Internal combustion engine

Abstract: Internal combustion engine for an outboard motor comprising a pulley, a flywheel, and a recoil starter capable of engaging with the pulley secured to the top end of a crankshaft, the dimension H1 of the flywheel in the height direction is made to overlap with the dimension H2 of the recoil starter in the height direction.

Description: This invention relates to an internal combustion engine, in particular an outboard motor, especially the structure of a recoil starter and a flywheel, as indicated in the introductory portion of claim 1, and as shown for example in document US 5 031 591 A. Engines of outboard motors may be started manually or electrically. In the case the engine is started manually, a recoil starter is attached to a flywheel secured to the top of the crankshaft, and a starter rope is provided to be pulled for starting the engine. However, the outboard motor with the conventional recoil starter has a problem that the engine height cannot be reduced because of the presence of a large unused space between the recoil starter and the flywheel. Accordingly, it is an objective of the present invention to provide an internal combustion engine to solve the above problem by providing an engine structure for outboard motors in which the engine height may be reduced by optimizing the layout of the recoil starter and the flywheel. According to the present invention, said objective is performed by an internal combustion engine having the features of claim 1. Preferred embodiments are laid down in the further subclaims. Embodiments of the invention will be hereinafter described with reference to the appended drawings. FIG. 1 shows an outboard motor partially in cross section, with a breather chamber structure as an embodiment of the invention; FIG. 2(A) shows a cross section of a swivel bracket 6 shown in FIG. 1 and its vicinity. FIG. 2(B) shows the cross section B-B in FIG. 2(A); FIG. 3 is an enlarged cross-sectional view of the engine shown in FIG. 1; FIG. 4 shows a cross section cut along the line X-X in FIG. 1 and seen in the arrow direction; and FIG. 5(A) shows an enlarged cross section of an essential part of FIG. 3. FIG. 5(B) is a plan view of the flywheel. FIGs. 1 to 5 show an embodiment of the engine structure of this invention for outboard motors. FIG. 1 is a side view partially in cross section of an outboard motor. Incidentally, the same components in different drawings are provided with the same reference numerals and their explanations are omitted, and 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 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. The numeral 43 denotes a carburetor and the numeral 47 denotes a silencer. FIG. 2(A) shows a cross section of the swivel bracket 6 and its vicinity in FIG. 1. 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. A bush 28a is interposed between the upper tube 8 and the mounts 28. FIG. 3 shows an enlarged cross section of the engine shown in FIG. 1. FIG. 4 shows a cross section cut along the line X-X in FIG. 1 and seen in the arrow direction. 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. The axis of the exhaust valve 24 (also of the intake valve 23) is tilted relative to the mating surface 52 between the cylinder head 16 and the cylinder body 17 to form a wedge-shaped combustion chamber 50. The mating surface 51 between the cylinder head 16 and the head cover 15 is tilted forward in the vertical direction relative to the axis of the exhaust valve 24. 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. A valve drive chamber 35 is formed with the cylinder head 16 and the head cover 15. The exhaust valve 24 and the intake valve 23 extend 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. 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 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 secured to the cylinder body 17. A magnet 45a is disposed around the flywheel 45. An ignition coil 53 is disposed in the vicinity of outside circumference of the flywheel 45. A recessed breather chamber 47 is formed in the top part of the cylinder head 16 and tightly closed with a plate 49. A splasher gear 44 is provided to be driven with the crankshaft 22 and to splash oil into the cylinder body 17. Features of the embodiment will be hereinafter described in reference to FIG. 5. FIG. 5(A) shows an enlarged cross section of an essential part of FIG. 3. FIG. 5(B) is a plan view of the flywheel. According to the invention, it is arranged that the dimension H1 of the flywheel 45 in the height direction overlaps with the dimension H2 of the recoil starter 26 in the height direction so as to reduce the engine height while retaining the mass of the flywheel 45. The arrangement will be hereinafter described in detail. The flywheel 45 and the pulley 54 of a bowl shape are secured with a bolt 55 to the top end of the crankshaft 22. The flywheel 45 is made up of a disk-shaped base plate 45b and projections 45c, 45d extending up and down from the peripheral part of the base plate 45b. A water drain hole 45e is bored in the base plate 45b. The outside circumference of the pulley 54 is also formed with a plurality of engagement recesses 54a. A rotor 56 and a guide member 60 are rotatably mounted on the underside of the starter cover 46. The rotor 56 is connected through a rope 57 to a starter handle 59. The guide member 60 is provided in its central part with a recess 60a and a guide portion 60b formed at the lower peripheral part of the recess 60a and is mounted in a position so that the bolt 55 is located within the recess 60a. An engagement arm 61 rotatable about a shaft 61 a is attached to the underside of the rotor 56. The engagement arm 61, the pulley 54, and the rotor 56 constitute a one-way clutch. When the starter handle 59 is pulled, the rotor 56 is rotated with the rope 57, the engagement arm 61, as guided with the guide member 60, engages with the engagement recess 54a of the pulley 54, so that the pulley 54 and the crankshaft 22 rotate. Once the engine starts, the one-way clutch works to disengage the engagement arm 61. While an embodiment of the invention is described above, the invention is not limited to the above embodiment but may be embodied in various ways. For example, while the invention is applied to a single cylinder, overhead valve, four-stroke type of engine in the above embodiment, the invention may also be applied to multicylinder engines, overhead camshaft type of engines, or two-stroke cycle engines. As is clear from the above description, the engine height may be reduced by optimizing the layout of the recoil starter and the flywheel. With the invention, the flywheel mass may be secured to absorb variations in revolution. With the invention, water is prevented from collecting in the flywheel. The crankshaft is based of iron-based material while the cylinder can be made of an aluminium based alloy including aluminium.

Claims: Internal combustion engine, in particular for an outboard motor, comprising a crankshaft (22) and a flywheel (45) secured to one end thereof and a recoil starter (26) which is disposed above the flywheel (45) such that a height (H2) of a recoil starter (26) overlaps with the height (H1) of the flywheel. Internal combustion engine according to claim 1, wherein the recoil starter comprises; a rotor rotated with a rope, an engagement arm rotatably disposed on the rotor, and a guide member for enabling the engagement arm to engage with the pulley, characterized in that a recess is formed in the central part of the guide member, and a bolt for securing the flywheel to the crankshaft is disposed in the recess. Internal combustion engine according to claim 1 or 2, wherein the peripheral part of the flywheel is provided with projections extending in up and down directions. Internal combustion engine according to at least one of the preceding claims 1 to 3, wherein the flywheel is provided, in its top surface, with a water drain hole. Internal combustion engine according to at least one of the preceding claims 1 to 4, wherein a cylinder axis (L2) of the cylinder is displaced laterally offset with respect to a parallel line intersecting the axis of the crankshaft (22). Internal combustion engine according to at least one of the preceding claims 1 to 5, wherein the cylinder axis (L2) is displaced in a direction opposite to the direction of a lateral component of thrust (F) acting on the piston (21) relative to said line (L1) extending in parallel to the cylinder axis (L2) and intersecting the axis of the crankshaft (22). Internal combustion engine according to at least one of the preceding claims 1 to 6, wherein the axis of a piston pin (45) 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 (20). Internal combustion engine according to one of the preceding claims 1 to 7, wherein engine components, in particular a camshaft (32), a fuel pump (42), and a carburetor (43) are disposed in the area of a side surface of the engine that is opposite to the direction of displacement of the cylinder axis (L2). Internal combustion engine according to at least one of the preceding claims 1 to 8, wherein some engine components, in particular a carburetor (43) and a fuel tank (27), are disposed in the area of a side surface of the engine that is opposite to the direction of displacement of the cylinder axis (L2), some of the engine components such as the camshaft (32) are disposed in the area on a side surface of the engine that complies with the displacement direction of the cylinder axis (L2) with respect to the line (L1) extending in parallel and intersecting the axis of the crankshaft (22) and some of the engine components, in particular the fuel pump (42) are disposed outside of a cylinder block body (17) of the engine. Internal combustion engine according to at least one of the preceding claims 1 to 9, wherein mounts (28) are provided to support the engine, said mounts (28) having a variable wall thickness such that the wall thickness of parts of each of the mounts (28) on the side opposite to the displacement direction of the cylinder axis (L2) is increased compared to the side extending towards the direction of displacement of the cylinder axis (L2). Internal combustion engine according to at least one of the preceding claims 1 to 10, wherein a valve drive chamber (35) is formed in a cylinder head (16) and a head cover (15) of the engine wherein the valves (23,24) are driven via a rocker arm mechanism (39) and a lifter (40), said lifter (40) being in contact with an end of the rocker arm (39) through a push rod (41) and, on the other hand, being slidably disposed in the cylinder body (17), is operated by a cam of the camshaft (32) which is in contact with said end of the lifter (40). Internal combustion engine according to at least one of the preceding claims 1 to 11, wherein the camshaft (42) is driven from the crankshaft (22) by means of gears (33,34) being in mesh with each other. Internal combustion engine according to at least one of the preceding claims 1 to 12, wherein the crankshaft (22) is made of iron-based material while the cylinder can be made of an aluminium based alloy including aluminium. An outboard motor having an internal combustion engine according to at least one of the preceding claims, wherein the crankshaft (22) is disposed substantially vertically.

Inventors: TSUJII EIICHIRO, TSUJII, EIICHIRO
Applicants: YAMAHA MARINE KK, YAMAHA MARINE KABUSHIKI KAISHA
Application year: 2000
Main classification: F02N3
IPC codes: F02B61, F02F7, F02B75