JP2010132206A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device which uses a three-phase brushless motor for detecting an error such as a contact failure of a relay contact of a motor relay in a motor driver circuit. <P>SOLUTION: The electric power steering device forcibly excites an A-phase motor relay 42 and a B-phase motor relay 44, sets the duty ratio of a PWM signal for driving a switching element in the motor drive circuit as a specific duty ratio for an error diagnosis to detect an A-phase motor current, determines whether or not the absolute value of the A-phase motor current is equal to or larger than a predetermined threshold value, and determines whether a relay contact 42a of the A-phase motor relay and a relay contact 44a of the B-phase motor relay are normal or abnormal. When it is determined that the relay contacts are abnormal, the normal/abnormal determination process is repeated a predetermined number of times. When it is determined that the relay contacts are abnormal even after the several times of determining, the abnormal determination is settled, and a fail-safe process is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering device, and more particularly, to an electric power steering device including an abnormality diagnosis device capable of diagnosing abnormality of a relay contact of a motor relay mounted on the motor circuit.

  An electric power steering device for a vehicle detects a steering torque and a vehicle speed generated in a steering shaft by operating a steering handle, and a control target value of a motor current supplied to a motor that generates a steering assist force based on the detection signal On the other hand, the current control value is controlled so that the deviation between the current command value and the detected current value becomes zero by detecting the motor current that actually flows to the motor and feeding back to the current command value. There is one configured to drive a motor with a value and supply a steering assist force corresponding to a steering torque to a steering system.

  Such control is executed by driving a control device composed of a microcomputer (CPU) to which a torque sensor for detecting steering torque, a vehicle speed sensor for detecting vehicle speed, and other sensors are connected by software. The

  The motor current is controlled by the current control value output from the control device described above, and the motor drive circuit for driving the motor uses a bridge circuit in which the semiconductor switching element and the motor are bridge-connected, and the current control value described above is used. 2. Description of the Related Art A motor drive circuit configured to control a motor current by controlling ON / OFF of a semiconductor switching element based on a duty ratio of a PWM signal determined based on the PWM signal is widely used. Recently, a three-phase brushless motor is used as a motor. in use. Hereinafter, the motor drive circuit of the three-phase brushless motor will be briefly described.

  In a brushless DC motor, an armature coil is arranged on a stator, a rotor is composed of a permanent magnet, and the permanent magnet magnetic field and the magnetic field generated by the armature coil are made to be orthogonal according to the rotational position of the permanent magnet. It is configured to take the timing of the direct current that flows through the coil of the magnetic pole corresponding to the position of the magnet. The rotation sensor for detecting the rotational position of the permanent magnet is arranged on the stator, and the number of detection elements of the sensor is proportional to the number of phases constituting the motor, and three detection elements are required for a three-phase motor. To do. A Hall element or the like is used as a detection element of the rotation sensor.

  FIG. 12 is a block diagram illustrating a schematic configuration of a motor drive circuit that drives a three-phase brushless motor. The motor drive circuit 100 is an inverter circuit composed of six semiconductor switching elements, and is composed of a combination of switching elements S1 and S2, a combination of switching elements S3 and S4, and a combination of switching elements S5 and S6. The rotation sensor for detecting the electrical angle of the motor M is composed of three detection elements (Hall elements) H1, H2, and H3. The detection elements H1, H2, and H3 are neutral in each phase as shown in FIG. The phase current values I1, I2, and I3 of each phase are turned on / off in response to the rising and falling of the detection elements H1, H2, and H3 that detect the electrical angle of the motor M. Controlled off.

  FIG. 13 is a diagram for explaining the rise and fall timings of the detection elements H1, H2, and H3 of the rotation sensor and the on / off control timings of the switching elements S1 to S6. At the rise of the detection element H1, the switching element S1 is turned on, and at the rise of the detection element H2, the switching element S1 is turned off to excite the A phase. The switching element S4 is turned on until it rotates 60 ° from the rise of the detection element H1, and the switching element S6 is turned on after the rotation of 60 °, and the B phase and the C phase are excited so as to have opposite polarities. Since two phases are excited simultaneously, the motor M can be driven efficiently. To reverse the motor M, the on / off control relationship of the switching elements S1 to S6 corresponding to the rising and falling of the detection elements H1 to H3 may be reversed.

  When the breakdown of the switching element of the motor drive circuit as described above occurs, an unexpected current may occur due to abnormal current flowing through the motor, causing the motor to burn out, or the motor to operate as an electromagnetic brake and stop suddenly. In order to prevent this, a motor relay that opens the motor terminal from the switching element is interposed in the motor drive circuit.

  However, when a motor relay is installed, foreign matter may adhere to the relay contact, or the relay contact may be defective due to being covered with an oxide film, and the relay contact will be open even if the motor relay is excited. May occur.

  In addition, if the motor current detection means fails, the accurate motor current cannot be measured, and an appropriate current control value cannot be output from the control device. As a result, excessive current flows to the motor and becomes excessive. Inadequate steering assisting force, or a sufficient amount of steering assisting force cannot be supplied because a current necessary for the motor does not flow.

In order to avoid the unexpected situation due to the above-mentioned failure, the control device has an initial diagnosis function built in. When starting the engine, the initial diagnosis function is executed and the motor current is forced to flow. The present applicant has proposed a detector configured to confirm the operation of the detection means and the relay contact of the motor relay (see Patent Document 1).
JP-A-8-91239

  In the initial diagnosis function incorporated in the control device described above, abnormality diagnosis is also performed for these motor relays. In this case, the relay contact welding failure is conventionally detected without fail. However, the relay contact open failure, that is, the continuity failure that occurs due to foreign matter adhering to the contact has been positive in the past. Was not configured to detect.

  Conventionally, when an open failure of a relay contact occurs, an abnormal state similar to that when a motor circuit ground fault or ground fault occurs occurs. Therefore, the occurrence of an open failure of a relay contact is estimated from the generated abnormal state. It was. However, the relay contact open failure often has poor reproducibility, and failure analysis is difficult. In addition, when detecting an open failure of a relay contact, if it is possible to identify which relay has caused the open failure, failure analysis can be performed more quickly. The resulting relay could not be identified.

  On the other hand, the cause of an open failure of a relay contact is one of the causes of adhesion of insulating foreign matter to the relay contact, but in a state where an inrush current (current that flows at the moment when the relay contact closes) flows. In usage patterns in which the relay contacts are closed, relay contact open failures do not occur, and in usage patterns in which current does not flow at the moment when the relay contacts are closed, relay contact open failures occur at a certain frequency. It is empirically known to occur.

  This is because in a usage configuration in which the relay contact closes in a state where an inrush current flows, the foreign matter adhering to the contact is removed by the inrush current, whereas no current flows when the relay contact is closed, and the contact is closed. It is presumed that the foreign matter cannot be removed by the current in the usage mode in which the current flows through the relay contact in the above state. Therefore, it is possible to expect an effect that the occurrence of an open failure of the relay contact can be suppressed by removing foreign matter attached to the contact by performing an operation in which a current flows at the moment when the relay contact is closed.

The present invention has been made in view of the above viewpoint, and provides an electric power steering device including a control device that enables diagnosis of an open failure of a relay contact while suppressing the occurrence of an open failure of a relay contact. Objective.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. The invention according to claim 1 is a steering torque signal generated at least on a steering shaft in an electric power steering apparatus for a vehicle that uses a three-phase brushless motor as a supply source of steering assist force. The current command value that is the control target value of the motor current is calculated based on the current value, and the duty ratio of the PWM signal that drives the plurality of switching elements is determined by the current control value of each phase of the motor determined based on the current command value And a control device for driving the motor by controlling ON / OFF of the switching element at the determined duty ratio, and the switching element corresponding to the A phase terminal and the B phase terminal of the motor and the A phase and the B phase of the motor. A-phase motor relay and B-phase motor relay that are interposed between and actuate in the direction in which the relay contact closes by excitation. An A-phase motor current detector mounted on the A-phase motor circuit, and the control device excites the A-phase motor relay and the B-phase motor relay during the initial diagnosis period of the control system when the engine is started and An electric power steering apparatus characterized by forcibly controlling a switching element at a preset specific duty ratio and determining a state of a relay contact of a phase A and phase B motor relay based on a detected phase A motor current is there.

  In addition, during the initial diagnosis period of the control system when the engine is started, the control device excites and detects the A-phase motor relay and the B-phase motor relay after forcibly controlling the switching element at a preset specific duty ratio. The state of the relay contacts of the A-phase and B-phase motor relays may be determined based on the A-phase motor current.

  And the said control apparatus shall determine with the relay contact of A phase and B phase motor relay being normal, when the absolute value of A phase motor current is more than a predetermined threshold value.

  When the absolute value of the A-phase motor current is zero, the control device determines that the relay contact of the A-phase motor relay is abnormal when the number of failure determinations is equal to or greater than a predetermined value.

  According to a fifth aspect of the present invention, in the electric power steering apparatus for a vehicle that uses a three-phase brushless motor as a supply source of the steering assist force, the motor current control target value is based on at least a steering torque signal generated in the steering shaft. The current command value is calculated, the duty ratio of the PWM signal for driving the plurality of switching elements is determined by the current control value of each phase of the motor determined based on the current command value, and the switching element is determined with the determined duty ratio. The control device that drives the motor by ON / OFF control, and the A-phase terminal and B-phase terminal of the motor and switching elements corresponding to the A-phase and B-phase of the motor are relayed by excitation. A-phase motor relay and B-phase motor relay that operate in the direction to close the contacts, and A-phase motor mounted on the A-phase motor circuit A current detector, and a C-phase motor current detector mounted on the C-phase motor circuit, wherein the control device is an A-phase motor relay or a B-phase motor relay in the initial diagnosis period of the control system at the time of engine startup. And forcibly controlling the switching element at a predetermined duty ratio set in advance, and determining the state of the relay contact of the A-phase or B-phase motor relay based on the detected A-phase motor current or C-phase motor current This is an electric power steering device.

  In addition, during the initial diagnosis period of the control system when the engine is started, the control device excites the A-phase motor relay or the B-phase motor relay after forcibly controlling the switching element with a predetermined duty ratio set in advance. The state of the relay contact of the phase A or phase B motor relay may be determined based on the phase A motor current.

  The control device determines that the relay contact of the A-phase or C-phase motor relay is normal when the absolute value of the A-phase motor current or the C-phase motor current is equal to or greater than a predetermined threshold value.

  When the absolute value of the A-phase motor current or the C-phase motor current is less than a predetermined threshold, the control device can detect the A-phase motor relay or the C-phase motor relay when the failure determination count is equal to or greater than a predetermined value. It is assumed that the relay contact is determined to be abnormal.

  According to a ninth aspect of the present invention, in the electric power steering device for a vehicle that uses a three-phase brushless motor as a supply source of the steering assist force, the motor current control target value is based on at least a steering torque signal generated in the steering shaft. The current command value is calculated, the duty ratio of the PWM signal for driving the plurality of switching elements is determined by the current control value of each phase of the motor determined based on the current command value, and the switching element is determined with the determined duty ratio. The control device that drives the motor by ON / OFF control, and the A-phase terminal and B-phase terminal of the motor and switching elements corresponding to the A-phase and B-phase of the motor are relayed by excitation. A-phase motor relay and B-phase motor relay that operate in the direction to close the contacts, and A-phase motor mounted on the A-phase motor circuit A current detector, and a C-phase motor current detector mounted on the C-phase motor circuit, wherein the control device is configured to output an A-phase motor relay and a B-phase motor relay during an initial diagnosis period of the control system when the engine is started. And forcibly controlling the switching element with a predetermined duty ratio set in advance, and determining the state of the relay contacts of the A-phase and B-phase motor relays based on the detected A-phase motor current. This is an electric power steering device.

  In addition, during the initial diagnosis period of the control system when the engine is started, the control device excites and detects the A-phase motor relay and the B-phase motor relay after forcibly controlling the switching element at a preset specific duty ratio. The state of the relay contacts of the A-phase and B-phase motor relays may be determined based on the A-phase motor current.

  And the said control apparatus shall determine with the relay contact of A phase and B phase motor relay being normal, when the absolute value of A phase motor current is more than a predetermined threshold value.

  When the absolute value of the A-phase motor current is less than a predetermined threshold value and the absolute value of the C-phase motor current is equal to or greater than the predetermined threshold value, the control device further determines the absolute value of the A-phase motor current and the C-phase value. When the absolute value of the motor current is equal and the number of times of failure determination exceeds a predetermined value, it is determined that the relay contact of the B-phase motor relay is abnormal.

  When the absolute value of the A-phase motor current is less than a predetermined threshold and the absolute value of the C-phase motor current is less than the predetermined threshold, the controller determines that the number of times of failure determination is equal to or greater than a predetermined value. The relay contacts of the A-phase motor relay and the B-phase motor relay are determined to be abnormal.

  Furthermore, the control device performs fail-safe processing when it is determined that the relay contact of the A-phase motor relay and / or the B-phase motor relay is abnormal.

  According to the first to fourth aspects of the present invention, in the initial diagnosis period of the control system at the time of starting the engine, the A phase motor relay and the B phase motor relay are excited to close the relay contact, and the switching element is set in advance. Because it is forcibly controlled by the ratio and the state of the relay contacts of the A-phase and B-phase motor relays is determined from the A-phase motor current detected at this time, the motor current flows when the relay contacts are closed. Even when foreign matter adheres to the contact, it is possible to eliminate the foreign matter, and it is possible to accurately determine the state of the relay contact by removing the foreign matter.

  According to the fifth to eighth aspects of the invention, similar to the first and second aspects of the invention, even when foreign matter adheres to the relay contact, the state of the relay contact can be accurately determined by removing the foreign matter. In addition, the state of the relay contact of the A-phase motor relay and the relay contact of the B-phase motor relay can be determined separately, and the motor relay in which an abnormality has occurred can be identified.

  According to the ninth to thirteenth aspects of the invention, as in the first and second aspects of the invention, even when a foreign object adheres to the relay contact, it is possible to accurately determine the state of the relay contact by eliminating the foreign object. In addition, the state of the relay contacts of the two motor relays can be determined at the same time, and quick determination is possible.

  In the initial diagnosis period, after the switching element is forcibly controlled at a specific duty ratio set in advance, the A phase motor relay and / or the B phase motor relay is excited and detected in the initial diagnosis period. When determining the relay contact state of the A-phase and B-phase motor relays based on the phase motor current, the state in which the motor current flows is set reliably at the moment when the relay contact is closed. The possibility of removal can be further increased.

  Embodiments of the present invention will be described below. Since the motor used in the electric power steering apparatus according to the embodiment of the present invention is basically the same as the three-phase brushless DC motor described in the background art above, description of the motor configuration is omitted here. To do. In the following description, the three-phase brushless DC motor may be simply referred to as a motor.

[Outline of control device configuration and operation]
FIG. 1 is a block diagram for explaining the outline of a control circuit 10 and its peripheral circuit elements constituting a control device for an electric power steering apparatus according to an embodiment of the present invention, and FIG. FIG. 3 is a diagram for explaining the configuration of the PID calculator 16.

  In FIG. 1, the steering torque detected by the torque sensor 11 and the vehicle speed detected by the vehicle speed sensor 12 are input to a target current calculator 13 that constitutes a target current calculation means, and a control target value I of the motor current is calculated. Is done. The calculated control target value I of the motor current is input to the phase current calculator 14, and the three phases (A of the motor M) are selected according to the electrical angle of the motor M detected by the rotation sensor 23 which is a motor rotation number detector. Are converted into three phase current values I1, I2, and I3 corresponding to (phase, B phase, and C phase).

  In the comparator 15, a motor current detection value i1 output from an A-phase motor current detector 41 (to be described later) is fed back to the phase current value I1, and feedback control is performed.

  Specifically, as shown in FIG. 3, the PID calculator 16 includes a proportional calculator 16a, an integral calculator 16b, a differential compensator 16c, and an adder 16d. The PID calculators 32 and 36 described later have the same configuration.

  The proportional calculator 16a outputs a proportional value proportional to the difference between the phase current value I1 and the motor current detection value i1. Further, the output of the proportional calculator 16a is integrated and output by the integral calculator 16b in order to improve the characteristics of the feedback system. Since the differential compensator 16c increases the response speed of the motor current with respect to the phase current value I1, the differential value of the phase current value I1 is output. The adder 16d adds the outputs of the proportional calculator 16a, the integral calculator 16b, and the differential compensator 16c, and the addition result is output as a voltage control value E1.

  The adder 17 adds the compensation value Z output from the compensation calculator 18 to the voltage control value E1, and the voltage control value E11 obtained by adding the compensation value Z is output to the switching circuit 20 at the subsequent stage. The

  The compensation calculator 18 receives the voltage applied to the motor M detected by the voltage detector 22 and the electrical angle detected by the rotation sensor 23 that detects the rotation angle of the motor M, and receives back electromotive force generated in the motor. And a compensation value Z for compensating for a harmonic ripple or the like included in the motor current is calculated and output to the adder 17.

  As shown in FIG. 2, the switching circuit 20 controls the voltage control values E11, E21, and E31 output from the adders 17, 33, and 37 to turn on and off the semiconductor switching elements (hereinafter referred to as FETs). Converter 21 for converting to a duty ratio of A, FET A and FET 2 for A phase corresponding to the three phases of motor M controlled ON / OFF by the duty ratio output from converter 21, FET 3 and FET 4 for B phase, C It consists of six FETs, FET5 and FET6.

  The A-phase motor current detector 41 detects the A-phase motor current flowing in the motor M, detects the current value from the voltage across the resistor Ra inserted in series in the A-phase circuit, and detects the detected current value. i1 is output to the comparator 15, a motor current detection calculator 34 described later, and an abnormality determiner 45.

  The voltage detector 22 detects the voltage applied to the terminal of the motor M, and outputs the detected voltage value to the compensation calculator 18.

  The above configuration is the circuit of the phase current value I1 output from the phase current calculator 14, but the circuit of the phase current value I3 is exactly the same, and the comparator 35, PID calculator 36, adder 37, switching circuit. 20 and a C-phase motor current detector 43.

  The circuit of the phase current value I2 is the same as the circuit of the phase current value I1 in that the comparator 31, the PID calculator 32, the adder 33, and the switching circuit 20 are the same. Instead, a motor current detection computing unit 34 is provided, and the current value i1 that is the output of the A-phase motor current detector 41 and the current value i3 that is the output of the C-phase motor current detector 43 are input, and the output current is The difference is that the value i2 is input to the comparator 31 and calculated from the phase current value I2 output from the phase current calculator 14 and input to the PID calculator 32.

  The configuration of the control circuit 10 described above is a technique commonly used in three-phase control of a brushless DC motor.

  Next, the operation will be briefly described. Based on the steering torque detected by the torque sensor 11 and the vehicle speed detected by the vehicle speed sensor 12, the target current calculator 13 calculates the control target value I of the motor current, and the control target value I is calculated by the phase current calculator. 14, the on / off control is performed in accordance with the electrical angle of the motor M detected by the rotation sensor 23 comprising a Hall element or the like, and converted into three phase current values I1, I2, and I3.

  The phase current value I1 is adjusted to a predetermined control amount by the PID calculator 16 and converted to a voltage control value E1, and then the compensation value Z output from the compensation calculator 18 is added to the phase current value I1. The control value E11 is output to the switching circuit 20, and the corresponding switching element is controlled. The motor current value i1 detected by the A phase motor current detector 41 is fed back to the phase current value I1 through the comparator 15.

  The phase current values I2 and I3 are processed in the same manner, and the corresponding switching element of the switching circuit 20 is controlled by the voltage control value E21, and the corresponding switching element of the switching circuit 20 is controlled by the voltage control value E31. The motor current value i3 detected by the C-phase motor current detector 43 is fed back to the phase current value I3 via the comparator 35.

  In the operation of the switching circuit 20 in the normal running state, the duty ratio of the PWM signal corresponding to the voltage control values E11, E21, E31 output from the adders 17, 33, 37 is determined and determined in the converter 21. The A phase FET1 and FET2, B phase FET3 and FET4, C phase FET5 and FET6 are ON / OFF controlled according to the duty ratio, and the motor M is driven.

  Next, a configuration for disconnecting the motor M from the switching circuit 20 when an abnormality in the motor current is detected will be described.

  In FIG. 1, the relay contact 42a of the A-phase motor relay 42 is inserted in the A-phase circuit of the motor M, and the relay contact 44a of the B-phase motor relay 44 is inserted in the B-phase circuit. The A-phase motor relay 42 and the C-phase motor relay 44 are driven by a motor relay drive circuit 46 controlled by an abnormality determiner 45, and relays when the relay coils of the A-phase motor relay 42 and the C-phase motor relay 44 are energized. The contacts 42a and 44a are closed and the motor M is connected to the switching circuit 20. When the energization of the relay coil is stopped, the relay contacts 42a and 44a are opened and the motor M is disconnected from the switching circuit 20.

  The abnormality determination unit 45 receives the A-phase motor current value i1 detected by the A-phase motor current detector 41 and the C-phase motor current value i3 detected by the C-phase motor current detector 43 as inputs. The presence / absence of an abnormality is determined according to the state of the current and the C-phase motor current. When it is determined that an abnormality has occurred, an operation command signal is output to the motor relay drive circuit 46, and the relay contacts 43a and B of the A-phase motor relay 42 are output. The relay contact 44 a of the phase motor relay 44 is opened, and the motor M is disconnected from the switching circuit 20.

[Outline of abnormality detection operation of relay contact at initial diagnosis]
Next, details of the abnormality detection operation of the relay contact of the motor relay at the time of initial diagnosis executed by the control device will be described. The abnormality detection operation at the time of the initial diagnosis is performed for a short time immediately after starting the engine and before starting the running. The normal control operation of the control device is prohibited, and the determination operation by the abnormality determination unit 45 executed in the normal control operation described above is not performed. However, in the abnormality detection operation at the initial diagnosis described below, the motor current is Diagnose the relay contact abnormality from the state of.

  In the abnormality detection operation at the time of initial diagnosis, the duty ratio of the PWM signal is set to a specific duty ratio determined in advance for the abnormality detection operation, and the switching elements FET1 to FET6 of the switching circuit 20 are forced to have this specific duty ratio. To drive. The motor relay is forcibly excited to close the relay contact, and the abnormality of the relay contact is diagnosed from the state of the A-phase to C-phase motor current detected by the current detector at that time. There are a plurality of examples of the abnormality diagnosis operation. Hereinafter, description will be made sequentially.

[First Example of Abnormality Diagnosis Operation]
A first embodiment of the relay contact abnormality diagnosis operation will be described. 4 and 5 are flowcharts for explaining an abnormality diagnosis operation for the A-phase relay contact and the B-phase relay contact.

  The flowchart in FIG. 4 is a flowchart for explaining the first half of the diagnostic processing of the first embodiment, and is also a flowchart for explaining the first half of diagnostic processing of the second and third embodiments described later. The flowchart of FIG. 4 includes the flowchart of FIG. 4 (a) and the flowchart of FIG. 4 (b), which are slightly different from each other, but shows processes that can be substituted for each other. In addition, the portions described as “A phase and / or B phase” in the flowcharts of FIGS. 4A and 4B are “A phase and B phase” in the first and third embodiments. In the second embodiment, it means “A phase (or B phase)”.

  FIG. 6 is a diagram for explaining the flow of the A-phase motor current in the first embodiment, and FIG. 7 is a timing chart for explaining the abnormality diagnosis operation.

  The abnormality diagnosis operation will be described with reference to the flowcharts of FIGS. In the first embodiment, the A-phase motor current flows in the direction indicated by the arrow a in FIG. 6, that is, the resistance Ra, the A-phase relay contact 42a, the motors M, B from the switching circuit 20 to the A-phase motor current detector 41. A state of flowing in the direction toward the switching circuit 20 through the phase relay contact 44a is set, and a state of flowing in the opposite direction is set to perform abnormality diagnosis.

  The timing chart shown in FIG. 7 shows a state when the A-phase relay contact 42a and the B-phase relay contact 44a are normal, and shows that the A-phase motor current flows when the B-phase relay contact 44a is closed. ing.

  First, the flowchart of FIG. 4A will be described. The A phase motor relay 42 and the B phase motor relay 44 are forcibly excited to set the closed state of the A phase relay contact 42a and the closed state of the B phase relay contact 44a (step P1). Waiting for the elapse of a predetermined stabilization time during which the closed state of the relay contact is stabilized (step P2), the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P3). The operation timing may be referred to the timing chart of FIG.

  Further, instead of this processing, as shown in the flowchart of FIG. 4B, the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P1a), and then the A-phase motor relay and the B-phase motor relay are turned on. Excitation may be forced (step P2a). According to this process, since the motor current flows at the moment when the relay contact is closed, it is possible to further enhance the effect of removing foreign matters attached to the relay contact. The operation timing may be referred to the timing chart of FIG.

  Moving to the flowchart of FIG. 5, the state of the A-phase motor current is detected by the A-phase motor current detector 41, and whether or not the absolute value of the A-phase motor current is larger than a predetermined threshold (| A-phase current | ≧ threshold) ?) Is determined (step P11). If the determination result is affirmative, it is determined that the relay contact 42a of the A-phase motor relay and the relay contact 44a of the B-phase motor relay are normal (step P12), and the process proceeds to the next initial diagnosis process.

  If the determination result in step P11 is negative, it is determined whether the absolute value of the A-phase motor current is 0 (zero) (| A-phase current | = 0?), That is, whether the A-phase motor current is flowing. (Step P13). When the determination result is affirmative, it is determined whether or not the count value N of a failure determination counter that counts the number of times of failure determination is greater than or equal to a predetermined determination value n1 (N ≧ n1) (step P14). If the determination result is affirmative, the abnormality determination of the A-phase motor relay is confirmed, a fail safe process is executed (step P15), and the process proceeds to the next initial diagnosis process.

  If the determination result in step P14 is negative, the excitation of the A-phase motor relay is released, 1 is added to the count value of the failure determination counter (step P16), and the process returns to step P1 (or step P1a).

  If the determination result of step P13 is negative, it is determined whether or not the count value N of the failure determination counter is equal to or greater than a predetermined determination value n2 (N ≧ n2) (step P17). If the determination result is affirmative, the abnormality determination of the B-phase motor relay is confirmed, a fail safe process is executed (step P18), and the process proceeds to the next initial diagnosis process. If the determination result in step P17 is negative, the excitation of the B-phase motor relay is released, 1 is added to the count value of the failure determination counter (step P19), and the process returns to step P1 (or step P1a).

  When it is determined in the above abnormality diagnosis that the motor current flows, the motor relay is forcibly excited and the switching element is driven at a specific duty ratio (see FIG. 7). Thereby, the unnatural movement of the steering wheel transmitted from the motor to the steering person through the steering column can be reduced.

  In addition, in order to perform accurate abnormality diagnosis, the duty ratio of the PWM signal for driving the A-phase and B-phase FETs is adjusted according to the battery voltage, and the motor has a constant voltage V (average value) regardless of the battery voltage level. Is preferably applied.

  FIG. 8 is a diagram for explaining the relationship between the battery voltage VBA and the duty ratio D of the PWM signal, and the motor voltage V (average value). When the detected battery voltage is VBA1, the duty ratio D is set to D1. A voltage V (average value) is applied to the motor. When the detected battery voltage is VBA2, the duty ratio D is set to D2. In this case also, the voltage V (average value) is applied to the motor. Thus, by adjusting the duty ratio according to the detected battery voltage VBA, the voltage V (average value) can be applied to the motor regardless of the level of the battery voltage.

  Whether the motor current flows is determined by determining the motor current value detected by the A-phase motor current detector 41 and the C-phase motor current detector 43 by the abnormality determiner 45. The determination threshold is at least the motor current detection. Shall be greater than or equal to the offset value determined by the characteristics of the vessel.

  In addition, the time during which the motor current is passed to perform the abnormality diagnosis is shorter than the mechanical time constant of the motor M, and is equal to or longer than the electrical time constant, and the motor M is operated so as not to rotate. The driver shall be protected by suppressing the rotation of the steering wheel.

  An example of a specific duty ratio of a PWM signal for forcibly driving FET1 to FET6 which are switching elements of A phase to C phase in the abnormality diagnosis of the first embodiment will be described.

(1) A phase FET1 (upper) 60%, A phase FET2 (lower) 40%
B-phase FET3 (upper) 40%, B-phase FET4 (lower) 60%
C-phase FET5 (upper) 50%, C-phase FET6 (lower) 50%
(2) A phase FET1 (upper) 40%, A phase FET2 (lower) 60%
B-phase FET3 (upper) 60%, B-phase FET4 (lower) 40%
C-phase FET5 (upper) 50%, C-phase FET6 (lower) 50%
The specific duty ratio may be set in any of the above (1) and (2). For the C phase, the gates of both FET5 (upper stage) and FET6 (lower stage) may be set OFF.

[Second Embodiment of Abnormality Diagnosis Operation]
A second embodiment of the relay contact abnormality diagnosis operation will be described. FIG. 9 is a diagram for explaining the flow of the A-phase current to the C-phase current in the second embodiment of the relay contact abnormality diagnosis operation.

  In the second embodiment, the A-phase motor current is in the direction indicated by the arrow b1 in FIG. 9, that is, the resistor Ra, the A-phase relay contact 42a, the motor M, and the C-phase motor from the switching circuit 20 to the A-phase motor current detector 41. The state of flowing through the first path toward the switching circuit 20 through the resistor Rc of the current detector 44, and the direction of the B-phase motor current indicated by the arrow b2 in FIG. 9, that is, from the switching circuit 20 to the B-phase relay contact 44a, An abnormality diagnosis is performed by setting a state of flowing through the second path toward the switching circuit 20 through the resistance Rc of the motor M and the C-phase motor current detector 44.

  FIG. 4 used in the first embodiment is also used as a flowchart for explaining the abnormality diagnosis operation of the A-phase relay contact and the B-phase relay contact of the second embodiment. An abnormality diagnosis operation for the A-phase relay contact and the B-phase relay contact will be described with reference to the flowcharts of FIGS. The abnormality diagnosis operation of the A-phase relay contact and the abnormality diagnosis operation of the B-phase relay contact are only different in the relay and the contact. Therefore, the abnormality diagnosis operation of the A-phase relay and its contact will be described. Abnormality diagnosis operation is also described in parentheses and redundant explanation is omitted. In FIG. 4A and FIG. 4B, “A phase and / or B phase” means “A phase (or B phase)”.

  First, the flowchart of FIG. 4A will be described. The A-phase motor relay 42 (B-phase motor relay 44) is forcibly excited to set the closed state of the A-phase relay contact 42a (B-phase relay contact 44a) (step P1). Waiting for the elapse of a predetermined stabilization time during which the closed state of the relay contact is stabilized (step P2), the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P3).

  Further, instead of this process, as shown in the flowchart of FIG. 4B, the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P1a), and then the A phase motor relay 42 (B phase motor) The relay 44) may be forcibly excited (step P2a). According to this process, since the motor current flows at the moment when the relay contact is closed, it is possible to further enhance the effect of removing foreign matters attached to the relay contact.

  Moving to the flowchart of FIG. 10, the state of the A phase (B phase) motor current is detected by the A phase motor current detector 41 (C phase motor current detector 43), and the absolute value of the A phase (C phase) motor current is calculated. It is determined whether it is larger than a predetermined threshold (| A-phase (C-phase) current | ≧ threshold?) (Step P21). If the determination result is affirmative, it is determined that the relay contact 42a of the A-phase motor relay (the relay contact 44a of the B-phase motor relay) is normal (step P22), and the process proceeds to the next initial diagnosis process.

  If the determination result of step P21 is negative, it is determined whether or not the count value N of the failure determination counter is equal to or greater than a predetermined determination value n1 (N ≧ n1) (step P23). If the determination result is affirmative, the abnormality determination of the A phase (B phase) motor relay is confirmed, a fail safe process is executed (step P24), and the process proceeds to the next initial diagnosis process.

  If the determination result in step P23 is negative, the excitation of the A-phase (B-phase) motor relay is released, 1 is added to the count value of the failure determination counter (step P25), and the process returns to step P1 (or step P1a). .

  An example of a specific duty ratio of a PWM signal for forcibly driving FET1 to FET6 which are switching elements of A phase to C phase in the abnormality diagnosis of the second embodiment will be described.

(1) When diagnosing the A-phase relay contact 42a
A phase FET1 (upper) 60%, A phase FET2 (lower) 40%
B phase FET3 (upper) 50%, B phase FET4 (lower) 50%
Or both B-phase FET3 (upper) and FET4 (lower) gates are OFF
C-phase FET5 (upper) 40%, C-phase FET6 (lower) 60%
Or
A phase FET1 (upper) 40%, A phase FET2 (lower) 60%
B phase FET3 (upper) 50%, B phase FET4 (lower) 50%
Or both B-phase FET3 (upper) and FET4 (lower) gates are OFF
C-phase FET5 (upper) 60%, C-phase FET6 (lower) 40%
(2) When diagnosing B-phase relay contact 44a
A phase FET1 (upper) 50%, A phase FET2 (lower) 50%
Or both A-phase FET1 (upper) and FET2 (lower) are gate-off.
B-phase FET3 (upper) 60%, B-phase FET4 (lower) 40%
C-phase FET5 (upper) 40%, C-phase FET6 (lower) 60%
Or
A phase FET1 (upper) 50%, A phase FET2 (lower) 50%
Or both A-phase FET1 (upper) and FET2 (lower) are gate-off.
B-phase FET3 (upper) 40%, B-phase FET4 (lower) 60%
C-phase FET5 (upper) 60%, C-phase FET6 (lower) 40%
In the above abnormality diagnosis, when it is determined that the motor current flows, the motor relay is forcibly excited and the driving of the switching element at the specified duty ratio is immediately stopped. Thereby, the unnatural movement of the steering wheel transmitted from the motor to the steering person through the steering column can be reduced.

  In addition, in order to perform an accurate abnormality diagnosis, the duty ratio of the PWM signal for driving the A-phase and B-phase FETs is adjusted according to the battery voltage in the same manner as in the first embodiment, regardless of whether the battery voltage is high or low. A constant voltage V (average value) is applied to the motor, a determination threshold value for determining whether or not the motor current flows, and a time during which the motor current is supplied to perform an abnormality diagnosis. The diagnosis should be performed by setting the time shorter than the constant, equal to or longer than the electrical time constant, and switching the direction of the current flowing through the relay contact.

[Third embodiment of abnormality diagnosis operation]
A third embodiment of the abnormality diagnosis operation for diagnosing abnormality of the relay contact will be described. 4 used in the first embodiment is also used as a flowchart for explaining the abnormality diagnosis operation of the A-phase relay contact and the B-phase relay contact of the third embodiment. 4A and 4B, “A phase and / or B phase” means “A phase and B phase”.

  9 used in the second embodiment is also used as a diagram for explaining the flow of the A-phase current to the C-phase current in the third embodiment.

  In the third embodiment, the A-phase motor current is in the direction indicated by the arrow b1 in FIG. 9, that is, the resistor Ra, the A-phase relay contact 42a, the motor M, and the C-phase motor current from the switching circuit 20 to the A-phase motor current detector 41. The state of flowing through the first path toward the switching circuit 20 through the resistor Rc of the detector 44, and the direction of the B phase motor current indicated by the arrow b2 in FIG. 9, that is, from the switching circuit 20 to the B phase relay contact 44a, the motor An abnormality diagnosis is performed by simultaneously setting the state of flowing through the second path toward the switching circuit 20 via the resistance Rc of the M and C phase motor current detectors 44.

  The abnormality diagnosis operation will be described with reference to the flowcharts of FIGS. First, the flowchart of FIG. 4A will be described. The A-phase motor relay 42 and the B-phase motor relay 44 are forcibly excited to set the closed state of the A-phase relay contact 42a and the closed state of the B-phase relay contact 44a (step P1). Waiting for the elapse of a predetermined stabilization time during which the closed state of the relay contact is stabilized (step P2), the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P3).

  Further, instead of this processing, as shown in the flowchart of FIG. 4B, the FET1 to FET6 of the switching circuit 20 are forcibly driven at a specific duty ratio (step P1a), and then the A-phase motor relay 42 and the B-phase motor are driven. The relay 44 may be forcibly excited (step P2a). According to this process, since the motor current flows at the moment when the relay contact is closed, it is possible to further enhance the effect of removing foreign matters attached to the relay contact.

  Moving to the flowchart of FIG. 11, the state of the A-phase motor current is detected by the A-phase motor current detector 41, and whether or not the absolute value of the A-phase motor current is larger than a predetermined threshold (| A-phase current | ≧ threshold) ?) Is determined (step P31). When the determination result is affirmative, it is determined that the relay contact 42a of the A-phase motor relay and the relay contact 44a of the B-phase motor relay are normal (step P32), and the process proceeds to the next initial diagnosis process.

  If the determination result in step P31 is negative, the state of the C-phase motor current is detected by the C-phase motor current detector 43, and whether or not the absolute value of the C-phase motor current is greater than a predetermined threshold (| C phase Current | ≧ threshold?) Is determined (step P33).

  If the determination result of step P33 is negative, it is determined whether or not the count value N of the failure determination counter is equal to or greater than a predetermined determination value n1 (N ≧ n1) (step P34). When the determination result is affirmative, the abnormality determination of the A-phase motor relay and the B-phase motor relay is confirmed, fail-safe processing is executed (step P35), and the process proceeds to the next initial diagnosis processing. If the determination result in step P34 is negative, the excitation of the A-phase motor relay and the B-phase motor relay is released, 1 is added to the count value of the failure determination counter (step P36), and the process returns to step P1 (or step P1a). .

  If the determination result in step P33 is affirmative, it is determined whether the A-phase motor current absolute value and the C-phase motor current absolute value are equal (| A-phase current | = | C-phase current |?) (Step) P37). If the determination result is affirmative, it is determined whether or not the count value N of the failure determination counter is greater than or equal to a predetermined determination value n2 (N ≧ n2) (step P38). When the determination result is affirmative, the abnormality determination of the B-phase motor relay is confirmed, a fail safe process is executed (step P39), and the process proceeds to the next initial diagnosis process. If the determination result in step P38 is negative, the excitation of the B-phase motor relay is released, 1 is added to the count value of the failure determination counter (step P40), and the process returns to step P1 (or step P1a).

  If the determination result in step P37 is negative, it is determined whether or not the count value N of the failure determination counter is equal to or greater than a predetermined determination value n3 (N ≧ n3) (step P41). If the determination result is affirmative, the abnormality determination of the A-phase motor relay is confirmed, a fail safe process is executed (step P42), and the process proceeds to the next initial diagnosis process. If the determination result in step P41 is negative, the excitation of the A-phase motor relay is released, 1 is added to the count value of the failure determination counter (step P43), and the process returns to step P1 (or step P1a).

  An example of the specific duty ratio of the PWM signal for forcibly driving the FET1 to FET6 which are switching elements of A phase to C phase in the abnormality diagnosis of the third embodiment will be described.

A phase FET1 (upper) 60%, A phase FET2 (lower) 40%
B-phase FET3 (upper) 60%, B-phase FET4 (lower) 40%
C-phase FET5 (upper) 30%, C-phase FET6 (lower) 70%
Or
A phase FET1 (upper) 40%, A phase FET2 (lower) 60%
B-phase FET3 (upper) 40%, B-phase FET4 (lower) 60%
C-phase FET5 (upper) 70%, C-phase FET6 (lower) 30%
In the above abnormality diagnosis, when it is determined that the motor current flows, the motor relay is forcibly excited and the driving of the switching element at the specified duty ratio is immediately stopped. Thereby, the unnatural movement of the steering wheel transmitted from the motor to the steering person through the steering column can be reduced.

  In addition, in order to perform an accurate abnormality diagnosis, the duty ratio of the PWM signal for driving the A-phase and B-phase FETs is adjusted according to the battery voltage in the same manner as in the first embodiment, regardless of whether the battery voltage is high or low. A constant voltage V (average value) is applied to the motor, a determination threshold value for determining whether or not the motor current flows, and a time during which the motor current is supplied to perform an abnormality diagnosis. The diagnosis should be performed by setting the time shorter than the constant, equal to or longer than the electrical time constant, and switching the direction of the current flowing through the relay contact.

  In the third embodiment, the B phase current is not directly detected, but the determination threshold for the C phase motor current is twice the determination threshold for the A phase motor current, and the C phase motor current is equal to the A phase motor current. It is also possible to determine that a current has passed through the A-phase motor relay 41 and the B-phase motor relay 44, that is, the relay contacts 42a and 44a are normal.

  This is an electric power steering device using a three-phase brushless motor provided with an abnormality detecting means for detecting an abnormality such as a contact failure of a relay contact of a motor relay interposed in a motor circuit of a steering assist motor.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram explaining the control apparatus of the electric power steering apparatus of embodiment of this invention, the circuit element of the periphery, and the operation | movement outline | summary. 3A and 3B illustrate a structure of a switching circuit. The figure explaining the structure of the PID calculating unit of a control circuit. The flowchart explaining the first half of the 1st thru | or 3rd Example of abnormality diagnosis operation | movement of a relay contact. The flowchart explaining the second half of 1st Example of the abnormality diagnosis operation | movement of a relay contact. The figure explaining the flow of the motor electric current in 1st Example. The timing chart explaining abnormality diagnosis operation | movement. The figure explaining the relationship between the duty ratio D of the battery voltage VBA and the PWM signal, and the motor voltage V (average value). The figure explaining the flow of the motor current in 2nd Example and 3rd Example. The flowchart explaining the second half of 2nd Example of abnormality diagnosis operation | movement of a relay contact. The flowchart explaining the second half of 3rd Example of abnormality diagnosis operation | movement of a relay contact. The block diagram explaining the schematic structure of the motor drive circuit which drives a three-phase brushless motor. The figure explaining the rise / fall timing of the detection element of a rotation sensor, and the timing of ON / OFF control of a switching element.

Explanation of symbols

10 Control device (control circuit)
DESCRIPTION OF SYMBOLS 11 Torque sensor 12 Vehicle speed sensor 13 Target current calculator 14 Phase current calculator 15 Comparator 16, 32, 36 PID calculator 17, 33, 37 Adder 18 Compensation calculator 20 Switching circuit 21 Converter 22 Voltage detector 23 Rotation Sensor 31, 35 Comparator 34 Motor current detection calculator 41 A phase motor current detector 42 A phase motor relay 42a Relay contact (A phase motor relay contact)
43 Phase C motor current detector 44 Phase B motor relay 44a Relay contact (B phase motor relay contact)
45 Abnormality determination device 46 Motor relay drive circuit FET, FET1, FET2, FET3, FET4, FET5, FET6 Semiconductor switching element M Motor (three-phase brushless motor)

Claims (14)

In an electric power steering device for a vehicle that uses a three-phase brushless motor as a supply source of steering assist force,
Based on at least a steering torque signal generated in the steering shaft, a current command value that is a control target value of the motor current is calculated, and a plurality of switching elements are set based on the current control value of each phase of the motor determined based on the current command value. A control device for determining the duty ratio of the PWM signal to be driven, and driving the motor by controlling ON / OFF of the switching element at the determined duty ratio;
An A-phase motor relay and a B-phase motor that are interposed between the A-phase terminal and the B-phase terminal of the motor and switching elements corresponding to the A-phase and B-phase of the motor and operate in a direction in which a relay contact is closed by excitation. Relay,
A phase A motor current detector mounted on the phase A motor circuit,
In the initial diagnosis period of the control system at the time of engine start-up, the control device excites the A-phase motor relay and the B-phase motor relay and forcibly controls the switching element with a preset specific duty ratio. An electric power steering apparatus characterized by determining a state of a relay contact of an A phase and B phase motor relay based on an A phase motor current. In the initial diagnosis period of the control system when the engine is started, the control device is detected by exciting the A-phase motor relay and the B-phase motor relay after forcibly controlling the switching element with a predetermined duty ratio set in advance. 2. The electric power steering apparatus according to claim 1, wherein the state of the relay contacts of the A-phase and B-phase motor relays is determined based on the A-phase motor current. 3. The control device according to claim 1, wherein the control device determines that the relay contacts of the A-phase and B-phase motor relays are normal when the absolute value of the A-phase motor current is equal to or greater than a predetermined threshold value. The electric power steering apparatus as described. 4. The control device according to claim 3, wherein when the absolute value of the A-phase motor current is zero, the relay contact of the A-phase motor relay is determined to be abnormal when the number of failure determinations exceeds a predetermined value. The electric power steering device described in 1. In an electric power steering device for a vehicle that uses a three-phase brushless motor as a supply source of steering assist force,
Based on at least a steering torque signal generated in the steering shaft, a current command value that is a control target value of the motor current is calculated, and a plurality of switching elements are set based on the current control value of each phase of the motor determined based on the current command value. A control device for determining the duty ratio of the PWM signal to be driven, and driving the motor by controlling ON / OFF of the switching element at the determined duty ratio;
An A-phase motor relay and a B-phase motor that are interposed between the A-phase terminal and the B-phase terminal of the motor and switching elements corresponding to the A-phase and B-phase of the motor and operate in a direction in which a relay contact is closed by excitation. Relay,
A phase A motor current detector mounted on the phase A motor circuit, and a phase C motor current detector mounted on the phase C motor circuit;
With
In the initial diagnosis period of the control system at the time of engine start-up, the control device excites the A-phase motor relay or the B-phase motor relay and forcibly controls the switching element at a predetermined duty ratio set in advance. An electric power steering device characterized by determining a state of a relay contact of an A phase or B phase motor relay based on an A phase motor current or a C phase motor current. In the initial diagnosis period of the control system at the time of engine startup, the control device is detected by exciting the A-phase motor relay or the B-phase motor relay after forcibly controlling the switching element with a predetermined duty ratio set in advance. 6. The electric power steering apparatus according to claim 5, wherein the state of the relay contact of the A-phase or B-phase motor relay is determined based on the A-phase motor current. The control device determines that the relay contact of the A-phase or C-phase motor relay is normal when the absolute value of the A-phase motor current or the C-phase motor current is equal to or greater than a predetermined threshold value. Alternatively, the electric power steering apparatus according to claim 6. When the absolute value of the A-phase motor current or the C-phase motor current is less than a predetermined threshold, when the failure determination count is equal to or greater than the predetermined value, the control device is connected to the relay contact of the A-phase motor relay or the C-phase motor relay. The electric power steering apparatus according to claim 5, wherein the electric power steering apparatus is determined to be abnormal. In an electric power steering device for a vehicle that uses a three-phase brushless motor as a supply source of steering assist force,
Based on at least a steering torque signal generated in the steering shaft, a current command value that is a control target value of the motor current is calculated, and a plurality of switching elements are set based on the current control value of each phase of the motor determined based on the current command value. A control device for determining the duty ratio of the PWM signal to be driven, and driving the motor by controlling ON / OFF of the switching element at the determined duty ratio;
An A-phase motor relay and a B-phase motor that are interposed between the A-phase terminal and the B-phase terminal of the motor and switching elements corresponding to the A-phase and B-phase of the motor and operate in a direction in which a relay contact is closed by excitation. Relay,
A phase A motor current detector mounted on the phase A motor circuit, and a phase C motor current detector mounted on the phase C motor circuit;
With
In the initial diagnosis period of the control system at the time of engine start-up, the control device excites the A-phase motor relay and the B-phase motor relay and forcibly controls the switching element with a preset specific duty ratio. An electric power steering apparatus characterized by determining a state of a relay contact of an A phase and B phase motor relay based on an A phase motor current. In the initial diagnosis period of the control system when the engine is started, the control device is detected by exciting the A-phase motor relay and the B-phase motor relay after forcibly controlling the switching element with a predetermined duty ratio set in advance. 10. The electric power steering apparatus according to claim 9, wherein the state of the relay contacts of the A-phase and B-phase motor relays is determined based on the A-phase motor current. The control device determines that the relay contacts of the A-phase and B-phase motor relays are normal when the absolute value of the A-phase motor current is greater than or equal to a predetermined threshold value. The electric power steering apparatus as described. When the absolute value of the A phase motor current is less than a predetermined threshold value and the absolute value of the C phase motor current is equal to or greater than the predetermined threshold value, the control device further includes the absolute value of the A phase motor current and the C phase motor current. The electric power steering apparatus according to claim 11, wherein when the number of failure determinations is equal to or greater than a predetermined value, the relay contact of the B-phase motor relay is determined to be abnormal. When the absolute value of the A-phase motor current is less than a predetermined threshold value and the absolute value of the C-phase motor current is less than the predetermined threshold value, 11. The electric power steering apparatus according to claim 9, wherein the relay contacts of the phase motor relay and the B phase motor relay are determined to be abnormal. The said control apparatus performs a fail safe process, when it determines with the relay contact of A-phase motor relay and / or B-phase motor relay being abnormal, The claim 4, Claim 8, Claim 12 characterized by the above-mentioned. The electric power steering apparatus according to claim 13.

Images