JP2010120447A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device considered in power saving to immediately generate steering assist force according to an operation of a steering wheel when a vehicle mounted with an idle stop system is returned from an idle stop. <P>SOLUTION: A volatile neutral point storing part 48 storing a neutral point is continued to be energized during the idle stop, even in ignition off (such as a stopping time of an ignition signal or a stopping time of a fuel injection signal). When the vehicle is returned from the idle stop, an accurate steering assist force control can be immediately started based on the neutral point stored in the volatile neutral point storing part 48. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering device for a vehicle that reduces the steering force of the steering wheel by transmitting the power of an actuator such as an electric motor to a steering system so that the vehicle can turn with a light steering force of the steering wheel.

  When the steering assist force generating actuator is controlled in accordance with the steering amount from the middle point of the steering wheel, the traveling direction of the vehicle may be biased if the middle point is inaccurate. Therefore, it is required to determine the midpoint as accurately as possible.

  For example, it is determined whether or not the position of the steering wheel corresponds to the straight traveling state of the vehicle based on detection values such as the yaw rate and lateral acceleration of the vehicle, and the position of the steering wheel is determined to correspond to the straight traveling state of the vehicle The steering amount detected by the steering amount sensor is stored as a midpoint.

  However, the memorized midpoint is erased when the ignition switch is opened, and is fixed to determine whether the position of the steering wheel corresponds to the straight traveling state of the vehicle after the ignition switch is closed thereafter. Takes time. Therefore, there is a problem that the start of control according to the steering amount from the middle point is delayed.

  A technique for solving this problem has been proposed (Patent Document 1). In the technique according to Patent Document 1, each time the ignition switch is closed, it is determined whether or not the position of the steering wheel is in a position corresponding to the straight traveling state of the vehicle, and is determined to be in a position corresponding to the straight traveling state of the vehicle. At that time, the steering amount (steering angle) of the steering wheel by the resolver, which is a relative angle sensor, is stored as a midpoint in the midpoint storage volatile memory (the midpoint is identified). The resolver operates when the ignition switch is closed, and does not operate when open because no power is supplied.

  Further, in the technique according to Patent Document 1, a steering angle sensor that detects the relative rotation angle of the steering shaft is provided, and the steering angle sensor is always supplied with electric power and opened even when the ignition switch is closed. Even if it is, the rudder angle sensor operates.

  In this case, the resolution of the resolver is about 0.1 [°], and the resolution of the rudder angle sensor is about 1 [°].

  In the technique according to Patent Document 1, the steering amount of the steering wheel by the resolver and the rotation angle of the steering wheel by the steering angle sensor are both stored in a nonvolatile memory.

  In the technique according to Patent Document 1, when the ignition switch is closed (time t1), the resolver when the ignition switch immediately after time t1 is opened (time t0 before time t1) is resolved. Steering amount from the middle point {the steering amount stored in the non-volatile memory and the steering angle θ1 (absolute angle from the middle point). } And the rotation angle detected by the steering angle sensor between the time t0 and the time t1 (that is, by operating the steering wheel while the ignition switch is opened) {the rotation angle stored in the non-volatile memory] Therefore, it is assumed that the steering angle θ2 (relative angle). } And the steering amount {steering angle θ3 (relative angle) by the resolver from the time point t1 to the time point t2 immediately after the time point t1. } (Θ1 + θ2 + θ3) is regarded as the steering amount (steering angle) from the midpoint (until a new midpoint is identified), and this deemed steering amount (θ1 + θ2 + θ3) It describes that an electric motor which is an actuator for generating a steering assist force is driven.

JP 2008-37350 A

  As described above, in the technique according to Patent Document 1, when the ignition switch is closed, the steering assist force corresponding to the operation of the steering wheel is immediately generated by the steering amount (θ1 + θ2 + θ3) only from the middle point. The generated electric power steering control can be performed.

  By the way, recent vehicles are equipped with an idle stop system in which the engine automatically stops when waiting for a signal or when there is a traffic jam in order to improve fuel efficiency.

  However, the technology according to Patent Document 1 does not describe anything about the relationship between the idle stop system and the midpoint holding of the steering shaft.

  Moreover, in the technology according to Patent Document 1, since the steering angle sensor is always energized in the state where the ignition switch is open, the power is wasted when the vehicle is not moved for a long period of time. In such a case, there is a risk that the battery will rise.

  The present invention has been made in consideration of such problems, and immediately generates a steering assist force according to the operation of the steering wheel when the vehicle equipped with the idle stop system is returned from the idle stop. An object of the present invention is to provide an electric power steering device in which power saving is considered.

  An electric power steering apparatus according to the present invention includes a steering wheel, an actuator that generates a steering assist force in response to an operation of the steering wheel, a steering amount sensor that detects a steering amount of the steering wheel by a relative angle sensor, In an electric power steering apparatus comprising: a volatile midpoint storage unit that stores a steering amount detected by the steering amount sensor at a time when it is determined that the position of the steering wheel corresponds to a straight traveling state of the vehicle; When the vehicle on which the electric power steering device is mounted is in the ignition off state, the idle stop state determining unit that determines whether or not the vehicle is in the idling stop state, and the idle stop state determining unit, the vehicle is in the ignition off state and In idle stop state If it is determined that is characterized in that it comprises a power supply controller to continuously energizing the midpoint storage unit.

  According to the present invention, even when the ignition is off (for example, when the ignition signal is stopped, when the fuel injection signal is stopped, etc.), at the time of idling stop, the volatile midpoint storage unit storing the midpoint is energized. Therefore, the steering assist force control can be performed immediately from the midpoint position stored in the volatile midpoint storage unit when returning from the idle stop. In addition, when the ignition is off and the engine is not idling, the volatile midpoint storage unit is not energized, so that power is not consumed unnecessarily.

  In this case, when the idle stop state determination unit determines that the vehicle is in the ignition off state and in the idle stop state, the steering amount sensor is continuously energized so that the driver or the like can perform steering during the idle stop. Even when the wheel is operated and the steering angle is changed, the steering amount (steering angle position) from the midpoint can be recognized when the idle stop is returned. That is, the steering assist force control can be immediately performed based on the steering amount obtained by adding the rudder angle change detected by the steering amount sensor to the midpoint position stored in the volatile midpoint storage unit.

  The electric power steering apparatus according to the present invention includes a steering wheel, an actuator that generates a steering assist force in response to an operation of the steering wheel, a steering amount sensor that detects a steering amount of the steering wheel by a relative angle sensor, A non-volatile midpoint storage unit that stores a steering amount detected by the steering amount sensor at the time when the position of the steering wheel is determined to correspond to a straight traveling state of the vehicle as a midpoint. In the above, when the vehicle on which the electric power steering device is mounted is in the ignition off state, the idle stop state determining unit that determines whether or not the vehicle is in the idling stop state and the idle stop state determining unit cause the vehicle to turn off the ignition. And idle stop If it is determined that the state, characterized in that it comprises a power supply controller to continuously energizing the steering amount sensor.

  According to the present invention, even when the ignition is off (for example, when the ignition signal is stopped or when the fuel injection signal is stopped), the steering amount sensor continues to be energized during the idle stop. Even when the steering angle is changed and the steering angle is changed, the steering amount from the middle point (steering angle from the straight traveling state) can be recognized at the time of return from idle stop, and accurate steering assist force control can be performed immediately.

  According to the present invention, when the vehicle equipped with the idle stop system is returned from the idle stop, the electric power in consideration of the power saving capable of generating an accurate steering assist force according to the operation of the steering wheel immediately. A steering device is provided.

A. Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an electric power steering device 10 for a vehicle according to an embodiment of the present invention.

  FIG. 2 is a block diagram of the electric power steering apparatus 10 including detailed functions of an EPSECU (Electric Power Steering Electronic Control Unit) 30 constituting the electric power steering apparatus 10.

  The ECU includes a microcomputer, and the microcomputer functions as a function execution unit (function execution means) that executes various functions when the CPU executes a program stored in the memory.

  As shown in FIG. 1, the electric power steering apparatus 10 includes wheels (operating wheels) including a rack and pinion mechanism 18 including a pinion 18 a and a rack 18 b and an auxiliary rack and pinion mechanism 38 including an EPS motor 36 that is an electric motor. The steering mechanism 11 is provided.

  The steering force of the steering wheel 12 by the driver is transmitted to the rack and pinion mechanism 18 constituting the steering mechanism 11 via the steering shaft 14. The steering shaft 14 is provided with a steering torque sensor 16 that detects a steering torque (steering torque) Ts, and a steering amount sensor 42 that detects a steering amount (steering angle) θs of the steering wheel 12 by a relative angle sensor. .

  In this case, the rotational force received by the pinion 18 a from the steering shaft 14 is converted into a linear motion in the axial direction of the rack 18 b and changes the operating direction of the wheels 22 via the tie rod 20.

  At this time, the steering torque St detected by the steering torque sensor 16 is input to the EPS ECU 30 in order to assist the manual steering force of the steering wheel 12.

  The EPS ECU 30 is supplied with various input information such as the vehicle speed V from the vehicle speed sensor 32, the yaw rate Yr from the yaw rate sensor 34, and the steering amount θs from the steering amount sensor 42 in addition to the steering torque Ts.

  The steering assist torque determining unit 43 shown in FIG. 2 of the EPSECU 30 determines the steering assist torque Tsa based on the input information and supplies the determined steering assist torque Tsa to the motor driving unit 44.

  The motor drive unit 44 generates a motor current Ieps that generates the steering assist torque Tsa and supplies the motor current Ieps to the EPS motor 36.

  A midpoint learning unit 46 including a midpoint storage unit 48 that is a volatile memory such as a RAM is referred to as a midpoint of the steering amount sensor 42 that is a relative angle sensor (referred to as zero point, a steering amount during straight travel, or a steering angle during straight travel). ) For learning, a straight traveling state is detected and stored as a midpoint in the midpoint storage unit 48.

  In this case, detection of the straight-ahead state is performed, for example, by regarding that the detection values of the following (1) to (4) are in a straight-ahead state when each of the detection values is within the reference value range.

  (1) The yaw rate Yr detected by the yaw rate sensor 34, (2) the vehicle speed V detected by the vehicle speed sensor 32, (3) the change amount of the vehicle speed V within a predetermined time, and (4) the steering amount θs within the predetermined time. The amount of change.

  Then, the steering amount θs, which is the output value of the steering amount sensor 42 when it is regarded as being in the straight traveling state, is learned as the midpoint {0 [deg]} and stored in the midpoint storage unit 48. Therefore, after storing the midpoint in the midpoint storage unit 48, the midpoint (by subtracting the midpoint steering amount θs stored in the midpoint storage unit 48 from the steering amount θs detected by the steering amount sensor 42. 0 [deg]), the steering amount (steering angle from the straight direction) θs can be detected.

  The steering assist torque determination unit 43 uses a vehicle speed V as a parameter as basic control (referred to as basic EPS control). The steering assist torque determination unit 43 increases the steering assist torque Tsa that increases as the vehicle speed V increases and increases in proportion to the steering torque Ts. A known control is performed (see, for example, FIG. 1 of Japanese Patent Laid-Open No. 11-49000).

  Actually, after the middle point is stored, the steering assist torque Tsa based on the basic EPS control is corrected according to the steering amount θs from the stored middle point by the steering amount sensor 42. For example, when the steering amount θs from the middle point is less than or equal to a set value, the stability of straight traveling is increased by controlling so as not to generate the steering assist force torque Tsa even if the steering torque Ts increases. Convergence to the middle point position of the steering wheel 12 is improved by changing the steering assist torque Tsa according to the steering amount θs from the middle point when the control or the steering amount θs from the middle point is reduced. Control and so on. These correction controls are also known (for example, paragraph [0015] of Patent Document 1).

  Therefore, holding the midpoint of the steering amount sensor 42 in the midpoint storage unit 48 is important for obtaining an appropriate steering force. Here, since the midpoint storage unit 48 includes a volatile memory, the midpoint stored in the midpoint storage unit 48 disappears when the energization (power supply) to the midpoint storage unit 48 is stopped. (Volatile).

  On the other hand, the steering amount sensor 42 is constituted by a resolver, for example, and outputs a steering amount θs when energized, and outputs nothing when not energized.

  In this embodiment, energization of the midpoint storage unit 48 and the steering amount sensor 42 is performed through the energization control unit 50.

  The energization control unit 50 determines whether to continue energizing the midpoint storage unit 48 and the steering amount sensor 42 based on the determination result of the idle stop state determination unit 52.

  The vehicle on which the electric power steering device 10 is mounted has a main switch 100. When the main switch 100 is closed, the power supply voltage Vbat of the vehicle-mounted battery 66 is not only EPSECU 30, but also the engine ECU 60, idle stop ECU 64, EPS motor. 36, the vehicle speed sensor 32, the steering torque sensor 16, the yaw rate sensor 34, the brake switch 70, the shift lever switch 72, the accelerator pedal switch 74, and the like.

  Here, as shown in the flowchart of FIG. 3, when the closing operation of the main switch 100 is detected in step S2, the engine ECU 60 starts the engine 62 (engine on) in step S4, and in step S6 the ignition. An on signal IGON is generated. The ignition on signal IGON is substituted with, for example, an ignition signal, a fuel injection signal, or a crank angle signal.

  Further, in step S8, it is determined whether or not the idle step flag Fis is turned on. If it is turned on, an ignition off signal IGOFF is generated, and then the engine 62 is stopped in step S12 (engine Off) (engine stopped). The ignition off signal IGOFF is substituted by the stop of the ignition signal, the stop of the fuel injection signal, or the stop of the crank angle signal.

  After the engine is turned off in step S12, the state of the idle stop flag Fis is determined in step S8. If the idle stop flag Fis is returned to Fis = on, the idle is returned and the main switch 100 in step S2 is closed. The engine 62 is restarted in step S4 on the condition that it is.

  If the main switch 100 has been opened in step S2, the engine 62 is stopped (engine off) in step S14.

  Next, as shown in the flowchart of FIG. 4, the idle stop ECU determines whether or not an idle stop condition is satisfied in step S22.

  In this embodiment, the idle stop condition is that the shift lever switch 72 is in the D range (D range of the AT car), the accelerator pedal switch 74 is off (the accelerator pedal is not depressed), and the brake switch 70 is on ( In step S24, the idle stop flag Fis is set to Fis = on.

  In this state, when the brake switch 70 is turned off (when the foot is released from the brake pedal), the idle stop flag Fis is set to Fis = off to return to the idle return state.

  As shown in FIG. 1, the idle stop flag Fis generated from the idle stop ECU 64 is supplied to an idle stop state determination unit 52 that constitutes the engine ECU and the EPS ECU.

  The idle stop state determination unit 52 is further supplied with an ignition on signal IGON or an ignition off signal IGOFF from the engine ECU 60.

  The idle stop state determination unit 52 controls the energization control unit 50 based on the opening / closing of the main switch 100, the ignition off signal IGOFF, and the idle stop flag Fis.

  Next, operations of EPSECU 30, particularly operations of idle stop state determination unit 52 and energization control unit 50, will be described with reference to the flowchart of FIG. 5.

  In step S30, the energization control unit 50 determines that the main switch 100 is closed by supplying the battery voltage Vbat. At this time, the energization control unit 50 supplies power based on the battery voltage Vbat to the entire EPS ECU 30 and the steering amount sensor 42.

  When the main switch 100 is in the closed state, the idle stop state determination unit 52 determines whether or not the ignition off signal IGOFF is supplied in step S32.

  When the ignition off signal IGOFF is not supplied and the ignition switch on signal IGON is supplied, the idle stop state determination unit 52, in step S36, determines the steering amount sensor 42 and the midpoint storage unit by the energization control unit 50. In step S38, the basic EPS control described above and the EPS control in consideration of the midpoint are performed after the midpoint is detected in step S38.

  On the other hand, if the ignition stop signal IGOFF is supplied in the determination by the idle stop state determination unit 52 in step S32, it is determined in step S34 whether the idle stop flag Fis is on or not. Judgment by.

  If it is determined that the idle stop flag Fis is Fis = on and the engine is in the idle stop state, in step S40, the energization control unit 50 determines that the middle point storage unit 48, steering, as indicated by the dotted arrow in FIG. Electric power (battery voltage Vbat) is supplied only to the quantity sensor 42 and the idle stop state determination unit 52, and supply of electric power to other units in the EPS ECU 30 is stopped.

  In practice, when the idle stop flag Fis is turned on, the parts of the battery 66 that require power are indicated by the steering amount sensor 42, the midpoint storage unit 48, the energization indicated by the solid line frame shown in FIG. The control unit 50, the idle stop state determination unit 52, the engine ECU 60, the idle stop ECU 64, the brake switch 70, the shift lever switch 72, and the accelerator pedal switch 74. Since no energization is required, power can be saved.

B. Summary As described above, the electric power steering apparatus 10 according to the above-described embodiment includes the steering wheel 12, the EPS motor 36 as an actuator that generates a steering assist force in response to the operation of the steering wheel 12, and the relative angle sensor. The steering amount sensor 42 for detecting the steering amount θs of the steering wheel 12 and the steering amount θs detected by the steering amount sensor 42 when it is determined that the position of the steering wheel 12 corresponds to the straight traveling state of the vehicle is set as a middle point. Whether or not the vehicle on which the electric power steering apparatus 10 is mounted outputs an ignition-off signal IGOFF, whether or not the vehicle is in an idle stop state. Idle stop state determination unit 52 for determining, When it is determined that the vehicle outputs the ignition-off signal IGOFF and is in the idling stop state (Fis = on), the midpoint storage unit 48 and the steering amount sensor 42 are energized. An energization control unit 50.

  According to this embodiment, the steering wheel 12 is operated during idling stop by continuously energizing the steering amount sensor 42 in addition to the midpoint storage unit 48 at idling stop (first embodiment: best mode). Even when the steering amount θs is changed, accurate steering force assist control based on the changed steering amount θs can be started immediately upon return of the idle stop.

  Since the midpoint storage unit 48 and the steering amount sensor 42 are not energized when the ignition is turned off except during idling stop, unnecessary power consumption can be avoided, and the electric power steering device 10 in consideration of power saving can be provided. it can.

  It should be noted that the steering amount sensor 42 is not energized at the time of idling stop, but is energized only to the midpoint storage unit 48 (second embodiment), and immediately after returning from idling stop (Fis = off), the steering wheel is immediately activated. Therefore, it is possible to generate an appropriate steering assist force according to the operation of No. 12, and when the ignition is turned off other than at the time of idling stop, the midpoint storage unit 48 is not energized. The electric power steering apparatus 10 considered can be provided.

  In the first and second embodiments described above, a volatile memory is used as the midpoint storage unit 48, but a nonvolatile memory such as an EEPROM (nonvolatile midpoint storage) is used as the midpoint storage unit 48. Part) can also be used (third embodiment). When the nonvolatile memory is used, the energization control unit 50 energizes the steering amount sensor 42 when the idle stop state determination unit 52 determines that the vehicle is in the ignition off state and in the idle stop state. (The energization of the non-volatile midpoint storage unit 48 is not necessary). Thus, as described above, even when the steering wheel 12 is operated during the idling stop and the steering amount θs is changed, an accurate steering force based on the changed steering amount θs is returned when the idling stop is restored. Auxiliary control can be performed.

  In particular, the present invention provides a motor auxiliary that is integrally provided with a generator / motor (generator / motor) in an engine as a driving source for vehicle travel, and the generator / motor is used as an auxiliary driving source for assisting the output of the engine. When applied to an electric power steering device for a hybrid vehicle, it is possible to smoothly control idle stop, which is preferable.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

1 is a schematic configuration diagram of an electric power steering device for a vehicle according to an embodiment of the present invention. In FIG. 1, it is a block diagram which shows the structural example of EPSECU. It is a flowchart with which operation | movement description of engine ECU regarding an energization control and idle stop is provided. It is a flowchart with which operation | movement description of idle stop ECU regarding an energization control and an idle stop is provided. It is a flowchart provided for operation | movement description of EPSECU regarding energization control and idle stop. It is explanatory drawing of the electricity supply site | part by an electricity supply control, and a non-energization site | part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus 11 ... Steering mechanism 12 ... Steering wheel 16 ... Steering torque sensor 30 ... EPSECU 36 ... EPS motor 42 ... Steering amount sensor 48 ... Middle point memory | storage part 50 ... Current supply control part 52 ... Idle stop state judgment part

Claims (3)

A steering wheel,
An actuator that generates a steering assist force in response to an operation of the steering wheel;
A steering amount sensor for detecting the steering amount of the steering wheel by a relative angle sensor;
A volatile midpoint storage unit that stores, as a midpoint, the steering amount detected by the steering amount sensor when it is determined that the position of the steering wheel corresponds to a straight traveling state of the vehicle;
In an electric power steering apparatus comprising:
An idle stop state determination unit that determines whether or not the vehicle on which the electric power steering device is mounted is in an idle stop state when the ignition is off;
When it is determined by the idle stop state determination unit that the vehicle is in an ignition off state and in an idle stop state, an energization control unit that continues to energize the midpoint storage unit;
An electric power steering apparatus comprising: The electric power steering apparatus according to claim 1,
The energization control unit
The electric power steering apparatus, wherein when the vehicle is in an ignition-off state and in an idle stop state by the idle stop state determination unit, the steering amount sensor is continuously energized. A steering wheel,
An actuator that generates a steering assist force in response to an operation of the steering wheel;
A steering amount sensor for detecting the steering amount of the steering wheel by a relative angle sensor;
A non-volatile midpoint storage unit that stores the steering amount detected by the steering amount sensor at the time when the position of the steering wheel is determined to correspond to the straight traveling state of the vehicle as a midpoint;
In an electric power steering apparatus comprising:
An idle stop state determination unit that determines whether or not the vehicle on which the electric power steering device is mounted is in an idle stop state when the ignition is off;
When the idle stop state determination unit determines that the vehicle is in an ignition off state and in an idle stop state, an energization control unit that continues to energize the steering amount sensor;
An electric power steering apparatus comprising:

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