JP2556707B2 - Ship propulsion equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propulsion device for a ship such as an outboard motor and an inboard / outboard motor that is horizontally rotated and steered with respect to the ship. .

[Prior Art] Conventionally, there is a propulsion device for a ship in which a pair of propellers arranged so as to face each other rotate in opposite directions (for example, JP-A-57-160794 and JP-A-59-70292). (See the official gazette). The third example of an outboard motor equipped with this type of propulsion device
Shown in Figures and FIG.

In FIG. 3, an outboard motor 20 is attached to a boat (ship) S by a clamp bracket 21. Reference numeral 22 denotes a swivel bracket, which supports the outboard motor main body 23 horizontally and rotatably with respect to the clamp bracket 21. That is,
The propulsion device 24 of the outboard motor 20 is horizontally rotated and steered with respect to the boat S.

As shown in FIG. 4, the propulsion device 24 has a pair of propellers 25 and 26 whose busbars 25a and 26a are substantially parallel to each other.
The propellers 25 and 26 are rotated in opposite directions. The busbars 25a and 26a referred to here are the propellers 2 described above.
As shown in Fig. 4, 5, 26 are outlines that appear when the cross section is taken at any position in the radial direction.
The surfaces of 25 and 26 are formed by the set of busbars 25a and 26a. The radius of the rear propeller 26 is set to be 10% to 15% smaller than that of the front propeller 25. Accordingly, the contracted flow A, which is accelerated by the front propeller 25 and is pushed out to the rear propeller 26, is further accelerated by the rear propeller 26, and propulsion efficiency is improved as is well known.

[Problems to be Solved by the Invention] In the outboard motor 20 and the like, when the rudder is steered, the propulsion device 24 is rotated horizontally with respect to the watercraft S (Fig. 1), and therefore the watercraft travels. An angle α is formed between the direction B and the centerline C of the propulsion device 24. At this time, the contracted flow A
Is inclined by the angle α and is inclined as indicated by the chain double-dashed line. Therefore, the vicinity of the tip portion (hereinafter, referred to as a chip) 26b of the rear propeller 26 is largely deviated from the range of the contracted flow A.

Here, the rear propeller 26 is designed on the premise that the contracted flow A accelerated by the front propeller 25 is further pushed rearward. Therefore, as described above, when the vicinity of the chip 26b greatly deviates from the range of the contracted flow A, a force larger than the set value is applied to the vicinity of the chip 26b, or cavitation occurs. There are cases. For example, after such a large force is applied,
In case of cavitation, rear propeller 26
The load applied to is drastically reduced. Therefore, since the steering force changes abruptly and the propelling direction of the propeller changes abruptly, the steering feeling is not good.

The present inventor has conducted various studies on the above points and found that the tip 25b of the front propeller 25 and the tip 26b of the rear propeller 26 are apart from each other in the axial direction E, and thus the above-mentioned inconvenience occurs. did. Therefore, the inventor of the present invention, as shown in FIG.
It was considered that the distance in the axial direction E between the two chips 25b and 16b is made smaller by tilting the direction forward G rather than parallel and setting the rake angle θ negative, for example. However, when this is done, a predetermined minimum gap D is required between the rotational trajectories F1 and F2 (shown by broken lines) of both propellers 25 and 16, while the propeller 16 has a shape peculiar to the rear propeller 16 due to its unique shape. Since it is inevitable that the vicinity 16c of the root of the rotation locus F2 swells to the front G, the distance in the axial direction E between the two chips 25b, 16b cannot be made sufficiently small.

Also, in this type of propulsion device, the steering angle is 20
In some cases, the direction of the contracted flow A changes greatly from 20 ° to 30 ° in the case of the conventional example shown in Fig. 4 when such a large steering angle is taken. , The tip 26b of the rear propeller 26 stalls. From this, the steering force changes stepwise due to a partial stall from the high load state on the front and rear propellers depending on the size of the traveling speed and steering speed of the ship, and the operating force of the steering device changes. , There is a possibility that the maneuvering will be uncomfortable.

The present invention has been made in view of the above circumstances, and it is possible to avoid occurrence of an abnormal state such as a stall due to the front and rear propellers receiving a substantially even flow regardless of the change in the direction of the contraction flow due to steering. An object of the present invention is to provide a marine vessel propulsion device that can ensure steering stability and that can avoid the occurrence of chip vortex cavitation without lowering propulsion efficiency.

[Means for solving the problem]

In order to achieve the above-mentioned object, according to the present invention, a front propeller and a rear propeller that rotate in mutually opposite directions are axially adjacent to each other and are arranged at a rear portion of a propulsion device. Is formed linearly,
The rake angle is set to a positive value, the rear propeller is set to have a smaller radius than the front propeller, and the generatrix of the propeller inclines forward as it goes to the tip side, so that the front propeller Axially close to the tip.

[Operation] According to the present invention, the generatrix of the rear propeller is curved forward as it goes to the tip side, so that a sufficient gap can be maintained at the base of the propeller,
The axial distance between chips can be reduced.

Also, even when the steering angle is set to a large value of 20 ° to 30 °, the effect of the rear propeller on the contraction flow is less inside the steering direction and more outside, and it becomes dominant, and the steering force is larger than normal. The moderate increase makes steering stability a desirable situation for this type of propulsion system. Also,
The propeller shape itself is a shape that is unlikely to cause an abnormal situation such as stall.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a propulsion device 24 of an outboard motor 20 is provided with a front propeller 25 and a rear propeller 6 that rotate in opposite directions and are adjacent to each other in an axial direction E. As is well known, the two propellers 25 and 6 are rotationally driven in opposite directions by one or two drive shafts (not shown) (for example, see Japanese Patent Laid-Open No. 60-259594).

In FIG. 2, both propellers 25 and 6 are shown as inner cylinders 1a and 2a and ribs.
It is integrally formed with the propeller bosses 1 and 2 composed of 1b and 2b and outer cylinders 1c and 2c, and has a wing shape (not shown). The front propeller 25 has a straight generatrix 25a and a positive rake angle θ, like a normal propeller.
The rear propeller 6 has its busbar 6a inclined forward G in a curved shape as it goes to the side of the tip 6b, and is close to the tip 25b of the front propeller 25 in the axial direction E. The rear end virtual plane 25d on the rotation locus F1 of the front propeller 25 and the front end virtual plane 6d on the rear locus F2 of the propeller 6 are:
They are set substantially parallel to each other, and a required predetermined minimum gap D is set between the rear end virtual surface 25d and the front end virtual surface 6d. Other configurations are similar to those of the conventional example, and the same parts or corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted.

In the above configuration, according to the present invention, since the generatrix 6a of the rear propeller 6 is curvedly curved forward G, the root portion 6c of the rear propeller 6 is not inclined forward G much.
There is no possibility that the vicinity 6c of the root of the front end virtual surface 6d on the rotation locus F2 will bulge forward. Therefore, both rotation trajectories F1, F
Rear virtual surface 25d and front virtual surface 6d in 2 and the vicinity of the base
The gap D of 25c and 6c can be sufficiently maintained, and both chips can be
The distance in the axial direction E between 25b and 6b can be reduced. Therefore, the vicinity of the tip 6b of the rear propeller 6 is unlikely to largely deviate from the contracted flow A (indicated by the chain double-dashed line) when the rudder is steered. As a result, the possibility that a force larger than the set value will be applied to the vicinity of the chip 6b is reduced, and the possibility of cavitation is reduced. Further, because of this, there is no fear that the load applied to the rear propeller 6 will suddenly decrease, and therefore the steering force will not change abruptly.
The feeling of steering is improved.

Particularly, in this embodiment, the rear end virtual surface 25d of both trajectories F1 and F2 is
Since the front end virtual surface 6d and the front end virtual surface 6d are set substantially parallel to each other, the distance between the chips 25b and 6b is minimized, so that the effect of the invention described above is maximized.

As described above, according to the present invention, the forward propeller has the positive rake angle and the generatrix is formed in a straight line.
A uniform force can be applied in the radial distribution of the propeller, and on top of that, the rear propeller mother ship, which has a smaller radius than the front propeller, tilts forward in a curved shape as it goes to the tip side, and the front propeller Since it is axially close to the tip, the rear propeller pushes the contracted flow toward the larger diameter side, and the propulsion efficiency can be improved as a whole. Moreover, since the rear propeller is located forward as it goes to the tip side, the centrifugal force acts on the rear propeller in the direction in which the centrifugal force cancels out a part of the stress applied to the propeller by water pressure. Since it can be manufactured thinner, the requirement for the rear propeller that wants to have a smaller cross section than the front propeller in view of the action of contraction can be fulfilled, and the propeller efficiency can be improved also from this aspect. Moreover, there is no possibility that a force larger than the set value will be applied to the vicinity of the tip of the rear propeller, or that cavitation will occur. Moreover, even if the direction of the contraction changes drastically by 20 ° to 30 ° due to the steering, the front and rear propellers continue to receive the flow substantially evenly, and it is possible to avoid the occurrence of abnormal conditions such as stalling, and the rear propeller. The effect of the contraction on the contraction flow is small inside the steering direction and increases outside the steering direction, and the steering force increases moderately compared to the normal time, so it is possible to keep the steering more stable. It has the effect of being able to.

[Brief description of drawings]

1 is a side view of an outboard motor showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a side view of a conventional outboard motor, and FIG. Is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 is a plan sectional view of a propulsion device not included in the present invention. 6 ... rear propeller, 6a ... busbar, 6b ... chip, 6d
...... Front virtual surface, 24 ...... Propulsion device, 25 ...... Front propeller, 25a ...... Bus, 25b ...... Chip, 25d ...... Rear virtual surface, E ...... Axial direction, F1, F2 ...... Rotation locus , G …… forward,
S: Ship (boat).

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-160794 (JP, A) JP-A-59-70292 (JP, A) JP-A-62-149598 (JP, A) JP-A-60- 259595 (JP, A)

Claims (2)

(57) [Claims] 1. A propulsion device for a ship which is horizontally rotated and steered with respect to a ship, wherein a front propeller and a rear propeller, which rotate in mutually opposite directions, are axially adjacent to each other, and the rear part of the propulsion device. The front propeller has its generatrix formed linearly and the rake angle is set to be positive, and the rear propeller has a radius smaller than that of the front propeller. At the same time, the propulsion device for a ship is arranged such that its bus bar inclines forward as it goes to the tip side and is axially close to the tip of the forward propeller. 2. The rear end virtual plane in the rotation trajectory of the front propeller and the front end virtual plane in the rotation trajectory of the rear propeller are set to be substantially parallel to each other. Ship propulsion device.