Propulsion unit for marine drive

Abstract

A marine propulsion unit having an oil circulation system is provided. In the oil circulation system, lubricant is delivered from a bevel gear mechanism adjacent a drive shaft through an oil passage defined in a lower casing to a journal bearing supporting the drive shaft. From the drive shaft journal bearing, the lubricant flows through a gap between the drive shaft and the inner peripheral wall of a drive shaft chamber in the lower casing and then returns to the bevel gear mechanism.

1 . A marine drive having an engine and a propulsion unit, the propulsion unit comprising a drive shaft driven by the engine, a bevel gear mechanism, a propeller shaft driven by the drive shaft via the bevel gear mechanism, a lower casing adapted to support the propeller shaft, bevel gear mechanism, and drive shaft, the propeller shaft having a projection projecting generally rearward from the lower casing, a drive shaft bearing for rotatably supporting a journal of the drive shaft, the drive shaft having a bevel gear mechanism attachment part, and a lubricant circulating system adapted to circulate lubricant between the bevel gear mechanism attachment part and the drive shaft bearing, the lubricant circulating system comprising a first lubricant passage extending in the lower casing from the bevel gear mechanism attachment part to the drive shaft bearing and a second lubricant passage defined in a gap between the drive shaft and an inner peripheral wall of a drive shaft chamber in the lower casing and extending from the drive shaft bearing to the bevel gear mechanism attachment part, wherein the lubricant circulating system is configured so that lubricant flows from the bevel gear mechanism attachment part to the drive shaft bearing through the first passage, and from the drive shaft bearing to the bevel gear mechanism attachment part through the second passage. 
     
     
         2 . A marine drive as in  claim 1 , wherein the bevel gear mechanism is adapted to function as a pump to urge lubricant into the first lubricant passage upon rotation of the drive shaft. 
     
     
         3 . A marine drive as in  claim 2 , wherein the drive shaft has a spiral groove disposed in the periphery thereof, the spiral grove delivering lubricant downward upon rotation of the drive shaft. 
     
     
         4 . A marine drive as in  claim 2 , wherein the first lubricant passage is at least partially defined by a shift shaft chamber having a shift shaft disposed therein, the shift shaft selectively setting the bevel gear mechanism to a forward drive mode or a reverse drive mode. 
     
     
         5 . A marine drive as in  claim 2 , wherein the marine drive comprises an outboard motor. 
     
     
         6 . A marine drive as in  claim 1 , wherein the drive shaft has a spiral groove disposed in the periphery thereof, the spiral grove delivering lubricant downward upon rotation of the drive shaft. 
     
     
         7 . A marine drive as in  claim 6 , wherein the first lubricant passage is at least partially defined by a shift shaft chamber having a shift shaft disposed therein, the shift shaft selectively setting the bevel gear mechanism to a forward drive mode or a reverse drive mode. 
     
     
         8 . A propulsion unit for a marine drive, comprising a drive shaft adapted to be driven by an engine of the marine drive, a bevel gear mechanism chamber enclosing a bevel gear mechanism that connects to a lower portion of the drive shaft and is driven by the drive shaft, a propeller shaft having a forward portion that is connected to the bevel gear mechanism and is driven by the drive shaft via the bevel gear mechanism, a lower casing comprising the bevel gear mechanism chamber, a drive shaft journal bearing disposed above the bevel gear mechanism chamber for rotatably supporting the drive shaft, and a lubricant circulation system adapted to circulate lubricant between the bevel gear mechanism chamber and the drive shaft journal bearing, the lubricant circulation system comprising a first passage extending generally upwardly from the bevel gear mechanism chamber to the drive shaft journal bearing and a second passage defined in a gap between the drive shaft and an inner peripheral wall of a drive shaft chamber in the lower casing and extending from the drive shaft journal bearing to the bevel gear mechanism chamber, wherein the lubricant circulation system is configured so that lubricant flows from the bevel gear mechanism chamber into the first passage to the drive shaft journal bearing and then through the second passage back to the bevel gear mechanism chamber. 
     
     
         9 . A propulsion device as in  claim 8 , wherein the bevel gear mechanism functions as a pump to urge lubricant into the first passage upon rotation of the drive shaft. 
     
     
         10 . A propulsion device as in  claim 9 , wherein the drive shaft has a spiral groove disposed in the periphery thereof, the spiral grove delivering lubricant downward upon rotation of the drive shaft. 
     
     
         11 . A propulsion device as in  claim 8 , wherein the first passage is at least partially defined by a shift shaft chamber having a shift shaft disposed therein, the shift shaft selectively setting the bevel gear mechanism to a forward drive mode or a reverse drive mode.