JP2014238363A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque sensor capable of, even while reducing the number of magnetic detection elements in use, obtaining as high reliability as a conventional one.SOLUTION: A torque sensor includes a torque magnetic field generation unit 3 for generating a torque magnetic field in response to torque received by a coupling shaft 2; a pulse magnetic field generation unit 11 for generating a pulse magnetic field; two magnetic detection elements 4a and 4b for detecting a superimposed magnetic field which is generated by a superimposing of the torque magnetic field and the pulse magnetic field; a pulse magnetic field intensity determination unit 13 for determining whether a variation between outputs by the pulse magnetic field extracted from an output of both the magnetic detection elements 4a and 4b is within a threshold range for intensity of the pulse magnetic field; a failure determination unit 14 for determining a failure of both the magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 on the basis of determination of the pulse magnetic field intensity determination unit 13; and a torque calculation unit 15 for calculating the torque received by the coupling shaft 2 by using the output of the magnetic detection elements 4a and 4b which are not determined to be in failure on the basis of determination of the failure determination unit 14.

Description

  The present invention relates to a torque sensor used in an electric power steering device for a vehicle.

  2. Description of the Related Art There is known an electric power steering device that drives an electric motor to assist steering and reduce a burden on a driver.

  In an electric power steering apparatus, an input steering is detected by detecting a twist generated in a connecting shaft that connects an input shaft connected to a steering member (steering wheel, steering wheel) and an output shaft connected to a traveling wheel by a pinion, a rack, or the like. A torque sensor for detecting torque is provided. In the electric power steering apparatus, drive control of an electric motor for steering assistance linked to the output shaft is performed based on the steering torque value detected by the torque sensor.

  As a conventional torque sensor, Patent Document 1 discloses a ring-shaped multipolar permanent magnet fixed to an input shaft, and a magnetic yoke that is fixed to an output shaft and disposed in the magnetic field of the permanent magnet to form a magnetic circuit. And two magnetic flux collecting rings that are magnetically coupled to the magnetic yoke and induce magnetic flux, and two magnetic sensing elements that detect the magnetic flux induced by the magnetic flux collecting ring, and based on the outputs of the two magnetic sensing elements, an input shaft Some have been proposed that detect the torque applied to.

  Since the torque sensor of Patent Literature 1 includes two magnetic detection elements, it is possible to detect a failure of the magnetic detection element by comparing the outputs of both magnetic detection elements. However, it is not possible to determine which of the two magnetic detection elements has failed by simply comparing the outputs of the two magnetic detection elements. Therefore, if one of the two magnetic detection elements is detected, the torque sensor can be used. As a result, the electric power steering apparatus cannot be used, and the steering assist cannot be continued.

  Patent Document 2 proposes a torque sensor including three magnetic detection elements. In the torque sensor disclosed in Patent Document 2, for example, when the output of only one magnetic detection element greatly changes compared to other magnetic detection elements (when the deviation from the other becomes large), the magnetic detection element fails. It is possible to determine that the magnetic detection element has failed, and by comparing the outputs of the three magnetic detection elements. Therefore, in the torque sensor disclosed in Patent Document 2, even when one of the magnetic detection elements fails, it is possible to continue the steering assistance using the output of the magnetic detection element that has not failed, and high reliability can be realized. .

Japanese Patent No. 4073384 JP 2010-203960 A

  However, in order to identify a failed magnetic detection element as described above, it is necessary to provide at least three magnetic detection elements, which is expensive. In addition, in order to detect the magnetism with high accuracy by the three magnetic detection elements, it is necessary to accurately arrange the three magnetic detection elements at predetermined positions, and there is a problem that the manufacturing tolerance range is narrow and the manufacturing is difficult. .

  In order to reduce costs and facilitate manufacture, it is desirable to reduce the number of magnetic detection elements as much as possible, and while reducing the number of magnetic detection elements to be used, high reliability equivalent to the conventional one can be obtained. A torque sensor is desired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a torque sensor that can obtain the same high reliability as the conventional one while reducing the number of magnetic detection elements to be used.

  The present invention was devised to achieve the above object, and a torque magnetic field which is a magnetic field according to the torque received by the connecting shaft when the connecting shaft connecting the input shaft and the output shaft is torsionally deformed. A torque magnetic field generation unit that generates a magnetic field, a pulse magnetic field generation unit having a coil that generates a predetermined pulse magnetic field, two magnetic detection elements that detect a superimposed magnetic field that is a magnetic field in which the torque magnetic field and the pulse magnetic field are superimposed, Pulse magnetic field strength determination for extracting fluctuations due to the pulse magnetic field from the outputs of the both magnetic detection elements and determining whether the fluctuations in the output due to the pulse magnetic field are within a preset threshold range for pulse magnetic field strength A failure determination unit that determines a failure of both the magnetic detection elements and the pulse magnetic field generation unit based on the determination of the pulse magnetic field strength determination unit, and the failure determination Based on the determination of a torque sensor and a torque calculation unit for calculating a torque which the connecting shaft is received by using an output of the magnetic sensor is not determined malfunction.

  The pulse magnetic field strength determination unit determines that the output fluctuation amount due to the pulse magnetic field is normal when it is within a preset pulse magnetic field strength threshold range, and abnormal when it is out of range, and the failure determination unit includes: When the two magnetic detection elements are determined to be normal by the pulse magnetic field strength determination unit, it is determined that the two magnetic detection elements and the pulse magnetic field generation unit are normal, and the one magnetic detection element is normal. When it is determined that the other magnetic detection element is abnormal, it is determined that one of the magnetic detection elements and the pulse magnetic field generation unit are normal and that the other magnetic detection element has failed, When the detection element is determined to be abnormal, and the absolute value of the difference between the outputs of the two magnetic detection elements is within a preset output threshold range, it is determined that a failure has occurred in the pulse magnetic field generation unit, Both magnetism Is determined detecting element is abnormal and, when the an absolute value of the threshold range for the output of the difference of the outputs of the magnetic sensor may be configured to determine that a system failure.

  You may further provide the forced operation | movement stop part which stops operation | movement forcibly when the said failure determination part determines with a system failure.

  When the failure determination unit determines that a failure has occurred in the magnetic detection element or the pulse magnetic field generation unit, the failure determination unit may further include a failure signal transmission unit that transmits a failure signal.

  ADVANTAGE OF THE INVENTION According to this invention, the torque sensor which can acquire the high reliability equivalent to the past can be provided, reducing the number of the magnetic detection elements to be used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the torque sensor which concerns on one embodiment of this invention, (a) is a disassembled perspective view and the principal part enlarged view, (b) is a block diagram. (A), (b) is a figure explaining operation | movement of the torque magnetic field generation part used for the torque sensor of FIG. (A) is a graph which shows the output of both magnetic detection elements when a 2nd magnetic detection element fails, (b) when a pulse magnetic field generation | occurrence | production part fails. It is a flowchart which shows the control flow of the torque sensor of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1A and 1B are diagrams showing a torque sensor according to the present embodiment, where FIG. 1A is an exploded perspective view and an enlarged view of a main part, and FIG. 1B is a block diagram.

  As shown in FIGS. 1A and 1B, the torque sensor 1 is a magnetic field corresponding to the torque received by the connecting shaft 2 when the connecting shaft 2 connecting the input shaft and the output shaft is torsionally deformed. A torque magnetic field generator 3 that generates a certain torque magnetic field and two magnetic detection elements 4a and 4b (first magnetic detection element 4a and second magnetic detection element 4b) made of a Hall IC or the like are provided.

  The input shaft is rotated by steering of a steering member such as a steering wheel. The output shaft is connected to a member responsible for the operation of the direction of the wheel, such as a pinion or a rack. The connecting shaft 2 connects the input shaft and the output shaft, and receives the torque generated by the relative displacement between the input shaft and the output shaft and is torsionally deformed. In the present embodiment, a torsion bar is used as the connecting shaft 2.

  The torque magnetic field generator 3 is fixed to the input shaft and has a multipolar permanent magnet 5 in which N poles and S poles are alternately arranged along the circumferential direction, and is fixed to the output shaft and is not in contact with the outer periphery of the permanent magnet 5. And two cylindrical magnetic yokes 6a and 6b provided to face each other in the axial direction.

  The magnetic yokes 6a and 6b are two protruding in the axial direction toward the opposing magnetic yokes 6b and 6a from the inner periphery of the circular tube portions 7a and 7b and the circular tube portions 7a and 7b surrounding the permanent magnet 5 in a non-contact manner. It consists of claw portions 8a and 8b having an equilateral triangle shape. The claw portions 8a and 8b are periodically formed at a pitch equal to the arrangement pitch of the same magnetic pole (N pole or S pole) of the permanent magnet 5 along the inner periphery of the circular pipe portions 7a and 7b. Both the magnetic yokes 6a and 6b are arranged such that both the claw portions 8a and 8b face each other at a half pitch with respect to the arrangement pitch of the same magnetic poles of the permanent magnet 5.

  As shown in FIG. 2A, in the neutral state where the connecting shaft 2 is not receiving torque, the tips of the claw portions 8a and 8b of the magnetic yokes 6a and 6b are at the boundary between the N pole and the S pole of the permanent magnet 5. It is supposed to be located. At this time, since the area facing the N pole and the area facing the S pole in the claw portions 8a and 8b are equal, the magnetic flux entering from the N pole and the magnetic flux exiting to the S pole are equal in both magnetic yokes 6a and 6b. There is no difference in magnetic polarity between the magnetic yokes 6a and 6b.

  On the other hand, when the connecting shaft 2 is twisted by receiving torque, the area facing the N pole and the area facing the S pole in the claw portions 8a and 8b are different as shown in FIG. In the example of FIG. 2B, the area facing the south pole is large in the claw portion 8a of the magnetic yoke 6a, and the area facing the north pole is large in the claw portion 8b of the magnetic yoke 6b. As a result, a magnetic polarity difference occurs between the magnetic yokes 6a and 6b, and a magnetic field is generated.

  In the present embodiment, the magnetic fields from the magnetic yokes 6a and 6b are applied to the positions where the outer yokes 9a and 9b, which are provided in a non-contact manner on the outer periphery of the magnetic yokes 6a and 6b, and the outer yokes 9a and 9b face each other. The torque magnetic field generation unit 3 is configured to be guided to the two magnetic detection elements 4a and 4b by the proximity yokes 10a and 10b provided so as to protrude in the directions close to each other. These outer yokes 9a and 9b, proximity yokes 10a and 10b, and magnetic detection elements 4a and 4b are supported by a fixed body around the input shaft and the output shaft. Each yoke 6a, 6b, 9a, 9b, 10a, 10b is made of a soft magnetic material.

  The torque magnetic field generation unit 3 described here is merely an example, and the configuration of the torque magnetic field generation unit 3 is not limited to this. That is, the torque magnetic field generator 3 may have any configuration as long as it generates a torque magnetic field according to the torque received by the connecting shaft 2.

  Now, the torque sensor 1 according to the present embodiment further includes a pulse magnetic field generation unit 11, a pulse magnetic field strength determination unit 13, a failure determination unit 14, and a torque calculation unit 15.

  The pulse magnetic field generation unit 11 generates a predetermined pulse magnetic field, and outputs an instruction signal to the coil 16, the coil power supply unit 17 that supplies an excitation current to the coil 16, and the coil power supply unit 17. And an instruction unit 18 that performs on / off control of the power supply unit 17 at a predetermined cycle.

  The magnetic detection elements 4a and 4b are configured to detect a superimposed magnetic field that is a magnetic field in which the torque magnetic field generated by the torque magnetic field generation unit 3 and the pulse magnetic field generated by the coil 16 of the pulse magnetic field generation unit 11 are superimposed. In the present embodiment, the magnetic detection elements 4a and 4b are disposed between the proximity yokes 10a and 10b, and the coil 16 is disposed between the magnetic detection elements 4a and 4b.

  Both the magnetic detection elements 4a and 4b may be installed anywhere as long as both the torque magnetic field and the pulse magnetic field (that is, the superimposed magnetic field) can be detected. However, as in the torque sensor 1 according to the present embodiment, by arranging the coil 16 between the two magnetic detection elements 4a and 4b, the intensity of the pulse magnetic field detected by the two magnetic detection elements 4a and 4b is approximately the same. Further, the pulse magnetic field generated in the coil 16 can be detected with high accuracy, and there is an advantage that the coil 16 can be downsized and the excitation current can be reduced.

  The pulse magnetic field strength determination unit 13 extracts fluctuations due to the pulse magnetic field from the outputs (magnetic signals) of the both magnetic detection elements 4a and 4b, and the pulse magnetic field strength threshold value for which the fluctuation of the output due to the pulse magnetic field is set in advance. Each is determined whether it is within the range.

  Specifically, the pulse magnetic field strength determination unit 13 obtains the maximum value and the minimum value of the outputs of the magnetic detection elements 4a and 4b in a predetermined period (a period similar to the period of the pulse magnetic field), and calculates the maximum value from the obtained maximum value. A value obtained by subtracting the minimum value is obtained as an output fluctuation due to the pulse magnetic field, and it is determined whether the obtained output fluctuation due to the pulse magnetic field is within a preset pulse magnetic field strength threshold range.

  That is, the pulse magnetic field strength determination unit 13 determines whether the magnetic detection elements 4a and 4b can accurately detect the pulse magnetic field generated in the coil 16. Here, for convenience, it is assumed that the pulse magnetic field strength determination unit 13 determines that the output fluctuation amount due to the pulse magnetic field is normal when the amount of fluctuation in the pulse magnetic field is within a preset threshold range for pulse magnetic field strength, and abnormal when it is out of the range. (Normal or abnormal here indicates the state of detection of the pulse magnetic field for the sake of convenience, and does not indicate the presence or absence of a failure). The threshold range for the pulse magnetic field strength that is the determination criterion is determined in consideration of the magnetic field strength generated in the coil 16, the positional relationship between the magnetic detection elements 4a and 4b and the coil 16, and the like.

  The failure determination unit 14 determines a failure of both the magnetic detection elements 4 a and 4 b and the pulse magnetic field generation unit 11 based on the determination of the pulse magnetic field strength determination unit 13.

  Specifically, the failure determination unit 14 determines that both the magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 are normal when the pulse magnetic field strength determination unit 13 determines that both the magnetic detection elements 4a and 4b are normal ( It is determined that the system is healthy.

  The failure determination unit 14 determines that one of the magnetic detection elements 4a (or 4b) is normal and the other magnetic detection element 4b (or 4a) is abnormal when the pulse magnetic field strength determination unit 13 determines that one of the magnetic detection elements 4a (or 4b) is abnormal. It is determined that the detection element 4a (or 4b) and the pulse magnetic field generator 11 are normal, and a failure has occurred in the other magnetic detection element 4b (or 4a).

In FIG. 3 (a), an example of outputs of the magnetic detection elements 4a, 4b in the case where a failure by the elapsed time t ₁ to the second magnetic detection element 4b has occurred. Here, a case is shown in which both magnetic detection elements 4a and 4b detect the same pulse magnetic field, and the thin solid line in the figure represents the output when only the magnetic field is detected by both magnetic detection elements 4a and 4b.

In the case of FIG. 3A, after the elapsed time t ₁ , the fluctuation amount of the output due to the pulse magnetic field in the second magnetic detection element 4b becomes 0, so that the second magnetic detection element is determined by the pulse magnetic field strength determination unit 13. 4b is determined to be abnormal. On the other hand, for the first magnetic detecting element 4a, there is no change in the output variation by the pulse magnetic field even elapsed time t ₁ later, it will be determined to be normal at the pulse magnetic field intensity determination section 13. The fact that the first magnetic detection element 4a is determined to be normal means that the pulse magnetic field generator 11 is generating a predetermined pulse magnetic field, and it is determined that the pulse magnetic field generator 11 is also normal. it can. Therefore, in this case, the failure determination unit 14 determines that the first magnetic detection element 4a and the pulse magnetic field generation unit 11 are normal, and only the second magnetic detection element 4b has failed. .

  When the pulse magnetic field strength determination unit 13 determines that both the magnetic detection elements 4a and 4b are abnormal, the pulse magnetic field generation unit 11 is out of order, and both the magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 A case where at least two or more of them have failed can be considered. If at least two of the latter magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 are out of order, they cannot be used (system failure), but the former pulse magnetic field generation unit 11 fails. If so, both magnetic detection elements 4a and 4b have the correct output and can be used continuously.

  Therefore, when the failure determination unit 14 determines that both the magnetic detection elements 4a and 4b are abnormal, the outputs of both the magnetic detection elements 4a and 4b are further compared, and the outputs of the magnetic detection elements 4a and 4b are correct. Judgment whether or not.

  That is, the failure determination unit 14 determines that the pulse magnetic field strength determination unit 13 determines that both the magnetic detection elements 4a and 4b are abnormal, and outputs the absolute value of the difference between the outputs of the two magnetic detection elements 4a and 4b in advance. When it is within the threshold value range, it is determined that a failure has occurred in the pulse magnetic field generator 11.

  Furthermore, the failure determination unit 14 determines that the both magnetic detection elements 4a and 4b are abnormal in the pulse magnetic field strength determination unit 13, and the absolute value of the difference between the outputs of the both magnetic detection elements 4a and 4b is the output threshold value. When it is out of range, it is configured to determine a system failure.

FIG. 3B shows an example of the output of each of the magnetic detection elements 4a and 4b when the pulse magnetic field generator 11 fails at the elapsed time t ₁ and no pulse magnetic field is generated. In this case, after the elapsed time t ₁ , the output fluctuation due to the pulse magnetic field becomes 0 in both the magnetic detection elements 4a and 4b, and therefore, both the magnetic detection elements 4a and 4b are determined to be abnormal by the pulse magnetic field strength determination unit 13. Will be.

  On the other hand, as shown in FIG. 3B, if both the magnetic detection elements 4a and 4b are operating normally, regardless of whether or not the pulse magnetic field generation unit 11 has failed, both magnetic detection elements 4a and 4b The output difference is a substantially constant value. Therefore, even when both magnetic detection elements 4a and 4b are determined to be abnormal by the pulse magnetic field strength determination unit 13, the absolute value of the difference between the outputs of both magnetic detection elements 4a and 4b is within the output threshold range. If there is, it can be determined that both magnetic detection elements 4a and 4b are normal.

  The torque calculator 15 calculates the torque received by the connecting shaft 2 based on the outputs of the magnetic detection elements 4a and 4b. The torque calculation unit 15 calculates the torque received by the connecting shaft 2 using an output value obtained by removing the fluctuation due to the above-described pulse magnetic field from the outputs of the magnetic detection elements 4a and 4b. The calculated torque is output to the assist motor 19 as a torque value signal.

  In the present embodiment, the torque calculation unit 15 calculates the torque received by the connecting shaft 2 using the outputs of the magnetic detection elements 4a and 4b that are not determined to be failure based on the determination of the failure determination unit 14. Become. When both the magnetic detection elements 4a and 4b are not determined to be in failure, the torque may be calculated by averaging the torque values calculated using both outputs, or only one of the outputs is used. Thus, the torque may be calculated.

  The torque sensor 1 includes a forced operation stop unit 20 that forcibly stops the operation of the torque sensor 1 when the failure determination unit 14 determines a system failure, and the failure determination unit 14 detects the magnetic detection elements 4a and 4b or pulses. When it is determined that a failure has occurred in the magnetic field generator 11 (including when it is determined that the system has failed), a failure signal transmitter 21 that transmits a failure signal to the failure display / storage unit 22 (such as a failure display lamp). Is further provided.

  The pulse magnetic field strength determination unit 13, the failure determination unit 14, the torque calculation unit 15, the forced operation stop unit 20, the failure signal transmission unit 21, and the instruction unit 18 are provided on the control board 24 in the electronic control unit (ECU) 23 of the vehicle. It is mounted and realized by appropriately combining memories such as ROM and RAM, CPU, I / O interface, software, and the like.

  Next, the control flow of the torque sensor 1 will be described with reference to FIG. The torque sensor 1 is configured to repeatedly execute the control flow of FIG.

First, in step S1, the pulse magnetic field strength determination unit 13 causes the output variation ΔV ₁ due to the pulse magnetic field of the first magnetic detection element 4a and the output variation ΔV ₁ due to the pulse magnetic field of the second magnetic detection element 4b. Detect ₂

After that, in step S2, the pulse magnetic field strength determination unit 13 determines whether the output fluctuation ΔV ₁ due to the pulse magnetic field of the first magnetic detection element 4a is within a preset pulse magnetic field threshold range. If YES is determined in step S2, the process proceeds to step S3. If NO is determined, the process proceeds to step S4.

In step S3, the pulse magnetic field strength determination unit 13 determines whether the output variation ΔV ₂ due to the pulse magnetic field of the second magnetic detection element 4b is within a preset pulse magnetic field threshold range. If YES is determined in step S3, the process proceeds to step S5. If NO is determined, the process proceeds to step S6.

In step S5, since it is determined that both ΔV ₁ and ΔV ₂ are within the pulse magnetic field threshold range (that is, both magnetic detection elements 4a and 4b are normal), the failure determination unit 14 determines that the system is healthy, and step S15. Proceed to

In step S6, it is determined that ΔV ₁ is within the pulse magnetic field threshold range and ΔV ₂ is out of the pulse magnetic field threshold range (that is, the first magnetic detection element 4a is normal and the second magnetic detection element 4b is abnormal). Therefore, the failure determination unit 14 determines that the second magnetic detection element 4b is defective, and the failure signal transmission unit 21 transmits a failure signal in step S7, and then the process proceeds to step S15.

In step S4, as in step S3, it is determined whether the output fluctuation ΔV ₂ due to the pulse magnetic field of the second magnetic detection element 4b is within a preset pulse magnetic field threshold range. If YES is determined in step S4, the process proceeds to step S8. If NO is determined, the process proceeds to step S10.

In step S8, it is determined that ΔV ₁ is outside the pulse magnetic field threshold range and ΔV ₂ is within the pulse magnetic field threshold range (that is, the first magnetic detection element 4a is abnormal and the second magnetic detection element 4b is normal). Therefore, the failure determination unit 14 determines that the first magnetic detection element 4a has failed, and after the failure signal transmission unit 21 transmits a failure signal in step S9, the process proceeds to step S15.

In step S10, since both ΔV ₁ and ΔV ₂ are determined to be outside the pulse magnetic field threshold range (that is, both magnetic detection elements 4a and 4b are abnormal), the outputs of both magnetic detection elements 4a and 4b are compared. It is determined whether both magnetic detection elements 4a and 4b are healthy.

  That is, in step S10, it is determined whether or not the absolute value of the difference between the outputs of the magnetic detection elements 4a and 4b is within a preset output threshold range. If YES is determined in step S10, the process proceeds to step S11. If NO is determined, the process proceeds to step S13.

In step S11, ΔV ₁ and ΔV ₂ are both outside the pulse magnetic field threshold range (that is, both magnetic detection elements 4a and 4b are abnormal), and the absolute value of the difference between the outputs of both magnetic detection elements 4a and 4b is output. Failure determination unit 14 determines that the pulse magnetic field generation unit 11 is in failure, and the failure signal transmission unit 21 detects a failure signal in step S12. Is sent to step S15.

In step S13, ΔV ₁ and ΔV ₂ are both outside the pulse magnetic field threshold range (that is, both magnetic detection elements 4a and 4b are abnormal), and the absolute value of the difference between the outputs of both magnetic detection elements 4a and 4b is output. Is out of the threshold range for use (that is, one or both of the magnetic detection elements 4a and 4b have failed), the failure determination unit 14 determines that the system has failed, and in step S14, the forced operation stop unit 20 determines that the torque sensor 1 Forcibly stop the operation.

  In step S15, the torque calculation unit 15 calculates the torque received by the connecting shaft 2 using the magnetic detection elements 4a and 4b that are not determined to be faulty, outputs the calculation result as a torque value signal, and ends the process. .

  The operation of the present embodiment will be described.

  In the torque sensor 1 according to the present embodiment, a torque magnetic field generator 3 that generates a torque magnetic field according to the torque received by the connecting shaft 2, a pulse magnetic field generator 11 having a coil 16 that generates a pulse magnetic field, and torque Two magnetic detection elements 4a and 4b that detect a superimposed magnetic field in which a magnetic field and a pulse magnetic field are superimposed, and the fluctuation in output due to the pulse magnetic field extracted from the outputs of both magnetic detection elements 4a and 4b are within the pulse magnetic field intensity threshold range. A pulse magnetic field strength determination unit 13 that determines whether there is a failure, a failure determination unit 14 that determines a failure of both the magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 based on the determination of the pulse magnetic field strength determination unit 13, and a failure determination unit A torque calculation unit 15 that calculates the torque received by the connecting shaft 2 using the outputs of the magnetic detection elements 4a and 4b that are not determined to be faulty based on the determination of No. 14; There.

  With this configuration, even when one of the two magnetic detection elements 4a and 4b and the pulse magnetic field generation unit 11 is damaged, it is possible to identify the failed member, which is healthy. Torque detection can be continued using the member.

  In the present embodiment, only two magnetic detection elements 4a and 4b are used, and the number of magnetic detection elements 4a and 4b to be used is reduced, but it is equivalent to a conventional torque sensor using three magnetic detection elements. High reliability can be obtained. Since the torque sensor 1 uses a small number of magnetic detection elements 4a and 4b, the cost can be reduced and the manufacturing can be facilitated.

  The torque sensor 1 can be used for an electric steering device, for example. Since the electric steering device requires high reliability, the torque sensor 1 of the present invention can be used particularly preferably.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Torque sensor 2 Connecting shaft 3 Torque magnetic field generation part 4a, 4b Magnetic detection element 11 Pulse magnetic field generation part 13 Pulse magnetic field strength determination part 14 Failure determination part 15 Torque calculation part 16 Coil

Claims (4)

A torque magnetic field generator that generates a torque magnetic field that is a magnetic field according to the torque received by the connecting shaft when the connecting shaft that connects the input shaft and the output shaft is torsionally deformed;
A pulse magnetic field generator having a coil for generating a predetermined pulse magnetic field;
Two magnetic detection elements for detecting a superimposed magnetic field that is a magnetic field in which the torque magnetic field and the pulse magnetic field are superimposed;
Pulse magnetic field strength determination for extracting fluctuations due to the pulse magnetic field from the outputs of the both magnetic detection elements and determining whether the fluctuations in the output due to the pulse magnetic field are within a preset threshold range for pulse magnetic field strength And
Based on the determination of the pulse magnetic field strength determination unit, a failure determination unit that determines a failure of both the magnetic detection elements and the pulse magnetic field generation unit;
Based on the determination of the failure determination unit, a torque calculation unit that calculates the torque received by the connecting shaft using the output of the magnetic detection element that is not determined to be a failure;
A torque sensor comprising: The pulse magnetic field strength determination unit determines that the output fluctuation amount due to the pulse magnetic field is normal when it is within a preset pulse magnetic field strength threshold range, and abnormal when it is out of range,
The failure determination unit
When the pulse magnetic field strength determination unit determines that both the magnetic detection elements are normal, it is determined that the both magnetic detection elements and the pulse magnetic field generation unit are normal,
When it is determined that the one magnetic detection element is normal and the other magnetic detection element is abnormal, the one magnetic detection element and the pulse magnetic field generation unit are normal, and the other magnetic detection element has a failure. Determine that it occurred,
When it is determined that both the magnetic detection elements are abnormal and the absolute value of the difference between the outputs of the two magnetic detection elements is within a preset output threshold range, it is determined that a failure has occurred in the pulse magnetic field generation unit. And
The system is configured to determine that a system failure has occurred when both the magnetic detection elements are determined to be abnormal and an absolute value of a difference between outputs of the two magnetic detection elements is outside the output threshold range. Torque sensor. The torque sensor according to claim 2, further comprising a forcible operation stop unit that forcibly stops the operation when the failure determination unit determines that a system failure has occurred. The torque sensor according to any one of claims 1 to 3, further comprising a failure signal transmission unit that transmits a failure signal when the failure determination unit determines that a failure has occurred in the magnetic detection element or the pulse magnetic field generation unit. .