Steering system

Abstract

The present application provides a steering system capable of detecting an abnormality of a steering shaft generated by a load in a bending direction. In the present application, a controller is configured to execute: input determination processing (S101) that determines the presence or absence of an input of an external force to the vehicle based on front-rear acceleration; position determination processing (S102) that, in the case where there is an input of an external force, determines an input tire, which is a tire to which an external force is input, among a plurality of tires based on air pressures of the respective tires (81 to 84); load calculation processing (S103) that, in the case where the input tire is a tire of a steering wheel (91, 92), calculates a deceleration of the vehicle or acquires information of the deceleration, and calculates a load received by the input tire by the external force based on a difference between the front-rear acceleration and the deceleration; and abnormality determination processing (S104) that determines the presence or absence of an abnormality of a steering shaft (511) based on the load and a steering angle.

Description

Technical Field

[0001] This invention relates to steering systems. Background Technology

[0002] In a rack and pinion steering mechanism, the rack of the rack arm meshes with the pinion of the pinion shaft, and the tie rod moves with the movement of the rack arm, thereby turning the steering wheel. The rack arm is one of the steering shafts (steering rods). Furthermore, for example, Japanese Patent Application Publication No. 2019-104488 discloses a steering system for detecting abnormalities in a transmission device that transmits the output of an electric motor to the steering shaft.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-104488

[0006] A technique for detecting abnormalities in the steering shaft caused by loads applied in a bending direction to the rack and pinion shaft has not yet been established. The bending direction is orthogonal to the axial direction of the steering shaft. Applying a load in a bending direction to the steering shaft can cause abnormalities such as shaft bending. For example, abnormalities caused by loads in a bending direction to the rack and pinion shaft may include deformation or breakage of the rack portion, or poor meshing between the rack and pinion shaft. As a result, the rack and pinion mechanism may lock or become unresponsive.

[0007] For example, consider a system where the steering wheel and rack are mechanically linked. The driver perceives any abnormality in the rack by operating the steering wheel. However, in such a system, the driver may not perceive any abnormality in the rack (including any potential abnormal states). In particular, in systems like steer-by-wire systems where the steering wheel and rack are not mechanically linked, the likelihood of the driver not perceiving any abnormality in the rack through steering wheel operation is high. Summary of the Invention

[0008] The object of the present invention is to provide a steering system capable of detecting abnormalities in the steering shaft caused by loads in a bending direction.

[0009] The steering system of the present invention includes: a steering actuator having a steering shaft, a steering motor that applies driving force to the steering shaft, and a conversion mechanism that converts the rotation of the steering motor into axial movement of the steering shaft, the steering actuator turning a steering wheel; a steering angle sensor for detecting the steering angle of the steering wheel; an acceleration sensor for detecting the longitudinal acceleration of the vehicle as a forward-reverse acceleration; a tire pressure sensor for detecting the tire pressure of each tire; and a controller having one or more processors, the controller being configured to acquire information about the steering angle, the longitudinal acceleration, and the tire pressure, and the controller being configured to execute... The process includes: input determination processing, which determines the presence or absence of an external force input to the vehicle based on the front-to-back acceleration; position determination processing, which, in the case of an external force input, determines the input tire among the multiple tires as the tire into which the external force input is input based on the tire pressure of each tire; load calculation processing, which, in the case that the input tire is the tire of the steering wheel, calculates the deceleration of the vehicle or obtains the deceleration information, and calculates the load on the input tire due to the external force based on the difference between the front-to-back acceleration and the deceleration; and anomaly determination processing, which determines the presence or absence of an anomaly of the steering shaft based on the load and the steering angle.

[0010] Invention Effects

[0011] According to the present invention, for example, when an external force is input to the tire due to climbing over a curb, the input tire is determined and the load on the input tire is calculated. The load applied to the steering shaft in the bending direction is affected by the load in the longitudinal direction and the steering angle. The greater the load in the longitudinal direction, the greater the load applied to the steering shaft in the bending direction. Furthermore, the greater the extension of the steering shaft relative to the input tire, the greater the moment length, and the greater the load applied to the steering shaft in the bending direction. The extension of the steering shaft corresponds to the steering angle. The controller determines the presence or absence of an abnormality in the steering shaft based on the load and the steering angle. Thus, according to the present invention, abnormalities in the steering shaft caused by loads in the bending direction can be detected. Attached Figure Description

[0012] Figure 1 This is a configuration diagram of the steering system in this embodiment.

[0013] Figure 2 This is a structural diagram of the gear and rack pair mechanism of this embodiment.

[0014] Figure 3 This is a conceptual diagram used to illustrate the orientation of the load applied to the rack in this embodiment.

[0015] Figure 4This is a conceptual diagram used to illustrate the orientation of the load applied to the rack in this embodiment.

[0016] Figure 5 This is a flowchart used to explain the anomaly detection and control process of this embodiment.

[0017] Figure 6 This is a flowchart used to explain the detailed process of anomaly detection and control in this embodiment.

[0018] Figure 7 This is a conceptual diagram representing the anomaly determination mapping diagram of this embodiment.

[0019] Figure 8 This is a flowchart illustrating the detailed process of anomaly detection and control in this embodiment.

[0020] Figure 9 This is a conceptual diagram representing an example of an anomaly detection mapping.

[0021] Figure 10 This is a diagram illustrating the configuration of the steering system in this embodiment from another perspective.

[0022] Figure 11 This is a conceptual diagram representing an example of an anomaly detection mapping.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1: Steering system; 10: Controller; 10a: Processor; 21: Acceleration sensor; 22: Air pressure sensor; 23: Vehicle height sensor; 25: Steering angle sensor; 27: Seat sensor; 510: Steering actuator; 511: Rack and pinion (steering shaft); 513: Pinion shaft; 515: Steering motor; 516: Conversion mechanism; 521: Steering wheel (operating component); 5A: Pinion; 5B: Rack and pinion. Detailed Implementation

[0025] Hereinafter, a steering system 1, as an embodiment of the present invention, will be described in detail with reference to the accompanying drawings. It should be noted that, in addition to the embodiments described below, the present invention can be implemented in various ways with various modifications and alterations based on the knowledge of those skilled in the art. The figures are conceptual diagrams.

[0026] like Figure 1As shown, the steering system 1 of this embodiment includes a controller 10, a steering device 51, and an operating device 52. The controller 10 is an electronic control unit (ECU) or computer equipped with one or more processors 10a and one or more memories 10b. The controller 10 is connected to various sensors in a communicable manner. For example, the controller 10 is communicably connected to vehicle-mounted sensors such as an acceleration sensor 21, multiple air pressure sensors 22, multiple vehicle height sensors 23, a pressure sensor 24, and a steering angle sensor 25. It should be noted that in-vehicle communication is conducted via CAN (vehicle area network or controllable area network).

[0027] Accelerometer 21 detects the vehicle's forward and backward acceleration. Accelerometer 21 sends the detection result to controller 10. Multiple tire pressure sensors 22 detect the tire pressure of tires 81-84 respectively. Each tire pressure sensor 22 sends the detection result to controller 10.

[0028] The vehicle height sensor 23 detects physical quantities related to vehicle height. Specifically, the vehicle height sensor 23 detects the change in vehicle height, i.e., the vehicle height travel. The controller 10 can determine the direction of the change in vehicle height, i.e., whether it is an upward or downward change, based on the detection results of the vehicle height sensor 23, for example, based on the sign (positive or negative) of the detected current.

[0029] Although not shown, the vehicle height sensor 23 includes, for example, a lever mechanism and a variable resistor. The vehicle height sensor 23 is configured to detect vehicle height travel based on changes in the lever mechanism. In this embodiment, the vehicle height sensor 23 is provided at each wheel 91-94 to measure changes in the distance between the suspension arm and the vehicle body. It should be noted that the vehicle height sensor 23 is not limited to the above configuration and may also be other known configurations. Furthermore, the vehicle height sensor 23 may, for example, be provided only at the steering wheels 91 and 92. Additionally, the vehicle height sensor 23 may also be a sensor for detecting vehicle height.

[0030] Pressure sensor 24 detects the hydraulic pressure corresponding to the hydraulic pressure of the wheel cylinders 61, 62, 63, 64 of the braking devices 71, 72, 73, 74 respectively located on the multiple wheels 91, 92, 93, 94 of the vehicle. Although not shown, the braking devices 71 to 74 are each configured to include, for example, a brake rotor, brake pads, and pistons that press the brake pads against the brake rotor based on the hydraulic pressure of the wheel cylinders 61 to 64. The braking force applied to each corresponding wheel 91 to 94 is determined based on the hydraulic pressure of the wheel cylinders 61 to 64.

[0031] Each braking device 71-74 has wheel cylinders 61-64 connected to a hydraulic adjustment device 70 (hydraulic circuit diagram omitted) that adjusts the hydraulic pressure (hereinafter also referred to as "wheel pressure") of wheel cylinders 61-64. Although not shown, the hydraulic adjustment device 70 includes a reservoir, a pressure regulating device with an electric motor, and multiple solenoid valves. The hydraulic adjustment device 70 may include, for example, an ESC actuator and / or an electric cylinder. The hydraulic adjustment device 70 is controlled by the brake ECU 70a.

[0032] Pressure sensors 24 can be installed for each wheel cylinder 61-64, or one can be installed for each of the front wheel system's wheel cylinders 61 and 62 and the rear wheel system's wheel cylinders 63 and 64, or one can be installed in either system. If pressure sensors 24 are not installed for each wheel cylinder 61-64, the brake ECU 70a calculates the wheel pressure based on the detection result of one pressure sensor 24 and the control settings of solenoid valves, etc. Furthermore, wheel pressure corresponds to the deceleration generated by vehicle braking. The brake ECU 70a calculates the vehicle deceleration generated by hydraulic braking based on the wheel pressures.

[0033] The controller 10 receives the detection results from the pressure sensor 24, the wheel pressures calculated by the brake ECU 70a, and / or the deceleration calculated by the brake ECU 70a, as information related to the deceleration of the vehicle.

[0034] A steering angle sensor 25 is installed on the steering device 51 that controls the steering wheels 91 and 92 of the vehicle, and detects the steering angle of the steering wheels 91 and 92. In this embodiment, the steering wheels 91 and 92 are a pair of front wheels. The steering system 1 in this embodiment is a steer-by-wire type steering system. Therefore, the steering device 51 and the operating device 52 are mechanically independent. The controller 10, which functions as a steering ECU, is connected to the steering device 51 and the operating device 52 in a communicable manner. It should be noted that the steering system 1 may also have a steering ECU that controls the steering device 51 and the operating device 52 separately from the controller 10.

[0035] The operating device 52 includes a steering wheel 521, a steering shaft 522, a steering column 523, a reaction force applying mechanism 524, and an operating angle sensor 525. The steering wheel 521 is an operating component for the driver's steering operations. The steering shaft 522 is a shaft component on which the steering wheel 521 is mounted. The steering column 523 is a component that holds the steering shaft 522 in a rotatable position and supports it to the instrument panel reinforcement.

[0036] The reaction force applying mechanism 524 uses a reaction force motor 526, which is an electric motor supported on the steering column 523, as a power source to apply a reaction force for steering operation to the steering wheel 521 via the steering shaft 522. The reaction force applying mechanism 524 is a mechanism with a general structure including a reducer, etc. A rotation angle sensor 526a is provided in the reaction force motor 526. The operation angle sensor 525 detects the operation angle of the steering wheel 521 to obtain the steering operation amount.

[0037] Furthermore, in the operating device 52, similar to a typical power steering system, a torsion bar 527 is mounted on the steering shaft 522. The operating device 52 has an operating torque sensor 528 for detecting the operating torque, which is the operating force applied by the driver to the steering wheel 521, based on the amount of torsion of the torsion bar 527.

[0038] Wheels 91-94 are supported on the vehicle body in a steering manner via steering knuckles 539, which are components of the suspension system. Steering device 51 rotates a pair of front wheels 91 and 92 together by rotating steering knuckles 539. Steering device 51 has a steering actuator 510 as its main component.

[0039] like Figure 1 and Figure 2 As shown, the rudder actuator 510 includes a rack 511 serving as the rudder shaft, a housing 512, a pinion shaft 513, a tie rod 514, a rudder motor 515, and a conversion mechanism 516. The rack 511 is a component whose two ends are connected to the left and right steering knuckles 539 respectively via the tie rod 514. In other words, the left end of the rack 511 is connected to the steering knuckle 539 of the left front wheel 91 via the left tie rod 514, and the right end of the rack 511 is connected to the steering knuckle 539 of the right front wheel 92 via the right tie rod 514.

[0040] The housing 512 is a component that supports the rack 511 so that it can move left and right and is fixedly held to the vehicle body. Each end of the housing 512 is provided with a sleeve 512a that covers the connection portion between the rack 511 and the tie rod 514.

[0041] The pinion shaft 513 is configured to intersect with the rack 511 and has a pinion 5A that meshes with the rack 5B formed on the rack 511. The pinion shaft 513 and the rack 511 constitute a gear and rack pair mechanism. The pinion shaft 513 is configured to rotate according to axial movement (left-right direction) of the rack 511. A rotation angle sensor 25 is provided on the pinion shaft 513 to detect the rotation angle of the pinion shaft 513. The rotation angle of the pinion shaft 513 corresponds to the left-right movement of the rack 511, and the left-right movement of the rack 511 corresponds to the steering angle of the steering wheels 91 and 92. That is, the steering angle of the steering wheels 91 and 92 can be calculated based on the rotation angle sensor that detects the rotation angle of the pinion shaft 513. It should be noted that the steering angle sensor 25 can also be a sensor that directly detects the movement of the rack 511.

[0042] This embodiment utilizes a conventional system, such as a power steering system where the rack and pinion mechanism including the rack and pinion 511 and pinion shaft 513 is mechanically connected to the steering shaft 522. This embodiment eliminates the mechanical connection between the operating device 52 and the pinion shaft 513, thus creating a steer-by-wire system. In other words, the steering system 1 of this embodiment utilizes a conventional rack and pinion mechanism as the steer angle sensor 25. Alternatively, a pinion auxiliary motor can be installed in the rack and pinion mechanism as the steering motor.

[0043] The steering motor 515 is an electric motor that provides driving force to the rack 511 via a conversion mechanism 516. The conversion mechanism 516 converts the rotational motion of the steering motor 515 into the linear motion of the rack 511. The conversion mechanism 516 includes, for example, a large pulley 5a, a small pulley 5b, a belt 5c, and a transmission gear 5d. The belt 5c is wound around the large pulley 5a and the small pulley 5b. The transmission gear 5d is connected to the large pulley 5a. The small pulley 5b is connected to the output shaft of the steering motor 515 and rotates under the driving force of the steering motor 515. The rotation of the small pulley 5b is transmitted to the large pulley 5a via the belt 5c. This causes the transmission gear 5d, connected to the large pulley 5a, to rotate. The transmission gear 5d meshes with a gear 51C formed on the rack 511. The conversion mechanism 516 is configured to move the rack 511 in the left-right direction by the rotation of the transmission gear 5d.

[0044] The controller 10 sets the target steering angle based on the input of the steering wheel 521 or the command value in the automatic driving system. The controller 10 controls the steering motor 515 based on the target steering angle and the actual steering angle (the detection result of the steering angle sensor 25) in a way that the difference between the target steering angle and the actual steering angle becomes smaller.

[0045] The pinion shaft 513 is located offset from the center in the vehicle width direction to one end. The steering motor 515 and the conversion mechanism 516 are located offset from the center in the vehicle width direction to the other end. In this embodiment, the pinion shaft 513 is positioned to the right of the center position in the left-right direction of the housing 512, and the steering motor 515 and the conversion mechanism 516 are positioned to the left of the center position in the left-right direction of the housing 512. That is, relative to the center position in the left-right direction of the rack 511, the rack 5B is located on the right and the gear 51C is located on the left. It should be noted that, alternatively, the pinion shaft 513 and the rack 5B can be positioned to the left, and the steering motor 515 and the conversion mechanism 516 can be positioned to the right.

[0046] In this embodiment, when a load is applied to the right front wheel 92, the support point of the rack 511, which exerts a force in the bending direction, becomes the pinion shaft 513 of the rack and pinion mechanism located on the opposite right side. That is, when a load is applied to the right front wheel 92, the portion of the rack 511 corresponding to the pinion shaft 513 is subjected to a load in the bending direction. On the other hand, when a load is applied to the left front wheel 91, the support point of the rack 511, which exerts a force in the bending direction, becomes the conversion mechanism 516 located on the opposite left side. That is, when a load is applied to the left front wheel 91, the portion of the rack 511 corresponding to the conversion mechanism 516 is subjected to a load in the bending direction.

[0047] Regarding rack 5B, the cross-section formed by cutting rack 511 in a plane orthogonal to the axis of rack 511 (hereinafter also referred to as the "orthogonal cross-section") is not circular, but rather... Figure 3 As shown, this is a portion formed by cutting away a part that is originally a circle. In the portion 50b of the rack 511 where the rack 5B is located, the section modulus differs in the circumferential direction. The section modulus is the strength under load in the bending direction. Regarding the direction towards the rack 5B in portion 50b (e.g., refer to...), the section modulus varies. Figure 3 The section modulus of the load (indicated by the dashed arrow) is smaller than that of the load on other parts of the rack 511. That is, the rack 511 is relatively easy to deform under load in that direction. The gear 51C is formed along the entire circumference of the rack 511, and the section modulus in the circumferential direction is almost identical.

[0048] In addition, such as Figure 4As shown, in most cases, the axial direction of the tie rod 514 is inclined relative to the axial direction of the rack rod 511. In this disclosure, this angle of inclination is referred to as the tie rod inclination angle Ra. The tie rod inclination angle Ra varies depending on the vehicle height. Furthermore, when an external force is applied to the tire, this force is transmitted to the rack rod 511 via the tie rod 514. Regarding the force on the rack rod 511, it can be considered that the force transmitted to the rack rod 511 is decomposed into an axial force on the rack rod 511 and a force in the bending direction of the rack rod 511 (see reference). Figure 4 (arrow).

[0049] For example, when the vehicle is moving forward and the right front wheel 92 climbs onto a curb, at the moment of climbing, a rearward and upward force is applied to the rack 511 via the tie rod 514. This force acts in a way that bends the right end of the rack 511 rearward. The force input to the right front wheel 92 will have a relatively large effect on the rack and pinion mechanism located on the opposite right side. The bending direction of the rack 511 refers to any direction orthogonal to the axis of the rack 511. The direction of the load (force) on the rack 511 in the bending direction is affected by the tie rod inclination angle Ra. That is, the magnitude of the tie rod inclination angle Ra affects the orientation of the load applied to the rack 511, i.e., the orientation of the load on the rack 511.

[0050] like Figure 3 As indicated by the dashed arrow, it is believed that when a load is applied to the rack 5B, which has a relatively small section modulus in the rack 511, poor gear meshing, deformation / damage to the rack 511, etc., are likely to occur, making the rack 511 prone to abnormalities. Figure 3 It is believed that when force is applied to rack 511 along the arrow from the upper left to the lower right, abnormalities are more likely to occur.

[0051] The controller 10, by acquiring the relationship between the tie rod inclination angle Ra and the vehicle height, and the relationship between the tie rod inclination angle Ra and the direction of the load, can determine whether a load is applied towards the rack 5B based on the vehicle height information when the tire is subjected to external force. The controller 10 has pre-set relationships between the tie rod inclination angle Ra and the vehicle height, and between the tie rod inclination angle Ra and the direction of the load. The controller 10 can determine the orientation of the load applied to the rack 511 based on the detection results of the vehicle height sensor 23.

[0052] Thus, the steering system 1 of this embodiment includes: a steering actuator 510 having a rack 511, a steering motor 515 that applies driving force to the rack 511, and a conversion mechanism 516 that converts the rotation of the steering motor 515 into axial movement of the rack 511; the steering actuator 510 turns the steering wheels 91 and 92; a steering angle sensor 25 that detects the steering angle of the steering wheels 91 and 92; an acceleration sensor 21 that detects the forward and backward acceleration of the vehicle; a tire pressure sensor 22 that detects the tire pressure of each tire 81 to 84; and a controller 10 having one or more processors 10a configured to acquire steering angle information, forward and backward acceleration information, and tire pressure information. The steering system 1 of this embodiment is a steer-by-wire type system in which the steering actuator 510 and the steering wheel 521, which serves as an operating member, are not mechanically connected.

[0053] (Anomaly Detection and Control)

[0054] The anomaly detection control implemented by controller 10 is described. For example... Figure 5 As shown, the controller 10 is configured to perform input determination processing S101, position determination processing S102, load calculation processing S103, and anomaly determination processing S104 based on information obtained from various sensors, as an anomaly detection control.

[0055] Input determination processing S101 determines the presence or absence of an external force input to the vehicle based on the front-to-rear acceleration. Position determination processing S102, when an external force is input, determines the input tire among the multiple tires 81-84 that received the external force based on the air pressure of each tire 81-84. Load calculation processing S103, when the input tire is the tire of the steering wheel 91 or 92, calculates the vehicle's deceleration or obtains deceleration information, and calculates the load on the input tire due to the external force based on the difference between the front-to-rear acceleration and the deceleration. Anomaly determination processing S104 determines the presence or absence of an anomaly in the rack 511 based on the load, steering angle, and the detection results of the vehicle height sensor 23. It should be noted that in this embodiment, the detection results of the vehicle height sensor 23 are used when it is necessary to determine the orientation of the load, and are not used when this determination is not required.

[0056] Reference Figure 6The abnormality detection control for detecting abnormalities caused by the load on rack 5B is described. Controller 10 receives information about the front-to-back acceleration Gf from acceleration sensor 21 (S201). Controller 10 determines whether the front-to-back acceleration Gf is greater than the acceleration threshold Tg (S202). If the front-to-back acceleration Gf is below the acceleration threshold Tg (S202: No), controller 10 determines that there is no abnormal external force input and returns the abnormality detection control to the initial step (S201). If the front-to-back acceleration Gf is greater than the acceleration threshold Tg (S202: Yes), controller 10 determines that there is an abnormal external force input and confirms the air pressure information of each tire 81-84 (S203).

[0057] The controller 10 determines whether tires 81-84 have a pressure change rate Pa greater than the pressure threshold Ta during the period from when the external force is input until a predetermined period has elapsed (hereinafter referred to as the "determination period") (S204). The change rate Pa is the amount of pressure change per unit time. It should be noted that the amount of pressure change can also be set as the comparison element with the threshold instead of the change rate Pa. If the pressure change rate Pa of all tires 81-84 is below the pressure threshold Ta (S204: No), the controller 10 determines that an abnormal external force has not been applied to tires 81-84 and returns the abnormality detection control to the initial step.

[0058] If tires 81-84 have a pressure change rate Pa greater than the pressure threshold Ta (S204: Yes), the controller 10 determines whether the wheel with the tire that has received an abnormal external force (hereinafter referred to as the "input tire") is the designated steering wheel 92, i.e., the right front wheel 92 in this example (S205). The detection results of each pressure sensor 22 are correlated with the positions of tires 81-84 through ID information, etc. Therefore, the controller 10 can identify which tire's pressure information is being detected by the pressure sensor 22. When a tire climbs onto a curb, etc., the tire will be flattened, the tire volume will decrease, and the pressure will increase. For example, if the pressure of the input tire increases sharply, it is highly likely that an abnormal external force has been applied.

[0059] If the wheel corresponding to the input tire is not the right front wheel 92 (S205: No), the controller 10 determines that there is no effect on the rack 5B and proceeds to process Z. Process Z will be described later. If the wheel corresponding to the input tire is the right front wheel 92 (S205: Yes), the controller 10 confirms the information of each wheel pressure Pw when the external force is input in order to investigate the effect on the rack 5B (S206). The controller 10 calculates the load L applied to the input tire by the external force based on the wheel pressure Pw and the front-rear acceleration Gf (S207). In other words, the controller 10 estimates the assumed load on the input tire through calculation. The load L can also be said to be the input load at the location of the input tire.

[0060] The load L is calculated based on the difference between the acceleration Gf and the deceleration Gd. The deceleration Gd is calculated based on the wheel pressure Pw. For example, the deceleration of a wheel is calculated based on the wheel pressure Pw, the caliper cylinder bore, the friction coefficient of the brake pads, the effective braking radius / tire dynamic load radius, and the estimated road surface friction coefficient. The formula is as follows: Deceleration of a wheel = Wheel pressure × Caliper cylinder bore × Brake pad friction coefficient × (Effective braking radius / tire dynamic load radius) × Estimated road surface friction coefficient.

[0061] The overall vehicle deceleration Gd is calculated by calculating the deceleration of each wheel (91-94). The controller 10 can also obtain the deceleration Gd information from the brake ECU 70a. That is, the controller 10 can also receive the deceleration Gd information calculated by the brake ECU 70a.

[0062] The load L is calculated based on the front-to-rear acceleration Gf, deceleration Gd, and the assumed vehicle weight W. For example, the load L can be calculated by multiplying the difference between the front-to-rear acceleration Gf and the deceleration Gd by the assumed vehicle weight W. The formula is L = (Gf - Gd) × W. The assumed vehicle weight W is the weight of the vehicle and is set based on an initial setting value (e.g., vehicle weight only) stored in the controller 10. The controller 10 may, for example, set the assumed vehicle weight W as an initial setting value plus the weight of the passengers and / or the weight of the cargo. It should be noted that the controller 10 may also set the initial setting value as the assumed vehicle weight W.

[0063] The controller 10 determines the number and / or weight of occupants based on the detection results of the seat sensors 27 installed in each seat, and adds the occupant weight to the initial set value according to the detection results of each seat sensor 27. This allows for the calculation of the load L based on a weight more closely approximating the actual situation, thereby improving the accuracy of the load L calculation and consequently improving the accuracy of anomaly detection. Furthermore, the controller 10 can also add the weight of the cargo obtained through the function of the cargo weight detection unit or through user settings to the assumed vehicle weight W. The seat sensors 27 are, for example, load sensors that detect changes in load or capacitive sensors that detect changes in electrostatic capacitance.

[0064] The controller 10 determines whether the calculated load L is greater than the load threshold Tl (S208). If the load L is below the load threshold Tl (S208: No), the controller 10 determines that an abnormal load has not been applied to the input tire and returns the abnormality detection control to the initial step. If the load L is greater than the load threshold Tl (S208: Yes), the controller 10 confirms the vehicle height information during the determination period (S209).

[0065] Controller 10 determines whether the vehicle height stroke Ch exceeds the vehicle height threshold Th during the determination period (S210). The vehicle height stroke Ch corresponds to the orientation of the load. Based on knowledge obtained through simulation, experimentation, etc., in this embodiment, it can be determined that the orientation of the load is not towards the rack 5B when the vehicle height stroke Ch is small. It should be noted that the relationship between the vehicle height stroke Ch or vehicle height Hv and the orientation of the load towards the rack 511 varies depending on the vehicle configuration.

[0066] If, during the judgment period, the vehicle height travel Ch is below the vehicle height threshold Th (S210: No), the controller 10 determines that the load orientation is not the orientation corresponding to the rack 5B and returns the anomaly detection control to the initial step. In step S210, the controller 10 can also be configured to compare the maximum value of the vehicle height travel Ch during the judgment period with the vehicle height threshold Th. The controller 10 can calculate the current vehicle height Hv based on the initial set vehicle height and vehicle height travel Ch. That is, the vehicle height travel Ch can be converted into vehicle height Hv.

[0067] If the vehicle height travel Ch exceeds the vehicle height threshold Th during the determination period (S210: Yes), the controller 10 confirms the steering angle Sa of the steering wheels 91 and 92 during the determination period (S211). The steering angle Sa corresponds to the extension amount of the rack 511; the larger the steering angle Sa, the greater the extension amount of the rack 511 to one side. The extension amount of the rack 511 is the amount of movement of the rack 511 from the neutral position to one side axially. In other words, when the rack 511 moves to the left, the extension amount of the rack 511 is the amount of movement of the left end of the rack 511 from the neutral position to the left; when the rack 511 moves to the right, the extension amount of the rack 511 is the amount of movement of the right end of the rack 511 from the neutral position to the right. The neutral position of the rack 511 is the position where the vehicle is traveling straight.

[0068] When the vehicle turns, the rack 511 protrudes on one side (left or right) and retracts on the other side. When the tire on the side of the rack 511 that protrudes is the input tire, the greater the extension of the rack 511, the greater the torque length, and the greater the load applied to the rack 511 in the bending direction. Therefore, the controller 10 determines whether the steering angle Sa during the determination period is greater than the steering angle threshold Ts (S212). The steering angle Sa may change during the period when an external force is input, but the controller 10 confirms the steering angle Sa during the determination period, and this change also becomes a determination.

[0069] If the steering angle Sa is below the steering angle threshold Ts during the judgment period (S212: No), the controller 10 determines that the external force has little effect on the rack 511 and returns the anomaly detection control to the initial step. If the steering angle Sa exceeds the steering angle threshold Ts during the judgment period (S212: Yes), the controller 10 determines the presence or absence of an anomaly in the rack 511 based on the pre-set anomaly judgment mapping M1, the steering angle Sa, and the vehicle height information (S213). The vehicle height information is the vehicle height travel Ch of the wheel corresponding to the input tire, i.e., the right front wheel 92, or the vehicle height Hv based on the vehicle height travel Ch.

[0070] like Figure 7 As shown, the anomaly determination mapping M1 in this example is a mapping where the horizontal axis is set to the steering angle and the vertical axis is set to the vehicle height. Regarding the horizontal axis, the more the steering angle value moves to the right (+) from the origin O, the greater the extension of the rack 511 to the right; conversely, the more the steering angle value moves to the left (-) from the origin O, the greater the extension of the rack 511 to the left. The controller 10 can determine the protrusion direction of the rack 511 based on the detection results of the steering angle sensor 25. The anomaly determination mapping M1 is set to determine the presence or absence of anomalies in the rack 5B; therefore, the situation where the rack 511 protrudes to the right from the neutral position becomes the object of anomaly determination.

[0071] Regarding the longitudinal axis, the lower the vehicle height Hv value is from the origin O (-), the greater the vehicle's sinking, i.e., the bounce; conversely, the higher the vehicle height Hv value is from the origin O (+), the greater the vehicle's rising, i.e., the rebound. For example, when a tire climbs onto a curb, the input tire will move up and down, and the vehicle height detected at the wheel corresponding to the input tire will also move up and down. The determination period is set to a period greater than or equal to the assumed period of vertical movement of the vehicle height caused by external forces. In this embodiment, it is assumed that the external force is continuously input for a specified period through a single collision or climbing.

[0072] In the anomaly determination mapping diagram M1, the regions determined as abnormal by the controller 10 are set in the first quadrant and the fourth quadrant. A first region A1 is set in the first quadrant, and a second region A2 is set in the fourth quadrant. If the horizontal axis is set to X and the vertical axis to Y, then in each region A1 and A2, the following limits are set: lower limit of extension amount ≤ X ≤ upper limit of extension amount, and lower limit of vehicle height ≤ Y ≤ upper limit of vehicle height. It should be noted that the upper limit of extension amount and upper limit of vehicle height can also be omitted. The range of steering angles corresponding to each region A1 and A2 corresponds to a first specified range, and the range of vehicle height Hv or vehicle height travel Ch corresponding to each region A1 and A2 corresponds to a second specified range. That is, in the load calculation processing S103, if the load L is greater than the load threshold, and the steering angle Sa is within the first specified range and the vehicle height travel Ch or vehicle height Hv is within the second specified range during the determination period, the controller 10 determines that there is an anomaly in the rack 511. It should be noted that the XY coordinates used in the determination can be either (Sa, Hv) or (Sa, Ch).

[0073] The controller 10 determines whether the coordinates (Sa, Hv) are within the first region A1 or the second region A2 during the determination period (S213). If the coordinates (Sa, Hv) are within the first region A1 or the second region A2 (S213: Yes), the controller 10 determines that there is an abnormality in the rack 511, sets an abnormality flag, and performs abnormality handling (S214).

[0074] The handling of abnormal situations includes illuminating a warning light, displaying a warning on the monitor, or issuing an audible warning, which is a process to inform the driver that there is an abnormality in the rack 511. On the other hand, if the coordinates (Sa, Hv) do not fall within the first region A1 or the second region A2 (S213: No), the controller 10 determines that there is no abnormality in the rack 511 and returns the abnormality detection control to the initial step.

[0075] It should be noted that the order of comparisons between various information and thresholds can be appropriately changed; for example, the order of steps S210 and S212 can be swapped. Furthermore, the controller 10 can omit the comparison between the steering angle Sa and the steering angle threshold Ts, and the comparison between the vehicle height travel Ch and the vehicle height threshold Th, and instead perform the comparison between the coordinates (Sa, Hv) and the anomaly determination mapping map M1. That is, in anomaly detection control, steps S210 and S212 can also be omitted. Additionally, the vertical axis of the anomaly determination mapping map M1 can be the vehicle height travel Ch instead of the vehicle height Hv.

[0076] (Regarding the handling of Z)

[0077] As described above, in the anomaly detection control, if the input tire is not the right front wheel 92 (S205: No), the controller 10 executes process Z. Figure 8 As shown, in process Z, the controller 10 determines whether the input tire is the left front wheel 91 (S301). If the input tire is not the left front wheel 91 (S301: No), the controller 10 determines that there is no external force affecting the rack 511 and returns the abnormality detection control to the initial step (S201).

[0078] When the input tire is the left front wheel 91 (S301: Yes), similar to steps S206 and S207, the controller 10 calculates the load L based on the front and rear acceleration Gf, deceleration Gd, and the assumed vehicle weight W (S302). The controller 10 determines whether the load L is greater than the load threshold Tl2 (S303). If the load L is below the load threshold Tl2 (S303: No), the controller 10 determines that the load is not applied to the input tire to an abnormal degree and returns the abnormality detection control to the initial step.

[0079] If the load L is greater than the load threshold Tl2 (S303: Yes), the steering angle Sa during the judgment period is checked (S304). The controller 10 determines whether the steering angle Sa during the judgment period is greater than the steering angle threshold Ts2 (S305). If the steering angle Sa is less than the steering angle threshold Ts2 (S305: No), it is determined that the impact on the part of the rack 511 on the conversion mechanism 516 side is small, and the abnormality detection control returns to the initial step. The input of external force to the left front wheel 91 will affect the part corresponding to the conversion mechanism 516, which is the support point on the left side of the rack 511. It should be noted that, as described above, the input of external force to the right front wheel 92 will affect the part 50b corresponding to the pinion shaft 513, which is the support point on the right side of the rack 511.

[0080] If the steering angle Sa is greater than the steering angle threshold Ts2 (S305: Yes), the controller 10 determines that the load in the bending direction corresponding to the support point of the rack 511, i.e., the part of the conversion mechanism 516, is large, indicating an abnormality in the rack 511. Then, similar to step S214, the controller 10 sets an abnormality flag and performs abnormality handling (S306). It should be noted that, for example, it could also be, as... Figure 9 As shown, the controller 10 stores an anomaly determination mapping M2, which is set as an anomaly determination region, specifically a third region A3. Regarding the portion of the rack 511 corresponding to the conversion mechanism 516, unlike the rack 5B, the section modulus of the rack 511 is approximately the same throughout its entire circumference. Therefore, the controller 10 can determine the presence or absence of an anomaly based on the magnitude of the load L and the steering angle Sa, regardless of the vehicle height stroke Ch or vehicle height Hv.

[0081] (Effects of this implementation method)

[0082] According to this embodiment, when an external force is input to tires 81-84 due to climbing over a curb or similar obstacle, the input tire is determined and the load on the input tire is calculated. The load applied to the rack 511 in the bending direction is affected by the load L in the longitudinal direction and the steering angle Sa. The larger the load L in the longitudinal direction, the larger the load applied to the rack 511 in the bending direction. Furthermore, the larger the extension of the rack 511 relative to the input tire, the larger the torque length, and the larger the load applied to the rack 511 in the bending direction. The extension of the rack 511 corresponds to the steering angle Sa. The controller 10 determines the presence or absence of an abnormality in the rack 511 based on the load L and the steering angle Sa. Thus, according to this embodiment, an abnormality in the rack 511 caused by the load in the bending direction can be detected. In particular, the steering system 1 of this embodiment is a steer-by-wire type steering system, so it is difficult for the driver to sense an abnormality in the rack 511. However, according to this embodiment, an abnormality in the rack 511 can be detected.

[0083] In this embodiment, the controller 10 also determines the presence or absence of an abnormality in the rack 511 based on vehicle height information. In this embodiment, the rack 511, which has a rack 5B meshing with a pinion 5A, is used as the steering shaft. The controller 10 is configured to acquire vehicle height information. The controller 10 is configured to determine the presence or absence of an abnormality in the rack 511 based on load L, steering angle Sa, and vehicle height travel Ch in the abnormality determination process S104.

[0084] The effect of loads on rack 511 in the bending direction varies depending on the tie rod inclination angle Ra and the extension of rack 511. The size of the tie rod inclination angle Ra affects the orientation of the load applied to rack 511, and the extension of rack 511 is equivalent to the moment length, thus affecting the magnitude of the load applied to rack 511. Furthermore, since rack 5B is formed on rack 511, the strength, i.e., the section modulus, for loads in the bending direction varies circumferentially on rack 511.

[0085] The vehicle height stroke Ch corresponds to the tie rod inclination angle Ra, which in turn corresponds to the orientation of the load. Furthermore, the steering angle Sa corresponds to the extension amount of the rack 511. Therefore, the orientation and magnitude of the load applied to the rack 511 can be calculated based on the vehicle height stroke Ch (or vehicle height Hv) when an external force is applied and the steering angle Sa. Therefore, according to this embodiment, for abnormalities in the rack 511 caused by a load applied in the bending direction, high-precision detection considering the section modulus of the rack 5B is possible. According to this embodiment, by estimating the orientation of the load and determining whether a load has been applied towards the rack 5B, the presence or absence of an abnormality in the rack 511 can be determined with higher precision.

[0086] Furthermore, in the load calculation process S103, the weight of the occupant is taken into account and the assumed vehicle weight W is set using the detection results of the seat sensor 27. The steering system 1 includes seat sensors 27 disposed in one or more seats to detect the presence or absence of an occupant. In the load calculation process S103, the controller 10 calculates the load L based on the forward and backward acceleration Gf, deceleration Gd, and the assumed vehicle weight W. The controller 10 sets the assumed vehicle weight W to a value that includes the weight of the occupant based on the detection results of the seat sensor 27. Thus, the load L corresponding to the riding state can be calculated.

[0087] (other)

[0088] This invention is not limited to the embodiments described above. For example, this invention can be applied not only to steering systems with steer-by-wire capability, but also to systems such as power steering systems where the steering actuator 510 and the operating device 52 are mechanically connected. This invention can also be applied to, for example, a steering system 1 where the steering wheel 521 and the pinion shaft 513 are mechanically connected. In this case, for example, a pinion auxiliary motor is connected to the pinion shaft 513. In this case, the pinion auxiliary motor is equivalent to a "steering motor," and the pinion shaft 513 is equivalent to a "conversion mechanism."

[0089] Furthermore, the steering shaft can be not only a rack and pinion 511, but also a ball nut type shaft member. In this case, the conversion mechanism becomes a ball nut mechanism. Additionally, one or more electric motors that impart driving force to the steering shaft can be, for example, any one or more of a rack-and-pinion auxiliary motor, a pinion auxiliary motor, and a column auxiliary motor. The conversion mechanism is configured to correspond to the steering motor, and as a result, it is a mechanism that transmits the driving force of the steering motor to the steering shaft. Furthermore, this invention can also be applied to autonomous vehicles.

[0090] Furthermore, the steering actuator 510 can also be a so-called double-pinion-assisted type device, in which the rack rod 511 is moved by two rack and pinion mechanisms. That is, it can also be that two pinion shafts 513 are arranged on the left and right sides for the rack rod 511, and each pinion shaft 513 is equipped with a pinion auxiliary motor to rotate the pinion shaft 513. In other words, the steering actuator 510 has two separate rack and pinion mechanisms (conversion mechanisms) and two pinion auxiliary motors (steering motors). In this case, even if the input tire corresponds to either the right front wheel 92 or the left front wheel 91, the support point will be one of the pinion shafts 513, which may apply a load towards the rack 5B. In this case, for example, as... Figure 11 As shown, the controller 10 can also determine the presence or absence of an anomaly based on the anomaly determination mapping map M3, which also has anomaly determination areas A4 and A5 set in the second and third quadrants.

[0091] Furthermore, when the external force input to the left steering shaft affects the configuration of the support point relative to the right, such as... Figure 11 As shown, it is also possible to set an anomaly detection area not only in the first and fourth quadrants, but also in the second and third quadrants. Similarly, if the external force input to the right steering shaft affects the configuration of the support point relative to the left, it is also possible to set an anomaly detection area not only in the second and third quadrants, but also in the first and fourth quadrants.

[0092] Alternatively, the anomaly determination maps M1 and M2 can be set according to each load L, for example, according to multiple ranks related to load L within a specified range. For example, in controller 10, the range of the first load rank can be set as load threshold < load L ≤ L1, the second load rank as L1 < L ≤ L2, and the third load rank as L2 < L. In this case, controller 10 can store anomaly determination maps for load L within the first load rank range, load L within the second load rank range, and load L within the third load rank range. Accordingly, for example, it can be set so that even if the extension of the steering shaft (e.g., rack 511) is small, an anomaly in the steering shaft can be determined even if the load L is abnormally large. That is, anomaly determination corresponding to load L can be performed.

[0093] Alternatively, multiple anomaly determination maps can be set in a manner corresponding to the size of the cross-sectional coefficient of the steering shaft. For example, the controller 10 may also store anomaly determination maps for cases where a load is applied towards a portion with a relatively small cross-sectional coefficient and for cases where a load is applied towards a portion with a relatively large cross-sectional coefficient. The anomaly determination map can also be set according to the orientation of the load. In this case, the controller 10 determines the orientation of the load based on the vehicle height information, selects an anomaly determination map according to the orientation of the load, and determines whether an anomaly exists. Furthermore, in this disclosure, "load" can be replaced with "force".

[0094] It should be noted that the steering system 1 of this disclosure can be described in another way as follows. That is, as... Figure 10As shown, the steering system 1 includes: an input determination unit 111, which determines whether an external force is input to the vehicle based on information about the front-rear acceleration Gf; a position determination unit 112, which, when an external force is input, determines the input tire among the multiple tires 81-84 as the tire into which the external force is input based on information about the tire pressure of each tire; a load calculation unit 113, which, when the input tire is the tire of the steering wheel 91 or 92, calculates the vehicle deceleration Gd or obtains information about the deceleration Gd, and calculates the load L experienced by the input tire by the external force based on the difference between the front-rear acceleration Gf and the deceleration Gd; and an anomaly determination unit 114, which determines whether there is an anomaly in the steering shaft of the steering device 51 based on the load L and the steering angle Sa. The anomaly determination unit 114 determines whether there is an anomaly in the rack rod 511 based on the load L, the steering angle Sa, and the vehicle height travel Ch. If the load L is greater than the load threshold Tl, and the steering angle Sa is within a first predetermined range and the vehicle height travel Ch or vehicle height Hv is within a second predetermined range during the period from when the external force is input until a predetermined period has elapsed (i.e., the judgment period), the anomaly determination unit 114 determines that there is an anomaly in the rack 511. The load calculation unit 113 calculates the load L based on the front and rear acceleration Gf, deceleration Gd, and assumed vehicle weight W, and sets the assumed vehicle weight W to a value that includes the weight of the passenger based on the detection result of the seat sensor 27. Among the multiple tires 81 to 84, it can also be determined that two or more tires are input tires.

[0095] Furthermore, the technology disclosed herein can also be described as follows. The controller 10 of this disclosure includes one or more processors 10a, the controller 10 being configured to acquire information about the vehicle's longitudinal acceleration Gf (as acceleration in the longitudinal direction), information about the tire pressure of each tire of the vehicle, information about the deceleration Gd generated by the vehicle's braking, and information about the steering angle Sa of the vehicle's steering wheels 91 and 92. As described above, the controller 10 is configured to execute input determination processing S101, position determination processing S102, load calculation processing S103, and anomaly determination processing S104.

Claims

1. A steering system, comprising: A steering actuator has a steering shaft, a steering motor that applies driving force to the steering shaft, and a conversion mechanism that converts the rotation of the steering motor into axial movement of the steering shaft, the steering actuator turning a steering wheel. A steering angle sensor detects the steering angle of the steering wheel; An accelerometer sensor detects the vehicle's forward and backward acceleration. The tire pressure sensor detects the tire pressure of each tire; as well as A controller having one or more processors is configured to acquire information about the steering angle, the forward and backward acceleration, and the air pressure. The controller is configured to perform: Input determination processing determines the presence or absence of external force input to the vehicle based on the forward and backward acceleration; The position determination process, in the case of the input of the external force, determines the input tire among the plurality of tires as the tire into which the external force was input, based on the air pressure of each of the tires; The load calculation process calculates the deceleration of the vehicle or obtains information about the deceleration when the input tire is the tire of the steering wheel, and calculates the load on the input tire caused by the external force based on the difference between the front and rear acceleration and the deceleration. as well as The anomaly detection process determines whether there is an anomaly in the steering shaft based on the load and the steering angle. If the load input to the steering wheel is greater than the load threshold and the steering angle is greater than the steering angle threshold, it is determined that there is an anomaly in the steering shaft caused by the load in the bending direction.

2. The steering system according to claim 1, further comprising: The vehicle height sensor detects the vehicle's height travel or vehicle height. The steering shaft is a rack and pinion with a rack that meshes with a pinion. In the anomaly detection process, the controller determines whether there is an anomaly in the rack and pinion based on the load, the steering angle, and the detection results of the vehicle height sensor.

3. The steering system according to claim 2, wherein, In the anomaly detection process, if the load is greater than the load threshold and the steering angle is within a first specified range and the vehicle height travel or the vehicle height is within a second specified range during the period from when the external force is input until a specified period has elapsed, the controller determines that there is an anomaly in the rack.

4. The steering system according to any one of claims 1 to 3, comprising: Seat sensors, installed in one or more seats, detect the presence or absence of occupants. In the load calculation process, the controller calculates the load based on the forward and backward acceleration, the deceleration, and the assumed vehicle weight. The controller sets the assumed vehicle weight to a value that includes the weight of the occupants, based on the detection results from the seat sensors.

5. The steering system according to any one of claims 1 to 3, wherein, The steering system is a steer-by-wire system in which the rudder actuator and the operating components are not mechanically connected.

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