JP2007038880A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of suppressing the vehicle behavior becoming unstable in association with the steering operation of a driver, while the sense of incongruity is reduced, owing to a variation in the steering force when an unstable behavior is generated. <P>SOLUTION: The steering device for the vehicle is equipped with a motor 5 to apply a steering assist force to the steering system, a gear ratio changing mechanism 14 to change the gear ratio as ratio of the steering wheel turning angle relative to the tire steered angle, and a controller 13 to drive the gear ratio changing mechanism 14 in the direction of stabilizing the vehicle behavior when an unstable behavior exceeding the stable behavior limit of the vehicle is generated in the vehicle according to the steering wheel turning angle, wherein the controller 13 works when the described unstable behavior is generated in the vehicle and drives the motor 5 in the direction of suppressing the steering wheel turning operation to the direction in which the vehicle behavior becomes unstable before a gear ratio change to the direction in which the vehicle behavior becomes stable is conducted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a vehicle steering apparatus that changes a gear ratio, which is a ratio of a steering wheel angle to a tire turning angle, in a direction in which the vehicle behavior is stable when unstable behavior occurs in the vehicle.

Conventionally, in a vehicle steering system equipped with a gear ratio actuator and an electric power steering device, the amount of steering force in consideration of the gear ratio change is changed by changing the motor assist amount according to the gear ratio changed by the gear ratio actuator. Assist is realized (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-34893

  In general, when unstable vehicle behavior occurs, active front steering that automatically steers the tire turning angle in a direction where the vehicle motion is stable regardless of the driver's steering is very effective in suppressing vehicle unstable behavior. Means. However, since the active front steering changes the relationship between the steering input, which is the driver's intention, and the vehicle behavior, it gives a great sense of incongruity to the driver other than in an emergency operation such as when unstable behavior occurs. Become. Therefore, it is preferable to change the gear ratio by active front steering little by little or during emergency avoidance.

  However, in the above prior art, since the motor assist amount is changed according to the gear ratio, if the gear ratio change as described above is performed according to the scene, the steering force felt by the driver has an unstable behavior. Will change when you are. On the other hand, the unstable behavior of the vehicle occurs when the steering wheel is operated by the driver's intention and steering beyond the inherent limit of the vehicle is performed. Therefore, there is a problem that it is not possible to avoid the vehicle falling into an unstable behavior by the driver's operation only by controlling the steering force according to the gear ratio.

  The present invention has been made paying attention to the above-mentioned problem, and the object of the present invention is to reduce the uncomfortable feeling caused by the fluctuation of the steering force when the unstable behavior occurs, and to make the vehicle behavior more unstable as the driver operates the steering wheel. An object of the present invention is to provide a vehicle steering apparatus that can suppress the above.

In order to achieve the above object, the present invention provides:
A steering force actuator for applying a steering assist force to the steering system;
A gear ratio actuator that varies a gear ratio that is a ratio of a steering wheel angle to a tire turning angle;
Steering control means for driving and controlling the gear ratio actuator in a direction in which the vehicle behavior becomes stable when an unstable behavior exceeding the stable behavior limit of the vehicle occurs in the vehicle according to the steering wheel angle;
In a vehicle steering apparatus comprising:
When the unstable behavior occurs in the vehicle, the steering control means suppresses the steering operation in the direction in which the vehicle behavior becomes unstable before changing the gear ratio in the direction in which the vehicle behavior becomes stable. The steering force actuator is driven and controlled.

  In the present invention, before changing the gear ratio in a direction in which the vehicle behavior becomes stable, the steering force actuator is driven and controlled in a direction to suppress the steering operation in the direction in which the vehicle behavior becomes unstable. In other words, by suppressing the steering operation that makes the vehicle behavior unstable before the gear ratio is changed, the vehicle behavior becomes more unstable as the driver steers the steering wheel while reducing the uncomfortable feeling caused by the fluctuation of the steering force when the unstable behavior occurs. Can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 to 5.

First, the configuration will be described.
FIG. 1 is a configuration diagram of a vehicle steering apparatus according to a first embodiment.
A torque sensor 4 that detects a steering torque applied to the steering wheel 1 on a steering shaft 3 that connects a steering wheel 1 for steering operation of the driver and a steering mechanism 2 that performs a steering operation, and a motor that assists the steering force of the driver (steering) Force actuator) 5 is arranged.

  The handle 1 is provided so as to be rotatable around an axis at a position facing a driver in a vehicle interior (not shown). The steering mechanism 2 is constituted by a rack and pinion type steering device including a pinion 6 integrally formed at the lower end of the steering shaft 3 and a rack shaft 7 meshing with the pinion 6. The rack shaft 7 is fixed to the front portion of the vehicle (not shown) so as to be slidable in the left-right direction. Both ends of the rack shaft 7 are connected to the steering wheels 10 and 11 for steering through the left and right tie rods 8 and 9. Yes.

  The motor 5 is coupled to the steering shaft 3 via a speed reducer 12 that converts torque generated by the motor 5 into rotational torque of the steering shaft 3. The motor current supplied to the motor 5 is controlled by a controller (steering control means) 13.

  The steering shaft 3 is provided with a variable gear ratio mechanism (gear ratio actuator) 14 that can mechanically change the gear ratio between the angle of the handle 1 and the angle of the pinion 6. The variable gear ratio mechanism 14 is provided with a motor 15 that changes a gear ratio that is a ratio of a steering wheel angle (steering amount of the steering wheel) to a tire turning angle (hereinafter referred to as a tire angle) (a steering wheel angle / a tire angle). The motor current supplied to the motor 15 is controlled by the controller 13.

  The controller 13 is connected with a torque sensor 4 and an encoder 16 for detecting the angle of the motor 5 as signals for detecting the steering amount of the driver. The encoder 16 measures the rotation angle of the motor 5 and converts the reduction ratio of the speed reducer 12 in the controller 13 to obtain the handle angle.

  The controller 13 is connected with a vehicle speed sensor 17 for detecting the vehicle running speed and a yaw rate sensor 18 for detecting the yaw rate of the vehicle as signals for detecting the vehicle behavior state quantity. A battery 20 is connected to the controller 13 as an operating power source for the controller itself and a power source for supplying power to the motors 5 and 15.

  Next, the configuration and operation of the control system of the first embodiment will be described with reference to the control block diagram of FIG.

[Steering assist control block]
When the steering wheel 1 is steered by the driver, the steering wheels 10 and 11 mechanically connected to the steering wheel 1 are steered. At this time, the torsional load input to the torque sensor 4 is input to the controller 13 as a steering torque. Further, a signal from the vehicle speed sensor 17 or the like is given to the controller 13.

  The target current calculation unit 101 calculates a basic assist current corresponding to the steering torque and the vehicle speed. This basic assist current characteristic generally increases the assist amount in proportion to the steering torque and reduces the driver's steering torque. Further, the load on the driver is reduced by decreasing the assist amount in proportion to the vehicle speed and increasing the assist amount at a low speed to reduce the driver's steering torque. Then, at high speeds, the amount of assist is reduced and the steering torque is increased, thereby suppressing excessive steering by the driver during high speed traveling.

  The adder 102 determines a target current value of the assist motor 5 by adding a basic assist current and a correction current described later. In the comparator 103, in order to perform current servo, a value of a current sensor 106 described later is fed back to create a current command value, and the control voltage calculation unit 104 converts the current command value into a voltage command value for PWM voltage control, or Convert to duty ratio.

The drive circuit 105 is composed of a transistor or the like, and controls the amount and direction of the current flowing to the motor 5 to drive the motor 5. The current flowing through the motor 5 is detected by the current sensor 106 and fed back to the current servo (comparator 103).
With the above configuration and operation, a current flows through the motor 5, and the operation load on the driver is reduced by the assist torque of the motor 5.

[Variable gear ratio control block]
The controller 13 also controls a variable gear ratio mechanism 14 that variably controls the gear ratio, which is the ratio of the steering wheel angle to the tire angle, according to the vehicle speed.
The target gear ratio calculation unit 107 calculates a reference gear ratio for changing the gear ratio according to the vehicle speed. The gear ratio generally increases the steering wheel angle relative to the tire angle as the vehicle speed increases (hereinafter, the gear ratio is increased). At low speeds, the gear ratio is reduced. For example, in a vehicle speed range where the steering wheel operation amount tends to be large when parked or stopped, the tires can move greatly with a small steering wheel operation amount, thereby reducing the driver's operation load. On the other hand, by increasing the gear ratio at high speed, for example, by preventing the vehicle from moving too much with respect to a minute steering operation during high-speed traveling, the straight running stability is improved.

  The adder 108 determines a target gear ratio value of the variable gear ratio mechanism 14 by adding a basic gear ratio and a correction gear ratio described later. In the comparator 109, in order to perform current servo, a current command value is created by feeding back a value of a current sensor 112 described later, and the current command value is converted into a voltage command value for PWM voltage control by the control voltage calculation unit 110, or Convert to duty ratio.

The drive circuit 111 is composed of a transistor or the like, and controls the amount and direction of current flowing to the motor 15 to drive the motor 15. The current flowing through the motor is detected by the current sensor 112 and fed back to the current servo (comparator 109).
[Correction amount calculation block]
An unstable amount calculation unit (unstable amount calculation means) 113 determines an unstable amount of the vehicle (a degree of instability of the vehicle behavior) from the vehicle speed, the steering wheel angle, and the vehicle behavior state amount. A correction amount for correcting the basic assist is calculated by the correction amount calculation unit 114 in accordance with the calculated instability amount. Further, the correction of the vehicle speed (vehicle speed correction unit 115) and the turning speed (steering speed correction unit 116) are calculated. Correction is performed, and the assist motor 5 is controlled by adding the basic assist and the main correction amount by the adder 102.

  Further, the correction amount calculation unit 117 calculates a correction amount for correcting the gear ratio of the variable gear ratio mechanism 14 according to the calculated instability amount, and the adder 108 adds the basic gear ratio and the main correction gear ratio. Thus, the gear ratio of the variable gear ratio mechanism 14 is controlled.

[Unstable amount calculation block]
FIG. 3 is a control block diagram of the unstable amount calculator 113 according to the first embodiment. The unstable amount calculator 113 includes a vehicle model 201 and an unstable amount calculation map 202.

  As the vehicle model 201, for example, a general two-wheel model is used, and an ideal reference yaw rate is output in response to steering wheel angle input. In the unstable amount calculation map 202, the unstable amount of the vehicle is calculated by comparing the reference yaw rate output from the vehicle model 201 with the actual yaw rate output from the yaw rate sensor 18. The instability calculation map 202 has a relationship of a solid line A when the horizontal axis is the reference yaw rate and the vertical axis is the actual yaw rate.

  When the steering angle is input in a ramp shape as shown in FIG. 4A, if a strong oversteer occurs, a yaw rate larger than the reference yaw rate is generated as shown by the broken line in FIG. 4B. On the other hand, when understeering such as strong front drift occurs, only an actual yaw rate smaller than the reference yaw rate is generated, as indicated by the one-dot chain line in FIG. Therefore, by comparing the relationship between the solid line A, the actual reference yaw rate, and the actual yaw rate, it is possible to determine whether oversteering or understeering and to what extent. In the first embodiment, the difference between the reference yaw rate and the actual yaw rate is an unstable amount.

[Calculation method of assist correction amount and gear ratio correction amount]
Next, a method for calculating the assist correction amount and the gear ratio correction amount according to the vehicle unstable behavior will be described using the maps of FIGS. 5 (a) and 5 (b).

  As shown in FIG. 5 (a), when the horizontal axis is the value obtained by subtracting the actual yaw rate from the reference yaw rate, the absolute value of the value obtained by subtracting the actual yaw rate from the reference yaw rate is the right (left) turn. When the value is equal to or greater than the first set value α, the assist amount is generated in the left (right) direction. Since the reference assist assists the steering torque to be light, the assist is generated in the right direction (left) when turning right (left). Therefore, the sum of the reference assist and the correction amount is smaller than that of the reference assist, and the steering torque becomes heavier.

  As shown in FIG. 5B, the gear ratio correction amount is first set to a predetermined gear ratio regardless of the occurrence of unstable behavior, where the horizontal axis is the value obtained by subtracting the actual yaw rate from the reference yaw rate. (B in FIG. 5B). When the absolute value of the value obtained by subtracting the actual yaw rate from the reference yaw rate is equal to or larger than the second setting value β that is larger than the first setting value α at which the assist correction is started, the gear ratio is corrected to a larger value.

[Oversteer inhibitory action]
The operation during oversteer will be described with reference to FIG.
If the steering wheel angle is input in a ramp shape as shown in FIG. 6A, the vehicle is in a strong oversteer state when the control of the first embodiment is not performed.

  In the first embodiment, when the actual yaw rate starts to become larger than the reference yaw rate due to the behavior of the yaw rate (time point t1), the assist amount is corrected so that the steering torque becomes heavier (FIG. 6 (c)). As a result, the steering wheel angle input is suppressed (dashed line after time t1 in FIG. 6A), and as a result, the generation of the yaw rate is also suppressed (dashed line after time t1 in FIG. 6B). When the handle 1 is further increased from there and the difference between the reference yaw rate and the actual yaw rate is further increased (time point t2 in FIG. 6B), the gear ratio is changed to be increased. When the gear ratio increases, as shown in FIG. 6 (d), even if the steering wheel angle is operated in the increasing direction, the tire angle moves in the direction opposite to the steering wheel operation direction, and the oversteering has progressed. The counter operation is automatically performed in the strong oversteer mode.

[Understeer suppression]
Next, the operation during understeer will be described with reference to FIG.
If the steering wheel angle is input in a ramp shape as shown in FIG. 7A, understeer occurs and the vehicle enters a drift-out state when the control of the first embodiment is not performed.

  In the first embodiment, when the actual yaw rate starts to become smaller than the reference yaw rate due to the behavior of the yaw rate (time point t1), the assist amount is corrected so that the steering torque becomes heavier (FIG. 7 (c)). As a result, the steering wheel angle input is suppressed (broken line after time t1 in FIG. 7A), and as a result, the steering wheel increase that promotes understeer is suppressed (broken line after time t1 in FIG. 7A). When the handle 1 is further increased from there and the difference between the reference yaw rate and the actual yaw rate is further increased (time t2 in FIG. 7B), the gear ratio is changed to be increased. If the gear ratio is increased, the tire angle does not increase in proportion to the steering wheel operation even if the steering wheel angle is increased as shown in FIG.

Next, the effect will be described.
In the vehicle steering apparatus according to the first embodiment, the following effects can be obtained.

  (1) A motor 5 that applies a steering assist force to the steering system, a variable gear ratio mechanism 14 that changes a gear ratio that is a ratio of a steering wheel angle to a tire turning angle, and a stable behavior of the vehicle according to the steering wheel angle. When the unstable behavior exceeding the limit occurs, the controller 13 for driving and controlling the variable gear ratio mechanism 14 in a direction in which the vehicle behavior is stabilized. When the behavior occurs, the motor 5 is driven and controlled in a direction to suppress the steering operation in the direction in which the vehicle behavior becomes unstable before changing the gear ratio in the direction in which the vehicle behavior becomes stable. Therefore, it is possible to suppress the vehicle behavior from becoming more unstable as the driver steers the steering wheel while reducing the uncomfortable feeling due to the steering force fluctuation when the unstable behavior occurs.

  (2) The controller 13 includes an encoder 16 that detects a steering wheel angle, a yaw rate sensor 18 that detects a yaw rate of the vehicle, and an unstable amount calculator 113 that calculates an unstable amount of the vehicle from the steering wheel angle and the yaw rate 18. The steering assist force and gear ratio are changed according to the amount of instability. Therefore, the amount of vehicle instability can be calculated more accurately from the steering wheel angle and the yaw rate, and the instability behavior of the vehicle can be reliably suppressed.

  (3) Since the controller 13 changes the steering assist force according to the steering wheel angle and the yaw rate, it is possible to realize steering force control that guides the driver's steering operation so that the yaw rate becomes an appropriate value according to the steering wheel angle.

  (4) The controller 13 continuously changes the steering assist force. That is, by continuously changing the steering force control during normal times, the steering force control aimed at suppressing the occurrence of unstable behavior of the vehicle itself, and the steering force control when the unstable behavior of the vehicle occurs. The steering force fluctuation can be suppressed to a small level, and the uncomfortable feeling given to the driver can be suppressed.

  (5) The controller 13 changes the steering assist force when the unstable amount is equal to or greater than the first set value α, and changes the gear ratio when equal to or greater than the second set value β (> α). In other words, the steering force control aimed at suppressing the occurrence of unstable behavior of the vehicle itself and the steering force control when the unstable behavior of the vehicle occur are performed based on the same amount of instability, so that the vehicle can be reliably controlled. The steering force control aiming at suppressing the occurrence of the stable behavior itself can be performed before the steering force control when the unstable behavior of the vehicle occurs.

  The second embodiment is an example in which the assist correction amount is decreased as the gear ratio is increased. In addition, since the structure of Example 2 is the same as that of Example 1, description is abbreviate | omitted.

  As shown in FIG. 8, in the second embodiment, the assist correction amount is set according to the gear ratio when the unstable behavior occurs, and the assist correction amount is decreased as the gear ratio when the unstable behavior occurs. . That is, when the gear ratio is large, the vehicle behavior gain with respect to the driver's steering wheel input decreases, so that it is not necessary to make a large correction when unstable behavior occurs. Therefore, by increasing the assist correction amount as the gear ratio increases, it is possible to realize a steering characteristic with less sense of incongruity.

Next, the effect will be described.
In the vehicle steering apparatus of the second embodiment, the following effects are obtained in addition to the effects (1) to (5) of the first embodiment.

  (6) Since the controller 13 changes the steering assist force according to the gear ratio, the steering force is generated in a direction in which the unstable behavior of the vehicle is unlikely to occur before the unstable behavior of the vehicle due to the driver's steering operation. Since the driver's operation can be suppressed, the occurrence of unstable behavior of the vehicle itself can be suppressed. Furthermore, in addition to the steering force control described above, the operation of the variable gear ratio mechanism 14 in the direction to stabilize the vehicle behavior leads to the driver's operation in the vehicle stable direction even with the steering force, so that the vehicle behavior is surely unstable. Can be suppressed.

  The third embodiment is an example in which the assist correction amount is varied according to the steering state. In addition, since the structure of Example 3 is the same as that of Example 1, description is abbreviate | omitted.

  As shown in FIG. 9, in Example 3, in the case of a right (left) turn (solid line in FIG. 9), the actual value from the reference yaw rate is greater than the case where the value obtained by subtracting the actual yaw rate from the reference yaw rate is negative (positive). When the value obtained by subtracting the yaw rate is positive (negative), the assist correction amount is increased. That is, the assist correction amount in the case of oversteer is made larger than that in the case of understeer. As a result, a sufficient vehicle behavior stabilization effect can be obtained during oversteering where vehicle behavior is more unstable.

Next, the effect will be described.
In the vehicle steering apparatus of the third embodiment, the following effects can be obtained in addition to the effects (1) to (5) of the first embodiment.

  (7) The unstable amount calculation unit 113 calculates the unstable amount based on the steer state, and sets the unstable amount in the oversteer state larger than the unstable amount in the understeer state. Therefore, according to the steer state where the vehicle behavior becomes unstable, it is possible to generate a steering assist force in a stable direction during oversteer and understeer, and even during oversteer where the vehicle behavior becomes more unstable Sufficient vehicle behavior stabilization effect can be obtained.

  The fourth embodiment is an example in which the assist correction amount for the unstable amount is increased as the vehicle speed is higher. In addition, since the structure of Example 4 is the same as that of Example 1, description is abbreviate | omitted.

  As shown in FIG. 10, in the fourth embodiment, the assist correction amount corresponding to the unstable behavior of the vehicle is increased as the vehicle speed increases, and the steering amount of the driver is increased by decreasing the assist amount. At this time, the difference between the first set value α for starting the steering force control and the second set value β for starting the gear ratio control is increased by setting the first set value α to a smaller value α ′ as the vehicle speed increases.

  By adopting such a configuration, as the vehicle has a characteristic that the gain of the vehicle behavior with respect to the steering wheel angle input increases as the vehicle speed increases, the steering torque is increased according to the vehicle speed when the unstable behavior occurs. This makes it possible to effectively suppress the unstable behavior of the vehicle.

  In other words, the vehicle behavior tends to become unstable as the vehicle speed increases, and the state change from stable to unstable becomes faster. However, the vehicle becomes unstable depending on the vehicle speed by increasing the assist amount as the vehicle speed increases. Steering force control aiming to suppress the occurrence of behavior itself can be performed earlier than steering force control when unstable behavior of the vehicle occurs, and the occurrence of unstable behavior of the vehicle itself can be suppressed. .

Next, the effect will be described.
In the vehicle steering apparatus of the fourth embodiment, the following effects can be obtained in addition to the effects (1) to (5) of the first embodiment.

  (8) Since the controller 13 sets a larger difference between the first set value α and the second set value β as the vehicle speed becomes higher, the occurrence of unstable behavior of the vehicle can be suppressed regardless of the vehicle speed.

  The fifth embodiment is an example in which the assist correction amount for the unstable amount is increased as the turning speed (= steering wheel angular velocity) is higher. In addition, since the structure of Example 4 is the same as that of Example 1, description is abbreviate | omitted.

  As shown in FIG. 11, in the fifth embodiment, the assist correction amount corresponding to the unstable behavior of the vehicle is increased as the turning speed is increased, and the driver's steering torque is increased by decreasing the assist amount. At this time, the difference between the first set value α for starting the steering force control and the second set value β for starting the gear ratio control is increased by setting the first set value α to a smaller value α ′ as the turning speed increases. .

  That is, the vehicle behavior tends to become unstable as the turning angle increases or the turning speed increases, and the state change from stable to unstable becomes faster, but the assist correction amount increases as the turning speed increases. Therefore, the steering force control aiming at suppressing the occurrence of unstable behavior of the vehicle itself according to the change in the steering amount can be controlled at the time of occurrence of the unstable behavior of the vehicle. It becomes possible to carry out earlier than the steering force control, and the occurrence of unstable behavior of the vehicle itself can be suppressed.

Next, the effect will be described.
In the vehicle steering apparatus of the fifth embodiment, the following effects are obtained in addition to the effects (1) to (5) of the first embodiment.

  (9) Since the controller 13 sets a larger difference between the first set value α and the second set value β as the turning speed becomes higher, the occurrence of unstable behavior of the vehicle can be suppressed regardless of the turning speed.

(Other examples)
As mentioned above, although the best form for implementing this invention was demonstrated based on Examples 1-5, the concrete structure of this invention is not limited to Examples 1-5, The invention Design changes and the like within a range that does not depart from the gist are also included in the present invention.

  For example, in the first embodiment, the vehicle yaw rate is used as the vehicle behavior state quantity, and the unstable amount of the vehicle is calculated based on the yaw rate. However, the lateral G and the vehicle body slip angle, which are other vehicle behavior state quantities, combinations thereof, Alternatively, the amount of vehicle instability may be calculated based on a combination of these change rates and the like.

In the first embodiment, the method of obtaining the handle angle from the encoder 16 is used. However, the handle angle may be directly measured from the rotation angle of the steering shaft 3 or the like. Further, the steering wheel angle may be estimated by integrating the signal of the angular velocity sensor such as the tacho generator.
In the first embodiment, the motor control of the variable gear ratio mechanism 14 is shown as current control. However, the gear ratio of the variable gear ratio mechanism may be directly measured and fed back.

1 is a configuration diagram of a vehicle steering apparatus according to Embodiment 1. FIG. FIG. 3 is a control block diagram according to the first embodiment. FIG. 3 is a control block diagram of an unstable amount calculation unit according to the first embodiment. It is a figure which shows the unstable behavior determination method of Example 1. FIG. 2 is an assist correction amount calculation map and a gear ratio correction amount calculation map according to the first embodiment. 3 is a time chart showing an oversteer suppressing action of Example 1. 3 is a time chart showing an understeer suppressing action of Example 1. 6 is an assist correction amount calculation map according to the second embodiment. 12 is an assist correction amount calculation map according to the third embodiment. 14 is an assist correction amount calculation map according to the fourth embodiment. 14 is an assist correction amount calculation map according to the fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Handle 2 Steering mechanism 3 Steering shaft 4 Torque sensor 5 Motor 6 Pinion 7 Rack 8, 9 Tie rod 10, 11 wheel 12 Reducer 13 Controller 14 Variable gear ratio mechanism 15 Motor 16 Encoder 17 Vehicle speed sensor 18 Yaw rate sensor 20 Battery

Claims (10)

A steering force actuator for applying a steering assist force to the steering system;
A gear ratio actuator that varies a gear ratio that is a ratio of a steering wheel angle to a tire turning angle;
Steering control means for driving and controlling the gear ratio actuator in a direction in which the vehicle behavior becomes stable when an unstable behavior exceeding the stable behavior limit of the vehicle occurs in the vehicle according to the steering wheel angle;
In a vehicle steering apparatus comprising:
When the unstable behavior occurs in the vehicle, the steering control means suppresses the steering operation in the direction in which the vehicle behavior becomes unstable before changing the gear ratio in the direction in which the vehicle behavior becomes stable. A steering apparatus for a vehicle, wherein the steering force actuator is driven and controlled. The vehicle steering apparatus according to claim 1,
Steering amount detection means for detecting the steering amount of the steering wheel;
Vehicle behavior state quantity detecting means for detecting a vehicle behavior state quantity generated in the vehicle;
An unstable amount calculating means for calculating an unstable amount of the vehicle from the steering amount and the vehicle behavior state amount;
With
The vehicle steering apparatus, wherein the steering control means changes the steering assist force and the gear ratio according to the unstable amount. The vehicle steering apparatus according to claim 2,
The vehicle steering apparatus, wherein the steering control means changes the steering assist force in accordance with at least one of the steering amount and the vehicle behavior state amount. The vehicle steering apparatus according to any one of claims 1 to 3,
The vehicle steering apparatus, wherein the steering control means changes the steering assist force in accordance with the gear ratio. The vehicle steering apparatus according to any one of claims 1 to 4, wherein:
The vehicle steering apparatus, wherein the steering control means changes the steering assist force in at least two or more stages or continuously. The vehicle steering apparatus according to any one of claims 2 to 5,
The unstable amount calculation means calculates the unstable amount based on a steer state, and sets the unstable amount in the oversteer state to be larger than the unstable amount in the understeer state. apparatus. The vehicle steering apparatus according to any one of claims 2 to 6,
The steering control means changes the steering assist force when the unstable amount is greater than or equal to a first set value, and changes the gear ratio when the unstable amount is greater than or equal to a second set value greater than the first set value. A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 7, wherein
The vehicle steering apparatus, wherein the steering control means sets a difference between the first set value and the second set value as the vehicle speed increases. The vehicle steering apparatus according to claim 8, wherein
The vehicle steering apparatus according to claim 1, wherein the steering control means sets a difference between the first set value and the second set value as the change rate of the steering amount increases. In a vehicle steering apparatus for changing a gear ratio, which is a ratio of a steering wheel angle to a tire turning angle, in a direction in which the vehicle behavior is stable when an unstable behavior exceeding the stable behavior limit of the vehicle occurs in the vehicle,
When the unstable behavior occurs in the vehicle, the steering assist force is generated in a direction to suppress the steering operation in the direction in which the vehicle behavior becomes unstable before changing the gear ratio in the direction in which the vehicle behavior becomes stable. A vehicle steering apparatus characterized by the above.

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