JPH08188192A - Propeller fluctuating pressure absorbing device for marine vessel - Google Patents

Abstract

PURPOSE: To prevent the generation of shock, vibration and noise even when a fluctuating pressure by a propeller is caused on a stern bottom by mounting a rubber film containing fluid on the stern bottom on which the pressure fluctuation by the propeller vigorously acts. CONSTITUTION: A substantially circular rubber film 6 is fixed along the outer circumference of a recess 6a on the stern bottom of a stern part 2 on which the pressure fluctuation by a propeller 1 vigorously acts. A feed pipe 8 for introducing the ballast water of a ballast tank 7 and a return pipe 1 connected to the ballast tank 7 through a control valve 12 are connected to the rubber film 6, respectively. A pump 9 and an opening and closing valve 10 are provided on the upstream side and downstream side of the feed pipe 8, respectively, so that the ballast water in the ballast tank 7 is introduced into the rubber film 6, and the ballast water in the rubber film 6 is returned to the ballast tank 7 through the pipe by the pressure fluctuation of the propeller 1. Thus, the transmitting force of a wave impact force to a main hull can be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propeller fluctuating pressure absorber suitable for reducing shock, vibration and noise of a ship.

[0002]

2. Description of the Related Art Conventionally, as shown in the side view of FIG. 5, the stern structure of a ship which is propelled by propeller propelling is a ship bottom steel plate 3 of a stern portion 2 immediately above a propeller 1, a stern assistant plate 4, and a floor material. 5 and 5. Here, conventionally, no special means has been taken in the stern bottom 3 for absorbing pressure fluctuations from the propeller.

[0003]

As described above, this type of ship obtains propulsion by the rotation of the propeller 1 in the fluid. However, due to the complicated stern shape, the flow field near the propeller becomes non-uniform, and the pressure fluctuation at the tip of the propeller blade occurs in the fluid in combination with the rotation of the propeller blade in the fluid. This pressure fluctuation hits the stern bottom 3 directly above the propeller, so that the stern part 2 receives a large impact force, not only generates vibration and noise in the living area, but also the stern part 2 may be damaged by this. There is.

The present invention has been proposed in view of the above circumstances, and is intended to provide a highly efficient and comfortable ship that does not generate shock, vibration, or noise even if a fluctuating pressure due to a propeller is generated at the stern bottom. An object of the present invention is to provide a propeller fluctuating pressure absorbing device.

[0005]

To this end, the present invention is characterized in that a rubber film containing a fluid is attached to the stern bottom of the stern where the pressure fluctuation due to the propeller acts violently.

[0006]

According to this structure, the fluctuating pressure of the propeller does not directly act on the stern bottom, but indirectly acts on the stern bottom through the rubber film, so Since the transmission force transmitted is reduced and the peak of the impact force is mitigated, it is possible to prevent the generation of impact, vibration and noise, and to minimize the damage to the hull.

[0007]

1 is a longitudinal sectional view of the stern portion thereof, FIG. 2 is a lateral sectional view taken along the line II--II of FIG. 1, and FIG. 3 is a stern portion of FIG. FIG. 4 is a mechanical equivalent model diagram showing vibration characteristics, and FIG. 4 is a diagram showing a hull vibration response according to the present invention.

In the above drawing, the same reference numerals as those in FIG. 5 designate the same members and equipments as in the same drawing. This is because the plate was fitted with a rubber film filled with liquid over almost the entire width.

That is, first, in FIGS.
Is a substantially circular rubber film 6 whose periphery is fixed along the outer circumference of a relatively shallow recess 6a formed over the outer plate of the propeller 1 of the stern 2 over an appropriate area. Is enclosed. Reference numeral 8 is a water supply pipe for guiding the ballast water in the ballast tank 7 into the rubber film 6, a pump 9 is provided upstream of the pipe 8 and an opening / closing valve 1 is provided downstream thereof.
0 is equipped respectively. Reference numeral 11 is a return pipe for connecting the water filling the rubber film 6 to the ballast tank 7 via the control valve 12.

In such a structure, if the relationship between the flow rate of water to the rubber film 6 and the natural frequency is obtained in advance, the stern structure shown in FIG. Is equivalent. This is because the rubber film 6 is deformed like a wavy line due to pressure fluctuations as shown in FIG. 7A because the enclosed water in the rubber film has a mass m and a spring as shown in FIG. By performing an action equivalent to that of a vibration system having a constant k and a damping force f. Therefore, by adjusting the vibration system with one degree of freedom shown in FIG. 7B so as to be synchronized by changing the period of pressure fluctuation and the mass of the internal fluid, the function as a dynamic vibration absorber is performed, and the propeller blades are operated. The resulting pressure fluctuation can be absorbed.

By the way, if a compressible gas such as air is used instead of ballast water, the member corresponding to the mass m is very small. Shock absorber-like shock absorption cannot be expected.

Since seawater is always easily replenished in a ship, the effect as a dynamic vibration absorber can be enhanced in combination with its incompressibility and viscous friction force.

[0013]

According to such a structure, when the internal fluid amount of this device is changed in order to exert the optimum shock absorbing capacity in accordance with the propeller speed, the navigation speed, and the wave height, the tension of the rubber film is reduced. As shown in FIG. 4, it is possible to reduce the transmission force of the wave impact force to the main hull.

In short, according to the present invention, by attaching a rubber film containing a fluid to the bottom of the stern where the pressure fluctuations due to the propeller act violently, even if a fluctuating pressure due to the propeller occurs at the stern bottom, shock, vibration and noise are generated. INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it provides a propeller fluctuating pressure absorbing device for a ship that does not generate high performance and is highly livable.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a stern part of a ship according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the stern part of the ship shown in FIG.

FIG. 3 is a mechanical equivalent model diagram of the propeller fluctuating pressure absorbing device in FIGS. 1 and 2.

FIG. 4 is a diagram showing a ship vibration response according to the present invention.

FIG. 5 is a vertical cross-sectional view showing a conventional ship stern.

[Explanation of symbols]

 1 Propeller 2 Stern 3 Stern Ship bottom 4 Stern auxiliary plate 5 Floor material 6 Rubber film 6a Recess 7 Ballast tank 8 Water supply pipe 9 Pump 10 Open / close valve 11 Return pipe 12 Control valve

Claims (1)

[Claims] 1. A propeller fluctuating pressure absorbing device for a ship, characterized in that a rubber film containing a fluid is attached to the bottom of the stern where the pressure fluctuates greatly due to the propeller.