JP2009029362A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device ensuring excellent operability in the case where any auxiliary force is not given. <P>SOLUTION: A main shaft 21 has an upper shaft 211 and a lower shaft 212 which are slidable to each other. A sun gear 211a is formed on the shaft 211. A straight gear 212a is formed on the shaft 212, and a plurality of planetary gears 212b to be engaged with a ring gear 222a fixed to a vehicle body are assembled thereto. When the assist torque Ta is not present, an auxiliary force giving means (an electric motor) is temporarily operated, and the tooth position is adjusted by relatively rotating the gear 211a and the gear 212b by a small amount so that the gear 211a is engaged with the gear 212b. The steering torque t is reduced by reliably increasing the reduction gear ratio between the shaft 211 and the shaft 212. Thus, the excellent operability is ensured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steering means operated by a driver, a transmission shaft for connecting the steering means and a steered wheel and transmitting a steering force input via the steering means to the steered wheel, and the transmission shaft The present invention relates to a vehicle steering apparatus including an auxiliary force applying unit that is connected to the vehicle and applies a predetermined auxiliary force to the operation of the steering unit.

2. Description of the Related Art Conventionally, in a vehicle steering apparatus provided with auxiliary force applying means (for example, an electric motor) for reducing a steering force necessary for operating a steering means (for example, a steering wheel) by a driver, the operation of the auxiliary force applying means is performed. Proposals have been made to suppress the deterioration of the steering performance when the vehicle stops. For example, in Patent Document 1 below, detection torque is taken in from detection means operating normally among detection means for estimating a plurality of steering states, and the assist torque by the electric motor is monitored while monitoring the read detection information. An electric power steering control device that reduces the urging force is shown. According to this conventional electric power steering control device, it is possible to prevent a sudden decrease in assist torque due to the stop of the electric motor, so that a good steering feeling is ensured.
JP 2005-67262 A

  By the way, even in the conventional electric power steering control device disclosed in Patent Document 1, the assist torque (assisting force) is not applied after the operation of the electric motor is completely stopped. For this reason, in order for the driver to rotate the steering means (steering handle), a large steering force (for example, steering torque) is required, which imposes a physical burden on the driver. Therefore, it is desired that the driver can easily rotate the steering means (steering handle) even in a situation where some abnormality occurs and the assist torque (assist force) is not applied.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus that ensures good operability in a situation where no auxiliary force is applied.

  In order to achieve the above object, the present invention is characterized in that a steering means operated by a driver, and a steering force inputted through the steering means by connecting the steering means and the steered wheels to the steered wheels. In the vehicle steering apparatus, the transmission shaft is connected to the transmission shaft and applies auxiliary force applying means for applying a predetermined auxiliary force to the operation of the steering means. A first shaft disposed on the means side, and a second shaft disposed on the steered wheel side that slidably accommodates the first shaft in the axial direction, and the auxiliary force In a normal state in which the applying means applies the auxiliary force, the straight-tooth input gear formed on the first shaft and the first gear formed on the second shaft are meshed with each other and the first shaft with respect to the rotational speed of the first shaft. The reduction ratio indicating the ratio of the rotational speeds of the two axes is set to “1”, and the auxiliary force applying means is The input gear and the second gear formed on the second shaft are engaged with the relative displacement in the axial direction between the first shaft and the second shaft in a state where the auxiliary force is not applied. In addition, the first reduction gear has a reduction means for changing the reduction ratio to a value larger than “1” and an electric drive means for electrically driving the first input gear and the second gear to mesh with each other. Displacement means for relatively displacing the shaft and the second shaft in the axial direction, determination means for determining whether or not the input gear and the second gear are in mesh with each other, and application of the auxiliary force Adjusting means for adjusting the tooth position where the input gear and the second gear mesh with each other by rotating the input gear and the second gear relatively by temporarily operating the auxiliary force applying means in a stopped state; It is in having. In this case, the first shaft and the second shaft may form a steering main shaft provided in a steering column.

  In this case, for example, the determination unit determines whether the input gear and the second gear are engaged with each other based on a change in driving current when the electric driving unit of the displacement unit is driven. The determination unit may determine whether the input gear and the second gear are in mesh with each other based on, for example, a change in driving amount when the electric driving unit of the displacement unit is driven. It is good to judge.

  In this case, for example, the auxiliary force applying means is electrically driven to apply the auxiliary force, and the determining means is driving the auxiliary force applying means that is temporarily operated by the adjusting means. Based on the current change, it may be determined whether or not the input gear and the second gear are in mesh. Further, for example, the auxiliary force applying means is electrically driven to apply the auxiliary force, and the determining means is adapted to change the driving amount of the auxiliary force applying means that is temporarily operated by the adjusting means. Based on this, it may be determined whether or not the input gear and the second gear are in mesh.

  Further, in this case, when the determination means determines that the input gear and the second gear are not engaged with each other, the adjustment means temporarily operates the auxiliary force applying means to The tooth position where the input gear and the second gear mesh with each other may be adjusted by relatively rotating the second gear.

  According to these, in the normal state in which the auxiliary force applying means applies the auxiliary force, the input gear formed on the first shaft and the first gear formed on the second shaft are engaged with each other, and the reduction ratio becomes “ 1 ", that is, the first shaft and the second shaft are directly connected. Thereby, the driver can steer the steered wheels by the steering force input via the steering unit and the auxiliary force applied by the auxiliary force applying unit. On the other hand, in the auxiliary force application stop state in which the auxiliary force application means does not apply the auxiliary force, the displacement means relatively displaces the first axis and the second axis in the axial direction, so that the speed reduction means becomes the first axis. The formed input gear and the second gear formed on the second shaft mesh with each other, so that the reduction ratio is greater than “1”.

  At this time, the adjustment means can adjust the tooth position where the input gear and the second gear mesh with each other by temporarily operating the auxiliary force application means even in the auxiliary force application stop state. Further, the determination means is based on a change in drive current or drive amount of the electric drive means constituting the displacement means, or on the basis of a change in drive current or drive amount of the electrically driven auxiliary force applying means. It can be determined whether or not the second gear is in mesh with the second gear. Furthermore, for example, when it is determined by the determination means that the input gear and the second gear are not engaged, the adjusting means temporarily operates the auxiliary force application means even in the auxiliary force application stop state, The tooth position where the input gear and the second gear mesh can be adjusted. Thereby, the input gear and the second gear can be reliably meshed with each other, and the rotational speed of the second shaft can be reliably decelerated with respect to the rotational speed of the first shaft. As a result, the steering force required to steer the steered wheels can be reduced. Therefore, even in the auxiliary force application stop state, the driver can easily steer the steered wheels only with the steering force input via the steering means, and can ensure good operability.

  The displacement means may be configured to relatively displace the first axis and the second axis in the axial direction when the traveling behavior of the vehicle is stable. More specifically, when the vehicle is less than a predetermined vehicle speed or when the vehicle is in a straight traveling state, the front displacement means relatively moves the first shaft and the second shaft in the axial direction. It is good to displace. According to these, the input gear is shifted from the meshing state with the first gear to the meshing state with the second gear in a state where the relative movement between the first shaft and the second shaft is small, particularly in the rotational direction. be able to. Therefore, the meshing state of the input gear and the second gear can be more reliably realized.

  The first gear is a straight tooth gear formed in a predetermined length parallel to the axial direction of the second shaft, and the second gear is a straight tooth ring gear fixed to the vehicle body side. It is good to comprise a plurality of straight-toothed planetary gears that are engaged and assembled at a position separated from the first gear by a predetermined distance and that rotate and revolve around the input gear in a state of being engaged with the input gear. .

  According to this, since the straight first gear can be formed to a predetermined length, the input gear can be displaced in the axial direction by a predetermined length with respect to the first gear. For this reason, in a normal state, for example, so-called telescopic operation in which the distance between the driver and the steering means is appropriately adjusted is also possible. Further, the second gear can be composed of a plurality of planetary gears that mesh with a ring gear fixed to the vehicle body. Thereby, the structure for enlarging the reduction ratio can be simplified, and the size can be greatly reduced. In addition, the gear ratio between the ring gear and the input gear, in other words, by appropriately changing the inner diameter dimension of the ring gear and the outer diameter dimension of the input gear, a reduction ratio larger than “1” can be set very easily. be able to. Therefore, the steering force input by the driver can be appropriately reduced in the auxiliary force application stop state.

  Hereinafter, a vehicle steering apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows the overall configuration of an electric power steering apparatus as a vehicle steering apparatus according to an embodiment.

  This electric power steering apparatus includes a steering handle 1 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 1 is assembled to a steering column 2, and the steering column 2 is connected to a steering gear 5 via an intermediate shaft 3 and a pinion shaft 4. The steering gear 5 is connected to the left and right front wheels FW1, FW2.

  As specifically shown in FIG. 2, the steering column 2 is supported in an inclined posture so that the front side of the vehicle is positioned downward with respect to a steering support member SS provided in the instrument panel reinforcement IR. The instrument panel reinforcement IR and the steering support member SS are vehicle body side members that are assembled and fixed to the vehicle body. The steering column 2 includes a steering main shaft 21 that supports the steering handle 1 so as to be rotatable, and a column tube 22 that accommodates the steering main shaft 21 and fixes the vehicle body.

  As shown in FIG. 3, the steering main shaft 21 includes an upper shaft 211 as a first axis and a lower shaft 212 as a second axis. The upper shaft 211 and the lower shaft 212 are formed in a hollow shape, and the lower end side of the upper shaft 211 is slidably inserted into the upper end side of the lower shaft 212.

  The upper shaft 211 is connected to the steering handle 1 on the upper end side. Further, on the lower end side of the upper shaft 211, a straight gear 211a as an input gear having the number Ns of teeth having teeth parallel to the axial direction is formed on the outer peripheral surface thereof. In the following description, the straight gear 211a formed on the upper shaft 211 is also referred to as a sun gear 211a as necessary.

  The lower shaft 212 is a first gear having teeth parallel to the axial direction so as to mesh with a straight gear 211a formed on the upper shaft 211 from the substantially central portion toward the upper end side on the inner peripheral surface thereof. The direct-tooth gear 212a is formed. Here, the straight gear 212a is formed to have a predetermined length in the axial direction of the lower shaft 212 in accordance with the pulling amount of the steering handle 1 adjusted by the driver, that is, the telescopic stroke range. Needless to say, the number of teeth of the straight gear 212a is the same as the number of teeth Ns of the straight gear 211a formed on the upper shaft 211.

  Further, the lower shaft 212 has an enlarged upper end side, and this enlarged portion (hereinafter referred to as a large-diameter portion) can be engaged with a sun gear 211a formed on the upper shaft 211. A plurality of planetary gears 212b (for example, three in this embodiment) constituting the gears are assembled. Note that the planetary gear 212b and the direct gear 212a are arranged apart from each other by a predetermined distance.

  The planetary gear 212b has straight teeth parallel to the rotational axis direction, that is, the axial direction of the lower shaft 212 in order to mesh with the sun gear 211a as described later. The planetary gears 212b are assembled at equal intervals in the circumferential direction in the large diameter portion of the lower shaft 212. Thereby, the lower shaft 212 itself becomes a planet carrier of the planetary gear 212b. The planetary gear 212b has a diameter larger than the wall thickness of the large diameter portion of the lower shaft 212. Thereby, in a state where the planetary gear 212b is assembled to the lower shaft 212, the straight teeth of the planetary gear 212b protrude to the inner peripheral surface side and the outer peripheral surface side of the lower shaft 212.

  As shown in FIG. 2, the column tube 22 includes an upper tube 221 and a lower tube 222. As shown in FIG. 3, the upper tube 221 and the lower tube 222 are formed in a hollow shape, and the upper end side of the lower tube 222 is slidably inserted into the lower end side of the upper tube 221. ing. Note that, for example, a liner is formed at the insertion position of the upper tube 221 and the lower tube 222, and the liner is supported without rattling against the relative displacement in the axial direction of the upper tube 221 and the lower tube 222. It has become so.

  The upper tube 221 supports the upper shaft 211 so as to be rotatable and not axially displaceable by a bearing integrally fixed to an inner peripheral surface on the upper end side thereof. Further, a nut 233 constituting an electric telescopic operation unit 23 as a displacement means described later is integrally fixed to the lower end side of the upper tube 221.

  The lower tube 222 supports the lower shaft 212 so as to be rotatable and not axially displaceable. Therefore, a ring gear 222 a that meshes with the planetary gear 212 b assembled to the lower shaft 212 is integrally formed on the inner peripheral surface on the upper end side of the lower tube 222. The ring gear 222 a has straight teeth parallel to the axial direction of the lower tube 222, that is, the axial direction of the lower shaft 212. Here, the number of teeth of the ring gear 222a is the number of teeth Nr. As described above, the planetary gear 212a and the ring gear 222a mesh with each other, so that the lower shaft 212 is rotatably supported with respect to the lower tube 222. Further, an electric motor 231 constituting the electric telescopic operation unit 23 is integrally fixed to the upper end side of the lower tube 222.

  As shown in FIGS. 1 to 3, the electric telescopic operation unit 23 includes an electric motor 231, and this electric motor 231 is connected to a screw 232 via a predetermined reduction gear (not shown) so as to be able to transmit rotation. . The screw 232 extends parallel to the axial direction of the upper tube 221 and is screwed to a nut 233 fixed on the outer peripheral surface of the upper tube 221. With this configuration, when the electric motor 231 is rotationally driven to rotate the screw 232, the nut 233 screwed to the screw 232 is relatively displaced in the axial direction. As a result, the upper tube 221 is displaced relative to the lower tube 222, whereby the upper shaft 211 accommodated in the upper tube 221 is displaced relative to the lower tube 212.

  As shown in FIGS. 1 and 2, an EPS unit 24 as an auxiliary force applying means is assembled on the front side of the steering column 2 with respect to the vehicle. The EPS unit 24 applies assist torque Ta to the steering main shaft 21 for reducing the steering torque t input when the driver rotates the steering handle 1.

  The EPS unit 24 includes a housing 241 connected to the lower end of the lower tube 222 by fastening means such as bolts, and an electric motor 242 assembled to the housing 241. Housed in the housing 241 are a connecting shaft 243 that connects the lower shaft 212 and the intermediate shaft 3 to each other, and a speed reducer (not shown) that reduces the rotational speed of the electric motor 242 and transmits it to the connecting shaft 243. Has been. The connecting shaft 243 accommodated in the housing 241 and the lower shaft 212 are connected, so that the lower shaft 212 cannot be displaced in the axial direction with respect to the lower tube 222.

  As shown in FIGS. 1 and 2, the intermediate shaft 3 is connected to the steering column 2 (more specifically, the connecting shaft 243) via a universal joint 31. The intermediate shaft 3 is divided into two parts and can be expanded and contracted. A universal joint 31 is assembled on one end side, and a universal joint 32 is assembled on the other end side. The intermediate shaft 3 is connected to the pinion shaft 4 via a universal joint 32.

  As shown in FIG. 1, the pinion shaft 4 connects the intermediate shaft 3 and a pinion gear 51 of the steering gear 5 that employs a rack and pinion system. The steering gear 5 includes a rack bar 52 that meshes with the pinion gear 51, and the rotation of the pinion gear 51 is transmitted to the rack bar 52. Thus, when torque is transmitted to the rack bar 52 along with the rotation of the pinion gear 51, the rack bar 52 is displaced to the left and right in the axial direction, and the left and right front wheels FW1, FW2 connected to both ends of the rack bar 52 are It is steered left and right.

  In this embodiment, a so-called column assist type electric power steering device in which the EPS unit 24 is provided in the steering column 2 is used. However, the EPS unit (more specifically, the electric motor) is implemented using, for example, a pinion assist type electric power steering device that transmits assist torque to the pinion shaft 4, or the rack bar 52 of the steering gear 5. Needless to say, the present invention can also be implemented using a rack assist type electric power steering device that transmits assist torque to the motor.

  Next, the electric control device 6 that controls the operation of the electric telescopic operation unit 23 (more specifically, the electric motor 231) and the EPS unit 24 (more specifically, the electric motor 242) will be described. As shown in FIG. 1, the electric control device 6 includes a vehicle speed sensor 61, a steering torque sensor 62, a steering angle sensor 63, a turning angle sensor 64, an EPS motor rotation angle sensor 65, and a telescopic motor rotation angle sensor 66. . The vehicle speed sensor 61 detects and outputs the vehicle speed V of the vehicle. The steering torque sensor 62 is assembled in the EPS unit 24 (more specifically, the connecting shaft 243), and detects and outputs the steering torque t input via the steering handle 1. The steering torque t represents a torque that rotates the steering wheel 1 in the right direction with respect to the forward direction of the vehicle as a positive value, and a torque that rotates the steering wheel 1 in the left direction as a negative value.

  The steering angle sensor 63 is assembled to the steering main shaft 21 (more specifically, the upper shaft 211), detects the rotation angle of the steering handle 1, and outputs it as the steering angle θ. The turning angle sensor 64 is assembled to the steering gear 5, detects the amount of displacement of the rack bar 52 in the axial direction, and outputs the turning angle δ of the left and right front wheels FW1, FW2 corresponding to the detected amount of displacement. To do. Note that the steering angle θ represents the rotation angle of the steering handle 1 in the right direction with respect to the forward direction of the vehicle as a positive value, and the rotation angle in the left direction as a negative value. Further, the turning angle δ represents the rotation angle of the left and right front wheels FW1 and FW2 corresponding to the displacement in the right direction from the neutral position of the rack bar 52 where the vehicle goes straight, and the displacement in the left direction. The rotation angles of the corresponding left and right front wheels FW1, FW2 are represented by negative values.

  The EPS motor rotation angle sensor 65 is assembled in, for example, the motor housing of the electric motor 242 of the EPS unit 24, detects the rotation angle of the motor rotation shaft, and outputs it as the motor rotation angle θe. The telescopic motor rotation angle sensor 66 is assembled in, for example, the motor housing of the electric motor 23 of the electric telescopic operation unit 23, detects the rotation angle of the motor rotation shaft, and outputs it as the motor rotation angle θt. The motor rotation angle θe represents a rotation angle in the direction in which the steering main shaft 21 is rotated in the right direction as a positive value, and a rotation angle in the direction in which the steering main shaft 21 is rotated in the left direction as a negative value. To express. Further, the motor rotation angle θt represents a rotation angle in a direction in which the upper tube 221 (upper shaft 211) is displaced toward the rear side of the vehicle (that is, the vehicle interior direction) as a positive value, and the upper tube 221 (upper shaft 211). The rotation angle in the direction in which the vehicle is displaced toward the front side of the vehicle (that is, the direction outside the passenger compartment) is represented by a negative value.

  These sensors 61 to 66 are connected to the electronic control unit 67. The electronic control unit 67 includes a microcomputer including a CPU, a ROM, a RAM, a timer, and the like as main components, and executes various programs including programs described later using detection values of the sensors 61 to 66. Thus, the operation of the electric telescopic operation unit 23 (electric motor 231) and the EPS unit 24 (electric motor 242) is controlled. For this reason, a drive circuit 68 for driving and controlling the electric motor 231 is connected to the output side of the electronic control unit 67, and a drive circuit 69 for driving and controlling the electric motor 242 is connected. Here, in the drive circuits 68 and 69, current detectors 68a and 69a for detecting drive currents flowing in the electric motor 231 and the electric motor 242 are provided. The drive current detected by the current detectors 68a and 69a is fed back to the electronic control unit 67 in order to drive and control the electric motor 231 and the electric motor 242.

  In addition, the electric power steering apparatus includes an alarm device 7 that notifies the driver that the electric motor 242 of the EPS unit 24 has stopped and the assist torque Ta has not been applied (hereinafter referred to as the assist stop state). Is provided. The alarm device 7 is connected to the electronic control unit 67 and includes a display unit 71 assembled at a position (for example, in a meter cluster) that can be visually recognized by the driver, and an audio output unit 72 that outputs audio. ing. The display unit 71 includes, for example, a lamp, a display panel, and the like, and notifies the driver of the assist stop state by lighting the lamp or switching the display panel. The voice output unit 72 includes, for example, a speaker and notifies the driver of the assist stop state by outputting voice.

  Next, the operation of the electric power steering apparatus configured as described above will be described in detail. In a state where the EPS unit 24 can be operated to apply the assist torque Ta, that is, in a normal state, the electronic control unit 67 (more specifically, the CPU) is appropriate for the turning operation of the steering handle 1 by the driver. A predetermined program (not shown) is executed in order to apply a proper assist torque Ta. As a result, the electric motor 242 of the EPS unit 24 is driven to apply an appropriate assist torque Ta, and the steering torque t required for the turning operation of the steering handle 1 can be reduced.

  More specifically, the electronic control unit 67 inputs the vehicle speed V detected by the vehicle speed sensor 61 and the steering torque t detected by the steering torque sensor 62. Then, the electronic control unit 67 determines a preset assist torque Ta based on the input vehicle speed V and the steering torque t. Here, the magnitude of the assist torque Ta increases, for example, as the detected vehicle speed V decreases (decreases in speed) and decreases as the detected vehicle speed V increases (increases in speed). Is set.

  When the electronic control unit 67 determines the assist torque Ta, the electronic control unit 67 determines a drive current for driving the electric motor 242 corresponding to the determined assist torque Ta, and drives the drive circuit 69 to determine the drive. Current is supplied to the electric motor 242. At this time, the electronic control unit 67 inputs a drive current flowing from the current detector 69 a of the drive circuit 69 to the electric motor 242 and performs feedback control on the drive circuit 69. As a result, the electric motor 242 is rotationally driven by the supplied drive current, and the assist torque Ta determined by the electronic control unit 67 is transmitted to the steering main shaft 21.

  In this normal state, when the vehicle is traveling at a low speed, the electronic control unit 67 determines a large assist torque Ta as described above. Accordingly, since the electric motor 242 transmits a large assist torque Ta to the steering main shaft 21, the steering torque t input by the driver to steer the left and right front wheels FW1, FW2 can be greatly reduced. Therefore, the driver can turn the steering handle 1 with a small steering torque t, and can extremely easily steer the left and right front wheels FW1, FW2 up to a large turning angle.

  In the normal state, when the vehicle is traveling at high speed, the electronic control unit 67 determines a small assist torque Ta as described above. Thus, since the electric motor 242 transmits a small assist torque Ta to the steering main shaft 21, the steering torque t input by the driver for turning the left and right front wheels FW1, FW2 can be made relatively large. Accordingly, the driver can rotate the steering handle 1 while inputting a relatively large steering torque t, in other words, while perceiving a firm reaction force, and thus can stably rotate the steering handle 1. be able to. As described above, in the normal state, the assist torque Ta is appropriately applied by driving the electric motor 242. Therefore, the driver rotates the steering handle 1 with an appropriate steering torque t according to the vehicle speed V. be able to.

  Further, in a normal state, the straight gear 211a formed on the upper shaft 211 and the straight gear 212a formed on the lower shaft are maintained in mesh with each other. Accordingly, the driver operates the electric telescopic operation unit 23 to appropriately set the distance between the steering wheel 1 and the steering wheel 1 that is seated in the driver's seat by pulling out or pushing in the steering wheel 1 within the telescopic stroke range. Telescopic operation for adjustment can be performed. Specifically, the driver can displace the steering handle 1 by operating a telescopic operation switch (not shown) provided in the vicinity of the steering handle 1.

  That is, when the driver operates the telescopic operation switch, the electronic control unit 67 supplies electric power from the drive circuit 68 to the electric motor 231 of the electric telescopic operation unit 23 based on this operation state. Thereby, the nut 233 screwed to the screw 232 is relatively displaced in the axial direction when the electric motor 231 rotates the screw 232. Thus, when the nut 233 is relatively displaced in the axial direction of the screw 232, the upper tube 221 to which the nut 233 is integrally fixed is displaced in the axial direction together with the upper shaft 211. Thereby, the steering handle 1 assembled | attached to the upper shaft 211 can be displaced suitably.

  On the other hand, when the driver stops operating the telescopic operation switch, the electronic control unit 67 cuts off the electric power supplied to the electric motor 231 via the drive circuit 68. Thereby, the rotational drive of the electric motor 231 stops and the rotation of the screw 232 also stops. As described above, when the rotation of the screw 232 is stopped, the nut 233 to be screwed cannot be displaced in the axial direction due to the frictional force between the screw 232 and the shafts of the upper tube 221 and the upper shaft 211. Directional displacement is also impossible. Therefore, in a state where the electric motor 231 is not driven, that is, after a telescopic operation, the distance between the steering wheel 1 and the driver is appropriately maintained.

  Here, when the electric motor 231 displaces, for example, the upper tube 221 (the upper shaft 211 and the steering handle 1) in the telescopic stroke range to the most front side of the vehicle (hereinafter, this displacement position is referred to as the vehicle front side telescopic stroke). The motor rotation angle θt (referred to as an end) is rotationally driven with the reference rotation angle as a reference rotation angle. The telescopic motor rotation angle sensor 66 detects the rotation angle of the electric motor 231 from this reference rotation angle as the motor rotation angle θt. As a result, the electronic control unit 67 determines the reference based on the motor rotation angle θt of the electric motor 231 detected by the telescopic motor rotation angle sensor 66 (in other words, the rotation speed of the electric motor 231) and the lead amount of the screw 232. The position of the nut 233 from the vehicle front side telescopic stroke end corresponding to the rotation angle, that is, the telescopic stroke amount is grasped. The electronic control unit 67 controls the rotational drive of the electric motor 231 via the drive circuit 68 so that the telescopic stroke amount is within the telescopic stroke range when the driver operates the telescopic operation switch.

  By the way, the electronic control unit 67 stops the driving of the electric motor 242 of the EPS unit 24 according to the fail-safe idea, for example, when an abnormality occurs in the operation state of each of the sensors 61 to 65, and the electric power steering. The operation state of the apparatus is shifted from the normal state to the assist stop state. As described above, when the assist state is shifted from the normal state, the driver has to rotate the steering handle 1 with a large steering torque t. For this reason, the electronic control unit 67 (more specifically, the CPU) reduces the steering torque t so that the driver can easily rotate the steering handle 1 even when the assist is stopped. In order to mesh the sun gear 211a and the planetary gear 212b of the lower shaft 212, a reduction ratio changing program shown in FIG. 4 is executed. Hereinafter, this reduction ratio changing program will be described in detail.

  When an ignition switch (not shown) is turned on by the driver, the electronic control unit 67 executes a predetermined initialization program and then repeatedly executes a reduction ratio changing program every predetermined short time. That is, the electronic control unit 67 starts execution of the reduction ratio changing program in step S10, and in step S11, the vehicle speed sensor 61, the steering torque sensor 62, the steering angle sensor 63, the turning angle sensor 64, and the EPS motor rotation. Each detection value detected by the angle sensor 65, specifically, the vehicle speed V, the steering torque t, the steering angle θ, the turning angle δ, and the motor rotation angle θe are input. And if the electronic control unit 67 inputs each detection value from each sensor 61-65, it will progress to step S12.

  In step S12, the electronic control unit 67 determines whether each sensor 61-65 is operating normally based on each detection value input in the said step S11. That is, the electronic control unit 67 determines whether or not each of the sensors 61 to 65 is operating normally based on, for example, the correlation between the input detection values.

  For example, the electronic control unit 67 compares the vehicle speed V with an acceleration detected by an acceleration sensor (not shown) mounted on the vehicle, so that the vehicle speed sensor 61 operates normally. It is determined whether or not. In other words, if the vehicle speed V is substantially “0” when the detected acceleration in the left-right direction of the vehicle is a certain large value, the electronic control unit 67 indicates that an abnormality has occurred in the operating state of the vehicle speed sensor 61. judge.

  Further, the electronic control unit 67 compares the steering torque t, the steering angle θ, the turning angle δ, and the motor rotation angle θe with each other, for example, so that the steering torque sensor 62, the steering angle sensor 63, the turning angle sensor 64, and It is determined whether or not the EPS motor rotation angle sensor 65 is operating normally. That is, when the vehicle is turning rightward, the steering torque t, the steering angle θ, the turning angle δ, and the motor rotation angle θe should be positive values, for example, the detected turning angle δ is negative. If the value is, the electronic control unit 67 determines that an abnormality has occurred in the operating state of the turning angle sensor 64.

  Thus, in step S12, the electronic control unit 67 causes an abnormality in any of the vehicle speed sensor 61, the steering torque sensor 62, the steering angle sensor 63, the turning angle sensor 64, and the EPS motor rotation angle sensor 65. If it is, “No” is determined, and the process proceeds to step S13. On the other hand, if no abnormality has occurred in any of the sensors 61 to 65, the electronic control unit 67 determines “Yes”, proceeds to step S23, and temporarily ends the execution of the reduction ratio changing program. That is, when each of the sensors 61 to 65 operates normally, the electric motor 242 of the EPS unit 24 can be driven to apply an appropriate assist torque Ta. Therefore, the electronic control unit 67 maintains the operation state of the electric power steering device in the normal state and does not operate the electric telescopic operation unit 23 described later.

  Here, in the normal state, as described above, the axial displacement range of the upper tube 221 of the column tube 22 is restricted within the telescopic stroke range. As a result, the state in which the straight gear 211a of the upper shaft 211 and the straight gear 212a of the lower shaft 212 are engaged with each other with the same number of teeth Ns is maintained. For this reason, in a normal state, when the reduction ratio as the ratio of the rotation speed (output side) of the lower shaft 212 to the rotation speed (input side) of the upper shaft 211 is α, the reduction ratio α is “1”. Maintained in a state.

  That is, in the normal state, the rotation of the lower shaft 212 is not increased or decreased with respect to the rotation of the upper shaft 211. Therefore, when the upper shaft 211 and the lower shaft 212 rotate integrally, the driver can steer the left and right front wheels FW1, FW2 with a small amount of rotation (rotation angle) of the steering handle 1. In this case, the steering torque t input by the driver to the upper shaft 211 via the steering handle 1 is transmitted from the straight gear 211a to the lower shaft 212 via the straight gear 212a.

  In step S13, the electronic control unit 67 stops the driving of the electric motor 242 of the EPS unit 24, and shifts the operating state of the electric power steering device from the normal state to the assist stop state. That is, the electronic control unit 67 controls the drive circuit 69 to cut off the power supply to the electric motor 242. As a result, the application of the assist torque Ta due to the drive of the electric motor 242 is eliminated, and the operating state of the electric power steering device shifts to the assist stop state. And if the electronic control unit 67 stops the drive of the electric motor 242, it will progress to step S14. In the state where the electric power supply to the electric motor 242 is cut off as described above, the electric motor 242 rotates freely with the rotation of the steering main shaft 21, that is, the turning operation of the steering handle 1 by the driver (so-called It will come around.

  In step S14, the electronic control unit 67 notifies the driver of the shift to the assist stop state using the display unit 71 and the audio output unit 72 of the alarm device 7. That is, the electronic control unit 67 operates the display unit 71 to turn on a warning lamp or display a message indicating that the assist stop state has been entered in the display panel, for example. Further, the electronic control unit 67 operates the audio output unit 72 to output, for example, an alarm sound from the speaker, or to output a message indicating that the assist stop state is entered from the speaker. Furthermore, after notifying the shift to the assist stop state, the electronic control unit 67 notifies the driver to stop the vehicle safely. When the electronic control unit 67 prompts a safe stop of the vehicle, the electronic control unit 67 proceeds to step S15.

  In step S15, the electronic control unit 67 determines whether or not the vehicle speed V is equal to or lower than a predetermined vehicle speed at which the traveling behavior of the vehicle is stabilized, for example, the vehicle speed V is substantially “0”. That is, if the driver stops the vehicle according to the notification in step S14 and the vehicle speed V detected by the vehicle speed sensor 61 is approximately “0”, the electronic control unit 67 determines “Yes” and proceeds to step S16. move on. On the other hand, if the detected vehicle speed V is not substantially “0”, the electronic control unit 67 determines “No” and repeats the determination process in step S15 until the detected vehicle speed V becomes approximately “0”. repeat.

  In step S16, the electronic control unit 67 drives the electric motor 231 of the electric telescopic operation unit 23 to rotate forward so that the upper tube 221 (the upper shaft 211 and the steering handle 1) is located at the rearmost side of the telescopic stroke range. (Hereafter, this displacement position is displaced toward the vehicle rear side telescopic stroke end). That is, the electronic control unit 67 supplies power from the drive circuit 68 to the electric motor 231. As a result, the nut 233 screwed to the screw 232 is relatively displaced in the axial direction, and the upper tube 221 starts to be displaced toward the vehicle rear side telescopic stroke end together with the upper shaft 211. Then, when the electronic control unit 67 drives the electric motor 231 to rotate forward via the drive circuit 68, the electronic control unit 67 proceeds to step S17.

  In step S17, the electronic control unit 67 is displaced until the distance L between the sun gear 211a and the planetary gear 212b shown in FIG. 5 is less than a predetermined distance Lo as the upper shaft 211 is displaced. It is determined whether or not. This will be specifically described below.

  As described above, the electronic control unit 67 inputs the motor rotation angle θt of the electric motor 231 from the telescopic motor rotation angle sensor 66, so that the nut 233, that is, the upper tube 221 and the upper shaft are referenced with respect to the vehicle front side telescopic stroke end. The telescopic stroke amount 211 can be grasped. As a result, the electronic control unit 67 forms a vehicle front side formation end portion of the straight gear 212a of the lower shaft 212 corresponding to the vehicle front side telescopic stroke end and a vehicle rear side formation of the sun gear 211a formed on the upper shaft 211. The distance Ls between the ends can also be grasped. On the other hand, as shown in FIG. 5, the front telescopic stroke end of the vehicle, in other words, between the formation end of the straight gear 212a of the lower shaft 212 on the vehicle front side and the formation end of the planetary gear 212b on the vehicle front side. The distance La is a predetermined value set in advance. For this reason, the electronic control unit 67 can calculate the distance L between the sun gear 211a and the planetary gear 212b according to (La−Ls).

  Based on this, the electronic control unit 67 inputs the motor rotation angle θt of the electric motor 231 from the telescopic motor rotation angle sensor 66, and between the sun gear 211a and the planetary gear 212b based on the input motor rotation angle θt. The distance L is calculated. The electronic control unit 67 determines “No” if the distance L is equal to or greater than the predetermined distance Lo, and repeats steps S16 and S17 until the distance L becomes less than the predetermined distance Lo. On the other hand, if the distance L is less than the predetermined distance Lo, the electronic control unit 67 determines “Yes” and proceeds to step S18.

  In step S18, the electronic control unit 67 supplies power again to the electric motor 242 of the EPS unit 24 whose driving is stopped in step S13 via the drive circuit 69, and temporarily turns the electric motor 242 on. Drive forward and reverse by a minute amount. In other words, the electronic control unit 67 is in a state where the distance L between the sun gear 211a and the planetary gear 212b is less than the predetermined distance Lo, in other words, immediately before the sun gear 211a reaches a position where it engages with the planetary gear 212b. The 242 is driven forward and backward by a minute amount to adjust the tooth position where the straight tooth of the sun gear 211a and the straight tooth of the planetary gear 212b mesh with each other. Even in this case, the electronic control unit 67 continues to supply power to the electric motor 231 via the drive circuit 68, and it goes without saying that the sun gear 211a is displaced in the direction close to the planetary gear 212b. Nor. Then, the electronic control unit 67 proceeds to step S19.

  In step S19, the electronic control unit 67 determines whether or not the sun gear 211a and the planetary gear 212b are engaged with each other. Hereinafter, this determination will be specifically described.

  In this embodiment, the electronic control unit 67 determines whether or not the sun gear 211a and the planetary gear 212b are engaged with each other based on a change in drive current flowing through the electric motor 231 of the electric telescopic operation unit 23. That is, as shown in FIG. 6, when the straight teeth of the sun gear 211a and the straight teeth of the planetary gear 212b do not match, the teeth can mesh with each other, so that the sun gear 211a is connected to the planetary gear 212b. And can be displaced in the axial direction. Thereby, since the upper tube 221 and the nut 233 can also be displaced in the axial direction, the electric motor 242 is driven to rotate smoothly, and the drive current flowing through the motor 242 is constant.

  On the other hand, when the tooth positions of the direct teeth of the sun gear 211a and the planetary gear 212b coincide with each other, the teeth contact each other, so that the sun gear 211a cannot be displaced in the axial direction. For this reason, since the upper tube 221 and the nut 233 cannot be displaced in the axial direction, the rotational drive of the electric motor 242 is inhibited and the drive current flowing through the motor 242 increases.

  For this reason, the electronic control unit 67 inputs the motor rotation angle θt (corresponding to the number of rotations) of the electric motor 231 detected by the telescopic rotation angle sensor 66 and flows to the electric motor 231 detected by the current detector 68a. Input drive current. Then, based on the change characteristics shown in FIG. 6, the electronic control unit 67 determines “No” if the input drive current increases with respect to the change in the input motor rotation angle θt, and proceeds to step S20. . In step S20, the electronic control unit 67 drives the electric motor 231 in the reverse direction until the distance L between the sun gear 211a and the planetary gear 212b becomes a predetermined distance Lo. And the electronic control unit 67 performs step S18 and step S19.

  On the other hand, based on the change characteristic shown in FIG. 6, the electronic control unit 67 determines “Yes” if the input drive current is constant with respect to the input change in the motor rotation angle θt, and proceeds to step S21. In step S <b> 21, the electronic control unit 67 interrupts the power supply to the electric motor 242 via the drive circuit 69 and stops the forward rotation drive and the reverse rotation drive of the electric motor 242. In other words, in this case, the teeth of the sun gear 211a and the planetary gear 212b do not coincide with each other, and the sun gear 211a and the planetary gear 212b are properly meshed with each other. Therefore, the electronic control unit 67 keeps the rotational drive of the electric motor 242 of the EPS unit 24 stopped again. And if the electronic control unit 67 stops the rotational drive of the electric motor 242, it will progress to step S22.

  In step S22, the electronic control unit 67 normally rotates the electric motor 231 so that the upper tube 221 (upper shaft 211) is displaced to a position set in advance as a position where the sun gear 211a and the planetary gear 212b appropriately mesh with each other. Drive. Then, when the electronic control unit 67 displaces the upper tube 221 (upper shaft 211) to a preset position, in step S23, the execution of the reduction ratio changing program is terminated.

  Thus, in a state where the sun gear 211a and the planetary gear 212b are appropriately meshed beyond the telescopic stroke range, as shown in FIG. 7, the planetary gear mechanism including the sun gear 211a, the planetary gear 212b, and the ring gear 222a The rotation of the steering handle 1, that is, the rotation of the upper shaft 211 is decelerated and transmitted to the lower shaft 212. Therefore, the steering torque t input by the driver to the upper shaft 211 via the steering handle 1 is transmitted from the sun gear 211a to the lower shaft 212 via the planetary gear 212b, and thus is greatly reduced.

  Specifically, as described above, the lower tube 222 in which the ring gear 222a is integrally formed is fixed to the vehicle body so as not to rotate. Therefore, in the planetary gear mechanism, the ring gear 222a is a fixed gear that does not rotate. As a result, when the sun gear 211a rotates in accordance with the turning operation of the steering handle 1 by the driver, the planetary gear 212b rotates and revolves, and the lower shaft 212 as the planet carrier rotates about the axis in the same direction as the upper shaft 211. Rotate to. Therefore, in this case, the sun gear 211a serves as an input gear, and the planetary gear 212b that rotates and revolves by meshing with the ring gear 222a serves as an output gear.

For this reason, the reduction ratio α can be expressed as shown in the following formula 1, using the number of teeth Ns of the sun gear 211a and the number of teeth Nr of the ring gear 222a.
α = (Ns + Nr) / Ns Equation 1
According to Equation 1, the reduction ratio α is greater than “1”. In other words, the rotational speed of the upper shaft 211 is reduced and transmitted to the lower shaft 212. Therefore, in the state where the sun gear 211a and the planetary gear 212b are engaged with each other, the steering torque t required for turning the left and right front wheels FW1, FW2 can be reduced. Therefore, even in the assist stop state, the driver can steer the left and right front wheels FW1, FW2 relatively easily.

  As can be understood from the above description, according to the present embodiment, in the normal state where the EPS unit 24 applies the assist torque Ta (auxiliary force), the straight gear 211a and the lower shaft 212 formed on the upper shaft 211. In this state, the reduction gear ratio α becomes “1”, that is, the upper shaft 211 and the lower shaft 212 are directly connected. Accordingly, the driver can steer the left and right front wheels FW1 and FW2 by the steering torque t input via the steering handle 1 and the assist torque Ta applied by the EPS unit 24.

  On the other hand, in the assist stop state where the EPS unit 24 does not apply the assist torque Ta (assist force application stop state), the electric motor 231 of the electric telescopic operation unit 23 is driven to move the upper shaft 211 and the lower shaft 212 in the axial direction. By relatively displacing beyond the telescopic stroke range, the straight gear 211a (sun gear 211a) formed on the upper shaft 211 and the planetary gear 212b assembled to the lower shaft 212 are engaged with each other, so that the reduction ratio α is “1”. Can be in a larger state.

  At this time, when the electronic control unit 67 meshes the sun gear 211a and the planetary gear 212b, the electric motor 242 of the EPS unit 24 is temporarily driven to move the sun gear 211a and the planetary gear 212b to the sun gear 211a. By rotating the planetary gear 212b by a relatively small amount, it is possible to adjust the positions of the teeth meshing with each other. Further, the electronic control unit 67 determines whether or not the sun gear 211a and the planetary gear b are in mesh with each other based on the change in the drive current with respect to the motor rotation angle θt of the electric motor 231 constituting the electric telescopic operation unit 23. Can be determined. Further, when it is determined that the sun gear 211a and the planetary gear 212b are not meshed with each other, the electronic control unit 67 continuously operates the electric motor 242 by a minute amount to adjust the tooth position where the input gear and the second gear mesh with each other. can do.

  Thereby, the sun gear 211a and the planetary gear 212b can be reliably meshed, and the rotational speed of the lower shaft 212 can be reduced with respect to the rotational speed of the upper shaft 211. As a result, the steering torque t required to steer the left and right front wheels FW1, FW2 can be reduced. Accordingly, even in the assist stop state, the driver can easily steer the left and right front wheels FW1, FW2 with only the steering torque t input via the steering handle 1, and ensure good operability. Can do.

  In addition, since the straight gear 212a of the lower shaft 212 can be formed to a predetermined length, so-called telescopic operation in which the distance between the driver and the steering handle 1 is appropriately adjusted in a normal state is also possible. It becomes. In addition, by adopting the planetary gear 212b that can change the reduction ratio α to a large value, the structure can be simplified and the size can be greatly reduced. Furthermore, the number of teeth (Nr−Ns) between the ring gear 222a and the sun gear 211a meshing with the planetary gear 212b, in other words, by appropriately setting the inner diameter dimension of the ring gear 222a and the outer diameter dimension of the sun gear 211a, is extremely easy. It is possible to set a reduction ratio α larger than “1”. Therefore, the steering torque t input by the driver can be appropriately reduced in the assist stop state.

  In the above embodiment, in step S19, whether or not the sun gear 211a and the planetary gear 212b are engaged with each other based on the change of the drive current with respect to the motor rotation angle θt of the electric motor 231 of the electric telescopic operation unit 23 in the electronic control unit 67. It carried out to judge. On the other hand, based on the driving amount of the electric motor 231, that is, the time change of the distance L between the sun gear 211a and the planetary gear 212b, it is determined whether or not the sun gear 211a and the planetary gear 212b are engaged. It is also possible. 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 modification, the electronic control unit 67 executes the reduction ratio changing program shown in FIG. 4 as in the above embodiment. However, in the first modification, the processing content in step S19 is slightly different. That is, the electronic control unit 67 inputs the motor rotation angle θt from the telescopic motor rotation angle sensor 66 provided in the electric motor 231 of the electric telescopic operation unit 23, and calculates the distance L between the sun gear 211a and the planetary gear 212b. To do.

  Here, when the tooth positions of the direct teeth of the sun gear 211a and the planetary gear 212b do not match, as described above, the teeth can mesh with each other. It decreases uniformly with. On the other hand, when the tooth position of the direct tooth of the sun gear 211a and the direct tooth of the planetary gear 212b match, the teeth come into contact with each other, so that the distance L is constant over time as shown in FIG. It does not change as a value.

  Based on this, the electronic control unit 67 determines “Yes” in step S19 if the calculated distance L decreases uniformly with the passage of time, and after step S21 as in the above-described embodiment. Each step process is executed. On the other hand, if the calculated distance L does not change with the passage of time, “No” is determined in step S19, and step S20 is executed as in the above-described embodiment. And each process from step S18 to step S20 is repeatedly performed until the calculated distance L decreases uniformly with the passage of time.

  Therefore, also in this first modified example, the same effect as in the above embodiment can be expected.

  In the above embodiment and the first modification, the sun gear 211a and the planetary gear 212b are changed in step S19 in the reduction ratio changing program shown in FIG. 4 based on the operating state of the electric motor 231 of the electric telescopic operating unit 23. It carried out so that it might be judged whether it was meshing. On the other hand, based on the operating state of the electric motor 242 of the EPS unit 24 that is temporarily operated in step S18, the electronic control unit 67 determines whether or not the sun gear 211a and the planetary gear 212b are engaged in step S19. It is also possible to carry out such a determination. Hereinafter, although this 2nd modification is demonstrated in detail, the same code | symbol is attached | subjected to the same part as the said embodiment and 1st modification, and the detailed description is abbreviate | omitted.

  Also in the second modification, the electronic control unit 67 executes the reduction ratio changing program shown in FIG. 4 as in the above embodiment. However, in the second modification, the processing contents in step S19 are slightly different. That is, the electronic control unit 67 inputs the motor rotation angle θe from the EPS motor rotation angle sensor 65 provided in the electric motor 242 of the EPS unit 24 that performs forward rotation and reverse rotation by a minute amount in the step S18.

  Here, when the tooth positions of the direct teeth of the sun gear 211a and the planetary gear 212b do not match, the teeth can mesh with each other as described above. For this reason, when the electric motor 242 is driven forward and backward, as shown in FIG. 9, the time change of the motor rotation angle θe changes similarly before and after the sun gear 211a and the planetary gear 212b are engaged. On the other hand, when the tooth positions of the direct teeth of the sun gear 211a and the planetary gear 212b coincide, the teeth come into contact with each other, so that the smooth forward drive and reverse drive of the electric motor 242 are inhibited, As shown by a thick line in FIG. 9, the time change of the motor rotation angle θe is greatly different before and after the sun gear 211a and the planetary gear 212b are engaged.

  Based on this, the electronic control unit 67 determines “Yes” in step S19 if the time change state of the input motor rotation angle θe has not changed before and after the sun gear 211a and the planetary gear 212b mesh with each other. As in the embodiment described above, each step processing after step S21 is executed. On the other hand, if the time change state of the input motor rotation angle θe is changed before and after the sun gear 211a and the planetary gear 212b are engaged, it is determined as “No” in step S19, and similarly to the above-described embodiment, step S20 is performed. Execute. And each process from step S18 to step S20 is repeatedly performed until the calculated distance L decreases uniformly with the passage of time.

  Thus, also in this second modification, the same effect as in the above embodiment can be expected.

  In the second modification, the engagement between the sun gear 211a and the planetary gear 212b is determined based on the time change state of the motor rotation angle θe of the electric motor 242 of the EPS unit 24. Incidentally, in a situation where the time change state of the motor rotation angle θe changes, the drive current flowing through the electric motor 242 also changes. For this reason, for example, the electronic control unit 67 determines that the sun gear 211a and the planetary gear 212b are engaged based on a change in the drive current of the electric motor 242 detected by the current detector 69a of the drive circuit 69. Is also possible.

  In this case, when the sun gear 211a and the planetary gear 212b are engaged with each other, the electric motor 242 can smoothly perform forward rotation and reverse rotation, so that the absolute value of the drive current flowing through the motor 241 is constant. . On the other hand, in a state where the sun gear 211a and the planetary gear 212b do not mesh with each other, the electric motor 242 cannot smoothly perform forward rotation and reverse rotation, and thus the absolute value of the drive current flowing through the motor 241 increases.

  Therefore, in step S19, the electronic control unit 67 can determine whether the sun gear 211a and the planetary gear 212b are engaged based on the drive current from the current detector 69a. The same effect as the embodiment can be expected.

  In carrying out the present invention, the present invention is not limited to the above embodiment and the first and second modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment and each modification, by pulling the upper shaft 211 toward the passenger compartment side with respect to the lower shaft 212, in other words, by extending the steering main shaft 21, the straight gear 211a (sun gear 211a ) Is switched from a state of meshing with the direct gear 212a to a state of meshing with the planetary gear 212b. That is, in each of the above embodiments, the straight gear 212a is formed from the substantially inner center of the hollow lower tube 212 toward the upper end, and the planetary gear 212b is assembled in the vicinity of the upper end portion of the lower tube 212.

  On the other hand, for example, as shown in FIG. 10, the arrangement of the straight gear 212a and the planetary gear 212b on the lower shaft 212 is reversed, and more specifically, the planetary gear 212b is arranged at the center of the inner surface of the lower tube 212. It is also possible to assemble and form a straight gear 212a near the upper end of the lower tube 212. In this case, it goes without saying that the ring gear 222a formed integrally with the lower tube 222 is arranged in accordance with the arrangement change of the planetary gear 212b.

  By arranging the straight tooth 212a and the planetary gear 212b in this way, the straight tooth gear 211a (sun gear 211a) is moved by pushing the steering handle 1 from the passenger compartment side, in other words, by contracting the steering main shaft 21. The state of meshing with the direct gear 212a can be switched to the state of meshing with the planetary gear 212b.

  In the above embodiment and each modification, the electronic control unit 67 determines in step S15 whether or not the vehicle speed V of the vehicle is substantially “0”, that is, a predetermined vehicle speed or less. The motor 231 was rotationally driven to start the displacement of the upper tube 221 and the upper shaft 211. In this case, it is also possible to determine whether the running behavior of the vehicle is stable, for example, whether the vehicle is in a straight traveling state, and start the displacement of the upper tube 221 and the upper shaft 211.

  In this case, the electronic control unit 67 determines whether or not the steering angle θ detected by the steering angle sensor 63 is substantially “0”, for example, instead of the vehicle speed determination process in step S15. Good. Also by this, the direct gear 211a (sun gear 211a) and the planetary gear 212b can be meshed with each other in a state where the relative movement in the rotational direction of the upper shaft 211 and the lower shaft 212 is small. α can be increased.

  In the above embodiment and each modification, the electric motor 242 of the EPS unit 24 is driven forward and backward by a minute amount in step S18, and whether the sun gear 211a and the planetary gear 212b are engaged in step S19. It was carried out to determine whether or not. However, for example, after it is determined in step S19 that the sun gear 211a and the planetary gear 212b are not engaged with each other, the electric motor 242 of the EPS unit 24 is driven forward and reverse by a minute amount so that the sun gear 211a and the planetary gear 212b The tooth position may be adjusted.

  Moreover, in the said embodiment and each modification, although implemented using the rack and pinion type for the steering gear 5, you may implement using a ball screw mechanism, for example.

  Furthermore, in the said embodiment, it implemented by employ | adopting the electric power steering apparatus provided with the EPS unit 24 which provides the assist torque Ta for reducing a driver | operator's steering torque t. However, if the assist torque Ta for reducing the steering torque t of the driver can be applied, the present invention is applied to, for example, a power steering apparatus including a hydraulic system instead of the EPS unit 24. Can also be implemented. In the case of using a hydraulic system, it is preferable that the upper shaft 211 and the lower shaft 212 are rotated in the forward and reverse directions by a minute amount relative to each other by switching the hydraulic path for applying the assist torque Ta. Therefore, even in this case, in the assist stop state where the assist torque Ta is not applied, the straight gear 211a (sun gear 211a) is surely switched from the state of meshing with the direct gear 212a to the state of meshing with the planetary gear 212b. It is possible to expect the same effect as the above embodiment.

1 is a schematic view showing an entire vehicle steering apparatus according to an embodiment of the present invention. It is the schematic for demonstrating the structure of the steering column of FIG. FIG. 2 is a schematic cross-sectional view for explaining a configuration of a steering main shaft and a column tube in FIG. 1. It is a flowchart which shows the reduction ratio change program performed by the electronic control unit of FIG. It is sectional drawing for demonstrating determination of the meshing state of a sun gear and a planetary gear. It is a graph which shows the relationship between a motor rotation angle (rotation speed) and a drive current. It is sectional drawing which shows the meshing state of the sun gear and planetary gear in an assist stop state. It is the graph which showed the time change of the distance between a sun gear and a planetary gear roughly concerning the 1st modification of this invention. It is a graph which shows the time change of the motor rotation angle of the electric motor of an EPS unit roughly concerning the 2nd modification of this invention. FIG. 2 is a schematic cross-sectional view for explaining a change in configuration of a steering main shaft and a column tube in FIG. 1.

Explanation of symbols

FW1, FW2 ... front wheels, 1 ... steering handle, 2 ... steering column, 21 ... steering main shaft (transmission shaft), 211 ... upper shaft (first shaft), 211a ... straight gear (sun gear), 212 ... lower shaft ( (Second axis), 212a ... straight gear (first gear), 212b ... planetary gear (second gear), 22 ... column tube, 221 ... upper tube, 222 ... lower tube, 222a ... ring gear (fixed gear), 23 ... Electric telescopic operation unit (displacement means), 231 ... Electric motor, 24 ... EPS unit (auxiliary force applying means), 242 ... Electric motor

Claims (10)

A steering means operated by a driver, a transmission shaft for connecting the steering means and the steered wheels and transmitting a steering force input via the steering means to the steered wheels, and connected to the transmission shaft. In a vehicle steering apparatus comprising: an auxiliary force applying unit that applies a predetermined auxiliary force to the operation of the steering unit;
The transmission shaft includes a first shaft disposed on the steering means side, and a second shaft disposed on the steered wheel side with the first shaft slidably received in the axial direction. Has been
The rotation speed of the first shaft is obtained by meshing the straight-tooth input gear formed on the first shaft and the first gear formed on the second shaft in the normal state where the auxiliary force applying means applies the auxiliary force. A reduction ratio that represents a ratio of the rotation speed of the second shaft to the first shaft is set to “1”, and the first shaft and the second shaft are in a state in which the auxiliary force applying means does not apply the auxiliary force and the auxiliary force application is stopped. A reduction means for meshing the input gear and the second gear formed on the second shaft with a relative displacement in the axial direction between the two and changing the reduction ratio to a value larger than "1";
Displacement means having electric drive means for electrically driving, and relatively displacing the first shaft and the second shaft in the axial direction to mesh the input gear and the second gear. ,
Determination means for determining whether or not the input gear and the second gear are engaged with each other;
While the auxiliary force application is stopped, the auxiliary force applying means is temporarily operated to relatively rotate the input gear and the second gear, thereby adjusting a tooth position where the input gear and the second gear mesh with each other. And a vehicle steering apparatus. In the vehicle steering apparatus according to claim 1,
The determination means includes
A vehicle steering apparatus characterized by determining whether or not the input gear and the second gear are in mesh with each other based on a change in drive current when the electric drive means of the displacement means is driven. In the vehicle steering apparatus according to claim 1,
The determination means includes
A vehicle steering apparatus characterized by determining whether or not the input gear and the second gear are engaged with each other based on a change in driving amount when the electric driving means of the displacing means is driven. In the vehicle steering apparatus according to claim 1,
The auxiliary force applying means is electrically driven to apply the auxiliary force,
The determination means includes
It is determined whether or not the input gear and the second gear are in mesh with each other based on a change in driving current of the auxiliary force applying means that is temporarily operated by the adjusting means. Steering device. In the vehicle steering apparatus according to claim 1,
The auxiliary force applying means is electrically driven to apply the auxiliary force,
The determination means includes
It is determined whether or not the input gear and the second gear are engaged with each other based on a change in driving amount of the auxiliary force applying means that is temporarily operated by the adjusting means. Steering device. In the vehicle steering apparatus according to claim 1,
The adjusting means includes
When the determination means determines that the input gear and the second gear are not meshed with each other, the auxiliary force applying means is temporarily operated to relatively rotate the input gear and the second gear. And adjusting a tooth position where the input gear and the second gear mesh with each other. In the vehicle steering apparatus according to claim 1,
The displacement means is
A vehicle steering apparatus characterized in that the first shaft and the second shaft are relatively displaced in the axial direction when the traveling behavior of the vehicle is stable. The vehicle steering apparatus according to claim 7, wherein
The displacement means is
A vehicle steering apparatus characterized in that the first shaft and the second shaft are relatively displaced in the axial direction when the vehicle is less than a predetermined vehicle speed or when the vehicle is traveling straight. . In the vehicle steering apparatus according to claim 1,
The first gear is a straight tooth gear formed in a predetermined length parallel to the axial direction of the second shaft,
The second gear meshes with a straight-tooth ring gear fixed to the vehicle body side, and is assembled at a position away from the first gear by a predetermined distance, and around the input gear in a state of meshing with the input gear. A vehicle steering apparatus comprising a plurality of straight-toothed planetary gears that rotate and revolve.   2. The vehicle steering apparatus according to claim 1, wherein the first shaft and the second shaft form a steering main shaft provided in a steering column.

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