JP2011225175A - Steering gear for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering gear for a vehicle, which can suppress a steering operation reaching the proximity of a maximum steering angle of wheels to be turned.SOLUTION: When a steering angle exceeds a predetermined steering angle near the maximum steering angle of the wheels to be turned, a microcomputer 41 brings about a greater position-proportional gain for controlling a motor 13 of a transfer-ratio variable device 8, as a vehicle speed is higher or the steering angle is larger. When the steering angle exceeds the predetermined steering angle near the maximum steering angle of the wheels to be turned, the microcomputer 41 brings about a greater derivative gain for controlling the motor 13 of the transfer-ratio variable device 8, as the steering angle is larger.

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 turning angle with respect to the steering operation is increased at low vehicle speeds to reduce the burden on the driver, and the amount of change is reduced at high vehicle speeds to reduce the amount of change and high steering stability. It is possible to achieve excellent steering characteristics such as ensuring the performance.

JP 2005-170129 A JP 2006-020392 A

  However, the ACT angle generated by the operation of the transmission ratio variable device is held by the motor torque. That is, when an external force greater than the holding torque is applied, the ACT angle cannot be held. Therefore, even when the turning angle reaches the steering end (rack end) that is the maximum steering angle, the steering angle is already set to the maximum steering angle by performing the steering operation against the holding torque. Despite this, the driver can add more steering than the original limit.

In other words, if the steering shaft integrated rotation type transmission ratio variable device is compared (for example, refer to Patent Document 2), the steering shaft is twisted like a spring in the transmission ratio variable device portion. As a result, particularly in such a steering shaft integrated rotation type variable transmission ratio variable device, the input shaft on the steering side rotates beyond the allowable rotation range of the spiral cable device for supplying driving power, and thus the flexible flat cable In this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus that can suppress the steering operation that has reached the vicinity of the maximum steering angle of the steered wheels. is there.

In order to solve the above-mentioned problem, the invention according to claim 1 adds the second turning angle of the steered wheel based on motor drive to the first steered angle of the steered wheel based on the steering operation. A transmission ratio variable device that varies a transmission ratio between the steering angle of the steering wheel and the turning angle of the steered wheels, a steering angle detection unit that detects the steering angle, a vehicle speed detection unit that detects a vehicle speed, Based on the steering angle and the vehicle speed, the turning angle calculating means for detecting or calculating the turning angle of the steered wheel, the second turning angle calculating means for detecting or calculating the second turning angle, Target value output means for outputting a target value of the steering angle of 2, control amount output means for outputting a control amount of the motor based on the target value, and motor control for controlling the motor based on the control amount And the control amount output means includes a vehicle speed and Position proportional gain determining means for determining a position proportional gain based on the steering angle; and the position proportional gain as a deviation between the target value of the second steering angle and the detected or calculated second steering angle. Position proportional control means for outputting a position deviation proportional term control amount by multiplication, first differential gain determination means for determining a first differential gain based on a steering angle, and differential change amount of the second turning angle Differential control means for outputting a differential control amount based on the above, and a subtraction means for calculating a subtraction value obtained by subtracting the differential control quantity from the positional deviation proportional term control quantity, wherein the differential control means comprises the second control means. A first differential control unit that outputs a first differential control amount obtained by multiplying the differential change amount of the steering angle by the first differential gain as the differential control amount, and the position proportional gain determination unit includes the steering angle Is set near the maximum steering angle of the steered wheels. When a predetermined steering angle is exceeded, the position proportional gain is increased as the vehicle speed is faster or the steering angle is larger, and the first differential gain determining means is configured to increase the steering angle. The gist is to increase the first differential gain as the turning angle increases when a predetermined steering angle set near the maximum steering angle of the steering wheel is exceeded.

According to the above configuration, when the turning angle exceeds a predetermined steering angle set in the vicinity of the maximum steering angle of the steered wheels, the position proportional gain is increased as the vehicle speed increases or the steering angle increases. As a result, a large current command is calculated even with a small deviation, so that the motor torque generated by the drive motor, that is, the holding torque of the transmission ratio variable device also increases. Further, when the turning angle exceeds a predetermined steering angle in the vicinity of the maximum steering angle of the steered wheels, the damper effect increases by increasing the first differential gain as the turning angle increases. As a result, the “twisted state” described above is less likely to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

According to a second aspect of the present invention, the control amount output means includes second differential gain determination means for determining a second differential gain based on a turning angular velocity calculated by differentiating the turning angle. The differential control means includes second differential control means for outputting, as the differential control quantity, a second differential control quantity obtained by multiplying the first differential control quantity by the second differential gain, and the second differential gain determining means includes: The gist is that, when the turning angular velocity exceeds a predetermined turning angular velocity, the second differential gain is increased as the turning angular velocity increases.

According to the above configuration, when the turning angular velocity exceeds a predetermined turning angular velocity, the damper effect can be further increased by increasing the second differential gain as the turning angular velocity increases. As a result, the “twisted state” described above is more difficult to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

According to a third aspect of the present invention, there is provided a steering torque detecting means for detecting a steering torque, wherein the control amount output means is a torque proportional gain determining means for determining a torque proportional gain based on a turning angle, and the steering torque. By multiplying the torque proportional gain by the torque proportional control means for outputting a torque proportional term control amount, and an adding means for adding the torque proportional term control amount to the subtracted value. The gist is that, when the turning angle exceeds a predetermined steering angle set in the vicinity of the maximum steering angle of the steered wheels, the torque proportional gain is increased as the steering torque is increased.

According to the above configuration, when the turning angle exceeds a predetermined steering angle set in the vicinity of the maximum steering angle of the steered wheels, the torque proportional gain is increased as the steering torque is increased. The holding torque can be further increased. As a result, the “twisted state” described above is more difficult to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

According to a fourth aspect of the present invention, the transmission ratio variable device includes a lock device that mechanically fixes the second turning angle, and a lock control unit that controls an operation of the lock device, and the lock control. When the steering angle exceeds a predetermined steering angle set near the maximum steering angle of the steered wheel, and the absolute value of the angular velocity of the second steering angle is less than a predetermined threshold, The gist is to operate the locking device.

According to the above configuration, by operating the lock device while avoiding the high speed operation of the transmission ratio variable device, it is possible to reduce the load on the lock device. In combination with the variable control of each gain, oscillation associated with the use of a high feedback gain can be prevented.

ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can suppress the steering operation which reached the maximum steering angle vicinity of a steered wheel can be provided.

The schematic block diagram of the steering apparatus for vehicles. (A) (b) Action explanatory drawing of variable transmission ratio control. The schematic block diagram of a transmission ratio variable apparatus. The control block diagram of the steering device for vehicles. The gain block diagram of a gain calculating part. The map explaining the aspect of position control proportional gain variable control. The map explaining the aspect of torque proportional gain variable control. The map explaining the aspect of 1st differential gain variable control. The map explaining the aspect of 2nd differential gain variable control. The flowchart which shows the process sequence of an excess steering detection part. The flowchart which shows the process sequence of a lock control part.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus including a transmission ratio variable device will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus 1 according to the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed by the rack and pinion mechanism. 4 is converted into a reciprocating linear motion of the rack shaft 5. Then, the steering angle of the steered wheels 6, that is, the steered angle is changed by the reciprocating linear motion of the rack shaft 5, thereby changing the vehicle traveling direction.

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

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

That is, as shown in FIGS. 2 (a) and 2 (b), the transmission ratio variable device 8 uses the steering angle of the steered wheels based on the motor drive (the steered steer angle θts) based on the steering operation (steer steered angle θts). 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).

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

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

In this embodiment, the differential mechanism 12 rotates a pair of circular splines 21 and 22 arranged coaxially, a flex spline 23 meshed with each spline inside these splines, and a meshing portion thereof. A known wave gear mechanism comprising a wave generator 26 is employed. One circular spline 21 is fixed to the housing 14 so as to be coaxial with the housing 14, and the other circular spline 22 is connected coaxially to the second shaft 11 via a connecting member 25. .

Each circular spline 21, 22 has a different number of teeth, and the flex spline 23 is arranged inside each of these gears while being bent in an elliptical shape so that its external teeth The inner teeth of the gears are partially engaged with each other. Then, the circular spline 21 rotates together with the housing 14, and the rotation of the circular spline 21 is transmitted to the circular spline 22 via the flex spline 23, so that the rotation of the first shaft 10 accompanying the steering operation is the first. Two shafts 11 are transmitted.

A wave generator 26 that constitutes the differential mechanism 12 together with the circular splines 21 and 22 is disposed inside the flexspline 23. The wave generator 26 is connected to the motor shaft 13a, and rotates inside the flex spline 23 as the motor shaft 13a rotates, so that the flexed spline 23 has an elliptical shape, that is, the circular spline 21. , 22 is rotated. Then, based on the difference in the number of teeth between the circular spline 21 and the circular spline 22, the circular spline 22 rotates, so that the rotation of the motor shaft 13a is decelerated and transmitted to the second shaft 11. It has become.

In the transmission ratio variable device 8 of the present embodiment, the spiral cable device 27 is provided on the upper wall portion 13a of the housing 14. The spiral cable device 27 electrically connects the motor 13 and IFSECU 9 and a solenoid 33a, which is a drive source of the lock device 33 described later, and IFSECU 9 in a predetermined rotation range (allowable rotation range). ing. For details of the spiral cable device 27, refer to the configuration described in Patent Document 2, for example.

Further, the transmission ratio variable device 8 has a first arm by engaging a lock arm 31 provided on the housing 14 side with a lock holder 32 that is fixed to one end of the motor shaft 13a and rotates integrally with the motor shaft 13a. The relative rotation between 10 and the second shaft 11 is restricted. That is, a lock device 33 for mechanically fixing the ACT angle θta is provided. Then, the IFSECU 9 operates the lock device 33 (lock control ON), for example, when the ignition is off or when an abnormality of the electric power steering device is detected. For details of such a locking device, refer to, for example, the configuration described in Japanese Patent Application Laid-Open No. 2003-320943.

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 19 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 electric power steering device (EPS) in which a motor 7 as a driving source thereof is arranged coaxially with the rack 5, and via a ball screw mechanism (not shown). By transmitting the assist torque generated by the motor 7 as a drive source to the rack shaft 5, an assist force is applied to the steering system.

In the present embodiment, the IFSECU 9 for controlling the transmission ratio variable device 8 and the EPSECU 19 for controlling the EPS actuator 17 are connected via an in-vehicle network 38, and the in-vehicle network 38 is for detecting a vehicle state. Multiple sensors are connected. Specifically, a steering angle sensor 36, a torque sensor 35, and a vehicle speed sensor 37 are connected. A plurality of vehicle state quantities detected by the sensors, that is, the steering angle θs, the steering torque τ, and the vehicle speed V are input to the IFSECU 9 and the EPSECU 19 via the in-vehicle network 38.

Next, the electrical configuration and control mode of the vehicle steering apparatus of the present embodiment will be described.
As shown in FIG. 1, the IFSECU 9 receives the steering angle θs (steering speed ωs) detected by the steering angle sensor 36, the steering torque τ detected by the torque sensor 35, and the vehicle speed V detected by the vehicle speed sensor 37. It is designed to be entered. The IFSECU 9 controls the rotation of the motor 13 based on the steering angle θs (steering speed ωs), the steering torque τ, 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. 4, the IFSECU 9 includes a microcomputer 41 that outputs a motor control signal, a drive circuit 42 that supplies driving power to the motor 13 based on the motor control signal, and a lock that is locked based on the lock control signal. And a drive circuit 52 for supplying drive power to a solenoid 33a for driving the device 33.

The microcomputer 41 includes an ACT angle command unit 43 as target value output means including a differential steer control calculation unit 43a, a gear ratio variable control calculation unit 43b, an ACT angle control unit 47 as control amount output means, and a motor as motor control means. A control signal output unit 49, an excessive steering detection unit 55 as a lock control means, and a lock control unit 53 are provided.

The differential steer control calculator 43a receives the vehicle speed V and the steering speed ωs, and the gear ratio variable control calculator 43b receives the steering angle θs and the vehicle speed V. The differential steer control calculation unit 43a calculates a differential steer command angle θls *, which is a control target component for improving the responsiveness of the vehicle, according to the steering speed ωs, and the gear ratio variable control calculation unit 43b A gear ratio variable command angle θgr *, which is a control target component for varying the gear ratio (transmission ratio) according to V, is calculated.

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

The ACT angle control unit 47 includes a torque proportional control unit 47a as a torque proportional control unit, a position proportional control unit 47b as a position proportional control unit, and a differential control unit 47c as a first differential control unit and a second differential control unit. And a gain calculation unit 48 that determines the gain of each control unit.

The torque proportional control unit 47a calculates the torque proportional control amount εt1 by multiplying the steering torque τ input from the EPS ECU by the in-vehicle CAN by the torque proportional gain Kt. Then, the position proportional control unit 47b calculates the position proportional control amount εp1 by multiplying the deviation Δθta between the ACT command angle θta * and the detected ACT angle θta by the position control proportional gain Kp. Then, the differential control unit 47c calculates the differential change amount (ACT angular velocity ωta) of the detected ACT angle θta, and multiplies the differential change amount by the first differential gain Kd and the second differential gain Kdv, thereby obtaining the first differential. A control amount εd1 and a second differential control amount εd2 are calculated.

 In the present embodiment, the position proportional control amount εp1 calculated by the position proportional control unit 47b and the differential control amount εd2 calculated by the differential control unit 47c are input to the subtractor 46a. The output of the subtractor 46a and the torque proportional control amount εt1 calculated by the torque proportional control unit 47a are input to the adder 46b. That is, the ACT angle control unit 47 calculates the ACT control angle θta ** by subtracting the differential control amount εd2 from the position proportional control amount εp1 and adding the torque proportional control amount εt1, and outputs it to the motor control signal output unit 49. To do.

The motor control signal output unit 49 outputs a motor control signal to the drive circuit 42 based on the input ACT control angle θta **, and the drive circuit 42 outputs three-phase (U) to the motor 13 based on the motor control signal. , V, W). The gear ratio is varied by being driven by the motor 13 and operating the variable gear ratio actuator 8 to change the ACT angle θta.

In the present embodiment, the ACT angle control unit 47 includes a position control proportional gain Kp in the position proportional control unit 47b, a first differential gain Kd and a second differential gain Kdv in the differential control unit 47c, and a torque proportional control unit according to the vehicle state. A gain calculating section 48 is provided as a gain varying means for varying the torque proportional gain Kt in 47a. The position proportional control unit 47b, the differential control unit 47c, and the torque proportional control unit 47a are respectively a position control proportional gain Kp, a first differential gain Kd, a second differential gain Kdv, and a torque proportional gain determined by the gain calculation unit 48. Based on Kt, a position proportional control amount εp1, differential control amounts εd1, εd2, and a torque proportional control amount εt1 are calculated.

More specifically, as shown in FIG. 5, the gain calculation unit 48 includes a position control proportional gain calculation unit 48 a that receives the vehicle speed V and the turning angle θt and outputs a position control proportional gain Kp, and a steering torque value τ. A torque proportional gain calculator 48b that outputs a torque proportional gain Kt with a turning angle θt as an input, a first differential gain calculator 48c that outputs a first differential gain Kd with a turning angle θt as an input, and a turning angular velocity ωt And a second differential gain calculator 48d that outputs a second differential gain Kdv.

More specifically, as shown in FIG. 6, in the position control proportional gain map 48aa provided in the position control proportional gain calculator 48a, the position control proportional gain Kp that is the output of the position control proportional gain calculator 48a is a low speed region. It is set so as to increase linearly as the vehicle speed V increases from (V0: predetermined vehicle speed threshold) and to be a constant value in a high speed region (V1: predetermined vehicle speed threshold, about 80 km / h or more). Further, the position control proportional gain Kp is set to a small value until the turning angle θt exceeds a predetermined steering angle θt0 (predetermined steering angle threshold) in the vicinity of the maximum steering angle of the steered wheels. The position control proportional gain Kp takes a large constant value regardless of the vehicle speed V when the steering angle θt is in the vicinity (500 deg to 550 deg) of the steering angle θt_end corresponding to the maximum steering angle. Further, the position control proportional gain Kp is such that the turning angle θt exceeds a predetermined steering angle θt0 in the vicinity of the maximum steering angle of the steered wheel, and the steering angle θt is in the vicinity of the steering angle θt_end corresponding to the maximum steering angle (500 deg). Until reaching the value, it increases with a predetermined inclination.

Next, as shown in FIG. 7, in the torque proportional gain map 48bb provided in the torque proportional gain calculation unit 48b, the torque proportional gain Kt that is output from the torque proportional gain calculation unit 48b has a maximum turning angle θt. Until reaching the vicinity (500 deg to 550 deg) of the steering angle θt_end corresponding to the angle, it becomes 0 regardless of the magnitude of the steering torque. The torque proportional gain Kt, which is the output of the torque proportional gain calculation unit 48b, increases when the steering angle θt is in the vicinity (500 deg to 550 deg) of the steering angle θt_end corresponding to the maximum steering angle. It increases linearly with (τ0: predetermined steering torque threshold to τ_end: maximum steering torque threshold).

As shown in FIG. 8, in the first differential gain map 48cc provided in the first differential gain calculation unit 48c, the first differential gain Kd that is the output of the first differential gain calculation unit 48c is the turning angle θt. When (absolute value) is equal to or smaller than a predetermined threshold value θt0 (| θt | ≦ θt0), the predetermined value Kdl is set (Kd = Kdl). When the turning angle θt (the absolute value thereof) is equal to or greater than the maximum turning angle θt_end (| θt | ≧ θt_end), the first differential gain Kd becomes a predetermined value Kdh that is larger than the predetermined value Kdl. (Kd = Kdh, Kdh> Kdl).

In a region where the turning angle θt (the absolute value thereof) is larger than the predetermined threshold θt0 and smaller than the maximum turning angle θt_end (θt0 <| θt | <θt_end), the first differential gain Kd is In order to perform linear interpolation between the predetermined value Kdl and the predetermined value Kdh, the predetermined value Kdl and the predetermined value Kdh are set so that the value increases as the turning angle θt increases.

As shown in FIG. 9, in the second differential gain map 48dd provided in the second differential gain calculation unit 48d, the second differential gain Kdv that is the output of the second differential gain calculation unit 48d is the turning angular velocity ωt. When (absolute value) is equal to or smaller than a predetermined turning angular velocity threshold value ωt0 (| ωt | ≦ ωt0), the predetermined value Kvdl is set (Kvd = Kvdl). When the turning angular velocity ωt (the absolute value thereof) is equal to or greater than a predetermined turning angular velocity threshold value ωt1 (| ωt | ≧ ωt1), the second differential gain Kdv is a predetermined value larger than the predetermined value predetermined value Kvdl. The values are set to be Kvdh (Kvd = Kvdh, Kvdh> Kvdl).

Then, in the region (ωt0 <| ωt | <ωt1) where the turning angular velocity ωt (the absolute value thereof) is larger than the predetermined turning angular velocity threshold ωt0 and smaller than the predetermined turning angular velocity threshold ωt1, the second differentiation is performed. The gain Kdv is set so that its value increases as the turning angular velocity ωt increases until the predetermined value Kvdl and the predetermined value Kvdh are linearly interpolated between the predetermined value Kvdl and the predetermined value Kvdh. Has been.

The IFSECU 9 includes a drive circuit 52 for lock control that supplies drive power to the solenoid 33a of the lock device 33 in addition to the drive circuit 42 for driving the motor, and the microcomputer 41 operates the drive circuit 52. A lock control unit 53 that generates a lock control signal for control is provided. In the present embodiment, the lock control unit 53 receives an IG on / off signal S_ig and an abnormal signal S_tr indicating an abnormality of the electric power steering device or the transmission ratio variable device 8 via an in-vehicle network (not shown). It has become.

When the IG on / off signal S_ig indicates “IG off”, or when the abnormal signal S_tr is input, the lock control unit 53 sets the control signal output to the drive circuit 52 to the locked state. Change to one that has the value that should be done. In the present embodiment, the drive circuit 52 includes a switching element (power MOSFET), and the lock control signal is output as the duty (on duty) of the switching element. When the lock is activated, the lock control unit 53 sets the lock control signal to “OFF (Duty = 0)”, thereby controlling the solenoid 33a to be turned off, that is, the lock device 33 to be locked.

Further, the vehicle steering apparatus of the present embodiment includes an excessive steering detection unit 55. As described above, in the vehicle steering apparatus 1 including the transmission ratio variable device 8, the excessive steering operation (excess steering) up to the maximum steering angle of the steered wheels 6, that is, the vicinity of the steering end becomes a problem. In view of this point, in the present embodiment, the microcomputer 41 is provided with an excessive steering detection unit 55 that detects the occurrence of such excessive steering. When the microcomputer 41 detects the occurrence of excessive steering according to the flowchart of FIG. 10 configured in the excessive steering detection unit 55, the microcomputer 41 controls the lock device 33 to be in a locked state.

More specifically, in this embodiment, the steering angle θt and the ACT angular velocity ωta are input to the excessive steering detection unit 55. In the present embodiment, the turning angle θt is calculated by the turning angle calculating means based on the motor rotation angle θm output from the rotation angle sensor 46 to the steer turning angle θts calculated based on the steering angle θs. A calculated value obtained by adding the ACT angle θta is used (see FIGS. 2A and 2B). And the excessive steering detection part 55 detects generation | occurrence | production of excessive steering based on each state quantity input.

Specifically, the excessive steering detection unit 55 determines whether or not the absolute value of the detected ACT angular velocity ωta is larger than a predetermined ACT angular velocity ωtaα. Next, it is determined whether or not the detected turning angle θt is in the vicinity of the steering angle θt_end corresponding to the mechanical maximum steering angle of the steered wheels 6.
The absolute value of the ACT angular velocity ωta is larger than the predetermined ACT angular velocity ωtaα, and the detected turning angle θt is in the vicinity of the steering angle θt_end corresponding to the mechanical maximum steering angle of the steered wheels 6, and the above state If the steering angle continues for a certain period of time, the driver determines that he is trying to turn the steering wheel at a higher speed than the limit even though the turning angle is already near the maximum steering angle, and locks. An excessive steering detection signal S_ed is output to the control unit 53.

Next, a processing procedure of the excessive steering detection unit in this embodiment will be described.
As shown in the flowchart of FIG. 10, when the microcomputer 41 detects each of the state quantities (the turning angle θt and the ACT angular velocity ωta) (step 101), the absolute value of the ACT angular velocity ωta is larger than a predetermined ACT angular velocity ωtaα. (| Ωta |> ωtaα, step 102), and when the absolute value of the ACT angular velocity ωta is larger than the predetermined ACT angular velocity ωtaα (step 102: YES), the turning angle θt of the steered wheels 6 It is determined whether or not it is in the vicinity of the steering angle θt_end corresponding to the mechanical maximum steering angle (| θt_end | − | θt | <γ, step 103).

When the steered angle θt is in the vicinity of the steered angle θt_end corresponding to the mechanical maximum steered angle of the steered wheels 6 (step 103: YES), it is determined that excessive steering occurs, and the excessive steering detection counter CTR1. Is counted up (step 104). If the excessive steering detection counter CTR1 is counting up (step 104: YES), the excessive steering detection signal S_ed is output to the lock control unit 53 (step 106).

If the excess steering detection counter CTR1 has not been counted up (step 104: NO), the excess steering detection counter CTR1 is incremented (step 105), and the process returns to step 101. If step 102 or step 103 is NO, no processing is performed.

Further, in the present embodiment, the excessive steering detection signal S_ed output from the excessive steering detection unit 55 is input to the lock control unit 53 together with the ACT angular velocity ωta. Then, the lock control unit 53 receives the excessive steering detection signal S_ed.
And when the absolute value of the ACT angular velocity ωta is less than the predetermined ACT angular velocity ωta0 continues for a predetermined time or longer, the above-described lock control is turned “ON”.

Next, a processing procedure of the lock control unit in the present embodiment will be described.
As shown in the flowchart of FIG. 11, when the microcomputer 41 detects each state quantity (excess steering detection signal S_ed and ACT angular velocity ωta) (step 201), it determines whether the excessive steering detection signal S_ed is on or off (step 201). Step 202) When the excessive steering detection signal S_ed is on, it is determined whether or not the absolute value of the ACT angular velocity ωta is smaller than a predetermined ACT angular velocity ωta0 (| ωta | <ωta0, step 203).

If the absolute value of the ACT angular velocity ωta is smaller than the predetermined ACT angular velocity ωta0 (step 203: YES), it is determined that excessive steering is suppressed, and it is determined whether or not the excessive steering suppression detection counter CTR2 is counting up. Determination is made (step 204). If the excessive steering suppression detection counter CTR2 is counting up (step 204: YES), the lock control is turned on (step 206).

If the excessive steering suppression detection counter CTR2 has not been counted up (step 204: NO), the excessive steering suppression detection counter CTR2 is incremented (step 205), and the process returns to step 201. If step 202 or step 203 is NO, no processing is performed.

That is, it is possible to reduce the load on the lock device 33 while avoiding the high speed operation of the transmission ratio variable device 8. In combination with the various gain variable controls described above, it is possible to prevent oscillation associated with the use of high gain.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) When the steered angle exceeds a predetermined steered angle near the maximum steered angle of the steered wheels, the higher the vehicle speed or the greater the steered angle, the more the position control proportional gain is increased. Even if there is a deviation, a large current command is calculated, so that the motor torque generated by the drive motor, that is, the holding torque of the transmission ratio variable device also increases. Further, when the turning angle exceeds a predetermined steering angle in the vicinity of the maximum steering angle of the steered wheels, the damper effect increases by increasing the first differential gain as the turning angle increases. As a result, the “twisted state” described above is less likely to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

(2) When the turning angular velocity exceeds a predetermined turning angular velocity, the damper effect can be further increased by increasing the second differential gain as the turning angular velocity increases. As a result, the “twisted state” described above is more difficult to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

(3) When the steering angle exceeds a predetermined steering angle near the maximum steering angle of the steered wheels, the holding torque of the transmission ratio variable device is further increased by increasing the torque proportional gain as the steering torque increases. be able to. As a result, the “twisted state” described above is more difficult to occur, and the steering operation that reaches the vicinity of the maximum steering angle of the steered wheels can be suppressed.

(4) When it is determined that excessive steering occurs, the lock control is turned “ON” when the absolute value of the ACT angular velocity ωta is less than the predetermined ACT angular velocity ωta0. That is, by operating the lock device 33 while avoiding the high speed operation of the transmission ratio variable device 8, the load on the lock device 33 can be reduced. In combination with each of the gain variable controls, oscillation associated with the use of high gain can be prevented.

In addition, you may change this embodiment as follows.
In the present embodiment, the various gains are switched in the vicinity of the steering angle θt_end where the steering angle θt corresponds to the mechanical maximum steering angle of the steered wheels 6.
However, the present invention is not limited to this, and various gains may be switched, for example, on the steering angle θs side (| θs |> | θs_end |) instead of the turning angle θt side. In this case, the steering angle θs_end is a steering angle corresponding to the steering end.

In this embodiment, when the second differential gain Kdv is increased based on the steering speed ωs, the second differential gain Kdv corresponding to the steering speed ωs before the decrease is maintained even after the steering speed ωs is decreased. It is good to have a configuration. As a result, it is possible to prevent “fluctuation” associated with a sudden change in the second differential gain Kdv.

As shown in FIG. 1, the transmission ratio variable device 8 of the present embodiment is of a so-called intermediate shaft type, but is not limited to this, and other types of transmission ratios such as a column type and a steering gear integrated type. You may actualize to the thing provided with the variable apparatus.

1: vehicle steering device, 2: steering, 3: steering shaft,
4: rack and pinion mechanism, 5: rack shaft, 6: steered wheel,
8: Transmission ratio variable device, 9: IFSECU, 10: first shaft,
11: second shaft, 12: differential mechanism, 13: motor, 13a: motor shaft,
14: housing, 14a: upper wall part, 15: connecting part, 17: EPS actuator, 19: EPSECU, 21, 22: circular rice spline,
23: Flex spline, 26: Wave generator, 27: Spiral cable device,
31: Lock arm, 32: Lock holder, 33: Lock device,
33a: Solenoid, 35: Torque sensor, 36: Steering angle sensor, 37: Vehicle speed sensor, 38: In-vehicle network, 41: Microcomputer, 42: Motor drive circuit,
43: ACT angle command unit, 43a: differential steer control calculation unit,
43b: gear ratio variable control calculation unit, 44: adder, 46a: subtractor, 46b: adder,
47: ACT angle control unit, 47a: torque proportional control unit, 47b: position proportional control unit,
47c: differentiation control unit, 48: gain calculation unit,
48a: Position control proportional gain calculation unit, 48aa: Position control proportional gain map,
48b: Torque proportional gain calculation unit, 48bb: Torque proportional gain map,
48c: first differential gain calculation unit, 48cc: first differential gain map,
48d: second differential gain calculation unit, 48dd: second differential gain map,
49: Motor control signal output unit, 52: Solenoid drive circuit, 53: Lock control unit,
55: Excess steering detection unit,
θs: steering angle, ωs: steering speed,
θt: turning angle, ωt: turning angular velocity, ωt0: predetermined turning angular velocity threshold,
ωt1: predetermined turning angular velocity threshold, ωtα: predetermined turning angular velocity threshold,
θt0: predetermined turning angle threshold, θt_end: maximum turning angle, θts: steer turning angle,
θta: ACT angle, θta *: ACT command angle, θta **: ACT control angle, Δθta: deviation,
ωta: ACT angular velocity, ωta0: predetermined ACT angular velocity, ωtaα: predetermined ACT angular velocity,
τ: steering torque, τ0: predetermined steering torque threshold, τ_end: maximum steering torque threshold,
V: vehicle speed, V0: predetermined vehicle speed threshold, V1: predetermined vehicle speed threshold,
θls *: Differential steering command angle, θgr *: Gear ratio variable command angle,
Kt: torque proportional gain, εt1: torque proportional control amount,
Kp: position control proportional gain, εp1: position proportional control amount, Kd: first differential gain,
εd1: first differential control amount, Kdv: second differential gain, εd2: second differential control amount,
S_ed: excessive steering detection signal, S_ig: IG on / off signal, S_tr: abnormal signal CTR1: excessive steering detection counter, C1: excessive steering detection counter count-up CTR2: excessive steering suppression detection counter, C2: excessive steering suppression detection counter count up

Claims (4)

By adding the second turning angle of the steered wheel based on the motor drive to the first steered angle of the steered wheel based on the steering operation, the steering angle between the steering wheel and the steered angle of the steered wheel is increased. A transmission ratio variable device that varies the transmission ratio;
Steering angle detection means for detecting the steering angle;
Vehicle speed detection means for detecting the vehicle speed;
A turning angle calculation means for detecting or calculating a turning angle of the turning wheel;
Second turning angle calculation means for detecting or calculating the second turning angle;
Target value output means for outputting a target value of the second turning angle based on a steering angle and a vehicle speed;
Control amount output means for outputting a control amount of the motor based on the target value;
Motor control means for controlling the motor based on the control amount,
The control amount output means includes
Position proportional gain determining means for determining a position proportional gain based on the vehicle speed and the steering angle;
Position proportional control means for outputting a position deviation proportional term control amount by multiplying the deviation between the target value of the second turning angle and the detected or calculated second turning angle by the position proportional gain; ,
First differential gain determining means for determining a first differential gain based on the steering angle;
Differential control means for outputting a differential control amount based on the differential change amount of the second turning angle;
Subtracting means for calculating a subtraction value obtained by subtracting the differential control amount from the position deviation proportional term control amount;
The differential control means includes
First differential control means for outputting, as the differential control amount, a first differential control amount obtained by multiplying the differential change amount of the second turning angle by the first differential gain;
The position proportional gain determining means includes
When the steered angle exceeds a predetermined steered angle set near the maximum steered angle of the steered wheels, the higher the vehicle speed or the greater the steered angle, the higher the position proportional gain,
The first differential gain determining means includes
When the steered angle exceeds a predetermined steered angle set near the maximum steered angle of the steered wheels, the larger the steered angle, the higher the first differential gain;
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 1,
The control amount output means includes second differential gain determination means for determining a second differential gain based on a turning angular velocity calculated by differentiating the turning angle,
The differential control means includes second differential control means for outputting, as the differential control quantity, a second differential control quantity obtained by multiplying the first differential control quantity by the second differential gain,
The second differential gain determining means increases the second differential gain as the turning angular speed increases when the turning angular speed exceeds a predetermined turning angular speed.
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to claim 2,
Steering torque detection means for detecting steering torque is provided,
The control amount output means includes
Torque proportional gain determining means for determining a torque proportional gain based on the turning angle;
Torque proportional control means for outputting a torque proportional term control amount by multiplying the steering torque by the torque proportional gain;
Adding means for adding the torque proportional term control amount to the subtraction value;
The torque proportional gain determining means, when the steering angle exceeds a predetermined steering angle set in the vicinity of the maximum steering angle of the steered wheels, increasing the torque proportional gain as the steering torque increases;
A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to any one of claims 1 to 3, wherein the transmission ratio variable device includes a lock device that mechanically fixes the second turning angle, and an operation of the lock device. Lock control means for controlling the steering wheel, wherein the lock control means exceeds a predetermined steering angle set in the vicinity of the maximum steering angle of the steered wheel and the angular velocity of the second steering angle is A vehicle steering apparatus, wherein the locking device is operated when an absolute value is less than a predetermined threshold value.

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