JP2018084514A - Sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor device that can suppress a fall in accuracy of detection due to aging of a magnetoresistive element.SOLUTION: A sensor device 1 comprises: a first bridge 10 that is composed of each of half bridges 11a and 11b; an output switch circuit 30 that detects an angle detection signal indicative of a potential difference in midpoint potential between each of the half bridges 11a and 11b; and a computation output circuit 60 that outputs a computation result of the angle detection signal detected by the output switch circuit 30. In each of the half bridges 11a and 11b, each of detection resistance RR1 and RR2 is parallel-series connected, respectively. The output switch circuit 30 is configured to detect each electric current value-purpose detection signal, and each resistance value-purpose detection signal in addition to detection of the angle detection signal. The computation output circuit 60 is configured to set a correction value on the basis of each electric current value-purpose detection signal, and each resistance value-purpose detection signal, and compute a computation result, using a post-corrected angle detection signal having the correction value overlapped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor device.

  The midpoint potential of the pair of half-bridge circuits is detected by using a full-bridge circuit configured by arranging a pair of half-bridge circuits in which two magnetoresistive elements are connected in series between the power source and the ground. As a sensor apparatus, there exists a thing of patent document 1, for example.

  In the sensor device of Patent Document 1, two full bridge circuits are used to detect the angular position (rotational angle) of the rotating body with the rotating body as a detection target. The resistance values of the magnetoresistive elements of the two full-bridge circuits change when the detection target rotates, and changes in the resistance values appear as changes in the midpoint potential. That is, the change in the midpoint potential changes according to the angular position of the detection target.

JP2015-94724A

  Normally, the sensor device is designed so that the resistance values of the magnetoresistive elements facing each other in the full-bridge circuit match, the current values match between the pair of half-bridge circuits, and these relationships are satisfied. Is done. However, when the resistance value of the magnetoresistive element changes, the initial design relationship is shifted. As this cause, for example, a change in resistance value due to aging of the magnetoresistive element can be considered. In this case, there is a concern about a decrease in detection accuracy of the sensor device.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sensor device capable of suppressing a decrease in detection accuracy due to aged deterioration of a magnetoresistive element.

  A sensor device that solves the above problem includes a first half-bridge circuit in which two magnetoresistive elements are connected in series, and a second half-bridge circuit in which two magnetoresistive elements are connected in series. Are arranged in parallel between the power source and the ground, a detection circuit for detecting a detection signal indicating a potential difference of the midpoint potential of each half-bridge circuit, and the detection detected by the detection circuit An arithmetic output circuit for outputting a calculation result of the signal, and the first half-bridge circuit includes a first current detection unit for detecting a first current value flowing through the first half-bridge circuit. A resistor is connected in series, and a second current detection resistor for detecting a second current value flowing through the second half bridge circuit is connected in series to the second half bridge circuit. In addition to detecting the detection signal, the detection circuit detects a first current value detection signal indicating the first current value and a second current value indicating the second current value. Detection signal, and each resistance value detection signal indicating the resistance value of each magnetoresistive element is detected, and the arithmetic output circuit includes the first current value detection signal and the second current value. Based on the detection signal for value and the detection signal for each resistance value, a correction value for correcting the detection signal is set, and the calculation result is calculated using the corrected detection signal on which the correction value is superimposed. I try to calculate.

  Here, the change in the resistance value due to the aging of the magnetoresistive element as described in the above [Problems to be solved by the invention] not only appears as a deviation of the initial design of the resistance value of each magnetoresistive element. This also appears as a deviation in the initial design of the current value of each half-bridge circuit.

  On the other hand, in the above configuration, the resistance value of each magnetoresistive element can be detected by detecting each resistance value detection signal. Further, the current value of each half bridge circuit can be detected by detecting the first current value detection signal and the second current value detection signal. Thereby, it is possible to detect a deviation in the relationship of the magnetoresistive elements at the time of detection of the detection signal with respect to the initial design based on each resistance value detection signal. Further, a deviation in the relationship between the current values of the half-bridge circuits at the time of detection of the detection signal with respect to the initial design can be detected based on each current value detection signal.

  Then, a correction value is set for the deviation of the relationship, and the detection signal can be corrected with respect to a change in the resistance value of the magnetoresistive element from the initial design. Therefore, even if the resistance value of the magnetoresistive element changes from the initial design, the calculation result can be calculated using the corrected detection signal that corrects the deviation in the relationship at the initial design. A decrease in detection accuracy due to deterioration over time can be suppressed.

  In the sensor device, each half bridge circuit detects a midpoint potential detection circuit for detecting a midpoint potential of each halfbridge circuit, and detects the first current value and the second current value. A switching circuit for switching so that a current value detection circuit for detecting the resistance value and a resistance value detection circuit for detecting the resistance value of each magnetoresistive element are configured, and the detection circuit is connected to the switching circuit. Is switched, in addition to detecting the detection signal through the midpoint potential detection circuit, the first current value detection signal and the second current value detection through the current value detection circuit. It is desirable to detect a detection signal and detect each of the resistance value detection signals through the resistance value detection circuit.

  According to the above configuration, by switching the full bridge circuit, each detection signal for each current value and each detection signal for each resistance value necessary for correcting the detection signal can be detected together with the detection signal. As a result, the detection of each other signal is prevented from interfering with the detection of other signals. Therefore, various detection signals can be detected suitably.

  In the sensor device, the first resistance detection signal of the first magnetoresistive element of the first half bridge circuit and the first magnetoresistive element of the second half bridge circuit The first initial value set as the reference value of the difference between the fourth resistance value detection signals of the fourth magnetoresistive elements facing each other and the first magnetoresistive element of the first half-bridge circuit A second resistance value detection signal of a different second magnetoresistive element and a third resistance value of the third magnetoresistive element facing the second magnetoresistive element of the second half bridge circuit Set as a reference value for a difference between a second initial value set as a reference value for a difference from the detection signal for the first current value, a detection signal for the first current value, and a detection signal for the second current value. A storage unit for storing a third initial value; The circuit includes a first difference value that is a difference between the first resistance value detection signal and the fourth resistance value detection signal, the second resistance value detection signal, and the third resistance value detection signal. A second difference value that is a difference from the resistance value detection signal, a third difference value that is a difference between the first current value detection signal and the second current value detection signal; Respectively calculating and setting a first correction value based on a change in the first difference value relative to the first initial value and a change in the third difference value relative to the third initial value; A second correction value is set based on a change in the second difference value with respect to the second initial value and a change in the third difference value with respect to the third initial value, and the first correction Calculating the calculation result using the corrected detection signal in which a value and the second correction value are superimposed on the detection signal Desirable.

  In the above configuration, the relationship between the resistance values of the first magnetoresistive element and the fourth magnetoresistive element facing each other in the full bridge circuit at the beginning of the design, and the resistance values of the second magnetoresistive element and the third magnetoresistive element. Therefore, the deviation in the relationship at the beginning of the design appears as the first difference value, the second difference value, and the third difference value when the detection signal is detected. Then, by storing each initial value indicating the initial design relationship in advance in the storage unit at the time of design, at least when each initial value is stored, the resistance value of the magnetoresistive element from the initial design is stored. The detection signal can be corrected. Accordingly, it is possible to suitably suppress a decrease in detection accuracy due to aging of the magnetoresistive element from the time when each initial value is stored.

  In the sensor device, the detection circuit detects the detection signal of the second half bridge circuit as a positive value, detects the detection signal of the first half bridge circuit as a negative value, and the arithmetic output circuit includes: Based on the change in the first difference value and the change in the third difference value, an increase or decrease in the resistance value of the first magnetoresistive element or the fourth magnetoresistive element is detected. When detecting an increase in one magnetoresistive element or the fourth magnetoresistive element, the first correction value is set so as to decrease the detection signal, while the first magnetoresistive element or the first magnetoresistive element When detecting the decrease of the magnetoresistive element 4, the first correction value is set so as to increase the detection signal, and the change of the second difference value and the change of the third difference value are set. Based on the second magnetoresistive element or the When the increase / decrease in the resistance value of the third magnetoresistive element is detected and the increase in the second magnetoresistive element or the third magnetoresistive element is detected, the second correction is performed so as to increase the detection signal. When a value is set while a decrease in the second magnetoresistive element or the third magnetoresistive element is detected, it is preferable to set the second correction value so as to decrease the detection signal.

According to the above configuration, if the detection signal uses the power supply voltage, the following equation:
S = (R4) / (R2 + R4) × E− (R3) / (R1 + R3) × E
(However, S: detection signal, R1-R4: resistance values of the first to fourth magnetoresistive elements, E: power supply voltage)
Can be expressed as

  For example, when the resistance value (R1) of the first magnetoresistive element or the resistance value (R4) of the fourth magnetoresistive element increases with respect to the above formula, the detection signal (S) increases with respect to the above formula. . In this case, the arithmetic output circuit sets the first correction value so as to decrease the detection signal (S) by the increase in the detection signal (S) with respect to the change in the resistance value.

  When the resistance value (R2) of the second magnetoresistive element or the resistance value (R3) of the third magnetoresistive element increases with respect to the above expression, the detection signal (S) decreases with respect to the above expression. . In this case, the arithmetic output circuit sets the second correction value so as to increase the detection signal (S) by the decrease of the detection signal (S) with respect to the change in resistance value.

Thus, with the above configuration, it is possible to suitably correct the influence of the change in the resistance value of the magnetoresistive element on the detection signal.
In the sensor device, the first current detection resistor and the second current detection resistor are between the power source and a magnetoresistive element adjacent to the power source, or between the ground and the magnetic field adjacent to the ground. It is desirable to connect between the resistance elements.

  According to the above configuration, the current detection resistors can be arranged symmetrically, and the symmetry of the circuit can be ensured. In this case, a full bridge circuit that can be relatively stable as a circuit and has symmetry in the first place is particularly effective.

  According to the present invention, it is possible to suppress a decrease in detection accuracy due to aged deterioration of the magnetoresistive element.

The figure which shows schematic structure of a sensor apparatus. The figure which shows the structure of the circuit for the midpoint potential detection in the sensor apparatus. The figure which shows the structure of the circuit for the resistance value detection in the sensor apparatus. The figure which similarly shows the structure of the circuit for resistance value detection. The figure which shows the structure of the circuit for the electric current value detection in the sensor apparatus. The flowchart which shows the flow of the detection process which the calculation output circuit performs in the sensor apparatus. (A), (b) is a table | surface explaining the aspect that the calculation output circuit sets a correction value.

Hereinafter, an embodiment of the sensor device will be described.
As shown in FIG. 1, the sensor device 1 detects, for example, a rotating body such as a steering shaft of a vehicle as a detection target, and detects a change in magnetism of a bias magnet attached to the rotating body, thereby detecting the angle of the rotating body. Used to detect the position.

  The sensor device 1 outputs a sensor IC 2 that outputs various sensor signals, and angle information θ, which is information indicating the angular position of the rotating body, as the calculation result of the sensor signals output from the sensor IC 2 (for example, vehicle control). And a microcomputer (hereinafter referred to as “microcomputer”) 3 for outputting to the apparatus. The sensor IC 2 includes a sensor chip 4 having a plurality of magnetoresistive elements, and an IC chip 5 that detects an electrical signal (voltage signal) from the sensor chip 4 and outputs it as a sensor signal to the microcomputer 3.

Here, the configuration of the sensor chip 4 will be described.
The sensor chip 4 includes a first bridge circuit (hereinafter referred to as “first bridge”) 10 and a second bridge circuit (hereinafter referred to as “second bridge”) 20. Each of the first bridge 10 and the second bridge 20 includes four magnetoresistive elements (M1 to M4, M5 to M8) arranged in a bridge shape.

  Specifically, the first bridge 10 includes a first magnetoresistive element (hereinafter referred to as “first magnetoresistance”) M1 and a third magnetoresistive element (hereinafter referred to as “third magnetoresistance”) M3 in series. A first half-bridge circuit (hereinafter referred to as “first half-bridge”) 11a is connected. The first bridge 10 includes a second magnetoresistive element (hereinafter referred to as “second magnetoresistance”) M2 and a fourth magnetoresistive element (hereinafter referred to as “fourth magnetoresistance”) M4 connected in series. A second half-bridge circuit (hereinafter referred to as “second half-bridge”) 11b is included. The first half bridge 11a and the second half bridge 11b are connected in parallel between the power supply V (power supply voltage E) and the ground G, respectively. The resistance values of the first magnetic resistance M1 and the fourth magnetic resistance M4 facing each other in the first bridge 10 are configured to match each other. Similarly, the resistance values of the second magnetic resistance M2 and the third magnetic resistance M3 facing each other in the first bridge 10 are designed to match each other. In this case, the first bridge 10 is designed so that the respective current values coincide between the half bridges 11a and 11b.

  The second bridge 20 has the same configuration as the first bridge 10, and the fifth to eighth magnetoresistive elements (fifth to eighth magnetoresistors) M5 to M5 correspond to the magnetoresistors M1 to M4. It has M8, and has third and fourth half bridge circuits (third and fourth half bridges) 21a and 21b so as to correspond to the half bridges 11a and 11b. In other words, the fifth magnetic resistor M5 and the eighth magnetic resistor M8 are designed to have the same resistance value, and the sixth magnetic resistor M6 and the seventh magnetic resistor M7 are designed to have the same resistance value. ing. In this case, the current values are designed to match between the half bridges 21a and 21b.

  The second bridge 20 is different from the first bridge 10 in that the corresponding magnetic resistances M5 to M8 are 45 ° counterclockwise in FIG. 1 with respect to the arrangement of the magnetic resistances M1 to M4. It is a point arranged in rotation.

  A first current detection resistor (hereinafter referred to as “first detection resistor”) RR1 is connected in series to the first half bridge 11a between the power source V and a first magnetic resistor M1 adjacent to the power source V. . In addition, a second current detection resistor (hereinafter referred to as “second detection resistor”) RR2 is connected in series between the power source V and a second magnetic resistor M2 adjacent to the power source V in the second half bridge 11b. Yes. Each of the detection resistors RR1 and RR2 is a so-called shunt resistor, and the resistance value is set to be sufficiently smaller than each of the magnetic resistors M1 to M4. In the second bridge 20, the detection resistors RR5 and RR6 corresponding to the detection resistors RR1 and RR2 are connected to the half bridges 21a and 21b, respectively.

  The first bridge 10 has a plurality (six in this embodiment) of detection points P0 to P5, and an electric signal corresponding to the potential of each of the detection points P0 to P5 is detected by the IC chip 5, respectively. It is configured. For example, at the detection point P3, the potential at the connection point between the first magnetic resistance M1 and the third magnetic resistance M3 is detected. Further, at the detection point P4, the potential at the connection point between the second magnetic resistance M2 and the fourth magnetic resistance M4 is detected. The second bridge 20 has detection points P6 to P11 corresponding to the detection points P0 to P5.

  In the first bridge 10, a first switching circuit 13 is connected to the first half bridge 11a. The second switching circuit 14 is connected to the second half bridge 11b. The first switching circuit 13 connects (ON) or shuts off (OFF) the voltage dividing resistor R connected to the power source V and the detection point P3 via the switch SW1 and also connects to the ground G. R and the detection point P3 are connected (ON) or disconnected (OFF) via the switch SW2. In addition, the second switching circuit 14 connects (ON) or disconnects (OFF) the voltage dividing resistor R connected to the power source V and the detection point P4 via the switch SW3 and also connects to the ground G. The piezoelectric resistor R and the detection point P4 are connected (ON) or disconnected (OFF) via the switch SW4. In the present embodiment, the voltage dividing resistors R are set to the same resistance value. In the second bridge 20, the switching circuits 15 and 16 corresponding to the switching circuits 13 and 14 are connected to the half bridges 21a and 21b, and the switches SW5 to SW5 corresponding to the switches SW1 to SW4 are connected. SW8 is connected.

Next, the configuration of the IC chip 5 will be described.
The IC chip 5 includes an output switching circuit 30 that selectively switches and outputs an electrical signal detected by the sensor chip 4, an amplification circuit 40 that differentially amplifies the electrical signal output by the output switching circuit 30, and an amplified circuit. And a conversion circuit 50 for digitally converting (A / D conversion) the electrical signal. In the present embodiment, the output switching circuit 30 and the amplifier circuit 40 are examples of a detection circuit.

  The output switching circuit 30 detects electrical signals from the detection terminals t0 to t5 that detect electrical signals from the detection points P0 to P5 (first bridge 10) and from the detection points P6 to P11 (second bridge 20), respectively. Detection terminals t6 to t11. In addition, the output switching circuit 30 includes an output terminal t (+) connected to the non-inverting input terminal (“+”) of the amplifier circuit 40 so that an electrical signal can be output, and an inverting input terminal (−) of the amplifier circuit 40. And an output terminal t (−) connected to be capable of outputting an electrical signal. The detection terminals t0 to t11 are connected to the output terminals t (+) and t (−) via the corresponding switches SWt0 to SWt11.

  Specifically, each of the detection terminals t1 to t4 and t7 to t10 can be connected to one of the output terminals t (+) and t (−) via the corresponding switches SWt1 to SWt4 and SWt7 to SWt10, respectively. is there. The detection terminals t0 and t6 can be connected to the output terminal t (+) via the corresponding switches SWt0 and SWt6, respectively. The detection terminals t5 and t11 can be connected to the output terminal t (−) through the corresponding switches SWt5 and SWt11.

  The output switching circuit 30 selectively outputs electrical signals to the amplifier circuit 40 by selectively switching the switches SWt0 to SWt11. The electric signals output from the output terminals t (+) and t (−) are differentially amplified by the amplifier circuit 40 and output. The amplified electrical signal is digitally converted by the conversion circuit 50 and output as various sensor signals.

Next, the configuration of the microcomputer 3 will be described together with its function.
The microcomputer 3 includes an arithmetic output circuit 60 composed of a digital circuit, and a storage unit 70 that stores information necessary for arithmetic operations in the arithmetic output circuit 60.

  The arithmetic output circuit 60 controls switching of the switches SW1 to SW8 of the sensor chip 4 and controls switching of the switches SWt0 to SWt11 of the IC chip 5. Thereby, the arithmetic output circuit 60 acquires various sensor signals as necessary information from the sensor IC2.

  Angle detection signals S1 and S2 for calculating angle information θ are acquired as various sensor signals. The angle detection signal S1 is acquired as a potential difference between the midpoint potentials of the half bridges 11a and 11b of the first bridge 10. The angle detection signal S2 is acquired as a potential difference between the midpoint potentials of the half bridges 21a and 21b of the second bridge 20.

  For example, as shown in FIG. 2, the angle detection signal S1 is detected by a circuit configured by switching all the switches SW1 to SW4 of the sensor chip 4 to off. In this case, the first bridge 10 switches to form a circuit that detects the midpoint potential of the first half bridge 11a at the detection point P3 and detects the midpoint potential of the second half bridge 11b at the detection point P4. It is done. In the present embodiment, the circuit thus switched is an example of a midpoint potential detection circuit for detecting a potential difference between the midpoint potentials of the half bridges 11a and 11b.

  As shown in the figure, the angle detection signal S1 is generated when the switch SWt3 of the IC chip 5 is turned on with respect to the output terminal t (−), the switch SWt4 is turned on with respect to the output terminal t (+), and Acquired by switching off other switches. In this case, in the amplifier circuit 40, the midpoint potential (potential of the detection point P3) of the second half bridge 11b is input to the non-inverting input terminal (“+”) and also to the inverting input terminal (“−”). Is inputted with the midpoint potential of the first half bridge 11a (the potential of the detection point P4). The amplifier circuit 40 outputs a value proportional to the difference between the midpoint potentials of the half bridges 11a and 11b. A value proportional to the difference between the midpoint potentials of the half bridges 11a and 11b is acquired as the angle detection signal S1.

Note that the angle detection signal S2 is acquired by switching the corresponding switch in the same manner as the angle detection signal S1, and therefore the detailed description thereof is omitted.
Further, as various sensor signals, resistance value detection signals ΔV1, ΔV2, ΔV3, ΔV4, ΔV5, ΔV6, ΔV7, and ΔV8 for calculating the resistance values of the magnetic resistors M1 to M8 of the bridges 10 and 20 are obtained. Is done. The resistance value detection signals ΔV1 to ΔV8 are acquired as the resistance values of the magnetic resistors M1 to M8 of the bridges 10 and 20, respectively.

  For example, as shown in FIG. 3, the resistance value detection signals ΔV1 and ΔV4 are detected by a circuit configured by turning on the switches SW2 and SW3 of the sensor chip 4 and turning off the other switches. . In this case, the first bridge 10 detects the potential on the low potential side of the first magnetic resistance M1 at the detection point P3 together with the voltage dividing circuit that detects the potential on the high potential side of the first magnetic resistance M1 at the detection point P1. It is switched to constitute a voltage dividing circuit. The first bridge 10 is a circuit that detects the potential on the low potential side of the fourth magnetic resistor M4 at the detection point P5 together with the voltage dividing circuit that detects the potential on the high potential side of the fourth magnetic resistor M4 at the detection point P4. To be configured. In the present embodiment, the circuit switched as described above is an example of a resistance value detection circuit for detecting the resistance values of the magnetic resistances M1 and M4.

  Then, as shown on the upper side in the figure, the resistance value detection signal ΔV1 (first resistance value detection signal) turns on the switch SWt1 of the IC chip 5 with respect to the output terminal t (+), and the switch SWt3. Is turned on with respect to the output terminal t (−) and other switches are switched off. In this case, in the amplifier circuit 40, the non-inverting input terminal (“+”) receives the high-potential side potential of the first magnetic resistance M1, and the inverting input terminal (“−”) receives the first magnetic resistance. The potential on the low potential side of M1 is input. In this case, the amplifier circuit 40 outputs a voltage that is applied to the first magnetic resistance M1 and is proportional to the resistance value of the first magnetic resistance M1. A value proportional to the resistance value of the first magnetic resistance M1 is acquired as the resistance value detection signal ΔV1.

  In addition, as shown on the lower side in the figure, the resistance value detection signal ΔV4 (fourth resistance value detection signal) turns on the switch SWt4 of the IC chip 5 with respect to the output terminal t (+). SWt5 is turned on and other switches are turned off. In this case, in the amplifier circuit 40, the non-inverting input terminal (“+”) receives the high-potential side potential of the fourth magnetic resistance M4, and the inverting input terminal (“−”) receives the fourth magnetic resistance. The potential on the low potential side of M4 is input. In this case, the amplifier circuit 40 outputs a voltage applied to the fourth magnetic resistor M4, which is proportional to the resistance value of the fourth magnetic resistor M4. A value proportional to the resistance value of the fourth magnetic resistance M4 is acquired as the resistance value detection signal ΔV4.

  Further, as shown in FIG. 4, the resistance value detection signals ΔV2 and ΔV3 are detected by a circuit configured by turning on the switches SW1 and SW4 of the sensor chip 4 and turning off the other switches. . In this case, the first bridge 10 detects the potential on the low potential side of the second magnetic resistance M2 at the detection point P4 together with the voltage dividing circuit that detects the potential on the high potential side of the second magnetic resistance M2 at the detection point P2. It is switched to constitute a voltage dividing circuit. The first bridge 10 is a circuit that detects the potential on the low potential side of the third magnetic resistor M3 at the detection point P5 together with the voltage dividing circuit that detects the potential on the high potential side of the third magnetic resistor M3 at the detection point P3. To be configured. In the present embodiment, the circuit switched in this way is an example of a resistance value detection circuit for detecting the resistance values of the magnetic resistors M2 and M3.

  Then, as shown on the lower side in the figure, the resistance value detection signal ΔV2 (second resistance value detection signal) turns on the switch SWt2 of the IC chip 5 with respect to the output terminal t (+). It is obtained by turning on SWt4 with respect to the output terminal t (−) and turning off other switches. In this case, in the amplifier circuit 40, the high-potential side potential of the second magnetic resistance M2 is input to the non-inverting input terminal (“+”), and the second magnetic resistance is input to the inverting input terminal (“−”). The potential on the low potential side of M2 is input. In this case, the amplifier circuit 40 outputs a voltage applied to the second magnetic resistor M2, which is proportional to the resistance value of the second magnetic resistor M2. A value proportional to the resistance value of the second magnetic resistance M2 is acquired as the resistance value detection signal ΔV2.

  In addition, as shown on the upper side in FIG. 8, the resistance value detection signal ΔV3 (third resistance value detection signal) turns on the switch SWt3 of the IC chip 5 with respect to the output terminal t (+), and switches SWt5. Is obtained by turning on and turning off other switches. In this case, in the amplifier circuit 40, the non-inverting input terminal (“+”) receives the high-potential side potential of the third magnetic resistance M3, and the inverting input terminal (“−”) receives the third magnetic resistance. The potential on the low potential side of M3 is input. In this case, the amplifier circuit 40 outputs a voltage applied to the third magnetic resistor M3 and proportional to the resistance value of the third magnetic resistor M3. A value proportional to the resistance value of the third magnetic resistance M3 is acquired as the resistance value detection signal ΔV3.

  The resistance value detection signals ΔV5 to ΔV8 are obtained by switching the corresponding switches as in the case of the resistance value detection signals ΔV1 to ΔV4, and thus detailed description thereof is omitted.

  Further, as various sensor signals, current value detection signals ΔRR1V, ΔRR2V, ΔRR5V, ΔRR6V for calculating a current value flowing through each half bridge 11a, 11b, 21a, 21b of each bridge 10, 20 are acquired. The current value detection signals ΔRR1V and ΔRR2V are acquired as current values flowing through the half bridges 11a and 11b of the first bridge 10. The current value detection signals ΔRR5V and ΔRR6V are acquired as current values flowing through the half bridges 21a and 21b of the second bridge 20.

  For example, as illustrated in FIG. 5, the current value detection signals ΔRR1V and ΔRR2V are detected by a circuit configured by switching all the switches SW1 to SW4 of the sensor chip 4 to off. In this case, the first bridge 10 has a circuit for detecting the potential on the high potential side of the first detection resistor RR1 at the detection point P0 and the voltage division for detecting the potential on the low potential side of the first detection resistor RR1 at the detection point P1. It is switched to constitute a circuit. The first bridge 10 has a circuit for detecting the potential on the high potential side of the second detection resistor RR2 at the detection point P0 and a voltage dividing circuit for detecting the potential on the low potential side of the second detection resistor RR2 at the detection point P2. To be configured. In the present embodiment, the circuit switched in this way is an example of a current value detection circuit for detecting a current value flowing through each half bridge 11a, 11b.

  Then, as shown in the upper side of the figure, the current value detection signal ΔRR1V (first current value detection signal) turns on the switch SWt0 of the IC chip 5 and switches the switch SWt1 to the output terminal t (−). ON, and other switches are detected to be turned OFF. In this case, in the amplifier circuit 40, the high potential side potential of the first detection resistor RR1 is input to the non-inverting input terminal (“+”), and the first detection resistor is input to the inverting input terminal (“−”). The potential on the low potential side of RR1 is input. In this case, the amplifier circuit 40 outputs a voltage applied to the first detection resistor RR1, which is proportional to the value of the current flowing through the first half bridge 11a. A value proportional to the value of the current flowing through the first half bridge 11a is acquired as the current value detection signal ΔRR1V.

  In addition, as shown on the lower side in the figure, the current value detection signal ΔRR2V (second current value detection signal) turns on the switch SWt0 of the IC chip 5 and switches the switch SWt2 to the output terminal t (−). On the other hand, it is detected by switching on and switching off other switches. In this case, in the amplifier circuit 40, the high potential side potential of the second detection resistor RR2 is input to the non-inverting input terminal (“+”), and the second detection resistor is input to the inverting input terminal (“−”). The potential on the low potential side of RR2 is input. In this case, the amplifier circuit 40 outputs a voltage applied to the second detection resistor RR2, which is proportional to the value of the current flowing through the second half bridge 11b. A value proportional to the current value flowing through the second half bridge 11b is acquired as the current value detection signal ΔRR2V.

  The current value detection signals ΔRR5V and ΔRR6V are obtained by switching the corresponding switches in the same manner as the current value detection signals ΔRR1V and ΔRR2V, and thus detailed description thereof is omitted.

  Among the above circuits, in the midpoint potential detection circuit shown in FIG. 2, when the bias magnet attached to the rotating body rotates together with the rotating body to be detected, the magnets of the bridges 10 and 20 of the sensor chip 4 are rotated. Resistance values of the resistors M1 to M8 change. As the resistance values of the magnetic resistances M1 to M8 change, the angle detection signals S1 and S2 change.

In the present embodiment, the angle detection signal S1 is expressed by the following equation (c1),
S1 = I2 * R4-I1 * R3 (c1)
(For convenience of explanation, the proportional constant of the amplifier circuit 40 is omitted).

If the power supply voltage E is used for each term of the above formula (c1), the following formula (c2),
S1 = (R4) / (R2 + R4) × E− (R3) / (R1 + R3) × E (c2)
(However, S1: Angle detection signal, R1 to R4: Resistance values of the first to fourth magnetic resistors M1 to M4, I1, I2: Current values of the first and second half bridges, E: Power supply voltage, R1 = R4 , R2 = R3, I1 = I2)
Can be expressed as The same applies to the angle detection signal S2.

  The amplitude change of each angle detection signal S1, S2 can be expressed as sin (sine wave) or cos (cosine wave). For example, the angle detection signal S1 is sin with respect to the rotation of the rotating body to be detected. Is a sin signal that changes in a shape, and the angle detection signal S2 is a cos signal that changes in a cos shape with respect to the rotation of the rotation value to be detected. Then, the calculation output circuit 60 can calculate the angle information θ based on the sin signal of the angle detection signal S1 and the cos signal of the angle detection signal S2.

  The angle detection signal S1 of the above formula (c2) is positioned as a theoretical value for design only after satisfying the conditions of “R1 = R4”, “R2 = R3”, and “I1 = I2”. On the other hand, each of the magnetic resistances M1 to M4 generally has individual differences in resistance values. Therefore, in this embodiment, the angle detection signal S1 is initially corrected using the actual measurement result of the midpoint potential detection circuit (FIG. 2) at the time of manufacture, such as at the time of factory shipment. Thereby, the individual difference of the resistance value of each magnetic resistance M1-R4 at the time of manufacture can be absorbed.

  For this reason, the initial correction value necessary for the initial correction is stored in advance in the storage unit 70 at the time of manufacture. The arithmetic output circuit 60 uses the angle detection signal S1 as the angle detection signal S1 as a value obtained by adding (superimposing) the initial correction value stored in the storage unit 70 to the actual measurement result of the midpoint potential detection circuit (FIG. 2). It is configured to be used for calculating θ.

  Further, the resistance values of the magnetic resistances M1 to M4 may increase or decrease due to aging deterioration in addition to individual differences. Therefore, in the present embodiment, the angle detection signal S1 is manufactured by detecting a deviation from the relationship between the resistance values of the magnetic resistors M1 to M4 at the time of manufacture, which is the initial design, and the current values flowing through the half bridges 11a and 11b. The offset is corrected against time. As a result, changes due to aging of the resistance values of the magnetic resistors M1 to M4 from the time of manufacture are absorbed.

  For this reason, various initial values required for offset correction are stored in advance in the storage unit 70 at the time of manufacture. As various initial values, a first initial value (hereinafter referred to as “first initial value”) RXst, a second initial value (hereinafter referred to as “second initial value”) RYst, and a third initial value (hereinafter referred to as “first initial value”). Ist) is stored.

In the present embodiment, the first initial value RXst is expressed by the following equation (c3),
RXst = ΔV1st−ΔV4st (c3)
(However, ΔV1st, ΔV4st: detection signals ΔV1, ΔV4 for each resistance value at the time of manufacture)
Can be expressed as

  The first initial value RXst is a value at the time of manufacture of a difference value between the resistance value detection signal ΔV1 and the resistance value detection signal ΔV4, and serves as a reference value for offset correction. The first initial value RXst is a difference (mainly individual difference) in manufacturing the resistance values of the first magnetic resistance M1 and the fourth magnetic resistance M4, and is zero if there is no difference. This combination is determined in consideration of the relationship of “R1 = R4”, which is a condition satisfied by the above formula (c2).

The second initial value RYst is expressed by the following formula (c4),
RYst = ΔV2st−ΔV3st (c4)
(However, ΔV2st, ΔV3st: detection signals ΔV2, ΔV3 for each resistance value at the time of manufacture)
Can be expressed as

  The second initial value RYst is a value at the time of manufacture of the difference value between the resistance value detection signal ΔV2 and the resistance value detection signal ΔV3, and serves as a reference value for offset correction. The second initial value RYst is a difference (mainly individual difference) between the resistance values of the second magnetic resistance M2 and the third magnetic resistance M3, and is zero if there is no difference. This combination is determined in consideration of the relationship “R2 = R3”, which is a condition satisfied by the above formula (c2).

The third initial value Ist is expressed by the following formula (c5),
Ist = ΔRR1Vst−ΔRR2Vst (c5)
(However, ΔRR1Vst, ΔRR2Vst: detection signals ΔRR1V, ΔRR2V for each current value at the time of manufacture)
Can be expressed as

  The third initial value Ist is a value at the time of manufacture of a difference value between the current value detection signal ΔRR1V and the current value detection signal ΔRR2V, and serves as a reference value for offset correction. The third initial value Ist is a difference in resistance values (mainly individual differences) between the first magnetic resistance M1 and the fourth magnetic resistance M4, or a difference in resistance values between the second magnetic resistance M2 and the third magnetic resistance M3 ( Mainly based on individual differences), and if there is no such difference, it is zero.

  In addition, about the change of the resistance value by an individual difference or aged deterioration, it is the same as that of each magnetic resistance M1-M4 also about each magnetic resistance M5-M8. For this reason, the angle detection signal S2 is configured such that changes due to aging of the resistance values of the magnetic resistances M5 to M8 from the time of manufacture are absorbed by the initial correction and the offset correction similarly to the angle detection signal S1. .

  When the calculation output circuit 60 acquires the angle detection signals S1 and S2 in order to calculate the angle information θ, each of the resistance value detection signals ΔV1 to ΔV4 and the current value detection signals ΔRR1V, ΔRR2V is acquired, and offset correction is executed through comparison with the initial values RXst, RYst, and Ist.

  Hereinafter, the signal acquisition process executed when the arithmetic output circuit 60 acquires the angle detection signals S1 and S2 will be described in detail. The arithmetic output circuit 60 repeatedly executes the following processing for each control cycle. The arithmetic output circuit 60 performs the same processing when acquiring each angle detection signal S1, S2. Therefore, in the following, for convenience, only the process executed when acquiring the angle detection signal S1 will be described, and detailed description of the process executed when acquiring the angle detection signal S2 will be omitted.

  As shown in FIG. 6, in the signal acquisition process, the arithmetic output circuit 60 acquires the resistance value detection signals ΔV1 and ΔV4 (step S10). In step S10, the arithmetic output circuit 60 switches the switches SW1 to SW8 of the sensor chip 4 on and off to detect the resistance value of the first bridge 10 to detect the resistance values of the magnetic resistors M1 and M4. Switch to the circuit (Fig. 3). Further, the arithmetic output circuit 60 acquires the resistance value detection signals ΔV1 and ΔV4 by switching on and off the switches SWt0 to SWt11 of the IC chip 5, and temporarily stores them in a predetermined storage area of the storage unit 70, respectively. .

  Subsequently, the arithmetic output circuit 60 acquires the resistance value detection signals ΔV2 and ΔV3 (step S20). In step S20, the arithmetic output circuit 60 switches the switches SW1 to SW8 of the sensor chip 4 on and off to detect the resistance values of the first bridge 10 to detect the resistance values of the magnetic resistors M2 and M3. Switch to the circuit (Fig. 4). Further, the arithmetic output circuit 60 acquires the resistance value detection signals ΔV2 and ΔV3 by switching on and off the switches SWt0 to SWt11 of the IC chip 5, and temporarily stores them in a predetermined storage area of the storage unit 70, respectively. .

  Subsequently, the arithmetic output circuit 60 acquires the current value detection signals ΔRR1V and ΔRR2V (step S30). In step S30, the arithmetic output circuit 60 switches on / off of the switches SW1 to SW8 of the sensor chip 4 to detect the current value for detecting the current value flowing through the first bridge 10 to the half bridges 11a and 11b. Switch to the circuit for use (FIG. 5). Further, the arithmetic output circuit 60 acquires the current value detection signals ΔRR1V and ΔRR2V by switching on and off the switches SWt0 to SWt11 of the IC chip 5, and temporarily stores them in a predetermined storage area of the storage unit 70, respectively. .

  Subsequently, the arithmetic output circuit 60 sets the first correction value Xrm and the second correction value Yrm for offset correction based on the various sensor signals acquired in steps S10 to S30 (step S40). Each is temporarily stored in a predetermined storage area of the storage unit 70. In step S <b> 40, the arithmetic output circuit 60 reads the sensor signal acquired in steps S <b> 10 to S <b> 30 from the storage unit 70 and compares it with each initial value RXst, RYst, Ist stored in the storage unit 70.

  Specifically, the arithmetic output circuit 60 includes a first difference value (hereinafter referred to as “first resistance difference”) ΔRX, a second difference value (hereinafter referred to as “second resistance difference”) ΔRY, and a third difference value. A difference value (hereinafter referred to as “current difference”) ΔI is calculated.

In the present embodiment, the first resistance difference ΔRX is expressed by the following equation (c6),
ΔRX = ΔV1-ΔV4 (c6)
This is a difference value between the resistance value detection signal ΔV1 and the resistance value detection signal ΔV4 when detecting various sensor signals, and corresponds to the first initial value RXst. The first resistance difference ΔRX coincides with the first initial value RXst in the first magnetic resistance M1 and the fourth magnetic resistance M4 if there is no change due to the aging deterioration of the resistance value, and there is a change due to the aging deterioration of the resistance value. For example, the first initial value RXst is increased or decreased.

The second resistance difference ΔRY is expressed by the following formula (c7),
ΔRY = ΔV2−ΔV3 (c7)
This is a difference value between the resistance value detection signal ΔV2 and the resistance value detection signal ΔV3 when detecting various sensor signals, and corresponds to the second initial value RYst. The second resistance difference ΔRY coincides with the second initial value RYst in the second magnetic resistance M2 and the third magnetic resistance M3 if the resistance value does not change due to aging, and the resistance value may change due to aging. For example, it increases or decreases with respect to the second initial value RYst.

Further, the current difference ΔI is expressed by the following equation (c8),
ΔIRX = ΔRR1V−ΔRR2V (c8)
This is a difference value between the current value detection signal ΔRR1V and the current value detection signal ΔRR2V when various sensor signals are detected, and corresponds to the third initial value Ist. The current difference ΔI is equal to the third initial value Ist if there is no change due to aging of the resistance value in each of the magnetic resistances M1 to M4, and the third initial value Ist if there is a change due to aging of the resistance value. Increase or decrease.

  Then, the arithmetic output circuit 60 has a change in the first resistance difference ΔRX with respect to the first initial value RXst, a change in the second resistance difference ΔRY with respect to the second initial value RYst, and a change in the current difference ΔI with respect to the third initial value Ist, respectively. Determine the increase or decrease. In the present embodiment, as a change in the first resistance difference ΔRX with respect to the first initial value RXst and a change in the second resistance difference ΔRY with respect to the second initial value RYst, no offset correction is required when there is no change, and each correction value Xrm and Yrm are set to zero values. The arithmetic output circuit 60 estimates the resistance of the magnetoresistors M1 to M4 that have changed due to aging from the time of manufacture based on the increase or decrease of these changes, and the estimated resistance of the magnetoresistance. Is estimated to be increasing or decreasing.

  In the present embodiment, when the current difference ΔI is increased (> third initial value Ist), the increase in the current value I1 of the first half bridge 11a is estimated, and the increase in the current value I1 corresponds to each of the first half bridges 11a. It is estimated that the change in the resistance value of any one of the magnetic resistances M1 and M3 has an influence. When the current difference ΔI decreases (<third initial value Ist), an increase in the current value I2 of the second half bridge 11b is estimated, and the increase in the current value I2 corresponds to each of the magnetoresistances M2, M4 of the second half bridge 11b. It is estimated that any one of the resistance values changes.

  When the first resistance difference ΔRX increases (> first initial value RXst), either the resistance value of the first magnetic resistance M1 is increasing or changing, or the resistance value of the fourth magnetic resistance M4 is decreasing or changing. presume. In this case, if the current difference ΔI is increased, the resistance value of the first magnetic resistance M1 is increasing, and if the current difference ΔI is decreasing, the resistance value of the fourth magnetic resistance M4 is decreasing. Is estimated.

  When the first resistance difference ΔRX decreases (<first initial value RXst), it is determined whether the resistance value of the first magnetic resistance M1 is decreasing or the resistance value of the fourth magnetic resistance M4 is increasing. presume. In this case, if the current difference ΔI is increased, the resistance value of the first magnetic resistance M1 is decreasing, and if the current difference ΔI is decreasing, the resistance value of the fourth magnetic resistance M4 is increasing. Is estimated.

  When the second resistance difference ΔRY is increased (> second initial value RYst), either the resistance value of the second magnetic resistance M2 is increasing or changing, or the resistance value of the third magnetic resistance M3 is decreasing or changing. presume. In this case, it is estimated that if the current difference ΔI increases, the resistance value of the second magnetic resistance M2 shifts high, and if the current difference ΔI decreases, the resistance value of the third magnetic resistance M3 shifts low. Is done.

  When the second resistance difference ΔRY is decreased (<second initial value RYst), it is estimated whether the resistance value of the second magnetic resistance M2 is decreasing or the resistance value of the third magnetic resistance M3 is increasing. In this case, if the current difference ΔI is increased, the resistance value of the second magnetic resistance M2 is decreasing, and if the current difference ΔI is decreasing, the resistance value of the third magnetic resistance M3 is increasing. Is estimated.

  When the resistance value of the first magnetic resistance M1 is increasing or changing, or the resistance value of the fourth magnetic resistance M4 is increasing, the resistance value R1 or the resistance value R4 increases with respect to the angle detection signal S1. From this, an increase with respect to the value at the time of manufacture which is the theoretical value of the formula (c2) is estimated. The same applies to the case where the resistance value R2 of the second magnetic resistance M2 is decreasing or the resistance value R3 of the third magnetic resistance M3 is decreasing.

  Further, when the resistance value R1 of the first magnetic resistance M1 is decreasing or the resistance value R4 of the fourth magnetic resistance M4 is decreasing, the resistance value R1 or the resistance value R4 is about the angle detection signal S1. From the decrease, a decrease with respect to the manufacturing value, which is the theoretical value of the above formula (c2), is estimated. The same applies to the case where the resistance value R2 of the second magnetic resistance M2 is increasing or the resistance value R3 of the third magnetic resistance M3 is increasing.

  As shown in FIGS. 7A and 7B, the arithmetic output circuit 60 sets the correction values Xrm and Yrm based on the respective increase / decrease determination results. The storage unit 70 includes a map that defines the relationship among the correction values Xrm, Yrm, the increase / decrease amounts of the resistance differences ΔRX, ΔRY, and the increase / decrease amount of the current difference ΔI. In this map, when values for increasing the angle detection signal S1 are set as the correction values Xrm and Yrm, a larger value is set as the increase / decrease amount of each resistance difference ΔRX, ΔRY and the increase / decrease amount of the current difference ΔI are larger. Has been. Further, in this map, when the values for decreasing the angle detection signal S1 are set as the correction values Xrm and Yrm, the larger the increase / decrease amount of each resistance difference ΔRX, ΔRY and the increase / decrease amount of the current difference ΔI, the greater the value. Is set.

  As shown in the offset correction column “decrease” in FIG. 7A, the arithmetic output circuit 60 produces the angle detection signal S1 based on the increase / decrease in the first resistance difference ΔRX and the increase / decrease in the current difference ΔI. When an increase relative to the hour value is estimated, the first correction value Xrm is set so as to decrease the angle detection signal S1.

  That is, the arithmetic output circuit 60 is a case where the first resistance difference ΔRX is increased and the current difference ΔI is increased, or the first resistance difference ΔRX is decreased and the current difference ΔI is decreased. When R1 is increasing or the resistance value R4 of the fourth magnetic resistance M4 is increasing, the first correction value Xrm is set so as to decrease the angle detection signal S1.

  In addition, as shown in the offset correction column “Increase” in FIG. 7A, the arithmetic output circuit 60 calculates the angle detection signal S1 based on the increase / decrease in the first resistance difference ΔRX and the increase / decrease in the current difference ΔI. The first correction value Xrm is set so as to increase the angle detection signal S1 when a decrease with respect to the manufacturing value is estimated.

  That is, the arithmetic output circuit 60 is a case where the first resistance difference ΔRX is increased and the current difference ΔI is decreased, or the first resistance difference ΔRX is decreased and the current difference ΔI is increased. If R1 is decreasing or the resistance value R4 of the fourth magnetic resistance M4 is decreasing, the first correction value Xrm is set so as to increase the angle detection signal S1.

  In addition, as shown in the offset correction column “decrease” in FIG. 7B, the arithmetic output circuit 60 determines the angle detection signal S1 based on the increase / decrease in the second resistance difference ΔRY and the increase / decrease in the current difference ΔI. The second correction value Yrm is set so as to decrease the angle detection signal S1 when an increase relative to the manufacturing value is estimated.

  That is, the arithmetic output circuit 60 is a case where the second resistance difference ΔRY increases and the current difference ΔI increases, or the second resistance difference ΔRY decreases and the current difference ΔI decreases. If R2 is decreasing or the resistance value R3 of the third magnetic resistance M3 is decreasing, the second correction value Yrm is set so as to decrease the angle detection signal S1.

  In addition, as shown in the offset correction column “increase” in FIG. 7B, the arithmetic output circuit 60 determines the angle detection signal S1 based on the increase / decrease in the second resistance difference ΔRY and the increase / decrease in the current difference ΔI. The second correction value Yrm is set so as to increase the angle detection signal S1 when a decrease with respect to the manufacturing value is estimated.

  That is, the arithmetic output circuit 60 is a case where the second resistance difference ΔRY is increased and the current difference ΔI is decreased, or the second resistance difference ΔRY is decreased and the current difference ΔI is increased. When R2 is increasing or the resistance value R3 of the third magnetic resistance M3 is increasing, the second correction value Yrm is set so as to decrease the angle detection signal S1.

  Subsequently, the arithmetic output circuit 60 acquires the angle detection signal S1 (step S50). In step S50, the arithmetic output circuit 60 detects the potential difference between the midpoint potentials of the half bridges 11a and 11b by switching the switches SW1 to SW8 of the sensor chip 4 on and off. Switch to (Fig. 2). The arithmetic output circuit 60 acquires the angle detection signal S1 by switching on and off the switches SWt0 to SWt11 of the IC chip 5.

  Subsequently, the arithmetic output circuit 60 reads the correction values Xrm and Yrm set in step S40 together with the initial correction value, and adds (superimposes) the correction values Xrm and Yrm together with the initial correction value to the angle detection signal S1. The corrected detection signal S1rm that is the corrected detection signal that is the calculated value is calculated (step S60), and is temporarily stored in a predetermined storage area of the storage unit 70.

  Thereafter, the calculation output circuit 60 uses the corrected detection signal S1rm calculated in step S60 and the corrected detection signal S2rm, which is a corrected detection signal of the angle detection signal S2 calculated in the same manner, to obtain angle information θ. Is calculated and output.

According to the present embodiment described above, the following operations and effects are achieved.
(1) Here, regarding the first bridge 10, changes due to aging of the resistance values of the magnetic resistors M <b> 1 to M <b> 4 not only appear as a shift in the relationship of the resistance values of the magnetic resistors M <b> 1 to M <b> 4 during manufacturing, It also appears as a deviation in the relationship between the current values of the half bridges 11a and 11b during manufacture. In the present embodiment, the relationship between the resistance values of the magnetic resistors M1 to M4 during manufacture is the first initial value RXst and the second initial value RYst. Moreover, the relationship at the time of manufacture of the electric current value of each half bridge 11a, 11b is the 3rd initial value Ist. The same applies to the second bridge 20.

  On the other hand, in this embodiment, the resistance values of the magnetic resistors M1 to M8 can be detected by detecting the resistance value detection signals ΔV1 to ΔV8. Further, the current values of the half bridges 11a and 11b can be detected by detecting the current value detection signals ΔRR1V and ΔRR2V.

  As a result, the first initial value of the first resistance difference ΔRX calculated based on the resistance detection signals ΔV1, ΔV4 is the deviation of the relationship between the magnetic resistances M1, M4 when detecting various sensor signals with respect to the manufacturing time. It can be detected from the increase / decrease with respect to RXst. Further, the deviation of the relationship between the magnetic resistances M2 and M3 at the time of detecting various sensor signals with respect to the manufacturing time is calculated based on the second initial value RYst of the second resistance difference ΔRY calculated based on the resistance value detection signals ΔV2 and ΔV3. It can be detected from the increase or decrease to Further, the third initial value of the current difference ΔI calculated based on the current value detection signals ΔRR1V and ΔRR2V is the deviation of the relationship between the current values of the half bridges 11a and 11b when detecting various sensor signals with respect to the manufacturing time. It can be detected from an increase or decrease with respect to Ist.

  Then, the correction values Xrm and Yrm are set for the deviation of these relations, and the angle detection signal S1 can be corrected with respect to changes in the resistance values of the magnetic resistors M1 to M4 from the time of manufacture. This is the same for changes in the resistance values of the magnetic resistors M5 to M8 from the time of manufacture, and the angle detection signal S2 can be similarly corrected. Therefore, even if the resistance values of the magnetic resistors M1 to M8 change from the time of manufacture, the angle information θ can be calculated using the corrected detection signals S1rm and S2rm that correct the deviation in the relationship at the time of manufacture. Thus, it is possible to suppress a decrease in detection accuracy due to the aging of each of the magnetic resistances M1 to M8.

  (2) In this embodiment, each circuit necessary for correcting the angle detection signal S1 together with the angle detection signal S1 by switching the circuit configuration of the first bridge 10 by switching the switches SW1 to SW4 of the sensor chip 4 on and off. The current value detection signals ΔRR1V and ΔRR2V and the resistance value detection signals ΔV1 to ΔV4 can be detected. The same applies to the second bridge 20, and the corresponding sensor signals are detected together with the angle detection signal S2 by switching the circuit configuration by switching the switches SW5 to SW8 of the sensor chip 4 on and off. Can do. As a result, the detection of each other signal is prevented from interfering with the detection of other signals. Therefore, various sensor signals can be suitably detected.

  (3) In the present embodiment, it is related to the resistance values of the first magnetic resistance M1 and the fourth magnetic resistance M4 facing each other at the first bridge 10 at the time of manufacture, and the resistance values of the second magnetic resistance M2 and the third magnetic resistance M3. Therefore, the deviation in the relationship at the time of manufacture appears as the first resistance difference ΔRX, the second resistance difference ΔRY, and the current difference ΔI when detecting various sensor signals. Each initial value RXst, RYst, Ist indicating the relationship at the time of manufacture is stored in advance in the storage unit 70 at the time of manufacture, so that at least the initial value RXst, RYst, Ist from the time of manufacture at the time when the initial value is stored. The angle detection signal S1 can be corrected with respect to changes in the resistance values of the magnetic resistors M1 to M4. This is the same for changes in the resistance values of the magnetic resistors M5 to M8 from the time of manufacture, and the angle detection signal S2 can be similarly corrected. Therefore, it is possible to suitably suppress a decrease in detection accuracy due to aged deterioration of the magnetic resistances M1 to M8 from the time when the initial values RXst, RYst, and Ist are stored.

(4) According to the present embodiment, the angle detection signal S1 can be expressed by the above formula (c2) when the power supply voltage E is used. The same applies to the angle detection signal S2.
For example, when the resistance value R1 of the first magnetic resistance M1 or the resistance value R4 of the fourth magnetic resistance M4 increases with respect to the formula (c2), the angle detection signal S1 increases with respect to the formula (c2). In this case, the arithmetic output circuit 60 sets the first correction value Xrm so as to decrease the angle detection signal S1 by the increment of the angle detection signal S1 with respect to the change of the resistance value (FIG. 7A).

  When the resistance value R2 of the second magnetic resistance M2 or the resistance value R3 of the third magnetic resistance M3 increases with respect to the above formula (c2), the angle detection signal S1 decreases with respect to the above formula (c2). In this case, the arithmetic output circuit 60 sets the second correction value Yrm so as to increase the angle detection signal S1 by the decrease of the angle detection signal S1 with respect to the change in resistance value (FIG. 7B).

Thus, in this embodiment, the influence which the change of the resistance value of each magnetic resistance M1-M8 has on each angle detection signal S1, S2 can be corrected suitably.
(5) In the first bridge 10, the detection resistors RR1 and RR2 are connected in series between the power source V and the magnetic resistors M1 and M2 adjacent to the power source V. The same applies to the second bridge 20, and the detection resistors RR1 and RR2 are connected in series between the power supply V and the magnetic resistances M5 and M6 adjacent to the power supply V. Thereby, in each bridge | bridging 10, 20, each detection resistance RR1, RR2 can be arrange | positioned symmetrically, and the symmetry of a circuit can be ensured. In this case, the bridges 10 and 20 constituting a full bridge circuit that can be relatively stable as a circuit and have symmetry in the first place are particularly effective.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the first bridge 10, the detection resistors RR1 and RR2 may be connected in series between the ground G and the magnetic resistors M3 and M4 adjacent to the ground G. The same applies to the second bridge 20. In this case, the same operation and effect as (5) of the above embodiment are achieved.

  The position where the first detection resistor RR1 is connected may be changed as long as the current value of the first half bridge 11a can be detected. Further, the position where the second detection resistor RR2 is connected may be changed as long as the current value of the second half bridge 11b can be detected. In these cases, the detection resistors RR <b> 1 and RR <b> 2 may not have symmetry in the first bridge 10. The same applies to the second bridge 20.

  The map for setting each correction value Xrm, Yrm is a map of each correction value Xrm, Yrm and each resistance difference ΔRX, ΔRY according to the characteristics of each magnetic resistance M1 to M4, the usage environment of the sensor device 1, etc. The relationship between the increase / decrease amount and the increase / decrease amount of the current difference ΔI may be changed. In addition, a dead zone may be set in the map. This dead zone may be set based on the increase / decrease amount of each resistance difference ΔRX, ΔRY or the increase / decrease amount of the current difference ΔI.

When the correction values Xrm and Yrm are added together, only one of the dominant values may be added.
The initial values RXst, RYst, and Ist may be the conditions of “R1 = R4”, “R2 = R3”, and “I1 = I2” that are satisfied by the above formula (c2). That is, the initial values RXst, RYst, and Ist are all zero. When offset correction is performed using these as reference values, the angle detection signal S1 can be offset corrected including individual differences in the resistance values of the magnetic resistors M1 to M4. The same applies to the angle detection signal S2. In this modification, it is possible to reduce the process of setting the initial correction value at the time of manufacturing, or to reduce the initial correction process when detecting various sensor signals.

  The combination of the magnetic resistances M1 to M4 in the initial values RXst and RYst and the resistance differences ΔRX and ΔRY may be changed as long as the magnetic resistances constituting the half bridges 11a and 11b are combined one by one. . The same applies to the combination of the magnetic resistances M5 to M8.

  In each expression representing each initial value RXst, RYst, Ist, the contents of the subtracted term and the content of the subtracted term may be interchanged. In this case, the resistance differences ΔRX and ΔRY and the current difference ΔI may be similarly replaced.

  The switching circuits 13 and 14 may be configured to detect the current value detection signals ΔRR1V and ΔRR2V and the resistance value detection signals ΔV1 to ΔV4 in addition to the angle detection signal S1. The specific configuration such as the configuration of the voltage dividing circuit for the bridge 10 can be changed. The same applies to the second bridge 20.

  -The resistance value of each of the magnetic resistances M1 to M4 is detected by a parameter having a correlation with the resistance value, for example, the temperature of the magnetic resistance, instead of detecting the potential difference like the detection signals ΔV1 to ΔV4 for each resistance value. Then, it may be converted.

  A plurality of amplifier circuits 40 may be provided. In this case, the number of switches of the output switching circuit 30 can be reduced. Further, as the amplifier circuit 40, the angle detection signal S1, the resistance value detection signals ΔV1 to ΔV4, and the current value detection signals ΔRR1V and ΔRR2V in the first bridge 10 are respectively switched without switching the switch of the output switching circuit 30. A plurality (in this case, seven) may be provided so as to be detected. The various sensor signals in the second bridge 20 may be configured similarly.

  The arithmetic output circuit 60 may arbitrarily change the execution frequency of the processes in steps S10 to S40 of the signal acquisition process, that is, the process related to offset correction. For example, if the sensor device 1 is mounted on a vehicle, processing relating to offset correction may be executed at the timing of ignition on.

The signal acquisition process may be configured by only the processes of steps S10 to S40, and the processes of steps S50 and S60 may be performed by other processes.
The arithmetic output circuit 60 may be configured to store and hold the first resistance difference ΔRX, the second resistance difference ΔRY, and the current difference ΔI before one control cycle in the storage unit 70. In this case, when the calculation output circuit 60 newly calculates the first resistance difference ΔRX, the second resistance difference ΔRY, and the current difference ΔI for offset correction, the value before one control cycle stored in the storage unit 70 On the other hand, by determining whether the newly calculated value has increased or decreased, it is possible to detect an abnormality in the first bridge 10, the output switching circuit 30, or the like. For example, when the newly calculated value is significantly increased or decreased with respect to the value before one control cycle stored in the storage unit 70 (not expected in design), a short circuit abnormality or the like is caused in the first bridge 10. It is possible to detect that there is a possibility that an abnormality has occurred.

  The sensor chip 4 may include only one of the first bridge 10 and the second bridge 20. In this case, for example, a torque that detects a torque value acting on the rotating body by detecting a change in magnetism of a bias magnet attached to the rotating body with a rotating body such as a steering shaft of a vehicle as a detection target. It can be used as a sensor device.

The initial values RXst, RYst, and Ist stored in the storage unit 70 may be newly updated at the maintenance timing of the sensor device 1.
Each modification may be applied in combination with each other. For example, the embodiment of the torque sensor device and the configuration of other modifications may be applied in combination with each other.

Next, a technical idea that can be grasped from the embodiment and the modification will be described.
(A) The sensor device is used as a rotation angle detection sensor that outputs angle information indicating an angular position of the rotating body as the calculation result by detecting a magnetic change of a bias magnet attached to the rotating body. When the full bridge circuit is a first full bridge circuit, the full bridge circuit further includes a second full bridge circuit having the same configuration as the first full bridge circuit, and the detection circuit includes the first full bridge circuit. A second detection signal indicating a potential difference of a midpoint potential of each half bridge circuit for the second full bridge circuit. The calculation output circuit calculates the angle information based on the first detection signal and the second detection signal. According to this configuration, it can be applied to a so-called rotation angle detection sensor that detects the angular position of the rotating body, and it is possible to improve the detection accuracy of the rotation angle detection sensor and improve the reliability. it can.

DESCRIPTION OF SYMBOLS 1 ... Sensor apparatus, 10 ... 1st bridge, 11a, 11b ... 1st, 2nd half bridge, 13, 14 ... 1st, 2nd switching circuit, 20 ... Bridge, 30 ... Output switching circuit, 40 ... Amplifying circuit, 60 ... arithmetic output circuit, 70 ... storage unit, .theta .... angle information, G ... ground, V ... power source, .DELTA.I ... current difference, I1, I2 ... current value, M1-M4 ... first to fourth magnetic resistances, R1-. R4 ... resistance value, S1, S2 ... angle detection signal, .DELTA.RX ... first resistance difference, .DELTA.RY ... second resistance difference, .DELTA.V1-.DELTA.V8 ... resistance value detection signal, Ist ... third initial value, RR1, RR2 ... first. , Second detection resistor, Xrm: first correction value, Yrm: second correction value, RXst: first initial value, RYst: second initial value, S1rm, S2rm: detection signal after correction, ΔRR1V, ΔRR2V: current Detection signal for value.

Claims (5)

It has a first half bridge circuit in which two magnetoresistive elements are connected in series and a second half bridge circuit in which two magnetoresistive elements are connected in series, and each half bridge circuit is parallel between a power source and a ground. A full bridge circuit configured in
A detection circuit for detecting a detection signal indicating a potential difference of a midpoint potential of each half-bridge circuit;
An operation output circuit that outputs an operation result of the detection signal detected by the detection circuit,
The first half-bridge circuit is connected in series with a first current detection resistor for detecting a first current value flowing through the first half-bridge circuit, and the second half-bridge circuit. Is connected in series with a second current detection resistor for detecting a second current value flowing through the second half-bridge circuit,
In addition to detecting the detection signal, the detection circuit detects a first current value detection signal indicating the first current value and a second current value detection signal indicating the second current value. And detecting each resistance value detection signal indicating the resistance value of each magnetoresistive element,
The calculation output circuit corrects the detection signal based on the first current value detection signal, the second current value detection signal, and each resistance value detection signal. And a sensor device that calculates the calculation result using a corrected detection signal on which the correction value is superimposed. Each half-bridge circuit includes a mid-point potential detection circuit for detecting a mid-point potential of each half-bridge circuit, and a current value for detecting the first current value and the second current value. A switching circuit for switching so that a detection circuit and a resistance value detection circuit for detecting the resistance value of each magnetoresistive element are respectively configured is connected,
In addition to detecting the detection signal through the midpoint potential detection circuit by switching the switching circuit, the detection circuit detects the first current value detection signal through the current value detection circuit. 2. The sensor device according to claim 1, wherein the second current value detection signal is detected, and each of the resistance value detection signals is detected through the resistance value detection circuit. A first magnetoresistance element detection signal for the first magnetoresistive element of the first half-bridge circuit and a fourth magnetoresistor facing the first magnetoresistive element of the second half-bridge circuit A first initial value set as a reference value of the difference between the fourth resistance value detection signals of the element;
A second resistance value detection signal of a second magnetoresistive element different from the first magnetoresistive element of the first half bridge circuit, and the second magnetoresistive element of the second half bridge circuit A second initial value set as a reference value of a difference from the third resistance value detection signal of the third magnetoresistive element opposed to
A storage unit for storing a third initial value set as a reference value of a difference between the first current value detection signal and the second current value detection signal;
The arithmetic output circuit is:
A first difference value which is a difference between the first resistance value detection signal and the fourth resistance value detection signal; the second resistance value detection signal; and the third resistance value A second difference value that is a difference from the detection signal, a third difference value that is a difference between the first current value detection signal and the second current value detection signal are respectively calculated. ,
A first correction value is set based on a change in the first difference value with respect to the first initial value and a change in the third difference value with respect to the third initial value, and the second correction value Setting a second correction value based on a change in the second difference value relative to an initial value and a change in the third difference value relative to the third initial value;
The sensor device according to claim 1, wherein the calculation result is calculated using the corrected detection signal obtained by superimposing the first correction value and the second correction value on the detection signal. The detection circuit detects the detection signal of the second half bridge circuit as a positive value, detects the detection signal of the first half bridge circuit as a negative value,
The arithmetic output circuit is:
Based on the change in the first difference value and the change in the third difference value, an increase or decrease in the resistance value of the first magnetoresistive element or the fourth magnetoresistive element is detected. When detecting an increase in one magnetoresistive element or the fourth magnetoresistive element, the first correction value is set so as to decrease the detection signal, while the first magnetoresistive element or the first magnetoresistive element 4 to detect a decrease in the magnetoresistive element, the first correction value is set to increase the detection signal;
Based on the change in the second difference value and the change in the third difference value, an increase or decrease in the resistance value of the second magnetoresistive element or the third magnetoresistive element is detected. When detecting an increase in the second magnetoresistive element or the third magnetoresistive element, the second correction value is set so as to increase the detection signal, while the second magnetoresistive element or the second magnetoresistive element is increased. 4. The sensor device according to claim 3, wherein when the decrease of the magnetoresistive element is detected, the second correction value is set so as to decrease the detection signal. The first current detection resistor and the second current detection resistor are between the power source and the magnetoresistive element adjacent to the power source, or between the ground and the magnetoresistive element adjacent to the ground. The sensor device according to claim 1, which is connected to the sensor device.

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