JP2004257481A - Self-follow-up type resonance device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system of simple structure for changing resonance frequency to follow up input vibration. <P>SOLUTION: In this self-follow-up type resonance device, one end of a lever 2 is pivotally supported by a support point 5, and a free end 7 at the other end is born by a damping spring 6. The lever 2 forms an inclination angle θ to lift the free end 7. A mass 3 is provided to be movable on it, so that a dynamic damper 1 is composed of the mass 3 and the damping spring 6. In the self-follow-up type resonance device, as vibration is inputted to the free end 7, the mass 3 moves to a balance point between centrifugal force F and gravitational force G downward. The resonance frequency of the dynamic damper 1 thus automatically follows up input vibration to change itself to correspond to the input vibration. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a self-tracking type resonance device which is a kind of a dynamic damper and is capable of automatically changing a resonance frequency according to input vibration.
[0002]
[Prior art]
2. Description of the Related Art A dynamic damper for damping vibration by combining a mass and a spring is known. In this dynamic damper, since the resonance frequency is fixed by the mass and the spring constant, it is also known to control the mass with an external force in order to change the resonance frequency according to the input vibration (Patent Document 1) 1).
There is also a vibration system in which a lever is provided, and a mass is provided at the tip of the lever to change its position (see Patent Document 2).
[0003]
[Patent Document 1] Japanese Patent Publication No. 6-1097 [Patent Document 2] Japanese Patent Publication No. 8-16497
[Problems to be solved by the invention]
By the way, the above-mentioned conventional example has an advantage that the resonance frequency can be made variable, but on the other hand, it becomes a large and complicated system for controlling the mass and is expensive. Therefore, it is desired to realize this with a relatively simple structure and at low cost, and the present invention aims to realize this demand.
[0005]
[Means for Solving the Problems]
Claim 1 according to the self-tracking type resonance device of the present application for solving the above-mentioned problem is a lever whose free end side is rotatably supported by a fulcrum, and a mass which is movably supported on the lever. A damping spring provided on the free end side of the lever, and by rotating the free end side of the lever by input vibration, a centrifugal force for moving the mass to the free end side and moving the mass to the fulcrum side are provided. The resonance frequency is automatically changed in accordance with the input vibration by applying a return force to move the mass to a balance point between the centrifugal force and the return force.
[0006]
A second aspect of the present invention is that, in the first aspect, the lever is lifted and inclined so that the free end side is higher than the fulcrum, and a force that causes the mass to slide down on the lever to the fulcrum side by gravity acts as a return force. Features.
[0007]
According to a third aspect of the present invention, in the first aspect, the lever is made horizontal, and the return force is forcibly generated by a spring or a magnetic force.
[0008]
【The invention's effect】
According to the first aspect, since the mass is balanced by the centrifugal force and the return force, when the lever rotates by the input vibration, the centrifugal force according to the rotation acts on the mass and moves to a balance point with the return force. I do. As a result, when the moment of the mass acting on the damping spring is replaced by the virtual mass located on the damping spring, the resonance frequency is determined by the equivalent mass and the spring constant of the damping spring. Changes due to the actual movement of the mass, so that the resonance frequency also changes. Therefore, the resonance frequency can be changed by moving the mass by the centrifugal force according to the input vibration, and a self-tracking type resonance device having a simple structure, small size and light weight can be obtained.
[0009]
According to the second aspect, by tilting the lever, the force due to gravity acting on the mass can be used as a return force, so that the structure is the simplest.
[0010]
According to the third aspect, since the lever is horizontal and the mass is forcibly moved by a spring or a magnetic force to provide the return force, the return force can be obtained with a relatively simple structure.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments will be described with reference to the drawings. 1 to 4 relate to the first embodiment, FIG. 1 is a schematic diagram of the entire apparatus, FIG. 2 is an explanatory diagram of the operation, FIG. 3 is a principle diagram using an equivalent mass, and FIG. FIG.
[0012]
In FIG. 1, the dynamic damper 1 includes a lever 2, a mass 3 supported on the lever 2 so as to be movable in the axial direction, a fulcrum 5 rotatably supporting one end of the lever 2 on a support portion 4, and a lever 2. And a damping spring 6 attached to the free end of the second damper. Reference numeral 7 denotes a free end, and reference numeral 8 denotes a support base of the dynamic damper 1.
[0013]
The lever 2 is made of a suitable material such as a round bar or the like, for example, having a low frictional surface. The lever 2 is attached to the support portion 4 so as to form an inclination angle θ with respect to a horizontal plane. It is higher than the fulcrum 5. In this example, a state in which the lever 2 forms the inclination angle θ is a basic state.
[0014]
The mass 3 is made of metal or the like and has an appropriate mass. For example, a through hole 9 is provided, and the lever 2 is passed through the through hole 9 so that the mass 3 can move on the lever 2 in the length direction. However, the support structure of the mass 3 by the lever 2 is not limited to the above, and can be arbitrarily set, such as a monorail type guide. The magnitude of the mass can be arbitrarily set according to the desired dynamic damper characteristics.
[0015]
The damping spring 6 suppresses the vertical movement at the free end of the lever 2, and its spring constant can be set arbitrarily according to the desired dynamic damper characteristic. The material is arbitrary such as metal or rubber, and the shape can be a coil spring or other various shapes.
[0016]
The dynamic damper 1 inputs vibration to the free end side and the like of the lever 2 and rotates the lever 2 up and down to produce a dynamic damper effect due to the interaction between the rotating mass 3 and the damping spring 6. Vibration is damped.
[0017]
The operation principle of the dynamic damper 1 will be described with reference to FIGS. The symbols and symbols used below are as follows. The length of the lever 2 is L, the mass of the mass 3 is m, the distance on the lever 2 from the fulcrum 5 to the mass 3 is r, the force of gravity acting on the mass 3 is G, the gravitational acceleration is g, and the centrifugal force is F. The velocity when the mass 3 vibrates is v, the angular velocity when the lever 2 rotates is ω, the amplitude is x ₀ , and the spring constant of the damping spring 6 is K.
[0018]
Here, the mass 3 on the lever 2 that is rotated by the input vibration is applied to the force G by the gravity to slide down on the lever 2 to the fulcrum 5 side, and the centrifugal force by the vibration causes the lever 2 to move on the lever 2 toward the free end 7. And acts to the opposite direction. The force G due to gravity is a return force. The values of centrifugal force and G are as follows.
[0019]
Centrifugal force F = mv ² / r = m (x ₀ ω) ² / r
Force due to gravity G = m · g · sin θ
When the mass 3 stops moving on the lever 2 at the balance point between the forces F and G in the opposite directions, F = G.
[0020]
Here, the equivalent mass M is defined by the simplified model shown in FIG. That is, the moment force acts on the damping spring 6 at the point at a distance L from the fulcrum 5, ie, at the free end 7, by the mass 3 located at a point r from the fulcrum 5 on the lever 2. The virtual mass on the damping spring that exerts a force due to gravity equal to
[0021]
In this dynamic damper system, the resonance frequency is
ω _n = (K / M) ^1/2 = {(K / m) (L / r)} ^1/2
From this, M = m · (r / L)
It becomes.
[0022]
Next, the behavior when the lever 2 rotates by vibration input will be described. When the lever 2 rotates at the vibration frequency due to the vibration input, a centrifugal force F corresponding to the vibration acts on the mass 3. Generally, as the frequency increases, the centrifugal force increases.
[0023]
Then, when the centrifugal force F increases and exceeds the force G due to gravity, the mass 3 moves on the lever 2 to the balance point. Assuming that the position on the lever 2 at this time is r, the resonance frequency ωn at that point is determined by the equivalent mass M at that time, and the equivalent mass M is also determined by m · (r / L). Therefore, the mass 3 moves according to the frequency of the input vibration, and the resonance frequency ωn of the dynamic damper 1 automatically changes.
[0024]
Further, since the equivalent mass M has a relationship of m · (r / L), the larger the r is, that is, the larger the mass moves toward the free end 7 closer to L, the larger it becomes. On the other hand, according to the above equation, the resonance frequency ωn becomes lower as the equivalent mass M increases. Therefore, when the frequency of the input vibration increases, the centrifugal force F increases, and the mass 3 moves on the lever 2 to the free end 7 side. Conversely, the resonance frequency ωn decreases due to the increase in the equivalent mass M.
[0025]
Furthermore, as shown in FIG. 4, the amplitude x ₀ of the general vibration decreases as increasing the frequency increases toward the resonance point, frequency increases past the resonance point.
[0026]
This means that the movement of the mass 3 on the lever 2 moves toward the free end 7 until the resonance frequency ωn is reached. However, when the mass 3 is further moved beyond the resonance frequency ωn, the equivalent mass M becomes too large and the resonance frequency ωn is increased. The centrifugal force F decreases because the amplitude decreases, and as a result, the centrifugal force returns to the resonance point. For this reason, the mass 3 is automatically moved in a balanced manner to a position substantially serving as a resonance point.
[0027]
That is, it means that the dynamic damper 1 automatically adjusts the resonance frequency according to the frequency of the input vibration. As a result, a self-tracking type resonance device having a simple structure, small size and light weight can be obtained. In addition, since gravity is used as the return force, the structure can be further simplified.
[0028]
FIG. 5 shows a second embodiment, in which a damper 10 is provided at the free end 7 in parallel with the damping spring 6. In this case, since the damping is performed by the damper 10, the vibration damping effect can be further increased.
[0029]
FIG. 6 shows a third embodiment in which a sliding resistor 11 made of viscous oil or the like is provided on the lever 2 or on the sliding portion of the mass 3 or on both sides thereof. Can be prevented from changing.
[0030]
7 and thereafter show an example in which the basic state of the lever 2 is horizontal and the return force is other than the force due to gravity. FIG. 7 shows a fourth embodiment in which the lever 2 cantilevered at the fulcrum 5 is leveled, the mass 3 is supported on the lever 2 movably in the axial direction, and the return spring 12 urges the fulcrum 5 toward the fulcrum 5. . Thereby, the return spring 12 applies the return force R to the mass 3. Except for this point, the resonance frequency can be automatically adjusted as in the previous embodiments. On the free end 7 side, the damping spring 6 may be used alone or in combination with the damper 10.
[0031]
FIG. 8 shows a fifth embodiment, in which magnets 13 and 14 are provided between the mass 3 and the free end 7 of the lever 2, and the sides facing each other have the same polarity. The magnet can be either a permanent magnet or an electromagnet. As a result, when the mass 3 approaches the free end 7, the magnets 13 and 14 repel with the same polarity and push the mass 3 back to the fulcrum 5 side by magnetic force. In this case, the magnetic force becomes the return force R.
[0032]
Note that a pair of magnets made of a combination of different poles may be arranged between the fulcrum 5 and the mass 3 so as to face each other, and the magnetic force may be used as the attraction force. In any of these cases, when the return force R is a magnetic force, the return force R is proportional to the square of the amount of displacement of the mass 3 on the lever 2, so that the movement to the resonance point can be performed quickly. .
[0033]
FIG. 9 shows a sixth embodiment, in which a fulcrum 5 is provided at an intermediate portion of the lever 2, a damping spring 6 is provided at one end of the lever 2, and the other end is a free end 7, between the fulcrum 5 and the free end 7. The mass 3 is supported movably in the axial direction, and is pulled toward the fulcrum 5 by a return spring 12.
[0034]
In this way, the magnitude of the equivalent mass M can be increased by the lever ratio with respect to the movement amount of the mass 3. The damper 10 can be used in combination with the damping spring 6. Further, this fulcrum structure can be applied to other embodiments including the first to third embodiments.
[0035]
FIG. 10 shows a seventh embodiment, in which the mass 3 is accommodated in a cylindrical body 15 in which an incompressible liquid is sealed, is slidable in the axial direction as a piston, and is moved by an orifice 16 provided in the mass 3. To allow liquid transfer between the two sides of the device.
[0036]
One end of the cylindrical body 15 is rotatably supported by the fulcrum 5, and a damping spring 6 and a damper 10 are provided on the free end 7 side of the other end. Also, a return spring 12 is provided as a return force between the end of the fulcrum 5 side of the cylinder 15 and the mass 3. Use of the damper 10 is optional.
[0037]
When vibration is input to the free end 7 and the cylinder 15 is rotated, the mass 3 moves within the cylinder 15 in accordance with the frequency of the input vibration. At this time, the mass 3 is attenuated by the orifice 16. Therefore, a resistance to the movement of the mass 3 is provided, and this resistance is at the orifice 16 and can be adjusted arbitrarily. The structure in which the mass 3 is accommodated in the cylindrical body 15 and the resistance is provided by the orifice 16 can be applied to the inclined support structure in the first to third embodiments.
[Brief description of the drawings]
FIG. 1 is a schematic view of an entire apparatus according to a first embodiment. FIG. 2 is an operation explanatory view according to the first embodiment. FIG. 3 is a principle diagram using an equivalent mass according to the first embodiment. FIG. 5 is a schematic diagram according to a second embodiment, FIG. 6 is a schematic diagram according to a third embodiment, FIG. 7 is a schematic diagram according to a fourth embodiment, FIG. 8 Schematic diagram of the fifth embodiment [FIG. 9] Schematic diagram of the sixth embodiment [FIG. 10] Schematic diagram of the seventh embodiment [Description of symbols] 1: Dynamic damper, 2: Lever, 3: Mass, 5: fulcrum, 6: damping spring, 7: free end, 10: damper, 11: return spring, 12: magnet, 13: magnet, 14: incompressible liquid, 15: cylindrical body, 16: orifice

Claims (3)

A lever rotatably supported on the free end side by a fulcrum, a mass movably supported on the lever, and a damping spring provided on the free end side of the lever;
By rotating the free end side of the lever by the input vibration, a centrifugal force for moving the mass to the free end side and a return force for moving the mass to the fulcrum side are given, and a balance point between the centrifugal force and the return force is given. A self-tracking type resonance apparatus characterized in that a resonance frequency is automatically changed in accordance with an input vibration by moving a mass. 2. The self-following type according to claim 1, wherein the lever is lifted and tilted so that the free end side is higher than a fulcrum, and a force is applied to the mass to slide down the lever on the fulcrum side by gravity to thereby provide a return force. Resonator. 2. The self-tracking resonance device according to claim 1, wherein the lever is horizontal, and the return force is forcibly generated by a spring or a magnetic force.

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