Shock absorber for propeller unit, propeller unit, and vessel propulsion apparatus

1. A propeller unit for connection to a propeller shaft of a vessel propulsion apparatus, the propeller unit comprising:

an inner hub that includes a rib provided on an inner peripheral surface of the inner hub;

an outer hub that is disposed and connected to the inner hub coaxially with the inner hub and that includes a plurality of blades provided on an outer peripheral surface of the outer hub;

a bushing for connection to the propeller shaft and that includes a rib provided on an outer peripheral surface of the bushing; and

a shock absorber to be driven by the propeller shaft and that includes a damper made of an elastic material, the damper being disposed between the outer peripheral surface of the bushing of the propeller unit and the inner peripheral surface of the inner hub of the propeller unit, the damper including:

a first portion facing the rib of the bushing in a circumferential direction of the bushing;

a second portion facing the rib of the inner hub in the circumferential direction; and

a connector by which the first portion and the second portion are connected to each other; wherein

neither the rib of the inner hub nor the rib of the bushing is located between the first portion of the damper and the second portion of the damper;

a deformation-absorbing space is defined between the first portion and the second portion in a state in which the damper has not been elastically deformed by relative rotation between the bushing and the inner hub;

the deformation-absorbing space is deformable such that the first portion and the second portion approach each other in a state in which the damper has been elastically deformed by relative rotation between the bushing and the inner hub;

the inner hub includes a flange that is disposed at a rear end of the inner hub, extends inwardly in the radial direction, and restricts a movement of the bushing in an axial direction of the inner hub by contact between the flange and the bushing; and

the first portion is cylindrical and the second portion is cylindrical.

2. The propeller unit according to claim 1 , further comprising a plurality of the deformation-absorbing spaces extending in the axial direction.

3. The propeller unit according to claim 1 , wherein, in a cross-section perpendicular or substantially perpendicular to the axial direction, a cross-sectional area of the deformation-absorbing space is within a range of about 30% to about 80% of a cross-sectional area of the damper.

4. The propeller unit according to claim 1 , wherein the shock absorber further includes a plurality of dampers spaced apart in the circumferential direction on the outer peripheral surface of the bushing.

5. The propeller unit according to claim 1 , wherein the shock absorber further includes:

a pair of dampers that are disposed on the outer peripheral surface of the bushing and are spaced apart in the circumferential direction; and

a first connection arm by which first ends of the pair of dampers are connected to each other in the axial direction of the bushing.

6. The propeller unit according to claim 5 , wherein the shock absorber further includes a second connection arm by which second ends of the pair of dampers in the axial direction of the bushing are connected to each other.

7. The propeller unit according to claim 1 , wherein the shock absorber includes an integral and unitary cylindrical member in which a plurality of dampers are integrally connected to each other in the circumferential direction.

8. The propeller unit according to claim 7 , wherein

the deformation-absorbing space includes a first concave portion that extends inwardly in the radial direction from an outer peripheral surface of the cylindrical member; and

the first concave portion extends in the axial direction from a first end of the cylindrical member in the axial direction toward a second end of the cylindrical member in the axial direction.

9. The propeller unit according to claim 7 , wherein

the deformation-absorbing space includes a second concave portion that extends outwardly in the radial direction from an inner peripheral surface of the cylindrical member; and

the second concave portion extends in the axial direction from a first end of the cylindrical member in the axial direction toward a second end of the cylindrical member in the axial direction.

10. The propeller unit according to claim 7 , wherein the deformation-absorbing space includes:

a first concave portion that extends inwardly in the radial direction from an outer peripheral surface of the cylindrical member and that extends in the axial direction from a first end of the cylindrical member in the axial direction toward a second end of the cylindrical member in the axial direction; and

a second concave portion that extends outwardly in the radial direction from an inner peripheral surface of the cylindrical member and that extends in the axial direction from the first end of the cylindrical member toward the second end of the cylindrical member.

11. The propeller unit according to claim 7 , wherein the damper includes a first concave portion that extends inwardly in the radial direction from an outer peripheral surface of the damper, and a second concave portion that extends outwardly in the radial direction from an inner peripheral surface of the damper;

the first concave portion and the second concave portion are spaced apart from each other in the circumferential direction; and

in a cross-section perpendicular to the axial direction, a cross-sectional area of the deformation-absorbing space is within a range of about 30% to about 80% of a space between the first concave portion and the second concave portion in the circumferential direction.

12. The propeller unit according to claim 1 , wherein the rib of the inner hub has a cross-sectional shape that is tapered toward an inner end of the rib of the inner hub.

13. The propeller unit according to claim 1 , wherein the inner hub includes a plurality of ribs spaced apart in the circumferential direction.

14. The propeller unit according to claim 1 , wherein the bushing includes a plurality of ribs spaced apart in the circumferential direction.

15. The propeller unit according to claim 1 , wherein the bushing includes spline teeth provided on the inner peripheral surface of the bushing to be spline-coupled to the propeller shaft.

16. A vessel propulsion apparatus comprising:

an engine;

a drive shaft rotated by the engine;

a drive gear fixed to the drive shaft;

a forward gear engaging the drive gear;

a backward gear that rotates in a direction opposite to a rotational direction of the forward gear while engaging the drive gear;

a dog clutch that selectively engages the forward gear and the backward gear;

a propeller shaft rotated together with the dog clutch; and

a propeller unit connected to the propeller shaft, the propeller unit including:

an inner hub that includes a rib provided on an inner peripheral surface of the inner hub;

an outer hub that is disposed and connected to the inner hub coaxially with the inner hub and that includes a plurality of blades provided on an outer peripheral surface of the outer hub;

a bushing connected to the propeller shaft and that includes a rib provided on an outer peripheral surface of the bushing; and

a shock absorber to be driven by the propeller shaft and that includes a damper made of an elastic material, the damper being disposed between the outer peripheral surface of the bushing of the propeller unit and the inner peripheral surface of the inner hub of the propeller unit, the damper including:

a first portion facing the rib of the bushing in a circumferential direction of the bushing;

a second portion facing the rib of the inner hub in the circumferential direction; and

a connector by which the first portion and the second portion are connected to each other; wherein

neither the rib of the inner hub nor the rib of the bushing is located between the first portion of the damper and the second portion of the damper;

a deformation-absorbing space is defined between the first portion and the second portion in a state in which the damper has not been elastically deformed by relative rotation between the bushing and the inner hub;

the deformation-absorbing space is deformable such that the first portion and the second portion approach each other in a state in which the damper has been elastically deformed by relative rotation between the bushing and the inner hub;

the inner hub includes a flange that is disposed at a rear end of the inner hub, extends inwardly in the radial direction, and restricts a movement of the bushing in an axial direction of the inner hub by contact between the flange and the bushing; and

the first portion is cylindrical and the second portion is cylindrical.

17. A propeller unit for connection to a propeller shaft of a vessel propulsion apparatus, the propeller unit comprising:

an inner hub that includes a rib provided on an inner peripheral surface of the inner hub;

an outer hub that is disposed and connected to the inner hub coaxially with the inner hub and that includes a plurality of blades provided on an outer peripheral surface of the outer hub;

a bushing for connection to the propeller shaft and that includes a rib provided on an outer peripheral surface of the bushing; and

a shock absorber to be driven by the propeller shaft and that includes a damper made of an elastic material, the damper being disposed between the outer peripheral surface of the bushing of the propeller unit and the inner peripheral surface of the inner hub of the propeller unit, the damper including:

a first portion facing the rib of the bushing in a circumferential direction of the bushing;

a second portion facing the rib of the inner hub in the circumferential direction; and

a connector by which the first portion and the second portion are connected to each other; wherein

neither the rib of the inner hub nor the rib of the bushing is located between the first portion of the damper and the second portion of the damper;

a deformation-absorbing space is defined between the first portion and the second portion in a state in which the damper has not been elastically deformed by relative rotation between the bushing and the inner hub;

the deformation-absorbing space is deformable such that the first portion and the second portion approach each other in a state in which the damper has been elastically deformed by relative rotation between the bushing and the inner hub;

the inner hub includes a flange that is disposed at a rear end of the inner hub, extends inwardly in the radial direction, and restricts a movement of the bushing in an axial direction of the inner hub by contact between the flange and the bushing; and

a cylindrical main body of the inner hub is tapered such that a radius of the cylindrical main body becomes smaller from a front of the propeller unit towards a rear of the propeller unit.

18. The propeller unit according to claim 1 , wherein

the deformation-absorbing space is at least one of a first space and a second space;

the first space is defined by the first portion, the second portion, the connector, and the inner hub; and

the second space is defined by the first portion, the second portion, the connector, and the bushing.

19. The vessel propulsion apparatus according to claim 16 , wherein

the deformation-absorbing space is at least one of a first space and a second space;

the first space is defined by the first portion, the second portion, the connector, and the inner hub; and

the second space is defined by the first portion, the second portion, the connector, and the bushing.

20. The propeller unit according to claim 1 , wherein the deformation-absorbing space is located between the first portion and the second portion in the circumferential direction of the bushing.

21. The vessel propulsion apparatus according to claim 16 , wherein the deformation-absorbing space is located between the first portion and the second portion in the circumferential direction of the bushing.