JP6084587B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering system.

  According to Patent Document 1, a method for diagnosing a failure of a rudder angle sensor that is an absolute angle sensor in an EPS (Electronic Power Steering) system in which a steering shaft and a steered shaft are mechanically connected is specifically described. Describes a failure diagnosis method related to the steering angle sensor 17 (see the summary of Patent Document 1, claims 1 to 5).

Japanese Patent Laid-Open No. 2002-104211

  However, Patent Document 1 discloses a failure diagnosis method relating to a steering angle sensor that is an absolute angle sensor in a SBW (Steer By Wire) system, specifically, a steering angle sensor and a steering angle sensor. Is not disclosed.

  Therefore, an object of the present invention is to provide a vehicle steering system capable of diagnosing a steering angle sensor failure in an SBW system.

  One aspect of the present invention is a steering unit having a steering reaction force actuator that applies a steering reaction force to a steering member that is operated when steering a steered wheel of a vehicle, and detects a steering angle related to the steering member. A steering angle detection unit that performs the steering wheel and a steering actuator that applies a steering force to steer the steered wheel, and the steered wheel can be steered in a state of being mechanically separated from the steering unit. A steering unit, a steering angle detection unit that detects a steering angle related to the steered wheel, and a state in which the steering unit and the steering unit are mechanically connected or disconnected are performed. A clutch device having a switching actuator; a control unit that performs drive control of the steered actuator so that an actual steered angle of the steered wheel follows at least a target steered angle calculated based on the steered angle; Steering angle detector and the turning angle detector A storage unit that stores information based on a measurement value, and the control unit controls the clutch device to be in a mechanically connected state when the IG is off, and stores information on the steering angle and the turning angle. In addition to storing in the storage unit, at the next start-up, referring to the information stored in the storage unit, it is confirmed whether the relationship between the steering angle stored at the previous end and the turning angle is maintained. When the relationship is not maintained, it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed.

In general, in a steer-by-wire system having a mechanical connection mechanism using a clutch mechanism, the steering wheel and the tire (steered wheels) are mechanically connected immediately after the clutch is engaged and before the clutch is released. . For this reason, it is known that the relationship between the steering wheel angle and the tire angle, for example, the phase angle difference, maintains a predetermined state.
According to the present invention, by utilizing the relationship, the failure diagnosis of these steering angle sensors is performed based on the values sensed from the existing steering angle sensor and the rack stroke sensor. Therefore, it is not particularly necessary to separately provide a sensor for failure diagnosis. Therefore, it is possible to construct a vehicle steering system that has a simple and low-cost function for diagnosing a steering angle sensor failure in an SBW system.

  The control unit executes a mode other than the SBW mode when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed.

  According to such a configuration, when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed, a mode other than the SBW mode is executed. This avoids executing the SBW mode when at least one of the steering angle detection unit and the turning angle detection unit has failed. Thereby, the safety | security of driving | running | working is ensured.

  The steering angle detector and the steered angle detector are absolute angle sensors.

  According to such a configuration, even when the steering angle detection unit and the turning angle detection unit are configured by an absolute angle sensor whose resolution is not relatively higher than that of the relative angle sensor, the failure diagnosis is performed. Can do.

  The vehicle further includes vehicle behavior detection means, and when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed, The steering angle is compared, and it is determined whether or not the steering angle detection unit has failed.

  According to such a configuration, in a vehicle including vehicle behavior detection means, when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed, the failure is detected. It can be determined whether or not it is due to a failure of the turning angle detection unit. Thereby, a more specific failure diagnosis can be performed.

  The information is a phase angle difference that is a difference between phase angles detected by the steering angle detection unit and the turning angle detection unit, respectively.

  According to such a configuration, the amount of information to be stored can be halved as compared with the case where the information of the phase angle detected by the steering angle detection unit and the turning angle detection unit is stored. Therefore, the storage capacity of the storage unit can be reduced, and cost reduction can be achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the steering system for vehicles which can perform the failure diagnosis of the steering angle sensor in a SBW system can be provided.

1 is a schematic configuration diagram of a vehicle steering system according to an embodiment of the present invention. It is a flowchart explaining the SBW system completion | finish process which the failure diagnosis part of the steering system for vehicles which concerns on one Embodiment of this invention performs. It is a flowchart explaining the SBW system starting process which the failure diagnosis part of the steering system for vehicles which concerns on one Embodiment of this invention performs.

Hereinafter, an embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram of a vehicle steering system according to the present embodiment.
The vehicle steering system 11 is a steer-by-wire (SBW) type steering device. The vehicle steering system 11 has a function (SBW mode) for generating a steering force by driving a steering motor 29 described later. In addition, for example, in the case of a system failure such as a failure of the steering reaction force motor 16, an electric power steering (Electronic Power Steering) that generates an assist force for manual steering by the driver by driving the steering motor 29. (EPS) function (EPS mode) is also provided. Furthermore, for example, when the steering reaction force motor 16 and the steering motor 29 fail, a function (manual steering mode) that allows the driver to perform manual steering is also provided.

  In order to realize the above functions, the vehicle steering system 11 includes a steering unit 12, a steering reaction force generating device 15, a steering device 17, a clutch mechanism 19 (coupling mechanism), and a control device as shown in FIG. 40 and so on. The vehicle steering system 11 is mounted on the vehicle V. The vehicle V includes a pair of steered wheels 21a and 21b.

  The steering unit 12 is a device to which an operation input of a handle 13 (steering member) for steering the vehicle V is input. The steering wheel 13 of the steering unit 12 is a member for steering the vehicle V that is operated according to the driver's driving intention. A steering shaft 23 is provided on the handle 13. The steering shaft 23 is configured to rotate around the shaft in accordance with the operation of the handle 13 by the driver.

  The steering reaction force generator 15 has a function of generating a reaction force (response) related to steering, that is, a steering reaction force, at the driver's hand holding the handle 13 when the vehicle steering system 11 is operating in the SBW mode. Have The steering reaction force generator 15 includes a steering reaction force motor 16 (steering reaction force actuator). A steering shaft 23 is connected to the steering reaction force motor 16. The steering reaction force motor 16 generates a steering torque for rotating the steering shaft 23 around the axis. Thereby, when the vehicle steering system 11 is operating in the SBW mode, a reaction force (hand response) related to the steering is transmitted to the hand of the driver who holds the handle 13.

  The steered device (steering gear box) 17 has a function of converting the rotational motion of the steered shaft 25 into linear motion of the rack shaft 27 via a well-known rack and pinion mechanism (not shown). In this rack and pinion mechanism, the rack and the pinion mesh with each other and are housed in the housing of the steering gear box 17. The rack is formed on the rack shaft 27. The steering device 17 has a steering motor 29 (steering actuator). A steered shaft 25 and a rack shaft 27 are connected to the steered motor 29. The turning motor 29 generates a turning torque for causing the rack shaft 27 to linearly move along the axial direction. A pair of steered wheels 21a and 21b are connected to the rack shaft 27 via tie rods (not shown). The pair of steered wheels 21 a and 21 b are steered by the linear motion of the rack shaft 27. The steered shaft 25, the rack shaft 27, the steered device 17, and the like constitute a steered mechanism 51 that steers the steered wheels 21a and 21b.

The clutch mechanism 19 has a function of selectively connecting or disconnecting the steering shaft 23 and the steered shaft 25. In order to realize such a function, the clutch mechanism 19 includes a planetary gear mechanism 31. The planetary gear mechanism 31 includes an internal gear 31a, a planetary gear 31b, a sun gear 31c, and a planet carrier 31d.
The clutch mechanism 19 includes a locking gear 33 and a locking device 35. The lock device 35 includes a lock pin 39 that engages with a tooth groove of the lock gear 33 and an electromagnetic solenoid 37 that drives the lock pin 39.

The internal gear 31 a is fixed to the lower end side of the steering shaft 23 and is configured to rotate integrally with the steering shaft 23. The sun gear 31c is configured to freely rotate around a rotation axis coaxial with the steered shaft 25. A plurality of planetary gears 31b are provided so as to engage with each of the sun gear 31c and the internal gear 31a. Each of the plurality of planetary gears 31b is rotatably supported with respect to a planet carrier 31d that rotates integrally with the steered shaft 25.
The locking gear 33 is an external gear. The locking gear 33 is configured to rotate integrally with the sun gear 31c. The lock pin 39 is urged in a direction approaching the locking gear 33 by an urging means (elastic member) (not shown). When the lock pin 39 is engaged with the tooth groove of the locking gear 33, the rotational movement of the locking gear 33 is restricted.

The electromagnetic solenoid 37 operates to release the engagement between the lock pin 39 and the locking gear 33 by displacing the lock pin 39 by supplying an exciting current.
The lock device 35 operates in accordance with a control signal sent from the control device 40. The control device 40 operates to release the engagement of the lock pin 39 with the lock gear 33 by supplying an excitation current to the electromagnetic solenoid 37.
Next, the operation of the clutch mechanism 19 will be described. When the lock pin 39 engages with the tooth groove of the locking gear 33, the rotational movement of the sun gear 31c that rotates integrally with the locking gear 33 is restricted.

  When the driver operates the handle 13 in a state where the rotational movement of the sun gear 31 c is restricted, the internal gear 31 a rotates as the steering shaft 23 rotates. At this time, since the rotational movement of the sun gear 31c is restricted, the planetary gear 31b revolves around the sun gear 31c while rotating. Due to the revolution of the planetary gear 31b, the planetary carrier 31d that pivotally supports the planetary gear 31b and the turning shaft 25 that rotates integrally with the planetary carrier 31d rotate. The ratio of the rotation angle of the steered shaft 25 to the rotation angle of the steering shaft 23 at this time is mechanically determined in the clutch mechanism 19.

In short, in a state where the electromagnetic solenoid 37 is OFF and the lock pin 39 is engaged with the tooth groove of the locking gear 33, the clutch mechanism 19 is in a connected state in which the steering shaft 23 and the steered shaft 25 are connected. At this time, the rotational force of the steering shaft 23 is transmitted to the steered shaft 25.
On the other hand, when the electromagnetic solenoid 37 is turned on and the engagement of the lock pin 39 with the tooth groove of the lock gear 33 is released, the sun gear 31c that rotates together with the lock gear 33 becomes rotatable. .

When the driver operates the handle 13 with the sun gear 31c being rotatable, the internal gear 31a is rotated with the rotation of the steering shaft 23. At this time, the planetary gear 31b tries to revolve around the sun gear 31c while rotating. However, the steered wheels 21 a and 21 b are connected to the planetary carrier 31 d via the steered shaft 25 and the rack shaft 27. For this reason, the resistance force against the rotation of the planet carrier 31d is much larger than the resistance force against the rotation of the sun gear 31c in a rotatable state. Therefore, when the planetary gear 31b rotates, the sun gear 31c rotates (rotates), and the planet carrier 31d does not rotate. That is, the steered shaft 25 does not rotate.
In short, in a state where the electromagnetic solenoid 37 is turned on and the engagement of the lock pin 39 with the tooth groove of the lock gear 33 is released, the clutch mechanism 19 disconnects between the steering shaft 23 and the steered shaft 25. It will be in the disconnected state. At this time, the rotational force of the steering shaft 23 is not transmitted to the steered shaft 25.

For the convenience of explanation, when “the clutch mechanism 19 is engaged” is described below, the electromagnetic solenoid 37 is OFF and the lock pin 39 is engaged with the tooth groove of the locking gear 33. To do. At this time, the clutch mechanism 19 is in a connected state in which the steering shaft 23 and the steered shaft 25 are connected, and the rotational force of the steering shaft 23 is transmitted to the steered shaft 25.
On the other hand, when “the clutch mechanism 19 is disengaged” is described, the electromagnetic solenoid 37 is ON, and the engagement of the lock pin 39 with the tooth groove of the lock gear 33 is canceled. Shall. At this time, the clutch mechanism 19 is in a disconnected state where the steering shaft 23 and the steered shaft 25 are disconnected, and the rotational force of the steering shaft 23 is not transmitted to the steered shaft 25.

The control device 40 is a control device for controlling the vehicle steering system 11. The control device 40 is configured around a microcomputer.
A steering angle sensor 41, a steering torque sensor 43, a steering reaction force motor resolver 45, a steered motor resolver 47, and a rack stroke sensor 49 are connected to the control device 40 as an input system.
The steering angle sensor 41 and the steering torque sensor 43 are provided on the steering shaft 23. The steering angle sensor 41 detects the steering rotation amount (steering angle) of the handle 13 by the driver, and provides the detected steering angle information to the control device 40.

The steering torque sensor 43 (steering torque information acquisition unit) detects the steering torque of the steering wheel 13 by the driver, and gives information (steering torque information) regarding the detected steering torque to the control device 40.
The steering reaction force motor resolver 45 is provided in the steering reaction force motor 16. The steering reaction force motor resolver 45 detects the rotational operation amount (steering angle) of the steering reaction force motor 16 and supplies the detected steering angle information to the control device 40.

The steered motor resolver 47 is provided in the steered motor 29. The steered motor resolver 47 detects the rotational operation amount (steered angle) of the steered motor 29 and provides the detected steered angle information to the control device 40.
The rack stroke sensor 49 is provided on the rack shaft 27. The rack stroke sensor 49 detects the linear movement amount (steering angle) of the rack shaft 27 and provides the detected turning angle information to the control device 40.
The steering angle sensor 41 for detecting the steering angle of the handle 13 and the rack stroke sensor 49 for detecting the turning angle of the steered wheels 21a and 21b calculated from the linear movement amount of the rack shaft 27 have a relatively high resolution. There is no absolute angle sensor.
On the other hand, the steering reaction force motor resolver 45 and the steered motor resolver 47 are composed of relative angle sensors with higher resolution than the steering angle sensor 41 and the rack stroke sensor 49.
These absolute angle steering angle sensors, specifically, the steering angle sensor 41 and the rack stroke sensor 49, are resolvers that are high-resolution relative angle sensors corresponding to the startup of the SBW system, specifically, the steering reaction sensor. More specifically, for the force motor resolver 45 and the steered motor resolver 47, the steering angle sensor 41 is for the steering reaction force motor resolver 45, and the rack stroke sensor 49 is for the steered motor resolver 47. It serves to notify the target marker (the midpoint of the steering angle or the midpoint of the turning angle) that serves as a sensing reference point.
On the other hand, the control device 40 is connected to the steering reaction force motor 16, the steered motor 29, and the electromagnetic solenoid 37 as an output system.

In addition, the control device 40 can communicate with an ECU 71, an operation unit 73, and the like that control traveling of the vehicle V via a CAN (Controller Area Network) 75.
Here, the ECU 71 may be a power unit that drives the vehicle V, that is, a control device that controls an internal combustion engine or an electric motor mounted on the vehicle V, for example. The ECU 71 can grasp the state of the power unit and notify the control device 40 of this information.

  The operation unit 73 is a lever, a switch, or the like provided in an instrument panel of the vehicle V, for example, and is a device for the driver to manually switch the mode from the EPS mode to the SBW mode.

Next, the contents of control executed by the control device 40 will be described.
The control device 40 includes a failure diagnosis unit 60, a first mode control unit 61, a second mode control unit 62, a mode switching unit 63, and a steering angle storage unit 64.

The failure diagnosis unit 60 in the present embodiment is a diagnosis unit that performs failure diagnosis of the steering angle sensor 41 that is the steering angle sensor of the handle 13 and the rack stroke sensor 49 that is the steering angle sensor of the steered wheels 21a and 21b. .
As a premise that this embodiment is performed, when the SBW system is terminated, for example, when the IG (ignition) of the power unit is turned off, the clutch mechanism 19 is engaged every time, for example, by the ECU 71. It shall be controlled as follows.
On the other hand, when the SBW system is started by turning on the IG of the power unit, for example, the ECU 71 releases the engaged state of the clutch mechanism 19 every time, for example, so as to be in the disengaged state. Shall be controlled.
At this time, the failure diagnosis unit 60, for example, at the time of SBW system termination, the relationship between the steering angle of the handle 13 when the clutch mechanism 19 is engaged and the turning angle of the steered wheels 21a and 21b (for example, the phase angle) The difference (phase angle difference) is stored in the rudder angle storage unit 64. For example, specifically, the value of the steering angle sensor 41, the value of the rack stroke sensor 49, and the calculated value of the phase angle difference that is the difference between the two are stored in the steering angle storage unit 64.
When the SBW system is activated next time, the steering angle of the steering wheel 13 and the steered angles of the steered wheels 21a and 21b are sensed before the clutch mechanism 19 is released. Calculate the relationship (eg, phase angle difference).
Next, the failure diagnosis unit 60 refers to the previous measurement value stored in the rudder angle storage unit 64, and before and after the on / off of the SBW system, both values are calculated, for example, between the calculated phase angle differences. Are substantially coincident with each other. In other words, the sensing values relating to the steering angle of the steering wheel 13 and the turning angles of the steered wheels 21a and 21b are the values before the clutch mechanism 19 is disengaged when the SBW system is started and when the clutch mechanism 19 is immediately before the SBW system is terminated. It is determined whether the same relationship is maintained with the value stored in the engaged state. Here, “substantially coincidence” may be determined, for example, by determining whether or not the difference (or ratio) of the values to be compared is within a predetermined threshold range.
At this time, if it is determined that the two values are substantially the same, the failure diagnosis unit 60 inputs the steering angle sensor 41 and the rack stroke sensor 49 without any failure. The angle information is determined to be a correct value. Then, the failure diagnosis unit 60 sends a command to the mode switching unit 63 so as to transition to the SBW mode.
Further, at this time, if the values cannot be said to be substantially the same, and it is not determined that the values are correct, the failure diagnosis unit 60 selects either the steering angle sensor 41 or the rack stroke sensor 49. Is determined to have failed, and a command is sent to the mode switching unit 63 so as to transition to the failure mode of the rudder angle sensor.
In this determination method, the handle 13 and the steered wheels 21a and 21b are mechanically connected immediately after the clutch mechanism 19 is engaged and before the clutch mechanism 19 is disengaged. For this reason, the relationship (for example, phase angle difference) between the steering angle of the steering wheel 13 and the turning angles of the steered wheels 21a and 21b is performed by utilizing the property of keeping a predetermined state.
The failure diagnosis unit 60 also performs a failure diagnosis related to the engagement of the clutch mechanism 19. When it is determined that the clutch mechanism 19 has failed, the failure mode of the clutch mechanism 19 is executed (details will be described later).

  Next, the first mode control unit 61 controls the SBW mode (first mode). That is, when the first mode control unit 61 receives a command for starting the SBW mode (first mode) from the mode switching unit 63, the first mode control unit 61 turns the clutch mechanism 19 (the electromagnetic solenoid 37 thereof), the steering motor 29, and the reaction force motor 16. Control and execute the SBW mode. That is, when operating the SBW mode, the first mode control unit 61 operates the electromagnetic solenoid 37 to maintain the state where the steering unit 12 side and the steering mechanism 51 side are disconnected by the clutch mechanism 19. Then, the first mode control unit 61 drives the steered motor 29 so that the steered angle according to the operation state of the handle 13 detected by the steering angle sensor 41 is obtained. In other words, the first mode control unit 61 causes the steered motor to cause the actual steered angles of the steered wheels 21a and 21b to follow the target steered angle calculated based on the value sensed by the steering angle sensor 41. 29 drive control is performed. Further, the first mode control unit 61 applies a steering reaction force according to the turning state (detected by the rack stroke sensor 49 (or the turning motor resolver 47)) by the turning mechanism 51 to the handle 13. The steering reaction force motor 16 is driven. Accordingly, the first mode control unit 61 can generate a turning force by driving the turning motor 29.

  The second mode control unit 62 controls a mode other than the SBW mode, for example, an EPS mode (second mode). The second mode is executed in the steering angle sensor failure mode or when the clutch mechanism 19 cannot be released. When the second mode control unit 62 receives an instruction to start the EPS mode (second mode) from the mode switching unit 63, the second mode control unit 62 controls the clutch mechanism 19 (the electromagnetic solenoid 37 thereof), the steered motor 29, and the reaction force motor 16. The EPS mode is executed. That is, the second mode control unit 62 does not drive the electromagnetic solenoid 37, and the steering unit 12 side and the steering mechanism 51 side are connected while the lock pin 39 remains engaged with the locking gear 33. The state (state in which manual steering force is transmitted to the steering mechanism 51) is maintained. The second mode control unit 62 drives at least one of the steering reaction force motor 16 and the steered motor 29 based on the steering torque information detected by the steering torque sensor 43. As a result, the second mode control unit 62 can generate an assist force for manual steering by the driver.

The mode switching unit 63 receives a mode switching command from the failure diagnosis unit 60 and performs mode switching control between the SBW mode by the first mode control unit 61 and the EPS mode by the second mode control unit 62 ( As described above, there is also a manual mode, but the details of the manual mode and the description of switching to the manual mode are omitted). That is, the mode switching unit 63 normally maintains the SBW mode, but performs control to switch from the SBW mode to the EPS mode when a malfunction occurs in the system, such as detection of an abnormality in the steering reaction force motor 16.
By the way, after switching to the EPS mode in this way, the problem of the system may be solved while the EPS mode is operating. In this case, the mode switching unit 63 also controls to return from the EPS mode to the SBW mode.

The steering angle storage unit 64 uses the failure diagnosis unit 60 to determine the relationship between the steering angle of the handle 13 when the clutch mechanism 19 is engaged and the steered angles of the steered wheels 21a and 21b (for example, at the end of the SBW system). This is a storage unit that stores a phase angle difference (phase angle difference). As described above, specifically, for example, the value of the steering angle sensor 41, the value of the rack stroke sensor 49, the calculated value of the phase angle difference that is the difference between the two, and the like can be stored.
Further, at the time of starting the SBW system next time, the relationship value regarding the steering angle of the steering wheel 13 and the steered angle of the steered wheels 21a and 21b stored by the failure diagnosis unit 60 in the steered angle storage unit 64, specifically The previous measurement value, phase angle difference, etc. are referred to for. Thus, as described above, the failure diagnosis unit 60 determines whether or not the values of the both before and after the on / off of the SBW system are substantially the same, for example.
Note that the rudder angle storage unit 64 may store only the value of the phase angle difference calculated based on the values sensed by the failure diagnosis unit 60 from the steering angle sensor 41 and the rack stroke sensor 49. Alternatively, only the values sensed from the steering angle sensor 41 and the rack stroke sensor 49 are stored in the rudder angle storage unit 64, and the phase angle difference is calculated each time the failure diagnosis unit 60 reads data. It is good also as composition to do. In short, it is assumed that the steering angle storage unit 64 stores information on the phase angle difference itself or information that can indirectly calculate the phase angle difference.

Next, a failure diagnosis flow of the steering angle sensor and the rack stroke sensor in the SBW system of the present embodiment will be described with reference to FIGS.
As described above, as a premise for executing this control flow, when the SBW system is terminated due to, for example, turning off the IG (ignition) of the power unit, the clutch mechanism 19 is engaged each time by the ECU 71, for example. It shall be controlled to be in a state.
Further, when the SBW system is started by turning on the IG of the power unit, for example, the ECU 71 is controlled so as to release the engaged state of the clutch mechanism 19 and to be in the disengaged state every time. Shall be.

First, a flowchart illustrating an example of control related to the termination process of the SBW system will be described with reference to FIG.
When the IG is turned off, in step S10, the failure diagnosis unit 60 of the control device 40 determines whether or not the clutch mechanism 19 is engaged. This determination is made using, for example, a sensor (not shown) that detects whether or not the lock pin 39 of the clutch mechanism 19 is engaged with the locking gear 33.
If YES in step S10, that is, if it is determined that the clutch mechanism 19 is engaged, the process proceeds to step S20. On the other hand, if it is determined No in step S10, that is, if it is determined that the clutch mechanism 19 is not engaged, the process proceeds to step S30.

  In step S20, the failure diagnosis unit 60 determines the relationship between the steering angle of the steering wheel 13 and the steered angles of the steered wheels 21a and 21b (for example, the phase angle difference, which is the difference between the phase angles), and the steering angle storage unit 64. To remember. Specifically, the value of the steering angle sensor 41, the value of the rack stroke sensor 49, the phase angle difference calculated therefrom, and the like are stored in the steering angle storage unit 64, and this flow is finished.

  In step S30, the failure diagnosis unit 60 determines that the clutch mechanism 19 has failed because the clutch mechanism 19 that should have been engaged is not engaged. Run the mode. Here, the failure mode of the clutch mechanism 19 may be, for example, informing the driver with a warning lamp or a warning sound (not shown). Thereafter, this flow is terminated.

Next, a flowchart illustrating an example of control related to the activation process of the SBW system will be described with reference to FIG.
In step S100, the failure diagnosis unit 60 of the control device 40 determines whether or not the clutch mechanism 19 is engaged. This determination may be performed in the same manner as in step S10.
In Step S100, if No, that is, if it is determined that the clutch mechanism 19 is not engaged, the process proceeds to Step S150. In addition, when it determines with No by step S10 of FIG. 2, possibility that it will determine with No also in step S100 is high.

  In step S150, the failure diagnosis unit 60 executes the failure mode of the clutch mechanism 19. This may be performed in the same manner as in step S30. Thereafter, this flow is terminated.

  If Yes in step S100, the process proceeds to step S110. In step S110, the failure diagnosis unit 60 senses the steering angle of the steering wheel 13 and the turning angles of the steered wheels 21a and 21b before the engagement state of the clutch mechanism 19 is released. Calculate the relationship (eg, phase angle difference). Further, these values are compared with the previous measured value stored in the rudder angle storage unit 64 or the calculated value (for example, phase angle difference) based thereon.

  Next, in step S120, the failure diagnosis unit 60 determines whether or not both values, for example, the calculated phase angle differences are substantially the same.

  If NO in step S120, that is, if it cannot be said that the value based on the current sensing and the value referenced from the rudder angle storage unit 64 substantially match, the process proceeds to step S140.

  In step S140, the failure diagnosis unit 60 determines that at least one of the steering angle sensor 41 and the rack stroke sensor 49 has failed. Then, a command other than the SBW mode, for example, the EPS mode (second mode) described above, is sent as a failure mode of the rudder angle sensor, and a command is sent to the mode switching unit 63 to end the present flow.

  If YES in step S120, that is, if it can be said that the value based on the current sensing and the value referenced from the rudder angle storage unit 64 substantially match, the process proceeds to step S130. In this case, the failure diagnosis unit 60 determines that both the steering angle sensor 41 and the rack stroke sensor 49 are operating normally.

  Next, in step S130, the failure diagnosis unit 60 sends a command to the mode switching unit 63 in order to execute the SBW mode (first mode), and ends this flow. The clutch mechanism 19 is released from the engaged state at this stage. That is, the steering shaft 23 and the steered shaft 25 are mechanically disconnected, and the rotational force of the steering shaft 23 is not transmitted to the steered shaft 25 (see FIG. 1).

(Action / Effect)
The actions and effects of this embodiment are summarized as follows.
Generally, in the SBW system having the clutch mechanism 19, the handle 13 and the steered wheels 21 a and 21 b are mechanically connected immediately after the clutch mechanism 19 is engaged and before the engagement is released. For this reason, it is known that the relationship (for example, phase angle difference) between the steering angle of the handle 13 and the steered angles of the steered wheels 21a and 21b maintains a predetermined state.

  Therefore, in the embodiment of the present invention, by utilizing this property, the failure diagnosis of these steering angle sensors is performed based on the values sensed from the existing steering angle sensor 41 and the rack stroke sensor 49. Therefore, it is not necessary to provide a separate sensor for failure diagnosis. For this reason, there exists an effect that a simple and low-cost vehicle steering system can be constructed.

Further, when the vehicle V is separately equipped with known vehicle behavior detection means such as a yaw rate sensor, the steering angle sensor that has failed in the process of step S140 is replaced with the steering angle by the following method. It can also be determined whether the sensor 41 or the rack stroke sensor 49.
More specifically, for example, under the forward straight traveling condition where the vehicle speed is equal to or greater than a positive predetermined value and the vehicle behavior amount sensed by the vehicle behavior detection means is near 0, the rack stroke sensor 49 Focus on the sensed steering angle. At this time, when the vehicle behavior amount is compared with the steered angle, and the steered angle obviously outputs a value that is not in a straight traveling state, the rack stroke sensor 49 has failed. It can be determined as a thing.

(Modification)
Furthermore, when the vehicle V is equipped with a known vehicle behavior detection means, the condition for determining the rudder angle sensor is not limited to the straight traveling condition of the forward movement as described above.
Specifically, for example, under the forward right turn traveling condition in which the vehicle speed is a positive positive value or more and the vehicle behavior amount sensed by the vehicle behavior detection means is a value indicating a right turn, the rack stroke Focus on the turning angle sensed by the sensor 49. Then, when the vehicle behavior amount and the turning angle are compared with each other and the turning angle clearly outputs a value that is not right-turning, the rack stroke sensor 49 has failed. Can be determined. However, here, it is assumed that the vehicle is not traveling in a counter steer state.
In addition, for example, under a forward left turn traveling condition where the vehicle speed is a positive positive value or more and the vehicle behavior value is a value indicating a left turn, the turning angle clearly outputs a value that is not a left turn. Even in such a case, it can be determined that the rack stroke sensor 49 has failed. Here, however, it is assumed that the vehicle is not traveling in a counter steer state.
In addition, from the technical point of view, the determination logic is not limited to when moving forward, and can be determined in the same manner when moving backward.

  The above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the described configurations.

  In addition, control lines, information lines, and power supply lines are those that are considered necessary for the description, and not all control lines, information lines, and power supply lines are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  In addition, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and a part or all of the configuration of another embodiment can be added to the configuration of one embodiment. It is.

  In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

Specifically, although the said embodiment demonstrated in the example that the steered wheels 21a and 21b are two wheels, it is not restricted to this. The embodiment of the present invention can be applied without particularly questioning the number of steered wheels.
For example, in a vehicle equipped with a four-wheel steering system such as 4WS, all four wheels are steered. Further, considering the case of a two-wheeled vehicle or a three-wheeled vehicle equipped with the SBW system, the steered wheel is one wheel. Further, in a vehicle having five or more wheels such as a large truck or a trailer, the number of steered wheels may be many accordingly. In these cases, the embodiment of the present invention can be applied in the same manner.

  In addition, it goes without saying that the embodiment of the present invention can be applied regardless of whether the steered wheels 21a and 21b are drive wheels or non-drive wheels of the vehicle V.

DESCRIPTION OF SYMBOLS 11 Vehicle steering system 12 Steering part 13 Handle (steering member)
16 Steering reaction force motor (steering reaction force actuator)
19 Clutch mechanism (clutch device)
29 Steering motor (steering actuator)
37 Electromagnetic solenoid (switching actuator)
40 Control device (control unit)
41 Steering angle sensor (steering angle detector)
43 Steering torque sensor 45 Steering reaction force motor resolver 47 Steering motor resolver 49 Rack stroke sensor (steering angle detector)
51 Steering mechanism (steering part)
60 Failure diagnosis unit 61 First mode control unit 62 Second mode control unit 63 Mode switching unit 64 Steering angle storage unit (storage unit)
71 ECU (control unit)
V Vehicle EPS Electric power steering SBW Steer-by-wire

Claims (5)

A steering unit having a steering reaction force actuator that applies a steering reaction force to a steering member that is operated when steering the steered wheels of the vehicle;
A steering angle detector that detects a steering angle of the steering member;
A steering unit that provides a steering force for steering the steered wheels, and capable of steering the steered wheels in a state of being mechanically separated from the steering unit; and
A turning angle detector for detecting a turning angle associated with the steered wheel;
A clutch device having a switching actuator that performs an operation of bringing the steering unit and the steered unit into a mechanically connected state or a disconnected state;
A control unit that performs drive control of the steered actuator so that an actual steered angle of the steered wheel follows at least a target steered angle calculated based on the steered angle;
A storage unit that stores information based on measurement values of the steering angle detection unit and the turning angle detection unit;
The control unit controls the clutch device to be in a mechanically connected state when the IG is off, stores information on the steering angle and the turning angle in the storage unit, and stores the information in the storage unit at the next startup. With reference to the stored information, it is checked whether or not the relationship between the steering angle stored at the previous end and the turning angle is maintained. If the relationship is not maintained, at least the steering angle detection is performed. The vehicle steering system is characterized in that it is determined that any one of the steering unit and the turning angle detection unit has failed.   The control unit executes a mode other than the SBW mode when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed. The vehicle steering system according to claim 1.   The vehicle steering system according to claim 1, wherein the steering angle detection unit and the turning angle detection unit are absolute angle sensors.   The vehicle further includes vehicle behavior detection means, and when it is determined that at least one of the steering angle detection unit and the turning angle detection unit has failed, The vehicle steering system according to any one of claims 1 to 3, wherein a steering angle is compared to determine whether or not the steering angle detection unit has failed.   5. The information according to claim 1, wherein the information is a phase angle difference that is a difference between phase angles detected by the steering angle detection unit and the turning angle detection unit. The vehicle steering system described.

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