Vehicle Steering System

Abstract

To simply acquire a contact load when a steering wheel of a vehicle collides with an edge stone or the like, and a rack is brought into contact with a stopper.SOLUTION: Contact speed w is determined on the basis of vehicle speed v and a steering amount θp at the time when collision of a steering wheel with an edge stone or the like starts. A relation between the vehicle speed v and the steering amount θp is previously determined, and the contact speed w is calculated using the relation. Subsequently, a contact load F is determined on the basis of the calculated contact speed w. A relation between the contact speed w and the contact load F is previously determined, and the contact load F is calculated using the relation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steering system for a vehicle, and more particularly to estimating damage to a steering gear that converts the rotational motion of a steering wheel into linear motion. [Background technology]

[0002] A vehicle steering system converts the rotational movement of the steering wheel operated by the driver into linear movement using a steering gear to steer the wheels. The linear motion element of the steering gear has its operating range restricted by stoppers.

[0003] The steering device (1) disclosed in Patent Document 1 below has a linear motion element (rack shaft 22) of a steering gear (steering mechanism 6). The linear motion element (22) is housed in a rack housing (23), and its operating range is defined by an end (23a) of the rack housing (23). The end (23a) of the rack housing serves as a stopper that defines the operating range of the linear motion element (22). In Patent Document 1 below, the amount of damage caused when the linear motion element (22), particularly the rack end (27), abuts against the end (23a) is calculated based on the rotation angle (pinion angle θp), angular velocity (ω), and angular acceleration (α) of the pinion (21) that rotates in association with the linear motion of the linear motion element (22). Note that the component names and symbols in parentheses above are those used in Patent Document 1 below and are unrelated to the component names and symbols used in the description of the embodiments of the present application. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-127082 Summary of the Invention [Problem to be solved by the invention]

[0005] The behavior of the linear motion element when it abuts against the stopper is very short, and to determine the angular velocity and angular velocity during this time, high resolution is required for measuring the pinion angle, which increases the calculation load on the processing unit and the communication load between devices.

[0006] An object of the present invention is to more easily estimate damage to a steering system. [Means for solving the problem]

[0007] The vehicle steering system of the present invention includes a steering gear that converts the rotational movement of the steering wheel into linear movement of a linear-acting element, a steering amount sensor that detects the steering amount of the steered wheels that are steered in accordance with the linear movement of the linear-acting element, a vehicle speed sensor that detects the vehicle speed, which is the traveling speed of the vehicle, a collision estimation unit that estimates the collision of the steered wheels with an obstacle, and a contact load acquisition unit that acquires the contact load expected when the linear-acting element contacts a stopper that defines the operating range of the linear-acting element, based on the steering amount and vehicle speed at the start of the collision.

[0008] By estimating the contact load of the linear element on the stopper based on the steering amount and vehicle speed at the time of the collision start, there is no need to calculate the speed and acceleration, which reduces the calculation load and communication load between devices.

[0009] In the above-described vehicle steering system, the contact load acquisition unit may acquire a contact speed based on the steering amount and vehicle speed, and acquire the contact load based on the acquired contact speed of the linear motion element. The contact speed may be acquired using a predetermined relationship between the steering amount and vehicle speed and the contact speed of the linear motion element expected when the linear motion element contacts the stopper. Furthermore, the contact load may be acquired using a predetermined relationship between the contact speed and the contact load.

[0010] By determining the relationships between variables in advance and using these relationships, the computational load can be reduced.

[0011] In the above-described vehicle steering system, the steering gear may include a rotating element that rotates in response to rotation of the steering wheel, the turning amount sensor may be a turning angle sensor that detects the turning angle of the turning element, and the turning amount may be the turning angle of the turning element. An existing device may be used.

[0012] In the above-described vehicle steering system, the steering system may further include a vehicle acceleration sensor that detects deceleration of the vehicle, and the collision estimation unit may estimate that the steered wheels have collided when the deceleration detected by the vehicle acceleration sensor is equal to or greater than a predetermined value and the linear motion element has reached the end of its operating range. Cases in which the linear motion element has not come into contact with the stopper can be narrowed down.

[0013] The steering system for a vehicle described above may further include a contact load memory unit that stores the contact load, and the stored information can be used later.

[0014] The steering system for a vehicle described above may further include an image acquisition unit that acquires an image of the area ahead of the vehicle, and an image storage unit that stores the image acquired by the image acquisition unit when the collision estimation unit estimates a collision of the steered wheels. Recording the image helps to later determine whether a collision of the steered wheels has actually occurred. [Effects of the Invention]

[0015] By estimating the contact load of the linear element on the stopper based on the steering amount and vehicle speed at the time of the collision start, there is no need to calculate the speed and acceleration, which reduces the calculation load and communication load between devices. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a steering system according to an embodiment of the present invention; [Figure 2]FIG. 10 is a block diagram showing a flow of calculation of a contact load based on a vehicle speed and a steering amount. [Figure 3] FIG. 10 is a diagram showing a processing flow relating to acquisition of a contact load of a rack. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a vehicle steering system 10 according to this embodiment. The steering system 10 includes a steering device 12 that changes the direction of the wheels, i.e., steers the wheels, when operated by a driver. The steering device 12 includes a steering wheel 14 operated by the driver and a steering gear 16 that converts the rotational motion of the steering wheel 14 into linear motion. The steering gear 16 includes a steering pinion 18 that rotates in response to the rotation of the steering wheel 14, and a steering rack 22 that has rack teeth 20 that mesh with the steering pinion 18. Hereinafter, the steering pinion 18 will be referred to as the pinion 18, and the steering rack 22 will be referred to as the rack 22. The steering wheel 14 and pinion 18 are mechanically connected by a steering shaft 24, and the rotation angles of the steering wheel 14 and pinion 18 are equal.

[0018] The rack 22 is a rod-shaped member having rack ends 28 at both ends that are connected to tie rods 26. The rack ends 28 and the ends of the tie rods 26 form ball joints, which allow the rack 22 and tie rods 26 to bend at their connection points. The tie rods 26 are further connected to knuckle arms 32, which are part of a knuckle that rotatably supports the steered wheels 30. The tie rods 26 and knuckle arms 32 are also connected to each other at their connection points so that they can bend.

[0019] When the driver turns the steering wheel 14, the pinion 18 rotates, causing the rack 22 to move. As the rack 22 moves, the tie rod 26 moves, which in turn moves the knuckle arm 32. The movement of the knuckle arm 32 rotates the knuckle, and the steered wheels 30 rotate together with the knuckle, i.e., are steered.

[0020] The rack 22 is housed in a generally cylindrical rack housing 34. A shaft through-hole 36 through which the steering shaft 24 passes is provided on a side of the rack housing 34. The rack 22 and the rack housing 34 are arranged coaxially, and the rack 22 is guided by the rack housing 34, allowing linear movement along the axial direction. The range of linear movement of the rack 22 is defined by the rack housing 34, particularly its end 38. When the rack 22 moves and the rack end 28 abuts against the end 38 of the rack housing 34, the movement of the rack 22 is stopped, thereby defining the range of movement. Therefore, the end 38 of the rack housing 34 serves as a stopper that stops the movement of the rack 22 and defines the range of movement of the rack 22. Hereinafter, the end 38 of the rack housing 34 will be referred to as the stopper 38. The stopper 38 may also include a damper that absorbs impact when the rack 22 abuts against the stopper 38. The damper may be an annular member made of an elastic material such as rubber and arranged to surround the rack 22.

[0021] The steering shaft 24 is provided with a rotation angle sensor 40 that detects the rotation angle of the steering shaft 24. The steering shaft 24 is mechanically coupled to the steering wheel 14, and the rotation angle sensor 40 is a sensor that detects the rotation angle of the steering wheel 14, i.e., the steering angle θs. The steering shaft 24 is also mechanically coupled to the pinion 18, and the rotation angle sensor 40 also functions as a sensor that detects the rotation angle θp of the pinion 18. Hereinafter, the rotation angle θp of the pinion 18 will be referred to as the pinion angle θp. The pinion 18 meshes with the rack teeth 20, and there is a unique relationship between the pinion angle θp and the amount of movement of the rack 22. Furthermore, there is a unique relationship between the steering angle θt, which is the rotation angle of the steered wheels 30 supported by a knuckle connected to the rack 22 via a tie rod 26, and the amount of movement of the rack 22. From these, the amount of steering of the steerable wheels 30 can be expressed by the steering angle θt, the amount of movement of the rack 22, and the pinion angle θp. Below, the amount of steering will be expressed by the pinion angle θp. The rotation angle sensor 40 will be referred to as the steering amount sensor 40, and the pinion angle θp will be referred to as the steering amount θp. The steering amount θp is set to 0 in the neutral position, that is, when the vehicle is traveling straight.

[0022] Steering system 10 also includes a vehicle speed sensor 42 that detects the vehicle's traveling speed, an acceleration sensor 44 that detects the acceleration and deceleration of the vehicle, and an on-board camera 46 that captures images of the area in front of the vehicle. Steering system 10 also includes a processing device 48 that processes information from steering amount sensor 40, vehicle speed sensor 42, acceleration sensor 44, on-board camera 46, etc. Processing device 48 acquires the load when rack end 28 abuts stopper 38, for example, based on information obtained from steering amount sensor 40 and vehicle speed sensor 42. Processing device 48 also estimates whether steered wheels 30 have collided with an obstacle such as a curb, based on information from acceleration sensor 44 and steering amount sensor 40. Hereinafter, a collision of steered wheels 30 with an obstacle such as a curb will be referred to as a "curb collision."

[0023] When the steerable wheels 30 collide with a curb, the input from the curb may force the steerable wheels 30 to turn, causing the rack end 28 to abut against the stopper 38. The input load at this time may be large due to the inertia of the vehicle, causing significant damage to the steering device 12, particularly the steering gear 16. By recording this damage, it can be used as a reference for future vehicle maintenance. Hereinafter, the event in which the rack end 28 of the rack 22 abuts against the stopper 38 will be referred to as "end abutment," and the input load on the stopper 38 at that time will be referred to as a abutment load F.

[0024] A method for acquiring the contact load F at the end contact will be described. The processing device 48 operates in accordance with a predetermined program, and functions as a contact load acquisition unit 48a that acquires, based on the vehicle speed v and the steering amount θp, the contact load F (estimated contact load) that is estimated when end contact occurs from the state of the vehicle speed v and the steering amount θp. The processing device 48 constantly acquires the outputs (v, θp) of the vehicle speed sensor 42 and the steering amount sensor 40, and acquires the contact load F estimated from this state based on these outputs. For example, the contact speed w, which is the speed of the rack 22 at the end contact, may be calculated from the vehicle speed v and the steering amount θp, and the estimated contact load F may be calculated from the contact speed w. The relationship between the vehicle speed v, the steering amount θp, and the contact speed w is calculated in advance, and the contact speed w is calculated based on the detected vehicle speed v and the steering amount θp using this relationship. The relationship between the contact speed w and the contact load F is also calculated in advance, and the contact load F is calculated based on the calculated contact speed w using this relationship. The contact load F obtained at this stage is a calculated value regardless of whether or not a curb collision actually occurred, and is therefore a provisional value.

[0025] FIG. 2 is a block diagram showing the process for acquiring the contact load F based on the vehicle speed v and the steering amount θp. Block 60 calculates the contact speed w based on the vehicle speed v and the steering amount θp at the time when the steered wheel 30 first contacts an obstacle such as a curb, i.e., at the start of the collision, using the relationship between the vehicle speed v, the steering amount θp, and the speed of the rack 22 when end contact occurs (contact speed w). The graph shown in block 60 shows the relationship between the vehicle speed v, the steering amount θp, and the contact speed w at the start of the collision. If the steering amount θp at the start of the collision is small, the distance and time until the rack end 28 contacts the stopper 38 become longer, and the rack 22 accelerates more by the time of contact, which tends to increase the contact speed w. Curve A illustrates the case where the steering amount θp at the start of the collision is relatively small, while curve B illustrates the case where the steering amount θp is relatively large. In either case, the contact speed w increases as the vehicle speed v increases. Furthermore, at the start of a collision, even if the vehicle speed v is the same, if the steering amount θp is small, that is, if the distance to the end of the operating range of the rack 22 is large, the contact speed w will be large. Experimentally, a function f expressing the relationship between the vehicle speed v and the steering amount θp as two variables is determined in advance. w=f(v,θp) The processing device 48 constantly acquires the vehicle speed v and the steering amount θp, and calculates the contact speed w on the basis of the function f each time.

[0026] In block 62, the contact load F is calculated based on the contact speed w of the rack 22 and the relationship between the contact speed w and the contact load F. The graph shown in block 62 is a graph showing the relationship between the contact speed w of the rack 22 and the contact load F. The faster the contact speed w, the larger the contact load F. A function g that expresses the relationship between the contact speed w and the contact load F is experimentally determined in advance. F=g(w) The processing device 48 calculates the contact load F based on the function g every time it calculates the contact speed w. The contact load F is calculated at a predetermined sampling period, and is calculated sequentially even if end contact does not actually occur. The calculated contact load F is saved as a temporary value for a predetermined period, and is deleted after the predetermined period has elapsed.

[0027] A method for estimating whether a curb collision of the steered wheel 30 has occurred will be described. The processing device 48 operates according to a predetermined program to function as a collision estimation unit 48b that estimates whether a curb collision has occurred based on the output (α) of the vehicle acceleration sensor 44 and the output (θp) of the steering amount sensor 40. For example, the processing device 48 estimates that a collision has occurred when the vehicle deceleration α is equal to or greater than a predetermined value αth and the absolute value of the steering amount θp is equal to or greater than a predetermined value θpth. The predetermined value αth of the vehicle deceleration corresponds to a sudden deceleration of the vehicle due to a collision of the steered wheel 30. The predetermined value θpth of the steering amount corresponds to a value when the rack 22 has reached almost the end of its operating range. For example, if the operating range of the rack 22 is ±S, the absolute value of the steering amount θp corresponding to 0.9 × S is set to the predetermined value θpth. If a neutral point deviation occurs in the steering amount sensor 40, end contact may actually occur even if the steering amount θp is a value that has not reached the end of the operating range. For this reason, 0.9×S, which is slightly narrower than the operating range (±S), is set as the threshold value for determining whether the rack 22 has reached the end of the operating range, i.e., the rack end 28 has come into contact with the stopper 38, when the absolute value of the steering amount θp reaches a predetermined value θpth.

[0028] When the steered wheels 30 collide with a curb, the vehicle suddenly decelerates, so it is possible to estimate a collision by monitoring the vehicle deceleration α. ​​Furthermore, it is possible to estimate end hit by monitoring the steering amount θp. By monitoring both the vehicle deceleration α and the steering amount θp, it is possible to exclude cases where the steered wheels 30 collide but end hit does not occur. Furthermore, by monitoring both the vehicle deceleration α and the steering amount θp, it is possible to exclude cases where end hit occurs due to steering by the driver. When end hit occurs due to steering by the driver, the contact speed w of the rack 22 is low, so the contact load F is small and the damage to the steering gear 16 is also small. Therefore, it is desirable to exclude it from the damage assessment.

[0029] When the collision estimation unit 48b estimates that the steered wheel 30 will collide with a curb, the contact load acquisition unit 48a of the processing device 48 extracts the contact load F at the time corresponding to the collision from the stored tentative contact load F, and sets this contact load F as the contact load F when the end hit actually occurred. The contact load F when the end hit occurred is then stored in the storage device 50. There is a slight time delay between the start of the collision, when the steered wheel 30 first comes into contact with the curb or the like, and the time when the vehicle actually decelerates and the end hit occurs. As described above, the contact load F is calculated based on the steering amount θp and the vehicle speed v at the start of the collision. Therefore, the processing device 48 extracts the contact load F based on detection of a time or period that is a predetermined time before the end hit occurred, taking into account the time delay from the start of the collision to the occurrence of the end hit, and stores the extracted contact load F in the storage device 50. The time to go back can be determined in advance through experiments. If the period from the start of the collision to the occurrence of the end hit is equal to the sampling period for acquiring the contact load F, the latest contact load F may be stored as the contact load F when the end hit actually occurred.

[0030] Furthermore, the processing device 48 may store in the storage device 50 images of the area in front of the vehicle captured by the on-board camera 46 for a predetermined period of time, including the start of the collision, in association with the contact load F. A vehicle maintenance technician determines, based on the stored images, whether the stored contact load F corresponds to an actual collision with a curb or the like. Alternatively, a collision determination may be made using a device that has been trained in advance using images of actual collisions and images of no collisions. The maintenance technician determines the accumulated damage from the contact load when a collision of the steered wheels 30 actually occurs, and uses this as a reference for maintenance.

[0031] 3 is a diagram showing the processing flow related to acquisition of the contact load of the rack 22 in the steering system 10. In the steering system 10, a flow related to calculation of the contact load expected at the time of end contact, a flow related to detection of the occurrence of a collision of the steered wheels 30 with a curb or the like, and a flow related to photographing the area in front of the vehicle are processed in parallel.

[0032] In the flow of calculating the contact load, first, the vehicle speed v and the steering amount θp are detected by the vehicle speed sensor 42 and the steering amount sensor 40 (S100). Based on the detected vehicle speed v and steering amount θp, the contact speed w of the rack 22 is calculated in accordance with a function determined in advance, for example, by experiment (S102). Furthermore, based on the contact speed w of the rack 22, the contact load F is calculated in accordance with a function determined in advance, for example, by experiment (S104). The calculated contact load F is saved (S106), and data of the contact load F that has been saved for a predetermined period of time is deleted (S108). The data of the contact load F is saved for a predetermined period of time, and is deleted sequentially starting with the data that has been saved for the longest period of time. Therefore, data from the present to the past for a predetermined period of time is always saved.

[0033] In the flow of detecting a collision of steered wheels 30, first, vehicle deceleration α is detected by acceleration sensor 44 (S110), and deceleration monitoring continues until deceleration equals or exceeds predetermined value αth, that is, a predetermined large deceleration occurs (S112). When vehicle deceleration α exceeds predetermined value αth, steering amount θp is detected by steering amount sensor 40 (S114), and if the absolute value of steering amount θp at that time exceeds predetermined value θpth (e.g., 0.9 × θp) at which end contact is assumed (S116), it is determined that end contact has occurred (S118). If end contact is not determined, the process returns to step S110.

[0034] As for the flow of photographing the view ahead of the vehicle, the view ahead of the vehicle is photographed by the in-vehicle camera 46, and the photographed image is stored for a predetermined period of time (S120).

[0035] If it is determined in step S118 that an end hit has occurred, that is, if a collision of the steered wheels 30 is estimated, data for the time or period corresponding to the end hit is extracted from the stored data of contact load F, and data for the period corresponding to the end hit is also extracted from the stored video data. Then, the extracted data of contact load F and the extracted video data of the area ahead of the vehicle are stored in storage device 50 (S122).

[0036] The contact load F may be obtained directly from the vehicle speed v and the steering amount θp, without using the contact speed w of the rack 22. The relationship between the vehicle speed v, the steering amount θp, and the contact load F may be determined in advance through experiments, and this relationship may be used to obtain the contact load F based on the detected vehicle speed v and steering amount θp. The relationship between the vehicle speed v, the steering amount θp, and the contact load F may be expressed as a function with the vehicle speed v and the steering amount θp as two variables.

[0037] The contact speed w of the rack 22 may be obtained based on a correspondence table showing the correspondence relationship between the vehicle speed v and the steering amount θp and the contact speed w. The correspondence table is created in advance through experiments, and the contact speed w is obtained by referring to this correspondence table. Similarly, the contact load F may also be obtained by creating in advance a correspondence table showing the correspondence relationship with the contact speed w or a correspondence table showing the relationship between the vehicle speed v and the steering amount θp, and then the contact load F may be obtained.

[0038] In addition, instead of always obtaining the contact load F from the vehicle speed v and the steering amount θp, the contact load F may be obtained based on the vehicle speed v and the steering amount θp when it is estimated that the steered wheel 30 will collide with a curb.

[0039] Furthermore, instead of acquiring images using the vehicle-mounted camera 46, information on obstacles ahead may be acquired by acquiring images using laser distance measurement.

[0040] In addition, the above-described method for obtaining the contact load F can also be applied to a steer-by-wire steering device in which the steering wheel and rack are not mechanically connected.

[0041] In addition, the storage device 50 may be installed outside the vehicle, such as in an operations control room that manages and monitors the operation of the vehicle, and may be configured to receive and store information such as contact load through communication between the vehicle and the operations control room, etc. [Explanation of symbols]

[0042] 10 steering system, 12 steering device, 14 steering wheel, 16 steering gear, 18 (steering) pinion, 20 rack teeth, 22 (steering) rack, 28 rack end, 30 steered wheel, 34 rack housing, 38 stopper, 40 steering amount sensor (rotation angle sensor), 42 vehicle speed sensor, 44 acceleration sensor, 46 on-board camera, 48 processing device, 50 storage device, α vehicle deceleration, F contact load, v vehicle speed, w contact speed, θp steering amount (pinion angle).

Claims

1. a steering gear that converts the rotational motion of the steering wheel into the linear motion of a linear motion element; a steering amount sensor that detects a steering amount of a steered wheel that is steered in accordance with the linear motion of the linear motion element; a vehicle speed sensor that detects a vehicle speed, which is the traveling speed of the vehicle; a collision estimation unit that estimates a collision of the steered wheels with an obstacle; a contact load acquisition unit that acquires a contact load that is expected when the linear motion element contacts a stopper that defines a motion range of the linear motion element, based on the steering amount and the vehicle speed at the start of the collision; A vehicle steering system including:

2. 2. A vehicle steering system according to claim 1, The contact load acquisition unit acquiring the contact speed based on the steering amount and the vehicle speed, using a predetermined relationship between the steering amount, the vehicle speed, and a contact speed of the linear motion element that is expected when the linear motion element contacts the stopper; acquiring the contact load based on the acquired contact speed of the linear motion element using a predetermined relationship between the contact speed and the contact load. Vehicle steering system.

3. 2. A vehicle steering system according to claim 1, the steering gear includes a rotating element that rotates in response to rotation of the steering wheel, The steering amount sensor is a rotation angle sensor that detects a rotation angle of the rotation element, and the steering amount is the rotation angle of the rotation element. Vehicle steering system.

4. 2. A vehicle steering system according to claim 1, further comprising a vehicle acceleration sensor for detecting deceleration of the vehicle; the collision estimation unit estimates that the steered wheels have collided when the deceleration detected by the vehicle acceleration sensor is equal to or greater than a predetermined value and the linear motion element has reached an end of an operating range of the linear motion element. Vehicle steering system.

5. 5. The vehicle steering system according to claim 1, further comprising a contact load storage unit that stores the contact load.

6. 6. A vehicle steering system according to claim 5, further comprising: an image acquisition unit that acquires an image of the area ahead of the vehicle; an image storage unit that stores an image acquired by the image acquisition unit when a collision of the steered wheels is estimated by the collision estimation unit; A vehicle steering system including:

Images