JP4449832B2 - Electric power steering device - Google Patents

Description

  The present invention relates to a power supply apparatus for an electric power steering apparatus including an electric motor that applies a steering force to a steered wheel in accordance with a turning operation of a steering handle.

Conventionally, this type of electric power steering apparatus has been provided with an electric motor so as to apply a steering assist force to the turning operation of the steering wheel, and the assist force is controlled by changing the current amount of the electric motor. Adjust.
Such an electric power steering apparatus uses a battery as its power source. In consideration of power supply abnormality, the one in Patent Document 1 is provided with two power supplies of the same voltage, and when an abnormality occurs in one power supply, the power supply is switched from the other power supply. Is adopted.
JP 2004-291852 A

  However, because the electric power consumption of the electric motor of the electric power steering is large, when trying to configure a system using a high voltage type battery as a power source, another high voltage type power source is used as a backup for power failure. A battery is required. For this reason, the cost of the power source for electric power steering becomes very high, which is not preferable.

  An object of the present invention is to address the above-described problems, and an object of the present invention is to perform power backup at a low cost in a power steering device using a high voltage type battery.

In order to achieve the above object, a feature of the present invention is that an electric motor supplied with power from a power supply device and motor control means for controlling the operation of the electric motor are provided, and the electric motor is operated according to a steering state of a steering wheel. In the electric power steering apparatus that operates the motor to apply a steering force to the steered wheels, the power supply device includes a main power supply unit having a high voltage battery having a first voltage , and a low voltage battery having a second voltage lower than the first voltage. In parallel with at least two power supply units with a sub power supply unit having a power supply to the electric motor from the main power supply unit in normal time, when the output voltage of the main power supply unit is reduced, the voltage of the low voltage battery of the auxiliary power supply unit is boosted by the booster circuit be one that power supplied to the electric motor, the power supply output line of the main power supply unit The power supply output line of the secondary power supply unit connected via a backflow prevention device, in the provision of the booster circuit to the power supply merging line joined by the connection.

  In the present invention configured as described above, power is preferentially supplied to the electric motor from the main power supply unit having a high-voltage battery, but when the output voltage of the main power supply unit decreases as the voltage of the high-voltage battery decreases, The voltage of the low-voltage battery is boosted by a booster circuit and supplied to the electric motor. Therefore, it is not necessary to prepare two sets of high-voltage batteries, and a low-voltage battery used for a general electric load can be used as a backup power source for the high-voltage battery. It becomes possible.

In this case, the power supply output line of the main power supply unit is connected to the power supply output line of the sub power supply unit via a backflow prevention element, and a booster circuit is provided in the connected power supply merge line. Therefore, power from the main power supply unit does not flow to the sub power supply unit, and power is automatically supplied from the power supply unit with the higher output voltage according to the magnitude relationship between the output voltages of both power supply units. The Therefore, it can be configured not to provide a switching device for switching the power supply unit. In addition, even when the output voltage of the power supply unit on the power supply side is lowered, the voltage can be boosted to a predetermined voltage by the booster circuit and supplied to the electric motor. Can exhibit predetermined performance.

  A Zener diode may be used as the backflow prevention element. According to this, while preventing the flow of power from the main power supply unit to the sub power supply unit, when regenerative power is generated by the electric motor, the regenerative power can be flowed and absorbed to the low voltage battery side. it can.

Another feature of the present invention includes an electric motor supplied with power from a power supply device and motor control means for controlling the operation of the electric motor, and operates the electric motor in accordance with the steering state of the steering wheel. In the electric power steering apparatus for applying steering force to the steered wheels, the power supply device includes a main power supply unit having a high voltage battery having a first voltage and a sub power supply having a low voltage battery having a second voltage lower than the first voltage. At least two power supply units with the supply unit are provided in parallel, and power is supplied to the electric motor from the main power supply unit in normal times, and the sub power supply is supplied when the output voltage of the main power supply unit is lowered the voltage of the low voltage battery parts and boosted by the booster circuit be one that power supplied to the electric motor, the power supply output line and the sub-power supply of the main power supply unit One of the power supply output line, for detecting a mechanical relay that connects to a power supply confluence line to the electric motor, a power supply voltage supplied to the power supply confluence line through the mechanical relay When the voltage detection means and normally the mechanical relay is connected to the power supply output line side of the main power supply section and the voltage detection means detects a drop in the power supply voltage, the mechanical relay is When switching between the relay switching means for switching to power supply from the sub power supply unit and the mechanical relay, the motor control means temporarily reduces the drive current of the electric motor from that during normal control. And a switching motor current control means for limiting . For example, when a backflow prevention element such as a diode is provided in the power supply output line of the sub power supply section, a new detection circuit is required to detect the abnormality of the backflow prevention element or the sub power supply section. However, according to the present invention, it is possible to detect the abnormality of the mechanical relay and the abnormality of the sub power supply unit by switching the power supply unit by the mechanical relay and detecting the output voltage.

Since the when switching the mechanical relay is provided with a switching time of the motor current control means for limiting temporarily the driving current of the electric motor to be less than the normal control by said motor control means, mechanical Contact welding is prevented because a large current does not flow when the relay is switched.
In this case, it may be detected that the voltage detecting means has switched to the power supply output line side from the sub power supply unit, and the restriction of the drive current is terminated and the current control is returned to the normal state. Alternatively, the time for limiting the drive current may be set to be equal to or longer than the time required for the mechanical relay to switch.
According to this, contact welding of a mechanical relay can be reliably prevented.

As another feature of the present invention, the mechanical relay is alternately switched between the power supply output line side of the main power supply unit and the power supply output line side of the sub power supply unit, and A relay failure detection means for detecting a failure of the mechanical relay is provided based on the voltage of each power supply output line detected by the voltage detection means.
For example, if the mechanical relay is normal, the voltage detection means should be able to detect voltage fluctuation when the power supply unit is switched, but if such voltage fluctuation cannot be detected, the mechanical relay is out of order. It can be judged. Therefore, according to the present invention, it is possible to easily detect a failure of the mechanical relay.

Further, as another feature of the present invention, even when the voltage of the main power supply unit is lowered, the main power supply unit is not limited as long as the voltage of the power supply output line of the main power supply unit is higher than a predetermined voltage. The output voltage from is boosted by the booster circuit and supplied to the electric motor.
According to this, the booster circuit is used not only for boosting the voltage of the low-voltage battery but also when the output voltage of the main power supply unit is lowered. That is, even when the booster circuit is effectively used and the power backup from the sub power supply unit is not performed, the output of the main power supply unit can be boosted to an appropriate voltage to supply power to the electric motor. As a result, the electric motor can exhibit predetermined performance.

  Another feature of the present invention is that current saving means for suppressing the drive current of the electric motor from the normal time is provided to the motor control means when the booster circuit is operating. According to this, it is possible to reduce adverse effects on other electric loads sharing the high voltage battery. That is, if the operation of the electric power steering (energization to the electric motor) is performed as it is in a state where the high voltage battery voltage is lowered, the high voltage battery voltage is further lowered, and the power supply to other electric loads is deteriorated. Sometimes. Therefore, in the present invention, under such circumstances, by suppressing the drive current of the electric motor, the degree of consumption of the high voltage battery is reduced, and malfunction of other electric loads is prevented.

In this case, when the current saving means is operating, a notifying means for notifying the driver when the required drive current of the electric motor is a predetermined value or more may be provided. This prompts the driver to replace the battery at an appropriate timing.
Further, a boosting operation time limiting means for limiting a continuous time for supplying power by operating the booster circuit within a predetermined time may be provided. According to this, consumption of the high-voltage or low-voltage battery can be suppressed, and malfunction of other electric loads can be prevented.

  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.

  This electric power steering device is roughly divided into a steering assist mechanism 10 that applies a steering assist force to the steered wheels, an assist control device 30 that drives and controls the electric motor 15 of the steering assist mechanism 10, and a power supply device 40. Is done.

  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 adjusts 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 speed of the vehicle, thereby increasing the steering assist force. The electronic control device 31 for assisting, the main part of which is configured by a microcomputer, and a motor drive circuit 32 for driving the electric motor 15 by a motor control signal from the electronic control device 31 for assisting.
In the present embodiment, a three-phase brushless motor is used as the electric motor 15, and a three-phase drive current is caused to flow to the electric motor by an inverter circuit as the motor drive circuit 32. Various motors and drive circuits can be adopted such as driving control of the motor.
In addition, the assisting electronic control device 31 is connected to a notification device 29 that prompts the driver to replace the battery.

  As shown in FIG. 2, the power supply device 40 is roughly divided into a main power supply unit 50, a sub power supply unit 60 serving as a backup power supply, a booster circuit 70, and a power supply control device 80.

The main power supply unit 50 includes a high voltage battery 51 that generates electric power of a first voltage V1H (for example, V1H = 288 V in the present embodiment) at a normal time, a high voltage side relay 52 that opens and closes the power line of the high voltage battery 51, A step-down circuit 53 (DC-DC converter) that steps down the high-voltage battery voltage V1H to a step-down voltage V1L (for example, V1L = 42V in the present embodiment), and a regeneration generated by the electric motor 15 provided on the secondary side of the step-down circuit 53 And a regenerative absorption circuit 54 for absorbing electric power.
The regenerative absorption circuit 54 is provided with a resistance element 55 and an absorption switching element 56 on a ground line branched from the stepped-down power supply line. When regenerative power is generated, the regenerative power is turned on to generate regenerative power. It is something to escape.
The secondary side of the step-down circuit 53 is a power supply output line 57 of the main power supply unit.

  The sub power supply unit 60 includes a low voltage battery 61 that generates a second voltage V2L (for example, V2L = 12 V in the present embodiment) and a low voltage side relay 62 that opens and closes the power line of the low voltage battery 61 in a normal state. A diode 63 as a backflow prevention element is provided in the power supply output line 64 of the sub power supply unit 60 with its cathode side on the power output side and anode on the low voltage battery 61 side.

  The power supply units 50 and 60 are provided in parallel, and the power supply output line 57 of the main power supply unit 50 and the power supply output line 64 of the sub power supply unit 60 are connected. A booster circuit 70 is provided in the merge line 90.

  The booster circuit 70 includes a booster coil 71 provided in series with the power supply junction line 90, a first switching element SW1 provided on a ground line branched from the power supply junction line 90 on the output side of the booster coil 71, A second switching element SW2 provided in series with the power supply junction line 90 is provided. A noise removing capacitor 72 is provided on the power output line 91 on the secondary side of the booster circuit 70.

Each of the first and second switching elements SW1 and SW2 is turned on and off at a fast cycle by a pulse signal from the power supply control device 80, and generates a reference output voltage V0 (for example, V0 = 42V in the present embodiment) as its output. . That is, the boost operation is performed with the boost target voltage set to V0. In this case, the first and second switching elements SW1 and SW2 are turned on and off in synchronization. However, as shown in FIG. 3, their operations are opposite to each other (when the first switching element SW1 is on, the second switching element SW2 Is set to be off), the boosting operation is performed by the boosting coil 71.
The output of the booster circuit 70 is supplied to the motor drive circuit 32 as the output of the power supply device 40. Hereinafter, the output of the booster circuit 70 is referred to as a power supply output, and the output voltage is referred to as a power supply output voltage.

The power supply control device 80 includes a microcomputer as a main part, and monitors the input voltage Vin (voltage of the power supply merging line 90) and the power supply output voltage Vout (output voltage of the booster circuit 70) of the booster circuit 70, and monitors them. Based on the voltage, boost control described later is performed.
The power control device 80 and the assisting electronic control device 31 are supplied with power from the low voltage battery 61 via a power supply line (not shown).

Next, the basic operation of the power supply device 40 will be described.
In this power supply device, the relays 52 and 62 are turned on when the ignition key is turned on. Accordingly, the power supply having the higher output voltage is used from the relationship between the output voltage of the main power supply unit 50 and the output voltage of the sub power supply unit 60.

  When the capacity of the high voltage battery 51 is sufficient, in this example, the output voltage V1L of the main power supply unit 50 is 42V, which exceeds the output voltage (12V) of the sub power supply unit 60. Will be. In this case, in the booster circuit 70, since the input voltage Vin (42V) is equal to the boost target voltage V0, the substantial boost operation is not performed, and the power from the main power supply unit 50 is supplied to the motor drive circuit 32 as it is. The

  When the high voltage battery 51 deteriorates or the power consumption of other loads increases and the battery voltage decreases, the output voltage of the step-down circuit 53 also decreases. In this case, if the output voltage of the main power supply unit 50 (the output voltage of the step-down circuit 53) exceeds 12V, it exceeds the output voltage of the sub power supply unit 60. Supplied. At this time, since the booster circuit 70 controls the switching elements SW1 and SW2 so that the power supply output voltage Vout becomes the boost target voltage 42V, the power supply output voltage is maintained at 42V.

When the high voltage battery 51 further deteriorates and the output voltage of the main power supply unit 50 falls below 12V, the output voltage of the sub power supply unit 60 exceeds the output voltage of the main power supply unit 50, and power is supplied from the sub power supply unit 60. Will be. Even in this case, the booster circuit 70 performs the boosting operation in the same manner, so that the power supply output voltage is 42V.
Note that the boost target voltage varies according to the input voltage Vin. For example, the boost target voltage may be set lower in proportion to the lower input voltage Vin.

  The above is the basic operation of the power supply device 40. In this case, although there is an advantage that the switching of the power supply unit can be performed naturally from the magnitude relationship of the output voltage, the voltage of the high voltage battery 51 is considerably high. The power supply has been switched at a time when it has declined. Therefore, there are concerns about problems such as adverse effects on other electric control systems receiving power supply from the high voltage battery 51 and heat generation of the step-down circuit 53.

Therefore, in a system in which such a problem is a concern, the switching timing from the main power supply unit 50 to the sub power supply unit 60 is controlled by the power supply control device 80 as described below.
FIG. 4 shows a power supply control routine of the first embodiment executed by the power supply control device 80, stored as a control program in the ROM in the power supply control device 80, and repeatedly executed in a short cycle. This control routine is started by turning on an ignition key (not shown). In synchronism with this, the high-voltage relay 52 and the low-voltage relay 62 are turned ON, and a flag F described later is set to zero.

  First, in order to check whether or not regenerative power is generated from the electric motor 15, the output voltage Vout is compared with a regenerative reference voltage Vk (for example, 50V) in step S1. When regenerative electric power is generated from the electric motor 15, the output switching voltage Vout exceeds the regenerative reference voltage Vk, so that the absorption switching element 56 is turned on in step S2. Therefore, the regenerative power can be released to the ground through the absorption switching element 56, and the circuit protection of the entire power supply device 40 can be achieved.

On the other hand, when the regenerative power is not generated, the absorption switching element 56 is maintained in the off state (S3).
Subsequently, it is determined whether or not the flag F is set to 1 (S4). This flag F is set to 1 when the boosting operation is prohibited, as will be understood from the subsequent processing. Then, if F = 1, this routine is temporarily terminated. If F = 1 is not satisfied, next, the input voltage Vin to the booster circuit 70 is V0 which is the rated output voltage of the power supply device 40 (for example, the present embodiment). Then, it is determined whether or not the voltage is lower than 42V) (S5). If the input voltage Vin is equal to or higher than the rated output voltage V0, the following step-up operation is not necessary and the routine is terminated. In this case, the count value Tx of the timer that measures the step-up operation time is cleared to zero (S6). ).

  On the other hand, when the input voltage Vin is lower than the rated output voltage V0 (S5: YES), the step-up operation is performed. First, the degree of decrease of the input voltage Vin is determined. That is, in step S7, it is determined whether or not the input voltage Vin is lower than a low reference voltage V01 (for example, V01 = 30V in the present embodiment) that is higher than the rated voltage (12V) of the low voltage battery 61 by a predetermined voltage (S7). ).

When the high voltage battery 51 is not deteriorated, the input voltage Vin is almost equal to the rated output voltage V0 of the power supply device 40. However, when the high voltage battery 51 is deteriorated, the output voltage of the step-down circuit 53 is reduced and the rated output voltage is reduced. It becomes less than V0. In step S7, the input voltage Vin is compared with the low reference voltage V01 in order to determine how much the input voltage Vin decreases. If the input voltage Vin is lower than the low reference voltage V01, the high-voltage side relay 52 is turned off (S8). Conversely, if the input voltage Vin is equal to or higher than the low reference voltage V01, the high-voltage side relay 52 remains on. Keep.
In other words, although the deterioration of the high voltage battery 51 is detected, but the degree thereof is small and the input voltage Vin is higher than the low reference voltage V01, power is supplied from the high voltage battery 51 to the booster circuit 70, and conversely, the input voltage Vin is If the voltage is lower than the low reference voltage V01, the power supply from the high voltage battery 51 is cut off and the power supply is switched from the low voltage battery 61.

Subsequently, a boosting operation is performed in step S9. The step-up operation in step S9 is performed by alternately turning on and off in synchronization with the first and second switching elements SW1 and SW2. In this case, while monitoring the output voltage Vout, the first and second switching elements SW1 and SW2 are controlled so that the output voltage Vout becomes the rated output voltage V0.
When this boosting operation is being performed, a motor drive current save command (assist save command) is output to the assisting electronic control unit 31 (S10), and a timer count for measuring the boosting operation continuous time is counted. The value Tx is incremented (S11).

Next, it is determined whether or not the count value Tx of the timer has reached a predetermined value T0 (S12). When the time is up (Tx> T0), the boosting operation by the booster circuit 70 is stopped (S13). . That is, the switching operation by the first and second switching elements SW1 and SW2 is stopped, the first switching element SW1 is turned off, and the second switching element SW2 is kept on. Then, the flag F is set to 1 and this routine is temporarily terminated (S14). In this case, the assist control for applying the steering torque by driving the electric motor 15 ends.
On the other hand, if it is determined in step S12 that the time has not yet expired, this routine is once terminated.

By repeatedly executing this control routine, boost control according to battery deterioration, motor drive current save command, and regenerative power absorption control are performed.
According to the power supply control routine of the present embodiment described above, if the capacity of the high-voltage battery 51 is sufficient (S5: NO), the booster circuit 70 does not operate and the power of the high-voltage battery 51 passes through the step-down circuit 53. Then, it is sent to the motor drive circuit 32 as it is. When the capacity of the high-voltage battery 51 decreases and the output voltage of the step-down circuit 53 falls below the rated output voltage V0 (S5: YES), if the voltage is equal to or higher than the low reference voltage V01 (S7: NO), the output of the step-down circuit 53 is stepped up and supplied to the motor drive circuit 32. If the output is lower than the low reference voltage V02 (S7: YES), the power supply to the high-voltage battery 51 is stopped and the low-voltage battery 61 Is boosted to supply power.

Therefore, even when the high voltage battery 51 is deteriorated, the power supply can be backed up by the low voltage battery 61. Moreover, although the high voltage battery 51 is used also in other high voltage loads, since the power supply used for this electric power steering is restricted, the operation of the other high voltage loads can be protected.
In addition, since the continuous time for performing the boosting operation is limited, the power supply line from the low voltage battery 61 can be narrowed. Further, heat generation in the booster circuit 70 can be prevented. Moreover, the further capacity | capacitance fall of both the batteries 51 and 61 can be prevented, and the malfunctioning of another electric load can be prevented.
Further, when the high-voltage battery 41 is deteriorated, the efficiency of the step-down circuit 53 is reduced and a problem of heat generation occurs. However, since the output voltage of the step-down circuit 53 is reduced, switching to power supply from the sub power supply unit 60 causes such a problem. Is prevented.
Further, when regenerative power is generated from the electric motor 15, the step-down circuit 53 can be protected because the regenerative power is released by turning on the absorption switching element 56.

  Next, an assist control process corresponding to the above-described power supply control process will be described. FIG. 5 shows an assist control routine executed by the assist electronic control device 31, which is stored as a control program in the ROM of the assist electronic control device 31, and is repeatedly executed in a short cycle.

  First, in step S21, it is determined whether or not an assist save command is output from the power supply control device 80. This assist save command is output from the power supply control device 80 during the boosting operation performed in step S10 of the power supply control routine described above. When this save command is output, the assist limit mode is set. When the save command is not output (S22), the assist normal mode is set (S23). At this time, when the assist restriction mode is set, the flag F is set to 1, and when the assist normal mode is set, the flag F is set to 0.

  Then, the required assist current ASI corresponding to the mode is determined (S24). In this embodiment, the vehicle speed V detected by the vehicle speed sensor 28 and the steering torque TR detected by the difference between the rotation angle signals of the resolvers 22 and 23 of the steering torque sensor 20 are input, and the assist current table is referred to. A required assist current ASI corresponding to the input vehicle speed V and steering torque TR is calculated. The assist current table is stored in the ROM of the assist electronic control device 31, and as shown in FIG. 6, the required assist current ASI increases as the steering torque TR increases, and the vehicle speed V decreases. It is set to a large value.

In this case, in the assist save mode, as shown in FIG. 6, the maximum value (upper limit value) of the necessary assist current ASI is limited to a lower value than in the normal mode. That is, the necessary assist current ASI is limited to a preset upper limit value ASImax or less. Therefore, when the calculated necessary assist current ASI exceeds the upper limit value ASImax, the value is replaced with the upper limit value ASImax.
In the next step S25, the motor drive circuit 32 (inverter circuit) is controlled according to the calculated required assist current ASI. For example, by generating a three-phase pulse train signal having a pulse width substantially proportional to the required assist current ASI and energizing the switch circuit (not shown) of the inverter, the required assist current as a drive current is supplied to the electric motor 15. ASI is flowed to generate a predetermined assist torque.

Subsequently, in step S26, it is determined whether or not the flag F is set to 1, that is, whether or not the assist save mode is set. If it is the assist save mode, it is further determined in step S24. It is determined whether the assist current ASI is larger than a predetermined value ASI0 (S27).
If the required assist current ASI is larger than the predetermined value ASI0, the alarm device 29 is activated to notify the driver that the battery has deteriorated and the electric power steering device is in the save operation (S28). In this case, a buzzer or a lamp can be used as the alarm device 29.

  In steps S27 and S28, when the required assist current ASI is larger than the predetermined value ASI0, the alarm 29 is activated to alert the driver to the battery deterioration. In addition to this processing, the vehicle speed sensor 28 On the basis of the vehicle speed signal, the alarm 29 may be operated only when the vehicle speed V is equal to or lower than the reference speed V0, that is, during low speed traveling that requires a large assist torque.

  According to the assist control process described above, during the boosting operation when the battery is deteriorated, the maximum value of the drive current energized to the electric motor 15 can be limited, so that the consumption of the battery can be suppressed. Sufficient power supply to the electric load can be ensured. As a result, even when the battery is deteriorated, the power consumption balance with various electric loads can be kept good, and the overall control system of the vehicle can be kept good.

  In this embodiment, the diode 63 is provided as a backflow prevention element to the sub power supply unit 60. However, a switching element 65 (for example, a MOS-FET) is provided as shown in FIG. The switching element 65 may be turned on by detecting that the input voltage Vin has dropped to a predetermined voltage. In this case, the voltage drop is smaller than that of the diode 63, and there is an effect that heat generation is small even when a large current is passed.

Further, as shown in FIG. 8, a Zener diode 66 may be provided so that regenerative power can be absorbed. In this case, the Zener voltage is set to be higher than the rated output voltage V1L of the step-down circuit 53 of the main power supply unit 50 and the operating voltage Vk of the regenerative absorption circuit 54, and from the element breakdown voltage of the power control device 80 and the assist electronic control device 31. A low setting is recommended.
Further, in the above-described embodiment, the booster circuit 70 is operated by setting the target boost voltage so that the rated output voltage is always obtained. However, in the case where the input voltage Vin is extremely decreased, the target boost voltage is decreased. It may be.

Next, the power supply device of 2nd Embodiment is demonstrated.
In the power supply device of the first embodiment described above, a failure of the diode 63 provided in the sub power supply output line 64 of the sub power supply unit 60 or an abnormality of the low voltage battery 61 cannot be detected. Therefore, in the power supply device of the second embodiment, the power supply is switched using a mechanical relay.
FIG. 9 is a schematic configuration diagram of an electric power steering device including a power supply device as a second embodiment. In the following, the same components as those in the first embodiment are denoted by the same reference numerals in the drawings and description thereof is omitted.

  The power supply device 140 includes a main power supply unit 50, a sub power supply unit 60 serving as a backup power supply, a mechanical relay 100 that switches power supply from the two power supply units 50 and 60, a booster circuit 70, a power supply It is roughly divided into a control device 180.

The mechanical relay 100 has a movable contact and the contact is switched by an electric signal, and includes two power input terminals 101 and 102 and one power output terminal 103. The main power supply output line 57 of the main power supply unit 50 is connected to the power input terminal 101, and the sub power supply output line 64 of the sub power supply unit 60 is connected to the other power input terminal 102. A booster circuit 70 is connected to the power output terminal 103.
Then, one of the power input terminals 101 and 102 is electrically connected to the power output terminal 103 by a switching control signal from the power control device 180.
The sub power supply output line 64 is not provided with a backflow prevention element such as a diode.

The power controller 180 also monitors the input voltage Vin and the output voltage Vout of the booster circuit, and performs the power supply control process shown below.
First, a process performed when the electric power steering apparatus is activated will be described.
FIG. 10 shows a start-up power supply check control routine performed by the power supply control device 180, which is performed by executing a control program stored in the ROM in the power supply control device.
When the ignition key is turned on, the high voltage side relay 52 and the low voltage side relay 62 are turned on, and this routine is started.

First, a switching control signal is output to the mechanical relay 100 so that the contact is switched to the power input terminal 102 side (sub power supply unit 60 side) (S31). Therefore, the power supply state from the sub power supply unit 60 is established. Subsequently, the input voltage Vin is detected, and it is determined whether or not the input voltage Vin is equal to or higher than a preset reference voltage Vin0 (S32).
If the input voltage Vin is not equal to or higher than the reference voltage Vin0, it is determined that the low voltage battery 61 is exhausted and the steering assist control of the electric power steering device is stopped (S33). That is, the assist control of the steering force by the electric motor 15 is prohibited.

On the other hand, if “NO” in step S32, that is, if it is determined that the low voltage battery 61 is not consumed, the contact of the mechanical relay 100 is connected to the power input terminal 101 side (main power supply unit 50 side) and the power input terminal. A switching control signal is output so as to alternately and repeatedly switch to the 102 side (sub power supply unit 60 side) (S34).
At this time, if the mechanical relay 100 is normal, the input voltage Vin should change in accordance with the output timing of the switching signal. Therefore, when a switching signal is output to the mechanical relay 100 in step S34, it is determined whether or not a change in the input voltage Vin is detected at a timing synchronized with the switching signal output (S35). If the change timing of the input voltage Vin is not appropriate for the switching signal output, the process proceeds to step S33 and assist control is stopped.

  On the other hand, when the change of the input voltage Vin is detected at the appropriate timing, the contact of the mechanical relay 100 is instructed to be switched to the power input terminal 101 side (main power supply unit 50 side) (S36), and assist electronic control is performed. An assist control start signal is output to the device 31 (S37), and this control routine is terminated.

  Next, steering force assist control will be described. The steering force assist control is performed in the same manner as in the first embodiment, but the processing at the time of power supply switching in step S8 is different. That is, when the output voltage of the main power supply unit 50 decreases during the assist control, in the first embodiment, the power control device 80 is instructed to turn off the high-voltage side relay 52. In the embodiment, instead of the processing, a switching signal is output so that the mechanical relay 100 is switched to the sub power supply unit 60 side.

Further, in order to prevent contact welding of the mechanical relay 100, the motor drive current is temporarily suppressed.
That is, as shown in FIG. 11, when it is detected in step S7 that the input voltage Vin is lower than the low reference voltage V01, first, the drive current flowing through the electric motor 15 is temporarily reduced or set to 0 ( S81). During the assist control, a required assist current ASI is calculated and a drive current corresponding to the calculated assist current ASI is supplied to the electric motor 15. In step S81, the assist current (drive current) supplied to the electric motor 15 is reduced. That is why.
And it waits until the elapsed time T1x after outputting the assist current reduction command by the timer exceeds the predetermined time T10 (S82, S83), and outputs a switching signal to the mechanical relay 100 (S84). Subsequently, the process waits until the elapsed time T1x by the timer exceeds the predetermined time T11 (T11> T10) (S85), outputs a return command for the assist current ASI (S86), and clears the timer T1x to zero.
That is, in this process, when the mechanical relay 100 is actually switched, welding of the contacts is prevented by preventing a large current from flowing. For example, as shown in FIG. 12, at time t1 when the output voltage of the main power supply unit 50 has decreased to V01, first, a command to reduce the assist current ASI is output (for example, assist current ASI = 0), and then actually A switching signal is output to the mechanical relay 100 at time t <b> 2 after waiting for a time necessary for completion of reduction of the current flowing through the power supply junction line 90. Subsequently, a return command for the assist current ASI is issued after waiting for a time required for the switching of the contacts of the mechanical relay 100 to be completed (time t3).
As a result, contact welding of the mechanical relay 100 can be reliably prevented.
In place of the process of step S85, as shown in step S88 of FIG. 13, it is detected that the input voltage Vin is equal to or lower than V02 (for example, 12V that is the output voltage of the sub power supply unit 60). It may be determined that the mechanical relay 100 has been switched.

The electric power steering apparatus 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, as shown in FIG. 14, as a modification of the second embodiment, a booster circuit 70 may be disposed between the sub power supply unit 60 and the mechanical relay 100. In this case, after the output voltage of the main power supply unit 50 decreases and the mechanical relay 100 is switched to the sub power supply unit 60 side, the voltage of the low-voltage battery 61 may be boosted by the booster circuit 70. Can be configured in the same manner as in the second embodiment.
Further, the voltage values (battery voltage, step-down voltage, step-up voltage, reference voltage, etc.) in each embodiment can be arbitrarily set.

1 is an overall configuration diagram of an electric power steering apparatus according to a first embodiment of the present invention. It is a schematic circuit block diagram of the power supply device of 1st Embodiment. It is explanatory drawing showing the signal to the switching element for pressure | voltage rise. It is a flowchart showing the power supply control routine of 1st Embodiment. It is a flowchart showing the assist control routine of 1st Embodiment. It is explanatory drawing showing an assist torque table. It is a schematic circuit block diagram of the power supply device as a modification of 1st Embodiment. It is a schematic circuit block diagram of the power supply device as a modification of 1st Embodiment. It is a schematic circuit block diagram of the power supply device as 2nd Embodiment. It is a flowchart showing the power supply check control routine of 2nd Embodiment. It is a flowchart showing the power supply control routine of 2nd Embodiment. It is a graph showing the time transition of an input voltage and a drive current. It is a flowchart showing the modification of the power supply control routine of 2nd Embodiment. It is a schematic circuit block diagram as a modification of the power supply device of 2nd Embodiment.

Explanation of symbols

Steering assist mechanism 10, electric motor 15, assist control device 30, assist electronic control device 31, motor drive circuit 32, power supply device 40, main power supply unit 50, high voltage battery 51, high voltage side Relay ... 52, step-down circuit ... 53, regenerative absorption circuit 54, absorption switching element ... 56, auxiliary power supply unit ... 60, low-voltage battery ... 61, diode ... 63, Zener diode ... 66, boost circuit ... 70, boost coil ... 71, switching elements SW1, SW2, power supply control devices 80, 180, mechanical relays 100.

Claims (11)

An electric motor that includes an electric motor supplied with power from a power supply device and motor control means for controlling the operation of the electric motor, and operates the electric motor according to the steering state of the steering handle to apply a steering force to the steered wheels. In the power steering device,
The power supply is
A main power supply unit having a high voltage battery of a first voltage and a sub power supply unit having a low voltage battery of a second voltage lower than the first voltage are provided in parallel,
In the normal time, the electric power is supplied from the main power supply unit to the electric motor, and when the output voltage of the main power supply unit is lowered, the voltage of the low voltage battery of the sub power supply unit is boosted by a booster circuit. Supplying power to the electric motor ,
The power supply output line of the main power supply unit is connected to the power supply output line of the sub power supply unit via a backflow prevention element, and a booster circuit is provided in the connected power supply merge line. An electric power steering device. The electric power steering apparatus according to claim 1 , wherein a Zener diode is used as the backflow preventing element. An electric motor that includes an electric motor supplied with power from a power supply device and motor control means for controlling the operation of the electric motor, and operates the electric motor according to the steering state of the steering handle to apply a steering force to the steered wheels. In the power steering device,
The power supply is
A main power supply unit having a high voltage battery of a first voltage and a sub power supply unit having a low voltage battery of a second voltage lower than the first voltage are provided in parallel,
In the normal time, the electric power is supplied from the main power supply unit to the electric motor, and when the output voltage of the main power supply unit is lowered, the voltage of the low voltage battery of the sub power supply unit is boosted by a booster circuit. Supplying power to the electric motor,
A mechanical relay that connects one of the power supply output line of the main power supply unit and the power supply output line of the sub power supply unit to the power supply junction line to the electric motor;
Voltage detecting means for detecting a power supply voltage supplied to the power supply confluence line through the mechanical relay,
Normally, the mechanical relay is connected to the power supply output line side of the main power supply unit, and when the voltage detection means detects a drop in the power supply voltage, the mechanical relay is switched to switch the sub power supply. Relay switching means for switching to power supply from the supply unit ;
When switching the mechanical relay, switching motor current control means for temporarily limiting the drive current of the electric motor to be smaller than that during normal control by the motor control means;
An electric power steering apparatus comprising: By detecting that the switching to the power supply output line side from the secondary power supply unit by the voltage detection means, according to claim 3, characterized in that return to the current control of the normal to exit limit of the driving current The electric power steering apparatus as described. 4. The electric power steering apparatus according to claim 3 , wherein the time for limiting the drive current is set to be equal to or longer than the time required for the mechanical relay to switch. When starting the electric power steering control, the mechanical relay switch to the power supply output line side of the secondary power supply unit, by the voltage detecting means, according to claim 3 which includes a sub-power supply monitoring means for monitoring the power supply voltage The electric power steering device according to any one of claims 5 to 5 . The mechanical relay is alternately switched between the power supply output line side of the main power supply unit and the power supply output line side of the sub power supply unit, and each power supply detected by the voltage detection means at that time The electric power steering apparatus according to any one of claims 3 to 6 , further comprising relay failure detection means for detecting a failure of the mechanical relay based on a voltage of an output line. Even when the voltage of the main power supply unit drops, as long as the voltage of the power supply output line of the main power supply unit is higher than a predetermined voltage, the output voltage from the main power supply unit is boosted by the booster circuit. to an electric power steering device according to any one of claims 1 to claim 7, characterized in that supplied to the electric motor. When operating the booster circuit, any claims 1, characterized in that with a current saving means for suppressing than the normal drive current of the electric motor relative to the motor control means according to claim 8 The electric power steering device according to claim 1. 10. The notification device according to claim 9 , further comprising a notification unit that notifies a driver when the required drive current of the electric motor is equal to or greater than a predetermined value when the current saving unit is operating. Electric power steering device. The electric power steering apparatus according to any one of claims 1 to claim 10, characterized in that it comprises a step-up operation time limiting means for limiting by operating the boosting circuit the power supply continuous time within a predetermined time.

Images