Steering device, steering control device, abnormality detection method for steering device, and program

Abstract

A steering device (700) has: a movable member (26); a housing (50); a motor (5); a rotation-linear motion conversion mechanism (70); elastic bodies (80, 80) for elastically supporting the rotation-linear motion conversion mechanism against the housing; and a control device (500) for outputting, to the motor, a first control signal (SG20) for moving the rotation-linear motion conversion mechanism relative to the movable member beyond the amount of displacement of the elastic support by the elastic body when a triggering condition or the like is met, acquiring a physical quantity relating to the movement amount of the movable member from the first control signal, determining the presence or absence of an abnormality on the basis of the physical quantity relating to the movement amount of the movable member, and outputting an abnormality determination signal when it is determined that there is an abnormality.

Description

Steering device, steering control device, method for detecting abnormality in steering device, and program

[0001] The present invention relates to a steering device, a steering control device, a method for detecting an abnormality in a steering device, a program, and the like.

[0002] Patent Document 1 discloses a steering device equipped with an abnormality diagnosis function that detects failures and abnormalities and diagnoses the presence or absence of an abnormality. Claim 1 of the document states, "The steering actuator drive command signal includes a steering drive command signal and a test drive command signal for abnormality detection. The test drive command signal is output to the steering actuator to steer the steered wheels. The abnormality diagnosis unit determines the presence or absence of an abnormality in the steering device based on a signal related to the operation of the steering actuator in response to the test drive command signal." Claim 7 of the document also states, "The controller includes a steering angle detection unit, and the steering angle detection unit detects the steering angle of the steered wheels based on a signal related to the operation of the steering actuator in response to the test drive command signal." Claim 9 of the document also states, "In the steering device described in claim 7, the test drive command signal moves the steered wheels to the stroke ends on both the left and right sides of the steered wheels." Paragraph

[0175] of the document also states, "An abnormality diagnosis is possible by detecting phenomena specific to abnormal conditions, such as a decrease in the motor rotation speed or periodic fluctuations in the motor rotation speed." Furthermore, in the abnormality diagnosis of the document, when detecting a failure or abnormality, the steered wheels need to be moved considerably, so if there is an obstacle such as a curb around the steered wheels, the movement of the steered wheels is hindered and accurate abnormality detection is not possible. As a countermeasure to this, as described in paragraphs

[0108] and

[0109] of the document or in step S22 of Figure 8, as a prerequisite for abnormality detection, first, an image of the area around the steered wheels is taken with an imaging camera or the like to check that there are no obstacles.

[0003] 2 of Patent Document 2, for example, paragraph

[0007] and Figure 2 show a steering device including a steered shaft that is movable in the axial direction, a ball screw that transmits driving force generated by an electric motor to the steered shaft, a bearing that rotatably supports a nut of the ball screw in a housing, and an elastic body that supports the bearing in the axial direction of the steered shaft. Paragraph

[0042] of the same document states that "the elastic body deforms in the axial direction of the steered shaft," and paragraph

[0003] of the same document states that "the elastic body has the effect of reducing vibrations and operating noise caused by axial displacement of the bearing, or the effect of damping impact loads acting on the bearing in the axial direction."

[0004] For example, paragraph

[0004] of Patent Document 3 states, "In a steering device, when a load is applied to the rack bar, the transmission part of the reducer that reduces the output rotation of the steering motor elastically deforms, and a deviation occurs between the position of the steering member and the rotational position of the steering motor by the amount of this elastic deformation, which may result in a control error of the steering angle." Furthermore, as a countermeasure, for example, paragraph

[0022] of the same document states, "In order to prevent a decrease in the control accuracy of the steering angle due to elastic deformation of the transmission part of the reducer, etc."

[0005] JP 2020-37315 A International Publication No. 2020 / 170417 JP 2023-38726 A

[0006] In Patent Document 1, a steering actuator is operated by a test drive command signal, and the steering angle of the steering wheels is detected to detect a failure or abnormality in the steering actuator. Furthermore, when detecting a failure or abnormality, the steering wheels are moved to the stroke ends on both the left and right sides of the steering wheels. In this case, the travel distance of the steering shaft, i.e., the stroke amount, becomes longer, and the time required to detect the steering angle becomes longer.

[0007] Furthermore, as described in Patent Documents 2 and 3, it is known that a steering device has an elastic body that displaces in the axial direction of the steered shaft, or that a transmission unit of a reducer or the like elastically deforms. However, as described in Patent Document 3, elastic deformation of a transmission unit of a reducer or the like is recognized as one cause of steering angle control errors. In other words, the elastic deformation is recognized as a factor that adversely affects the steering angle control accuracy. Therefore, Patent Document 3 implements a process to compensate for the decrease in control accuracy by a compensation calculation of a computer. In other words, conventionally, elastic deformation of a transmission unit of a reducer or the like has not contributed at all to detecting an abnormality in a steering device.

[0008] An object of the present invention is to shorten the stroke amount and time of a movable member such as a steering shaft, which is required to detect an abnormality in which the normal movement of the movable member is restricted by, for example, rust or ice.

[0009] As a result of extensive research, the inventors have discovered that while a driving force for detecting an abnormality is being applied to a movable member such as a steering shaft, the stroke amount of a temporary, reversible minute displacement caused by an elastic body or the like differs between when an abnormality is present and when no abnormality is present, and that therefore it is possible to determine the presence or absence of an abnormality based on that minute displacement. The present invention was completed based on these findings.

[0010] The present disclosure will be described below.

[0011] According to one aspect of the present disclosure, a steering device (700) attached to a vehicle (10) for steering steered wheels (31, 31) of the vehicle includes a movable member (26) connected to the steered wheels to steer the steered wheels, a housing (50) that covers at least a portion of the movable member and is fixed to the body of the vehicle, a motor (5) that applies a steering force to the movable member, a rotary-to-linear motion conversion mechanism (70) that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits it to the movable member, and a rotary-to-linear motion conversion mechanism that is provided between the rotary-to-linear motion conversion mechanism and the housing and is configured to rotate relative to the housing. A steering device is provided which has elastic bodies (80, 80) that elastically support a rotary-to-linear motion conversion mechanism, and a control device (500) that outputs to a motor a first control signal (SG20) that moves the rotary-to-linear motion conversion mechanism relative to a movable member beyond the amount of displacement elastically supported by the elastic body in response to the establishment of a condition that triggers operation confirmation or a predetermined condition, acquires a physical quantity related to the amount of movement of the movable member due to the first control signal, determines whether or not there is an abnormality based on the physical quantity related to the amount of movement of the movable member, and outputs an abnormality determination signal (SG35) when an abnormality is determined.

[0012] According to another aspect of the present disclosure, there is provided a steering control device (500) for controlling the operation of a steering device (700) that steers steered wheels of a vehicle, the steering control device (500) including: a movable member (26) that is attached to a vehicle (10) and connected to steered wheels (31, 31) to steer the steered wheels; a housing (50) that covers at least a portion of the movable member and is fixed to the body of the vehicle; a motor (5) that applies a steering force to the movable member; a rotary-to-linear motion conversion mechanism (70) that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits the linear motion to the movable member; elastic bodies (80, 80) that are provided between the rotary-to-linear motion conversion mechanism and the housing and elastically support the rotary-to-linear motion conversion mechanism with respect to the housing; or a driving medium (63) and elastic bodies (80, 80) that are expected to deform and that are included in a transmission mechanism (44) that is provided between the motor and the rotary-to-linear motion conversion mechanism and transmits a driving force generated by the rotation of the motor to the rotary-to-linear motion conversion mechanism, the steering control device (500) controlling the operation of a steering device (700) that steers steered wheels of a vehicle, the steering control device (500) including: a movable member (26) that is attached to a vehicle (10) and connected to steered wheels (31, 31) to steer the steered wheels; a housing (50) that covers at least a portion of the movable member and is fixed to the body of the vehicle; a motor (5) that applies a steering force to the movable member; a rotary-to-linear motion conversion mechanism (70) that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits the linear motion to the movable member; a first process for generating an abnormality detection driving force for abnormality detection that can cause temporary and reversible deformation in the elastic body, or in each of the driving medium and elastic body that are expected to deform, but cannot move the movable member against the frictional force acting on the movable member, and applying the abnormality detection driving force to the movable member; and a second process for measuring a minute displacement of the movable member that corresponds to the deformation of the elastic body during the period that the abnormality detection driving force is applied to the movable member, or the total deformation of the driving medium and elastic body that are expected to deform, to obtain an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that there is an abnormality if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when there is no abnormality.

[0013] According to yet another aspect of the present disclosure, there is provided an abnormality detection device for a steering device (700) for turning the steered wheels of a vehicle, the abnormality detection device including: a movable member (26) attached to a vehicle (10) and connected to the steered wheels (31, 31) to turn the steered wheels; a housing (50) covering at least a portion of the movable member and fixed to the body of the vehicle; a motor (5) for applying a turning force to the movable member; a rotary-to-linear motion conversion mechanism (70) provided within the housing for converting rotational motion transmitted from the motor into linear motion and transmitting the linear motion to the movable member; and elastic bodies (80, 80) provided between the rotary-to-linear motion conversion mechanism and the housing for elastically supporting the rotary-to-linear motion conversion mechanism with respect to the housing, or a driving medium (63) and elastic bodies (80, 80) which may be deformed and which are included in a transmission mechanism (44) provided between the motor and the rotary-to-linear motion conversion mechanism for transmitting driving force due to rotation of the motor to the rotary-to-linear motion conversion mechanism. a first step of providing an abnormality detection drive command to a motor, thereby generating an abnormality detection drive force that cannot move the movable member against the frictional force acting on the movable member but that can cause temporary, reversible deformation in the elastic body, or in the drive medium and elastic body that are expected to deform, and applying the abnormality detection drive force to the movable member; and a second step of measuring a minute displacement of the movable member that corresponds to the deformation of the elastic body or the total deformation of the drive medium and elastic body that are expected to deform, which occurs temporarily while the abnormality detection drive force is being applied to the movable member, to obtain an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that there is an abnormality if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when there is no abnormality.

[0014] According to yet another aspect of the present disclosure, there is provided a program for causing a computer to operate as the above-described steering control device of the present invention.

[0015] According to the present invention, it is possible to detect an abnormality based on the extremely small displacement caused by the deformation of an elastic body, without moving the movable member constituting the steering shaft or the like from a normal mechanical viewpoint. By using an abnormality detection method that is fundamentally different from conventional methods, it is possible to significantly reduce the stroke amount of the movable member required for abnormality detection and the time required for abnormality detection compared to conventional methods.

[0016] Furthermore, according to the present invention, it is possible to provide a steering control device that is capable of quickly detecting an abnormality in the steering device based on minute displacements.

[0017] Furthermore, according to the present invention, it is possible to provide a method for detecting an abnormality in a steering device that is capable of quickly detecting an abnormality in the steering device based on minute displacements.

[0018] Furthermore, according to the present invention, it is possible to provide a program that enables a steering control device to be easily constructed using a computer.

[0019] 1 is a diagram showing an example of the overall configuration of a steering system according to an embodiment of the present invention. FIG. 2 is a diagram showing another example of the configuration of the steering control device in FIG. 1. FIG. 3 is a cross-sectional view of an example of a rotary-to-linear conversion mechanism using a ball screw. FIG. 4 is a characteristic diagram showing the relationship between the compression load and the compression amount of an elastic body. FIG. 5 is a cross-sectional view of an example of a transmission mechanism using a worm and a worm wheel, which is provided with an elastically deformable member. FIG. 6 is a characteristic diagram showing an example of the displacement of the motor rotation angle with respect to time in a normal case in self-diagnosis processing. FIG. 7 is a characteristic diagram showing an example of the displacement of the motor rotation angle with respect to time in a normal case in self-diagnosis processing. FIG. 8 is a characteristic diagram showing an example of the displacement of the motor rotation angle with respect to time in a normal case in self-diagnosis processing. FIG. 9 is a diagram showing the motor rotation angle and the time required for abnormality detection in the self-diagnosis processing of an embodiment of the present invention, compared with a conventional example. FIG. 10 is a diagram showing an example of a determination processing when an obstacle such as a curb is present near the steered wheels, but the self-diagnosis processing determines that the system is normal. FIG. 11 is a diagram showing an example of a determination processing when an obstacle such as a curb is present in contact with the steered wheels, and the self-diagnosis processing determines that an obstacle such as a curb is present. FIG. 12 is a flowchart showing an example of the overall processing procedure of self-diagnosis processing. FIG. 13 is a flowchart showing an example of the processing procedure of the processing for determining whether or not to perform the self-diagnosis processing.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. The embodiments shown in the accompanying drawings are merely examples of the present invention, and the present invention is not limited to these embodiments.

[0021] <First Embodiment> Please refer to Fig. 1. Fig. 1 is a diagram showing an example of the overall configuration of a steering system according to an embodiment of the present invention. A steering system 200 mounted on a vehicle 10 has a steering operation input device 300 and a steering device 700. The steering device 700 has a steering control device 500 and a steering device 800. In this specification, the steering control device may be simply referred to as a "control device."

[0022] The steering system 200 shown in FIG. 1 is a so-called steer-by-wire steering system in which the steering wheel 301 and the steered wheels 31, 31 are mechanically separated and the steering angle of the steered wheels 31, 31 can be independently controlled in response to the operation angle of the steering wheel 301.

[0023] The steering operation input device 300 has a steering wheel 301, a steering shaft 302, an operation angle sensor 303 that detects the operation angle of the steering wheel 301, an operation torque sensor 304 that detects the operation torque of the steering wheel 301, and a reaction motor 305 that is a reaction actuator that applies a reaction torque to the steering wheel 301.

[0024] The steering control device 500 may be configured with, for example, one or more microprocessors. The steering control device 500 has a control unit 501. The control unit 501 has a motor control unit 403 and an abnormality detection unit 409. The motor control unit 403 has a self-diagnosis feasibility determination unit 405 and an abnormality detection drive command issuance unit 407. The abnormality detection unit 409 has an abnormality determination unit 411.

[0025] The control unit 501 receives various information required for electronic control of the steering device from various sensors 600 that detect the operating state and driving state of the vehicle 10 and an ECU (Electronic Control Unit) 601 .

[0026] The ECU 601 can operate the notification unit 603 to notify the occupants of the vehicle 10, including the driver, of various types of information.

[0027] The steering device 800 comprises a movable member 26 as a steering shaft that is connected to the steered wheels 31, 31 via knuckle arms 29, 29 and steers the steered wheels 31, 31, a housing 50 that covers at least a portion of the movable member 26 and is fixed to the body of the vehicle 10, a motor 5 that applies a steering force to the movable member 26, a rotary-to-linear motion conversion mechanism 70 that is provided within the housing 50 and converts rotational motion transmitted from the motor 5 via a transmission mechanism 44 such as a reducer into linear motion and transmits it to the movable member 26, and elastic bodies 80, 80 that are provided between the rotary-to-linear motion conversion mechanism 70 and the housing 50 and elastically support the rotary-to-linear motion conversion mechanism 70 relative to the housing 50.

[0028] The motor 5, the transmission mechanism 44, the rotary-to-linear motion conversion mechanism 70, and the elastic bodies 80, 80 constitute a steering actuator. However, a steering actuator not provided with the transmission mechanism 44 may also be envisioned.

[0029] The elastic bodies 80, 80 may be made of, for example, a rubber material or a wave washer.

[0030] The steering device 700 is also provided with a rotation angle sensor 2 that detects the rotation angle of the motor 5 .

[0031] In the example of Figure 1, the transmission mechanism 44 has an input side pulley 61, an output side pulley 62, and a belt 63 as a driving medium that transmits the rotation of the input side pulley 61 to the output side pulley 62 and drives the output side pulley.

[0032] The belt 63 as the driving medium is, for example, an endless belt whose main material is rubber. For example, synthetic rubber or urethane rubber, which has excellent abrasion resistance, oil resistance, heat resistance, and bending resistance, can be used. Note that the belt 63 may also have glass fiber or steel wire embedded inside as a core material.

[0033] The input pulley 61 and the output pulley 62 are rotated synchronously via a belt 63 serving as a driving medium, so that the rotational force of the input pulley 61 can be transmitted to the output pulley 62 .

[0034] Since the belt 63 is mainly made of rubber, slight expansion and contraction during use is expected. In other words, the belt 63 is a driving medium that is expected to be deformed during use.

[0035] In the example of FIG. 1, it is assumed that a ball screw is used as the rotary-to-linear motion conversion mechanism 70.

[0036] The ball screw has a nut 73 and a rolling bearing 74. Hereinafter, the "rolling bearing" may be simply referred to as the "bearing."

[0037] However, the present invention is not limited to this example, and instead of the ball screw, a rack and pinion, for example, may be used as the rotary-linear motion conversion mechanism 70 .

[0038] In a normal state, the movable member 26 as a steering shaft can move linearly to the stroke end in both a first direction DR1 and a second direction DR2 opposite to the first direction.

[0039] For example, if the first direction DR1 corresponds to the left direction as seen by the occupants, including the driver, of the vehicle 10, the "first direction" can be rephrased as the "left direction," and similarly, if the second direction DR2 corresponds to the left direction as seen by the occupants, including the driver, of the vehicle 10, the "second direction" can be rephrased as the "right direction."

[0040] A control unit 501 included in the steering control device 500 performs necessary calculations based on the detection signal SG1 from the steering angle sensor 303, the detection signal SG2 from the operation torque sensor 304, the detection signals from the various sensors 600, and various information supplied from the ECU 601, to generate a control signal SG3 for the reaction motor 305, which controls the reaction torque of the reaction motor 305 using this control signal SG3, and also generates a motor control signal SG19, which controls the driving force of the motor 5, for example, the steering torque, using this motor control signal SG19. These control functions are control functions that are normally provided in the control device 500 of the steer-by-wire steering system 200.

[0041] In the example of FIG. 1, the control unit 501 has, in addition to the normal control function described above, an abnormality detection function for detecting an abnormality in which the normal movement of the movable member 26 is restricted due to rust, icing, or the like.

[0042] 1, there is a movement obstruction Abn such as rust or ice between the nut 73 and the movable member 26. For this reason, the movable member 26 is in an abnormal state where normal movement is obstructed.

[0043] The above-mentioned abnormal state can be detected by the operation of each part of the abnormality detection part 409, which includes the self-diagnosis feasibility determination part 405, the drive command issuing part 407 for abnormality detection, and the abnormality determination part 411, which are provided in the motor control part 403.

[0044] In other words, the steering control device 500 has the function of outputting a first control signal SG20 to the motor 5 in response to the condition that triggers operation confirmation or a predetermined condition being met, which causes the rotary-to-linear motion conversion mechanism 70 to move relative to the movable member 26 beyond the displacement amount of elastic support by the elastic bodies 80, 80, etc., acquiring a physical quantity related to the amount of movement of the movable member 26 due to the first control signal SG20, for example as a detection signal from the rotation angle sensor 2, determining whether or not there is an abnormality based on the physical quantity related to the amount of movement of the movable member 26, and outputting an abnormality determination signal SG35 to, for example, the ECU 601 when an abnormality is determined.

[0045] In the example of Figure 1, the steering device 700 is configured to have, in addition to the elastic bodies 80, 80, components that cause temporary, reversible deformation during the period when a drive command for abnormality detection is given to the motor 5 as a first control signal, a belt 63 as a driving medium that may be subject to deformation, which is provided between the motor 5 and the rotary-to-linear motion conversion mechanism 70 and included in the transmission mechanism 44 that transmits the driving force generated by the rotation of the motor 5 to the rotary-to-linear motion conversion mechanism 70.

[0046] However, it is also conceivable that the transmission mechanism 44 is not provided. In this case, the only components that cause temporary, reversible deformation during the period when the drive command for abnormality detection as the first control signal is given to the motor 5 are the elastic bodies 80, 80.

[0047] In this specification, a configuration having only elastic bodies 80, 80 as components that cause temporary, reversible deformation may be referred to as a "first configuration," and a configuration having, in addition to elastic bodies 80, 80, a driving medium 63 that may be expected to deform and is included in a transmission mechanism 44 that is provided between the motor 5 and the rotary-to-linear motion conversion mechanism 70 and transmits the driving force generated by the rotation of the motor 5 to the rotary-to-linear motion conversion mechanism 70 may be referred to as a "second configuration."

[0048] As explained above, the steering control device 500 includes the motor control unit 403 that controls the motor 5, and the abnormality detection unit 409 that detects an abnormality in which the normal movement of the movable member 26 is restricted.

[0049] The self-diagnosis process for detecting an abnormality is outlined below: First, the self-diagnosis possibility determination unit 405 of the motor control unit 403 determines whether or not self-diagnosis is possible.

[0050] In a preferred embodiment of the present invention, a self-diagnosis is performed in advance before the vehicle 10 is put into a running state, thereby preventing accidents and the like caused by abnormalities from occurring.

[0051] Therefore, the self-diagnosis feasibility determination unit 405 confirms at least one of the following: for example, that the start switch such as the ignition switch is turned off; that the parking brake is turned on; that the vehicle speed of the vehicle 10 is zero; and that the input of steering commands from the occupants, including the driver, to the motor control unit 403 is blocked, and if these confirmations are made, it determines that self-diagnosis is possible.

[0052] Thereafter, the self-diagnosis possibility determination unit 405 turns on a trigger signal required for the self-diagnosis process and a signal indicating a predetermined condition, thereby satisfying the conditions for starting the self-diagnosis.

[0053] Specifically, the self-diagnosis feasibility determination unit 405 inputs a start signal as a trigger signal to the motor control unit 403 when the ignition switch is turned on, for example, or when a self-diagnosis start switch is turned on by a passenger including the driver, and in response to this, inputs a self-diagnosis start signal as a trigger signal to the motor control unit 403.

[0054] Thereafter, the self-diagnosis possibility determination unit 405 issues a self-diagnosis start command SG10 to the abnormality detection drive command issuing unit 407, and also issues a self-diagnosis start notification signal SG11 to the abnormality detection unit 409 to notify the start of self-diagnosis.

[0055] As a result of these determinations, in a preferred embodiment, the motor control unit 403 and the abnormality detection unit 409 perform self-diagnosis processing to determine whether or not there is an abnormality while the vehicle 10 is not running. This makes it possible to determine an abnormality through self-diagnosis in advance before the vehicle 10 is in a running state, and can prevent accidents or breakdowns caused by the movement of movable parts being restricted by rust, ice, etc.

[0056] Furthermore, for example, the motor control unit 403 and the abnormality detection unit 409 perform a self-diagnosis process to determine whether or not there is an abnormality when the vehicle 10 is stopped with a start switch such as an ignition switch turned on, in other words, when the vehicle is in an idle stop state, and there is no steering operation input from the occupants, including the driver of the vehicle 10.

[0057] This makes it possible to determine abnormalities in advance through self-diagnosis, for example, even during an idle stop period while the vehicle 10 is in motion, provided that there is no steering input, and makes it possible to prevent accidents or breakdowns caused by the movement of movable parts being restricted by rust, icing, etc.

[0058] Upon receiving the self-diagnosis start command SG10, the abnormality detection drive command issuing unit 407 gives the motor 5 a drive command SG20 for abnormality detection as a first control signal.

[0059] Upon receiving this drive command SG for abnormality detection, the motor 5 rotates, and as a result, the movable member 26 cannot be moved against the frictional force caused by the sliding resistance, etc., of the movable member 26 as the steering axis, but an abnormality detection drive force is generated that can cause deformation in each of the belt 63 and elastic bodies 80, 80 as the drive medium, which may be deformed in the transmission mechanism 44.

[0060] If the transmission mechanism 44 is not provided, a driving force for detecting an abnormality is generated that may cause deformation in each of the elastic bodies 80, 80.

[0061] Here, the deformation of the elastic bodies 80, 80 that occurs during the period when the driving force for detecting an abnormality is applied to the movable member 26 is preferably the maximum possible elastic deformation of each of the elastic bodies 80, 80. The amount of displacement corresponding to the maximum possible elastic deformation of the elastic bodies 80, 80 can be uniquely determined at the design stage. Therefore, the amount of minute displacement under normal conditions can be uniquely determined in advance.

[0062] Furthermore, the total deformation of the driving medium 63 and the elastic bodies 80, 80 that may temporarily occur while the driving force for abnormality detection is being applied to the movable member 26 is preferably the sum of the maximum possible elastic deformation of the elastic bodies 80, 80 and the expected normal deformation of the driving medium 63 when the driving force for abnormality detection is being applied. The amount of displacement corresponding to the expected normal deformation of the driving medium 63 is uniquely determined at the design stage. Therefore, the amount of minute displacement under normal conditions can be uniquely determined in advance.

[0063] The generated driving force for abnormality detection is transmitted to the movable member 26 via a reduction gear as the transmission mechanism 44 , and the driving force for abnormality detection is applied to the movable member 26 .

[0064] The abnormality detection unit 409 measures, for example, by the rotation angle sensor 2, minute displacements of the movable member 26 along the first direction DR1 or the second direction DR2 corresponding to temporary and reversible deformation of the elastic bodies 80, 80 that occurs during the period in which the driving force for abnormality detection is applied to the movable member 26, or the total deformation of the belt 63 as a driving medium and the elastic bodies 80, 80, whose deformation may be expected, and acquires a physical quantity corresponding to the minute displacement, for example, an actual measurement value of the rotation angle of the motor 5, in other words, a detection value. Data on this actual measurement value is supplied to an abnormality determination unit 411 of the abnormality detection unit 409 as a detection signal SG30 of the rotation angle sensor 2.

[0065] However, the physical amount of the minute displacement may be a detection value obtained by detecting the rotation angle of a pinion 509 that meshes with a rack serving as the movable member 26 using a rotation angle sensor 510. In this case, the detection value of the rotation angle of the pinion 509, in other words, a detection signal SG21, is supplied to the abnormality determination unit 411.

[0066] The physical amount of the minute displacement may be a detected value obtained by detecting the displacement of the rack as the movable member 26 using a non-contact sensor 511 .

[0067] In FIG. 1, an optical displacement sensor can be used as the non-contact sensor 511, in which a marking 513 for detecting positional displacement is provided on a rack as the movable member 26, which is the object, and light is irradiated onto the marking 513 from a light-emitting unit 515 and the reflected light is received by a light-receiving unit 517.

[0068] By utilizing the fact that the light receiving position in the light receiving section 517 moves in accordance with the displacement of the movable member 26, which is the object, it is possible to measure minute displacements of the movable member 26.

[0069] In this case, the detection value of the displacement amount detected by the light receiving unit 517, in other words, the detection signal SG23, is supplied to the abnormality determination unit 411.

[0070] It is also possible to use a combination of two or more of the above measurement methods. That is, the actual measured value of the physical quantity of the minute displacement may be at least one of the detected value of the rotation angle of the motor 5, the detected value of the rotation angle of the pinion 509 that meshes with the rack serving as the movable member 26, and the detected value obtained by detecting the displacement of the rack serving as the movable member 26 with the non-contact sensor 511.

[0071] The abnormality determination unit 411 in the abnormality detection unit 409 determines that an abnormality exists, for example, when the first stroke amount corresponding to the minute displacement indicated by the received actual measurement value is smaller than the second stroke amount corresponding to the normal minute displacement that occurs when there is no abnormality.

[0072] In other words, if the normal movement of the movable member (rack) is restricted by rust, freezing, etc., an abnormality in the stroke amount will occur even with respect to the above-mentioned minute displacement, and the presence or absence of an abnormality can be determined based on that minute displacement.

[0073] In a preferred example, the abnormality determination can be performed by threshold determination. Here, if the "stroke amount corresponding to the minute displacement based on the actual measurement value" is defined as the "first stroke amount" and the "stroke amount of the minute displacement that can be assumed under normal circumstances" is defined as the "second stroke amount," then, for example, a threshold value that satisfies the relationship "first stroke amount < threshold value ≦ second stroke amount" is set, and normality / abnormality can be determined by determination based on the threshold value.

[0074] Here, the threshold value is equal to or less than the second stroke amount, and the upper limit of the maximum range in which the threshold value can be set is determined by the second stroke amount. Considering this, the determination using the above threshold value can be rephrased as a determination that an abnormality exists when the first stroke amount corresponding to the actual measurement value is smaller than the second stroke amount under normal conditions.

[0075] When the abnormality determination unit 411 detects an abnormality, the abnormality detection unit 403 supplies an abnormality determination signal SG35 to, for example, the ECU 601. When the ECU 601 receives the abnormality determination signal SG35, it can, for example, control the notification unit 603 to issue notification information to notify the occupants of the vehicle 10, including the driver, of the abnormality. In addition, in order to reduce danger, it is also possible to temporarily restrict the driving functions by stopping some of the functions related to the driving of the vehicle 10. In this specification, these processes may be referred to as "abnormality countermeasure processes."

[0076] In this way, in the example of Figure 1, the movable member 26 is not moved at the normal mechanical level, but rather attention is paid to the extremely small, reversible displacement that occurs temporarily during the period when the driving force for abnormality detection is generated in the motor 5 in response to the driving command for abnormality detection, and an abnormality is determined based on that small displacement.

[0077] This allows the stroke amount of the movable member 26 required for detecting an abnormality to be reduced to 1 / 100 or less of the conventional amount.

[0078] Furthermore, unlike conventional examples, there is no need to detect phenomena specific to abnormalities, such as a decrease in the motor's rotation speed or periodic fluctuations in the motor's rotation speed. Abnormalities can be determined by simplified threshold judgment, which significantly reduces the burden on the device required for abnormality judgment.

[0079] Furthermore, in the past, the rack was moved to move the steered wheels by a considerable amount, so if there were obstacles such as curbs around the steered wheels, the movement of the wheels would be hindered and accurate abnormality detection would not be possible. Therefore, as a prerequisite for abnormality detection, an image of the area around the steered wheels was first taken with an image capturing camera or the like to check for the absence of obstacles. However, in the present invention, the steered wheels 31, 31 do not substantially move, so there is no need to detect obstacles by taking such images, which also reduces the burden on the device in this respect.

[0080] However, even in the present invention, from a microscopic viewpoint, it is considered that the steered wheels also displace very slightly in response to the minute displacement of the rack, and therefore, if a curb or the like is in close contact with the steered wheels, it cannot be said that this will not have an adverse effect on the measurement of the stroke amount of the minute displacement of the present invention.

[0081] Therefore, in another preferred embodiment of the present invention, countermeasure processing is also implemented when an obstacle such as a curb is present. More specifically, a re-diagnosis is performed to prevent erroneous determinations due to the adverse effects of a curb or the like. This re-diagnosis is handled in software using an algorithm for detecting abnormalities, and does not require imaging using an imaging camera as in the past. This re-diagnosis also reduces the processing load, and it is possible to prevent a decrease in the accuracy of abnormality detection. The details of the re-diagnosis will be described later.

[0082] As described above, according to a preferred embodiment of the present invention, the time required for anomaly detection can be significantly reduced, the burden of anomaly detection processing can be reduced, and the algorithm for anomaly detection can be simplified.

[0083] Next, reference will be made to Fig. 2. Fig. 2 is a diagram showing another example of the configuration of the steering control device in Fig. 1. In Fig. 2, parts common to Fig. 1 are given the same reference numerals.

[0084] The motor control unit 403 shown in FIG. 2 includes the self-diagnosis possibility determination unit 405 and the abnormality detection drive command issuing unit 407 shown in FIG. 1, but for the sake of convenience, these are not shown.

[0085] 2, the motor control unit 403 has a motor history storage unit 406 in addition to a self-diagnosis feasibility determination unit 405 and an abnormality detection drive command issuing unit 407. This motor history storage unit 406 stores and accumulates data indicating the usage history of the motor 5, specifically, accumulated data such as the accumulated value of the number of rotations of the motor 5 or the accumulated value of the usage time of the motor 5, as needed.

[0086] In the example of FIG. 2, the abnormality determination unit 411 in the abnormality detection unit 409 is provided with a threshold setting unit 413 and a threshold determination unit 415 .

[0087] The threshold setting unit 413 is supplied with history data from the motor history storage unit 406. The threshold setting unit 413 is also supplied with data on the ambient temperature detected by a temperature sensor 417 that detects the ambient temperature of the vehicle 10.

[0088] The threshold setting unit 413 can variably control the threshold for determining an abnormality based on at least one of the ambient temperature of the vehicle 10 and the driving history of the vehicle 10 .

[0089] The ambient temperature of the vehicle 10 can be detected based on the ambient temperature data supplied from the temperature sensor 417. The driving history of the vehicle 10 can be detected based on the history data supplied from the motor history accumulation unit 406.

[0090] Generally, as the ambient temperature rises, the belt 63 serving as the driving medium in the transmission mechanism 44 tends to become more stretchable due to the rubber material, etc., and the degree of extension of the minute displacement that occurs when a driving force is applied tends to increase compared to the initial value.

[0091] Furthermore, with continued use, the belt 63 serving as the driving medium in the transmission mechanism 44 will experience wear and deterioration of the rubber material, etc., causing the degree of extension of the minute displacement that occurs when a driving force is applied to differ from the initial value. Generally, as the period of use increases, the amount of extension of the minute displacement of the belt 63 when a driving force is applied tends to increase from the initial value.

[0092] As described above, the threshold setting unit 413 variably controls the threshold for determining an abnormality, in other words, adaptively controls the threshold, based on at least one of the ambient temperature of the vehicle 10 and the driving history of the vehicle 10. Therefore, the threshold for detecting an abnormality can be appropriately fine-tuned according to the ambient temperature and the usage history.

[0093] The threshold determination unit 415 determines whether or not an abnormality exists using an appropriately adjusted threshold, thereby preventing a decrease in the accuracy of abnormality determination.

[0094] 2, the control device 500 has stored in memory 503 a program 505 that causes the computer to operate as either the steering control device of Fig. 1 or Fig. 2. By operating the computer in accordance with the program 505, it is possible to easily construct a steering control device that has an abnormality detection function based on minute displacement.

[0095] Next, reference is made to Fig. 3. Fig. 3 is a cross-sectional view of a rotary-to-linear motion conversion mechanism using a ball screw. In Fig. 3, parts common to Fig. 1 are given the same reference numerals.

[0096] 3, a "ball screw" is used as the rotary-to-linear motion conversion mechanism 70, and the movable member 26 is a "steering shaft" that steers the wheels 31, 31. In the following description, it may be referred to as a "ball screw 70" or as a steering shaft 26.

[0097] The ball screw 70 is a type of rotary-to-linear motion conversion mechanism that converts rotary motion into linear motion. The ball screw 70 is composed of a threaded portion 71 formed on the movable member 26 as a steering shaft, a plurality of balls 72, and a nut 73 connected to the threaded portion 71 via the plurality of balls 72.

[0098] The nut 73 is an annular member that surrounds the steered shaft 26 and is provided rotatably relative to the steered shaft 26. The nut 73 has a spiral groove on its inner periphery, which forms a nut-side ball screw groove. The steered shaft 26 has a spiral groove on its outer periphery, which forms a steered-shaft-side ball screw groove.

[0099] A ball circulation groove is formed by the nut-side ball screw groove and the steered-shaft-side ball screw groove when the nut 73 is inserted into the steered shaft 26. A plurality of metal balls 72 are filled inside the ball circulation groove.

[0100] When the motor 5 rotates, the output pulley 62 rotates via the belt 63 which is the drive medium of the transmission mechanism 44, and the nut 73 rotates accordingly.

[0101] When the nut 73 rotates, the balls 72 move inside the ball circulation groove, and the steering shaft 26 moves linearly in the axial direction, in other words, the longitudinal direction, relative to the nut 73. This converts the rotational movement of the nut 73 into linear movement, i.e., direct motion.

[0102] The housing 50 is made up of a first housing 51 and a second housing 52, and the first housing 51 and the second housing 52 are fixed to each other with bolts, thereby forming an integrated unit.

[0103] The nut 73 is rotatably supported by the housing 50 via a bearing 74, and its axial movement relative to the bearing 74 is restricted.

[0104] The bearing 74 is located inside the storage chamber 53 between the first end face 55 and the second end face 57 , and is fitted to the inner circumferential surface 58 of the storage chamber 53 .

[0105] A minute gap exists between the inner peripheral surface 58 of the storage chamber 53 and the outer peripheral surface 74a of the bearing 74. Therefore, when an axial load acts on the bearing 74, the bearing 74 can be slightly displaced along the axial direction of the steered shaft 26 relative to the inner peripheral surface 58 of the storage chamber 53.

[0106] The bearing 74 can be configured as a "rolling bearing" such as a ball bearing or a roller bearing. A pair of annular support portions 75, 75 are located on both sides of the outer ring 74b of the bearing 74. The pair of support portions 75, 75 face each other in the axial direction of the steered shaft 26, sandwiching the bearing 74 therebetween. In this way, the bearing 74 and the pair of support portions 75, 75 are located inside the storage chamber 53, between the first surface 55 and the second end surface 57.

[0107] The side surface of the outer ring 74b of the bearing 74 is elastically supported in the axial direction of the steered shaft 26 by a pair of annular support portions 75, 75 over the entire circumference, in other words, is supported in a floating manner.

[0108] As a result, the nut 73 is indirectly supported elastically in the axial direction of the steered shaft 26 via the bearing 74 .

[0109] A pair of support portions 75 are provided, but the following description will be given taking one of them as an example.

[0110] The support portion 75 is made up of an annular elastic body 80 and an annular collar 90 that supports the elastic body 80. The elastic body 80 and the collar 90 are combined with each other in the axial direction of the steered shaft 26 and are integrated together.

[0111] The elastic body 80 is an annular member made of an elastic material that supports the entire periphery of the side surface of the outer ring 74b of the bearing 74 in the axial direction of the steered shaft 26. Examples of the elastic material that makes up the elastic body 80 include rubber alone, resin alone, a combination of rubber and resin, and a two-color molded product of rubber and resin.

[0112] The collar 90 is made of a metal material or a hard resin material and is interposed between the elastic body 80 and the housing 50 in the axial direction of the steering shaft 26, and the movement of the collar 90 along the axial direction of the steering shaft 26 is controlled by the housing 50.

[0113] As explained above, the nut 73, which is a component of the ball screw 70 as a rotary-to-linear motion conversion mechanism, is indirectly supported elastically in the axial direction of the steered shaft 26 via the bearing 74, and the bearing 74 is supported in the axial direction of the steered shaft 26 by a support part 75 which includes an elastic body 80 and a collar 90, and the collar 90 is interposed between the elastic body 80 and the housing 50 in the axial direction of the steered shaft 26.

[0114] Therefore, in other words, the elastic body 80 can be described as "a member that is provided between the rotary-to-linear motion conversion mechanism 26 and the housing 50 and elastically supports the rotary-to-linear motion conversion mechanism 26 relative to the housing 50."

[0115] Next, reference is made to Fig. 4. Fig. 4 is a characteristic diagram showing the relationship between the compressive load and the amount of compression of an elastic body.

[0116] In the example of FIG. 4, the elastic body 80 has a first load characteristic and a second load characteristic.

[0117] The first load characteristic is a characteristic in which the ratio of the compression load per unit compression amount of deformation in the axial direction of the steered shaft 26, i.e., the spring rate, gradually increases. The second load characteristic is a characteristic in which the ratio of the compression load per unit compression amount, i.e., the spring rate, increases sharply compared to the first load characteristic.

[0118] 4 shows the characteristic of the compression amount δ of the elastic body 80 relative to the compression load fc, that is, the load characteristic, with the vertical axis representing the compression load fc input to the elastic body 80 and the horizontal axis representing the compression amount δ of the elastic body 80.

[0119] In FIG. 4, the compression load corresponding to the reference compression amount δa is the reference compression load fca.

[0120] The range A1 of compression amounts from the origin to a preset reference compression amount δa is referred to as a first range A1. The range A2 of compression amounts from the reference compression amount δa to an upper limit compression amount δb, which is located after the first range A1, is referred to as a second range A2.

[0121] The first range A1 is a range that indicates a first load characteristic, and the second range A2 is a range that indicates a second load characteristic.

[0122] As mentioned above, "the deformation of the elastic bodies 80, 80 that occurs during the period when the driving force for abnormality detection is applied to the movable member 26 is preferably the maximum possible elastic deformation of each of the elastic bodies 80, 80," and the compression amount corresponding to this "maximum possible elastic deformation" corresponds to the maximum compression amount δb in Figure 6.

[0123] The amount of displacement corresponding to the maximum possible elastic deformation of the elastic bodies 80 can be determined univocally at the design stage, and therefore the amount of minute displacement under normal conditions can be determined univocally in advance.

[0124] In addition, the driving force for abnormality detection can be described as "a driving force that cannot move the movable member 26 against the frictional force acting on the movable member 26 as the steering axis, but can cause the maximum deformation δb in the elastic body 80."

[0125] In a preferred embodiment, the driving force for abnormality detection can be described as "a driving force that cannot move the movable member 26 against the frictional force acting on the movable member 26 as the steering axis, but is equal to or greater than the minimum driving force that can cause maximum deformation in the elastic body 80."

[0126] Furthermore, in consideration of reducing erroneous judgments, it is more preferable that the driving force for abnormality detection be "a driving force that cannot move the movable member 26 against the frictional force acting on the movable member 26 as the steering axis, but is sufficiently greater than the minimum driving force that can cause the maximum deformation δb in the elastic body 80."

[0127] Furthermore, when the driving force for abnormality detection is uniquely determined by focusing on the characteristics of the elastic body 80, the amount of normal deformation, i.e., the amount of normal expansion and contraction, that can be expected in the driving medium 63, such as a belt, that can be expected to deform in response to that determined driving force is uniquely determined.

[0128] 1, in an example in which a driving medium 63 such as a belt and an elastic body 80 are provided, the "total deformation of each of the driving medium 63 and the elastic body 80 that may temporarily occur while the driving force for abnormality detection is being applied to the movable member 26, which is the steering shaft, and which may be expected to occur" is the "total deformation obtained by adding the maximum possible elastic deformation δb of the elastic body 80 to the expected normal deformation of the driving medium 63 as a belt when the driving force for abnormality detection is being applied," and this can be determined uniquely at the design stage. This makes it possible to set an appropriate threshold for abnormality detection.

[0129] Next, reference is made to Figure 5. This is a cross-sectional view showing an example of a transmission mechanism using a worm and a worm wheel, which is provided with an elastically deformable member.

[0130] 1 and 3, a ball screw is used as the transmission mechanism for transmitting the driving force, but in the example of Fig. 5, a transmission mechanism using a worm and worm wheel is used as the transmission mechanism. Note that in the example of Fig. 5, it is assumed that a rack and pinion is used as the rotary-to-linear motion conversion mechanism.

[0131] The transmission mechanism in Figure 5 includes the motor body 24, the motor output shaft 25, the housing 113, the worm wheel 610, the worm 620, the shaft portion 622, the first bearing 630, the second bearing 640, an elastic body 700A made of a rubber material or the like that constitutes the first worm damper, an elastic body 700B that constitutes the second worm damper, and a coupling 650 that transmits the rotation of the motor output shaft 25 to the shaft portion 622 and the worm 620.

[0132] The joint 650 includes a bushing 653 which is an elastic member made of rubber or the like.

[0133] In the example of Figure 5, the worm 620 and the motor output shaft 25 are connected via a joint 650, and the bushing 653 of the joint 650, the first elastic body 700A, or the second elastic body 70A elastically deforms in the axial direction of the shaft portion 622, allowing the worm 620 to be slightly displaced in the axial direction.

[0134] Furthermore, since the worm wheel 610 is engaged with the worm 620, the bushing 653 of the joint 650, the first elastic body 700A, or the second elastic body 70A elastically deforms in the axial direction of the shaft portion 622, which indirectly allows the worm wheel 610 to be slightly displaced in the axial direction of the shaft portion 622.

[0135] 1 is engaged with the output shaft 611 of the worm wheel 610. In this case, when the worm wheel 610 rotates, the pinion 509 shown in FIG. 1 rotates, and the movable member 26 serving as the steering shaft moves in the axial direction of the shaft portion 622 in the example of FIG. 5.

[0136] In this case, the movable member 26, which is the steering axis, can be said to be indirectly elastically supported relative to the housing 113 via the worm wheel 610, the worm 620, the elastic bodies 700A, 700B, the first bearing 630, or the second bearing 640.

[0137] Here, the elastic bodies 700A and 700B in FIG. 5 are members corresponding to the elastic bodies 80 and 80 in the ball screw in FIG. 2, and the bush 653 as an elastic member in FIG. 5 is a member corresponding to the elastically deformable driving medium 63 of the transmission mechanism 44 in the ball screw in FIG. 2.

[0138] The elastic bodies 700A and 700B in the example of Figure 5 can be rephrased as "members that are provided between the rotary-to-linear motion conversion mechanism 26 shown in Figure 1 and the housing 113, and that elastically support the rotary-to-linear motion conversion mechanism 26 relative to the housing 113."

[0139] Therefore, the present invention can also be applied to an example in which a worm 620 and a worm wheel 610 are used as the transmission mechanism and a rack and pinion is used as the rotary-to-linear motion conversion mechanism, as shown in FIG.

[0140] Next, reference is made to Fig. 6. Fig. 6 is a characteristic diagram showing an example of the change in motor rotation angle with time in the normal case in the self-diagnosis process.

[0141] In Fig. 6, the same parts as in Fig. 1 and Fig. 3 are denoted by the same reference numerals. However, for the sake of convenience, Fig. 6 shows the main parts of the rotary-to-linear motion conversion mechanism in a simplified manner, and the transmission members are not shown.

[0142] As shown in A-1 of Figure 6, the movable member 26 as the steering shaft is indirectly supported elastically on the housings 50, 50 by elastic bodies 80, 80 via a nut 73 of a ball screw 70 as a rotary-linear motion conversion mechanism and a bearing 74.

[0143] 6A-1, there is no rust or ice on the movable member 26. Furthermore, there are no obstacles such as curbs near the steered wheels 31 connected to the movable member 26 via the knuckle arms 29. This is a normal state, and when a driving force for detecting an abnormality is applied to the movable member 26, the movable member 26 is capable of normal small displacement along the first and second directions DR1 and DR2.

[0144] 6A-2 shows an example of fluctuation in the rotation angle of the motor 5 over time when an abnormality is detected. In the following description, the rotation angle of the motor 5 may be referred to as the "motor rotation angle."

[0145] In A-2 of FIG. 6, the period from time t1 to t5 is a self-diagnosis period for detecting abnormalities, and during this period, a driving force for detecting abnormalities is applied to the movable member 26 as the steering shaft.

[0146] As explained above, in one preferred embodiment, the driving force for abnormality detection is a driving force that can cause "the total deformation obtained by adding the maximum possible elastic deformation of the elastic bodies 80, 80 to the possible normal deformation of the belt 63 as the driving medium when the driving force for abnormality detection is generated."

[0147] The motor rotation angle "+Rn" is the rotation angle of the motor 5 corresponding to the "amount of displacement obtained by adding the displacement of the elastic body 80 to the elongation of the belt 63 as the driving medium of the transmission member 44" in the first direction DR1.

[0148] The motor rotation angle "-Rn" is the rotation angle of the motor 5 corresponding to the amount of displacement obtained by adding the displacement of the elastic body 80 to the elongation of the belt 63 serving as the drive medium of the transmission member 44 in the second direction DR2.

[0149] "+Rth" is a first threshold value for determining an abnormality in the first direction DR1. This first threshold value "+Rth" may be the same value as "+Rn", but in a preferred embodiment, in order to reduce erroneous determination, it is set to "the value of the rotation angle corresponding to the elongation in the first direction DR1 of the belt 63 serving as the drive medium of the transmission member 44, i.e., a value greater than "+Rs" and smaller than "+Rn" in A-2 of FIG. 7."

[0150] "-Rth" is a first threshold value for determining an abnormality in the second direction DR2. This second threshold value "-Rth" may be the same value as "-Rn", but in a preferred embodiment, it is set to a value that is smaller than "-Rs" in A-2 of FIG. 7 and larger than "-Rn", which is the rotation angle value corresponding to the elongation in the second direction DR2 of the belt 63 serving as the drive medium of the transmission member 44.

[0151] In A-2 of FIG. 6, the shaded area indicates the range of fluctuation of the motor rotation angle.

[0152] In A-2 of FIG. 6, the amount of change in the motor rotation angle during the self-diagnosis period exceeds the first threshold value "+Rth" in the first direction DR1, and falls below the second threshold value "-Rth" in the second direction DR2.

[0153] Therefore, the abnormality determination unit 411 in the abnormality detection unit 409 shown in FIG. 1 determines that the state is "normal."

[0154] Next, reference is made to Fig. 7, which is a characteristic diagram showing an example of the change in motor rotation angle over time in the case of an abnormality in the self-diagnosis process. In Fig. 7, the same parts as in Fig. 6 are given the same reference numerals.

[0155] 7, a movement obstruction Abn such as rust or ice exists between the nut 73 of the ball screw 70, which is the rotary-to-linear motion conversion mechanism, and the movable member 26, which is the steering shaft. As a result, the movable member 26 is in an abnormal state in which normal movement is obstructed.

[0156] Due to this abnormality, the nut 73 cannot move in the axial direction of the movable member 26, which is the steering shaft, and therefore the elongation of the elastic bodies 80, 80, in other words the "minute displacement", is zero.

[0157] Therefore, the only “minor displacement” that can be detected is the minor displacement of the belt 63 that is the drive medium of the transmission member 44 .

[0158] 7A-2, the only fluctuation in the motor rotation angle in the first direction DR1 that occurs during the self-diagnosis period is a fluctuation corresponding to the motor rotation angle "+Rs" that corresponds to the elongation in the first direction DR1 of the belt 63 that serves as the drive medium for the transmission member 44. In other words, the detected motor rotation angle is below the first threshold value "+Rs" in the first direction DR1.

[0159] Similarly, the only fluctuation in the motor rotation angle in the second direction DR2 that occurs during the self-diagnosis period is the fluctuation corresponding to the motor rotation angle "-Rs" which corresponds to the elongation in the first direction DR2 of the belt 63 serving as the drive medium for the transmission member 44. In other words, the detected motor rotation angle exceeds the second threshold value "-Rth" in the second direction DR2.

[0160] Therefore, the abnormality determination unit 411 in the abnormality detection unit 409 shown in FIG. 1 determines that an "abnormality" has occurred.

[0161] Next, reference is made to FIG. 8. FIG. 8 is a diagram showing the motor rotation angle and the time required for abnormality detection in the self-diagnosis process of one embodiment of the present invention in comparison with a conventional example. Note that A-2 in FIG. 8 is an enlarged view of a portion of A-1 in FIG. A-2 in FIG. 8 shows the fluctuations in the motor rotation angle in the present invention in more detail.

[0162] In A-1 of Figure 8, the dashed characteristic line Q1 indicates the range of fluctuation in the motor rotation angle and the time required to detect an abnormality when the movable member, which is the steering axis, is moved at its full stroke, i.e., the maximum possible stroke, in order to detect an abnormality in a conventional example.

[0163] Furthermore, characteristic line Q2, shown as a thick, very short solid line, indicates the range of fluctuation in the motor rotation angle and the time required to detect an abnormality when a minute driving force for abnormality detection is applied to the movable member, which is the steering shaft, during the self-diagnosis period, causing a temporary, reversible minute displacement in an embodiment of the present invention.

[0164] In the conventional example, for example, when the movable member 26, which is a steered wheel, is moved in the first direction DR1, the motor rotation angle varies from "0" to "R20", and the variation amount is "RB". Furthermore, the time required for abnormality detection is the period "TB" from time t10 to t20.

[0165] In contrast, in the embodiment of the present invention, the motor rotation angle fluctuates from "0" to "R10", and the amount of fluctuation is "RA". The time required to detect an abnormality is the period "TA" from time t10 to t11. More precisely, as shown in A-2 of FIG. 8, the motor rotation angle in the embodiment of the present invention displaces in the positive direction from "0" as the reference, and then displaces in the negative direction from "0" as the reference. In other words, the motor rotation angle oscillates in both the positive and negative directions.

[0166] Here, in a preferred example, the fluctuation amount RA of the motor rotation angle in the embodiment of the present invention is 1 / 100 or less of the fluctuation amount RB in the conventional example. Specifically, if the full stroke amount of the movable member, which is the steering shaft, is 100 mm, the normal small displacement occurring in the movable member in the embodiment of the present invention is 1 mm or less, and fluctuation in the motor rotation angle can be significantly reduced compared to the conventional example.

[0167] Similarly, in a preferred example, the time TA required for anomaly detection in the embodiment of the present invention is 1 / 100 or less of the time TB required in the conventional example. Therefore, the time required for anomaly detection can be significantly reduced compared to the conventional example.

[0168] Second Embodiment In this embodiment, an example of a determination process when an obstacle such as a curb is present near the steered wheels will be described.

[0169] Please refer to Fig. 9. Fig. 9 is a diagram showing an example of the determination process when an obstacle such as a curb is present near the steered wheels, but the self-diagnosis process determines that the vehicle is normal. In Fig. 9, the same parts as in Fig. 6 are assigned the same reference numerals.

[0170] 9A-1, a curb 90 serving as an obstacle exists at a distance LA near the steered wheels 31. In other words, since the curb 90 is separated from the steered wheels 31 by the distance LA, the movable member 26, which is the steered wheels, can be slightly displaced within the range of the distance LA.

[0171] In A-2 of FIG. 9, the shaded area indicates the range of minute displacement of the movable member 26.

[0172] As explained above, "+Rs" and "-Rs" are motor rotation angles corresponding to the elongation of the belt 63, which serves as the drive medium for the transmission member 44, in the first and second directions DR1 and DR2.

[0173] Furthermore, the motor rotation angles "+Rn" and "-Rn" are the rotation angles of the motor 5 corresponding to the "amount of displacement obtained by adding the displacement of the elastic body 80 to the elongation of the belt 63 as the driving medium of the transmission member 44" in the first and second directions DR1 and DR2.

[0174] As shown in A-2 of Figure 9, during the self-diagnosis period, the maximum displacement of the motor rotation angle reaches the motor rotation angle values ​​"+Rn" and "-Rn", and if an abnormality is determined using the first and second threshold values ​​"+Rth" and "-Rth", it is determined to be "normal".

[0175] Next, reference is made to Fig. 10. Fig. 10 is a diagram showing an example of the determination process when an obstacle such as a curb is present in contact with the steered wheels and the self-diagnosis process determines that an obstacle such as a curb is present. In Fig. 10, the same parts as in Fig. 9 are given the same reference numerals.

[0176] In A-1 of Fig. 10, a curb 90, which is an obstacle, is in contact with the steered wheel 31. Unlike the example of A-1 of Fig. 9, there is no gap between the steered wheel 31 and the curb 90, and therefore the curb 90 prevents minute displacement of the steered wheel 31. Therefore, minute displacement of the movable member 26, which serves as the steering axis, in the first direction DR1 does not occur.

[0177] However, although the displacement of the movable member 26 is zero, the friction between the movable member 26 and the nut 73 causes the elastic body 80 located on the second direction DR2 side relative to the bearing 74 to contract, causing a slight displacement of the bearing 74 and the nut 73 on the second direction DR2 side.

[0178] The minute displacement due to the contraction of the elastic body 80 is the maximum deformation within the deformable range of the elastic body 80, and the minute displacement amount due to the deformation is represented as "W," and the motor rotation angle corresponding to this minute displacement amount is represented as "RW." This motor rotation angle RW will be described in A-4 of FIG. 10.

[0179] Since the displacement of the movable member 26 is zero, in A-2 of Figure 10, the motor rotation angle observed during the self-diagnosis period is only the motor rotation angle "+Rs" corresponding to the elongation in the first direction DR1 of the belt 63 as the driving medium of the transmission member 44.

[0180] In this case, the motor rotation angle falls below the first threshold value "+Rth", which may result in a situation that may be determined as "abnormal".

[0181] However, this situation is indistinguishable from the situation described above with reference to A-2 in FIG. 7 where there is a movement obstruction Abn such as rust or ice.

[0182] In other words, it is not possible to distinguish whether there is an obstacle Abn such as rust or ice obstructing movement, as in A-1 of Figure 7, or whether there is an obstacle 10 such as a curb in contact with the steered wheel 31, as in Figure 10.

[0183] If an obstacle 10 such as a curb is present as shown in A-1 of Figure 10, when the vehicle 10 moves and the steered wheels 31 are released from contact with the obstacle 10 such as the curb, the movable member 26 can be slightly displaced in the first direction DR1, and the result of the self-diagnosis can be determined to be "normal."

[0184] In other words, the situation of A-1 in Figure 10 can be said to be "a situation in which there is no movement obstruction Abn such as rust or ice and the situation is normal, but the presence of an obstacle such as a curb makes it appear to be abnormal," and is clearly distinguishable from "a situation in which an abnormality has occurred due to the presence of movement obstructions Abn such as rust or ice" shown in Figure 7A-1.

[0185] Therefore, during self-diagnosis, it is preferable to detect the situation A-1 in Figure 10 and take countermeasures when an obstacle 10 such as a curb is present, such as notifying the occupants of the vehicle 10, including the driver.

[0186] In order to distinguish the situation of A-1 in FIG. 7 from the situation of A-1 in FIG. 10 and to detect the situation of A-1 in FIG. 10, in A-3 in FIG. 10, the driving force for abnormality detection is increased and a process is performed to displace the movable member 26 in the second direction DR2.

[0187] Here, if an obstacle 90 such as a curb is present in contact with the steered wheel 31 located on the first direction DR1 side relative to the movable member 26, there is usually no obstacle such as a curb on the steered wheel located on the opposite side, the second direction DR2 side.

[0188] In other words, it can be assumed that the minute displacement of the movable member 26 in the second direction DR2 is not hindered by an obstacle such as a curb.

[0189] Therefore, when a driving force for detecting an abnormality is applied to the movable member 26, a slight displacement occurs in the second direction DR2 of the movable member 26. Furthermore, a slight displacement also occurs in the bearing 74 and the nut 73 in the first direction DR1 due to friction between the movable member 26 and the nut 73.

[0190] Here, attention is focused on the expansion and contraction of the pair of elastic bodies 80, 80 in A-3 of Fig. 10. As explained above, in A-1 of Fig. 10, the elastic body 80 undergoes the maximum deformation within its deformable range, and the deformation causes a displacement "W" in the elastic body 80.

[0191] In A-3 of Figure 10, the elastic body 80, which was contracted in A-1 of Figure 10, stretches by a displacement "W", returns to a neutral position where the displacement amount is zero, and then stretches by a displacement "W" from that neutral position.

[0192] On the other hand, the elastic body 80, which was stretched at A-1 in Figure 10, contracts by a displacement "W", returns to a neutral position where the displacement amount is zero, and then contracts further by a displacement "W" from that neutral position, returning to a contracted state.

[0193] That is, at A-3 in FIG. 10, a minute displacement of "2W" occurs in the elastic body 80.

[0194] Here, the driving force for abnormality detection in A-1 of Figure 10 is a driving force that generates a small displacement obtained by adding the displacement of the elastic body 80 ``W'' to the displacement due to the extension of the belt 63 as the driving medium of the transmission member 44.

[0195] On the other hand, in A-3 of Figure 10, the driving force for abnormality detection is increased to produce a driving force that generates a small displacement obtained by adding the displacement of the elastic body 80, 2W, to the displacement due to the extension of the belt 63 serving as the driving medium for the transmission member 44.

[0196] As a result, in A-3 of FIG. 10, a fluctuation in the motor rotation angle occurs corresponding to the "small displacement obtained by adding the displacement of the elastic body 80 "2W" to the displacement due to the extension of the belt 63 serving as the drive medium of the transmission member 44."

[0197] Attention is now focused on the latter half of the self-diagnosis period in A-4 of FIG. 10, that is, the period from time t3 to t5.

[0198] During this period, a driving force is applied to the movable member 26 to cause a small displacement in the second direction DR2, and in this case, the fluctuation amount of the motor rotation angle is the sum of the motor rotation angle "Rs" corresponding to the elongation of the belt 63, the motor rotation angle "RW" corresponding to the displacement W until the belt 63 returns to the neutral position, and the motor rotation angle "RW" corresponding to the displacement W from the neutral position to the maximum displacement position.

[0199] In A-4 of Fig. 10, "-Rth2" is used as the threshold value for detecting an abnormality during the period from time t3 to time t4. Here, when comparing absolute values ​​ignoring polarity, "Rth2>Rth" holds. Since the driving force for detecting an abnormality is increased, a threshold value Rth2 with a larger absolute value is used as the threshold value for detecting an abnormality accordingly. In other words, taking polarity into consideration, the presence or absence of an abnormality is determined using the threshold value "-Rth2".

[0200] In A-4 of Figure 10, during the period from time t3 to t4, the range of fluctuation in the motor rotation angle, i.e., the maximum fluctuation in the range of the area indicated by diagonal lines and sand patterns in the figure, is below the threshold value "-Rth2", and therefore it is determined that normal minute displacement is occurring in the movable member 26 in the second direction DR2.

[0201] 10, an abnormality is detected in the first direction DR1, but no abnormality is detected when the driving force is increased and the abnormality detection process is performed in the second direction DR2. Therefore, in such a case, it is possible to determine that there is an obstacle such as a curb that is preventing the displacement of the steered wheels in the first direction DR1. The processing procedure for detecting the presence of an obstacle such as a curb will be described in detail later.

[0202] Third Embodiment In this embodiment, an example of a processing procedure in a self-diagnosis process for detecting an abnormality will be described.

[0203] Please refer to Fig. 11. Fig. 11 is a flowchart showing an example of the overall processing procedure of the self-diagnosis processing.

[0204] In step S1, the steering control device 500 determines whether or not self-diagnosis processing is possible. For example, it checks whether at least one of the following is true: an activation switch such as an ignition switch is off; the parking brake is on; the vehicle speed of the vehicle 10 is zero; input of steering commands from occupants including the driver to the motor control unit 403 is blocked; and if any of these checks is true, it is determined that self-diagnosis is possible.

[0205] If the answer is Y in step S1, the process proceeds to step S2, and if the answer is N, step S1 is repeated.

[0206] In step S2, it is determined whether it is time to start the self-diagnosis process. If the answer is "Y", the process proceeds to step S3, and if the answer is "N", the process returns to step S1.

[0207] In step S3, the steering control device 500 turns on a trigger signal required for the self-diagnosis process and a signal indicating a predetermined condition, thereby satisfying the conditions for starting the self-diagnosis.

[0208] Specifically, for example, when the ignition switch is turned on, a start signal is input as a trigger signal to the motor control unit 403, or a self-diagnosis start switch is turned on by a passenger, including the driver, and a self-diagnosis start signal is input as a trigger signal to the motor control unit 403.

[0209] In step S4, a self-diagnosis process is executed.

[0210] In step S5, it is determined whether or not there is an abnormality. If the answer is N, that is, if there is an abnormality, the process proceeds to step S6, and if the answer is Y, that is, if there is no abnormality, the process proceeds to step S7.

[0211] In step S6, an abnormality countermeasure process is carried out, such as a process of notifying the abnormality or a process of restricting some of the vehicle's operations, and then the process proceeds to step S7.

[0212] In step S7, a process for ending the self-diagnosis is carried out, for example, a process for returning operations and measures that have been restricted while the self-diagnosis is being carried out to an unrestricted state is carried out.

[0213] Next, reference is made to Fig. 12. Fig. 12 is a flowchart showing an example of the processing procedure for determining whether or not the self-diagnosis processing should be performed. That is, Fig. 12 shows a specific example of the processing procedure of step S1 shown in Fig. 11.

[0214] In step S11, it is determined whether or not the self-diagnosis process is possible.

[0215] In step S12, it is determined whether or not a vehicle stoppage measure, etc., is being executed while the vehicle is stopped. If the answer is No, the process returns to step S11, and if the answer is Yes, the process proceeds to step S13.

[0216] In step S13, the steering command input from the steering wheel is invalidated.

[0217] In step S14, it is confirmed whether the steering command input from the steering wheel is disabled. In the present invention, very small displacements are detected. If the steering command input is enabled, it becomes impossible to detect the small displacements. Therefore, in step S14, it is carefully confirmed whether the steering command input is disabled. If the answer is N in step S14, the process returns to step S13, and if the answer is Y, the process proceeds to step S15.

[0218] In step S15, the self-diagnosis process is permitted.

[0219] Next, reference will be made to Fig. 13. Fig. 13 is a flowchart showing an example of a specific procedure for the self-diagnosis process. That is, Fig. 13 shows an example of a specific procedure for the process of step S4 shown in Fig. 11.

[0220] In step S10, the steering control device issues a drive command for detecting an abnormality to the motor.

[0221] In step S20, a driving force for detecting an abnormality is applied to the movable member.

[0222] In step S30, a temporary and reversible minute displacement caused by deformation of the elastic body is measured.

[0223] In step S40, the actual measured value of the physical quantity corresponding to the minute displacement is acquired.

[0224] In step S50, it is determined whether the relationship between the actual measured stroke amount and the normal stroke amount is "actual measured stroke amount < normal stroke amount." If the answer is "Yes," the process proceeds to step S60, and if the answer is "No," the process proceeds to step S80.

[0225] In step S60, it is determined that an abnormality has occurred, and then in step S70, abnormality countermeasure processing is executed, such as issuing a notification of the abnormality or restricting some of the vehicle's operations.

[0226] In step S80, it is determined that there is no abnormality, and the self-diagnosis process ends.

[0227] Next, reference is made to Fig. 14. Fig. 14 is a flowchart showing another example of the specific processing procedure of the self-diagnosis processing. That is, Fig. 14 shows an example of the processing procedure of an application example including the processing of detecting an obstacle such as a curb in the execution of the self-diagnosis processing in step S4 in Fig. 11.

[0228] 14, for convenience of explanation, the "first direction DR1" shown above is the left direction as seen by the occupants including the driver, and is therefore referred to as "left" or "leftward." Also, the "second direction DR2" shown above is the right direction as seen by the occupants including the driver, and is therefore referred to as "right" or "rightward."

[0229] In the processing procedure of Figure 14, in the self-diagnosis processing for detecting abnormalities, driving forces are applied in both the left and right directions to the movable member 26, which is the steering axis, to detect minute displacements in each direction, and the presence or absence of abnormalities and obstacles such as curbs is determined based on the actual measured values ​​of the minute displacements in each direction.

[0230] In other words, in the example of Figure 14, it is possible to distinguish and detect whether there is an abnormality in which the movement of the movable member is restricted due to rust, icing, etc., and whether there is no such abnormality but the presence of an obstacle such as a curb is preventing the slight displacement of the steered wheels.

[0231] 14, it is also possible to determine whether the friction in each of the left and right directions of the movable member 26, i.e., the deviation in stroke value due to friction (hereinafter referred to as friction deviation), is excessive, and to detect the presence or absence of an abnormality based on the result of this determination, which allows for more careful and more reliable abnormality detection.

[0232] In step S100, it is determined whether there is any abnormality in the left direction. That is, a driving force for detecting an abnormality is applied to the movable member 26, and the actual measurement value of the resulting minute displacement is obtained and compared with a predetermined threshold value prepared in advance. For example, if the actual measurement value as an absolute value is equal to or greater than the absolute threshold value, it is determined that there is no abnormality, i.e., the movement is normal.

[0233] If the answer is Y in step S100, the process proceeds to step S101, and if the answer is N, the process proceeds to step S200. Step S200 and the subsequent steps will be described later.

[0234] In step S101, it is similarly determined whether there is no abnormality in the right direction. If the answer is No in step S101, the process proceeds to step S301. Step S301 and the subsequent steps will be described later.

[0235] If the answer is Y in step S101, that is, if it is determined that there is no abnormality in the right direction as well, then, in principle, it is assumed that no abnormality was detected in this self-diagnosis, and the process proceeds to step S103, where the self-diagnosis termination process can be performed.

[0236] In other words, if there is no abnormality in either the left or right direction, it can be determined that the condition is normal.

[0237] However, in the example of the processing procedure of FIG. 14, in order to be more cautious and reduce erroneous determinations, the determination in step S102 may be performed before the processing in step S103 is performed.

[0238] When step S102 is carried out, it is determined whether the friction deviation estimated from the minute displacement in each of the left and right directions, i.e., the left and right friction deviation, is within a predetermined allowable range, in other words, within a normal range, or in other words, whether it is in a situation where it exceeds the normal range and is judged to be excessive.

[0239] That is, after the judgments of steps S100 and S200, it is determined that there is no abnormality in either the left or right direction, but if there is a difference between the stroke amount of the first minute displacement in the left direction and the stroke amount of the second minute displacement in the right direction, and if this difference in stroke amount exceeds a preset tolerance range or normal range, i.e., if the friction deviation exceeds the normal range and is excessive, it can be estimated that there is a high possibility that movement of the movable member serving as the steering axis has been restricted in at least one direction, left or right, due to the effects of rust, icing, etc., even if it may be minor.

[0240] Therefore, if the answer is N in step S102, it is determined that an abnormality has occurred as a matter of caution, and the process proceeds to step S308. Note that step S308 and the subsequent processes will be described later.

[0241] Next, the processing of steps S200 to S204 will be described. The series of processing steps S201 to S204 shows an example of the processing for re-diagnosis when an abnormality is determined in either the left or right direction, in other words, a procedure for re-diagnosis processing after an initial determination that an abnormality exists.

[0242] Even if the primary determination determines that there is an abnormality in each of the left and right directions, there is a possibility of an erroneous determination because the present invention detects extremely small displacements. Also, as explained above in A-1 of Figure 10, it is possible that there is no actual abnormality due to rust, icing, or the like, but the presence of an obstacle such as a curb in contact with the steered wheels results in an apparent abnormality.

[0243] Therefore, in the example of the processing procedure of FIG. 14, as an extra precaution, re-diagnosis is performed in steps S201 to S204 to reduce the possibility of erroneous determination.

[0244] In step S200, similarly to step S101 described above, it is determined whether or not there is any abnormality in the right direction.

[0245] If the answer is Y in step S200, the process proceeds to step S301. Step S301 and subsequent processes will be described later.

[0246] If the answer is N in step S200, the process proceeds to step S201. As explained above, even if the primary determination determines that an abnormality exists in either the left or right direction, there is a possibility of an erroneous determination, so as to be cautious, a re-diagnosis process, in other words, a retry process, is carried out.

[0247] In step S201, in order to ensure its effectiveness, the re-diagnosis process is started with the driving force for abnormality determination increased compared to the initial determination in steps S100 and S200.

[0248] The re-diagnosis may be carried out multiple times. In this case, it is preferable to increase the driving force for detecting abnormalities in each re-diagnosis in order to improve the effectiveness of the re-diagnosis.

[0249] In addition, the extent to which the driving force is increased can be determined in advance at the design stage in order to prevent erroneous determination. For example, as previously described in A-3 of Fig. 10, the presence or absence of a curb or the like can be detected by applying to the movable member 26 a driving force that can generate "a displacement that is twice the displacement of the elastic body 80 plus the displacement due to the elongation of the belt 63 of the transmission member 44."

[0250] Taking this into consideration, for example, in the primary determination, i.e., steps S100 and S200, a driving force that can cause "a displacement obtained by adding the displacement of the elastic body 80 to the displacement due to the elongation of the belt 63 of the transmission member 44, etc." may be applied to the movable member 26, while in the re-diagnosis, i.e., steps S201 to S204, an increased driving force that can cause "a displacement obtained by adding twice the displacement of the elastic body to the displacement due to the elongation of the belt 63 of the transmission member 44, etc." may be applied to the movable member 26.

[0251] In step S202, it is determined whether there is any abnormality in the left direction. That is, an increased driving force for abnormality detection is applied to the movable member, and the resulting actual measurement value of the small displacement is obtained and compared with a pre-prepared threshold value corresponding to the increased driving force. For example, if the actual measurement value as an absolute value is equal to or greater than the absolute threshold value, it is determined that there is no abnormality, i.e., the movement is normal.

[0252] If the answer is Y in step S202, the process proceeds to step S203, and if the answer is N, the process proceeds to step S204.

[0253] In step S203, it is similarly determined whether there is no abnormality in the right direction. If the result in step S203 is Y, a re-diagnosis, i.e., a retry, has determined that there is no abnormality in either the left or right direction. Therefore, in this case, it is determined to be normal, and then the process proceeds to step S103, where the self-diagnosis termination process is performed.

[0254] If the answer is N in step S203, it means that the re-diagnosis performed with the driving force increased found no abnormality in the left direction, but determined that there was an abnormality in the right direction. In this case, there is a high possibility that an obstacle such as a curb is in contact with the steered wheels in the right direction. Therefore, in this case, the process proceeds to step S306 as a general rule. In step S306, an obstacle such as a curb is detected.

[0255] The reason why it is stated that "in principle, proceed to step S306" is that, as with step S102, to be cautious, it may be determined in step S305 whether the friction deviation between the left and right is within the allowable range.

[0256] When step S305 is performed, if the answer is N in this step S305, it can be estimated that there is a high possibility that movement of the movable member serving as the steering axis is being restricted in at least one direction, left or right, due to the influence of rust, icing, etc., even if it may be minor. Therefore, to be cautious, it is determined that there is an abnormality, and the process proceeds to step S308.

[0257] If the answer is YES in step S305, the process proceeds to step S306, where an obstacle such as a curb is detected.

[0258] In step S307, a process is performed to notify the occupants, including the driver, that an obstacle such as a curb has been detected. Then, the process proceeds to step S103, where a process to end the self-diagnosis is performed.

[0259] In step S204, it is determined whether there is an abnormality in the right direction. If the answer is No in step S204, it means that the re-diagnosis performed after increasing the driving force also determined that there is an abnormality in both the left and right directions. In this case, the process proceeds to step S308.

[0260] In this case, an abnormality in which the displacement of the movable member is hindered by rust, icing, or the like is detected in step S308. Subsequently, in step S309, an abnormality countermeasure process is implemented. For example, measures such as notifying the occupants including the driver that an abnormality has occurred, or restricting some of the vehicle's operations, such as temporarily halting the vehicle's travel, are implemented.

[0261] Furthermore, if the result in step S204 is Y, this means that in the re-diagnosis performed with the driving force increased, an abnormality was determined in the left direction, but no abnormality was determined in the right direction. In this case, there is a high possibility that an obstacle such as a curb is in contact with the steered wheels in the left direction. Therefore, in this case, the process generally proceeds to step S306. In this step S306, an obstacle such as a curb is detected. However, as explained above, step S305 may be performed before performing step S306.

[0262] Next, the processing of steps S301 to S304 will be described. This series of processing is related to re-diagnosis when the result of the primary diagnosis is that one of the left and right sides is normal, but the other side is abnormal.

[0263] In this case, it may be determined that there is an obstacle such as a curb in the direction determined to be abnormal. That is, although an initial determination of the presence of a curb or the like is possible, there is also the possibility of an erroneous determination. Therefore, in the example of the processing procedure in FIG. 14, a re-diagnosis process is performed after the initial determination of the presence of a curb or the like in order to reduce erroneous determinations and be cautious.

[0264] In step S301, in order to ensure its effectiveness, the re-diagnosis process is started with a driving force for abnormality determination increased compared to the initial determination in steps S100 and S101.

[0265] The re-diagnosis may be carried out multiple times. In this case, it is preferable to increase the driving force for detecting abnormalities in each re-diagnosis in order to improve the effectiveness of the re-diagnosis.

[0266] The extent to which the driving force is to be increased can be determined in advance at the design stage in order to prevent erroneous determination. As an example, the method of increasing the driving force described above in step S201 can be applied.

[0267] In step S302, it is determined whether there is any abnormality in the left direction. That is, an increased driving force for abnormality detection is applied to the movable member, and the resulting actual measurement value of the small displacement is obtained and compared with a pre-prepared threshold value corresponding to the increased driving force. For example, if the absolute actual measurement value is equal to or greater than the absolute threshold value, it is determined that there is no abnormality, i.e., the movement is normal.

[0268] If the answer is Y in step S302, the process proceeds to step S303, and if the answer is N, the process proceeds to step S304.

[0269] In step S303, it is similarly determined whether there is no abnormality in the right direction. If the answer is Y in step S303, a re-diagnosis, i.e., a retry, can determine that there is no abnormality in either the left or right direction. In other words, it becomes clear that there is no relationship to an obstacle such as a curb. Therefore, in principle, the process proceeds to step S103, and the self-diagnosis termination process is performed. However, as explained above, step S102 may be performed before performing step S103.

[0270] If the answer is N in step S303, it means that the re-diagnosis performed with increased driving force found no abnormality in the left direction, but determined that there was an abnormality in the right direction. In this case, there is a high possibility that an obstacle such as a curb is in contact with the steered wheels in the right direction. Therefore, in this case, the process generally proceeds to step S306. In step S306, an obstacle such as a curb is detected. However, as explained above, step S305 may be performed before performing step S306.

[0271] In step S304, it is determined whether there is an abnormality in the right direction. If the answer is No in step S304, it means that the re-diagnosis performed after increasing the driving force also determined that there is an abnormality in both the left and right directions. In this case, the process proceeds to step S308.

[0272] In this case, an abnormality in which the displacement of the movable member is hindered by rust, icing, or the like is detected in step S308. Subsequently, in step S309, an abnormality countermeasure process is implemented. For example, measures such as notifying the occupants including the driver that an abnormality has occurred, or restricting some of the vehicle's operations, such as temporarily halting the vehicle's travel, are implemented.

[0273] Furthermore, if the result in step S304 is Y, this means that in the re-diagnosis performed with the driving force increased, an abnormality was determined in the left direction, but no abnormality was determined in the right direction. In this case, there is a high possibility that an obstacle such as a curb is in contact with the steered wheels in the left direction. Therefore, in this case, the process proceeds to step S306 as a general rule. In step S306, an obstacle such as a curb is detected. However, as explained above, step S305 may be performed before performing step S306.

[0274] An example of the configuration and effects of the embodiment of the present invention described above is as follows: According to a first aspect of the steering device of the present invention, a steering device (700) attached to a vehicle (10) for steering steered wheels (31, 31) of the vehicle includes a movable member (26) connected to the steered wheels to steer the steered wheels, a housing (50) covering at least a part of the movable member and fixed to the body of the vehicle, a motor (5) for applying a steering force to the movable member, a rotary-to-linear motion conversion mechanism (70) provided in the housing for converting rotational motion transmitted from the motor into linear motion and transmitting the linear motion to the movable member, and a housing (70) provided between the rotary-to-linear motion conversion mechanism and the housing. A steering device is provided, comprising: an elastic body (80, 80) that elastically supports a rotary-to-linear motion conversion mechanism relative to a movable member; and a control device (500) that outputs a first control signal (SG20) to a motor to move the rotary-to-linear motion conversion mechanism relative to a movable member beyond the amount of displacement elastically supported by the elastic body in response to the establishment of a trigger condition for operation confirmation or a predetermined condition, acquires a physical quantity related to the amount of movement of the movable member caused by the first control signal, determines whether or not an abnormality exists based on the physical quantity related to the amount of movement of the movable member, and outputs an abnormality determination signal (SG35) when an abnormality is determined. According to the first aspect, it is possible to determine an abnormality based on the extremely small displacement caused by deformation of the elastic body without moving a movable member constituting a steering shaft or the like from a normal mechanical perspective. By using an abnormality detection method that is essentially different from conventional methods, the stroke amount of the movable member required for abnormality detection and the time required for abnormality detection can be significantly reduced compared to conventional methods.

[0275] In a second aspect dependent on the first aspect, the steering device has a first configuration having only an elastic body (80, 80) as a component that generates temporary and reversible deformation during a period when a drive command for abnormality detection as a first control signal is given to the motor, or a second configuration having, in addition to the elastic body, a drive medium (63) that is expected to deform and that is included in a transmission mechanism (44) that is provided between the motor and the rotary-to-linear motion conversion mechanism and transmits the drive force generated by the rotation of the motor to the rotary-to-linear motion conversion mechanism, and the control device (500) has a motor control unit (403) that controls the motor, and an abnormality detection unit (409) that detects an abnormality that restricts normal movement of a movable member, and the motor control unit outputs the drive command for abnormality detection as the first control signal upon detection of an abnormality. The abnormality detection unit may apply an abnormality detection driving force to the motor, which may generate an abnormality detection driving force that cannot move the movable member against the frictional force acting on the movable member but may deform the elastic body, or the driving medium and the elastic body that may be deformed, and apply the abnormality detection driving force to the movable member. The abnormality detection unit may measure a temporary, reversible deformation of the elastic body that occurs during the period when the abnormality detection driving force is applied to the movable member, or a minute displacement of the movable member that corresponds to the total deformation of the driving medium and the elastic body that may be deformed, to obtain an actual measurement value of the physical quantity corresponding to the minute displacement, and determine that an abnormality exists if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when no abnormality exists. According to the second aspect, it is possible to determine an abnormality based on a very slight, reversible minute displacement that temporarily occurs due to the elastic body, etc., during the period when the motor is generating the abnormality detection driving force in response to the abnormality detection driving command, without moving the movable member, such as a rack bar that constitutes the steering shaft, from a normal mechanical perspective. This minute displacement can be thought of as a vibration or fluctuation in the steering actuator, and is a very slight, temporary, and recoverable displacement, which is essentially different from the conventional concept of mechanically moving a movable member. Therefore, according to the present invention, the stroke amount of the movable member required for abnormality detection can be reduced to, for example, 1 / 100 or less of the conventional amount, and the time required for abnormality detection can be reduced to 1 / 100 or less of the conventional amount.Furthermore, unlike the conventional example, there is no need to detect phenomena specific to abnormalities, such as a decrease in the rotation speed of the motor or periodic fluctuations in the rotation speed of the motor, and abnormalities can be easily determined, for example, by a simplified threshold judgment. Furthermore, in the conventional example, because the steered wheels are moved by a fairly large amount by moving the movable member, if there are obstacles such as curbs around the steered wheels, the movement of the steered wheels is hindered and accurate abnormality detection is not possible, so as a prerequisite for abnormality detection, it was first necessary to capture images of the area around the steered wheels using an imaging camera or the like to check that there are no obstacles. However, in the present invention, the steered wheels do not substantially move, so such obstacle detection by imaging is not necessary, and therefore the abnormality detection process is facilitated.

[0276] In a third aspect dependent on the second aspect, the deformation of the elastic body occurring during the period when the driving force for abnormality detection is applied to the movable member may be the maximum possible elastic deformation of the elastic body, or the total deformation of the drive medium and the elastic body that may temporarily occur during the period when the driving force for abnormality detection is applied to the movable member may be the sum of the maximum possible elastic deformation of the elastic body and the expected normal deformation of the drive medium when the driving force for abnormality detection is applied. In the third aspect, the driving force for abnormality detection is a driving force that may cause the maximum possible elastic deformation of the elastic body, or a driving force that may cause the total deformation of the maximum possible elastic deformation of the elastic body plus the expected normal deformation of the drive medium when the driving force for abnormality detection is applied. The maximum possible elastic deformation of the elastic body or the expected normal deformation of the drive medium when the driving force for abnormality detection is applied can be uniquely determined, for example, at the design stage. Therefore, the driving force for abnormality detection can also be uniquely determined to an appropriate value.

[0277] In a fourth aspect dependent on the first or second aspect, the actual measured value of the physical quantity corresponding to the minute displacement may be at least one of a detected value of the rotation angle of the motor, a detected value of the rotation angle of the pinion (509) meshing with the rack as a movable member, and a detected value obtained by detecting the displacement of the rack as a movable member with a non-contact sensor (511). In the fourth aspect, the minute displacement can be accurately detected using the rotation angle of the motor constituting the actuator of the steering device, or can also be accurately detected using the rotation angle of the pinion meshing with the rack as a movable member, or can also be accurately detected using the latest non-contact sensors such as optical displacement sensors. Therefore, the present invention can be put into practical use.

[0278] In a fifth aspect dependent on at least one of the first to fourth aspects, the anomaly detection unit uses a threshold value to determine an anomaly, and defines a first case as a case where only the elastic body is deformed and a second case as a case where both the driving medium and the elastic body, which are expected to deform, deform. In the first case, the threshold value may be set to a stroke value smaller than the stroke value of a minute displacement corresponding to a maximum possible elastic deformation of the movable member, and in the second case, the threshold value may be set to a stroke value larger than the stroke value of a minute displacement corresponding to a maximum possible elastic deformation of the elastic body and smaller than the stroke value of a minute displacement corresponding to a total deformation obtained by adding a possible normal deformation of the driving medium when a driving force for anomaly detection is applied to the maximum possible elastic deformation of the elastic body. According to the fifth aspect, by a simple technique of setting an appropriate threshold value and comparing an actual measurement value with the threshold value, it is possible to perform highly reliable anomaly detection without increasing the burden on the anomaly detection unit.

[0279] In a sixth aspect dependent on the fifth aspect, the abnormality detection unit may variably control the threshold value based on at least one of the ambient temperature of the vehicle and the driving history of the vehicle. According to the sixth aspect, the threshold value for determining an abnormality is variably, in other words, adaptively controlled based on at least one of the ambient temperature of the vehicle and the driving history of the vehicle. Therefore, the threshold value for detecting an abnormality can be appropriately fine-tuned according to the ambient temperature and the driving history.

[0280] In a seventh aspect dependent on any one of the first to sixth aspects, the motor control unit and the abnormality detection unit may perform a self-diagnosis process to determine whether or not an abnormality exists when the vehicle is not running. According to the seventh aspect, the self-diagnosis can be performed in advance before the vehicle 10 is in a running state, thereby making it possible to prevent accidents and the like caused by the occurrence of an abnormality from occurring.

[0281] In an eighth aspect dependent on any one of the first to sixth aspects, the motor control unit and the abnormality detection unit may perform a self-diagnosis process to determine whether or not there is an abnormality when the vehicle is stopped with the vehicle start switch on and there is no steering input by the vehicle occupant. According to the eighth aspect, for example, even during an idle stop period while the vehicle is traveling, it is possible to determine an abnormality in advance by self-diagnosis, provided that there is no steering input, and it is possible to prevent accidents or malfunctions caused by movement of movable parts being restricted by rust, icing, etc.

[0282] In a ninth aspect dependent on any one of the first to eighth aspects, the movable member is movable in a first direction and a second direction opposite to the first direction, the elastic body includes a first elastic body deformable in the first direction by contraction deformation and a second elastic body deformable in the second direction by contraction deformation, the motor control unit applies a driving force for abnormality detection to the movable member to perform a first operation to deform the first elastic body in the first direction and a second operation to deform the second elastic body in the second direction, and the abnormality detection unit may determine that an abnormality exists if an abnormality is detected in both a first abnormality determination process corresponding to the first operation and a second abnormality determination process corresponding to the second operation. According to the ninth aspect, abnormalities in the first and second directions are diagnosed separately, and if abnormalities are determined in both the first and second directions, the abnormality detection unit determines that an abnormality exists. The abnormality determination is performed by comprehensively taking into account abnormalities in the first and second directions, thereby reducing the possibility of erroneous determination.

[0283] In a tenth aspect dependent on the ninth aspect, when an abnormality is detected in both the first abnormality determination process and the second abnormality determination process, the control device performs a first re-diagnosis before determining that an abnormality exists, and when the driving force for abnormality detection applied to the movable member during the first abnormality determination process or the second abnormality determination process is set to the first driving force, in the first re-diagnosis, the motor control unit applies a second driving force greater than the first driving force to the movable member and re-executes the first and second abnormality determination processes, and the abnormality detection unit In the first re-diagnosis, if an abnormality is detected in both the first abnormality determination process and the second abnormality determination process, an abnormality is determined to exist. If an abnormality is detected in only one of the first and second abnormality determination processes in the first re-diagnosis, an obstacle is determined to be in contact with the steered wheel in the direction corresponding to the abnormality determination process in which the abnormality was detected, and a countermeasure for the presence of an obstacle is implemented. If no abnormality is detected in either the first abnormality determination process or the second abnormality determination process in the first re-diagnosis, a normal state may be determined. In the tenth aspect, similar to the ninth aspect, abnormalities in the first and second directions are individually diagnosed, and if abnormalities are determined in both the first and second directions, an abnormality is determined to exist. However, in this aspect, to be cautious, an abnormality is not immediately determined to exist, but an additional first re-diagnosis is performed to further reduce the possibility of an erroneous determination. In the first re-diagnosis, the driving force for abnormality detection is increased from the driving force used in the primary determination. Even when the first re-diagnosis is performed with the driving force increased, if an abnormality is determined in each of the first and second directions, as in the primary determination, it is highly likely that an abnormality actually exists, thereby enabling more reliable abnormality detection. Furthermore, if no abnormality is found in either the first or second direction in the first re-diagnosis, it may be determined to be normal. Furthermore, if the first re-diagnosis is performed with the driving force increased and one of the first and second directions is determined to be normal, and the other is determined to be abnormal, it is highly likely that an abnormality due to rust, icing, or the like has not occurred, since one of the first and second directions is normal. It may be inferred that the abnormality determination in the other direction is due to another event, i.e., the presence of an obstacle such as a curb in contact with the steered wheels, in other words, the wheels of the vehicle.Therefore, if the driving force is increased and the first self-diagnosis determines that an abnormality is detected in only one of the first and second directions, it is determined that there is no abnormality due to rust, icing, etc., but that the displacement of the steered wheels is being hindered by an obstacle such as a curb, and appropriate countermeasures are taken, such as a process of notifying the driver, etc. of the presence of a curb, etc. In this way, according to this aspect, by adding the first re-diagnosis, it is possible to clearly distinguish and detect abnormalities that are the original detection target due to rust, icing, etc., from apparent abnormalities due to the presence of a curb, etc., and therefore the accuracy of abnormality determination can be improved.

[0284] In an eleventh aspect dependent on any one of the first to eighth aspects, the movable member is movable in a first direction and a second direction opposite to the first direction, the elastic body includes a first elastic body that is deformable in the first direction by contraction deformation and a second elastic body that is deformable in the second direction by contraction deformation, the motor control unit applies a driving force for abnormality detection to the movable member to perform a first operation to deform the first elastic body in the first direction and a second operation to deform the second elastic body in the second direction, and the abnormality detection unit, when an abnormality is detected in either the first abnormality determination process corresponding to the first operation or the second abnormality determination process corresponding to the second operation, performs a second re-diagnosis before determining that an abnormality exists, and In the eleventh aspect, when the driving force for abnormality detection applied to the movable member is the first driving force, in the second re-diagnosis, the motor control unit applies a third driving force greater than the first driving force to the movable member and re-executes the first and second abnormality determination processes, and the abnormality detection unit determines that an abnormality exists if an abnormality is detected in both the first abnormality determination process and the second abnormality determination process in the second re-diagnosis, and if an abnormality is detected in only one of the first and second abnormality determination processes in the first re-diagnosis, it determines that an obstacle exists in contact with the steered wheels in the direction corresponding to the abnormality determination process in which the abnormality was detected and implements a countermeasure process for the presence of an obstacle, and if an abnormality is not detected in both the first abnormality determination process and the second abnormality determination process in the second re-diagnosis, it determines that the normal state is established. However, in this aspect, unlike the tenth aspect, if the primary determination determines that one of the first and second directions is normal and the other direction is abnormal, the second re-diagnosis is performed. In this case, as explained in the ninth aspect, there is a possibility that an obstacle such as a curb is preventing the steered wheels from moving. However, rather than immediately making such a determination, the driving force is increased and the second re-diagnosis is performed as a precaution, thereby reducing the possibility of an erroneous determination.As a result of performing the second re-diagnosis with increased driving force, if an abnormality is determined in only one of the first and second directions, as in the primary determination, it is highly likely that an obstacle such as a curb is present. In this case, it is determined that an obstacle such as a curb is present, and appropriate corrective action is taken. Furthermore, if an abnormality is detected in both directions in the second re-diagnosis performed with increased driving force, it is highly likely that an abnormality due to rust, icing, or the like is occurring, and therefore it is determined that an abnormality is present. Furthermore, if the second re-diagnosis determines that there is no abnormality in either the first or second direction, it is determined that the vehicle is normal. Thus, according to this aspect, by adding the second re-diagnosis, it is possible to clearly distinguish and detect abnormalities that are the original detection target due to rust, icing, or the like from apparent abnormalities due to the presence of a curb, or the like. In particular, the accuracy of determining the presence of a curb, or the like is improved, thereby further improving the accuracy of abnormality determination.

[0285] In a twelfth aspect dependent on any one of the first to eighth aspects, the movable member is movable in a first direction and a second direction opposite to the first direction, the elastic body includes a first elastic body that is deformable in the first direction by contraction deformation and a second elastic body that is deformable in the second direction by contraction deformation, the motor control unit applies a driving force for abnormality detection to the movable member to perform a first operation to deform the first elastic body in the first direction and a second operation to deform the second elastic body in the second direction, and the abnormality detection unit performs a first abnormality determination process corresponding to the first operation and a second abnormality determination process corresponding to the second operation. In a twelfth aspect, when a first normal determination state is reached in which no abnormality is detected in either the first abnormality determination process corresponding to the first operation or the second abnormality determination process corresponding to the second operation, but a second normal determination state is reached in which a normal determination is made as a result of re-diagnosis, the controller 100 may further determine whether the deviation of the stroke value obtained based on the actual measured values ​​of the physical quantity corresponding to the minute displacement in each of the first and second directions or the actual measured values ​​of the minute displacement itself is excessively large beyond a normal range, and if the deviation is determined to be excessive, the controller 100 may determine that an abnormality exists. In other words, in this embodiment, it is determined whether the friction deviation estimated from the minute displacement in each of the first and second directions, i.e., the friction deviation in each of the first and second directions, is within a predetermined allowable range, in other words, a normal range, or in other words, whether it is in a situation where it exceeds the normal range and is determined to be excessive.That is, even if the primary diagnosis or re-diagnosis indicates that no abnormality exists, if there is a difference between the stroke amount of the first minute displacement in the first direction and the stroke amount of the second minute displacement in the second direction, and if the difference in the stroke amounts exceeds a preset tolerance or normal range, i.e., if the friction deviation exceeds the normal range and is excessive, it can be estimated that there is a high possibility that the movable member serving as the steering shaft is experiencing a restriction in movement in at least one of the first and second directions, even if it may be minor, due to the influence of rust, icing, or the like. Therefore, in this aspect, in such cases, it is determined that an abnormality has occurred, as a matter of caution. This makes it possible to further reduce the possibility of an erroneous diagnosis.

[0286] In a thirteenth aspect dependent on any one of the first to twelfth aspects, the rotary-to-linear motion conversion mechanism is a ball screw mechanism, and the ball screw mechanism includes a ball nut, an inner race portion provided in the ball nut, an outer race portion provided within a housing, and a ball bearing having a plurality of balls disposed between the inner race portion and the outer race portion. When one axial end of the movable member of the outer race portion is defined as a first end face and the other axial end face is defined as a second end face, an elastic body that elastically supports the ball bearing relative to the housing may be provided on at least one of the first end face and the second end face. In this aspect, the rotary-to-linear motion conversion mechanism uses a ball screw mechanism that is versatile, has very little friction loss, and has high energy conversion efficiency. This can enhance the practicality of a steering device to which the present invention is applied, for example.

[0287] In a fourteenth aspect dependent on any one of the first to thirteenth aspects, the transmission mechanism that transmits the driving force generated by the rotation of the motor to the rotary-to-linear motion conversion mechanism is a reduction mechanism that is provided between the motor and the ball screw mechanism and includes an input pulley on the motor side, an output pulley on the ball screw mechanism side, and a belt wound between the input pulley and the output pulley, and the driving member that may be deformed may be the belt. In this aspect, a versatile reducer or the like that uses pulleys and a belt is used as the transmission mechanism. This can, for example, enhance the practicality of a steering device to which the present invention is applied.

[0288] In a fifteenth aspect, a steering control device is a steering control device that controls the operation of a steering device that steers steered wheels of a vehicle, and includes: a movable member that is attached to a vehicle and is connected to the steered wheels to steer the steered wheels; a housing that covers at least a part of the movable member and is fixed to the body of the vehicle; a motor that applies a steering force to the movable member; a rotary-to-linear motion conversion mechanism that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits the linear motion to the movable member; an elastic body that is provided between the rotary-to-linear motion conversion mechanism and the housing and elastically supports the rotary-to-linear motion conversion mechanism with respect to the housing; or a drive medium and elastic body that are likely to deform and are included in a transmission mechanism that is provided between the motor and the rotary-to-linear motion conversion mechanism and transmits driving force generated by rotation of the motor to the rotary-to-linear motion conversion mechanism, and and a second process of measuring a minute displacement of the movable member corresponding to the deformation of the elastic body or the total deformation of the driving medium and the elastic body during the period when the driving force for abnormality detection is applied to the movable member, thereby obtaining an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that an abnormality exists if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement occurring when no abnormality exists. According to this aspect, a steering control device can be provided that can quickly detect an abnormality in the steering device based on the minute displacement.

[0289] In a sixteenth aspect, a method for detecting an abnormality in a steering device includes a movable member attached to a vehicle and connected to the steered wheels to steer the steered wheels, a housing covering at least a portion of the movable member and fixed to a body of the vehicle, a motor applying a steering force to the movable member, a rotary-to-linear motion conversion mechanism provided within the housing to convert rotational motion transmitted from the motor into linear motion and transmit the linear motion to the movable member, and an elastic body provided between the rotary-to-linear motion conversion mechanism and the housing to elastically support the rotary-to-linear motion conversion mechanism with respect to the housing, or a driving medium and an elastic body which may be deformed and which are included in a transmission mechanism provided between the motor and the rotary-to-linear motion conversion mechanism and which transmits driving force generated by rotation of the motor to the rotary-to-linear motion conversion mechanism, and a second step of measuring a minute displacement of the movable member corresponding to the deformation of the elastic body or the total deformation of the driving medium and the elastic body that are expected to deform while the driving force for abnormality detection is being applied to the movable member, thereby obtaining an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that an abnormality exists if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when no abnormality exists.

[0290] In a seventeenth aspect, the program is a program that causes a computer to operate as the steering control device of the fifteenth aspect. According to this aspect, it is possible to provide a program that enables a steering control device to be easily constructed using a computer.

[0291] The present invention is not limited to the above-described embodiments, and various modifications and applications are possible. For example, various materials can be used for the elastic body and the driving medium such as the belt in the transmission mechanism. Furthermore, various configurations of the rotary-linear motion conversion mechanism and transmission mechanism other than those described in the embodiments can be used.

[0292] As long as the functions and effects of the present invention are exhibited, the present invention is not limited to the examples.

[0293] The present invention is useful as a steering device for a four-wheeled vehicle, for example.

[0294] DESCRIPTION OF SYMBOLS 2: Rotation angle sensor 5: Motor (steering actuator) 10: Vehicle 24: Motor body 25: Motor output shaft 26: Movable member (steering shaft) 29: Knuckle arm 31: Steering wheel (wheel) 44: Transmission mechanism (reduction gear, etc.) 50: Housing 51: First housing 52: Second housing 53: Storage chamber 55: First end face 57: Second end face 58: Inner peripheral surface 61: Input pulley 62: Output pulley 63: Driving medium (belt) 70: Rotation-to-linear motion conversion mechanism (ball screw) 71: Threaded portion 72: Ball 73: Nut 74: Bearing (rolling bearing) 74a: Outer peripheral surface of bearing 74b: Outer ring of bearing 75: Support portion (annular support portion) 80: Elastic body 90: Collar 113: Housing 200: Steering system 300: Steering operation input device 301: Steering wheel 302: Steering shaft 303: Operation angle sensor 304: Operation torque sensor 305: Reaction motor (reaction actuator) 403: Motor control unit 405: Self-diagnosis possibility determination unit 406: Motor history accumulation unit 407: Abnormality detection drive command issuing unit 409: Abnormality detection unit 411: Abnormality determination unit 413: Threshold setting unit 415: Threshold determination unit 417: Temperature sensor 500: Steering control device (control device) 501: Control unit 503: Memory 505: Program 509: Pinion 510: Rotation angle sensor 511: Non-contact sensor (non-contact displacement sensor, optical displacement sensor) 513: Marking 515: Light emitting unit 517: Light receiving unit 600: Various sensors 601: ECU (Electronic Control Unit) 603: Notification unit 610: Worm wheel 620: Worm 622: Shaft portion 630: First bearing 640: Second bearing 650: Joint 653: Bush (elastic member) 700: Steering device 700A: Elastic body (first worm damper) 700B: Elastic body (second worm damper) 800: Steering device DR1: First direction (e.g., left direction)DR2: Second direction (for example, rightward) Abn: Movement obstructions such as rust or ice

Claims

1. A steering device attached to a vehicle for steering the steerable wheels of the vehicle, comprising: a movable member connected to the steerable wheels to turn the wheels; a housing covering at least a portion of the movable member and fixed to the body of the vehicle; a motor for applying a steering force to the movable member; a rotary-to-linear motion conversion mechanism provided within the housing for converting rotational motion transmitted from the motor into linear motion and transmitting the linear motion to the movable member; an elastic body provided between the rotary-to-linear motion conversion mechanism and the housing for elastically supporting the rotary-to-linear motion conversion mechanism with respect to the housing; and a control device which, in response to the establishment of a condition that triggers operation confirmation or a predetermined condition, outputs a first control signal to the motor to move the rotary-to-linear motion conversion mechanism relative to the movable member beyond the amount of displacement elastically supported by the elastic body, obtains a physical quantity related to the amount of movement of the movable member caused by the first control signal, determines whether or not there is an abnormality based on the physical quantity related to the amount of movement of the movable member, and outputs an abnormality determination signal if an abnormality is determined.

2. The steering device has a first configuration having only the elastic body as a component that causes temporary, reversible deformation during the period when the abnormality detection drive command as the first control signal is given to the motor, or a second configuration having, in addition to the elastic body, a drive medium that is expected to deform and is included in a transmission mechanism that is provided between the motor and the rotary-to-linear motion conversion mechanism and transmits the drive force generated by the rotation of the motor to the rotary-to-linear motion conversion mechanism, the control device comprises: a motor control unit that controls the motor; and an abnormality detection unit that detects an abnormality that restricts the normal movement of the movable member, and when the abnormality is detected, the motor control unit gives the abnormality detection drive command as the first control signal to the motor, thereby generating an abnormality detection drive force that cannot move the movable member against the frictional force acting on the movable member but that can cause deformation in the elastic body, or the drive medium that is expected to deform and the elastic body, and applies the abnormality detection drive force to the movable member, and the abnormality detection unit 2. The steering device according to claim 1, wherein a minute displacement of the movable member corresponding to a temporary and reversible deformation of the elastic body that occurs during a period in which the driving force for abnormality detection is applied to the movable member, or a total deformation of the driving medium and the elastic body for which the deformation is expected, is measured, and an actual measurement value of the physical quantity corresponding to the minute displacement is obtained, and an abnormality is determined to exist if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when the abnormality is not present.

3. A steering device as described in claim 2, wherein the deformation of the elastic body occurring during the period when the driving force for abnormality detection is applied to the movable member is the maximum elastic deformation that the elastic body can deform, or the total deformation of the driving medium and the elastic body that can be expected to temporarily occur during the period when the driving force for abnormality detection is applied to the movable member is the total deformation obtained by adding the maximum elastic deformation that the elastic body can deform to the normal deformation that can be expected of the driving medium when the driving force for abnormality detection is being applied.

4. A steering device as described in claim 2, wherein the actual measured value of the physical quantity corresponding to the minute displacement is at least one of the detected value of the rotation angle of the motor, the detected value of the rotation angle of a pinion that meshes with the rack as the movable member, and the detected value obtained by detecting the displacement of the rack as the movable member with a non-contact sensor.

5. The steering device of claim 2, wherein the abnormality detection unit performs a judgment using a threshold value when judging the abnormality, and wherein a first case is a case where only the elastic body is deformed, and a second case is a case where both the driving medium and the elastic body, for which the deformation is expected, are deformed, in the first case, the threshold value is set to a stroke value smaller than the stroke value of the minute displacement corresponding to the maximum possible elastic deformation of the movable member, and in the second case, the threshold value is set to a stroke value larger than the stroke value of the minute displacement corresponding to the maximum possible elastic deformation of the elastic body and smaller than the stroke value of the minute displacement corresponding to the total deformation obtained by adding the maximum possible elastic deformation of the elastic body to the expected normal deformation of the driving medium when the driving force for abnormality detection is generated.

6. A steering device according to claim 5, wherein the abnormality detection unit variably controls the threshold value based on at least one of the ambient temperature of the vehicle and the driving history of the vehicle.

7. The steering device according to claim 2, wherein the motor control unit and the abnormality detection unit perform a self-diagnosis process to determine whether or not an abnormality exists when the vehicle is not running.

8. A steering device according to claim 2, wherein the motor control unit and the abnormality detection unit perform a self-diagnosis process to determine whether or not an abnormality exists when the vehicle is stopped with the vehicle start switch turned on and there is no steering operation input by an occupant of the vehicle.

9. A steering device as described in claim 2, wherein the movable member is movable in a first direction and a second direction opposite to the first direction, the elastic body includes a first elastic body that is deformable in the first direction by contraction deformation and a second elastic body that is deformable in the second direction by contraction deformation, the motor control unit applies the driving force for abnormality detection to the movable member to perform a first operation that deforms the first elastic body in the first direction and a second operation that deforms the second elastic body in the second direction, and the abnormality detection unit determines that an abnormality exists when an abnormality is detected in both a first abnormality determination process corresponding to the first operation and a second abnormality determination process corresponding to the second operation.

10. When an abnormality is detected in both the first abnormality determination process and the second abnormality determination process, the control device performs a first re-diagnosis before determining that an abnormality exists; when the driving force for abnormality detection applied to the movable member during the first abnormality determination process or the second abnormality determination process is used as the first driving force, in the first re-diagnosis, the motor control unit applies a second driving force greater than the first driving force to the movable member and re-executes the first and second abnormality determination processes; the abnormality detection unit determines that an abnormality exists if an abnormality is detected in both the first abnormality determination process and the second abnormality determination process during the first re-diagnosis; when an abnormality is detected in only one of the first and second abnormality determination processes during the first re-diagnosis, it determines that an obstacle exists in contact with the steered wheel in the direction corresponding to the abnormality determination process in which the abnormality was detected, and implements countermeasure processing in the case of the presence of an obstacle; The steering device according to claim 9, wherein, in the first re-diagnosis, if no abnormality is detected in both the first abnormality determination process and the second abnormality determination process, the steering device is determined to be normal.

11. The movable member is movable in a first direction and a second direction opposite to the first direction, and the elastic body includes a first elastic body that is deformable in the first direction by contraction deformation and a second elastic body that is deformable in the second direction by contraction deformation, and the motor control unit applies the driving force for abnormality detection to the movable member to perform a first operation to deform the first elastic body in the first direction and a second operation to deform the second elastic body in the second direction, and the abnormality detection unit performs a second re-diagnosis before determining that there is an abnormality when an abnormality is detected in either a first abnormality determination process corresponding to the first operation or a second abnormality determination process corresponding to the second operation, and when the driving force for abnormality detection applied to the movable member during the first abnormality determination process or the second abnormality determination process is used as a first driving force, in the second re-diagnosis, the motor control unit 3. The steering device according to claim 2, wherein a third driving force greater than the first driving force is applied to the movable member to re-execute the first and second abnormality determination processes, and the abnormality detection unit: determines that an abnormality exists if an abnormality is detected in both the first abnormality determination process and the second abnormality determination process in the second re-diagnosis; determines that an obstacle exists in contact with the steered wheels in the direction corresponding to the abnormality determination process in which the abnormality was detected in the first re-diagnosis, and implements a countermeasure process for when an obstacle exists; and determines that the steering device is normal if no abnormality is detected in both the first abnormality determination process and the second abnormality determination process in the second re-diagnosis.

12. The movable member is movable in a first direction and a second direction opposite to the first direction, and the elastic body includes a first elastic body that is deformable in the first direction by contraction deformation and a second elastic body that is deformable in the second direction by contraction deformation, and the motor control unit applies the driving force for abnormality detection to the movable member to perform a first operation that deforms the first elastic body in the first direction and a second operation that deforms the second elastic body in the second direction, and the abnormality detection unit: when no abnormality is detected in either the first abnormality determination process corresponding to the first operation or the second abnormality determination process corresponding to the second operation and a first normal determination state is reached in which the device can be determined to be normal, or when an abnormality is detected in at least one of the first abnormality determination process corresponding to the first operation and the second abnormality determination process corresponding to the second operation and a second normal determination state is reached in which the device can be determined to be normal as a result of performing re-diagnosis, 3. The steering device according to claim 2, further comprising: a determination as to whether or not a deviation of a stroke value obtained based on an actual measurement value of a physical quantity corresponding to the minute displacement in each of the first and second directions or an actual measurement value of the minute displacement itself is excessive beyond a normal range of deviation; and if it is determined that the deviation is excessive, it is determined that an abnormality exists.

13. A steering device as described in claim 2, wherein the rotary-linear motion conversion mechanism is a ball screw mechanism, the ball screw mechanism having: a ball nut; an inner race portion provided on the ball nut; an outer race portion provided within the housing; and a ball bearing having a plurality of balls provided between the inner race portion and the outer race portion; and wherein, when one side of the outer race portion in the axial direction of the movable member of the outer race portion is defined as a first end face and the other side opposite to the first end face is defined as a second end face, the elastic body that elastically supports the ball bearing relative to the housing is provided on at least one of the first end face and the second end face.

14. A steering device as described in claim 2, wherein the transmission mechanism that transmits the driving force generated by the rotation of the motor to the rotary-to-linear motion conversion mechanism is a reduction mechanism that is provided between the motor and the ball screw mechanism and is composed of an input pulley on the motor side, an output pulley on the ball screw mechanism side, and a belt wound between the input pulley and the output pulley, and the driving member that may be expected to deform is the belt.

15. A steering control device for controlling the operation of a steering device that steers the steerable wheels of a vehicle, comprising: a movable member that is attached to a vehicle and connected to the steerable wheels to steer the steerable wheels; a housing that covers at least a part of the movable member and is fixed to the body of the vehicle; a motor that applies a steering force to the movable member; a rotary-to-linear motion conversion mechanism that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits the linear motion to the movable member; an elastic body that is provided between the rotary-to-linear motion conversion mechanism and the housing and elastically supports the rotary-to-linear motion conversion mechanism with respect to the housing; or a driving medium that may be deformed and the elastic body that is provided between the motor and the rotary-to-linear motion conversion mechanism and is included in a transmission mechanism that transmits driving force generated by rotation of the motor to the rotary-to-linear motion conversion mechanism, the steering control device carrying out an abnormality detection process that detects an abnormality in which normal movement of the movable member is restricted, the abnormality detection process comprising: a first process of generating an abnormality detection driving command to the motor, thereby generating an abnormality detection driving force that cannot move the movable member against the frictional force acting on the movable member but can cause temporary and reversible deformation in the elastic body, or in the driving medium and the elastic body whose deformation is expected, and applying the abnormality detection driving force to the movable member; and a second process of measuring a minute displacement of the movable member corresponding to the deformation of the elastic body during a period in which the abnormality detection driving force is applied to the movable member, or the total deformation of the driving medium and the elastic body whose deformation is expected, to obtain an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that there is an abnormality if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when there is no abnormality.

16. A method for detecting an abnormality in a steering device that steers the steered wheels of a vehicle, the method comprising: a movable member that is attached to a vehicle and connected to the steered wheels to steer the steered wheels; a housing that covers at least a part of the movable member and is fixed to the body of the vehicle; a motor that applies a steering force to the movable member; a rotary-to-linear motion conversion mechanism that is provided within the housing and converts rotational motion transmitted from the motor into linear motion and transmits the linear motion to the movable member; an elastic body that is provided between the rotary-to-linear motion conversion mechanism and the housing and elastically supports the rotary-to-linear motion conversion mechanism with respect to the housing; or a driving medium that may be deformed and the elastic body that are provided between the motor and the rotary-to-linear motion conversion mechanism and are included in a transmission mechanism that transmits driving force generated by rotation of the motor to the rotary-to-linear motion conversion mechanism, a first step of providing an abnormality detection drive command to the motor, thereby generating an abnormality detection drive force that cannot move the movable member against the frictional force acting on the movable member but that can cause temporary and reversible deformation in the elastic body, or in the driving medium and the elastic body whose deformation is expected, and applying the abnormality detection drive force to the movable member; and a second step of measuring a minute displacement of the movable member that corresponds to the deformation of the elastic body or the total deformation of the driving medium and the elastic body whose deformation is expected, which is temporarily generated during the period that the abnormality detection drive force is applied to the movable member, to obtain an actual measurement value of a physical quantity corresponding to the minute displacement, and determining that an abnormality exists if a first stroke amount corresponding to the minute displacement indicated by the actual measurement value is smaller than a second stroke amount corresponding to a normal minute displacement that occurs when there is no abnormality.

17. A program that causes a computer to operate as the steering control device according to claim 15.

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