JP4442400B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a steering system provided in a vehicle, and more particularly to detection of an abnormality in a steering system.

A general vehicle steering system at present has a motor in a steering device that steers wheels, and the operation force applied to a steering operation member (such as a steering wheel) is assisted by the driving force of the motor. In the state, the system is a so-called power steering system in which the wheels are steered. At present, a system that steers wheels according to the steering operation by controlling the driving force of the motor provided in the steering device, regardless of the operating force applied to the steering operation member, so-called steer. A by-wire type steering system has been studied. As a steer-by-wire type steering system, for example, there is a technique described in the following patent document.
JP 2001-26277 A JP 2000-52955 A

  Regardless of the power steering system or the steer-by-wire system, the steering device includes a motor and a mechanism for transmitting the driving force of the motor as the steering force. It is desirable to accurately detect an abnormality in the steering device. In particular, in the steer-by-wire system, the steering operation is performed in a state where the steering operation member and the steered device are mechanically separated from each other. Therefore, it is highly important to detect an abnormality in the steered device. . In the technique described in Patent Document 2, abnormality detection of the steering device is performed based on the operation amount of the steering operation member. However, the steering system is divided into an operation device provided with a steering operation member and a steering device that steers the wheel, and an abnormality occurs in the steering device in detection based on the operation amount of the steering operation member. It is difficult to determine whether or not there is an abnormality in the operating device. Therefore, it is difficult to say that the abnormality detection of the steering device based on the operation amount of the steering operation member is sufficiently accurate. The problem listed here is only an example, but it is considered that the practicality of the steering system can be improved by making various improvements and improvements regarding abnormality detection. This invention is made | formed in view of such a situation, and makes it a subject to provide a highly practical steering system.

In order to solve the above problems, a vehicle steering system according to the present invention is a steer-by-wire steering system,
A steering operation member;
An operation angle sensor for detecting an operation angle of the steering operation member;
(A) A steering rod that is provided so as to reciprocate in the vehicle width direction and steers the wheel, (B) a motor, and (C) a driving force of the motor is transmitted as a reciprocating motion force of the steering rod. A steering mechanism comprising: a transmission mechanism; (D) a motor operation amount detector that detects the operation amount of the motor; and (E) a steering amount detector that detects a steering amount of a wheel;
(i) At the start of the vehicle, based on the turning amount detected by the turning amount detector, a motor operating amount corresponding to the turning amount is detected by the motor operating amount detector at that time. (Ii) determining a target turning amount based on the operation angle of the steering operation member detected by the operation angle sensor, and corresponding to the target turning amount. By using the motor operation amount as a target motor operation amount, the steering operation is performed by feedback-controlling the motor so that a deviation of the actual motor operation amount detected by the motor operation amount detector with respect to the target motor operation amount is reduced. A control device that performs steering of the wheel according to the operation of the member;
An actual turning state amount detector that detects an actual turning state amount that indicates an actual turning state of the vehicle that relies on the actual wheel turning amount;
Assuming that the actual turning state amount detector and the motor operation amount detector are normal, (a) a theoretical vehicle estimated based on the motor operation amount detected by the motor operation amount detector. Based on the first theoretical turning state quantity indicating the turning state and the actual turning state quantity detected by the actual turning state quantity detector, a difference between the first theoretical turning state quantity and the actual turning state quantity is set. When the steering threshold is exceeded, it is detected that the steering device is abnormal, and (b) the theoretical vehicle estimated based on the steering amount detected by the steering amount detector. When the second theoretical turning state quantity indicating the turning state is estimated and the second theoretical turning state quantity does not match the actual turning state quantity, the turning amount detector is abnormal in the turning device. And the second theoretical turning state quantity and actual turning When the state quantity and the match, the turning device abnormality detection apparatus in which the transmission mechanism in the turning device is recognized as abnormal
It is comprised so that it may comprise.

Since the motor of the steered device is a drive source for the steered device, according to the present invention, an abnormality is detected based on the operation amount of the drive source and the actual steered amount. Therefore, for example, since it is possible to detect the abnormality of the operation device and the like, it is possible to accurately recognize the abnormality of the steering device. Further, it is possible to recognize which of the transmission mechanism and the steering amount detector is abnormal with respect to the abnormality of the steering device. By having such advantages, the vehicle steering system of the present invention becomes a practical steering system.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”, a concept including the present invention) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

In the following paragraphs, (1), (2), (6), (7), (8) are combined, and the specific configuration of the steering device, control of the steering system, What added the limitation regarding abnormality detection of a steering device is equivalent to Claim 1, and what combined (3) term and (4) term is Claim 2, and (5) is Claim 3. , (7) corresponds to claim 4, and (9) corresponds to claim 4 .

(1) A vehicle steering system including a steering device that includes a motor and performs a steering operation of a wheel according to a steering operation,
The steering device has a motor operation amount detector that detects an operation amount of the motor,
The vehicle steering system is
An actual turning state amount detector that detects an actual turning state amount that indicates the actual turning state of the vehicle that depends on the actual wheel turning amount;
A theoretical turning state amount that indicates a theoretical turning state of the vehicle estimated based on the motor operation amount detected by the motor operation amount detector, and an actual turning state detected by the actual turning state amount detector A steering system for a vehicle, comprising: a steering device abnormality detection device that detects abnormality of the steering device based on a quantity.

  In the aspect described in this section, abnormality detection is performed based on the operation amount of the motor included in the steering device. Since the motor functions as a drive source in the steered device, an abnormality may occur in the steered device based on the drive amount of the drive source and the actual turning state amount determined depending on the actual steered amount of the wheels. Therefore, the steering system according to this aspect can accurately detect an abnormality in the steering device. Due to such advantages, according to the aspect of this section, a practical steering system is realized.

  The steering system to which the aspect of this section is applied is a system that assists the operation force applied to the steering operation member by the driving force of the motor included in the steering device, that is, a so-called power steering system. There may also be a system that controls the driving force of the motor provided in the steering device, regardless of the operating force applied to the steering operation member, and steers the wheels according to the steering operation, that is, so-called A steer-by-wire steering system may be used. In the steer-by-wire type steering system, the steering operation is performed in a state where the steering operation member and the steered device are mechanically separated from each other, so that the necessity of detecting an abnormality of the steered device becomes higher. . In view of this point, it is more desirable that the aspect of this section is applied to a steer-by-wire type steering system. In view of this, the following description will focus on the steer-by-wire type steering system.

  The configuration of the steering system to which this aspect can be applied is not particularly limited, and the aspect of this section is a known configuration as long as it includes a detector for detecting the motor operation amount of the steered device. Widely applicable to any system. The configuration of the “steering device” is not limited. For example, a housing, a so-called steered rod held in the housing so as to be capable of reciprocating in the vehicle width direction, the motor supported by the housing, and the driving force of the motor are transmitted as the reciprocating motion force of the steered rod. What is necessary is just to be comprised including a transmission mechanism. More specifically, for example, by forming a rack on the steering rod and arranging a pinion that meshes with the rack, the rack and pinion mechanism is adopted as the transmission mechanism, and the pinion is rotated by the motor. It can also be a steered device that performs a steered operation, and also a ball screw is screwed to the steered rod, a bearing ball is held and a nut that is screwed to the ball screw is disposed, A ball screw mechanism can be adopted as a transmission mechanism, and a turning device that performs a turning operation by rotating a nut by a motor can be provided.

  The “motor operation amount” referred to in this section means, for example, a motor rotation amount (rotation angle) or the like. Specifically, for example, in the case of a motor with a speed reducer starting with the amount of rotation of the main shaft (rotating shaft) of the motor, various operating amounts up to the transmission mechanism, such as the amount of rotation of the output shaft, etc. It can be thought of as a working amount. Further, the motor operation amount is, for example, a value representing an operation position based on the neutral operation position corresponding to the neutral position of the wheel (the steered position where the vehicle is in a straight traveling state), that is, an absolute operation amount. For example, it may be a value representing a displacement from an operating position at an arbitrary time to an operating position at another arbitrary time, that is, a relative operating amount.

  The specific structure of the “motor operation amount detector” for detecting the motor operation amount is not particularly limited. For example, various structures such as an encoder, a resolver, a synchro, and a potentiometer can be adopted. . The motor operation amount detector may be, for example, an absolute type detector that can measure the rotational angle position of the motor, and an incremental type detector that can measure how much the rotational angle has changed. There may be.

  In addition, the amount of wheel turning in this section means a value indicating what kind of turning state the wheel is, for example, the turning angle of the wheel, the moving position of the turning rod, etc. To do. Further, the “turning state quantity” means a parameter indicating what turning state the vehicle is in. Specifically, for example, there are various lateral accelerations generated in the vehicle body (hereinafter may be abbreviated as “lateral G”), lateral force received by the vehicle, cornering force, vehicle slip angle, vehicle yaw rate, etc. Can be adopted. The “actual turning state quantity” is the actual turning state quantity of the vehicle, and the “actual turning state quantity detector” that detects the actual turning state quantity is a known appropriate sensor according to the type of turning state quantity employed, and If necessary, it may be configured to include means for converting the detected value of the sensor into the turning state quantity employed by calculation. In view of the fact that detection and estimation are relatively easy and that many of the current vehicles are equipped with a lateral G sensor, a lateral G sensor is adopted as a turning state quantity detector, and the lateral G is set as a turning state quantity. It is desirable to adopt. The “theoretical turning state amount” is estimated based on the motor operation amount. For example, if a certain motor operation amount, the wheel has a certain turning amount, and if a certain turning amount, a certain turning amount. It means the amount of turning state estimated based on the process of becoming a state. Specifically, for example, it may be estimated based on a map in which turning state amounts corresponding to various turning amounts are stored, and a calculation indicating a relationship between these turning amounts and turning state amounts. It may be estimated based on an expression.

  The “steering device abnormality detection device” in this section is a device capable of detecting an abnormality based on the actual turning state amount and the theoretical turning state amount as described above. More specifically, for example, by comparing the turning state that should be natural when the motor has a certain operation amount with the actual turning state, the operation amount of the motor and the actual turning amount of the wheel match. It is possible to make a device that detects whether or not the steering device is abnormal based on the recognition. The detected “abnormality of the steering device” is not particularly limited in the type of abnormality, and the steering device abnormality detection device in the aspect of this section is, for example, a motor driving force as described later. It can also be configured to detect abnormalities in the transmission mechanism, i.e., abnormalities that occur in the mechanical structure, and sensor abnormalities such as motor operation amount detectors and steering amount detectors can be detected. It can also be configured to detect. Note that the steering device abnormality detection device is a device that executes processing centered on processing such as calculation and parameter comparison, and therefore can be a computer-based device.

  (2) When the steering device abnormality detecting device determines that the difference between the theoretical turning state amount and the actual turning state amount exceeds a set threshold amount, the turning device is determined to be abnormal, The vehicle steering system according to item (1), which detects an abnormality.

  As explained above, when the steering device is operating normally, the theoretical turning state quantity and the actual turning state quantity are basically the same, or there is a large difference even if there is a disturbance or the like. Must not. The mode described in this section is a mode in which an abnormality is detected using this. The threshold amount is preferably set to an appropriate value in consideration of, for example, a deviation between a theoretical turning state amount and an actual turning state amount that can normally occur due to a disturbance or the like.

  (3) The steering device abnormality detection device includes a theoretical turning state amount estimation unit that estimates a theoretical turning state amount based on the motor operation amount detected by the motor operation amount detector. The steering system for a vehicle according to the item.

  The mode described in this section is a mode in which the turning device abnormality detection device estimates the theoretical turning state amount by itself.

  (4) The theoretical turning state amount estimation unit estimates the theoretical turning state amount based on the motor operation amount detected by the motor operation amount detector and the vehicle traveling speed. Vehicle steering system.

  The turning state can generally be determined by two parameters, the amount of steering and the vehicle traveling speed. Based on these two parameters, it is possible to estimate the theoretical turning state amount relatively accurately.

  (5) Any of the items (1) to (4), wherein the steering device abnormality detection device is configured not to detect the abnormality of the steering device when there is a large factor that varies the amount of turning state. A vehicle steering system according to claim 1.

  When the vehicle is turning, a slip occurs due to wheel slip. When the running speed of the vehicle is high, the side slip becomes large when the turning amount is large, etc., and when the road surface μ is small, the side slip of the vehicle becomes large, and an accurate theoretical turning state amount can be estimated. It becomes difficult. That is, these “the vehicle traveling speed becomes excessive” and the like are factors that cause the amount of turning state to fluctuate. The mode of this section is a mode that takes this into consideration, and is a mode of determining whether or not the abnormality detection process is performed by determining the magnitude of the turning state amount variation factor. Specifically, for example, an aspect in which detection is not performed when the vehicle traveling speed exceeds a set speed, and when the motor operation amount represents an operation amount from the neutral operation position, the operation amount is present. A mode in which detection is not performed when the threshold amount is exceeded, a mode in which detection is not performed when the road surface μ is smaller than a set value based on road surface μ information obtained from a brake system, or the like, or It can be set as various aspects, such as an aspect which combined those plurality.

  (6) The steering device abnormality detection device includes a driving force transmission mechanism abnormality detection unit that detects an abnormality of the driving force transmission mechanism of the motor in the steering device as an abnormality of the steering device. Item 6. The vehicle steering system according to any one of Items (5) to (5).

  The mode described in this section is a mode for detecting an abnormality caused by a malfunction or failure of a mechanical part of the steering device, specifically, a mechanical force transmission mechanism in the steering device. According to the aspect described in this section, in the case where it can be determined that the motor operation amount detector is functioning normally, for example, any improper fixing of any component constituting the transmission mechanism (for example, looseness), It is possible to detect an abnormality or the like caused by a relative positional shift between the constituent elements, a breakage of one of the constituent elements, or the like.

  (7) The turning device has a turning amount detector that detects a turning amount of a wheel, and the turning device abnormality detection device is abnormal in either the transmission mechanism or the turning amount detector. The steering system for a vehicle according to item (6), which has an abnormal part recognition unit that recognizes whether or not.

  On the other hand, the convenience and reliability of steering control can be improved by providing a plurality of detectors in the steering device. Therefore, it is conceivable to provide a turning amount detector that directly detects the turning amount of the wheel. In such a case, when the motor operation amount and the turning amount detected by the turning amount detector do not match, it is possible to determine which of the turning amount detector and the transmission mechanism is abnormal. It is a difficult situation. The mode of this section is an effective mode in such a case. For example, when the process of matching the motor operation amount and the turning amount detected by the turning amount detector is executed, the theoretical turning state amount acquired after that and the actual turning state amount do not match Then, a second theoretical turning state quantity, which is another theoretical turning state quantity, is estimated based on the turning quantity detected by the turning quantity detection device, and the second theoretical turning state quantity and the actual turning state quantity are estimated. Can be recognized as abnormal when the steering amount detector is abnormal. Further, even when the second theoretical turning state quantity and the actual turning state quantity coincide with each other, when the theoretical turning state quantity based on the motor operation amount and the actual turning state quantity do not coincide with each other, the transmission mechanism is It can be recognized as abnormal. The specific structure of the “steering amount detector” for detecting the amount of steering is not particularly limited. It is desirable to detect the moving position of the steered rod directly or indirectly. For example, inductosin, magnescale or the like can be used as a direct detection, and as an indirect one, for example, a rack is formed on the steered rod and a pinion that meshes with it is provided ( It is possible to adopt a structure in which the rotation amount of the pinion is detected by an encoder, resolver, or the like.

  (8) The vehicle steering system controls the motor of the steering device to steer the wheels according to the operation of the steering operation member, regardless of the steering force applied to the steering operation member. The vehicle steering system according to any one of (1) to (7), which is a system.

  The mode described in this section is a mode as a so-called steer-by-wire type steering system. As described above, in the steer-by-wire system, the steering operation member and the steered device are separated from each other. Therefore, it is significant to detect an abnormality of the steered device.

(9) The vehicle steering system includes an operation force transmission device that enables transmission of the operation force applied to the steering operation member to the steering device,
When the turning device abnormality detection device detects an abnormality of the turning device, the operation force-based turning realizing unit that controls the operation force transmission device and enables the wheel to be turned by the operation force. The vehicle steering system according to item (8).

  The operating force transmission device in this section is a device that enables a turning operation by the operating force applied to the steering operation member. For example, a situation where the power supply to the motor is cut off, or the control device has failed. When such a situation occurs, it becomes a means to demonstrate effectiveness. The aspect of this section enables appropriate steering using such a device when an abnormality of the steering apparatus is detected. According to the aspect of this section, high reliability is achieved. A steer-by-wire type steering system will be realized.

(Application to power steering system)
In the power steering system, the mechanical connection between the steering operation member and the steering device is maintained, and the operation amount of the steering operation member and the steering amount of the wheel are basically matched. However, in the power steering system, since the operation force is assisted by the driving force of the motor provided in the steering device, the operation amount and the steering amount do not match in a transitional state of the steering operation. . For example, when there is an abnormality in the transmission mechanism from the motor, the steering amount does not sufficiently follow the operation amount because the appropriate assist force cannot be obtained, etc. A situation such as a delay occurs. Therefore, it is possible to detect an abnormality in the steering device by monitoring the relationship between the theoretical turning state quantity and the actual turning state quantity in a transient state of the steering operation. Specifically, for example, when the delay in the change in the actual turning state amount with respect to the change in the theoretical turning state amount exceeds the set value, it is determined that the transmission mechanism is abnormal and is detected. Can do. By adopting such an aspect, even in a power steering system, the system can recognize its own abnormality.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition to the following examples, the present invention is implemented in various modes including various modes modified and improved based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. be able to.

  FIG. 1 schematically shows a vehicle steering system according to an embodiment. In this system, the operation unit 10 and the steering unit 12 are mechanically separated, and the power of the power source provided in the steering unit 12 is not dependent on the operation force applied to the steering wheel 14 as a steering operation member. Is a steering system that steers a steered wheel (hereinafter sometimes simply referred to as “wheel”) 16. Moreover, this system is provided with the connection part 18 which mechanically connects the operation part 10 and the steering part 12 as needed, when abnormality generate | occur | produces. Therefore, for example, when the power source of the steered portion 12 cannot be used, the operating force is transmitted to the steered portion 12 by the connecting portion 18, and the wheels are steered by the operating force applied to the steering wheel 14. Have been able to do.

  The operation unit 10 is provided with a steering wheel 14 and a steering operation device (hereinafter sometimes simply referred to as “operation device”) 20 that supports the steering wheel 14 so as to be operable. The operating device 20 is a device to which a steering operation is input, and a main shaft 30 having a steering wheel 14 attached to a rear end portion that is an end portion on the vehicle rear side, that is, a driver side, and the main shaft 30 can be rotated. A spring reaction force mechanism 32 that applies an operation reaction force toward the neutral position to the steering wheel 14 by a spring, and an operation angle sensor 34 for obtaining an operation angle that is an operation amount of the steering wheel 14. A reaction force motor 36 that applies an operation reaction force to the steering wheel 14 by applying a driving force to the main shaft 30 is provided.

  The connecting portion 18 determines whether or not the connection between the output shaft 38 that outputs the operating force to the steered portion 12 and the presence or absence of transmission of the operating force between the main shaft 30 and the output shaft 38 is switched. And an electromagnetic clutch 40 for switching. The electromagnetic clutch 40 connects the main shaft 30 and the output shaft 38 in a demagnetized state where power is not supplied, and releases the connection in an excited state. The output shaft 38 is connected to the operating force input shaft 54 of the steered portion 12 via the universal joint 50 and the intermediate shaft 52, and outputs the operating force to the steered portion 12. With such a configuration, the connecting portion 18 functions as an operating force transmission device.

  The turning unit 12 is provided with a turning device 60 that performs a turning operation, that is, turns the wheels 16. The steered device 60 includes a housing 62 and a steered rod 64 supported while penetrating the housing 62 in the vehicle width direction. The steered rod 64 is connected to a tie rod 68 via a ball joint 66 at both ends. The tie rod 68 is connected to a knuckle arm 74 fixed to a steering knuckle 72 that rotatably holds the wheel 16 via another ball joint 70. The steered device 60 turns the steering knuckle 72 by driving the steered rod 64 to the left and right to steer the wheels 16.

  In FIG. 2, the cross section seen from the bottom of the steering apparatus 60 is shown. In the present embodiment, the steering device 60 includes a first drive unit 84 that drives the steered rod 64 by two steered motors (hereinafter simply referred to as “motors”) 80 and 82, and an operating force. And a second drive part 86 for driving the steered rod 64. The second drive unit 86 includes a pinion gear 90 that is integrally connected to the operation force input shaft 54, and a rack gear 92 that is formed on the steered rod 64 so as to mesh with the pinion gear 90. By the function of the connecting portion 18 described above, the pinion gear 90 is rotated by the steering force when the electromagnetic clutch 40 is in a demagnetized state (connected state), but the electromagnetic clutch 40 is in an excited state (non-connected state). If it is, it cannot be rotated by operating force. That is, when the electromagnetic clutch 40 is in a demagnetized state, the pinion gear 90 is rotated by the operating force of the steering operation to drive the steered rod 64 in the axial direction, but the electromagnetic clutch 40 is in the excited state. If so, the pinion gear 90 is rotated in accordance with the turning operation of the turning rod 64, that is, the axial movement. In addition, since the steering is performed by the first drive unit 84 at normal times, the electromagnetic clutch 40 is in an excited state, and the operation force is not transmitted to the second drive unit 86.

  The turning device 60 is provided with a turning amount sensor 94 that is a sensor for acquiring the rotational position of the pinion gear 90. Since the pinion gear 90 is rotated as the steered rod 64 moves in the axial direction, the movement amount of the steered rod 64, that is, the steered amount is obtained by obtaining the rotational position of the pinion gear 90. Can be done. That is, the steering amount sensor 94 has a function as a steering amount detector.

  The first drive unit 84 has two steering motors 80, 82, that is, a right steering motor (left motor in the figure) 80, a left steering motor (right motor in the figure) 82, and a housing 62. A motor shaft 96 that is rotatably supported by the two steering motors 80 and 82, and a ball screw mechanism 98 that moves the steering rod 64 in the axial direction by the rotation of the motor shaft 96. I have. The two steered motors 80 and 82 are arranged side by side in the axial direction of the steered rod 64. Each of the two steered motors 80 and 82 includes a stator coil 100 fixed to the inner peripheral surface of the housing 62 and a permanent magnet 102 fixed to the outer peripheral portion of the motor shaft 96. . The motor shaft 96 has a hollow shape, and penetrates the hollow portion in a state in which the steered rod 64 can be relatively moved. The ball screw mechanism 98 is formed on a ball nut 110 fixed to one end portion of the motor shaft 96 so as not to be relatively rotatable and a steered rod 64 that is screwed through a bearing ball 112 held by the ball nut 110. And a ball screw 114. The ball screw mechanism 98 converts the rotation of the motor shaft 96 (specifically, a ball nut) into movement of the steered rod 64 in the axial direction, thereby converting the driving force of the two steered motors 80 and 82 into the steered force. It functions as a mechanism for converting to a motor, that is, a motor driving force transmission mechanism (hereinafter also referred to as “driving force transmission mechanism”).

  Further, the steering device 60 is provided with a motor rotation angle sensor 120 for acquiring the rotation angle of the motor shaft 96 on the right side (left side in the drawing) of the right steering motor 80. The motor rotation angle sensor 120 detects the rotation angle of the pulse rotor that rotates together with the motor shaft 96 by an electromagnetic pickup. That is, the motor rotation angle is a motor operation amount, and the motor rotation angle sensor 120 has a function as a motor operation amount detector.

  FIG. 3 shows an enlarged view of the ball screw mechanism 98. A stepped holding portion 130 is formed on the inner periphery of one end of the motor shaft 96, and the above-described ball nut 110 is held in the holding portion 130 so as not to be relatively rotatable. A female screw 132 is formed in the opening of the holding portion 130, and a lock ring 136 having a male screw 134 formed on the outer periphery thereof is screwed into the female screw 132, whereby the ball nut 110 moves in the axial direction with respect to the motor shaft 96. The structure is prohibited (see FIG. 3A). A through hole 138 is formed at the center of the lock ring 136, and the steered rod 64 is disposed so as to be movable in the axial direction through the through hole 138.

  This steering system is controlled by a steering electronic control unit 200 (steering ECU, hereinafter simply referred to as ECU) 200 provided in the steering system. As shown in the functional blocks in FIG. 4, the ECU 200 includes a drive circuit such as various motors and various devices, with a computer 202 as a main component. The computer 202 includes an input / output interface 203. The input / output interface 203 includes an operation angle sensor 34, a motor rotation angle sensor 120, a turning amount sensor 94, a wheel speed sensor 204, and a lateral acceleration sensor as an actual turning state amount detector. (It is shown as a lateral G sensor in the figure. Hereinafter, it may be referred to as a lateral G sensor in the text.) Various sensors such as 206 are connected. The input / output interface 203 is connected to an indicator 210 (provided on the instrument panel, see FIG. 1) for displaying various information to the driver. Further, the reaction force motor 36, the two steered motors 80 and 82, the electromagnetic clutch 40, and the like are connected to the input / output interface 203 through the respective drive circuits 212. The storage unit of the computer 202 of the ECU 200 stores various programs such as a steering control program and an abnormality detection program, various data used for control, and the like.

  In terms of functions, the ECU 200 includes a steering control unit 220 that performs steering of the wheels 16 according to a steering operation (also performs control of an operation reaction force by the reaction force motor 36 and the like). Specifically, the steering control unit 220 determines the target turning amount from the operation angle acquired based on the detection signal of the operation angle sensor 34, and sets the motor rotation angle corresponding to the target turning amount to the target motor. As the rotation angle, the motors 80 and 82 are feedback-controlled so that the deviation between the actual motor rotation angle detected by the motor rotation angle sensor and the target motor rotation angle is reduced, and the wheel 16 is steered according to the steering operation. Do. That is, in this system, the steering operation is controlled using the motor rotation angle as the control value of the steering device 60. Note that the steering control unit 220 normally performs control to maintain the disconnected state between the operation unit 10 and the steering unit 12 by supplying excitation power to the electromagnetic clutch 40.

  The ECU 200 further includes a theoretical turning state amount estimation unit 222 that estimates the theoretical lateral acceleration based on the motor rotation angle or the turning amount, an abnormality detection unit 224 that detects an abnormality of the turning device 60, and a side slip of the vehicle. In the case where the factor causing the lateral G to fluctuate (a kind of variation factor of the turning state amount) is large, the fluctuation factor dependence detection prohibiting unit 226 that prohibits the abnormality detection processing described later and the abnormality detecting unit 224 When it is detected that an abnormality has occurred in the rudder device 60, an operation force-based steering realizing unit 228 is provided for realizing the steering control by the steering operation force of the driver. More specifically, the anomaly detection unit 224 includes the theoretical lateral G (which is a kind of theoretical turning state quantity) estimated by the above-described theoretical turning state quantity estimation unit 222 and the actual lateral G (actual side) acquired by the lateral G sensor 206. The driving force transmission mechanism abnormality detection unit 230 that detects that an abnormality has occurred in the turning device 60 by comparing the amount of rotation state) and the turning device 60 when an abnormality is detected. By comparing the second theoretical lateral G and the actual lateral G estimated based on the steering amount detected by the steering amount sensor 94, an abnormality occurs in either the ball screw mechanism 98 or the steering amount sensor 206. And an abnormal point recognition unit 232 for certifying whether or not

  If the abnormality detection process executed by the ECU 200 is further described, for example, even if the motors 80 and 82 are rotated by a predetermined rotation angle in order to steer the wheels by a target turning amount according to the steering operation of the driver, When the actual turning amount does not match the target turning amount, the theoretical lateral G estimated based on the motor rotation angle and the actual lateral G detected by the lateral G sensor 206 do not coincide. In such a case, the abnormality detection processing in this system recognizes that an abnormality has occurred in the steering device 60 on the assumption that the motor rotation angle sensor 120 is normal, and further performs the turning by the turning amount sensor 94. By estimating the second theoretical lateral acceleration based on the amount and the vehicle speed, a process for identifying which of the ball screw mechanism 98 and the turning amount sensor 94 is abnormal is performed.

  In the present embodiment, in order to simplify the description, the description will be made by limiting to a specific phenomenon as an abnormality of the ball screw mechanism 98. The phenomenon is the loosening of the lock ring 136 described above. As shown in FIG. 3 (b), when the lock ring 136 is loosened in the ball screw mechanism 98, the ball nut 110 is movable in the axial direction with respect to the motor shaft 96. This is a state in which a so-called play has occurred. Even if the steered motors 80 and 82 are rotated in this state, the ball nut 110 moves in the axial direction while rotating together with the motor shaft 96, and the axial movement of the steered rod 64 is delayed or requested. A situation occurs in which the expected amount of turning cannot be obtained because the amount of movement differs from the actual amount of movement. Further, even when the steered motors 80 and 82 are stopped, the steered rod 64 may move due to the movement of the ball nut 110 corresponding to the looseness, and the steered angle of the wheels 16 may change. . As described above, when an abnormality occurs in the ball screw mechanism 98 as the driving force transmission mechanism, the theoretical lateral G does not coincide with the actual lateral G. Even in this state, if the actual turning amount is accurately detected by the turning amount sensor 94, the second theoretical lateral G coincides with the actual lateral G.

  On the other hand, even when there is an abnormality in the steering amount sensor 94 included in the steering device 60, the system is in a state where appropriate steering control cannot be performed. The steered amount sensor 94 is used in alignment processing (so-called calibration) when the ignition key is inserted and turned on. In the alignment process, the reaction force motor 36 is driven to rotate the steering wheel 14 so that the operation angle matches the turning amount detected by the turning amount sensor 94, and the detected turning amount is set. Based on this, the value of the motor rotation angle corresponding to the turning amount is set as the motor rotation angle at that time. Therefore, when an abnormality has occurred in the turning amount sensor 94, the neutral position of the wheel 16 is shifted from the neutral position of the steering wheel 14, and the neutral position of the wheel and the neutral operation position of the motors 80 and 82 are determined. This causes a problem such as slippage. Here, in order to simplify the description, in this embodiment, the abnormality of the steering amount sensor 94 is specified as an abnormality that causes such a shift in the neutral position. In this system, such an abnormality of the steering amount sensor 94 is monitored by the system itself by executing an abnormality detection process. Specifically, if an abnormality has occurred in the turning amount sensor 94, even if the ball screw mechanism 98 is normal and the rotation amounts of the turning motors 80 and 82 are transmitted as accurate turning amounts, The theoretical lateral G and the second theoretical lateral G are not in agreement with the actual lateral acceleration. In this system, such a phenomenon is monitored to perform a process for detecting an abnormality of the steering amount sensor 94.

  Next, the abnormality detection process will be specifically described. The abnormality detection process is performed by the ECU 200 repeatedly executing the abnormality detection program with a short time interval (for example, 50 msec). FIG. 5 shows a flowchart of the abnormality detection program, and the abnormality detection process will be described along the flowchart. As described above, the steering device 60 and the like are controlled by the steering control program. The steering control program operates the steering device 60 and the like when an abnormality is detected in the steering device 60. The program performs a process of changing the aspect.

  First, in step S1 (hereinafter simply referred to as S1. The same applies to other steps), the motor rotation angle θ that is the operation amount of the motors 80 and 82 is detected. More specifically, the value detected by the motor rotation angle sensor 120 is acquired as the motor rotation angle θ. Incidentally, the motor rotation angle θ is a value representing the operating position of the motors 80 and 82 from the neutral operating position aligned by the alignment process (calibration process) described above, and the absolute operating position is 0. Get as value.

  Next, at S2, it is determined whether or not the vehicle is in a steered state in which the steering angle of the vehicle is maintained for a certain period. The motor rotation angle θ detected by the previous execution of this program is stored for a set time (for example, 0.3 sec), and in this embodiment, the amount of change in the motor rotation angle θ within the set time is previously stored. When it is smaller than the set value, it is determined that the steering is maintained. If the motor rotation angle θ has changed by more than the set value, the vehicle is not in the steered state, so the determination in S2 is NO and one execution of this program ends. When the vehicle is not in the steering holding state, it is a transient state of steering, and the estimated lateral G and the actual lateral G do not match due to a delay in the behavior of the vehicle with respect to the steering operation. It is supposed not to do. On the other hand, if the vehicle is in the steering-holding state, the determination in S2 is YES, and the process proceeds to S3, where the abnormality detection process is performed. In this program, the steering state is determined based on the detection value of the motor rotation angle sensor 120, but the target motor rotation angle is obtained based on the operation angle of the steering wheel 14 in the steering control program. Based on the change state of the target motor rotation angle, it is also possible to determine whether or not the vehicle is in the steered state. It is also possible to determine whether or not the steering wheel 14 is in a state of being held based on the change in the operation angle of the steering wheel 14. Furthermore, in this embodiment, the steered state is determined every time the program is executed. However, the steered state may be determined at each set time.

In the subsequent S3, the vehicle traveling speed (hereinafter may be abbreviated as “vehicle speed”) V is detected. In the present embodiment, a wheel speed sensor 204 is provided for each of the four wheels 16, and an average value of the four wheel speeds detected by the wheel speed sensors 204 is acquired as the vehicle speed V. Next, in S4, whether or not the vehicle speed V is greater than the set speed V ₀ is determined. When the vehicle speed V is higher than the set speed V _0, there is a high possibility that an excessive side slip of the vehicle will occur and the estimated lateral G cannot be accurately estimated. It is a treatment. That is, in this case, the determination in S4 is NO, and one execution of this program ends. On the other hand, if the vehicle speed V is less than or equal to the set speed V ₀ , the determination in S4 is YES and the process proceeds to S5.

In S5, the theoretical lateral acceleration Gy ₁ is estimated based on the previously obtained motor rotation angle θ and vehicle speed V. In the ECU 200, data indicating the relationship between the motor rotation angle θ and the lateral G that should be generated for each vehicle speed V is stored as map data in consideration of the characteristics unique to the vehicle as shown in FIG. For example, when the vehicle speed is V ₁ , the relationship between the motor rotation angle θ and the lateral G is a relationship like a straight line indicating V ₁ . In the figure, the cases of V ₁ , V ₂ and V ₃ are illustrated in order from the lowest speed. The lateral acceleration estimated based on this map data is acquired as the theoretical lateral acceleration Gy ₁ .

Next, in S6, the actual lateral acceleration Gy ₀ is detected. Specifically, the detection value detected by the lateral G sensor 206 is acquired as the actual lateral acceleration Gy ₀ . Then the process proceeds to S7, the theoretical lateral acceleration Gy ₁ and the actual lateral acceleration Gy ₀ and the threshold amount ΔGy whether the difference is less than the absolute value is set which is set in advance of the difference is determined. The threshold amount ΔGy is a value that considers detection errors and the like. When the difference is smaller than the threshold amount ΔGy, that is, when it is determined that the theoretical lateral acceleration Gy ₁ and the actual lateral acceleration Gy ₀ substantially coincide with each other, it is recognized that there is no abnormality in the steering device 60. . That is, the determination in S7 is YES, and one execution of this program ends. On the other hand, if the difference between the theoretical lateral acceleration Gy ₁ and the actual lateral acceleration Gy ₀ is greater than or equal to the threshold amount ΔGy, the determination in S7 is NO, and the process proceeds to S8 and later.

In S8, the turning amount δ of the wheel 16 is detected. Specifically, the detection value detected by the turning amount sensor 94 is acquired as the turning amount δ. In subsequent S9, on the basis of its steering amount δ and the vehicle speed V, the second theoretical lateral acceleration Gy ₂ is estimated. More specifically, map data similar to the map data shown in FIG. 6 is stored in advance for the steering amount δ, the vehicle speed V, and the lateral G, and the second theoretical lateral acceleration Gy ₂ is estimated based on the map data. The

In the next S10, the absolute value whether or not the setting value ΔGy smaller than the difference between the second theoretical lateral acceleration Gy ₂ and the actual lateral acceleration Gy ₀ is determined. The set value ΔGy may be the same value as the value used in S7 or may be set to a different value. That is, if it is determined that the second theoretical lateral acceleration Gy ₂ and the actual lateral acceleration Gy ₀ substantially match, the determination in S10 is YES. In this case, although abnormality in the steering device 60 has occurred, by a second theoretical lateral acceleration Gy ₂ and the actual lateral acceleration Gy ₀ is substantially coincident, the detection value of the turning amount sensor 94 It can be considered that the actual steered amount is accurately reflected, and it is determined in S11 that an abnormality has occurred in the ball screw mechanism 98, that is, the driving force transmission mechanism. If an abnormality has occurred in the ball screw mechanism 98, a notification process for notifying the driver of the fact is executed in S12. Specifically, an instruction for performing an abnormal display to that effect is output to the indicator 210.

On the other hand, if the difference between the second theoretical lateral acceleration Gy ₂ and the actual lateral acceleration Gy ₀ exceeds the set value ΔGy, the determination in S10 is NO. As described above, if neither the theoretical lateral acceleration Gy ₁ nor the second theoretical lateral acceleration Gy ₂ is substantially equal to the actual lateral acceleration Gy ₀ , the steering amount sensor 94 is abnormal. Think. Therefore, in that case, it progresses to S13, it is recognized that abnormality has arisen in the steering amount sensor 94, and the alerting | reporting process for alert | reporting that to a driver | operator is subsequently performed in S14. Specifically, as in the previous notification process, an instruction for performing an abnormal display to that effect is output to the indicator 210.

  Regardless of whether the process proceeds to S12 or S14, the process proceeds to S15 and the operation force steering is switched. Specifically, supply of current to the steering motors 80 and 82 and the reaction force motor 36 is prohibited, and the electromagnetic clutch 40 is brought into a non-excited state so that the operation unit 10 and the steering unit 12 are connected. Thus, the wheel can be steered by the operation force of the steering operation performed on the steering wheel 14. This completes one execution of the program.

  As is apparent from the above description, in the present embodiment, the theoretical turning state quantity estimating unit 222 is configured to include the portions that execute S5 and S9 among the portions that execute the abnormality detection program of the ECU 200. In addition, the driving force transmission mechanism abnormality detection unit 230 is configured including the part that executes S7, and the abnormal part recognition unit 232 is configured including the part that executes S10, S11, and S13, and thereby, abnormality detection is performed. Part 224 is configured. Further, the variation factor dependence detection prohibiting unit 226 is configured to include the part that executes S4, and the operation force-based steering realizing unit 228 is configured to include the part that executes S15. Then, the turning device abnormality detection device is configured including the theoretical turning state amount estimation unit 222, the abnormality detection unit 224, the variation factor dependence detection prohibition unit 226, and the operation force dependence steering realization unit 228. It is.

  According to the system of the present embodiment, the abnormality of the steering device 60 can be detected accurately. In addition, when an abnormality is detected, a highly reliable steer-by-wire type steering system is realized by switching to steering by operating force. As described above, the case where the present invention is applied to the steer-by-wire type steering system has been described. However, even in a so-called power steering system, the system can recognize its own abnormality based on the theoretical lateral acceleration and the actual lateral acceleration. It is.

1 is a diagram conceptually showing a steering system that is one embodiment of the present invention. FIG. It is sectional drawing which shows the steering apparatus with which the steering system shown in FIG. It is a figure which expands and shows the ball screw mechanism which the steering apparatus shown in FIG. 2 has. It is a functional block diagram for demonstrating the control apparatus of the steering system shown in FIG. It is a flowchart of the abnormality detection program performed by the control apparatus shown in FIG. It is a chart which shows typically map data for estimating theoretical lateral acceleration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Operation part 12: Steering part 14: Steering wheel (steering operation member) 16: Wheel 18: Connection part 20: Operation apparatus 60: Steering apparatus 80, 82: Steering motor 84: 1st drive part 86: 1st Second drive unit 94: Steering amount sensor (steering amount detector) 98: Ball screw mechanism (driving force transmission mechanism) 120: Motor rotation angle sensor (motor operation amount detector) 200: Steering electronic control unit (ECU) ( 204: Wheel speed sensor 206: Lateral G sensor (actual turning state amount detector) 220: Steering control unit 222: Theoretical turning state amount estimation unit 224: Abnormality detection unit 226: Detection of variation factor Prohibition unit 228: Operation force-based steering realization unit 230: Driving force transmission mechanism abnormality detection unit 232: Abnormal point recognition unit

Claims (4)

A steering operation member;
An operation angle sensor for detecting an operation angle of the steering operation member;
(A) A steering rod that is provided so as to reciprocate in the vehicle width direction and steers the wheel, (B) a motor , and (C) a driving force of the motor is transmitted as a reciprocating motion force of the steering rod A steering mechanism comprising: a transmission mechanism; (D) a motor operation amount detector that detects an operation amount of the motor ; and (E) a steering amount detector that detects a steering amount of a wheel ;
(i) At the start of the vehicle, based on the turning amount detected by the turning amount detector, a motor operating amount corresponding to the turning amount is detected by the motor operating amount detector at that time. (Ii) determining a target turning amount based on the operation angle of the steering operation member detected by the operation angle sensor, and corresponding to the target turning amount. By using the motor operation amount as a target motor operation amount, the steering operation is performed by feedback-controlling the motor so that the deviation of the actual motor operation amount detected by the motor operation amount detector with respect to the target motor operation amount is reduced. A control device that performs steering of the wheel according to the operation of the member;
An actual turning state amount detector that detects an actual turning state amount that indicates the actual turning state of the vehicle that depends on the actual wheel turning amount;
Assuming that the actual turning state amount detector and the motor operation amount detector are normal, (a) a theoretical vehicle estimated based on the motor operation amount detected by the motor operation amount detector. a first theoretical turning state quantity that indicates a turning state, a difference between the-out based on the actual turning state quantity detected by the actual turning state quantity detector, they first theoretical turning state quantity and the actual turning state quantity When the set threshold is exceeded, it is detected that the turning device is abnormal, and (b) a theoretical value that is estimated based on the turning amount detected by the turning amount detector. When the second theoretical turning state quantity indicating the turning state of the vehicle is estimated and the second theoretical turning state quantity does not match the actual turning state quantity, the turning amount detector is abnormal in the turning device. The second theoretical turning state quantity and actual turning When the quantity of state and matches, steer-by-wire type steering system of a vehicle equipped with a steering device abnormality detection apparatus in which the transmission mechanism in the turning device is recognized as abnormal. The steering device abnormality detection device,
The first theoretical turning state amount is estimated based on the motor operation amount detected by the motor operation amount detector and the vehicle travel speed, and the turning amount vehicle travel speed detected by the steering amount detector 2. The vehicle steering system according to claim 1, further comprising a theoretical turning state quantity estimating unit that estimates the second theoretical turning state quantity based on 3. The vehicle steering system according to claim 1, wherein the steering device abnormality detection device is configured not to detect abnormality of the steering device when a factor that varies the amount of turning state is large. . Steering system for that vehicle, an operation force transmission device capable of transmitting to the steering device of the operation force said applied to the steering operation member,
When the turning device abnormality detection device detects an abnormality of the turning device, the operation force-based turning realizing unit that controls the operation force transmission device and enables the wheel to be turned by the operation force. The vehicle steering system according to any one of claims 1 to 3, further comprising:

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