JPH025388Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an electromagnetic damping device that is effective as a damping means for a mechanical system having moving parts.
More specifically, the present invention relates to an electromagnetic damping device that can replace oil damping devices conventionally used in electronic scales and the like.

(Prior Art) An electronic scale is designed to place an object to be measured on a saucer, electrically measure the displacement of a beam coupled to the tray, and measure the weight of the object.

In this case, a damping device is attached to the beam so that the displacement of the beam quickly settles into a position corresponding to the weight.

Conventionally, oil damping devices have been used in such electronic scales, but oil damping devices have the disadvantage of being difficult to use in high-precision electronic scales because the viscosity of the oil changes depending on factors such as temperature. Ta.

Therefore, an electromagnetic damping device using an electrical method has been proposed. This electromagnetic damping device is equipped with a detection means for detecting displacement, velocity, acceleration, etc. of the beam in a part of the beam, and after amplifying the signal from this detection means, it is coupled to the beam at a location separate from the detection means. The beam is fed back to the force coil of the force motor, which is running, and the force generated by the force motor applies damping to the beam.

(Problem to be solved by the invention) However, in the conventional electromagnetic damping device with such a configuration, a detection means for detecting the point of application of the force due to the feedback generated by the force motor and the movement of the beam is attached. There is a problem that the system becomes unstable because the locations are different.

The present invention was devised in view of these problems, and its purpose is to realize an electromagnetic damping device that has a simple configuration and operates stably.

(Means for Solving the Problems) The configuration of the present invention for solving the above-mentioned problems includes a force motor comprising a braking coil coupled to a beam to be braked and a magnet applying a magnetic field to the braking coil. In electromagnetic damping devices,
A speed detection coil is provided in the braking coil so as to be coupled to the beam at the same point as the braking coil, and the signal from the speed detection coil is amplified by an amplifier and then negatively fed back to the braking coil. be.

(Operation) When the beam moves, the detection coil moves in the magnetic field, which generates an induced voltage, which is amplified by an amplifier and applied to the braking coil.
This signal generates a braking force in the braking coil that increases damping with respect to the beam motion displacement x.

(Example) FIG. 1 is a conceptual diagram of the configuration of an apparatus related to the present invention. In the figure, 1 is the beam, 10 is the beam 1
The fulcrum, 2, indicates a spring connected to one end of the beam 1. 3 is a force motor connected to the other end of the beam 1, which is connected to a permanent magnet 31, a yoke 32, and the beam at the same point with the same diameter and moves together so as to cut the magnetic flux generated by the permanent magnet 31. It consists of a detection coil 41 and a braking coil 42.

FIG. 2 is an electrical circuit diagram of this device, in which a detection coil 41 is connected to the input end of an operational amplifier 43, and a braking coil 42 is connected to the output end of the operational amplifier 43. 44 is a detection coil 41 and a braking coil 4
It is a low resistor connected between the common connection point of 2 and ground.

Next, the operation of the apparatus configured as described above will be explained with reference to the operation explanatory diagram of FIG. 3.

In FIG. 3, an external force F, such as a weight to be measured, is applied to the position of the beam 1 on the spring 2, and the beam 1 is displaced θ (displacement amount due to the external force F) about the fulcrum 10 as shown by the broken line. x), at this time, the detection coil 41 and the braking coil 42 coupled to the beam are connected to the permanent magnet 31.
As each of these moves across the magnetic field, an induced voltage is generated in each of them. The voltage induced in the detection coil 41 is amplified by an amplifier 43,
Negative feedback is provided to the braking coil 42. If the current flowing from the amplifier 43 to the braking coil 42 is i, then equation (1) holds true.

I _M d ² θ/dt ² +C′dθ/dt+B ₂・θ・k+B・li=F
・B...(1) However, B: In the beam 1, the distance between the fulcrum 10 and the point where the external force F is applied, and the distance between the fulcrum 10 and the connection point between the detection coil 41 and the braking coil 42 of the force motor 3 I _M : Rotational inertia of the beam C': Friction constant due to air in the movable parts including the beam 1, the detection coil 41, and the braking coil 42 k: Equivalent spring constant of the spring l: The number of turns n of the braking coil, and the magnetic flux Φ due to the permanent magnet 31. Divide both sides of equation (1) by B to obtain equation (2).

I _M /B・d ² θ/dt ² +C′/B・dθ/dt+B・θ・k
+li=F...(2) In formula (2), θ is a minute angle, and if we set θ=x/B (where x is the displacement of the point of application of external force F and the connection point of braking coil 42), d ² θ/dt ² = 1/B d ² x/
dt ² , dθ/dt=1/B dx/dt, and by substituting this into equation (2), equation (3) is obtained.

I _M ／B ² d ² x／dt ² ＋C′／B ² dx／dt＋kx＋li＝F…(
3) In equation (3), I _M /B ² is the equivalent mass m of the moving part
And, if C'/B ² is represented by the viscosity constant C of the fluid surrounding the moving part, then equation (3) yields an equation of motion like equation (4).

md ² x/dt ² +Cdx/dt+kx+l・i=F...(4) On the other hand, the voltage V _C induced in the detection coil 41 is:
Equation (5) is obtained.

V _C = n・Φ・dx/dt …(5) Where, n: Number of turns of the detection coil 41 Φ: Magnetic flux cut by the detection coil when the detection coil 41 is displaced by unit length When formula (5) is converted to Laplace, (6 ) formula is obtained.

V _C =n・Φ・S・x…(6) This voltage V _C is amplified by the negative feedback amplifier 43,
It is applied to the braking coil 42. Negative feedback amplifier 43
If the mutual inductance of the detection coils 41 and 42 is M and the resistance value of the resistor 44 is R, the feedback rate β is β=M/R・S, so the current i flowing through the control coil 42 is (7) It is expressed by the formula.

i=n・Φ・x・S/R・1/1+M/R・S…(7)
In equation (7), if 1≫M/R, equation (7) becomes as shown in equation (8).

i=nΦx.S/R (8) On the other hand, when formula (4) is Laplace transformed, formula (9) is obtained.

mS ² x+CSx+kx+li=F(S)...(9) By substituting equation (8) into equation (9), equation (10) is obtained.

x{mS ² + (C+l・nΦ/R)s+k}=F(S)...(10) In equation (10), the constant l corresponds to the product of the number of turns n of the detection coil 41 and the magnetic flux Φ, so l = nΦ, the displacement x can be expressed as (11).

x=F(S)/mS ² +{C+(nφ) ² /R}S+k…(
11) The damping constant when no braking is applied is ξ ₀₁ as shown in equation (12) according to vibration engineering theory.

Also, from equations (11) and (12), the damping constant ξ when braking is applied is as shown in equation (13).

ξ=ξ ₀₁・{1+(nΦ) ² /C・R} …(13) As is clear from equation (13), the damping constant ξ can be adjusted arbitrarily by changing the value of the resistor R. , a large damping effect can be obtained.

Therefore, in FIG. 1, the braking force due to the current flowing through the braking coil 42 of the force motor 3 acts to increase damping against the motion displacement x of the beam 1. Therefore, the vibration of the beam 1 that occurs when the external force F is applied to the beam 1 can be effectively suppressed.

(Effects of the invention) As explained above, according to the invention, a detection coil is attached to the braking coil, and the signal from this speed detection coil is amplified and negatively fed back to the braking coil. It is easy to configure and
Furthermore, since the beam displacement detection means and the braking coil are coupled to the beam 1 at the same point, an electromagnetic damping device with stable operation can be realized.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the configuration of the device according to the present invention, Figure 2
The figure is an electric circuit diagram, and FIG. 3 is an operation explanatory diagram. 1...beam, 2...spring, 3...force motor,
41...detection coil, 42...braking coil, 43...amplifier, R...resistance.

Claims (1)

[Scope of utility model registration request] In an electromagnetic damping device equipped with a force motor consisting of a braking coil coupled to a beam to be damped and a magnet providing a magnetic field to this braking coil,
a speed detection coil coupled to the beam at the same point as the braking coil; an amplifier that amplifies the signal from the speed detection coil and negative feedback of the output signal to the braking coil; and a common connection between the braking coil and the detection coil. An electromagnetic damping device with a resistor connected between the connection point and ground.