JP2004129402A - Motor-driven power steering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor-driven power steering apparatus which has a plurality of motors each for supplementing a steering force and which increases the distributing quantity of a supplementary steering force imparted to a normal motor when at least one of the plurality of the motors is faulted and which relieves the driver load. <P>SOLUTION: The motor-driven power steering apparatus includes a target current distributing unit 50 for increasing a distribution of the auxiliary steering force imparted to a normal motor when at least one of a plurality of motors 19A, 19B is faulted to alleviate the driver load, by increasing the amount of the distribution of the force imparted to the normal motor. Further, the apparatus includes a current limit value setting unit 63 for setting a current limit value of the plurality of the motors to set the current-limiting value of the normal motor to a fault time current-limiting value by the setting unit. Capability of the normal motor is performed at the maximum by distributing the motor current, in response to the faulted time current limit value via a current distribution deciding unit 62 to be input by the faulted time current limit value by the target current distributing unit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly, to an electric power steering apparatus in which a plurality of motors are provided in a steering system and a steering force is assisted for the steering system.
[0002]
[Prior art]
2. Description of the Related Art An electric power steering device is a support device that assists a steering force by linking a motor when a driver operates a steering wheel (steering wheel) while driving a car (for example, see Patent Document 1). In the electric power steering device, motor control is performed by using a steering torque signal from a steering torque detection unit that detects a steering torque generated on a steering shaft by a driver's steering operation, and a vehicle speed signal from a vehicle speed detection unit that detects a vehicle speed. The driving of an assisting motor that outputs an auxiliary steering force based on the control operation of a control unit (ECU) is controlled to reduce the driver's manual steering force (for example, see Patent Document 2). In the control operation of the motor control unit, a target current value of a motor current to be supplied to the motor is set based on the steering torque signal and the vehicle speed signal, and a signal (a target current signal) relating to the target current value is actually transmitted to the motor. A difference from a motor current signal fed back from a motor current detector for detecting a flowing motor current is obtained, a proportional / integral compensation process (PI control) is performed on the difference signal, and a PWM signal for driving and controlling the motor is obtained. Is occurring.
[0003]
Conventionally, electric power steering devices have been mainly developed for small vehicles. In recent years, however, it has become particularly necessary to equip large vehicles (such as 2000cc class or more passenger vehicles) with a view to saving fuel consumption and expanding the vehicle control range. Has arisen. When the electric power steering device is applied to a large vehicle, the weight of the vehicle is large, so that a configuration using one motor requires a large motor that outputs a large assisting force. For this reason, the size of the motor becomes large, the mounting layout (mounting ability) on an actual vehicle is deteriorated, and a large motor other than a standard product and a dedicated motor control drive unit are required, thereby increasing the manufacturing cost. Become. Therefore, conventionally, a configuration using two support motors has been proposed as a configuration suitable for the electric power steering device for a large vehicle as described above (for example, see Patent Documents 1 to 3).
[0004]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 2001-525292 (FIG. 1)
[Patent Document 2]
JP 2001-260908 A (Paragraph 0040, Paragraph 0041, FIG. 1)
[Patent Document 3]
JP 2001-151125 A (FIG. 1)
[0005]
[Problems to be solved by the invention]
In the case where the electric power steering apparatus is provided with two assisting motors as described above, even if one of the motors fails, the steering force manually operated by the driver by the other motor and the auxiliary steering force by the motor are reduced. It is possible to reduce than not at all. However, the magnitude of the auxiliary steering force by the normal motor that is not out of order remains the magnitude of the auxiliary steering force when the two motors are operating normally, and the two motors operate normally. In order to perform the same steering as in the case in which the steering is performed, the burden of the driver's manual steering force is large. Further, when the burden of steering or the like at the time of stopping is large, the driver cannot bear the load with one motor but bears the burden. In particular, in heavy vehicles, the thrust of the steering gear box is large, so that the burden on the driver is large.
[0006]
FIG. 11 is a diagram showing a relationship between a motor and a load of a driver in a conventional electric power steering device. In the electric power steering apparatus, the ratio between the assisting steering force of the motor and the steering force of the driver is about 10: 1. In particular, in the case of an electric power steering device provided with two motors, the ratio between the respective assisting steering force and the driver's steering force which the two motors take is about 5: 5: 1. When the two motors, the A motor and the B motor, are operating normally, the load on the driver is small as shown by the diagonal lines in the graph on the left side of the figure. Here, if the A motor fails, the driver's load is only the auxiliary steering force of the B motor, so the driver receives the load corresponding to the auxiliary steering force of the A motor. That is, the load ratio between the A motor, the B motor, and the driver is 0: 5: 6. For this reason, as shown in the graph on the right side of the graph at the time of failure of the A motor, the load applied by the driver is up to the auxiliary steering force that should be assisted by the A motor. This is because the magnitude of the auxiliary steering force by the B motor is the same as when the A motor and the B motor are operating normally. A limit value of a current to be supplied to a normal motor is set based on characteristics and durability of the motor, and a current larger than the current limit value cannot be supplied. It cannot provide power and is a burden on the driver.
[0007]
An object of the present invention is to solve the above problem effectively in view of the above problems, and an electric power steering device provided with a plurality of motors, wherein at least one of the plurality of motors fails. Another object of the present invention is to provide an electric power steering apparatus that increases the amount of auxiliary steering force to be given to a normal motor and reduces the burden on the driver.
[0008]
Means and action for solving the problem
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0009]
A first electric power steering device (corresponding to claim 1) is an electric power steering device provided with a plurality of motors for applying a force in a direction to steer a steered wheel. And a current distribution determining unit that increases a distribution amount of an auxiliary steering force applied to a normal motor when at least one of the plurality of motors fails. It is characterized.
[0010]
In the above-described electric power steering device, when at least one of the plurality of motors fails, the current distribution determination unit of the distribution unit increases the distribution amount of the auxiliary steering force applied to the normal motor. Can be lightened.
[0011]
The second electric power steering device (corresponding to claim 2) in the above-described first configuration, preferably, the steering assist force corresponds to the motor current applied to the motor, and the current of each of the plurality of motors is adjusted. A current limit value setting unit for setting a limit value, wherein when at least one of the plurality of motors fails, the current limit value setting unit sets a current limit value of a normal motor to a failure current limit value; The distribution unit distributes the motor current according to the current limit value at the time of failure, via the current distribution determination unit to which the current limit value at the time of the failure is input.
[0012]
According to the second electric power steering device, when at least one of the plurality of motors fails, the current limit value setting unit sets the current limit value of the normal motor to the current limit value at the time of failure, and the distribution unit It is possible to distribute the motor current equal to or greater than the normal current limit value in accordance with the fault current limit value so that the current distribution determination unit of the normal motor exerts the normal motor capacity to the maximum. Thus, the burden on the driver can be further reduced.
[0013]
The third electric power steering apparatus (corresponding to claim 3) is preferably configured such that, in the above-mentioned first configuration, preferably, a state in which a normal motor current value is larger than a normal current limit value continues for a predetermined time. A time-measuring unit (timer) for detecting is provided, and the current limit value setting unit returns from the fault-time current limit value to the normal current limit value on condition that the detection has continued for a predetermined time.
[0014]
According to the third electric power steering device, the current limit value setting unit sets the normal motor current value from the fault current limit value to the normal condition on condition that the state in which the normal motor current value is larger than the normal current limit value has continued for a predetermined time. , The normal motor can be used to the maximum extent in accordance with the durability of the normal motor, and the burden on the driver can be further reduced.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0016]
The configurations, shapes, sizes, and arrangements described in the embodiments are merely schematically shown to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the embodiments described below, and can be modified in various forms without departing from the scope of the technical idea described in the claims.
[0017]
A typical configuration of the electric power steering device according to the present invention will be described with reference to FIGS. FIG. 1 is a view conceptually showing basic components (only one of the two motors is shown) of an electric power steering apparatus of a two-motor type, and FIG. 2 shows two motors and a gear box. FIG. 3 is a diagram showing an external appearance layout of an actual device of a rack shaft provided.
[0018]
The electric power steering device 10 is mounted on, for example, a passenger vehicle. The electric power steering device 10 is configured to apply auxiliary steering torque to a steering shaft 12 and the like connected to a steering wheel 11. An upper end of the steering shaft 12 is connected to the steering wheel 11, and a pinion gear (or pinion) 13 is attached to a lower end. Here, a portion of the lower end of the steering shaft 12 to which the pinion gear 13 is attached is referred to as a pinion shaft 12a. Actually, the upper steering shaft 12 and the lower pinion shaft 12a are connected by a universal joint (not shown). A rack shaft 14 provided with a rack gear 14a that meshes with the pinion gear 13 is disposed. A rack and pinion mechanism 15 is formed by the pinion gear 13 and the rack gear 14a.
[0019]
A rack and pinion mechanism 15 formed between the pinion shaft 12a and the rack shaft 14 is housed in a first gear box 23A. The appearance of the gear box 23A is shown in FIG.
[0020]
Tie rods 16 are provided at both ends of the rack shaft 14, and a front wheel 17 is attached to an outer end of each tie rod 16. The front wheels 17 function as steered wheels of the vehicle.
[0021]
A motor 19A is further provided to the pinion shaft 12a via a power transmission mechanism 18. The power transmission mechanism 18 includes a worm gear provided on an output shaft (worm shaft) 19A-1 of the motor 19A, and a worm wheel fixed to the pinion shaft 12a. The power transmission mechanism 18 is incorporated in the gear box 23A.
[0022]
The steering shaft 12 is provided with a steering torque detector 20. The steering torque detector 20 detects a steering torque applied to the steering shaft 12 when the steering torque generated by the driver operating the steering wheel 11 is applied to the steering shaft 12. The steering torque detector 20 is also incorporated in the gear box 23A. Reference numeral 21 denotes a vehicle speed detection unit that detects the vehicle speed of the vehicle, and reference numeral 30 denotes a control device (ECU) configured by a computer system using a microcomputer or the like. The control device 30 takes in the steering torque signal T output from the steering torque detection unit 20, the vehicle speed signal V output from the vehicle speed detection unit 21, and the like, and controls the motor 19A and the like based on information related to the steering torque and the vehicle speed. A drive control signal SG1 for controlling the rotation operation is output. In addition, a motor rotation angle detection unit 22 is attached to the motor 19A and the like. A signal SG2 related to the rotation angle (electric angle) of the motor rotation angle detection unit 22 is input to the control device 30.
[0023]
In the electric power steering apparatus according to the present embodiment, another motor (19B in FIG. 2) having the same performance as the motor 19A is attached, and is configured as a two-motor type. Another motor 19B is shown in FIG. The motor 19B has the same configuration as the motor 19A, and is controlled by the control device 30.
[0024]
As shown in FIG. 2, the rack shaft 14 has a second gear box 23B in addition to the first gear box 23A. Like the first gear box 23A, the gear box 23B includes a rack gear formed on the rack shaft 14, a pinion gear that meshes with the rack gear, and a pinion shaft to which the pinion gear is fixed and rotatably supported. Have been. Another motor 19B is attached to the second gear box 23B via a power transmission mechanism 18. The output shaft of the motor 19B has a transmission shaft (worm shaft) as described above, and a worm gear is provided on the transmission shaft, while a worm wheel that meshes with the worm gear is fixed to the pinion shaft.
[0025]
The configuration of the gear box 23B is basically the same as the configuration of the gear box 23A. When the motor 19B is driven, a driving force is transmitted to the rack shaft 14 via an output shaft, a worm gear, a worm wheel, a pinion shaft, a pinion gear, and a rack gear.
[0026]
As described above, the electric power steering apparatus 10 according to the present embodiment includes the two motors 19A and 19B as assisting motors, and is configured to assist the manual steering force. In the above description, the electric power steering apparatus 10 has a steering torque detecting unit 20, a vehicle speed detecting unit 21, a control device 30, a first and a second two gear boxes 23A and 23B, The motors 19A and 19B are provided with two power transmission mechanisms 18 attached thereto.
[0027]
In the above configuration, when the driver operates the steering wheel 11 to perform steering in the traveling direction during traveling of the automobile, the rotational force based on the steering torque applied to the steering shaft 12 is reduced by the lower pinion shaft 12a and the rack. It is converted into linear motion in the axial direction of the rack shaft 14 via the pinion mechanism 15, and further attempts to change (steer) the running direction of the front wheel 17 via the tie rod 16. At this time, at the same time, the steering torque detector 20 attached to the pinion shaft 12a detects a steering torque corresponding to the steering by the driver on the steering wheel 11 and converts it into an electric steering torque signal T. A steering torque signal T is output to the control device 30. The vehicle speed detection unit 21 detects the vehicle speed of the vehicle, converts the vehicle speed into a vehicle speed signal V, and outputs the vehicle speed signal V to the control device 30. Control device 30 generates a motor current for driving two motors 19A and 19B based on steering torque signal T and vehicle speed signal V. The motors 19A and 19B driven by the motor current apply auxiliary steering torque to the rack shaft 14 via the power transmission mechanisms 18 and the gear boxes 23A and 23B, respectively. As described above, the driver's steering force applied to the steering wheel 11 is reduced by driving the two motors 19A and 19B.
[0028]
FIG. 3 is a block diagram illustrating an internal configuration of the control device 30 according to the first embodiment of the present invention. The control device 30 sets a target current based on the steering torque signal T and the vehicle speed signal V and outputs a target current signal M based on the motor drive control unit 31A for the motor 19A, the motor drive control unit 31B for the motor 19B. A unit 41, a failure detection unit 42 for detecting a failure of the motors 19A and 19B, and a target current distribution unit 50 for distributing a target current to the motors 19A and 19B. The motor drive control unit 31A includes a gate drive circuit 32A and a motor drive circuit 33A, and the motor drive control unit 31B includes a gate drive circuit 32B and a motor drive circuit 33B. Electric power is supplied from the battery 24 to the motor drive circuits 33A and 33B. Note that the failure detection unit 42 detects a failure based on, for example, the duty factors duty1 and duty2 of the PWM signals supplied from the gate drive circuits 32A and 32B to the motor drive circuits 33A and 33B, respectively.
[0029]
The motor current described above is a current supplied from the motor drive control units 31A and 31B to the motors 19A and 19B, respectively. The gate drive circuit 32A of the motor drive control unit 31A outputs a PMW signal based on the current signal SA distributed by the target current distribution unit 50, and causes the motor drive circuit 33A to perform a switching operation based on the duty of the PMW signal. As a result, the motor current is supplied to the motor 19A. Also in the motor drive control unit 31B for the motor 19B, the gate drive circuit 32B and the motor drive circuit 33B operate similarly based on the current signal SB distributed by the target current distribution unit 50. Upon receiving the failure signal K from the failure detection unit 42, the target current distribution unit 50 determines the failed motor, and increases the motor current given to the non-failed and normal motor according to the determination result. Change the current signals SA and SB.
[0030]
FIG. 4 is a block diagram showing the internal configuration of the target current distribution unit 50. The target current distribution unit 50 receives the failure signal K, determines a failed motor, determines a failed motor, and receives the target current signal M, determines a current to be distributed to the motors 19A and 19B, and determines a current signal. It comprises a current distribution determining unit 52 that outputs SA and SB. The failed motor determination unit 51 receives the failure signal K and determines whether the failed motor is the motor 19A or the motor 19B. The failed motor determination unit 51 outputs a signal KM relating to a normal motor to the current distribution determination unit 52. The current distribution determining unit 52 receives the target current signal M and the signal KM relating to a normal motor, and determines a current to be supplied to the motors 19A and 19B. For example, when the motor 19A is out of order, the current to the motor 19A is set to zero and the current to the motor B is increased.
[0031]
FIG. 5 is an operation flowchart of the target current distribution unit 50. The target current signal M is read from the target current setting section 41 (Step S101). The failure signal K is received from the failure detection unit 42. The failure signal K is, for example, a 2-bit signal. "00" indicates that the motors 19A and 19B are normal, "01" indicates that the motor 19A is normal, the motor 19B is malfunctioning, and "10" indicates that the motor 19A is malfunctioning. , The motor 19B is normal, and “11” indicates that the motors 19A and 19B are out of order. It is determined from the failure signal K whether the motors 19A and 19B have failed (step S102). Here, it is determined whether "1" is present in any of the 2-bit signals. If there is no faulty motor, that is, if the motor is operating normally, normal control is performed (step S105). Here, the normal control means that when the two motors have the same magnitude, the same current flows, and when the two motors have different magnitudes, the current is distributed according to the magnitude. I do. Alternatively, the motor may be energized first without energizing the motors at the same time.
[0032]
If there is a faulty motor, it is determined which motor is faulty and which is normal (step S103). Here, when there is no normal motor, that is, when the failure signal K is “11”, the control of the electric power steering device is stopped (step S106). If it is determined that there is a normal motor, that is, if the failure signal K is “01” or “10”, the amount of current distribution to the normal motor is increased according to the failure signal K (step S104).
[0033]
FIG. 6 is a diagram showing the relationship between the motor and the load on the driver. It is assumed that the ratio between the auxiliary steering force of the motor 19A and the motor 19B and the steering force by the driver in a normal state is 5: 5: 1. The hatched portion indicates the steering force by the driver. For example, when the motor 19A fails, the current supplied from the motor drive circuit 33B to the motor 19B by the target current distribution unit 50 increases, and the auxiliary steering force by the motor 19B increases. The graph on the right in FIG. 6 shows that the driver's steering force is reduced by the assisting steering force of the motor 19B. Here, the ratio between the auxiliary steering force of the motor 19B and the steering force by the driver is about 7: 4.
[0034]
FIG. 7 is a block diagram illustrating an internal configuration of the control device 30 according to the second embodiment of the present invention. Elements substantially the same as those shown in FIG. 3 of the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated. In the control device 30 of the second embodiment, current detection units 34A and 34B that measure the current flowing through the motor drive circuits 33A and 33B are provided. The current detectors 34A and 34B detect current from the resistance values of the shunt resistors R1 and R2 and the potential difference between both ends of the shunt resistors R1 and R2, and output current signals IA and IB. The detected currents flowing through the motor drive circuits 33A and 33B are input to the target current distribution unit 60 as current signals IA and IB.
[0035]
FIG. 8 is a block diagram showing the internal configuration of the target current distribution unit 60. The target current distribution unit 60 receives the failure signal K, determines a failed motor, determines a failed motor, and receives the target current signal M, determines a motor current to be distributed to the motors 19A and 19B, A current distribution determining unit 62 that outputs the current signals SA ′ and SB ′; a current limit value setting unit 63 that receives a signal from the failed motor determination unit 61 and sets a current limit value of a normal motor; And a timer 64 that operates based on the current flowing through the motor.
[0036]
The failed motor determination unit 61 determines which motor has failed based on the failure signal K, and outputs, for example, a signal KM relating to a normal motor to the current distribution determination unit 62 and the current limit value setting unit 63. Note that the failed motor determination unit 61 does not output the signal KM to the current limit value setting unit 63 when there is no failure. The current limit value setting section 63 receives the signal KM relating to a normal motor, and sets the current limit value of the normal motor to the fault current limit value. The current limit value at the time of failure is set to be larger than a normal current limit value in order to increase the auxiliary steering force by a normal motor when one motor fails. The current distribution determining unit 62 receives the target current signal M, the signal KM relating to a normal motor, and the current limit value signal L, and determines a current to be supplied to the motor 19A and the motor 19B. For example, when the motor 19A fails and the motor 19B is normal, the current to the motor 19A is set to 0, and the current of the motor 19B is set to a current larger than the normal current limit according to the failure current limit. To
[0037]
FIG. 9 is an operation flowchart of the target current distribution unit 60. The failure signal K is received from the failure detection unit 42. The failure signal K is, for example, a 2-bit signal. "00" indicates that the motors 19A and 19B are normal, "01" indicates that the motor 19A is normal, the motor 19B is malfunctioning, and "10" indicates that the motor 19A is malfunctioning. , The motor 19B is normal, and “11” indicates that the motors 19A and 19B are out of order. It is determined from the failure signal K whether or not the motors 19A and 19B have failed (step S201). Here, it is determined whether "1" is present in any of the 2-bit signals. If there is no faulty motor, that is, if the motor is operating normally, C described below is set to 0 (step S209). If there is a faulty motor, it is determined which motor is faulty and which is normal (step S202). Here, when there is no normal motor, that is, when the failure signal K is “11”, the control of the electric power steering device is stopped (step S208). If it is determined that there is a normal motor, that is, if the failure signal K is “01” or “10”, the current limit value of the normal motor is set as the failure limit value (step S203). If the current limit value of the normal motor is set to the limit value at the time of failure, it becomes possible to flow a motor current higher than the normal current limit value to the normal motor, so that the normal motor current It is checked whether the current is flowing beyond the current limit value (step S204). If the current value of the normal motor is smaller than the normal current limit value, C described below is set to 0 (step S209). If the normal motor current is equal to or greater than the normal current limit value, the timer 64 is operated and C is counted by one (step S205). It is not preferable from the viewpoint of durability that the current value of the motor is equal to or higher than the normal current limit value, but within a predetermined time, the current value exceeds the normal current limit value within the durability range. is there. Therefore, an auxiliary steering force that cannot be output when a normal current limit value is set at the time of failure can be output by setting the current limit value at the time of failure. For the above reason, it is necessary that the predetermined time during which the current value of the motor exceeds the normal current limit value does not fall outside the range of the durability of the motor. Therefore, when the count C of the timer 64 becomes larger than α (step S206), the current limit value is returned to the normal current limit value (step S207).
[0038]
In the above process, after one of the motors has failed and the other motor is normal after the operation of the timer 64, the process goes through step S203 again. At this time, the current limit value of the normal motor is held at the failure limit value. The normal motor current value is compared with the normal current limit value (step S204). At this time, when the current value of the normal motor is lower than the normal current limit value, the load on the motor is not more than usual, so that the count C of the timer 64 is set to 0 (step S209). Thereby, the motor can be operated more efficiently.
[0039]
FIG. 10 is a diagram showing the relationship between the motor and the load on the driver. It is assumed that the ratio between the auxiliary steering force of the motor 19A and the motor 19B and the steering force of the driver during normal operation is 5: 5: 1. The hatched portion represents the steering force of the driver. For example, when the motor 19A fails, the current limit value of the motor 19B becomes the current limit value at the time of failure by the current limit value setting unit 63 of the target current distribution unit 60. As a result, a current equal to or larger than the normal current limit value can flow through the motor 19B. For this reason, the auxiliary steering force by the motor 19B becomes larger. The graph on the right in FIG. 6 shows that the driver's steering force is reduced by the assisting steering force of the motor 19B. This means that the driver's steering force is lighter than when the amount of distribution of the motor current is simply changed as shown in FIG. 6 of the first embodiment. Here, the ratio between the auxiliary steering force of the motor 19B and the steering force by the driver is about 8: 2.
[0040]
【The invention's effect】
As apparent from the above description, the present invention has the following effects.
[0041]
As described above, according to the electric power steering apparatus of the present invention, a plurality of motors that apply a force in a direction in which a steered wheel is steered are provided, and a distribution unit that distributes an auxiliary steering force applied to the plurality of motors is provided. The distributing unit increases the distribution amount of the assisting steering force applied to the normal motor when at least one of the plurality of motors fails, so that the burden on the driver when the motor fails is reduced. Can be. Also provided is a current limit value setting section for setting current limit values of a plurality of motors, and when at least one of the plurality of motors fails, the current limit value setting section sets the current limit value of a normal motor to failure. Since the current limit value is set, the motor current that is equal to or larger than the normal current limit value can be distributed so that the normal motor performance is maximized, and the burden on the driver can be further reduced.
[Brief description of the drawings]
FIG. 1 is a diagram conceptually showing basic components of an electric power steering apparatus according to the present invention.
FIG. 2 is a diagram illustrating an external layout of an actual device of a rack shaft including two motors and a gear box.
FIG. 3 is a block diagram illustrating an internal configuration of a control device according to the first embodiment of the present invention.
FIG. 4 is a block diagram showing an internal configuration of a target current distribution unit.
FIG. 5 is an operation flowchart of a target current distribution unit.
FIG. 6 is a diagram showing a relationship between a motor and a load of a driver.
FIG. 7 is a block diagram illustrating an internal configuration of a control device according to a second embodiment of the present invention.
FIG. 8 is a block diagram illustrating an internal configuration of a target current distribution unit.
FIG. 9 is an operation flowchart of a target current distribution unit.
FIG. 10 is a diagram showing a relationship between a motor and a load of a driver.
FIG. 11 is a diagram showing a relationship between a motor and a driver's load in a conventional electric power steering device.
[Explanation of symbols]
Reference Signs List 10 electric power steering device 11 steering wheel 19A motor 19B motor 20 steering torque detector 21 vehicle speed detector 22 motor rotation angle detector 23A gear box 23B gear box 30 controller 31A, 31B motor drive controller 32A, 32B gate drive circuit 33A , 33B Motor drive circuits 34A, 34B Current detection unit 41 Target current setting unit 42 Fault detection unit 50 Target current distribution unit 51 Faulty motor determination unit 52 Current distribution determination unit 60 Target current distribution unit 61 Faulty motor determination unit 62 Current distribution determination unit 63 Current limit value setting section 64 Timer

Claims (3)

In an electric power steering device provided with a plurality of motors that apply a force in a direction to steer a steered wheel,
Distributing means for distributing auxiliary steering force to the plurality of motors,
The electric power, comprising: current distribution determining means for increasing a distribution amount of auxiliary steering force applied to a normal motor when at least one of the plurality of motors fails. Steering device. The auxiliary steering force corresponds to a motor current given to the motor,
A current limit value setting means for setting a current limit value of each of the plurality of motors,
When at least one of the plurality of motors has failed, the current limit value setting means sets the current limit value of a normal motor to a fault current limit value, and the distribution means includes a fault current limit value. 2. The electric power steering apparatus according to claim 1, wherein the motor current is distributed according to the current limit value at the time of failure through the current distribution determining means to which the motor current is inputted. A timer for detecting whether or not a state in which the current value of the normal motor is larger than a normal current limit value continues for a predetermined time; provided that the current limit value setting means has a fault on condition that the predetermined time has continued; 3. The electric power steering apparatus according to claim 2, wherein the hourly current limit value is returned to a normal current limit value.

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