MAGNETIC SENSOR SYSTEM

Abstract

Magnetic sensor system comprising a scale and a magnetic sensor arranged in a relative position ratio that is variable in a first direction, wherein the magnetic sensor system is designed to detect a physical quantity related to the relative position ratio between the scale and the magnetic sensor, characterized in that The magnetic sensor includes a first detection circuit located at a first position and a second detection circuit located at a second position. The first detection circuit outputs a first detection signal that varies depending on a first magnetic field applied to the first detection circuit. The second detection circuit outputs a second detection signal that varies depending on a second magnetic field applied to the second detection circuit. Both the first and second detection circuits contain several magnetoresistive elements connected in series, Each of the several magnetoresistive elements contains: a magnetized layer with a magnetization in a fixed direction; a free layer with a magnetization that varies depending on an applied magnetic field; and a tunnel barrier layer located between the magnetized layer and the free layer. Both the first and the second magnetic fields periodically change their direction in response to a change in the relative positional relationship between the scale and the magnetic sensor, and the first position and the second position differ from each other by 1.25% of a division or less, where a division is a measure of change in the relative positional ratio between the scale and the magnetic sensor, which changes the direction of both the first and second magnetic fields by one period, wherein the magnetic sensor system further comprises a computing unit which generates an exception detection signal indicating the occurrence of an exception in the magnetic sensor by calculation using the first detection signal and the second detection signal, wherein the exception includes an event occurring in the first or second detection circuit due to a short circuit between the magnetized layer and the free layer in one or more of the plurality of magnetoresistive elements included in the first or second detection circuit, and wherein the computing unit further determines the presence of the exception in the magnetic sensor by introducing and monitoring an upper and a lower limit for the value of the exception detection signal, within which it can be determined that neither the first nor the second detection circuit exhibits any exception.whether the exceptional case determination signal falls within the range defined by the upper and lower limits.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to a magnetic sensor system for detecting a physical quantity in relation to the relative position ratio between a scale and a magnetic sensor. 2. Description of the state of the art

[0002] In recent years, magnetic sensor systems have been used in a variety of applications to detect a physical quantity related to the rotational or linear motion of a moving object. Typically, a magnetic sensor system includes a scale and a magnetic sensor, and the magnetic sensor is designed to generate a signal related to the relative position between the scale and the magnetic sensor.

[0003] The scale of the magnetic sensor system for use with a rotating object is generally a rotating body that moves in response to the motion of the moving object. The rotating body can be, for example, a multipole magnetized magnet with several pairs of N and S poles arranged alternately in a circumferential direction, or a gear with teeth made of a magnetic material. In this case, the magnetic sensor system detects, for example, the rotational position and / or the rotational speed of the rotating body as the physical quantity.

[0004] The scale of the magnetic sensor system for use with a linearly moving object is, for example, a linear scale with multiple pairs of N and S poles arranged alternately in a linear pattern. In this case, either the linear scale or the magnetic sensor moves in response to the movement of the object, and the magnetic sensor system detects the relative position and / or velocity of the linear scale with respect to the magnetic sensor as the physical quantity.

[0005] The magnetic sensor system is used, for example, in motor vehicles to detect the rotational speed of the axle shaft, the angle of the crankshaft, the camshaft angle, and so on. The magnetic sensor system for use in motor vehicles must, in particular, include means for detecting exceptional cases within the magnetic sensor.

[0006] JP 2003-194598A discloses an exceptional detection device comprising a first sensor and a second sensor whose outputs respond to a change in a physical quantity with mutually opposite output characteristics. The exceptional detection device identifies either the first or second sensor as abnormal if the sum of the outputs of the first and second sensors is not a constant value. In this exceptional detection device, the first sensor contains a first detection circuit, and the second sensor contains a second detection circuit. The first and second detection circuits are arranged side-by-side in the same plane. Each detection circuit contains a bridge circuit consisting of four resistors.Each resistive element is formed by depositing a thin film of NiCo in an offset shape on a support layer and can be described as an anisotropic magnetoresistive element.

[0007] The exceptional case detector disclosed in JP 2003-194598A is designed such that, assuming the direction of a magnetic flux passing through the first detection circuit and the direction of a magnetic flux passing through the second detection circuit are the same, the respective output values ​​of the first and second sensors have mutually opposite output characteristics. The four resistive elements (anisotropic magnetoresistive elements) contained in each detection circuit require a relatively large footprint. This results in a relatively large difference in position between the first and second detection circuits.This exceptional case detector is suitable for a system in which magnetic fluxes flow in the same direction over a wide area, so that the magnetic flux passing through the first detection circuit and the magnetic flux passing through the second detection circuit are in the same direction. However, in practice, it is difficult to use this detector with the aforementioned magnetic sensor system, which includes the scale and the magnetic sensor. The reason for this is described below.

[0008] In the aforementioned magnetic sensor system, continuous changes in the relative positional relationship between the scale and the magnetic sensor cause periodic changes in the direction of a magnetic field at a certain point within the magnetic sensor. The magnitude of a change in the relative positional relationship between the scale and the magnetic sensor that alters the direction of the magnetic field by one period at a given point is referred to as a division. The exceptional case detector disclosed in JP 2003-194598A can be applied to the magnetic sensor system such that the magnetic sensor incorporates the first and second sensing circuits disclosed in JP 2003-194598A. In this case, the difference between the positions of the first and second sensing circuits would be significantly larger compared to a division.This would cause a significant difference between the direction of the magnetic flux passing through the first sensing circuit and the direction of the magnetic flux passing through the second sensing circuit. Consequently, the respective output values ​​of the first and second sensors could not have mutually opposite output characteristics. This, in turn, would mean that the overall output value would not be constant, even if neither the first nor the second sensor exhibited an exceptional case, making it impossible to detect the occurrence of an exceptional case in either sensor.

[0009] To solve this problem, it would be conceivable to arrange the first and second sensors of the same configuration at a distance of 1 / 2 division, so that the output values ​​of the first and second sensors have mutually opposite output characteristics, allowing an outlier in the first or second sensor to be identified within the overall output. However, this approach introduces the following problem. In the case of a magnetic sensor system, the scale can vary depending on the system in which the magnetic sensor system is used, and the size of a division can vary accordingly. Therefore, even if the first and second sensors are arranged at a distance of 1 / 2 division according to a specific scale used to construct a magnetic sensor system, a change in the size of a division resulting from a change in the scale would mean that the difference between the positions of the first and second sensors would no longer be 1 / 2 division.This would in turn mean that the entire output value would not be a constant value, even if neither the first nor the second sensor has an exception, making it impossible to detect the occurrence of an exception in the first or second sensor.

[0010] JP 2011 - 185 747 A shows a device for detecting anomalies in magnetic sensing elements for a magnetic encoder.

[0011] DE 10 2008 045 000 A1 shows a rotation detection sensor for detecting both a rotation position and a rotation direction of a rotating body. TASK AND BRIEF DESCRIPTION OF THE INVENTION

[0012] It is an object of the present invention to provide a magnetic sensor system comprising a scale and a magnetic sensor that is capable of detecting the occurrence of an exceptional case in the magnetic sensor.

[0013] A magnetic sensor system of the present invention comprises a scale and a magnetic sensor arranged in a relative positional ratio that is variable in a first direction, and is designed to detect a physical quantity related to the relative positional ratio between the scale and the magnetic sensor. In the magnetic sensor system of the present invention, the magnetic sensor comprises a first detection circuit arranged at a first position and a second detection circuit arranged at a second position. The first detection circuit outputs a first detection signal that varies depending on a first magnetic field applied to the first detection circuit. The second detection circuit outputs a second detection signal that varies depending on a second magnetic field applied to the second detection circuit.Both the first and second sensing circuits contain a magnetoresistive element. The magnetoresistive element comprises: a magnetized layer with magnetization in a fixed direction; a free layer with magnetization that varies depending on an applied magnetic field; and a non-magnetic layer located between the magnetized layer and the free layer. Both the first and second magnetic fields periodically change their direction in response to a change in the relative positional ratio between the scale and the magnetic sensor. The first and second positions differ from each other by 1.25% of a division or less, where a division is the magnitude of a change in the relative positional ratio between the scale and the magnetic sensor that alters the direction of both the first and second magnetic fields by one period.The magnetic sensor system also includes a computing unit that generates an exception detection signal, indicating the occurrence of an exception in the magnetic sensor by calculation using the first detection signal and the second detection signal.

[0014] In the magnetic sensor system of the present invention, the second detection signal can have a phase difference of 175.5° to 184.5° with respect to the first detection signal. In this case, the calculation by the computer unit can include determining the sum of the first detection signal and the second detection signal.

[0015] In the magnetic sensor system of the present invention, the second detection signal can have a phase difference of -4.5° to 4.5° with respect to the first detection signal. In this case, the calculation by the computer unit can include determining the difference between the first detection signal and the second detection signal.

[0016] In the magnetic sensor system of the present invention, the first position and the second position in the first direction can be the same.

[0017] In the magnetic sensor system of the present invention, the scale can be a rotating body that rotates about a predetermined central axis. In this case, the rotation of the rotating body changes the relative positional relationship between the scale and the magnetic sensor. The first direction is the direction of rotation of the rotating body. The first division is indicated at an angle to the direction of rotation of the rotating body.

[0018] The rotating body can have multiple pairs of N and S poles arranged alternately around its circumference. In this case, both the first and second magnetic fields are generated by the rotating body and change direction as the body rotates. One division is the angle formed by two straight lines connecting the central axis to the centers of two adjacent N poles of the rotating body.

[0019] The rotating body can be a gear with teeth made of a magnetic material. The magnetic sensor system can further include a magnet with a fixed positional ratio to the magnetic sensor. In this case, both the first and second magnetic fields are generated by the magnet and change their direction as the gear rotates. One division is the angle formed by two straight lines connecting the central axis to the centers of two adjacent teeth.

[0020] In the magnetic sensor system of the present invention, the scale can have several pairs of N and S poles arranged alternately in a linear configuration. In this case, the first direction is the direction in which the N and S poles of the scale are arranged. Both the first and second magnetic fields are generated by the scale. One division is the distance between the centers of two adjacent N poles of the scale.

[0021] In the magnetic sensor system of the present invention, the non-magnetic layer of the magnetoresistive element is a tunnel barrier layer.

[0022] In the magnetic sensor system of the present invention, both the first and second sensing circuits contain a so-called magnetoresistive spin valve element, that is, a magnetoresistive element comprising a magnetized layer, a free layer, and a non-magnetic layer. The magnetoresistive spin valve element enables a significant reduction in the footprint compared to an anisotropic magnetoresistive element. The present invention thus allows the first and second sensing circuits to be arranged such that the difference between the first position and the second position is 1.25% of a division or less, provided the division size falls within a practical range.Thus, the present invention makes it possible for the magnetic sensor system with the scale and the magnetic sensor to detect the occurrence of an exceptional case in the magnetic sensor from the exceptional case detection signal, which is generated by calculation using the first detection signal and the second detection signal.

[0023] Other and further tasks, features and advantages of the present invention will become more fully apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing the general configuration of a magnetic sensor system according to a first embodiment of the invention. Fig. Figure 2 is a top view showing the general configuration of the magnetic sensor system according to the first embodiment of the invention. Fig. Figure 3 is a side view showing a scale and first and second detection circuits of the first embodiment of the invention. Fig. Figure 4 is a top view showing the first and second detection circuits of the first embodiment of the invention. Fig. Figure 5 is a side view of an MR element located in Fig. 4 is shown. Fig. Figure 6 is a circuit diagram showing a first example of the circuit configuration of the magnetic sensor system according to the first embodiment of the invention. Fig. Figure 7 is a circuit diagram showing a second example of the circuit configuration of the magnetic sensor system according to the first embodiment of the invention. Fig. Figure 8 is a waveform diagram showing the first and second detection signals of the first embodiment of the invention. Fig. Figure 9 is a waveform diagram showing an exceptional case detection signal under normal conditions in the first embodiment of the invention. Fig. Figure 10 is a waveform diagram showing an example of the exceptional case detection signal under abnormal conditions in the first embodiment of the invention. Fig. Figure 11 is a side view showing a scale and a first and second detection unit of a magnetic sensor system of a comparison example. Fig. Figure 12 is a circuit diagram showing the first and second detection units of the magnetic sensor system of the comparison example. Fig. Figure 13 is a waveform diagram showing an example of an exceptional case detection signal under normal conditions and that under abnormal conditions of the magnetic sensor system of the comparison example. Fig. Figure 14 is a side view showing a substitute scale and the first and second sensing units of the magnetic sensor system of the comparison example. Fig. Figure 15 is a waveform diagram showing an example of the exceptional case detection signal under normal conditions and that under abnormal conditions when the substitute scale is used in the magnetic sensor system of the comparison example. Fig. Figure 16 is a perspective view showing the general configuration of a magnetic sensor system according to a second embodiment of the invention. Fig. Figure 17 is an explanatory diagram showing the operation of the magnetic sensor system according to the second embodiment of the invention. Fig. Figure 18 is a circuit diagram showing an example of the circuit configuration of a magnetic sensor system of a third embodiment of the invention. Fig. Figure 19 is a perspective view showing the general configuration of a magnetic sensor system according to a fourth embodiment of the invention. Fig. Figure 20 is a side view showing a scale and a first and second detection circuit of the fourth embodiment of the invention. Fig. Figure 21 is a top view showing the first and second detection circuits of the fourth embodiment of the invention. Fig. Figure 22 are characteristic curves showing the relationship between the difference between the first and second positions and the phase difference of the second detection signal with respect to the first detection signal in the fourth embodiment of the invention. Fig. Figure 23 is a waveform diagram showing an example of an exceptional case detection signal under normal conditions and that under abnormal conditions in the fourth embodiment of the invention. Fig. Figure 24 are characteristic curves showing the ratio between the minimum value of the exceptional case detection signal under normal conditions and the maximum value of the exceptional case detection signal under abnormal conditions in the fourth embodiment of the invention. Fig. Figure 25 is a perspective view showing the general configuration of a magnetic sensor system according to a fifth embodiment of the invention. Fig. Figure 26 is a perspective view showing the general configuration of a magnetic sensor system according to a sixth embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EXECUTIONS [First embodiment]

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, we will refer to Fig. 1 to Fig. 3 Reference is made to describe the general configuration of a magnetic sensor system according to a first embodiment of the invention. Fig. Figure 1 is a perspective view showing the general configuration of the magnetic sensor system according to the first embodiment. Fig. Figure 2 is a top view showing the general configuration of the magnetic sensor system according to the first embodiment. Fig. Figure 3 is a side view showing a scale and a first and second detection circuit of the first embodiment.

[0025] As in Fig. 1 to Fig. Figure 3 shows that the magnetic sensor system of the first embodiment comprises a scale 1 and a magnetic sensor 2 arranged in a relative positional relationship that is variable in a first direction D1, and is designed to detect a physical quantity related to the relative positional relationship between the scale 1 and the magnetic sensor 2. The scale 1 of the first embodiment is a rotating body that rotates about a predetermined central axis C in response to the motion of a rotating object (not shown). The rotation of the rotating body changes the relative positional relationship between the scale 1 and the magnetic sensor 2. The first direction D1 is the direction of rotation of the rotating body. The magnetic sensor system detects, for example, the rotational position and / or the rotational speed of the rotating body as the physical quantity.

[0026] As in Fig. 1 and Fig. As shown in Figure 2, the rotating body of the first embodiment is a multipole magnetized magnet 5 with several pairs of N and S poles arranged alternately in a circumferential direction. In the example shown in Figure 2, the rotating body is a multipole magnet 5 with several pairs of N and S poles arranged alternately in a circumferential direction. Fig. 1 and Fig. As shown in Figure 2, the magnet 5 has 12 pairs of N and S poles. The magnetic sensor 2 is arranged so that it faces the outer circumferential surface of the magnet 5.

[0027] The definition of directions in the first embodiment will now be given with reference to Fig. 1 and Fig. 2 described. First, the direction is parallel to the central axis C, which is in Fig. 1 is shown, and from bottom to top in Fig. 1 runs as defined by the Z-direction. In Fig. 2 is the Z-direction, defined as the direction outside the plane of Fig. Figure 2 illustrates this. Then, two directions perpendicular to the Z-direction and orthogonal to each other are defined as the X-direction and the Y-direction. Fig. In diagram 2, the X-direction is represented as the direction to the right, and the Y-direction is represented as the direction upwards. Furthermore, the direction opposite to the X-direction is defined as the -X-direction, and the direction opposite to the Y-direction is defined as the -Y-direction.

[0028] The magnetic sensor 2 contains a first detection circuit 10 and a second detection circuit 20. For better understanding, see in Fig. 1 and Fig. 2 the first and second detection circuits 10 and 20 compared to those in Fig. 3 shown larger. Although the first and second detection circuits are 10 and 20 in Fig. Although the first and second detection circuits 10 and 20 are shown as separate components, they can also be integrated into a single component. Fig. 1 and Fig. 3 are arranged in the vertical direction, the order of the arrangement can also be changed with respect to those which are in Fig. 1 and Fig. 3 is shown, the reverse should be true.

[0029] The first detection circuit 10 is located at a first position P1, detects a first magnetic field MF1 applied to the first detection circuit 10, and outputs a first detection signal S1 that varies depending on the first magnetic field MF1. The second detection circuit 20 is located at a second position P2, detects a second magnetic field MF2 applied to the second detection circuit 20, and outputs a second detection signal S2 that varies depending on the second magnetic field MF2. Fig. 1 to Fig. 3 is the first position P1 as the position of the center of the first detection circuit 10, while the second position P2 is the position of the center of the second detection circuit 20.

[0030] In the first embodiment, as in Fig. 2 and Fig. As shown in Figure 3, the first position P1 and the second position P2 in the first direction D1 are the same. Consequently, the first magnetic field MF1 and the second magnetic field MF2 essentially run in the same direction. In the Fig. 2 and Fig. In the example shown, the first position P1 and the second position P2 are the same in the X and Y directions and differ in the Z direction.

[0031] Both the first magnetic field MF1 and the second magnetic field MF2 periodically change their direction in response to a change in the relative positional relationship between the scale 1 and the magnetic sensor 2. In the first embodiment, both the first and the second magnetic fields MF1 and MF2 are generated by the magnet 5 and change their direction as the rotating body or the magnet 5 rotates. Fig. 2 The hollow arrow, labeled MF1, MF2, indicates the direction of the first and second magnetic fields MF1 and MF2 when the relative position ratio between scale 1 and magnetic sensor 2 is as shown. Fig. Figure 2 shows the changes in the direction of the first and second magnetic fields MF1 and MF2 when the magnet 5 moves out of the space in Fig. The direction of the first magnetic field MF1 rotates around the first position P1 in the XY plane. The direction of the second magnetic field MF2 rotates around the second position P2 in the XY plane.

[0032] Herein, the extent of a change in the relative positional relationship between the scale 1 and the magnetic sensor 2, which changes the direction of both the first magnetic field MF1 and the second magnetic field MF2 by one period, is defined as a division. In the first embodiment, a division is specified as an angle in the direction of rotation of the rotating body or the magnet 5. In particular, a division is the angle formed by two straight lines connecting the central axis C to the centers of two adjacent N poles of the magnet 5. Fig. 1 and Fig. In Figure 2, the two straight lines mentioned above are represented as dashed lines, and the angle formed by the two straight lines is denoted by the symbol α. In the example shown in Fig. 1 and Fig. As shown in Figure 2, the angle α is 30°. In this example, a rotation of magnet 5 causes the direction of both the first magnetic field MF1 and the second magnetic field MF2 to rotate 12 times, that is, to change by 12 periods. One period of the first and second detection signals S1 and S2, i.e., an electrical angle of 360°, corresponds to 1 / 12 of a rotation of magnet 5, i.e., a 30-degree angle of rotation of magnet 5.

[0033] In the first embodiment, the difference between the first position P1 and the second position P2 in the first direction D1, hereinafter referred to as the position difference, is defined by an angle in the direction of rotation of the rotating body or magnet 5, the angle being formed by two straight lines connecting the central axis C to the first and second positions P1 and P2. As will be described later with respect to another embodiment, it is necessary that the position difference be 1.25% of a division or less. Since in the example described in Fig. 1 and Fig. As shown in Figure 2, if the division or angle α is 30°, the position difference must be 0.375° or less. Since, in the first embodiment, the first position P1 and the second position P2 are the same in the first direction D1, the position difference is 0° and thus fulfills the requirement described above. Considering the production accuracy of the magnetic sensor system and other factors, the first position P1 and the second position P2 in the first direction D1 may differ slightly to such an extent that the position difference is 1.25% of a division or less.

[0034] The first detection circuit 10 and the second detection circuit 20 each contain magnetoresistive (MR) elements. As will be described in detail later, all MR elements contained in the first and second detection circuits 10 and 20 of the first embodiment are MR spin-valve elements. Each of the MR elements contains a magnetized layer with magnetization in a fixed direction, a free layer with magnetization that varies depending on an applied magnetic field, and a non-magnetic layer located between the magnetized layer and the free layer. The first detection circuit 10 is arranged such that the plane of the layers forming each of the MR elements is perpendicular to a straight line connecting the first position P1 and the central axis C.The second detection circuit 20 is arranged such that the plane of the layers forming each of the MR elements is perpendicular to a straight line connecting the second position P2 and the central axis C. In the first embodiment, the plane of the layers forming each of the MR elements of the second detection circuit 20 is parallel to the plane of the layers forming each of the MR elements of the first detection circuit 10.

[0035] An anisotropic magnetoresistive element consists of an elongated conductive path of a magnetic material and therefore requires a relatively large footprint. In contrast, an MR spin-valve element contains several stacked layers and can be supplied with current in a direction perpendicular to the plane of these layers, thus enabling a significant reduction in footprint compared to the anisotropic magnetoresistive element. Furthermore, the spin-valve MR element, although small, is extremely sensitive to magnetic fields. Therefore, the first embodiment allows the first detection circuit 10 and the second detection circuit 20 to be positioned sufficiently close to each other to meet the aforementioned requirement.

[0036] The magnetic sensor system also includes a computer unit 30 for generating an exception detection signal, which indicates the occurrence of an exception in the magnetic sensor 2 by calculation using the first detection signal S1 and the second detection signal S2. The computer unit 30 will be described in detail later.

[0037] The configurations of the first and second detection circuits 10 and 20 are now described in detail with reference to Fig. 4 described. Fig. Figure 4 is a top view showing the first and second detection circuits 10 and 20. The first detection circuit 10 contains MR element groups R11 and R12 connected in series, a power supply terminal V1, a ground terminal G1, and an output terminal E1. Each of the MR element groups R11 and R12 contains several MR elements 50 connected in series. A first end of the MR element group R11 is connected to the power supply terminal V1. A second end of the MR element group R11 is connected to a first end of the MR element group R12 and to the output terminal E1. A second end of the MR element group R12 is connected to the ground terminal G1. A power supply voltage of a predetermined value is applied to the power supply terminal V1. The ground terminal G1 is earthed. The output terminal E1 outputs the first detection signal S1.

[0038] The second detection circuit 20 has a similar configuration to the first detection circuit 10. In particular, the second detection circuit 20 includes MR element groups R21 and R22 connected in series, a power supply terminal V2, a ground terminal G2, and an output terminal E2. Each of the MR element groups R21 and R22 contains several MR elements 50 connected in series. A first end of the MR element group R21 is connected to the power supply terminal V2. A second end of the MR element group R21 is connected to a first end of the MR element group R22 and to the output terminal E2. A second end of the MR element group R22 is connected to the ground terminal G2. A power supply voltage of a predetermined value is applied to the power supply terminal V2. The ground terminal G2 is earthed. The output terminal E2 outputs the second detection signal S2.

[0039] As in Fig. As shown in Figure 4, the MR element groups R11, R12, R21, and R22 are aligned in the Z direction. However, the arrangement of the MR element groups R11, R12, R21, and R22 is not limited to the example shown in Figure 4. Fig. 4 is shown.

[0040] In the first embodiment, the MR elements 50 are MR spin-valve elements, each comprising a magnetized layer, a free layer, and a non-magnetic layer. The MR elements 50 can be TMR elements or GMR elements. If the MR elements 50 are TMR elements, the non-magnetic layer is a tunnel barrier layer. If the MR elements 50 are GMR elements, the non-magnetic layer is a non-magnetic conductive layer. In each MR element 50, the magnetization of the free layer varies depending on the magnetic field applied to the free layer. In particular, the direction and magnitude of the magnetization of the free layer vary depending on the direction and magnitude of the magnetic field applied to the free layer. The resistance of each MR element 50 also varies depending on the direction and magnitude of the magnetization of the free layer.For example, if the free layer has a constant magnetization, the resistance of the MR element reaches its minimum value when the magnetization direction of the free layer is the same as that of the magnetized layer, and reaches its maximum value when the magnetization direction of the free layer is opposite to that of the magnetized layer. Fig. 4 The arrow drawn in each MR element 50 indicates the magnetization direction of the layer of the MR element 50 that is fixed in the magnetization.

[0041] In the first detection circuit 10, the magnetized layers of the multiple MR elements 50 contained in the MR element group R11 are magnetized in the X direction, and the magnetized layers of the multiple MR elements 50 contained in the MR element group R12 are magnetized in the -X direction. In this case, the potential at the output terminal E1 varies depending on the strength of a component of the first magnetic field MF1 in a direction parallel to the X and -X directions. The first detection circuit 10 thus detects the strength of the component of the first magnetic field MF1 in the direction parallel to the X and -X directions and outputs the first detection signal S1, which indicates the strength.

[0042] In the second detection circuit 20, the magnetized layers of the multiple MR elements 50 contained in the MR element group R21 are magnetized in the -X direction, and the magnetized layers of the multiple MR elements 50 contained in the MR element group R22 are magnetized in the X direction. In this case, the potential at the output terminal E2 varies depending on the strength of a component of the second magnetic field MF2 in the direction parallel to the X and -X directions. The second detection circuit 20 thus detects the strength of the component of the second magnetic field MF2 in the direction parallel to the X and -X directions and outputs the second detection signal S2, which indicates the strength.

[0043] The MR element groups R11 and R21 are oriented oppositely in the magnetization direction of the magnetized layers of the multiple MR elements 50 contained therein. The MR element groups R12 and R22 are oriented oppositely in the magnetization direction of the magnetized layers of the multiple MR elements 50 contained therein. Consequently, the second detection signal S2 has a phase difference of 180° with respect to the first detection signal S1.

[0044] With regard to the production accuracy of the MR elements 50 and other factors, the layers of the multiple MR elements 50 fixed in the magnetization in the detection circuits 10 and 20 may be magnetized in directions that differ slightly from the directions described above.

[0045] Each of the MR element groups R11, R12, R21, and R22 further comprises several lower electrodes and several upper electrodes (not shown) for electrical connection of the multiple MR elements 50. In each of the MR element groups R11, R12, R21, and R22, the multiple lower electrodes are arranged with a space between adjacent ones on a support layer (not shown) such that they together form a meandering shape. Each lower electrode is elongated in one direction. On the upper surface of each lower electrode, two MR elements 50 are arranged longitudinally near opposite ends. The multiple upper electrodes are arranged on the multiple MR elements 50. Each upper electrode is elongated in one direction and electrically connects two adjacent MR elements 50, which are arranged side by side on two lower electrodes in the longitudinal direction of the lower electrodes.In such a configuration, the multiple MR elements 50 in each of the MR element groups R11, R12, R21 and R22 are connected in series by the multiple lower and upper electrodes.

[0046] An example of the configuration of each MR element 50 will now be given with reference to Fig. 5 described. Fig. Figure 5 shows an MR element 50 of Fig. 4. The in Fig. The MR element 50 shown in Figure 5 comprises a substrate 51, an antiferromagnetic layer 52, a magnetization-fixed layer 53, a non-magnetic layer 54, a free layer 55, and a protective layer 56, stacked in that order, with the substrate 51 closest to the bottom electrode. The substrate 51 and the protective layer 56 are conductive. The substrate 51 serves to eliminate the effects of the crystal axis of the support layer (not shown) and to improve the crystallinity and orientability of each layer formed on the substrate 51. The substrate 51 can be made of, for example, Ta or Ru. The antiferromagnetic layer 52 serves to fix the magnetization direction of the magnetization-fixed layer 53 by exchange coupling with the magnetization-fixed layer 53.The antiferromagnetic layer 52 is formed from an antiferromagnetic material such as IrMn or PtMn.

[0047] The magnetization direction of the magnetized layer 53 is fixed by exchange coupling between the antiferromagnetic layer 52 and the magnetized layer 53 at the interface between them. In the Fig. In the example shown in Figure 5, the magnetized layer 53 contains an outer layer 531, a non-magnetic intermediate layer 532, and an inner layer 533, which are stacked in this order on the antiferromagnetic layer 52, and is thus formed as a so-called synthetic fixed layer. The outer layer 531 and the inner layer 533 are each made of a soft magnetic material such as CoFe, CoFeB, or CoNiFe. The magnetization direction of the outer layer 531 is fixed by exchange coupling between the outer layer 531 and the antiferromagnetic layer 52. The outer layer 531 and the inner layer 533 are antiferromagnetically coupled to each other, and their magnetizations are thus fixed in mutually opposite directions.The non-magnetic intermediate layer 532 induces an antiferromagnetic exchange coupling between the outer layer 531 and the inner layer 533, such that the magnetizations of the outer layer 531 and the inner layer 533 are fixed in opposite directions. The non-magnetic intermediate layer 532 is formed from a non-magnetic material such as Ru. If the magnetized layer 53 contains the outer layer 531, the non-magnetic intermediate layer 532, and the inner layer 533, the magnetization direction of the magnetized layer 53 is related to that of the inner layer 533.

[0048] If the MR element 50 is a TMR element, the non-magnetic layer 54 is a tunnel barrier layer. The tunnel barrier layer can be formed by oxidizing part or all of a magnesium layer. If the MR element 50 is a GMR element, the non-magnetic layer 54 is a non-magnetic conductive layer. The free layer 55 is formed, for example, from a soft magnetic material such as CoFe, CoFeB, NiFe, or CoNiFe. The protective layer 56 is provided to protect the underlying layers. The protective layer 56 can be formed, for example, from Ta, Ru, W, or Ti.

[0049] The base 51 is connected to the lower electrode and the protective layer 56 is connected to the upper electrode. The MR element 50 is designed to be supplied with current through the lower and upper electrodes. The current is conducted in a direction that intersects the plane of the layers forming the MR element 50, i.e., a direction perpendicular to the plane of the layers forming the MR element 50.

[0050] It will now be on Fig. 6 and Fig. 7 Reference is made to describe the circuit configuration of the magnetic sensor system according to the first embodiment and the computer unit 30. Fig. Figure 6 is a circuit diagram showing a first example of the circuit configuration of the magnetic sensor system according to the first embodiment. Fig. Figure 7 is a circuit diagram showing a second example of the circuit configuration of the magnetic sensor system according to the first embodiment.

[0051] In the first example, which is in Fig. As shown in Figure 6, the computer unit 30 contains two computer circuits 31 and 32, a window comparator (hereinafter referred to simply as the comparator) 33, an analog-to-digital converter (hereinafter referred to as the A / D converter) 34, and a data processing circuit 35. The computer circuit 31 has two inputs and one output. The two inputs of the computer circuit 31 are connected to the output terminal E1 of the first detection circuit 10 and the output terminal E2 of the second detection circuit 20, respectively. The computer circuit 31 generates an exceptional event detection signal Sa, which indicates the occurrence of an exceptional event in the magnetic sensor 2, by calculation using the first and second detection signals S1 and S2. The calculation for generating the exceptional event detection signal Sa may include determining the sum of the first detection signal S1 and the second detection signal S2.

[0052] The computer circuit 32 has two inputs and one output. The two inputs of the computer circuit 32 are connected to the output terminal E1 of the first detection circuit 10 and the output terminal E2 of the second detection circuit 20, respectively. The computer circuit 32 generates a third detection signal Sb by calculation using the first and second detection signals S1 and S2, corresponding to the relative position ratio between the scale 1 and the magnetic sensor 2.

[0053] Comparator 33 has one input and one output. The input of comparator 33 is connected to the output of computer circuit 31. Comparator 33 outputs a signal indicating whether the exception detection signal Sa falls within a predetermined range. If the exception detection signal Sa falls within the predetermined range, it is determined that magnetic sensor 2 is functioning normally. If the exception detection signal Sa is outside the predetermined range, it is determined that magnetic sensor 2 is experiencing an exception.

[0054] The A / D converter 34 has one input and one output. The input of the A / D converter 34 is connected to the output of the computer circuit 32. The A / D converter 34 converts the third detection signal Sb into a digital signal and outputs the digital signal.

[0055] The data processing circuit 35 has two inputs. These two inputs are connected to the output of the comparator 33 and the output of the A / D converter 34, respectively. Based on the output signal from the comparator 33, the data processing circuit 35 detects an anomaly in the magnetic sensor 2 and, by calculation using the third detection signal Sb, determines the magnitude and / or rate of any change in the relative position between the scale 1 and the magnetic sensor 2, i.e., the rotational position and / or the rotational speed of the rotating body or the magnet 5. The data processing circuit 35 can, for example, be implemented by a microcomputer.

[0056] In the second example, which is in Fig. As shown in Figure 7, the computer unit 30 contains an analog-to-digital converter (ADC) 36 instead of the comparator 33. The ADC 36 has one input and one output. The input of the ADC 36 is connected to the output of the computer circuit 31. The output of the ADC 36 is connected to one of the two inputs of the data processing circuit 35. The ADC 36 converts the exception detection signal Sa into a digital signal and outputs the digital signal. The data processing circuit 35 uses the exception detection signal Sa, converted into the digital signal, to determine whether the magnetic sensor 2 is experiencing an exception.

[0057] The first to third detection signals S1, S2 and Sb will now be identified with reference to Fig. 8 described. Fig. Figure 8 is a waveform diagram showing the first and second detection signals S1 and S2. Fig. Figure 8 represents the horizontal axis as the electrical angle of the first and second detection signals S1 and S2, while the vertical axis represents the potential of the first and second detection signals S1 and S2.

[0058] In the first embodiment, the second detection signal S2, as mentioned above, has a phase difference of 180° with respect to the first detection signal S1. However, in the present invention, the phase difference of the second detection signal S2 with respect to the first detection signal S1 is not limited to 180°. As described later with respect to other embodiments, the second detection signal S2 can have a phase difference in the range of 175.5° to 184.5° or in the range of -4.5° to 4.5° with respect to the first detection signal S1.

[0059] The computer circuit 32 generates the third acquisition signal Sb, which is the difference between the first acquisition signal S1 and the second acquisition signal S2, that is, S1 minus S2, plus an offset voltage of a predetermined value. The offset voltage is intended to equalize the average value of the third acquisition signal Sb with the average value of the first and second acquisition signals S1 and S2. In the Fig. In the example shown, both the first and second detection signals S1 and S2 have a central level of 2500 mV. In this case, the offset voltage is 2500 mV.

[0060] In the first embodiment, as described above, the third detection signal Sb is generated by a calculation that includes determining the difference between the first detection signal S1 and the second detection signal S2. This enables the generation of the third detection signal Sb with reduced noise when noises of the same phase are superimposed on the first detection signal S1 and the second detection signal S2.

[0061] It will now be on Fig. 9 and Fig. 10 Reference is made to describe the exceptional case detection signal Sa and the effects of the magnetic sensor system according to the first embodiment. Fig. Figure 9 is a waveform diagram showing the exceptional case detection signal Sa under normal conditions. Fig. Figure 10 is a waveform diagram showing an example of the exceptional case detection signal Sa under abnormal conditions. Fig. 9 and Fig. 10 The horizontal axis represents the electrical angle of the first and second detection signals S1 and S2, while the vertical axis represents the potential of the exceptional case detection signal Sa.

[0062] For example, the computer circuit 31 generates the sum of the first detection signal S1 and the second detection signal S2, divided by 2, as the exception detection signal Sa. The average value of the exception detection signal Sa is equal to the central level of the first to third detection signals S1, S2, and Sb.

[0063] If magnetic sensor 2 is not experiencing an exceptional case, that is, if magnetic sensor 2 is operating under normal conditions, the exceptional case detection signal Sa has a constant value, since the phase difference of the second detection signal S2 with respect to the first detection signal S1 is 180°. In the example shown in Fig. The value of the exceptional case detection signal Sa 2500 mV is shown in figure 9.

[0064] On the other hand, if an exceptional case occurs in the first or second detection circuit 10 or 20, the first detection signal S1 or the second detection signal S2 differs from that under normal conditions. This causes the exceptional case detection signal Sa to not have a constant value. An exceptional case in the first or second detection circuit 10 or 20 can be caused primarily by a short circuit in an MR element 50, if the MR element 50 is a TMR element, or by an open circuit in one of the MR element groups R11, R12, R21, and R22. In particular, a short circuit in an MR element 50 refers to one that occurs between the magnetized layer 53 and the free layer 55 in a TMR element.Regardless of the cause, the resistance value of one of the MR element groups R11, R12, R21, and R22 differs from that under normal conditions, and consequently, the first detection signal S1 or the second detection signal S2 differs from that under normal conditions. The exceptional detection signal Sa is now described under abnormal conditions, specifically using as an example the case where an exceptional event in the first or second detection circuit 10 or 20 is caused by a short circuit in an MR element 50.

[0065] Fig. Figure 10 shows an example in which each of the MR element groups R11, R12, R21 and R22, which are in Fig. Figure 4 shows twenty MR elements 50, and one of the MR elements 50 in the MR element group R21 is short-circuited to cause an exceptional case in the second detection circuit 20. In the Fig. In the case shown in Figure 10, the value of the exceptional case detection signal Sa changes periodically in phase with the first detection signal S1, and the average value of the exceptional case detection signal Sa becomes greater than that under normal conditions, as in Fig. Figure 9 shows that if two or more of the MR elements 50 in the MR element group R21 are short-circuited, the exceptional detection signal Sa has a larger amplitude compared to that shown in Figure 9. Fig. 10 examples shown.

[0066] If one or more of the MR elements 50 in the MR element group R11 are short-circuited to cause an exceptional case in the first detection circuit 10, the value of the exceptional case detection signal Sa changes periodically in phase with the second detection signal S2, and the average value of the exceptional case detection signal Sa becomes larger than that under normal conditions, as in Fig. 9 shown.

[0067] If one or more of the MR elements 50 in the MR element group R12 are short-circuited to cause an exceptional case in the first detection circuit 10, the value of the exceptional case detection signal Sa changes periodically in phase with the second detection signal S2, and the average value of the exceptional case detection signal Sa becomes smaller than that under normal conditions, as in Fig. 9 shown.

[0068] If one or more of the MR elements 50 in the MR element group R22 are short-circuited to cause an exceptional case in the second detection circuit 20, the value of the exceptional case detection signal Sa changes periodically in phase with the first detection signal S1, and the average value of the exceptional case detection signal Sa becomes smaller than that under normal conditions, as in Fig. 9 shown.

[0069] The first embodiment uses the features of the exceptional case detection signal Sa described above to detect the occurrence of an exceptional case in the first or second detection circuit 10 or 20, thereby enabling the detection of an exceptional case in the magnetic sensor 2. In particular, the occurrence of an exceptional case in the magnetic sensor 2 can be detected, for example, by setting an upper and a lower limit for the value of the exceptional case detection signal Sa, within which it can be determined that neither the first nor the second detection circuit 10 and 20 has an exceptional case, and by monitoring whether the value of the exceptional case detection signal Sa falls within the range defined by the upper and lower limits. Such a detection is performed by the comparator 33 in the first example, which is shown in Fig. 6 is shown, and by the data processing circuit 35 in the second example, which is in Fig. 7 is shown.

[0070] The effects of the first embodiment will now be described in more detail in comparison to a magnetic sensor system of a comparative example. First, the configuration of the magnetic sensor system of the comparative example will be described with reference to... Fig. 11 and Fig. 12 described. Fig. Figure 11 is a side view showing a scale and a first and second detection unit of the magnetic sensor system of the comparison example. Fig. Figure 12 is a circuit diagram showing the first and second detection units of the magnetic sensor system in the comparison example. Fig. 11 and Fig. Figure 12 shows an example in which the magnetic sensor system of the comparison example uses the same scale 1 as that of the first embodiment, that is, the magnet 5.

[0071] The magnetic sensor system of the comparison example includes a magnetic sensor 102 instead of the magnetic sensor 2 of the first embodiment. The magnetic sensor 102 is arranged such that it is associated with the outer circumferential surface of the magnet 5. The magnetic sensor 102 includes a first sensing unit 110, which is arranged at a first position P101, and a second sensing unit 120, which is arranged at a second position P102. In the magnetic sensor system of the comparison example, the first position P101 and the second position P102 are different in the first direction D1. In the example described in Fig. As shown in Figure 11, the first position P101 and the second position P102 are different in the X-direction and the same in the Z-direction. Although not shown, the first position P101 and the second position P102 are the same in the Y-direction. The difference between the first position P101 and the second position P102 in the first direction D1, that is, the position difference there, is equal to 1 / 2 of the angle α, which represents one division of magnet 5, that is, equal to 1 / 2 of a division of magnet 5.

[0072] A first magnetic field MF101 is applied to the first detection unit 110 and a second magnetic field MF102 is applied to the second detection unit 120. In Fig. Figure 12 shows that the two hollow arrows, labeled MF101 and MF102, indicate the directions of the magnetic fields MF101 and MF102, respectively, when they are in the state shown in Figure 12. Fig. 11 is shown. As in Fig. As shown in Figure 12, the direction of the first magnetic field MF101 and the direction of the second magnetic field MF102 are opposite to each other.

[0073] Both the first detection unit 110 and the second detection unit 120 contain several MR elements 50. The MR elements 50 are designed in the same way as those of the magnetic sensor system according to the first embodiment. The first detection unit 110 is arranged such that the plane of the layers formed by each of the MR elements 50 is perpendicular to a straight line connecting the first position P101 and the central axis C (see Fig. 1 and Fig. 2) Likewise, the second detection unit 120 is arranged such that the plane of the layers formed by each of the MR elements 50 is perpendicular to a straight line connecting the second position P102 and the central axis C.

[0074] The first acquisition unit 110 contains MR element groups R111 and R112, a power supply connection V101, a ground connection G101, and an output connection E101. The second acquisition unit 120 contains MR element groups R121 and R122, a power supply connection V102, a ground connection G102, and an output connection E102. One end of MR element group R111 is connected to the power supply connection V101. The other end of MR element group R111 is connected to the first end of MR element group R122 and the output connection E101. The other end of MR element group R122 is connected to the ground connection G102. A predetermined power supply voltage is applied to the power supply connection V101. The ground connection G102 is grounded.

[0075] One end of the MR element group R121 is connected to the power supply terminal V102. A second end of the MR element group R121 is connected to the first end of the MR element group R112 and the output terminal E102. A second end of the MR element group R112 is connected to the ground terminal G101. A predetermined power supply voltage is applied to the power supply terminal V102. The ground terminal G101 is grounded.

[0076] Each of the MR element groups R111, R112, R121 and R122 contains several MR elements 50 connected in series. In Fig. 12 The solid arrows indicate the magnetization direction of the layers 53 of the MR elements 50 that are fixed in the magnetization. As in Fig. As shown in Figure 12, the layers 53 of the MR elements 50 that are fixed in the magnetization are magnetized in the X direction in all of the MR element groups R111, R112, R121 and R122.

[0077] Output terminal E101 outputs a first detection signal S101, and output terminal E102 outputs a second detection signal S102. The arrangement of scale 1 and detection units 110 and 120, as shown in Fig. As shown in Figure 11, the second detection signal S102 achieves a phase difference of 180° with respect to the first detection signal S101.

[0078] The magnetic sensor system of the comparative example contains the same computing unit 30 as that of the magnetic sensor system according to the first embodiment. The computing unit 30 generates a third detection signal by calculation using the first and second detection signals S101 and S102. In particular, the computing unit 30 generates as the third detection signal the difference between the first detection signal S101 and the second detection signal S102, that is, S101 minus S102, plus an offset voltage of a predetermined value. This third detection signal corresponds to the third detection signal Sb of the magnetic sensor system according to the first embodiment.

[0079] The exceptional case detection signal of the magnetic sensor system of the comparison example is now evaluated with reference to Fig. 13 described. Fig. Figure 13 is a waveform diagram showing the exceptional case detection signal under normal conditions and that under abnormal conditions of the magnetic sensor system of the comparison example. Fig. In Figure 13, the horizontal axis represents the electrical angle of the first and second detection signals S101 and S102, while the vertical axis represents the potential of the exceptional case detection signal. Furthermore, in Fig. 13. Reference numeral Sa1 denotes the exceptional case detection signal under normal conditions, while reference numeral Sa2 denotes the exceptional case detection signal under abnormal conditions. Furthermore, reference numerals V H and V L the upper limit or the lower limit for the value of the exceptional case detection signal, within which it can be determined that neither the first nor the second detection unit 110 and 120 has an exceptional case. Fig. Figure 13 shows an example of the case where each of the MR element groups R111, R112, R121 and R122, which are in Fig. 12 are shown, contains twenty MR elements 50 and one of the MR elements 50 in the MR element group R112 or R122 is short-circuited to cause an exceptional case in the magnetic sensor 102.

[0080] In the magnetic sensor system of the comparative example, the computer unit 30 generates the exceptional detection signal by calculation using the first and second detection signals S101 and S102. Specifically, the computer unit 30 generates the exceptional detection signal by dividing the sum of the first detection signal S101 and the second detection signal S102 by 2. If no exceptional condition is present in the magnetic sensor 102, the second detection signal S102 has a phase difference of 180° with respect to the first detection signal S101, and therefore the exceptional detection signal Sa1 has a constant value, like the exceptional detection signal Sa of the magnetic sensor system according to the first embodiment, so that it falls within the range defined by the upper limit V. H and the lower limit V L is determined.

[0081] If an exceptional case occurs in the magnetic sensor 102, the exceptional case detection signal Sa2 falls out of the range defined by the upper limit V H and the lower limit V L is determined. In the Fig. In example 13, the value of the exceptional case detection signal Sa2 is less than the lower limit V. L If one of the MR elements 50 in the MR group R111 or R121 is short-circuited to cause an exceptional case in the magnetic sensor 102, the value of the exceptional case detection signal Sa2 will be greater than the upper limit V H , in contrast to the one in Fig. Example 13 illustrates this. This allows monitoring to determine whether the value of the exceptional case detection signal falls within the range defined by the upper limit V. H and the lower limit V L is specified, a detection of the occurrence of an exceptional case in the magnetic sensor 102.

[0082] The following is a description of a problem with the magnetic sensor system of the comparison example that can arise when a change in the size of a division is caused by changing the scale without changing the configuration of the first and second sensing units 110 and 120. Here, it is assumed that scale 1 is changed to scale 101. Fig. Figure 14 is a side view showing the scale 101 and the first and second detection units 110 and 120. The scale 101 is a multipole magnetized magnet 105 with several pairs of N and S poles arranged alternately in a circumferential direction, like the magnet 5. A division of the magnet 105 is specified as an angle β, which is smaller than the angle α in the case of the magnet 5.

[0083] The first and second recording units 110 and 120 are arranged in positions that are the same as those in Fig. Figure 11 is shown. Consequently, the position difference, i.e., the difference between the first position P101 and the second position P102 in the first direction D1, is greater than 1 / 2 of a division β of magnet 105. Fig. 11. The position difference is equal to an electrical angle of 180° between the first and second detection signals S101 and S102. Fig. 14 the position difference is equal to an electrical angle of 188° of the first and second detection signals S101 and S102.

[0084] It will now be on Fig. 15 Reference is made to describe the exceptional case detection signal resulting from the use of scale 101 in the magnetic sensor system of the comparison example. Fig. Figure 15 is a waveform diagram showing the exceptional detection signal under normal conditions and that under abnormal conditions when scale 101 is used in the magnetic sensor system of the comparison example. Fig. 15, the horizontal axis represents the electrical angle of the first and second detection signals S101 and S102, while the vertical axis represents the potential of the exceptional case detection signal. Furthermore, in Fig. 15. Reference symbol Sa3 denotes the waveform of the exceptional circumstances signal under normal conditions when scale 101 is used, and reference symbol Sa4 denotes the waveform of the exceptional circumstances signal under abnormal conditions when scale 101 is used. The upper limit V H and the lower limit V L as in Fig. 13 shown are in Fig. 15 is shown in the same way.

[0085] As in Fig. As shown in Figure 15, the value of the exceptional case detection signal Sa3 is not constant under normal conditions when using scale 101. In the example shown in Figure 15, the value of the exceptional case detection signal Sa3 is not constant under normal conditions. Fig. As shown in Figure 15, the value of the exceptional case detection signal Sa3 falls outside the range defined by the upper limit V under normal conditions. H and the lower limit V L The minimum value of the exceptional case detection signal Sa3 under normal conditions is less than the maximum value of the exceptional case detection signal Sa4 under abnormal conditions. Since, in this case, the range of the exceptional case detection signal Sa3 under normal conditions overlaps with the range of the exceptional case detection signal Sa4 under abnormal conditions, it is impossible to detect the occurrence of an exceptional case in the magnetic sensor 102 from the exceptional case detection signal.

[0086] Even if, in the case of the magnetic sensor system of the comparative example, the first and second detection units 110 and 120 are arranged at a distance of 1 / 2 division from each other according to a certain scale 1 (magnet 5), as described above, a change of scale 1 to another scale 101 (magnet 105), which differs from scale 1 by the size of one division, causes the position difference da not to correspond to the 1 / 2 division of scale 101. This leads to the problem that, even if no exceptional case exists in the magnetic sensor 102, the exceptional case detection signal does not have a constant value, and the range of the exceptional case detection signal under normal conditions overlaps with the range of the exceptional case detection signal under abnormal conditions, making it impossible to detect the occurrence of an exceptional case in the magnetic sensor 102.For the magnetic sensor system of the comparison example, a similar problem obviously arises when a division is increased by changing the scale.

[0087] In contrast, the first embodiment is designed such that the first position P1, where the first detection circuit 10 is located, and the second position P2, where the second detection circuit 20 is located, are the same in the first direction D1. Consequently, even if the scale 1 is changed to a different scale that differs from scale 1 by the size of one division, the phase difference of the second detection signal S2 with respect to the first detection signal S1 remains the same, so that the exceptional case detection signal Sa has a constant value under normal conditions. The first embodiment thus enables the detection of the occurrence of an exceptional case in the magnetic sensor 2 from the exceptional case detection signal Sa, regardless of the size of one division.

[0088] Even if, as described later in reference to another embodiment, the first position P1 and the second position P2 are different in the first direction D1, it is possible to detect the occurrence of an exceptional case in the magnetic sensor 2 from the exceptional case detection signal Sa if the position difference or the difference between the first position P1 and the second position P2 in the first direction D1 is 1.25% of a division or less. [Second embodiment]

[0089] A second embodiment of the invention is now described with reference to Fig. 16 and Fig. 17 described. Fig. Figure 16 is a perspective view showing the general configuration of a magnetic sensor system according to the second embodiment. Fig. Figure 17 is an explanatory diagram showing the operation of the magnetic sensor system according to the second embodiment.

[0090] The configuration of the magnetic sensor system according to the second embodiment differs from that of the magnetic sensor system according to the first embodiment in the following way. In the magnetic sensor system according to the second embodiment, the scale 1 is a rotating body that rotates about a predetermined central axis C, as in the first embodiment; however, the rotating body of the second embodiment is a gear 6 with teeth 6a formed from a magnetic material. The magnetic sensor 2 is arranged such that it faces the outer circumferential surface of the gear 6.

[0091] The magnetic sensor system according to the second embodiment includes a magnet 7 with a fixed position ratio with the magnetic sensor 2. Fig. Figure 16 shows an example in which the magnet 7 with the magnetic sensor 2 is arranged between the magnet 7 and the gear 6. The N pole of the magnet 7 points towards the gear 6. Fig. 17 The arrows labelled MF7 indicate a magnetic flux generated by magnet 7.

[0092] The first detection circuit 10 of the magnetic sensor 2 is arranged at a first position P1 and detects a first magnetic field MF1 applied to the first detection circuit 10. The second detection circuit 20 of the magnetic sensor 2 is arranged at a second position P2 and detects a second magnetic field MF2 applied to the second detection circuit 20. In the second embodiment, both the first and the second magnetic fields MF1 and MF2 are generated by the magnet 7 and change their direction while the gear 6 rotates. Fig. The hollow arrows labeled MF1 and MF2 indicate the direction of the first and second magnetic fields MF1 and MF2, respectively. The direction of the first and second magnetic fields MF1 and MF2 corresponds to the direction of the magnetic flux MF7 as it passes through the first and second detection circuits 10 and 20.

[0093] As described in the section on the first embodiment, a division is the extent of a change in the relative positional relationship between the scale 1 and the magnetic sensor 2, which changes the direction of both the first magnetic field MF1 and the second magnetic field MF2 by one period. In the second embodiment, a division is specified as an angle in the direction of rotation of the rotating body or the gear 6. In particular, a division is the angle formed by two straight lines connecting the central axis C to the centers of two adjacent teeth 6a of the gear 6. Fig. In Figure 16, the aforementioned straight lines are represented as dashed lines, and the angle formed by the two straight lines is denoted by the symbol γ. In the Fig. In the example shown in Figure 16, the angle γ is 15°. In this example, a rotation of the gear 6 causes the direction of both the first magnetic field MF1 and the second magnetic field MF2 to change by 24 periods. One period of the first and second detection signals S1 and S2, i.e., an electrical angle of 360°, corresponds to 1 / 24 of a rotation of the gear 6, i.e., a 15-degree angle of rotation of the gear 6.

[0094] The first position P1 and the second position P2 are the same in the first direction D1. As described in the section on the first embodiment, it is necessary that the position difference, i.e., the difference between the first position P1 and the second position P2 in the first direction D1, be 1.25% of a division or less. Since in the Fig. In the example shown in Figure 16, if a division or the angle γ is 15°, the position difference must be 0.1875° or less. Since, in the second embodiment, the first position P1 and the second position P2 are the same in the first direction D1, the position difference is 0° and thus fulfills the aforementioned requirement. In the example shown in Figure 16, the position difference is 0°. Fig. In the 16 illustrated example, the first position P1 and the second position P2 are different in a direction parallel to the central axis C.

[0095] Parts (a), (b), (c) and (d) of Fig. Figure 17 shows four relative positional relationships between the scale 1 and the magnetic sensor 2. Part (a) shows a state in which the center of one of the teeth 6a of the gear 6 is closest to the magnet 7. Part (b) shows a state in which the gear 6 has been rotated 3° counterclockwise from the state shown in Part (a). Part (c) shows a state in which the gear 6 has been rotated 4.5° counterclockwise from the state shown in Part (b), that is, the gear 6 has been rotated 1 / 2 division (7.5°) counterclockwise from the state shown in Part (a). Part (d) shows a state in which the gear 6 has been rotated 4.5° counterclockwise from the state shown in Part (c).

[0096] Both the first and second magnetic fields MF1 and MF2 change their direction as follows when the gear 6 rotates. Here, attention is focused on two adjacent teeth 6a1 and 6a2 of the gear 6. In the states shown in parts (a) and (b) of Fig. As shown in Figure 17, the distance between tooth 6a1 and magnet 7 is smaller than the distance between tooth 6a2 and magnet 7. In the state shown in part (c) of Fig. As shown in Figure 17, the distance between tooth 6a1 and magnet 7 is equal to the distance between tooth 6a2 and magnet 7. In the state shown in part (d) of Fig. As shown in Figure 17, the distance between tooth 6a2 and magnet 7 is smaller than the distance between tooth 6a1 and magnet 7.

[0097] First, in the state described in part (a) of Fig. As shown in Figure 17, the first and second magnetic fields MF1 and MF2 are oriented in the direction from the first and second positions P1 and P2 towards tooth 6a1, that is, in the downward direction. Fig. 17. When gear 6 then rotates into the state described in part (b) of Fig. As shown in Figure 17, the first and second magnetic fields MF1 and MF2 are oriented in the direction from the first and second positions P1 and P2 towards tooth 6a1, that is, in the downward left direction. Fig. 17. When gear 6 then rotates into the state described in part (c) of Fig. As shown in Figure 17, the first and second magnetic fields MF1 and MF2 are oriented in the direction from the first and second positions P1 and P2 to the midpoint between tooth 6a1 and tooth 6a2, that is, in the downward direction. Fig. 17. When gear 6 then rotates into the state described in part (d) of Fig. As shown in Figure 17, the first and second magnetic fields MF1 and MF2 are oriented in the direction from the first and second positions P1 and P2 towards tooth 6a2, that is, in the downward right direction. Fig. 17.

[0098] In this way, the first and second magnetic fields MF1 and MF2 change direction as the gear 6 rotates, so that from the first and second positions P1 and P2 they are oriented towards tooth 6a, which is the shortest distance from magnet 7. In the example shown in Fig. As shown in Figure 17, the direction of both the first and second magnetic fields MF1 and MF2 changes periodically from the downward direction to the direction downwards to the left, then to the downward direction and then to the direction downwards to the right in this sequence.

[0099] The first detection circuit 10, for example, detects the strength of a component of the first magnetic field MF1 in the horizontal direction in Fig. 17 and outputs a first detection signal indicating the strength. The second detection circuit 20, for example, detects the strength of a component of the second magnetic field MF2 in the horizontal direction in Fig. 17 and outputs a second detection signal indicating the strength. The second detection signal has a phase difference of 180° with respect to the first detection signal.

[0100] The remaining configurations, functions and effects of the second embodiment are similar to those of the first embodiment. [Third embodiment]

[0101] A third embodiment of the invention is now described with reference to Fig. 18 described. Fig. Figure 18 is a circuit diagram showing an example of the circuit configuration of a magnetic sensor system according to the third embodiment. In the third embodiment, the magnetization directions of the magnetized layers of the MR elements 50 contained in the second detection circuit 20 are opposite to those in the first embodiment. In particular, as shown in Fig. As shown in Figure 18, in the second detection circuit 20, the magnetized layers of the MR elements 50 contained in the MR element group R21 are magnetized in the X direction, and the magnetized layers of the MR elements 50 contained in the MR element group R22 are magnetized in the -X direction. In the third embodiment, the phase difference of the second detection signal S2 with respect to the first detection signal S1 is 0°.

[0102] Fig. Figure 18 shows a computing unit 30, which is designed in the same way as the computing unit 30 shown in Fig. Figure 6 is shown, which was described in the section on the first embodiment. However, the content of the calculation by the computer unit 30 in the third embodiment differs from that in the first embodiment. The computer circuit 31 generates the exceptional case detection signal Sa by calculation using the first and second detection signals S1 and S2. In the third embodiment, the calculation for generating the exceptional case detection signal Sa includes determining the difference between the first detection signal S1 and the second detection signal S2. In particular, the computer circuit 31 generates, for example, the difference between the first detection signal S1 and the second detection signal S2, that is, S1 minus S2, plus an offset voltage of a predetermined value, as the exceptional case detection signal Sa.Furthermore, the computer circuit 32 generates, for example, the sum of the first detection signal S1 and the second detection signal S2 divided by 2 as the third detection signal Sb.

[0103] The rotating body, which serves as the scale 1 of the third embodiment, can be the magnet 5 described in the section on the first embodiment, or the gear 6 described in the section on the second embodiment. Furthermore, the computing unit 30 of the third embodiment can be designed in the same way as the one described in Fig. Figure 7 shows the computer unit 30, which is described in the section on the first embodiment. The remaining configurations, functions, and effects of the third embodiment are similar to those of the first or second embodiment. [Fourth embodiment]

[0104] A fourth embodiment of the invention will now be described. First, the configuration of a magnetic sensor system according to the fourth embodiment will be described with reference to Fig. 19 and Fig. 20 described. Fig. Figure 19 is a perspective view showing the general configuration of the magnetic sensor system according to the fourth embodiment. Fig. Figure 20 is a side view showing the scale and the first and second detection circuits of the fourth embodiment.

[0105] The configuration of the magnetic sensor system according to the fourth embodiment differs from that of the magnetic sensor system according to the first embodiment in the following way. In the fourth embodiment, as in Fig. 19 and Fig. As shown in Figure 20, the first position P1 and the second position P2 are different in the first direction D1. It should be noted that in Fig. 19. The distance between the first position P1 and the second position P2 is exaggerated for better understanding. In the example given in Fig. As shown in Figure 20, the first position P1 and the second position P2 are different in the X-direction but the same in the Z-direction. Although not shown, the first position P1 and the second position P2 are the same in the Y-direction.

[0106] Both the first detection circuit 10 and the second detection circuit 20 contain the MR elements 50, which are described in the section on the first embodiment (see Fig. 5) For example, the first and second detection circuits 10 and 20 are arranged such that the plane of the layers forming the MR elements 50 contained therein is perpendicular to a straight line connecting the central axis C with the midpoint between the first and second positions P1 and P2.

[0107] Fig. Figure 20 shows the angle α, which represents a division of the magnet 5. Here, the position difference, or the difference between the first position P1 and the second position P2 in the first direction D1, is denoted by the symbol dp. In the fourth embodiment, the position difference dp is defined by an angle in the direction of rotation of the rotating body or magnet 5, the angle being formed by two straight lines connecting the central axis C to the first and second positions P1 and P2. It is necessary that the position difference dp be 1.25% of a division or less. For example, if, as in the first embodiment, the angle α is 30°, the position difference dp must be 0.375° or less.

[0108] Since the multipole magnetized magnet 5 must be magnetized such that the N and S poles are arranged alternately in a circumferential direction, the distance between the centers of two adjacent N poles on the outer circumferential surface of the magnet 5 must be of a certain size. In practice, a sufficient distance between the centers of two adjacent N poles is expected to be 4 mm or greater. Assuming that the distance between the centers of two adjacent N poles is 4 mm, the distance between the first position P1 and the second position P2 in the fourth embodiment must be 50 µm or less. As described in the section on the first embodiment, the MR elements 50, which are included in both the first and second detection circuits 10 and 20, are MR spin-valve elements. The MR spin-valve elements 50 allow for a significant reduction in footprint compared to anisotropic magnetoresistive elements.Therefore, if, according to the fourth embodiment, the distance between the centers of two adjacent N-poles or the size of a division falls within a practical range, it is possible to arrange the first and second sensing circuits 10 and 20 such that the position difference dp is 1.25% of a division or less. Even if the distance between the centers of two adjacent N-poles is less than 4 mm, offsetting the first and second sensing circuits 10 and 20 relative to each other in the Z-direction, as in the first embodiment, allows the first and second sensing circuits 10 and 20 to be arranged such that the position difference dp is 1.25% of a division or less.

[0109] The configurations of the first and second detection circuits 10 and 20 are now described with reference to Fig. 21 described.

[0110] Fig. Figure 21 is a top view showing the first and second detection circuits 10 and 20. The arrangement of the first and second detection circuits 10 and 20 in the fourth embodiment differs from that in the first embodiment. As shown in Fig. As shown in Figure 21, the first detection circuit 10 and the second detection circuit 20 are arranged side by side in the X direction. The MR element group R11 and the MR element group R12 of the first detection circuit 10 are arranged side by side in the Z direction. The MR element group R21 and the MR element group R22 of the second detection circuit 20 are arranged side by side in the Z direction.

[0111] The first detection circuit 10 detects the strength of a component of the first magnetic field MF1 in a direction parallel to the X and -X directions and outputs a first detection signal S1 indicating the strength. The second detection circuit 20 detects the strength of a component of the second magnetic field MF2 in a direction parallel to the X and -X directions and outputs a second detection signal S2 indicating the strength. Since, in the fourth embodiment, the first position P1 and the second position P2 differ in the first direction D1, the first magnetic field MF1 and the second magnetic field MF2 are oriented in opposite directions, so that the phase difference of the second detection signal S2 with respect to the first detection signal S1 is not 180°.

[0112] The exceptional case detection signal Sa in the fourth embodiment is now described. The exceptional case detection signal Sa in the fourth embodiment is generated in the same way as in the first embodiment. In particular, for example, the sum of the first detection signal S1 and the second detection signal S2, divided by 2, is generated as the exceptional case detection signal Sa in the fourth embodiment. Since, in the fourth embodiment, the phase difference of the second detection signal S2 with respect to the first detection signal S1 is not 180°, the exceptional case detection signal Sa does not have a constant value, even if neither the first nor the second detection circuit 10 and 20 exhibits an exceptional case.However, if the position difference dp is 1.25% of a division or less, and the phase difference of the second detection signal S2 with respect to the first detection signal S1 falls within the range of 175.5° to 184.5°, it is possible to detect the occurrence of an exceptional case in the first or second detection circuit 10 or 20 from the exceptional case detection signal Sa. This is described in detail below.

[0113] First, the focus will be on Fig. Reference is made to paragraph 22 to describe the relationship between the position difference dp and the phase difference of the second detection signal S2 with respect to the first detection signal S1. Fig. Figure 22 are characteristic curves that show the relationship between the position difference dp and the phase difference of the second detection signal S2 with respect to the first detection signal S1. Fig. Figure 22 represents the horizontal axis dp / α, that is, the position difference dp divided by the angle α, while the vertical axis represents the phase difference of the second detection signal S2 with respect to the first detection signal S1. Fig. 22 dp / α is given as a percentage. Fig. Figure 22 shows an example of the case where the magnet 5 rotates in the direction from the first position P1 to the second position P2.

[0114] As from Fig. As can be seen in Figure 22, if the angle α in the example above is constant, the phase difference of the second detection signal S2 with respect to the first detection signal S1 is greater than 180°, and the difference between the phase difference and 180° increases with increasing position difference dp if the position difference dp is greater than 0. If the magnet 5 rotates in the direction from the second position P2 to the first position P1, the phase difference of the second detection signal S2 with respect to the first detection signal S1 is less than 180°, and the difference between the phase difference and 180° increases with increasing position difference dp if the position difference dp is greater than 0.

[0115] An example of the exceptional case determination signal will now be given with reference to Fig. 23 described. Fig. Figure 23 is a waveform diagram showing an example of the exceptional case detection signal under normal conditions and that under abnormal conditions. Fig. 23 The horizontal axis represents the electrical angle of the first and second detection signals S1 and S2, while the vertical axis represents the potential of the exceptional case detection signal. Furthermore, in Fig. 23. The reference symbol Sa5 denotes the exceptional case detection signal under normal conditions, the reference symbol Sa6 denotes the exceptional case detection signal under abnormal conditions, the reference symbol Va denotes the minimum value of the exceptional case detection signal Sa5, and the reference symbol Vb denotes the maximum value of the exceptional case detection signal Sa6. The exceptional case detection signal Sa6 under abnormal conditions in Fig. Figure 23 shows an example of the case where each of the MR element groups R11, R12, R21 and R22, which are in Fig. 21 are shown, contains twenty MR elements 50 and one of the MR elements 50 in the MR element group R12 or R22 is short-circuited to cause an exceptional case in the first or second detection circuit 10 or 20.

[0116] In the Fig. In the example shown in Figure 23, the exceptional detection signal Sa6 under abnormal conditions is of a lower value than the exceptional detection signal Sa5 under normal conditions. Furthermore, the minimum value Va of the exceptional detection signal Sa5 under normal conditions is greater than the maximum value Vb of the exceptional detection signal Sa6 under abnormal conditions, so that the range of the exceptional detection signal Sa5 under normal conditions does not overlap with the range of the exceptional detection signal Sa6 under abnormal conditions. Although not shown, if one of the MR elements 50 in the MR group R11 or R21 is short-circuited to cause an exceptional case in the first or second detection circuit 10 or 20, the exceptional detection signal Sa6 under abnormal conditions is of a higher value than the exceptional detection signal Sa5 under normal conditions, in contrast to the one shown in Figure 23. Fig. Example 23. In this case, the minimum value of the exceptional detection signal Sa6 under abnormal conditions is greater than the maximum value of the exceptional detection signal Sa5 under normal conditions, so that the range of the exceptional detection signal Sa5 under normal conditions does not overlap the range of the exceptional detection signal Sa6 under abnormal conditions.

[0117] If the range of the exceptional case detection signal Sa5 under normal conditions does not overlap the range of the exceptional case detection signal Sa6 under abnormal conditions as described above, it is possible to detect the occurrence of an exceptional case in the magnetic sensor 2 from the exceptional case detection signal, as in the first embodiment.

[0118] It will now be on Fig. 22 and Fig. 24 Referenced to describe the range of the phase difference of the second detection signal S2 with respect to the first detection signal S1 and the range of the position difference dp. Fig. Figure 24 shows the relationship between the minimum value Va of the exceptional case detection signal Sa5 under normal conditions and the maximum value Vb of the exceptional case detection signal Sa6 under abnormal conditions. Fig. Figure 24 represents the horizontal axis as the difference between 180° and the phase difference of the second detection signal S2 with respect to the first detection signal S1, which is subsequently referred to as the magnitude of a phase shift, while the vertical axis represents the minimum value Va and the maximum value Vb. The maximum value Vb in Fig. 24 was conducted under the same conditions as in the one in Fig. 23 examples are defined, with the exception of the extent of a phase shift.

[0119] As in Fig. As shown in Figure 24, with increasing magnitude of the phase shift, the minimum value Va decreases and the maximum value Vb increases. If the minimum value Va becomes equal to or less than the maximum value Vb, it becomes impossible to detect the occurrence of an exceptional case in magnetic sensor 2 from the exceptional case detection signal. Therefore, it is necessary that the magnitude of the phase shift has a value at which the minimum value Va is greater than the maximum value Vb. For the [unclear] in Fig. In example 24, the magnitude of the phase shift must be 4.5° or less.

[0120] As previously described, if one of the MR elements 50 in the MR element group R11 or R21 is short-circuited, causing an exceptional case in the first or second detection circuit 10 or 20, the exceptional case detection signal Sa6 receives a higher value under abnormal conditions than the exceptional case detection signal Sa5 under normal conditions. In this case, the magnitude of the phase shift increases, the maximum value of the exceptional case detection signal Sa5 under normal conditions rises, and the minimum value of the exceptional case detection signal Sa6 under abnormal conditions decreases.If the magnitude of a phase shift is 4.5° or less, then in this case too the maximum value of the exceptional case detection signal Sa5 under normal conditions is smaller than the minimum value of the exceptional case detection signal Sa6 under abnormal conditions, so that it is possible to detect the occurrence of an exceptional case in the magnetic sensor 2 from the exceptional case detection signal.

[0121] A phase shift of 4.5° is equivalent to a phase difference of 175.5° or 184.5° between the second detection signal S2 and the first detection signal S1. As shown in the dashed lines in Fig. As shown in Figure 22, a phase difference of 184.5° corresponds to a dp / α of 1.25%. Therefore, the position difference dp must be less than or equal to 1.25% of the angle α or a division, so that the phase difference falls within the range of 175.5° to 184.5°. Setting the position difference dp in this way allows the occurrence of an exceptional event in the magnetic sensor 2 to be detected from the exceptional event detection signal.

[0122] If an exceptional case occurs in the first or second detection circuit 10 or 20 due to an interruption inside one of the MR element groups R11, R12, R21 and R22, the difference between the central level of the exceptional case detection signal Sa5 under normal conditions and the central level of the exceptional case detection signal Sa6 under abnormal conditions is greater, that is, the range of the exceptional case detection signal Sa5 under normal conditions and the range of the exceptional case detection signal Sa6 under abnormal conditions overlap with a lower probability compared to the case where one of the MR elements 50 is short-circuited.Furthermore, if the number of MR elements 50 forming each of the MR element groups R11, R12, R21, and R22 decreases and the number of short-circuited MR elements 50 increases, the difference between the central level of the exceptional detection signal Sa5 under normal conditions and the central level of the exceptional detection signal Sa6 under abnormal conditions also increases; that is, the range of the exceptional detection signal Sa5 under normal conditions and the range of the exceptional detection signal Sa6 under abnormal conditions overlap with a lower probability. Typically, up to twenty MR elements 50 can be considered sufficient to form each of the MR element groups R11, R12, R21, and R22.Thus, a phase shift magnitude of 4.5° or less, determined under the conditions that the number of MR elements 50 forming each of the MR element groups R11, R12, R21 and R22 is twenty, and the number of short-circuited MR elements 50 is one, is a reasonable value as an acceptable phase shift magnitude.

[0123] In the fourth embodiment, the magnetized layers of the MR elements 50 contained in the second detection circuit 20 can be magnetized in the same directions as those in the third embodiment, so that the exceptional detection signal Sa and the third detection signal Sb can be generated by the same calculation as those in the third embodiment. In this case, the ratio between the position difference dp and the phase difference of the second detection signal S2 with respect to the first detection signal S1 is the same as that calculated in Fig. 22 is shown, except that each value is on the vertical axis of Fig. 22 is reduced by 180°. Furthermore, the ratio between the minimum value Va and the maximum value Vb is the same as that found in Fig. 24 is shown, with the exception that the phase difference of the second detection signal S2 with respect to the first detection signal S1 is the extent of a phase shift of Fig. 24. In order for the occurrence of an exceptional case in the magnetic sensor 2 to be detected from the exceptional case detection signal, it is therefore necessary that the phase difference of the second detection signal S2 with respect to the first detection signal S1 falls within the range of -4.5° to 4.5°.

[0124] The rotating body, which serves as scale 1 of the fourth embodiment, can be the gear 6 described in the section on the second embodiment. The remaining configurations, functions, and effects of the fourth embodiment are similar to those of the first through third embodiments. [Fifth embodiment]

[0125] A fifth embodiment of the invention is now described with reference to Fig. 25 described. Fig. Figure 25 is a perspective view showing the general configuration of a magnetic sensor system according to the fifth embodiment. The magnetic sensor system according to the fifth embodiment differs from that according to the first embodiment in the following way. In the magnetic sensor system according to the fifth embodiment, the scale 1 is a linear scale 8 with several pairs of N and S poles arranged alternately in a linear form. In the Fig. In the example shown in Figure 25, the linear scale 8 has a side surface 8a parallel to the direction in which the N and S poles are arranged. The magnetic sensor 2 is arranged such that it faces the side surface 8a of the linear scale 8.

[0126] Either the linear scale 8 or the magnetic sensor 2 moves linearly in response to the motion of a moving object (not shown). This changes the relative position ratio between the scale 1 and the magnetic sensor 2. The magnetic sensor system detects the relative position and / or velocity of the linear scale 8 with respect to the magnetic sensor 2 as the physical quantity related to the relative position ratio between the scale 1 and the magnetic sensor 2. The first direction D1 in which the relative position ratio between the scale 1 and the magnetic sensor 2 changes is the direction in which the N and S poles of the linear scale 8 are oriented.

[0127] The first detection circuit 10 of the magnetic sensor 2 is arranged at a first position P1 and detects a first magnetic field applied to the first detection circuit 10. The second detection circuit 20 of the magnetic sensor 2 is arranged at a second position P2 and detects a second magnetic field applied to the second detection circuit 20. The first position P1 and the second position P2 are the same in the first direction D1. In the Fig. In the example shown in Figure 25, the first position P1 and the second position P2 are the same in a direction orthogonal to the side surface 8a and are in the vertical direction in Fig. 25 different ones.

[0128] In the fifth embodiment, both the first and second magnetic fields are generated by the linear scale 8 and change their direction as the linear scale 8 moves. Although not shown, the direction of the first magnetic field rotates around the first position P1 in a plane perpendicular to the side face 8a and parallel to the first direction D1. The direction of the second magnetic field rotates around the second position P2 in the plane perpendicular to the side face 8a and parallel to the first direction D1.

[0129] As described in the section on the first embodiment, a division is the extent of a change in the relative positional relationship between the scale 1 and the magnetic sensor 2, which changes the direction of both the first and second magnetic fields by one period. In the fifth embodiment, a division is the distance L between the centers of two adjacent N poles of the linear scale 8.

[0130] Both the first detection circuit 10 and the second detection circuit 20 contain the MR elements 50, which are described in the section on the first embodiment (see Fig. 5) The first and second detection circuits 10 and 20 are arranged such that the plane of the layers formed by the MR elements 50 contained therein is parallel to the side surface 8a of the linear scale 8.

[0131] The first and second detection circuits 10 and 20 of the fifth embodiment can be designed in the same way as the one described in Fig. 4. Example shown, which is described in the section on the first embodiment. In this case, the first and second detection circuits 10 and 20 can be arranged such that the first direction D1 of the fifth embodiment runs parallel to the X-direction, which in Fig. 4 is shown, and that the direction is orthogonal to the side surface 8a of the linear scale 8 and parallel to the Y-direction, which is shown in Fig. 4 is shown. Furthermore, according to the fifth embodiment, the magnetic sensor system can have the same circuit design as the one shown in Fig. 6 or Fig. The 7 illustrated example is described in the section on the first embodiment.

[0132] Furthermore, in the fifth embodiment, the magnetized layers of the MR elements 50 contained in the second detection circuit 20 can be magnetized in directions that are the same as those in the example of Fig. 18 are as described in the section on the third embodiment, so that the exceptional case detection signal Sa and the third detection signal Sb can be generated by the same calculation as in the third embodiment. The remaining configurations, functions, and effects of the fifth embodiment are similar to those of the first or third embodiments. [Sixth embodiment]

[0133] A sixth embodiment of the invention is now described with reference to Fig. 26 described. Fig. Figure 26 is a perspective view showing the general configuration of a magnetic sensor system according to the sixth embodiment. Differences between the magnetic sensor system according to the sixth embodiment and the magnetic sensor system according to the fifth embodiment are described below. In the sixth embodiment, as shown in Fig. As shown in Figure 26, the first position P1 and the second position P2 are different in the first direction D1. In the figure shown in Fig. In the example shown, the first position P1 and the second position P2 are in the direction orthogonal to the side surface 8a of the linear scale 8 and in the vertical direction in Fig. 26 of the same.

[0134] As in the fourth embodiment, the position difference dp, i.e., the difference between the first position P1 and the second position P2 in the first direction D1, is less than or equal to 1.25% of a division or distance L.

[0135] The first and second detection circuits 10 and 20 of the sixth embodiment can be designed in the same way as the one described in Fig. The example shown in Figure 21, which is described in the section on the fourth embodiment, is shown. In this case, the first and second detection circuits 10 and 20 can be arranged such that the first direction D1 of the sixth embodiment is parallel to the X-direction shown in Figure 21. Fig. 21 is shown, and that the direction is orthogonal to the side surface 8a of the linear scale 8 and parallel to the Y-direction, which is shown in Fig. 21 is shown.

[0136] The remaining configurations, functions and effects of the sixth embodiment are similar to those of the fourth or fifth embodiment.

[0137] The present invention is not limited to the preceding embodiments and various modifications can be made to it. For example, provided the requirements of the appended claims are met, the arrangement of the first and second detection circuits 10 and 20 is not limited to the examples shown in the preceding embodiments, but can be chosen as desired. For example, the first detection circuit 10 and the second detection circuit 20 can be stacked on top of each other.

Claims

[1] Magnetic sensor system comprising a scale and a magnetic sensor arranged in a relative position ratio which is variable in a first direction, wherein the magnetic sensor system is designed to detect a physical quantity related to the relative position ratio between the scale and the magnetic sensor, characterized by , that The magnetic sensor includes a first detection circuit located at a first position and a second detection circuit located at a second position. The first detection circuit outputs a first detection signal that varies depending on a first magnetic field applied to the first detection circuit. The second detection circuit outputs a second detection signal that varies depending on a second magnetic field applied to the second detection circuit. Both the first and second detection circuits contain several magnetoresistive elements connected in series, Each of the several magnetoresistive elements contains: a magnetized layer with a magnetization in a fixed direction; a free layer with a magnetization that varies depending on an applied magnetic field; and a tunnel barrier layer located between the magnetized layer and the free layer. Both the first and the second magnetic fields periodically change their direction in response to a change in the relative positional relationship between the scale and the magnetic sensor, and the first position and the second position differ from each other by 1.25% of a division or less, where a division is a measure of change in the relative positional ratio between the scale and the magnetic sensor, which changes the direction of both the first and second magnetic fields by one period, wherein the magnetic sensor system further comprises a computing unit which generates an exception detection signal indicating the occurrence of an exception in the magnetic sensor by calculation using the first detection signal and the second detection signal, wherein the exception includes an event occurring in the first or second detection circuit due to a short circuit between the magnetized layer and the free layer in one or more of the plurality of magnetoresistive elements included in the first or second detection circuit, and wherein the computing unit further determines the presence of the exception in the magnetic sensor by introducing and monitoring an upper and a lower limit for the value of the exception detection signal, within which it can be determined that neither the first nor the second detection circuit exhibits any exception.whether the exceptional case determination signal falls within the range defined by the upper and lower limits. [2] Magnetic sensor system according to claim 1, wherein the second detection signal has a phase difference of 175.5° to 184.5° with respect to the first detection signal and The calculation by the computer unit involves determining the sum of the first and second detection signals. [3] Magnetic sensor system according to claim 1, wherein the second detection signal has a phase difference of -4.5° to 4.5° with respect to the first detection signal and The calculation by the computer unit involves determining a difference between the first detection signal and the second detection signal. [4] Magnetic sensor system according to claim 1, wherein the first position and the second position in the first direction are the same. [5] Magnetic sensor system according to one of claims 1 to 4, wherein the scale is a body of revolution that rotates around a predetermined central axis, The rotation of the rotating body changes the relative position ratio between the scale and the magnetic sensor. the first direction is a direction of rotation of the rotating body, and where one division is specified as an angle in the direction of rotation of the rotating body. [6] Magnetic sensor system according to claim 5, wherein the body of revolution has several pairs of N and S poles arranged alternately in a circumferential direction, Both the first and second magnetic fields are generated by the rotating body and change their direction as the rotating body rotates, and one division is an angle formed by two straight lines connecting the central axis to the centers of two adjacent N-poles of the body of revolution. [7] Magnetic sensor system according to claim 5, wherein the rotating body is a gear with teeth made of a magnetic material, The magnetic sensor system further comprises a magnet with a fixed position relative to the magnetic sensor. Both the first and second magnetic fields are generated by the magnet and change their direction as the gear rotates, and one division is an angle formed by two straight lines connecting the central axis to the centers of two adjacent teeth. [8] Magnetic sensor system according to any one of claims 1 to 4, wherein the scale has several pairs of N and S poles arranged alternately in a linear form, the first direction is a direction in which the N and S poles of the scale are arranged, Both the first and second magnetic fields are generated by the scale and where one division is a distance between the centers of two adjacent N-poles of the scale.

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