JPS604479B2 - electromagnetic pick-up device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic pickup for an electric piano, and more particularly to an electromagnetic pickup that eliminates the difference in relative vibration level between odd harmonics and even harmonics.

A pickup device that uses a vibrating piece as an electric piano to be struck from a slave, and a pickup arranged opposite to the vibrating piece electrically converts the mechanical vibration of the vibrating piece to extract an electrical output. are well known, and the structure of their electrodes and magnetic poles is shown in detail in, for example, US Pat. No. 3,038,363.

Generally speaking, there are two types of pickups: one that uses an electromagnetic pickup and one that uses a static pickup.The configuration of the electromagnetic pickup that is commonly used as an electromagnetic pickup is as shown in Figure 1. be.

That is, a plurality of vibrating pieces 2 corresponding to each scale are held cantilevered on a base 1 having a large mass formed approximately in a U-shape, and a suitable gap is arranged at the tip of the vibrating piece. A magnetic pole 3 is inserted into the central axis of a bobbin 4, a magnet S is attached to a counterbore 5 bored in the upper end of the bobbin 4 as shown in the figure, and a winding 8 is wound around L. The bobbin 4 is attached to the letter-shaped metal fitting 7.
is fixed and a metal fitting is fixed to the base 1, and by hitting the vibrating piece 2 with a hammer 9, the magnetic flux generated in the magnetic pole 3 due to the mechanical vibration of the vibrating piece 2 is cut off, and the zero vibration piece is attached to the winding. The equivalent circuit having the magnetic pole configuration shown in FIG. 1 is shown in FIG. If the axis misalignment (hereinafter referred to as deviation) between the magnetic pole 3 and the vibrating piece 2 is b, then when the tip of the vibrating piece vibrates in a sinusoidal wave with an amplitude A and a frequency 〆, the magnetic resistance R is R=k{120(b+A・cos2 bamboo t
)2}, and the magnetic flux J becomes J = vine, where F is the lotus magnetic force due to the permanent magnet 5.

The induced voltage in the winding 8 is e=-, where n is the number of turns in the winding.
It yields and exceeds the signal voltage of the wind type such as n. This signal voltage is the third
As shown in the figure, it is a periodic function with period T (=÷), but T/
2 becomes a waveform that is symmetrical at the center 'D', and To is given by the formula [2']. T when the deviation b approaches zero. = 壬, and the period is T/2, that is, the vibration waveform is twice the fundamental frequency.

The spectrum distribution of the waveform shown in FIG. 3 of an electromagnetic pickup having such a configuration is as shown in FIGS. 4A, B, and C.
That is, Fig. 4 A, B, and C show the harmonic order n on the machine axis and the relative vibration level on the vertical axis. FIG. 4B shows the spectral distribution when the deviation b is large, FIG. 4B shows the spectral distribution when the deviation b is small, and FIG. 4C shows the spectral distribution when the deviation b is zero.

The pitch (pitch) of an electric piano is determined by the basic and harmonic components of the spectral distribution shown in Figure 4 A to C based on the voltage waveform shown in Figure 3 (when the harmonic order is 1, the fundamental tone, 2, 3, etc.) ...
・Hereafter referred to as overtones) is determined by the intensity relationship. The pitch of a sound depends on the fundamental tone, which is the fundamental frequency, but even if the fundamental tone is absent, we can feel something corresponding to the fundamental tone as a difference tone of overtones. In the conventional electromagnetic pickup device, as shown in Fig. 4 A to C, the odd harmonic order components of harmonic order 1, 3, 5, etc. Therefore, in the case of Figure 4-A and B, the difference tone between even-order components (an octave corresponding to twice the frequency of the fundamental tone) is smaller than the difference tone between even-order components (the pitch of a sound equivalent to the fundamental tone). The pitch of the upper pitch) becomes very dark, and the so-called pitch becomes very uncertain. In the case of C in Figure 4, there is no odd-numbered component, so the sound sounds completely an octave higher than the conventional example in Figure 1. As mentioned above, there is a drawback that the pitch of the sound is very uncertain, which causes poor sound separation and a poor sense of pitch.

In order to eliminate the above-mentioned drawbacks, an electromagnetic pickup that detects changes in the magnetic flux of the vibrating element 2 only during a half cycle is also described in the above-mentioned US patent.

This configuration is as shown in FIG. 5, and the same parts as in FIG. The vibrating piece 2 is attached to the substrate 1 in a fixed manner as shown in the figure. FIG. 6 shows the voltage waveform extracted from the winding 8 by hitting the vibrating piece 2 with a hammer, and FIG. 7 shows its spectral distribution. The spectral distribution in this case is the opposite of that in Figure 4B, with the fundamental being the loudest, and the 2nd, 4th, 6th... harmonics being relatively smaller than the odd-numbered components. However, since there is always a fundamental tone, the element of uncertainty in pitch shown in FIG. 4 does not occur. However, as shown in the voltage waveform shown in Fig. 6, no voltage is generated in the half cycles between 0 and T/4 and between 3/4T and T, so the detection ability is extremely lost, and the
As shown in the figure, the form of the spectrum cannot be changed by adjusting the deviation b between the magnetic pole 3 and the vibrating element 2, resulting in a drawback that the sound is simple. Furthermore, the above-mentioned US patent discloses a pickup in which the mechanical vibration of the vibrating piece is detected as a change in capacitance by statically coupling between the vibrating piece 2 and the electrode 3, as shown in FIG. Reference numeral 3 shows a structure that follows the trajectory of the tip of the vibrating piece 2 when the vibrating piece 2 is hit with the hammer 9.

The signal waveform obtained by a pickup having such a configuration is shown in FIG. 9, and its spectral distribution is shown in FIG. 10.

As is clear from this spectral distribution, with such a spectral distribution, there will be no uncertainty in the pitch as described in FIG. 7. However, this electrode configuration is a static pickup method, and has the disadvantage that it exhibits a spectral distribution that gradually attenuates as it goes higher, similar to the spectral distribution shown in Figure 7 with an electromagnetic pickup, resulting in a simple sound. . In order to eliminate the above-mentioned drawbacks, the present invention prevents the absence of odd harmonics in an electromagnetic pickup without deteriorating detection efficiency, eliminates the difference in the relative vibration level between odd and even orders, and improves the sound quality. An object of the present invention is to provide an electromagnetic pickup device that can improve uncertainty in height and obtain a spectral distribution for obtaining good tone.

The present invention will be described in detail below with reference to FIG.

FIG. 11 shows the principle magnetic pole structure of the present invention, in which the shape of the magnetic pole 3 in FIG. 2 is changed from a point magnetic pole to a traverse magnetic pole having a length a. Letting A be the period of vibration of the single vibrating piece 2, the length a of the magnetic pole 3 is set so as to satisfy Expression 3. 0<
akuA……[31 In Fig. 11, the vibrating piece is hit by the hammer.
When free vibration (frequency N) begins at the position , a voltage expressed by the '41 formula is induced in the winding 8 during the period from to to the tip of the magnetic pole 2.

*Next, during the period from t to t2 when the oscillation becomes zero, no change in magnetic flux occurs, so the induced voltage becomes zero. (et, .about.ra=0) Next, during the period t8, which oscillates in the opposite direction from t2 and reaches the maximum oscillation A, a voltage shown in equation '51 is induced. The above vibrations are repeated in half a cycle, and the same changes are repeated in reverse to complete one cycle.

This voltage waveform is shown in FIG. I broke the first plate.
= o, t. = Australia C Satoshi - (nose), t2 = harm, t3 = sound, and has a point symmetry around T/2, that is, an odd function waveform.
The spectral distribution in this case is shown in FIG. In the case of a ratio, the length of the magnetic pole a can eliminate the level difference between the even-order component and the odd-order component shown in the third equation, and can exhibit a complicated distribution with peaks and valleys compared to FIGS. 4 and 7. can.

Since the waveforms of these distributions are odd functions, the harmonic amplitudes of these distributions can be obtained from the Fourier coefficients bn shown in the following equation. -bn,
=, Shizuku' sound e (t)●Sin (n-2 middle t) dtl...
...{6' In the spectral distribution shown in Figure 4, the integral interval of equation '6) is [0-T.

] and [T. -1] If we consider it separately, ±・lbnl = 1 sheep.
De e(t) Sin(n-2 怀Ha) dt+・ノde e(t)
‐Sin(n●2 Kano t) dtle(t) is from Figure 3 [
0-T.

] and [T. Since the waveforms between the two sides are opposite and almost symmetrical,
For example, when n = 1 (fundamental tone component), the integral value of the first term and the integral value of the second term in equation (7) have opposite polarities and are almost equal, so lb and l when n = 1 are It is very small, and when n=2, the integral value of the first term and the integral value of the second term are the same polarity and are almost equal, so lb2l produces the maximum amplitude bell, and the following spectral distribution as shown in Figure 4 follows. In addition, the spectral distribution of the subordinate shown in Fig. 7 has the 6th spectral distribution because the integral interval is
The formula is determined by the following 8th formula. Since the output voltage in this case has the waveform given in Figure 6, the integral value at that time is N=
When N=1, it is the maximum, and when N=2, it is small, resulting in a distribution as shown in FIG. In the case of the present invention, Equation 61 can be divided into integral intervals such as the following Equation '9'.

Sin (n・2 t) dtl・・・・・・・・・・・・
(91) The output voltage in this case is et.

~t, (t) is the '4' formula, and et2~8(t) is the {5' formula. The spectral distribution in FIG. 7 becomes as shown in FIG. 13 depending on the integral value of the term.

The integral value of the first term can be changed by selecting the voltage 0 or the magnetic pole size a shown in equation '4) within the range of equation '3}. As a result, the spectral distribution can be changed from the state shown in Figure 4 to the range shown in Figure 7, eliminating the level difference between relatively odd and even harmonic components as shown in Figure 13, and making the entire envelope have peaks and valleys. characteristics. As a result of the above, the uncertainty in the pitch due to the relative amplitude level difference between odd and even orders (Figure 4) is improved, and the simplicity of the timbre due to the simplicity of the envelope of the spectral distribution shown in Figure 7 is improved. It is possible to obtain a spectral distribution that produces a good tone.

An embodiment of the present invention based on the principle as described above will be described in detail with reference to FIGS. 14 to 16. Although the same parts as in FIG. 1 are given the same reference numerals and repeated explanations are omitted, FIG. 15 is a perspective view showing the state in which the vibrating element of the present invention is attached, and FIG. 14 is a side view. A weight 10 that determines the basic vibration frequency is added to the tip of the vibrating piece 2, and an L-shaped fitting 11 is arranged on the bobbin 4 along the upper protruding piece 7a of the L-shaped mounting fitting 7. Screw 1
2 allows the pickup to be adjusted vertically, and the screw 13 screwed into the lower projecting piece 7M of the L-shaped mounting bracket 7 adjusts the pickup horizontally. In addition, the magnetic pole 3 is held so as to maintain a gap 1 against the vibration of the vibrating piece 2, and its length a is selected as shown in formula '3'. In the perspective view of FIG. and an electromagnetic pickup are attached, and the maximum amplitude A of each vibrating piece decreases as the keys move from low to high, but in Fig. 14, the arc-shaped dimension a of the magnetic pole of the present invention is a/A for each key. It is arranged to decrease as the maximum amplitude A of the vibrating element decreases so that the relationship remains approximately constant. FIG. 16 shows an embodiment in which a conventional point magnetic pole 3 is used to bend the tip of the cantilevered vibrating piece 2 into an arc shape.

Assuming that the bending dimension is a, the gap between the cantilevered vibrating piece and the magnetic pole is constant during this period, and no change in magnetic flux occurs, making it possible to obtain the same effect as the above-described configuration. Also, the maximum amplitude A when hitting the vibrating piece with a hammer is due to the action structure of the keyboard.
The relationship between the maximum amplitude value A and the length a of the magnetic pole 3 of the electric piano (7 strength) of the present invention is as shown in FIG. It is.

The machine axis in Fig. 17 is the bass scale key number, the vertical axis is the amplitude, and the curve 14 represents the maximum amplitude A of each keyboard.
A stepped curve 15 represents the length a of the magnetic pole 3 added to each key. In particular, the maximum amplitude A of the vibrating element due to a lower key number, that is, a lower scale key, increases as the scale goes lower, and the length a of the magnetic pole increases in a stepwise manner as the scale goes lower.

It can be seen that the value of a/A also increases at an approximately constant rate as the scale goes lower. Conventional pickup devices adjust the timbre by moving the magnetic pole left and right to adjust the spectral distribution and changing the deviation for each key, but according to the present invention, the a/A is approximately constant as you move toward the lower notes. By setting the dimensions of the opposing magnetic poles so that they increase at the rate of You can get a great tone.

In addition, by appropriately selecting the magnetic pole dimension a within a range smaller than the vibration amplitude A in the spectral distribution of the sound source, the level difference between the even-order and even-order overtone components can be eliminated, and a spectral distribution with relatively complex peaks and valleys can be obtained. This has the effect of improving pitch uncertainty and obtaining good tones with good separation in each scale.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional pickup device, Fig. 2 is an equivalent circuit diagram of Fig. 1, Fig. 3 is a signal voltage waveform diagram of Fig. 1, and Fig. 4 A to C are signals of Fig. 3. Voltage spectrum distribution diagram, Figure 5 is a perspective view of a conventional pickup device, Figure 6 is a signal voltage waveform diagram of Figure 5, Figure 7 is a spectrum distribution diagram of Figure 6, and Figure 8 is a conventional pickup device. A perspective view of the device, FIG. 9 is a signal voltage waveform diagram of FIG. 8, FIG. 10 is a spectrum distribution diagram of FIG. 8, FIG. 11 is a principle diagram of the pick-up device of the present invention, and FIG. 12 is a diagram of FIG. 11. Signal voltage waveform diagram, 1st
3 is a spectral distribution diagram of FIG. 12, FIG. 14 is a side sectional view of one embodiment of the pickup diagonal of the present invention, FIG. 15 is a perspective view of FIG. 14, and FIG. 16 is a diagram of another embodiment of the present invention. FIG. 17 is a side sectional view showing the embodiment, and is a curve diagram showing the relationship between the length of the magnetic pole and the maximum vibration. 1 is a base, 2 is a vibrating piece, 3 is a magnetic pole, and 8 is a coil. Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 12Figure 13Figure 14Figure 16Figure 15Figure 17 figure

Claims (1)

[Scope of Claims] 1. A pick-up in which mechanical vibrations generated by attaching a vibrating piece to a base and hitting it with a hammer are extracted by an electromagnetic pickup that picks up the vibrating piece with an appropriate gap between the vibrating piece and the vibrating piece. In the device, with respect to the maximum amplitude A that occurs when the vibrating piece is struck, a dimension a of the magnetic pole that faces the magnetic pole during a part of the half cycle of the vibration of the vibrating piece is set such that 0.1A<a<
An electromagnetic pickup device characterized by:A. 2. Claim 1, in which the ratio a/A of the dimension a of the magnetic pole and the opposing magnetic pole to the maximum amplitude A of the vibrating element increases in an approximately constant relationship as one goes lower in the bass scale. The electromagnetic pickup device described in Section 1.