Steering system

Abstract

The steering system includes: a steering shaft (21) that rotates with the operation of the steering wheel (11); a motor configured to generate torque applied to the steering shaft (21); and a control unit configured to control the motor. The control unit is configured to control the motor so that when the steering wheel (11) rotates automatically as an adjustment process for adjusting the rotational position of the steering wheel (11), the rotational speed of the steering wheel (11) gradually decreases to zero when the automatic rotation of the steering wheel (11) stops.

Description

Technical Field

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

[0002] Steering systems known as steer-by-wire already exist, in which power transmission between the steering wheel and the steering wheels is interrupted. The steering system includes a reaction mechanism and a steering mechanism. The reaction mechanism includes a reaction 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 turning the steering wheels. When the vehicle is in motion, the control unit for the steering system generates the steering reaction force by controlling the power supply to the reaction motor, and turns the steering wheels by controlling the power supply to the steering motor.

[0003] In such a 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, there is a possibility that 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 angle of the steering wheels and the steering angle of the steering wheel.

[0004] Therefore, for example, in the steering system disclosed in Japanese Unexamined Patent Application Publication No. 2006-321434 (JP 2006-321434 A), a process for correcting the rotational position of the steering wheel is performed when the vehicle is powered on. 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 displacement 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 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 in the positional relationship between the steering wheel and the steering wheels. Here, the steering wheel rotates automatically when the vehicle is powered on to correct the positional relationship between the steering wheel and the steering wheels. The driver may experience discomfort due to the automatic rotation of the steering wheel.

[0006] The present invention provides a steering system that can reduce driver discomfort caused by automatic rotation of the steering wheel.

[0007] According to one aspect of the present 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 is configured to: when the steering wheel is automatically rotated as part of an adjustment process to adjust the rotational position of the steering wheel, control the motor such that when the automatic rotation of the steering wheel stops, the rotational speed of the steering wheel gradually decreases to zero.

[0008] This configuration allows the steering wheel's rotation speed to gradually decrease as it stops rotating automatically. By suppressing the sudden stop of a rotating steering wheel, driver discomfort is reduced.

[0009] In a steering system according to this aspect, the control unit can be configured to control the motor so that, when the steering wheel is automatically rotated as an adjustment process, the rotational speed of the steering wheel gradually increases at the start of the automatic rotation of the steering wheel.

[0010] With this configuration, the steering wheel's rotation speed gradually increases as automatic rotation begins. That is, the steering wheel begins to rotate more smoothly. By suppressing sudden steering wheel rotation, driver discomfort is reduced.

[0011] In a steering system according to this aspect, the control unit can be configured to perform steering angle feedback control, which is used to bring the steering angle, which is the rotation angle of the steering wheel, to a target steering angle set from the perspective of adjusting the rotation position of the steering wheel. In this case, the control unit can be configured to gradually change the rotation speed of the steering wheel by gradually changing the value of the target steering angle to the final target steering angle set from the perspective of adjustment, while limiting the value of the target steering angle, and when the automatic rotation of the steering wheel stops.

[0012] Using this configuration, the steering wheel rotation speed can be gradually increased or decreased by gradually changing the target steering angle value to a final target steering angle set from the perspective of adjusting the steering wheel rotation position while limiting the target steering angle value as the target value of the steering angle.

[0013] In a steering system according to this aspect, the adjustment process can be a process that makes the rotational position of the steering wheel correspond to the steering position of the vehicle's steering wheels when the vehicle's power supply switches from a de-off state to a energized state.

[0014] With this configuration, when performing the process of making the rotation position of the steering wheel correspond to the steering position of the steering wheel, the driver's discomfort caused by the automatic rotation of the steering wheel can be reduced.

[0015] The steering system according to this aspect may also include a stop mechanism configured to restrict the rotation of the steering wheel. In this case, the control unit may be configured to: control the motor to perform a rotation operation of the steering wheel to a first operating end and then to perform a reverse rotation operation of the steering wheel to a second operating end, and calculate the neutral position of the steering wheel based on the rotation angle of the motor at the start time and the rotation angle at the end time of the reverse rotation operation of the steering wheel, as an adjustment process.

[0016] Using this configuration, driver discomfort caused by the automatic rotation of the steering wheel can be reduced when calculating the neutral position of the steering wheel. 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. In this case, the motor can be configured to generate a steering reaction force, which is applied to the steering shaft and is a torque in the opposite direction to the steering direction.

[0017] Using this configuration, the steering system in this aspect is suitable for a so-called steer-by-wire steering system.

[0018] By using the steering system according to this aspect of the invention, driver discomfort caused by automatic rotation of the steering wheel can be reduced. Attached Figure Description

[0019] 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, wherein similar reference numerals denote similar elements, and in the drawings:

[0020] Figure 1 This is a diagram showing the configuration of the steering system according to the first embodiment;

[0021] Figure 2 This is a block diagram showing the reaction control unit according to the first embodiment;

[0022] Figure 3 It is a graph showing the time-based variation of the variable limit width set by the reaction control unit according to the first embodiment;

[0023] Figure 4 It is a graph showing the time-based variation of the steering angle according to the first embodiment;

[0024] Figure 5 Part (a) is a front view showing the rotational position of the steering wheel before correction according to the first embodiment. Figure 5 Parts (b), (c), and (d) are front views illustrating the change in the rotational position of the steering wheel during correction according to the first embodiment. Figure 5Part (e) is a front view showing the corrected rotational position of the steering wheel according to the first embodiment;

[0025] Figure 6 Part (a) is a graph showing the time-based change in the steering angle caused by the execution of the process of correcting the rotational position of the steering wheel according to the first embodiment, and Figure 6 Part (b) is a graph showing the time-based change in steering angular velocity caused by the execution of the process of correcting the rotational position of the steering wheel according to the first embodiment;

[0026] Figure 7 This is a rear view of the steering wheel according to the second embodiment;

[0027] Figure 8 Part (a) is a graph showing the time-based change in steering angular velocity caused by the execution of the process of setting the midpoint of the steering angle according to the second embodiment, and Figure 8 Part (b) is a graph showing the time-based change in the steering angle caused by the execution of the process for setting the midpoint of the steering angle according to the second embodiment; and

[0028] Figure 9 This is a block diagram showing the reaction control unit according to the third embodiment. Detailed Implementation

[0029] First Implementation Method

[0030] 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 unit 20 that applies a steering reaction force to the vehicle's steering wheel 11; and a steering unit 30 that steers 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 the steering reaction force to the steering wheel 11, a suitable reaction feel can be given to the driver.

[0031] 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.

[0032] 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.

[0033] A rotation angle sensor 24 is disposed in the reaction motor 22. The rotation angle sensor 24 detects the rotation angle θ of the reaction 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 .

[0034] 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 reaction control unit 27 controls the rotation angle θ of the reaction motor 22 relative to the neutral steering position of the steering wheel 11. a The number of rotations is counted (in the following text, the rotation angle θ corresponding to the neutral turning position will be used). a (Referring to the "motor midpoint"). The reaction control unit 27 calculates the total angle, which is obtained by using the motor midpoint as the origin and rotating by the angle θ. a The angle is obtained by summing the results, 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 is stored as the steering angle midpoint information in the reaction control unit 27.

[0035] The reaction control unit 27 executes actions to generate the steering torque T by controlling the drive of the reaction motor 22. h The steering reaction force is controlled by the reaction control unit 27. 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 difference between the target steering angle and the control angle is used to control the power supply to the reaction motor 22 so that the difference is canceled out. 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.

[0036] 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 in the vehicle width direction (…). Figure 1It extends in the left and right direction. The left and right steering wheels 12 are connected to the two ends of the steering shaft 31 via tie rods 13.

[0037] Steering motor 32 is the source of steering force. For example, a three-phase brushless motor is used as steering motor 32. Steering motor 32 is connected to pinion shaft 34 via reduction gear 33. The pinion teeth 34a of pinion shaft 34 mesh with the rack teeth 31a of steering shaft 31. The torque generated by steering motor 32 is applied as steering force to steering shaft 31 via pinion shaft 34. Steering shaft 31 rotates in the vehicle width direction as steering motor 32 rotates. Figure 1 It moves in the left and right directions. The steering angle θ of the steering wheel 12 is... w It changes as the steering shaft 31 moves.

[0038] A rotation angle sensor 35 is disposed in the steering motor 32. The rotation angle sensor 35 detects the rotation angle θ of the steering motor 32. b The steering control unit 36 ​​executes steering control to steer 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 To calculate the rotation angle θ of the pinion shaft 34 p The steering control unit 36 ​​calculates the target rotation angle of the pinion shaft 34 based on the target steering angle calculated by the reaction control unit 27. Here, the target rotation angle of the pinion shaft 34 is calculated from the viewpoint of achieving 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 steering control unit 36 ​​uses the rotation angle θ of the steering motor 32 detected by the rotation angle sensor 35 to cancel out the difference between them. b Vector control is performed on steering motor 32.

[0039] The functional configuration of the reaction control unit 27 will be described in detail below. For example... Figure 2 As shown, the reaction control unit 27 includes a target steering angle calculation unit 51, a protection setting unit 52, a protection processing unit 53, a steering angle feedback control unit 54, and a power control unit 55.

[0040] 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 by adjusting the steering torque T h Feedback control is used to calculate the target steering reaction force, so that the steering torque T hThe calculated target steering torque is achieved. The target steering angle calculation unit 51 calculates the target steering reaction force and steering torque T based on the calculated target steering angle. 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, when using the target steering reaction force and steering torque T h When the sum of these values ​​is taken as the input torque, the steering angle θ of the steering wheel 11 corresponding to the ideal steering angle based on the input torque is determined in advance through experiments or simulations. s Modeling is performed.

[0041] Protection setting unit 52 sets the target steering angle θ to limit the target steering angle during a predetermined operating cycle. s The limit value Δθ for the change in *. The protection processing unit 53 limits the target steering angle θ calculated by the target steering angle calculation unit 51 based on the limit value Δθ set by the protection setting unit 52. s The change in *.

[0042] The target is turned to the control angle θ during the predetermined operation cycle by the protection setting unit 52 and the protection processing unit 53. s The change in * is limited by a predetermined limit value Δθ, a so-called time-based change limiting function.

[0043] Steering angle feedback control unit 54 receives the target steering angle θ processed by protection processing unit 53. s * and the rotation angle θ based on the reaction motor 22 a Calculated steering angle θ s The steering angle feedback control unit 54 controls the steering angle θ. s The feedback control is used to calculate the target steering reaction force T*, so that the rotation angle θ based on the reaction motor 22 is... a Calculated steering angle θ s To achieve the target steering angle θ s *

[0044] 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 so that the difference is canceled out. Therefore, the reaction motor 22 generates torque corresponding to the target steering reaction force T*.

[0045] In the steering system 10 with on-line steering, since the steering wheel 11 is not restricted by the steering unit 30, there is a possibility that the following events may occur.

[0046] That is, when the vehicle is powered on, the steering wheel 11 and the steering wheels 12 are synchronized with each other. Therefore, the positional relationship between the steering wheel 11 and the steering wheels 12 is maintained at a positional relationship 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 can 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.

[0047] Therefore, when the vehicle is powered on again, the steering system 10 has the function of automatically adjusting the rotational position of the steering wheel 11 as an initial operation. For example, if the steering wheel 11 has rotated a predetermined angle counterclockwise (positive direction) during a vehicle power outage, when the vehicle is powered on again, the steering wheel 11 is rotated by that predetermined angle clockwise (negative direction) through drive control of the reaction 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.

[0048] like Figure 1 As shown, the reaction control unit 27 includes a storage unit 27m. When the vehicle's power supply is switched from ON to OFF (i.e., from the on state to the off state), the reaction control unit 27 applies the previously calculated steering angle θ. s The reference steering angle θ0 is stored in the storage unit 27m. The reference steering angle θ0 is used as a reference to determine whether the steering wheel 11 was rotated during the period when the vehicle was powered off.

[0049] When the vehicle's power supply is switched from OFF to ON (i.e., from off to on), the reaction control unit 27 compares the reference steering angle θ0 stored in the storage unit 27m with the steering angle θ calculated immediately after the vehicle is powered on. s The comparison is used to determine whether adjusting the position of steering wheel 11 is necessary.

[0050] The steering angle θ before the vehicle loses power. s The reference steering angle θ0 and the steering angle θ immediately after the vehicle is powered on again. s When the components are matched, the reaction control unit 27 determines that position adjustment of the steering wheel 11 is not necessary. This is because the steering angle θ remains constant during the period from when the vehicle is powered off until it is powered back on. s Nothing has changed, so it is obvious that the steering wheel 11 does not rotate. The reaction control unit 27 begins to operate based on the steering torque T. hThe usual reaction control that generates steering reaction force.

[0051] The steering angle θ before the vehicle loses power. s The reference steering angle θ0 and the steering angle θ immediately after the vehicle is powered on again. s In cases of mismatch, the reaction control unit 27 determines that position adjustment of the steering wheel 11 is necessary and performs the position adjustment of the steering wheel 11. For example, the reaction control unit 27 calculates the reference steering angle θ0 and the steering angle θ immediately following the vehicle being powered on. s The difference between the reference steering angle θ0 and the steering angle θ immediately following vehicle power-on is offset. Specifically, the reaction control unit 27 adjusts the power supply to the reaction motor 22 to cancel out this difference. s The difference between them is used to calculate the target steering angle θ. s * and perform steering control angle θ s Feedback control makes the steering angle θ s To achieve the calculated target steering angle θ s *. When the reference steering angle θ0 and the current steering angle θ s When they are matched, the position adjustment of steering wheel 11 is complete.

[0052] However, due to the automatic rotation of the steering wheel 11, the driver, unaware that such an initial operation is being performed, may experience discomfort. Therefore, in this embodiment, based on the viewpoint of reducing driver discomfort caused by the automatic rotation of the steering wheel 11, the rotation speed of the steering wheel 11 is varied during the period from the start to the end of the initial operation. The reaction control unit 27 changes the target steering angle θ. s The * limit value Δθ is used to change the rotation speed of the steering wheel 11.

[0053] like Figure 3 As shown in the graph, the reaction control unit 27 operates in the first time period ΔT1—from the start of the initial operation until the target turns at the steering angle θ. s * Initial value (= Steering angle θ) s The absolute value of ) and the target steering angle θ s The limit value Δθ is gradually increased from "0" to the maximum limit value Δθ until the difference between the absolute values ​​of the current values ​​reaches the first difference threshold. max Maximum limit value Δθ max The target steering angle θ is the angle of control within a predetermined operating cycle (i.e., each predetermined operating cycle). s The maximum allowable value for * variations.

[0054] The reaction control unit 27 operates in the second time period ΔT2—at the target steering angle θ. s The absolute value of the initial value of * and the target steering angle θ s After the difference between the absolute values ​​of the current values ​​of * reaches the first difference threshold, the final target will turn at the control angle θ. s The absolute value of * and the target steering angle θ s The limit value Δθ will be maintained at the maximum limit value Δθ until the difference between the absolute values ​​of the current values ​​reaches a value less than the second difference threshold. max Place.

[0055] The reaction control unit 27 operates in the third time period ΔT3—at the final target steering angle θ. s The absolute value of * and the target steering angle θ s After the difference between the absolute values ​​of the current values ​​of * reaches a value less than the second difference threshold, the final target will turn at the control angle θ. s The absolute value of * and the target steering angle θ s The difference between the absolute values ​​of the current values ​​of * reaches "0"—the limit value Δθ will be reduced from the maximum limit value Δθ. max Gradually decrease to "0".

[0056] like Figure 4 As shown in the graph, up to the steering angle θ s The value reaches the final target steering angle θ s *The steering angle θ for each predetermined operating cycle during the time period up to this point. s The change in θ increases as the limit value Δθ increases. On the other hand, the steering angle θ for each predetermined operating cycle... s The change in θ decreases as the limit value Δθ decreases. When the limit value Δθ is constant, the steering angle θ for each predetermined operating cycle... s The change is a constant value corresponding to the limit value Δθ.

[0057] The operation of the steering wheel 11 during the initial operation of the steering system 10 will be described below. For example... Figure 5 As shown in section (a), as a prerequisite state, with the vehicle's power supply switched from ON to OFF, the steering wheel 11 is rotated clockwise by an angle -α relative to the steering wheel 12. The positional relationship between the steering wheel 11 and the steering wheel 12 is maintained differently from the original positional relationship corresponding to a predetermined steering angle ratio. Here, the steering wheel 12 is in a neutral steering position (steering angle θ) corresponding to the vehicle's straight-line forward movement. w =0°). Therefore, the steering wheel 11 needs to be inherently located in a neutral steering position (steering angle θ) corresponding to the straight-line forward movement of the vehicle. s =0°).

[0058] When the vehicle's power is switched from OFF to ON, the reaction control unit 27 begins adjusting the position of the steering wheel 11. An overview of the series of operations performed on the steering wheel 11 at this time is as follows.

[0059] like Figure 5 As shown in part (b), the steering wheel 11 begins to rotate counterclockwise (clockwise), and the rotational speed of the steering wheel 11 gradually increases. Figure 5 As shown in part (c), the rotational speed of the steering wheel 11 reaches a constant speed. Figure 5 As shown in part (d), as the amount of rotation of the steering wheel 11 approaches angle +α in the counterclockwise direction, the rotational speed of the steering wheel 11 gradually decreases. Figure 5 As shown in part (e), the position adjustment of the steering wheel 11 is completed when the amount of rotation of the steering wheel 11 reaches an angle +α in the counterclockwise direction. By rotating the steering wheel 11 relative to its initial position—which is achieved by rotating it clockwise by an angle -α relative to the steering position of the steering wheel 12—by an angle +α in the counterclockwise direction, the positional relationship between the steering wheel 11 and the steering wheel 12 returns to the original positional relationship corresponding to the predetermined steering angle ratio.

[0060] The following will describe in detail the steering angular velocity ω and steering angle θ from the start to the end of the steering wheel 11 position adjustment. s The time-based changes. Here, the premise state and... Figure 5 The state shown in part (a) is the same. The steering angular velocity ω is synonymous with the rotational speed of the steering wheel 11.

[0061] like Figure 6 As shown in the graph in part (b), when the position adjustment of the steering wheel 11 begins (time T10), the steering wheel 11 starts to rotate counterclockwise (clockwise), and the steering angular velocity ω of the steering wheel 11 gradually increases. This is because the limit value Δθ is the target steering angle θ. s The absolute value of * is directed towards the final target, with the control angle θ s *(θ in this article) s *=0°) gradually increases. For example Figure 6 As shown in the graph in part (a), the steering angle θ s The absolute value of the direction is taken as the original steering angle θ corresponding to the neutral steering position. s The "0°" gradually decreases. Here, θ is the steering angle per unit time. s The slope of the change gradually increases. This makes the steering wheel 11 move more smoothly, thus reducing driver discomfort.

[0062] like Figure 6 As shown in the graph in part (b), the steering angular velocity ω of the steering wheel 11 reaches a constant speed (time T11). This is because the limit value Δθ is the target steering angle θ. s The absolute value of * is maintained at a constant value. For example... Figure 6 As shown in the graph in part (a), the steering angle θ s The absolute value of the direction is taken as the original steering angle θ corresponding to the neutral steering position. s The "0°" gradually decreases. Here, θ is the steering angle per unit time. s The slope of the change in the quantity is maintained at a constant slope.

[0063] like Figure 6 As shown in parts (a) and (b), at the steering angle θ s The absolute value of θ approaches the original steering angle θ corresponding to the neutral steering position. s After reaching the value of "0°" (time T12), the steering angular velocity ω of steering wheel 11 gradually decreases. This is because the limit value Δθ is the target steering angle θ. s The absolute value of * is directed towards the final target, with the control angle θ s * Gradually decreases. For example... Figure 6 As shown in the graph in part (a), the steering angle θ s The absolute value gradually decreases to the original steering angle θ corresponding to the neutral steering position. s The "0°" here refers to the steering angle θ per unit time. s The slope of the change gradually decreases.

[0064] like Figure 6 As shown in parts (a) and (b), when the steering angle θ of the steering wheel 11... s The absolute value of θ is taken as the original steering angle θ corresponding to the neutral steering position. s At "0°" (time T13), the operation of steering wheel 11 stops. The steering angular velocity ω of steering wheel 11 becomes "0". Figure 6 As shown in the graph in part (a), the steering angle θ s The absolute value of the final target steering angle θ s *(θ in this article) s *=θ w =0°) matching. That is, the positional relationship between the steering wheel 11 and the steering wheel 12 returns to the original positional relationship corresponding to the predetermined steering angle ratio. Since the rotational speed of the steering wheel 11 gradually decreases before the position adjustment of the steering wheel 11 is completed, driver discomfort can be reduced.

[0065] Advantages of the first embodiment

[0066] Therefore, according to the first embodiment, the following advantages can be achieved: (1) Immediately after the position adjustment of the steering wheel 11 begins, the rotation speed of the steering wheel gradually increases. That is, the steering wheel 11 begins to rotate more smoothly. Since sudden rotation of the steering wheel 11 is suppressed, driver discomfort can be reduced.

[0067] (2) Before the position adjustment of the steering wheel 11 is completed, the rotation speed of the steering wheel gradually decreases. Since the sudden stop of the rotating steering wheel 11 is suppressed, the driver's discomfort can be reduced.

[0068] (3) By gradually increasing and decreasing the rotational speed of the steering wheel 11 as described in (1) and (2) above, driver discomfort immediately following the start of steering wheel 11 position adjustment and immediately before the end of steering wheel 11 position adjustment can be reduced. Therefore, the steering wheel 11 can be rotated at a higher speed during periods when its rotational speed is maintained at a constant speed. Thus, smoother rotational behavior of the steering wheel 11 can be achieved, and the time required from the start to the end of steering wheel 11 position adjustment can be reduced.

[0069] Second Implementation Method

[0070] A steering system according to a second embodiment of the present invention will now be described. This embodiment essentially has the same... Figure 1 and Figure 2 The configuration shown in the first embodiment is the same. This embodiment can be implemented in combination with the first embodiment.

[0071] like Figure 7 As shown, the reaction unit 20 includes a stop mechanism 40. The stop mechanism 40 is configured to limit the steering angle θ of the steering wheel 11. s The stop mechanism 40 limits the steering wheel 11 from rotating more than one full turn (360°). Figure 7 This is the rear view of steering wheel 11.

[0072] 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 at 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 along the direction of rotation 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 positioned corresponding to a neutral position of the steering wheel 11.

[0073] 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 side of the steering wheel 11. 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 rotation direction of the steering shaft 21. Therefore, the steering wheel 11 moves between a first limiting position at the contact point of the first limiting surface 41a of the second limiting member 42 and the first limiting surface 41b of the first limiting member 41 and the first limiting member 42.

[0074] When the angle formed by the first limiting surface 41a and the second limiting surface 41b is set to, for example, 20°, when the steering wheel 11 is rotated 170° to the right relative to its neutral position, 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° to the left relative to its neutral position, the second limiting member 42 contacts the second limiting surface 41b of the first limiting member 41. That is, the operating range of the steering wheel 11 is limited to ±170° relative to its neutral position, i.e., the total range is 340°.

[0075] 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 is turned throughout its entire steering range. Here, since the operating range of the steering wheel 11 is limited to less than 360°, the steering wheel 12 can be turned throughout the entire steering range without rotating the steering wheel 11 one full turn. That is, it is not necessary to perform a hand-switching operation (cross-operation) on the steering wheel 11.

[0076] In the steering system 10, the steering angle θ is based on the steering wheel 11. s To control the steering motor 32. 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 at a positional relationship corresponding to a predetermined steering angle ratio, it is necessary to match the neutral steering position of the steering wheel 11 and the neutral steering position of the steering wheel 12.

[0077] For example, when the battery is removed from the vehicle during a battery replacement, no power is supplied to the reaction control unit 27. Therefore, the steering angle midpoint information stored in the reaction 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 at a position corresponding to a predetermined steering angle ratio. Therefore, when the vehicle is powered on for the first time after a new battery is attached, the reaction control unit 27 resets the steering angle midpoint information.

[0078] The reaction control unit 27 is first based on the rotation angle θ of the reaction motor 22 at the point when the vehicle is energized. a To calculate the current steering angle θ s This serves as the initial position for the steering wheel 11, and temporarily stores the calculated steering angle θ. s .

[0079] Then, the reaction control unit 27 uses the steering angle θ stored as the initial position of the steering wheel 11. s The first target steering angle is set such 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 control unit 27 executes steering angle feedback control to set the steering angle θ when the second limiting member 42 contacts the first limiting surface 41a of the first limiting member 41. s Temporarily stored as the first corner.

[0080] Then, the reaction control unit 27 uses the steering angle θ stored as the initial position of the steering wheel 11. s The second target steering angle is set such 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 control unit 27 executes steering angle feedback control to set the steering angle θ at which the second limiting member 42 contacts the second limiting surface 41b of the first limiting member 41. s Temporarily stored as the second corner.

[0081] Then, the reaction control unit 27 calculates half the sum of the first and second end angles as the steering angle θ. s midpoint θ s0 The calculated steering angle θ s midpoint θ s0 Corresponding to the motor midpoint, which is the rotation angle θ of the reaction motor 22 when the steering wheel 11 is in the neutral steering position. a The reaction control unit 27 will calculate the steering angle θ. s midpoint θ s0The motor midpoint is stored as the steering angle midpoint information. This completes the process of setting the steering angle midpoint.

[0082] Subsequently, the reaction control unit 27 will store the steering angle θ, which is the midpoint information of the steering angle. s midpoint θ s0 The value is set to the third target steering angle, causing the steering wheel 11 to rotate to the position corresponding to the steering angle θ. s The true midpoint θ s0 The reaction control unit 27 rotates the steering wheel 11 to the steering angle θ by performing steering angle feedback control. s The position matches the third target steering angle. Therefore, the rotation position of the steering wheel 11 reaches the position corresponding to the steering angle θ. s The true midpoint θ s0 The location.

[0083] When performing the steering angle midpoint setting process, the steering wheel automatically rotates when the vehicle's power is turned on. The driver may experience discomfort due to this automatic rotation of the steering wheel. This occurs when the steering wheel 11 rotates to a first limit position relative to the vehicle's power-on position, when the steering wheel 11 rotates in the opposite direction from the first limit position to a second limit position, and when the steering wheel 11 rotates from the second limit position to the steering angle θ. s midpoint θ s0 At times, the smooth behavior of the steering wheel 11 may not be achieved. For example, the steering wheel 11 may suddenly rotate or suddenly stop.

[0084] Therefore, in this embodiment, when performing the steering angle midpoint setting process, the rotational speed of the steering wheel 11 is gradually increased and decreased in the same manner as when the function of automatically adjusting the rotational position of the steering wheel 11 is performed in the first embodiment. That is, immediately after the automatic rotation of the steering wheel 11 begins, the rotational speed of the steering wheel 11 is gradually increased. Just before the automatic rotation of the steering wheel 11 stops, the rotational speed of the steering wheel 11 is gradually decreased.

[0085] like Figure 8 As shown in the graph of part (a), when the steering wheel 11 rotates to the first limit position relative to the vehicle's power-on position, the steering angular velocity ω of the steering wheel 11 gradually increases and eventually reaches a constant speed (time T21). After the rotational position of the steering wheel 11 approaches the first limit position (time T22), the steering angular velocity ω of the steering wheel 11 gradually decreases. When the rotational position of the steering wheel 11 reaches the first limit position (time T23), the rotation of the steering wheel 11 stops.

[0086] As the steering wheel 11 rotates in the opposite direction from the first limiting position to the second limiting position, the steering angular velocity ω of the steering wheel 11 gradually increases and eventually reaches a constant speed (time T31). After the rotational position of the steering wheel 11 approaches the second limiting position (time T32), the steering angular velocity ω of the steering wheel 11 gradually decreases. When the rotational position of the steering wheel 11 reaches the second limiting position (time T33), the rotation of the steering wheel 11 stops.

[0087] Finally, when the steering wheel 11 is rotated from the second limit position to the steering angle θ s midpoint θ s0 As the steering wheel 11 rotates, its angular velocity ω gradually increases and eventually reaches a constant velocity (time T41). When the steering wheel 11's rotational position approaches the steering angle θ... s midpoint θ s0 Afterwards (at time T42), the steering angular velocity ω of the steering wheel 11 gradually decreases. The steering wheel 11 reaches its rotational position at the steering angle θ. s midpoint θ s0 At time T43, the rotation of steering wheel 11 stops.

[0088] like Figure 8 As shown in the graph in part (b), the target steering angle θ is changed according to the steering situation. s *Limit value Δθ, steering angle θ s It can change more smoothly without suddenly (drastically) increasing or decreasing.

[0089] Therefore, according to the second embodiment, the following advantages can be achieved. (4) Immediately after the automatic rotation of the steering wheel 11 begins, the rotation speed of the steering wheel gradually increases. That is, the steering wheel 11 begins to rotate more smoothly. Since the sudden rotation of the steering wheel 11 is suppressed, the driver's discomfort can be reduced.

[0090] (5) The rotation speed of the steering wheel 11 gradually decreases before the automatic rotation of the steering wheel 11 stops. Since the sudden stop of the rotating steering wheel 11 is suppressed, the driver's discomfort can be reduced.

[0091] (6) By gradually increasing and decreasing the rotational speed of the steering wheel 11 as described in (4) and (5) above, driver discomfort immediately following the start of automatic rotation of the steering wheel 11 and immediately before the end of automatic rotation of the steering wheel 11 can be reduced. Therefore, the steering wheel 11 can be rotated at a higher speed during periods when its rotational speed is maintained at a constant speed. Thus, smoother rotational behavior of the steering wheel 11 can be achieved, and the time required from the start to the end of the steering angle midpoint setting process can be reduced.

[0092] Third Implementation Method

[0093] A steering system according to a third embodiment of the present invention will now be described. This embodiment essentially has the same... Figure 1 The configuration shown in the first embodiment is the same, except that the configuration of the reaction control unit 27 differs from that of the first embodiment. This embodiment can be implemented in combination with the second embodiment.

[0094] like Figure 9 As shown, the reaction 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 performs drive control via the reaction motor 22 to generate a steering torque T corresponding to the steering torque. h The first control unit 27a includes a target steering reaction force calculation unit 61, an axial force calculation unit 62, and a subtractor 63.

[0095] Target steering reaction force calculation unit 61 based on steering torque T h Calculate the target steering reaction force T1*. The target steering reaction force T1* is the target value of the steering reaction force generated by the reaction motor 22. The target steering reaction force calculation unit 61 calculates its absolute value as a function of the steering torque T. h The absolute value of the target increases, and the target's reaction force T1* increases accordingly.

[0096] 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 steering motor 32 b The axial force applied to the steering shaft 31 via the steering wheel 12 is calculated using at least one of the values, and the equivalent torque value (i.e., the steering reaction force based on the axial force) T2* is calculated by converting the calculated axial force into torque.

[0097] 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.

[0098] 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 automatic adjustment processing 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 protection setting unit 72, a protection processing unit 73, a steering angle feedback control unit 74, and a steering angle calculation unit 75.

[0099] Steering angle calculation unit 75 is based on the rotation angle θ of pinion shaft 34 p The rotation angle θ corresponding to the pinion shaft 34 is calculated by comparing it with the steering angle. p Steering angle θ s The target steering angle calculation unit 71, protection setting unit 72, protection processing unit 73, and steering angle feedback control unit 74 essentially have the same characteristics as... Figure 2 The target steering angle calculation unit 51, protection setting unit 52, protection processing unit 53, and steering angle feedback control unit 54 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 protection processing unit 73. s * and the rotation angle θ based on the reaction motor 22 a Calculated steering angle θ s And by steering the angle θ s The feedback control is used to calculate the target steering reaction force T4*, so that the received steering angle θ s To achieve the target steering angle θ s *

[0100] 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 the position adjustment of the steering wheel 11 is necessary but not yet completed. When the vehicle is powered on, the flag setting circuit 27e sets the value of flag F to "1" if the position adjustment of the steering wheel 11 is necessary and completed, or if the position adjustment of the steering wheel 11 is not necessary.

[0101] Based on the value of flag F, switch 27c selects one of 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 the final target steering reaction force T5*. 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*.

[0102] The power control unit 27d supplies power to the reaction 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) to (3) of the first embodiment or (4) to (6) of the second embodiment, the following advantages can also be achieved.

[0103] (7) Based on whether the process of adjusting the rotational position of the steering wheel 11 has been completed, the normal reaction control and the control for adjusting the rotational position of the steering wheel 11 executed by the first control unit 27a are selectively executed (i.e., the control switches between the normal reaction control and the control for adjusting the rotational position of the steering wheel 11). Therefore, the normal reaction control and the control for adjusting the rotational position of the steering wheel 11 can be prevented from interfering with each other.

[0104] Other implementation methods

[0105] 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 battery replacement. However, for example, the steering angle midpoint setting process can also be performed when the vehicle's power is turned on regardless of whether battery replacement has been performed.

[0106] 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 unit 20, but the steering angle θ corresponding to the position deviating from the neutral position of the steering wheel 11 can be used. s The reference point used for the operation of the reaction unit 20 is as long as it can be relative to the steering angle θ of the steering wheel 12. w Anything related is acceptable.

[0107] In the second embodiment, when the steering wheel 11 is rotated to the first limit position relative to the vehicle's power-on position, the amount of rotation angle of the steering wheel 11 from the vehicle's power-on position to the first limit position cannot be determined, and therefore, the gradual increase and decrease of the steering wheel 11's rotation speed may not be properly executed. In this case, during the steering angle midpoint setting process, the gradual increase and decrease of the steering wheel 11's rotation speed may be omitted only during the period when the steering wheel 11 is rotated from the vehicle's power-on position to the first limit position, or the following processing may be performed.

[0108] That is, before performing the steering angle midpoint setting process, the approximate surface positional relationship between the steering wheel 11 and the steering wheel 12 is determined, and the steering wheel 11 is preset to near the neutral position. Then, when the steering wheel 11 is rotated to the right from the neutral position, assuming that the steering wheel 11 has rotated by the angle at which it contacts the first limiting surface 41a of the first limiting member 41, that is, assuming that the steering wheel 11 has rotated 170° in the right steering direction, the rotational speed of the steering wheel 11 is gradually increased and decreased.

[0109] like Figure 1 As shown by alternating long and two short dashed lines, in the first to third embodiments, for example, when a notification unit 28 is provided in the vehicle cabin, 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 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 sending 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 automatically stops, driver discomfort can be reduced.

[0110] In the first to third embodiments, the rotation angle θ based on the reaction motor 22 is used. a Calculated steering angle θ s However, when the steering system 10 is configured to include a steering angle sensor, the steering angle θ detected by the steering angle sensor can be used. s .

[0111] In the first to third embodiments, the steering angle ratio is set to an appropriate value according to product specifications, etc. For example, the steering angle ratio may be "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 steering angle θ w The displacement is 30°. Therefore, the steering angle θ is adjusted. s and steering angle θ w It is better to synchronize with each other correctly.

[0112] In the first to third embodiments, the rotational speed of the steering wheel 11 gradually increases immediately after the automatic rotation of the steering wheel 11 begins; however, the rotational speed of the steering wheel 11 may not gradually increase. That is, immediately after the automatic rotation of the steering wheel 11 begins, the steering wheel 11 can be rotated by executing steering angle feedback control.

[0113] In the first to third embodiments, the reaction 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 auxiliary power supply (ACC power supply) or an ignition power supply (IG power supply).

[0114] 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.

[0115] The second embodiment can be applied to an electric power steering system in which the steering shaft 21 and steering shaft 31 are connected, for example, via a rack and pinion mechanism. In this case, the reaction 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, include: The steering shaft (21), which rotates with the operation of the steering wheel (11), cuts off the power transmission between itself and the vehicle's steering wheels; An electric motor is configured to generate torque applied to the steering shaft (21); as well as A control unit, configured to control the motor. The control unit is configured to: when the steering wheel (11) rotates automatically as an adjustment process to adjust its rotational position, control the motor so that when the automatic rotation of the steering wheel (11) stops, the rotational speed of the steering wheel (11) gradually decreases to zero. The control unit has: a first control unit configured to perform reaction force control that generates a steering reaction force as a torque in the opposite direction to the steering direction based on the steering torque; The second control unit is configured to perform the adjustment process. The control unit is configured to switch between the reaction force control based on the first control unit and the adjustment process based on the second control unit, depending on whether the rotational position of the steering wheel (11) needs to be adjusted.

2. The steering system according to claim 1, characterized in that, The second control unit is configured to control the motor so that when the steering wheel (11) is automatically rotated as part of the adjustment process, the rotation speed of the steering wheel (11) gradually increases when the automatic rotation of the steering wheel (11) begins.

3. The steering system according to claim 2, characterized in that: The second control unit is configured to perform steering angle feedback control, which is used to make the steering angle, which is the rotation angle of the steering wheel (11), reach a target steering angle set from the viewpoint of adjusting the rotation position of the steering wheel (11); and The second control unit is configured to gradually change the rotation speed of the steering wheel (11) by gradually changing the value of the target steering angle to a final target steering angle set based on the adjustment viewpoint while limiting the value of the target steering angle when the automatic rotation of the steering wheel (11) begins and when the automatic rotation of the steering wheel (11) stops.

4. The steering system according to any one of claims 1 to 3, characterized in that, The adjustment process is a process that makes the rotation position of the steering wheel (11) correspond to the steering position of the vehicle's steering wheels when the vehicle's power supply switches from a state of being off to a state of being on.

5. The steering system according to any one of claims 1 to 3, characterized in that, Also includes: A stop mechanism is configured to limit the rotation of the steering wheel (11). The second control unit is configured to: control the motor to cause the steering wheel (11) to perform a rotation operation to the first operating end and then cause the steering wheel (11) to perform a reverse rotation operation to the second operating end, and calculate the neutral position of the steering wheel (11) based on the rotation angle of the motor at the start time and the rotation angle at the end time of the reverse rotation operation of the steering wheel (11), as the adjustment process.

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