Ship propulsion machine

Abstract

A ship propulsion machine includes a power unit and a drive shaft that includes a power transmission device configured to selectively transmit at least one of a first power output from a first motor shaft of a first motor and a second power output from a second motor shaft of a second motor to the drive shaft. The first motor and the second motor are arranged in an upper part of the ship propulsion machine. The first motor shaft, the second motor shaft, and the drive shaft extend vertically. The second motor is arranged above the first motor. An upper portion of the drive shaft passes through the first motor shaft to be rotatable independently of the first motor shaft and reaches a region between the first motor and the second motor. The power transmission device is arranged between the first motor and the second motor.

What is claimed is: 
     
         1 . A ship propulsion machine comprising:
 a power unit configured to generate power;   a propeller; and   a drive shaft configured to transmit the power generated by the power unit to the propeller,   wherein the power unit comprises:
 a first motor comprising a first motor shaft; 
 a second motor comprising a second motor shaft; and 
 a power transmission device configured to transmit at least one of a first power output from the first motor shaft and a second power output from the second motor shaft to the drive shaft, and switch power to be transmitted to the drive shaft such that at least one of the first power and the second power is selected, 
   wherein the first motor and the second motor are arranged in an upper part of the ship propulsion machine,   wherein each of the first motor shaft, the second motor shaft, and the drive shaft extends vertically,   wherein the second motor is arranged above the first motor,   wherein an upper portion of the drive shaft passes through the first motor shaft so as to be rotatable independently of the first motor shaft and reaches a region between the first motor and the second motor, and   wherein the power transmission device is arranged between the first motor and the second motor.   
     
     
         2 . The ship propulsion machine according to  claim 1 , wherein the power transmission device is configured to transmit one or both of the first power and the second power to the drive shaft, and switch the power to be transmitted to the drive shaft so as to be selectable from among (a) both of the first power and the second power, (b) the first power, and (c) the second power. 
     
     
         3 . The ship propulsion machine according to  claim 1 ,
 wherein the power transmission device comprises a dog clutch,   wherein the dog clutch is attached to the upper portion of the drive shaft so as to be non-rotatable with respect to the drive shaft and movable vertically with respect to the drive shaft,   wherein a lower portion of the dog clutch is provided with a first fitting portion,   wherein an upper portion of the dog clutch is provided with a second fitting portion,   wherein an upper portion of the first motor shaft is provided with a first fitted portion,   wherein a lower portion of the second motor shaft is provided with a second fitted portion, and   wherein in response to the dog clutch moving downward, the first fitting portion is fitted with the first fitted portion and a fitting between the second fitting portion and the second fitted portion is released, and in response to the dog clutch moving upward, the second fitting portion is fitted with the second fitted portion and a fitting between the first fitting portion and the first fitted portion is released.   
     
     
         4 . The ship propulsion machine according to  claim 2 ,
 wherein the power transmission device comprises a dog clutch,   wherein the dog clutch is attached to the upper portion of the drive shaft so as to be non-rotatable with respect to the drive shaft and movable vertically within a predetermined movement range with respect to the drive shaft,   wherein a lower portion of the dog clutch is provided with a first fitting portion,   wherein an upper portion of the dog clutch is provided with a second fitting portion,   wherein an upper portion of the first motor shaft is provided with a first fitted portion,   wherein a lower portion of the second motor shaft is provided with a second fitted portion, and   wherein in response to the dog clutch moving to a lower position within the movement range, the first fitting portion is fitted with the first fitted portion, and a fitting between the second fitting portion and the second fitted portion is released, in response to the dog clutch moving to an upper position within the movement range, the second fitting portion is fitted with the second fitting portion, and a fitting between the first fitting portion and the first fitted portion is released, and in response to the dog clutch moving to a middle position within the movement range, the first fitting portion is fitted with the first fitted portion, and the second fitting portion is fitted with the second fitting portion.