JP6409509B2 - Sensor system - Google Patents

Description

  The present invention relates to a torque sensor that outputs a detection signal of a steering torque input via a steering wheel, and is connected to the torque sensor via a signal line, and receives the detection signal of the torque sensor via the signal line. The present invention also relates to a sensor system including a control device used for torque control of an electric motor that applies torque to steered wheels of a vehicle.

  For example, Patent Document 1 discloses a sensor system including a torque sensor including two Hall ICs (sensing units) that detect steering torque, and an ECU (control device) that performs steering assist control based on the output of the torque sensor. Is described. Specifically, each of the Hall ICs is connected to the ECU by a different signal line, and the detected value of the steering torque is transmitted from each of the Hall ICs to the ECU as an analog voltage signal. Then, the ECU determines whether the received analog signal is abnormal based on the received analog voltage signal.

JP 2010-76637 A

  In the case of the torque sensor, since each of the Hall ICs is connected to the ECU via different signal lines, the cost is increased. In the case of the torque sensor, the analog voltage signal output from the Hall IC becomes a signal having a voltage value lower than the actual value due to a voltage drop or the like at the connector portion connecting the signal line and the ECU. There is concern about misrecognition. When the ECU misrecognizes the value of the steering torque, the accuracy of determining the presence / absence of an abnormality also decreases. Therefore, even if the determination processing for the presence / absence of an abnormality is performed, there is a concern that the accuracy of assist control may be decreased. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sensor system capable of reducing the number of signal lines and suppressing a reduction in accuracy of steering torque recognized by a control device. There is to do.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
1. A torque sensor that outputs a steering torque detection signal that is input via the steering wheel, and a detection signal that the torque sensor transmits to a signal line that is a serial line are received, and torque is applied to the steered wheels of the vehicle. A control device used for torque control of an electric motor, wherein the torque sensor senses the steering torque, converts the sensed steering torque into an analog electrical signal, and outputs the analog torque signal; and An A / D converter that converts an electrical signal output from the sensing unit into digital data, and digital data corresponding to each electrical signal of the sensing unit is output as the detection signal to the control device via the signal line. And an output unit configured to output digital data corresponding to the electrical signal, and a detection value detected by the sensing unit is out of a predetermined range. In addition to the detection abnormality determination processing unit that determines that there is an abnormality in the detection value of the sensing unit and the detection abnormality determination processing unit, the detection value by the sensing unit based on the state of the signal line A system abnormality determination processing unit that determines that there is an abnormality in the transmission system.

  According to the above configuration, detection signals from two or more sensing units are transmitted to the control device via the serial line. For this reason, the number of signal lines can be reduced. Moreover, according to the said structure, the detection signal by a sensing part is transmitted to a signal line as digital data. The digital data has resistance against an analog change of a signal propagating through the signal line. For this reason, it can suppress that the precision of the steering torque which a control apparatus recognizes resulting from the resistance value in the connection location of a signal wire | line and a control apparatus becoming large falls.

Therefore, in cooperation with the provision of the detection abnormality determination processing unit and the system abnormality determination processing unit, it is possible to suitably suppress a decrease in the accuracy of the steering torque recognized by the control device.
The “signal line state” includes not only the state of whether a predetermined signal is propagated through the signal line but also the transition state of the logical value when the signal is propagated through the signal line. .

  2. 2. The sensor system according to claim 1, wherein the control device uses at least a period of time until the control device is turned off at least for a detection value determined by the sensing unit that is determined to be abnormal by the detection abnormality determination processing unit. During this time, the torque control is not used.

  In the above configuration, the detection value by the sensing unit determined to be abnormal is not used for torque control at least during the period until the control device is once turned off. For this reason, since it is possible to reduce the probability that a detected value having an abnormality is used for torque control, it is possible to suppress a decrease in the reliability of torque control.

  3. 3. The sensor system according to 1 or 2, wherein the two or more sensing units include a first sensing unit and a second sensing unit different from the first sensing unit, and the control device is based on the detection abnormality determination processing unit. Based on the determination result, the first sensing unit performs the torque control on condition that the detection value by the first sensing unit is out of a predetermined range and the detection value by the second sensing unit is within the predetermined range. The detection value by the second sensing unit is used without using the detection value by.

In the above configuration, even when it is determined that there is an abnormality in the detection value by the first sensing unit, torque control can be performed based on the detection value by the second sensing unit.
4). 4. The sensor system according to any one of 1 to 3, wherein the output unit has absolute values that are greater than zero and different from each other depending on whether the digital data is logic H or logic L. The system abnormality determination processing unit outputs a detected value transmitted by the sensing unit to the transmission system on the condition that a current corresponding to the logic H and a current corresponding to the logic L are not output. It is determined that there is an abnormality.

  In the above configuration, the output unit outputs a signal expressing each of logic H and logic L by current values. For this reason, it is suppressed that the value of a signal changes by the poor connection etc. between a signal wire | line and a control apparatus. Further, it is possible to distinguish between an abnormality in the transmission system when a current corresponding to the logical value is not output and an abnormality in the transmission system due to a short between the signal line and the ground.

  5. 4. The sensor system according to any one of the above 1 to 3, wherein the output unit outputs a pulsed voltage signal, and the voltage signal is a logic L or a logic L of the digital data. Depending on whether or not the pulse widths are different from each other, the system abnormality determination processing unit does not output a voltage signal having a pulse width corresponding to the logic H and a voltage signal having a pulse width corresponding to the logic L. As a result, it is determined that there is an abnormality in the transmission system of the detection value by the sensing unit.

  In the above configuration, each of logic H and logic L is expressed by the pulse width of the voltage signal. For this reason, even if the peak value (voltage value) of the pulse changes due to poor connection between the signal line and the control device, it is possible to suppress the logical value from changing. It is also possible to distinguish between a transmission system abnormality when a voltage signal having a pulse width corresponding to a logical value is not output and a transmission system abnormality due to a short between the signal line and the ground.

  6). 6. The sensor system according to 4 or 5, wherein the output unit is digital data corresponding to electrical signals of a first sensing unit and a second sensing unit different from the first sensing unit among the two or more sensing units. And data for evaluating the reliability of the digital data separately from the digital data corresponding to the electrical signals are sequentially transmitted as a data stream of a predetermined bit length, Both digital data corresponding to the respective electrical signals of the first sensing unit and the second sensing unit are included.

  In the above configuration, one data stream includes digital data corresponding to both the detection value by the first sensing unit and the detection value by the second sensing unit. For this reason, the timing at which the control device recognizes the detection value by the first sensing unit and the timing at which the control device recognizes the detection value by the second sensing unit, compared to the case where these detection values are included in different data streams. It is easy to shorten the time difference between On the other hand, when included in data streams different from each other, for example, corresponding to the detection value by the second sensing unit during or after the process of evaluating the reliability of the data stream corresponding to the detection value by the first sensing unit. Prone to receiving data streams. For this reason, the time difference between the timing at which the control device recognizes the detection value by the first sensing unit and the timing at which the control device recognizes the detection value by the second sensing unit tends to be long.

  7). 6. The sensor system according to 6, wherein one data stream includes an error detection code for detecting data in the data stream as an error detection target, and the system abnormality determination processing unit is based on the error detection code. On condition that error detection is performed, a process for determining that there is an abnormality in the transmission system of both the detection value by the first sensing unit and the detection value by the second sensing unit is performed, and the control device The detected value of the transmission system determined to be abnormal by the system abnormality determination processing unit is not used for the torque control at least during the period until the control device is once turned off.

  In the above configuration, the reliability of the data stream can be enhanced by including an error detection code in the data stream and using this to detect data errors in the data stream.

8). 8. The sensor system according to 6 or 7, wherein the A / D converter is provided for each of the sensing units.
In the above configuration, by providing an A / D converter for each sensing unit, it is easy to synchronize the sampling timing by the A / D converter between sensing units that are different from each other.

  9. The sensor system according to any one of 6 to 8, wherein a counter that is updated each time sampling is performed by the A / D converter is provided for each A / D converter, and the first sensing unit, And the counter value corresponding to each of the second sensing units is included in one data stream, and the system abnormality determination processing unit matches the previous value and the current value of the counter included in the data stream. On the condition that the sensing unit corresponding to the counter performs a process of determining that there is an abnormality in the transmission system of the detection value, and the control device transmits the transmission determined to be abnormal by the system abnormality determination processing unit The detected value of the system is not used for the torque control at least during the period until the control device is once turned off.

  Since the value of the counter is updated each time sampling is performed by the A / D converter, it is considered that an abnormality has occurred in the counter when the values of the counters in the adjacent data streams are equal to each other. In this case, it is considered that the reliability of the digital data corresponding to the electrical signal of the sensing unit corresponding to the counter is lowered. In the above configuration, in view of this point, the transmission system abnormality is determined based on the value of the counter, and when the abnormality is determined, the detected value corresponding to the determined transmission system is not used for torque control. For this reason, the fall of the reliability of torque control can be suppressed.

  10. 10. The sensor system according to any one of 1 to 9, wherein a first sensing unit of the two or more sensing units and a second sensing unit different from the first sensing unit are configured to control the steering torque. The output characteristics of the electrical signal with respect to the change are opposite to each other, and the detection abnormality determination processing unit is configured to convert the digital data value corresponding to the electrical signal of the first sensing unit and the electrical signal of the second sensing unit. A process for determining that there is an abnormality in at least one of the first sensing unit and the second sensing unit is executed on the condition that the sum of the corresponding digital data values is out of a specified range.

  When the output characteristics of the first sensor and the second sensor are as described above, the sum of their output values is a constant value that does not depend on the magnitude of the steering torque. For this reason, when the sum deviates from the specified range, it can be determined that the detection value by the first sensing unit and the detection value by the second sensing unit are significantly different from each other, and abnormality has occurred in at least one of them.

  11. The sensor system according to any one of 1 to 10 further includes a magnetic circuit that changes a magnetic flux density according to a steering torque input via the steering wheel, and the torque sensor is configured by the magnetic circuit. The generated magnetic flux may be detected as a steering torque.

The block diagram which shows the structure of the power steering apparatus concerning one Embodiment. The perspective view which shows the disassembled perspective structure of the sensor unit concerning the embodiment. The block diagram which shows the electrical structure of the torque sensor of the embodiment. (A)-(c) is a figure which shows the output characteristic of the torque sensor of the embodiment. 6 is an exemplary flowchart illustrating a procedure of frame counter update processing by the DSP according to the embodiment; The figure which shows the structure of the data stream concerning the embodiment. The time chart which shows the transition example of the current signal which the output part concerning the embodiment outputs. The flowchart which shows the procedure of the abnormality determination process concerning the embodiment. 6 is a flowchart showing a procedure of frame counter abnormality detection processing according to the embodiment. The flowchart which shows the procedure of Da and Db abnormality detection processing concerning the embodiment. The perspective view which expands and shows a part of sensor unit concerning the modification of the embodiment. The time chart which shows the transition example of the voltage signal which the output part concerning the modification of the embodiment outputs.

Hereinafter, an embodiment in which a sensor system is embodied in an electric power steering apparatus will be described with reference to the drawings.
The electric power steering apparatus (EPS 10) shown in FIG. 1 includes a steering mechanism 20 that steers the steered wheels 14 based on the user's operation of the steering wheel 12, and an assist mechanism 30 that assists the user's steering operation.

  The steering mechanism 20 includes a steering shaft 22 that serves as a rotating shaft of the steering wheel 12. The steering shaft 22 includes a column shaft 23 connected to the steering wheel 12, an intermediate shaft 24 connected to the lower end portion of the column shaft 23, and a pinion shaft 25 connected to the lower end portion of the intermediate shaft 24. A rack shaft 28 is connected to the lower end portion of the pinion shaft 25 via a rack and pinion mechanism 26. In the steering mechanism 20, when the steering shaft 22 rotates in accordance with the user's operation of the steering wheel 12, the rotational motion is converted into a reciprocating linear motion in the axial direction of the rack shaft 28 via the rack and pinion mechanism 26. The reciprocating linear motion of the rack shaft 28 is transmitted to the steered wheels 14 through tie rods 29 connected to both ends thereof, whereby the steered angle of the steered wheels 14 is changed and the traveling direction of the vehicle is changed.

  The assist mechanism 30 includes a motor 32 that applies assist torque to the steering shaft 22. The rotation of the motor 32 is transmitted to the column shaft 23 via the speed reducer 34, whereby a motor torque is applied to the steering shaft 22 and the steering operation is assisted.

  The EPS 10 includes a sensor unit 50 that detects torque (steering torque) applied to the steering shaft 22 by a user's steering operation on the column shaft 23. The sensor unit 50 includes a magnetic circuit 52 and a torque sensor 70. The output of the torque sensor 70 is taken into the control device (ECU 40). The ECU 40 sets the target assist torque based on the steering torque detected by the torque sensor 70, and the current supplied to the motor 32 so that the assist torque applied from the motor 32 to the steering shaft 22 follows the target assist torque. To control. Thus, assist control for applying motor torque to the steering shaft 22 is executed.

FIG. 2 shows the configuration of the magnetic circuit 52.
As shown in FIG. 2, the column shaft 23 is connected to the input shaft 23a connected to the steering wheel 12 and the output shaft 23c connected to the intermediate shaft 24 on the same axis m via the torsion bar 23b. Have a structure.

  The magnetic circuit 52 includes a cylindrical holding member 54 and annular yokes 56 and 58 disposed around the holding member 54 with a predetermined gap therebetween. The holding member 54 is fitted on the lower end portion of the input shaft 23a, and rotates together with the input shaft 23a. A multipolar magnet 54 a in which N poles and S poles are alternately arranged in the circumferential direction is attached to the outer peripheral surface of the holding member 54. The yokes 56 and 58 are connected to the output shaft 23c via a connection structure (not shown), and rotate integrally with the output shaft 23c. On the inner peripheral surface of the yoke 56 disposed on the input shaft 23a side, a plurality of claw portions 56a extending toward the output shaft 23c are formed at predetermined angular intervals. A plurality of claw portions 58a extending toward the input shaft 23a are formed at predetermined angular intervals on the inner peripheral surface of the yoke 58 disposed on the output shaft 23c side.

  The magnetic circuit 52 includes an annular magnetic flux collecting ring 60 disposed around the yoke 56 with a predetermined gap therebetween, and an annular magnetic flux collecting ring disposed around the yoke 58 with a predetermined gap therebetween. 62. The magnetism collecting rings 60 and 62 are made of a magnetic member, and are fixed to a housing (not shown) that covers the periphery of the column shaft 23. As shown in the enlarged view in the figure, the magnetic flux collecting rings 60 and 62 are formed with magnetic flux collecting portions 60a and 62a that are opposed to each other with a predetermined gap in the direction of the axis m.

  Magnetic flux that comes out of the N pole of the multipole magnet 54a and enters the S pole passes through the yokes 56 and 58 via the claw portions 56a and 58a. At this time, when the magnetic flux density is different between the magnetic flux collecting rings 60 and 62 arranged around the yokes 56 and 58, a magnetic flux is generated between the magnetic flux collecting portions 60a and 62a.

  A torque sensor 70 is sandwiched between the magnetism collecting units 60a and 62a. The torque sensor 70 is a semiconductor integrated circuit that outputs digital data corresponding to the magnetic flux density between the magnetic flux collectors 60a and 62a.

  Here, when the user inputs steering torque via the steering wheel 12, the steering torque is transmitted from the input shaft 23a to the output shaft 23c via the torsion bar 23b. At that time, torsional deformation corresponding to the steering torque occurs in the torsion bar 23b, and relative rotational displacement occurs between the input shaft 23a and the output shaft 23c. Therefore, the relative positional relationship between the multipolar magnet 54a and the claw portions 56a and 58a of the yokes 56 and 58 changes, and the magnetic flux density between the magnetic collecting portions 60a and 62a changes. That is, when the relative rotation angle of the output shaft 23c with respect to the input shaft 23a, in other words, the torsion angle of the torsion bar 23b changes, the magnetic flux density between the magnetic flux collecting portions 60a and 62a changes. Here, the torsion angle is an amount having a positive correlation with the steering torque. For this reason, the magnetic flux density between the magnetic flux collectors 60a and 62a has a correlation with the steering torque. The torque sensor 70 detects the magnetic flux density between the magnetic flux collectors 60a and 62a as a steering torque.

FIG. 3 shows the configuration of the torque sensor 70.
As shown in FIG. 3, the torque sensor 70 is connected to a signal line L1 that is a serial line, and communicates with the ECU 40 via the signal line L1. The torque sensor 70 is connected to the power supply line L3 and the ground line L2, and electric power is supplied through these. Note that the power supply source may be the ECU 40.

  The torque sensor 70 includes Hall elements 72a and 72b, A / D converters 74a and 74b, digital processing devices (DSPs 76a and 76b), and an output unit 78. Each of the hall elements 72a and 72b senses the magnetic flux density as a steering torque, and outputs voltage signals Va and Vb, which are analog electric signals corresponding to the sensed magnetic flux density. FIG. 4A and FIG. 4B show the voltage signals Va and Vb. As illustrated, the voltage signal Va and the voltage signal Vb are both “V1” when the steering torque is “0”. The voltage signals Va and Vb have a one-to-one correspondence relationship with the steering angle in a region where the absolute value of the steering torque is equal to or less than the value to be twisted to the assumed maximum torsion angle of the torsion bar 23b. In FIG. 4, the upper limit voltage VH and the lower limit voltage VL correspond to the absolute value of the steering torque that causes the torsion bar 23b to be twisted to the assumed maximum twist angle. The value of the voltage signal Vb when the steering torque is not zero is equal to the value of the voltage signal Va when the sign of the steering torque is inverted. That is, the hall element 72a and the hall element 72b have output characteristics opposite to each other with respect to a change in steering torque. Therefore, as shown in FIG. 4C, “Va + Vb”, which is the sum of the voltage signal Va and the voltage signal Vb, is a constant value “2 × V1”.

  Each of the A / D converters 74a and 74b shown in FIG. 3 converts the voltage signals Va and Vb into digital data Da0 and Db0 at a predetermined cycle, and outputs them. Each of the DSPs 76a and 76b performs predetermined processing on the digital data Da0 and Db0, and each time the new digital data Da0 and Db0 are sampled by the A / D converters 74a and 74b, respectively, the frame counter. Each of Ca and Cb is updated. The digital data Da and Db output from the DSPs 76a and 76b may be obtained by performing predetermined digital processing such as known temperature correction on the digital data Da0 and Db0 output from the A / D converters 74a and 74b. . However, the digital data output from the DSP 76a is digital data corresponding to the voltage signal Va of the Hall element 72a, and the digital data output from the DSP 76b is digital data corresponding to the voltage signal Vb of the Hall element 72b.

  FIG. 5 shows a procedure for updating the frame counter Ca by the DSP 76a. The process shown in FIG. 5 is repeatedly executed by the DSP 76a, for example, at a predetermined cycle. Since the update process of the frame counter Cb by the DSP 76b is the same, the description thereof is omitted.

  In the series of processing shown in FIG. 5, the DSP 76a first acquires the digital data Da0 newly output by the A / D converter 74a (S10). Subsequently, the DSP 76a updates the frame counter Ca (S12). Specifically, the DSP 76a increments the counter value in binary notation, such as “00 → 01 → 10 → 11”, initializes the counter value, and then increments the counter value again. 2 bits), the value of the frame counter Ca is updated every time new digital data Da0 is acquired.

  The output unit 78 shown in FIG. 3 combines the digital data Da and Db and the frame counters Ca and Cb into one data stream DS, and the signal line L1 has the same cycle as the sampling cycle of the A / D converters 74a and 74b. To the ECU 40 via

  FIG. 6 shows the configuration of one data stream. As shown in FIG. 6, one data stream includes four frames F1 to F4. Each of the frames F1 to F4 includes a start bit, data bits D0 to D8, and a parity bit P. Here, a part of the bit group constituting the digital data Da is assigned to the data bits D0 to D8 of the first frame F1. Further, a part of the bit group constituting the digital data Db is assigned to the data bits D0 to D3 of the second frame F2, and the digital data Da is constituted of the data bits D4 to D7 of the second frame F2. A part of the bit group is assigned. A sensor ID is assigned to the data bit D8 of the second frame F2. The sensor ID is for specifying which one of the EPS 10 includes a plurality of torque sensors 70, and is not used in the present embodiment. A part of the bit group constituting the digital data Db is assigned to the data bits D0 to D8 of the third frame F3. Frame counters Ca and Cb and an error detection code Ed by cyclic redundancy check (CRC) are assigned to data bits D0 to D8 of the fourth frame F4.

  The output unit 78 illustrated in FIG. 3 outputs the data stream DS to the signal line L1 as a current signal. FIG. 7 illustrates a current signal output to the signal line L1. As shown in the figure, in the present embodiment, the logic H and the logic L are both values larger than zero and are expressed as current values having different values. The output unit 78 performs a self-diagnosis process for determining whether there is an internal abnormality. If it is determined that there is an abnormality, the output unit 78 stops outputting the current signal and stops responding to the ECU 40.

  The ECU 40 recognizes the value of the steering torque indicated by the digital data Da as a detected value of the steering torque by the hall element 72a, and recognizes the value of the steering torque indicated by the digital data Db as a detected value of the steering torque by the hall element 72b. Then, the assist control is executed based on the detected value of the steering torque. However, the ECU 40 executes an abnormality determination process based on the data stream DS before using the digital data Da and Db for assist control.

FIG. 8 shows the procedure of the abnormality determination process. This process is repeatedly executed by the ECU 40, for example, at a predetermined cycle.
In this series of processes, the ECU 40 first determines whether or not the transmission stop state of the data stream DS continues (S20). This process is for determining whether or not the torque sensor 70 has stopped responding by the self-diagnosis by the output unit 78 described above. When determining that the torque sensor 70 has not stopped the response (S20: NO), the ECU 40 receives the data stream DS (S22). Next, the ECU 40 executes error detection processing of the data stream DS using the parity and the CRC (S24). If the ECU 40 determines that the data stream DS is normal as a result of the error detection process (S26: YES), the ECU 40 initializes an error counter Ne for error detection (S28). On the other hand, if the ECU 40 determines that the data stream DS is abnormal as a result of the error detection processing (S26: NO), the ECU 40 increments the error counter Ne for error detection, and the digital stream in the data stream DS received this time. The data Da and Db are not used, and the previous value is substituted for the assist control (S30). After initializing the error counter Ne in step S28, the ECU 40 executes an abnormality detection process for the frame counters Ca and Cb (S32).

FIG. 9 shows the procedure of abnormality detection processing for the frame counters Ca and Cb.
As shown in FIG. 9, the ECU 40 first sets the current value “Ca (n)” of the frame counter Ca equal to the previous value “Ca (n−1)” and the current value “Cb (n) of the frame counter Cb. ) ”And the previous value“ Cb (n−1) ”are determined (S50). This process is for determining whether or not there is an abnormality in the transmission system of the detection value by the Hall element 72a and the detection value by the Hall element 72b. That is, since the frame counters Ca and Cb are sequentially updated by the processing shown in FIG. 5 and the like, the current values are obtained when the transmission systems of the output signals of the DSPs 76a and 76b and the DSPs 76a and 76b are normal. And the previous value are different. For this reason, when the previous value is equal to the current value, it is considered that there is an abnormality in the transmission system of the output signals of the DSPs 76a and 76b and the DSPs 76a and 76b. On the other hand, the DSP 76a is a transmission system of detection values by the Hall element 72a, and the DSP 76b is a transmission system of detection values by the Hall element 72b. For this reason, when the previous value is equal to the current value, it is considered that there is an abnormality in the transmission system of the detection value by the Hall element 72a and the detection value by the Hall element 72b.

  If an affirmative determination is made in step S50, the ECU 40 increments both the error counters NCa and NCb, assuming that both the detection value transmission system by the Hall element 72a and the detection value transmission system by the Hall element 72b are abnormal. (S52). In this case, the ECU 40 does not use the digital data Da and Db of the current data stream DS for assist control, and substitutes the previous values of the digital data Da and Db.

  When the ECU 40 makes a negative determination in step S50, the current value “Ca (n)” of the frame counter Ca is different from the previous value “Ca (n−1)” and the current value “Cb ( n) ”and the previous value“ Cb (n−1) ”are determined (S54). This process is for determining whether or not there is an abnormality in the transmission system of the detection value by the Hall element 72b, although there is no abnormality in the transmission system of the detection value by the Hall element 72a. When the ECU 40 makes a positive determination in step S54, it initializes the error counter NCa and increments the error counter NCb (S56). In this case, the ECU does not use the digital data Db in the current data stream DS for assist control.

  When the ECU 40 makes a negative determination in step S54, the current value “Ca (n)” of the frame counter Ca is equal to the previous value “Ca (n−1)”, and the current value “Cb (n) of the frame counter Cb is determined. ) ”And the previous value“ Cb (n−1) ”are determined (S58). This process is for determining whether or not there is an abnormality in the transmission system of the detection value by the Hall element 72a although there is no abnormality in the transmission system of the detection value by the Hall element 72b. If the determination in step S58 is affirmative, the ECU 40 initializes the error counter NCb and increments the error counter NCa (S60). In this case, the ECU does not use the digital data Da in the current data stream DS for assist control.

ECU40 once complete | finishes the process of FIG.8 S32, when the process of step S52, S56, S60 is completed, or when negative determination is made in step S58.
Then, the ECU 40 determines whether or not an abnormality is detected in both the frame counters Ca and Cb by the frame counter abnormality detection process (S33). If the ECU 40 determines that at least one is normal (S33: NO), the ECU 40 executes an abnormality detection process for the digital data Da and Db (S34 in FIG. 8).

  FIG. 10 shows details of the abnormality detection process for the digital data Da and Db. In this series of processing, the ECU 40 first determines whether both the frame counters Ca and Cb are normal and both the digital data Da and Db are out of the range between the lower limit value LD and the upper limit value HD. (S70). Here, the lower limit value LD corresponds to the lower limit voltage VL of FIG. 4, and the upper limit value HD corresponds to the upper limit voltage VH of FIG. When the digital data Da and Db are smaller than the lower limit value LD or larger than the upper limit value HD, the detected values of the Hall elements 72a and 72b are out of a predetermined range determined by the upper limit voltage VH and the lower limit voltage VL. It can be determined that Da and Db are abnormal. Note that the condition that both the frame counters Ca and Cb are normal avoids determining that the digital data Da and Db are abnormal due to the abnormalities of the DSPs 76a and 76b and its downstream side. I am aiming for that.

  When an affirmative determination is made in step S70, the ECU 40 increments the error counters NDa and NDb (S72). In this case, the ECU 40 does not use the current values of the digital data Da and Db for assist control, but substitutes the previous values.

  When a negative determination is made in step S70, the ECU 40 determines whether the frame counter Ca is normal and the digital data Da is less than the lower limit value LD or exceeds the upper limit value HD (S74). If the ECU 40 makes a positive determination in step S74, it increments the error counter NDa (S76). In this case, the ECU 40 does not use the current value of the digital data Da for assist control. If the current value of the digital data Db can be used, the ECU 40 uses this for assist control. On the other hand, if the current value of the digital data Db cannot be used, the ECU 40 substitutes the previous values of the digital data Da and Db.

  When a negative determination is made in step S74, the ECU 40 determines whether the frame counter Cb is normal and the digital data Db is less than the lower limit value LD or exceeds the upper limit value HD (S78). If the ECU 40 makes a positive determination in step S78, it increments the error counter NDb (S80). In this case, the ECU 40 does not use the current value of the digital data Db for assist control. If the current value of the digital data Da can be used, the ECU 40 uses this for assist control. On the other hand, if the current value of the digital data Da cannot be used, the ECU 40 substitutes the previous values of the digital data Da and Db.

  When the ECU 40 makes a negative determination in step S78, both the frame counters Ca and Cb are normal, and the sum “Da + Db” of the digital data Da and Db is within a specified range defined by the threshold values DthL and DthH. Whether or not (S82). Here, the threshold values DthL and DthH are set according to a range of values that the sum “Da + Db” can take when the digital data Da and Db are normal. That is, according to FIG. 4C, the sum “Da + Db” is a constant value. For this reason, when the digital data Da and Db are normal, it is considered that the sum “Da + Db” does not greatly deviate from a constant value. The process of step S82 is for determining whether or not the deviation amount between the steering torques indicated by the digital data Da and Db is within an allowable range.

  When an affirmative determination is made in step S82, the ECU 40 initializes error counters NDa and NDb (S84). On the other hand, when a negative determination is made in step S82, the ECU 40 determines whether one of the frame counters Ca and Cb is abnormal (S85). This process is for determining whether or not the reason for the negative determination in step S82 is due to the frame counters Ca and Cb. If the ECU 40 makes a negative determination in step S85, it increments the error counters NDa and NDb (S86). In this case, the ECU 40 does not use the current values of the digital data Da and Db for assist control, but substitutes the previous values. When the ECU 40 makes an affirmative determination in step S85, or when completing the processes of steps S72, S76, S80, S84, and S86, it ends the process of step S34 of FIG.

  When the process of step S34 is completed or when an affirmative determination is made in step S33, the ECU 40 proceeds to step S36. In step S36, the ECU 40 determines that the error counter Ne is equal to or greater than the threshold value Neth, that at least one of the error counter NCa and the error counter NDa is abnormal and at least one of the error counter NCb and the error counter NDb is abnormal. And whether or not the logical sum of these is true. This process is for determining whether or not there is an abnormality in which both of the detected values of the steering torque by the hall elements 72a and 72b cannot be used. Note that the threshold values Neth, NCth, and NDth are set to values of “2” or more in order to avoid the determination that the abnormality is caused by sudden abnormality detection caused by noise or the like.

  If the ECU 40 makes an affirmative determination in step S36 or makes a negative determination in step S20, the ECU 40 notifies the user and stops the assist control (S38). That is, the assist control is not executed not only during the current control cycle but also after the next control cycle. This can be realized by storing the abnormality history in a memory or the like that stores and holds data regardless of whether the ECU 40 is on or off, and stopping the assist control when the abnormality history is stored. Thus, the assist control is not executed until the abnormality history is reset at the dealer or the like and the abnormality history is reset.

  When the ECU 40 makes a negative determination in step S36, it is one of at least one of the error counter NCa and the error counter NDa being abnormal and at least one of the error counter NCb and the error counter NDb being abnormal. Whether or not (S40). This process is for determining whether or not there is an abnormality in which only one of the detected values of the steering torque by the hall elements 72a and 72b cannot be used. If the ECU 40 makes an affirmative determination in step S40, it notifies the user to that effect and executes assist control using only the available one of the digital data Da and Db (S42). Thereby, not only the current control cycle but also the next control cycle and thereafter, the assist control using only the available one of the digital data Da and Db is executed. This is because the history of one-side abnormality is stored in a memory or the like that stores data regardless of whether the ECU 40 is on or off, and when one-side abnormality history is stored, the assist control using only one side is executed. Can be realized. As a result, the assist control using only one side is executed until the dealer deals with the abnormality and the one-side abnormality history is reset.

  When the processes in steps S30, S38, and S42 are completed, the ECU 40 updates the variable n that determines the sampling numbers and the like of the frame counters Ca and Cb (S44), and once ends this series of processes.

Here, the operation of the present embodiment will be described.
When the steering torque input via the steering wheel 12 is detected by the hall elements 72a and 72b, digital data Da and Db and frame counters Ca and Cb corresponding to the detected voltage signals Va and Vb are output to the output unit. 78 is output. The output unit 78 generates a data stream DS including the digital data Da and Db and the frame counters Ca and Cb, and outputs a current signal corresponding to the logical value of each bit of the data stream DS to the signal line L1. That is, the output unit 78 controls the current flowing through the signal line L1 to a value corresponding to the logical value of each bit of the data stream DS. For this reason, even if the resistance value at the connection point between the signal line L1 and the ECU 40 is increased to some extent, the current value detected on the ECU 40 side depends on whether it is logic H or logic L, respectively. It becomes a fixed value. The ECU 40 grasps the logical value of each bit of the data stream DS based on the current value of the signal line L1, and based on this, after executing the abnormality determination process shown in FIG. 8, the digital data Da and Db can be used. If so, the steering torque value indicated by the digital data Da, Db is recognized as a detection value by the hall elements 72a, 72b, and assist control is executed.

According to the present embodiment described above, the following effects can be obtained.
(1) The number of signal lines L1 can be reduced by outputting digital data Da, Db corresponding to the voltage signals Va, Vb of the hall elements 72a, 72b to the ECU 40 via the signal line L1, which is a serial line. it can.

(2) By outputting the digital data Da and Db as current signals, the accuracy of the steering torque recognized by the ECU 40 can be maintained high.
(3) When only one of the digital data Da and Db is abnormal, the assist control is executed based on the other (S42). Thereby, the situation where assist control is stopped immediately can be controlled. For this reason, the user can execute assist control at the time of limp home operation up to the dealer.

  (4) If the detection values by the Hall elements 72a, 72b are output to the ECU 40 as digital data Da, Db and the detection values are out of the predetermined range (S70, S74, S78: YES) Judged. Thus, since the detection value used for determination is suppressed from being output from the torque sensor 70 to the signal line L1 and before being sampled by the ECU 40, the determination accuracy can be improved. it can.

  (5) The detection values by the Hall elements 72a and 72b are output to the ECU 40 as digital data Da and Db, and the condition is that the sum of the digital data Da and the digital data Db is out of the specified range (S82: NO). It was determined that there was. Thereby, since the value used for the determination is suppressed from being output from the torque sensor 70 to the signal line L1 until being sampled by the ECU 40, the determination accuracy can be improved. .

  (6) One data stream DS includes both digital data Da and Db, CRC, frame counters Ca and Cb, and the like. For this reason, compared with the case where the digital data Da and Db are included in different data streams, it is easy to reduce the time difference between the timings at which the ECU 40 recognizes the detection values of the hall elements 72a and 72b.

  (7) CRC is included in one data stream DS. Thereby, the presence or absence of abnormality of the transmission system of the detected value by Hall elements 72a and 72b can be detected by CRC.

(8) Different A / D converters 74a and 74b are allocated to the Hall elements 72a and 72b. This makes it easy to synchronize the sampling of the digital data Da0 and Db0.
(9) Frame counters Ca and Cb are provided. Thereby, the presence or absence of abnormality of the transmission system of the detection value by the Hall element 72a and the presence or absence of abnormality of the transmission system of the detection value by the Hall element 72b can be detected separately.

<Other embodiments>
Each of the above embodiments may be modified as follows.
・ About Data Stream
Error detection codes for detecting data errors in the data stream are not limited to parity, CRC, and frame counter. For example, only the CRC may be used. Further, for example, forward error correction may be used instead of CRC. Further, for example, a data stream may be configured by 1-bit parity and data that is subject to error detection by the parity, and only this 1-bit parity may be used as an error detection code.

・ "About the output characteristics of Hall elements 72a and 72b"
The output characteristics of the electrical signal with respect to the change of the steering torque are not limited to those illustrated in FIG. For example, the voltage value when the steering torque is zero may be different between the hall element 72a and the hall element 72b. However, the output characteristics of the electrical signal with respect to the change in the steering torque are not limited to those opposite to each other.

・ "About detection abnormality judgment processing part (Fig. 10)"
For example, when the Hall elements 72a and 72b output the same electrical signal with respect to the same steering torque, the digital data values corresponding to the electrical signals are compared, and the deviation amount is within a predetermined range. What is necessary is just to determine that there exists abnormality on the condition that it remove | deviates.

  In the above embodiment, when an affirmative determination is made in step S78 of FIG. 10, only the error counter NDb is incremented. This includes a process of not incrementing the error counter NDa when it is determined that the frame counter Cb is normal and the frame counter Ca is abnormal. However, when there is an abnormality in the frame counter Ca, not only the error counter NCa but also the error counter NDa may be incremented. Similarly, when there is an abnormality in the frame counter Cb, not only the error counter NCb but also the error counter NDb may be incremented.

  In the above embodiment, the error counters NDa and NDb are determined to be abnormal when the error counters NDa and NDb are equal to or greater than the predetermined threshold NDth greater than “1”, but the present invention is not limited to this. For example, the digital data Da and Db are subjected to low-pass filtering, and the value after filtering exceeds the upper limit value HD, falls below the lower limit value LD, the sum of the values after filtering is less than the threshold value DthL, If it exceeds DthH, it may be determined that there is an abnormality immediately.

・ "About system abnormality judgment processing part (S20, S24, S32)"
For example, the data stream DS may not include a frame counter, and the process of step S32 may be deleted. Further, for example, CRC and parity may be deleted from the data stream, and the process of S24 may be deleted. Further, for example, the output of the output unit 78 may be a voltage signal, and the process of step S20 may be deleted. That is, in the case of a voltage signal, if there is no transmission from the torque sensor 70, the ECU 40 can determine that the logical value is constant. Can be determined.

・ "Period not used for torque control"
In the above embodiment, when the error counter Ne is greater than or equal to the threshold value Neth, or when the error counters NCa and NCb are greater than or equal to the threshold value NCth, torque control (assist processing) is performed until the history of abnormality is deleted by a dealer or the like. Stopped. If a negative determination is made in step S20, the torque control is stopped until the abnormality history is deleted by a dealer or the like. However, the stop period is not limited to this. For example, the ECU 40 may be temporarily reset by turning off the main power supply of the ECU 40. This is because the abnormality of the electronic device can be resolved by restarting. Incidentally, this can be realized by storing the abnormality history in a memory capable of holding data only while the main power supply of the ECU 40 is on.

  In the above-described embodiment, when an abnormality is determined for only one of the hall elements 72a and 72b in the process of step S32 or the process of step S34, the corresponding one of the digital data Da and Db is torque controlled (assist process). However, it is not limited to this. For example, the use stop period may be until the ECU 40 is once reset by turning off the main power supply of the ECU 40.

・ About the output section
In the configuration illustrated in FIG. 3, the power supply line L3 and the signal line L1 may be shared. In this case, when the electric power is supplied from the ECU 40 to the signal line L1, the value of the current flowing through the signal line L1 may be controlled by the output unit 78 to a value corresponding to the logic H and a value corresponding to the logic L. Incidentally, in this case, the output current from the output unit 78 has a negative value if the current traveling from the output unit 78 to the ECU 40 side is positive. In this case, a current having the same absolute value as that of the signal line L1 also flows through the ground line L2, but the detection signal transmitted by the torque sensor 70 is time-series data of logical values based only on the current value of the signal line L1, which is a serial line. Can be grasped by the ECU 40. In this case, if the abnormality is determined by the self-diagnosis process in the torque sensor 70, the output of the logic H and logic L current signals may be stopped. For example, the value of the current flowing through the signal line L1 is not changed. It may be. However, even if the output current of the output unit 78 is positive, if it is determined as abnormal by the self-diagnosis process in the torque sensor 70, the output of the current itself is not stopped, but the logic H and logic L It is also possible to stop the output of the current signal. In other words, when the abnormality is determined by the self-diagnosis process in the torque sensor 70, a current having a value that does not correspond to either logic H or logic L may be output.

  Depending on each of logic H and logic L, it is not limited to outputting currents having absolute values greater than zero and different from each other. For example, as shown in FIG. 12, a voltage signal having a different pulse width between logic H and logic L may be output. FIG. 12 illustrates a voltage signal in which the voltage transits once from the high voltage (VSH volts) to the low voltage (0 volts) during the period Tc. The pulse width of the high voltage pulse signal within the period Tc is longer in the pulse width Wp2 when the logic is H than when the pulse width Wp1 is when the logic is L. According to such setting, even if the peak value (voltage value) of the pulse changes due to poor connection between the signal line L1 and the ECU 40, it is possible to suppress the logical value from changing. In FIG. 5, the longer pulse width is set to logic H, but the reverse is also possible.

  Further, for example, voltages having different values for logic H and logic L may be output. Even in this case, it is possible to suppress the occurrence of a situation in which the logical value of each bit recognized by the ECU 40 is different from the logical value of the bit output from the torque sensor 70. Compared with the case of outputting, it is possible to suppress a decrease in the accuracy of the steering torque recognized by the ECU 40.

  Note that it is not essential for the output unit to execute the process of generating the data stream DS. For example, a selector may be provided in the output unit, and processing for outputting the digital data Da and Db output from the DSPs 76a and 76b in a time division manner may be executed.

・ "About sensing elements (Hall elements 72a, 72b)"
It is not limited to one that senses the magnetic flux density and outputs an electrical signal corresponding to the magnetic flux density. For example, a strain gauge or the like provided in a portion to which a force according to the steering torque is applied may be used.

・ About the torque sensor
The number of sensing units provided in one torque sensor is not limited to two. For example, it may be three or more.

  Each of the sensing units is not limited to having different DSPs. In addition, when it is set as the structure which one DSP processes the signal which Hall elements 72a and 72b detect, it is desirable to use one frame counter. However, this does not mean that two frame counters are necessarily used when different DSPs process the signals detected by the Hall elements 72a and 72b. That is, for example, a single frame counter may be realized in the output unit. Furthermore, without providing a DSP, the digital data Da0 and Db0 output from the A / D converters 74a and 74b may be included in the data stream DS as digital data corresponding to the voltage signals Va and Vb.

  The Hall elements 72a and 72b are not limited to those having different A / D converters. Even when the signals detected by the Hall elements 72a and 72b are sampled in a time division manner by a single A / D converter, if the sampling frequency is increased, the signals detected by the Hall elements 72a and 72b are detected. It is possible to consider that the sampling timing is almost simultaneous.

  The number of torque sensors provided in the EPS is not limited to one and may be two or more. FIG. 11 shows a case where two torque sensors 70a and 70b are provided. In this example, magnetism collecting portions 60a and 62a are provided corresponding to the torque sensor 70a, and magnetism collecting portions 60b and 62b are provided corresponding to the torque sensor 70b.

Note that the configuration of the magnetic circuit 52 is not limited to that illustrated in FIG. 2, but may be anything as long as it generates a magnetic flux density according to the steering torque.
・ "About torque control"
It is not limited to assist control. For example, in a steer-by-wire system, if steering torque is used as an input parameter for torque control of an electric motor that applies torque to steered wheels, torque control for steer angle control in a steer-by-wire system Also good.

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 12 ... Steering wheel, 14 ... Steering wheel, 20 ... Steering mechanism, 22 ... Steering shaft, 23 ... Column shaft, 23a ... Input shaft, 23b ... Torsion bar, 23c ... Output shaft, 24 ... Intermediate Itoshaft, 25 ... Pinion shaft, 26 ... Rack and pinion mechanism, 28 ... Rack shaft, 29 ... Tie rod, 30 ... Assist mechanism, 32 ... Motor, 34 ... Reducer, 40 ... ECU, 50 ... Sensor unit, 52 ... Magnetic Circuit 54. Holding member 54 a Multipole magnet 56 Yoke 56 a Claw part 58 Yoke 58 a Claw part 60 Magnetic collecting ring 60 a Magnetic collecting part 60 b Magnetic collecting part 62 ... Magnetic collecting ring, 62a ... Magnetic collecting part, 62 ... Magnetic collecting part, 70, 70a, 70b ... Rukusensa, 72a, 72b ... Hall elements, 74a, 74b ... A / D converter, 76a, 76b ... DSP, 78 ... output section.

Claims (10)

A torque sensor that outputs a detection signal of steering torque that is torque input via the steering wheel;
The torque sensor includes a control device that receives a detection signal transmitted to a signal line that is a serial line, and that is used for torque control of an electric motor that applies torque to a steered wheel of a vehicle,
The torque sensor
Two or more sensing units for sensing the steering torque, converting the sensed steering torque into an analog electrical signal, and outputting the analog electrical signal;
An A / D converter that converts an electrical signal output from the sensing unit into digital data;
An output unit that outputs digital data corresponding to each electrical signal of the sensing unit as the detection signal to the control device via the signal line;
The control device includes:
A detection abnormality determination processing unit that determines that there is an abnormality in the detection value of the sensing unit on the condition that the digital data corresponding to the electrical signal is input and the detection value by the sensing unit is out of a predetermined range;
In addition to the detection abnormality determination processing unit, a system abnormality determination processing unit that determines that there is an abnormality in the transmission system of the detection value by the sensing unit based on the state of the signal line,
The output unit outputs currents having absolute values greater than zero and different from each other, depending on whether the digital data is logic H or logic L,
The system abnormality determination processing unit determines that there is an abnormality in a transmission system of a detection value detected by the sensing unit on condition that a current corresponding to the logic H and a current corresponding to the logic L are not output . The sensor system according to claim 1, wherein the output unit stops output of a current signal when it is determined as abnormal by a self-diagnosis process inside the torque sensor. The control device does not use, for the torque control, at least a period until the control device is turned off, at least until the control device is turned off. The sensor system according to claim 1 or 2 . The two or more sensing units include a first sensing unit and a second sensing unit different from the first sensing unit,
The control device is based on a determination result by the detection abnormality determination processing unit, provided that a detection value by the first sensing unit is out of a predetermined range and a detection value by the second sensing unit is within a predetermined range. The sensor system according to any one of claims 1 to 3 , wherein the detection value by the second sensing unit is used for the torque control without using the detection value by the first sensing unit. The output unit includes digital data corresponding to the electrical signals of the first sensing unit and the second sensing unit different from the first sensing unit among the two or more sensing units, and digital data corresponding to the electrical signals. Apart from the above, data for evaluating the reliability of the digital data is sequentially transmitted as a data stream having a predetermined bit length, and the first sensing unit and the second sensing unit are transmitted to one data stream. The sensor system according to any one of claims 1 to 4, including both digital data corresponding to each of the electrical signals. One data stream includes an error detection code for detecting data in the data stream as an error detection target,
The system abnormality determination processing unit has an abnormality in the transmission system of both the detection value by the first sensing unit and the detection value by the second sensing unit on condition that error detection is performed based on the error detection code. Execute the process to determine the effect,
The control device does not use the detected value of the transmission system determined to be abnormal by the system abnormality determination processing unit for the torque control at least during a period until the control device is temporarily turned off. Item 6. The sensor system according to Item 5 . The sensor system according to claim 5 or 6, wherein the A / D converter is provided separately for each of the sensing units. A counter that is updated each time sampling is performed by the A / D converter is provided for each A / D converter,
A counter value corresponding to each of the first sensing unit and the second sensing unit is included in one data stream;
The system abnormality determination processing unit determines that there is an abnormality in the transmission system of the detection value by the sensing unit corresponding to the counter on condition that the previous value and the current value of the counter included in the data stream match. Execute the process to
The control device does not use the detected value of the transmission system determined to be abnormal by the system abnormality determination processing unit for the torque control at least during a period until the control device is temporarily turned off. Item 8. The sensor system according to any one of Items 5 to 7 . The first sensing part of the two or more sensing parts and the second sensing part different from the first sensing part are such that output characteristics of an electric signal with respect to a change in the steering torque are opposite to each other.
The detection abnormality determination processing unit determines that a sum of a value of digital data corresponding to the electrical signal of the first sensing unit and a value of digital data corresponding to the electrical signal of the second sensing unit is out of a specified range. The sensor system according to any one of claims 1 to 8 , wherein a process for determining that at least one of the first sensing unit and the second sensing unit is abnormal is performed as a condition. A magnetic circuit for changing a magnetic flux density according to a steering torque input via the steering wheel;
The torque sensor, the sensor system according to the magnetic flux that is generated in any one of claims 1 to 9 and detects the steering torque by the magnetic circuit.