Steering system

Abstract

A steering system includes a steering shaft (21); a motor (22) configured to generate torque applied to the steering shaft (21); and a control unit configured to control the motor (22). The control unit has a function of performing steering angle feedback control as an adjustment process for adjusting the rotational position of a steering wheel (11), the steering angle feedback control being used to achieve a target steering angle, which is the rotational angle of the steering wheel (11), set based on the viewpoint of adjusting the rotational position of the steering wheel (11). The control unit is configured to set a limit value for limiting the range of variation of the target steering angle relative to the steering angle at each moment during the period when the automatic rotation of the steering wheel (11) is hindered while the adjustment process is being executed.

Description

Technical Field

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

[0002] A so-called steer-by-wire system already exists in which the power transmission between the steering wheel and the steering wheels is cut off. This steering system includes a reaction force mechanism and a steering mechanism. The reaction force mechanism includes a reaction force motor as the source of the steering reaction force applied to the steering shaft, and the steering mechanism includes a steering motor as the source of the steering force for changing the direction of the steering wheels. When the vehicle is in motion, the control unit for the steering system generates a steering reaction force by controlling the power supply to the reaction force motor and changes the direction of the steering wheels by controlling the power supply to the steering motor.

[0003] In this steer-by-wire system, the steering wheel is not restricted by the steering mechanism. Therefore, when an external force is applied to the steering wheel while the vehicle is powered off, the steering wheel may rotate. At this time, since the steering wheels are not engaged, 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 steering wheel's turning angle and the steering wheel's steering angle.

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

[0005] The steering system disclosed in JP 2006-321434 A reliably improves the deviation in the positional relationship between the steering wheel and the steering wheels. However, the steering system disclosed in JP 2006-321434A has the following problem: It is conceivable that while the adjustment process for adjusting the steering wheel's rotational position is being executed, the driver may be holding the steering wheel, or the automatically rotating steering wheel may come into contact with the driver's body or an object. In this situation, because the automatic rotation of the steering wheel is hindered, the difference between the target steering angle (which is the target value of the steering wheel's rotation angle) and the actual steering angle may increase. Therefore, when the cause hindering the automatic rotation of the steering wheel is resolved, the steering wheel may suddenly rotate to the target steering angle, and the driver may experience discomfort due to the sudden rotation of the steering wheel.

[0006] The present invention provides a steering system that can reduce driver discomfort in situations where, while the automatic adjustment process for adjusting the rotational position of the steering wheel is being performed, the automatic rotation of the steering wheel is impeded and subsequently the impeded automatic rotation is released.

[0007] According to one aspect of the invention, a steering system is provided, comprising: a steering shaft that rotates with operation of a steering wheel; a motor configured to generate torque applied to the steering shaft; and a control unit configured to control the motor. The control unit has the function of performing steering angle feedback control as an adjustment process for adjusting the rotational position of the steering wheel, the steering angle feedback control being used to make the steering angle, which is the rotational angle of the steering wheel, reach a target steering angle set based on the viewpoint of adjusting the rotational position of the steering wheel. The control unit is configured to set a limit value for limiting the range of variation of the target steering angle relative to the steering angle at each moment during the period when the automatic rotation of the steering wheel is hindered, provided that the automatic rotation of the steering wheel is hindered while the adjustment process is being performed.

[0008] When the automatic rotation of the steering wheel is hindered while the adjustment process for adjusting the steering wheel's rotation position is being executed, the range of change of the target steering angle is limited at each moment during the period of hindered automatic rotation, relative to a set limit value for the steering angle. Therefore, the increase in the difference between the target steering angle and the steering angle can be suppressed. As a result, when the cause hindering the automatic rotation of the steering wheel is resolved, sudden changes in the steering wheel's rotation position can be suppressed. Since undesirable steering wheel movements are suppressed, driver discomfort can be reduced.

[0009] In a steering system according to this aspect, the control unit may have a limiting function that restricts the amount of change of the target steering angle per unit time. In this case, the control unit may be configured to disable the limiting function during the period when the automatic rotation of the steering wheel is hindered while the adjustment process is being performed.

[0010] Using this configuration, regardless of the amount of change in the target steering angle during a predetermined operating cycle, the value of the target steering angle can be limited to a limit value relative to the steering angle set at each moment.

[0011] In a steering system according to this aspect, the adjustment process may include: a process that corresponds the rotational position of the steering wheel to the steering position of the vehicle's steering wheels when the vehicle's power supply is switched from a de-off state to a OFF state.

[0012] With this configuration, when the automatic rotation of the steering wheel is hindered while the process of aligning the rotation position of the steering wheel with the steering position of the vehicle's steering wheels is being executed, the driver's discomfort when the obstruction is removed can be reduced.

[0013] The steering system according to this aspect may also include a stop mechanism configured to limit the rotation of the steering wheel. In this case, the adjustment process may include the following: controlling the motor to rotate the steering wheel to a first operating end and then rotating the steering wheel in the opposite direction to a second operating end, and calculating the neutral position of the steering wheel based on the rotation angle of the motor at the start and end points of the reverse rotation of the steering wheel.

[0014] This configuration can reduce driver discomfort when the automatic rotation of the steering wheel is hindered while the process of calculating the neutral position of the steering wheel is being executed.

[0015] In a steering system according to this aspect, the power transmission between the steering shaft and the vehicle's steering wheels can be cut off. The motor can be configured to generate a steering reaction force, which is applied to the steering shaft and is a torque in the direction opposite to the steering direction.

[0016] With this configuration, the steering system is suitable for so-called steer-by-wire systems.

[0017] Using the steering system according to this aspect of the invention, driver discomfort can be reduced in situations where the automatic rotation of the steering wheel is hindered and subsequently the hindered automatic rotation is released while the adjustment process for automatically adjusting the rotational position of the steering wheel is being performed. Attached Figure Description

[0018] 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:

[0019] Figure 1 This is a simplified diagram illustrating the configuration of the steering system according to the first embodiment;

[0020] Figure 2 This is a block diagram illustrating the reaction force control unit according to the first embodiment;

[0021] Figure 3 It is a graph showing the time-based variation of the target steering angle and the steering angle according to the first embodiment;

[0022] Figure 4 This is a rear view of the steering wheel according to the second embodiment; and

[0023] Figure 5 This is a block diagram illustrating the reaction force control unit according to the third embodiment. Detailed Implementation

[0024] First Implementation Method

[0025] The steering system according to a first embodiment of the present invention will be described below. Figure 1 As shown, the vehicle's steering system 10 includes a reaction force unit 20 that applies a steering reaction force to the vehicle's steering wheel 11 and a steering unit 30 that changes the direction of the vehicle's steering wheels 12. The steering reaction force represents a torque applied in the direction opposite to the direction of operation of the steering wheel 11 operated by the driver. By applying a steering reaction force to the steering wheel 11, the driver can be given an appropriate responsiveness.

[0026] The reaction force unit 20 includes a steering shaft 21, a reaction force motor 22, a reduction mechanism 23, a rotation angle sensor 24, a torque sensor 25, and a reaction force control unit 27. The steering shaft 21 is connected to a steering wheel 11.

[0027] The reaction motor 22 is the source from which the steering reaction force is generated. 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.

[0028] A rotation angle sensor 24 is installed in the reaction force motor 22. The rotation angle sensor 24 detects the rotation angle θ of the reaction force motor 22. a A torque sensor 25 is disposed in the portion of the steering shaft 21 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 .

[0029] The reaction force control unit 27 is based on the rotation angle θ of the reaction force motor 22 detected by the rotation angle sensor 24. a Calculate the steering angle θ, which is the rotation angle of the steering axis 21. s The reaction force control unit 27 controls the rotation angle θ of the reaction force motor 22 corresponding to the neutral steering position of the steering wheel 11. a (In the following text, the rotation angle θ corresponding to this neutral turning position) a The number of revolutions is counted using a reference point (referred to as the "motor midpoint"). The reaction force control unit 27 calculates the rotation angle θ by using the motor midpoint as the origin. a The total angle obtained by accumulating the angles is calculated, and the steering angle θ of the steering wheel 11 is calculated 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 force control unit 27.

[0030] The reaction force control unit 27 performs actions to generate a steering torque T by controlling the drive of the reaction force motor 22. h Correspondingly, the reaction force control unit 27 controls the steering reaction force based on the steering torque T detected by the torque sensor 25. h 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 force control unit 27 calculates the rotation angle θ based on the reaction force motor 22. a The calculated steering angle θ s The difference between the target steering angle and the control angle is calculated, and the power supply to the reaction force motor 22 is controlled to eliminate the difference. The reaction force control unit 27 uses the rotation angle θ of the reaction force motor 22 detected by the rotation angle sensor 24. a Vector control is performed on the reaction motor 22.

[0031] The steering unit 30 includes a steering shaft 31, a steering motor 32, a reduction mechanism 33, a pinion shaft 34, a rotation angle sensor 35, and a steering control unit 36. The steering shaft 31 is located along the vehicle width direction ( Figure 1 (Extending in the left and right directions). The left and right steering wheels 12 are respectively connected to the two ends of the steering shaft 31 via tie rods 13.

[0032] The reversing motor 32 is the source from which the reversing force is generated. For example, a three-phase brushless motor is used as the reversing motor 32. The reversing 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 reversing shaft 31. The torque generated by the reversing motor 32 is applied as a reversing force to the reversing shaft 31 via the pinion shaft 34. The reversing shaft 31 rotates along the vehicle width direction as the reversing motor 32 rotates. Figure 1 The steering wheel 12 moves in the left-right direction. The steering angle θ of the steering wheel 12... w It changes with the movement of the reversing shaft 31.

[0033] A rotation angle sensor 35 is disposed in the reversing motor 32. The rotation angle sensor 35 detects the rotation angle θ of the reversing motor 32. b The steering control unit 36 ​​performs steering control for changing the direction of the steering wheels 12 based on the steering state by driving the steering motor 32. The steering control unit 36 ​​bases its control on the rotation angle θ of the steering motor 32 detected by the rotation angle sensor 35. b Calculate the rotation angle θ of the pinion shaft 34. pThe steering control unit 36 ​​calculates the target rotation angle of the pinion shaft 34 based on the target steering angle calculated by the reaction force control unit 27. Here, the target rotation angle of the pinion shaft 34 is calculated from the perspective of achieving (i.e., obtaining) a predetermined steering angle ratio. The steering control unit 36 ​​calculates the target rotation angle of the pinion shaft 34 and the actual rotation angle θ. p The difference between the two is eliminated by controlling the power supply to the reversing motor 32. The reversing control unit 36 ​​uses the rotation angle θ of the reversing motor 32 detected by the rotation angle sensor 35. b Vector control is performed on the reversing motor 32.

[0034] The functional configuration of the reaction force control unit 27 will be described in detail below. For example... Figure 2 As shown, the reaction force control unit 27 includes a target steering angle calculation unit 51, a warning setting unit 52, a warning processing unit 53, a steering angle feedback control unit 54, and a power control unit 55.

[0035] The target steering angle calculation unit 51 is based on the steering torque T detected by the torque sensor 25. h To calculate the target steering torque, and through the steering torque T h Feedback control is used to calculate the target steering reaction force, so that the steering torque T h The calculated target steering torque is achieved. The target steering angle calculation unit 51 is based on the calculated target steering reaction force and steering torque T. h To calculate the target steering angle θ of steering wheel 11 s *. The target steering angle calculation unit 51 calculates the target steering angle θ, for example, based on an ideal model. s * In this ideal model, the reaction force and steering torque T of the target are... h When the sum is used as the input torque, the steering angle θ of the steering wheel 11 corresponding to the ideal steering angle based on that input torque is... s It is modeled in advance through experiments or simulations.

[0036] Warning setting unit 52 sets the target steering angle θ to limit the target's turning angle during a predetermined operating cycle (e.g., one operating cycle). s The limit value Δθ of the change in *. Based on the limit value Δθ set by the warning setting unit 52, the warning processing unit 53 limits the target steering angle θ calculated by the target steering angle calculation unit 51. s *Changes.

[0037] The target steering angle θ during the predetermined operating cycle sThe so-called time-based change limit function, which limits the change of * to a predetermined limit value Δθ, is implemented by the warning setting unit 52 and the warning processing unit 53.

[0038] Steering angle feedback control unit 54 receives the target steering angle θ processed by warning processing unit 53. s * and the rotation angle θ based on the reaction force motor 22 a Calculated steering angle θ s The steering angle feedback control unit 54, based on the steering angle θ, s Feedback control is used to calculate the target steering reaction force T*, so that the rotation angle θ based on the reaction force motor 22 is... a Calculated steering angle θ s Achieve the target steering angle θ s *

[0039] The power control unit 55 supplies power to the reaction motor 22 corresponding to the target steering reaction force T*. Specifically, the power control unit 55 calculates a current command value for the reaction motor 22 based on the target steering reaction force T*. The power control unit 55 calculates the difference between the current command value and the actual current value detected by a sensor (not shown), and controls the power supply to the reaction motor 22 to eliminate this difference. Therefore, the reaction motor 22 generates torque corresponding to the target steering reaction force T*.

[0040] In the steering-by-wire system 10, since the steering wheel 11 is not restricted by the steering unit 30, the following events may occur: When the vehicle is powered 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 is maintained based on a predetermined steering angle ratio. When a certain external force is applied to the steering wheel 11 while the vehicle is powered off, the steering wheel 11 may rotate. At this time, since the steering shaft 31 is not working, the positional relationship between the steering wheel 11 and the steering wheels 12 may become different from the original positional relationship based on the predetermined steering angle ratio.

[0041] Therefore, the steering system 10 has the function of automatically adjusting the rotational position of the steering wheel 11 as an initial operation when the vehicle power is re-engaged. For example, if the steering wheel 11 rotates a predetermined angle counterclockwise (positive direction) during vehicle power deactivation, when the vehicle power is re-engaged, the steering wheel 11 rotates a predetermined angle clockwise (negative direction) by drive control of the reaction force motor 22. Thus, the positional relationship between the steering wheel 11 and the steering wheel 12 returns to the original positional relationship based on a predetermined steering angle ratio.

[0042] like Figure 1As shown, the reaction force control unit 27 includes a storage unit 27m. When the vehicle's power supply switches from on to off (i.e., from on state to off state), the reaction force control unit 27 will store the steering angle θ calculated before the switch. s The reference steering angle is stored in storage unit 27m. This reference steering angle is used as a reference for determining whether the steering wheel 11 has rotated during the period when the vehicle power is turned off.

[0043] When the vehicle's power supply switches from off to on (i.e., from off state to on state), the reaction force control unit 27 compares the reference steering angle stored in the storage unit 27m with the steering angle θ calculated immediately after the vehicle's power is turned on. s A comparison is made to determine whether it is necessary to adjust the position of the steering wheel 11.

[0044] The steering angle θ before the vehicle's power is cut off s The reference steering angle is the steering angle θ immediately after the vehicle is re-energized. s When the forces are matched, the reaction force control unit 27 determines that position adjustment of the steering wheel 11 is unnecessary. This is because the steering angle θ remains constant during the period from when the vehicle's power is cut off until the power is re-engaged. s There was no change, so it's clear that the steering wheel 11 did not rotate. The reaction force control unit 27 initiated operation based on the steering torque T. h Normal reaction force control that generates steering reaction force.

[0045] The steering angle θ before the vehicle's power is cut off s The reference steering angle is the steering angle θ immediately after the vehicle is re-energized. s When the steering wheel and steering wheel are mismatched, the reaction force control unit 27 determines that position adjustment is necessary and performs the adjustment. For example, the reaction force control unit 27 calculates the reference steering angle and the steering angle θ immediately after the vehicle is powered on. s The difference between the reference steering angle and the steering angle θ immediately after the vehicle is powered on is eliminated. Specifically, the reaction force control unit 27 calculates the power supply to the reaction force motor 22 to eliminate the difference. s The target steering angle θ is calculated from the difference between them. s * and perform for steering angle θ s Feedback control makes the steering angle θ s Achieve the calculated target steering angle θ s * When the reference steering angle is different from the current steering angle θ s When they are matched, the position adjustment of steering wheel 11 is complete.

[0046] Additionally, the reaction force control unit 27 can use the following value as a reference steering angle: That is, the reaction force control unit 27 immediately obtains the rotation angle θ of the pinion shaft 34 from the steering control unit 36 ​​after the vehicle's power supply switches from off to on. p And based on the steering angle ratio, the rotation angle θ with the obtained pinion shaft 34 is calculated. p The corresponding steering angle θ s The reaction force control unit 27 uses the calculated rotation angle θ of the pinion shaft 34. p The corresponding steering angle θ s This serves as a reference steering angle. Using this configuration, the rotational position of the steering wheel 11 can be corrected to correspond to the steering position of the steering wheel 12.

[0047] In a steering system 10 that automatically adjusts the rotational position of the steering wheel 11, the following problem may exist. Specifically, it is conceivable that while the adjustment process for adjusting the rotational position of the steering wheel 11 is being executed, the driver may be holding the steering wheel 11, or the automatically rotating steering wheel 11 may be in contact with the driver's body or some other object. In this situation, because the automatic rotation of the steering wheel 11 is hindered, the target steering angle θ of the steering wheel 11 is affected. s *Compared to actual steering angle θ s The difference between them is likely to increase. This is because the target steering angle θ s *The variable limit function gradually increases to the final target steering angle θ. s *, but the actual steering angle θ s For example, this does not change when the steering wheel 11 is held. Therefore, when the cause preventing the steering wheel 11 from rotating automatically is resolved, for example, when the driver releases their hands from the steering wheel 11, the steering wheel 11 may suddenly rotate to the target steering angle θ. s * and the driver may feel uncomfortable due to the sudden rotation of the steering wheel 11.

[0048] Therefore, in this embodiment, when the automatic rotation of the steering wheel 11 is hindered while the process of adjusting the rotational position of the steering wheel 11 is being performed, the reaction force control unit 27 adopts the following configuration to suppress the sudden rotation of the steering wheel 11 when the cause of the obstacle to the automatic rotation of the steering wheel 11 is resolved.

[0049] like Figure 2As illustrated, the reaction force control unit 27 includes a determination unit 56. The determination unit 56 determines whether the automatic rotation of the steering wheel 11 is obstructed while the process of adjusting the rotational position of the steering wheel 11 is being executed. For example, the determination unit 56 determines that the automatic rotation of the steering wheel 11 is obstructed when at least one of the following two conditions (A1) and (A2) is met. When neither condition (A1) nor (A2) is met, the determination unit 56 determines that the automatic rotation of the steering wheel 11 is not obstructed.

[0050] (A1)|θ s *|-|θ s |≥|θ th |

[0051] Here, “θ s * represents the target steering angle. Target steering angle θ s The value of * gradually shifts towards the final target angle θ through the change constraint function. s *Change. “θ” s "Based on the rotation angle θ of the reaction force motor 22" a The calculated steering angle. "θ" th "This is the angle difference threshold. The angle difference threshold is the target steering angle θ." s *and steering angle θ s The difference between the values ​​is used as a reference for determining whether the automatic rotation of the steering wheel 11 is obstructed.

[0052] (A2)|T h |≥|T th |

[0053] Here, "T" h "The steering torque is detected by torque sensor 25." th "This is the torque threshold. The torque threshold is the steering torque T used as a reference to determine whether the automatic rotation of the steering wheel 11 is hindered." h The value of .

[0054] When the determination result from the determination unit 56 indicates that the automatic rotation of the steering wheel is obstructed, the warning setting unit 52 performs the following two processes (B1) and (B2).

[0055] (B1) The variation restriction function is disabled, that is, the function used to limit the target steering angle θ. s The limit value Δθ for the change of * is disabled. (B2) Set the upper limit value θ UL and lower limit θ LL As a means to limit the target steering angle θ s * The limit of the range of variation.

[0056] The process of disabling the change restriction function (B1) includes not only the case where the execution of the change restriction function is stopped, but also the case where the change restriction process is actually ineffective due to the execution of the process (B2).

[0057] As expressed in expression (C1), the warning setting unit 52 sets the warning angle θ based on the reaction force motor 22. a The calculated turning angle θ at each moment s Add the set value α to calculate the upper limit value θ UL The setpoint α is based on suppressing the target steering angle θ. s *and steering angle θ s The view that the difference between them increases—that is, the suppression of the steering angle θ when the cause of the resistance to automatic rotation of the steering wheel 11 is resolved. s The sudden change in perspective—and the setting.

[0058] θ UL＝ θ s +α…(C1)

[0059] As expressed in expression (C2), the warning setting unit 52 determines the warning setting unit based on the rotation angle θ of the reaction force motor 22. a The calculated turning angle θ at each moment s The lower limit θ is calculated by subtracting the set value α from the middle value. LL .

[0060] θ UL＝ θ s -α…(C2)

[0061] When the change restriction function is disabled, regardless of the target steering angle θ in the predetermined operating cycle... s Regardless of the change in *, the target can be turned by the angle θ. s The value of * is limited to the steering angle θ at each time step. s The set upper limit value θ UL and lower limit θ LL .

[0062] The alert processing unit 53 is based on the upper limit value θ set by the alert setting unit 52. UL and lower limit θ LL To perform the calculation of the target steering angle θ by the target steering angle calculation unit 51 s * A restriction is applied. That is, the warning processing unit 53 adjusts the target turning angle θ. s The value of * and the upper limit θ UL Compare and set the target turning angle θ s The value of * and the lower limit θ LL Comparison. When the target turning angle θ sThe value of * is greater than the upper limit value θ. UL At that time, the warning processing unit 53 will turn the target by an angle θ. s The value of * is limited to the upper limit θ. UL When the target turning angle θ s The value of * is less than the lower limit value θ LL At that time, the warning processing unit 53 will turn the target by an angle θ. s The value of * is limited to the lower limit θ. LL The target steering angle θ, which has been restricted by the warning processing unit 53, is... s *The final target steering angle θ s *Provided to the steering angle feedback control unit 54. At the target steering angle θ s The value of * is at the upper limit θ UL With the lower limit value θ LL Within the range between, the target steering angle θ calculated by the target steering angle calculation unit 51 is... s *The final target steering angle θ is taken without any changes. s *Provided to the steering angle feedback control unit 54.

[0063] The following describes the time-based changes in the target steering angle and steering angle when the automatic rotation of the steering wheel 11 is hindered while the process of adjusting the rotational position of the steering wheel 11 is being executed.

[0064] Here, it is assumed that the following description is based on the premise that the driver intervenes in steering because the reason for preventing the automatic rotation of the steering wheel 11 is the cause of the driver's steering intervention. It is assumed that when the vehicle's power is switched off from on, the steering wheel 11 rotates clockwise (negative direction) by a predetermined angle relative to the steering wheel 12. That is, the positional relationship between the steering wheel 11 and the steering wheel 12 is maintained differently from the original positional relationship based on a predetermined steering angle ratio. Here, it is assumed that the steering wheel 12 is in a neutral steering position (steering angle θ) corresponding to the straight-line motion of the vehicle. w＝ 0°). In this case, the steering wheel 11 needs to be in the neutral steering position (steering angle θ) that corresponds to the straight-line movement of the vehicle. s＝ 0°).

[0065] When the vehicle's power supply switches from off to on, the reaction force control unit 27 begins to adjust the rotational position of the steering wheel 11. Figure 3 In the curve diagram shown, characteristic line L1 represents the target steering angle θ when steering intervention occurs. s The characteristic curve L2 represents the steering angle θ. s The changing characteristics. For example, by Figure 3 The characteristic line L1 in the curve graph represents the target steering angle θ as the adjustment of the steering wheel 11 begins (time T0).s The absolute value of * is directed toward the final target angle θ by the execution of the change restriction function. s * Gradually decreases (here, θ) s *=0°). For example, by Figure 3 The characteristic line L2 in the curve represents the steering angle θ. s The absolute value of the turning angle θ towards the final target s * Gradually decrease, to match the target steering angle θ s The changes are consistent. That is, the steering wheel 11 begins to rotate counterclockwise (clockwise). The rotational speed of the steering wheel 11 is constant.

[0066] For example, the situation where the so-called steering holding state is maintained (time T1) is assumed to be the case of driver steering intervention. In this steering holding state, the rotational position of the steering wheel 11 is maintained by applying torque to the steering wheel 11 in a clockwise direction (negative direction) opposite to the rotational direction in the adjustment process. In this case, the reaction force control unit 27 is based on the target steering angle θ. s *and steering angle θ s The increase in the difference between them or the steering torque T h The increase in the value of θ determines whether driver steering intervention has been performed (time T2). Thereafter, the reaction force control unit 27 disables the variation limit function and, based on the steering angle θ at each moment... s To calculate the upper limit value θ UL and lower limit θ LL .

[0067] exist Figure 3 In the curves shown in the figure, characteristic line L3 represents the target steering angle θ without steering intervention. s *The changing characteristics. Without driver intervention, such as by Figure 3 The characteristic line L3 in the curve represents the target steering angle θ calculated by the target steering angle calculation unit 51. s The absolute value of * is directed toward the final target angle θ by the execution of the change restriction function. s * Gradually decreases. On the other hand, when the driver keeps the steering wheel 11 in the steering hold state, the target steering angle θ calculated by the target steering angle calculation unit 51... s The value of * is limited to the upper limit θ. UL Due to the upper limit θ UL This is achieved by adding the setpoint α to the steering angle θ at each moment. s Therefore, the target steering angle θ is calculated. s *and steering angle θ s The difference between them is not greater than the set value α (that is, the difference does not exceed the set value α).

[0068] Subsequently, based on the target steering angle θ s *and steering angle θ s The difference between them or the steering torque T h When it is determined that the steering wheel 11's steering holding state has been released (i.e., canceled) (time T3), the reaction force control unit 27 re-activates the change limiting function. Therefore, the target steering angle θ s The absolute value of *, through the execution of the change restriction function, begins again to turn towards the final target angle θ. s * Gradually decreases (here, θ) s *=0°).

[0069] Next, for example, the case where the steering wheel 11 turns clockwise (negative direction) in the opposite direction of rotation during the adjustment process (time T4) is assumed to be a case of driver intervention in steering. In this case, with the operation of the steering wheel 11, the steering angle θ s The force gradually increases in the negative direction, opposite to the direction of rotation of the steering wheel 11 during adjustment. The reaction force control unit 27 is based on the target steering angle θ. s *and steering angle θ s The difference between them or the steering torque T h It was determined that driver steering intervention was performed (time T5). Subsequently, the reaction force control unit 27 disabled the variation limit function and, based on the steering angle θ at each moment... s To calculate the upper limit value θ UL and lower limit θ LL The target steering angle θ is calculated by the target steering angle calculation unit 51. s The absolute value of * is limited to the upper limit θ. UL And therefore, it gradually increases in the negative direction to match the steering angle θ. s The changes are consistent. Target steering angle θ s * and steering angle θ s The difference between them is not greater than the set value α.

[0070] Subsequently, based on the target steering angle θ s *and steering angle θ s The difference between them or the steering torque T h When it is determined that the steering wheel's negative direction steering has been released (i.e., canceled) (time T6), the reaction force control unit 27 reactivates the change limiting function. Therefore, the target steering angle θ s The absolute value of * begins to move towards the final target angle θ through the execution of the change restriction function. s * Gradually decreases (here, θ) s *=0°).

[0071] For example, the case where the steering wheel 11 turns counterclockwise (forward) in the same direction as the rotation direction in the adjustment process (T7) is assumed to be a case of driver steering intervention. In this case, with the operation of the steering wheel 11, the steering angle θ s The force initially increases gradually in the positive direction, the same as the direction of rotation of the steering wheel 11 during adjustment. The reaction force control unit 27 is based on the target steering angle θ. s *and steering angle θ s The difference between them or the steering torque T h It was determined that driver steering intervention was performed (time T8). Subsequently, the reaction force control unit 27 disabled the variation limit function and, based on the steering angle θ at each moment... s To calculate the upper limit value θ UL and lower limit θ LL The target steering angle θ is calculated by the target steering angle calculation unit 51. s The absolute value of * is restricted to the lower bound θ. LL And therefore, it turns towards the final target angle θ s * Gradually decreases (where θ) s *=0°), with the steering angle θ s The changes are consistent. Target steering angle θ s *and steering angle θ s The difference between them is no greater than the set value α. Thereafter, based on the target steering angle θ... s *and steering angle θ s The difference between them or the steering torque T h When it is determined that the steering wheel's positive direction steering has been released (time T9), the reaction force control unit 27 re-activates the change limiting function. Therefore, the target steering angle θ s The absolute value of *, through the execution of the change restriction function, begins again to turn towards the final target angle θ. s * Gradually decreases (here, θ) s *=0°). Finally, the steering angle θ s The absolute value reaches the final target steering angle θ s * That is, the rotation position of the steering wheel 11 reaches the position corresponding to the steering position of the steering wheel 12.

[0072] In this way, the assumed driver steering intervention while the process of adjusting the rotational position of the steering wheel 11 is being executed includes various intervention modes (maintaining steering hold, and steering in the positive or negative direction). In any intervention mode, the target steering angle θ s *and steering angle θ sThe absolute values ​​of the differences between them are all no greater than the set value α. Therefore, when the driver's steering intervention is released while the process of adjusting the rotation position of the steering wheel is being executed by the reaction force control unit 27 (i.e., when the driver's steering intervention stops), the rotation position of the steering wheel 11 will not change suddenly.

[0073] Furthermore, if the automatic rotation of the steering wheel 11 is hindered due to contact between the automatically rotating steering wheel 11 and the driver's body or an object, similar to the case of driver steering intervention, the target steering angle θ is also adjusted. s *Restriction processing. Therefore, when the automatic rotation of the steering wheel 11 is hindered while the adjustment process for the rotational position of the automatic steering wheel 11 is being executed, sudden rotation of the steering wheel 11 can be suppressed when the hindered automatic rotation is released. Therefore, since unintentional movement of the steering wheel 11 is suppressed, driver discomfort can be reduced.

[0074] Advantages of the first embodiment

[0075] Therefore, according to the first embodiment, the following advantages can be achieved. (1) When the automatic rotation of the steering wheel 11 is hindered while the adjustment process of the rotation position of the automatic steering wheel 11 is being executed, the target steering angle θ s The value of * is restricted, making the target steering angle θ s *and steering angle θ s The absolute value of the difference between the target steering angle and the steering angle is not greater than the set value α. The set value α is based on the viewpoint of suppressing the increase of the difference between the target steering angle and the steering angle—that is, suppressing the increase of the steering angle θ when the cause hindering the automatic rotation of the steering wheel 11 is resolved. s The design is based on the concept of preventing sudden changes in the steering wheel's rotation position. Therefore, when the automatic rotation of the steering wheel 11 is hindered while the adjustment process for adjusting the rotation position of the steering wheel 11 is being performed by the reaction force control unit 27, the sudden change in the rotation position of the steering wheel 11 when the hindered automatic rotation is released can be suppressed. Since unintentional movement of the steering wheel 11 is suppressed, driver discomfort can be reduced.

[0076] Second Implementation Method

[0077] The steering system according to a second embodiment of the present invention will now be described. This embodiment essentially has the same characteristics as... Figure 1 and Figure 2 This embodiment has the same configuration as the first embodiment shown. This embodiment can be implemented in conjunction with the first embodiment.

[0078] like Figure 4 As shown, the reaction force unit 20 includes a stop mechanism 40. The stop mechanism 40 is configured to limit the steering angle θ of the steering wheel 11. sThe stop mechanism 40 limits the steering wheel 11 from rotating more than one full turn (360°). Figure 4 This is the rear view of steering wheel 11.

[0079] The stop mechanism 40 includes a first limiting member 41 and a second limiting member 42. The first limiting member 41 is fixed to a steering column 43 that supports the steering shaft 21 on the vehicle body. The first limiting member 41 extends radially along the steering shaft 21. The first limiting member 41 includes a first limiting surface 41a and a second limiting surface 41b located on opposite sides in the rotational direction of the steering shaft 21. The first limiting surface 41a and the second limiting surface 41b are inclined such that these limiting surfaces approach each other toward the steering shaft 21 radially. The first limiting member 41 is configured to correspond to the neutral position of the steering wheel 11.

[0080] The second limiting member 42 is fixed to the outer peripheral surface of the steering shaft 21. The second limiting member 42 is located near the end of the steering shaft 21 on the steering wheel 11 side. The second limiting member 42 extends in a direction perpendicular to the rotation center axis of the steering shaft 21. The second limiting member 42 is configured to contact the first limiting member 41 in the rotational direction of the steering shaft 21. Therefore, the steering wheel 11 moves between a first limiting position and a second limiting position. In the first limiting position, the second limiting member 42 and the first limiting surface 41a of the first limiting member 41 are in contact, and in the second limiting position, the second limiting member 42 and the second limiting surface 41b of the first limiting member 41 are in contact.

[0081] When the angle formed by the first limiting surface 41a and the second limiting surface 41b is set to, for example, 20°, the second limiting member 42 contacts the first limiting surface 41a of the first limiting member 41 when the steering wheel 11 is rotated 170 degrees to the right relative to the neutral position of the steering wheel 11. The second limiting member 42 contacts the second limiting surface 41b of the first limiting member 41 when the steering wheel 11 is rotated 170 degrees to the left relative to the neutral position of the steering wheel 11. That is, the operating range of the steering wheel 11 is limited to a range of ±170° relative to the neutral position of the steering wheel 11, i.e., a total range of 340°.

[0082] The positional relationship between the steering wheel 11 and the steering wheel 12 is maintained at a positional relationship corresponding to a predetermined steering angle ratio. For example, when the steering wheel 11 is operated throughout its entire operating range, the steering wheel 12 changes direction throughout its entire turning range. Here, since the operating range of the steering wheel 11 is limited to less than 360°, the steering wheel 12 can change direction throughout the entire turning range without rotating the steering wheel 11 one full turn. That is, it is not necessary to perform a hand-switching operation (hand-changing operation) on the steering wheel 11.

[0083] In the steering system 10, the steering motor 32 is driven by the steering angle θ of the steering wheel 11. s And is controlled. The steering system 10 includes a steering angle θ that is configured to limit the steering wheel 11. s The stop mechanism 40. Therefore, in order to maintain the positional relationship between the steering wheel 11 and the steering wheel 12 in a positional relationship corresponding to a predetermined steering angle ratio, the neutral steering position of the steering wheel 11 needs to match the neutral steering position of the steering wheel 12.

[0084] For example, during battery replacement, when the battery is removed from the vehicle, no power is supplied to the reaction force control unit 27. Therefore, the steering angle midpoint information stored in the reaction force control unit 27 is lost. Consequently, it may be difficult to maintain the positional relationship between the steering wheel 11 and the steering wheel 12 in a position corresponding to a predetermined steering angle ratio. Therefore, after a new battery has been attached to the vehicle, when the vehicle is first powered on, the reaction force control unit 27 resets the steering angle midpoint information.

[0085] The reaction force control unit 27 obtains the steering angle midpoint information by performing adjustment processing to adjust the rotational position of the steering wheel 11. That is, the reaction force control unit 27 first bases its information on the rotational angle θ of the reaction force motor 22 at the moment the vehicle's power is first engaged. a Calculate the current steering angle θ of steering wheel 11 s This serves as the initial position for the steering wheel 11, and temporarily stores the calculated steering angle θ. s .

[0086] Then, the reaction force control unit 27 uses the steering angle θ stored as the initial position of the steering wheel 11. s A first target steering angle is set so that the steering wheel 11 is rotated to the right until the second limiting member 42 contacts the first limiting surface 41a of the first limiting member 41. The reaction force control unit 27 temporarily stores the steering angle θ when the second limiting member 42 contacts the first limiting surface 41a of the first limiting member 41 by performing steering angle feedback control. s As the first corner.

[0087] Then, the reaction force control unit 27 uses the steering angle θ stored as the initial position of the steering wheel 11. s A second target steering angle is set so that the steering wheel 11 is rotated to the left until the second limiting member 42 contacts the second limiting surface 41b of the first limiting member 41. The reaction force control unit 27 temporarily stores the steering angle θ when the second limiting member 42 contacts the second limiting surface 41b of the first limiting member 41 by performing steering angle feedback control. s As the second end angle.

[0088] Then, the reaction force control unit 27 calculates the value as half of the sum of the first end angle and the second end angle as the steering angle θ. s The midpoint. The calculated steering angle θ s The midpoint corresponds to the motor midpoint, which is the rotation angle θ of the reaction force motor 22 when the steering wheel 11 is in the neutral steering position. a The reaction force control unit 27 stores the calculated steering angle θ. s The midpoints of the engine and the motor are used as the steering angle midpoint information. In this way, the setting process of the steering angle midpoint is completed.

[0089] Subsequently, the reaction force control unit 27 stores the steering angle θ as the steering angle midpoint information. s The midpoint value is set as the third target steering angle so that the steering wheel 11 is rotated to the same angle as the steering angle θ. s The position corresponding to the actual midpoint. The reaction force control unit 27 rotates the steering wheel 11 to the steering angle θ by executing steering angle feedback control. s The position matches the steering angle of the third target. Therefore, the rotation position of the steering wheel 11 reaches the position matching the steering angle θ. s The position corresponding to the actual midpoint. In this way, the adjustment of the rotation position of the steering wheel 11 is completed when the steering angle midpoint information is obtained.

[0090] In the steering system 10 with the function of automatically setting the steering angle midpoint, there is a concern regarding the following issue: It is conceivable that while the steering angle midpoint setting process is being executed, the driver may be holding the steering wheel 11, or the automatically rotating steering wheel 11 may be in contact with the driver's body or an object. In this situation, the automatic rotation of the steering wheel 11 is hindered, thus affecting the target steering angle θ. s * Gradually turn towards the final target angle θ using the change restriction function. s *Changes, but the actual steering angle θ s The target steering angle θ of steering wheel 11 remains unchanged. s *Compared to actual steering angle θ s The difference between them will increase. Therefore, when the cause preventing the steering wheel 11 from rotating automatically is resolved, for example, when the driver releases their hands from the steering wheel 11, the steering wheel 11 may suddenly rotate to the target steering angle θ. s * and the driver may feel uncomfortable due to the sudden rotation of the steering wheel 11.

[0091] Therefore, in this embodiment, when performing the steering angle midpoint setting process, the target steering angle θ is limited when the automatic rotation of the steering wheel 11 is hindered, in the same manner as when performing the process of adjusting the rotation position of the steering wheel 11 in the first embodiment. sThe range of * suppresses the target steering angle θ s *and steering angle θ s The difference between them increases.

[0092] The reaction force control unit 27, for example, is used to adjust the steering angle θ of the steering wheel 11. s When steering angle feedback control, matched to the first target steering angle, is being executed, and the driver intervenes in the steering, the following process is performed to bring the second limiting member 42 into contact with the first limiting surface 41a of the first limiting member 41. That is, the reaction force control unit 27 disables the variation limiting function during the driver's steering intervention and, based on the steering angle θ at each moment... s Set the target steering angle θ s * Upper limit θ UL and lower limit θ LL The target steering angle θ is calculated by the target steering angle calculation unit 51. s The range of * is subject to the upper limit θ. UL and lower limit θ LL Restrictions.

[0093] The reaction force control unit 27, for example, is used to adjust the steering angle θ of the steering wheel 11. s When steering angle feedback control, matched to the second target steering angle, is being executed and the driver intervenes, the following process is also performed to bring the second limiting member 42 into contact with the second limiting surface 41b of the first limiting member 41. That is, the reaction force control unit 27 disables the variation limiting function during the driver's steering intervention and, based on the steering angle θ at each moment... s Set the target steering angle θ s * Upper limit θ UL and lower limit θ LL .

[0094] The reaction force control unit 27, for example, is used to control the steering angle θ s When steering angle feedback control, matched with the third target steering angle, is being executed, and the driver intervenes in the steering, the following process is also performed to rotate the steering wheel 11 to a position consistent with the steering angle θ. s The position corresponding to the true midpoint. That is, the reaction force control unit 27 disables the change limit function, for example, during the driver's steering intervention, and based on the steering angle θ at each moment. s Set the target steering angle θ s * Upper limit θ UL and lower limit θ LL .

[0095] In this way, the driver's assumed steering intervention at the midpoint of the steering angle, while being executed, includes various intervention modes (maintaining steering hold, and steering in either the positive or negative direction). In any intervention mode, the target steering angle θ s *(These are the steering angles of the first, second, and third targets) and steering angle θ s The absolute values ​​of the differences between them are all no greater than the set value α. Therefore, when the driver's steering intervention is performed while the steering angle midpoint setting process is being executed, the sudden change in the rotational position of the steering wheel 11 can be suppressed when the steering intervention is released (i.e., when the steering intervention stops).

[0096] Furthermore, in cases where the automatic rotation of the steering wheel 11 is hindered due to contact between the automatically rotating steering wheel 11 and the driver's body or an object, the steering angle θ is adjusted to the target angle, similar to the case of driver intervention. s *(This refers to the restriction processing of the first target steering angle, the second target steering angle, and the third target steering angle). Therefore, when the automatic rotation of the steering wheel 11 is hindered while the steering angle midpoint setting process is being executed, sudden rotation of the steering wheel 11 when the hindered automatic rotation is released can be suppressed. Therefore, since unintentional movement of the steering wheel 11 is suppressed, driver discomfort can be reduced.

[0097] According to the second embodiment, the following advantages can be achieved. (2) For example, when the automatic rotation of the steering wheel 11 is hindered due to the driver's steering intervention while the steering angle midpoint setting process is being executed, the target steering angle θ s The value of * is restricted, making the target steering angle θ s *(These are the steering angles of the first, second, and third targets) and steering angle θ s The absolute value of the difference between them is not greater than the set value α. The set value α is based on the suppression steering angle θ. s The design is based on the concept of preventing sudden changes in steering wheel position. Therefore, when the automatic rotation of the steering wheel 11 is hindered while the steering angle midpoint setting process is being executed by the reaction force control unit 27, the sudden change in the rotational position of the steering wheel 11 when the hindered automatic rotation is released can be suppressed. As a result, since unintentional movement of the steering wheel 11 is suppressed, driver discomfort can be reduced.

[0098] Third Implementation Method

[0099] The steering system according to a third embodiment of the present invention will now be described. This embodiment essentially has the same characteristics as... Figure 1The configuration shown in this embodiment is the same as that of the first embodiment, except that the configuration of the reaction force control unit 27 differs from that of the first embodiment. This embodiment can be implemented in conjunction with the second embodiment.

[0100] like Figure 5 As shown, the reaction force control unit 27 includes a first control unit 27a, a second control unit 27b, a switch 27c, a power control unit 27d, and a flag setting circuit 27e. The first control unit 27a is the unit that performs normal reaction force control, which is used to generate a steering torque T through the drive control of the reaction force motor 22. h The corresponding steering reaction force. The first control unit 27a includes a target steering reaction force calculation unit 61, an axial force calculation unit 62, and a subtractor 63.

[0101] Target steering reaction force calculation unit 61 based on steering torque T h The target steering reaction force T1* is calculated. The target steering reaction force T1* is the target value of the steering reaction force generated by the reaction force motor 22. The target steering reaction force calculation unit 61 calculates the target steering reaction force T1*, and the absolute value of the target steering reaction force T1* varies with the steering torque T. h The absolute value of it increases as it increases.

[0102] Axial force calculation unit 62, for example, is based on the rotation angle θ of pinion shaft 34. p The value and the current I of the reversing motor 32 b At least one of the values ​​is used to calculate the axial force applied to the steering shaft 31 via the steering wheel 12, and to calculate the equivalent torque value (i.e., the steering reaction force based on the axial force) T2* obtained by converting the calculated axial force into torque.

[0103] Subtractor 63 calculates target steering reaction force T3* by subtracting the equivalent torque value T2* calculated by axial force calculation unit 62 from the target steering reaction force T1* calculated by target steering reaction force calculation unit 61.

[0104] The second control unit 27b is a unit that performs the processing of adjusting the rotational position of the steering wheel 11. The processing of adjusting the rotational position of the steering wheel 11 refers to the adjustment processing of the automatic adjustment of the rotational position of the steering wheel 11 according to the first embodiment or the steering angle midpoint setting processing according to the second embodiment. The second control unit 27b includes a target steering angle calculation unit 71, a warning setting unit 72, a warning processing unit 73, a steering angle feedback control unit 74, a steering angle calculation unit 75, and a determination unit 76.

[0105] Steering angle calculation unit 75 is based on the rotation angle θ of pinion shaft 34p The rotation angle θ with the pinion shaft 34 is calculated by comparing the rotation angle with the steering angle. p The corresponding steering angle θ s The target steering angle calculation unit 71, warning setting unit 72, warning processing unit 73, steering angle feedback control unit 74, and decision unit 76 basically have the same characteristics as... Figure 2 The target steering angle calculation unit 51, warning setting unit 52, warning processing unit 53, steering angle feedback control unit 54, and determination unit 56 in the first embodiment shown have the same functions. The target steering angle calculation unit 71 is based on the steering angle θ calculated by the steering angle calculation unit 75. s To calculate the target steering angle θ s *. The steering angle feedback control unit 74 receives the target steering angle θ that has been processed by the warning processing unit 73. s * and the rotation angle θ based on the reaction force motor 22 a Calculated steering angle θ s And by adjusting the steering angle θ s Feedback control is used to calculate the target steering reaction force T4*, so that the received steering angle θ s Achieve the target steering angle θ s *

[0106] Switch 27c receives the target steering reaction force T3* calculated by the first control unit 27a and the target steering reaction force T4* calculated by the second control unit 27b as data input. Switch 27c receives the flag F set by the flag setting circuit 27e as control input. When the vehicle is powered on, the flag setting circuit 27e sets the value of flag F to "0" if it is necessary to adjust the position of the steering wheel 11 but the adjustment has not yet been completed. When the vehicle is powered on, the flag setting circuit 27e sets the value of flag F to "1" if it is necessary to adjust the position of the steering wheel 11 and the adjustment has been completed, or if it is not necessary to adjust the position of the steering wheel 11.

[0107] Switch 27c selects either the target steering reaction force T3* calculated by the first control unit 27a or the target steering reaction force T4* calculated by the second control unit 27b as the final target steering reaction force T5* based on the value of flag F. When the value of flag F is "0", switch 27c selects the target steering reaction force T4* calculated by the second control unit 27b as the final target steering reaction force T5*. When the value of flag F is "1", switch 27c selects the target steering reaction force T3* calculated by the first control unit 27a as the final target steering reaction force T5*.

[0108] The power control unit 27d supplies power to the reaction force motor 22 corresponding to the final target steering reaction force T5* selected by the switch 27c. Therefore, according to the third embodiment, in addition to the advantages described in (1) of the first embodiment or (2) of the second embodiment, the following advantages can also be achieved.

[0109] (3) The normal reaction force control and the control for adjusting the rotational position of the steering wheel 11 executed by the first control unit 27a are selectively executed based on whether the processing for adjusting the rotational position of the steering wheel 11 has been completed (i.e., switching control between normal reaction force control and control for adjusting the rotational position of the steering wheel 11). Therefore, mutual interference between normal reaction force control and control for adjusting the rotational position of the steering wheel 11 can be prevented.

[0110] Other implementation methods

[0111] The first to third embodiments can be modified as follows. In the second embodiment, the steering angle midpoint setting process is performed when the vehicle's power is first turned on after the battery has been replaced. However, for example, the steering angle midpoint setting process can be performed when the vehicle's power is turned on, regardless of whether the battery replacement has been performed.

[0112] In the second embodiment, the steering angle θ corresponding to the neutral position of the steering wheel 11 is... s midpoint θ s0 The reference point is used for the operation of the reaction force unit 20, but the steering angle θ can correspond to the position deviating from the neutral position of the steering wheel 11. s The reference point used for the operation of the reaction force unit 20 is determined by the steering angle θ. s It can be related to the steering angle θ of the steering wheel 12 w Simply link them together.

[0113] like Figure 1 As shown by the alternating long and two short dashed lines, in the first to third embodiments, for example, when a notification unit 28 is provided in the passenger compartment, the reaction force 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 and the start and end of the steering angle midpoint setting process. Examples of notification operations using the notification unit 28 include displaying messages using text and issuing messages using voice. With this configuration, since the driver can recognize that the steering wheel 11 is automatically rotating and that the automatically rotating steering wheel 11 is automatically stopping, driver discomfort can be reduced.

[0114] In the first to third embodiments, a rotation angle θ based on the reaction force motor 22 was used. a Calculated steering angle θ sHowever, when using a configuration that includes a steering angle sensor as the steering system 10, the steering angle θ detected by the steering angle sensor can be used. s In the first to third embodiments, the angle difference threshold θ can be used as a reference for determining whether the automatic rotation of the steering wheel 11 is hindered. th Set to be equal to or different from the upper limit value θ used to calculate the target steering angle. UL and lower limit θ LL The value of the set value α (see expressions (C1) and (C2)).

[0115] In the first to third embodiments, the steering angle ratio is set to an appropriate value according to 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, in a steering angle ratio of "θ s :θ w =1:3” and steering angle θ s When the offset is 10°, the change angle θ w The offset is 30°. Therefore, it is more preferable to make the steering angle θ s and the change angle θ w They are correctly synchronized with each other.

[0116] In the first to third embodiments, depending on product specifications, the reaction force control unit 27 may be configured to omit the variation restriction function. With this configuration, when the automatic rotation of the steering wheel 11 is hindered while the process of adjusting the rotational position of the steering wheel 11 is being executed, or when the process of setting the midpoint of the steering angle is being executed, the process of disabling the variation restriction function is omitted.

[0117] In the first to third embodiments, the reaction force control unit 27 and the steering control unit 36 ​​can be configured as a single control unit. In the first to third 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).

[0118] In the first to third embodiments, 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, a structure in which power transmission between the steering shaft 21 and the steering wheel 12 can be cut off by a clutch can also be used. 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.

[0119] The second embodiment can be applied to an electric power steering system in which the steering shaft 21 and the steering shaft 31 are connected, for example, via a rack and pinion mechanism. In this case, the reaction force motor 22 serves as a source of auxiliary force, which is a force used to assist the operation of the steering wheel 11.

Claims

1. A steering system, characterized in that, The steering system includes: Steering shaft (21), which rotates with the operation of steering wheel (11); A motor configured to generate torque applied to the steering shaft (21); and Control unit, the control unit being configured to control the motor, The control unit has a function of performing steering angle feedback control as an adjustment process for adjusting the rotational position of the steering wheel (11), the steering angle feedback control being used to make the steering angle, which is the rotational angle of the steering wheel (11), reach a target steering angle set based on the viewpoint of adjusting the rotational position of the steering wheel (11); and The control unit is configured to set a limit value, which is used to limit the range of change of the target steering angle relative to the steering angle at each moment during the period when the automatic rotation of the steering wheel (11) is hindered while the adjustment process is being performed.

2. The steering system according to claim 1, characterized in that: The control unit has a function to limit the change in the target steering angle per unit time; and The control unit is configured to disable the limiting function during the period when the automatic rotation of the steering wheel (11) is obstructed while the adjustment process is being performed.

3. The steering system according to claim 1, characterized in that, The adjustment process includes: when the vehicle's power supply is switched from a state of off to a state of on, the rotation position of the steering wheel (11) corresponds to the steering position of the vehicle's steering wheels.

4. The steering system according to any one of claims 1 to 3, characterized in that, The steering system also includes: A stop mechanism configured to restrict the rotation of the steering wheel (11), The adjustment process includes the following process: controlling the motor to make the steering wheel (11) perform a rotation operation to reach the first operating end and then making the steering wheel (11) perform a reverse rotation operation to reach the second operating end, and calculating the neutral position of the steering wheel (11) based on the rotation angle of the motor at the start time and end time of the reverse rotation operation of the steering wheel (11).

5. The steering system according to any one of claims 1 to 3, characterized in that: The power transmission between the steering shaft (21) and the vehicle's steering wheels is cut off; and The motor is configured to generate a steering reaction force, which is applied to the steering shaft (21) and is a torque in the direction opposite to the steering direction.

Images