JP2009061851A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device specifying the cause of an abnormality fast and informing a driver of generation of the abnormality fast. <P>SOLUTION: The electric power steering device is provided with an abnormality detection part 110 for detecting an abnormality of the electric power steering device or the vehicle; an abnormality storage part 111 for storing the abnormality detected by the abnormality detection part 110; and a detection condition setting part 112 for setting the detection condition of the abnormality detection part 110. The detection condition of the detection condition setting part 112 is changed according to the storage of the abnormality storage part 111. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering device that applies a steering assist force to a steering system, and in particular, when an electric power steering device (drive control device, torque sensor, motor, etc.) or a vehicle abnormality (including a failure) is detected. The present invention relates to an electric power steering apparatus having a function for quickly identifying and restoring the cause of an abnormality.

  The general configuration of the electric power steering apparatus will be described with reference to FIG. 9. The column shaft 2 of the steering handle 1 is connected to the tie rod 6 of the steering wheel via the reduction gear 3, the universal joints 4 A and 4 B and the pinion rack mechanism 5. It is connected. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is connected to the column shaft 2 via the reduction gear 3. ing. Electric power is supplied from the battery 14 to the control unit 100 that controls the electric power steering apparatus, and an ignition key signal is input via the ignition key 11. The control unit 100 calculates the steering assist command value I of the assist (steering assist) command based on the steering torque T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and the calculated steering Based on the auxiliary command value I, the current supplied to the motor 20 is controlled. An engine speed sensor 15 for detecting the engine speed is provided, and the detected value Rs is input to the control unit 100.

  The control unit 100 is mainly composed of a CPU (or MPU or MCU). FIG. 10 shows general functions executed by a program inside the CPU.

  The function and operation of the control unit 100 will be described with reference to FIG. 10. The steering torque T detected by the torque sensor 10 is phase-compensated and phase-compensated by the phase compensator 101 in order to improve the stability of the steering system. The steering torque TA is input to the steering assist command value calculation unit 102. Further, the vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculation unit 102. The steering assist command value calculation unit 102 refers to an assist map (lookup table) 103 based on the input steering torque TA and vehicle speed V, and a steering assist command value that is a control target value of the current supplied to the motor 20. Iref is determined.

  The steering assist command value Iref is input to the subtraction unit 100A and is also input to the feedforward differential compensation unit 104 for increasing the response speed. The deviation (Iref-i) obtained by the subtraction unit 100A is the proportional calculation unit 105. And is input to the integral calculation unit 106 for improving the characteristics of the feedback system. The output of the proportional calculation unit 105 and the output of the integral calculation unit 106 are respectively input to the addition unit 100B, the output of the differential compensation unit 104 is also added to the addition unit 100B, and the current command value E as the addition result in the addition unit 100B is obtained. The motor drive signal 107 is input as a motor drive signal. The motor current value of the motor 20 is detected by the motor current detection circuit 108, and the detected motor current detection value i is input to the subtraction unit 100A and fed back. Electric power is supplied from the battery 14 to the motor drive circuit 107, and the motor drive circuit 107 is configured by an H bridge (in the case of a two-phase motor) or a three-phase bridge (in the case of a three-phase motor) of drive elements such as FETs.

  In such an electric power steering device, for example, in the device disclosed in Japanese Patent Application Laid-Open No. 2004-299616 (Patent Document 1), a steering torque sensor that detects a steering torque, a vehicle speed sensor that detects a vehicle speed, and these steering torque sensors And a control means for controlling the assist means based on each signal from the vehicle speed sensor. The control unit includes an output unit that specifies an assist signal from the input torque signal and the vehicle speed signal and outputs the assist signal to a driving unit for driving the motor, and the assist unit outputs the assist signal. An abnormality detection unit is provided for calculating a difference between the signal and the current value output from the driving means and fed back, and determining whether the difference is abnormal. In such a configuration, when an abnormality is detected, the motor drive is stopped and switched to manual steering, and the threshold for judging whether or not there is an abnormality is changed according to the driving situation, so that the actual situation can be changed. It is possible to perform appropriate fail-safe control.

Further, in the apparatus disclosed in Japanese Patent Laid-Open No. 2005-8105 (Patent Document 2), the abnormality detection time for determining whether or not there is an abnormality in the abnormality detection means is controlled by changing according to the traveling situation. In JP 2005-8106 A (Patent Document 3), the threshold value for determining whether or not there is an abnormality in the abnormality detection means and the abnormality determination time are changed according to the traveling situation, so that it is appropriate for the actual situation. Fail-safe control is possible.
JP 2004-299616 A JP 2005-8105 A JP 2005-8106 A

  In the electric power steering devices described in Patent Documents 1 to 3 described above, in order to perform appropriate fail-safe control according to the traveling situation, an abnormality is detected under an abnormality determination condition according to the traveling situation, and the abnormality is detected. If this happens, the motor is stopped. However, if the same abnormality detection condition is used for detecting the same abnormality next to the abnormality once detected, the reproducibility of the abnormality may be lowered. For example, the reproducibility of the abnormality may be lowered depending on the environment such as the temperature rise / drop of the component, vibration, or the like. For this reason, there is a problem that it becomes difficult to identify the cause of the abnormality at an early stage and repair the failure that causes the abnormality. Conversely, the reproducibility of the abnormality may be increased. In this case, there is a problem that the drive of the motor is stopped and the frequency at which the electric power steering device is stopped increases.

  The present invention has been made under the circumstances described above, and an object of the present invention is to increase the reproducibility of the abnormality, identify the cause of the abnormality at an early stage, and inform the driver that the abnormality has occurred at an early stage. An object is to provide an electric power steering apparatus. It is another object of the present invention to provide an electric power steering apparatus that lowers the reproducibility of the abnormality, shortens the time during which the steering assist is stopped due to the abnormality, and lengthens the duration for applying the steering assist force.

  The present invention relates to an electric power steering apparatus that calculates a current command value based on a steering torque and a vehicle speed, and controls a motor that assists in steering steering based on the current command value. The object of the present invention is to provide an abnormality detection unit for detecting an abnormality of the electric power steering device or the vehicle, an abnormality storage unit for storing an abnormality detected by the abnormality detection unit, and a detection condition for setting a detection condition of the abnormality detection unit. And a setting unit, and the detection condition of the detection condition setting unit is changed according to the storage of the abnormality storage unit.

  The above-mentioned object of the present invention is that the detection condition is changed so as to lower the detection degree, and then the abnormality detected by the abnormality detection unit satisfies the first condition which is the detection condition before the change, but the detection after the change When the second condition, which is the condition, is not satisfied, a warning is issued, or after the detection condition is changed to lower the detection degree, the abnormality detected by the abnormality detection unit is changed. When the first condition that is the previous detection condition is satisfied but the second condition that is the detection condition after the change is not satisfied, the steering assist is limited or the detection condition is detected. When the abnormality detected by the abnormality detection unit satisfies the second condition that is the detection condition after the change, the steering assistance is stopped or the steering assistance is limited, Issue warning Or after the detection condition is changed to increase the degree of detection, the abnormality detected by the abnormality detection unit satisfies the third condition which is the detection condition after the change. An abnormality detected by the anomaly detection unit by issuing a warning when the first condition which is the previous detection condition is not satisfied, or after changing the detection condition to increase the detection degree When the third condition that is the detection condition after the change is satisfied but the first condition that is the detection condition before the change is not satisfied, the steering assist is limited, or the detection condition is After changing to increase the degree of detection, when the abnormality detected by the abnormality detection unit satisfies the first condition that is the detection condition before the change, the steering assistance is stopped or the steering assistance is restricted. Both By adapted to alert, it is more effectively achieved.

  Further, the object of the present invention is to detect the abnormality by increasing the degree of detection of an abnormality that leads to a malfunction of the steering wheel, or when the abnormality that increases the degree of detection is detected by the steering torque detection. System, motor current detection system, motor drive system, or the abnormality detection is performed by reducing the degree of detection of abnormality that does not lead to malfunction of the handle, or The abnormality that lowers the detection degree is more effectively achieved by the abnormality relating to the battery voltage abnormality, the vehicle speed signal abnormality, the engine speed abnormality, and the relay abnormality.

  According to the electric power steering apparatus according to the present invention, it is possible to increase the reproducibility of the abnormality early by storing the occurrence of the abnormality of the electric power steering apparatus and the vehicle including the drive control device, the torque sensor, the motor, and the like. Since the cause of the abnormality is identified and the driver is informed that the abnormality has occurred at an early stage, the electric power steering device and the vehicle can be repaired at an early stage. Also, for abnormalities that do not lead to malfunction of the steering wheel, the reproducibility of the abnormalities is lowered, the time when the steering assist is stopped due to the abnormality is shortened, and the duration for applying the steering assist force is lengthened. The burden of the driver's steering operation force can be reduced.

  In the present invention, once an abnormality (including a failure) is detected, the abnormality analysis is quickly performed by increasing the degree of abnormality detection (detection level), and the failure causing the abnormality is repaired at an early stage. The duration time during which the steering assist force is applied is lengthened by reducing the degree of detection. Abnormalities that can lead to malfunction of the steering wheel, such as abnormalities in the steering torque detection system, motor current detection system, motor drive system, etc., are detected once the abnormality is detected, and the reproducibility of the abnormality is increased. The risk of operation is reduced, and abnormality analysis proceeds promptly. In addition, by reducing the degree of detection for abnormalities that are unlikely to cause malfunction of the steering wheel, such as battery voltage abnormality, vehicle speed signal abnormality, engine speed abnormality, relay abnormality, etc., the duration of applying the steering assist force is lengthened. In this way, the burden on the driver's operating force is reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system diagram showing an abnormality detection system of the electric power steering apparatus according to the present invention corresponding to FIG. 10, and includes a calculation system of a steering assist command value Iref, a differential compensation unit 104, a proportional calculation unit 105, and The current control system or the like of the integral calculation unit 106 is not limited to the configuration shown in FIG.

  As shown in FIG. 1, the electric power steering apparatus according to the present invention includes an abnormality detection unit 110 that detects an abnormality in the control unit 100, an abnormality storage unit 111 that stores an abnormality detection part, and the like, and an abnormality detection unit 110. A detection condition setting unit 112 that sets each detection condition and an alarm unit 113 that outputs an alarm when an abnormality is detected by the abnormality detection unit 110 are provided. Steering torque T from the torque sensor 10, vehicle speed V from the vehicle speed sensor 12, engine speed Rs from the engine speed sensor 15, motor current i detected by the motor current detection circuit 108 and battery voltage detection circuit 109. The battery voltage Vb and the operation signal Ws composed of the voltage and current from the motor drive circuit 107 are input to the abnormality detection unit 110, and the abnormality detection unit 110 detects abnormality of each part under the detection condition set by the detection condition setting unit 112. When an abnormality is detected, an alarm is output from the alarm unit 113, and the abnormal part is stored in the abnormality storage unit 111. The detection condition of the detection condition setting unit 112 is set by a setting signal, and the detection condition is corrected based on the stored data from the abnormality storage unit 111. Abnormality detection in the abnormality detection unit 110 is performed with a predetermined detection logic, and detection of a predetermined time and a predetermined number of samplings are performed, and an abnormality is detected depending on whether each input signal exceeds each threshold value.

  Causes of the abnormality detected by the abnormality detection unit 110 include a steering torque detection system including the torque sensor 10, a motor current detection system including the motor current detection circuit 108, an abnormality in the motor drive system including the motor drive circuit 107, and a battery voltage. There may be an abnormality in the battery voltage detection circuit 109 that causes an abnormality, an abnormality in the vehicle speed sensor 12 that causes an abnormality in the vehicle speed signal, an abnormality in the engine speed sensor 15 that causes an abnormality in the engine speed, an abnormality related to a relay abnormality, or the like. . When an abnormality is detected by the abnormality detection unit 110, the abnormality is stored in the abnormality storage unit 111. When an abnormality is detected, the alarm unit 113 may output an alarm.

  When an abnormality is detected and the abnormality is already stored in the abnormality storage unit 111, the abnormality detection condition of the detection condition setting unit 112 is changed from the initial condition. As a case where the degree of abnormality detection is increased so that the abnormality can be easily detected, there is a case where the abnormality leads to a malfunction of the steering wheel. For example, this is the case when the cause of the abnormality is an abnormality in the steering torque detection system, motor current detection system, or motor drive system. If such an abnormality is left unattended, malfunctions of the steering wheel frequently occur, and the effect of the electric power steering apparatus that reduces the burden on the driver by the steering assist force cannot be exhibited. For this reason, by increasing the degree of abnormality detection and increasing the reproducibility of the abnormality, the abnormality analysis can be performed quickly, the cause of the abnormality can be identified, and the failure causing the abnormality can be repaired at an early stage. . In addition, depending on the manufacturer of the finished vehicle, there is a case where a fail-safe idea of “stop suspicious things” is employed. In this case, the degree of abnormality detection is set to be increased.

  As a case where it is difficult to detect an abnormality by reducing the degree of detection of the abnormality, there is a case where the abnormality is unlikely to lead to a malfunction of the steering wheel. For example, this may be the case when the cause of the abnormality is a battery voltage abnormality, a vehicle speed signal abnormality, an engine speed abnormality, or a relay system abnormality. Such an abnormality leads to deterioration of the performance of the electric power steering apparatus, but the degree of detection of the abnormality is lowered rather than stopping the motor drive every time an abnormality is detected and increasing the driver's handle operation burden. Therefore, it is better to reduce the burden on the driver by extending the duration of the steering assist. In addition, depending on the manufacturer of the finished vehicle, there is a case where a fail-safe idea of “continuing assistance as much as possible” is employed. In this case, the degree of detection of abnormality is set to be lowered.

  In such a configuration, when an abnormality occurs in the electric power steering apparatus or the vehicle, a procedure for identifying and recovering from the abnormality at an early stage will be described with reference to the flowcharts shown in FIGS.

  FIG. 2 is a flowchart showing a procedure for identifying and recovering from an abnormality at an early stage when it is difficult to detect the abnormality by reducing the degree of abnormality detection.

  First, after the ignition key is turned on and the engine is started (step S1), it is determined whether or not an abnormality is already stored in the abnormality storage unit 111 (step S2). If no abnormality is stored, it is determined whether or not an abnormality is detected by the abnormality detection unit 110 under the first condition that is an abnormality detection initial condition (step S3). If it is determined in step S3 that no abnormality has been detected, it is determined whether the ignition key is turned off (step S4). If it is determined that the ignition key is turned off, the engine is Stop and exit. If it is determined in step S4 that the ignition key is not turned OFF, the process returns to step S2.

  If it is determined in step S3 that an abnormality has been detected under the first condition, specific control B is performed (step S5). The control content performed in the specific control B is, for example, stop of steering assistance or restriction of steering assistance. Further, the abnormality detection unit 110 continues to detect an abnormality under the first condition and store the detected abnormality in the abnormality storage unit 111 (step S6), and the alarm unit 113 lights a warning lamp (step S6). S7). Further, the abnormality detection condition (second condition) changed in the detection condition setting unit 112 according to the abnormality detected in step S3 is added to the condition for performing abnormality detection in the abnormality detection unit 110 (step S8). ). Here, the detection condition of the second condition is lower than that of the first condition, and it is difficult to detect an abnormality.

  Then, it is determined whether or not the abnormality is recovered and the steering assist is continued (step S9). If it is determined in step S9 that the abnormality has been recovered and the steering assist is not being continued, it is determined whether or not the ignition key is turned off (step S10), and the ignition key is turned off. If determined, the engine is stopped and terminated. If it is determined in step S10 that the ignition key is not turned OFF, the process returns to step S9. When it is determined in step S9 that the abnormality has been recovered and the steering assist is being continued, the process proceeds to step S11.

  If it is determined in step S2 that an abnormality has been stored in the abnormality storage unit 111, or if it is determined in step S9 that the abnormality has been recovered and steering assistance has been continued, the abnormality detection unit 110 performs the first operation. It is determined whether or not an abnormality has been detected under the conditions (step S11). If it is determined that no abnormality is detected under the first condition, the process proceeds to step S4. If it is determined that an abnormality is detected under the first condition, whether or not an abnormality is detected in the abnormality detection unit 110 under the second condition where the degree of abnormality detection is lower than the first condition (it is difficult to detect) Is determined (step S12).

  When it is determined that no abnormality is detected under the second condition, the specific control A is performed (step S13). Although the control content of the specific control A varies depending on the type of abnormality, there are lighting of a warning lamp or restriction of steering assistance. Further, the abnormality is detected and stored in the first condition (step S14), and the process proceeds to step S9.

  When it is determined in step S12 that an abnormality is detected under the second condition, the specific control B is performed (step S15), and the abnormality under the second condition is detected and the abnormality is stored (step S16). ), The warning light is turned on in the alarm unit 113 (step S17). Then, the process proceeds to step S9.

  FIG. 3 summarizes the control contents in each situation when the above detection degree is lowered to make it difficult to detect an abnormality. When the abnormality is not stored in the abnormality storage unit 111 and an abnormality is detected in the first condition in the abnormality detection unit 110, the specific control B is performed, and the steering assistance is stopped or the steering assistance is restricted. Further, the detected abnormality is stored in the abnormality storage unit 111 and a warning lamp is turned on.

  In the state where the abnormality is stored in the abnormality storage unit 111, an abnormality is detected in the first condition in the abnormality detection unit 110, but an abnormality is detected in the second condition in which the degree of detection is lower than the first condition. If not, specific control A is performed. The control content of the specific control A varies depending on the type of abnormality, and when the steering assist is limited and the warning light does not light (Example 1), when the steering assistance is continued and the warning light is lit (Example 2), There are cases where the warning light is turned on with restriction (example 3), the steering assistance is continued and the warning light is not turned on (example 4), and the like. Further, the detected abnormality is stored in the abnormality storage unit 111.

  In the specific control A, for example, when a warning lamp is turned on and steering assistance is continued, the driver is informed that an abnormality has occurred without increasing the burden on the steering wheel operation. The cause failure can be repaired at an early stage. In the case where the steering assist is limited by the specific control A, the progress of a failure that causes an abnormality while maintaining the minimum steering assist force without maintaining the steering assist force in a state where the performance of the electric power steering apparatus is deteriorated. / Can prevent expansion.

  When an abnormality is stored in the abnormality storage unit 111, an abnormality is detected in the first condition in the abnormality detection unit 110, and an abnormality is detected even in the second condition in which the degree of detection is lower than the first condition. Specific control B is performed, and steering assistance is stopped or steering assistance is restricted. Further, the detected abnormality is stored in the abnormality storage unit 111 and a warning lamp is turned on.

  Next, a procedure for identifying and recovering from an abnormality at an early stage when increasing the degree of abnormality detection to facilitate the detection of the abnormality will be described with reference to the flowchart shown in FIG.

  First, after the ignition key is turned on and the engine is started (step S101), it is determined whether or not an abnormality is already stored in the abnormality storage unit 111 (step S102). It is determined whether or not an abnormality is detected by the abnormality detection unit 110 under the first condition, which is an initial detection condition (step S103). If no abnormality is detected, whether or not the ignition key is turned off. Is determined (step S104). If the ignition key is turned off, the engine is stopped and terminated. If the ignition key is not turned off, the process returns to step S102.

  When it is determined in step S103 that an abnormality has been detected under the first condition, specific control B such as stop of steering assistance or restriction of steering assistance is performed (step S105). Further, the detection of the abnormality under the first condition and the storage of the abnormality are continued (step S106), and the warning lamp is turned on in the alarm unit 113 (step S107). Further, the abnormality detection condition (third condition) changed in the detection condition setting unit 112 according to the abnormality detected in step S103 is added to the condition for performing abnormality detection in the abnormality detection unit 110 (step S108). . Here, the third condition has a higher degree of detection than the first condition, and is a condition that makes it easy to detect an abnormality.

  Then, it is determined whether or not the abnormality is recovered and the steering assist is continued (step S109). If it is determined in step S109 that the abnormality has been recovered and the steering assist is not being continued, it is determined whether or not the ignition key is turned off (step S110). In step S109, the abnormality is recovered and the steering assist is not performed. If it is determined that the process is continued, the process proceeds to step S111. If it is determined in step S110 that the ignition key is turned off, the engine is stopped and the process ends. If it is determined in step S110 that the ignition key is not turned OFF, the process returns to step S109.

  If it is determined in step S102 that an abnormality has been stored, or if it is determined in step S109 that the abnormality has been recovered and steering assistance has been continued, the degree of detection is increased from the first condition to make it easier to detect the abnormality. It is determined whether or not an abnormality is detected by the abnormality detection unit 110 under the third condition (step S111). If it is determined in step S111 that no abnormality is detected under the third condition, the process proceeds to step S104. If an abnormality is detected in the third condition in step S111, it is determined whether or not an abnormality is detected in the first condition, which has a lower degree of detection than the third condition (it is difficult to detect an abnormality) (step S112). When it is determined in step S112 that an abnormality has been detected under the first condition, the process proceeds to step S105, and the specific control B is performed.

  If it is determined in step S112 that no abnormality is detected under the first condition, specific control C is performed (step S113). Although the control content of the specific control C varies depending on the type of abnormality, there are lighting of a warning lamp or restriction of steering assistance. Further, in step S114, the abnormality detection unit 110 detects an abnormality under the third condition and the abnormality storage unit 111 stores the abnormality, and the process proceeds to step S109.

  The control contents in each situation when the abnormality detection degree is increased to make it easier to detect the abnormality are summarized in the table of FIG. In the case where no abnormality is stored in the abnormality storage unit 111, when the abnormality detection unit 110 detects an abnormality under the first condition, the specific control B is performed, and the steering assistance is stopped or the steering assistance is restricted. Further, the abnormality storage unit 111 stores the abnormality, and the alarm unit 113 turns on the warning lamp.

  In the case where an abnormality is stored in the abnormality storage unit 111, the abnormality detection unit 110 has a low degree of detection according to the first condition, and an abnormality is detected under the third condition where the abnormality is easily detected. If no is detected, the specific control C is performed. The control content of the specific control C varies depending on the type of abnormality, and the steering assist is limited and the warning light does not light (Example 1), the steering assist is continued and the warning light is lit (Example 2), There are cases where the warning light is turned on with restriction (example 3), the steering assistance is continued and the warning light is not turned on (example 4), and the like. Further, the detected abnormality is stored in the abnormality storage unit 111.

  When an abnormality is stored in the abnormality storage unit 111 and an abnormality is detected under the first condition in the abnormality detection part 110, the specific control B is performed, and steering assistance is stopped or steering assistance is restricted. . Further, the abnormality storage unit 111 stores the abnormality, and the alarm unit 113 turns on a warning lamp.

Hereinafter, examples of the electric power steering apparatus according to the embodiment of the present invention will be described more specifically.
[Example 1]
A procedure for dealing with the abnormality when an abnormality occurs in the torque sensor 10 will be described with reference to FIG.

  First, the ignition key is turned on (step S201), and an abnormality occurs in the torque sensor 10 (step S202). This abnormality is detected by the abnormality detection unit 110 (step S203), and the abnormality is stored in the abnormality storage unit 111 (step S204). Next, the abnormality detection condition change corresponding to the abnormality of the torque sensor 10 is performed on the detection condition setting unit 112 (step S205). A malfunction of the steering torque detection system that causes an abnormality of the torque sensor 10 leads to a malfunction of the steering wheel. Therefore, the abnormality detection condition is changed so as to increase the degree of abnormality detection, but here the abnormality detection time is shortened. To do. In step S206, the ignition key is once turned off, the engine is stopped, and the ignition key is turned on again (step S207). In this process, the abnormality is temporarily recovered and the changed abnormality detection condition is not satisfied. After turning on the ignition key, the abnormality of the torque sensor 10 occurs again (step S208), the abnormality is detected again under the abnormality detection condition changed in step S205 (step S209), and the process returns to step S206.

As described above, in the case of an abnormality in the torque sensor 10, by changing the abnormality detection condition so that the abnormality can be easily detected, the reproducibility of the abnormality is improved, and abnormality analysis is performed early to identify a failure that causes the abnormality. Can be repaired.
[Example 2]
When a battery voltage drop abnormality occurs, a procedure for dealing with the abnormality will be described with reference to FIG.

  After turning on the ignition key (step S301), a battery voltage drop abnormality occurs (step S302). This abnormality is detected by the abnormality detection unit 110 (step S303), and the abnormality is stored in the abnormality storage unit 111 (step S304). Next, the detection condition setting unit 112 changes the abnormality detection condition corresponding to the battery voltage drop abnormality (step S305). Since a malfunction related to battery voltage abnormality is unlikely to lead to malfunction of the steering wheel, the abnormality detection condition is changed so as to reduce the degree of abnormality detection. Here, the threshold value for determining that the battery voltage is abnormal is lowered. Since an abnormality is detected in step S303, the steering assist is stopped (step S306). When the battery voltage is temporarily restored to normal (step S307), the steering assist is restored (step S308). When the battery voltage drop abnormality occurs again (step S309), the abnormality is detected again under the abnormality detection condition changed in step S305 (step S310), and the process returns to step S307.

In this way, for a failure of the battery voltage detection circuit 109 that causes a battery voltage drop abnormality, changing the abnormality detection condition makes it difficult to detect the abnormality. As a result, the stop of the steering assist can be suppressed, the steering assist can be continued as much as possible, and the burden on the driver's steering operation can be reduced.
[Example 3]
In each case of the abnormality detection initial condition and the changed abnormality detection condition, ON / OFF of the detection flag of the abnormality detection unit 110, ON / OFF of the warning light of the alarm unit 113, and normal / stop of the steering assist. The (or restriction) control will be described with reference to the time chart of FIG. FIG. 8A shows the ignition key ON and abnormality occurrence timing, and FIG. 8B shows an operation example of the detection flag, warning light, and steering assist in the abnormality detection initial condition. (C) shows an operation example when the detection condition is raised, and FIG. 8 (D) shows an operation example when the detection condition is lowered.

  First, consider a case where the ignition key is turned on at the timing (time t1) shown in FIG. 8A, and then an abnormality occurs at time t2. When the abnormality satisfies the abnormality detection initial condition, as shown in FIG. 8B, the detection flag of the abnormality detection unit 110 is turned on at time t4, the warning light is turned on, and the steering assist is stopped from normal. Or it becomes a restriction. On the other hand, in the case of FIG. 8C in which the detection condition makes it easy to detect an abnormality and the degree of detection is high, when the abnormality occurs at the time t2, the detection flag is turned on at a time t3 earlier than the case of the abnormality detection initial condition. At the same time, the warning light is turned on, and the steering assist is stopped or restricted from normal.

In the case of FIG. 8D where the degree of detection is low, the detection flag is turned on at the time t5 later than the case of the abnormality detection initial condition after the abnormality occurs at the time t2, and the warning lamp is also turned on. Thus, the steering assist is also stopped or restricted from normal.
If the degree of detection is lowered, at time t4 before the detection flag is turned ON, the warning lamp may be turned ON to notify the driver of the abnormality when the abnormality satisfies the abnormality detection initial condition. Also at the time t4 before the detection flag is turned ON, the steering assist may be limited in order to prevent the progress / expansion of the failure causing the abnormality at the stage where the abnormality satisfies the abnormality detection initial condition. good.

It is a block block diagram which shows the abnormality detection system of the electric power steering apparatus which concerns on this invention. It is a flowchart which shows the operation example at the time of reducing the detection degree of abnormality of this invention. It is the table | surface which put together the control content in each condition at the time of reducing the detection degree of abnormality. It is a flowchart which shows the operation example at the time of raising the detection degree of abnormality of this invention. It is the table | surface which put together the control content in each condition at the time of raising the detection degree of abnormality. It is a flowchart which shows an example of the coping procedure when abnormality of a torque sensor generate | occur | produces. It is a flowchart which shows an example of the coping procedure when a battery voltage drop abnormality occurs. It is a time chart which shows the relationship between ON / OFF of the abnormality detection flag and warning lamp in each abnormality detection condition, and normal / stop (or restriction | limiting) of steering assist control. It is a figure showing an example of composition of a general electric power steering device. It is a block diagram which shows the structural example of the control system of an electric power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Column shaft 3 Reduction gear 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 14 Battery 15 Engine rotation speed sensor 20 Motor 100 Control unit 102 Steering assist command value calculating part 103 Assist map 107 Motor drive circuit 108 Motor current detection circuit 109 Battery voltage detection circuit 110 Abnormality detection unit 111 Abnormality storage unit 112 Detection condition setting unit 113 Alarm unit

Claims (11)

In the electric power steering apparatus configured to calculate a current command value based on the steering torque and the vehicle speed and to control a motor for assisting steering of the steering mechanism based on the current command value, the electric power steering apparatus or An abnormality detection unit that detects an abnormality of the vehicle, an abnormality storage unit that stores an abnormality detected by the abnormality detection unit, and a detection condition setting unit that sets a detection condition of the abnormality detection unit, the abnormality storage unit The electric power steering apparatus is characterized in that the detection condition of the detection condition setting unit is changed according to the stored information. After changing the detection condition so as to lower the detection degree, the abnormality detected by the abnormality detection unit satisfies the first condition that is the detection condition before the change, but the second condition that is the detection condition after the change is The electric power steering apparatus according to claim 1, wherein a warning is issued when the condition is not satisfied. After changing the detection condition so as to lower the detection degree, the abnormality detected by the abnormality detection unit satisfies the first condition that is the detection condition before the change, but the second condition that is the detection condition after the change is The electric power steering apparatus according to claim 1 or 2, wherein the steering assist is limited when the steering is not satisfied. After the detection condition is changed so as to reduce the degree of detection, when the abnormality detected by the abnormality detection unit satisfies the second condition that is the detection condition after the change, the steering assistance is stopped or the steering assistance is performed. The electric power steering apparatus according to any one of claims 1 to 3, wherein the electric power steering apparatus is configured to perform a restriction and to issue a warning. After changing the detection condition so as to increase the degree of detection, the abnormality detected by the abnormality detection unit satisfies the third condition that is the detection condition after the change, but the first condition that is the detection condition before the change is The electric power steering apparatus according to any one of claims 1 to 4, wherein a warning is issued when the condition is not satisfied. After changing the detection condition so as to increase the degree of detection, the abnormality detected by the abnormality detection unit satisfies the third condition that is the detection condition after the change, but the first condition that is the detection condition before the change is The electric power steering apparatus according to any one of claims 1 to 5, wherein the steering assist is limited when not satisfied. After the detection condition is changed to increase the degree of detection, when the abnormality detected by the abnormality detection unit satisfies the first condition that is the detection condition before the change, the steering assistance is stopped or the steering assistance is performed. The electric power steering apparatus according to any one of claims 1 to 6, wherein the electric power steering apparatus is configured to issue a warning while restricting the above. The electric power steering apparatus according to any one of claims 1 to 7, wherein the abnormality is detected with an increased degree of detection for an abnormality that leads to a malfunction of the steering wheel. The electric power steering apparatus according to claim 8, wherein the abnormality that increases the degree of detection is an abnormality in a steering torque detection system, a motor current detection system, and a motor drive system. The electric power steering apparatus according to any one of claims 1 to 9, wherein the abnormality is detected by lowering the degree of detection of an abnormality that does not lead to a malfunction of the steering wheel. The electric power steering apparatus according to claim 10, wherein the abnormality that lowers the detection degree is abnormality relating to battery voltage abnormality, vehicle speed signal abnormality, engine speed abnormality, and relay abnormality.

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