Planetary transmission arrangements for marine propulsion devices

1. A transmission for a marine propulsion device having an internal combustion engine that drives a propulsor for propelling a marine vessel in water, the transmission comprising:

an input shaft that is driven into rotation by the engine;

an output shaft that drives the propulsor into rotation,

a forward planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into forward rotation;

a reverse planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into reverse rotation,

a forward brake that engages the forward planetary gearset in a forward gear in which the forward planetary gearset drives the output shaft into the forward rotation; and

a reverse brake that engages the reverse planetary gearset in a reverse gear in which the reverse planetary gearset drives the output shaft into the reverse rotation;

wherein actuation of neither of the forward brake and the reverse brake actuates a neutral gear in which the output shaft is disconnected from the input shaft;

wherein the forward planetary gearset comprises a forward ring gear that is fixed to and rotates with the input shaft, the forward ring gear comprising a radially inwardly facing gear surface;

wherein the forward planetary gearset further comprises a forward sun gear that is disposed on the output shaft, the forward sun gear comprising a radially outwardly facing gear surface;

wherein the forward sun gear comprises a radially inwardly facing bearing surface that bears on the output shaft such that the forward sun gear is rotatable with respect to the output shaft; and

wherein the forward planetary gearset further comprises a forward brake drum that rotates with the forward sun gear;

wherein the forward planetary gearset further comprises a plurality of forward planet gears that are rotatable about their own center axis and that are radially disposed between the forward ring gear and the forward sun gear, wherein each forward planet gear in the plurality of forward planet gears comprises a radially outwardly facing gear surface that is engaged with the radially inwardly facing gear surface of the forward ring gear and the radially outwardly facing gear surface of the forward sun gear;

wherein the forward planetary gearset further comprises a forward carrier that retains the plurality of forward planet gears, wherein the forward carrier is fixed to and rotates with the output shaft, and wherein the forward carrier is rotatable with respect to the forward ring gear and the forward sun gear;

wherein the reverse planetary gearset comprises a reverse sun gear that is fixed to and rotates with the input shaft, the reverse sun gear comprising a radially outwardly facing gear surface;

wherein the reverse planetary gearset further comprises a reverse ring gear that is fixed to and rotates with the forward carrier, the reverse ring gear comprising radially inwardly facing gear surface;

wherein the reverse planetary gearset further comprises a plurality of reverse planet gears that are rotatable about their own center axis and that are radially disposed between the reverse ring gear and the reverse sun gear, wherein each reverse planet gear in the plurality of reverse planet gears comprises a radially outwardly facing gear surface that is engaged with the radially inwardly facing gear surface of the reverse ring gear and the radially outwardly facing gear surface of the reverse sun gear;

wherein the reverse planetary gearset further comprises a reverse carrier that retains the plurality of reverse planet gears, wherein the reverse carrier is rotatable with respect to the reverse ring gear and the reverse sun gear;

wherein in neutral gear, rotation of the input shaft does not cause rotation of the output shaft;

wherein in neutral gear, forward rotation of the input shaft causes forward rotation of the reverse sun gear, which causes reverse rotation of the plurality of reverse planet gears, which causes forward rotation of the reverse carrier and reverse drum; and wherein forward rotation of the input shaft further causes forward rotation of the forward ring gear, which causes forward rotation of the plurality of forward planet gears and thus reverse rotation of the forward sun gear.

2. The transmission according to claim 1 , further comprising a reverse drum that rotates with the reverse carrier.

3. The transmission according to claim 2 , wherein the forward brake and the reverse brake are band brakes that act on the forward drum and reverse drum, respectively.

4. The transmission according to claim 3 , wherein at least one of the forward and reverse brakes comprises a double-wrapped band brake.

5. The transmission according to claim 2 , further comprising an actuator that actuates at least one of the forward and reverse brakes.

6. The transmission according to claim 1 , wherein in forward gear:

the forward drum and the forward sun gear are held stationary by the forward brake; and forward rotation of the input shaft causes forward rotation of the forward ring gear, which causes forward rotation of the plurality of forward planet gears and forward rotation of the forward carrier and the output shaft.

7. The transmission according to claim 6 , wherein in reverse gear;

the reverse carrier is held stationary by the reverse brake, which prevents the plurality of reverse planet gears from rotating about the reverse sun gear; and

forward rotation of the input shaft causes forward rotation of the reverse sun gear, which causes reverse rotation of the plurality of reverse planet gears about their own axis, which causes reverse rotation of the reverse ring gear, which causes reverse rotation of the forward carrier and the output shaft.

8. The transmission according to claim 7 , wherein rotation of the input shaft simultaneously directly powers the forward planetary gearset via the forward ring gear and the reverse planetary gearset via the reverse sun gear.

9. The transmission according to claim 1 , wherein rotation of the input shaft simultaneously directly powers both of the forward and reverse planetary gearsets.

10. The transmission according to claim 1 , wherein the output shaft and input shaft are coaxially aligned.

11. The transmission according to claim 10 , comprising a first plurality of bearings that supports the forward planetary gearset and a second plurality of bearings that supports the reverse planetary gearset, wherein the first and second pluralities of bearings are coaxially aligned.

12. The transmission according to claim 1 , comprising a belt that connects the input shaft to a lubrication pump such that rotation of the input shaft powers the lubrication pump.

13. The transmission according to claim 1 , comprising a water pump connected to the input shaft, wherein rotation of the input shaft powers the water pump.

14. A transmission for a marine propulsion device having an internal combustion engine that drives a propulsor for propelling a marine vessel in water, the transmission comprising:

an input shaft that is driven into rotation by the engine;

an output shaft that drives the propulsor into rotation;

a forward planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into forward rotation;

a reverse planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into reverse rotation;

a forward brake that engages the forward planetary gearset in a forward gear wherein the forward planetary gearset drives the output shaft into the forward rotation; and

a reverse brake that engages the reverse planetary gearset in a reverse gear wherein the reverse planetary gearset drives the output shaft into the reverse rotation;

wherein the forward and reverse planetary gearsets both provide the same speed reduction from the input shaft to the output shaft.

15. A transmission for a marine propulsion device having an internal combustion engine that drives a propulsor for propelling a marine vessel in water, the transmission comprising:

an input shaft that is driven into rotation by the engine;

an output shaft that drives the propulsor into rotation;

a forward planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into forward rotation;

a reverse planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into reverse rotation;

a forward brake that engages the forward planetary gearset in a forward gear wherein the forward planetary gearset drives the output shaft into the forward rotation; and

a reverse brake that engages the reverse planetary gearset in a reverse gear wherein the reverse planetary gearset drives the output shaft into the reverse rotation;

wherein the forward planetary gearset comprises

a forward ring gear that is fixed to and rotates with the input shaft, the forward ring gear comprising a radially inwardly facing gear surface,

a forward sun gear that is disposed on the output shaft, the forward sun gear comprising a radially outwardly facing gear surface,

a radially inwardly facing bearing surface that bears on the output shaft such that the forward sun gear is rotatable with respect to the output shaft,

a forward brake drum that rotates with the forward sun gear,

a plurality of forward planet gears that are rotatable about their own center axis and that are radially disposed between the forward ring gear and the forward sun gear, wherein each forward planet gear in the plurality of forward planet gears comprises a radially outwardly facing gear surface that is engaged with the radially inwardly facing gear surface of the forward ring gear and the radially outwardly facing gear surface of the forward sun gear, and

a forward carrier that retains the plurality of forward planet gears, wherein the forward carrier is fixed to and rotates with the output shaft, and wherein the forward carrier is rotatable with respect to the forward ring gear and the forward sun gear, and

wherein in forward gear the forward drum and the forward sun gear are held stationary by the forward brake, and forward rotation of the input shaft causes forward rotation of the forward ring gear, which causes forward rotation of the plurality of forward planet gears and forward rotation of the forward carrier and the output shaft.

16. A transmission for a marine propulsion device having an internal combustion engine that drives a propulsor for propelling a marine vessel in water, the transmission comprising:

an input shaft that is driven into rotation by the engine;

an output shaft that drives the propulsor into rotation;

a forward planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into forward rotation, the forward planetary gearset comprising a forward carrier;

a reverse planetary gearset that connects the input shaft to the output shaft so as to drive the output shaft into reverse rotation;

a forward brake that engages the forward planetary gearset in a forward gear wherein the forward planetary gearset drives the output shaft into the forward rotation; and

a reverse brake that engages the reverse planetary gearset in a reverse gear wherein the reverse planetary gearset drives the output shaft into the reverse rotation;

wherein the reverse planetary gearset comprises

a reverse sun gear that is fixed to and rotates with the input shaft, the reverse sun gear comprising a radially outwardly facing gear surface,

a reverse ring gear that is fixed to and rotates with the forward carrier, the reverse ring gear comprising radially inwardly facing gear surface,

a plurality of reverse planet gears that are rotatable about their own center axis and that are radially disposed between the reverse ring gear and the reverse sun gear, wherein each reverse planet gear in the plurality of reverse planet gears comprises a radially outwardly facing gear surface that is engaged with the radially inwardly facing gear surface of the reverse ring gear and the radially outwardly facing gear surface of the reverse sun gear,

a reverse carrier that retains the plurality of reverse planet gears, wherein the reverse carrier is rotatable with respect to the reverse ring gear and the reverse sun gear, and

a reverse drum that rotates with the reverse carrier,

wherein in the reverse gear the reverse carrier is held stationary by the reverse brake, which prevents the plurality of reverse planet gears from rotating about the reverse sun gear, and forward rotation of the input shaft causes forward rotation of the reverse sun gear, which causes reverse rotation of the plurality of reverse planet gears about their own axis, which causes reverse rotation of the reverse ring gear, which causes reverse rotation of the forward carrier and the output shaft.