JP6394881B2 - Sensor system - Google Patents

Description

  The present invention relates to a sensor system.

  For example, in Patent Document 1, two sensor ICs having two torque detection units are provided, and torque is detected by each sensor IC. In this configuration, it is possible to determine the torque detected normally and the torque not detected normally by abnormally determining the torque detected by each sensor IC. Therefore, even if one sensor IC cannot detect a normal torque, the other sensor IC can detect a normal torque. Therefore, the torque can be detected more reliably.

JP2013-253806A

  By providing a plurality of sensors from the viewpoint of redundancy as in Patent Document 1, the reliability of detection is certainly improved. However, for example, two digital signals generated by two sensors are output to the outside at the same timing. Therefore, two digital signals may be simultaneously affected by disturbances such as electromagnetic noise. In particular, in digital communication, for example, if a part of a digital signal is missing, there is a possibility that a completely different digital signal is obtained. In that case, even if redundancy is used, the two digital signals are similarly completely different digital signals, and even if they are compared, there is a possibility that there is no abnormality because they match.

  Therefore, even if a plurality of digital communications made redundant by disturbance is inhibited, a device is required to prevent all the digital communications from being similarly inhibited.

  A sensor system that can achieve the above-described object includes a plurality of sensor ICs that detect the same state quantity for the same detection target and generate digital signals according to the detection results, and the digital signals from the plurality of sensor ICs. And an arithmetic unit that receives the signal. The plurality of sensor ICs output the digital signal to the arithmetic unit at different timings.

  According to this configuration, since the sensor ICs output digital signals at different timings, even if one digital signal is affected by disturbance, it is possible to reduce the influence of other digital signals.

  Each of the plurality of sensor ICs includes a detection unit that generates the digital signal and a communication unit that outputs the digital signal to the calculation unit. It is preferable that the timing at which the digital signal is output to the arithmetic unit is made different by providing a time difference in the timing at which the digital signals of the plurality of communication units are output to the arithmetic unit.

According to this configuration, there is a time difference in the timing of outputting the digital signals of the plurality of communication units, so that the timing of output can be shifted depending on the internal configuration of the sensor IC.
The plurality of communication units may start outputting the digital signal to the arithmetic unit by receiving an external command.

  According to this configuration, the plurality of communication units simultaneously receive external commands and start outputting digital signals to the calculation unit. Therefore, it is not necessary to provide a configuration for adjusting the communication timing of each communication unit in an external device.

The communication unit may convert the digital signal so as to be a different communication frame between the communication units.
According to this configuration, by communicating the digital signals with different communication frames, it is possible to reduce the influence of disturbance even if they are simultaneously communicated.

  The same detection target may be a torsion bar that is twisted through application of steering torque. The plurality of sensor ICs may detect the amount of twist of the torsion bar as the same state quantity.

According to this configuration, the sensor IC is provided to detect the steering torque, and each of the plurality of sensor ICs can detect the torsion amount of the torsion bar.
A plurality of sensor ICs that detect the same state quantity for the same detection target and generate digital signals according to the detection results; and an arithmetic unit that receives the digital signals from the plurality of sensor ICs. Yes. Each of the plurality of sensor ICs includes a detection unit that generates the digital signal and a communication unit that outputs the digital signal to the calculation unit. The plurality of communication units generate the digital signals so as to be different communication frames.

  According to this configuration, since the sensor ICs output digital signals in different communication frames, even if one digital signal is affected by disturbance, it can be reduced that other digital signals are affected.

  According to the sensor system of the present invention, it is possible to further reduce occurrence of similar abnormalities in digital signals generated by a plurality of sensor ICs.

The block diagram which shows the structure of the steering device in 1st Embodiment. (A), (b) is a perspective view which shows the disassembled perspective structure of the torque sensor in 1st Embodiment. The block diagram which shows the electrical structure of the torque sensor in 1st Embodiment. (A), (b) is a figure which shows the relationship between the output value of each Hall element mounted in the torque sensor in 1st Embodiment, and the magnetic strength. (A), (b), (c) is a wave form diagram which shows an example of a signal pattern when the output timing of the digital signal produced | generated by each sensor IC in 1st Embodiment is varied. (A), (b), (c) is a figure which shows an example of a structure of the communication frame of the digital signal in 2nd Embodiment. The block diagram which shows an example of the torque sensor in other embodiment.

Hereinafter, an embodiment in which the sensor system is applied to a torque sensor of a power steering device for a vehicle will be described.
As shown in FIG. 1, the EPS 10 controls the steering mechanism 20 that steers the steered wheels 29 based on the operation of the driver's steering wheel 21, the steering assist mechanism 30 that assists the driver's steering operation, and the steering assist mechanism 30. ECU (electronic control unit) 40 is provided.

  The steering mechanism 20 includes a steering wheel 21 and a steering shaft 22 that rotates integrally with the steering wheel 21. The steering shaft 22 includes a column shaft 23 connected to the steering wheel 21, 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 lower end portion of the pinion shaft 25 is connected to a rack shaft 26 extending in a direction intersecting with the pinion shaft 25. Therefore, the rotational movement of the steering shaft 22 is caused by a reciprocating straight line in the axial direction of the rack shaft 26 via a rack and pinion mechanism 27 including a pinion gear provided at the tip of the steering shaft 22 and a rack carved in the rack shaft 26. Converted into movement. The reciprocating linear motion is transmitted to the left and right steered wheels 29 via the tie rods 28 respectively connected to both ends of the rack shaft 26, whereby the steered angle of the steered wheels 29 changes and the traveling direction of the vehicle changes. Be changed.

  The steering assist mechanism 30 includes a motor 31 that is a source of steering assist force. A rotation shaft 31 a of the motor 31 is connected to the column shaft 23 via a speed reduction mechanism 32. The reduction mechanism 32 reduces the rotation of the motor 31 and transmits the reduced rotational force to the column shaft 23. That is, the rotational force (torque) of the motor 31 is applied to the steering shaft 22 as a steering assist force, thereby assisting the driver's steering operation.

  The ECU 40 controls the motor 31 based on detection results of various sensors provided in the vehicle. Examples of various sensors include a torque sensor 41, a rotation angle sensor 42, and a vehicle speed sensor 43. The torque sensor 41 is provided on the column shaft 23, and the rotation angle sensor 42 is provided on the motor 31. The torque sensor 41 detects a steering torque τ applied to the steering shaft 22 in accordance with the driver's steering operation. The rotation angle sensor 42 detects the rotation angle θ of the rotation shaft 31a. The vehicle speed sensor 43 detects the traveling speed V of the vehicle. The ECU 40 sets a target steering assist force based on the output of each sensor, and feedback-controls the current supplied to the motor 31 so that the steering assist force becomes the target steering assist force. The ECU 40 and the torque sensor 41 constitute a sensor system.

Next, the structure of the torque sensor 41 will be described.
As shown in FIG. 2A, the column shaft 23 has a structure in which an input shaft 23a on the steering wheel 21 side and a lower shaft 23b on the intermediate shaft 24 side are connected on the same axis m via a torsion bar 23c. Consists of. When a steering torque τ is applied to the input shaft 23a in accordance with the operation of the steering wheel 21, the steering torque τ is transmitted to the lower shaft 23b from the input shaft 23a via the torsion bar 23c. Torsional deformation occurs. As a result, a relative rotational displacement corresponding to the steering torque τ occurs between the input shaft 23a and the lower shaft 23b.

  The torque sensor 41 is an annular ring fixed to the outer periphery of the lower end portion of the input shaft 23a and fixed to the lower shaft 23b and facing the outer peripheral surface of the holding member 50 with a predetermined gap therebetween. The two yokes 51 and 52 are provided. On the outer peripheral surface of the holding member 50, a multipolar magnet 50a in which the magnetic poles of the N pole and the S pole are alternately arranged in the circumferential direction is provided.

  The first yoke 51 is located on the upper side in the figure, and the second yoke 52 is located on the lower side in the figure. A plurality of claw portions 51 a extending downward along the axis m are formed on the inner peripheral surface of the first yoke 51. A plurality of claw portions 52 a extending upward along the axis m are formed on the inner peripheral surface of the second yoke 52. The two yokes 51 and 52 are arranged to face each other in the direction along the axis m in such a manner that the respective claw portions 51a and 52a are alternately meshed with each other.

  The torque sensor 41 includes an annular first magnetism collecting ring 53 disposed so as to surround the periphery of the first yoke 51 with a predetermined gap therebetween, and a periphery of the second yoke 52. An annular second magnetism collecting ring 54 is provided so as to surround the periphery thereof at a predetermined interval. The magnetism collecting rings 53 and 54 are made of a magnetic material.

  As shown in an enlarged view in FIG. 2B, the first magnetism collecting ring 53 and the second magnetism collecting ring 54 are opposed to each other in the direction along the axis m. Two magnetism collecting portions 53 a and 53 b are provided below the first magnetism collecting ring 53. The magnetic flux collecting portions 53 a and 53 b are provided so as to protrude toward the outer side in the radial direction of the first magnetic flux collecting ring 53 with an interval in the circumferential direction of the first magnetic flux collecting ring 53. The second magnetism collecting ring 54 is also provided with two magnetism collecting portions 54 a and 54 b similar to the first magnetism collecting ring 53. The two magnetic flux collectors 53a and 54a face each other in the direction along the axis m. Similarly, the two magnetic flux collectors 53b and 54b are also opposed to each other in the direction along the axis m. A first sensor IC 60 is disposed between the magnetic flux collectors 53a and 54a, and a second sensor IC 70 is disposed between the magnetic flux collectors 53b and 54b. Each of the first sensor IC 60 and the second sensor IC 70 generates an electrical signal corresponding to the magnetic strength applied to itself.

  In the torque sensor 41, when the steering torque τ is input to the input shaft 23a, a relative rotational displacement is generated between the input shaft 23a and the lower shaft 23b. When such relative rotational displacement occurs, the positional relationship between the holding member 50 and the yokes 51 and 52 changes, so that the strength of magnetism collected by the yokes 51 and 52 changes. For this reason, the intensity of magnetism acting on the first sensor IC 60 and the second sensor IC 70 also changes. The first sensor IC 60 and the second sensor IC 70 generate an electrical signal corresponding to the relative rotational displacement of the input shaft 23a and the lower shaft 23b, that is, an electrical signal corresponding to the torsion angle of the torsion bar 23c.

Next, the structure of the first sensor IC 60 and the second sensor IC 70 will be described in detail.
As shown in FIG. 3, the first sensor IC 60 includes a first detection unit 61, a second detection unit 62, a nonvolatile memory 63, an oscillator 64, and a first communication unit 65. .

  The first detection unit 61 includes a first Hall element 61a as a magnetic detection element, a temperature sensor 61b, and a first A / D conversion unit (analog / digital conversion unit) 61c. The first Hall element 61a generates a Hall voltage corresponding to the magnetic strength applied to itself. The temperature sensor 61b detects the temperature of the first hall element 61a and the multipolar magnet 50a. As the first A / D converter 61c, for example, a digital signal processor (DSP) is used. The first A / D converter 61c converts the Hall voltage, which is an analog signal generated by the first Hall element 61a, into a digital signal. The first A / D conversion unit 61 c generates a digital signal based on the clock signal generated by the oscillator 64.

  The first A / D converter 61c performs a correction process on the analog signal when generating the digital signal. For example, the first Hall element 61a and the multipolar magnet 50a each have temperature dependency. For this reason, it is preferable that the first A / D converter 61c corrects the analog signal (Hall voltage) based on the temperature. The first A / D converter 61 c reads information necessary for signal processing from the temperature sensor 61 b and the memory 63. The memory 63 stores various information necessary for correction such as temperature correction values in advance. The first A / D converter 61c corrects the analog signal generated by the first Hall element 61a based on the information read from the memory 63, and converts the corrected analog signal into a detection signal S1 that is a digital signal. To do. The detection signal S1 is a signal that changes in proportion to the twist angle of the torsion bar 23c.

  The second detection unit 62 has the same configuration as the first detection unit 61. That is, the second detection unit 62 includes a second Hall element 62a, a temperature sensor 62b, and a second A / D conversion unit 62c. However, the second Hall element 62 a generates a voltage signal different from that of the first Hall element 61 a of the first detection unit 61. As shown in FIG. 4A, the first Hall element 61a generates an analog signal having a positive correlation with the magnetic strength acting on the first Hall element 61a. On the other hand, the second Hall element 62a generates an analog signal having a negative correlation with the inverse correlation with the first Hall element 61a, that is, the strength of the acting magnetism. As shown in FIG. 4B, the sum of the analog signal of the first Hall element 61a and the analog signal of the second Hall element 62a is an allowable error regardless of the strength of the acting magnetic field. It becomes a constant value within the range.

  The first communication unit 65 converts the digital signals respectively generated by the first A / D conversion unit 61c and the second A / D conversion unit 62c into a detection signal S1 having a predetermined communication frame. The first communication unit 65 performs bidirectional communication with the ECU 40. Further, the first communication unit 65 has a function as a so-called register that stores (holds) the detection signal S1 until a request from the ECU 40 is received.

  The second sensor IC 70 has basically the same configuration as the first sensor IC 60. That is, the second sensor IC 70 includes a third detection unit 71 that is the same as the first detection unit 61, a fourth detection unit 72 that is the same as the second detection unit 62, a memory 73, an oscillator 74, and a second communication unit 75. In addition, a delay unit 76 is provided.

  As shown in the graph of FIG. 4A, the third Hall element 71a has the same electrical characteristics (output characteristics) as the first Hall element 61a, and the fourth Hall element 72a has the same electrical characteristics (output characteristics) as the second Hall element 62a. Yes. Therefore, as shown in the graph of FIG. 4B, the sum of the analog signals of the third Hall element 71a and the fourth Hall element 72a is an allowable error regardless of the strength of the acting magnetism. It becomes a constant value within the range.

  As the delay unit 76, a delay circuit or a resistor is used. The delay unit 76 delays the output timing of the detection signal S2 generated by the second communication unit 75 by a predetermined delay time dt. The output timing of the detection signal S2 in the second communication unit 75 is different from the output timing of the detection signal S1 in the first communication unit 65 by the delay time dt.

  The ECU 40 obtains the torsion angle of the torsion bar 23c based on the detection signals S1 and S2 output from the two sensor ICs 60 and 70. Then, the ECU 40 calculates the steering torque τ by multiplying the calculated torsion angle by the spring constant of the torsion bar 23c. The ECU 40 determines whether the detection signals S1 and S2 and the steering torque τ are abnormal, and controls the motor 31 using the steering torque τ when it is determined to be normal.

The operation of the sensor system of the present embodiment described above will be described.
When the steering wheel 21 rotates with the steering operation, a steering torque τ acts on the input shaft 23a. When the steering torque τ is transmitted from the input shaft 23a to the lower shaft 23b via the torsion bar 23c, torsional deformation occurs in the torsion bar 23c. When a relative rotational displacement occurs between the input shaft 23a and the lower shaft 23b, the positional relationship between the holding member 50 and the yokes 51 and 52 changes and acts on the first sensor IC 60 and the second sensor IC 70. Magnetic strength also changes. Each Hall element changes the output Hall voltage in accordance with the strength of the magnetic field applied. Therefore, the Hall voltage output by each Hall element changes due to the relative rotational displacement between the input shaft 23a and the lower shaft 23b.

  The first detection unit 61 of the first sensor IC 60 detects a change in the Hall voltage of the first Hall element 61a. The first A / D converter 61c performs correction using the output of the first Hall element 61a and the temperature of the temperature sensor 61b, and generates a digital signal from the analog signal (Hall voltage). Similarly, the second detector 62, the third detector 71, and the fourth detector 72 also detect changes in the Hall voltage of the second to fourth Hall elements 62a, 71a, 72a. The second to fourth A / D converters 62c, 71c, 72c correct these Hall voltages and convert them into digital signals. In this way, the generated digital signal is output to the first communication unit 65 in the first sensor IC 60 and to the second communication unit 75 in the second sensor IC 70.

  The first communication unit 65 generates a detection signal S1 having a predetermined communication frame from the digital signals acquired from the first detection unit 61 and the second detection unit 62. Similarly, the second communication unit 75 generates a detection signal S2 having a predetermined communication frame from the digital signals acquired from the third detection unit 71 and the fourth detection unit 72. The first communication unit 65 and the second communication unit 75 store the detection signals S1 and S2 until the triggers T1 and T2 from the ECU 40 are input. Note that the detection signal S1 stored in the first sensor IC 60 has the same value as the detection signal S2 stored in the second sensor IC 70. The same value includes not only the case where the detection signal S1 and the detection signal S2 are exactly the same value but also the case where the detection signal S1 and the detection signal S2 are the same within an allowable error range.

  The ECU 40 outputs triggers T1 and T2 simultaneously to the first communication unit 65 and the second communication unit 75, respectively, when information on the steering torque τ is required. When receiving the triggers T1 and T2, the first communication unit 65 and the second communication unit 75 output the stored detection signals S1 and S2 to the ECU 40. However, in the second sensor IC 70, since the delay unit 76 is provided between the second communication unit 75 and the ECU 40, the timing at which the detection signal S2 is supplied to the ECU 40 is shifted by a predetermined delay time dt. The triggers T1 and T2 are output every 500 μs, for example.

  FIG. 5A shows an example in which the communication timings of the detection signal S1 and the detection signal S2 are shifted. The detection signal S1 and the detection signal S2 are formed by repeating a communication frame at time t1 and a portion without a communication frame at time t2 with the same period t. When the detection signal S1 and the detection signal S2 are output at the same time, usually, the timings of the communication frames of the two detection signals S1 and S2 match. However, in the present embodiment, the detection signal S2 is supplied to the ECU 40 after being delayed by the delay unit 76 by the delay time dt. By the way, time t1 is set shorter than time t2. Therefore, by setting the delay time dt to be longer than the time t1 and shorter than the difference (t−dt) between the period t and the delay time dt, the communication frame of the detection signal S2 is temporally different from the communication frame of the detection signal S1. It can be made not to overlap.

  Here, the influence of the disturbance in the torque detection in the vehicle will be specifically described. In vehicles, digital communication may be hindered by various factors (disturbances). Examples of the disturbance include various forms such as ignition of a spark plug, motor system, air conditioner, car navigation system, vehicle body vibration, radio, high-voltage line, and lightning strike. For example, when a spark plug is ignited, electromagnetic noise is generated due to a high voltage flowing. Due to these disturbances, there is a risk that communication will be interrupted and some data may be damaged in digital communication. In particular, in digital communication, for example, if a part of a digital signal is missing, there is a possibility that the digital signal is completely different. When the detection signal S1 and the detection signal S2 are simultaneously output to the ECU 40 in a state where there is such a disturbance, the same portions of the detection signal S1 and the detection signal S2 are affected by the disturbance. When communication is interrupted by disturbance, even if redundancy is achieved by providing two sensor ICs, for example, the digital signal that should be communicated when disturbance occurs from the detection signal S1 and the detection signal S2 is Not communicated. In addition, when a part of the digital signal is lost due to disturbance and becomes a completely different digital signal, the detection signal S1 and the detection signal S2 may be different digital signals as well. In such a case, even if the abnormality detection unit for detecting the abnormality by providing redundancy and comparing both is provided, the detection signal S1 and the detection signal S2 indicate the same digital signal, so the abnormality detection unit S1 and S2 are determined to be normal. Then, the ECU 40 may calculate the steering torque τ using the abnormal detection signals S1 and S2 that are affected by the disturbance. The ECU 40 may control the EPS 10 with an abnormal steering torque τ.

  In the present embodiment, the delay part 76 is provided in the second sensor IC 70, so that the detection signal S2 is delayed from the detection signal S1 by the delay time dta. By setting the delay time dta according to the communication frame time ta1 and the period ta, it is possible to set the communication frames of the detection signal S1 and the detection signal S2 so as not to overlap as shown in FIG. . By setting the communication frames so that they do not overlap in this way, for example, even if the detection signal S1 is interrupted due to a disturbance, the other detection signal S2 is not affected by the disturbance, so that the communication is inhibited. Can be reduced.

  In this case, the ECU 40 calculates the steering torque τ using the corresponding communication frame of the detection signal S2 that can be normally communicated without using the communication frame of the detection signal S1 that has been disconnected. Even if communication can be performed normally, the information of the detection signal S1 and the detection signal S2 may be rewritten due to disturbance. Therefore, the ECU 40 determines whether or not the calculated steering torque τ is abnormal based on a determination criterion that is predetermined for the ECU 40. Examples of the determination criterion include that the amount of steering torque τ that can be steered by human beings is clearly not found, and error detection by an error detection function such as parity. Then, when the steering torque τ is not abnormal, the ECU 40 temporarily controls the motor 31 using the steering torque τ. When the communication disconnection is improved, the ECU 40 determines whether or not the detection signal S1 and the detection signal S2 match. If they match, the ECU 40 calculates the steering torque τ based on the detection signals S1 and S2, and controls the motor 31 using the steering torque τ. In addition, although it can communicate normally and steering torque (tau) is also a value which can be a normal value, when detection signal S1 and detection signal S2 do not correspond, it is judged, for example, that the Hall element is broken or deteriorated.

Further, the first and second sensor ICs 60 and 70 may generate the following detection signals S1 and S2.
As shown in FIG. 5B, the detection signal S1 and the detection signal S2 are formed by repeating a communication frame at time tb1 and a portion without a communication frame at time tb2 at the same period tb. In the detection signal S1 and the detection signal S2, the portion where the communication frame exists is generated as the Hi level, and the portion where the communication frame does not exist is generated as the Lo level, and the switching between Hi and Lo continues at the period tb. Since the time tb1 is longer than the time tb2, even if the delay time dtb of the detection signal S2 is adjusted, the portion where the communication frame of the detection signal S2 does not overlap with the portion where the communication frame of the detection signal S1 does not overlap I can't do it. Therefore, the communication frame of the detection signal S1 partially overlaps with the detection signal S2.

  If there is an influence due to disturbance at the timing at which the communication frames of the detection signal S1 and the detection signal S2 overlap, both communication frames are certainly affected. However, even when there is an influence due to disturbance, it is possible to determine when switching from Lo to Hi and when switching from Hi to Lo. For example, even when communication disconnection occurs when the communication frame of the detection signal S1 switches from Hi to Lo, the moment when the communication frame of the detection signal S2 switches from Hi to Lo is output at a different timing. Therefore, by determining Hi and Lo, normal detection signals S1 and S2 can be detected, so that communication inhibition can be reduced. And ECU40 calculates steering torque (tau) by detection signal S1, S2.

Further, the first and second sensor ICs 60 and 70 may generate the following detection signals S1 and S2.
As shown in FIG. 5C, the detection signal S1 and the detection signal S2 each have a communication frame in which a plurality of Lo / Hi switching is combined. In the detection signal S1 and the detection signal S2, the communication frame at time tc1 and the portion where the communication frame at time tc2 does not exist are repeated with the same period tc. Since the time tc1 is longer than the time tc2, even if the delay time dtc of the detection signal S2 is adjusted, the portion where the communication frame of the detection signal S2 does not overlap with the portion where the communication frame of the detection signal S1 does not overlap I can't do it.

  If there is an influence due to disturbance at the timing at which the communication frames of the detection signal S1 and the detection signal S2 overlap, both communication frames are certainly affected. Conventionally, the detection signal S1 and the detection signal S2 are similarly changed to a non-normal digital signal due to a disturbance, and may be determined to be normal although they are not normal because they match when they are compared. It was. However, even if a part of the communication frame of the detection signal S1 is lost due to disturbance, for example, the part of the detection signal S2 digitally communicated at different timings may be different in the communication frame. Therefore, the detection signal S1 and the detection signal S2 are suppressed from changing to the same digital signal, and even if the detection signal S1 and the detection signal S2 are compared, they are not determined to be the same digital signal. Therefore, it can be determined that the both are non-normal digital signals but are determined to be normal.

According to the sensor system described above, the following effects can be obtained.
(1) By changing the timing of digital communication between the detection signal S1 of the first sensor IC 60 and the detection signal S2 of the second sensor IC 70, even if one detection signal is affected by disturbance, the other The detection signal can be normally digitally communicated. When it is possible to completely prevent the communication frames of the detection signals from overlapping, the ECU 40 can calculate the steering torque τ from the communication frame that is not affected by the disturbance. Further, it is possible to prevent both the detection signals S1 and S2 from rewriting data in the same manner.

  (2) Even when communication frames overlap each other, if the communication frame is a detection signal that periodically switches between Hi and Lo, one of the detection signals is disturbed by detecting the switching between Hi and Lo. Even if it is affected by this, normal detection signals S1 and S2 can be detected by detecting the switching of Hi and Lo in the other detection signal. Therefore, the ECU 40 can calculate a normal steering torque τ.

  (3) Even if the detection signal S1 and the detection signal S2 are configured to partially shift the digital communication timing of a communication frame in which a plurality of Lo / Hi switching is combined, the influence of disturbance can be reduced. . That is, since the detection signal S1 and the detection signal S2 are communicated at different times, the change to the same digital signal is suppressed. Therefore, although the detection signal S1 and the detection signal S2 are not normal digital signals, they can be prevented from being determined to be normal because they are the same when compared. Therefore, the ECU 40 can calculate the normal steering torque τ more reliably.

  (4) The temperature sensors 61b, 62b, 71b, 72b are provided in the first to fourth detectors 61, 62, 71, 72, respectively, and the first to fourth Hall elements 61a, 62a, 71a, 72a and the holding member 50, respectively. Measure the temperature of the magnet. The first to fourth A / D converters 61c, 62c, 71c, 72c convert each analog signal (Hall voltage) into a digital signal more accurately according to the temperature obtained from each temperature sensor 61b, 62b, 71b, 72b. It can be corrected and converted. Therefore, a more accurate steering torque τ can be calculated.

Second Embodiment
Next, a second embodiment will be described.
The difference between the first embodiment and the second embodiment will be described with reference to FIG. In the present embodiment, the second sensor IC 70 is not provided with the delay unit 76, and the detection signal S2 of the second communication unit 75 is directly output to the ECU 40. Therefore, the first communication unit 65 and the second communication unit 75 simultaneously output the detection signals S1 and S2 when the triggers T1 and T2 from the ECU 40 are input.

  Further, unlike the first embodiment, the second detector 62 and the third detector 71 are interchanged. Therefore, the first sensor IC 60 is provided with Hall elements 61a and 71a that show a positive correlation in the relationship between the strength of the acting magnetic force and the voltage signal. Further, the second sensor IC is provided with Hall elements 62a and 72a showing a negative correlation.

  The first communication unit 65 and the second communication unit 75 generate detection signals S1 and S2 having predetermined communication frames from the digital signals from the respective A / D conversion units. An example of the communication frame is as shown in FIG. As shown in the figure, the digital signal (representing the Hall voltage) output from the first detector 61 is represented by bits a (0) to a (12). The digital signal output from the second detection unit 62 is represented by bits b (0) to b (12). The sum of the digital signals represented by these bits a (0) to a (12) and bits b (0) to b (12) depends on the strength of the acting magnetism, as shown in FIG. It becomes a constant value without depending on it. Similarly, the digital signal of the third detector 71 is represented as bits c (0) to c (12), and the digital signal of the fourth detector 72 is represented as bits d (0) to d (12). The sum of the digital signals represented by the bits c (0) to c (12) and the bits d (0) to d (12) is also a constant value regardless of the strength of the acting magnetism. The sum of digital signals is the sum of Hall voltages.

  The first communication unit 65 rearranges the bits a (0) to a (12) and c (0) to c (12), thereby detecting the detection signal S1 having the communication frame shown in FIG. Is generated. The second communication unit 75 rearranges the bits b (0) to b (12) and d (0) to d (12), thereby detecting the detection signal S2 having the communication frame shown in FIG. Is generated. Bits a (0) to a (12) are arranged at positions different from the same numbered bits of bits b (0) to b (12). Similarly, in the bits c (0) to c (12) and the bits d (0) to d (12), the bits having the same number are arranged at different positions. For example, bit b (12) is communicated simultaneously with bit a (1).

  In addition, a cyclic redundancy check (CRC) is performed between the first communication unit 65, the second communication unit 75, and the ECU 40, for example, in order to detect an error in the detection signals S1, S2. CRC is a method used to detect errors during communication. That is, when an error occurs during communication between the communication units 65 and 75 on the transmission side and the ECU 40 on the reception side, the CRC value of the communication units 65 and 75 and the CRC value on the ECU 40 side do not match.

Next, the operation of this embodiment will be described. In addition, about the same effect | action as 1st Embodiment, it abbreviate | omits.
In this embodiment, since the delay part 76 is not provided in the 2nd sensor IC70, detection signal S1, S2 is output simultaneously. When a disturbance occurs, both the detection signal S1 and the detection signal S2 are affected by bits in the same column of the communication frame. As a result, the bit information in the same column is lost or becomes different bit information.

  Therefore, in this embodiment, the detection signals S1 and S2 are detected so that the corresponding bits of the digital signals respectively generated by the first detection unit 61 and the second detection unit 62 are not affected by the disturbance at the same time. The arrangement of bits in the communication frame is set. Further, the arrangement is set so that the corresponding bits of the digital signal of the third detection unit 71 corresponding to the digital signal of the first detection unit 61 are not affected by the disturbance at the same time. For example, it is assumed that a disturbance occurs at the timing of outputting the bit a (1) and the bit information of the bit a (1) is rewritten. In this case, bit a (1), bit c (12), bit b (12), and bit d (1) are affected by disturbance. However, even if the bits a (1) and b (12) are rewritten, the digital signal represented by the bits a (0) to a (12) and the bits b (0) to b (12) If the value of the sum with the digital signal to be expressed is normal, it is a constant value regardless of the strength of the acting magnetism. Similarly, if the sum of the digital signal represented by bits c (0) to c (12) and the digital signal represented by bits d (0) to d (12) is normal, It is a constant value regardless of the magnetic strength. The sum of the digital signal represented by bits a (0) to a (12) and the digital signal represented by bits b (0) to b (12) within an allowable range set with this constant value as a reference. If there is no, it can be determined that the detection signal S1 is abnormal. In such a case, the ECU 40 limits or stops control of the motor 31 using the steering torque τ calculated based on the detection signals S1 and S2.

  Since bits a (0) to a (12) are the result of detecting the same twist angle of the torsion bar as bits c (0) to c (12), their data are essentially equal. Conventionally, since the order of bits is not rearranged, when bits are rewritten due to disturbance, bits a (0) to a (12) and bits c (0) to c (12) are the same part. May be rewritten. For this reason, for example, even if the torsion angle of the torsion bar 23c is detected by a plurality of sensor ICs to make them redundant, the sensor ICs are similarly compared and matched with each other, and therefore the ECU 40 detects the detection signals S1, S2. Can be misjudged as not abnormal.

  In this regard, in the present embodiment, the bits a (0) to a (12) and the bits c (0) to c (12) are output at different timings of the corresponding bits. For example, when bit a (1) is output, bit c (12) is output. At this time, if the bit a (1) is rewritten due to disturbance, the bit c (12) may be similarly rewritten. However, since different bit information may be rewritten, a digital signal represented by bits a (0) to a (12) and a digital signal represented by bits c (0) to c (12) Are inconsistent when compared between the two. Therefore, even if some bits are rewritten to different bit information due to disturbance, the detection signals S1 and S2 can be determined to be abnormal if the two digital signals are not matched. The same applies to digital signals represented by bits b (0) to b (12) and digital signals represented by bits d (0) to d (12).

  Furthermore, when the communication frame is rewritten due to disturbance, the CRC data may be rewritten. In this case, the CRC value calculated in the ECU 40 does not match the CRC value included in the detection signals S1 and S2. Therefore, the ECU 40 can detect that an abnormality has occurred in the detection signals S1, S2.

According to this embodiment, the following effects can be obtained.
(1) Since the corresponding bits are not digitally communicated simultaneously by changing the communication frame, even if the bit information is rewritten due to disturbance, the corresponding bit information is not rewritten at the same time. For this reason, the digital signals of the Hall elements that show opposite correlations are usually constant when the sum of the two digital signals (Hall voltages) is taken, but when the bit information is rewritten or lost It is not a constant value. Thereby, abnormality determination can be performed. Therefore, by changing the bit configuration of the communication frame, even if the bit information is rewritten due to disturbance, it is possible to determine the abnormality more accurately.

  (2) When an abnormality is determined by comparing the digital signals of the Hall elements that exhibit the same correlation, the abnormality can be detected more reliably by changing the communication frame. Conventionally, when the bit information of one communication frame is rewritten due to disturbance, the same bit information of another redundant communication frame can be rewritten at the same time. Therefore, even if an abnormality is determined in this state, there is a possibility that both are equal and it is determined that there is no abnormality. However, in the present embodiment, the same bit information is not communicated at the same time, and therefore an abnormality can be determined by simply comparing the detection signals.

  (3) Since the CRC information is included in the communication frame, even if the bit information of the communication frame is rewritten due to disturbance, an abnormality can be detected by comparing with the CRC calculated by the ECU 40. That is, when the CRC value in the detection signals S1 and S2 does not match the CRC value of the ECU 40, it can be determined that there is an abnormality.

<Other embodiments>
In addition, you may change both embodiment as follows. The following other embodiments can be combined with each other within a technically consistent range.

  In both embodiments, the temperature sensors 61b, 62b, 71b, and 72b are provided in the first to fourth detectors 61, 62, 71, and 72, respectively, but each of the first sensor IC 60 and the second sensor IC 70 has one. They may be provided one by one or not at any part. When a temperature sensor is not provided, it is preferable to use a Hall element and a magnet having a small temperature dependency.

In both embodiments, only one ECU 40 is provided, but an ECU 40 that performs separate processing on the output from each sensor IC may be provided.
In both embodiments, the first communication unit 65 and the second communication unit 75 output the detection signals S1 and S2 to the ECU 40 by the triggers T1 and T2 from the ECU 40, but the request may not be from the ECU 40. For example, it may be a request from an external device, or the torque sensor 41 may be intermittently driven at regular intervals to communicate the detection results S1 and S2 to the ECU 40.

  -You may implement combining 1st Embodiment and 2nd Embodiment. In this case, it is preferable that the communication frames are digitally communicated at different timings as shown in FIG.

  In the first embodiment, the output timing of the communication frame is varied by providing the delay unit 76 in the second sensor IC 70. However, the timings of the first and second communication units 65 and 75 are set to be different from each other. The output timings of the detection signals S1 and S2 may be made different by performing communication at regular intervals with the shifted clock signal. Further, the output timing of the detection signals S1 and S2 may be varied by providing a resistor in the signal path inside the second communication unit 75.

  -In 1st Embodiment, although the timing which outputs a communication frame was varied by providing the delay part 76 in the 2nd sensor IC70, the delay part 76 is not provided but the timing of trigger T1, T2 from ECU40 is set. By making them different, the output timings of the detection signals S1, S2 may be made different.

In both embodiments, two sensor ICs are provided, but three or more may be used.
In both embodiments, each sensor IC is provided with two detection units. However, for example, as shown in FIG. Each sensor IC may be provided with three or more detection units.

  In both embodiments, a Hall element is used as a magnetic detection element, but an MR sensor may be used, for example. Furthermore, the present invention is not limited to a magnetic detection element, but may be any sensor that measures a state quantity.

  In both embodiments, the temperature sensor 61b is provided to correct the output of the sensor (for example, the first Hall element 61a). However, the temperature sensor 61b may be corrected based on another state quantity. For example, a pressure sensor may be provided instead of the temperature sensor, and correction may be made from the change in Hall voltage pressure.

In the second embodiment, CRC is adopted as an error detection method for the detection signals S1 and S2, but other methods may be adopted. For example, a parity check may be employed.
-In 2nd Embodiment, although error detection of detection signal S1, S2 was performed by CRC, error detection does not need to be performed. In this case, it is not necessary to provide a CRC value in the communication frame.

  In the first embodiment, when communication of one detection signal is hindered, if the steering torque τ calculated from the other detection signals is not abnormal, the steering torque τ is adopted. The previous value of torque τ may be used.

  In the second embodiment, the communication frames as shown in FIGS. 6A and 6B are adopted. However, in the second embodiment, the configuration is such that the same bit of each detection signal does not overlap at the same timing. May be. For example, a configuration as shown in FIG.

  In this example, the temperature correction is performed when the A / D conversion unit converts the signal into a digital signal. However, the multiplexer may be provided and the A / D conversion may be performed after the multiplexer corrects the temperature. In addition, a total of 4 is provided between the first and second A / D conversion units 61c and 62c and the first communication unit 65, and between the third and fourth A / D conversion units 71c and 72c and the second communication unit 75, respectively. Two hard logic circuits may be provided. A digital signal generated by each A / D converter is processed by each hard logic circuit.

  In both embodiments, the torque sensor 41 that detects the torsion angle of the torsion bar 23c has been described as an example, but may be embodied in another sensor system such as a steering angle sensor.

  DESCRIPTION OF SYMBOLS 10 ... EPS, 20 ... Steering mechanism, 21 ... Steering wheel, 22 ... Steering shaft, 23 ... Column shaft, 23a ... Input shaft, 23b ... Lower shaft, 23c ... Torsion bar (detection object), 24 ... Intermediate shaft, 25 DESCRIPTION OF SYMBOLS ... Pinion shaft, 26 ... Rack shaft, 27 ... Rack and pinion mechanism, 28 ... Tie rod, 29 ... Steering wheel, 30 ... Steering assist mechanism, 31 ... Motor, 31a ... Rotating shaft of motor 31, 32 ... Deceleration mechanism, 40 ... ECU, 41 ... torque sensor, 42 ... rotation angle sensor, 43 ... vehicle speed sensor, 50 ... holding member, 51, 52 ... yoke, 51a, 52a ... claw part, 53, 54 ... magnetic flux collecting ring, 60 ... first sensor IC, 61 ... first detector, 62 ... second detector, 61a, 62a ... first and second Hall elements , 61b, 62b ... temperature sensor, 61c, 62c ... first and second A / D converters, 63 ... memory, 64 ... oscillator, 65 ... first communication unit, 70 ... second sensor IC, 71 ... third detection 72, fourth detector, 71a, 72a, third and fourth Hall elements, 71b, 72b, temperature sensor, 71c, 72c, third, fourth A / D converter, 73, memory, 74, oscillator, 75: Second communication unit, 76: Delay unit.

Claims (6)

A plurality of sensor ICs that detect the same amount of state for the same detection target and generate digital signals according to the detection results;
A sensor system having an arithmetic unit that receives the digital signals from the plurality of sensor ICs,
The plurality of sensor ICs output the digital signal to the arithmetic unit at different timings. The sensor system according to claim 1,
Each of the plurality of sensor ICs includes a detection unit that generates the digital signal and a communication unit that outputs the digital signal to the arithmetic unit.
The sensor system which makes the timing which outputs the said digital signal to the said calculating part differ by providing a time difference in the timing which outputs the said digital signal of the said some communication part to the said calculating part. The sensor system according to claim 2,
The plurality of communication units are sensor systems that start outputting the digital signal to the calculation unit when an external command is input. The sensor system according to claim 2 or 3,
The plurality of communication units convert the digital signal so as to be different communication frames between the communication units. In the sensor system according to any one of claims 1 to 4,
The same detection target is a torsion bar that twists through application of steering torque,
The plurality of sensor ICs each detect a twist amount of the torsion bar as the same state quantity. A plurality of sensor ICs that detect the same amount of state for the same detection target and generate digital signals according to the detection results;
An arithmetic unit that receives the digital signals from the plurality of sensor ICs,
Each of the plurality of sensor ICs includes a detection unit that generates the digital signal and a communication unit that outputs the digital signal to the arithmetic unit.
The plurality of communication units generate the digital signals so as to be different communication frames.