JP2006103428A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly respond to abnormality of a disconnector for selectively and mechanically connecting a steering wheel and steered wheels in a steer-by-wire system steering device of a vehicle. <P>SOLUTION: The steer-by-wire system steering device of the vehicle is provided solenoid clutches 32, 33 and a cable (intermediate member) 31 between a steering input shaft 12 connected to the steering wheel 11 and a steering output shaft 24 mechanically connected to left and right front wheels FW1, FW2 such that the steering wheel 11 and the left and right front wheels FW1, FW2 are mechanically connected in abnormality of an electric motor 22 for steering. When abnormality of erroneous connection that it is always connected to one of the solenoid clutches 32, 33 is generated, steering characteristic of the left and right front wheels FW1, FW2 is changed to the steering characteristic of mechanical connection. Further, when abnormality of erroneous disconnection that it is always disconnected with one of the solenoid clutches 32, 33 is generated, a traveling speed of the vehicle is restricted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a steer-by-wire vehicle steering apparatus.

Conventionally, the steering wheel and the steered wheel are mechanically separated, and the steering wheel is steered at the same time as the steered wheel is steered by operating the electric actuator provided on the steered wheel side according to the steering operation of the steering handle 2. Description of the Related Art A steering apparatus for a vehicle that employs a steer-by-wire system in which an electric actuator provided on the steering handle side is controlled to apply a steering reaction force in response thereto is well known. In this type of steering device, for example, as shown in Patent Document 1 below, an intermediate member is provided between the input member connected to the steering handle and the output member connected to the steered wheel, A first electromagnetic clutch is provided between the member and the intermediate member, a second electromagnetic clutch is provided between the intermediate member and the output member, a first electric motor is connected to the intermediate member, and a second is provided to the output member. An electric motor is connected. In a normal state, the first electromagnetic clutch is set to the connected state and the second electromagnetic clutch is set to the disconnected state. The steering reaction force is applied to the steering handle by the first electric motor, and the steered wheels are set by the second electric motor. To steer. In addition, when the second electric motor is abnormal, the first electromagnetic clutch is set to a disconnected state and the second electromagnetic clutch is set to a connected state so that the steered wheels are steered by the first electric motor.
JP 2001-301039 A

  The above-mentioned Patent Document 1 mentions detection of an abnormality of the electric motor, but does not mention a coping method for the abnormality of the electromagnetic clutch.

  The present invention has been made to cope with the above-described problems, and an object of the present invention is to provide a first between the input member on the steering wheel side, the output member on the steered wheel side, and an intermediate member between them. It is an object of the present invention to provide a steer-by-wire type vehicle steering apparatus that can accurately cope with an abnormality in the first and second interrupters.

  In order to achieve the above object, the features of the present invention include an input member connected to a steering handle and displaced in conjunction with the steering handle, an output member connected to a steered wheel and displaced in conjunction with the steered wheel, An intermediate member provided between the input member and the output member, and interposed between the input member and the intermediate member and selectively switched to a disconnected state and a connected state, The intermediate member is disconnected so as not to be able to transmit power, and is connected between the intermediate member and the output member while being connected between the input member and the intermediate member so that power can be transmitted in the connected state, and the disconnected state and the connected state. And a second interrupter that disconnects the intermediate member and the output member so that power cannot be transmitted in the disconnected state, and connects the intermediate member and the output member so that power can be transmitted in the connected state, and the input member or intermediate Connect to member The first electric actuator that displaces the input member or the intermediate member, the second electric actuator that is connected to the output member and displaces the output member, and the operation of the first electric actuator according to the steering operation of the steering handle And a reaction force application control means for applying a reaction force to the steering operation of the steering handle, and a steering for turning the steered wheels by controlling the operation of the second electric actuator according to the steering operation of the steering handle. In a steer-by-wire vehicle steering apparatus including a control means, an abnormality detection means for detecting an abnormality in the first and second interrupters, and an abnormality in one of the first and second interrupters is detected by the abnormality detection means. And a limiting means for limiting the movement of the vehicle.

  In this case, for example, the reaction force application control means may control the operation of the first electric actuator so as to apply a steering reaction force having a magnitude corresponding to the steering angle of the steering wheel to the steering operation of the steering wheel. Further, the reaction force application control means may change the steering reaction force according to the vehicle speed. Further, the steering control means may control the second electric actuator so as to steer the steered wheels to a steered angle having a magnitude corresponding to the steering angle of the steering handle, for example. Further, the turning control means may change the turning angle according to the vehicle speed.

  In the present invention configured as described above, the restricting means restricts the movement of the vehicle before the abnormality occurs in both the first and second interrupters and the vehicle cannot be stably operated. Therefore, the running stability of the vehicle is ensured.

  Another feature of the present invention is that when the abnormality detecting means detects an abnormality in which one of the first and second interrupters is always connected, the restricting means controls the steering control means to control the steering wheel. This is to change the turning characteristics of the steered wheels according to the steering operation. In this case, the steering characteristic of the steered wheels changed by the limiting means is, for example, the steering operation of the steering handle when mechanically coupled from the steering handle to the steered wheels by connecting the first and second interrupters. It is the steering characteristic of the steered wheel according to.

  When an abnormality that causes a constant connection state occurs in one of the first and second interrupters and an abnormality that causes a constant connection state occurs in the other interrupter, the steering wheel and the steered wheels are mechanically coupled. The In this state, the steering control means controls the second electric actuator to steer the steered wheels, and the steered wheels steer according to the steering operation of the steering handle by the mechanical connection. Because the steering handle is driven by the second electric actuator regardless of the driver's steering operation or against the driver's will, the driver feels uncomfortable with the steering operation of the steering wheel. However, according to the other feature of the present invention, the steering characteristic of the steered wheel by the steered control means is changed before the abnormal connection always occurs in both the first and second interrupters, for example, the steering handle To the turning characteristics of the steered wheels according to the steering operation of the steering wheel when mechanically connected from the steered wheels to the steered wheels. Therefore, there is a situation in which an abnormal connection always occurs in both the first and second interrupters, and the steering handle is mechanically coupled to the steered wheels via the input member, the intermediate member, and the output member. However, the driver can safely drive the vehicle without feeling uncomfortable with the steering feel of the steering wheel.

  Another feature of the present invention is that the change of the turning characteristics of the steered wheels by the limiting means is performed on the condition that the steered wheels have the same turning angle before and after the change of the turning characteristics. There is in doing so. According to this, since the steering state of the steered wheels is not changed suddenly regardless of the steering operation of the steering wheel by the driver, the driver feels uncomfortable with the steering operation of the steering wheel. No need.

  Another feature of the present invention is that the turning characteristics of the steered wheels are changed gradually by the limiting means. According to this, the change in the steering characteristics of the steered wheels with respect to the steering operation of the steering wheel by the driver is alleviated, and the driver's uncomfortable feeling with respect to the steering operation of the steering wheel is alleviated.

  Another feature of the present invention is that when the abnormality detecting means detects an abnormality in which one of the first and second interrupters is always disconnected, the restricting means restricts the traveling speed of the vehicle or prevents the vehicle from traveling. This is because it was made impossible. In this case, if the first electric actuator is connected to the input member, the turning of the steered wheels becomes impossible at all if an abnormality occurs in the second electric actuator. In addition, even if the first electric actuator is connected to the intermediate member, if an abnormality that is always disconnected occurs in the second interrupter, the steered wheels are steered when the abnormality occurs in the second electric actuator. It becomes impossible at all. However, according to another feature of the present invention, when an abnormality is detected in which one of the first and second interrupters is always disconnected, the traveling speed of the vehicle is limited or the traveling of the vehicle is impossible. Therefore, the running stability of the vehicle is ensured.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of a vehicle steering apparatus according to the first embodiment.

  This vehicle steering device mechanically includes a steering operation device 10 that is steered by a driver and a steering device 20 that steers left and right front wheels FW1 and FW2 as steered wheels according to the steering operation of the driver. The steer-by-wire method is used. The steering operation device 10 includes a steering handle 11 as an operation unit that is rotated by a driver. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force electric motor (electric actuator) 13 is assembled to the lower portion of the steering input shaft 12. The steering reaction force electric motor 13 drives the steering input shaft 12 to rotate about the axis via the speed reduction mechanism 14.

  The steered device 20 includes a rack bar 21 that extends in the left-right direction of the vehicle. The left and right front wheels FW1 and FW2 are connected to both ends of the rack bar 21 via a tie rod and a knuckle arm (not shown) so as to be steerable. The left and right front wheels FW1, FW2 are steered to the left and right by the displacement of the rack bar 21 in the axial direction. On the outer periphery of the rack bar 21, a steering electric motor (electric actuator) 22 assembled in a housing (not shown) is provided. The rotation of the steered electric motor 22 is decelerated by the screw feed mechanism 23 and is converted into an axial displacement of the rack bar 21. The steering device 20 also has a steering output shaft 24 that can rotate around an axis. A pinion gear 25 is fixed to the lower end of the steering output shaft 24. The pinion gear 25 meshes with rack teeth 21a provided on the rack bar 21, and the rack bar 21 is axially rotated by rotation around the axis of the steering output shaft 24. It is displaced to.

  A cable 31 as an intermediate member is disposed between the steering input shaft 12 and the steering output shaft 24. The cable 31 transmits the rotation around the axis of the steering input shaft 12 to the steering output shaft 24. A first electromagnetic clutch 32 is disposed between the fixing member 31 a at the upper end of the cable 31 and the lower end of the steering input shaft 12. The first electromagnetic clutch 32 is set in a disconnected state in a non-energized state, disconnects the cable 31 and the steering input shaft 12 so that power cannot be transmitted, and is set in a connected state in an energized state, so that the cable 31 and the steering input shaft 12 are disconnected. Are connected so that power can be transmitted. A second electromagnetic clutch 33 is disposed between the fixing member 31 b at the lower end of the cable 31 and the upper end of the steering output shaft 24. The second electromagnetic clutch 33 is set to a disconnected state in a non-energized state, disconnects the cable 31 and the steering output shaft 24 so that power cannot be transmitted, and is set to a connected state in an energized state to set the cable 31 and the steering output shaft 24. Are connected so that power can be transmitted.

  Next, the electric control device 40 that inspects and controls the steering reaction force electric motor 13, the steering electric motor 22, and the electromagnetic clutches 32 and 33 will be described. The electric control device 40 includes a steering angle sensor 41, a turning angle sensor 42, rotation angle sensors 43 and 44, and a vehicle speed sensor 45. The steering angle sensor 41 is assembled to the steering input shaft 12 and measures the rotation angle around the axis of the steering input shaft 12 to detect the rotation angle from the neutral position of the steering handle 11 and output it as the steering angle θh of the steering wheel. To do. The steering wheel steering angle θh represents a neutral position of the steering wheel 11 as “0”, a right steering angle is represented by a positive value, and a left steering angle is represented by a negative value. The turning angle sensor 42 is assembled to the rack bar 21 and measures the axial displacement of the rack bar 21 to detect and output the actual turning angle δ of the left and right front wheels FW1, FW2. The actual turning angle δ is represented by a positive value for the rightward turning angle of the left and right front wheels FW1 and FW2, with the neutral position of the left and right front wheels FW1 and FW2 being “0”, and the leftward direction of the left and right front wheels FW1 and FW2. The steering angle of is expressed as a negative value.

  The rotation angle sensors 43 and 44 are assembled to the steering reaction force electric motor 13 and the steering electric motor 22, respectively, and detect the rotation angles θm1 and θm2 from the reference positions of the electric motors 13 and 24, respectively. These rotation angles θm1 and θm2 also have a neutral value “0”, and the rotation angles in the direction corresponding to the right steering of the steering handle 11 and the right steering of the left and right front wheels FW1 and FW2 are positive values. And the rotation angle in the direction corresponding to the leftward steering of the steering handle 11 and the leftward steering of the left and right front wheels FW1, FW2 is represented by a negative value, respectively. In the present embodiment, the rotation angle sensor 43 functions as a sensor that detects the rotational displacement of the steering input shaft 12, and the rotation angle sensor 44 detects the rotational displacement of the steering output shaft 24 and the displacement of the rack bar 21 in the axial direction. It functions as a sensor. The vehicle speed sensor 45 detects and outputs the vehicle speed V.

  The electric control device 40 includes an inspection electronic control unit (hereinafter referred to as an inspection ECU) 46, a steering reaction force electronic control unit (hereinafter referred to as an steering reaction force ECU) 47, and a steering device that are connected to each other. An electronic control unit (hereinafter referred to as a steering ECU) 48 is provided. The rotation angle sensors 43 and 44 are connected to the inspection ECU 46. A steering angle sensor 41 and a vehicle speed sensor 45 are connected to the steering reaction force ECU 47. A steering angle sensor 41, a turning angle sensor 42, and a vehicle speed sensor 45 are connected to the turning ECU 48.

  These ECUs 46 to 48 each have a microcomputer composed of a CPU, a ROM, a RAM and the like as main components. The inspection ECU 46 detects the abnormality of the electromagnetic clutches 32 and 33 by executing the inspection program of FIG. During execution of this inspection program, the inspection ECU 46 switches and controls the first and second electromagnetic clutches 32 and 33 via the drive circuit 51, and the steering reaction force electric motor 13 and the drive circuits 52 and 53. The steering electric motor 22 is drive-controlled. Further, the inspection ECU 46 causes the alarm device 54 to generate an alarm when the abnormality of the first or second electromagnetic clutch 32, 33 is detected. The steering reaction force ECU 47 executes the steering reaction force control program shown in FIG. 3 to drive and control the steering reaction force electric motor 13 via the drive circuit 52. The steering ECU 48 executes the steering control program shown in FIG. 4 to drive and control the steering electric motor 22 via the drive circuit 53.

  An engine control device 55 is also connected to the ECUs 46 to 48. The engine control device 55 incorporates a microcomputer composed of a CPU, ROM, RAM, etc., inputs the vehicle speed V from the vehicle speed sensor 45, and controls the engine in accordance with an instruction from the inspection ECU 46 to control the running speed of the vehicle. To do.

  Next, the operation of the embodiment configured as described above will be described. By turning on the ignition switch, the inspection ECU 46 executes the inspection program only once immediately after turning on the ignition switch. In addition, when the ignition switch is turned on, the steering reaction force ECU 47 and the steering ECU 48 start to repeatedly execute the steering reaction force control program and the steering control program every predetermined short time.

  The execution of the inspection program is started in step S10 in FIG. 2, and the inspection ECU 46 controls the steering reaction force electric motor 13 to the locked state in step S11. Specifically, the inspection ECU 46 sends a control current for generating a static magnetic field to the steering reaction force electric motor 13 in cooperation with the drive circuit 52 and does not rotate the rotor of the steering reaction force electric motor 13. Keep in state. The lock control of the steering reaction force electric motor 13 means that rotational displacement about the axis of the steering input shaft 12 is prohibited, and the steering reaction force is controlled by the rotation force of the steering electric motor 22 described later. The control current for generating the static magnetic field is set to a large value so that the electric motor 13 is not rotated. Next, in step S12, the inspection ECU 46 energizes the first and second electromagnetic clutches 32 and 33 in cooperation with the drive circuit 51, and puts the first and second electromagnetic clutches 32 and 33 into a connected state. Control each one.

  After the process of step S12, the inspection ECU 46 sends a drive current for rotating the steering electric motor 22 for a predetermined short period of time in cooperation with the drive circuit 53 in step S13, thereby turning the steering electric motor. The motor 22 is driven and controlled. In step S13, in parallel with the drive control of the electric motor 22 for turning, the inspection ECU 46 inputs a signal representing the rotation angle θm2 from the rotation angle sensor 44, and the electric motor 22 for turning. Inspect for rotation. Next, in step S14, the inspection ECU 46 determines whether or not the rotation of the steering electric motor 22 has been detected by the inspection in step S13. The rotation detection of the steering electric motor 22 and the same type of processing described later correspond to detection of rotational displacement around the axis of the steering output shaft 24 and displacement of the rack bar 21 in the axial direction.

  First, a case where both the first and second electromagnetic clutches 32 and 33 are normal will be described. In this case, the first and second electromagnetic clutches 32 and 33 are in the connected state by the process of step S12, and the rotational displacement of the steering input shaft 12 is prohibited by the lock control of the steering reaction force electric motor 13 in step S11. Therefore, the rotational displacement of the steering output shaft 24 and the displacement of the rack bar 21 are also prohibited through the cable 31. Therefore, the steered electric motor 22 does not rotate, it is determined “No” in step S14, and the program proceeds to step S15.

  The processing of these steps S12 to S14 is an abnormality in which the first or second electromagnetic clutch 32, 33 is kept in a normally disconnected state regardless of the control (an erroneous disconnection abnormality of the first or second electromagnetic clutch 32, 33). Is detected. The determination of “No” in step S14 means that no erroneous disconnection abnormality has occurred in the first and second electromagnetic clutches 32 and 33.

  In step S <b> 15, the inspection ECU 46 controls the first electromagnetic clutch 32 to be in a connected state by energizing the first electromagnetic clutch 32 in cooperation with the drive circuit 51, and cancels the energization of the second electromagnetic clutch 33. Then, the second electromagnetic clutch 33 is controlled to be in a disconnected state. Next, the inspection ECU 46 determines whether or not the turning electric motor 22 is rotated in a state in which the turning electric motor 22 is driven and controlled only for a predetermined short time by the processing in step S16 similar to the processing in step S13. Inspect. In step S17, the inspection ECU 46 determines whether or not the rotation of the steering electric motor 22 has been detected by the inspection in step S16. In this case, since the second electromagnetic clutch 33 is in a disconnected state and the steering electric motor 22 rotates, it is determined “Yes” in step S17, and the program proceeds to step S18.

  The processes in steps S15 to S17 are to detect an abnormality (the second electromagnetic clutch 33 is erroneously connected) such that the second electromagnetic clutch 33 continues to be kept in a constantly connected state regardless of the control. The determination of “Yes” in step S17 means that no erroneous connection abnormality has occurred in the second electromagnetic clutch 33.

  In step S <b> 18, the inspection ECU 46 controls the first electromagnetic clutch 32 to be in a disconnected state by energizing the first electromagnetic clutch 32 and energizes the second electromagnetic clutch 33 in cooperation with the drive circuit 51. Then, the second electromagnetic clutch 33 is controlled to the connected state. Next, the inspection ECU 46 determines whether or not the turning electric motor 22 is rotated in a state in which the turning electric motor 22 is driven and controlled for a predetermined short time by the processing in step S19 similar to the processing in step S13. Inspect. In step S20, the inspection ECU 46 determines whether or not the rotation of the steering electric motor 22 has been detected by the inspection in step S19. In this case, since the first electromagnetic clutch 32 is in a disconnected state and the steered electric motor 22 rotates, “Yes” is determined in step S20.

  The processes in steps S18 to S20 are to detect an abnormality (the first electromagnetic clutch 32 is erroneously connected) that keeps the first electromagnetic clutch 32 kept in a constantly connected state regardless of the control. The determination of “Yes” in step S20 means that no erroneous connection abnormality has occurred in the second electromagnetic clutch 33.

  Next, in step S21, the inspection ECU 46 sets the abnormality flag MBF indicating the normal and abnormal states of the first and second electromagnetic clutches 32 and 33 to a value “0” indicating the normality of both the electromagnetic clutches 32 and 33. Then, after the processing of steps S22 to S24, the execution of this inspection program is terminated in step S25.

  In step S <b> 22, the inspection ECU 46 releases the energization of the steering reaction force electric motor 13 in cooperation with the drive circuit 52 to release the lock state of the steering reaction force electric motor 13. In step S23, the inspection ECU 46 releases the energization of the first and second electromagnetic clutches 32 and 33 in cooperation with the drive circuit 51, and sets both the electromagnetic clutches 32 and 33 to the disconnected state. In step S24, the inspection ECU 46 outputs the abnormality flag MBF set to “0” to the steering ECU 48 and outputs an inspection end signal to the steering reaction force ECU 47 and the steering ECU 48, respectively.

  On the other hand, the steering reaction force ECU 47 repeatedly executes the steering reaction force control program of FIG. 3 every predetermined short time after the ignition switch is turned on. Execution of this steering reaction force control program is started in step S40, and the steering reaction force ECU 47 determines whether or not an inspection end signal has been input from the inspection ECU 46 in step S41. If the inspection end signal has not yet been input after the ignition switch is turned on, the steering reaction force ECU 47 determines “No” in step S41, and once executes the steering reaction force control program in step S46. finish. In this state, the steering reaction force ECU 47 does not execute substantial processing and waits for the input of the inspection end signal.

  As described above, when the inspection ECU 46 ends the inspection of the first and second electromagnetic clutches 32 and 33 and outputs the inspection end signal, the steering reaction force ECU 47 determines “Yes” in step S41, The processing after step S42 starts to be executed. In step S42, the steering reaction force ECU 47 inputs the steering wheel steering angle θh from the steering angle sensor 41, the vehicle speed V from the vehicle speed sensor 45, and the steering fail flag STF from the steering ECU 48. The steering fail flag STF is set by the steering ECU 48 as will be described in detail later, and “0” indicates the normal state of the steering control system including the steering electric motor 22 and the drive circuit 53. "1" represents an abnormal state of the steering control system.

  Also in this case, the description is continued for the case where the steering control system is normal. Therefore, the steering reaction force ECU 47 determines that “Yes” in step S43, that is, the steering fail flag STF is “0”, and advances the program to step S44.

  In step S44, the steering reaction force ECU 47 refers to a steering reaction force table provided in the ROM, and calculates a target steering reaction force Th * that changes according to the steering angle θh and the vehicle speed V. As shown in FIG. 6, this steering reaction force table stores a plurality of target steering reaction forces Th * that increase nonlinearly as the steering wheel steering angle θh increases for each of a plurality of representative vehicle speed values. Instead of using this steering reaction force table, the target steering reaction force Th * that changes according to the steering angle θh and the vehicle speed V is defined in advance by a function, and the target steering is performed by using the function. The reaction force Th * may be calculated.

  Next, in step S45, the steering reaction force ECU 47 causes the steering reaction force electric motor 13 to flow a drive current corresponding to the calculated target steering reaction force Th * in cooperation with the drive circuit 52, thereby causing the step. In S46, the execution of the steering reaction force control program is temporarily terminated. The steering reaction force electric motor 13 drives the steering input shaft 12 with a rotational torque corresponding to the target steering reaction force Th *. As a result, the target steering reaction force Th * by the steering reaction force electric motor 13 is given to the turning operation of the steering handle 11, and the driver rotates the steering handle 11 while feeling an appropriate steering reaction force. Can be operated.

  Further, the turning ECU 48 repeatedly executes the turning control program shown in FIG. 4 every predetermined short time after the ignition switch is turned on. Execution of this steering control program is started in step S50, and the steering ECU 4 determines whether an inspection end signal has been input from the inspection ECU 46 in step S51. If the inspection end signal has not yet been input after the ignition switch is turned on, the steering ECU 48 determines “No” in step S51, and temporarily ends the execution of the steering control program in step S63. . In this state, the steering ECU 48 does not execute substantial processing and waits for the input of the inspection end signal.

  As described above, when the inspection ECU 46 finishes the inspection of the first and second electromagnetic clutches 32 and 33 and outputs the inspection end signal, the steering ECU 48 determines “Yes” in step S51, and the step In S52, it is determined whether the steering fail flag STF is “0”. As described above, since the steering fail flag STF is currently set to “0”, the steering ECU 48 determines “Yes” in step S52 and advances the program to step S53.

  In step S53, the steering ECU 48 checks whether or not the steering control system including the steering electric motor 22 and the drive circuit 53 has failed. In this case, the steering ECU 48 inputs a signal from the drive circuit 53 for disconnection, short circuit, and other abnormalities of the electric motor 22 to inspect whether an abnormality has occurred in the steering control system. Next, the steering ECU 48 determines in step S54 whether or not a failure is detected by the process of step S53. Also in this case, the description will be continued for the case where no failure is detected by the determination processing in steps S53 and S54. That is, after the determination of “No” in step S54, the steering ECU 48 sets the steering fail flag STF to “0” in step S55, and executes the processing from step S56. The steering fail flag STF is stored and held in a non-volatile memory area when the steering ECU 48 is not in operation so that the value is held even when the ignition switch is turned off.

  In step S56, the steering ECU 48 controls the steering wheel steering angle θh from the steering angle sensor 41, the actual steering angle δ from the steering angle sensor 42, the vehicle speed V from the vehicle speed sensor 45, and the abnormality from the inspection ECU 46. Each flag MBF is input. Next, in step S57, it is determined whether or not the input abnormality flag MBF is “2”. Also in this case, as described above, the description will be continued assuming that the abnormality flag MBF is set to “0”.

  Therefore, the steering ECU 48 determines “No” in step S57, and executes the processes in and after step S58. In step S58, by referring to the first turning angle table stored in the ROM, the steered wire target turning angle δa * that changes according to the steering wheel steering angle θh is calculated. The target turning angle δa * for by-wire is set as the target turning angle δ *. The first turning angle table stores a target turning angle δa * for a standby wire that increases non-linearly as the steering wheel steering angle θh increases as shown by a solid line in FIG. The rate of change of the steer-by-wire target steering angle δa * with respect to the steering wheel steering angle θh is small within a small range of the steering wheel steering angle θh absolute value | θh |, and the steering steering angle θh absolute value | θh | is large. It is set so as to increase. Instead of using this first turning angle table, a function indicating the relationship between the steering angle θh of the steering wheel and the target turning angle δa * for the steer-by-wire is prepared in advance, and this function is used. Thus, the steer-by-wire target turning angle δa * may be calculated.

  Next, in step S59, the steering ECU 48 refers to the vehicle speed coefficient table stored in the ROM, calculates the vehicle speed coefficient Ka for the standby wire that changes according to the vehicle speed V, and calculates the same. The vehicle speed coefficient Ka for the steer-by-wire is set as the vehicle speed coefficient K. The vehicle speed coefficient table is larger than “1” within a small range of the vehicle speed V, smaller than “1” within a large range of the vehicle speed V, and “1” as the vehicle speed V increases, as indicated by a solid line in FIG. The vehicle speed coefficient Ka for the steer-by-wire that decreases non-linearly across the wheel is stored. Instead of using the vehicle speed coefficient table, a function indicating the relationship between the vehicle speed V and the vehicle speed coefficient Ka for the standby wire is prepared in advance, and the vehicle speed coefficient Ka for the standby wire is obtained using the function. May be calculated.

After the determination of the target turning angle δ * and the vehicle speed coefficient K, the steering ECU 48 corrects the target turning angle δ * by the vehicle speed coefficient K by executing the calculation of the following equation 1 in step S60. The final target turning angle δ * is calculated.
δ * = K · δ * Equation 1
In step S61, the difference δ * −δ between the turning angles δ * and δ is used via the drive circuit 53 so that the actual turning angle δ becomes equal to the final target turning angle δ *. The rotation of the electric motor 22 for turning is controlled. As a result, the steering electric motor 22 is rotationally driven, drives the rack bar 21 in the axial direction via the screw feed mechanism 23, and steers the left and right front wheels FW1, FW2 to the target turning angle δ *.

  By such steering control, as shown by the solid line in FIG. 8, the left and right front wheels FW1, FW2 are steered small with respect to the change in the steering angle θh in a small range of the steering angle θh, and the steering angle θh Is steered greatly with respect to the change in the steering angle θh. As a result, the left and right front wheels FW1, FW2 are steered to a large steered angle without changing the steering handle 11. 9, the left and right front wheels FW1 and FW2 are steered greatly with respect to the steering wheel steering angle θh when the vehicle speed V is low, and are steered small with respect to the steering wheel steering angle θh when the vehicle speed V increases. Is done. After the process of step S61, the steering ECU 48 outputs a steering fail flag STF to the steering reaction force ECU 47 in step S62, and ends the execution of the steering control program in step S63.

  Next, a case where a failure occurs in the turning control system will be described. In this case, the steering ECU 48 determines “Yes” in step S54 of FIG. 4, sets the steering fail flag STF to “1” in step S64, and in step S65, the steering electric motor. The operation control of 22 is stopped and the operation of the electric motor 22 for turning is stopped. Next, in step S66, the steering ECU 48 energizes the first and second electromagnetic clutches 32, 33 in cooperation with the drive circuit 51 to connect the first and second electromagnetic clutches 32, 33. To control. Then, the steering fail flag STF set to “1” in step S62 is output to the steering reaction force ECU 47, and the execution of this steering control program is temporarily terminated in step S63.

  Then, once the steering fail flag STF is set to “1” in this way, the steering ECU 48 subsequently determines “No” in step S52, and performs the processing in steps S65, S66, and S62 described above. Execute. Therefore, the steering electric motor 22 does not perform the steering control on the left and right front wheels FW1, FW2. On the other hand, the steering input shaft 12 is connected to the steering output shaft 24 via the first electromagnetic clutch 32, the cable 31, and the second electromagnetic clutch 33 so that power can be transmitted. The left and right front wheels FW1 and FW2 are transmitted to the left and right front wheels FW1 and FW2 via the cable 31, the steering output shaft 24, and the rack bar 21, and the left and right front wheels FW1 and FW2 are steered by the turning operation force of the steering handle 11.

  On the other hand, in this state, the steering reaction force ECU 47 inputs the steering fail flag STF that is set to “1” by the process of step S42 in FIG. 3, and determines “No” in step S43. The program proceeds to step S47. In step S47, the steering reaction force ECU 47 refers to an assist command value table provided in the ROM, and calculates a target assist torque Ta * that changes according to the steering angle θh and the vehicle speed V. As shown in FIG. 7, the assist command value table stores a plurality of target assist torques Ta * that increase nonlinearly as the steering wheel steering angle θh increases for each of a plurality of representative vehicle speed values. Instead of using the assist command value table, a target assist torque Ta * that changes according to the steering angle θh and the vehicle speed V is defined in advance by a function, and the target assist torque is used by using the function. Ta * may be calculated.

  Next, in step S48, the steering reaction force ECU 47 causes the steering reaction force electric motor 13 to pass a drive current corresponding to the calculated target assist force Ta * in cooperation with the drive circuit 52. Thus, the steering reaction force electric motor 13 drives the steering input shaft 12 with a rotational torque corresponding to the target assist force Ta *. As a result, when the left and right front wheels FW1 and FW2 cannot be steered by the steering electric motor 22, the steering of the left and right front wheels FW1 and FW2 by the turning operation of the steering handle 11 is assisted by the target assist force Ta *. The driver can easily rotate the steering handle 11.

  Next, a case where an erroneous disconnection abnormality has occurred in either one of the first and second electromagnetic clutches 32 and 33 will be described. In this case, even if the first and second electromagnetic clutches 32 and 33 are controlled to be in the connected state by the process of step S12 of FIG. An electromagnetic clutch in which an abnormality has occurred is kept in a disconnected state. Therefore, the steering input shaft 12 and the steering output shaft 24 are separated so that power cannot be transmitted, and the rotation of the steering electric motor 22, that is, the rotational displacement of the steering output shaft 24, is detected by the processing of steps S13 and S14. Therefore, the inspection ECU 46 determines “Yes” in step S14 and advances the program to step S26 and subsequent steps.

  In step S26, the inspection ECU 46 sets the abnormality flag MBF to “1”. Then, the abnormality flag MBF set to “1” is output to the steering ECU by the process of step S24 described above. After the process of step S26, the inspection ECU 46 controls the alarm device 54 in step S27 to indicate that an erroneous disconnection abnormality has occurred in at least one of the first and second electromagnetic clutches 32 and 33. An alarm is generated in the alarm device 54. Next, the inspection ECU 46 outputs a speed control signal to the engine control device 55 in step S28.

  In this case, the steering ECU 48 inputs the abnormality flag MBF set to “1” by the process of step S56 of FIG. However, the steering ECU 48 determines “No” in step S57, and performs steering control on the left and right front wheels FW1 and FW2 by the processing in steps S58 to S61 described above. Accordingly, in this case, the left and right front wheels FW1 and FW2 are steer-by-wire target turning angles δa * (in FIG. 8), as in the case where the first and second electromagnetic clutches 32 and 33 are normal. The vehicle is steered to a target turning angle δ * (= Ka · δa *) in accordance with a solid line) and a vehicle speed coefficient Ka (solid line in FIG. 9).

  On the other hand, the engine control device 55 that has received the speed limit signal by the processing of the inspection ECU 46 in step S28 in FIG. Limit to below the specified vehicle speed. That is, when an erroneous disconnection abnormality occurs in at least one of the first and second electromagnetic clutches 32 and 33, the traveling speed of the vehicle is limited to a predetermined vehicle speed or less.

  This is because the steering handle 11 and the left and right front wheels FW1 and FW2 are connected via the cable 31 so that power can be transmitted when the left and right front wheels FW1 and FW2 cannot be steered by the steering electric motor 22 in the future. This is to limit the driving of the vehicle so that the fail-safe function cannot be performed. The predetermined vehicle speed for limiting the traveling speed of the vehicle may be set to a relatively small value. Further, the vehicle stability may be ensured by setting the predetermined vehicle speed to “0” and prohibiting the vehicle from traveling. Further, the vehicle traveling speed may be limited to a predetermined vehicle speed or less for a predetermined time for moving the vehicle to a safe place, and thereafter the vehicle traveling may be prohibited. As a result, traveling stability of the vehicle is ensured.

  Next, a case where an erroneous connection abnormality has occurred in the second electromagnetic clutch 33 will be described. In this case, even if the first electromagnetic clutch 32 is controlled to be in the connected state and the second electromagnetic clutch 33 is controlled to be in the disconnected state by the process of step S15 in FIG. The second electromagnetic clutch 33 is kept connected. Therefore, the steering input shaft 12 and the steering output shaft 24 are connected so as to be able to transmit power, and the rotation of the steering electric motor 22, that is, the rotational displacement of the steering output shaft 24 is not detected by the processing of steps S16 and S17. Therefore, the inspection ECU 46 determines “No” in step S17 and advances the program to step S29 and subsequent steps.

  In step S29, the inspection ECU 46 sets the abnormality flag MBF to “2”. Then, the abnormality flag MBF set to “2” is output to the steering ECU by the process of step S24 described above. After the processing in step S29, the inspection ECU 46 controls the alarm device 54 in step S30 to cause the alarm device 54 to generate an alarm indicating that an erroneous connection abnormality has occurred in the second electromagnetic clutch 33.

  In addition, when an erroneous connection abnormality has occurred in the first electromagnetic clutch 32, the first electromagnetic clutch 32 is controlled to be disconnected and the second electromagnetic clutch 33 is connected by the processing in step S18 of FIG. Even if controlled to the state, the first electromagnetic clutch 32 in which the erroneous connection abnormality has occurred is kept in the connected state. Therefore, also in this case, the steering input shaft 12 and the steering output shaft 24 are coupled so as to be able to transmit power, and the rotation of the steering electric motor 22, that is, the rotational displacement of the steering output shaft 24 is performed by the processing of steps S 19 and S 20. Is not detected. Accordingly, the inspection ECU 46 determines “No” in step S20, and executes the processes of steps S29 and S30 described above, similarly to the case where an erroneous connection abnormality has occurred in the second electromagnetic clutch 33. . However, in the process of step S30, an alarm is issued that an erroneous connection abnormality has occurred in the second electromagnetic clutch 33.

  On the other hand, in this case, the steering ECU 48 inputs the abnormality flag MBF set to “2” in step S56 of FIG. And it determines with "Yes" in step S57, and a program is advanced to step S67. In step S67, the steering ECU 48 executes a switching control routine.

  As shown in detail in FIG. 5, the switching control routine is started in step S70. In step S71, the steering ECU 48 has steered the steering wheel 11 beyond a predetermined steering angle, that is, the absolute value | θh | of the steering wheel steering angle θh has changed from a value smaller than a predetermined value to a predetermined value or more. Determine whether. More specifically, the absolute value | θh | of the steering wheel steering angle θh at the time of execution of the previous switching control routine is less than a predetermined value, and the absolute value of steering wheel angle θh at the time of execution of the current switching control routine | θh It is determined that | is equal to or greater than a predetermined value. If this condition is satisfied, the steering ECU 48 determines “Yes” in step S71, and after executing the processes in steps S72 to S76, advances the program to step S77 and subsequent steps. On the other hand, if the condition is not satisfied, “No” is determined in step S71, and the program is directly advanced to step S77 and subsequent steps.

  In step S72, “1” is added to the variable m, and in step S73, it is determined whether the variable m is equal to or greater than a predetermined value M. The variable m counts the number of times the steering handle 11 has been steered beyond a predetermined steering angle, and is initially set to “0”. The predetermined value M prescribes the speed at which the turning characteristic for the steering wheel steering angle θh of the left and right front wheels FW1 and FW2 to be described later is updated, and is set to a predetermined positive integer value. If the variable m is not equal to or greater than the predetermined value M, “No” is determined in step S73, and the program proceeds to step S77. If the variable m is greater than or equal to the predetermined value M, “Yes” is determined in step S73, the variable m is initially set to “0” in step S74, and the variable n is greater than or equal to the predetermined value N in step S75. Determine if there is. The variable n is a variable for changing the turning characteristic with respect to the steering wheel steering angle θh of the left and right front wheels FW1 and FW2, and is initially set to “1”. The predetermined value N defines a change amount of the turning characteristic with respect to the steering angle θh of the left and right front wheels FW1 and FW2, and is set to a predetermined positive integer value.

  If the variable n is equal to or greater than the predetermined value N, “Yes” is determined in step S75, and the program proceeds to step S77. If the variable n is not equal to or greater than the predetermined value N, “No” is determined in step S75, “1” is added to the variable n in step S76, and the program proceeds to step S77. As a result of the processes in steps S71 to S76, the variable n is sequentially increased from “1” to “1” by a predetermined value N every time the number of times the steering handle 11 is steered to a predetermined steering angle or more becomes M times. In this case, if the predetermined value M is set to “1”, the variable n increases by “1” every time the steering wheel 11 is steered beyond a predetermined steering angle.

  In step S77, the steering ECU 48 changes in accordance with the steering angle θh with reference to the first turning angle table stored in the ROM in the same manner as the processing in step S58 in FIG. The steer-by-wire target turning angle δa * is calculated, and the calculated steer-by-wire target turning angle δa * is set as the first target turning angle δ1 *. In step S77, the second turning angle table stored in the ROM is referred to calculate a target turning angle δb * for mechanically connected steering that changes according to the steering angle θh. The calculated target turning angle δb * for mechanically connected steering is set as the second target turning angle δ2 *. The second turning angle table stores a target turning angle δb * for mechanically connected steering that increases linearly as the steering wheel steering angle θh increases, as indicated by a broken line in FIG. Instead of using this second turning angle table, a function indicating the relationship between the steering wheel steering angle θh and the target turning angle δb * for mechanically connected steering is prepared in advance, and the same function is used. Then, the target turning angle δb * for mechanically connected steering may be calculated.

  Next, in step S78, the steering ECU 48 refers to the vehicle speed coefficient table stored in the ROM in the same manner as in the process of step S59, and for the steering wire that changes according to the vehicle speed V. The vehicle speed coefficient Ka is calculated, and the calculated vehicle speed coefficient Ka for the steer-by-wire is set as the first vehicle speed coefficient K1. In step S78, the second vehicle speed coefficient K2 is set to a constant Kb. The constant Kb is set to “1.0” as indicated by a broken line in FIG.

After determining the first and second target turning angles δ1 *, δ2 * and the first and second vehicle speed coefficients K1, K2, the steering ECU 48 executes the calculation of the following equation 2 in step S79. The final target turning angle δ * is calculated, and the execution of this switching control routine is terminated in step S80.
δ * = {K1 + n · (K2−K1) / N} · {δ1 * + n · (δ2 * −δ1 *) / N} Equation 2
As the variable n is changed from “1” to a predetermined value N by executing the calculation of Expression 2, the target turning angle that gradually changes from the first target turning angle δ1 * to the second target turning angle δ2 *. δ * is calculated.

  After the execution of the switching control routine, the steering ECU 48 causes the left and right front wheels FW1, FW2 to become equal to the target turning angle δ * by the process of step S61 in FIG. 4 described above. Is steered to the target turning angle δ *. In this case, as described above, the variable n increases from “1” to the predetermined value N as the number of times of steering more than the predetermined steering angle of the steering handle 11 increases, and as the variable n increases from “1” to the predetermined value N. Since the target turning angle δ * gradually changes from the first target turning angle δ1 * to the second target turning angle δ2 *, the left and right front wheels FW1, FW2 are the first target turning angles δ1 * for the standby wires. Gradually changes to a second target turning angle δ2 * for mechanically connected steering.

  This assumes that when an erroneous connection abnormality occurs in one of the first and second electromagnetic clutches 32 and 33, an erroneous connection abnormality also occurs in the other electromagnetic clutch in the future. In this case, the steering input shaft 12 and the steering output shaft 24 are connected via the cable 31 so that power can be transmitted, and the steering handle 11 is mechanically connected to the left and right front wheels FW1 and FW2. On the other hand, if the switching control routine is not executed, the left and right front wheels FW1 and FW2 are shown in FIG. 8 with respect to the steering angle θh when the erroneous connection abnormality occurs in both the first and second electromagnetic clutches 32 and 33. It turns with the turning characteristic as shown by the broken line. This steering characteristic is different from the steering characteristic by the steer-by-wire system. In this state, the difference between the steering characteristics of the left and right front wheels FW1 and FW2 by the steering electric motor 22 and the steering characteristics by mechanical connection of the steering handle 11 and the left and right front wheels FW1 and FW2 via the cable 31 are different. Thus, since the steering handle 11 is driven by the steering electric motor 22 regardless of the driver's steering operation or against the driver's intention, the driver can operate the steering handle 11 such as self-steering and steering lock. I feel uncomfortable.

  On the other hand, by executing the switching control routine in step S67, the left and right with respect to the turning operation of the steering handle 11 from the time of detecting an erroneous connection abnormality of one of the first and second electromagnetic clutches 32 and 33 is detected. The turning characteristics of the front wheels FW1, FW2 gradually change from the first target turning angle δ1 * for the steer-by-wire to the turning characteristic according to the second target turning angle δ2 * for mechanically connected steer, and the vehicle speed The correction of the first target turning angle δ1 * by V also changes gradually. Therefore, when an erroneous connection abnormality occurs in both the first and second electromagnetic clutches 32 and 33, the steering characteristics of the left and right front wheels FW1 and FW2 are switched from the steer-by-wire system to the mechanical coupling system. Since the steering characteristics of the left and right front wheels FW1, FW2 with respect to the steering operation of the steering handle 11 do not change, the driver does not feel uncomfortable. In addition, since the turning characteristic is gradually changed, the driver does not feel uncomfortable even when the turning characteristic is changed.

  Note that the ignition switch is turned off for the abnormality flag MBF indicating the abnormality of the first and second electromagnetic clutches 32 and 33 and the variables m and n for gradually changing the steering characteristics of the left and right front wheels FW1 and FW2. Even if the electric control device including the ECUs 46 to 48 is not stored when the operation is stopped, after the abnormality of the first and second electromagnetic clutches 32 and 33 is once detected, it is non-volatile like the steering fail flag STF. It may be stored in the memory area. According to the former, abnormality of the first and second electromagnetic clutches 32 and 33 is determined every time the ignition switch is turned on, and the turning characteristics of the left and right front wheels FW1 and FW2 are newly changed gradually every time the ignition switch is turned on. Will be. According to the latter, once an abnormality in the first and second electromagnetic clutches 32, 33 is detected, the steering characteristics of the left and right front wheels FW1, FW2 are continuously and gradually changed thereafter.

  As can be understood from the above description of operation, according to the above embodiment, the steering characteristics of the left and right front wheels FW1 and FW2 are changed when an abnormality occurs in one of the first and second electromagnetic clutches 32 and 33. Or travel of the vehicle is restricted. Therefore, before the first and second electromagnetic clutches 32 and 33 are abnormal and it becomes impossible to stably control the vehicle, the movement of the vehicle is limited and the running stability of the vehicle is ensured. Is done.

  Next, the change of the turning characteristics of the left and right front wheels FW1, FW2 of the above embodiment is executed on condition that the turning angle δ is the same before and after the change of the turning characteristics. A modification of the embodiment will be described. In this modification, the steering ECU 48 executes the switching control routine of FIG. 10 instead of the switching control routine of FIG. Other parts are the same as those in the above embodiment.

  In the switching control routine of FIG. 10, the process of step S101 for setting the change prohibition flag NCG to “1” is added between steps S75 and S76 of FIG. This change prohibition flag NCG indicates that the change of the steering characteristics of the left and right front wheels FW1 and FW2 is prohibited by “1”, and that the change of the steering characteristics is permitted by “0”. Is set to “0”. And even if the process of this step S101 is the change timing of the steering characteristic of the right and left front wheels FW1 and FW2 specified by the process of steps S71 to S76, the steering characteristic is changed until a condition described later is satisfied. This is a process for temporarily prohibiting.

  Further, in the switching control routine of FIG. 10, the process of step S79 of FIG. 5 is partially changed as step S79 ', and the processes of steps S102 to S107 are added. In step S79 ', the target turning angle calculated by executing the calculation of Equation 2 is set as the new target turning angle δnew *. In step S102, it is determined whether the change prohibition flag NCG is “1”. In this case, if the change prohibition flag NCG is “0” and represents the change permission state of the steering characteristics of the left and right front wheels FW1 and FW2, “No” is determined in step S102, and the program proceeds to step S106. Proceed. In step S106, the final target turning angle δ * is set to the new target turning angle δnew *, and in step S80, the execution of this switching control routine is ended. Therefore, in this case, the operation is the same as in the above embodiment.

If the change prohibition flag NCG is “1” and represents a change prohibition state of the steering characteristics of the left and right front wheels FW1, FW2, “Yes” is determined in step S102, and the program proceeds to step S107. In step S103, the old target turning angle δold * is calculated by executing the calculation of the following formula 3.
δold * = {K1 + (n−1) · (K2−K1) / N}
・ {Δ1 * + (n−1) ・ (δ2 * −δ1 *) / N} Equation 3
In Formula 3, the value (n−1) is a variable value that determines the turning characteristics of the left and right front wheels FW1 and FW2 immediately before the variable n is changed by the process of Step S76. The old target turning angle δold * calculated in step S103 represents the target turning angle δ * according to the turning characteristic immediately before being changed.

  In step S104, the steering ECU 48 determines whether or not the new target turning angle δnew * and the old target turning angle δold * are equal. If the new target turning angle δnew * and the old target turning angle δold * are not equal, “No” is determined in step S104, and the final target turning angle δ * is changed to the old target turning angle δold *. Set to. Therefore, in this case, even if the variable n is changed by the process of step S76, the final target turning angle δ * (= δold *) is determined according to the immediately preceding turning characteristic.

  On the other hand, when the new target turning angle δnew * becomes equal to the old target turning angle δold *, the steering ECU 48 determines “Yes” in step S104, and sets the change prohibition flag NCG to “0” in step S105. Then, the final target turning angle δ * is set to the new target turning angle δnew * by the process of step S106 described above. Thereafter, until the variable n is newly changed by the process of step S76, it is determined as “No” in the above-described step S102, and the process of step S106 is executed. The angle δ * is set to the new target turning angle δnew *.

  By such added processing in steps S101 to S107, the new target turning angle δnew * according to the changed turning characteristic becomes equal to the old target turning angle δold * according to the turning characteristic before the change. Until the steering characteristics are not changed. Then, when the new target turning angle δnew * and the old target turning angle δold * become equal, the turning characteristics are changed. Therefore, according to this modified example, the steering state of the left and right front wheels FW1 and FW2 is not changed suddenly regardless of the steering operation of the steering handle 11 by the driver. There is no need to feel uncomfortable with the steering operation. In particular, even if the degree of change in the steering characteristics is increased, the driver does not have to feel a great sense of discomfort.

  Further, the switching control routine of FIG. 10 is simplified and modified as the switching control routine of FIG. In the switching control routine of FIG. 11, the processes of steps S79 'and S102 to S107 of FIG. 10 described above are changed to processes of steps S111 to S115. That is, it is determined whether or not the change prohibition flag NCG is “1” by the processing in step S111 similar to step S102. Then, if the change prohibition flag NCG is “0” and represents the change permission state of the steering characteristics of the left and right front wheels FW1 and FW2, in step S114, the same expression 2 as the process in step S79 ′ is followed. By executing the above calculation, the final target turning angle δ * is calculated.

  If the change prohibition flag NCG is “1”, indicating that the change of the steering characteristics of the left and right front wheels FW1, FW2 is prohibited, it is determined in step S112 whether the steering angle θh is “0”. If the steering wheel steering angle θh is “0”, the steering ECU 48 determines “Yes” in step S112, sets the change prohibition flag NCG to “0” in step S113, and The process of step S114 is executed. On the other hand, if the steering wheel steering angle θh is not “0”, the steering ECU 48 determines “No” in step S112, and follows the same expression 3 as the process of step S103 by the process of step S115. By executing the above calculation, the final target turning angle δ * is calculated.

  That is, when the variable n for changing the steering characteristics of the left and right front wheels FW1 and FW2 is changed by the processing of step S76, the steering of the left and right front wheels FW1 and FW2 is continued until the steering wheel steering angle θh becomes “0”. The characteristics are not changed. When the steering wheel steering angle θh becomes “0”, the turning characteristics of the left and right front wheels FW1, FW2 are changed. This is because if the steering wheel steering angle θh is “0”, the first and second target turning angles δ1 * and δ2 * calculated by the processing in step S77 are both “0”. This is because the calculation result by is always “0”. In other words, if the steering wheel steering angle θh is “0”, the target turning angle δ * calculated by the processing of steps S114 and S115 is both set regardless of the variable n, that is, the turning characteristics of the left and right front wheels FW1 and FW2. It becomes “0”.

  Therefore, according to this modification, the steering characteristic is limited to the case where the steering wheel steering angle θh is “0”. However, the steering characteristic is not made until the target steering angle δ * before and after the change of the steering characteristic becomes equal. Is changed. Therefore, according to this modification, the steering state of the left and right front wheels FW1 and FW2 is not changed suddenly regardless of the steering operation of the steering handle 11 by the driver. You don't have to feel uncomfortable with the steering operation. Further, as described above, there is no problem even if the change amount of the steering characteristic is increased.

  Furthermore, the present invention is not limited to the above-described embodiment and its modifications, and various modifications can be employed within the scope of the present invention.

  For example, in the above-described embodiment and its modification, the inspection program is executed only once immediately after the ignition switch is turned on. However, instead of this, the inspection ECU executes the inspection program shown in FIG. 2 on the condition that the shift lever is switched to the parking position, the driver operates the parking brake, or the vehicle speed V changes to “0”. It is possible to execute inspection of the first and electromagnetic clutches 32 and 33. Further, immediately after the ignition switch is turned on, immediately after the shift lever is switched to the parking position, after the parking brake is started, the first and second electromagnetic clutches 62 are inspected by appropriately combining the conditions of the vehicle speed “0”. You may do it.

  Further, as in the processing of the switching control routine, the amount of change in the turning characteristic from the steering characteristic for the left and right front wheels FW1 and FW2 to the turning characteristic for mechanical connection is indicated by the steering handle 11 exceeding a predetermined angle. Instead of increasing as the number of times of steering is increased, the amount of change in the steering characteristic may be increased as the time during which the steering handle 11 is steered beyond a predetermined angle increases. In this case, the processing of steps S71 to S76 in the switching control routine of FIG. 5 may be changed so that the variable n becomes a larger value as the accumulated time during which the steering handle 11 is steered beyond a predetermined angle increases. .

  Further, the turning characteristic may be simply changed over time. In this case as well, the processing in steps S71 to S76 may be changed to processing in which the variable n increases as the accumulated time after the switching control routine is executed increases. Further, the turning characteristic may be gradually changed according to the number of times the ignition switch is turned on. In this case as well, the processing of steps S71 to S76 is performed each time the ignition switch is turned on after the switching control routine is executed, or every time the ignition switch is turned on a predetermined number of times. What is necessary is just to change to the process which increases n.

  In the above-described embodiment and its modification, the rotation of the steering reaction force electric motor 13, the steering handle 11, and the steering input shaft 12 is detected based on the rotation angle θm1 detected by the rotation angle sensor 43, and the rotation is performed. Based on the rotation angle θm2 detected by the angle sensor 44, the rotation of the steering electric motor 22 and the steering output shaft 24, the axial displacement of the rack bar 21, and the steering of the left and right front wheels FW1, FW2 are detected. did. However, instead of these rotation angles θm1 and θm2, the steering wheel steering angle θh and the actual turning angle δ detected by the steering angle sensor 41 and the turning angle sensor 42 may be used.

  Further, in the above-described embodiment and its modification, the cable 31 is employed as an intermediate member that connects the steering input shaft 12 and the steering output shaft 24, and the power transmission between the steering input shaft 12 and the steering output shaft 24 is cabled. This is realized by 31 rotations (or twists). However, instead of this, a conversion mechanism for converting the rotational force around the axis of the steering input shaft 12 and the steering output shaft 24 into a tensile force is provided on each connection end side of the steering input shaft 12 and the steering output shaft 24. You may make it employ | adopt as a middle member the cable which can transmit tension | tensile_strength to a conversion mechanism. Further, a rotation shaft that can rotate coaxially with the steering input shaft 12 and the steering output shaft 24 is disposed between the steering input shaft 12 and the steering output shaft 24, and the rotation shaft is employed as an intermediate member. Also good.

  Further, in the above embodiment, the steering reaction force electric motor 13 is connected to the steering input shaft 12 to rotate the steering input shaft 12. However, instead of this, the electric motor 13 may be connected to the fixing members 31a and 31b of the cable 31 as an intermediate member, and the cable 31 may be rotationally driven. Further, when a rotating shaft is employed as an intermediate member instead of the cable 31, the steering reaction force electric motor 13 may be connected to the rotating shaft so that the rotating shaft is driven to rotate.

  In this case, if the steering reaction force and steering electric motors 13 and 22 and their drive control systems are normal and the first and second electromagnetic clutches 32 and 33 are normal, the first electromagnetic clutch 32 is connected. And the second electromagnetic clutch 33 is set to the disengaged state, the steering reaction force is applied to the steering handle 11 by the steering reaction force electric motor 13, and the left and right front wheels FW1, FW2 are turned by the turning electric motor. Try to steer. Further, when an erroneous connection abnormality occurs in the second electromagnetic clutch 33, the steering reaction force electric motor 13 may be switched to the steering assist for the left and right front wheels FW1, FW2, or the operation thereof may be stopped. And other control should just be carried out similarly to the said embodiment.

  Furthermore, in the said embodiment and modification, what was rotated as the steering handle 11 was employ | adopted. However, the present invention is also applied to a vehicle steering apparatus that uses a steering handle that steers the left and right front wheels FW1 and FW2 by a linear operation such as a joystick instead of the steering handle 11.

1 is an overall schematic diagram of a vehicle steering apparatus according to an embodiment of the present invention. 3 is a flowchart of an inspection program executed by the inspection ECU in FIG. 1. It is a flowchart of the steering reaction force control program executed by the steering reaction force ECU of FIG. It is a flowchart of the steering control program performed by ECU for steering of FIG. 5 is a flowchart showing details of a switching control routine of FIG. It is a graph which shows the relationship between a steering wheel steering angle and a target steering reaction force. It is a graph which shows the relationship between a steering wheel steering angle and a target assist torque. It is a graph which shows the relationship between a steering wheel steering angle and a target turning angle. It is a graph which shows the relationship between a vehicle speed and a vehicle speed coefficient. It is a flowchart which shows the switching control routine which concerns on the modification of the said embodiment. It is a flowchart which shows the switching control routine which concerns on the other modification of the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Steering handle, 12 ... Steering input shaft, 13 ... Electric motor for steering reaction force, 21 ... Rack bar, 22 ... Electric motor for turning, 24 ... Steering output shaft, 31 ... Cable, 32, 33 ... Electromagnetic clutch, DESCRIPTION OF SYMBOLS 41 ... Steering angle sensor, 42 ... Steering angle sensor, 43, 44 ... Rotation angle sensor, 45 ... Vehicle speed sensor, 46 ... Inspection ECU, 47 ... Steering reaction force ECU, 48 ... Steering ECU, 55 ... Engine Control device

Claims (6)

An input member connected to the steering handle and displaced in conjunction with the steering handle;
An output member connected to the steered wheel and displaced in conjunction with the steered wheel;
An intermediate member provided between the input member and the output member;
It is interposed between the input member and the intermediate member and selectively switched to a disconnected state and a connected state, and in the disconnected state, the input member and the intermediate member are disconnected so that power cannot be transmitted, and the connected state is established. A first interrupter for connecting the input member and the intermediate member so that power can be transmitted;
It is interposed between the intermediate member and the output member and selectively switched to a disconnected state and a connected state, and in the disconnected state, the intermediate member and the output member are disconnected so as not to be able to transmit power to a connected state. A second interrupter for connecting the intermediate member and the output member so that power can be transmitted;
A first electric actuator connected to the input member or the intermediate member to displace the input member or the intermediate member;
A second electric actuator connected to the output member to displace the output member;
Reaction force application control means for controlling the operation of the first electric actuator in accordance with a steering operation of the steering wheel to apply a reaction force to the steering operation of the steering wheel;
In a steer-by-wire vehicle steering apparatus comprising steering control means for steering the steered wheels by controlling the operation of the second electric actuator according to the steering operation of the steering handle,
An abnormality detecting means for detecting an abnormality of the first and second interrupters;
A vehicle steering apparatus comprising: a restricting means for restricting the movement of the vehicle when one of the first and second interrupters is detected by the abnormality detecting means.   The limiting means controls the turning control means to control the turning according to the steering operation of the steering wheel when the abnormality detecting means detects an abnormality in which one of the first and second interrupters is always connected. The vehicle steering apparatus according to claim 1, wherein the steering control means is controlled so as to change a steering characteristic of the steered wheels.   The turning characteristics of the steered wheels changed by the limiting means correspond to the steering operation of the steering wheel when mechanically coupled from the steering handle to the steered wheel by connecting the first and second interrupters. The vehicle steering apparatus according to claim 2, wherein the steering characteristic is a steered characteristic of steered wheels.   The change of the turning characteristic of the steered wheels by the restriction means is executed on the condition that the steered angle of the steered wheels is the same before and after the change of the steered characteristics. The vehicle steering device described in 1.   The vehicle steering apparatus according to any one of claims 2 to 4, wherein the turning characteristic of the steered wheels by the limiting means is gradually changed. The limiting means limits the traveling speed of the vehicle or disables traveling of the vehicle when the abnormality detecting means detects an abnormality in which one of the first and second interrupters is always disconnected. Item 2. A vehicle steering apparatus according to Item 1.

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