Title:
LUBRICATING STRUCTURE FOR MARINE DRIVE
Kind Code:
A1


Abstract:
A lubricating structure for a marine drive includes a lubricating oil supplying system that supplies lubricating oil to a meshing portion of a driven bevel gear and a drive bevel gear by utilizing centrifugal force exerted by rotation of the bevel gears and one or more passages formed in one or both of the bevel gears.



Inventors:
Fukuoka, Yoshihito (Shizuoka-ken, JP)
Asakaze, Ken (Shizuoka-ken, JP)
Application Number:
11/779800
Publication Date:
01/24/2008
Filing Date:
07/18/2007
Assignee:
YAMAHA MARINE KABUSHIKI KAISHA (Shizuoka-ken, JP)
Primary Class:
Other Classes:
440/75
International Classes:
F01M9/10; B63H20/14; B63H21/38; F16H57/02; F16H57/037; F16H57/038; F16H57/039; F16H57/04
View Patent Images:
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Primary Examiner:
SICONOLFI, ROBERT
Attorney, Agent or Firm:
KNOBBE MARTENS OLSON & BEAR LLP (IRVINE, CA, US)
Claims:
What is claimed is:

1. A lubricating structure for a marine drive having a drive shaft driven by an engine, a bevel gear mechanism, a propeller shaft driven by the drive shaft via the bevel gear mechanism, the bevel gear mechanism having a drive bevel gear attached to the drive shaft and a driven bevel gear attached to the propeller shaft and meshing with the drive bevel gear, and a lubricating oil supplying system for supplying lubricating oil to a meshing portion of the drive and driven bevel gears, the lubricating oil supplying system comprising an oil intake passage formed in one of the drive or driven bevel gears, the oil intake passage configured so that as the corresponding bevel gear rotates, lubricating oil is drawn through the oil intake passage by centrifugal force and delivered at or adjacent the meshing portion of the drive and driven bevel gears.

2. The lubricating structure of claim 1, wherein the bevel gear mechanism comprises a forward driven bevel gear and a reverse driven bevel gear, and the oil intake passage is formed in at least one of the driven bevel gears.

3. The lubricating structure of claim 1, wherein the oil intake passage formed in the bevel gear axially extends from a non-toothed-side end of the bevel gear to an opening at or adjacent a toothed face of the bevel gear.

4. The lubricating structure of claim 3, wherein the opening of the oil intake passage at a toothed-side end is generally upstream of the opening at the non-toothed-side end in a rotational direction of the bevel gear.

5. The lubricating structure of claim 1, wherein the oil intake passage formed in the bevel gear axially extends from a non-toothed-side end of the driven bevel gear and further radially extends to open in a surface of the gear within the meshing portion.

6. The lubricating structure of claim 5, wherein the opening of the oil intake passage at a toothed-side end is generally upstream of the opening at the non-toothed-side end in a rotational direction of the bevel gear.

7. The lubricating structure of claim 1, wherein the oil intake passage formed in the bevel gear is tilted further outward with respect to a rotation axis of the bevel gear from a non-toothed-side end toward a toothed face of the bevel gear.

8. The lubricating structure of claim 7, wherein a pipe member is inserted into the opening of the oil intake passage at the non-toothed-side end such that the pipe member projects from the non-toothed side.

9. The lubricating structure of claim 8, wherein a projection of the pipe member is formed such that an opening in the projection is substantially oriented opposed to the rotational direction of the driven bevel gear.

10. The lubricating structure of claim 8, wherein a second pipe member is inserted into the opening of the oil intake passage at a toothed-side end, and the second pipe member has an opening generally directed toward the meshing portion.

11. A marine drive comprising an engine, a drive shaft, a propeller shaft and a bevel gear mechanism, the engine driving the drive shaft, which in turn drives the propeller shaft through the bevel gear mechanism, the bevel gear mechanism having a drive bevel gear attached to the drive shaft and a driven bevel gear attached to the propeller shaft and meshing with the drive bevel gear at a meshing portion, and a lubricating oil supplying system is adapted to supply lubricating oil to the meshing portion, the lubricating oil supplying system comprising an oil intake passage formed in one of the drive or driven bevel gears, the oil intake passage configured so that as the corresponding bevel gear rotates, lubricating oil is drawn through the oil intake passage by centrifugal force and delivered at or adjacent the meshing portion of the drive and driven bevel gears.

12. The marine drive of claim 11, wherein the bevel gear mechanism comprises a forward driven bevel gear and a reverse driven bevel gear, and the oil intake passage is formed in at least one of the driven bevel gears.

13. The marine drive of claim 12, wherein each of the forward and reverse driven gears comprises an oil intake passage.

14. The marine drive of claim 13, wherein each of the forward and reverse driven gears comprises an oil intake passage, and the oil intake passage in the forward driven gear has a different orientation than the oil intake passage in the reverse driven gear.

15. The marine drive of claim 12, wherein an opening of the oil intake passage at a toothed-side end is generally upstream of an opening at a non-toothed-side end in a rotational direction of the bevel gear.

16. The marine drive of claim 12, wherein an opening of the oil intake passage at a toothed-side end of the bevel gear is farther from a center axis of the bevel gear than is an opening at a non-toothed-side end of the bevel gear.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application Serial No. 2006-195404, filed on Jul. 18, 2006, the entire contents of which are expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a marine drive having a propeller shaft driven by rotation of the drive shaft via a bevel gear mechanism. More particularly, the invention relates to a lubricating structure for a meshing portion in the bevel gear mechanism.

2. Description of the Related Art

A marine drive such as an outboard motor on a boat or the like is constructed to transmit a rotational force of an engine through a drive shaft via a bevel gear mechanism to a propeller shaft to thereby generate thrust.

For example, in an outboard motor of this type, a lower case that houses the drive shaft, the bevel gear mechanism, and the propeller shaft directly receives resistance from water during running. Hence, it is desired to minimize the dimension of the lower case in the widthwise direction of the boat, which limits a layout space for the bevel gear mechanism and the like.

A meshing portion and bearings of the bevel gear mechanism disposed in such a limited space in the lower case are cooled and lubricated by circulating lubricating oil to thereby increase their service lives as long as possible. In this circulating system, the lubricating oil is typically circulated through a bevel gear mechanism accommodating chamber, a drive shaft accommodating chamber, and a shift rod accommodating chamber in the lower case.

A forward bevel gear of the bevel gear mechanism typically is disposed at a boundary between the shift rod accommodating chamber and the bevel gear mechanism accommodating chamber can make it difficult for the lubricating oil to flow easily, and thus hinders smooth circulation of the oil. Japanese Publication No. 05-321992 discloses a configuration in which an oil passage that connects the shift rod accommodating chamber to the bevel gear mechanism accommodating chamber is formed in the forward bevel gear.

This configuration helps the flow of lubricating oil. However, Applicants have determined that lubrication of the meshing portion in the bevel gear mechanism remains insufficient. Hence, a concern arises that the temperature of the lubricating oil in the meshing portion is likely to rise, which may result in wearing of the meshing portion and shortening of service life of the bevel gear.

SUMMARY

Accordingly, there is a need in the art for a lubricating structure that allows lubricating oil to flow smoothly and also sufficiently lubricates a meshing portion in a bevel gear mechanism.

In accordance with one embodiment, the present invention provides a lubricating structure for a marine drive having a drive shaft driven by an engine, a bevel gear mechanism, and a propeller shaft driven by the drive shaft via the bevel gear mechanism. The bevel gear mechanism has a drive bevel gear attached to the drive shaft and a driven bevel gear attached to the propeller shaft and meshing with the drive bevel gear. A lubricating oil supplying system is provided for supplying lubricating oil to a meshing portion of the drive and driven bevel gears. The lubricating oil supplying system comprises an oil intake passage formed in one of the drive or driven bevel gears. The oil intake passage is configured so that as the corresponding bevel gear rotates, lubricating oil is drawn through the oil intake passage by centrifugal force and delivered at or adjacent the meshing portion of the drive and driven bevel gears.

In one such embodiment, the bevel gear mechanism comprises a forward driven bevel gear and a reverse driven bevel gear, and the oil intake passage is formed in at least one of the driven bevel gears.

In another such embodiment, the oil intake passage formed in the bevel gear axially extends from a non-toothed-side end of the bevel gear to an opening at or adjacent a toothed face of the bevel gear. In another embodiment, the opening of the oil intake passage at a toothed-side end is generally upstream of the opening at the non-toothed- side end in a rotational direction of the bevel gear.

In a further embodiment, the oil intake passage formed in the bevel gear axially extends from a non-toothed-side end of the driven bevel gear and further radially extends to open in a surface of the gear within the meshing portion.

In yet another embodiment, the oil intake passage formed in the bevel gear is tilted further outward with respect to a rotation axis of the bevel gear from a non-toothed-side end toward a toothed face of the bevel gear.

In a still further embodiment, a pipe member is inserted into the opening of the oil intake passage at the non-toothed-side end such that the pipe member projects from the non-toothed side. In one embodiment, a projection of the pipe member is formed such that an opening in the projection is substantially oriented opposed to the rotational direction of the driven bevel gear. In another embodiment, a second pipe member is inserted into the opening of the oil intake passage at a toothed-side end, and the second pipe member has an opening generally directed toward the meshing portion.

In accordance with another embodiment, A marine drive is provided comprising an engine, a drive shaft, a propeller shaft and a bevel gear mechanism. The engine drives the drive shaft, which in turn drives the propeller shaft through the bevel gear mechanism. The bevel gear mechanism has a drive bevel gear attached to the drive shaft and a driven bevel gear attached to the propeller shaft and meshing with the drive bevel gear at a meshing portion. A lubricating oil supplying system is adapted to supply lubricating oil to the meshing portion. The lubricating oil supplying system comprises an oil intake passage formed in one of the drive or driven bevel gears. The oil intake passage is configured so that as the corresponding bevel gear rotates, lubricating oil is drawn through the oil intake passage by centrifugal force and delivered at or adjacent the meshing portion of the drive and driven bevel gears.

In one embodiment, the bevel gear mechanism comprises a forward driven bevel gear and a reverse driven bevel gear, and the oil intake passage is formed in at least one of the driven bevel gears. In another such embodiment, each of the forward and reverse driven gears comprises an oil intake passage. In yet another such embodiment, each of the forward and reverse driven gears comprises an oil intake passage, and the oil intake passage in the forward driven gear has a different orientation than the oil intake passage in the reverse driven gear.

In another embodiment, an opening of the oil intake passage at a toothed-side end of the bevel gear is farther from a center axis of the bevel gear than is an opening at a non-toothed-side end of the bevel gear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an outboard motor according to one embodiment of the invention.

FIG. 2 is a sectional view of a propulsion unit of the outboard motor.

FIG. 3 is a sectional view of a lubricating section of a bevel gear mechanism of the propulsion unit.

FIG. 4 is a view of a forward bevel gear of the bevel gear mechanism as viewed from a side of a toothed face.

FIG. 5 is a sectional view of the forward bevel gear.

FIG. 6 is a sectional view of a lubricating section of a bevel gear mechanism according to another embodiment.

FIG. 7 is a side view of a lower case that houses a propulsion unit according to the embodiment of FIG. 8.

FIG. 8 is a view of a forward bevel gear of the propulsion unit as viewed from a side of a toothed face.

FIG. 9 is a view of the forward bevel gear as viewed from a side opposite from the toothed face.

FIGS. 10(a) and 10(b) are sectional views of the forward bevel gear.

FIG. 11 is a sectional view of a portion of an oil intake passage of the forward bevel gear.

FIG. 12 is a sectional view of a forward bevel gear according to yet another embodiment.

FIG. 13 is a sectional view of a portion of an oil intake passage of the forward bevel gear of FIG. 12.

FIG. 14 is a sectional view of a forward bevel gear according to still another embodiment.

FIG. 15 is a sectional view of a forward bevel gear according to a yet further embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments will be described hereinafter with reference to the accompanying drawings. In the embodiments discussed herein, front, rear, left, and right directions each refer to front, rear, left, and right directions as viewed from the rear of the hull.

In the drawings, reference numeral 1 denotes an outboard motor mounted on a stem 2a of a hull 2. The outboard motor 1 is supported at the stem 2a for vertical swinging motion through a clamp bracket 3 fixed to the stern 2a and for lateral steering through a pivot shaft 5.

With initial reference to FIG. 1, the outboard motor 1 has a structure schematically described below. An upper case 8 is connected to an upper surface of a lower case 7 that houses a propulsion unit 6. An engine 10 is mounted on an upper surface of the upper case 8. A cowling 11 is attached to the upper surface of the upper case 8, while covering the engine 10. The engine 10 is longitudinally arranged such that a crankshaft 10a stands substantially vertically when the hull 2 is running on water.

The illustrated propulsion unit 6 has: a drive shaft 12 that is coaxially connected to the crankshaft 10a and rotated by the engine 10; a propeller shaft 14 that is disposed generally horizontally so as to be perpendicular to the drive shaft 12 and that is rotated by the drive shaft 12 through a bevel gear mechanism 13; the lower case 7 that houses the propeller shaft 14 and the drive shaft 12; and a propeller 15 attached to a projection 14a of the propeller shaft 14, the projection 14a projecting rearward from the lower case 7.

With additional reference to FIGS. 2 and 3, the illustrated bevel gear mechanism 13 has a drive bevel gear 17, a forward bevel gear 18, and a reverse bevel gear 19. The drive bevel gear 17 is attached to a lower end 12a, at which the bevel gear mechanism 13 is attached, of the drive shaft 12 for rotation therewith. The forward and reverse bevel gears 18 and 19 are attached to a front end 14b, at which the bevel gear mechanism 13 is attached, of the propeller shaft 14 for relative rotation, and constantly mesh with the drive bevel gear 17.

The illustrated forward bevel gear 18 has a spiral bevel gear structure. As shown in FIGS. 4 and 5, an umbrella section 18c is formed on a shaft section 18b. The shaft section 18b has a shaft hole 18a, into which the propeller shaft 14 is inserted. A number of spiral teeth 18d are formed on the umbrella section 18c preferably at circumferentially regular intervals.

Each spiral tooth 18d extends in a curved line such that a portion closer to an outer end 18d″ with respect to an inner end 18d′ produces a more forward curve in a rotational direction A. Therefore, the spiral teeth 18d are formed to have a pitch between each adjacent spiral teeth 18d that gradually increases from an inner pitch W2 to an outer pitch W1. Meanwhile, each of the drive bevel gear 17 and the reverse bevel gear 19 has a spiral bevel gear structure conforming to the forward bevel gear 18.

With reference again to FIGS. 2 and 3. the illustrated bevel gear mechanism 13 is provided with a forward/reverse switching mechanism 20. The forward/reverse switching mechanism 20 is positioned between the forward and reverse bevel gears 18 and 19 on the propeller shaft 14. The mechanism 20 is provided with: a dog clutch 21 spline-fitted to the propeller shaft 14 to be movable in an axial direction of the propeller shaft 14 and rotatable therewith; a shift sleeve 22 inserted into the front end 14b of the propeller shaft 14 to be slidable in the axial direction; a shift rod 24 coupled to the shift sleeve 22 via a shift cam 23; and a shift lever (not shown) coupled to the shift rod 24 and located closer to the hull 2. The shift sleeve 22 is connected to the dog clutch 21 with a pin 25. The pin 25 is located in a pin receptacle 14e between the forward and reverse bevel gears 18 and 19 on the propeller shaft 14.

The dog clutch 21 is movable among a neutral position at which the clutch 21 meshes with neither the forward bevel gear 18 nor the reverse bevel gear 19, a forward position to mesh with the forward bevel gear 18, and a rear position to mesh with the reverse bevel gear 19.

When the shift lever is operated to switch from the neutral position to one of the forward and rear positions, the shift rod 24 rotates, and the shift cam 23 converts the rotation of the shift rod 24 into frontward/backward motion of the shift sleeve 22. Hence, the dog clutch 21 meshes with a corresponding one of the forward and reverse bevel gears 18 and 19. Thus, the rotational force of the drive shaft 12 is transmitted to the propeller shaft 14.

The lower case 7 is formed into a substantially bullet profile in section perpendicular to the drive shaft 12. A drive shaft accommodating chamber 7a that extends vertically and has an opening at its upper end is formed at an approximate center of the lower case 7 in a front-rear direction. The drive shaft 12 is housed in the drive shaft accommodating chamber 7a.

A bevel gear mechanism accommodating chamber 7b that extends in the front-rear direction and has an opening at its rear end is formed in a lower end portion of the drive shaft accommodating chamber 7a. The bevel gear mechanism 13 is housed in the bevel gear mechanism accommodating chamber 7b.

A cylindrical bearing housing 30 that seals a gap between the drive shaft accommodating chamber 7a and the upper end opening of the chamber 7a is fixedly inserted into the opening. A pair of upper and lower sealing members 31, 31 for sealing a gap between the drive shaft 12 and the housing 30 are disposed in the housing 30.

The upper end 12b of the drive shaft 12 within the illustrated lower case 7 is journalled by the housing 30 through a needle bearing 32, and the lower end 12a of the drive shaft 12 is journalled by a needle bearing 33 at the lower end opening of the drive shaft accommodating chamber 7a.

A conical bearing 35 that journals the forward bevel gear 18 is provided at a front end of the bevel gear mechanism accommodating chamber 7b, and a ball bearing 37 that journals the reverse bevel gear 19 is provided at a rear end opening of the chamber 7b via a gear housing 36, which will be described later.

A shift rod accommodating chamber 7c extending parallel with the drive shaft accommodating chamber 7a is formed in front of the drive shaft accommodating chamber 7a in the lower case 7. The shift rod 24 is housed in the shift rod accommodating chamber 7c. A lower end opening of the shift rod accommodating chamber 7c is communicated with the front end of the bevel gear mechanism accommodating chamber 7b.

The forward bevel gear 18 and the conical bearing 35 are disposed in a communicating section 7i, through which the shift rod accommodating chamber 7c communicates with the bevel gear mechanism accommodating chamber 7b, so as to substantially block the communicating section 7i. A sealing member 38 that seals a gap between the shift rod 24 and an upper end opening of the shift rod accommodating chamber 7c is fixedly inserted into the upper end opening.

A cooling water suction passage 7d extending parallel with the shift rod accommodating chamber 7c is formed in front of the chamber 7c in the illustrated embodiment. Cooling water flows into the cooling water suction passage 7d through suction ports 7g formed in left and right side walls of the lower case 7.

A cooling water jacket 7h that surrounds an outer circumferential surface of the drive shaft accommodating chamber 7a is formed in the illustrated lower case 7. Cooling water that flows through the cooling water jacket 7h cools lubricating oil in the drive shaft accommodating chamber 7a. Lubricating oil in the shift rod accommodating chamber 7c is cooled by cooling water that flows through the cooling water suction passage 7d and the cooling water jacket 7h.

An exhaust gas discharging passage 7e is formed at the rear of the drive shaft accommodating chamber 7a in the lower case 7. The cooling water jacket 7h is disposed between the exhaust gas discharging passage 7e and the drive shaft accommodating chamber 7a. The discharging passage 7e communicates with an outlet port 7f formed in a rear end surface of the lower case 7. Exhaust gas from the engine 10 is discharged by way of an upper case 8 and the exhaust gas discharging passage 7e into water through the outlet port 7f.

The gear housing 36 is inserted into the bevel gear mechanism accommodating chamber 7b of the lower case 7 and is positioned to pass through the exhaust gas discharging passage 7e. The gear housing 36 partitions the exhaust gas discharging passage 7e from the bevel gear mechanism accommodating chamber 7b.

The illustrated gear housing 36 has: a cylindrical body 36b in which a propeller shaft accommodating hole 36a is formed; a large-diameter section 36c that is formed continuous with a front end of the cylindrical body 36b to outwardly protrude in a bowl shape; a plurality of ribs 36d that extend from a rear end of the cylindrical body 36b in outwardly radial directions perpendicular to the axial direction of the body 36b; and an annular flange 36e that connects outer circumferential surfaces of the ribs 36d.

The flange 36e is fixed to a periphery of the outlet port 7f of the lower case 7 with a plurality of bolts 40 inserted from the rear. Exhaust gas is discharged into water through gaps between the ribs 36d on the outlet port 7f.

An outer circumferential surface of the large diameter section 36c is attached to a rear end opening of the bevel gear mechanism accommodating chamber 7b, and the ball bearing 37 is attached to an inner circumferential surface of the large diameter section 36c.

The propeller shaft 14 is inserted into the propeller shaft accommodating hole 36a in the illustrated gear housing 36. The front end 14b of the propeller shaft 14 is inserted through shaft holes 18a and 19a in the forward and reverse bevel gears 18 and 19, and supported for relative rotation through a metal bearing 42 disposed in the shaft hole 18a in the forward bevel gear 18. A gap is provided between the propeller shaft 12 and the shaft hole 19a in the reverse bevel gear 19.

A pair of front and rear sealing members 44, 44 that seal a gap between the propeller shaft 12 and a rear end of the propeller shaft accommodating hole 36a in the gear housing 36 preferably are provided at the rear end of the hole 36a.

A needle bearing 43 that journals the rear end 14d of the propeller shaft 14 preferably is disposed in front of the sealing member 44 in the propeller shaft accommodating hole 36a in the gear housing 36.

The illustrated propulsion unit 6 is provided with an oil circulating system 47 that circulates lubricating oil filled in the lower case 7. The oil circulating system 47 causes lubricating oil to circulate through the drive shaft accommodating chamber 7a, the bevel gear mechanism accommodating chamber 7b, the shift rod accommodating chamber 7c, and the propeller shaft accommodating hole 36a. The oil level of the lubricating oil preferably is at a level of the needle bearing 32, which is the upper one of the needle bearings 32 and 33 in the drive shaft accommodating chamber 7a, and is at the same level also in the shift rod accommodating chamber 7c.

The illustrated oil circulating system 47 has: a drive shaft circulating system 48 that causes lubricating oil “a” to circulate through the attaching section, at which the drive bevel gear 17 is attached to the drive shaft 12, the upper and lower needle bearings 32 and 33, and then through the forward/rearward switching mechanism 20; and a propeller shaft circulating system 49 that causes lubricating oil “b” to circulate through an attaching section 14b, at which the forward and reverse bevel gears 18 and 19 are attached to the propeller shaft 14, and then through the needle bearing 43 that journals the rear end 14d of the propeller shaft 14. The propulsion unit 6 also includes, as shown in FIG. 3, a lubricating oil supplying system 50 that supplies lubricating oil “c” to a meshing surface of the forward bevel gear 18 and the drive bevel gear 17 by utilizing centrifugal force exerted by rotation of the forward bevel gear 18.

The illustrated drive shaft circulating system 48 has; an axially extending oil passage 48a in a gap between the drive shaft 12 and the drive shaft accommodating chamber 7a in the lower case 7; a screw pump section 48b defined by an axial center of the drive shaft 12 and an inner circumferential wall of the drive shaft accommodating chamber 7a; and a return passage 48c for communicating an upper end, at which the needle bearing 32 is provided, of the oil passage 48a with the shift rod accommodating chamber 7c.

The screw pump section 48b is formed by providing a small gap between an upwardly-extending counterclockwise spiral groove 12c in an outer circumferential surface of the drive shaft 12 and an inner circumferential wall of the drive shaft accommodating chamber 7a. The screw pump section 48b pressurizes lubricating oil in the oil passage 48a and delivers it upward.

When the drive shaft 12 rotates, lubricating oil is pressurized by the screw pump section 48b and delivered upward through the oil passages 48a. The lubricating oil “a” that has ascended through the oil passages 48a lubricates the needle bearing 32, then flows through the return passage 48c into the shift rod accommodating chamber 7c to lubricate sliding portions in the forward/rearward switching mechanism 20 and the conical bearing 35, and thereafter returns into the bevel gear mechanism accommodating chamber 7b. The lubricating oil “a” in the bevel gear mechanism accommodating chamber 7b is delivered upward by the screw pump section 48b, while lubricating a meshing portion in the bevel gear mechanism 13 and the needle bearing 33, which is the lower one of the needle bearings 32 and 33.

Cooling water flowing through the cooling water jacket 7h cools the lubricating oil “a” that flows through the drive shaft accommodating chamber 7a and the shift rod accommodating chamber 7c.

The illustrated propeller shaft circulating system 49 has an oil passage 49c that axially extends from the front end 14b, at which the forward and reverse bevel gears 18 and 19 are provided, of the propeller shaft 14 to a portion near the needle bearing 43 and further radially extends to have an opening near the needle bearing 43, and a return passage 49d formed in a gap between the propeller shaft 14 and the propeller shaft accommodating hole 36a in the gear housing 36.

When the shift lever is operated to cause the dog clutch 21 to mesh with one of the forward and reverse bevel gears 18 and 19, the propeller shaft 14 is rotated, and centrifugal force exerted by rotation of the propeller shaft 14 causes the lubricating oil “b” to be discharged from the opening of the oil passage 49c. The discharged lubricating oil “b” lubricates the needle bearing 43, then lubricates the ball bearing 37 and the meshing portion in the bevel gear mechanism 13, while flowing through the return passage 49d, and returns to the bevel gear mechanism accommodating chamber 7b. Rotation of the propeller shaft 14 causes the lubricating oil “b” in the bevel gear mechanism accommodating chamber 7b to flow into the oil passage 49c.

With reference to FIGS. 2-5, the illustrated lubricating oil supplying system 50 includes oil intake passages 50a formed in the shaft section 18b of the forward bevel gear 18 at circumferential regular intervals. Each oil intake passage 50a extends parallel to a rotation axis C of the forward bevel gear 18. An inlet port 50b of each oil intake passage 50a opens into a non-toothed-side end face 18e of the forward bevel gear 18, and an outlet port 50c of the oil intake passage 50a opens into a toothed-side end face 18f.

The toothed-side end face 18f preferably is a vertical surface perpendicular to the rotation axis C. The non-toothed-side end face 18e preferably is a surface inwardly tapered in relation to the rotation axis C, and the inlet port 50b opens into the tapered surface. Hence, the inlet port 50b is substantially oriented opposed to the rotational direction A of the forward bevel gear 18.

Centrifugal force exerted by rotation of the forward bevel gear 18 causes the lubricating oil “a” in the shift rod accommodating chamber 7c to be taken in via the inlet port 50b of the oil intake passages 50a. The thus-taken-in lubricating oil “c” flows out of the outlet port 50c through the oil intake passages 50a toward the teeth 18d. More specifically, the lubricating oil “c” out of each oil intake passage 50a is radially discharged so as to be oriented toward corresponding tooth 18d in the umbrella section 18c. The discharged lubricating oil “c” is supplied to the meshing portion between the forward bevel gear 18 and the drive bevel gear 17, and flows to the oil passage 48a through the meshing portion.

According to the illustrated embodiment, the oil intake passages 50a that extend from the non-toothed-side end face 18e parallel with the rotation axis C to open into the toothed-side end face 18f are formed in the forward bevel gear 18 so that the lubricating oil “c” is supplied to the meshing portion between the forward bevel gear 18 and the drive bevel gear 17 by utilizing centrifugal force of the forward bevel gear 18. Hence, the lubricating oil “c” is allowed to flow from the shift rod accommodating chamber 7c into the bevel gear mechanism accommodating chamber 7b smoothly and to be supplied to the meshing portion between the forward bevel gear 18 and the drive bevel gear 17. This lowers the temperature of the lubricating oil at the meshing portion of the forward bevel gear 18 and forms a lubricating film on a tooth surface of each tooth 18d. Consequently, wearing of the bevel gear mechanism 13 is suppressed, which increases the service life of the bevel gear mechanism 13.

In another embodiment, the oil intake passage 50a may be tilted so as to have a larger distance from the rotation axis C toward the inlet port 50c. This arrangement may supply the lubricating oil more reliably to the meshing portion by centrifugal force.

In the illustrated embodiment, the oil intake passages 50a that form the lubricating oil supplying system 50 are in the shaft section 18b of the forward bevel gear 18. Hence, since the forward bevel gear 18 functions as a centrifugal pump for taking the lubricating oil “c” into the oil intake passage 50a, the lubricating oil “c” is allowed to reliably flow and lubricate the meshing portion.

In a preferred embodiment, the inlet port 50b of each oil intake passage 50a is tapered so as to be substantially oriented opposed to the rotational direction A of the forward bevel gear 18. Hence, since centrifugal force exerted by rotation of the forward bevel gear 18 facilitates intake of the lubricating oil “c” via the inlet ports 50b, the flow of the lubricating oil “c” and lubrication of the meshing portion in the bevel gear mechanism 13 are further enhanced.

Although this embodiment has described a configuration in which the oil intake passages 50a is provided in the forward bevel gear 18, it is to be understood that in other embodiments the oil intake passage may be provided in the reverse bevel gear or in both the forward and reverse bevel gears.

FIG. 6 is an explanatory view illustrating another embodiment having certain aspects in common with the embodiments discussed above. In FIG. 6, identical or similar parts to those in FIG. 3 are denoted by the identical reference numerals.

In this embodiment, the lubricating oil supplying system 50 includes the oil intake passages 50a formed in the shaft section 18b of the forward bevel gear 18 at circumferential regular intervals.

Each oil intake passage 50a includes a shaft hole 50d that extends from the non-toothed-side end face 18e of the shaft section 18b of the forward bevel gear 18 parallel with the rotation axis C and a branch shaft hole 50e that extends generally radially from a portion of the shaft hole 50d. Each branch shaft hole 50e opens into a bottom surface between adjacent teeth 18d, 18d in the umbrella section 18c.

According to the illustrated embodiment, each oil intake passage 50a in the forward bevel gear 18 is formed with the shaft hole 50d extending from the non-toothed-side end face 18e parallel with the rotation axis, and the branch shaft hole 50e radially extending from the shaft hole 50d to open into the bottom surface. Hence, since the forward bevel gear 18 functioning as the centrifugal pump directly supplies the lubricating oil “c” to the bottom surface of each tooth 18d, the meshing portion between the forward bevel gear 18 and the drive bevel gear 17 is lubricated more reliably.

The shaft hole 50d may be tilted so as to be increasingly spaced from the rotation axis C toward the outlet port. In this case, the lubricating oil can be supplied to the meshing portion by centrifugal force more reliably. In other embodiments, the shaft hole 50d is generally perpendicular to the rotation axis C.

FIGS. 7 to 11 are explanatory views illustrating a lubricating structure for an outboard motor according to another embodiment of the invention. FIG. 7 is a side view of the lower case of a marine drive such as an outboard motor. FIGS. 8 to 10 are a front view, a rear view, and a sectional view of the forward bevel gear of the bevel gear mechanism, respectively. FIG. 11 is a sectional view of a portion of the same. In FIGS. 7 to 11, identical or similar parts to those in FIGS. 3 to 5 are denoted by the identical reference numerals.

As shown in FIG. 7, in this embodiment, an oil circulating system 47 has a drive shaft circulating mechanism 48, a propeller shaft circulating system 49, and a lubricating oil supplying system 51. The drive shaft circulating mechanism 48 causes lubricating oil “a” to circulate through an attaching section 12a, at which a drive bevel gear 17 is attached to a drive shaft 12, upper and lower needle bearings 32 and 33, and a forward/rearward switching mechanism 20. The propeller shaft circulating system 49 causes lubricating oil “b” to circulate through an attaching section 14b, at which forward and reverse bevel gears 18 and 19 are attached to a propeller shaft 14, and a needle bearing 43 that journals a rear end 14d of the propeller shaft 14. The lubricating oil supplying system 51 supplies lubricating oil “c” by utilizing centrifugal force exerted by rotation of the forward and reverse bevel gears 18 and 19 to the meshing surface of the forward and reverse bevel gears 18 and 19, and the drive bevel gear 17. For ease of description, this embodiment has substantially the same basic configuration as the embodiment discussed above.

The lubricating oil supplying system 51 according to the illustrated embodiment includes oil intake passages 51a, 51b formed in the forward and reverse bevel gears 18, 19, respectively, at circumferential regular intervals.

Each oil intake passage 51a in the forward bevel gear 18 is tilted so as to be, from a non-toothed-side end face 18e toward a toothed-side end face 18f of the forward bevel gear 18, increasingly separated from a rotation axis C (FIG. 10(a)) as well as to be further upstream in the rotational direction A (FIG. 10 (b)).

An inlet port 51c of the oil intake passage 51a opens into the non-toothed-side end face 18e, and an outlet port 51d opens into the toothed-side end face 18f. This arrangement causes the outlet port 51d to be deviated radially outward and upstream in the rotational direction with respect to the inlet port 51c.

According to the illustrated embodiment, the oil intake passages 51a in the forward bevel gear 18 are formed such that each passage 51a is tilted further outward with respect to the rotation axis C from the non-toothed-side end face 18e toward the toothed-side end face 18f. Hence, when the oil intake passage 51a is rotated by rotation of the forward bevel gear 18, the rotation velocity of the outlet port 51d is higher than that of the inlet port 51c. Therefore, a greater centrifugal force is imparted on the outlet port 51d than on the inlet port 51c. Accordingly, since a flow rate of the lubricating oil “c” that flows through the oil intake passage 51a increases toward the outlet port 51d, the flow of the lubricating oil “c” and lubrication of the meshing portion between the forward bevel gear 18 and the drive bevel gear 17 are further enhanced.

In the embodiment illustrated in FIG. 7, the reverse bevel gear 19 preferably has oil intake passages 51b that are outwardly tilted in a similar manner as the passages 51a. However, each oil intake passage 51b of the reverse bevel gear 19 is upright to form approximately 60 degrees with respect to a rotation axis of the reverse bevel gear 19. An inlet port 51e of the oil intake passage 51b opens into a shaft hole 19a, and an outlet port 51f opens into the bottom surface; thus, lubricating oil “c” at a high flow rate is directly supplied to the meshing portion between the reverse bevel gear 19 and the drive bevel gear 17. In another embodiment, both the forward and reverse bevel gears have oil intake passages that are substantially the same in construction.

FIGS. 12 and 13 are explanatory views illustrating a lubricating structure for an outboard motor according to yet another embodiment of the invention. In FIGS. 12 and 13, identical or similar parts to those in FIGS. 10 and 11 are denoted by the identical reference numerals.

Each oil intake passage 51a according to the illustrated embodiment is tilted further outward with respect to a rotation axis C from a non-toothed-side end face 18e toward a toothed-side end face 18f of a forward bevel gear 18. For ease of description, this embodiment has substantially the same basic configuration as the embodiment above.

A pipe member 52 is inserted into an inlet port 5 1c opened into the non-toothed-side end face 18e of each oil intake passage 51a to project forward from the end face 18e. A projection 52a of the pipe member 52 is positioned to the rear of a front end face 18′ of the forward bevel gear 18.

In this embodiment, since the pipe member 52 is inserted into the inlet port 51c of the oil intake passage 51a so as to project forward from the non-toothed-side end face 18e, intake of lubricating oil “c” by centrifugal force exerted by rotation of the forward bevel gear 18 is further facilitated.

FIG. 14 depicts yet another embodiment in which the projection 52a of the pipe member 52 is inwardly bent such that an opening 52b in the projection 52a is oriented opposed to the rotational direction of the forward bevel gear 18. Since the opening 52b is oriented opposed to the rotational direction, the lubricating oil “c” is taken in through the pipe member 52 even more reliably. In one preferred embodiment, the opening is oriented towards the lubricant oil in the chamber so as the gear rotates, oil is scooped into the opening.

FIG. 15 depicts a still further embodiment in which the pipe member 52 is inserted into the inlet port 51c and a pipe member 53 is inserted into the outlet port 51d of the oil intake passage 51a. The projection 52a of the pipe member 52 at the inlet port is inwardly bent such that its opening 52b is oriented opposed to the rotational direction of the forward bevel gear 18. A projection 53a of the pipe member 53 at the outlet port is bent such that its opening 53b is oriented along the rotational direction of the forward bevel gear 18. According to this variation, both intake and discharge of the lubricating oil can be performed reliably.

The embodiments discussed above have been illustrated in connection with an outboard motor having a generally consistent structure. This has been done to streamline discussion of the various embodiments. It is to be understood that other embodiments may be used in other applications having different structure. For example, other types of marine drives, such as stem drives, can employ principles discussed herein. Also, various structures, such as seals, the lower case profile and organization, bearings, bevel gear shapes, the water jacket, the exhaust gas discharging passage, the oil circulation system structure, and the like may be constructed differently than as discussed herein, or may not be present in some embodiments. In yet another embodiment, oil passages as discussed in the forward and/or reverse bevel gears may alternatively or in addition be provided in a drive bevel gear.

Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. For example, both the forward and reverse bevel gears can have the same oil passage structure, can have different ones of the structures discussed herein, or may have other structures consistent with the principles discussed herein. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.