JPH0645360B2 - Dynamic vibration absorber - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a dynamic vibration reducer for suppressing vibration of a ship main engine or the like.

[Prior art]

When a diesel engine is mounted on a ship, the engine and the hull have the natural frequency of the system with the engine as the mass and the hull as the spring, but the diesel engine structurally has a periodical origin depending on the rotational speed etc. Since a vibrating force is generated, when the natural frequency and the frequency of the exciting force match, a resonance phenomenon occurs in the system,
Large amplitudes appeared in the engine and hull. When such resonance appears, a dynamic vibration reducer is used as one of methods for suppressing vibration. The dynamic vibration absorber is composed of a mass-spring system and a damping mechanism with a natural frequency equal to the frequency of the main vibration body, and has excellent damping performance, but the damping effect changes depending on the damping amount of the device. There is a characteristic to do. Further, the damping performance has a characteristic that the greater the mass of the dynamic vibration absorber-the mass of the spring system, the better. The structure principle of the dynamic vibration absorber will be explained with reference to FIG.
36 and a spring 37 represent a mass-spring system forming the main vibrating body 35, and the dynamic vibration reducer 30 has a mass 31, a spring 32, and a damping which have a natural frequency equal to the frequency of the main vibrating body 35. It is composed of a mechanism 33, and is solidified to the main vibrating body 35 to perform a vibration damping action. In a practical dynamic vibration absorber, in addition to the damping of the damping mechanism 33, there is a hysteresis damping 34 of the spring 32 and a structural damping 34 'caused by the structure of the spring 32. The conventional dynamic vibration absorber 38 will be described with reference to FIG.
Are fixed by a spring group 43 whose both ends are supported by a casing 42, and the natural frequency of this mass-spring system is made to match the frequency of the main vibrating body. The spring group 43 is composed of a large number of springs for ensuring the rigidity of the springs, and these springs are in close contact with each other. Therefore, when the dynamic vibration reducer 38 is activated, friction of the contact surface causes friction damping. This corresponds to so-called structural damping shown in FIG. This damping has a large limitation on the effect of the dynamic vibration absorber because the damping action is large and cannot be adjusted. In FIG. 3, the relationship between the damping action of the dynamic vibration reducer and the vibration amplitude of the main vibrating body will be described using resonance lines. A curve 45 shows the response of the main vibration body when the dynamic vibration absorber is not provided. Curve 46 This is the response when the damping of the dynamic vibration absorber is infinitely large, that is, when only the mass of the dynamic vibration absorber is added to the main vibrating body, and the response is close to that of curve 45 without the dynamic vibration absorber. The vibration suppressing effect does not appear on the main vibration body. Curves 47 and 47 'are the responses when the dynamic vibration absorber has no damping, and the vibration amplitude of the main vibrator becomes zero near the resonance frequency of the response curve 46 when the damping is infinite, but It shows that two new resonance points appear on the left and right of 46. Curves 48 and 10 show the response when different damping is applied, curve 10 shows the best response to a wide range of forced frequencies when ideal damping is applied, and curve 48 shows The damping effect at the resonance point is low due to the response when damping greater than ideal damping is given. In the conventional dynamic vibration absorber, the structural damping due to the structure of the spring group 43 shown in FIG. 6 is large and exceeds the ideal damping.
The vibration damping effect was not fully exhibited. Therefore, it is necessary to increase the mass of the dynamic vibration reducer in order to obtain a vibration damping effect equivalent to that when ideal damping is applied. A curve 51 shows a response when the mass of the conventional dynamic vibration absorber having a large amount of structural damping is increased, and shows that the vibration damping effect is improved by increasing the mass.

[Problems to be Solved by the Invention]

As described in the prior art, the dynamic vibration absorber has excellent vibration damping performance, but the conventional dynamic vibration absorber has insufficient vibration damping effect due to excessive structural damping due to the structure of the spring, and has a large mass. However, there is a drawback that the use of a dynamic vibration absorber of the shape is required. It is difficult to install a large-mass dynamic vibration absorber directly in a diesel engine in terms of space, and as shown in Fig. 5, it is necessary to install the dynamic vibration absorber away from the diesel engine and connect it with a highly rigid stay or the like. However, there was a problem that installation was not possible due to restrictions on installation in an engine room with limited space.

In order to solve the above problems, the present invention provides a dynamic vibration reducer in which ideal damping can be obtained by operating a damping mechanism by reducing structural damping. By improving the vibration damping efficiency of the above, the same level of vibration damping effect as the conventional large-scale dynamic vibration absorber can be realized with a small-sized, small-capacity device and installed in the body of a diesel engine, etc. Reduced,
The purpose is to expand the application of dynamic vibration absorbers.

[Action]

The dynamic vibration absorber provided by the present invention sandwiches a plurality of diaphragms with the spacers between the bases, and the spacers are arranged with a thickness such that the diaphragms do not come into contact with the adjacent diaphragms during operation. The diaphragm vibrates independently, and the diaphragm does not cause friction damping during operation of the dynamic vibration absorber, and the damping is only a slight hysteresis damping of the diaphragm. As described above, since the damping due to the friction of the spring is removed to reduce the structural damping, the damping amount that can be finely adjusted allows the damping amount to be widely adjusted, and the ideal damping can be provided.

【Example】

An embodiment will be described with reference to the drawings. In FIGS. 1 and 2, a diesel engine 2 is installed in an engine room of a hull 1, and a dynamic vibration absorber 3 is fixedly installed on the top of the diesel engine 2. ing. Explaining the structure of the dynamic vibration reducer 3, a vibration plate 4 to which an additional weight 5 can be pivotally attached forms a mass and a spring system, and one end of the vibration plate 4 is provided with a through bolt / nut 7 through a spacer 6. It is erected, and the natural frequency of each cantilever can be set. The required number of the vibrating plates 4 can be installed via the spacers 6 according to the mass of the main vibrating body. The casing 8 of the dynamic vibration reducer 3 also has an oil pan function,
Since it has a function of holding a viscous liquid 9 such as oil, it has a damping mechanism capable of adjusting the damping by applying a required amount of liquid to immerse all the diaphragms 4 at a constant level.

【effect】

Since the present invention is configured as described above, it has the following effects. Since the dynamic vibration reducer uses the mass of the diaphragm itself as the mass and the mass of the spring system, it has a high natural frequency and can suppress the vibration of the main vibrating body having a high frequency, thus widening the applicable range. The diaphragm can adjust its natural frequency according to the natural frequency of the main vibrating body.By combining diaphragms with different frequencies, vibration can be suppressed simultaneously for multiple co-frequency. It is possible. In addition, since each diaphragm is arranged with an appropriate spacing, structural damping due to friction during operation is extremely small, and it is possible to set the ideal damping state by the damping mechanism, which is small in size. Shows high damping effect.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an engine room using the dynamic vibration reducer of the present invention. FIG. 2 is a schematic sectional view of the dynamic vibration reducer of the present invention. FIG. 3 schematically shows the response curve of the main vibration body depending on the damping amount of the dynamic vibration reducer.
FIG. 4 is a schematic view of the structural principle of the dynamic vibration reducer. FIG. 5 is a schematic cross-sectional view of an engine room using a conventional dynamic vibration reducer. FIG. 6 is a schematic sectional view of a conventional dynamic vibration reducer. 1 …… Hull 2 …… Diesel engine 3 …… Dynamic vibration absorber 4 …… Vibration plate 5 …… Additional weight 6 …… Spacer 7 …… Through bolt / nut 8 …… Casing 9 …… Liquid 10 …… Curve

Claims (1)

[Claims] 1. A base of a plurality of vibrating plates 4 is erected upwardly in a cantilever state via a spacer 6 on the bottom of a casing 8, and an additional weight 5 is pivotally attached to the tip of the vibrating plate 4. Further, the casing 8 holds the liquid 9 such as oil at an appropriate level to enable setting of the natural vibrator of each diaphragm 4, and a dynamic vibration absorber.