EP1092850B1

EP1092850B1 - Outboard motor

Info

Publication number: EP1092850B1
Application number: EP00122172A
Authority: EP
Inventors: Eiichiro Tsujii
Original assignee: Yamaha Marine Co Ltd
Current assignee: Yamaha Marine Co Ltd
Priority date: 1999-10-12
Filing date: 2000-10-12
Publication date: 2006-04-19
Anticipated expiration: 2020-10-12
Also published as: EP1092850A2; EP1092850A3

Description

This invention relates to an outboard motor.
Small sized outboard motors are frequently transported or laid horizontally in daily use. In such a situation, there is a problem that, in four-stroke cycle engines, engine oil finds its way from the crank chamber through the cylinder into the combustion chamber, wets the ignition plug, and makes starting the engine difficult. Conventionally, the crankcase volume is enlarged to cope with the above problem.
From EP 0 779 412 A2 there is known a lubricating system of a hand-held 4-cycle engine, said lubricating system comprising an oil reservoir chamber, a crank chamber and a valve operating chamber. The oil reservoir chamber, the crank chamber and the valve operating chamber are connected by a circulating passageway in order to circulate the lubricating oil. Therein, the crank chamber is connected to a valve chamber provided below a lower surface of the crankcase, said valve chamber being connected to the valve operating chamber. Said valve operating chamber is connected to an uppermost chamber defined between the ceiling walls of the cover and communicating with the valve operating chamber. Said uppermost chamber communicates with an oil return chamber through a single oil passage provided in the cylinder block and the crankcase.
From US 5,243,937 there is known a further hand-held four-stroke cycle engine, having a communicating pipe connecting the crank chamber and the cylinder head including the valve chamber.
However, the problem with the conventional solution is that, because the crankcase is enlarged, the engine width increases undesirably and the size of the outboard motor increases accordingly.
Accordingly, it is an objective of the present invention to provide an outboard motor with an oil passage structure for the outboard motor capable of preventing oil from finding its way into the combustion chamber while securing the compact size of the outboard motor.
Said objective is performed, according to the present invention, by an outboard motor having the features of claim 1.
Thus, the oil passage is formed on that side of the engine on which a manual handlebar for manually controlling the outboard motor is located. This enables the operator to stabilize the outboard motor when the outboard motor is placed laterally with the handlebar downwards.
Embodiments of the invention will be hereinafter described with reference to the appended drawings.

FIG. 1 is a side view partially in cross section of an outboard motor, showing an embodiment of the oil passage structure for the outboard motor;
FIG. 2(A) shows a cross section of the swivel bracket 6 and its vicinity. FIG. 2(B) shows the cross section B-B in FIG. 2(A);
FIG. 3 is a cross-sectional view as seen in the direction of arrows X-X in FIG. 1;
FIG. 4 shows an enlarged cross section of an essential part of FIG. 1; and
FIG. 5 shows cross-sectional front views as seen in the direction of arrow Y in FIG. 4.

FIGS. 1 to 5 show an embodiment of the oil passage structure for outboard motors. FIG. 1 is a side view partially in cross section of an outboard motor. Incidentally, the same parts in different drawings are provided with the same reference numerals and their explanations are sometimes omitted in the following description. Furthermore, the terms 'the front' and 'the rear' as used herein are respectively meant with respect to the advancing direction and the reverse direction of the boat.
As shown in FIG. 1, an outboard motor 1 is provided with; a clamp bracket 3 removably attached to the rear part of a hull 2, a swivel bracket 6 supported for up and down swinging about a tilt shaft 5 on the clamp bracket 3, and a propulsion unit 7 supported for horizontal swiveling on the swivel bracket 6. The propulsion unit 7 has an upper case 9 rotatably supported with the swivel bracket 6, and a lower case 10 attached to the lower part of the upper case 9. The upper and lower cases 9 and 10 constitute a single casing as a whole. A propeller 11 is attached to the lower case 10. A bottom cowling 12 is attached to the top of the upper case 9. A top cowling 13 is removably attached to the bottom cowling 12.
An engine 14 is mounted on the upper case 9. The engine 14 is, for example, of the single cylinder, overhead valve, four-stroke cycle type. An engine body comprises; a head cover 15, a cylinder head 16, a cylinder body 17, and a crankcase 19 serving also as an oil pan. A cylinder 20 and a piston 21 are disposed horizontally, and a crankshaft 22 is disposed vertically. The cylinder head 16 is provided with an intake valve 23, an exhaust valve 24, and an exhaust port 25. A recoil starter 26 is attached to the top of the crankshaft 22. The numeral 18 denotes a drive shaft connected to the crankshaft 22, and the numeral 27 denotes a fuel tank laid to extend from the front to the side of the cylinder body 17.
FIG. 2(A) shows a cross section of the swivel bracket 6 in FIG.1 and its vicinity. FIG. 2(B) shows the cross section B-B in FIG. 2(A). An upper tube 8 for supporting the engine 14 is formed in tubular shape with an internal exhaust passage 8a. In the exhaust passage 8a are disposed; the drive shaft 18, a shift rod 62, and a cooling water pipe 61 in the vertical direction. An oil pan connecting portion 8b flaring like a dish is formed in the upper part of the upper tube 8. A small diameter tubular portion 8c is formed in the lower part of the upper tube 8. The swivel bracket 6 is formed in tubular shape and its inside circumference is formed with support flanges 6a extending horizontally in two, upper and lower positions. When the swivel bracket 6 is installed around the upper tube 8, mounts 28 made of an elastic material such as rubber are disposed between the tubular portion 8c of the upper tube 8 and the support flanges 6a of the swivel bracket 6 in two, upper and lower positions. In this way, a full pivot type of outboard motor that enables the boat to go forward and backward is constituted in which the upper tube 8 is supported for 360 degree rotation on the swivel bracket 6 through the mounts 28. Incidentally, a bush 28a is interposed between the upper tube 8 and the mounts 28.
FIG. 3 is a cross-sectional view as seen in the direction of arrows X-X in FIG. 1. The crankshaft 22 is provided with a crank pin 29 and counterweights 30. The crank pin 29 is connected through a connecting rod 31 to the piston 21. A camshaft 32 is disposed in the cylinder body 17 parallel to the crankshaft 22 so that the rotation of the crankshaft 22 is transmitted to the camshaft 32 through gears 33 and 34. In the drawing is shown a carburetor 43 and an ignition plug 44.
In this embodiment, the axis L2 of the cylinder 20 is displaced by a distance D1 in the direction opposite the direction of the lateral component of the thrust acting on the piston 21 with respect to the line L1 that is parallel to the cylinder 20 and passes the axis of the crankshaft 22. Also, the axis of the piston pin 45 is displaced by a distance D2 in the direction of the lateral component of the thrust with respect to the axis L2 of the cylinder 20. In this way, the moment acting on the piston pin 45 is reduced, operation efficiency and durability are improved, and slapping noise is reduced. This arrangement also makes it possible to displace the cylinder 20 and the cylinder head 16 toward the right to produce a space where engine components such as the camshaft 32, the fuel pump 42, and the carburetor 43 are disposed. Thus, the engine is made compact without increasing the weight and without changing the direction of rotation. Moreover, since the crankshaft 22 made of a heavy, iron-based material is not displaced, the amount of displacement of center of gravity is held small, so that the amount of vibration is held to a minimum.
A valve drive chamber 35 is formed with the cylinder head 16 and the head cover 15. The exhaust valve 24 (also the intake valve 23) extends through the cylinder head 16 into the valve drive chamber 35 and comes into contact with one end of a rocker arm 39 through a valve spring 36 and a retainer 37. A lifter 40 is slidably disposed in the cylinder body 17. One end of the lifter 40 is in contact with a cam of the camshaft 32. The other end of the lifter 40 is in contact with the other end of the rocker arm 39 through a push rod 41. The plunger of a fuel pump 42 is also in contact with the cam of the camshaft 32. With the above constitution, when the camshaft 32 rotates, the lifter 40 and the push rod 41 slide to rock the rocker arm 39, and to drive the intake valve 23 and the exhaust valve 24 to be opened and closed against the valve spring 36, and the fuel pump 42 is driven.
Next, the features of the embodiment will be described in reference to FIGS. 4 and 5. FIG. 4 is an enlarged cross-sectional view of an essential part of FIG. 1. FIG. 5(A) is front view of a cross section Y-Y of the cylinder body as seen in the direction of arrow Y in FIG. 4. FIG. 5(B) is a front view of a cross section Z-Z of the cylinder head as seen in the direction of arrow Y in FIG. 4. As shown in FIG. 4, a flywheel 45 is attached to the top part of the crankshaft 22. A recoil starter 26 is attached to the top of the flywheel 45. The recoil starter 26 and the flywheel 45 are covered with a starter cover 46. A breather chamber 47 is recess-formed on the top of the cylinder head 16 and tightly closed with a plate 49. A cooling water passage 51 is also formed and provided with a thermostat 50.
As shown in FIG. 5(A), the cooling water passage 51 is formed around the cylinder 20 in the cylinder body 17. Two oil passages 52 are formed in the upper and lower side walls of the cylinder body 17 to make fluid communication with the crankcase 19. As shown in FIG, 5(B), oil passages 53 are formed in the upper and lower side walls of the cylinder head 16 to make fluid communication between the oil passages 52 and the valve drive chamber 35. With the above-described constitution, when the outboard motor is placed to lie on its side so that the side 17a of the cylinder body 17 shown in FIG. 3 is placed on the ground, oil in the crankcase 19 flows through the oil passages 52, 53 into the valve drive chamber 35 and collects in the lower part of the cylinder 20. As a result, oil is prevented from flowing into the combustion chamber.
The oil passages 52, 53 are formed on the side toward which the cylinder 20 and the cylinder head 16 are displaced, namely on the side opposite the side on which the carburetor 43 is located. This makes it possible to reduce the width of the outboard motor. Forming the oil passages 52, 53 on the side on which a manual handle bar 55 for manually controlling the outboard motor is located makes it possible, when the outboard motor is placed laterally with the manual handle bar 55 downward, to stabilize the outboard motor as oil collects in its lower part.
While, in the above, an embodiment has been described, the invention is not limited to the embodiment but may be modified in various ways. For example, while the above embodiment is an example of an OHV type of engine, the subject may be multi-cylinder engines or an OHC type of engines.
As is clear from the above description, oil is prevented from flowing into the combustion chamber while retaining the compact size of the outboard motor.
With the embodiment, stability of the outboard motor when it is placed to lie on its side is improved.
With the embodiment, the outboard motor can be made compact.
Regarding the suppression of vibrations the disposal of a counterweight is preferred wherein the center of gravity of said counterweight associated to the crankshaft is positioned on or close to said parallel line intersecting the axis of the crankshaft, when the piston is in one of its top or bottom dead center positions.
A line interconnecting the axis of a crank pin which is rotatably connected to one end of a connecting rod, the other end of which is connected to the piston through a piston pin, the axis of the crankshaft and the axis of the piston pin when said piston is in either one of a top or bottom dead center position defining an angle with the line intersecting the axis of the crankshaft and extending in parallel to the cylinder axis.
The amount of displacement γ of the center of gravity relative to the line L3 interconnecting the axis P2 of the crank pin, the axis P1 of the crankshaft and the axis P3 of the piston pin is set to be $0 < γ \leq (α + β) / 2$
wherein α is assumed to be the angle between the line L3 connecting the axes (P2,P1,P3) of the crank pin (29), the crankshaft (22) and the piston pin (45) and the line (L1) extending in parallel to the cylinder axis (L2) and intersecting the axis of the crankshaft (22) with the piston (21) being at its top dead center position while β is assumed to define the same geometrical relationship between the afore-indicated lines (L3,L1) when the piston is in its bottom dead center position.
The position of the center of gravity (G) when the piston 21 assumes its top or bottom dead center positions is adjusted by adapting the counterweight 30 in shape, providing a recess therein or adding a weight thereto.
The axis of a piston pin is displaced by a distance D2 in the direction of a lateral component of the thrust F with respect to the axis L2 of the cylinder.

Claims

Outboard motor having an internal combustion engine, in particular four-stroke cycle engine, comprising a cylinder body (17) and a cylinder head (16) comprising a valve drive chamber (35), wherein at least one oil passage (52,53) is disposed in at least one side wall of the cylinder body (17) and/or the cylinder head (16) communicating with the valve drive chamber (35), and comprising a manual handlebar (55) for manually controlling same, said oil passage (52,53) being formed on the manual handlebar side of the engine.