JP2019171905A - Steering system and vehicle comprising the same - Google Patents

Abstract

To provide a steering system which reduces a brake distance by assisting a brake and thereby can increase safety of a vehicle, in a sudden brake operation or in an emergency situation such as when a brake system is abnormal, and to provide a vehicle comprising the steering system.SOLUTION: A steering system 101 includes: a first steering device 11; a second steering device 150 equipped with a mechanism unit 150a for individually steering left and right wheels according to drive of steering actuators, and a control unit 150b for controlling the steering actuators; and a vehicle information detector 110 for detecting a vehicle speed and brake force. The control unit 150b includes: determination means 33 for determining whether or not an emergency braking state has occurred from the vehicle speed and the brake force; and emergency braking state toe angle control means 36 for controlling the steering actuators so that the left and right wheels are set to a defined toe angle, when the determination means 33 determines that the emergency braking state has occurred.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a steering system and a vehicle including the steering system, and to a technique for improving the safety of the vehicle.

In a vehicle such as a general automobile, a steering wheel and a steering device are mechanically connected, and both ends of the steering device are connected to the left and right wheels by tie rods. Therefore, the turning angle of the left and right wheels due to the movement of the handle is determined by the initial setting.
Vehicle geometry includes (1) “Parallel geometry” where the left and right wheels have the same turning angle. (2) The turning inner wheel angle is turned larger than the turning outer wheel angle so that the turning center becomes one place. Ackermann geometry is known.

The geometry of the vehicle affects the stability and safety of running.
For example, Patent Documents 1 and 2 have been proposed regarding a mechanism in which the steering geometry is variable in accordance with the traveling state. In Patent Literature 1, the steering geometry is changed by relatively changing the knuckle arm and the joint position. In Patent Document 2, two motors are used, and both the toe angle and the camber angle can be tilted to an arbitrary angle. Patent Document 3 proposes a four-wheel independent steering mechanism.

  The Ackermann geometry is the difference in steering angle between the left and right wheels so that each wheel turns around a common point in order to make the vehicle turn smoothly when turning at low speeds where the centrifugal force acting on the vehicle can be ignored. Is set. However, in high-speed turning where the centrifugal force cannot be ignored, it is desirable that the wheels generate a cornering force in a direction that balances with the centrifugal force. Therefore, the parallel geometry is preferable to the Ackermann geometry.

As described above, since a general vehicle steering device is mechanically connected to a wheel, generally only a single fixed steering geometry can be taken, and an intermediate between the Ackermann geometry and the parallel geometry. Often set to static geometry.
According to the proposals in Patent Documents 1 and 2, the steering geometry can be changed, but there is the following problem.

  In Patent Document 1, the knuckle arm and the joint position are relatively changed to change the steering geometry. However, including a motor actuator that obtains a large force enough to change the vehicle geometry in such a part is as follows. It is very difficult due to space constraints. Further, the change in the wheel angle due to the change at this position is small, and in order to obtain a large effect, it is necessary to change it greatly, that is, to move it greatly.

In Patent Document 2, since two motors are used, not only the cost increases due to the increase in the number of motors, but also the control becomes complicated.
In Patent Document 3, since the hub bearing is cantilevered with respect to the steered shaft, the rigidity is lowered, and there is a possibility that the steering geometry changes due to generation of an excessive traveling lateral force.
The conventional mechanism having an auxiliary turning function as described above has a complicated structure because it aims to arbitrarily change the toe angle or camber angle of the wheel in the vehicle. In addition, it is difficult to ensure rigidity because of the large number of components, and the entire mechanism is increased in size and weight to ensure rigidity.

JP 2009-226972 A German Patent Application Publication No. 10201206337 JP 2014-061744 A

In a vehicle in which the wheel and the steering device are mechanically connected, the toe angle of the wheel cannot be changed during traveling.
In addition, it is difficult to ensure rigidity because of the large number of components, and the entire mechanism is increased in size and weight to ensure rigidity.
Usually, the function of stopping the vehicle is only the brake, and it is difficult to stop the vehicle when an abnormality occurs in the brake.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steering system capable of improving the safety of a vehicle by assisting the brake and reducing the braking distance in the event of an emergency such as sudden braking or when the braking system is abnormal. Is to provide a vehicle.

A steering system 101 of the present invention is a steering system provided in a vehicle 100,
A first steering device 11 for turning the wheels 9 of the vehicle 100 in accordance with a steering amount command output by the steering command devices 200 and 200A;
A mechanism unit 150a that individually steers left and right wheels 9 and 9 by driving a steering actuator 5 provided in a tire housing 105 of the vehicle 100, and a control unit 150b that controls the steering actuator 5 are provided. A second steering device 150 having
A vehicle information detection unit 110 that detects vehicle information including vehicle speed and braking force,
The controller 150b includes emergency braking state toe angle control means 36 that performs toe angle control on the steering actuator 5 when a sudden brake command is output from the brake command means.
The brake command means is an automatic brake device or a brake pedal force sensor. The automatic brake device outputs the "sudden brake command" when it is judged that the collision condition has been satisfied by recognizing the surrounding conditions of other vehicles, obstacles, etc. from sensors such as cameras or millimeter wave radars. . The brake pedal force sensor is a sensor that is output in accordance with the brake pedal force of the brake operation means by the driver. The brake pedal force (brake force) that is output from the sensor is equal to or greater than a threshold value, and the amount of change in the brake pedal force is a threshold value. In this case, the brake pedal force is the “sudden brake command”.
When the vehicle 100 is equipped with an automatic brake device, the emergency braking state toe angle control means 36 performs toe angle control when a sudden brake command is output from either or both of the automatic brake device and the brake pedal force sensor. Do.
When the vehicle 100 is not equipped with an automatic brake device, the emergency braking state toe angle control means 36 performs toe angle control when a sudden braking command is output from the brake pedal force sensor.

  According to this configuration, the first steering device 11 turns the wheels according to the steering amount command output by the steering command devices 200 and 200A. As the steering command devices 200 and 200A, for example, a driver's steering wheel or an automatic steering command device can be applied. Adjustment of the direction of the vehicle 100 by such a steering command device or the like can be performed similarly to a conventional vehicle.

  The second steering device 150 drives the steering actuator 5 provided in the tire housing 105 to individually steer the left and right wheels 9 and 9. When a sudden brake command is output from the brake command means, the emergency braking state toe angle control means 36 in the control unit 150 b performs toe angle control on the steering actuator 5. As a result, in an emergency braking state, the rotational resistance of each wheel is increased to shorten the braking distance and improve the vehicle safety, compared to when each wheel is in a straight traveling state (toe angle is zero degrees), for example. be able to.

  The emergency braking state toe angle control means 36 may use the toe angle as a maximum angle. In this case, the braking resistance can be further shortened by increasing the rotational resistance of the left and right wheels 9, 9 to the maximum. Further, since the toe angle is unconditionally set to the maximum angle when a sudden braking command is output, the control system can be simplified.

  The emergency braking state toe angle control means 36 may determine the toe angle according to the vehicle speed. The relationship between the vehicle speed and the toe angle is determined using, for example, a map or an arithmetic expression. According to this configuration, it is possible to prevent the wheel 9 from being undesirably locked and to prevent the braking force from being lowered. This is because when the toe angle is suddenly changed from the high speed range, the wheels are undesirably locked and the tires slip, which may reduce the braking force.

The control unit 150b includes a determination unit 33 that determines whether or not the vehicle is in an emergency braking state based on the vehicle speed and the braking force, and the emergency braking state toe angle control unit 36 uses the determination unit 33 to determine whether or not the emergency braking state has occurred. When it is determined that the vehicle is in a braking state, the steering actuator 5 may be controlled so that a predetermined toe angle is obtained.
The determined toe angle is a toe-in or toe-out toe angle arbitrarily determined by design or the like, and is determined by obtaining an appropriate toe angle by, for example, one or both of testing and simulation.

  The vehicle 100 includes a brake device 21 that brakes the vehicle 100 according to the braking force, and the emergency braking state toe angle control means 36 uses an auxiliary braking force that assists the braking force by the brake device 21 as described above. It may be given to the vehicle 100. According to this configuration, for example, when an abnormality occurs in the brake device 21 and a desired braking force cannot be generated, the second steering device 150 that turns the left and right wheels 9 and 9 individually is used to assist. A braking force can be applied to the vehicle 100.

The mechanism 150a of the second steering device 150 is
A hub unit body 2 having a hub bearing 15 for supporting the wheel 9;
A unit support member 3 provided on the undercarriage frame component 6 of the suspension device 12 and rotatably supporting the hub unit body 2 about a turning axis A extending in the vertical direction;
The steering unit 5 may be provided to rotate the hub unit body 2 about the turning axis A.

According to this configuration, the hub unit body 2 including the hub bearing 15 that supports the wheels 9 can be freely rotated around the turning axis A within a certain range by driving the rolling actuator 5. For this reason, steering can be performed independently for each wheel, and the toe angle of the wheel 9 can be arbitrarily changed according to the traveling state of the vehicle 100.
Further, during turning, the difference in steering angle between the left and right wheels 9, 9 can be changed according to the traveling speed. For example, the steering geometry can be changed during traveling, such as parallel geometry for turning in a high speed region and Ackermann geometry for turning in a low speed region. Thus, since the wheel angle can be arbitrarily changed during traveling, it is possible to improve the motion performance of the vehicle 100 and travel stably and safely. Further, by appropriately changing the turning angle of the left and right steered wheels, the turning radius of the vehicle 100 in turning traveling can be reduced, and the turning performance can be improved.

  The control unit 150b of the second steering device 150 is input from the auxiliary steering control unit 151 that outputs a current command signal corresponding to the given steering angle command signal and the auxiliary steering control unit 151. Actuator drive control units 31R and 31L that drive and control the rolling actuator 5 by outputting a current according to a current command signal may be provided.

  According to this configuration, the auxiliary turning control unit 151 outputs a current command signal corresponding to the given turning angle command signal. The actuator drive control units 31R and 31L drive and control the rolling actuator 5 by outputting a current corresponding to the current command signal input from the auxiliary steering control unit 151. Therefore, the wheel angle can be arbitrarily changed by adding to the steering by the driver's steering operation or the like.

The mechanism 150a of the second steering device 150 may steer either one or both of the left and right front wheels 9, 9 and the left and right rear wheels 9, 9. When the mechanism 150a is applied to the left and right front wheels 9 and 9, the direction of the wheel 9 is steered together with the entire hub unit by a driver's handle operation or the like. Auxiliary steering can be performed independently for each wheel.
When the mechanism portion 150a is applied to the left and right rear wheels 9, 9, the entire hub unit is not steered, but the auxiliary steer function allows the steering at a slight angle independently for each wheel as with the front wheels. Yes.

  The vehicle according to the present invention includes the steering system having the above-described configuration according to the present invention. Therefore, each effect mentioned above about the steering system of this invention is acquired.

  The steering system according to the present invention is a steering system provided in a vehicle, and is provided in a tire steering housing of the first steering device that steers the wheels of the vehicle in accordance with a steering amount command output from the steering command device. A second steering device having a mechanism that individually steers the left and right wheels by driving the steering actuator, a controller that controls the steering actuator, and vehicle information including vehicle speed and braking force. An emergency braking state toe angle control means for controlling a toe angle with respect to the steering actuator when a sudden brake command is output from the brake command means. Have. For this reason, in the event of an emergency such as a sudden braking operation or an abnormality in the brake system, the braking distance can be reduced by assisting the brake, and the safety of the vehicle can be improved.

  In the vehicle according to the present invention, the mechanism portion of the second steering device includes a steering system that steers one or both of the left and right front wheels and the left and right rear wheels. In the event of an emergency such as a system malfunction, the braking distance can be shortened by assisting the brake, and the safety of the vehicle can be improved.

1 is a diagram schematically illustrating a conceptual configuration of a steering system according to a first embodiment of the present invention. It is a longitudinal cross-sectional view which shows the structure of the mechanism part of the 2nd steering apparatus in the steering system, and its periphery. It is a horizontal sectional view showing composition of a mechanism part etc. of the 2nd steering device. It is a perspective view which shows the external appearance of the mechanism part of the 2nd steering apparatus. It is a disassembled front view of the mechanism part of the 2nd steering device. It is a side view of the mechanism part of the 2nd steering device. It is a top view of the mechanism part of the 2nd steering device. It is the VIII-VIII sectional view taken on the line of FIG. It is a block diagram which shows the conceptual structure of the steering system. It is a figure which shows the relationship between a vehicle speed and a toe angle. It is a flowchart which shows the process which controls a toe angle in the control part of the said 2nd steering apparatus in steps. It is a block diagram which shows the structure of the auxiliary steering control part of the 2nd steering apparatus. It is a graph which shows the example of a relationship between an actual lateral acceleration / standard lateral acceleration, a tire angle, and a friction coefficient. It is a figure which shows schematically the conceptual structure of the steering system which concerns on 2nd Embodiment of this invention. It is a figure which shows schematically the conceptual structure of the steering system which concerns on 3rd Embodiment of this invention.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram schematically showing a conceptual configuration of a vehicle 100 such as an automobile equipped with a steering system 101 according to this embodiment. The vehicle 100 is a four-wheel vehicle having left and right wheels 9 and 9 as front wheels and left and right wheels 9 and 9 as rear wheels, and the driving method is any of front wheel drive, rear wheel drive, and four wheel drive. It may be.

The steering system 101 is a system for turning the vehicle 100, and includes a first steering device 11, a second steering device 150, and a vehicle information detection unit 110.
The first steering device 11 is a device that steers the left and right wheels 9 and 9 that are the steered wheels of the vehicle 100 by a driver's operation with respect to a steering command device such as the steering wheel 200. Has been.

The second steering device 150 is a device that performs auxiliary steering by control according to the state of the vehicle 100, and includes a mechanism unit 150a and a control unit 150b. The mechanism part 150a is a mechanism provided for each of the wheels 9 and 9 to be subjected to auxiliary turning. This mechanism part 150a is provided in the tire housing 105 of the vehicle 100, and individually turns the wheels 9 by driving the steering actuator 5 (FIG. 2). The control unit 150b performs control based on vehicle information representing the state of the vehicle 100 detected by the vehicle information detection unit 110.
In other words, the steering system 101
The left and right wheels 9 and 9 serving as the front wheels of the vehicle 100 are mechanically interlocked, and the left and right wheels 9 and 9 serving as the front wheels of the vehicle 100 are connected to the left and right wheels 9 according to the steering amount command output by the steering command device. The first steering device 11 that is steered by changing the angles of the knuckles 6 and 6 that are left and right underbody frame parts of the suspension device 12 on which the suspension device 9 is installed,
By driving auxiliary steering actuators (steering actuators 5 (FIG. 2)) provided for the left and right wheels 9, 9, the wheels 9, 9 for the knuckle 6, 6 as the underbody frame parts. A second steering device 150 for individually steering the left and right wheels 9, 9 by changing the angle of
A vehicle information detection unit 110 to be described later.

The vehicle information detection unit 110 is a means for detecting the state of the vehicle 100 and refers to a group of various sensors. The vehicle information detected by the vehicle information detection unit 110 is transferred to the control unit 150b of the second steering device 150 via the main ECU 130.
The ECU 130 is a control device that performs cooperative control or overall control of the vehicle 100, and is also referred to as a VCU.

<Configuration of first steering device 11>
The first steering device 11 is a system that interlocks the left and right wheels 9 and 9 that are the front wheels of the vehicle 100 in response to an input to the steering wheel 200 by the driver, and includes a steering shaft 32, a rack and pinion ( (Not shown), a tie rod 14 and the like, including a known mechanical configuration. When the driver inputs rotation to the handle 200, the steering shaft 32 also rotates in conjunction with it. When the steering shaft 32 is rotated, the tie rod 14 connected to the steering shaft 32 is moved in the vehicle width direction by the rack and pinion, so that the direction of the wheels 9 is changed, and the left and right wheels 9, 9 are interlocked and steered. Is possible.

<Schematic configuration of second steering device 150>
As shown in FIGS. 1 and 9, the second steering device 150 can steer the left and right wheels 9 and 9 independently. A right wheel hub unit 1R and a left wheel hub unit 1L are provided as a mechanism portion 150a of the second steering device 150. The right wheel hub unit 1 </ b> R and the left wheel hub unit 1 </ b> L steer the wheels 9 and 9 by a steering actuator 5 (FIG. 2) provided in the tire housing 105.

<Specific Configuration Example of Mechanism 150a of Second Steering Device 150>
As described above, the mechanism portion 150a of the second steering device 150 includes the right wheel hub unit 1R and the left wheel hub unit 1L. Both of the right wheel hub unit 1R and the left wheel hub unit 1L are shown in FIG. It is configured as a hub unit 1 with a rudder function.
As shown in FIG. 2, the hub unit 1 includes a hub unit main body 2, a unit support member 3, a rotation allowable support component 4, and a steering actuator 5. The unit support member 3 is provided integrally with a knuckle 6 that is a suspension frame part.

As shown in FIG. 5, the actuator main body 7 of the steering actuator 5 is provided on the inboard side of the unit support member 3, and the hub unit main body 2 is provided on the outboard side of the unit support member 3. With the hub unit 1 (FIG. 2) mounted on the vehicle, the vehicle width direction outer side of the vehicle is referred to as an outboard side, and the vehicle width direction center side of the vehicle is referred to as an inboard side.
As shown in FIGS. 3 and 4, the hub unit main body 2 and the actuator main body 7 are connected by a joint portion 8. Usually, the joint portion 8 is provided with a boot (not shown) for waterproofing and dustproofing.

  As shown in FIG. 2, the hub unit body 2 is supported by the unit support member 3 via the rotation-allowing support parts 4 and 4 at two upper and lower positions so as to be rotatable around the turning axis A extending in the vertical direction. Has been. The turning axis A is an axis different from the rotation axis O of the wheel 9 and is different from a kingpin axis that performs main turning. In a normal vehicle, the kingpin angle is set to 10 to 20 degrees for the purpose of improving the straight running stability of the vehicle traveling. However, the hub unit 1 of this embodiment has an angle (axis) different from the kingpin angle. It has a steering shaft. The wheel 9 includes a wheel 9a and a tire 9b.

  As shown in FIG. 1, the hub unit 1 (FIG. 2) of this embodiment is added to the steering of the left and right wheels 9, 9 as front wheels by the first steering device 11, and has a small angle for each of the left and right wheels. As a mechanism for turning (about ± 5 deg), the knuckle 6 of the suspension device 12 is integrally provided. The first steering device 11 is of a rack and pinion type, but any type of steering device may be used. For example, although the strut suspension mechanism that directly fixes the shock absorber to the knuckle 6 is applied to the suspension device 12, a multi-link suspension mechanism or other suspension mechanisms may be applied.

<About hub unit body 2>
As shown in FIG. 2, the hub unit main body 2 includes a hub bearing 15 for supporting the wheels 9, an outer ring 16, and an arm portion 17 (FIG. 4) that is a turning force receiving portion described later.
As shown in FIG. 8, the hub bearing 15 includes an inner ring 18, an outer ring 19, and rolling elements 20 such as balls interposed between the inner and outer rings 18, 19. 2).

  In the illustrated example, the hub bearing 15 is an angular ball bearing in which the outer ring 19 is a fixed ring, the inner ring 18 is a rotating ring, and the rolling elements 20 are in a double row. The inner ring 18 includes a hub ring portion 18a having a hub flange 18aa and constituting a race surface on the outboard side, and an inner ring portion 18b constituting a race surface on the inboard side. As shown in FIG. 2, the wheel 9a of the wheel 9 is bolted to the hub flange 18aa so as to overlap the brake rotor 21a. The inner ring 18 rotates around the rotation axis O.

As shown in FIG. 8, the outer ring 16 includes an annular portion 16a fitted to the outer peripheral surface of the outer ring 19, and a trunnion shaft-shaped mounting shaft portion that protrudes upward and downward from the outer periphery of the annular portion 16a. 16b, 16b. Each attachment shaft portion 16 b is provided coaxially with the turning shaft center A.
As shown in FIG. 3, each wheel 9 is provided with a brake 21 that is a brake device for braking the vehicle. The brake 21 includes a brake rotor 21a and a brake caliper 21b. The brake caliper 21b is mounted on two upper and lower brake caliper mounting portions 22 (FIG. 6) formed integrally with the outer ring 19 so as to project into an arm shape.

<About rotation-supporting support parts and unit support members>
As shown in FIG. 8, each rotation-allowing support component 4 is composed of a rolling bearing. In this example, a tapered roller bearing is applied as the rolling bearing. The rolling bearing includes an inner ring 4a fitted to the outer periphery of the mounting shaft portion 16b, an outer ring 4b fitted to the unit support member 3, and a plurality of rolling elements 4c interposed between the inner and outer rings 4a and 4b.

  The unit support member 3 includes a unit support member main body 3A and a unit support member combined body 3B. A substantially ring-shaped unit support member assembly 3B is detachably fixed to the end of the unit support member main body 3A on the outboard side. Partial concave spherical fitting hole forming portions 3a are respectively formed on the upper and lower portions of the side surface of the inboard side of the unit support member assembly 3B.

  As shown in FIGS. 7 and 8, partial concave spherical fitting hole forming portions 3Aa are formed in the upper and lower portions of the outboard side end of the unit support member main body 3A. As shown in FIG. 4, the unit support member combined body 3B is fixed to the outboard side end of the unit support member main body 3A, and the fitting hole forming portions 3a and 3Aa (FIG. 7) are combined with each other for each upper and lower portion. As a result, a fitting hole is formed continuously around the entire circumference. The outer ring 4b is fitted in this fitting hole. In FIG. 4, the unit support member 3 is indicated by a one-dot chain line.

  As shown in FIG. 8, each mounting shaft portion 16b in the outer ring 16 is formed with a female screw portion extending in the radial direction, and is provided with a bolt 23 that is screwed into the female screw portion. A disc-like pressing member 24 is interposed on the end surface of the inner ring 4a, and a preload is applied to each rotation-allowing support component 4 by applying a pressing force to the end surface of the inner ring 4a by a bolt 23 that is screwed into the female screw portion. Giving. Thereby, the rigidity of each rotation permission support component 4 can be improved. Even when the weight of the vehicle acts on the hub unit, the initial preload is set so as not to be released. Note that the rolling bearing of the rotation-allowing support component 4 is not limited to the tapered roller bearing, and an angular ball bearing can be used depending on use conditions such as a maximum load. Even in that case, a preload can be applied in the same manner as described above.

  As shown in FIG. 3, the arm portion 17 is a portion that serves as an action point for applying a steering force to the outer ring 19 of the hub bearing 15, and is formed on a part of the outer periphery of the annular portion 16 a or a part of the outer periphery of the outer ring 19. Protruding together. The arm portion 17 is rotatably connected to the linear motion output portion 25 a of the steering actuator 5 via the joint portion 8. As a result, when the linear motion output portion 25a of the steering actuator 5 advances and retreats, the hub unit body 2 rotates around the turning axis A (FIG. 2), that is, is steered.

<About the steering actuator 5>
As shown in FIG. 4, the steering actuator 5 includes an actuator body 7 that drives the hub unit body 2 to rotate about the turning axis A (FIG. 2).
As shown in FIG. 3, the actuator body 7 converts a motor 26, a speed reducer 27 that decelerates the rotation of the motor 26, and a forward / reverse rotation output of the speed reducer 27 into a reciprocating linear motion of the linear motion output unit 25a. And a linear motion mechanism 25. The motor 26 is, for example, a permanent magnet type synchronous motor, but may be a DC motor or an induction motor.

  As the speed reducer 27, a wrapping type transmission mechanism such as a belt transmission mechanism or a gear train can be used. In the example of FIG. 3, a belt transmission mechanism is used. The reducer 27 includes a drive pulley 27a, a driven pulley 27b, and a belt 27c. A drive pulley 27 a is coupled to the motor shaft of the motor 26, and a driven pulley 27 b is provided in the linear motion mechanism 25. The driven pulley 27b is disposed in parallel to the motor shaft. The driving force of the motor 26 is transmitted from the drive pulley 27a to the driven pulley 27b via the belt 27c. The drive pulley 27a, the driven pulley 27b, and the belt 27c constitute a winding-type speed reducer 27.

  As the linear motion mechanism 25, a feed screw mechanism such as a slide screw or a ball screw, a rack and pinion mechanism, or the like can be used. In this example, a feed screw mechanism using a trapezoidal screw slide screw is used. Since the linear motion mechanism 25 includes a feed screw mechanism that uses a sliding screw of the trapezoidal screw, the effect of preventing reverse input from the tire 9b can be enhanced. The actuator body 7 including the motor 26, the speed reducer 27, and the linear motion mechanism 25 is assembled as a semi-assembly and is detachably attached to the case 6b with bolts or the like. A mechanism that directly transmits the driving force of the motor 26 to the linear motion mechanism 25 without using a reduction gear is also possible.

  The case 6 b is integrally formed with the unit support member main body 3 </ b> A as a part of the unit support member 3. The case 6 b is formed in a bottomed cylindrical shape, and is provided with a motor housing portion that supports the motor 26 and a linear motion mechanism housing portion that supports the linear motion mechanism 25. A fitting hole for supporting the motor 26 at a predetermined position in the case is formed in the motor housing portion. The linear motion mechanism accommodating portion is formed with a fitting hole for supporting the linear motion mechanism 25 at a predetermined position in the case, a through hole for allowing the linear motion output portion 25a to advance and retreat.

  As shown in FIG. 4, the unit support member main body 3A includes the case 6b, a shock absorber mounting portion 6c serving as a shock absorber mounting portion, and a steering device coupling serving as a coupling portion of the first steering device 11 (FIG. 3). Part 6d. The shock absorber mounting portion 6c and the steering device coupling portion 6d are also integrally formed with the unit support member main body 3A. A shock absorber mounting portion 6c is formed on the upper portion of the outer surface portion of the unit support member main body 3A so as to protrude. A steering device coupling portion 6d is formed on the side surface portion of the outer surface portion of the unit support member main body 3A so as to protrude.

<Configuration of Vehicle Information Detection Unit 110>
As shown in FIG. 9, vehicle information detection section 110 detects vehicle information and outputs it to ECU 130. The vehicle information detection unit 110 includes a vehicle speed detection unit 111, a steering angle detection unit 112, a vehicle height detection unit 113, an actual yaw rate detection unit 114, an actual lateral acceleration detection unit 115, an accelerator pedal sensor 116, and a brake pedal sensor 117.

The vehicle speed detection unit 111 detects the speed of the vehicle (vehicle speed) based on the output of a sensor (not shown) such as a speed sensor attached to the inside of a transmission provided in the vehicle, and sends vehicle speed information (simply “ It is also called "vehicle speed".
The steering angle detection unit 112 detects the steering angle based on the output of a sensor (not shown) such as a resolver attached to the motor unit included in the first steering device 11, for example, and sends the steering angle information (simply “ Steering angle ").

  The vehicle height detection unit 113 measures the distance between the chassis of the vehicle 100 (FIG. 1) and the ground using a laser displacement meter, or the angle of the upper arm or lower arm (not shown) in the suspension device 12 (FIG. 1) of the vehicle 100. The vehicle height of each wheel 9 (FIG. 1) to be steered by the second steering device 150 is detected by a method of detecting the angle with an angle sensor. Then, the vehicle height detection unit 113 outputs the detected vehicle height to the ECU 130 as vehicle height information.

The actual yaw rate detection unit 114 detects the actual yaw rate based on the output of a sensor such as a gyro sensor attached to the vehicle 100 (FIG. 1), for example, and outputs the actual yaw rate information to the ECU 130.
The actual lateral acceleration detection unit 115 detects the actual lateral acceleration based on the output of a sensor such as a gyro sensor attached to the vehicle 100 (FIG. 1), for example, and outputs the actual lateral acceleration information to the ECU 130. The accelerator pedal sensor 116 detects an input to the accelerator pedal 210 by the driver, and outputs the detected value to the ECU 130 as an accelerator command value. A brake pedal sensor (brake pedal force sensor) 117 serving as a brake command means detects an input to the brake pedal 220 by the driver as a brake pedal force, and outputs the detected value to the ECU 130 as a brake command value. The ECU 130 outputs vehicle information including the turning angle command signal to the control unit 150b of the second steering device 150.

<Control Unit 150b of Second Steering Device 150>
The control unit 150b of the second steering device 150 acquires vehicle information including vehicle speed information, steering angle information, vehicle height information, actual yaw rate information, actual lateral acceleration information, an accelerator command value, and a brake command value from the ECU 130. The auxiliary steering control unit 151 controls the right wheel actuator drive control unit 31R and the left wheel actuator drive control unit 31L based on the acquired vehicle information, so that the right wheel hub unit 1R and the left wheel hub unit are controlled. The motor 26 provided in 1L is driven, and the left and right wheels can be steered independently.

In the control unit 150b, the relationship between each information such as the steering angle information as the vehicle information and the command value for driving the motor 26 is determined as a control rule using, for example, a map or an arithmetic expression. Control using rules.
The control unit 150b is provided as a dedicated ECU, for example, but may be provided as a part of the main ECU 130.

  The auxiliary turning control unit 151 in the control unit 150 b includes a determination unit 33 and an emergency braking state toe angle control unit 36. The determination means 33 determines whether or not an emergency braking state (when a sudden brake command is output) from the vehicle speed and braking force acquired from the ECU 130. The emergency braking state means that in this vehicle running state, the brake pedal force detected by the brake pedal sensor 117 by the driver's operation of the brake pedal 220 is equal to or greater than a threshold value, and the amount of change in the brake pedal force is equal to or greater than the threshold value. (Specifically, when sudden braking is activated), or an automatic brake device 220A described later recognizes other vehicles, vehicle surrounding conditions such as obstacles, etc. from sensors such as a camera or millimeter wave radar. This is when the sudden brake command is automatically generated and output when the collision determination is satisfied. When a sudden brake command is output from the automatic brake device 220A, the brake command generation means of the ECU 130 controls the normal brake 21 (FIG. 3) to operate. The automatic brake system includes an automatic brake device 220A, the brake command generation means, and a brake 21 (FIG. 3). Whether or not the vehicle is in a running state is determined from the vehicle speed obtained from the vehicle speed detection unit 111 via the ECU 130. Each of the threshold values is a value arbitrarily determined by design or the like, and is determined by determining an appropriate threshold value by one or both of testing and simulation, for example.

  The emergency braking state toe angle control means 36 determines that the right and left wheels 9 and 9 are in a toe-in state (left and right wheels indicated by dotted lines in FIG. 1) when the determination means 33 determines that the braking state is emergency. 9 and 9), the steering actuator 5 (FIG. 2) is controlled so that the maximum steering angle or the toe angle corresponding to the vehicle speed is obtained. The emergency braking state toe angle control means 36 performs toe angle control in the emergency braking state in both cases of straight running and turning. This emergency braking state toe angle control means 36 gives the vehicle an auxiliary braking force that assists the braking force by the brake 21 (FIG. 3). Since the left and right wheels 9, 9 (FIG. 1) can obtain stable braking if they are toe-in rather than toe-out, in this embodiment, the left and right wheels 9, 9 (FIG. 1) are toe-in in an emergency braking state. However, you can use toe-out. Even in toe-out, the braking resistance can be shortened by increasing the rotational resistance of each wheel.

  As shown in FIGS. 9 and 10, the emergency braking state toe angle control means 36 has the maximum toe angle Bdeg and the vehicle speed in the middle and high speed range (when the vehicle speed is low (VLkm / h or less) in the emergency. (Greater than VLkm / h), the toe angle is gradually decreased as the vehicle speed increases. This is because when the toe angle is suddenly changed from the high speed range, the wheels are undesirably locked and the tires slip, which may reduce the braking force. Further, the emergency braking state toe angle control means 36 maximizes the left and right wheels 9 and 9 (FIG. 1) regardless of the vehicle speed when the normal brake 21 (FIG. 3) is determined to be abnormal in the emergency. Control the toe-in angle. The emergency braking state toe angle control means 36 outputs, for example, a brake pedal force by operating the brake pedal 220 or a sudden brake command (referred to as “brake command etc.” together with the brake pedal force) by the automatic brake device 220A. However, when the vehicle is not decelerating (in other words, the relationship between the wheel speed or the wheel angular velocity with respect to the brake command or the like is out of the predetermined range), some abnormality occurs in the system of the normal brake 21 (FIG. 3). Judge that

<Flowchart>
FIG. 11 is a flowchart showing the process of controlling the toe angle step by step. This will be described with reference to FIGS. 9 and 10 as well. When the automatic brake device 220A outputs an emergency brake command (rapid brake command) and the emergency brake command is given to the determination means 33 (step S1: Yes) while the vehicle is running, the emergency braking state toe angle control means 36 is provided. Determines whether the normal brake 21 (FIG. 3) is abnormal (step S2).

  When it is determined that there is no abnormality in the normal brake 21 (FIG. 3) (step S2: No), the emergency braking state toe angle control means 36 determines the toe angle according to the vehicle speed (step S3), and the normal brake When it is determined that there is an abnormality in 21 (FIG. 3) (step S2: Yes), the emergency braking state toe angle control means 36 keeps the maximum toe angle (X + Bdeg) constant (step S4). Thereafter, the process proceeds to step S7 described later.

When there is no emergency brake command from the automatic brake device 220A (step S1: No), the determination means 33 has the brake pedal force detected by the brake pedal sensor 117 equal to or greater than a threshold value and the amount of change in the brake pedal force equal to or greater than the threshold value (abrupt It is determined whether or not the brake is activated (step S5). If it is determined that the sudden braking is in operation (step S5: Yes), the process proceeds to step S2.
If it is determined that it is not during the sudden braking operation (step S5: No), the controller 150b determines a toe angle in accordance with the brake pedaling force (step S6). In step S6, the control unit 150b performs control such that the toe angle increases as the brake pedal force increases, for example. Thereafter, the process proceeds to step S7.

  The control unit 150b calculates the driving conditions of each steering actuator (such as a current flowing through the motor 26) (step S7), and drives each steering actuator (step S8). Next, when the control unit 150b determines that the vehicle speed obtained from the vehicle speed detection unit 111 via the ECU 130 is “0” km / h (step S9: Yes), this process is terminated. If it is determined that the vehicle is traveling (step S9: No), the process returns to step S1.

In addition to the emergency braking state toe angle control, the auxiliary turning control unit 151 performs control for independently turning the left and right wheels as follows.
As shown in FIG. 12, the auxiliary steering control unit 151 includes a reference lateral acceleration calculation unit 152, a right wheel tire angle calculation unit 153, a left wheel tire angle calculation unit 154, a right wheel road surface friction coefficient calculation unit 155, and a target yaw rate calculation unit. 156, a left wheel road surface friction coefficient calculation unit 157, a target yaw rate correction unit 158, a target left and right wheel tire angle calculation unit 159, a right wheel command value calculation unit 160, and a left wheel command value calculation unit 161.

  The right wheel tire angle calculation unit 153 and the left wheel tire angle calculation unit 154 acquire steering angle information and vehicle height information from the ECU 130 at a predetermined cycle. The right wheel tire angle calculation unit 153 and the left wheel tire angle calculation unit 154 calculate the current angle of the tire to be steered by the second steering device 150 (FIG. 9) based on the acquired steering angle information and vehicle height information. The calculated tire angle information is output to the reference lateral acceleration calculation unit 152.

  The reference lateral acceleration calculation unit 152 calculates the reference lateral acceleration based on the vehicle speed information acquired from the ECU 130 and the tire angle information. The reference lateral acceleration calculation unit 152 outputs the calculated reference lateral acceleration as reference lateral acceleration information to the right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157.

FIG. 13 is a diagram showing a map for calculating the road surface friction coefficient, and this map is stored in the right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157 shown in FIG.
The right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157 calculate road surface friction coefficients based on the actual lateral acceleration information acquired from the ECU 130 and the reference lateral acceleration information input from the reference lateral acceleration calculation unit 152. I do. Specifically, when the reference lateral acceleration information is input from the reference lateral acceleration calculation unit 152, the right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157 receive the right wheel tire angle calculation unit 153 and the left wheel tire. Tire angle information is acquired from the angle calculation unit 154. The right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157 calculate the road surface friction coefficient from the actual lateral acceleration / reference lateral acceleration and the tire angle based on the map (FIG. 13). The right wheel road surface friction coefficient calculating unit 155 and the left wheel road surface friction coefficient calculating unit 157 include right wheel road surface friction coefficient information that is the calculated road surface friction coefficient of the right wheel and left wheel road surface friction coefficient information that is the road surface friction coefficient of the left wheel. And output to the target yaw rate correction unit 158.

The target yaw rate calculation unit 156 calculates a target yaw rate based on vehicle speed information and steering angle information acquired from the ECU 130 at a predetermined cycle, and outputs the calculated target yaw rate to the target yaw rate correction unit 158 as target yaw rate information.
When the right wheel road surface friction coefficient information and the left wheel road surface friction coefficient information are input from the right wheel road surface friction coefficient calculation unit 155 and the left wheel road surface friction coefficient calculation unit 157, the target yaw rate correction unit 158 receives the target yaw rate calculation unit 156 from the target yaw rate calculation unit 156. The yaw rate information is acquired, and the target yaw rate is corrected according to the road surface friction coefficient represented by the right wheel road surface friction coefficient information and the left wheel road surface friction coefficient information. The target yaw rate correction unit 158 outputs the corrected target yaw rate to the target left and right wheel tire angle calculation unit 159 as corrected yaw rate information.

  When the corrected left and right wheel tire angle calculation unit 159 receives the corrected yaw rate information, the target left and right wheel tire angle calculation unit 159 acquires the actual yaw rate information, the accelerator command value, and the brake command value from the ECU 130, and the right wheel road surface friction coefficient information and the left wheel road surface friction coefficient information. And the target left and right wheel tire angle, which is the target value of the tire angle of the left and right wheels, is calculated. Specifically, the target left and right wheel tire angle calculation unit 159 calculates the target angle of each of the left and right tires based on the following formula (1).

In equation (1), θ _y is the actual vehicle yaw rate amount represented by the actual yaw rate information, X _A is the accelerator command value, X _B is the brake command value, μ _R is the right wheel road surface friction coefficient, and μ _L is the left wheel. the road surface friction coefficient, θ _tR1 the target tire angle of the right wheel, θ _tL1 is the target tire angle of the left wheel.
The target left and right wheel tire angle calculation unit 159 outputs the calculated target tire angles of the left and right wheels to the right wheel command value calculation unit 160 and the left wheel command value calculation unit 161 as target tire angle information.

  When the target wheel angle information is input, the right wheel command value calculation unit 160 and the left wheel command value calculation unit 161 represent the current tire angle from the right wheel tire angle calculation unit 153 and the left wheel tire angle calculation unit 154. Tire angle information is acquired, and the target tire angle represented by the target tire angle information is compared with the current tire angle. If there is a deviation as a result of comparing the target tire angle with the current tire angle, the right wheel rotation indicating the amount by which each of the right wheel hub unit 1R (FIG. 9) and the left wheel hub unit 1L (FIG. 9) is steered. Steering amount information and left wheel turning amount information are generated. The right wheel command value calculation unit 160 outputs the generated right wheel turning amount information (current command signal) to the right wheel actuator drive control unit 31R, and the left wheel command value calculation unit 161 generates the generated left wheel turning amount information. (Current command signal) is output to the actuator drive control unit 31L for the left wheel.

Each actuator drive control unit 31R, 31L includes an inverter. Each actuator drive control part 31R, 31L controls the current to the motor 26 (FIG. 9) of each steering actuator based on the right wheel turning amount information and the left wheel turning amount information.
Specifically, as shown in FIGS. 9 and 12, each actuator drive control unit 31R, 31L receives the right wheel turning amount information and the left wheel turning amount from the right wheel command value calculation unit 160 and the left wheel command value calculation unit 161. When the information is input, position information of each motor 26 indicating the turning angle of the current right wheel hub unit 1R and the left wheel hub unit 1L is acquired, and based on the right wheel turning amount information and the left wheel turning amount information. The target position of the motor 26 is determined, and the current flowing to each motor 26 is controlled.

  That is, as shown in FIG. 4, each actuator drive control unit 31 </ b> R, 31 </ b> L outputs a current corresponding to the current command signal input from the auxiliary turning control unit 151 to drive and control the turning actuator 5. The actuator drive controllers 31R and 31L control the power supplied to the coil of the motor 26. The actuator drive control units 31R and 31L constitute, for example, a half bridge circuit using a switch element (not shown), and perform PWM control for determining a motor applied voltage based on an ON-OFF duty ratio of the switch element. Thereby, in addition to the steering by a driver | operator's steering wheel operation, a wheel can change a small angle.

<Effect>
According to the steering system 101 described above, the first steering device 11 turns the wheels 9 and 9 according to the steering amount command output by the steering command device. As the steering command device, for example, the driver's handle 200 or an automatic steering command device can be applied. Adjustment of the direction of the vehicle 100 by such a steering command device or the like can be performed similarly to a conventional vehicle.

  The second steering device 150 drives the steering actuator 5 provided in the tire housing 105 to individually steer the left and right wheels 9 and 9. Of the control unit 150b of the second steering device 150, the determination means 33 determines whether or not the vehicle is in an emergency braking state based on the vehicle speed and the braking force. When the emergency braking state toe angle control means 36 determines that the emergency braking state is in effect, the right and left wheels 9 and 9 turn the steering actuator 5 so that the maximum turning angle is obtained in the toe-in state, for example. Control. Thereby, in the emergency braking state, the rotational resistance of each wheel is increased to shorten the braking distance and improve the safety of the vehicle, compared to when each wheel is in a straight traveling state (the toe angle is zero degrees), for example. be able to. Further, for example, even when an abnormality occurs in the brake 21 and a desired braking force cannot be generated, the emergency braking state toe angle control means 36 determines that it is in an emergency braking state, Since the steering actuator 5 is controlled so that the left and right wheels 9 and 9 have, for example, the maximum turning angle in the toe-in state, an auxiliary braking force can be applied to the vehicle.

In the mechanism portion 150a of the second steering device 150, the hub unit body 2 including the hub bearing 15 can be freely rotated around the turning axis A within a certain range by driving the turning actuator 5. it can. For this reason, steering can be performed independently for each wheel, and the toe angle of the wheel 9 can be arbitrarily changed according to the traveling state of the vehicle 100.
Further, during turning, the difference in steering angle between the left and right wheels 9, 9 can be changed according to the traveling speed. For example, the steering geometry can be changed during traveling, such as parallel geometry for turning in a high speed region and Ackermann geometry for turning in a low speed region. Thus, since the wheel angle can be arbitrarily changed during traveling, it is possible to improve the motion performance of the vehicle 100 and travel stably and safely. Further, by appropriately changing the turning angle of the left and right steered wheels, the turning radius of the vehicle 100 in turning traveling can be reduced, and the turning performance can be improved.

<About other embodiments>
In the following description, the same reference numerals are given to portions corresponding to the matters described in advance in the respective embodiments, and overlapping descriptions are omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in advance unless otherwise specified. The same effect is obtained from the same configuration. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

[Second Embodiment]
As shown in FIG. 14, the steering system 101 according to the second embodiment is the first embodiment in that the first steering device 11 and the second steering device 150 steer different wheels 9 from each other. Different from form. That is, in this steering system 101, the first steering device 11 steers the left and right front wheels 9, 9 of the vehicle 100, and the second steering device 150 steers the left and right rear wheels 9, 9 of the vehicle 100. I do. The mechanism portion 150 b of the second steering device 150 is installed in the rear wheel tire housing 105.

[Third Embodiment]
As shown in FIG. 15, the steering system 101 according to the third embodiment is different from the first embodiment in that it includes _{two second} steering devices 150 ₁ and 150 ₂ .
One second steering device 150 ₁ performs the turning of the same wheels 9,9 in the first steering device 11, the second steering device 150 ₂ on the other, the wheel different from the second steering device 150 9 and 9 are steered. That is, the second steering device 150 ₂ on one performs the same operation as the second steering device 150 according to the first embodiment, the second steering device 150 ₂ on the other, to a second embodiment The same operation as that of the second steering device 150 is performed.

According to this steering system 101, by providing a plurality (two in this example) of the second steering devices 150 ₁ and 150 ₂ , it becomes possible to more independently independently steer four wheels. Thus, it becomes possible to improve the running stability of the vehicle 100 and reduce the fuel consumption.

Further, as a vehicle including a steering system according to another embodiment, the left and right wheels are each provided with a second steering device that can be steered independently, and each wheel is independently driven by a steering actuator. These steering devices may be, for example, steer-by-wire types that are not mechanically coupled to the steering command device.
In each of the embodiments described above, the steering command device is the handle 200. However, a manual steering command device other than the handle 200, for example, a joystick may be used. The steering command device 200A may be used. This automatic steering command device 200A is a device that recognizes a vehicle surrounding situation from the vehicle surrounding situation detection means 230 and automatically generates a steering command. The vehicle surrounding state detection means 230 is, for example, a sensor such as a camera or a millimeter wave radar.

  The automatic steering command device 200A recognizes white lines and obstacles on the road, for example, and generates and outputs a steering command. The automatic steering command device 200A may be a part of a device that performs automatic driving of a vehicle or a device that supports steering by manual driving. Even in a vehicle equipped with such a steering command device 200A that automatically generates a steering command, by providing the second steering device 150, operations that cannot be performed by the first steering device 11, such as toe angle control, can be performed. It is also possible to perform main steering in the traveling direction of the vehicle with the first steering device 11 and to correct it with the second steering device 150, and to correct the vehicle direction with respect to the steering amount command. Thus, it is possible to maintain the running stability of the vehicle.

  As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 2 ... Hub unit main body, 3 ... Unit support member, 5 ... Actuator for steering, 6 ... Knuckle (suspension frame part), 9 ... Wheel, 11 ... First steering device, 12 ... Suspension device, 15 ... Hub bearing 31R, 31L ... Actuator drive control unit, 33 ... Determination means, 36 ... Emergency braking state toe angle control means, 100 ... Vehicle, 101 ... Steering system, 105 ... Tire housing, 110 ... Vehicle information detection unit, 150 ... No. 2 steering device, 150a ... mechanism unit, 150b ... control unit, 151 ... auxiliary steering control unit, 200 ... steering wheel (steering command device), 200A ... automatic steering command device

Claims (9)

A steering system provided in a vehicle,
A first steering device that steers the wheels of the vehicle according to a steering amount command output by the steering command device;
A second steering device having a mechanism for individually turning left and right wheels by driving a steering actuator provided in a tire housing of the vehicle, and a control unit for controlling the steering actuator;
A vehicle information detection unit that detects vehicle information including vehicle speed and braking force,
The control unit includes an emergency braking state toe angle control unit that controls a toe angle with respect to the steering actuator when a sudden brake command is output from the brake command unit.   The steering system according to claim 1, wherein the emergency braking state toe angle control means sets the toe angle to a maximum angle.   The steering system according to claim 1, wherein the emergency braking state toe angle control means determines a toe angle according to a vehicle speed.   4. The steering system according to claim 1, wherein the control unit includes a determination unit that determines whether or not the vehicle is in an emergency braking state based on a vehicle speed and a braking force, and the emergency braking is performed. The state toe angle control means controls the steering actuator so that a predetermined toe angle is obtained when it is determined by the determination means that the braking state is in an emergency.   The steering system according to any one of claims 1 to 4, wherein the vehicle includes a brake device that brakes the vehicle according to the braking force, and the emergency braking state toe angle control means includes: A steering system for giving an auxiliary braking force for assisting a braking force by the brake device to the vehicle. The steering system according to any one of claims 1 to 5,
The mechanism portion of the second steering device is
A hub unit body having a hub bearing for supporting the wheel;
A unit support member provided on a suspension frame part of the suspension device and rotatably supporting the hub unit body about a turning axis extending in the vertical direction;
A steering system comprising: the steering actuator that rotates the hub unit body about the turning axis.   The steering system according to any one of claims 1 to 6, wherein the control unit of the second steering device outputs a current command signal corresponding to a given turning angle command signal. A steering system comprising: a rudder control unit; and an actuator drive control unit that drives and controls the rolling actuator by outputting a current corresponding to a current command signal input from the auxiliary steering control unit.   The steering system according to any one of claims 1 to 7, wherein the mechanism portion of the second steering device steers one or both of left and right front wheels and left and right rear wheels. system.   A vehicle comprising the steering system according to claim 8.

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