JPS59202995A - Vessel with dynamic vibration damper - Google Patents

Abstract

PURPOSE:To absorb the vibration of the hull without any special dynamic damper by making the structure of the bottom of a cargo hold partitioned and supported by both sides of a vessel and lateral fore and aft bulkheads possess a nutural frequency of vertical flexing that can dynamically absorb the vibration relative to the frequency of a vibration source. CONSTITUTION:The structure of the bottom of a central cargo hold which is partitioned and supported by both sides 10a, 10b of a vessel and fore and aft lateral bulkheads 11a, 11b is made to possess a natural frequency of vertical flexing that can dynamically absorb the vibration relative to a frequency of a vibration source such as the rotation of the propelling device at the stern. In this manner, without providing any special dynamic damper such as flexing member and airtight chamber, the absorption of the vibration of the hull can be effectively achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ship designed to reduce hull vibration, and particularly to a ship equipped with a dynamic vibration absorption function.

Ships are generally equipped with things that cause hull vibration, such as the main engine and propulsion unit, and vibration countermeasures are an important issue for ships equipped with large-horsepower main engines. Since the characteristics of vibration are extremely complex, it is often difficult to take measures against vibration.

By the way, dynamic vibration damping devices are used as vibration isolation measures for small equipment, etc., but when this is applied to huge structures such as ships, the dynamic vibration damping devices themselves are also large. Something becomes necessary.

Therefore, as a large dynamic vibration absorber that can be applied to ships,
Conventionally, the means shown in Fig. 1 (plan view), Fig. 2 (cross-sectional view taken along the line ■-■ in Fig. 1), and Fig. 3 (cross-sectional view taken along the -■ arrow in Fig. 1) have been proposed. In this means, the inner bottom plate 3 of the cargo hold 2 is supported by pneumatic pressure, so that the vertical vibration of the cargo 7 loaded in the hold is utilized as a dynamic vibration absorption device. In addition, the code|symbol 1 in FIGS. 1-3 is a ship, 4 is a flexible member, 5 is a bottom member, 6 is an airtight chamber, and 8 is an air supply port.

Furthermore, a dynamic vibration absorption device has also been proposed in which the bottom shell plate is separated from the hull and supported by air springs so that it can vibrate in the vertical direction.

However, the above-mentioned dynamic vibration absorbers all have a problem in that maintenance and inspection work is cumbersome and difficult.

The present invention aims to solve these problems, and focuses on the vertical vibration frequency as a dynamic characteristic of the cargo hold ship bottom structure, which is designed from the viewpoint of static strength. It is an object of the present invention to provide a dynamic vibration absorption type ship that can be provided with a function as a dynamic vibration absorption device by utilizing this.

For this reason, the dynamic vibration absorption type ship of the present invention is a ship that is equipped with a propeller propulsion device at the stern and a baggage hold in the main part of the ship including the center of the ship, and the bottom structure of the baggage hold is It is characterized in that it is configured to have a vertical deflection natural frequency that can dynamically absorb vibrations with respect to the frequency of the excitation force while being supported by the transverse bulkhead.

Hereinafter, a dynamic vibration absorption type ship as an embodiment of the present invention will be explained with reference to the drawings. Figure #4 is a longitudinal sectional view thereof, Figure 5 is a sectional view taken along the V-V arrow in Figure 4, and Figure 6 is a sectional view thereof. FIG. 2 is a perspective view showing the structure of the bottom of the cargo hold.

As shown in FIGS. 4 to 6, a propeller propulsion device (not shown) is provided at the stern of the hull 1, and several cargo holds 2 are provided in the main part of the hull including the center of the hull.

3- The bottom structure of each cargo hold 2 is supported by both ship side parts 10a, 1(lb) and front and rear transverse bulkheads 11a, 11b, and the bottom structure of each cargo hold 2 is It is configured to have a vertical deflection natural frequency that can absorb dynamic vibrations, and as shown in FIG. 6, the inner bottom plate 9a and the bottom outer plate 9
A plurality of girder plates 12 and a plurality of floor plates 13 are provided perpendicularly to each other between the
It has a compartmental double bottom structure.

With regard to the vibration behavior of the bottom 9, it has been found that the entire ship's bottom 9 vibrates like a single plate in low-order vibrations using computational analysis using the finite element method.

When determining the above-mentioned frequency, the ship bottom 9 is surrounded by both ship side parts 10a, 10b and the front and rear transverse bulkheads 11a.
.

111], the frequency f can be expressed by the following equation.

Where, f is the frequency of vibration of the bottom (H2), π is the pi 1g is the force acceleration, D is the bending rigidity of the bottom structure, and Ill is the weight per unit area of the bottom structure (including the weight of cargo in the hold). ), a
is the length of the hold and the distance between the front and rear transverse bulkheads 11a and 11b),
1] is the width of the hold (distance between both ship sides 10a and 10b),
τ is a coefficient representing the influence of seawater outside the bottom of the ship, γ is the weight per unit volume of seawater, and C is an empirical coefficient.

The vibration behavior of the ship's bottom structure is that it vibrates in the vertical direction at the frequency f expressed by equation (1), but at this time, the weight of the cargo in the hold and the seawater outside the ship's bottom vibrate together with the ship's bottom structure. These together with the weight of the bottom structure itself form the mass part of the oscillator.

In other words, regarding the spring part and mass part of a so-called dynamic vibration absorber, in the above case, the bending rigidity of the ship's bottom structure becomes the spring part, and the mass of the ship's bottom structure, the mass of cargo in the hold, and the mass of seawater outside the ship's bottom (additional water mass) ) is the mass part of the oscillator.

Therefore, the frequency of the excitation force that induces vibration in the hull 1 is f. Then, the above-mentioned ship bottom frequency f becomes the excitation force frequency “0
By setting it to approximately match the , the bottom structure will act and be effective as a dynamic vibration absorber.
Vibration of the hull 1 can be suppressed.

As detailed above, according to the dynamic vibration absorption type ship of the present invention,
In a ship that is equipped with a propeller propulsion unit at the stern and a baggage hold in the main part of the hull including the center of the ship, when the bottom structure of the baggage hold is supported by both ship sides and the front and rear transverse bulkheads, It has a simple structure that has a vertical deflection natural frequency that can dynamically absorb vibrations at the frequency of the vibration force, and can be used even in a large ship hull without the need for a separate dynamic vibration absorber. A sufficient vibration absorption effect can be obtained.

[Brief explanation of drawings]

Figures 1 to 3 show a conventional dynamic vibration absorber for a ship. Figure 1 is a plan view thereof, Figure 2 is a sectional view taken along the ■-II arrow in Figure 1, and Figure 3 is a sectional view of Figure 1. ■-■ It is a cross-sectional view in the direction of arrows, and the fourth to
Fig. 6 shows a dynamic vibration absorption type ship as an embodiment of the present invention, Fig. 4 is a longitudinal cross-sectional view thereof, and Fig. 5 is a cross-sectional view taken from ■-■ in Fig. 4.
6 is a perspective view showing the structure of the bottom of the cargo hold. -6= 1...Hull, 2...Luggage hold, 9...Bottom, 9a...Inner bottom plate, 91]...Bottom outer plate, 10a, 10b...Ship side part,
11a, 11b...transverse bulkhead, 12...-goo plate, 13...floor plate. Sub-Agent Patent Attorney Yoshihiko Iinuma7- Figure 1 Figure 1 ■ Figure 2 Figure 3

Claims (1)

[Claims] In a ship that is equipped with a propeller propulsion unit at the stern and a baggage hold in the main part of the hull including the center of the ship, when the bottom structure of the baggage hold is supported by both ship sides and the front and rear transverse bulkheads, 1. A dynamic vibration damping type ship, characterized in that it is configured to have a vertical deflection natural frequency capable of dynamic vibration damping with respect to the frequency of vibration force.