JP3603827B2 - Arrangement structure of engine decompression device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a decompression device for a motorcycle engine, and more particularly to an arrangement structure of a decompression device that facilitates cranking during an engine start operation.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, at the time of an engine start operation of a motorcycle, particularly in the case of a four-cycle single-cylinder engine or the like, there is a case where it is difficult to generate the momentum of the crank rotation due to a large compression resistance in a combustion chamber when a piston is operated.
Therefore, in the case of a rocker arm engine, the decompression shaft is attached to the head cover, the rocker arm is rocked by rotating the decompression shaft, and the exhaust valve is lifted to open to reduce the compression in the combustion chamber. There is known a method for improving the startability of the engine.
[0003]
[Problems to be solved by the invention]
However, it is common sense to cool the engine and install an exhaust gas purification system based on recent engine performance and regulation of exhaust gas, so there is a frame, radiator, water hose, Since a cooling fan, an exhaust pipe, a secondary air system, and the like are collectively arranged, it is very difficult to configure a compact decompression device.
[0004]
The present invention has been made in view of the above-mentioned conventional problems, and has an object to provide an arrangement structure of an engine decompression device which has a simple configuration, saves space, and has excellent maintainability. I do.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a four-stroke, single-cylinder, water-cooled engine in which the engine decompression device is tilted slightly forward almost in the center of the vehicle body, and includes two exhaust valves and an intake valve in a cylinder head. An exhaust pipe is disposed on the front side of the engine through an exhaust manifold downward from the front of the engine in the vehicle body direction, and a radiator for cooling the engine is provided with a cooling fan in front of the water-cooled engine. A decompression device is provided, and a decompression shaft is disposed substantially parallel to the camshaft in a direction substantially perpendicular to the vehicle traveling direction. The decompression shaft has a valve operation unit that opens an exhaust valve with rotation. An operation lever for rotating the decompression shaft on an engine side in a direction substantially orthogonal to a vehicle traveling direction while being disposed; It provided, in this arrangement of the decompression apparatus for an engine has a structure in which the operating lever is operated, the frame is arranged in front of the exhaust manifold of the cylinder head tilted slightly along the engine from the engine above the operating wire , viewed in a plan view of the vehicle, the plug is substantially positioned at the center of and the cylinder head between the exhaust manifold plug hole and the intake manifold to be mounted, it is arranged on the camshaft for opening and closing the exhaust valve and the intake valve that cam sprocket is disposed on one side of the cylinder head Rutotomoni, support portion for supporting the decompression shaft is disposed on the other side of the counter-cam sprocket side of the cylinder head, as viewed from the side of the vehicle, said decompression A supporting portion for supporting the shaft is provided with an exhaust manifold of the cylinder head. A top of the exhaust pipe of de side, is characterized in that disposed behind the cooling fan.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is an overall view showing the configuration of an engine equipped with a decompression device according to the present embodiment, FIG. 2 is a side view showing the configuration of the engine, FIG. 3 is a cross-sectional view of a cylinder head showing the configuration of the decompression device, FIG. 4A is a plan sectional view of a cylinder head showing the configuration of the decompression device, and FIG. 4B is a view taken in the direction of an arrow A showing the details of the configuration of the decompression device.
[0008]
In this embodiment, as shown in FIGS. 1 and 2, a four-stroke, single-cylinder, water-cooled engine (hereinafter, referred to as an “engine”) 1 of a direct-cam type is provided at a substantially center of a vehicle body (not shown). It is placed upside down and tilted.
The engine 1 is a four-valve type having two exhaust valves 2 and two intake valves 3 as shown in FIGS. 3 (a) and 4 (a). , The upper surfaces of the cup-shaped tappets 6 and 7 are periodically pushed down to open and close the exhaust valve 2 and the intake valve 3 according to the cycle.
Bearing portions 8 and 9 for rotatably holding cam shafts 4a and 5a (journal portions) of a rotating body integrally having the cams 4 and 5 are provided between valves (between two exhaust valves 2 and two intake valves). (Between the valves 3) and the chain chamber 11 side.
In this case, the camshafts 4a, 5a are cantilevered with the cams 4, 5 extending toward the opposite side of the chain chamber 11. The upper portions of the two bearing portions 8, 9 are connected and covered by bridge-shaped covers 8a, 9a, and are reinforced.
The cam sprockets (not shown) of the camshafts 4a, 5a are arranged at one end of the cylinder head 10 on the side of the chain chamber 11.
Reference numeral 10a denotes a plug hole into which a plug is inserted, and 11a denotes an upper guide for guiding a cam chain (not shown) to a cam sprocket.
[0009]
Radiators 12 and 13 for cooling the engine are arranged in front of the cylinder head 10 of the engine 1. Further, a frame 15 (down tube) is disposed in front of the cylinder head 10 so as to be slightly inclined from above the engine 1 along the engine 1 to a lower portion of the engine 1.
The radiators 12 and 13 have a vertically long, substantially rectangular cross-sectional shape, and have two widths of the engine body (crankcase 17 + clutch case 18 + magneto case 19) at two locations substantially in the left and right direction with the frame 15 interposed therebetween. The width is substantially the same as the width of the first. A cooling fan 21 is disposed at a lower portion of the back of the radiator 12.
[0010]
An exhaust pipe 24 is provided on the front side of the cylinder head 10 via an exhaust manifold 22 so as to extend downward from the front of the engine 1 in the vehicle body direction toward the engine 1 and further rearward. , An intake path such as a carburetor 29 and an air cleaner 30 is arranged behind the engine 1 via an intake manifold 26.
Above the exhaust manifold 22 of the cylinder head 10, a secondary air pipe 31 is connected. A secondary air switching valve 32 is disposed at the front center of the engine 1 behind the exhaust pipe 24 and on the front left side of a cylinder case 33.
[0011]
A decompression device 40 is provided on the left side of the cylinder head 10 toward the vehicle body.
As shown in FIGS. 3A, 3B, 4A, and 4B, the decompression device 40 includes a decompression shaft disposed in a direction substantially orthogonal to the axis center with respect to the traveling direction of the vehicle body. 41, which is disposed close to the tappet 6 for the exhaust valve on the side opposite to the chain chamber in the cylinder head 10, and at least a part thereof comes into contact with the top surface of the tappet 6 and is pressed with the rotation of the decompression shaft 41. An operation lever 43 for rotating the decompression shaft 41 is provided on a side of the cylinder head 10 substantially perpendicular to the traveling direction of the vehicle body.
The valve operating section 42 is formed by forming a portion (a non-operating portion) in which a part of a cross-sectional circle is cut out flatly, and a portion (an operating portion) having the remaining cross-sectional arc.
[0012]
A decompression shaft supporting portion 45 for supporting the decompression shaft 41 is formed on the opposite side of the chain of the cylinder head 10 in an opening substantially in the same direction as the axis of the camshaft 4a. A bearing 46 is disposed on the decompression shaft support portion 45, and the decompression shaft 41 is rotatably supported via the bearing 46.
One end of the decompression shaft 41 is disposed outside the cylinder head 10 and has the operation lever 43 attached thereto. The other end of the decompression shaft 41 is disposed inside the cylinder head 10 and, as shown in FIG. 3, when the operation lever 43 is at the stop position and the flat portion of the valve operation portion 42 is It is arranged at a position facing the upper surface without contacting the upper surface.
[0013]
As shown in FIG. 4B, the operation lever 43 has a lock portion 47 for restricting rotation and an operation wire 48 connected to a decompression bar (not shown) attached to a bundle bar (not shown). Has a lever operation unit 50 to which one end of the lever operation unit is attached. The operation lever 43 is urged by a torsion coil spring 52 in a direction in which the operation wire 48 is pulled.
The decompression shaft 41 is held on the side of the cylinder head 10 by a decompression holder 54.
In the decompression holder 54, a locking portion stopper 56 is formed at a decompression operation movement limit position of the locking portion 47 of the operation lever 43, and an operation portion stopper 57 is formed at a decompression return limit position of the lever operation portion 50. . The operation portion stopper 57 regulates a position where the operation lever 43 is urged by the torsion coil spring 52 in a direction in which the operation wire 48 is pulled, and operates.
[0014]
Next, the operation of the decompression device 40 of the present embodiment will be described.
When the engine 1 is started, a cranking operation is performed after pulling a decompression bar (not shown) disposed at an appropriate position on a handlebar (not shown).
At this time, the operation wire 48 is pulled, and the operation lever 43 rotates by a predetermined amount. Along with this, as the decompression shaft 41 rotates, the circumferential portion (operating portion) of the valve operating portion 42 comes into contact with the upper surface of the tappet 6, and further pushes down against the valve spring 60. Thus, even when the exhaust cam 4 is closed, the exhaust valve 2 is opened, and the combustion chamber is opened. (See FIG. 3B)
If the cranking is performed in this state, a part of the mixed gas in the combustion chamber flows out through the exhaust port to the outside during the compression process, so that the pressure in the combustion chamber decreases. Therefore, the cranking operation can be easily performed at the time of starting.
[0015]
Then, by returning the decompressor at a predetermined timing during the cranking operation, the operation wire 48 is pulled back, and the decompression shaft 41 is returned, so that the flat portion (non-operating portion) of the valve operating portion 42 is again moved to the tappet 6. It is returned to the position facing the upper surface. At this time, the tappet 6 is pushed up by the reaction force of the valve spring 60. Thus, the exhaust valve 6 is closed, and the combustion chamber is closed.
When the cranking is performed in this state, the normal compression process is performed, so that the engine can be started at the ignition timing.
[0016]
According to the above configuration, since the decompression device 40 is disposed on the side surface of the engine 1, the decompression device 40 can be configured without protruding in the vehicle body traveling direction. Therefore, a compact vehicle body configuration can be realized.
Further, the side surface of the engine 1 is less affected by components such as the radiators 12 and 13, the cooling fan 21, the exhaust hype 24 and the carburetor 29.
In particular, when the engine 1 is brought closer to the radiators 12 and 13, the decompression device 40 projects to the left, so that there is no interference with the cooling fan 21. Therefore, the engine 1 can be brought very close to the radiators 12 and 13.
[0017]
Further, since the decompression shaft 41 is supported on the side opposite to the camshaft 4a, the valve operation portion 42 can be easily attached without interfering with the cam 4, so that the decompression device 40 can be configured compact.
Further, by arranging the decompression shaft 41 substantially in parallel with the cam shaft 4a, the amount of protrusion of the cylinder head 10 on the exhaust side can be suppressed, and the configuration of the current exhaust / intake system is not significantly changed. There are advantages.
[0018]
In the present embodiment, a four-stroke single-cylinder water-cooled engine of a direct-cam type is used. However, the present invention is not limited to this, and may be applied to a multi-cylinder engine. You may. In addition, the engine 1 has two exhaust valves and two intake valves in the valve configuration. However, the present invention is characterized in that the valves are independently operated by the rotating shaft, and the number of valves is not limited. .
[0019]
Further, in the present embodiment, the valve operating portion 42 has a part of a cylindrical outer peripheral portion formed in a flat shape. However, the present invention is not limited to this, and with the rotation of the rotating shaft, As long as at least a part of the tappet is in contact with the top surface, the tappet may have, for example, a cam shape used for operation of an exhaust / intake valve. In this case, a contact portion with the top surface of the tappet Since there is little motion fluctuation, the operation is smoothed.
[0020]
【The invention's effect】
As described above, according to the present invention, the rotating shaft provided with the valve operating section is disposed in a direction substantially orthogonal to the axial center with respect to the traveling direction of the vehicle body, and the rotating shaft is rotated around the engine. By providing the valve operating means for moving, the decompression device can be made compact. Further, since the configuration can be made without projecting the decompression device in the traveling direction of the vehicle body, a compact vehicle configuration can be realized, and the decompression device excellent in maintenance can be provided.
[Brief description of the drawings]
FIG. 1 is an overall view showing a configuration of an engine equipped with a decompression device according to an embodiment of the present invention.
FIG. 2 is a side view showing a configuration of the engine.
FIG. 3A is a sectional view of a cylinder head showing a configuration of the decompression device, and FIG. 3B is an explanatory diagram showing an operation of an exhaust valve by the decompression device.
FIG. 4A is a plan cross-sectional view of a cylinder head showing a configuration of the decompression device, and FIG. 4B is a view taken in the direction of an arrow A showing details of a configuration of the decompression device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust valve 3 Intake valve 4, 5 Cam 4 a, 5 a Camshaft 6, 7 Tappet 8, 9 Bearing unit 10 Cylinder head 11 Chain chamber 40 Decompression device 41 Decompression shaft 42 Valve operation unit 43 Operating lever 45 Decompression shaft support unit 46 Bearing 47 Locking part 48 Operating wire 50 Lever operating part 52 Torsion coil spring 54 Decomp holder 56 Locking part stopper 57 Operating part stopper

Claims (1)

A four-stroke, single-cylinder, water-cooled engine that leans slightly forward in the center of the body, with two exhaust valves and two intake valves on the cylinder head, and an exhaust pipe on the front side via an exhaust manifold. An engine cooling radiator provided with a cooling fan is provided in front of the water-cooled engine in a downward direction from the vehicle body direction front of the engine, and the decompression device is substantially orthogonal to the vehicle body traveling direction. A decompression shaft is disposed substantially parallel to the camshaft, and a valve operating portion for opening an exhaust valve with rotation is disposed on the decompression shaft, while the decompression shaft is disposed in a direction substantially perpendicular to the vehicle body traveling direction. A structure in which an operation lever for rotating the decompression shaft is provided on a side portion, and the operation lever is operated by an operation wire. In the arrangement of the decompression device of the engine,
A frame is arranged in front of the exhaust manifold of the cylinder head by slightly tilting along the engine from above the engine,
In plan view of the vehicle, the plug is substantially positioned at the center of and the cylinder head between the plug hole the exhaust manifold and the intake manifold to be mounted, is arranged on the camshaft for opening and closing the exhaust valve and the intake valve Rutotomoni cam sprocket is disposed on one side of the cylinder head, a support portion for supporting the decompression shaft is disposed on the other side of the counter-cam sprocket side of the cylinder head,
As viewed from the side of the vehicle, the decompression support portion for supporting the shaft a above the exhaust pipe of the exhaust manifold side of the cylinder head, the engine, characterized in that disposed behind the cooling fan Arrangement structure of decompression device.

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