JP3010999B2 - 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 magnetic bubbles, and more particularly to an improvement in a driving circuit of a read coil for detecting a rotational speed.

[0002]

2. Description of the Related Art The applicant of the present invention has disclosed a rotational speed detector using a magnetic bubble, as disclosed in Japanese Patent Application No. 61-81901 (hereinafter referred to as "Prior Art 1").
An application is filed in Japanese Patent Application No. 62-212208 (hereinafter referred to as Precedent Example 2) and the principle thereof is widely known. FIG. 4 is a diagram illustrating the operation principle of a rotation speed detector using magnetic bubbles, FIG. 5 is a diagram illustrating a pattern example of a transfer element loop provided on the magnetic bubble element in FIG. 4, and FIG.
FIG. 6 is an enlarged view of a stretcher portion of the transfer element loop of FIG.

In FIG. 4, 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:
As shown in FIG. 6, magnetic bubble detecting elements 12, 13 and aluminum wiring patterns 14, 15, 16 are formed.
Each of the magnetic bubble detection elements 12 and 13 is constituted by a magnetoresistive element (for example, permalloy). Further, a transfer element 11 formed 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 (see FIGS. 5 and 6). Although one transfer element loop is shown in FIG. 5, a plurality of transfer element loops are provided on the actual magnetic bubble element 1. This is for counting a larger number of rotations with a small number of transfer elements according to the "Vernier principle". On each of the transfer element loops, a predetermined number of magnetic bubbles are written 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. 4).
), 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. Reading coils 3 and 4 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 rotations of the ring magnet 5, and generate a rotating magnetic field by passing an alternating current through the coils to generate magnetic bubbles 17, 18 and 1.
Transfer 9 The read coils 3 and 4 are described in detail in Prior Examples 1 and 2.

[0005] Reference numeral 5 denotes a ring magnet formed of a permanent magnet, which 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. 4 shows an example of a ring magnet magnetized with eight poles. In this case, when the rotation axis rotates once, the magnetic field rotates four times, so that the magnetic bubbles move by four transfer elements 11.

In each transfer element loop shown in FIG. 5, a predetermined number of magnetic bubbles are written in accordance with a special arrangement pattern based on the “principle of the memory wheel” described in the preceding example 2. Such a special arrangement pattern indicating the presence or absence of a magnetic bubble is defined as a pattern in which a certain number of consecutive bits extracted from a certain position in all the bit patterns are the same in number of bits extracted from any other position. It is a pattern with the characteristic that it does not become the same. Therefore, by reading out a continuous pattern of several bits from a certain position of the transfer element loop, it is possible to know the transfer shift amount of the bit pattern indicating the presence or absence of magnetic bubbles in the loop.

The magnetic bubble is detected by a magnetic bubble detector 10 arranged at a certain position on the transfer element loop. The magnetic bubble detector 10 includes magnetic bubble detection elements 12 and 13 shown in FIG. The magnetic bubble detecting element 12,
13, a constant current is passed through the aluminum wiring patterns 14, 15, 16 in advance (the aluminum wiring pattern 16).
Is the ground potential). Then, the magnetic bubble detecting elements 12, 1
When the magnetic bubbles 17, 18, 19 move to the portion 3, the resistance value changes.
5 changes. These two aluminum wiring patterns 1
A differential detection signal of a magnetic bubble is obtained by performing a differential operation on the potential signals 4 and 15 by a differential amplifier (not shown).

In the magnetic bubble element 1 as described above,
On the transfer element loop, for example, a bit pattern of eight bits per loop (01
110100) is formed by the presence or absence of magnetic bubbles. In the embodiment shown in FIG. 5, there are more bits (for example, around 49 bits), but here, 8 bits will be described for easy understanding of the invention. When the ring magnet 5 rotates, the eight-digit bit pattern circulates on the transfer element loop in accordance with the rotation. The circulating operation is performed even if the device shown in FIG. Normally done. For example, when the ring magnet 5 rotates 10 times while the power of the rotation speed detector shown in FIG. 4 is stopped and its operation is stopped electronically, for example, the 8-bit magnetic bubble is placed at a position corresponding to the 10 rotations. Is moving. When the power is restored, the read coils 3 and 4 are operated to measure the number of rotations of the ring magnet 5 to generate a rotating magnetic field, and the position of the bit pattern of the magnetic bubble is sequentially moved by, for example, three transfer elements. (See the preceding example 2). Accordingly, a 3-bit bit pattern corresponding to the presence or absence of a magnetic bubble is read out from the magnetic bubble detector 10 in a time series according to the movement of the bit pattern of the magnetic bubble. Can be known. 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 bit pattern of the magnetic bubble by three transfer elements and return to the original position before detection. As described above, unless the bit pattern of the magnetic bubble once transferred to read the cumulative rotation speed of the rotating shaft is returned to the original position, the accumulated value is added to the cumulative rotation speed of the rotating shaft to obtain an accurate rotation speed. Will be gone.

Incidentally, a high voltage is required to generate a rotating magnetic field having a relatively high frequency in such a reading coil. Therefore, in the current apparatus, a power supply voltage is boosted to charge a capacitor with necessary electric charge, and the electric charge is used as a power supply to drive a drive circuit of a read coil. Here, the electric charge required for driving the read coil is proportional to the length of the rotating magnetic field generation time, and increases in proportion to the number of bits of the magnetic bubble to be read. When the number of bits of a magnetic bubble to be read becomes large, a capacitor and a charging circuit having a large capacity are required.

[0010]

However, the number of bits of a magnetic bubble to be read is increased in order to improve reliability, for example, a redundant bit is required to detect an error in reading a magnetic bubble. . As a result, a capacitor having a large capacitance must be used as a capacitor, and a large-scale capacitor must be used as a charging circuit.

That is, in the current apparatus, there is a problem that it is difficult to reduce the size and increase the cost in order to increase the reliability in reading magnetic bubbles. An object of the present invention is to solve such a problem, and an object of the present invention is to provide a rotation speed detector which has improved reliability, reduced size, and reduced cost.

[0012]

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 a capacitor. An alternating current is applied to the readout coil using the charged electric power as a power source to generate a rotating magnetic field to forcibly move the magnetic bubble, and the bit pattern of the magnetic bubble is detected by the magnetic bubble detecting element, thereby detecting the rotation axis. In a rotational speed detector for measuring the cumulative rotational speed, when the number of bits required for measuring the cumulative rotational speed of the rotating shaft is N, the magnetic bubble is forcibly moved by N / 2 bits in the first direction. The readout coil is driven in a first rotation mode for returning to the original position after returning to the original position and in a second rotation mode for returning to the original position after forcibly moving N / 2 bits in the second direction. Characterized in that a means that.

[0013]

The number of bits required for measuring the cumulative number of rotations of the rotating shaft is N.
Is read out twice in N / 2-bit units. As a result, the number of read bits per operation is reduced to half that of the current device, so that the capacitance of the capacitor can be reduced to half and the size of the charging circuit can be reduced.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a main part of an embodiment of the present invention, and portions common to FIG. 4 are denoted by the same reference numerals. In the figure, reference numeral 21 denotes a sequencer that outputs a control signal to each unit in a predetermined time relationship, and is controlled by a calculator (not shown). 22 is a read coil driver,
By causing an alternating current to flow through the read coils 3 and 4 to generate a rotating magnetic field, the magnetic bubbles are forcibly moved from the initial position on the transfer element loop by N / 2 steps (bits) alternately in both the left and right directions. For example, the process of moving N / 2 steps clockwise from the initial position and returning to the initial position again is referred to as a first rotation mode.
The process of moving back by 1/2 steps and returning to the initial position again is the second
Rotation mode. A charging circuit 23 charges the capacitors C1 and C2, and the read coil driver 22 is driven by using the electric charges charged in the capacitors C1 and C2 as a power supply. Numeral 24 denotes a shift register, which takes in serial data representing the presence or absence of magnetic bubbles, which is output from the magnetic bubble element 1 in response to the driving of the read coils 3 and 4 by 1, 0 in each rotation mode in accordance with a read synchronization signal. 2
Temporarily store bits. Reference numeral 25 denotes an N-bit register which transfers and stores serial data taken into the shift register 24 as parallel data by dividing into upper N / 2 bits and lower N / 2 bits for each rotation mode.

The operation of FIG. 2 will be described with reference to the timing charts of FIGS. FIG. 3 is an enlarged view of the "rotation" portion of FIG. When a pattern reading request REQ is added to the sequencer 21 from a computing unit (not shown), the sequencer 21 instructs the charging circuit 23 to start charging (A). The charging circuit 23 receives the charging start command and charges the capacitors C1 and C2 with + Vc (C) and -Vc (D). When the potential of each of the capacitors C1 and C2 reaches a predetermined value, the charging circuit 23 outputs a charge completion signal to the sequencer. 21 (B).

On the other hand, the sequencer 21 instructs the read coil driver 22 to rotate clockwise CW or counterclockwise CCW as the initial rotation direction (E). In this embodiment, CCW is designated as the first rotation mode, and CW is designated as the second rotation mode.
Is instructed. After instructing the initial rotation direction, the sequencer 21 gives a start signal to the read coil driver 22 to instruct the start of the read operation (F). The read coil driver 22 generates a magnetic bubble on the transfer element loop,
In the rotation mode, N / 2 bits are forcibly transferred to the CCW from the initial position and then returned to the CW by N / 2 bits. In the second rotation mode, the NW bits are forcibly transferred to the CW from the initial position and then transferred to the CCW. Automatic switching drive is performed so as to return N / 2 bits (K, L). Read coil driver 2
Reference numeral 2 denotes a read rotation signal for which a predetermined rotation direction (for example, C
W), output to the shift register 24 (G, M),
A read completion signal is returned to the sequencer 21.

The sequencer 21 designates the upper and lower parts of the register 25 (eg, the lower part in the first rotation mode and the upper part in the second rotation mode) by the register address (H). The data is transferred and stored in the register 25 (I). When the first rotation mode and the second rotation mode are completed in this way, the register 25 stores N-bit magnetic bubble pattern data. The data in the register 25 is taken into the arithmetic unit after the end signal is returned from the sequencer 21 to the arithmetic unit (J).

With this configuration, the number of bits N required for measuring the cumulative number of rotations of the rotating shaft is read out in two N / 2-bit steps, so that the driving time per read coil is one. / 2, and the charge for driving the readout coil is reduced by half, so that the capacitance of the capacitor may be reduced by half, and the size of the charging circuit can be reduced. In addition, when the scale of the capacitor and the charging circuit is fixed, the number of redundant bits can be increased because the magnetic bubble pattern data having a relatively double bit number can be taken, and the error detection oversight rate can be reduced. Reliability can be improved.

In the above embodiment, an example in which two capacitors are charged with + Vc and -Vc has been described. However, the number of capacitors is not limited to two and may be one depending on conditions.

[0020]

As described above, according to the present invention,
It is possible to provide a rotation speed detector that realizes improved reliability, downsizing, and cost reduction.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of an embodiment of the present invention.

FIG. 2 is a timing chart illustrating the operation of FIG.

FIG. 3 is a timing chart in which a rotation section of FIG. 2 is enlarged.

FIG. 4 is an operation principle diagram of a rotation speed detector using magnetic bubbles.

5 is an exemplary pattern diagram of a transfer element loop provided on the magnetic bubble element of FIG. 4;

FIG. 6 is an enlarged view of a stretcher section of the transfer element loop of FIG.

[Explanation of symbols]

 21, 22 register 23, 24 shift register 25 clock source 26 counter 27, 28 comparator 29 AND gate 30 sequencer

Claims (1)

(57) [Claims] 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 an alternating current is supplied to a read coil using electric charges charged in a capacitor as a power supply. In a rotation speed detector for generating a rotating magnetic field to forcibly move the magnetic bubble and detecting a bit pattern of the magnetic bubble with a magnetic bubble detecting element to measure a cumulative rotation speed of the rotation shaft, Assuming that the number of bits necessary for measuring the cumulative rotation speed is N, the magnetic bubble is forcibly moved in the first direction by N / N.
The read coil is moved in a first rotation mode for returning to the original position after moving by 2 bits, and in a second rotation mode for returning to the original position after forcibly moving N / 2 bits in the second direction. A rotation speed detector provided with driving means.