JP6484520B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a steer-by-wire vehicle steering apparatus.

  Some recent vehicles are equipped with a vehicle steering device of the type called Steer By Wire. In a steer-by-wire (hereinafter abbreviated as “SBW method”) vehicle steering apparatus, a steering unit having a steering handle (hereinafter abbreviated as “handle”) and a steering reaction force motor; The steering motor and the steered portion having the steered wheels are mechanically disconnected.

  For example, in Patent Document 1, in a cargo handling vehicle (forklift) equipped with a SBW-type vehicle steering device, when a large steering angle is steered when the vehicle is stopped or traveling at a low speed, the target turning angle is limited. A technique for limiting to a limit value between a normal value and zero is disclosed.

  According to the vehicle steering apparatus of the SBW system according to Patent Document 1, when steering with a large steering angle is performed at the time of stopping or at a low speed, the target turning angle is limited to the limit value. When starting or increasing the traveling speed from a very low speed, a situation in which the actual steering angle becomes excessively large is suppressed, and as a result, the traveling resistance can be reduced.

JP 2010-264833 A

  However, a problem arises when steering with a large steering angle is performed when the steering member is operated when the vehicle is stopped or traveling at a low speed. That is, in the technology according to Patent Document 1 configured to limit the target turning angle to the limit value, when the actual turning angle is near the terminal turning angle that defines the steerable range, for example, In a case where turning is impossible by hitting an obstacle such as a curb, excessive current continues to flow through the turning motor until the target turning angle reaches the limit value. In other words, the technique according to Patent Document 1 has a problem that in the above-described case, the request for power saving cannot be satisfied.

  The present invention has been made in view of the above circumstances, and when the turning angle is in the vicinity of the terminal turning angle at the time of stationary, turning becomes impossible because the turning wheel hits an obstacle. It is an object of the present invention to provide a vehicle steering apparatus that can meet the demand for power saving even if it encounters a case.

In order to solve the above-mentioned problem, the invention according to (1) provides a steering unit having a steering member operated when turning a steered wheel of a vehicle, and a turning force for turning the steered wheel. A turning unit that has a turning motor to be applied and is capable of turning the steered wheels in a state where the steered wheels are mechanically separated from the steering unit; and a steered angle that detects a steered angle associated with the steered wheels A detection unit; a vehicle speed detection unit that detects a vehicle speed of the vehicle; and a drive control of the steering motor so that a turning angle of the steered wheel follows a target turning angle based on an operation of the steering member. And a control unit that predicts a start time at which the steered wheels start rolling from a stationary state, and the control unit has a vehicle speed that is less than a predetermined vehicle speed threshold and that is associated with the steered wheels. When the absolute value of the steering angle exceeds a predetermined turning angle threshold, the vehicle speed is equal to or higher than the vehicle speed threshold. There row drive control of the steering motor with a maximum current when outright laid lower than the traveling time of the current upper limit value is a current upper limit value of the steering motor during some, of the steered wheels by the prediction unit When the start time is predicted, the steering motor drive control is most preferably performed using a start current upper limit value lower than the stationary current upper limit value in a predetermined period including the start time. Main features.

The invention according to (1) assumes a case where turning is impossible when the turning wheel hits an obstacle when the turning angle is close to the terminal turning angle at the time of stationary, and in such a case It is intended to save power.
Therefore, in the invention according to (1), when the vehicle speed is less than the predetermined vehicle speed threshold value and the absolute value of the turning angle related to the steered wheels exceeds the predetermined turning angle threshold value, that is, at the time of stationary operation. When the turning angle is in the vicinity of the terminal turning angle, the control unit uses the stationary current upper limit value that is lower than the traveling current upper limit value when the vehicle speed is equal to or higher than the vehicle speed threshold. Drive control was performed.
By the way, even when the target turning angle based on the operation of the steering member is set to the terminal turning angle, the drive control of the turning motor is performed using the current upper limit value at stationary time that is lower than the current upper limit value at traveling. When this is done, the steered wheels are positioned in the vicinity of the final turning angle without being steered to the final turning angle due to insufficient driving force. However, when the turning angle is in the vicinity of the final turning angle at the time of stationary, even if the steered wheel is not steered to the final turning angle as described above, it may be positioned near the final turning angle. No particular problem will occur.
Moreover, the invention which concerns on (1) suppresses generation | occurrence | production of the mechanical noise which tends to arise in the turning part around a rack axis | shaft at the time of the start of a turning wheel.
At the time of start-up where the steered wheels equipped with tires start to roll from a stationary state while being positioned near the final steered angle by the drive control of the steered motor using the upper limit current value during stationary, Due to the effect of releasing the force acting on the direction (tire axial force), mechanical noise tends to be generated in the steered portion around the rack shaft.
Therefore, in the invention according to (1), when the prediction unit predicts the start time of the steered wheels from, for example, the release of the brake pedal force or the acceleration of the vehicle, the start time of the steered wheels is predicted by the prediction unit. In a predetermined period including time, the driving control of the steered motor is performed using a starting current upper limit value lower than the stationary current upper limit value.

According to the invention according to (1), when the turning angle is in the vicinity of the terminal turning angle at the time of stationary, a steering motor is used by using a stationary current upper limit value that is lower than the traveling current upper limit value. Therefore, even if a case where the steered wheel hits an obstacle makes it impossible to steer, the power saving request can be met.
Further, according to the invention according to (1), the driving control of the steered motor is performed using a starting current upper limit value lower than the stationary current upper limit value in a predetermined period including the starting time of the steered wheels. Therefore, it is possible to suppress the occurrence of mechanical noise that tends to occur in the steered portion around the rack shaft at the start.

The invention according to (2) is the vehicle steering apparatus according to the invention according to (1) , wherein the control unit gradually decreases the vehicle speed from the vehicle speed threshold value to less than the vehicle speed threshold value, And when the absolute value of the turning angle related to the steered wheel exceeds a predetermined turning angle threshold value, the current upper limit value at the time of stationary use having a characteristic of gradually decreasing according to the degree of gradually decreasing the vehicle speed is used. The driving control of the steering motor is performed.

Here, when the absolute value of the steered angle related to the steered wheel exceeds a predetermined steered angle threshold, the vehicle speed gradually decreases from the vehicle speed threshold to less than the vehicle speed threshold, and the invention according to (1) is applied. To do. At this time, if the driving current upper limit value is far from the stationary current upper limit value, the driver feels uncomfortable that the steering response is delayed when switching from the traveling current upper limit value to the stationary current upper limit value. There is a risk that the person will hold.
Therefore, in the invention according to (2) , the control unit gradually decreases the vehicle speed from the vehicle speed threshold value to less than the vehicle speed threshold value, and the absolute value of the turning angle related to the steered wheels exceeds a predetermined turning angle threshold value. In this case, the driving control of the steered motor is performed using the stationary current upper limit value having a characteristic of gradually decreasing according to the degree of gradually decreasing the vehicle speed.

According to the invention according to (2) , when the vehicle speed is gradually decreased from the vehicle speed threshold value to less than the vehicle speed threshold value, and the absolute value of the turning angle related to the steered wheels exceeds a predetermined turning angle threshold value, the vehicle speed Steering motor drive control is performed using the stationary current upper limit value that has a characteristic that gradually decreases in accordance with the degree of gradual decrease, so that the steering is turned when switching from the traveling current upper limit value to the stationary current upper limit value. The situation where the driver feels uncomfortable with a delayed response can be cleared.

According to the present invention, even when the turning angle is in the vicinity of the terminal turning angle at the time of stationary, even if a case in which turning is impossible due to the turning wheel hitting an obstacle, power saving is achieved. Can respond to the request. In addition, it is possible to suppress the occurrence of mechanical noise that tends to occur in the steered portion around the rack shaft at the start.

1 is a schematic configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is explanatory drawing which compares and represents the electric current upper limit characteristic of the turning motor with respect to the change of a turning angle at the time of driving | running | working and stationary. It is explanatory drawing showing the electric current upper limit characteristic of a steering motor which changes every moment according to the change of a driving | running | working scene with time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention.
The vehicle steering device 11 is a steer-by-wire (SBW) type steering device. This vehicle steering device 11 is operated by driving the steering motor 29 when the steering reaction motor 16 described later has a function of generating a steering force by driving the steering motor 29 (SBW mode). When an electric power steering (EPS) function (EPS mode) that generates an assisting force related to manual steering by the driver, and when the steering reaction force motor 16 and the steering motor 29 fail, the driver's manual (Manual steering mode).

  In order to realize the various functions described above, the vehicle steering device 11 includes a handle 13, a steering reaction force generating device 15, a steering device 17, and a clutch device 19, as shown in FIG. The vehicle steering device 11 is mounted on the vehicle V. The vehicle V includes a pair of steered wheels 21a and 21b.

  The handle 13 is a member that is operated in accordance with a driving intention related to the steering of the driver. The handle 13 corresponds to the “steering member” of the present invention. A steering shaft 23 is provided on the handle 13. The steering shaft 23 is configured to rotate around the shaft in accordance with the operation of the handle 13 by the driver.

The steering reaction force generating device 15 has a function of generating a reaction force (response) related to steering at the driver's hand holding the handle 13 when the vehicle steering device 11 is operating in the SBW mode. The steering reaction force generator 15 has a steering reaction force motor 16. A steering shaft 23 is connected to the steering reaction force motor 16. The steering reaction force motor 16 generates a steering torque for rotating the steering shaft 23 around the axis. Thereby, when the vehicle steering device 11 is operating in the SBW mode, a reaction force (responsiveness) related to steering is transmitted to the hand of the driver who holds the handle 13.
The steering reaction force generator 15 having the handle 13, the steering shaft 23, and the steering reaction force motor 16 corresponds to the “steering unit” of the present invention.

The steered device 17 has a function of converting the rotational motion of the steered shaft 25 into the linear motion of the rack shaft 27 via a rack and pinion mechanism (not shown). The steering device 17 has a steering motor 29. A steered shaft 25 and a rack shaft 27 are connected to the steered motor 29. The turning motor 29 generates a turning torque for causing the rack shaft 27 to linearly move along the axial direction. A pair of steered wheels 21a and 21b are connected to the rack shaft 27 via tie rods (not shown). The pair of steered wheels 21 a and 21 b are steered by a linear motion of the rack shaft 27.
The steered device 17 having the steered shaft 25, the rack shaft 27, and the steered motor 29 corresponds to the “steered portion” of the present invention.

  The clutch device 19 has a function of connecting or disconnecting the steering shaft 23 and the steered shaft 25. In order to realize such a function, the clutch device 19 includes a planetary gear mechanism 31. The planetary gear mechanism 31 includes an internal gear 31a, a planetary gear 31b, a sun gear 31c, and a planet carrier 31d.

  The clutch device 19 includes a locking gear 33 and a locking device 35. The lock device 35 includes a lock pin 39 that engages with a tooth groove of the lock gear 33, and an electromagnetic solenoid 37 that drives the lock pin 39.

  The internal gear 31 a is fixed to a side end portion of the steering device 17 in the steering shaft 23 and is configured to rotate integrally with the steering shaft 23. The sun gear 31c is configured to freely rotate around a rotation axis coaxial with the steered shaft 25. A plurality of planetary gears 31b are provided so as to engage with each of the sun gear 31c and the internal gear 31a. Each of the plurality of planetary gears 31b is rotatably supported with respect to a planet carrier 31d that rotates integrally with the steered shaft 25.

The locking gear 33 is an external gear. The locking gear 33 is configured to rotate integrally with the sun gear 31c. The lock pin 39 is urged in a direction close to the locking gear 33 by an urging means (not shown). When the lock pin 39 is engaged with the tooth groove of the locking gear 33, the rotational movement of the locking gear 33 is restricted.
The electromagnetic solenoid 37 operates to release the engagement between the lock pin 39 and the locking gear 33 by displacing the lock pin 39 by supplying the exciting current.
The locking device 35 is configured to operate according to a control signal sent from the control device 40. The control device 40 operates to release the engagement of the lock pin 39 with the locking gear 33 by supplying an excitation current to the electromagnetic solenoid 37.

Next, the operation of the clutch device 19 will be described. When the lock pin 39 engages with the tooth groove of the locking gear 33, the rotational movement of the sun gear 31c that rotates together with the locking gear 33 is restricted.
When the driver operates the handle 13 in a state where the rotational movement of the sun gear 31 c is restricted, the internal gear 31 a rotates as the steering shaft 23 rotates. At this time, since the rotational movement of the sun gear 31c is restricted, the planetary gear 31b revolves around the sun gear 31c while rotating. Due to the revolution of the planetary gear 31b, the planetary carrier 31d that pivotally supports the planetary gear 31b and the turning shaft 25 that rotates integrally with the planetary carrier 31d rotate.

  In short, in a state where the lock pin 39 is engaged with the tooth groove of the locking gear 33, the clutch device 19 is in a connected state in which the steering shaft 23 and the steered shaft 25 are connected. At this time, the rotational force of the steering shaft 23 is transmitted to the steered shaft 25.

On the other hand, when the engagement of the lock pin 39 with the tooth groove of the locking gear 33 is released, the sun gear 31c that rotates integrally with the locking gear 33 becomes rotatable.
When the driver operates the handle 13 with the sun gear 31c being rotatable, the internal gear 31a is rotated with the rotation of the steering shaft 23. At this time, the planetary gear 31b tries to revolve around the sun gear 31c while rotating. However, the steered wheels 21 a and 21 b are connected to the planetary carrier 31 d via the steered shaft 25 and the rack shaft 27. For this reason, the resistance force against the rotation of the planet carrier 31d is much larger than the resistance force against the rotation of the sun gear 31c in a rotatable state. Therefore, when the planetary gear 31b rotates, the sun gear 31c rotates (rotates), and the planet carrier 31d does not rotate. That is, the steered shaft 25 does not rotate.

  In short, in a state where the engagement of the lock pin 39 with the tooth groove of the locking gear 33 is released, the clutch device 19 is in a disconnected state in which the steering shaft 23 and the steered shaft 25 are disconnected. At this time, the rotational force of the steering shaft 23 is not transmitted to the steered shaft 25.

Next, an input / output system for the control device 40 will be described.
The control device 40 includes, as input systems, a steering angle sensor 41, a steering torque sensor 43, a steering reaction force motor resolver 45, a steered motor resolver 47, a rack stroke sensor 49, a vehicle speed sensor 51, a yaw rate sensor 53, and an acceleration sensor. 55 is connected.

  The steering angle sensor 41 and the steering torque sensor 43 are provided on the steering shaft 23. The steering angle sensor 41 detects the steering angle of the steering wheel 13 by the driver, and gives the detected steering angle information to the control device 40. The steering torque sensor 43 detects the steering torque of the handle 13 by the driver, and provides the detected steering torque information to the control device 40.

  The steering reaction force motor resolver 45 is provided in the steering reaction force motor 16. The steering reaction force motor resolver 45 detects the rotational operation amount (steering angle) of the steering reaction force motor 16 and supplies the detected steering angle information to the control device 40.

  The steered motor resolver 47 is provided in the steered motor 29. The steered motor resolver 47 detects the rotational operation amount (steered angle) of the steered motor 29 and provides the detected steered angle information to the control device 40. The steered motor resolver 47 corresponds to the “steering angle detector” of the present invention.

  The rack stroke sensor 49 is provided on the rack shaft 27. The rack stroke sensor 49 detects a rack stroke (steering angle), which is a linear movement amount of the rack shaft 27, and provides the detected turning angle information to the control device 40. The rack stroke sensor 49 is also equivalent to the “steering angle detector” of the present invention, like the steered motor resolver 47.

  The vehicle speed sensor 51 detects the speed (vehicle speed) VS of the vehicle V and gives the detected vehicle speed information to the control device 40. The vehicle speed sensor 51 corresponds to the “vehicle speed detector” of the present invention. The yaw rate sensor 53 detects the yaw rate of the vehicle V and provides the detected yaw rate information to the control device 40. The acceleration sensor 55 detects the lateral acceleration (lateral G) and the longitudinal acceleration (vertical G) of the vehicle V, and gives the detected lateral G information and vertical G information to the control device 40.

  On the other hand, the control device 40 is connected to the steering reaction force motor 16, the steering motor 29, and the electromagnetic solenoid 37 as an output system.

  The control device 40 sets the steering mode of the vehicle steering device 11 to the SBW mode, the EPS based on the detection signal input via the input system and the abnormality diagnosis result related to various components of the vehicle steering device 11. A control signal for controlling the driving of the steering reaction force motor 16, the steering motor 29, and the electromagnetic solenoid 37 is generated according to the function for determining either the mode or the manual steering mode and the determined steering mode. And a function of performing drive control of the steering reaction force motor 16, the steered motor 29, and the electromagnetic solenoid 37 based on the generated control signal.

  When the vehicle steering device 11 is operating in the SBW mode, the control device 40 controls driving of the steering reaction force motor 16 so as to perform appropriate steering with respect to the driver's hand holding the handle 13. Operates to convey reaction force (response).

  Further, when the vehicle steering device 11 is operating in the SBW mode, the control device 40 sets the turning angles of the steered wheels 21a and 21b to a target turning angle calculated based on the steering angle, the steering torque, and the like. By performing drive control of the steered motor 29 so as to follow, the steered wheels 21a and 21b are steered according to the driver's driving intention.

Further, the control device 40 steers as the turning angles of the steered wheels 21a and 21b approach the end turning angle SAend (see FIG. 2) that defines the end of the steerable range related to the steered wheels 21a and 21b. By performing drive control of the steering reaction force motor 16 so as to create a wall reaction force by increasing the reaction force, the steerable range related to the steered wheels 21a and 21b can be increased for the driver by increasing the steering reaction force. It works to manifest itself as a feeling of responsiveness.
The end turning angle SAend is a fixed value set according to the design requirements of the turning mechanism.

  Furthermore, in order to respond to a request for power saving, the control device 40 is constantly changing according to a change in the running scene including a change in the vehicle speed VS of the vehicle V and the absolute value SA of the turning angle related to the steered wheels 21a and 21b. The drive control of the steered motor 29 is performed using the current upper limit characteristic (see FIG. 3) of the steered motor 29 that changes.

  In order to realize the various functions, the control device 40 includes a prediction unit 61, a current upper limit characteristic storage unit 63, and a control unit 65.

  The predicting unit 61 is based on, for example, brake operation information by a brake sensor (not shown) that detects an operation amount of a brake pedal (not shown), acceleration information of the vehicle V by the acceleration sensor 55, and the like. Has a function of predicting the starting time when the motor starts rolling from a stationary state. Specifically, the prediction unit 61 regards the timing of receiving brake operation information indicating that the brake pedal force has been released and acceleration information indicating that the vehicle V has started as the start time of the steered wheels 21a and 21b.

The current upper limit characteristic storage unit 63 is a current of the turning motor 29 that changes from moment to moment according to changes in the running scene including changes in the vehicle speed VS of the vehicle V and the absolute value SA of the turning angle related to the turning wheels 21a and 21b. It has a function of storing the upper limit characteristic (see FIG. 3). The current upper limit characteristic of the steered motor 29 that is stored in the current upper limit characteristic storage unit 63 and changes according to the change of the traveling scene is referred to when the control unit 65 performs drive control of the steered motor 29.
The current upper limit characteristic of the steered motor 29 will be described later in detail.

As shown in FIGS. 1 to 3, the control unit 65 is configured such that the vehicle speed VS of the vehicle V is less than a predetermined vehicle speed threshold value VSth, and the absolute value SA of the turning angle related to the steered wheels 21a and 21b When the steering angle threshold value SAth1 is exceeded, the stationary current upper limit value Isp_max is lower than the traveling current upper limit value Irn_max that is the current upper limit value of the steering motor 29 when the vehicle speed VS is equal to or higher than the vehicle speed threshold value VSth. Drive control of the steering motor 29 is performed.
As the vehicle speed threshold VSth, for example, an extremely low speed value such as 5 km / h may be set as appropriate.

  Further, as shown in FIGS. 1 to 3, the control unit 65 gradually decreases the vehicle speed VS of the vehicle V from the vehicle speed threshold value Vth to less than the vehicle speed threshold value Vth (see time t <b> 1 in FIG. 3). When the absolute value SA of the turning angle relating to 21a and 21b exceeds the first turning angle threshold value SAth1 (see FIG. 2), the stationary current upper limit value has a characteristic of gradually decreasing according to the degree of gradually decreasing the vehicle speed VS. The drive control of the steered motor 29 is performed using Isp_max (see FIGS. 2 and 3).

  Then, as shown in FIGS. 1 to 3, when the start time t3 (see FIG. 3) at which the steered wheels 21 a and 21 b start rolling from the stationary state is predicted, the control unit 65 starts the start time t3 (FIG. 3). In the starting period Tst (see FIG. 3) including the reference), the driving control of the steered motor 29 is performed using the starting current upper limit value Ist_max which is lower than the stationary current upper limit value Isp_max.

  Next, the operation of the control device 40 when the steering mode of the vehicle steering device 11 is the SBW mode will be described with reference to FIGS. FIG. 2 is an explanatory view showing the current upper limit characteristic of the steered motor 29 relative to the change in the steered angle SA during traveling and stationary. FIG. 3 is an explanatory diagram showing the current upper limit characteristic of the steered motor 29 that changes from moment to moment according to changes in the driving scene over time.

  When the vehicle V is traveling with a vehicle speed VS equal to or higher than the vehicle speed threshold VSth (VS ≧ VSth), as shown in FIGS. 2 and 3, the current upper limit characteristic of the steered motor 29 is the steered wheels 21a and 21b. Regardless of the magnitude of the absolute value SA of the corner, the traveling current upper limit value Irn_max, which is a fixed value, is set. Here, the traveling current upper limit value Irn_max of the steering motor 29, which is a fixed value, does not give the driver a particular sense of discomfort when the vehicle V is traveling (VS ≧ VSth), and is the minimum turning radius of the vehicle V. It is set to an appropriate value in consideration of various conditions that the steerable wheels 21a and 21b can be steered quickly to both end portions that define no steerable range.

It is assumed that the vehicle speed VS of the vehicle V is decelerated from the vehicle speed threshold value Vth to the vehicle speed threshold value Vth (see times t1 to t2 in FIG. 3) while the vehicle V is traveling. Then, at the same time t1 to t2 (VS <VSth) when the vehicle speed VS is less than the vehicle speed threshold value VSth, the current upper limit characteristic of the steered motor 29 is the first absolute value SA of the steered angle related to the steered wheels 21a and 21b. When the turning angle threshold value SAth1 is exceeded, the stationary current upper limit value Isp_max, which is a variable value lower than the traveling current upper limit value Irn_max, is set.
When the vehicle speed VS is less than the vehicle speed threshold value VSth, but the absolute value SA of the turning angle related to the steered wheels 21a and 21b is equal to or less than the first turning angle threshold value SAth1, the current upper limit characteristic of the turning motor 29 is The traveling current upper limit value Irn_max is maintained as it is.

Here, the stationary upper limit current value Isp_max, which is a variable value, is set to an appropriate value in consideration of the current value of the turning motor 29 that does not operate the heating suppression control function of the turning motor 29 included in the control device 40. The
Specifically, as shown in FIG. 2, the magnitude of the absolute value SA of the steered angles relating to the steered wheels 21a and 21b ranges from a first steered angle threshold SAth1 to a second steered angle threshold SAth2 (where SAth1 < In the range of SAth2), the larger the absolute value SA of the turning angle, the smaller the value is set.
In the range (SAth2 <SA ≦ SAend) where the absolute value SA of the steered angle relating to the steered wheels 21a and 21b exceeds the second steered angle threshold value SAth2 (SAth1 <SAth2), the current of the steered motor 29 As shown in FIG. 2, the upper limit characteristic maintains the minimum value of the stationary current upper limit value Isp_max (the stationary current upper limit value Isp_max when SA = SAth2).

Further, the stationary current upper limit value Isp_max, which is a variable value, is such that the absolute value SA of the turning angle associated with the steered wheels 21a and 21b exceeds the first turning angle threshold value SAth1, as shown in FIG. When the vehicle speed VS is less than the vehicle speed threshold VSth, the vehicle speed VS is set to a smaller value as the vehicle speed VS is lower.
In short, the stationary current upper limit value Isp_max, which is a variable value, is set as a function of the vehicle speed VS of the vehicle V and the absolute value SA of the turning angle associated with the steered wheels 21a and 21b.
However, a configuration is adopted in which the stationary current upper limit value Isp_max, which is a variable value, is set as a function of one of the vehicle speed VS of the vehicle V and the absolute value SA of the turning angle associated with the steered wheels 21a and 21b. May be.

Next, it is assumed that the vehicle V stops (VS = 0, see times t2 to t3 in FIG. 3). Then, at the same time t2 to t3 when the vehicle V is stopped (VS = 0), the current upper limit characteristic of the steered motor 29 is that the absolute value SA of the steered angle related to the steered wheels 21a and 21b is the first steered. When the angle threshold value SAth1 is exceeded, the stationary current upper limit value Isp_max, which is a variable value lower than the traveling current upper limit value Irn_max, is set.
Note that, at the same time t2 to t3 when the vehicle V is stopped (VS = 0), the stationary current upper limit value Isp_max, which is a variable value, is set to the magnitude of the absolute value SA of the turning angle related to the steered wheels 21a and 21b. In the range of the first turning angle threshold value SAth1 to the second turning angle threshold value SAth2 (SAth1 <SA <SAth2), a configuration is adopted in which the larger the absolute value SA of the turning angle is, the smaller the value is set. May be.

Next, it is assumed that the steered wheels 21a and 21b of the vehicle V start rolling from a stationary state (when starting, refer to “starting period Tst” related to times t3 to t4 in FIG. 3). Then, in the start period Tst (for example, an appropriate period such as 1 second) related to the same time t3 to t4, the current upper limit characteristic of the steered motor 29 is the minimum value (SA = SAth2) of the stationary current upper limit value Isp_max. Is set to the starting current upper limit value Ist_max, which is lower than the current stationary current upper limit value Isp_max).
The starting current upper limit value Ist_max is mechanically determined in the turning device (steering unit) 17 around the rack shaft 27 at the time of starting the steered wheels 21a and 21b (predicted by the predicting unit 61). It is set to an appropriate value in consideration of the current value of the steering motor 29 capable of suppressing such abnormal noise.

Next, it is assumed that the vehicle V has accelerated to the vehicle speed VS that reaches the vehicle speed threshold value Vth from the start (see times t4 to t5 in FIG. 3). Then, at the same time t4 to t5 (VS <VSth), which is a period until the vehicle speed VS reaches the vehicle speed threshold value Vth (after the start period Tst has elapsed), the current upper limit characteristics of the steered motor 29 are the steered wheels 21a, When the absolute value SA of the turning angle according to 21b exceeds the first turning angle threshold value SAth1, the stationary current upper limit value Isp_max, which is a variable value lower than the traveling current upper limit value Irn_max, is set.
Note that the setting method of the stationary current upper limit value Isp_max, which is a variable value, is the same as the setting method at the times t1 to t2 in FIG.

  Next, it is assumed that the vehicle V is traveling at a vehicle speed VS equal to or higher than the vehicle speed threshold VSth (VS ≧ VSth, see time t5 in FIG. 3). Then, the current upper limit characteristic of the steered motor 29 is a fixed current value regardless of the magnitude of the absolute value SA of the steered angle relating to the steered wheels 21a and 21b, as before time t1 in FIG. The upper limit value Irn_max is set.

[Operational Effects of the Vehicle Steering Device 11 According to the Embodiment of the Present Invention]
The vehicle steering device 11 based on the first aspect (corresponding to claim 1) has a steering reaction force generator having a handle (steering member) 13 operated when turning the steered wheels 21a, 21b of the vehicle V. (Steering portion) 15 and a steering motor 29 for applying a turning force for turning the steered wheels 21a and 21b, which are mechanically separated from the steering reaction force generating device (steering portion) 15. A steerable device (steering portion) 17 capable of steering the steered wheels 21a, 21b in a state of being turned, and a steered motor resolver (steering angle detecting portion) 47 for detecting the steered angles related to the steered wheels 21a, 21b; The vehicle speed sensor (steering angle detection unit) 51 that detects the vehicle speed VS of the vehicle V and the turning angles of the steered wheels 21a and 21b are made to follow the target turning angle based on the operation of the handle (steering member) 13. a control unit 65 for controlling the drive of the steering motor 29 as the steering Comprising 21a, a prediction unit 61 for 21b to predict a time of starting to start rolling from a stationary state, the.
When the vehicle speed VS of the vehicle V is less than the predetermined vehicle speed threshold value VSth and the absolute value SA of the turning angle related to the steered wheels 21a and 21b exceeds the first turning angle threshold value SAth1, the control unit 65 The drive control of the steered motor 29 is performed by using a stationary current upper limit value Isp_max that is lower than the traveling current upper limit value Irn_max that is the current upper limit value of the steered motor 29 when VS is equal to or higher than the vehicle speed threshold value VSth. In addition, when the prediction unit 61 predicts the start time of the steered wheels, the control unit 65 has a starting current upper limit value Ist_max that is lower than the stationary current upper limit value Isp_max in the starting period Tst including the starting time. Is used to control the drive of the steering motor 29.

According to the vehicle steering apparatus 11 based on the first aspect, when the turning angle (absolute value) SA is in the vicinity of the terminal turning angle SAend (see FIG. 2) at the time of stationary, FIG. 2 and FIG. As shown in FIG. 3, since the driving control of the steered motor 29 is performed using the stationary current upper limit value Isp_max that is lower than the traveling current upper limit value Irn_max, the steered wheels 21a and 21b temporarily hit the obstacle. Even if the vehicle encounters a case where it is impossible to turn the vehicle, it can respond to a request for power saving (improvement of fuel consumption and power consumption of the vehicle V).
Further, according to the vehicle steering device 11 based on the first aspect, the starting current upper limit value Ist_max is lower than the stationary current upper limit value Isp_max in the starting period Tst including the starting time of the steered wheels 21a and 21b. Since the driving control of the steered motor 29 is performed, the mechanical noise that tends to occur in the steered device (steered portion) 17 around the rack shaft 27 when the steered wheels 21a and 21b are started is suppressed. be able to.

Further, the vehicle steering apparatus 11 based on the second aspect (corresponding to claim 2 ) is the vehicle steering apparatus 11 based on the first aspect, and the control unit 65 is configured so that the vehicle speed VS is greater than or equal to the vehicle speed threshold value Vth. When the absolute value SA of the steered angle relating to the steered wheels 21a and 21b exceeds the first steered angle threshold value SAth1 gradually decreasing below the vehicle speed threshold Vth, the vehicle speed VS gradually decreases according to the degree of gradual decrease. The drive control of the steered motor 29 is performed using the stationary current upper limit value Isp_max having characteristics.

According to the vehicle steering device 11 based on the second aspect , the vehicle speed VS gradually decreases from the vehicle speed threshold value Vth to less than the vehicle speed threshold value Vth, and the absolute value SA of the turning angle related to the steered wheels 21a and 21b is obtained. When the first turning angle threshold value SAth1 is exceeded, the turning motor 29 is used by using the stationary current upper limit value Isp_max (see times t1 to t2 in FIG. 3) having a characteristic of gradually decreasing according to the degree of gradually decreasing the vehicle speed VS. Therefore, the situation where the driver feels uncomfortable that the turning response is delayed when the traveling current upper limit value Irn_max is switched to the stationary current upper limit value Isp_max can be eliminated.

[Other Embodiments]
The embodiments described above show examples of realization of the present invention. Therefore, the technical scope of the present invention should not be limitedly interpreted by this. This is because the present invention can be implemented in various forms without departing from the gist or main features thereof.

  For example, in the description according to the embodiment of the present invention, an example in which the clutch device 19 having the planetary gear mechanism 31 is provided has been described, but the present invention is not limited to this example. The clutch device 19 may have any configuration as long as the steering shaft 23 and the steered shaft 25 can be connected or disconnected.

11 Vehicle Steering Device 13 Handle (Steering Member)
15 Steering reaction force generator (steering part)
17 Steering device (steering part)
21a, 21b Steering wheel 25 Steering shaft (steering part)
27 Rack shaft (steering part)
29 Steering motor 47 Steering motor resolver (steering angle detector)
49 Rack stroke sensor (steering angle detector)
61 Predictor 65 Controller V Vehicle

Claims (2)

A steering unit having a steering member operated when turning the steered wheels of the vehicle;
A steering unit that provides a steering force for steering the steered wheels, and capable of steering the steered wheels in a state of being mechanically separated from the steering unit; and
A turning angle detector for detecting a turning angle associated with the steered wheel;
A vehicle speed detector for detecting the vehicle speed of the vehicle;
A control unit that performs drive control of the steered motor so that the steered angle related to the steered wheel follows the target steered angle based on the operation of the steering member;
A prediction unit that predicts a start time when the steered wheels start rolling from a stationary state , and
The control unit is configured such that when the vehicle speed is less than a predetermined vehicle speed threshold and the absolute value of the turning angle related to the steered wheel exceeds a predetermined turning angle threshold, the vehicle speed is equal to or higher than the vehicle speed threshold. There row drive control of the steering motor with a maximum current when outright laid lower than the traveling time of the current upper limit value is a current upper limit value of the steering motor when,
When the start time of the steered wheels is predicted by the prediction unit, the steered motor using a start current upper limit value lower than the current upper limit current value during the predetermined period including the start time The vehicle steering apparatus characterized by performing drive control of this . The vehicle steering device according to claim 1,
The controller is configured to reduce the vehicle speed when the vehicle speed gradually decreases from the vehicle speed threshold value to less than the vehicle speed threshold value, and the absolute value of the turning angle related to the steered wheels exceeds a predetermined turning angle threshold value. A vehicle steering apparatus, wherein drive control of the steered motor is performed using the stationary current upper limit value having a characteristic of gradually decreasing according to the degree of gradually decreasing.

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