JPH0749381Y2 - RPM detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a rotation speed detector using a magnetic bubble.

<Prior Art> The present application is disclosed in Japanese Patent Application No. 62-126991 "rotation speed detector" (hereinafter
It is an improvement of the previous application).

Regarding the rotation speed detector using a magnetic bubble, the applicant of the present invention has a Japanese Patent Application No. 61-81901 (referred to as the first example) and a Japanese Patent Application No. 6-81901.
The application was filed in No. 2-212208 (referred to as Prior Art 2) and the principle is widely known. FIG. 6 is a diagram showing the operating principle of a rotation speed detector using a magnetic bubble, FIG. 7 is a diagram showing an example of a pattern of transfer element loops formed on the magnetic bubble element of FIG. 6, and FIG. FIG. 7 is an enlarged view of the stretcher portion of the transfer element loop of FIG. 7.

In FIG. 6, reference numeral 1 denotes a magnetic bubble element, which is made of a material that generates a magnetic bubble. In addition, the magnetic bubble has a cylindrical shape in a perpendicular magnetic film epitaxially grown by several μm on GGG (gadolinium-gallium-garnet) by applying a perpendicular magnetic field (bias magnetic field) of appropriate strength. Occurs in. This magnetic bubble element 1 includes magnetic bubble detection elements 12, 13 and an aluminum wiring pattern 1
4, 15 and 16 are formed (see FIG. 8). The magnetic bubble detection elements 12 and 13 are magnetic resistance elements (for example, permalloy).
Composed of. Further, a transfer element 11 made of thin film permalloy is formed in the magnetic bubble element 1 in a loop shape, and the magnetic bubble is transferred along the transfer element 11 (see FIGS. 7 and 8). Although FIG. 7 shows one transfer element loop, a plurality of transfer element loops are provided on the actual magnetic bubble element 1. On each transfer element loop, a magnetic bubble is written in the bit pattern of the memory wheel as known in the prior art 2. The plane on which the magnetic bubble element 1 is arranged is referred to as an xy plane for convenience.

Reference numeral 2 is a set of two bias magnets (see FIG. 6), a constant magnetic field (bias magnetic field) perpendicular to the magnetic bubble element.
And has a function of holding a bubble-shaped magnetic domain.

Read coils 3 and 4 are arranged around the magnetic bubble element 1 as shown in FIG. And this read coil 3,4
Is used when reading the number of rotations of the ring magnet 5, and an alternating current is passed through the coil to generate a rotating magnetic field to transfer the magnetic bubbles 17, 18 and 19. The read coils 3 and 4 are described in detail in the prior arts 1 and 2.

Reference numeral 5 denotes a ring magnet, which is a permanent magnet attached to a rotating shaft (not shown). The ring magnet 5 gives an in-plane magnetic field parallel to the magnetic bubble element 1,
This in-plane magnetic field rotates as the rotating shaft rotates. The magnetic bubble circulates in the transfer element loop with one step / one rotating magnetic field. FIG. 6 shows an example of a ring magnet magnetized to have eight poles. In this case, when the rotating shaft makes one rotation, the magnetic bubbles move by four transfer elements 11.

Magnetic bubbles having a special arrangement pattern based on the "principle of the memory wheel" described in the prior art 2 are written in each transfer element loop shown in FIG. The special array 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, the shift amount of the loop can be known by reading a pattern of several consecutive bits from a certain fixed position.

The magnetic bubble is detected by the magnetic bubble detector 10 arranged at the certain position. The magnetic bubble detector 10 is composed of magnetic bubble detecting elements 12 and 13 shown in FIG. The magnetic bubble detecting elements 12, 13 are provided with aluminum wiring patterns 14, 15, 1
A constant current is previously passed through 6 (aluminum wiring pattern 16 is ground potential). And the magnetic bubble detection element 12,1
When the magnetic bubbles 17, 18, 19 move to the portion of 3, the resistance value changes, so that the potentials of the aluminum wiring patterns 14, 15 change. The potential signals of the two patterns 14 and 15 are differentially calculated by a differential amplifier (not shown) to obtain a magnetic bubble detection signal.

In the magnetic bubble element 1 as described above, the transfer element loop has a bit pattern (01110100) of 8 bits, which is determined by the "principle of the memory wheel", for example.
Are formed by the presence or absence of magnetic bubbles. In the embodiment shown in FIG. 7, there are a larger number of bits (for example, around 49 bits), but here, in order to make the device easier to understand,
Explain in bits. When the ring magnet 5 rotates, this 8-digit bit pattern circulates on the transfer element loop according to the rotation. This patrol operation is normally performed even when the device shown in FIG. 6 is in a power failure state. For example, when the ring magnet 5 makes, for example, 10 rotations when the power supply of the rotation speed detector shown in FIG. 6 is stopped and its operation is stopped by an electronic circuit, the ring magnet 5 is moved to a position corresponding to the 10 rotations. Bit pattern magnetic bubbles are moving.

When the power is restored, in order to measure the number of rotations of the ring magnet 5, the read coils 3 and 4 are operated to generate a rotating magnetic field, and the magnetic bubbles are moved in positions in order of, for example, three transfer elements. (See the preceding example 2). Therefore, three time-series bit patterns are read from the magnetic bubble detection unit 10, and the cumulative number of rotations of the ring magnet 5 can be known from this pattern by the principle of the memory wheel. After the detection, the read coils 3 and 4 apply a rotating magnetic field in the opposite direction to the above to the magnetic bubble element 1 to move the magnetic bubbles by the amount of three transfer elements and return them to their original positions.

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 from the} ring magnet 5 are superimposed and applied to the magnetic bubble element 1. Then, in a region where the vector direction of the magnetic field H _R of the ring magnet 5 and the vector direction of the magnetic field H _M of the read coil are oriented in the same direction, the magnetic bubble detection element 1 made of permalloy 1
There is a problem that 2 and 13 are magnetically saturated and the magnetic bubbles 17, 18 and 19 cannot be detected.

This will be described with reference to FIGS. 4 and 5. Magnetic bubble
In order to transfer 17,18,19, an in-plane magnetic field of 40
You need to add more than Gauss. When the magnetic field H _R generated by the ring magnet 5 is 40 gauss, the vector locus of the small circle in FIG. 4 is obtained when the ring magnet 5 attached to the shaft rotates. When the ring magnet 5 is stopped at the angle of the vector ▲ ▼ and the cumulative number of rotations of the ring magnet 5 is measured by the read coils 3 and 4, the rotating magnetic field (for example, H _M = 90 gauss) of the read coils 3 and 4 is measured. The vector locus becomes a great circle centered on the point A (see FIG. 4). That is, when viewed from the origin o, the vector sum ▲ ▼ changes between 50 and 130 gauss.

On the other hand, the characteristic of the change in the magnetic field-resistance value of the magnetic bubble detection elements 12, 13 is as shown in FIG. 5, and the change in resistance value is saturated at about 60 gauss. If the magnetic bubbles are arranged so as to detect the magnetic bubbles when the vector sum is directed to ▲ ▼ in Fig. 4, the magnetic bubbles 17, 18, 19 are caused by the saturation of the magnetic bubble detection elements 12, 13 (60 gauss or more from Fig. 4). The magnetic flux of can not be detected.

In view of such a point, the present applicant solved the problem by applying for Japanese Patent Application No. Sho 62-126991. In this prior application, the x and y components of the magnetic field H _R due to the ring magnet are measured using two Hall elements, and a DC current that cancels this magnetic field H _R is superimposed on the read coil.

<Problems to be Solved by the Invention> Although the invention of the prior application is extremely effective, the Hall element measures the magnetic field of the ring magnet.

The Hall element outputs a voltage proportional to the strength of the applied magnetic field, but outputs a certain voltage (called an unbalanced voltage) even when the magnetic field is zero. Generally, this unbalanced voltage in the Hall element is relatively large, and the Hall element also has a large temperature coefficient of sensitivity and unbalanced voltage. Therefore, for example, when used in the temperature range of −10 to + 70 ° C., the measurement accuracy of the magnetic field deteriorates due to the unbalanced voltage component and the temperature drift of sensitivity. As a result, the magnetic field HR generated by the ring magnet 5 cannot be canceled appropriately.

An object of the present invention is to provide a rotation speed detector that can accurately cancel the magnetic field generated by the ring magnet 5 without using a Hall element.

<Means for Solving the Problems> In order to solve the above problems, the present invention applies a magnetic field of a permanent magnet (5) attached to a rotating shaft to a magnetic bubble element (1) to form a magnetic field composed of a plurality of bits. Cumulative rotation of the rotating shaft by moving the bubble and flowing an alternating current in the read coil to generate a rotating magnetic field, forcibly moving the magnetic bubble and detecting the bit pattern of the magnetic bubble with the magnetic bubble detection element. In a device for measuring the number, a rotation angle detector that outputs a signal according to the rotation angle of the rotation axis, and a magnetic field strength of an X-axis component that a permanent magnet applies to a magnetic bubble element at an address corresponding to the rotation angle value. And a signal corresponding to the strength of the magnetic field of the Y-axis component applied by the permanent magnet to the magnetic bubble element at the address corresponding to the rotation angle value. Based on the signal stored in the second storage means and the signals introduced from the first and second storage means, a direct current for canceling the magnetic field applied to the magnetic bubble element by the permanent magnet is superimposed on the alternating current and supplied to the read coil. The circuit means and the means consisting of are taken.

<Operation> The strength of the magnetic field applied from the permanent magnet attached to the rotating shaft to the magnetic bubble element has a certain relationship with the rotation angle of the rotating shaft. Each of the rotation angle values a1, a is stored in the first and second storage means.
2, ..., and magnetic fields H _X1 , H _X2 , ...
, And signals corresponding to the magnetic fields H _Y1 , H _Y2 , ... Of the Y-axis component are respectively written. Then, the signals (H _X1 , H _X2 , H _X2 , corresponding to the rotation angle value of the rotation axis measured by the rotation angle detector 21
..., in which reading H _Y1, H _Y2, ... a) from the first and second storage means, the permanent magnets on the basis of this was to cancel the magnetic field applying to the magnetic bubble elements.

<Example> Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a main part of a rotation speed detector according to the present invention, FIG. 2 is a time chart of the circuit of FIG. 1, and FIG. 3 is a diagram showing a vector locus of a magnetic field by a ring magnet and a read coil. Is.

In FIG. 1, reference numerals 3 and 4 are read coils, which are the same as those already described with reference to FIG. That is, the magnetic bubble element 1 is arranged in the coils 3 and 4.

Reference numeral 5 is a ring magnet, which is also the same as that already described in FIG.

Reference numeral 21 denotes a rotation angle detector, which outputs a signal according to a rotation angle θ _n of a rotation shaft (not shown) to which the ring magnet 5 is attached. As the rotation angle detector 21, for example, an optical encoder which the applicant of the present application filed in Japanese Patent Application No. 62-70078 and is already widely known can be used.

Reference numeral 22 is a latch that takes in the output of the rotation angle detector 21 and latches it at the application timing of the REQ signal.

Reference numeral 23 is an angle / address converter, which converts the rotation angles θ ₁ , θ ₂ , ... Of the rotary shaft fetched via the latch 22 into the address values of the X-axis ROM and the Y-axis ROM described later. is there.

Reference numeral 33 denotes a first storage means, in which 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 at the address corresponding to the rotation angle value. Since a ROM is usually used as the first storage means, hereinafter, X
Marked as ROM 33 for axis.

Reference numeral 34 denotes a second storage means in which a signal corresponding to the strength of the magnetic field of the Y-axis component applied to the magnetic bubble element 1 by the ring magnet 5 is written at an address corresponding to the rotation angle value. This second storage means is hereinafter referred to as Y-axis ROM 34.

The contents of the X-axis ROM 33 and the Y-axis ROM 34 will be described with reference to FIG. 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. Since the 8-pole magnetized ring magnet 5 is used in FIG. 1, when the ring magnet makes one revolution, the magnetic field vector in FIG. 3 (1) makes four revolutions. Considering the X and Y components separately, the magnetic field changes sinusoidally as the ring magnet rotates. In the figure, a1, a2, ... Are the actual rotation angles θ ₁ , of the rotation shaft (not shown) to which the ring magnet 5 is attached.
It is a value according to θ ₂ , ... And the relationship is an = 4 · θ _n . Then, the following contents are written in the R0M33 for the X axis and the ROM 34 for the Y axis.

Rotation angle For X axis R0M For Y axis ROM a1 ADX1 H _X1 ADY1H _Y1 a2 ADX2 H _X2 ADY2H _Y2 :::::: an ADXn H _Xn ADYnH _Yn where ADX1, ADX2, ... are the addresses of the X axis ROM. Yes, ADY1, ADY2, ... Are the addresses of the Y-axis ROM.

Since the magnetic vector applied from the ring magnet 5 to the magnetic bubble element 1 is uniquely determined by the rotation angle θ _n (= an / 4) of the ring magnet 5, the a1, a2, ...
The relationship between _X1 , H _X2 , ... And H _Y1 , H _Y2 , ... Can be known, and this value can be written in the X-axis ROM and the Y-axis ROM.

The contents written in the X-axis ROM 33 and the Y-axis ROM 34 (for example, H
_X1 , H _X2 , ...) may be signals corresponding to the magnetic field strength, not the magnetic field strength itself. To add a further explanation, it may mean the value of current flowing through the read coils 3 and 4 in order to generate a magnetic field that cancels this magnetic field (H _X1 , H _X2 , ...).

Also, since the magnetic field makes four rotations for one rotation of the rotating shaft,
The value of the magnetic field written in each ROM is only 1/4 rotation of the rotation axis.

35 and 36 are digital / analog converters (hereinafter simply referred to as DACs) for converting digital signals into analog signals,
Known ones can be used.

The configuration after DAC35,36 is exactly the same as the previous application. That is,
A two-phase oscillator 25 outputs two AC signals (Io · sin ωt, / Io · cos ωt) having 90 ° different phases. These two AC signals are applied to subtractors 28 and 29 via switches 26 and 27 that are turned on when measuring the cumulative rotation speed of the ring magnet 5. The switches 26 and 27 are turned off by a controller (not shown) during a period in which the cumulative rotation speed of the ring magnet 5 is not measured.

28 and 29 are subtracters, which are D from the output signal of the two-phase oscillator 25.
The output It, Ir of AC 35, 36 is subtracted.

Reference numerals 30 and 31 denote coil drivers, which amplify the outputs of the subtracters 28 and 29, and respectively provide the X-axis coil (readout coil 3) and the Y-axis coil (readout coil 4) with FIGS. A drive current as shown in is added.

The operation of the rotation speed detector constructed as above will be described. It is assumed that the ring magnet 5 has stopped its rotation. When measuring the cumulative number of rotations of the ring magnet 5, a REQ signal (operation start signal) as shown in FIG. 2 (1) is applied to the latch 22, and the rotation angle θ of the ring magnet 5 (rotation axis) is measured. Latch the value of _n .

The value of θ _n is converted into address signals ADXn and ADYn by the angle / address converter 23 and added to the X-axis ROM 33 and the Y-axis ROM 34.

Then, the values of H _Xn and H _Yn stored at this address are read out and converted into analog signals It and Ir by the DACs 35 and 36.

That is, the DAC 35 outputs a DC current value It necessary to cancel the X-axis component magnetic field applied to the magnetic bubble element 1 by the ring magnet 5, and the DAC 36 cancels the Y-axis component magnetic field. The required DC current value Ir is output.

Then, for example, the switches 26 and 27 are turned on at the falling edge of the REQ signal in FIG. 2 (1). Therefore, 2
The outputs It and Ir of the DACs 35 and 36 are subtracted from the two-phase signals Io · com ωt and Io · sin ωt of the phase oscillator 25, respectively. As a result, as shown in FIGS. 2 (2) and 2 (3), the offset component
The current (Io · com ωt−It) minus It, Ir and (Io · s
in ωt-Ir) is applied to the X-axis coil (reading coil 3) and the Y-axis coil (reading coil 4) via the coil drivers 30 and 31, respectively.

FIG. 3 (2) is a diagram showing the movement of the magnetic field vector in the device of the present application. Now, assuming that the magnetic field vector of the ring magnet 5 is stopped toward ▲ ▼, the angle ab at this time is measured by the rotation angle detector 21, and from this measured value, the magnetic field is measured by the ring magnet 5. The X-axis component H _XB and the Y-axis component H _YB of the magnetic field applied to the valve element 1 are X
It is read from ROM 33 for axis and ROM 34 for Y axis.

Then, the magnetic fields ▲ ▼ of the ring magnets 5 are canceled by the electric currents (−It) and (−Ir), and only the rotating magnetic field with a radius of 50 gauss (the magnetic field by the reading coils 3 and 4) is generated.
(See (2) solid line in FIG. 3). Further, since the magnitude of the rotating magnetic field applied from the read coils 3 and 4 is constant, the magnetic field received by the magnetic bubble detecting elements 12 and 13 is 50 gauss, and the signal can be stably detected without being saturated.

In the above embodiment, the ring magnet with 8 poles is used, but any ring magnet with 2n poles can be used.

When the ring magnet 5 having a large temperature coefficient such as a ferrite magnet is used, it is necessary to perform temperature correction of the canceling magnetic field (magnetic field by the read coil). The temperature correction in such a case can be performed by providing the temperature detector 37 in FIG. That is, the temperature inside the rotation speed detector is measured by the temperature detector 37. Then, the angle / address converter 23 corrects the measured angle value.

<Effects of the Invention> As described above, according to the invention, it is possible to know the magnetic field strength of the ring magnet without using a Hall element having a large temperature coefficient. Therefore, since the strength of the magnetic field can be known in a stable manner, the magnetic field generated by the ring magnet can be canceled over a wide temperature range.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a main part of a rotation speed detector according to the present invention, FIG. 2 is a time chart of the circuit of FIG. 1, and FIG. 3 is a diagram showing a vector locus of a magnetic field by a ring magnet and a read coil. , FIG. 4 to FIG. 8 are diagrams for explaining a conventional example. 1 ... Magnetic bubble element, 3, 4 ... Read-out coil, 5 ...
Ring magnet, 21 ... Rotation angle detector, 23 ... Angle / address converter, 33 ... X-axis ROM, 34 ... Y-axis ROM.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Sakamaki 2-932 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Electric Co., Ltd. (56) References JP-A-63-15115 (JP, A) JP-A-SHO 60-73316 (JP, A) Actually opened 64-33072 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A rotating magnetic field by applying a magnetic field of a permanent magnet (5) attached to a rotating shaft to a magnetic bubble element (1) to move a magnetic bubble composed of a plurality of bit patterns and passing an alternating current through a read coil. In a device for measuring the cumulative number of rotations of the rotating shaft by forcibly moving the magnetic bubble and detecting the bit pattern of the magnetic bubble with a magnetic bubble detecting element, which corresponds to the rotation angle of the rotating shaft. A rotation angle detector which outputs a signal, a first storage means in which a signal corresponding to the strength of the magnetic field of the X-axis component applied by the permanent magnet to the magnetic bubble element is written at an address corresponding to the rotation angle value, Introduced from the second storage means in which a signal according to the strength of the magnetic field of the Y-axis component applied by the permanent magnet to the magnetic bubble element is written at the address corresponding to the angle value, and the first and second storage means. And a circuit means for superimposing a direct current for canceling the magnetic field applied by the permanent magnet to the magnetic bubble element on the basis of the signal to flow the alternating current to the read coil.