JP2015059859A - Rotation detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation detection device capable of accurately detecting timing at which rotor teeth are located on a detection reference axis.SOLUTION: First and second magnetoresistive element bridges 40a and 40b are placed at symmetrical positions to third and fourth magnetoresistive element bridges 40c and 40c, respectively about a line Y3 that connects points at equal distance from a line Y1 passing through a median B1 and a line Y2 passing through a median B2 out of lines parallel to a magnetic central axis M. The medians B1 and B2 are medians connecting the first and second magnetoresistive element bridges 40a and 40b to the third and fourth magnetoresistive element bridges 40c and 40d, respectively. Distance between the line Y1 passing through the median B1 and the line Y2 passing through the median B2 out of the lines parallel to the magnetic central axis M is set equal to distance between two edges 2aa and 2ab of teeth 2a of a rotor 2. With this configuration, the edges 2aa and 2ab can be detected with the line Y3 set as a detection reference axis.

Description

  The present invention relates to a rotation detection device that detects rotation information of a detected rotating body using a change in resistance value of a magnetoresistive element.

  2. Description of the Related Art Conventionally, for example, a device described in Patent Document 1 is known as a rotation detection device that detects rotation information of a rotation body to be detected using a resistance value change of a magnetoresistive element. This rotation detecting device is configured such that a sensor chip provided with a first magnetoresistive element bridge and a second magnetoresistive element bridge is arranged so as to face a rotor that is a detected rotating body. The first magnetoresistive element bridge is configured by connecting a first magnetoresistive element and a second magnetoresistive element in series. Similarly, the second magnetoresistive element bridge is configured by connecting a third magnetoresistive element and a fourth magnetoresistive element in series. In this rotation detection device, the midpoint potential of the first magnetoresistive element and the second magnetoresistive element is used as the output of the first magnetoresistive element bridge, and the fluctuation of the magnetic vector applied to the first magnetoresistive element bridge Perceived as a corner. Similarly, the midpoint potential of the third magnetoresistive element and the fourth magnetoresistive element is used as the output of the second magnetoresistive element bridge, and is detected as the deflection angle of the magnetic vector applied to the second magnetoresistive element bridge. .

  A bias magnet that generates a bias magnetic field in the first and second magnetoresistive element bridges is disposed in the vicinity of the sensor chip. Further, the rotor facing the sensor chip is provided with crests and troughs alternately in a gear shape on the outer periphery thereof. Here, when the gear-type rotor made of a magnetic material rotates, the angle of the magnetic vector changes in such a way that the bias magnetic field generated from the bias magnet is dragged to the peak as the rotor rotates. Swing in the direction. Then, such a change in the deflection angle of the magnetic vector is detected as a change in the output value of each magnetoresistive element constituting the first and second magnetoresistive element bridges, that is, a change in the resistance value. Position information with respect to the valley (rotor rotation information) is detected.

  In this rotation detection device, a calculation is performed on a differential deflection angle that is a difference between a deflection angle of a magnetic vector applied to the first magnetoresistive element bridge and a deflection angle of a magnetic vector applied to the second magnetoresistive element bridge. As a result, the rotation angle of the rotor is detected. In other words, the calculation is performed on the difference between the output of the first magnetoresistive element bridge and the output of the second magnetoresistive element bridge, that is, the differential output (signal) between the first magnetoresistive element bridge and the second magnetoresistive element bridge. As a result, the rotation angle of the rotor is detected. More specifically, the rotation angle of the rotor is detected based on the change of the logic level of the sensor output at the intersection of the differential output and a predetermined threshold voltage.

  Here, in such a detection method, a “mechanical-electrical angle difference” that is a difference in rotation angle obtained by an electrical sensing process with respect to a mechanical rotation angle that is an actual rotation angle of the rotor is usually used. Occurs. As this “mechanical-electrical angle difference”, for example, the following are known.

  First, there is a “mechanical-electrical angle difference” that occurs when the air gap (the distance between the magnetoresistive element and the rotor) fluctuates. For example, the smaller the air gap, the larger the deflection angle of the magnetic vector generated in the first and second magnetoresistive element bridges, and the larger the amplitude of the differential output. For this reason, the amplitude of the differential output is larger in the low gap than in the high gap. The position where the differential output crosses the threshold voltage also changes in accordance with the waveform change of the differential output itself, and this change appears as a variation in “mechanical-electrical angle difference”.

  In addition, there is a “mechanical-electrical angle difference” that occurs when the shape of the rotor to be detected, particularly the edge shape of the peak, fluctuates. In the rotation detecting device as described above, the deflection angle of the magnetic vector sensed by the first and second magnetoresistive element bridges changes so as to be dragged by the crest of the rotor, and particularly corresponds to the edge position of the crest. It changes in a way. For this reason, signal waveforms such as the deflection angle of the magnetic vector, the differential output (signal), and the sensor output are also greatly affected by the shape of the rotor, particularly the edge shape of the peak.

  There is also a “mechanical-electrical angle difference” that occurs when the environmental temperature varies. For example, the lower the temperature, the greater the change in resistance value sensed by the first and second magnetoresistive element bridges, and the larger the amplitude of the differential output. For this reason, the amplitude of the differential output is larger at a low temperature than at a high temperature. As in the case of the air gap, the position at which this differential output crosses the threshold voltage also changes according to the waveform change of the differential output itself, and this change is the “mechanical-electrical angle difference”. Appears as variation.

  Therefore, in the device described in Patent Document 1, even if the air gap fluctuates, the air gap characteristic minimum point, which is a point that generates an equivalent output for the same tooth angle, is taken into consideration. The output value at the gap characteristic minimum point is set as the threshold voltage. With this setting, this device generates an equivalent output for the same tooth angle regardless of the size of the air gap, and “mechanical-electrical when the air gap fluctuates. The target angle difference is less likely to occur.

JP 2006-1113015 A

  In the apparatus described in Patent Document 1, as described above, the rotation information of the rotor is detected based on switching of the logic level of the sensor output based on the threshold voltage. The threshold voltage is set to match the output value at the air gap characteristic minimum point in order to make it difficult for the “mechanical-electrical angle difference” due to the air gap variation to occur. Here, since the air gap characteristic minimum point varies depending on the shape of the teeth of the rotor and the arrangement of the magnetoresistive elements, the threshold voltage also varies with the variation of the air gap characteristic minimum point. Become. As a result, in this apparatus, the sensor output representing the rotation information (position information) of the rotor also varies.

  For this reason, in the apparatus described in Patent Document 1, the timing at which the sensor output indicating the detection of the teeth of the rotor is made varies depending on the shape of the teeth of the rotor and the arrangement of the magnetoresistive elements. More specifically, the timing at which the sensor output indicating that the rotor teeth (peaks) are located on the detection reference axis (hereinafter referred to as the detection reference axis) is the shape of the rotor teeth. And fluctuate depending on the arrangement of magnetoresistive elements. For this reason, this device basically indicates that the teeth (peaks) of the rotor are positioned at the timing when the portions (valleys) other than the teeth of the rotor are actually positioned on the detection reference axis. A “mechanical-electrical angle difference” occurs, for example, when a sensor output is made. That is, in this apparatus, the timing at which the rotor teeth (peaks) are located on the detection reference axis and the timing at which portions other than the rotor teeth (valleys) are located on the detection reference axis are accurately determined. It is impossible to detect the rotation information determined in the above.

  Furthermore, this apparatus cannot cope with the “mechanical-electrical angle difference” when the environmental temperature varies among the above-mentioned “mechanical-electrical angle difference”.

  In view of the above, the present invention provides a rotation detection device that detects rotation information of a rotating body to be detected using a resistance value change of a magnetoresistive element. It is an object of the present invention to provide a configuration capable of accurately detecting the timing at which the teeth of the rotor are located on the detection reference axis so that the “difference” does not easily occur.

  In order to achieve the above object, in the first aspect of the present invention, the sensor chip 4 includes at least three magnetoresistive element bridges 40a to 40d on one surface 4a thereof. Further, the magnetoresistive element bridges constituting one set are arranged at positions symmetrical with respect to the magnetoresistive element bridge constituting the other set, with the straight line Y3 as the axis of symmetry. Further, of the straight lines parallel to the magnetic central axis M of the bias magnet 3, the distance (β) between the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 is the both edges of the teeth 2a of the rotor 2. The configuration is equal to the distance (α) between 2aa and 2ab. Here, the straight line Y3 is a straight line connecting points at equal distances from the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic central axis M of the bias magnet 3. . The midpoint B1 is a midpoint of the line segment connecting the magnetoresistive element bridges constituting one set, and the midpoint B2 is a line segment connecting the magnetoresistive element bridges constituting the other set. Is the middle point.

  With such a configuration, both edges 2aa and 2ab of the teeth 2a of the rotor 2 can be detected using the straight line Y3 (magnetic central axis M) as a detection reference axis. More specifically, the one-side edge 2aa can be detected based on the maximum value of the first differential output V1, which is the difference between the outputs of the magnetoresistive element bridges constituting one set. Further, the other-side edge 2ab can be detected based on the maximum value of the second differential output V2, which is the difference between the outputs of the magnetoresistive element bridges constituting the other set.

  Here, the timing at which the first and second differential outputs V1 and V2 take the maximum value is almost constant even if the air gap and the environmental temperature fluctuate. For this reason, according to the rotation detection device 1 according to the present invention, a “mechanical-electrical angle difference” due to a difference in air gap or a difference in environmental temperature hardly occurs, and the teeth 2a of the rotor 2 are positioned on the detection reference axis. Timing can be accurately detected.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a top view which shows typically the outline of the planar structure of the rotation detection apparatus in 1st Embodiment of this invention including the relationship with the rotor which is a detection detection rotary body. It is the figure which expanded the part enclosed by the dashed-dotted line in FIG. It is a circuit diagram which shows the equivalent circuit inside the sensor chip of the rotation detection apparatus shown in FIG. (A)-(g) is a time chart which shows the position detection aspect of the edge of the one side of the rotor tooth | gear by the rotation detection apparatus shown in FIG. 1 in the form corresponding to rotation of a rotor. (A)-(g) is a time chart which shows the position detection mode of the edge of the other side on the opposite side to the one side of the rotor tooth | gear by the rotation detection apparatus shown in FIG. 1 in the form corresponding to rotation of a rotor. (A)-(d) is a time chart which shows the position detection mode of both the edges of the rotor tooth | gear by the rotation detection apparatus shown in FIG. 1 in the form corresponding to rotation of a rotor. FIG. 3 is a view corresponding to FIG. 2 when the positions of two of the four magnetoresistive element bridges of the rotation detecting device shown in FIG. 1 are changed. It is a figure which expands and shows the part corresponded to the part enclosed with the dashed-dotted line in FIG. 1 of the rotation detection apparatus in 1st Embodiment about the rotation detection apparatus in 2nd Embodiment of this invention. It is a figure which expands and shows the part corresponded to the part enclosed with the dashed-dotted line in FIG. 1 of the rotation detection apparatus in 1st Embodiment about the rotation detection apparatus in 3rd Embodiment of this invention. FIG. 10 is a diagram showing a portion corresponding to the portion shown in FIG. 9 when the position of one of the three magnetoresistive element bridges of the rotation detecting device shown in FIG. 9 is changed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A rotation detection device 1 according to a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the rotation detection device 1 according to this embodiment includes a bias magnet 3 that generates a bias magnetic field toward teeth 2a of a rotor 2 that includes a plurality of teeth 2a made of a magnetic material, and four magnetoresistive resistors. Sensor chip 4 provided with element bridges 40a, 40b, 40c, and 40d. As shown in FIG. 2, the magnetoresistive element bridge 40a (first magnetoresistive element bridge) is configured to include a first magnetoresistive element 40aa and a second magnetoresistive element 40ab. Similarly, the magnetoresistive element bridge 40b (second magnetoresistive element bridge) has a third magnetoresistive element 40ba and a fourth magnetoresistive element 40bb. Similarly, the magnetoresistive element bridge 40c (third magnetoresistive element bridge) includes a fifth magnetoresistive element 40ca and a sixth magnetoresistive element 40cb. Similarly, the magnetoresistive element bridge 40d (fourth magnetoresistive element bridge) has a seventh magnetoresistive element 40da and an eighth magnetoresistive element 40db.

  In the rotation detection device 1 according to the present embodiment, a change in the magnetic vector of the bias magnetic field accompanying the rotation of the rotor 2 is detected as a change in resistance value of each of the magnetoresistive elements 40aa to 40db, and the rotation mode of the rotor 2 is detected. The rotation detection device 1 according to the present embodiment is used as, for example, a sensor that detects a crank angle or a cam angle of an engine.

  As described above, the rotor 2 is configured to include a plurality of teeth 2a made of a magnetic material. In this embodiment, as an example, the entire rotor 2 is configured as a magnetic body, and as shown in FIG. 1, the rotor 2 is provided with crests 2 a and troughs 2 b alternately on the outer periphery thereof in a gear shape. It is configured.

  The bias magnet 3 is a magnet that generates a bias magnetic field toward the teeth 2 a of the rotor 2. The bias magnet 3 is molded into a hollow cylinder having a through hole in the longitudinal direction. In this embodiment, a mold resin 4b that seals a sensor chip 4 to be described later is inserted into the through hole and fixed with an adhesive or the like at a predetermined position.

  The sensor chip 4 is disposed so as to face the rotor 2 that is a detected rotating body. The sensor chip 4 is sealed with a mold resin 4b together with its processing circuit. Specifically, the sensor chip 4 is mounted on one end of a lead frame (not shown) inside the mold resin 4b, and terminals T1 to T3 such as a power supply terminal T1, an output terminal T2, and a GND terminal T3 are respectively connected to the outside from the other end. The structure is drawn out.

  The sensor chip 4 is configured such that the first to fourth magnetoresistive element bridges 40a to 40d described above are provided on one surface 4a thereof. As shown in FIG. 2, the first to fourth magnetoresistive element bridges 40 a to 40 d are sequentially arranged so as to be separated from each other in the direction of a straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3. Yes.

  Here, two sets of the first to fourth magnetoresistive element bridges 40a to 40d are used as a set to form two sets of magnetoresistive element bridges. In the present embodiment, one set (hereinafter referred to as a first set) is referred to as first and second magnetoresistive element bridges 40a and 40b, and the other set (hereinafter referred to as a second set) is referred to as third and fourth magnetoresistive element bridges. 40c and 40d. Further, the midpoint of the line segment connecting the first and second magnetoresistive element bridges 40a and 40b constituting the first set is defined as a midpoint B1, and the third and fourth magnetoresistive element bridges 40c constituting the second set are provided. The midpoint of the line segment connecting 40d is defined as a midpoint B2 (see FIG. 2). At this time, in this embodiment, a straight line Y3 connecting points that are at an equal distance from a straight line Y1 passing through the middle point B1 and a straight line Y2 passing through the middle point B2 among straight lines parallel to the magnetic central axis M is the bias magnet 3. It is set as the structure located on the magnetic center axis | shaft M of this. Further, in the present embodiment, the first to fourth magnetoresistive element bridges 40a to 40d are at equal distances from the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic center axis M. They are arranged so as to be line symmetric with respect to a straight line Y3 connecting certain points. More specifically, the first and second magnetoresistive element bridges 40a and 40b constituting the first set are connected to the third and fourth magnetoresistive element bridges 40c and 40d constituting the second set with the straight line Y3 as the axis of symmetry. They are arranged at symmetrical positions. In the present embodiment, in particular, the first to fourth magnetoresistive element bridges 40 a to 40 d are arranged on a straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3.

  In this embodiment, the distance (β) between the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic center axis M of the bias magnet 3 is The configuration is equal to the distance (α) between both edges 2aa and 2ab of the tooth 2a.

  The first magnetoresistive element bridge 40a is configured by connecting a first magnetoresistive element 40aa and a second magnetoresistive element 40ab in series. The second magnetoresistive element bridge 40b is configured by connecting a third magnetoresistive element 40ba and a fourth magnetoresistive element 40bb in series. The third magnetoresistive element bridge 40c is configured by connecting a fifth magnetoresistive element 40ca and a sixth magnetoresistive element 40cb in series. The fourth magnetoresistance element bridge 40d is configured by connecting a seventh magnetoresistance element 40da and an eighth magnetoresistance element 40db in series. The first to fourth magnetoresistive element bridges 40a to 40d are arranged on the one surface 4a of the sensor chip 4 so as to face the rotor 2 that is a detected rotating body.

  The first and second magnetoresistive elements 40aa and 40ab constituting the first magnetoresistive element bridge 40a are arranged so as to have a “C” shape. More specifically, the first magnetoresistive element 40aa is arranged to make an angle of 45 ° clockwise with respect to the center line of the letter C, and the second magnetoresistive element 40ab is counterclockwise. It arrange | positions so that the angle of 45 degrees may be made. Similarly, the 3rd-8th magnetoresistive elements 40ba-40db which comprise the 2nd-4th magnetoresistive element bridges 40b-40d are also arrange | positioned so that it may become a "C" shape mutually, respectively.

  In the rotation detection device 1 according to the present embodiment, when the rotor 2 having a plurality of teeth 2a made of a magnetic material rotates, the teeth (peaks) 2a and the portions (valleys) 2b other than the teeth are in the vicinity of the sensor chip 4. , And approaches the bias magnet 3. The angle of the magnetic vector of the bias magnetic field generated by the bias magnet 3 changes so as to be dragged to the peak 2 a as the rotor 2 rotates. Thus, as the rotor 2 rotates and the portion of the rotor 2 passing through the vicinity of the sensor chip 4 transitions from the peak 2a to the valley 2b and from the valley 2b to the peak 2a, the magnetic The deflection angle of the vector changes. In the present embodiment, such a change in the magnetic vector is detected as a change in the resistance value of each of the magnetoresistive elements 40aa to 40db constituting the first to fourth magnetoresistive element bridges 40a to 40d. And the position information (rotation information of the rotor 2) between the valley portion 2b and the valley portion 2b are detected.

  Next, the electrical configuration of the sensor chip 4 will be described with reference to the equivalent circuit shown in FIG. As shown in FIG. 3, the first to fourth magnetoresistive element bridges 40a to 40d are each configured as a half bridge in which two magnetoresistive elements 40aa to 40db are connected in series.

  In the present embodiment, the midpoint potential Va of the first magnetoresistive element 40aa and the second magnetoresistive element 40ab is the output of the first magnetoresistive element bridge 40a. Further, the midpoint potential Vb of the third magnetoresistive element 40ba and the fourth magnetoresistive element 40bb is output from the second magnetoresistive element bridge 40b.

  The outputs of the first and second magnetoresistive element bridges 40a and 40b constituting the first set are respectively input to the first differential amplifier 41, and the first difference is a differential output between the midpoint potential Va and the midpoint potential Vb. The dynamic output V1 (signal A1) is further input to the first comparator 42. Here, the first comparator 42 is a part that performs binarization processing for outputting the first differential output V1 as a binarized signal (pulse signal) based on a predetermined first threshold voltage Vth1. In the present embodiment, the first differential output V1 is compared with the first threshold voltage Vth1 by the first comparator 42, and a binary output (signal B1) of the first differential output V1 is obtained.

  In the present embodiment, as shown in FIG. 3, as a processing circuit for the first differential output V1, one side edge for detecting one side edge (reference numeral 2aa in FIG. 2) of each tooth 2a of the rotor 2 is further provided. A detection circuit is provided. The one-side edge detection circuit is configured as a circuit that detects the maximum value of the first differential output V1, and includes a differentiation circuit, a counter circuit, and the like. Here, as an example, the one-side edge detection circuit has a differentiating circuit 43. The differentiation circuit 43 is a well-known circuit configured to include, for example, a capacitor 43a and a branch resistor 43b.

  In the present embodiment, a differential output (signal C1) of the first differential output V1 is obtained from the differentiating circuit 43. The differential output of the first differential output V1 is further input to the second comparator 44. The second comparator 44 is a part that performs binarization processing of the differential output of the first differential output V1 based on the second threshold voltage Vth2 set at the zero cross point of the differential output of the first differential output V1. is there. In the second comparator 44 in the present embodiment, the settings of the inverting input terminal and the non-inverting input terminal of the first comparator 42 are opposite to each other. In the present embodiment, the binarized output (signal B1) output from the first comparator 42 and the binarized output (signal D1) output from the second comparator 44 are the logic of these two signals. A logical product (AND) circuit 45 that takes a product is input to obtain a logical product output (signal E1).

  The configuration of the processing circuit related to the first and second magnetoresistive element bridges 40a and 40b constituting the first set has been described above, but the process related to the third and fourth magnetoresistive element bridges 40c and 40d constituting the second set. The same applies to the circuit configuration.

  That is, the midpoint potential Vc of the fifth magnetoresistive element 40ca and the sixth magnetoresistive element 40cb is the output of the third magnetoresistive element bridge 40c, and the midpoint potential of the seventh magnetoresistive element 40da and the eighth magnetoresistive element 40db. Vd is the output of the fourth magnetoresistive element bridge 40d.

  The outputs of the third and fourth magnetoresistive element bridges 40c and 40d constituting the second set are respectively input to the second differential amplifier 46, and a second difference which is a differential output between the midpoint potential Vc and the midpoint potential Vd. The dynamic output V2 (signal A2) is further input to the third comparator 47. Here, the third comparator 47 is a part that performs binarization processing for outputting the second differential output V2 as a binarized signal (pulse signal) based on a predetermined third threshold voltage Vth3. In the present embodiment, the third comparator 47 compares the second differential output V2 with the third threshold voltage Vth3 to obtain a binarized output (signal B2) of the second differential output V2. In the present embodiment, the third threshold voltage Vth3 is set to the same value as the first threshold voltage Vth1.

  In the present embodiment, as shown in FIG. 3, the processing circuit for the second differential output V2 further detects the other edge (reference numeral 2ab in FIG. 2) on the opposite side to one of the teeth 2a of the rotor 2. The other side edge detection circuit is provided. This other side edge detection circuit is configured as a circuit that detects the maximum value of the output of the second differential output V2, and has a differentiating circuit, a counter circuit, etc., as in the case of the above one side edge detection circuit. It is said. Here, as an example, the other edge detection circuit has a differentiating circuit 43.

  In the present embodiment, a differential output (signal C2) of the second differential output V2 is obtained from the differentiating circuit 43. The differential output of the second differential output V2 is further input to the fourth comparator 48. The fourth comparator 48 is a part that performs binarization processing of the differential output of the second differential output V2 based on the fourth threshold voltage Vth4 set at the zero cross point of the differential output of the second differential output V2. is there. In this embodiment, the binarized output (signal B2) output from the third comparator 47 and the binarized output (signal D2) output from the fourth comparator 48 are the logic of these two signals. A logical product (AND) circuit 49 that takes a product is input to obtain a logical product output (signal E2). It should be noted that the fourth comparator 48 in the present embodiment has the inverting input terminal and the non-inverting input terminal set opposite to the third comparator 47. In the present embodiment, the fourth threshold voltage Vth4 is set to the same value as the second threshold voltage Vth2.

  In the present embodiment, two logical product outputs (signals E1 and E2) are obtained by the above processing. As will be described in detail later, the edge 2aa on one side of the tooth 2a of the rotor 2 is detected based on the signal E1 that is the logical product output obtained by the one-side edge detection circuit. Further, the other edge 2ab of the tooth 2a of the rotor 2 is detected based on the signal E2 which is a logical product output obtained by the other edge detection circuit.

  4 to 6 are diagrams showing a rotation detection mode of the rotor 2 in the rotation detection device 1 including such a processing circuit as a time chart accompanying the rotation of the rotor 2. Among these, FIG. 4A, FIG. 5A, and FIG. 6A show the shape of the rotor 2 linearly for convenience, and FIG. 4B to FIG. 5G and FIG. 6 (g) and FIGS. 6 (b) to 6 (d) show transitions of signals processed in the processing circuit shown in FIG. 3 as the rotor 2 rotates.

  First, the processing circuit of the first differential output V1 will be described with reference to FIG. FIG. 4 (b) shows changes in the outputs (midpoint potentials Va and Vb) of the first and second magnetoresistive element bridges 40a and 40b. FIG. 4 (c) The change of the 1st differential output V1 (signal A1) which is a differential output of electric potential Va and Vb is shown.

  As shown in FIG. 4C, the change in the first differential output V1 changes with a pseudo sine wave shape in the form indicated by the solid line in FIG. In the present embodiment, the first differential output V1 output in this way is compared with a predetermined threshold voltage Vth1 indicated by a one-dot chain line in FIG. A binarization process is performed at.

  As a result, in the form shown in FIG. 4D, a pulse-like binarized output whose logic level is inverted at the point a and the point b where the first differential output V1 and the first threshold voltage Vth1 intersect. (Signal B1) is obtained. Here, the first threshold voltage Vth1 is set to a value such that the first differential output V1 takes the maximum value in the range of the rotation angle of the rotor 2 that is at the logic H (high) level based on this threshold voltage. ing.

  On the other hand, FIG. 4E shows the transition of the differential output (signal C1) obtained by differentiating the first differential output V1 (signal A1) by the differentiation circuit 43. This differential output (signal C1) changes in a so-called zero-crossing manner at the timing (t5 in the figure) at which the first differential output V1 reaches the maximum value, as indicated by a solid line in the figure. The differential output (signal C1) output in this way is based on a comparison with the second threshold voltage Vth2 indicated by a one-dot chain line in the figure corresponding to the zero cross point (symbol e in the figure). The second comparator 44 performs binarization processing.

  As a result of the binarization processing, as shown in FIG. 4F, the binarized output of the signal C1 (signal D1) is logically at the point e where the signal C1 and the threshold voltage Vth2 intersect. Is binarized (pulsed) based on the threshold voltage Vth2. Further, as described above, the inverting input terminal and the non-inverting input terminal of the second comparator 44 are set opposite to those of the first comparator 42. Therefore, as shown in FIG. 4 (f), the signal D1 becomes the logic L (low) level during the period when the signal C1 exceeds the second threshold voltage Vth2, and conversely, the signal C1 has the second threshold voltage Vth2. During a period that is not satisfied, the logic H (high) level is set.

  At this time, the rising edge of the pulse whose logic level is reversed at the point e indicates the position of the edge 2aa on one side of the tooth 2a of the rotor 2. This will be described below. At the point e, that is, the timing at which the first differential output V1 (signal A1) takes the maximum value (t5 in FIG. 4), the rotor 2 and the first and second magnetoresistive element bridges 40a and 40b are shown in FIG. The positional relationship is as shown in a). That is, at the timing of the point e (t5), the edge 2aa on one side of the tooth 2a of the rotor 2 is a straight line passing through the midpoint B1 and the straight line passing through the midpoint B1 among the straight lines parallel to the magnetic center axis M. It is located on a straight line Y3 connecting points at equal distances from Y2. In the present embodiment, with the straight line Y3 as a detection reference axis, the rising edge of the signal D1 is synchronized with the position of the edge 2aa on one side of the teeth 2a of the rotor 2. In the present embodiment, the detection reference axis Y3 is the same as the magnetic central axis M.

  Thereafter, a logical product of the signal D1 binarized in this way and the signal B1 binarized through the first comparator 42 is taken through a logical product (AND) circuit 45. As a result, as shown in FIG. 4G, the logical product output in which the rising edge is synchronized with the position of the edge 2aa on one side of the tooth 2a of the rotor 2 as in the case of the pulse whose logic level is inverted at the point e. (Signal E1) is obtained. The logical product output (signal E1) is input to the both-edge detection unit 100 described later.

  Next, a processing circuit for the second differential output V2 will be described with reference to FIG. As described above, the processing circuit of the second differential output V2 performs the same processing as that of the processing circuit of the first differential output V1, and therefore the same output is applied to the processing circuit of the second differential output V2. Is obtained. Accordingly, the processing circuit for the second differential output V2 basically has a time chart having the same waveform as that for the first differential output V1. As shown in FIG. 5, the processing circuit of the second differential output V2 has the same waveform as the case of the first differential output V1, but is a fixed time with respect to the time chart in the processing circuit of the first differential output V1. The time chart is only out of phase.

  As in the case of the signals C1 and D1 in the processing circuit of the first differential output V1, the processing circuit of the second differential output V2 also performs the binarization processing of the third comparator 47 in FIG. A differential output (signal C2) as shown is obtained. The differential output (signal C2) is binarized by the fourth comparator 48 based on the comparison with the fourth threshold voltage Vth4 corresponding to the zero-cross point f indicated by the alternate long and short dash line in FIG. Is made.

  As a result of the binarization processing, as shown in FIG. 5F, the binarized output of the signal C2 (signal D2) has a logical level at the point f where the signal C2 and the threshold voltage Vth4 intersect. Is binarized (pulsed) based on the threshold voltage Vth4.

  At this time, the rising edge of the pulse whose logic level is reversed at the point f indicates the position of the edge 2ab on the other side of the tooth 2a of the rotor 2. This will be described below. At the point f, that is, the timing at which the second differential output V2 (signal A2) takes the maximum value (t6 in FIG. 5), the teeth 2a of the rotor 2 and the third and fourth magnetoresistive element bridges 40c and 40d are illustrated. The positional relationship is as shown in FIG. That is, at the timing of the point f (t6), the other edge 2ab of the tooth 2a of the rotor 2 is positioned on the detection reference axis Y3. For this reason, the rising edge of the signal D2 is synchronized with the position of the edge 2ab on the other side of the tooth 2a of the rotor 2.

  Thereafter, a logical product of the signal D2 binarized in this way and the signal B2 binarized through the third comparator 47 is taken through a logical product (AND) circuit 49. As a result, as shown in FIG. 5G, the logical product output whose rising edge is synchronized with the position of the edge 2ab on the other side of the tooth 2a of the rotor 2 is the same as the pulse whose logic level is inverted at the point f. (Signal E2) is obtained. The logical product output (signal E2) is input to the both-edge detection unit 100 described later, as is the logical product output (signal E1).

  The two logical product outputs (signals E1 and E2) output by the above processing are respectively input to both edge detection units 100 as described above. The both edge detection units 100 are circuits for detecting one edge 2aa and the other edge 2ab of the teeth 2a of the rotor 2 based on the signals E1 and E2. For example, in the present embodiment, both edge detection units 100 are configured to output a signal F whose logic level is switched by the rising edges of the signals E1 and E2 (see FIG. 6D). Therefore, in this embodiment, the signal F whose logic level is switched by the rising of each of the signals E1 and E2 is obtained through the both edge detection unit 100.

  In the present embodiment, the sensor output (signal F) as the rotation detection device 1 finally obtained in this way has a logic level in synchronism with each of the two edges 2aa and 2ab of the teeth 2a of the rotor 2. In other words, it becomes a pulse signal indicating both-edge passing information.

  The configuration of the rotation detection device 1 according to the present embodiment has been described above. Next, the operation and effect of the rotation detection device 1 according to the present embodiment will be described.

  As described above, in the rotation detection device 1 according to the present embodiment, the sensor chip 4 includes the first to fourth magnetoresistive element bridges 40a to 40d on the one surface 4a. The first to fourth magnetoresistive element bridges 40a to 40d are sequentially arranged so as to be separated from each other in the direction of the straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3. In the present embodiment, the first and second magnetoresistive element bridges 40a and 40b constituting the first set are further connected to the third and fourth magnetoresistive element bridges 40c and 40d constituting the second set with the straight line Y3 as the axis of symmetry. They are arranged at symmetrical positions. In the present embodiment, in particular, the first to fourth magnetoresistive element bridges 40 a to 40 d are arranged on a straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3. In the present embodiment, the distance (β) between the straight line (Y1) passing through the middle point B1 and the straight line (Y2) passing through the middle point B2 among the straight lines parallel to the magnetic central axis M of the bias magnet 3 is set. The distance between the two edges 2aa and 2ab of the tooth 2a of the rotor 2 is equal to (α). Here, the straight line Y3 is a straight line connecting points at equal distances from the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic central axis M of the bias magnet 3. . The midpoint B1 is the midpoint of the line segment connecting the first and second magnetoresistive element bridges 40a and 40b constituting the first set, and the midpoint B2 is the third, 4 is the midpoint of the line segment connecting the magnetoresistive element bridges 40c and 40d.

  With this configuration, in the present embodiment, both edges 2aa and 2ab of the teeth 2a of the rotor 2 can be detected using the straight line Y3 (magnetic center axis M) as a detection reference axis. More specifically, the edge 2aa on one side is detected based on the maximum value of the first differential output V1, which is the difference between the outputs of the first and second magnetoresistive element bridges 40a and 40b constituting the first set. Can do. Further, the other edge 2ab can be detected based on the maximum value of the second differential output V2, which is the difference between the outputs of the third and fourth magnetoresistive element bridges 40c and 40d constituting the second set.

  Here, the timings at which the first and second differential outputs V1 and V2 take the maximum value (t5 and t6 in FIG. 6) are almost constant even if the air gap and the environmental temperature fluctuate. For this reason, according to the rotation detection device 1 according to the present embodiment, a “mechanical-electrical angle difference” due to a difference in air gap or a difference in environmental temperature hardly occurs, and the teeth 2a of the rotor 2 are formed on the detection reference axis. The position timing can be accurately detected.

  In the present embodiment, since all of the first to fourth magnetoresistive element bridges 40a to 40d are arranged on the straight line X as described above, the detection reference axis is the straight line Y3 (magnetic central axis M). It is supposed to match. When at least one of the first to fourth magnetoresistive element bridges 40a to 40d is arranged at a position other than the straight line X, the detection reference axis does not coincide with the straight line Y3. That is, in this case, the positions of the two edges 2aa and 2ab of the teeth 2a of the rotor 2 at the timing when the differential outputs V1 and V2 take the maximum value are deviated from the straight line Y. However, even in this case, the magnetoresistive element bridges 40a and 40b constituting the first set are arranged at positions symmetrical with respect to the magnetoresistive element bridges 40c and 40d constituting the second set with the straight line Y3 as the axis of symmetry. As long as it is done, both edges 2aa and 2ab can be detected.

  That is, for example, as shown in FIG. 7, even when the second and third magnetoresistive element bridges 40b and 40c are arranged in the direction of the magnetic central axis M, an axis different from the straight line Y3 is used as a detection reference axis. Both edges 2aa and 2ab of the teeth 2a of the rotor 2 can be detected. Also in this case, since the first to fourth magnetoresistive element bridges 40a to 40d are arranged at symmetrical positions as described above, the waveform of the first differential output V1 and the waveform of the second differential output V2 are not shifted. As in the case of (5), they are identical to each other and have the same phase difference. Therefore, even in this case, the time from the timing when the first differential output V1 takes the maximum value to the timing when the second differential output V2 takes the maximum value is the same as before shifting. For this reason, even when the second and third magnetoresistive element bridges 40b and 40c are shifted as described above, the detection reference axis does not coincide with the straight line Y3, but both edges 2aa and 2ab are detected with reference to another detection reference axis. Is that you can.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the arrangement of the first to fourth magnetoresistive element bridges 40a to 40d is changed with respect to the first embodiment. In the present embodiment, the first and third magnetoresistive element bridges 40a and 40c are a first set, and the second and fourth magnetoresistive element bridges 40b and 40d are a second set. In this embodiment, the difference between the outputs of the first and third magnetoresistive element bridges 40a and 40c constituting the first set is defined as the first differential output V1, and the second and fourth magnetoresistive elements constituting the second set. The difference between the outputs of the bridges 40b and 40d is the second differential output V2. Since other aspects are the same as those in the first embodiment, description thereof is omitted here.

  In the present embodiment, the midpoint of the line segment connecting the first and third magnetoresistive element bridges 40a and 40c constituting the first set is defined as a middle point B1, and the second and fourth magnetoresistive elements constituting the second set. The midpoint of the line segment connecting the bridges 40b and 40d is defined as a midpoint B2 (see FIG. 8). In the present embodiment, when the midpoints B1 and B2 are taken in this way, the straight line passing through the midpoint B1 and the straight line passing through the midpoint B2 among the straight lines parallel to the magnetic central axis M, as in the first embodiment. A straight line Y3 connecting points at equal distances from Y2 is configured to be located on the magnetic central axis M. In addition, the first to fourth magnetoresistive element bridges 40a to 40d connect points at equal distances from a straight line Y1 passing through the middle point B1 and a straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic central axis M. The straight line Y3 is arranged to be line symmetric with respect to the axis of symmetry. More specifically, unlike the first embodiment, the first and third magnetoresistive element bridges 40a and 40c constituting the first set include the second and fourth pieces constituting the second set with the straight line Y3 as the axis of symmetry. The magnetoresistive element bridges 40b and 40d are arranged at symmetrical positions. Similarly to the first embodiment, the first to fourth magnetoresistive element bridges 40 a to 40 d are arranged on a straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3. Similarly to the first embodiment, the distance (β) between the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic center axis M of the bias magnet 3 is the rotor. The distance between the two edges 2aa and 2ab of the second tooth 2a is equal to (α).

  By adopting such a configuration, also in the present embodiment, at the timing when the first differential output V1 that is the output of the magnetoresistive element bridge constituting the first set takes the maximum value, the teeth 2a of the rotor 2 are used. Is located on a straight line Y3. Further, at the timing when the second differential output V2 that is the output of the magnetoresistive element bridge constituting the second set takes the maximum value, the other edge 2ab is positioned on the straight line Y3.

  Therefore, also in the present embodiment, both edges 2aa and 2ab of the teeth 2a of the rotor 2 can be detected using the straight line Y3 (magnetic central axis M) as a detection reference axis. More specifically, the edge 2aa on one side is detected based on the maximum value of the first differential output V1, which is the difference between the outputs of the first and third magnetoresistive element bridges 40a and 40c constituting the first set. Can do. Further, the other edge 2ab can be detected based on the maximum value of the second differential output V2, which is the difference between the outputs of the second and fourth magnetoresistive element bridges 40b and 40d constituting the second set.

  Then, according to the rotation detection device 1 according to the present embodiment, as in the first embodiment, a “mechanical-electrical angle difference” due to a difference in air gap or a difference in environmental temperature is unlikely to occur on the detection reference axis. The timing at which the teeth 2a of the rotor 2 are located can be accurately detected.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the fourth magnetoresistive element bridge 40d is deleted and the arrangement of the first to third magnetoresistive element bridges 40a to 40c is changed with respect to the first embodiment. In the present embodiment, the first and second magnetoresistive element bridges 40a and 40b are a first set, and the second and third magnetoresistive element bridges 40b and 40c are a second set. Thus, in this embodiment, it is supposed that the common magnetoresistive element bridge 40b is taken by the 1st group and the 2nd group. In this embodiment, the difference between the outputs of the first and second magnetoresistive element bridges 40a and 40b constituting the first set is defined as the first differential output V1, and the second and third magnetoresistive elements constituting the second set. The difference between the outputs of the bridges 40b and 40c is the second differential output V2. Since other aspects are the same as those in the first embodiment, description thereof is omitted here.

  In the present embodiment, the midpoint of the line segment connecting the first and second magnetoresistive element bridges 40a and 40b constituting the first set is defined as a midpoint B1, and the second and third magnetoresistive elements constituting the second set. The midpoint of the line segment connecting the bridges 40b and 40c is defined as a midpoint B2 (see FIG. 9). In the present embodiment, when the midpoints B1 and B2 are taken in this way, the straight line passing through the midpoint B1 and the straight line passing through the midpoint B2 among the straight lines parallel to the magnetic central axis M, as in the first embodiment. A straight line Y3 connecting points at equal distances from Y2 is configured to be located on the magnetic central axis M. In addition, the first to third magnetoresistive element bridges 40a to 40c connect points that are at an equal distance from the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic central axis M. The straight line Y3 is arranged to be line symmetric with respect to the axis of symmetry. More specifically, unlike the first embodiment, the first and second magnetoresistive element bridges 40a and 40b constituting the first set have the second and third pieces constituting the second set with the straight line Y3 as the axis of symmetry. The magnetoresistive element bridges 40b and 40c are arranged at symmetrical positions. Similarly to the first embodiment, the first to third magnetoresistive element bridges 40 a to 40 c are arranged on a straight line X parallel to the radial direction with respect to the magnetic central axis M of the bias magnet 3. Similarly to the first embodiment, the distance (β) between the straight line Y1 passing through the middle point B1 and the straight line Y2 passing through the middle point B2 among the straight lines parallel to the magnetic center axis M of the bias magnet 3 is the rotor. The distance between the two edges 2aa and 2ab of the second tooth 2a is equal to (α).

  By adopting such a configuration, also in the present embodiment, at the timing when the first differential output V1 that is the output of the magnetoresistive element bridge constituting the first set takes the maximum value, the teeth 2a of the rotor 2 are used. Is located on a straight line Y3. Further, at the timing when the second differential output V2 that is the output of the magnetoresistive element bridge constituting the second set takes the maximum value, the other edge 2ab is positioned on the straight line Y3.

  Therefore, also in the present embodiment, both edges 2aa and 2ab of the teeth 2a of the rotor 2 can be detected using the straight line Y3 (magnetic central axis M) as a detection reference axis. More specifically, the edge 2aa on one side is detected based on the maximum value of the first differential output V1, which is the difference between the outputs of the first and second magnetoresistive element bridges 40a and 40b constituting the first set. Can do. Further, the other edge 2ab can be detected based on the maximum value of the second differential output V2, which is the difference between the outputs of the second and third magnetoresistive element bridges 40b and 40c constituting the second set.

  And according to the rotation detection apparatus 1 which concerns on this embodiment, the effect similar to 1st Embodiment is acquired only by providing three magnetoresistive element bridges 40a-40c fewer than the case of 1st Embodiment. . That is, only by providing the three magnetoresistive element bridges 40a to 40c, a "mechanical-electrical angle difference" due to a difference in air gap or a difference in environmental temperature hardly occurs, and the teeth 2a of the rotor 2 on the detection reference axis. It is possible to accurately detect the timing at which is located.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  As is clear from the description in the first embodiment, in the rotation detection device 1 according to the present invention, all of the first to fourth magnetoresistive element bridges 40a to 40d are arranged on the straight line X. It is not a mandatory requirement. Therefore, in the second and third embodiments, a part of the first to fourth magnetoresistive element bridges 40a to 40d may be arranged at a position other than the straight line X. For example, in the third embodiment, the first to third magnetoresistive element bridges 40a to 40c may be arranged as shown in FIG. Even in this case, although the detection reference axis does not coincide with the straight line Y3, both edges 2aa and 2ab can be detected using another detection reference axis as a reference.

  In the present invention, it is only necessary to detect the passage of the teeth 2a of the rotor 2 that is rotated in conjunction with the rotation of the rotor 2 by the magnetic sensor 4. For this reason, the rotor 2 only needs to have a structure in which the outer peripheral surface has a different magnetic resistance in which a portion of the tooth 2a made of a magnetic material and a portion located between the teeth 2a are alternately repeated. That is, as the rotor 2, not only the outer peripheral portion is made of irregularities but the outer peripheral surface is made up of a convex portion that becomes a magnetic body and a space that becomes a non-magnetic body, and the outer peripheral surface is a portion that becomes a magnetic body. The rotor etc. which were comprised with the insulator used as a nonmagnetic material are also included.

2 rotor 2a tooth 2aa one edge 2ab other edge 3 bias magnet 4 sensor chip 40a first magnetoresistive element bridge 40b second magnetoresistive element bridge 40c third magnetoresistive element bridge 40d fourth magnetoresistive element bridge

Claims (4)

A bias magnet (3) for generating a bias magnetic field toward the teeth of the rotor (2) having a plurality of teeth (2a) made of a magnetic material;
And having at least three magnetoresistive elements (40a, 40b, 40c, 40d) whose output values change according to the magnetic vector of the bias magnetic field directed to the teeth of the rotor. And a sensor chip (4).
In the rotation detection device for detecting the rotation mode of the rotor by sensing the change in the magnetic vector of the bias magnetic field accompanying the rotation of the rotor as the resistance value change of the magnetoresistive element,
The three or more magnetoresistive elements are sequentially arranged so as to be separated from each other in the direction of a straight line parallel to the radial direction with respect to the magnetic central axis (X) of the bias magnet,
When two sets of two magnetoresistive elements are taken out of the three or more magnetoresistive elements,
Of the straight lines parallel to the magnetic central axis of the bias magnet, the first straight line (Y1) passing through the midpoint (B1) of the line segment connecting the two magnetoresistive elements of one of the two sets. And a second straight line (Y2) passing through the middle point (B2) of the line segment connecting the two magnetoresistive elements of the other set of the two sets, and a third point connecting points that are at equal distances A straight line (Y3) is configured to be located on the magnetic central axis of the bias magnet,
The two magnetoresistive elements of one set of the two sets are symmetrical with respect to the two magnetoresistive elements of the other set of the two sets, with the third straight line as the axis of symmetry. It is assumed that the configuration is arranged in
Of the straight lines parallel to the magnetic central axis of the bias magnet, the distance between the first straight line and the second straight line is equal to the distance between both edges (2aa, 2ab) of the teeth of the rotor. And
A difference in output between the two magnetoresistive elements in one of the two sets is defined as a first differential output (Vb−Va), and the two magnetoresistive elements in the other of the two sets. The difference in output between the second differential output (Vd-Vc),
One edge (2aa) of the rotor teeth is detected based on the maximum value of the first differential output, and one of the rotor teeth is detected based on the maximum value of the second differential output. And a rotation detecting device for detecting the other edge (2ab) on the opposite side. The three or more magnetoresistive elements are four elements including a first magnetoresistive element (40a), a second magnetoresistive element (40b), a third magnetoresistive element (40c), and a fourth magnetoresistive element (40d). The first magnetoresistive element, the second magnetoresistive element, the third magnetoresistive element, the first magnetoresistive element in a linear direction parallel to the radial direction with respect to the magnetic central axis of the bias magnet. 4 magnetoresistive elements are arranged in this order,
The first magnetoresistive element and the second magnetoresistive element are set as one of the two sets, and the third magnetoresistive element and the fourth magnetoresistive element are set as the other of the two sets. The rotation detection device according to 1. The three or more magnetoresistive elements are four elements including a first magnetoresistive element (40a), a second magnetoresistive element (40b), a third magnetoresistive element (40c), and a fourth magnetoresistive element (40d). The first magnetoresistive element, the second magnetoresistive element, the third magnetoresistive element, the first magnetoresistive element in a linear direction parallel to the radial direction with respect to the magnetic central axis of the bias magnet. 4 magnetoresistive elements are arranged in this order,
The first magnetoresistive element and the third magnetoresistive element are set as one of the two sets, and the second magnetoresistive element and the fourth magnetoresistive element are set as the other of the two sets. The rotation detection device according to 1. The three or more magnetoresistive elements include three magnetoresistive elements including a first magnetoresistive element (40a), a second magnetoresistive element (40b), and a third magnetoresistive element (40c), The first magnetoresistive element, the second magnetoresistive element, and the third magnetoresistive element are arranged in this order in a linear direction parallel to the radial direction with respect to the magnetic central axis of the bias magnet,
The first magnetoresistive element and the second magnetoresistive element are one of the two sets, and the second magnetoresistive element and the third magnetoresistive element are the other of the two sets. The rotation detection device according to 1.

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