JP3232032B2 - Variable steering angle ratio steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable steering angle ratio steering device that changes the ratio of the steered angles of steered wheels by an electric motor in accordance with the steering angle of a steering wheel, and a target steering angle ratio based on a vehicle speed signal. A failure of the steering angle ratio sensor is detected based on a signal or an estimated steering angle ratio signal estimated from a drive control signal of the electric motor and an actual steering angle ratio signal from the steering angle ratio sensor, and the steering angle ratio is fixed when the failure occurs. The present invention relates to a variable steering angle ratio steering device capable of maintaining the running of a vehicle.

[0002]

2. Description of the Related Art A conventional variable steering angle ratio steering device (variable gear ratio mechanism device) uses a variable gear ratio mechanism such as a worm sector, a ball nut, a rack, and a pinion to increase the gear ratio in the vicinity of straight traveling and lock the steering. It is known to improve the responsiveness of the vehicle in a manual steering system by reducing the side gear ratio.

Further, in the variable gear ratio mechanism device incorporated in the conventional electric power steering system, the steering force is small when the overall steering ratio is increased, but the steering becomes frequent due to an increase in the number of rotations of the steering wheel. In addition, the overall steering ratio is made small as a whole to reduce an increase in the number of rotations of the steering wheel. As for the steering characteristics, the gear ratio on the lock side is reduced, the gear ratio near the straight running is increased, the lock-to-lock rotation speed is reduced, and the steering wheel has a margin so as not to be quick during straight running.

Further, in the variable gear ratio mechanism device incorporated in the conventional electric power steering system, the operability and the responsiveness to the steering operation of the steering are agile, and the responsiveness to the variable gear ratio of the steering is improved. In order to change the gear ratio of the steering in real time, a motor is used to control the variable operation of the variable gear ratio mechanism because of the need for agility and accuracy.

[0005]

The conventional variable steering angle ratio steering device (variable gear ratio mechanism device) changes the steering angle ratio (gear ratio) of the steering in real time using an electric motor. There are the following issues.

When the position of the motor controlling the gear ratio of the steering is determined, if the steering angle ratio sensor (gear ratio sensor) fails for any reason, the position of the motor cannot be determined and the gear ratio cannot be determined. There is a problem that control becomes uncertain.

Also, when controlling the gear ratio of the steering, if the steering angle ratio sensor (gear ratio sensor) for detecting the position of the electric motor fails, the gear ratio cannot be detected.

Further, even when the steering angle ratio sensor (gear ratio sensor) system (including the signal harness) malfunctions, the system operation as the variable steering angle ratio steering device (variable gear ratio mechanism device) is continued. There are issues that cannot be done.

The present invention has been made to solve such a problem, and an object of the present invention is to detect a failure of a steering angle ratio sensor based on a difference between a target steering angle ratio and an actual steering angle ratio, and provide a driver with the failure. It is an object of the present invention to provide a variable steering angle ratio steering device capable of notifying a failure and, when a failure of a steering angle ratio sensor is detected, fixing a steering angle ratio and appropriately continuing steering.

[0010]

According to a first aspect of the present invention, there is provided a variable steering angle ratio steering device in which a drive control unit outputs a drive control signal having a predetermined value or more to a steering angle ratio control unit. However, when the difference between the target rudder angle ratio and the actual rudder angle ratio is equal to or greater than a predetermined value and continues for a predetermined time or more, a failure detection means for determining that the steering angle ratio sensor is malfunctioning is provided. It is characterized by the following.

In the variable steering angle ratio steering device according to the first aspect, the target steering angle ratio and the actual steering angle ratio are output to the steering angle ratio control means even though the drive control means outputs a drive control signal of a predetermined value or more. When the difference from the steering angle ratio is equal to or more than a predetermined value and continues for a predetermined time or more,
Since the failure detection means for determining that the steering angle ratio sensor has failed is provided, a failure or abnormality of the steering angle ratio sensor can be detected from the determination result of the failure detection means.

According to a second aspect of the present invention, the variable steering angle ratio steering device estimates the steering angle ratio from the drive control signal from the drive control unit to the steering angle ratio control unit, and calculates the estimated steering angle ratio and the actual steering angle. When the difference from the ratio is equal to or greater than a predetermined value and continues for a predetermined time or more, a failure detection unit that determines that the steering angle ratio sensor is in failure is provided.

According to a second aspect of the present invention, a variable steering angle ratio steering device estimates a steering angle ratio from a drive control signal from a drive control unit to a steering angle ratio control unit, and calculates the estimated steering angle ratio and the actual steering angle ratio. If the difference of the steering angle ratio sensor is equal to or more than a predetermined value and continues for a predetermined time or more, the failure detection means for determining that the steering angle ratio sensor is malfunctioning is provided. Abnormality can be detected.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is based on a steering angle ratio signal based on a signal of a target steering angle ratio based on a vehicle speed signal or a signal of an estimated steering angle ratio estimated from a drive control signal of an electric motor and an actual steering angle ratio signal from a steering angle ratio sensor. An object of the present invention is to provide a variable steering angle ratio steering device capable of detecting a failure of a ratio sensor and fixing the steering angle ratio at the time of failure detection so that the steering of the vehicle can be continuously and appropriately executed.

FIG. 1 is an overall configuration diagram of a variable steering angle ratio steering apparatus according to the present invention. The variable steering angle ratio steering device 1 includes a variable gear ratio mechanism 5 and a motor 30 that changes the gear ratio via a connection shaft 4 provided with universal joints 4 a and 4 b on a steering shaft 3 provided integrally with a steering wheel 2. The pinion 10 of the output shaft 10b of the variable steering angle ratio steering device 1 is mechanically connected to the rack shaft 7 which reciprocates.

Variable steering angle ratio steering device (variable gear ratio mechanism)
Is an input shaft 10a connected to the steering shaft 3.
And an intermediate shaft protruding at a position eccentric from the center of the output shaft 10b, between the rack 7a and the output shaft 10b integrally formed with the pinion 10, and the input shaft 10a of the intermediate shaft is provided.
, The steering angle ratio between the steering shaft 3 and the pinion 10 can be changed.

The variable steering angle ratio steering device (variable gear ratio mechanism) is provided with a partial worm wheel for moving the intermediate shaft on the intermediate shaft in order to change the amount of eccentricity. Electric motor (for VGS)
By rotating at 30, the steering angle ratio can be varied.

Further, the variable steering angle ratio steering device (gear ratio variable mechanism) is provided with a steering angle ratio sensor 22 for detecting a steering angle ratio (gear ratio), and an actual steering angle ratio signal G (gear ratio signal). Is supplied to the steering angle ratio control means 13.

The steering angle ratio sensor 22 is constituted by a cam and a differential transformer integrated with a variable gear, and the vehicle speed sensor 16 is constituted by a rotating disk having a slit, a photocoupler, etc., and the actual steering angle corresponding to the position of the motor. The ratio signal G is supplied to the steering angle ratio control means 13. The vehicle speed sensor 16 detects a vehicle speed signal V corresponding to the front-rear direction and the vehicle speed of the vehicle, and supplies the vehicle speed signal V to the steering angle ratio control means 13.

The steering angle ratio control means 13 includes a steering angle ratio sensor 22
The motor (for VGS) 30 is PWM-controlled by an electric motor drive signal Mg (for example, a PWM signal) obtained by processing the actual steering angle ratio signal G detected by the vehicle and the vehicle speed signal V detected by the vehicle speed sensor 16.
The vehicle is driven so as to obtain a steering angle ratio corresponding to the steering operation and the vehicle speed.

The steering angle ratio control means 13 compares the target steering angle ratio set from the vehicle speed sensor signal V with the actual steering angle ratio signal G detected by the steering angle ratio sensor 22. If there is no difference, it is determined that the steering angle ratio is normal. If the difference is equal to or greater than the predetermined value and the drive control signal Mc is equal to or greater than the predetermined value even after the lapse of the predetermined time, the steering angle ratio sensor 22 is determined to have failed.

FIG. 2 is a block diagram of a main part of an embodiment of the variable steering angle ratio steering apparatus according to the first aspect. In the present invention, the steering angle ratio is compared based on the target steering angle ratio signal set based on the vehicle speed signal and the actual steering angle ratio signal, and the drive control signal is output at a predetermined value or more. If the difference between the target steering angle ratio and the actual steering angle ratio is equal to or greater than a predetermined value and this state continues for a predetermined time or longer, it is determined that the steering angle ratio sensor has failed.

In FIG. 2, the variable steering angle ratio steering device comprises a vehicle speed sensor 16, a steering angle ratio sensor 22, a steering angle ratio control means 13, an electric motor (for VGS) 30, and an alarm output means 2.
8 is comprised.

FIG. 4 shows the input angle (α) of the variable steering angle ratio steering device.
FIG. 4 shows an output angle (β) characteristic diagram. In FIG. 4, the input angle α
Is the rotation angle of the steering wheel 2, and the output angle β is the rotation angle of the pinion 10. Since the deviation amount (a0, a1, a2) of the axis between the input shaft 10a and the output shaft 10b increases (a2>a1> a0) as the vehicle speed V increases, the ratio between the output angle β and the input angle α is obtained. (Steering angle ratio) also increases as the vehicle speed increases.

The steering angle ratio control means 13 includes various arithmetic means, comparison means processing means, memory,
It is composed of an FET, a logic circuit, and the like, and includes a vehicle speed detecting unit 17, a steering angle ratio detecting unit 23, a target steering angle ratio setting unit 18, a drive control unit 19, a subtractor 21, a motor driving unit 20, and a failure detecting unit 14.

The vehicle speed detecting means 17 detects a corresponding vehicle speed detection signal V based on the absolute value of the signal V from the vehicle speed sensor 16.
s to the target steering angle ratio setting means 18

The steering angle ratio detecting means 23 includes a steering angle ratio sensor 22.
Supplies the corresponding actual steering angle ratio signal Gs to the subtractor 21, the failure detection means 14, and the drive control means 19 based on the absolute value of the actual steering angle ratio signal G.

The target steering angle ratio setting means 18 includes a memory such as a ROM, and an arithmetic means. Based on experimental values and theoretical values, the input angle (α) using the vehicle speed V shown in FIG.
-Output angle (β) characteristic data is set, and a ratio of the output angle β and the input angle α corresponding to the vehicle speed detection signal Vs is calculated to obtain a target steering angle ratio (β / α). The signal Cg is supplied to the subtractor 21 and the failure detecting means 14.

The subtractor 21 is provided with a target steering angle ratio signal Cg supplied from the target steering angle ratio setting means 18 and a steering angle ratio detecting means 23.
, And a difference signal Sg (= Cg−Gs) is supplied to the drive control means 19.

The drive control means 19 includes a memory such as a ROM,
A target rotation speed Ns obtained by converting a deviation signal Sg supplied from the subtracter 21 by a predetermined transfer function and an actual steering angle ratio signal Gs supplied from the steering angle ratio detecting means 23 are provided. Is calculated, and the target rotation speed Ns and the steering angle ratio change speed Nj are calculated.
After calculating the deviation ΔN from the above, the deviation ΔN is subjected to PID (proportional / integral / differential) compensation to determine the duty factor D of the PWM signal that is the drive signal of the electric motor.

FIG. 5 shows a characteristic diagram of the speed deviation (ΔN) -duty factor (D). In FIG. 5, the duty factor D is linear as the speed deviation ΔN increases.
It has the characteristic of saturating after it has been increased.

The PWM signal generator generates a PWM signal having a duty factor D corresponding to the speed deviation ΔN, and supplies the PWM signal as a drive control signal Mc to the motor drive means 20 and the failure detection means 14.

The motor driving means 20 forms a bridge circuit with switching elements such as FETs (field effect transistors) and IGBTs (insulated gate bipolar transistors), and a drive control signal M supplied from the drive control means 19.
c, generates a motor drive signal Mg based on the
PWM drive (for VGS).

When the steering angle ratio sensor 22 fails based on the failure signal As (for example, H level) provided from the failure detecting means 14, the motor driving means 20
The motor drive signal Mg is immediately set to 0, and the motor 30 is stopped and the steering angle ratio is fixed as it is, or the motor drive signal Mg is output in a direction to increase the steering angle ratio for a predetermined time and then fixed after processing. Stop 30. If the method of fixing after increasing the steering angle ratio is used, the steering angle ratio sensor 2
2, it is possible to prevent the steering force from increasing due to the fact that the steering angle ratio is fixed at a small value due to the failure.

The failure detecting means 14 includes a comparing means, a timer,
It comprises a logic circuit, a memory, and the like, includes a rate comparison unit 25, a time management unit 26, an output determination unit 27, a logical product 29, outputs a drive control signal Mc of a predetermined value or more, and outputs a target steering angle ratio signal Cg When the state where the difference between the actual steering angle ratio signals Gs is equal to or greater than a predetermined value continues for a predetermined time or longer, it is determined that the steering angle ratio sensor 22 has failed, and a failure signal As is output.

The rate comparing means 25 is constituted by a comparator such as a comparator, and the target steering angle ratio signal Cg supplied from the target steering angle ratio setting means 18 and the actual steering angle supplied from the steering angle ratio detecting means 23. When the difference d between the target steering angle ratio signal Cg and the actual steering angle ratio signal Gs is equal to or larger than a predetermined value Tv (d = | Cg−Gs | ≧ Tv), for example, The comparison signal Rc at the H level is supplied to the AND operation means 29. On the other hand, the target steering angle ratio signal Cg and the actual steering angle ratio signal Gs
Is smaller than a predetermined value Tv set in advance (d <T
v), the L level comparison signal Rc is applied to the AND operation means 2
9.

The output judging means 27 comprises a comparing means such as a comparator, and compares the driving control signal Mc supplied from the driving control means 19 with a preset reference value Mk. In the above case (Mc ≧ Mk)
For example, an H-level output determination signal Mv is supplied to the AND means 29, and when the drive control signal Mc falls below the reference value Mk (Mc <Mk), the L-level output determination signal Mv is output to the AND operation means. 29.

When the output determination signal Mv is at the H level, the drive control signal Mc is normal, and when the output determination signal Mv is at the L level, the drive control signal Mc is abnormal.

The AND operation means 29 has an AND circuit or an AND function of software control, and performs the AND operation of the comparison signal Rc supplied from the rate comparison means 25 and the output judgment signal Mv supplied from the output judgment means 27. And the logical product signal W
t is supplied to the time management means 26.

When both the comparison signal Rc and the output determination signal Mv are at the H level, the AND signal Wt goes to the H level. In this state, the target steering angle ratio signal Cg and the actual steering angle ratio signal G
This indicates that the difference d of s is equal to or greater than a predetermined value Tv and that the output determination signal Mv is normal.

On the other hand, when the comparison signal Rc is at L level, the AND signal Wt is at L level regardless of whether the output determination signal Mv is at H level or L level. This state is
The difference d between the target steering angle ratio signal Cg and the actual steering angle ratio signal Gs is smaller than a predetermined value Tv, indicating that the output determination signal Mv is normal or abnormal.

The time management means 26 includes a timer means and a latch means, and starts time counting by using the H-level AND signal Wt supplied from the AND operation means 29 as a trigger. If the measured time continues for a predetermined value Ct or more, the failure signal As is latched (held) at the H level.
Then, the H-level failure signal As is supplied to the alarm output means 28 and the motor drive means 20. On the other hand, if the time counted by the H-level AND signal Wt is less than the predetermined value Ct,
The level failure signal As is supplied to the alarm output means 28 and the motor drive means 20.

FIG. 6 shows the target steering angle ratio signal Cg of the failure detecting means.
FIG. 9 is a time lapse characteristic diagram of an actual steering angle ratio signal Gs with respect to FIG. 6, when the target steering angle ratio signal Cg is output and the electric motor 30 shown in FIG. 2 is driven, the actual steering angle ratio signal G is detected by the steering angle ratio sensor 22, and the actual steering angle ratio signal Gs It increases with the lapse of t and approaches the target steering angle ratio signal Cg.

When the steering angle ratio sensor 22 is normal, the actual steering angle ratio signal Gs quickly matches the target steering angle ratio signal Cg within a predetermined time Ct (Cg-Gs = 0). 22 is out of order, the actual steering angle ratio signal Gs becomes the predetermined time C
Even after t, the target steering angle ratio signal Cg does not become the target steering angle ratio signal Cg, and the difference d between the target steering angle ratio signal Cg and the actual steering angle ratio signal Gs becomes equal to or larger than the predetermined value Tv. (D = | Cg-Gs | ≧ Tv)

The reason for providing the time management means 26 in the failure detection means 14 is that the difference d between the target steering angle ratio signal Cg and the actual steering angle ratio signal Gs instantaneously exceeds a predetermined value Tv due to noise or the like. It is to prevent the angle ratio sensor 22 from detecting a failure.

The alarm output means 28 comprises a visual display such as an LED (light emitting diode) or an LCD (liquid crystal display), and an audible display such as an audio output device, and the failure detection means 14 (logical product operation means 29). When the failure signal As supplied from the controller is at the H level, the failure of the steering angle ratio sensor 22 is notified to the driver.

As described above, in the variable steering angle ratio steering device 1 according to the first aspect, the steering angle ratio control means 13 includes the drive control means 19
When the difference d between the target steering angle ratio Cg and the actual steering angle ratio Gs is equal to or greater than the predetermined value Tv and continues for equal to or more than the predetermined time Ct in spite of outputting the drive control signal Mc equal to or greater than the predetermined value Mk, Since the failure detection means 14 for determining that the steering angle ratio sensor 22 is in failure is provided, a failure or abnormality of the steering angle ratio sensor 22 can be detected from the determination result of the failure detection means 14.

FIG. 3 is a block diagram of a main part of an embodiment of a variable steering angle ratio steering apparatus according to the second aspect. In the configuration of this figure, the drive control of the electric motor is performed based on the vehicle speed signal and the actual steering angle ratio signal, and the estimated steering angle ratio is estimated based on the drive control signal. When the difference from the angle ratio is equal to or more than a predetermined value and continues for a predetermined time or more, a failure of the steering angle ratio sensor is determined.

In FIG. 3, the variable steering angle ratio steering device comprises a vehicle speed sensor 16, a steering angle ratio sensor 22, steering angle ratio control means 33, a motor (for VGS) 30, and an alarm output means 2.
8 is comprised.

The steering angle ratio control means 33 includes various arithmetic means, comparison means processing means, memory,
It is composed of an FET, a logic circuit, and the like, and includes a vehicle speed detecting unit 17, a steering angle ratio detecting unit 23, a target steering angle ratio setting unit 18, a drive control unit 19, a subtracter 21, an electric motor driving unit 20, and a failure detecting unit 34.

The vehicle speed detecting means 17, the steering angle ratio detecting means 23, the target steering angle ratio setting means 18, the drive control means 19, the subtracter 21, and the motor driving means 20 have the same structure and function as those shown in FIG. The description is omitted because it is the same.

The failure detecting means 34 includes a comparing means, a timer,
It comprises a memory or the like and includes an estimated steering angle ratio setting means 24, a rate comparison means 25, a time management means 26, and a drive control signal M
c, the estimated steering angle ratio setting signal Es is compared with the actual steering angle ratio signal Gs, and the difference between the estimated steering angle ratio setting signal Es and the actual steering angle ratio signal Gs is calculated. Is longer than a predetermined value and continues for a predetermined time or more, it is determined that the steering angle ratio sensor 22 has failed, and a failure signal As is output.

The estimated steering angle ratio setting means 24 has a rewritable memory, an arithmetic means or an arithmetic function of software control.
Based on the drive control signal Mc supplied from the drive control unit 19, the estimated steering angle ratio Es is estimated by calculation from Equation 1, and the estimated steering angle ratio signal Es is supplied to the rate comparison unit 25.

[0054]

Es = Gsk + K × Mc where Gsk is an actual steering angle ratio detected a predetermined time ago, and K is a constant.

The rate comparing means 25 is composed of a comparator such as a comparator, and the estimated steering angle ratio signal Es supplied from the estimated steering angle ratio setting means 24 and the actual steering angle supplied from the steering angle ratio detecting means 23. When the difference dc between the estimated steering angle ratio signal Es and the actual steering angle ratio signal Gs is equal to or larger than a predetermined value Tv (dc = | Es−Gs | ≧ Tv), for example, The H level comparison signal Rc is transmitted to the time management
To supply. On the other hand, when the difference dc between the estimated steering angle ratio signal Es and the actual steering angle ratio signal Gs is smaller than a predetermined value Tv (dc <Tv), an L level comparison signal Rc is supplied to the time management means 26. .

The time management means 26 includes a timer means and a latch means, and starts time counting by using the H level comparison signal Rc supplied from the rate comparing means 25 as a trigger. If the failure signal As continues for more than the value Ct, the failure signal As is latched (held) at the H level,
The level failure signal As is supplied to the alarm output means 28 and the motor drive means 20. On the other hand, the H-level comparison signal R
If the measured time of c is shorter than the predetermined value Ct, an L-level failure signal As is supplied to the alarm output means 28 and the motor drive means 20.

FIG. 7 shows the estimated steering angle ratio signal Es of the failure detecting means.
FIG. 9 is a time lapse characteristic diagram of an actual steering angle ratio signal Gs with respect to FIG. 7, when the estimated steering angle ratio signal Es is output and the electric motor 30 shown in FIG. 3 is driven, the steering angle ratio sensor 22 detects the actual steering angle ratio signal G, and the actual steering angle ratio signal Gs It increases with the lapse of t and approaches the estimated steering angle ratio signal Es.

When the steering angle ratio sensor 22 is normal, the actual steering angle ratio signal Gs quickly matches the estimated steering angle ratio signal Es within a predetermined time Ct (Es-Gs = 0). 22 is out of order, the actual steering angle ratio signal Gs becomes the predetermined time C
Even after t, the estimated steering angle ratio signal Es does not become the estimated steering angle ratio signal Es, and the difference dc between the estimated steering angle ratio signal Es and the actual steering angle ratio signal Gs becomes equal to or larger than the predetermined value Tv. (Es = | Cg−Gs | ≧ Tv)

As described above, in the variable steering angle ratio steering apparatus 1 according to the second aspect, the steering angle ratio control means 33 includes the drive control means 19
The steering angle ratio Es is estimated based on the drive control signal Mc from the controller, and the difference dc between the estimated steering angle ratio Es and the actual steering angle ratio Gs is equal to a predetermined value Tv.
As described above, the failure detection means 34 for determining that the steering angle ratio sensor 22 is faulty when the predetermined time Ct or more has been provided is provided. Abnormality can be detected.

It should be noted that the failure detecting means 14 shown in FIG.
Although the failure detecting means 34 is constituted by positive logic (H level) drive, it may be constituted by negative logic (L level) drive.

[0061]

As described above, in the variable steering angle ratio steering apparatus according to the first aspect of the present invention, the drive control means outputs a drive control signal of a predetermined value or more to the steering angle ratio control means. Nevertheless, when the difference between the target steering angle ratio and the actual steering angle ratio is equal to or greater than a predetermined value and continues for a predetermined time or more, failure detection means for determining that the steering angle ratio sensor is malfunctioning is provided. Since a failure or abnormality of the steering angle ratio sensor can be detected from the determination result of the means, it is possible to notify the driver of the failure of the steering angle ratio sensor and to continue appropriate steering while fixing the steering angle ratio. .

The variable steering angle ratio steering device according to the second aspect estimates the steering angle ratio to the steering angle ratio control means from the drive control signal from the drive control means, and calculates the estimated steering angle ratio and the actual steering angle. When the difference from the ratio is equal to or greater than a predetermined value and continues for a predetermined time or more, the steering angle ratio sensor is provided with failure detection means for determining that a failure has occurred. Since a failure or abnormality can be detected, the driver can be notified of the failure of the steering angle ratio sensor, and the steering angle ratio can be fixed to continue appropriate steering.

Therefore, a failure of the steering angle ratio sensor is detected from the difference between the target steering angle ratio and the actual steering angle ratio and the duration thereof, and if a failure is detected, the steering angle ratio is fixed and an appropriate steering is performed. Can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a variable steering angle ratio steering device according to the present invention.

FIG. 2 is a block diagram showing a main part of an embodiment of a variable steering angle ratio steering device according to claim 1;

FIG. 3 is a block diagram of a main part of an embodiment of a variable steering angle ratio steering device according to claim 2;

FIG. 4 is a characteristic diagram of an input angle (α) -output angle (β) of a variable steering angle ratio steering device.

FIG. 5: Speed deviation (ΔN) -duty factor (D)
Characteristic diagram

FIG. 6 is a time lapse characteristic diagram of the actual steering angle ratio signal Gs with respect to the target steering angle ratio signal Cg of the failure detection means.

FIG. 7 is a time-lapse characteristic diagram of the actual steering angle ratio signal Gs with respect to the estimated steering angle ratio signal Es of the failure detection means.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Variable steering angle ratio steering device, 2 ... Handle, 3 ... Steering shaft, 4 ... Connecting shaft, 4a, 4b ... Universal joint, 5 ... Variable gear ratio mechanism, 6 ... Manual steering force generation means, 7 ... Rack shaft, 7a: rack, 8: tie rod, 9: front wheel, 10 ...
Pinion, 10a: input side axis, 10b: output side axis, 13
... steering angle ratio control means, 14, 34 ... failure detection means, 16 ...
Vehicle speed sensor, 17: vehicle speed detecting means, 18: target steering angle ratio setting means, 19: drive control means, 20: electric motor drive means,
21: subtractor, 22: steering angle ratio sensor, 23: steering angle ratio detecting means, 24: estimated steering angle ratio setting means, 25: rate comparing means, 26: time management means, 27: output determining means, 28 ...
Alarm output means, 29: AND operation means, 30: electric motor (for VGS), 31: electric power supply for driving the motor, As: failure signal, Cg: target steering angle ratio signal, Ct: predetermined time, D ...
Deity factor, d, dc: difference value, Es: estimated steering angle ratio setting signal, G, Gs: actual steering angle ratio signal, Mc: drive control signal, Mg: motor drive signal, Mv: output determination signal, △
N: speed deviation, Rc: comparison signal, Sg: deviation signal, Tv
... predetermined value level, V: vehicle speed signal, Vs: vehicle speed detection signal,
Wt: AND signal.

Continuation of front page (56) References JP-A-6-1254 (JP, A) JP-A-4-283168 (JP, A) JP-A-5-124533 (JP, A) JP-A 8-26128 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 5/04

Claims (2)

(57) [Claims] An electric motor for varying a steering angle ratio of a steering system;
A steering angle ratio sensor that detects an actual steering angle ratio of the steering system, a vehicle speed sensor that detects the speed of the vehicle, and a target steering angle ratio setting unit that sets a target steering angle ratio corresponding to a vehicle speed signal from the vehicle speed sensor. Steering angle ratio control means including drive control means for controlling driving of the electric motor based on a target steering angle ratio signal from the target steering angle ratio setting means and an actual steering angle ratio signal from the steering angle ratio sensor; Wherein the steering angle ratio control means outputs a target steering angle ratio and an actual steering angle ratio despite the fact that the drive control means outputs a drive control signal of a predetermined value or more. And a failure detection means for determining that the steering angle ratio sensor has failed when the difference between the steering angle ratio sensor and the vehicle has continued for a predetermined time or more. 2. An electric motor for varying a steering angle ratio of a steering system,
A steering angle ratio sensor that detects an actual steering angle ratio of the steering system, a vehicle speed sensor that detects the speed of the vehicle, and a target steering angle ratio setting unit that sets a target steering angle ratio corresponding to a vehicle speed signal from the vehicle speed sensor. Steering angle ratio control means including drive control means for controlling driving of the electric motor based on a target steering angle ratio signal from the target steering angle ratio setting means and an actual steering angle ratio signal from the steering angle ratio sensor; Wherein the steering angle ratio control means estimates a steering angle ratio from a drive control signal from the drive control means, and calculates a difference between the estimated steering angle ratio and the actual steering angle ratio. If it continues for more than a predetermined value for a predetermined time,
A variable steering angle ratio steering device, comprising: a failure detection unit that determines that the steering angle ratio sensor has failed.