JP3358330B2 - Control device for electric power 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 control device for an electric power steering device provided with a failure detecting device for fail-safe means.

[0002]

2. Description of the Related Art For example, a fail-safe relay as a fail-safe means provided in a control device of an electric power steering device is opened when an overcurrent flows through a motor for generating an auxiliary steering force, for example. The electric power steering device is turned off, thereby improving safety. However, if a failure occurs such as the relay contact welding due to abnormal discharge or the like, for example, the fail-safe relay cannot be opened, and the current continuously flows through the motor, so that the role of the fail-safe relay is not fulfilled. So, in general,
When the ignition switch is turned on, the relay contact is opened to determine whether or not the terminal voltage of the relay contact is equal to or lower than a predetermined value, thereby detecting the failure of the fail-safe relay.

[0003] Conventionally, an electric power steering apparatus provided with an abnormality detection device for this type of fail-safe relay is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-283568. In this conventional example, when the fail-safe relay is opened and the terminal voltage is read, when the handle is rotated, an electromotive force is generated by the electric motor, and this voltage is applied to the relay circuit to perform accurate abnormality detection. Focusing on the point that it is not possible, the rotation state of the steering wheel is detected by a torque sensor, etc., the fail-safe relay is opened in the non-rotation state, and the terminal voltage of the relay contact is read by the relay abnormality detection means. Is determined whether or not the fail-safe relay is in an abnormal state due to welding or the like by comparing whether or not is smaller than a predetermined value.

[0004]

However, in the above conventional example, when the non-rotational state of the steering wheel is detected, an abnormality is detected as to whether or not the fail-safe relay is in a non-conductive state. If the steering wheel is slightly rotated, it may be erroneously determined that the steering wheel is in a non-rotating state despite the rotating state. Is uncertain.

Further, in the above conventional example, if the driver is turning the steering wheel at the time of the abnormality inspection, the abnormality cannot be detected until the steering wheel becomes non-rotating.
Even if there is an abnormality such as welding at the relay contact, the electric power steering device is in the operating state, and when an abnormality such as overcurrent etc. flows to the electric motor, the fail-safe relay does not work and safety is not ensured Has problems.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a control device for an electric power steering device which solves the above-mentioned problems and can surely perform a non-conductivity test of a fail-safe means even when a steering wheel is rotated. And

[0007]

In order to achieve the above object, a control apparatus for an electric power steering apparatus according to the present invention comprises a torque detecting means for detecting a steering torque of a steering system, as shown in FIG. Detecting means, an electric motor for generating a steering assist force to a steering system, clutch means interposed between the electric motor and the steering system, and at least a torque detection value of the torque detecting means. Control means for outputting a control signal for controlling the electric motor, and a drive current from a power supply is supplied via a fail-safe means responsive to an opening / closing command, and the electric motor is controlled based on a control signal from the control means. the control apparatus for an electric power steering device and a driving means for driving the front
At the time of the abnormality inspection for the fail-safe means, the clutch means is disconnected, and in a state where the release command is output to the fail-safe means, the output voltage of the fail-safe means is detected. A fail-safe abnormality detecting means for comparing the set value and detecting an abnormality is provided.

[0008]

According to the present invention, abnormality detection such as short-circuiting of the fail-safe means is performed during a predetermined abnormality inspection, for example, when an ignition switch is turned on or off. Abnormality detection is performed after disengaging the clutch means inserted between the system and the system.
Since the clutch is disengaged, the electric motor does not rotate even when the steering wheel is rotated, and no electromotive force is generated by the electric motor. Therefore, the voltage generated by the electric motor does not appear at the detection terminal of the fail-safe means at the time of the abnormality test for the fail-safe means.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram of the electric power steering device according to the present invention. In the drawing, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel is transmitted to a steering shaft 2 including an input shaft 2a and an output shaft 2b. One end of the input shaft 2a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2b via a torque sensor 3 as a vehicle detecting means. The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4, and further transmitted to the lower shaft 5.
Is transmitted to the pinion shaft 7 via the The steering force is
Further, the steering wheel 8 is transmitted to the tie rod 9 to steer the steered wheels. The steering gear 8 is formed in a rack-and-pinion shape having a pinion 8a and a rack 8b, and converts the rotational motion transmitted to the pinion 8a into a linear motion by the rack 8b.

A reduction gear 10 for transmitting an auxiliary steering force (assist force) to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The reduction gear 10 transmits and blocks the auxiliary steering force. An output shaft of an electric motor 12 for generating an auxiliary steering force is connected via an electromagnetic clutch device 11 of, for example, an electromagnetic type as a clutch means for performing. The electromagnetic clutch device 11 has a solenoid. When an exciting current is supplied to the solenoid by a controller 13 described later, the reduction gear 10 and the electric motor 12 are mechanically connected to each other, and are separated when the supply of the exciting current is stopped. You.

The torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torque sensor 3 detects the steering torque of the torsion bar inserted between the input shaft 2a and the output shaft 2b. It is configured to convert the torsional angular displacement and to detect the torsional angular displacement with a potentiometer. This torque sensor 3 is, for example,
As shown in FIG. 3, when the input torque is zero, a torque detection value T having a predetermined neutral voltage V ₀ is output, and when turning right, a voltage that increases from the neutral voltage V ₀ according to the steering torque at that time is output. When the steering wheel is turned to the left, a voltage lower than the neutral voltage V ₀ is output according to the steering torque at that time. Then, the output torque detection value T is input to the controller 13.

The controller 13 controls the electric motor 12 according to the detected torque value T and the detected current value of the electric motor 12.
Control the drive current supplied to the
3, a signal corresponding to the drive current of the electric motor 12 is fed back, and the current output from the controller 13 to the electric motor 12 is feedback-controlled by the feedback signal. Furthermore, the controller 1
3 includes an ignition switch 14 and a fuse 1
An electric current is supplied from the battery 16 via 5a, and an electric current is supplied from the battery 16 only through the fuse 15b. The current of the battery 16 supplied only through the fuse 15b is supplied to, for example, a backup memory. Furthermore, for example, a vehicle speed detection signal V _p from a vehicle speed sensor 17 for generating a pulse signal having a period corresponding to the output speed of the transmission is input to the controller 13, the steering assist force corresponding to the vehicle speed is generated.

As shown in FIG. 4, the controller 13
The phase of the torque detection value T supplied from the torque sensor 3 is compensated to enhance the stability of the electric power steering device,
A phase compensation circuit 18 for outputting a compensated torque detection value T _P to the A / D converter 20a, and integrates the number of pulses per unit of supplied vehicle speed detection signal V _P time from the vehicle speed sensor 17 vehicle speed detecting value V And a counter circuit 19 for resetting the count value by the microcomputer 21 when the vehicle speed detection value V is read by the microcomputer 21 described later, a phase-compensated torque detection value _TP , and a terminal described later. voltage Vi and the motor current detection signal I _R, and converts the I _L into a digital signal, respectively the torque detection value T _D, the terminal voltage value Vir and motor current detection value i _R,
an A / D converter 20a to 20d to output a i _L, the counter circuit 19 and the A / D converter output signal 20a to 20d, the microcomputer 21 the detection signal I _G of the ignition switch 14 is supplied to further below When,
Motor driving circuit 2 as driving means for driving electric motor 12 based on an output signal of microcomputer 21
2, a fail-safe relay circuit 23 as a fail-safe means for supplying the input power supply current to the motor drive circuit 22, a clutch drive circuit 24 for driving the electromagnetic clutch device 11 based on an output signal of the microcomputer 21, detecting the magnitude and direction of the motor current supply its motor current detection signal I _R, a current detection circuit 25 that feeds back the I _L in the microcomputer 21, after off of the ignition switch 14, a power supply at a predetermined time the microcomputer 21 And a stabilized power supply circuit VR. The phase compensation circuit 18, the A / D converter 20a, and the microcomputer 21 constitute control means.

[0014] The microcomputer 21 includes an input interface 21a counter circuit 19 and the A / D output signal of the transducer 20a to 20d, the further detection signal I _G is input
The abnormality detection process of the fail-safe relay circuit 23 is executed, and the electric motor 12 is controlled according to the torque detection value T.
Central processing unit (CPU) 21 for executing drive control processing
b, a memory 21c for storing a processing procedure for detecting an abnormality of the fail-safe relay circuit 23, and for storing a drive control processing procedure for the electric motor 12, and a backup memory for storing that there is an abnormality in the fail-safe relay circuit 23. 21d and an output interface 21e.

An output interface 21e outputs a motor drive signal S, which will be described later, output from the central processing unit 21b.
Pulse width modulation signal PWM the pulse width of which changes in accordance with the voltage value of _M, and outputs the right direction signal D _R and the left direction signal D _L defining the direction of rotation of the electric motor 12, each of these signals are both motor-driven The relay control signal S _R , the clutch control signal S _C, and the warning display signal A are output to the fail-safe relay circuit 23, the clutch drive circuit 24, and the warning display circuit 26, respectively. Supplied.

The microcomputer 21 is supplied with the current of the battery 16 via a power supply holding circuit VK and a stabilized power supply circuit VR. Even after the ignition switch 14 is turned off, the power holding circuit VK
Power is supplied to the microcomputer 21 for a predetermined time to enable predetermined control processing, and the stabilized power supply circuit VR outputs the power supplied from the power supply holding circuit VK to the microcomputer 21 at a constant voltage.

The power holding circuit VK is a drive circuit VKD and the power supply holding relay VKR, the driving circuit VKD, is inputted detection signal I _G supplied from the ignition switch 14, a high-level detection driving circuit VKd by the input signal I _G is turned on, thereby being supplied exciting current to the driving coil of the power supply holding relay VKR closed power holding relay VKR, supply current of the battery 16 is supplied to the microcomputer 21 . Also,
The driving circuit VKd is supplied with the power supply holding signal S _V from the output interface 21e, the drive circuit VKd is a driving circuit VKd off state when the power supply holding signal S _V and the detection signal I _G are both at low level It has an AND circuit. Therefore, the drive circuit VKd is turned off when the power supply holding signal of the low level S _V and detection signal I _G is supplied together, thereby, the power supply holding relay VKr
Is opened, and the power supply to the microcomputer 21 is cut off.

Here, power is constantly supplied to the backup memory 21d via the fuse 15b. Further, the detection signal I _G applied to the input interface 21a via the ignition switch 14 becomes a high level during on of the ignition switch 14, a low level when off. Thus, the microcomputer 21 detects the on / off state of the ignition switch 14.

The motor drive circuit 22 includes the gate drive circuit 2
2a, an H bridge circuit 22b, and a step-up power supply 22c. The gate drive circuit 22a outputs the supplied left and right direction signals D _{R and} D _L to the H-bridge circuit 22b and shapes the supplied pulse width modulation signal PWM so as to improve the response of the electric motor 12. The pulse width modulation signal PWM is switched and output in accordance with the supplied left and right direction signals D _{R and} D _L. For example, when a right direction signal D _R is supplied, when outputting a pulse width modulation signal PWM only 22 b 2 FET (Field Effect Transistor), described later, of the H-bridge circuit 22b, a left direction signal D _L is supplied, later The pulse width modulation signal PWM is output only to the FET 22b1 which performs the pulse width modulation.

The H-bridge circuit 22b supplies a drive current to the electric motor 12 based on an output signal of the gate drive circuit 22a, and supplies four switching transistors, for example,
It has N-channel power MOS type FETs 22b1 to 22b4, and has a source terminal of the FET 22b1 and an FET 22b3.
Series circuit with the drain terminal of
A series circuit in which the source terminal of the FET 22b2 and the drain terminal of the FET 22b4 are connected is arranged in parallel, and the electric motor 12 is interposed between the connection parts of the FETs in each series circuit. In the upper side of the gate terminals of the FET22b1 and 22 b 2, the left-right direction current from the gate driver circuit 22a D _R, D
Pulse width modulation signal PWM in response to _L is supplied to the gate terminal of each FET22b3 and 22b4 of the lower side, the right direction signal D _R and the left direction signal D _L each of which is supplied from the gate driver circuit 22a. A fail-safe relay circuit 23 is connected to the drain terminals of the FETs 22b1 and 22b2.
The current of the battery 16 is supplied via the fuse 15a and the ignition switch 14, and the FET 2
Source terminals of 2b3 and FET 22b4 are grounded via current detection resistors R1 and R2, respectively.

Here, the FET 22b3 and the FET 22b4
, When the right direction signal D _R and the left direction signal D _L each Le base Haile turned on. When the FET 22b3 is ON, the pulse width modulation signal PW is supplied to the FET 22b2.
When M is supplied, the motor drive current becomes FET
It flows from 22b2 to the direction of the electric motor 12 and the FET 22b3. On the other hand, when the FET 22b4 is on, the FE
When the pulse width modulation signal PWM is supplied to T22b1, the motor drive current flows from the FET 22b1 toward the electric motor 12 and the FET 22b4.

The step-up power supply 22c is an H-bridge circuit 22b
Among them, a voltage which is required to drive the FETs 22b1 and 22b2, for example, a voltage which is twice as high as the battery voltage is supplied to the gate drive circuit 22a. In addition,
In order to drive the FETs 22b3 and 22b4, the battery voltage is supplied to the gate drive circuit 22a via the fail-safe relay 23a.

The fail-safe relay circuit 23 includes a fail-safe relay 23a having a relay contact 23c and a relay drive circuit 23b for supplying an exciting current to a drive coil of the fail-safe relay 23a. It is controlled by the supplied relay control signal S _R. One end of the relay contact 23c is connected to the battery 16 via the fuse 15a and the ignition switch 14, and the other end is connected to the H-bridge circuit 22.
Are connected to the respective drain terminals of the FETs 22b1 and 22b2, and are connected to the input interface 21a via the A / D converter 20b, and the microcomputer 21 executes the abnormality detection of the terminal voltage Vi at the other end.
In this embodiment, when the relay control signal S _R is at the high level, the relay driving circuit 23b is the exciting current to the driving coil of the fail safe relay 23a turned on is supplied closed relay contacts 23c, whereas the relay control signal when S _R is low, the relay driving circuit 23b is the relay contact 23c turned off is opened. Generally, during operation of the electric power steering device, the relay contact 23c is closed, and when an abnormality occurs in the motor drive circuit 22 or the like, the relay contact 23c is opened for ensuring safety.

The clutch drive circuit 24 amplifies the supplied clutch control signal S _C and outputs a signal for controlling the drive of the electromagnetic clutch device 11. In this embodiment, a clutch control signal S _C is an electromagnetic clutch device when the high level 11
Is in the connected state, and is kept in the disconnected state when it is at the low level. Current detection circuit 25, the inputted current detecting resistor R _R, R to amplify the terminal voltages of the _L detects the respective motor drive current to remove noise, the motor current detection signal I of the detected right _R and leftward motor current detection signal I _L, respectively a / D converters 20c and 20d
Through the input interface 21a. As a result, the microcomputer 21 corrects the pulse width of the pulse width modulation signal PWM and stops the operation of the electric power steering device when an abnormality occurs, according to the actually measured value of the motor current.

Next, FIG. 5 shows a processing procedure according to the present embodiment in which when a power is supplied to the microcomputer and the electric power steering apparatus is brought into the operating state, the central processing unit detects an abnormality of the relay contact. This will be described based on a flowchart. This process is executed as a part of the process in the initial state when the ignition switch is turned on.

First, when power is supplied to the microcomputer 21 by turning on the ignition switch 14, at step S1, the backup memory 21 is turned on.
The abnormality detection flag stored in the predetermined storage area d is read. The backup memory 21d stores an abnormality detection flag having a logical value "1" indicating an abnormal state when an abnormality of the relay contact 23c is detected in an abnormality detection process when the ignition switch 14 is in an OFF state described later. You. Therefore, when the microcomputer 21 is started, the abnormality detection flag stored in the backup memory 21d is read. Here, the microcomputer 2
1, when the high level detection signal _IG is input, the high level power supply holding signal S from the output interface 21c.
Outputs a _V to the drive circuit KVd to maintain the operating state of the power holding circuit VK, after the ignition switch 14 executes a predetermined process when turned off, and outputs a power supply holding signal S _V for the low level, the power supply The holding relay VKr is opened to stop the power supply to the microcomputer 21.

Next, the process proceeds to step S2, where it is determined whether or not the abnormality detection flag is "1". When it is determined that the logical value is "1", the process proceeds to step S3. In step S3, a high-level warning signal is output from the output interface 21e to the warning display circuit 26, for example, turning on a warning light provided on the instrument panel of the driver's seat to indicate that the relay contact is in an abnormal state. I do.
Then, the process proceeds to step S4, and an upper-level program such as a main processing program is notified of an abnormality that the abnormality detection flag is "1" so that the motor drive control processing of the electric power steering apparatus shown in FIG. 6 is not executed. Then, the abnormality detection processing ends.

[0028] In the judgment of step S2, the abnormality detection flag when the logic value "0" indicating the normal state, the process proceeds to Step 5, and outputs a relay control signal S _R of low level from the output interface 21e, Relay drive circuit 2
3b is turned off. As a result, the energization of the relay coil is cut off, and the relay contact 23c is opened by, for example, a biasing force of a spring or the like. And step S
6, the output interface 21e outputs a low-level clutch control signal S _C for turning off the clutch, and holds the electromagnetic clutch device 11 in the disconnected state. In the present embodiment, the electromagnetic clutch device 11 is kept in the disconnected state until the abnormality check on the relay contact 23c is completed.

Next, the process proceeds to step S7 to read the terminal voltage value Vir of the relay contact 23c and store it in a predetermined storage area of the memory 21c. Then, the process proceeds to step S8 to compare the terminal voltage value Vir with the preset voltage Vr preset in the memory 21c to determine whether the terminal voltage value Vir is equal to or lower than the preset voltage Vr. If the relay contact 23c is not contacted by welding or the like, it is normal that Vir ≦ V
On the other hand, when there is an abnormality due to contact welding or the like, conduction between the relay contacts causes substantially the same voltage as that of the battery 16 to appear at the measurement terminal, and Vir> Vr. Here, the same voltage as the set voltage Vr is set to H
Even when the electric power is supplied to the bridge circuit 22b, the electric motor 12 is set to an upper limit value at which the electric motor 12 is not driven. By the above steps S5 to S8, a fail-safe relay abnormality detecting process as a fail-safe abnormality detecting means is executed.

As a result of the comparison between the terminal voltage Vir and the set voltage Vr, if Vir ≦ Vr, the flow shifts to step S9. In step S9, a high-level relay control signal S _R is output from the output interface 21e, and the relay drive circuit 23
b is turned on, the relay contact 23c of the fail-safe relay 23a is closed, and the current of the battery 16 is supplied to the H-bridge circuit 22b. Then, step S1
The output goes to 0 to output a high-level clutch control signal S _C from the output interface 21 e to bring the electromagnetic clutch device 11 into the connected state. Thus, the abnormality detection processing ends, and thereafter, the motor drive control processing of the power steering apparatus shown in FIG. 6 starts.

As a result of the determination in step S8, Vir> Vr
As determined relay contact 23c is abnormal when, the process proceeds to step S11, the pulse width modulation signal PWM outputted from the output interface 21e, the right direction signal D _R,
And the left direction signal D _L is set to a low level. As a result, the drive signal is not supplied to the H-bridge circuit 22b, so that the operation of the power steering device is not performed.

Then, the process proceeds to step S12, and similarly to step S3, a warning lamp is turned on to indicate that the state is abnormal. Next, in step S13, similarly to step S4, the abnormality detection flag is set to "1" so as not to execute the motor drive control processing of the electric power steering apparatus, and the upper-level program such as the main processing program is set. This abnormality notification is performed and the abnormality detection processing ends.

Next, the processing procedure of the drive control processing of the electric power steering apparatus started by the host program when it is determined that there is no abnormality as a result of the abnormality detection processing will be described with reference to the flowchart shown in FIG. I do. This motor drive control process is performed by a timer interrupt every predetermined time set in advance.
This is executed every ec.

First, in step S21, the A / D converter 2
Via 0a, the torque voltage value T from the torque sensor 3 that has undergone phase compensation by the phase compensator 18 is read. Then
The process proceeds to step S22, where an operation of T = T−V ₀ is performed, and an offset process is performed so that the detected torque value T at the time of neutralization becomes zero. Next, the process proceeds to step S23, in which the count value of the counter 19, that is, the vehicle speed detection value V is read, a reset signal is output to the counter 19 to reset the counter value, and then the process proceeds to step S24, where FIG. For example, a motor current corresponding to a detected torque value T and a detected vehicle speed value V is searched for with reference to a characteristic diagram showing the correspondence between the steering torque, the vehicle speed, and the motor current shown in FIG. Set as _I.

This characteristic diagram shows that the steering shaft 2
FIG. 4 shows a correspondence between a motor current required to drive the electric motor 12 to generate a steering assist force corresponding to the steering torque input to the electric motor 12, a steering torque, and a vehicle speed. The motor current command value is set to increase as the vehicle speed decreases, and the motor current command value increases as the steering torque increases.

Then, the process proceeds to step S25, in which the motor current command value S _I is differentiated to obtain a differentiated value f _D. Then, in step S26, the rightward motor current detection value i _R and the left direction read motor current detection value i _L, the right direction of the motor current detection value i _R a positive value, setting the leftward motor current detection value i _L as a negative value, the motor current detected from the sum of these detection signals Calculate the value i _M.
That is calculated by i _M = i _R -i _L.

Here, in the current detection circuit 25, it is assumed that sufficient filtering is performed on each signal so as to obtain the effective values of the motor current detection values i _R and i _{L in} the horizontal direction. Next, the process proceeds to step S27, for example, where an abnormality monitoring process as shown in the flowchart of FIG. 8 is performed.

In the abnormality monitoring process, first, in step S27a
Then, it is determined whether or not the absolute value | i _M | of the motor current detection value i _M is smaller than a preset maximum current value I _MAX that is regarded as normal operation of the motor drive circuit 22. When the absolute value | i _M | is smaller than the maximum current value I _MAX ,
It is determined that the motor drive current is within the normal range, and the process returns to the motor drive control processing program.

On the other hand, as a result of the determination in step S27a, |
If i _M | ≧ I _MAX , it is determined that an excessive current is flowing through the H-bridge circuit 22b and an abnormality has occurred, and the flow shifts to step S27b. In step S27b, the respective command signals S _M , D _R , and D _L to the gate drive circuit 22a are output as “LOW”, whereby the energization of the H-bridge circuit 22b is cut off. Next, the process proceeds to step S27c, in which the output of the clutch control signal S _C to the clutch drive circuit 24 is stopped, so that the electromagnetic clutch device 11 is operated to operate the output shaft of the electric motor 12 and the reduction gear 10.
And are in a detached state.

Then, the process shifts to step S27d to set the relay control signal S _R to the relay drive circuit 23b to "LOW".
Output as fail-safe relay 2
2a is opened and the H-bridge circuit 2
The power supply to 2b is cut off. Next, in step S27e,
For example, an abnormality notification is sent to a higher-level program such as a main processing program, and the process ends. Thereafter, the motor drive control process is not executed in the host program.

If no abnormality is detected in the motor drive current as a result of the abnormality monitoring process in step S27, the process proceeds to step S28. At step S28, the motor current command value S _I and Step S2 set in step S24
6, the difference from the detected motor current value i _M ,
The current deviation e _M is calculated according to e _M = S _I −i _M.

Next, in step S29, the current deviation e _M
Is multiplied by a predetermined proportional gain to obtain a proportional processing value f _P. Further, in step S30, the proportional processing value f _P is integrated and this is set as an integration processing value f _I to obtain a proportional processing value f _P and an integration processing. The value f _I is stored in a predetermined storage area of the memory 21c. Then, in step S31, the differential processing value f
_D , the proportional processing value f _P and the integration processing value f _I are added,
This was a motor drive signal S _M, the process proceeds to step S32.

[0043] In step S32, the motor drive signal S _M is equal to or a S _M ≧ 0, when a S _M ≧ 0 is the step S33 as a steering wheel 1 is rightward steering migrated, the right direction signal D _R for setting the direction of rotation of the electric motor 12 in the normal rotation direction "HIG
"With a, a left direction signal D _L" H output as LOW ". In addition, it outputs a motor drive signal S _M to the output interface 21e, on the basis of the sawtooth wave generated in the output interface 21e, converts the voltage of the motor drive signal S _M to the pulse width modulation signal PWM having a predetermined pulse width and supplies it to the H-bridge circuit 22b it through the gate drive circuit 22a. then, end the motor drive control program And return to the main program.

On the other hand, if S _M ≧ 0 is not satisfied in step S32, it is determined that the steering wheel 1 has been steered to the left, and the flow shifts to step S34 to change the rotation direction of the electric motor 12 to the reverse rotation direction. Left direction signal D to be set
_L together with a "HIGH", the right direction signal D _R "L
Output as OW ". Also, by converting the motor drive signal S _M to the pulse width modulation signal PWM, and supplies the H-bridge circuit 22b via the gate drive circuit 22a. Then, exit the motor driving control processing program To return to the main program.

Next, a processing procedure according to the present embodiment for detecting an abnormality of the relay contact by the central processing unit when the power applied to the electric power steering device is turned off will be described with reference to a flowchart shown in FIG. It will be described based on the following. This process is also executed by, for example, a timer interrupt process for a predetermined main program at predetermined time intervals.

First, in step S1a, it is detected whether or not the ignition switch 14 has been turned off.
In the embodiment, when the detection signal _IG is at a low level, the ignition switch 14 is turned off. If the off state of the ignition switch 14 is not detected,
Return to the main program. On the other hand, when the off state of the ignition switch 14 is detected, step S
Shift to 5a.

In step S5a, a low-level clutch control signal S _C is output from the output interface 21e, and the electromagnetic clutch device 11 is kept in a disconnected state. Then control proceeds to step S6a, outputs a relay control signal S _R of low level, to turn off the relay driving circuit 23b. Then, similarly to the abnormality detection performed when the ignition switch 14 is turned on, the processing of steps S7 and S8 is executed. The above step S5a,
In S6a, S7, and S8, a fail-safe relay abnormality detection process as a fail-safe abnormality detection unit is executed.

In step S8, as a result of comparison between the terminal voltage value Vir and the set voltage Vr, when Vir ≦ Vr, it is determined that the relay contact 23c is normal, and the flow shifts to step S51 where the low-level power supply holding signal It stops the power supply to the microcomputer 21 outputs a S _V, and ends the processing of the abnormality detection. As a result of the comparison in step S8, Vir>
At Vr, it is determined that the relay contact 23c is abnormal, and the process shifts to step S52. In step S52,
For example, an abnormality detection flag having a logical value “1” indicating an abnormal state is stored in a predetermined storage area of the backup memory 21d. Then, the process proceeds to step S53,
As in the case of 51, a low-level power holding signal S _V is output to stop the power supply to the microcomputer 21 and the abnormality detection processing ends.

Next, the overall operation of this embodiment will be described.
In the present embodiment, first, when the ignition switch 14 is turned on, a process of determining whether or not the abnormality detection flag is set to "1" in the backup memory 21d as shown in step S1 is executed. When the abnormality detection flag is set to "1", a warning lamp provided on the instrument panel is turned on to warn the driver that the relay contact is in an abnormal state. When the abnormality detection flag is set to “0”, the electromagnetic clutch device 11 is disconnected, an abnormality such as contact welding of the relay contact 23c is detected, and the process of detecting the terminal voltage of the relay contact 23c is performed. Be executed. When the abnormality of the relay contact 23c is detected, the operation of the electric power steering device is not performed. When the abnormality is not detected, the process shifts to the control of the normal auxiliary steering torque, and the drive control process of the electric power steering device is executed.

Similarly, when the ignition switch 14 is turned off, the electromagnetic clutch device 11 is disconnected, and the process of detecting the abnormality of the relay contact 23c is executed. When an abnormality is detected, the backup memory 21
d stores an abnormal state, and the relay contact 23c is checked by the next abnormality check when the ignition switch 14 is turned on.
Is displayed on the warning light. If no abnormality is detected, the abnormality detection process is terminated.

As described above, according to the present embodiment, at the time of the abnormality detection processing of the fail-safe relay when the ignition switch is turned on and off, the terminal of the relay contact of the fail-safe relay is set after the electromagnetic clutch device is disconnected. It checks whether the voltage is below a certain value. Therefore, during the abnormality detection processing, the electric motor does not rotate even if the steering wheel is rotated, so that the influence of the power generation due to the rotation of the steering wheel can be avoided, and the abnormality such as welding of the relay contact can be reliably performed. Can be detected. Further, it is also possible to prevent the abnormality detection processing from being executed until the steering wheel is in a non-rotating state. When the ignition switch is turned on, abnormality detection of the relay contact is executed, and when the abnormality is detected, the electric power steering device is activated. Is stopped, so safety is ensured. In particular, when an abnormality is found in the fail-safe relay as a result of abnormality detection when the ignition switch is turned off, the abnormality is stored, and an abnormal state is displayed by turning on a warning light or the like when the vehicle starts. . Therefore, the driver can surely know at the time of starting that the fail safe relay has an abnormality.

Although the relay circuit is used as the fail-safe means in the above embodiment, a switching semiconductor element such as a transistor or a F
You may comprise using ET etc. Further, in the above embodiment, the abnormality of the terminal voltage of the fail-safe relay is detected when the ignition switch is turned on. However, the present invention is not limited to this. An abnormality detection of the safe relay may be performed.

In the above embodiment, the ignition
Although the failure detection of the fail-safe relay is performed when the switch is turned on and off, the above effect can be obtained even if the failure is detected when the switch is turned on or off. Further, the abnormality detection of the terminal voltage of the relay contact is performed by the comparator. For example, the set voltage Vr is input to one input terminal of the comparator, and the terminal voltage Vi of the fail-safe relay is input to the other input terminal. May be compared to detect an abnormality.

In the above embodiment, the motor drive signal value output from the central processing unit is converted into a pulse width modulation signal to drive the electric motor, but the motor drive signal value is converted into a pulse width modulation signal. The voltage is converted to an analog voltage signal without conversion, and the voltage proportional to this analog voltage is applied to the base terminal of each NPN transistor by using an NPN transistor instead of each FET to which the pulse width modulation signal PWM is input. Thus, a configuration in which the electric motor is driven may be adopted.

Further, in the above embodiment, the motor drive signal value is calculated by performing all the processes of the proportional process, the integration process, and the differentiation process. May be set arbitrarily. Further, in the above embodiment, the case where the fail-safe abnormality detecting means is formed by a microcomputer has been described. However, the present invention is not limited to this, and it is possible to combine electronic circuits such as an arithmetic circuit, an adder circuit, and a logic circuit. It is.

In the above embodiment, the case where the motor drive circuit is constituted by the FET has been described. However, the present invention is not limited to this, and another switching element such as a bipolar transistor can be applied. Also, in detecting an abnormality of the fail-safe relay when the ignition switch is turned off, the motor drive current is gradually reduced to reduce kickback that occurs when the drive current is stopped instantaneously while steering the steering wheel. May be lowered. In this case, the current supplied to the fail-safe relay circuit 23 is supplied not from the ignition switch 14 and the fuse 15a but from the output of the stabilized power supply circuit VR,
A drive current can be supplied to the motor drive circuit even after the ignition switch 14 is turned off. When it is determined in step S1a that the ignition switch 14 is off, the microcomputer 21 outputs, for example, a pulse width modulation signal PWM in which the pulse width on the high level side is gradually narrowed to reduce the motor drive current. After gradually decreasing the motor current detection value, the process proceeds to step S5a to release the clutch.

Further, in the above embodiment, the motor drive control for detecting the steering state based on only the detected torque value and generating the auxiliary steering torque according to the detected torque value has been described. When changing the traveling lane during high-speed driving, in addition to the steering torque, the steering state is detected in accordance with the steering angular velocity and the steering angular acceleration of the steering wheel, and an auxiliary torque corresponding to these values is generated. Motor drive control may be performed. FIG. 10 is a schematic block diagram of a control circuit that detects a steering state based on the detected torque value, the steering angular velocity value, and the steering angular acceleration value.

As shown, the control circuit 21A includes a current command calculator 31, an adder / subtractor 32, a proportional calculator 33, an integration calculator 34, an adder 35, a steering angular velocity acceleration calculation circuit 36, a damper Coefficient circuit 37 and inertia compensation coefficient circuit 3
And 8. The torque detection value T is determined by the control circuit 21
Is input to the current command calculator 31 A, after being converted into a predetermined motor current command value S _I, is supplied to the adder-subtracter 32. In addition to the motor current command value S _I , the adder / subtractor 32 further outputs a current detection signal i _M , a damper signal D _I , which is an output signal of each of the current detection circuit 25, the damper coefficient circuit 37, and the inertia compensation coefficient circuit 38. The inertia signal K _I is supplied, and the current detection signal i _M is supplied to the motor current command value S _I.
Subtraction, subtraction of the damper signal D _I, and the processing of the addition of the inertial signal K _I is performed. The proportional calculator 33 to which the output signal of the adder / subtractor 32 is supplied is multiplied by a predetermined proportional gain.
The multiplied value is directly supplied to the adder 35, and is also supplied to the adder 35 via the integration calculator 34 that performs a predetermined integration process. Then, a predetermined motor drive signal is output from the adder 35 to the motor drive circuit 22. The motor drive circuit 22 outputs a pulse width modulation signal PWM having a predetermined pulse width to the steering angular velocity acceleration calculation circuit 36 and supplies a motor drive current to the electric motor 12. Then, from the electric motor 12, the motor drive current value i is transmitted to the steering angular velocity acceleration calculation circuit 36 and the current detection circuit 2.
5 is output. The steering angular velocity acceleration calculation circuit 36 outputs the steering angular velocity ω ₀ calculated based on the input pulse width modulation signal PWM and the motor current value i to the damper coefficient circuit 37, and outputs the calculated steering angular acceleration ω ₁ to the inertia. Output to the compensation coefficient circuit 38.

The calculation of the steering angular velocity ω ₀ and the steering angular acceleration ω ₁ in the steering angular velocity acceleration calculation circuit 36 is performed as follows.
First, using the duty ratio D of the pulse width modulation signal PWM and the power supply voltage V _BAT , the average voltage V supplied to the electric motor 12 can be expressed by the following equation. V = D · V _BAT (1) When the electric motor 12 rotates, a back electromotive force is generated. If the back electromotive force constant is k _T , the electric motor 12
Is equal to k _T · ω ₀ , so the average voltage V supplied to the electric motor 12 having the coil resistance R can be expressed by the following equation.

V = k _T · ω ₀ + R · i (2) From equations (1) and (2), the steering angular velocity ω ₀ is obtained as follows. ω ₀ = (D · V _BAT −R · i) / k _T (3) By differentiating equation (3) with time t, the steering angular acceleration ω
₁ is calculated. The calculated steering angular velocity ω ₀ is multiplied by a predetermined damper coefficient K _{V in} a damper coefficient circuit 37, and the multiplied value is subtracted from the motor current command value S _I to execute damper control, whereby the steering system is controlled. An electric viscous resistance is given to improve the stability of the vehicle. Further, the calculated steering angular acceleration omega ₁ is multiplied by the inertia compensation coefficient circuit 38 with a predetermined inertia compensation factor K _G, and executes the inertia compensation control by adding the multiplication value and the motor current command value S _I ,
A delay in motor responsiveness due to motor inertia is compensated. Incidentally, the steering angular acceleration ω ₁ may be directly detected by a sensor.For example, an angle value detected by an angle sensor attached to a motor shaft is differentiated with respect to time t to obtain a steering angular velocity ω ₀ first. Differentiate again and steer angular acceleration ω
You may ask for ₁ .

[0061]

As described above, according to the present invention, at the time of the failure inspection of the fail-safe means, the failure detection is performed after the clutch means inserted between the electric motor and the steering system is disconnected. ing. For this reason, even if the steering wheel is rotated at the time of the abnormality inspection, the electric motor does not rotate, so that there is no power generation, and it is possible to reliably detect the non-conduction abnormality of the fail-safe means.

Further, at the time of the abnormality inspection, the abnormality detection processing is executed irrespective of the rotation state of the steering wheel. Therefore, it is possible to prevent the electric power steering apparatus from operating while the fail-safe means is in an abnormal state. This has the effect of improving the safety of the vehicle.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims according to the present invention.

FIG. 2 is a schematic configuration diagram of an electric power steering device showing one embodiment of the present invention.

FIG. 3 is a characteristic diagram of a torque detection signal.

FIG. 4 is a block diagram of a control device of the electric power steering device according to the embodiment.

FIG. 5 is a flowchart showing a processing procedure for detecting an abnormality of a relay contact by the central processing unit when the ignition switch is turned on according to the embodiment.

FIG. 6 is a flowchart showing a control processing procedure by the central processing unit when the electric power steering device according to the embodiment is operated.

FIG. 7 is a characteristic diagram showing a motor current command value with respect to a steering torque using a vehicle speed as a parameter.

FIG. 8 is a flowchart illustrating a motor drive current abnormality monitoring procedure according to the embodiment;

FIG. 9 is a flowchart showing a processing procedure for detecting an abnormality of a relay contact by the central processing unit when the ignition switch is turned off according to the embodiment.

FIG. 10 is a schematic block diagram of a control circuit that detects a steering state based on a detected torque value, a steering angular velocity value, and a steering angular acceleration value.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 steering shaft 3 torque sensor 10 reduction gear 11 electromagnetic clutch device 12 electric motor 13 controller 14 ignition switch 17 vehicle speed sensor 21 microcomputer 22 motor drive circuit 23 fail-safe relay circuit 24 clutch drive circuit S5 to S8 abnormality detection processing (Abnormality detection means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-283568 (JP, A) JP-A-6-298104 (JP, A) JP-A-2-81769 (JP, A) JP-A-7- 33033 (JP, A) JP-A-60-67262 (JP, A) JP-A-63-215461 (JP, A) JP-A-2-270675 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00-6/06 B62D 5/00-5/32

Claims (1)

(57) [Claims] 1. A torque detecting means for detecting a steering torque of a steering system, an electric motor for generating a steering assist force for the steering system, and a clutch means interposed between the electric motor and the steering system. And control means for outputting a control signal for controlling the electric motor based on at least the torque detection value of the torque detection means, and drive current from a power supply is supplied via fail-safe means responding to an open / close command, and A drive unit for driving the electric motor based on a control signal of the control unit, wherein the clutch unit is in a non-connected state when an abnormality is checked for the fail-safe unit , and Detecting the output voltage of the fail-safe means in a state where an open command is output to the fail-safe means, and setting the detected voltage value and A control device for an electric power steering device, comprising: fail-safe abnormality detecting means for detecting an abnormality by comparing with a fixed value.