Steering system

Abstract

The present invention relates to a steering system comprising: a steering shaft (21); a reaction motor (22); and a control unit configured to control the reaction motor (22). The control unit has the function of performing a correction process when the vehicle is powered on and the rotational position of the steering wheel differs from the correct rotational position corresponding to the rotational position of the steering wheels. This correction process uses the reaction motor (22) to rotate the steering wheel (11) such that the displacement of the rotational position of the steering wheel (11) relative to the correct rotational position is reduced. The control unit is configured to perform the correction process when the displacement is equal to or greater than a predetermined allowable value, and not to perform the correction process when the displacement is less than the allowable value.

Description

Technical Field

[0001] This invention relates to the steering system of a vehicle. Background Technology

[0002] So-called steer-by-wire systems already exist, in which power transmission between the steering wheel and the steering wheels is cut off. Such a steering system includes: a reaction mechanism comprising a reaction motor, which is the source of the steering reaction force applied to the steering shaft; and a rotation mechanism comprising a rotation motor, which is the source of the rotational force for rotating the steering wheels. When the vehicle is in motion, the steering system's control unit generates the steering reaction force through power control of the reaction motor and rotates the steering wheels through power control of the rotation motor.

[0003] In such a steer-by-wire system, the steering wheel is not restricted by the rotation mechanism. Therefore, when an external force is applied to the steering wheel while the vehicle's power is off, there is a possibility that the steering wheel may rotate. At this time, since the steering wheels are not rotating, the positional relationship between the steering wheel and the steering wheels may differ from the original positional relationship corresponding to a predetermined steering angle ratio. Here, the steering angle ratio refers to the ratio between the rotation angle of the steering wheels and the steering angle of the steering wheel.

[0004] Therefore, for example, in the steering system disclosed in unexamined Japanese Patent Application Publication No. 2006-321434 (JP 2006-321434A), the process of correcting the rotational position of the steering wheel is performed when the vehicle power is turned on. The steering system control device stores the rotational position of the steering wheel when the vehicle power is off. The control device calculates the displacement of the steering wheel rotational position by comparing the rotational position of the steering wheel when the vehicle power is off with the rotational position of the steering wheel when the vehicle power is on, and drives the reaction motor to make the displacement zero. Summary of the Invention

[0005] The steering system disclosed in JP 2006-321434 A reliably improves the displacement of the positional relationship between the steering wheel and the steering wheels. However, the steering system disclosed in JP 2006-321434 A has the following problem: The steering wheel automatically rotates when the vehicle's power is turned on to correct the positional relationship between the steering wheel and the steering wheels. This automatic rotation of the steering wheel may cause discomfort to the driver. Furthermore, the driver cannot start the vehicle after the vehicle's power is turned on until the process of correcting the steering wheel's rotational position is completed. Therefore, the driver may experience stress.

[0006] The present invention provides a steering system that can reduce driver discomfort or stress caused by the process of correcting the positional relationship between the steering wheel and the steering wheels.

[0007] According to an aspect of the invention, a steering system is provided, comprising: a steering shaft that rotates according to operation of a steering wheel, wherein power transmission between the steering shaft and the steering wheels of a vehicle is interrupted; a reaction motor configured to generate a steering reaction force, the steering reaction force being a torque applied to the steering shaft in a direction opposite to the steering direction; and a control unit configured to control the reaction motor. The control unit has the function of performing a correction process when the vehicle's power is turned on and the rotational position of the steering wheel differs from a correct rotational position corresponding to the rotational position of the steering wheels, the correction process using the reaction motor to rotate the steering wheel such that the displacement of the steering wheel's rotational position relative to the correct rotational position is reduced. The control unit is configured to perform the correction process when the displacement is equal to or greater than a predetermined allowable value, and not to perform the correction process when the displacement is less than the allowable value.

[0008] With this configuration, when the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position is equal to or greater than a predetermined allowable value, a process to correct the steering wheel's rotational position is performed. Conversely, when the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position is less than the predetermined allowable value, the process to correct the steering wheel's rotational position is not performed. This reduces the likelihood of the steering wheel automatically rotating when the vehicle's power is turned on. Therefore, driver discomfort can be reduced. Since the likelihood of the driver waiting for the steering wheel's rotational position correction process to complete is reduced, driver stress can be decreased.

[0009] In a steering system according to this aspect, the correction process may include a first correction process of rotating the steering wheel to reduce the displacement to zero and a second correction process of rotating the steering wheel to reduce the displacement to an allowable value. In this case, the control unit may be configured to perform the first correction process when the displacement is greater than a predetermined limit value, and to perform the second correction process when the displacement is equal to or greater than the allowable value and equal to or less than the limit value.

[0010] With this configuration, when the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position exceeds a predetermined limit, a first correction process is executed. By executing this first correction process, the steering wheel's rotational position is synchronized with the position corresponding to the steering wheel's rotational position (i.e., matched to the position corresponding to the steering wheel's rotational position). Therefore, the vehicle can begin to move smoothly without causing discomfort to the driver.

[0011] When the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position is equal to or greater than the permissible value and equal to or less than the limit value, a second correction process is executed. By executing this second correction process, the steering wheel's rotational position is corrected so that its displacement relative to the steering wheel's rotational position reaches the permissible value. Because the steering wheel's rotational position is not perfectly synchronized with the corresponding steering wheel's rotational position (i.e., not perfectly matched), the time from the start to the stop of the steering wheel's automatic rotation can be shortened. Since the waiting time for the steering wheel to stop rotating is shortened, driver stress is reduced.

[0012] In a steering system according to this aspect, the correction process can be the rotation of the steering wheel to make the displacement zero. With this configuration, when the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position is equal to or greater than a predetermined allowable value, the correction process synchronizes the steering wheel's rotational position with the position corresponding to the steering wheel's rotational position (i.e., matches the position corresponding to the steering wheel's rotational position). Therefore, the vehicle can begin to move smoothly without causing discomfort to the driver.

[0013] In a steering system according to this principle, the correction process can be the rotation of the steering wheel to reduce the displacement to an acceptable value. With this configuration, when the vehicle's power is turned on and the displacement of the steering wheel's rotational position relative to the steering wheel's rotational position is equal to or greater than a predetermined acceptable value, the correction process reduces the displacement of the steering wheel's rotational position to the acceptable value. Therefore, the vehicle can begin to move smoothly without causing discomfort to the driver.

[0014] The steering system according to this aspect may also include: a rotation shaft that rotates the steering wheels, wherein power transmission between the steering wheel and the rotation shaft is interrupted; and a rotation motor configured to generate a rotational force, which is a torque applied to the rotation shaft to rotate the steering wheels. In this case, the control unit may be configured to: when the vehicle begins to move, if the rotational position of the steering wheel is different from the rotational position corresponding to the rotational position of the steering wheels, control the rotation motor to change the rotational position of the steering wheels to the position corresponding to the rotational position of the steering wheel.

[0015] With this configuration, when the vehicle begins to move, if the steering wheel's rotation position is not synchronized with the steering wheel's rotation position (i.e., not matched with the steering wheel's rotation position), the steering wheel's rotation position is corrected to correspond to the steering wheel's rotation position. Therefore, it allows the vehicle to begin moving while suppressing driver discomfort.

[0016] The steering system according to this aspect of the invention can reduce driver discomfort or stress caused by the process of correcting the positional relationship between the steering wheel and the steering wheels. Attached Figure Description

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and in the drawings:

[0018] Figure 1 It is a diagram illustrating the configuration of the steering system according to an embodiment;

[0019] Figure 2 It is a flowchart of the synchronization control process executed by the reaction control unit according to the implementation method;

[0020] Figure 3 Each of parts (a) and (b) is a front view illustrating a first example of the change in the rotational position of the steering wheel according to the embodiment after the vehicle is powered on.

[0021] Figure 4 Each of parts (a) and (b) is a front view illustrating a second example of the change in the rotational position of the steering wheel according to the embodiment after the vehicle's power is turned on;

[0022] Figure 5 Each of parts (a), (b), and (c) is a front view illustrating a third example of the change in the rotational position of the steering wheel according to the embodiment after the vehicle's power is turned on. Detailed Implementation

[0023] The steering system according to an embodiment of the present invention will be described below. For example... Figure 1 As illustrated, the vehicle's steering system 10 includes: a reaction unit 20 that applies a steering reaction force to the vehicle's steering wheel 11; and a rotation unit 30 that rotates the vehicle's steering wheels 12. The steering reaction force is a torque applied in the opposite direction to the direction of operation of the steering wheel 11 by the driver. By applying the steering reaction force to the steering wheel 11, the driver can be given an appropriate responsiveness.

[0024] The reaction unit 20 includes: a steering shaft 21 connected to the steering wheel 11, a reaction motor 22, a reduction mechanism 23, a rotation angle sensor 24, a torque sensor 25, and a reaction control unit 27.

[0025] The reaction motor 22 is the source of the steering reaction force. For example, a three-phase brushless motor is used as the reaction motor 22. The reaction motor 22 is connected to the steering shaft 21 via a reduction gear 23. The torque generated by the reaction motor 22 is applied to the steering shaft 21 as the steering reaction force.

[0026] A rotation angle sensor 24 is installed in the reaction motor 22. The rotation angle sensor 24 detects the rotation angle θ of the reaction motor 22. a The torque sensor 25 is disposed in the portion of the steering shaft 21 located between the reduction gear 23 and the steering wheel 11. The torque sensor 25 detects the steering torque T applied to the steering shaft 21 by rotating the steering wheel 11. h .

[0027] The reaction control unit 27 is based on the rotation angle θ of the reaction motor 22 detected by the rotation angle sensor 24. a To calculate the steering angle θ, which is the rotation angle of the steering axis 21. s The rotation angle θ of the reaction control unit 27 relative to the reaction motor 22 corresponding to the neutral steering position of the steering wheel 11. a The revolutions of the reaction motor 22 are counted (in the following text, the rotation angle θ corresponding to the neutral steering position). a (This will be referred to as the "motor midpoint"). The reaction control unit 27 calculates the total angle, which is the rotation angle θ using the motor midpoint as the origin. a The angle obtained by adding the two values ​​is calculated, and the reaction control unit 27 calculates the steering angle θ of the steering wheel 11 by multiplying the calculated total angle by a conversion factor based on the reduction ratio of the reduction mechanism 23. s The motor midpoint, as the steering angle midpoint information, is stored in the reaction control unit 27.

[0028] The reaction control unit 27 performs reaction control to generate a steering torque T by controlling the drive of the reaction motor 22. h The corresponding steering reaction force. The reaction control unit 27 is based on the steering torque T detected by the torque sensor 25. h To calculate the target steering reaction force, and based on the calculated target steering reaction force and steering torque T h The target steering angle of the steering wheel 11 is calculated. The reaction control unit 27 calculates the rotation angle θ based on the reaction motor 22. a Calculated steering angle θ s The reaction control unit 27 calculates the difference between the target steering angle and the actual steering angle, and controls the power supply to the reaction motor 22 to eliminate this difference. The reaction control unit 27 uses the rotation angle θ of the reaction motor 22 detected by the rotation angle sensor 24. a Vector control is performed on the reaction motor 22.

[0029] The rotation unit 30 includes: a rotation shaft 31, a rotation motor 32, a reduction mechanism 33, a pinion shaft 34, a rotation angle sensor 35, and a rotation control unit 36. The rotation shaft 31 is along the vehicle width direction ( Figure 1 It extends in the left and right directions. The left and right steering wheels 12 are connected to the two ends of the rotating shaft 31 via tie rods 13.

[0030] The rotary motor 32 is the source of rotational force. For example, a three-phase brushless motor is used as the rotary motor 32. The rotary motor 32 is connected to the pinion shaft 34 via a reduction gear 33. The pinion teeth 34a of the pinion shaft 34 engage with the rack teeth 31a of the rotary shaft 31. The torque generated by the rotary motor 32 is applied as rotational force to the rotary shaft 31 via the pinion shaft 34. The rotary shaft 31 moves along the vehicle width direction as the rotary motor 32 rotates. Figure 1 (Moves left and right in the direction of the steering wheel 12). The rotation angle θ of the steering wheel 12. w It changes with the movement of the rotating shaft 31.

[0031] A rotation angle sensor 35 is installed in the rotary motor 32. The rotation angle sensor 35 detects the rotation angle θ of the rotary motor 32. b The rotation control unit 36 ​​performs rotation control to rotate the steering wheel 12 based on the steering state by driving the rotation motor 32. The rotation control unit 36 ​​is based on the rotation angle θ of the rotation motor 32 detected by the rotation angle sensor 35. b To calculate the rotation angle θ of the pinion shaft 34 p The rotation control unit 36 ​​is based on the steering angle θ. s The target rotation angle of the pinion shaft 34 is calculated using the target steering angle calculated by the reaction control unit 27. Here, the target rotation angle of the pinion shaft 34 is calculated based on the viewpoint of achieving a predetermined steering angle ratio. The rotation control unit 36 ​​calculates the target rotation angle of the pinion shaft 34 and the actual rotation angle θ. p The rotation control unit 36 ​​uses the rotation angle θ of the rotation motor 32 detected by the rotation angle sensor 35 to eliminate the difference between the two. b Vector control is performed on the rotating motor 32.

[0032] In the online steering system 10, since the steering wheel 11 is not restricted by the rotation unit 30, there is a possibility that the following events may occur.

[0033] That is, when the vehicle's power is on, the steering wheel 11 and the steering wheels 12 are synchronized. Therefore, the positional relationship between the steering wheel 11 and the steering wheels 12 remains at a positional relationship corresponding to a predetermined steering angle ratio. When the vehicle's power is off and a certain external force is applied to the steering wheel 11, there is a possibility that the steering wheel 11 may rotate. At this time, since the rotation shaft 31 does not rotate, the positional relationship between the steering wheel 11 and the steering wheels 12 may become different from the original positional relationship corresponding to the predetermined steering angle ratio.

[0034] Therefore, when the vehicle's power is turned back on, the steering system 10 performs synchronization control as an initial operation to synchronize the rotational position of the steering wheel 11 with the rotational position of the steering wheels 12. The steering system 10 may perform the following process as an example of synchronization control.

[0035] For example, if the steering wheel 11 rotates a predetermined angle counterclockwise (positive direction) while the vehicle's power is off, when the vehicle's power is turned back on, the steering wheel 11 rotates that predetermined angle clockwise (negative direction) through drive control of the reaction motor 22. Therefore, the positional relationship between the steering wheel 11 and the steering wheel 12 returns to its original positional relationship corresponding to the predetermined steering angle ratio.

[0036] like Figure 1 As illustrated, the reaction control unit 27 includes a storage unit 27a. When the vehicle's power supply switches from on to off (i.e., from on state to off state), the reaction control unit 27 will calculate the steering angle θ just before the vehicle's power supply switches from on to off. s The steering angle is stored in storage unit 27a as a reference angle. The reference steering angle is used as a reference to determine whether the steering wheel 11 has been rotated while the vehicle's power is off.

[0037] When the vehicle's power supply switches from off to on (i.e., from off state to on state), the reaction control unit 27 calculates the steering angle θ immediately after the vehicle's power supply is turned on by combining the reference steering angle stored in the storage unit 27a with the steering angle θ calculated immediately after the vehicle's power supply is turned on. s The comparison is used to determine whether the position of steering wheel 11 needs to be adjusted.

[0038] When the steering angle θ is the angle just before the vehicle's power is about to be cut off. s The reference steering angle and the steering angle θ immediately after the vehicle's power is turned on again. s When matched, the reaction control unit 27 determines that no position adjustment of the steering wheel 11 is required. This is due to the steering angle θ. sThere was no change after the vehicle's power was disconnected until it was restored, so it was noticeable that the steering wheel 11 did not rotate. The reaction control unit 27 initiated normal reaction control based on the steering torque T. h It generates a turning reaction force.

[0039] When the steering angle θ is the angle just before the vehicle's power is about to be cut off. s The reference steering angle and the steering angle θ immediately after the vehicle's power is turned on again. s When the steering wheel 11 is mismatched, the reaction control unit 27 determines that the steering wheel 11 needs to be adjusted and performs the adjustment. For example, the reaction control unit 27 calculates a reference steering angle and a steering angle θ immediately following the vehicle's power-on. s The difference between the reference steering angle and the target steering angle is controlled, and the power supply to the reaction motor 22 is adjusted to eliminate the difference. Specifically, the reaction control unit 27 sets the reference steering angle as the target steering angle, which is the steering angle θ. s The target value, and the steering angle θ s Executing feedback control makes the steering angle θ s The target steering angle is reached. When the target steering angle and the current steering angle θ... s When they are matched, the position of steering wheel 11 is adjusted.

[0040] Additionally, the reaction control unit 27 can use the following value as a reference steering angle: That is, immediately after the vehicle's power is switched from off to on, the reaction control unit 27 obtains the rotation angle θ of the pinion shaft 34 from the rotation control unit 36. p The rotation angle θ with the obtained pinion shaft 34 is calculated based on the steering angle ratio. p The corresponding steering angle θ s The reaction control unit 27 will adjust the calculated rotation angle θ of the pinion shaft 34. p The corresponding steering angle θ s Used as a reference steering angle. With this configuration, the rotational position of the steering wheel 11 can also be corrected to correspond to the rotational position of the steering wheel 12.

[0041] To correct the positional relationship between the steering wheel 11 and the steering wheel 12, the steering wheel 11 rotates automatically when the vehicle's power is turned on. This automatic rotation of the steering wheel may cause discomfort to the driver. The driver cannot start the vehicle after the power is turned on until the process of correcting the steering wheel's rotational position is complete. Therefore, the driver may experience stress.

[0042] Therefore, in this embodiment, based on the viewpoint of reducing driver discomfort or stress caused by the process of correcting the positional relationship between the steering wheel and the steering wheel, the following process is performed as an initial operation when the vehicle's power is switched from off to on.

[0043] like Figure 2 As illustrated in the flowchart, the reaction control unit 27 first calculates the displacement Δθ of the rotational position of the steering wheel 11 relative to the rotational position of the steering wheel 12 (step S101). The displacement Δθ is also the amount of rotation of the steering wheel 11, which is required to rotate by this amount to correct the rotational position of the steering wheel 11 to a position corresponding to the rotational position of the steering wheel 12. The reaction control unit 27 calculates the displacement Δθ, for example, using expression (A).

[0044] Δθ=|θ s0 -θ s |…(A)

[0045] Here, “θ s0 "θ is the reference steering angle stored in storage unit 27a just before the vehicle's power is about to be disconnected." s "θ" refers to the steering angle immediately following the vehicle's power being switched on. s The symbol, for example, relative to the neutral steering position (θ) of steering wheel 11. s The right turn direction (=0°) is defined as negative, while the left turn direction is defined as positive.

[0046] Then, the reaction force control unit 27 determines whether the displacement Δθ is less than the first angle threshold θ1 (step S102). The first angle threshold θ1 is set, for example, based on the angle setting such that when the rotation position of the steering wheel 12 is corrected at this angle to correspond to the rotation position of the steering wheel 11 when the vehicle begins to move, the driver will not feel uncomfortable.

[0047] When the displacement Δθ is less than the first angle threshold θ1 (yes in step S102), the reaction control unit 27 terminates the process. In this case, the steering wheel 11 will not rotate automatically.

[0048] When the displacement Δθ is equal to or greater than the first angle threshold θ1 (not in step S102), the reaction control unit 27 determines whether the displacement Δθ is greater than the second angle threshold θ2 (step S103). The second angle threshold θ2 is set, for example, based on the following angle setting: when the vehicle starts to move, the driver may feel uncomfortable when the rotation position of the steering wheel 12 is corrected at this angle to correspond to the rotation position of the steering wheel 11.

[0049] When the displacement Δθ is greater than the second angle threshold θ2 (yes in step S103), the reaction control unit 27 executes the first synchronization control (step S104) and ends the process. The first synchronization control is used to correct the rotational position of the steering wheel 11 to a position corresponding to the rotational position of the steering wheel 12. The reaction control unit 27 controls the power supply to the reaction motor 22, making the displacement Δθ calculated in step S101 become "0". More specifically, the reaction control unit 27 references the steering angle θ... s0 Set the target steering angle, and adjust the steering angle θ. s Execute feedback control to make the steering angle θ s The set target steering angle is achieved. When the steering angle θ... s The first synchronization control is completed when the target steering angle is reached (i.e., matched).

[0050] When the displacement Δθ is not greater than the second angle threshold θ2 (not in step S103), that is, when the displacement Δθ is equal to or less than the second angle threshold θ2, the reaction control unit 27 executes the second synchronization control (step S105) and ends the process. The second synchronization control is used to reduce the displacement Δθ to a lower value rather than reducing the displacement Δθ to "0". By executing the second synchronization control, the rotational position of the steering wheel 11 is corrected to a position such that when the vehicle begins to move, even when the rotational position of the steering wheel 12 is corrected to correspond to the rotational position of the steering wheel 11, the driver will not feel discomfort. For example, the reaction control unit 27 can correct the rotational position of the steering wheel 11 so that the steering angle θ s The first angle threshold θ1 is reached. The reaction control unit 27 sets the first angle threshold θ1 as the target steering angle and adjusts the steering angle θ. s Execute feedback control to make the steering angle θ s The set target steering angle is achieved. When the steering angle θ... s When the target steering angle is reached (i.e. matched), the second synchronization control is completed.

[0051] When the steering angle θ calculated by the reaction control unit 27 s The current rotation angle θ of the pinion shaft 34 after the process of adjusting the rotational position of the steering wheel 11 has been completed by the reaction control unit 27. p When they do not correspond, the control unit 36 ​​rotates the pinion shaft 34 by an angle θ. p Maintain the current rotation angle θ p Then, the rotation control unit 36 ​​controls the power supply to the rotation motor 32, for example, causing the pinion shaft 34 to rotate at an angle θ when the vehicle begins to move. p Corrected to the steering angle θ s The corresponding angle. The rotation control unit 36 ​​is based on the vehicle speed or steering torque T.h To determine whether the vehicle has started moving.

[0052] In this embodiment, the first angle threshold θ1 corresponds to the allowable value of displacement Δθ. The second angle threshold θ2 corresponds to the limit value of displacement Δθ. The first synchronization control corresponds to a first correction process that rotates the steering wheel 11 so that the displacement Δθ becomes zero. The second synchronization control corresponds to a second correction process that rotates the steering wheel 11 so that the displacement Δθ becomes the first angle threshold (allowable value).

[0053] The behavior of the steering wheel 11 and the steering wheel 12 after the vehicle is powered on, until the rotational positions of the steering wheel 11 and the steering wheel 12 are synchronized, will be described in three cases.

[0054] Here, it is assumed that immediately after the vehicle's power is turned on, the steering wheel 12 is in a neutral steering position (rotation angle θ) corresponding to the vehicle's linear motion. w =0°). The steering wheel 11 must be inherently located in the neutral steering position corresponding to the straight-line motion of the vehicle (steering angle θ). s =0°). The steering angle ratio is used as the turning angle θ. w With steering angle θ s The ratio between them is "1:1", that is, the value of the steering angle ratio is "1".

[0055] First, the first scenario will be described. For example... Figure 3 As illustrated in part (a), immediately after the vehicle's power is switched on, the steering wheel 11 is positioned at a rotational position where its rotational position relative to the steering wheel 12 has shifted by an angle α less than the first angle threshold θ1 in the clockwise direction (negative direction). That is, the displacement Δθ of the steering wheel 11's rotational position relative to the steering wheel 12's rotational position is angle α. In this case, neither the first nor the second synchronization control is executed on the steering wheel 11, and the state of the steering system 10 transitions to a state where normal reaction control and rotation control (i.e., SBW normal control) can be executed. Figure 3 As illustrated in part (b), for example, when the vehicle begins to move (i.e., at startup), the rotational position of the steering wheel 12 is synchronized with the rotational position of the steering wheel 11. Here, since the value of the steering angle ratio is "1", the steering wheel 12 is rotated clockwise by an angle α.

[0056] Next, the second scenario will be described. For example... Figure 4As illustrated in part (a), immediately after the vehicle's power is switched on, the steering wheel 11 is positioned at a rotational position where its rotational position relative to the steering wheel 12 has shifted by an angle β greater than the second angle threshold θ2 in the clockwise direction (negative direction). That is, the displacement Δθ of the steering wheel 11's rotational position relative to the rotational position of the steering wheel 12 is angle β. In this case, first synchronization control is performed on the steering wheel 11. Figure 4 As illustrated in section (b), by executing the first synchronization control, the rotational position of the steering wheel 11 is synchronized with the rotational position of the steering wheel 12. Here, since the steering angle ratio is "1", the steering wheel 11 rotates counterclockwise by an angle β as displacement Δθ. After the first synchronization control is completed, the state of the steering system 10 changes to a state where normal reaction control and rotation control can be executed.

[0057] Finally, the third case will be described below. For example... Figure 5 As illustrated in part (a), immediately after the vehicle's power is switched on, the steering wheel 11 is positioned at a rotational position relative to the steering wheel 12, shifted clockwise (negative direction) by an angle γ, where the angle γ is equal to or greater than a first angle threshold θ1 and equal to or less than a second angle threshold θ2. That is, the displacement Δθ of the steering wheel 11's rotational position relative to the steering wheel 12's rotational position is the angle γ. In this case, a second synchronization control is performed on the steering wheel 11. Figure 5 As illustrated in part (b), the steering wheel 11 rotates counterclockwise (clockwise) by the absolute value of the difference between a first angle threshold θ1 and angle γ. After this, the steering system 10 transitions to a state where normal reaction control and turn control (i.e., SBW normal control) can be executed. Figure 5 As illustrated in section (c), for example, when the vehicle begins to move (i.e., at startup), the rotational position of the steering wheel 12 is synchronized with the rotational position of the steering wheel 11. Here, since the value of the steering angle ratio is "1", the steering wheel 12 rotates clockwise by the same angle as the first angular threshold θ1, which is the displacement Δθ.

[0058] Therefore, according to this embodiment, the following advantages can be obtained. (1) When the vehicle is powered on and the displacement Δθ of the rotational position of the steering wheel 11 relative to the rotational position of the steering wheel 12 is less than the first angle threshold θ1, synchronization control is not performed. Overall, this reduces the likelihood that the steering wheel 11 will automatically rotate when the vehicle is powered on, because synchronization control is not performed when the displacement Δθ is less than the first angle threshold θ1. Therefore, driver discomfort can be reduced. Since the likelihood of the driver waiting for the position adjustment of the steering wheel 11 to be completed is reduced, the driver's stress can be reduced.

[0059] (2) When the vehicle's power is turned on and the displacement Δθ is greater than the second angle threshold θ2, the first synchronization control is executed. By executing the first synchronization control, the rotational position of the steering wheel 11 is completely synchronized with the position corresponding to the rotational position of the steering wheel 12 (i.e., completely matched with the position corresponding to the rotational position of the steering wheel 12). This prevents, for example, the rotational position of the steering wheel 12 from suddenly changing to the position corresponding to the rotational position of the steering wheel 11 when the vehicle begins to move. Therefore, the driver can start the vehicle smoothly without feeling discomfort.

[0060] (3) When the vehicle's power is turned on and the displacement Δθ is equal to or greater than the first angle threshold θ1 and equal to or less than the second angle threshold θ2, the second synchronization control is executed. By executing the second synchronization control, the rotation position of the steering wheel 11 is adjusted such that the steering angle θ s The first angle threshold θ1 is reached. The time from the start to the stop of the automatic rotation of the steering wheel 11 is shortened because the rotation position of the steering wheel 11 is not completely synchronized with the position corresponding to the rotation position of the steering wheel 12 (i.e., it is not completely matched with the position corresponding to the rotation position of the steering wheel 12). Since the time waiting for the steering wheel 11 to stop rotating is shortened, the driver's stress can be reduced.

[0061] (4) As described in (1) and (3), when the vehicle is powered on and the rotation position of the steering wheel 11 is not fully synchronized with the rotation position of the steering wheel 12, for example, when the displacement Δθ is less than the first angle threshold θ1, the rotation position of the steering wheel 12 is changed to a position corresponding to the rotation position of the steering wheel 11 when the vehicle begins to move. Here, the first angle threshold θ1 is set based on an angle at which the driver will not feel discomfort when the rotation position of the steering wheel 12 is corrected to correspond to the rotation position of the steering wheel 11 when the vehicle begins to move. Therefore, when the vehicle begins to move, the rotation position of the steering wheel 12 can be changed to a position corresponding to the rotation position of the steering wheel 11 while suppressing the driver's discomfort.

[0062] The aforementioned implementation method can be modified as follows. For example... Figure 1 As indicated by the lines in the diagram, in the aforementioned embodiments, for example, when the notification unit 28 is located in the vehicle's passenger compartment, the reaction control unit 27 can use the notification unit 28 to notify the driver of the start and end of the steering wheel 11 position adjustment. Examples of notification operations using the notification unit 28 include displaying text messages and issuing voice messages. With this configuration, since the driver can recognize that the steering wheel 11 is automatically rotating and that the automatically rotating steering wheel 11 has automatically stopped, driver discomfort can be reduced.

[0063] In the aforementioned embodiment, a rotation angle θ based on the reaction motor 22 was used. aCalculated steering angle θ s However, if the steering system 10 employs a configuration that includes a steering angle sensor, the steering angle θ detected by the steering angle sensor can also be used. s .

[0064] In the aforementioned embodiment, the steering angle ratio is set to an appropriate value based on product specifications, etc. The steering angle ratio can be, for example, "θ". s θ w =1:1" or "θ" s θ w =1:3". For example, when the steering angle ratio is θ s θ w =1:3” and steering angle θ s When the displacement is 10°, the rotation angle θ w The displacement is 30°. Therefore, more preferably, the steering angle θ is adjusted. s and rotation angle θ w They are perfectly synchronized with each other.

[0065] In the foregoing embodiments, when the vehicle's power is turned on and the displacement Δθ is equal to or greater than the first angle threshold θ1 and equal to or less than the second angle threshold θ2, the second synchronization control is executed; however, the first synchronization control may also be executed. In this case, at least the same advantages as described above in (2) can be obtained.

[0066] In the aforementioned embodiments, when the vehicle's power is turned on and the displacement Δθ is greater than the second angle threshold θ2, the first synchronization control is executed; however, the second synchronization control can also be executed. In this case, at least the same advantages as described above in (3) and (4) can be obtained.

[0067] In the aforementioned embodiments, when the vehicle's power is on and the rotational position of the steering wheel 11 is not fully synchronized with the rotational position of the steering wheel 12—for example, when the displacement Δθ is less than the first angle threshold θ1—the rotational position of the steering wheel 12 synchronizes with the rotational position of the steering wheel 11 when the vehicle begins to move. However, the following process can be performed: That is, if the first angle threshold θ1 is set to a small value that will not cause discomfort to the driver when the vehicle begins to move, the rotation control unit 36 ​​may not perform the process of synchronizing the rotational position of the steering wheel 12 with the rotational position of the steering wheel 11 when the vehicle begins to move.

[0068] In the foregoing embodiments, the vehicle's power supply may include, for example, an accessory power supply (ACC power supply) or an ignition power supply (IG power supply). The reaction control unit 27 and the rotation control unit 36 ​​may be configured as a single control unit.

[0069] In the aforementioned embodiment, the vehicle's steering system 10 has a so-called linkageless structure, in which power transmission between the steering shaft 21 and the steering wheel 12 is cut off. However, the vehicle's steering system 10 may also have a structure capable of cutting off power transmission between the steering shaft 21 and the steering wheel 12 via a clutch. When the clutch is disengaged, power transmission between the steering wheel 11 and the steering wheel 12 is cut off. When the clutch is engaged, power is transmitted between the steering wheel 11 and the steering wheel 12.

Claims

1. A steering system, characterized in that... include: Steering shaft (21), which rotates according to the operation of steering wheel (11), and the power transmission between steering shaft (21) and the steering wheels of the vehicle is cut off; A reaction motor (22) configured to generate a steering reaction force, which is a torque applied to the steering shaft (21) in the opposite direction to the steering direction; as well as A control unit configured to control the reaction motor (22), The control unit has the function of performing a correction process when the vehicle's power is turned on and the rotational position of the steering wheel (11) is different from the correct rotational position corresponding to the rotational position of the steering wheels. This correction process uses the reaction motor (22) to rotate the steering wheel (11) so that the displacement of the steering wheel (11) relative to the correct rotational position is reduced. The control unit is configured to: perform the correction process when the displacement is equal to or greater than a predetermined allowable value, and not perform the correction process when the displacement is less than the allowable value. The correction process includes a first correction process of rotating the steering wheel (11) to make the displacement zero and a second correction process of rotating the steering wheel (11) to make the displacement the allowable value; and The control unit is configured to perform the first correction process when the displacement is greater than a predetermined limit value, and to perform the second correction process when the displacement is equal to or greater than the allowable value and equal to or less than the limit value.

2. The steering system according to claim 1, characterized in that... Also includes: A rotating shaft (31) causes the steering wheel to rotate, and the power transmission between the steering wheel (11) and the rotating shaft (31) is cut off; as well as A rotary motor (32) is configured to generate rotational force, which is a torque applied to the rotating shaft (31) to rotate the steering wheel. The control unit is configured to, when the vehicle begins to move, control the rotation motor (32) so that the rotation position of the steering wheel (11) is different from the rotation position corresponding to the rotation position of the steering wheel, so that the rotation position of the steering wheel becomes the position corresponding to the rotation position of the steering wheel (11).

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