JP3280732B2 - Fail judgment method of steering angle sensor - Google Patents

Abstract

PURPOSE:To provide a method of enabling the failure judgment of a steering angle sensor even in the case of mounting small diameter spare wheels. CONSTITUTION:In an FF-type automobile 1, the rotating speed of lateral rear wheels 9, 10, driven wheels, is detected by wheel rotating speed sensors 20, 21, while steering angles are detected by a steering angle sensor 17. The rotating speed difference between both rear wheels 9, 10 is computed by a control unit C, and in the case of the steering angle being unchanged when the rotating speed difference is changed from the steady state, it means that the change of the steering angle is not detected by the steering angle sensor 17 in spite of the automobile 1 starting to turn, so that the steering angle sensor 17 is judged to be in failure. With such failure judgment, failure judgment is made regardless of the rotating speed itself of both rear wheels 9, 10, so that failure judgment can be made correctly even in the case of small diameter spare wheels being mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging a failure of a steering angle sensor.

[0002]

2. Description of the Related Art Generally, in a vehicle, if the driving force applied to the driving wheels is too large relative to the road surface μ, the driving wheels slip and the power loss increases. Therefore, in recent years, vehicles equipped with a traction control device that detects a slip ratio of a drive wheel and feedback-controls a driving force so that the slip ratio follows a target slip ratio corresponding to a road surface μ are becoming widespread. Also, during braking,
If the braking force applied to the wheels is too large with respect to the road surface μ, the wheels will be locked and the braking force will be reduced. Therefore, in recent years, vehicles equipped with an ABS control device that prevents the wheels from being locked by adjusting the braking force applied to each wheel according to the road surface μ during braking are becoming widespread.

[0003] The slip characteristics at the time of driving the wheels or the grip characteristics at the time of braking are greatly affected by the steering angle. Therefore, the steering angle is indispensable control information for performing traction control or ABS control. For this reason, a vehicle provided with a traction control device or an ABS control device is provided with a steering angle sensor for detecting a steering angle of a front wheel. For example, an encoder-type steering angle sensor is often used as such a steering angle sensor. (See, for example, JP-A-2-48211).

In general, a sensor may fail due to various causes. When the steering angle sensor fails, traction control or ABS control is performed based on an incorrect steering angle. The braking performance is significantly reduced. Therefore, when the steering angle sensor fails, it is necessary to immediately stop the traction control or the ABS control. For this reason, in the steering angle sensor, it is particularly necessary to accurately determine the presence or absence of the failure.

[0005] As a method for judging the failure of the steering angle sensor, the left wheel rotational speed and the right wheel rotational speed are compared, and when there is a difference between the two, it is determined that the vehicle is in a turning state. Conventionally, a method of determining that the steering angle sensor has failed when the steering angle detected by the steering angle sensor at the time is 0 (straight running state) has been frequently used.

[0006]

By the way, in recent years, a spare wheel (spare tire) for temporarily using at the time of a puncture or the like.
In order to reduce the weight of automobiles, they are often made smaller in diameter and narrower than ordinary wheels. In a vehicle equipped with such spare wheels, when the wheels involved in the failure determination of the rudder angle sensor are punctured or replaced with spare wheels, the two wheels involved in the fail determination of the rudder angle sensor are replaced. Since there is a difference in rotational speed between the wheels even in a straight traveling state, there is a problem that the rudder angle sensor cannot make a failure determination.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and provides a method capable of judging a failure of a steering angle sensor without any trouble even when a small-diameter spare wheel is mounted. The purpose is to do.

[0008]

In order to achieve the above object, a first aspect of the present invention is to provide (i) a method in which a predetermined number of rotations of a left wheel and a number of rotations of a predetermined right wheel are sequentially measured by a wheel rotation number sensor. On the other hand, the steering angle sensor detects the steering angle over time, and (ii) calculates the difference between the rotation speed of the left wheel and the rotation speed of the right wheel, and determines whether the rotation speed difference is in a steady state. Is determined over time, and when the rotational speed difference is in a steady state, the vehicle is determined to be in a straight running state, and the failure determination of the steering angle sensor is not performed. (Iii) The previous rotational speed difference is in a steady state. And when the current rotational speed difference has changed from the previous rotational speed difference, and when the current steering angle has not changed from the previous steering angle, it is determined that the steering angle sensor has failed. Method for judging failure of steering angle sensor To provide.

According to a second aspect of the present invention, in the method for judging a failure of the steering angle sensor according to the first aspect, a predetermined left wheel and a predetermined right wheel are respectively set to follower wheels. And a method for determining a failure.

According to a third aspect of the present invention, in the method for judging failure of the steering angle sensor according to the second aspect of the invention, when the vehicle is a front wheel drive vehicle, a predetermined left wheel and a predetermined right wheel are respectively positioned on the rear wheel side. A method for determining a failure of a steering angle sensor is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.
As shown in FIG. 2, in an FF type (front engine / front drive) automobile 1 in which traction control and ABS control (anti-skid brake control) are performed, the FF type (front engine / front drive) automobile is disposed horizontally at the front of the vehicle body. The output torque of the engine 2 is shifted by the transmission 3, and further through the front differential device 4 and the left and right front axle shafts 5, 6, the left and right front wheels 7, 8.
(Drive wheels). Further, right and left rear wheels 9 and 10, which are driven wheels, are attached to a tie rod 11 at a rear portion of the automobile 1.

The automobile 1 is provided with a steering wheel 14 (handle) operated by a driver. The steering wheel 14 is connected to a steering shaft 15. Here, when the steering wheel 14 (the steering shaft 15) is turned clockwise by the driver, the direction of the left and right front wheels 7, 8 is changed to the right by the action of the steering gear mechanism 13, and the automobile 1 Turns to the right. Conversely, when the steering wheel 14 is turned in the counterclockwise direction, the directions of the left and right front wheels 7, 8 are changed to the left, and the vehicle 1 turns left.

In the automobile 1, the traction control and the ABS control are performed by the control unit C. Therefore, in order to detect various control information required for these controls, a steering angle sensor for detecting a steering angle. 17
A front left wheel rotation speed sensor 18 for detecting the rotation speed of the left front wheel 7, a right front wheel rotation speed sensor 19 for detecting the rotation speed of the right front wheel 8, and a left rear wheel rotation for detecting the rotation speed of the left rear wheel 9. A number sensor 20 and a right rear wheel rotation speed sensor 21 for detecting the rotation speed of the right rear wheel 10 are provided. Although not shown, various other sensors such as a vehicle speed sensor and a throttle sensor are also provided.

Since the traction control and the ABS control are performed by a well-known ordinary method, a detailed description thereof will be omitted, but the traction control is performed by the front wheels 7 and 8 and the rear wheels 9 and 10.
The slip ratio of the front wheels 7, 8 (driving wheels) is calculated from the rotational speed difference between the vehicle and the output torque of the engine 2 or the output torque of the engine 2 so that the slip ratio follows the target slip ratio set according to the road surface μ or the like. The driving force of the front wheels 7, 8 is feedback-controlled by changing the braking force on the front wheels 7, 8, or the like. In addition, the ABS control is based on the road surface μ.
The braking force applied to each of the wheels 7 to 10 is adjusted according to, for example, to prevent the wheels 7 to 10 from being locked.

Hereinafter, an encoder type steering angle sensor 17 particularly related to the gist of the present invention will be described. As shown in FIG. 3, the steering angle sensor 17 is provided with a disk 32 which is attached to the steering shaft 15 and rotates integrally with the steering shaft 15. Are formed at regular intervals along the entire circumference in the circumferential direction. On the inner side of the outer slit 33, a number of inner slits 34 are formed circumferentially at regular intervals over the entire circumference. here,
The rows of the outer slits 33 and the rows of the inner slits 34 are arranged so as to be out of phase with each other by a predetermined angle in the circumferential direction.

On one side (left side in FIG. 3) of the disc 32, a first LED 35 (light emitting diode) for projecting light toward the outer slit 33 and a light is projected toward the inner slit 34. A second LED 36 is provided. On the other hand, on the other side (the right side in FIG. 3) of the disc 32, a first phototransistor 37 that receives light projected from the first LED 35 and passed through the outer slit 33, and an inner slit 34 projected from the second LED 36 And a second phototransistor 38 for receiving the light passing through the second phototransistor.

In the steering angle sensor 17, when the steering wheel 14 is rotated clockwise, the disk 52 attached to the steering shaft 15 rotates clockwise. At this time, the first LED 35 and the first phototransistor 37 are rotated. Since light is input to the first phototransistor 37 only when the outer slit 33 is located between the first phototransistor 37 and
For example, a pulse signal as shown by broken line G ₁ in FIG. 4 (a) is output. Similarly, the second phototransistor 38, a pulse signal as shown by the broken line G ₂ in FIG. 4 (a) is output. In FIG. 4, a state of level 1 indicates a state where light is input to the phototransistors 37 and 38, and a state of level 0 indicates a state where light is not input. Thus, from the pattern and the number of pulses of the output signals of the first and second phototransistors 37 and 38,
The rotation angle of the disk 32 and, consequently, the steering angle of the vehicle 1 are determined. The broken lines G ₃ and G ₄ in FIG.
When the steering wheel 14 is turned counterclockwise, respectively, the first and second phototransistors 37, 3
8 shows a signal output from FIG.

However, in the above-described steering angle detection method, the amount of change in the steering angle in the right or left direction is obtained from the pulse signals output from the first and second phototransistors 37 and 38. The steering angle relative to the steering angle at the start of detection (relative steering angle) can be obtained by integrating the steering angle change amounts, but the absolute steering angle, that is, the actual steering angle of the automobile 1 is obtained. It is impossible. For this reason, the relative steering angle when the absolute steering angle becomes 0, that is, the zero point position is determined, and the relative steering angle corresponding to the zero point position is subtracted from the momentary relative steering angle detected by the steering angle sensor 17. Therefore, it is necessary to determine the absolute steering angle. Therefore, in the present embodiment, the relative steering angle detected when the vehicle 1 is in a predetermined straight traveling state is set to the zero point position.

When the steering angle sensor 17 fails, the traction control or the ABS control is hindered as described above.
The control unit C accurately determines the presence or absence of a failure of the steering angle sensor 17. Hereinafter, a specific fail determination method by the control unit C will be described according to the flowchart shown in FIG. 1 and appropriately referring to FIGS.

In this fail determination method, basically, it is determined over time whether or not the rotational speed difference between the left rear wheel 9 and the right rear wheel 10, which are driven wheels, is in a steady state. In the case where the previous rotation speed difference is in a steady state and the current rotation speed difference has changed from the previous rotation speed difference, and the current steering angle has not changed from the previous steering angle, the steering angle sensor 17 is determined to have failed.

Specifically, first, in step # 1, the steering angle θ
And the rotation speed Vrl of the left rear wheel 9 as a driven wheel (left rear wheel rotation speed Vrl) and the rotation speed Vrr of the right rear wheel 10 as a driven wheel (right rear wheel rotation speed Vrr) are read. In step # 2,
The absolute value K of the rotation speed difference between the left rear wheel rotation speed Vrl and the right rear wheel rotation speed Vrr is calculated (K ← │Vrr-Vrl│).

Next, at step # 3, it is compared and determined whether or not the absolute value K of the current rotational speed difference has changed from the previous K, and if it is determined that it has not changed (NO). Since it is not possible to determine the presence or absence of a failure of the steering angle sensor 17, all subsequent steps are skipped and the process returns to step # 1.

On the other hand, in step # 3, the current K is
Is determined to have changed (YES), it is further compared and determined in step # 4 whether or not the previous K was in a steady state. Whether or not a K is in a steady state depends on the K and some previous Ks stored in memory.
The determination is made based on whether or not the average rate of change with respect to the time of a plurality of Ks is equal to or less than a predetermined value. In order to simplify the calculation, it may be determined whether or not the previous K is in a steady state based on whether or not the amount of change of the previous K with respect to K two times before is not more than a predetermined value.

If the previous K was in a steady state, it has already been determined in step # 3 that the current K has changed from the previous K, so that a rotational speed difference starts to occur from this time. Therefore, this means that the car 1 has begun to turn from this time. Therefore, if the steering angle sensor 17 is normal, the current steering angle θ should have changed from the previous steering angle θ ′. In other words, if the current steering angle θ has not changed from the previous steering angle θ ′, the change in the steering angle θ is detected by the steering angle sensor 17 even though the car 1 has started turning. Since there is not, the rudder angle sensor 17 has failed.

If it is determined in step # 4 that the previous K was in the steady state (YES), step # 5
It is determined whether or not the current steering angle θ has changed from the previous steering angle θ ′, and if the current steering angle θ has changed,
(YES) In step # 6, it is determined that the steering angle sensor 17 is normal, and if the current steering angle θ has not changed (NO).
In step # 7, it is determined that the steering angle sensor 17 has failed. Thereafter, the process returns to step # 1. In addition,
If it is determined in step # 4 that the previous K was not in the steady state (NO), it means that K has been continuously changing from before the previous time, and the steering angle sensor 17 has failed. Since it is not possible to determine whether or not it is, the subsequent steps are skipped and the process returns to step # 1.

According to the failure determination method, if the rotational speed difference K (absolute value) between the left rear wheel 9 and the right rear wheel 10 is steady, that is, almost constant, the two rear wheels 9, 10 It is determined that the vehicle 1 is in a straight running state irrespective of the rotation speed itself, and if K changes from the steady state, it is determined that the vehicle 1 has started turning. Therefore, even when the diameter of the left rear wheel 9 and the diameter of the right rear wheel 10 are different, it is possible to accurately determine whether or not the vehicle 1 is in a straight traveling state. Can be accurately determined. Therefore, the left rear wheel 9 or the right rear wheel 1
Spare wheel (spare tire) with small diameter due to puncture of 0
Even if it is exchanged, the presence or absence of a failure of the steering angle sensor 17 can be accurately determined.

Since the rear wheels 9 and 10 are not steered,
The detection accuracy of the rotation speed is increased, and therefore, the rotation speed difference K between the two wheels is more accurately obtained.
, The accuracy of the failure determination is further improved.

[0028]

According to the first aspect of the present invention, if the rotational speed difference between the left wheel and the right wheel is steady, it is determined that the vehicle is in a straight running state regardless of the rotational speeds of both wheels. . If the rotation speed changes from the steady state, it is determined that the vehicle has started to turn, and when it is determined that the vehicle has started to turn, the steering angle detected by the steering angle sensor is determined. If not, it is determined that the steering angle sensor has failed. For this reason,
Even when the diameters of the two wheels are different, it is possible to accurately determine whether or not the vehicle is in a straight traveling state, and therefore, it is possible to accurately determine whether the steering angle sensor has failed. Therefore, even if a small-diameter spare wheel is mounted, the presence or absence of a failure of the steering angle sensor can be accurately determined.

According to the second aspect, basically the same operation and effect as those of the first aspect can be obtained. Further, since it is determined whether or not the vehicle is in a straight running state based on the rotational speed difference of the driven wheels that hardly slips, the accuracy of the determination is increased, and therefore, the accuracy of the failure determination is further enhanced.

According to the third aspect, basically the same operation and effect as those of the second aspect can be obtained. Further, since it is determined whether or not the vehicle is in a straight running state from the rotational speed difference of the rear wheels that are not steered, the accuracy of such determination is further enhanced, and thus the accuracy of the failure determination is further enhanced.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a method of determining a failure of a steering angle sensor.

FIG. 2 is a schematic view of an automobile including an encoder-type steering angle sensor.

FIG. 3 is a schematic diagram showing a configuration around a disk of the encoder-type steering angle sensor shown in FIG. 2;

FIG. 4 is a diagram showing a characteristic of an output signal of a phototransistor of a steering angle sensor with respect to time.

[Explanation of symbols]

 C ... Control unit 1 ... Car 7 ... Left front wheel 8 ... Right front wheel 9 ... Left rear wheel 10 ... Right rear wheel 17 ... Rudder angle sensor 18 ... Left front wheel rotation speed sensor 19 ... Right front wheel rotation speed sensor 20 ... Left rear wheel rotation Number sensor 21: Right rear wheel speed sensor

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 6/00-6/06

Claims (3)

(57) [Claims] 1. A method for detecting a rotation speed of a predetermined left wheel and a rotation speed of a predetermined right wheel over time by a wheel rotation speed sensor, and detecting a steering angle over time by a steering angle sensor, The difference between the rotation speed and the rotation speed of the right wheel is calculated, and it is determined with time whether or not the rotation speed difference is in a steady state.When the rotation speed difference is in a steady state, the vehicle goes straight. If the previous rotation speed difference is in a steady state and the current rotation speed difference has changed from the previous rotation speed difference, the current steering A method for determining a failure of a steering angle sensor, comprising determining that the steering angle sensor has failed when the angle has not changed from the previous steering angle. 2. The method for judging a failure of a steering angle sensor according to claim 1, wherein a predetermined left wheel and a predetermined right wheel are respectively set on the driven wheel side. Method. 3. The method of claim 2, wherein when the vehicle is a front wheel drive vehicle, a predetermined left wheel and a predetermined right wheel are respectively set on the rear wheel side. A method for judging a failure of a steering angle sensor, comprising: