JP5768472B2 - Vehicle steering system - Google Patents

Description

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

  Conventionally, in a steering apparatus for a vehicle, a steering angle (steering angle) of a steering wheel is obtained by adding a second steering angle (ACT angle) of a steered wheel based on a motor drive to a first rudder angle of a steered wheel based on a steering operation. There is a device provided with a transmission ratio variable device that varies a transmission ratio between a steering angle and a steering gear ratio. Such a vehicle steering device performs variable transmission ratio control according to the steering angle so that the steering gear ratio becomes a quicker value in the small steering angle region near the steering neutral. Yes (for example, see Patent Document 1 and FIG. 6).

  That is, by setting the steering gear ratio in the vicinity of the steering neutral to a quick value, it is possible to improve the responsiveness of the vehicle to the infeed steering when shifting from the straight traveling state to the turning state. As a result, the so-called “steering rigidity” including the response in the straight traveling state can be enhanced, thereby realizing a more excellent steering feeling.

JP 2005-170129 A

  However, on the other hand, there is a problem that the steering characteristic deviates from the driver's feeling during the switchback steering. That is, normally, the response in the vicinity of the steering neutral is set to be low, and the steering is generally returned to the neutral position relatively slowly during the return steering. Therefore, by setting the steering gear ratio in the vicinity of the steering neutral as a quick value as described above, the driver may feel that the return to the neutral position is abrupt. In addition, there was room for improvement.

  The present invention has been made to solve the above-described problems, and its object is to improve the responsiveness at the time of turning steering in the vicinity of the steering neutral without causing a sense of incongruity at the time of turning back steering. The object is to provide a vehicle steering system.

  In order to solve the above problems, the invention according to claim 1 is a transmission ratio variable device provided in the middle of the steering system so that the steering gear ratio can be changed, and a control for controlling the operation of the transmission ratio variable device. And the control means is a vehicle steering device that controls the operation of the transmission ratio variable device based on a steering angle so that the steering gear ratio becomes a quick value in the vicinity of steering neutrality, The control means determines a steering state, and controls the operation of the transmission ratio variable device so that the immediately preceding steering gear ratio is maintained when the steering state is switchback steering. The gist.

  According to the above configuration, as long as the switchback steering continues, the steering gear ratio remains constant at the “switchback time” value. Therefore, in the vicinity of the steering neutral position, the steering gear ratio at the time of the return steering becomes a slower value than the steering gear ratio at the time of the turning steering, and the steering gear position is shifted from any steering angle position to the switching back steering. In the steering neutral position, the steering angle coincides with the turning angle. As a result, the steering can be gently returned to the neutral position without destroying the relationship between the steering angle and the turning angle. As a result, the responsiveness at the time of turning steering can be improved in the vicinity of the steering neutral without causing a sense of incongruity at the time of turning back steering.

Further, at the time of the turning steering, the control means uses the value of the steering angle at the time when the turning steering is started as a reference point, and calculates the steering angle gain based on the steering angle change from the reference point. The steering gear ratio is changed based on the steering angle, and the steering angle gain is set to be a quick steering gear ratio in a region where the steering angle change is small .

According to the above configuration, the reference point for calculating the steering angle gain at the time of the turning steering is shifted to the steering angle value at the time of the turning start, so that not only the small steering angle region near the steering neutral but also other Even in the steering angle region, the steering gear ratio at the initial cutting is quick. In combination with the invention of claim 1, the steering can be gently returned to the neutral position without breaking the relationship between the steering angle and the turning angle. As a result, it is possible to improve the responsiveness to the steering operation and realize a good steering feeling without causing the driver to feel uncomfortable even during the return steering.
The invention according to claim 2 is provided in the middle of the steering system, and a transmission ratio variable that varies a steering gear ratio by adding a second rudder angle based on motor drive to a first rudder angle based on a steering operation. And a control means for controlling the operation of the transmission ratio variable device, the control means varying the transmission ratio based on a steering angle so that the steering gear ratio becomes a quick value in the vicinity of a steering neutral position. A vehicle steering apparatus that controls the operation of the apparatus, wherein the control means determines a steering state, and when the steering state is a switchback steering, the immediately preceding steering gear ratio is maintained. And controlling the operation of the transmission ratio variable device, wherein the control means is a variable obtained by multiplying a ratio of the base gear to the target gear ratio by a steering angle gain calculated based on the steering angle. And the second steering angle component based on the motor drive based on the variable gear ratio, and the variable gear ratio used for the calculation of the second steering angle component is calculated last time. The gist is to calculate the second steering angle component based on the variable gear ratio held as a previous value when the steering wheel is held back as a value and at the time of switchback steering.

  According to the present invention, it is possible to provide a vehicle steering apparatus capable of improving the response at the time of turning steering in the vicinity of the steering neutral without causing a sense of incongruity at the time of turning back steering.

The schematic block diagram of the steering apparatus for vehicles. (A) (b) Action explanatory drawing of transmission ratio variable control. The control block diagram of the steering device for vehicles. The block diagram which shows schematic structure of the gear ratio variable control calculating part in 1st Embodiment. Action | operation explanatory drawing of the gear ratio variable control in each embodiment. Explanatory drawing of the effect | action of the gear ratio variable control in 1st Embodiment. The block diagram which shows schematic structure of the gear ratio variable control calculating part in 2nd Embodiment.

[First Embodiment]
Hereinafter, a first embodiment of the present invention 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 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. Then, the rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. Note that the steering shaft 3 of the present embodiment has a known configuration in which three shaft members, a column shaft, an intermediate shaft, and a pinion shaft, are connected in order from the steering 2 side. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to the knuckle (not shown) via the tie rods connected to both ends of the rack shaft 5, whereby the steered wheels 6 are steered. The corner, that is, the traveling direction of the vehicle is changed.

  The vehicle steering apparatus 1 of the present embodiment is a so-called rack assist type electric power steering apparatus (EPS). Specifically, a rack in which a motor 7 as a drive source thereof is arranged coaxially with the rack shaft 5. It is a coaxial EPS. The motor torque is converted into an axial pressing force by a ball screw mechanism (not shown) and transmitted to the rack shaft 5, thereby providing an assist force to the steering system.

  Further, the vehicle steering apparatus 1 according to the present embodiment is provided in the middle of the steering system so that the transmission ratio (steering gear ratio) between the steering 2 (the steering angle) and the steered wheels 6 (the steering angle) can be changed. The transmission ratio variable device 8 and an ECU 9 as control means for controlling the operation of the transmission ratio variable device 8 are provided.

  More specifically, in the present embodiment, the transmission ratio variable device 8 is provided on the intermediate shaft 3 a constituting the steering shaft 3. Specifically, the intermediate shaft 3a of the present embodiment includes a first shaft 10 located on the steering 2 side (upper side in the figure) and a second shaft located on the rack shaft 5 side (lower side in the figure). It consists of a shaft 11. The transmission ratio variable device 8 includes a differential mechanism 12 that connects the first shaft 10 and the second shaft 11, and a motor 13 that drives the differential mechanism 12.

  That is, the transmission ratio variable device 8 of the present embodiment transmits the rotation based on the motor drive to the rotation of the first shaft 10 accompanying the steering operation and transmits the rotation to the second shaft 11. The transmission ratio between the steering wheel 2 and the steered wheel 6 can be arbitrarily changed by increasing (or decelerating) the rotation of the steering shaft 3 input to the rack and pinion mechanism 4. ing.

  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.

  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).

Next, the electrical configuration and control mode of the vehicle steering apparatus of the present embodiment will be described.
In the present embodiment, a brushless motor is employed as the motor 13 that is a drive source of the transmission ratio variable device 8, and the motor 13 is supplied with three-phase (U, V, W) drive power from the ECU 9. To rotate. The ECU 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. 1, the ECU 9 receives the steering angle θs (steering speed ωs) detected by the steering angle sensor 16 and the vehicle speed V detected by the vehicle speed sensor 17. Yes. Then, the ECU 9 controls the rotation of the motor 13 based on the steering angle θs (steering speed ωs) and the vehicle speed V, thereby performing the operation of the transmission ratio variable device 8, that is, the transmission ratio variable control.

  More specifically, as shown in FIG. 3, the ECU 9 includes a microcomputer 21 that outputs a motor control signal and a drive circuit 22 that supplies drive power to the motor 13 based on the motor control signal.

  The control blocks shown below are realized by a computer program executed by the microcomputer 21. Then, the microcomputer 21 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  The microcomputer 21 of this embodiment includes a gear ratio variable control calculation unit 23 and a differential steer control calculation unit 24. The gear ratio variable control calculation unit 23 calculates a gear ratio variable command angle θvg * based on the vehicle speed V and the steering angle θs (gear ratio variable control), and the differential steer control calculation unit 24 calculates the steering speed ωs (and Based on the vehicle speed V), the differential steering command angle θls * is calculated (differential steering control).

  The gear ratio variable command angle θvg * and the differential steer command angle θls * calculated by the gear ratio variable control calculation unit 23 and the differential steer control calculation unit 24 are input to the adder 25. Then, the microcomputer 21 superimposes the gear ratio variable command angle θvg * and the differential steer command angle θls * in the adder 25, so that the pinion ACT angle θpa corresponding to the ACT angle θta is used as the pinion ACT angle θpa. The ACT angle command value θpa * is calculated (see FIGS. 2A and 2B).

  In the present embodiment, the rotation angle of the portion of the steering shaft 3 that is positioned closer to the rack and pinion mechanism than the transmission ratio variable device 8 (see FIG. 1, lower than the second shaft 11) is the pinion angle (θp). Is defined as Of the pinion angle (θp), the additional amount superimposed by the operation of the transmission ratio variable device 8 corresponds to the pinion ACT angle θpa.

  In the microcomputer 21 of the present embodiment, the pinion ACT angle command value θpa * calculated in this way is input to the motor control signal generator 27. Further, the motor control signal generator 27 is inputted with a motor rotation angle θm detected by a motor resolver (rotation angle sensor) 26. The motor control signal generation unit 27 calculates the pinion ACT angle θpa based on the motor rotation angle θm, and sets the pinion ACT angle θpa, which is an actual value, to the pinion ACT angle command value θpa * as the control target value. A motor control signal is generated by executing the rotation angle feedback control to follow.

  The microcomputer 21 of the present embodiment outputs the motor control signal thus generated by the motor control signal generation unit 27 to the drive circuit 22. The ECU 9 of the present embodiment is configured such that the drive circuit 22 controls the operation of the transmission ratio variable device 8 by supplying drive power based on the motor control signal to the motor 13.

(Gear ratio variable control)
Next, the aspect of the gear ratio variable control in this embodiment will be described.
As shown in FIG. 4, the gear ratio variable control calculation unit 23 of the present embodiment includes a speed increase rate calculation unit 31 that calculates the speed increase rate α based on the vehicle speed V and the steering angle θs. The gear ratio variable control calculation unit 23 calculates the gear ratio variable command angle θvg * by integrating the value obtained by multiplying the speed increase rate α by the change amount (Δθs) of the steering angle θs.

  Specifically, in the gear ratio variable control calculation unit 23 of the present embodiment, the speed increase rate α calculated by the speed increase rate calculation unit 31 is input to the gear ratio variable command angle calculation unit 32 together with the steering angle θs. The gear ratio variable command angle calculation unit 32 also outputs the previous value θs_pr of the steering angle θs input in the previous calculation cycle and the previous value θvg_pr * of the gear ratio variable command angle θvg * output in the previous calculation cycle. Hold. Then, by calculating the change amount Δθs of the steering angle θs based on the input steering angle θs and the previous value θs_pr to be held, the gear ratio variable command in the current calculation cycle is calculated based on the following equation (1). Calculate the angle θvg *.

θvg * = θvg_pr * + (Δθs × α) (1)
More specifically, the acceleration rate calculation unit 31 of the present embodiment monitors the change in the steering angle θs so that the state of the steering operation by the driver (steering state) is “cut” or “turn back” (or A steering state determination unit 34 is provided for determining which one of “steering”). Note that “cutting” is a steering operation in a direction to increase the steering angle θs (absolute value), and “turning back” is a steering operation in a direction to decrease the steering angle θs (absolute value).

  Further, the acceleration rate calculating unit 31 includes a cutting gear ratio calculating unit 35 and a returning gear ratio calculating unit 36. Then, based on the result of the steering state determination, the speed increase rate calculation unit 31 selects either the cutting gear ratio Rvg_in or the switching gear ratio Rvg_out calculated by both the gear ratio calculation units. The speed increase rate α is calculated by subtracting “1” from the value.

  Specifically, the gear ratio calculation unit 35 at the time of cutting is a target gear ratio calculation unit 41 that calculates a target gear ratio Rgr_vs based on the vehicle speed V, and a ratio (gear ratio: Rvg0) of the base gear ratio Rgr_bs to the target gear ratio Rgr_vs. = Rgr_bs / Rgr_vs) is provided.

  In the present embodiment, the target gear ratio Rgr_vs and the base gear ratio Rgr_bs are represented by an overall gear ratio. The target gear ratio calculation unit 41 has a quick steering gear ratio (overall gear ratio: small) in the low vehicle speed region and a slow steering gear ratio (overall gear ratio: large) in the high vehicle speed region. Then, the target gear ratio Rgr_vs corresponding to the vehicle speed V is calculated.

  Further, the cutting gear ratio calculation unit 35 includes a steering angle gain calculation unit 43 that calculates the steering angle gain Kan. The cutting gear ratio calculation unit 35 calculates the cutting gear ratio Rvg_in by multiplying the steering angle gain Kan by the gear ratio Rvg0 in the multiplier 44.

  Here, the gear ratio calculation unit 35 at the time of cutting of the present embodiment is provided with a reference point calculation unit 45 that calculates a reference point θ0 when the steering angle gain calculation unit 43 calculates the steering angle gain Kan. . Specifically, a steering state signal S_st indicating the steering angle θs and the determination result of the steering state determination unit 34 is input to the reference point calculation unit 45 of the present embodiment. The unit 45 calculates the value of the steering angle θs at the time when the steering state signal S_st is changed to the one indicating “cut” as the reference point θ0. In the steering angle gain calculation unit 43, a value obtained by subtracting the reference point θ0 from the steering angle θs in the subtractor 46, that is, a reference steering angle θk indicating a steering angle change from the time when the turning steering is started. Entered.

  The rudder angle gain calculation unit 43 of the present embodiment is configured to calculate the rudder angle gain Kan that provides a quicker steering gear ratio as the reference rudder angle θk (absolute value) is smaller. .

  That is, at the time of turning steering, by shifting the reference point θ0 when calculating the steering angle gain Kan to the value of the steering angle θs at the start of turning, only the small steering angle region near the steering neutral (θs = 0) can be obtained. In addition, also in other steering angle regions, the steering gear ratio at the initial stage of cutting can be made quick. And in this embodiment, it is the structure which improves the response with respect to a steering operation of a driver | operator, and implement | achieves a favorable steering feeling by this.

  On the other hand, the gear ratio calculation unit 36 at the time of switching back returns the current (immediately previous) steering angle θt based on the steering angle θs and the gear ratio variable command angle θvg * output from the gear ratio variable command angle calculation unit 32. A turning angle calculation unit 47 for calculating is provided. Further, the switchback gear ratio calculation unit 36 includes a steering gear ratio calculation unit 48 that calculates the current (immediately preceding) steering gear ratio Rgr based on the calculated turning angle θt and steering angle θs. Further, the gear ratio calculation unit 36 at the time of switching back calculates the ratio of the base gear ratio Rgr_bs to the calculated steering gear ratio Rgr in the gear ratio calculation unit 49. The switchback gear ratio calculation unit 36 is configured to output the calculated ratio as a switchback gear ratio Rvg_out (Rvg_out = Rgr_bs / Rgr).

  In the present embodiment, the cutting gear ratio Rvg_in and the switching gear ratio Rvg_out are input to the switching control unit 50 together with the steering state signal S_st output from the steering state determination unit 34. When the input steering state signal S_st indicates “cut”, the switching control unit 50 outputs the gear ratio Rvg_in at the time of cut, and when the steering state signal S_st indicates “turn back”. Is output to the gear ratio Rvg_out at the time of switching back.

  Then, the acceleration rate calculating unit 31 of the present embodiment uses the subtractor 51 to subtract the value obtained by subtracting “1” from the cutting gear ratio Rvg_in or the switching back gear ratio Rvg_out output from the switching control unit 50. It is configured to output to the gear ratio variable command angle calculation unit 32 as α.

  That is, as shown in FIG. 5, when the steering is performed from the steering neutral position (θs = 0), the steering gear ratio (the locus L0 indicated by the solid line in the figure) is It becomes a quick value in the vicinity of the steering neutral (θs = 0) at the beginning of cutting. As the steering angle θs increases, the value changes to a slower value.

  On the other hand, at the time of switchback steering, the switchback gear ratio Rvg_out, which is the basis for calculating the speed increase rate α, is a value corresponding to the current (immediately preceding) steering gear ratio Rgr. The value is maintained as long as the switchback steering continues. Therefore, the steering gear ratio at the time of switching back (trajectories L1 and L2 shown by the one-dot chain line in the figure) is constant at the immediately preceding value, that is, the value of “switching back”.

  Specifically, for example, when the shift to the return steering is performed at a point P1 in the figure, the steering gear ratio at the time of the return return steering is a value (A1 / 1) at the point P1 as indicated by the locus L1. It becomes constant at B1). Similarly, when the transition point to the return steering is the point P2, the value (A2 / B2) at the point P2 is constant as indicated by the locus L2.

  That is, in the vicinity of the steering neutral position, the steering gear ratio (trajectory L1, L2) at the time of turning-back steering becomes a slower value than the steering gear ratio (trajectory L0) at the time of turning steering. Then, even if the transition to the return steering is performed from any point in time, the locus indicating the steering gear ratio at the time of the return steering has a fixed slope and is linearly “(θs, θt) = (0,0) ".

  For example, as shown in FIG. 6, turning steering is performed from the steering neutral position (θs = 0), turning back at the point P3 in the drawing, turning again at the point P4, and then turning back again from the point P5. Suppose.

  At this time, the steering gear ratio at the time of the first switchback steering is constant at the value (A3 / B3) at the point P3 at the time of the switchback, and the origin is the locus L3 as in the example shown in FIG. Exists on the extension line.

  Next, at the time of turning steering from the point P4, the speed increase rate α is calculated based on the cutting gear ratio Rvg_in, and the reference point θ0 when calculating the steering angle gain Kan is the point P4 as described above. It is shifted to (θs = A4). That is, the steering gear ratio at the time of re-cutting is quick in the vicinity of the point P4 in the same manner as at the time of the first turning from the steering neutral (θs = 0) (the locus L0), and the steering angle θs thereafter. As the value increases, the value changes to a slower value (trajectory L4). At the time of re-switching from the point P5, the steering gear ratio becomes constant at the value (A5 / B5) at the point P5, so that the locus L5 passes through the origin in a straight line.

In this embodiment, this makes it possible to gently return the steering to the neutral position without destroying the relationship between the steering angle θs and the turning angle θt.
As described above, according to the present embodiment, the following effects can be obtained.

  (1) The gear ratio variable control calculation unit 23 has a gear ratio variable command angle θvg * corresponding to the steering angle θs so that the steering gear ratio becomes a quicker value in the small steering angle region near the steering neutral. Is calculated. Further, the gear ratio variable control calculation unit 23 includes a steering state determination unit 34 that determines whether the steering operation state (steering state) by the driver is “cut” or “turn back”. Then, when the steering state is “switchback”, the gear ratio variable control calculation unit 23 calculates the gear ratio variable command angle θvg * so that the immediately preceding steering gear ratio is maintained.

  According to the above configuration, as long as the switchback steering continues, the steering gear ratio remains constant at the “switchback time” value. Therefore, in the vicinity of the steering neutral position, the steering gear ratio at the time of the return steering becomes a slower value than the steering gear ratio at the time of the turning steering, and even when the steering gear shifts from any steering angle position. At the steering neutral position, the steering angle θs coincides with the turning angle θt (θs = θt = 0). As a result, the steering can be gently returned to the neutral position without destroying the relationship between the steering angle θs and the turning angle θt. As a result, the responsiveness at the time of turning steering can be improved in the vicinity of the steering neutral without causing a sense of incongruity at the time of turning back steering.

  (2) The gear ratio variable control calculation unit 23 calculates the gear ratio variable command angle θvg * based on the steering angle gain Kan during the turning steering. Further, the gear ratio variable control calculation unit 23 calculates the value of the steering angle θs at the time when the turning steering is started as the reference point θ0 when calculating the steering angle gain Kan. The steering angle gain Kan is a value obtained by subtracting the reference point θ0 from the steering angle θs, that is, a reference steering angle θk (absolute value) indicating a change in the steering angle from the time when the turning steering is started is small. The steering gear ratio is set to be quicker.

  According to the above configuration, the reference point θ0 when calculating the steering angle gain Kan at the time of turning steering is shifted to the value of the steering angle θs at the beginning of turning, so that the steering point is close to neutral (θs = 0). The steering gear ratio in the initial cutting is quick not only in the steering angle region but also in other steering angle regions. In combination with the configuration (1), the steering can be gently returned to the neutral position without breaking the relationship between the steering angle θs and the turning angle θt. As a result, it is possible to improve the responsiveness to the steering operation and realize a good steering feeling without causing the driver to feel uncomfortable even during the return steering.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 7, the gear ratio variable control calculation unit 60 of this embodiment includes a target gear ratio calculation unit 61 that calculates a target gear ratio Rgr_vs based on the vehicle speed V, and a base gear ratio Rgr_bs relative to the target gear ratio Rgr_vs. And a gear ratio calculation unit 62 for calculating a ratio (gear ratio: Rvg0 = Rgr_bs / Rgr_vs).

  Further, the gear ratio variable control calculation unit 60 of the present embodiment includes a steering angle gain calculation unit 63 that calculates a steering angle gain K_an based on the steering angle θs, and the multiplier 64 calculates the steering angle gain K_an as described above. By multiplying the gear ratio Rvg0, a variable gear ratio Rvg realized by the gear ratio variable control is calculated. Then, the steering angle gain calculation unit 63 of the present embodiment is such that the variable gear ratio Rvg becomes a value corresponding to a quicker steering gear ratio in the small steering angle region near the steering neutral (θs = 0). The steering angle gain K_an corresponding to the steering angle θs is calculated. Specifically, the steering angle gain K_an is calculated so that the steered gear ratio becomes quicker as the steering angle θs (absolute value) becomes smaller.

  Further, the gear ratio variable control calculation unit 60 of the present embodiment subtracts “1” from the variable gear ratio Rvg in the subtractor 65, thereby obtaining an ACT gear ratio Rvg_act indicating a variable component in the variable gear ratio Rvg. Calculate. In the multiplier 66, the gear ratio variable command angle θvg * is calculated by multiplying the steering angle θs by the ACT gear ratio Rvg_act.

  In addition, the gear ratio variable control calculation unit 60 is provided with a steering state determination unit 68 that determines a state of steering operation (steering state) by the driver by monitoring a change in the steering angle θs. Then, the gear ratio variable control calculation unit 60 of the present embodiment sets the gear ratio variable command angle θvg * so that the immediately preceding steering gear ratio is maintained when the steering state is “return”. Calculate.

  More specifically, the gear ratio variable control calculation unit 60 of the present embodiment includes a previous value holding unit 69 that holds the previous value (variable gear ratio previous value Rvg_pr) of the variable gear ratio Rvg calculated in the previous calculation cycle. ing. Further, the gear ratio variable control calculation unit 60 is provided with a switching control unit 70. The variable gear ratio previous value Rvg_pr is the variable gear ratio Rvg calculated in the current calculation cycle and the steering state determination unit 68. Is input to the switching control unit 70 together with the steering state signal S_st output. When the input steering state signal S_st indicates “cut”, the switching control unit 70 outputs the variable gear ratio Rvg of the current cycle to the subtractor 65, and the steering state signal S_st is “ When “switch back” is indicated, the previous value Rvg_pr of the variable gear ratio is output to the subtractor 65.

  That is, at the time of turning steering, the ACT gear ratio Rvg_act is calculated based on the variable gear ratio Rvg newly calculated in each calculation cycle. Therefore, as shown in FIG. 5, the steering gear ratio becomes a quick value near the steering neutral (θs = 0) due to the operation of the steering angle gain K_an, and according to the increase of the steering angle θs, It changes to a slower value (trajectory L0).

  On the other hand, at the time of switchback steering, the ACT gear ratio Rvg_act is calculated based on the previous variable gear ratio value Rvg_pr. Therefore, as long as the switchback steering continues, the steering gear ratio is the previous value, that is, “switchback”. It becomes constant at the value of “time point” (trajectory L1, L2).

  In this embodiment, as in the first embodiment, this makes it possible to gently return the steering to the neutral position without destroying the relationship between the steering angle θs and the turning angle θt. ing.

As described above, according to the present embodiment, the following effects can be obtained.
The gear ratio variable control calculation unit 60 calculates a ratio of the base gear ratio Rgr_bs to the target gear ratio Rgr_vs (gear ratio: Rvg0 = Rgr_bs / Rgr_vs), and a steering angle gain K_an based on the steering angle θs. And a steering angle gain calculation unit 63 for calculation. The gear ratio variable control calculation unit 60 calculates the gear ratio variable command angle θvg * by multiplying the variable gear ratio Rvg obtained by multiplying the gear ratio Rvg0 by the steering angle gain K_an and the steering angle θs. Further, the gear ratio variable control calculation unit 60 includes a previous value holding unit 69 that holds the previous value (variable gear ratio previous value Rvg_pr) of the variable gear ratio Rvg calculated in the previous calculation cycle. Then, when the steering state is “cut”, the gear ratio variable command angle θvg * is calculated based on the variable gear ratio Rvg of the current cycle, and when it is “turn back”, the variable gear ratio last time is calculated. The gear ratio variable command angle θvg * is calculated based on the value Rvg_pr.

  According to the above configuration, at the time of incision steering, the steering gear ratio is changed to a slower value as the steering angle θs increases as the steering angle θs becomes a quick value when the steering is steered. The gear ratio variable command angle θvg * can be calculated. Further, the gear ratio variable command angle θvg * that maintains the immediately preceding steering gear ratio can be calculated at the time of the return steering.

In addition, you may change the said embodiment as follows.
In each of the above embodiments, the transmission ratio variable device 8 is provided in the middle of the intermediate shaft 3a, but may be embodied in a configuration provided on a column shaft or a pinion shaft. In addition to the integral rotation type in which the motor 13 that is the driving source rotates with the steering shaft 3, the motor 13 may be embodied in a non-rotation type in which the motor does not rotate.

  In the first embodiment, at the time of switchback steering, the current (immediately) turning angle θt is calculated based on the steering angle θs and the gear ratio variable command angle θvg *, and the turning angle θt and the steering angle are calculated. Based on θs, the current (immediately preceding) steering gear ratio Rgr is calculated. Then, the transmission ratio variable control is performed so that the immediately preceding steering gear ratio is maintained by calculating the gear ratio variable command angle θvg * based on the switchback gear ratio Rvg_out corresponding to the steering gear ratio Rgr. Run. In the second embodiment, the variable gear ratio Rvg corresponding to the ratio of the base gear ratio Rgr_bs to the target gear ratio Rgr_vs is calculated at a predetermined period, and the gear ratio variable command angle θvg * is calculated based on the variable gear ratio Rvg. While calculating, the previous value (variable gear ratio previous value Rvg_pr) of the variable gear ratio Rvg calculated in the previous calculation cycle is held. At the time of switchback steering, the gear ratio variable command angle θvg * is calculated on the basis of the previous variable gear ratio value Rvg_pr to execute the transmission ratio variable control so that the immediately preceding steering gear ratio is maintained. It was decided.

  However, the present invention is not limited to this, and the actual steering gear ratio is calculated for each calculation cycle by other methods. Then, at the time of switchback steering, the transmission ratio variable control may be executed by calculating the gear ratio variable command angle θvg * using the actual steering gear ratio as a control target value. The “actual steering gear ratio” can be obtained, for example, by calculating the turning angle θt (or pinion angle θp) from the motor rotation angle θm, the speed increase rate α, the ACT gear ratio Rvg_act, or the like.

  In each of the above embodiments, by monitoring the change in the steering angle θs, it is determined whether the steering operation state, specifically, the steering state is the “cut” or “turn back”. It was decided. However, the present invention is not limited to this. For example, the steering state may be determined by other methods such as considering the influence of the vehicle speed V or using a steering torque.

  In the first embodiment, at the time of turning steering, the reference point θ0 when calculating the steering angle gain Kan is shifted to the value of the steering angle θs at the start of turning. Then, the steering angle gain Kan is calculated such that the smaller the reference steering angle θk (the absolute value thereof), the quicker the steering gear ratio becomes. However, the present invention is not limited to this, and the variable gear ratio Rvg is a value corresponding to a quicker steering gear ratio in the small steering angle region near the steering neutral (θs = 0), as in the second embodiment. As described above, the steering angle gain K_an corresponding to the steering angle θs is calculated. Then, the gear ratio Rvg_in at the time of cutting may be calculated by multiplying the steering angle gain K_an by the gear ratio Rvg0.

Next, technical ideas that can be grasped from the above embodiments will be described together with effects.
(A) A control method of a transmission ratio variable device provided in the middle of the steering system so that the steering gear ratio can be changed, and the steering angle is set so that the steering gear ratio becomes a quick value near the steering neutral position. And controlling the operation of the transmission ratio variable device on the basis of the above, determining the state of the steering operation, and in the case of switchback steering, the transmission ratio variable device so that the immediately preceding steering gear ratio is maintained. A method for controlling the transmission ratio variable device, characterized by controlling the operation of the transmission ratio. Thereby, the responsiveness at the time of turning steering can be improved in the vicinity of the steering neutral without causing a sense of incongruity at the time of turning back steering.

  (B) The transmission ratio variable device varies the steering gear ratio by adding a second steering angle based on motor drive to a first steering angle based on a steering operation. .

  (C) In (b) above, a variable gear ratio corresponding to the ratio of the base gear to the target gear ratio is calculated at a predetermined period, and a second steering angle component based on the motor drive is calculated based on the variable gear ratio. The second steering angle component is calculated by holding the previous value of the variable gear ratio and calculating the second steering angle component based on the previous value of the variable gear ratio during switchback steering.

  (D) In (b) above, the actual steering gear ratio is calculated for each calculation cycle, and at the time of switchback steering, the actual steering gear ratio is set as the control target value, and the second steering angle based on the motor drive The component is calculated.

  DESCRIPTION OF SYMBOLS 1 ... Steering device for vehicles, 2 ... Steering, 3 ... Steering shaft, 3a ... Intermediate shaft, 4 ... Rack & pinion mechanism, 6 ... Steering wheel, 8 ... Transmission ratio variable device, 9 ... ECU, 10 ... 1st shaft , 11 ... second shaft, 12 ... differential mechanism, 13 ... motor, 21 ... microcomputer, 23 ... gear ratio variable control calculation unit, 26 ... motor resolver, 27 ... motor control signal generation unit, 31 ... speed increase rate calculation unit, 32... Gear ratio variable command angle calculation section 34. Steering state determination section 35 35. Cutting gear ratio calculation section 36. Switch back gear ratio calculation section 41. Target gear ratio calculation section 42 and 49. Calculation unit 43 ... steering angle gain calculation unit 44 ... multiplier 45 ... reference point calculation unit 46,51 ... subtractor 47 ... steering angle calculation unit 48 ... steering gear ratio calculation unit 50 ... switching control , 60 ... gear ratio variable control calculation unit, 61 ... target gear ratio calculation unit, 62 ... gear ratio calculation unit, 63 ... steering angle gain calculation unit, 64, 66 ... multiplier, 65 ... subtractor, 68 ... steering state determination , 69 ... previous value holding unit, 70 ... switching control unit, θs ... steering angle, θs_pr ... previous value, Δθs ... change amount, α ... acceleration rate, θt ... turning angle, θts ... steer turning angle, θta ... ACT angle, V: vehicle speed, θvg *: gear ratio variable command angle, θvg_pr *: previous value, θpa *: pinion ACT angle command value, θm: motor rotation angle, θpa: pinion ACT angle, Rvg_in: gear ratio at cutting Rgr_vs: target gear ratio, Rgr_bs: base gear ratio, Rvg0: gear ratio, Kan: rudder angle gain, θ0: reference point, θk: reference rudder angle, Rvg_out: gear ratio at switchback, Rgr: steering gear ratio, K_an: steering Angular gain, Rvg ... variable gear ratio, Rvg_pr ... variable gear ratio previous value, Rvg_a ct ... ACT gear ratio, S_st ... steering state signal.

Claims (2)

A transmission ratio variable device provided in the middle of the steering system so that the steering gear ratio can be changed, and a control means for controlling the operation of the transmission ratio variable device, wherein the control means is arranged near the steering neutral ratio. Is a vehicle steering device that controls the operation of the transmission ratio variable device based on the steering angle so that the value becomes a quick value,
The control means determines a steering state, and when the steering state is switchback steering, controls the operation of the transmission ratio variable device so that the immediately preceding steering gear ratio is maintained ,
The control means uses the steering angle value at the time when the turning steering is started as a reference point at the time of the turning steering, and calculates the steering angle gain based on the steering angle change from the reference point. And changing the steering gear ratio based on
The vehicle steering apparatus according to claim 1, wherein the steering angle gain is set so as to have a quick steering gear ratio in a region where the change in the steering angle is small . Provided in the middle of steering rudder system, the variable transmission ratio device for varying the steering gear ratio by superimposing the second steering angle based on the activation of the motor to the first steering angle based on the steering operation, the variable transmission ratio device And a control means for controlling the operation of the transmission ratio variable device based on a steering angle so that the steering gear ratio becomes a quick value in the vicinity of a neutral steering position. A steering device,
The control means determines a steering state, and when the steering state is switchback steering, controls the operation of the transmission ratio variable device so that the immediately preceding steering gear ratio is maintained ,
The control means calculates a variable gear ratio obtained by multiplying a ratio of the base gear to the target gear ratio by a steering angle gain calculated based on the steering angle at a predetermined period, and performs the motor drive based on the variable gear ratio. Calculating the second rudder angle component based on, and holding the variable gear ratio used for the calculation of the second rudder angle component as a previous value,
A steering apparatus for a vehicle, characterized in that the second steering angle component is calculated based on the variable gear ratio held as a previous value at the time of return steering .

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