Outboard motor

When a shift member is in a first position, a first clutch couples a second drive shaft to a first drive shaft. When the shift member is in the first position, a second clutch decouples a first gear from the first drive shaft. When the shift member is in the first position, a third clutch decouples a second gear from the second drive shaft.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2019-126057 filed on Jul. 5, 2019. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an outboard motor.

2. Description of the Related Art

An outboard motor includes a drive shaft and a shift mechanism. Rotation of the drive shaft is transmitted to a propeller shaft, while being switched in direction by the shift mechanism. Accordingly, the rotation of the propeller shaft is switched between a forward moving direction and a backward moving direction.

For example, a shift mechanism, described in Japan Laid-open Patent Application Publication No. 2015-202849, includes an upper gear, an intermediate gear, a lower gear and a dog clutch. The upper gear is connected to a first input shaft. The dog clutch is unitarily rotated with a second input shaft. The intermediate gear is constantly meshed with the upper gear and the lower gear. When moved upward, the dog clutch is engaged with the upper gear. Accordingly, the rotation of the first input shaft is transmitted to the second input shaft through the upper gear and the dog clutch. When moved downward, the dog clutch is engaged with the lower gear. Accordingly, the rotation of the first input shaft is transmitted to the second input shaft through the upper gear, the intermediate gear, the lower gear and the dog clutch.

In the outboard motor described above, the intermediate gear is used for transmitting rotation in one of forward movement and backward movement without being used for transmitting rotation in the other. However, the intermediate gear is constantly rotated by the rotation transmitted thereto from the drive shaft in both forward movement and backward movement. Because of this, high abrasion resistance is demanded for the intermediate gear.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide enhanced abrasion resistance of a gear used to transmit rotation outputted from a drive shaft in an outboard motor.

According to a preferred embodiment of the present invention, an outboard motor includes an engine, a first drive shaft, a second drive shaft, a shifter, a propeller shaft, and a transmission. The first drive shaft is connected to the engine and extends in an up-and-down direction. The second drive shaft extends in the up-and-down direction. The shifter switches a direction of rotation to be transmitted therethrough from the first drive shaft to the second drive shaft. The propeller shaft extends in a back-and-forth direction. The transmission transmits the rotation transmitted to the second drive shaft to the propeller shaft.

The shifter includes a first gear, a second gear, a third gear, a shift member, a first clutch, a second clutch, and a third clutch. The first gear is concentric with the first drive shaft. The first gear is rotatable relative to the first drive shaft. The second gear is concentric with the second drive shaft. The second gear is rotatable relative to the second drive shaft. The third gear is connected to the first gear and the second gear. The third gear reverses the direction of the rotation transmitted to the first gear in transmitting the rotation of the first gear to the second gear. The shift member is movable to a first position and a second position.

The first clutch is connected to the shift member. When the shift member is in the first position, the first clutch couples the second drive shaft to the first drive shaft. When the shift member is in the second position, the first clutch decouples the second drive shaft from the first drive shaft. The second clutch is connected to the shift member. When the shift member is in the first position, the second clutch decouples the first gear from the first drive shaft. When the shift member is in the second position, the second clutch couples the first gear to the first drive shaft. The third clutch is connected to the shift member. When the shift member is in the first position, the third clutch decouples the second gear from the second drive shaft. When the shift member is in the second position, the third clutch couples the second gear to the second drive shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be hereinafter explained with reference to drawings.FIG. 1is a side view of an outboard motor1according to a preferred embodiment of the present invention. The outboard motor1is attached to the stern of a watercraft. As shown inFIG. 1, the outboard motor1includes an engine11and an engine cover12. The engine11generates a thrust to propel the watercraft. The engine11is disposed inside the engine cover12. The engine11includes a crankshaft13. The crankshaft13extends in an up-and-down direction.

The outboard motor1includes a housing14, a drive shaft15, a propeller shaft16, a clutch17, a shifter18, a shift shaft19, and a transmission20. The drive shaft15, the propeller shaft16, the clutch17, the shifter18, the shift shaft19, and the transmission20are disposed inside the housing14. The housing14includes an upper housing21and a lower housing22. The lower housing22is disposed below the upper housing21. The drive shaft15is connected to the crankshaft13. The drive shaft15extends in the up-and-down direction.

FIG. 2is a cross-sectional side view of a lower portion of the outboard motor1. As shown inFIG. 2, the drive shaft15includes a first drive shaft25and a second drive shaft26. The first drive shaft25is connected to the crankshaft13. The first drive shaft25includes an upper shaft27and a lower shaft28. The upper shaft27and the lower shaft28extend in the up-and-down direction. The upper shaft27is connected to the crankshaft13. The lower shaft28is disposed below the upper shaft27. The lower shaft28is concentric with the upper shaft27. The lower shaft28is connected to the upper shaft27through the clutch17.

The clutch17is disposed between the upper shaft27and the lower shaft28. The clutch17is switched between an engaged state and a disengaged state. When the clutch17is in the engaged state, the lower shaft28is connected to the upper shaft27. When the clutch17is in the disengaged state, the lower shaft28is disconnected from the upper shaft27. For example, the clutch17includes a plurality of clutch discs. When the plurality of clutch discs make contact with each other, the clutch17is switched to the engaged state. When the plurality of clutch discs separate from each other, the clutch17is switched to the disengaged state.

The second drive shaft26is disposed below the first drive shaft25. The axis of the first drive shaft25and that of the second drive shaft26are oriented in an identical direction. The second drive shaft26is concentric with the first drive shaft25. The second drive shaft26is connected to the first drive shaft25through the shifter18. More specifically, the second drive shaft26is connected to the lower shaft28of the first drive shaft25through the shifter18.

The shifter18is disposed between the first drive shaft25and the second drive shaft26. The shifter18is disposed inside the upper housing21. The shifter18switches the direction of rotation to be transmitted from the first drive shaft25to the second drive shaft26between a forward moving direction and a backward moving direction.FIGS. 3 to 5are close-up side views of the shifter18and the surroundings thereof. As shown inFIG. 3, the shifter18includes a first gear31, a second gear32, a third gear33, a shift member34, a first clutch35, a second clutch36, and a third clutch37.

The first gear31is concentric with the first drive shaft25. The first gear31is disposed on the outer periphery of the first drive shaft25. The first gear31is rotatably supported by a bearing51. The first gear31is rotatable relative to the first drive shaft25. The second gear32is concentric with the second drive shaft26. The second gear32is disposed on the outer periphery of the second drive shaft26. The second gear32is rotatably supported by a bearing52. The second gear32is rotatable relative to the second drive shaft26. The axis of the first gear31and that of the second gear32extend in the up-and-down direction.

The third gear33is connected to the first gear31and the second gear32. The axis of the third gear33extends in a back-and-forth direction. The third gear33is rotatably supported by a bearing53. The third gear33reverses the rotation of the first gear31and transmits the reversed rotation to the second gear32. The first to third gears31to33are preferably bevel gears. The first gear31is meshed with the third gear33. The third gear33is meshed with the second gear32.

The shift member34is movable in the direction of the axis of the second drive shaft26. In other words, the shift member34is movable in the up-and-down direction. The shift member34is connected to the shift shaft19. The shift shaft19extends in the up-and-down direction. The shift shaft19may be connected to an actuator (not shown in the drawings). The actuator may be, for instance, an electric motor. The shift shaft19may be driven by the actuator in response to a shift operation performed by an operator. Alternatively, the shift shaft19may be connected to a shift cable. The shift shaft19may be driven by the shift cable in response to the shift operation performed by the operator.

The shift shaft19moves the shift member34to a first position, a second position, and a third position. For example, the shift shaft19includes a cam (not shown in the drawings). When the shift shaft19is rotated in one direction about the axis thereof, the cam elevates the shift member34. When the shift shaft19is rotated in the other direction about the axis thereof, the cam lowers the shift member34.

The shifter18includes a first movable member54, a first coupling member55, a second movable member56, and a second coupling member57. The first movable member54is disposed on the outer periphery of the first drive shaft25. The first movable member54and the first coupling member55are disposed above the first gear31. The first movable member54is coupled to the first drive shaft25through the first coupling member55. The first movable member54and the first coupling member55are rotated together with the first drive shaft25. The first drive shaft25includes an elongated hole58elongated in the direction of the axis of the first drive shaft25. The first coupling member55is inserted into the elongated hole58of the first drive shaft25. The first coupling member55is movable in the axial direction of the first drive shaft25along the elongated hole58of the first drive shaft25. Therefore, the first movable member54and the first coupling member55are movable in the axial direction of the first drive shaft25.

The second movable member56is disposed on the outer periphery of the second drive shaft26. The second movable member56and the second coupling member57are disposed between the first gear31and the second gear32. The second movable member56is coupled to the second drive shaft26through the second coupling member57. The second movable member56and the second coupling member57are rotated together with the second drive shaft26. The second drive shaft26includes an elongated hole59elongated in the axial direction of the second drive shaft26. The second coupling member57is inserted into the elongated hole59of the second drive shaft26. The second coupling member57is movable in the axial direction of the second drive shaft26along the elongated hole59of the second drive shaft26. Therefore, the second movable member56and the second coupling member57are movable in the axial direction of the second drive shaft26.

The shifter18includes a first movable shaft61and a second movable shaft62. The first movable shaft61is disposed inside the first drive shaft25. The first movable shaft61is movable in the axial direction of the first drive shaft25with respect to the first drive shaft25. The first movable shaft61is connected to the first movable member54through the first coupling member55. The first coupling member55is moved together with the first movable shaft61in the axial direction of the first drive shaft25.

The second movable shaft62is disposed at least partially inside the second drive shaft26. The second movable shaft62protrudes upward from the second drive shaft26. The second movable shaft62is connected at an upper portion thereof to the first movable shaft61. The second movable shaft62is rotatable about the axis of the second drive shaft26with respect to the first movable shaft61. The second movable shaft62is movable in the axial direction of the second drive shaft26with respect to the second drive shaft26. The second movable shaft62is connected to the second movable member56through the second coupling member57. The second coupling member57is moved together with the second movable shaft62in the axial direction of the second drive shaft26.

The second movable member56is movable up and down in conjunction with the first movable member54. The second movable member56is connected to the shift member34. The second movable member56is provided with a recess63on the outer peripheral surface thereof. The recess63extends in the circumferential direction of the second movable member56. The distal end of the shift member34is disposed inside the recess63. When the shift member34is moved up and down, the shift member34presses up and down the first movable member54. Accordingly, the first movable member54and the second movable member56are moved up and down.

The first to third clutches35to37are preferably dog clutches, for example. However, the first to third clutches35to37are not limited to dog clutches and may be another type of clutch. The first clutch35is connected to the shift member34. The first clutch35includes first clutch teeth64and second clutch teeth65. The first clutch teeth64are provided on the first drive shaft25. The first clutch teeth64are rotated together with the first drive shaft25. The second clutch teeth65are provided on the second movable member56. The second clutch teeth65are rotated together with the second movable member56. The second clutch teeth65are moved together with the second movable member56in the up-and-down direction.

When the second movable member56is moved upward in accordance with the motion of the shift member34, the second clutch teeth65are moved toward the first clutch teeth64. The second clutch teeth65are then meshed with the first clutch teeth64such that the first clutch35couples the second drive shaft26to the first drive shaft25. Therefore, when the shift member34is in the first position shown inFIG. 4, the first clutch35couples the second drive shaft26to the first drive shaft25. When the shift member34is in either the third position shown inFIG. 3or the second position shown inFIG. 5, the first clutch35decouples the second drive shaft26from the first drive shaft25. The second position is located below the first position. The third position is located between the first position and the second position.

The second clutch36is connected to the shift member34through the first movable shaft61, the second movable shaft62, and the second movable member56. The third gear33is located at least partially at a height equal to a height of the first clutch35in the up-and-down direction of the outboard motor1. The second clutch36includes third clutch teeth66and fourth clutch teeth67. The third clutch teeth66are provided on the first movable member54. The third clutch teeth66are moved together with the first movable member54in the up-and-down direction. The third clutch teeth66are rotated together with the first drive shaft25. The fourth clutch teeth67are provided on the first gear31. The fourth clutch teeth67are rotated together with the first gear31.

When the first and second movable shafts61and62are moved downward in accordance with the motion of the shift member34, the third clutch teeth66are moved toward the fourth clutch teeth67. The third clutch teeth66are then meshed with the fourth clutch teeth67such that the second clutch36couples the first gear31to the first drive shaft25. Therefore, when the shift member34is in the second position shown inFIG. 5, the second clutch36couples the first gear31to the first drive shaft25. When the shift member34is in either the third position shown inFIG. 3or the first position shown inFIG. 4, the second clutch36decouples the first gear31from the first drive shaft25.

The third clutch37is connected to the shift member34. The third gear33is located at least partially at a height equal to a height of the third clutch37in the up-and-down direction of the outboard motor1. The third clutch37includes fifth clutch teeth68and sixth clutch teeth69. The fifth clutch teeth68are provided on the second movable member56. The fifth clutch teeth68are rotated together with the second drive shaft26. The fifth clutch teeth68are moved together with the second movable member56in the up-and-down direction. The sixth clutch teeth69are provided on the second gear32. The sixth clutch teeth69are rotated together with the second gear32.

When the second movable member56is moved downward in accordance with the motion of the shift member34, the fifth clutch teeth68are moved toward the sixth clutch teeth69. The fifth clutch teeth68are then meshed with the sixth clutch teeth69such that the third clutch37couples the second gear32to the second drive shaft26. Therefore, when the shift member34is in the second position shown inFIG. 5, the third clutch37couples the second gear32to the second drive shaft26. When the shift member34is in either the first position shown inFIG. 4or the third position shown inFIG. 3, the third clutch37decouples the second gear32from the second drive shaft26.

As shown inFIG. 3, when the shift member34is in the third position, the first clutch35decouples the second drive shaft26from the first drive shaft25. The second clutch36decouples the first gear31from the first drive shaft25. Besides, the third clutch37decouples the second gear32from the second drive shaft26. Due to the above, the rotation of the first drive shaft25is not transmitted to the second drive shaft26. Additionally, the rotation of the first drive shaft25is not transmitted to the first to third gears31to33.

When the shift member34is moved from the third position to the first position, the first movable member54and the second movable member56are both moved upward. As shown inFIG. 4, when the shift member34is in the first position, the first clutch35couples the second drive shaft26to the first drive shaft25. The second clutch36decouples the first gear31from the first drive shaft25. Additionally, the third clutch37decouples the second gear32from the second drive shaft26. Due to the above, the rotation of the first drive shaft25is transmitted to the second drive shaft26through the first clutch35. Therefore, the second drive shaft26is rotated in the forward moving direction that is identical to the rotational direction of the first drive shaft25. On the other hand, the rotation of the first drive shaft25is not transmitted to the first to third gears31to33.

When the shift member34is moved from the third position to the second position, the first movable member54and the second movable member56are both moved downward. As shown inFIG. 5, when the shift member34is in the second position, the first clutch35decouples the second drive shaft26from the first drive shaft25. The second clutch36connects the first gear31to the first drive shaft25. Additionally, the third clutch37connects the second gear32to the second drive shaft26. Due to the above, the rotation of the first drive shaft25is transmitted to the second drive shaft26through the second clutch36, the first gear31, the third gear33, the second gear32, and the third clutch37. Therefore, the second drive shaft26is rotated in the backward moving direction that is opposite from the rotational direction of the first drive shaft25.

FIG. 6is a close-up side view of the propeller shaft16and the transmission20. The propeller shaft16and the transmission20are disposed inside the lower housing22. The propeller shaft16extends in the back-and-forth direction. The propeller shaft16is connected to the second drive shaft26through the transmission20. The propeller shaft16includes a first propeller shaft41and a second propeller shaft42. A first propeller43is attached to the first propeller shaft41. A second propeller44is attached to the second propeller shaft42.

The second propeller shaft42is concentric with the first propeller shaft41. The first propeller shaft41includes a hole45extending in the back-and-forth direction. The hole45of the first propeller shaft41penetrates the first propeller shaft41in the direction of the axis of the first propeller shaft41. The second propeller shaft42is inserted into the hole45of the first propeller shaft41. The second propeller shaft42protrudes forward from the first propeller shaft41. The second propeller shaft42protrudes backward from the first propeller shaft41.

The transmission20transmits rotation of the second drive shaft26to the first propeller shaft41and the second propeller shaft42. The transmission20includes a first bevel gear46, a second bevel gear47, and a third bevel gear48. The first bevel gear46is fixed to the second drive shaft26. The second bevel gear47is meshed with the first bevel gear46. The second bevel gear47is fixed to the first propeller shaft41. The third bevel gear48is meshed with the first bevel gear46. The third bevel gear48is fixed to the second propeller shaft42. The third bevel gear48transmits rotation of the first bevel gear46to the second propeller shaft42such that the transmitted rotation is oriented in the opposite direction from the rotation of the first propeller shaft41. Therefore, the first and second propeller shafts41and42are rotated in opposite directions. Fins of the second propeller44are twisted in the opposite direction from those of the first propeller43. Therefore, when the first and second propeller shafts41and42are rotated in the opposite directions, a thrust generated by the first propeller shaft41and that generated by the second propeller shaft42are oriented in an identical direction.

In the outboard motor1according to the preferred embodiments described above, when the shift member34is in the second position, the rotation of the first drive shaft25is transmitted to the second drive shaft26through the second clutch36, the first gear31, the third gear33, the second gear32, and the third clutch37. When the shift member34is in the first position, the rotation of the first drive shaft25is transmitted to the second drive shaft26through the first clutch35but is not transmitted to the first to third gears31to33. Due to this, the first to third gears31to33have enhanced abrasion resistance.

In the above-described preferred embodiments, the outboard motor1preferably includes two propellers. However, as shown inFIG. 7, the outboard motor1may include only one propeller. The structure and/or layout of the shifter18may not be limited to those/that in the above-described preferred embodiments and may be changed. For example, the first to third gears31to33may not be limited to the bevel gears and may be another type of gear.

FIG. 8is a view of the shifter18according to a modified preferred embodiment of the present invention. As shown inFIG. 8, the first and second gears31and32are spur gears, for example. The third gear33includes a plurality of gears71to73. The gears71to73are spur gears. The gears71and72are fixed to a shaft74. The gear73is fixed to a shaft75. The gear71is meshed with the first gear31. The gear72is meshed with the gear73. The gear73is meshed with the second gear32.

In the above-described preferred embodiments, when the shift member34is in the first position, the second drive shaft26is rotated in the forward moving direction. By contrast, when the shift member34is in the second position, the second drive shaft26is rotated in the backward moving direction. However, when the shift member34is in the second position, the second drive shaft26may be rotated in the forward moving direction. By contrast, when the shift member34is in the first position, the second drive shaft26may be rotated in the backward moving direction.