Steer-by-wire steering system

Abstract

To provide a steer-by-wire type steering system which enables a driver to surely sense a situation where a direction of a steering wheel reaches a stroke end through a steering wheel, and can automatically control vehicle travel when a mechanical defect of a steering lock device occurs during travel of a vehicle.SOLUTION: A steer-by-wire type steering system includes: a steering lock device 7 which can switch between a lock state capable of blocking rotation of a steering wheel 1 by mechanical engagement between the side of the steering wheel 1 and a stationary side, and a free state of permitting rotation of the steering wheel 1; and an electronic control device 8 which controls switching between the free state and the lock state, monitors whether rotation block of the steering wheel 1 mismatched with a control situation in an electrically free state occurs, and automatically controls a steering actuator 2 when detecting the rotation block of the steering wheel 1.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a steer-by-wire steering system that steers a steering wheel while the steering wheel and the steered wheels are mechanically disengaged from each other. 【Background Art】 【0002】 As a steering device that changes the direction of the steered wheels of a vehicle according to the rotation operation of a steering wheel by a driver, a steer-by-wire type is known (for example, Patent Document 1). The steer-by-wire steering system has a steering sensor that detects the operation amount of the steering wheel, and a steering actuator that is provided separately from the steering wheel in a mechanically disengaged manner. The steering actuator operates according to the operation amount of the steering wheel detected by the steering sensor to change the direction of the steered wheels. 【0003】 This steer-by-wire steering system once converts the operation amount of the steering wheel by the driver into an electric signal, and controls the operation of the steering actuator based on the electric signal. Therefore, for example, the amount of change in the direction of the steered wheels when the steering wheel is rotated can be adjusted according to the running speed of the vehicle. It is possible to optimize the correspondence relationship between the operation amount of the steering wheel and the operation amount of the steering actuator according to the running state of the vehicle, and it is expected to improve the running stability and motion performance of the vehicle. 【0004】 Generally, in a steer-by-wire steering system of a vehicle, it has a reaction force motor that applies a steering reaction force calculated based on the vehicle speed, the operation amount of the steering wheel, etc. to the steering wheel, and a reaction force controller that controls the reaction force motor. For example, in Patent Document 1, the reaction force controller performs control to correct and increase the magnitude of the steering reaction force generated by the reaction force motor when the direction of the steered wheels reaches the stroke end. Thereby, the driver can sense through the steering wheel that the direction of the steered wheels has reached the stroke end. 【0005】 Furthermore, in recent years, autonomous driving technology has been developed that involves equipping vehicles with forward-facing cameras, radar devices, and various sensors to monitor driving conditions and electronically control the vehicle according to the detected conditions (for example, Patent Documents 2 and 3). [Prior art documents] [Patent Documents] 【0006】 [Patent Document 1] Japanese Patent Publication No. 2020-168952 [Patent Document 2] Japanese Patent Publication No. 2021-172097 [Patent Document 3] Japanese Patent Publication No. 2019-43365 [Overview of the Initiative] [Problems that the invention aims to solve] 【0007】 However, in the steer-by-wire steering system described in Patent Document 1, the reaction motor informs the driver of the steering limit. Therefore, if the driver turns the steering wheel with an operating force exceeding the torque output by the reaction motor, there is a problem in that the rotation of the steering wheel is not prevented. 【0008】 To solve this problem, the inventors of this invention considered employing a steering lock device that can switch between a locked state, which prevents the rotation of the steering wheel by mechanical engagement between the steering wheel side and the fixed side, and a free state, which allows the rotation of the steering wheel, and controlling this switching with an electronic control unit of a steer-by-wire steering system. The aforementioned mechanical engagement makes it possible to reliably prevent the rotation of the steering wheel. Therefore, if the system is controlled to switch to the locked state when the direction of the steering wheel reaches the stroke end, the driver can reliably sense through the steering wheel that the direction of the steering wheel has reached the stroke end. 【0009】 However, if a steering lock device that prevents the steering wheel from rotating through mechanical engagement is used, there is a concern that if the steering lock device mechanically fails while the vehicle is in motion, it could result in unintended steering wheel rotation being prevented from being controlled by the steer-by-wire steering system, making it impossible for the driver to control the vehicle's movement through steering wheel operation. 【0010】 In light of the above background, the problem that this invention aims to solve is to provide a steer-by-wire steering system that allows the driver to reliably sense, through the steering wheel, when the direction of the steering wheel has reached the stroke end, and that can automatically control the vehicle's movement if a mechanical failure of the steering lock device occurs while the vehicle is in motion. [Means for solving the problem] 【0011】 To solve the above problems, this invention adopts a configuration 1 in which a steer-by-wire steering system comprising a steering wheel and a steering actuator provided mechanically detached from the steering wheel and which changes the direction of the steering wheel according to the amount of operation of the steering wheel is further comprising: a steering lock device that can switch between a locked state in which the rotation of the steering wheel can be prevented by mechanical engagement between the steering wheel side and a fixed side, and a free state in which the rotation of the steering wheel can be permitted; and an electronic control device that controls the switching between the free state and the locked state, monitors whether or not a rotation prevention of the steering wheel has occurred that is inconsistent with the control state when it is electrically free, and automatically controls the steering actuator when this rotation prevention of the steering wheel is detected. 【0012】 According to the above configuration 1, the steering lock device is switched to the locked state as appropriate under the control of the electronic control device, and the rotation of the steering wheel is prevented by mechanical engagement, so that the driver can reliably sense through the steering wheel when the direction of the steering wheel has reached the stroke end. Furthermore, if the steering lock device mechanically fails, the rotation of the steering wheel will be prevented inconsistent with the control state when it is electrically free, but the electronic control device that detects this will automatically control the steering actuator, making it possible to automatically control the vehicle's movement. 【0013】 In the above configuration 1, it is preferable to adopt configuration 2, in which the steering lock device comprises a shaft that rotates integrally with the steering wheel, a fixed member fixed so as not to rotate, an inner member connected to one of the shaft and the fixed member, an outer ring connected to the other of the shaft and the fixed member and surrounding the inner member, an engaging element positioned between the inner member and the inner circumference of the outer ring, a retainer supported to be circumferentially movable between an engagement position that holds the engaging element and engages the engaging element between the inner member and the inner circumference of the outer ring, and an engagement release position that releases the engagement of the engaging element between the inner member and the inner circumference of the outer ring, an armature supported to be axially movable, an electromagnet that attracts the armature and moves it in the axial direction by energizing it, and an operation conversion mechanism that moves the retainer circumferentially from one of the engagement position and the engagement release position to the other in accordance with the movement of the armature. 【0014】 According to the above configuration 2, mechanical engagement can be achieved by engaging an engaging element between the steering wheel side and the stationary side based on the current supply control to the electromagnet. 【0015】 In the above configuration 2, it is preferable to adopt configuration 3, in which the electronic control device monitors whether the electromagnet is in a free state based on the result of detecting the current flowing through it, and only when it is in a free state does it monitor whether the rotation of the steering wheel is blocked. 【0016】 According to configuration 3 above, by utilizing the fact that either the state in which current flows through the electromagnet (the state in which the armature is attracted) or the state in which current does not flow through the electromagnet (the state in which the armature is not attracted) corresponds to the free state of the steering lock device, the electronic control unit can determine whether or not the device is in a free state based on the detection result of the current flowing through the electromagnet. Furthermore, since the electronic control unit only monitors for the presence or absence of mismatched steering wheel rotation prevention when it determines that the device is in a free state, the processing load on the electronic control unit during normal operation can be reduced. 【0017】 In any one of the above configurations 1 to 3, it is preferable to adopt configuration 4, which further includes a torque sensor that detects torque on an axis that rotates integrally with the steering wheel, and the electronic control unit detects whether or not rotation of the steering wheel is blocked based on the torque detected by the torque sensor. 【0018】 According to the above configuration 4, when the steering wheel rotation is prevented by the steering lock device, if the driver attempts to turn the steering wheel, the torque on the shaft that rotates integrally with the steering wheel increases sharply. Based on the torque detected by the torque sensor, the electronic control unit can detect that the steering wheel rotation has been prevented. 【0019】 In any one of the above configurations 1 to 4, it is preferable to adopt configuration 5, which further includes a reaction motor that provides steering reaction force to the steering wheel, and the electronic control unit detects whether or not rotation of the steering wheel is blocked based on the current flowing through the reaction motor. 【0020】 According to the above configuration 5, when the rotation of the steering wheel is blocked by the steering lock device, even if the reaction force motor tries to apply a steering reaction force, the reaction force motor cannot rotate, and an abnormal current flows through the reaction force motor. Based on the detected current, the electronic control unit can detect that the rotation of the steering wheel has been blocked. 【0021】 In any one of the above configurations 1 to 5, it is preferable to adopt a configuration 6 in which the electronic control unit performs automatic parking control on the road shoulder when automatically controlling the steering actuator. 【0022】 According to the above configuration 6, when there is a mechanical failure of the steering lock device, the vehicle can be safely parked by being moved closer to the road shoulder under the control of the electronic control unit. 【0023】 In the above configuration 6, it is preferable to adopt a configuration 7 in which a communication device is further provided, and when the electronic control unit performs the automatic parking control, the communication device is commanded to notify a predetermined contact. 【0024】 According to the above configuration 7, it is possible to notify a predetermined contact of an abnormal situation of the vehicle. 【Advantages of the Invention】 【0025】 As described above, by adopting the above configuration 1, the driver can surely sense through the steering wheel the situation where the direction of the steered wheel has reached the stroke end, and when a mechanical failure of the steering lock device occurs during vehicle travel, the steer-by-wire type steering system can automatically control the vehicle travel. 【Brief Description of the Drawings】 【0026】 [Figure 1] A diagram schematically showing a steer-by-wire type steering system according to an embodiment as an example of the present invention [Figure 2] A plan view of a vehicle equipped with the steer-by-wire type steering system of FIG. [Figure 3] Cross-sectional view of the area near the steering lock device in Figure 1. [Figure 4] Figure 3 shows a magnified view of the vicinity of the motion conversion mechanism. [Figure 5] Cross-sectional view along line VV in Figure 3 [Figure 6] Enlarged view of the area around the engaging element in Figure 5. [Figure 7] Figure 6 shows the retainer in the position where it has moved to the engagement position. [Figure 8] A flowchart showing an example of vehicle fail-safe control using an electronic control unit, as shown in Figure 1. [Modes for carrying out the invention] 【0027】 The steer-by-wire steering system illustrated in Figure 1 converts the amount of movement of the steering wheel 1 by the driver (not shown) of the vehicle 100 illustrated in Figure 2 into an electrical signal, and controls the steering actuator 2 based on that electrical signal to change the direction of the left and right pair of steering wheels 3 of the vehicle. 【0028】 This steer-by-wire steering system comprises a steering wheel 1 rotated by the driver, a steering shaft 4 directly connected to the steering wheel 1, a steering sensor 5 that detects the amount of steering wheel 1 operated, a reaction motor 6 that provides steering reaction force to the steering wheel 1, a steering lock device 7 attached to the reaction motor 6, a steering actuator 2 mechanically disconnected from the steering wheel 1, and an electronic control device 8 that controls the steering actuator 2 and the like. 【0029】 The steering shaft 4 is connected to the steering wheel 1 so as to rotate together with the steering wheel 1 when the steering wheel 1 is rotated. 【0030】 The steering sensor 5 is attached to the steering shaft 4. The steering sensor 5 is, for example, a rotation sensor that detects the rotational angle position corresponding to the rotational position of the steering wheel 1. 【0031】 The reaction motor 6 is an electric motor that generates rotational torque when energized. The reaction motor 6 is connected to the end of the steering shaft 4. By inputting rotational torque to the steering shaft 4, the reaction motor 6 applies a steering reaction force to the steering wheel 1 via the steering shaft 4. 【0032】 The steering actuator 2 comprises a steering shaft 10, a steering shaft housing 11, a steering motor 12 for moving the steering shaft 10 in the left-right direction of the vehicle, and a steering sensor 13 for detecting the position of the steering shaft 10. The steering shaft 10 is supported by the steering shaft housing 11 so as to be movable in the left-right direction of the vehicle. The steering shaft housing 11 accommodates the central part of the steering shaft 10 such that both the left and right ends of the steering shaft 10 protrude from the steering shaft housing 11. 【0033】 The steering motor 12 and steering sensor 13 are mounted on the steering shaft housing 11. Between the steering motor 12 and the steering shaft 10, a motion conversion mechanism (not shown) is incorporated to convert the rotation output by the steering motor 12 into linear motion of the steering shaft 10. Both the left and right ends of the steering shaft 10 are connected to a pair of left and right steering wheels 3 via tie rods 14, so that when the steering shaft 10 moves axially, the orientation of the pair of left and right steering wheels 3 changes in conjunction with it. 【0034】 As shown in Figures 1 and 3, the reaction motor 6 has a motor shaft 15 and a motor body 16 that applies rotational torque to the motor shaft 15. The motor body 16 consists of a cylindrical casing and an annular stator (not shown) housed in this casing. The motor body 16 is fixed to a stationary part on the vehicle body side within its casing and is always in a constant positional relationship with respect to the steering wheel 1 installed in the driver's cab and the steering shaft 4 directly connected thereto. 【0035】 As shown in Figure 3, the motor shaft 15 has a portion that protrudes axially from the motor body 16 to one side (upper side in the figure) and a portion that protrudes axially from the motor body 16 to the other side (lower side in the figure). The lower end of the steering shaft 4 is coaxially connected to the upper portion of the motor shaft 15 in the figure, and the steering lock device 7 is coaxially connected to the lower portion of the motor shaft 15 in the figure. The steering shaft 4 and the motor shaft 15 constitute a transmission system that can rotate integrally with the steering wheel 1. 【0036】 The steering lock device 7 is capable of switching between a locked state, which can be prevented by mechanical engagement between the steering wheel 1 and the fixed side that remains stationary relative to the body of the vehicle 100 shown in Figure 2, and a free state, which allows the steering wheel to rotate. 【0037】 The steering lock device 7 shown in Figures 1 and 3 is mounted coaxially with the motor shaft 15, which acts as a shaft. When power is supplied to the steering lock device 7, it enters a locked state that prevents the rotation of the steering wheel 1, and when the power is cut off, it enters a free state that allows the rotation of the steering wheel 1. Based on this power supply control, the rotation of the steering wheel 1 can be prevented at any angle. 【0038】 Specifically, as shown in Figures 3 to 5, the steering lock device 7 includes an inner member 21 mounted on the outer circumference of the motor shaft 15, an outer ring 22 surrounding the inner member 21, a brake case 23 as a fixing member fixed so as not to rotate relative to the outer ring 22 and the motor body 16, an engaging element 26 positioned between a cam surface 24 formed on the outer circumference of the inner member 21 and a cylindrical surface 25 formed on the inner circumference of the outer ring 22, a retainer 27 holding these engaging elements 26, an armature 28 supported so as to be movable in the axial direction, an electromagnet 29 that attracts the armature 28 and moves it in the axial direction when energized, and an action conversion mechanism 30 that moves the retainer 27 in the circumferential direction in accordance with the movement of the armature 28. 【0039】 The inner member 21 is spline-fitted to the outer circumference of the motor shaft 15 so that it can rotate integrally with the motor shaft 15. 【0040】 The outer ring 22 is fitted into the brake case 23. The brake case 23 is a cylindrical member that houses all the components of the steering lock device 7 (inner member 21, engaging element 26, retainer 27, armature 28, electromagnet 29, etc.). A flange portion extending radially outward is formed at one axial end of the brake case 23, and it is fixed to the axial end face of the casing of the motor body 16 with bolts (not shown) at this flange portion. 【0041】 The outer ring 22 is prevented from coming off the brake case 23 by a retaining ring 31 mounted on the inner circumference of the brake case 23. As shown in Figure 5, a common key member 34 is fitted into a keyway 32 formed on the inner circumference of the brake case 23 and a keyway 33 formed on the outer circumference of the outer ring 22, and this key member 34 fixes the outer ring 22 in place so that it does not rotate. 【0042】 As shown in Figure 3, a bearing 35 is positioned between the inner circumference of the outer ring 22 and the inner member 21, which rotatably supports the inner member 21 relative to the outer ring 22. 【0043】 As shown in Figures 4 and 5, multiple cam surfaces 24 are formed on the outer circumference of the inner member 21. The cam surfaces 24 are radially opposite to the cylindrical surface 25 of the outer ring 22. Between each cam surface 24 and the cylindrical surface 25, a wedge space is formed that gradually narrows from the circumferential center to both ends in the circumferential direction. 【0044】 The retainer 27 has multiple pockets 36 that penetrate radially and are spaced apart in the circumferential direction. Each pocket 36 houses an engaging element 26. A roller is used as the engaging element 26. The retainer 27 is supported so as to be circumferentially movable with respect to the inner member 21, between an engagement position in which the engaging element 26 is engaged between the cam surface 24 and the cylindrical surface 25 by moving the engaging element 26 circumferentially from the circumferential center of the cam surface 24, and an engagement release position in which the engaging element 26 is released from the cam surface 24 and the cylindrical surface 25 by moving the engaging element 26 to the circumferential center of the cam surface 24. 【0045】 As shown in Figures 3 and 4, the armature 28 is supported on the outer circumference of the inner member 21 so as to be movable in the axial direction. The armature 28 is a disc-shaped member made of a magnetic material (such as iron or silicon steel). 【0046】 The electromagnet 29 is positioned opposite the armature 28 in the axial direction. The electromagnet 29 is fixed to the brake case 23 so as not to move in either the axial or circumferential direction. A separation spring 37 is positioned between the armature 28 and the electromagnet 29 to bias the armature 28 away from the electromagnet 29. 【0047】 The electromagnet 29 has an annular field core 38 with a C-shaped cross-section that opens axially toward the armature 28, and a solenoid coil 39 wound around the field core 38. When current is supplied to the solenoid coil 39, a magnetic circuit is formed through the field core 38 and the armature 28, and the armature 28 is attracted to the field core 38. The brake case 23 has a through hole for passing lead wires 40 that supply power to the solenoid coil 39. A rubber grommet 41 is fitted into this through hole. 【0048】 As shown in Figure 4, the motion conversion mechanism 30 includes a plate 42 that is fixed to the armature 28 and fixed to the retainer 27 in a state that allows relative movement in the axial direction with respect to the armature 28, and a centering spring 43 that elastically holds the retainer 27 in the disengaged position. 【0049】 The outer circumference of the plate 42 is formed with engaging projections 45 that engage with engaging recesses 44 formed in the retainer 27. The plate 42 is prevented from rotating by the retainer 27 by the engagement of these engaging projections 45 and engaging recesses 44, so as to move circumferentially together with the retainer 27. The plate 42 also has projections 46 that extend axially toward the armature 28. The armature 28 has holes 47 into which the projections 46 of the plate 42 are slidably inserted axially. The plate 42 is prevented from rotating by the armature 28 by the engagement of these projections 46 and holes 47, so as to move circumferentially together with the armature 28, while being able to move axially relative to the armature 28. 【0050】 As shown in Figure 5, the centering spring 43 consists of a C-shaped annular portion 48 made by winding steel wire in a C shape, and a pair of extension portions 49 that extend radially outward from both ends of the C-shaped annular portion 48. The C-shaped annular portion 48 is fitted into a circular spring housing recess 50 formed on one axial end face of the inner member 21. The pair of extension portions 49 are inserted into radial grooves 51 formed on the axial end face of the inner member 21 so as to penetrate radially outward from the spring housing recess 50. 【0051】 The extension portion 49 of the centering spring 43 protrudes from the radial outer end of the radial groove 51 of the inner member 21, and this protruding portion is inserted into a notch 52 formed in the retainer 27. The radial groove 51 and the notch 52 are formed to have the same circumferential width. The extension portion 49 of the centering spring 43 contacts the inner surface of the radial groove 51 of the inner member 21 and the inner surface of the notch 52 of the retainer 27, respectively, and the circumferential force acting on the contact portion elastically holds the retainer 27 in the disengaged position. 【0052】 In the steering lock device 7 shown in Figures 3 to 5, the free state that allows rotation of the inner member 21 corresponds to the state in which the electromagnet 29 is not energized. That is, when the electromagnet 29 is not energized, the armature 28 separates from the electromagnet 29 by the biasing force of the separation spring 37, and the armature 28 becomes able to rotate freely relative to the electromagnet 29. At this time, the retainer 27 is held in the disengaged position by the elastic restoring force of the centering spring 43, so that no matter whether the inner member 21 is rotated in forward or reverse direction, the engaging element 26 does not engage between the cam surface 24 of the inner member 21 and the cylindrical surface 25 of the outer ring 22, and the inner member 21 and the motor shaft 15 can rotate freely in both forward and reverse directions relative to the outer ring 22. 【0053】 On the other hand, in the steering lock device 7, the locked state that prevents the rotation of the inner member 21 corresponds to the state in which the electromagnet 29 is energized and the armature 28 is attracted. That is, when the electromagnet 29 is energized, the armature 28 is attracted to the electromagnet 29 and the armature 28 is in frictional contact with the electromagnet 29. At this time, when the inner member 21 is rotated, the armature 28, which is in frictional contact with the electromagnet 29, is prevented from rotating by the retainer 27 via the plate 42, so the rotation of the retainer 27 is restricted, and the inner member 21 rotates relative to the retainer 27. As a result, the retainer 27 moves from the disengaged position to the engaged position against the elastic force of the centering spring 43, and the engaging element 26 engages between the cam surface 24 of the inner member 21 and the cylindrical surface 25 of the outer ring 22, thereby preventing the rotation of the inner member 21, and consequently preventing the rotation of the motor shaft 15, steering shaft 4, and steering wheel 1, which are integrated with the inner member 21. 【0054】 Thus, in this steering lock device 7, as shown in Figure 6, there is play such as a gap set between the pocket 36 of the retainer 27 and the engaging element 26, and a gap required to achieve a free state between the wedge space formed by the cam surface 24 and the cylindrical surface 25 and the engaging element 26. Therefore, as the inner member 21 (motor shaft, steering shaft, steering wheel) rotates further after switching to the locked state, the retainer 27 and engaging element 26, which are in the disengaged position shown in Figure 6, move circumferentially by the aforementioned play amount α to the engaged position shown in Figure 7, until the engaging element 26 engages between the cam surface 24 and the cylindrical surface 25, that is, until the rotation of the inner member 21 is prevented, the inner member 21 rotates freely relative to the outer ring 22. This free rotation causes the steering shaft 4 and steering wheel 1 shown in Figure 1 to rotate. Note that Figures 6 and 7 illustrate the case where the inner member 21 rotates to the left in the locked state, but the same free rotation due to play occurs when rotating to the right, only in the opposite direction. 【0055】 The electronic control unit 8 shown in Figure 1 is electrically connected to each of the controlled objects under its control, which are mounted on the vehicle 100 shown in Figures 1 and 2, and electronically determines the control content to control the controlled objects under its control. 【0056】 The electronic control unit 8 includes a steering control unit 8a that commands the steering system of the vehicle 100, and a vehicle control unit 8b that commands the drive system, braking system, steering control unit 8a, and other equipment of the vehicle 100. 【0057】 The steering control unit 8a is electrically connected to the steering sensor 5, reaction force motor 6, steering lock device 7, steering actuator 2, steering sensor 13, torque sensor 61, and vehicle control unit 8b. The vehicle control unit 8b is electrically connected to the brake force generating device 62, drive device 63, driving monitoring device 64, brake 65, and communication device 66. 【0058】 The torque sensor 61 detects the torque on the shaft (inner member 21) that rotates integrally with the steering wheel 1. The torque sensor 61 outputs the detected torque value to the steering control unit 8a. The torque sensor 61 may also detect the torque on the motor shaft 15 or the steering shaft 4. 【0059】 The brake force generating device 62 supplies braking force to the brake 65. The brake 65 brakes the steering wheel 3 by frictional contact with the steering wheel 3 side using the supplied braking force. The brake force generating device 62 adjusts the braking force or stops supplying braking force according to commands from the vehicle control unit 8b. 【0060】 The drive unit 63 drives the steering wheels 3 of the vehicle 100. The drive unit 63 has a drive source such as an engine or an electric motor, and a transmission system that changes the speed of the output rotation of the drive source and outputs it to the steering wheels 3. The drive unit 63 adjusts the driving force according to commands from the vehicle control unit 8b, or stops driving the steering wheels 3 by stopping the drive source, cutting off the driving force, etc. 【0061】 The driving monitoring device 64 monitors the driving status (vehicle driving conditions) of the vehicle 100 and outputs the detection results of the driving conditions to the vehicle control unit 8b. The driving monitoring device 64 has sensors such as a camera 64a, an acceleration sensor 64b, a radar 64c, and a vehicle speed sensor 64d, and detects the vehicle driving conditions based on the detection results of one or more sensors. 【0062】 Camera 64a captures images of the area in front of the vehicle 100. Camera 64a is, for example, a digital camera having a solid-state image sensor. One or more cameras 64a are mounted on any location on the vehicle 100, such as the top of the front windshield or the rearview mirror. Camera 64a captures images of the area in front of the vehicle 100, for example, repeatedly and periodically. Camera 64a may be a stereo camera. 【0063】 The acceleration sensor 64b detects the acceleration of the vehicle 100 in the longitudinal, lateral, and vertical directions. The vehicle speed sensor 64d detects the vehicle speed of the vehicle 100. 【0064】 The radar 64c emits millimeter-wave or other radio waves in front of the vehicle 100 and detects the position (distance and direction) of an object by detecting the radio waves reflected by the object. One or more radars 64c can be mounted at any location on the vehicle 100, such as inside the front bumper. It is also possible to use a laser radar as the radar 64c, and when multiple radars are installed, radars with different detection principles, such as radio wave radar and laser radar, may be used in combination. 【0065】 The driving monitoring device 64 recognizes the position, type, speed, etc., of objects in front of or around the vehicle 100 based on the image captured by the camera 64a. The driving monitoring device 64 also detects objects in front of the vehicle 100 and objects moving in front of the vehicle 100 based on at least one of the recognition results from the image captured by the camera 64a and the detection results from the radar 64c, and detects the type, position, and speed of those objects. The driving monitoring device 64 also uses at least one of the recognition results from the image captured by the camera 64a and the detection results from the radar 64c to detect the position of road shoulders, road signs, lane markers such as white lines indicating driving lines. 【0066】 Furthermore, the driving monitoring device 64 detects the attitude (vehicle posture) of the vehicle 100 using at least one of the recognition results of the image captured by the camera 64a and the detection results of the acceleration sensor 64b. The driving monitoring device 64 also detects impacts to the vehicle 100 using at least one of the recognition results of the image captured by the camera 64a, the detection results of the acceleration sensor 64b, and the detection results of the vehicle speed sensor 64d. The driving monitoring device 64 outputs these detection results to the vehicle control unit 8b. The driving monitoring device 64 also stores predetermined detection results, including impact detection, as history information. 【0067】 The communication device 66 consists of a communication device capable of communicating with the outside of the vehicle. The communication device 66 may be connected to the vehicle control unit 8b by wire, or it may be connected to the vehicle control unit 8b wirelessly by short-range wireless communication. The communication device 66 may be a mobile phone terminal belonging to a mobile communication network, or it may be an on-board wireless device installed in the vehicle 100. 【0068】 When the vehicle control unit 8b detects, based on the detection results input from the steering control unit 8a, that an abnormal rotation blockage of the steering wheel 1 has occurred while the vehicle 100 is in motion, it determines the content of the automatic driving control according to the vehicle's driving conditions based on the detection results input from the driving monitoring device 64, and outputs a command to the corresponding control target to implement that control content. The content of the automatic driving control is set to automatic stopping control to stop on the shoulder of the road. The automatic stopping control includes commanding the steering control unit 8a to perform steering according to the driving conditions. In addition, the vehicle 100's turn signals, hazard lights, and parking brake may be activated as appropriate during the automatic stopping control. 【0069】 Furthermore, after the vehicle has stopped on the shoulder of the road, the vehicle control unit 8b instructs the communication device 66 to notify a designated contact. Examples of designated contacts include the vehicle manufacturer's customer service center and a call center arbitrarily set by the driver. Means of communication include telephone calls using the mobile phone network and email. Examples of the content of the notification include that vehicle 100 is in an emergency, information indicating the location of vehicle 100, and information about the owner and driver of vehicle 100. 【0070】 The steering control unit 8a appropriately controls the steering lock device 7 by switching between the locked and free states, and the steering motor 12 and reaction motor 6 of the steering actuator 2, in order to implement commands from the vehicle control unit 8b. 【0071】 Furthermore, if the vehicle control unit 8b does not perform automatic steering of the vehicle 100 and allows steering by the driver's operation of the steering wheel 1, the steering control unit 8a operates the steering motor 12 according to the amount of steering (rotation angle position, etc.) of the steering wheel 1 detected by the steering sensor 5, and controls the direction of the left and right pair of steering wheels 3, and also operates the reaction force motor 6 so that a steering reaction force of a magnitude corresponding to the amount of steering wheel 1 is operated and the vehicle driving conditions is generated. 【0072】 Furthermore, if the vehicle control unit 8b does not perform automatic steering of the vehicle 100 and allows steering by the driver's operation of the steering wheel 1, the steering control unit 8a determines whether the direction of the steering wheel 3 has reached the stroke end based on the position of the steering axis 10 detected by the steering sensor 13. When it is determined that the direction of the steering wheel 3 has not reached the stroke end, the steering control unit 8a holds the steering lock device 7 in the free state. On the other hand, when it is determined that the direction of the steering wheel 3 has reached the stroke end, the steering control unit 8a switches the steering lock device 7 to the locked state. In addition, if it is possible to maintain a state in which the phase of the steering wheel 1 and the steering actuator are aligned, it is also possible for the steering control unit 8a to monitor the rotational position of the steering wheel 1 detected by the steering sensor 5 and perform control to switch the steering lock device 7 to the locked or free state according to that rotational position. 【0073】 The steering control unit 8a monitors whether the steering is in a free state based on the result of detecting the current flowing through the electromagnet 29 (see also Figures 3 and 4; the same applies hereinafter). For example, since the steering lock device 7 shown in the figure is an excitation-operated type, it can detect the current flowing through the electromagnet 29, determine the detection result using a threshold, and determine that the steering is in a locked state when the current is above the threshold, and in a free state when the current is below the threshold or no current is flowing. In the case of a non-excitation-operated steering lock device, it can determine that the steering is in a free state when the current is above the threshold, and in a locked state when the current is below the threshold or no current is flowing. 【0074】 The steering control unit 8a monitors whether a rotation blockage of the steering wheel 1 has occurred that is inconsistent with the control state in which the steering lock device 7 is electrically in a free state, and when it detects such a occurrence, it outputs the detection result to the vehicle control unit 8b. 【0075】 The steering control unit 8a detects whether or not rotation of the steering wheel 1 is being blocked based on the torque detected by the torque sensor 61. When the steering control unit 8a is performing energization control to hold the steering lock device 7 in the locked state, if the driver attempts to turn the steering wheel 1, the mechanical engagement of the engaging element 26 between the cylindrical surface 25 and the cam surface 24 prevents the integrated rotation of the inner member 21, motor shaft 15, steering shaft 4, and steering wheel 1, causing the torque on the inner member 21 detected by the torque sensor 61 to rise sharply. Also, when the steering control unit 8a is performing energization control to hold the steering lock device 7 in the free state, the aforementioned mechanical engagement occurs due to mechanical failure of the steering lock device 7, preventing the integrated rotation of the inner member 21, motor shaft 15, steering shaft 4, and steering wheel 1, causing the torque detected by the torque sensor 61 to rise sharply at the time of this blockage. By determining whether or not this sharp torque change is present, it is possible to detect whether or not rotation of the steering wheel 1 is being blocked. 【0076】 Furthermore, the steering control unit 8a detects whether or not rotation of the steering wheel 1 is being blocked based on the current flowing through the reaction force motor 6. When the steering wheel 1 is blocked from rotating by the steering lock device 7, which is either locked or mechanically failed, the reaction force motor 6 cannot rotate even if it attempts to apply steering reaction force to the steering shaft 4, resulting in an abnormal current flowing through the reaction force motor 6. By determining the presence or absence of this abnormal current, it is possible to detect whether or not rotation of the steering wheel 1 is being blocked. 【0077】 Mechanical failure of the steering lock device 7 can occur, for example, due to damage to the retainer 27, engaging element 26, cam surface 24, cylindrical surface 25, centering spring 43, etc., or due to foreign matter getting caught, which may result in the retainer 27 being fixed in an incorrect engagement position or the engaging element 26 getting caught on the cam surface 24 and cylindrical surface 25. If the steering wheel 1 is prevented from rotating due to mechanical failure of the steering lock device 7, even though the electromagnet 29 is in an electromagnetic state corresponding to the free state, then the rotation of the steering wheel 1 will be prevented in a manner inconsistent with the control state in which the electrically free state is present. 【0078】 The electronic control device 8 described above consists of hardware resources such as an information processing unit, an information storage device, and a communication device mounted on the vehicle 100, and software resources executed by the hardware resources. The information storage device stores the software resources necessary for the information processing unit to calculate and determine the vehicle attitude control content, as well as predetermined initial information. 【0079】 Furthermore, the driving monitoring device 64 has hardware resources such as an information processing unit and an information storage device mounted on the vehicle 100, and software resources executed by the hardware resources. The information processing unit stores the software resources necessary for detecting driving conditions such as image recognition and radar detection, as well as predetermined initial information, in the information storage device. 【0080】 The driving monitoring device 64 and the electronic control unit 8 may be implemented by a single processor or by distributed processors. In the latter case, the driving monitoring device 64 and the electronic control unit 8 may each be configured as one or more ECUs (Electronic Control Units). The writing process for storing the aforementioned initial information in the electronic control unit 8 and the driving monitoring device 64 may be performed at an appropriate time, such as during the assembly of the steer-by-wire steering system or during system configuration. 【0081】 Figure 8 shows an example of fail-safe control in which the electronic control unit 8 monitors for mechanical failure in the steering lock device 7 and automatically drives the vehicle 100 when such failure occurs. 【0082】 The electronic control unit 8 starts the fail-safe control shown in Figure 8 when a situation arises in which the steering wheel 1 may rotate and the steering wheels 3 may change direction, or when such a situation has occurred. The situation that triggers this start can be based on appropriate switch operations such as starting the vehicle 100 (turning the driver's key ON), starting this steer-by-wire steering system, or situation detection. 【0083】 At startup, the electronic control unit 8 is in a manual driving mode that allows the vehicle 100 to move in response to the driver's operation of the steering wheel 1, accelerator, brakes, etc. Specifically, the steering control unit 8a controls the steering lock device 7 to a free state, and the vehicle control unit 8b starts monitoring the vehicle driving conditions detected by the driving monitoring device 64. 【0084】 After starting, the steering control unit 8a monitors whether the steering lock device 7 is in a free state based on the detection result of the current flowing through the electromagnet 29 (step S1). 【0085】 If the steering control unit 8a determines in step S1 that the steering is in a free state, it detects the torque on the shaft (inner member 21) with the torque sensor 61 (step S2), and also detects the current flowing to the reaction force motor (step S3). 【0086】 The steering control unit 8a determines whether or not a sudden increase in abnormal torque has occurred based on the torque detection result in step S2 (step S4). If it determines that abnormal torque has occurred, it outputs a detection result to the vehicle control unit 8b indicating that rotation of the steering wheel 1 has been blocked, which is inconsistent with the control state in which the steering wheel 1 is electrically free. If it determines that no abnormal torque has occurred, it returns to step S2. 【0087】 Furthermore, the steering control unit 8a determines whether or not an abnormal current has occurred based on the current detection result in step S3 (step S5). If it determines that an abnormal current has occurred, it outputs a detection result to the vehicle control unit 8b indicating that rotation of the steering wheel 1 has been blocked, which is inconsistent with the control state of being electrically free. If it determines that no abnormal torque has occurred, it returns to step S3. 【0088】 When the vehicle control unit 8b detects in at least one of step S4 and step S5 that a rotation blockage of the steering wheel 1 has occurred that is inconsistent with the control state in which the vehicle is electrically free, it cancels the manual driving mode and performs predetermined automatic driving control. As part of this predetermined automatic driving control, the vehicle control unit 8b performs automatic attitude control to maintain the stability of the vehicle attitude and automatic stopping control to bring the vehicle 100 to a stop on the shoulder of the road, based on the vehicle driving conditions such as the vehicle attitude and vehicle speed detected by the driving monitoring device 64 (step S6). 【0089】 In step S6, the vehicle control unit 8b determines control content such as steering angle and braking force according to the vehicle driving conditions so that the vehicle attitude is stable, and commands the steering control unit 8a to set the steering angle, the braking force generator 62 to set the braking force, and the drive unit 63 to set the output value according to the control content. The vehicle control unit 8b also sets a stopping position for the vehicle 100 by referring to the position of the road shoulder, vehicle speed, etc. detected by the driving monitoring device 64, and determines control content such as steering angle and braking force to stop at that position, and commands the steering control unit 8a to set the steering angle, the braking force generator 62 to set the braking force, and the drive unit 63 to set the output value according to the control content. The controlled object that receives these commands from the vehicle control unit 8b executes the commanded content. For example, when the steering control unit 8a receives a steering command from the vehicle control unit 8b, it drives the steering motor 12 so that the steering angle of the steering wheel 3 becomes the commanded angle. Thus, even when the rotation of the steering wheel 1 is prevented due to a mechanical failure of the steering lock device 7, the steering actuator 2 can be automatically controlled by the electronic control device 8. 【0090】 The vehicle control unit 8b determines whether the vehicle 100 has stopped on the shoulder of the road after step S6 (step S7). Here, the vehicle control unit 8b repeats steps S6 and S7 until it determines that the vehicle 100 has stopped on the shoulder of the road. On the other hand, when it determines that the vehicle 100 has stopped on the shoulder of the road, the vehicle control unit 8b commands the communication device 66 mounted on the vehicle 100 to contact the call center (step S8), and terminates the fail-safe control. 【0091】 This steer-by-wire steering system (see Figures 1 to 8 as appropriate) includes, as described above, a steering wheel 1, a steering actuator 2 that is mechanically disconnected from the steering wheel 1 and changes the direction of the steering wheels 3 according to the amount of steering wheel 1 is operated, a steering lock device 7 that can switch between a locked state in which the rotation of the steering wheel 1 can be prevented by mechanical engagement between the steering wheel 1 side and the fixed side (the brake case 23 side as a fixed member), and a free state in which the rotation of the steering wheel 1 can be permitted, and an electronic control device 8 that controls the switching between the free state and the locked state, monitors whether a rotation prevention of the steering wheel 1 has occurred that is inconsistent with the control state when it is electrically in the free state, and automatically controls the steering actuator 2 when this rotation prevention of the steering wheel 1 is detected. As a result, the steering lock device 7 can be appropriately switched to the locked state under the control of the electronic control device 8, and the rotation of the steering wheel 1 can be prevented by mechanical engagement, so that the driver can reliably sense through the steering wheel 1 that the direction of the steering wheels 3 has reached the stroke end. Furthermore, if the steering lock device 7 mechanically fails, the steering wheel 1 will be prevented from rotating, which is inconsistent with the control state where it is electrically free. However, the electronic control device 8 can detect this and automatically control the steering actuator 2, thus enabling automatic control of the vehicle's movement. 【0092】 Thus, this steer-by-wire steering system allows the driver to reliably sense, through the steering wheel 1, when the direction of the steering wheel 3 has reached the stroke end, and enables automatic control of the vehicle's movement in the event of a mechanical failure of the steering lock device 7 while the vehicle is in motion. 【0093】 Furthermore, the steering lock device 7 includes a shaft (motor shaft 15) that rotates integrally with the steering wheel 1, a fixed member (brake case 23) that is fixed so as not to rotate, an inner member 21 connected to one of the shaft (motor shaft 15) and the fixed member (brake case 23), an outer ring 22 connected to the other of the shaft (motor shaft 15) and the fixed member (brake case 23) and surrounding the inner member 21, an engaging element 26 positioned between the inner member 21 and the inner circumference of the outer ring 22, an engagement position that holds the engaging element 26 and engages the engaging element 26 between the inner member 21 and the inner circumference of the outer ring 22, and the inner member 21 and the outer ring The steering wheel 22 has a retainer 27 that is circumferentially supported to move between a disengagement position and a retainer 27 that is circumferentially supported to move between a disengagement position and a retainer 27 that is circumferentially supported to move between a retainer 27 and a disengagement position that disengages the retainer 27 from one of the engagement position and disengagement position to the other, and an action conversion mechanism 30 that moves the retainer 27 circumferentially from one of the engagement position and disengagement position to the other in accordance with the movement of the armature 28. By controlling the energization of the electromagnet 29, the retainer 27 can be engaged between the steering wheel 1 side (cam surface 24 of the inner member 21) and the fixed side (cylindrical surface 25 of the outer ring 22) to achieve mechanical engagement. 【0094】 Furthermore, the electronic control unit 8 monitors whether the steering wheel 1 is in a free state based on the detection of the current flowing through the electromagnet 29, and only when it is in a free state does it monitor whether rotation of the steering wheel 1 is being blocked. By utilizing the fact that either the state in which current is flowing through the electromagnet 29 (attracting the armature 28) or the state in which current is not flowing through the electromagnet 29 (not attracting the armature 28) corresponds to the free state of the steering lock device 7, the electronic control unit 8 can determine whether the steering wheel 1 is in a free state based on the detection of the current flowing through the electromagnet 29. In addition, since the electronic control unit 8 only monitors for the presence or absence of mismatched rotation blocking of the steering wheel 1 when it determines that it is in a free state, the processing load on the electronic control unit 8 during normal operation can be reduced. 【0095】 Furthermore, this steer-by-wire steering system is further equipped with a torque sensor 61 that detects torque on an axis (inner member 21) that rotates integrally with the steering wheel 1. The electronic control unit 8 detects whether or not rotation of the steering wheel 1 is blocked based on the torque detected by the torque sensor 61. By utilizing the fact that the torque on the axis (inner member 21) that rotates integrally with the steering wheel 1 increases sharply when the driver attempts to turn the steering wheel 1 while the steering lock device 7 is blocking its rotation, the electronic control unit 8 can detect, based on the torque detected by the torque sensor 61, that rotation of the steering wheel 1 is blocked. 【0096】 Furthermore, this steer-by-wire steering system is further equipped with a reaction motor 6 that provides steering reaction force to the steering wheel 1. The electronic control unit 8 detects whether or not rotation of the steering wheel 1 is blocked based on the current flowing through the reaction motor 6. By utilizing the fact that when the steering wheel 1 is blocked from rotating by the steering lock device 7, the reaction motor 6 cannot rotate even if it tries to provide steering reaction force, and an abnormal current flows through the reaction motor 6, the electronic control unit 8 can detect whether rotation of the steering wheel 1 is blocked based on the detected current. 【0097】 Furthermore, this steer-by-wire steering system allows the vehicle 100 to move to the shoulder and stop safely under the control of the electronic control unit 8 when the steering lock device 7 mechanically fails, by having the electronic control unit 8 automatically control the steering actuator 2 and perform automatic stopping control to the shoulder. 【0098】 Furthermore, this steer-by-wire steering system is further equipped with a communication device 66. When the electronic control unit 8 performs automatic stopping control, it commands the communication device 66 to notify a designated contact, thereby informing the designated contact of the abnormal situation of the vehicle 100, and enabling the contact to provide early assistance to the driver. 【0099】 As described above, this embodiment has been explained using a vehicle 100 having a pair of left and right steering wheels 3 as an example, but this invention can be applied to steer-by-wire steering systems for vehicles such as construction machinery, agricultural machinery, all-terrain vehicles, and multi-purpose four-wheeled vehicles. 【0100】 Furthermore, although this embodiment shows an example in which the steering lock device 7 is positioned on the side opposite the steering wheel 1 relative to the reaction force motor 6, this invention can also be applied when the steering lock device is positioned between the reaction force motor and the steering wheel. 【0101】 Furthermore, although this embodiment illustrates a case where the steering lock device 7 is connected to the motor shaft 15 of the reaction motor 6, this invention can also be applied to a steer-by-wire steering system that does not have a reaction motor. In this case, the steering lock device can be connected to any shaft belonging to the axial system that always rotates integrally with the steering wheel 1. 【0102】 Furthermore, in this embodiment, a brake case 23 is used as the fixing member of the steering lock device 7. However, in this invention, the outer ring and the brake case are made of a single, seamless case member, and a separate fixing member is made of a stationary member on the body side of the vehicle or the like. 【0103】 Furthermore, in this invention, the rotational position and rotational speed of the steering wheel 1 can be detected by detecting the rotational position corresponding to the rotational position of the steering wheel 1 and the rotational speed corresponding to the rotational speed of the steering wheel 1, and converting them as appropriate as necessary. When detecting the rotational angle position and angular velocity as in this embodiment, the rotational angle position and angular velocity at any position in the axial system that rotates integrally with the steering wheel 1 always coincide with the rotational angle position and angular velocity of the steering wheel 1. Therefore, the rotational angle position and angular velocity of any shaft in that axial system (steering shaft 4 or motor shaft 15) can be used directly as information indicating the rotational position and rotational speed of the steering wheel 1 for control of the electronic control device 8. 【0104】 Furthermore, although an excitation-operated steering lock device 7 is used in this embodiment, it is also possible to use a non-excitation-operated steering lock device in this invention. 【0105】 Furthermore, in this embodiment, the electronic control unit 8 employs torque detection by the torque sensor 61 and detection of the current flowing to the reaction motor 6, but it is not necessary to employ both, and it is possible to employ only one of them. By employing both as in this embodiment, and by having the electronic control unit perform automatic operation when at least one of abnormal torque or abnormal current occurs, fail-safe operation by the electronic control unit can be achieved even if mechanical failure of the steering lock device and failure of the torque sensor or current detection means occur simultaneously. 【0106】 The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications in the sense and scope equivalent to the claims are intended to be included. [Explanation of symbols] 【0107】 1. Steering wheel 2. Steering actuator 3 steering wheels 6. Reaction motor 7. Steering lock device 8. Electronic control unit 15 Motor shaft (shaft) 21 Inner member 22 Outer ring 23 Brake case (fixing component) 26 Engagement element 27 Cage 28 Armature 29 Electromagnet 30. Operation conversion mechanism 61 Torque Sensor 66 Communication equipment

Claims

[Claim 1] In a steer-by-wire steering system comprising a steering wheel and a steering actuator mechanically separated from the steering wheel and which changes the direction of the steering wheel according to the amount of steering wheel operation, A steering lock device that can switch between a locked state, which prevents the rotation of the steering wheel by mechanical engagement between the steering wheel side and the fixed side, and a free state, which allows the rotation of the steering wheel. A steer-by-wire steering system further comprising: an electronic control device that controls the switching between the free state and the locked state, monitors whether or not a rotation blockage of the steering wheel occurs that is inconsistent with the control state when the steering wheel is electrically free, and automatically controls the steering actuator when this rotation blockage of the steering wheel is detected. [Claim 2] The steering lock device, A shaft that rotates integrally with the steering wheel, A fixing member that is fixed so as not to rotate, An inner member connected to one of the shaft and the fixing member, The shaft and the other of the fixing members are connected to an outer ring that surrounds the inner member, An engaging element is disposed between the inner member and the inner circumference of the outer ring, A retainer is supported so as to be movable in the circumferential direction between an engagement position in which the engaging element is engaged between the inner member and the inner circumference of the outer ring, and an engagement release position in which the engagement element is released from between the inner member and the inner circumference of the outer ring, An armature supported to be movable in the axial direction, An electromagnet that attracts the armature and moves it in the axial direction by applying current, The steer-by-wire steering system according to claim 1, further comprising: an motion conversion mechanism that moves the retainer circumferentially from one of the engagement position and the disengagement position to the other in accordance with the movement of the armature. [Claim 3] The steer-by-wire steering system according to claim 2, wherein the electronic control device monitors whether the electromagnet is in a free state based on the result of detecting the current flowing through the electromagnet, and monitors whether the rotation of the steering wheel is blocked only when it is in a free state. [Claim 4] The system further includes a torque sensor that detects torque on an axis that rotates integrally with the steering wheel, The steer-by-wire steering system according to claim 1 or 2, wherein the electronic control unit detects whether or not rotation of the steering wheel is blocked based on the torque detected by the torque sensor. [Claim 5] The steering wheel is further equipped with a reaction motor that provides steering reaction force, The steer-by-wire steering system according to claim 1 or 2, wherein the electronic control device detects whether or not rotation of the steering wheel is blocked based on the current flowing through the reaction force motor. [Claim 6] The steer-by-wire steering system according to claim 1 or 2, wherein the electronic control device performs automatic stopping control to the shoulder of the road when automatically controlling the steering actuator. [Claim 7] Equipped with further communication devices, The steer-by-wire steering system according to claim 6, wherein when the electronic control device performs the automatic stopping control, it instructs the communication device to notify a predetermined contact.

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