JPH1159457A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of correcting the neutral points of steered wheels not mechanically connected to a steering wheel to accurately adapt an output signal showing the tire angle of a wheel to the steering angle of the steering wheel. SOLUTION: Actuators 14, 16 are provided to steer steered wheels FL, FR not mechanically connected to a steering wheel 10. The actuators 14, 16 have a sensor to detect tire angles θL, θR and a sensor to detect king pin shaft torque TL, TR, respectively. Self-aligning torque to be generated when the steered wheels FL, FR are located at a neutral point and self-aligning torque to be actually generated are detected as neutral reference torque and neutral actual torque, respectively. The detection value for a tire angle is corrected by the sensors in accordance with a deviation between the neutral actual torque and the neutral reference torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system, and more particularly to a vehicle steering system suitable for correcting a neutral point of a steering wheel not mechanically connected to a steering wheel.

[0002]

2. Description of the Related Art Conventionally, in the field of vehicles, there has been known an apparatus for steering rear wheels of a vehicle using an electric actuator, as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-244645. In the above conventional device, the actuator is controlled so that the tire angle of the rear wheel becomes an angle corresponding to the steering angle of the steering wheel.

In the above-described conventional apparatus, it is necessary to accurately detect the tire angle of the rear wheel in order to operate the actuator with high accuracy. As disclosed in the above literature, the tire angle of a wheel can be detected using an electric sensor such as a potentiometer.

[0004]

However, the output characteristics of an electric sensor such as a potentiometer may change due to aging or the like. Therefore, when the tire angle of the wheel is detected using an electric sensor such as a potentiometer, it is necessary to appropriately correct the output signal of the wheel and the tire angle so as to correspond exactly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been modified to an output signal representing a tire angle so that the output signal representing the tire angle of a wheel and the steering angle of a steering wheel correspond exactly. It is an object of the present invention to provide a vehicle steering device capable of performing the following.

[0006]

The above object is achieved by the present invention.
As described in, the steering wheel is not mechanically connected to the steering wheel, an actuator for electrically steering the steering wheel, a tire angle detection mechanism for detecting the tire angle of the steering wheel, the tire angle A self-aligning torque to be generated when a steered wheel is located at a neutral point in a vehicle steering device that drives the actuator such that a tire angle detected by a detection mechanism is an angle corresponding to a steering angle of a steering wheel. A neutral reference torque detecting means for detecting the self-aligning torque acting on the steered wheels when the steering wheel is located at the neutral point as a neutral actual torque, and a steering wheel. When located at the neutral point, the deviation between the neutral actual torque and the neutral reference torque is calculated as the neutral torque. A neutral torque deviation detecting means for detecting a deviation, and the tire angle correcting means for correcting the detected value of the tire angle detection means based on the neutral torque deviation is achieved by a vehicle steering device comprising a.

In the present invention, when the steering wheel is located at the neutral point, the steered wheels have a tire angle detected by the tire angle detecting means (hereinafter referred to as a detected tire angle).
Is steered to be at the neutral point. When the steered wheel is located at the neutral point, the neutral actual torque acting on the steered wheel matches the neutral reference torque. On the other hand, when the steered wheels are shifted from the neutral point, a neutral torque deviation corresponding to the shift amount occurs between the neutral actual torque acting on the steered wheels and the neutral reference torque.

[0008] In other words, when a neutral torque deviation occurs between the neutral actual torque and the neutral reference torque when the steering wheel is located at the neutral point, the tire angle actually generated on the steered wheels at that time. (Hereinafter, referred to as a neutral actual tire angle) can be recognized as being shifted from an original neutral point by an angle corresponding to the neutral torque deviation. Such a situation occurs when an error is superimposed on the detected tire angle by an angle corresponding to the neutral torque deviation.

In the present invention, the detected tire angle is corrected based on the neutral torque deviation in order to eliminate the above error. When the above-described correction is performed, the tire angle actually occurring on the steered wheels (hereinafter, referred to as an actual tire angle) and the detected tire angle can be accurately matched. In a situation where the actual tire angle exactly corresponds to the detected tire angle, the steered wheels can be steered such that the actual tire angle exactly corresponds to the steering angle of the steering wheel.

According to a second aspect of the present invention, in the vehicle device according to the first aspect, a self-aligning torque to be generated with respect to a tire angle of a steered wheel is detected as a reference torque. Reference torque detecting means,
Based on actual torque detection means for detecting the self-aligning torque acting on the steered wheels as actual torque, based on the reference torque and the actual torque corresponding to the same tire angle,
A correction coefficient calculating means for calculating a correction coefficient for converting the reference torque into the actual torque; and a neutral reference torque correcting means for correcting the neutral reference torque by using the correction coefficient. The detecting means is achieved by a vehicle steering device for detecting a deviation between the actual torque and the neutral reference torque corrected by the neutral reference torque correcting means.

In the present invention, the neutral reference torque (self-aligning torque to be generated when the steering wheel is located at the neutral point) and the neutral actual torque (act on the steering wheel when the steering wheel is located at the neutral point). The deviation amount between the neutral actual tire angle and the original neutral point is detected based on the deviation (neutral torque deviation) from the self-aligning torque. Then, the detected tire angle is corrected based on the deviation amount.

Therefore, in order to accurately correct the detected tire angle, it is necessary that the neutral reference torque accurately coincides with the self-aligning torque generated when the steered wheel is located at the neutral point. . The self-aligning torque generated when the steered wheels are located at the neutral point changes due to changes in tire conditions and road surface conditions. Therefore,
In order to accurately correct the detected tire angle, a preset neutral reference torque (hereinafter, referred to as a basic neutral reference torque) is corrected, and a neutral reference torque reflecting the above change, that is, It is necessary to generate a neutral reference torque (hereinafter, referred to as an actual neutral reference torque) that exactly matches the self-aligning torque actually acting on the steered wheels when the wheel is located at the neutral point.

When the neutral reference torque changes according to the condition of the tire or the road surface, the difference between the reference torque to be generated for the tire angle and the actual torque actually generated for the tire angle is obtained. Occurs. In this case, the ratio between the basic neutral reference torque and the actual neutral reference torque substantially matches the ratio between the reference torque and the actual torque. In the present invention, a correction coefficient for converting the reference torque into the actual torque is obtained based on the reference torque and the actual torque, and the basic neutral reference torque is corrected using the correction coefficient. According to the above correction, a neutral reference torque that matches the actual neutral reference torque can be generated.

In the present invention, the detected tire angle is corrected based on a deviation between the neutral actual torque and the neutral reference torque generated by the above correction. In this case, the detected tire angle can be accurately corrected irrespective of the tire state or the road surface state. Therefore, according to the present invention, the tire angles of the steered wheels can be made to accurately correspond to the steering angles of the steering wheel without being affected by the tire state or the road surface state.

[0015]

FIG. 1 is a perspective view showing the main components of a vehicle steering system according to one embodiment of the present invention. The vehicle steering system according to the present embodiment includes a steering wheel 10. A steering reaction device 12 is connected to the steering wheel 10. When the steering wheel 10 is steered, the steering reaction force device 12 transmits a reaction force corresponding to the steering angle to the steering wheel 10.

The vehicle steering system according to the present embodiment includes actuators 14 and 16. Actuator 14, 1
6 is connected to the shock absorber 2 via belts 18 and 20.
2, 24 are connected. Shock absorber 22,
24 are fixed to the left front wheel FL and the right front wheel FR, respectively. The shock absorbers 22, 24 can rotate around their axes. The left and right front wheels FL and FR are respectively provided with shock absorbers 22 and 2 respectively.
4 can be rotated in the steering direction with the kingpin axis (ie, the steering center axis).

The actuators 14 and 16 are provided with shock absorbers 2 according to the steering angle of the steering wheel 10.
A motor for rotating the motor 2 and 24 is built in. Therefore, the left and right front wheels FL and FR are electrically steered by the actuators 14 and 16 when the steering wheel 10 is steered. FIG. 2 is a block diagram showing an electric structure of the vehicle steering system according to the present embodiment. The vehicle steering system according to the present embodiment includes an electronic control unit 26 (hereinafter referred to as E).
CU 26).

The above-described steering reaction force control device 12 is connected to the ECU 26. The steering reaction force control device 12 includes:
A motor for transmitting a steering reaction force to the steering wheel 10 and a steering sensor for generating a signal according to the steering state of the steering wheel 10 are built in. The ECU 26 detects a steering angle MA of the steering wheel 10 based on an output signal emitted from a steering sensor. Also, the ECU 26 calculates the steering angle MA
An appropriate drive signal is supplied to the motor of the steering reaction force control device 12 in order to generate a steering reaction force according to the following.

A vehicle speed sensor 28 is connected to the ECU 26. The vehicle speed sensor 28 generates a pulse signal at a cycle corresponding to the vehicle speed V. The ECU 26 detects the vehicle speed V based on the output signal of the vehicle speed sensor 28. Drive circuits 32 and 34 are also connected to the ECU 26. The drive circuits 32 and 34 are circuits for supplying an appropriate drive current to the motors built in the actuators 14 and 16. When the steering wheel 10 is steered, the ECU 26 drives the drive circuits 30 and 32 so that the tire angles θ _L and θ _R corresponding to the steering angle MA are generated on the left and right front wheels FL and FR.

The above-described actuator 14 has a built-in tire angle sensor and torque sensor. Similarly, the actuator 16 also includes a tire angle sensor and a torque sensor. Output signals from these sensors are supplied to the ECU 26. The ECU 26 determines the tire angle θ _{L of the} left front wheel FL based on the output signals of the tire angle sensors built in the actuators 14 and 16, respectively.
And the tire angle θ _R of the right front wheel FR is detected. Also, E
The CU 26 performs a self-aligning torque (hereinafter referred to as a left kingpin torque _TL or a right kingpin torque) acting around the kingpin axis of the left front wheel FL and the right front wheel FR based on the output signals of the torque sensors incorporated in the actuators 14 and 16, respectively. T _R referred to) is detected.

In the vehicle steering system of the present embodiment, the left and right front wheels FL, FR and the steering wheel 10 are not mechanically connected. For this reason, the ECU 26 includes the steering angle MA of the steering wheel 10 and the left and right front wheels FL, FL.
It is required to drive the actuators 14 and 16 so that the tire angles θ _L and θ _R accurately correspond to each other. As described above, the ECU 26 detects the tire angles θ _L and θ _R of the left and right front wheels FL and FR based on the output signals of the tire angle sensors built in the actuators 14 and 16. ECU2
6, the detected tire angle theta _L as described above, using a theta _R, left and right front wheels FL, as the tire angle theta _L of FR, theta _R is an angle corresponding to the steering angle MA of the steering wheel, the actuator 14 , 16 are feedback controlled. According to such a method, appropriate tire angles θ _L , θ _R can be given to the left and right front wheels FL, FR.

However, the tire angle θ detected by the ECU 26
_L, and theta _R, for example, such as when the change over time in the tire angle sensor occurs, the real tire angle theta _L, may be a value that does not match the theta _R. Hereinafter, the tire angle theta _L of ECU26 is detected based on the output signal of the tire angle sensor, theta _R detected tire angle theta] D _L, and theta] D _R, also the left and right front wheels FL, FR
Of the reality of the tire angle θ _L, θ _R the actual tire angle θR _L, θR
Called _R.

[0023] Detection tire angle theta] D _L, theta] D _R and the actual tire angle .theta.R _L, when the .theta.R _R do not match, executing the feedback control described above, the actual tire angle .theta.R _L, .theta.R _R
And the steering angle MA of the steering wheel cannot be accurately matched. In order to avoid such inconvenience, the vehicle steering system according to the present embodiment is configured such that the neutral point of the steering wheel 10 and the neutral point of the left and right front wheels FL and FR match.
Detection tire angle theta] D _L, is characterized in that applying correction theta] D _R. Hereinafter, the above-mentioned characteristic portions will be described with reference to FIGS.

FIG. 3 is a plan view showing the left front wheel FL steered to the neutral point. As shown in FIG. 3, in the present embodiment, a position where the left front wheel FL is inclined toward the toe-in side by the neutral angle θ ₀ is determined as a neutral point of the left front wheel FL. Similarly, in the present embodiment, the position of the front right wheel FR is inclined only toe side neutral angle theta ₀ is defined as the neutral point of the left front wheel FR. In the following description, the left and right front wheels FL,
The direction in which the FR travels straight is defined as the origin (point 0) of the tire angle, the toe-in direction is defined as the positive direction of the tire angle, and the toe-out direction is defined as the negative direction of the tire angle.

In the vehicle steering system, the left and right front wheels FL,
Actual tire angle .theta.R _L of FR, .theta.R _R a to precisely adapt the steering angle MA of the steering wheel 10, when a steering angle MA is "0", the left and right front wheels FL, actual tire angle .theta.R _L of FR , ΘR _R need to be θ ₀ . Also,
In the present embodiment, in order to satisfy the above requirements, the actual tire angle .theta.R _L, when .theta.R _R is theta _0, detected tire angle theta] D _L, that theta] D _R matches exactly theta ₀ is necessary.

[0026] Figure 4 shows the actual tire angle .theta.R _L, and .theta.R _R right kingpin torque T _L, the relationship between T _R. When the left and right front wheels FL, FR are steered to a different direction as the straight direction, the left and right front wheels FL, the FR, the left and right kingpin torque T _L that tries direct their wheels in the straight direction, T _R acts. In the present embodiment, the left and right front wheels FL, left and right orientation to rotate the FR to toe-out direction kingpin torque T _L, the positive direction of T _R. Therefore, the left and right front wheels FL,
If FR is steered to the neutral point, i.e., the left and right front wheels FL, actual tire angle .theta.R _L of FR, .theta.R _R neutral angle theta ₀
When controlled, the the their wheels positive right kingpin torque T _L, is T _R acts. Hereinafter referred right and left kingpin torque T _L, the T _R and the neutral reference torque T _M.

As shown in FIG. 4, the left and right kingpin torque T
_L, T _R is the actual tire angle .theta.R _L, .theta.R _{when R} varies in the vicinity of the neutral angle theta ₀ is approximately the actual tire angle .theta.R _L, .theta.R
_Shows a linear change with respect to _R. In the system of the present embodiment, when the detected tire angle theta] D _L, an error in the theta] D _R are superimposed, when the steering angle MA is "0", the actual tire angle .theta.R _L, .theta.R _R a neutral angle theta ₀ And a shift corresponding to the error occurs.

[0028] Under such circumstances, when the steering angle MA is "0", by the torque sensor, the neutral reference torque T _M different lateral kingpin torque T _L, T _R is detected. Hereinafter, the left and right kingpin torque detected by the torque sensor T _L, T _R, respectively actual torque TR
_L and TR _R. The actual torques TR _L and TR _R detected when the steering angle MA is “0” are particularly referred to as neutral actual torques TR _ML and TR _MR .

In other words, in the system of this embodiment, the neutral reference torque T _M and the neutral actual torques TR _ML , TR _MR
(Hereinafter referred to as the neutral torque deviation Δ
T _ML, if referred to deltaTR _MR) occurs, detecting a tire angle theta] D _L, it can be determined that the error has occurred in the theta] D _R. In this case, the detection tire angle theta] D _L, the error of the theta] D _R is neutral actual torque TR _ML, the deviation amount caused in the TR _MR, i.e., a value proportional to the magnitude of the neutral torque deviation ΔT _ML, ΔT _MR. Therefore, according to the system of the present embodiment, the neutral torque deviation [Delta] T _ML, based on [Delta] T _MR, detected tire angle theta] D _L, it is possible to detect the error of the theta] D _R.

FIG. 5 shows a flowchart of an example of a control routine executed by the ECU 26 in this embodiment. E
CU26 is, theta] D detected tire angle by executing the routine shown in FIG. 5 _L, to detect the error of the theta] D _R, performs correction for canceling the error. The routine shown in FIG. 5 is a periodic interruption routine that is started every predetermined time. FIG.
Is activated, first, the process of step 100 is executed.

In step 100, it is determined whether or not the steering angle MA of the steering wheel 10 is "0".
As a result, when MA = 0 is not established, it can be determined that the steering wheel 10 is deviated from the neutral point. In this case, the current routine is terminated without any further processing. On the other hand, if it is determined that MA = 0 holds, the process of step 102 is executed next.

In step 102, the output of the tire angle sensor is output.
Tire angle θD detected based on force signal _L, ΘD_RIs detected
And the vehicle speed based on the output signal of the vehicle speed sensor 28.
V is detected. Further, in this step 102, the torque
Actual torque TR detected by sensor_L, TR_RBut
Neutral actual torque TR_ML, TR_MRIs stored as above
According to the processing, the actual torque when the steering angle MA is “0” is obtained.
Qu TR_L, TR_RIs the neutral actual torque TR_ML, TR_MRAs
Can be memorized.

In step 104, the neutral reference torque T_M
Is calculated. Neutral reference torque T_MIs, as described above,
Tire angle θR_L, ΘR_RIs the neutral angle θ₀Left and right if
With self-aligning torque acting on front wheels FL and FR
is there. Its value is the neutral angle θ₀The vehicle speed V
It changes by changing. More specifically, a neutral group
Quasi-torque T_MIs larger as the vehicle speed V is higher,
Is smaller at lower speeds. Therefore, this step 1
04, the neutral reference torque T in relation to the vehicle speed V _MIs calculated
Is done.

FIG. 6 shows a map defining the relationship between the vehicle speed V and the neutral reference torque T _M. The ECU 26 calculates the neutral reference torque T _M based on the vehicle speed V with reference to the map shown in FIG. According to the above processing, the actual tire angle θ is independent of the value of the vehicle speed V.
_{R L,} θR R can be defined self-aligning torque generated at a neutral angle theta ₀ as a neutral reference torque T _M.

In step 106, the neutral torque deviation ΔT
_ML and ΔT _MR are calculated. As described above, the neutral torque deviations ΔT _ML , ΔT _MR are respectively the neutral actual torques TR _ML , T
It is calculated by the following equation by subtracting the neutral reference torque T _M from R _MR . _{ΔT ML = TR ML -T M ΔT} MR = TR MR -T M ··· (1) According to the above-mentioned process, shifted to the toe side real tire angle .theta.R _L, .theta.R _R is compared to the neutral angle theta ₀ , The neutral torque deviations ΔT _ML and ΔT _MR are calculated as positive values. On the other hand, if the actual tire angle .theta.R _L, .theta.R _R is shifted in the toe-out side than the neutral angle theta ₀ is neutral torque deviation Δ
T _ML and ΔT _MR are calculated as negative values.

In step 108, the neutral torque deviation ΔT
Correction angles Δθ _L , Δθ _R are calculated based on _ML , ΔT _MR . The correction angles Δθ _L , Δθ _R are the detected tire angles θD _L , θ
When the error angle superimposed on D _R , that is, the steering angle MA is “0”, the neutral angle θ ₀ of the left and right front wheels FL and FR is set.
And the actual tire angles θD _L , θD _R. Neutral torque deviation ΔT _ML , ΔT _MR
Is the correction amount, that is, the correction angle Δθ _L , Δ
shows almost proportional change relative theta _R. Accordingly, the neutral torque deviations ΔT _ML and ΔT _MR are _calculated by calculating the proportional coefficient K _V and the correction angle Δθ.
_L and Δθ _R can be expressed as in the following equation.

ΔT _ML = K _V × Δθ _L ΔT _MR = K _V × Δθ _R (2) By the way, when the correction angles Δθ _L and Δθ _R are constant, the neutral torque deviations ΔT _ML and ΔT _MR are: It increases as the vehicle speed V increases, and decreases as the vehicle speed V decreases. Therefore, in order to establish the relationship of the above equation (2) regardless of the vehicle speed V, it is necessary to change the proportionality coefficient K _V according to the vehicle speed V.

FIG. 7 shows a map that defines the relationship between the proportional coefficient K _V and the vehicle speed V that satisfy the relationship of the above equation (2). That is, in the system according to the present embodiment, when the proportional coefficient K _V with respect to the vehicle speed V is obtained according to the relationship shown in FIG. 7, the neutral torque deviations ΔT _ML and ΔT _MR and the correction angles Δθ _L and Δθ _R and the proportional coefficient K _V are obtained. In the meantime, the relationship of the above equation (2) can always be established.

The relation of the above equation (2) can be rewritten as the following equation. Δθ _L = (1 / K _V ) × ΔT _ML Δθ _R = (1 / K _V ) × ΔT _MR (3) According to the above equation (3), the proportional coefficient K _V and the neutral torque deviation ΔT _ML , by using the [Delta] T _MR, detected tire angle theta] D _L, theta] D
_The correction angles Δθ _L and Δθ _R superimposed on _R can be obtained. In step 108, the process of calculating the proportional coefficient K _V based on the vehicle speed V with reference to the map shown in FIG. 7, and the proportional coefficient K _V and the neutral torque deviation Δ
The process of calculating the correction angles Δθ _L , Δθ _R according to the above equation (3) using T _ML , ΔT _MR is executed.

According to the above processing, the correction angles Δθ _L and Δθ _R can always be accurately obtained without being affected by the vehicle speed V. According to the above processing, the actual tire angle θ
R _L, if .theta.R _R is shifted in the toe side than the neutral angle theta ₀ (neutral torque deviation [Delta] T _ML, if [Delta] T _MR is a positive value) is corrected angle [Delta] [theta] _L, [Delta] [theta] _R is a positive value Is calculated as On the other hand, the actual tire angle .theta.R _L, .theta.R _{when R} is deviated toe side than the neutral angle theta ₀ (if the neutral torque deviation [Delta] T _ML, [Delta] T _MR is a negative value) is corrected angle [Delta] [theta] _L,
Δθ _R is calculated as a negative value.

In step 110, the correction angle average value Δθ
_LAVE and Δθ _RAVE are calculated. Average correction angle Δθ _LAVE ,
Δθ _RAVE is an average value of the correction angles Δθ _L and Δθ _R calculated in the current processing cycle and the past processing cycle. In step 110, specifically, the correction angle average values Δθ _LAVE and Δθ _RAVE are calculated according to the following equations. Δθ _LAVE (current value) = {(n−1) / n} · Δθ _LAVE (previous value) + (1 / n) · Δθ _L Δθ _RAVE (current value) = {(n−1) / n} · Δθ _RAVE (previous value) + (1 / n) · Δθ R ··· (4) According to the above process, every time the correction angle [Delta] [theta] _L, is [Delta] [theta] _R is newly calculated, the ratio of (1 / n) Can be reflected in the correction angle average values Δθ _LAVE and Δθ _RAVE .

In step 112, the above step 110
It is determined whether or not the absolute value | Δθ _LAVE | of the correction angle average value calculated in the above is equal to or greater than a predetermined threshold value TH. As a result, | [Delta] [theta] _Lave | if ≧ TH is determined to be taken, it can be determined that the error to apply a correction to the detected tire angle theta] D _L is superimposed. In this case, the process of step 114 is performed next. On the other hand, if the above conditions are not satisfied, it can be determined that the error to apply a correction to the detected tire angle theta] D _L is not superimposed. In this case, step 114 is jumped, and then the process of step 116 is executed.

In step 114, the detected tire angle θD _L
Is corrected. In step 114, specifically, the detected tire angle θD detected in step 102 is used.
_A process of adding the correction angle average value Δθ _LAVE to _L is executed.
In step 116, the absolute value | Δθ _RAVE | of the correction angle average calculated in step 110 is set to a predetermined threshold value T.
It is determined whether it is H or more. As a result, | Δθ
_RAVE | If ≧ TH is determined to be taken, it can be determined that the error to apply a correction to the detected tire angle theta] D _R is superimposed. In this case, the process of step 118 is executed next. On the other hand, if the above conditions are not satisfied, it can be determined that the error to apply a correction to the detected tire angle theta] D _R is not superimposed. In this case, step 118 is jumped,
This routine is immediately terminated.

In step 118, the detected tire angle θD _R
Is corrected. In this step 118, specifically, the detected tire angle θD detected in step 102
_A process of adding the correction angle average value Δθ _RAVE to _R is executed.
When the process of step 118 ends, the current routine ends. According to the above processing, the actual tire angle θ
R _L, .theta.R _{when R} is deviated toe side than the neutral angle theta _0, that is, the actual tire angle .theta.R _L, .theta.R _R is greater than the neutral angle theta ₀ is detected tire angle theta] D _L , Θ
D _R is corrected to a larger value. On the other hand, the actual tire angle θ
R _L, .theta.R _{when R} is deviated toe side than the neutral angle theta _0, that is, the actual tire angle .theta.R _L, .theta.R _R is smaller than the neutral angle theta ₀ is detected tire angle theta] D _L ,
theta] D _R is corrected to a smaller value.

In the system of this embodiment, the steering angle MA
There "0" is in situations actual tire angle .theta.R _L, .theta.R _R a situation which is controlled to toe side than the neutral angle theta ₀ is detected tire angle theta] D _L, theta] D _R is the actual tire angle .theta.R _L, This occurs when the tire angle is smaller than θR _R. Under such circumstances, the detected tire angles θD _L , θD
_{When R} is corrected to a larger value, the detected tire angle θ
D _L, theta] D _R and the actual tire angle .theta.R _L, is matched with the .theta.R _R, the actual tire angle .theta.R _L corresponding to the steering angle MA = 0, θR
_R can be accurately matched with the central angle θ ₀ .

[0046] In addition, in the system of the present embodiment, in the circumstances under which a steering angle MA is "0" the actual tire angle θR _L, θR
Situation _{in which R} is controlled to be toe-out side than the neutral angle theta ₀ is detected tire angle theta] D _L, theta] D _R is the actual tire angle .theta.R _L,
This occurs when the tire angle is larger than θR _R. Under such circumstances, as described above, the detected tire angle θD
_L, and theta] D _R is corrected to a smaller value, detected tire angle theta] D _L, theta] D _R and the actual tire angle .theta.R _L, is matched with the .theta.R _R, the actual tire angle .theta.R _L corresponding to the steering angle MA = 0, θ
R _R can be made to exactly coincide with the central angle θ ₀ .

Therefore, according to the vehicle steering system of the present embodiment, even if the output characteristics of the tire angle sensors incorporated in the actuators 14 and 16 change with time, the neutralization of the left and right front wheels FL and FR is achieved. Point and steering wheel 10
And the neutral point can be exactly matched. Therefore, according to the vehicle steering system of the present embodiment, the actual tire angle θ
R _L, it is possible to properly steer the left and right front wheels FL, the FR while accurately made to correspond to and θR _R and the steering angle MA.

Next, referring to FIG. 8 to FIG.
The second embodiment will be described. Vehicle steering of this embodiment
The apparatus is the same as the system configuration shown in FIGS.
Then, the ECU 26 controls the control routine shown in FIG.
Implemented by executing the control routine shown in FIG.
Is done. In the first embodiment described above, the ECU 26
Detected tire angle θD_L, ΘD_RTo correct the error of
Regular angle Δθ_L, Δθ_RWith the neutral torque deviation ΔT_ML, ΔT_MR
Is detected based on Neutral torque deviation ΔT_ML, ΔT
_MRIs the neutral reference torque T _MAnd neutral actual torque TR_ML, TR
_MRIs the deviation from Therefore, the detected tire angle θD_L, ΘD
_RIn order to correct accurately, the neutral reference torque T_MIs positive
It needs to be certain.

The neutral reference torque T _M, as described above, the actual tire angle .theta.R _L, .theta.R _R is self-alignment torque acting left and right front wheels FL, the FR in the case of neutral angle theta _0. The self-alignment torque acting left and right front wheels FL, the FR, the actual tire angle .theta.R _L, except that changes according to .theta.R _R, even actual tire angle .theta.R _L, is .theta.R _R identical, the tire condition and road condition (Coefficient of friction of the road surface). Therefore, the first embodiment of the method detection tire angle .theta.R with _L, and the to correct accurately the .theta.R _R is a proper value the neutral reference torque T _M in accordance with the state of the state and the road surface of the tire It needs to be corrected.

The vehicle steering system according to the present embodiment has the above-described requirements.
Neutral according to tire condition and road surface condition to satisfy
Reference torque T_MHas the characteristic of correcting
I have. Hereinafter, the characteristic portions of the vehicle steering system according to the present embodiment will be described.
Will be explained. FIG. 8 shows the actual tire angle θR._L, ΘR_RAnd Kin
Gupin torque T_L, T_RThe relationship is shown below. The solid line in FIG.
Is the reference torque T (θ) and the actual tire angle θR._L,
θR _RThe relationship is shown below. The reference torque T (θ) is
When the state of the road and the state of the road surface are the reference state (hereinafter,
This state is referred to as the reference state).
Kingpin torque T to use_L, T_RIt is. Reference torque
The characteristic of T (θ) is determined in advance using the vehicle speed V as a parameter.
Can be In the present embodiment, the ECU 26 includes:
Reference torque T set in advance using vehicle speed V as a parameter
A plurality of (θ) characteristics are stored.

The curve shown by the dashed line in FIG. 8 is the actual torque TR _L
(Theta), indicated as TR _R (theta) the actual tire angle .theta.R _L, the relationship between .theta.R _R. The actual torque TR _L (θ), TR _R shown in FIG.
(Theta) is the left and right front wheels FL, kingpin torque acting on the FR T _L, T _R when the vehicle is traveling with under different specific environmental reference state. Actual torque TR _L (θ), T
The characteristics of R _R (θ) change according to the condition of the tire and the condition of the road surface.

The ECU 26 controls the torque sensor during running of the vehicle.
The actual torque TR detected by the _L, TR_RIs the vehicle speed V
And detected tire angle θD_L, ΘD_RAs a parameter
Organize the actual torque TR for each vehicle speed V_L(Θ), TR
_RLearn the characteristics of (θ). Therefore, the ECU 26
Is a plurality of reference torques T having the vehicle speed V as a parameter.
(Θ) and a plurality of actual torques TR_L(Θ),
TR_RThe characteristic of (θ) is stored.

The basic neutral reference torque T shown in FIG.
(Θ ₀ ) indicates that the vehicle is running under the reference environment, and
Actual tire angle θR _L, θR _R is kingpin torque T _L acting on the left and right front wheels FL, FR when matching the neutral angle theta _0, a T _R. If the vehicle is traveling under the reference environment, by executing a routine shown in FIG 5 the basic neutral reference torque T a (theta ₀₎ as a neutral reference torque T _M, detected tire angle theta] D _L, theta] D _R Can be accurately corrected.

On the other hand, the actual neutral reference torque TR shown in FIG.
_L(Θ₀), TR_R(Θ₀) Is the specific vehicle mentioned above
Running under the environment and actual tire angle θR_L, ΘR
_RIs the neutral angle θ₀To the front left and right wheels FL and FR
Working Kingpin Torque T _L, T_RIt is. Therefore,
Detected when the vehicle is running in the specific environment described above
Tire angle θD_L, ΘD_RIn order to correct the
Neutral reference torque TR_L(Θ₀), TR_R(Θ₀) Neutral
Reference torque T_MAnd execute the routine shown in FIG.
It is necessary to

In this embodiment, the actual torque T
The values of R _L (θ) and TR _R (θ) are calculated based on the actual tire angle θR _L ,
Regardless of the value of θR _R , the ratio is almost constant with respect to the value of the reference torque T (θ). Therefore, the actual torque TR
_When the ratio between _L (θ), TR _R (θ) and the reference torque T (θ) is known, the basic neutral reference torque T (θ ₀ ) is calculated by performing a proportional calculation using the ratio. TR _L
(Θ ₀ ) and TR _R (θ ₀ ).

FIG. 9 shows the actual torque TR _L (θ), TR
_A correction coefficient K _T used for correcting the basic neutral reference torque T (θ ₀ ) based on a ratio between _R (θ) and the reference torque T (θ).
4 is a flowchart of an example of a control routine executed by the ECU 26 to obtain the control routine. The routine shown in FIG. 9 is an interrupt routine started every predetermined time. When the routine shown in FIG. 9 is started, first, the process of step 120 is executed.

In step 120, the detected tire angle θ
D _L, with theta] D _R is loaded, the left and right front wheels FL, F
The actual torques TR _L and TR _R acting on _R are read. Then, the actual torque TR _L, TR _R is detected tire angle theta] D _L, in relation to the theta] D _R, the actual torque TR _L (theta),
Stored as TR _R (θ). In step 120, the vehicle speed V is further determined based on the output signal of the vehicle speed sensor 28.
Is detected.

In step 122, the reference torque T (θ)
Is calculated. As described above, the ECU 26, the reference torque T (theta) and the actual tire angle .theta.R _L, a map that defines the relationship between the .theta.R _R, which stores a plurality of vehicle speed V as a parameter. In this step 122, a map to be referred to is determined based on the vehicle speed V detected in step 120, and based on the map,
The reference torque T (θ) corresponding to the detected tire angles θD _L , θD _R detected in the above is calculated.

In step 124, the left and right front wheels FL, FR
, The correction coefficients K _TL and K _TR according to the following equations
Is calculated. K _TL = TR _L (θ) / T (θ) K _TR = TR _R (θ) / T (θ) (5) According to the above processing, the actual torque TR detected in the current processing cycle _L (θ), TR _R (θ) and reference torque T
(Θ) can be used as correction coefficients K _TL and K _TR .

In step 126, correction coefficients K _TL (V), K corresponding to the vehicle speed V detected in the current processing cycle
Processing for updating _TR (V) is executed. Step 12
In step 6, specifically, the correction coefficients K _TL and K _TR calculated in step 124 are reflected at a predetermined ratio.
The correction coefficients K _TL (V) and K _TR (V) are updated. When the process of step 126 ends, the current routine ends.

According to the above processing, the correction coefficients K _TL (V) and K _TR (V) can be appropriately updated while the vehicle is running. Therefore, according to the above processing, when the tire condition or the road surface condition changes, the change can be promptly reflected in the correction coefficients K _TL (V) and K _TR (V).
Figure 10 shows a flowchart of an example of a control routine that detects a tire angle theta] D _L, the ECU26 to perform the correction of the theta] D _R to run. In FIG. 10, steps that execute the same processing as the steps shown in FIG. 5 are given the same reference numerals, and descriptions thereof will be omitted. In the routine shown in FIG. 10, in step 100, the steering angle MA is set to "0".
After the determination is made, the processing of step 130 is performed via step 102.

In step 130, the basic neutral reference torque T (θ ₀ ) is detected by referring to the map corresponding to the vehicle speed V detected in the current processing cycle. In step 132, the correction coefficient K _TL (V) for the left front wheel
Is greater than the predetermined value 1 + α or the predetermined value 1
It is determined whether it is smaller than -α. As a result, 1 + α
If it is determined that <K _TL (V) or K _TL (V) <1−α holds, the actual torque TR _L (θ) and the reference torque T
It can be determined that there is a deviation to be corrected between (θ). In this case, the process of step 134 is executed next. On the other hand, if none of the above conditions is satisfied, it can be determined that there is no deviation to be corrected between the actual torque TR _L (θ) and the reference torque T (θ). In this case, the process of step 136 is executed next.

In step 134, the neutral reference torque T _ML of the left front wheel FL is calculated according to the following equation. T _ML = T (θ ₀ ) · K _TL (V) (6) If the actual torque TR _L (θ) shows a tendency to be smaller than the reference torque T (θ), the neutral reference torque T _ML is used. It is appropriate that the value be smaller than the basic neutral reference torque T (θ ₀ ). Under such circumstances, the correction coefficient K _TL (V) has a smaller value than “1”. Therefore, according to the above equation (6), under such circumstances, the neutral reference torque T _ML can be made smaller than the basic neutral reference torque T (θ ₀ ).

When the actual torque TR _L (θ) tends to be larger than the reference torque T (θ), the neutral reference torque T _ML is set to a value larger than the basic neutral reference torque T (θ ₀ ). Is appropriate. Under such circumstances, the correction coefficient K _TL (V) has a larger value than “1”. Therefore, according to the above equation (6), under such circumstances, the neutral reference torque T _ML can be set to a value larger than the basic neutral reference torque T (θ ₀ ).

In step 136, the basic neutral reference torque T (θ ₀ ) is directly used as the neutral reference torque T (left front wheel FL).
_The process for making the _ML is executed. According to the above processing, when the actual torque TR _L (θ) and the reference torque T (θ) show the same tendency, the basic neutral torque T (θ) can be used as it is as the neutral reference torque T _ML. it can. In step 138, it is determined whether the correction coefficient K _TR (V) for the right front wheel is larger than the predetermined value 1 + α or smaller than the predetermined value 1−α. As a result, 1 + α <K _TR
If it is determined that (V) or K _TR (V) <1−α holds, the actual torque TR _R (θ) and the reference torque T (θ)
Can be determined to have a deviation to be corrected. In this case, the process of step 140 is performed next. On the other hand, if none of the above conditions is satisfied, the actual torque T
It can be determined that there is no deviation to be corrected between R _R (θ) and the reference torque T (θ). In this case, the process of step 142 is performed next.

In step 138, a neutral reference torque T _MR of the right front wheel FR is calculated according to the following equation. T _MR = T (θ ₀ ) · K _TR (V) (7) If the actual torque TR _R (θ) shows a tendency to be smaller than the reference torque T (θ), the neutral reference torque T _MR is used. It is appropriate that the value be smaller than the basic neutral reference torque T (θ ₀ ). Under such circumstances, the correction coefficient K _TR (V) has a smaller value than “1”. Therefore, according to the above equation (7), under such circumstances, the neutral reference torque T _ML can be made smaller than the basic neutral reference torque T (θ ₀ ).

When the actual torque TR _R (θ) tends to be larger than the reference torque T (θ), the neutral reference torque T _MR is set to a value larger than the basic neutral reference torque T (θ ₀ ). Is appropriate. Under such circumstances, the correction coefficient K _TR (V) has a larger value than “1”. Therefore, according to the above equation (7), under such circumstances, the neutral reference torque T _MR can be set to a value larger than the basic neutral reference torque T (θ ₀ ).

In step 142, the basic neutral reference torque T (θ ₀ ) is converted to the neutral reference torque T
_The process of setting as _MR is executed. According to the above processing, when the actual torque TR _R (θ) and the reference torque T (θ) show the same tendency, the basic neutral torque T (θ) can be used as it is as the neutral reference torque T _MR. it can. In step 144, neutral torque deviations ΔT _ML and ΔT _MR are calculated. The neutral torque deviations ΔT _ML and ΔT _MR are calculated in step 1 above.
By subtracting the neutral reference torques T _ML , T _MR calculated in the processes of steps 130 to 142 from the neutral actual torques TR _ML , TR _MR stored in step 02, the following equation is calculated.

ΔT _ML = TR _ML −T _ML ΔT _MR = TR _MR −T _MR (8) In this routine, when the processing in step 144 is completed, the processing in steps 108 to 118 is performed thereafter. the Rukoto, detection tire angle theta] D _L, the correction of theta] D _R is performed. In this case, the detection tire angle θD _L, θD _R
Is the neutral torque deviation Δ calculated in step 144 above.
The correction is made based on T _ML and ΔT _MR .

By the above processing, the detected tire angle θD _L ,
θD _{for R} to accurately correct the above (8) Neutral torque deviation [Delta] T _ML is calculated according to equation, [Delta] T _MR is under circumstances a steering angle MA is "0", the actual tire angle .theta.R _L, .theta.R
_The amount of deviation occurring between _R and the neutral angle θ ₀ , that is,
Detection tire angle theta] D _L, it is necessary that accurately correspond to the error component superimposed on the theta] D _R.

The neutral reference torque shown in the above equation (8)
T_ML, T_MRIs the detected tire angle θR_L, ΘR_RSuperimposed on
Even if the error is the same, the tire condition and road surface condition
Is a value that changes following the change.
Therefore, the neutral reference torque T_ML, T _MRIs always a constant value
If the tire condition or road surface condition changes,
Tire angle θR_L, ΘR_RAnd the error superimposed on
Neutral torque deviation ΔT calculated according to equation (8)_ML, Δ
T_MRMay not correspond exactly.

On the other hand, according to the above processing,
(8) Neutral reference torque T shown in equation _ML, T_MRThe tire of
The value can be set according to the state or the road surface state. others
Therefore, according to the vehicle steering system of the present embodiment, the state of the tire
Regardless of the road condition or the road surface condition, the detection
Ear angle θD_L, ΘD_RExactly match the error superimposed on
The corresponding neutral torque deviation ΔT_ML, ΔT_MRCan be calculated
it can. Therefore, according to the vehicle steering system of the present embodiment,
Detected tire angle θD_L, ΘD_RCorrects exactly, always left
Actual tire angles θR of front right wheels FL and FR_L, ΘR_RAnd steer
Make the steering angle MA of the ring wheel 10 correspond exactly.
be able to.

In the above embodiment, the left and right front wheels F
L and FR correspond to the "steered wheels" of the first embodiment, and the tire angle sensors incorporated in the actuators 14 and 16 correspond to the "tire angle detection mechanism" of the first embodiment, respectively. By executing the processing of step 104, the “neutral reference torque detecting means” according to claim 1 can execute the processing of steps 100 and 102.
By executing the processing of (1), the "neutral actual torque detecting means" of the first aspect executes the processing of the step 106, thereby causing the "neutral torque deviation detecting means" of the first aspect to execute the step 108. The "tire angle correcting means" according to claim 1 is realized by executing the processing of -118.

In the above embodiment, the ECU 2
6. The “reference torque detecting means” according to claim 2 executes the processing in step 122, whereby the “reference torque detecting means” executes the processing in step 120.
3. The "actual torque detecting means" described above executes the processing of steps 124 and 126, and the "correction coefficient calculating means" described in claim 2 executes the processing of steps 134 and 140. The "neutral reference torque correction means" described in the item 2
The "torque deviation detecting means" according to claim 2 is realized by executing the processing of (2).

[0075]

As described above, according to the first aspect of the present invention, when the steering wheel is located at the neutral point, the tire angle detecting means is arranged so that the tire angle of the steered wheel coincides with the original neutral point. Can be corrected. Therefore,
According to the present invention, the tire angle of a steered wheel can be controlled to an angle that exactly corresponds to the steering angle of the steering wheel without being affected by a specific change in the output of the tire angle detecting means.

According to the second aspect of the present invention, by correcting the basic neutral reference torque, a neutral reference torque that exactly matches the actual neutral reference torque can be generated. For this reason, according to the present invention, the detected tire angle can be accurately corrected without being affected by the tire condition or the road surface condition, and the tire angle of the steered wheel can be accurately associated with the steering wheel steering angle. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing main components of a vehicle steering system according to first and second embodiments of the present invention.

FIG. 2 is a block diagram showing an electric structure of the vehicle steering system according to the first and second embodiments of the present invention.

FIG. 3 is a plan view of a left front wheel FL steered to a neutral point.

[4] the actual tire angle θR _L, θR _R and the left and right kingpin torque T _L, is a diagram showing the relationship between T _R.

FIG. 5 shows a detected tire angle θD in the first embodiment of the present invention.
_L, and an example flowchart of a control routine executed in order to correct the theta] D _R.

FIG. 6 is an example of a map that defines a relationship between a vehicle speed V and a neutral reference torque T _M.

FIG. 7 shows a proportional coefficient K used in the routine shown in FIG.
₅ is an example of a map that defines a relationship between _V and a vehicle speed V.

8 is a series of maps showing the actual tire angle θR _L, θR _R and king pin torque T _L, the relationship between T _R.

FIG. 9 is a flowchart of an example of a control routine executed to obtain a correction coefficient K _T in the second embodiment of the present invention.

FIG. 10 shows a detected tire angle θ in a second embodiment of the present invention.
4 shows a flowchart of an example of a control routine executed to correct D _L and θ D _R.

[Explanation of symbols]

10 steering wheel 12 steering reaction force device 14, 16 actuator 22 shock absorber 26 electronic control unit (ECU) FL left front wheel FR right front wheel theta ₀ central angle theta] D _L, theta] D _R detected tire angle θR _L, θR _R actual tire angle TR _ML, TR _MR neutral actual torque _{TR L, TR R; TR L} (θ), TR R (θ) actual torque T _M neutral reference torque ΔT _ML, ΔT _MR neutral torque deviation [Delta] [theta] _L, [Delta] [theta] _R correction angle [Delta] [theta] _Lave, Δθ _RAVE correction angle average value TH threshold value K _V proportional coefficient T (θ) Reference torque T (θ ₀ ) Basic neutral reference torque TR _L (θ ₀ ), TR _R (θ ₀ ) Actual neutral reference torque K _TL , K _TR , K _TL (V), K _TR (V) Correction coefficient MA Steering angle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B62D 113: 00 119: 00

Claims (2)

[Claims] A steering wheel that is not mechanically connected to a steering wheel; an actuator that electrically steers the steering wheel; and a tire angle detection mechanism that detects a tire angle of the steering wheel. A self-aligning torque to be generated when a steered wheel is located at a neutral point in a vehicular steering apparatus that drives the actuator such that a tire angle detected by a detection mechanism is an angle corresponding to a steering angle of a steering wheel. Neutral steering torque detecting means for detecting the self-aligning torque acting on the steered wheels when the steering wheel is located at the neutral point, as neutral neutral torque detecting means, and a steering wheel. When located at the neutral point, the deviation between the neutral actual torque and the neutral reference torque is calculated as the neutral torque. A vehicle steering system comprising: a neutral torque deviation detecting unit that detects a deviation; and a tire angle correcting unit that corrects a detection value of the tire angle detecting unit based on the neutral torque deviation. 2. A vehicle steering system according to claim 1, wherein a reference torque detecting means for detecting, as a reference torque, a self-aligning torque to be generated with respect to a tire angle of the steered wheel, An actual torque detecting means for detecting a lining torque as an actual torque; and a correction coefficient for converting the reference torque into the actual torque based on the reference torque and the actual torque corresponding to the same tire angle. A correction coefficient calculating means, and a neutral reference torque correcting means for correcting the neutral reference torque using the correction coefficient, wherein the torque deviation detecting means corrects by the actual torque and the neutral reference torque correcting means. A steering device for a vehicle, which detects a deviation from a neutral reference torque after the rotation.