JP2015197390A - magnetic detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic detection device that enables failures to be surely diagnosed even at a time of a system start when an inspection object is not yet operated, and enables reduction in power consumption.SOLUTION: A magnetic detection device is configured to comprise: a detection circuit 10 including a plurality magnetoresistive elements each varying its resistance value according to a direction of an applied magnetic field, the magnetoresistive elements being connected in the form of a bridge, in which a voltage from a power supply unit (power supply voltage Vcc) is applied across facing ends in the bridge to output a detection signal corresponding to a change in the resistance value from middle points in the bridge; an amplification circuit 20 which amplifies the detection signal to output the amplified detection signal; a diagnostic circuit 30 which applies a prescribed voltage to an input terminal of the amplification circuit 20 by a diagnostic signal, and performs a failure detection by detecting an output of the amplification circuit 20; and a switch unit 40 that is disposed between the detection circuit 10 and the power supply unit, and is operative by the diagnostic signal.

Description

  The present invention relates to a magnetic detection device, and more particularly to a magnetic detection device having a diagnostic function.

  There is a rotation angle detection device in which the rotation of the rotor gear that rotates integrally with the steering shaft is decelerated by a reduction mechanism configured by a planetary gear mechanism, and the rotation after deceleration is transmitted to the reduction-side detection gear (for example, Patent Document 1). In this rotation angle detection device, since the shafts of the respective gears constituting the speed reduction mechanism are in the same direction, the rotation of the steering shaft can be transmitted to the speed reduction side detection gear with less play. Therefore, it is said that the rotation angle of the steering shaft can be detected more accurately because there is little backlash in the speed reduction mechanism (see, for example, Patent Document 1).

  In addition, it has a fault diagnosis unit that compares the approximate absolute angle output from the steering angle conversion unit of the deceleration mechanism side calculation unit with the detailed absolute angle output from the steering angle conversion unit of the speed increase mechanism side calculation unit. If the difference in absolute angle exceeds a certain value, it is assumed that a failure has occurred in the MR sensor, and a failure diagnosis result is output to the external device. MR sensor malfunctions by using only the speed reduction mechanism, the speed reduction detection gear, the speed reduction mechanism side arithmetic unit, the speed increase side detection gear, and the speed increase mechanism side arithmetic unit necessary to detect the steering rotation angle. Therefore, it is said that failure diagnosis can be performed without increasing costs and increasing the size because no separate member is provided for failure diagnosis.

  In addition, there is a magnetic detection device that can reliably perform failure diagnosis even when the system is started when the detection target is not operating (see, for example, Patent Document 2). This magnetic detection device connects a plurality of MR elements whose resistance values change according to the direction of the applied magnetic field in a bridge shape, outputs a detection signal according to the change in resistance value, and a detection signal Amplifying circuit for amplifying and outputting, and a diagnostic circuit comprising a diagnostic terminal for diagnosing normal operation by applying a predetermined voltage to the input terminal of the amplifying circuit and detecting the output of the amplifying circuit It is set as the structure which has. By applying a predetermined voltage to the diagnosis terminals (DIAG1, DIAG2), it can be determined whether or not a failure has occurred based on the output signals Vout1 and Vout2 of the magnetic sensor device.

JP 2008-51668 A JP 2010-25730 A

  However, according to the rotation angle detection device of Patent Document 1, when the steering shaft rotates and the rotor gear, the planetary gear mechanism, and the like are rotating, the MR sensor can be diagnosed for failure, but the vehicle is running. If there is not, for example, at the time of starting the system, there is a problem that failure diagnosis of the MR sensor cannot be performed because the rotor gear or the planetary gear mechanism does not rotate.

  Further, according to the magnetic detection device of Patent Document 2, a voltage is applied to a detection circuit in which MR elements are connected in a bridge shape even during failure diagnosis by a diagnostic circuit, so that current consumption increases. There is.

  Accordingly, an object of the present invention is to provide a magnetic detection device capable of reliably performing a failure diagnosis even at the time of system start when a detection target is not operating and capable of reducing current consumption.

[1] In order to achieve the above object, according to the present invention, a plurality of magnetoresistive elements whose resistance values change according to the direction of an applied magnetic field are connected in a bridge shape, and the bridge-shaped opposing ends are connected. A detection circuit that outputs a detection signal corresponding to a change in the resistance value from the bridge-shaped midpoint, an amplification circuit that amplifies and outputs the detection signal, and a voltage applied from a power supply unit, A diagnosis circuit that detects a failure by applying a predetermined voltage to the input terminal by a diagnosis signal and detecting the output of the amplifier circuit, and is arranged between the detection circuit and the power supply unit, and operates by the diagnosis signal. And a switch unit.

[2] In the magnetic detection device according to [1], the voltage applied from the power supply unit is turned off when the diagnostic circuit is operated by the diagnostic signal. There may be.

[3] The magnetic detection device according to [2], wherein the switch unit turns off the voltage application from the power supply unit by a sleep signal for setting the detection circuit to a sleep state. May be.

[4] The amplifier circuit is configured by an operational amplifier, the diagnostic circuit is configured by a switching circuit, and the switching circuit is operated by applying a predetermined voltage to a diagnostic terminal of the diagnostic circuit. The magnetic detection device according to any one of [1] to [3], wherein failure diagnosis is performed by setting a non-inverting input terminal or an inverting input terminal of an operational amplifier to a substantially ground level. .

[5] Further, a steady magnetic detection operation for outputting a detection signal from the amplifier circuit is performed by inputting a signal at a level that does not operate the switching circuit to the diagnostic terminal of the diagnostic circuit. The magnetic detection device according to any one of [1] to [4] may be used.

  According to the present invention, it is possible to reliably perform failure diagnosis even at the time of system start when the detection target is not operating, and it is possible to reduce current consumption.

FIG. 1 is a circuit diagram of a magnetic detection device 1 according to an embodiment of the present invention. FIG. 2 is a configuration block diagram of an example in which the magnetic detection device 1 according to the embodiment of the present invention is applied to a steering rotation angle sensor. FIG. 3 is a flowchart of failure diagnosis when the diagnosis function of the magnetic detection device 1 according to the embodiment of the present invention is applied to the detection of the steering rotation angle of the vehicle.

  Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

[Embodiments of the present invention]
FIG. 1 is a circuit diagram of a magnetic detection device 1 according to an embodiment of the present invention. FIG. 2 is a configuration block diagram of an example in which the magnetic detection device 1 according to the embodiment of the present invention is applied to a steering rotation angle sensor. FIG. 3 is a flowchart of failure diagnosis when the diagnosis function of the magnetic detection device 1 according to the embodiment of the present invention is applied to the detection of the steering rotation angle of the vehicle.

(Configuration of the magnetic detection device 1)
As shown in FIG. 1, the magnetic detection device 1 according to the embodiment of the present invention includes a detection circuit 10, an amplification circuit 20, a diagnosis circuit 30, and a switch unit 40. The magnetic detection device 1 connects a plurality of magnetoresistive elements whose resistance values change according to the direction of an applied magnetic field in a bridge shape, and a voltage from a power supply unit (power supply voltage Vcc) is connected to the opposite ends of the bridge shape. Is applied, and a detection circuit 10 that outputs a detection signal corresponding to a change in the resistance value from the midpoint of the bridge shape, an amplification circuit 20 that amplifies and outputs the detection signal, and a diagnostic input to the input terminal of the amplification circuit 20 A diagnosis circuit 30 that detects a failure by applying a predetermined voltage according to a signal and detecting an output of the amplifier circuit 20; a switch unit 40 that is disposed between the detection circuit 10 and the power supply unit and operates according to the diagnosis signal; It is set as the structure which has.

  The magnetic detection device 1 according to the embodiment of the present invention is configured as described above, so that the switch unit 40 is turned off (off state) at the time of failure diagnosis or in the sleep state (sleep mode). Thus, the voltage application from the power supply unit is turned off, the detection circuit 10 is not operated, and current consumption is suppressed.

  The detection circuit 10 includes a first MR bridge 11 in which first to fourth magnetoresistive elements (hereinafter referred to as MR elements) Ra, Rb, Rc, Rd are connected in a bridge shape, and fifth to eighth MR. The device includes a second MR bridge 12 in which elements Re, Rf, Rg, and Rh are connected in a bridge shape. The first MR bridge 11 and the second MR bridge 12 are inclined by 45 ° from each other, and the phases of the output signals are different by π / 2.

  In the first MR bridge 11, the power supply voltage Vcc is supplied to the first MR element Ra and the third MR element Rc, and the second MR element Rb and the fourth MR element Rd are connected to the ground. . The connection point between the first MR element Ra and the second MR element Rb is outputted as the first midpoint voltage V1, and the connection point between the third MR element Rc and the fourth MR element Rd is the second midpoint. It is output as voltage V2.

  Similarly, in the second MR bridge 12, the power supply voltage Vcc is supplied to the fifth MR element Re and the seventh MR element Rg, and the sixth MR element Rf and the eighth MR element Rh are grounded. It is connected to the. The connection point between the fifth MR element Re and the sixth MR element Rf is output as the third midpoint voltage V3, and the connection point between the seventh MR element Rg and the eighth MR element Rh is the fourth midpoint voltage. Output as voltage V4.

The amplifier circuit 20 includes operational amplifiers 21 and 22. Inverting is connected to the input terminal resistor R1 of the operational amplifier 21, resistors R _i1 which is connected to the inverting input _terminal, an inverting amplifier with resistor R _f1 is connected between the inverting input terminal and the output terminal OUT1 is configured. Similarly, non-inverting is connected to the input terminal resistance of the operational amplifier 22 R2, inversion is connected to the input terminal resistor R _i2, is composed is an inverting amplifier with resistor R _f2 is connected between the inverting input terminal and the output terminal OUT2 Yes.

The output signal Vout1 at the output terminal OUT1 is a signal obtained by inverting and amplifying the input (V1-V2) to the operational amplifier 21, and the gain is _-Rf1 / _Ri1 . Similarly, the output signal Vout2 of the output terminal OUT2 becomes a reversed amplified signal input (V3-V4) to the operational amplifier 22, the gain is a _-R f2 _{/ R i2,} the phase difference between Vout1 and [pi / 2 Have

  The diagnosis circuit 30 includes a switching circuit for independently setting the inverting input terminal and the non-inverting input terminal of the operational amplifiers 21 and 22 to the Hi level (hereinafter referred to as H) or Lo level (hereinafter referred to as L). This switching circuit includes G1, G2, G3, and G4 formed of N-channel MOSFETs. The gates of G1 and G2 are connected to the terminal of DIAG1, respectively, and the gates of G3 and G4 are connected to the terminal of DIAG2. G1 has a source / drain connected to the inverting input terminal and ground of the operational amplifier 21, G2 represents a source / drain connected to the non-inverting input terminal and ground of the operational amplifier 22, and G3 represents a non-inverting input terminal and ground of the operational amplifier 21. In addition, the source / drain of G4 is connected to the inverting input terminal of the operational amplifier 22 and the ground.

  When the DIAG1 terminal is set to H by the diagnosis signal, the gates G1 and G2 become H and the FET becomes conductive, and the inverting input terminal of the operational amplifier 21 and the non-inverting input terminal of the operational amplifier 22 are each set to the ground level. Further, by setting the terminal of DIAG2 to H, the gates G3 and G4 become H and the FET becomes conductive, and the non-inverting input terminal of the operational amplifier 21 and the inverting input terminal of the operational amplifier 22 are each set to the ground level. When each of the gates G1 to G4 is set to L level as a signal that does not operate the switching circuit, the FET does not conduct, and each inverting input terminal and non-inverting input terminal have a first middle point. The voltage V1 to the fourth midpoint voltage V4 are input as they are.

  The terminals of DIAG 1 and DIAG 2 are connected to the input side of the OR circuit 31. The output of the OR circuit 31 is connected to the gate of the switch unit 40 described later via the OR circuit 32. To the input side of the OR circuit 32, terminals of DIAG1 and DIAG2 are connected and a SLEEP terminal is connected. The SLEEP terminal is for outputting a switch signal for setting the magnetic detection device 1 or at least the detection circuit 10 (the first MR bridge 11 and the second MR bridge 12) to the sleep mode (standby mode). As can be easily seen from FIG. 1, when any one of the DIAG1, DIAG2, and SLEEP terminals becomes H level, the output of the OR circuit 32 becomes H level.

  The switch section 40 is formed of a P-channel MOSFET, the gate is the output terminal of the OR circuit 32, the source and drain are the power supply voltage Vcc, the terminal 15 of the first MR bridge 11, and the terminal 16 of the second MR bridge 12, respectively. It is connected. According to such a configuration, when any one of the DIAG1, DIAG2, and SLEEP terminals becomes H level, the output of the OR circuit 32 becomes H level. It becomes a conductive state. That is, the detection circuit 10 (the first MR bridge 11 and the second MR bridge 12) does not operate, and current consumption is suppressed.

  The detection circuit 10, the amplification circuit 20, the diagnosis circuit 30, and the switch unit 40 are formed as a chip as one magnetic detection device 1 or formed in a packaged state. When the power supply voltage Vcc is supplied from the outside and all of the diagnosis terminal and the SLEEP terminal are set to the L level, the magnetic detection device 1 performs a normal magnetic detection operation for outputting a detection signal from the amplifier circuit 20.

  The case where the diagnosis function of the magnetic detection device 1 according to the embodiment of the present invention is applied to the detection of the steering rotation angle of the vehicle will be described.

  In the configuration block diagram of FIG. 2, a magnet 102 magnetized with S and N poles is mounted on a rotating member 101 of a vehicle steering device 100 (only part of which is shown), and close to the magnet 102, the magnetic detection device 1. Is placed. A magnet 102 rotates together with the rotating member 101 by a steering operation (not shown), and a change in the magnetic field is applied to the magnetic detection device 1.

  The sensor ECU 200 includes a processing unit 201, a determination unit 202, and a storage unit 203.

  The processing unit 201 receives output signals Vout1 and Vout2 from the magnetic detection device 1, and also outputs an interface unit, a waveform signal processing unit, an A / D or a D / A conversion unit to output to the control target device as a rotation angle output. Etc. By calculating Arctan (Vout2 / Vout1) from the output signals Vout1 and Vout2 whose phases are shifted by π / 2, the steering angle (steering angle) of the steering device can be detected. The detected steering angle is output to various on-vehicle equipment ECUs as an analog signal or a digital signal as necessary.

  The determination unit 202 applies a voltage to the diagnosis terminals (DIAG1, DIAG2) with respect to the magnetic detection device 1 in order to perform failure diagnosis based on a flowchart based on a diagnosis function described later. Based on the output signals Vout1 and Vout2 of the magnetic detector 1, it is determined whether or not a failure has occurred. When it is determined that there is a failure, a warning signal or the like is output to the control target device.

  The storage unit 203 is composed of a ROM and stores parameters such as a diagnostic program for executing a diagnosis function and a judgment reference value for determining whether the output signals Vout1, Vout2, etc. from the magnetic detection device 1 are within the normal range. And is referred to by the determination unit 202 as necessary.

(Failure diagnosis operation)
The failure diagnosis in the case where the diagnostic function of the magnetic detection device 1 according to the embodiment of the present invention is applied to the detection of the steering rotation angle of the vehicle is shown by a flowchart as shown in FIG. Note that the SLEEP pin is always set to L during fault diagnosis operations.

(Step 01 (S01))
When the ignition switch of the vehicle is turned on and the system for detecting the steering rotation angle starts, in step 01, it is determined by the determination unit 202 of the sensor ECU 200 whether the system is starting. When the system is started, the vehicle is often not running and there is no change in the steering rotation angle. Whether or not the system is started can be set in various settings such as whether or not a predetermined time has elapsed since the system was started or whether or not the output signal from the magnetic detection device 1 has changed. If it is determined that the system has been started, the process proceeds to step 02. If it is determined that the system has not been started, the process proceeds to step 11 where failure diagnosis is performed at normal times.

(Step 02 (S02))
A diagnosis signal is input from the determination unit 202 of the sensor ECU 200 to set the DIAG1 terminal of the magnetic detection device 1 to H and the DIAG2 terminal to L. At this time, if the output signals Vout1 and Vout2 from the magnetic detection device 1 become H and L, it is determined as normal. If the output signal is abnormal, it is determined that there is a failure (S21), and a warning (S22) or the like is given if necessary. During this fault diagnosis, since the OR circuits 31 and 32 are H and the switch unit 40 is in the OFF state, the detection circuit 10 (the first MR bridge 11 and the second MR bridge 12) has a current. It is not supplied and current consumption can be suppressed.

(Step 03 (S03))
Contrary to step 02, the terminal of DIAG1 is set to L and the terminal of DIAG2 is set to H. When the output signals Vout1 and Vout2 from the magnetic detection device 1 are L and H, it is determined that the signal is normal. If the output signal is abnormal, it is determined that there is a failure (S21), and a warning (S22) or the like is given if necessary. Similarly to step 02, since the OR circuits 31 and 32 are H and the switch unit 40 is in the OFF state, the detection circuit 10 (the first MR bridge 11 and the second MR bridge 12) has a current. It is not supplied and current consumption can be suppressed. If it is determined that the operation is normal, the process returns to step 01, and failure diagnosis is performed by the diagnosis function repeatedly at predetermined time intervals.

(Step 11 (S11))
In the normal state, the terminal of DIAG 1 of the magnetic detection device 1 is set to L and the terminal of DIAG 2 is set to L from the determination unit 202 of the sensor ECU 200. Since the OR circuits 31 and 32 are L and the switch unit 40 is in an ON state, a current is supplied to the detection circuit 10 (the first MR bridge 11 and the second MR bridge 12) so that a magnetic detection operation is possible. It is. As a result, the steering rotation angle detection signals are output to the processing unit 201 of the sensor ECU 200 as output signals Vout1 and Vout2.

(Step 12 (S12))
It is determined whether the output signals Vout1 and Vout2 are within the normal range with reference to the parameters of the storage unit 203. If it is within the normal range, the process returns to step 12 again, and the failure diagnosis at the normal time is performed repeatedly at predetermined time intervals. If it is determined that there is a failure (S21), a warning (S22) or the like is given if necessary. Note that the processing unit 201 calculates the steering angle based on the output signals Vout1 and Vout2, and outputs the calculated steering angle to the on-vehicle equipment that is required as an analog signal or a digital signal.

  When the ignition switch of the vehicle is turned off or when a failure is detected in step 21, the above-described flow ends.

(sleep mode)
The sleep mode (standby mode) is a mode in which the magnetic detection device 1 is not operated in order to prevent the battery from being exhausted when the vehicle is not traveling or the like and is set in an operable state by a predetermined return signal. . In this sleep mode, the SLEEP terminal is set to the H level, the switch unit 40 is turned off, and the power supply voltage Vcc is not supplied to the detection circuit 10 (first MR bridge 11 and second MR bridge 12). On the other hand, the sleep mode can be canceled by quickly returning to the normal operation by setting the SLEEP terminal to the L level and switching the switch unit 40 from the off state to the on state. Since the aforementioned SLEEP terminal is connected to the input side of the OR circuit 32, the sleep mode can be turned on and off by switching the H and L of the SLEEP terminal.

[Effect of the embodiment of the present invention]
The above-described embodiment of the present invention has the following effects.
(1) The magnetic detection device 1 connects a plurality of magnetoresistive elements whose resistance values change in accordance with the direction of an applied magnetic field in a bridge shape, and a power supply unit (power supply voltage Vcc) is connected to the opposite ends of the bridge shape. ), A detection circuit 10 that outputs a detection signal corresponding to a change in the resistance value from the bridge-shaped midpoint, an amplification circuit 20 that amplifies and outputs the detection signal, and an input of the amplification circuit 20 A diagnosis circuit 30 for detecting a failure by applying a predetermined voltage to the terminal by a diagnosis signal and detecting the output of the amplification circuit 20, and a switch section that is arranged between the detection circuit 10 and the power supply unit and operates by the diagnosis signal 40. Thereby, the current consumption can be suppressed without operating the detection circuit 10 by setting the switch unit 40 to the non-conduction state (off state) at the time of failure diagnosis or sleep mode.
(2) Since the diagnosis circuit 30 is included in the magnetic detection device 1 as described above, it is possible to reliably perform failure diagnosis even when the system is not operating and the current consumption is reduced. Can be possible.
(3) Since the OR circuit 32 to which the sleep signal (SLEEP) for setting the detection circuit 10 to the sleep mode is input is provided, it is not necessary to externally attach the sleep mode circuit, and the size can be reduced. In addition, by incorporating the sleep mode circuit, it is strong against external noise, and the reliability of the magnetic detection device is improved.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from or changing the technical idea of the present invention. Although typical embodiment and the example of illustration which concern on this invention were illustrated, the said embodiment and example of illustration do not limit the invention based on a claim. Therefore, it should be noted that not all the combinations of features described in the above embodiments and the illustrated examples are essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1 ... Magnetic detection apparatus, 10 ... Detection circuit, 11 ... 1st MR bridge, 12 ... 2nd MR bridge, 20 ... Amplification circuit, 21, 22 ... Operational amplifier, 30 ... Diag circuit, 31 ... OR circuit, 32 ... OR circuit, 40 ..., switch unit, 100 ... steering device, 101 ... rotating member, 102 ... magnet, 200 ... sensor ECU, 201 ... processing unit, 202 ... judgment unit, 203 ... storage unit

Claims (5)

A plurality of magnetoresistive elements whose resistance values change according to the direction of the applied magnetic field are connected in a bridge shape, and a voltage is applied from the power supply unit to the opposite ends of the bridge shape. A detection circuit that outputs a detection signal according to a change in the resistance value from
An amplification circuit that amplifies and outputs the detection signal;
A diagnosis circuit that detects a failure by applying a predetermined voltage to the input terminal of the amplification circuit by a diagnosis signal and detecting the output of the amplification circuit;
A switch unit disposed between the detection circuit and the power supply unit and operated by the diagnostic signal;
A magnetic detection device comprising:   2. The magnetic detection device according to claim 1, wherein when the diagnostic circuit is operated by the diagnostic signal, the switch unit is configured to turn off voltage application from the power supply unit.   The magnetic detection device according to claim 2, wherein the switch unit turns off voltage application from the power supply unit by a sleep signal that puts the detection circuit in a sleep state. The amplifier circuit is composed of an operational amplifier,
The diagnostic circuit is composed of a switching circuit,
A failure diagnosis is performed by applying a predetermined voltage to a diagnostic terminal of the diagnostic circuit to operate the switching circuit to bring the non-inverting input terminal or the inverting input terminal of the operational amplifier to a substantially ground level. The magnetic detection device according to claim 1.   The steady magnetic detection operation of outputting a detection signal from the amplifier circuit is performed by inputting a signal at a level that does not operate the switching circuit to the diagnostic terminal of the diagnostic circuit. 5. The magnetic detection device according to any one of 4 above.

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