EP1092849B1

EP1092849B1 - Internal combustion engine

Info

Publication number: EP1092849B1
Application number: EP00122171A
Authority: EP
Inventors: Eiichiro Tsujii; Kazuyuki Kitajima; Kentaro Kameoka
Original assignee: Yamaha Marine Co Ltd
Current assignee: Yamaha Marine Co Ltd
Priority date: 1999-10-12
Filing date: 2000-10-12
Publication date: 2006-06-28
Anticipated expiration: 2020-10-12
Also published as: EP1092849A2; JP2001107800A; EP1092849A3

Description

This invention relates to an internal combustion engine, in particular four-stroke cycle engine, according to the preamble part of the independent claim 1.
In a conventionally known method of making the four-stroke cycle engine compact, as disclosed for example in JP-A-2-274691, the engine as a whole is displaced relative to the drive shaft to produce a space where various devices of the intake system, fuel supply system, and exhaust system are disposed on both sides of the engine body.
However, the above method has problems: Since the engine as a whole is displaced with respect to the drive shaft by the use of gears, the weight of the engine increases. Moreover, since the rotating direction of the engine is changed by the use of gears, the engine must be modified to cope with the reverse rotation as by providing gears also on the rotating component side. Moreover, since the entire engine is displaced, the center of gravity is also displaced and the problem of vibration is aggravated.
From JP-A-10 238 359 an internal combustion engine as indicated above is known.
Accordingly, it is an objective of the present invention to provide improve an internal combustion engine as indicated above so as to enable an improvement of vibration.
According to the present invention, said objective is solved by an internal combustion engine having the features of the independent 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. Incidentally, the terms "the front" and "the rear" as used herein are respectively meant with respect to the advancing direction and the opposite direction of a boat.

FIG. 1 is a side view of a four-stroke cycle engine in which the invention is embodied and which is mounted in an outboard motor as an example;
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);
FIG. 3 is a cross-sectional view as seen in the direction of arrows X-X in FIG. 1;
FIG. 4 shows a cross section of an essential part of FIG. 3 in a larger scale;
FIG. 5 is a side view partially in cross section of the four-stroke cycle engine of the invention applied to an outboard motor as another form of embodiment;
FIG. 6 is a cross-sectional view as seen in the direction of arrows X-X in FIG. 5; and
FIG. 7 is a horizontal cross-sectional view of still another embodiment of the invention.

FIG. 1 is a side view of a four-stroke cycle engine in which the invention is embodied and which is mounted in an outboard motor as an example. The outboard motor 1 is provided with; a clamp bracket 3 removably attached to the a 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 supported for rotation 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 disposed in front of the cylinder body 17.
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. 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. Incidentally, the same parts are provided with the same reference numerals and their explanations are sometimes omitted in the following description. 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.
A valve drive chamber 35 is formed in 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 will be described the features of this invention in reference to FIG. 4. FIG. 4 shows a cross section of an essential part of FIG. 3 in a larger scale. One end of the connecting rod 31 is rotatably connected to the crank pin 29 using bolts 46. The other end of the connecting rod 31 is connected to the piston 21 through a piston pin 45. When the piston 21 is thrust down to rotate the crankshaft 22 in the direction of the arrow R as shown, a lateral component F of the thrust exists on the piston pin 45 (the direction of the lateral component is hereinafter simply referred to as the thrust direction). As a result, operation efficiency is lowered and durability becomes poor.
Therefore, in this embodiment, the an axis L2 of the cylinder 20 is displaced by a distance D1 in the direction opposite the direction of the lateral component F of the thrust acting on the piston 21 with respect to the a 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 slap noise is reduced. This arrangement also makes it possible as shown in FIG. 3 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. In this way, the engine is made compact without increasing 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.
When the cylinder 20 is displaced as described above, the amount of vibration occurring at the mounts 28 shown in FIG. 2 is greater on the side opposite the displacement direction side. Therefore in this embodiment, the wall thickness of each mount 28 is increased on the side opposite the displacement direction side, so that the amount of vibration is reduced.
FIGs. 5 and 6 show a four-stroke cycle engine as another embodiment of the invention. FIG. 5 is a side view partially in cross section of the engine applied to an outboard motor as an example. FIG. 6 is a cross-sectional view as seen in the direction of arrows X-X in FIG. 5. Incidentally, the same parts as those in the previous embodiment are provided with the same reference numerals and their explanations are omitted.
In this embodiment too, the axis L2 of the cylinder 20 is displaced by the distance D1 in the direction opposite the thrust component direction with respect to the line L1 that is parallel to the cylinder 20 and passes the axis of the crankshaft 22. In this way, it is possible to shift the cylinder 20 and the cylinder head 16 toward the right to produce a space which is utilized as shown in FIG. 6 to dispose the carburetor 43 and the fuel tank 27 on the left side of the engine, the camshaft 32 on the right inside the cylinder body 17, and the fuel pump 42 outside the cylinder body 17, so that the engine is made compact. A silencer 47 is shown in FIG. 5.
FIG. 7 is a horizontal cross-sectional view of still another embodiment of the invention. This embodiment shows an example of a double overhead camshaft type of multicylinder four-stroke cycle engine, with an intake cam 49 and an exhaust cam 50. In this embodiment too, the axis L2 of the cylinder 20 is displaced by the distance D1 in the direction opposite the thrust component direction with respect to the line L1 that is parallel to the cylinder 20 and passes the axis of the crankshaft 22. In this way, it is possible to shift the cylinder 20 and the cylinder head 16 toward the right to produce a space which is utilized to dispose the auxiliary devices 52 such as an alternator, an oil pump, and a water pump on the left of the engine, and to provide a balancer 51 in the left inside corner of the cylinder body 17, so that the engine is made compact.
While embodiments of the invention are described above, the invention is not limited to those embodiments but may be modified in various ways. For example, while the above embodiments are explained by way of examples in which the engine is applied to the outboard motor, the subject of application is not limited to the outboard motor but may include marine inboards, snowmobiles, road vehicles, etc.
As is clear from the above description, the invention makes it possible to improve operation efficiency and durability by reducing the lateral component of the thrust acting on the piston, to make the engine compact without increasing weight and without changing the direction of rotation. And since the crankshaft made of a heavy iron-based material is not shifted, the amount of vibration is held to a minimum as the amount of center of gravity shift is reduced. As a result, since the lateral component of the thrust acting on the cylinder is reduced, an iron-made sleeve can be disused, an aluminium-made cylinder can be used, resulting in the reduction in weight and cost.
The invention makes it possible to dispose the engine components in the space produced by shifting the cylinder and the cylinder head with respect to the crankshaft.
The invention makes it possible to hold down the vibration and reduce the size of the engine especially effectively when the invention is applied to the outboard motor that is used at high revolutions and subject to wide variation in the revolution.
The invention makes it possible to further reduce vibration.

Claims

Internal combustion engine (14), in particular four-stroke cycle engine, comprising at least one cylinder (20) formed in an engine body, a piston (21) slidingly disposed in said cylinder (20), and a crankshaft (22) connected to the piston (21) through a connecting rod (31), wherein a cylinder axis (L2) of the cylinder (20) is displaced laterally offset with respect to a parallel line (L1) intersecting an axis of the crankshaft (22), characterized in that an axis of a piston pin (45) is displaced by a distance (D2) towards the parallel line (L1) in a direction of a lateral component of thrust (F) acting on the piston (21) with respect to the axis (L2) of the cylinder (20), wherein mounts (28) are provided to support the engine, said mounts (28) having a varying wall thickness such that the wall thickness of parts of each of the mounts (28) on the side opposite to a displacement direction of the cylinder axis (L2) is increased compared to the side extending towards the displacement direction of the cylinder axis (L2).
Internal combustion engine according to claim 1, characterized in that the cylinder axis (L2) is displaced in a direction opposite to the direction of the 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 claim 1 or 2, characterized in that 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 3, characterized in that 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 4, characterized in that the engine forms part of an outboard motor and the crankshaft (22) is disposed substantially vertically.
Internal combustion engine according to at least one of the preceding claims 1 to 5, characterized in that 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 6, characterized in that 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 7, characterized in that the crankshaft (22) is made of iron-based material while the cylinder can be made of aluminium based alloy including aluminium.