JP5407123B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a vehicle steering control device that changes a transmission ratio that is a ratio between a steering amount and a turning amount in accordance with a vehicle speed.

  Conventionally, in the vehicle steering control device of Patent Document 1, the steering feeling is improved by changing the transmission ratio, which is the ratio of the steering amount and the turning amount, according to the vehicle speed. Generally, the transmission ratio is set to be small at a low speed and the steering response is quick, and is set to be large at a high speed and the steering response is slow.

In addition, if the transmission ratio changes suddenly when the vehicle speed changes while maintaining a constant steering angle, the driver will feel uncomfortable. Therefore, if the vehicle speed change is greater than this threshold, the threshold will be used as a reference. As a result, the driver's uncomfortable feeling is reduced.
JP 2001-151139 A

  However, in the above prior art, at very low speeds, the transmission ratio is set to be small and the steering response becomes sensitive, so steering is rather difficult when passing on narrow roads, entering the garage, traveling on low μ roads, etc. There was a problem that the feeling deteriorated.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle steering control device that avoids a sensitive steering response at extremely low speeds while ensuring steering feeling.

In order to achieve the above-mentioned object, in the present invention, the transmission ratio, which is the ratio between the steering amount of the steering wheel and the turning amount of the steered wheels, is changed, and the response of the turning amount to the steering amount is set to the quick side or the slow side. The vehicle steering control device includes: a transmission ratio variable means that changes to the side; and a control means that calculates a target transmission ratio based on the vehicle speed and outputs a transmission ratio command value to the transmission ratio variable means based on the target transmission ratio. When the target transmission ratio is changed to the quick side during acceleration of the vehicle, the control means limits the shift of the transmission ratio command value to the quick side as the steering amount increases. it was decided to perform the transmission ratio limit control for limiting a quick side movement of said transmission ratio command value in the vicinity of the rack end with the maximum.

  Therefore, it is possible to provide a vehicle steering control device that avoids a sensitive steering response at extremely low speeds while ensuring steering feeling.

  Hereinafter, the best mode for carrying out the present invention will be described based on an embodiment shown in the drawings.

[System configuration]
FIG. 1 is a system configuration diagram of a vehicle steering control device. The steering control device includes a steering wheel SW, steered wheels FL and FR, a steering angle sensor 1, a vehicle speed sensor 2, a control controller 3, and a steering actuator 4.

  The steering wheel SW is connected to the rack shaft 5 via the steering actuator 4. The steering actuator 4 is a steering assist mechanism that assists the steering force while changing the transmission ratio R, which is the ratio of the steering angle θ and the turning angle φ, and is provided on the rack shaft 5 side with the gear provided on the steering wheel SW side. The transmission ratio R is controlled by changing the gear ratio of the provided gear.

  If the transmission ratio R is decreased, the steering response becomes quick, and the turning angle φ with respect to the steering angle θ becomes larger than that during non-control. On the other hand, if the transmission ratio R is increased, the steering response becomes slow, and the turning angle φ with respect to the steering angle θ becomes smaller than that during non-control.

  The controller 3 calculates the target turning angle φ * s based on the detected values of the steering angle sensor 1 and the vehicle speed sensor 2 and the actual turning angle command value φs that is the current command value for the steering actuator 4, and the drive current I The steering actuator 4 is driven by converting into (φ * s).

[Control controller block diagram]
FIG. 2 is a control block diagram of the controller 3.
The target turning angle calculation unit 31 calculates the target turning angle φ * and the target transmission ratio Rref based on the steering angle θ and the vehicle speed V. Here, the target transmission ratio Rref is read from the map of FIG. 3 based on the vehicle speed V, and the target turning angle φ * is calculated by the following equation.
Target turning angle φ * = steering angle θ / target transmission ratio Rref
Alternatively, the target turning angle φ * may be obtained from a map, and the target transmission ratio Rref may be calculated using the relationship of the above formula.

The turning angle command limiter 32 calculates a target turning angle command value φ * s based on the steering angle θ, the vehicle speed V, the target turning angle φ *, and the target transmission ratio Rref.
The servo calculation output unit 33 drives the drive current I (φ * s of the steering actuator 4 based on the target turning angle command value φ * s and the actual turning angle command value φs that is the basis of the current actual driving current I (φs). ) Is calculated.

[Block diagram of turning angle command value limiter]
FIG. 4 is a control block diagram of the turning angle command value limiting unit 32.
The restriction determination unit 321 sets a restriction mode (see FIGS. 5 and 7) based on the steering angle θ, the vehicle speed V, the target transmission ratio Rref, and the transmission ratio restriction amount RL (calculated by the transmission ratio restriction unit 322).

  The transmission ratio limiter 322 calculates a transmission ratio limit amount RL based on the limit mode and the target transmission ratio Rref, and outputs a transmission ratio command value Rs based on the transmission ratio limit amount RL. If the target transmission ratio Rref decreases (shifts to the quick side) during acceleration turning, the transmission ratio command value Rs = the limit amount RL, otherwise Rs = target transmission ratio Rref (see FIGS. 5 and 6). ).

  The turning angle command value determining unit 323 determines the target turning angle command value φ * s based on the steering angle θ, the restriction mode, the target turning angle φ *, and the transmission ratio command value Rs.

[Restricted mode table]
5 and 7 are tables of transmission ratio limiting modes set in the limit determining unit 321. FIG. FIG. 5 shows the transmission ratio limit start (start determination), and FIG. 7 shows the limit release (release determination). FIG. 6 shows a restriction start determination region in the transmission ratio R map, and FIG. 8 shows a restriction release determination region.

(At the start of restriction)
At the start of the restriction, the restriction mode is determined based on the steering state (turning or straight traveling), the acceleration / deceleration state of the vehicle, and the change in the target transmission ratio Rref. The steering state and the acceleration / deceleration state are determined based on the threshold value of the steering angle θ and the threshold value of the vehicle speed change rate ΔV, respectively. Further, the target transmission ratio Rref is determined to decrease (quick) or increase (slow) by comparing the previous value with the current value.

  When the vehicle is accelerating and the turning angle φ is large (when the vehicle behavior is in a non-linear region), there is an oversteer tendency, so the transmission ratio command value is accompanied by a decrease in the target transmission ratio Rref (change to the quick side) When Rs shifts to the quick side, the steering response becomes hypersensitive and the oversteer tendency becomes larger, and the steering feeling is deteriorated.

  On the other hand, when the steering neutral state and the turning angle φ are small, the vehicle behavior is stable and the oversteer tendency is small. For this reason, when the transmission ratio command value Rs becomes slow, the steering response delay given to the driver becomes remarkable.

  Therefore, the amount of change to the quick side of the transmission ratio command value Rs in which the target transmission ratio Rref has decreased during the acceleration turn is limited (restriction mode A). In other cases, the transmission ratio command value Rs is not limited, and the target transmission ratio Rref = transmission ratio command value Rs is set (see FIG. 5). As a result, the steering feeling is ensured by setting the transmission ratio command value Rs suitable for the vehicle speed V under other conditions while suppressing the oversteer tendency during acceleration turning.

  As shown in FIG. 6, the target transmission ratio Rref monotonously decreases on the low vehicle speed V side with respect to the vehicle speed VX0, and monotonically increases on the high vehicle speed V side from X0. Therefore, the target transmission ratio Rref change rate is negative (quick side) in the region where the vehicle speed is VX0 or less, and the transmission ratio command value Rs is limited if acceleration turning is being performed in the region where the vehicle speed V ≦ X0.

(When restriction is released)
When the restriction is released, the restriction mode is determined depending on the steering state (turning or straight line) and the magnitude of the target transmission ratio Rref and the transmission ratio restriction amount RL. Regardless of whether the vehicle is turning or traveling straight, if the target transmission ratio Rref increases (changes to the slow side) while the transmission ratio is being restricted (restriction mode A), the restriction on the transmission ratio command value Rs is released (OFF).

  As shown in FIG. 7, the transmission ratio limit amount RL = RL1 when the vehicle speed V = X1 (<X0) is entered into the transmission ratio limit mode. During the restriction, the transmission ratio command value Rs = the transmission ratio restriction amount RL1 is maintained regardless of the value of the target transmission ratio Rref. With this transmission ratio limit amount RL1 as a reference, if the target transmission ratio Rref is on the quick side, the transmission ratio command value Rs is continuously limited, and if the target transmission ratio Rref is on the slow side, the restriction is released.

  Accordingly, when the vehicle enters the restriction mode at the vehicle speed V = X1 (transmission ratio RL1), the vehicle speed V-target transmission ratio Rref map has a region between X1 and X2 where the target transmission ratio Rref = the transmission ratio restriction amount RL1. Transmission ratio command value Rs is limited to RL1. When moving to other areas, the restriction is lifted.

  As a result, the increase in the target transmission ratio Rref (change to the slow side) and the release of the restriction on the transmission ratio command value Rs are synchronized to reduce the influence of the fluctuation in the transmission ratio command value Rs on the vehicle behavior. Therefore, the uncomfortable feeling of steering feeling is reduced.

[Transmission ratio restriction start / release flow]
FIG. 9 is a transmission ratio restriction start / release flow executed by the turning angle command restriction unit 32 (see FIGS. 2 and 4). Hereinafter, each step will be described.

  In step S1, the target transmission ratio Rref is calculated based on the vehicle speed V, the transmission ratio limit amount RL1 in the previous control is acquired, and the process proceeds to step S2.

  In step S2, the turning state is determined based on the steering angle θ, and the process proceeds to step S3.

  In step S3, acceleration / deceleration is determined by calculating a change rate ΔV of the vehicle speed V, and the process proceeds to step S4.

  In step S4, it is determined whether or not the restriction mode M = A (restricted state). If YES, the process proceeds to step S5, and if NO, the process proceeds to step S7.

  In step S5, it is determined whether target transmission ratio Rref ≧ transmission ratio limit amount RL1. If YES, transmission ratio R is slow and the process proceeds to step S6. If NO, transmission ratio R is quick and the process proceeds to step S11. .

  In step S6, the restriction mode M = OFF (restriction release state), and the process proceeds to step S11.

  In step S7, it is determined whether or not the vehicle is in a turning state (steering angle θ ≧ turning determination threshold θx). If YES, the process proceeds to step S8, and if NO, the process proceeds to step S11.

  In step S8, it is determined whether the vehicle is in an acceleration state (vehicle speed change rate ΔV ≧ threshold value ΔVx). If YES, the process proceeds to step S9, and if NO, the process proceeds to step S11.

  In step S9, it is determined whether or not it is a quick change (target transmission ratio Rref <threshold Rref0). If YES, the process proceeds to step S10, and if NO, the process proceeds to step S11.

  In step S10, the restriction mode M = A (restricted state) is set, and the process proceeds to step S11.

  In step S11, the transmission ratio command value Rs is limited to the transmission ratio limit amount RL1, and the process returns to step S1.

[Transfer ratio limit amount RL calculation flow]
FIG. 10 is a flowchart of the transmission ratio restriction amount RL calculation executed by the transmission ratio restriction unit 322.

  In step S111, the target transmission ratio Rref is read from the vehicle speed V-transmission ratio R map (see FIG. 3), and the process proceeds to step S112.

  In step S112, the current restriction mode M is acquired, and the process proceeds to step S113.

  In step S113, it is determined whether or not the current restriction mode M = A (restricted state). If YES, the process proceeds to step S114. If NO, the process proceeds to step S116.

  In step S114, it is determined whether or not the previous restriction mode M = OFF (non-restricted state). If YES, the process proceeds to step S115, and if NO, the process proceeds to step S117.

  In step S115, the transmission ratio command value Rs is limited to the transmission ratio limit amount RL1, and the process proceeds to step S117.

  In step S116, the transmission ratio command value Rs is limited to the transmission ratio limit amount RL1, and the process proceeds to step S117.

  In step S117, the previous restriction mode M0 = current restriction mode M is set, and the process returns to step S111.

[Change over time in transmission ratio limit control]
FIG. 11 is a time chart of transmission ratio limiting control.
(Time t0)
At time t0, steering is increased, and the actual turning angle φ of the steered wheels (front wheels) FL and FR increases. Steering angle θ ≧ turning determination threshold value θx, so that it is determined that the vehicle is turning.

(Time t1)
At time t1, the vehicle speed V starts to increase, and accordingly, the target transmission ratio Rref shifts to the quick side (see FIG. 3).

(Time t2)
At time t2, the vehicle speed V becomes X1, and the vehicle speed change rate ΔV ≧ acceleration determination threshold value ΔVx. As a result, the acceleration state is determined, and restriction of the transmission ratio command value Rs is started, the restriction mode M = A is established, and the transmission ratio command value Rs = the restriction amount RL1. The transmission ratio limit amount RL1 remains constant at the value RL1 at the vehicle speed V = X1.
Thereafter, until time t3, the transmission ratio limit amount RL1> target transmission ratio Rref, and the transmission ratio command value Rs for the steering actuator 4 is fixed to RL1 regardless of the value of the target transmission ratio Rref.

(Time t3)
At time t3, the target transmission ratio Rref = the transmission ratio limit amount RL1, and the restriction of the transmission ratio command value Rs is released, and the restriction mode M = OFF. Thereafter, a command according to the target transmission ratio Rref is output to the steering actuator 4.

[Effect of Example 1]
(1) Transmission ratio R which is a ratio of the steering wheel SW, the steered wheels FL, FR, and the steering angle θ (steering amount) of the steering wheel SW and the steered angle φ (steering amount) of the steered wheels FL, FR. And the target transmission ratio Rref is calculated on the basis of the steering actuator 4 (transmission ratio variable means) for changing the response of the steering angle φ to the quick side or the slow side with respect to the steering angle θ and the vehicle speed V, and this target transmission ratio In a vehicle steering control device including a controller 3 (control means) that outputs a transmission ratio command value Rs to a steering actuator 4 based on Rref,
When the target transmission ratio Rref changes to the quick side during acceleration of the vehicle, the control controller 3 executes the transmission ratio limiting control for limiting the quick side transition of the transmission ratio command value Rs.

  Thereby, the steering feeling can be ensured by setting the transmission ratio command value Rs suitable for the vehicle speed V under other conditions while suppressing the oversteer tendency during acceleration.

  (2) When the steering angle θ is equal to or greater than the straight travel determination threshold θx (predetermined value), the controller 3 executes the transmission ratio limiting control.

  When the turning angle φ is large, there is an oversteer tendency, and when the transmission ratio command value Rs shifts to the quick side, the oversteer tendency further increases. On the other hand, when the turning angle φ is small, the oversteer tendency is small, and when the transmission ratio command value Rs becomes slow, the steering response delay given to the driver becomes significant.

  Therefore, by executing the transmission ratio limit control only during turning using the straight traveling determination threshold value θx, the effect (1) can be obtained more effectively.

  (3) When the target transmission ratio Rref shifts to the slow side from the current transmission ratio command value Rs during execution of the transmission ratio limiting control, the control controller 3 cancels the transmission ratio limiting control.

  As a result, the increase in the target transmission ratio Rref (change to the slow side) and the release of the restriction on the transmission ratio command value Rs are synchronized to reduce the influence of the fluctuation in the transmission ratio command value Rs on the vehicle behavior. Therefore, the uncomfortable feeling of the steering feeling can be reduced.

  Example 2 will be described. Since the basic configuration is the same as that of the first embodiment, only different points will be described. In the first embodiment, the condition for canceling the transmission ratio restriction is the same regardless of whether the vehicle is turning or going straight. However, the second embodiment is different in that the releasing condition is changed between turning and going straight.

[Gradual restriction release mode]
FIG. 12 is a diagram illustrating a restriction release mode table according to the second embodiment, and FIG. 13 is a diagram illustrating a restriction release determination region in the transmission ratio map. The restriction mode A shows a transmission ratio restriction state similar to that in the first embodiment, and the restriction mode B shows a state where the restriction of the transmission ratio command value Rs is gradually released.

  In the first embodiment, when the transmission ratio restriction amount becomes quicker (smaller) than the target transmission ratio Rref during the transmission ratio restriction, the restriction state is set regardless of the turning state. On the other hand, in the second embodiment, when the transmission ratio restriction amount becomes quicker than the target transmission ratio Rref during the transmission ratio restriction, the restriction state is continued if the vehicle is turning (restriction mode A), and gradually when the vehicle is traveling straight. The restriction is released (restriction mode B).

  As shown in FIG. 13, when executing the restriction mode B in the transmission ratio restriction region Dα (X1 ≦ vehicle speed V ≦ X2), the transmission ratio restriction amount RL is determined from RL1 (the transmission ratio restriction amount when the restriction mode A enters). Gradually move to the quick side (RL1 → RL2 → RL3), and finally set the value as the target transmission ratio Rref at the speed V = X0.

  Accordingly, the value of the lower limit value X1 of the transmission ratio limiting region Dα increases, the value of the upper limit value X2 decreases, and the transmission ratio limiting region Dα is reduced. Finally, X1 and X2 become the same value, and the transmission ratio limiting region Dα disappears.

Further, when executing the restriction mode B, the transmission ratio restriction amount RL is gradually shifted to the quick side according to the following equation.
RL = RL (previous value) − | RL (previous value) −target transmission ratio Rref | × α
... (a)
Α is a numerical value defined by the vehicle speed V-correction coefficient α map in FIG. By setting the correction coefficient α large at low speeds and small at high speeds, the limit amount RL is quickly reduced (shifted to the quick side) at low speeds and gradually reduced at high speeds.

[Transmission ratio restriction start / release flow in Example 2]
FIG. 15 is a transmission ratio restriction start / release flow executed by the turning angle command restriction unit 32 (see FIGS. 2 and 4). Hereinafter, each step will be described.

  Steps S21 to S31 are the same as steps S1 to S11 in FIG.

  In step S32, it is determined whether the vehicle is in the straight traveling state by comparing the steering angle θ with the straight traveling determination threshold θx. If YES, the process proceeds to step S33, and if NO, the process proceeds to step S34.

  In step S33, the restriction mode M = B (the restriction is gradually released), and the process proceeds to step S31.

  In step S34, the restriction mode M = A (restricted state) is set, and the process proceeds to step S31.

[Transfer Ratio Limit Amount Calculation Flow in Embodiment 2]
FIG. 16 is a transmission ratio limit amount calculation flow executed by the transmission ratio limiter 322.

  Steps S211 and S212 are the same as steps S111 and S112 in FIG.

  In step S213a, it is determined whether or not the restriction mode M = OFF (non-restricted state). If YES, the process proceeds to step S216, and if NO, the process proceeds to step S213b.

  In step S213b, it is determined whether or not the restriction mode M = A (restricted state). If YES, the process proceeds to step S217, and if NO, the process proceeds to step S214.

  Steps S214 to S216 are the same as steps S114 to S116 in FIG.

  In step S217, the correction mode α is determined from the map of FIG. 14 based on the vehicle speed V with the restriction mode M = B (gradual release of restriction), and the process proceeds to step S218.

  In step S128, the transmission ratio limit amount RL is calculated based on the above equation (a), and the process proceeds to step S219.

  In step S219, the previous value RL0 = current value RL of the transmission ratio limit amount is set, and the process proceeds to step S220.

  In step S220, the previous restriction mode M0 = current restriction mode M is set, and the process returns to step S211.

[Change over time of transmission ratio limiting control in Embodiment 2]
FIG. 17 is a time chart of transmission ratio limiting control.
(Time t10)
At time t10, steering is increased, and the actual turning angle φ of the steered wheels (front wheels) FL and FR increases. Steering angle θ ≧ turning determination threshold value θx, so that it is determined that the vehicle is turning.

(Time t11)
At time t11, the vehicle speed V starts increasing, and accordingly, the target transmission ratio Rref shifts to the quick side (see FIG. 3).

(Time t12)
At time t2, the vehicle speed V becomes X1, and the vehicle speed change rate ΔV ≧ acceleration determination threshold value ΔVx. As a result, the acceleration state is determined, and restriction of the transmission ratio command value Rs is started, the restriction mode M = A is established, and the transmission ratio command value Rs = the restriction amount RL1. The transmission ratio limit amount RL1 remains constant at the value RL1 at the vehicle speed V = X1.

(Time t13)
At time t13, the steering angle θ falls below the straight travel determination threshold θx, and it is determined that the vehicle has shifted from the turning state to the straight traveling state. Therefore, the restriction mode M = B is set (see FIG. 12), and the transmission ratio restriction amount gradually decreases (shifts to the quick side) from RL1 to RL2.
Accordingly, the speed X1 increases (shifts to the slow side), X2 decreases (shifts to the quick side), and the region Dα sandwiched between the speeds X1 and X2 also decreases (see FIG. 13).

(Time t14)
At time t14, the steering angle θ again exceeds the straight traveling determination threshold θx, and it is determined that the vehicle has shifted from the straight traveling state to the turning state. Therefore, the restriction mode = A (restricted state) is set again, and the transmission ratio command value Rs is fixed to the transmission ratio restriction amount RL2 at time t14.
Thereafter, until time t15, the transmission ratio limit amount RL2> target transmission ratio Rref, and the transmission ratio command value Rs for the steering actuator 4 is fixed to RL2 regardless of the value of the target transmission ratio Rref.

(Time t15)
At time t15, the target transmission ratio Rref = transmission ratio limit amount RL2, and the restriction of the transmission ratio command value Rs is released and the limit mode M = OFF. Thereafter, transmission ratio command value Rs = target transmission ratio Rref.

(Time t16)
At time t16, the target transmission ratio Rref and the transmission ratio limit amount RL1 coincide. In the first embodiment, the restriction on the transmission amount command value Rs is released at this point, but in the second embodiment, the control mode B is introduced and the transmission ratio restriction amount RL is gradually decreased (shifted to the quick side). Transmission ratio control is released at a timing earlier than in Example 1.

[Effect of Example 2]
(4) The controller 3 gradually releases the transmission ratio limiting control when the vehicle goes straight during the transmission ratio limiting control. As a result, the transmission ratio limitation can be released in stages while the vehicle behavior is relatively stable, and deterioration of the vehicle behavior due to the change in the transmission ratio can be avoided.

  Example 3 will be described. The basic configuration is the same as in the second embodiment. In the second embodiment, an example in which the transmission ratio limitation is gradually approached to the target transmission ratio when entering the restriction mode B in which the transmission ratio restriction is gradually released is shown. In the third embodiment, whether or not the restriction mode B has been entered. An example in which the transmission ratio is made closer to the target transmission ratio regardless of the above.

[Calculation of transmission ratio limit based on steering angle]
FIG. 18 is a diagram showing a restriction release determination region in the transmission ratio map. As in the second embodiment, when the transmission ratio restriction amount RL becomes quicker than the target transmission ratio Rref during the transmission ratio restriction, the restriction state is continued during turning (restriction mode A: see FIG. 12).

In the third embodiment, when entering the restriction mode A, the transmission ratio restriction amount RL is calculated by the following equation (b). The equation (b) is the same as the equation (a) in the second embodiment except that the correction coefficient is changed to β.
RL = RL (previous value) − | RL (previous value) −target transmission ratio Rref | × β
... (b)

  Here, the correction coefficient β is a value defined by the absolute value of the steering angle θ, and is set so as to converge from 1 to zero as | θ | increases (see FIG. 19). This avoids a sensitive steering response when the vehicle is turning.

  Regardless of whether or not there is a transition to the limit mode B (gradually release the limit), the second term on the right side of the above equation (b) converges to zero as the steering angle θ increases, and the transmission ratio limit amount automatically. Converges to a constant value RL1β (see FIG. 21: time t24).

[Transfer Ratio Limit Amount Calculation Flow in Embodiment 3]
FIG. 20 is a transmission ratio limit amount calculation flow in the third embodiment. This is basically the same as the transmission ratio limit calculation flow (FIG. 16) of the second embodiment.

  Steps S311 and S312 are the same as steps S211 and S212 in FIG.

  In step S312a, the steering angle θ is acquired, and the process proceeds to step S313.

  In step S313, it is determined whether or not the restriction mode M = A. If YES, the process proceeds to step S314, and if NO, the process proceeds to step S316.

  Steps S314 to S316 are the same as steps S214 to S216 in FIG.

  In step S317, the correction coefficient β is determined based on the map of FIG. 19, and the process proceeds to step S318.

  In step S318, the transmission ratio limit amount RL is calculated based on the above equation (b), and the process proceeds to step S319.

  Steps S319 and S320 are the same as steps S219 and 220 in FIG.

[Change over time of transmission ratio restriction control in Embodiment 3]
FIG. 21 is a time chart of transmission ratio limiting control in the third embodiment.
(Time t20 to t21)
Times t20 to t21 are the same as Example 2: times t10 to t11 in FIG.

(Time t22)
At time t22, the vehicle speed V becomes X1, and the vehicle speed change rate ΔV ≧ acceleration determination threshold value ΔVx. As a result, it is determined that the vehicle is in the acceleration state, and the restriction of the transmission ratio command value Rs is started. The restriction mode M = A (see FIG. 12) is established, and the transmission ratio command value Rs = the restriction amount RL1.
Further, the transmission ratio limit amount RL is calculated based on the above formula (b), and RL gradually decreases (shifts to the quick side). Along with this, the transmission ratio command value Rs gradually shifts to the quick side.

(Time t23)
At time t23, sharp increase is performed, and the steering angle θ increases rapidly. As a result, the value of the correction coefficient β suddenly decreases (see FIG. 19), and the decreasing gradient of the value of the transmission ratio limit amount RL becomes small.

(Time t24)
At time t24, as the steering angle θ increases, the value of the correction coefficient β becomes almost zero, and the transmission ratio limit amount RL converges to a constant value RL1β. Thereafter, since β≈0 until time t25, the transmission ratio limit amount RL also remains the constant value RL1β.

(Time t25)
At time t25, the target transmission ratio Rref = constant value RL1β, the restriction of the transmission ratio command value Rs is released, and the restriction mode M = OFF. Thereafter, transmission ratio command value Rs = target transmission ratio Rref.

(Time t26)
At time t26, the target transmission ratio Rref and the transmission ratio limit amount RL1 coincide. In the first embodiment, the restriction on the transmission amount command value Rs is released at this time point. However, in the third embodiment as in the second embodiment, the transmission ratio restriction amount RL is gradually decreased using the above formula (b) ( The transmission ratio control is released at a timing earlier than that of the first embodiment.

[Effect of Example 3]
(5) The controller 3 limits the quick side shift of the transmission ratio command value Rs as the steering angle θ or the turning angle φ increases during the transmission ratio restriction control.

  By making it difficult for the transmission ratio to make a quick transition near the rack end where the turning angle is maximum, it is possible to prevent an excessive electrical and mechanical load on the controlled object. In other cases, by limiting the transmission ratio according to the steering angle θ, an appropriate transmission ratio can be obtained regardless of the limiting mode.

(Other examples)
The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to the embodiments, and the design does not depart from the gist of the invention. Any changes and the like are included in the present invention.

It is a system configuration figure of the steering control device for vehicles. 3 is a control block diagram of a control controller 3. FIG. It is a vehicle speed-target transmission ratio map. 5 is a control block diagram of a turning angle command value limiting unit 32. FIG. It is a table | surface of the transmission ratio restriction | limiting mode set in the restriction | limiting determination part 321 (start determination). It is a figure which shows the restriction | limiting start determination area | region in a target transmission ratio map. It is a table | surface of the transmission ratio restriction | limiting mode set in the restriction | limiting determination part 321 (release determination). It is a figure which shows the restriction release determination area | region in a target transmission ratio map. It is a transmission ratio restriction start / release flow executed by the turning angle command restriction unit 32. It is a transmission ratio restriction amount RL calculation flow executed by the transmission ratio restriction unit 322. It is a time chart of transmission ratio restriction control. 10 is a transmission ratio restriction release mode table according to the second embodiment. It is a figure which shows the restriction | limiting cancellation | release determination area | region in the target transmission ratio map of Example 2. FIG. It is a vehicle speed V-correction coefficient alpha map. It is a transmission ratio restriction start / release flow executed by the turning angle command restriction unit 32. It is a transmission ratio restriction amount calculation flow executed by the transmission ratio restriction unit 322. 6 is a time chart of transmission ratio restriction control in Embodiment 2. It is a figure which shows the restriction release determination area | region in the target transmission ratio map of Example 3. FIG. 10 is a | θ | -β map of Example 3. It is a transmission ratio restriction amount calculation flow in the third embodiment. 10 is a time chart of transmission ratio restriction control in Embodiment 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering angle sensor 2 Vehicle speed sensor 3 Control controller 4 Steering actuator 5 Rack shaft 31 Target turning angle calculation part 32 Turning angle command restriction part 32 Steering angle command value restriction part 33 Servo calculation output part 321 Restriction determination part 322 Transmission ratio Limiting unit 323 Steering angle command value determining unit SW Steering wheel

Claims (4)

A steering wheel,
Steered wheels,
A transmission ratio variable means for changing a transmission ratio that is a ratio of a steering amount of the steering wheel and a turning amount of the steered wheel, and changing a response of the steering amount to the steering amount to a quick side or a slow side;
In a vehicle steering control device comprising: a control means that calculates a target transmission ratio based on a vehicle speed and outputs a transmission ratio command value to the transmission ratio variable means based on the target transmission ratio;
When the target transmission ratio changes to the quick side during acceleration of the vehicle, the control means limits the shift of the transmission ratio command value to the quick side as the steering amount increases, so that the steering amount is maximized. the vehicular steering control apparatus characterized by performing a transmission ratio limit control for limiting a quick side shift transmission ratio command value in the vicinity of the rack end made. The vehicle steering control device according to claim 1,
The vehicle steering control device, wherein the control means executes the transmission ratio restriction control when the steering amount is a predetermined value or more. In the vehicle control device according to claim 1 or 2,
The control means cancels the transmission ratio limiting control when the target transmission ratio shifts to a slower side than the current transmission ratio command value during execution of the transmission ratio limiting control. Control device. The vehicle steering control device according to any one of claims 1 to 3,
The vehicle steering control device, wherein the control means gradually releases the transmission ratio limiting control when the vehicle is in a straight traveling state during the transmission ratio limiting control.

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