Shift mechanism of boat propulsion unit

Abstract

A shift mechanism transmits rotation of a drive shaft of an engine to a propeller shaft by engaging a shift clutch with a forward gear or a reverse gear is provided. The shift clutch includes a dog clutch movably coupled to the propeller shaft in an axial direction and a synchro clutch movably coupled to the dog clutch in the axial direction. When the dog clutch is moved to the forward gear side or the reverse gear side to make a shift-in, an end surface of the synchro clutch is adapted to be frictionally engaged with an abutting surface provided on the forward gear or an abutting surface provided on the reverse gear before dog engagement between a pawl of the dog clutch and a pawl of the forward gear or a pawl of the reverse gear. Through this arrangement, it is possible to provide a shift mechanism of a boat propulsion unit provided with a synchronization mechanism that realizes a smooth shift-in.

1 . A shift mechanism of a boat propulsion unit arranged to transmit rotation of a drive shaft of an engine to a propeller shaft by engaging a shift clutch with a forward gear or a reverse gear, the shift mechanism comprising:
 a dog clutch movably coupled to the propeller shaft in an axial direction; and   a synchro clutch movably coupled to the dog clutch in the axial direction; wherein   the dog clutch and the synchro clutch are arranged such that when the dog clutch is moved to the forward gear or the reverse gear to perform a shift-in operation, an end surface of the synchro clutch frictionally engages with an abutting surface provided on the forward gear or the reverse gear before a pawl of the dog clutch makes dog engagement with a pawl of the forward gear or the reverse gear.   
   
   
       2 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the synchro clutch is coupled to an outer periphery of the dog clutch. 
   
   
       3 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the shift clutch includes an urging device arranged to apply an urging force against the synchro clutch to the dog clutch. 
   
   
       4 . The shift mechanism of a boat propulsion unit according to  claim 3 , wherein when the shift clutch performs the shift-in operation, the synchro clutch is moved integrally together with the dog clutch by the urging force given by the urging device until the end surface of the synchro clutch is moved to abut on the abutting surface provided on the forward gear or the reverse gear from the neutral position of the shift clutch. 
   
   
       5 . The shift mechanism of a boat propulsion unit according to  claim 4 , wherein when the shift clutch performs the shift-in operation, the dog clutch moves independently from the synchro clutch against the urging force since the end surface of the synchro clutch abuts on the abutting surface provided on the forward gear or the reverse gear until the pawl of the dog clutch makes dog engagement with the pawl of the forward gear or the reverse gear. 
   
   
       6 . The shift mechanism of a boat propulsion unit according to  claim 5 , wherein during the relative movement between the dog clutch and the synchro clutch the synchro clutch rotates synchronously with the forward gear or the reverse gear with frictional engagement between the end surface of the synchro clutch and the abutting surface provided on the forward gear or the reverse gear, while the dog clutch coupled to the synchro clutch rotates integrally with the synchro clutch. 
   
   
       7 . The shift mechanism of a boat propulsion unit according to  claim 3 , wherein the urging device includes a detent mechanism. 
   
   
       8 . The shift mechanism of a boat propulsion unit according to  claim 7 , wherein the detent mechanism includes a groove arranged on the outer periphery of the dog clutch, a spring disposed in the groove, and a ball engaged with a groove on an inner periphery of the synchro clutch while being urged by the spring. 
   
   
       9 . The shift mechanism of a boat propulsion unit according to  claim 7 , wherein the detent mechanism positions the shift clutch to the neutral position. 
   
   
       10 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the synchro clutch is key-coupled to the dog clutch. 
   
   
       11 . The shift mechanism of a boat propulsion unit according to  claim 10 , wherein the dog clutch is coupled to a shift sleeve that moves the dog clutch in the axial direction via a cross pin, and keys defined in both sides of the cross pin on the outer periphery of the dog clutch are engaged with a keyway provided on the inner periphery of the synchro clutch. 
   
   
       12 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the synchro clutch is spline-coupled to the dog clutch. 
   
   
       13 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the synchro clutch is defined by a cone clutch whose end surface is a conical surface. 
   
   
       14 . The shift mechanism of a boat propulsion unit according to  claim 13 , wherein a tilt angle of the conical surface of one end surface of the synchro clutch is different from that of the other end surface of the synchro clutch. 
   
   
       15 . The shift mechanism of a boat propulsion unit according to  claim 13 , wherein the abutting surface of the forward gear or the reverse gear is a conical surface. 
   
   
       16 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein when the synchro clutch is in the neutral position, the distance between the one end surface of the synchro clutch and the abutting surface of the forward gear is different from the distance between the other end surface of the synchro clutch and the abutting surface of the reverse gear. 
   
   
       17 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein when the shift clutch is moved to the neutral position to make a shift-out, the synchro clutch moves integrally together with the dog clutch in response to the urging force applied by the urging device until the other end surface of the synchro clutch is moved to abut on the abutting surface provided on the forward gear or the reverse gear and then the dog clutch moves independently from the synchro clutch against the urging force to return to the neutral position. 
   
   
       18 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein the synchro clutch is made of different material from that of the forward gear or the reverse gear. 
   
   
       19 . The shift mechanism of a boat propulsion unit according to  claim 17 , wherein the synchro clutch is made of copper alloy. 
   
   
       20 . The shift mechanism of a boat propulsion unit according to  claim 1 , wherein a groove arranged to preserve lubricant is defined on a portion of the end surface of the synchro clutch. 
   
   
       21 . A boat propulsion unit comprising a shift mechanism according to  claim 1 .