JP2009109516A - Rotation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation detector optimized to the detection characteristics of rotation information according to the shape of a rotor to be detected, and to provide a designing method of the rotation detector useful for optimizing the detection characteristics. <P>SOLUTION: The rotation detector includes: a sensor chip 3d having at least four magnetoresistive element bridges A-D; and a bias magnet 2 for giving a bias magnetic field to the magnetoresistive element bridges A-D. Especially, rotation detection characteristics demanded according to the shape of a rotor are optimized by changing the amplification factor of main component output based on the differential output of middle-point potentials V3, V4 between the magnetoresistive element bridges positioned inside the magnetoresistive element bridges A-D and correction component output based on the differential output of middle-point potentials V1, V2 between the magnetoresistive element bridges positioned outside. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotation detection device that detects rotation information of a rotor made of a magnetic material by using a magnetoresistive element (MRE) whose resistance value changes in accordance with a magnetic field change.

  As is well known, for example, a rotation detection device using a magnetoresistive element (MRE) to detect rotation information of a gear-shaped rotor provided on a crankshaft, a camshaft or the like of a vehicle-mounted internal combustion engine as a detection target. Is used. This type of rotation detection device has a bias magnet that generates a bias magnetic field toward the rotor, and a sensor chip that includes a magnetoresistive element whose resistance value changes in accordance with a change in the magnetic vector of the bias magnetic field. The change in the resistance value of the magnetoresistive element is electrically processed to detect the rotation mode of the rotor. That is, in the bias magnetic field generated toward the detection target, the deflection angle of the magnetic vector changes corresponding to the crest and trough of the rotor as the rotor rotates. In accordance with the change in the deflection angle of the magnetic vector, the resistance value of the magnetoresistive element also changes periodically in a manner corresponding to the peaks and valleys of the rotor.

  In general, the deflection angle of the magnetic vector varies depending on the air gap, that is, the distance between the sensor chip and the rotor with respect to the same rotation angle of the rotor. On the other hand, even when the air gap fluctuates, there is a point at which the deflection angle of the magnetic vector becomes equal to the same rotor rotation angle, that is, a so-called air gap characteristic minimum point. Therefore, if the electric signal corresponding to the change in the resistance value of the magnetoresistive element is binarized using the minimum value of the air gap characteristic as a threshold value, the rotation angle of the rotor can be detected with high accuracy regardless of the size of the air gap. be able to. For this reason, when using this air gap characteristic minimum point, it has been desired to develop a rotation detection device that can maintain the air gap characteristic minimum point constant even if the rotor shape changes. According to such a rotation detection device, a work load such as individually setting a threshold value according to the shape of the rotor is greatly reduced.

  In recent years, for example, as disclosed in Patent Document 1, a rotation detection device has been proposed that can maintain a constant magnetic vector deflection angle, which is the minimum point of air gap characteristics, regardless of the rotor shape. In this rotation detection device, four magnetoresistive element bridges formed in a line on the sensor chip are used, and the rotation information of the rotor to be detected is detected by obtaining the differential output from these magnetoresistive element bridges. I am doing so.

FIG. 21 shows a configuration of a sensor chip employed in such a rotation detection device.
As shown in FIG. 21, in this rotation detection device, four magnetoresistive element bridges A, B, C, and D are formed in a row on a substrate 140 constituting the sensor chip 104. Further, the respective divided outputs V1, V2, V3, V4 by the magnetoresistive element bridges A to D are inputted to a differential circuit, and a single differential output Vd (Vd = 2 × (V3) is inputted through the differential circuit. -V4)-(V1-V2)) is obtained as a differential operation. The differential output Vd thus obtained makes it possible to keep the minimum air gap characteristic constant regardless of the shape of the rotor.

  22 and 23 show output waveforms of the differential output Vd in different rotor shapes. Here, the rotor shape means that determined by the difference in the length of the crest and trough of the rotor.

For example, FIG. 22 shows the waveform of the differential output Vd when both the crest and trough of the rotor are relatively narrow. Since the differential output Vd changes in accordance with the magnetic vector deflection angle of the bias magnetic field, the differential output Vd is represented here as a magnetic vector deflection angle. As apparent from FIG. 22, the minimum point of the air gap characteristic in this case is about 10 degrees.

  On the other hand, FIG. 23 shows the waveform of the differential output Vd when both the crest and trough of the rotor are relatively long. As shown in FIG. 23, the air gap characteristic minimum point is about 10 degrees in this case as well.

  As described above, the four magnetoresistive element bridges A to D are used, and the differential outputs Vd (Vd = 2 × (V3−V4) − (V1) from the respective divided outputs V1 to V4 by the magnetoresistive element bridges A to D. By obtaining -V2)), even when the rotor shapes are different, the air gap characteristic minimum point is maintained at a substantially constant value. Therefore, by binarizing the differential output Vd using the minimum air gap characteristic as a threshold value, it becomes possible to detect the rotation information of the rotor easily and with high accuracy.

JP 2003-269995 A

  In this way, the differential output Vd (Vd = 2 × (V3−V4) − (V1−V2)) is obtained from each divided output by the four magnetoresistive element bridges A to D arranged in a row. Thus, the air gap characteristic minimum point can be maintained almost constant regardless of the shape of the rotor.

  However, as apparent from FIGS. 22 and 23, if the rotor shape is different, the waveform of the differential output Vd naturally changes. For example, in the rotor shape illustrated in FIG. 22, the differential output waveforms corresponding to the crests and troughs of the rotor are both substantially sine waves. On the other hand, in the rotor shape illustrated in FIG. 23, both the differential output waveforms corresponding to the crest and trough of the rotor are greatly attenuated in the center of the crest and trough, and so-called magnetostriction phenomenon occurs. Yes.

  FIG. 24 summarizes the change tendency of the output waveform depending on the rotor shape. As shown in FIG. 24, in the case of the rotor shape a, that is, when both the crest and trough of the rotor are relatively narrow, the waveform of the differential output (magnetic vector deflection angle) corresponding to the crest and trough Becomes a nearly sine wave. In addition, in the case of the rotor shape b, that is, when the crest of the rotor is relatively narrow and the trough is relatively long, the differential output waveform corresponding to the crest is substantially sinusoidal but corresponds to the trough. The differential output waveform is greatly attenuated at the center of the valley. In the case of the rotor shape c, that is, when both the crest and trough of the rotor are relatively long, the amplitude of the differential output waveform is greatly attenuated at the center of each crest and trough. . In the following, for convenience, the rotor shapes a, b, and c illustrated in FIG. 24 are defined as “narrow mountain rotor”, “equal pitch rotor”, and “Nagayama rotor”, respectively.

  If the waveform of the differential output Vd changes depending on the shape of the rotor in this way, when detecting rotation information based on the differential output Vd, the degree of margin and angular accuracy required for the detection are also increased. It will change subtly. 25 and 26 show the concept of these margins and angular accuracy.

FIG. 25 shows the concept of the margin based on the relationship between various air gaps and the output waveform of the differential output Vd. As shown in FIG. 25, the amplitude of the differential output Vd decreases as the air gap increases. Then, the amplitude of the differential output Vd is minimized at the center of the crest or trough of the rotor. At this time, the smaller of the difference between the minimum value of the output amplitude corresponding to the peak and the minimum value of the air gap characteristic, or the difference between the minimum value of the output amplitude corresponding to the valley and the minimum value of the air gap characteristic is less. Degree. That is, when the margin decreases to a predetermined level or less, an erroneous pulse is generated and erroneous rotation information is detected.

  FIG. 26 is an enlarged view of a part of the output waveform illustrated in FIG. 25 (region indicated by a dotted line) in the concept of angle accuracy. In FIG. 26, the magnetic vector deflection angle corresponding to the intersection P1 of the differential output Vd when the air gap is “large” and when the air gap is “small” is the minimum air gap characteristic. When the intersection between the differential output Vd in the case of the air gap “medium” and this air gap characteristic minimum point is P2, the rotation angle α1 of the rotor corresponding to the intersection P1 and the rotation of the rotor corresponding to the intersection P2 An angle difference (Δα = α1−α2) is generated between the angle α2. The angle difference Δα is the angle accuracy. In other words, the angular accuracy can be said to be the accuracy of a point that intersects the threshold value when binarizing the rotation information based on the waveform of the differential output Vd.

  As described above, when the output waveform of the differential output Vd changes depending on the rotor shape, the margin and the angular accuracy for detecting the rotor rotation information also change. For example, in an in-vehicle internal combustion engine, as described above, such a rotation detection device is used to detect the rotation of the crankshaft or camshaft. However, as a matter of fact, it is used to detect the rotation of the crankshaft. The rotation detection device and the rotation detection device used for detecting the rotation of the camshaft have different requirements for the margin and the angular accuracy. Specifically, in the case of a Nagayama rotor that is provided on a camshaft or the like for cylinder discrimination, a high margin is required rather than angular accuracy, and conversely, it is provided on a crankshaft or the like for detecting rotational speed (angle). In the case of a narrow rotor, high angular accuracy is required rather than margin. However, in the case of the conventional rotation detection device, such a requirement is not always satisfied.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotation detection device optimized for the detection characteristics of the rotation information according to the shape of the rotor to be detected.

In order to achieve such an object, according to the first aspect of the present invention, a sensor chip including a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element are provided, and peaks and troughs are alternately arranged on the outer periphery. Rotation of the rotor by sensing a change in the magnetic vector generated in cooperation with the bias magnetic field as a change in the resistance value of the magnetoresistive element when the magnetic rotor provided in the rotor rotates in the vicinity of the sensor chip. As a rotation detection device for detecting an aspect, the sensor chip is configured to include at least four magnetoresistive element bridges that are bridge-connected and arranged in a direction corresponding to the rotation direction of the rotor, and the magnetoresistance Based on the differential output of the midpoint potential of at least two magnetoresistive element bridges located inside the element bridge And a second differential circuit for obtaining a correction component output based on a differential output of a midpoint potential of at least two magnetoresistive element bridges located outside the magnetoresistive element bridge. A third differential circuit for obtaining a single differential output corresponding to the rotation information of the rotor based on a further differential output of the obtained principal component output and correction component output,
(A) Threshold value and amplitude at the time of binarizing the rotation information of the rotor based on the waveform of the single differential output in which the characteristics required in the shape of the crest and trough of the rotor are obtained The first differential is used when a rotor having a large magnetostriction such as the aforementioned “Nagayama rotor” provided on the camshaft of the in-vehicle internal combustion engine is to be detected. The amplification factor of the circuit is K1, the amplification factor of the second differential circuit is K2, and these are expressed as “(K1 × principal component output) − (K2 × correction component output)> (2 × principal component output) − (correction). Component output) ”is set.
According to the above configuration, the waveform amplitude of the single differential output obtained as described above can be suitably increased as the correction component output is reduced, and a larger margin can be secured.

  As described above, in a rotation detection device including a magnetoresistive element bridge in such a manner, normally, a midpoint potential change (resistance value change) and an outer side of at least two magnetoresistive element bridges positioned on the inside are provided. With the midpoint potential change (resistance value change) in at least two magnetoresistive element bridges positioned, the change mode based on the change in the magnetic vector is naturally different. However, according to the above-described configuration, which includes first to third differential circuits and obtains a single differential output corresponding to the principal component output, the correction component output, and the rotation information of the rotor, respectively, It is possible to adjust the single differential output corresponding to the rotation information of the rotor to be finally output by so-called electrical processing such as setting the amplification factor of the differential circuit 3 separately. It becomes. For this reason, even with this configuration, it is optimal for the detection characteristics of different rotation information required according to the shape of the rotor to be detected, such as the “narrow mountain rotor”, “equal pitch rotor”, and “Nagayama rotor” described above. It is possible to realize a rotation detection device.

According to a second aspect of the present invention, a sensor chip including a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element are provided, and crests and troughs are alternately provided on the outer periphery. When the magnetic rotor rotates in the vicinity of the sensor chip, a change in the magnetic vector generated in cooperation with the bias magnetic field is detected as a change in the resistance value of the magnetoresistive element to detect the rotation mode of the rotor. As the rotation detecting device, the sensor chip is configured to include at least four magnetoresistive element bridges that are bridge-connected and arranged in a direction corresponding to the rotation direction of the rotor. A first differential circuit for obtaining a principal component output based on a differential output of a midpoint potential of at least two magnetoresistive element bridges located inside. A second differential circuit that obtains a correction component output based on a differential output of a midpoint potential of at least two magnetoresistive element bridges located outside the magnetoresistive element bridge, and a main component output obtained therefrom, A third differential circuit for obtaining a single differential output corresponding to the rotation information of the rotor based on a further differential output with the correction component output;
(B) a threshold required for binarizing the rotation information of the rotor based on the required single differential output waveform as a characteristic required for the shape of the peak and valley of the rotor; When ensuring the angular accuracy that is the accuracy of the intersecting point, that is, the above-mentioned “narrow mountain rotor” and “equal pitch rotor” provided on the crankshaft of the on-vehicle internal combustion engine, there is almost no magnetic distortion at least at the mountain part. When the rotor is a detection target, the amplification factor of the first differential circuit is set as K1, the amplification factor of the second differential circuit is set as K2, and these are set in a relationship of “K1 / K2 <2.”
With such a configuration, the edge detection accuracy for the peak portion of the rotor can be improved through the correction component output, and as a result, the angle accuracy can be kept high.

Further, as in the invention according to claim 3,
A magnetic rotor provided with a sensor chip having a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element, and having a crest and a trough alternately provided on the outer periphery, rotates in the vicinity of the sensor chip. As a rotation detecting device for detecting a rotation mode of the rotor by sensing a change in magnetic vector generated in cooperation with the bias magnetic field as a change in resistance value of the magnetoresistive element, each of the sensor chips is bridged It is configured to include at least four magnetoresistive element bridges that are connected and arranged in a direction corresponding to the rotation direction of the rotor, and among the at least two magnetoresistive element bridges located inside the magnetoresistive element bridges. A first differential circuit for obtaining a principal component output based on a differential output of a point potential, and on the outside of the magnetoresistive element bridge A second differential circuit for obtaining a correction component output based on a differential output of a midpoint potential of at least two magnetoresistive element bridges, and further differential output of the obtained main component output and correction component output And a third differential circuit for obtaining a single differential output corresponding to the rotation information of the rotor based on
(C) a threshold value when binarizing the rotation information of the rotor based on the required single differential output waveform is a characteristic required in the shape of the crest and trough of the rotor; The above-mentioned “equal pitch rotor” provided on the crankshaft of the on-board internal combustion engine, for example, when ensuring both the margin that is the difference from the amplitude and the angular accuracy that is the accuracy of the point that intersects the threshold In the case where a rotor in which a magnetostriction hardly occurs in the peak portion but a relatively large magnetostriction is detected in the valley portion, the amplification factor of the first differential circuit is K1, and the second differential circuit The amplification factor of the circuit is set as K2, and these are set to a relationship of “K1 / K2 <2.”
With this configuration, as in the case (b), the edge detection accuracy for the peak portion of the rotor is improved through the correction component output, and the angle accuracy is kept high. In the case of such an “equal pitch rotor”, it has been confirmed by a magnetic simulation by the inventor that a sufficient margin is ensured even if the correction component output is set to be relatively large.

  In the rotation detection device according to any one of claims 1 to 3, as in the invention according to claim 4, the amplification factor of the third differential circuit is set to “1.0”. It is desirable to set the above value in order to ensure the above-described binarization accuracy.

The block diagram which shows the structure of the outline of the rotation detection apparatus with the rotor used as the rotation detection object about the 1st comparative example compared with embodiment concerning this invention. The top view which showed typically the structure of the sensor chip used for the rotation detection apparatus. The circuit diagram which shows the structure of the differential circuit used for the rotation detection apparatus. The graph which shows the relationship between the arrangement position of a magnetoresistive element bridge, and a margin. The graph which shows the relationship between the arrangement position of a magnetoresistive element bridge, and angle accuracy. (A) to (c) in the first comparative example, in the case where the Nagayama rotor is the rotation detection target, the arrangement position of the magnetoresistive element bridge, the differential output Vd, and the main that forms the differential output Vd The graph which shows the relationship between a component and a correction component. The block diagram which shows the structure of the outline of the rotation detection apparatus with the rotor used as the rotation detection object about the 2nd comparative example compared with embodiment concerning this invention. The top view which showed typically the structure of the sensor chip used for the rotation detection apparatus. The graph which shows the relationship between the arrangement position of a magnetoresistive element bridge, and a margin. (A)-(c) is a graph which shows the relationship between the arrangement | positioning position of a magnetoresistive element bridge | bridging, and the differential output Vd in the case of making a narrow mountain rotor into rotation detection object about the 2nd comparative example. (A)-(c) is the figure which expanded and showed the air gap characteristic minimum point vicinity shown by FIG. 10, and was a graph which showed the relationship between the arrangement position of a magnetoresistive element bridge | bridging, and angle accuracy. The graph which shows the general | schematic structure of the rotation detection apparatus in the case of making this equal pitch rotor into rotation detection object with an equal pitch rotor about the said 2nd comparative example. The graph which shows the relationship between the arrangement position of a magnetoresistive element bridge | bridging, and a margin, when making an equivalent pitch rotor into rotation detection object. The top view which showed typically the structure of the sensor chip used for the rotation detection apparatus about 1st Embodiment concerning this invention. The circuit diagram which shows the structure of the differential circuit used for the rotation detection apparatus. The graph which shows the relationship between the gain of a differential amplifier, and a margin, when using a Nagayama rotor as a rotation detection object. The graph which shows the relationship between the amplification factor of a differential amplifier, and angle accuracy. (A) to (c) are graphs showing the relationship between the amplification factor K2 of the differential amplifier A2a, the differential output Vd, the main component forming the differential output Vd, and the correction component in the first embodiment. . The top view which showed typically the structure of the differential circuit used for the rotation detection apparatus about 2nd Embodiment concerning this invention. The graph which shows the relationship between the gain of a differential amplifier, and a margin, when a narrow mountain rotor is made into rotation detection object. The top view which shows the structure of the conventional sensor chip. The graph which shows the differential output in the case of a narrow mountain rotor as an example in the structure of the conventional sensor chip. The graph which shows the differential output in the case of a Nagayama rotor as an example in the structure of the conventional sensor chip. The graph which shows the output waveform example of the differential output Vd in various rotor shape. The graph which shows the waveform example of the differential output for showing the concept of a margin. The graph which shows the waveform example of the differential output for showing the concept of angle accuracy.

(First comparative example)
The first comparative example will be described below with reference to FIGS. 1 to 6 prior to description of the embodiment in which the rotation detection device according to the present invention is embodied. Note that the rotation detection device of the present comparative example is optimized to detect, for example, the Nagayama rotor provided for cylinder discrimination on the camshaft of the on-vehicle internal combustion engine.

FIG. 1 shows a schematic configuration of a rotation detection device 1a according to this comparative example together with a rotor that is a rotation detection target.
As shown in FIG. 1, the rotation detection device 1a includes a bias magnet 2 that generates a bias magnetic field toward a long mountain rotor 6 made of a magnetic material, and a sensor chip 3a in which a magnetoresistive element (MRE) bridge is formed. It is configured with. Here, the bias magnet 2 is formed in a hollow shape, and the sensor chip 3a is inserted and fixed in the hollow portion. The sensor chip 3a is molded with a thermosetting resin such as an epoxy resin while being mounted on a lead frame made of a highly conductive metal material.

  The bias magnet 2 is arranged so that the central axis (the central axis of the sensor chip 3) that is the magnetic center thereof faces the rotation axis of the Nagayama rotor 6. Thereby, the deflection angle of the magnetic vector of the bias magnetic field emitted from the bias magnet 2 changes as the Nagayama rotor 6 rotates. Then, a change in the deflection angle of the magnetic vector of the bias magnetic field is detected, and the resistance value of the magnetoresistive element formed on the sensor chip 3a changes. Such a change in the resistance value of the magnetoresistive element is taken out as a change in the midpoint potential of the bridge circuit and is differentially calculated by the differential circuit 5.

  FIG. 2 is a plan view schematically showing the configuration of the sensor chip 3a, particularly the sensor portion. As shown in FIG. 2, the sensor chip 3a includes four magnetoresistive element bridges A, B, C, and D as first to fourth magnetoresistive element bridges formed on a common substrate. . Among these, the outer two magnetoresistive element bridges A and B are formed at positions symmetrical with respect to the magnetic central axis 20 of the bias magnet 2. The two inner magnetoresistive element bridges C and D are also symmetrical with respect to the magnetic central axis 20 of the bias magnet 2, and the magnetic central axis 20 and the magnetoresistive element bridge A And B, respectively. 2, the distance L1 between the magnetoresistive element bridges A and C, the distance L4 between the magnetoresistive element bridges B and D, and the magnetoresistive element bridges C and D and the central axis 20 The distances L2 and L3 are set to be the same.

In this comparative example, the outer two magnetoresistive element bridges A and B are arranged away from the rotor side end surface of the bias magnet 2 rather than the inner two magnetoresistive element bridges C and D. Yes. That is, in FIG. 2, the distance D2 between the magnetoresistive element bridges A and B and the rotor side end face of the bias magnet 2 is greater than the distance D1 between the magnetoresistive element bridges C and D and the rotor side end face of the bias magnet 2. Is set longer (D2> D1).

  Each of the magnetoresistive element bridges A to D is actually composed of four magnetoresistive elements that are bridge-connected in the manner illustrated in FIG. A change in the magnetic vector of the bias magnetic field generated from the bias magnet 2 is detected as a change in the resistance value of each of the magnetoresistive elements. Further, the detected change in the resistance value of the magnetoresistive element is taken out as the midpoint potentials V1 to V4 of each bridge circuit and input to the differential circuit 5 as described above.

  FIG. 3 is a circuit diagram showing a configuration of the differential circuit 5. As shown in FIG. 3, the differential circuit 5 includes three differential amplifiers A1, A2, and A3. Here, the differential amplifier A1 outputs the differential output “2 × (V3−V4)” of the midpoint potentials V3 and V4 of the magnetoresistive element bridges C and D with a double amplification factor. The differential amplifier A2 outputs a differential output “V1−V2” of the midpoint potentials V1 and V2 of the magnetoresistive element bridges A and B. In the differential amplifier A3, the outputs of the differential amplifiers A1 and A2 are further differentially calculated to obtain a single differential output “Vd = 2 × (V3−V4) − (V1−V2)”. . In the rotation detection device of this comparative example, the rotation information of the rotor 6 is detected based on this single differential output Vd.

  Thus, in the differential circuit 5, as the differential output Vd, the midpoint potential output from the magnetoresistive element bridges C and D as the main components and the midpoint potential from the magnetoresistive element bridges A and B as the correction components are obtained. Outputs a signal consisting of two components. Therefore, by changing the amplitude of the output waveform of the correction component with respect to the main component, the output waveform as the differential output Vd can also be changed to a desired amplitude or shape.

  Therefore, in the present comparative example, as described above, the two outer magnetoresistive element bridges A and B that form the correction component are arranged at positions separated from the rotor-side end surface of the bias magnet 2, thereby correcting the correction component. Is reduced, and as a result, the amplitude of the differential output Vd is increased. As a result, the margin for rotation information detection as the rotation detection device 1a with the Nagayama rotor 6 as a detection target can be accurately increased.

Hereinafter, the relationship between the arrangement positions of the magnetoresistive element bridges A and B and the margin will be described with reference to FIG.
FIG. 4 shows that the inner two magnetoresistive element bridges C and D forming the main component are fixed at predetermined positions. (A) The magnetoresistive element bridges A and B are biased more than the magnetoresistive element bridges C and D. When it arrange | positions in the position spaced apart from the rotor side end surface of 2 (D2> D1).
(B) When the magnetoresistive element bridges A to D are arranged in a line (D2 = D1).
(C) When the magnetoresistive element bridges A and B are disposed closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2 <D1).
The result of the magnetic simulation performed about each of these is shown.

As is apparent from FIG. 4, in the same air gap, when “D2> D1” in (a) above, that is, the magnetoresistive element bridges A and B are biased magnets rather than the magnetoresistive element bridges C and D. The margin is the highest when it is disposed at a position away from the end surface on the rotor side. Further, when “D2 <D1” in (c) above, that is, when the magnetoresistive element bridges A and B are disposed closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D. On the contrary, the margin is greatly reduced. As a whole, the greater the distance D2 between the magnetoresistive element bridges A and B and the rotor side end face of the bias magnet 2, the higher the margin. On the other hand, it is also clear from the simulation results of FIG. 4 that the margin tends to decrease as the air gap increases. Therefore, when the magnetoresistive element bridges A and B are arranged closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D, the margin becomes the reference value when the air gap increases. (Margin = 1) or less. Here, the reference value (margin = 1) is the output amplitude of the differential output Vd that is required to prevent an erroneous pulse when generating a pulse signal by binarizing the differential output Vd. It is.

  Thus, the arrangement positions of the magnetoresistive element bridges A and B have a great influence on the margin for rotation information detection as the rotation detection device 1a. In the case of the Nagayama rotor 6, the magnetoresistive element bridges A and B are arranged at a position further away from the rotor side end face of the bias magnet 2 with respect to the arrangement position of the magnetoresistive element bridges C and D. This margin can be increased.

  On the other hand, the arrangement positions of the magnetoresistive element bridges A and B also affect the angular accuracy when detecting rotation information of the rotor. FIG. 5 shows the result of magnetic simulation for this effect. In FIG. 5, in addition to the Nagayama rotor 6, simulation results for the narrow mountain rotor and the equal pitch rotor are also shown.

  As is clear from FIG. 5, in any rotor shape, the magnetoresistive element bridges A and B are positioned close to the rotor side end surface of the bias magnet 2 with respect to the arrangement position of the magnetoresistive element bridges C and D. By disposing (D2 <D1), the angular accuracy increases. Then, the shorter the distance D2 between the magnetoresistive element bridges A and B and the rotor side end face of the bias magnet 2, the higher the same angle accuracy. When the distance D2 is the same, the angular accuracy is the highest when the narrow mountain rotor is set as the detection target, and the angular accuracy decreases in the order of the equal pitch rotor and the long mountain rotor.

  However, as described above, in the case of the Nagayama rotor 6 provided for cylinder discrimination on the camshaft or the like of the in-vehicle internal combustion engine, a high margin is required rather than angular accuracy. This is because, in the case of a rotation detection device provided as a cylinder discrimination sensor on the camshaft, unlike a so-called crank angle sensor, it is only necessary to detect rotation information for cylinder discrimination once after the engine is started. This is because it is desired to secure a larger margin (degree of freedom) for the air gap. Therefore, in this comparative example, the angular resistance is somewhat sacrificed by disposing the magnetoresistive element bridges A and B at positions farther from the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D. However, a high margin is ensured.

  FIG. 6 shows the relationship between the arrangement position of the magnetoresistive element bridges A and B, the differential output Vd, the main component constituting the differential output Vd, and the correction component when the Nagayama rotor 6 is a detection target. Is shown. Among these, FIG. 6A shows a case where the magnetoresistive element bridges A and B are disposed closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2 <D1). The differential output Vd, its main component, and the correction component waveform are shown. FIG. 6B shows the differential output Vd, its main component, and the correction component output waveform when the magnetoresistive element bridges A to D are arranged in a line (D2 = D1). FIG. 6C shows the difference in the case where the magnetoresistive element bridges A and B are disposed at positions separated from the rotor side end face of the bias magnet 2 relative to the magnetoresistive element bridges C and D (D2> D1). The dynamic output Vd, its main component, and the correction component waveform are shown.

As apparent from FIGS. 6A to 6C, the amplitude of the output waveform of the correction component “V1-V2” as the magnetoresistive element bridges A and B are separated from the rotor side end face of the bias magnet 2. As a result, the amplitude of the differential output Vd increases. Accordingly, when the margin in FIG. 6 (a) is Wa, the margin in FIG. 6 (b) is Wb, and the margin in FIG. 6 (c) is Wc, the relationship is Wa <Wb <Wc. The margin will surely be increased.

As described above, according to the rotation detection device of this comparative example, the following effects can be obtained.
In the embodiment illustrated in FIG. 2, the two outer magnetoresistive element bridges A and B are disposed at a position farther from the rotor side end face of the bias magnet 2 than the two inner magnetoresistive element bridges C and D. . As a result, the amplitude of the correction component “V1−V2” is decreased and the amplitude of the differential output Vd is increased, and the margin for detecting rotation information when the Nagayama rotor 6 is a detection target is increased. It becomes possible to raise it suitably.

(Second comparative example)
Hereinafter, a second comparative example will be described with reference to FIGS. Note that the rotation detection device of this comparative example is optimized to detect, for example, a narrow rotor provided on a crankshaft of an in-vehicle internal combustion engine for detecting a rotation speed (angle). Further, in the rotation detection device of this comparative example, in the previous first comparative example, the magnetoresistive element bridges A and B are positioned closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D. The other structure is the same as that of the first comparative example. For this reason, the overlapping description about these common parts is omitted.

FIG. 7 shows a schematic configuration of the rotation detection device 1b according to this comparative example together with the narrow mountain rotor 7 to be the rotation detection target.
As shown in FIG. 7, the rotation detection device 1b includes a bias magnet 2 that generates a bias magnetic field toward a narrow mountain rotor 7 made of a magnetic material, and a sensor chip 3b in which a magnetoresistive element (MRE) bridge is formed. It is configured with.

  FIG. 8 is a plan view schematically showing the configuration of the sensor chip 3b, particularly the sensor portion. As shown in FIG. 8, the distance D2 between the two outer magnetoresistive element bridges A and B and the end face of the bias magnet 2 on the rotor side is equal to the two inner magnetoresistive element bridges C and D and the bias magnet 2. This is shorter than the distance D1 between the rotor side end face (D2 <D1). That is, the magnetoresistive element bridges A and B are arranged at positions closer to the rotor side end face of the bias magnet 2 than the arrangement positions of the magnetoresistive element bridges C and D.

  Also in this comparative example, the differential output “2 × (V3−V4)” of the midpoint potentials V3 and V4 of the two inner magnetoresistive element bridges C and D is a main component, and the two outer magnetoresistive elements are The differential output “V1−V2” of the midpoint potential of the bridges A and B is used as a correction component. Then, a further differential output of the main component and the correction component is obtained as a single differential output Vd (Vd = 2 × (V3−V4) − (V1−V2)), and based on the differential output Vd. Thus, rotation information of the narrow mountain rotor 7 is detected.

  By arranging the magnetoresistive element bridges A to D in this way, the accuracy of edge detection with respect to the peak portion of the narrow mountain rotor 7 is improved as the correction component increases, and further, the narrow mountain rotor 7 is detected. In this case, the angular accuracy required for detecting the rotation information is also preferably improved.

  Further, as already shown in FIG. 5, the shorter the distance between the magnetoresistive element bridges A and B and the end face of the bias magnet 2 on the rotor side, the higher the angular accuracy.

FIG. 9 shows the magnetoresistive element bridge C in the case where the narrow mountain rotor 7 is to be detected.
The result of having performed the magnetic simulation about the change of margin when D is fixed to a predetermined position and the arrangement position of magnetoresistive element bridges A and B is changed is shown. As shown in FIG. 9, the shorter the distance D2 between the magnetoresistive element bridges A and B and the rotor side end face of the bias magnet 2, the more the rotation information detected when the narrow mountain rotor 7 is detected. The degree of allowance for is increased.

  As described above, when the narrow mountain rotor 7 is to be detected, the magnetoresistive element bridges A and B are disposed as close as possible to the rotor side end face of the bias magnet 2 to ensure angular accuracy and allowance. It becomes possible to balance with ensuring.

  By the way, when the magnetoresistive element bridges A and B are arranged, the arrangement position is limited by a saturation magnetic field required for stably operating the magnetoresistive element. Further, the magnetic field intensity of the bias magnetic field decreases from the center of the bias magnet 2 toward the end surface thereof, and in the vicinity of the end surface, the bias magnetic field may become weaker than the necessary bias magnetic field. . For this reason, it is desirable to set the arrangement positions of the magnetoresistive element bridges A to D at positions where at least a saturation magnetic field (about −20 mT) can be secured. Therefore, in this comparative example, the sensor chip 3b is configured by arranging the magnetoresistive element bridges A to D on the equal magnetic force lines that become the saturation magnetic field.

If the saturation magnetic field can be secured, the magnetoresistive element bridges A to D do not necessarily have to be arranged on the lines of equal magnetic force.
FIG. 10 shows the relationship between the arrangement positions of the magnetoresistive element bridges A and B and the differential output Vd when the narrow mountain rotor 7 is a detection target. Among these, FIG. 10A shows a case where the magnetoresistive element bridges A and B are arranged at positions farther from the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2> D1). FIG. 4 shows waveforms of the differential output Vd in the case of various air gaps (large, medium, and small). FIG. 10B shows the waveform of the differential output Vd when the magnetoresistive element bridges A to D are arranged in a line (D2 = D1) and various air gaps (large, medium, small). Show. FIG. 10C shows a case where the magnetoresistive element bridges A and B are disposed closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2 <D1). The waveforms of the differential output Vd in the case of various air gaps (large, medium, and small) are shown. As shown in FIGS. 10A to 10C, the magnetic vector corresponding to the intersection of the waveform of the differential output Vd when the air gap is large and the waveform of the differential output Vd when the air gap is small. The deflection angle is the minimum air gap characteristic.

  FIGS. 11A to 11C are enlarged views showing the vicinity of the intersection of the output waveforms of the differential output Vd in the various air gaps shown in FIGS. 10A to 10C. As shown in FIG. 11A, when the magnetoresistive element bridges A and B are arranged at positions farther from the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2> D1). The angle accuracy required for rotation detection is Δα1. As shown in FIG. 11B, when the magnetoresistive element bridges A to D are arranged in a line (D2 = D1), the angular accuracy is Δα2. Then, as shown in FIG. 11C, when the magnetoresistive element bridges A and B are disposed closer to the rotor side end face of the bias magnet 2 than the magnetoresistive element bridges C and D (D2 <D1). ) Has an angle accuracy of Δα3. As is clear from FIGS. 11A to 11C, the angular accuracy indicates a relationship of “Δα1> Δα2> Δα3”. In other words, the closer the position of the magnetoresistive element bridges A and B to the rotor side end face of the bias magnet 2, the higher the angular accuracy required for rotation detection.

Thus, when the narrow mountain rotor 7 provided for detecting the rotational speed (angle) on the crankshaft of the on-vehicle internal combustion engine is to be detected, the magnetoresistive element bridges A and B are connected to the bias magnet 2.
In particular, it is easy to ensure angular accuracy by disposing at a position closer to the rotor side end surface.

As described above, according to the rotation detection device of this comparative example, the following effects can be obtained.
In the embodiment illustrated in FIG. 8, the two outer magnetoresistive element bridges A and B are disposed closer to the rotor side end surface of the bias magnet 2 than the two inner magnetoresistive element bridges C and D. did. As a result, the angular accuracy required for rotation detection when the narrow mountain rotor 7 is a detection target is preferably enhanced.

  In the above comparative example, the narrow mountain rotor 7 has been described as an example of the rotational speed (angle) detection rotor provided on the crankshaft of the in-vehicle internal combustion engine. As such a rotor, the above-described equal pitch rotor is used. Sometimes used. As described above, this equal pitch rotor has a structure in which the valleys are relatively long as compared with the narrow mountain rotor 7. As a result, the angular accuracy and margin required for rotation detection when this equal-pitch rotor is the detection target show a tendency different from that of the previous narrow mountain rotor 7.

  FIG. 12 shows a schematic configuration of the rotation detecting device 1c in the case where the equal pitch rotor 8 is a detection target together with the equal pitch rotor 8. In FIG. 12, the sensor chip 3c has substantially the same structure as the previous sensor chip 3b, that is, the two outer magnetoresistive element bridges A and B are the two inner magnetoresistive element bridges C and D. It is arranged at a position closer to the rotor side end face of the bias magnet 2. For this reason, the illustration and description which overlap here about this sensor chip 3c are omitted.

  FIG. 13 shows a case where the magnetoresistive element bridges C and D are fixed at predetermined positions and the arrangement positions of the magnetoresistive element bridges A and B are changed in the case where the equal pitch rotor 8 is set as a detection target. The result of having performed the magnetic simulation about the change of a margin is shown. As shown in FIG. 13, the margin increases as the disposition positions of the magnetoresistive element bridges A and B are separated from the rotor side end face of the bias magnet 2, that is, as the distance D2 is longer. This point is different from the previous narrow mountain rotor 7. As is apparent from FIG. 13, even when the distance D2 is small, a relatively high margin is secured with respect to the reference value (margin = 1).

  For this reason, when the above-described equal pitch rotor is to be detected, the sensor chip 3c is configured in the manner illustrated in FIG. Become figured.

(First embodiment)
Hereinafter, a first embodiment embodying a rotation detection device according to the present invention will be described with reference to FIGS. In the present embodiment, as in the first comparative example, for example, the Nagayama rotor provided for cylinder discrimination on the camshaft of the in-vehicle internal combustion engine is optimized for detection. However, the sensor chip 3d illustrated in FIG. 14 is used instead of the sensor chip 3a, and the differential circuit 5a illustrated in FIG. 15 is used instead of the differential circuit 5.

  That is, in the rotation detection device according to the present embodiment, as the sensor chip 3d, as shown in FIG. 14, a magnetoresistive element bridge A to D arranged in a line is used. Therefore, the midpoint potentials V1 to V4 of the magnetoresistive element bridges A to D are input to the differential circuit 5a in the manner shown in FIG.

  Here, the differential circuit 5a also basically includes a first differential amplifier A1, a second differential amplifier A2a, and a third differential amplifier A3 as shown in FIG. Configured. However, among these, the second differential amplifier A2a that generates the correction component has a differential output “0” of the midpoint potentials V1 and V2 of the magnetoresistive element bridges A and B with an amplification factor of “0.6”. .6 × (V1-V2) "is output. For this reason, the third differential amplifier A3 obtains an output such as “Vd = 2 × (V3−V4) −0.6 × (V1−V2)” as a single differential output Vd. In this embodiment, the rotation information of the Nagayama rotor 6 is detected based on the single differential output Vd “Vd = 2 × (V3−V4) −0.6 × (V1−V2)”. It becomes.

  Thus, since the amplitude value of the correction component is reduced by setting the amplification factor of the second differential amplifier A2a that outputs the correction component to “0.6”, the single differential output The waveform amplitude of Vd is preferably increased. As a result, the margin for rotation detection can be further increased.

  FIG. 16 shows the result of magnetic simulation of the relationship between the gain K2 and the margin of the second differential amplifier A2a when the Nagayama rotor 6 is a detection target.

  As shown in FIG. 16, the smaller the amplification factor K2, the higher the margin. Here, when the amplification factor K2 is set to “0.6”, the margin is significantly increased as compared with the conventional case (amplification factor K2 = 1).

  FIG. 17 shows the results of magnetic simulation on the relationship between the amplification factor K2 of the differential amplifier A2a and the angular accuracy in various rotor shapes. Here, in addition to the Nagayama rotor 6, magnetic simulation results for the narrow mountain rotor 7 and the equal pitch rotor 8 are also shown. As is apparent from FIG. 17, in any rotor shape, the angular accuracy tends to decrease as the amplification factor K2 decreases.

  On the other hand, as described above, in the case of the Nagayama rotor 6 provided for cylinder discrimination on a camshaft or the like of an in-vehicle internal combustion engine, a high margin is required rather than angular accuracy. For this reason, in the present embodiment, the amplification factor K2 of the second differential amplifier A2a is set to “0.6”, and a high margin is ensured while sacrificing the angular accuracy to some extent.

  FIG. 18 shows the relationship between the amplification factor K2 of the second differential amplifier A2a, the differential output Vd, the main component forming the differential output Vd, and the correction component when the Nagayama rotor 6 is a detection target. Is shown. Among these, FIG. 18A shows the waveforms of the differential output Vd, its main component, and the correction component when the amplification factor K2 is “1.4”. FIG. 18B shows waveforms of the differential output Vd, its main component, and correction component when the amplification factor K2 is “1.0”. FIG. 18C shows the waveforms of the differential output Vd, its main component, and the correction component when the amplification factor K2 is “0.6”. As apparent from FIGS. 18A to 18C, the lower the amplification factor K2 of the second differential amplifier A2a that outputs the correction component of the differential output Vd, the lower the differential output Vd “Vd”. = K2 × (V3−V4) −K1 × (V1−V2) ”is increased in amplitude. The margins Wa ′, Wb ′, and Wc ′ when the amplification factor K2 is “1.4”, “1.0”, and “0.6” are “Wa ′ <Wb ′ <Wc ′”. It is also clear from these FIGS. 18A to 18C that the relationship is established. That is, the lower the gain K2 of the second differential amplifier A2a that outputs the correction component of the differential output Vd, the higher the margin for rotation detection.

As described above, according to the rotation detection device according to the present embodiment, the following effects can be obtained.
In the present embodiment, the amplification factor K2 of the second differential amplifier A2a that outputs the correction component that forms the differential output Vd is set to “0.6”. For this reason, the amplitude of the correction component “V1−V2” is decreased and the amplitude of the differential output Vd is increased, and the margin for detecting rotation information when the Nagayama rotor 6 is a detection target. Can be suitably increased.

  In this embodiment, the amplitude of the differential output Vd is adjusted by an electrical method such as setting the amplification factor of the differential amplifier. For this reason, it is not necessary to change the arrangement positions of the magnetoresistive element bridges A to D, and the sensor chip 3 in which these magnetoresistive element bridges are arranged in a row can be used as a standardized part. Thereby, the same sensor chip 3 can be applied to rotors of various shapes, and its versatility is improved.

  In the above embodiment, the amplification factor K1 of the first differential amplifier A1 is set to “2” as in the first comparative example, but the main component of the differential output Vd is increased. In order to do this, the amplification factor K1 may be set to a value of “2” or more. In this case, since the differential output Vd is further amplified, a higher margin can be obtained.

  In the above embodiment, the amplification factor K2 of the second differential amplifier A2a is set to “0.6”. However, the present invention is not limited to this. You may make it set to the value of.

In the above embodiment, the amplification factors K1 and K2 of the first differential amplifier A1 and the second differential amplifier A2a are set to “2” and “0.6”, respectively. However, the present invention is not limited to this, and the following equation K1 × (V3−V4) −K2 × (V1−V2)
> 2 × (V3-V4)-(V1-V2)
That is,
(K1 × principal component output) − (K2 × correction component output)
> (2 × principal component output) − (correction component output)
If the above can be satisfied, the amplification factors K1 and K2 can be set to arbitrary values.

(Second Embodiment)
Hereinafter, a second embodiment of the rotation detection device according to the present invention will be described with reference to FIGS. As in the second comparative example, this embodiment is optimized to detect, for example, a narrow rotor provided on the crankshaft of an in-vehicle internal combustion engine for detecting the rotational speed (angle). It is. However, here, the differential circuit 5 b illustrated in FIG. 19 is used in place of the differential circuit 5. The sensor chip used in the present embodiment is the same as that illustrated in FIG.

Here, the midpoint potentials V1 to V4 of the magnetoresistive element bridges A to D are respectively input to the differential circuit 5b in the manner shown in FIG. As is apparent from FIG. 19, the differential circuit 5b also basically includes a first differential amplifier A1, a second differential amplifier A2b, and a third differential amplifier A3. It is configured. However, among these, the second differential amplifier A2b that outputs the correction component has a differential output of “1. 4x (V1-V2) "is output. For this reason, the third differential amplifier A3 obtains an output of “Vd = 2 × (V3−V4) −1.4 × (V1−V2)” as the single differential output Vd. In this embodiment, the rotation information of the narrow mountain rotor 7 is detected based on the single differential output Vd “Vd = 2 × (V3−V4) −1.4 × (V1−V2)”. It becomes.

  Thus, by setting the amplification factor of the second differential amplifier A2b that outputs the correction component to “1.4”, the amplitude value of the correction component is increased. Through this, the edge detection accuracy for the peak portion of the narrow rotor 7 is improved, and the angular accuracy is also kept high.

  FIG. 20 shows the result of magnetic simulation on the relationship between the gain K2 and the margin of the second differential amplifier A2b when the narrow mountain rotor 7 is a detection target.

  As shown in FIG. 20, the higher the amplification factor K2, the higher the margin. Here, when the amplification factor K2 is set to “1.4”, the margin is significantly increased as compared with the conventional case (amplification factor K2 = 1).

  Also, as already shown in FIG. 17, when the narrow rotor 7 is to be detected, the higher the amplification factor K2 of the second differential amplifier that outputs the correction component, the higher the angular accuracy. Can be enhanced.

  Thus, in the case of the narrow mountain rotor 7, the amplification factor K2 of the second differential amplifier A2b that outputs the correction component “V1-V2” that forms the single differential output Vd is set to “1.4”. By doing so, the angular accuracy can be easily secured.

As described above, according to the rotation detection device according to the present embodiment, the following effects can be obtained.
In the present embodiment, the amplification factor K2 of the second differential amplifier A2b that outputs the correction component “V1-V2” of the single differential output Vd with the narrow mountain rotor 7 as a detection target is set to “1.4”. It was decided to set. Thereby, the angular accuracy required for rotation detection is preferably improved.

  In this embodiment, the angle accuracy is optimized through an electrical method such as setting the amplification factor of the differential amplifier. For this reason, it is not necessary to change the arrangement position of the magnetoresistive element bridges A to D, and when changing the arrangement position of the magnetoresistive element bridges A and B, there is naturally a positional restriction such as securing a saturation magnetic field. Disappear. Further, the sensor chip 3d in which these magnetoresistive element bridges A to D are arranged in a row can be used as a standardized part. Thereby, the same sensor chip 3d can be applied to rotors of various shapes, and its versatility is enhanced.

In the above embodiment, the amplification factor K2 of the second differential amplifier A2b is set to “1.4”, but the present invention is not limited to this. In short, the amplification factor K1 of the first differential amplifier A1 and the amplification factor K2 of the second differential amplifier A2b are expressed by the following equation: K1 / K2 <2.
If the above condition is satisfied, the amplification factor K2 may be set to another value as appropriate.

  Further, in the above embodiment, the narrow mountain rotor 7 is set as the detection target. However, even when the equal pitch rotor 8 is set as the detection target, the rotation detection device according to the present embodiment can be applied. it can.

(Other embodiments)
In addition, each said embodiment can also be implemented with the following aspects.
In each of the above embodiments, the distances L1 to L4 are all equally spaced, but the distances L1 to L4 are not necessarily equal, for example, the distance L2 and the distance L
3 may be expanded as appropriate.

  In each of the above embodiments, the bias magnet 2 is formed to have a hollow portion. However, the shape of the bias magnet 2 is not limited to this, and may be other shapes such as a substantially U-shaped cross section. You may make it form suitably.

  In each of the above embodiments, the sensor chip 3 (3a to 3d) and the like are molded with resin. However, the sensor chip 3 is directly disposed on the bias magnet 2 without molding. May be.

  In each of the above embodiments, the four magnetoresistive element bridges A to D arranged at symmetrical positions with respect to the magnetic central axis 20 of the bias magnet 2 are used. Four or more magnetoresistive element bridges may be used, such as adding a fifth magnetoresistive element bridge E to the magnetic central axis 20 of the magnet 2.

  In each of the above embodiments, the amplification factor K3 of the differential amplifier A3 is set to “1”. However, the amplification factor K3 may be set to a value of “1” or more. Thereby, in any rotor shape, the amplitude of the differential output Vd is amplified, so that the margin is increased.

  In each of the above embodiments, the margin or angle accuracy is improved by setting the amplification factor K2 of the differential amplifiers A2a and A2b. However, instead of this, the setting of the arrangement positions of the magnetoresistive element bridges A and B and the setting of the amplification factors K1 to K3 of the differential amplifiers A1 to A3 may be performed simultaneously. Thereby, for example, even when the arrangement positions of the magnetoresistive element bridges A and B in the sensor chip 3 deviate from the desired positions, the desired values can be obtained through the setting of the amplification factors K1 to K3 of the differential amplifiers A1 to A3. A differential output can be obtained. Further, in this case, the sensor chip 3 does not become a defective product due to the displacement of the arrangement position of the magnetoresistive element bridge, and the manufacturing yield of the sensor chip 3 is reliably improved.

  DESCRIPTION OF SYMBOLS 1a, 1b, 1c ... Rotation detection apparatus, 2 ... Bias magnet, 3 (3a-3d) ... Sensor chip 5, 5a, 5b ... Differential circuit, A1 ... 1st differential amplifier, A2 ... 2nd difference Dynamic amplifier, A3 ... third differential amplifier, 6 ... Nagayama rotor, 7 ... Nagayama rotor, 8 ... equal pitch rotor, A, B, C, D ... magnetoresistive element bridge.

Claims (4)

A magnetic rotor provided with a sensor chip having a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element, and having a crest and a trough alternately provided on the outer periphery, rotates in the vicinity of the sensor chip. In the rotation detection device for detecting a rotation mode of the rotor by sensing a change in the magnetic vector generated in cooperation with the bias magnetic field as a change in the resistance value of the magnetoresistive element,
The sensor chip includes at least four magnetoresistive element bridges that are bridge-connected and arranged in a direction corresponding to the rotational direction of the rotor, and at least two magnetic elements located inside the magnetoresistive element bridges. A first differential circuit for obtaining a principal component output based on a differential output of a midpoint potential of a resistance element bridge, and a difference between midpoint potentials of at least two magnetoresistive element bridges located outside the magnetoresistive element bridge A second differential circuit for obtaining a correction component output based on the dynamic output, and a single differential corresponding to the rotation information of the rotor based on a further differential output of the principal component output and the correction component output obtained A third differential circuit for obtaining an output, and characteristics required for the shape of the crests and troughs of the rotor are obtained through the third differential circuit. When securing a margin, which is a difference between a threshold value and an amplitude when binarizing the rotation information of the rotor based on a single differential output waveform, the first to third differentials When the amplification factor of the circuit is K1, the amplification factor of the first differential circuit is K1, and the amplification factor of the second differential circuit is K2,
(K1 × principal component output) − (K2 × correction component output)
> (2 × principal component output) − (correction component output)
It is set to the relationship which becomes. The rotation detection apparatus characterized by the above-mentioned. A magnetic rotor provided with a sensor chip having a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element, and having a crest and a trough alternately provided on the outer periphery, rotates in the vicinity of the sensor chip. In the rotation detection device for detecting a rotation mode of the rotor by sensing a change in the magnetic vector generated in cooperation with the bias magnetic field as a change in the resistance value of the magnetoresistive element,
The sensor chip includes at least four magnetoresistive element bridges that are bridge-connected and arranged in a direction corresponding to the rotational direction of the rotor, and at least two magnetic elements located inside the magnetoresistive element bridges. A first differential circuit for obtaining a principal component output based on a differential output of a midpoint potential of a resistance element bridge, and a difference between midpoint potentials of at least two magnetoresistive element bridges located outside the magnetoresistive element bridge A second differential circuit for obtaining a correction component output based on the dynamic output, and a single differential corresponding to the rotation information of the rotor based on a further differential output of the principal component output and the correction component output obtained A third differential circuit for obtaining an output, and characteristics required for the shape of the crests and troughs of the rotor are obtained through the third differential circuit. When securing angular accuracy, which is the accuracy of the point that intersects the threshold value when binarizing the rotation information of the rotor based on the waveform of a single differential output, the first to third differences When the gain of the dynamic circuit is K1, the gain of the first differential circuit is K1, and the gain of the second differential circuit is K2.
K1 / K2 <2
It is set to the relationship which becomes. The rotation detection apparatus characterized by the above-mentioned. A magnetic rotor provided with a sensor chip having a magnetoresistive element and a bias magnet for applying a bias magnetic field to the magnetoresistive element, and having a crest and a trough alternately provided on the outer periphery, rotates in the vicinity of the sensor chip. In the rotation detection device for detecting a rotation mode of the rotor by sensing a change in the magnetic vector generated in cooperation with the bias magnetic field as a change in the resistance value of the magnetoresistive element,
The sensor chip includes at least four magnetoresistive element bridges that are bridge-connected and arranged in a direction corresponding to the rotational direction of the rotor, and at least two magnetic elements located inside the magnetoresistive element bridges. A first differential circuit for obtaining a principal component output based on a differential output of a midpoint potential of a resistance element bridge, and a difference between midpoint potentials of at least two magnetoresistive element bridges located outside the magnetoresistive element bridge A second differential circuit for obtaining a correction component output based on the dynamic output, and a single differential corresponding to the rotation information of the rotor based on a further differential output of the principal component output and the correction component output obtained A third differential circuit for obtaining an output, and characteristics required for the shape of the crests and troughs of the rotor are obtained through the third differential circuit. An angle that is a precision of a point crossing the threshold value and ensuring a margin that is a difference between the threshold value and the amplitude when the rotation information of the rotor is binarized based on a single differential output waveform When ensuring accuracy is achieved, the amplification factors of the first to third differential circuits are K1, the amplification factor of the first differential circuit, and K2 of the second differential circuit. and when,
K1 / K2 <2
It is set to the relationship which becomes. The rotation detection apparatus characterized by the above-mentioned. The rotation detection device according to any one of claims 1 to 3, wherein an amplification factor of the third differential circuit is set to "1.0" or more.

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