Patent ID: 12227277

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be hereinafter explained with reference to the drawings.FIG.1is a side view of an outboard motor2according to a first preferred embodiment. The outboard motor2is an exemplary marine propulsion device. The outboard motor2is attached to the stern of a watercraft (not shown in the drawings). The outboard motor2generates a thrust to propel the watercraft.

The outboard motor2includes a drive source3, a driveshaft4, a propeller shaft5, a shift mechanism6, and a propeller unit7.

The drive source3generates a rotational force or rotational torque to rotate the propeller shaft5. The drive source3is, for instance, an engine. The drive source3includes a crankshaft3a. The crankshaft3aextends in a vertical direction.

The driveshaft4is rotated by driving of the drive source3. The driveshaft4extends in the vertical direction. The driveshaft4is connected to the crankshaft3a.

The propeller shaft5supports a propeller10(to be described below). An axial direction A of the propeller shaft5corresponds to a back-and-forth direction of the outboard motor2. In other words, the propeller shaft5extends in the back-and-forth direction of the outboard motor2. It should be noted that in the following explanation, the axial direction A of the propeller shaft5will be referred to as “axial direction”, whereas a perpendicular direction to the axial direction A will be referred to as “radial direction”. On the other hand, one directional side indicated by arrow F will be referred to as “forward”, whereas the other directional side indicated by arrow B will be referred to as “backward”.

FIG.2is a schematic cross-sectional view of the propeller unit7. In more detail,FIG.2is a schematic cross-sectional view of the propeller unit7in a condition that the rotational force or torque is not being transmitted to the propeller shaft5from the drive source3.

As shown inFIG.2, the propeller shaft5includes a taper portion5a, a spline portion5b, and a male threaded portion5c. The taper portion5ais shaped to taper backward. The spline portion5bis disposed behind the taper portion5a. The male threaded portion5cis disposed behind the spline portion5b.

The shift mechanism6connects or disconnects the driveshaft4and the propeller shaft5to or from each other. The shift mechanism6switches a rotational direction of the propeller shaft5.

As shown inFIG.1, the shift mechanism6includes a drive gear6a, a forward moving gear6b, a backward moving gear6c, and a dog clutch6d. The drive gear6ais unitarily rotated with the driveshaft4. The forward moving gear6band the backward moving gear6care meshed with the drive gear6a. Rotation of the driveshaft4is transmitted to the forward/backward moving gear6b,6cthrough the drive gear6a.

The dog clutch6dis movable to a forward moving position, a neutral position, and a backward moving position. When the dog clutch6dis in the forward moving position, the forward moving gear6bis connected to the propeller shaft5such that the rotation of the driveshaft4is transmitted to the propeller shaft5through the forward moving gear6b. When the dog clutch6dis in the neutral position, the propeller shaft5is disconnected from both the forward moving gear6band the backward moving gear6csuch that the rotation of the driveshaft4is not transmitted to the propeller shaft5. When the dog clutch6dis in the backward moving position, the backward moving gear6cis connected to the propeller shaft5such that the rotation of the driveshaft4is transmitted to the propeller shaft5through the backward moving gear6c.

As shown inFIG.2, the propeller unit7is mounted to the propeller shaft5. The propeller unit7includes the propeller10, a bushing20, a damper30, a first spacer40, a second spacer50, a washer60, and a nut70.

The propeller10receives rotation of the propeller shaft5transmitted thereto through the damper30. When a thrust is generated by forward rotation (forward moving directional rotation) of the propeller10, the propeller10is moved in an approaching direction to the first spacer40by elastic deformation of the damper30.

The propeller10includes an inner tubular portion11, an outer tubular portion12, a plurality of blades13, and a plurality of ribs (not shown in the drawings).

Each of the inner tubular portion11and the outer tubular portion12has a tubular shape and extends in the axial direction. The inner tubular portion11is disposed inside the outer tubular portion12. The spline portion5bof the propeller shaft5is disposed inside the inner tubular portion11. The inner tubular portion11is disposed behind the first spacer40so as to be spaced apart therefrom in the back-and-forth direction. A gap of approximately 2 mm, for example, is provided between the inner tubular portion11and the first spacer40in the back-and-forth direction. The gap between the inner tubular portion11and the first spacer40in the back-and-forth direction preferably has a distance of at least 1 mm or greater and more preferably has a distance of 1.5 mm or greater, for example. When a thrust is generated by the forward rotation of the propeller10, the inner tubular portion11is moved in the approaching direction to the first spacer40(i.e., forward) by the elastic deformation of the damper30.

The outer tubular portion12covers the inner tubular portion11from the radial direction. The plurality of blades13radially extend from the outer peripheral surface of the outer tubular portion12. The plurality of ribs radially extend to connect the inner tubular portion11and the outer tubular portion12therethrough. The plurality of ribs are connected to the outer peripheral surface of the inner tubular portion11and the inner peripheral surface of the outer tubular portion12.

The bushing20has a tubular shape and extends in the axial direction. The bushing20is disposed radially between the inner tubular portion11and the propeller shaft5. The bushing20is fixed to the propeller shaft5and is unitarily rotated therewith. The inner peripheral surface of the bushing20is spline-coupled to the spline portion5bof the propeller shaft5.

The bushing20is disposed axially between the first spacer40and the second spacer50. The bushing20includes a front end20ato be brought into contact with the first spacer40and a rear end20bto be brought into contact with the second spacer50. The bushing20is prevented from axially moving by the taper portion5a, the first spacer40, the second spacer50, the washer60, and the nut70.

The damper30transmits the rotation of the propeller shaft5to the propeller10, and simultaneously, inhibits an impact from being transmitted to the propeller10from the propeller shaft5. The damper30absorbs a torque acting in the rotational direction of the propeller shaft5and this inhibits noises produced by repetitive collisions between the gears in the shift mechanism6due to torque fluctuations of the drive source3and an impact sound produced by the dog clutch6dduring a shift operation. The noises, produced by repetitive collisions between the gears in the shift mechanism6due to torque fluctuations of the drive source3, is likely to be produced when the rotational speed of the drive source3falls in a low-speed range (of, e.g., about 1500 rpm or less). It should be noted that the noises, produced by repetitive collisions between the gears in the shift mechanism6due to torque fluctuations of the drive source3, will be hereinafter simply referred to as “rattle sound” on an as-needed basis.

An elastic member having elastically deformable characteristics is provided as the damper30. The damper30is made of, for instance, rubber and has a tubular shape. The damper30extends in the axial direction. The damper30is fixed to the outer peripheral surface of the bushing20and is unitarily rotated with the propeller shaft5together with the bushing20. The inner peripheral surface of the damper30is fixed to the outer peripheral surface of the bushing20such that the damper30is immovable with respect to the bushing20. The damper30is disposed inside the inner tubular portion11and is fixed thereto by press-fitting, for example. The outer peripheral surface of the damper30is spline-coupled to the inner peripheral surface of the inner tubular portion11. Accordingly, the rotation of the propeller shaft5is transmitted to the propeller10through the bushing20and the damper30.

The first spacer40is an exemplary spacer. The first spacer40has a tubular shape. The first spacer40is disposed inside the outer tubular portion12. The first spacer40is mounted to the taper portion5aof the propeller shaft5. The inner peripheral surface of the first spacer40is in contact with the taper portion5aof the propeller shaft5. The first spacer40is prevented from moving forward by the taper portion5a.

The first spacer40is disposed in front of the bushing20on the propeller shaft5, while being spaced apart from the inner tubular portion11of the propeller10in the back-and-forth direction. The first spacer40is spaced apart from the inner tubular portion11of the propeller10in the back-and-forth direction, while in contact with the bushing20. The first spacer40positions the bushing20in place with respect to the propeller shaft5. The first spacer40prevents the bushing20from moving forward.

The first spacer40includes a positioning portion40a, a restriction portion40b, and a support portion40c. The positioning portion40aradially extends. The positioning portion40ais disposed opposite to the front end20aof the bushing20in the back-and-forth direction. A rear end surface of the first spacer40is provided as the positioning portion40a. The positioning portion40ais in contact with the front end20aof the bushing20so as to position the bushing20in place with respect to the propeller shaft5.

The restriction portion40bis disposed on a more front side than the positioning portion40a. The restriction portion40bextends radially. The restriction portion40bis disposed radially on an outer side than the positioning portion40a. The restriction portion40bis opposed to the inner tubular portion11in the back-and-forth direction. The restriction portion40bis disposed in front of the inner tubular portion11so as to be spaced apart therefrom in the back-and-forth direction.

The support portion40cis disposed between the positioning portion40aand the restriction portion40b. The support portion40cextends in the axial direction. The support portion40cis disposed in contact with the inner peripheral surface of a portion adjacent to the front end in the inner tubular portion11and radially supports the inner tubular portion11.

The second spacer50has a tubular shape. The second spacer50is disposed axially between the bushing20and the washer60. The second spacer50is mounted to the outer peripheral surface of the propeller shaft5. The front surface of the second spacer50is in contact with the rear end20bof the bushing20. The rear surface of the second spacer50is in contact with the washer60.

The washer60is disposed axially between the second spacer50and the nut70. The washer60is mounted to the male threaded portion5cof the propeller shaft5. The rear surface of the washer60is in contact with the nut70.

The nut70is fastened to the male threaded portion5cof the propeller shaft5. The bushing20, the second spacer50, and the washer60are interposed between, and held by, the nut70and the first spacer40.

FIG.3is a schematic cross-sectional view of the propeller unit7in a condition that the damper30is elastically deformed. In more detail,FIG.3is a schematic cross-sectional view of the propeller unit7in a condition that the damper30is elastically deformed when a load greater than a predetermined load acts on the damper30by a thrust generated in the forward rotation (forward moving directional rotation) of the propeller10.

The propeller10is movable from an initial position shown inFIG.2to a contact position shown inFIG.3in accordance with elastic deformation of the damper30. As shown inFIG.3, the propeller10includes a contact portion14. The contact portion14is disposed on the inner tubular portion11. The front-end surface of the inner tubular portion11is provided as the contact portion14. The contact portion14radially overlaps with the support portion40cof the first spacer40. The contact portion14is opposed to the restriction portion40bof the first spacer40in the back-and-forth direction. The contact portion14is disposed on a more front side than the front end20aof the bushing20. The contact portion14is brought into contact with the restriction portion40bin accordance with the elastic deformation of the damper30. A load, greater than a load tolerable by the damper30, is inhibited from acting on the damper30by the contact portion14.

When a load greater than a predetermined load acts on the damper30in a condition that a thrust is being generated in the forward rotation of the propeller10(hereinafter simply referred to as “forward moving condition”), the damper30is elastically deformed such that the contact portion14is brought into contact with the restriction portion40bof the first spacer40in the back-and-forth direction. The contact portion14is not kept in contact with the restriction portion40bunless a load greater than the predetermined load acts on the damper30in the forward moving condition. In other words, the inner tubular portion11is kept spaced apart from the first spacer40in the back-and-forth direction unless a load greater than the predetermined load acts on the damper30in the forward moving condition.

The predetermined load is set to be less than or equal to a limit load of the damper30. The limit load has a magnitude not enough to damage or break the damper30. Also, the magnitude of the limit load is not enough to impair the innate function of the damper30. For example, it is preferable that the magnitude of the limit load is not enough to cause plastic deformation of the damper30.

It should be noted that the contact portion14may be configured to be brought into contact with the restriction portion40bof the first spacer40in the back-and-forth direction by the elastic deformation of the damper30caused when a drive force, transmitted from the drive source3to the propeller shaft5, becomes greater than a predetermined drive force in the forward moving condition. In this case, the predetermined drive force is set to be less than or equal to the limit load of the damper30. Alternatively, the contact portion14may be configured to be brought into contact with the restriction portion40bof the first spacer40in the back-and-forth direction by the elastic deformation of the damper30caused when the rotational speed of the drive source3becomes greater than a predetermined rotational speed in the forward moving condition. In this case, the predetermined rotational speed is set to be less than or equal to a rotational speed corresponding to the limit load of the damper30. For example, the predetermined rotational speed is set to be less than or equal to about 2000 rpm. Besides, the predetermined rotational speed is preferably set to be greater than about 1000 rpm and is more preferably set to be greater than about 1500 rpm, for example.

Specifically, the predetermined rotational speed is preferably set to be greater than about 1500 rpm if rattle sounds are produced in the outboard motor2when the rotational speed of the drive source3is about 1500 rpm or less. Alternatively, the predetermined rotational speed is preferably set to be greater than about 1200 rpm if rattle sounds are produced in the outboard motor2when the rotational speed of the drive source3falls in a range of about 400 to about 1200 rpm, for example. Yet alternatively, the predetermined rotational speed is preferably set to be greater than about 1000 rpm if rattle sounds are produced in the outboard motor2when the rotational speed of the drive source3falls in a range of about 400 to about 1000 rpm, for example. It should be noted that, from the perspective of inhibiting transmission of a rotational force or torque from the drive source3to the propeller10in a path without being through the damper30, the predetermined rotational speed is preferably set to be more approximate to the rotational speed corresponding to the limit load of the damper30than to the maximum rotational speed in the rotational speed range in which rattle sounds are produced. For example, the predetermined rotational speed is preferably set to be greater than about 1800 rpm when the rotational speed corresponding to the limit load of the damper30is about 2100 rpm and the maximum rotational speed of the drive source3is about 1500 rpm in the rotational speed range in which rattle sounds are produced.

FIG.4is a diagram for explaining positioning of the propeller10with respect to the damper30. The damper30includes a recess31on the outer peripheral surface thereof so as to position the propeller10in place in the back-and-forth direction. The propeller10includes a protrusion15to be locked to the recess31.

The recess31is recessed in a direction from the outer peripheral surface of the damper30toward the inner peripheral surface of the damper30. The recess31includes a bottom31a, a first inner wall31b, and a second inner wall31c. The bottom31aextends in the axial direction. As shown inFIG.4, the first inner wall31bradially extends toward the inner tubular portion11from the front end of the bottom31ain the cross-sectional view. The first inner wall31blocks the protrusion15such that the propeller10is prevented from sliding forward with respect to the damper30. Because of this, it is easy to keep constant the gap between the contact portion14and the restriction portion40bof the first spacer40in the back-and-forth direction.

As shown inFIG.4, the second inner wall31cis shaped such that an angle defined between the bottom31aand the second inner wall31cis obtuse in the cross-sectional view. The second inner wall31cradially extends backward and toward the inner tubular portion11from the rear end of the bottom31ain the cross-sectional view.

The protrusion15is provided on the inner peripheral surface of the inner tubular portion11. The protrusion15is shaped to protrude in a direction from the outer peripheral surface of the inner tubular portion11toward the inner peripheral surface of the inner tubular portion11. The protrusion15is shaped to be fitted to the recess31. Because of the configuration, when the damper30is press-fitted to the inner tubular portion11, it is easy for the first inner wall31bto move over the protrusion15.

In the outboard motor2described above, the first spacer40has a gap with respect to the propeller10in the back-and-forth direction. Because of this, when a thrust is generated in the forward moving direction by rotation of the propeller10, friction is inhibited from being caused between the propeller10and the first spacer40. Accordingly, a torque transmitted to the propeller10through a friction force generated between the propeller10and the first spacer40is inhibited, so that a rotational force outputted from the drive source3is inhibited from being transmitted to the propeller10in a path without being through the damper30. As a result, an attenuating effect exerted by the damper30is obtained such that it is made possible to inhibit noises produced by repetitive collisions between the gears in the dog clutch6ddue to torque fluctuations of the drive source3and an impact sound produced by the dog clutch6dduring a shift operation.

Next, a series of steps of assembling the propeller unit7to the propeller shaft5in the outboard motor2will be explained.FIG.5is an exploded schematic cross-sectional view of the propeller unit7. It should be noted thatFIG.5omits illustration of the outer tubular portion12of the propeller10.

As shown inFIG.5, the components of the propeller10, the bushing20including the damper30fixed thereto, the first spacer40, the second spacer50, the washer60, and the nut70are provided. The first spacer40is fitted on the propeller shaft5. After the first spacer40is fitted to the propeller shaft5, the bushing20is fixed to the propeller shaft5with a gap between the first spacer40and the propeller10in the back-and-forth direction.

More specifically, the bushing20, including the damper30fixed thereto, is fixed to the inner tubular portion11of the propeller10by press-fitting, for example. The damper30positions the propeller10in place in the back-and-forth direction by locking the protrusion15to the recess31. It should be noted that the damper30may have been preliminarily fixed to the inner tubular portion11of the propeller10by press-fitting.

The bushing20, the second spacer50, and the washer60are fitted to the propeller shaft5, then, the bushing20is fixed to the propeller shaft5by screwing the nut70onto the male threaded portion5cuntil the front end20aof the bushing20is contacted with the positioning portion40aof the first spacer40. Here, the axial distance between the restriction portion40band the positioning portion40ain the first spacer40is set to be longer than that between the contact portion14of the propeller10and the front end20aof the bushing20. Because of this, when the bushing20is fixed to the propeller shaft5, the contact portion14of the propeller10is spaced apart from the restriction portion40bof the first spacer40in the back-and-forth direction as shown inFIG.2. It should be noted that a washer42(to be described below) may be provided to space the contact portion14of the propeller10apart from the restriction portion40bof the first spacer40in the back-and-forth direction.

Preferred embodiments of the present invention have been explained above. However, the present invention is not limited to the preferred embodiments described above, and a variety of changes can be made without departing from the gist of the present invention.

FIG.6is a diagram for explaining a first modification of the first spacer40. In the first modification of the first spacer40, the restriction portion40bis disposed on a more rear side than the positioning portion40aand does not radially overlap with the contact portion14. The support portion40cis omitted in the first modification. In this case, the contact portion14of the propeller10is disposed on a more rear side than the front end20aof the bushing20. Besides, the axial distance between the restriction portion40band the positioning portion40ain the first spacer40is set to be shorter than that between the contact portion14of the propeller10and the front end20aof the bushing20.

FIG.7is a diagram for explaining a second modification of the first spacer40. In the second modification of the first spacer40, the positioning portion40aand the restriction portion40bradially overlap with each other and do not radially overlap with the contact portion14. In other words, the restriction portion40bis flush with the positioning portion40a. The support portion40cis omitted in the second modification. In this case, the contact portion14of the propeller10is disposed on a more rear side than the front end20aof the bushing20.

FIG.8is a diagram for explaining a third modification of the first spacer40. In the third modification, the first spacer40includes a spacer body41and the washer42. The spacer body41includes the positioning portion40a, the restriction portion40b, and the support portion40c. The washer42is disposed axially between the spacer body41and the bushing20. The washer42adjusts a gap between the restriction portion40bof the spacer body41and the contact portion14of the propeller10in the back-and-forth direction. In this case, for instance, when the washer42is disposed between the spacer body41and the bushing20in an existing marine propulsion device, the propeller10is spaced apart from the spacer body41in the back-and-forth direction.

FIG.9is a diagram for explaining a modification of the propeller10and the damper30. In this modification, the damper30includes a protrusion32on the outer peripheral surface thereof to position the propeller10in place in the back-and-forth direction. In this modification, the propeller10includes a recess16to which the protrusion32is locked.

The recess16is provided on the inner peripheral surface of the inner tubular portion11. The recess16is recessed in a direction from the inner peripheral surface of the inner tubular portion11toward the outer peripheral surface of the inner tubular portion11. The recess16includes a bottom16a, a first inner wall16b, and a second inner wall16c. The bottom16aextends in the axial direction. The first inner wall16bradially extends toward the bushing20from the rear end of the bottom16ain the cross-sectional view. The second inner wall16cis shaped such that an angle defined between the bottom16aand the second inner wall16cis obtuse in the cross-sectional view. The second inner wall16cradially extends forward and toward the bushing20from the front end of the bottom16ain the cross-sectional view.

The protrusion32is provided on the outer peripheral surface of the damper30. The protrusion32is shaped to protrude in a direction from the inner peripheral surface of the damper30toward the outer peripheral surface of the damper30. The protrusion32is shaped to be fitted to the recess16.

In the preferred embodiments described above, the outboard motor2has been explained as an exemplary marine propulsion device. However, the present invention may be applied to another type of marine propulsion device such as an inboard engine outboard drive.

The drive source3may be an electric motor. Alternatively, the drive source3may be a hybrid system including an engine and an electric motor.

In the propeller unit7, the bushing20, the damper30, or the second spacer50may have a function of inhibiting or preventing the propeller10from sliding backward with respect to the damper30. For example, the second spacer50may be configured to be meshed with one or more cutouts (not shown in the drawings) provided on the rear end surface of the inner tubular portion11.

The recess31may be one of a plurality of recesses31disposed at intervals in the rotational direction of the propeller shaft5. The protrusion15may be one of a plurality of protrusions15disposed at intervals in the rotational direction of the propeller shaft5. The recess16may be one of a plurality of recesses16disposed at intervals in the rotational direction of the propeller shaft5. The protrusion32may be one of a plurality of protrusions32disposed at intervals in the rotational direction of the propeller shaft5.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.