JP2008018867A - Propulsion device of outboard motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a propulsion device of an outboard motor capable of reliably circulating lubricating oil while preventing the stay or the reverse flow of the lubricating oil. <P>SOLUTION: The propulsion device has an oil circulation system 48 in which lubricating oil a is made to pass through a shift shaft storage chamber (an oil passage) 7c formed in a lower case 7 from a bevel gear mechanism fitting part 12a of a drive shaft 12, and led to a drive shaft pivotably-supporting part pivotably supported by the lower case 7 via a bearing 32, and the lubricating oil a led to the drive shaft pivotably-supporting part is returned to the bevel gear mechanism fitting part 12a through a space between the drive shaft 12 and the drive shaft storage chamber 7a of the lower case. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a propulsion of an outboard motor including a drive shaft driven by an engine, a propeller shaft driven by the drive shaft via a bevel gear mechanism, and a lower case that accommodates and holds the propeller shaft and the drive shaft. Relates to the device.

  An outboard motor mounted on a small boat or the like generates a propulsive force by transmitting a rotational force of an engine from a drive shaft to a propeller shaft through a bevel gear mechanism.

  In this type of outboard motor, the lower case that accommodates and holds the drive shaft, the bevel gear mechanism, and the propeller shaft is directly subjected to the resistance of water during cruising. Therefore, the space for arranging the bevel gear mechanism and the like is limited.

  In order to extend the life of the bearing portion of the drive shaft and the meshing portion of the bevel gear mechanism arranged in a limited space in such a lower case as much as possible, cooling is performed by circulating lubricating oil.

For example, in Patent Literature 1, a spiral groove is formed between the upper and lower bearings of the drive shaft, and a screw pump is formed by providing a slight gap between the spiral groove and the drive shaft accommodation hole of the lower case. Then, the screw pump conveys the lubricating oil upward from the bevel gear mechanism accommodating chamber to each bearing, and from the upper bearing portion to the shift shaft accommodating chamber formed on the front side of the drive shaft accommodating hole, To the bevel gear mechanism housing chamber.
JP-A-57-182595

  By the way, as in the above-described conventional outboard motor, the oil circulation is such that the lubricating oil is transferred upward through the drive shaft accommodation hole by a screw pump, led from here to the shift shaft accommodation chamber, and then returned to the bevel gear mechanism accommodation chamber. When the route is adopted, the lubricating oil may stagnate without being circulated or may flow backward. As a result, the meshing part of the bevel gear mechanism and the bearing part of the drive shaft are likely to wear due to the temperature rise of the lubricating oil, which may shorten the life.

  The present invention has been made in view of the above-described conventional situation, and by preventing the stagnation and backflow of the lubricating oil and reliably circulating the lubricating oil, the life of the meshing portion of the bevel gear mechanism and the bearing portion of the drive shaft is achieved. The object is to provide a propulsion device for an outboard motor that can be extended.

  The inventor of the present invention has conducted studies on the cause of the stagnation or reverse flow of the lubricating oil and obtained the following knowledge. When the bevel gear mechanism rotates as the drive shaft rotates, the lubricating oil is agitated by the bevel gear mechanism and the lubricating oil is transferred in the direction opposite to the oil circulation path, that is, in the direction opposite to the transfer direction by the screw pump. It is thought that this caused the stagnation and backflow of the lubricating oil. The present inventor has conceived that the above problem can be solved by preventing the stagnation and backflow of the lubricating oil due to the oil stirring action as described above.

Accordingly, the present invention provides a drive shaft driven by an engine, a propeller shaft driven by the drive shaft via a bevel gear mechanism, a lower case that accommodates and holds the propeller shaft and the drive shaft, and the propeller shaft described above. In the outboard motor propulsion device provided with a propeller mounted on a protrusion protruding backward from the lower case,
Lubricating oil is guided through the oil passage formed in the lower case from the bevel gear mechanism mounting portion of the drive shaft to the drive shaft support portion that is supported by the lower case via a bearing, An oil circulation system is provided that returns the lubricating oil guided to the drive shaft support to the bevel gear mechanism mounting portion through a gap between the drive shaft and the drive shaft housing chamber of the lower case.

  According to a second aspect of the present invention, in the first aspect of the present invention, the outer circumferential surface of the drive shaft is provided with a spiral groove that conveys the lubricating oil downward along with the rotation of the drive shaft. .

  According to a third aspect of the present invention, in the first aspect, the bevel gear mechanism has a pump function of transferring lubricating oil to the oil passage side as the drive shaft rotates.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the oil passage is constituted by a shift shaft accommodating chamber in which a shift shaft for performing forward / reverse switching of the bevel gear mechanism is disposed. It is said.

  According to the propulsion device according to the present invention, the lubricating oil is guided to the drive shaft support portion of the drive shaft through the oil passage formed in the lower case from the bevel gear mechanism mounting portion of the drive shaft, and the drive shaft support portion. Since the lubricating oil introduced to the bevel gear mechanism is returned to the mounting portion of the bevel gear mechanism through the gap of the drive shaft housing chamber, the lubricating oil is circulated in the lubricating oil transfer direction by the lubricating oil stirring action of the bevel gear mechanism. It is possible to prevent stagnation and backflow of lubricating oil. As a result, the wear of the meshing portion of the bevel gear mechanism and the bearing portion of the drive shaft can be suppressed, and the component life can be extended.

  In the invention of claim 2, since the spiral groove for transferring the lubricant oil downward is formed on the outer peripheral surface of the drive shaft, the lubricant oil is transferred in the direction of the lubricant oil transfer direction of the bevel gear mechanism by the screw pump function of the drive shaft. It will be transferred in the same direction, whereby the circulation of the lubricating oil can be promoted, and the life of the parts can be further extended.

  In the invention of claim 3, since the lubricating oil is transferred to the oil passage side by the bevel gear mechanism, the bevel gear mechanism functions as a gear pump, and the circulation of the lubricating oil can be further promoted.

  In the invention of claim 4, since the oil passage is constituted by the shift shaft accommodating chamber, the oil circulation system can be formed by effectively utilizing the existing shift shaft accommodating chamber, the enlargement of the lower case can be suppressed, and the cost can be reduced. .

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 6 are views for explaining an outboard motor propulsion device according to an embodiment of the present invention. FIG. 1 is a side view of an outboard motor mounted on a hull, and FIGS. FIG. 4 is a plan view of the lower case, FIG. 5 and FIG. 6 are a front view and a sectional view of the forward bevel gear of the bevel gear mechanism.

  In the figure, reference numeral 1 denotes an outboard motor mounted on the stern 2 a of the hull 2. The outboard motor 1 is supported by a clamp bracket 3 fixed to the stern 2 a so as to be swingable up and down via a swivel arm 4, and supported so as to be steerable right and left via a pivot shaft 5.

  In the outboard motor 1, an upper case 8 is coupled to the upper surface of a lower case 7 in which the propulsion device 6 is accommodated, an engine 10 is mounted on the upper surface of the upper case 8, and the outer periphery of the engine 10 is surrounded. It has a schematic structure with a cowling 11 attached. The engine 10 is arranged vertically so that the crankshaft 10a is substantially vertical when traveling on water.

  The propulsion device 6 is connected to the crankshaft 10a so as to be coaxial, is driven to rotate by the engine 10, and is disposed in a substantially horizontal direction so as to be orthogonal to the drive shaft 12. A propeller shaft 14 that is rotationally driven by a shaft 12 via a bevel gear mechanism 13, the lower case 7 that accommodates and holds the propeller shaft 14 and the drive shaft 12, and a protruding portion that protrudes rearward from the lower case 7 of the propeller shaft 14. And a propeller 15 attached to 14a.

  The bevel gear mechanism 13 is always meshed with the drive bevel gear 17 and the drive bevel gear 17 that are mounted so as to rotate together with the lower end portion 12 a that is the bevel gear mechanism mounting portion of the drive shaft 12, and the propeller shaft 14. A forward bevel gear 18 and a reverse bevel gear 19 that are rotatably mounted on a front end portion 14b that is a bevel gear mechanism mounting portion.

  The forward bevel gear 18 has a spiral bevel gear structure, and as shown in FIGS. 5 and 6, an umbrella portion 18c is integrally formed on a shaft portion 18b having a shaft hole 18a into which the propeller shaft 14 is inserted. The umbrella portion 18c has a structure in which a number of spiral teeth 18d are formed at predetermined intervals in the circumferential direction.

  Each of the swirling teeth 18d extends so as to form a curve located on the forward side in the rotational direction A from the inner end portion 18d 'to the outer end portion 18d' 'of the swirling teeth 18d, and therefore, the adjacent swirling teeth 18d and 18d. Is formed so as to increase from the inner diameter side pitch w2 to the outer diameter side pitch w1. The drive bevel gear 17 and the reverse bevel gear 19 have a spiral bevel gear structure corresponding to the forward bevel gear 18.

  As a result, the bevel gear mechanism 13 generates a lubricating oil agitating action as the drive shaft 12 rotates, thereby serving as a gear pump for transferring the lubricating oil from the bevel gear mechanism accommodating chamber 7b described later to the shift shaft accommodating chamber 7c side. Fulfills the function.

The bevel gear mechanism 13 includes a forward / reverse switching mechanism 20. The forward / reverse switching mechanism 20 is disposed between the front and rear bevel gears 18 and 19 of the propeller shaft 14, and is a dog clutch spline-fitted to the propeller shaft 14 so as to be movable in the axial direction and to rotate together. 21, a shift sleeve 22 inserted in the front end portion 14 b of the propeller shaft 14 so as to be slidable in the axial direction, a shift shaft 24 connected to the shift sleeve 22 via a shift cam 23, and a connection to the shift shaft 24 And a shift lever (not shown) disposed on the hull 2 side. When the dog clutch 21 moves left and right, the shift sleeve 22 meshes with the forward and reverse bevel gears 18 and 19. The shift sleeve 22 is connected to the dog clutch 21 by a pin 25. The pin 25 is disposed in a pin hole 14 e formed between the front and reverse bevel gears 18 and 19 of the propeller shaft 14.

  The dog clutch 21 is movable between a neutral position that does not mesh with either the forward or reverse bevel gears 18 and 19 and a front or reverse clutch-in position that meshes with either the front or reverse bevel gears 18 or 19. It has become.

  When the shift lever is switched from the neutral position to either the forward or reverse clutch-in position, the shift shaft 24 rotates, and the shift cam 23 converts the rotation of the shift shaft 24 into the longitudinal movement of the shift sleeve 22. Then, the dog chic 21 meshes with either the forward or reverse bevel gears 18 and 19. Thereby, the rotational force of the drive shaft 12 is transmitted to the propeller shaft 14.

  The lower case 7 is formed to have a substantially bullet shape in a cross-sectional view orthogonal to the drive shaft 12. A drive shaft housing chamber 7a extending in the vertical direction and opening upward is formed at a substantially central portion of the lower case 7 in the front-rear direction, and the drive shaft 12 is housed in the drive shaft housing chamber 7a.

  A bevel gear mechanism accommodating chamber 7b extending in the front-rear direction and opening rearward is formed at the lower end of the drive shaft accommodating chamber 7a, and the bevel gear mechanism 13 is accommodated in the bevel gear mechanism accommodating chamber 7b. ing.

  A cylindrical bearing housing 30 for oil-tight sealing between the drive shaft housing chamber 7a and the housing chamber 7a is inserted into the upper end opening of the drive shaft housing chamber 7a. The housing 30 is provided with a pair of upper and lower sealing materials 31 and 31 for oil-tight sealing with the drive shaft 12.

  The upper end portion 12b of the drive shaft 12 in the lower case 7 is pivotally supported by the housing 30 via a needle bearing 32, and the lower end portion 12a is disposed at the lower end opening of the drive shaft accommodating chamber 7a. It is supported by a needle bearing 33.

  A tapered roller bearing 35 that pivotally supports the forward bevel gear 18 is disposed at the front end of the bevel gear mechanism accommodating chamber 7b, and the reverse bevel gear 19 is pivoted at the rear end opening via a gear housing 36, which will be described later. A supporting ball bearing 37 is arranged.

  A shift chamber accommodating chamber 7c is formed in front of the drive shaft accommodating chamber 7a of the lower case 7 so as to extend in parallel with the drive shaft accommodating chamber 7a, and the shift shaft 24 is accommodated in the shift shaft accommodating chamber 7c. Yes. A flange portion 24a is formed at the lower end portion of the shift shaft 24 so as to be in sliding contact with the inner peripheral surface of the shift shaft accommodating chamber 7c and support the shift shaft 24, and an oil communication groove 24b is formed in the flange portion 24a. Has been.

  The lower end portion of the shift shaft accommodating chamber 7c communicates with the bevel gear mechanism accommodating chamber 7b. A seal member 38 that oil-tightly seals between the shift shaft 24 and the shift shaft 24 is inserted into the upper end opening of the shift shaft accommodating chamber 7c.

  A cooling water suction passage 7d extending in parallel with the shift shaft housing chamber 7c is formed on the front side of the shift shaft housing chamber 7c. Cooling water flows into the cooling water suction passage 7d from a suction port 7g formed in the left and right side walls of the lower case 7.

  The lower case 7 is formed with a cooling water jacket 7h surrounding the outer periphery of the drive shaft housing chamber 7a, and the lubricating oil in the drive shaft housing chamber 7a is cooled by the cooling water flowing in the cooling water jacket 7h. . The lubricating oil in the shift shaft housing chamber 7c is cooled by the cooling water flowing through the cooling water suction passage 7d and the cooling water jacket 7h.

  An exhaust gas discharge passage 7e is formed at the rear side of the drive shaft housing chamber 7a of the lower case 7, and the cooling water jacket 7h is disposed between the exhaust gas discharge passage 7e and the drive shaft housing chamber 7a. ing. The exhaust passage 7e communicates with an exhaust port (not shown) formed in the rear end surface of the lower case 7, and exhaust gas from the engine 10 passes through the exhaust gas exhaust passage 7e from the upper case 8. It is discharged into the water from the outlet.

  The above-described gear housing 36 disposed so as to pass through the exhaust gas discharge passage 7e is inserted into the bevel gear mechanism accommodation chamber 7b of the lower case 7. The gear gear housing 36 defines the exhaust gas discharge passage 7e and the bevel gear mechanism housing chamber 7b.

  The gear housing 36 includes a cylindrical body portion 36b in which a propeller shaft accommodating hole 36a is formed, a bowl-shaped large-diameter portion 36c formed at the front end portion of the cylindrical body portion 36b, and a rear end of the cylindrical body portion 36b. It has a plurality of ribs 36d formed so as to extend radially outward in the direction perpendicular to the axis, and a flange portion 36e formed at the outer peripheral end of the rib 36d. The flange portion 36e is fixed to the peripheral edge portion of the discharge port of the lower case 7 by a plurality of bolts 40 inserted from the rear.

  The outer peripheral surface of the large-diameter portion 36c is oil-tightly inserted into the rear end opening of the bevel gear mechanism accommodating chamber 7b, and the inner peripheral surface of the large-diameter portion 36c and the boss portion of the reverse bevel gear 19 The ball bearing 37 is inserted between the two.

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

  A pair of front and rear sealing materials 44, 44 for oil-tight sealing between the propeller shaft 14 and the propeller shaft 14 are disposed at the rear end portion of the propeller shaft accommodation hole 36a of the gear housing 36.

  A needle bearing 43 that pivotally supports the rear end portion 14d of the propeller shaft 14 is disposed on the front side of the seal material 44 of the propeller shaft accommodation hole 36a of the gear housing 36.

  The propulsion device 6 includes an oil circulation system 47 that circulates the lubricating oils a and b filled in the lower case 7. The oil circulation system 47 circulates the lubricating oils a and b through the drive shaft housing chamber 7a, the bevel gear mechanism housing chamber 7b, the shift shaft housing chamber 7c, and the propeller shaft housing hole 36a. The oil surface of the lubricating oil is located at the upper needle bearing 32 portion in the drive shaft housing chamber 7a, and the oil surface is at the same height in the shift shaft housing chamber 7c.

  The oil circulation system 47 circulates lubricating oil a from the bevel gear mechanism mounting portion (lower end) 12a of the drive shaft 12 through the forward / reverse switching mechanism 20 and through the upper and lower needle bearings 32, 33. A propeller shaft circulation system 49 that circulates the system 48 and the lubricating oil b from the bevel gear mechanism mounting portion (front end portion) 14b of the propeller shaft 14 through the needle bearing 43 that pivotally supports the rear end portion 14d of the propeller shaft 14. And.

  The propeller shaft circulation system 49 extends in the diametrical direction from a shaft hole 49a extending in the axial direction from the bevel gear mechanism mounting portion 14b of the propeller shaft 14 to the vicinity of the needle bearing 43, and an extended end portion of the shaft hole 49a. An oil passage 49c having a shaft right angle hole 49b opened in the vicinity of the needle bearing 43 and a return passage 49d formed by a gap between the propeller shaft 14 and the propeller shaft accommodation hole 36a of the gear housing 36 are provided. .

  The shaft hole 49 a of the oil passage 49 c is opened to the pin hole 14 e of the propeller shaft 14, and the shaft right angle hole 49 b is opened near the front side of the needle bearing 43.

  When the dog clutch 21 is engaged with any of the forward and reverse bevel gears 18 and 19 by the switching operation of the shift lever, the propeller shaft 14 is rotated, and the centrifugal force of the propeller shaft 14 causes the lubricating oil from the shaft perpendicular hole 49b of the oil passage 49c. b is ejected, and the ejected lubricating oil b lubricates the needle bearing 43, and from there through the return passage 49d, lubricates the meshing portion of the ball bearing 37 and the bevel gear mechanism 13, and enters the bevel gear mechanism accommodating chamber 7b. Return. The lubricating oil b in the bevel gear mechanism accommodating chamber 7b flows into the shaft hole 49a of the oil passage 49c by the rotation of the propeller shaft 14.

  The drive shaft circulation system 48 is an oil extending in the axial direction formed in a gap between the shift shaft housing chamber 7 c constituting the oil passage of the circulation system 48 and the drive shaft 12 and the drive shaft housing chamber 7 a of the lower case 7. The return passage 48a, the screw pump portion 48b formed by the axial center of the drive shaft 12 and the inner peripheral wall of the drive shaft housing chamber 7a, the needle shaft 32 of the shift shaft housing chamber 7c and the oil return passage 48a. And a communication passage 48c communicating with the portion.

  The screw pump portion 48b is formed by providing a slight gap between the spiral groove 12c formed on the outer peripheral surface of the drive shaft 12 and extending clockwise downward and the inner peripheral wall of the drive shaft accommodating chamber 7a. Thus, the lubricating oil a in the oil passage 48a is pressurized and transferred downward.

  When the drive shaft 12 rotates, the screw pump portion 48b pressurizes the lubricating oil a and moves downward in the oil passage 48a, and the bevel gear mechanism 13 rotates and the lubricating oil a in the bevel gear mechanism accommodating chamber 7b is rotated. Is transferred into the cyst shaft accommodating chamber 7c while stirring.

  The lubricating oil a that has flowed into the shift shaft accommodating chamber 7c due to the lubricating oil stirring action of the bevel gear mechanism 13 rises in the shift shaft accommodating chamber 7c through the oil communication groove 24b while lubricating the forward / reverse switching mechanism 20; The oil flows from the upper end of the shift shaft housing chamber 7c into the oil return passage 48a through the communication passage 48c. The lubricating oil a flowing into the return passage 48a is pressurized and transferred downward by the screw pump portion 48b while lubricating the needle bearing 32 on the upper side of the drive shaft 12, and the lower needle bearing 33, the bevel gear mechanism. The meshing portion 13 and the bearings 35 and 37 are lubricated and returned to the bevel gear mechanism accommodating chamber 7b. The lubricating oil a in the bevel gear mechanism accommodating chamber 7b is transferred again to the shift shaft accommodating chamber 7c by the bevel gear mechanism 13.

  The lubricating oil a flowing in the shift shaft housing chamber 7c and the drive shaft housing chamber 7a is cooled by the cooling water flowing in the cooling water suction passage 7d and the cooling water jacket 7h.

  According to the present embodiment, the lubricating oil a in the drive shaft circulation system 48 is transferred from the bevel gear mechanism housing chamber 7b to the shift shaft housing chamber 7c by the stirring action of the bevel gear mechanism 13, and is continuously communicated from the shift shaft housing chamber 7c. The oil is introduced into the oil return passage 48a through the passage 48c, guided to the needle bearing 32 of the drive shaft 12, and the lubricating oil a introduced to the bearing 32 is transferred downward by the screw pump portion 48b, and passes through the return passage 48a. Therefore, the lubricating oil a can be circulated in the lubricating oil transfer direction (direction of arrow a) by the lubricating oil stirring action of the bevel gear mechanism 13 so that the lubricating oil can be circulated. Stagnation and backflow can be prevented. Thereby, wear of the meshing part of the bevel gear mechanism 13 and the bearing part of the drive shaft 12 can be suppressed, and the life of the parts can be extended.

  In the present embodiment, since the spiral groove 12c for transferring the lubricating oil a downward is formed on the outer peripheral surface of the drive shaft 12, the drive shaft 12 functions as a screw pump. It is transferred in the same direction as the lubricating oil transfer direction of the mechanism 13. As a result, the circulation of the lubricating oil a can be promoted, the lubricating oil a can be maintained at an appropriate temperature, its life can be extended, and the life of the parts can be further extended.

  In the present embodiment, since the lubricating oil a is transferred from the bevel gear mechanism accommodating chamber 7b to the shift shaft accommodating chamber 7c by the bevel gear mechanism 13, the bevel gear mechanism 13 functions as a gear pump. The circulation of a can be further promoted.

  That is, since the lubricating oil a is caused to flow from the shift shaft accommodating chamber 7c to the drive shaft accommodating chamber 7a side by utilizing the lubricating oil stirring action of the bevel gear mechanism 13, the transfer direction of the bevel gear mechanism 13 and the screw pump portion 48b can be made to coincide with the transfer direction, and the stagnation and backflow of the lubricating oil can be reliably prevented.

  In the present embodiment, since the shift shaft housing chamber 7c is used as an oil passage, the existing circulation shaft housing chamber 7c can be effectively used to form an oil circulation system, and the enlargement of the lower case 7 can be suppressed, and the cost can be reduced. Can be reduced.

  Further, since the shift shaft housing chamber 7c is used as an oil passage, the shift shaft housing chamber 7c is surrounded by the cooling water suction passage 7d and the cooling water jacket 7h and is located away from the exhaust gas discharge passage 7e. The cooling performance of the lubricating oil a passing through the shift shaft accommodating chamber 7c can be enhanced.

  In the above embodiment, the shift shaft accommodating chamber 7c is used as an oil passage. However, in the present invention, an oil passage may be formed separately from the shift shaft accommodating chamber.

1 is a side view of an outboard motor according to an embodiment of the present invention. It is a side view of the lower case where the outboard motor propulsion device is disposed. It is sectional drawing of the said lower case. It is a top view of the said lower case. It is a figure of the forward bevel gear of the said propulsion apparatus. It is sectional drawing of the said forward bevel gear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outboard motor 6 Propulsion device 7 Lower case 7a Drive shaft accommodation chamber 7b Bevel gear mechanism accommodation chamber 7c Shift shaft accommodation chamber (oil passage)
DESCRIPTION OF SYMBOLS 10 Engine 12 Drive shaft 12a Bevel gear mechanism mounting part 12c Spiral groove 13 Bevel gear mechanism 14 Propeller shaft 14a Protrusion 15 Propeller 24 Shift shaft 32 Needle bearing (drive shaft support)
48 Drive shaft circulation system (oil circulation system)
a Lubricating oil

Claims (4)

A drive shaft driven by the engine; a propeller shaft driven by the drive shaft via a bevel gear mechanism; a lower case for housing and holding the propeller shaft and the drive shaft; and a rear case projecting from the lower case of the propeller shaft In an outboard motor propulsion device having a propeller mounted on a protruding portion that
Lubricating oil is guided through the oil passage formed in the lower case from the bevel gear mechanism mounting portion of the drive shaft to the drive shaft support portion that is supported by the lower case via a bearing, An outboard motor comprising an oil circulation system for returning lubricating oil guided to the drive shaft support to the bevel gear mechanism mounting portion through a gap between the drive shaft and a drive shaft housing chamber of a lower case. Propulsion device. 2. The outboard motor propulsion device according to claim 1, wherein a spiral groove is provided on the outer peripheral surface of the drive shaft to convey the lubricant oil downward as the drive shaft rotates. 2. The outboard motor propulsion device according to claim 1, wherein the bevel gear mechanism has a pump function of transferring lubricating oil to the oil passage side as the drive shaft rotates. 4. The outboard motor propulsion according to claim 1, wherein the oil passage is constituted by a shift shaft housing chamber in which a shift shaft for switching forward and backward of the bevel gear mechanism is disposed. apparatus.

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