JP2011121474A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the possibility of securing a maximum steered state in emergency avoiding. <P>SOLUTION: This steering device 1 for a vehicle includes an electric power steering device 19 for imparting steering assisting force generated by an electric motor 25 driven in response to operation of a steering member 2 to a steered mechanism 10 and a transmission ratio variable mechanism 5 for variably setting the transmission ratio being the ratio of a steered angle θ2 of the steered mechanism 10 to an operation angle θ1 of the steering member 2. Electric power of the electric motor 25 is limited in response to a predetermined electric power limiting condition. A control part 29 determines whether or not an operation state of the vehicle is a predetermined emergency avoiding state. The control part 29 sets an auxiliary target value corresponding to a target value of the steering assisting force to an ordinary target value when not in the emergency avoiding state, and sets the value in an emergency avoiding target value when in the emergency avoiding state. The control part 29 sets the target transmission ratio to the ordinary transmission ratio when not in the emergency avoiding state, and sets the ratio in the emergency avoiding transmission ratio when in the emergency avoiding state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus including an electric power steering device and a transmission ratio variable device.

The electric power steering device is configured to assist steering by transmitting a driving force of an electric motor driven in accordance with an operation of a steering wheel to a steering mechanism. For example, a target value related to the steering assist force is set according to the steering torque applied to the steering wheel, and the electric motor is controlled according to this target value.
The transmission ratio variable device is a device that variably sets the ratio (transmission ratio) between the steering wheel operating angle and the steering angle of the steering device. The transmission ratio variable device transmits the rotation of the input shaft on the steering wheel side to the output shaft on the steering device side while increasing or decreasing the speed. The transmission ratio is variably set according to the vehicle speed, for example. For example, the steering wheel operation during parking can be reduced by increasing the transmission ratio as the vehicle speed decreases.

  A vehicle steering apparatus including an electric power steering apparatus and a transmission ratio variable apparatus is disclosed in Patent Document 1, for example. In the configuration of Patent Document 1, when the steering wheel is suddenly operated during low-speed traveling (when the transmission ratio is large), the transmission ratio is reduced. Thereby, the control followability of the electric power steering apparatus is ensured.

Japanese Patent Laid-Open No. 2005-112025 JP 2009-10802 A

  Since the transmission ratio increases during low-speed traveling, a large current is supplied to the electric motor of the electric power steering device in order to follow the higher the steering speed. On the other hand, in order to avoid heat generation and abnormal rotation of the electric motor, when a large current is supplied to the electric motor, control (current limiting control) for limiting the current may be executed. Therefore, if sudden steering is performed in a low-speed traveling state, current limit control is executed, and steering assistance may not be obtained.

  When sudden steering is performed for emergency avoidance, it is preferable that steering assistance is performed for as long as possible and a steering angle as large as possible is secured. The configuration of Patent Document 1 ensures the followability of the electric power steering device by reducing the transmission ratio at the time of sudden steering, but at the time of emergency avoidance, it is not always possible to perform the maximum switching before the current limit control is executed. It is not always possible to ensure the steering amount (steering angle).

  SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle steering apparatus that increases the possibility of ensuring maximum steering during emergency avoidance.

  In order to achieve the above object, the invention according to claim 1 is an electric motor that applies to the steering mechanism (10) the steering assist force generated by the electric motor (25) driven in accordance with the operation of the steering member (2). A power steering device (19) and a transmission ratio variable device (variably setting a transmission ratio, which is a ratio of the turning angle (θ2) of the steering mechanism (10) to the operating angle (θ1) of the steering member (2)) 5), power limiting means 86 for limiting the electric power of the electric motor (25) according to a predetermined power limiting condition, and emergency avoidance determining means (51) for determining whether the driving state of the vehicle is a predetermined emergency avoidance state. , 81) and the auxiliary target value corresponding to the target value of the steering assist force are set to the normal target value when the emergency avoidance determination means (81) determines that the emergency avoidance state is not set, and the emergency avoidance determination By means (81) When the emergency avoidance state is determined, auxiliary target value setting means (80, 82, 83) for setting an emergency avoidance target value different from the normal target value, and target transmission which is the target value of the transmission ratio The ratio (R) is set to the normal transmission ratio when the emergency avoidance determining means (51) determines that the emergency avoidance state is not established, and the emergency avoidance determining means (51) determines that the emergency avoidance state is established. And a target transmission ratio setting means (50, 52, 53) for setting an emergency avoidance transmission ratio different from the normal transmission ratio. In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in below-mentioned embodiment, it is not the meaning which limits a claim to embodiment. The same applies hereinafter.

  According to this configuration, in the emergency avoidance state, the assist force target value and the target transmission ratio are respectively set to an emergency avoidance target value and an emergency avoidance transmission ratio that are different from the normal time (when not in the emergency avoidance state) (for example, Set according to different characteristics). Accordingly, by appropriately setting the emergency avoidance target value and the emergency avoidance transmission ratio, for example, the steering assist force generation time until the electric motor power (supply power) is limited is maximized, or the electric motor power is It is possible to maximize the amount of change in the turning angle until is limited.

The power limit condition may include the motor current value reaching a predetermined limit value. Further, the power limit condition may include that the state where the motor current value reaches the predetermined limit value continues for a predetermined time.
The emergency avoidance state may include a sudden steering state in which the operation speed of the steering member exceeds a predetermined threshold value (claim 2). The emergency avoidance state may include an abrupt deceleration state in which the acceleration of the vehicle is less than a predetermined negative threshold (claim 3).

The auxiliary target value may be a target drive value (target current value, target voltage value, etc.) for the electric motor, or may be a target value of torque to be generated from the electric motor.
The target transmission ratio may be a value that directly corresponds to the transmission ratio, or may be another value that can be converted into a transmission ratio.
The combination of the emergency avoidance target value and the emergency avoidance transmission ratio may be set so that the steering assist force generation time and / or the turning angle change amount until the power limit is executed is maximized in the emergency avoidance state. preferable. Such a combination of the emergency avoidance target value and the emergency avoidance transmission ratio can be determined by a steering experiment (including simulation).

  More specifically, the combination of the emergency avoidance target value and the emergency avoidance transmission ratio can be determined by applying a method for obtaining a multivariable optimal solution using learning. For example, by setting various auxiliary target values and target transmission ratios, conducting a steering experiment (including simulation) corresponding to an emergency avoidance state, and evaluating the time until power limit is executed and the turning angle change amount Also good. Then, the combination of the auxiliary target value and the target transmission ratio with the best evaluation score may be determined as the combination of the emergency avoidance target value and the emergency avoidance transmission ratio. In the steering experiment (learning), for example, according to the learning rules shown in Table 1 below, the combination of the auxiliary target value and the target transmission ratio for the next steering experiment may be determined based on the result of each steering experiment (evaluation). Good.

By following this learning rule, it is possible to converge to an appropriate auxiliary target value and target transmission ratio.
According to a fourth aspect of the present invention, when a predetermined emergency avoidance operation is performed on the steering member (2), an evaluation value relating to a time until the power limitation by the power limitation means (86) is executed, The emergency avoidance target value and the emergency value are set so that the sum total with the evaluation value related to the turning angle change amount of the turning mechanism (10) until the power restriction by the power restriction means (86) is executed is maximized. The vehicle steering device (1) according to any one of claims 1 to 3, wherein an avoidance transmission ratio is defined. With this configuration, it is possible to maximize the time during which the steering assist force is generated and the amount of change in the turning angle as much as possible in the emergency avoidance state.

The emergency avoidance operation may be, for example, an operation at a constant steering speed determined so that a constant turning angle change amount (for example, 1000 degrees) is obtained within a certain time (for example, 10 seconds).
According to a fifth aspect of the present invention, when a predetermined emergency avoidance operation is performed on the steering member (2), the time until the power limitation by the power limitation means (86) is executed is the longest. The vehicle steering apparatus according to any one of claims 1 to 3, wherein the emergency avoidance target value and the emergency avoidance transmission ratio are defined. With this configuration, it is possible to lengthen the time during which the steering assist force is generated in the emergency avoidance state.

  According to a sixth aspect of the present invention, when a predetermined emergency avoidance operation is performed on the steering member (2), the turning mechanism (10) until the power limitation by the power limitation means (86) is executed. The vehicle steering device (1) according to any one of claims 1 to 3, wherein the emergency avoidance target value and the emergency avoidance transmission ratio are determined so that the amount of change in the turning angle of ). With this configuration, it is possible to increase the turning angle change amount until the power limitation is executed in the emergency avoidance state.

  According to the seventh aspect of the present invention, when the emergency avoidance determining means (51, 81) determines that the state is an emergency avoidance state, the time until the power limiting by the power limiting means (86) is executed and And / or an evaluation means (S9) for monitoring and evaluating the amount of change in the turning angle, and an emergency avoidance application value updating means for updating the emergency avoidance target value and the emergency avoidance transmission ratio based on the evaluation result by the evaluation means ( The vehicle steering device (1) according to any one of claims 1 to 6, further comprising S10).

  According to this configuration, as a result of applying the emergency avoidance target value and the emergency avoidance transmission ratio, the time until the electric motor is subjected to power limitation and / or the amount of change in the turning angle is monitored, and an evaluation is given to them. It is done. Based on the evaluation result, the emergency avoidance target value and the emergency avoidance transmission ratio are updated. Thereby, when it becomes an emergency avoidance state next, the emergency avoidance target value and emergency avoidance transmission ratio which were excellent in the evaluation result can be applied. In this way, the emergency avoidance target value and the emergency avoidance transmission ratio can be updated by learning during actual system operation. As a result, the emergency avoidance target value and the emergency avoidance transmission ratio adapted to the actual use state incorporated in the vehicle can be set.

  The invention according to claim 8 is characterized in that the evaluation means evaluates whether the time until the power limitation is executed is larger or smaller than a predetermined reference time, and the emergency avoidance application value updating means. When the time until the power limit is executed is larger than the reference time, the emergency avoidance target value is increased, and the time until the power limit is executed is compared with the reference time. The vehicle steering apparatus according to claim 7, wherein the emergency avoidance target value is reduced when it is small. When the time until the power limit is executed is long, there is a margin for supplying more electric power to the electric motor. Therefore, the emergency avoidance target value is increased when the time until the power limit is executed is increased, and conversely, the emergency avoidance target value is decreased when the time until the power limit is executed is decreased. The value can be led to a reasonable value.

  According to a ninth aspect of the present invention, the evaluation means evaluates whether the turning angle change amount until the power restriction is executed is larger or smaller than a predetermined reference turning angle change amount. The emergency avoidance application value updating means reduces the emergency avoidance transmission ratio when the turning angle change amount until the power restriction is executed is larger than the reference turning angle change amount, and the power The vehicle steering apparatus according to claim 7 or 8, wherein the emergency avoidance transmission ratio is increased when a turning angle change amount until the restriction is executed is smaller than the reference turning angle change amount. It is. When the turning angle change amount until the power limit is small, it is preferable to secure a larger turning angle change amount. Further, when the amount of change in the turning angle until the power limit is large, the possibility that the power limit is executed early increases. Therefore, the emergency avoidance transmission ratio is increased to a reasonable value by increasing the emergency avoidance transmission ratio when the turning angle change amount is small, and conversely by decreasing the emergency avoidance transmission ratio when the turning angle change amount is large. Can lead.

It is a mimetic diagram showing a schematic structure of a steering device for vehicles concerning one embodiment of the present invention. It is the side view which represented a part of transmission ratio variable mechanism with the cross section. It is a control block diagram related to a transmission ratio variable mechanism. It is a characteristic view for setting a basic transmission ratio. It is a control block diagram related to a steering assist force applying mechanism (electric power steering device). It is a characteristic view for setting a basic target current value. It is a flowchart for demonstrating the setting of a target transmission ratio and a target electric current value.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus 1 according to an embodiment of the present invention. The vehicle steering device 1 performs steering by applying a steering torque applied to a steering member 2 such as a steering wheel to the left and right steered wheels 4L and 4R via a steering shaft 3 as a steering shaft. And has a VGR (Variable Gear Ratio) function capable of changing the transmission ratio θ2 / θ1 as the ratio of the turning angle θ2 of the steered wheels to the operation angle θ1 of the steering member 2.

The vehicle steering apparatus 1 includes a steering member 2 and a steering shaft 3 connected to the steering member 2. The steering shaft 3 includes first to third shafts 11 to 13 arranged coaxially with each other. The first axis A as the central axis of the first to third shafts 11 to 13 is also the rotational axis of the first to third shafts 11 to 13.
Hereinafter, the axial direction S of the steering shaft 3 is simply referred to as the axial direction S, the radial direction R of the steering shaft 3 is simply referred to as the radial direction R, and the circumferential direction C of the steering shaft 3 is simply referred to as the circumferential direction C.

  A steering member 2 is connected to one end of the first shaft 11 so as to be able to rotate together. The other end portion of the first shaft 11 and the one end portion of the second shaft 12 are connected so as to be capable of differential rotation via a transmission ratio variable mechanism 5 (transmission ratio variable device) as a differential mechanism. The other end of the second shaft 12 and one end of the third shaft 13 are connected via a torsion bar 14 so that they can be elastically rotated relative to each other and can transmit power.

The other end of the third shaft 14 is connected to the steered wheels 4L and 4R via the universal joint 7, the intermediate shaft 8, the universal joint 9, the steering mechanism 10, and the like.
The steered mechanism 10 includes a pinion shaft 15 connected to the universal joint 9, and a rack shaft 16 as a steered shaft that has a rack 16a that meshes with the pinion 15a at the tip of the pinion shaft 15 and extends in the left-right direction of the vehicle. Yes. Knuckle arms 18L and 18R are connected to the pair of ends of the rack shaft 16 via tie rods 17L and 17R, respectively.

  With the above configuration, the rotation of the steering member 2 is transmitted to the steering mechanism 10 via the steering shaft 3 and the like. In the turning mechanism 10, the rotation of the pinion 15 a is converted into the axial movement of the rack shaft 16. The axial movement of the rack shaft 16 is transmitted to the corresponding knuckle arms 18L and 18R via the tie rods 17L and 17R, and the knuckle arms 18L and 18R rotate. Accordingly, the corresponding steered wheels 4L and 4R connected to the knuckle arms 18L and 18R are respectively steered.

  The transmission ratio variable mechanism 5 is for changing the rotation transmission ratio (transmission ratio θ2 / θ1) between the first and second shafts 11 and 12 of the steering shaft 3. In this embodiment, the nutation gear is used. It is a mechanism. The transmission ratio variable mechanism 5 includes an input member 20 provided at the other end of the first shaft 11, an output member 22 provided at one end of the second shaft 12, and the input member 20 and the output member 22. And a bearing ring unit 39 interposed therebetween.

The input member 20 is connected to the first shaft 11 so as to be coaxial and rotatable, and the output member 22 is connected to the second shaft 12 and coaxially rotatable. The first axis A is also the center axis and the rotation axis of the input member 20 and the output member 22.
The output member 22 is connected to the steered wheels 4L and 4R via the second shaft 12, the steered mechanism 10, and the like.

The bearing ring unit 39 has a second axis B as a central axis inclined with respect to the first axis A, and an inner ring 391 as a first bearing ring and an outer ring as a second bearing ring. 392 and rolling elements 393 such as balls interposed between the inner ring 391 and the outer ring 392.
The inner ring 391 connects the input member 20 and the output member 22 so as to be differentially rotatable, and is engaged with each of the input member 20 and the output member 22 so as to be able to transmit rotation. The inner ring 391 is rotatable about the second axis B by being rotatably supported by the outer ring 392 via the rolling elements 393. Further, the inner ring 391 can rotate around the first axis A as the transmission ratio variable mechanism motor 23, which is an electric motor as an actuator for driving the outer ring 392, is driven. The inner ring 391 and the outer ring 392 can perform Coriolis motion (swing motion) around the first axis A.

The transmission ratio variable mechanism motor 23 is arranged coaxially with the first and second shafts 11 and 12 in order to drive the transmission ratio variable mechanism 5. The first axis A is also the central axis of the transmission ratio variable mechanism motor 23. The transmission ratio variable mechanism motor 23 changes the transmission ratio θ2 / θ1 by changing the rotational speed of the outer ring 392 around the first axis A.
In this embodiment, the transmission ratio variable mechanism motor 23 is composed of a brushless motor disposed coaxially with the steering shaft 3, and includes a cylindrical rotor 231 that holds the raceway ring unit 39, a rotor 231, and a housing 24. And a stator 232 fixed to the main body.

  The vehicle steering device 1 further includes a steering assist force applying mechanism 19 (electric power steering device) for applying a steering assist force to the steering shaft 3. The steering assist force applying mechanism 19 includes the second shaft 12 as an input shaft continuous with the output member 22 of the transmission ratio variable mechanism 5, the third shaft 13 as an output shaft continuous with the steering mechanism 10, A torque sensor 44 for detecting torque transmitted between the second shaft 12 and the third shaft 13, a steering assist motor 25 as a steering assist actuator, the steering assist motor 25, and a third shaft. 13 and a speed reduction mechanism 26 interposed between them.

The steering assist motor 25 is an electric motor such as a brushless motor. The output of the steering assist motor 25 is transmitted to the third shaft 13 via the speed reduction mechanism 26.
The speed reduction mechanism 26 is composed of, for example, a worm gear mechanism, and is connected to a worm shaft 27 as a drive gear connected to the output shaft 25 a of the steering assist motor 25, meshed with the worm shaft 27 and connected to the third shaft 13 so as to be able to rotate together. And a worm wheel 28 as a driven gear.

The transmission ratio variable mechanism 5 and the steering assist force applying mechanism 19 are accommodated in a housing 24. The housing 24 is disposed in a passenger compartment (cabin) of the vehicle. The housing 24 may be disposed so as to surround the intermediate shaft 8 or may be disposed in the engine room of the vehicle.
The driving of the transmission ratio variable mechanism motor 23 and the steering assist motor 25 is controlled by a control unit 29 including a CPU, a RAM, and a ROM, respectively. The control unit 29 is connected to the transmission ratio variable mechanism motor 23 via the drive circuit 40, and is connected to the steering assist motor 25 via the drive circuit 41.

The control unit 29 includes an operation angle sensor 42, a motor resolver 43 as a rotation angle sensor that detects the rotation angle of the rotor 231 of the transmission ratio variable mechanism motor 23, a torque sensor 44, a turning angle sensor 45, and a vehicle speed sensor 46. Are connected to each other.
From the operation angle sensor 42, a signal regarding the rotation angle of the first shaft 11 is input to the control unit 29 as a value corresponding to the operation angle θ <b> 1 that is the operation amount from the straight position of the steering member 2.

From the motor resolver 43, a signal regarding the rotation angle θr of the rotor 231 of the transmission ratio variable mechanism motor 23 is input to the control unit 29.
From the torque sensor 44, a signal regarding the torque acting between the second and third shafts 12, 13 is input to the control unit 29 as a value corresponding to the steering torque T acting on the steering member 2.

From the turning angle sensor 45, a signal regarding the rotation angle of the third shaft 13 is input to the control unit 29 as a value corresponding to the turning angle θ2.
From the vehicle speed sensor 46, a signal regarding the vehicle speed V is input to the control unit 29.
The control unit 29 controls the drive of the transmission ratio variable mechanism motor 23 and the steering assist motor 25 based on the signals of the sensors 42 to 46.

  With the above configuration, the torque from the steering member 2 and the torque from the transmission ratio variable mechanism 5 are transmitted to the steering mechanism 10 via the steering assist force applying mechanism 19. Specifically, the steering torque input to the steering member 2 is input to the input member 20 of the transmission ratio variable mechanism 5 via the first shaft 11 and input from the input member 20 to the inner ring 391. In addition to the torque from the steering member 2, torque from the transmission ratio variable mechanism motor 25 transmitted to the inner ring 391 via the outer ring 392 and the rolling elements 393 is transmitted to the inner ring 391, and these torques are output to the output member 22. Is transmitted to. The torque transmitted to the output member 22 is transmitted to the second shaft 12. The torque transmitted to the second shaft 12 is transmitted to the torsion bar 14 and the third shaft 13, and combined with the output (assist torque) from the steering assist motor 25, the universal joint 7, the intermediate shaft 8, and the universal shaft. This is transmitted to the steering mechanism 10 via the joint 9.

Thus, the power transmission path D which transmits the torque of the steering member 2 to the steering mechanism 10 is configured. The power transmission path D includes the first shaft 11, the input member 20, the inner ring 391, the output member 22, the second shaft 12, the torsion bar 14 and the third shaft 13, the universal joint 7, the intermediate shaft 8, and the universal joint 9. This is a route through
FIG. 2 is a side view showing a part of the transmission ratio variable mechanism 5 in cross section. The input member 20 is formed in a ring shape. By providing the first concavo-convex engaging portions 64 on the opposing surfaces of the input member 20 and the inner ring 391, the input member 20 and the inner ring 391 can transmit power. The output member 22 is also formed in a ring shape. By providing the second uneven engagement portion 67 on each of the opposing surfaces of the inner ring 391 and the output member 22, the inner ring 391 and the output member 22 can transmit power.

  The first concave-convex engaging portion 64 is formed on the first convex portion 65 formed on the power transmission surface 70 as one end surface of the input member 20 and the first end surface 71 as one end surface of the inner ring 391. 1st recessed part 66 engaged with the 1 convex part 65 is included. The power transmission surface 70 and the first end surface 71 are opposed to each other in the axial direction S of the steering shaft 3, and the first uneven engagement portion 64 can transmit power to the power transmission surface 70 and the first end surface 71. Engage with. Of course, the arrangement of the first convex portion 65 and the arrangement of the first concave portion 66 may be interchanged.

  The second concavo-convex engaging portion 67 is formed on the second convex portion 68 formed on the power transmission surface 72 as one end surface of the output member 22 and the second end surface 73 as the other end surface of the inner ring 391. 2nd recessed part 69 engaged with the 2 convex part 68 is included. The power transmission surface 72 and the second end surface 73 are opposed to each other in the axial direction S of the steering shaft 3, and the second uneven engagement portion 67 can transmit power to the power transmission surface 72 and the second end surface 73. Engage with. Of course, the arrangement of the second convex portion 68 and the arrangement of the second concave portion 69 may be interchanged.

  The first convex portions 65 are formed at equal intervals over the entire circumference of the input member 20 in the circumferential direction. Similarly, the first recesses 66 are formed at equal intervals over the entire circumference of the inner ring 391 in the circumferential direction. For example, 38 first protrusions 65 are formed. The number of first recesses 66 is different from the number of first projections 65 (for example, 40). Depending on the difference between the number of first protrusions 65 and the number of first recesses 66, differential rotation can be generated between the input member 20 and the inner ring 391.

Since the second axis B of the inner ring 391 is inclined by a predetermined angle θ with respect to the first axis A of the input member 20 and the output member 22, some of the plurality of first convex portions 65 are included. Only the first convex portion 65 and only a part of the first concave portions 66 of the plurality of first concave portions 66 mesh with each other.
Similarly, the second protrusions 68 are formed at equal intervals over the entire circumference of the output member 22 in the circumferential direction. The second recesses 69 are formed at equal intervals over the entire circumference of the inner ring 391 in the circumferential direction. For example, 40 second protrusions 68 are formed. The number of second recesses 69 may be the same as the number of second protrusions 68.

Since the second axis B of the inner ring 391 is inclined by a predetermined angle θ with respect to the first axis A of the input member 20 and the output member 22, a part of the plurality of second convex portions 68 is formed. Only the second convex portion 68 and only a part of the second concave portions 69 among the plurality of second concave portions 69 mesh with each other.
Next, an example of the operation of the transmission ratio variable mechanism 5 will be described. In the following, (i) the rotation of the rotor 231 of the transmission ratio variable mechanism motor 23 is restricted, and (ii) the rotor 231 of the transmission ratio variable mechanism motor 23 is rotating, and the input member 20 A case where rotation is restricted and a case where (iii) the rotor 231 of the transmission ratio variable mechanism motor 23 is rotating and the input member 20 is rotating will be described. The rotation of the rotor 231 can be restricted by a lock mechanism (not shown) or by controlling the transmission ratio variable mechanism motor 23 to a rotation stop state.

In any of the cases (i), (ii), and (iii), the number of the first convex portions 65 of the first concave / convex engaging portion 64 is 38 and the number of the first concave portions 66 is 40, In the following description, it is assumed that the number of the second convex portions 68 of the second concave-convex engaging portion 67 is 40 and the number of the second concave portions 69 is 40.
In the case of (i) above, that is, when the rotation of the rotor 231 of the transmission ratio variable mechanism motor 23 is restricted, when the first shaft 11 is rotated by the operation of the steering member 2, the first of the input member 20 The convex portion 65 rotates around the first axis A. At this time, the bearing ring unit 39 does not perform the Coriolis motion that rotates around the first axis A, and only the inner ring 391 rotates around the second axis B. By this rotation, the inner ring 391 provided with the first recess 66 is rotated, and the second shaft 12 is further rotated. As a result, the inner ring 391 rotates 38/40 when the input member 20 rotates once. At this time, the output member 22 rotates 38/40. That is, the rotation of the input member 20 is decelerated to 19/20.

  In the case of (ii) above, that is, when the rotor 231 of the transmission ratio variable mechanism motor 23 is rotating and the rotation of the input member 20 is restricted by the driver holding the steering member 2. As the rotor 231 rotates around the first axis A, the bearing ring unit 39 performs a Coriolis motion. As a result, the inner ring 391 attempts to rotate the input member 20 and the output member 22 in the opposite directions. However, because the rotation of the input member 20 is restricted, only the output member 22 rotates. At this time, as a result of the number of the first concave portions 66 being increased by two as compared with the number of the first convex portions 65, when the outer ring 392 of the track ring unit 39 makes one rotation, the inner ring 391 The phase advances by an amount corresponding to the difference in the number of teeth (two). This is the rotation of the inner ring 391. As a result, when the outer ring 392 rotates once, the inner ring 391 rotates by an amount corresponding to the difference in the number of teeth, and the output member 22 rotates 2/40. As described above, the rotation of the rotor 231 of the transmission ratio variable mechanism motor 23 is reduced to 1/20 and output.

  In the case of (iii), that is, when the rotor 231 of the transmission ratio variable mechanism motor 23 is rotating and the input member 20 is rotating because the driver is steering the steering member 2. The rotation amount of the output member 22 is a value obtained by adding the rotation amount of the input member 20 (steering member) to the rotation amount of (ii) above. As a result, the function of assisting the driver's steering by amplifying the operation angle θ1 can be exhibited.

  For example, when the vehicle is traveling at a relatively low speed, the transmission ratio variable mechanism motor 23 is driven, and the operation angle θ1 is amplified. That is, the transmission ratio is made larger than 1. Thereby, a driver | operator's steering can be assisted. Further, when the vehicle is traveling at a relatively high speed, the transmission ratio variable mechanism motor 23 is maintained in a stopped state, for example. Thereby, a transmission ratio becomes small. In addition, the vehicle stability control (posture stability control) may be performed by increasing or decreasing the rotation of the rotor 231 of the transmission ratio variable mechanism motor 23.

  FIG. 3 is a control block diagram related to the transmission ratio variable mechanism 5. The control unit 29 functions as a basic transmission ratio setting unit 50, an emergency avoidance state determination unit 51, a transmission ratio coefficient setting unit 52, a coefficient multiplication unit 53, a target angle calculation unit 54, a deviation calculation unit 55, PI (proportional). An integration) control unit 56, an addition unit 57, and a PWM conversion unit 58. The controller 29 receives the vehicle speed V detected by the vehicle speed sensor 46, the operation angle θ1 detected by the operation angle sensor 42, and the motor rotation angle θr detected by the motor resolver 43.

Basic transmission ratio setting unit 50, based on vehicle speed V, the set of basic transmission ratio R _B. Basic transmission ratio R _B is set according to the vehicle speed V becomes smaller (as the low speed) larger properties. For example, the basic transmission ratio setting unit 50 sets the 4 large fixed value than 1 basic transmission ratio R _B in the low-speed range lower than the first predetermined vehicle speed V1 (e.g. 1.4), the 2 in the predetermined vehicle speed V2 or more speed ranges set the basic transmission ratio R _B 1, in the first and speed range between the second predetermined vehicle speed V1, V2 decreases monotonically from said predetermined value with an increase in vehicle speed V to 1 It sets the basic transmission ratio R _B according to the characteristic.

  The emergency avoidance state determination unit 51 obtains the steering speed by differentiating the operation angle θ1 with respect to time, and obtains the vehicle acceleration by differentiating the vehicle speed V with respect to time. Then, the emergency avoidance state determination unit 51 determines whether the steering speed exceeds a predetermined threshold value (for example, 5 rad / sec) (that is, sudden steering state) or the vehicle acceleration has a predetermined negative threshold value (for example, 1). It is determined that the vehicle is in an emergency avoidance state when any one of the following conditions is satisfied (that is, a value corresponding to a deceleration of 15 km / h or more per second).

Transmission ratio coefficient setting unit 52 generates a transmission ratio coefficient k _T corresponding to the determination result by the emergency avoidance state determining unit 51. The transmission ratio factor _{k T} is the coefficient multiplication portion 53 is multiplied by the basic transmission ratio _{R B.} Specifically, the transmission ratio coefficient setting unit 52 generates a transmission ratio coefficient k _T = 1 when the emergency avoidance state determination unit 51 determines that it is not in the emergency avoidance state. Therefore, in this case, the coefficient multiplication portion 53, the correction for the basic transmission ratio R _B is not performed. When the emergency avoidance state determination unit 51 determines that the emergency avoidance state is in an emergency avoidance state, the transmission ratio coefficient setting unit 52 uses a predetermined emergency avoidance transfer ratio coefficient (a value other than “1”) as the transfer ratio. produced as a coefficient _{k T.} By this emergency avoidance coefficient is multiplied by the basic transmission ratio R _B in the coefficient multiplying unit 53, a correction to the basic transmission ratio R _B is added. As a result, different transmission ratios R (= k _T × R _B ) are set between the normal time and the emergency avoidance time.

The target angle calculation unit 54 generates a target angle θr ^* , which is a target value of the rotation angle of the transmission ratio variable mechanism motor 23, based on the transmission ratio R and the operation angle θ1 corrected by the coefficient multiplication unit 53. As described above, the operation angle θ1 of the steering member 2 is increased or decreased (or neither increased nor decreased) by the rotation of the outer ring 392 of the track ring unit 39 and is transmitted to the steering mechanism 10. Therefore, the target angle calculation unit 54 obtains the target turning angle by multiplying the operation angle θ1 by the transmission ratio R, and sets the target angle θr ^* of the transmission ratio variable mechanism motor 23 so that the target turning angle is achieved. Set.

The deviation calculator 55 calculates a deviation (θr ^* −θr) of the motor rotation angle θr with respect to the target angle θr ^* . A motor current target value is obtained by performing PI (proportional integration) calculation by the PI control unit 56 on this deviation. Further, the adder 57 adds the current correction value corresponding to the target angle θr ^* to the motor current target value. Thus, feedback control and feedforward control are performed on the motor rotation angle, and a motor current target value (an example of an auxiliary target value) is obtained.

The PWM conversion unit 58 generates a PWM drive signal corresponding to the motor current target value. When the drive circuit 40 is driven by the PWM drive signal, the transmission ratio variable mechanism motor 23 is driven. As a result, the rotation angle of the transmission ratio variable mechanism motor 23 is guided to the target angle θr ^* corresponding to the transmission ratio R _B and the operation angle θ.
FIG. 5 is a control block diagram related to the steering assist force applying mechanism 19 (electric power steering device). The control unit 29 includes, as function processing units, a target current value setting unit 80, an emergency avoidance state determination unit 81, an assist coefficient setting unit 82, a coefficient multiplication unit 83, a deviation calculation unit 84, a PI control unit 85, a current limiting unit 86, And a PWM converter 87. The control unit 29 includes an operation angle θ1 detected by the operation angle sensor 42, a steering torque T detected by the torque sensor 44, a vehicle speed V detected by the vehicle speed sensor 46, and a motor current detected by the current detection unit 30. A value has been entered. The current detection unit 30 is configured to detect the current value of the steering assist motor 25.

Target current-value setting unit 80 based on the steering torque and the vehicle speed V, the sets the basic target current value I _B. Basic target current value I _B, as shown in FIG. 6, is set to a positive value or a negative value depending on the direction of the steering torque T. For example, the target current value setting unit 80, indicated assist characteristic in FIG. 6 - according to (steering torque target current value characteristic), generates a basic target current value I _B. For the steering torque T, for example, the torque for steering in the right direction is a positive value, and the torque for steering in the left direction is a negative value. Also, the basic target current value I _B, when the steering assist motor 25 to generate a steering assist force for rightward steering is a positive value, the steering assist for the steering assist motor 25 in the left steering Negative values are used when force should be generated. Basic target current value I _B, relative to the positive value of the steering torque T takes a positive value, a negative value for negative values of the steering torque T. Steering torque -T1～T1 (e.g., T1 = 0.4 N · m) when the small value of the range (the torque dead zone) is the basic target electric current value _{I B} is zero.

Furthermore, the basic target current value I _B increases as the vehicle speed increases, being a smaller value of the absolute value. Thus, vehicle speed sensitive control is performed in which the steering assist force is reduced as the vehicle travels at a higher speed.
The emergency avoidance state determination unit 81 has the same function as the emergency avoidance state determination unit 51 described above, and may be a function processing unit common to the emergency avoidance state determination unit 51. That is, the emergency avoidance state determination unit 81 obtains the steering speed by differentiating the operation angle θ1 with respect to time, and obtains the vehicle acceleration by differentiating the vehicle speed V with respect to time. Then, the emergency avoidance state determination unit 81 determines whether the steering speed exceeds a predetermined threshold value (that is, sudden steering state) or the vehicle acceleration is less than a predetermined negative threshold value (that is, rapid deceleration state). When any one of the conditions is satisfied, the emergency avoidance state is determined.

The assist coefficient setting unit 82 generates an assist coefficient k _A according to the determination result by the emergency avoidance state determination unit 81. The assist coefficient k _A is multiplied by the basic target current value I _B by the coefficient multiplier 83. Specifically, the assist coefficient setting unit 82 generates the assist coefficient k _A = 1 when the emergency avoidance state determination unit 81 determines that it is not in the emergency avoidance state. Therefore, in this case, the coefficient multiplication unit 83, the correction for the basic target current value I _B is not performed. In addition, when the emergency avoidance state determination unit 81 determines that the emergency avoidance state determination unit 81 is in the emergency avoidance state, the assist coefficient setting unit 82 sets a predetermined emergency avoidance coefficient (a value other than “1”) as the assist coefficient I _B. Generate. By this emergency avoidance coefficient is multiplied in the coefficient multiplying portion 83 to the basic target current value I _B, is corrected to the basic target current value I _B is added. As a result, a different target current value I ^* is set for normal and emergency avoidance.

Deviation calculation unit 84 calculates a deviation of motor current value I from target current value I ^* . A motor current target value is obtained by performing PI calculation by the PI control unit 85 on the deviation (I ^* −I).
The current limiter 86 limits the motor current target value when the motor current value becomes equal to or greater than a predetermined limit value (for example, rated current). The current limiting unit 86 may limit the motor current target value on condition that a state where the motor current value is equal to or greater than the predetermined limit value continues for a predetermined time (for example, 2 msec). The limitation on the motor current target value may be, for example, a process for forcibly setting the motor target current value to a predetermined limit value current value (for example, a value of about 90% of the rated current).

The PWM converter 87 generates a PWM drive signal corresponding to the motor current target value. When the drive circuit 41 is driven by the PWM drive signal, the steering assist motor 25 is driven. As a result, the steering assist motor 25 generates a steering assist force according to the target current value I ^* .
FIG. 7 is a flowchart for explaining the setting of the target transmission ratio and the target current value (auxiliary target value). The emergency avoidance state determination unit 51 obtains the steering speed and the vehicle acceleration (step S1). Further, the emergency avoidance state determination unit 51 determines whether or not it is in an emergency avoidance state based on the steering speed and the vehicle acceleration (step S2). Specifically, when the steering speed exceeds a predetermined threshold value or the acceleration is less than a predetermined negative threshold value, the emergency avoidance state determination unit 51 determines that the state is an emergency avoidance state. When none of these conditions is satisfied, the emergency avoidance state determination unit 51 determines that the state is not the emergency avoidance state. That is, when sudden steering or sudden deceleration is detected, it is determined that the vehicle is in an emergency avoidance state. Otherwise, it is determined that the vehicle is not in an emergency avoidance state.

If it is determined not to be an emergency avoidance state (either in step S2 and S3 NO), the transmission ratio coefficient k _T is set to "1", the transmission ratio R in accordance transmission ratio characteristics of the normal (see FIG. 4) It is set (step S4). The assist coefficient k _A is set to "1", the target current value I ^* is set according to the assist characteristic of the normal (see FIG. 6) (step S5).
On the other hand, if it is determined that the state is an emergency avoidance state (YES in step S2 or S3), the transmission ratio coefficient setting unit 52 sets a transmission ratio coefficient (a value other than 1) for emergency avoidance. Thereby, the target transmission ratio R is set to an emergency avoidance transmission ratio that is different from the normal time (step S6). Further, the assist coefficient setting unit 82 sets an assist coefficient k _A (a value other than 1) for emergency avoidance. Thus, the target current value I ^* is set to the emergency avoidance target current value I ^* that is different from the normal time (step S7). As a result, the time until the target current value I ^* is limited by the current limiting unit 86 is maximized, and the turning angle change amount (cutting angle) until the current limit is maximized.

  Furthermore, in this embodiment, when it determines with it being an emergency avoidance state, the control part 29 measures the time by which electric current limitation is carried out, and the turning angle variation | change_quantity (step S8). The turning angle change amount is obtained by monitoring the output of the turning angle sensor 45. Further, the control unit 29 evaluates the time until the current limit is executed and the turning angle change amount (step S9). Based on the evaluation result, the control unit 29 updates the transmission ratio coefficient and the assist coefficient for emergency avoidance as necessary, and records the updated coefficients in the internal memory 29M (see FIG. 1). (Step S10). When the emergency avoidance state is subsequently determined, the updated transmission ratio coefficient and assist coefficient are applied.

In this way, since the learning function is provided for the coefficient setting for emergency avoidance, more appropriate transmission ratio coefficient and assist coefficient are set as the vehicle is used. Of course, a coefficient adapted to the secular change of the components of the vehicle steering system and other factors is set.
Table 2 below shows an example of a rule (learning rule) for changing the transmission ratio coefficient and the assist coefficient for emergency avoidance. When the time until the power limit is long, there is a margin for supplying more current to the steering assist motor 25. Therefore, when the time until power limit is long (the evaluation result of step S9), the assist coefficient for emergency avoidance is increased (step S10). Conversely, when the time until the power limit is short (the evaluation result in step S9), the emergency avoidance assist coefficient is reduced (step S10). On the other hand, when the amount of change in the turning angle up to the power limit is small (the evaluation result in step S9), it is preferable to secure a larger amount of change in the turning angle, so that the transmission ratio coefficient for emergency avoidance is increased ( Step S10). Conversely, when the amount of change in the turning angle up to the power limit is large (result of evaluation in step S9), the possibility that the drive power of the steering assist motor 25 is limited increases, so the transmission ratio coefficient for emergency avoidance is It is made smaller (step S10).

  A reference time serving as a comparison reference for whether the time until the power limit is executed is long or short may be set in advance. Similarly, a reference turning angle change amount that is a criterion for whether the turning angle change amount until the power limit is executed is large or small may be set in advance. The reference time and the reference turning angle change amount may be appropriately determined by performing a steering experiment assuming an emergency avoidance state, for example. More specifically, the reference time and the reference turning angle change amount may be set based on experimental values for the transmission ratio coefficient and the assist coefficient for emergency avoidance that are initially set.

The initial combination of transmission ratio coefficient and assist coefficient for emergency avoidance is such that when a predetermined emergency avoidance operation is performed, the time until the current limit is executed and the amount of change in the turning angle are maximized. Set to Such a combination of the transmission ratio coefficient and the assist coefficient for emergency avoidance can be determined by a steering experiment (including simulation).
More specifically, the combination of the transmission ratio coefficient and the assist coefficient for emergency avoidance can be determined by applying a method for obtaining a multivariable optimal solution using learning. For example, a steering experiment corresponding to an emergency avoidance state (for example, a simulation experiment) is performed by setting various transmission ratio coefficients and assist coefficients, and the time until the current limit is executed and the amount of change in the turning angle are evaluated. Good. Furthermore, specifically, when a predetermined emergency avoidance operation is performed on the steering member 2, the time until the current limit is executed and the amount of change in the turning angle are obtained, and the evaluation values are respectively obtained. give. And what is necessary is just to define the combination of the transmission ratio coefficient for emergency avoidance, and an assist coefficient so that the sum total with those evaluation values may become the maximum.

The emergency avoidance operation may be, for example, an operation at a constant steering speed determined so that a constant turning angle change amount (for example, 1000 degrees) is obtained within a certain time (for example, 10 seconds).
In the steering experiment (learning), the combination of the transmission ratio coefficient and the assist coefficient for the next steering experiment may be determined according to the learning rule shown in Table 2 on the basis of the steering experiment result (evaluation) of each round. By following this learning rule, it is possible to converge to an appropriate transmission ratio coefficient and assist coefficient.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, an example in which the transmission ratio coefficient and the assist coefficient for emergency avoidance are determined so that the sum of the evaluation point for the time until the current limit and the evaluation point for the turning angle change amount until the current limit is maximized. Although shown, this is only an example. For example, the transmission ratio coefficient and the assist coefficient for emergency avoidance may be determined so that the time until the current limit is maximized when a predetermined emergency avoidance operation is performed. Further, the transmission ratio coefficient and the assist coefficient for emergency avoidance may be determined so that the turning angle change amount up to the current limit becomes maximum when a predetermined emergency avoidance operation is performed.

In the above-described embodiment, the transmission ratio variable mechanism 5 including the nutation gear mechanism is shown. However, a wave gear device, a planetary gear mechanism, and other forms of transmission ratio variable mechanisms may be used.
In the above-described embodiment, an example is shown in which the power limitation of the steering assist motor 25 is performed by limiting the current. However, the power limitation can also be performed by limiting the voltage.
Further, the turning angle sensor 45 may be omitted. In this case, the operation angle θ1 may be multiplied by the transmission ratio R _B (or R) every predetermined period, and the integral value of the multiplication value θ1 × R _B (or R) may be set as the turning angle θ2.

  In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering member, 5 ... Transmission ratio variable mechanism, 10 ... Steering mechanism, 19 ... Steering assistance force provision mechanism, 25 ... Steering assistance motor

Claims (9)

An electric power steering device for giving a steering assisting force to a steering mechanism generated by an electric motor driven in accordance with an operation of a steering member;
A transmission ratio variable device that variably sets a transmission ratio that is a ratio of a steering angle of the steering mechanism to an operation angle of the steering member;
Power limiting means for limiting the power of the electric motor according to a predetermined power limiting condition;
Emergency avoidance judging means for judging whether or not the driving state of the vehicle is a predetermined emergency avoidance state;
An auxiliary target value corresponding to the target value of the steering assist force is set to a normal target value when the emergency avoidance determining unit determines that the emergency avoidance state is not in an emergency avoidance state, and the emergency avoidance determination unit is in an emergency avoidance state. Auxiliary target value setting means for setting an emergency avoidance target value different from the normal target value when it is determined;
The target transmission ratio, which is the target value of the transmission ratio, is set to the normal transmission ratio when it is determined by the emergency avoidance determination means that it is not in the emergency avoidance state, and is determined to be in the emergency avoidance state by the emergency avoidance determination means. And a target transmission ratio setting means for setting an emergency avoidance transmission ratio different from the normal transmission ratio.   The vehicle steering apparatus according to claim 1, wherein the emergency avoidance determination unit determines that the emergency avoidance state is in an emergency avoidance state when an operation speed of the steering member exceeds a predetermined threshold value.   The vehicle steering apparatus according to claim 1, wherein the emergency avoidance determining unit determines that the vehicle is in an emergency avoidance state when the vehicle is in a sudden deceleration state where the acceleration of the vehicle is less than a predetermined negative threshold value.   When a predetermined emergency avoidance operation is performed on the steering member, the evaluation value related to the time until the power limit by the power limit unit is executed, and the power limit by the power limit unit is executed. The emergency avoidance target value and the emergency avoidance transmission ratio are determined so that the sum total with the evaluation value regarding the amount of change in the turning angle of the turning mechanism is maximized. The steering apparatus for vehicles as described.   When the predetermined emergency avoidance operation is performed on the steering member, the emergency avoidance target value and the emergency avoidance transmission ratio are set so that the time until the power limit by the power limiter is executed is the longest. The vehicle steering apparatus according to any one of claims 1 to 3, wherein the steering apparatus is defined.   When the predetermined emergency avoidance operation is performed on the steering member, the emergency avoidance is performed so that the amount of change in the turning angle of the steering mechanism until the power limitation by the power limiting unit is executed is maximized. The vehicle steering apparatus according to any one of claims 1 to 3, wherein a target value and the emergency avoidance transmission ratio are determined. An evaluation unit that monitors and evaluates the time until the power limitation by the power limiting unit is executed and / or the amount of change in the turning angle when the emergency avoidance determining unit determines that the state is an emergency avoidance state; ,
The vehicle steering according to any one of claims 1 to 6, further comprising emergency avoidance application value updating means for updating the emergency avoidance target value and the emergency avoidance transmission ratio based on an evaluation result by the evaluation means. apparatus. The evaluation means evaluates whether the time until the power limit is executed is larger or smaller than a predetermined reference time,
The emergency avoidance application value update means increases the emergency avoidance target value when the time until the power limit is executed is larger than the reference time, and sets the time until the power limit is executed. The vehicle steering apparatus according to claim 7, wherein the emergency avoidance target value is decreased when the time is smaller than the reference time. The evaluation means evaluates whether the turning angle change amount until the power restriction is executed is larger or smaller than a predetermined reference turning angle change amount,
The emergency avoidance application value updating means reduces the emergency avoidance transmission ratio when the turning angle change amount until the power restriction is executed is larger than the reference turning angle change amount, and the power restriction The vehicle steering apparatus according to claim 7 or 8, wherein the emergency avoidance transmission ratio is increased when a turning angle change amount until execution of is is smaller than the reference turning angle change amount.

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