JP2008062786A - Variable transmission ratio steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable transmission ratio steering device capable of ensuring good steering operability by a driver and well protecting a variable transmission ratio actuator from input of external force.
When a torque Tm input to a variable gear ratio actuator 20 is greater than a lock reference torque value Tth1, a VGRSECU 51 places the lock mechanism 22 in a locked state. At this time, the ECU 51 changes the reference torque value Tth1 to a small value based on at least one of the steering angular velocity, the turning angular velocity, and the motor angular velocity that increase in accordance with the magnitude of the torque Tm. As a result, the ECU 51 can quickly lock the lock mechanism 22 when the torque Tm is large. Further, the ECU 51 maintains the lock mechanism 22 in the unlocked state if the torque Tm is equal to or less than the reference torque value Tth1. Therefore, it is possible to achieve both good steering operability and protection of the actuator 20.
[Selection] Figure 4

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, Patent Document 1 shown below discloses a steering gear ratio variable steering device that can prevent an excessive torque load from being applied to a differential gear mechanism that constitutes the gear ratio variable steering device due to an excessive collision with a curb. ing. This steering gear ratio variable steering device is provided between the output shaft side sleeve and the input shaft side sleeve when the tire collides with a curb or the like and there is an input of torque far exceeding the normal steering torque. The stopper engaging portion thus formed is engaged. As a result, the input torque is transmitted between the output shaft and the input shaft, and an excessive torque load can be prevented from being applied to the differential gear mechanism.
JP-A-4-208673

  By the way, in the above-described conventional steering gear ratio variable steering device, the stopper engaging portion as a lock mechanism is provided on the output shaft (steering) with respect to torque (external force) acting on the differential gear mechanism (transmission ratio variable actuator). A reference value for determining whether to engage (lock) between the output shaft) side sleeve and the input shaft (steering input shaft) side sleeve is set as a fixed value in advance. In general, when a reference value for determining whether or not the lock mechanism is to be locked is set as a fixed value, the lock mechanism does not respond to an input of torque (steering force) accompanying a normal steering operation by the driver. It is desirable to set the reference value so that the locking mechanism is locked against an input of a large torque (external force) without locking.

  Here, it takes time to operate the lock mechanism until the lock mechanism completes the transition to the locked state. For this reason, for example, if the reference value is set near the allowable value of the mechanical strength in the differential gear mechanism (transmission ratio variable actuator), a large torque (external force) exceeding the allowable value is transmitted before the transition to the locked state is completed. In some cases, the differential gear mechanism (transmission ratio variable actuator) may be damaged. For this reason, if the reference value is set smaller than the allowable value in order to protect the differential gear mechanism (transmission ratio variable actuator), the transition to the locked state is completed at an early stage with respect to the input of a large external force. Therefore, the differential gear mechanism (transmission ratio variable actuator) can be well protected.

  However, if the reference value is set smaller than the permissible value, the input torque (steering force) that accompanies normal steering operation may exceed the reference value, causing an unintentional shift to the locked state and causing the driver to feel uncomfortable. Problems such as remembering. Thus, when the reference value for determining whether or not to shift the lock mechanism to the locked state is set as a fixed value in advance, good steering operability and the differential gear mechanism (transmission ratio variable actuator) It becomes difficult to achieve both good protection.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to ensure good steering operability by the driver and to protect the variable transmission ratio actuator from input of external force. The object is to provide a transmission ratio variable steering device.

  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 steering output shaft side to decelerate the rotation of the electric motor, and the steering with respect to the rotation amount of the steering input shaft A transmission ratio variable actuator that changes the transmission ratio of the rotation amount of the output shaft to rotate the steering output shaft, a lock mechanism that limits relative rotation between the steering input shaft and the steering output shaft, and In the transmission ratio variable steering apparatus including a lock mechanism operation control apparatus that controls the operation of the lock mechanism, the lock mechanism operation control apparatus includes an external force detection unit that detects an external force acting on the transmission ratio variable actuator, and the detection Is External force determination that determines whether or not an external force is greater than a lock reference value that determines whether or not to shift the lock mechanism to a locked state that restricts relative rotation between the steering input shaft and the steering output shaft Means, a steering related quantity detecting means for detecting a steering related quantity that changes due to a turning operation of the steering handle, and a reference value changing means for changing the lock reference value in accordance with the detected steering related quantity. And switching control means for switching and controlling the lock mechanism between an unlocked state and a locked state that allow relative rotation of the steering input shaft and the steering output shaft.

  In this case, the external force detection means detects an external force input from the road surface side to the steered wheel and transmitted to the reduction gear of the variable transmission ratio actuator via the steered output shaft. Good. The external force determination means may determine whether or not the external force detected by the external force detection means continues for a predetermined time in a state where the external force is greater than the lock reference value.

  The reference value changing means may change the lock reference value to a smaller value as the steering related quantity detected by the steering related quantity detecting means increases. In this case, the steering related amount detection means steers at least one of, for example, a rotation amount of the steering input shaft, a rotation amount of the steering output shaft, and a rotation amount of the electric motor of the transmission ratio variable actuator. It may be detected as a related quantity. In addition, the steering related amount detection means, for example, at least one of the rotational angular velocity of the steering input shaft, the rotational angular velocity of the steering output shaft, and the rotational angular velocity of the electric motor of the transmission ratio variable actuator is the steering related speed. It may be detected as a quantity. Further, the steering related amount detecting means may detect, for example, at least one of a current value and a voltage value flowing through the electric motor of the transmission ratio variable actuator as the steering related amount. Further, the steering-related amount detection means includes, for example, at least one of a change rate of an external force detected by the external force detection means, a change rate of a current value flowing through the electric motor of the variable transmission ratio actuator, and a change rate of a voltage value. One may be detected as the steering-related amount.

  According to these, the lock mechanism operation control device continues the detected external force, more specifically, the external force input from the road surface side to the steered wheels and transmitted to the speed reducer constituting the transmission ratio variable actuator for a predetermined time. If it is larger than the lock reference value, the lock mechanism can be switched from the unlocked state to the locked state. At this time, the lock mechanism operation control device can change the lock reference value to a smaller value as the detected steering-related amount increases.

  Here, the steering-related amount is a physical amount that changes due to the turning operation of the steering handle by the driver, and the rotation amount and rotation angular velocity of the steering input shaft, the rotation amount and rotation angular velocity of the steering output shaft, The rotation amount and rotation angular velocity of the electric motor constituting the transmission ratio variable actuator can be employed. Further, the steering-related amount is a physical amount that changes due to the turning operation of the steering wheel by the driver, and includes the change rate of the detected external force, the current value flowing through the electric motor, the change rate of the current value, The voltage value flowing through the motor and the rate of change of the voltage value can be employed.

  Thereby, if the external force input from the road surface with respect to a steered wheel is below a lock reference value, the lock mechanism control apparatus can make a lock mechanism into an unlocked state. Therefore, in a state where the driver is performing a normal steering operation, the transmission ratio is appropriately changed by allowing the operation of the transmission ratio variable actuator, and the driver can obtain good steering operability.

  Specifically, for example, when the vehicle is traveling at a high speed, the transmission ratio of the variable transmission ratio actuator is changed to a small transmission ratio, thereby stabilizing the behavior of the vehicle with respect to the steering wheel turning operation. And good steering operability can be obtained. Further, for example, when the vehicle is traveling at a low speed, the transmission ratio of the variable transmission ratio actuator is changed to a large transmission ratio, thereby reducing the amount of turning operation of the steering handle and turning the vehicle greatly. And good steering operability can be obtained.

  Since the lock mechanism is unlocked during normal steering operation, the transmission ratio is variable even when the driver performs emergency avoidance steering to avoid collision with an obstacle, for example. The steered wheel can be appropriately steered by operating the actuator. Therefore, emergency avoidance steering by the driver can be favorably assisted.

  On the other hand, the lock mechanism control device, for example, if the steered wheel contacts a curb installed on the road surface (road) and a large external force is input to the steered wheel, and the input external force is greater than the lock reference value. The lock mechanism can be in a locked state. Here, when a large external force is input, the steering related amount changes to a large related amount, so the lock reference value is changed to a small value. Therefore, when a large external force is input, the lock mechanism control device can switch the lock mechanism to the locked state at an early stage, so that the relative rotation between the steering input shaft and the steered output shaft is prevented. Can be prohibited. Thereby, the transmission ratio variable actuator can be well protected.

  Further, by adopting the above-described physical quantities of the steering input shaft, the steering output shaft, and the electric motor as the steering-related amounts, it is possible to accurately and easily detect that a large external force has been input to the steered wheels. it can. Therefore, by changing the lock reference value based on these physical quantities, the transmission ratio variable actuator can be more reliably protected. The protection of the transmission ratio variable actuator includes protection of the gear structure constituting the speed reducer and protection of the electric motor against an excessive load.

  Furthermore, the lock reference value is changed to a small value when the steering related amount becomes a large related amount.In other words, the lock reference value is increased when the steering related amount is a small related amount in normal steering operation. By changing (maintaining), switching control to an unnecessary lock state in a normal steering operation is prevented. Therefore, the uncomfortable feeling perceived by the driver can be eliminated with the switching control between the locked state and the unlocked state.

  Hereinafter, a variable transmission ratio 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 apparatus according to this 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 a variable gear ratio actuator 20 as a transmission ratio variable actuator.

  The variable gear ratio actuator 20 appropriately changes the rotation amount (or rotation angle) of the connected steering output shaft 13 with respect to the rotation amount (or rotation angle) of the steering input shaft 12. For this reason, the variable gear ratio 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 has a motor housing 21a integrally connected to the steering input shaft 12, and rotates integrally in accordance with a turning operation of the steering handle 11 by the driver. The proximal end side of the drive shaft 21b of the VGRS motor 21 is connected to the lock mechanism 22, and the distal end side of the drive shaft 21b is connected to the speed reducer 23 so that the rotational force of the VGRS motor 21 is applied to the speed reducer 23. It is to be transmitted. In the present embodiment, 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 approaches 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.

  In addition, the lock lever 22b is rotated at the substantially central portion thereof to the other end side of the lock pin 22c that is arranged in parallel with the axial direction of the motor housing 21a and is fixed integrally to the housing 21a at one end 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 reduction gear 23 is configured by a predetermined gear mechanism (for example, a harmonic drive (registered trademark) mechanism or a planetary gear mechanism), and the turning 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. can do. Therefore, the variable gear ratio actuator 20 connects the steering input shaft 12 and the steered output shaft 13 through the drive shaft 21 b of the VGRS motor 21 so as to be relatively rotatable. The ratio of the rotation amount (or rotation angle) of the steering output shaft 13 to the rotation amount (or rotation angle), that is, the transmission ratio (gear ratio) of rotation from the steering input shaft 12 to the steering output shaft 13 is appropriately changed. be able to.

  Further, the steering device includes a steered gear unit 30 connected to the lower end 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 integrally assembled to the lower end of the steered output shaft 13 is transmitted to the rack bar 32. It has become. The steered gear unit 30 includes an electric motor 33 (hereinafter referred to as an EPS motor) as an operation force reducing actuator for reducing the steering force (steering torque) input to the steering handle 11 by the driver. 33), and 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, 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.

  Further, the steering apparatus includes a vehicle speed sensor 41, a steering angle sensor 42 as a steering related amount detection means, a rotation angle sensor 43 and a turning angle sensor 44, and a torque sensor 45 as an external force detection means. The vehicle speed sensor 41 detects and outputs the vehicle speed V of the vehicle. The steering angle sensor 42 detects the rotation amount of the steering handle 11, that is, the rotation amount of the steering input shaft 12, and outputs it as a rotation angle θa (corresponding to the steering angle of the steering handle 11). The rotation angle sensor 43 detects the rotation amount of the drive shaft 21b of the VGRS motor 21 and outputs it as the rotation angle θb. The turning angle sensor 44 detects the rotation amount of the turning output shaft 13 and outputs it as a rotation angle θc (corresponding to the actual turning angle of the left and right front wheels FW1, FW2). Note that the rotation angle θa, the rotation angle θb, and the rotation angle θc have a neutral position of “0”, a leftward rotation is represented by a positive value, and a rightward rotation is represented by a negative value. The torque sensor 45 detects a twist generated in the steering output shaft 13 and outputs a torque Tm corresponding to the generated twist.

  Next, the electric control device 50 that controls the operation of the above-described variable gear ratio actuator 20 (specifically, the VGRS motor 21 and the solenoid 22d) and the turning 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 variable gear ratio 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 comprising a CPU, ROM, RAM, timer, 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.

  A vehicle speed sensor 41, a steering angle sensor 42, a rotation angle sensor 43, a turning angle sensor 44, and a torque sensor 45 are connected to the input side of the VGRSECU 51, and the steering angle sensor 42 and the torque sensor 45 are connected to the input side of the EPS ECU 52. A torque sensor 45 is connected. Thereby, VGRESCU51 and EPSECU52 execute various programs using each detected value by each connected sensor, 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 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 for continuously changing the transmission ratio G by driving the VGRS motor 21 of the variable gear ratio 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 driver starts the turning operation of the steering handle 11 in the state where the transmission ratio G is determined, the steering input shaft 12, the variable gear ratio actuator 20, and the steering output shaft 13 also start to rotate. In accordance with the turning operation of the steering handle 11 by the driver, the VGRS ECU 51 inputs the rotation angle θa of the steering input shaft 12 detected by the steering angle sensor 42, and the input rotation angle θa and the determined transmission ratio G To calculate the target rotation angle θch of the steering output shaft 13 (that is, the target turning angle of the left and right front wheels FW1, FW2) with respect to the rotation angle θa of the steering input shaft 12 (that is, the steering angle of the steering handle 11). .

Next, the VGRS ECU 51 calculates the operation amount of the VGRS motor 21 necessary for realizing the calculated target rotation angle θch of the steered output shaft 13, that is, the target rotation angle θbh 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 steered output shaft 13 according to 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 θbh so that the turning output shaft 13 becomes the target rotation angle θch with respect to the rotation angle θa of the steering input shaft 12. That is, the VGRSECU 51 calculates the target rotation angle θbh of the drive shaft 21b according to the following formula 1.
θbh = θch−θa Equation 1

  Then, when the VGRS ECU 51 calculates the target rotation angle θbh according to the above equation 1, the VGRS ECU 51 controls the drive circuit 53 without overshooting until the rotation angle θb detected by the rotation angle sensor 43 reaches the target rotation angle θbh. The drive shaft 21b of the motor 21 is rotated. As a result, the steering output shaft 13 is added to or subtracted from the rotation angle θa of the steering input shaft 12 by the target rotation angle θbh (that is, the rotation angle θb) of the drive shaft 21b. Is rotated to a target rotation angle θch that is a transmission ratio G with respect to the rotation angle θa. Accordingly, the pinion gear 31 integrally assembled with the steering output shaft 13 also rotates to the target rotation angle θch, and the rack bar 32 is displaced in the axial direction in accordance with the rotation of the pinion gear 31, whereby the left and right front wheels FW1. , FW2 is steered to a target turning angle corresponding to the target rotation angle θch.

  As described above, the left and right front wheels FW1 and FW2 are steered to the turning angle corresponding to the target rotation angle θch (that is, the rotation angle θc), so that the driver can obtain good steering operability (steering fee) according to the vehicle speed V. Ring). Specifically, since the transmission ratio G is determined to be small when the detected vehicle speed V increases, the steered output shaft 13 is rotated in the opposite direction relative to the rotational direction of the steering input shaft 12. That is, in this case, the turning output shaft 13 is rotated to the target rotation angle θch by subtracting the rotation angle θb from the rotation angle θa. For this reason, the left and right front wheels FW1 and FW2 are small 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 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 turning output shaft 13 is rotated to the target rotation angle θch by adding the rotation angle θb to the rotation angle θa. Therefore, the left and right front wheels FW1 and FW2 are large 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 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 θa from the steering angle sensor 42 and the torque Tm from the torque sensor 45, and drives the EPS motor 33 in accordance with the input rotation angle θa and the magnitude of the torque Tm. Set the control amount. Then, the EPS ECU 52 controls the drive circuit 55 based on the set control amount without causing overshoot to drive the EPS motor 33. 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.

  As described above, in the steering apparatus employing the variable gear ratio actuator 20, the steering input shaft 12 connected to the steering handle 11 and the steering output shaft 13 connected to the left and right front wheels FW1 and FW2 are variable gear ratio actuators 20. Are coupled so as to be relatively rotatable. Accordingly, the VGRS ECU 51 can drive the VGRS motor 21 to rotate the steering output shaft 13 relative to the steering input shaft 12 and rotate the steering output shaft 13 to the rotation angle θc.

  By the way, a large external force may be input to the variable gear ratio actuator 20 that allows the steering input shaft 12 and the steered output shaft 13 to be connected to each other so as to allow relative rotation. That is, when the vehicle is traveling, for example, when the left and right front wheels FW1 and FW2 are in contact with a curb installed on the road (on the road surface), a large external force accompanying the contact (hereinafter, this external force is referred to as an impact torque). ) Is input to the left and right front wheels FW1, FW2. Further, when the vehicle is traveling, for example, an external force caused by road surface conditions such as road surface unevenness and road surface friction coefficient (hereinafter, this external force is referred to as road surface reaction force torque) is input to the left and right front wheels FW1, FW2. Is done.

  The large impact torque and road reaction force torque input to the left and right front wheels FW1 and FW2 are input to the variable gear ratio actuator 20 via the steered output shaft 13. Here, in a situation where a large impact torque is input to the variable gear ratio actuator 20, when the drive of the VGRS motor 21 is continued, a large impact torque and a motor driving force are input to the speed reducer 23. There is a possibility that the speed reducer 23 may be greatly damaged. In a situation where road reaction force is input to the variable gear ratio actuator 20, for example, when the driver quickly turns the steering handle 11, the VGRS motor 21 is driven to follow the turning operation. However, there is a possibility that the VGRS motor 21 may reverse due to the road surface reaction force.

  For this reason, the VGRS ECU 51 is a lock mechanism for protecting the variable gear ratio actuator 20 by mechanically stopping the driving of the VGRS motor 21 in a situation where a large external force acts on the speed reducer 23 or in a situation where the VGRS motor 21 reverses. 22 is activated. Specifically, VGRSECU 51 repeatedly executes the lock mechanism operation control program shown in FIG. 4 to appropriately operate the lock mechanism 22. Hereinafter, the lock mechanism operation control program will be described in detail.

  When the ignition switch (not shown) is turned on, the VGRSECU 51 starts executing the lock mechanism operation control program in step S10. And VGRSECU51 inputs each detection value detected by the sensor in step S11. Here, in this embodiment, the VGRS ECU 51 detects the rotation angle θa of the steering input shaft 12 detected by the steering angle sensor 42, the rotation angle θb of the drive shaft 21 b detected by the rotation angle sensor 43, and the turning angle sensor 43. The rotation angle θc of the steering output shaft 13 detected by the above is input. As described above, when the detection value is input from each sensor, the VGRSECU 51 proceeds to step S12.

  In step S12, the VGRSECU 51 clears the timer J1 that measures the lock state transition determination time until the lock mechanism 22 is shifted to the locked state, as will be described later. Then, VGRSECU 51 proceeds to step S13.

  In step S13, the VGRSECU 51 determines whether or not the lock mechanism 22 is in an unlocked state by executing the lock mechanism operation control program up to the previous time. In other words, the VGRSECU 51 determines “Yes” based on the operating state of the solenoid 22d if the lock mechanism 22 has already been unlocked. And VGRSECU51 performs the process of each step after step S14, ie, a lock control process.

  On the other hand, in step S27 described later, for example, if the lock mechanism 22 is still in the locked state for some reason despite the unlock control of the lock mechanism 22, the VGRS ECU 51 determines “No”. . And VGRSECU51 performs the process of each step after step S21, ie, an unlock control process.

  In step S14, the VGRS ECU 51 determines whether the detection state of the torque Tm by the torque sensor 45 is good, in other words, whether the torque Tm detected by the torque sensor 45 is an effective value. That is, when the signal representing the detected torque Tm supplied from the torque sensor 45 is within a predetermined range, the detection state of the torque sensor 45 is good and the detected torque Tm is an effective value. For this reason, if the detection state of the torque sensor 45 is good, the VGRSECU 51 determines “Yes” and proceeds to step S15. In step S15, VGRSECU 51 inputs an effective torque Tm detected by the torque sensor 45, and proceeds to step S16.

  On the other hand, when the signal representing the detected torque Tm supplied from the torque sensor 45 is shifted outside a predetermined range due to the influence of noise or the like, for example, the detection state of the torque sensor 45 is defective and the detection Torque Tm is not a valid value. For this reason, if the detection state of the torque sensor 45 is poor, the VGRSECU 51 determines “No” in step S14. And VGRSECU51 continues determining with "No" in step S14 until the detection state of the torque sensor 45 becomes favorable, and repeatedly performs the process of each step of step S11-step S13.

  In step S16, the VGRSECU 51 determines that the absolute value of the detected torque Tm is a reference torque value Tth1 for determining that the lock mechanism 22 is shifted to the locked state (hereinafter, this reference torque value is referred to as a lock reference torque value Tth1). Or greater). Hereinafter, this determination process will be described in detail.

  As described above, when a large external force is input via the left and right front wheels FW1, FW2, the variable gear ratio actuator 20 needs to be protected from the external force. In particular, the impact torque that is input when the left and right front wheels FW1, FW2 come into contact with a curbstone or the like is an allowable mechanical strength that is set to ensure good operation of the variable transmission ratio actuator 20 (especially the speed reducer 23). The torque value may be exceeded. Therefore, when the impact torque is input, the damage received by the speed reducer 23 is further increased.

  For this reason, by setting a lock reference torque value Tth1 smaller than the allowable torque value of the mechanical strength, when a large external force is input, the rotation of the VGRS motor 21 is quickly locked and the turning output shaft 13 and It is necessary to prohibit relative rotation with the steering input shaft 12 so that the input external force is transmitted to the steering handle 11 via the steering input shaft 12. In this way, by transmitting a large external force to the steering handle 11, the driver can perceive that, for example, the left and right front wheels FW1, FW2 are in contact with a curbstone or the like via the steering handle 11.

  However, as described above, in the lock mechanism 22, the VGRS motor 21 is locked when the engaging portion 22b1 of the lock lever 22b is engaged with the groove portion 22a1 formed on the outer periphery of the lock holder 22a. For this reason, in order to completely shift the VGRS motor 21 to the locked state, the time until the engaging portion 22b1 of the lock lever 22b moves along the outer periphery of the lock holder 22a and engages with the groove portion 22a1 (hereinafter, referred to as the following) , It's called free running time). Due to the existence of the idle running time, there is a case where the VGRS motor 21 cannot be locked before the maximum value (peak) of the impact torque exceeds the allowable torque value depending on the setting of the lock reference torque value Tth1. This will be specifically described with reference to FIG.

  FIG. 5 schematically shows a time change (impact torque waveform) of the impact torque input to the steering output shaft 13 (reduction gear 23) by a solid line. As shown in FIG. 5, the impact torque may change to a large value with time and may exceed the allowable torque value of mechanical strength. In this case, as shown by the one-dot chain line in FIG. 5, when the lock reference torque value S1 set smaller than the allowable torque value is adopted to determine the transition of the lock mechanism 22 to the locked state, the impact torque becomes the allowable torque. After the value is exceeded, the lock state is entered.

  That is, as shown in FIG. 5, when the VGRSECU 51 cuts off the energization to the solenoid 22d at the time point a when the impact torque is input and exceeds the lock reference torque value S1, the engaging portion 22b1 of the lock lever 22b is a-A After the idle running time indicated by is passed, it engages with the groove 22a1 of the lock holder 22a, and the VGRS motor 21 is locked. Thus, when the lock reference torque value S1 close to the allowable torque value is set, the transition of the VGRS motor 21 to the locked state is delayed. As a result, an impact torque exceeding the allowable torque value may be input to the speed reducer 23 before the transition to the locked state is completed.

  On the other hand, as shown by a two-dot chain line in FIG. 5, when the lock reference torque value S2 set smaller than the lock reference torque value S1 is adopted to determine the shift of the lock mechanism 22 to the locked state, It is possible to shift to the locked state before the impact torque exceeds the allowable torque value. That is, as shown in FIG. 5, when the VGRSECU 51 cuts off the energization to the solenoid 22d at the time point b when the impact torque is input and exceeds the lock reference torque value S2, the engaging portion 22b1 of the lock lever 22b is b-B After elapse of the idle running time indicated by, it engages with the groove 22a1 of the lock holder 22a. Therefore, if a smaller lock reference torque value S2 is set with respect to the allowable torque value, the transition of the VGRS motor 21 to the locked state is completed at an early stage, and an impact torque exceeding the allowable torque value is input to the speed reducer 23. Can be prevented.

  However, when the lock reference torque value S2 smaller than the allowable torque value is employed in this manner, the driver turns the steering handle 11 at a normal steering speed against the input road surface reaction force. (Hereinafter, this rotation operation state is referred to as a normal steering state), the VGRS motor 21 may shift to the locked state. More specifically, the temporal change (normal torque waveform) of the normal torque input to the turning output shaft 13 (reduction gear 23) in the normal steering state changes as schematically shown by the broken line in FIG. If a small lock reference torque value S2 is adopted with respect to this change in normal torque, the normal torque may exceed the lock reference torque value S2 even in the normal steering state, and an unintended lock state may be entered. Transition occurs. As described above, when the VGRS motor 21 is shifted to the locked state, the transmission ratio G is not appropriately changed, so that the driver feels uncomfortable with the turning state of the vehicle with respect to the turning operation of the steering handle 11.

  For this reason, when setting the lock reference torque value Tth1, the lock mechanism 22 is operated early in a situation where a large external force is input, and the VGRS motor 21 is shifted to the locked state, and in the normal steering state, the shift to the locked state is performed. Must be set to prevent. For this reason, in the present embodiment, the lock reference torque value Tth1, as schematically shown in FIG. 6, is the rotational angular velocity of the steering input shaft 12, that is, the steering angular velocity of the steering handle 11, and the rotational angular velocity of the steering output shaft 13. The angle is changed according to the magnitude of at least one of the turning angular velocities of the left and right front wheels FW1 and FW2 and the rotational angular velocity of the shaft 21b of the VGRS motor 21 (hereinafter, this rotational angular velocity is referred to as the motor angular velocity). Hereinafter, the lock reference torque value Tth1 in the present embodiment will be specifically described. Since the mutual relationship among the steering angular velocity, the turning angular velocity, and the motor angular velocity is substantially proportional, the lock reference torque value Tth1 can be similarly set regardless of which angular velocity is used.

  First, the change characteristic of the lock reference torque value Tth1 with respect to the change of the steering angular velocity will be described. When the driver rotates the steering handle 11 at a large steering angular velocity, the steering input shaft 12 rotates at a large rotational angular velocity, and this rotation is transmitted to the VGRS motor 21 of the variable gear ratio actuator 20. As described above, when the rotation associated with the turning operation of the steering handle 11 is transmitted, the VGRS motor 21 follows the transmitted rotation and rotationally drives the drive shaft 21b to the target rotation angle θbh as described above. .

  In this case, when following the steering angular velocity, a large motor driving force is input to the speed reducer 23 by driving the VGRS motor 21. Also, as the steering angular velocity increases, the load on the VGRS motor 21 increases, and the VGRS motor 21 may reverse when a road surface reaction force is input.

  Therefore, in order to protect the speed reducer 23 from a large motor driving force and to protect the VGRS motor 21 from reverse rotation due to a road surface reaction force, the lock reference torque value Tth1 is small in a region where the steering angular velocity is large as shown in FIG. (For example, about the lock reference torque value S2 in FIG. 5). Thereby, the VGRS ECU 51 can shift the lock mechanism 22 to the locked state at an early stage in a state where the VGRS motor 21 generates a large motor driving force in order to follow the turning operation of the steering handle 11. On the other hand, when the steering angular velocity is outside the large region, the lock reference torque value Tth1 is set large (for example, about the lock reference torque value S1 in FIG. 5). Thereby, VGRSECU51 can prevent the transition to the lock state which is not intended in a normal steering state.

  Next, change characteristics of the lock reference torque value Tth1 with respect to changes in the steering angular speed and the motor angular speed will be described. When the left and right front wheels FW1, FW2 come into contact with the curbstone and a large impact torque is input, the steering output shaft 13 rotates at a large rotational angular velocity, that is, the steering angular velocity, and the rotation based on the input impact torque ( Rotational torque) is transmitted to the speed reducer 23 of the variable gear ratio actuator 20. On the other hand, as described above, the VGRS motor 21 transmits the motor driving force to the speed reducer 23 via the drive shaft 21b in accordance with the turning operation of the steering handle 11.

  For this reason, in the speed reducer 23, the damage to the speed reducer 23 increases as the rotational angular speed of the turning output shaft 13 based on the impact torque, that is, the turning angular speed and the motor angular speed of the VGRS motor 21 increase. If a large impact torque is input and the VGRS motor 21 is driven, rotation based on the input impact torque may be transmitted to the steering input shaft 12 in some cases. In this case, the steering angular velocity of the steering input shaft 12 also increases.

  Therefore, in order to protect the speed reducer 23, as shown in FIG. 6, the lock reference torque value Tth1 is small in a region where the turning angular velocity and the motor angular velocity are large (for example, about the lock reference torque value S2 in FIG. 5). Is set. Thereby, VGRSECU51 can transfer the lock mechanism 22 to a locked state at an early stage. On the other hand, when the turning angular velocity and the motor angular velocity are outside the large regions, the lock reference torque value Tth1 is set to be large (for example, about the lock reference torque value S1 in FIG. 5). Thereby, VGRSECU51 can prevent the transition to the lock state which is not intended in a normal steering state.

  Then, the VGRSECU 51 determines whether or not the absolute value of the torque Tm input in step S15 is larger than the lock reference torque value Tth1, using the lock reference torque value Tth1 set in this way. More specifically, the VGRS ECU 51 first calculates the steering angular speed, the turning angular speed, and the motor angular speed by time-differentiating the detected rotational angle θa, the detected rotational angle θb, and the detected rotational angle θc input in step S11. . Then, the VGRS ECU 51 determines the lock reference torque value Tth1 using at least one of the calculated steering angular velocity, turning angular velocity, and motor angular velocity.

  If the input torque Tm is larger than the lock reference torque value Tth1 determined in this way, the VGRSECU 51 determines “Yes” and proceeds to step S17. On the other hand, if the absolute value of the input torque Tm is equal to or less than the lock reference torque value Tth1, the VGRS ECU 51 determines “No”. Then, the VGRSECU 51 returns to step S11 and repeatedly executes the processes of steps S11 to S15 until it is determined as “Yes” in step S16.

  In step S17, the timer J1 is incremented by "1" every program execution cycle. That is, if the VGRSECU 51 determines in step S16 that the input torque Tm is larger than the lock reference torque value Tth1, the timer J1 is incremented. Thereby, the VGRSECU 51 can grasp the time during which the state where the input torque Tm is larger than the lock reference torque value Tth1 is continued. As described above, when the timer J1 is incremented by “1”, the VGRSECU 51 proceeds to step S18.

  In step S18, it is determined whether or not the value of the timer J1 is greater than a predetermined time t1 set for a predetermined short time. Thus, by comparing and determining the value of the timer J1, in other words, the duration of the state in which the input torque Tm is greater than the lock reference torque value Tth1 and the predetermined time t1, the value between the locked state and the unlocked state is determined. The migration frequency can be greatly reduced. That is, if the value of the timer J1 is greater than the predetermined time t1, the VGRSECU 51 determines that the input torque Tm is greater than the lock reference torque value Tth1, and thus determines “Yes” and proceeds to step S19. On the other hand, if the value of the timer J1 is equal to or less than the predetermined time t1, it is determined as “No” because the state where the input torque Tm is greater than the lock reference torque value Tth1 does not continue. Then, VGRSECU 51 returns to step 12 and executes the processes of steps S12 to S17.

  In step S19, the VGRS ECU 51 controls the drive circuit 54 so that the lock mechanism 22 of the variable gear ratio actuator 20 is locked, and cuts off the energization to the solenoid 22d. Thereby, the lock lever 22b rotates around the axis of the lock pin 22c by the biasing force of the spring, and the engaging portion 22b1 and the groove portion 22a1 of the lock holder 22a are engaged to shift to the locked state.

  After the lock control in step S19, the VGRSECU 51 maintains the lock state of the lock mechanism 22 for a predetermined time tk in step S20. In this way, by maintaining and controlling the locked state for a predetermined time tk, inadvertent transition from the locked state to the unlocked state can be prevented.

  In step S21, the VGRSECU 51 clears the timer J2 that measures the unlock state transition determination time until the lock mechanism 22 is shifted to the unlock state. Then, VGRSECU 51 proceeds to step S22.

  In step S22, the VGRSECU 51 is in a good detection state of the torque Tm by the torque sensor 45, in other words, whether the torque Tm detected by the torque sensor 45 is an effective value, as in step S14. Determine. That is, when the signal representing the detected torque Tm supplied from the torque sensor 45 is changing within a predetermined range, the detection state of the torque sensor 45 is good, so that the VGRESCU 51 determines “Yes” and performs the step. Proceed to S23. In step S23, the VGRSECU 51 inputs an effective torque Tm detected by the torque sensor 45, and proceeds to step S24.

  On the other hand, when the signal representing the detected torque Tm supplied from the torque sensor 45 is shifted outside a predetermined range due to the influence of noise or the like, for example, the detection state of the torque sensor 45 is bad. The VGRSECU 51 determines “No”. And VGRSECU51 repeats and executes the clear process of step S21 until the detection state of the torque sensor 45 becomes good.

  In step S24, the VGRSECU 51 determines that the absolute value of the detected torque Tm is a reference torque value Tth2 for determining that the lock mechanism 22 is to be shifted to the unlocked state (hereinafter, this reference torque value is referred to as the unlock reference torque). It is determined whether it is smaller than the value Tth2.

  The unlock reference torque value Tth2 is set to be smaller by a predetermined amount than the above-described lock reference torque value Tth1, as indicated by a broken line in FIG. The unlock reference torque value Tth2 is also changed according to the magnitude of at least one of the steering angular speed, the turning angular speed, and the motor angular speed, similarly to the lock reference torque value Tth1. That is, the unlock reference torque value Tth2 is set small in a region where the steering angular velocity, the turning angular velocity, and the motor angular velocity are large in accordance with the change characteristic of the lock reference torque value Tth1, and the steering angular velocity, the turning angular velocity, and the motor angular velocity are large. Largely set outside the area.

  The VGRSECU 51 determines whether or not the absolute value of the torque Tm input in step S23 is smaller than the unlock reference torque value Tth2, using the unlock reference torque value Tth2 set in this way. More specifically, the VGRS ECU 51 first calculates the steering angular speed, the turning angular speed, and the motor angular speed by time-differentiating the detected rotational angle θa, the detected rotational angle θb, and the detected rotational angle θc input in step S11. . Then, the VGRS ECU 51 determines the unlock reference torque value Tth2 using at least one of the calculated steering angular velocity, turning angular velocity, and motor angular velocity.

  If the torque Tm input with respect to the unlock reference torque value Tth2 thus determined is small, the VGRSECU 51 determines “Yes” and proceeds to step S25. On the other hand, if the absolute value of the input torque Tm is equal to or greater than the unlock reference torque value Tth2, the VGRSECU 51 determines “No”. Then, the VGRSECU 51 returns to step S21 and repeatedly executes the processes of steps S21 to S23 until it is determined as “Yes” in step S24.

  In step S25, the timer J2 is incremented by "1" every program execution cycle. That is, if the VGRSECU 51 determines in step S24 that the input torque Tm is smaller than the unlock reference torque value Tth2, the timer J2 is incremented. Thereby, the VGRSECU 51 can grasp the time during which the state where the input torque Tm is smaller than the unlock reference torque value Tth2 continues. In this way, when the timer J2 is incremented by “1”, the VGRSECU 51 proceeds to step S26.

  In step S26, it is determined whether or not the value of the timer J2 is greater than a predetermined time t2 set to a predetermined short time. Thus, by comparing and determining the value of the timer J2, in other words, the duration of the state in which the input torque Tm is greater than the unlock reference torque value Tth2 and the predetermined time t2, the lock state and the unlock state are The migration frequency can be greatly reduced. That is, if the value of the timer J2 is greater than the predetermined time t2, the VGRSECU 51 determines that the input torque Tm is smaller than the unlock reference torque value Tth2, and therefore determines “Yes” and proceeds to step S27. . On the other hand, if the value of the timer J2 is equal to or less than the predetermined time t2, it is determined as “No” because the state where the input torque Tm is smaller than the unlock reference torque value Tth2 does not continue. And VGRSECU51 returns to step 22, and performs the process of each step of the same step S22-step S25.

  In step S27, the VGRS ECU 51 controls the drive circuit 54 so that the lock mechanism 22 of the variable gear ratio actuator 20 is unlocked, and starts energizing the solenoid 22d. As a result, the solenoid 22d rotates the lock lever 22b around the axis of the lock pin 22c against the urging force of the spring, and the engagement portion 22b1 and the groove portion 22a1 of the lock holder 22a are disengaged and unlocked. Migrate to

  As described above, when the lock mechanism 22 is unlocked in step S27, the VGRSECU 51 temporarily ends the execution of the program in step S28. And VGRSECU51 starts execution of a locking mechanism action | operation control program again in step S10 after progress for a predetermined short time.

  As can be understood from the above description, according to this embodiment, the VGRSECU 51 is inputted from the road surface side with respect to the torque Tm as the external force detected by the torque sensor 45, more specifically, the left and right front wheels FW1, FW2. The lock mechanism 22 can be switched from the unlocked state to the locked state by comparing the torque Tm caused by the external force transmitted to the speed reducer 22 of the variable gear ratio actuator 20 and the lock reference torque value Tth1. At this time, the VGRS ECU 51 can change the lock reference torque value Tth1 to a small value as at least one of the detected steering angular velocity, the turning angular velocity, and the motor angular velocity as the steering related amount increases.

  That is, the VGRSECU 51 unlocks the lock mechanism 22 if the input torque Tm resulting from an external force (impact torque or road surface reaction torque) input from the road surface to the left and right front wheels FW1, FW2 is equal to or less than the lock reference torque value Tth1. It can be in a locked state. Thereby, in the normal steering state, the transmission ratio G is appropriately changed by allowing the operation of the variable gear ratio actuator 20, and the driver can obtain a good steering operability.

  Specifically, when the vehicle is traveling at high speed, the transmission ratio G of the variable gear ratio actuator 20 is changed to a small transmission ratio, thereby stabilizing the behavior of the vehicle with respect to the turning operation of the steering handle 11. And good steering operability can be obtained. Further, when the vehicle is traveling at a low speed, the transmission ratio G of the variable gear ratio actuator 20 is changed to a large transmission ratio, thereby reducing the turning operation amount of the steering handle 11 and turning the vehicle greatly. And good steering operability can be obtained.

  Furthermore, the variable gear ratio actuator 20 can be operated in the normal steering state. Therefore, for example, even when the driver performs emergency avoidance steering to avoid collision with an obstacle, the variable gear ratio actuator 20 is operated to appropriately steer the left and right front wheels FW1, FW2. Therefore, emergency avoidance steering by the driver can be favorably assisted.

  On the other hand, for example, the VGRSECU 51 inputs a large external force to the left and right front wheels FW1 and FW2 when the left and right front wheels FW1 and FW2 come in contact with the curb installed on the road (on the road surface), and an impact caused by the input external force. If the torque is larger than the lock reference torque value Tth1, the lock mechanism 22 can be locked. Here, when a large impact torque is input, the steering angular speed, the turning angular speed, and the motor angular speed all change to a large speed, so that the lock reference torque value Tth1 can be changed to a small value. Therefore, when a large external force is input to the left and right front wheels FW1 and FW2, the VGRS ECU 51 can switch the lock mechanism 22 to the locked state at an early stage, so that the steering output shaft 13 and the steering input shaft 12 are The relative rotation of can be prohibited. Thereby, the variable gear ratio actuator 20 can be favorably protected.

  Further, by adopting at least one of the steering angular velocity, the turning angular velocity, and the motor angular velocity as the steering related amount, it is accurately and easily detected that a large external force is input to the left and right front wheels FW1 and FW2. be able to. Therefore, the variable gear ratio actuator 20 can be protected more reliably by changing the lock reference torque value Tth1 based on these angular velocities.

  As described above, when the steering angular velocity, the turning angular velocity, and the motor angular velocity become large, the lock reference torque value Tth1 is changed to a small value.In other words, the steering angular velocity, the turning angular velocity, and the motor angular velocity are changed in the normal steering state. When the lock reference torque value Tth1 is changed (maintained) to a large value when it is small to some extent, switching control to an unnecessary lock state in the normal steering state is prevented. Therefore, the uncomfortable feeling perceived by the driver can be eliminated with the switching control between the locked state and the unlocked state with respect to the lock mechanism 22.

  Further, since the variable gear ratio actuator 20 can be well protected, for example, occurrence of tooth skipping in a predetermined gear structure that constitutes the reduction gear 23 can be prevented. In addition, since the variable gear ratio actuator 20 can be well protected, the VGRS motor 21 can be downsized.

  Further, since the transition to the locked state can be completed at an early stage, the impact when the lock lever 22b is engaged with the lock holder 22a can be reduced. Thereby, while the lifetime of the component of the lock mechanism 22 can be lengthened, a component can be reduced in size. Further, since the impact between the lock holder 22a and the lock lever 22b can be reduced, the hitting sound between these members during engagement can be reduced. In addition, since the impact between the lock holder 22a and the lock lever 22b can be reduced, in particular, the deformation due to the engagement of the lock lever 22b can be extremely reduced, and therefore, with other members disposed around the lock lever 22b. Interference does not occur.

  In addition, since the transition to the locked state can be completed at an early stage, the reverse rotation of the VGRS motor 21 can be prevented, thereby making it difficult for the driver to perceive a sense of incongruity regarding the turning state of the vehicle. Furthermore, since the transition to the locked state can be completed at an early stage, the VGRS motor 21 is not operated wastefully, and as a result, an energy saving effect can be expected.

  In the above embodiment, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are determined based on at least one of the steering angular velocity, the turning angular velocity, and the motor angular velocity. On the other hand, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are determined based on the rotation angle θa of the steering input shaft 12 (steering angle of the steering handle 11) and the rotation angle θc of the steering output shaft 13 (left and right front wheels FW1, It is also possible to carry out the determination based on at least one of the rotation angle θb of the drive shaft 21b of the VGRS motor 21 (hereinafter referred to as the motor angle). Hereinafter, although this 1st modification is demonstrated, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.

  Also in the first modified example, the VGRSECU 51 executes the lock mechanism operation control program as in the above embodiment. However, in this first modification, the VGRESCU 51 compares the lock reference torque value Tth1 determined based on the change characteristic shown in FIG. 7 and the absolute value of the input torque Tm in step S16.

  The lock reference torque value Tth1 in the first modification is changed according to the magnitude of at least one of the steering angle, the turning angle, and the motor angle. Hereinafter, the lock reference torque value Tth1 in the first modification will be specifically described. Note that since the mutual relationship among the steering angle, the turning angle, and the motor angle is substantially proportional, the lock reference torque value Tth1 can be similarly set regardless of which of these angles is used.

  When the driver rotates the steering handle 11 to a large steering angle, the left and right front wheels FW1 and FW2 are steered to a large turning angle in accordance with the rotating operation. That is, when the steering handle 11 is turned, the rotation angle θa of the steering input shaft 12, the rotation angle θb of the drive shaft 21b, and the rotation angle θc of the steered output shaft 13 increase, and as a result, the left and right front wheels FW1, FW2 is steered to a large steered angle.

  In this case, when the driver further rotates the steering handle 11, up to a steering position where the steering range of the left and right front wheels FW1, FW2 is mechanically determined (hereinafter, this steering position is referred to as a mechanical end position). The left and right front wheels FW1, FW2 are steered. Since the left and right front wheels FW1 and FW2 are forced to stop the steering at the mechanical end position, a large impact torque may be input to the variable gear ratio actuator 20. Further, since the drive shaft 21b is rotated to a large rotation angle θb, the load on the VGRS motor 21 increases, and the VGRS motor 21 may reverse when a road surface reaction force is input.

  Therefore, in order to protect the variable gear ratio actuator 20 from the input of this large impact torque and the reverse rotation of the VGRS motor 21, as shown in FIG. 7, the lock reference torque value Tth1 has a steering angle, a turning angle, and a motor angle. It is set small in a large region (for example, about the lock reference torque value S2 in FIG. 5). Accordingly, the VGRSECU 51 can quickly shift the lock mechanism 22 to the locked state in the steered state in which the left and right front wheels FW1 and FW2 are close to the mechanical end position. On the other hand, when the steering angle, the turning angle, and the motor angle are outside the large range, the lock reference torque value Tth1 is set to be large (for example, about the lock reference torque value S1 in FIG. 5). Thereby, VGRSECU51 can prevent the transition to the lock state which is not intended in a normal steering state.

  Then, using the lock reference torque value Tth1 set in this way, the VGRSECU 51 determines whether the absolute value of the torque Tm input in step S15 is larger than the lock reference torque value Tth1 as in the above embodiment. Determine whether. However, in this first modification, the VGRESCU 51 determines the lock reference torque value Tth1 using at least one of the detected rotation angle θa, the detected rotation angle θb, and the detected rotation angle θc input in step S11. To do.

  In the first modification, the VGRESCU 51 compares the unlock reference torque value Tth2 determined based on the change characteristic shown in FIG. 7 with the absolute value of the input torque Tm in step S24. The unlock reference torque value Tth2 in the first modification is also set to be smaller by a predetermined amount than the above-described lock reference torque value Tth1, as indicated by a broken line in FIG. Therefore, the unlock reference torque value Tth2 is also changed according to the magnitude of at least one of the steering angle, the turning angle, and the motor angle. That is, the unlock reference torque value Tth2 is set to be small in a region where the steering angle, the turning angle, and the motor angle are large, and is set large outside the region where the steering angle, the turning angle, and the motor angle are large.

  Then, the VGRSECU 51 uses the unlock reference torque value Tth2 set in this way, and the absolute value of the torque Tm input in step S23 is smaller than the unlock reference torque value Tth2 as in the above embodiment. It is determined whether or not. However, in this first modification, the VGRS ECU 51 uses the at least one of the detected rotation angle θa, the detected rotation angle θb, and the detected rotation angle θc input at step S11 to calculate the unlock reference torque value Tth2. decide.

  As can be understood from the above description, in the first modification, the lock reference torque value Tth1 is determined using at least one of the detected rotation angle θa, the detected rotation angle θb, and the detected rotation angle θc. Can do. When the detected rotation angle θa, the detected rotation angle θb, and the detected rotation angle θc are in a large region, the lock reference torque value Tth1 can be determined to be small. Therefore, also in this first modified example, the same effect as in the above embodiment can be expected.

  In the above embodiment, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are determined based on at least one of the steering angular velocity, the turning angular velocity, and the motor angular velocity. On the other hand, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are based on at least one of a current value (hereinafter referred to as a motor current value) flowing through the VGRS motor 21 and a voltage value (hereinafter referred to as a motor voltage value). It is also possible to carry out as determined. Hereinafter, although this 2nd modification is demonstrated, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.

  In the second modified example, as indicated by a broken line in FIG. 1, a current / voltage detection sensor 46 is provided as a steering-related amount detection means for detecting a motor current value and a motor voltage value flowing through the VGRS motor 21. Yes. The current / voltage detection sensor 46 detects the motor current value Im and the motor voltage value Vm flowing in the VGRS motor 21 and outputs them to the VGRS ECU 51.

  And also in this 2nd modification, VGRSECU51 performs a lock mechanism action | operation control program similarly to the said embodiment. However, in the second modification, the VGRESCU 51 inputs the motor current value Im and the motor voltage value Vm from the current / voltage detection sensor 46 in step S11.

  In this second modification, the VGRESCU 51 compares the lock reference torque value Tth1 determined based on the change characteristic shown in FIG. 8 and the absolute value of the input torque Tm in step S16. The lock reference torque value Tth1 in the second modification is changed according to the magnitude of at least one detection value of the motor current value and the motor voltage value. Hereinafter, the lock reference torque value Tth1 in the second modification will be specifically described. Here, the motor current value and the motor voltage value are substantially proportional to the magnitudes of the steering angle, the turning angle, and the motor angle. For this reason, the change characteristic of the lock reference torque value Tth1 in the second modification can be set to have the same change characteristic as in the above-described embodiment and the first modification.

  When the driver turns the steering handle 11, the left and right front wheels FW1 and FW2 are steered in accordance with the turning operation. That is, when the steering handle 11 is turned, the rotation angle θa of the steering input shaft 12, the rotation angle θb of the drive shaft 21b, and the rotation angle θc of the steered output shaft 13 increase, and as a result, the left and right front wheels FW1, FW2 is steered. For this reason, the motor current value and the motor voltage value flowing through the VGRS motor 21 change substantially in proportion to the rotation angle θb (motor angle) of the drive shaft 21b.

  In this case, when the driver further rotates the steering handle 11, the steering of the left and right front wheels FW1 and FW2 is forcibly stopped at the mechanical end position, so that a large impact torque is applied to the variable gear ratio actuator 20. May be entered. In addition, since the drive shaft 21b is rotated to a large rotation angle θb, the load on the VGRS motor 21 is increased, and the VGRS motor 21 may reverse even when a small road reaction force is input. In such a situation where a large impact torque is input or the load on the VGRS motor 21 increases, the motor current value and the motor voltage value increase.

  Therefore, in order to protect the variable gear ratio actuator 20 from the input of this large impact torque and the reverse rotation of the VGRS motor 21, as shown in FIG. 8, the lock reference torque value Tth1 is a region where the motor current value and the motor voltage value are large. (For example, about the lock reference torque value S2 in FIG. 5). Accordingly, the VGRSECU 51 can quickly shift the lock mechanism 22 to the locked state in the steered state in which the left and right front wheels FW1 and FW2 are close to the mechanical end position. On the other hand, when the motor current value and the motor voltage value are outside the large range, the lock reference torque value Tth1 is set to be large (for example, about the lock reference torque value S1 in FIG. 5). Thereby, VGRSECU51 can prevent the transition to the lock state which is not intended in a normal steering state.

  Then, using the lock reference torque value Tth1 set in this way, the VGRSECU 51 determines whether the absolute value of the torque Tm input in step S15 is larger than the lock reference torque value Tth1 as in the above embodiment. Determine whether. However, in the second modified example, the VGRESCU 51 determines the lock reference torque value Tth1 using at least one of the motor current value Im and the motor voltage value Vm input in step S11.

  In the second modification, the VGRESCU 51 compares the unlock reference torque value Tth2 determined based on the change characteristic shown in FIG. 8 with the absolute value of the input torque Tm in step S24. The unlock reference torque value Tth2 in the second modification is also set to be smaller by a predetermined amount than the above-described lock reference torque value Tth1, as indicated by a broken line in FIG. Therefore, the unlock reference torque value Tth2 is also changed according to at least one of the motor current value and the motor voltage value. That is, unlock reference torque value Tth2 is set to be small when the motor current value and motor voltage value are large, and is set to be large when the motor current value and motor voltage value are large.

  Then, the VGRSECU 51 uses the unlock reference torque value Tth2 set in this way, and the absolute value of the torque Tm input in step S23 is smaller than the unlock reference torque value Tth2 as in the above embodiment. It is determined whether or not. However, in this second modification, the VGRESCU 51 determines the unlock reference torque value Tth2 using at least one of the motor current value Im and the motor voltage value Vm input in step S11.

  As can be understood from the above description, in the second modification, the lock reference torque value Tth1 can be determined using at least one of the motor current value and the motor voltage value. When the motor current value and the motor voltage value are in a large region, the lock reference torque value Tth1 can be determined to be small. Therefore, also in this second modification, the same effect as in the above embodiment can be expected.

  In the above embodiment, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are determined based on at least one of the steering angular velocity, the turning angular velocity, and the motor angular velocity. On the other hand, the lock reference torque value Tth1 and the unlock reference torque value Tth2 are determined based on the change rate of the torque Tm detected by the torque sensor 45, the change rate of the motor current value Im flowing in the VGRS motor 21, and the motor voltage value Vm. It is also possible to carry out the determination based on at least one of the rate of change. Hereinafter, although this 3rd modification is demonstrated, the same code | symbol is attached | subjected to the same part as the said embodiment, and the detailed description is abbreviate | omitted.

  In the third modified example, the VGRSECU 51 executes a lock mechanism operation control program as in the above embodiment. However, in this third modification, the VGRESCU 51 inputs the motor current value Im and the motor voltage value Vm from the current / voltage detection sensor 46 in step S11.

  In the third modification, the VGRESCU 51 compares the lock reference torque value Tth1 determined based on the change characteristic shown in FIG. 9 and the absolute value of the input torque Tm in step S16. The lock reference torque value Tth1 in the third modification is changed according to the magnitude of at least one of the detected values of the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value. Hereinafter, the lock reference torque value Tth1 in the third modification will be specifically described. Here, since the mutual relationship among the rate of change of input torque, rate of change of motor current value, and rate of change of motor voltage value is almost proportional, the lock reference can be used regardless of which rate of change is used. The torque value Tth1 can be set similarly.

  When the left and right front wheels FW1, FW2 come into contact with the curbstone and a large impact torque is input, the large impact torque is input via the steering output shaft 13. For this reason, when the impact torque is input, the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value increase. For this reason, in the speed reducer 23, the damage to the speed reducer 23 increases as the rate of change in input torque, the rate of change in motor current value, and the rate of change in motor voltage value increase.

  Further, even when the steering operation of the left and right front wheels FW1, FW2 is forcibly stopped at the mechanical end position, a large impact torque may be input to the variable gear ratio actuator 20. Even when this impact torque is input, the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value increase.

  Therefore, in order to protect the variable gear ratio actuator 20 from such an input of a large impact torque, as shown in FIG. 9, the lock reference torque value Tth1 includes the change rate of the input torque, the change rate of the motor current value, and the motor The voltage value change rate is set to be small (for example, about the lock reference torque value S2 in FIG. 5) in a large region. Thereby, the VGRSECU 51 can shift the lock mechanism 22 to the locked state at an early stage in a situation where a large impact torque is input. On the other hand, when the rate of change of the input torque, the rate of change of the motor current value, and the rate of change of the motor voltage value are outside the large range, the lock reference torque value Tth1 is large (for example, about the lock reference torque value S1 in FIG. 5). Is set. Thereby, VGRSECU51 can prevent the transition to the lock state which is not intended in a normal steering state.

  Then, using the lock reference torque value Tth1 set in this way, the VGRSECU 51 determines whether the absolute value of the torque Tm input in step S15 is larger than the lock reference torque value Tth1 as in the above embodiment. Determine whether. Specifically, the VGRS ECU 51 first calculates the rate of change of the motor current value and the rate of change of the motor voltage value using the motor current value Im and the motor voltage value Vm input in step S11. Further, the VGRS ECU 51 calculates the rate of change of the input torque using the torque Tm input in step S15. Then, VGRSECU 51 determines the lock reference torque value Tth1 using at least one of the calculated input torque change rate, motor current value change rate, and motor voltage value change rate.

  In the third modification, the VGRESCU 51 compares the unlock reference torque value Tth2 determined based on the change characteristic shown in FIG. 9 and the absolute value of the input torque Tm in step S24. The unlock reference torque value Tth2 in the third modification is also set to be smaller by a predetermined amount than the above-described lock reference torque value Tth1, as indicated by a broken line in FIG. Accordingly, the unlock reference torque value Tth2 is also changed according to at least one of the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value. That is, the unlock reference torque value Tth2 is set to be small in a region where the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value are large, and the change rate of the input torque, the change rate of the motor current value, and It is set large outside the region where the rate of change of the motor voltage value is large.

  Then, the VGRSECU 51 uses the unlock reference torque value Tth2 set in this way, and the absolute value of the torque Tm input in step S23 is smaller than the unlock reference torque value Tth2 as in the above embodiment. It is determined whether or not. Specifically, the VGRS ECU 51 first calculates the rate of change of the motor current value and the rate of change of the motor voltage value using the motor current value Im and the motor voltage value Vm input in step S11. Further, the VGRSECU 51 calculates the rate of change of the input torque using the torque Tm input in step S23. Then, VGRSECU 51 determines the lock reference torque value Tth2 using at least one of the calculated input torque change rate, motor current value change rate, and motor voltage value change rate.

  As can be understood from the above description, in the third modification, the lock reference torque value is obtained using at least one of the input torque change rate, the motor current value change rate, and the motor voltage value change rate. Tth1 can be determined. When the change rate of the input torque, the change rate of the motor current value, and the change rate of the motor voltage value are in a large region, the lock reference torque value Tth1 can be determined to be small. Therefore, also in this third modified example, the same effect as in the above embodiment can be expected.

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

  For example, in the said embodiment and each modification, the torque sensor 45 was provided in the steering output shaft 13, and it implemented. However, it is also possible to provide the steering input shaft 12 with the torque sensor 45. Even in this case, by using the torque Tm detected by the torque sensor 45, it is possible to obtain the same effects as those of the above-described embodiment and each modification.

  Further, in the above-described embodiment and each modified example, when determining the lock reference torque value Tth1 and the unlock reference torque value Tth2, the determination is performed using the same physical quantity. However, the physical quantity for determining the lock reference torque value Tth1 and the physical quantity for determining the unlock reference torque value Tth2 may be different. In this way, by using the lock reference torque value Tth1 and the unlock reference torque value Tth2 determined by different physical quantities, for example, the lock mechanism 22 can be appropriately set to the locked state and the unlocked state according to the traveling state of the vehicle. It is possible to switch.

  Moreover, in the said embodiment and each modification, it comprised so that the turning angle sensor 44 might be assembled | attached to the turning output shaft 13, and it implemented so that rotation angle (theta) c of the turning output shaft 13 could be detected directly. However, when the axial displacement of the rack bar 32 can be detected, the rotation angle θc of the steered output shaft 13 can be calculated corresponding to the axial displacement. Even in this case, the same effects as those of the above-described embodiment and each modification can be expected.

  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 view of a vehicle steering apparatus according to an embodiment of the present invention. 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 VGRESCU of FIG. 1 according to the embodiment of the present invention. It is a figure for demonstrating the lock state completion time of a lock mechanism when a lock reference torque value is changed with respect to the time change of the input impact torque and normal torque. 4 is a graph showing a change characteristic of a lock reference torque value and an unlock reference torque value with respect to changes in a steering angular velocity, a turning angular velocity, and a motor angular velocity according to the embodiment of the present invention. 6 is a graph illustrating a change characteristic of a lock reference torque value and an unlock reference torque value with respect to changes in a steering angle, a turning angle, and a motor angle according to a first modification of the embodiment of the present invention. It is a graph which shows the change characteristic of the lock reference torque value and unlock reference torque value with respect to the change of a motor current value and a motor voltage value concerning the 2nd modification of embodiment of this invention. It is a graph which shows the change characteristic of the lock reference torque value and unlock reference torque value with respect to the 3rd modification of embodiment of this invention with respect to a torque change rate, a motor current value change rate, and a motor voltage value change rate.

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 ... Steering angle sensor, 45 ... Torque sensor, 46 ... Current and voltage detection sensor, 51 ... VGRSECU, 52 ... EPSECU, 53, 54, 55 ... Drive circuit

Claims (8)

A steering input shaft that rotates integrally with a turning operation of the steering handle, 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 side; A reduction gear connected to the steering output shaft side and decelerating the rotation 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 to change the rotation. A transmission ratio variable actuator that rotates the rudder output shaft, a lock mechanism that restricts relative rotation between the steering input shaft and the steering output shaft, and a lock mechanism operation control device that controls the operation of the lock mechanism. In the transmission ratio variable steering device provided, the lock mechanism operation control device,
An external force detecting means for detecting an external force acting on the variable transmission ratio actuator;
Whether or not the detected external force is larger than a lock reference value that determines whether or not to shift the lock mechanism to a locked state that restricts relative rotation between the steering input shaft and the steered output shaft. External force determination means for determining;
Steering-related amount detection means for detecting a steering-related amount that changes due to the turning operation of the steering handle;
Reference value changing means for changing the lock reference value according to the detected steering-related amount;
Variable transmission ratio characterized by comprising switching control means for switching control of the lock mechanism between the unlocked state and the locked state allowing relative rotation of the steering input shaft and the steering output shaft. Steering device. In the transmission ratio variable steering apparatus according to claim 1,
The external force detection means includes
A transmission ratio variable steering characterized by detecting an external force input from the road surface side to the steered wheel and transmitted to the speed reducer of the transmission ratio variable actuator via the steered output shaft. apparatus. In the transmission ratio variable steering apparatus according to claim 1,
The external force determination means includes
A transmission ratio variable steering apparatus, wherein it is determined whether or not the external force detected by the external force detection means continues for a predetermined time in a state where the external force is larger than the lock reference value. In the transmission ratio variable steering apparatus according to claim 1,
The reference value changing means includes
The transmission ratio variable steering apparatus, wherein the lock reference value is changed to a small value as the steering related amount detected by the steering related amount detecting means increases. In the transmission ratio variable steering apparatus according to claim 4,
The steering related amount detection means includes
A transmission ratio variable, wherein at least one of a rotation amount of the steering input shaft, a rotation amount of the steering output shaft, and a rotation amount of an electric motor of the transmission ratio variable actuator is detected as the steering related amount. Steering device. In the transmission ratio variable steering apparatus according to claim 4,
The steering related amount detection means includes
A transmission ratio variable characterized in that at least one of a rotational angular velocity of the steering input shaft, a rotational angular velocity of the steering output shaft, and a rotational angular velocity of an electric motor of the transmission ratio variable actuator is detected as the steering related amount. Steering device. In the transmission ratio variable steering apparatus according to claim 4,
The steering related amount detection means includes
A transmission ratio variable steering apparatus, wherein at least one of a current value and a voltage value flowing through an electric motor of the transmission ratio variable actuator is detected as the steering related amount. In the transmission ratio variable steering apparatus according to claim 4,
The steering related amount detection means includes
Detecting at least one of a change rate of an external force detected by the external force detection means, a change rate of a current value flowing through the electric motor of the variable transmission ratio actuator, and a change rate of a voltage value as the steering-related amount. A variable transmission ratio steering device.

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