JP3003061B2 - Speed detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational speed detector using a magnetic bubble, and more particularly to an improvement in a driving circuit of a read coil.

[0002]

2. Description of the Related Art As to a rotational speed detector using a magnetic bubble, the present applicant has filed a Japanese Patent Application No. 61-81901 (referred to as Prior Art 1) or Japanese Patent Application No. 62-212208 (referred to as Prior Art 2). And the principle is widely known. FIG. 6 is a diagram illustrating the principle of operation of a rotational speed detector using magnetic bubbles, and FIG.
8 is a pattern example diagram of a transfer element loop provided on the magnetic bubble element, and FIG. 8 is an enlarged view of a stretcher portion of the transfer element loop of FIG.

In FIG. 6, reference numeral 1 denotes a magnetic bubble element, which is made of a material that generates magnetic bubbles. In addition, a magnetic bubble is 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 detecting elements 12, 13 and aluminum wiring patterns 14, 15, 16 are formed (see FIG. 8). Each of the magnetic bubble detection elements 12 and 13 is constituted by a magnetoresistive element (for example, permalloy). Further, the magnetic bubble element 1 includes
The transfer element 11 made of a thin-film permalloy is formed in a loop shape, and the magnetic bubbles are transferred along the loop (see FIGS. 7 and 8). FIG. 7 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 on each transfer element loop in a bit pattern based on the “memory wheel principle” as known in the preceding example 2. Note that the plane on which the magnetic bubble element 1 is arranged is referred to as x for convenience.
-Called y surface.

Reference numeral 2 denotes a pair of bias magnets (see FIG. 6).
), And has a function of applying a constant vertical magnetic field (bias magnetic field) to the magnetic bubble element 1 to maintain a bubble-like magnetic domain. Reference numerals 3 and 4 denote read coils, which are arranged around the magnetic bubble element 1 as shown in FIG. These read coils 3 and 4 are used when reading the number of revolutions of the ring magnet 5, and generate a rotating magnetic field by passing an alternating current through the coils to transfer the magnetic bubbles 17, 18 and 19. Regarding the read coils 3 and 4, the prior art examples 1 and 2
Is described in detail.

[0005] 5 is a ring magnet consisting of a permanent magnet,
It is attached to 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 rotation of a rotation axis. The magnetic bubble circulates around the transfer element loop with one step / one rotating magnetic field. FIG. 6 shows an example of a ring magnet magnetized to eight poles. In this case, when the rotating shaft makes one rotation, the magnetic bubbles move by four transfer elements 11.

In each transfer element loop shown in FIG. 7, magnetic bubbles having a special arrangement pattern based on the “principle of the memory wheel” described in the preceding example 2 are written. The special arrangement pattern is a pattern having a feature 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 any other position. Therefore, by reading out a pattern of several consecutive bits from a certain position of the transfer element loop, the transfer shift amount of the bit pattern in the loop can be known.

[0007] The magnetic bubble is detected by the magnetic bubble detector 10 arranged at a certain position as described above. The magnetic bubble detector 10 includes magnetic bubble detection elements 12 and 13 shown in FIG. A constant current is applied to the magnetic bubble detection elements 12 and 13 in advance via the aluminum wiring patterns 14, 15 and 16 (the aluminum wiring pattern 16 has a 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 differential signal of the potential signals of the two aluminum wiring patterns 14 and 15 is calculated 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 (0
1110100) is formed depending on the presence or absence of a magnetic bubble. Although the embodiment shown in FIG. 7 has a larger number of bits (for example, around 49 bits), here, 8 bits will be described to make the invention easier to understand. When the ring magnet 5 rotates, the 8-digit bit pattern circulates on the transfer element loop according to the rotation. This circulating operation is performed normally even if the device shown in FIG. 6 stops its operation in an electric circuit due to a power failure or the like. For example, if the ring magnet 5 rotates 10 times while the power of the rotation speed detector shown in FIG. 6 is stopped and its operation is stopped in an electronic circuit, for example, the 8-bit magnetic field is positioned at the position corresponding to the 10 rotations. The bubble is moving. When the power is restored, in order to measure how many times the ring magnet 5 has rotated, the read coils 3 and 4 are excited to generate a rotating magnetic field, and the magnetic bubble is moved in order by, for example, three transfer elements. (See Prior Example 2). Therefore, three time-series bit patterns are read from the magnetic bubble detector 10, and the cumulative number of rotations of the ring magnet 5 can be known from these patterns by the principle of the memory wheel. 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.

Here, when the read coils 3 and 4 are operated, the magnetic field H _M generated by the read coils 3 and 4 and the magnetic field H _R by the ring magnet 5 are superimposed and applied to the magnetic bubble element 1. Then, in the region where the vector direction of the magnetic field H _M of the vector direction and read coil 3, 4 of the magnetic field H _R of the ring magnet 5 facing the same direction, magnetic bubble sensing element 12, 13 made of a permalloy magnetic saturation Thus, there is a problem that the magnetic bubbles 17, 18, and 19 cannot be detected.

This will be described with reference to FIGS. 9 and 10.
In order to transfer the magnetic bubbles 17, 18, and 19, it is necessary to apply, for example, 40 gauss or more as an in-plane magnetic field.
Assuming that the magnetic field H _R generated by the ring magnet 5 is 40 Gauss, the vector locus of the small circle in FIG. 9 is obtained by rotating the ring magnet 5 attached to the rotating shaft. Vector O
At the angle A, the ring magnet 5 stops, and the read coils 3 and
When the cumulative number of rotations of the ring magnet 5 is measured by using 4, the vector trajectory of the rotating magnetic field (for example, H _M = 90 Gauss) by the read coils 3 and 4 becomes a great circle centering on the point A (see FIG. 9). . That is, when viewed from the origin O, the vector sum OB changes 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. 10, and the resistance change is saturated at about 60 gauss. In FIG. 9, if the magnetic bubble is arranged so as to detect the magnetic bubble when the vector sum is directed to the OC, the magnetic flux of the magnetic bubbles 17, 18 and 19 is reduced due to the saturation of the magnetic bubble detection elements 12 and 13 (60 gauss or more in FIG. It cannot be detected.

The present applicant has solved this problem by filing an application for Japanese Utility Model Application No. 62-126991 (hereinafter referred to as Prior Example 3).
In the prior example 3, the x and y components of the magnetic field H _R by the ring magnet are measured using two Hall elements, and a direct current for canceling the magnetic field H _R is superimposed on the read coil.
Although the invention of the preceding example 3 is extremely effective, the measurement of the magnetic field of the ring magnet is performed using a Hall element.

The Hall element outputs a voltage proportional to the strength of the applied magnetic field, and outputs a voltage at which the magnetic field is zero (called an unbalanced voltage). In general, the unbalanced voltage in a Hall element is relatively large, and the Hall element also has a large sensitivity and a large temperature coefficient of the unbalanced voltage. Therefore, when used in a temperature range of, for example, −10 ° C. to + 70 ° C., the measurement accuracy of the magnetic field decreases due to the temperature drift of the unbalanced voltage and the sensitivity. As a result, the magnetic field H _R generated by the ring magnet 5 cannot be appropriately canceled.

In order to solve the inconvenience caused by using such a Hall element, the present applicant has further filed Japanese Utility Model Application No. 2-4864 (described as Prior Example 4). In the prior example 4, the strength of the magnetic field of the ring magnet was known without using the Hall element, and the relationship between the rotation angle of the ring magnet and the magnetic field vector was checked in advance, and the data was stored in the ROM.
, And the data is taken out according to the rotation angle.

FIG. 11 is a diagram showing an example of a configuration of a main part of the preceding example 4.
6 are denoted by the same reference numerals. In the figure, 21 is a rotational angle detector, and outputs a signal corresponding to the rotation angle theta _n of the rotary shaft (not shown) the ring magnet 5 is attached. As the rotation angle detector 21, for example, an optical encoder filed by the present applicant as Japanese Patent Application No. 62-70078 can be used.

Reference numeral 22 denotes a latch, which takes in the output of the rotation angle detector 21 at the application timing of the REQ signal and latches the output. 23 is the angle / address translator, the rotation angle theta _n of the rotating shaft taken through the latch 22 X
This is converted into the address values of the axis ROM 33 and the Y axis ROM. A signal corresponding to the strength of the magnetic field of the X-axis component applied to the magnetic bubble element 1 by the ring magnet 5 is written into the X-axis ROM 33 at an address corresponding to the rotation angle value, and the Y-axis RO
In M34, a signal corresponding to the strength of the Y-axis component magnetic field applied to the magnetic bubble element 1 by the ring magnet 5 is written at an address corresponding to the rotation angle value.

Referring to FIG. 12A, the X-axis ROM 3
3 and the contents of the Y-axis ROM 34 will be described. The locus of the magnetic field vector of the ring magnet 5 applied to the magnetic bubble element 1 is, for example, as shown in FIG. In FIG. 11, since the ring magnet 5 having eight poles is used, when the ring magnet 5 makes one rotation, the magnetic field vector shown in FIG. If these magnetic fields are divided into X and Y components, they change in a sinusoidal manner with the rotation of the ring magnet 5. FIG.
In _{(1), a 1, a} 2, ... an actual rotation angle theta ₁ of the rotary shaft ring magnet 5 is mounted, theta _2, a value corresponding to ..., the relationship, a _n = 4 · θ _n .

The ROM 33 for the X axis and the ROM for the Y axis
The following contents are written in 34. Rotation angle X-axis ROM33 for Y-axis _{ROM34 a 1 AD X1 H X1 AD} Y1 H Y1 a 2 AD X2 H X2 AD Y2 H Y2::::: a n AD Xn H Xn AD Yn H Yn Here, AD _X1 , AD _X2 , ..., AD _Xn are the ROM 3 for the X axis.
A third _{address, AD Y1, AD Y2, ...} , AD Yn is Y
This is the address of the axis ROM 34.

[0018] Since the magnetic vectors applied from the ring magnet 5 to the magnetic bubble device 1 is uniquely determined by the rotation angle theta _n ring magnets 5, above _{a 1, a 2, ...,} a n
, H _X1 , H _X2 ,..., H _Xn and H _Y1 , H _{Y2 ,.}
33 and the Y-axis ROM 34. The contents to be written in the X-axis ROM 33 and the Y-axis ROM 34 need not be the strength of the magnetic field itself, but may be a signal corresponding to the strength of the magnetic field. That is, it may mean a current value flowing through the read coils 3 and 4 to generate a magnetic field that cancels this magnetic field. Further, since the magnetic field rotates four times for one rotation of the rotation axis, each of the ROMs 33, 34
The value of the magnetic field to be written only to the 軸 rotation of the rotation axis.

Reference numerals 35 and 36 denote D / A converters (hereinafter referred to as DACs) for converting digital signals into analog signals.
Known ones can be used. Reference numeral 37 denotes a temperature detector, which is used to correct the temperature of the canceling magnetic field when a ring magnet 5 having a large temperature coefficient such as a ferrite magnet is used. The temperature detector 37 measures the temperature inside the rotation speed detector and inputs the measured temperature to the angle / address converter 23 to correct the measured angle value.

Reference numeral 25 denotes a two-phase oscillator, which outputs two AC signals (I _o · sin ωt, I _o · cos ωt) having phases different from each other by 90 °. Switches 26 and 27 which are turned on when measuring the cumulative number of rotations of ring magnet 5 are output from these two AC signals.
Are added to the subtracters 28 and 29 via During the period in which the cumulative number of rotations of the ring magnet 5 is not measured, the switches 26,
27 is turned off by a controller (not shown).

The subtracters 28, 28 output the output of the two-phase oscillator 25.
The output I of the DAC 35, 36 from the signal _t, I_rIs subtracted.
30 and 31 are coil drivers, and subtracters 28 and 29
Amplify the output of each X-axis coil (reading coil
3) and the Y-axis coil (reading coil 4) as shown in FIG.
A drive current as shown in (3) is applied.

The operation of the configuration shown in FIG. 11 will be described. It is assumed that the rotation of the ring magnet 5 has stopped now. When measuring the cumulative rotational speed of the ring magnet 5, REQ signal as shown in FIG. 13 (1) (operation start signal) is applied to the latch 22 to latch the value of the rotation angle theta _n of the ring magnet 5. The value of the rotation angle theta _n the angle / address translator 23
, _Are converted into address signals AD _Xn and AD _Yn , and are applied to the ROM 33 for the X axis and the ROM 34 for the Y axis. And
H _Xn stored in this address, the analog signal at DAC35,36 the value of H _Yn is read I _t, is converted into I _r.

That is, the ring magnet 5 is output from the DAC 35.
X-axis component magnetic field applied to the magnetic bubble element 1 by
DC current I required to cancel_tIs output and the DAC
DC current required to cancel the Y-axis component magnetic field from 36
I_rIs output. Then, for example, as shown in FIG.
At the falling edge of the REQ signal, switches 26 and 27
Is turned on, and the two-phase signal I of the two-phase oscillator 25_O・ Cosωt
I_O・ Output of DAC35 and DAC36 from sinωt
I_t, I_rIs subtracted. As a result, FIG.
As shown in (3), the offset component I_t, I_rDeduct
Current (I _O・ Cosωt-I_t) And (I_O・ Sinωt-
I_r) Are read via the coil drivers 30 and 31, respectively.
It is applied to output coils 3 and 4.

FIG. 12B is an explanatory diagram of the movement of the magnetic field vector in the apparatus shown in FIG. Assuming now that the magnetic field vector of the ring magnet 5 faces OB and stops,
The angle ab at this time is measured by the rotation angle detector 21, and based on the measured value, the X-axis component H _XB and the Y-axis component H _YB of the magnetic field applied to the magnetic bubble element 1 by the ring magnet 5 are X It is read from the axis ROM 33 and the Y axis ROM 34.

[0025] Then, the current (-I _t), - the magnetic field OB ring magnets 5 by (I _r) is canceled, the rotating magnetic field of the radius of 50 gauss due to read coil 3, 4 shown by a solid line only 12 (2) Is added to the magnetic bubble element 1. Further, since the magnitude of the rotating magnetic field applied from the read coils 3 and 4 is constant, the magnetic field applied to the magnetic bubble detecting elements 12 and 13 is 50 Gauss, and a signal can be detected stably without saturation.

[0026]

However, the conventional circuit shown in FIG. 11 has a problem that the circuit scale becomes large because a relatively large number of analog circuits are used. SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation speed detector capable of accurately canceling a magnetic field generated by a ring magnet with a relatively simple circuit configuration having a small number of analog circuits and being compact.

[0027]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention applies a magnetic field of a permanent magnet attached to a rotating shaft to a magnetic bubble element to move a magnetic bubble composed of a plurality of bit patterns and read the magnetic bubble. The number of rotations for measuring the cumulative number of rotations of the rotating shaft by generating a rotating magnetic field by flowing an exciting current through the coil to forcibly move the magnetic bubbles and detecting a bit pattern of the magnetic bubbles with a magnetic bubble detecting element. In the detector, a switch circuit in which a switch element is connected so as to form a bridge between both ends of the read coil, a DC power supply for supplying an exciting current to the read coil through the switch circuit, Magnetic field detecting means for detecting the intensity of the magnetic field of the X-axis component and the Y-axis component applied to the bubble element, and a permanent magnet based on the magnetic field detection signal On the switching circuit generates a switching driving signal for canceling the magnetic field in the X-axis component and a Y-axis component added to the magnetic bubble device, but with the switch drive means for turning off the drive, the.

[0028]

The exciting current flowing through the read coil is integrated by the inductance of the coil to form a waveform suitable for the movement of the magnetic bubble. Then, the magnetic fields of the X-axis component and the Y-axis component applied to the magnetic bubble element by the rotating permanent magnet are canceled by the exciting current flowing through the reading coil.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a main part of a rotation speed detector according to the present invention, and portions common to FIG. 11 are denoted by the same reference numerals. In the actual device, the read coils 3, 4
Are similarly configured, but FIG. 1 shows a system of one read coil 3 (X-axis coil).

In FIG. 1, four switch elements SW1 to SW1 are formed so as to form a bridge between both ends of the read coil 3.
A switch circuit composed of SW4 is connected. That is, the switch elements SW1 and SW
2 is connected, and the other end of the read coil 3 is connected to a connection point of the switch elements SW3 and SW4. A DC power supply 41 for supplying an exciting current to the read coil 3 is connected to a connection point between the switch elements SW1 and SW3, and a connection point between the switch elements SW2 and SW4 is connected to a common potential point.

Reference numeral 42 denotes an arithmetic unit, which is a rotation angle detector 21
The information necessary for the operation is read out from the ROM 33 based on the angle signal output from the CPU, and a signal corresponding to the strength of the magnetic field of the X-axis component and the Y-axis component applied by the permanent magnet 5 to the magnetic bubble element 1 is calculated. A pulse width for controlling on / off of the switch elements SW1 to SW4 constituting the switch circuit so that a DC current for canceling a magnetic field applied to the magnetic bubble element by the permanent magnet 5 is superimposed on the excitation current based on the calculation result. Operate on data.

Reference numeral 43 denotes a switch control unit.
Each of the switch elements SW1 to SW4 constituting the switch circuit is individually turned on based on the pulse width data calculated in
A control signal for off control is generated and output. FIG. 2 is a specific example diagram of the switch circuit of FIG. 1, and FIG. 3 is a waveform diagram illustrating the switch operation of FIG. In FIG. 2, the switching element S
P-channel MOSFETs are used as W1 and SW4, and N-channel MOSFETs are used as switch elements SW2 and SW3. And each MOSF
Diodes are connected in parallel between the source and the drain of the ET. Each of these MOSFETs is driven by logic signals S1 to S4 via a MOS driver. SW1 is S1, SW2 is S2, SW3 is S3, S3.
W4 is driven by S4. In the following description, the internal resistance of the MOSFET is ignored. Thereby, V _L in FIG. 2 becomes substantially equal to V _O. After detecting the magnetic bubble, it is necessary to rotate the rotating magnetic field in the forward and reverse directions in order to return the magnetic bubble to its original position, but each shows only one direction.

In FIG. 3, (A) shows the current flowing through the coil 3, and (B) shows the voltage applied to the coil 3. In these (A) and (B), the solid line shows a basic operating state when no DC component is applied, and the dotted line gives a DC component to cancel the magnetic field applied to the magnetic bubble element 1 by the permanent magnet 5. It shows the operation state in the case where it is performed. (C) shows the on / off operation state of the switch elements SW1 and SW4, and (D) shows the switch elements SW2 and SW3.
Of FIG.

First, the operation when the DC component shown by the solid line is not applied will be described. Pulse width T of the first section
The switch elements SW1 and SW4 are turned on by the PS, and the voltage shown in FIG. That is, the coil current flows from the DC power supply 41 to the common potential point through the path of the switch element SW1, the coil 3, and the switch element SW4. At this time, since the current flowing through the coil 3 is integrated by the inductance of the coil 3, the current becomes an exponential waveform.

In the pulse width TP2 of the second section, the switch elements SW2 and SW3 are turned on, and the coil current flows from the DC power supply 41 to the common potential point through the path of the switch element SW3 → coil 3 → switch element SW2. At this time, since the voltage applied to the coil 3 is opposite to that at the time of TPS, the current flowing through the coil 3 attenuates exponentially,
Eventually, the current in the opposite direction to the TPS increases.

In the pulse width TP3 of the third section, the switching elements SW1 and SW4 are turned on again, and the voltage applied to the coil 3 is reversed from that in the case of TP2, and the current flowing through the coil 3 is also reversed. One cycle of the coil current ends in the middle of the pulse width TP3, and then the second cycle starts. After the same operation is repeated in the order of TP2 → TP3 → TP2, the pulse width TPE in the fourth section is executed. As a result, the coil 3 is excited three times repeatedly.

Next, the operation when a DC component is given as shown by the dotted line will be described. Here, addition to the plus side is considered. Basically, each pulse width is
Has an internal resistance in addition to the inductance, so it is determined exponentially. The relationship between the pulse width TPS in the first section and the coil current is determined exponentially by the voltage, the resistance value, and the inductance. However, if the resistance is smaller than the inductance, the second approximation is TPS = ( _{L * I L / V L)} + (L * R * I L 2/2 *
V _L ²⁾ _L: Inductance R: Internal resistance I _L: current value after TPS lapse V _L: can be approximated by a voltage applied to the coil.

In the pulse width TP2 'of the second section and the pulse width TP3' of the third section, the duty is 50% (T
If P2 '= TP3' = TP2 = TP3), the DC component becomes almost zero. Further, the relationship between the duty and the addition becomes substantially linear. ΔD = -R (1-exp ( -T 0)) * exp (-T 0/2) *
i _DC / 2 * V _L T ₀ = (R / L) * T T: coil operating cycle i _DC : DC component added to coil current ΔD: increment from 50% duty TP2, TP3 have a duty of D = 0. Assuming 5
It can also be obtained by the following equation.

TP2 = (D + ΔD) * T TP3 = {1− (D + ΔD)} * T TPE is also determined exponentially, and is also obtained by the following equation when the resistance is smaller than the inductance. _{TPE = (- L * I L} / V L) - (1 * L 2 * I L 2 * R /
2 * V _L ² ) Each of the pulse widths is calculated by the calculation unit 42 based on the quadratic expression as described above, and based on the calculation results, the switch control unit 43 controls the on / off of the switch elements SW1 to SW4. By generating and outputting the drive signal, a desired DC component can be given to the coil current. And
According to such driving, the read coil is excited by the substantially triangular wave signal, so that the magnetic bubbles can also move smoothly.

FIG. 4 is a diagram showing a specific example of the switch control unit 43. The switch control section 43 includes counters CTR1 to CTR
It is composed of TR5 and a drive signal generator SG. Each of the counters CTR1 to CTR5 can set initial value data by a load signal LD, and is controlled by an enable signal E. The counters CTR to CTR4 are provided with registers REG1 to REG4, respectively.

The counter CRT1 generates a pulse width TPS ', the counter CRT2 generates a pulse width TP2',
The counter CRT3 generates a pulse width TP3 ', and the counter CRT4 generates a pulse width TPE'. Counter C
TR5 specifies the frequency. The drive signal generator SG is configured by logic, and each of the counters CTR1 to CTR5
Of each counter CTR1 to CT
Upon receiving carry signal C of R5, switch elements SW1 to SW
It generates and outputs drive signals S1 to S4 for controlling ON and OFF of W4.

The operation of FIG. 4 will be described with reference to the timing chart of FIG. It is assumed that initial value data is already stored in the registers REG1 to REG4 of the counters CTR to CTR4, and the count value of the counters has been reset. SW1 to SW4 are turned off. First, the coil start signal is supplied to the drive signal generator SG
, The load signals LD1 to LD4 become L level, and the data stored in the respective registers REG1 to REG4 are loaded into the counters CTR to CTR4 as the count initial value.

Next, the enable signal E1 of the counter CTR1 becomes L level, and the counter CTR1 starts counting the clock CLK from the count initial value.
Then, the drive signal generator SG outputs drive signals S1 and S4 for turning on SW1 and SW4. When the count value reaches a predetermined value, the counter CTR1 outputs a carry signal C1 to the drive signal generator SG. Upon receiving the carry signal C1, the drive signal generator SG sets the enable signal E1 to the H level to stop the counting operation of the counter CTR1, and simultaneously sets the enable signal E2 to the L level to cause the counter CTR2 to generate the clock CLK from the initial count value. Start the count operation. Also,
The enable signal E5 is also set to the L level and the counter CTR5 is set.
Is also started. Furthermore, SW1, SW4
Are turned off, and drive signals S1 to S4 for turning on SW2 and SW3 are output.

When the count value reaches a predetermined value, the counter CTR2 outputs a carry signal C2 to the drive signal generator SG. Upon receiving the carry signal C2, the drive signal generator SG sets the enable signal E2 to H level to stop the counting operation of the counter CTR2, and simultaneously sets the enable signal E3 to L level to cause the counter CTR3 to output the clock CLK from the initial count value. Start the count operation. Further, SW1 and SW4 are turned on again and SW
2. It outputs drive signals S1 to S4 for turning off SW3.

The drive signal generator SG is provided with a counter CTR3
The load signal LD of the counter CRT2 during the counting operation of
2 is set to the L level to load the data of the pulse width TP2 'into the counter CRT2. When the count value reaches a predetermined value, the counter CTR3 outputs a carry signal C3 to the drive signal generator SG. Upon receiving the carry signal C3, the drive signal generator SG sets the enable signal E3 to the H level to stop the counting operation of the counter CTR3, and simultaneously sets the enable signal E2 to the L level to cause the counter CTR2 to again output the clock CLK from the initial count value. Is started. Further, the drive signal generator SG sets the load signal LD3 of the counter CRT3 to L level during the count operation of the counter CTR2, and outputs the data of the pulse width TP3 'to the counter CRT3.
To load. Further, drive signals S1 to S4 for turning off SW1 and SW4 again and turning on SW2 and SW3 are set.
S4 is output.

Carry signal C2 from counter CTR2
Is output, the counter CTR2 is stopped and the counter CRT3 is operated again. Then, the drive signal generator S
G outputs drive signals S1 to S4 for turning on SW1 and SW4 and turning off SW2 and SW3. These alternate operations of the counter CTR2 and the counter CRT3 are repeated until the carry signal C5 is output from the counter CTR5.

The carry signal C5 is output from the counter CTR5.
Is output, the enable signal E4 is set to the L level, and the counter CTR4 outputs the clock CLK from the count initial value.
To generate a switch drive signal related to the pulse width TPE ′, and output drive signals S1 to S4 for turning on SW1 and SW4 and turning off SW2 and SW3 during the pulse width TPE ′. I do. When the carry signal C4 is output, a series of operations ends, and SW1 to SW1 are output.
SW4 is turned off.

As described above, the switch elements SW1 to SW4
Are generated and output. Here, in changing each pulse width, the values of the registers REG1 to REG4 of the counters CTR to CTR4 may be changed. The counter CTR5 relating to the frequency may be designed to be able to count only the required frequency. The frequency of the counter CTR5 can be changed by providing a register like other counters.

In the above embodiment, the detector for detecting the magnitude of the magnetic field by the ring magnet is a rotation angle detector and a ROM.
Although the above example has been described, the magnetic field components in the x and y directions may be measured by a Hall element, a magnetoresistive element, or the like. The configuration of the switch control unit is not limited to the embodiment, and other circuit configurations may be used as long as an output signal having a desired pulse width can be obtained.

The switch element constituting the switch circuit is N
Not limited to the combination of MOS and PMOS, but NM
The OS alone may be used. Further, the present invention is not limited to the MOSFET, and may be, for example, a combination of a bipolar transistor and a diode. In the above description, MO
Although the internal resistance of the SFET is neglected, if it cannot be neglected, it may be considered by including it in the internal resistance of each equation of TPS, ΔD, and TPE.

[0051]

As described above, according to the rotation speed detector of the present invention, the magnetic field generated by the ring magnet can be canceled accurately with a relatively simple circuit configuration having a small number of analog circuits and a small size. it can. According to such a configuration, most circuits can be integrated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a rotation speed detector according to the present invention.

FIG. 2 is a diagram illustrating a specific example of the switch circuit of FIG. 1;

FIG. 3 is a waveform diagram illustrating the switch operation of FIG.

FIG. 4 is a specific example diagram of a switch control unit in FIG. 1;

FIG. 5 is a timing chart illustrating the operation of FIG.

FIG. 6 is an operation principle diagram of a rotation speed detector using a magnetic bubble.

7 is an exemplary pattern diagram of a transfer element loop provided on the magnetic bubble element of FIG. 6;

FIG. 8 is an enlarged view of a stretcher portion of the transfer element loop of FIG. 7;

FIG. 9 is a diagram illustrating a vector of a rotating magnetic field.

FIG. 10 is a graph showing a characteristic example of a magnetic field-resistance change of a magnetic bubble detection element.

FIG. 11 is a diagram illustrating an example of a configuration of a main part of a preceding example 4.

FIG. 12 is a diagram illustrating a vector of a rotating magnetic field.

FIG. 13 is an operation explanatory diagram of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic bubble element 3, 4 Reading coil 5 Ring magnet 21 Angle rotation detector 33 ROM 41 DC power supply 42 Operation part 43 Switch control part

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01P 3/487 G01D 5/245

Claims (1)

(57) [Claims] 1. A magnetic field comprising a plurality of bit patterns is moved by applying a magnetic field of a permanent magnet attached to a rotating shaft to a magnetic bubble element, and a rotating magnetic field is generated by supplying an exciting current to a read coil to generate the magnetic field. In a rotation speed detector for measuring a cumulative rotation speed of a rotation shaft by forcibly moving a bubble and detecting a bit pattern of a magnetic bubble with a magnetic bubble detection element, a bridge is formed between both ends of the reading coil. A switching circuit having a switching element connected thereto, a DC power supply for supplying an exciting current to the readout coil via the switching circuit, an X-axis component and a Y component applied by the permanent magnet to the magnetic bubble element.
Magnetic field detection means for detecting the strength of the magnetic field of the axial component; and a switch drive signal for canceling the magnetic field of the X-axis component and the Y-axis component applied to the magnetic bubble element by the permanent magnet based on the magnetic field detection signal. Turn on the switch circuit,
A rotation speed detector including a switch driving unit that performs off driving.