JPS6357654B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electromagnetic springs with remotely adjustable stiffness.

For example, to give an example of a spring for adjusting the natural frequency of a vibration detection pendulum (seismograph), the configuration of a conventional vibration detection pendulum having a magnetic circuit and a moving coil is as shown in Figure 1 A and B. .

In the figure, 1 is a vibrating mass, 2 is a suspension spring that supports it, 3 is a moving coil fixed to the vibrating mass 1, and a magnetic circuit consisting of a permanent magnet 4, a yoke 5, and a pole piece 6 is connected to a storage case 7. is fixed. When vibration is applied to this device, a relative movement occurs between the moving coil 3 and the radial magnetic field generated in the magnetic circuit air gap 8, and a voltage proportional to the speed of movement is generated across the moving coil 3.
By measuring this voltage, the amount of vibration applied can be determined.

The relative motion depends on the specifications mainly of the natural frequency of the pendulum system composed of the suspension spring 2 and the part supported by it (vibrating mass 1 + moving coil 3). Therefore, when it is necessary to adjust the natural frequency among the specifications to obtain a predetermined characteristic, conventionally, purely mechanical methods such as increasing or decreasing the vibrating mass 1 or adjusting the stiffness of the suspension spring 2 are used. In particular, remote adjustment requires a complicated mechanism, and the range of adjustable natural frequencies is also limited due to various mechanical conditions, such as size constraints.

The present invention eliminates these conventional drawbacks and uses an electromagnetic spring to adjust the natural frequency of the pendulum.One embodiment of the present invention will be described in detail below with reference to the drawings. .

FIG. 2 is a partially cutaway front view showing an embodiment in which the electromagnetic spring of the present invention is used in a vibration detection pendulum.
In the figure, reference numerals 9a and 9b denote a pair of stiffness adjustment coils, which are the same as in FIG. 1 except that they are arranged above and below the moving coil 3, and their explanation will be omitted. Third
The figure shows the relative positional relationship between each coil and the magnetic circuit air gap. If the relative displacement x between the magnetic circuit air gap 8 and each coil 3, 9a, 9b is x=0, that is, neutral, then In the case of >0, similarly indicates the case of x<0. In the figure, as the relative displacement x changes, the electromagnetic constant G, which is the sum of the products of the magnetic flux density B and the coil winding unit length dl ∫ ^l ₀ Bdl, remains almost unchanged in the moving coil 3. However, it is recognized from FIG. 3 that the stiffness adjustment coils 9a and 9b vary differentially with respect to each other. In addition, in FIG. 3, U is a strand fixed to the magnetic circuit in the direction in which each coil moves in the magnetic circuit air gap 8.

If the magnetic flux change rate dB/dU with respect to the coordinate U of the part where the stiffness adjustment coils 9a and 9b are located are constants Ca and Cb, and the total winding lengths of these coils are la and lb, respectively, then the electromagnetic constants Ga and Gb of these coils are is expressed as Ga=∫ ^la ₀ Bdl=∫ ^la ₀ Ba+Cax)dl=Bala+Calax Ga=∫ ^lb ₀ Bdl=∫ ^lb ₀ Bb+Cbx)dl=Bblb+Cblbx...(1). However, Ba and Bb are the average magnetic flux densities of the portions where the respective coils are located at x=0.

If currents i _a and i _b are supplied to each coil having such electromagnetic constants Ga and Gb, Fa=Gai _a = (Bala+Calax) i _a Fb=Gbi _b = (Bblb+Cblbx) i _b ...(2) Generates electromagnetic forces Fa and Fb. Now, if _{i a and} i _b are adjusted so that the following condition is satisfied, the sum F of each electromagnetic force is F = Fa + Fb = (Calaia + Cblbib) x (4). As is clear from equation (4), the electromagnetic force F is the restoring force of the electromagnetic spring with stiffness (Calai _a + Cblbi _b ), and is proportional to the relative displacement x. In addition, since the stiffness is a function of i _a and i _b , the parallel stiffness of the suspension spring 2 and the electromagnetic spring can be arbitrarily set by adjusting i _a and i _b , and as a result, the pendulum The natural frequency can be adjusted. Naturally, it is also possible to make the stiffness of the electromagnetic spring negative depending on the polarity of i _a and i _b .

Figure 4 shows the currents i _a and i _b in each coil in Figure 3.
is an example of a circuit that supplies two coils 9
A and 9b are connected to the DC power supply 20 in parallel, in series, and independently. In addition, variable resistor 2
1 and 22 are for adjusting the coil currents i _a and i _b ,
Further, a telephone key 23 is provided to switch the polarity of the currents i _a and i _b . In addition, in the series system of (),
In particular, if there is no need to adjust the balance of currents i _a and i _b , the variable resistor 22 is unnecessary and the adjustment coil 9
a and 9b may be wound with one continuous wire,
There is no need to separate in the middle and provide an intermediate tap.

It is also clear that the stiffness can be easily adjusted remotely by adjusting the currents i _a and i _b via the cables. Also, to simplify the explanation, the rate of change in magnetic flux density dB/dU = Ca (or Cb in short) was used as a constant, but Ca and Cb are complementary so that (Calai _a + Cblbi _b ) is kept constant. It's okay to change.

As explained above, the natural frequency of the pendulum system can be adjusted by adjusting the magnitude and polarity of the DC constant current flowing through the stiffness adjustment coils 9a and 9b. Therefore, it is possible to obtain a pendulum natural frequency regulator that has a wide adjustment range without being subject to mechanical constraints and that can be easily adjusted remotely, and that also converts vibrations caused by conventional magnetic circuits and moving coils into electrical signals. There are effects such as no loss of functionality.

Although the following embodiment describes a case where an electromagnetic spring is used in a vibration detection vibrator that senses a vertical component, the spring of the present invention can also be used in a vibration detection pendulum that senses a horizontal component. Of course it can be used. Furthermore, the configuration of the spring of the present invention is not limited to the configuration shown in FIG. 2; for example, the adjusting coils 9a and 9b may be arranged in the center of the moving coil 3 as shown in FIG. It's okay. Note that the same parts as in FIG. 2 are given the same reference numbers. Moreover, FIG. 6 shows the magnetic flux density distribution in the magnetic circuit of FIG. 5. That is, in the embodiment shown in FIG. 2, the directions of the currents i _a and i _b were set to have opposite polarities to each other in order to realize equation (3), but in the embodiment shown in FIG.
It is necessary to make the directions of i _a and i _b the same polarity. Therefore, in each circuit shown in FIG. 4, the coils are connected with their winding directions aligned. In each embodiment, the magnetic field is generated by a permanent magnet, but it may be generated by an electromagnet. Further, although the coil has been described as one that moves linearly, it may be a so-called rotary meter that moves around a rotation axis, such as a moving coil ammeter.

As explained in detail above, since the present invention configures an electromagnetic spring using a magnetic field and a coil,
Precise stiffness adjustment is possible, and it is highly effective when used in various measurement and indicating instruments that use springs, including spring scales and galvanometers for pen recorders.

[Brief explanation of drawings]

Fig. 1 shows a conventional pendulum for vibration detection having a magnetic circuit and a moving coil. A partially cutaway front view showing an embodiment used in a pendulum, Fig. 3 I shows the relative positional relationship between each coil and the magnetic circuit air gap, and Fig. 4 I shows the relative positional relationship between each coil and the magnetic circuit air gap, respectively. An embodiment of a circuit diagram for supplying current, FIG. 5 is another embodiment of the present invention, and A is a longitudinal sectional front view thereof;
FIG. 6 is a magnetic flux density distribution diagram in the magnetic circuit of FIG. 5. 1... Vibration mass, 2... Suspension spring,
3... Moving coil, 4... Permanent magnet, 5... Yoke, 6... Pole piece, 7... Storage case, 8
... Magnetic circuit air gap, 9a, 9b ... Stiffness adjustment coil, 20 ... DC power supply, 2
1, 22...variable resistor, 23...telephone key.

Claims (1)

[Claims] 1. The electromagnetic constant G, which is expressed as the sum of the products of the unit length dl of the conductor length l and the effective magnetic flux density B of the part where it is located, is as follows: G=∫ ^l ₀ Bdl=kx , an electromagnetic device that is a linear function of the relative displacement or relative angular displacement x between the conductor and the magnetic field, and a power supply circuit that can supply an arbitrarily adjustable DC constant current to the conductor. An electromagnetic spring. 2. A pair of magnetic circuits and a pair of mutually fixed coils that vibrate in linkage with the magnetic flux generated by the magnetic circuit so that the electromagnetic constant G differentially increases or decreases with respect to relative displacement or relative angular displacement x. An electromagnetic spring according to claim 1, comprising an electromagnetic device consisting of: