JPH11237255A - Magnetic bubble detecting method and r.p.m. detector employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect magnetic bubble stably over a wide range by driving a read coil through an H bridge circuit and varying the duty ratio of a control signal to cancel the field from a ring magnet thereby separating a detection signal from noise components. SOLUTION: Switching circuits 22-25, 28-31 of H bridge circuits 200, 201 are turned on/off with control signals 100-107 from a control circuit 34 and the current waveform of an Hy direction read coil 32 aligned with the center line of a ring magnet in the plane of a magnetic bubble element at the time of CW AND CCW, and the current waveform of an Hx direction read coil 26 orthogonal to the Hy direction are obtained. Offset components in Hx and Hy directions are added by varying the duty ration of the control signals 100-107 to cancel the field from the ring magnet. According to the arrangement, a magnetic bubble detection signal can be separated from noise using H bridge circuits 200, 201 and the magnetic bubble can be detected stably over a wide signal width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bubble detecting method, and more particularly to a magnetic bubble detecting method for separating a magnetic bubble detecting signal and noise to obtain a stable and wide magnetic bubble detecting signal.

[0002]

2. Description of the Related Art The principle of a rotational speed detector using a magnetic bubble is widely known, but the outline will be described here. Figure 66
Fig. 6 is a diagram showing the operating principle of a rotational speed detector using a magnetic bubble.
7 is a pattern diagram of a transfer element loop formed on the magnetic bubble element of FIG. 66, and FIG. 68 is an enlarged view of a stretcher portion of the transfer element loop of FIG.

In FIG. 66, a magnetic bubble element 1 is made of a material that generates magnetic bubbles. If you add a description,
Magnetic bubbles are generated in a cylindrical shape in a perpendicular magnetic film epitaxially grown by several μm on GGG (gadolinium-gallium-garnet) by applying a perpendicular magnetic field having an appropriate strength. The magnetic bubble element 1 includes magnetic bubble detection elements 12 and 13 and aluminum wiring patterns 14,
15 and 16 are formed (see FIG. 68). Each of the magnetic bubble detection elements 12 and 13 is constituted by a magnetoresistive element (for example, permalloy). Further, a transfer element 11 made of a thin-film permalloy is formed in the magnetic bubble element 1 in a loop shape, and the magnetic bubbles are transferred along the loop (FIG. 6).
7, see FIG. 68). FIG. 67 shows one transfer element loop, but a plurality of transfer element loops are provided on the actual magnetic bubble element 1. Magnetic bubbles are written in each transfer element loop in a bit pattern of a memory wheel. The plane on which the magnetic bubble element 1 is arranged is called an xy plane for convenience.

A pair of bias magnets 2, 2 '(FIG. 66)
2) has a function of applying a constant bias magnetic field perpendicular to the magnetic bubble element 1 and maintaining a bubble-like magnetic domain. The read coils 3 and 4 are arranged around the magnetic bubble element 1 as shown in FIG. The read coils 3 and 4 are used when reading the cumulative number of rotations of the rotating shaft to which the ring magnet 5 is fixed. The read coils 3 and 4 generate a rotating magnetic field by flowing an alternating current, and generate magnetic bubbles 17, 18 and 19.
To transfer.

[0005] The ring magnet 5 is a permanent magnet mounted on a rotating shaft (not shown). The ring magnet 5 applies a parallel in-plane magnetic field to the magnetic bubble element 1, and the in-plane magnetic field is rotated by the rotation of the rotating shaft. The magnetic bubble circulates around the transfer element loop with one transfer element / one rotating magnetic field. FIG. 66 shows an example of a ring magnet magnetized to eight poles.
When rotated, the magnetic bubbles move four transfer elements 11.

In each transfer element loop shown in FIG. 67, magnetic bubbles of a special arrangement pattern based on the "principle of the memory wheel" are written. The special arrangement pattern is a pattern having a characteristic that a continuous bit pattern cut out from a certain position in all bit patterns is not the same as a pattern having the same number of bits cut out from another position. Therefore, by reading a pattern of several consecutive bits from a certain fixed position, the rotation shift amount of the loop can be known.

[0007] Magnetic bubbles are detected by the magnetic bubble detector 10 arranged at the certain position. The magnetic bubble detector 10 includes magnetic bubble detection elements 12 and 13 shown in FIG. The magnetic bubble detection elements 12 and 13 include:
A constant current is previously passed through the aluminum wiring patterns 14, 15, 16 (the aluminum wiring pattern 16 is at ground potential). When the magnetic bubbles 17, 18, 19 move to the magnetic bubble detecting elements 12, 13, the resistance value changes, so that the potential of the aluminum wiring patterns 14, 15 changes. The potential signal of the two wiring patterns 14 and 15 is subjected to a differential operation by a differential amplifier (not shown) to obtain a magnetic bubble detection signal.

In the magnetic bubble element 1 as described above,
On the transfer element loop, for example, a bit pattern (01110100) of 8 bits per loop determined by the “principle of the memory wheel” is formed depending on the presence or absence of a magnetic bubble. In the embodiment shown in FIG. 67, there are more bits (for example, around 49 bits), but here, 8 bits will be described for easy understanding. When the ring magnet 5 rotates, the 8-bit bit pattern circulates on the transfer element loop according to the rotation. This circulating operation is performed normally even when the apparatus in FIG. 66 is in a power outage state.

For example, if the ring magnet 5 rotates ten times while the power supply of the rotation speed detector shown in FIG. 66 is stopped and its operation is stopped in an electronic circuit, the 8-bit data is stored at a position corresponding to the ten rotations. The magnetic bubbles in the pattern are moving. When the power is restored, the read coils 3 and 4 are operated to measure the number of rotations of the ring magnet to generate a rotating magnetic field, and the position of the magnetic bubble is sequentially moved by, for example, three transfer elements. Therefore, three time-series bit patterns are read from the magnetic bubble detector 10, and from this pattern, the cumulative number of rotations of the ring magnet 5 can be known from the "memory wheel principle". After detection, the read coils 3 and 4 apply a rotating magnetic field in the opposite direction to the magnetic bubble element 1 to move the magnetic bubbles by three transfer elements and return to the original position.

As described above, unless the magnetic bubble once transferred to read the cumulative rotational speed of the rotary shaft is returned to the position where the magnetic bubble is located, the cumulative value is added to the cumulative rotational speed of the rotary shaft to obtain an accurate cumulative rotational speed. Is no longer possible.

Here, when the read coils 3 and 4 are operated, the magnetic field HM generated by the read coils 3 and 4 and the magnetic field HR generated by the ring magnet 5 are superimposed, and the magnetic bubble detecting elements 12 and 13 is added. And
In a region in which the vector direction of the magnetic field HR of the ring magnet 5 and the vector direction of the magnetic field HM of the read coils 3 and 4 are in the same direction, the magnetic bubble detecting elements 12 and 13 made of permalloy are magnetically saturated and magnetic bubbles are generated. 17, 18, 19
However, there is a problem that the data cannot be detected.

These will be described with reference to FIGS. 69 and E. In order to transfer the magnetic bubbles 17, 18, 19,
It is necessary to apply, for example, 40 gauss or more as an in-plane magnetic field. Assuming that the magnetic field HR generated by the ring magnet 5 is 40 gauss, the vector locus of the small circle in FIG. 69 is obtained by rotating the ring magnet 5 attached to the shaft. When the ring magnet 5 stops at the angle of the vector OA and the reading coils 3 and 4 measure the cumulative number of rotations of the ring magnet 5, the rotating magnetic field (for example, HM
(= 90 Gauss) is a great circle centered on the point A (see FIG. 69). That is, when viewed from the origin 0,
The vector sum OB varies between 50 and 130 Gauss.

On the other hand, the magnetic field-resistance change characteristics of the magnetic bubble detection elements 12 and 13 are as shown in FIG. 70, and the resistance change is saturated at about 60 gauss. When the magnetic bubble is arranged so as to be detected when the vector sum is directed to the OC in FIG. 69, the magnetic bubble detecting elements 12 and 13 are saturated (60 Gauss or more in FIG.
The magnetic flux of 8, 19 cannot be detected.

In view of such a point, the present applicant has solved the problem by applying for Japanese Utility Model Application No. 62-126991. This prior application uses a Hall element to detect magnetism, or directly measures the angle of a ring magnet, and calculates the detected magnetic field, or the magnetic field generated by the ring magnet based on the angle, and calculates the magnetic field generated by the ring magnet. The x and y components of HR are measured, and DC currents Hx offset and Hy offset for canceling the magnetic field HR are superimposed on the read coils 3 and 4. FIG. 71 shows the ring magnet 5 of this prior application.
FIG. 2 is a perspective view showing a positional relationship among the Hall elements 20, 21 and the magnetic bubble element 1. Here, X of the magnetic bubble element 1
The X-axis Hall element 20 for measuring the axial magnetic field (magnetic field generated by the ring magnet 5) is arranged so as to coincide with the coordinate axis X direction, and the Y-axis Hall element 21 is arranged so as to coincide with the coordinate axis Y direction. FIG. 72 is a configuration diagram showing a circuit configuration for generating DC current Hx offset and Hy offset. With such a configuration, the magnetic field from the ring magnet on the magnetic bubble element is canceled by the DC current Hx offset and the Hy offset.

The magnetic bubbles are detected by the magnetic bubble detecting elements 12 and 13, and a detection signal as shown in FIG. 73 is obtained. In this case, in order to easily read magnetic bubbles, it is necessary that the S / N of the detection signal is good and the width of the detection signal is wide.

[0016]

However, noise is superimposed on the detection signal as shown in FIG. This noise is switching noise (called Barkhausen noise) generated by the magnetic bubble detection element itself, and cannot be eliminated. This Barkhausen noise is shown in FIG.
As shown in (1), when a magnetic field oscillating in the Hy direction, which should have no sensitivity, is generated at a constant Hy value. That is, the fall of the detection signal (FIG. 73) is advanced and S /
It is this Barkhausen noise that makes N worse.

In the sensitivity curve of the magnetic bubble detecting element in the Hx direction, there is a dead zone as shown in FIG. 75 (same scale as FIG. 74). Therefore, the detection signal is not output unless the magnetic field in the Hx direction becomes large to some extent. It is this dead zone that delays the rise of the detection signal and narrows the width of the detection signal.

For the reasons described above, in the magnetic bubble reading using the rotating magnetic field symmetrical to the origin, when a disturbance magnetic field is applied, stable magnetic bubble reading cannot be performed due to the deterioration of S / N and the phenomenon of the signal width. There was a case.

The improvement of the magnetic bubble signal is described in Japanese Patent Application No.
However, since a triangular wave or a sine wave is used for the shape of the read drive waveform,
In a read driving waveform using an H-type bridge circuit which is well known in a magnetic bubble memory or the like, an offset method for improving a magnetic bubble signal is different.

That is, although the conventional drive waveform for magnetic bubble reading is "diamond-shaped," an H-type bridge circuit capable of reducing the number of components of the drive circuit is employed due to demands for cost reduction and miniaturization. In such a case, the drive waveform is distorted and is no longer "diamond-shaped." Due to this change, the magnetic bubble signal shifts back and forth, and when the pulse width of the magnetic bubble signal is small, the magnetic bubble signal is crushed.

Here, Lissajous waveform due to an ideal triangular wave current or magnetic field having a phase difference of 90 degrees is referred to. Specifically, it refers to a magnetic field generated by a conventional analog amplifier system. The major difference from the H-bridge method is that the vertices of the Lissajous are on the x-axis and the y-axis. In the H-bridge method, since the portion near the straight line of the rising part of the exponential curve is used, it does not become an ideal triangular wave, and the vertex of the Lissajous deviates from the x-axis and the y-axis.

For this reason, a problem arises in that the magnetic bubble element that outputs a magnetic bubble signal with a narrow pulse width, which did not cause a problem with the conventional "diamond-shaped" drive waveform, cannot be used, and the yield of the magnetic bubble element is extremely reduced. Have done
Although the H-type bridge circuit is employed for cost reduction, the cost of the magnetic bubble element increases.

The present invention has been made in view of such a point, and an object thereof is to separate a magnetic bubble detection signal and a noise component even when an H-type bridge circuit is used, and Another object of the present invention is to provide a magnetic bubble detection method capable of obtaining a stable wide magnetic bubble detection signal that facilitates signal processing in a subsequent stage.

[0024]

In order to achieve the above object, the present invention according to claim 1 of the present invention uses a stretcher and a thin film type magnetic bubble detecting element by a magnetoresistive effect to read out. In a magnetic bubble detection method in which a magnetic field is forcibly moved by generating a rotating magnetic field in a coil and a bit pattern of the magnetic bubble is detected by a magnetic bubble detection element, the read coil is driven by an H-type bridge circuit. The H-type bridge circuit is used by changing the duty ratio of the control signal supplied to the H-type bridge circuit and applying a rotating magnetic field obtained by adding a cancel magnetic field in a direction to cancel the magnetic field from the ring magnet to the magnetic bubble element. Thus, the magnetic bubble detection signal and noise can be separated, and a stable and wide magnetic bubble detection signal can be obtained.

According to a second aspect of the present invention, a magnetic bubble is forcibly moved by using a stretcher and a thin-film type magnetic bubble detecting element based on a magnetoresistive effect and generating a rotating magnetic field in a read coil. In the magnetic bubble detection method of detecting a bit pattern of a magnetic bubble with a magnetic bubble detection element, the driving of the read coil is set to H.
By applying a rotating magnetic field to the magnetic bubble element by adding a cancel magnetic field in a direction to cancel the magnetic field from the ring magnet by changing the phase of the control signal supplied to the H-type bridge circuit. Even if a type bridge circuit is used, the magnetic bubble detection signal and noise can be separated, and a stable and wide magnetic bubble detection signal can be obtained.

According to a third aspect of the present invention, a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect are used, and a magnetic field is forcibly moved by generating a rotating magnetic field in a read coil. In the magnetic bubble detection method of detecting a bit pattern of a magnetic bubble with a magnetic bubble detection element, the driving of the read coil is set to H.
The method is performed by a type bridge circuit, and an offset of a read drive waveform in a direction coinciding with a center line of the ring magnet is determined on the plane of the magnetic bubble element based on a rotation angle of the ring magnet, and a duty of a control signal supplied to the H type bridge circuit is obtained. By applying a rotating magnetic field to the magnetic bubble element such that the offset is constant by changing the ratio,
The bit pattern can be read regardless of the rotation angle of the ring magnet.

According to a fourth aspect of the present invention, a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect are used, and a rotating magnetic field is generated in a read coil to forcibly move a magnetic bubble. In the magnetic bubble detection method of detecting a bit pattern of a magnetic bubble with a magnetic bubble detection element, the driving of the read coil is set to H.
The offset of the read drive waveform in the direction coincident with the center line of the ring magnet is determined on the plane of the magnetic bubble element based on the rotation angle of the ring magnet and the phase of the control signal supplied to the H-bridge circuit is determined. By applying a rotating magnetic field to the magnetic bubble element so as to make the offset constant by changing the bit pattern, the bit pattern can be read regardless of the rotation angle of the ring magnet.

According to a fifth aspect of the present invention, a magnetic bubble is forcibly moved by using a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect and generating a rotating magnetic field in a read coil. In the magnetic bubble detection method of detecting a bit pattern of a magnetic bubble with a magnetic bubble detection element, the driving of the read coil is set to H.
In addition to determining the offset of the read drive waveform in the direction coincident with the center line of the ring magnet on the magnetic bubble element plane based on the rotation angle of the ring magnet, the timing of the strobe signal is determined based on the rotation angle of the ring magnet. By shifting, the bit pattern can be read regardless of the rotation angle of the ring magnet.

According to the sixth aspect of the present invention, a magnetic bubble is forcibly moved by using a stretcher and a thin-film type magnetic bubble detecting element based on a magnetoresistive effect and generating a rotating magnetic field in a read coil. In the magnetic bubble detecting method of detecting the bit pattern of the magnetic bubble with the magnetic bubble detecting element, the pulse change width of the magnetic bubble signal is detected at two different rotation angles of the ring magnet, and the pulse width change by the electric circuit is detected. By calculating the magnetic circuit error by subtraction, the magnetic circuit error can be obtained indirectly.

According to a seventh aspect of the present invention, in the magnetic bubble detecting method according to the sixth aspect, the read coil is driven by an H-type bridge circuit and the magnetic field is determined based on the rotation angle of the ring magnet. The offset of the read drive waveform in the direction coinciding with the center line of the ring magnet in the bubble element plane is determined, and the offset due to the magnetic circuit error is compensated to change the duty ratio of the control signal supplied to the H-type bridge circuit. By applying a rotating magnetic field such that the compensated offset becomes constant to the magnetic bubble element, a more stable and wider magnetic bubble detection signal can be obtained.

According to an eighth aspect of the present invention, in the magnetic bubble detection method according to the sixth aspect, the read coil is driven by an H-type bridge circuit and the magnetic field is determined based on the rotation angle of the ring magnet. The offset of the read drive waveform in the direction coinciding with the center line of the ring magnet in the bubble element plane is determined, and the offset of the magnetic circuit error is compensated to change the phase of the control signal supplied to the H-type bridge circuit to change By applying a rotating magnetic field such that the compensated offset becomes constant to the magnetic bubble element, a more stable and wider magnetic bubble detection signal can be obtained.

According to a ninth aspect of the present invention, a magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop to form a magnetic bubble forming a bit pattern. An H-type bridge circuit that drives the read coil, and a rotation angle of the ring magnet, which is moved on a transfer element loop and detects the number of rotations of the rotation axis by reading the bit pattern. A rotation angle detector for detecting, and a ring magnet for obtaining an offset of a read drive waveform in a direction coinciding with a center line of the ring magnet in a plane of the magnetic bubble element based on a rotation angle of the ring magnet and for making the offset constant A correction circuit that outputs a correction value corresponding to the rotation angle of the control signal, and a duty ratio of a control signal based on the correction value. Properly by further comprising a control circuit for controlling the offset by changing the phase at a constant value irrespective of the angle of rotation of the ring magnet, it is possible to read the bit pattern regardless of the angle of rotation of the ring magnet.

According to a tenth aspect of the present invention, a magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is formed. An H-type bridge circuit that drives a read coil in a rotation speed detector that detects a rotation speed of the rotation shaft by reading the bit pattern by moving on a transfer element loop, A magnetic field measuring circuit for detecting a magnetic field, and an offset of a read drive waveform in a direction coinciding with a center line of the ring magnet in a magnetic bubble element plane is determined based on an output signal of the magnetic measuring circuit, and the offset is fixed. A correction circuit that outputs a correction value corresponding to the rotation angle of the ring magnet, and a control signal based on the correction value. And a control circuit for controlling the offset to a constant value regardless of the rotation angle of the ring magnet by changing the duty ratio or the phase, so that the bit pattern can be read regardless of the rotation angle of the ring magnet. .

According to an eleventh aspect of the present invention, the magnetic bubble from the ring magnet attached to the rotating shaft is applied to a magnetic bubble element provided with a transfer element loop to form a magnetic bubble forming a bit pattern. An H-type bridge circuit that drives the read coil, and a rotation angle of the ring magnet, which is moved on a transfer element loop and detects the number of rotations of the rotation axis by reading the bit pattern. A rotation angle detector for detecting,
A magnetic bubble detection circuit that shifts the timing of the strobe signal based on the rotation angle of the ring magnet, and a direction in which the magnetic field from the ring magnet is canceled by changing the duty ratio or phase of the control signal supplied to the H-type bridge circuit. The provision of the control circuit for adding the cancel magnetic field makes it possible to read the bit pattern irrespective of the rotation angle of the ring magnet.

According to a twelfth aspect of the present invention, a magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is formed. In a rotation speed detector for detecting the rotation speed of the rotation shaft by reading the bit pattern by moving on a transfer element loop, an H-type bridge circuit for driving the read coil, A magnetic field measuring circuit for detecting a magnetic field of the magnetic field, a magnetic bubble detecting circuit for shifting a timing of a strobe signal based on an output signal of the magnetic field measuring circuit, and changing a duty ratio or a phase of a control signal supplied to the H-type bridge circuit. A control circuit for adding a cancel magnetic field in a direction to cancel the magnetic field from the ring magnet. More, it is possible to read the bit pattern regardless of the angle of rotation of the ring magnet. [Detailed description of the invention]

[0036]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and is a diagram showing the periphery of a stretcher and a magnetic bubble detecting element. FIG. 2 shows an H-type bridge circuit and a control circuit at the time of reading, FIG. 3 shows a current superimposed with a drive waveform and an offset current by the H-type bridge circuit when the rotation direction is CW, and FIG. . The H-type bridge circuit is often used in a magnetic bubble memory or the like.
23, 24, 25, 28, 29, 30 and 31 are switch circuits, 26 is a read coil for Hx, 32 is a read coil for Hy, 27 and 33 are voltage sources, and 34 is a control circuit. Also, 100, 101, 102, 103, 10
4, 105, 106 and 107 are control signals for the respective switch circuits. Further, 22 to 27 and 28 to 33 constitute H-bridge circuits 200 and 201.

One end of the voltage source 27 is connected to one end of the switch circuits 22 and 24, and the other end of the switch circuit 22 is connected to one end of the switch circuit 23 and one end of the coil 26. The other end of the switch circuit 24 is connected to a switch circuit 25.
And the other end of the coil 26. Similarly, one end of the voltage source 33 is connected to one end of the switch circuits 28 and 30, and the other end of the switch circuit 28 is connected to one end of the switch circuit 29 and one end of the coil 32. The other end of the switch circuit 30 is connected to one end of the switch circuit 31 and the other end of the coil 32.

Further, the other ends of the voltage sources 27 and 33 and the other ends of the switch circuits 23, 25, 29 and 31 are grounded.
Switch circuits 22, 23, 24, 25, 28, 29, 3
Control signals 0, 31 and control signals 100, 101, 102, 103, 104, 105, 1
06 and 107 are respectively connected.

FIG. 5 shows the operation of each switch circuit in FIG. 2 and its current waveform. H-type bridge circuit 20
Each of the switch circuits 0 and 201 is a semiconductor switch circuit and is used for normal rotation and reverse rotation of the motor. As shown in (a) to (c) of FIG.
By controlling "ON / OFF" of each switch circuit by the switch 7, the current waveform of the read coil 26 for Hx shown in (d) of FIG. 5 and the Hy waveform shown in (e) and (f) of FIG.
Current waveforms of the reading coil 32 for CW and CCW can be obtained.

As described above, the duty ratio “XT1: XT
By shifting 2 "and" YT1: YT2 "from" 1: 1 ", the offset shown in FIGS. 3 and 4 can be generated to cancel the magnetic field from the ring magnet.

Here, the Hy direction is the direction that coincides with the center line of the ring magnet in the plane of the magnetic bubble element,
The direction is a direction perpendicular to the Hy direction.

At this time, the offset in the Hx direction is changed by changing the ratio of "XT1" and "XT2" in FIG. 5, in other words, the duty ratio, and the offset in the Hy direction is also changed to "YT1" in FIG. By changing the duty ratio of “YT2” and the duty ratio of “YT2”, an offset component is added as shown by a broken line portion in FIGS. 6 and 7 (addition correction). Also, even if the phases of Hx and Hy are changed as shown in FIG. 8 (phase correction), an offset occurs as shown by the broken line in FIG. 9, and the vertex of the Lissajous is similarly placed on the x-axis. Can be. For example, as shown in FIG. 7, the vertex of the Lissajous can be placed on the x-axis.

Here, the H-type bridge circuits 200 and 20
1 will be described. FIG. 10 is a circuit diagram for explaining the operation of the H-bridge circuit, and the reference numerals are the same as those of the H-bridge circuit 200. FIG. 11 is a waveform diagram showing a voltage waveform applied to the coil 26 and a current waveform flowing therethrough.

The output voltage of the voltage source 27 is "Vo", the current flowing through the coil 26 is "i1" and "i2", respectively, and the inductance and resistance components of the coil 26 are "L" and "L".
r, and using the times “T1” and “T2” and the current values “I00” and “I01” in FIG. 11, i1 = (I00−Vo / r) × exp {−r × (t−T0) / L} + Vo / r (1) i2 = (I01 + Vo / r) × exp {−r × (t−T1) / L} −Vo / r (2)

"I1 = I01", "t-T0 = ΔT"
1 "," i2 = I00 = I02 "and" t-T2 = .DELTA.T
2 ”(“ ΔT1 ”,“ I002 ”and“ ΔT2 ”
1), the direct current component of the current value is Ia
Assuming that ve = (I00 + I01) / 2 ", from equation (1) and equation (2), Iave = −Vo / {r × (1-exp [−r × T / L])} × {exp (− r × ΔT1 / L) −exp (−r × ΔT2 / L)} (3) where T = ΔT1 + ΔT2.

This DC component "Iave" becomes a cancel magnetic field that cancels the magnetic field HR due to the ring magnet. Therefore, a desired triangular wave can be obtained by calculating “ΔT1” and “ΔT2” back using Equation (3) using an approximate value and the like, and controlling the duty ratio and the like in the control circuit.

Here, referring to FIG. 12 and subsequent figures, the positional relationship between the stretcher and the magnetic bubble detecting element, the magnetic field rotation direction,
The relationship between the bubble detection phase and the offset will be described in detail for each case.

FIG. 12 is a diagram showing the relationship between the stretcher S and the magnetic bubble detecting element 12 and the direction of the magnetic field. FIG. 13 is a diagram showing a relationship between noise and a detection signal when the rotating magnetic field is rotated in the CW direction of FIG. 12, and FIG. 14 is a diagram showing noise and detection when the rotating magnetic field is rotated in the CCW direction of FIG. FIG. 4 is a diagram illustrating a relationship with a signal. In these figures,
This is the case where the bias magnetic field HB is from the back of the paper to the front, and the front side of the magnetic bubble is the south pole. in this case,
The detection signal detected by the magnetic bubble detecting element 12 (13) is generated when a magnetic field is directed in the X direction of the stretcher on which the magnetic bubble detecting element 12 is placed. Also,
The phase at which the switching noise occurs is determined only by the rotating direction of the rotating magnetic field, and is independent of the position of the stretcher S and the magnetic bubble detecting element 12 and the direction of the bias magnetic field.

By adding the offset Hx in the X direction to the right in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the sensitivity curve in the Hx direction. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

Assuming that the magnetic field is rotated in the CW direction (shown in FIG. 13) in the configuration of FIG. 12, the offset Hy in the Y direction is moved upward in the figure to add to the detection signal. The timing of noise (switching noise generated by the magnetic bubble detection element itself) and the fall timing of the detection signal can be separated, and the S / N can be improved.

FIG. 15 is a diagram showing a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that of FIG. FIG. 16 is a diagram showing a relationship between noise and a detection signal when the rotating magnetic field is rotated in the CW direction of FIG. 15, and FIG. 17 is a diagram showing noise and detection when the rotating magnetic field is rotated in the CCW direction of FIG. FIG. 4 is a diagram illustrating a relationship with a signal. In this case, by adding the offset Hx in the X direction to the left direction in the drawing, the magnetic bubble detecting element can quickly escape from the dead zone in the sensitivity curve in the Hx direction. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

Assuming that the magnetic field is rotated in the CCW direction (shown in FIG. 17) in the configuration of FIG. 15, by moving the offset Hy in the Y direction upward in the drawing,
The timing of the noise (switching noise generated by the magnetic bubble detection element itself) added to the detection signal can be separated from the fall timing of the detection signal, and the S / N can be improved.

FIG. 18 is a view showing a case where the orientation of the stretcher is different from that shown in FIGS. In this case, X
By adding the directional offset Hx in the right direction in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the Hx direction sensitivity curve. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

Assuming that the magnetic field is rotated in the CCW direction in the configuration of FIG. 18 (shown in FIG. 20), the offset Hy in the Y direction is moved downward to add the detection signal. The timing of noise (switching noise generated by the magnetic bubble detection element itself) and the fall timing of the detection signal can be separated, and the S / N can be improved.

FIG. 21 shows a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that of FIG. In this case, by adding the offset Hx in the X direction to the left direction in the drawing, the magnetic bubble detecting element can quickly escape from the dead zone in the sensitivity curve in the Hx direction. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

Assuming that the magnetic field is rotated in the CW direction in the configuration shown in FIG. 21 (shown in FIG. 22), the offset Hy in the Y direction is moved downward to add the detection signal. The timing of noise (switching noise generated by the magnetic bubble detection element itself) and the fall timing of the detection signal can be separated, and the S / N can be improved.

From the above, the offset directions suitable for reading (the signal width of the detection signal can be widened) are as follows.

Hx offset: Determined by the positional relationship between the stretcher and the magnetic bubble detecting element. That is, it is the direction in the X direction on the side of the stretcher where the magnetic bubble detection element is arranged. ... Hy offset: It is determined by the positional relationship between the stretcher and the magnetic bubble detecting element and the direction of rotation of the magnetic field. That is,
In the stretcher, the direction in the X direction on the side where the magnetic bubble detection element is disposed is the direction in the Y direction such that the stretcher rotates 90 degrees opposite to the magnetic field rotation direction. … Also, the rotation direction of the magnetic field suitable for reading (the signal width can be widened) is the direction in which the bubbles rise from the hem to the top along the ridgeline on the side where the magnetic bubble detection element is placed in the stretcher. , The distance between the vertex in the X direction on the side to be detected and the center line of the Hy waveform. Next, a case where the bias magnetic field HB goes from the front to the back of the drawing and the front side of the magnetic bubble is the N pole will be described with reference to FIG. In this case, the detection signal detected by the magnetic bubble detection element 12 (13) is generated when the magnetic field is turned in the direction opposite to the X direction of the stretcher on which the magnetic bubble detection element 12 is placed. The phase at which the switching noise occurs is determined only by the rotation direction of the rotating magnetic field, and is independent of the position of the stretcher S and the magnetic bubble detecting element 12 and the direction of the bias magnetic field.

By adding the X-direction offset Hx to the left direction in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the Hx-direction sensitivity curve. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

In the configuration of FIG. 24, assuming that the magnetic field is rotated in the CW direction (shown in FIG. 25), the offset Hy in the Y direction is moved downward to add the detection signal. The timing of noise (switching noise generated by the magnetic bubble detection element itself) and the fall timing of the detection signal can be separated, and the S / N can be improved.

FIG. 27 is a diagram showing a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that shown in FIG. In this case, by adding the offset Hx in the X direction to the right direction in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the Hx direction sensitivity curve. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

In the configuration of FIG. 27, assuming that the magnetic field is rotated in the CCW direction (shown in FIG. 29), the offset Hy in the Y direction is moved downward in the drawing to obtain
The timing of the noise (switching noise generated by the magnetic bubble detection element itself) added to the detection signal can be separated from the fall timing of the detection signal, and the S / N can be improved.

FIG. 30 is a diagram showing a case where the orientation of the stretcher is different from that of FIGS. 24 and 27. In this case, X
By adding the direction offset Hx in the left direction in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the Hx direction sensitivity curve. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

Assuming that the magnetic field is rotated in the CCW direction in the configuration of FIG. 30 (shown in FIG. 32), by moving the offset Hy in the Y direction upward in the drawing,
The timing of the noise (switching noise generated by the magnetic bubble detection element itself) added to the detection signal can be separated from the fall timing of the detection signal, and the S / N can be improved.

FIG. 33 is a diagram showing a case where the position of the magnetic bubble detecting element 12 with respect to the stretcher is different from that of FIG. In this case, by adding the offset Hx in the X direction to the right direction in the figure, the magnetic bubble detecting element can quickly escape from the dead zone on the Hx direction sensitivity curve. For this reason, the rise of the detection signal is accelerated, and the width of the detection signal can be increased.

In the configuration of FIG. 33, assuming that the magnetic field is rotated in the CW direction (shown in FIG. 34), the offset Hy in the Y direction is moved upward in the figure to add to the detection signal. The timing of noise (switching noise generated by the magnetic bubble detection element itself) and the fall timing of the detection signal can be separated, and the S / N can be improved.

From the above, the offset directions suitable for reading (the signal width of the detection signal can be widened) are as follows.

Hx offset: Determined by the positional relationship between the stretcher and the magnetic bubble detecting element. That is, the direction in the X direction is opposite to the side of the stretcher where the magnetic bubble detecting element is arranged. ... Hy offset: It is determined by the positional relationship between the stretcher and the magnetic bubble detecting element and the direction of rotation of the magnetic field. That is,
The direction in the Y direction is such that the stretcher is rotated by 90 degrees in the magnetic field rotation direction from the direction in the X direction on the side where the magnetic bubble detection element is disposed in the stretcher. The rotation direction of the readout magnetic field suitable for readout (allowing a wide signal width) is such that the bubble rises from the hem to the top along the ridge line on the side where the magnetic bubble detecting element is placed in the stretcher. And the distance between the vertex in the X direction on the detected side and the center line of the Hy waveform. ... Therefore, the direction of the rotating magnetic field does not change (=) even when HB changes.

FIG. 36A shows an outline of an eye pattern of a detection signal waveform when an offset is given in accordance with the offset condition (,,,) obtained as described above.
FIG. 36B shows an eye pattern of a detection signal waveform in the case where there is no offset, and FIG. 36C shows an eye pattern of a detection signal in the case where an offset is applied contrary to the present embodiment. As is clear from these figures, the direction of the offset in this embodiment is effective.

As a result, by controlling the offset in the Hy direction by addition correction or phase correction to cancel the magnetic field from the ring magnet, the magnetic bubble detection signal and noise can be separated even by using the H-type bridge circuit. In addition, a stable and wide magnetic bubble detection signal can be obtained.

When the ring magnet fixed to the shaft is rotated, the magnetic field applied to the magnetic bubble element changes. When the bit pattern is read at the time when the rotation of the ring magnet is stopped or when the rotation of the ring magnet is performed at a sufficiently low speed, a read driving magnetic field is generated while adding a magnetic field in a direction to cancel the magnetic field from the ring magnet. Therefore, the added value differs depending on the rotation angle (magnetic field angle) of the ring magnet, and the drive waveform is distorted.

For example, when the magnetic field angle at which the added value in the Hy direction becomes the maximum is “90 degrees” or “270 degrees”, H
Distortion in the y direction becomes noticeable. However, in the Hx direction, since the added value is "0", distortion is small. Similarly, the magnetic field angle at which the added value in the Hx direction becomes the maximum is “0 degree” or “1”.
At the time of "80 degrees", the distortion in the Hx direction becomes remarkable. However, the distortion is small in the Hy direction since the added value is "0".

As described above, the manner of distortion of the read drive waveform changes depending on the rotation angle of the ring magnet, and the manner of distortion of the Lissajous waveform also changes. On the magnetic bubble element, the read drive magnetic field rotates around the origin due to the cancellation of the added value and the magnetic field from the ring magnet, but the Lissajous waveform remains distorted.

For example, FIGS. 37 and 38 are waveform diagrams showing a "diamond" drive waveform and a drive waveform by an H-type bridge circuit when a magnetic field is rotated in the CW direction and the CCW direction. In FIG. 37, “A” and “B” are drive waveforms by the H-type bridge circuit, and “C” is a “diamond” drive waveform. In FIG. 38, “D” and “E” are drive waveforms by the H-type bridge circuit, and “F” is a “diamond” drive waveform. Here, even if the offset is set so that “Hy1 = −Hy2”, there is a change between “A” and “B” as shown in “ΔY1” and “ΔY2” in FIG. Similarly, "Hy3" is between "D" and "E".
= −Hy4 ″ even if the offset is set.
8, fluctuations occur as indicated by “ΔY3” and “ΔY4”.

The magnetic bubble signals read out with the driving waveforms shown in FIGS. 37 and 38 correspond to FIGS.
become that way. That is, the rising and falling timings of the magnetic bubble signal are shifted due to the distortion of the driving waveform.

Consider a case where such a magnetic bubble signal is detected by a magnetic bubble detection circuit as shown in FIG. 41, reference numerals 35 and 37 denote constant current sources, 36 and 38 denote magnetic bubble detection elements, 39 denotes a differential amplifier circuit, 40 denotes a comparison circuit, 41 denotes a flip-flop circuit, and 108 denotes a strobe signal.

One end of the constant current source 35 is connected to one end of the magnetic bubble detecting element 36 and the non-inverting input terminal of the differential amplifier 39, and one end of the constant current source 37 is connected to the magnetic bubble detecting element 38.
And one terminal of the differential amplifier circuit 39. The output of the differential amplifier circuit 39 is connected to the input terminal of the flip-flop circuit 41 via the comparison circuit 40. The strobe signal 108 is supplied to the flip-flop circuit 41.
Constant current sources 35 and 37
And the other ends of the magnetic bubble detecting elements 36 and 38 are grounded.

By obtaining the difference between the voltage changes generated in the magnetic bubble detecting elements 36 and 38 by the differential amplifier circuit 39, the magnetic bubble signal shown in FIG. 39 and the like can be obtained. Such a magnetic bubble signal is compared by the comparison circuit 40. "
The signal is converted into a signal of "0" or "1", and is held and output by the flip-flop circuit 41 at the timing of the strobe signal 108.

As shown by "a", "b" and "c" in FIG. 42, the drive waveform is distorted due to the difference in magnetic angle.
When the timing such as the rise of the magnetic bubble signal is shifted, “S001”, “S002” and “S0” in FIG.
03 "is output from the comparison circuit 40. When these output signals are held in the flip-flop circuit 41 at the timing shown by" d "," b "in FIG. 42, the magnetic bubble signal indicated by “a” in FIG. 42 cannot be detected, but the bit pattern cannot be read due to the stop angle of the ring magnet. Will happen.

In order to solve such a phenomenon, the offset is controlled by irrespective of the rotation angle of the ring magnet, as shown in FIG.
7, the variation such as “ΔY1” or “ΔY2” may be set to a constant value. As the offset control method, the above-mentioned "addition correction" or "phase correction" is used.

Here, the case of performing the addition correction based on the rotation angle of the ring magnet will be described. For example, the current "I01" flowing through the coil 26 at a certain rotation angle of the ring magnet shown in FIG. 11 changes the phase "T" shown in FIG. 6 to "t-T1".
Then, the cancellation magnetic field can be obtained from Expression (2) as the sum of the “cancellation magnetic field” and the “driving magnetic field amplitude value converted into the current value”. Therefore, by subtracting the cancellation magnetic field obtained from Expression (3) from the current “I01”, Conversely, a magnetic field (converted to a current value) indicated by “ΔY (Hy offset = ΔY)” in FIG. 14 is obtained. Further, if the efficiency (Oe / A) of the coil 26 is used, the value of the magnetic field of “ΔY” can be obtained. Similarly, “ΔY” at each rotation angle is obtained.

For example, FIG. 43 is a characteristic curve diagram showing the variation of “ΔY” with respect to the rotation angle of the ring magnet.
The middle “A” is “ΔY” obtained as described above. In FIG. 43, “B” is an approximate expression “F (d) obtained based on“ A ”in order to stabilize“ ΔY ”around, for example,“ −6 Oe ”.
eg) is the change in “ΔY” after correction by “”.
The correction formula of “ΔY” at this time is “F ′ (deg) = 60”
eF (deg) ".

FIG. 44 and FIG.
FIG. 44 is a waveform chart showing an eye pattern of a magnetic bubble signal when “ΔY” changes like “A” and “B”.
As can be seen from FIG. 45 and FIG. 45, the fluctuation of the magnetic bubble signal is improved by the addition correction.

On the other hand, a case where the phase is corrected based on the rotation angle of the ring magnet will be described. In FIG. 8, the phase “ΦA”
Is changed to “ΦB”, “ΔY” becomes “0”. In other words, by appropriately selecting the phase difference with respect to the rotation angle of the ring magnet, it becomes possible to keep “ΔY” constant.

For example, as described above, the current flowing through the coil 26 at a certain rotation angle of the ring magnet shown in FIG.
If the phase “ΦB” shown in FIG. 8 is “t−T1”, I01 ”can be obtained from Equation (2) as the sum of“ cancel magnetic field ”and“ drive magnetic field amplitude value converted into current value ”.

Then, by transforming equation (2) so that “ΔY (cancel magnetic field)” becomes constant to obtain “ΦB” and controlling the phase of the drive waveform, regardless of the rotation angle of the ring magnet, The value of “ΔY” becomes constant.

FIG. 46 shows such addition correction or
FIG. 3 is a configuration diagram illustrating an example of an H-type bridge circuit that performs phase correction and a control unit. In FIG. 46, 34, 200 and 2
Reference numeral 01 denotes the same reference numeral as in FIG. 2, and reference numeral 42 denotes a magnetic field measurement circuit that detects a magnetic field from a ring magnet using a Hall element, or a rotation angle that directly detects the rotation speed of a shaft to which the ring magnet is attached. A detector (hereinafter, described as a rotation angle detector) 43 is a correction circuit.

The basic connection relationship is the same as that of FIG. 2 except that the output of the rotation angle detector 42 is connected to the correction circuit 43, and the output of the correction circuit 43 is connected to the control circuit 34. is there.

The operation of the circuit shown in FIG. 46 will now be described. The rotation angle detector 42 detects the rotation angle of the ring magnet and outputs it to the correction circuit 43. The correction circuit 43 outputs a correction value corresponding to the rotation angle of the ring magnet to the control circuit 34 using the above-described correction formula or the like. The control circuit 34 controls the offset of the drive waveform by addition correction or phase correction based on the correction value, and controls “ΔY” to a constant value regardless of the rotation angle of the ring magnet.

As a result, an offset “ΔY” in the Hy direction of the read drive waveform is obtained based on the rotation angle of the ring magnet, and addition correction or phase correction is performed so that the value of “ΔY” is constant. Thus, the bit pattern can be read regardless of the rotation angle of the ring magnet.

Further, ".DELTA.Y" is not only obtained by calculation, but the fluctuation of ".DELTA.Y" may be measured by actually rotating the ring magnet itself. Further, a correction value may be obtained by providing a data table corresponding to the rotation angle of the ring magnet instead of the correction formula. Further, the magnetic field from the ring magnet may be directly detected using a Hall element instead of the rotation angle detector.

When the offset “ΔY” in the Hy direction fluctuates due to the rotation angle of the ring magnet, the bit pattern may not be read due to the stop angle of the ring magnet as described with reference to FIG. This is because the strobe signal 108 has a constant timing regardless of the rotation angle of the ring magnet. Therefore, the timing of the strobe signal 108 may be changed according to the rotation angle of the ring magnet.

For example, in FIG. 42, "a", "b" and "
When the drive waveform is distorted due to the difference in the magnetic angle as shown by "c" and the timing such as the rising of the magnetic bubble signal is shifted, "S001" and "S002" in FIG.
And the output signal as shown in "S003"
Will be output. If these output signals are held in the flip-flop circuit 41 at the timing indicated by “d” or “e” according to the rotation angle of the ring magnet,
The strobe signal 10 at the timing indicated by "d" in FIG.
In FIG. 8, the magnetic bubble signals “b” and “c” in FIG. 42 are detected, and in the strobe signal 108 at the timing “e” in FIG. 42, the magnetic bubble signals “a” and “b” in FIG. Will be detected.

As a result, “ΔY” corresponds to the variation of the cancel magnetic field, in other words, the strobe signal 1 based on the rotation angle of the ring magnet since it corresponds to the rotation angle of the ring magnet.
By shifting the timing of 08, the bit pattern can be read regardless of the rotation angle of the ring magnet.

In the conventional magnetic bubble detection method, the magnetic field applied to the magnetic bubble element is calculated based on the rotation angle of the ring magnet, or the magnetic fields in the x and y directions from the ring magnet are directly applied by two Hall elements. A magnetic field is calculated by measurement, and a read drive magnetic field is generated by adding a cancel magnetic field from the calculated magnetic field.

In the former case, the strength of the magnetic field actually applied to the magnetic bubble element depends on the dimensional accuracy of the base, the dimensional accuracy of the magnetic bubble element, the dimensional accuracy of the substrate, or the dimensional accuracy of the mounting of the magnetic bubble element on the substrate. And an error occurs between the calculated magnetic field and the magnetic field calculated based on the rotation angle of the ring magnet.

In the latter case, since the Hall element cannot be formed directly on the magnetic bubble element, it is actually installed at a place different from the magnetic bubble element and the magnetic field applied to the magnetic bubble element in consideration of the positional relationship. Can be said to be the same as above.

That is, it cannot be said that the magnetic circuit error caused by the dimensional accuracy of the base, the dimensional accuracy of the magnetic bubble element, the dimensional accuracy of the substrate, or the dimensional accuracy of the mounting of the magnetic bubble element to the substrate cannot be directly measured. There was a problem.

Here, a method for indirectly measuring such a magnetic circuit error will be described. First, FIG. 47 and FIG. 48 are waveform diagrams showing Lissajous waveforms in the case of rotating in the CW direction and no offset in the Hy direction, and in the case of a certain rotation. FIGS. 49 and 50 are waveform diagrams showing the eye patterns of the magnetic bubble signals in the cases of FIGS. 47 and 48.

It can be seen that the width changes from "A1" and "B1" shown in FIG. 49 to "A2" and "B2" shown in FIG. 50 due to the change of the offset in the Hy direction. Further, the change amount is changed from “B1” to “B2”.
The change to is more pronounced.

Similarly, FIG. 51 and FIG. 52 are waveform diagrams showing Lissajous waveforms in the case where there is no offset in the Hy direction when rotated in the CCW direction and in the case where there is a certain offset. FIGS. 53 and 54 are waveform diagrams showing the eye patterns of the magnetic bubble signals in the cases of FIGS. 51 and 52.

It can be seen that the width changes from "A3" and "B3" shown in FIG. 53 to "A4" and "B4" shown in FIG. 54 due to the change of the offset in the Hy direction. Further, the change amount is changed from “B3” to “B4”.
The change to is more pronounced.

The difference between the CW direction and the CCW direction is that, in the CW direction, when an offset is applied to the positive side of Hy, “B1” is expanded, and in the CCW direction, when an offset is applied in the negative direction of Hy, “B3” is expanded. Will be.

On the other hand, FIGS. 55 and 56 are waveform diagrams showing Lissajous waveforms when there is no offset in the Hx direction and when there is an offset. FIGS. 57 and 58 are waveform diagrams showing the eye patterns of the magnetic bubble signals in the cases of FIGS. 55 and 56.

It can be seen that the width changes from "A5" and "B5" shown in FIG. 57 to "A6" and "B6" shown in FIG. 58 due to the change in the offset in the Hx direction. In the case of an offset in the Hx direction, CW
Alternatively, if an offset is applied in the Hx direction regardless of the CCW direction, "A5" and "B5" are widened.

The time variation width of "A2-A1" is H
The amount of change in the previous pulse width due to the offset in the y direction is "B
2-B1 "is measured with respect to the post-pulse width change amount by the offset in the Hy direction, and the change rate is calculated from the change amount to the pre-pulse change rate" FY (sec / Oe) and the post-pulse change rate "B
Y (sec / Oe) ", where" FY "and" B
The sign of Y ″ is reversed depending on the CW direction or the CCW direction.

Similarly, in the Hx direction, the pre-pulse change rate “FX (sec / Oe)” and the “post-pulse change rate” B
X (seconds / Oe) ", where" FX "and" B "
X "has the same sign regardless of the CW direction or CCW direction.

Second, FIGS. 59, 60, 61 and 6
The method of calculating the magnetic circuit error will be specifically described with reference to FIG. FIG. 59 is a waveform diagram showing a Lissajous waveform of the rotating magnetic field by the ring magnet, FIG. 60 is a waveform diagram in which the rotating magnetic field intensity by the ring magnet is plotted using angle as a parameter, and FIG.
1 is a waveform diagram showing a Lissajous waveform, and FIG. 62 is a characteristic curve diagram showing a magnetic bubble signal with time as a parameter.

A case is considered where the design value of the magnetic field strength of the ring magnet on the magnetic bubble element is "Hr" and a magnetic circuit error of "+ α" occurs due to a positional shift due to a mechanical error in the mechanical size of the magnetic bubble element. Since the magnetic circuit error “+ α” is an error due to machine dimensions, an error of “+ α” is added to the entire “Hr”. That is, "Hr +" as shown in FIG.
A rotating magnetic field of α ″ is applied to the magnetic bubble element.

For example, when the ring magnet is fixed at a rotation angle of “0 °”, as shown in FIG. 60, “Hr +” in the “Hx” direction.
The magnetic field in the “Hy” direction becomes “0” when the magnetic field of “α” is applied.The Lissajous waveform in this state is, as shown in FIG. 61, compared with the case where there is no error “+ α” shown in FIG. "
It is shifted in the “Hx” direction by αx ”.
62, the front pulse and the rear pulse slightly spread as shown in FIG.

Next, when the rotation angle is fixed to “90 degrees” by rotating the ring magnet, as shown in FIG.
A magnetic field of “Hr + α” is applied in the “direction”, and the magnetic field in the “Hx” direction becomes “0.” In this state, the Lissajous waveform has no error “+ α” shown in FIG. Compared to the case shown in FIG. 49, this is shifted in the “Hy” direction by “αy.” This corresponds to the case shown in FIG.

In the case of the H-type bridge circuit, the offset in the “Hy” direction changes without the magnetic circuit error “+ α”.
"Measure the offset variation" HYe "in the direction,
By subtracting the pulse width change due to HYe ”from the pulse width change shown in FIG. 62, a pure magnetic circuit error“ α ”is obtained.
, A pulse width change is obtained.

That is, assuming that the preceding pulse width change is “ΔAα” and the subsequent pulse width change is “ΔBα” among the pulse width changes due to the magnetic circuit error “α”, ΔAα = ΔA−HYe × FY (4) ΔBα = ΔB−HYe × BY (5) In FIG. 62, the threshold voltage “Vth” is “ΔA”.
And “ΔB”, the first term of the equations (4) and (5) is obtained, and the second term is obtained by “HYe”, so that the equations “ΔAα” and “ΔBα” are obtained.

Therefore, ΔAα = α × (FX + FY) (6) ΔBα = α × (BX + BY) (7), and the magnetic circuit error “α” is calculated by modifying the equations (6) and (7). be able to.

As a result, the magnetic circuit error is calculated indirectly by detecting the pulse change width of the magnetic bubble signal at two different rotation angles of the ring magnet and subtracting the pulse width change by the electric circuit to calculate the magnetic circuit error. A magnetic circuit error can be obtained.

Incidentally, either one of the X and Y offsets may be added according to the above conditions. Further, it is also possible to generate an offset magnetic field by tilting the bias magnet.

Also, a description has been given using a chevron stretcher butt-arranged as shown in FIG. 63 as the stretcher S. However, a nested type chevron stretcher shown in FIG. 64 and an asymmetrical chevron stretcher shown in FIG. It is also possible to use

Further, even in the case of addition correction or phase correction, a more stable and wider magnetic bubble detection signal can be obtained by considering the above-described magnetic circuit error.

Further, when the timing of the strobe signal 108 is shifted based on the rotation angle of the ring magnet, a more stable and wider magnetic bubble detection signal can be obtained by taking the above-mentioned magnetic circuit error into consideration.

In the method of calculating the magnetic circuit error, the case where the rotating magnetic field by the ring magnet is a circle is described. However, when the rotating magnetic field is an ellipse, “Hy = C” and “Hx = D”,
The error when the rotation angle is “0 °” and “90 °” is “α”
If (0 deg) ”and“ α (90 deg) ”, α (0 deg) = α (90 deg) × D / C (8), and can be obtained in the same manner as described above.

In the above description, the pulse change width is detected at two points where the rotation angle of the ring magnet is “0 °” and “90 °”. If it is known, the error in the radial direction at that time can be calculated by decomposing the error in the "Hy" and "Hx" directions at the rotation angle.

Further, by using the magnetic bubble detecting method as described above, it is possible to sufficiently use even a magnetic bubble element having a specification which could not be used for a rotational speed detector or the like. Therefore, the yield of the magnetic bubble element is improved.

[0124]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first and second aspects of the present invention, by controlling the offset in the Hy direction by addition correction or phase correction to cancel the magnetic field from the ring magnet, a magnetic bubble detection signal can be obtained even when an H-type bridge circuit is used. And noise can be separated, and a stable and wide magnetic bubble detection signal can be obtained.

Further, according to the third, fourth, ninth and tenth aspects of the present invention, the read drive waveform offset "Y" in the Hy direction based on the rotation angle of the ring magnet.
By performing addition correction or phase correction so that the value of “ΔY” is constant, the bit pattern can be read regardless of the rotation angle of the ring magnet.

Further, claim 5, claim 11, and claim 1
According to the second aspect, by shifting the timing of the strobe signal based on the rotation angle of the ring magnet, the bit pattern can be read regardless of the rotation angle of the ring magnet.

According to the sixth aspect of the present invention, the pulse width of the magnetic bubble signal is detected at two different rotation angles of the ring magnet, and the pulse width variation due to the electric circuit is subtracted. , It is possible to indirectly obtain a magnetic circuit error.

According to the seventh and eighth aspects of the present invention, even in the case of addition correction or phase correction, the magnetic circuit error is taken into account, so that a wider and wider magnetic bubble detection signal can be obtained. Is obtained. Also, when the timing of the strobe signal is shifted based on the rotation angle of the ring magnet, a more stable and wider magnetic bubble detection signal can be obtained by taking the above-described magnetic circuit error into consideration.

Further, by using the magnetic bubble detecting method as described above, it is possible to sufficiently use even a magnetic bubble element having a narrow pulse width which could not be used for a rotational speed detector or the like until now. Therefore, the yield of the magnetic bubble element is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an entire magnetic bubble element.

FIG. 2 is a configuration block diagram showing an H-type bridge circuit and a control circuit at the time of reading.

FIG. 3 is a waveform diagram showing a driving waveform by an H-type bridge circuit and a current on which an offset current is superimposed.

FIG. 4 is a waveform diagram showing a drive waveform by an H-type bridge circuit and a current on which an offset current is superimposed.

5 is a waveform diagram showing the operation of each switch circuit in FIG. 2 and the current waveform.

FIG. 6 is a waveform diagram showing a current waveform.

FIG. 7 is a waveform diagram showing a Lissajous waveform.

FIG. 8 is a waveform diagram showing a current waveform.

FIG. 9 is a waveform chart showing a Lissajous waveform.

FIG. 10 is a circuit diagram illustrating the operation of the H-type bridge circuit.

FIG. 11 is a waveform diagram showing a waveform of a voltage applied to the coil 26 and a waveform of a flowing current.

FIG. 12 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 13 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG.

FIG. 14 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG.

FIG. 15 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

16 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG.

17 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG.

FIG. 18 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 19 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 18;

20 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG.

FIG. 21 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 22 is an explanatory diagram illustrating a relationship between a detection signal and an offset in the configuration illustrated in FIG. 21;

FIG. 23 is an explanatory diagram illustrating a relationship between a detection signal and an offset in the configuration illustrated in FIG. 21;

FIG. 24 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 25 is an explanatory diagram illustrating a relationship between a detection signal and an offset in the configuration illustrated in FIG. 24;

FIG. 26 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 24;

FIG. 27 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 28 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 27;

FIG. 29 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 27;

FIG. 30 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 31 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 30;

FIG. 32 is an explanatory diagram showing a relationship between a detection signal and an offset in the configuration shown in FIG. 30;

FIG. 33 is an explanatory diagram showing a positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 34 is an explanatory diagram illustrating a relationship between a detection signal and an offset in the configuration illustrated in FIG. 33;

FIG. 35 is an explanatory diagram illustrating a relationship between a detection signal and an offset in the configuration illustrated in FIG. 33;

FIG. 36 is an explanatory diagram showing an eye pattern of a detection signal when an offset is changed in comparison;

FIG. 37 is a waveform diagram showing a “diamond” drive waveform and a drive waveform by an H-type bridge circuit when a magnetic field is rotated in the CW direction.

FIG. 38 is a waveform diagram showing a “diamond” drive waveform and a drive waveform by an H-type bridge circuit when a magnetic field is rotated in the CCW direction.

FIG. 39 is a waveform diagram showing a magnetic bubble signal read out with a drive waveform as shown in FIG. 37.

FIG. 40 is a waveform chart showing a magnetic bubble signal read out with a drive waveform as shown in FIG. 38.

FIG. 41 is a circuit diagram illustrating an example of a magnetic bubble detection circuit.

FIG. 42 is a waveform diagram showing a case where timing such as a rise of a magnetic bubble signal is shifted due to a difference in magnetic angle.

FIG. 43 is a characteristic curve diagram showing variation of “ΔY” with respect to the rotation angle of the ring magnet.

FIG. 44 is a waveform diagram showing an eye pattern of a magnetic bubble signal when “ΔY” changes.

FIG. 45 is a waveform diagram showing an eye pattern of a magnetic bubble signal when “ΔY” changes.

FIG. 46 is a configuration diagram illustrating an example of an H-type bridge circuit and a control unit that perform addition correction or phase correction.

FIG. 47 is a waveform diagram showing a Lissajous waveform in a case where an image is rotated in the CW direction and there is an offset in the Hy direction.

FIG. 48 is a waveform diagram showing a Lissajous waveform in a case where the laser beam is rotated in the CW direction and there is no offset in the Hy direction.

FIG. 49 is a waveform chart showing an eye pattern of a magnetic bubble signal in the case of FIG. 47;

50 is a waveform chart showing an eye pattern of a magnetic bubble signal in the case of FIG. 48.

FIG. 51 is a waveform diagram showing a Lissajous waveform when the image is rotated in the CCW direction and there is an offset in the Hy direction.

FIG. 52 is a waveform diagram showing a Lissajous waveform when the image is rotated in the CCW direction and there is no offset in the Hy direction.

FIG. 53 is a waveform diagram showing an eye pattern of a magnetic bubble signal in the case of FIG. 51.

FIG. 54 is a waveform diagram showing an eye pattern of a magnetic bubble signal in the case of FIG. 52;

FIG. 55 is a waveform chart showing a Lissajous waveform when there is an offset in the Hx direction.

FIG. 56 is a waveform chart showing a Lissajous waveform when there is no offset in the Hx direction.

FIG. 57 is a waveform chart showing an eye pattern of a magnetic bubble signal in the case of FIG. 55;

FIG. 58 is a waveform diagram showing an eye pattern of a magnetic bubble signal in the case of FIG. 56;

FIG. 59 is a waveform diagram showing a Lissajous waveform of a rotating magnetic field by a ring magnet.

FIG. 60 is a waveform diagram in which the rotating magnetic field strength by the ring magnet is plotted using angle as a parameter.

FIG. 61 is a waveform chart showing a Lissajous waveform.

FIG. 62 is a characteristic curve diagram showing a magnetic bubble signal using time as a parameter.

FIG. 63 is an explanatory diagram showing an example of the arrangement of the stretchers.

FIG. 64 is an explanatory diagram showing an example of the arrangement of the stretchers.

FIG. 65 is an explanatory diagram showing an example of the arrangement of the stretchers.

FIG. 66 is an explanatory diagram showing an arrangement around a magnetic bubble element.

FIG. 67 is an explanatory diagram showing an arrangement of a stretcher and a magnetic bubble detection element.

FIG. 68 is an explanatory diagram showing the arrangement of the stretchers and the magnetic bubble detection elements in detail;

FIG. 69 is an explanatory diagram showing the strengths of a bias magnetic field and a rotating magnetic field.

FIG. 70 is a characteristic diagram showing characteristics of the magnetic bubble detection element.

FIG. 71 is a perspective view showing the periphery of a magnetic bubble detection element.

FIG. 72 is a circuit diagram showing a circuit configuration for generating a magnetic field for reading.

FIG. 73 is a waveform chart showing a detection signal.

FIG. 74 is an explanatory diagram showing a Hy-direction sensitivity curve of the magnetic bubble detection element.

FIG. 75 is an explanatory diagram showing an Hx direction sensitivity curve of the magnetic bubble detection element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic bubble element 2, 2 'bias magnet 3, 4 Readout coil 5 Ring magnet 10 Magnetic bubble detector 11 Transfer element 12, 13, 36, 38 Magnetic bubble detection element 14, 15, 16 Aluminum wiring pattern 17, 18, 19 Magnetic bubble 20,21 Hall element 22,23,24,25,28,29,30,31 Switch circuit 26 Read coil for Hx 32 Read coil for Hy 27,33 Voltage source 34 Control circuit 35,37 Constant current source 39 Difference Dynamic amplification circuit 40 Comparison circuit 41 Flip-flop circuit 42 Magnetic field measurement circuit or rotation angle detector 43 Correction circuit 100, 101, 102, 103, 104, 105, 1
06,107 Control signal 108 Strobe signal 200,201 H-type bridge circuit S Stretcher

Claims (12)

[Claims] The present invention uses a stretcher and a thin-film type magnetic bubble detecting element based on a magnetoresistive effect to generate a rotating magnetic field in a read coil to forcibly move the magnetic bubbles and to change the bit pattern of the magnetic bubbles. In the magnetic bubble detection method of detecting by a detection element, the read coil is driven by an H-type bridge circuit, and a duty ratio of a control signal supplied to the H-type bridge circuit is changed to cancel a magnetic field from a ring magnet. A magnetic bubble detecting method for applying a rotating magnetic field obtained by adding a canceling magnetic field in a direction to a magnetic bubble element. 2. The magnetic bubble is forcibly moved by generating a rotating magnetic field in a read coil using a stretcher and a thin film type magnetic bubble detecting element by a magnetoresistive effect, and the bit pattern of the magnetic bubble is changed. In the magnetic bubble detection method of detecting by a detection element, the driving of the readout coil is performed by an H-type bridge circuit, and a direction of canceling a magnetic field from a ring magnet by changing a phase of a control signal supplied to the H-type bridge circuit. A magnetic field detecting method for applying a rotating magnetic field obtained by adding a canceling magnetic field to a magnetic bubble element. 3. The magnetic bubble is forcibly moved by generating a rotating magnetic field in a read coil using a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect. In the magnetic bubble detection method of detecting with a detection element, the read coil is driven by an H-type bridge circuit and a read drive waveform in a direction coinciding with a center line of the ring magnet in a magnetic bubble element plane based on a rotation angle of the ring magnet. A magnetic field detecting method comprising: applying a rotating magnetic field such that the offset is constant to a magnetic bubble element by obtaining an offset of the control signal and changing a duty ratio of a control signal supplied to the H-type bridge circuit. 4. Using a stretcher and a thin-film type magnetic bubble detecting element based on a magnetoresistive effect, a magnetic field is forcibly moved by generating a rotating magnetic field in a read coil, and a bit pattern of the magnetic bubble is changed. In the magnetic bubble detection method of detecting with a detection element, the read coil is driven by an H-type bridge circuit and a read drive waveform in a direction coinciding with a center line of the ring magnet in a magnetic bubble element plane based on a rotation angle of the ring magnet. A magnetic field detecting method characterized in that a magnetic field is applied to the magnetic bubble element such that the offset is constant and the phase of a control signal supplied to the H-type bridge circuit is changed to make the offset constant. 5. A magnetic bubble is forcibly moved by generating a rotating magnetic field in a read coil using a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect. In the magnetic bubble detection method of detecting with a detection element, the read coil is driven by an H-type bridge circuit and a read drive waveform in a direction coinciding with a center line of the ring magnet in a magnetic bubble element plane based on a rotation angle of the ring magnet. A magnetic bubble detecting method, wherein the offset of the strobe signal is obtained and the timing of the strobe signal is shifted based on the rotation angle of the ring magnet. 6. A magnetic bubble is forcibly moved by generating a rotating magnetic field in a read coil using a stretcher and a thin film type magnetic bubble detecting element based on a magnetoresistive effect, and a bit pattern of the magnetic bubble is changed. In a magnetic bubble detection method of detecting by a detection element, a magnetic circuit error is calculated by detecting a pulse change width of a magnetic bubble signal at two different rotation angles of a ring magnet and subtracting a pulse width change by an electric circuit. A method for detecting a magnetic bubble. 7. The read coil is driven by an H-type bridge circuit, and an offset of a read drive waveform in a direction coinciding with a center line of the ring magnet in a plane of the magnetic bubble element is obtained based on a rotation angle of the ring magnet. The offset is compensated by a magnetic circuit error, and a duty ratio of a control signal supplied to the H-type bridge circuit is changed to apply a rotating magnetic field to the magnetic bubble element so that the compensated offset is constant. The method for detecting a magnetic bubble according to claim 6. 8. The read coil is driven by an H-type bridge circuit, and an offset of a read drive waveform in a direction coinciding with a center line of the ring magnet in a plane of the magnetic bubble element is obtained based on a rotation angle of the ring magnet. The offset is compensated by a magnetic circuit error, and the phase of a control signal supplied to the H-type bridge circuit is changed to apply a rotating magnetic field to the magnetic bubble element so that the compensated offset is constant. The method for detecting a magnetic bubble according to claim 6. 9. A magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is moved on the transfer element loop. A rotation number detector that detects a rotation number of the rotation shaft by reading a pattern; an H-type bridge circuit that drives the readout coil; a rotation angle detector that detects a rotation angle of the ring magnet; Based on the rotation angle of the magnet, the offset of the read drive waveform in the direction coinciding with the center line of the ring magnet in the plane of the magnetic bubble element is obtained, and a correction value corresponding to the rotation angle of the ring magnet is output so that the offset is constant. A correction circuit for changing the duty ratio or the phase of the control signal based on the correction value, and A control circuit for controlling the set to a constant value regardless of the rotation angle of the ring magnet. 10. A magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is moved on the transfer element loop. A rotation speed detector for detecting a rotation speed of the rotation shaft by reading a pattern; an H-type bridge circuit for driving a read coil; a magnetic field measurement circuit for detecting a magnetic field from the ring magnet by a Hall element; A correction value corresponding to the rotation angle of the ring magnet such that the offset of the read drive waveform in the direction coinciding with the center line of the ring magnet in the plane of the magnetic bubble element is determined based on the output signal of the magnetic measurement circuit and the offset is constant. And a duty ratio or phase of the control signal based on the correction value. A control circuit for controlling the offset to a constant value irrespective of the rotation angle of the ring magnet. 11. A magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is moved on the transfer element loop. A rotation number detector that detects a rotation number of the rotation shaft by reading a pattern; an H-type bridge circuit that drives the readout coil; a rotation angle detector that detects a rotation angle of the ring magnet; A magnetic bubble detection circuit that shifts the timing of the strobe signal based on the rotation angle of the magnet; and a cancel magnetic field in a direction that cancels the magnetic field from the ring magnet by changing the duty ratio or phase of the control signal supplied to the H-type bridge circuit. And a control circuit for adding the number of rotations. 12. A magnetic field from a ring magnet attached to a rotating shaft is applied to a magnetic bubble element provided with a transfer element loop, and a magnetic bubble forming a bit pattern is moved on the transfer element loop. A rotation speed detector for detecting a rotation speed of the rotation shaft by reading a pattern; an H-type bridge circuit for driving the readout coil; a magnetic field measurement circuit for detecting a magnetic field from the ring magnet by a Hall element; A magnetic bubble detection circuit that shifts the timing of a strobe signal based on an output signal of the magnetic field measurement circuit; and a direction that cancels a magnetic field from the ring magnet by changing a duty ratio or phase of a control signal supplied to the H-type bridge circuit. And a control circuit for adding a cancel magnetic field to the rotation speed detector.