JPH0431173A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To detect abnormality without provision of two steering angle detecting means by judging to be abnormality of a steering angle detecting means, when a steering angle detected value is over a maximum steering angle setting value corresponding to vehicle speed, or when a steering angle speed detected value is over a maximum steering angle speed setting value. CONSTITUTION:In a control device 6 which controls a motor 1 and a clutch 2 based on output of a torque sensor 3, a vehicle speed sensor 4, and a steering angle sensor 5, a steering force assisting quantity control means 7, a steering angle reading means 16, a steering angle speed detecting means 8, and an abnormality detecting means 9 are provided. The steering angle signal from the steering angle sensor 5 is read by steering angle reading means 16 to detect the steering angle, and the steering angle speed is detected (computed) from the steering angle detected value by the steering angle speed detecting means 8. When the steering angle detected value is over the maximum steering angle setting value set to decrease corresponding to increase of vehicle speed or when the steering angle speed detected value is over the maximum steering angle speed setting value, it is judged to be abnormal by the abnormality detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric power steering device for, for example, an automobile.

2. Description of the Related Art In this type of power steering device, a steering angle sensor is used to detect the steering angle of a wheel, thereby controlling the return of the steering wheel (steering wheel), damping control, etc.

Problems to be Solved by the Invention However, in conventional power steering devices, there is no effective means for detecting failures in the steering angle sensor or the steering angle signal input circuit. An unexpected situation for the driver occurs and is extremely dangerous.

Although it is possible to detect an abnormality by using two steering angle sensors and detecting a difference between their output signals exceeding a certain value, this increases the cost of the device.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that solves the above problems and can easily detect a failure in the steering angle detection means.

Means for Solving the Problems An electric power steering device according to the present invention includes a steering angle detection means, a steering angle speed detection means for detecting a steering angle speed based on a steering angle detected by the steering angle detection means, and a steering angle detection value. The vehicle is equipped with abnormality detection means for detecting an abnormality in the steering angle detection means when the detected value is equal to or greater than the maximum steering angle setting value corresponding to the vehicle speed, or when the detected steering angle speed is equal to or greater than the maximum steering angle speed setting value.

For example, the maximum steering angle setting value is set to decrease as the vehicle speed increases.

The maximum steering angular speed setting value is set in consideration of, for example, the maximum steering angular speed that can be steered by a human, kickback, and the like.

In a working vehicle, the amount of steering angle that can be steered depends on the vehicle speed, and there is also a limit to the steering angle speed that can be steered by a human.

Therefore, if the detected steering angle value exceeds the maximum steering angle setting value corresponding to the vehicle speed, or if the detected steering angle speed value exceeds the maximum steering angle speed setting value, it is determined that there is an abnormality in the steering angle detection means. By this, even without providing two steering angle detection means,
Abnormalities in the steering angle detection means are easily detected.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of an electric power steering device.

This device uses an electric motor (1) to assist the steering force.
, an electromagnetic clutch (2) provided between the motor (1) and the steering system; a torque sensor (3) for detecting the input torque of the steering shaft; a vehicle speed sensor (4) for detecting the vehicle speed; A steering angle sensor (5) for detecting the steering angle, and these sensors (3)
4) A control device (6) is provided that controls the motor (1) and clutch (2) based on the output of (5).

The control bag Wl (6) is constituted by a microcomputer, and includes a steering force assist amount control means (7), a steering angle reading means (
■6), steering angular speed detection means (8) and abnormality detection means (
9). Power supply circuit (10) of control device (6)
However, the battery (main power supply) is connected via the key switch (11).
(12).

The motor (1) and the clutch (2) are connected to a control device (6) via a motor drive circuit (13) and a clutch drive circuit (14), respectively. Motor drive circuit (
13) and the clutch drive circuit (14) are connected to the battery (12) via a fail relay (15),
The fail relay (15) is connected to the control device (6) via a relay drive circuit (17). Further, the motor drive circuit (13) is connected to the control device (6) via a current detection circuit (18).

A key switch (11), a lux sensor (3), a vehicle speed sensor (4) and a steering angle sensor (5) of a battery (12) are connected to a control device (6) via an interface (19). The steering angle sensor (5), its steering angle signal input circuit, and steering angle reading means (IB) constitute a steering angle detection means. Also, the alarm lamp (2) connected to the key switch (11) of the battery (12)
o) is connected to the control device (6) via the alarm lamp drive circuit (21).The rudder angle reading means (1B) reads the rudder angle signal from the rudder angle sensor (5), and Detect corners.

The steering angular speed detecting means (8) detects (calculates) the steering angular speed from the detected value of the steering angle of the steering angle reading means (16).

The steering force assist amount control means (7) includes the detected torque of the torque sensor (3), the detected speed of the vehicle speed sensor (4), the detected value of the steering angle of the steering angle reading means (!6), and the steering angle speed detection means (8). The motor drive circuit (13)
etc., thereby controlling the amount of steering force assistance by the motor (1).

The abnormality detection means (9) detects the steering angle sensor (2) based on the detected value of the steering angle by the steering angle reading means (16), the detected value of the steering angle speed of the steering angle speed detection means (8), and the detected speed of the vehicle speed sensor (4).
5) and detect an abnormality in the steering angle signal input circuit. That is, the maximum steering angle setting value and the maximum steering angular speed setting value are set in advance in the abnormality detection means (9). The maximum steering angle setting value depends on the vehicle speed, and decreases as the vehicle speed increases, as shown in FIG. 2, for example.

Note that the relationship between vehicle speed and maximum steering angle setting value is set in a table in the abnormality detection means (9). The maximum steering angular speed setting value is set to a constant value in consideration of, for example, the maximum steering angular speed that a human can steer, the kick pack, and the like.

Then, if the detected steering angle value exceeds the maximum steering angle setting value corresponding to the vehicle speed at that time, or if the detected steering angular velocity value exceeds the maximum detected steering angular velocity value, it is determined that there is an abnormality.

Next, the above processing will be explained in more detail with reference to the flowcharts of FIGS. 3 to 5.

FIG. 3 shows abnormality detection processing using the detected steering angle value, and FIG. 4 shows abnormality detection processing using the detected steering angular velocity value. In addition,
These programs are executed repeatedly at regular time intervals.

In FIG. 183, first, it is checked whether the timer has timed up (step 101). This timer is used to determine the time interval for abnormality detection processing, and if this timer has not timed up, it means that the time for abnormality detection processing has not arrived, and the processing is terminated and the timer is not up. For example, the abnormality detection processing from step 102 onwards is performed. In step 102, the vehicle speed is read from the vehicle speed sensor (4). Next, the maximum steering angle setting value corresponding to the vehicle speed at this time is read from the table (step 103). Next, read the steering angle from the steering angle sensor (5) and use this as the detected value θ (step 104).
. Next, it is checked whether the detected steering angle value θ is greater than or equal to the maximum steering angle setting value 08 (step 105), and if not, it is determined that there is no abnormality in terms of the steering angle, and the NG timer is cleared. Step toe), the process ends. If the detected steering angle value θ is greater than or equal to the maximum steering angle setting value 08 in step 105, it is determined that there is a possibility of an abnormality, and the NG timer is incremented by 1 (step 10
7). Next, it is checked whether or not the NG timer has timed up (step 108), and if the NG timer has not timed up, the process is immediately terminated. If the NG timer times up in step 10g, this means that the detected rudder angle value has been greater than or equal to the maximum rudder angle setting value for a certain period of time, so it is determined that there is an abnormality and fail-safe processing is performed (step 1゜9).

An example of fail-safe processing in step 109 is shown in FIG.

In FIG. 5, first, the fail relay (15) is turned off (step 301). Next, clutch (2) is turned off (step 3o2). Next, the output to the motor (1) is turned off (Step 7'303).

Then turn on the alarm lamp (2o) Step 3
04) Return to step 301.

In FIG. 4, first, it is checked whether the timer has timed up (step 201). This timer is used to determine the time interval for abnormality detection processing, similar to the timer for abnormality processing based on steering angle. , performs abnormality detection processing from step 202 onwards. In step 202, the steering angle is read by the steering angle reading means (16). Next, the steering angle speed is calculated by calculating the difference between the current detected steering angle value θn and the previous detected steering angle value θn−1, and this is calculated as the detected steering angle speed value V
n (step 203). Next, the detected steering angular velocity value V
It is checked whether n is greater than or equal to the maximum steering angular speed setting value Vs (step 204), and if not, it is determined that there is no abnormality in terms of steering angular speed, and the NG timer is cleared (step 205), and the process is performed. finish.

If the detected steering angular velocity value Vn is equal to or greater than the maximum steering angular velocity setting value VS in step 204, it is determined that there is a possibility of an abnormality, and the NG timer is incremented by one (step 206). Next, it is checked whether the NG timer has timed up (step 207), and if it has not timed up, the process is immediately terminated. Step 20
If the NG timer times up in step 7, this means that the detected steering angular velocity value has been greater than or equal to the maximum steering angular velocity setting value for a certain period of time, so it is determined that there is an abnormality and the same fail-safe processing as described above is performed ( Step 208
).

Effects of the Invention According to the electric power steering device of the present invention, as described above, an abnormality in the steering angle detection means can be easily detected without providing two steering angle detection means, and the steering angle detection means can be easily detected. Accidents due to abnormalities in the means can be prevented and the safety of the device can be increased.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an electric power steering device showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between vehicle speed and maximum steering angle setting value, and Fig. 3 is a diagram of abnormality detection processing based on the steering angle. FIG. 4 is a flowchart showing an example of abnormality detection processing based on steering angular velocity, and FIG. 5 is a flowchart showing an example of fail-safe processing. (4)... Vehicle speed sensor, (5)... Rudder angle sensor, (
8)... Rudder angular speed detection means, (9)... Abnormality detection means, (1B)... Rudder angle reading means. that's all

Claims (1)

[Claims] Rudder angle detection means, Rudder angle speed detection means for detecting the Rudder angle speed based on the Rudder angle detected by the Rudder angle detection means, and Rudder angle speed detection when the Rudder angle detection value is equal to or greater than the maximum Rudder angle set value according to the vehicle speed. An electric power steering device comprising abnormality detection means for detecting an abnormality in the steering angle detection means when the value is equal to or greater than a maximum steering angle speed setting value.