JP2007302113A - Exhaust structure of outboard motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide exhaust structure of an outboard motor capable of reducing noise of exhaust, restricting reduction of propelling force of a propeller due to discharge of the exhaust gas when propelling the hull forward and backward, and having simple structure easy to be manufactured. <P>SOLUTION: The exhaust structure of an outboard motor is provided with an anti-cavitation plate 9 and the propeller 7 positioned under the anti-cavitation plate 9. An exhaust opening 9 as an outlet of an exhaust gas flow passage is provided under a rear part of the anti-cavitation plate 9. A water suction opening 15 communicated with the exhaust gas flow passage is provided under a front part of the anti-cavitation plate 9. The water flowed into from the water suction opening 15 is discharged with the exhaust gas from the exhaust opening 14. When propelling the hull backward, the water flowed into from the exhaust opening 14 is discharged with the exhaust gas from the water suction opening 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust structure for an outboard motor.

As conventional examples of the exhaust structure of an outboard motor, for example, the following two can be cited (for example, refer to Patent Document 1).
As an example, as shown in FIG. 7A, an exhaust gas flow passage 24 extending obliquely downward in the gear case 23 is formed above the propeller 25 protruding from the vicinity of the lower end of the gear case 23 of the outboard motor. The exhaust gas is discharged from the exhaust port at the lower end of the flow passage 24. In this exhaust structure, the exhaust gas C is exhausted from above the propeller 25 supported by the gear case 23 toward the rear of the propeller 25.
In another example, as shown in FIG. 7B, an exhaust gas flow passage 28 is provided in a propeller hub 27 that is mounted on a gear case 26 of an outboard motor, and an exhaust port 30 is provided at the center of the propeller 29. It is the structure which provided. In this exhaust structure, the exhaust gas D is exhausted rearward from the center of the propeller 29. In FIG. 7B, reference numeral 31 denotes an anti-cavitation plate.
No. 5-6239

As shown in FIG. 7A, when exhaust gas C is exhausted obliquely downward from above the propeller 25, there is a problem in that exhaust noise is large. In particular, when the outboard motor is trimmed up, the exhaust noise tends to increase.
Further, since the exhaust gas C is exhausted from the exhaust port to the rear of the propeller 25, the propeller 25 is easy to entrain the exhaust gas especially when the hull is moving backward, and the propeller reverse thrust (reverse thrust) is reduced. There is a problem that thrust (thrust) corresponding to the rotational speed cannot be obtained.

On the other hand, as shown in FIG. 7B, when a structure for exhausting the exhaust gas D from the exhaust port 30 provided at the center of the propeller 29 is adopted, the exhaust gas flow passage 28 is provided in the propeller hub 27. Therefore, the gear case 26 becomes large. If the gear case 26 is large, for example, when the hull is turned at high speed, the force applied to the outboard motor from the side increases, so the structure of the outboard motor is designed with high strength to withstand this force. Must.
Further, since the high-temperature exhaust gas D passes through the exhaust passage in the propeller hub 27, the temperature of the propeller bush (not shown) provided between the propeller 29 and the propeller shaft rises, and is composed of a core metal and rubber. There is a problem that the propeller bushing is prone to slip.
Further, when the hull is moved backward, the propeller 29 rotates with the exhaust gas discharged from the exhaust port 30, and therefore a reverse thrust (reverse thrust) corresponding to the rotation speed of the propeller cannot be obtained.

In addition, the exhaust structure of the outboard motor shown in FIGS. 7 (a) and 7 (b) is such that when the hull is moved backward, water enters from the exhaust port and the exhaust gas flow passage is blocked. As a result, there is a problem that exhaust cannot be performed smoothly and the engine load increases.
Therefore, the object of the present invention is to reduce the noise of the exhaust gas, and to suppress the reduction of the propeller thrust due to the exhaust gas exhaust, both when the hull moves forward and backward, An object of the present invention is to provide an exhaust structure for an outboard motor that has a simple structure and can be easily manufactured.

The present invention provides the following [1] to [4].
[1] An exhaust structure of an outboard motor having an anti-cavitation plate and a propeller positioned below the anti-cavitation plate, and an exhaust port which is an outlet of an exhaust gas flow path below the rear portion of the anti-cavitation plate An exhaust structure for an outboard motor, wherein a water intake port communicating with the exhaust gas flow passage is provided below the front portion of the anti-cavitation plate.
[2] The exhaust structure for an outboard motor according to [1], wherein the exhaust port is provided at a position that does not overlap the rotation trajectory of the propeller when viewed from the rear.
[3] The exhaust structure for an outboard motor according to [2], wherein the exhaust port is divided and arranged on each of the left and right sides around the rotation axis of the propeller.
[4] The outboard motor exhaust structure according to [1], wherein a trim tab is provided below the rear portion of the anti-cavitation plate, and the exhaust port is provided in the trim tab.

According to the exhaust structure of the outboard motor of the present invention, an exhaust port that is an outlet of the exhaust gas flow path is provided below the rear portion of the anti-cavitation plate, and the lower side of the front portion of the anti-cavitation plate In addition, since the water intake port communicating with the exhaust gas flow passage is provided, the water flowing in from the water intake port is mixed with the exhaust gas in the exhaust gas flow passage, and this mixture is discharged from the exhaust port. As a result, it is possible to reduce the noise of the exhaust gas as compared with the case where only the exhaust gas is discharged from the exhaust port.
Further, according to the exhaust structure of the outboard motor of the present invention, when the hull moves backward, water flows in from the exhaust port and is discharged from the water intake port together with the exhaust gas, contrary to when the hull moves forward. There is no problem such as an increase in engine load caused by water blocking the flow passage. Further, in this case, since the exhaust gas is discharged to the front of the propeller, the amount of the exhaust gas that the propeller entrains is reduced compared to the case where the exhaust gas is discharged to the rear of the propeller, and the reverse thrust of the propeller (reverse thrust) ) Can be suppressed.
Furthermore, according to the exhaust structure for an outboard motor of the present invention, it is not necessary to increase the size of the gear case that is the covering of the propeller support structure. Can be reduced.

As the exhaust structure of the outboard motor according to the present invention, when adopting a form in which an exhaust port is provided at a position that does not overlap with the propeller's rotation trajectory when viewed from the rear, the amount of exhaust gas caught by the propeller is reduced. , Can increase the propeller thrust. Further, in this case, if the exhaust port is arranged by dividing the left and right sides around the rotation axis of the propeller, the point directly above the rotation axis of the propeller (that is, the point closest to the rotation path of the propeller) ) Is not discharged, the amount of exhaust gas that the propeller is involved in can be further reduced, and the propeller thrust can be further increased.
Further, when the exhaust structure of the outboard motor of the present invention adopts a form in which a trim tab is suspended below the rear portion of the anti-cavitation plate and an exhaust port is provided in the trim tab, Since exhaust gas is exhausted from a relatively deep position, exhaust noise can be further reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a side view showing an example of an outboard motor including an exhaust structure of the present invention, FIG. 2 is a cross-sectional view of the outboard motor shown in FIG. 1, and FIG. 3 is an exhaust when the outboard motor is viewed from the rear. FIG. 4 is a front view showing a modified example of the exhaust structure of FIG. 3, FIG. 5 is a side view showing an example of the exhaust structure including a trim tab, and FIG. 6 is an exhaust structure including the trim tab. It is a bottom view which shows the other example.
In this specification, the forward direction of the outboard motor (the direction toward the hull side; the left side in FIG. 1) is referred to as “front”, and the reverse direction of the outboard motor (the opposite side of the hull). The direction toward the right side in FIG.

In FIG. 1, an engine cover 3 is joined to the upper end of the drive shaft housing 2 of the outboard motor 1. An engine is installed inside the engine cover 3.
In front of the drive shaft housing 2, a steering bracket 4 to which an operation lever 4a for controlling the traveling direction of the hull is connected and a clamp bracket 5 as a suspension device for attaching the outboard motor 1 to the hull are attached. ing.
A gear case 6 is joined to the lower end of the drive shaft housing 2. Near the lower end of the gear case 6, a propeller shaft 8 that is a rotation shaft of the propeller 7 is rotatably mounted. Further, an anti-cavitation plate 9 protrudes behind the gear case 6 and above the propeller 7.
Below the rear portion of the anti-cavitation plate 9, an exhaust port 14 that is an outlet of the exhaust gas flow passage 13 (see FIG. 2) is provided. Further, a water suction port 15 communicating with the exhaust gas flow passage 13 (see FIG. 2) is provided below the front portion of the anti-cavitation plate 9. The exhaust port 14 and the water intake port 15 will be described in detail later.
In this specification, “the lower side of the rear portion of the anti-cavitation plate” means the lower portion of the anti-cavitation plate itself in the rear portion of the anti-cavitation plate (the portion behind the plane of rotation of the propeller). It includes the case where it means a part and the case where it means a part of another object attached below the anti-cavitation plate. Therefore, an exhaust port of the trim tab described later (see reference numeral 20a in FIG. 5 and reference numeral 22a in FIG. 6) corresponds to “an exhaust port provided on the lower side of the rear portion of the anti-cavitation plate”.
Further, in this specification, “the lower side of the front portion of the anti-cavitation plate” means the lower side of the anti-cavitation plate itself in the front side portion of the anti-cavitation plate (the portion in front of the plane of rotation of the propeller). It includes the case where it means a part and the case where it means a part of another object attached below the anti-cavitation plate. Therefore, unlike what is indicated by reference numeral 15 in FIGS. 1 and 6, for example, a water suction port is provided on another object (accessory for water absorption) attached to the lower surface of the front portion of the anti-cavitation plate. However, it corresponds to “a water inlet provided below the front portion of the anti-cavitation plate”.

In FIG. 2, two bevel gears 8a and 8b, which are rotatably supported coaxially with a propeller shaft 8 in the gear case 6, are engaged so as to mesh with a bevel gear 10a of a drive shaft 10 connected to an engine (not shown). ing.
Near the front end of the propeller shaft 8, the lower end of the shift rod 11 is connected. The shift rod 11 controls the position of a shifter dog 8c provided integrally with the propeller shaft 8 and selectively meshes the shifter dog 8c with one of the bevel gears 8a and 8b, thereby changing the rotation direction of the propeller 7. It is for setting. The shift rod 11 is operated by a shift operation lever (not shown).

  The forward or backward movement of the hull is performed as follows. First, when the engine in the engine cover 3 is driven, the drive shaft 10 rotates. The bevel gear 10a of the drive shaft 10 is engaged with one of the bevel gears 8a and 8b by rotating the propeller shaft 8 by controlling the position of the shifter dog 8c by a shift operation lever (not shown). By rotation of one of the bevel gears 8a and 8b (for example, the bevel gear 8b), the propeller shaft 8 rotates in one direction to advance the hull. The rotation of the other of the bevel gears 8a and 8b (for example, the bevel gear 8a) causes the propeller shaft 8 to reversely rotate, causing the hull to move backward.

Next, embodiments of the exhaust port and the water intake port of the exhaust structure of the present invention will be described.
[First Embodiment]
1 and 2, the exhaust is formed in a form (for example, the form shown in FIG. 3) in which a part of the anti-cavitation plate 9 is deformed to form an opening below the rear portion of the anti-cavitation plate 9. A mouth 14 is provided. The exhaust port 14 communicates with the exhaust gas flow passage 12 (flow passage in the drive shaft housing 2) and the exhaust gas flow passage 13 (flow passage in the gear case 6). The exhaust gas flow passage 12 and the exhaust gas flow passage 13 integrally form one flow passage.
Under the front portion of the anti-cavitation plate 9, a part of the anti-cavitation plate 9 is deformed to form an opening (for example, the same form as the exhaust port 14 shown in FIG. 3). A water inlet 15 communicating with the passage 13 is provided.

The exhaust mechanism of the outboard motor will be described.
In FIG. 2, when the hull moves forward, the exhaust gas A exhausted from the engine (not shown) in the engine cover 3 circulates in the exhaust gas flow passages 12 and 13 as shown by arrows, and The cavitation plate 9 is discharged into the water from an exhaust port 14 provided on the lower side of the rear portion.
At this time, the exhaust gas A is mixed with the water B flowing in from the water inlet 15 provided below the front portion of the anti-cavitation plate 9 in the exhaust gas flow passage 13 before being discharged into the water. . In FIG. 2, the direction in which water B enters is indicated by arrows.
In the present invention, exhaust gas A and water B are mixed in the exhaust gas flow passage 13 and this mixture is discharged from the lower exhaust port 14 of the anti-cavitation plate 9, so that only the exhaust gas A is exhausted. Compared with the case where the exhaust gas is discharged from the exhaust gas 14, the noise of the exhaust gas is reduced, and the amount of exhaust gas that the propeller 7 entrains is reduced, so that the thrust of the propeller 7 is prevented from being lowered.
Further, in the present invention, when the water B flows into the exhaust gas flow passage 13 from the water inlet 15, the pressure in the exhaust gas flow passage 13 decreases, and the exhaust gas flow passage 12 passes through the exhaust gas flow passage 13. Since the exhaust gas is sucked in the direction, the mixture of the exhaust gas A and the water B in the exhaust passage 13 is smoothly discharged from the exhaust port 14. Therefore, the engine load is reduced as compared with the case where the water inlet 15 is not provided.

Contrary to the forward movement of the hull, the water B flows into the exhaust gas flow passage 13 from the exhaust port 14 and is mixed with the exhaust gas A in the exhaust gas flow passage 13 to absorb water as a mixture. It is discharged from the mouth 15. In this case, the increase in the engine load due to the blockage of the exhaust gas flow path due to the entry of the water B, which is observed when the water inlet is not provided, does not occur. Further, since the exhaust gas is discharged from the water inlet 15, the amount of the exhaust gas that the propeller 7 entrains is reduced, and the decrease in the reverse thrust of the propeller 7 is suppressed.
Thus, according to the exhaust structure of the outboard motor of the present invention, the water is discharged by the exhaust port 14 and the water intake port 15 provided on the lower side of the anti-cavitation plate 9 when the hull moves forward and backward. Inflow and discharge are smoothly performed, and the mixture of water and exhaust gas is discharged into water by either the exhaust port 14 or the water intake port 15. For this reason, it is possible to obtain an effect of reducing exhaust noise, reducing engine load, and suppressing reduction in thrust of the propeller 7 both when the hull moves forward and when it moves backward.

As shown in FIG. 3, the exhaust port 14 is preferably arranged at a position that does not overlap the rotation locus 7 a of the propeller 7. In this case, the amount of exhaust gas that the propeller 7 entrains is reduced, and the effect of suppressing a reduction in thrust of the propeller 7 is improved.
As shown in FIG. 3, the exhaust port 14 can be divided into two as exhaust ports 16 and 17 on each of the left and right sides around the rotation axis of the propeller 7. If comprised in this way, the amount of the exhaust gas caught in the propeller 7 will decrease at the time of advance of a hull, and the effect which suppresses the fall of the thrust of the propeller 7 will improve further. That is, when the exhaust port 14 is formed without being divided, the exhaust gas discharged from the vicinity of the point directly above the rotation axis of the propeller 7 is very close to the locus 7 a of the propeller 7. It will cause the thrust of the to decrease. In this regard, when the exhaust port 14 is divided into two exhaust ports 16 and 17, the exhaust gas discharged from the exhaust ports 16 and 17 hardly overlaps the locus 7a of the propeller 7, and the thrust of the propeller 7 is reduced. Less likely to cause a drop.
As shown in FIG. 1, the water suction port 15 is preferably formed at a position that does not overlap the rotation locus 7 a of the propeller 7, similarly to the exhaust port 14. In this case, even when the hull moves backward, the amount of exhaust gas caught in the propeller 7 is reduced as in the case where the hull moves forward, and the effect of suppressing a reduction in thrust of the propeller 7 is improved.
As with the exhaust port 14, the water intake port 15 is preferably divided into two parts on the left and right sides around the rotation axis of the propeller 7. In this case, the effect of suppressing the reduction in thrust of the propeller 7 can be further improved.

  FIG. 4 shows another example in which the exhaust port 14 is divided into two. In FIG. 4, the two exhaust ports 18 and 19 constituting the exhaust port 14 each have a lower surface (propeller side surface) shaped along the circumference of the rotation locus 7 a of the propeller 7 when viewed from the rear (the circumference). (A shape located slightly above). In this case, the total area of the exhaust port 14 can be increased as compared with the embodiment shown in FIG.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a side view of the exhaust structure according to the second embodiment of the present invention (however, the peripheral structure of the propeller shaft 8 is shown as a cross-sectional view). In FIG. 5, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In FIG. 5, the exhaust structure of the outboard motor is configured by suspending a trim tab 20 below the rear portion of the anti-cavitation plate 9 and providing an exhaust port 20 a in the trim tab 20. The trim tab 20 is fixed to the lower surface of the anti-cavitation plate 9 with bolts 21.
The trim tab 20 has an exhaust port 20 a composed of a plurality of exhaust ports at the rear of the blade surface, and has a passage communicating with the exhaust gas flow passage 13 in the anti-cavitation plate 9 inside the trim tab 20. Yes.
In this way, when the trim tab 20 is suspended below the rear portion of the anti-cavitation plate 6 and the exhaust gas is discharged from the exhaust port 20a provided on the blade surface of the trim tab 20, the exhaust gas is As compared with the one shown in FIG. 1, since it is discharged into the water from a deeper position, the effect of reducing exhaust noise can be improved.

FIG. 6 shows another embodiment in which an exhaust port is provided in the trim tab. In FIG. 6, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In FIG. 6, the trim tab 22 is suspended below the rear portion of the anti-cavitation plate 9 using a bolt 21. The lower surface of the trim tab 22 is open and forms an exhaust port 22a.
As described above, when the exhaust port 22a is provided on the lower surface of the trim tab 22, the exhaust gas is discharged into the water from a deeper position than that shown in FIG. can do.
In addition, the discharge port provided in a trim tab can also be comprised as what has the form shown in FIG. 5, and the form shown in FIG.

It is a side view showing an example of an outboard motor including an exhaust structure of the present invention. It is sectional drawing of the outboard motor shown in FIG. It is a front view which shows an example of the exhaust structure at the time of seeing an outboard motor from back. It is a front view which shows the modification of the exhaust structure of FIG. It is a side view which shows an example of the exhaust structure containing a trim tab. It is a bottom view which shows the other example of the exhaust structure containing a trim tab. It is a side view which shows the exhaust structure of the conventional outboard motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outboard motor 2 Drive shaft housing 3 Engine cover 4 Steering bracket 4a Operation lever 5 Clamp bracket 6 Gear case 7 Propeller 7a Propeller rotation locus 8 Propeller shaft 8a, 8b Bevel gear 8c Shifter dog 9 Anti-cavitation plate 10 Drive shaft 10a Bevel gear 11 Shift Rod 12 Exhaust gas flow passage (flow passage in the drive shaft housing)
13 Exhaust gas flow passage (flow passage in gear case)
14 Exhaust port 15 Water intake port 16, 17, 18, 19 Discharge port (part constituting the exhaust port)
DESCRIPTION OF SYMBOLS 20 Trim tab 20a Exhaust port 21 Bolt 22 Trim tab 22a Exhaust port 23 Gear case 24 Exhaust port 25 Propeller 26 Gear case 27 Propeller hub 28 Exhaust gas flow path 29 Propeller 30 Exhaust port 31 Anti-cavitation plate

Claims (4)

  An exhaust structure for an outboard motor having an anti-cavitation plate and a propeller positioned below the anti-cavitation plate, and an exhaust port serving as an outlet of an exhaust gas flow passage is provided below the rear portion of the anti-cavitation plate. An exhaust structure for an outboard motor, wherein a water intake port communicating with the exhaust gas flow passage is provided below the front portion of the anti-cavitation plate.   The exhaust structure for an outboard motor according to claim 1, wherein the exhaust port is provided at a position that does not overlap the rotation locus of the propeller when viewed from the rear.   The exhaust structure of an outboard motor according to claim 2, wherein the exhaust port is divided and arranged on each of the left and right sides around the rotation axis of the propeller. 2. The exhaust structure for an outboard motor according to claim 1, wherein a trim tab is suspended below the rear portion of the anti-cavitation plate, and the exhaust port is provided in the trim tab.

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