JPH04331838A - Dynamic vibration absorber - Google Patents

Abstract

PURPOSE:To permit the use of a dynamic vibration absorber (dynamic damper) installed for absorbing the vibration having a frequency component, even in a system in which the characteristic frequency of the system varies or the excitation frequency varies. CONSTITUTION:Electromagnets 8 and 9 are arranged, keeping a certain internal from the magnetic pole of a permanent magnet 5, and either the permanent magnet 5 or the electromagnets 8 and 9 is fixed on a vibration suppressed body 13, and the other can be shifted in the direction for varying the interval between the magnetic poles. The shift of the vibration suppress body 13 and the relative shift between the electromagnets 8 and 9 and the permanent magnet 5 are detected by the displacement meters 14 and 7. These detection signals are inputted into a control circuit 29 through a signal amplifier 15, and the optimum excitation current is allowed to flow in the electromagnets 8 and 9 through an amplifier 16 by the control circuit 29.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dynamic vibration absorbers (dynamic dampers), and more particularly to improvements in magnetic repulsion type dynamic vibration absorbers.

0002

2. Description of the Related Art Dynamic vibration absorbers have conventionally been provided to absorb vibrations having specific frequency components, and their basic configuration is approximately as shown in FIG.

In the figure, a rigid body 1 is a vibrating body with a mass m, and a spring 2 is a linear spring with a spring constant k that supports the rigid body. On the other hand, the rigid body 3 has a mass md and is supported on the rigid body 1 by a spring 4 having a spring constant kd. Now, a periodic external force Po sinωt is applied to the rigid body 1 (Po: force amplitude, ω: angular velocity,
t: time), the displacement of rigid body 1 is X, the displacement of rigid body 2 is Xd,

0004

[Equation 1] Obtain the equation of motion. The above equation can be easily solved and the solution can be written as follows.

Now, assuming that Xo = Po /k, the amplitude ratios |X/Xo | and |Xd /Xo | have the characteristics shown in FIG. 7 from the above equation. However, Ω-(m/k)1/2
, Ωd=(md/kd)1/2, and γ=ω/Ω.

[0006] Here, the combination of the rigid body 3 and spring 4 shown in FIG. 6 is called a dynamic vibration absorber. If this dynamic vibration absorber is not provided (for example, if md = 0 in equation (2)), the amplitude X of the rigid body 1 becomes infinite when γ = 1 (ω = Ω (m/k) 1/2).

This is because the external excitation frequency coincides with the natural frequency of the system, resulting in so-called resonance. However, due to the dynamic vibration absorber, as shown in Fig. 7, γ=1
Even so, the amplitude (|X/Xo |) of the rigid body 1 is ideally zero.

That is, by installing a dynamic vibration reducer, it is possible to suppress the amplitude of the system that was vibrating with an infinitely large amplitude when γ=1. However, as shown in Figure 7, the amplitude increases on both sides of γ = 1 (for example, when γ is approximately equal to 0.78 and 1.26), so dynamic vibration absorbers generally have a constant excitation frequency from the outside. It can only be applied to vibrating bodies.

Furthermore, in order to maximize the effect with such a small dynamic vibration absorber, there are restrictions on the combination of md and kd, and as shown in FIG. 8, the closer Ωd/Ω is to 1, the higher the effect can be obtained. Note that in the above explanation, the damping of the system is ignored for simplicity, but this tendency remains the same unless the damping becomes extremely large.

0010

For example, in a machine having a complicated link mechanism, such as a robot arm, the natural frequency of the system (arm part) changes as the arm expands and contracts. Therefore, in the above equation, Ω changes arbitrarily, so Ωd to obtain an optimal dynamic vibration absorber cannot be determined. Furthermore, in a system including a rotating machine, the frequency of excitation changes depending on the rotational speed of the machine, so that γ=ω/Ω changes, making it impossible to determine the optimal dynamic vibration absorber. In other words, dynamic vibration reducers cannot be applied to systems where the natural frequency of the system changes or the excitation frequency changes. In view of the above problems, an object of the present invention is to provide a dynamic vibration absorber that is effective even in a system where the natural frequency and excitation frequency of the system change. [Structure of the invention]

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a permanent magnet and two electromagnets arranged at a predetermined distance from each magnetic pole of the permanent magnet, One of the magnets or electromagnets is fixed to the object to be damped, and the other is configured to be movable in the direction in which the distance between the magnetic poles changes, and the displacement of the object to be damped and the relative displacement between the electromagnet and the permanent magnet are controlled. The magnetic repulsion is detected by a displacement meter, and the excitation current of the electromagnet is controlled based on these detection signals to constantly generate magnetic repulsion between the permanent magnet and the electromagnet. In other words, as Ω changes, Ωd is changed to be approximately equal to Ω, and even if the external excitation frequency ω changes, Ωd is also changed by applying electromagnetic force to the spring constant of the dynamic vibration absorber. Always change the optimum Ωd.
Configure it to get .

0012

[Operation] The present invention is constructed as described above. For example, when the natural frequency Ω of the controlled system changes, or when the excitation frequency ω from the outside changes, Ωd =
By optimally controlling kd out of (kd/md)1/2, an ideal dynamic vibration absorber can always be obtained.

[0013]

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an embodiment of a dynamic vibration absorber according to the present invention, and the damped body is omitted.

In FIG. 1, near the center of the figure, a permanent magnet 5 is supported by a leaf spring 6 attached to a support 28 so as to be able to swing vertically, with the upper part serving as the north pole and the lower part serving as the south pole. A non-contact type displacement meter 7 is disposed in the direction in which the leaf spring 6 swings. Although this displacement meter 7 is modeled as a non-contact displacement meter in this figure, it is not particularly limited as long as it can basically extract an electric signal according to the displacement of a permanent magnet.

Above and below the permanent magnet 5, electromagnets 8 and 9 are supported and fixed to a frame 12 via supports 10 and 11, respectively, at a predetermined interval. These electromagnets 8
, 9 are provided with their respective magnetic poles facing the magnetic poles of the permanent magnet 5, and the magnetic poles of the permanent magnet 5 and the electromagnets 8 and 9 have the same polarity facing each other, so that a repulsive force is generated between them. .

Further, portions 8a and 9a in the figure show cross sections of the electromagnetic coil group. The strength of the magnetic fields of the electromagnets 8 and 9 is arbitrarily variable depending on the strength of the current flowing through the coils 8a and 9a, and is controlled by the control system shown in FIG.

That is, in FIG. 2, changes in the permanent magnet 5 are measured by a displacement meter 7 and displacements of the damped body 13 are measured by a displacement meter 14, and each signal is amplified by a signal amplifier 15 and sent to a control circuit 29. The control circuit 29 performs arithmetic processing on each signal (for example, in an analog circuit, a differentiation circuit is provided, and in a digital circuit, processing such as differentiation is performed after A/D conversion), and the output signal is amplified by an amplifier 16. The strength of the magnetic field of the electromagnets 8 and 9 is controlled by changing the magnitude of the current. A magnetic repulsive force always acts between the permanent magnet 5 and the electromagnets 8 and 9, but as the strength of the magnetic field changes, this repulsive force also changes.

Since the goal of control is to reduce the vibration of the damped body 13, the electromagnetic force acting on the permanent magnet 5 movably attached to the damped body 13 with a plate spring 6, that is, the spring and damping Control is performed to create an optimal dynamic vibration reducer system by changing the effect.

FIG. 3 shows the results of a simulation analysis based on the configuration of the above embodiment.
Figure 3 shows how 3 is vibrating with an amplitude of about 6 mm (both amplitudes).
Shown in (a). FIG. 3(a) shows the results when the dynamic vibration absorber according to the present invention is not attached to the damped body 13.

Next, FIG. 3(b) shows the vibration amplitude of the damped body 13 when the dynamic vibration absorber according to the present invention is installed and optimal control is applied. From this result, it can be seen that the vibration amplitude in FIG. 3(b) is reduced to about 1/3 compared to FIG. 3(a). In this case, considering the vibration energy, it is reduced to about 1/9, and it can be said that the vibration damping effect is extremely large.

Next, another embodiment of the present invention will be described. A permanent magnet 17 is fixed on the vibration-damped body by a support 18,
Two electromagnets 19 facing each other sandwiching this permanent magnet
, 20 are fixed on a movable cart 21, and the electromagnets 19 and 20 have the same effect, but the electromagnets 19 and 20 are movable. Note that the displacement of the cart to which the electromagnets 19 and 20 are fixed is measured by a displacement meter 22, and
used for control. The control method is as described above.

FIG. 5 shows a dynamic vibration absorber for reducing the lateral vibration of the object to be damped, and as in FIG.
This is an example in which the fifth side is movable, and FIG. 5(b) is a longitudinal sectional view, and FIG. 5(a) is a view of this from above the page.

In FIG. 5, two sets of electromagnets 24 and 25 fixed on a cart 23 face each other with a permanent magnet 26 in between, and the permanent magnet 26 and the electromagnets 24 and 25 are arranged so as to generate a repulsive force with each other. It is configured. The displacement of the truck is detected by a displacement meter 27 and used to control the electromagnets 24 and 25.

[0024]

[Effects of the Invention] As described above, according to the present invention, even if the natural frequency of the system changes or the excitation frequency changes, the magnetic field of the electromagnet can be controlled to the optimal strength. , it is possible to provide a dynamic vibration absorber that is always stable and reliable.

[Brief explanation of drawings]

[Fig. 1] A schematic diagram showing the configuration of an embodiment of a dynamic vibration absorber of the present invention.

[Fig. 2] Schematic diagram showing the control system of the dynamic vibration absorber of the present invention

[Figure 3
] A diagram showing an example of simulation results showing the effects of the present invention

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

[Figure 6] Schematic diagram showing the configuration of a general dynamic vibration absorber

[Figure 7]
Graph showing the frequency response of the system shown in Figure 6

[Figure 8] Graph showing the relationship between the ratio of the system's natural frequency Ω to the dynamic vibration absorber's natural frequency Ωd and the amplitude ratio of the damped body |X/Xo |

[Explanation of symbols]

1...Rigid body (damped body) 2...Spring
3...Rigid body 4...Spring 5...Permanent magnet
6... Leaf spring 7... Displacement meter 8... Electromagnet
9... Electromagnet 10... Support 11... Support
12... Frame 13... Vibration controlled body 14... Displacement meter
15...Signal amplifier 16...Signal amplifier 17...Permanent magnet
18... Support 19... Electromagnet 20... Electromagnet
21... Movable trolley 22... Displacement meter 23... Trolley
24...Electromagnet 25...Electromagnet 26...Permanent magnet
27...Displacement meter

Claims (2)

[Claims] Claim 1: A permanent magnet and two electromagnets arranged at a predetermined distance from each magnetic pole of the permanent magnet, one of the permanent magnets or electromagnets is fixed to a vibration-damped body, and the other is fixed to a vibration-controlled body. One side is configured to be able to vary in the direction in which the spacing between the respective magnetic poles changes, and a displacement meter detects the displacement of the damped object and the relative displacement between the electromagnet and the permanent magnet, and based on these detection signals, the electromagnet A dynamic vibration reducer characterized by controlling the excitation current of the magnet to constantly generate magnetic repulsion between a permanent magnet and an electromagnet. [Claim 2] The magnetic repulsion between the permanent magnet and the electromagnet is
2. The dynamic vibration reducer according to claim 1, wherein the strength of the magnetic field of each of the two electromagnets is controlled by the magnitude of the current flowing through the coil so that the vibration of the vibration damped body is minimized.