Outboard motor

An outboard motor cam have a power transmission mechanism for transmitting rotational power of a crankshaft of an engine to a propeller through a drive shaft, an advancing/reversing-switching mechanism and a propeller shaft, and adapted to be propelled by the propeller being driven for rotation. A torque variation-absorbing device can be disposed in a coupling section between the crankshaft and the drive shaft, and supported through bearings.

PRIORITY INFORMATION

The present application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application Ser. No. 2004-193498, filed Jun. 30, 2004, the entire contents of which is hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTIONS

1. Field of the Inventions

The present inventions relate to an outboard motor mounted, for example, on a small watercraft or the like.

2. Description of the Related Art

Typically, outboard motors include a power transmission mechanism for transmitting rotational power of the crankshaft of an engine to a propeller through a drive shaft. An advancing/reversing-switching mechanism (also known as a forward-reverse-neutral transmission) connects the drive shaft with a propeller shaft and allows the propeller shaft to be shifted between neutral, forward, and reverse thrust modes.

The connections between various components of the drive trains typically used in outboard motors are provided with small clearances, often referred to as mechanical “play” to reduce friction at these connections and for other reasons. As such, the components forming the connections collide with each other at various times. For example, when the transmission is shifted, and when there are variations in the torque output from the engine, these components strike each other.

The collisions between these parts generate noises. These noises are particularly noticeable in large outboard motors such as those including high horse power four-stroke engines. Further, in outboard motors with high horsepower, the passengers of the associated boat can experience unpleasant shocks due to abrupt change in propulsion force produced, for example, at the time of shifting.

Thus, several different designs have been proposed for absorbing shocks, such as those designs in Japanese Patent Nos. JP-A-Sho 60-215495 (P1–P7, FIG. 1–FIG. 13) and JP-A-2000-280983 (P1–P10, FIG. 1–FIG. 13).

Japanese Patent No. JP-A-Sho 60-215495 discloses an arrangement in which a drive shaft is divided into a driving section and a driven section, and a shock absorbing device is disposed between the two sections. Japanese Patent No. JP-A-2000-280983 discloses an arrangement in which either a drive shaft or a propeller shaft is divided into a driving section and a driven section, and a shock absorbing device is disposed between two sections.

SUMMARY OF THE INVENTIONS

An aspect of at least one of the embodiments disclosed herein includes the realization that by supporting a portion of the drivetrain of an outboard motor with a bearing in the vicinity of a torque-variation absorbing device, a more effective torque variation absorbing device can be used. For example, a bearing can provide support to a drive train such that a softer, more compliant absorbing device, such as an absorbing device partially made with rubber or rubber-like materials, can be used in the vicinity of the bearing without sacrificing the integrity of the drivetrain.

Thus, in accordance with an embodiment, an outboard motor comprises an engine having a crankshaft, a drive shaft, an advancing/reversing-switching mechanism, a propeller shaft, a propeller, and a torque variation-absorbing device disposed in a coupling section between the crankshaft and the drive shaft. The torque variation-absorbing device can be supported through a bearing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Non-limiting embodiments of an outboard motor are described below. These preferred embodiments are not intended to limit the scope of the inventions disclosed herein.

The embodiments disclosed herein are described in the context of a marine propulsion system of a small boat because these embodiments have particular utility in this context. However, the embodiments and inventions herein can also be applied to other marine vessels, such as personal watercraft and small jet boats, as well as other vehicles.

The outboard motor1of the illustrated embodiment is attached, through a clamping bracket2, to a transom plate50aprovided on a hull50of a small watercraft (partially shown). An outboard motor body1A of the outboard motor1is supported on the clamping bracket2for up and down pivotal movement about a tilting shaft3provided on the clamping bracket2.

The outboard motor body1A can have a cowling comprising a top cowling4a1and a lower cowling4a2. The top cowling4a1is configured to removable from the lower cowling4a2. Additionally, the outboard motor body1A can include a casing made up of an upper casing4b1and a lower casing4b2.

In the upper part of the outboard motor body1A, an engine5can be housed in the top cowling4a1and the lower cowling4a2. The engine5can be a four-stroke engine. However, this is merely one type of engine that can be used with the inventions disclosed herein. Engines having any number of cylinders, any cylinder arrangement, any cylinder orientation (e.g., upright cylinder banks, V-type, and W-type), and operating on any combustion principle (e.g., two stroke, diesel, and rotary) are all practicable for use with the inventions disclosed herein.

Below the outboard motor body1A, a propeller20is supported on the lower casing4b2. Rotational forces from the engine5are transmitted to the propeller20through a power transmission mechanism10housed in the upper casing4b1and lower casing4b2.

The engine5can have a plurality of cylinders arranged vertically and a crankshaft disposed in the vertical direction, extending downwardly from the engine5. The power transmission mechanism10can comprises a drive shaft11, an advancing/reversing-switching mechanism12(a.k.a. forward/neutral/reverse transmission), a propeller shaft13and the like.

The drive shaft11is coupled to the crankshaft7with a torque variation-absorbing device60. The drive shaft11extends downwardly from the engine5. The advancing/reversing-switching mechanism12is configured to shift the rotational direction of the drive shaft11between forward and reverse. The propeller20can be attached to the rear end of the propeller shaft13an can be coupled to the advancing/reversing-switching mechanism12at the output side.

In the middle of the drive shaft11can be provided a water pump21driven by the drive shaft11. Switching between advancing and reversing in the advancing/reversing-switching mechanism12can be accomplished with a shift rod22.

With reference toFIG. 2toFIG. 7, the torque variation-absorbing device60can have a crankshaft-side coupling body61spline-fitted in the crankshaft7, a drive shaft-side coupling body62spline-fitted on the drive shaft11, and a torque variation-absorbing body63that is disposed between the crankshaft-side coupling body61and the drive shaft-side coupling body62. However, other arrangements can also be used.

With reference toFIGS. 5(a) and5(b), the crankshaft-side coupling body61can be formed from a metallic material, through a process, such as, but without limitation, forging. The body61can have a flange coupling61aand a spline coupling-shaft section61b, as shown inFIG. 2andFIG. 5.

The flange coupling61acan have a cylinder portion61a1, a flange portion61a2formed at one end of the cylinder portion61a1, and three flange portions61a3extending outwardly from the flange portion61a2at positions angularly spaced by approximately 120°, however, other arrangements and other numbers of flanges can also be used.

The flange portion61a2can be formed with mounting female screw holes61a4for the coupling to the spline coupling-shaft section61b, at four locations angularly spaced by approximately 90°, however, other arrangements can also be used. Also, each of the three mounting portions61a3can be formed with a mounting female screw hole61a5for the coupling to the torque variation-absorbing body63.

The spline coupling-shaft section61bcan have a spline shaft portion61b1, and a flange portion61b2formed at the end of the spline shaft portion61b1. The flange portion61b2can be formed with mounting through-holes61b3for the coupling to the flange coupling61a, at four locations.

The flange coupling61aand the spline coupling-shaft section61bcan be coupled together with four fastening members or bolts64each inserted into the mounting through-hole61b3of the spline coupling-shaft section61band fitted in the mounting female screw hole61a4of the flange coupling61afor fixing, although other arrangements and connections can also be used.

With reference toFIGS. 6(a) and6(b), the drive shaft-side coupling body62can be formed from a metallic material by a process such as, for example, but without limitation, forging. The body62can have a flange coupling62aand a spline coupling-shaft section62b, as shown inFIG. 2andFIG. 6. The flange coupling62acan have a cylinder portion62a1, a flange portion62a2formed at the end of the cylinder portion62a1, and three flange portions62a3extending outwardly from the flange portion62a2at positions angularly spaced by approximately 120°, although other arrangements and numbers of flanges can also be used.

Each of the three mounting portions62a3can be formed with a mounting female screw hole62a4for the coupling to the torque variation-absorbing body63. Also, the cylinder portion62a1can be formed with a mounting spline hole62a5for the coupling to the spline coupling-shaft section62b, at its axial center.

The spline coupling-shaft section62bcan have a spline bottomed cylinder portion62b1, a flange portion62b2formed at the bottom of the spline bottomed cylinder portion62b1, and a mounting spline shaft portion62b3formed at the bottom of the spline bottomed cylinder portion62b1and extending in the axial direction, as shown inFIG. 2.

The flange coupling62aand the spline coupling-shaft section62bcan be coupled together, with the mounting spline shaft portion62b3of the spline coupling-shaft section62bspline-fitted in a mounting spline hole62a5of the flange coupling62aand with a nut66fastened through a washer65to the mounting spline shaft portion62b3for fixing. However, other arrangements and connections can also be used.

With reference toFIGS. 7(A) and 7(b), the torque variation-absorbing body63can be made up of insert metals and rubber members, having six insert metals63a1–63a6and six rubber members63b1–63b6, as shown inFIG. 2andFIG. 7. However, other arrangements and numbers of insert metals and rubber members can also be used.

The six insert members63a1–63a6can be located at the corners of an equilateral hexagon, respectively, as shown inFIG. 7, although other arrangements can also be used. The six rubber members63b1–63b6can each be coupled to their respective insert metals63a1–63a6, so that the torque variation-absorbing body63can be formed in the annular shape of an equilateral hexagon.

Of the insert metals63a1–63a6, the insert metals63a2,63a4,63a6can each be disposed so as to be offset by a distance D1. The non-offset insert metals63a1,63a3,63a5can be formed with mounting through-holes63a11,63a31,63a51for the mounting to the flange coupling61a.

The offset insert metals63a2,63a4,63a6can be formed with mounting through-holes63a21,63a41,63a61for the mounting to the flange coupling62a, respectively. The torque variation-absorbing body63can be disposed between the crankshaft-side coupling body61and the drive shaft-side coupling body62. Regarding the drive shaft-side coupling body62, an oil seal70and a bushing71can be supported on the cylinder portion62a1of the flange coupling62aby a circlip72, and the cylinder portion62a1can be fitted in the cylinder portion61a1of the flange coupling61ato assemble the crankshaft-side coupling body61and the drive shaft-side coupling body62.

Regarding the torque variation-absorbing body63and the crankshaft-side coupling body61, the insert metals63a1,63a3,63a5can be assembled to the three mounting portions61a3of the flange coupling61athrough spring pins73. Crankshaft-side fastening members67can be inserted in the mounting through-holes63a11,63a31,63a51to be screwed in the female screw holes61a5for fixing.

Regarding the torque variation-absorbing body63and the drive shaft-side coupling body62, the insert metals63a2,63a4,63a6of the torque variation absorbing body63can be assembled to the three mounting portions62a3of the flange coupling62athrough spring pins74. Crankshaft-side fastening members68can be inserted in the mounting through-holes63a21,63a41,63a61to be screwed in the female screw holes62a4for fixing.

As described above, since the torque variation-absorbing body63can be fastened fixedly to the crankshaft-side coupling body61and the drive shaft-side coupling body62, easy and firm integration can be effected without using a special fixing structure.

In the drive shaft-side coupling body62, two bearings75can be supported on the spline bottomed cylinder portion62b1of the spline coupling-shaft section62bby a circlip76. A collar77can be disposed between the two bearings75.

On the two bearings75, a bearing holder78can be held by a circlip79. Thus, the torque variation-absorbing device60and the bearings75can be assembled in advance and arranged as a torque variation-absorbing unit A, thereby providing easy assembly between the engine5and the guide exhaust90or between the guide exhaust90and the upper casing4b1.

In this torque variation-absorbing unit A, the spline shaft portion61b1of the spline coupling-shaft section61bcan be spline fitted into the spline hole section7aof the crankshaft7, the spline bottomed cylinder portion62b1of the spline coupling-shaft section62bcan be spline-fitted on the drive shaft11at the spline upper end11athereof, and the bearing holder78can be disposed so as to be attached to a bracket81of a block80.

The bracket81can have a bearing holder-mounting portion81aand a block-mounting portion81b, as shown inFIG. 2andFIG. 3. The bearing holder-mounting portion81aand the bearing holder78of the bracket81can be fastened fixedly with bolts82. The block-mounting portion81band the block80can be fastened fixedly with bolts83. As such, the bearings75can be fixed relative to the crankcase99while rotatably supporting the driveshaft11.

The block80can be disposed between the engine5and the guide exhaust member90, as shown inFIG. 2andFIG. 3. Onto the top side of the block80can be fastened fixedly a crankcase99with bolts95. Below the block80, the guide exhaust90and an exhaust box91can be mounted with bolts96.

The block80can be provided with an exhaust gas passage80a, a cooling water passage80b, a supply-lubricating oil passage80cand a return-lubricating oil passage80d, as shown inFIG. 3andFIG. 4. The guide exhaust90can be provided with an exhaust gas passage90a, a cooling water passage90b, a supply-lubricating oil passage90cand a return-lubricating oil passage90d, as shown inFIG. 2andFIG. 3.

The exhaust gas passage80a, cooling water passage80b, supply-lubricating oil passage80cand return-lubricating oil passage80din the block80can be in communication with the exhaust gas passage90a, cooling water passage90b, supply-lubricating oil passage90cand return-lubricating oil passage90dof the guide exhaust90, respectively. Thus, various kinds of passages can be formed in the block80, thereby providing easy communication between these various kinds of passages.

In addition, a cover85for covering the torque variation-absorbing device60can be fastened fixed to the block80with bolts86, as shown inFIG. 2andFIG. 4. The cover85can have a portion85acovering the upper side of the torque variation-absorbing device and a portion85bcovering half the side thereof, and opens downwardly.

A recessed portion80eof the block80can cover approximately a half of the torque variation-absorbing device60in the lateral direction. The cover85can be configured to cover the torque variation-absorbing device60from the upper side and approximately half of the device60in the lateral direction, as viewed inFIG. 4. As such, the cover85can prevent electric wires or the like from contacting the torque variation-absorbing device60.

The block80can be supported on the upper casing4b1and the bearings75can be mounted to the block80through the bearing holder78and bracket81. As such, the block80allows easy formation of various kinds of passages and a simple mounting structure.

Further, the guide exhaust90can be arranged such that it can be formed like a block, with one portion extending upwardly. The bearings75can be mounted to the guide exhaust90in the same construction. The guide exhaust90can be supported on the upper casing4b1. Utilizing the guide exhaust90allows simple and reliable mounting of the bearings75.

In this embodiment, as shown inFIG. 9, a flywheel magneto can be provided above the crankshaft7of the engine5. During operation, rotational power of the crankshaft7can be transmitted to the propeller20through the torque variation-absorbing device60, drive shaft11, advancing/reversing-switching mechanism12and propeller shaft13. The advancing/reversing-switching mechanism12can have a pinion12a, gears12band a dog clutch12c. Although mechanical play still exists between the various parts of the power transmission mechanism from the drive shaft11to the propeller shaft13and torque variations are produced during engine operation, the torque variations and vibrations from collisions can be absorbed by the torque variation-absorbing body63of the torque variation-absorbing device60. As such, the noise of colliding parts can be reduced. Further, riders will experience less unpleasant shocks.

In this embodiment, as shown inFIG. 9, since the torque variation-absorbing device60can be disposed in a coupling section between the crankshaft7and drive shaft11and the coupling section of the power transmission mechanism can be utilized to dispose the torque variation-absorbing device60, a simple structure can be obtained without need of dividing the drive shaft11, for example. In addition, the section where torque variations can be absorbed can be supported reliably through bearings75. As such, collision noises of the power transmission mechanism can be reduced and unpleasant shock feelings transmitted to riders can be reduced.

Further, as described above, the torque variation-absorbing device60can be disposed between the crankshaft7and the drive shaft II, so that the space under the engine can be utilized to dispose a shift operation member88or the like without interference. Furthermore, since the torque variation-absorbing device60can be located above the drive shaft11, its assembly or maintenance can be performed easily from the engine side.

The torque variation-absorbing device60comprises a torque variation-absorbing body63, a crankshaft-side coupling body61and a drive shaft-side coupling body62, providing a simple structure in which the coupling section of the crankshaft7and the drive shaft11can be utilized to dispose the torque variation-absorbing device60. Further, the drive shaft-side coupling body62located below the torque variation-absorbing device60can be supported reliably by the bearings75.