JP4715688B2 - Variable transmission ratio steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission ratio variable steering device in which the generated noise associated with the operation of a locking mechanism is hardly perceived by a driver. <P>SOLUTION: A VGRSECU 51 determines whether or not the absolute value of the rotational angle &theta;p of a pinion gear 31 integrally rotated with a turning output shaft 13 is not less than the lock angle &theta;_lock in Step S13. It further determines whether or not, if the rotational angle &theta;p is not less than the lock angle &theta;_lock, the absolute value of the steering angular velocity &omega;s of a steering wheel 11 is not less than the lock steering angular velocity &omega;_lock. If the steering angular velocity &omega;s is not less than the lock steering angular velocity &omega;_lock, an ECU 51 immediately shifts the lock mechanism 22 to the lock state in Step S15. Thus, generation timing of the lock sound associated with the shift to the lock state can be substantially simultaneous with that of the end-hitting sound associated with the stop by mechanical stoppers of right and left front wheels FW1, FW2, and the lock sound is hardly recognized. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a transmission ratio variable steering apparatus including a transmission ratio variable means for changing a transmission ratio of a rotation amount of a steering output shaft to a rotation amount of a steering input shaft.

  In recent years, this type of transmission ratio variable steering apparatus has been actively developed. For example, in Patent Document 1 below, a variable gear ratio unit that varies a transmission ratio by an electric motor is interposed in a steering transmission system that connects a steering wheel and a steered wheel, and an input side and an output of the variable gear ratio unit are output. There is shown a vehicle steering apparatus for operating a limiting means for limiting the operation of a variable gear ratio unit when the deviation of the angle on the side is equal to or greater than a predetermined value set based on the transmission ratio. As a result, the vehicle steering apparatus maintains the relationship between the steering amount of the steering wheel and the steering amount of the steered wheels even when there is an excessive input during traveling.

  Further, for example, in Patent Document 2 below, in the vicinity of the maximum turning angle at which the wheel turning angle exceeds the threshold value, the fixed state of the transmission ratio variable mechanism is maintained by the action of the friction torque of the transmission ratio variable mechanism itself. There is shown a vehicle steering control device that restricts a control signal that is normally set to a drive motor to the extent possible and operates the drive motor by the restricted control signal. As a result, this vehicle steering control device suppresses heat generation accompanying an increase in the load of the drive motor of the transmission ratio variable mechanism near the maximum turning angle, while preventing a sudden change in the transmission ratio due to the stop of the drive motor. It is designed to eliminate the uncomfortable feelings that people remember.

Further, for example, in Patent Document 3 below, when the steering is steered to the maximum turning angle, the change of the transmission ratio is prohibited, or the change of the target operating angle is prohibited, and the actuator of the transmission ratio variable mechanism A vehicle steering control device that restricts the operation of the vehicle is shown. As a result, when the steering ratio is changed to the quick side when the steering control apparatus for a vehicle is steered to the maximum turning angle, the driving force of the transmission ratio variable mechanism acts on the steering wheel side. Is prevented from occurring.
Japanese Patent Laid-Open No. 11-1175 JP 2001-151134 A JP 2001-48027 A

  By the way, in general, this kind of transmission ratio variable steering device is transmitted when, for example, the driver steers the steered wheels to the maximum turning angle by operating the steering handle greatly. In order to protect the ratio variable actuator (variable gear ratio unit, transmission ratio variable mechanism) and other devices, as shown in Patent Document 1, the relative relationship between the steering input shaft and the steering output shaft is mechanically determined. A lock mechanism that prohibits rotation is provided. However, this lock mechanism is generally made of metal in order to strongly prohibit relative rotation between the steering input shaft and the steered output shaft, and a loud sound (for example, a hitting sound) is generated with the operation. ) May occur.

  For this reason, when the locking mechanism is operated, for example, when the hitting sound is generated alone without being mixed with other noises, the generated hitting sound may be recognized as an annoying sound by the driver. There is. Therefore, it goes without saying that by operating the lock mechanism, the transmission ratio variable actuator (variable gear ratio unit, transmission ratio variable mechanism) and other devices are surely protected, and the sound generated by the operation of the lock mechanism. It is desirable to make it difficult for the driver to perceive it.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a transmission ratio variable steering apparatus in which the sound generated by the operation of the lock mechanism is hardly perceived by the driver.

  In order to achieve the above object, the present invention is characterized by a steering input shaft that rotates integrally with a turning operation of a steering handle, and a steering output shaft that is connected to a steering mechanism that steers steered wheels. And an electric motor connected to the steering input shaft side and a speed reducer connected to the steered output shaft side and decelerating the rotation of the drive shaft of the electric motor, to the amount of rotation of the steering input shaft The transmission ratio variable actuator that changes the transmission ratio of the rotation amount of the steering output shaft to rotate the steering output shaft, and prohibits or allows relative rotation between the steering input shaft and the steering output shaft. In a transmission ratio variable steering apparatus comprising a lock mechanism and an operation control apparatus for controlling the operation of the transmission ratio variable actuator and the operation of the lock mechanism, the operation control apparatus detects the amount of rotation of the steering output shaft. Steer Rotation amount of the steering output shaft that is set smaller than the maximum rotation amount of the steering output shaft corresponding to a stopper position that mechanically determines the steerable range of the steered wheels Lock operation start rotation set in advance to shift the lock mechanism to a locked state in which relative rotation between the steering input shaft and the steered output shaft is prohibited until the absolute value of the value reaches the maximum rotation amount. The lock operation start is determined by comparing the amount and the absolute value of the detected rotation amount of the steering output shaft, and determining whether the detected absolute value of the rotation amount is equal to or greater than the lock operation start rotation amount. An absolute value of the rotation amount of the steering output shaft that rotates following the operation of the steering handle is determined from the lock operation start amount to the maximum rotation. Before the amount The lock operation start operation speed set in advance to shift the lock mechanism to the locked state is compared with the detected absolute value of the steering wheel operation speed, and the detected absolute value of the operation speed is An operation speed determination unit that determines whether or not the lock operation start operation speed is equal to or higher than the lock operation start operation speed; And when it is determined that the absolute value of the steering wheel operation speed detected by the operation speed determination means is equal to or higher than the lock operation start operation speed, the lock mechanism is immediately put into the locked state. It is constituted by the lock operation control means to be shifted.

  In this case, the steering output shaft rotation amount detection means includes, for example, a steering input shaft rotation amount detection means that detects the rotation amount of the steering input shaft, and a motor drive shaft that detects the rotation amount of the drive shaft of the electric motor. A rotation amount detection unit and a rotation amount calculation unit that calculates the rotation amount of the steered output shaft using the detected rotation amount of the steering input shaft and the detected rotation amount of the drive shaft may be configured. .

  According to these, the operation control device determines that the absolute value of the rotation amount of the steering output shaft is greater than or equal to the lock operation start rotation amount by the lock operation start determination, and the operation speed determination means determines the operation speed of the steering wheel. Is determined to be equal to or higher than the lock operation start operation speed, the lock mechanism can immediately shift the lock mechanism to the locked state. Here, the lock operation start rotation amount is set to be smaller than the maximum rotation amount corresponding to the stopper position that mechanically determines the steerable range of the steered wheel, and the rotation amount of the steered output shaft The absolute value is set based on the amount of rotation necessary to shift the lock mechanism to the locked state until the steered wheel reaches the stopper position until the absolute value reaches the maximum amount of rotation. In addition, the lock operation start operation speed is determined until the absolute value of the rotation amount of the steering output shaft that rotates following the steering input shaft reaches the maximum rotation amount from the lock operation start rotation amount. It is set based on the time required to shift the lock mechanism to the locked state in accordance with the timing to reach the position.

  Here, in any steering device including a variable transmission ratio steering device, a stopper for mechanically determining the steerable range of the steered wheels is provided. When the steered wheels steer to the stopper position, A sound accompanying the contact between the steering wheel and the stopper inevitably occurs. Therefore, as described above, the lock operation start rotation amount and the lock operation start operation speed are set, the absolute value of the rotation amount of the steering output shaft is equal to or greater than the lock operation start rotation amount, and the absolute value of the operation speed of the steering wheel. When the operation speed exceeds the lock operation start speed, the lock mechanism is immediately shifted to the locked state, so that the sound generated by the shift to the locked state (for example, hitting sound) and the steered wheels hit the stopper. The generation timing of the sound generated by touching can be made substantially simultaneous.

  As a result, the lock mechanism can be shifted to the locked state immediately before the steered wheels contact the stopper, so that the transmission ratio variable actuator and other devices can be well protected. And since the sound accompanied by the operation of the lock mechanism can be mixed into the sound inevitably generated when the steered wheel comes into contact with the stopper, it is difficult for the driver to perceive the annoying sound. .

  Another feature of the present invention is that the operation control device is further set to be smaller than the lock operation start rotation amount, and between the rotation amount of the drive shaft of the electric motor and the rotation amount of the steering input shaft. A maintenance operation start rotation amount set in advance to start a maintenance operation in which the electric motor is operated in accordance with the rotation of the steering input shaft in a state where the relative rotation amount difference is maintained, and the detected A maintenance operation start determination means for comparing the absolute value of the rotation amount of the steered output shaft and determining whether the detected absolute value of the rotation amount is equal to or greater than the maintenance operation start rotation amount; and the maintenance operation Motor maintenance operation control means for causing the electric motor to perform the maintenance operation when the absolute value of the detected rotation amount of the steering output shaft is determined to be equal to or greater than the maintenance operation start rotation amount by the start determination means. Configured There is also that.

  In this case, the motor maintenance operation control means has the steering input shaft at the time when the absolute value of the rotation amount of the steering output shaft detected by the maintenance operation start determination means becomes equal to or greater than the maintenance operation start rotation amount. While maintaining the relative rotation amount difference between the rotation amount of the drive shaft of the electric motor that realizes a transmission ratio of the rotation amount of the steering output shaft to the rotation amount of the steering input shaft, The electric motor may be maintained and operated. Further, the motor maintenance operation control means may set the feedback gain used for feedback control to be large so as to maintain the electric motor.

  According to these, the operation control device determines that the absolute value of the rotation amount of the steering output shaft is equal to or larger than the maintenance operation start rotation amount set smaller than the lock operation start rotation amount by the maintenance operation start determination unit. And the motor maintenance operation control means to maintain the electric motor while maintaining the relative rotation amount difference between the rotation amount of the drive shaft of the electric motor of the variable transmission ratio actuator and the rotation amount of the steering input shaft. Can do. Thereby, in the situation where the electric motor is controlled to be maintained, the rotational speed of the drive shaft of the electric motor can be made substantially the same as the rotational speed of the steering input shaft.

  Here, the absolute value of the rotational speed of the steering output shaft is larger than the absolute value of the rotational speed of the steering input shaft, in other words, the absolute value of the rotational speed of the electric motor that rotates the steering output shaft is the steering input. In a situation where the rotational speed of the shaft is larger than the absolute value, when the lock mechanism shifts to the locked state, the sound generated with the shift of the lock mechanism to the locked state becomes larger. On the other hand, when the electric motor is in the maintenance operation state, the rotation speed of the electric motor is substantially equal to the rotation speed of the steering input shaft, that is, between the rotation speed of the electric motor and the rotation speed of the steering input shaft. Since the rotational speed difference is substantially “0”, the rotational speed of the electric motor is small, and the sound generated when the lock mechanism shifts to the locked state is further reduced.

  As a result, when the absolute value of the rotation amount of the steering output shaft exceeds the lock operation start rotation amount and the absolute value of the steering handle operation speed exceeds the lock operation start operation speed, the lock mechanism is immediately locked. By shifting to, it is possible to mix a small sound generated with the shift to the locked state into a sound generated when the steered wheel comes into contact with the stopper. Therefore, it is possible to make it more difficult for the driver to perceive a harsh sound.

  According to another feature of the present invention, the operation control device further includes an absolute value of the rotation amount of the steered output shaft detected by the lock operation start determination means being less than the lock operation start rotation amount. When the determination is made, the lock mechanism is shifted to an unlock state allowing relative rotation between the steering input shaft and the steered output shaft, and the lock is controlled by the unlock operation control means. When the mechanism is shifted to the unlocked state, and it is determined that the absolute value of the rotation amount of the steered output shaft detected by the maintenance operation start determination unit is less than the maintenance operation start rotation amount, A motor normal operation control means for normally operating the electric motor in order to change the transmission ratio of the rotation amount of the steering output shaft to the rotation amount of the steering input shaft. A.

  According to this, the operation control device maintains the lock mechanism in a locked state if the absolute value of the rotation amount of the steering output shaft is equal to or greater than the lock operation start rotation amount, and the absolute value of the rotation amount of the steering output shaft is If it becomes less than the lock operation start rotation amount, the lock mechanism can be shifted to the unlock state by the unlock operation means. In addition, after the lock mechanism is shifted to the unlocked state, the operation control device turns the electric motor if the absolute value of the rotation amount of the steered output shaft is less than the lock operation start rotation amount and greater than the maintenance operation start rotation amount. Normal operation control of the motor to change the transmission ratio of the rotation amount of the steering output shaft to the rotation amount of the steering input shaft if the absolute value of the rotation amount of the steering output shaft is less than the maintenance operation start rotation amount. The electric motor can be normally operated by the means.

  Therefore, the operation state of the electric motor can be the same when the lock mechanism shifts from the unlocked state to the locked state and when the lock mechanism shifts from the locked state to the unlocked state. As a result, the operation of the lock mechanism can be switched very smoothly, and the operational feeling of the steering wheel associated with the switching of the operation can be changed very smoothly.

a. First Embodiment Hereinafter, a transmission ratio variable steering device (hereinafter simply referred to as a steering device) mounted on a vehicle according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a steering device common to the first embodiment and the second embodiment.

  This steering device includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to the transmission ratio variable actuator 20.

  The transmission ratio variable actuator 20 connects the steering input shaft 12 and the steering output shaft 13 so as to be relatively rotatable, and the connected steering output shaft 13 with respect to the rotation amount (or rotation angle) of the steering input shaft 12. The amount of rotation (or rotation angle) is appropriately changed. Therefore, the transmission ratio variable actuator 20 includes an electric motor 21 (hereinafter, this electric motor is referred to as a VGRS motor 21), a lock mechanism 22 that allows (unlocks) or restricts (locks) the rotation of the motor 21, and a deceleration. Machine 23.

  The VGRS motor 21 is, for example, a three-phase AC brushless motor, and the motor housing 21a is integrally connected to the steering input shaft 12 so as to rotate integrally in accordance with the turning operation of the steering handle 11 by the driver. It has become. The proximal end side of the drive shaft 21b of the VGRS motor 21 is connected to a lock mechanism 22 fixed in the motor housing 21a, and the distal end side of the drive shaft 21b is connected to the speed reducer 23. . In the following description, the motor housing 21a of the VGRS motor 21 is integrally (directly) connected to the steering input shaft 12. However, for example, the motor housing 21a is integrally connected to the steering input shaft 12. It is also possible to carry out the VGRS motor 21 fixedly accommodated in the casing member.

  As shown in FIG. 2, the lock mechanism 22 includes a lock holder 22a fixed to the outer periphery of the drive shaft 21b, and a lock lever 22b that comes into contact with or separates from the lock holder 22a. The lock holder 22a is a disk-like member that rotates integrally with the drive shaft 21b, and a plurality of groove portions 22a1 are formed on the outer periphery thereof. The lock lever 22b has an engagement portion 22b1 that engages with a groove portion 22a1 formed in the lock holder 22a at a tip portion thereof.

  Further, the lock lever 22b rotates at the substantially central portion thereof in parallel with the axial direction of the drive shaft 21b and rotates toward the other end portion of the lock pin 22c that is integrally fixed to the motor housing 21a at one end portion side. It is slidably assembled. Further, the lock lever 22b is connected to the solenoid 22d at the base end portion thereof. The solenoid 22d contracts according to the energized state based on operation control described later.

  In the state where the energization to the solenoid 22d is interrupted, the lock mechanism 22 rotates the lock lever 22b around the axis of the lock pin 22c by the urging force of a spring (not shown), and the engaging portion 22b1 is connected to the lock holder 22a. Engages with the groove 22a1. In the following description, this engaged state is referred to as a locked state. On the other hand, in the state where the solenoid 22d is energized, the lock mechanism 22 rotates around the axis of the lock pin 22c by the contraction operation of the solenoid 22d, and the engaging portion 22b1 is separated from the groove portion 22a1 of the lock holder 22a. . In the following description, this separated state is referred to as an unlocked state.

  The speed reducer 23 is configured by a predetermined gear mechanism (for example, a harmonic drive (registered trademark) mechanism or a planetary gear mechanism), and one end side of the steered output shaft 13 is connected to the gear mechanism. Thereby, when the rotational force of the VGRS motor 21 is transmitted through the drive shaft 21b, the speed reducer 23 appropriately reduces the rotation of the drive shaft 21b by a predetermined gear mechanism and transmits the rotation to the steered output shaft 13. To do. Therefore, the transmission ratio variable actuator 20 connects the steering input shaft 12 and the steered output shaft 13 via the drive shaft 21b of the VGRS motor 21 so as to be relatively rotatable, and the rotation amount of the steering input shaft 12 (or The ratio of the rotation amount (or rotation angle) of the steering output shaft 13 to the rotation angle), that is, the transmission ratio of rotation from the steering input shaft 12 to the steering output shaft 13 can be changed as appropriate.

  Further, the steering device includes a steered gear unit 30 connected to the other end side of the steered output shaft 13. The steered gear unit 30 is, for example, a gear unit adopting a rack and pinion type, and the rotation of the pinion gear 31 assembled integrally with the steered output shaft 13 is transmitted to the rack bar 32. Yes. The steered gear unit 30 is provided with an electric motor 33 (hereinafter referred to as an EPS motor 33) for reducing a steering force (steering torque) input to the steering handle 11 by the driver. Thus, the torque (assist force) generated by the EPS motor 33 is transmitted to the rack bar 32.

  With this configuration, the rotational force of the steering output shaft 13 is transmitted to the rack bar 32 via the pinion gear 31 that rotates integrally, and the assist force of the EPS motor 33 is transmitted to the rack bar 32. As a result, the rack bar 32 is displaced in the axial direction by the rotational force from the pinion gear 31 and the assist force of the EPS motor 33. Therefore, the left and right front wheels FW1, FW2 connected to both ends of the rack bar 32 are steered left and right.

  The steering device further includes a vehicle speed sensor 41, a steering angle sensor 42, a rotation angle sensor 43, a torque sensor 44, and a motor current value detection sensor 45. The vehicle speed sensor 41 detects and outputs the vehicle speed V of the vehicle. The steering angle sensor 42 detects the amount of rotation of the steering input shaft 12, that is, the amount of rotation of the steering handle 11, and outputs it as a rotation angle θs (corresponding to the steering angle of the steering handle 11). The rotation angle sensor 43 is assembled to the motor housing 21a of the VGRS motor 21, detects the rotation amount of the drive shaft 21b with respect to the rotation amount of the steering input shaft 12 (that is, the motor housing 21a), and outputs it as the rotation angle θm. The torque sensor 44 detects a twist generated in the steering output shaft 13 and outputs a torque T corresponding to the generated twist. The motor current value detection sensor 45 detects and outputs a current value I flowing through the VGRS motor 21.

  Next, the electric control device 50 that controls the operation of the transmission ratio variable actuator 20 (specifically, the VGRS motor 21 and the solenoid 22d) and the steering gear unit 30 (specifically, the EPS motor 33) will be described.

  The electric control device 50 includes an electronic control unit 51 that controls the operation of the VGRS motor 21 of the transmission ratio variable actuator 20 and the solenoid 22d of the lock mechanism 22 (hereinafter, this electronic control unit is referred to as VGRSECU 51), and the turning gear unit 30. An electronic control unit 52 that controls the operation of the EPS motor 33 (hereinafter, this electronic control unit is referred to as an EPS ECU 52) is provided. These VGRSECU 51 and EPSECU 52 are mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The VGRSECU 51 and the EPS ECU 52 can communicate with each other via, for example, a communication line A constructed in the vehicle.

  Further, a vehicle speed sensor 41, a steering angle sensor 42, a rotation angle sensor 43, and a motor current value detection sensor 45 are connected to the input side of the VGRSECU 51, and the steering angle sensor 42 and the torque sensor 44 are connected to the input side of the EPS ECU 52. Is connected. Thereby, VGRESCU51 and EPSECU52 execute the various programs including the various programs mentioned later using each detection value by these connected sensors, and control the operation of VGRS motor 21, solenoid 22d, and EPS motor 33, respectively. For this reason, drive circuits 53 and 54 for driving the VGRS motor 21 and the solenoid 22d are connected to the output side of the VGRSECU 51, and a drive circuit 55 for driving the EPS motor 33 is connected to the output side of the EPS ECU 52. Has been.

  Next, the operation in the first embodiment of the steering apparatus configured as described above will be described. When an ignition switch (not shown) is turned on, the VGRS ECU 51 starts transmission ratio variable control that continuously changes the transmission ratio G by driving the VGRS motor 21 of the transmission ratio variable actuator 20. The EPS ECU 52 starts torque assist control for driving the EPS motor 33 of the steered gear unit 30 to reduce the operating force of the steering handle 11 by the driver. Hereinafter, the transmission ratio variable control by the VGRS ECU 51 and the torque assist control by the EPS ECU 52 will be briefly described.

  First, the transmission ratio variable control will be described. The VGRSECU 51 inputs the current vehicle speed V from the vehicle speed sensor 41 and, for example, refers to a table as shown in FIG. 3 to determine the transmission ratio according to the detected vehicle speed V. Determine G. The transmission ratio G has a characteristic that decreases nonlinearly and continuously as the vehicle speed V increases. When the transmission ratio G is determined and the driver starts the turning operation of the steering handle 11, the steering input shaft 12, the transmission ratio variable actuator 20, the steering output shaft 13 and the pinion gear 31 also start to rotate. To do. In association with the turning operation of the steering handle 11 by the driver, the VGRS ECU 51 inputs the rotation angle θs of the steering input shaft 12 detected by the steering angle sensor 42. Then, the VGRS ECU 51 multiplies the input rotation angle θs by the determined transmission ratio G, so that the target rotation angle θph of the pinion gear 31 with respect to the rotation angle θs of the steering input shaft 12 (that is, the steering angle of the steering wheel 11). That is, the target turning angle of the left and right front wheels FW1, FW2 is calculated.

Next, the VGRS ECU 51 calculates the operation amount of the VGRS motor 21 necessary for realizing the calculated target rotation angle θph of the pinion gear 31, that is, the target rotation angle θmh of the drive shaft 21b. More specifically, the motor housing 21a of the VGRS motor 21 connected integrally with the steering input shaft 12 rotates in accordance with the turning operation of the steering handle 11 by the driver. At this time, the VGRS ECU 51 controls the drive circuit 53 to drive the VGRS motor 21 in order to rotate the pinion gear 31 integrally connected to the steered output shaft 13 in accordance with the rotation of the motor housing 21a. In the drive control of the VGRS motor 21, the VGRS ECU 51 calculates the target rotation angle θmh so that the pinion gear 31 becomes the target rotation angle θph with respect to the rotation angle θs of the steering input shaft 12. That is, the VGRS ECU 51 calculates the target rotation angle θmh of the drive shaft 21b with respect to the steering input shaft 12 according to the following equation 1.
θmh = θph−θs = (G−1) · θs Equation 1
In the following description, (G−1) in the formula 1 is also referred to as a variable assist ratio Kv.

  Then, when the VGRS ECU 51 calculates the target rotation angle θmh according to the equation 1, the VGRS ECU 51 controls the drive circuit 53 without overshooting until the rotation angle θm detected by the rotation angle sensor 43 reaches the target rotation angle θmh, and VGRS The drive shaft 21b of the motor 21 is rotated. Thereby, the pinion gear 31 connected to the steering output shaft 13 is added or subtracted by the target rotation angle θmh of the drive shaft 21b with respect to the rotation angle θs of the steering input shaft 12, in other words, the steering input shaft With respect to twelve rotation angles θs, the rotation is performed to a target rotation angle θph that is a transmission ratio G. Accordingly, when the rack bar 32 is displaced in the axial direction in accordance with the rotation of the pinion gear 31, the left and right front wheels FW1 and FW2 are steered to a target turning angle corresponding to the target rotation angle θph.

  Thus, the driver obtains good steering operability (steering feeling) according to the vehicle speed V by turning the left and right front wheels FW1, FW2 to the target turning angle corresponding to the target rotation angle θph. Can do. Specifically, when the detected vehicle speed V increases, the transmission ratio G is determined to be small, so that the pinion gear 31 is rotated in the opposite direction relative to the rotation direction of the steering input shaft 12. That is, in this case, the target rotation angle θph of the pinion gear 31 is calculated by subtracting the target rotation angle θmh of the drive shaft 21b from the rotation angle θs of the steering input shaft 12 (steering handle 11). Therefore, the left and right front wheels FW1 and FW2 are small with respect to the amount of turning operation of the steering handle 11 by the driver. In other words, the left and right front wheels FW1 and FW2 are gently steered with respect to the turning operation of the steering handle 11. It becomes like this. As a result, the driver can easily operate the steering handle 11 and can stabilize the behavior of the vehicle during high-speed traveling.

  On the other hand, when the detected vehicle speed V decreases, the transmission ratio G is set to be large, so that the steered output shaft 13 rotates relatively in the rotational direction of the steering input shaft 12. That is, in this case, the target rotation angle θph of the pinion gear 31 is calculated by adding the target rotation angle θmh of the drive shaft 21b to the rotation angle θs of the steering input shaft 12 (steering handle 11). Therefore, the left and right front wheels FW1 and FW2 are large with respect to the turning operation amount of the steering handle 11 by the driver. In other words, the left and right front wheels FW1 and FW2 are quickly steered with respect to the turning operation of the steering handle 11. . Thereby, for example, in garage entry, the amount of rotation operation of the steering handle 11 by the driver can be reduced, and the operation burden on the driver can be reduced.

  Next, torque assist control will be described. The EPS ECU 52 drives the EPS motor 33 to reduce the steering torque required for the turning operation according to the amount of the turning operation of the steering handle 11 and the magnitude of the torque (that is, the steering torque) by the driver. Assist force is transmitted to 32. That is, the EPS ECU 52 receives the rotation angle θs from the steering angle sensor 42 and the torque T from the torque sensor 44, and drives the EPS motor 33 in accordance with the input rotation angle θs and the magnitude of the torque T. Set the control amount. Then, the EPS ECU 52 controls the drive circuit 55 to drive the EPS motor 33 without overshooting based on the set control amount. Thereby, the steering torque accompanying the turning operation of the steering handle 11 by the driver is reduced, and the physical burden on the driver can be reduced.

  Thus, in the steering device employing the transmission ratio variable actuator 20, as described above, particularly when the detected vehicle speed V is low, the amount of turning operation of the steering handle 11 by the driver is reduced to improve the vehicle. Can be swiveled. In other words, in a situation where the detected vehicle speed V is low, the turning angle of the left and right front wheels FW1, FW2 can be made larger than the steering angle of the steering handle 11 by the driver. Therefore, in a situation where the detected vehicle speed V is low, the pinion gear 31 is up to a maximum angle corresponding to a mechanical stopper position that mechanically determines the steerable range of the left and right front wheels FW1, FW2 (hereinafter, this maximum angle is referred to as a mechanical end angle θ_end). The frequency at which the rotation angle θp changes is increased.

  By the way, when the rotation angle θp of the pinion gear 31 changes to the mechanical end angle θ_end, the turning operation of the left and right front wheels FW1, FW2 is forcibly stopped by the mechanical stopper. For this reason, for example, the VGRSECU 51 operates so that the lock mechanism 22 is locked in order to reduce damage to the transmission ratio variable actuator 20 caused by the external force input with the forced stop of the left and right front wheels FW1, FW2. Control. In accordance with the operation control by the VGRS ECU 51, the lock mechanism 22 shifts to the locked state by engaging the engagement portions 22b1 formed on the lock lever 22b with the plurality of grooves 22a1 formed on the outer periphery of the lock holder 22a. . Here, when the lock mechanism 22 shifts to the locked state, particularly when the lock holder 22a rotates at a high speed, a hitting sound (hereinafter referred to as the hitting force) caused by the contact between the lock lever 22b and the lock holder 22a. (The sound is called a lock sound), and this lock sound may be recognized as an annoying sound by the driver.

  For this reason, the VGRSECU 51 executes the lock mechanism operation control program shown in FIG. 4, and when the rotation angle θp of the pinion gear 31 changes to the mechanical end angle θ_end, the lock sound is hardly recognized by the driver. As described above, the lock mechanism 22 is shifted to the locked state. Hereinafter, the operation control program will be specifically described.

  When an ignition switch (not shown) is turned on, the VGRSECU 51 starts execution of the lock mechanism operation control program in step S10, and inputs the rotation angle θs of the steering input shaft 12 from the steering angle sensor 42 in step S11. At the same time, the rotation angle θm of the drive shaft 21 b of the VGRS motor 21 is input from the rotation angle sensor 43. And VGRSECU51 will progress to step S12, if each detection value is input.

In step S12, the VGRS ECU 51 calculates the rotation angle θp of the pinion gear 31 according to the following equation 2 using the rotation angle θs and the rotation angle θm input in step S11.
θp = θs + θm · Kb Equation 2
However, Kb in the said Formula 2 represents the gear ratio of the reduction gear 23. FIG.

  In the subsequent step S13, the VGRS ECU 51 determines whether or not the calculated absolute value of the rotation angle θp is equal to or larger than the lock angle θ_lock as the lock operation start rotation amount set smaller than the mechanical end angle θ_end. Here, the lock angle θ_lock is experimentally set in advance based on the rotation amount of the drive shaft 21b necessary for the lock mechanism 22 to shift to the locked state, more specifically, based on the formation interval of the groove 22a1 of the lock holder 22a. Is a constant. If the absolute value of the calculated rotation angle θp is greater than or equal to the lock angle θ_lock, the VGRSECU 51 determines “Yes” and proceeds to step S14.

  On the other hand, if the absolute value of the calculated rotation angle θp is less than the lock angle θ_lock, the VGRSECU 51 determines “No” in order to maintain the lock mechanism 22 in the unlocked state. Then, the VGRSECU 51 continues to determine “No” until the absolute value of the rotation angle θp becomes equal to or larger than the lock angle θ_lock, and repeatedly executes each step process of step S11 and step S12.

  In step S14, the VGRS ECU 51 determines whether or not the absolute value of the steering angular speed ωs of the steering handle 11 by the driver is equal to or higher than a lock steering angular speed ω_lock as a preset lock operation start operation speed. Here, the lock steering angular velocity ω_lock takes into account the response time of the solenoid 22d, the formation interval of the groove 22a1 formed in the lock holder 22a, and the like, so that the rotation angle θp of the pinion gear 31 reaches the mechanical end angle θ_end from the lock angle θ_lock. Immediately before setting, the constant is set based on experiments so that the lock mechanism 22 can shift to the locked state.

  More specifically, for example, the VGRS ECU 51 calculates the steering angular velocity ωs by differentiating the rotation angle θs of the steering input shaft 12, that is, the steering handle 11 input in step S 11 with respect to time. If the calculated absolute value of the steering angular velocity ωs is equal to or greater than the lock steering angular velocity ω_lock, the VGRSECU 51 determines “Yes” to immediately shift the lock mechanism 22 to the locked state, and proceeds to step S15.

  In step S15, the VGRSECU 51 sets a current value (hereinafter, this current value is referred to as a lock current value I_lock) supplied to the solenoid 22d via the drive circuit 54 to “0” in order to place the lock mechanism 22 in the locked state. The power supply to the solenoid 22d is cut off. As a result, the contraction operation of the solenoid 22d is released, and the lock lever 22b rotates around the axis of the lock pin 22c by a biasing force of a spring (not shown). And the engaging part 22b1 formed in the front-end | tip part of the lock lever 22b engages with the groove part 22a1 formed on the outer periphery of the lock holder 22a, and the lock mechanism 22 will be in a locked state.

  Here, when the steering handle 11 is turned by the driver, the VGRS motor 21 of the transmission ratio variable actuator 20 follows the turning operation of the driver and the pinion gear connected to the steering output shaft 13. 31 is rotated to steer the left and right front wheels FW1, FW2. Therefore, when the steering handle 11 is turned by the driver at a large steering angular velocity ωs, the VGRS motor 21 rotates at high speed to quickly steer the left and right front wheels FW1, FW2. Then, when the VGRS motor 21 is rotating at a high speed, when the lock mechanism 22 shifts to the locked state, the generated lock sound increases.

  On the other hand, when the left and right front wheels FW1 and FW2 are steered to the maximum turning angle corresponding to the mechanical end angle θ_end and the steering operation of the left and right front wheels FW1 and FW2 is forcibly stopped, A sound (hereinafter referred to as a hit sound at the end) is inevitably generated. The end hit sound also increases as the left and right front wheels FW1, FW2 are steered quickly.

  Meanwhile, the lock steering angular velocity ω_lock is set so that the lock mechanism 22 shifts to the locked state immediately before the rotation angle θp of the pinion gear 31 rotating at high speed reaches the mechanical end angle θ_end. Therefore, when the absolute value of the steering angular velocity ωs is equal to or higher than the lock steering angular velocity ω_lock, the timing at which the lock sound is generated and the timing at which the end hitting sound are generated can be made substantially coincident. As a result, a lock sound that is harsh to the driver can be mixed with the end hit sound that is inevitably generated, and the driver can hardly recognize the lock sound.

  As described above, when the lock mechanism 22 is immediately shifted to the locked state, the VGRSECU 51 once ends the execution of the program in step S17. And VGRSECU51 starts execution of a locking mechanism action | operation control program again in step S10, after progress for a predetermined short time.

  On the other hand, if the calculated absolute value of the steering angular velocity ωs is less than the lock steering angular velocity ω_lock, the VGRS motor 21 rotates relatively slowly and the generated lock sound becomes relatively small. Therefore, VGRSECU 51 determines “No” in step S14 and proceeds to step S16. In step S <b> 16, for example, the VGRS ECU 51 shifts the lock mechanism 22 to the locked state by the normal lock operation control in a state where the maximum value Im_max of the drive current value Im flowing through the VGRS motor 21 is limited.

  More specifically, as shown in FIG. 5, for example, the VGRS ECU 51 sets the drive current value that is set when the absolute value of the rotation angle θp of the pinion gear 31 calculated in step S12 is less than the lock angle θ_lock. When the absolute value of the rotation angle θp is equal to or larger than the lock angle θ_lock with respect to the Im maximum value Im_max (a constant value), the maximum value Im_max is linearly decreased as the absolute value of the rotation angle θp increases. Thus, in a situation where the absolute value of the rotation angle θp of the pinion gear 31 changes to the mechanical end angle θ_end, the VGRESCU 51 is based on the changed maximum value Im_max and the current value I detected by the motor current value detection sensor 45. Then, the drive circuit 53 is controlled to rotate the VGRS motor 21 more slowly. The VGRS ECU 51 shifts the lock mechanism 22 to the locked state when, for example, the absolute value of the rotation angle θp matches the mechanical end angle θ_end while the VGRS motor 21 is rotating slowly. As a result, it is possible to reduce the lock sound generated with the shift to the locked state, and to make it difficult for the driver to recognize the lock sound.

  As described above, when the lock mechanism 22 is shifted to the locked state, the VGRSECU 51 once ends the execution of the program in step S17. And VGRSECU51 starts execution of a locking mechanism action | operation control program again in step S10, after progress for a predetermined short time.

  Here, when the lock mechanism 22 is in the locked state by executing the lock mechanism operation control program, for example, the absolute value of the rotation angle θp of the pinion gear 31 is locked as the driver rotates the steering handle 11. When it becomes less than the angle θ_lock, the VGRSECU 51 shifts the lock mechanism 22 to the unlocked state. That is, the VGRS ECU 51 controls the drive circuit 54 to start supplying the lock current value I_lock set to a predetermined magnitude to the solenoid 22d. As a result, the solenoid 22d starts to contract and rotates the lock lever 22b about the axis of the lock pin 22c against the biasing force of a spring (not shown). Therefore, the engaging portion 22b1 of the lock lever 22b and the groove portion 22a1 of the lock holder 22a are separated from each other, and the lock mechanism 22 shifts to the unlocked state in which the engagement is released.

  As can be understood from the above description, according to the first embodiment, the VGRSECU 51 rotates the rotation angle θp of the pinion gear 31 that rotates integrally with the steered output shaft 13 in step S13 of the lock mechanism operation control program. Is determined to be greater than or equal to the lock angle θ_lock, and when the absolute value of the steering angular velocity ωs of the steering handle 11 is determined to be greater than or equal to the lock steering angular velocity ω_lock in step S14, the lock mechanism 22 is determined in step S15. Can be immediately shifted to the locked state. As a result, it is possible to make the generation timing of the locking sound generated with the shift to the locked state and the end hitting sound generated when the left and right front wheels FW1, FW2 contact the mechanical end stopper substantially the same.

  As a result, the lock mechanism 22 can be shifted to the locked state immediately before the left and right front wheels FW1, FW2 come into contact with the mechanical end stopper, so that the transmission ratio variable actuator 20 can be well protected. Since the left and right front wheels FW1 and FW2 come into contact with the mechanical end stopper and the end hitting sound inevitably generated, the locking sound accompanying the operation of the locking mechanism 22 can be mixed in. Sound can be made difficult to perceive.

b. Second Embodiment In the first embodiment, the lock mechanism operation control program is executed in a state where the VGRS motor 21 is caused to follow the fast turning operation of the steering handle 11 by the driver, and the generated lock sound is detected as the end hit sound. It was carried out to make it difficult for the driver to recognize the lock sound. However, in a state where the VGRS motor 21 is rotating at a high speed, the lock sound may become extremely loud depending on the contact state between the engagement portion 22b1 of the lock lever 22b and the groove portion 22a1 of the lock holder 22a. May cause the lock sound to be recognized.

  Therefore, in the second embodiment, in a situation where the left and right front wheels FW1, FW2 are steered toward the mechanical end angle θ_end, VGRS is prevented so that relative rotational displacement does not occur between the steering input shaft 12 and the drive shaft 21b. With the rotation speed of the motor 21 controlled, the lock mechanism 22 is shifted to the locked state. Hereinafter, although this 2nd Embodiment is described in detail, the same code | symbol is attached | subjected to the same part as the said 1st Embodiment, and the detailed description is abbreviate | omitted.

  In the second embodiment, in order to appropriately control the rotation speed of the VGRS motor 21 according to the magnitude of the absolute value of the rotation angle θp of the pinion gear 31 that rotates integrally with the steered output shaft 13, the VGRSECU 51 Executes the motor rotation speed control program shown in FIG. This motor rotation speed control program is repeatedly executed at predetermined short time intervals when an ignition switch (not shown) is turned on.

  More specifically, the VGRS ECU 51 starts the motor rotation speed control program in step S30, and inputs detection values detected by the sensors in the subsequent step S31. That is, the VGRSECU 51 inputs the vehicle speed V from the vehicle speed sensor 41, the rotation angle θs from the steering angle sensor 42, and the rotation angle θm from the rotation angle sensor 43, respectively. And if each detection value is input, VGRESCU51 will progress to step S32.

  In step S32, the VGRSECU 51 calculates the rotation angle θp of the pinion gear 31 according to the equation 2 described in the first embodiment. Then, after calculating the rotation angle θp, the VGRSECU 51 proceeds to step S33.

  In step S33, the VGRS ECU 51 determines whether or not the absolute value of the calculated rotation angle θp is equal to or greater than the motor rotation fixed angle θ_lim as the maintenance operation start rotation amount set smaller than the lock angle θ_lock. Here, the motor rotation fixed angle θ_lim is set so that the drive shaft 21b of the VGRS motor 21 does not produce a rotational displacement relative to the steering input shaft 12, in other words, between the steering input shaft 12 and the drive shaft 21b. Is a constant set in advance to start the drive control of the VGRS motor 21 so that a relative rotational angular velocity difference does not occur.

  That is, if the absolute value of the calculated rotation angle θp is equal to or greater than the motor rotation fixed angle θ_lim, the VGRSECU 51 determines “Yes” and proceeds to step S34, and the relative rotation between the steering input shaft 12 and the drive shaft 21b. A maintenance drive control routine for controlling the drive of the VGRS motor 21 while maintaining the displacement is executed. On the other hand, if the absolute value of the calculated rotation angle θp is less than the motor rotation fixed angle θ_lim, the VGRSECU 51 determines “No” and proceeds to step S35, and the relative rotation between the steering input shaft 12 and the drive shaft 21b. A normal drive control routine for controlling the drive of the VGRS motor 21 while allowing the displacement is executed. Hereinafter, the maintenance drive control routine and the normal drive control routine will be described in detail, but for the sake of easy understanding, the normal drive control routine will be described first.

As shown in FIG. 7, the normal drive control routine is started in step S50. In step S51, the VGRS ECU 51 calculates the target rotation angle θmh of the VGRS motor 21 with respect to the rotation of the steering input shaft 12 in accordance with the following equation 3 expressed in the same manner as the equation 1.
θmh = Kv · θs Equation 3
However, Kv in Equation 3 represents a variable assist ratio.

As described above, after calculating the target rotation angle θmh, the VGRS ECU 51 calculates the target rotation angle θmh and the actual rotation angle θm detected by the rotation angle sensor 43 in order to perform feedback control of the VGRS motor 21 in step S52. By calculating the difference, the angle deviation Δθm of the drive shaft 21b is calculated according to the following equation 4.
Δθm = θmh−θm Equation 4

Further, by VGRSECU51 is for calculating a difference between the currently normal deviation Δθm calculated by executing the drive control routine _(t) and deviation Δθm calculated when executing the previous routine _(t-1), the drive shaft 21b The rotational angular velocity deviation Δω is calculated according to the following formula 5.
Δω = Δθm _(t) −Δθm _(t-1) Equation 5
When VGRSECU 51 calculates the angular deviation Δθm and the rotational angular velocity deviation Δω, the process proceeds to step S53.

  In step S <b> 53, the VGRS ECU 51 sets a feedback gain for performing feedback control of the VGRS motor 21. That is, the VGRSECU 51 sets the feedback gains Pfb and Dfb corresponding to the angular deviation Δθm and the rotational angular velocity deviation Δω to small values with reference to the characteristic table shown in FIG. Thereby, for example, the ripple fluctuation width can be suppressed to be small, and the VGRS motor 21 can be driven and controlled stably. In this normal drive control routine, the change characteristics of the feedback gains Pfb and Dfb are made constant with respect to the vehicle speed V. However, the change characteristics of the feedback gains Pfb and Dfb are changed with respect to the vehicle speed V according to the control state. Needless to say, the present invention can be implemented by changing. Then, after setting the feedback gains Pfb and Dfb, the VGRSECU 51 proceeds to step S54.

In step S54, the VGRS ECU 51 sets the drive current value Im for driving the VGRS motor 21 to the angular deviation Δθm and the rotational angular velocity deviation Δω calculated in step S52, and the feedback gain Pfb, set in step S53. It calculates according to the following formula 6 using Dfb.
Im = Δθm · Pfb + Δω · Dfb Equation 6
In step S55, the VGRS ECU 51 controls the drive circuit 53 so that the drive current value Im flows through the VGRS motor 21 based on the current value I detected by the motor current value detection sensor 45, and the VGRS motor 21 is normally driven.

  As a result, the drive shaft 21b rotates relative to the steering input shaft 12 up to the target rotational angle θmh calculated according to the above equation 3, and the pinion gear 31 connected to the steered output shaft 13 has the rotational angle θs and the target rotational angle. The rotation angle θp is represented by the sum of the rotation angle θmh (that is, the rotation angle θm). As a result, the left and right front wheels FW1, FW2 are steered so as to have a transmission ratio G, and the driver can obtain a good steering feeling.

  When the VGRS motor 21 is normally driven in this way, the VGRS ECU 51 ends the execution of the normal drive control routine in step S56. Then, VGRSECU 51 returns to the motor rotation speed control program, and once the execution of the program is terminated in step S38. Then, after a predetermined short time has elapsed, in step S30, execution of the motor rotation speed control program is started again.

  Next, the sustain drive control routine will be described. As shown in FIG. 9, the maintenance drive control routine is started in step S70. In step S71, the VGRS ECU 51 sets the target rotation angle θmh of the drive shaft 21a of the VGRS motor 21 to a fixed target rotation angle θmhf as a fixed value.

  More specifically, when the maintenance drive control routine is executed for the first time after determining “Yes” in step S33 of the motor rotation speed control program, the VGRS ECU 51 performs the normal drive control performed immediately before this “Yes” determination. The target rotation angle θmh calculated in step S51 of the routine is set as the fixed target rotation angle θmhf. When this maintenance drive control routine is executed for the second time and thereafter, the fixed target rotation angle θmhf set when the previous routine is executed is continuously maintained. In this way, by setting the fixed target rotation angle θmhf, the relative rotational position relationship between the rotational position of the steering input shaft 12 and the rotational position of the drive shaft 21b of the VGRS motor 21 is fixed, more specifically, The rotational angular velocity of the steering input shaft 12 and the rotational angular velocity of the drive shaft 21b can be made substantially coincident.

Subsequently, in step S72, the VGRS ECU 51 performs an angular deviation between the fixed target rotation angle θmhf set in step S71 and the actual rotation angle θm detected by the rotation angle sensor 43 in order to perform feedback control of the VGRS motor 21. Δθmf is calculated according to Equation 7 below.
Δθmf = θmhf−θm Equation 7

Further, the VGRS ECU 51 calculates the difference between the deviation Δθmf _(t) calculated by executing the current maintenance drive control routine and the deviation Δθmf _(t−1) calculated when the previous routine is executed, thereby driving the drive shaft 21b. Is calculated according to the following equation (8).
Δωf = Δθmf _(t) −Δθmf _(t-1) Equation 8
When VGRSECU 51 calculates the angular deviation Δθmf and the rotational angular velocity deviation Δωf, the process proceeds to step S73.

  In step S <b> 73, the VGRS ECU 51 sets a feedback gain for performing feedback control of the VGRS motor 21. That is, the VGRSECU 51 sets the feedback gains Pfb and Dfb corresponding to the angular deviation Δθmf and the rotational angular velocity deviation Δωf to a larger value than when the above-described normal drive control routine is executed with reference to the characteristic table shown in FIG. .

  Thereby, for example, the drive shaft 21b of the VGRS motor 21 is extremely responsive to the rotational change of the steering input shaft 12, in other words, the relative rotational speed difference between the steering input shaft 12 and the drive shaft 21b is substantially “0”. Thus, the VGRS motor 21 can be maintained and controlled. In this maintenance drive control routine, the change characteristics of the feedback gains Pfb and Dfb are set constant with respect to the vehicle speed V. However, the change characteristics of the feedback gains Pfb and Dfb are changed with respect to the vehicle speed V according to the control state. Needless to say, the present invention can be implemented by changing. Then, after setting the feedback gains Pfb and Dfb, the VGRSECU 51 proceeds to step S74.

In step S74, the VGRS ECU 51 calculates the angular deviation Δθmf and the rotational angular velocity deviation Δωf calculated in step S72 for the sustain drive current value ΔIm for maintaining the VGRS motor 21 in response to the rotation change of the steering input shaft 12. And the following calculation using the feedback gains Pfb and Dfb set in step S73.
ΔIm = Δθmf · Pfb + Δωf · Dfb Equation 9
Then, VGRSECU 51 proceeds to step 75 after calculating sustain drive current value ΔIm.

In step S <b> 75, the VGRS ECU 51 maintains and drives the VGRS motor 21. More specifically, the VGRS ECU 51 maintains the drive current value Imf _(t) for maintaining the relative rotational position relationship between the rotational position of the steering input shaft 12 and the rotational position of the drive shaft 21b of the VGRS motor 21. Calculation is performed according to the following equation 10 using the drive current value ΔIm.
Imf _(t) = Imf _(t-1) + ΔIm Equation 10
However, Imf _{(t−1) in} Equation 10 was calculated in order to maintain the relative rotational positional relationship between the steering input shaft 12 and the drive shaft 21b when the maintenance drive control routine was executed last time. Represents the drive current value.

Based on the current value I detected by the motor current value detection sensor 45, the VGRS ECU 51 controls the drive circuit 53 so that the drive current value Imf _(t) appropriately flows through the VGRS motor 21, and maintains the VGRS motor 21. Drive. Accordingly, the drive shaft 21b of the VGRS motor 21 can rotate in a state where the relative rotational angular velocity difference with respect to the rotation of the steering input shaft 12 is extremely small, that is, in a state where the drive input shaft 12 is rotated.

  When the VGRS motor 21 is maintained and driven in step S75, the VGRS ECU 51 inputs the detected value after the sustain driving of the VGRS motor 21 detected by each sensor in step S76. That is, the VGRSECU 51 inputs the vehicle speed V from the vehicle speed sensor 41, the rotation angle θs from the steering angle sensor 42, and the rotation angle θm from the rotation angle sensor 43, respectively. And if each detection value is input, VGRESCU51 will progress to step S77. In step S <b> 77, the VGRS ECU 51 calculates the current rotation angle θp of the pinion gear 31 after the VGRS motor 21 is maintained and driven according to the above equation 2.

  When the VGRS motor 21 is maintained and controlled in this way, the VGRS ECU 51 terminates the execution of the maintenance drive control routine in step S78. Then, the VGRSECU 51 returns to the motor rotation speed control program, and in step S36, whether or not the absolute value of the rotation angle θp of the pinion gear 31 calculated in step S77 of the maintenance drive control routine is equal to or larger than the lock angle θ_lock. Determine. That is, if the absolute value of the rotation angle θp is less than the lock angle θ_lock, the VGRESCU 51 determines “No” and returns to step S33, and again determines whether or not the rotation angle θp is equal to or greater than the motor rotation fixed angle θ_lim. To do.

  On the other hand, if the absolute value of the rotation angle θp of the pinion gear 31 is equal to or larger than the lock angle θ_lock, the VGRSECU 51 determines “Yes” in order to set the lock mechanism 22 in the locked state, and the first implementation is performed in step S37. The execution of the lock mechanism operation control program described in the embodiment is started. Then, the VGRSECU 51 once ends the execution of the motor speed control program program in step S38, and after a predetermined short time has elapsed, starts executing the program again in step S30.

  Here, at the time of execution of the lock mechanism operation control program in the second embodiment, the VGRS motor 21 is controlled to be driven so as not to cause a relative rotational speed difference from the steering input shaft 12. Thereby, since the drive shaft 21b (lock holder 22a) rotates relatively slowly, the lock sound generated when the lock mechanism 22 shifts to the locked state is greatly reduced. Therefore, it is possible to satisfactorily mix with the end hit sound that inevitably generates a lock sound that is harsh to the driver, and the driver can hardly recognize the lock sound.

  In the second embodiment, as described above, the VGRSECU 51 shifts the lock mechanism 22 to the locked state and then locks the lock mechanism 22 in accordance with the turning operation of the steering handle 11 toward the neutral position by the driver. The lock mechanism 22 in the state is unlocked, and the VGRS motor 21 is smoothly shifted from the maintenance drive control to the normal drive control. For this reason, VGRSECU 51 executes the return control program shown in FIG. Hereinafter, the return control program will be specifically described.

  When an ignition switch (not shown) is turned on, the VGRSECU 51 starts executing the return control program at step S90 at a predetermined short time interval. And VGRSECU51 inputs the detected value detected by each sensor in subsequent step S91. That is, the VGRSECU 51 inputs the vehicle speed V from the vehicle speed sensor 41, the rotation angle θs from the steering angle sensor 42, and the rotation angle θm from the rotation angle sensor 43, respectively. And if each detection value is input, VGRESCU51 will progress to step S92.

  In step S92, the VGRSECU 51 calculates the current rotation angle θp of the pinion gear 31 according to Equation 2 described in the first embodiment. Then, VGRSECU 51 proceeds to step S93. In step S93, the VGRSECU 51 determines whether or not the absolute value of the calculated rotation angle θp is equal to or larger than the lock angle θ_lock set smaller than the mechanical end angle θ_end.

  If the calculated absolute value of the rotation angle θp is equal to or greater than the lock angle θ_lock, the lock mechanism 22 needs to be maintained in the locked state, so the VGRSECU 51 determines “Yes” and proceeds to step S94. In step S94, the VGRSECU 51 controls the drive circuit 54 to maintain the lock current value I_lock with respect to the solenoid 22d of the lock mechanism 22 in an interrupted state, thereby maintaining the lock mechanism 22 in the locked state. On the other hand, if the absolute value of the rotation angle θp calculated in step S92 is less than the lock angle θ_lock, the VGRSECU 51 determines that the lock mechanism 22 is in the unlocked state, so that the VGRSECU 51 determines “No” and the step S95. Proceed to

  In step S95, the VGRSECU 51 controls the drive circuit 54 to start supplying the lock current value I_lock set to a predetermined magnitude to the solenoid 22d of the lock mechanism 22. As a result, the solenoid 22d starts to contract and rotates the lock lever 22b about the axis of the lock pin 22c against the biasing force of a spring (not shown). Therefore, the engaging portion 22b1 of the lock lever 22b and the groove portion 22a1 of the lock holder 22a are separated from each other, and the lock mechanism 22 shifts to the unlocked state in which the engagement is released.

  In step S96, VGRSECU 51 executes a maintenance drive control routine. Since the sustain drive control routine is as described above, the description thereof is omitted. Then, after executing the maintenance drive control routine, the VGRS ECU 51 determines whether the absolute value of the rotation angle θp of the pinion gear 31 calculated in step S77 in the routine is equal to or larger than the motor rotation fixed angle θ_lim in step S97. Determine whether. That is, if the absolute value of the rotation angle θp is equal to or greater than the motor rotation fixed angle θ_lim, the VGRS ECU 51 determines “Yes” to maintain and drive the VGRS motor 21 in the unlocked state of the lock mechanism 22, and step S93, Each step process of 95 and step S96 is performed.

  On the other hand, if the absolute value of the rotation angle θp is less than the motor rotation fixed angle θ_lim, “No” is determined to switch the VGRS motor 21 from the maintenance drive control to the normal drive control, and the process proceeds to step S98. In step S98, VGRSECU 51 executes a normal drive control routine. Since this normal drive control routine is also as described above, its description is omitted. Then, after executing the normal drive control routine, the VGRSECU 51 ends the return control program in step S99.

  As can be understood from the above description, according to the second embodiment, the VGRSECU 51 rotates the rotation angle θp of the pinion gear 31 that rotates integrally with the steered output shaft 13 in step S33 in the motor rotation speed control program. Is determined to be equal to or larger than the motor rotation fixed angle θ_lim set smaller than the lock angle θ_lock, the sustain drive control routine is executed. The VGRS ECU 51 maintains the relative rotational positional relationship between the rotational angle θm of the drive shaft 21b of the VGRS motor 21 and the rotational angle θs of the steering input shaft 12 in step S75 of the routine. Keep driving.

  As a result, the absolute value of the rotation angle θp of the pinion gear 31 that rotates integrally with the steering output shaft 13 becomes equal to or larger than the lock angle θ_lock and the steering angular velocity ωs of the steering handle 11 is increased by executing the lock mechanism operation control program described above. When the absolute value becomes equal to or higher than the lock steering angular velocity ω_lock, the lock mechanism 22 is immediately shifted to the locked state, so that a smaller lock sound is generated when the left and right front wheels FW1, FW2 come into contact with the mechanical end stopper. It can be mixed into the winning sound. Therefore, it is possible to make it more difficult for the driver to perceive a harsh sound.

  Further, the VGRSECU 51 executes the return control program so that the absolute value of the rotation angle θp of the pinion gear 31 that rotates integrally with the turning output shaft 13 is greater than or equal to the lock angle θ_lock in step S93 of the program. If the lock mechanism 22 is maintained in the locked state and the absolute value of the rotation angle θp of the pinion gear 31 is less than the lock angle θ_lock, the lock mechanism 22 can be shifted to the unlocked state in step S95. If the absolute value of the rotation angle θp of the pinion gear 31 that rotates integrally with the steered output shaft 13 is less than the lock angle θ_lock and greater than or equal to the motor rotation fixed angle θ_lim, the VGRS ECU 51 performs the sustain drive control in step S96. A routine is executed to maintain and drive the VGRS motor 21. If the absolute value of the rotation angle θp of the pinion gear 31 that rotates integrally with the steered output shaft 13 is less than the motor rotation fixed angle θ_lim, the VGRS ECU 51 executes a normal drive control routine in step S98 to execute the VGRS. The motor 21 can be normally driven.

  Thereby, the operation state of the VGRS motor 21 can be made the same when the lock mechanism 22 shifts from the unlocked state to the locked state and when the lock mechanism 22 shifts from the locked state to the unlocked state. Thereby, the operation switching of the lock mechanism 22 can be performed very smoothly, and the operational feeling of the steering handle 11 accompanying the operation switching can be changed very smoothly.

  In implementing the present invention, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the object of the present invention.

  For example, in each of the above embodiments, the actual rotation angle θp of the pinion gear 31 is set to the actual rotation angle θs of the steering input shaft 12 detected by the steering angle sensor 42 and the drive of the VGRS motor 21 detected by the rotation angle sensor 43. The calculation was performed according to the equation 2 using the actual rotation angle θm of the shaft 21b. However, for example, the steering device can detect the rotation angle θp of the steering output shaft 13, that is, the pinion gear 31 (for example, the rotational angle sensor that detects the rotation of the steering output shaft 13 or the axial displacement of the rack bar 32. When a displacement sensor to detect, a turning angle sensor to detect the turning angle of the left and right front wheels FW1, FW2, etc.) are provided, the actual rotation angle θp detected by this sensor can be used. . Even in this case, the lock mechanism operation control program described in the first embodiment, the motor rotation speed control program and the return control program described in the second embodiment can be executed in exactly the same way, As a result, the same effect can be obtained.

  In the second embodiment, when maintaining and controlling the VGRS motor 21, the feedback gains Pfb and Dfb that are larger than those in the normal drive control are set, and the drive shaft 21b of the VGRS motor 21 is set to the steering input shaft 12. This was carried out so as to follow the rotation with good responsiveness. On the other hand, for example, by supplying the same current value to each phase of the VGRS motor 21 unconditionally (so-called phase fixing), the relative rotational displacement between the steering input shaft 12 and the drive shaft 21b. It is also possible to implement so that the relationship does not change. Thereby, the maintenance drive control content can be simplified.

  In each of the above embodiments, the lock mechanism operation control program, the motor rotation speed control program, and the return control program are applied to the control of the VGRS motor 21 and the lock mechanism 22 of the transmission ratio variable actuator 20 provided in the steering device. Carried out. However, the above programs can be applied to devices having other configurations (for example, steer-by-wire steering devices and steering handle lock devices) that control the operation of the lock mechanism in accordance with the rotation amount of the electric motor. Needless to say. As described above, even when the above-described programs are applied to an apparatus having another configuration, it is possible to make it difficult to recognize the lock sound that is generated when shifting to the locked state.

  Furthermore, in the said embodiment and each modification, the EPS gear 33 was provided in the steering gear unit 30, and it comprised and comprised so that assist force might be transmitted to the rack bar 32, and implemented. However, regarding the arrangement of the EPS motor 33, for example, if the assist force can be transmitted to the turning operation of the steering handle 11 by the driver, the EPS motor 33 is disposed so as to transmit the assist force to the steering output shaft 13, for example. Any arrangement may be used. Moreover, in the said embodiment and each modification, although implemented using the rack and pinion type | formula for the steering gear unit 30, it can also implement, for example, employ | adopting a ball screw mechanism.

1 is a schematic diagram of a vehicle steering apparatus common to first and second embodiments of the present invention. FIG. It is a figure for demonstrating the structure of a locking mechanism. It is a graph which shows the relationship between a vehicle speed and a transmission ratio. 4 is a flowchart illustrating a lock mechanism operation control program executed by the VGRSECU in FIG. 1 according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining a change characteristic of a maximum value of a drive current value supplied to a VGRS motor during normal lock control in the lock mechanism operation control program of FIG. FIG. 6 is a flowchart illustrating a motor rotation speed control program executed by the VGRSECU in FIG. 1 according to the second embodiment of the present invention. It is a flowchart which shows the normal drive control routine in the motor rotational speed control program of FIG. It is a graph which shows the relationship between a vehicle speed and a feedback gain. It is a flowchart which shows the maintenance drive control routine in the motor rotational speed control program of FIG. It is a flowchart which shows the return control program which concerns on 2nd Embodiment of this invention and is performed by VGRSECU of FIG.

Explanation of symbols

FW1, FW2 ... front wheel, 11 ... steering handle, 12 ... steering input shaft, 13 ... steering output shaft, 20 ... variable gear ratio actuator, 21 ... VGRS motor, 21a ... motor housing, 21b ... drive shaft, 22 ... lock mechanism 22a ... Lock holder, 22b ... Lock lever, 22d ... Solenoid, 23 ... Reducer, 30 ... Steering gear unit, 31 ... Pinion gear, 32 ... Rack bar, 33 ... EPS motor, 41 ... Vehicle speed sensor, 42 ... Steering Angle sensor, 43 ... Rotation angle sensor, 44 ... Torque sensor, 45 ... Motor current detection sensor, 51 ... VGRSECU, 52 ... EPSECU, 53, 54, 55 ... Drive circuit

Claims (6)

A steering input shaft that rotates integrally with the turning operation of the steering wheel, a steering output shaft that is connected to a steering mechanism that steers the steered wheels, and an electric motor that is connected to the steering input shaft. A reduction gear connected to the steering output shaft side and decelerating the rotation of the drive shaft of the electric motor, and changing the transmission ratio of the rotation amount of the steering output shaft to the rotation amount of the steering input shaft. A transmission ratio variable actuator that rotates the steered output shaft, a lock mechanism that prohibits or allows relative rotation between the steering input shaft and the steered output shaft, and the operation and lock of the variable transmission ratio actuator. In a transmission ratio variable steering apparatus comprising an operation control apparatus that controls the operation of the mechanism, the operation control apparatus comprises:
A turning output shaft rotation amount detecting means for detecting a rotation amount of the turning output shaft;
The absolute value of the rotation amount of the steered output shaft is set to be smaller than the maximum rotation amount of the steered output shaft corresponding to a stopper position that mechanically determines the steerable range of the steered wheels, and the maximum rotation amount Until the lock mechanism shifts to a locked state in which relative rotation between the steering input shaft and the steering output shaft is prohibited, and the detected rotation amount. A lock operation start determination means that compares the absolute value of the rotation amount of the rudder output shaft and determines whether or not the absolute value of the detected rotation amount is equal to or greater than the lock operation start rotation amount;
An operation speed detecting means for detecting an operation speed of the steering wheel;
It is set in advance to shift the lock mechanism to the locked state until the absolute value of the rotation amount of the steering output shaft that rotates following the operation of the steering handle reaches the maximum rotation amount from the lock operation start amount. The lock operation start operation speed is compared with the detected absolute value of the steering wheel operation speed, and it is determined whether or not the detected absolute value of the operation speed is equal to or higher than the lock operation start operation speed. Operating speed determination means for
The absolute value of the rotation amount of the steered output shaft detected by the lock operation start determining means is determined to be greater than or equal to the lock operation start rotation amount, and the steering wheel detected by the operation speed determining means is A transmission ratio variable steering apparatus comprising: a lock operation control unit that immediately shifts the lock mechanism to a locked state when it is determined that an absolute value of an operation speed is equal to or higher than the lock operation start operation speed. In the transmission ratio variable steering apparatus according to claim 1,
The turning output shaft rotation amount detection means,
Steering input shaft rotation amount detection means for detecting the rotation amount of the steering input shaft;
Motor drive shaft rotation amount detection means for detecting the rotation amount of the drive shaft of the electric motor;
A transmission ratio comprising: a rotation amount calculating means for calculating a rotation amount of the steered output shaft using the detected rotation amount of the steering input shaft and the detected rotation amount of the drive shaft. Variable steering device. In the transmission ratio variable steering apparatus according to claim 1,
The operation control device further includes:
The steering motor is steered in a state where the rotation amount of the drive shaft of the electric motor and the rotation amount of the steering input shaft are set relative to each other and the rotation amount of the steering input shaft is maintained. The maintenance operation start rotation amount set in advance to start the maintenance operation to be operated following the rotation of the input shaft is compared with the detected absolute value of the rotation amount of the steered output shaft. Maintenance operation start determining means for determining whether or not the absolute value of the rotation amount is equal to or greater than the maintenance operation start rotation amount;
If the absolute value of the rotation amount of the steering output shaft detected by the maintenance operation start determination unit is determined to be greater than or equal to the maintenance operation start rotation amount, a motor maintenance operation control unit that causes the electric motor to perform the maintenance operation. And a transmission ratio variable steering device. In the transmission ratio variable steering apparatus according to claim 3,
The motor maintenance operation control means includes
The rotation of the steering output shaft relative to the amount of rotation of the steering input shaft when the absolute value of the amount of rotation of the steering output shaft detected by the maintenance operation start determination means becomes equal to or greater than the maintenance operation start rotation amount. The electric motor is maintained in a state of maintaining a relative rotation amount difference between a rotation amount of the drive shaft of the electric motor and a rotation amount of the steering input shaft that realizes a transmission ratio of the amount. A transmission ratio variable steering device. In the transmission ratio variable steering apparatus according to claim 3,
The motor maintenance operation control means includes
A transmission ratio variable steering apparatus, wherein a large feedback gain used for feedback control is set to maintain the electric motor. In the transmission ratio variable steering apparatus according to claim 3,
The operation control device further includes:
When it is determined that the absolute value of the rotation amount of the steering output shaft detected by the lock operation start determination unit is less than the lock operation start rotation amount, the lock mechanism is connected to the steering input shaft and the steering output. Unlocking operation control means for shifting to an unlocking state allowing relative rotation with the shaft;
The lock mechanism is shifted to the unlocked state by the unlock operation control means, and the absolute value of the rotation amount of the steering output shaft detected by the maintenance operation start determination means is less than the maintenance operation start rotation amount. If it is determined, the motor normal operation control means for normally operating the electric motor to change the transmission ratio of the rotation amount of the steering output shaft to the rotation amount of the steering input shaft. A transmission ratio variable steering device.

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