Clutch mechanism of an outboard motor
A clutch mechanism of an outboard motor includes a forward gear and a reverse gear that are always driven in opposite directions by a drive shaft driven by a drive system, and a dog gear disposed around the output shaft. The forward gear, the reverse gear, and the dog gear are provided with a plurality of engaging projections and engaging recesses that can be engaged with each other, with the dog gear being engaged with either the forward gear or with the reverse gear by forceably moving the dog gear toward one side in the axial direction. A drive shaft has a drive gear and is driven by the drive system generating a maximum output power of about 300 ps or more, the forward gear and the reverse gear have input gears respectively which are always engaged with the drive gear, and the engaging projections and the engaging recesses are located radially inside of the input gears and disposed at least seven in a row along a circumference thereof.
1. A clutch mechanism for an outboard motor comprising:
a forward gear and a reverse gear arranged to rotate freely around an output shaft to drive a propeller, each of the forward gear and the reverse gear including an input gear driven by a drive gear on a drive shaft so as to rotate in opposite directions; and
a dog gear disposed around the output shaft between the forward gear and the reverse gear, the dog gear arranged to be movable in an axial direction relative to the output shaft and to be rotationally immovable in a circumferential direction relative to the output shaft; wherein
a plurality of engaging projections on engaging areas of the forward gear and the reverse gear are arranged to be engaged with a plurality of engaging recesses on engaging areas of the dog gear;
the dog gear is arranged to be engaged with either the forward gear or with the reverse gear resulting in the plurality of engaging recesses being engaged with the plurality of engaging projections to drive the output shaft;
the engaging projections and the engaging recesses are located radially inside the input gears, and include at least seven and no more than ten of the engaging projections and the engaging recesses, respectively, in a row along a circumference of the forward gear, the reverse gear, and the dog gear;
the engaging projections and the engaging recesses are located radially outside of a center axis of the output shaft in a range of about 20 mm to about 32 mm from the center axis;
at the time of engagement, a transmitted torque is dispersed to driving force transmitting surfaces defined by surfaces of the engaging projections and the engaging recesses facing each other in the circumferential direction; and
a sloping portion is arranged on tops of engaging portions between the engaging recesses of the dog gear and at least one of tops of the engaging projections of the forward gear and tops of the engaging projections of the reverse gear to guide the engaging projections into the engaging recesses.
2. The clutch mechanism of an outboard motor according to claim 1 , wherein an aggregate area of all the driving force transmitting surfaces on the engaging areas of the forward gear and the dog gear, and on the engaging areas of the reverse gear and the dog gear is at least about 340 mm 2 .
3. The clutch mechanism of an outboard motor according to claim 1 , wherein an outer edge on each driving force transmitting surface is arranged to be aligned in a direction substantially perpendicular to an axial direction of the output shaft, and an aggregate length of all the outer edges on each of the engaging areas is at least about 70 mm.
4. The clutch mechanism of an outboard motor according to claim 1 , wherein an aggregate area of all the driving force transmitting surfaces on the engaging areas of the forward gear and the dog gear, and on the engaging areas of the reverse gear and the dog gear is at least about 390 mm 2 .
5. The clutch mechanism of an outboard motor according to claim 1 , wherein the engaging projections and the engaging recesses include nine of the engaging projections and the engaging recesses, respectively, in a row along a circumference of the forward gear, the reverse gear, and the dog gear.
6. The clutch mechanism of an outboard motor according to claim 1 , wherein each of the engaging projections has a length along the circumference of the forward gear and the reverse gear that is smaller than a length of each of the engaging recesses along the circumference of the dog gear by more than 3 degrees to about 12 degrees in terms of an angle about the center axis of the output shaft.