JP2004058743A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively deal with even a failure of a mechanical lock in a steering device for vehicle which interposes a transmission ratio variable unit driven by a motor varying the transmission ratio in the middle of a steering transmission system connecting the steering wheel shaft of the steering wheel and the wheel steering shaft, and locks the transmission ratio variable function with the mechanical locking device at an abnormal time. <P>SOLUTION: A lock current which generates electromagnetic holding force holding the output shaft of the motor in a nonrotatable state, is carried and the motor is electrically locked. The electric locking device which stops the transmission ratio variable function of the transmission ratio variable unit by directly connecting the wheel shaft and the wheel steering shaft at transmission ratio of 1 to 1, is provided along with a mechanical lock device. When the mechanical lock actuates normally, the electrical lock does not actuate, and when the mechanical lock does not actuate normally, the electrical lock is actuated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steering device for a vehicle such as an automobile.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a steering device for a vehicle, particularly a steering device for an automobile, as one of further enhancements in functionality, an operation angle (steering wheel operation angle) of a steering wheel and a wheel steering angle are not fixed at a 1: 1 ratio. A vehicle equipped with a so-called variable steering angle conversion ratio mechanism has been developed in which a conversion ratio (steering angle conversion ratio) of a steering wheel operating angle to a wheel steering angle is variable according to a driving state of a vehicle.
[0003]
As the driving state of the vehicle, for example, a vehicle speed (vehicle speed) can be exemplified. In high-speed driving, the steering angle conversion ratio is reduced so that the steering angle does not increase rapidly with an increase in the steering wheel operation angle. Then, high-speed running can be stabilized. On the other hand, when driving at low speeds, conversely, by increasing the steering angle conversion ratio, it is possible to reduce the number of rotations of the steering wheel required to turn the steering wheel to the full, and to increase the steering angle such as garage parking, parallel parking, or width shifting. The driving operation can be performed very easily.
[0004]
As a mechanism for varying the steering angle conversion ratio (transmission ratio), for example, as disclosed in Japanese Patent Application Laid-Open No. H11-334604, a steering wheel shaft and a wheel steering shaft are connected by a gear-type transmission unit having a variable gear ratio. However, this configuration has a disadvantage that the gear ratio changing mechanism of the gear transmission unit is complicated. Therefore, a type in which the handle shaft and the wheel steering shaft are separated and the wheel steering shaft is rotationally driven by an actuator such as a motor has been proposed in, for example, Japanese Patent Application Laid-Open No. H11-334628. Specifically, based on a steering wheel operation angle detected by the angle detection unit and a steering angle conversion ratio determined according to the vehicle driving state, a finally required wheel steering angle is calculated by computer processing, and the calculated angle is calculated. The wheel steering shaft mechanically separated from the handle shaft is rotationally driven by an actuator (motor) so that the obtained wheel steering angle is obtained.
[0005]
[Problems to be solved by the invention]
In the above-described transmission ratio variable unit, when energization of the motor serving as the main body of the actuator is not performed normally due to, for example, a failure of the CPU (or a failure of the motor), a predetermined transmission ratio control is executed. In this case, the steering shaft and the wheel steering shaft are fixed so as to be mechanically directly connected at a transmission ratio of 1: 1 and the variable transmission ratio function of the variable transmission ratio unit is stopped (ineffective). One that has a mechanical lock device has been proposed.
However, the possibility of failure of the mechanical lock device cannot be said to be zero, and in that sense, it can be said that adding a further safety system is meaningful.
An object of the present invention is to provide a vehicle steering system including a variable transmission ratio unit that can effectively cope with a failure of a mechanical lock device.
[0006]
Means for Solving the Problems and Effects of the Invention
The present invention interposes a transmission ratio variable unit driven by a motor that varies a transmission ratio in the middle of a steering transmission system that connects a handle shaft of a steering wheel and a wheel steering shaft, and the transmission ratio is a predetermined element. In the vehicle steering device that controls according to
A mechanical lock device for fixing the handle shaft and the wheel steering shaft so as to be mechanically directly connected at a transmission ratio of 1: 1 to stop a variable transmission ratio function of the variable transmission ratio unit;
The motor is electrically locked by applying a lock current for generating an electromagnetic holding force for holding a motor output shaft in a non-rotatable state to an electromagnetic force generating unit of the motor that drives the variable transmission ratio unit, thereby electrically locking the motor, An electric lock device for directly connecting a shaft and a wheel steering shaft at a transmission ratio of 1: 1 to stop a variable transmission ratio function of the variable transmission ratio unit;
Preferably, when the mechanical lock device is operating normally, the electric lock device is not operated, and when the mechanical lock device is not operating properly, the electric lock device is operated.
[0007]
If the electric lock device is used in this way, even if a situation occurs where the mechanical lock device does not operate normally, the electric lock device is operated instead, and the transmission ratio between the handle shaft and the wheel steering shaft is 1: 1. The transmission ratio variable function of the transmission ratio variable unit can be stopped directly. Therefore, the reliability with respect to the abnormality of the transmission ratio variable unit is improved. The electric lock device electrically locks the motor by an electromagnetic holding force based on applying a lock current for holding the motor output shaft in a non-rotatable state to an electromagnetic force generating portion of the motor originally required as an actuator. Therefore, the motor can be used also as the lock device by changing the method of supplying electricity to the motor, and there is an advantage that the structure is not complicated since a dedicated electric lock device is not required.
It should be noted that not only the position of the electric lock device that is temporarily activated when the mechanical lock device fails, but also that the mechanical lock device is omitted and that the transmission ratio variable function is stopped when the transmission ratio variable unit fails, etc. An electric lock device can also be used.
[0008]
When operating the electric lock device, if the lock current is kept flowing for a long time, the motor may be overheated.Therefore, make the lock current flow only when necessary (under specific conditions). Alternatively, it is possible to change the lock current in accordance with the steering situation or the like, and to reduce the lock current when a small lock current is sufficient. Alternatively, the lock current value can be increased when the required electromagnetic holding force is large, for example, when the steering is turned large or suddenly.
[0009]
In order to prevent the motor from overheating during the operation of the electric lock, or to secure a sufficient lock function according to the situation, for example, when the steering wheel angle, which is the rotation operation angle of the steering wheel, is under a specific condition, or When the relationship between the steering wheel angle and the steering angle, which is the rotation angle of the wheel steering shaft that steers the steered wheels, is under specific conditions, the supply of the lock current to the motor is stopped and the electric lock is temporarily stopped. The electromagnetic holding force can be temporarily reduced or increased by releasing the lock or changing the lock current value to be supplied to the motor.
[0010]
Particularly, for example, the following control is effective for preventing overheating of the motor due to the electric lock operation. Specifically, when the steering wheel angle, which is the rotational operation angle of the steering wheel, is at or near the neutral position, the supply of the lock current to the motor is stopped to temporarily release the electric lock, or The value of the lock current supplied to the motor is lowered to temporarily reduce the electromagnetic holding force. When the steering wheel angle is near neutral, the vehicle is traveling almost straight and little steering torque is applied.Therefore, it is safe to release the electric lock, or a small electromagnetic holding force is sufficient. Is cut off or reduced to suppress overheating of the motor.
[0011]
Alternatively, when the angle difference between the steering wheel angle and the steering angle is equal to or smaller than a predetermined value, the lock current that is supplied to the motor is stopped to temporarily release the electrical lock, or the lock that is supplied to the motor is released. The current value is lowered to temporarily reduce the electromagnetic holding force. When the difference between the steering wheel angle and the steering angle is small, it means that a large (or strong) steering wheel operation is not being performed. In this case as well, when the vehicle is going straight, the electric lock is released or the lock current value is reduced. Is effective in preventing overheating of the motor. In addition, it is not a simple angle difference between the steering wheel angle and the steering angle, but an increasing (or decreasing) rate of the angle difference, in other words, an increasing or decreasing rate of the angle difference (an increasing rate based on positive or negative: it can be said that the difference is an angle difference differential). Value, etc.), it is also possible to perform control of stopping the supply of the lock current and reducing the current value. That is, it can be said that the control is based on or related to the angle difference between the steering wheel angle and the steering angle. The same applies to the case where the steering wheel angle is viewed alone, based not only on the value of the steering wheel angle with respect to the neutral position, but also on the increase or decrease rate (positive / negative increasing rate) of the steering wheel angle. In addition, it is possible to stop or reduce the supply of the lock current. For example, if the increasing rate of the steering wheel angle or the increasing rate of the angle difference between the steering wheel angle and the steering angle is negative (decreasing tendency), it can be estimated that the steering wheel operation is nearing the end, and the lock current is turned off or reduced. Thus, the load on the motor can be reduced. Conversely, if the rate of increase is positive (increase tendency), it can be estimated that the steering operation is performed more continuously, and the lock current is not turned off (lock operation). It is also possible to perform control or increase the lock current to obtain a stronger lock function.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an example of the overall configuration of a vehicle steering control system to which the present invention is applied. (In the present embodiment, “vehicle” is an automobile, but the present invention is not applied. The target is not limited to this.) The vehicle steering control system 1 has a configuration in which a handle shaft 3 directly connected to a steering handle 2 and a wheel steering shaft 8 are mechanically separated. The wheel steering shaft 8 is driven to rotate by a motor 6 as an actuator. The tip of the wheel steering shaft 8 extends into the steering gear box 9, and the pinion 10, which rotates together with the wheel steering shaft 8, reciprocates the rack bar 11 in the axial direction, thereby changing the steering angle of the wheels 13, 13. . In the vehicle steering control system 1 of the present embodiment, a power steering system in which the reciprocating motion of the rack bar 11 is assisted by a well-known hydraulic, electric or electro-hydraulic power assist mechanism 12 is employed. I have.
[0013]
The angle position φ of the handle shaft 3 is detected by a handle shaft angle detection unit 101 including a known angle detection unit such as a rotary encoder. On the other hand, the angular position θ of the wheel steering shaft 8 is detected by a steering shaft angle detection unit 103 also including an angle detection unit such as a rotary encoder. In the present embodiment, a vehicle speed detection unit (vehicle speed sensor) 102 that detects a vehicle speed V is provided as a driving state detection unit that detects the driving state of the vehicle. The vehicle speed detection unit 102 includes, for example, a rotation detection unit (for example, a rotary encoder or a tachogenerator) that detects the rotation of the wheel 13. Then, the steering control unit 100 determines the target angular position θ ′ of the wheel steering shaft 8 based on the detected angular position φ of the handle shaft 3 and the vehicle speed V, and the angular position θ of the wheel steering shaft 8 is determined. The operation of the motor 6 is controlled so as to approach the target angular position θ ′.
[0014]
A lock mechanism 19 is provided between the handle shaft 3 and the wheel steering shaft 8 so that the lock mechanism 19 can be switched between a locked state in which the two are integrally rotatably locked and an unlocked state in which the lock connection is released. Have been. In the locked state, the rotation angle of the handle shaft 3 is transmitted to the wheel steering shaft 8 without being converted (that is, the steering angle conversion ratio is 1: 1), and manual steering becomes possible. The switching of the lock mechanism 19 to the locked state is performed by a command from the steering control unit 100 when an abnormality occurs.
[0015]
FIG. 2 shows a configuration example of a drive unit unit of the wheel steering shaft 8 by the motor 6 in a state of being attached to an automobile. In the drive unit 14, when the handle shaft 3 is rotated by operating the handle 2 (FIG. 1), the motor case 33 rotates integrally with the motor 6 mounted inside the handle. In the present embodiment, the handle shaft 3 is connected to the input shaft 20 via a universal joint 319, and the input shaft 20 is connected to the first coupling member 22 via bolts 21, 21. The pin 31 is integrated with the first coupling member 22. On the other hand, the pin 31 is fitted and engaged in a sleeve 32a extending rearward from the center of one plate surface of the second coupling member 32. On the other hand, the cylindrical motor case 33 is integrated with the other plate surface side of the second coupling member 32. Reference numeral 44 denotes a cover made of rubber or resin, which rotates integrally with the handle shaft 3. Reference numeral 46 denotes a case for housing the drive unit 14 integrated with the cockpit panel 48, and reference numeral 45 denotes a seal ring for sealing between the cover 44 and the case 46.
[0016]
The stator portion 23 of the motor 6 including the coils 35 is integrally assembled inside the motor case 33. A motor output shaft 36 is rotatably mounted inside the stator portion 23 via a bearing 41. An armature 34 made of a permanent magnet is integrated with the outer peripheral surface of the motor output shaft 36, and coils 35, 35 are arranged so as to sandwich the armature 34. A power supply terminal 50 is taken out of the coils 35, 35 so as to be continuous with the rear end surface of the motor case 33, and power is supplied to the coils 35, 35 by the power supply cable 42 at the power supply terminal 50.
[0017]
As described later, in the present embodiment, the motor 6 is a brushless motor, and the power supply cable 42 is configured as a band-shaped collective cable in which elementary wires that individually supply power to the coils 35 of each phase of the brushless motor are assembled. ing. A cable case 43 having a hub 43a is provided adjacent to the rear end of the motor case 33, and the power supply cable 42 is housed therein in a form wound around the hub 43a in a spiral manner. . The end of the power supply cable 42 opposite to the end connected to the power supply terminal 50 is fixed to the hub 43 a of the cable case 43. When the handle shaft 3 rotates in the forward or reverse direction together with the motor case 33 and the power supply terminal 50, the power supply cable 42 in the cable case 43 winds or extends around the hub 43a, thereby causing the motor case 33 to rotate. Plays a role in absorbing the rotation of
[0018]
The rotation of the motor output shaft 36 is transmitted to the wheel steering shaft 8 after being reduced at a predetermined ratio (for example, 1/50) via the reduction mechanism 7. In this embodiment, the speed reduction mechanism 7 is constituted by a harmonic drive speed reducer. That is, an elliptical bearing 37 with an inner race is integrated with the motor output shaft 36, and a deformable thin external gear 38 is fitted on the outside thereof. Outside the external gear 38, internal gears 39 and 139 in which the wheel steering shaft 8 is integrated via a coupling 40 are engaged. The internal gears 39 and 139 include an internal gear (hereinafter, also referred to as a first internal gear) 39 and an internal gear (hereinafter, also referred to as a second internal gear) 139 arranged coaxially. The second internal gear 139 is fixed to the motor case 33 and rotates integrally with the motor case 33, while the second internal gear 139 is not fixed to the motor case 33 and is rotatable relative to the motor case 33. The first internal gear 39 has no difference in the number of teeth from the external gear 38 meshing with the first internal gear 39, and does not cause relative rotation with the external gear 38 (that is, the first internal gear 39 has a first rotation with respect to the rotating motor output shaft 36). It can also be said that the internal gear 39 and thus the motor case 33 and the handle shaft 3 are freely rotatably connected. On the other hand, when the number of teeth of the second internal gear 139 is larger than that of the external gear 38 (for example, 2), the number of teeth of the internal gear 139 is N, and the difference between the number of teeth of the external gear 38 and the internal gear 139 is n, the motor output is The rotation of the shaft 36 is transmitted to the wheel steering shaft 8 in a form reduced to n / N. In the present embodiment, the input shaft 20, the motor output shaft 36, and the wheel steering shaft 8 of the handle shaft 3 are coaxially arranged on the internal gears 39, 139 in order to reduce the size.
[0019]
Next, the lock mechanism 19 includes a lock member 51 fixed to a lock base portion (the motor case 33 in the present embodiment) that cannot rotate relative to the handle shaft 3 and a lock receiving base portion (in the present embodiment). Has a lock receiving member 52 provided on the motor output shaft 36 side). As shown in FIG. 3, the lock member 51 can move forward and backward between a lock position engaged with a lock receiving portion 53 formed on the lock receiving member 52 and an unlock position retracted from the lock receiving portion 53. Is provided. In the present embodiment, a plurality of lock receiving portions 53 are formed at predetermined intervals in a circumferential direction of a lock receiving member 52 that rotates integrally with the wheel steering shaft 8, and a lock portion 51 a provided at the tip of the lock member 51 is provided. In accordance with the rotation angle phase of the wheel steering shaft 8, any one of the plurality of lock receiving portions 53 is selectively engaged. The handle shaft 3 is non-rotatably connected to the motor case 33 (in this embodiment, by the coupling 22 and the pin). When the lock member 51 and the lock receiving member 52 are disengaged (unlocked state), the motor output shaft 36 rotates with respect to the motor case 33, and the rotation is transmitted via the external gear 38 to the first internal gear 39 and The power is transmitted to the second internal gear 139, respectively. The first internal gear 39 fixed to the motor case 33 does not rotate relative to the external gear 38 as described above, and consequently rotates at the same speed as the handle shaft 3 (that is, rotates following the handle operation). Do). Further, the second internal gear 139 transmits the rotation of the motor output shaft 36 to the wheel steering shaft 8 at a reduced speed, and performs the rotation driving of the wheel steering shaft 8. On the other hand, when the lock member 51 and the lock receiving member 52 are engaged and locked, the motor output shaft 36 cannot rotate relative to the motor case 33. Since the first internal gear 39 among the internal gears 39 and 139 of the reduction mechanism 7 is fixed to the motor case 33, the handle shaft is arranged in the order of the first internal gear 39, the external gear 38 and the second internal gear 139. 3 is transmitted directly to the wheel steering shaft 8.
[0020]
In the present embodiment, the lock receiving member 52 is attached to the outer peripheral surface of one end of the motor output shaft 36, and each lock receiving portion 53 is formed in a concave shape cut in the radial direction from the outer peripheral surface of the lock receiving member 52. Have been. As shown in FIG. 2, the lock member 51 is attached to a rotation base 300 provided in the motor case 33 so as to be rotatable around an axis substantially parallel to the wheel steering shaft 8, and has a rear end 55 a coupled thereto. Have been. Further, an elastic member 54 is provided for elastically returning the lock member 51 to the original position when the bias of the solenoid 55 is released. By the operation of urging and releasing the urging of the solenoid 55, the lock formed at the distal end of the lock member 51 via the convex portion 55a provided at the distal end of the solenoid 55a and the groove formed at one end 51b of the lock member 51. The portion 51a approaches / separates from the lock receiving member 52 for the lock / unlock described above. That is, in this example, a mechanical lock device is configured including the lock member 51, the lock receiving portion 53, and the elastic member 54 (hereinafter, this is also abbreviated as a mechanical lock or the like).
[0021]
FIG. 4 is a block diagram illustrating an example of an electrical configuration of the steering control unit 100. The main components of the steering control unit 100 are two microcomputers 110 and 120. The main microcomputer 110 has a main CPU 111, a ROM 112 storing a control program, a main CPU-side RAM 113 serving as a work area for the CPU 111, and an input / output interface 114. The sub microcomputer 120 has a sub CPU 121, a ROM 122 storing a control program, a sub CPU RAM 123 serving as a work area of the sub CPU 121, and an input / output interface 124. It is the main microcomputer 110 that directly controls the operation of the motor 6 (actuator) that drives the wheel steering shaft 8, and the sub-microcomputer 120 performs data processing required for operation control of the motor 6, such as calculation of necessary parameters. In parallel with 110, the result of the data processing is communicated with the main microcomputer 110 to monitor and confirm whether the operation of the main microcomputer 110 is normal and to supplement the information as necessary. It performs the function of an auxiliary control unit. In the present embodiment, data communication between the main microcomputer 110 and the sub-microcomputer 120 is performed by communication between the input / output interfaces 114 and 124. Note that the microcomputers 110 and 120 receive the power supply voltage Vcc (for example, +5 V) from a stabilizing power supply (not shown) even after the operation of the vehicle is completed (that is, after the ignition is turned off), and the RAMs 113 and 123 or the EEPROM (described later). ) 115 is stored.
[0022]
Outputs of the handle shaft angle detection unit 101, the vehicle speed detection unit 102, and the steering shaft angle detection unit 103 are distributed and input to input / output interfaces 114 and 124 of the main microcomputer 110 and the sub microcomputer 120, respectively. In this embodiment, each of the detection units is constituted by a rotary encoder, and the count signal from the encoder is directly input to the digital data ports of the input / output interfaces 114 and 124 via a Schmitt trigger unit (not shown). A solenoid 55, which is a driving unit of the lock mechanism 19, is connected to the input / output interface 114 of the main microcomputer 110 via a solenoid driver 56.
[0023]
The motor 6 is constituted by a brushless motor, in this embodiment a three-phase brushless motor. As shown in FIG. 5, the coils 35, 35 shown in FIG. 2 are composed of three-phase coils U, V, W arranged at intervals of 120 °, and these coils U, V, W, the armature 34, Are detected by a Hall IC which forms an angle sensor provided in the motor. Then, upon receiving the outputs of these Hall ICs, the motor driver 18 of FIG. 1 switches the energization of the coils U, V, W to W → U (1), U → V (3), V → W (5) is sequentially switched cyclically (in the case of forward rotation: in the case of reverse rotation, the switching is performed in the reverse order described above). FIG. 8B shows an energizing sequence of the coils of each phase in the case of forward rotation (“H” indicates energization and “L” indicates non-energization: in the case of reverse rotation, The sequence is reversed left and right). The numbers in parentheses in the figure represent the angular positions of the armature 34 at the corresponding numbers in FIG.
[0024]
Returning to FIG. 4, the rotation control of the motor 6 includes the duty ratio control by the PWM signal from the drive control unit 100 (the main microcomputer 110 in the present embodiment) in the energization switching sequence of each phase of the coils U, V, and W. The sequence is performed in a superimposed manner. FIG. 7 shows a circuit example of the motor driver 18, and FETs (semiconductor switching elements) 75 to 80 corresponding to the terminals u, u ', v, v', w, w 'of the coils U, V, W. Are arranged so as to constitute a well-known H-type bridge circuit (reference numerals 87 to 92 are flywheel diodes that form a bypass path for an induced current accompanying switching of the coils U, V, and W). . The AND gates 81 to 86 generate a logical product signal of the switching signal from the Hall IC (angle sensor) on the motor side and the PWM signal from the drive control unit 100, and use this to drive the FETs 75 to 80 for switching. Can be selectively energized by PWM for the coil of the phase involved in the current. Note that, depending on the PWM energization method, the PWM signal may be input only to the upper (75, 77, 79) or lower (76, 78, 80) FETs of the H-type bridge circuit. In this case, the AND gate 81 It is possible to omit the corresponding one of 〜86 and directly input the switching signal from the Hall IC.
[0025]
The timing for sequentially providing the PWM signals to the FETs 75 to 80 on the drive control unit 100 side may be recognized by distributing a signal from a Hall IC (angle sensor) to the drive control unit 100. In the embodiment, this is separately detected by using a rotary encoder as an angle sensor. This rotary encoder detects the rotation angle of the motor output shaft 36, and the detected angle value has a unique correspondence with the angular position of the wheel steering shaft 8 after deceleration. Therefore, in the present embodiment, this rotary encoder is used as the steering shaft angle detection unit 103.
[0026]
FIG. 8 (a) schematically shows the above rotary encoder. In order to control the energizing sequence of the brushless motor, bits for specifying coil energizing patterns in a time-sequential appearance order are specified. The patterns (angle identification patterns) are formed at regular angular intervals in the circumferential direction of the disk. In the present embodiment, the bit pattern is a slit indicated by a hatched area in the drawing, and a plurality of sets of slits formed by defining sections in the circumferential direction of the disk forming the rotating body in the radial direction of the disk (this embodiment). In the embodiment, three sets are formed. As the detection unit, a not-shown transmission optical sensor (for example, a photocoupler or the like) corresponding to each slit group is used, and a combination of whether or not a slit is detected at a position where each slit group is formed in the radial direction is determined. A bit pattern indicating the rotation angle phase of the disk is output.
[0027]
In the present embodiment, since a three-phase brushless motor is used, (1) to (6) (FIG. 5) are obtained so that the energizing sequence of the coils U, V, and W shown in FIG. 6) are formed at intervals of 60 ° in the circumferential direction of the disk. Therefore, when the armature 34 of the motor 6 rotates, the rotary encoder that rotates synchronously therewith outputs a bit pattern specifying the coil to be energized at present. Therefore, by reading the bit pattern of the encoder, the drive control unit 100 can spontaneously determine the terminal of the coil to which the PWM signal is to be sent (that is, the FETs 75 to 80 in FIG. 7).
[0028]
Since the rotation of the motor output shaft 36 is transmitted to the wheel steering shaft 8 after being decelerated, the motor output shaft 36 provided with the rotary encoder rotates plural times while the wheel steering shaft 8 makes one rotation. Therefore, the absolute angular position of the wheel steering shaft 8 cannot be known from the bit pattern of the encoder indicating only the absolute angular position of the motor output shaft 36. Therefore, as shown in FIG. 4, a counter (steering shaft angle position counter) for counting the number of times a bit pattern change is detected is formed in the RAM 113 (123), and the steering shaft angle position (θ) is obtained from the counted number. It is like that. Therefore, it can be considered functionally equivalent to an incremental rotary encoder. Since the absolute angular position of the motor output shaft 36 (the armature of the motor 6) can be read according to the type of the bit pattern, if the change order of the bit pattern is monitored, the motor output shaft 36 and the wheel steering shaft 8 can be read. (That is, the direction in which the steering wheel is turned). Therefore, the steering shaft angle detection unit 103 increments the above counter if the rotation direction of the wheel steering shaft 8 is positive, and decrements the counter if the rotation direction is opposite.
[0029]
The motor driver 18 is connected to a vehicle-mounted battery 57 serving as a power supply for the motor 6. The voltage (power supply voltage) Vs of the battery 57 received by the motor driver 18 changes as needed (for example, 9 to 14 V) depending on the state of loads distributed to various parts of the vehicle and the power generation state of the alternator. In the present embodiment, such a fluctuating battery voltage Vs is directly used as a motor power supply voltage without passing through a stabilized power supply circuit. Since the steering control unit 100 controls the motor 6 on the premise of using the power supply voltage Vs that fluctuates in a considerable width as described above, a measurement unit for the power supply voltage Vs is provided. In the present embodiment, a branch path for voltage measurement is drawn out from a power supply path to the motor 6 (immediately before the motor driver 18), and a voltage measurement signal is extracted through voltage dividing resistors 60 provided therein. The voltage measurement signal is smoothed by a capacitor 61 and then input to an input port with an A / D conversion function (hereinafter, referred to as an A / D port) of input / output interfaces 114 and 124 via a voltage follower 62.
[0030]
In addition, a current detection unit is provided on a power supply path to the motor 6 to monitor the power supply state of the motor 6 such as occurrence of overcurrent. Specifically, the voltage difference between both ends of the shunt resistor (current detection resistor) 58 provided on the path is measured by the current sensor 70, and is input to the A / D ports of the input / output interfaces 114 and 124. For example, as shown in FIG. 6, the current sensor 70 extracts the voltage between both ends of the shunt resistor 58 through voltage followers 71 and 72, and amplifies the voltage by a differential amplifier 75 including an operational amplifier 73 and a peripheral resistor 74. Output. Since the output of the differential amplifier 75 is proportional to the value of the current flowing through the shunt resistor 58, this can be used as the measured current value Is. Note that, other than the shunt resistor, a probe that detects a current based on an electromagnetic principle, such as a Hall element or a current detection coil, may be used.
[0031]
Returning to FIG. 4, the following memory areas are formed in the RAMs 113 and 123 of the microcomputers 110 and 120, respectively.
(1) Vehicle speed measurement value memory: The current vehicle speed measurement value from the vehicle speed sensor 102 is stored.
{Circle over (2)} Handle axis angle position (φ) counter memory: counts a count signal from the rotary encoder constituting the handle axis angle position detection unit 101 and stores the count value indicating the handle axis angle position φ. Note that a rotary encoder capable of identifying the rotation direction is used. In the case of forward rotation, the counter is incremented, and in the case of reverse rotation, the counter is decremented.
(3) Steering angle conversion ratio (α) calculated value memory: The steering angle conversion ratio α calculated based on the measured vehicle speed is stored.
(4) Target steering shaft angle position (θ ′) calculation value memory: a target value of the steering shaft angle position calculated by, for example, φ × α from the current value of the handle shaft angle position φ and the steering angle conversion ratio α; That is, the value of the target steering shaft angle position θ ′ is stored.
(5) Steering shaft angle position (θ) counter memory: counts a count signal from a rotary encoder forming the steering shaft angle detection unit 103, and stores the count value indicating the steering shaft angle position θ.
(6) Δθ calculated value memory: Stores a calculated value of Δθ (≡θ'-θ) between the target steering axis angle position θ 'and the current steering axis angle position θ.
(7) Power supply voltage (Vs) measured value memory: Stores the measured value of the power supply voltage Vs of the motor 6.
(8) Duty ratio (η) determined value memory: The duty ratio η determined based on Δθ and the power supply voltage Vs for energizing the motor 6 with PWM is stored.
(9) Current (Is) measured value: The measured value of the current Is by the current sensor 70 is stored. Further, the CPU 111 or 121 calculates the angle difference Δβ between the steering wheel angle (the steering shaft angle position) φ and the steering angle (the steering shaft angle position) θ, and stores the angle difference memory for temporarily storing the angle difference Δβ in the RAM. Is provided.
[0032]
The input / output interface 114 of the main microcomputer 110 is provided with an EEPROM 115 as a second storage unit for storing the angular position of the wheel steering shaft 8 at the end of the operation (that is, when the ignition is turned off), that is, the end angular position. Have been. The EEPROM 115 (PROM) can only read data by the main CPU 111 at the first operating voltage (+5 V) at which the main CPU 111 reads / writes data from / to the main CPU RAM 112. By setting a second operating voltage different from the voltage (+5 V) (a voltage higher than the first operating voltage is employed in this embodiment: for example, +7 V), data can be written by the main CPU 111. Therefore, even if the main CPU 111 runs away, the contents will not be rewritten by mistake. The second operating voltage is generated by a booster circuit (not shown) interposed between the EEPROM 115 and the input / output interface 114.
[0033]
Hereinafter, the operation of the vehicle steering control system 1 will be described.
FIG. 12 shows the flow of processing of the main routine of the control program by the main microcomputer 110. S1 is an initialization process, in which the end angle position (described later) of the wheel steering shaft 8 written in the EEPROM 115 in the end process when the ignition switch was turned OFF last time is read out, and the end angle position is determined at the start of the process. The point is to set as the initial angular position of the wheel steering shaft 8. Specifically, a counter value indicating the end angle position is set in the above-mentioned steering shaft angle position counter memory. Note that a data write completion flag to the EEPROM 115 described later is cleared at this time.
[0034]
When the initialization process is completed, the process proceeds to S2, where the steering control process is performed. The steering control process is repeatedly executed at a constant period (for example, several hundred μs) in order to equalize the parameter sampling intervals. The details will be described with reference to FIG. In S201, the current measured value of the vehicle speed V is read, and then, in S202, the handle shaft angular position φ is read. In S203, a steering angle conversion ratio α for converting the steering shaft angle position φ into the target angle position θ ′ of the steering shaft is determined from the calculated value of the vehicle speed V. Different values are set for the steering angle conversion ratio α according to the vehicle speed V. Specifically, as shown in FIG. 10, when the vehicle speed V is higher than a certain value, the steering angle conversion ratio α is set to a small value, and when the vehicle speed V is lower than a certain value, the steering angle conversion ratio α is set to a large value. Is done. In the present embodiment, a table 130 for setting the steering angle conversion ratio α corresponding to various vehicle speeds V is stored in the ROM 112 (122) as shown in FIG. The steering angle conversion ratio α corresponding to the vehicle speed V is calculated by an interpolation method. In the present embodiment, the vehicle speed V is used as the information indicating the driving state of the vehicle. However, in addition to this, the lateral pressure received by the vehicle, the inclination angle of the road surface, and the like are used as information indicating the driving state of the vehicle. And it is possible to set the steering angle conversion ratio α to a specific value according to the detected value. It is also possible to determine the basic value of the steering angle conversion ratio α in accordance with the vehicle speed V, and to use the basic value as needed based on information other than the vehicle speed as described above.
[0035]
In S204, the target steering shaft angle position θ ′ is calculated by multiplying the detected steering shaft angle position φ by the determined steering angle conversion ratio α. Then, in S205, the current steering shaft angle position θ is read. The steering shaft angle position θ is specifically determined as follows. First, the steering shaft angle position θ is counted by a steering shaft angle position counter using a change in the bit pattern from the rotary encoder in FIG. 8 as a count signal, and given by the count value. Whether the bit pattern has changed can be detected by storing the bit pattern detected in the previous cycle in a memory or latching it in hardware, and comparing it with the next incoming bit pattern to determine whether or not they match. As described above, since each bit pattern individually represents the rotation phase of the disk of the encoder, the change sequence of the bit pattern also changes according to the rotation direction of the disk. Therefore, the direction of rotation is identified by checking which bit pattern has changed to the bit pattern before or after it, and whether the count value of the counter is incremented or decremented is determined.
[0036]
In S206, the difference Δθ (= θ′−θ) between the current steering shaft angle position θ updated and determined as described above (determined from the steering shaft angle position counter) and the target steering shaft angle position θ ′. Is calculated. Further, in S207, the current measured value of the power supply voltage Vs is read. The motor 6 rotationally drives the wheel steering shaft 8 so that the difference Δθ between the target steering shaft angle position θ ′ and the current steering shaft angle position θ decreases. When Δθ is large, the rotation speed of the motor 6 is increased, and when Δθ is small, the motor 6 is rotated so that the steering shaft angle position θ can quickly and smoothly approach the target steering shaft angle position θ ′. The rotation speed of the motor. Basically, proportional control is performed using Δθ as a parameter. However, in order to suppress overshoot and hunting and stabilize the control, it is desirable to perform well-known PID control in consideration of the differentiation or integration of Δθ. .
[0037]
The motor 6 is under PWM control as described above, and the rotation speed is adjusted by changing the duty ratio η. If the power supply voltage Vs is constant, the rotation speed can be almost uniquely adjusted by the duty ratio. However, in the present embodiment, the power supply voltage Vs is not constant as described above. Therefore, the duty ratio η is determined in consideration of the power supply voltage Vs. For example, as shown in FIG. 11, a two-dimensional duty ratio conversion table 131 that provides a duty ratio η corresponding to each combination of various power supply voltages Vs and Δθ is stored in the ROM 112 (122), and the power supply voltage Vs And the value of the duty ratio η corresponding to the calculated value of Δθ can be read and used. Note that the rotation speed of the motor 6 also varies depending on the load. In this case, the state of the motor load can be estimated based on the measured value of the motor current Is by the current sensor 70, and the duty ratio η can be corrected and used.
[0038]
The processing so far is executed in parallel by both the main microcomputer 110 (main CPU 111) and the sub microcomputer 120 (sub CPU 121) in FIG. For example, whether the operation of the main microcomputer 110 is normal or not is determined by transferring the calculation result of each parameter stored in the RAM 113 of the main microcomputer 110 to the sub-microcomputer 120 at any time. By performing the collation, it is possible to monitor whether or not an abnormality has occurred. On the other hand, the main microcomputer 110 generates a PWM signal based on the determined duty ratio η. Then, the PWM signal is output to the FET (FIG. 7) that switches the coil of the phase involved in the energization with respect to the motor driver 18 with reference to the signal from the rotary encoder forming the steering shaft angle detection unit 103, The motor 6 is PWM-controlled.
[0039]
Returning to FIG. 12, in S3, it is confirmed whether or not the ignition switch is turned off. If the ignition switch is turned off, the end processing of S4 is performed. That is, when the ignition switch is turned off, it means that the operation of the vehicle has been completed. Therefore, the main microcomputer 110 reads out the end angle position of the wheel steering shaft 8 stored in the steering shaft angle position counter. This is stored in the EEPROM 115, and the data write completion flag provided in the RAM 113 is set, thus ending the processing.
[0040]
Next, when a current supply abnormality to the motor 6 as an actuator of the variable transmission ratio unit (for example, a runaway of the CPU or other system abnormality) occurs, the abnormality is stored in, for example, the motor stored in the memory. By comparing the expected current value with the actual motor current detection value detected by the current sensor 70, a large gap between the two is detected, or an unexpected angle difference between the steering wheel angle and the steering angle is detected. Is detected, the system detects the abnormality.
[0041]
When the abnormality is detected, the solenoid 55 in FIG. 3 is deactivated (demagnetized), and the lock member 51 at the unlock position is biased by the elastic member 54 so that the lock receiving member 52 is locked. Move to the locked position to fit into one of the parts 53. As a result, the handle shaft 3 and the vehicle steering shaft 8 are directly connected (fixed at a transmission ratio of 1: 1), and the variable transmission ratio function of the variable transmission ratio unit is locked. This is a so-called mechanical lock (mechanical lock). This mechanical lock should continue the lock action unless the solenoid 55 is excited to move the lock member 51 to the unlock position. However, in consideration of the case where the mechanical lock does not function normally for some reason, FIG. A routine for conceptually determining a mechanical lock failure is executed.
[0042]
When the signal of the mechanical lock is output in step P1 (the solenoid 55 is demagnetized), the process proceeds to a step of determining an abnormality of the mechanical lock in P2. In order to detect this lock abnormality (failure), for example, a mechanical lock abnormality (failure) detection sensor 180 such as an optical sensor, an electromagnetic proximity sensor, or a contact type microsensor can be provided near the lock member 51. The sensor 180 is connected to at least one of the CPUs 111 and 121. When the lock member 51 shown in FIG. 3 is displaced from the lock receiving portion 53 so as to be separated from the lock receiving portion 53, the sensor 180 can output a mechanical lock abnormality signal to the CPU. it can. Further, as a function of the sensor 180, for example, a mechanical lock signal is output, and a signal (normal signal) for confirming that the lock of the solenoid 55 has been released and the lock member has reached the lock position is output (by movement to the lock position). (If there is a confirmation signal, it is normal, if there is no confirmation signal, it is abnormal.) Further, after outputting a mechanical lock signal, after outputting a confirmation signal that the lock member 51 has moved to the lock position, the lock member 51 is moved from the lock position. The detachment is monitored by the sensor 180, and if the detachment is detected, it can also be output as a mechanical lock abnormality signal.
[0043]
In addition to providing such a dedicated sensor 180, by causing the CPU to perform processing such as calculation of the angle difference between the handle shaft angle position φ and the steering shaft angle position θ, this can be used as a mechanical lock abnormality detection device. You can also. That is, after a time period in which the mechanical lock signal (lock command signal) is output and the mechanical lock is estimated to be completed has elapsed, if the mechanical lock is working normally, the relative rotation between the handle shaft 3 and the wheel steering shaft 8 becomes impossible. Therefore, there should be no relative change between the steering shaft angle position φ and the steering shaft angle position θ. On the other hand, the occurrence of a change in the angle between the handle shaft angle position φ and the steering shaft angle position θ after the mechanical lock signal is output and the mechanical lock is presumed to be actuated is determined by the steering angle detection unit 101 and the steering angle detection unit 101 in FIG. If it is determined by taking in the angles φ and θ from the shaft angle detection 103 and calculating the relative change by the CPU (calculation of φ−θ, etc.), it can be determined that the mechanical lock is abnormal (failure).
[0044]
In any case, if it is determined that the mechanical lock is abnormal in P2 of FIG. 14, in P3, in order to cover the failure of the mechanical lock, the electromagnetic force generating unit (coil unit) of the motor 6 that drives the transmission ratio variable unit includes: A lock current for generating an electromagnetic holding force for holding the motor output shaft (and, consequently, the wheel steering shaft 8) in a non-rotatable state is applied to electrically lock the motor. The motor lock, in other words, the electric lock device is turned on, whereby the handle shaft 3 and the wheel steering shaft 8 are directly connected at a transmission ratio of 1: 1 to stop the variable transmission ratio function of the variable transmission ratio unit. . Therefore, the reliability when the mechanical lock breaks can be enhanced.
[0045]
If such a motor lock follows the example of FIG. 5, as shown in the concept of FIG. 17, the lock current is applied to the coils U, V, and W of the motor 6 simultaneously and continuously, for example, and The energization causes a magnetic field (electromagnetic force) to be attracted to the S and N poles of the rotor of the motor 6 in each of the coils U, V, W. As a result, the magnetic pole of the rotor of the motor 6 attracts the coil on the stator side to generate an electromagnetic holding force for maintaining the motor output shaft in a fixed state, and this is an electric lock (motor lock). It is not essential to supply the lock current to all the coils of the motor 6 as long as a certain electromagnetic holding force can be obtained. It is also possible to fulfill. The energization of the motor 6 with such an electric lock is performed via the motor driver 18 by the CPU 111 or the like reading out the energization pattern and issuing an execution command according to a program previously written in a ROM or the like.
[0046]
In the routine for the non-operation of the mechanical lock shown in FIG. 15, it is determined whether the mechanical lock is turned on at R1. If the mechanical lock is not turned on, the above-described normal transmission ratio control is performed at R2, but the mechanical lock is turned on. Then, whether an abnormality (failure) has occurred in the mechanical lock at R3 is checked as described above. If there is no abnormality in the mechanical lock, since the handle shaft 3 and the wheel steering shaft 8 are directly fixed, the electric lock does not operate. On the other hand, if it is determined that there is an abnormality in the mechanical lock, a step of calculating a lock current is interposed in R4 instead of simply supplying a constant lock current to the motor 6. In other words, the motor 6 is likely to overheat if a constant lock current is kept flowing, so that a small lock current flows when the vehicle is going straight, and a lock current that corresponds to the steering torque (also referred to as a steering angle or a steering wheel angle) during steering. This has the purpose of preventing overheating of the motor when the mechanical lock is not operated.
[0047]
For example, when the lock current is plotted on the vertical axis and the steering angle (steering torque or steering wheel angle) is plotted on the horizontal axis, if the steering angle is close to zero, the vehicle is close to a straight running state, and the lock current is small or zero. Also, even if the steering angle is large (even if the steering wheel is turned large), if the steering is slow (the steering torque is small), the lock current is small, and even if the steering angle is small, the steering operation is strong (for example, when the steering is sharp, etc.). When the operating torque is large, the lock current is increased. The steering torque at the time of steering is calculated, for example, by calculating the angle difference (strictly, the absolute value of the difference) between the target steering angle (for example, plotting the steering wheel angle) and the actual steering angle (for example, plotting the steering angle of the vehicle). The magnitude of the difference can be used as the steering torque (estimated value). That is, as an element for determining how much lock current should be supplied to the motor, a steering angle indicating how much the steering wheel is turned is extracted, and the lock current to be supplied is determined by the angle difference (steering torque). ) Is determined as a function of the steering angle having a coefficient, and a lock current to be energized is determined by calculation or reference based on a preset function formula or conversion table. The lock current determined in this way is supplied to the motor 6 at R5 to perform electric lock.
[0048]
The routine shown in FIG. 16 is an example in which the lock current is determined based on the steering angle (the steering wheel angle sequentially detected (sampled) by the steering shaft angular position (φ) detecting unit 103 in FIG. 4). T1, T2, and T3 are the same as R1, R2, and R3 described above. When an abnormality of the mechanical lock is detected (T3), the magnitude of the steering wheel angle φ or the rate of increase (dφ / dt) is detected or calculated at T4. The magnitude of the steering wheel angle indicates how much the steering wheel is turned, and the increasing rate of the steering wheel angle indicates whether the operation of turning the steering wheel (steering operation) is going to proceed further (positive increasing rate or increasing tendency, etc.), It can be said that it reflects whether the end is approaching (negative increase rate or decreasing trend). Therefore, in the former case, it can be estimated that the steering torque is large, and in the latter case, it can be estimated that the steering torque is small.
[0049]
Then, at T5, it is determined whether the steering wheel angle φ or its increase rate (dφ / dt) is equal to or less than a set value. If the handle angle exceeds the set value, a normal lock current (specified current) is supplied and electric lock is performed. If the lock current is not more than the set value (T7), the lock current can be reduced to apply a loose electric lock, or the lock current can be prevented from being applied without supplying the lock current (T6). Since such a process is executed at a predetermined cycle time, the value of the current supplied for the electric lock changes every moment, and the lock current becomes zero (temporary release of the electric lock) according to the situation. Can do. In such a case, the energization of the lock current may be intermittent, and the energization of the lock current itself may be intermittently performed in a predetermined cycle from the beginning. When the operation is performed intermittently, the lock current can be duty ratio controlled to suppress overheating of the motor or to reduce power consumption.
Although FIG. 16 has been described on the premise that the lock current is adjusted depending on whether or not the threshold value is exceeded, similarly to R4 in FIG. 15, as T8, the handle shaft angle position φ of T4 and the rate of increase thereof are set. It is also possible to form a formula or a conversion table as a lock current adjusting element, determine an optimum lock current value based on the formula or the conversion table, and perform lock current control for energizing the motor.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the overall configuration of a vehicle steering control system according to the present invention.
FIG. 2 is a longitudinal sectional view showing one embodiment of a drive unit.
FIG. 3 is a sectional view taken along line AA of FIG. 2;
FIG. 4 is a block diagram showing an example of an electrical configuration of a vehicle steering control system according to the present invention.
FIG. 5 is a diagram illustrating the operation of a three-phase brushless motor used in the embodiment of the present invention.
FIG. 6 is a diagram showing a circuit example of a current sensor.
FIG. 7 is a circuit diagram showing an example of a driver portion of the three-phase brushless motor.
FIG. 8 is an explanatory diagram of a rotary encoder used in the three-phase brushless motor of FIG.
FIG. 9 is a schematic diagram of a table for giving a relationship between a steering angle conversion ratio and a vehicle speed.
FIG. 10 is a schematic diagram showing an example of a pattern for changing a steering angle conversion ratio according to a vehicle speed.
FIG. 11 is a schematic diagram of a two-dimensional table for determining a duty ratio based on a motor power supply voltage and an angle deviation Δθ.
FIG. 12 is a flowchart showing an example of a main routine of computer processing in the vehicle steering control system of the present invention.
FIG. 13 is a flowchart illustrating an example of details of the steering control process of FIG. 12;
FIG. 14 is a flowchart illustrating an example of a process at the time of mechanical lock failure determination.
FIG. 15 is a flowchart showing a modification of FIG. 14;
FIG. 16 is a flowchart showing a further modified example of FIG.
FIG. 17 is a conceptual diagram showing an example of a motor lock (electric lock).
[Explanation of symbols]
3 Handle axis
6. Motor (actuator)
8 Wheel steering shaft
51 Lock member
52 Lock receiving member
100 Steering control unit
101 Handle shaft angle detector
103 Steering axis angle detector
111 Main CPU (angle determination means)
121 sub CPU (angle determination means)
180 Mechanical lock abnormality detection sensor

Claims (8)

A variable transmission ratio unit driven by a motor that varies the transmission ratio is interposed in the middle of a steering transmission system that connects the handle shaft of the steering wheel and the wheel steering shaft, and controls the transmission ratio according to a predetermined element. In a vehicle steering system,
The motor is electrically locked by applying a lock current that generates an electromagnetic holding force that holds a motor output shaft in a non-rotatable state to the electromagnetic force generating unit of the motor that drives the transmission ratio variable unit, and electrically locks the motor, A vehicle steering system comprising: an electric lock device that directly connects a handle shaft and a wheel steering shaft at a transmission ratio of 1: 1 to stop a variable transmission ratio function of the variable transmission ratio unit. A variable transmission ratio unit driven by a motor that varies the transmission ratio is interposed in the middle of a steering transmission system that connects the handle shaft of the steering wheel and the wheel steering shaft, and controls the transmission ratio according to a predetermined element. In a vehicle steering system,
A mechanical lock device for fixing the handle shaft and the wheel steering shaft so as to be mechanically directly connected at a transmission ratio of 1: 1 to stop a variable transmission ratio function of the variable transmission ratio unit;
The motor is electrically locked by applying a lock current for generating an electromagnetic holding force for holding a motor output shaft in a non-rotatable state to an electromagnetic force generating unit of the motor that drives the variable transmission ratio unit, thereby electrically locking the motor, An electric lock device for directly connecting a shaft and a wheel steering shaft at a transmission ratio of 1: 1 to stop a variable transmission ratio function of the variable transmission ratio unit;
A vehicle steering system comprising: The vehicle steering system according to claim 2, wherein the electric lock device is not operated when the mechanical lock device is operating normally, and the electric lock device is operated when the mechanical lock device is not operating normally. A mechanical lock abnormality detection device for detecting an abnormality of the mechanical lock device,
When an abnormality is detected in the mechanical lock device, an electric lock control device that operates the electric lock device immediately or under specific conditions,
The vehicle steering system according to claim 2 or 3, further comprising: Under a specific condition, the electric lock control device stops applying a lock current to the motor to release the electric lock, or changes a lock current value to the motor to change the electromagnetic holding force. The vehicle steering apparatus according to any one of claims 1 to 4, wherein the value is decreased or increased. The electric lock control device is configured such that, when a steering wheel angle, which is a rotation operation angle of the steering wheel, is under a specific condition, or a relationship between the steering wheel angle and a steering angle, which is a rotation angle of a wheel steering shaft that steers a steering wheel. Is under specific conditions, the supply of the lock current to the motor is stopped to temporarily release the electric lock, or the lock current value to be supplied to the motor is changed to reduce the electromagnetic holding force. The vehicle steering device according to any one of claims 1 to 5, wherein the vehicle steering device is temporarily reduced or increased. When the steering wheel angle, which is the rotation operation angle of the steering wheel, is at or near the neutral position, the electric lock control device stops supplying the lock current to the motor to temporarily release the electric lock. The vehicle steering apparatus according to any one of claims 1 to 6, wherein the value of the lock current supplied to the motor is reduced to temporarily reduce the electromagnetic holding force. The electric lock control device is configured to control the motor when an angle difference between a steering wheel angle that is a rotation operation angle of the steering wheel and a steering angle that is a rotation angle of a wheel steering shaft that steers a steered wheel is equal to or less than a predetermined value. 8. An electric lock is temporarily released by stopping energization of a lock current to be energized, or a value of a lock current to be energized to the motor is reduced to temporarily reduce an electromagnetic holding force. 2. The vehicle steering system according to claim 1.

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