JP2007182136A - Gear case of outboard motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sailing speed, accelerating performance and fuel economy, etc. by suppressing downward force generated by difference in shape between upper and lower members in a propeller shaft storing part. <P>SOLUTION: A gear case 6 of an outboard motor has a shell-shaped propeller shaft storing part 38 horizontally journaling a propeller shaft 20 at the inside and a vertically wing-shaped drive shaft storing part 39 located in an upper part of the propeller shaft storing part 38 to vertically journal a drive shaft 18 for driving the propeller shaft 20 at the inside. In the propeller shaft storing part 38, a plurality of recessed parts 44 are formed on an outer peripheral surface to be a lower side of the propeller shaft 20 in side view. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gear case for an outboard motor.

  The gear case of the outboard motor is vertically supported by a propeller shaft housing portion in which the propeller shaft is horizontally supported and a drive shaft that is located above the propeller shaft housing portion and drives the propeller shaft. And a vertical wing-shaped drive shaft housing portion.

  A bevel gear mechanism and a forward / reverse switching mechanism are provided at the intersection of the lower end portion of the drive shaft and the propeller shaft, and a predetermined outer diameter is given to the propeller shaft accommodating portion for convenience of accommodating the bevel gear mechanism and the forward / reverse switching mechanism. The propeller shaft housing portion is formed in a streamlined shell shape that is narrowed forward so that this does not become water flow resistance.

  Also, a vertical wing-shaped rectifying plate that is thinner and smaller than the drive shaft housing is provided below the propeller shaft housing.

  As described above, the size (cross-sectional area) of the drive shaft housing portion and the rectifying plate provided above and below the propeller shaft housing portion is asymmetrical, and therefore flows in the upper half side of the propeller shaft housing portion during navigation of the outboard motor. The water flow velocity flowing in the lower half side becomes faster than the water flow velocity, and as a result, the surface pressure on the lower half side of the propeller shaft housing portion is lowered like a wing of an airplane, and the force pulling the propeller shaft housing portion downward (Negative lift) is generated.

  Due to the downward pulling force, a part of the propulsive force generated by the propeller is converted to a downward force and lost, and thus the traveling speed is lowered, the acceleration performance is lowered, and the fuel consumption is inevitably deteriorated.

As disclosed in Patent Document 1, as a technique for reducing the water flow resistance of a gear case of an outboard motor, there is one that suppresses the generation of vortices at the rear end of the gear case.
JP 2005-132150 A

  However, the outboard motor gear case described in Patent Document 1 cannot suppress the downward force generated by the difference between the upper and lower member shapes of the propeller shaft accommodating portion as described above.

  The present invention has been made to solve the above-described problem, and suppresses downward force generated by the difference in the shape of the upper and lower members of the propeller shaft housing portion, thereby improving cruising speed, acceleration performance, fuel consumption, and the like. An object of the present invention is to provide a gear case for an outboard motor.

  In order to achieve the above object, an outboard motor gear case according to the present invention includes a shell-shaped propeller shaft housing portion in which a propeller shaft is horizontally supported, and an internal portion located above the propeller shaft housing portion. And a drive shaft housing portion having a vertical wing shape on which a drive shaft for driving the propeller shaft is vertically supported, and the propeller shaft housing portion is recessed in an outer peripheral surface which is lower than the propeller shaft in a side view. Is formed.

  The outboard motor gear case according to the present invention is characterized in that the recess is formed in front of the drive shaft in a side view.

  Furthermore, the gear case of the outboard motor according to the present invention is characterized in that a plurality of the concave portions are formed along the water flow direction during navigation.

  And the gear case of the outboard motor which concerns on this invention formed the row | line | column of the several recessed part along the said water flow direction in multiple rows up and down.

  According to the outboard motor gear case of the present invention, as a result of forming a recess in the outer peripheral surface of the propeller shaft housing portion that is lower than the propeller shaft and forward of the drive shaft in a side view, the lower side of the propeller shaft housing portion. Some turbulence occurs in a part of the water flow that touches the half surface, and it becomes turbulent with respect to the water flow that touches the upper half surface of the propeller shaft housing part, so the shape of the upper and lower parts of the propeller shaft housing part The downward force generated by the difference is suppressed. For this reason, traveling speed, acceleration performance, fuel consumption, etc. can be improved.

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

  FIG. 1 is a left side view showing an example of an outboard motor equipped with a gear case according to the present invention. The outboard motor 1 has an engine 2 mounted on the top thereof, and an engine holder 3, an oil pan block 4, a drive shaft housing 5, and a gear case 6 are sequentially assembled to the lower portion of the engine 2. The middle cover is covered with a synthetic resin upper cover 8, a middle cover 9, and a lower cover 10.

  The engine 2 is, for example, a water-cooled four-cycle V-type six-cylinder type, with the crankshaft 12 vertically oriented with the crankcase 13 on the front side and the pair of left and right cylinder heads 14 on the rear side. It is fixed on the holder 3.

  The rotation of the crankshaft 12 is decelerated by the drive gear 16 and the driven gear 17 and transmitted to the drive shaft 18, and the rotation of the drive shaft 18 is transmitted to the propeller shaft 20 and the propeller 21 via the bevel gear mechanism 19. The rotation of the drive shaft 18 that always rotates in one direction is switched between forward and reverse by the forward / reverse switching mechanism 22 to advance or reverse the hull. The drive shaft 18 passes vertically through the oil pan block 4, the drive shaft housing 5, and the gear case 6, and the propeller shaft 20 is supported horizontally within the gear case 6.

  The engine holder 3 and the drive shaft housing 5 are provided with a pair of left and right engine mounts 24 and 25, the upper engine mount 24 is connected to the upper steering bracket 26, and the lower engine mount 25 is connected to the lower steering bracket 27. It is connected.

  The upper steering bracket 26 and the lower steering bracket 27 are fixed to the upper end and the lower end of a vertically extending pilot shaft 31, respectively. The pilot shaft 31 is rotatably supported by a swivel bracket 32. The clamp bracket 34 is fixed to the stern portion 35 of the hull.

  FIG. 2 is a perspective view of the gear case 6 as viewed obliquely from the left front. The gear case 6 is formed in a hollow container shape in which a propeller shaft accommodating portion 38 and a drive shaft accommodating portion 39 located on the upper portion thereof are integrated. The lower portion of the drive shaft 18 is vertically supported inside the drive shaft housing 39, the propeller shaft 20 is horizontally supported inside the propeller shaft housing 38, and the bevel gear mechanism 19 and the forward / reverse switching mechanism 22 Is housed.

  The propeller shaft accommodating portion 38 has a predetermined inner and outer diameter in order to clear the outer diameter of the bevel gear mechanism 19, and is formed in a streamlined bullet shape that is narrowed forward so as not to have a large water flow resistance. On the other hand, the drive shaft accommodating portion 39 is also shaped into a vertical wing shape having an airfoil cross-sectional shape in order to reduce water flow resistance.

  Also, a vertical wing-shaped rectifying plate 40 that is thinner and smaller than the drive shaft accommodating portion 39 is provided below the propeller shaft accommodating portion 38, and a cavitation plate 41 is integrally formed at the upper portion of the gear case 6.

  As shown in the longitudinal sectional view of FIG. 3, a plurality of concave portions 44 are formed on the outer peripheral surface of the propeller shaft housing portion 38. These recesses 44 are formed in a range below the axis of the propeller shaft 20 and in front of the axis of the drive shaft 18 in a side view (see FIG. 1). Further, it is preferable to form the plurality of recesses 44 in a row along the direction of water flow when the outboard motor 1 is sailing. Furthermore, it is preferable to form a plurality of rows of the plurality of concave portions 44 along the water flow direction in this way, for example, three to four rows.

  The length of each concave portion 44 along the water flow direction is, for example, the smallest in the foremost concave portion 44 and becomes longer toward the rear, but may be the same length. These recesses 44 are recessed by about several millimeters with respect to the outer surface of the propeller shaft housing portion 38, and are rounded and embossed so as not to be rapidly recessed with respect to the outer surface of the propeller shaft housing portion 38.

  As a result of providing such a recess 44 on the outer peripheral surface of the propeller shaft housing portion 38, when the outboard motor 1 is sailing, a water flow A flowing while touching the upper half surface of the propeller shaft housing portion 38 as shown in FIG. In contrast to the laminar flow, a slight turbulence occurs in a part of the water flow B that flows while touching the lower half surface of the propeller shaft accommodating portion 38, resulting in a light turbulence.

  Originally, since the cross-sectional area of the rectifying plate 40 located at the lower part of the propeller shaft housing part 38 is much smaller than the cross-sectional area of the drive shaft housing part 39 located at the upper part of the propeller shaft housing part 38, Due to the difference in the shape of the member, the speed of the water flow B becomes faster than the speed of the water flow A when the outboard motor 1 is navigating. As a result, the surface pressure on the lower half side of the propeller shaft accommodating portion 38 is greatly reduced. Negative lift that pulls the shaft accommodating portion 38 downward is generated.

  However, the surface pressure on the lower half side of the propeller shaft accommodating portion 38 does not decrease due to the weak turbulent flow of the water flow B due to the provision of the recess 44 on the outer peripheral surface of the lower half of the propeller shaft accommodating portion 38 as described above. Negative lift is no longer generated. For this reason, the outboard motor 1 does not tend to sink during navigation, and a part of the propulsive force generated by the propeller 21 is not converted to a downward force and is not damaged. Can greatly contribute to the improvement.

  Further, since the concave portion 44 is formed in a range below the axis of the propeller shaft 20 and in front of the axis of the drive shaft 18 in a side view, the water flow B flowing while touching the lower half surface of the propeller shaft accommodating portion 38 It is possible to effectively generate turbulent flow and promote the above-mentioned effects.

  Note that the shape and arrangement of the recesses 44 are not necessarily limited to those described above. For example, as shown in FIG. 5, a large number of small dimple-like recesses 46 may be arranged on the outer peripheral surface of the propeller shaft accommodating portion 38. Further, an outboard motor that does not include the current plate 40 may be used.

The left view which shows an example of the outboard motor provided with the gear case which concerns on this invention. The figure which shows one Embodiment of this invention with the perspective view which looked at the gear case from diagonally left front. FIG. 3 is a longitudinal sectional view taken along line III-III in FIG. 2. The left view which shows the state of the water flow which flows through the surface of a propeller shaft accommodating part. The left view of the gear case which shows another embodiment of a recessed part.

Explanation of symbols

1 Outboard 2 Engine 6 Gear case
18 Drive shaft
19 Bevel gear mechanism
20 Propeller shaft
21 propeller
38 Propeller shaft housing
39 Drive shaft housing
40 Rectifier plate
44 Recess A, B Direction of water flow during navigation

Claims (4)

A vertical wing in which a bullet-shaped propeller shaft housing portion in which a propeller shaft is horizontally supported and a drive shaft which is positioned above the propeller shaft housing and drives the propeller shaft is vertically supported An outboard motor gear case, comprising: a drive shaft housing portion having a shape, wherein the propeller shaft housing portion is formed with a recess in an outer peripheral surface that is lower than the propeller shaft in a side view. The outboard motor gear case according to claim 1, wherein the concave portion is formed in front of the drive shaft in a side view. The outboard motor gear case according to claim 1 or 2, wherein a plurality of the concave portions are formed along a water flow direction during navigation. The outboard motor gear case according to claim 3, wherein a plurality of rows of concave portions along the water flow direction are vertically formed.

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