Steer-by-wire mechanism for vehicle

Abstract

A steer-by-wire mechanism (1) for a vehicle comprises a first steering shaft (2) that transmits a steering reaction force to a steering unit, a second steering shaft (3) that transmits a turning force to steered wheels, and a clutch (4). The clutch (4) mechanically connects the first steering shaft (2) and the second steering shaft (3) to each other. The second steering shaft (3) is disposed either on the right side or on the left side in the vehicle width direction relative to the first steering shaft (2).

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 when 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] However, in the steer-by-wire system disclosed in Patent Document 1, the first steering shaft, the second steering shaft, and the clutch are arranged on the same axis, so the second steering shaft passes through the dash panel in front of the driver's seat, which places restrictions on the design of the brake pedal and accelerator pedal.

[0005] An object of the present invention is to improve the degree of freedom in designing brake pedals and accelerator pedals.

[0006] A steer-by-wire mechanism according to one aspect of the present invention includes a first steering shaft that transmits a steering reaction force to a steering unit, a second steering shaft that transmits a steering force to steered wheels, and a clutch. The clutch mechanically connects the first steering shaft and the second steering shaft. The second steering shaft is disposed on either the right or left side of the first steering shaft in the vehicle width direction.

[0007] The steer-by-wire mechanism described above allows for greater freedom in designing the brake pedal and accelerator pedal.

[0008] Fig. 1 is a plan view of a steer-by-wire mechanism according to an embodiment, as seen 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 plan view of the steer-by-wire mechanism of Fig. 1, as seen from above in the vertical direction of the column. Fig. 4 is a perspective view of a main part of the steer-by-wire mechanism of Fig. 1. Fig. 5 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 Figures 1 to 5, a steer-by-wire mechanism 1 according to this embodiment is applied to a steer-by-wire steering system for 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 first steering shaft 2 to which the driver's steering rotation is input, and a second steering shaft 3 that transmits a 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 first steering shaft 2 and the second steering shaft 3.

[0011] When the steer-by-wire system is functioning normally, the first steering shaft 2 and the second steering shaft 3 are mechanically separated by the clutch 4. However, when an abnormality occurs in the steer-by-wire system, the first steering shaft 2 and the second steering 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 first steering shaft 2 by the driver.

[0012] The first steering shaft 2, also called a column shaft, is housed inside a steering column 5 and is rotatable about 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 a left side panel and a right side panel of the vehicle body 6. The steering column 5 is fixed to the steering member 7 via a column bracket 8 fixed to the steering column 5. A steering wheel 9, which serves as a steering unit, is attached to the input end of the first steering shaft 2, and steering rotation by the driver is input to the first steering shaft 2 via the steering wheel 9. The shape of the steering unit is not particularly limited and may be, for example, circular, D-shaped, U-shaped, etc.

[0013] A brake pedal 10 and an accelerator pedal 11 are disposed in front of and below the steering column 5. The brake pedal 10 and the accelerator pedal 11 are suspended pedals. The vehicle V of this embodiment is equipped with an automatic transmission and is not provided with a clutch pedal.

[0014] The second steering shaft 3, also called an intermediate shaft, has an output end mechanically connected to a pinion gear shaft 13 of a steering gear box 12 via a Cardan joint 14. The Cardan joint 14 is a type of universal joint and has non-uniform velocity. That is, if the central axis of the second steering shaft 3 is at an angle with respect to the central axis of the pinion gear shaft 13, when the second steering shaft 3 is rotated at a uniform speed around its central axis, the pinion gear shaft 13 rotates at a non-uniform speed around its central axis. As a result, fluctuations also occur in the torque transmitted between the second steering shaft 3 and the pinion gear shaft 13.

[0015] 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.

[0016] The pinion gear shaft 13 of the steering gear box 12 passes through a dash panel 16, and the second steering 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.

[0017] The steer-by-wire mechanism 1 includes a reaction motor 17, which is a second motor. The reaction motor 17 applies a steering reaction force to the first steering shaft 2, which is mechanically separated from the second steering shaft 3. An output shaft 20 of the reaction motor 17 is mechanically connected to the first steering shaft 2 via a reaction reducer 18, which is a second reducer. The reaction reducer 18 is configured with a worm drive mechanism, and includes a reaction worm wheel 19 provided on the first steering shaft 2, and a reaction worm shaft 20, which is also the output shaft 20 of the reaction motor 17.

[0018] The output rotation of the reaction motor 17 is reduced in speed and torque amplified by the reaction motor reducer 18, and transmitted as a steering reaction force to the steering wheel 9 attached to the first steering 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, the reaction motor reducer 18, and the reaction motor ECU 21 configure a reaction actuator 22, which is a second actuator, and is disposed on the passenger compartment side of the dash panel 16.

[0019] In other words, the reaction force reducer 18 is provided between the reaction force motor 17 and the first steering shaft 2, and reduces the rotation speed of the reaction force motor 17 before transmitting it to the first steering shaft 2. The driver's steering rotation is input to the first steering shaft 2 via the steering wheel 9. At the same time, the steering reaction force generated by the reaction force motor 17 is transmitted to the first steering shaft 2 via the reaction force reducer 18. The first steering shaft 2 transmits the steering reaction force to the steering wheel 9, allowing the driver to feel the steering reaction force when turning the steering wheel 9.

[0020] Steer-by-wire mechanism 1 includes a first motor, namely, steering motor 23. Steering motor 23 applies a steering force to second steering shaft 3, which is mechanically separated from first steering shaft 2, to steer the steered wheels. An output shaft 27 of steering motor 23 is mechanically connected to second steering shaft 3 via steering reducer 24, which is a first reducer. Steering reducer 24 is formed by a worm drive mechanism, and includes a steering worm wheel 26 mechanically connected to second steering shaft 3 via Cardan joint 25, and a steering worm shaft 27, which is also output shaft 27 of steering motor 23.

[0021] 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 mechanically connected to second steering shaft 3. Steering motor 23 is configured integrally with steering motor ECU 28 that controls steering motor 23. Steering motor 23, steering reducer 24 and steering motor ECU 28 configure steering actuator 29, which is a first actuator, and is arranged on the passenger compartment side of dash panel 16.

[0022] In other words, steering reducer 24 is provided between steering motor 23 and second steering shaft 3, and reduces the rotation speed of steering motor 23 before transmitting it to second steering shaft 3. Furthermore, the steering force generated by steering motor 23 is transmitted to second steering shaft 3 via steering reducer 24, and then transmitted from second steering shaft 3 to the steered wheels via steering gearbox 12.

[0023] 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.

[0024] 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. Engagement portions 4A and 4B are each rotatable around a clutch central axis O that is parallel to the vehicle width direction. Rotation shaft 20 is connected to engagement portion 4A so as to rotate integrally with engagement portion 4A. Rotation shaft 27 is connected to engagement portion 4B so as to rotate integrally with engagement portion 4B.

[0025] 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.

[0026] 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.

[0027] In this embodiment, the central axis of rotating shaft 20 and the central axis of rotating shaft 27 are arranged on clutch central axis O, which is the central axis of clutch 4. Therefore, the central axes of reaction force worm shaft 20, output shaft 20 of reaction force motor 17, steering worm shaft 27, and output shaft 27 of steering motor 23 are also arranged on clutch central axis O.

[0028] The clutch 4 is housed in a casing 30. The reaction force reducer 18 and the steering reducer 24 are also housed inside the casing 30. The casing 30 is fixed to the steering member 7 by fixing parts 32 provided at positions corresponding to the engaging parts 4A, 4B of the clutch 4.

[0029] The casing 30 has a notch 31 formed therein, which is a weakened portion. The rotating shaft 20 also has a small diameter portion 33 formed therein, which is a weakened portion. The small diameter portion 33 locally reduces the outer diameter of the rotating shaft 20. The small diameter portion 33 is disposed near the notch 31 of the casing 30. The notch 31 and the small diameter portion 33 are disposed between the reaction force reducer 18 and the engagement portion 4A of the clutch 4 in the vehicle width direction.

[0030] 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.

[0031] Reaction motor ECU 21 and steering motor ECU 28 communicate with each other to determine whether the steer-by-wire system is operating normally or abnormally. If reaction motor ECU 21 and 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, reaction motor ECU 21 causes reaction motor 17 to generate a steering reaction force on first steering shaft 2, and steering motor ECU 28 causes steering motor 23 to steer the steered wheels. At this time, reaction motor 17 and steering motor 23 are mechanically separated.

[0032] 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 9 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.

[0033] When steer-by-wire control is not being executed, output shaft 20 is mechanically connected to output shaft 27 by clutch 4, thereby mechanically connecting first steering shaft 2 to second steering shaft 3. As a result, steering wheel 9 is mechanically connected to the steered wheels, so that the driver can turn the steered wheels by rotating steering wheel 9.

[0034] In addition, reaction force reducer 18 functions as a speed increaser that increases the rotation of first steering shaft 2 and transmits it to reaction force worm shaft 20. The driver's steering rotation input from steering wheel 9 to first steering shaft 2 is increased in speed and transmitted to reaction force worm shaft 20 via reaction force worm wheel 19. The steering rotation transmitted to reaction force worm shaft 20 is transmitted at a constant speed to steering worm shaft 27 via engaged clutch 4, and then further reduced in speed by steering reducer 24 before being transmitted to second steering shaft 3. When either reaction force motor 17 or steering motor 23 is drivable, that motor can be used as an assist force generating source for the power steering function.

[0035] In this embodiment, the central axis of the first steering shaft 2, i.e., the central axis of the reaction force worm wheel 19, is geometrically skewed with respect to the central axis of the reaction force worm shaft 20. That is, the central axis of the first steering shaft 2 and the clutch central axis O do not intersect or are not parallel to each other. The angle between these two central axes is approximately 90 degrees. Furthermore, the central axis of the rotation of the steering worm wheel 26 is geometrically skewed with respect 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 clutch central axis O do not intersect or are not parallel to each other. The angle between these two central axes is approximately 90 degrees. Note that the angle formed by two lines that are skewed in three-dimensional space is the angle formed by two lines on a plane that includes the intersecting two lines when one line is translated so as to intersect with the other line.

[0036] Furthermore, the central axis of the first steering shaft 2, the central axis of the second steering shaft 3, and the clutch central axis O are geometrically skewed relative to one another. That is, the central axis of the first steering shaft 2, the central axis of the second steering shaft 3, and the clutch central axis O do not intersect with one another, nor are they parallel to one another. The first steering shaft 2 and the second steering shaft 3 are disposed offset in the vehicle width direction. In this embodiment, the second steering shaft 3 is disposed on the left side of the first steering shaft 2.

[0037] In this embodiment, second steering shaft 3 is disposed on the same side as first steering shaft 2 with respect to reference plane P (see FIG. 1 ), and further outward in the vehicle width direction than first steering shaft 2. Reference plane P is a plane perpendicular to the vehicle width direction that passes through the center of vehicle V in the vehicle width direction. Also, in this embodiment, clutch 4, reaction force actuator 22, and steering actuator 29 are disposed side by side in a direction that intersects with a vertical plane that includes the central axis of first steering shaft 2. In other words, the angle between this vertical plane and the arrangement direction of clutch 4, reaction force actuator 22, and steering actuator 29 is greater than 0 degrees. This arrangement direction is defined as a direction parallel to a line that passes through output shaft 20 of reaction force motor 17 and output shaft 27 of steering motor 23.

[0038] The effects of the steer-by-wire system 1 according to this embodiment will be described.

[0039] (1) In the steer-by-wire mechanism 1, the second steering shaft 3 is disposed to the left of the first steering shaft 2. That is, the second steering shaft 3 is disposed offset in the vehicle width direction relative to the first steering shaft 2. This increases the design freedom for the placement of the brake pedal 10 and the accelerator pedal 11. Furthermore, because the brake pedal 10 and the accelerator pedal 11 move back and forth, interference with the intermediate shafts is usually a problem. To avoid this interference, the pedal stays may be lengthened or bent. In the steer-by-wire mechanism 1, the second steering shaft 3, which corresponds to the intermediate shaft, is disposed offset in the vehicle width direction relative to the first steering shaft 2, allowing the pedal placement and pedal shape to be optimized. In particular, in the steer-by-wire mechanism 1, the central axis of the first steering shaft 2, the central axis of the second steering shaft 3, and the clutch central axis O do not intersect or are parallel to one another. This allows the second steering shaft 3 to be offset more significantly in the vehicle width direction relative to the first steering shaft 2 within a narrow space in the vehicle's fore-and-aft direction. That is, the degree of freedom in the arrangement of the second steering shaft 3 relative to the first steering shaft 2 is further improved. Note that the offset direction is not limited to the above. In other embodiments, the second steering shaft 3 may be arranged on the right side of the first steering shaft 2.

[0040] (2) The steer-by-wire mechanism 1 includes a clutch 4 that mechanically couples the first steering shaft 2 and the second steering shaft 3. Therefore, when an abnormality occurs in the steer-by-wire system, the clutch 4 can mechanically couple the first steering shaft 2 and the second steering shaft 3. As a result, the driver can steer the steered wheels by inputting a steering rotation to the first steering shaft 2 via the steering wheel 9, thereby improving limp-home performance.

[0041] (3) In the steer-by-wire mechanism 1, the second steering shaft 3 is disposed on the same side as the first steering shaft 2 with respect to the reference plane P, and further outward in the vehicle width direction than the first steering shaft 2. That is, the first steering shaft 2 and the second steering shaft 3 are disposed offset in the vehicle width direction. Therefore, even if a collision load is input to the second steering shaft 3 during a frontal collision of the vehicle V, the collision load is prevented from being directly transmitted to the first steering shaft 2. This suppresses rearward movement of the steering wheel 9, thereby improving occupant protection performance. Furthermore, because the second steering shaft 3 is disposed further outward in the vehicle width direction than the first steering shaft 2, it is possible to effectively utilize the space in the central region of the front passenger compartment in the vehicle width direction.

[0042] (4) Steer-by-wire mechanism 1 is equipped with steering actuator 29. Steering actuator 29 has steering motor 23 that generates a steering force, and steering reducer 24 that reduces the rotation of steering motor 23 and transmits it to second steering shaft 3. Steering actuator 29 is located on the passenger compartment side of dash panel 16. That is, because steering motor 23 is located inside the passenger compartment, high watertightness is not required, and there is no need to provide steering motor 23 with a watertight structure. This allows the structure of steering motor 23 to be simplified, and manufacturing costs to be reduced. Furthermore, heat dissipation from steering motor 23 can be promoted compared to when a watertight structure is used.

[0043] (5) The steer-by-wire mechanism 1 includes a reaction force actuator 22. The reaction force actuator 22 includes a reaction force motor 17 that generates a steering reaction force, and a reaction force reducer 18 that reduces the rotation speed of the reaction force motor 17 and transmits it to the first steering shaft 2. The reaction force actuator 22 is disposed on the passenger compartment side of the dash panel 16. That is, because the reaction force motor 17 is disposed inside the passenger compartment, high watertightness is not required, and there is no need to provide the reaction force motor 17 with a watertight structure. This simplifies the structure of the reaction force motor 17, thereby reducing its manufacturing costs. Furthermore, heat dissipation from the reaction force motor 17 can be promoted compared to when a watertight structure is employed.

[0044] (6) In the steer-by-wire mechanism 1, the clutch 4, the reaction force actuator 22, and the steering actuator 29 are arranged side by side in a direction intersecting a vertical plane including the central axis of the first steering shaft 2. Therefore, compared to when these are arranged side by side on the vertical plane, the clutch 4, the reaction force actuator 22, and the steering actuator 29 can be arranged in the vehicle cabin more space-efficiently.

[0045] (7) In the steer-by-wire mechanism 1, the output shaft 20 of the reaction motor 17, the reaction worm shaft 20, the output shaft 27 of the steering motor 23, and the steering worm shaft 27 are arranged along the clutch center axis O, which is parallel to the vehicle width direction. Therefore, the reaction actuator 22, the clutch 4, and the steering actuator 29 can be arranged in the vehicle interior with even greater space efficiency.

[0046] (8) In the steer-by-wire mechanism 1, the small diameter portion 33, which is a weakened portion, is provided between the reaction force reducer 18 and the engagement portion 4A of the clutch 4. The small diameter portion 33 deforms or breaks due to the collision load input to the second steering shaft 3 during a collision of the vehicle V. This more reliably reduces the collision load input to the first steering shaft 2, further suppressing the rearward movement of the steering wheel 9 during a vehicle collision, thereby further improving occupant protection performance. In addition, in the steer-by-wire mechanism 1, the casing 30 also has a notch 31, which is a weakened portion, formed in a position near the small diameter portion 33. Therefore, according to the steer-by-wire mechanism 1, the casing 30 deforms or breaks starting from the notch 31 during a collision of the vehicle V, thereby more reliably deforming or breaking the small diameter portion 33. Furthermore, because the weakened portion is provided between the reaction force reducer 18 and the engagement portion 4A of the clutch 4, the distance between the weakened portion and the second steering shaft 3 is greater than if the weakened portion were provided closer to the steering actuator 29 than in the range. Therefore, the weak portion can be more reliably deformed or broken by the collision load input to the second steering shaft 3.

[0047] (9) In the above embodiment, the diameter of the steering worm wheel 26 of the steering reducer 24 is larger than the diameter of the reaction worm wheel 19 of the reaction reducer 18 (see FIG. 5). In other words, when the reduction ratio of the steering reducer 24 is smaller than the reduction ratio of the reaction reducer 18 and the clutch 4 is in the engaged state, the rotation of the steering wheel 9 is reduced in speed by the reaction reducer 18 and the steering reducer 24 and is transmitted to the second steering shaft 3. Therefore, the steering force required for steering can be reduced when steer-by-wire control is not being executed.

[0048] 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.

[0049] For example, in the above embodiment, the small diameter portion 33 is formed on the rotating shaft 20 as the weak portion. However, a flexible coupling may be provided as the weak portion at the position of the small diameter portion 33. The flexible coupling can transmit rotational power while allowing for eccentricity, angular misalignment, and runout of the rotating shaft 20. Flexible couplings of various types, such as slit type, disk type, and Oldham type, can be used as the flexible coupling.

[0050] Furthermore, in the above embodiment, the clutch central axis O is located below the rotational center axis of the reaction force worm wheel 19. However, the clutch central axis O may be located above the rotational center axis of the reaction force worm wheel 19. Similarly, in the above embodiment, the clutch central axis O is located below the rotational center axis of the steering worm wheel 26. However, the clutch central axis O may be located above the rotational center axis of the steering worm wheel 26. Furthermore, the rotational center axis of the reaction force worm wheel 19 and the rotational center axis of the steering worm wheel 26 may be located on opposite sides of the clutch central axis O.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 in plane symmetry with respect to the reference plane P.

[0055] This application claims priority to International Application PCT / JP2023 / 006131, filed February 21, 2023, the entire contents of which are incorporated herein by reference.

[0056] DESCRIPTION OF SYMBOLS 1 Steer-by-wire mechanism 2 First steering shaft 3 Second steering shaft 4 Clutch 4A, 4B Clutch engagement portion 16 Dash panel 17 Reaction motor (second motor) 18 Reaction reducer (second reducer) 22 Reaction actuator (second actuator) 23 Turning motor (first motor) 24 Turning reducer (first reducer) 29 Turning actuator (first actuator) 31 Notch (weakened portion) 33 Small diameter portion (weakened portion) P Reference plane (plane perpendicular to the vehicle width direction) V Vehicle

Claims

1. A steer-by-wire mechanism for a vehicle, comprising: a first steering shaft that transmits a steering reaction force to the steering unit; a second steering shaft that transmits a steering force to the steered wheels; a clutch that mechanically couples the first steering shaft and the second steering shaft; a first actuator including a first motor that generates the steering force and a first reducer that reduces the rotation of the first motor and transmits the reduced rotation to the second steering shaft, A steer-by-wire mechanism, wherein the first actuator and the second steering shaft are arranged on the same side as the first steering shaft with respect to the center of the vehicle in the vehicle width direction, and further outward in the vehicle width direction than the first steering shaft.

2. 2. The steer-by-wire system according to claim 1, wherein the first actuator is disposed on a passenger compartment side of a dash panel.

3. a second actuator including a second motor that generates the steering reaction force and a second reducer that reduces the rotation speed of the second motor and transmits the reduced rotation speed to the first steering shaft; 3. The steer-by-wire system according to claim 1, wherein the second actuator is disposed on a passenger compartment side of a dash panel.

4. 4. The steer-by-wire mechanism according to claim 3, wherein the clutch, the first actuator, and the second actuator are arranged side by side along a direction intersecting a vertical plane including a central axis of the first steering shaft.

5. 5. The steer-by-wire mechanism according to claim 3, wherein a weakened portion that is deformed or broken by a collision load input to the second steering shaft in the event of a collision of the vehicle is provided between the second reduction gear and the engagement portion of the clutch.