JP2010215067A - Steering angle ratio variable device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering angle ratio variable device for a vehicle enhancing presumption accuracy of steering torque. <P>SOLUTION: A motor current Ivg flowing when drive of a steering angle ratio adjustment motor 22 is controlled by a steering angle ratio ECU 50 is detected and the steering torque is presumed from the motor current Ivg. When the steering torque is presumed, an output shaft 22a of the steering angle ratio adjustment motor 22 is slightly vibrated. Thereby, since the friction state of the steering angle ratio adjustment motor 22 always becomes dynamical friction, standing-up characteristic of the motor current Ivg at starting of rotation of the motor can be made to a linear shape. Accordingly, the steering torque can be presumed from the motor current Ivg at high accuracy. The presumed steering torque is fed to an electric power steering device 200. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering angle ratio variable device that varies a steering angle ratio by an electric motor.

  2. Description of the Related Art Conventionally, there is known a steering angle ratio variable device that uses an electric motor to change a steering angle ratio, which is a ratio of a steering angle of a steered wheel to a steering angle of a steering wheel. The steering angle ratio variable device is provided between an input steering shaft having a steering handle fixed to the upper end and an output steering shaft having a pinion gear meshing with the rack bar fixed to the lower end, and is controlled by an electric motor with respect to the rotation angle of the input steering shaft. The relative rotation angle of the output steering shaft is continuously changed. The steering angle ratio means the ratio (β / α) of the steered wheel turning angle β to the rotated angle α of the input steering shaft. The larger the steered angle ratio, the larger the steered wheel is rotated with less steering operation. The steering wheel can be steered, and the smaller the steering angle ratio, the larger the steering wheel operation is required to steer the steered wheels. Since the steering angle of the steered wheel is uniquely determined from the rotation angle of the output steering shaft, the steering angle ratio can be controlled by controlling the ratio of the rotation angle of the output steering shaft to the rotation angle of the input steering shaft. .

  In addition to the steering angle ratio variable device, there is also known a vehicle steering device that includes an electric power steering device that outputs a steering assist torque for assisting a driver to rotate the steering wheel. The electric power steering apparatus generally sets a target assist torque based on the steering torque and the vehicle speed, and controls energization of the electric motor so as to obtain the target assist torque. Therefore, if an abnormality occurs in the steering torque sensor, an appropriate target assist torque cannot be set. Therefore, for example, in the vehicle steering device proposed in Patent Document 1, when an abnormality of the steering torque sensor is detected, the steering torque is estimated based on the amount of current flowing through the electric motor of the steering angle ratio variable device.

JP2007-283891

  However, a frictional force acts on the electric motor, and the frictional force changes at the start of rotation as shown in FIG. This is because the friction state changes from static friction to dynamic friction. Therefore, when estimating the steering torque based on the amount of current flowing through the electric motor, the estimation accuracy of the steering torque is reduced because the rise of the motor current changes as shown in FIG. 11 at the start of rotation of the electric motor. .

  The present invention has been made to address the above-described problem, and an object thereof is to improve the estimation accuracy of steering torque.

In order to achieve the above object, the present invention is characterized in that an electric motor for changing a steering angle ratio, which is a ratio of a steering angle of a steered wheel to a steering angle of a steering wheel, and a target steering angle ratio can be obtained. A motor control means for driving and controlling the electric motor, a current detection means for detecting a current flowing through the electric motor, and a steering torque estimating means for estimating a steering torque based on the current flowing through the electric motor. In the steering angle ratio variable device of
The motor control means includes vibration addition means that always vibrates the rotation shaft of the electric motor in the forward and reverse rotation directions when the steering torque estimation means estimates the steering torque.

  In the present invention, the steering angle ratio is changed by controlling the drive of the electric motor so that the target steering angle ratio is obtained. The steering angle ratio is defined as a ratio (β / α) of the steering wheel turning angle β to the rotation angle α of the input steering shaft. The electric motor is provided, for example, between an input steering shaft connected to a steering handle and an output steering shaft connected to a rack bar via a pinion gear, and relative rotation between the input steering shaft and the output steering shaft is performed. Change the angle. The motor control means drives and controls the electric motor so that the relative rotation angle is maintained at an angle corresponding to the target steering angle ratio. For example, the target rudder angle ratio is set to decrease as the vehicle speed increases and to increase as the vehicle speed decreases.

  When the electric motor is driven and controlled in this way, a motor torque sufficient to resist the steering torque input to the steering shaft is generated. The amount of current flowing through the electric motor is proportional to the steering torque. Therefore, the steering torque estimating means estimates the steering torque by detecting a current flowing through the electric motor (hereinafter referred to as a motor current). The estimated steering torque can be output as steering torque information. For example, it can be used as steering torque information of an electric power steering device. The electric power steering apparatus includes a vehicle speed sensor and a steering torque sensor, sets a target assist torque based on the steering torque and the vehicle speed detected by both sensors, and sets a steering assist motor to obtain the target assist torque. Drive control. Therefore, when an abnormality occurs in the steering torque sensor of the electric power steering apparatus, the steering assist motor is supplied by supplying the steering torque estimated by the steering angle ratio variable apparatus to the electric power steering apparatus as steering torque information. The drive can be controlled appropriately. The estimated steering torque may be used not only in the electric power steering device but also in other vehicle control devices.

  When estimating the steering torque from the motor current, the current value changes due to a change in the friction state (change from static friction to dynamic friction) at the start of rotation of the electric motor. To do. Therefore, in the present invention, vibration adding means is provided in the motor control means. The vibration adding means causes the rotation shaft of the electric motor to vibrate slightly in the forward and reverse rotation directions when the steering torque estimating means estimates the steering torque. For example, a minute vibration signal component that alternately outputs a signal component that generates a small torque in the forward rotation direction and a signal component that generates a small torque in the reverse rotation direction of the electric motor is superimposed on the motor drive signal. As a result, the electric motor always vibrates slightly in the forward / reverse rotation direction.

  Therefore, the friction state of the electric motor is maintained at dynamic friction. As a result, the rising waveform of the motor current at the start of rotation of the electric motor becomes linear, and the estimation accuracy of the steering torque estimated based on the motor current is improved.

1 is a schematic system configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is a flowchart showing a steering angle ratio control routine. It is a graph showing a vehicle speed-coefficient map. It is a wave form diagram of additional voltage Vvib for vibration. It is a wave form diagram of target command voltage V *. It is a graph showing the relationship between steering torque and motor current. It is a graph showing the rising characteristic of a motor current. It is a flowchart showing a steering assist control routine. It is a graph showing an assist torque map. It is a graph showing a motor frictional force characteristic. It is a graph showing the rising characteristic of a motor current.

  A vehicle steering angle ratio variable device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a vehicle steering apparatus including a steering angle ratio variable apparatus 100 and an electric power steering apparatus 200 as an embodiment.

  A vehicle steering apparatus includes a steering handle 11 that is turned by a driver and fixed to a steering shaft 12. The steering shaft 12 includes a steering shaft 12a (hereinafter referred to as an input steering shaft 12a) for fixing the steering handle 11 to the upper end, and a steering shaft 12b (hereinafter referred to as an output steering shaft 12b) for fixing the pinion gear 13 to the lower end. The upper and lower parts are divided into two. The pinion gear 13 meshes with the rack teeth of the rack bar 14. The rack bar 14 extends in the left-right direction (vehicle width direction), and both ends of the rack bar 14 are connected to the knuckle of the left and right front wheels 15a, 15b as steering wheels via a tie rod (not shown). Accordingly, the rotation of the steering handle 11 is transmitted to the rack bar 14 via the steering shaft 12 and the pinion gear 13, and the rack bar 14 is displaced in the axial direction to steer the left and right front wheels 15a and 15b.

  A steering angle ratio, which is a ratio of the steering angles of the front wheels (steering wheels) 15a and 15b to the steering angle of the steering handle 11, is set between the input steering shaft 12a and the output steering shaft 12b of the steering shaft 12 divided in two. A steering angle ratio variable mechanism 20 to be changed is interposed. The steering angle ratio variable mechanism 20 includes a cylindrical casing 21 connected so as to rotate integrally with a lower end portion of the input steering shaft 12a. An electric motor 22 is fixed in the casing 21. An output shaft 22a of the electric motor 22 is rotatably supported by the casing 21, and is connected to the output steering shaft 12b so as to be integrally rotatable at the lower end. The electric motor 22 has a built-in speed reduction mechanism, and the rotation of the electric motor 22 is decelerated and output to the output shaft 22a. Hereinafter, the electric motor 22 is referred to as a steering angle ratio adjustment motor 22.

  The rack bar 14 is provided with a power assist mechanism 30 that outputs a steering assist torque to assist the driver in turning the steering handle. The power assist mechanism 30 includes an electric motor 31 and a ball screw mechanism 32. The rotation of the electric motor 31 is converted into an axial movement of the rack bar 14 by the ball screw mechanism 32 and transmitted to the rack bar 14, and a steering force is applied to the left and right front wheels 15a and 15b to allow the driver to perform a steering operation. Assist. Hereinafter, the electric motor 31 is referred to as an assist motor 31.

  A steering angle sensor 41 and a steering torque sensor 42 are provided in the steering mechanism. The steering angle sensor 41 is assembled to the input steering shaft 12a and detects the rotation angle from the neutral position of the steering handle 11, that is, the steering angle θin. The steering torque sensor 42 is assembled to the output steering shaft 12b and detects torque acting on the output steering shaft 12b, that is, steering torque Tr accompanying steering of the left and right front wheels 15a and 15b.

  A relative angle sensor 43 is provided in the steering angle ratio variable mechanism 20. The relative angle sensor 43 is assembled to the output shaft 22a of the steering angle ratio adjusting motor 22 and detects the rotation angle Δθv of the output steering shaft 12b with respect to the casing 21. The rotation angle of the pinion gear 13 meshing with the rack bar 14 (that is, the rotation angle of the output steering shaft 12b) is equal to the sum of the steering angle θin and the rotation angle Δθv of the output steering shaft 12b with respect to the casing 21. The rotation angle Δθv means a relative rotation angle of the output steering shaft 12b with respect to the input steering shaft 12a, and is hereinafter referred to as a relative angle Δθv. The steering angle θin, the steering torque Tr, and the relative angle Δθv represent a left angle and torque by a positive value, and a right angle and torque by a negative value.

  The steering angle ratio adjustment motor 22 of the steering angle ratio variable mechanism 20 is driven and controlled by a steering angle ratio electronic control unit 50 (hereinafter referred to as a steering angle ratio ECU 50). The steering angle ratio ECU 50 includes a microcomputer unit 51 including a microcomputer including a CPU, a ROM, a RAM, and the like as main parts, and a motor drive circuit 52. The motor drive circuit 52 is provided with a current sensor 53 that detects a current Ivg (hereinafter referred to as a motor current Ivg) flowing through the steering angle ratio adjusting motor 22. The microcomputer unit 51 connects a steering angle sensor 41, a relative angle sensor 43, a vehicle speed sensor 44 that detects a vehicle speed, and a current sensor 53 via an input interface (not shown), and a signal that represents the steering angle θin and a signal that represents the relative angle Δθv. A signal representing the vehicle speed v and a signal representing the motor current Ivg are input. Further, the motor drive circuit 52 is an H bridge circuit or an inverter circuit, and the duty ratio of the internal switching element is controlled by the PWM control signal output from the microcomputer unit 51, and the energization amount of the steering angle ratio adjustment motor 22. And adjust the direction of rotation.

  The steering angle ratio variable device 100 includes the steering angle ratio variable mechanism 20, the steering angle ratio ECU 50, and the above-described sensors (the steering angle sensor 41, the relative angle sensor 43, the vehicle speed sensor 44, and the current sensor 53). The steering angle ratio adjusted by the steering angle ratio variable device 100 means the ratio (β / α) of the turning angle β of the front wheels 15a, 15b to the rotation angle α of the input steering shaft 12a. The larger the wheel, the larger the front wheels 15a, 15b can be steered with fewer steering operations, and the smaller the steering angle ratio, the larger the steering operation required to steer the front wheels 15a, 15b. Since the turning angle δ of the front wheels 15a, 15b is uniquely determined from the rotation angle θout of the output steering shaft 12b, the ratio of the rotation angle θout of the output steering shaft 12b to the rotation angle θin of the input steering shaft 12a (θout / θin) By controlling the steering angle ratio, the steering angle ratio can be controlled. The rotation angle θout of the output steering shaft 12b is equal to the sum of the steering angle θin and the relative angle Δθv. Therefore, the steering angle ratio can be controlled to the target value by the rotation angle control of the steering angle ratio adjustment motor 22 by the steering angle ratio ECU 50.

  Next, a configuration for controlling the assist motor 31 of the power assist mechanism 30 will be described. The assist motor 31 of the power assist mechanism 30 is driven and controlled by a steering assist electronic control unit 60 (hereinafter referred to as a steering assist ECU 60). The steering assist ECU 60 includes a microcomputer unit 61 including a microcomputer including a CPU, a ROM, a RAM, and the like as main parts, and a motor drive circuit 62. The motor drive circuit 62 is provided with a current sensor 63 that detects a current Ias flowing through the assist motor 31 (hereinafter referred to as a motor current Ias). The microcomputer unit 61 connects the steering angle sensor 41, the steering torque sensor 42, the vehicle speed sensor 44, and the current sensor 63 via an input interface (not shown), and obtains a signal indicating the steering angle θin, a signal indicating the steering torque Tr, and the vehicle speed v. A signal indicating the motor current Ias is input. The motor drive circuit 62 is an H bridge circuit or an inverter circuit, and the duty ratio of the internal switching element is controlled by the PWM control signal output from the microcomputer unit 61 to adjust the energization amount and the rotation direction of the assist motor 31. To do.

  The electric power steering apparatus 200 includes the power assist mechanism 30, the steering assist ECU 60, and the above-described sensors (the steering angle sensor 41, the steering torque sensor 42, the vehicle speed sensor 44, and the current sensor 63). The electric power steering device 200 and the steering angle ratio variable device 100 are communicably connected between the microcomputer units 51 and 61 via a communication interface (not shown).

  In the electric power steering apparatus 200, the target assist torque is set based on the steering torque Tr detected by the steering torque sensor 42 and the vehicle speed v detected by the vehicle speed sensor 44 as described later. The steering torque Tr cannot be detected when there is an abnormality. On the other hand, in the steering angle ratio variable device 100, it is not necessary to detect the steering torque when performing the steering angle ratio control, but the steering torque can be estimated from the current value flowing through the steering angle ratio adjustment motor 22. Therefore, in the present embodiment, the steering torque ratio variable device 100 calculates the steering torque by estimation, and when the abnormality of the steering torque sensor 42 (hereinafter referred to as torque sensor failure) occurs, the electric power steering device 200 Information on the estimated value of steering torque (referred to as estimated steering torque) can be supplied.

  Next, the steering angle ratio control process performed by the steering angle ratio variable device 100 will be described. FIG. 2 shows a steering angle ratio control routine performed by the microcomputer unit 51. This steering angle ratio control routine is stored as a control program in the ROM of the microcomputer unit 51. The routine is started when a predetermined initial diagnosis is completed by turning on an ignition switch (not shown), and is repeatedly executed in a short cycle.

When the steering angle ratio control routine is started, the microcomputer unit 51 detects the vehicle speed v detected by the vehicle speed sensor 44, the steering angle θin detected by the steering angle sensor 41, and the relative angle sensor 43 in step S11. The relative angle Δθv is read. Subsequently, in step S12, the microcomputer unit 51 calculates the target relative angle Δθv * by executing the following expression. The coefficient Kc in the following formula is a predetermined constant. The coefficient Kv is determined by referring to a vehicle speed-coefficient map (see FIG. 3) provided in the ROM of the microcomputer unit 51, and from a predetermined value larger than “1.0” to “1.0” as the vehicle speed v increases. The value gradually decreases to "".
Δθv * = Kc · (Kv−1) · θin

  Subsequently, in step S13, the microcomputer unit 51 calculates a deviation (Δθv * −Δθv) between the calculated target relative angle Δθv * and the actual relative angle Δθv input from the relative angle sensor 43, and the deviation (Δθv * The basic target voltage V0 * corresponding to −Δθv) is calculated. Subsequently, in step S14, a value obtained by adding the vibration additional voltage Vvib to the basic target voltage V0 * is calculated as a target command voltage V * (= V0 * + Vvib).

  The vibration additional voltage Vvib is a voltage that gives a vibration torque component for causing the output shaft 22a of the steering angle ratio adjusting motor 22 to vibrate slightly in the forward and reverse rotation directions (turning slightly in the forward and reverse rotation directions alternately). It is. Therefore, the vibration additional voltage Vvib is alternately switched between a positive value and a negative value at a predetermined fast cycle, as shown in FIG. Accordingly, the target command voltage V * obtained by adding the vibration additional voltage Vvib to the basic target voltage V0 * changes in a vibration manner as shown in FIG. The vibration additional voltage Vvib adopts an arbitrary configuration as long as it is a signal to which a vibration torque component can be applied, such as a configuration that alternately switches between a positive value and zero or a configuration that switches alternately between a negative value and zero. can do.

  Subsequently, the microcomputer unit 51 outputs a PWM control signal corresponding to the target command voltage V * to the motor drive circuit 52 in step S15. In this case, a pulse train signal having a duty ratio corresponding to the target command voltage V * is output as a PWM control signal. As a result, the steering angle ratio adjusting motor 22 is feedback-controlled so that the output steering shaft 12b is at a rotational position rotated by the target relative angle Δθv * with respect to the input steering shaft 12a. Thus, the turning angle δ of the front wheels 15a and 15b is controlled to be equal to the angle set in the steering angle ratio characteristic.

  Subsequently, in step S16, the microcomputer unit 51 reads the motor current Ivg detected by the current sensor 53, and in subsequent step S17, estimates the steering torque acting on the output steering shaft 12b from the motor current Ivg. Hereinafter, this estimated steering torque is referred to as estimated torque Trs. As shown in FIG. 6, the steering torque and the motor current flowing through the steering angle ratio adjusting motor 22 can be regarded as having a proportional relationship. Therefore, the estimated torque Trs can be calculated by multiplying the motor current Ivg detected by the current sensor 53 by the torque constant. Since the steering angle ratio adjusting motor 22 is driven by a target command voltage V * obtained by adding the vibration additional voltage Vvib to the basic target voltage V0 *, the motor current Ivg includes a vibration component. The estimated torque Trs may be calculated after the vibration component is removed from the detected value by low-pass filter processing.

  Subsequently, in step S <b> 18, the microcomputer unit 51 outputs information representing the estimated torque Trs to the microcomputer unit 61 of the electric power steering device 200. When the process of step S18 is performed, the steering angle ratio control routine is once ended. The steering angle ratio control routine is repeated at a short cycle until an ignition switch (not shown) is turned off.

  According to this steering angle ratio control routine, the target relative angle Δθv * corresponding to the vehicle speed v is repeatedly calculated according to the vehicle speed-coefficient map, and the steering angle ratio is set so that the actual relative angle Δθv becomes equal to the target relative angle Δθv *. The adjustment motor 22 is driven and controlled. Accordingly, the lower the vehicle speed v, the larger the left and right front wheels 15a and 15b are steered with respect to the rotation of the steering handle 11. That is, as the vehicle speed v decreases, the steering angle ratio increases, and the turning performance of the vehicle during low-speed traveling improves. Further, the running stability of the vehicle during high speed running is improved.

  Further, when the steering angle ratio adjustment motor 22 is driven and controlled by the steering angle ratio control, the motor current (current value) Ivg flowing through the steering angle ratio adjustment motor 22 is detected, and the steering torque is detected from the detected motor current Ivg. Is estimated. Then, the estimated estimated torque Trs is output to the microcomputer unit 61 of the electric power steering device 200. Therefore, the electric power steering apparatus 200 can appropriately perform steering assist control using the estimated torque Trs even when a torque sensor failure occurs.

  In addition, when estimating the steering torque, the output shaft 22a of the steering angle ratio adjusting motor 22 is always slightly vibrated in the forward and reverse rotation directions, so there is no state where the output shaft 22a is stopped, and the steering angle ratio adjusting motor. The frictional state 22 is dynamic friction. For this reason, as shown in FIG. 7, the rising waveform of the motor current is linear. As a result, the estimated torque Trs estimated from the motor current Ivg can be accurately calculated.

  In calculating the estimated torque Trs, the direction of the torque is easily determined based on the sign (positive or negative) of the steering angular velocity, which is the change amount (differential value) of the steering angle θin detected by the steering angle sensor 41. can do. Further, the direction of the torque may be determined using the sign (positive or negative) of the rotational angular velocity that is the change amount (differential value) of the rotational angle of the rudder angle ratio adjusting motor 22.

  Next, a steering assist control process performed by the electric power steering apparatus 200 will be described. FIG. 8 shows a steering assist control routine performed by the microcomputer unit 61. This assist control routine is stored as a control program in the ROM of the microcomputer unit 61, is activated when an ignition switch (not shown) is turned on and a predetermined initial diagnosis is completed, and is repeatedly executed in a short cycle.

  When the steering assist control routine is activated, the microcomputer unit 61 first determines in step S21 whether or not a torque sensor failure has occurred. The torque sensor failure refers to an abnormal state in which the steering torque cannot be normally detected, such as an abnormality in the transmission path of the sensor signal as well as an abnormality in the steering torque sensor 42 itself. The occurrence of the torque sensor failure is, for example, by detecting a state where the detected value of the steering torque sensor 42 is out of the normal range, a state where the output signal of the steering torque sensor 42 does not change with respect to the change of the steering angle θin, Can be determined. The microcomputer unit 61 detects a torque sensor failure by executing a sensor failure monitoring routine (not shown), and reads the determination result in the sensor failure monitoring routine in step S21.

  If the torque sensor failure has not occurred (S21: No), the microcomputer unit 61 reads the steering torque Tr detected by the steering torque sensor 42 in step S22. On the other hand, when a torque sensor failure has occurred (S21: Yes), in step S23, the estimated torque Trs output by the microcomputer unit 51 of the steering angle ratio variable device 100 is read, and in the subsequent step S24, the estimated torque Trs is read. Is replaced with steering torque Tr (Tr ← Trs). That is, the estimated torque Trs is regarded as the steering torque Tr.

  Subsequently, the microcomputer unit 61 reads the vehicle speed v detected by the vehicle speed sensor 44 and the assist current Ias detected by the current sensor 63 in step S25.

  Subsequently, in step S26, a target assist torque Tr * set according to the input vehicle speed v and steering torque Tr is calculated with reference to the assist torque map shown in FIG. The assist torque map is stored in the ROM of the microcomputer unit 61, and sets a target assist torque Tr * that increases as the steering torque Tr increases. In this case, the target assist torque Tr * is set so as to increase as the vehicle speed v decreases. Regarding the calculation of the target assist torque Tr *, for example, the steering angle θin is read from the steering angle sensor 41, the return force to the neutral position of the steering shaft 12 that increases in proportion to the steering angle θin, and the steering handle 11 A return torque corresponding to the resistance force opposed to the rotation of the steering shaft 12 that increases in proportion to the steering angular velocity may be calculated and added to the target assist torque Tr * as a compensation torque.

  Subsequently, in step S27, the microcomputer unit 61 calculates a target current Ias * necessary for generating the target assist torque Tr *. The target current Ias * is obtained by dividing the target assist torque Tr * by the torque constant.

Next, in step S28, the microcomputer unit 61 calculates a deviation ΔIas between the target current Ias * and the actual current Ias, and calculates a target command voltage Vas * based on the deviation ΔIas. The actual current Ias used for the calculation in step S28 is the assist current Ias detected by the current sensor 63.
The target command voltage Vas * is calculated by, for example, the following PI control (proportional integral control) equation.
Vas * = Kp · ΔIas + Ki · ∫ΔIas dt
Here, Kp is the control gain of the proportional term in PI control, and Ki is the control gain of the integral term in PI control.

  Next, the microcomputer unit 61 outputs a PWM control signal corresponding to the target command voltage Vas * to the motor drive circuit 62 in step S29. In this case, a pulse train signal having a duty ratio corresponding to the target command voltage Vas * is output as a PWM control signal. Thus, the target motor Ias * in a direction rotating in the same direction as the driver's steering direction flows through the assist motor 31 by current feedback control. As a result, the assist motor 31 outputs a torque equal to the target assist torque Tr * to assist the driver's steering operation.

  When the process of step S29 is performed, the steering assist control routine is once ended. The steering assist control routine is repeated at a short cycle until an ignition switch (not shown) is turned off.

  According to this assist control routine, even if a torque sensor failure occurs, the target assist torque Tr * is set using the estimated torque Trs provided by the steering angle ratio variable device 100, so that an appropriate Steering assist can be performed.

  As mentioned above, although the steering apparatus of the vehicle as embodiment of this invention was demonstrated, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention.

  For example, in this embodiment, information representing the estimated torque Trs estimated by the steering angle ratio variable device 100 is supplied to the electric power steering device 200, but is supplied to other vehicle control systems. Also good. Further, the steering angle ratio control routine shown in FIG. 2 is executed only when the occurrence of torque sensor failure is detected, and when the occurrence of torque sensor failure is not detected, the normal steering angle ratio control routine is executed. Should be executed. For example, a receiving unit that receives a torque sensor fail signal from the electric power steering device 200 is provided on the steering angle ratio variable device 100 side, and only when the torque sensor fail signal is input to the receiving unit, the above-described FIG. A steering angle ratio control routine is executed. On the other hand, when the torque sensor fail signal is not input, it is preferable to execute processing excluding the processing (S14, S16 to S17) for estimating the steering torque. The steering torque sensor 42 may not be provided in the steering mechanism. In this case, the estimated torque Trs is always supplied from the steering angle ratio variable device 100 to the electric power steering device 200.

  DESCRIPTION OF SYMBOLS 11 ... Steering handle, 12 ... Steering shaft, 12a ... Input steering shaft, 12b ... Output steering shaft, 13 ... Pinion gear, 14 ... Rack bar, 15a, 15b ... Front wheel (steering wheel), 20 ... Steering angle ratio variable mechanism, 21 ... casing, 22 ... rudder angle ratio adjusting motor, 22a ... output shaft, 30 ... power assist mechanism, 31 ... assist motor, 41 ... steering angle sensor, 42 ... steering torque sensor, 43 ... relative angle sensor, 44 ... vehicle speed sensor, DESCRIPTION OF SYMBOLS 50 ... Steering angle ratio electronic control unit, 51 ... Microcomputer part, 52 ... Motor drive circuit, 53 ... Current sensor, 60 ... Steering assist electronic control unit, 61 ... Microcomputer part, 62 ... Motor drive circuit, 63 ... Current sensor, 100 ... rudder angle ratio variable device, 200 ... electric power steering device.

Claims (1)

An electric motor for changing a steering angle ratio, which is a ratio of a steering angle of a steered wheel to a steering angle of a steering wheel;
Motor control means for driving and controlling the electric motor so as to obtain a target steering angle ratio;
Current detecting means for detecting a current flowing through the electric motor;
In a steering angle ratio variable device for a vehicle, comprising: a steering torque estimating means for estimating a steering torque based on a current flowing through the electric motor;
The motor control means includes a vibration adding means that always vibrates the rotation shaft of the electric motor in the forward and reverse rotation directions when the steering torque estimation means estimates the steering torque. Angle ratio variable device.

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