outboard motor

Abstract

To reduce a forward axial load applied on a bearing for supporting a front driven gear on a case of an outboard engine during ship advancement.SOLUTION: A contra-rotating propeller type outboard engine comprises: an outer propeller shaft 4 and an inner propeller shaft 6 which are coaxially arranged; a rear driven gear 43 engaged, from a rear side, with a main drive gear 38 coupled with a lower end side of a drive shaft and coupled with a front end side of the outer propeller shaft 4; a front driven gear engaged with the main drive gear 38 from a front side, and coupled with the front end side of the inner propeller shaft 4; and a lower case 11 covering a front part of the outer propeller shaft 4, a front part of the inner propeller shaft 6, the main drive gear 38, the rear driven gear 43, and the front driven gear. On an outer peripheral side of the front part of the outer propeller shaft 4, a bearing 48 for rotatably supporting the outer propeller shaft 4 on the lower case 11 and receiving a forward axial load applied on the outer propeller shaft 4 is provided.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a contra-rotating propeller outboard motor. [Background technology]

[0002] Contra-rotating propellers are propulsion devices that generate thrust by rotating two coaxially arranged propellers in opposite directions, and are widely used in outboard motors. Patent Document 1 listed below describes an example of a contra-rotating propeller outboard motor.

[0003] Fig. 5 is a cross-sectional view showing the inside of the lower part of a conventional contra-rotating propeller outboard motor. The outboard motor 121 in Fig. 5 has a similar configuration to the outboard motor shown in Fig. 2 of Patent Document 1.

[0004] The outboard motor 121 is provided with a drive shaft 122 that transmits power from a power source located at the top of the outboard motor 121 to the bottom of the outboard motor 121. The drive shaft 122 extends in the vertical direction, and a drive gear 128 is coupled to the bottom end of the drive shaft 122.

[0005] A lower case 123 is provided at the bottom of the outboard motor 121, i.e., the portion that is submerged below the water surface. An outer propeller shaft 124 and an inner propeller shaft 125 are also provided at the bottom of the outboard motor 121. These two propeller shafts 124, 125 each extend in the fore-and-aft direction and are arranged coaxially with each other. The outer propeller shaft 124 is formed in a cylindrical shape, and the inner propeller shaft 125 is arranged on the inner peripheral side of the outer propeller shaft 124.

[0006] A front propeller 126 is attached to the rear portion of the outer propeller shaft 124, and the front portion of the outer propeller shaft 124 is disposed within the lower case 123. The outer propeller shaft 124 is rotatably supported by the lower case 123 via a bearing 131 that is disposed in the middle portion of the outer propeller shaft 124 in the front-to-rear direction. A rear driven gear 129 is coupled to the front end portion of the outer propeller shaft 124. The rear driven gear 129 is rotatably supported by the lower case 123 via a bearing 132.

[0007] A rear propeller 127 is attached to the rear portion of the inner propeller shaft 125, and a front portion of the inner propeller shaft 125 is disposed within the lower case 123. The inner propeller shaft 125 is rotatably supported by the outer propeller shaft 124 and the rear driven gear 129 via a bearing 133 disposed slightly rearward of the middle portion of the inner propeller shaft 125 in the front-to-rear direction, and a bearing 134 disposed in a front end portion of the inner propeller shaft 125. A front driven gear 130 is coupled to the front end portion of the inner propeller shaft 125. The front driven gear 130 is rotatably supported by the lower case 123 via a bearing 135.

[0008] Additionally, the drive gear 128, the rear driven gear 129, and the front driven gear 130 are each bevel gears. The rear driven gear 129 is disposed rearward of the drive gear 128, and the front driven gear 130 is disposed forward of the drive gear 128, with the rear driven gear 129 and the front driven gear 130 meshing with the drive gear 128. When the drive shaft 122 rotates, the outer propeller shaft 124 and the inner propeller shaft 125 rotate in opposite directions. This causes the front propeller 126 and the rear propeller 127 to rotate in opposite directions, generating propulsion for the vessel. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-88275 Summary of the Invention [Problem to be solved by the invention]

[0010] 5 , when the outboard motor 121 is operated to move the boat forward, a forward axial load (thrust load) acting on the inner propeller shaft 125 is transmitted via the front driven gear 130 to a bearing 135 that supports the front driven gear 130 on the lower case 123. At this time, a forward axial load acting on the outer propeller shaft 124 is transmitted to the bearing 135 via a stopper 136 that supports the rear driven gear 129 in the axial direction relative to the outer propeller shaft 124, the rear driven gear 129, the bearing 134 that supports the inner propeller shaft 125 rotatably relative to the front driven gear 130, the inner propeller shaft 125, and the front driven gear 130. That is, in the conventional outboard motor 121, the bearing 135 receives both a forward axial load acting on the outer propeller shaft 124 and a forward axial load acting on the inner propeller shaft 125 when the boat is moving forward.

[0011] In a conventional outboard motor 121, if the output of the power source of the outboard motor 121 is increased, the axial load acting on the two propeller shafts 124, 125 increases. For this reason, it is necessary to use a bearing with a large load capacity as the bearing 135 that bears this axial load, thereby increasing the durability of the bearing 135. However, if a large bearing with a large load capacity is used as the bearing 135, it is necessary to increase the size of the lower case 123 that houses the bearing 135. Increasing the size of the lower case 123 has disadvantages, such as increasing water resistance during sailing, and is therefore undesirable.

[0012] The present invention has been made in consideration of the problems described above, and an object of the present invention is to provide an outboard motor that can reduce the forward axial load applied to the bearing that supports the front driven gear on the outboard motor case when the boat is moving forward. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a contra-rotating propeller outboard motor comprising: a cylindrical outer propeller shaft extending in the fore-and-aft direction and having a first propeller attached to its rear; an inner propeller shaft extending in the fore-and-aft direction and disposed on the inner periphery of the outer propeller shaft and having a second propeller attached to its rear; a rear driven gear disposed rearward of a drive gear connected to the lower end of a drive shaft extending in the up-and-down direction, meshing with the drive gear and connected to the front end of the outer propeller shaft; the outer propeller shaft is provided with a first bearing on the outer circumferential surface of the front portion of the outer propeller shaft, the first bearing supporting the outer propeller shaft on the case so as to be rotatable therewith and receiving a forward axial load acting on the outer propeller shaft; A second bearing is provided on the outer circumferential side of the outer propeller shaft and rearward of the first bearing, the second bearing rotatably supporting the outer propeller shaft on the case, and the first bearing has a larger load capacity in the axial direction than the second bearing. It is characterized by: [Effects of the Invention]

[0014] According to the present invention, when the boat is moving forward, the forward axial load applied to the bearing that supports the front driven gear on the outboard motor case can be reduced. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is an explanatory diagram showing the outboard motor according to the embodiment of the present invention as viewed from the left side. [Figure 2] FIG. 2 is a cross-sectional view showing the inside of a lower portion of the outboard motor according to the embodiment of the present invention. [Figure 3]3 is an enlarged cross-sectional view showing the front part of the lower case in FIG. 2. [Figure 4] 3 is an enlarged cross-sectional view showing a lower rear portion of the lower case in FIG. 2. [Figure 5] FIG. 10 is a cross-sectional view showing the inside of a lower portion of a conventional outboard motor. DETAILED DESCRIPTION OF THE INVENTION

[0016] An outboard motor according to an embodiment of the present invention is a contra-rotating propeller outboard motor that includes a drive shaft extending in the vertical direction, and an outer propeller shaft and an inner propeller shaft extending in the longitudinal direction. The outer propeller shaft is cylindrical and has a first propeller attached to its rear. The inner propeller shaft is located on the inner periphery of the outer propeller shaft and has a second propeller attached to its rear.

[0017] The outboard motor of this embodiment also includes a gear mechanism that transmits rotation of the drive shaft to the outer propeller shaft and the inner propeller shaft. The gear mechanism includes a drive gear, a rear driven gear, and a front driven gear. The drive gear is coupled to the lower end of the drive shaft. The rear driven gear is located rearward of and meshes with the drive gear. The rear driven gear is coupled to the front end of the outer propeller shaft. The front driven gear is located forward of and meshes with the drive gear. The front driven gear is coupled to the front end of the inner propeller shaft.

[0018] The outboard motor of this embodiment also includes a case that covers the front portion of the outer propeller shaft, the front portion of the inner propeller shaft, the drive gear, the rear driven gear, and the front driven gear.

[0019] In the outboard motor of this embodiment, a new bearing is provided on the outer peripheral side of the front portion of the outer propeller shaft to rotatably support the outer propeller shaft on the case and to bear the forward axial load acting on the outer propeller shaft.

[0020] With the outboard motor of this embodiment, the new bearing can bear most of the forward axial load acting on the outer propeller shaft when the boat is moving forward. This prevents the forward axial load acting on the outer propeller shaft when the boat is moving forward from being applied to the front driven gear bearing (a bearing corresponding to bearing 135 of the conventional outboard motor 121 shown in FIG. 5 ), which supports the front driven gear on the case, as occurs with the conventional outboard motor. Therefore, with the outboard motor of this embodiment, the forward axial load acting on the front driven gear bearing when the boat is moving forward can be reduced compared to the conventional outboard motor. [Example]

[0021] An embodiment of the outboard motor of the present invention will be described. In the embodiment, when describing the directions of up (Ud), down (Dd), front (Fd), rear (Bd), left (Ld), and right (Rd), please refer to the arrows drawn at the bottom right of Figures 1 to 4.

[0022] FIG. 1 shows an outboard motor 1 according to an embodiment of the present invention. As shown in FIG. 1, the outboard motor 1 is a contra-rotating propeller outboard motor. The outboard motor 1 includes an engine 2 as a power source, a front propeller 3, an outer propeller shaft 4 to which the front propeller 3 is attached, a rear propeller 5, an inner propeller shaft 6 to which the rear propeller 5 is attached, and a power transmission mechanism 7 that transmits the power of the engine 2 to the propeller shafts 4, 6. The engine 2 is disposed at the top of the outboard motor 1, and the propeller shafts 4, 6 are disposed at the bottom of the outboard motor 1, with the power transmission mechanism 7 being disposed between the engine 2 and the propeller shafts 4, 6. The front propeller 3 is a specific example of a "first propeller," and the rear propeller 5 is a specific example of a "second propeller."

[0023] The power transmission mechanism 7 also includes an upper drive shaft 21, an upper gear mechanism 22, a clutch 27, an intermediate drive shaft 35, a connecting member 36, a lower drive shaft 38, and a lower gear mechanism 41. The upper drive shaft 21 extends vertically, with its upper end connected to the engine 2 and its lower end extending into the lower case 11. The upper drive shaft 21 rotates in one direction by the power of the engine 2. Hereinafter, the rotation direction of the upper drive shaft 21 is referred to as the forward direction.

[0024] The engine 2 is covered by a bottom cowl 8 and a top cowl 9. The upper drive shaft 21 is disposed in an upper case 10. The upper gear mechanism 22, clutch 27, intermediate drive shaft 35, connecting member 36, lower drive shaft 38, and lower gear mechanism 41 are disposed in a lower case 11 provided at the bottom of the outboard motor 1. The front portions of the outer propeller shaft 4 and the inner propeller shaft 6 are disposed in the lower case 11. The lower case 11 is a specific example of a "case."

[0025] Fig. 2 shows a cross section of components provided at the bottom of the outboard motor 1, viewed from the left, along a plane extending in the front-to-rear and up-to-down directions including the axes of the drive shafts 21, 35, 38 and the propeller shafts 4, 6. Fig. 3 shows an enlarged view of the front portion of the lower case 11 in Fig. 2. Fig. 4 shows an enlarged view of the lower rear portion of the lower case 11 in Fig. 2.

[0026] As shown in FIG. 2 , the lower case 11 is formed in a roughly box-like shape with an open top, and a cover member 12 is provided on the top of the lower case 11 to cover a portion of the top of the lower case 11. A drive shaft insertion hole 13 is formed in the cover member 12. An upper gear chamber 14 is provided in the front upper part of the lower case 11. The drive shaft insertion hole 13 is in communication with the upper gear chamber 14. A lower gear chamber 15 is provided in the front lower part of the lower case 11. A drive shaft arrangement hole 16 is formed between the upper gear chamber 14 and the lower gear chamber 15 in the lower case 11, providing communication between the two chambers. A propeller shaft arrangement hole 17 is formed in the lower case 11 behind the lower gear chamber 15. The propeller shaft arrangement hole 17 is in communication with the lower gear chamber 15.

[0027] As shown in FIG. 3 , an upper gear mechanism 22 is disposed within the upper gear chamber 14 of the lower case 11. The upper gear mechanism 22 generates rotation in the opposite direction to the rotation of the upper drive shaft 21. The upper gear mechanism 22 includes three bevel gears: a reverse drive gear 23, a reverse intermediate gear 24, and a reverse output gear 25. The reverse drive gear 23 is disposed at the top of the upper gear chamber 14 with its teeth facing downward and is rotatably supported by the cover member 12. The reverse drive gear 23 is coupled to the lower end of the upper drive shaft 21, which enters the upper gear chamber 14 through the drive shaft insertion hole 13, and rotates integrally with the upper drive shaft 21. The reverse intermediate gear 24 is disposed at the front of the upper gear chamber 14 with its teeth facing backward and is rotatably supported by the lower case 11. The reverse output gear 25 is disposed in the lower part of the upper gear chamber 14 with its toothed portion facing upward, and is rotatably supported by the lower case 11. The reverse drive gear 23 meshes with the reverse intermediate gear 24, which meshes with the reverse output gear 25. When the reverse drive gear 23 rotates in the forward direction, the rotation is transmitted to the reverse output gear 25 via the reverse intermediate gear 24, causing the reverse output gear 25 to rotate in the reverse direction.

[0028] A clutch 27 is disposed between the reverse drive gear 23 and the reverse output gear 25. The clutch 27 is a dog clutch formed in a cylindrical shape with clutch pawls 28 formed on the upper and lower end surfaces. A through hole 26 is formed in the center of the reverse output gear 25, and the upper end portion of the intermediate drive shaft 35 passes through the through hole 26 and enters between the reverse drive gear 23 and the reverse output gear 25. The diameter of the through hole 26 is larger than the diameter of the upper end portion of the intermediate drive shaft 35, so that the through hole 26 and the upper end portion of the intermediate drive shaft 35 are spaced apart from each other. The clutch 27 is connected to the upper end portion of the intermediate drive shaft 35 so that it cannot move circumferentially relative to the intermediate drive shaft 35 but can move axially. As a result, the clutch 27 and the intermediate drive shaft 35 rotate together, but the clutch 27 can move up and down relative to the intermediate drive shaft 35.

[0029] Also provided within the lower case 11 are a shift member 30 connected to the clutch 27 and a clutch control unit 31 that controls the vertical movement of the shift member 30. The shift member 30 is connected to the clutch 27 so that the clutch 27 can be moved up and down while allowing rotation of the clutch 27. The clutch control unit 31 moves the shift member 30 up and down, thereby moving the clutch 27 up and down. When the clutch 27 moves up, a clutch pawl 28 formed on the upper end surface of the clutch 27 engages with a clutch pawl 32 formed on the lower end surface of the reverse drive gear 23. This directly transmits the rotation of the upper drive shaft 21 to the intermediate drive shaft 35, causing the intermediate drive shaft 35 to rotate in the forward direction. On the other hand, when the clutch 27 moves down, a clutch pawl 28 formed on the lower end surface of the clutch 27 engages with a clutch pawl 33 formed on the upper end surface of the reverse output gear 25. This transmits the rotation of the reverse output gear 25 to the intermediate drive shaft 35, causing the intermediate drive shaft 35 to rotate in the reverse direction.

[0030] Additionally, an intermediate drive shaft 35 is disposed within the lower case 11 in the region extending from the upper gear chamber 14 to the drive shaft mounting hole 16. A lower drive shaft 38 is disposed within the drive shaft mounting hole 16. The intermediate drive shaft 35 and the lower drive shaft 38 each extend vertically and are disposed coaxially with the upper drive shaft 21. The lower end of the intermediate drive shaft 35 and the upper end of the lower drive shaft 38 are connected to each other by a connecting member 36, and the two shafts rotate integrally. The connecting member 36 and the lower drive shaft 38 are rotatably supported in the drive shaft mounting hole 16 via bearings. The lower drive shaft 38 is a specific example of a "drive shaft."

[0031] A lower gear mechanism 41 is disposed within the lower gear chamber 15 of the lower case 11. The lower gear mechanism 41 is a mechanism that transmits the power of the engine 2, which is transmitted via the upper drive shaft 21, the upper gear mechanism 22, the clutch 27, the intermediate drive shaft 35, the connecting member 36, and the lower drive shaft 38, to the outer propeller shaft 4 and the inner propeller shaft 6. The lower gear mechanism 41 includes three bevel gears, namely, a main drive gear 42, a rear driven gear 43, and a front driven gear 45. The main drive gear 42 is a specific example of a "drive gear."

[0032] The main drive gear 42 is disposed in the upper part of the lower gear chamber 15 with the toothed portion facing downward. The main drive gear 42 is integrally formed with the lower end of the lower drive shaft 38 and rotates integrally with the lower drive shaft 38.

[0033] The rear driven gear 43 is disposed at the rear of the lower gear chamber 15 so that the toothed portion faces forward. The rear driven gear 43 is rotatably supported by the lower case 11 via a bearing 44. The rear driven gear 43 is disposed behind the main drive gear 42 and is in mesh with the main drive gear 42.

[0034] The bearing 44 is, for example, a tapered roller bearing (tapered roller bearing), and is disposed between the boss of the rear driven gear 43 and the bearing housing 47. The bearing 44 is disposed so that the outer ring raceway surface, the inner ring raceway surface, and the apex of the roller cone of the bearing 44 are located rearward of the bearing 44, and can bear the axial load acting rearward from the rear driven gear 43 on the bearing 44. The bearing 44 is a specific example of a "third bearing."

[0035] The front driven gear 45 is disposed in the front part of the lower gear chamber 15 so that the toothed portion faces rearward. The front driven gear 45 is rotatably supported by the lower case 11 via a bearing 46. The front driven gear 45 is disposed in front of the main drive gear 42 and is in mesh with the main drive gear 42.

[0036] The bearing 46 is, for example, a tapered roller bearing, and is disposed between the boss of the front driven gear 45 and the lower case 11. The bearing 46 is disposed so that the outer ring raceway surface, the inner ring raceway surface, and the apex of the roller cone of the bearing 46 are located in front of the bearing 46, and can bear the axial load acting on the bearing 46 in the forward direction from the front driven gear 45.

[0037] As shown in Fig. 2, a bearing housing 47 is provided in the propeller shaft arrangement hole 17 in the lower case 11. The bearing housing 47 is formed in a cylindrical shape, is fixed inside the lower case 11, and holds a bearing 44 for the rear driven gear 43, and bearings 48, 49 for the outer propeller shaft 4. The front portions of the outer propeller shaft 4 and the inner propeller shaft 6 are inserted into the inner peripheral side of the bearing housing 47.

[0038] The outer propeller shaft 4 is formed in a cylindrical shape and extends in the front-to-rear direction. A front portion of the outer propeller shaft 4 is supported by a bearing housing 47 via bearings 48 and 49 so as to be rotatable relative to the bearing housing 47. A rear driven gear 43 is coupled to the front end portion of the outer propeller shaft 4, and the rear driven gear 43 and the outer propeller shaft 4 rotate integrally. A front propeller 3 is attached to the rear portion of the outer propeller shaft 4, and the outer propeller shaft 4 and the front propeller 3 rotate integrally. A seal member 50 is provided between the outer propeller shaft 4 and the rear end portion of the bearing housing 47.

[0039] The bearing 48 is, for example, a tapered roller bearing. As shown in FIG. 4 , the bearing 48 is disposed between the front end portion of the outer propeller shaft 4 and the bearing housing 47. In this embodiment, the bearing 48 is disposed on the outer peripheral side of the rear end portion of the boss of the rear driven gear 43, which is connected to the front end portion of the outer propeller shaft 4. The bearing 48 is disposed rearward of the bearing 44, which supports the rear driven gear 43 on the bearing housing 47, and adjacent to the bearing 44. The bearing 48 is disposed such that the outer ring raceway surface, the inner ring raceway surface, and the apex of the roller cone of the bearing 48 are located forward of the bearing 48, allowing the inner ring 48B of the bearing 48 to withstand an axial load applied forward from its rear side. The bearing 48 has a larger axial load capacity than the bearing 49. The bearing 48 is a specific example of a "first bearing."

[0040] Furthermore, a step 51 and a rear stopper 52 are provided on the outer periphery of the front end portion of the outer propeller shaft 4 as a load transmission mechanism that transmits a forward axial load acting on the outer propeller shaft 4 to the bearing 48. The step 51 is formed on the outer periphery of the front end portion of the outer propeller shaft 4. The step 51 has a forward-facing surface, and is located rearward of a portion of the front end portion of the outer propeller shaft 4 to which the rear driven gear 43 is coupled. The rear stopper 52 is formed in an annular shape, and is attached to the outer periphery of the front end portion of the outer propeller shaft 4. Furthermore, the rear stopper 52 is located between the step 51 and the bearing 48.

[0041] The rear end of rear stopper 52 contacts the forward-facing surface of step 51, and the rear inner circumferential surface and rear surface of inner ring 48B of bearing 48 contact the front part of rear stopper 52. As a result, the forward axial load acting on outer propeller shaft 4 is transmitted to bearing 48.

[0042] The front inner peripheral surface of the inner ring 48B of the bearing 48 contacts the outer peripheral surface of the rear end of the boss of the rear driven gear 43. The front end of the rear stopper 52 is spaced apart from the rear end of the boss of the rear driven gear 43.

[0043] Additionally, a spacer 53 and a front stopper 54 are provided within the lower case 11 as a bearing support mechanism that supports the bearing 48 so that it does not displace forward relative to the lower case 11. Additionally, the bearing housing 47 and the step portion 56 formed on the lower case 11 also function to support the bearing 48 so that it does not displace forward relative to the lower case 11, and therefore can be considered to be included as components of the bearing support mechanism.

[0044] The spacer 53 is formed in an annular shape and is disposed within the bearing housing 47 between the outer ring 48A of the bearing 48 and the outer ring 44A of the bearing 44. The front stopper 54 is formed in an annular shape and is attached to the front end portion within the bearing housing 47. Threads are formed on the outer peripheral surface of the front stopper 54 and on the inner peripheral surface of the front end portion of the bearing housing 47. The front stopper 54 is screwed into the bearing housing 47 and fastened in place.

[0045] The outer peripheral surface of the outer ring 48A of the bearing 48 contacts the inner peripheral surface of the bearing housing 47, and the front surface of the outer ring 48A of the bearing 48 contacts the rear surface of the spacer 53. In addition, the front surface of the spacer 53 contacts the rear surface of the outer ring 44A of the bearing 44, and the front surface of the outer ring 44A of the bearing 44 contacts the rear surface of the front stopper 54. This supports the bearing 48 so that it does not move forward relative to the bearing housing 47.

[0046] Furthermore, a step 56 having a rearward-facing surface is formed in the lower case 11 near the boundary between the propeller shaft arrangement hole 17 and the lower gear chamber 15. The front end of the bearing housing 47 is supported by the rearward-facing surface of the step 56 via a washer shim 55. This supports the bearing housing 47 so that it does not move forward relative to the lower case 11. The rear end of the bearing housing 47 is supported by a fixing member 57 fixed to the rear opening of the propeller shaft arrangement hole 17. The fixing member 57 is formed in an annular shape and is screwed into the rear opening of the propeller shaft arrangement hole 17 and fastened in place.

[0047] The bearing 49 is, for example, a double-row needle bearing, and is disposed between the longitudinal middle portion of the outer propeller shaft 4 and the bearing housing 47. The bearing 49 is disposed rearward of the bearing 48. The bearing 49 is a specific example of a "second bearing."

[0048] As shown in FIG. 2 , the inner propeller shaft 6 extends in the front-to-rear direction and is disposed on the inner peripheral side of the outer propeller shaft 4. The inner propeller shaft 6 is disposed coaxially with the outer propeller shaft 4. A front end portion of the inner propeller shaft 6 protrudes forward from the outer propeller shaft 4. The front end portion of the inner propeller shaft 6 is supported by the rear driven gear 43 via a bearing 58 so as to be rotatable relative to the rear driven gear 43. A middle portion of the inner propeller shaft 6 in the front-to-rear direction is supported by the outer propeller shaft 4 via a bearing 59 so as to be rotatable relative to the outer propeller shaft 4. A front driven gear 45 is coupled to the front end of the inner propeller shaft 6, and the front driven gear 45 and the inner propeller shaft 6 rotate integrally. A rear portion of the inner propeller shaft 6 protrudes rearward from the outer propeller shaft 4. A rear propeller 5 is attached to the rear part of the inner propeller shaft 6, and the inner propeller shaft 6 and the rear propeller 5 rotate together. In addition, a seal member 60 is provided between the inner propeller shaft 6 and the rear end part of the outer propeller shaft 4.

[0049] The bearing 58 is, for example, a tapered roller bearing, and is arranged between the front end portion of the inner propeller shaft 6 and the rear driven gear 43. The bearing 58 is arranged so that the outer ring raceway surface, the inner ring raceway surface, and the apex of the roller cone of the bearing 58 are located rearward of the bearing 58. As shown in FIG. 4 , the outer peripheral surface and rear surface of the outer ring 58A of the bearing 58 are in contact with the inner peripheral portion of the rear driven gear 43. The inner peripheral surface of the inner ring 58B of the bearing 58 is in contact with the outer peripheral surface of the inner propeller shaft 6, and the front surface of the inner ring 58B of the bearing 58 is in contact with the rear-facing surface of a step 61 formed on the inner propeller shaft 6.

[0050] The bearing 59 is, for example, a needle bearing. As shown in Fig. 2, the bearing 59 is arranged between the rear part of the inner propeller shaft 6 and the rear end part of the outer propeller shaft 4. In this embodiment, two single-row needle bearings 59 are provided adjacent to each other, but instead, one double-row needle bearing may be provided.

[0051] In Figure 2, when the main drive gear 42 rotates integrally with the lower drive shaft 38, the rotation is transmitted to the rear driven gear 43 and the front driven gear 45, respectively. As a result, the outer propeller shaft 4 and the inner propeller shaft 6 each rotate. At this time, the outer propeller shaft 4 and the inner propeller shaft 6 rotate in opposite directions. As the outer propeller shaft 4 and the inner propeller shaft 6 rotate, the front propeller 3 and the rear propeller 5 each rotate.

[0052] Furthermore, when the clutch 27 transmits the rotation of the upper drive shaft 21 in the forward direction to the outer propeller shaft 4 and inner propeller shaft 6 via the intermediate drive shaft 35, the lower drive shaft 38, the lower gear mechanism 41, etc., a thrust force that moves the vessel forward is generated by the front propeller 3 and the rear propeller 5. When the clutch 27 transmits the rotation of the reverse output gear 25 in the reverse direction to the outer propeller shaft 4 and inner propeller shaft 6 via the intermediate drive shaft 35, the lower drive shaft 38, the lower gear mechanism 41, etc., a thrust force that moves the vessel backward is generated by the front propeller 3 and the rear propeller 5.

[0053] Furthermore, when the vessel moves forward, that is, when the front propeller 3 and the rear propeller 5 generate a propulsive force that moves the vessel forward, a forward axial load acts on each of the outer propeller shaft 4 and the inner propeller shaft 6. In FIG. 4, most of the forward axial load acting on the outer propeller shaft 4 is transmitted to the bearing 48 via the stepped portion 51 and the rear stopper 52 of the outer propeller shaft 4. The bearing 48 is also connected to the spacer 53, the outer ring 44A of the bearing 44, and the Front stopper 54 46。 As a result, the bearing 48 bears most of the forward axial load acting on the outer propeller shaft 4. On the other hand, in FIG. 2, most of the forward axial load acting on the inner propeller shaft 6 is transmitted to the bearing 46 via the front driven gear 45. The bearing 46 bears most of the forward axial load acting on the inner propeller shaft 6. In this way, in the outboard motor 1, the forward axial load acting on the outer propeller shaft 4 is mainly borne by the bearing 48 when the boat is moving forward, and the forward axial load acting on the inner propeller shaft 6 is mainly borne by the bearing 46.

[0054] As described above, in the outboard motor 1 according to the embodiment of the present invention, the outer propeller shaft 4 is rotatably supported by a bearing housing 47 fixed to the lower case 11 on the outer peripheral side of the front end portion thereof, and the bearing 48 is provided to receive a forward axial load acting on the outer propeller shaft 4. This configuration allows the bearing 48 to receive most of the forward axial load acting on the outer propeller shaft 4 when the boat is moving forward. This prevents the forward axial load acting on the outer propeller shaft 4 from being applied to the bearing 46 that supports the front driven gear 45 on the lower case 11 when the boat is moving forward. This reduces the forward axial load applied to the bearing 46 when the boat is moving forward, compared to the conventional outboard motor. This allows a smaller bearing with a smaller load capacity to be used as the bearing 46, thereby enabling the lower case 11 that houses the bearing 46 to be made smaller. Furthermore, compared to conventional outboard motors, the output of the power source of the outboard motor 1 can be increased without employing a large bearing with a large load capacity as the bearing 46. This prevents the lower case 11 from becoming larger in size as the output of the power source of the outboard motor 1 increases, allowing for the realization of a compact, high-output outboard motor 1.

[0055] In the outboard motor 1 of this embodiment, a step 51 and a rear stopper 52 are provided on the outer periphery of the front end portion of the outer propeller shaft 4 as a load transfer mechanism that transfers the forward axial load acting on the outer propeller shaft 4 to the bearing 48. Furthermore, a spacer 53 and a front stopper 54 are provided inside the lower case 11 as a bearing support mechanism that supports the bearing 48 so that it does not displace forward relative to the lower case 11. With this configuration, the structure in which the bearing 48 receives the forward axial load acting on the outer propeller shaft 4 when the boat is moving forward can be formed compactly without significantly expanding the component accommodation space inside the lower case 11. This prevents the lower case 11 from becoming too large.

[0056] Furthermore, in the outboard motor 1 of this embodiment, the bearing 48 is disposed on the outer periphery of the boss of the rear driven gear 43. With this configuration, space for arranging the bearing 48 can be easily created by slightly expanding the space in the lower case 11 in which the bearing 44 that supports the rear driven gear 43 on the bearing housing 47 is disposed. Therefore, the bearing 48 can be provided inside the lower case 11 while preventing the lower case 11 from becoming too large.

[0057] Furthermore, in the outboard motor 1 of this embodiment, the bearing 48 is disposed adjacent to and behind the bearing 44 that supports the rear driven gear 43 in the bearing housing 47. With this configuration, too, space for arranging the bearing 48 can be easily created simply by slightly expanding the space in the lower case 11 where the bearing 44 is disposed rearward, and the bearing 48 can be provided within the lower case 11 while preventing the lower case 11 from becoming larger.

[0058] Furthermore, in the outboard motor 1 of this embodiment, a bearing 49 is provided on the outer circumferential side of the outer propeller shaft 4 and rearward of the bearing 48, which rotatably supports the outer propeller shaft 4 in a bearing housing 47 fixed to the lower case 11. With this configuration, the outer propeller shaft 4 can be supported in the bearing housing 47 at two locations spaced apart in the fore-and-aft direction by the bearings 48 and 49. This makes it possible to suppress axial runout of the propeller shafts 4, 6, and reduce vibration during operation of the outboard motor 1.

[0059] Furthermore, in the outboard motor 1 of this embodiment, the bearing 48 has a larger axial load capacity than the bearing 49. This increases the durability of the bearing 48, which bears most of the forward axial load acting on the outer propeller shaft 4 when the boat is moving forward, and extends the life of the bearing 48.

[0060] In the above embodiment, the bearing 48, which bears most of the forward axial load acting on the outer propeller shaft 4 when the ship moves forward, is disposed on the outer peripheral side of the boss of the rear driven gear 43. However, the bearing 48 may be disposed rearward of the boss of the rear driven gear 43. In the above embodiment, the bearing 48 is disposed adjacent to the bearing 44, but the bearing 48 may be disposed away from the bearing 44.

[0061] In addition, in the above embodiment, a rear stopper 52 is provided and the inner ring 48B of the bearing 48 is brought into contact with the rear stopper 52, but the rear stopper 52 may be eliminated and the inner ring 48B of the bearing 48 may be brought into contact with the step portion 51 of the outer propeller shaft 4.

[0062] Furthermore, in the above embodiment, a spacer 53 and a front stopper 54 are provided and used to support the bearing 48 so that it does not displace forward relative to the bearing housing 47, but the bearing 48 may also be supported so that it does not displace forward relative to the bearing housing 47 by forming a step with a rearward-facing surface in the bearing housing 47 and bringing the outer ring 48A of the bearing 48 into contact with the rearward-facing surface of the step.

[0063] Furthermore, the present invention may be modified as appropriate within the scope of the claims and the spirit or concept of the invention as can be read from the entire specification, and outboard motors incorporating such modifications are also included within the technical concept of the present invention. [Explanation of symbols]

[0064] 1 outboard motor 3 Front propeller (first propeller) 4 outer propeller shaft 5 Rear propeller (second propeller) 6 Inner propeller shaft 11 Lower case (case) 38 Lower drive shaft (drive shaft) 42 Main drive gear (drive gear) 43 Rear driven gear 44 bearing (third bearing) 45 Front driven gear 48 Bearing (First Bearing) 49 Bearing (second bearing) 51 Step (load transmission mechanism) 52 Rear stopper (load transmission mechanism) 53 Spacer (bearing support mechanism) 54 Front stopper (bearing support mechanism)

Claims

1. A contra-rotating propeller outboard motor, a cylindrical outer propeller shaft extending in the fore-and-aft direction and having a first propeller attached to its rear portion; an inner propeller shaft extending in the fore-and-aft direction, disposed on an inner peripheral side of the outer propeller shaft, and having a second propeller attached to a rear portion thereof; a rear driven gear that is disposed rearward of a drive gear coupled to a lower end of a drive shaft that extends in the vertical direction, meshes with the drive gear, and is coupled to a front end of the outer propeller shaft; a front driven gear disposed forward of the drive gear, meshing with the drive gear, and coupled to a front end side of the inner propeller shaft; a case that covers a front portion of the outer propeller shaft, a front portion of the inner propeller shaft, the drive gear, the rear driven gear, and the front driven gear, a first bearing is provided on an outer peripheral side of a front portion of the outer propeller shaft, the first bearing rotatably supporting the outer propeller shaft on the case and receiving a forward axial load acting on the outer propeller shaft; a second bearing is provided on the outer circumferential side of the outer propeller shaft and rearward of the first bearing, the second bearing rotatably supporting the outer propeller shaft on the case, an axial load capacity of the first bearing being greater than that of the second bearing;

2. the first bearing is disposed between a front portion of the outer propeller shaft and the case; a load transmission mechanism that transmits a forward axial load acting on the outer propeller shaft to the first bearing is provided on an outer peripheral side of a front portion of the outer propeller shaft, 2. An outboard motor according to claim 1, wherein the case is provided with a bearing support mechanism that supports the first bearing so that it does not displace forward relative to the case.

3. 3. An outboard motor according to claim 1, wherein the first bearing is disposed on the outer periphery of the boss of the rear driven gear or behind the boss of the rear driven gear.

4. 4. An outboard motor according to claim 1, wherein the first bearing is disposed adjacent to a third bearing that rotatably supports the rear driven gear on the case, and rearward of the third bearing.

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