Vehicle steer-by-wire mechanism

Abstract

This steer-by-wire mechanism (1) for a vehicle comprises: a column shaft (2) capable of tilting about a tilt center axis (O); and a clutch (4) having a first rotating shaft (20) mechanically coupled to the column shaft (2) and a second rotating shaft (27) mechanically coupled to a steering wheel. The center axis of the first rotating shaft (20) coincides with the tilt center axis (O).

Description

Steer-by-wire mechanism for vehicles

[0001] The present invention relates to a steer-by-wire system for a vehicle.

[0002] Patent Document 1 discloses a vehicle steering device. In this steering device, if neither the reaction force actuator nor the steering actuator has a malfunction, the clutch mechanism is maintained in a disengaged state and operation continues in steer-by-wire mode. If either one has a malfunction, the clutch mechanism is engaged, and the ambient temperature detected by the first ECU or the second ECU is acquired, and an engagement completion time corresponding to the temperature is estimated based on the temperature-clutch engagement time characteristic. The estimated time is set as a standby time for switching to EPS mode, and if the standby time has elapsed, steering assist is initiated. If the standby time has not elapsed, the previous steering state is continued until the standby time has elapsed.

[0003] JP 2016-132264 A

[0004] In the steer-by-wire mechanism of Patent Document 1, to achieve a tilt function for the first steering shaft, it is necessary to swing the second steering shaft and the clutch in addition to the first steering shaft. However, these steering transmission mechanisms are usually located near the brake pedal, accelerator pedal, air conditioning unit, and air conditioning duct, making it difficult to secure sufficient space for the above-mentioned swinging.

[0005] An object of the present invention is to provide a steer-by-wire mechanism that can achieve the tilt function of the column shaft in a smaller swing space.

[0006] A steer-by-wire mechanism according to one aspect of the present invention includes a column shaft that is tiltable around a tilt central axis, and a clutch having a first rotating shaft mechanically connected to the column shaft and a second rotating shaft mechanically connected to a steered wheel, the central axis of which coincides with the tilt central axis.

[0007] According to the steer-by-wire mechanism, the tilt function of the column shaft can be realized in a smaller swing space.

[0008] Fig. 1 is a plan view of a steer-by-wire mechanism according to an embodiment, viewed from above in the vertical direction of a column. Fig. 2 is a side view of the steer-by-wire mechanism of Fig. 1. Fig. 3 is a side view of a tilt mechanism integrated into the steer-by-wire mechanism of Fig. 1. Fig. 4 is a plan view of the steer-by-wire mechanism of Fig. 1, viewed from above in the vertical direction of the column. Fig. 5 is a perspective view of a main part of the steer-by-wire mechanism of Fig. 1. Fig. 6 is a cross-sectional view of a main part of the steer-by-wire mechanism of Fig. 1.

[0009] A steer-by-wire system according to an embodiment will be described below with reference to the drawings. In the following description, components having the same functions as those already described will be assigned the same reference numerals and will not be described again. In each drawing, FR and RR indicate the front and rear in the longitudinal direction of the vehicle, respectively, LH and RH indicate the left and right in the width direction of the vehicle, and UP and DN indicate the upper and lower, respectively. In the following description, the left and right sides in the width direction of the vehicle and the front and rear in the longitudinal direction of the vehicle will be simply referred to as the "left side," "right side," "front," and "rear," respectively.

[0010] As shown in FIGS. 1 to 6 , a steer-by-wire mechanism 1 according to the embodiment is applied to a steer-by-wire steering system of a vehicle V. The vehicle V is a left-hand drive vehicle, with the front left seat being the driver's seat. The steer-by-wire mechanism 1 has a column shaft 2 to which the driver's steering rotation is input, and an intermediate shaft 3 that transmits the steering force for turning the steered wheels to the steered wheels. The steer-by-wire mechanism 1 also has a clutch 4 that mechanically couples the column shaft 2 and the intermediate shaft 3. The intermediate shaft 3 is also referred to as a steering shaft.

[0011] When the steer-by-wire system is functioning normally, the column shaft 2 and the intermediate shaft 3 are mechanically separated by the clutch 4. However, when an abnormality occurs in the steer-by-wire system, the column shaft 2 and the intermediate shaft 3 are mechanically connected by the clutch 4. This makes it possible to mechanically steer the steered wheels directly by the steering rotation input to the column shaft 2 by the driver.

[0012] The column shaft 2 is housed inside a steering column 5 and is rotatable around its central axis. The steering column 5 is attached to a steering member 7 fixed to a vehicle body 6. The steering member 7 is bridged between the left and right side panels of the vehicle body 6. The steering column 5 is fixed to the steering member 7 via a tilt bracket 8 attached to the steering column 5. The tilt bracket 8 is provided with a tilt mechanism for the steering column 5. The steering column 5 is held by the tilt bracket 8 so that it can swing.

[0013] A tilt lever 9 is provided on the tilt bracket 8. The pivot position of the steering column 5, i.e., the tilt position, is locked or unlocked by the tilt lever 9. In the unlocked state, the steering column 5 can be pivoted up and down around the tilt central axis O. In other words, the column shaft 2 can be tilted around the tilt central axis O. A curved guide elongated hole 10 (see FIG. 3) is formed in the tilt bracket 8 to guide the pivoting of the steering column 5. The tilt central axis O is parallel to the vehicle width direction.

[0014] A steering wheel 11 is attached to the input end of the column shaft 2, and steering rotation by the driver is input to the column shaft 2 via the steering wheel 11. The shape of the steering portion is not particularly limited and may be, for example, circular, D-shaped, U-shaped, etc. A brake pedal and an accelerator pedal are disposed in front of and below the steering column 5. The brake pedal and the accelerator pedal are suspended pedals. The vehicle V of this embodiment is equipped with an automatic transmission and is not provided with a clutch pedal.

[0015] The output end of the intermediate shaft 3 is mechanically connected to the pinion gear shaft 13 of the steering gear box 12 via a Cardan joint 14. The Cardan joint 14 is a type of universal joint and has non-uniform velocity. In other words, if the central axis of the intermediate shaft 3 is at an angle with respect to the central axis of the pinion gear shaft 13, when the intermediate shaft 3 is rotated at a uniform speed around its central axis, the pinion gear shaft 13 will rotate at a non-uniform speed around its central axis. As a result, fluctuations also occur in the torque transmitted between the intermediate shaft 3 and the pinion gear shaft 13.

[0016] The steering gear box 12 includes a pinion gear formed on a pinion gear shaft 13 and a rack gear formed on a rack bar (not shown) inside the steering gear box 12. When the pinion gear shaft 13 rotates, the rotational motion is converted into linear motion by the meshing of the pinion gear and the rack gear, and the converted linear motion moves the rack bar in its axial direction. As the rack bar moves axially, a steering drive force is transmitted to knuckle arms of hub carriers of the steered wheels via tie rods 15 attached to both ends of the rack bar so as to be able to swing, and the steered wheels are turned.

[0017] The pinion gear shaft 13 of the steering gear box 12 passes through a dash panel 16, and the intermediate shaft 3 is disposed on the passenger compartment side of the dash panel 16. The dash panel 16 is a partition plate that separates the engine room or motor room from the passenger compartment in the longitudinal direction of the vehicle, and is also called a front bulkhead.

[0018] The steer-by-wire mechanism 1 includes a reaction motor 17, which is a first motor. The reaction motor 17 applies a steering reaction force to the column shaft 2, which is mechanically separated from the intermediate shaft 3. An output shaft 20, which is a first output rotation shaft of the reaction motor 17, is mechanically connected to the column shaft 2 via a reaction reducer 18, which is a first reducer. The reaction reducer 18 is configured with a worm drive mechanism, and includes a reaction worm wheel 19, which is a first worm wheel provided on the column shaft 2, and a reaction worm shaft 20, which is a first worm shaft. The reaction worm wheel 19 and the reaction worm shaft 20 are in mesh with each other.

[0019] The output rotation of the reaction motor 17 is reduced in speed and torque amplified by the reaction motor reducer 18, and transmitted as steering reaction force to the steering wheel 11 attached to the column shaft 2. The reaction motor 17 is configured integrally with a reaction motor ECU (Electrical Control Unit) 21 that controls the reaction motor 17. The reaction motor 17, reaction motor reducer 18, and reaction motor ECU 21 configure a reaction actuator 22, which is a first actuator, and is disposed on the passenger compartment side of the dash panel 16.

[0020] In other words, the reaction force reducer 18 is provided between the reaction force motor 17 and the column shaft 2, and reduces the rotation speed of the reaction force motor 17 before transmitting it to the column shaft 2. The driver's steering rotation is input to the column shaft 2 via the steering wheel 11. At the same time, the steering reaction force generated by the reaction force motor 17 is transmitted to the column shaft 2 via the reaction force reducer 18. The column shaft 2 transmits the steering reaction force to the steering wheel 11, allowing the driver to feel the steering reaction force when turning the steering wheel 11.

[0021] Steer-by-wire mechanism 1 is equipped with steering motor 23, which is a second motor. Steering motor 23 applies a steering force to intermediate shaft 3, which is mechanically separated from column shaft 2, to turn the steered wheels. Output shaft 27, which is a second output rotation shaft of steering motor 23, is mechanically connected to intermediate shaft 3 via steering reducer 24, which is a second reducer. Steering reducer 24 is formed by a worm drive mechanism, and is equipped with steering worm wheel 26, which is a second worm wheel mechanically connected to intermediate shaft 3, and steering worm shaft 27, which is a second worm shaft. Steering worm wheel 26 is mechanically connected to intermediate shaft 3 via Cardan joint 25, which is a universal joint. Steering worm wheel 26 and steering worm shaft 27 are in mesh with each other.

[0022] The Cardan joint 25 is a type of universal joint and has non-uniform velocity. That is, when the steering worm wheel 26 rotates at a uniform speed around its central axis, the intermediate shaft 3 connected via the Cardan joint 25 rotates at a non-uniform speed around its central axis. As a result, the torque transmitted between the steering worm wheel 26 and the intermediate shaft 3 also fluctuates.

[0023] The output rotation of steering motor 23 is reduced in speed and torque amplified by steering reducer 24, and transmitted as a steering force to pinion gear shaft 13 of steering gearbox 12, which is mechanically connected to intermediate shaft 3. Steering motor 23 is configured integrally with steering motor ECU 28, which controls steering motor 23. Steering motor 23, steering reducer 24, and steering motor ECU 28 configure steering actuator 29, which is a second actuator, and is arranged on the passenger compartment side of dash panel 16.

[0024] In other words, steering reducer 24 is provided between steering motor 23 and intermediate shaft 3, and reduces the rotation of steering motor 23 before transmitting it to intermediate shaft 3. Furthermore, the steering force generated by steering motor 23 is transmitted to intermediate shaft 3 via steering reducer 24, and then transmitted from intermediate shaft 3 to the steered wheels via steering gearbox 12.

[0025] Each worm drive mechanism may have a known backlash suppression mechanism built in. The backlash suppression mechanism suppresses backlash by using the elastic restoring force of a spring to bias the worm shafts 20, 27 toward the worm wheels 19, 26. This allows play in the reaction reducer 18 and the steering reducer 24 to be sufficiently suppressed.

[0026] Clutch 4 is provided between reaction force actuator 22 and steering actuator 29, and includes an engagement portion 4A on the reaction force actuator 22 side and an engagement portion 4B on the steering actuator 29 side. Rotation shaft 20, which is the first rotation shaft of clutch 4, is connected to engagement portion 4A so as to rotate integrally with engagement portion 4A. Rotation shaft 27, which is the second rotation shaft of clutch 4, is connected to engagement portion 4B so as to rotate integrally with engagement portion 4B.

[0027] In this embodiment, the clutch 4 is a friction-type electromagnetic clutch. When not energized, the friction plates, which are the engagement portions 4A and 4B, are pressed together by the biasing force of an internal spring, and the clutch 4 is in an engaged state. When energized, the electromagnetic force generated by an internal coil releases the pressure on the friction plates against the biasing force of the spring, and the clutch 4 is in a disengaged state. In other words, the clutch 4 can be switched between an engaged state in which torque can be transmitted between the rotating shaft 20 and the rotating shaft 27, and a disengaged state in which torque transmission is interrupted.

[0028] In this embodiment, the rotating shaft 20 is the reaction worm shaft 20 of the reaction reducer 18 and the output shaft 20 of the reaction motor 17. The rotating shaft 27 is the steering worm shaft 27 of the steering reducer 24 and the output shaft 27 of the steering motor 23. The rotating shaft 20, the reaction worm shaft 20, and the output shaft 20 of the reaction motor 17 may be formed from a single shaft member, or may be composed of multiple shaft members connected to each other by a well-known connecting method such as spline connection. Similarly, the rotating shaft 27, the steering worm shaft 27, and the output shaft 27 of the steering motor 23 may be formed from a single shaft member, or may be composed of multiple shaft members.

[0029] In this embodiment, the central axis of the rotation shaft 20 and the central axis of the rotation shaft 27 coincide with the tilt central axis O. Therefore, the central axes of the reaction force worm shaft 20, the output shaft 20 of the reaction force motor 17, the steering worm shaft 27, and the output shaft 27 of the steering motor 23 also coincide with the tilt central axis O.

[0030] As shown in Figure 5, clutch 4 is built into the joint between first case 30 of reaction force reducer 18 and second case 31 of steering reducer 24. At the joint, the cylindrical end of first case 30 is inserted into the cylindrical end of second case 31 so as to be rotatable around tilt central axis O.

[0031] A fixing portion 32 that fixes the second case 31 to the steering member 7 is provided on the outer peripheral surface of the second case 31 at the joint. Therefore, the steering actuator 29 including the steering reducer 24 is fixed to and supported by the steering member 7 by the fixing portion 32.

[0032] On the other hand, the first case 30 rotates around the tilt central axis O in accordance with the swing of the column shaft 2. Specifically, at the joint, the first case 30 is configured to be rotatable around the tilt central axis O relative to the second case 31 fixed to the steering member 7.

[0033] Lubricating oil for lubricating the reaction force reducer 18 and the steering reducer 24 is sealed inside the first case 30 and the second case 31. At the joint, a seal 33 such as an O-ring is provided between the outer peripheral surface of the first case 30 and the inner peripheral surface of the second case 31 to prevent leakage of the lubricating oil to the outside. The seal 33 is housed in a groove formed on the inner peripheral surface of the second case 31 at the joint. Alternatively, a groove may be formed on the outer peripheral surface of the first case 30 at the joint, and the seal may be housed inside the groove. The seal structure at the joint is not particularly limited, and in addition to an O-ring, any well-known seal structure such as a mechanical seal may be used.

[0034] Reaction motor ECU 21 and steering motor ECU 28 are connected to the communication network of vehicle V so as to be able to communicate with each other. In addition to clutch 4, various sensors such as a torque sensor built into steering column 5 are connected to reaction motor ECU 21. Reaction motor ECU 21 calculates the steering angle of the steered wheels based on detection values ​​of various sensors such as the torque detected by the torque sensor, information on the running state of vehicle V, etc., and transmits the calculation result to steering motor ECU 28, and controls steering motor 23 via steering motor ECU 28.

[0035] The reaction force motor ECU 21 and the steering motor ECU 28 communicate with each other to determine whether the steer-by-wire system is operating normally or abnormally. If the reaction force motor ECU 21 and the steering motor ECU 28 determine that there is no abnormality in the steer-by-wire system, they disengage clutch 4 and execute steer-by-wire control. When steer-by-wire control is executed, the reaction force motor ECU 21 causes the reaction force motor 17 to generate a steering reaction force on the column shaft 2, and the steering motor ECU 28 causes the steering motor 23 to steer the steered wheels. At this time, the reaction force motor 17 and the steering motor 23 are mechanically separated.

[0036] On the other hand, if, for example, one of reaction force motor 17 and steering motor 23 does not operate normally, reaction force motor ECU 21 or steering motor ECU 28 determines that an abnormality has occurred in the steer-by-wire system and stops steer-by-wire control. When steer-by-wire control is not being executed, reaction force motor ECU 21 or steering motor ECU 28 connects clutch 4 as a fail-safe, mechanically connecting steering wheel 11 to the steered wheels. Note that "connection to the steered wheels" refers to a connection related to the steering mechanism of the steered wheels, and not a connection related to the rotation mechanism of the steered wheels.

[0037] When steer-by-wire control is not being executed, the output shaft 20 and the output shaft 27 are mechanically connected by the clutch 4, thereby mechanically connecting the column shaft 2 and the intermediate shaft 3. As a result, the steering wheel 11 is mechanically connected to the steered wheels, so that the driver can turn the steered wheels by rotating the steering wheel 11.

[0038] Furthermore, the reaction force reducer 18 functions as a speed increaser 18 that increases the rotation of the column shaft 2 and transmits it to the reaction force worm shaft 20. The driver's steering rotation input from the steering wheel 11 to the column shaft 2 is increased in speed and transmitted to the reaction force worm shaft 20 via the reaction force worm wheel 19. The steering rotation transmitted to the reaction force worm shaft 20 is transmitted at a constant speed to the steering worm shaft 27 via the engaged clutch 4, and is further reduced in speed by the steering reducer 24 before being transmitted to the intermediate shaft 3. When either the reaction force motor 17 or the steering motor 23 is drivable, that motor can be used as a source of assist force for the power steering function.

[0039] In this embodiment, the central axis of the column shaft 2, i.e., the central axis of the reaction force worm wheel 19, is geometrically twisted relative to the central axis of the reaction force worm shaft 20. That is, the central axis of the column shaft 2 and the tilt central axis O do not intersect, nor are they parallel to each other. The angle between these two central axes is approximately 90°. Furthermore, the central axis of the rotation of the steering worm wheel 26 is geometrically twisted relative to the central axis of the steering worm shaft 27. That is, the central axis of the rotation of the steering worm wheel 26 and the tilt central axis O do not intersect, nor are they parallel to each other. The angle between these two central axes is approximately 90°. Note that the angle formed by two lines that are twisted in three-dimensional space is the angle formed by two lines on a plane that contains the two intersecting lines when one line is translated so that it intersects the other line.

[0040] Furthermore, the central axis of the column shaft 2, the central axis of the intermediate shaft 3, and the tilt central axis O are geometrically skewed relative to one another. In other words, the central axis of the column shaft 2, the central axis of the intermediate shaft 3, and the tilt central axis O do not intersect with one another, nor are they parallel to one another. The column shaft 2 and the intermediate shaft 3 are disposed offset in the vehicle width direction.

[0041] In this embodiment, the column shaft 2 and the intermediate shaft 3 are located on the left side of the vehicle V. Furthermore, the intermediate shaft 3 is located on the left side of the column shaft 2, that is, on the outer side in the vehicle width direction.

[0042] The effects of the steer-by-wire system 1 according to this embodiment will now be described.

[0043] (1) The steer-by-wire mechanism 1 includes a column shaft 2 that can tilt around a tilt central axis O, and a clutch 4. The clutch 4 has a rotating shaft 20 mechanically connected to the column shaft 2 and a rotating shaft 27 mechanically connected to the steered wheels. The clutch 4 is switchable between a connected state in which torque can be transmitted between the rotating shafts 20 and 27, and a disconnected state in which the torque transmission is interrupted. The central axis of the rotating shaft 20 coincides with the tilt central axis O. Therefore, when tilting the column shaft 2, only the steering transmission mechanism on the steering wheel 11 side, such as the column shaft 2, from the rotating shaft 20 can be rotated or swung around the tilt central axis O. In other words, to achieve the tilt function, there is no need to ensure a swing space for the steering transmission mechanism on the steered wheels side, such as the intermediate shaft 3. Therefore, the steer-by-wire mechanism 1 allows the tilt function of the column shaft 2 to be achieved with a smaller swing space. In particular, when the clutch 4 is in the disengaged state, the steering transmission mechanism on the steering wheel 11 side from the rotating shaft 20 is mechanically separated from the steering transmission mechanism on the steered wheel side from the rotating shaft 27. Therefore, the rotation of the steering transmission mechanism on the steering wheel 11 side from the rotating shaft 20 about the tilt central axis O is not impeded by the steering transmission mechanism on the steered wheel side from the rotating shaft 27. This makes it possible to reduce the force required to swing the column shaft 2 up and down.

[0044] (2) The steer-by-wire system 1 includes a speed-increasing gear 18 disposed between the column shaft 2 and the rotating shaft 20, which increases the rotation of the column shaft 2 and transmits the rotation to the rotating shaft 20. Therefore, the magnitude of rotation of the column shaft 2 caused by a tilt operation when the clutch 4 is engaged can be reduced to the inverse of the speed-increasing ratio of the speed-increasing gear 18, compared to a case in which the speed-increasing gear 18 is not provided. For example, when the column shaft 2 is tilted by a tilt angle α with the clutch 4 engaged, the reaction worm wheel 19 rotates by the tilt angle α around the reaction worm shaft 20, which is connected to the steering transmission mechanism on the steered wheel side and whose rotation is constrained (see FIG. 3 ). In this case, if the speed-increasing ratio of the speed-increasing gear 18 is 20 / 1, for example, the steering wheel 11 rotates by 1 / 20 of the tilt angle α. The steer-by-wire system 1 includes the speed-increasing gear 18, which can suppress rotation of the column shaft 2 caused by a tilt operation, particularly when the clutch 4 is engaged.

[0045] (3) The steer-by-wire mechanism 1 is equipped with a reaction motor 17 that applies a steering reaction force to the column shaft 2. The speed increaser 18 is a reaction reducer 18 that reduces the rotation of the reaction motor 17 and transmits the reduced rotation to the column shaft 2. The center axis of the output shaft 20 of the reaction motor 17 coincides with the center axis of the rotation shaft 20 of the clutch 4. Therefore, when steer-by-wire control is not being executed, the clutch 4 can be connected and the reaction motor 17 can be used as an assist force generating source for the power steering function.

[0046] (4) Steer-by-wire mechanism 1 includes steering motor 23 that generates a steering force for steering the steered wheels, intermediate shaft 3 that is mechanically connected to rotating shaft 27 and transmits the steering force to the steered wheels, and steering reducer 24. Steering reducer 24 is provided between steering motor 23 and intermediate shaft 3, and reduces the rotation of steering motor 23 before transmitting it to intermediate shaft 3. The central axis of output shaft 27 of steering motor 23 coincides with the central axis of rotating shaft 27 of clutch 4. Therefore, when steer-by-wire control is not being executed, clutch 4 can be connected and steering motor 23 can be used as a source of assist force for the power steering function.

[0047] (5) In the steer-by-wire mechanism 1, the first case 30 of the reaction force reducer 18 and the second case 31 of the steering reducer 24 are relatively rotatable about the central axis of the rotation shaft 20 (i.e., the tilt central axis O). Therefore, during a tilt operation, only the steering transmission mechanism on the steering wheel 11 side from the clutch 4 swings about the tilt central axis O, and the steering transmission mechanism on the steered wheel side from the clutch 4 does not swing. Therefore, with the steer-by-wire mechanism 1, the tilt function of the column shaft 2 can be achieved in a smaller swing space. In particular, because the geometry of the steering reducer 24, the intermediate shaft 3, and the steering gearbox 12 does not change before and after a tilt operation, vehicle behavior during steering can be stabilized regardless of the tilt position of the steering column 5.

[0048] (6) In the steer-by-wire mechanism 1, a Cardan joint 25 is provided between the steering reducer 24 and the intermediate shaft 3. In the steer-by-wire mechanism 1, the geometry of the steering transmission mechanism from the clutch 4 to the steered wheels does not change before and after a tilt operation, and therefore the torque fluctuation of the Cardan joint 25 also does not change before and after a tilt operation. The steer-by-wire mechanism 1 stabilizes the vehicle behavior during steering regardless of the tilt position of the steering column 5, while improving the degree of freedom in the layout of the steering transmission mechanism from the clutch 4 to the steered wheels.

[0049] (7) In the steer-by-wire mechanism 1, the reaction force reducer 18 has a reaction force worm wheel 19 connected to the column shaft 2 and a reaction force worm shaft 20 that meshes with the reaction force worm wheel 19. The steering reducer 24 has a steering worm wheel 26 mechanically connected to the intermediate shaft 3 and a steering worm shaft 27 that meshes with the steering worm wheel 26. In other words, the reaction force reducer 18 and the steering reducer 24 are constructed from a worm drive mechanism. Therefore, the power transmission path of the steer-by-wire mechanism 1 can be made crank-shaped, bent at a substantially right angle, in the reaction force reducer 18 and the steering reducer 24. In the steer-by-wire mechanism 1, the reaction force worm shaft 20 and the steering worm shaft 27 are provided on the tilt central axis O, so the central axes of the reaction force worm shaft 20 and the steering worm shaft 27 can be set to the tilt central axis O. Therefore, the steer-by-wire mechanism 1 makes it possible to achieve the tilt function of the column shaft 2 with a simpler structure.

[0050] The above-described embodiments are merely examples described to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the above-described embodiments, etc., but also includes various modifications, changes, alternative techniques, etc. that can be easily derived therefrom.

[0051] For example, in the above embodiment, the tilt mechanism is a manual mechanism that operates the tilt lever 9, but the tilt mechanism may be an electric mechanism that uses a motor or the like.

[0052] Also, in the above embodiment, the tilt central axis O is located below the rotation central axis of the reaction force worm wheel 19. However, the tilt central axis O may be located above the rotation central axis of the reaction force worm wheel 19. Similarly, in the above embodiment, the tilt central axis O is located below the rotation central axis of the steering worm wheel 26. However, the tilt central axis O may be located above the rotation central axis of the steering worm wheel 26. Also, the rotation central axis of the reaction force worm wheel 19 and the rotation central axis of the steering worm wheel 26 may be located on opposite sides of the tilt central axis O.

[0053] Furthermore, the clutch 4 in the above embodiment is a disc-type friction clutch. However, the clutch 4 may be another type of friction clutch, such as a drum-type friction clutch or a cone-type friction clutch. Alternatively, the clutch 4 may be another type of clutch, such as a dog clutch, such as a roller clutch or a tooth clutch.

[0054] Furthermore, in the above embodiment, the reaction force reducer 18 and the steering reducer 24 use a worm drive mechanism, but other types of reducers may also be used. For example, a reducer can be constructed using a bevel gear or the like. However, the worm drive mechanism has the advantage of being able to obtain a large reduction ratio, and also has the advantage of being able to incorporate the above-mentioned backlash suppression mechanism.

[0055] In the above embodiment, the reduction ratio of the steering reducer 24 is set to be smaller than the reduction ratio of the reaction force reducer 18, but the relationship between the reduction ratios is not particularly limited. The reduction ratio of the steering reducer 24 may be set to be larger than the reduction ratio of the reaction force reducer 18, or the two reduction ratios may be set to be the same.

[0056] In the above embodiment, the steer-by-wire mechanism 1 is applied to a steer-by-wire steering system for a left-hand drive vehicle, but the present invention is not limited to this. The steer-by-wire mechanism 1 can also be applied to a right-hand drive vehicle by arranging each component symmetrically.

[0057] DESCRIPTION OF SYMBOLS 1 Steer-by-wire mechanism 2 Column shaft 3 Intermediate shaft (steering shaft) 4 Clutch 14, 25 Cardan joint (universal joint) 17 Reaction motor (first motor) 18 Reaction reducer (speed increaser, first reducer) 19 Reaction worm wheel (first worm wheel) 20 Reaction worm shaft (first worm shaft), clutch rotating shaft (first rotating shaft), reaction motor output shaft (first output rotating shaft) 22 Reaction actuator (first actuator) 23 Turning motor (second motor) 24 Turning reducer (second reducer) 26 Turning worm wheel (second worm wheel) 27 Turning worm shaft (second worm shaft), clutch rotating shaft (second rotating shaft), turning motor output shaft (second output rotating shaft) 29 Turning actuator (second actuator) 30 First case 31 Second case O Tilt center axis V Vehicle

Claims

1. A steer-by-wire mechanism for a vehicle, comprising a column shaft tiltable about a tilt center axis, and a clutch having a first rotation axis and a second rotation axis, the clutch being switchable between a connected state in which torque can be transmitted between the first rotation axis and the second rotation axis and a disconnected state in which the torque transmission is interrupted. The first rotation axis is mechanically connected to the column shaft, the second rotation axis is mechanically connected to a steered wheel, and a central axis of the first rotation axis coincides with the tilt center axis. A steer-by-wire mechanism.

2. The steer-by-wire mechanism according to claim 1, further comprising a speed increaser provided between the column shaft and the first rotation axis, the speed increaser increasing the rotation speed of the column shaft and transmitting it to the first rotation axis.

3. The steer-by-wire mechanism according to claim 2, further comprising a first motor that applies a steering reaction force to the column shaft, the speed increaser being a first speed reducer that reduces the rotation of the first motor and transmits it to the column shaft, and a central axis of a first output rotation shaft of the first motor coincides with a central axis of the first rotation axis of the clutch.

4. The steer-by-wire mechanism according to claim 3, further comprising a second motor that generates a steering force for steering the steered wheel, a steering shaft mechanically connected to the second rotation axis and transmitting the steering force to the steered wheel, and a second speed reducer provided between the second motor and the steering shaft, the second speed reducer reducing the rotation of the second motor and transmitting it to the steering shaft. A central axis of a second output rotation shaft of the second motor coincides with a central axis of the second rotation axis of the clutch.

5. The steer-by-wire mechanism according to claim 4, wherein a first case of the first speed reducer and a second case of the second speed reducer are relatively rotatable about a central axis of the first rotation axis.

6. The steer-by-wire mechanism according to claim 4 or 5, wherein a universal joint is provided between the second speed reducer and the steering shaft.

7. The first speed reducer has a first worm wheel connected to the column shaft and a first worm shaft meshing with the first worm wheel. The second speed reducer has a second worm wheel mechanically connected to the steering shaft and a second worm shaft meshing with the second worm wheel. The first worm shaft and the second worm shaft are provided on the tilt central axis. The steer-by-wire mechanism according to claim 4.

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