JP2011016429A - Control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: when a transmission ratio is locked immediately when the motor temperature exceeds a limit point before the transmission ratio of a transmission ratio variable means becomes 1, a neutral position of a steering wheel is deviated from a straight steering position, and a discomfort may be given to a driver.SOLUTION: A load to be applied to a front wheel turning actuator is calculated. When the load to be applied to the front wheel turning actuator becomes larger than a set value, a lateral acceleration is lowered.

Description

  The present invention relates to a vehicle control device that controls a vehicle.

  For example, conventionally, as described in Patent Document 1, the transmission system (steering angle ratio) of the steering amount between the steering handle and the steering wheel is appropriately set in the transmission system between the steering handle (steering wheel) and the steering wheel. There is known a steering device that includes a transmission ratio variable means (steering angle variable means) for changing, and controls a transmission ratio by driving a motor (actuator) provided in the transmission ratio variable means. In the steering apparatus described in Patent Document 1, when the temperature of the motor of the transmission ratio variable means becomes a preventive temperature (X ° C.) or higher, the transmission ratio variable means is changed so that the transmission ratio becomes 1, and the transmission ratio becomes 1. Then, the transmission ratio variable means is locked. Further, if the motor temperature becomes higher than the limit point (Y ° C.) higher than the prevention temperature (X ° C.) before the transmission ratio becomes 1, the transmission ratio variable means is immediately locked. When the motor is not overheated (the temperature of the motor is lower than the prevention temperature, not more than a predetermined temperature Z ° C.), the transmission ratio variable means is unlocked.

JP 2001-270453 A

  In the above prior art, when the temperature of the motor exceeds the limit point before the transmission ratio becomes 1, the transmission ratio variable means is immediately locked, so that the neutral position of the steering wheel and the straight-ahead steering position are deviated. There was a risk of discomfort to the person.

  In order to solve the above-described problem, in the present invention, the load acting on the front wheel steering actuator is calculated, and when the load acting on the front wheel steering actuator exceeds a set value, the lateral acceleration of the vehicle is reduced. did.

  Therefore, the actuator can earn time for waiting until the steering angle ratio becomes 1, and the shift of the neutral position of the steering wheel and the position of the straight steering can be suppressed.

1 is an overall system diagram of a vehicle steering apparatus for a vehicle according to a first embodiment. FIG. 3 is a control block diagram of the steering angle ratio variable controller according to the first embodiment. FIG. 3 is a control block diagram of a braking / driving force correction amount calculation unit according to the first embodiment. 3 is a flowchart illustrating a flow of braking / driving force correction amount calculation processing according to the first embodiment. 3 is a time chart of the first embodiment. FIG. 10 is a control block diagram of a braking / driving force correction amount calculation unit according to the second embodiment. 7 is a flowchart illustrating a flow of braking / driving force correction amount calculation processing according to the second embodiment. 6 is a time chart of Example 2.

[Example 1]
〔overall structure〕
FIG. 1 is an overall system diagram of a vehicle control device 1 mounted on a vehicle 30 of the first embodiment. In the vehicle control device 1, the front wheel 4 of the front wheels 4 and the rear wheels 18 is a steered wheel, and the steering angle ratio that is the ratio of the steering angle of the front wheel 4 to the steering angle of the steering wheel 2 is made variable. It is equipped with a variable steering angle ratio system.

  The vehicle control device 1 includes a steering wheel 2, a front wheel steering mechanism 5 including a rack 9 connected to the front wheel 4, a pinion gear 8 geared to a rack gear provided on the rack 9, as a front wheel side mechanism, A pinion shaft 7 connected to the pinion gear 8, a steering shaft 6 coupled to the steering wheel 2, and a steering angle ratio variable mechanism 19 (steering angle ratio variable means) provided between the pinion shaft 7 and the steering shaft 6 And a front wheel steering actuator 10 (actuator) that drives the steering angle ratio variable mechanism to vary the steering angle ratio.

  The front wheel steering actuator 10 includes, for example, a motor and a speed reducer, and is driven by a drive current from the steering angle ratio variable controller 11 (steering angle ratio control means). The steering angle ratio varying mechanism 19 (steering angle varying means) inputs a steering angle, which is a rotation angle of the steering shaft 6 by the steering of the steering wheel 2 by driving the front wheel steering actuator 10, and the front wheels with respect to the inputted steering angle. The ratio of the rotation angle of the pinion shaft 7 to the steering angle of the steering wheel 2 is made variable by outputting the rotation angle obtained by adjusting the auxiliary turning angle to the pinion shaft 7. Since the relationship between the rotation angle of the pinion shaft 7 and the turning angle of the front wheel 4 is uniquely determined by the gear ratio between the pinion gear 8 and the rack gear (that is, the gear ratio of the so-called rack and pinion mechanism), the pinion shaft Hereinafter, the rotation angle of 7 is referred to as a steering angle, and the ratio of the rotation angle (steering angle) of the pinion shaft 7 to the rotation angle (steering angle) of the steering shaft 6 is referred to as a steering angle ratio.

  As a control system of the vehicle control device 1, a steering angle sensor 3 (steering angle detection means) that detects the steering angle θh of the steering wheel 2, a vehicle speed sensor 12 that detects the vehicle speed Vx, and a lateral acceleration Vy that acts on the vehicle 30. A lateral acceleration sensor 13 for detecting ', a front wheel steering actuator 10 and an internal combustion engine actuator 16 as an actuator for varying the driving force of the vehicle, such as a throttle actuator, and a brake actuator 17 for controlling a brake fluid pressure. The steering angle ratio variable controller 11 that calculates the correction amount of the internal combustion engine, the internal combustion engine controller 14 that controls the internal combustion engine actuator 16, and the brake controller 15 that controls the brake actuator 17 are included. The load on the front wheel steering actuator 10 increases as the lateral acceleration Vy ′ detected by the lateral acceleration sensor 13 increases.

ここで、

である。また、

である。 [Control block]
FIG. 2 is a control block diagram of the steering angle ratio variable controller 11 of the vehicle control device 1.
The steering angle ratio variable controller 11 includes a front wheel steering actuator rotation angle target value calculation unit 20, a steering angle servo control unit 21, an actuator temperature detection unit 22, and a braking / driving force correction amount calculation unit 23 (lateral acceleration correction means). And have.
(Front wheel steering actuator rotation angle target value calculation unit)
The front wheel steering actuator rotation angle target value calculation unit 20 calculates vehicle parameters using the vehicle model shown below. In general, assuming a two-wheel model, the yaw rate ψ ′ and the lateral velocity Vy of the vehicle 30 can be expressed by the following equation (1).

here,

It is. Also,

It is.

となる。

Obtaining the transfer function of the yaw rate and lateral velocity for front wheel steering from the state equation,

It becomes.

ここで、

The yaw rate transfer function is expressed by the following equation (5) from equation (3).

here,

が求められる。
上記の車両パラメータを用いて、操舵角θh、車速Vxから目標ヨーレートψ'*、目標ヨー加速度ψ''*を求める。 From the above, vehicle parameters

Is required.
Using the vehicle parameters described above, the target yaw rate ψ ′ * and the target yaw acceleration ψ ″ * are determined from the steering angle θh and the vehicle speed Vx.

The target yaw rate ψ ′ * and the target yaw acceleration ψ ″ * are expressed by the following equation (7).

ただし、yrate_gain_map，yrate_omegn_map，yrate_zeta_map，yrate_zero_mapはチューニングパラメータである。
目標ヨーレートψ'*から目標前輪転舵角θ*を演算する。

このモデルから下記の式(10)を得る。

Here, the parameter of the target yaw rate ψ ′ * is expressed by the following equation (11).

However, yrate_gain_map, yrate_omegn_map, yrate_zeta_map, and yrate_zero_map are tuning parameters.
The target front wheel turning angle θ * is calculated from the target yaw rate ψ ′ *.

From this model, the following equation (10) is obtained.

(Rudder angle servo controller)
Next, in the steering angle servo controller 21 calculates the drive current I _theta for driving the front wheels turning actuator 10.
A deviation e between the actual turning angle θ of the front wheels 4 and the target front wheel turning angle θ * obtained by the front wheel turning actuator rotation angle target value calculation unit 20 is obtained by the following equation (11).

なお、比例ゲインP、微分ゲインDおよび積分ゲインIは、チューニングパラメータである。 The drive current I _θ is obtained by the following equation (12) from the deviation e, the proportional gain P, the differential gain D, and the integral gain I obtained by the above equation (11).

The proportional gain P, differential gain D, and integral gain I are tuning parameters.

(Actuator temperature detector)
The actuator temperature detecting unit 22, and the temperature of the front wheel turning actuator 10 determines the actuator temperature Tact to input driving current I _theta from the steering angle servo controller 21. In the actuator temperature detection unit 22, to the temperature of the front wheel turning actuator 10 may be directly actuator temperature Tact, it may be estimated actuator temperature Tact from the driving current I _theta, an actuator temperature Tact using the driving current I _theta May be corrected.

(Braking / driving force correction amount calculation unit)
The braking / driving force correction amount calculation unit 23 inputs the steering angle θh, the lateral acceleration Vy ′, the actuator rotation angle θact, and the actuator temperature Tact, and outputs the driving force correction value Δa output to the internal combustion engine controller 14 and the brake controller 15. The braking force correction value Δb to be output is calculated and obtained.

  FIG. 3 is a control block diagram of the braking / driving force correction amount calculation unit 23. The braking / driving force correction amount calculation unit 23 includes an addition unit 23a, a lateral acceleration correction gain calculation unit 23b, a multiplication unit 23e, a lateral acceleration limiting unit 23f, an addition / subtraction unit 23g, and a multiplication unit 23h. The lateral acceleration correction gain calculation unit 23b includes an acceleration correction gain calculation unit 23c and a deceleration correction gain calculation unit 23d.

The adder 23a outputs the sum of the steering angle θh and the actuator rotation angle θact as the pinion angle θp.
The acceleration correction gain calculation unit 23c calculates an acceleration correction gain Ka1 corresponding to the pinion angle θp. The acceleration correction gain calculation unit 23c has a map of the acceleration correction gain Ka1 with respect to the pinion angle θp. In this map, when the pinion angle θp is zero, the acceleration correction gain Ka1 is also zero, and as the pinion angle θp increases, the acceleration correction gain Ka1 also increases. Above the predetermined pinion angle θp, the acceleration correction gain Ka1 is constant. Indicates the value.

  The deceleration correction gain calculation unit 23d calculates a deceleration correction gain Kb1 corresponding to the pinion angle θp. The deceleration correction gain calculation unit 23d has a map of the deceleration correction gain Kb1 with respect to the pinion angle θp. This map shows that the deceleration correction gain Kb1 is also zero when the pinion angle θp is zero, and the deceleration correction gain Kb1 increases as the pinion angle θp increases. Kb1 indicates a constant value.

The lateral acceleration limiting unit 23f inputs the lateral acceleration Vy '. When the lateral acceleration Vy' is smaller than the lateral acceleration limit value Vy'_lim, the lateral acceleration Vy 'is output as it is, and the lateral acceleration Vy' is the lateral acceleration limit value Vy'_lim. When it is above, the lateral acceleration limit value Vy'_lim is output. The lateral acceleration limit value Vy'_lim is a value that can be determined so that the load acting on the front wheel actuator 10 becomes large (in the state as it is, the temperature of the front wheel actuator 10 rises and becomes overheated). Is a value set in advance.
The adder / subtractor 23g obtains a deviation e _{Vy ′} that is a difference between the lateral acceleration Vy ′ and the value output from the lateral acceleration limiting unit 23f. The deviation e _{Vy ′} is expressed by the following equation (13).

乗算部２３ｈでは、次の式(15)より制動力補正量Δbを求め、ブレーキコントローラ１５に出力する。ブレーキコントローラ１５は、この制動力補正量Δbにより、運転者のブレーキ操作によって発生している制動力を大きく補正する。すなわちブレーキコントローラ１５は、運転者のブレーキ操作によって発生しているブレーキ液圧に対して、制動力補正量Δbに相当する液圧分ブレーキ液圧を増大させるように、ブレーキアクチュエータ１７を制御する。

The multiplying unit 23e obtains the driving force correction amount Δa from the following equation (14) and outputs it to the internal combustion engine controller 14. The internal combustion engine controller 14 corrects the driving force generated by the driver's accelerator operation to be small with this driving force correction amount Δa. That is, an operation amount (accelerator opening) of an accelerator (not shown) operated by the driver is input to the internal combustion engine controller 14, and the internal combustion engine controller 14 opens the accelerator according to the input accelerator operation of the driver. The internal combustion engine actuator 16 is controlled based on a value obtained by reducing the driving force by the driving force correction amount Δa from the driving force calculated based on the degree, thereby controlling the driving force of the vehicle.

The multiplication unit 23h obtains the braking force correction amount Δb from the following equation (15) and outputs the braking force correction amount Δb to the brake controller 15. The brake controller 15 greatly corrects the braking force generated by the driver's braking operation based on the braking force correction amount Δb. That is, the brake controller 15 controls the brake actuator 17 so as to increase the brake fluid pressure corresponding to the braking force correction amount Δb with respect to the brake fluid pressure generated by the driver's brake operation.

[Braking / driving force correction processing]
FIG. 4 is a flowchart showing a flow of processing performed in the braking / driving force correction amount calculation unit 23.
In step S1, it is determined whether or not the lock flag is in operation. If the lock flag is in operation, the process proceeds to step S2, and if the lock flag is not in operation, the process proceeds to step S5. During operation, this lock flag indicates that the steering angle ratio variable mechanism 19 is locked and the steering angle ratio is fixed.

  In step S2, it is determined whether or not the actuator temperature Tact is equal to or higher than T3 ° C. When the actuator temperature Tact is equal to or higher than T3 ° C, the process proceeds to step S3, and when it is lower than T3 ° C, the process proceeds to step S4. The relationship between the temperature T3 ° C. and the temperatures T1 ° C. and T2 ° C. described later is T3 <T1 <T2.

Note that if the actuator temperature Tact is a temperature lower than the actuator temperature Tact, the actuator temperature Tact is sufficiently low and there is no problem even if the front wheel steering actuator 10 is normally operated. The temperature T2 ℃ is the actuator temperature Tact. When the temperature reaches the above temperature, the front wheel steering actuator 10 is overheated and is a temperature (limit temperature) at which the front wheel steering actuator 10 needs to be stopped. The temperature T1 ° C. is a high actuator temperature Tact. The temperature at which the rudder actuator 10 may be overheated (temperature T2 ° C. or higher). These are predetermined temperatures based on experiments and the performance of the front wheel steering actuator 10.
In step S3, the steering angle ratio variable mechanism 19 is kept locked, the lock flag is held, and the process is terminated.
In step S4, the lock of the steering angle ratio variable mechanism 19 is released, and the lock flag is closed.

In step S5, it is determined whether or not the actuator temperature Tact is equal to or higher than T1 ° C. If it is equal to or higher than T1 ° C, the process proceeds to step S6, and if it is lower than T1 ° C, the process proceeds to step S13.
In step S6, it is determined whether or not the actuator temperature Tact is equal to or lower than T2 ° C. If it is equal to or lower than T2 ° C, the process proceeds to step S7, and if it is higher than T2 ° C, the process proceeds to step S12.

In step S7, it is determined whether or not the ratio (steering angle ratio) between the steering angle θh and the steering angle θ (pinion angle θp) is 1, and when the steering angle ratio is 1, the process proceeds to step S9. When the steering angle ratio is not 1, the process proceeds to step S8.
In step S8, it is determined whether or not the lateral acceleration Vy 'is greater than or equal to the lateral acceleration limit value Vy'_lim (limit value). If the lateral acceleration Vy' is greater than or equal to the lateral acceleration limit value Vy'_lim, the process proceeds to step S10. When the lateral acceleration Vy ′ is less than the lateral acceleration limit value Vy′_lim, the process proceeds to step S11.

In step S9, the steering angle ratio variable mechanism 19 is locked, a lock flag is set, and the procedure is terminated.
In step S10, the braking / driving force correction amounts Δa and Δb are calculated and the treatment is terminated.
In step S11, the braking / driving force correction amounts Δa and Δb are set to zero and the treatment is terminated.
In step S12, the lock of the steering angle ratio variable mechanism 19 is actuated, the lock flag is set, and the treatment is terminated.
In step S13, the braking / driving force correction amounts Δa and Δb are set to zero and the treatment is terminated.

[Braking / braking force correction processing operation]
While the lock flag is in operation, the process proceeds from step S1 to step S2. In step S2, when the actuator temperature Tact is equal to or higher than T3 ° C., it is determined that the front wheel steering actuator 10 is not sufficiently cooled, and the process proceeds to step S3 to continue locking the steering angle ratio variable mechanism 19. In step S2, when the actuator temperature Tact is less than T3 ° C., it is determined that the front wheel steering actuator 10 has been sufficiently cooled, and the routine proceeds to step S3 where the steering angle ratio variable mechanism 19 is unlocked.

  When the lock flag is not in operation and the actuator temperature Tact is lower than T1 ° C., the process proceeds from step S1 to step S5 to step s13. When the actuator temperature Tact is less than T1 ° C., the front wheel steering actuator 10 determines that the temperature is within the normal range, and sets the braking / driving force correction amounts Δa and Δb to zero.

  When the lock flag is not in operation and the actuator temperature Tact is higher than T2 ° C., the process proceeds from step S1 to step S5 to step S6 to step S12. When the actuator temperature Tact is higher than T2 ° C., it is determined that the front wheel turning actuator 10 has entered the limit region, the process proceeds to step S12, and the steering angle ratio variable mechanism 19 is locked.

  When the lock flag is not in operation and the actuator temperature Tact is T1 ° C. or higher and T2 ° C. or lower, the process proceeds from step S1 to step S5 to step S6 to step S7. When the actuator temperature Tact is equal to or higher than T1 ° C. and equal to or lower than T2 ° C., it is determined that the front wheel steering actuator 10 is entering the limit region, and the process proceeds to step S7 to lock the steering angle ratio variable mechanism 19 and the steering angle ratio is 1. It is determined whether or not it can be operated at the time.

When the steering angle ratio becomes 1 in step S7, the steering angle ratio variable mechanism 19 is locked in step S9.
When the steering angle ratio is not 1 in step S7, the process proceeds to step S8. In step S8, when the lateral acceleration Vy ′ is equal to or greater than the lateral acceleration limit value Vy′_lim, it is determined that the actuator temperature Tact increases and exceeds T2 ° C. in the state as it is, and the process proceeds to step S10 and the braking / driving force is increased. The correction amounts Δa and Δb are calculated. The lateral acceleration is reduced by correcting the braking / driving force using the braking / driving force correction amounts Δa and Δb, and the load on the front wheel steering actuator 10 is reduced to suppress the temperature rise. On the other hand, when the lateral acceleration Vy ′ is less than the lateral acceleration limit value Vy′_lim (limit value), the process proceeds to step S11, and the braking / driving force correction amounts Δa and Δb are set to zero. At this time, since the lateral acceleration Vy ′ is small and the load on the front wheel steering actuator 10 is small, the temperature rise is suppressed and the braking / driving force suitable for the driver's operation is output.

[Action]
When the temperature of the front wheel steering actuator 10 exceeds the limit temperature, the front wheel steering actuator 10 cannot be driven, and thus it is necessary to immediately activate the lock of the steering angle ratio variable mechanism 19. If the steering angle ratio is not 1 when the lock of the steering angle ratio variable mechanism 19 is operated, the neutral position of the steering wheel 2 and the straight-ahead steering position are shifted, and the driver feels uncomfortable.

Therefore, in the first embodiment, when the load (lateral acceleration) acting on the front wheel steering actuator 10 exceeds a set value, the lateral acceleration is decreased.
FIG. 5 is a time chart when the braking / driving force correction process of Example 1 is performed (one-dot chain line) and when the braking / driving force correction process is not performed (solid line). As shown in FIG. 5, when the actuator temperature Tact exceeds T1 ° C., the lateral acceleration Vy ′ is equal to or greater than the lateral acceleration limit value Vy′_lim. At this time, as indicated by the one-dot chain line in FIG. 5, the driving force and the braking force are corrected to decrease the vehicle speed Vx. As the vehicle speed Vx decreases, the lateral acceleration Vy ′ decreases, and the current of the front wheel steering actuator 10 decreases. Therefore, an increase in the actuator temperature Tact is suppressed, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the shift of the neutral position of the steering handle from the position of straight-ahead steering.

  In the first embodiment, the higher the lateral acceleration Vy ′ of the vehicle, the higher the load. That is, as the lateral acceleration Vy ′ is higher, the axial force input to the front wheels 4 is larger, and the front wheel turning actuator 10 outputs an output against this axial force, so that the load is increased. Therefore, the load input to the front wheel steering actuator 10 using the lateral acceleration sensor 13 can be obtained with high accuracy.

In the first embodiment, the lateral acceleration Vy ′ is reduced by correcting the driving force to be small. That is, by reducing the driving force, the vehicle speed Vx can be reduced, and the lateral acceleration Vy ′ can be reduced.
In the first embodiment, the lateral acceleration Vy ′ is reduced by largely correcting the braking force. That is, by increasing the braking force, the vehicle speed Vx can be reduced and the lateral acceleration Vy ′ can be reduced.

  In the first embodiment, when the lateral acceleration Vy ′ is greater than or equal to the set value, the lateral acceleration is decreased by correcting the driving force to be smaller as the difference between the lateral acceleration Vy ′ and the lateral acceleration limit value Vy′_lim is larger. I made it. That is, the greater the load, the faster the actuator temperature Tact increases, and it is possible to make the actuator temperature Tact less likely to exceed the limit temperature by further decreasing the lateral acceleration Vy ′. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the shift of the neutral position of the steering handle from the position of straight-ahead steering.

  Further, in the first embodiment, when the lateral acceleration Vy ′ is equal to or greater than the set value, the lateral acceleration is decreased by correcting the braking force as the difference between the lateral acceleration Vy ′ and the lateral acceleration limit value Vy′_lim increases. I made it. That is, the greater the load, the faster the actuator temperature Tact rises. By further reducing the lateral acceleration, the actuator temperature Tact can be made less likely to exceed the limit temperature. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the shift of the neutral position of the steering handle from the position of straight-ahead steering.

〔effect〕
Next, effects of the vehicle steering apparatus 1 of the first embodiment are listed below.
(1) A steering angle ratio variable mechanism 19 that varies a steering angle ratio that is a ratio between the steering angle θh of the steering wheel 2 and the steering angle θ of the front wheels 4 that are steered in accordance with the steering of the steering wheel 2; The front wheel steering actuator 10 that drives the steering angle ratio variable mechanism 19, the steering wheel ratio variable controller 11 that controls the steering wheel ratio by controlling the front wheel steering actuator 10, and the load that acts on the front wheel steering actuator 10 A braking / driving force correction amount calculation unit 23 is provided that detects that the load is greater than or equal to a predetermined load and detects that the load acting on the front wheel steering actuator 10 is greater than or equal to the predetermined load. It was.
Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the deviation of the neutral position of the steering wheel 2 from the position of the straight-ahead steering.

(2) The braking / driving force correction amount calculation unit 23 detects that the load is equal to or greater than a predetermined load when the lateral acceleration of the vehicle is equal to or greater than a predetermined lateral acceleration limit value.
Therefore, the load input to the front wheel steering actuator 10 using the lateral acceleration sensor 13 can be obtained with high accuracy.

(3) The braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by correcting the driving force to be small.
Therefore, by reducing the driving force, the vehicle speed can be reduced and the lateral acceleration can be reduced.

(4) The braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by largely correcting the braking force.
Therefore, by increasing the braking force, the vehicle speed can be reduced and the lateral acceleration can be reduced.

(5) When the lateral acceleration is equal to or greater than the limit value, the braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by correcting the driving force to be smaller as the difference between the lateral acceleration and the limit value is larger. .
The greater the load, the faster the actuator temperature Tact rises. By further reducing the lateral acceleration, the actuator temperature Tact can be made less likely to exceed the limit temperature. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the shift of the neutral position of the steering handle from the position of straight-ahead steering.

(6) When the lateral acceleration is greater than or equal to the limit value, the braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by correcting the braking force to a greater extent as the difference between the lateral acceleration and the limit value increases. .
The greater the load, the faster the actuator temperature Tact rises. By further reducing the lateral acceleration, the actuator temperature Tact can be made less likely to exceed the limit temperature. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the shift of the neutral position of the steering handle from the position of straight-ahead steering.

[Example 2]
In the second embodiment, the load on the front wheel steering actuator 10 is obtained from the pinion angle θp (the turning angle of the front wheel 4) and the vehicle speed Vx or the longitudinal acceleration V ′.

[Control block diagram]
FIG. 2 is a control block diagram of the steering angle ratio variable controller 11 of the vehicle steering apparatus 1.
The steering angle ratio variable controller 11 includes a front wheel steering actuator rotation angle target value calculation unit 20, a steering angle servo control unit 21, an actuator temperature detection unit 22, and a braking / driving force correction amount calculation unit 23. .

(Braking / driving force correction amount calculation unit)
The braking / driving force correction amount calculation unit 23 inputs the steering angle θh, the vehicle speed Vx, and the actuator rotation angle θact, and outputs the driving force correction value Δa output to the internal combustion engine controller 14 and the braking force correction value output to the brake controller 15. Calculate Δb.

  FIG. 6 is a control block diagram of the braking / driving force correction amount calculation unit 23. The braking / driving force correction amount calculation unit 23 includes an addition unit 23i, an acceleration limit value calculation unit 23j, an acceleration limit unit 23k, an addition / subtraction unit 23m, an acceleration correction gain output unit 23n, a multiplication unit 23o, a differentiation calculation unit 23p, and a vehicle speed limit value calculation. A unit 23q, a vehicle speed limiting unit 23r, an addition / subtraction unit 23s, a vehicle speed correction gain output unit 23t, a multiplication unit 23u, an addition unit 23v, a vehicle speed correction gain output unit 23w, and a multiplication unit 23x.

The adder 23i outputs the sum of the steering angle θh and the actuator rotation angle θact as the pinion angle θp.
The acceleration limit value calculation unit 23j calculates the acceleration limit value Vx′_lim from the pinion angle θp. The acceleration limit value calculation unit 23j has a map of the acceleration limit value Vx′_lim with respect to the pinion angle θp. This map is set so that the acceleration limit value Vx′_lim decreases as the pinion angle θp increases. The acceleration limit value Vx′_lim means that when the vehicle acceleration is higher than the pinion angle, the load increasing speed of the front wheel steering actuator 10 is high, and the temperature of the front wheel steering actuator 10 ( The acceleration can be determined that the actuator temperature Tact) may exceed the limit temperature, and a map obtained in advance by experiment or the like is used as the map.

The differential calculation unit 23p calculates the longitudinal acceleration Vx ′ by differentiating the vehicle speed Vx.
The acceleration limiting unit 23k inputs the longitudinal acceleration Vx ′, and outputs the longitudinal acceleration Vx ′ as it is when the longitudinal acceleration Vx ′ is smaller than the acceleration limiting value Vx′_lim, and the longitudinal acceleration Vx ′ is equal to or greater than the acceleration limiting value Vx′_lim. Sometimes the acceleration limit value Vx'_lim is output.
The adder / subtractor 23m obtains a deviation e _{Vx ′} that is a difference between the longitudinal acceleration Vx ′ and the value output from the acceleration limiting unit 23k. The deviation e _{Vx ′} is expressed by the following equation (16).

The acceleration correction gain output unit 23n outputs an arbitrary acceleration correction gain K _{Vx ′} . The acceleration correction gain K _{Vx ′} is a value that is appropriately set according to the characteristics of the vehicle 30.
The multiplication unit 23o obtains the driving force correction amount Δa1 from the following equation (17).

The vehicle speed limit value calculation unit 23q calculates the vehicle speed limit value Vx_lim from the pinion angle θp. The vehicle speed limit value calculation unit 23q has a map of the vehicle speed limit value Vx_lim with respect to the pinion angle θp. This map is set so that the vehicle speed limit value Vx_lim decreases as the pinion angle θp increases.
Note that the vehicle speed limit value Vx_lim is that when the vehicle speed is higher than the pinion angle, the load on the front wheel steering actuator 10 is large, and the temperature of the front wheel steering actuator 10 (actuator temperature Tact) is It is a speed at which it can be determined that there is a possibility of exceeding the limit temperature.
The vehicle speed limiter 23r receives the vehicle speed Vx, outputs the vehicle speed Vx as it is when the vehicle speed Vx is smaller than the vehicle speed limit value Vx_lim, and outputs the vehicle speed limit value Vx_lim when the vehicle speed Vx is equal to or higher than the vehicle speed limit value Vx_lim.
The adder / subtractor 23s obtains a deviation _eVx that is a difference between the vehicle speed Vx and the value output from the vehicle speed limiter 23r. The deviation e _Vx is expressed by the following equation (18).

加算部２３ｖでは、次の式(20)より駆動力補正量Δaを求め、この駆動力補正量Δaを内燃機関コントローラ１４に出力する。内燃機関コントローラ１４は実施例1と同様に、この駆動力補正量Δaにより、運転者のアクセル操作によって発生している駆動力を小さく補正する。

The vehicle speed correction gain output unit 23t outputs an arbitrary vehicle speed correction gain K _Vx1 . The vehicle speed correction gain K _Vx1 may be appropriately set according to the characteristics of the vehicle 30.
The multiplication unit 23u obtains the driving force correction amount Δa2 from the following equation (19).

The adding unit 23v obtains the driving force correction amount Δa from the following equation (20), and outputs the driving force correction amount Δa to the internal combustion engine controller 14. As in the first embodiment, the internal combustion engine controller 14 corrects the driving force generated by the driver's accelerator operation to be small by this driving force correction amount Δa.

The vehicle speed correction gain output unit 23w outputs an arbitrary vehicle speed correction gain K _Vx2 . The vehicle speed correction gain K _Vx2 may be appropriately set according to the characteristics of the vehicle 30.
The multiplication unit 23x obtains the driving force correction amount Δb from the following equation (21), and outputs the driving force correction amount Δb to the brake controller 15. As in the first embodiment, the brake controller 15 largely corrects the braking force generated by the driver's braking operation using the braking force correction amount Δb.

[Braking / driving force correction processing]
FIG. 7 is a flowchart showing a flow of processing performed in the braking / driving force correction amount calculation unit 23.
In step S20, the vehicle speed limit value Vx_lim and the acceleration limit value Vx′_lim are calculated, and the process proceeds to step S21.

In step S21, it is determined whether or not the vehicle speed Vx is greater than or equal to the vehicle speed limit value Vx_lim, or the longitudinal acceleration Vx ′ is greater than or equal to the acceleration limit value Vx′_lim, and it is determined that the vehicle speed Vx or the longitudinal acceleration Vx ′ is greater than or equal to the limit value. If so, the process proceeds to step S22. If it is determined that the value is less than the limit value, the process proceeds to step S23.
In step S22, the braking / driving force correction values Δa and Δb are calculated, and the process ends.
In step S23, the braking / driving force correction values Δa and Δb are set to zero, and the process ends.

[Braking / braking force correction processing operation]
When the vehicle speed Vx is equal to or greater than the vehicle speed limit value Vx_lim or the longitudinal acceleration Vx ′ is equal to or greater than the acceleration limit value Vx′_lim, the process proceeds from step S20 to step S21 to step S22. In step S22, the braking / driving force correction values Δa and Δb are calculated, and the driving force is reduced or the braking force is increased.

  When the vehicle speed Vx is less than the vehicle speed limit value Vx_lim and the longitudinal acceleration Vx ′ is less than the acceleration limit value Vx′_lim, the process proceeds from step S20 to step S21 to step S23. In step S22, the braking / driving force correction values Δa and Δb are set to zero so that the driving force and the braking force are not corrected.

[Action]
In an operation such as a so-called accelerator turn in which acceleration is performed with the steering wheel 2 being steered to near the rack end, the rise of the lateral acceleration Vy ′ becomes steep. In the variable steering angle control, the steering angle ratio is increased when the vehicle speed Vx is low, and the steering angle ratio is decreased when the vehicle speed Vx is high. That is, when the vehicle speed Vx is low, the rotation angle (operation amount) of the front wheel steering actuator 10 is increased to increase the steering angle of the front wheels 4 with respect to the steering angle θh. Therefore, when the accelerator turn is performed, the load on the front wheel steering actuator 10 increases rapidly, and the temperature of the front wheel steering actuator 10 easily exceeds the limit temperature.

  In such a case, if the control of reducing the lateral acceleration Vy ′ is performed after judging the magnitude of the load of the front wheel steering actuator 10 from the lateral acceleration Vy ′ detected by the lateral acceleration sensor 13, the front wheel steering actuator 10 There is a risk that the load reduction control will not be in time.

  Therefore, in the second embodiment, the acceleration limit value Vx′_lim is set to be smaller as the turning angle θ (pinion angle θp) of the front wheel 4 is larger, and the longitudinal acceleration Vx ′ is equal to or greater than the acceleration limit value Vx′_lim. Sometimes, the lateral acceleration Vy 'was lowered. That is, the increase in load can be calculated in a feed-forward manner using the pinion angle θp and the longitudinal acceleration Vx ′, and control for reducing the lateral acceleration Vy ′ can be performed early. Therefore, it is possible to prevent a sudden increase in the load on the front wheel steering actuator 10 and make it difficult for the temperature of the front wheel steering actuator 10 to exceed the limit temperature.

  In the second embodiment, the vehicle speed limit value Vx_lim is set to be smaller as the turning angle θ (pinion angle θp) of the front wheel 4 is larger. When the vehicle speed Vx is equal to or higher than the vehicle speed limit value Vx_lim, the lateral acceleration Vy ′ is set. To lower. That is, the load can be calculated in a feed-forward manner based on the pinion angle θp and the vehicle speed Vx, and control for reducing the lateral acceleration Vy ′ can be performed early. Therefore, it is possible to prevent a sudden increase in the load on the front wheel steering actuator 10 and make it difficult for the temperature of the front wheel steering actuator 10 to exceed the limit temperature.

  FIG. 8 shows a case where the braking / driving force correction processing of the second embodiment is performed (one-dot chain line) and a case where the braking / driving force correction processing is not performed when acceleration is performed while the steering wheel 2 is steered to near the rack end. It is a time chart of (solid line). As indicated by the one-dot chain line in FIG. 8, the driving force and the braking force are corrected to decrease the vehicle speed Vx. As the vehicle speed Vx decreases, the lateral acceleration Vy ′ decreases, and the current of the front wheel steering actuator 10 decreases. Therefore, an increase in the actuator temperature Tact is suppressed, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature. Therefore, the front-wheel steering actuator 10 can earn time to wait until the steering angle ratio becomes 1, and it is possible to suppress the shift of the neutral position of the steering handle from the position of the straight steering.

  In the second embodiment, when the longitudinal acceleration Vx ′ is equal to or greater than the acceleration limit value Vx′_lim, the lateral acceleration Vy is corrected by correcting the driving force to be smaller as the difference between the longitudinal acceleration Vx ′ and the acceleration limit value Vx′_lim is larger. 'Decreased'. That is, the greater the load, the faster the actuator temperature Tact increases, and it is possible to make the actuator temperature Tact less likely to exceed the limit temperature by further decreasing the lateral acceleration Vy ′. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the deviation of the neutral position of the steering wheel 2 from the position of the straight-ahead steering.

  In the second embodiment, when the vehicle speed Vx is equal to or higher than the vehicle speed limit value Vx_lim, the lateral acceleration Vy ′ is decreased by correcting the braking force to be smaller as the difference between the vehicle speed Vx and the vehicle speed limit value Vx_lim is larger. That is, the greater the load, the faster the actuator temperature Tact increases, and it is possible to make the actuator temperature Tact less likely to exceed the limit temperature by further decreasing the lateral acceleration Vy ′. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the deviation of the neutral position of the steering wheel 2 from the position of the straight-ahead steering.

〔effect〕
Next, effects of the vehicle steering apparatus 1 according to the second embodiment will be listed below.
(7) The braking / driving force correction amount calculation unit 23 detects that the load is equal to or greater than a predetermined load when the longitudinal acceleration of the vehicle is equal to or greater than a predetermined limit value.
Therefore, the load of the front wheel steering actuator 10 can be prevented from increasing rapidly, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature.

(8) An acceleration limit value calculation unit 23j that calculates and sets the acceleration limit value Vx′_lim is provided.
The acceleration limit value calculation unit 23j calculates the acceleration limit value Vx′_lim smaller as the turning angle (pinion angle) of the front wheel 4 is larger.
Therefore, the load of the front wheel steering actuator 10 can be prevented from increasing rapidly, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature.

(9) The braking / driving force correction amount calculation unit 23 detects that the load is equal to or higher than a predetermined load when the vehicle speed is equal to or higher than a predetermined vehicle speed limit value.
Therefore, the load of the front wheel steering actuator 10 can be prevented from increasing rapidly, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature.

(10) A vehicle speed limit value calculating unit 23q for calculating and setting the vehicle speed limit value Vx_lim is provided.
The vehicle speed limit value calculating unit 23q is configured to calculate the vehicle speed limit value Vx_lim smaller as the turning angle (pinion angle) of the front wheel 4 is larger.
Therefore, the load of the front wheel steering actuator 10 can be prevented from increasing rapidly, and the temperature of the front wheel steering actuator 10 can be made difficult to exceed the limit temperature.

(11) When the longitudinal acceleration is equal to or greater than the limit value, the braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by correcting the driving force to be smaller as the difference between the longitudinal acceleration and the limit value is larger. .
Therefore, the greater the load, the faster the actuator temperature rises, and it is possible to make it difficult for the actuator temperature to exceed the limit temperature by further reducing the lateral acceleration. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the deviation of the neutral position of the steering wheel 2 from the position of the straight-ahead steering.

(12) When the vehicle speed is equal to or higher than the limit value, the braking / driving force correction amount calculation unit 23 reduces the lateral acceleration by correcting the braking force to a greater extent as the difference between the vehicle speed and the limit value increases.
Therefore, the greater the load, the faster the actuator temperature rises, and it is possible to make it difficult for the actuator temperature to exceed the limit temperature by further reducing the lateral acceleration. Therefore, the front-wheel steering actuator 10 can earn time for waiting until the steering angle ratio becomes 1, and can suppress the deviation of the neutral position of the steering wheel 2 from the position of the straight-ahead steering.

[Other embodiments]
Although the best mode for carrying out the present invention has been described based on the first and second embodiments, the specific configuration of the present invention is not limited to the first and second embodiments. The present invention includes any design changes that do not depart from the spirit of the invention.

The vehicle steering apparatus 1 according to the first embodiment and the second embodiment is a four-wheel active steering system in which the steering angle of only the front wheels 4 is variable, but the steering angles of the front wheels 4 and the rear wheels 18 are variable. May be.
In the vehicle steering apparatus 1 according to the first and second embodiments, the steering shaft 6 and the pinion shaft 7 are always connected, but a clutch is provided between the steering shaft 6 and the pinion shaft 7. A so-called steer-by-wire system in which the transmission of force between the steering shaft 6 and the pinion shaft 7 is disconnected may be used.

DESCRIPTION OF SYMBOLS 1 Vehicle steering device 2 Steering wheel 4 Front wheel 10 Front wheel steering actuator (actuator)
11 Steering angle ratio variable controller (steering angle ratio control means)
12 Vehicle speed sensor 13 Lateral acceleration sensor 19 Steering angle ratio variable mechanism (steering angle variable means)
23 Braking / driving force correction amount calculation unit (lateral acceleration correction means)
30 vehicles

Claims (12)

A steering angle ratio variable means for varying a steering angle ratio which is a ratio of a steering angle of a steering wheel and a steering angle of a front wheel which is steered with steering of the steering wheel;
An actuator for driving the steering angle ratio variable means;
Rudder angle ratio control means for controlling the rudder angle ratio by controlling the actuator;
Load detecting means for detecting that a load acting on the actuator is a predetermined load or more;
Lateral acceleration correcting means for controlling the vehicle so as to reduce the lateral acceleration of the vehicle when the load detecting means detects that the load acting on the actuator is equal to or greater than a predetermined load;
A vehicle control device characterized by comprising: The vehicle control device according to claim 1,
The vehicle load control unit detects that the load is equal to or greater than a predetermined load when the lateral acceleration of the vehicle is equal to or greater than a predetermined lateral acceleration limit value. The vehicle control device according to claim 1,
The vehicle control device, wherein the load detection means detects that the load is greater than or equal to a predetermined load when the longitudinal acceleration of the vehicle is greater than or equal to a predetermined longitudinal acceleration limit value [N1]. The vehicle control device according to claim 3,
A longitudinal acceleration limit value calculating means for calculating and setting the longitudinal acceleration limit value;
The longitudinal acceleration limit value calculating means calculates the longitudinal acceleration limit value smaller as the turning angle of the front wheel is larger. The vehicle control device according to claim 1,
The load detection means is a vehicle control device that detects that the load is equal to or higher than a predetermined load when the vehicle speed is equal to or higher than a predetermined vehicle speed limit value. The vehicle control device according to claim 5,
Vehicle speed limit value calculating means for calculating and setting the vehicle speed limit value;
The vehicle control apparatus according to claim 1, wherein the vehicle speed limit value calculating means calculates the vehicle speed limit value to be smaller as the turning angle of the front wheel is larger. The vehicle control device according to any one of claims 1 to 6,
The lateral acceleration correction means reduces the lateral acceleration by correcting the driving force to be small, and the vehicle control device. In the vehicle control device according to any one of claims 1 to 4,
The lateral acceleration correcting means reduces the lateral acceleration by largely correcting a braking force. The vehicle control device according to claim 2,
The lateral acceleration correcting means reduces the lateral acceleration by correcting the driving force to be smaller as the difference between the lateral acceleration and the lateral acceleration limit value is larger when the lateral acceleration of the vehicle is equal to or greater than the lateral acceleration limit value. A control apparatus for a vehicle. The vehicle control device according to claim 2,
When the lateral acceleration of the vehicle is equal to or greater than the lateral acceleration limit value, the lateral acceleration correction means reduces the lateral acceleration by correcting the braking force as the difference between the lateral acceleration and the lateral acceleration limit value increases. A control device for a vehicle, characterized in that The vehicle control device according to claim 3,
When the longitudinal acceleration is greater than or equal to the longitudinal acceleration limit value, the lateral acceleration correction means reduces the lateral acceleration by correcting the driving force to be smaller as the difference between the longitudinal acceleration and the longitudinal acceleration limit value is larger. A control apparatus for a vehicle. The vehicle control device according to claim 5,
When the vehicle speed is equal to or higher than the vehicle speed limit value, the lateral acceleration correction means reduces the lateral acceleration by correcting the braking force as the difference between the vehicle speed and the vehicle speed limit value increases. The vehicle control device.

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