JP5656016B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a steering shaft that supports a steering wheel operated by a driver, an electric motor that applies assist torque to the operation of the steering wheel, and steering torque acquisition means that detects steering torque input to the steering shaft. And an assist control means for calculating a target assist torque using the steering torque acquired by the steering torque acquisition means and drivingly controlling the electric motor based on the calculated target assist torque. .

  Conventionally, for example, as shown in Patent Document 1 below, this type of electric power steering apparatus is widely known. This conventional electric power steering apparatus includes an electric motor, a steering torque sensor, a vehicle speed sensor, a steering angle sensor, control means, electric motor drive means, and electric motor current detection means. In this conventional electric power steering apparatus, when it is determined that the steering torque sensor has failed, the control means controls the steering torque based on the vehicle speed signal from the vehicle speed sensor and the steering angle signal from the steering angle sensor. And the drive of the electric motor is controlled based on the estimated steering torque.

JP 11-59447 A

  In the above-described conventional electric power steering apparatus, even if the steering torque sensor fails, the steering torque can be estimated using the detection values of other sensors, and based on the estimated steering torque, The driving of the electric motor is controlled, that is, the assist torque can be continuously applied to the operation of the steering wheel by the driver. By the way, when the steering torque is estimated using the detection value of another sensor, it is naturally considered that the accuracy is deteriorated as compared with the steering torque detected by the steering torque. Therefore, as in the case of the above-described conventional electric power steering device, when the steering torque is estimated using the detection values of other sensors and the assist torque is continuously applied, the steering torque sensor is appropriately equivalent to that when the steering torque sensor is normal. It may be difficult to apply a proper assist torque.

  Here, the steering torque sensor (steering torque acquisition means) may include a plurality of (for example, two) different sensors. In this case, if an abnormality occurs in any of the sensors constituting the steering torque sensor (steering torque acquisition means), it is generally determined that the entire steering torque sensor (steering torque acquisition means) has failed, and the conventional electric motor Unlike the power steering device, the steering torque (steering torque) detected by the steering torque sensor (steering torque acquisition means) determined to be out of order is not adopted. However, in this case, among the plurality of sensors constituting the steering torque sensor (steering torque acquisition means), there may be a sensor that is operating normally. For this reason, from the viewpoint of applying the assist torque with higher accuracy, a sensor in which an abnormality has occurred among a plurality of sensors constituting the steering torque sensor (steering torque acquisition means) is identified with high accuracy, and an abnormality occurs. It is desired to continuously apply the assist torque by determining the steering torque using the value detected by the normal sensor that is not.

  The present invention has been made in order to cope with the above-described problems. The purpose of the present invention is to accurately determine whether each of a plurality of sensors constituting a torque sensor is normal or abnormal, and to use detection values from the normal sensors. Another object of the present invention is to provide a vehicle steering control device that can apply assist torque.

  In order to achieve the above object, a vehicle steering control apparatus (this apparatus) according to the present invention includes a steering shaft, an electric motor, steering torque acquisition means, and assist control means. The steering shaft supports a steering handle operated by a driver. The electric motor applies assist torque to the operation of the steering wheel. The steering torque acquisition means includes a plurality of sensors for detecting steering torque input to the steering shaft. The assist control means calculates a target assist torque using the steering torque acquired by the steering torque acquisition means, and drives and controls the electric motor based on the calculated target assist torque. Thus, the steering torque input to the steering shaft via the steering handle for turning the vehicle by the driver is reduced by applying the assist torque corresponding to the target assist torque by the electric motor.

  One of the features of this apparatus is that the plurality of sensors constituting the steering torque acquisition means detect the same physical quantity that changes due to fluctuations in the torque input to the steering shaft, respectively. It is to output a signal corresponding to the physical quantity. Here, each of the plurality of sensors may detect a magnetic flux density that changes due to a variation in torque input to the steering shaft as the physical quantity. In this case, the magnetic flux density It may be changed by torsion around the axis of the steering shaft due to variation in torque input to the steering shaft. According to this, the plurality of sensors constituting the steering torque acquisition means output a signal corresponding to the physical quantity (magnetic flux density) detected by each of the sensors, that is, a signal representing torque corresponding to the fluctuation of the torque input to the steering shaft. Can be output.

  One of the features of this apparatus is that it includes a sensor signal output means. The sensor signal output means drives the electric motor under a predetermined condition to vary the torque input to the steering shaft, and outputs the signal corresponding to the physical quantity detected by each of the plurality of sensors. In this case, in the case of including an acquired steering torque abnormality determining unit that determines whether or not the steering torque acquired by the steering torque acquiring unit is abnormal, the sensor signal output unit is configured to output the acquired steering torque. When the abnormality determination means determines that the steering torque is abnormal, the signal is output to each of the plurality of sensors. According to these, the sensor signal output means always outputs signals from a plurality of sensors at predetermined time intervals, or when it is determined that the steering torque acquired by the steering torque acquisition means is abnormal. Signals can be output from a plurality of sensors.

  At this time, at least the first shaft connected to the steering handle, the second shaft connected to the electric motor, and the first shaft and the second shaft are twisted around the axis. The sensor signal output means may rotate the second shaft around the axis as the predetermined condition as long as the sensor signal output means is connected to be rotatable relative to each other via the deformable elastic body. The electric motor is driven under a condition in which the elastic body is twisted and deformed so as not to displace the steering handle connected to the first shaft in the rotational direction, and the torque input to the steering shaft is changed. More specifically, the sensor signal output means is configured such that, as the predetermined condition, the first shaft and the second shaft connected to each other via the elastic body with respect to the first shaft and the second shaft via the second shaft. When the elastic body is vibrated in the torsional direction around the axis, only the second shaft vibrates and the first shaft does not vibrate and has an anti-resonance frequency that is greater than the anti-resonance frequency. When the body is vibrated in the torsional direction around the axis, the torque input to the steering shaft is changed by a frequency smaller than the resonance frequency at which the second shaft and the first shaft resonate and vibrate. The electric motor is driven.

  According to these, the electric motor is driven under a predetermined condition for appropriately twisting and deforming the elastic body, and the torque input to the steering shaft including the first shaft, the elastic body, and the second shaft is fluctuated, and a plurality of sensors Can output a signal. Therefore, even when the sensor signal output means outputs signals from a plurality of sensors as necessary, the displacement of the steering wheel can be effectively suppressed, so that the driver does not feel uncomfortable. .

  In addition, one of the features of the present apparatus is that an abnormality occurrence sensor specifying unit is provided. When the signal is output from the plurality of sensors by the sensor signal output unit, the abnormality occurrence sensor specifying unit converts the output signal into torque input to the steering shaft, and performs the same conversion. A torque is compared with a judgment torque set in advance as a torque input to the steering shaft when the electric motor is driven under the predetermined condition, and an abnormality has occurred in the plurality of sensors. Identify the sensor. According to this, the abnormality occurrence sensor specifying means can accurately specify a sensor in which an abnormality has occurred among a plurality of sensors. In other words, the abnormality occurrence sensor specifying means can specify a sensor that is operating normally properly among the plurality of sensors. Further, by using the output of the normally operating sensor, the assist control means can continuously apply the assist torque.

  Furthermore, one of the other characteristics of the present apparatus is that the steering torque acquisition means is detected by a sensor that is not specified as an abnormal sensor by the abnormality occurrence sensor specifying means among the plurality of sensors. The steering torque is acquired using a physical quantity, and the assist control means calculates the target assist torque using the steering torque acquired by the steering torque acquisition means, and based on the calculated target assist torque. The electric motor may be driven and controlled. According to this, the steering torque acquisition means can acquire an accurate steering torque by specifying a normally operating sensor and using a signal from this sensor. Therefore, since the assist control means can calculate an appropriate target assist torque using this accurate steering torque, even if there is an abnormal sensor among a plurality of sensors, the target assist torque can be calculated. The drive control of the electric motor based on the torque can be continued.

It is the schematic which shows the structure of the electric power steering apparatus to which the steering control apparatus which concerns on this invention is applied. It is a schematic sectional drawing for demonstrating the structure of the torque sensor of FIG. (A)-(c) is the schematic for demonstrating the positional relationship of the circumferential direction of the magnetic pole nail | claw of a magnetic yoke and the magnetic pole of a magnet in the torque sensor of FIG. 2 is a graph showing assist characteristics representing a relationship between a steering torque detected by a torque sensor of FIG. 1 and a target assist torque. FIG. 2 is an examination model diagram for explaining an anti-resonance frequency and a resonance frequency in the electric power steering apparatus of FIG. 1.

  Hereinafter, a vehicle steering control device (hereinafter also simply referred to as “this device”) according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an electric power steering apparatus 10 to which the present apparatus can be applied. The electric power steering apparatus 10 includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed and supported at the upper end of the steering shaft 12, and the lower end of the steering shaft 12 is connected to the steered gear unit U. The steering shaft 12 includes a main shaft 12a connected to the upper end of the steering handle 11, a pinion shaft 12c connected to the steered gear unit U, and the main shaft 12a and the pinion shaft 12c via universal joints 12d and 12e. And an intermediate shaft 12b. Here, in this embodiment, the main shaft 12a includes an input side shaft 12a1 as a first shaft to which the steering handle 11 is connected, and an output side shaft 12a2 as a second shaft connected to the intermediate shaft 12b. It is formed.

  The electric motor 13 is assembled to the steering shaft 12, more specifically, to the output side shaft 12 a 2 forming the main shaft 12 a via a reduction mechanism (not shown). Hereinafter, the electric motor 13 is referred to as “EPS motor 13”. The EPS motor 13 is, for example, a three-phase synchronous permanent magnet motor (brushless motor), and rotationally drives the output side shaft 12a2 forming the main shaft 12a around its axis via a speed reduction mechanism. Thereby, the EPS motor 13 gives an assist force (more specifically, assist torque) for reducing the operation force (more specifically, steering torque) input to the steering handle 11 by the driver. .

  The steered gear unit U is, for example, a gear unit adopting a rack and pinion type, and the rotation of the pinion gear 14 integrally assembled to the lower end of the steering shaft 12 (more specifically, the pinion shaft 12c) It is transmitted to the rack bar 15. With this configuration, the steering torque input to the steering shaft 12 in accordance with the turning operation of the steering handle 11 by the driver is transmitted to the rack bar 15 via the pinion gear 14, and the assist torque by the EPS motor 13 is transmitted to the pinion gear. 14 and transmitted to the rack bar 15. As a result, the rack bar 15 is displaced in the axial direction by the steering torque and the assist torque from the pinion gear 14, and the left and right front wheels FW1, FW2 connected to both ends of the rack bar 15 are steered in the left and right direction. Yes.

  Moreover, the electric control device C as the present device applied to the electric power steering device 10 configured as described above includes a torque sensor 20 as a torque acquisition unit. As shown in FIG. 2, the torque sensor 20 is provided between the input side shaft 12 a 1 and the output side shaft 12 a 2 that form the main shaft 12 a, and is input to the steering shaft 12 via the steering handle 11. (Equivalent to steering torque) is detected. The torque sensor 20 includes a torsion bar 21 as an elastic body that connects the input side shaft 12a1 and the output side shaft 12a2 so as to be relatively rotatable on the same axis, and an end portion of the input side shaft 12a1 (or one end portion of the torsion bar 21). A magnet 22 (hard magnetic body) assembled to the output side, a pair of magnetic yokes 23 (soft magnetic body) assembled to the end of the output side shaft 12a2 (or the other end of the torsion bar 21), and this one Magnetic sensors 24A and 24B (hereinafter referred to as a pair of sensors) that detect a magnetic flux density generated between a pair of magnetic yokes 23A and 23B (hereinafter also collectively referred to as magnetic yokes 23). , Collectively referred to as a magnetic sensor 24).

  Both ends of the torsion bar 21 are fixed to the input side shaft 12a1 and the output side shaft 12a2 by pins, respectively, and set torsion / torque characteristics (specifically, elastic or rigid) according to the purpose. Thus, when a rotational torque is applied to the steering shaft 12, that is, the input side shaft 12a1 and the output side shaft 12a2, the torsion bar 21 is twisted and deformed by the action of the rotational torque, and the input side shaft 12a1 and the output side shaft 12a2 In the meantime, a relative angular displacement corresponding to the magnitude of the rotational torque input in the rotational torque input direction occurs.

  The magnet 22 is provided in a ring shape, and a plurality of S poles and N poles are alternately magnetized in the circumferential direction as schematically shown in FIG. The set of magnetic yokes 23A and 23B is an annular body disposed close to the outer periphery of the magnet 22 as schematically shown in FIGS. 2 and 3, and the same number as the N pole and S pole of the magnet 22, respectively. Magnetic pole claws 23a are provided at equal intervals on the entire circumference. The pair of magnetic yokes 23A and 23B are fixed so that the magnetic claws 23a are alternately arranged in the circumferential direction.

  Here, as shown in FIG. 3B, the pair of magnetic yokes 23A and 23B and the magnet 22 are not twisted in the torsion bar 21 (that is, between the input side shaft 12a1 and the output side shaft 12a2). In a state where no rotational torque is applied between them, the centers of the magnetic claws 23a provided in the magnetic yokes 23A and 23B and the boundary between the S pole and the N pole of the magnet 22 are arranged to coincide with each other. In such an assembled state, the magnetic pole claws 23a of the two magnetic yokes 23A and 23B are identical in the magnetic field formed between the S and N poles adjacent to each other on the circumference of the magnet 22. The magnetic flux generated in the annular yoke body connecting the bases of the magnetic pole claws 23a is the same.

  On the other hand, when relative angular displacement occurs due to torsion of the torsion bar 21 between the input side shaft 12a1 assembled with the magnet 22 and the output side shaft 12a2 assembled with the pair of magnetic yokes 23A and 23B, respectively. The phases of the magnetic pole claws 23a of the magnetic yokes 23A and 23B and the S and N poles of the magnet 22 change in opposite directions as shown in FIG. 3 (a) or FIG. 3 (c). When the phase change occurs in this way, the magnetic field lines having opposite polarities increase in the magnetic pole claws 23a of one magnetic yoke 23A and the magnetic pole claws 23a of the other magnetic yoke 23B, and the magnetic yokes 23A and 23B Positive and negative magnetic fluxes are generated in the yoke body. The sign of the magnetic flux generated at this time is determined according to the direction of the relative angular displacement generated between the magnet 22 and the magnetic yokes 23A and 23B, that is, between the input side shaft 12a1 and the output side shaft 12a2. The density corresponds to the magnitude of this relative angular displacement.

  As shown in FIG. 2, the pair of magnetic sensors 24A and 24B includes two magnetic flux collecting rings 25A and 25B (hereinafter collectively referred to as the magnetic flux collecting ring 25) disposed outside the magnetic yokes 23A and 23B. The magnetic flux density generated between the magnetic yokes 23A and 23B is detected by being inserted into an air gap provided between the magnetic flux collecting projections 25a formed so as to face each other in the axial direction. . Here, as the magnetic sensors 24A and 24B, for example, a Hall element, a Hall IC, a magnetoresistive element, or the like can be adopted, and the detected magnetic flux density is converted into an electric signal (for example, a voltage signal) and output. Note that the magnetic sensors 24A and 24B are fixed to a housing, a column tube, or the like not shown in detail without contacting the magnetic yokes 23A and 23B.

  The output of each magnetic sensor 24 (24A, 24B) varies depending on the magnetic flux generated inside the yoke body of the magnetic yoke 23 (23A, 23B) facing the magnetism collecting ring 25 (25A, 25B). As described above, this corresponds to the phase change of the magnetic yoke 23 (23A, 23B) with respect to the magnet 22, in other words, the relative angular displacement between the input side shaft 12a1 and the output side shaft 12a2. Accordingly, the output of each magnetic sensor 24 (24A, 24B) is applied to the input side shaft 12a1 and the output side shaft 12a2, and corresponds to the direction and magnitude of the rotational torque that causes relative angular displacement. Therefore, the torque sensor 20 detects rotational torques T1 and T2 (corresponding to the steering torque) applied to the input side shaft 12a1 and the output side shaft 12a2 based on the output change of each magnetic sensor 24 (24A, 24B). And signals corresponding to the detected rotational torques T1 and T2 can be output. In the following description, the rotational torques T1 and T2 may be simply referred to as “rotational torque T”.

  In addition, the electric control device C includes a steering angle sensor 26 and a vehicle speed sensor 27 as shown in FIG. The steering angle sensor 26 detects a steering angle θ as a rotation angle of the steering shaft 12 accompanying a turning operation of the steering handle 11 by the driver, and outputs a signal corresponding to the steering angle θ. The vehicle speed sensor 27 detects the vehicle speed V of the vehicle and outputs a signal corresponding to the detected vehicle speed V.

  Furthermore, as shown in FIG. 1, the electric control device C includes an electronic control unit 28 that controls the operation of the EPS motor 13. The electronic control unit 28 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operation of the EPS motor 13. For this reason, the sensors 20, 26, 27 are connected to the input side of the electronic control unit 28, and the EPS motor 13 is driven using the detection values detected by the sensors 20, 26, 27. To control. On the other hand, a drive circuit 29 for driving the EPS motor 13 is connected to the output side of the electronic control unit 28.

  Next, the drive control of the EPS motor 13 (hereinafter, this drive control is referred to as “assist control”) by the electric control device C (more specifically, the electronic control unit 28) configured as described above will be specifically described. explain. The electronic control unit 28 controls the driving of the EPS motor 13 in order to reduce the burden associated with the turning operation of the steering handle 11 by the driver, that is, performs assist control to apply an appropriate assist torque.

  For this reason, the electronic control unit 28 calculates the target assist torque Ta for reducing the steering torque Ts input by the driver via the steering handle 11 and causes the EPS motor 13 to generate the calculated target assist torque Ta. . In calculating the target assist torque Ta, the electronic control unit 28 calculates the target assist torque Ta using the rotational torques T1 and T2 detected by the torque sensor 20. Specifically, the electronic control unit 28 acquires output signals corresponding to the rotational torques T1 and T2 from the torque sensor 20 (more specifically, the magnetic sensors 24A and 24B) at a predetermined sampling period. A deviation ΔT between the rotational torque T1 and the rotational torque T2 represented by the acquired output signal is calculated. For example, the electronic control unit 28 determines whether or not the calculated deviation ΔT is equal to or smaller than a predetermined value Tg that is set in advance. If the deviation ΔT is equal to or smaller than the predetermined value Tg, the electronic control unit 28 configures the torque sensor 20. It is determined that the rotational torque T1 and the rotational torque T2 that are the outputs of the two magnetic sensors 24A and 24B are normal, that is, the torque sensor 20 is normal.

  If both the rotational torque T1 and the rotational torque T2 output by the two magnetic sensors 24A and 24B constituting the torque sensor 20 by the determination process are normal, the electronic control unit 28 acquires the acquired rotational torque. The average value of one or both of T1 and rotational torque T2 is determined and adopted as the steering torque Ts acquired by the torque sensor 20. Then, the electronic control unit 28 calculates a target assist torque Ta that increases as the absolute value of the adopted steering torque Ts increases. In this case, the electronic control unit 28 calculates the target assist torque Ta corresponding to the absolute value of the steering torque Ts adopted as described above with reference to the assist torque map as shown in FIG. 4, for example. The assist torque map is set for each representative vehicle speed V. As the vehicle speed V detected by the vehicle speed sensor 27 increases, the target assist torque Ta becomes relatively small and the vehicle speed V decreases. Accordingly, the target assist torque Ta is set to be relatively large.

  When the target assist torque Ta is calculated in this way, the electronic control unit 28 determines a motor current command value representing a current to be supplied to the EPS motor 13 in a predetermined relationship with the calculated target assist torque Ta. Then, the electronic control unit 35 supplies the determined motor current command value to the drive circuit 29, and the drive circuit 29 supplies a drive current corresponding to the supplied motor current command value to the EPS motor 13. Thereby, the EPS motor 13 can transmit the target assist torque Ta to the rack bar 15, and the driver can turn the steering handle 11 while perceiving a good steering feeling.

  On the other hand, when the deviation ΔT calculated as described above exceeds the predetermined value Tg, the electronic control unit 28 abnormally detects at least one of the two magnetic sensors 24A and 24B constituting the torque sensor 20. It is determined that an abnormality has occurred in the torque sensor 20. By the way, in such a situation where an abnormality has occurred in the torque sensor 20, more specifically, in a situation where an abnormality has occurred in at least one of the magnetic sensor 24A and the magnetic sensor 24B, The steering torque Ts cannot be determined using the rotational torque T1 and the rotational torque T2, which are the outputs of the magnetic sensors 24A and 24B, unless it is specified whether an abnormality has occurred in the sensor 24. Therefore, when an abnormality occurs in the torque sensor 20, the electronic control unit 28 specifies which magnetic sensor 24 is abnormal. Hereinafter, this specification will be described in detail.

  As described above, when the magnetic sensors 24A and 24B cause a relative angular displacement in the input side shaft 12a1 and the output side shaft 12a2, the magnetic flux density corresponding to the direction and magnitude of the applied rotational torque, in other words, rotation Torques T1 and T2 can be detected, respectively, and signals corresponding to the detected rotational torques T1 and T2 can be output. Therefore, when the relative angular displacement is forcibly generated in the input side shaft 12a1 and the output side shaft 12a2, the rotational torques T1 and T2 represented by the signals output from the magnetic sensors 24A and 24B are confirmed. It is possible to identify the magnetic sensor 24 in which an abnormality has occurred.

  However, in the input side shaft 12a1 and the output side shaft 12a2, the input side shaft 12a1 is connected to the steering handle 11, and the output side shaft 12a2 is connected to the steered gear unit U. For this reason, when the relative angular displacement is forcibly generated in the input side shaft 12a1 and the output side shaft 12a2, the steering handle 11 is turned and the left and right front wheels FW1, FW2 are rotated due to the relative angular displacement. It is necessary to twist the torsion bar 21 to cause relative angular displacement so that the rudder operation does not occur or becomes extremely small even if it occurs.

  Here, when the torsional deformation of the elastic body such as the torsion bar 21 is used as described above, the rotational torque Tt applied from the EPS motor 13 is fluctuated to vibrate the elastic body in the torsional direction around the axis. The generation behavior of the relative angular displacement between the input side shaft 12a1 and the output side shaft 12a2 changes depending on the magnitude of the frequency to be applied (hereinafter, this frequency is referred to as an excitation frequency). That is, when one end portion of the elastic body is vibrated in the torsional direction with a small excitation frequency, the elastic body does not undergo torsional deformation, and the one end side and the other end side vibrate integrally and vibrate. As the frequency is increased, torsional deformation occurs on one end side and the other end side. This amount of torsional deformation tends to decrease as the excitation frequency is increased. In such a system, there is a frequency at which the input side shaft 12a1 does not vibrate (rotate) and only the output side shaft 12a2 vibrates (rotates). Hereinafter, the excitation frequency at this time is particularly referred to as “anti-resonance frequency”. When the excitation frequency is increased from this anti-resonance frequency and the excitation frequency is increased to some extent, there is a frequency at which the one end side and the other end side resonate. Hereinafter, the excitation frequency at this time is particularly referred to as “resonance frequency”.

  This will be described for the input side shaft 12a1, the torsion bar 21, and the output side shaft 12a2 using a study model as shown in FIG. In this study model, the elastic modulus (or rigidity) of the torsion bar 21 is Kt, and the rigidity (or elastic modulus) of the input side shaft 12a1 is Kc. Further, the rotational angle of the output side shaft 12a2 caused by the rotational torque Tt applied to the output side shaft 12a2 by driving the EPS motor 13 is set to θm, the rotational angle of the input side shaft 12a1 is set to θc, The rotation angle of the steering handle 11 is θw. Further, the inertia moment of the output side shaft 12a2 is Jm, the inertia moment of the input side shaft 12a1 is Jc, and the inertia moment of the steering handle 11 is Jw.

  The inventor of the present application performs various experiments on such a model to vibrate (rotate) only the anti-resonance frequency in the above model, that is, one end side of the torsion bar 21, and vibrate (rotate) the other end side. In addition to specifying the excitation frequency that does not occur, the resonance frequency in the above model, that is, the excitation frequency at which one end side and the other end side of the torsion bar 21 resonate was specified. The anti-resonance frequency and the resonance frequency in the above model are the physical properties described above, specifically, the elastic modulus Kt of the torsion bar 21, the rigidity (elastic modulus) Kc of the input side shaft 12a1, and the inertia of the output side shaft 12a2. The moment Jm, the inertia moment Jc of the input side shaft 12a1 and the inertia moment Jw of the steering handle 11 can be changed by appropriately setting. Further, the resonance frequency specified as described above may be a frequency at which resonance first occurs in the output side shaft 12a2 and the input side shaft 12a1 when the frequency is increased from the antiresonance frequency.

  By the way, when the rotational torque Tt by the EPS motor 13 is changed by the excitation frequency, that is, when the output side shaft 12a2 is vibrated in the twisting direction, the input side shaft 12a1 is also vibrated in the twisting direction. For this reason, the steering handle 11 connected to the input side shaft 12a1 also vibrates in the turning direction.

  Accordingly, when the relative angular displacement is forcibly generated in the input side shaft 12a1 and the output side shaft 12a2 in order to identify the magnetic sensor 24 in which an abnormality has occurred, the turning of the steering handle 11 and the left and right front wheels FW1, In order to prevent the steering operation of FW2 from occurring or to make it extremely small even if it occurs, the rotational torque Tt applied to the output side shaft 12a2 by the EPS motor 13 is a frequency larger than the anti-resonance frequency. And it may be varied at a frequency smaller than the resonance frequency. As a result, the torsion bar 21 connecting the input side shaft 12a1 and the output side shaft 12a2 can be appropriately twisted and deformed so that the turning of the steering handle 11 and the turning operation of the left and right front wheels FW1, FW2 do not occur. Alternatively, even if it occurs, it can be made extremely small.

  Therefore, if the electronic control unit 28 determines that an abnormality has occurred in the torque sensor 20, it first determines whether or not the vehicle is traveling in a straight traveling state. That is, the electronic control unit 28 receives the signal output from the steering angle sensor 26 to acquire the steering angle θ (corresponding to the rotation angle θw of the steering handle 11), and inputs the signal output from the vehicle speed sensor 27. To obtain the vehicle speed V. For example, if the value of the steering angle θ is approximately “0” and the value of the vehicle speed V is a positive value, it can be determined that the vehicle is traveling straight. When the electronic control unit 28 thus determines that the vehicle is traveling in a straight traveling state, the excitation frequency that is set in advance as a frequency that is higher than the anti-resonance frequency and lower than the resonance frequency. The EPS motor 13 is driven via the drive circuit 29 so that the output side shaft 12a2 vibrates in the torsional direction (hereinafter referred to as “specific excitation frequency”), and the output side shaft 12a2 has a predetermined size. The rotational torque Tt is varied and applied.

  In this manner, the EPS motor 13 varies and applies the predetermined rotational torque Tt according to the specific excitation frequency, whereby the output side shaft 12a2 vibrates in the torsional direction and is connected via the torsion bar 21. 12a1 does not vibrate. That is, a relative angular displacement is forcibly generated between the input side shaft 12a1 and the output side shaft 12a2. Thus, the two magnetic sensors 24A and 24B constituting the torque sensor 20 output signals representing the rotational torques T1 and T2 corresponding to the relative angular displacement to the electronic control unit 28, respectively.

  In the electronic control unit 28, signals output from the magnetic sensors 24A and 24B are input, and rotational torques T1 and T2 represented by these signals are acquired. Here, when the electronic control unit 28 drives the EPS motor 13 at a specific excitation frequency and applies a predetermined rotational torque Tt to the output side shaft 12a2, the torque sensor 20 (ie, the magnetic sensors 24A and 24B) outputs the torque. A determination torque Tref that can be experimentally determined as the rotational torque to be stored is stored in advance. Thus, the electronic control unit 28 compares the acquired rotational torques T1 and T2 with the determination torque Tref, and outputs the rotational torque on the side substantially equal to the determination torque Tref out of the rotational torque T1 and the rotational torque T2. The determined magnetic sensor 24 is determined to be normal. That is, the magnetic sensor 24 that outputs the rotational torque T that does not coincide with the determination torque Tref is specified as the magnetic sensor 24 in which an abnormality has occurred.

  When the abnormal magnetic sensor 24 is identified in this way, the electronic control unit 28 adopts the rotational torque T output by the normal magnetic sensor 24 as the steering torque Ts, and continues the assist control described above. . In this case, the rotational torque T output from the normal magnetic sensor 24, that is, the steering torque Ts is obtained by directly detecting the torque input to the steering shaft 12, and is extremely accurate and accurate. . For this reason, the assist control using the rotational torque T output by the normal magnetic sensor 24 is equivalent to when the torque sensor 20 is normal (that is, when the two magnetic sensors 24A and 24B are both normal). The target assist torque Ta can be calculated.

  Therefore, the electronic control unit 28 determines a motor current command value having a predetermined relationship with the calculated target assist torque Ta and supplies the motor current command value to the drive circuit 29. The drive circuit 29 corresponds to the supplied motor current command value. The driving current to be supplied can be supplied to the EPS motor 13. As a result, even if an abnormality occurs in the torque sensor 20, the EPS motor 13 can transmit an appropriate and accurate target assist torque Ta to the rack bar 15, and the driver perceives a good steering feeling. The steering handle 11 can be rotated while being operated.

  As can be understood from the above description, according to the above embodiment, when an abnormality occurs in the torque sensor 20, signals indicating the rotational torques T1 and T2 are forcibly output from the two magnetic sensors 24A and 24B. Thus, it is possible to accurately identify the magnetic sensor 24 in which an abnormality has occurred by using the output rotational torques T1 and T2 (output signals). At this time, the EPS motor 13 is driven at a specific excitation frequency that is higher than the anti-resonance frequency and lower than the resonance frequency, and the torque applied to the output side shaft 12a2 is varied to vibrate the output side shaft 12a2 in the torsional direction. As a result, the relative angular displacement is appropriately generated in the input side shaft 12a1 and the output side shaft 12a2, while the large turning of the steering handle 11 and the large turning operation of the left and right front wheels FW1, FW2 are prevented from occurring. be able to. Thus, even when the electronic control unit 28 specifies whether or not an abnormality has occurred in one of the two magnetic sensors 24A and 24B, the driver does not feel uncomfortable.

  Furthermore, the magnetic sensor 24 in which an abnormality has occurred can be specified, in other words, the magnetic sensor 24 that is operating normally can be specified, and the rotational torque T by the normal magnetic sensor 24 can be adopted as the steering torque Ts. As a result, even when an abnormality occurs in the torque sensor 20, extremely appropriate assist control equivalent to that when the torque sensor 20 is normal (that is, when the two magnetic sensors 24A and 24B are both normal). Can be continued. As a result, the burden when the driver operates the steering handle 11 can be reduced appropriately, and the driver can rotate the steering handle 11 while perceiving a good steering feeling. Very suitable.

  The implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment, when an abnormality occurs in the torque sensor 20, the electronic control unit 28 determines whether an abnormality has occurred in one of the two magnetic sensors 24A, 24B that constitute the torque sensor 20. It carried out to judge. On the other hand, regardless of whether or not an abnormality has occurred in the torque sensor 20, the electronic control unit 28 has an abnormality in one of the two magnetic sensors 24A and 24B at all times or at a predetermined time interval. It is also possible to determine whether or not it has occurred. Thereby, the operating state of the torque sensor 20 (that is, the two magnetic sensors 24A and 24B) can always be properly monitored, and appropriate assist control can always be executed.

  Moreover, in the said embodiment, it implemented so that the torque sensor 20 might be comprised from two magnetic sensors 24A and 24B as a some sensor. In this case, the number of the magnetic sensors 24 constituting the torque sensor 20 is not limited to two, and the torque sensor 20 can be implemented using three or more magnetic sensors 24. Needless to say. Even in this case, similarly to the above-described embodiment, the magnetic sensor 24 in which an abnormality has occurred can be accurately identified, and thus the same effect as in the above-described embodiment can be obtained.

  In the above-described embodiment, the so-called column assist type electric power steering apparatus is configured such that the EPS motor 13 is connected to the output side shaft 12a2 constituting the main shaft 12a1 in the electric power steering apparatus 10 so as to transmit the driving force. 10 was employed. In this case, the arrangement position of the EPS motor 13 is not limited as long as the relative angular displacement can be generated between the input side shaft 12a1 and the output side shaft 12a2. For example, the EPS motor 13 with respect to the pinion shaft 12c is not limited. The so-called pinion assist type electric power steering device 10 is used to transmit the driving force, and the EPS motor 13 can be transmitted to the rack bar 15 constituting the steered gear unit U. It is also possible to employ a so-called rack-assist type electric power steering device 10 that is connected to the vehicle. Even in these cases, since the relative angular displacement can be surely generated in the input side shaft 12a1 and the output side shaft 12a2, the same effect as the above embodiment can be obtained.

  Moreover, in the said embodiment, it implemented so that the torque sensor 20 might be comprised from two magnetic sensors 24A and 24B. In this case, if a physical quantity that changes due to fluctuations in the torque input to the steering shaft 12 is detected so that the torque sensor 20 can output the steering torque Ts, for example, an angle associated with torsion is detected. The torque sensor 20 may be composed of any plurality of sensors such as a plurality of resolver sensors. Even in this case, the normality or abnormality of the plurality of sensors constituting the torque sensor 20 can be accurately determined as in the above embodiment, and as a result, the assist control can be continued properly.

  Furthermore, in the said embodiment, it implemented by applying this apparatus to the electric power steering apparatus 10 which generates the assist torque by driving the electric motor 13 (EPS motor 13). In this case, it is needless to say that the present apparatus can be applied to a power steering apparatus that generates assist torque by a driving force other than the electric motor 13 (EPS motor 13) such as a hydraulic mechanism. Thus, even when a drive source other than the electric motor 13 (EPS motor 13) is employed, the torque sensor 20 is configured if the drive source can be driven at a specific excitation frequency. Since the magnetic sensors 24A and 24B as the two sensors can be forcibly output, the magnetic sensor 24 on the side where an abnormality has occurred can be accurately identified as in the above embodiment. Therefore, the same effect as the above embodiment can be expected.

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 11 ... Steering handle, 12 ... Steering shaft, 12a ... Main shaft, 12a1 ... Input side shaft (first shaft), 12a2 ... Output side shaft (second shaft), 12b ... Intermediate shaft , 12c ... pinion shaft, 12d, 12e ... universal shaft, 13 ... EPS motor (electric motor), 14 ... pinion gear, 15 ... rack bar, 20 ... torque sensor (torque acquisition means), 21 ... torsion bar (elastic body) , 22 ... magnets, 23A, 23B ... magnetic yokes, 24A, 24B ... magnetic sensors (multiple sensors), 25A, 25B ... magnetic flux collecting rings, 26 ... steering angle sensor, 27 ... vehicle speed sensor, 28 ... electronic control unit, 29 ... Drive circuit, C ... Electric control device (steering control device), U ... Turning A unit

Claims (6)

A steering shaft for supporting a steering handle operated by a driver; an electric motor for applying assist torque to the operation of the steering handle; and a plurality of sensors for detecting steering torque input to the steering shaft. A steering torque acquisition unit configured to calculate a target assist torque using the steering torque acquired by the steering torque acquisition unit, and drive control of the electric motor based on the calculated target assist torque A vehicle steering control device comprising:
Each of the plurality of sensors constituting the steering torque acquisition means detects the same physical quantity that changes due to a change in torque input to the steering shaft, and outputs a signal corresponding to the detected physical quantity. Is,
Sensor signal output means for driving the electric motor according to a predetermined condition to vary the torque input to the steering shaft, and outputting the signal corresponding to the physical quantity detected by each of the plurality of sensors;
When the signals are output from the plurality of sensors by the sensor signal output means, the output signals are converted into torques input to the steering shaft, respectively, and the converted torque and the predetermined condition An abnormality occurrence sensor specification that compares a determination torque set in advance as a torque input to the steering shaft when the electric motor is driven and identifies a sensor in which an abnormality has occurred among the plurality of sensors and means,
The steering shaft is at least
The first shaft connected to the steering handle, the second shaft connected to the electric motor, and the first shaft and the second shaft are axially connected to each other via an elastic body that can be torsionally deformed around the axis. It is constituted by being connected so as to be relatively rotatable around,
The elastic body has one end side depending on the magnitude of the excitation frequency that varies the torque applied from the electric motor to the second shaft to vibrate the elastic body in the torsional direction around the axis. When it is vibrated in the torsional direction at a small excitation frequency, the one end and the other end vibrate integrally without causing torsional deformation, and the one end and the other end increase as the excitation frequency increases. And the amount of torsional deformation of the torsional deformation decreases as the excitation frequency is increased.
The sensor signal output means includes
The torque input to the steering shaft is fluctuated by torsionally deforming the elastic body so that the steering handle connected to the first shaft is not displaced in the rotational direction even when the second shaft is rotated around the axis. A vehicle steering control apparatus , wherein the electric motor is driven with a predetermined condition as a condition to be performed. In the vehicle steering control device according to claim 1,
An acquired steering torque abnormality determination unit that determines whether or not the steering torque acquired by the steering torque acquisition unit is abnormal;
The sensor signal output means includes
A vehicle steering control device, wherein when the acquired steering torque abnormality determining means determines that the steering torque is abnormal, the plurality of sensors output each of the signals. In the vehicle steering control device according to claim 1 ,
The sensor signal output means includes
The second shaft when the elastic body is vibrated in the torsional direction around the axis with respect to the first shaft and the second shaft connected to each other via the elastic body. And the second shaft when the elastic body is vibrated in the torsional direction around the axis via the second shaft, and the anti-resonance frequency at which the first shaft does not vibrate. Steering a vehicle characterized in that the electric motor is driven with the condition that the torque input to the steering shaft is fluctuated by a frequency smaller than a resonance frequency at which the first shaft resonates and vibrates. Control device. In the steering control device for a vehicle according to any one of claims 1 to 3 ,
The steering torque acquisition means
Of the plurality of sensors, the steering torque is acquired using a physical quantity detected by a sensor not specified as a sensor in which an abnormality has occurred by the abnormality occurrence sensor specifying means,
The assist control means includes
The vehicle steering control apparatus, wherein the target assist torque is calculated using the steering torque acquired by the steering torque acquisition means, and the electric motor is driven and controlled based on the calculated target assist torque. . In the vehicle steering control device according to any one of claims 1 to 4 ,
Each of the plurality of sensors is
A steering control apparatus for a vehicle, wherein a magnetic flux density that changes due to a fluctuation in torque input to the steering shaft is detected as the physical quantity. In the vehicle steering control device according to claim 5 ,
The magnetic flux density is
A steering control device for a vehicle, wherein the steering control device changes due to torsion around an axis of the steering shaft due to fluctuations in torque input to the steering shaft.

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