JP5205981B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device that assists steering by the rotational force of a motor.

  An electric power steering apparatus for assisting steering by driving a steering assist motor in accordance with the steering torque applied to the steering wheel and transmitting the rotational force of the motor to the steering mechanism has been put into practical use. . Specifically, the electric power steering apparatus includes a torque sensor that detects a steering torque applied to the steering wheel, a motor for assisting steering, and an ECU (Electronic Control Unit) that controls driving of the motor. The ECU is composed of a control unit, a motor drive unit, and other various circuits. A power source is connected to a power supply terminal of the ECU via a power supply line, and power is supplied to the control unit and the motor drive unit. . The steering torque value detected by the torque sensor is given to the control unit, and the control unit gives the motor drive unit a control signal corresponding to the steering torque value detected by the torque sensor, thereby controlling the drive of the motor and performing steering assistance. .

In general, the electric power steering device detects a failure between the power source and the drive unit, for example, breakage of a power supply line connecting the power source and the drive unit, poor contact, deterioration of the power source, etc., in order to ensure vehicle driving safety. When an abnormality is detected, the motor drive is stopped. In the electric power steering apparatus according to Patent Document 1, the terminal voltage of the ECU is detected, and when the terminal voltage falls below a predetermined threshold, it is determined that there is a failure. Further, focusing on the fact that the terminal voltage fluctuates due to fluctuations in the motor current, the threshold value is changed in accordance with the motor current to enable more accurate abnormality detection.
JP-A-8-324448

  However, in the electric power steering device according to Patent Document 1, it has been a problem because it is not possible to quickly identify whether the cause of the failure is the power source or the feeder line. For example, when inspecting an electric power steering apparatus that has stopped abnormally, it is necessary to inspect various parts to identify a faulty part, and it is difficult to perform the inspection efficiently.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electric power steering device that can quickly identify which of the power source and the feeder line has the cause of failure.

An electric power steering apparatus according to a first aspect of the present invention is such that a motor is driven by a drive unit provided in an ECU connected to a power source via a power supply line , and steering is assisted by the rotational force of the motor. in is provided outside the ECU, a battery sensor for detecting a current flowing through the output voltage and the power supply line of the power supply, the ECU is connected to the power supply via the feed line, wherein the drive unit A positive terminal for supplying power to the power supply, an ECU terminal voltage detector for detecting a voltage applied to the positive terminal, and a difference between the voltages detected by the battery sensor and the ECU terminal voltage detector. Means for calculating a threshold for determining an abnormality of the battery based on the current detected by the battery sensor, the battery sensor and the ECU Child voltage detection unit is characterized in that it comprises a comparing means for comparing the the difference between the voltage detection threshold.

According to a second aspect of the present invention, there is provided an electric power steering apparatus that includes a motor current detecting unit that detects a motor current flowing through the motor, and an estimation that estimates a current flowing through the feeder line based on the motor current detected by the motor current detecting unit. And means for comparing the current estimated by the estimation means and the current detected by the battery sensor.

According to the first invention, the battery sensor detects the output voltage of the power source, and the ECU terminal voltage detection unit detects the input voltage to the drive unit. Then, the comparison unit compares the difference between the output voltage of the power source and the input voltage to the drive unit with a threshold value. Since the voltage of this difference increases as the electric resistance of the feeder line increases, this is an index indicating whether or not the feeder line is normal. For example, the difference when the power supply line is abnormal is larger than the difference when the power supply line is normal and the power supply is abnormal.
Therefore, if the threshold value is appropriately set, it is possible to quickly identify whether the power source or the power supply line has the cause of failure by referring to the comparison result of the comparison unit.

Further, the battery sensor detects the current flowing through the drive unit, and calculates a threshold value corresponding to the magnitude of the current. Since the difference between the output voltage of the power supply and the input voltage of the drive unit varies depending on the magnitude of the current flowing through the drive unit, the boundary voltage between the difference when the power supply line is normal and the difference when the power supply line is abnormal also varies. However, the threshold can be changed accordingly.
Therefore, regardless of the magnitude of the current flowing through the drive unit, it is possible to more accurately specify whether the power supply or the power supply line has a cause of failure.

According to the second invention, the current flowing through the drive unit is obtained by a different method. In the first method, the battery sensor directly detects the current flowing through the drive unit. In the second method, the motor current is detected, and the current flowing through the drive unit is specified based on the motor current. Then, the currents specified by the first method and the second method are compared. The comparison result is an index for determining whether or not the battery sensor and the motor current detection means are normal.
Therefore, it is possible to identify an abnormality in the current detection system or the drive unit.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1
FIG. 1 is a schematic diagram showing a configuration of an electric power steering apparatus according to the present invention. The electric power steering apparatus according to the present invention includes a rack and pinion type steering mechanism 1. The steering mechanism 1 includes a rack shaft 10 that is supported so as to be movable in the axial direction in a rack housing 11 that extends in the left-right direction of a vehicle body (not shown), and a pinion housing 20 that crosses the rack housing 11 in the middle. And a pinion shaft 2 rotatably supported.

  Both ends of the rack shaft 10 projecting outward from the left and right sides of the rack housing 11 are connected to left and right front wheels 13 and 13 as steering wheels via separate tie rods 12 and 12, respectively. Further, the upper end of the pinion shaft 2 protruding outside from the pinion housing 20 is connected to a steering wheel 30 as a steering member via the steering shaft 3. A pinion (not shown) is integrally formed at a lower portion of the pinion shaft 2 extending inside the pinion housing 20, and the pinion is formed in an intermediate portion of the rack shaft 10 at an intersection with the rack housing 11. Meshed with the rack.

  The steering shaft 3 is rotatably supported inside a cylindrical column housing 31. The column housing 31 is mounted in a not-shown interior of a vehicle compartment while maintaining an inclined posture with the front facing down. The pinion shaft 2 is connected to the lower end of the steering shaft 3 that protrudes below the column housing 31, and the steering wheel 30 is fixed to the upper end of the steering shaft 3 that protrudes above the column housing 31.

  With the above configuration, the steering shaft 3 is rotated by the rotation operation of the steering wheel 30 for steering, and this rotation is transmitted to the pinion shaft 2, and the rotation of the pinion shaft 2 is performed at the meshing portion of the pinion and the rack. The movement of the shaft 10 is converted into the movement in the axial length direction, and such movement of the rack shaft 10 is transmitted to the left and right front wheels 13 and 13 via the separate tie rods 12 and 12 for steering.

  In the middle of the column housing 31 that supports the steering shaft 3, a torque sensor 4 that detects a steering torque applied to the steering shaft 3 by a rotation operation of the steering wheel 30 is provided. A steering assist motor 5 is attached below the torque sensor 4.

  The steering assisting motor 5 is attached to the outside of the column housing 31 with its axis substantially orthogonal, and, for example, a worm fixed to the output end extending inside the column housing 31 is fixedly fitted to the steering shaft 3 by external fitting. The rotation of the motor 5 is decelerated by the worm and the worm wheel and transmitted to the steering shaft 3 to assist the steering performed as described above.

The steering assist motor 5 attached in this way is driven and controlled by the ECU 6.
FIG. 2 is a block diagram schematically showing the configuration of the ECU 6. The ECU 6 includes an assist control unit 61. The assist control unit 61 includes a CPU, a ROM, a RAM, an input interface, and an output interface that are connected to each other via an internal bus. The CPU reads the control program stored in the ROM into the RAM, and executes it. Assist control is performed.
A torque sensor 4, a vehicle speed sensor 7, and a motor current detection unit 50 (motor current detection means) are connected to the input interface, and the steering torque value T detected by the torque sensor 4 and detected by the vehicle speed sensor 7. The vehicle speed value V and the motor current value Im detected by the motor current detection unit 50 are respectively input.

  FIG. 3 is a functional block diagram of the assist control unit 61. The steering torque value T is given to the phase compensator 61a of the assist controller 61. In order to stabilize the control system, the phase compensation unit 61a performs a phase compensation process such as advancing the phase with respect to the steering torque value T given by the torque sensor 4, and performs the phase compensation process. The obtained steering torque value T is given to the target drive current calculation unit 61b. Further, the vehicle speed value V is given to the target drive current calculation unit 61b.

  The target drive current calculation unit 61b has an assist map indicating the relationship between the steering torque value T and the target drive current value, and applies the given steering torque value T to the assist map to obtain the target drive current value. The obtained target drive current value is given to the subtractor 61c. There are a plurality of assist maps for each vehicle speed value, and the target drive current calculation unit 61b is configured to select one assist map corresponding to the vehicle speed value V and obtain the target drive current value based on the selected assist map. ing.

  The subtractor 61c is also given a motor current value Im output by the motor current detector 50 that detects the current flowing through the motor 5. The subtractor 61c calculates the output value of the target drive current calculation unit 61b, that is, the deviation between the target drive current value and the motor current value Im, and gives this deviation to the motor drive unit 64 (drive unit).

  The motor drive unit 64 includes a PWM signal generation unit (not shown). The PWM signal generation unit generates a PWM signal based on the deviation given from the assist control unit 61, and the motor drive unit 64 generates a coil of each phase (not shown) of the motor 5, a power source and a ground terminal by the PWM signal. The motor 5 is PWM driven.

  The ECU 6 also includes a positive terminal 65 and a negative terminal 66 for supplying power to the assist control unit 61 and the motor driving unit 64, and the on-vehicle battery 9 (power source) is connected to the positive terminal 65 via a power supply line 91. Are connected, and the negative terminal 66 is grounded.

  Further, the ECU 6 determines whether or not there is a failure between the ECU terminal voltage detection unit 62 that detects the ECU terminal voltage value Vecu applied to the positive terminal 65 and the in-vehicle battery 9 and the motor drive unit 64, and determines that there is a failure. A failure determination unit 63 that stops motor driving by the motor driving unit 64. Further, the failure determination unit 63 has a function of determining which of the in-vehicle battery 9 and the power supply line 91 has the cause of the failure when the electric power steering apparatus is stopped.

  The failure determination unit 63 is given the ECU terminal voltage value Vecu detected by the ECU terminal voltage detection unit 62 and the output voltage value (battery voltage value Vb) of the in-vehicle battery 9 detected by the battery sensor 8. Performs a failure determination as shown below based on the ECU terminal voltage value Vecu and the battery voltage value Vb, and gives a stop signal for stopping the motor drive to the motor drive unit 64 as necessary. The motor driving unit 64 to which the stop signal is given stops driving the motor.

  FIG. 4 is a flowchart illustrating a processing procedure of the failure determination unit 63. First, the failure determination unit 63 captures the ECU terminal voltage value Vecu (step S11), and determines whether or not the captured ECU terminal voltage value Vecu is within the normal range (step S12). When it is determined that the ECU terminal voltage value Vecu is within the normal range (step S12: YES), the failure determination unit 63 ends the process related to the failure determination.

  When it is determined that the ECU terminal voltage value Vecu is not within the normal range (step S12: NO), the failure determination unit 63 stops the motor drive (step S13).

Next, failure determination unit 63 captures battery voltage value Vb (step S14), and determines whether the absolute value of the deviation between the captured battery voltage value Vb and ECU terminal voltage value Vecu is equal to or greater than a predetermined threshold value. (Step S15). The threshold value is a value stored in a non-volatile memory (not shown). For example, when the voltage drop in the normal power supply line 91 is 0.5V, the threshold value may be set to 1 to 2V.
When the power supply line 91 is disconnected, the battery voltage value Vb is 12V and the ECU terminal voltage value Vecu is 0V. Therefore, the absolute value of the deviation is about 12V, and is determined to be equal to or greater than the threshold value in step S15. Further, when a sufficient voltage is not applied to the ECU 6 due to poor contact although not disconnected, the deviation is 2V to 12V, and is determined to be equal to or greater than the threshold value. On the other hand, when the power supply line 91 is normal, the absolute value of the deviation is about 0.5 V, so it is determined that the power supply line 91 is less than the threshold value.

  When it determines with it being more than a threshold value by step S15 (step S15: YES), the failure determination part 63 determines with the electric power supply line 91 having abnormality, for example, a disconnection, or a poor contact (step S16), and the process which concerns on failure determination Finish. When it determines with it being less than a threshold value (step S15: NO), the failure determination part 63 determines with the vehicle-mounted battery 9 having abnormality (step S17), and complete | finishes the process which concerns on failure determination.

  In addition, what is necessary is just to comprise so that a determination result may be displayed, for example by lighting or extinction of a light emitting diode. In addition, an output terminal for failure determination may be provided, and a high level or low level signal may be output to the inside or outside of the vehicle according to the failure part. Further, the determination result in step S16 or 17 may be recorded in a storage means (not shown) such as an EEPROM such as a flash memory.

In the electric power steering apparatus configured as described above, when the electric power steering apparatus abnormally stops, it is possible to quickly identify which of the in-vehicle battery 9 and the power supply line 91 has the cause of failure.
Therefore, the failure check of the electric power steering device can be performed efficiently.

  In the first embodiment, the column assist type electric power steering device is exemplified, but the present invention may be applied to other types of electric power steering devices such as a rack assist type and a pinion assist type.

Embodiment 2
FIG. 5 is a block diagram schematically showing another configuration of the ECU 206 according to the present invention. Similar to the first embodiment, the ECU 206 includes an assist control unit 61, an ECU terminal voltage detection unit 62, a failure determination unit 263, a motor drive unit 64, and the like. In the electric power steering apparatus according to the present invention, the battery sensor 208 detects the current value Ib flowing through the motor drive unit 64 in addition to the battery voltage value Vb, and the battery voltage value Vb and the current value Ib are input to the failure determination unit 263. The difference between the failure determination unit 263 and the electric power steering apparatus according to the first embodiment is that the failure determination unit 263 changes the threshold value according to the current value Ib. The point will be described. Note that the battery sensor 208 in the second embodiment functions as first voltage detection means and current detection means.

  FIG. 6 is a flowchart illustrating a processing procedure of the failure determination unit 263 according to the second embodiment. First, the failure determination unit 263 takes in the ECU terminal voltage value Vecu (step S211), and determines whether or not the taken in ECU terminal voltage value Vecu is within a normal range (step S212). When it is determined that the ECU terminal voltage value Vecu is within the normal range (step S212: YES), the failure determination unit 263 ends the process related to the failure determination.

When it is determined that the ECU terminal voltage value Vecu is not within the normal range (step S212: NO), the motor drive is stopped (step S213). Next, the failure determination unit 263 takes in the current value Ib flowing through the power supply line 91 and the motor drive unit 64 from the battery sensor 208 (step S214). Then, the failure determination unit 263 reads the resistance value R of the power supply line 91 stored in the nonvolatile memory (not shown) (step S215), and multiplies the current value Ib and the resistance value R to calculate a threshold value (step S215). S216). The threshold value calculated in this process corresponds to the voltage difference between the battery voltage value Vb and the ECU terminal voltage value Vecu in the normal power supply line 91. Therefore, when the voltage is used as the threshold value, it is possible to accurately determine the abnormality of the power supply line 91.
Note that by executing the processing of steps S215 and 216, the failure determination unit 263 functions as a means for calculating a threshold value.

  When the process of step S216 is completed, the same process as that of step S14 to step S17 in the first embodiment, that is, the process for determining whether the power supply line 91 or the in-vehicle battery 9 has a failure cause is performed in steps S217 to S217. Run at 220.

  In the electric power steering apparatus according to the second embodiment, since the threshold value is changed based on the current flowing through the power supply line 91, regardless of the magnitude of the current flowing through the power supply line 91, It can be specified more accurately whether the in-vehicle battery 9 or the power supply line 91 has a cause of failure.

  Other configurations and operations of the electric power steering apparatus according to the second embodiment are the same as those of the electric power steering apparatus according to the first embodiment. Detailed description thereof is omitted.

Embodiment 3
FIG. 7 is a block diagram schematically showing another configuration of the ECU 306 according to the present invention. As in the first embodiment, the ECU 306 includes an assist control unit 61, an ECU terminal voltage detection unit 62, a failure determination unit 363, a motor drive unit 64, and the like. The electric power steering apparatus according to Embodiment 3 is configured such that the motor current value Im is input to the failure determination unit 363, and the threshold value is changed according to the motor current value Im. Since it is different from the electric power steering apparatus according to the first embodiment, the difference will be mainly described below.

  FIG. 8 is a flowchart illustrating a processing procedure of the failure determination unit 363 according to the third embodiment. First, the failure determination unit 363 takes in the ECU terminal voltage value Vecu (step S311), and determines whether or not the taken in ECU terminal voltage value Vecu is within a normal range (step S312). When it is determined that the ECU terminal voltage value Vecu is within the normal range (step S312: YES), the failure determination unit 263 ends the process related to the failure determination.

  When it is determined that the ECU terminal voltage value Vecu is not within the normal range (step S312: NO), the motor drive is stopped (step S313). Next, the motor current value Im is captured (step S314), and the current value Ib flowing through the feeder 91 is estimated based on the motor current value Im (step S315). Failure determination unit 363 calculates current value Ib based on a conversion formula stored in advance in a non-volatile memory (not shown) and motor current value Im.

Then, the failure determination unit 363 reads the resistance value R of the feeder 91 (step S316) and multiplies the current value Ib and the resistance value R to calculate a threshold value (step S317).
The failure determination unit 363 functions as an estimation unit by executing step S315, and functions as a unit for calculating a threshold value by executing steps S316 and 317.

  When the process of step S317 is completed, the same process as that of step S14 to step S17 in the first embodiment, that is, the process for determining which of the power supply line 91 or the in-vehicle battery 9 has a failure cause is performed in steps S318 and S318. Execute at 321.

  In the electric power steering apparatus according to the third embodiment, the current flowing through the feeder 91 and the motor drive unit 64 is estimated based on the motor current, and the threshold is changed based on the current. Regardless of the magnitude of the current flowing through the power supply line 91, it is possible to more accurately identify whether the vehicle-mounted battery 9 or the power supply line 91 has a cause of failure.

  Further, since the current flowing through the power supply line 91 and the motor drive unit 64 is estimated using the motor current detection unit 50 necessary for motor rotation control, the current value on the vehicle battery 9 side can be detected. It is not necessary to provide the battery sensor 8, and the electric power steering apparatus having the above-described effects can be configured with low cost and a simple configuration.

  Other configurations and operations of the electric power steering apparatus according to the third embodiment are the same as those of the electric power steering apparatus according to the first embodiment, and therefore corresponding parts are denoted by the same reference numerals. Detailed description thereof is omitted.

Embodiment 4
FIG. 9 is a block diagram schematically showing another configuration of the ECU 406 according to the present invention. Similar to the first embodiment, the ECU 406 includes an assist control unit 61, an ECU terminal voltage detection unit 62, a failure determination unit 463, a motor drive unit 64, and the like. The electric power steering apparatus according to the fourth embodiment is configured such that the current flowing through the power supply line 91 and the motor drive unit 64 is specified by different methods, and the presence or absence of a failure in the current detection system is determined. Therefore, the difference will be mainly described below.

  The battery sensor 408 is configured to detect the current value Ib flowing through the motor drive unit 64 in addition to the battery voltage value Vb, and to input the battery voltage value Vb and the current value Ib to the failure determination unit 463. The motor current value Im is input to the failure determination unit 463.

  10 and 11 are flowcharts showing the processing procedure of the failure determination unit 463 in the fourth embodiment. First, the failure determination unit 463 captures the ECU terminal voltage value Vecu (step S411), and determines whether or not the captured ECU terminal voltage value Vecu is within the normal range (step S412). When it is determined that the ECU terminal voltage value Vecu is within the normal range (step S412: YES), the failure determination unit 463 ends the process related to the failure determination.

  When it is determined that the ECU terminal voltage value Vecu is not within the normal range (step S412: NO), the motor drive is stopped (step S413). Next, the motor current value Im is captured (step S414), and the current value Ib1 flowing through the feeder 91 is estimated based on the motor current value Im (step S415). Moreover, the failure determination unit 463 directly takes in the current value Ib2 flowing through the power supply line 91 (step S416).

  Next, the failure determination unit 463 determines whether or not the absolute value of the deviation between the estimated current value Ib1 and the directly detected current value Ib2 is greater than or equal to a predetermined first threshold value (step S417). . Note that the first threshold value is a numerical value stored in advance by the failure determination unit 463. When it determines with it being more than a 1st threshold value (step S417: YES), the failure determination part 463 determines that there exists abnormality in a current detection system (step S418), and complete | finishes the process which concerns on failure determination.

  When it is determined in step S417 that it is less than the first threshold value (step S417: NO), failure determination unit 463 performs the same processing as that in steps S316 to 321 in the third embodiment, that is, either power supply line 91 or in-vehicle battery 9 A process for determining whether or not there is a failure cause is executed in steps S419 to S424.

  In the electric power steering apparatus according to the fourth embodiment, the abnormality of the current detection system or the motor drive unit 64 can be specified by obtaining and comparing the current flowing through the feeder 91 by different methods.

Further, by determining whether or not the current detection system is normal, it is possible to prevent erroneous determination of the faulty part due to an abnormal threshold calculated based on the current value.
Therefore, it is possible to more accurately determine whether the power supply line 91 or the in-vehicle battery 9 is abnormal.

The other configurations, operations, and effects of the electric power steering apparatus according to Embodiment 4 are the same as the configurations, operations, and effects of the electric power steering apparatus according to Embodiment 1. The detailed description is omitted.
In addition, it should be considered that the embodiment disclosed this time is illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a mimetic diagram showing the composition of the electric power steering device concerning the present invention. It is a block diagram which shows typically the structure of ECU. It is a functional block diagram of an assist control part. It is a flowchart which shows the process sequence of a failure determination part. It is a block diagram which shows typically the other structure of ECU which concerns on this invention. 6 is a flowchart illustrating a processing procedure of a failure determination unit according to the second embodiment. It is a block diagram which shows typically the other structure of ECU which concerns on this invention. 10 is a flowchart illustrating a processing procedure of a failure determination unit in the third embodiment. It is a block diagram which shows typically the other structure of ECU which concerns on this invention. 10 is a flowchart illustrating a processing procedure of a failure determination unit according to the fourth embodiment. 10 is a flowchart illustrating a processing procedure of a failure determination unit according to the fourth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Steering mechanism, 5 Motor, 8 Battery sensor (1st voltage detection means, current detection means), 9 Vehicle-mounted battery (power supply), 50 Motor current detection part (motor current detection means), 62 ECU terminal voltage detection part (1st 2 voltage detection means), 63 failure determination section (comparison means, estimation means), 64 motor drive section (drive section)

Claims (2)

In the electric power steering apparatus configured to drive a motor by a drive unit provided in an ECU connected to a power source via a power supply line and assist steering by the rotational force of the motor,
A battery sensor which is provided outside the ECU and detects an output voltage of the power source and a current flowing through the power supply line ;
The ECU
It is connected to the power supply via the feed line, a positive terminal for supplying power to the drive unit,
An ECU terminal voltage detector for detecting a voltage applied to the positive terminal;
Means for calculating a threshold value for determining an abnormality of the power supply line based on a difference between the voltages detected by the battery sensor and the ECU terminal voltage detection unit based on a current detected by the battery sensor;
An electric power steering apparatus comprising: a comparison unit that compares a difference between the voltages detected by the battery sensor and the ECU terminal voltage detection unit with the threshold value. Motor current detecting means for detecting a motor current flowing through the motor;
Estimating means for estimating the current flowing through the feeder line based on the motor current detected by the motor current detecting means;
The electric power steering apparatus according to claim 1, further comprising: means for comparing the current estimated by the estimation means and the current detected by the battery sensor.

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