A marine propulsion unit comprising a compound planetary gear

Abstract

A marine propeller propulsion unit has a compound planetary gear for driving a propeller, a propulsion motor for driving the compound planetary gear, and a housing for enclosing the propulsion motor and the compound planetary gear. The compound planetary gear comprises a sun gear, a ring gear, a planet carrier, a first planet gear and a second planet gear. The radius of the second planet gear exceeds the radius of the first planet gear and the first and second planet gears are rotationally fixed to one another. The ring gear meshes with the first planet gear and the sun gear meshes with the second planet gear. The sun gear is adapted to be connected to the propulsion motor and the ring gear is adapted to be connected to the propeller.

1 . A marine propeller propulsion unit comprising a compound planetary gear for driving a propeller, a propulsion motor for driving the compound planetary gear, and a housing for enclosing the propulsion motor and the compound planetary gear, the compound planetary gear comprising
 a sun gear,   a ring gear,   a planet carrier, and   a first planet gear and a second planet gear, wherein the radius of the second planet gear exceeds the radius of the first planet gear and the first and second planet gears are rotationally fixed to one another,   wherein the ring gear meshes with the first planet gear and the sun gear meshes with the second planet gear, and   
       wherein the sun gear is adapted to be connected to the propulsion motor and the ring gear is adapted to be connected to the propeller. 
     
     
         2 . The marine propeller propulsion unit of  claim 1 , wherein the propulsion motor is an electric motor. 
     
     
         3 . The marine propeller propulsion unit of  claim 1 , wherein the marine propeller propulsion unit comprises one single propulsion motor. 
     
     
         4 . The marine propeller propulsion unit of  claim 1 , wherein the marine propulsion unit is configured such that the housing at least during operation is completely submerged under water. 
     
     
         5 . The marine propeller propulsion unit of  claim 1 , wherein the radiuses of the sun gear and the first planet gear are essentially equal or differ by up to 20 percent. 
     
     
         6 . The marine propeller propulsion unit of  claim 1 , wherein the radius of the second planet gear is 1.5 to 3 times the radius of the first planet gear. 
     
     
         7 . The marine propeller propulsion unit of  claim 1 , wherein the compound planetary gear is adapted to during operation be arranged with its longitudinal axis arranged essentially in plane with a vessel that comprises, and during operation is propelled by, the marine propeller propulsion unit. 
     
     
         8 . The marine propeller propulsion unit of  claim 1 , wherein the compound planetary gear comprises helical gears and is configured to cancel out any axial forces generated by the compound planetary gear during operation. 
     
     
         9 . The marine propeller propulsion unit of  claim 1 , wherein the marine propeller propulsion unit does not comprise any moving part positioned radially outside the ring gear or the first or second planet gear, apart from the propeller. 
     
     
         10 . The marine propeller propulsion unit of  claim 1 , wherein the sun gear is connected to the propulsion motor such that the sun gear and the propulsion motor are adapted to rotate at the same velocity. 
     
     
         11 . The marine propeller propulsion unit of  claim 1 , wherein the compound planetary gear is configured for driving a first and a second propeller, wherein the ring gear is adapted to be connected to the first propeller, and the planet carrier is adapted to be connected to the second propeller. 
     
     
         12 . The marine propeller propulsion unit of  claim 11 , comprising one single input shaft connecting the compound planetary gear and the propulsion motor. 
     
     
         13 . The marine propeller propulsion unit of  claim 12 , wherein the propulsion motor is directly connected to the input shaft such that the propulsion motor and the input shaft are adapted to rotate at the same velocity. 
     
     
         14 . The marine propeller propulsion unit of  claim 1 , wherein the marine propeller propulsion unit is configured as a rearward drive propulsion unit, and the first propeller is a front propeller and the second propeller is a rear propeller or, wherein the marine propeller propulsion unit is configured as a forward drive propulsion unit, and the first propeller is a rear propeller and the second propeller is a front propeller. 
     
     
         15 . The marine propeller propulsion unit of  claim 1 , comprising a brake configured to directly or indirectly brake the ring gear to increase the rotational speed of the planet carrier and/or to directly or indirectly brake the planet carrier to increase the rotational speed of the ring gear. 
     
     
         16 . The marine propeller propulsion unit of  claim 1 , wherein the compound planetary gear comprises helical gears and is configured to cancel out any axial forces generated by the compound planetary gear during operation. 
     
     
         17 . The marine propeller propulsion unit of  claim 16 , wherein helical gears of the sun gear and of the ring gear have opposite helix hands. 
     
     
         18 . The marine propeller propulsion unit of  claim 1 , wherein the compound planetary gear comprises three of four pairs of first and second planet gears. 
     
     
         19 . Use of a compound planetary gear in a marine propeller propulsion unit for driving a first and a second propeller by means of an input shaft, wherein the compound planetary gear comprises: a sun gear; a ring gear; a planet carrier; and a first planet gear and a second planet gear, wherein the radius of the second planet gear exceeds the radius of the first planet gear and the first and second planet gears are rotationally fixed to one another; wherein the ring gear meshes with the first planet gear and the sun gear meshes with the second planet gear; and the sun gear is adapted to be connected to the input shaft, the ring gear is adapted to be connected to the first propeller, and the planet carrier is adapted to be connected to the second propeller. 
     
     
         20 . A marine vessel comprising the marine propeller propulsion unit of  claim 1 .