JP2008296700A - Variable rear wheel toe angle control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear wheel toe angle control device for a vehicle, capable of improving the stability of the vehicle by appropriately controlling a rear wheel toe angle regardless of a road surface condition, tire characteristics or weight of the vehicle. <P>SOLUTION: This rear wheel toe angle control device 20 arranged in a variable rear wheel toe angle vehicle 1 with the rear wheel toe angle variably controlled and controlling the rear wheel toe angle &theta; includes; a steered angle sensor 14 detecting a front wheel steered angle &delta;<SB>f</SB>; a ground sensor 15 detecting the actual body slip angle &beta;<SB>act</SB>; a target slip angle setting section 22 setting a target body slip angle &beta;<SB>ideal</SB>based on the result (&delta;<SB>f</SB>) detected by the steered angle sensor 14; and a target rear wheel toe angle setting section 23 setting a target rear wheel toe angle based on a difference between the target slip angle &beta;<SB>ideal</SB>and the actual body slip angle &beta;<SB>act</SB>. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a rear wheel toe angle control device provided in a rear wheel toe angle variable vehicle in which a rear wheel toe angle is variably controlled and used for controlling the rear wheel toe angle.

  In a vehicle that steers only the front wheels, when turning at low speed, there is almost no slip angle between the front and rear wheel tires, so the traveling direction of the vehicle body is half the front wheel steering angle, There is a deviation (hereinafter referred to as a vehicle slip angle) between the vehicle and the traveling direction. On the other hand, when turning at high speed, each tire requires a large slip angle in order to generate a large cornering force. In this case, it is possible to increase the slip angle by cutting the steering wheel largely, but the rear wheel increases the slip angle by causing the rear part of the vehicle body to flow outside the corner by centrifugal force, so-called `` oblique running ''. I have to. For this reason, the vehicle body slip angle is opposite to that when driving at low speed, and the vehicle body slip angle during high-speed turning increases as the vehicle speed increases.

Here, the steady value of the vehicle body slip angle β of the vehicle that steers only the front wheels is given by the following equation.
beta = _{{[(1-m / l) ·} (l f / l r k r) · V 2 ] ^{/ (1 + AV 2)}} · (δ f · l r / l) ··· (1)
Where m: vehicle mass, l: wheel base, l _f , l _r : center of gravity axis distance, δ _f : front wheel rudder angle, A: stability factor, and V: vehicle speed.
Then, when the characteristics of the vehicle body slip angle β are graphed with respect to the understeer, neutral steer, and oversteer characteristics, they are expressed as shown in FIG. The vertical axis of FIG. 4 represents the vehicle body slip angle beta / front wheel steering angle [delta] _f, the horizontal axis represents the vehicle speed V. As can be seen, the beta / [delta] _f, when the vehicle speed is 0 is one-half regardless of the steering characteristic, slide into changes to a negative value As the vehicle speed increases. As can be seen from Equation 1 and FIG. 3, the vehicle slip angle β has a characteristic that decreases in accordance with the vehicle speed V in any of the steer characteristics.

  As described above, when the vehicle slip angle β greatly changes depending on the vehicle speed V, the driving operation of the driver becomes difficult. Thus, a rear wheel toe angle control device that individually changes the left and right rear wheel toe angles is known in order to improve operability (see Patent Document 1). This device adopts a configuration in which a linear displacement actuator such as a hydraulic cylinder is provided at a connecting portion between a lateral link or a trailing link of a suspension device that supports left and right rear wheels and a hydraulic cylinder is driven to extend and contract.

In the conventional rear wheel toe angle control device planned as a simple type of the rear wheel steering device including the technique described in Patent Document 1, the rear wheel steering angle is controlled in accordance with the vehicle behavior when the vehicle turns. The control target value of the rear wheel rudder angle is generally determined according to the front wheel rudder angle, lateral acceleration, or yaw rate. For example, the rear wheel rudder angle is controlled so that the vehicle body slip angle becomes zero. Is known (see Patent Document 2).
Japanese Patent Publication No. 8-25482 Japanese Patent No. 3179271

  According to the rear wheel toe angle control device using the parameters described in Patent Document 2, the driver's intention is reflected in the rear wheel toe angle control by operating the front wheel steering angle to change the lateral acceleration or the yaw rate. On the other hand, it has been difficult to control the slip angle of the vehicle body with high accuracy in response to changes in the actual driving environment, that is, changes in road surface conditions, and changes in vehicle characteristics such as tire characteristics and load capacity.

  The present invention has been devised to eliminate the disadvantages of the prior art, and its main purpose is to properly control the rear wheel toe angle regardless of the road surface condition, tire characteristics, or vehicle weight. Accordingly, an object of the present invention is to provide a vehicle rear wheel toe angle control device that achieves improved vehicle stability.

  In order to solve the above problems, the invention of claim 1 is provided in a rear wheel toe angle variable vehicle in which a rear wheel toe angle is variably controlled, and is used for control of the rear wheel toe angle. In the apparatus, a target vehicle slip angle is set based on a detection result of a front wheel steering angle detection unit that detects a front wheel steering angle, an actual vehicle slip angle detection unit that detects an actual vehicle slip angle, and the front wheel steering angle detection unit. Target vehicle slip angle setting means and target rear wheel toe angle setting means for setting a target rear wheel toe angle based on a difference between the target vehicle slip angle and the actual vehicle slip angle are provided.

  According to a second aspect of the present invention, in the rear wheel toe angle variable control device of the first aspect, the actual vehicle slip angle detecting means is a ground sensor.

  According to the present invention, the rear wheel toe angle can be appropriately controlled so that the vehicle body slip angle becomes the target value regardless of changes in road surface conditions, tire characteristics, or vehicle weight. Therefore, appropriate vehicle behavior control is performed to improve the vehicle stability, and to improve the operability of the vehicle without causing the driver to feel uncomfortable.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, for the wheels and members disposed therewith, that is, tires, actuators, and the like, suffixes L or R indicating left and right are added to the reference numerals, respectively, for example, rear wheel 5L (left) The rear wheel 5R (right) is referred to as the rear wheel 5 when collectively referred to.

<< Configuration of Embodiment >>
<Schematic configuration of automobile>
FIG. 1 shows an outline of a rear wheel toe angle variable vehicle 1 to which the rear wheel toe angle control device according to the embodiment is applied. The rear wheel toe angle variable vehicle 1 includes front wheels 3L and 3R to which tires 2L and 2R are mounted, and rear wheels 5L and 5R to which tires 4L and 4R are mounted. These front wheels 3L and 3R and rear wheels The wheels 5L and 5R are suspended from the vehicle body by front wheel suspension devices 6L and 6R and rear wheel suspension devices 7L and 7R, each of which includes a suspension arm, a spring, a damper, and the like. The rear wheel toe angle variable vehicle 1 includes a front wheel steering device 9 that directly steers the left and right front wheels 3L and 3R by steering the steering wheel 8, and left and right trailing arms 10L in the left and right rear wheel suspension devices 7L and 7R. , 10R, and left and right actuators 11L, 11R that individually change the toe angles of the rear wheels 5L, 5R by being individually changed in length.

  The rear wheel toe angle variable vehicle 1 includes an ECU (Electronic Control Unit) 12 for overall control of various systems, a vehicle speed sensor 13, and a steering angle sensor 14 for detecting the steering angle of the steering wheel 8 (front wheel steering angle detection means). ), To the left and right to detect the toe angles of the rear wheels 5L and 5R from the displacement amounts of the ground sensor 15 and the actuators 11L and 11R that detect the actual vehicle slip angle, that is, the angle difference between the direction of the vehicle body and the actual traveling direction. Toe angle sensors 16L and 16R are installed, and these detection signals are also input to the ECU 12. The ECU 12 varies the length of the actuators 11L and 11R based on the outputs of these sensors, and controls the toe angles of the rear wheels 5L and 5R.

  Each of the actuators 11L and 11R uses a known appropriate linear displacement actuator such as a rotary motion / linear motion conversion device that combines an electric motor with a speed reducer and a screw mechanism, or a cylinder device that linearly drives a piston rod with fluid pressure. be able to. Each toe angle sensor 16L, 16R can be a known displacement sensor such as a potentiometer. However, considering durability, a non-contact sensor such as an electromagnetic sensor is preferable. As the ground sensor 15, a known sensor that measures a side slip angle by using a spatial filter type speed detector that measures a speed in a straight direction and a lateral direction can be applied.

  According to the rear wheel toe angle variable vehicle 1 configured in this way, the left and right actuators 11L and 11R are simultaneously symmetrically displaced, so that the toe-in / to-out of the rear wheels 5L and 5R can be performed under appropriate conditions. In addition to being freely controllable, if one of the left and right actuators 11L and 11R is extended and the other is contracted, both rear wheels 5L and 5R can be steered to the left and right.

  The ECU 12 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and each actuator 11 and each sensor via a communication line (CAN (Controller Area Network) in this embodiment). 13 to 16 etc. are connected.

<Schematic configuration of rear wheel toe angle control device>
FIG. 2 is a block diagram showing a schematic configuration of the rear wheel toe angle control device 20 according to the embodiment. As shown in FIG. 2, the rear wheel toe angle control device 20 includes a vehicle speed sensor 13, a steering angle sensor 14, a ground sensor 15, left and right toe angle sensors 16L and 16R, an ECU 12, and left and right actuators 11L, 11R.

The ECU 12 sets a target vehicle slip angle β _ideal based on the input interface 21 to which the vehicle speed sensor 13, the steering angle sensor 14, the ground sensor 15, the toe angle sensors 16 </ b _> L and 16 </ b _> R are connected, and the detected value of the steering angle sensor 14. A target rear wheel toe angle setting unit 22 for calculating a target rear wheel toe angle θ _ideal from the target vehicle body slip angle β _ideal and the detection value of the ground sensor 15; and a target rear wheel toe angle θ _The drive signal generation unit 24 generates drive signals for the actuators 11L and 11R based on the _{ideal and the} like, and the output interface 25 outputs the drive signals generated by the drive signal generation unit 24 to the actuators 11L and 11R. .

<Operation of Embodiment>
Next, the procedure of rear wheel toe control by the rear wheel toe angle control device 20 according to the present embodiment will be described with reference to FIG. When the rear wheel toe angle variable vehicle 1 starts driving, the ECU 12 executes the rear wheel toe angle processing shown in the flowchart of FIG. 3 at a predetermined processing interval (for example, 10 ms).

When starting the rear wheel toe angle control, first, in step 1, the target vehicle body slip angle setting section 22 performs the process depicted in the following equation, i.e., by multiplying the front wheel steering angle [delta] _f the vehicle slip angle transmission characteristic G Set the target vehicle slip angle β _ideal .
β _ideal = G · δ _f (2)
Vehicle slip angle transmission characteristic G is a preset function as the target vehicle body slip angle characteristic of the vehicle 1, the relationship between the vehicle body slip angle beta / front wheel steering angle [delta] _f and the vehicle speed V (corresponding to the graph of FIG. 3) It represents. Specifically, based on the detection result of the vehicle speed sensor 13 (vehicle speed V), the vehicle body slip angle beta / front wheel steering angle [delta] _f is calculated. The target vehicle slip angle setting unit 22 calculates the target vehicle slip angle β _ideal by multiplying this value by the detected value of the steering angle sensor 14 (front wheel steering angle δ _f ).

The target vehicle slip angle β _ideal may be set using a map instead of using the vehicle slip angle transmission characteristic G. In this case, the target vehicle slip angle setting unit 22 searches the map stored in the ROM and multiplies the search result by the front wheel steering angle δ _f to set the target vehicle slip angle β _ideal . Further, a predetermined coefficient may be used for the vehicle body slip angle transmission characteristic G so that the target vehicle body slip angle characteristic becomes constant regardless of the vehicle speed V.

Next, in step 2, the target rear wheel toe angle setting unit 23 obtains the target rear wheel toe angle θ _ideal based on the following equation. That is, by subtracting the detected value (actual vehicle slip angle β _act ) of the ground sensor 15 from the target vehicle slip angle β _ideal calculated by the target vehicle slip angle setting unit 22 and multiplying this value by a predetermined coefficient K. The target rear wheel toe angle θ _ideal is calculated.
θ _ideal = K (β _ideal −β _act ) (3)

As obtained by substituting Equation 2 into Equation 3, the target rear wheel toe angle θ _ideal calculated through the target vehicle slip angle setting unit 22 and the target rear wheel toe angle setting unit 23 is expressed by the following equation. Will be.
θ _ideal = K (G · δ _f -β) (4)

Next, in step 3, the drive signal generator 24 calculates the target rear wheel toe angle θ _ideal by calculating the left and right actuators 11L and 11R and the left and right rear wheels 5L and 5R by the target rear wheel toe angle setting unit 23. The control amounts of the left and right actuators 11L and 11R necessary for changing to the above are calculated, and an actuator drive signal is generated based on these values. The actuator drive signal is output to the left and right actuators 11L and 11R via the output interface 25.

Since the drive signal generator 24 receives a signal indicating the actual displacement amount (actual toe angle θ _act ) of the left and right actuators 11L and 11R detected by the left and right toe angle sensors 16L and 16R (see FIG. 2). In step 4, the drive signal generator 24 determines whether θ _act is equal to θ _ideal , that is, whether the left and right actuators 11L, 11R are driven according to the signal generated by the drive signal generator 24. Determine whether. If θ _act is equal to θ _ideal (Yes), go to return and repeat the above procedure. On the other hand, when θ _act is not equal to θ _ideal (No), the drive signal generation unit 24 generates a drive signal for the actuator based on the difference between θ _{act and} θ _ideal . As described above, feedback control of whether the left and right rear wheels 5L and 5R have the target rear wheel toe angle θ _ideal enables accurate control of the toe angles of the rear wheels 5L and 5R and the actuator. It is also possible to detect abnormalities in 11L and 11R.

  As described above, according to the present embodiment, the rear wheel toe angle θ can be appropriately controlled so that the vehicle body slip angle β becomes the target value regardless of changes in road surface conditions, tire characteristics, or vehicle weight. Accordingly, appropriate behavior control of the rear wheel toe angle variable vehicle 1 is performed to improve the vehicle stability, and the operability of the vehicle is also improved without causing the driver to feel uncomfortable.

This is the end of the description of specific embodiments. However, aspects of the present invention are not limited to these embodiments. For example, in the above embodiment, the ground sensor is used as the actual vehicle slip angle detecting means, but the actual vehicle slip angle may be calculated based on the yaw rate, the lateral acceleration, and the vehicle speed. In this case, the rear wheel toe angle variable vehicle is configured to further include a yaw rate sensor and a lateral acceleration sensor, and the actual vehicle slip angle β _act may be obtained by the following equation.
β _act = α _y / V−γ (5)
However, α _{y is the} lateral acceleration, and γ is the yaw rate.
By adopting such an embodiment, even if an expensive ground sensor is not provided, a relatively inexpensive sensor other than the ground sensor is used, and the actual vehicle slip angle is calculated by calculating based on the detection values of these sensors. A substantially equal value can be obtained. Therefore, the present invention can be implemented at a lower cost.

  In the above embodiment, the rear wheel toe angle control device is applied to a rear wheel toe angle variable vehicle in which an actuator is connected to the trailing arm of both rear wheels. You may apply to an angle variable vehicle. Furthermore, the actuators that change the rear wheel toe angle need not be provided on the left and right rear wheels, respectively, and may be configured such that the left and right rear wheels are driven in the same direction by one actuator. In addition, as long as it does not deviate from the gist of the present invention, the specific configuration of the vehicle and the rear wheel toe angle control device, the specific method of control, and the like can be appropriately changed.

Schematic configuration diagram of a rear wheel toe angle variable vehicle to which the rear wheel toe angle control device according to the embodiment is applied. The block diagram which shows schematic structure of the rear-wheel toe angle control apparatus which concerns on embodiment. Flowchart showing a procedure of rear wheel toe angle control according to the embodiment Graph showing the relationship between side slip angle / steering angle and speed

Explanation of symbols

1 Rear wheel toe angle variable vehicles 11L, 11R Actuator 13 Vehicle speed sensor 14 Steering angle sensor (front wheel steering angle detecting means)
15 Ground sensor (Actual vehicle slip angle detection means)
16L, 16R Toe angle sensor 20 Rear wheel toe angle control device 22 Target vehicle slip angle setting unit 23 Target rear wheel toe angle setting unit δ _f Front wheel steering angle β _act Actual vehicle slip angle β _Ideal target vehicle slip angle θ _Ideal target rear wheel Toe angle G Car body slip angle transmission characteristic K factor

Claims (2)

A rear wheel toe angle control device provided in a rear wheel toe angle variable vehicle in which a rear wheel toe angle is variably controlled and used for controlling the rear wheel toe angle,
Front wheel rudder angle detecting means for detecting the front wheel rudder angle;
An actual vehicle slip angle detecting means for detecting an actual vehicle slip angle;
Based on the detection result of the front wheel rudder angle detection means, target vehicle slip angle setting means for setting a target vehicle slip angle; and
A rear wheel toe angle control device comprising target rear wheel toe angle setting means for setting a target rear wheel toe angle based on a difference between the target vehicle body slip angle and the actual vehicle body slip angle.   The rear wheel toe angle control device according to claim 1, wherein the actual vehicle slip angle detecting means is a ground sensor.

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