JPH0455166A - Electric power steering device - Google Patents

Abstract

PURPOSE:To prevent an accident previously, and improve the safety by detecting abnormality of a clutch when a difference between a maximum value and a minimum value of relative rotational position of an electric motor detected by a rotation detecting means exceeds a value corresponding to a difference between right and left maximum steering positions of a steering wheel CONSTITUTION:When slip is generated in a clutch 2, rotation quantity of a motor 1 becomes larger in comparison with rotation quantity of a steering wheel, and a difference between a maximum value and a minimum value of relative rotational position of the motor 1 detected by a rotation detecting means 8 exceeds a difference between a rotational position that the steering wheel is turned left to the maximum steering position, and a rotational position that the steering wheel is turned right to the maximum steering position. This excess is detected as abnormality by a monitoring means 9, and steering auxiliary by the motor 1 is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an electric power steering device for automobiles and the like.

2. Description of the Related Art As this type of electric power steering device, one is known that uses an electric motor to assist in steering force via a clutch.

Problems to be Solved by the Invention In such an electric power steering device,
Even if the clutch engagement torque decreases due to a drop in the voltage of the clutch drive power supply or a failure in the clutch drive circuit, and slippage occurs in the clutch during steering force assistance, this cannot be detected and the amount of steering force assistance decreases. Not only is this insufficient, but if this condition continues for a long time, the clutch may seize up, which is extremely dangerous.

An object of the present invention is to solve the above problems and provide a safe electric power steering device that can detect clutch slippage.

Means for Solving the Problems An electric power steering device according to the present invention includes: an electric motor for assisting steering force via a clutch; a rotation sensor for detecting rotation of the electric motor; and a rotation sensor for detecting rotation of the electric motor from the output of the rotation sensor. a rotation detection means for detecting the rotation of the electric motor, and a rotation detection means for monitoring the difference between the maximum and minimum relative rotational positions of the electric motor detected by the rotation detection means, and detecting that this difference corresponds to the difference between the maximum steering positions of the left and right sides of the steering wheel. The present invention is equipped with a monitoring means for detecting a clutch abnormality when the value exceeds the threshold value, and a means for prohibiting steering force assistance by the electric motor when an abnormality is detected by the monitoring means.

If there is no slippage in the operating clutch, the amount of rotation of the motor and the amount of rotation of the steering wheel correspond, and the rotational position of the motor is the rotational position when the steering wheel is turned to the left to the maximum steering position and the rotational position when the steering wheel is turned to the right. The rotational position changes within a certain range between the rotational position when the steering wheel is turned to the maximum steering position. Therefore, the difference between the maximum and minimum relative rotational positions of the motor is the difference between the rotational position when the steering wheel is turned to the left maximum steering position and the rotational position when the steering wheel is turned to the right maximum steering position. There's nothing to overcome.

When the clutch slips, the amount of rotation of the motor becomes larger than the amount of rotation of the steering wheel, and the difference between the maximum and minimum relative rotational positions of the motor becomes the difference when the steering wheel is turned to the maximum left steering position. The difference between the rotational position and the rotational position when the steering wheel is turned to the maximum right steering position is exceeded. Then, this is detected as an abnormality by the monitoring means, and steering force assistance by the motor is prohibited.

Embodiments Hereinafter, embodiments of the present invention will be described 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 input torque of the steering shaft, a vehicle speed sensor (4) for detecting vehicle speed, and a motor. A rotation sensor (5) for detecting the rotation of (1), and these sensors (
3) It is equipped with a control device (6) that controls the motor (1) and the clutch (2) based on the outputs of (4) and (5).

The control device (6) is composed of a microcomputer, and includes steering force assistance amount control means (7) and rotation detection means (8).
, monitoring means (9) and fail-safe means (10). The power supply circuit (11) of the control device (8) connects to the battery (main power source) via the key switch (12).
3) is connected to.

The motor (1) and the clutch (2) are connected to a control device (6) via a motor drive circuit (14) and a clutch drive circuit (15), respectively. Motor drive circuit (
14) and the clutch drive circuit (15) are connected to the battery (13) via a fail relay (16),
The fail relay (16) is connected to the control device (6) via a relay drive circuit (17). Further, the motor drive circuit (14) is connected to the control device (6) via a current detection circuit (18).

The key switch (12), torque sensor (3), vehicle speed sensor (4) and rotation sensor (5) are connected to the interface (
19) to the control device (6). Also, the alarm lamp (
20) is connected to the control device (6) via an alarm lamp drive circuit (21).

The rotation detection means (8) reads the rotation signal from the rotation sensor (5) and detects the rotational position of the motor (1). In addition, as the rotation sensor (5), for example, Japanese Patent Application Laid-Open No. 2-24
Appropriate known materials such as those disclosed in Japanese Patent No. 266 can be used.

The steering force assist amount control means (7) controls the motor drive circuit (14) etc. based on the detected torque of the torque sensor (3), the detected speed of the vehicle speed sensor (4), etc., and thereby controls the motor drive circuit (14) etc. Controls the amount of steering force assistance.

The monitoring means (9) updates the maximum and minimum values of the relative rotational position of the motor (1) from the output of the rotation detection means (8) while the clutch (2) is on. difference(
Clutch (2) is determined based on this difference.
Detect slippage.

That is, the monitoring means is configured to detect in advance the difference in rotational position of the motor (1) (the maximum amount of rotation of the motor (1)) corresponding to the difference between the maximum steering positions of the left and right sides of the steering wheel (the maximum amount of rotation of the steering wheel). This is set as the maximum allowable rotation amount of the motor (1). This maximum allowable rotation amount corresponds to the rotation amount of the motor (1) when the handle is turned from the left maximum steering position to the right maximum steering position when the clutch (2) is not slipping. The monitoring means (9) monitors the maximum rotational difference of the motor (1), and if this difference exceeds the maximum allowable rotational amount, it is determined that the clutch (2) is slipping. and,
When slippage of the clutch (2) is detected by the monitoring means (9), the fail-safe means (lO) causes the motor (1
) is performed as a fail-safe process that prohibits steering force assistance.

If the clutch (2) is not slipping, the motor (
The amount of rotation in 1) corresponds to the amount of rotation of the handle, and the rotation position of motor (1) is the rotation position when the handle is turned to the left maximum steering position and the rotation position when the handle is turned to the right maximum steering position. varies within a certain range between rotational positions.

Therefore, the difference between the maximum and minimum relative rotational positions of motor (1) (maximum rotational difference) is the rotational position when the steering wheel is turned to the left maximum steering position and the rotational position when the steering wheel is turned to the right maximum steering position. The difference in rotational position (maximum allowable rotation amount) when

However, when slipping occurs in the clutch (1), the amount of rotation of the motor (1) becomes larger than the amount of rotation of the handle, and the maximum rotation difference of the motors exceeds the maximum allowable amount of rotation. Therefore, slippage of the clutch (2) can be detected by monitoring whether the maximum rotation difference of the motor (1) exceeds the maximum allowable rotation amount as described above.

In addition, the motor (1) detected by the rotation detection means (8)
The rotational position can also be used for steering wheel return control, damping control, etc. by the steering force assist amount control means (7).

Next, the above processing will be explained in more detail with reference to the flowchart shown in FIG. Note that this program is repeatedly executed at regular time intervals.

In FIG. 2, first, the motor rotational position θ is read from the rotation sensor (5) (step 101).

Next, the detected motor rotation position θ is the maximum value θll1aX
It is checked whether it is larger than that (step 102), and if it is larger, θ is set to θl1lax and θ+nax is updated (step 103), and the process proceeds to step 104.

If θ is not larger than θmax in step 102, proceed to step 1 without updating 0IIlaX.
Proceed to 04. In step 104, it is checked whether the motor rotational position θ is smaller than the minimum value θ1n, and if it is,
Set θ to θ1n and update θmin Step 1
05), proceed to step 106. If θ is not smaller than θmin in step 104, the process directly proceeds to step 106 without updating θmin. Step 1
In step 06, the difference θS (maximum rotational difference) between θ+++aX and θmin is determined.

Next, it is determined whether the maximum rotational difference θS is smaller than the maximum allowable rotation amount θa (step 107), and if it is,
It is determined that there is no slippage in the clutch (2), and the process is terminated. If θS is not smaller than θa in step 107, it is determined that clutch (2) is slipping, and fail-safe processing is performed (step 108).
.

An example of the failsafe process of step 108 is shown in FIG.

In FIG. 3, first, the fail relay (16) is turned off (step 201). Next, clutch (2) is turned off (step 202). Next, the output to the motor (1) is turned off (step 203). Then, the alarm lamp (20) is turned on (step 204) and the process returns to step 201.

Figure 4 shows the rotation sensor (5) and its reading circuit (22).
An example of this is shown.

In FIG. 4, a two-phase incremental shift encoder (23) is used as the rotation sensor (5). The reading circuit (22) has an up/down counter (24).
), and when the motor (1), that is, the encoder (23) rotates forward, the count value of the counter (24) is incremented by 1 each time a pulse is generated from the encoder (23), and the encoder (23)
When the encoder (28) rotates in the opposite direction, the count value of the counter (24) is decremented by one each time a pulse is generated from the encoder (28). And this count value is
The control device (6
) is input to the rotation detection means (8).

In the rotation detecting means (8), if the rotational position of the motor (1) is simply determined from the output of the counter (24), the number of bits of the counter (24) is limited, so the maximum It may not be possible to detect all rotational positions of the motor (1) from the steering position to the right maximum steering position.To make this possible, reduce the resolution of the encoder (23) or add an up/down counter. It is necessary to expand the number of output bits.However, lowering the resolution of the encoder (23) lowers the detection accuracy, and adding an up/down counter increases cost.

In this embodiment, in order to solve the above problem, the rotation detecting means (8) calculates the rotational position of the motor (+) from the output of one counter (24) by two times r as follows.・
The rotational position of the motor (1) is detected by counting. Therefore, as will be clear from the following explanation, the number of bits of the count can be expanded and the detection range can be expanded without reducing the resolution of the encoder (23) or adding an up/down counter. It becomes possible to detect all rotational positions of the motor (1) from the left maximum steering position to the right maximum steering position.

The memory of the rotation detecting means (8) has two count areas with the number of bits r, that is, an upper count area that stores 8-bit upper data (count value) θH, and an 8-bit lower data (color). A lower count area is provided to store the value) 6L. The lower count area has a counter (24
) is read as is. The upper count area is for expanding the output of the counter (24),
It is incremented or decremented by 1 by carrying up or down the lower data θL. Then, the number of bits of 2r is counted in these two count areas.

The rotation detection means (8) reads the output of the counter (24) at fixed sampling times. This sampling time is determined so that the amount of change in the output data of the counter (24) does not exceed a certain value (2'-'-1) under any steering conditions. Note that this value will be referred to as the judgment reference value θr. Then, at each sampling time, by comparing the amount of change between the previous value and the current value of the output of the counter (24) with the judgment reference value θr, it is determined whether there is carry-up or carry-down from the lower count area. , increments or decrements the upper count area as necessary.

Next, the above processing will be explained in more detail with reference to the flowchart of FIG. This program is executed repeatedly at regular time intervals.

In FIG. 5, first, it is checked whether the sampling timer has timed up (step 30). This timer is only used to determine the sampling time interval, and if the timer has not timed up, it means that the sampling time has not arrived, and the process is terminated. If the timer has timed up, step 30
2 or less detection processing is performed. In step 302, the output of the counter (24) is read and set in the current lower count area as the current lower data θL. Next, the previous lower data θLn-1 is read from the previous lower count area of the memory (step 303).
. In addition, the previous lower-order data 几. -1 is set in the previous lower count area at the time of previous sampling, as will be described later. Next, it is checked whether the current lower-order data eLn is larger than the previous lower-order data θL0-1 (step 304). θLn is θL.

The difference is larger when there is no carry in the lower data OL during forward rotation, or when there is a carry in the lower data θL during reverse rotation. In this case, θ1. ．． ．． -9
1. It is checked whether o-+ is larger than the judgment reference value θr (step 305). θL, -〇L. -1 is greater than or when the lower data θL0 has a carryover due to reverse rotation; in this case, the upper data θH7 in the upper count area is decremented by 1 (step 30G).
, proceed to step 307. In step 305 θ
L, -0Ln-1 is not greater than or when there is no carry in the lower data θL6 during normal rotation, and in this case, the process directly proceeds to step 307. In step 304, θL is not larger than θL6-1 because either there is no carry in the lower data θL0 during reverse rotation, or there is a carry in the lower data θLfi during forward rotation. In this case, 6L, I-flL, is the criterion value θ[
(step 308). θL
7-1-0 The wrinkle is larger than or when there is a carry in the lower data θL0 during forward rotation.In this case, the upper data θH,, in the upper count area is incremented by 1 (Step 309), Proceed to 307. In step 308, the wrinkle θLn-1-0 is not larger than or when there is no carry-down in the lower-order data θL due to reverse rotation, and in this case, the process directly proceeds to step 307.

In step 307, the current lower data eLo is set in the previous count area and the previous lower data θLn-
1 and terminates the process.

Effects of the Invention According to the electric power steering device of the present invention, as described above, it is possible to detect clutch slippage, prevent accidents caused by clutch slippage, and improve the safety of the device. can.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an electric power steering device showing an embodiment of the present invention, Fig. 2 is a flowchart showing an example of clutch slippage detection processing, and Fig. 3 is a flowchart showing an example of fail-safe processing. , FIG. 4 is a block diagram showing an example of a rotation sensor and its reading circuit, and FIG. 5 is a flowchart showing an example of rotation detection processing by the rotation detection means. (1)...Electric motor, (2)...Electromagnetic clutch,
(5)...Rotation sensor, (8)...Rotation detection means,
(9)...Monitoring means, (io)...Failsafe means. that's all

Claims (1)

[Claims] An electric motor for assisting steering force via a clutch, a rotation sensor for detecting rotation of the electric motor, rotation detection means for detecting rotation of the electric motor from the output of the rotation sensor, rotation detection. The difference between the maximum and minimum relative rotational positions of the electric motor detected by the means is monitored, and if this difference exceeds a value corresponding to the difference between the maximum steering positions of the left and right sides of the steering wheel, it is determined that the clutch is abnormal. An electric power steering device comprising a monitoring means for detecting the abnormality, and a means for prohibiting steering force assistance by an electric motor when an abnormality is detected by the monitoring means.