JP4978347B2 - Vehicle steering system - Google Patents

Description

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

Conventionally, by adding a second rudder angle (ACT angle) of a steered wheel based on motor drive to the first rudder angle of a steered wheel based on a steering operation, the steering angle of the steering wheel (steering angle) and the rudder of the steered wheel There is a vehicle steering apparatus including a transmission ratio variable device that varies a transmission ratio (gear ratio) between an angle (steering angle) (see, for example, Patent Document 1). By adopting such a steering device, the amount of change in the steering angle with respect to the steering operation is increased at low vehicle speeds to reduce the burden on the driver. It is possible to achieve excellent steering characteristics such as ensuring the performance.
JP 2005-170129 A

  By the way, when performing a steering operation for returning the steering to a neutral position, that is, a so-called steering return operation, many drivers use a road surface reaction force (self-aligning torque) acting on the steered wheels. That is, as shown in FIG. 14, during traveling, each steered wheel 61 has a force (self-aligning torque) for autonomously returning the steered wheel 61 to the neutral position based on the road surface reaction force. Works. Therefore, in the conventional steering device 60, the steering 62 can be returned to the neutral position only by weakening the steering torque applied to the steering 62.

  However, as shown in FIG. 15, in the vehicle steering apparatus 63 including the transmission ratio variable device 64 as described above, the transmission ratio variable device 64 operates to change the second steering angle based on the motor drive. At this time, a force (motor reaction force) that rotates the steering 62 in the direction opposite to the change direction of the second steering angle acts on the steering 62. That is, when the second steering angle is reduced as the steering angle is reduced at the time of the steering return as described above, the direction of the steering 62 to increase the steering angle, that is, the motor opposite to the steering return direction. Reaction force will act. Then, the self-aligning torque acting in the steering return direction is canceled by the motor reaction force, so that the steering returns to the neutral position, that is, the steering return characteristic is deteriorated.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a vehicle steering apparatus with a variable transmission ratio device that has excellent steering return characteristics.

  In order to solve the above problems, the invention according to claim 1 is directed to steering by adding a second rudder angle of the steered wheel based on motor drive to a first rudder angle of the steered wheel based on a steering operation. The vehicle steering apparatus includes a transmission ratio variable device that varies a transmission ratio between the wheel and the steered wheel, and a control unit that controls the operation of the transmission ratio variable device, wherein the steering returns to a neutral position. Determining means for determining whether or not the vehicle is in a steering return state, and when the control means determines that the vehicle is in the steering return state, the second steering angle according to a decrease in the steering angle And calculating a second control component having a value that cancels the first control component.

  That is, when the transmission ratio variable device operates to reduce the second steering angle in response to the reduction of the steering angle during the steering return operation, the steering tries to rotate the steering in the anti-steer return direction. Reaction force (motor reaction force) acts. Then, the self-aligning torque that the motor reaction force acts in the steering return direction cancels out the steering return characteristic.

  However, as in the above configuration, by calculating the second control component that generates the motor reaction force in the steering return direction and canceling the first control component that generates the motor reaction force in the anti-steer return direction, It can be used for steering return operation without weakening the self-aligning torque. As a result, a good steering return characteristic can be realized even in a vehicle steering device with a transmission ratio variable device.

  The gist of the invention described in claim 2 is that the control means calculates the second control component having a value that cancels the first control component larger as the steering angle is larger. To do.

  That is, the delay in steering return due to the influence of the motor reaction force in the anti-steer return direction based on the first control component becomes more prominent as a larger steering angle is generated. However, according to the above configuration, the influence of the motor reaction force acting in the anti-steer return direction can be appropriately eliminated, and the second rudder angle based on the motor drive is quickly reduced near the steering neutral position. can do. As a result, better steering return characteristics can be realized.

  According to a third aspect of the present invention, the control means calculates the second control component having a value that cancels the first control component larger as the contribution of the steering torque input to the steering is lower. The gist is to do.

  That is, the influence of the motor reaction force in the anti-steering direction based on the first control component is more significant when the steering torque input by the driver to the steering is small, that is, when the contribution of the steering torque is low. It will be something. However, according to the above configuration, the influence of the motor reaction force in the counter-steer return direction that is generated when the transmission ratio variable device operates to reduce the second steering angle based on the motor drive more appropriately can be eliminated. Can do. As a result, a better steering return characteristic can be realized, and in particular, a more remarkable effect can be obtained in the steering return state in the so-called “hand-off state”.

The gist of the invention described in claim 4 is that the control means calculates the second control component based on at least one of a steering speed and a vehicle speed.
That is, the influence of the motor reaction force in the anti-steering direction based on the first control component depends on the contribution of the steering torque input to the steering in the steering return operation. The magnitude of the contribution of the steering torque can be estimated from the steering speed or the vehicle speed. Therefore, according to the above configuration, it is possible to more appropriately eliminate the influence of the motor reaction force acting in the anti-steering return direction, thereby realizing an excellent steering return characteristic.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles with the transmission ratio variable apparatus excellent in the steering return characteristic can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus provided with a variable gear ratio system 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, a steering shaft 3 to which a steering (handle) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 in response to a steering operation is The pinion mechanism 4 converts the rack 5 into a reciprocating linear motion. The steering angle of the steered wheels 6, that is, the steered angle is varied by the reciprocating linear motion of the rack 5, whereby the traveling direction of the vehicle is changed.

  The vehicle steering apparatus 1 of the present embodiment includes a gear ratio variable actuator 7 serving as a transmission ratio variable apparatus that varies the transmission ratio (gear ratio) of the steered wheels 6 with respect to the steering angle (steering angle) of the steering 2, and the gear ratio. And an IFSECU 8 as a control means for controlling the operation of the variable actuator 7.

  More specifically, the steering shaft 3 includes a first shaft 9 to which the steering 2 is connected and a second shaft 10 to be connected to the rack and pinion mechanism 4. The variable gear ratio actuator 7 includes the first shaft 9 and the first shaft 9. A differential mechanism 11 that couples the two shafts 10 and a motor 12 that drives the differential mechanism 11 are provided. The gear ratio variable actuator 7 adds the rotation driven by the motor to the rotation of the first shaft 9 associated with the steering operation and transmits it to the second shaft 10, thereby inputting the steering shaft to the rack and pinion mechanism 4. The rotation of 3 is increased (or decelerated).

  That is, as shown in FIGS. 2 and 3, the gear ratio variable actuator 7 has the steered angle (ACT angle θta) of the steered wheels based on the motor drive to the steered angle (steer steered angle θts) of the steered wheels 6 based on the steering operation. ) Is added, the ratio of the turning angle θt of the steered wheels 6 to the steering angle θs, that is, the transmission ratio (gear ratio) is varied. The IFSECU 8 controls the control of the gear ratio variable actuator 7 through the supply of driving power to the motor 12, thereby controlling the transmission ratio (gear ratio) between the steering angle θs and the turning angle θt (gear ratio). Variable control).

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “gear ratio of the steering angle θt to the steering angle θs” is expressed as an overall gear ratio (steering angle θs / steering angle θt), the ACT angle θta in the same direction as the steering angle θts should be added. Thus, the overall gear ratio becomes small (large turning angle θt, see FIG. 2). Then, the overall gear ratio is increased by adding the ACT angle θta in the reverse direction (small turning angle θt, see FIG. 3). In this embodiment, the steer turning angle θts constitutes the first rudder angle, and the ACT angle θta constitutes the second rudder angle.

  As shown in FIG. 1, the vehicle steering apparatus 1 includes an EPS actuator 17 that applies an assist force for assisting a steering operation to the steering system, and an EPS ECU 18 that controls the operation of the EPS actuator 17. Yes.

  The EPS actuator 17 of the present embodiment is a so-called rack assist type EPS actuator in which a motor 22 as a driving source is provided in the rack 5, and assist torque generated by the motor 22 is generated by a ball screw mechanism (not shown). Is transmitted to the rack 5. The EPS ECU 18 controls the assist force applied to the steering system by controlling the assist torque generated by the motor 22 (power assist control).

  In the present embodiment, the IFSECU 8 that controls the gear ratio variable actuator 7 and the EPSECU 18 that controls the EPS actuator 17 are connected via an in-vehicle network (CAN: Controller Area Network) 23. Are connected to a plurality of sensors for detecting the vehicle state quantity. Specifically, a steering angle sensor 24, a torque sensor 25, wheel speed sensors 26a and 26b, a lateral G sensor 28, a vehicle speed sensor 29, a brake sensor 30, and a yaw rate sensor 31 are connected to the in-vehicle network 23. A plurality of vehicle state quantities detected by the sensors, that is, steering angle θs, steering torque τ, wheel speed Vtr, Vtl, turning angle θt, slip angle θsp, vehicle speed V, brake signal Sbk, and yaw rate Ry are as follows: The data is input to the IFSECU 8 and the EPSECU 18 via the in-vehicle network 23.

  In this embodiment, the turning angle θt is obtained by multiplying the steering angle θs by the base gear ratio of the rack and pinion mechanism 4, that is, by adding the ACT angle θta to the steering angle θts, and the slip angle θsp is obtained based on the lateral acceleration detected by the lateral G sensor 28 and the yaw rate Ry. The IFSECU 8 and EPSECU 18 transmit and receive control signals by mutual communication via the in-vehicle network 23. The IFSECU 8 and EPSECU 18 perform the gear ratio variable control and the power assist control in an integrated manner based on the vehicle state quantities and control signals input via the in-vehicle network 23.

Next, the electrical configuration and control mode of the vehicle steering apparatus of the present embodiment will be described.
FIG. 4 is a control block diagram of the vehicle steering apparatus of the present embodiment. As shown in the figure, the IFSECU 8 includes a microcomputer 33 that outputs a motor control signal and a drive circuit 34 that supplies drive power to the motor 12 based on the motor control signal.

  In the present embodiment, a brushless motor is employed as the motor 12 that is the drive source of the gear ratio variable actuator 7, and the drive circuit 34 is connected to the motor 12 based on the motor control signal input from the microcomputer 33. Three-phase (U, V, W) drive power is supplied. The microcomputer 33 generates a motor control signal to be output to the drive circuit 34 by executing a calculation (computer program) shown in each control block in FIG.

  More specifically, the microcomputer 33 includes an IFS control calculation unit 35, a gear ratio variable control calculation unit 36, a LeadSteer control calculation unit 37, and a steering return control calculation unit 38, and each control calculation unit is input. Based on the vehicle state quantity, the control component (and control signal) of the ACT angle θta corresponding to the purpose is calculated. The microcomputer 33 generates a motor control signal for controlling the operation of the motor 12, that is, the gear ratio variable actuator 7, based on the calculated control components.

  A steering angle θs, a turning angle θt, a vehicle speed V, a wheel speed Vtr, Vtl, a brake signal Sbk, a yaw rate Ry, and a slip angle θsp are input to the IFS control calculation unit 35. The IFS control calculation unit 35 calculates the control component of the ACT angle θta for controlling the yaw moment of the vehicle based on the so-called active steering function, that is, the vehicle model, based on these vehicle state quantities, and related control. Calculate the signal.

  Specifically, the IFS control calculation unit 35 calculates an OS / US characteristic value Val_st indicating a vehicle steering characteristic, and as a control component of the ACT angle θta for realizing an active steering function corresponding to the steering characteristic. , IFS_ACT command angle θifs * is calculated (IFS control calculation). If the steer characteristic is understeer (US) by this IFS control calculation, the steered wheel 6 is used to reduce the turning angle of the steered wheel 6, and if the steer characteristic is oversteer (OS), the steered wheel The IFS_ACT command angle θifs * for giving the steering angle (counter steer) in the direction opposite to the direction of the yaw moment to 6 is calculated.

  In the present embodiment, the OS / US characteristic value Val_st and the IFS_ACT command angle θifs * calculated by the IFS control calculation are also input to the EPS ECU 18 via the in-vehicle network 23 (see FIG. 1). The EPS ECU 18 is configured to execute power assist control in accordance with the steering characteristic and in cooperation with the operation of the gear ratio variable actuator 7 based on the OS / US characteristic value Val_st and the IFS_ACT command angle θifs *. ing.

  On the other hand, the steering angle θs, the turning angle θt, and the vehicle speed V are input to the gear ratio variable control calculation unit 36. The gear ratio variable control calculation unit 36 calculates a gear ratio variable ACT command angle θgr * as a control component for varying the gear ratio according to the vehicle speed V based on these vehicle state quantities (and control signals). To do.

  As shown in FIG. 5, in the low / medium speed region, the gear ratio variable control calculation unit 36 of the present embodiment is quicker as compared with the conventional steering gear ratio as the input vehicle speed V is lower. The gear ratio variable ACT command angle θgr * is calculated so as to obtain a steering gear ratio (such that a large steering angle θt is generated with a small steering angle θs). In the high vehicle speed region, the higher the input vehicle speed V, the slower the steering gear ratio compared to the conventional steering gear ratio (such that a small steering angle θt is generated at a large steering angle θs). Thus, the gear ratio variable ACT command angle θgr * is calculated. In FIG. 5, the broken line indicates the steering gear ratio of a normal type steering device without a transmission ratio variable device.

  The vehicle speed V and the steering speed ωs are input to the lead steer control calculation unit 37. The steering speed ωs is calculated by differentiating the steering angle θs (the same applies hereinafter). Then, the Lead Steer control calculation unit 37 calculates the LS_ACT command angle θ ls * as a control component for improving the responsiveness of the vehicle according to the steering speed based on the vehicle speed V and the steering speed ω s (Lead Steer control calculation). .

  In addition, the steering angle θs, the vehicle speed V, and the steering speed ωs are input to the steering return control calculation unit 38. Then, based on each of these state quantities, the steering return command angle is used as a control component for smoothly returning to the neutral position (θs = 0) of the steering wheel 2, that is, for improving the steering return characteristic. Calculate θsb **.

  The IFS control calculation unit 35, the gear ratio variable control calculation unit 36, the Lead Steer control calculation unit 37, and the steering return control calculation unit 38 are each control target component calculated by the corresponding control calculation, that is, the IFS_ACT command angle θifs *. The gear ratio variable ACT command angle θgr *, the LS_ACT command angle θls *, and the steering return command angle θsb ** are output to the adder 39. In the microcomputer 33 of the present embodiment, the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, the LS_ACT command angle θls *, and the steering return command angle θsb ** are superimposed in the adder 39. Thus, the ACT command angle θta *, which is the control target of the ACT angle θta, is calculated.

  The ACT command angle θta * calculated by the adder 39 is input to the F / F control calculation unit 40 and the F / B control calculation unit 41. Further, the ACT angle θta detected by the rotation angle sensor 42 provided in the motor 12 is input to the F / B control calculation unit 41. The F / F control calculation unit 40 calculates the control amount εff by feedforward calculation based on the input ACT command angle θta *, and the F / B control calculation unit 41 calculates the ACT command angle θta * and the ACT angle θta. The control amount εfb is calculated by feedback calculation based on the above.

  The control amount εff and the control amount εfb calculated by the F / F control calculation unit 40 and the F / B control calculation unit 41 are input to the adder 43. The adder 43 calculates the current command by superimposing the control amount εff and the control amount εfb, and outputs the current command to the motor control signal output unit 44. The motor control signal output unit 44 generates a motor control signal based on the input current command and outputs it to the drive circuit 34.

  That is, as shown in the flowchart of FIG. 6, when the microcomputer 33 takes in the sensor value from each of the sensors as the vehicle state quantity (step 101), it first performs an IFS control calculation (step 102), and then the gear ratio variable control. A calculation (step 103), a lead steer control calculation (step 104), and a steering return control calculation (step 105) are executed. Then, the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, the LS_ACT command angle θls *, and the steering return command angle θsb ** calculated by executing the respective calculation processes of Step 102 to Step 105 are calculated. By superimposing, the control target ACT command angle θta * is calculated.

  Next, the microcomputer 33 performs a feedforward calculation (step 106) and a feedback calculation (step 107) based on the ACT command angle θta * calculated as described above. Then, the motor control signal is output based on the current command calculated by each control calculation (step 108).

(Steering return control)
Next, the aspect of the steering return control in this embodiment will be described.
As described above, in the vehicle steering apparatus with the transmission ratio variable device, when the gear ratio variable actuator 7 is operated to change the second steering angle (ACT angle θta) based on the motor drive, A force (motor reaction force) is applied to rotate the steering in the direction opposite to the direction of change of the second steering angle. Therefore, when the second steering angle is reduced along with the reduction of the steering angle when the steering is returned, a motor reaction force opposite to the steering return direction acts, and the motor reaction force causes a self-advance. When the lining torque is canceled, there is a problem that the steering returns to the neutral position (θs = 0), that is, the steering return characteristic is deteriorated (see FIG. 15).

  In consideration of this point, in the IFSECU 8 of the present embodiment, the steering return control calculation unit 38 as a determination unit provided in the microcomputer 33 indicates that the current steering operation state is in the neutral position (θs = 0). It is determined whether or not the vehicle is in a so-called steering return state. When it is determined that the vehicle is in the steering return state, the steering return control calculation unit 38 generates the steering return command angle θsb ** as a control component for improving the steering return characteristic in the steering return state.

  More specifically, as shown in FIG. 7, the steering return control calculation unit 38 executes the calculation of the steering return command angle θsb * and the steering return determination unit 51 that determines whether or not the steering return state is present. And a steering return command angle calculation unit 52.

  In the present embodiment, the steering angle θs and the steering speed ωs are input to the steering return determination unit 51, and the steering return determination unit 51 receives the input steering angle θs and the steering speed ωs. It is determined whether the codes are different from each other (see FIG. 8, step 201). If these signs are different from each other (when the steering angle θs is “+” and the steering speed ωs is “−”, or when the steering angle θs is “−” and the steering speed ωs is “+”, step 201: YES). That is, when the steering angle direction given to the steering wheel 2 and the direction of change thereof are opposite, it is determined that the vehicle is in the steering return state (step 202). Note that the steering return determination unit 51 determines whether the steering angle θs and the steering speed ωs that are input have the same sign (step 201: NO), that is, the steering angle direction given to the steering 2 and the change direction thereof. If they are the same, it is determined that the vehicle is in the non-steering return state (step 203).

  On the other hand, the steering speed ωs and the vehicle speed V are input to the steering return command angle calculation unit 52 of the present embodiment. Then, the steering return command angle calculation unit 52 of the present embodiment is based on the input steering speed ωs and the vehicle speed V, and the gear ratio as the first control component calculated by the gear ratio variable control calculation unit 36. As a second control component having a value that cancels the variable ACT command angle θgr *, the steering return command angle θsb * is calculated.

  That is, as shown in FIG. 9, when the gear ratio variable actuator 7 is operated to reduce the ACT angle θta according to the decrease of the steering angle θs during the steering return operation, the steering 2 is connected to the steering 2 A motor reaction force that tries to rotate in the direction opposite to the steering return direction acts (motor reaction force A in the figure).

  On the other hand, the steering return command angle calculation unit 52 cancels the gear ratio variable ACT command angle θgr * calculated to reduce the ACT angle θta, that is, the steering return command angle θsb *, that is, the steering return A steering return command angle θsb * is calculated so that a motor reaction force acting in the direction (motor reaction force B in the figure) is generated.

  That is, the steering return command angle θsb * that generates the motor reaction force in the steering return direction (motor reaction force B in the figure) is calculated, and the motor reaction force in the counter steering return direction (motor reaction force A in the figure). By canceling the gear ratio variable ACT command angle θgr * that causes the self-aligning torque, the self-aligning torque can be used for the steering return operation without weakening. And the steering apparatus 1 for vehicles of this embodiment becomes a structure which aims at the improvement of the steering return performance by this.

  More specifically, the steering return command angle calculation unit 52 of the present embodiment is a map (three-dimensional map) in which the steering return command angle θsb * is associated with the steering speed ωs and the vehicle speed V as shown in FIG. 52a. The steering return command angle θsb * is calculated by referring to the input steering speed ωs and vehicle speed V in the map 52a.

  As shown in FIG. 11, in the map 52a, the steering return command angle θsb * is “−” when the sign of the steering speed ωs is “+”, and the sign of the steering speed ωs is “−”. In some cases, the value is set to “+”. That is, the map 52a is a value in a direction in which the ACT angle θta (absolute value) is increased in a steering return state in which the steering speed ωs is generated in a direction (steering return direction) in which the steering angle θs (absolute value) is decreased. Is designed so that a steering return command angle θsb * is calculated.

  Specifically, the map 52a is a steering return command angle θsb * having a value other than “0” in a steering speed region (−ω0 ≦ ωs ≦ ω0) in which the absolute value of the steering speed ωs is equal to or less than a predetermined value ω0, that is, The effective steering return command angle θsb * is designed to be calculated. More specifically, in the map 52a, the steering return command angle θsb * is the steering speed ωs in the steering speed region where the absolute value of the steering speed ωs is smaller than the predetermined value ω1 (−ω1 <ωs <ω1). The absolute value is set so as to increase as the absolute value increases. In the steering speed range (ω1 ≦ | ω | ≦ ω2) where the absolute value of the steering speed ωs is not less than the predetermined value ω1 and not more than the predetermined value ω2, the absolute value of the steering return command angle θsb * is the maximum. In a steering speed region exceeding the value ω2 (ω2 <| ω | ≦ ω0), the absolute value of the steering speed ωs is set to be smaller as the absolute value of the steering speed ωs is larger.

  Further, as shown in FIG. 12, the map 52a shows a steering return command angle θsb * having a value other than “0” in a vehicle speed region (V ≦ V0) where the vehicle speed V is equal to or lower than a predetermined vehicle speed V1, that is, effective steering. The return command angle θsb * is designed to be calculated.

  Specifically, in the map 52a, the steering return command angle θsb * is set so that the absolute value thereof increases as the vehicle speed V increases in a speed range (V <V1) slower than the predetermined vehicle speed V1. Has been. The steering return command angle θsb * has a maximum absolute value and is faster than the predetermined vehicle speed V2 in a vehicle speed region (V1 ≦ V ≦ V2) of the predetermined vehicle speed V1 or more and the predetermined vehicle speed V2 or less. In (V2 <V ≦ V0), the absolute value is set to decrease as the vehicle speed V increases.

  Here, in the map 52a, each of the predetermined values ω1, ω2 and the predetermined vehicle speeds V1, V2 related to the steering speed ωs has the lowest contribution of the steering torque input to the steering 2 in the steering return operation. It is set so as to correspond to the estimated steering speed region and the vehicle speed region.

  That is, the influence of the motor reaction force (see FIG. 9, motor reaction force A) based on the gear ratio variable ACT command angle θgr * calculated to reduce the ACT angle θta is that the driver can The smaller the steering torque input to, that is, the lower the contribution of the steering torque, the more prominent.

  In view of this point, the map 52a has a steering value having a value that cancels the gear ratio variable ACT command angle θgr * larger as the contribution of the steering torque input to the steering wheel 2 is estimated to be lower in the steering return operation. The return command angle θsb * is designed to be calculated.

  That is, the steering return command angle calculation unit 52 (steering return control calculation unit 38) of the present embodiment increases the gear ratio variable ACT command angle as the contribution of the steering torque input to the steering 2 in the steering return operation is lower. A steering return command angle θsb * (θsb **) having a value that cancels θgr * is calculated. As a result, during the steering return operation, the influence of the motor reaction force in the counter-steer return direction that occurs when the gear ratio variable actuator 7 operates to reduce the ACT angle θta can be appropriately eliminated, and a better steering can be achieved. It is the structure which aims at realization of a return characteristic.

  In the present embodiment, the predetermined values ω1 and ω2 and the predetermined vehicle speeds V1 and V2 related to the steering speed ωs are in a state where the driver has released his hand from the steering wheel 2 such as when turning at an intersection. Is set in correspondence with a steering speed region and a vehicle speed region in which it is assumed that the steering return operation is easily performed.

  Further, the steering operation in which the steering speed ωs in the direction opposite to the direction in which the steering angle θs is generated is originally a so-called “return operation”, and the “steer return” for returning the steering to the neutral position as described above. In addition to “operation”, “turn-back operation” that generates a steering angle in the opposite direction beyond the steering neutral position is also included. Therefore, strictly speaking, the steering return determination in the steering return determination unit 51 should be “switchback determination”, but in the present embodiment, in this map 52a, the high-speed steering region corresponding to the “switchback operation” is selected. By excluding, the validity of the “steering return determination” by the steering return determination unit 51 is ensured.

  As shown in FIG. 7, the steering return control calculation unit 38 of the present embodiment includes a steering angle gain calculation unit 53 that calculates a steering angle gain Ks corresponding to the steering angle θs. The steering angle gain calculator 53 of this embodiment has a map 53a in which the steering angle θs and the steering angle gain Ks are associated with each other as shown in FIG. 13, and the steering angle gain Ks is calculated based on the map 53a. Perform the operation.

  Specifically, in the map 53a, the steering angle gain Ks is set to “1” when the absolute value of the steering angle θs is equal to or larger than a predetermined value θ0. When the absolute value of the steering angle θs is smaller than the predetermined value θ0, the smaller the absolute value of the steering angle θs, the smaller the steering angle θs becomes “0”, that is, when the steering angle θs corresponds to the neutral position. 0 "is set.

  As shown in FIG. 7, the steering return command angle θsb * calculated by the steering return command angle calculation unit 52 is input to the multiplier 54 together with the steering angle gain Ks calculated by the steering angle gain calculation unit 53. The multiplier 54 is multiplied by the steering angle gain Ks, so that the larger the steering angle θs (the absolute value thereof), the larger the value that cancels the gear ratio variable ACT command angle θgr *. The steering return command angle θsb ** is calculated.

  That is, the delay in steering return due to the influence of the motor reaction force in the counter-steering return direction (see FIG. 9, motor reaction force A) based on the gear ratio variable ACT command angle θgr * is greater when a larger steering angle is generated. It becomes more prominent.

  In consideration of this point, the steering return control calculation unit 38 of the present embodiment, as described above, increases the value that cancels the gear ratio variable ACT command angle θgr * as the steering angle θs (absolute value) increases. The steering return command angle θsb ** is calculated. As a result, during the steering return operation, the influence of the motor reaction force in the anti-steer return direction that occurs when the ACT angle θta is reduced is appropriately eliminated, and the ACT angle θta is quickly reduced near the steering neutral position. Thus, it is configured to achieve better steering return characteristics.

  As shown in FIG. 7, in the present embodiment, the steering return command angle θsb ** after the steering angle gain Ks is multiplied together with the determination signal Sd indicating the determination result in the steering return determination unit 51, the switching control unit 55. Is input. When the determination signal Sd input from the steering return determination unit 51 indicates that the steering return state is present, the switching control unit 55 of the present embodiment outputs a steering return command angle θsb **, and the determination signal When Sd indicates that the steering is returning, “0” is output. Then, the steering return control calculation unit 38 of the present embodiment uses the determination signal Sd or “0” output from the switching control unit 55 as the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, and the LS_ACT command angle. The configuration is such that θls * is output to the adder 39 to which it is input.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The IFSECU 8 (microcomputer 33) includes a steering return control calculation unit 38, and the steering return control calculation unit 38 determines whether or not the current steering operation state is a steering return state. When the steering return state is set, the steering return command angle θsb ** having a value for canceling the gear ratio variable ACT command angle θgr * calculated to reduce the ACT angle θta as the steering angle θs decreases. Calculate.

  That is, when the gear ratio variable actuator 7 is operated to reduce the ACT angle θta according to the decrease of the steering angle θs during the steering return operation, the steering 2 is rotated in the anti-steer return direction. The motor reaction force is applied. Then, the self-aligning torque that the motor reaction force acts in the steering return direction cancels out the steering return characteristic.

  However, as in the above configuration, the steering return command angle θsb ** that generates the motor reaction force in the steering return direction is calculated, and the gear ratio variable ACT command angle θgr * that generates the motor reaction force in the anti-steer return direction is calculated. By canceling, the self-aligning torque can be used for the steering return operation without weakening. As a result, a good steering return characteristic can be realized even in a vehicle steering device with a transmission ratio variable device.

  (2) The steering return control calculation unit 38 calculates the steering return command angle θsb ** having a value that cancels out the gear ratio variable ACT command angle θgr * as the steering angle θs (absolute value) increases. .

  That is, the delay in steering return due to the influence of the motor reaction force in the counter-steer return direction based on the gear ratio variable ACT command angle θgr * becomes more prominent as a large steering angle is generated. However, according to the above configuration, the influence of the motor reaction force in the anti-steer return direction can be appropriately eliminated, and the ACT angle θta can be quickly reduced in the vicinity of the steering neutral. As a result, better steering return characteristics can be realized.

  (3) The steering return control calculation unit 38 has a steering return command having a value that cancels out the gear ratio variable ACT command angle θgr * as the contribution of the steering torque input to the steering wheel 2 in the steering return operation is lower. Calculate the angle θsb **.

  That is, the influence of the motor reaction force in the anti-steering direction based on the gear ratio variable ACT command angle θgr * is that when the steering torque input by the driver to the steering 2 is small in the steering return operation, that is, the contribution of the steering torque is The lower the value, the more prominent. However, according to the above configuration, it is possible to more appropriately eliminate the influence of the motor reaction force in the anti-steering return direction that occurs when the gear ratio variable actuator 7 operates to reduce the ACT angle θta. As a result, a better steering return characteristic can be realized, and in particular, a more remarkable effect can be obtained in the steering return state in the so-called “hand-off state”.

In addition, you may change this embodiment as follows.
In the present embodiment, the steering return determination unit 51 determines the steering return state based on whether or not the signs of the steering angle θs and the steering speed ωs are different from each other. However, the present invention is not limited to this, and the determination of the steering return state may be performed by other modes. For example, a differential value of the steering torque, that is, a viewpoint of a change in the steering torque input to the steering may be added, so that the steering return state can be determined with higher accuracy.

  In the present embodiment, the validity of the “steering return determination” by the steering return determination unit 51 is ensured by excluding the high-speed steering region corresponding to the “turnback operation” in the map calculation in the steering return command angle calculation unit 52. Although it is configured, the steering return determination unit 51 may perform a more strict “steering return determination”.

  In the present embodiment, the steering return command angle calculation unit 52 calculates the steering return command angle θsb * as the second control component by map calculation based on the steering speed ωs and the vehicle speed V. However, the calculation method of the steering return command angle θsb * may be performed based on either the steering speed ωs or the vehicle speed V, or may be performed based on a state quantity other than the steering speed ωs and the vehicle speed V. .

  In the present embodiment, the microcomputer 33 superimposes the IFS_ACT command angle θifs *, the gear ratio variable ACT command angle θgr *, the LS_ACT command angle θls *, and the steering return command angle θsb ** to superimpose the second steering angle. ACT command angle θta *, which is a control target, is calculated. However, the present invention is not limited to this, and the present invention calculates a control component corresponding to the gear ratio variable ACT command angle θgr * that is calculated to decrease the ACT angle θta in accordance with the decrease in the steering angle θs during the steering return operation. As long as it does, it may be embodied in other configurations.

  In the present embodiment, the steering return control calculation unit 38 constitutes a determination unit that determines whether or not the steering return state exists. However, the determination unit is provided outside the microcomputer 33 and the IFSECU 8. You may apply to.

The schematic block diagram of the steering apparatus for vehicles. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. The control block diagram of the steering device for vehicles. Explanatory drawing which shows the aspect of gear ratio variable control. The flowchart which shows the process sequence of the arithmetic processing in IFSECU. The control block diagram of a steering return control calculating part. The flowchart which shows the process sequence of steering return determination. The operation explanatory view of steering return control of this embodiment. The schematic block diagram of the map used for calculation of a steering return command angle. The schematic block diagram of the map used for calculation of a steering return command angle. The schematic block diagram of the map used for calculation of a steering return command angle. The schematic block diagram of the map used for the calculation of a steering angle gain. Explanatory drawing which shows the steering return state in a normal steering device. Explanatory drawing which shows the steering return state in the steering device for vehicles with a transmission ratio variable apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering, 6 ... Steering wheel, 7 ... Gear ratio variable actuator, 8 ... IFSECU, 33 ... Microcomputer, 36 ... Variable gear ratio control calculating part, 38 ... Steering return control calculating part, 39 ... Adder, 51 ... steering return determination unit, 52 ... steering return command angle calculation unit, 52a ... map, 53 ... steering angle gain calculation unit, 53a ... map, 55 ... switch control unit, θs ... steering angle, θ0 ... predetermined value , Ωs ... steering speed, ω0, ω1, ω2 ... predetermined values, V, V0, V1, V2 ... vehicle speed, θt ... steering angle, θts ... steer turning angle, θta ... ACT angle, θta * ... ACT command angle, θgr *: gear ratio variable ACT command angle, θsb *, θsb **: steering return command angle, Ks: steering angle gain, Sd: determination signal.

Claims (4)

A transmission ratio variable device that varies a transmission ratio between the steering wheel and the steered wheel by adding a second rudder angle of the steered wheel based on motor drive to the first steered angle of the steered wheel based on the steering operation; , A vehicle steering apparatus comprising control means for controlling the operation of the transmission ratio variable device,
Determination means for determining whether or not the steering is in a steering return state in which the steering is returned to a neutral position;
When it is determined that the control means is in the steering return state,
Calculating a first control component that reduces the second steering angle in response to a decrease in steering angle, and calculating a second control component having a value that cancels the first control component;
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 1,
The vehicle steering apparatus according to claim 1, wherein the control means calculates the second control component having a value that cancels the first control component larger as the steering angle is larger. In the vehicle steering device according to claim 1 or 2,
The control means calculates the second control component having a value that cancels out the first control component larger as the contribution of the steering torque input to the steering is lower;
A vehicle steering apparatus characterized by the above. In the steering device for vehicles according to any one of claims 1 to 3,
The vehicle steering apparatus, wherein the control means calculates the second control component based on at least one of a steering speed and a vehicle speed.

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