JP4333661B2 - Electric power steering device - Google Patents

Description

  The present invention relates to a technique for diagnosing the state of a power supply device in an electric power steering device that applies a steering torque by controlling an energization amount to an electric actuator according to a steering state of a steering wheel.

  Conventionally, this type of electric power steering device is a device that applies a steering torque by controlling the amount of current supplied to the electric motor in accordance with the steering state of the steering wheel, but the power consumption is considerably high. For this reason, when the capacity of the battery is reduced, the amount of power supplied to the electric motor that generates the steering torque is limited, and a predetermined steering torque cannot be obtained, or the power supply voltage to other electric control systems that operate simultaneously is reduced. There is a risk of lowering.

Therefore, it is important to detect a decrease in the battery state in advance before this situation occurs and to prompt the driver to replace the battery.
Thus, an electric power steering device having a function of diagnosing a battery state is known. For example, in Patent Document 1, two electric motors that apply drive torque to the steered wheels are provided, and one of the electric motors is driven in the left steered direction so as not to steer the wheels when the battery state is diagnosed. At the same time, the other electric motor is driven in the right steering direction, a large current is passed through each electric motor, and the battery voltage drop at this time is measured. When the battery voltage drop exceeds the threshold, it is determined that the battery has deteriorated or the remaining capacity has been reduced, and an alarm is issued to the driver.
JP-A-2005-28900

  However, in the thing of this patent document 1, it is necessary to provide two electric motors, and it cannot apply to a general electric power steering device.

  An object of the present invention is to cope with the above-described problem, and is applicable to a general electric power steering device, and moreover, to accurately diagnose the state of a power supply device.

  In order to achieve the above object, the present invention is characterized by an electric actuator that is supplied with electric power from a power supply device and applies a predetermined steering torque to a steered wheel, and energization of the electric actuator according to an operation state of a steering wheel. Actuator control means for controlling the amount; and power supply state diagnosis means for diagnosing the state of the power supply apparatus by detecting a current and a power supply voltage supplied from the power supply apparatus when the electric actuator is driven. In the electric power steering apparatus, the power steering apparatus includes a stationary operation determining unit that determines whether the operation of the steering handle is a stationary operation that is an operation at a predetermined vehicle speed or less, and the power state diagnosis unit is configured to determine the stationary operation. When it is determined by the means that the operation is a stationary operation, the state of the power supply device is diagnosed.

According to the present invention configured as described above, when the operation of the steering wheel is determined to be a stationary operation by the stationary operation determining unit, the amount of current and the power voltage supplied from the power supply device by the power state detection unit Is detected and the battery status is diagnosed.
Here, the stationary operation in the present invention is not only a steering operation when the vehicle is stopped traveling, but also during traveling at a predetermined vehicle speed or less which is a very low speed such as 10 km / h or 5 km / h. Handle operation in

In general, the lower the vehicle speed, the larger the steering torque necessary for steering the wheel, and a larger current flows through an electric actuator such as an electric motor. Therefore, when a stationary operation is performed, a large current flows through the electric actuator, and at this time, a power supply voltage fluctuation according to the state of the power supply device is obtained. For example, if the state of the battery constituting the power supply device is bad, a large voltage drop is detected.
In addition, since the amount of power generated by the generator (alternator) is small during the stationary operation, there is little adverse effect on battery diagnosis due to power generation.
As a result, it is possible to particularly diagnose the battery state satisfactorily based on voltage fluctuations when a large current is drawn from the power supply device, and high diagnostic accuracy is obtained.

  When diagnosing the state of the power supply device, the amount of energization to the electric actuator and the power supply voltage are detected and diagnosed by determining the relationship between them, for example, the amount of fluctuation of the power supply voltage with respect to the change in the amount of energization. Diagnosis may be made based on detection of energization when the voltage drops to a predetermined voltage.

  In addition, the detection of the current supplied from the power supply device when the electric actuator is driven is the detection of the current supplied to the entire electric power steering device (measurement of the current value) even when the current flowing through the electric actuator is measured (measurement of the current value). Current value measurement).

  Another feature of the present invention is that the electric actuator is supplied with power from the power supply device and applies a predetermined steering torque to the steered wheels, and the energization amount to the electric actuator is controlled in accordance with the operation state of the steering wheel. Electric power steering apparatus comprising actuator control means, and power supply state diagnosis means for diagnosing the state of the power supply apparatus by detecting current and power supply voltage supplied from the power supply apparatus when the electric actuator is driven The steering wheel operation determining means determines whether or not the operation of the steering wheel is an operation at or below a predetermined vehicle speed, and the power supply state diagnosis means includes a current supplied from the power supply device and Based on the result of detecting the power supply voltage a plurality of times, the state of the power supply device is diagnosed, and the detection result obtained a plurality of times is detected. The detection result when it is determined that the operation outright laid by the operation determining unit outright laid above, it is an gave a weight than detection result in the non-stationary steering operation.

  According to this, by detecting the amount of current supplied from the power supply device and the power supply voltage during a plurality of steering wheel operations, diagnosing the state of the power supply device based on these multiple detection results, Absorbing the effects of temporary voltage fluctuations, etc., a highly reliable diagnosis result is obtained, and the detection result at the time of stationary operation is given a weight, that is, it is easy to diagnose the power supply device. Since a weight is given to the detection result in a situation where a large current is drawn from the power supply device, a more accurate diagnosis result can be obtained.

For example, among a plurality of detection results, the detection result at the time of the stationary operation may be multiplied by a predetermined weight coefficient (> 1), and the weighted averaging process may be performed together with other detection results.
During the stationary operation, if a large current is drawn from the battery and the battery state is bad, a large voltage drop is detected. In addition, since the power generation amount of the generator (alternator) is small, there is little adverse effect on battery diagnosis due to power generation. For this reason, diagnosis of the battery which comprises a power supply device can be performed especially favorably.
When diagnosing the state of the power supply device, the amount of energization to the electric actuator and the power supply voltage are detected and diagnosed by determining the relationship between them, for example, the amount of fluctuation of the power supply voltage with respect to the change in the amount of energization. Diagnosis may be made based on detection of energization when the voltage drops to a predetermined voltage.

  Another feature of the present invention is that an engine is configured to flow a predetermined current to the electric actuator when an engine start command is issued when the power supply state diagnosis unit determines that the state of the power supply device is lower than a predetermined level. There is an energization means at the start.

  According to this, when the state of the power supply device is lowered, not only the engine starter but also the electric actuator of the electric power steering device is energized when starting the engine, so that the engine is difficult to start. For this reason, the driver can be made aware of the failure of the power supply device, and can be urged to maintain the power supply such as battery replacement.

  In this case, energization restriction means for storing start condition information indicating whether or not the engine has been started, and restricting energization to the electric actuator at the time of the engine start command by the engine start energization means according to the start condition It is good to have.

  According to this, since energization to the electric actuator is regulated in accordance with the engine starting condition, a problem that the engine cannot be completely started is prevented. For example, if there is a memory that the engine could not be started, energization of the electric actuator at the next engine start is prohibited.

  Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an electric power steering apparatus according to the embodiment.

  The electric power steering device 1 is roughly divided into a steering assist mechanism 10 that applies a steering assist force to the steered wheels, and an assist control device 30 that drives and controls the electric motor 15 of the steering assist mechanism 10.

  The steering assist mechanism 10 converts the rotation around the axis of the steering shaft 12 in conjunction with the turning operation of the steering handle 11 into the movement of the rack bar 14 in the axial direction by the rack and pinion mechanism 13. The left and right front wheels FW1 and FW2 that are steered wheels are steered in accordance with the movement in the direction. An electric motor 15 is assembled to the rack bar 14. The electric motor 15 applies assist force to the turning operation of the steering handle 11 by driving the rack bar 14 in the axial direction via the ball screw mechanism 16 according to the rotation. A rotation angle sensor 17 is attached to the electric motor 15, and a steering torque sensor 20 is assembled to the lower end portion of the steering shaft 12.

  The rotation angle sensor 17 is composed of a resolver, detects the rotation angle of the electric motor 15, and outputs a detection signal representing the detected rotation angle. The steering torque sensor 20 includes a torsion bar 21 that is interposed in the steering shaft 12 and has upper and lower ends connected to the steering shaft 12, and resolvers 22 and 23 that are assembled to the upper and lower ends of the torsion bar 21, respectively. . The resolvers 22 and 23 detect the rotation angles of the upper end and the lower end of the torsion bar 21 and output detection signals representing the detected rotation angles, respectively.

  The assist control device 30 includes an electronic control device 40 whose main part is constituted by a microcomputer, a motor drive circuit 50 that controls the drive of the electric motor 15 by a control signal from the electronic control device 40, power supply diagnostic measurement data, and start status And a nonvolatile memory 43 for storing data. Moreover, the electronic control unit 40 includes a power state diagnosis unit 41 and a motor control unit 42 in terms of its functions.

  The motor control unit 42 determines the energization amount to the electric motor 15 based on the detection signals from the rotation angle sensor 17, the steering torque sensor 20, and the vehicle speed sensor 28 that detects the vehicle speed, and controls the motor drive circuit 50. To generate a predetermined steering assist force. The motor control unit 42 is communicably connected to the engine control device 90 and inputs an engine start command signal and a start status signal indicating whether or not the engine has been started.

  On the other hand, the power supply state diagnosis unit 41 determines the power supply device 70 from the power supply voltage (power supply voltage supplied to the electric power steering device 1) when the electric motor 15 is driven and controlled by the motor control unit 42 and the energization amount thereof. In particular, the state of the battery 71 is diagnosed. A nonvolatile memory 43 for storing later-described measurement data used at the time of diagnosis, a notification device 29 for notifying the driver of a diagnosis result, and data in the nonvolatile memory 43 are stored. A reset switch 44 for inputting a signal for erasing is connected.

  As shown in FIG. 2, the motor drive circuit 50 constitutes a three-phase inverter circuit, and corresponds to each coil CL1, CL2, CL3 of the electric motor 15 (a three-phase brushless motor is used in this embodiment). It has switching elements SW11, SW12, SW21, SW22, SW31, SW32. These switching elements SW11, SW12, SW21, SW22, SW31, and SW32 use MOSFETs in this embodiment, and are on / off controlled by signals from the motor control unit 42. The motor drive circuit 50 is provided with current sensors 53a, 53b, and 53c for detecting the value of the current flowing through the electric motor 15 in each phase. Hereinafter, the three current sensors 53a, 53b, and 53c are collectively referred to as a current sensor 53.

Next, the configuration of the power supply system to the electric power steering apparatus 1 will be described with reference to FIG.
A power supply device 70 serving as a power source for the electric power steering device 1 includes a battery 71 (for example, a lead battery) and an alternator 72 that is a generator.
A power supply source line 62 connected to the power supply terminal (+ terminal) 73 of the battery 71 is connected to the ignition switch 80, and a control power supply line that supplies power to the electronic control unit 40 from the secondary side of the ignition switch 80. 63 and a drive power supply line 64 for supplying power to the motor drive circuit 50 from the primary side (power supply side) of the ignition switch 80.

The drive power supply line 64 is provided with a power supply relay 65, and a connection line 66 connecting the control power supply line 63 is provided on the load side of the power supply relay 65. The connection line 66 is provided with a diode 67 as a backflow prevention element that prevents current from flowing from the control power supply line 63 to the drive power supply line 64.
Further, the control power supply line 63 is provided with a diode 68 as a backflow prevention element for preventing the flow of current to the power supply side on the power supply side from the connection point with the connection line 66.

The control power supply line 63 is used for power supply to the electronic control device 40, and the drive power supply line 64 is used for a power supply path to the motor drive circuit 50 and the electronic control device 40. Therefore, the electronic control unit 40 is supplied with power from two systems.
The power relay 65 provided in the drive power supply line 64 is opened and closed by a signal from the electronic control device 40.
Further, the voltage detection of the power supplied to the electric power steering apparatus 1 is performed at two places: the voltage on the drive power supply line 64 side and the voltage on the control power supply line 63 side. Specifically, the primary voltage of the diode 67 and the primary voltage of the diode 68 are monitored by the power supply state diagnosis unit 41, and the lower one of the two monitor voltages is regarded as the power supply detection voltage Vx. .

Next, power state diagnosis control executed by the power state diagnosis unit of the electronic control unit 40 will be described.
FIG. 3 shows the power supply state diagnosis control routine, which is stored in the ROM of the electronic control unit 40 as a control program.
This power supply state diagnosis control routine is repeatedly performed in parallel with an assist control process performed by a motor control unit 42 described later, and is activated when the ignition switch 80 is turned on.

When this control routine is activated, it is first determined whether or not the steering operation of the steering handle 11 has been started by the driver (S1). Based on the control information of the motor control unit 42, the power state diagnosis unit 41 determines whether or not the steering operation of the steering handle 11 by the driver has started.
Since this control routine is repeatedly executed, this determination is repeated until the start of the steering operation is detected. When the steering operation is started (S1: YES), voltage / current measurement for diagnosing the state of the power supply device 70 is performed.

In the present embodiment, the current value flowing through the drive power supply line 64 is calculated from the current value measured by the current sensor 53 provided in the motor drive circuit 50, and the drive power supply line 64 side and the control power supply line 63 side are monitored. The lower voltage is measured as the power supply voltage Vx.
The motor control unit 42 calculates a necessary assist current for obtaining a desired assist torque based on the vehicle speed and the steering torque, as shown in FIG. The energization amount is feedback-controlled by adjusting the duty ratio of the switching elements SW11, SW12, SW21, SW22, SW31, and SW32 of the motor drive circuit 50 so that the assist current flows.
Therefore, the power supply state diagnosis unit 41 calculates the current value flowing through the drive power supply line 64 from the current value detected during the assist control performed by the motor control unit 42.
Note that an ammeter may be separately provided in the drive power supply line 64 from the power supply device 70 to measure the current.

Then, the measurement of the power supply voltage and the current is repeated until the steering operation of the steering handle 11 is finished (S3). In the present embodiment, voltage / current measurement is repeated only when the current value exceeds a preset set current value, and (voltage, current) at each measurement is stored.
When one steering operation is thus completed (S3: YES), it is determined whether or not the previous steering operation was a stationary operation (S4). The determination of the presence or absence of the stationary operation is performed to determine whether or not the steering operation is performed in a state where the vehicle is substantially stopped. In the present embodiment, the determination is made when the detected vehicle speed detected by the vehicle speed sensor 28 is equal to or lower than a predetermined vehicle speed. The determined steering operation is determined as a stationary operation.
If the operation is a stationary operation, the process proceeds to a power supply state diagnosis process. If not, the previous measurement result is deleted and the present control routine is temporarily terminated.

If it is determined in step S4 that it is a stationary operation, an index value K representing the state of the power supply device 70 is then calculated (S5). The index value K is calculated as follows based on the maximum value, the minimum value, and the maximum value and the minimum value of the power supply voltage measured in step S2.
K = (Minimum value of power supply voltage−Maximum value of power supply voltage) / (Maximum value of current−Minimum value of current)
The index value K is a rate of change of the power supply voltage with respect to a change in current, and represents the state of the power supply device 70, particularly the battery 71.
The index value K takes a negative value, and it can be determined that the smaller the value (the larger the absolute value), the worse the battery state.

Even if the battery 71 flows the same amount of current, the smaller the remaining capacity, the larger the voltage drop. Moreover, this phenomenon becomes more prominent as the current drawn from the battery 71 increases.
Therefore, in the present embodiment, the index value K is obtained during a stationary operation in which the energization amount to the electric motor 15 increases.
Further, since the power generation amount of the alternator 72 is small during the stationary operation, the influence of power generation is reduced, and the battery 71 itself can be diagnosed satisfactorily.

Subsequently, the index value K is stored in the nonvolatile memory 43 (S6). In the present embodiment, the index value K for the last n times is stored, and the previous stored values are sequentially erased.
Next, an average index value Kx is calculated from the stored index values K for the last n times (S7). This average index value Kx diagnoses the state of the power supply device 70, particularly the battery 71.

  Subsequently, it is determined whether or not the calculated average index value Kx is below a predetermined reference index value K0 (S8). If not, the control routine is temporarily exited because the power supply state is good (S8: NO). On the other hand, if the average index value Kx is lower than the reference index value K0, it is determined that the power state is defective, and the upper limit value of the assist current is limited (S9). In this case, it is preferable to simultaneously activate the alarm device 29 to prompt the driver to replace the battery 71.

This assist current represents the energization amount to the electric motor 15 calculated by the motor control unit 42 so as to obtain a desired assist torque, and is calculated from the steering torque and the vehicle speed as shown in the table of FIG.
If the power supply state is bad, an upper limit is imposed on the calculated required assist current. As shown in FIG. 5, the upper limit value Imax of the assist current is set to a smaller value as the absolute value of the average index value Kx is larger. Therefore, the lower the power supply device 70 is, the lower the upper limit value of the assist current is set.
As a result, the electric power that can be used from the power supply device 70 is restricted, and further reduction of the power supply voltage is prevented, so that the problem that the electric power steering device 1 suddenly stops functioning is also prevented. Further, it is possible to prevent adverse effects on other electric control systems (for example, a brake control system and an engine control system) due to a decrease in power supply voltage.

According to the power supply state diagnosis control routine of the present embodiment described above, the power supply device based on the change (voltage drop) in the power supply voltage with respect to the change in the current amount during the stationary operation in which a large current is drawn from the power supply device 70. Since the state of 70 is judged, the power supply state diagnosis accuracy is very high. Further, since the power generation amount of the alternator 72 is small during the stationary operation, the influence of power generation is reduced, and the battery 71 itself can be diagnosed satisfactorily.
And since the power is limited based on the highly accurate diagnosis result, the power supply voltage is excessively limited and the function of the electric power steering apparatus 1 cannot be fully utilized. It is possible to prevent such a problem that the function is suddenly stopped below the minimum operating voltage of the electronic control unit 40.

Next, assist control processing executed by the motor control unit 42 of the electronic control device 40 will be described.
FIG. 6 shows an assist torque control routine executed by the motor control unit 42, stored as a control program in the ROM of the electronic control unit 40, and repeatedly executed in a short cycle.

When this control routine is started by turning on the ignition switch 80, first, in step S101, a calculation is performed from the difference between the vehicle speed V detected by the vehicle speed sensor 28 and the rotation angle detected by the resolvers 22 and 23 of the steering torque sensor 20. The steering torque TR is read.
Subsequently, referring to the assist current table shown in FIG. 4, the necessary assist current Ias corresponding to the input vehicle speed V and steering torque TR is calculated (S102). The assist current table is stored in the ROM of the electronic control unit 40, and the required assist current Ias increases as the steering torque TR increases. In addition, the assist current table is set to increase as the vehicle speed V decreases. .

Next, the assist current upper limit value Imax determined by the power supply state diagnosis control routine described above is read (S103).
Subsequently, from the required assist current value Ias calculated in step S102 and the assist current upper limit value Imax read in step S103, the smaller current value is determined as the target assist current value to be passed through the electric motor 15 (S104). . Therefore, the target assist current value for energizing the electric motor 15 is the required assist current Ias if the required assist current value Ias is smaller than the upper limit current value Imax, and the upper limit current if the required assist current value Ias is larger than the upper limit current value Imax. The value is Imax.

Subsequently, the electric motor 15 is energized so as to have the determined target assist current value to generate a predetermined assist torque (S105).
By repeatedly executing such processing, an appropriate assist current according to the power supply state can be supplied to the electric motor 15.

Next, a power supply state diagnosis control routine as the second embodiment will be described.
In the power supply state diagnosis control routine of the first embodiment, the diagnosis is performed based on the measured values of the motor current and the power supply voltage during the stationary operation. However, in the second embodiment, the diagnostic is performed only during the stationary operation. Instead, the measurement data at the time of the steering operation during traveling is also averaged, and in the averaging process, the measurement data at the stationary operation is weighted.

FIG. 7 shows a power state diagnosis control routine as the second embodiment, and is stored as a control program in the ROM of the electronic control unit 40.
The power supply state diagnosis control routine is repeatedly performed in parallel with the assist control process performed by the motor control unit, and is activated when the ignition switch 80 is turned on.
In the following description, the processes common to the power supply state diagnosis control routine of the first embodiment are given the same step numbers and are simply described.

When the steering operation of the steering wheel 11 is started by the driver (S1: YES), voltage / current measurement for diagnosing the state of the power supply device 70 is performed as in the first embodiment.
Then, the measurement of the power supply voltage and the current is repeated until the steering operation of the steering handle 11 is finished (S2 to S3). In this case, voltage / current measurement is repeated only when the current value exceeds a preset set current value, and (voltage, current) at each measurement is stored.
When one steering operation is thus completed (S3: YES), an index value K representing the state of the power supply device is calculated (S5). The index value K is calculated as follows based on the maximum value, the minimum value, and the maximum value and the minimum value of the power supply voltage measured in step S2.
K = (Minimum value of power supply voltage−Maximum value of power supply voltage) / (Maximum value of current−Minimum value of current)

  Subsequently, it is determined whether or not the previous steering operation is a stationary operation (S4). If the steering operation is a stationary operation, the index value K is weighted (S10). In the present embodiment, a weighted average process is performed on the index value K in step S12 to be described later. A predetermined weight is set for the index value K at the time of the stationary operation at the time of the weighted average. For example, the index value K calculated during the stationary operation is set to a weight that is α (> 1) times the index value K calculated during the non-stationary operation.

Subsequently, the index value K is stored in the nonvolatile memory 43 together with the weighting coefficient α (S11). In this case, the index value K for the last n times is stored, and the previous stored values are sequentially deleted.
Next, an average index value Kx is calculated by weighted average processing from the stored index value K and weighting coefficient α for the last n times (S12), and if the average index value Kx is below the reference index value K0 (S8: YES) ) Assuming that the power supply state is bad, the upper limit value of the assist current is limited (S9).

According to the power supply state diagnosis control routine of the second embodiment described above, the index value at the time of the stationary operation is weighted to perform the weighted average processing with the index value at the time of the non-stationary operation. Like the power supply diagnostic accuracy is very high. In addition, since the influence of power generation is reduced, the diagnosis of the battery 71 itself can be performed satisfactorily. Further, since the measurement data at the time of non-stationary operation is also used, the power supply state can be diagnosed even when the stationary operation is not performed.
As a result, it becomes possible to perform power limitation based on a highly accurate diagnosis result, and it is not possible to fully utilize the functions of the electric power steering apparatus 1 by excessively limiting the power, or conversely due to insufficient power limitation. It is possible to prevent such a problem that the function suddenly stops.

Next, a modification of the power state index value calculation process will be described.
In the power supply state diagnosis control routine of the first and second embodiments described above, an index value representing the power supply state is calculated from the ratio of the change amount (voltage drop) of the power supply voltage to the change amount of the current in one steering operation. However, a modified example that replaces this calculation process will be described below.
It should be noted that the processes common to the first and second embodiments are simply described by attaching the same step numbers to the drawings.

First modification (FIG. 8)
As shown in FIG. 8, in the first modification, when a steering operation is performed (S1), the motor current is measured and the power supply voltage is measured, and the current measured during the one steering operation period is The power supply voltage when the maximum is reached is obtained as measurement data together with the maximum current (S21). Then, as shown in FIG. 12, this measurement data (maximum current, power supply voltage) is stored as data on the plane coordinates (S23). In this case, if the measurement is a stationary operation (S4: YES), the measurement data of one steering operation is weighted as measurement data for N times (S22) and stored in the nonvolatile memory 43 (S22). S23).

Since this control routine is repeatedly executed, each time a steering operation is performed, the measurement data is stored as data on the plane coordinates, and the distribution of the data (maximum current, power supply voltage) is linear on the plane coordinates. Approximate and calculate the slope of the straight line as the power state index value Kx (S24).
As in the first and second embodiments, when the index value Kx <the reference index value K0, the power supply state is determined to be defective, and the upper limit value of the assist current is limited according to the index value. (S8, S9).

Instead of storing the measurement data, the current when the power supply voltage becomes minimum during one steering operation period may be stored together with the power supply voltage.
In the modification, the measurement data at the time of the stationary operation is weighted, but the measurement data may be stored only at the time of the stationary operation.

Second modification (FIG. 9)
As shown in FIG. 9, in the second modification, when a steering operation is performed (S1), the current value I (n) is measured when the power supply voltage Vx falls below a preset voltage V0. (S25 to S26), the current value I (n) is set as an index value representing the state of the power supply device 70. That is, as shown in FIG. 13, after the steering operation is started, the power supply voltage is lowered with the increase of the energization current to the electric motor 15, and at the time t (n) when the power supply voltage Vx falls below the set voltage V0. The current value I (n) is used as an index value.

  In the power supply device 70, particularly the battery 71, the smaller the remaining capacity, the larger the voltage drop with respect to the drawn current amount. Accordingly, the power supply state is determined by measuring the current value I (n) that flows when the power supply voltage Vx falls below the set voltage V0. That is, it can be determined that the smaller the current value I (n), the worse the power state.

  If it is a stationary operation (S4: YES), the index value I (n) is weighted (S27), and the index value I (n) and the weighting coefficient α are combined to be non-volatile. Store in the memory 43 (S28). In this case, the index value I (n) for the latest n times is stored, and the previous stored values are sequentially erased.

  Subsequently, an average index value Ix is calculated by weighted average processing from the last n stored index values I (n) and the weighting coefficient α (S29), and if the average index value Ix is below the reference index value I0 ( S30: YES), the upper limit value of the assist current is limited (S9), assuming that the power supply state is bad. In this case, as shown in FIG. 14, the assist current upper limit value is set according to the average index value Ix.

  In the above modification, the index value I (n) at the time of the stationary operation is weighted, but the index value I (n) may be obtained only at the time of the stationary operation. Further, the current measurement value at the time of one stationary operation may be used as the index value Ix for power supply diagnosis without performing the process of obtaining the average value from the plurality of index values I (n).

Third modification (FIG. 10)
In the third modification, the power supply state is determined based on the frequency at which the power supply voltage falls below the set voltage V0. As shown in FIG. 10, when the steering operation is performed (S1), the power supply voltage Vx is The time t (n) when it falls below the preset set voltage V0 is read (S25, S31). That is, as shown in FIG. 13, after the steering operation is started, the power supply voltage is lowered with the increase of the energization current to the electric motor 15, and the time t (n) when the power supply voltage Vx falls below the set voltage V0. Read.

  If the operation is a stationary operation (S4: YES), this time t (n) is stored in the nonvolatile memory 43 (S32), and the power supply voltage Vx is set to the set voltage V0 at the last stationary operation. The elapsed time Δt from the time t (n−1) that has fallen is calculated (S33). This elapsed time Δt is an index value representing the state of the power supply device 70.

Subsequently, it is determined whether or not the index value Δt is lower than the reference index value Δt0 (S34). If Δt <Δt0, the power supply state is determined to be defective, and the upper limit value of the assist current is limited (S9). ).
That is, when the power supply voltage Vx falls below the set voltage V0 during the stationary operation, the time is stored in the nonvolatile memory 43 each time, and the time t (n−1) stored immediately before is stored. When the elapsed time from the current time to the time t (n) stored this time is equal to or shorter than a predetermined time, it is determined that the power supply state is defective and the assist current is limited.
In this case, as shown in FIG. 14, the assist current upper limit value is set according to Δt.

  Note that it is determined whether or not the number of occurrences of the power supply voltage drop (power supply voltage <V0) exceeds the reference number within a predetermined period. When it is determined that the reference number is exceeded, the assist current is determined according to the number of occurrences. The upper limit value may be limited. In this case, the upper limit value of the assist current is set smaller as the number of occurrences increases.

Fourth modification (FIG. 11)
This fourth modification is similar to the second and third modifications, and determines the power supply state based on the amount of change in the detected current value when the power supply voltage during the stationary operation falls below the set voltage V0. Is.
As shown in FIG. 11, first, when a steering operation is performed (S1), a current value I (n) when the power supply voltage Vx falls below a preset set voltage V0 is measured (S25 to S26). . That is, as shown in FIG. 13, after the steering operation is started, the power supply voltage decreases with the increase of the energization current to the electric motor 15, and the time t (n) when the power supply voltage Vx falls to the set voltage V0. The current value I (n) at is measured.

  If it is a stationary operation (S4: YES), this current value I (n) is stored in the nonvolatile memory 43 (S35), and the power supply voltage Vx is set to the set voltage V0 at the last stationary operation. A difference ΔI (= I (n) −I (n−1)) from the current value I (n−1) when the value is less than is calculated (S36). This ΔI becomes an index value representing the state of the power supply device 70. That is, since the current value I rapidly decreases when the power supply state deteriorates, the power supply state is determined based on the decrease ΔI (takes a negative value) of the current value I.

Then, it is determined whether or not the index value ΔI is below the reference index value ΔI0 (S37). If ΔI <ΔI0, the power supply state is determined to be defective, and the upper limit value of the assist current is limited (S9). .
That is, when the power supply voltage Vx falls below the set voltage V0 during the stationary operation, the current value I (n) at that time is stored in the non-volatile memory 43 and stored immediately before. When the difference ΔI from the current value I (n−1) falls below the reference index value ΔI0, it is determined that the power supply state is defective and the assist current is limited.
In this case, as shown in FIG. 5, the upper limit value of the assist current is set lower as the absolute value of the decrease ΔI is larger.

Next, an effective embodiment for prompting the driver to maintain the power supply device 70 when the power supply state is defective will be described.
FIG. 15 shows an engine start suppression control routine, which is stored as a control program in the ROM of the electronic control unit 40 and is repeatedly executed at a predetermined short cycle.
When this control routine is activated, it is first determined whether or not an engine start command (occupant's vehicle start operation) has been output (S50). The engine start command is determined by detecting the start command signal input from the engine control device 90 or the starter position of the ignition switch 80.

When an engine start command is detected (S50: YES), it is determined whether or not the index value Kx representing the state of the power supply device 70 is smaller than the reference index value K0 (S51). In other words, the index value K stored in the nonvolatile memory 43 is read, and it is determined whether or not the state of the power supply device 70 is defective based on the average value Kx. And if the state of the power supply device 70 is normal, this control routine is once exited as it is.
If the average index value Kx is also stored in the previous power state diagnosis control routine, the average value is not required in this step S51, and the stored value (index value Kx) may be read as it is.

On the other hand, if Kx <K0 (S51: YES), an energization amount to the electric motor 15 corresponding to the index value Kx is calculated (S52), and the electric motor 15 is energized with the calculated energization amount (S52). S53).
That is, it is difficult to start the engine by energizing the electric motor 15 of the electric power steering apparatus 1 when the engine is started. In this case, since the energization amount corresponding to the index value Kx representing the power state is set, the problem that the engine cannot be started at all is prevented. For example, a map for setting the energization amount to the electric motor 15 to be smaller as the index value Kx is smaller (as the power supply state is worse) is stored, and the current value is set with reference to this map, so Suppresses a large voltage drop. As a result, an appropriate voltage drop corresponding to the power supply state is obtained when the engine is started, and the engine start is moderately suppressed.

Depending on the driver, even if the alarm device 29 that prompts the user to replace the battery 71 is lit, the battery 29 is not used and the battery is not used. In such a case, not only good steering assist performance cannot be obtained, but there is also a possibility that the system of the electric power steering apparatus 1 is stopped due to a further decrease in the power supply voltage.
Therefore, in this control routine, it is possible to make the driver strongly recognize the necessity of maintenance of the power supply device 70 (battery replacement or the like) by making it difficult to start the engine.
As a result, the power supply state is kept good, and the desired steering assist performance can be obtained.

  Note that when the energization amount to the electric motor 15 is set based on the index value Kx representing the state of the power supply device 70, contrary to the above-described example, the energization amount to the electric motor 15 is increased as the power supply state is worse. The engine may not be started. In this case, the driver can be strongly encouraged to maintain the power supply device 70.

Next, Modification 1 of the engine start suppression control routine will be described.
FIG. 16 shows a first modification of the engine start suppression control routine, which is stored as a control program in the ROM of the electronic control unit 40 and is repeatedly executed at a predetermined short cycle.
The processes common to the previous engine start suppression control routine shown in FIG. 15 are given the same step numbers in the drawing and will be described briefly.

When this control routine is started and an engine start command is confirmed (S50: YES),
It is determined whether there is a record that the engine has not started (S54). This record is stored as data in the nonvolatile memory 43 when the process of step S56 described later is performed. Therefore, the determination in step S54 is performed by reading data from the nonvolatile memory 43.
If there is no record that the engine has not been started, the processes of steps S51 to S53 described above are performed. That is, the power supply state is determined based on the index value Kx representing the state of the power supply device 70. If the power supply state is defective, the electric motor 15 is energized with an energization amount corresponding to the index value Kx.

On the other hand, if the determination in step S54 is “YES”, that is, if there is a record that the engine has not started, the engine start suppression operation by energization of the electric motor 15 is not performed. That is, the start suppression operation is prohibited.
Then, after energizing an engine starter motor (not shown) by the current engine start command, it is determined whether or not the engine has been started (S55). This determination is made by inputting a start status signal from the engine control device 90. If the engine can be started, the control routine is immediately exited. If the engine cannot be started, start state data indicating that the engine could not be started is stored in the nonvolatile memory 43 (S56). Exit this control routine. Then, the same processing is repeatedly executed at a predetermined cycle.

According to the modified example 1 of the engine start suppression control routine described above, basically, the engine start is suppressed by energizing the electric motor 15 of the electric power steering device 1 when the power supply state is poor as in the previous embodiment. However, if the engine start status is sequentially stored as data and the engine has not been started in the past, the engine start will not be suppressed and the vehicle will not be able to start running. To prevent.
That is, it is possible to achieve a good balance between prompting the driver for power supply maintenance and starting the engine. In this case, it is preferable that the alarm device 29 prompts the user to replace the battery 71 at the same time.
When the engine can be started, the past history that the engine could not be started may be deleted from the start status data.

Next, a second modification of the engine start suppression control routine will be described.
FIG. 17 shows a second modification of the engine start suppression control routine, which is stored as a control program in the ROM of the electronic control unit 40 and is repeatedly executed at a predetermined short cycle.
Note that the same processing as that of the previous engine start suppression control routine shown in FIGS. 15 and 16 is given the same step number in the drawings and will be described briefly.
This control routine deals with a problem such that the driver does not maintain the power supply indefinitely in a situation where the power supply state is bad.

When this control routine is started and the engine start command is confirmed (S50: YES), next, the power supply state is determined based on the index value Kx representing the state of the power supply device 70 (S51). If it is defective (S51: YES), the value N is determined based on the number of times the engine has been restarted (S58).
The number of times the engine has been restarted is the number of times that the engine can be started in a state where the power supply state is determined to be defective, and is stored in the nonvolatile memory 43 in step S61 described later. The higher the number of times, the more the driver has continued to use the vehicle despite the power failure.

Then, as shown in FIG. 18, the value N is determined based on the number of engine restarts. This value N increases in proportion to the number of engine restarts and represents the degree to which engine start is suppressed.
Subsequently, it is determined whether or not the number of times that the engine has not been continuously started is greater than a value N (S59). If the number of times that the engine has not been started is equal to or less than the value N, the index value Kx is determined. Energization of the electric motor 15 of the electric power steering apparatus 1 is performed with the energization amount to suppress engine start (S52, S53).

On the other hand, in step S59, when the number of consecutive times the engine has not started exceeds the value N, such engine start is not suppressed.
That is, the number of times that the engine start is suppressed is increased in proportion to the number of times the engine is restarted in a situation where the power supply state is bad, and the number of ignition operations required until the engine can be restarted is increased. For example, if the engine is restarted five times, the engine start suppression process (S52, S53) is performed N times according to the number of times, and the engine is not restarted until the (N + 1) th ignition operation is performed. Enable to start.

  Subsequently, in step S55, based on the starting status signal from the engine control device 90, it is determined whether or not the engine has started, that is, whether or not the engine has started after the engine starter motor is energized. When the engine is started, the number of restarts is stored in the non-volatile memory 43, and this control routine is temporarily terminated (S61). Since this control routine is repeatedly executed, the number of restarts stored in the nonvolatile memory 43 is increased by one.

On the other hand, if it is determined in step S55 that the engine could not be started, the number of times the engine was not started stored in the nonvolatile memory 43 is incremented by 1, and the present control routine is temporarily exited (S60).
If NO in step S51, that is, if the power state is normal, the number of engine restarts stored in the nonvolatile memory 43 is cleared to zero, and the present control routine is temporarily exited. Then, the same processing is repeatedly executed at a predetermined cycle.

  According to the modification 2 of the engine start suppression control routine described above, basically, the engine start is suppressed by energizing the electric motor 15 of the electric power steering device 1 when the power supply state is poor, as in the previous embodiment. However, when the engine start status is stored sequentially as data and the driver does not maintain the power supply indefinitely, the engine start suppression is strengthened in proportion to the number of engine start, so it is sure to the driver. The power supply device 70 can be serviced.

  In the first and second modifications of the engine start suppression control routine, the index value Kx representing the power state is described. However, the index values described in the first to fourth modifications of the power supply state diagnosis control routine are described. Ix, ΔI, and Δt may be used.

By the way, when the electric motor 15 of the electric power steering apparatus 1 is energized when the engine is started, an assist torque is generated in the steering assist mechanism 10 and the steering handle 11 is rotated. Therefore, in each of the embodiments described above, only the d-axis of the electric motor 15 is energized so that the electric motor 15 does not rotate by energization.
Here, the energization control of the electric motor 15 will be briefly described.

The electric motor 15 of the present embodiment is a three-phase brushless motor, and forms a three-phase rotating magnetic field by flowing a three-phase current through the coils CL1 to CL3 wound around the stator, and a permanent magnet is formed in the three-phase rotating magnetic field. The fixed rotor rotates in accordance with the three-phase current. The motor control unit 42 calculates a two-phase command current when driving the electric motor 15.
That is, the motor control unit 42 calculates the two-phase command currents Id * and Iq * according to the assist torque determined according to the vehicle speed and the steering torque. In the rotating coordinate system in which the two-phase command currents Id * and Iq * are synchronized with the rotating magnetic flux generated by the permanent magnet on the rotor of the electric motor 15, the d-axis in the same direction as the permanent magnet and the q-axis orthogonal thereto. In the engine start suppression control routine of this embodiment, the command current is set to only Id and Iq is set to “0”.

Three-phase currents Iu, Iv, Iw flowing in the electric motor 15 detected by the current sensor 53 are converted into two-phase currents Id, Iq by a three-phase / two-phase conversion unit (not shown) in the motor control unit 42. This three-phase / two-phase conversion is performed by converting the rotation angle of the electric motor 15 obtained from the signal from the rotation angle sensor 17 into an electrical angle. Deviations (Id * −Id, Iq * −Iq) from the two-phase currents Id and Iq that actually flow with respect to the two-phase currents Id * and Iq * that are target currents are two-phase / 3-phase not shown The signal is converted into a three-phase signal by the conversion unit, and the switching elements SW11, SW12, SW21, SW22, SW31, and SW32 of the motor drive circuit 50 are on / off controlled by PWM control. In this case, since the two-phase command current is only Id, the electric motor 15 does not rotate because no torque in the rotational direction is generated.
Therefore, when the electric motor 15 is energized in order to suppress the engine start in the engine start suppression control routine, the electric motor 15 does not rotate, so that the steering handle 11 does not rotate and is safe.

According to the electric power steering apparatus 1 of the present embodiment described above, the following effects are obtained.
1. In a stationary operation in which a large current is drawn from the power supply device 70, the current value and the power supply voltage are measured to diagnose the power supply state, so that the diagnosis accuracy is extremely high.
In addition, during the stationary operation, the engine speed is low and the amount of power generated by the alternator 72 is small, so that it is possible to correctly diagnose the state of the battery 71 itself.
Further, since the power supply state is diagnosed based on the average index value Kx obtained by averaging the latest index values K, temporary measurement data fluctuations can be absorbed, and the reliability of the diagnostic accuracy is high.
Furthermore, when weighting the index value during the stationary operation and calculating the average index value using the index value during the non-stationary operation and the weighted average process, the power The apparatus 70 can be diagnosed satisfactorily.

2. Since the power supply state is diagnosed by using the energization of the electric motor 15 of the electric power steering apparatus 1, no special equipment such as an energizing apparatus is required.
Further, since current measurement is performed using the current sensor 53 provided in the motor drive circuit 50, there is no need to provide a special current sensor for battery diagnosis, and a cost merit is obtained.

3. Since the measurement data and the diagnosis result are stored in the nonvolatile memory 43, the data can be stored and retained even in the case where the power is cut off, and the measurement data so far can be used effectively.
In addition, when the power supply device 70 is serviced, such as by replacing the battery 71, the data stored in the nonvolatile memory 43 can be cleared and initialized by operating the reset switch 44. The latest accurate diagnostic results can be obtained.
In this case, reset means for automatically deciding the maintenance of the power supply device 70 such as replacement of the battery 71 without using the reset switch 44 and erasing the data in the nonvolatile memory 43 may be provided. For example, the power supply state diagnosis unit 41 may determine that maintenance of the power supply device 70 has been performed by detecting a large fluctuation of the index value indicating the power supply state to the normal side.

4). When it is diagnosed that the power supply state is defective, it is difficult to start the engine by energizing the electric motor 15 of the electric power steering device 1 at the time of starting the engine, and the necessity of maintenance of the power supply device 70 is strongly emphasized to the driver. Can be recognized.
In particular, when the deterioration state of the power supply device 70 is at such a level that the vehicle can be started but the electric power steering device 1 that consumes a large amount of power cannot be operated satisfactorily, the electric power steering device 1 itself is suspected of being abnormal. However, according to the present embodiment, the engine cannot be started satisfactorily, and erroneous determination of the cause of the abnormality can be prevented.
Further, since the engine cannot be started well, it is possible to strongly urge the driver to maintain the power supply device 70 (particularly, to replace the battery 71).

5. The deterioration level of the power supply device 70 can also be determined from the engine start state during the engine start suppression operation. That is, since the vehicle starting situation varies depending on the deterioration level of the power supply device 70, such as being unable to start / being difficult to start / somewhat difficult to start / startable, the deterioration level of the power supply device 70 is accurately determined from this starting situation. can do. This is particularly effective for lead batteries where it is difficult to diagnose the deterioration level.
Further, when the power supply device 70 is severely deteriorated, the vehicle cannot be started and cannot travel, so that there is no problem due to the operation restriction of the electric power steering device 1 during traveling, and safety is improved.

6). When performing the engine start suppression operation in the event of a power failure, the operation is limited in consideration of the past vehicle start conditions, so that it is possible to prevent problems such as the vehicle becoming completely inoperable, and the maintenance of the power supply for the driver A good balance between reminder and engine start can be achieved.
7). In the engine start suppression operation at the time of power failure, since only the d-axis of the electric motor 15 is energized, no rotational torque is generated, and the steering handle 11 is not rotated and is safe.

8). Since the upper limit value of the assist current is determined based on a highly accurate diagnosis, it is possible to prevent the amount of current supplied to the electric motor 15 from being excessively limited, and to obtain a steering assist torque appropriately. On the contrary, the problem that the upper limit current value to the electric motor 15 is set too high and the power supply amount to other electric control systems is excessively suppressed is also prevented. As a result, the limited power of the battery 71 can be distributed to each electric control system in a balanced manner.

The electric power steering apparatus 1 according to the present embodiment has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.
For example, the power supply state may be diagnosed without performing the index value averaging process. Moreover, the structure which does not perform the engine starting suppression control process performed at the time of an engine start may be sufficient.

1 is an overall configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a schematic circuit block diagram of an assist control apparatus. It is a flowchart showing the power supply state diagnostic control routine of 1st Embodiment. It is explanatory drawing showing the table for calculating an assist electric current. It is explanatory drawing showing the table which calculates | requires assist current upper limit from an index value. It is a flowchart showing an assist control routine. It is a flowchart showing the power supply state diagnostic control routine of 2nd Embodiment. It is a flowchart showing the modification 1 regarding the calculation process of the index value of a power supply state. It is a flowchart showing the modification 2 regarding the calculation process of the index value of a power supply state. 12 is a flowchart illustrating a third modification example regarding calculation processing of an index value of a power state. It is a flowchart showing the modification 4 regarding the calculation process of the index value of a power supply state. It is the graph which plotted the data of the measured conduction current and power supply voltage. It is a graph showing the fluctuation | variation of a power supply voltage and an electric current. It is explanatory drawing showing the table which calculates | requires assist current upper limit from an index value. It is a flowchart showing an engine start suppression control routine. 7 is a flowchart illustrating a first modification of the engine start suppression control routine. 12 is a flowchart illustrating a second modification of the engine start suppression control routine. It is explanatory drawing showing the table which calculates | requires the value N from the restart frequency of an engine.

Explanation of symbols

Electric power steering device ... 1, steering assist mechanism ... 10, electric motor ... 15, electronic control device ... 40, power supply state diagnosis unit ... 41, motor control unit ... 42, nonvolatile memory ... 43, motor drive circuit ... 50, current Sensor 53, power supply 70, battery 71, alternator 72, engine control 90.

Claims (4)

An electric actuator that is supplied with power from a power supply device and applies a predetermined steering torque to the steering wheel;
An actuator control means for controlling an energization amount to the electric actuator according to an operation state of the steering handle;
An electric power steering apparatus comprising: a power supply state diagnosis unit that detects a current and a power supply voltage supplied from the power supply device when the electric actuator is driven, and diagnoses a state of the power supply device.
A steering operation determining means for determining whether or not the operation of the steering wheel is a stationary operation that is an operation at a predetermined vehicle speed or less;
The electric power steering apparatus characterized in that the power supply state diagnosis means diagnoses the state of the power supply apparatus when it is determined that the operation is a stationary operation by the stationary operation determination means. An electric actuator that is supplied with power from a power supply device and applies a predetermined steering torque to the steering wheel;
An actuator control means for controlling an energization amount to the electric actuator according to an operation state of the steering handle;
An electric power steering apparatus comprising: a power supply state diagnosis unit that detects a current and a power supply voltage supplied from the power supply device when the electric actuator is driven, and diagnoses a state of the power supply device.
A steering operation determining means for determining whether or not the operation of the steering wheel is a stationary operation that is an operation at a predetermined vehicle speed or less;
The power supply state diagnosing means diagnoses the state of the power supply device based on a result of detecting a current supplied from the power supply device and a power supply voltage a plurality of times, and among the detection results obtained a plurality of times, An electric power steering apparatus characterized in that a detection result when it is determined as a stationary operation by the stationary operation determination means is given a weight more than a detection result during a non-stationary operation.   When the power supply state diagnosis means determines that the state of the power supply device is lower than a predetermined level, the power supply state diagnosis means includes an engine start energization means for supplying a predetermined current to the electric actuator when an engine start command is issued. The electric power steering apparatus according to claim 1 or 2. Energization regulation means for storing start status information indicating whether or not the engine has been started, and energizing the electric actuator at the time of the engine start command by the engine start energization means according to the start status; The electric power steering apparatus according to claim 3, wherein

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