JP2004264156A - Rotational speed sensing device of rotator for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a weight and a power consumption by reducing a sensor, broadening a range, simplifying a processing circuit, and reducing the entire size. <P>SOLUTION: The rotational speed sensing device of the rotator for an automobile includes magnetic sensors 21, 22 each for sensing the change of a periodic magnetic field in association with the rotation of a rotator 1 rotating synchronously with wheels for the automobile in which a magnetic element 11 having periodically changing magnetic properties, is arranged on an outer periphery, a signal processing circuit 23 for signal processing the change of the sensed periodic magnetic field, and an arithmetic circuit 3 for calculating the rotational speed of the rotator for the automobile. Further, the magnetic sensors 21, 22 each has two magnet impedance elements disposed so as to become a phase relation in response to the period of the change of the magnetic properties of the magnetic element 11. The signal processing circuit 23 has a magnet impedance magnetic detector 2 having one signal processing circuit for alternately switching and signal processing an output by switching means S1, S2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a magnetic body whose magnetic properties change periodically on the outer periphery of a rotating body for an automobile such as a wheel or an output shaft of an engine, so that a change in a periodic magnetic field accompanying rotation of the rotating body for an automobile is provided. A magnetic sensor for detecting, a signal processing circuit for performing signal processing on a detected change in the periodic magnetic field, and an arithmetic circuit for calculating the rotation speed of the rotating body for the vehicle based on an output signal output from the signal processing circuit. The present invention relates to a small-sized, low-power-consumption, rotational-speed detecting device for a rotating body for an automobile, which can be measured in a high-temperature atmosphere.
[0002]
[Prior art]
In recent years, with the development of automobile control systems, wheel speed (rotation speed) sensors have been required to have higher resolution and have to be mounted in the vicinity of a brake device. In order to reduce the cost, it must be small and lightweight and does not require high-precision assembly technology.
The conventional wheel rotation speed detecting device is arranged with a plurality of magnetic sensors including a Hall element, opposed to a magnetic encoder that is provided on a hat-shaped steel core and is magnetized in a multi-polar direction in a circumferential direction, and a plurality of signals are provided. The number of rotations of a wheel is detected by a processing circuit and an arithmetic circuit (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2002-340918 A (Page 3, FIGS. 1 to 3)
[0004]
[Problems to be solved by the invention]
The conventional wheel rotation speed detecting device is provided with a plurality of magnetic sensors including Hall elements, facing a magnetic encoder that is provided on a hat-shaped steel core and is magnetized in a multi-polar direction in a circumferential direction. Since the number of rotations of the wheel is detected by the signal processing circuit and the arithmetic circuit, the sensitivity is not sufficient, the sensor becomes large, the processing circuit becomes complicated, the whole becomes large, and the weight and power consumption increase. was there.
[0005]
That is, since the Hall element generally has low sensitivity, it is necessary to reduce the gap with the magnetic encoder. In particular, when the distance between the magnetic poles of the magnetic encoder is reduced to increase the resolution, the magnetic force is also weakened. Therefore, it is necessary to make the gap as small as possible, such as 0.5 mm or less. A precise assembling apparatus is required so that the encoder and the Hall element do not come into contact with each other, and there is a problem that cost reduction is hindered.
[0006]
On the other hand, in the periphery of the wheel of the automobile, the acting force such as acceleration / deceleration and vibration is large, and the gap has to be widened in order to avoid contact and collision between the rotating part and the fixed part due to eccentricity and backlash. Therefore, the conventional Hall element and the magnetoresistive element have a problem that the detection is likely to be unstable due to mixing of noise due to low sensitivity.
[0007]
In addition, if a high-magnification amplifier is used to compensate for the problem of low sensitivity of the Hall element, the signal-to-noise ratio deteriorates due to drift or thermal noise due to temperature, or the scale of some electronic circuits increases, and the cost increases. There was a problem of becoming.
[0008]
Therefore, the present inventor has proposed a magnetic sensor for detecting a change in a periodic magnetic field associated with rotation of a rotating body for an automobile, in which a magnetic substance whose magnetic properties are periodically changed is provided on the outer periphery, and a detected periodic magnetic field. A signal processing circuit for performing signal processing on the change of the rotation of the vehicle and a calculation circuit for calculating the rotation speed of the rotation body for the vehicle based on an output signal output from the signal processing circuit; The two magnetic sensors, which constitute the impedance magnetic detector, are arranged so that the magnetic properties of the magnetic material disposed on the outer periphery of the rotating body for the vehicle have a phase relationship in accordance with a cycle in which the magnetic properties change. The two magneto-impedance elements are constituted by a magneto-impedance element and the signal processing circuit is constituted by one signal processing circuit. Focusing on the technical idea of the present invention of alternately switching these outputs by switching means and performing signal processing, as a result of further research and development, the sensor was reduced, the processing circuit was simplified, and the overall size was reduced, The present invention has been achieved which achieves the purpose of reducing weight and power consumption.
[0009]
[Means for Solving the Problems]
An apparatus for detecting the number of revolutions of a rotating body for an automobile according to the present invention (the first invention according to claim 1) includes:
A magnetic sensor that detects a change in a periodic magnetic field caused by rotation of a rotating body for an automobile, in which a magnetic substance whose magnetic properties change periodically is disposed on an outer periphery, and performs a signal process on the detected change in the periodic magnetic field. A signal processing circuit and a rotation speed detection device for a vehicle rotation body including a calculation circuit for calculating a rotation speed of the vehicle rotation body based on an output signal output from the signal processing circuit,
The magnetic sensor is constituted by two magneto-impedance elements arranged so as to have a phase relationship in accordance with a cycle in which the magnetic properties of the magnetic body disposed around the rotating body for the vehicle change. With
The signal processing circuit includes a magneto-impedance magnetism detector including a single signal processing circuit that performs signal processing by alternately switching the output from the two magneto-impedance elements by switching means.
Things.
[0010]
According to a second aspect of the present invention, there is provided an apparatus for detecting the number of revolutions of a rotating body for an automobile.
In the first invention,
The arithmetic circuit calculates the number of revolutions of the rotating body for a vehicle from the frequency of the magnetic field change, which is an output signal output from the signal processing circuit connected by a two-wire lead, and the two magneto-impedance elements Calculates the direction of rotation of the rotating body for the vehicle based on the phase difference of the output signal from
Things.
[0011]
According to a third aspect of the present invention, there is provided an apparatus for detecting the number of revolutions of a rotating body for an automobile,
In the second invention,
The two magneto-impedance elements comprise an amorphous wire and a sensing coil wound around the amorphous wire;
The one signal processing circuit alternately switches the two magneto-impedance elements to supply a pulse, and alternately holds two magnetic signals obtained in synchronization with the pulse generator for a predetermined time. A set of electronic circuits consisting of sample and hold circuits that output in series
Things.
[0012]
According to a fourth aspect of the present invention, there is provided an apparatus for detecting the number of revolutions of a rotating body for an automobile,
In the third invention,
The two magneto-impedance elements and the set of electronic circuits are formed on the same substrate.
Things.
[0013]
Function and Effect of the Invention
According to the first aspect of the present invention, there is provided a rotation speed detecting apparatus for a rotating body for an automobile, wherein a magnetic field having a periodically changing magnetic property is disposed on an outer periphery of the rotating body for an automobile. A magnetic sensor for detecting a change in the detected periodic magnetic field, a signal processing circuit for performing signal processing on the detected change in the periodic magnetic field, and a calculation circuit for calculating the rotation speed of the rotating body for the vehicle based on an output signal output from the signal processing circuit. In the rotation speed detection device for a rotating body for a vehicle, the magnetic property of the magnetic body disposed on the outer periphery of the rotating body for a vehicle constituting the magnetic sensor as a magneto-impedance magnetism detector changes in a cycle in which the magnetic property changes. The two magneto-impedance elements arranged so as to have an appropriate phase relationship detect a change in a periodic magnetic field accompanying rotation of the rotating body of the vehicle, and configure the signal processing circuit. The one signal processing circuit performs the signal processing by alternately switching the output from the two magneto impedance elements by the switching means, so that when one magneto impedance element is operating, the other is used. Since the magneto-impedance element is not operating, it is not electromagnetically affected by the operation of the other magneto-impedance element, enabling high-precision rotation speed detection, miniaturizing the sensor, and simplifying the processing circuit. Thus, the size and the power consumption can be reduced as a whole.
[0014]
According to a second aspect of the present invention, in the first aspect of the present invention, the arithmetic circuit detects the rotational speed of the automobile based on a frequency of a magnetic field change which is an output signal output from the signal processing circuit. In addition to calculating the rotation speed of the body, the rotation direction of the vehicle rotation body is calculated based on the phase difference between the output signals from the two magneto-impedance elements. Since the signal is output, it is possible to detect the number of rotations and the direction of rotation of the rotating body for an automobile, and it is possible to easily arrange the lead wires.
[0015]
According to a third aspect of the present invention, in the second aspect of the present invention, the two magneto-impedance elements detect an ambient magnetic field when a pulse current is applied to an amorphous wire. A voltage is induced by a detection coil wound around a wire, and the electronic circuit as the one signal processing circuit is used for pulse application of a pulse generator for alternately switching the two magneto-impedance elements and applying a pulse. Since the two magnetic signals obtained by the sample-and-hold circuit in synchronization are alternately held for a predetermined time and output in a time series, when one of the magneto-impedance elements is energized by a pulse and is operating, the other of the magneto-impedance elements is operated. Since the impedance element is not operating because no pulse current is applied, the impedance element is not operated. Since the electromagnetic impedance of the other magneto-impedance element is not affected by the operation of the other magneto-impedance element, high-precision rotation speed detection is possible. Simultaneous energization of the two magneto-impedance elements and simultaneous Since no signal processing is performed, power consumption can be reduced and the processing circuit can be simplified.
[0016]
According to a fourth aspect of the present invention, there is provided a rotating speed detecting apparatus for a rotating body for an automobile according to the third aspect, wherein the two magneto-impedance elements and the one set of electronic circuits are formed on the same substrate. Since the characteristics of the two magneto-impedance elements can be made uniform, high-precision and stable measurement is possible, and the sensor is made smaller, the processing circuit is simplified, and the overall size is reduced. This has the effect of eliminating the need for precise work for mounting the device.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
(1st Embodiment)
As shown in FIGS. 1 to 4, the apparatus for detecting the number of revolutions of a rotating body for a vehicle according to the first embodiment includes a vehicle wheel provided with a magnetic body 11 whose magnetic properties change periodically on its outer periphery. The magnetic sensors 21 and 22 for detecting a change in the periodic magnetic field accompanying the rotation of the rotating body 1 rotating in synchronization, a signal processing circuit 23 for processing the detected change in the periodic magnetic field, and a signal processing circuit 23 In the rotation speed detecting device for a vehicle rotating body provided with a calculation circuit 3 for calculating the rotation speed of the vehicle rotating body based on the output signal output, the magnetic sensors 21 and 22 are provided on the outer periphery of the rotating body 1. The signal processing circuit 23 is configured by two magneto-impedance elements arranged so as to have a phase relationship according to a cycle in which the magnetic properties of the disposed magnetic body 11 change. One of the outputs from the magneto-impedance element is one that includes a magneto-impedance magnetic detector 2 consisting of one of the signal processing circuit for signal processing is switched alternately by the switching means S1, S2.
[0019]
As shown in FIG. 1, the rotation sensor according to the first embodiment detects a rotating body 1 composed of a circular magnetic body 11 having a plurality of magnets formed around the rotating body 1 and a magnetic field that periodically changes with rotation. A magneto-impedance magnetic sensor composed of two amorphous wires operable in a temperature environment of 120 ° C. as a sensor for switching the two magnetic signals alternately in a time series and outputting two magnetic signals. It comprises an impedance magnetism detector 2 and a pulse conversion circuit 3 as an arithmetic circuit for outputting a pulse which is a signal of a rotation speed and a rotation direction from a magnetic signal by the periodically changing magnetic field.
[0020]
In FIG. 1, a magnetic rotator 1 is a disk having a plurality of magnetic poles magnetized N and S around the periphery thereof. When the magnetic rotator rotates, two magneto-impedance elements 21 and 22 arranged close to each other form a sine. Detect a wave-like magnetic signal. The two magneto-impedance elements 21 and 22 are arranged at positions where the mutual detection phase is 90 degrees.
[0021]
In the magneto-impedance magnetic detector 2, the magneto-impedance elements 21 and 22 have a structure in which detection coils 211 and 221 are wound around amorphous wires 210 and 220, respectively, when a pulse current is applied to the amorphous wires. A voltage corresponding to the strength of the surrounding magnetic field is instantaneously generated in the detection coils 211 and 221.
[0022]
The signal processing circuit 23 applies a pulse current to the two amorphous wires 210 and 220, and samples and holds the voltages of the detection coils 211 and 221 to output the two amorphous wires 210 and 220. Since the pulse is applied alternately and the sample and hold is performed, the two magnetic signals are output alternately in time series. Therefore, since the two sensors 21 and 22 are handled by one signal processing circuit 23, the size and power consumption are reduced.
[0023]
The pulse conversion circuit 3 outputs a pulse corresponding to the frequency, that is, a rotation number signal, from the two sine wave signals output from the signal processing circuit 2, and determines and outputs a rotation direction from the phase of the two signals. Things.
[0024]
Further, the magneto-impedance magnetic detector 2 and the pulse conversion circuit 3 will be specifically described with reference to FIG. 2, focusing on the signal processing circuit 23 in the first embodiment.
[0025]
The signal processing circuit 23 in the magneto-impedance magnetic detector 2 includes a pulse generator 231 and a sample and hold circuit 232. The pulse generator 231 generates two pulse trains having a repetition frequency of 2 MHz, a pulse width of several tens of ns (nanoseconds), and synchronizing with a predetermined phase difference. (Microseconds) and output alternately.
[0026]
The output terminal P5 outputs a synchronization signal for alternately switching the pulse train every 5 μs, which is connected to the pulse conversion circuit 3 at the subsequent stage. Since the terminals P1 and P3 are connected to the two magneto-impedance elements 21 and 22 amorphous wires, a 2 MHz pulse train current is applied alternately every 5 μs.
[0027]
When a pulse is applied, a voltage corresponding to the surrounding magnetic field is instantaneously induced in each of the coils 211 and 221 of the magneto-impedance elements 21 and 22. When the pulses of the output terminals P2 and P4 of the pulse generator 231 are applied to the control terminals of the analog switches S1 and S2, the switches are closed for a very short time, so that the coils 211 and 221 of the magneto-impedance elements 21 and 22 are closed. Is held by the capacitor C of the sample and hold circuit 232.
[0028]
As described above, since the pulse train applied to the magneto-impedance element is 2 MHz, the measurement of the magnetic field is performed at a repetition of 2 MHz, but the analog switches S1 and S2, the capacitor C and the amplifier A form a sample-and-hold circuit 232. Therefore, the magnetic signal at the output terminal P6 has a substantially continuous waveform during 5 μs during which the pulse train of 2 MHz continues.
[0029]
However, as described above, the pulse generator 231 alternately outputs a pulse train with a set of P1 and P2 and a set of P3 and P4 with a period of 5 μs, so that the magnetic signal detected by the magneto-impedance elements 21 and 22 has a period of 5 μs The signals are output to the terminal P6 in a time series.
[0030]
In FIG. 1, when the rotating body 1 around which the magnetic body is disposed rotates, the signals detected by the two magneto-impedance elements 21 and 22 have a phase difference of 90 degrees as shown in FIG. Sine wave. This magnetic signal is applied to the sample-and-hold circuit 232 through the detection coils 211 and 221. As described above, the signals of the two magneto-impedance elements 21 and 22 are alternately switched every 5 μs. P6 has a waveform in which two sine waves having a phase difference of 90 degrees as shown in FIG. 3B are alternately chopped every 5 μs. Symbols A and B in the figure are signals corresponding to the magneto-impedance elements 21 and 22, respectively. The signal at the output terminal P6 is the output signal of the magneto-impedance magnetic detector 2.
[0031]
As described herein, the magneto-impedance magnetic detector 2 processes the signals of the two magneto-impedance elements by one electronic circuit and outputs a magnetic signal, thereby realizing the miniaturization of the electronic circuit and the reduction in power consumption. ing.
[0032]
Next, the pulse conversion circuit 3 as a calculating means for calculating the number of rotations of the rotating body will be described with reference to FIG. The pulse conversion circuit 3 is for extracting a rotation speed signal and a rotation direction signal from the output signal of the magneto-impedance magnetic detector 2, and is provided with a comparator 31 corresponding only to a positive voltage signal and chopping at 5 μs. Signal discriminating circuits 32 and 33 for discriminating a rectangular wave signal corresponding to the two sine waves A and B from the output signal of the magneto-impedance magnetic detector 2, and a waveform shaping circuit 34, a rotation direction discriminating circuit 35, and an output. It comprises a circuit 36.
[0033]
The comparator 31 corresponds to only the positive output signal of the magneto-impedance magnetic detector 2 and has a logic waveform as shown in FIG. In response to this, the discriminating circuits 32 and 33 composed of flip-flop circuits use the switching signal whose period of the output terminal P5 of the pulse generator 231 of FIG. A rectangular wave signal corresponding to two sine wave signals A and B in FIG. 3 is obtained. That is, d in FIG. 3 is a rectangular wave corresponding to the positive half cycle of the sine wave A. Further, e in FIG. 3 is a rectangular wave corresponding to the positive half cycle of the sine wave B.
[0034]
The waveform shaping circuit 34 comprises a differentiating circuit composed of a resistor and a capacitor and an OR circuit of a logic circuit. The output of the signal discriminating circuits 32 and 33 is differentiated to generate a pulse having a predetermined time width shown in FIG. Get. This pulse frequency is a signal corresponding to the frequency of the magnetic field change of the rotating body 1, that is, the number of rotations.
[0035]
The output pulse of the waveform shaping circuit 34 is connected to the transistor T1 of the output circuit 36, and the collector of the transistor is turned on and off through a resistor in response to logic "0""1". As shown by g, the current consumption of the power supply circuit increases / decreases through the terminal P7 which is a power supply / reception source.
[0036]
The rotation direction discrimination circuit 35 detects the rotation direction from the phases of the output signals of the signal discrimination circuits 32 and 33. If the output is, for example, "1", the output is clockwise, and if the output is "0", the output is right. Left rotation. This signal is connected to the transistor T2 of the output circuit 36, and the collector of the transistor is turned on and off through a predetermined resistor in response to "0" and "1" of the logic. Therefore, as shown in FIG. The current consumption increases or decreases.
[0037]
As described above, the output of the pulse conversion circuit 3, that is, the current signal at the output terminal P7 of the present rotation sensor is a current signal of the sum of the rotation speed signal pulses shown in FIGS. Is only a pulse of the rotation speed signal, and when the clockwise rotation is performed, the rotation speed signal is superimposed on a predetermined DC current. In this figure, the illustration of the waveform of the current consumed by the electronic circuit of the rotation sensor is omitted. As described above, it is possible to output signals of the number of rotations and the rotation direction of the rotation sensor only by two power supply lines, + and-.
[0038]
In FIG. 3, the power supply stabilization circuit 30 controls the DC current supplied to the magneto-impedance magnetism detector 2 and the pulse conversion circuit 3 to a stable voltage, but detailed description is omitted.
[0039]
As described above, the reason why the amorphous wire was adopted as the magneto-impedance element here is that, due to the intrinsic properties of the amorphous wire, stable operation can be performed even at a temperature environment of 120 ° C. This is for the purpose of use for detecting the rotation speed of a rotating body for an automobile such as engine rotation measurement.
[0040]
Since the rotation number detecting device for a rotating body for a vehicle according to the first embodiment withstands a severe temperature environment such as a recent automobile, and has a demand for a small, lightweight, and low power consumption type rotation sensor, it is possible to meet such needs. It is intended to propose a rotation sensor that can respond.
[0041]
Currently, a wheel speed sensor that outputs an AC signal using a generally used rotating gear and a coil wound around a magnet has a low frequency because the frequency per vehicle speed (the number of pulses per rotation) is low. Accordingly, the speed information becomes slow, the error becomes large, and the detection voltage decreases. Therefore, the measurement limit is several km / h per hour. On the other hand, there is a strong demand that measurement be possible at a lower speed (for example, 1 km / h or less) so as to widen the measurement limit in order to improve the quality of ABS and other control functions.
[0042]
As a method in which the detected voltage does not change even at a low vehicle speed (low rotational speed), there is a method of detecting the magnetic field strength using a Hall element and a magnetoresistive element. The detection voltage does not change even when the device becomes low in vehicle speed (low rotation speed).
[0043]
In the first embodiment, it is necessary to increase the number of magnetized poles per rotation in order to obtain predetermined speed information even at a low speed. It can be realized, and there is no need to use expensive magnets such as Alnico and Neodymium. This is because the magneto-impedance element has a high sensitivity, so that the magnetic measurement can be performed sufficiently stably even if the magnetic force is reduced due to the high-density magnetization.
[0044]
In the future vehicle control, rotation direction information is also required in electric vehicles, hybrid vehicles, and the like. However, since the first embodiment detects the rotation direction, the first embodiment can be applied to such applications.
[0045]
The periphery of the wheel becomes high temperature due to the generation of braking heat, and stable operation at around 120 ° C. is required. However, the magneto impedance magnetic detector of the first embodiment can operate at 120 ° C. It can respond to the demand for downsizing, low power consumption, high temperature range operation and low cost of automotive parts.
[0046]
In the first embodiment, since signal processing is performed and output in the package, the output can be set to a high level, so that noise is not mixed. Further, since the sensor unit and the signal processing circuit are housed in one package, the size is reduced. Easy to handle and assemble.
[0047]
Also, in the first embodiment, when one of the magneto-impedance elements is operating with the pulse current applied thereto, the other magneto-impedance element is not operating because the pulse current is not applied. Since there is no electromagnetic influence due to the operation accompanying the pulse energization of the element, high-precision rotation speed detection is enabled, and simultaneous energization of the two magneto-impedance elements and simultaneous signal processing in the signal processing circuit are performed. Therefore, the power consumption can be reduced without interference in signal processing.
[0048]
In the first embodiment, since the output of the pulse conversion circuit as the arithmetic circuit 3 is taken out using the two-wire system of the lead wire, it is easy to replace the already mounted current vehicle speed sensor. Things.
[0049]
(2nd Embodiment)
As shown in FIG. 5, the apparatus for detecting the number of revolutions of a rotating body for an automobile according to the second embodiment is an example in which a ring magnet 12 is used as the rotating magnetic body, and is attached to an existing rotating shaft 10. It is an example of the aspect which performs rotation measurement.
[0050]
In the second embodiment, the magnet is provided on the circumferential surface of the ring, and the two magneto-impedance elements 21 and 22 are arranged in the normal direction. Since the same operation and effect as those described above are obtained, the description is omitted.
[0051]
(Third embodiment)
As shown in FIG. 6, the rotation number detecting apparatus for a rotating body for an automobile according to the third embodiment detects a magnetic field of a gear made of a semi-hard magnetic material instead of using an active magnet as the rotating magnetic body. Thus, the configuration of the rotation sensor is simplified and the cost is reduced.
[0052]
The gear 101 in FIG. 6 is made of a semi-hard magnetic material, and generates weak magnetism by magnetization. Conventional Hall elements or magnetoresistive elements are insensitive to detection due to low sensitivity, but the two magneto-impedance magnetic detectors 21 and 22 are usually 100 to 10,000 times more sensitive, so that the gears are stable. 101 can be detected. Thus, an inexpensive rotation sensor can be realized without using a multi-pole magnetized magnet as the rotating body.
[0053]
(Fourth embodiment)
The rotation number detecting device for a rotating body for a vehicle according to the fourth embodiment realizes an inexpensive and highly stable rotation sensor. As shown in FIG. 7, a gear made of a semi-hard magnetic material is used as the rotating magnetic body. 111 and an inexpensive magnet 112 arranged near the teeth to magnetize the magnet.
[0054]
When the gear 111 rotates, the teeth are exposed to the magnetic field F of the magnet 112, so that each tooth is sequentially magnetized, and a magnetic field is generated from each tooth by residual magnetism. The rotation can be measured by detecting the magnetic field change accompanying the rotation by the magneto-impedance magnetic detector.
[0055]
In the fourth embodiment, by performing measurement while always magnetizing with the magnet 112, stable magnetic field measurement can be performed without being affected by disturbance. Here, since the magneto-impedance magnetic detector including the magneto-impedance elements 21 and 22 has high sensitivity, the magnetic field for the magnetization may be weak, and an inexpensive magnet can be used.
[0056]
Further, in the fourth embodiment, since high positional accuracy is not required for mounting the magnet 112, it is only necessary to place the magnet 112 near the teeth, and there are few restrictions on the structural design or manufacturing, and the cost can be reduced. An inexpensive and highly stable rotation sensor can be realized. The wheel speed sensor is a magnetic sensor that is attached to a magnetic member that rotates with the wheel and a bearing member that does not rotate with a predetermined gap (distance) therebetween, and thus enhances usefulness.
[0057]
When the distance between the magnetic poles is reduced, the magnetic field strength generally decreases. However, in order to stably detect this, it is necessary to bring the magnetic sensor close to the magnet. On the other hand, the acceleration and deceleration, vibration, and acting force around the wheel where the wheel speed sensor is mounted are large, so the gap must be widened to avoid the problem of eccentricity, backlash, etc., contact between the rotating and fixed parts and collisions. In the Hall element and the magneto-resistive element described above, the measurement may become unstable due to the contamination of noise or the like, but the fourth embodiment solves such a problem.
[0058]
That is, since the magneto-impedance magnetic detector according to the fourth embodiment has a sensitivity 100 to 1000 times higher than that of the Hall element, the gap can be made wider than that of the Hall element and the magnetoresistive element. The production cost is low, and the maintenance of the car user is easy.
[0059]
【Example】
Hereinafter, an example of a magnetic detector that can be used in the rotation speed detecting device for a rotating body for a vehicle according to the above-described embodiment will be described with reference to the drawings.
[0060]
(Example)
As shown in FIG. 8, the magnetic detector according to the present embodiment has a reduced size and a higher sensitivity in consideration of application in the field of automobiles, and will be described below with reference to FIGS.
[0061]
The size of the substrate 100 of the two magneto-impedance elements 21 and 22 constituting the magnetic detector 2 is 0.5 mm in width and 0.5 mm in height, and 3 mm in the longitudinal direction. Reference numeral 220 denotes an amorphous wire made of a CoFeSiB-based alloy and having a diameter of 30 μm or 20 μm and a length of 3 mm or less. The electromagnetic coils 211 and 221 are formed on one side 211A and 221A of the coil formed on the groove surface 100S of the groove 100G formed in the longitudinal direction of the substrate 100, and on the groove upper surface 100US (the upper surface SRU of the resin SR) of the groove 100G. It is formed by a two-layer structure of the remaining one side coil 211B and 221B.
[0062]
The coils 211A and 221A on one side and the coils 211B and 221B on the other side formed on the groove surface 111 and the groove upper surface 112 have grooves formed in the longitudinal direction of the electrode wiring board 1 as shown in FIGS. A conductive magnetic metal thin film forming a coil is formed by vapor deposition on the entire surface of the groove surface 100S of 100G and on the opposing portion and near portion (groove upper surface 100US) of the groove 100G so that the formed metal thin film remains spirally. By removing the conductive metal thin film portion forming the gap portion by the selective etching method, the entire length of the coil in the longitudinal direction is formed over a length of 1.5 mm or 2 mm. Note that FIG. 9 shows a state in which coils are formed in a rectangular shape on all four surfaces of the entire surface of the groove 100G for easy understanding regardless of the AA ′ cross section in FIG.
[0063]
The inner diameter of a circle equivalent to the circle of the electromagnetic coils 211 and 221 (diameter of a circle having the same area as the cross-sectional area formed by the height and width) is desirably 200 μm or 100 μm or less. The winding interval per turn (per unit length) of the electromagnetic coils 211 and 221 is desirably 100 μm / turn or less, and is set to 50 μm / turn as an example.
[0064]
By adopting 3 mm as the length of the element substrate 100, the amorphous wires 210 and 220 and the electromagnetic coils 211 and 221 of the two magneto-impedance elements 21 and 22 are integrally formed on the entire substrate BP as shown in FIG. The electronic circuit 23 as the signal processing circuit formed and connected via electrodes disposed at both ends of the magnetic detectors 21 and 22 is also formed on the same overall substrate BP, and the sensor from the electronic circuit 23 is provided. The output is shown in FIG.
[0065]
The magnetic detector of the present embodiment realizes miniaturization, thinning, and small volume (width 0.5 mm, height 0.5 mm, length in the longitudinal direction 3 mm) as described above in consideration of application in the automobile field. On the other hand, as is clear from FIG. 11, a linear output up to a full scale of 0.2 V at 40 Gauss (G) is obtained, realizing a linear measurement and a highly sensitive measurement.
[0066]
In addition, since the magnetic detector of this embodiment employs an amorphous wire as the magneto-impedance element, stable operation is possible even at a temperature environment of 120 ° C. due to the inherent properties of the amorphous wire. The stable operation is possible even in a temperature environment, and it is effective in detecting the rotation speed of a rotating body for an automobile.
[0067]
Further, in the magnetic detector of the present embodiment, in order to make the magneto-impedance element a magnetic sensor with higher sensitivity, the radius of the inner diameter corresponding to the circle of the electromagnetic coils 211 and 221 as the detection coil should be 200 μm or 100 μm or less. Desirably, in the present embodiment, it is set to 66 μm as an example and is extremely small, so that it is effective for increasing the electromagnetic coupling between the amorphous wire and the detection coil, and also effective for making the sensor thinner and smaller in capacity. It is.
[0068]
Further, the magnetic detector of this embodiment can be compact and easy to handle by mounting (loading) the two magneto-impedance elements and the signal processing circuit on one substrate. However, because of its high sensitivity, stable magnetic measurement can be performed even when the gap with the rotating body is increased to 1 mm or more, so there is no need for precise assembly work when mounting the product on a car, so a very large effect of suppressing production costs. To play.
[0069]
Further, in the present embodiment, two magneto impedance elements are manufactured by an automatic machine controlled with a predetermined accuracy, and two driver circuits of a pulse generator including an IC circuit for driving the two magneto impedance elements, respectively. In order to make the drive characteristics and the switch characteristics of the two analog switches of the corresponding sample-and-hold circuits the same, a mask is designed so that the circuits are formed in close proximity to each other, and the characteristics of the two magneto-impedance elements are compared with each other. Because they are equal, the characteristics of the two magneto-impedance elements can be made equal to each other.
[0070]
In the present embodiment, the size of the substrate 100 is 0.5 mm in width and 0.5 mm in height, the length in the longitudinal direction is 3 mm, and the length of the amorphous wire is 3 mm or less. As is clear from FIG. 11, since a linear output is obtained up to a full scale of 0.2 V at 40 Gauss, another coil is provided on the amorphous wire to eliminate the hysteresis characteristic and the non-linear characteristic, and a feedback current is supplied to the amorphous wire. This eliminates the need for a feedback technique for flowing a bias current or a bias current. As a result, it is not necessary to always supply a direct current, and power consumption can be reduced. Further, the bias coil can be omitted to simplify the magneto-impedance element.
[0071]
The above-described embodiment has been described by way of example, and the present invention is not limited to the embodiment. It will be recognized by those skilled in the art from the claims, the detailed description of the invention, and the drawings. Modifications and additions are possible without violating the technical idea of the present invention.
[0072]
In the above-described embodiment, the amorphous wire is employed as the magneto-impedance element because stable operation is possible even at a temperature of 120 ° C. due to the intrinsic properties of the amorphous wire, and the rotation of the wheels of the automobile is not possible. It can be used for detecting the rotation speed of a rotating body for automobiles such as measurement and engine rotation measurement. However, the present invention is not limited to these. Needless to say, it can be used in a place that requires
[Brief description of the drawings]
FIG. 1 is an overall block diagram illustrating an apparatus for detecting the number of revolutions of a rotating body for an automobile according to a first embodiment of the present invention.
FIG. 2 is a detailed circuit diagram showing details of a magneto impedance magnetic detector and a pulse conversion circuit according to the first embodiment.
FIG. 3 is a chart showing signal waveforms at various parts of a magneto-impedance magnetic detector and a pulse conversion circuit according to the first embodiment.
FIG. 4 is a chart showing signal waveforms for determining a rotation direction in the pulse conversion circuit of the first embodiment.
FIG. 5 is a perspective view showing a main part of a rotation speed detecting device for a rotating body for a vehicle according to a second embodiment of the present invention.
FIG. 6 is a partial front view showing a main part of a rotation speed detecting device for a rotating body for a vehicle according to a third embodiment of the present invention. .
FIG. 7 is a partial front view showing a main part of a rotation speed detecting device for a rotating body for a vehicle according to a fourth embodiment of the present invention. .
FIG. 8 is a plan view showing a magnetic detector according to the embodiment of the present invention.
FIG. 9 is a cross-sectional view of the magnetic detector according to the present embodiment, taken along line AA 'in FIG.
FIG. 10 is a plan view showing an example of the arrangement of two magneto-impedance elements and an electronic circuit on the entire substrate in this embodiment.
FIG. 11 is a diagram showing a relationship between an external magnetic field and an output voltage of the magnetic detector in the present embodiment.
[Explanation of symbols]
1 rotating body
11 Magnetic body
2 Magneto impedance magnetic detector
21,22 Magnetic sensor
23 signal processing circuit
3 Operation circuit
S1, S2 switching means

Claims (4)

A magnetic sensor that detects a change in a periodic magnetic field caused by rotation of a rotating body for an automobile, in which a magnetic substance whose magnetic properties change periodically is disposed on an outer periphery, and performs a signal process on the detected change in the periodic magnetic field. A signal processing circuit and a rotation speed detection device for a vehicle rotation body including a calculation circuit for calculating a rotation speed of the vehicle rotation body based on an output signal output from the signal processing circuit,
The magnetic sensor is constituted by two magneto-impedance elements arranged so as to have a phase relationship in accordance with a cycle in which the magnetic properties of the magnetic body disposed around the rotating body for the vehicle change. With
The signal processing circuit includes a magneto-impedance magnetism detector including one signal processing circuit that alternately switches the outputs from the two magneto-impedance elements by a switching unit and performs signal processing. A rotation speed detection device for rotating bodies for automobiles. In claim 1,
The arithmetic circuit calculates the number of rotations of the rotating body for a vehicle from the frequency of the magnetic field change which is the output signal output from the signal processing circuit, and based on the phase difference between the output signals from the two magneto impedance elements. An apparatus for detecting the rotational speed of a rotating body for an automobile, which calculates a rotating direction of the rotating body for an automobile and outputs a rotation speed signal and a rotation direction signal via a two-wire type lead wire. In claim 2,
The two magneto-impedance elements comprise an amorphous wire and a sensing coil wound around the amorphous wire;
The one signal processing circuit alternately switches the two magneto-impedance elements to supply a pulse, and alternately holds two magnetic signals obtained in synchronization with the pulse generator for a predetermined time. An apparatus for detecting the number of revolutions of a rotating body for an automobile, which is a set of electronic circuits including a sample-and-hold circuit that outputs the series. In claim 3,
An apparatus according to claim 1, wherein said two magneto-impedance elements and said set of electronic circuits are formed on the same substrate.

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