Steering column device

Abstract

A steering column device (1) comprises: a lower tube (22) which is attached to a vehicle body so as to be swingable in the vertical direction; a column shaft (2) to which a steering wheel (7) has been attached; an upper tube (21) which supports the column shaft (2) in a rotatable manner and which is attached to the lower tube (22) so as to be movable in the front-rear direction; a motor (41) which generates motor torque; a link mechanism (50) via which the lower tube (22) and the upper tube (21) are interlockably connected; and a power transmission mechanism (42) which operates so as to transmit the motor torque to the link mechanism (50). When the motor torque is transmitted to the link mechanism (50) by the power transmission mechanism (42), the link mechanism (50) operates so as to interlock the swinging of the lower tube (22) in the vertical direction and the movement of the upper tube (21) in the front-rear direction.

Description

[Technical field]

[0001] The present disclosure relates to a steering column apparatus. [Background technology]

[0002] For example, a vehicle is equipped with a steering column device described in Patent Document 1. The steering column device described in Patent Document 1 includes an outer column, an inner column, an electric tilt mechanism, and an electric telescopic mechanism. The outer column is attached to a vehicle body mounting bracket so as to be able to swing freely in the vertical direction of the vehicle. The inner column rotatably supports a steering shaft to which a steering wheel is attached. The inner column is attached to the outer column so as to be able to move freely in the longitudinal direction of the vehicle.

[0003] The electric tilt mechanism includes a tilt drive motor, a ball screw mechanism, and a link mechanism. The tilt drive motor operates the ball screw mechanism via a reduction mechanism unit integrated with the tilt drive motor. The ball screw mechanism operates to move the female screw member in the front-to-rear direction of the vehicle along the axis of the male screw shaft member as the male screw shaft member rotates. The link mechanism operates to swing the outer column in the vertical direction of the vehicle as the ball screw mechanism operates. This adjusts the position of the steering shaft in the vertical direction of the vehicle.

[0004] The electric telescopic mechanism includes a telescopic drive motor and a ball screw mechanism. The telescopic drive motor operates the ball screw mechanism via a reduction mechanism unit integrated with the telescopic drive motor. The ball screw mechanism operates to move the female screw member in the fore-and-aft direction of the vehicle along the axis of the male screw shaft member by rotating the male screw shaft member. In this case, the ball screw mechanism operates to move the inner column in the fore-and-aft direction of the vehicle relative to the outer column. This adjusts the position of the steering shaft in the fore-and-aft direction of the vehicle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-172002 A Summary of the Invention [Problem to be solved by the invention]

[0006] The steering column device described in Patent Document 1 requires two drive motors and two ball screw mechanisms to adjust the position of the steering axis in the vertical and longitudinal directions of the vehicle. However, from the viewpoint of improving the ease of mounting the steering column device on the vehicle, it is desirable to simplify the configuration of the steering column device and reduce its size. [Means for solving the problem]

[0007] A steering column device according to one aspect of the present disclosure includes a lower tube configured to be attached to a vehicle body so as to be swingable in the vertical direction of the vehicle, a column shaft configured to be attached to a steering wheel of the vehicle, an upper tube rotatably supporting the column shaft and attached to the lower tube so as to be movable in the longitudinal direction of the vehicle, a motor that generates a motor torque that is a power for swinging the lower tube in the vertical direction and moving the upper tube in the longitudinal direction, a link mechanism that connects the lower tube and the upper tube so as to be freely interlocked, and a power transmission mechanism that operates to transmit the motor torque to the link mechanism. The link mechanism is configured to operate to interlock the vertical swing of the lower tube and the longitudinal movement of the upper tube when the motor torque is transmitted to the link mechanism by the power transmission mechanism. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of a steering column device according to a first embodiment. [Diagram 2] FIG. 2 is a front view of the steering column device of FIG. [Diagram 3] FIG. 2 is a side view of the steering column device of FIG. [Figure 4] 4 is a cross-sectional view showing the peripheral configuration of a column shaft included in the steering column device of FIG. 3. [Diagram 5] 5A to 5C are diagrams illustrating the operation of a link mechanism in the steering column device of FIG. [Figure 6] 6 is a diagram for explaining the path taken by the position of the steering wheel in relation to the operation of the link mechanism in FIG. 5; [Figure 7] FIG. 7 is a perspective view of a steering column device according to a second embodiment. [Figure 8] FIG. 8 is a front view of the steering column device of FIG. 7. [Figure 9] FIG. 8 is a side view of the steering column device of FIG. 7. [Figure 10] 10 is a cross-sectional view showing the peripheral configuration of a column shaft included in the steering column device of FIG. 9. [Figure 11] 11A to 11C are diagrams illustrating the operation of a link mechanism in the steering column device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First Embodiment The first embodiment will be described below with reference to FIGS.

[0010] The steering column device 1 shown in Figs. 1 to 3 constitutes a part of an electric power steering device mounted on a vehicle, for example. The steering column device 1 is mounted on the vehicle. The steering column device 1 is mounted on the vehicle so that its axis extends in the front-rear direction of the vehicle. In Fig. 1, the left front side corresponds to the rear side of the vehicle, and the right rear side corresponds to the front side of the vehicle. In Fig. 2, the front side of the paper corresponds to the rear side of the vehicle, and the back side of the paper corresponds to the front side of the vehicle. In Fig. 3, the left side corresponds to the rear side of the vehicle, and the right side corresponds to the front side of the vehicle. In Figs. 1 to 3, the upper side corresponds to the upper side of the vehicle, and the lower side corresponds to the lower side of the vehicle. In the following description, the directions expressed by terms such as "front", "rear", "up", and "down" are defined based on the vehicle. The direction perpendicular to the "front-rear direction" and "up-down direction" of the vehicle means the "width direction" of the vehicle.

[0011] <Steering column device> As shown in Figs. 1 to 3, the steering column device 1 has a column shaft 2, a steering column 3, a steering actuator 4, and a position adjustment actuator 5. The column shaft 2 constitutes a part of a steering shaft 6. The steering column 3 rotatably supports the column shaft 2 therein. A first end on the rear side of the column shaft 2 is connected to a steering wheel 7 of the vehicle. A second end on the front side of the column shaft 2 is connected to an intermediate shaft (not shown). The intermediate shaft constitutes a power transmission path between the column shaft 2 and left and right steered wheels (not shown) of the vehicle. The column shaft 2, i.e., the steering shaft 6, rotates in conjunction with the rotation of the steering wheel 7. The rotation of the steering shaft 6 is converted into reciprocating motion in the axial direction of the rack shaft via a rack-and-pinion mechanism (not shown). The reciprocating motion of the rack shaft is transmitted to the left and right steered wheels, respectively, to change the steering angle of the steered wheels.

[0012] <About the column axis> As shown in FIG. 4, the column shaft 2 has an upper shaft 11 and a lower shaft 12. The upper shaft 11 and the lower shaft 12 are each made of a metal material. The upper shaft 11 is tubular in shape. The lower shaft 12 is cylindrical in shape. A first rear end of the upper shaft 11 is connected to the steering wheel 7. The lower shaft 12 is fitted into the inner periphery of a second front end of the upper shaft 11. As a result, the upper shaft 11 and the lower shaft 12 are connected to each other so as to be rotatable together and to be relatively movable in the front-rear direction, which is the axial direction.

[0013] <About the steering column> 1 to 3, the steering column 3 has an upper tube 21, a lower tube 22, and a housing 23. Metal materials are used as the materials for the upper tube 21, the lower tube 22, and the housing 23. The upper tube 21 and the lower tube 22 are each cylindrical in shape.

[0014] As shown in FIG. 4, the upper tube 21 and the lower tube 22 accommodate the upper shaft 11 and the lower shaft 12, i.e., the column shaft 2. The upper tube 21 rotatably supports the upper shaft 11, i.e., the column shaft 2, via a bearing 24. A first end of the upper shaft 11 protrudes from a first end on the rear side of the upper tube 21. A second end on the front side of the upper tube 21 is fitted into an inner periphery of the lower tube 22. As a result, the upper tube 21 is connected to the lower tube 22 so as to be relatively movable in the front-rear direction, which is the axial direction. The upper tube 21, i.e., the column shaft 2, is movable in the front-rear direction, which is a so-called telescopic direction. The position of the steering wheel 7 in the front-rear direction is adjusted by moving the upper tube 21 in the telescopic direction.

[0015] The upper tube 21 has a slit 21a. The slit 21a is provided in a lower portion of the upper tube 21. The slit 21a is an elongated through-hole extending in the front-rear direction, which is the axial direction of the upper tube 21. The lower tube 22 has a slit 22a. The slit 22a is provided in a lower portion of the lower tube 22. The slit 22a is an elongated through-hole extending in the front-rear direction, which is the axial direction of the lower tube 22. The slit 21a and the slit 22a are arranged to overlap in the radial direction.

[0016] Returning to the explanation of Figs. 1 to 3, the lower tube 22 has a second end on the front side opposite to the first end to which the upper tube 21 is fitted. The housing 23 is connected to the second end of the lower tube 22. The steering motor 25 is provided outside the housing 23. The reduction mechanism 26 is accommodated inside the housing 23. The reduction mechanism 26 reduces the speed of rotation of the steering motor 25 and transmits the reduced speed rotation to the lower shaft 12. In this embodiment, the reduction mechanism 26 is a worm reducer having a worm connected to the rotation shaft of the steering motor 25 so as to be rotatable together with the rotation shaft, and a worm wheel. The steering motor 25 and the reduction mechanism 26 constitute a part of the steering actuator 4. It can be said that the steering actuator 4 is accommodated in the housing 23 and constitutes a part of the steering column 3.

[0017] The steering column 3 has a column bracket 27 and a lower bracket 28. The column bracket 27 is fixed to a fixed part BD1 of the vehicle body by, for example, a bolt and a nut screwed onto the bolt. The lower tube 22 is fixed to the fixed part BD1 of the vehicle body via the column bracket 27. The lower bracket 28 is fixed to a fixed part BD2 of the vehicle body by, for example, a bolt and a nut screwed onto the bolt. The housing 23 is fixed to the fixed part BD2 of the vehicle body via the lower bracket 28.

[0018] The column bracket 27 has one or more bracket base portions 27a, a base connecting portion 27b, and one or more bracket plate portions 27c. The bracket base portion 27a is shaped like a flat plate. The bracket base portion 27a has a flat surface facing the fixed portion BD1 of the vehicle body. In this embodiment, the two bracket base portions 27a are disposed on both sides of the lower tube 22 in the width direction. The base connecting portion 27b is shaped like a long plate. The base connecting portion 27b extends in the width direction above the lower tube 22. The base connecting portion 27b connects the front ends of the two bracket base portions 27a to each other. The bracket plate portion 27c is shaped like a flat plate. The bracket plate portion 27c has a flat surface facing the lower tube 22 in the width direction. In this embodiment, one bracket plate portion 27c is provided for each of the two bracket base portions 27a. The two bracket plate portions 27c extend downward from opposite edges of the two bracket base portions 27a in the width direction.

[0019] The lower tube 22 is attached to the column bracket 27 via one or more support plate portions 22b. The support plate portion 22b is integrated with the lower tube 22 by, for example, welding or the like. The support plate portion 22b is provided at a first end on the rear side of the lower tube 22. The support plate portion 22b is shaped like a flat plate. The support plate portion 22b has a flat surface facing the lower tube 22 in the width direction. In this embodiment, the two support plate portions 22b are disposed on both sides of the lower tube 22 in the width direction. The flat surface of the support plate portion 22b opposite the lower tube 22 faces the flat surface of the bracket plate portion 27c. The two support plate portions 22b are connected to each other above the lower tube 22 by the support plate connecting portion 22c. The support plate connecting portion 22c has a tube pressing portion 31. The tube pressing portion 31 presses the upper tube 21 against the lower tube 22 by using, for example, a biasing force of a spring or the like. The tube pressing portion 31 prevents the upper tube 21 from rattling when the upper tube 21 moves in the front-rear direction relative to the lower tube 22.

[0020] The support plate portion 22b is connected to the corresponding bracket plate portion 27c by a link mechanism 50. The support plate portion 22b is connected to the corresponding bracket plate portion 27c so as to be able to swing freely in the up and down direction.

[0021] A first portion on the front side of the housing 23 has a tilt support shaft 29 extending in the width direction. The housing 23 is attached to a lower bracket 28 by the tilt support shaft 29. A first end of the lower tube 22, on which the support plate portion 22b is provided, is attached to the column bracket 27 so as to be able to swing up and down about the tilt support shaft 29 as a rotation center. The lower tube 22, i.e., the column shaft 2, is able to swing up and down, that is, in the so-called tilt direction. By swinging the lower tube 22 in the tilt direction, the height position of the steering wheel 7 in the up and down direction can be adjusted.

[0022] <About the position adjustment actuator> As shown in Figs. 1 to 3, the position adjustment actuator 5 has a position adjustment motor 41, a feed screw mechanism 42, and a speed reduction mechanism 43. The position adjustment motor 41 is provided outside the housing 23. The feed screw mechanism 42 has a screw shaft 44 and a feed nut 45. The feed screw mechanism 42 may be, for example, a ball screw mechanism. The screw shaft 44 is disposed below the lower tube 22. In this embodiment, the feed screw mechanism 42 is an example of a power transmission mechanism.

[0023] The threaded shaft 44 extends further rearward from a second portion, which is a rear portion of the housing 23. A thread groove 44a is formed on the outer periphery of the threaded shaft 44. The thread groove 44a extends within a range in which the slit 22a of the lower tube 22 extends in the axial direction.

[0024] The shape of the feed nut 45 is a rectangular parallelepiped. The feed nut 45 is disposed around the screw shaft 44. A thread groove 45a corresponding to the thread groove 44a of the screw shaft 44 is formed on the inner peripheral portion of the feed nut 45. The screw shaft 44 and the feed nut 45 are screwed together via the thread grooves 44a, 45a.

[0025] As shown in FIG. 4, the feed nut 45 is connected to a lower portion of the upper tube 21 via a nut connecting portion 46. The nut connecting portion 46 is fixed to the feed nut 45. The nut connecting portion 46 is inserted into the upper tube 21 via a slit 21a of the upper tube 21 and a slit 22a of the lower tube 22. The nut connecting portion 46 is fixed to an outer portion of the slit 21a in the width direction while being inserted into the upper tube 21. The nut connecting portion 46 is fixed to the upper tube 21 by a fastening member 47 such as a rivet. The feed nut 45 moves in the axial direction of the screw shaft 44 in conjunction with the rotation of the screw shaft 44. The feed nut 45 moves together with the upper tube 21 in the front-rear direction, which is the axial direction of the screw shaft 44.

[0026] When an external impact force acting on the steering column device 1 exceeds a predetermined separation load, the fastening between the nut connecting part 46 and the upper tube 21 via the fastening member 47 is released. The nut connecting part 46 inserted into the slit 21a of the upper tube 21 does not hinder the movement of the upper tube 21. This allows the upper tube 21 to move freely rearward relative to the lower tube 22.

[0027] The speed reducing mechanism 43 reduces the speed of rotation of the position adjustment motor 41 and transmits the reduced rotation to the screw shaft 44. In this embodiment, the speed reducing mechanism 43 is a worm speed reducing mechanism having a worm 43a connected to the rotating shaft 41a of the position adjustment motor 41 so as to be rotatable together with it, and a worm wheel 43b. The worm wheel 43b is fitted to the screw shaft 44. The worm wheel 43b is connected to the screw shaft 44 so as to be rotatable together with it. The speed reducing mechanism 43 can be changed as appropriate, for example, to a belt-type speed reducing mechanism having a belt that transmits the rotation of the position adjustment motor 41.

[0028] The motor torque of the position adjustment motor 41 is transmitted to the screw shaft 44 via the worm 43a and the worm wheel 43b, i.e., the reduction mechanism 43. The motor torque transmitted in this manner rotates the screw shaft 44. The motor torque of the position adjustment motor 41 is converted into power that rotates the screw shaft 44 and moves the feed nut 45 together with the upper tube 21 in the front-rear direction, i.e., the telescopic direction.

[0029] <About the link mechanism> 1 to 3, the link mechanism 50 has a nut link member 51 and one or more bracket link plates 52. The nut link member 51 interconnects the feed nut 45 and the bracket link plate 52. The bracket link plate 52 interconnects the nut link member 51, the lower tube 22, and the column bracket 27.

[0030] The nut link member 51 has one or more nut link plate portions 51a and a nut link connecting portion 51b. The nut link plate portion 51a has a flat shape. The nut link plate portion 51a has a flat surface that faces the feed nut 45 in the width direction. In this embodiment, two nut link plate portions 51a are arranged on both sides of the feed nut 45 in the width direction. The lower second ends of the two nut link plate portions 51a are connected to each other by the nut link connecting portion 51b. The nut link plate portion 51a has a nut link tip portion 51c that is a first end extending in a direction perpendicular to the second end. The nut link plate portion 51a is connected to the feed nut 45 by a fastening member 53 such as a rivet. The nut link plate portion 51a and the feed nut 45 are relatively rotatable around the fastening member 53 as a rotation center.

[0031] The bracket link plate 52 is shaped like a long plate. The bracket link plate 52 has a flat surface that faces both the lower tube 22 and the nut link plate portion 51a in the width direction. In this embodiment, two bracket link plates 52 are arranged on both sides of the lower tube 22 and the feed nut 45 in the width direction. Each bracket link plate 52 has a nut side end portion 52a that faces the corresponding nut link plate portion 51a in the width direction. The nut side end portion 52a is connected to the corresponding nut link tip portion 51c by a fastening member 54 such as a rivet. Each bracket link plate 52 and the corresponding nut link tip portion 51c are relatively rotatable around the fastening member 54.

[0032] Each bracket link plate 52 has a tube side end 52b facing the lower tube 22 in the width direction. The tube side end 52b has a covered portion 52c that is covered from the width direction by the column bracket 27, and an exposed portion 52d that is exposed from the width direction by the column bracket 27. Each covered portion 52c is connected to a corresponding bracket plate portion 27c by a fastening member 55 such as a rivet. Each bracket link plate 52 and the corresponding bracket plate portion 27c are relatively rotatable about the fastening member 55.

[0033] Each exposed portion 52d is connected to the corresponding support plate portion 22b by a fastening member 56 such as a rivet. Each bracket link plate 52 and the corresponding support plate portion 22b are relatively rotatable around the fastening member 56. Each exposed portion 52d has a guide hole 52e for moving the position of the center of relative rotation between the bracket link plate 52 and the support plate portion 22b. In this embodiment, the guide hole 52e is a through hole extending from the covering portion 52c to the exposed portion 52d.

[0034] The movement of the feed nut 45 is converted into the movement of the lower tube 22 relative to the column bracket 27 via the nut link member 51 and the bracket link plate 52. For example, when the feed nut 45 moves from the front to the rear, the bracket link plate 52 can rotate clockwise around the nut link tip portion 51c with the fastening member 54 as the rotation center in FIG. 3. At the same time, the bracket link plate 52 can rotate clockwise around the bracket plate portion 27c with the fastening member 55 as the rotation center in FIG. 3, and can rotate clockwise around the support plate portion 22b with the fastening member 56 as the rotation center in FIG. In other words, the motor torque of the position adjustment motor 41 is converted into a force that operates the nut link member 51 and the bracket link plate 52, thereby swinging the lower tube 22 up and down, i.e., in the tilt direction, relative to the column bracket 27.

[0035] <Operation of the link mechanism> The position adjustment motor 41 is connected to, for example, a motor control device 60. A position adjustment lever 70 is connected to the motor control device 60. The motor control device 60 controls the operation of the position adjustment motor 41 based on a lever operation, which is an operation by the driver on the position adjustment lever 70. The motor control device 60 controls the operation of the position adjustment motor 41 so as to generate a motor torque for rotating the screw shaft 44 in a first direction in response to a forward operation of the position adjustment lever 70. The first direction is a direction for moving the feed nut 45 forward, which is a direction approaching the housing 23. The motor control device 60 controls the operation of the position adjustment motor 41 so as to generate a motor torque for rotating the screw shaft 44 in a second direction opposite to the first direction in response to a rearward operation of the position adjustment lever 70. The second direction is a direction for moving the feed nut 45 backward, which is a direction away from the housing 23.

[0036] The state shown in FIG. 5A is a state in which the feed nut 45 is closest to the position adjustment motor 41, i.e., the housing 23. The nut link member 51 is in a state in which the nut link tip portion 51c is located at the lowest position. The bracket link plate 52 is in a state in which the nut side end portion 52a is located at the most forward position. In this case, the bracket link plate 52 is in a state in which the dimension in the vertical direction is the largest and the dimension in the front-rear direction is the smallest. The fastening member 54 and the fastening member 56 are in a state in which their positions in the front-rear direction are almost the same. The fastening member 56 is located above the fastening member 55. The upper tube 21 has moved to the most forward position, and the lower tube 22 has moved to the most upward position. The steering wheel 7 is in a state in which it is adjusted to the most forward position in the front-rear direction and to the most upper position in the vertical direction. In the following description, the state of the steering column 3 at this time is referred to as a first state.

[0037] In the first state, the position adjustment motor 41 rotates the screw shaft 44 by the motor torque generated by the rotation in the first direction. The feed nut 45 moves backward, which is a direction away from the housing 23, in conjunction with the rotation of the screw shaft 44. The nut link member 51 rotates so that the nut link tip portion 51c moves upward in conjunction with the movement of the feed nut 45. The bracket link plate 52 rotates so that the nut side end portion 52a moves backward in conjunction with the movement of the feed nut 45 and the rotation of the nut link member 51. In this case, the bracket link plate 52 is inclined so that the dimension in the up-down direction becomes smaller and the dimension in the front-rear direction becomes larger. The positions of the fastening member 54 and the fastening member 56 change in the front-rear direction. The fastening member 56 moves downward so as to approach the fastening member 55 in the up-down direction. As a result, the upper tube 21 moves rearward in conjunction with the movement of the feed nut 45, and the lower tube 22 moves downward in conjunction with the movement of the feed nut 45. The position of the steering wheel 7 is adjusted so that it moves rearward and downward. Thereafter, the position adjustment motor 41 maintains rotation in the first direction to rotate the threaded shaft 44, resulting in the feed nut 45 moving to approximately the center of the axial movable range of the threaded shaft 44. In the following description, the state of the steering column 3 at this time will be referred to as the intermediate state.

[0038] In the intermediate state, as shown in Fig. 5B, the position of the nut link tip 51c of the nut link member 51 is approximately aligned with the position of the screw shaft 44 in the vertical direction. The bracket link plate 52 is in a state in which the nut side end 52a is located rearward of the tube side end 52b. In this case, the position of the fastening member 56 is approximately aligned with the position of the fastening member 55 in the vertical direction. The upper tube 21 has moved to approximately the center of its movable range in the front-rear direction, and the lower tube 22 has moved to approximately the center of its movable range in the vertical direction. The steering wheel 7 is adjusted to approximately the center position in the front-rear direction and to approximately the center position in the vertical direction.

[0039] In the intermediate state, the position adjustment motor 41 further rotates the screw shaft 44 by the motor torque generated by the rotation in the first direction. The feed nut 45 moves further backward, that is, away from the housing 23, in conjunction with the rotation of the screw shaft 44. The nut link member 51 rotates so that the nut link tip portion 51c moves upward on the screw shaft 44 in conjunction with the movement of the feed nut 45. The bracket link plate 52 rotates so that the nut side end portion 52a moves further backward in conjunction with the movement of the feed nut 45 and the rotation of the nut link member 51. In this case, the bracket link plate 52 is tilted so that the dimension in the up-down direction becomes smaller and the dimension in the front-rear direction becomes larger. The positions of the fastening member 54 and the fastening member 56 are further deviated from each other in the front-rear direction. The fastening member 56 moves below the fastening member 55. As a result, the upper tube 21 moves further rearward in conjunction with the movement of the feed nut 45, and the lower tube 22 moves further downward in conjunction with the movement of the feed nut 45. The position of the steering wheel 7 is adjusted so that it moves further rearward and further downward. Thereafter, the position adjustment motor 41 maintains its rotation in the first direction to rotate the screw shaft 44, resulting in the feed nut 45 being furthest away from the housing 23. In the following description, the state of the steering column 3 at this time will be referred to as the second state.

[0040] In the second state, as shown in FIG. 5C, the nut link member 51 has the nut link tip 51c positioned at the uppermost position. The bracket link plate 52 has the nut side end 52a positioned at the rearmost position. In this state, the bracket link plate 52 has the smallest vertical dimension and the largest longitudinal dimension. The fastening member 54 and the fastening member 56 have the largest vertical positional deviation. The fastening member 56 is positioned below the fastening member 55. The upper tube 21 has moved to the rearmost position, and the lower tube 22 has moved to the lowermost position. The steering wheel 7 is adjusted to the frontmost position in the longitudinal direction and to the uppermost position in the vertical direction.

[0041] In the second state, the position adjustment motor 41 rotates the screw shaft 44 by the motor torque generated by the rotation in the second direction. The feed nut 45 moves forward in conjunction with the rotation of the screw shaft 44 to a position closest to the housing 23. The nut link member 51 rotates in conjunction with the movement of the feed nut 45 so that the nut link tip portion 51c moves to the lowest position. The bracket link plate 52 rotates in conjunction with the movement of the feed nut 45 and the rotation of the nut link member 51 so that the nut side end portion 52a moves to the most forward position. In this case, the bracket link plate 52 stands up so that the dimension in the vertical direction is the largest and the dimension in the front-rear direction is the smallest. The positions of the fastening member 54 and the fastening member 56 change in the front-rear direction. The fastening member 56 rises to approach the fastening member 55 in the vertical direction, and then moves above the fastening member 55. As a result, the upper tube 21 moves to the forwardmost position in conjunction with the movement of the feed nut 45, and the lower tube 22 moves to the uppermost position in conjunction with the movement of the feed nut 45. The steering wheel 7 is adjusted to the forwardmost position in the front-rear direction and to the uppermost position in the up-down direction. In other words, the state of the steering column 3 changes from the second state to the intermediate state and then to the first state.

[0042] According to this embodiment, the position adjustment motor 41 operates the link mechanism 50 via the feed screw mechanism 42. When the motor torque is transmitted to the link mechanism 50, the link mechanism 50 operates to link the swing of the lower tube 22 in the tilt direction with the movement of the upper tube 21 in the telescopic direction. This makes it possible to adjust the vertical position and the front-rear position of the steering wheel 7 at the same time.

[0043] In FIG. 6, the direction along the horizontal axis is the telescopic direction, and the direction along the vertical axis is the tilt direction. The position of the steering wheel 7 starts from position P1 corresponding to the first state in FIG. 5A, and ends at position P2 corresponding to the second state in FIG. 5C. In this case, the position of the steering wheel 7 moves in the tilt direction while moving in the telescopic direction from position P1 to position P2 along a first path defined in a two-dimensional plane. The position of the steering wheel 7 starts from position P2 corresponding to the second state in FIG. 5C, and ends at position P1 corresponding to the first state in FIG. 5A. In this case, the position of the steering wheel 7 moves in the tilt direction while moving in the telescopic direction from position P2 to position P1 along a second path defined in a two-dimensional plane. Both the first path and the second path pass through position P3 corresponding to the intermediate state in FIG. 5B. The first path and the second path are the same regardless of whether position P1 or position P2 is the start point or the end point.

[0044] In this way, the link mechanism 50 connects the upper tube 21 and the lower tube 22 so as to interlock them. When the position of the steering wheel 7 in either the up-down direction or the front-rear direction is determined, the other of the up-down direction and the front-rear direction is determined. In other words, the position of the steering wheel 7 is adjusted in such a way that the up-down position and the front-rear position are interlocked. For adjusting the position of the steering wheel 7, the position adjustment motor 41 and the feed screw mechanism 42 can be shared between the mechanism for adjusting the up-down position and the mechanism for adjusting the front-rear position.

[0045] <Advantages of the First Embodiment> (1-1) Regarding adjustment of the position of the steering wheel 7, the position adjustment motor 41 and the feed screw mechanism 42 can be shared between the mechanism for adjusting the vertical position and the mechanism for adjusting the front-rear position, so that the configuration of the steering column device 1 is simplified and the size is reduced. Therefore, the mountability of the steering column device 1 in a vehicle can be improved.

[0046] (1-2) Regarding adjustment of the position of the steering wheel 7, the reduction mechanism 43 can be shared between the mechanism for adjusting the vertical position and the mechanism for adjusting the front-rear position, in addition to the position adjustment motor 41 and the feed screw mechanism 42. This further simplifies the configuration of the steering column device 1 and further reduces the size of the device. This further improves the mountability of the steering column device 1 in a vehicle.

[0047] (1-3) The feed screw mechanism 42 requires a space extending in the front-rear direction for arranging the screw shaft 44 and for moving the feed nut 45. In this regard, in the present embodiment, by sharing the feed screw mechanism 42 between the mechanism for adjusting the vertical position and the mechanism for adjusting the front-rear position for adjusting the position of the steering wheel 7, the space required for the screw shaft 44 and the feed nut 45 is reduced by half compared to a case in which they are not shared. This is effective in improving the mountability of the steering column device 1 in a vehicle.

[0048] (1-4) The link mechanism 50 is not connected to the upper tube 21, and the feed nut 45 is connected to the upper tube 21 and the link mechanism 50. This allows the upper tube 21 to move smoothly in the front-rear direction in a configuration in which the upper tube 21 is fitted into the inner periphery of the lower tube 22. This is effective in smoothly linking the up-down swing of the lower tube 22 and the front-rear movement of the upper tube 21 in a configuration in which the upper tube 21 is fitted into the inner periphery of the lower tube 22.

[0049] (1-5) The motor control device 60 can be configured to control the operation of the position adjustment motor 41 so that the state of the steering column 3 becomes a first state, for example, when the driver gets off the vehicle. Also, the motor control device 60 can be configured to control the operation of the position adjustment motor 41 so that the state of the steering column 3 becomes a second state or an arbitrary state, for example, when the driver gets into the vehicle. The arbitrary state is a state between the first state and the second state, and is a state that the driver can set and store in advance.

[0050] In this case, when the driver gets off the vehicle, the steering wheel 7 can be adjusted to the first state. On the other hand, when the driver gets on the vehicle, the steering wheel 7 can be adjusted to any state. In this regard, if the vertical position and the front-rear position of the steering wheel 7 can be adjusted at once, the adjustment to the desired position can be completed quickly. Therefore, it is possible to improve the convenience for the driver when getting off or on the vehicle.

[0051] <Second embodiment> Next, a second embodiment will be described with reference to Figures 7 to 11. For ease of explanation, the same components as those in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

[0052] 7 to 9, the steering column 8 differs from the first embodiment in that, while the upper tube 21 in the first embodiment is fitted into the inner periphery of the lower tube 22, the lower tube 82 is fitted into the inner periphery of the upper tube 81. The configuration of the connection of the steering column 8 to the column bracket 87 is different from that of the first embodiment. The configuration of the link mechanism 100 is different from that of the first embodiment.

[0053] <About the steering column> 7 to 10, the steering column 8 has an upper tube 81, a lower tube 82, and a housing 83. The housing 83 is provided at a second end on the front side of the lower tube 82. A first end on the rear side of the lower tube 82 is fitted into the inner periphery of the upper tube 81.

[0054] The upper tube 81 is fixed to the fixed part BD1 of the vehicle body via a column bracket 87. The column bracket 87 has one or more bracket base parts 87a, a base connecting part 87b, and one or more bracket plate parts 87c. The bracket base part 87a is shaped like a flat plate. The bracket base part 87a has a flat surface facing the fixed part BD1 of the vehicle body. In this embodiment, two bracket base parts 87a are arranged on both sides in the width direction of the upper tube 81. The base connecting part 87b is shaped like a long plate. The base connecting part 87b extends in the width direction above the upper tube 81. The base connecting part 87b connects the two bracket base parts 87a to each other. The bracket plate part 87c is shaped like a flat plate. The bracket plate part 87c has a flat surface facing the upper tube 81 in the width direction. In this embodiment, one bracket plate part 87c is provided for each of the two bracket base parts 87a. The two bracket plate portions 87c extend downward from edges of the two bracket base portions 87a that face each other in the width direction.

[0055] The upper tube 81 is attached to the column bracket 87 via one or more support plate portions 81b. The support plate portions 81b are integrated with the upper tube 81 by, for example, welding or the like. The support plate portions 81b are shaped like a flat plate. The support plate portions 81b have a flat surface that faces the upper tube 81 in the width direction. In this embodiment, the two support plate portions 81b are disposed on both sides of the upper tube 81 in the width direction. The support plate portions 81b are connected to each other below the upper tube 81 by support plate connecting portions 81c.

[0056] The support plate portion 81b is connected to the corresponding bracket plate portion 87c by a link mechanism 100. The support plate portion 81b is connected to the corresponding bracket plate portion 87c so as to be able to swing freely in the up and down direction.

[0057] One or more link mounting portions 83a are provided in a second portion on the rear side of the housing 83. The link mounting portions 83a are columnar in shape. The link mounting portions 83a extend rearward from the second portion of the housing 83. In this embodiment, two link mounting portions 83a are disposed on both sides in the width direction of the lower tube 82. The link mounting portions 83a are connected to the corresponding bracket plate portions 87c by a link mechanism 100.

[0058] The lower tube 82 is attached to the column bracket 87 via the upper tube 81 and a link mechanism 100. A first portion of the lower tube 82 to which the upper tube 81 is provided is attached to the column bracket 87 so as to be freely swingable in the up and down direction around the tilt support shaft 29 as a rotation center.

[0059] <About the position adjustment actuator> 7 to 9, the position adjustment motor 91 of the position adjustment actuator 9 is provided outside the housing 83. A screw shaft 94 of the feed screw mechanism 92 is disposed on a first side, which is one side in the width direction of the upper tube 81 and the lower tube 82. In this embodiment, the first side is the same as the side on which the steering actuator 4 is provided. The screw shaft 94 extends further rearward from the second portion of the housing 83.

[0060] The feed nut 95 of the feed screw mechanism 92 has a cylindrical shape. The feed nut 95 is disposed around the screw shaft 94. The feed nut 95 is fixed to a support plate portion 81b provided on a first side of the upper tube 81. The feed nut 95 is integrated with the support plate portion 81b by, for example, welding. The feed nut 95 moves in the axial direction of the screw shaft 94 in conjunction with the rotation of the screw shaft 94. The feed nut 95 moves together with the upper tube 81 in the front-rear direction, which is the axial direction of the screw shaft 94.

[0061] When an external impact force acting on the steering column device 1 exceeds a predetermined separation load, the fixation of the support plate portion 81b to the upper tube 81 or the fixation of the feed nut 95 to the support plate portion 81b is released. This allows the upper tube 81 to freely move rearward relative to the lower tube 82.

[0062] <About the link mechanism> As shown in Figs. 7 to 9, the link mechanism 100 has one or more first link members 101, one or more second link members 102, and one or more third link members 103. The first link member 101 has a long plate shape. The first link member 101 has a flat surface that faces the support plate portion 81b in the width direction. In this embodiment, two first link members 101 are disposed on both sides of the upper tube 81 in the width direction.

[0063] A first end of each first link member 101 is connected to a corresponding support plate portion 81b. Each first link member 101 is connected to a corresponding support plate portion 81b by a fastening member 104 such as a rivet. The first link member 101 and the support plate portion 81b are relatively rotatable about the fastening member 104. A second end of each first link member 101 is connected to a corresponding third link member 103.

[0064] The second link member 102 has a long plate shape. The dimension of the long side of the second link member 102 is smaller than the dimension of the long side of the first link member 101. The second link member 102 has a flat surface that faces both the upper tube 81 and the column bracket 87 in the width direction. In this embodiment, two second link members 102 are disposed on both sides of the upper tube 81 in the width direction. A first end of each second link member 102 is connected to a corresponding bracket plate portion 87c.

[0065] Each second link member 102 is connected to the corresponding bracket plate portion 87c by a fastening member 105 such as a rivet. The second link member 102 and the bracket plate portion 87c are relatively rotatable about the fastening member 105. A second end of each second link member 102 is connected to a corresponding third link member 103.

[0066] The third link member 103 has a long plate shape. The dimension of the long side of the third link member 103 is greater than the dimension of the long side of the first link member 101. The third link member 103 has flat surfaces that face both the upper tube 81 and the lower tube 82 in the width direction. In this embodiment, two third link members 103 are disposed on both sides of the upper tube 81 and the lower tube 82 in the width direction.

[0067] A second end of each of the third link members 103 is connected to the corresponding link attachment portion 83a. Each of the third link members 103 is connected to the corresponding link attachment portion 83a by a fastening member 106 such as a rivet. The third link member 103 and the link attachment portion 83a are relatively rotatable around the fastening member 106 as a rotation center. A first end of each of the third link members 103 is connected to the second end of the corresponding first link member 101. Each of the third link members 103 is connected to the corresponding first link member 101 by a fastening member 107 such as a rivet. The third link member 103 and the first link member 101 are relatively rotatable around the fastening member 107 as a rotation center. An intermediate portion between the first end and the second end of each of the third link members 103 is connected to the second end of the corresponding second link member 102. The intermediate portion to which the second link member 102 is connected is a portion closer to the first end side than the center between the first end and the second end of the third link member 103. The intermediate portion of each third link member 103 is connected to the corresponding second link member 102 by a fastening member 108 such as a rivet. The third link member 103 and the second link member 102 are relatively rotatable about the fastening member 108 as the center of rotation.

[0068] The movement of the feed nut 95 is converted into the movement of the lower tube 82 relative to the column bracket 87 via the first link member 101, the second link member 102, and the third link member 103. For example, when the feed nut 95 moves from the front to the rear, the first link member 101 can rotate clockwise around the fastening member 104 as a rotation center relative to the support plate portion 81b in FIG. 9. At the same time, the third link member 103 can rotate counterclockwise around the first link member 101 as a rotation center at the fastening member 107, and can rotate counterclockwise around the link attachment portion 83a as a rotation center at the fastening member 106. At the same time, the second link member 102 can rotate clockwise around the third link member 103 as a rotation center at the fastening member 108, and can rotate clockwise around the bracket plate portion 87c as a rotation center at the fastening member 105 in FIG. 9. In other words, the motor torque of the position adjustment motor 91 operates the first link member 101, the second link member 102, and the third link member 103, and is thereby converted into power that swings the lower tube 82 up and down relative to the column bracket 87, i.e., in the tilt direction.

[0069] <Operation of the link mechanism> The first state shown in FIG. 11A is a state in which the feed nut 95 is closest to the position adjustment motor 91, i.e., the housing 83. The first link member 101 is in a state in which the first end to which the fastening member 104 is provided is located at the frontmost and uppermost position. The second link member 102 is in a state in which the second end to which the fastening member 108 is provided is located at the rearmost and lowermost position. The third link member 103 is in a state in which the first end to which the fastening member 107 is provided is located at the lowermost position. In this case, the entire link mechanism 100 is in a state in which the dimension in the front-rear direction is the smallest and the dimension in the up-down direction is the largest. The upper tube 81 has moved to the frontmost position, and the lower tube 82 has moved to the uppermost position. The steering wheel 7 is in a state in which it is adjusted to the frontmost position in the front-rear direction and to the uppermost position in the up-down direction.

[0070] In the first state, the position adjustment motor 91 rotates the screw shaft 94 by a motor torque generated by the rotation in the first direction. The feed nut 95 moves backward, which is a direction away from the housing 83, in conjunction with the rotation of the screw shaft 94. The upper tube 81 moves backward in conjunction with the movement of the feed nut 95. The first link member 101 rotates such that the first end moves backward and downward in conjunction with the movement of the upper tube 81. The third link member 103 rotates such that the first end moves upward in conjunction with the rotation of the first link member 101. The second link member 102 rotates such that the second end moves forward and upward in conjunction with the rotation of the third link member 103. In this case, the entire link mechanism 100 operates so that the dimension in the front-rear direction increases and the dimension in the up-down direction decreases. As a result, the upper tube 81 moves rearward in conjunction with the movement of the feed nut 95, and the lower tube 82 moves downward in conjunction with the movement of the feed nut 95. The position of the steering wheel 7 is adjusted so that it moves rearward and downward. Thereafter, the position adjustment motor 91 maintains rotation in the first direction to rotate the threaded shaft 94, and as a result, the steering column 3 reaches an intermediate state in which the feed nut 95 has moved to approximately the center of the axial movable range of the threaded shaft 94.

[0071] In the intermediate state, as shown in Fig. 11B, the first link member 101 rotates so that its first end moves rearward and downward, and as a result, the first link member 101 tilts approximately the same as the second link member 102. The third link member 103 is in a state in which the position of its first end approximately coincides with the position of the screw shaft 94 in the vertical direction. The upper tube 81 has moved to approximately the center of its movable range in the front-rear direction, and the lower tube 82 has moved to approximately the center of its movable range in the vertical direction. The steering wheel 7 is adjusted to approximately the center position in the front-rear direction and to approximately the center position in the vertical direction.

[0072] In the intermediate state, the position adjustment motor 91 further rotates the screw shaft 94 by the motor torque generated by the rotation in the first direction. The feed nut 95 moves further backward, in a direction away from the housing 83, in conjunction with the rotation of the screw shaft 94. The upper tube 81 moves further backward in conjunction with the movement of the feed nut 95. The first link member 101 rotates so that the first end moves further backward and downward in conjunction with the movement of the upper tube 81. The third link member 103 rotates so that the first end moves further upward in conjunction with the rotation of the first link member 101. The second link member 102 rotates so that the second end moves further forward and upward in conjunction with the rotation of the third link member 103. In this case, the entire link mechanism 100 operates so that the dimension in the front-rear direction becomes larger and the dimension in the up-down direction becomes smaller. As a result, the upper tube 81 moves further rearward in conjunction with the movement of the feed nut 95, and the lower tube 82 moves further downward in conjunction with the movement of the feed nut 95. The position of the steering wheel 7 is adjusted so that it moves further rearward and further downward. Thereafter, the position adjustment motor 91 maintains its rotation in the first direction to rotate the threaded shaft 94, and as a result, the steering column 3 reaches the second state in which the feed nut 95 is furthest from the housing 83.

[0073] In the second state, as shown in FIG. 11C, the first link member 101 has its first end positioned at the rearmost and lowest position. The second link member 102 has its second end positioned at the frontmost and highest position. The third link member 103 has its first end positioned at the highest position. In this state, the entire link mechanism 100 has its largest dimension in the front-to-rear direction and its smallest dimension in the up-to-down direction. The upper tube 81 has moved to the rearmost position, and the lower tube 82 has moved to the lowest position. The steering wheel 7 has been adjusted to its rearmost position in the front-to-rear direction and its lowest position in the up-to-down direction.

[0074] In the second state, the position adjustment motor 91 rotates the screw shaft 94 by the motor torque generated by the rotation in the second direction. The feed nut 95 moves forward in conjunction with the rotation of the screw shaft 94 to a position closest to the housing 83. The upper tube 81 moves forward in conjunction with the movement of the feed nut 95 to a position closest to the housing 83. The first link member 101 rotates in conjunction with the movement of the upper tube 81 so that the first end moves to the forward-most and uppermost position. The third link member 103 rotates in conjunction with the rotation of the first link member 101 so that the first end moves to the lowermost position. The second link member 102 rotates in conjunction with the rotation of the third link member 103 so that the second end moves to the rearmost and lowermost position. In this case, the entire link mechanism 100 operates so that the dimension in the front-rear direction becomes the smallest and the dimension in the up-down direction becomes the largest. As a result, the upper tube 81 moves to the forwardmost position in conjunction with the movement of the feed nut 95, and the lower tube 82 moves to the uppermost position in conjunction with the movement of the feed nut 95. The steering wheel 7 is adjusted to the forwardmost position in the front-to-rear direction and to the uppermost position in the up-down direction. In other words, the state of the steering column 3 changes from the second state to the intermediate state and then to the first state.

[0075] The position adjustment motor 91 operates the link mechanism 100 via the feed screw mechanism 92. When motor torque is transmitted to the link mechanism 100, the link mechanism 100 operates to link the swing of the lower tube 82 in the tilt direction with the movement of the upper tube 81 in the telescopic direction. This makes it possible to adjust the vertical position and the front-rear position of the steering wheel 7 at the same time, similar to the first embodiment.

[0076] In this way, the link mechanism 100 connects the upper tube 81 and the lower tube 82 so as to interlock them. Regarding adjustment of the position of the steering wheel 7, the position adjustment motor 91 and the feed screw mechanism 92 can be shared between the mechanism for adjusting the position in the up-down direction and the mechanism for adjusting the position in the front-rear direction.

[0077] <Effects of the second embodiment> (2-1) The link mechanism 100 is connected to the upper tube 81, and the feed nut 95 is connected only to the upper tube 81. As a result, in a configuration in which the lower tube 82 is fitted into the inner periphery of the upper tube 81, there is no need to connect the link mechanism 100 and the feed nut 95, and restrictions on the arrangement of the screw shaft 94 and the feed nut 95 can be alleviated. This is effective in improving the mountability of the steering column device 1 in a vehicle when a configuration in which the lower tube 82 is fitted into the inner periphery of the upper tube 81 is adopted.

[0078] <Other embodiments> The above-described embodiments may be modified as follows. In addition, the following other embodiments may be combined with each other to the extent that there is no technical contradiction.

[0079] In the first embodiment, the link mechanism 50 may be configured so that the lower tube 82 is in the most downward position when the upper tube 81 is in the most forward position. In this case, the link mechanism 50 only needs to be configured so that the lower tube 82 is in the most upward position when the upper tube 81 is in the most rearward position. When the other embodiments described here are adopted, the same effects as those of the first embodiment can be obtained. The same applies to the second embodiment.

[0080] In the first embodiment, the shape of the feed nut 45 can be changed as appropriate as long as the shape is capable of transmitting motor torque to the link mechanism 50. This also applies to the second embodiment.

[0081] In the first embodiment, the reduction mechanism 43 may be omitted. In this case, the rotation of the position adjustment motor 41 may be directly transmitted to the screw shaft 44. This also applies to the second embodiment.

[0082] In the first embodiment, the feed nut 45 can also be connected to the lower tube 22. In this case, a link mechanism may be added to allow the lower tube 22 to swing up and down in conjunction with the movement of the feed nut 45 in the front-rear direction. The link mechanism 50 may be configured so that the upper tube 21 moves in the front-rear direction in conjunction with the movement of the feed nut 45 in the front-rear direction described here. This is also true for the second embodiment.

[0083] In the first embodiment, the shapes of the nut link member 51 and the bracket link plate 52 of the link mechanism 50 can be changed as appropriate when the vertical position and the front-rear position can be adjusted with respect to the steering wheel 7. The same applies to the support plate portion 22b and the bracket plate portion 27c. The other embodiments described herein can be similarly applied to the second embodiment. In this case, in the second embodiment, the shapes of the first link member 101, the second link member 102, and the third link member of the link mechanism 100 can be changed as appropriate when the vertical position and the front-rear position can be adjusted with respect to the steering wheel 7. The same applies to the support plate portion 81b and the bracket plate portion 87c.

[0084] In each of the above embodiments, the steering column device 1 may constitute a part of a steer-by-wire type steering device in which the power transmission path between the steering wheel 7 and the steered wheels is mechanically separated.

Claims

1. a lower tube configured to be attached to a vehicle body so as to be freely swingable in a vertical direction of the vehicle; a column shaft configured to mount a steering wheel of a vehicle; an upper tube that rotatably supports the column shaft and is attached to the lower tube so as to be movable in the front-rear direction of the vehicle; a motor that generates a motor torque that is a power for swinging the lower tube in the up-down direction and moving the upper tube in the front-rear direction; a link mechanism that connects the lower tube and the upper tube so as to be freely interlocked with each other; a power transmission mechanism that operates to transmit the motor torque to the link mechanism; A steering column device configured to operate so as to link the vertical swing of the lower tube and the forward / backward movement of the upper tube when the motor torque is transmitted to the link mechanism by the power transmission mechanism.

2. a reduction mechanism that connects the motor to the power transmission mechanism, 2. The steering column device according to claim 1, wherein the speed reducing mechanism is configured to transmit the motor torque obtained by reducing the rotation speed of the motor to the power transmission mechanism.

3. The power transmission mechanism includes: a screw shaft extending in the front-rear direction and rotating about an axis extending in the front-rear direction by the motor torque; a feed nut connected to the upper tube and moving in the front-rear direction along the screw shaft as the screw shaft rotates, 3. The steering column device according to claim 1, wherein the feed nut is configured to move the upper tube in the fore-and-aft direction and to move the lower tube in the up-and-down direction via the link mechanism when the feed nut moves in the fore-and-aft direction.

4. a column bracket configured to be attached to the vehicle body; the upper tube is fitted to an inner peripheral portion of the lower tube, the link mechanism connects the lower tube to the column bracket and the feed nut, The steering column apparatus according to claim 3 , wherein the feed nut connects the upper tube to the link mechanism.

5. a column bracket configured to be attached to the vehicle body; the lower tube is fitted to an inner periphery of the upper tube, the link mechanism connects the upper tube to the column bracket, 4. The steering column device according to claim 3, wherein the feed nut is connected only to the upper tube.

6. A steering column device as described in any one of claims 1 to 5, wherein the link mechanism is configured to operate to link the upward or downward swinging of the lower tube along the vertical direction with the backward or forward movement of the upper tube along the fore-and-aft direction when the motor torque is transmitted to the link mechanism by the power transmission mechanism.

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