JP2010025730A - Magnetic sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sensor device surely performing a failure diagnosis even at the start of a system in which an object to be detected does not operate. <P>SOLUTION: This magnetic sensor device 1 includes a detection circuit 10 that includes a plurality of MR elements connected with each other in a bridge circuit having resistance values varied in accordance with an orientation of a magnetic field applied thereto, and outputs a detection signal in accordance with the variation of the resistance values. The magnetic sensor device 1 further includes an amplifier circuit 20 that amplifies the detection signal so as to output it, and a diagnosing circuit having a diagnosing terminal which is used in such a manner that a predetermined voltage is applied to an input terminal of the amplifier circuit 20 from the outside and the output of the amplifier circuit 20 is detected so as to diagnose whether the amplifier circuit 20 adequately operates. By applying a predetermined voltage to the diagnosing terminals (DIAG1, DIAG2), determination whether a failure occurs is made on the basis of output signals Vout1, Vout2 of the magnetic sensor device 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic sensor device, and more particularly to a magnetic sensor device having a diagnosis 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.

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.
JP 2008-51668 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.

  Accordingly, an object of the present invention is to provide a magnetic sensor device capable of reliably performing a failure diagnosis even when the system is started when the detection target is not operating.

[1] In order to achieve the above object, according to the present invention, a plurality of magnetoresistive elements (MR elements) whose resistance values change according to the direction of the applied magnetic field are connected in a bridge shape so that the resistance value changes. A detection circuit for outputting a corresponding detection signal; an amplification circuit for amplifying and outputting the detection signal; and applying a predetermined voltage from the outside to the input terminal of the amplification circuit to detect the output of the amplification circuit There is provided a magnetic sensor device comprising a diagnostic circuit having a diagnostic terminal for detecting a failure.

[2] The amplifier circuit is composed of an operational amplifier, the diagnosis circuit is composed of a switching circuit, and the operational circuit is operated by applying a predetermined voltage to the diagnosis terminal of the diagnosis circuit. The magnetic sensor device according to the above [1], wherein failure diagnosis is performed by setting the plus input terminal or minus input terminal to a substantially ground level.

[3] Further, by inputting a signal at a level that does not operate the switching circuit to the diagnosis terminal of the diagnosis circuit, a normal operation of outputting a detection signal from the amplification circuit is performed. The magnetic sensor device according to [1] or [2] may be used.

  According to the present invention, it is possible to provide a magnetic sensor device capable of reliably performing a failure diagnosis even at the time of system start when the detection target is not operating.

[Embodiments of the present invention]
FIG. 1 is a circuit diagram of a magnetic sensor device 1 according to an embodiment of the present invention. FIG. 2 is a configuration block diagram of an example in which the magnetic sensor 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 diagnostic function of the magnetic sensor 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 magnetic sensor device 1)
As shown in FIG. 1, the magnetic sensor device 1 according to the embodiment of the present invention includes a detection circuit 10, an amplification circuit 20, and a diagnosis circuit 30.

  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. An inverting amplifier is configured by the resistor R ₁ connected to the plus input terminal of the operational amplifier 21, the resistor R _i1 connected to the minus input terminal, and the resistor R _f1 connected between the minus input terminal and the output terminal OUT 1. Likewise, the resistance R ₂ is connected to the positive input terminal of the operational amplifier _22, resistor R _i2 is connected to the negative input terminal _and the inverting amplifier by a resistor R _f2 is connected between the negative input terminal and the output terminal OUT2 is configured Yes.

The output signal Vout1 at the output terminal OUT1 is a signal in which the input (V1−V2) of the operational amplifier 21 is inverted and amplified by the gain (−R _f1 / R _i1 ) and superimposed on the reference voltage of the plus terminal, and Vout1 = (V2 −V1) · R _f1 / R _i1 + Vcc · R ₄ / (R ₃ + R ₄ ). Similarly, the output signal Vout2 at the output terminal OUT2 becomes a signal in which the input (V3-V4) of the operational amplifier 22 is inverted and amplified by the gain ( _-Rf2 / _Ri2 ) and superimposed on the reference voltage of the plus terminal, and Vout2 a _{= (V4-V3) · R} f2 / R i2 + Vcc · R 4 / (R 3 + R 4). Vout1 and Vout2 have a phase difference of π / 2.

  The diagnosis circuit 30 includes a switching circuit for independently setting the negative input terminal and the positive input terminal of the operational amplifiers 21 and 22 to the Hi level (hereinafter referred to as H) or the Lo level (hereinafter referred to as L). By setting the terminal of DIAG1 to H, the gates G1 and G2 become H and the FET becomes conductive, and the negative input terminal of the operational amplifier 21 and the positive 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 positive input terminal of the operational amplifier 21 and the negative 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 the first midpoint voltage is applied to each of the negative input terminal and the positive input terminal. V1 to the fourth midpoint voltage V4 are input as they are.

  The detection circuit 10, the amplification circuit 20, and the diagnosis circuit 30 are formed as a single magnetic sensor device 1. The magnetic sensor device 1 is supplied with a power supply voltage from the outside, is applied with a voltage to the diagnosis terminals (DIAG1, DIAG2), and outputs a detection signal from the amplifier circuit 20 when all the diagnosis terminals are set to L level. Performs normal operation.

  The case where the diagnostic function of the magnetic sensor device 1 according to the embodiment of the present invention is applied to detection of a steering rotation angle of a 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 (only a part of which is shown) 100, and close to the magnet 102, the magnetic sensor 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 sensor 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 the output signals Vout1 and Vout2 from the magnetic sensor 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 sensor 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 sensor device 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 the diagnosis function and a judgment reference value for determining whether the output signals Vout1, Vout2, etc. from the magnetic sensor device 1 are within the normal range. And is referred to by the determination unit 202 as necessary.

  The failure diagnosis in the case where the diagnosis function of the magnetic sensor 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.

(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 to 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 sensor 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))
From the determination unit 202 of the sensor ECU 200, the terminal of DIAG1 of the magnetic sensor device 1 is set to H, and the terminal of DIAG2 is set to L. At this time, if the output signals Vout1 and Vout2 from the magnetic sensor 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.

(Step 03 (S03))
Contrary to step 02, the terminal of DIAG1 is set to L and the terminal of DIAG2 is set to H. If the output signals Vout1 and Vout2 from the magnetic sensor 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. 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 DIAG1 of the magnetic sensor device 1 is set to L and the terminal of DIAG2 is set to L from the determination unit 202 of the sensor ECU 200. With this setting, the steering rotation angle detection signals are output to the processing unit 201 of the sensor ECU 200 as they are as the 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.

[Effect of the embodiment of the present invention]
The above-described embodiment of the present invention has the following effects.
(1) A switching circuit for setting the negative input terminal and the positive input terminal of the operational amplifiers 21 and 22 to H or L level independently, and a diagnosis terminal (DIAG1, DIAG2) for operating the switching circuit Therefore, even when the system is not operating, the failure diagnosis and failure detection can be performed reliably.
(2) Since the diagnostic circuit 30 is included in the magnetic sensor device 1 as described above, failure detection can be performed without adding external components, leading to quality improvement of the magnetic sensor device.

  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.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic sensor device, 10 ... Detection circuit, 11 ... 1st MR bridge, 12 ... 2nd MR bridge, 20 ... Amplification circuit, 21, 22 ... Operational amplifier, 30 ... Diag circuit, 100 ... Steering device, 101 ... Rotating member 102 ... Magnet 200 ... Sensor ECU 201 ... Processing unit 202 ... Judgment unit 203 ... Storage unit

Claims (3)

A detection circuit that connects a plurality of magnetoresistive elements (MR elements) whose resistance values change according to the direction of the applied magnetic field in a bridge shape and outputs a detection signal according to the change in the resistance value;
An amplification circuit that amplifies and outputs the detection signal;
A diagnosis circuit comprising a diagnosis terminal for detecting a failure by applying a predetermined voltage to the input terminal of the amplification circuit from the outside and detecting the output of the amplification circuit;
A magnetic sensor device comprising: 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 the diagnostic terminal of the diagnostic circuit to operate the switching circuit to bring the positive input terminal or the negative input terminal of the operational amplifier to a substantially ground level. The magnetic sensor device according to claim 1. 3. A steady state 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. The magnetic sensor device according to 1.

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