JP4466355B2 - Rotation detector - Google Patents

Description

  The present invention relates to a rotation detection device used for detecting rotation of an engine mounted on a vehicle or rotation detection of various detected rotating bodies in a general machine, and in particular, using a change in resistance value of a magnetoresistive element, The present invention relates to a rotation detection device that detects rotation information.

  Conventionally, for example, a device described in Patent Document 1 is known as a rotation detection device that performs rotation detection using a change in the resistance value of a magnetoresistive element. FIG. 15 shows a planar structure of a rotation detection device that is generally used conventionally for detecting rotation, such as a crank angle sensor of an engine, including the rotation detection device described in Patent Document 1.

  As shown in FIG. 15, this rotation detection device includes a sensor chip 30 including a magnetoresistive element pair 1 composed of magnetoresistive elements MRE1 and MRE2 and a magnetoresistive element pair 2 composed of magnetoresistive elements MRE3 and MRE4. It arrange | positions so that the rotor 20 which is a detection rotary body may be opposed. The sensor chip 30 is integrated with the processing circuit, and is integrally molded with a mold resin 32. Specifically, the sensor chip 30 is mounted on one end of a lead frame (not shown) inside the mold resin 32, and terminals such as a power supply terminal T1, an output terminal T2, and a GND terminal T3 are drawn out from the other end. It has a structure. A bias magnet 22 for applying a bias magnetic field to the magnetoresistive element pairs 1 and 2 is disposed in the vicinity of the sensor chip 30 so as to surround the mold resin 32. The bias magnet 22 is molded into a hollow cylindrical shape having a through hole in its longitudinal direction, and the mold resin 32 is inserted into the through hole and fixed at a predetermined position by an adhesive or the like. Here, in the sensor chip 30, the magnetoresistive element pairs 1 and 2 are arranged in line symmetry with the magnetic center of the bias magnetic field as the axis of symmetry. The magnetoresistive elements MRE1 and MRE2 or the magnetoresistive elements MRE3 and MRE4 constituting the magnetoresistive element pairs 1 and 2 are “45 °” and “−45 °” with respect to the magnetic center of the bias magnetic field, respectively. Are arranged so as to form an angle of, i.e., to have a "C" shape.

  On the other hand, the rotor 20 facing the sensor chip 30 is alternately provided with crests 21 and troughs 20a in a gear shape on the outer periphery thereof. Here, when the gear-shaped rotor 20 made of a magnetic material rotates, the peak portion 21 and the valley portion 20 a pass through the vicinity of the sensor chip 30 and approach the bias magnet 22. The bias magnetic field generated from the bias magnet 22 changes the angle of the magnetic vector as it is dragged by the peak portion 21 in cooperation with the rotation of the rotor 20, and swings in the rotation direction of the rotor 20. As the rotor 20 rotates and the position of the teeth passing near the sensor chip 30 changes from the peak portion 21 to the valley portion 20a and from the valley portion 20a to the peak portion 21, the magnetic vector is changed. The swing angle changes. Then, by detecting such a change in the magnetic vector as a change in the resistance value of each of the magnetoresistive elements MRE1 to MRE4 constituting the magnetoresistive element pair 1 and 2, the positions of the peak portion 21 and the valley portion 20a are detected. Information (rotation information of the rotor 20) is detected.

Next, the electrical configuration of the sensor chip 30 including the processing circuit will be described with reference to the equivalent circuit shown in FIG.
As shown in FIG. 16, magnetoresistive element pairs 1 and 2 are electrically configured as half bridges in which two magnetoresistive elements MRE1 and MRE2 or magnetoresistive elements MRE3 and MRE4 are respectively connected in series. ing. The midpoint potential Va of the magnetoresistive elements MRE1 and MRE2 is the output of the magnetoresistive element pair 1, and the midpoint potential Vb of the magnetoresistive elements MRE3 and MRE4 is the output of the magnetoresistive element pair 2. These two outputs are respectively input to the differential amplifier 3, and the differential output (signal A) between the midpoint potential Va and the midpoint potential Vb is further input to the comparator 4. The comparator 4 is a part that performs the binarization processing of the differential output based on a predetermined threshold voltage Vth, and the binarized signal (pulse signal) is output from the output terminal T2.

  FIG. 17 shows a rotation detection mode of the rotor 20 (FIG. 15) by such a rotation detection device as a time chart accompanying the rotation of the rotor 20. Of these, FIG. 17 (a) shows the relative position change between the rotor 20 and the sensor chip 30, and FIGS. 17 (b) to 17 (d) correspond to the relative position change. The transition of the signal processed in the processing circuit is shown.

  That is, as shown in FIG. 17A, when the position of the teeth (mountain portion 21) facing the sensor chip 30 changes as shown in the states R1 to R4 as the rotor 20 rotates, the sensor chip The magnetic vectors applied to the magnetoresistive element pairs 1 and 2 in 30 also change in the manner indicated by arrows in FIG.

  For example, as shown in the state R1, when the sensor chip 30 faces the valley 20a, the magnetic vectors applied to the magnetoresistive element pairs 1 and 2 are each originally generated from the bias magnet 22. The direction along the magnetic flux curve is shown.

  Further, as shown in the state R2, when the rotor 20 rotates and the peak portion 21 approaches the magnetoresistive element pair 2, the magnetic vector applied to the magnetoresistive element pairs 1 and 2 is attracted to the peak portion 21. It changes in the mode to be used. For this reason, the deflection angle of the magnetic vector applied to the magnetoresistive element pair 2 is increased, and the deflection angle of the magnetic vector applied to the magnetoresistive element pair 1 is decreased.

  Further, as shown in the state R3, when the rotor 20 further rotates and the peak portion 21 moves away from the magnetoresistive element pair 1, the magnetic vector applied to the magnetoresistive element pairs 1 and 2 is the peak portion. 21 changes in a manner drawn. For this reason, the deflection angle of the magnetic vector applied to the magnetoresistive element pair 2 is reduced, and the deflection angle of the magnetic vector applied to the magnetoresistive element pair 1 is increased.

  Further, as shown in the state R4, when the sensor chip 30 again faces the valley 20a, the magnetic vector applied to the magnetoresistive element pairs 1 and 2 is the bias magnet 22 as in the state R1. The direction along the original magnetic force curve is indicated.

  Thus, the magnetic vector applied to the magnetoresistive element pairs 1 and 2 periodically changes as the rotor 20 rotates, and in particular, the edge position of the peak portion 21 is close to these magnetoresistive element pairs 1 and 2. Each time, the deflection angle of the applied magnetic vector changes so as to maximize.

  On the other hand, FIG. 17B shows the transition of the change in the deflection angle of the magnetic vector applied to the magnetoresistive element pair 1 and 2, and the magnetic vector applied to the magnetoresistive element pair 1 is shown in FIG. The transition is indicated by a broken line, and the transition of the magnetic vector applied to the magnetoresistive element pair 2 is indicated by a solid line. Here, the deflection angle of the magnetic vector applied to the magnetoresistive element pair 1 is sensed as a change in the resistance value of the magnetoresistive elements MRE1 and MRE2 in the sensor chip 30, and is output as a change in the midpoint potential Va. It is what is done. That is, a change in the magnetic vector of the magnetoresistive element pair 1 indicated by a broken line in FIG. 17B is output as a change in waveform of the midpoint potential Va of the magnetoresistive element pair 1. Similarly, the change in the magnetic vector of the magnetoresistive element pair 2 indicated by the solid line in FIG. 17B is output as the waveform change of the midpoint potential Vb of the magnetoresistive element pair 2.

  FIG. 17C shows the transition of the change in differential deflection angle, which is the difference between the deflection angles of the magnetic vectors applied to the magnetoresistive element pairs 1 and 2, and the differential deflection is shown in FIG. The change in the angle changes in a manner indicated by a solid line in FIG. This differential deflection angle is the difference between the midpoint potentials Va and Vb when the midpoint potentials Va and Vb of the magnetoresistive element pairs 1 and 2 are input to the differential amplifier 3 in the sensor chip 30, respectively. A differential output (signal A) is obtained.

The differential output (signal A) output in this way is compared with a predetermined threshold voltage Vth indicated by a one-dot chain line in FIG. Is applied.
As a result, a binarized signal (pulse signal) as shown in FIG. 17 (d) is obtained, and this binarized signal (pulse signal) has the differential output (signal A) and the threshold voltage Vth. The signal is output from the output terminal T2 as a signal whose logic level is inverted at the intersections a and b. As described above, in the conventional rotation detection device, the logical level of the sensor output is switched at the intersection of the differential output (signal A) of the magnetoresistive element pairs 1 and 2 and the predetermined threshold voltage Vth. The rotation angle of the rotor 20 is detected.
Japanese Patent Laid-Open No. 11-237256

  By the way, in the conventional rotation detecting device, as described above, the deflection angle of the magnetic vector sensed by the magnetoresistive element pairs 1 and 2 changes so as to be dragged by the peak portion 21 of the rotor 20. It changes in a way that corresponds to the edge position. That is, the differential output (signal A) also changes in a manner corresponding to the edge position of the peak portion 21, and the sensor output finally obtained is also detected in a manner corresponding to the edge position of the peak portion 21. Yes. However, in such a detection method, signal waveforms such as the deflection angle of the magnetic vector, the differential output (signal A), and the sensor output are greatly affected by the edge shape of the peak portion 21 in particular. For this reason, normally, a “mechanical-electrical angle difference” that is a difference in rotation angle obtained by electrical sensing processing with respect to a mechanical rotation angle that is an actual rotation angle of the rotor 20 is generated. .

  Here, the “mechanical-electrical angle difference” will be specifically described with reference to FIG. In FIG. 18, FIG. 18 (a) shows the shape of the rotor 20 linearly for convenience, and FIG. 18 (b) is similar to FIG. 17 (c). 12 is a time chart showing a waveform change of a differential output accompanying 20 rotations. FIG. 18C is also a time chart showing the waveform change of the binarized signal (pulse signal) obtained as the sensor output, as in FIG. 17D.

  As described above, the differential output (signal A) shown in FIG. 18B and the predetermined threshold voltage Vth intersect at points a and b. However, in general, such differential output is generated not only from the tooth shape of the rotor 20 (edge shape of the peak portion 21) but also from the external environment such as temperature or the distance between the rotor 20 and the magnetoresistive element pairs 1 and 2 (air gap). ) And the like are different, the waveform shape such as the amplitude changes. For this reason, even if the threshold voltage Vth is set to a constant value, the positions of the points a and b where the differential output and the threshold voltage Vth intersect change with the change of the above conditions. . That is, the relationship between the mechanical edges 21a and 21b of the crest portion 21 of the rotor 20 shown in FIG. 18A and the intersecting points a and b is, for example, in the form shown in FIG. Variations associated with changes in the above conditions will occur. As a result, the sensor output edges 21o and 21p obtained in the form corresponding to the intersecting points a and b also vary, and the mechanical edges 21a and 21b and the sensor output edges, The angle difference between the electrically detected edges 21o and 21p is “mechanical-electrical angle difference” L.

Next, the variation in the “mechanical-electrical angle difference” L will be described in more detail with reference to FIGS. 19A to 19C and FIG.
First, FIGS. 19A to 19C illustrate the relationship between the tooth shape of the rotor 20 (the edge shape of the peak portion 21) and the waveform of the sensor output obtained corresponding thereto.

  As shown in FIG. 19A, for example, when the peak portion 21 of the rotor 20 has a general rectangular shape, mechanical edges 21a and 21b are formed on the mechanical edges 21a and 21b as in the example shown in FIG. On the other hand, an angle difference is generated between the electrically detected edges 21o and 21p, and this is a “mechanical-electrical angle difference” L1.

  In addition, as shown in FIG. 19B, when the edges 21a and 21b of the peak portion 21 are formed in a trapezoidal shape with an inclined surface, the range detected as the mechanical edge 21a itself is There is a variation in distance from the portion 21c to the end portion 21d. For this reason, the range of the angular difference between the electrically detected edges 21o and 21p is also widened, and the “mechanical-electrical angular difference” L2 is the maximum value.

  In addition, as shown in FIG. 19C, when the edge tip 21c of the peak portion 21 is rounded, the “mechanical-electrical angle difference” is reduced with respect to the mechanical edges 21a and 21b. Tend to be. However, depending on the degree of roundness of the edge tip 21c, an angle difference is generated between the edges 21o and 21p that are also electrically detected, and this becomes a “mechanical-electrical angle difference” L3.

Thus, the “mechanical-electrical angle difference” L varies greatly depending on the shape of the rotor 20 to be detected, particularly the edge shape of the peak portion 21.
On the other hand, FIG. 20 shows the waveform change of the differential output (signal A) when conditions such as temperature and air gap are different. In FIG. 20, as an example, the differential output waveform in the case of high temperature and high air gap is indicated by a solid line, and the differential output waveform in the case of low temperature and low air gap is indicated by a broken line. As is well known, such a rotation detection device generally depends on the temperature of the electrical characteristics of various processing circuits in the sensor chip 30 (FIGS. 15 and 16) including the magnetoresistive element pairs 1 and 2 described above. To do. For example, the lower the temperature, the larger the resistance value change sensed by the magnetoresistive element pairs 1 and 2, and the larger the differential output amplitude. Further, the smaller the air gap, the larger the deflection angle of the magnetic vector applied to the magnetoresistive element pairs 1 and 2, and the larger the amplitude of the differential output. For this reason, the amplitude of the differential output is larger at a low temperature and a low gap than at a high temperature and a high gap. The position where the differential output intersects with the threshold voltage Vth also changes in accordance with the waveform change of the differential output itself, and this change appears as the above-described “mechanical-electrical angle difference” variation. It becomes like this.

  In addition, the absolute value of the differential output may vary up and down due to, for example, an unnecessary offset added to the waveform itself due to variations (individual differences) between products as a rotation detection device. For example, when the threshold voltage Vth is set in the manner shown in FIG. 20 with respect to the differential output indicated by the solid line in FIG. 20, the differential output and the threshold voltage Vth intersect at the point q. On the other hand, due to the variation between the products, for example, a negative offset occurs in the differential output waveform, and when the absolute value becomes small, the threshold voltage becomes relatively large. That is, with respect to the differential output similarly indicated by a solid line in FIG. 20, this threshold voltage relatively changes in a manner shown as a threshold voltage Vth ′ in FIG. 20, and the differential output and this threshold voltage Vth. It intersects with the point r. At this time, the edge difference L4 of the sensor output edge itself, that is, the electrically detected edge itself, varies, and this directly acts as a “mechanical-electrical angle difference”.

  As described above, in the conventional rotation detection device, a “mechanical-electrical angle difference” is caused by a difference in various conditions such as temperature and air gap. For this reason, the edge detection accuracy related to the peak portion 21 of the rotor 20 (FIG. 15) naturally has a limit, and in order to increase such detection accuracy as a rotation detection device, the above differential output is provided for each individual product. Adjustment for optimizing the relationship between the threshold voltage and the threshold voltage is unavoidable.

  After all, in such a conventional rotation detection device, the occurrence of "mechanical-electrical angle difference" due to differences in temperature, air gap, etc., including the shape of the rotor that is the target of rotation detection, is unavoidable. In order to eliminate such an angle difference, an enormous design load and a complicated work for the adjustment are forced.

  The present invention has been made in view of the above circumstances, and provides a rotation detection device that enables highly accurate rotation detection with high versatility that does not require internal adjustment for each rotor or individual to be detected. The purpose is to provide.

In order to achieve such an object, the rotation detection device according to each of the claims includes a sensor chip including a magnetoresistive element and a bias magnet that applies a bias magnetic field to the magnetoresistive element, in the vicinity of the sensor chip. A rotation detecting device for detecting a rotation mode of the rotor by sensing a change in a magnetic vector generated in cooperation with the bias magnetic field as a change in a resistance value of the magnetoresistive element when a gear-type rotor made of a magnetic material rotates. And a center detecting means for detecting the center of each tooth of the rotating rotor based on a change in the resistance value of the magnetoresistive element, and detecting the rotation mode of the rotor from the detected center passage information of each tooth. The configuration.

  Thus, by detecting the center of each tooth of the rotating rotor and detecting the rotation mode of the rotor from the detected center passage information of each tooth, the above-mentioned “mechanical-electrical angle” Even if a "difference" occurs, more accurate rotor rotation information (angle information) that does not depend on such an angle difference, that is, does not depend on the rotor shape (tooth edge shape), environmental temperature, gap specifications, etc. ) Can be obtained. In addition, since it does not depend on the rotor shape, environmental temperature, gap specifications, etc., the design load is greatly reduced, and the above-described adjustment work at the time of manufacture is no longer necessary. Costs can be significantly reduced.

Further, in such a configuration, the sensor chip includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor and electrically form a half-bridge circuit, respectively. When this differential output is binarized by comparing the differential output of the midpoint potential of the resistor element pair by the first comparator having the first threshold voltage set, Specifically, for example, according to the invention described in claim 1 ,
(A) a differentiating circuit for differentiating the differential output, a second comparator for binarizing the differentiated signal based on a comparison with a second threshold voltage, and the first comparison A logical product (AND) circuit that takes a logical product of the binarized output from the comparator and the binarized output from the second comparator, the logical product output being the center passage information of each detected tooth, What to do.
Alternatively, as in the invention according to claim 2 ,
(B) The third magnetoresistive element pair that electrically forms a half-bridge circuit and the midpoint potential of the third magnetoresistive element pair are binarized based on comparison with the second threshold voltage. A second comparator; and a logical product (AND) circuit that takes a logical product of the binarized output from the first comparator and the binarized output from the second comparator. Is the center passage information of each tooth detected.
Furthermore, according to the invention of claim 4 ,
(C) A third magnetoresistive element pair that electrically forms a half-bridge circuit, and an electric element disposed on either the front or rear side of the third magnetoresistive element pair in the direction facing the rotor. The fourth magnetoresistive element pair that forms a half-bridge circuit and the differential outputs of the midpoint potentials of the third and fourth magnetoresistive element pairs are compared with the second threshold voltage. A second comparator for binarization, and a logical product (AND) circuit that takes a logical product of the binarized output of the first comparator and the binarized output of the second comparator, This logical product output is used as the center passage information of each detected tooth.
It is effective to adopt such a configuration.

By the way, in the case of the configuration (A) (the invention according to claim 1 ), the differential circuit is provided so that a signal that zero-crosses in synchronism with the center position of the teeth of the rotor is generated purely electrically. By setting a voltage corresponding to the zero-crossing point as the second threshold voltage, the pulse signal that is output with the differential output binarized by the second comparator is In the portion corresponding to the tooth position, the rising edge or the falling edge itself is synchronized with the center position of the teeth of the rotor. Therefore, the pulse signal obtained as the logical product output of the logical product (AND) circuit of the pulse signal (binarized output) and the binary output of the first comparator is also the rising edge or the rising edge. The falling edge itself directly indicates the center position of the teeth of the rotor. Note that either the “rising edge” or “falling edge” of the pulse signal that is binarized and output by the second comparator or the pulse signal obtained as the logical product output is the center of the teeth of the rotor. Whether the position is indicated or not is determined by a comparison mode with the differential output by the second comparator.

Further, in the case of the configuration (b) (the invention according to claim 2 ), the transition of the midpoint potential of the third magnetoresistive element pair is the differential output in the configuration (b). The waveform corresponding to this waveform, more precisely, a waveform that changes substantially in point symmetry in synchronization with the center position of the teeth of the rotor. Therefore, in this case as well, the logical product (AND) of the binarized output obtained by setting the level of the symmetry point by the second comparator as the second threshold voltage and the binarized output by the first comparator. ) In the pulse signal obtained as the logical product output by the circuit, the rising edge or the falling edge itself directly indicates the center position of the teeth of the rotor. In this case as well, any of the “rising edge” and “falling edge” of the pulse signal that is binarized and output by the second comparator or the pulse signal obtained as the logical product output is the same as that of the rotor. Whether to indicate the center position of the tooth is determined by a comparison mode with the midpoint potential of the third magnetoresistive element pair by the second comparator. Also in this case, as according to the invention described in claim 3, by so disposing the third magnetoresistive element pairs in the middle of the first and second magnetoresistive element pairs, magnetism third The margin of the midpoint potential of the resistor element pair with respect to the second threshold voltage can be accurately increased.

In the case of the configuration (c) (the invention according to claim 4 ), the transition (waveform) of the differential output of each midpoint potential of the third and fourth magnetoresistive element pairs is The waveform corresponding to the differential output waveform in the configuration (a), that is, a waveform that changes substantially symmetrically with respect to the center position of the teeth of the rotor is shown. Therefore, in this case as well, the logical product (AND) of the binarized output obtained by setting the level of the symmetry point by the second comparator as the second threshold voltage and the binarized output by the first comparator. ) In the pulse signal obtained as the logical product output by the circuit, the rising edge or the falling edge itself directly indicates the center position of the teeth of the rotor. In this case as well, any of the “rising edge” and “falling edge” of the pulse signal that is binarized and output by the second comparator, or the pulse signal obtained as the logical product output, is Whether the center position of the tooth is indicated is determined by a comparison mode with the differential output of each midpoint potential of the third and fourth magnetoresistive element pairs by the second comparator. Also in this case, the third and fourth magnetoresistive element pairs are arranged in the center of the first and second magnetoresistive element pairs, as in the invention described in claim 5. It becomes possible to accurately increase the margin of the differential output of each midpoint potential of the third and fourth magnetoresistive element pairs with respect to the second threshold voltage.

In these configurations (a) to (c) (inventions according to claims 1 to 5 ), the center detecting means may be provided in the same chip as the sensor chip, or may be provided separately. It may be configured as a chip. Also, when selecting the “rising edge” and “falling edge”, the logic levels may be adjusted by inserting an inverter circuit which is a logic inversion circuit, for example.

In particular, in the case of the above configuration (c), that is, the configuration of the invention described in claim 4 or 5 , according to the invention described in claim 6 , at least the third and fourth magnetoresistive elements. For the pair, it is desirable to form them as a full bridge circuit in which each half bridge circuit is commonly connected to the same power source in such a manner that the output of one half bridge circuit is inverted. By adopting such a full bridge circuit, the sensitivity of the signal to be compared (binarized) in the second comparator is greatly increased, and this is also applied to the center position of the teeth of the rotor. As a result, the rising edge or the falling edge of the pulse signal obtained as the logical product output can be detected with higher accuracy.

On the other hand, a gear-type rotor made of a magnetic material rotates in the vicinity of the sensor chip, which has a sensor chip having a magnetoresistive element as described above and a bias magnet that applies a bias magnetic field to the magnetoresistive element. When detecting a rotation mode of the rotor by sensing a change in the magnetic vector that sometimes occurs in cooperation with the bias magnetic field as a change in the resistance value of the magnetoresistive element, based on the change in the resistance value of the magnetoresistive element, It includes a center detection means for detecting the center of each tooth of the rotating rotor, and a line detector for detecting the rotation mode of the rotor from the center passage information of each tooth issued該検, according the invention described in claim 7 As described above, the sensor chip is arranged along the rotation direction of the rotor to electrically form first and second magnetoresistive element pairs each forming a half-bridge circuit. When the rotor rotates, the change in the magnetic vector that occurs in cooperation with the bias magnetic field is detected as the change in the midpoint potential due to the first and second magnetoresistive element pairs. As the center detecting means, a third magnetoresistive element pair that is disposed in the center of the first and second magnetoresistive element pairs and electrically forms a half-bridge circuit, and the first magnetoresistive element A first differential amplifier that differentially amplifies the midpoint potential of the element pair and the midpoint potential of the third magnetoresistive element pair; and the midpoint potential and the second magnetism of the third magnetoresistive element pair A second differential amplifier that differentially amplifies the midpoint potential of the resistor element pair; and a third differential amplifier that further differentially amplifies each differentially amplified signal by the first and second differential amplifiers. With respect to the rotation of the rotor It is also effective to adopt a configuration such as to detect the center of each tooth of the rotor based on a variant of the third differential amplifier signal by the differential amplifier.

  In such a configuration, the transition of the differential amplification signal by the third differential amplifier corresponds to the waveform of the differential output in the configuration of (A), more precisely, the center of the teeth of the rotor. The waveform changes in a substantially point-symmetric manner in synchronization with the position. Therefore, also in this case, it becomes possible to detect the center of each tooth of the rotor based on the change mode of the differential amplification signal by the third differential amplifier with respect to the rotation of the rotor. That is, in this case, for the center position of the teeth of the rotor, for example, a differential amplification signal by the third differential amplifier, that is, a waveform that changes substantially in point symmetry in synchronization with the center position of the teeth of the rotor, It can be binarized with a voltage corresponding to a point that is the center of point symmetry, and can be detected as a rising edge or a falling edge of a pulse signal obtained by this binarization processing. In this case as well, which of the “rising edge” and “falling edge” of the pulse signal output after binarization indicates the center position of the teeth of the rotor depends on the third differential amplifier. It is determined by a comparison mode between the differential amplified signal and the voltage corresponding to the point which is the center of the point symmetry.

  Moreover, in the above configuration, two types of differential amplification signals obtained based on the respective midpoint potentials of the first to third magnetoresistive element pairs are further differentially amplified by the third differential amplifier, The center of each tooth of the rotor is detected based on a signal obtained by this differential amplification. For this reason, the magnitude of the signal used for detecting the center of each tooth of the rotor naturally increases, and the sensitivity of the same center detection is greatly increased.

Further, particularly in this case, as in the invention according to claim 8 , the first to third appearing when the center of each tooth of the rotating rotor and the third magnetoresistive element pair face each other. When the output values of the midpoint potentials of the magnetoresistive element pairs are represented as A, B, and C, the output values of the midpoint potentials of these first to third magnetoresistive element pairs are “A + B = 2C”. It is more practically desirable to arrange them in such a relationship.

  That is, according to such a configuration, when the center of each tooth of the rotor and the third magnetoresistive element pair face each other, the output value of the differential amplification signal by the first and second differential amplifiers Are represented as “A-C” and “C-B”, respectively, and the output value of the differential amplification signal by the third differential amplifier, which is the differential amplification signal of each of these differential amplification signals, is “A + B”. -2C ". Therefore, the first to third magnetoresistive element pairs are arranged so that the output value of each midpoint potential by the first to third magnetoresistive element pairs has a relationship of “A + B = 2C”. Then, when the center of each tooth of the rotating rotor and the third magnetoresistive element pair face each other, the output value of the differential amplification signal by the third differential amplifier becomes “0”, for example, When binarizing a differential amplification signal by the third differential amplifier, that is, a waveform that changes in a substantially point-symmetric manner in synchronization with the center position of the teeth of the rotor, with a voltage corresponding to the point that becomes the center of the point-symmetry, The voltage setting (voltage “0 V”) corresponding to the point that is the center of the same point symmetry becomes easy.

However, in the case where the differential amplified signal by the third differential amplifier is binarized with a voltage (threshold voltage) corresponding to the point that is the center of the point symmetry, for example, the third magnetoresistive element pair Chattering (incorrect determination) occurs in the pulse signal when it faces the rotor valley, and as a result, the reliability of the rising edge or falling edge of the pulse signal synchronized with the center position of the rotor teeth decreases. There is no doubt. Therefore, the center position of each tooth of the rotor, the rising edge of such a pulse signal or in the case of detecting the falling edge, such as by the invention of claim 9, as the central detection unit, wherein Hysteresis between two voltage values including the output value of the differential amplification signal by the third differential amplifier that appears when the center of each tooth of the rotating rotor and the third magnetoresistive element pair face each other. A hysteresis comparator in which a threshold voltage that crosses the differential amplification signal by the third differential amplifier is set while switching, and the binarized output by the hysteresis comparator is the center of each detected tooth It is more practically desirable to adopt what is used as passing information.

In such a configuration, the center detection means outputs the output value of the differential amplification signal by the third differential amplifier that appears when the center of each tooth of the rotor and the third magnetoresistive element pair face each other (above When the configuration according to claim 8 is adopted, a threshold voltage that crosses a differential amplification signal by the third differential amplifier while switching with hysteresis between two voltage values including “0 V”) A hysteresis comparator to be set, and the binarized output (pulse signal) from the hysteresis comparator is used as the center passage information of each detected tooth, so that the third magnetoresistive element pair is connected to the valley of the rotor. The occurrence of chattering in the pulse signal when facing the part is avoided, and a more accurate binary output corresponding to the center position of each tooth of the rotor can be obtained.

On the other hand, in the rotation detection device according to any one of claims 1 to 9 , in the invention according to claim 10 , each of the magnetoresistive element pairs has a change in the magnetic vector substantially in a current flow direction. In order to be applied around “45 °” and “−45 °”, it is arranged in a “C” shape in the direction facing the rotor.

In general, the resistance value of the magnetoresistive element changes in a range where the angle θ between the magnetic vector and the current vector is “0 to 90 °”, but the angle θ is in the vicinity of “0 °” or “90 °”. In the vicinity of, the linearity of such a change characteristic of the resistance value is greatly impaired. In this respect, such as by the invention described in claim 10, if to be arranged in the form "letter Ha" the direction opposite to the rotor of each of the magnetoresistive element pairs, with the rotation of the rotor, said The angle θ can also be swung around about “45 °” and “−45 °”, and it becomes possible to obtain a resistance value change more excellent in linearity as those magnetoresistive elements. In other words, the differential outputs obtained through the rotation detection device, and thus, the center output information of the teeth and the logical product output obtained can be obtained with higher reliability.

(First embodiment)
A first embodiment of a rotation detection device according to the present invention will be described below with reference to FIGS. Note that, in the rotation detection device according to this embodiment, the structure of the basic part thereof conforms to the structure illustrated in FIGS. 15 and 16 above.

  That is, as shown in FIG. 1, even in the rotation detection device according to this embodiment, the sensor chip 30a includes the first magnetoresistive element pair 1 including the magnetoresistive elements MRE1 and MRE2, and the magnetoresistive element. And a second magnetoresistive element pair 2 including MRE3 and MRE4. The magnetoresistive element pairs 1 and 2 are electrically configured as a half bridge circuit in which the magnetoresistive elements MRE1 and MRE2 or the magnetoresistive elements MRE3 and MRE4 are respectively connected in series. These two magnetoresistive elements connected in series, that is, the magnetoresistive elements MRE1 and MRE2, or the magnetoresistive elements MRE3 and MRE4, are at the magnetic center of the bias magnetic field with respect to each other as in the structure illustrated in FIG. They are arranged so as to form an angle of approximately “45 °” and “−45 °” with respect to each other, that is, in a “C” shape. The midpoint potential Va of the magnetoresistive elements MRE1 and MRE2 is the output of the magnetoresistive element pair 1, and the midpoint potential Vb of the magnetoresistive elements MRE3 and MRE4 is the output of the magnetoresistive element pair 2. These two outputs are respectively input to the differential amplifier 3, and the differential output (signal A) between the midpoint potential Va and the midpoint potential Vb is further input to the first comparator 4. Then, the comparator 4 compares the differential output (signal A) with the first threshold voltage Vth1 set to a predetermined value, and binarizes the differential output (signal A) (signal A). Signal B) is obtained.

  On the other hand, in the rotation detection device according to this embodiment, as a signal processing circuit, each of the teeth of the rotor 20 (FIG. 15) is further based on the change in the resistance values of the magnetoresistive elements MRE1 to MRE4. A center detection circuit 100 for detecting the center is provided. Next, the circuit configuration of the center detection circuit 100 will be specifically described.

  The center detection circuit 100 includes a differentiating circuit 110 for differentiating the differential output (signal A). The differentiation circuit 110 is a well-known circuit including, for example, a capacitor 111 and a branch resistor 112. From the differentiation circuit 110, a differential output (signal C1) of the differential output (signal A) is obtained. It is done. The differential output (signal C1) is further input to the second comparator 120. The comparator 120 is a part that performs binarization processing of the differential output (signal C1) based on the second threshold voltage Vth2 set at the zero cross point of the differential output (signal C1). In this embodiment, the setting of the inverting input terminal and the non-inverting input terminal of the comparator 120 is opposite to that of the first comparator 4. The binarized output (signal B) output from the comparator 4 and the binarized output (signal D1) output from the comparator 120 are logical products of these two signals. (AND) circuit 130, and the logical product output (signal E1) is output from output terminal T2 as a sensor output by the rotation detection device.

  FIG. 2 shows a rotation detection mode of the rotor 20 by a rotation detection device having such a processing circuit as a time chart accompanying the rotation of the rotor 20. Of these, FIG. 2A shows the shape of the rotor 20 linearly for convenience, and FIGS. 2B to 2F show the processing shown in FIG. 1 as the rotor 20 rotates. It shows the transition of the signal processed in the circuit.

  Here, FIG. 2B shows the transition of the change in the differential output (signal A) of each of the midpoint potentials Va and Vb of the magnetoresistive element pairs 1 and 2 as in FIG. 18B. The differential output (signal A) changes with a pseudo sine wave shape in the form shown by a solid line in FIG. Then, the differential output (signal A) output in this way is subjected to binarization processing by the comparator 4 based on a comparison with a predetermined threshold voltage Vth1 indicated by a one-dot chain line in FIG. Is done.

  As a result, as in the case of FIG. 18C, this is also the case shown in FIG. 2C, with the points a and b where the differential output (signal A) and the threshold voltage Vth1 intersect as a boundary. A pulse-like binarized output (signal B) whose logic level is inverted can be obtained.

  On the other hand, FIG. 2D shows the transition of the differential output (signal C 1) obtained by differentiating the differential output (signal A) by the differentiating circuit 110. This differential output (signal C1) changes in a so-called zero-crossing manner in synchronization with the maximum value of the differential output (signal A) as shown by the solid line in FIG. The differential output (signal C1) output in this way is binarized by the comparator 120 based on a comparison with the threshold voltage Vth2 corresponding to the zero cross point c indicated by a one-dot chain line in FIG. Processing is performed.

  As a result of the binarization processing, as shown in FIG. 2E, the binarized output (signal D1) of the differentiated output (signal C1) is the differential output (signal C1) and the threshold voltage Vth2. In the form of including a pulse signal whose logic level is inverted at a point c at which the point crosses, the signal is binarized (pulsed) under the same threshold voltage Vth2. At this time, the rising edge of the pulse whose logic level is inverted with the point c as a boundary indicates the center position m of the teeth (peaks 21) of the rotor 20. Since the comparator 120 has its inverting input terminal and non-inverting input terminal set opposite to those of the comparator 4 as described above, its binarized output (signal D1) is the same as that shown in FIG. ), The signal C1 is at the logic L (low) level while the signal C1 exceeds the threshold voltage Vth2, and conversely, the signal C1 is at the logic H (high) level when the signal C1 does not satisfy the threshold voltage Vth2.

  Thereafter, the binarized signal D1 and the signal B binarized through the comparator 4 (FIG. 2C) are logically ANDed through the AND circuit 130. As a result, as shown in FIG. 2 (f), the rising edge is synchronized with the center position m of the tooth (crest portion 21) of the rotor 20 as in the case of the pulse whose logic level is reversed at the point c. A logical product output (signal E1) is obtained. That is, the sensor output as the rotation detection device finally obtained in this way rises to the logic H level in synchronism with the center position m of the teeth (ridges 21) of the rotor 20 passing through. In other words, it becomes a pulse signal indicating center passage information.

As described above, according to the rotation detection device of this embodiment, the effects listed below can be obtained.
(1) The structure is such that the center of each tooth (mountain portion 21) of the rotating rotor 20 is detected, and the rotation mode of the rotor is detected from the center passage information of each detected tooth (mountain portion 21). Even if the above-mentioned “mechanical-electrical angle difference” is caused by such a structure, it does not depend on such an angle difference, that is, the shape of the rotor 20 (the edge shape of the teeth (mountain portion 21)) More accurate rotation information (angle information) of the rotor 20 that does not depend on the environmental temperature, the gap specification, and the like can be obtained. In addition, since it does not depend on the shape of the rotor 20, the environmental temperature, the gap specifications, etc., the design load is greatly reduced, and adjustment work at the time of manufacture becomes unnecessary, and production is improved along with the improvement in yield. Costs can be significantly reduced.

  (2) The center detection circuit 100 is provided as a center detection means for detecting the center of each tooth (mountain portion 21) of the rotating rotor 20, and the center detection circuit 100 is provided with a differentiation circuit 110. With such a structure, a zero crossing signal corresponding to the center position m of the teeth (peaks 21) of the rotor 20 can be generated purely electrically. That is, by setting the second threshold voltage Vth2 to the zero cross point (point c in FIG. 2 (d)), the binarized output of the differential output (signal C1) by the comparator 120 is raised. The edge includes a portion that is synchronized with the center position m of the tooth (mountain portion 21) of the rotor 20. Therefore, a pulse signal obtained as a logical product output (signal E1) of the binarized output (signal D1) and the binarized output (signal B) from the first comparator 4 also has a rising edge itself. The center position m of the teeth (mountain portion 21) of the rotor 20 is directly indicated.

  (3) In the direction in which the magnetoresistive elements MRE1 and MRE2 or the magnetoresistive elements MRE3 and MRE4 constituting the first magnetoresistive element pair 1 and the second magnetoresistive element pair 2 face the rotor 20, respectively. The structure is arranged in a “C” shape. With such a structure, as the rotor 20 rotates, the angle formed between the magnetic vector and the current vector swings about “45 °” and “−45 °”, and these magnetoresistive elements MRE1 to MRE4. As a result, it is possible to obtain a resistance value change with better linearity. That is, the differential output (signal A) obtained through the rotation detection device, and the logical product output (signal E1) obtained as the center passage information of each tooth (peak portion 21) are also more highly reliable. Will be able to get under.

(Second Embodiment)
Next, a second embodiment of the rotation detection device according to the present invention will be described with reference to FIGS. Also in this embodiment, the configuration of the basic part as the rotation detection device is the same as the device illustrated in FIG. 15 and FIG. 16 or the first embodiment, and the configuration of the sensor chip, specifically Is different from the first embodiment only in the configuration of the center detection circuit.

  FIG. 3 schematically shows the positional relationship among the teeth (mountain portion 21) of the rotor 20, the sensor chip 30b, and the bias magnet 22 in the rotation detection device according to this embodiment. As in the first embodiment, the first magnetoresistive element pair 1 and the second magnetoresistive element pair 2 are disposed on the side of the sensor chip 30b facing the rotor 20. In this embodiment, a third magnetoresistive element pair 210 constituting a center detection circuit described later is disposed between the magnetoresistive element pairs 1 and 2. The magnetoresistive element pair 210 is also electrically configured as a half bridge circuit in which the magnetoresistive elements MRE5 and MRE6 are connected in series. These magnetoresistive elements MRE5 and MRE6 are also substantially “45 °” and “−45 °” with respect to the magnetic center of the bias magnetic field, similarly to the magnetoresistive elements MRE1 and MRE2 or the magnetoresistive elements MRE3 and MRE4. Are arranged so as to form an angle of, i.e., to have a "C" shape.

FIG. 4 shows an equivalent circuit of the electrical configuration in the sensor chip 30b of the rotation detection device according to this embodiment, corresponding to FIG.
As shown in FIG. 4, in this embodiment, a center detection circuit 200 is provided instead of the center detection circuit 100 provided in the sensor chip 30a in the previous first embodiment. The center detection circuit 200 includes a magnetoresistive element pair 210 including the magnetoresistive elements MRE5 and MRE6, and a midpoint potential Vc (signal C2) of the magnetoresistive elements MRE5 and MRE6 is input to the second comparator 220. It is the composition which becomes. Here, the comparator 220 is a portion that performs binarization processing of the midpoint potential Vc (signal C2) based on a second threshold voltage Vth2 set to a predetermined value described below. In this embodiment as well, as in the first embodiment, the comparator 220 has the inverting input terminal and the non-inverting input terminal set opposite to the first comparator 4. It has become. As in the first embodiment, the binarized signal (signal B) output from the comparator 4 and the binarized output (signal D2) output from the comparator 220 are also obtained. The logical product (AND) circuit 230 outputs a logical product output (signal E2) of the respective binarized outputs from the output terminal T2 as a sensor output of the rotation detection device.

  FIG. 5 shows how the midpoint potential Vc (signal C2) of the magnetoresistive elements MRE5 and MRE6 constituting the magnetoresistive element pair 210 is changed in accordance with the rotation of the rotor 20 (FIG. 15). It is shown as a time chart whether it changes. Among these, FIG. 5A corresponds to the relative position change between the rotor 20 and the magnetoresistive element pair 210 in the sensor chip 30b, and FIG. 5B corresponds to such a relative position change. The transition of the magnetic deflection angle, that is, the transition of the midpoint potential Vc (signal C2) is shown.

  For example, as shown in FIG. 5 (a), it is assumed that the positions of the teeth (ridges 21) facing the sensor chip 30b change as shown in states R1 to R4 as the rotor 20 rotates. The magnetic vector applied to the magnetoresistive element pair 210 in the sensor chip 30b also changes in the manner indicated by the arrow in FIG. At this time, the midpoint potential Vc corresponds to the deflection angle of the magnetic vector applied to the magnetoresistive element pair 210, as shown in FIG. 5 (b). 21) and the magnetoresistive element pair 210 are opposed to each other at a point d where the level is reversed, that is, the point d is changed substantially in a point-symmetric manner. For this reason, the second threshold voltage Vth2 is determined corresponding to the point d, which is the symmetry point, and the second comparator 220 uses the threshold voltage Vth2 as shown in FIG. The midpoint potential Vc (signal C2) is binarized. As a result, a binarized output corresponding to the signal D1 (see FIG. 2E) obtained by the first embodiment can be obtained.

  FIG. 6 shows the rotation detection mode of the rotor 20 as a time chart associated with the rotation of the rotor 20 in the rotation detection device including the center detection circuit 200 corresponding to FIG. is there. Among these, FIG. 6A shows the shape of the rotor 20 linearly for convenience, as in FIG. 2A. 6 (b) and 6 (c) show the differential outputs of the midpoint potentials Va and Vb of the magnetoresistive element pairs 1 and 2 as in FIGS. 2 (b) and 2 (c). The transition of the signal A) and its binarized output (signal B) are shown. In the rotation detection device of this embodiment, the binarized output (signal B) obtained in this way is used, and the center of the tooth (mountain portion 21) in the manner shown in FIGS. 6 (d) to 6 (f). Information will be detected.

  First, FIG. 6 (d) shows the transition of the change in the midpoint potential Vc (signal C2) of the magnetoresistive element pair 210 shown in FIG. 5 (b). As described above, by setting the second threshold voltage Vth2 corresponding to the level of the point d that is the symmetric point, that is, in the form indicated by the alternate long and short dash line in FIG. The binarized output (signal D2) can be obtained in the manner shown in 6 (e). That is, also in this case, the binarized output (signal D2) is a pulse signal whose logic level is inverted at the point d where the midpoint potential Vc (signal C2) of the magnetoresistive element pair 210 and the threshold voltage Vth2 intersect. It is binarized in a form that includes In addition, the rising edge of the pulse whose logic level is reversed at the point d indicates the center position m of the teeth (peaks 21) of the rotor 20.

  Thereafter, the signal D2 binarized in this way and the signal B binarized through the comparator 4 (FIG. 6C) are logically ANDed through the AND circuit 230. As a result, as shown in FIG. 6 (f), the rising edge is synchronized with the center position m of the teeth (peaks 21) of the rotor 20, as in the case of the pulse whose logic level is reversed at the point d. A logical product output (signal E2) is obtained. That is, the sensor output as the rotation detection device finally obtained in this way rises to the logic H level in synchronism with the center position m of the teeth (ridges 21) of the rotor 20 passing through. In other words, it becomes a pulse signal indicating center passage information.

  As described above, the rotation detection device according to the second embodiment also obtains an effect equivalent to or equivalent to the effects (1) and (3) of the previous first embodiment. In addition, the following effects can be obtained.

  (4) A center detection circuit 200 is provided as center detection means for detecting the center of each tooth (mountain portion 21) of the rotating rotor 20, and based on the transition of the midpoint potential Vc of the third magnetoresistive element pair 210. The angle information through which the center of each tooth (mountain portion 21) passes is obtained. This midpoint potential Vc also changes (changes) in point symmetry in synchronization with the center position of each tooth (mountain portion 21). Therefore, a binarized output (signal D2) in which the level of the symmetry point by the second comparator 220 is set to the second threshold voltage Vth2 and a binarized output (signal B) by the first comparator 4 are used. As for the pulse signal obtained as the logical product output (signal E2), the rising edge itself directly indicates the center position m of the tooth (peak portion 21) of the rotor 20. In addition, the magnetoresistive elements MRE5 and MRE6 constituting the magnetoresistive element pair 210 are also arranged in a “C” shape in the direction facing the rotor 20. As a result, for the same reason as described above, the reliability of the midpoint potential Vc is also maintained high.

(Third embodiment)
Next, a third embodiment of the rotation detection device according to the present invention will be described with reference to FIGS. Also in this embodiment, the configuration of the basic part as the rotation detection device is the same as the device illustrated in FIG. 15 and FIG. 16 or the first and second embodiments, and the configuration of the sensor chip, Specifically, the configuration of the center detection circuit is different from the previous embodiments.

  FIG. 7 schematically shows the positional relationship among the teeth (ridges 21) of the rotor 20, the sensor chip 30c, and the bias magnet 22 in the rotation detection device according to this embodiment. On the side facing the rotor 20 of the sensor chip 30c, the first magnetoresistive element pair 1, the second magnetoresistive element pair 2, and the third magnetoresistive element are provided as in the second embodiment. Each element pair 311 is disposed. In this embodiment, the fourth magnetoresistive element pair 312 is further arranged on the rear side of the magnetoresistive element pair 311 in the direction facing the rotor 20. These magnetoresistive element pairs 311 and 312 are arranged in a straight line that is substantially parallel to the magnetic center of the bias magnet 22. Further, the magnetoresistive element pair 312 also has a magnetoresistive element MRE7 and MRE8 of approximately “45 ° with respect to the magnetic center of the bias magnetic field. ”And“ −45 ° ”, that is, they are arranged in a“ C ”shape with respect to each other. The magnetoresistive elements MRE7 and MRE8 constituting the magnetoresistive element pair 312 and the magnetoresistive elements MRE5 and MRE6 constituting the magnetoresistive element pair 311 are electrically inverted in output of one half bridge circuit. In this manner, each of the half bridge circuits is configured as a full bridge circuit commonly connected to the same power source.

FIG. 8 shows an equivalent circuit of the electrical configuration in the sensor chip 30c of the rotation detecting device according to this embodiment.
As shown in FIG. 8, in this embodiment, a center detection circuit 300 is provided in the sensor chip 30c. The center detection circuit 300 includes the magnetoresistive elements MRE5 to MRE8 connected in a full bridge in the above-described manner, and the midpoint potential Vc of the magnetoresistive elements MRE5 and MRE6 and the midpoint of the magnetoresistive elements MRE7 and MRE8. The potential Vd is input to the differential amplifier 313, respectively. Further, the differential output (signal C3) between the midpoint potential Vc and the midpoint potential Vd by the differential amplifier 313 is further input to the second comparator 320, and through this comparator 320, a predetermined description described below. The binarization process is performed based on the second threshold voltage Vth2 set to the value of. Also in this embodiment, as in the first and second embodiments, the comparator 320 sets the inverting input terminal and the non-inverting input terminal for the first comparator 4. Are opposite to each other. Then, the binarized output (signal D3) from the comparator 320 is input to the AND circuit 330 together with the binarized output (signal B) from the comparator 4, and these binarized outputs. The logical product output (signal E3) is output from the output terminal T2 as the sensor output of the rotation detecting device.

  FIG. 9 shows the rotation detecting device of FIG. 9, in which the midpoint potential Vc of the magnetoresistive elements MRE5 and MRE6 constituting the magnetoresistive element pairs 311 and 312 and the magnetoresistive element MRE7 in accordance with the rotation of the rotor 20 (FIG. 15). And a time chart showing how the midpoint potential Vd of the MRE 8 changes. 9A shows a relative position change between the rotor 20 and the magnetoresistive element pairs 311 and 312 in the sensor chip 30c, and FIG. 9B shows such a relative position change. The transition of the magnetic deflection angle corresponding to, that is, the transition of the midpoint potentials Vc and Vd are indicated by a broken line and a solid line respectively.

  For example, as shown in FIG. 9A, it is assumed that the positions of the teeth (ridges 21) facing the sensor chip 30c change as shown in the states R1 to R4 as the rotor 20 rotates. The magnetic vector applied to the magnetoresistive element pair 311 and 312 in the sensor chip 30c also changes in the manner indicated by the arrow in FIG. At this time, the midpoint potentials Vc and Vd correspond to the deflection angle of the magnetic vector applied to the magnetoresistive element pairs 311 and 312 as shown in FIG. 9B. It intersects at the point where the center of the tooth (crest portion 21) and the magnetoresistive element pairs 311 and 312 face each other. These midpoint potentials Vc and Vd change so that their amplitude directions are opposite to each other as the rotor 20 rotates.

  Here, FIG. 9C shows the transition of the change of the differential deflection angle which is the difference between the deflection angles of the magnetic vectors applied to the magnetoresistive element pairs 311 and 312, that is, the magnetoresistive element pairs 311 and 312. The transition of the differential output (signal C3) of each midpoint potential Vc and Vd is shown. Then, as shown in FIG. 9C, this differential output (signal C3) is a point e where the center of the teeth (peak portion 21) of the rotor 20 and the magnetoresistive element pairs 311 and 312 face each other. The level changes in such a manner that the level is inverted at the boundary, that is, in a manner that is substantially point-symmetric with respect to the point e. Here, the obtained differential output (signal C3) is basically the same as the transition of the midpoint potential Vc (signal C2) obtained by the second embodiment in which the shape that changes with the rotation of the rotor 20 is obtained. However, the amplitude is greatly expanded, and the sensitivity as the signal is greatly enhanced. In this embodiment, the second threshold voltage Vth2 is determined corresponding to the point e, which is the symmetry point, and the second comparator 320 uses the threshold voltage Vth2 in FIG. The differential output (signal C3) shown in c) is binarized. Thereby, a binarized output (signal D3) corresponding to the signal D2 (see FIG. 6E) obtained by the second embodiment can be obtained with higher accuracy.

  FIG. 10 shows the rotation detection mode of the rotor 20 as a time chart associated with the rotation of the rotor 20 in the rotation detection apparatus having such a center detection circuit 300. Of these, FIG. 10 (a) shows the shape of the rotor 20 linearly for convenience, as in FIGS. 2 (a) and 6 (a). 10 (b) and 10 (c) are similar to FIGS. 2 (b) and 2 (c) or FIGS. 6 (b) and 6 (c), respectively. The transitions of the differential output (signal A) of the midpoint potentials Va and Vb and the binarized output (signal B) are respectively shown. In the rotation detection device according to this embodiment, the binarized output (signal B) obtained in this way is used, and the center of the tooth (mountain portion 21) in the manner shown in FIGS. 10 (d) to 10 (f). Information will be detected.

  First, FIG. 10 (d) shows the transition of the change in the differential output (signal C3) of the magnetoresistive element pairs 311 and 312 shown in FIG. 9 (c). As described above, by determining the second threshold voltage Vth2 corresponding to the level of the point e which is the symmetric point, that is, in the form indicated by the alternate long and short dash line in FIG. The binarized output (signal D3) is obtained in the manner shown in FIG. That is, also in this case, the binarized output (signal D3) is a pulse whose logic level is inverted at the point e where the differential output (signal C3) of the magnetoresistive element pair 311 and 312 and the threshold voltage Vth2 intersect. It is binarized in a form that includes the signal. In addition, the rising edge of the pulse whose logic level is inverted at this point e indicates the center position m of the teeth (peaks 21) of the rotor 20.

  Then, the signal D3 binarized in this way and the signal B binarized through the comparator 4 (FIG. 10C) are logically ANDed through the AND circuit 330. As a result, as shown in FIG. 10 (f), the rising edge is synchronized with the center position m of the teeth (peaks 21) of the rotor 20 as in the case of the pulse whose logic level is reversed at the point e. A logical product output (signal E3) is obtained. That is, the sensor output as the rotation detection device finally obtained in this way rises to the logic H level in synchronism with the center position m of the teeth (ridges 21) of the rotor 20 passing through. In other words, it becomes a pulse signal indicating center passage information.

  As described above, the rotation detection device according to the third embodiment also obtains an effect equivalent to or equivalent to the effects (1) and (3) of the previous first embodiment. In addition, the following effects can be obtained.

  (5) A center detection circuit 300 is provided as a center detection means for detecting the center of each tooth (mountain portion 21) of the rotating rotor 20, and the third magnetoresistive element pair 311 and the fourth magnetoresistive element pair 312 are provided. Based on the transition of the differential output (signal C3) of each midpoint potential Vc and Vd, the angle information through which the center of each tooth (mountain 21) passes is obtained. Since each of these midpoint potentials Vc and Vd also changes (changes) substantially in point symmetry in synchronization with the center position of each tooth (peak portion 21), the differential outputs (signals) of these respective midpoint potentials Vc and Vd C3) also changes (changes) substantially in point symmetry in synchronization with the center position of each tooth (mountain portion 21), and its amplitude is enlarged. Therefore, a pulse signal obtained as a logical product output (signal E3) of the binarized output (signal D3) from the second comparator 320 and the binarized output (signal B) from the first comparator 4 However, the rising edge itself directly indicates the center position m of the tooth (mountain portion 21) of the rotor 20, and such an edge is detected with higher accuracy. Further, the magnetoresistive elements MRE5 and MRE6 or the magnetoresistive elements MRE7 and MRE8 constituting the magnetoresistive element pair 311 and 312 are also arranged in a “C” shape in the direction facing the rotor. Therefore, the reliability of the midpoint potentials Vc and Vd is also maintained high for the same reason as described above.

(Fourth embodiment)
Next, a fourth embodiment of the rotation detection device according to the present invention will be described with reference to FIGS. Note that the rotation detection device of this embodiment also includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor and electrically form a half-bridge circuit. The point that the rotation detection device senses the change in the magnetic vector that occurs in cooperation with the bias magnetic field as the rotor rotates as the change in the midpoint potential due to the first and second magnetoresistive element pairs. This is almost the same as the first to third embodiments.

  FIG. 11A schematically shows the positional relationship among the teeth (ridges 21) of the rotor 20, the sensor chip 30d, and the bias magnet 22 in the rotation detection device according to this embodiment. On the side facing the rotor 20 of the sensor chip 30d, the first magnetoresistive element pair 1, the second magnetoresistive element pair 2, and the third magnetoresistive element are provided, as in the second embodiment. Each element pair 411 is disposed. However, in this embodiment, as the positions of the teeth (ridges 21) facing the sensor chip 30d are sequentially changed to the states Ra to Rc, the respective midpoints by these magnetoresistive element pairs 1, 2, and 411 are used. The magnetoresistive element pairs 1, 2, and 411 are arranged so that the potentials Va, Vb, and Vc change as shown in FIG. 11B. Specifically, each midpoint potential by these magnetoresistive element pairs 1, 2, and 411 that appears in the state Rb where the center of the teeth (ridges 21) of the rotor 20 and the third magnetoresistive element pair 411 face each other. When the output values of Va, Vb, and Vc are expressed as A, B, and C, respectively, these magnetoresistive element pairs 1, 2, and 411 are arranged so that the output values are “A + B = 2C”. .

  Incidentally, when the magnetoresistive element pairs 1, 2, and 411 are arranged in this way, the bias magnetic field by the bias magnet 22 is in a state (initial state) that is not magnetically affected by the peak portion 21 of the rotor 20. In this case, as shown in FIG. 11A, the bias magnetic field acts on the magnetoresistive element pairs 1, 2, 411 at different angles. Therefore, as shown in FIG. 11 (b), the offset value of each midpoint potential by these magnetoresistive element pairs 1, 2, 411, that is, each intermediate by the magnetoresistive element pairs 1, 2, 411 in the initial state. The output values of the point potentials also appear as different ones.

FIG. 12 shows an equivalent circuit of the electrical configuration in the sensor chip 30d of the rotation detection device according to this embodiment.
As shown in FIG. 12, the rotation detection device according to this embodiment includes a center detection circuit 400 in the sensor chip 30d. The center detection circuit 400 includes magnetoresistive elements MRE5 and MRE6 constituting the third magnetoresistive element pair 411, and a midpoint potential Vc by the magnetoresistive elements MRE5 and MRE6 (third magnetoresistive element pair 411). And the midpoint potential Va by the first magnetoresistive element pair 1 are respectively input to the first differential amplifier 412. The midpoint potential Vc by the third magnetoresistive element pair 411 is also input to the second differential amplifier 413 together with the midpoint potential Vb by the second magnetoresistive element pair 2. In the first differential amplifier 412, the midpoint potential Vc by the third magnetoresistive element pair 411 is differentially amplified with respect to the midpoint potential Va by the first magnetoresistive element pair 1, that is, The differential amplification signal S1 “Va−Vc” is calculated. Further, in the second differential amplifier 413, the midpoint potential Vb by the second magnetoresistive element pair 2 is differentially amplified with respect to the midpoint potential Vc by the third magnetoresistive element pair 411, that is, The differential amplification signal S2 “Vc−Vb” is calculated.

  The differential amplification signals S1 and S2 are taken into the third differential amplifier 414 in the center detection circuit 400, and the third differential amplifier 414 performs differential amplification on the differential amplification signal S1. The differential amplification of the signal S2 is further calculated, that is, the differential amplification signal S3 “Va + Vb−2Vc” is calculated. The differential amplified signal S3 is compared and binarized by a comparator 415 in which a predetermined threshold voltage is set, and the binarized output (pulse signal) PS is output to each tooth (mountain portion) of the rotor 20. 21) is taken out from the sensor chip 30d through the output terminal T2 as a signal indicating the center position.

  As will be described later, the comparator 415 of this embodiment constitutes a hysteresis comparator, and the center of each tooth of the rotor 20 and the third magnetoresistive element pair 411 are used as the predetermined threshold voltage. Two voltage values Vth3a and Vth3b including the output value Vth3a of the differential amplification signal S3 appearing in the opposing state Rb (FIG. 11) are set. The comparator 415 switches the two voltage values Vth3a and Vth3b through the switching circuit 415a in a manner having hysteresis so as to intersect with the differential amplified signal S3 by the third differential amplifier 414, so that Binarization processing of the differential amplification signal S3 is performed.

  FIG. 13 shows a differential detection signal S1 generated by the first differential amplifier 412, a differential amplification signal S2 generated by the second differential amplifier 413, and the second differential amplifier 412 as the rotor 20 rotates. 3 is a time chart showing how the differential amplified signal S3 by the differential amplifier 414 of No. 3 changes. Among these, FIG. 13A shows a relative position change between the rotor 20 and the magnetoresistive element pairs 1, 2, 411 in the sensor chip 30d, and FIGS. The transition of the magnetic deflection angle corresponding to such a relative position change, that is, the transition of the differential amplification signals S1 to S3 is shown.

  For example, as shown in FIG. 13A, as the rotor 20 rotates, the positions of the teeth (ridges 21) facing the sensor chip 30d (FIG. 11) have changed in order as in the states Ra to Rc. And

  At this time, as shown in FIG. 13B, the midpoint potential Va by the first magnetoresistive element pair 1 and the midpoint potential Vc by the third magnetoresistive element pair 411 are indicated by dotted lines in the figure. It is as described above that each changes in shape. For this reason, as shown in FIG. 13B, the differential amplification signal S1 of these midpoint potentials Va and Vb changes as shown by the solid line in the figure as the rotor 20 rotates. Become. On the other hand, at this time, as shown in FIG. 13C, the midpoint potential Vc by the third magnetoresistive element pair 411 and the midpoint potential Vb by the second magnetoresistive element pair 2 are indicated by dotted lines in the figure. It is also as described above that each change in the form shown. For this reason, as shown in FIG. 13C, the differential amplification signal S2 of these midpoint potentials Vc and Vb changes as shown by the solid line in the figure as the rotor 20 rotates. Become.

  That is, as shown in FIG. 13D, as the rotor 20 rotates, the differential amplification signals S1 and S2 change as shown by dotted lines in the figure. Therefore, as shown in FIG. 13D, in the differential amplified signal S3 of the differential amplified signals S1 and S2, the center of the teeth of the rotor 20 and the third magnetoresistive element pair 411 face each other. It shows a waveform that changes substantially symmetrically with respect to the output value that appears in the state Rb. For this reason, the center of each tooth of the rotor 20 is detected by detecting the timing at which the differential amplified signal S3 from the third differential amplifier 414 becomes such an output value (a point that is the center of point symmetry). Can be detected.

  Moreover, as described above, in this embodiment, the magnetoresistive element pairs 1, 2, 411 have the output values of the midpoint potentials generated by the magnetoresistive element pairs 1, 2, 411 appearing in the state Rb. When expressed as A, B, and C, respectively, the output values of these midpoint potentials are arranged in a relationship of “A + B = 2C”. Therefore, the output value “A + B− that appears in the state Rb of the differential amplified signal S3 by the third differential amplifier 414 expressed as“ Va + Vb−2Vc ”with respect to the midpoint potentials Va, Vb, Vc. 2C "becomes" 0V ", and it is easy to detect the timing of the point f that is the center of the point symmetry.

  In this embodiment, the voltage value Vth3a is determined corresponding to the point f “0V” which is the center of the point symmetry, and the comparator 415 uses the voltage value Vth3a to generate the voltage value Vth3a. The differential amplification signal S3 shown in FIG. As a result, a binary output (pulse signal) PS alternating at the timing of the point f can be obtained, and the center position of each tooth of the rotor 20 is detected based on the alternating timing of the pulse signal PS. Will be able to.

  However, if the differential amplified signal S3 by the third differential amplifier 414 is simply binarized with the voltage value Vth3a corresponding to the point f which is the center of point symmetry, for example, the third magnetoresistive element When the pair 411 is in the state Ra, Rc facing the valley of the rotor 20, chattering (incorrect determination) may occur in the pulse signal PS. When chattering occurs in the binarized output PS, the reliability of the alternating timing of the same pulse signal PS synchronized with the tooth center position of the rotor 20 is lowered, and the detection accuracy of the tooth center position of the rotor 20 is reduced. Will fall.

  Therefore, in this embodiment, as described above, as the threshold voltage, the voltage value Vth3a and the two voltage values Vth3b smaller than the voltage value Vth3a are set in the comparator 415, and these two voltage values Vth3a are set. , Vth3b, the threshold voltage is switched in a manner having hysteresis. Accordingly, the threshold voltage by the comparator 415 crosses the differential amplification signal S3 while switching between the two voltage values Vth3a and Vth3b with hysteresis, and the differential amplification with respect to the threshold voltage is performed. Chattering is prevented from occurring in the binarized output (pulse signal) PS of the signal S3. That is, it is possible to obtain a binary output PS (FIG. 12) that alternates corresponding to the center position of the teeth of the rotor 20 accurately.

  FIG. 14 shows the rotation detection mode of the rotor 20 as a time chart associated with the rotation of the rotor 20 in the rotation detection device including the center detection circuit 400 as described above. Of these, FIG. 14 (a) shows the shape of the rotor 20 linearly for convenience, as in FIGS. 2 (a), 6 (a), and 10 (a).

  First, FIGS. 14B, 14C, and 14D show the differences between the first and second differential amplifiers 412 and 413, similarly to FIGS. 13B, 13C, and 13D. The transitions of the dynamic amplification signals S1 and S2 and the differential amplification signal S3 of the differential amplification signals S1 and S2 are shown respectively. Among these, the differential amplification signal S3 is, as described above, between two voltage values of the voltage value Vth3a corresponding to the level of the point f that is the center of the point symmetry and the voltage value Vth3b that is smaller than the voltage value Vth3a. And the comparator 415 obtains the binarized output PS in the manner shown in FIG. 14E. That is, here, the logic level of the binarized output PS is inverted at the points f and g where the differential amplified signal S3 and the threshold voltage set in the comparator 415 intersect. Since the point f is synchronized with the center position of the teeth of the rotor 20 as described above, the falling edge of the pulse whose logic level is inverted at the point f is the tooth (crest) of the rotor 20. The center position m of the part 21) is indicated. In other words, the sensor output as the rotation detection device finally obtained in this way has a logic level that rises to a logic L level in synchronism with the passage of the center position m of the teeth (ridges 21) of the rotor 20. It becomes a pulse signal indicating so-called center passing information.

  Even in the center detection circuit 400 of this embodiment, the timing at the point f where the differential amplification signal S3 and the threshold voltage by the comparator 415 intersect is the actual rotation angle of the rotor 20. It does not depend on the difference in rotation angle (mechanical-electrical angle difference) obtained by the electrical sensing process with respect to the mechanical rotation angle. That is, when such a “mechanical-electrical angle difference” occurs, the transition of each midpoint potential, the differential amplification signal S3, etc. by the magnetoresistive element pairs 1, 2, 411 accompanying the rotation of the rotor 20 Is certainly changed, but the relationship of “A + B = 2C” of the output values of the midpoint potentials Va, Vb, Vc by the magnetoresistive element pairs 1, 2, 411 is maintained. For this reason, when the center of the tooth (peak portion 21) of the rotor 20 and the third magnetoresistive element pair 411 face each other, the output value of the differential amplification signal S3 “Va + Vb−2Vc” is also “0V”. The center of each tooth of the rotor can be detected without being affected by the “mechanical-electrical angle difference”, that is, with higher reliability.

  As described above, the rotation detection device according to the fourth embodiment also obtains an effect equivalent to or equivalent to the effects (1) and (3) of the previous first embodiment. In addition, the following effects can be obtained.

  (6) Two types of differential amplification signals S1 and S2 obtained based on the respective midpoint potentials of the first to third magnetoresistive element pairs 1, 2, and 411 are output by the third differential amplifier 414. Further, differential amplification is performed, and the center of each tooth of the rotor 20 is detected based on the signal S3 obtained by the differential amplification. For this reason, the magnitude of the signal used for detecting the center of each tooth of the rotor naturally increases, and the sensitivity of the same center detection is greatly increased.

  (7) Each midpoint potential Va by the first to third magnetoresistive element pairs 1, 2, 411 that appears when the center of each tooth of the rotor 20 and the third magnetoresistive element pair 411 face each other. When the output values of Vb and Vc are expressed as A, B, and C, respectively, the output values of the midpoint potentials Va, Vb, and Vc are expressed as “A + B”. = 2C ". For this reason, the differential amplification signal S3 from the third differential amplifier 414, that is, the waveform corresponding to the point f that becomes the center of the point symmetry is obtained by changing the waveform that changes substantially point-symmetrically in synchronization with the center position of the teeth of the rotor 20. When the binarization is performed, voltage setting (voltage “0 V”) corresponding to the point f that is the center of the same point symmetry becomes easy.

  (8) As the threshold voltage, two voltage values of a voltage value Vth3a and a voltage value Vth3b smaller than the voltage value Vth3a are set in the comparator 415, and the threshold voltage is set between the two voltage values Vth3a and Vth3b. Were switched in a way that had hysteresis. Accordingly, the threshold voltage by the comparator 415 crosses the differential amplification signal S3 while switching between the two voltage values Vth3a and Vth3b with hysteresis, and the differential amplification with respect to the threshold voltage is performed. Chattering is prevented from occurring in the binarized output (pulse signal) PS of the signal S3. That is, it is possible to obtain a binarized output PS that alternates corresponding to the center position of the teeth of the rotor 20 accurately.

(Other embodiments)
Note that the rotation detection device according to the present invention is not limited to the configurations shown as the first to third embodiments, and can be implemented in a mode exemplified below in which these are appropriately changed.

  In the third embodiment, the fourth magnetoresistive element pair 312 is disposed behind the third magnetoresistive element pair 311 in the direction facing the rotor 20. It may be arranged in front of the magnetoresistive element pair 311. Further, when the pitch of the rotor teeth (peaks) is narrow, the center position of the rotor teeth (peaks) is detected for any pair of magnetoresistive elements including the second embodiment. A magnetoresistive element pair may be selected. Although the margin with respect to the second threshold voltage Vth2 varies depending on the arrangement position of the selected magnetoresistive element, in any case, the midpoint potential is synchronized with the center position of the teeth (peaks) of the rotor. It has been confirmed by the inventor that the point is substantially point-symmetric.

  In the third embodiment, a full bridge circuit is electrically configured by the magnetoresistive element pairs 311 and 312. However, basically, each of these two magnetoresistive element pairs 311 and 312 constitutes a separate half-bridge circuit, and from the differential output of each of the midpoint potentials to the center position of the rotor teeth (peaks). It is also possible to obtain a signal whose level is inverted in a substantially point symmetrical manner in synchronization.

  In each of the above embodiments, the binarized output (signals D1 to D3) is obtained by changing the setting of the inverting input terminal and the non-inverting input terminal of the second comparator (120, 220, 320). The “rising edge” of a part of the pulse signal to be generated indicates the center position m of the teeth (ridges 21) of the rotor 20. However, the present invention is not limited to this, and each input terminal is set in the same manner as the first comparator 4 so that the “falling edge” of the pulse signal indicates the center position m of the teeth (peaks 21) of the rotor 20. It may be. In short, any sensor output that satisfies the requirements can be obtained according to the specifications of the control device that takes in the sensor output and processes it. Further, when selecting “rising edge” or “falling edge”, for example, an inverter circuit which is a logic inversion circuit may be inserted to adjust the logic level.

  In each of the above embodiments, the center detection circuit (100, 200, 300) is provided in the sensor chip to detect the center position of the tooth (mountain portion 21) of the rotor 20, respectively. As long as the circuit can detect the center position of the tooth (the peak portion 21), the circuit configuration and the like are not limited to the circuits exemplified in the above embodiments. For example, a circuit that detects the peak value of the differential output (signal A) from the differential amplifier 3 and uses the timing as the center position of the teeth (ridges 21) of the rotor 20 can be used as appropriate. Particularly in the third embodiment, the differential amplifier 313 obtains the differential outputs of the midpoint potentials Vc and Vd of the third magnetoresistive element pair 311 and the fourth magnetoresistive element pair 312. However, the differential amplifier 313 may be omitted, and the midpoint potentials Vc and Vd may be directly input to the second comparator 320 to perform binarization processing. This also makes it possible to obtain a binarized output according to the signal D3 shown in FIG.

  In each of the above embodiments, the center detection circuits (100, 200, 300) are provided in the sensor chip. However, the center detection circuits (100, 200, 300) are provided separately from the sensor chip. It is good also as a structure provided as a chip | tip.

  In each of the above embodiments, the bias magnet 22 (FIG. 15) has a hollow cylindrical shape, but any biasing magnetic field can be applied to each of the magnetoresistive elements. A bias magnet having a cylindrical shape or a rectangular parallelepiped shape can also be appropriately employed.

  In general, an AMR element (anisotropic magnetoresistive element) is generally used as the magnetoresistive element, but other magnetoresistive elements such as barber pole type magnetoresistive elements, GMR elements (giant magnetism) A magnetoresistive element such as a resistor element, a TMR element (tunnel current type magnetoresistive element), or the like can also be employed. Incidentally, in the case of a magnetoresistive element such as an AMR element, the resistance value changes in the range of the angle θ between the magnetic vector and the current vector in the range of “0 to 90 °”, but the angle θ is in the vicinity of “0 °”. Alternatively, in the vicinity of “90 °”, the resistance value change is small, and the linearity of the resistance value change characteristic is greatly impaired. In this regard, in the barber pole type magnetoresistive element, a short-circuit electrode is formed on the magnetoresistive element film at a predetermined angle. Therefore, a sufficient resistance value change with excellent linearity can be obtained even in a region where the angle θ is, for example, in the vicinity of “0 °”, that is, a region where the external magnetic field applied to the magnetoresistive element is weak. Therefore, by adopting such a barber pole type magnetoresistive element, it becomes possible to increase the sensitivity of the change in resistance value particularly in the region where the magnetic field is weak and to improve the rotation detection accuracy in the same region. Similarly, when a GMR element or a TMR element is employed, the sensitivity of change in resistance value can be increased.

  In this sense, the arrangement of the magnetoresistive element pairs is not necessarily limited to the above-described “C” shape, and is arbitrary. In short, any structure may be used as long as it can sense a change in the magnetic vector generated in cooperation with the bias magnetic field as the rotor rotates as a change in the resistance value of the magnetoresistive element. Therefore, the number of the magnetoresistive elements is basically arbitrary. Whatever the basic configuration of the rotation detection device, by providing the center detection means such as the center detection circuit, accurate rotor rotation information that does not depend on the above-mentioned “mechanical-electrical angle difference” is obtained. I can.

  In the first to third embodiments, as in the case of the fourth embodiment, the binarized output (signals D1 to D3) by the comparator (120, 220, 320) has its threshold value. There is a risk of chattering (incorrect determination) in relation to the voltage Vth2. However, in the first to third embodiments, the pulse signal (signals E1 to E3) indicating the finally obtained center passage information is converted into a binarized output (signal B) and a binarized output (signal D1). To D3), and even if chattering occurs in the binarized output (signals D1 to D3), adverse effects on the center passage information are suppressed. For this reason, in the first to third embodiments, although it is less necessary to configure the comparators (120, 220, 320) as hysteresis comparators, it is possible to increase the reliability of detecting the center of the teeth of the rotor. These comparators (120, 220, 320) may be configured as hysteresis comparators.

The circuit diagram which shows the equivalent circuit inside the sensor chip about 1st Embodiment of the rotation detection apparatus concerning this invention. (A)-(f) is a time chart which shows the center position detection aspect of the rotor tooth | gear by the apparatus of 1st Embodiment in the form corresponding to rotation of a rotor. The top view which shows typically the relative relationship between a rotor and a sensor chip about 2nd Embodiment of the rotation detection apparatus concerning this invention. The circuit diagram which shows the equivalent circuit inside the sensor chip | tip about the 2nd Embodiment. (A) And (b) is a time chart which shows the center position detection principle of the rotor tooth | gear by the apparatus of the said 2nd Embodiment in the form corresponding to rotation of a rotor. (A)-(f) is a time chart which shows the center position detection mode of the tooth | gear of the rotor by the apparatus of 2nd Embodiment in the form corresponding to rotation of a rotor. The top view which shows typically the relative relationship between a rotor and a sensor chip about 3rd Embodiment of the rotation detection apparatus concerning this invention. The circuit diagram which shows the equivalent circuit inside the sensor chip about the same 3rd Embodiment. (A)-(c) is a time chart which shows the center position detection principle of the tooth | gear of the rotor by the apparatus of 3rd Embodiment in the form corresponding to rotation of a rotor. (A)-(f) is a time chart which shows the center position detection aspect of the rotor tooth | gear by the apparatus of 3rd Embodiment in the form corresponding to rotation of a rotor. (A) is a top view showing typically a relative relation between a rotor and a sensor chip about a 4th embodiment of a rotation detecting device concerning this invention. (B) is a time chart showing changes in the signal waveform of each midpoint potential by the first to third magnetoresistive element pairs as the rotor rotates. The circuit diagram which shows the equivalent circuit inside the sensor chip about the same 4th Embodiment. (A)-(d) is a time chart which shows the center position detection principle of the tooth | gear of the rotor by the apparatus of 4th Embodiment in the form corresponding to rotation of a rotor. (A)-(e) is a time chart which shows the center position detection aspect of the tooth | gear of the rotor by the apparatus of the said 4th Embodiment in the form corresponding to rotation of a rotor. The top view which shows typically the outline of the planar structure of the conventional rotation detection apparatus including the relationship with a to-be-detected rotation body. The circuit diagram which shows the equivalent circuit inside the sensor chip | tip about the conventional rotation detection apparatus. (A)-(d) is a time chart which shows the rotation detection aspect of a rotor by the same conventional rotation detection apparatus in the form corresponding to rotation of a rotor. (A)-(c) is a time chart which shows the "mechanical-electrical angle difference" which arises in a rotation detection apparatus. (A)-(c) is the schematic which shows the relationship between the shape change of a rotor shape and a sensor output, respectively about the said "mechanical-electrical angle difference". The time chart which shows the relationship between the differential output accompanying the environmental change of a rotation detection apparatus, and a threshold voltage.

Explanation of symbols

  1, 2, 210, 311, 312, 411, magnetoresistive element pair, 3, differential amplifier, 4, comparator, 100, 200, 300, 400, center detection circuit, 110, differentiation circuit, 111, capacitor, 112 ... Branch resistance, 313, 412, 413, 414 ... Differential amplifier, 120, 220, 320, 415 ... Comparator, 130, 230, 330 ... AND circuit, 20 ... Rotor, 20a ... Valley, 21 ... Mountain part, 21a, 21b ... Edge, 22 ... Bias magnet, 30, 30a, 30b, 30c ... Sensor chip, 32 ... Mold material, 415a ... Switching circuit, MRE1-MRE8 ... Magnetoresistive element, T1 ... Power supply terminal, T2 ... output terminal, T3 ... GND (ground) terminal.

Claims (10)

A sensor chip having a magnetoresistive element; and a bias magnet for applying a bias magnetic field to the magnetoresistive element. When a gear-shaped rotor made of a magnetic material rotates in the vicinity of the sensor chip, the sensor chip cooperates with the bias magnetic field. When detecting the rotation mode of the rotor by sensing the change of the magnetic vector generated as a result of the change of the resistance value of the magnetoresistive element, each tooth of the rotating rotor is detected based on the change of the resistance value of the magnetoresistive element. includes a center detection means for detecting the center, and the central passing information of each tooth issued該検 met rotation detecting device for detecting a rotation mode of the rotor,
The sensor chip includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor and electrically form a half-bridge circuit, and each of the magnetoresistive element pairs has a midpoint potential. The differential output is binarized by comparing the differential output with a first comparator in which a first threshold voltage is set, and the center detection means performs differential processing on the differential output. A differentiating circuit; a second comparator for binarizing the differentiated signal based on a comparison with a second threshold voltage; a binarized output from the first comparator; A rotation detection device comprising: a logical product (AND) circuit that takes a logical product with a binary output by a comparator, and using the logical product output as center passage information of each tooth detected. A sensor chip having a magnetoresistive element; and a bias magnet for applying a bias magnetic field to the magnetoresistive element. When a gear-shaped rotor made of a magnetic material rotates in the vicinity of the sensor chip, the sensor chip cooperates with the bias magnetic field. When detecting the rotation mode of the rotor by sensing the change of the magnetic vector generated as a result of the change of the resistance value of the magnetoresistive element, each tooth of the rotating rotor is detected based on the change of the resistance value of the magnetoresistive element. includes a center detection means for detecting the center, and the central passing information of each tooth issued該検 met rotation detecting device for detecting a rotation mode of the rotor,
The sensor chip includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor and electrically form a half-bridge circuit, and each of the magnetoresistive element pairs has a midpoint potential. The differential output is binarized by comparing the differential output with a first comparator set with a first threshold voltage, and the center detecting means electrically forms a half-bridge circuit. And the midpoint potential of the third magnetoresistive element pair and the third magnetoresistive element pair
A logical product of the second comparator that binarizes based on the comparison with the threshold voltage of the first output, the binarized output by the first comparator, and the binarized output by the second comparator is obtained. A rotation detection device comprising a logical product (AND) circuit, wherein the logical product output is used as center passage information of each tooth detected. The rotation detection device according to claim 2 , wherein the third magnetoresistive element pair is disposed in the center of the first and second magnetoresistive element pairs. A sensor chip having a magnetoresistive element; and a bias magnet for applying a bias magnetic field to the magnetoresistive element. When a gear-shaped rotor made of a magnetic material rotates in the vicinity of the sensor chip, the sensor chip cooperates with the bias magnetic field. When detecting the rotation mode of the rotor by sensing the change of the magnetic vector generated as a result of the change of the resistance value of the magnetoresistive element, each tooth of the rotating rotor is detected based on the change of the resistance value of the magnetoresistive element. includes a center detection means for detecting the center, and the central passing information of each tooth issued該検 met rotation detecting device for detecting a rotation mode of the rotor,
The sensor chip includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor and electrically form a half-bridge circuit, and each of the magnetoresistive element pairs has a midpoint potential. The differential output is binarized by comparing the differential output with a first comparator set with a first threshold voltage, and the center detecting means electrically forms a half-bridge circuit. A third magnetoresistive element pair and a fourth magnetoresistive element pair disposed in front of or behind the third magnetoresistive element pair in a direction facing the rotor to electrically form a half-bridge circuit. A second comparator that binarizes the differential output of the midpoint potential of each of the third and fourth magnetoresistive element pairs based on a comparison with a second threshold voltage; Binarized output by the first comparator; Rotation of the second comparator and a logical product (AND) circuit for taking a logical product of the binary output, characterized in that the center passage information of each tooth being the detection of the logical product output Detection device. The rotation detection device according to claim 4 , wherein the third and fourth magnetoresistive element pairs are arranged in the center of the first and second magnetoresistive element pairs. At least the third and fourth magnetoresistive element pairs are formed as a full bridge circuit in which each half bridge circuit is commonly connected to the same power source in a mode in which the output of one half bridge circuit is inverted. Item 6. The rotation detection device according to Item 4 or 5 . A sensor chip having a magnetoresistive element; and a bias magnet for applying a bias magnetic field to the magnetoresistive element. When a gear-shaped rotor made of a magnetic material rotates in the vicinity of the sensor chip, the sensor chip cooperates with the bias magnetic field. When detecting the rotation mode of the rotor by sensing the change of the magnetic vector generated as a result of the change of the resistance value of the magnetoresistive element, each tooth of the rotating rotor is detected based on the change of the resistance value of the magnetoresistive element. includes a center detection means for detecting the center, and the central passing information of each tooth issued該検 met rotation detecting device for detecting a rotation mode of the rotor,
The sensor chip includes first and second magnetoresistive element pairs that are arranged along the rotation direction of the rotor to electrically form a half-bridge circuit, and when the rotor rotates, A change in magnetic vector generated in cooperation is sensed as a change in each midpoint potential by the first and second magnetoresistive element pairs, and the center detecting means includes the first and second magnetoresistive elements. A third magnetoresistive element pair disposed in the center of the element pair and electrically forming a half-bridge circuit; and a midpoint potential by the first magnetoresistive element pair
And a first differential amplifier that differentially amplifies a midpoint potential by the third magnetoresistive element pair, a midpoint potential by the third magnetoresistive element pair, and a midpoint by the second magnetoresistive element pair A second differential amplifier that differentially amplifies the potential; and a third differential amplifier that further differentially amplifies each differential amplification signal by the first and second differential amplifiers, and rotation of the rotor A rotation detecting device for detecting a center of each tooth of the rotor based on a change mode of a differential amplification signal by the third differential amplifier . The first to third magnetoresistive element pairs are formed by the first to third magnetoresistive element pairs that appear when the center of each tooth of the rotating rotor and the third magnetoresistive element pair face each other. The rotation detection device according to claim 7 , wherein when the output values of the respective midpoint potentials are represented as A, B, and C, respectively, the output values of the midpoint potentials are respectively arranged in a relationship of “A + B = 2C”. . The center detection means includes two output values of a differential amplification signal by the third differential amplifier that appears when the center of each tooth of the rotating rotor and the third magnetoresistive element pair face each other. A hysteresis comparator in which a threshold voltage crossing a differential amplification signal by the third differential amplifier is set while switching between voltage values with hysteresis, and the binarized output by the hysteresis comparator The rotation detection device according to claim 7 or 8 , wherein the rotation detection device is used as center passage information of each tooth to be detected. Each of the magnetoresistive element pairs has a “c” in the direction facing the rotor so that the change in the magnetic vector is applied at about “45 °” and “−45 °” with respect to the current flow direction. The rotation detection device according to any one of claims 1 to 9 , wherein the rotation detection device is arranged in a shape of a character.

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