JP2008013096A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device capable of certainly accomplishing fail/safe while reducing short circuit risk between bus/ground lines. <P>SOLUTION: In operation of a lock device 30, IFSECU 9 turns all FETs 50a-50f of its drive circuit 42 OFF. Further, the IFSECU 9 (micro-computer 41) continues detection of a motor rotation angle θm even in lock operation and monitors rotation of the motor 13. Further, when the rotation is detected, a control mode of the motor 13 is turned to a regeneration mode, i.e., upper stage FETs 50a-50c on the side of a bus line of the drive circuit 42 are turned OFF and lower stage FETs 50d-50f on the side of the ground are turned ON. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus including a transmission ratio variable device.

  Conventionally, a vehicle steering apparatus provided with a transmission ratio variable device that varies a transmission ratio between a steering wheel and a steered wheel by adding a second steering angle based on a motor drive to a first steering angle based on a steering operation. There is. Usually, such a transmission ratio variable device is provided with a lock device that cannot change the second rudder angle by restricting the rotation of the motor (see, for example, Patent Document 1).

  That is, the second steering angle generated by the operation of the transmission ratio variable device is held by the motor torque, and when the motor cannot generate the required holding torque, the steering angle cannot be maintained. Therefore, when the abnormality occurs or when the ignition is off, the second steering angle at that time is mechanically fixed by operating the lock device to restrict the rotation of the motor.

Further, at the time of the lock operation, the control mode of the motor that is a drive source is generally set to a regenerative (regenerative brake) mode. That is, it is possible to brake the rotation of the motor by setting the control mode to the regenerative mode. And it becomes the structure which aims at fail safe more reliably by using this together as a backup of a locking device.
Japanese Patent Laid-Open No. 2003-320943

  However, in the regeneration mode, the switching elements on the bus line side (upper stage side) of the drive circuit (PWM inverter) are all turned off, and the switching elements on the ground line side (lower stage side) are all turned on. When a short circuit failure occurs in any of the above, the bus line and the ground line are short-circuited and a large current flows. That is, in the above-described conventional configuration, the regeneration mode is maintained for a relatively long time during the lock operation, and thus the risk of a short circuit between the bus and the ground line is high. Then, there is a possibility that problems such as energization of a large current due to the short circuit, heat generation due to the short circuit, and disconnection of the power line may occur. In this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus that can reliably fail-safe while reducing the risk of short circuit between a bus and a ground line. It is to provide.

  In order to solve the above problem, the invention according to claim 1 is characterized in that the second rudder angle of the steered wheel based on motor drive is added to the first rudder angle of the steered wheel based on a steering operation. A transmission ratio variable device that varies the transmission ratio between the steering angle of the steering wheel and the steering angle of the steered wheels, control means that controls the operation of the transmission ratio variable device through the supply of drive power to the motor, A lock device that disables the change of the second steering angle by restricting the rotation of the motor, and the control means includes a pair of series-connected switching elements connected in parallel, and each switching element is turned on / off. A vehicle steering apparatus having a drive circuit for supplying the drive power by turning off, wherein the control means turns on all the switching elements of the drive circuit when the lock device is activated. As well as off watching the rotation of the motor only when the rotation of the motor is detected, to the drive circuit and the regenerative mode, and the gist.

  According to a second aspect of the present invention, the steering angle of the steering wheel and the steering wheel are increased by adding the second steering angle of the steered wheel based on motor drive to the first rudder angle of the steered wheel based on the steering operation. A transmission ratio variable device that varies a transmission ratio between the steering angle, a control unit that controls the operation of the transmission ratio variable device through supply of drive power to the motor, and the rotation of the motor by restricting the rotation. A lock device that disables the change of the second rudder angle, and the control means is configured to connect the pair of switching elements connected in series in parallel, and to supply the driving power when each switching element is turned on / off. The vehicle steering apparatus having a drive circuit for performing the following operation, wherein the control means turns off all switching elements of the drive circuit and activates the motor when the lock device is operated. Rolling monitored only when rotation of the motor is detected, to the drive circuit and the phase fixed conductive mode, and the gist.

  According to each of the above configurations, all the switching elements of the drive circuit are turned off unless the lock is released by the locking device during the lock operation. Therefore, even if a short circuit failure occurs in any of the switching elements, the bus / There is no short circuit between the ground lines. When the lock by the locking device is released and the motor can be rotated, in the configuration of claim 1, the regenerative mode brake action is used, and in the configuration of claim 2, the phase fixing energization is used. By locking, the rotation can be suppressed. Therefore, it is possible to reliably achieve fail-safe while reducing the risk of short circuit between the bus / ground lines.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle steering device which can aim at fail-safe reliably, reducing the short circuit risk between bus | bath / ground lines can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus including a transmission ratio variable device will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus 1 according to the present embodiment. As shown in the figure, the steering shaft 3 to which the steering wheel 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed by the rack and pinion mechanism 4. Is converted into a reciprocating linear motion of the rack 5. Then, the steering angle of the steered wheels 6, that is, the steered angle is varied by the reciprocating linear motion of the rack 5, so that the vehicle traveling direction is changed. The vehicle steering apparatus 1 according to the present embodiment is a so-called rack assist type electric power steering apparatus (EPS), and generates an assist torque generated by a motor 7 as a drive source via a ball screw mechanism (not shown). By transmitting to the rack 5, an assist force is applied to the steering system.

  Further, the vehicle steering apparatus 1 of the present embodiment has a variable transmission ratio that varies the transmission ratio (gear ratio) between the steering angle (steering angle) of the steering 2 and the steering angle (steering angle) of the steered wheels 6. A device 8 and an IFSECU 9 as a control means for controlling the operation of the transmission ratio variable device 8 are provided.

  More specifically, the steering shaft 3 includes a first shaft 10 to which the steering 2 is connected and a second shaft 11 to be connected to the rack and pinion mechanism 4, and the transmission ratio variable device 8 includes the first shaft 10 and the first shaft 10. A differential mechanism 12 for connecting the two shafts 11 and a motor 13 for driving the differential mechanism 12 are provided. The transmission ratio variable device 8 adds the rotation driven by the motor to the rotation of the first shaft 10 accompanying the steering operation and transmits it to the second shaft 11, thereby inputting the steering shaft to the rack and pinion mechanism 4. 3 is increased (or decelerated), thereby changing the transmission ratio of the steered wheels 6 to the steering 2.

  That is, as shown in FIGS. 2 (a) and 2 (b), the transmission ratio variable device 8 uses the steered angle of the steered wheels (steer steered angle θts) based on the steering operation (steer steered angle θts) based on the motor drive. By adding the ACT angle θta), the transmission ratio between the steering angle θs and the turning angle θt is varied. Therefore, in this embodiment, the steer turning angle θts constitutes the first rudder angle, and the ACT angle θta constitutes the second rudder angle.

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “transmission ratio between the steering angle θs and the turning angle θt” is expressed as an overall gear ratio (steering angle θs / steering angle θt), the ACT angle θta in the same direction as the steering turning angle θts is By adding it, the overall gear ratio becomes small (large turning angle θt, see FIG. 2A). Then, the overall gear ratio is increased by adding the ACT angle θta in the reverse direction (small turning angle θt, see FIG. 2B).

  Further, the motor 13 of the present embodiment is a brushless motor, and rotates when three-phase (U, V, W) driving power is supplied from the IFSECU 9. The IFSECU 9 controls the operation of the transmission ratio variable device 8, that is, the ACT angle θta (transmission ratio variable control) by controlling the rotation of the motor 13 through the supply of the driving power.

  More specifically, as shown in FIG. 3, the transmission ratio variable device 8 of the present embodiment has a housing 14 formed in a substantially bottomed cylindrical shape, and the motor 13 is a motor that is a rotating shaft thereof. The shaft 13a and the housing 14 are fixed in the housing 14 so as to be coaxial. And the connection part 15 provided in the upper wall part 14a of the housing 14 is spline-fitted with the 1st shaft 10. As shown in FIG.

  In the present embodiment, the differential mechanism 12 rotates a pair of circular splines 21 and 22 coaxially arranged, a flex spline 23 meshed with each spline inside these splines, and a meshing portion thereof. A known wave gear mechanism comprising a wave generator 24 is employed.

  The circular spline 21 is fixed to the housing 14 so as to be coaxial with the housing 14, and the other circular spline 22 is connected coaxially to the second shaft 11 via a connecting member 25. Each of the circular splines 21 and 22 has a different number of teeth, and the flexspline 23 is arranged inside each of these gears in a state of being bent in an elliptical shape so that the external teeth are The inner teeth of each gear are partially meshed with each other. Then, the circular spline 21 rotates together with the housing 14, and the rotation of the circular spline 21 is transmitted to the circular spline 22 via the flex spline 23, whereby the rotation of the first shaft 10 accompanying the steering operation is transmitted to the second shaft 11. To be communicated to.

  The wave generator 24 is disposed inside the circular splines 21 and 22 and the flex spline 23. The wave generator 24 is connected to the motor shaft 13a, and rotates inside the flex spline 23 as the motor shaft 13a rotates, so that the flexed spline 23 has an elliptical shape, that is, a circular spline 21, The meshing part with 22 is rotated. Then, based on the difference in the number of teeth between the circular spline 21 and the circular spline 22, the circular spline 22 rotates, whereby the rotation of the motor shaft 13a is decelerated and transmitted to the second shaft 11. Yes.

  In the present embodiment, the spiral cable device 27 is provided on the upper wall portion 14a of the housing 14, and the solenoid 13a of the motor 13 and the lock device 30 to be described later is rotated within a predetermined rotation range ( In the allowable rotation range), it is electrically connected to the IFSECU 9.

  In the transmission ratio variable device 8 of this embodiment, the relative rotation between the first shaft 10 and the second shaft 11 is restricted by restricting the rotation of the motor shaft 13a, that is, the ACT angle θta is mechanically fixed. In addition, a lock device 30 that cannot be changed is provided. The lock device 30 includes a lock arm 31 provided on the housing 14 (main body of the motor 13) side, and a lock holder 32 that is fixed to one end of the motor shaft 13a and rotates integrally with the motor shaft 13a. By engaging the engaging claws 31 with the engaging grooves of the lock holder 32, the rotation of the motor shaft 13 a relative to the housing 14 is restricted. The IFSECU 9 mechanically fixes the ACT angle θta by operating the lock device 30 when, for example, an abnormality occurs or the ignition is off. For details of this type of locking device, refer to the configuration described in Patent Document 1, for example.

Next, the electrical configuration and control mode of the vehicle steering apparatus of the present embodiment will be described.
As shown in FIG. 1, the steering angle θs (steering speed ωs) detected by the steering angle sensor 36 and the vehicle speed V detected by the vehicle speed sensor 37 are input to the IFSECU 9. Then, the IFSECU 9 controls the rotation of the motor 13 based on the steering angle θs (steering speed ωs) and the vehicle speed V, thereby executing the operation of the transmission ratio variable device 8, that is, the transmission ratio variable control.

  Specifically, as shown in FIG. 4, the IFSECU 9 includes a microcomputer 41 that outputs a motor control signal, and a drive circuit 42 that supplies drive power to the motor 13 based on the motor control signal.

  The microcomputer 41 includes a gear ratio variable control calculation unit 43 and a differential steer control calculation unit 44, and the steering angle θs and the vehicle speed V are input to the gear ratio variable control calculation unit 43. Is input with the vehicle speed V and the steering speed ωs. The gear ratio variable control calculation unit 43 calculates a gear ratio variable command angle θgr *, which is a control target component for changing the gear ratio (transmission ratio) according to the vehicle speed V, and the differential steer control calculation unit 44 Then, the differential steering command angle θls *, which is a control target component for improving the responsiveness of the vehicle, is calculated according to the steering speed ωs.

  The gear ratio variable command angle θgr * and the differential steer command angle θls * calculated by the gear ratio variable control calculation unit 43 and the differential steer control calculation unit 44 are input to the adder 45. The adder 45 calculates the ACT command angle θta * by superimposing the gear ratio variable command angle θgr * and the differential steer command angle θls *.

  Further, the rotation angle sensor 46 provided in the motor 13 is connected to the IFSECU 9, and the ACT command angle θta * calculated by the adder 45 is based on the motor rotation angle θm detected by the rotation angle sensor 46. The calculated ACT angle θta is input to the position control calculation unit 48. In the present embodiment, the rotation angle sensor 46 is constituted by a Hall element. Then, the position control calculation unit 48 executes position control calculation (feedback calculation) so that the actual ACT angle θta follows the command value ACT command angle θta *, and obtains the current command ε obtained thereby. Output to the motor control signal output unit 49.

  The motor control signal output unit 49 outputs a motor control signal generated based on the current command ε to the drive circuit 42, and drive power based on the motor control signal is supplied from the drive circuit 42 to the motor 13. The operation of the motor 13, that is, the transmission ratio variable device 8 is controlled.

  Here, the drive circuit 42 of the present embodiment uses a PWM inverter composed of a plurality (2 × 3) of switching elements (FETs) corresponding to each phase of the motor 13. Specifically, the drive circuit 42 is formed by connecting each series of FETs 50a and 50d, FETs 50b and 50e, and FETs 50c and 50f in parallel, and connecting points of the FETs 50a and 50d, FETs 50b and 50e, and FETs 50c and 50f. 51u, 51v, and 51w are connected to each phase motor coil of the motor 13, respectively. The gate terminals of the FETs 50a to 50f are connected to the microcomputer 41, and the FETs 50a to 50f are turned on / off in response to the motor control signal output from the microcomputer 41 (motor control signal output unit 29). The DC power of the in-vehicle power source is converted into three-phase driving power and supplied to the motor 13.

  The IFSECU 9 includes a drive circuit 52 for lock control that supplies drive power to the solenoid 30a of the lock device 30 in addition to the drive circuit 42 for driving the motor, and the microcomputer 41 operates the drive circuit 52. A lock control unit 53 that generates a lock control signal for control is provided. In the present embodiment, the lock control unit 53 receives an IG on / off signal S_ig and an abnormal signal S_tr indicating an abnormality of the electric power steering device or the transmission ratio variable device 8 via an in-vehicle network (not shown). It has become. When the IG on / off signal S_ig indicates “ignition off” or when the abnormal signal S_tr is input, the lock control unit 53 outputs the lock control signal to be output to the drive circuit 52 to the locked state. Change to the one with the value that should be. In the present embodiment, the drive circuit 52 includes a switching element (power MOSFET), and the lock control signal is output as the duty (on duty) of the switching element. When the lock is activated, the lock control unit 53 sets the lock control signal to “OFF (Duty = 0)”, thereby controlling the solenoid 30 a to be turned off, that is, the lock device 30 is locked.

(Motor control during lock operation)
Next, motor control at the time of lock operation will be described.
In the present embodiment, when the lock device 30 is activated, the IFSECU 9 turns off all the FETs 50a to 50f of the drive circuit 42 (see FIG. 4). Further, the IFSECU 9 (microcomputer 41) continues to detect the motor rotation angle θm and monitors the rotation of the motor 13 even during the lock operation. When the rotation is detected, the control mode of the motor 13 is set to the regeneration mode, that is, the upper FETs 50a to 50c on the bus line side of the drive circuit 42 are turned off, and the lower FETs 50d to 50f on the ground side are turned on. To do.

  More specifically, as shown in FIG. 4, the lock control signal output from the lock control unit 53 is also input to the motor control signal output unit 49, and the motor control signal output unit 49 is connected to the motor control signal output unit 49. The operation of the locking device 30 is detected based on the control signal output unit 49. In the present embodiment, the motor control signal output unit 49 executes lock confirmation control for confirming the completion of the lock operation when the lock operation is performed. The lock confirmation control is performed by outputting a motor control signal to rotationally drive the motor 13.

  That is, the locking device 30 is brought into a completely locked state when the engaging claw of the lock arm 31 is engaged with the engaging groove on the lock holder 32 side. However, the engaging claw and the engaging groove are not necessarily in a corresponding positional relationship at the time of the locking operation. For this reason, the motor 13 is driven to rotate, and the engagement groove of the lock holder 32 is moved to a position corresponding to the engagement claw of the lock arm 31 so that the both are reliably engaged. Note that the completion of the engagement, that is, the completion of the locking operation, indicates whether or not the duty value of the motor control signal exceeds a predetermined threshold value, that is, the duty value is a value that cannot be taken when the motor shaft 13a is rotatable. This is done by determining whether or not. The motor control signal output unit 49 outputs a motor control signal for turning off all the FETs 50a to 50f of the drive circuit 42 when it is determined that the lock operation is completed by the lock confirmation control.

  Further, the motor rotation angle θm is input to the motor control signal output unit 49, and the motor control signal output unit 49 receives the motor 13 based on the motor rotation angle θm even after the lock operation is completed. Monitor the rotation. When the rotation is detected, a motor control signal for turning off the upper FETs 50a to 50c of the drive circuit 42 and turning on the lower FETs 50d to 50f is output.

  That is, as shown in the flowchart of FIG. 5, the motor control signal output unit 49 first detects the operation of the locking device 30 based on the lock control signal input from the lock control unit 53 (step 101). Next, when the operation of the lock device 30 is detected (step 101: YES), it is subsequently determined whether or not a lock completion flag indicating completion of the lock operation is already set (step 102). If the lock completion flag is not set (step 102: NO), the lock confirmation control described above is executed (step 103), the lock completion flag is set (step 104), and then all of the drive circuit 42 is set. A motor control signal is output to turn off the FETs 50a to 50f (step 105). When the operation of the locking device 30 is not detected in step 101, the motor control signal output unit 49 executes normal control based on the calculation result of the position control calculation unit 48 (step 106).

  If the lock completion flag has already been set in step 102 (step 102: YES), the motor control signal output unit 49 subsequently determines whether or not the motor 13 is rotating (step 107). . When rotation of the motor 13 is detected (step 107: YES), a motor control signal is sent to the regeneration mode, that is, to turn off the upper FETs 50a to 50c of the drive circuit 42 and to turn on the lower FETs 50d to 50f. Output (step 108). If the rotation of the motor 13 is not detected (step 107: NO), the process of step 105 is executed, that is, a motor control signal for turning off all the FETs 50a to 50f is output.

As described above, according to the present embodiment, the following operations and effects can be obtained.
When the lock device 30 is activated, the IFSECU 9 turns off all the FETs 50 a to 50 f of the drive circuit 42. Further, the IFSECU 9 (microcomputer 41) continues to detect the motor rotation angle θm and monitors the rotation of the motor 13 even during the lock operation. When the rotation is detected, the control mode of the motor 13 is set to the regeneration mode, that is, the upper FETs 50a to 50c on the bus line side of the drive circuit 42 are turned off, and the lower FETs 50d to 50f on the ground side are turned on. To do.

  According to the above configuration, all the FETs 50a to 50f of the drive circuit 42 are turned off unless the lock by the locking device 30 is released during the lock operation. Therefore, it is assumed that a short circuit failure has occurred in any of the FETs 50a to 50f. However, there is no short circuit between the bus / ground lines. When the lock by the lock device 30 is released and the motor 13 can be rotated, the rotation can be suppressed by the braking action in the regeneration mode. Therefore, it is possible to reliably achieve fail-safe while reducing the risk of short circuit between the bus / ground lines.

In addition, you may change this embodiment as follows.
In the present embodiment, a brushless motor is used as the motor 13 of the transmission ratio variable device 8, and three rows of arms (a series circuit including a pair of upper and lower FETs) are connected in parallel to the drive circuit 42. The following PWM inverter was used. However, the present invention is not limited to this, and the present invention may be applied to a vehicle steering apparatus including a transmission ratio variable device using a motor with a brush as a drive source and a control unit having a corresponding drive circuit.

  In the present embodiment, when the rotation of the motor 13 is detected, the control mode is set to the regenerative mode (see FIG. 5, step 108). Instead, the energized phase is fixed. The phase-fixed energization mode for energization is set. That is, it is good also as a structure which suppresses rotation of the motor 13 by electrically locking.

The schematic block diagram of the steering apparatus for vehicles. (A) (b) Action explanatory drawing of transmission ratio variable control. The schematic block diagram of a transmission ratio variable apparatus. The control block diagram of the steering device for vehicles. The flowchart which shows the aspect of the motor control at the time of a lock action.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering, 6 ... Steering wheel, 8 ... Transmission ratio variable device, 9 ... IFSECU, 13 ... Motor, 30 ... Locking device, 41 ... Microcomputer, 49 ... Motor control signal output part, 42 ... Drive circuit, 50a-50f ... FET, θm ... motor rotation angle.

Claims (2)

The transmission ratio between the steering angle of the steering wheel and the steering angle of the steered wheel is obtained by adding the second rudder angle of the steered wheel based on the motor drive to the first rudder angle of the steered wheel based on the steering operation. A variable transmission ratio variable device, control means for controlling the operation of the variable transmission ratio device through supply of driving power to the motor, and the second steering angle cannot be changed by restricting the rotation of the motor. And a control device, wherein the control means includes a drive circuit that connects a pair of switching elements connected in series in parallel and supplies the driving power when each switching element is turned on / off. A device,
The control means turns off all the switching elements of the drive circuit and monitors the rotation of the motor when the lock device is operated, and sets the drive circuit to the regeneration mode only when the rotation of the motor is detected. A vehicle steering apparatus characterized by that. The transmission ratio between the steering angle of the steering wheel and the steering angle of the steered wheel is obtained by adding the second rudder angle of the steered wheel based on the motor drive to the first rudder angle of the steered wheel based on the steering operation. A variable transmission ratio variable device, control means for controlling the operation of the variable transmission ratio device through supply of driving power to the motor, and the second steering angle cannot be changed by restricting the rotation of the motor. And a control device, wherein the control means includes a drive circuit that connects a pair of switching elements connected in series in parallel and supplies the driving power when each switching element is turned on / off. A device,
The control means turns off all the switching elements of the drive circuit and monitors the rotation of the motor when the locking device is operated, and the phase lock energization of the drive circuit is performed only when the rotation of the motor is detected. A vehicle steering apparatus characterized by having a mode.

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