JPS63278587A - Impulse exciter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) This invention uses a striking body such as a hammer equipped with a load detector to determine the vibration response characteristics of a mechanical structure to an excitation force. The present invention relates to a device that applies an excitation force that has a clear relationship with an excitation frequency by striking a structure.

(Prior Art) There is a H transfer function J as a method for easily expressing the vibration characteristics of a mechanical structure. This is the acceleration that a mechanical structure exhibits in response to the excitation force when a unit magnitude of excitation force is applied to the mechanical structure at each frequency.

Vibration responses such as speed and amplitude are hailed.

Random vibration and sine wave sweep vibration are used for vibration.

There are impulse vibrations, step vibrations, etc., and each has its advantages and disadvantages, so they are selected depending on the target structure.

Among these, impulse vibration is vibration that is struck by an impulse hammer with a load sensor attached near the tip,
The excitation force is detected by a load sensor.

This method has the advantage that it is not necessary to set up a vibrator as in random excitation or sine wave sweep excitation, and there is no change in vibration characteristics caused by connection of the vibrator.

Therefore, impulse excitation is often used to excite small structures that have small mass and rigidity and are easily affected by the connection of an exciter.

(Problem to be solved by the invention) Impulse hammers strike manually, so
Difficult to control excitation frequency. In particular, it is extremely difficult to shorten the impact time and apply a high frequency excitation force due to the balance between the impact time and the required impact force. Impulse hammers are often used for small structures, and such small structures tend to have high natural frequencies, so the above-mentioned problems associated with impact are a drawback in applying impulse hammers to small structures. It had become. In addition, this manual hammering method can cause vibrations when the target structure is returned immediately after hitting the target structure, double hammering due to slow pullback of the hammer, and unstable hitting postures. This has the disadvantage that errors occur due to the inability to accurately hit the same position.

The present invention eliminates the above-mentioned drawbacks and provides an impulse excitation device that accurately applies high frequency excitation force to the target impact point, and that does not cause measurement problems such as double hammer. The purpose is to provide

(Means for Solving the Problems) This invention combines two types of elastic bodies with different natural frequencies, and a first elastic body with a lower natural frequency has a higher natural frequency at its own end. supporting the second elastic body of the
A striking part equipped with a load detector is provided at the free end of the second elastic body, and after giving a predetermined deflection in opposite directions to the first and second elastic bodies, the second elastic body is caused to vibrate with free damping. The first wave of freely damped vibration of the elastic body toward the test subject is applied with a short impact time and the required impact force to the desired position, and the first wave of free damped vibration of the first elastic body with a long period is applied to the test subject. The second and subsequent free damped vibrations of the second elastic body are superimposed on the first wave in the opposite direction, and the second wave and subsequent free damped vibrations prevent the subject from being hit by the second and subsequent free damped vibrations. It is intended to serve its purpose as a composition that keeps people away.

In other words, this impulse excitation device includes a first elastic body whose one end is fixed to a mounting mechanism for an arbitrary fixed object that is mechanically independent of the subject and installed near the subject; a force-applying culm connected to a support provided on the free end side of the elastic body via a shaft perpendicular to the deflection direction of the first elastic body; a second elastic body having a higher natural frequency than the body; a striking body fixed to the free end side of the second elastic body and equipped with a load detector; The holding body is provided with a holding part provided at the end portion to hook and hold the free end of the second elastic body.

In this configuration, when the force applied to the applying force in the direction of the subject causes the free end of the first elastic body to deflect in the direction of the subject through the support, the applied force The holder at the tip of the culm is rotated about the shaft body in a direction opposite to the subject, and the free end of the second elastic body held by the holder is deflected in the direction opposite to the subject. 1st and 2nd
When the free end of the second elastic body is deflected by a predetermined amount, the distance between the shaft body and the tip of the holding part where the free end of the second elastic body is hooked becomes The distance between the free end of the second elastic body, which is held and deflected, and the shaft body is exceeded, and the free end of the second elastic body comes off from the holding portion of the holding body. This free end starts moving toward the subject due to the freely damped vibration of the second elastic body, and the striking body strikes the subject for a short period of time during the first wave of the vibration.

(Function) Since this device is mechanically independent from the subject and is attached to any fixed object installed near the subject using an attachment mechanism, the vibrations caused by this device do not disturb the vibrations of the subject. In this installation, the force rod is connected through the shaft perpendicular to the direction of deflection of the first elastic body, so when force is applied to the force rod, the force is transferred to the second elastic body through the shaft and the support. 1
is applied to the first elastic body, giving a deflection to the first elastic body.

The support body also has a natural vibration higher than that of the first elastic body, and its free end is held by a holder provided at the end of the force application culm opposite to the force application side. The free end of the second elastic body is held by hooking the free end of the second elastic body on the holding part of the holding body, so that the first elastic body is held by applying force to the applied culm. When the second elastic body is deflected in the direction of the subject, the holder at the tip of the applying culm rotates around the axis in the opposite direction to the subject, and the second elastic body is deflected in the opposite direction to the subject. The deflection of is given. When the deflection of the first and second elastic bodies in opposite directions has reached a predetermined amount, the distance between the shaft body and the tip of the holding section where the free end of the second elastic body is hooked is such that the deflection is reduced. Since the distance between the given free end of the second elastic body and the shaft body is exceeded, in this state, the free end of the second elastic body comes off from the holding part of the holding body and the first and the second elastic body both start free damping vibrations in opposite directions. Second
The support body to which one end of the elastic body is fixed is provided at the free end of the first elastic body, so the free end of the second elastic body is @1
A vibration waveform is drawn that is a composite of the free damped vibration of the second elastic body and the free damped vibration of the second elastic body. Since the second elastic body has a higher natural frequency than the first elastic body, immediately after the free vibration of @1 and the second elastic body starts, the free end of the first elastic body moves in the opposite direction from the subject. The first of the freely damped vibrations of the second elastic body does not move much.
At the wave, the free end of the second elastic body reaches the vicinity of the subject, and the striking body provided at the free end strikes the subject. At the time when the free end of the second elastic body is brought near the subject in the second wave of free damped vibration of the second elastic body, the amplitude of the free end of the first elastic body in the direction opposite to the subject becomes sufficiently large. Therefore, no blow is applied to the subject after the second wave of the freely damped vibration of the second elastic body. When the free vibration of the first elastic body passes approximately half a period, the subject is struck again, but by this point the processing of the data obtained from the striking has been completed, or There is also attenuation of the amplitude of the free end of the second elastic body, so that there is no problem in measurement.

(Example) An example of the present invention is shown in FIG. A fixed object 2, which is not connected to the mechanical structure that is the subject 1, is provided near the subject 1, and a mounting mechanism 3 is fixed to this. One end of the first elastic body 4 is fixed to this attachment mechanism 3.

In this embodiment, the first elastic body 4 is a leaf spring forming a long cantilever beam, and is provided with a circular opening 5. A support 6 is attached to the free end of the first elastic body 4. One end of the second elastic body 7 is fixed to this support body 6. In this embodiment, the second elastic body 7 is also a leaf spring forming a cantilever, and is shorter in length than the first elastic body 4. A striking body 9 equipped with a load detector 8 is provided at the free end of the second elastic body 7,
The striking body 9 is inserted into the opening 5 of the first elastic body 4 and is configured to strike the subject 1. The natural frequency of the second elastic body 7 is set so that the half period of vibration at the natural frequency is approximately equal to the predetermined short impact time that the impacting body 9 gives to the subject 1. It should be an even number multiple of the second elastic body 7. In this embodiment, it is designed to be approximately 4 times as large.

The support body 6 is also provided with a bottle-shaped shaft body 10 perpendicular to the deflection direction of the first and second elastic bodies 4 and 7, and a force applying rod 11 is attached to the support body 6 via the shaft body 10. It is coupled so that it can rotate around 1°. A force is applied to the right part of this force applying rod 11 in the direction of the arrow, and the first elastic body 4 is applied via the support body 6.
Gives deflection to.

At the tip of the force-applying rod 11 opposite to the force-applying side, a holder 12 is attached to the force-applying rod in a direction substantially perpendicular to the force-applying rod 11, that is, in a direction parallel to the direction of deflection of the first and second elastic bodies 4 and 7. 11. A holding part 13 is formed as a chevron-shaped recess on the vertical edge of the holding body 12, and the free end of the second elastic body 7 is hooked and held by this holding part 13.

When a force is applied to the force rod 11 in the direction of the subject 1, the force is transmitted to the free end of the first elastic body 4 via the support 6, and as described above, the force is transmitted to the free end of the first elastic body 4. deflects in one direction of the subject. At the same time, the force applying rod 11 rotates clockwise around the shaft body 1o, and in conjunction with this, the holding portion 13 of the holding body 12 also rotates in the clockwise direction. Therefore, the second elastic body 7, whose one end is fixed to the support body 6 and whose free end is held by the holding part 13, bends in the opposite direction to the subject 1. FIG. 2 shows the reaction force Pl in the shaft body 10 when a force Po in the direction of the subject 1 is applied to the end of the force-applying rod 11 + the force applied to the free end of the second elastic body 7 via the holding part 13 P2゜First elastic body 4
and the bending moment acting on the second elastic body 7) M, , M,
FIG. 2 is a schematic diagram of this device showing the The reaction force P on the shaft body 10 is also a force applied to the free body of the first elastic body base 4. Also, α is the shaft body 1
0 and the end of the applying force side of the applying rod 11.

b is the length of the second elastic body 7, and C is the length of the first elastic body 4. The state of deflection due to these forces and moments is schematically shown in FIG. 3 (IL).

As will be explained later, by appropriately selecting the dimensions, elastic modulus, and mass of the first and second elastic bodies 4 and 7, as well as the mass of the object added to these elastic bodies, the first and second elastic bodies become It is possible to have the natural frequency of the above-mentioned conditions and to always give almost the same deflection. Therefore, when the deflection of the second elastic body 7 reaches a value that provides the required striking force by releasing the deflection, the holding part 13 moves the second elastic body 9 free as shown in FIG. 3(b). Make sure it comes off the edge. For this purpose, when the deflection of the second elastic body 7 reaches a required value, the distance between the shaft body 10 and the point where the free end of the second elastic body 7 of the holding part 13 is hooked will give the deflection. The dimensions are set so that the distance r,>l between the free end of the second elastic body 7 and the shaft body 10 exceeds the distance 1Iiz.

When the free end of the second elastic body 7 comes off the holding part 13, the application of force to the force applying rod 11 is also stopped, and the first elastic body 4 is also allowed to vibrate freely.

FIG. 4 shows the vibration of the free end of the second elastic body 7 after it comes off from the holding part 13 and the impact force applied to the subject 1. (cL) shows the vibration of the free ends of the first and second elastic bodies 4 and 7 with respect to their respective fixed ends, where the dotted line shows the vibration of the free end of the first elastic body 4, and the solid line is the vibration of the free end of the second elastic body 7. Both of the two vibrations are damped vibrations. (b) shows the vibration of the free end of the second elastic body 7 relative to the fixed end of the first elastic body 4, that is, the vibration of the striking body, and is a combination of the two vibrations in (α). There is. (b) may be considered as vibration to the subject 1. The free end of the second elastic body 7, which has a high natural frequency, reaches the subject 1 side in a short time, but the free end of the first elastic body 4, which has a low natural frequency, has not been displaced much at this point. Therefore, as shown in (b'), the movement of the free end of the second elastic body 7 causes the subject 1 to
As shown in (C), a short-time impact force obtained by the load detector 8 is applied. The second elastic body 7 remains even after the impact.
The free end of the first elastic body 4 continues to vibrate freely, but when the second wave approaches the subject 1, the free end of the first elastic body 4 has swung greatly toward the opposite side of the subject 1. will not be hit. After further time elapses, the first elastic body 4
When the free end of the second object approaches subject 1 again, the second
The amplitude of the free end of the elastic body 7 has been reduced from the beginning due to damping, and furthermore, since the ratio of the natural frequencies of the first and second elastic bodies 4 and 7 is approximately 1:4, 2 elastic body 7
The free end of the second
No blow occurs. Furthermore, even if a second blow occurs at this point, the measurement results will not be disturbed because the data acquisition and arithmetic processing for the first blow have already been completed.

Figure 5 shows the waveform of the striking force shown in Figure 4 (C) at high speed 7-
The vertical axis shows the magnitude of the excitation force with respect to the excitation frequency on the horizontal axis, analyzed using a Rie transform device. The upper limit frequency of the excitation force at which the transfer function can be determined with the necessary accuracy is the first zero point of the excitation force, 1 to 1.5 f (H2), and is given by f: □. Therefore, it can be seen that the shorter the impact time τ(, rgC), the higher the upper limit frequency f can be obtained. Shortening τ in this manner can be achieved by increasing the natural frequency of the second elastic body 7, as shown in FIG.

As described above, in this invention, since the free vibration of the elastic body is used to give a blow to the subject 1, it is possible to give a short time blow by selecting the natural frequency of the elastic body. There is no fear. It is also possible to strike a desired striking position any number of times with good reproducibility.

Here, conditions for making the deflections of the first and second elastic bodies substantially equal and for setting the ratio of the natural frequencies of these elastic bodies to a predetermined value will be described.

First, regarding the deflection, if the free end of the elastic body of the cantilever beam is the origin, the X axis is in the length direction, and the y axis is in the deflection direction, the deflection at the free end is given by: Here, M is the moment acting on the beam,]
! X is Young's modulus, and x is the moment of inertia of area.

K = E.

k=k, and for the second elastic body, M=M2=7Pof (see Figure 2)K
= to 2 engineering = engineering.

Considering that, equation (1) is solved to find the deflection of the free ends of the first and second elastic bodies yot t yot . Therefore 1ffol= 1ffot l
This is a condition that makes the deflections of the first and second elastic bodies equal.

On the other hand, the natural frequency is derived by treating the cantilever beam as a simple vibration system consisting of a mass and a spring.

The length of the beam is l, and when a load W is applied to the free end; 0), the deflection y from the free end at the point Solving it gives us the following:

Here η. is the deflection of the free end is given by

Therefore, the vibration velocity i of the free end is given by (5). If the mass per unit length of the beam is ρ, then the dx detailed mass at 5 points on the beam is ρdt, so the kinetic energy El) of the beam is calculated by the mass added to the beam, which is concentrated at the free end. Considering this, the kinetic energy of the entire beam is = (S □ρ
t) η0 Here, 采′ is the mass of the beam. In other words, the beam vibrates in the same way as if it had a mass of -a=nh+u- at its free end.

The vibration period T at this time is given by T:zπ5nf7(9). δzt is the deflection of the free end when the free end is given a positive sign, and is expressed as W=mg g in equation (6), and therefore the vibration period T is given by. In the first elastic body, 11. .

l;a, lbc, E=ni,, koi:ko, and in the second elastic body, chicken:)1%9; chicken;, l=b, ni2Et
+ Engineering = Engineering.

becomes. Therefore, the natural frequency of the second elastic body is given by.

Therefore, equations (4) and (12) indicate that the first and second elastic bodies have equal deflection in response to an applied force, and that the natural frequency of the second elastic body is equal to that of the first elastic body. This is the condition for doubling the amount.

Further, if it is desired to give the first and second elastic bodies 4 and 7 a deflection of a certain ratio μ, the condition can be set as 1ffo+l=μ1ffHl.

FIG. 6 shows another embodiment of the invention. In this embodiment, the support 16 at the free end of the first elastic body 14 is provided on the subject 1 side, and the second elastic body 16 is provided at the position closest to the subject 1.
An elastic body 7 is fixed. In this embodiment, since no opening is provided in the first elastic body 14, there is an advantage that the conditions regarding the deflection and natural frequency of the first elastic body 14 can be accurately calculated.

FIG. 7 schematically shows a third embodiment of the present invention, in which the first elastic body z4 and the second elastic body 27 are both constructed of coil springs. In this example,
One end of the first elastic body 24 is fixed on the mounting mechanism 23, and the stepped member 21 and the support member 2 above it are attached to the free end of the first elastic body 24.
A support body 26 consisting of 2 is provided, and one end of a second elastic body 27 is fixed to a location one step below the stepped member z1. A force applying culm 11 having a holder 12 at its tip is connected to the support member 26 on the coil axis of the first elastic body 24 via the shaft body 10 . A striking body 9 equipped with a load detector 8 is fixed to the free end of the second elastic body 27 via a support rod 25 that extends through the inside of the coil spring.

A stop member 28 is provided at the free end of the second elastic body 27 and constitutes a part of the free end. Holding part 1 of holding body 12
The second elastic body 27 is held by hooking this stopper member 28 on the second elastic body 27 to give it deflection in the opposite direction to the subject 1.

In this configuration, @1 and the second elastic bodies 24 and 27 are both made of coil springs, which has the advantage of making the whole structure compact. Also, since the coil springs are used, the linearity of applied force and deflection is excellent. There is.

In each of the above embodiments, the holding part 13 of the holding body 12 was formed with a chevron-shaped recess, but a protrusion is provided on the edge of the holding body parallel to the direction of deflection of the elastic body, and this protrusion is Alternatively, the free end of the second elastic body may be held by the second elastic member.

(Effects of the Invention) In the present invention, since the freely damped vibration of the elastic body is used to apply a blow to the subject, a short-time blow containing a high frequency component can be applied with good reproducibility. It is also possible to adjust the frequency characteristics of the vibration by selecting the elastic body and adjusting the attached mass.

In addition, two types of elastic bodies with different natural frequencies are assembled and interlaced so that the vibrations of a high frequency are superimposed on the vibrations of a low frequency, so that the next blow after a -th blow will not occur. This will prevent the double hammer from occurring, or even if it does occur, it will occur after a sufficient amount of time has elapsed so that it will not cause any trouble, so that inconvenient double hammers can be avoided.

Furthermore, since the entire device is made into a device and attached to a fixed object, the positional relationship between the subject and the striking object can be set accurately.
It becomes easy to strike a target position of a very small structure with accuracy and good position repeatability.

As described above, the impulse excitation device according to the present invention is particularly effective for small-sized subjects that are difficult to excite by this type of impact.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram showing force and moment in the embodiment, Fig. 3 is a schematic diagram showing the operation of the embodiment of the invention, and Fig. 4 is a schematic diagram showing the operation of the embodiment of the invention. A graph showing the vibration and impact force waveforms of the free end of each elastic body and the impacting body in the embodiment of the invention, FIG. 5 is a graph showing the frequency characteristics of the excitation force, and FIGS. 6 and 7 are each of the present invention. It is a block diagram which shows a different Example. 1: Subject, 2: Fixed object, 3, 23: Mounting mechanism,
4.14.24: First elastic body, 6.16°26
: Support body, 7.27: Second elastic body, 8: Load detector,
9.; Impacting body, 1o: Shaft body, 11: Loading frame, 12: Holding body, 13: Holding portion. r'+q^fFJヱ1 Yamaguchi Jl: ,
,・\--/' [Figure 1 Figure 2 Figure 4 Figure 5. Figure 6 Figure 7

Claims (1)

[Claims] 1) In a device that applies an excitation force with a clear frequency characteristic of excitation to a subject by striking the subject with a striking body equipped with a load detector, A first elastic body having one end fixed to a mounting mechanism for an arbitrary fixed object installed near the subject independently, and a first elastic body attached to a support provided on the free end side of the first elastic body. a force-applying rod coupled via a shaft perpendicular to the direction of deflection of the elastic body; a second elastic body having one end fixed to the support body and having a higher natural frequency than the first elastic body; a striking body fixed to the free end side of the second elastic body and provided with a load detector; and a striking body provided at the end of the force application side of the force application rod for hooking the free end of the second elastic body. a holding body formed with a holding part for holding the first elastic body, and the force applied to the force rod in the direction of the subject causes the free end of the first elastic body to deflect in the direction of the subject through the support body. At the same time, the holder at the tip of the force applying rod is rotated around the shaft body in a direction opposite to the subject, and the free end of the second elastic body held by the holder is deflected in the opposite direction to the subject. , in a state where a predetermined amount of deflection is applied to the free ends of the first and second elastic bodies, the free ends of the second elastic bodies are detached from the holding part of the holding body, and the first wave of the free damped vibration is An impulse vibration device characterized by applying a short-time impact to the subject. 2) An impulse vibration device according to claim 1, wherein the first elastic body is a leaf spring. 3) An impulse vibration device according to claim 1, wherein the first elastic body is a coil spring. 4) An impulse vibration device according to any one of claims 1, 2, and 3, wherein the second elastic body is a leaf spring. 5) An impulse vibration device according to any one of claims 1, 2, and 3, characterized in that the second elastic body is a coil spring. 6) In the device according to any one of claims 1 to 5, the natural frequency of the second elastic body is the first
An impulse excitation device characterized in that the vibration frequency is approximately an even number multiple of the natural frequency of an elastic body. 7) In the device according to any one of claims 1 to 6, the holding part is a chevron-shaped recess formed on the edge of the holding body parallel to the deflection direction of the second elastic body. An impulse excitation device characterized by: 8) In the device according to any one of claims 1 to 7, it is provided that the holding part is a protrusion provided on the edge of the holding body parallel to the deflection direction of the second elastic body. Characteristic impulse excitation device.