm pivots (13) (33) is formed of sheet metal, and the rocker arm is provided with the rocker arm. The pivot (33) is of a pivot type. 8. The engine according to claim 1, wherein the engine is viewed in a direction parallel to the crankshaft center axis (8).
The cylinder (19) is inclined, and the valve operating cam shaft (9) and the tappet (1)
0, (10) and push rods (11), (11) are arranged.