JP2010276418A - Disconnection detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disconnection detecting device for a magnetic resistance sensor, capable of detecting by a simple structure whether or not a magnetoresistive element is disconnected even if a rotor does not finish one revolution. <P>SOLUTION: On the occasion of detecting disconnections of magnetoresistive elements R1, R2, R3, and R4 forming a magnetic resistance sensor 31 in the disconnection detecting device 7 formed in a motor 1, a composite signal VM is formed by compositing with a signal composition circuit 77, all comparison results acquired by individually comparing output voltages from the plurality of magnetoresistive elements R1, R2, R3, and R4 with a previously-set reference voltage Vref in comparison circuits 76+a, 76-a, 76+b, and 76-b. On that occasion, the composite signal VM is acquired as a signal which represents whether or not at least one out of the plurality of magnetoresistive elements R1, R2, R3, and R4 is disconnected. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a disconnection detecting device for detecting disconnection of a magnetoresistive element in a magnetoresistive sensor.

  In a brushless motor or the like, a magnetic recording medium for detecting a rotational position and a magnetic recording medium for detecting an origin are provided on the rotor side, and rotation for detecting A-phase and B-phase signals with respect to the magnetic recording medium. A configuration is adopted in which a magnetoresistive sensor for position detection and a magnetoresistive sensor for origin detection for detecting a Z-phase signal are arranged to face each other. In the motor configured as described above, the controller recognizes that the rotor is stopped if a disconnection occurs in the magnetoresistive sensor for detecting the rotational position and the A-phase and B-phase signals are not properly fed back. As a result, there is a possibility that an excessive current is supplied to the motor and the motor is burned out, or an excessive operation of the motor causes an accident such as a collision on the driven side.

  Therefore, based on the Z-phase signal, a period during which the rotor makes one rotation is set as a determination period, and it is determined whether or not the number of detected pulses of the rotational position detection magnetoresistive sensor within the determination period is appropriate. A configuration has been proposed for monitoring whether or not a disconnection has occurred in the magnetoresistive sensor for detecting the rotational position (see Patent Document 1).

JP-A-6-288791

  However, in the configuration described in Patent Document 1, it is determined whether or not the number of detected pulses of the rotational position detecting magnetoresistive sensor is appropriate based on the Z-phase signal obtained by the origin detecting magnetoresistive sensor. Since the determination period is set, it cannot be determined whether or not a disconnection has occurred in the magnetoresistive sensor for detecting the rotational position until the rotor has completed one rotation. Further, when the Z phase is also disconnected at the same time, there is a problem that it cannot be determined whether or not the magnetoresistive sensor is disconnected.

  In view of the above problems, an object of the present invention is to break a magnetoresistive sensor that can detect whether or not the magnetoresistive element is broken even if the rotor does not complete one rotation. It is to provide a detection device.

  In order to solve the above problems, the present invention is a disconnection detecting device for detecting disconnection of a magnetoresistive element in a magnetoresistive sensor in which a plurality of magnetoresistive elements to which a constant current is applied are opposed to a magnetic recording medium, A plurality of comparison circuits that respectively compare output voltages from the plurality of magnetoresistive elements with a preset reference voltage, and all the comparison results of the plurality of comparison circuits are combined, and at least one of the plurality of magnetoresistive elements. When it is recognized that a disconnection has occurred in at least one of the plurality of magnetoresistive elements based on the composite signal, and a signal combining circuit that generates a combined signal indicating whether one is disconnected or not And an error signal generator for generating an error signal.

  In the present invention, when detecting the disconnection of the magnetoresistive element constituting the magnetoresistive sensor, the comparison circuit uses the result of comparing each of the output voltages from the plurality of magnetoresistive elements with a preset reference voltage. For this reason, the period required for the determination of disconnection can be made shorter than one rotation period of the rotating body, so that the disconnection occurs in the magnetoresistive sensor even during the period when the rotating body does not complete one rotation such as immediately after the start of operation. It can be determined whether or not. In the comparison circuit, each of the output voltages from the plurality of magnetoresistive elements is compared with a preset reference voltage, and all the comparison results are synthesized by the signal synthesis circuit to generate a synthesized signal. A combined signal indicating whether or not a break has occurred in at least one of the resistive elements. For this reason, it is only necessary to provide a signal line for transferring only the synthesized result generated by the signal synthesizing circuit between the signal synthesizing circuit and the error signal generating unit, so that the circuit can be simplified. Further, unlike the case of using the output from another magnetoresistive sensor such as a Z-phase magnetoresistive sensor, there is an advantage that even when a disconnection occurs in the Z-phase magnetoresistive sensor, it can be detected.

  In the present invention, the reference voltage is an intermediate level between an output voltage from a magnetoresistive element in which no disconnection occurs and an output voltage from a magnetoresistive element in which a disconnection occurs among the plurality of magnetoresistive elements. In the comparison circuit, one of the binarized signals is output from the comparison circuit corresponding to the magnetoresistive element in which no disconnection occurs, and the comparison circuit corresponding to the magnetoresistive element in which the disconnection occurs Is preferably outputting the other of the binarized signals. According to this configuration, the signal synthesis circuit can generate a synthesis signal indicating whether or not a disconnection has occurred in at least one of the plurality of magnetoresistive elements with a simple logic circuit.

  In the present invention, it is preferable that the comparison circuit compares an output voltage from a magnetoresistive element of a magnetoresistive sensor having a shortest distance from the magnetic recording medium among the plurality of magnetoresistive sensors with the reference voltage. . A magnetoresistive sensor having the shortest distance to the magnetic recording medium is likely to cause disconnection, but such disconnection can be detected efficiently.

  In the present invention, the comparison circuit may compare an output voltage from a magnetoresistive element of a magnetoresistive sensor in which a protective layer is not formed on the surface of the magnetoresistive element among the plurality of magnetoresistive sensors with the reference voltage. preferable. In a magnetoresistive sensor in which a protective layer is not formed on the surface of the magnetoresistive element, disconnection is likely to occur, but such disconnection can be detected efficiently.

  In the present invention, the error signal generator is preferably configured in an application specific integrated circuit (ASIC). According to such a configuration, the other configuration may be the same as the case where the disconnection detecting device according to the present invention is not added, and there is an advantage that it is not necessary to change the design.

  In the present invention, when detecting the disconnection of the magnetoresistive elements constituting the magnetoresistive sensor, the comparison circuit uses the result of comparing each of the output voltages from the plurality of magnetoresistive elements with a preset reference voltage. For this reason, the period required for the determination of disconnection can be made shorter than one rotation period of the rotating body, so that the disconnection occurs in the magnetoresistive sensor even during the period when the rotating body does not complete one rotation such as immediately after the start of operation. It can be determined whether or not. In the comparison circuit, each of the output voltages from the plurality of magnetoresistive elements is compared with a preset reference voltage, and all the comparison results are synthesized by the signal synthesis circuit to generate a synthesized signal. A combined signal indicating whether or not a break has occurred in at least one of the resistive elements. For this reason, it is only necessary to provide a signal line for transferring only the synthesized result generated by the signal synthesizing circuit between the signal synthesizing circuit and the error signal generating unit, so that the circuit can be simplified.

It is explanatory drawing which shows the whole structure of the motor which concerns on embodiment of this invention. (A), (b) is explanatory drawing of the magnetoresistive sensor for rotational position detection in the motor which concerns on embodiment of this invention, and explanatory drawing of the sensor circuit part etc. with respect to the magnetoresistive sensor for rotational position detection. . In the motor according to the embodiment of the present invention, in the state where the magnetoresistive elements of the A-phase and B-phase magnetoresistive sensors are replaced with fixed resistors, the fixed resistance is normal and the + b phase signal in the disconnected state, -b phase It is explanatory drawing which shows the change of the output voltage equivalent to a signal, + a phase signal, and -a phase signal.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Embodiment]
(General configuration of motor)
FIGS. 1A and 1B are an explanatory diagram showing an overall configuration of a motor according to an embodiment of the present invention and an explanatory diagram of a disconnection detection signal processing circuit. A motor 1 shown in FIG. 1A is a brushless motor. In the motor 1, the rotor 11 includes a rotating shaft 13 coupled to a driven member and a rotor magnet 12 fixed to the rotating shaft 13, and a stator 15 is disposed so as to face the rotor magnet 12. Yes. In the rotor 11, a magnetic disk 40 for detecting a magnetic pole position on which a magnetic pole corresponding to the magnetic pole position of the rotor magnet 12 is formed is connected to the rotating shaft 13, so as to face the magnetic disk 40 for detecting the magnetic pole position. A plurality of rotation control sensors 50 are arranged. In this embodiment, as the rotation control sensor 50, three Hall elements 50U, 50V, and 50W having an electrical phase difference of 60 ° are arranged in a fixed state. .

  The rotating shaft 13 is connected to a magnetic drum 20 for detecting a rotational position. The magnetic drum 20 is used for detecting a rotational position (for generating a divided angle signal) at a position shifted in the motor axial direction. A magnetic recording medium 21 and a magnetic recording medium 22 for detecting an origin (for generating a reference position signal) are formed. The magnetic recording medium 21 for detecting the rotational position has N and S poles alternately magnetized on the circumference, and the magnetic recording medium 22 for detecting the origin corresponds to the N and S poles of the magnetic recording medium 21. N pole and S pole are magnetized at one position.

  For the magnetic drum 20, a rotational position detection magnetoresistive sensor 31 for detecting the A-phase and B-phase signals is arranged so as to face the rotational position detection magnetic recording medium 21, thereby detecting the origin. A magnetoresistive sensor 32 for detecting an origin for detecting a Z-phase signal is disposed so as to face the magnetic recording medium 22 for use. In this embodiment, the magnetoresistive sensor 31 and the magnetoresistive sensor 32 are configured on a fixed common substrate 30.

  Sensor circuit units 61A, 61B, 61Z each including a differential amplifier circuit are connected to the A-phase and B-phase magnetoresistive sensors 31 and the Z-phase magnetoresistive sensor 32. The output signals 61B and 61Z are output to the application specific integrated circuit 70 and the upper control unit 100. In addition, sensor circuit units 61U, 61V, 61W each including an amplifier circuit, an A / D conversion circuit, and the like are connected to the three hall elements 50U, 50V, 50W of the U phase, the V phase, and the W phase. The output signals of the sensor circuit units 61U, 61V, 61W are output to the application specific integrated circuit 70 and the upper control unit 100.

  The application specific integrated circuit 70 and the control unit 100 are connected by output lines 85A, 85 / A, 85B, 85 / B from the line drivers 80A, 80B. The application specific integrated circuit 70 and the control unit 100 are connected by a serial signal line (not shown) for outputting a counter value or the like from the application specific integrated circuit 70 to the control unit 100.

  The application-specific integrated circuit 70 includes a counter 71, a memory 72, and the like for detecting the rotational position of the rotor 11 based on detection results of the A-phase and B-phase magnetoresistive sensors 31 and the Z-phase magnetoresistive sensor 32. It has.

  The upper control unit 100 is connected to the coil of the stator 15 via the constant current circuit 110 and the switching circuit 120. The control unit 100 includes three hall elements 50U, 50V, U-phase, V-phase, and W-phase. Based on the detection result of 50 W, the magnetic pole position of the rotor 11 is detected, and based on the detection result of the magnetic pole position, the switching circuit 120 is controlled, thereby controlling the energization of the coil and controlling the rotation of the rotor 11. .

  As shown in FIGS. 1A and 1B, in the motor 1 of this embodiment, as will be described later, the disconnection for detecting the disconnection of the magnetoresistive elements used in the A-phase and B-phase magnetoresistive sensors 31. The disconnection detection device 7 includes an error signal generation unit 73 configured in the application specific integrated circuit 70 based on the result obtained by the disconnection detection signal processing circuit 75. When it is determined that a disconnection has occurred in the magnetoresistive element of the sensor 31, an error signal is generated.

(Configuration of the magnetoresistive sensor 31)
2 (a) and 2 (b) are explanatory diagrams of a magnetoresistive sensor for detecting a rotational position in the motor according to the embodiment of the present invention, and explanatory diagrams of a sensor circuit unit for the magnetoresistive sensor for detecting the rotational position. It is.

  As shown in FIGS. 2A and 2B, in the magnetic recording medium 21 for detecting the rotational position, the N pole and the S pole are alternately arranged at a pitch λ, and the pitch from the N pole to the N pole, and the S The pitch from the pole to the S pole is λ. In contrast, in the magnetoresistive sensor 31 for detecting the rotational position, the four magnetoresistive elements R1, R2, R3, R4 are arranged in parallel in the order of the magnetoresistive elements R1, R3, R2, R4. The pitch between adjacent magnetoresistive elements is λ / 4. A bias magnetic field is applied to the magnetoresistive elements R1, R2, R3, and R4. A bias voltage source Vcc is connected to one terminal of each of the magnetoresistive elements R1, R2, R3, and R4 through a power supply line 33. From the other terminal of the magnetoresistive elements R1, R2, R3, and R4, Each displacement detection signal is output. In this embodiment, as the displacement detection signal, a + b phase signal is output from the magnetoresistive element R1, a -b phase signal is output from the magnetoresistive element R2, a + a phase signal is output from the magnetoresistive element R3, and the magnetic A -a phase signal is output from the resistance element R4.

  Each of the magnetoresistive elements R1, R2, R3, and R4 includes an amplifier 67, transistors 62, 63, 64, and 65, and a constant current circuit 66 including various fixed resistors.

  In the magnetoresistive sensor 31, since the pitch between the magnetoresistive element R1 and the magnetoresistive element R2 is λ / 2, the resistance value of both changes with a phase difference of 180 ° due to the magnetic field received from the magnetic recording medium 21. Accordingly, the signal waveform of the + b phase signal extracted from the magnetoresistive element R1 and the signal waveform of the −b phase signal extracted from the magnetoresistive element R2 are 180 ° out of phase. Further, since the pitch between the magnetoresistive element R3 and the magnetoresistive element R4 is also λ / 2, the signal waveform of the + a phase signal extracted from the magnetoresistive element R3 and the signal of the −a phase signal extracted from the magnetoresistive element R4 The waveform has a phase shifted by 180 °. Since the pitch between adjacent magnetoresistive elements is λ / 4, the signal waveform of the + b phase signal extracted from the magnetoresistive element R1 and the signal waveform of the + a phase signal extracted from the magnetoresistive element R3 are: The phase is shifted by 90 °. In addition, the signal waveform of the -b phase signal extracted from the magnetoresistive element R2 and the signal waveform of the -a phase signal extracted from the magnetoresistive element R4 are 90 ° out of phase.

  Such magnetoresistive elements R1, R2, R3, R4 are generally formed by thin film elements by sputtering or the like, and the surface is usually entirely covered with a protective film.

  The other end of the magnetoresistive element R3 is connected to the non-inverting input terminal (+ terminal) of the differential amplifier 60a of the sensor circuit unit 61A, and the other end of the magnetoresistive element R4 is connected to the inverting input terminal (of the differential amplifier 60a). -Terminal) is connected. The other end of the magnetoresistive element R1 is connected to the non-inverting input terminal (+ terminal) of the differential amplifier 60b of the sensor circuit unit 61B, and the other end of the magnetoresistive element R2 is connected to the inverting input terminal (−) of the differential amplifier 60b. Terminal) is connected. In such a differential amplifier 60a, the output voltage is positively fed back using a feedback resistor, and an appropriate A-phase signal PA (rectangular wave) for the differential input is output. The differential amplifier 60b positively feeds back the output voltage using a feedback resistor and outputs an appropriate B-phase signal PB (rectangular wave) for the differential input.

(Configuration of disconnection detector)
FIG. 3 shows a state in which the fixed resistance is normal with the magnetoresistive elements R1, R2, R3, and R4 of the A-phase and B-phase magnetoresistive sensors 31 replaced with fixed resistors in the motor according to the embodiment of the present invention. It is explanatory drawing which shows the change of the output voltage corresponded to + b phase signal, -b phase signal, + a phase signal, and -a phase signal in the state which disconnected. Here, the used circuit is the same as the sensor circuit portions 61A and 61B for the magnetoresistive sensor 31, and the magnetoresistive elements R1, R2, R3, and R4 of the magnetoresistive sensor 31 and the fixed resistors are electrically equivalent. . Therefore, in the following description, each fixed resistor will be described as magnetoresistive elements R1, R2, R3, and R4.

  As shown in FIGS. 1A, 1 </ b> B, and 2 </ b> B, in the motor 1 of this embodiment, the disconnection detection device 7 is configured by the disconnection detection signal processing circuit 75 and the error signal generator 73. Yes. In the disconnection detecting device 7 of the present embodiment, as shown in FIG. 3, in the normal state and the disconnected state of the magnetoresistive elements R1, R2, R3, R4 of the A-phase and B-phase magnetoresistive sensors 31, the + a phase The fact that the output voltage corresponding to the signal, the -a phase signal, the + b phase signal, and the -b phase signal changes to, for example, 1 V or more and less than 1 V is used.

  More specifically, for example, as in the state (1) shown in FIG. 3, when all of the magnetoresistive elements R1, R2, R3, R4 are normal indicated by “◯”, the output voltage is 1.67V, 1.66V, 1.68V, 1.67V.

  On the other hand, as in the state (2) shown in FIG. 3, the magnetoresistive element R1 is in a disconnected state indicated by “x”, and the magnetoresistive elements R2, R3, R4 are normal indicated by “◯”. The output voltage from the magnetoresistive element R1 is 0.29V, and the output voltages from the other magnetoresistive elements R2, R3, and R4 are 2.30V, 2.32V, and 2.31V.

  When the magnetoresistive element R2 is in a disconnected state and the magnetoresistive elements R1, R3, and R4 are normal as in the state (3) shown in FIG. 3, the output voltage from the magnetoresistive element R2 is 0.29V. The output voltages from the other magnetoresistive elements R1, R3, and R4 are 2.32V, 2.32V, and 2.31V.

  Similarly, in the other states (4) to (9) shown in FIG. 3, the output voltage from the magnetoresistive element in which the disconnection has occurred is less than 1V, and the output voltage from the normal magnetoresistive element is 1V or more.

  Further, as in the state (9) shown in FIG. 3, the output voltage when all the magnetoresistive elements are disconnected is 0.09V, 0.08V, 0.09V, 0.08V, which is less than 1V. .

  When the power supply line 33 is disconnected as in the state (10) shown in FIG. 3, the output voltage from any magnetoresistive element is less than 1V.

  Therefore, in the present embodiment, as shown in FIGS. 1B and 2B, the disconnection detection signal processing circuit 75 has an output voltage (+ a) from the plurality of magnetoresistive elements R1, R2, R3, and R4. A plurality of comparison circuits 76 + a, 76-a, 76 + b, and 76-b that respectively compare a phase signal, a phase signal, a phase b signal, and a phase b signal) with a preset reference voltage Vref. In this embodiment, 1 V is set as the reference voltage Vref. In the comparison circuits 76 + a, 76-a, 76 + b, and 76-b, the output voltages of the magnetoresistive elements R1, R2, R3, and R4 are input to the non-inverting input terminal (+ terminal), and the reference voltage generating circuit 78 The reference voltage Vref output from is input to the inverting input terminal (− terminal). For this reason, when the magnetoresistive elements R1, R2, R3, and R4 are all normal, a high level signal is output from the comparison circuits 76 + a, 76-a, 76 + b, and 76-b. On the other hand, when any one of the magnetoresistive elements R1, R2, R3, and R4 is disconnected, the comparison circuits 76 + a, 76-a, corresponding to the disconnected magnetoresistive elements R1, R2, R3, and R4, A low level signal is output from 76 + b and 76-b. Here, if the signals corresponding to the high level and the low level are made to correspond to the logical values “1” and “0” of the binarized signal, if all of the magnetoresistive elements R1, R2, R3, R4 are normal, the comparison circuit A logic value “1” is output from any of 76 + a, 76-a, 76 + b, and 76-b, and if any one of the magnetoresistive elements R1, R2, R3, and R4 is disconnected, the circuit is disconnected. The comparison circuits 76 + a, 76-a, 76 + b, and 76-b corresponding to the magnetoresistive elements R1, R2, R3, and R4 output a logical value “0”.

  Further, the disconnection detection signal processing circuit 75 synthesizes all the comparison results in the plurality of comparison circuits 76 + a, 76-a, 76 + b, 76-b, and a plurality of magnetoresistive elements R1, R2, R3. , R4, a signal synthesis circuit 77 that generates a synthesis signal VM indicating whether or not a disconnection has occurred. In this embodiment, the comparison circuits 76 + a, 76-a, 76 + b, and 76-b output a signal having a logical value “0” when the magnetoresistive elements R1, R2, R3, and R4 are disconnected. Since the signal is output, the signal synthesis circuit 77 is constituted by a logic circuit composed of an AND circuit, for example. For this reason, when the magnetoresistive elements R1, R2, R3, and R4 are all normal, the synthesized signal VM output from the signal synthesizing circuit 77 is a logical value “1”, and the magnetoresistive elements R1, R2, R3, and R4 When at least one disconnection has occurred, the combined signal VM output from the signal combining circuit 77 has a logical value “0”.

  Therefore, when the composite signal VM is input from the signal synthesis circuit 77 to the application specific integrated circuit 70 via the signal line 79, the error signal generation unit 73 determines whether the composite signal VM has the logical value “1”. It is determined whether or not the value is “0”, and when the composite signal VM is a logical value “0”, an error signal is output as any one of the magnetoresistive elements R1, R2, R3, and R4 is disconnected. Even when the power supply line 33 is disconnected, since the composite signal VM has a logical value “0”, the error signal generation unit 73 outputs an error signal.

  In this embodiment, of the output lines 85A, 85 / A, 85B, 85 / B from the line drivers 80A, 80B for the A-phase signal and the B-phase signal, the ground line that connects the output lines 85B, 85 / B and the ground. 86B and 86 / B are formed, and transistors 81 and 82 are interposed in the ground lines 86B and 86 / B. Therefore, the error signal generator 73 controls the control signal applied to the bases of the transistors 81 and 82 when the synthesized signal VM output from the signal synthesizing circuit 77 is at the low level “0”, and the transistors 81 and 82 are controlled. Switch from off to on. As a result, since both of the two output lines 85B and 85 / B from the line driver 80B are at a low level, the controller 100 can recognize that a break has occurred in the magnetoresistive sensor 31. .

(Main effects of this form)
As described above, in the disconnection detecting device 7 configured in the motor 1 of the present embodiment, the comparison circuit 76 + a is used to detect disconnection of the magnetoresistive elements R1, R2, R3, R4 constituting the magnetoresistive sensor 31. 76-a, 76 + b, and 76-b, the results of comparing the output voltages from the plurality of magnetoresistive elements R1, R2, R3, and R4 with the preset reference voltage Vref are used. For this reason, since the period required for the determination of the disconnection can be made shorter than one rotation period of the rotor 11 (rotating body), the magnetoresistive sensor can be used even within a period in which the rotor 11 does not finish one rotation, such as immediately after the start of operation. It can be determined whether or not a disconnection has occurred at 31.

  Further, in the comparison circuits 76 + a, 76-a, 76 + b, 76-b, the output voltages from the plurality of magnetoresistive elements R1, R2, R3, R4 are respectively compared with a preset reference voltage Vref. Then, when all the comparison results are synthesized by the signal synthesis circuit 77 to generate the synthesized signal VM, the synthesis indicates whether at least one of the plurality of magnetoresistive elements R1, R2, R3, R4 is broken. Signal. For this reason, since only the signal line 79 for transferring only the synthesis result generated by the signal synthesis circuit 77 is provided between the signal synthesis circuit 77 and the error signal generator 73, the circuit can be simplified. Can do.

  Further, unlike the case where the output from another magnetoresistive sensor such as the Z phase magnetoresistive sensor 32 is used, even if a disconnection occurs in the Z phase magnetoresistive sensor 32, the A phase and B phase magnetoresistive sensors. There is an advantage that it is possible to detect whether or not a disconnection has occurred at 31.

  Further, in the present embodiment, the reference voltage Vref is the output voltage from the magnetoresistive element that is not disconnected among the plurality of magnetoresistive elements R1, R2, R3, and R4, and the magnetoresistive element that is disconnected. Is at an intermediate level from the output voltage from. For this reason, one of the binarized signals is output from the comparison circuit corresponding to the magnetoresistive element in which no disconnection occurs among the comparison circuits 76 + a, 76-a, 76 + b, and 76-b. The other of the binarized signals is output from the comparison circuit corresponding to the magnetoresistive element in which is generated. For this reason, the signal synthesis circuit 77 may generate a synthesis signal VM indicating whether or not a disconnection has occurred in at least one of the plurality of magnetoresistive elements R1, R2, R3, and R4 by a simple logic circuit. it can.

  In the present embodiment, the error signal generator 73 is configured in the application specific integrated circuit 70. For this reason, about the other structure of the motor 1, it may be the same as the case where the disconnection detection apparatus 7 is not added, and there exists an advantage that it is not necessary to change a design.

(Another embodiment)
In the above embodiment, only one set of the magnetoresistive sensor 31 for detecting the rotational position is formed. However, as the magnetoresistive sensor 31 for detecting the rotational position, for detecting the rotational position during normal operation. A magnetoresistive sensor and a magnetoresistive sensor for detecting the rotational position at the time of a power failure may be provided. In such a configuration, the disconnection detecting device 7 may be provided in both the magnetoresistive sensor for normal operation and the magnetoresistive sensor for power failure. In order to cope with this, the distance to the magnetic recording medium 21 is narrower than that of the magnetoresistive sensor for power failure. For this reason, since the magnetoresistive sensor for normal operation tends to be disconnected due to foreign matter or the like entering between the magnetic recording medium 21, the normal opera- tion sensor has a short facing distance to the magnetic recording medium 21. The disconnection detecting device 7 may be provided only in the magnetoresistive sensor.

  In the above embodiment, only one set of the magnetoresistive sensor 31 for detecting the rotational position is formed. However, as the magnetoresistive sensor 31 for detecting the rotational position, for detecting the rotational position during normal operation. When providing a magnetoresistive sensor and a magnetoresistive sensor for detecting the rotational position during a power failure, the magnetoresistive sensor for normal operation omits the protective film that covers the magnetoresistive element so that it can respond at high speed. Thus, the facing distance from the magnetic recording medium 21 may be narrowed. As described above, when there are a magnetoresistive sensor in which the magnetoresistive element is covered with the protective film and a magnetoresistive sensor in which the magnetoresistive element is not covered with the protective film, the magnetoresistive element is not covered with the protective film. The magnetoresistive sensor tends to be broken due to foreign matter entering the magnetic recording medium 21. Therefore, the disconnection detecting device 7 may be provided only in the magnetoresistive sensor in which the magnetoresistive element is not covered with the protective film.

  In the above embodiment, the error signal generation unit 73 is all configured in the specific application integrated circuit 70. However, the disconnection detection signal processing circuit 75, the sensor circuit units 61A, 61B, 61Z, the sensor circuit units 61U, 61V, A part or all of 61W may be configured in the application specific integrated circuit 70. The error signal generator 73 may be configured outside the application specific integrated circuit 70.

  In the above embodiment, the error signal generator 73 sets both the two output lines 85B and 85 / B from the line driver 80B of the B-phase signal PB as the error signal to the low level. Both of the two output lines 85A and 85 / A from the driver 80A may be at a low level. Further, the error signal generation unit 73 may serially transfer the error signal when transferring the counter value to the control unit 100 via a serial signal line (not shown).

DESCRIPTION OF SYMBOLS 1 Motor 7 Disconnection detection apparatus 11 Rotor 21 Magnetic recording medium 31 for rotational position detection Magnetoresistive sensor 40 for rotational position detection Magnetic disk 50 for magnetic pole position detection Rotation control sensor 50U, 50V, 50W Hall element 70 Application-specific integration Circuit (disconnection detection device)
73 Error signal generator 75 Disconnection detection signal processing circuit 76 + a, 76-a, 76 + b, 76-b Comparison circuit 77 Signal synthesis circuit 100 Upper control units R1, R2, R3, R4 Magnetoresistive element

Claims (5)

A disconnection detecting device for detecting disconnection of the magnetoresistive element in a magnetoresistive sensor in which a plurality of magnetoresistive elements to which a constant current is applied are opposed to a magnetic recording medium,
A plurality of comparison circuits each for comparing output voltages from the plurality of magnetoresistive elements with a preset reference voltage;
A signal synthesis circuit for synthesizing all the comparison results in the plurality of comparison circuits and generating a synthesis signal indicating whether or not a disconnection has occurred in at least one of the plurality of magnetoresistive elements;
An error signal generator for generating an error signal when recognizing that a break has occurred in at least one of the plurality of magnetoresistive elements based on the combined signal;
A disconnection detecting device characterized by comprising: The reference voltage is at an intermediate level between an output voltage from a magnetoresistive element in which no disconnection has occurred and an output voltage from a magnetoresistive element in which a disconnection has occurred, among the plurality of magnetoresistive elements,
Among the comparison circuits, one of the binarized signals is output from the comparison circuit corresponding to the magnetoresistive element in which no disconnection has occurred, and the binary value is output from the comparison circuit corresponding to the magnetoresistive element in which the disconnection has occurred. The disconnection detecting device according to claim 1, wherein the other signal is output.   The comparison circuit compares an output voltage from a magnetoresistive element of a magnetoresistive sensor having the shortest distance from the magnetic recording medium among the plurality of magnetoresistive sensors with the reference voltage. The disconnection detection apparatus according to 1 or 2.   The comparison circuit compares an output voltage from a magnetoresistive element of a magnetoresistive sensor in which a protective layer is not formed on the surface of the magnetoresistive element among the plurality of magnetoresistive sensors with the reference voltage. Item 3. The disconnection detection device according to item 1 or 2.   The disconnection detection device according to claim 1, wherein the error signal generation unit is configured in an application specific integrated circuit.

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