JP2011161938A - Steer-by-wire type steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steer-by-wire type steering device capable of adjusting a toe angle so as to substantially equalize cornering forces acting on inner/outer wheels when turning. <P>SOLUTION: The steer-by-wire type steering device includes: a turning power transmission mechanism 18 for transmitting rotation of a turning motor 6 to a turning shaft 10; and a toe angle adjusting power transmission mechanism 30 for adjusting a toe angle by rotation of a toe angle adjusting motor 7. The steering device includes: a switching mechanism 17 which achieves turning by switching transmission paths of each of the motors 6, 7 when the motors 6, 7 fail; and a steering control means for giving command signals of a turning angle and the toe angle to each of the motors 6, 7. The steering control means has a toe angle adjusting control unit for continuously performing toe angle adjustment according to vehicle speed and yaw rates. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a steer-by-wire steering apparatus in which steering is performed with a steering wheel that is not mechanically connected to a steered turning shaft.

  The vehicle steering device includes a steering shaft (rack bar) that is driven to the left and right by the operation of the steering wheel, and a turning angle changing means that changes the positional relationship between the tie rod that steers the wheel and the steering shaft. In the case of a predetermined value or less, the relationship between the turning angles of the left and right wheels is set to Ackermann geometry, and when the vehicle speed exceeds the predetermined value, the relationship between the turning angles of the left and right wheels is switched to the parallel geometry. Patent Document 1). In addition, there has been proposed a technique in which the relationship between the turning angles of the left and right wheels is not changed as in the steering device but is continuously changed according to the vehicle speed (Patent Document 2).

JP 2005-138709 A JP 2009-101857 A

In the steering devices disclosed in Patent Documents 1 and 2, the turning load of the outer wheel that can generate a larger cornering force is reduced by reducing the ground contact load of the turning inner wheel due to rolling during high-speed turning and increasing the contact load of the outer wheel. Increasing the steering angle of the inner ring is reduced. This method is established on the assumption that the cornering force increases uniformly as the tire ground contact load increases.
However, there is a limit to the cornering force that can be applied to the tire, and it is not preferable to increase the turning angle in accordance with the ground contact load because it will be closer to the limit.

  An object of the present invention is to provide a steer-by-wire type steering device that can adjust a toe angle so that cornering forces acting on inner and outer wheels during turning are substantially equal.

The steer-by-wire steering device of the present invention includes a steered shaft having tie rods provided at both left and right ends, a steering wheel that is not mechanically connected to the steered shaft, and a steering angle that detects the steering angle of the steering wheel. The toe angle is adjusted by the rotation of the sensor, the turning motor, the turning power transmission mechanism that transmits the turning of the turning motor to the turning shaft, the toe angle adjusting motor, and the toe angle adjusting motor. A toe angle adjusting power transmission mechanism for generating a steering angle command signal and a toe angle command signal based on the steering angle detected by the steering angle sensor, and adjusting the steering motor and the toe angle adjustment with these command signals. In a steer-by-wire type steering apparatus provided with a steering control means to be given to each motor,
The steering control means includes a toe angle adjustment control unit that controls the toe angle adjustment motor so as to continuously adjust the toe angle according to a vehicle speed and a yaw rate according to a predetermined rule. . The vehicle speed is a vehicle speed detected by a vehicle speed detection unit, and the yaw rate is a yaw rate calculated from a value detected by the yaw rate detection unit or a detection value of another detection unit.

  According to this configuration, the toe angle adjustment control unit of the steering control means continuously adjusts the toe angle according to the vehicle speed and the yaw rate. Therefore, the toe angle adjustment is performed according to changes in the vehicle speed and the yaw rate when turning. Can be done finely. For example, the toe angle can be finely adjusted when the toe angle is controlled so that the cornering forces acting on the inner and outer rings are substantially equal. Thereby, it is possible to equalize the load applied to the inner and outer wheels during turning and to move away from the dangerous area which is the tire limit. Further, the tire skid angle under a high ground load condition can be reduced, and the wear amount of the tire can also be reduced.

  In this invention, a dedicated yaw rate sensor for detecting the yaw rate may be provided near the center of gravity of the vehicle, and the toe angle adjustment control unit may use the yaw rate detected by the yaw rate sensor for toe angle adjustment control.

  In the present invention, a lateral force detection sensor for detecting lateral force acting on the wheels is provided on the hub of all the vehicle wheels, and the toe angle adjustment control unit outputs the output of the total lateral force detection sensor, the vehicle center of gravity, and each wheel. The yaw rate calculated on the basis of the positional relationship may be used for toe angle adjustment control.

In the present invention, the toe angle adjustment control unit may adjust the toe angle so that a difference in cornering force acting on the inner and outer wheels to be steered is not more than a set value. For example, the toe angle may be adjusted so that the cornering force acting on the inner and outer wheels to be steered is substantially equal. The toe angle adjustment by the steer-by-wire type steering device is based on the vehicle speed and the detected value of the yaw rate detection means to control the actual steering angle for the inner and outer wheels so that the difference in cornering force between the turning inner wheel and the outer wheel is less than the set value. Thus, the load can be equalized.
In the toe angle adjustment control unit, the toe angle may be set to the out side with respect to the same yaw rate as the vehicle speed increases. The toe angle that equalizes the cornering force approaches the toe-out side as the vehicle speed increases. Therefore, during high-speed turning, if the toe angle is adjusted to the out side according to the vehicle speed and the yaw rate, that is, the turning radius, it is safe and the tire burden is reduced.

In this invention, when the steering motor fails, the steering motor is disconnected from the steering power transmission mechanism, and a change in toe angle is stopped, and the steering motor is replaced with the steering motor. The rotation of the toe angle adjusting motor is transmitted to the steered power transmission mechanism to enable the steering, and when the toe angle adjusting motor fails, the toe angle adjusting power transmitting mechanism is set in a power transmission disabled state and the Provide a switching mechanism that allows only turning by the rudder motor,
The steered shaft is divided into two axially divided into a non-rotating divided shaft and a rotating divided shaft, and both the divided shafts are coupled to each other by a screw coupling portion concentric with the shaft center, By rotating the rotating split shaft to steer the steered wheel by axially moving the rotating split shaft and rotating the rotary split shaft with respect to the non-rotating split shaft, and adjusting the screwing length of the screw coupling portion, The rotating split shaft has a function of changing the toe angle of the steered wheel by changing the distance between the left and right tie rods. It is connected via a thrust bearing that can rotate around the center,
The steered power transmission mechanism is a mechanism for axially moving the non-rotating divided shaft and the rotating divided shaft of the steered shaft by the rotation of the steering motor,
The toe angle adjustment power transmission mechanism is a mechanism that rotates a rotation division shaft with respect to a non-rotation division axis of the steered shaft by rotation of the toe angle adjustment motor,
These steered power transmission mechanism and toe angle adjusting power transmission mechanism may be operated in cooperation with each other so that the steered angles of the left and right steered wheels coincide with the target value under the control of the steering control means. .

  According to this configuration, the left and right tie rods are moved in the same direction by axially moving the non-rotating split shaft and the rotating split shaft of the steered shaft via the steered power transmission mechanism by the rotation of the steering motor. To the same distance and steer the steered wheels. In addition, by rotating the toe angle adjusting motor, the screwing length of the screw coupling portion is adjusted by rotating the rotating split shaft with respect to the non-rotating split shaft of the steered shaft via the toe angle adjusting power transmission mechanism. Then, change the distance between the left and right tie rods to change the toe angle of the steered wheels. During the toe angle adjustment, the steered power transmission mechanism and the toe angle adjusted power transmission mechanism are operated in cooperation with each other so that the steered angles of the left and right steered wheels coincide with the target values under the control of the steering control means. It is done.

  When the steering motor fails, the switching mechanism separates the steering motor from the steering power transmission mechanism and stops the change of the toe angle, and instead of the steering motor, the toe angle adjusting motor The rotation is transmitted to the turning power transmission mechanism to enable turning. As a result, a fail-safe function capable of steering even when the steering motor fails is provided. When the toe angle adjusting motor fails, the switching mechanism causes the toe angle adjusting power transmission mechanism to be in a state where power cannot be transmitted, and only the turning by the steering motor is performed. As a result, when the toe angle adjusting motor fails, the toe angle adjusting mechanism is fixed and the vehicle can travel safely.

By turning the steered shaft into two parts, a non-rotating split shaft and a rotating split shaft, in the axial direction, these split shafts are connected to each other by a screw connection portion concentric with the shaft center. On the other hand, the distance between the left and right tie rods can be changed by rotating the rotary division shaft. The left and right tie rods can be directly connected to the non-rotating split shaft and the rotating split shaft, respectively. For this reason, the steer-by-wire type steering apparatus of the present invention has a compact configuration, can reduce the overall axial length of the portion where the steered shaft is provided, and is easily mounted on a vehicle.
In addition, when the steered shaft is not divided in the axial direction, an advancing / retreating member is provided at both ends of the steered shaft in accordance with the rotation of the steered shaft, and left and right tie rods are attached to these advancing / retreating members. Must be configured. Therefore, the entire axial length of the place where the steered shaft is provided is increased.
Further, when the toe angle is adjusted, the steered shaft is rotated, but the rotation division shaft is connected to the tie rod through a thrust bearing in addition to the ball joint, so that an axial load is applied. Even in this state, the friction torque between the rotary split shaft and the tie rod can be reduced. For this reason, the capacity | capacitance of the motor for toe angle adjustment which is a rotational drive source of a rotation division | segmentation axis | shaft can be made small, and the structure of a steer-by-wire type steering apparatus can be made more compact.

In the present invention, the toe angle adjusting motor may be a hollow motor, and the steered shaft may be inserted into a hollow motor shaft of a toe angle adjusting motor composed of the hollow motor. Further, the steering motor may be a hollow motor, and the components of the switching mechanism may be inserted into the hollow motor shaft of the steering motor composed of the hollow motor.
If it is set as said each structure, the toe angle adjustment motor and the motor for turning, and the components of a turning shaft and a switching mechanism can be arranged compactly.

In the present invention, a ball screw shaft portion is provided on a non-rotating split shaft of the steered shaft, and a ball nut screwed into the ball screw shaft portion is provided only for rotation, and the steered power transmission mechanism includes the steered power transmission mechanism. It is preferable that the ball nut is rotated by rotation of a motor for moving the steered shaft in the axial direction to perform the steer.
According to this structure, since the operation | movement location of a turning power transmission mechanism can be made only into a ball nut at the minimum, the structure of a turning power transmission mechanism can be simplified.

The ball nut may be a top type ball circulation system, and the ball nut may be supported by a double-row angular ball bearing and a deep groove ball bearing.
The top-type ball nut can reduce the outer diameter and has a good rotational balance. When the double row angular contact ball bearing and the deep groove ball bearing are combined to support the ball nut, it is possible to receive both an axial load and a moment load acting on the ball nut.

It is preferable that the outer diameter surface of the ball screw shaft portion of the non-rotating divided shaft of the steered shaft is supported by a slide bearing.
A steered shaft having a structure divided into two in the axial direction has low rigidity in the vicinity of the joint between the two split shafts, and it is necessary to increase support rigidity in the vicinity of the joint. In addition, it is necessary to avoid applying moment load to the ball screw shaft as much as possible. If the outer diameter surface of the ball screw shaft portion is supported by a slide bearing, the support rigidity in the vicinity of the coupling portion between the two split shafts can be improved and a moment load can be avoided from being applied to the ball screw shaft portion. It is effective if the axial direction position of the slide bearing is between the non-rotating split shaft and the coupling portion of the rotary split shaft and the ball nut.

A non-rotating means for preventing the non-rotating divided shaft of the steered shaft from rotating about the axis is provided. In that case, the detent means is formed on a non-rotating split shaft of the steered shaft, and is fixed to a non-concentric circle portion whose outer shape in a cross section perpendicular to the axial direction is different from the concentric circle at the shaft center, and the housing of the apparatus. Provided, and the non-concentric circular part can be constituted by a sliding bearing which is slidably fitted in the axial direction.
The anti-rotation means has a simple configuration and can reliably prevent the non-rotating divided shaft of the steered shaft.

In this invention, a spline shaft portion is provided on the rotation division shaft of the steered shaft, and a spline nut that engages with the spline shaft portion so as to be relatively movable in the axial direction is rotatably provided. By rotating the spline nut with a toe angle adjusting motor, the rotation division shaft of the steered shaft is rotated, and the screwing length of the screw coupling portion of the non-rotation division shaft and the rotation division shaft is adjusted. Thus, it is preferable to change the toe angle of the steered wheels by changing the length of the steered shaft.
According to this configuration, since the operating portion of the toe angle adjusting power transmission mechanism can be at least the spline nut, the configuration of the toe angle adjusting power transmission mechanism can be simplified.

  In the case of the above configuration, the spline teeth of the spline shaft portion of the steered shaft and the spline teeth of the spline nut may be in sliding contact or in rolling contact. In any case, the force can be satisfactorily transmitted from the spline nut to the spline shaft portion.

The screw coupling portion may be a square screw or a trapezoidal screw.
In the screw coupling portion in which the screw type is a square screw or a trapezoidal screw, the coupling between the non-rotating divided shaft and the rotating divided shaft is firm.

In the present invention, an inner diameter hole concentric with the center of the shaft is provided on the split shaft of the non-rotating split shaft and the rotating split shaft on which the female screw of the screw coupling portion is provided, and the male screw of the screw coupling portion is provided. A fitting shaft portion that fits into the inner diameter hole may be provided on the provided split shaft. In that case, it is desirable to provide a retaining means for restricting the relative axial positional relationship between the inner diameter hole and the fitting shaft portion so that the fitting shaft portion does not come off from the inner diameter hole.
By fitting the fitting shaft portion into the inner diameter hole, the coaxiality between the non-rotating divided shaft and the rotating divided shaft is maintained. Further, by providing the retaining means, it is possible to prevent the fitting shaft portion from being detached from the inner diameter hole, and to reliably maintain the coaxiality of the non-rotating divided shaft and the rotating divided shaft.

In the present invention, the toe angle adjusting motor may have a maximum generated torque smaller than a maximum generated torque of the steering motor.
The replacement of the toe angle adjustment by the toe angle adjustment motor during normal operation and the steering drive source when the steering motor fails is the operation that is performed when the vehicle is running. It is much smaller than the torque required for the steering motor. Therefore, the toe angle adjusting motor may be smaller than the steering motor.

  The steer-by-wire steering device of the present invention includes a steered shaft having tie rods provided at both left and right ends, a steering wheel that is not mechanically connected to the steered shaft, and a steering angle that detects the steering angle of the steering wheel. The toe angle is adjusted by the rotation of the sensor, the turning motor, the turning power transmission mechanism that transmits the turning of the turning motor to the turning shaft, the toe angle adjusting motor, and the toe angle adjusting motor. A toe angle adjusting power transmission mechanism for generating a steering angle command signal and a toe angle command signal based on the steering angle detected by the steering angle sensor, and adjusting the steering motor and the toe angle adjustment with these command signals. Steer-by-wire type steering apparatus provided with steering control means for each motor, the steering control means adjusts the toe angle according to the vehicle speed and yaw rate. Because you to have a toe angle adjustment control unit that continues to take place, cornering force acting on the inner and outer rings can be adjusted the toe angle so as to be substantially equal at the time of turning.

1 is a block diagram showing a schematic configuration of a steer-by-wire steering device according to an embodiment of the present invention. (A) is a horizontal sectional view at the time of normal operation of the steered shaft drive unit in the steer-by-wire type steering apparatus, and (B) is an enlarged view of the IIB part. (A) is a horizontal sectional view at the time of failure of the toe angle adjusting motor in the steered shaft drive section, and (B) is an enlarged view of the III-B section. (A) is a horizontal sectional view at the time of failure of the steering motor in the steered shaft drive section, and (B) is an enlarged view of the IVB section. (A), (B) is sectional drawing which shows each different state of the coupling thread part of the same steering shaft. It is VI-VI sectional drawing of FIG. It is a side view of the rotation control mechanism of the steered shaft drive unit, and (A) and (B) show different states. It is explanatory drawing which shows the tooth tip shape of the spline tooth | gear of a normal spline shaft. (A) is a side view of an example of the intermediate shaft of the steered shaft drive unit, and (B) is a front view of the same. (A) is a side view of another example of the intermediate shaft of the steered shaft drive unit, and (B) is a front view of the same. (A) is a side view of still another example of the intermediate shaft of the steered shaft drive unit, and (B) is a front view of the same. (A) is a side view of still another example of the intermediate shaft of the steered shaft drive unit, and (B) is a front view of the same. It is an expanded sectional view of the connection part of the rotation division | segmentation axis | shaft and a tie rod in the steer-by-wire type steering device. It is a graph which shows the result of having calculated the relationship between the toe angle and cornering force when turning the corner of R200 at a speed of 80 km / h. It is a graph which shows the result of having calculated the relationship between the toe angle and cornering force when turning the corner of R200 at a speed of 100 km / h. It is a graph which shows the result of having calculated the relationship between the toe angle and cornering force when turning the corner of R200 at a speed of 120 km / h. It is a graph which shows the result of having calculated the relationship between the toe angle and cornering force when turning the corner of R200 at a speed of 140 km / h. It is a block diagram which shows schematic structure of the steer-by-wire type steering apparatus concerning other embodiment of this invention.

  An embodiment of the present invention will be described with reference to the drawings. As shown schematically in FIG. 1, the steer-by-wire steering device includes a steering wheel 1, a steering angle sensor 2, a steering torque sensor 3, a steering reaction force motor 4, and left and right steerings. A steered shaft 10 that is axially movable for turning and connected to a wheel 13 via a knuckle arm 12 and a tie rod 11, a steered shaft drive unit 14 that drives the steered shaft 10, and a steered angle sensor 8 and an ECU (electric control unit) 5. The ECU 5 includes a steering control means 5a, a failure handling control means 5b, and a correction operation control means 5c. The ECU 5 and its respective control means 5a, 5b, 5c are constituted by a microcomputer and an electronic circuit including its control program.

  The steering wheel 1 is not mechanically connected to the turning shaft 10 for turning. A steering angle sensor 2 and a steering torque sensor 3 are provided for the steering wheel 1 and a steering reaction force motor 4 is connected thereto. The steering angle sensor 2 is a sensor that detects the steering angle of the steering wheel 1. The steering torque sensor 3 is a sensor that detects a steering torque that acts on the steering wheel 1. The steering reaction force motor 4 is a motor that applies reaction force torque to the steering wheel 1.

  2 to 4 are horizontal sectional views showing different states of the steered shaft drive unit 14. The steered shaft drive unit 14 includes a steered shaft 10, a steered mechanism 15 that steers the steered wheels 13 (FIG. 1), a toe angle adjusting mechanism 16 that adjusts the toe angle of the steered wheels 13, A switching mechanism 17 for switching the power transmission mechanisms 18 and 30 of the rudder mechanism 15 and the toe angle adjusting mechanism 16 is provided.

  The steered shaft 10 is divided into two in the axial direction, a non-rotating divided shaft 10A and a rotating divided shaft 10B, and these divided shafts 10A and 10B are coupled to each other by a screw coupling portion 10C concentric with the shaft center. The left and right tie rods 11 (FIG. 1) are connected to the distal end portions of the non-rotating split shaft 10A and the rotating split shaft 10B that protrude from the housing 19 of the steered shaft drive unit 14, respectively.

  As shown in FIG. 5, the screw coupling portion 10C includes a male screw 81 provided on the non-rotating divided shaft 10A and a female screw 82 provided on the rotating divided shaft 10B. The screw type is preferably a square screw or a trapezoidal screw. In the screw coupling portion 10C in which the screw type is a square screw or a trapezoidal screw, the coupling between the non-rotating divided shaft 10A and the rotating divided shaft 10B is firm.

  The male screw 81 is provided at the tip of a fitting shaft portion 83 that protrudes from the ball screw shaft portion 10a of the non-rotating divided shaft 10A toward the rotating divided shaft 10B. The female screw 82 is formed on the inner periphery of the cylindrical portion 84 of the rotary split shaft 10B. The rotating split shaft 10B is provided with an extended cylindrical portion 85 extending from the cylindrical portion 84 to the non-rotating split shaft 10A. The fitting shaft portion 83 is fitted into the inner diameter hole 86 of the extended cylindrical portion 85. Match. The inner diameter hole 86 is concentric with the axis center of the steered shaft 10.

  The screw coupling portion 10 </ b> C is provided with a retaining means 88 that prevents the fitting shaft portion 83 from coming out of the inner diameter hole 86. The retaining means 88 includes a circlip 90 that fits in an annular outer circumferential groove 89 formed on the outer periphery of the fitting shaft portion 83, and an annular inner circumferential groove 91 formed in the inner diameter surface of the inner diameter hole 86. Become. As shown in the partially enlarged view of FIG. 5A, the step surface 91a on the opposite side of the non-rotating divided shaft 10A of the inner peripheral groove 91 is tapered so that the groove depth gradually decreases toward the outside.

  Normally, as shown in FIG. 5A, the circlip 90 and the inner circumferential groove 91 are displaced in the axial direction, and the circlip 90 is pressed by the inner diameter surface of the inner diameter hole 86 to be reduced in diameter. ing. In this state, when the rotation division shaft 10B is rotated with respect to the non-rotation division shaft 10A, the screwing length of the screw coupling portion 10C is adjusted. As shown in FIG. 5B, when the circlip 90 and the inner circumferential groove 91 are in the same position in the axial direction, the circlip 90 expands in diameter by its own elastic repulsive force and engages with the inner circumferential groove 91. Thereby, the operation in the direction of shortening the screwing length of the screw coupling portion 10 </ b> C is restricted, and the fitting shaft portion 83 cannot be removed from the inner diameter hole 86. Since the step surface 91a of the inner circumferential groove 91 has a tapered shape as described above, the operation in the direction of shortening the screwing length of the screw coupling portion 10C is not restricted.

  The non-rotating divided shaft 10 </ b> A is made to advance and retreat in the axial direction with respect to the housing 19 of the steered shaft driving unit 14 and cannot rotate about the axis by the rotation preventing means 93. As shown in FIG. 6, the non-rotating means 93 is fixed to the non-concentric circular portion 10 b, which is a portion continuing to the outside of the ball screw shaft portion 10 a in the non-rotating divided shaft 10 A, and the housing 19. The part 10b is configured by a sliding bearing 94 that is slidably fitted in the axial direction. The shape of the cross section perpendicular to the axial direction of the non-concentric circular portion 10b is a shape whose outer shape is different from the concentric circle having the axial center. In this example, the non-concentric circular portion 10b has a cross-sectional shape obtained by cutting off a part of the circumference with a straight line, but may have another cross-sectional shape. The anti-rotation means 93 having this configuration is simple in configuration and can reliably prevent the non-rotating divided shaft 10A of the steered shaft 10 from rotating.

  The entire turning shaft 10 is supported by the housing 19 as follows. That is, the non-rotating split shaft 10A is supported by the double-row angular ball bearing 29a and the deep groove ball bearing 29b via a ball nut 26, which will be described later, and is also supported by the slide bearing 94. . Further, the rotary split shaft 10B is supported by a rolling bearing 44 via a spline nut 40 described later that is spline-fitted to the outer periphery thereof. Further, the outer diameter surface of the ball screw shaft portion 10 a is supported by the slide bearing 95. The axial position of the slide bearing 95 is between the screw coupling portion 10 </ b> C and the ball nut 26.

  The steered mechanism 15 steers the steered wheel 13 by integrally moving the non-rotating split shaft 10A and the rotating split shaft 10B of the steered shaft 10 in the axial direction. The turning mechanism 15 includes a turning motor 6 and a turning power transmission mechanism 18 that moves the turning shaft 10 in the axial direction by the rotation of the turning motor 6.

  The steered motor 6 is attached to the housing 19 of the steered shaft drive unit 14 in parallel with the steered shaft 10. The steered motor 6 is a hollow motor and has a cylindrical hollow motor shaft 20. The hollow motor shaft 20 is rotatably supported on the housing 19 by a pair of bearings 23. In the hollow portion of the hollow motor shaft 20, a steering intermediate shaft 21 provided in parallel with the steering shaft 10 is supported via a needle roller bearing 22 so as to be rotatable and movable in the axial direction. The steered intermediate shaft 21 and the toe angle adjusting intermediate shaft 35 described later, together with the reference actuator position shown in FIG. 2 and the toe angle adjusting motor failure position shown in FIG. The position is switched in the axial direction to each position of the steering motor failure position shown in FIG.

  The steered power transmission mechanism 18 rotates through a key (not shown) on the outer periphery of the hollow motor shaft 20 of the steered motor 6, the steered intermediate shaft 21, and the steered intermediate shaft 21. An output gear 24 fitted so as to be able to transmit, an input gear 25 meshing with the output gear 24 via a counter gear 24a, and a ball screw shaft of the non-rotating split shaft 10A of the steered shaft 10 fixed to the input gear 25 It consists of a ball nut 26 screwed into the portion 10a. The ball screw shaft portion 10a and the ball nut 26 constitute a ball screw mechanism A. As the ball nut 26, for example, a ball circulation system with a top type is used. The top-type ball nut 26 can reduce the outer diameter and has a good rotational balance.

  The output gear 24 is supported by the housing 19 via a rolling bearing 28. The ball nut 26 is rotatably supported by the housing 19 by double row angular ball bearings 29a and deep groove ball bearings 29b arranged on both sides in the axial direction. When the double row angular ball bearing 29 a and the deep groove ball bearing 29 b are combined to support the ball nut 26, both an axial load and a moment load acting on the ball nut 26 can be received. As described above, the turning intermediate shaft 21 is fitted to the hollow motor shaft 20 of the turning motor 6 via the needle roller bearing 22 and is fitted to the output gear 24 via the key. Therefore, movement in the axial direction is allowed.

  Spline teeth 20a made of inner teeth are formed on the inner periphery of the hollow motor shaft 20, and spline teeth 21a made of outer teeth are formed on the outer periphery of the turning intermediate shaft 21, respectively. In FIG. 2), these spline teeth 20a and 21a mesh with each other to form a spline fitting portion 27, whereby the hollow motor shaft 20 and the turning intermediate shaft 21 are connected so as to be able to transmit rotation. The spline teeth 20a of the hollow motor shaft 20 are long in the axial direction, and the spline teeth 21a of the intermediate shaft 21 for steering can mesh with any axial position.

  When the steered shaft drive unit 14 is in a normal state (FIG. 2), the rotational output of the steered motor 6 is passed through the steered intermediate shaft 21, the output gear 24, the counter gear 24a, and the input gear 25 to the ball nut 26. Then, the rotation of the ball nut 26 is converted into the movement of the steered shaft 10 in the axial direction, and the steer is performed.

  The toe angle adjusting mechanism 16 changes the distance between the left and right tie rods by rotating the rotary split shaft 10B relative to the non-rotating split shaft 10A and adjusting the screwing length of the screw coupling portion 10C. Change the toe angle of the wheel 13. The toe angle adjusting mechanism 16 includes a toe angle adjusting motor 7 and a toe angle adjusting power transmission mechanism 30 for adjusting the toe angle by the rotation of the toe angle adjusting motor 7.

  The toe angle adjusting motor 7 is attached to the housing 19 of the steered shaft drive unit 14 concentrically with the steered shaft 10. The toe angle adjusting motor 7 is also a hollow motor, and its cylindrical hollow motor shaft 31 is provided on the outer periphery of the screw coupling portion 10 </ b> C in the steered shaft 10.

  The toe angle adjusting power transmission mechanism 30 includes an output gear 32 fixed to the hollow motor shaft 31, a first intermediate gear 33 that meshes with the output gear 32 via a counter gear 32a, and the first intermediate gear 33 and a spline. A toe angle adjusting intermediate shaft 35 that meshes with the fitting portion 34, a second intermediate gear 37 that meshes with the toe angle adjusting intermediate shaft 35 and the spline fitting portion 36, and the second intermediate gear 37 and counter gear 39. The input gear 38 meshes with the input gear 38 and the spline nut 40 fixed to the input gear 38. The rotation division shaft 10B of the steered shaft 10 is a spline shaft having tooth grooves formed on the outer periphery, and the spline nut 40 is spline-fitted to the rotation division shaft 10B. The rotary split shaft 10B and the spline nut 40 may be in sliding contact with each other, or may be in rolling contact with each other via a ball (not shown). In any case, rotation can be satisfactorily transmitted from the spline nut 40 to the rotary split shaft 10B.

  The first intermediate gear 33, the second intermediate gear 37, and the toe angle adjusting intermediate shaft 35 are connected to the spline teeth 33a, 37a formed by internal teeth formed on the intermediate gears 33, 37 and the toe angle adjusting intermediate shaft 35, respectively. The spline fitting parts 34 and 36 are comprised by meshing with the spline teeth 35a and 35b which consist of the formed external tooth. The spline teeth 35b of the toe angle adjusting intermediate shaft 35 are long in the axial direction, and the spline teeth 37a of the second intermediate gear 37 can mesh with any axial direction portion.

  The hollow motor shaft 31 is provided via a rolling bearing 41, the first intermediate gear 33 is provided via a rolling bearing 42, the second intermediate gear 37 is provided via a rolling bearing 43, and the spline nut 40 is provided via a rolling bearing 44. It is supported by the housing 19. Further, a rolling bearing 45 is interposed between the first intermediate gear 33 and the second intermediate gear 37, and both the gears 33 and 37 are rotatable with respect to each other. As described above, since the toe angle adjusting intermediate shaft 35 is engaged with the second intermediate gear 37 by the spline fitting portion 36, movement in the axial direction is allowed. The steered intermediate shaft 21 and the toe angle adjusting intermediate shaft 35 are arranged coaxially adjacent to each other, and a thrust bearing 46 is interposed between shaft ends of the intermediate shafts 21 and 35 facing each other. . Thereby, both the intermediate shafts 21 and 35 can be rotated relative to each other.

  When the steered shaft drive unit 14 is in a normal state (FIG. 2), the rotational output of the toe angle adjusting motor 7 is the hollow motor shaft 31, the output gear 32, the counter gear 32a, the first intermediate gear 33, and the toe angle adjusting motor. It is transmitted to the spline nut 40 through the intermediate shaft 35, the second intermediate gear 37, the counter gear 39, and the input gear 38, and the rotation division shaft 10B of the steered shaft 10 is rotated by the rotation of the spline nut 40. By rotating the rotation division shaft 10B with respect to the non-rotation division shaft 10A, the screwing length of the screw coupling portion 10C is adjusted and the turning shaft 10 is expanded and contracted. Thereby, the distance between the left and right tie rods 11 is changed, and the toe angle of the steered wheels 13 (FIG. 1) is changed. During the toe angle adjustment, as will be described later, the turning power transmission mechanism 18 and the toe angle adjustment power transmission mechanism 30 are controlled by the steering control means 5a so that the turning angles of the left and right steered wheels 13 coincide with the target values. Are operated in cooperation with each other.

As shown in the enlarged sectional view of FIG. 13, the rotary split shaft 10 </ b> B is connected to the tie rod 11 through a thrust bearing 96 and a ball joint 97 so as to be relatively rotatable. Specifically, a bottom nut-like cylindrical member 99 is attached to the tip of the rotary split shaft 10B opposite to the screw coupling portion 10C side by screwing with a male screw 98 formed on the outer periphery thereof. In this cylindrical member 99, a double row thrust bearing 96 is supported concentrically with the axial center of the rotary division shaft 10B. The thrust bearing 96 includes a raceway ring 100A supported at the shaft end of the rotary split shaft 10B, a raceway ring 100B supported on the inner surface of the end wall 99a of the tubular member 99 via a disc spring 102, and both of these raceways. It consists of a double-row thrust ball bearing composed of a bearing ring 100C disposed at an intermediate position between the rings 100A and 100B and balls 101 interposed between the bearing rings 100A and 100C and between the bearing rings 100B and 100C. That is, the thrust bearing 96 is supported in the cylindrical member 99 in a state in which a preload is applied by the disc spring 102 toward the shaft end of the rotary division shaft 10B. The ball joint 97 has a spherical surface portion 103 fixed to the tie rod 11, and a shaft portion 104a of a socket-shaped spherical seat member 104 that holds the spherical surface portion 103. Each shaft provided on the cylindrical member end wall 99a and the raceway ring 100B. It penetrates through the part insertion holes 105, 106 and is connected to an intermediate ring 100 </ b> C of the thrust bearing 96.
The tie rod 11 is directly connected to the non-rotating split shaft 10A that is not driven to rotate.

  In this way, since the tie rod 11 is connected via the thrust bearing 96 in addition to the ball joint 97 to the rotation division shaft 10B of the steered shaft 10 that is rotationally driven during toe angle adjustment, the axial load is reduced. Even in the loaded state, the friction torque between the rotary split shaft 10B and the tie rod 11 can be reduced. For this reason, the capacity | capacitance of the toe angle adjustment motor 7 which is a rotational drive source of the rotation division shaft 10B can be made small.

  The switching mechanism 17 switches the power transmission system of the steering power transmission mechanism 18 and the toe angle adjustment power transmission mechanism 30 when the steering motor 6 fails and when the toe angle adjustment motor 7 fails. Is for. The switching mechanism 17 includes a steering intermediate shaft 21 and a toe angle adjusting intermediate shaft 35, a linear motion actuator 47 that moves the intermediate shafts 21 and 35 together in the axial direction, and both the intermediate shafts 21 and 35. Transmission of the transmission connecting portions of the pushing power transmission mechanism 18 and the toe angle adjusting power transmission mechanism 30 by the movement of the intermediate shafts 21 and 35 by the pressing mechanism 48 that applies a pressing force so as to be maintained in contact with each other. A transmission engagement / disengagement mechanism 49 is provided.

  The linear actuator 47 includes a spring member 51 and a spring engagement / disengagement mechanism 52. Further, the spring engagement / disengagement mechanism 52 includes a linear / rotational motion conversion mechanism 53 that converts linear motion of the spring member 51 into rotational motion, and a rotation restriction mechanism 54 that regulates the rotational motion obtained by the linear / rotational motion conversion mechanism 53. And become.

  In this example, the spring member 51 is a compression coil spring and urges the support member 55 in the left direction in FIGS. That is, the end of the spring member 51 on the side in contact with the support member 55 linearly moves in the left-right direction. The support members 55 are provided adjacent to each other on the same axis as the steering intermediate shaft 21. A thrust bearing 56 is interposed between the support member 55 and the steering intermediate shaft 21, and a thrust roller bearing 57 is interposed between the support member 55 and the spring member 51, and the support member 55 is rotatable about the central axis.

  Further, in this example, the linear / rotational motion conversion mechanism 53 is a ball screw mechanism, and includes a ball screw shaft 58 that is integral with the support member 55 and a ball nut 59 that is screwed to the ball screw shaft 58. The linear / rotational motion conversion mechanism 53 may have a configuration other than the ball screw mechanism, for example, a combination of a rack and a pinion.

  As shown in FIG. 7, the rotation restricting mechanism 54 includes a protrusion 60 provided on a ball screw shaft 58 that is a rotation shaft, and a lever 61 that plays a role of stopping the rotation of the ball screw shaft 58 by being caught by the protrusion 60. And a rotation restricting drive source 62 for operating the lever 61. The protrusion 60 is a plate-like member in which a part of the outer periphery becomes a protrusion 60a that protrudes to the outer diameter side than the others, and a step surface 60b that the lever 61 hits on one end in the circumferential direction of the protrusion 60a. Is formed. Strictly speaking, the protrusion 60 a of the protrusion 60 is a protrusion on which the lever 61 is caught. The lever 61 is rotatably provided on a rotation center shaft 61 a parallel to the ball screw shaft 58, and has a pair of hook portions 61 b and 61 c that are hooked on the protrusion portion 60 a of the protrusion 60. The rotation restricting drive source 62 is composed of a direct acting actuator, for example, a linear solenoid. The rotation restricting drive source 62 includes an advance / retreat rod 62 a that moves forward and backward in one direction (vertical direction), and the advance / retreat rod 62 a is connected to the lever 61 via a connection link 63.

  FIG. 7A shows a state of the rotation restricting mechanism 54 when the steered shaft drive unit 14 is in a normal state. In this state, one catching portion 61b of the lever 61 is hooked on the projection 60a of the projection 60, thereby restricting the rotation of the projection 60 and the ball screw shaft 58 integral therewith. For this reason, the ball screw shaft 58 cannot be moved in the axial direction by the action of the linear / rotational motion converting mechanism 53 including the ball screw mechanism, and the spring member 51 (FIG. 2) is restricted from pushing the support member 55 (FIG. 2). Has been. That is, the spring member 51 is held in a compressed state, and is in an unbiased state in which it is impossible to bias both the intermediate shafts 21 and 35 (FIG. 2) in the axial direction.

  When the advance / retreat rod 62a of the rotation restricting drive source 62 is retracted from the state shown in FIG. 7A, the catch between the catch 61b of the lever 61 and the projection 60a of the projection 60 is released, and the ball screw shaft 58 can rotate. become. Thereby, the ball screw shaft 58 moves to the left in FIG. 2 while rotating with respect to the ball nut 59 by the elastic repulsive force of the spring member 51. That is, the spring member 51 is released from the compressed state and urges both the intermediate shafts 21 and 35 in the axial direction. When the protrusion 60 rotates by a predetermined phase, the protrusion 60a of the protrusion 60 is caught by the other hook 61c of the lever 61 as shown in FIG. 7B, and the protrusion 60 and the ball screw shaft 58 rotate. Is restrained. In the meantime, both the intermediate shafts 21 and 35 move in the axial direction to the left, and become the position when the toe angle adjusting motor fails in FIG.

  When the advance / retreat rod 62a of the rotation restricting drive source 62 is advanced from the state of FIG. 7B, the catch between the catch 61c of the lever 61 and the projection 60a of the projection 60 is released, and the ball screw shaft 58 can rotate. become. Accordingly, as described above, the spring member 51 biases the intermediate shafts 21 and 35 in the axial direction, and both the intermediate shafts 21 and 35 move in the axial direction to the left. Accordingly, the axial positions of the protrusion 60 and the lever 61 are deviated. Therefore, even if the protrusion 60 rotates, the protrusion 60a does not get caught by any of the hooks 61b and 61c of the lever 61, and the spring member 51 moves to the end of the linear motion range. The positions of the intermediate shafts 21 and 35 when the spring member 51 moves to the end of the linear motion range is the position at the time of the failure of the steering motor in FIG.

  The spring engagement / disengagement mechanism 52 can also be described as follows when viewed from the operational aspect. That is, the spring engagement / disengagement mechanism 52 is disposed within the linear motion range of the spring member 51 or within the motion range of the ball screw shaft 58 that is a member that linearly moves together with the spring member 51, and the obstacle that prevents the linear motion, The obstacle removing mechanism B opens the spring member 51 from the compressed state by removing the obstacle. In this case, the obstacle is a lever 61 that is caught by a protrusion 60 attached to the ball screw shaft 58 and prevents the linear motion of the ball screw shaft 58, and the obstacle removing mechanism B is within the movement range of the ball screw shaft 58. This is a mechanism that combines a rotation restricting drive source 62 and a connecting link 63 that act to remove the lever 61 as a protruding obstacle.

  As shown in FIGS. 2 to 4, the pressing mechanism 48 is adjacent to the toe angle adjusting intermediate shaft 35 and is coaxially disposed with both the turning and toe angle adjusting intermediate shafts 21 and 35. And a coil spring 65 that elastically biases the pressing shaft 64 toward the side pressing the toe angle adjusting intermediate shaft 35. The pressing shaft 64 and the coil spring 65 are accommodated in a pressing mechanism accommodating portion 19 a that is a part of the housing 19. A thrust bearing 66 is disposed between the opposite ends of the pressing shaft 64 and the toe angle adjusting intermediate shaft 35, so that the toe angle adjusting intermediate shaft 35 is rotatable with respect to the pressing shaft 64. ing.

The transmission engagement / disengagement mechanism 49 includes first to third transmission engagement / disengagement mechanisms 71 to 73.
The first transmission engagement / disengagement mechanism 71 includes the hollow motor shaft 20 of the steering motor 6, the intermediate shaft 21 for steering, and the first intermediate gear 33 that is a drive side member for adjusting the toe angle. When both the intermediate shafts 21 and 35 are in the reference position of FIG. 2 and when the toe angle adjusting motor is in the failed position of FIG. 3, the spline teeth 20a of the hollow motor shaft 20 and the turning intermediate shaft 21 The spline teeth 21a mesh with each other to form the spline fitting portion 27, whereby the hollow motor shaft 20 and the turning intermediate shaft 21 are coupled. When both the intermediate shafts 21 and 35 are at the position where the steering motor fails in FIG. 4, the spline teeth 21 a of the steering intermediate shaft 21 are disengaged from the spline teeth 20 a of the hollow motor shaft 20. The teeth 21 a mesh with the spline teeth 33 a of the first intermediate gear 33 to form the spline fitting portion 74, whereby the turning intermediate shaft 21 is coupled to the first intermediate gear 33.

  The second transmission engagement / disengagement mechanism 72 includes a steering intermediate shaft 21, a first intermediate gear 33 that is a drive side member for toe angle adjustment, and an intermediate shaft 35 for toe angle adjustment. When both the intermediate shafts 21 and 35 are at the reference position in FIG. 2, the spline teeth 33 a of the first intermediate gear 33 and the spline teeth 35 a of the toe angle adjusting intermediate shaft 35 are engaged with each other to form the spline fitting portion 34. Thus, the first intermediate gear 33 and the toe angle adjusting intermediate shaft 35 are coupled. When the intermediate shafts 21 and 35 are at the toe angle adjusting motor failure position in FIG. 3 and at the steering motor failure position in FIG. 4, the spline fitting portion 34 is disengaged. Thus, the first intermediate gear 33 and the toe angle adjusting intermediate shaft 35 are disconnected.

  The third transmission engagement / disengagement mechanism 73 includes a toe angle adjusting intermediate shaft 35, a second intermediate gear 37 that is a toe angle adjusting driven member, and the housing 19. Spline teeth 75 a made of internal teeth are formed at the proximal end of the pressing mechanism housing portion 19 a of the housing 19. When both the intermediate shafts 21 and 35 are in the reference position of FIG. 2, the spline teeth 35 b of the toe angle adjusting intermediate shaft 35 and the spline teeth 37 a of the second intermediate gear 37 are engaged with each other to form the spline fitting portion 36. Thus, the toe angle adjusting intermediate shaft 35 and the second intermediate gear 37 are coupled. When the intermediate shafts 21 and 35 are at the toe angle adjusting motor failure position in FIG. 3 and at the steering motor failure position in FIG. 4, in addition to the spline fitting portion 36, The spline teeth 35b of the toe angle adjusting intermediate shaft 35 and the spline teeth 75a of the housing 19 mesh with each other to form a spline fitting portion 75. By this spline fitting portion 75, the toe angle adjusting intermediate shaft 35 is coupled to the housing 19 and its rotation is restricted.

  In the switching operation of the transmission engagement / disengagement mechanism 49, the toe angle adjusting intermediate shaft 35 is moved to the first intermediate gear 33 in the process in which both the intermediate shafts 21, 35 move in the axial direction from the reference position to the steering motor failure position. The positional relationship between the members is set so that the toe angle adjusting intermediate shaft 35 is coupled to the housing 19 prior to removal from the housing 19.

  In order to smoothly perform the switching operation of the transmission switching mechanism 49, the spline teeth 21a of the steering intermediate shaft 21 and the spline teeth 35a, 35b of the toe angle adjusting intermediate shaft 35 are formed of a normal spline shaft shown in FIG. It is desirable that the shape of the tooth tip is not flat like the spline tooth 80a in 80, and the shape of the tooth tip is an acute angle as shown in FIG. 9 or FIG. 10, for example. Alternatively, as another example, as shown in FIG. 11 or FIG. 12, it is desirable that the shape of the tooth tip of the spline teeth 21a, 35a, 35b is a tapered shape without the tooth tip protrusion.

  Further, as shown in FIG. 10 or FIG. 12, a protruding portion 76 is protruded from the spline teeth 21a toward the end of the shaft on the side facing the toe angle adjusting intermediate shaft 35 of the turning intermediate shaft 21. It may be provided. The outer diameter of the protrusion 76 is set to be equal to or smaller than the root radius of the spline teeth 21a. If such a protruding portion 76 is provided at the tip of the steering intermediate shaft 21, the steering intermediate shaft 21 and the toe angle adjusting intermediate shaft 35 are positioned from the reference position to the position when the steering motor has failed. At the time of switching, the spline teeth 35a of the toe angle adjusting intermediate shaft 35 are first disengaged from the spline teeth 33a of the first intermediate gear 33 by the length of the protruding portion 76 in the axial direction. The spline teeth 21 a mesh with the spline teeth 33 a of the first intermediate gear 33. That is, after the dynamic coupling between the toe angle adjusting motor 7 and the toe angle adjusting intermediate shaft 35 is released, the toe angle adjusting motor 7 and the turning intermediate shaft 21 are dynamically coupled. 2 to 4 employs a steering shaft intermediate shaft 21 having a shaft end shape shown in FIG. 10 or 12.

  The steering control means 5a of the ECU 5 controls the steering reaction force motor 4, the steering motor 6, and the toe angle adjusting motor 7. That is, the steering control means 5a is determined based on a steering angle signal detected by the steering angle sensor 2, a steering wheel rotation speed signal detected by a vehicle speed sensor (not shown), and signals of various sensors that detect driving conditions. The steering reaction force motor is controlled by setting a target steering reaction force and feeding back a steering torque signal detected by the steering torque sensor 3 so that the actual steering reaction force torque matches the target steering reaction force. To do. Further, by selectively setting the rotation direction and the rotation amount of the steering motor 6 and the toe angle adjusting motor 7, the steering wheel 13 and the toe angle adjustment are selectively performed. When adjusting the toe angle, the turning power transmission mechanism 18 and the toe angle adjustment power transmission mechanism 30 are operated in cooperation with each other so that the turning angles of the left and right steering wheels 13 coincide with the target values. This cooperative operation will be specifically described later.

  The steering control means 5a includes a toe angle adjustment control unit 111 that controls the toe angle adjusting motor 7 so that the toe angle adjustment is continuously performed according to the vehicle speed and the yaw rate. Here, a dedicated yaw rate sensor 112 (FIG. 1) for detecting the yaw rate is provided near the center of gravity of the vehicle. The toe angle adjustment control unit 111 uses the yaw rate detected by the yaw rate sensor 112 and the vehicle speed detected by the vehicle speed sensor 114 for toe angle adjustment control. Instead of the yaw rate sensor 112, as shown in FIG. 18, a lateral force detection sensor 113 for detecting a lateral force acting on the wheels 13, 13A may be provided on the hub 110 of all the wheels 13, 13A of the vehicle. In this case, the toe angle cooking control unit 111 calculates the yaw rate based on the output of the total lateral force detection sensor 113 and the positional relationship between the vehicle center of gravity and each of the wheels 13 and 13A, and the calculated yaw rate is controlled by the toe angle adjustment control. Used for.

  The toe angle adjustment control unit 111 continuously adjusts the toe angle according to the vehicle speed and the yaw rate according to a predetermined rule. However, the above “specified rule” may have any content. Further, it may be determined as a calculation formula, or may be determined as a table or the like. As an example of the “predetermined rule”, the toe angle adjustment is performed so that the difference in cornering force acting on the turning inner and outer wheels to be steered is not more than a set value. For example, the toe angle is adjusted so that the cornering forces acting on the turning inner and outer wheels are substantially equal to each other. The toe angle adjustment is based on the vehicle speed and yaw rate detection means 114, 112 (113) based on the vehicle speed and yaw rate so that the difference in cornering force between the turning inner wheel and the outer wheel is less than a set value. By controlling the corners, the load can be equalized.

  Further, the toe angle adjustment control unit 11 may set the toe angle to the out side as the vehicle speed increases for the same yaw rate. As the vehicle speed increases, the toe angle that equalizes the cornering force moves closer to the toe-out side, as will be described later with a graph. Therefore, during high-speed turning, if the toe angle is adjusted to the out side according to the vehicle speed and the yaw rate, that is, the turning radius, it is safe and the tire burden is reduced. Note that, with respect to the same yaw rate, the control for setting the toe angle to the out side as the vehicle speed increases may be performed only when the vehicle speed is arbitrarily determined or higher.

  The failure handling control means 5 b controls the rotation restricting drive source 62 of the switching mechanism 17. That is, when the failure handling control means 5b detects a failure of the steering motor 6 and a failure of the toe angle adjusting motor 7, the rotation restricting drive source 62 is operated in response to the failure, and the steering is controlled. Both the intermediate shafts 21 and 35 for adjusting the toe angle and adjusting the toe angle are moved in the axial direction from the reference position to the position at the time of the failure of the steering motor or the position at the time of the toe angle adjusting motor failure.

  The correction operation control means 5c corrects the control for moving both the intermediate shafts 21 and 35 in the axial direction by the failure handling control means 5b. Specifically, when the spline teeth 35b of the toe angle adjusting intermediate shaft 35 and the spline teeth 75a of the housing 19 are spline-fitted 75 to restrict the rotation of the toe angle adjusting intermediate shaft 35, the toe angle adjusting motor 7, the toe angle adjusting intermediate shaft 35 is rotated by one pitch or more of the spline teeth 35b, so that the phases of both the spline teeth 35b and 75a are aligned. By performing such a correction operation, the toe angle adjusting intermediate shaft 35 can be smoothly fixed to the housing 19 without malfunction.

  Next, the operation in the steered shaft drive unit 14 of this steer-by-wire type steering device will be described. When the steered motor 6 and the toe angle adjusting motor 7 are normal, the rotation of the hollow motor shaft 20 of the steered motor 6 is rotated via the steered power transmission mechanism 18 as shown in FIG. The rotation of the hollow motor shaft 31 of the toe angle adjusting motor 7 is transmitted to the spline nut 40 through the toe angle adjusting power transmission mechanism 30. The rotation of the ball nut 26 screwed into the ball screw shaft portion 10a of the non-rotating divided shaft 10A of the steered shaft 10 moves the non-rotating divided shaft 10A and the rotating divided shaft 10B integrally in the axial direction, and thereby steered wheels. 13 steering is performed. The rotation of the spline nut 40 that is spline-fitted to the rotation division shaft 10B of the steered shaft 10 rotates the rotation division shaft 10B, and this rotation causes the tie rods 11 connected to both ends of the steered shaft 10 to move forward and backward. Adjustments are made.

  Specifically, the toe angle adjustment is performed by an operation in which the turning power transmission mechanism 18 and the toe angle adjustment power transmission mechanism 30 cooperate with each other as follows. That is, when the spline nut 40 is rotated by the toe angle adjusting motor 7, the rotary split shaft 10 </ b> B rotates together with the spline nut 40. Since the rotation division shaft 10B is screwed to the non-rotation division wheel 10A by a concentric screw coupling portion 10C and is movable in the axial direction with respect to the spline nut 40, the rotation division shaft 10B rotates. The rotation division shaft 10B moves in the axial direction with respect to the non-rotation division shaft 10A by an axial distance corresponding to the rotation amount in the screw coupling portion 10C. Thereby, since the length of the steered shaft 10 including the non-rotating divided shaft 10A and the rotating divided shaft 10B is changed, the toe angle is changed. However, if the rotation division shaft 10B is moved, the turning angle changes. Therefore, the ball nut 26 is rotated by the steering motor 6, and the non-rotating divided shaft 10A is moved in the direction opposite to the moving direction of the rotating divided shaft 10B. In other words, the non-rotating divided shaft 10A is moved by the turning motor 6 by half the axial relative movement length of the rotating divided shaft 10B with respect to the non-rotating divided shaft 10A by the toe angle adjusting motor 7, thereby turning the turning shaft. The central position of the entire length of 10 is maintained. Thus, the toe angle adjustment is performed so that the turning angles of the left and right turning wheels 13 coincide with the target value, that is, without changing the turning angle. When the toe angle is adjusted, the steering control means 5a of the ECU 5 drives the steering motor 6 together with the toe angle adjusting motor 7 in this way, cancels the unbalanced movement of the rotary division shaft 10B, and changes the turning angle. Make toe angle adjustment without any problem.

  When the toe angle adjusting motor 7 has failed, the rotation restricting drive source 62 of the switching mechanism 17 is actuated by a command from the failure responding control means 5b of the ECU 5, so that the rotation restricting mechanism 54 is moved as shown in FIG. The state is switched to the state shown in FIG. As a result, due to the elastic repulsive force of the spring member 51 that constitutes the linear actuator 47, both the intermediate shafts 21 and 35 move axially to the position where the toe angle adjusting motor has failed in FIG.

  At the position of the toe angle adjusting motor failure, the first transmission engaging / disengaging mechanism 71 holds the steering intermediate shaft 21 while being coupled to the hollow motor shaft 20, and the second transmission engaging / disengaging mechanism 72 adjusts the toe angle. The intermediate shaft 35 is disconnected from the first intermediate gear 33, and the toe angle adjusting intermediate shaft 35 is connected to the housing 19 by the third transmission engagement / disengagement mechanism 73. That is, the toe angle adjusting power transmission mechanism 30 becomes incapable of transmitting power and the rotation of the toe angle adjusting intermediate shaft 35 is restricted. As a result, only the turning by the turning motor 6 is performed. As described above, the steered shaft drive section 14 employs the shaft end-shaped steered intermediate shaft 21 shown in FIG. 12 or FIG. 14, and the toe angle adjusting motor 7 and the toe angle adjusting intermediate shaft 21. After the dynamic coupling with the shaft 35 is released, the toe angle adjusting motor 7 and the turning intermediate shaft 21 are coupled dynamically, so that the transmission system can be switched smoothly.

  When the steering motor 6 has failed, the rotation restriction drive source 62 of the switching mechanism 17 is actuated by a command from the failure response control means 5b of the ECU 5, and the rotation restriction mechanism 54 is in the state shown in FIG. Then, after going through the state of FIG. 5B, the state of FIG. Thereby, the intermediate shafts 21 and 35 are moved in the axial direction by the elastic repulsive force of the spring member 51 to the steering motor failure position in FIG. 4 via the toe angle adjustment motor failure position. To do.

  At the time of the failure of the steering motor, the first transmission engagement / disengagement mechanism 71 and the second transmission engagement / disengagement mechanism 72 connect the steering intermediate shaft 21 and the hollow motor shaft 20, and the toe angle adjustment intermediate shaft 35. The first intermediate gear 33 is uncoupled, and the turning intermediate shaft 21 is newly coupled to the first intermediate gear 33, and the toe angle adjusting intermediate shaft 35 is coupled to the housing 19 by the third transmission engagement / disengagement mechanism 73. It becomes the state. That is, the steered motor 6 is disconnected from the steered power transmission mechanism 18 and the rotation of the toe angle adjusting intermediate shaft 35 is restricted, and the steered intermediate shaft 21 is connected to the toe angle adjusting power transmitting mechanism 30. Is done. Thereby, instead of the steering motor 6, the rotation of the toe angle adjusting motor 7 can be transmitted to the steering power transmission mechanism 18 to be steered.

  Thus, in this steer-by-wire type steering device, when the steering motor 6 fails by the switching mechanism 17, the steering motor 6 is disconnected from the steering power transmission mechanism 18 and the change in the toe angle is detected. By stopping and transmitting the rotation of the toe angle adjusting motor 7 to the steered power transmission mechanism 18 instead of the steered motor 6, the steerable can be steered even when the steered motor fails. A fail-safe function is provided. Further, when the toe angle adjusting motor 7 is lost by the switching mechanism 17, the toe angle adjusting power transmission mechanism 30 is set in a power transmission disabled state so that only the turning by the steering motor 6 is performed, thereby adjusting the toe angle. The toe angle adjusting mechanism 16 can be fixed and the vehicle can travel safely when the motor fails. A series of operations for switching the power transmission system of the steering power transmission mechanism 18 and the toe angle adjustment power transmission mechanism 30 at the time of the failure of the steering motor and the toe angle adjustment motor is performed by the linear actuator 47. By moving the intermediate shafts 21 and 35 for adjusting the toe angle and adjusting the toe angle in the axial direction, the transmission engagement / disengagement mechanism 49 is surely performed.

Further, the steered shaft 10 is divided into two in the axial direction, the non-rotating divided shaft 10A and the rotating divided shaft 10B, and both the divided shafts 10A and 10B are coupled to each other by a screw coupling portion 10C concentric with the shaft center. As a result, the distance between the left and right tie rods 11 can be changed by rotating the rotation division shaft 10B with respect to the non-rotation division shaft 10A. The left and right tie rods 11 can be directly connected to the non-rotating divided shaft 10A and the rotating divided shaft 10B, respectively. For this reason, this steer-by-wire type steering device has a compact configuration, can reduce the overall axial length of the portion where the steered shaft 10 is provided, and is easily mounted on a vehicle.
In addition, when the steered shaft is not divided in the axial direction, an advancing / retreating member is provided at both ends of the steered shaft in accordance with the rotation of the steered shaft, and left and right tie rods are attached to these advancing / retreating members. Must be configured. Therefore, the entire axial length of the place where the steered shaft is provided is increased.

  Further, since the tie rod 11 is connected via the thrust bearing 96 in addition to the ball joint 97 to the rotation split shaft 10B of the steered shaft 10 that is rotationally driven during toe angle adjustment, an axial load is applied. Even in this state, the friction torque between the rotary split shaft 10B and the tie rod 11 can be reduced, and the capacity of the toe angle adjusting motor 7 which is the rotational drive source of the rotary split shaft 10B can be reduced. For this reason, the structure of a steer-by-wire type steering apparatus can be made further compact.

  Since the steered shaft 10 having a structure divided into two in the axial direction has low rigidity in the vicinity of the screw coupling portion 10C of both the divided shafts 10A and 10B, it is necessary to increase support rigidity in the vicinity of the screw coupling portion 10C. Further, it is necessary to avoid applying a moment load to the ball screw shaft portion 10a as much as possible. As in this embodiment, if the outer diameter surface of the ball screw shaft portion 10a close to the screw coupling portion 10C is supported by the slide bearing 95, the support rigidity in the vicinity of the screw coupling portion 10C is improved and the ball screw shaft portion 10a The moment load can be avoided. It is effective if the axial position of the slide bearing 95 is between the screw coupling portion 10 </ b> C and the ball nut 26.

  By using a hollow motor as the steering motor 6 and the toe angle adjusting motor 7, the intermediate shaft 21 for steering and the steering shaft 10 can be inserted into the hollow portions of the hollow motors 6 and 7, respectively. . Therefore, each component of the steer-by-wire steering device can be arranged without difficulty in a narrow space, and the overall configuration can be made compact. The components of the switching mechanism 17 other than the steering intermediate shaft 21 may be disposed in the hollow portion of the steering motor 6. Only one of the steering motor 6 and the toe angle adjusting motor 7 may be a hollow motor. Further, the turning intermediate shaft 21 and the toe angle adjusting intermediate shaft 35 are arranged coaxially and freely movable in the axial direction, and both the intermediate shafts 21 and 35 are moved together in the axial direction by the linear actuator 47. With the configuration, the switching mechanism 17 can be made compact.

  A ball screw shaft portion 10a is provided on the non-rotating split shaft 10A of the steered shaft 10, and a ball nut 26 is screwed onto the ball screw shaft portion 10a. Only the nut 26 can be used, and the structure of the steering power transmission mechanism 18 is simplified. Further, the rotation division shaft 10B of the steered shaft 10 is used as a spline shaft portion, and the spline nut 40 is engaged with the rotation division shaft 10B, so that the operation position of the toe angle adjusting power transmission mechanism 30 is at least the spline nut 40 only. Thus, the configuration of the toe angle adjusting power transmission mechanism 30 is simplified.

  It should be noted that since the torsion angle adjustment by the toe angle adjustment motor 7 and the replacement as the steering drive source when the steering motor 6 fails is an operation performed when the vehicle is running, the maximum generated torque is This is much smaller than the torque required for the steering motor 6 during the cutting operation. Therefore, the toe angle adjusting motor 7 may be smaller than the steering motor 6.

  In particular, in this steer-by-wire type steering device, the toe angle adjustment control unit 111 of the steering control means 5a continuously adjusts the toe angle according to the vehicle speed and yaw rate. The toe angle of the inner and outer rings can be finely controlled according to changes, for example, so that the cornering force acting on the inner and outer rings is substantially equal (specifically, the difference in cornering force between the inner and outer rings is below a predetermined set value) To) toe angle can be controlled. Thereby, it is possible to equalize the load applied to the inner and outer wheels and move away from the dangerous area which is a tire limit. Further, the tire side slip angle under a high ground load condition can be reduced, and the amount of tire wear can also be reduced.

  FIGS. 14 to 17 show the constant speeds of 80 km / h, 100 km / h, 120 km / h, and 140 km / h at the corners of R200 using a three-degree-of-freedom (lateral, yawing, rolling) vehicle motion model. The graph shows the calculation result of how much the cornering force acting on the tire changes depending on the toe angle when turning at. The calculated data are shown in Tables 1 to 4.

  The danger region mentioned here is a region where the cornering force exceeds the tire friction force, and strictly speaking, it changes depending on the tire contact force. Here, simply assume a tire for a small vehicle with a road index of 84, and define a danger zone by slipping if a cornering force of 4000 N or more is applied, assuming that the maximum contact force is 500 kg and the friction coefficient of the dry road surface is 0.8. is doing.

  In the case of a vehicle speed of 80 km / h (FIG. 14), the cornering force acting on the inner and outer wheels of the front wheel being steered becomes uniform by setting the toe angle around −0.3 deg (slightly toe out). Since the sum of the cornering forces of the inner and outer rings is constant, it is possible to leave the danger area by equalizing both. It can be seen from the graphs of FIGS. 14 to 17 that the toe angle that equalizes the cornering force is closer to the negative side, that is, the toe-out side as the vehicle speed increases to 100 km / h, 120 km / h, and 140 km / h. Therefore, during high-speed turning, if the toe angle is adjusted to the out side according to the vehicle speed and the yaw rate, that is, the turning radius, it is safe and the tire burden is reduced.

DESCRIPTION OF SYMBOLS 1 ... Steering wheel 2 ... Steering angle sensor 5a ... Steering control means 6 ... Steering motor 7 ... Toe angle adjusting motor 10 ... Steering shaft 10A ... Non-rotation division shaft 10B ... Rotation division shaft 10C ... Screw coupling part 10a ... Ball screw shaft portion 10b ... non-concentric circle portion 11 ... tie rod 17 ... switching mechanism 18 ... turning power transmission mechanism 20 ... hollow motor shaft 21 ... intermediate shaft 26 for turning ... ball nut 30 ... toe angle adjusting power transmission mechanism 31 ... hollow Motor shaft 35 ... Toe angle adjusting intermediate shaft 40 ... Spline nut 81 ... Male screw 82 ... Female screw 83 ... Fitting shaft portion 86 ... Inner diameter hole 88 ... Retaining means 93 ... Non-rotating means 94, 95 ... Slide bearing 96 ... Thrust bearing 97 ... Ball joint 110 ... Hub 111 ... Toe angle adjustment control unit 112 ... Yaw rate sensor 113 ... Side force detection sensor

Claims (20)

A steering shaft provided with tie rods on both left and right ends, a steering wheel not mechanically connected to the steering shaft, a steering angle sensor for detecting the steering angle of the steering wheel, a steering motor, A steering power transmission mechanism for transmitting the rotation of the steering motor to the steering shaft, a toe angle adjustment motor, a toe angle adjustment power transmission mechanism for adjusting a toe angle by the rotation of the toe angle adjustment motor, Steering control means that generates a steering angle command signal and a toe angle command signal based on the steering angle detected by the steering angle sensor, and applies the command signals to the steering motor and toe angle adjustment motor, respectively. In the steer-by-wire type steering apparatus provided,
The steering control means has a toe angle adjustment control unit that controls a toe angle adjusting motor so as to continuously adjust the toe angle according to a predetermined rule according to a vehicle speed and a yaw rate. By-wire steering device.   The steer-by-wire steering system according to claim 1, wherein a dedicated yaw rate sensor for detecting a yaw rate is provided near the center of gravity of the vehicle, and the toe angle adjustment control unit uses the yaw rate detected by the yaw rate sensor for toe angle adjustment control.   2. The lateral force detection sensor for detecting the lateral force acting on the wheels is provided in a hub of all the vehicle wheels, and the toe angle adjustment control unit outputs the output of the all lateral force detection sensor, the vehicle center of gravity, and each wheel. A steer-by-wire steering device in which the yaw rate calculated based on the positional relationship is used for toe angle adjustment control.   The toe angle adjustment control unit according to any one of claims 1 to 3, wherein the toe angle adjustment control unit adjusts the toe angle so that a difference in cornering force acting on the turning inner and outer wheels to be steered is equal to or less than a set value. Steer-by-wire steering device.   5. The steer-by-wire steering system according to claim 4, wherein the toe angle adjustment control unit sets the toe angle to the out side as the vehicle speed increases for the same yaw rate. 6. The steering motor according to claim 1, wherein when the steering motor fails, the steering motor is disconnected from the steering power transmission mechanism and a change in toe angle is stopped. , Instead of the steering motor, the rotation of the toe angle adjusting motor is transmitted to the steering power transmission mechanism to enable the steering, and when the toe angle adjusting motor fails, the toe angle adjusting power is reduced. Provided a switching mechanism that makes the transmission mechanism in a state where power cannot be transmitted and that only allows the steering by the steering motor,
The steered shaft is divided into two axially divided into a non-rotating divided shaft and a rotating divided shaft, and both the divided shafts are coupled to each other by a screw coupling portion concentric with the shaft center, By rotating the rotating split shaft to steer the steered wheel by axially moving the rotating split shaft and rotating the rotary split shaft with respect to the non-rotating split shaft, and adjusting the screwing length of the screw coupling portion, The rotating split shaft has a function of changing the toe angle of the steered wheel by changing the distance between the left and right tie rods. It is connected via a thrust bearing that can rotate around the center,
The steered power transmission mechanism is a mechanism for axially moving the non-rotating divided shaft and the rotating divided shaft of the steered shaft by the rotation of the steering motor,
The toe angle adjustment power transmission mechanism is a mechanism that rotates a rotation division shaft with respect to a non-rotation division axis of the steered shaft by rotation of the toe angle adjustment motor,
The steered power transmission mechanism and the toe angle adjusting power transmission mechanism are steered to be operated in cooperation with each other so that the steered angles of the left and right steered wheels coincide with a target value under the control of the steering control means. By-wire steering device.   The steer-by-wire steering apparatus according to claim 6, wherein the toe angle adjusting motor is a hollow motor, and the steered shaft is inserted into a hollow motor shaft of the toe angle adjusting motor including the hollow motor.   The steer-by-wire steering apparatus according to claim 6, wherein the steering motor is a hollow motor, and the components of the switching mechanism are inserted into a hollow motor shaft of the steering motor including the hollow motor.   In any one of Claims 6 thru | or 8, A ball screw axial part is provided in the non-rotation division | segmentation axis | shaft of the said steering shaft, The ball nut screwed together with this ball screw axial part is provided only rotatably, The said The steered power transmission mechanism is a steer-by-wire steering device in which the ball nut is rotated by the rotation of the steering motor and the steered shaft is moved in the axial direction to perform the steering.   10. The steer-by-wire steering device according to claim 9, wherein the ball nut is a top-circulating ball system, and the ball nut is supported by a double-row angular ball bearing and a deep groove ball bearing.   The steer-by-wire steering device according to claim 9, wherein an outer diameter surface of the ball screw shaft portion of the non-rotating split shaft of the steered shaft is supported by a slide bearing.   The steer-by-wire type steering apparatus according to any one of claims 9 to 11, further comprising a detent means for preventing the non-rotating divided shaft of the steered shaft from rotating about the axis.   The non-concentric circle part according to claim 12, wherein the rotation preventing means is formed on a non-rotating divided shaft of the steered shaft, and has a non-concentric circular portion whose outer shape in a cross section perpendicular to the axial direction is different from a concentric circle at the shaft center. A steer-by-wire steering apparatus comprising a fixed bearing and a sliding bearing in which the non-concentric circular portion is slidably fitted in the axial direction.   In any one of Claims 5 thru / or 13, a spline shaft part is provided in the rotation division shaft of the steered shaft, and a spline nut meshing with the spline shaft part so as to be relatively movable in the axial direction is provided rotatably. The toe angle adjusting power transmission mechanism rotates the spline nut by the toe angle adjusting motor to rotate the rotating split shaft of the steered shaft, and screw connection of the non-rotating split shaft and the rotary split shaft A steer-by-wire steering device that changes the toe angle of the steered wheel by changing the length of the steered shaft by adjusting the screwing length of the portion.   The steer-by-wire steering device according to claim 14, wherein the spline teeth of the spline shaft portion of the steered shaft and the spline teeth of the spline nut are in sliding contact.   The steer-by-wire steering device according to claim 14, wherein the spline teeth of the spline shaft portion of the steered shaft and the spline teeth of the spline nut are in rolling contact.   The steer-by-wire steering device according to any one of claims 5 to 16, wherein the screw coupling portion is a square screw or a trapezoidal screw.   In any one of Claims 5 thru | or 17, the internal-diameter hole concentric with an axial center is provided in the division | segmentation axis | shaft in which the internal thread of the said screw coupling part is provided among the said non-rotation division | segmentation axis | shaft and rotation division | segmentation axes. A steer-by-wire steering apparatus in which a fitting shaft portion that fits into the inner diameter hole is provided on a split shaft provided with a male screw of the screw coupling portion.   The steer-by-wire steering device according to claim 18, further comprising a retaining means for restricting a relative axial positional relationship between the inner diameter hole and the fitting shaft portion so that the fitting shaft portion is not detached from the inner diameter hole.   The steer-by-wire steering apparatus according to any one of claims 5 to 19, wherein the toe angle adjusting motor has a maximum generated torque smaller than a maximum generated torque of the steering motor.

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