Steer-by-wire system

Abstract

To attain compactness.SOLUTION: A steer-by-wire system 100A having a rack shaft 4 which turns wheels 7 of a vehicle includes a first turning motor 31, a first pinion shaft 33 that accepts input of a drive force from the first turning motor 31 and is engaged with a rack gear 41 of the rack shaft 4, a second turning motor 36, and a second pinion shaft 38 that accepts input of a drive force from the second turning motor 36 and is engaged with the rack gear 41 of the rack shaft 4. The first pinion shaft 33 and the second pinion shaft 38 are inwardly inclined toward the center in the axial direction of the rack shaft 4 in a direction leading to the first turning motor 31 and second turning motor 36 from the rack gear 41.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a steer-by-wire system. [Background technology]

[0002] Patent Document 1 discloses a vehicle steering device with a steer-by-wire configuration, in which two pinion shafts meshing with a rack gear are inclined outward in a direction from the rack gear side toward each motor side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-030368 (see, for example, FIGS. 4-6) Summary of the Invention [Problem to be solved by the invention]

[0004] If the two pinion shafts are inclined outward, the two motors that drive the pinion shafts will be spaced apart due to the inclination (the distance between the motors will increase), which will increase the external dimensions and make it difficult to mount the system on a vehicle.

[0005] The present invention has been made in view of the above problems, and aims to achieve compactness. [Means for solving the problem]

[0006] The present invention is a steer-by-wire device having a rack shaft that steers the wheels of a vehicle, comprising: a first motor; a first pinion shaft that receives driving force from the first motor and meshes with a rack gear of the rack shaft; a second motor; and a second pinion shaft that receives driving force from the second motor and meshes with the rack gear of the rack shaft, wherein the first pinion shaft and the second pinion shaft are inclined inward toward the axial center of the rack shaft in a direction from the rack gear side toward the first motor side and the second motor side.

[0007] According to this invention, the inward inclination of the first pinion shaft and the second pinion shaft allows the first motor and the second motor to be moved inward, thereby suppressing the protrusion of the rack shaft in the axial direction (the direction in which the rack shaft extends), thereby making it possible to achieve compactness.

[0008] Furthermore, the present invention is characterized in that the first pinion shaft and the second pinion shaft are shifted from each other in the circumferential direction of the rack shaft.

[0009] According to this invention, one of the first pinion shaft and the second pinion shaft is displaced relative to the other, thereby making it possible to avoid interference with vehicle-mounted components that may occur due to an inward inclination.

[0010] Furthermore, the present invention is characterized in that the output shaft of the first motor and the output shaft of the second motor are provided along the rack shaft.

[0011] According to this invention, further compactness can be achieved by suppressing the protrusion of the first motor and the second motor in the radial direction of the rack shaft. [Effects of the Invention]

[0012] According to these inventions, compactness can be achieved. [Brief explanation of the drawings]

[0013] [Figure 1]1 is a schematic configuration diagram of a steer-by-wire system according to an embodiment of the present invention; [Figure 2] FIG. 10 is a diagram showing a main part of a first modified example. [Figure 3] FIG. 10 is a diagram showing a main part of a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] A steer-by-wire system 100A according to an embodiment of the present invention will be described with reference to Figure 1. Steer-by-wire system 100A is capable of steer-by-wire control for steering wheels 7 in accordance with the state of operation of steering wheel 1 by the driver, and includes steering wheel 1 which is steered by the driver, steering shaft 2 which rotates in accordance with the steering operation by the driver, rack shaft 4 which steers wheels 7, first steering motor 31 and second steering motor 36 which apply a steering force to rack shaft 4, and reaction motor 51 which applies a steering reaction force to steering shaft 2.

[0016] A steering angle sensor 21 is provided on the steering shaft 2 to detect the steering angle, which is the rotation angle of the steering wheel 1. Although not shown, the steering angle sensor 21 includes a center gear that rotates integrally with the steering shaft 2 and two outer gears that mesh with the center gear, and calculates the rotation angle of the center gear, i.e., the rotation angle of the steering shaft 2, based on changes in magnetic flux that accompany the rotation of the two outer gears.

[0017] Steer-by-wire device 100A is of a dual pinion type and includes first pinion shaft 33 to which driving force from first steering motor 31 is input, and second pinion shaft 38 to which driving force from second steering motor 36 is input. The driving forces of both first steering motor 31 and second steering motor 36 are used to steer wheels 7.

[0018] One of first steering motor 31 and second steering motor 36 also contributes to ensuring redundancy in case the other fails. For this reason, steer-by-wire device 100A is not provided with a clutch or other disconnection mechanism that enables mechanical steering of wheels 7 by steering operation in the event of a failure, and power is not transmitted between steering wheel 1 and wheels 7.

[0019] The driving force of first steering motor 31 has its rotational speed reduced by first reduction mechanism 32 and is then transmitted to first pinion shaft 33. First reduction mechanism 32 includes first worm shaft 32a connected to output shaft 31a of first steering motor 31, and first worm wheel 32b meshing with first worm shaft 32a and connected to first pinion shaft 33. First pinion shaft 33 has first pinion gear 33a that meshes with rack gear 41 formed on rack shaft 4, and meshes with rack shaft 4.

[0020] The driving force of second steering motor 36 has its rotational speed reduced by second reduction mechanism 37 and is then transmitted to second pinion shaft 38. Second reduction mechanism 37 includes second worm shaft 37a connected to output shaft 36a of second steering motor 36, and second worm wheel 37b meshing with second worm shaft 37a and connected to second pinion shaft 38. Second pinion shaft 38 has second pinion gear 38a that meshes with rack gear 41 formed on rack shaft 4, and meshes with rack shaft 4.

[0021] When first steering motor 31 and second steering motor 36 are driven in response to the steering operation of the driver, a steering force for steering wheels 7 is applied to rack shaft 4 through first pinion shaft 33 and second pinion shaft 38. At this time, the rotation of each pinion shaft 33, 38 is converted into linear motion by each pinion gear 33a, 38a and rack gear 41, and wheels 7 are turned via knuckle arm 6 by the linear motion of rack shaft 4.

[0022] A steering reaction force is applied by a reaction motor 51 in response to a steering operation by the driver. The driving force of the reaction motor 51 is input to the steering shaft 2 after the rotation speed is reduced by a third reduction mechanism 52. The third reduction mechanism 52 includes a worm shaft 52a connected to an output shaft 51a of the reaction motor 51, and a worm wheel 52b that meshes with the worm shaft 52a and is connected to the steering shaft 2. When the reaction motor 51 is driven, a steering reaction force is applied to the steering shaft 2, thereby imitating the weight of the steering wheel.

[0023] Steer-by-wire system 100A further comprises first turning controller 30 that controls the drive of first turning motor 31, second turning controller 35 that controls the drive of second turning motor 36, and reaction force controller 50 that controls the drive of reaction force motor 51. First turning controller 30, second turning controller 35 and reaction force controller 50 are connected so as to be able to communicate with each other, and controllers 30, 35 and 50 receive as input the detection signal of steering angle sensor 21 as well as vehicle state information such as vehicle speed.

[0024] In steer-by-wire control, steering controllers 30, 35 control steering motors 31, 36 in accordance with the operating state of steering wheel 1 to steer wheels 7. Steering controllers 30, 35 set a target steering angle based on the detection result of steering angle sensor 21 and the vehicle speed, and control steering motors 31, 36 so that the steering angle of wheels 7 matches the target steering angle. Also in steer-by-wire control, reaction force controller 50 controls reaction force motor 51 in accordance with the steering state of wheels 7 to apply a steering reaction force to steering wheel 1. Reaction force controller 50 sets a target steering reaction force equivalent to the reaction force received from the road surface in response to a steering operation, and controls reaction force motor 51 so that the steering reaction force applied to steering shaft 2 matches the target steering reaction force.

[0025] Steering motors 31, 36, speed reduction mechanisms 32, 37, pinion shafts 33, 38, and rack shaft 4 constitute steering mechanism S, which steers wheels 7 using the driving force of steering motors 31, 36. Steering mechanism S is required to avoid interference with vehicle structures and to ensure clearance, and if the external dimensions of steering mechanism S are large, it will be difficult to mount on the vehicle.

[0026] To this end, the steer-by-wire system 100A is configured as further described below.

[0027] First pinion shaft 33 inclines inward toward the axial center of rack shaft 4 in the direction from the rack gear 41 side toward first steering motor 31 side (the side to which first steering motor 31 is connected). Similarly, second pinion shaft 38 inclines inward toward the axial center of rack shaft 4 in the direction from the rack gear 41 side toward second steering motor 36 side (the side to which second steering motor 36 is connected).

[0028] The first pinion shaft 33 and the second pinion shaft 38 are inclined inward when viewed in the radial direction of the rack shaft 4. The first pinion shaft 33 is inclined inward when viewed in a direction perpendicular to the rack shaft 4 and the first pinion shaft 33 (as shown in FIG. 1), and the second pinion shaft 38 is inclined inward when viewed in a direction perpendicular to the rack shaft 4 and the second pinion shaft 38 (as shown in FIG. 1).

[0029] By inclining pinion shafts 33, 38 inward, it is possible to prevent steering motors 31, 36 from protruding in the axial direction of rack shaft 4. In other words, it is possible to reduce distance D between steering motors 31, 36 in the axial direction of rack shaft 4, and it is possible to configure steer-by-wire device 100A in a compact manner.

[0030] As mentioned above, no power is transmitted between the steering wheel 1 and the wheels 7. This alleviates layout restrictions such as requiring the pinion shafts 33, 38 to be inclined outward for connection with the steering wheel 1, thereby increasing design freedom. In other words, since there is no obstacle to inclining the pinion shafts 33, 38 inward, the pinion shafts 33, 38 can be inclined inward.

[0031] First pinion shaft 33 and second pinion shaft 38 are provided at the same position in the circumferential direction of rack shaft 4. In other words, pinion shafts 33, 38 are provided so that the direction perpendicular to rack shaft 4 and first pinion shaft 33 and the direction perpendicular to rack shaft 4 and second pinion shaft 38 are oriented in the same direction. For this reason, the distance between pinion shafts 33, 38 along the axial direction of rack shaft 4 is shorter on the steering motor 31, 36 side than on the rack gear 41 side.

[0032] The first pinion shaft 33 and the second pinion shaft 38 are provided symmetrically with respect to the axial direction of the rack shaft 4. The pinion shafts 33, 38 are provided symmetrically with respect to an imaginary plane that passes through the axial center of the rack shaft 4 and is perpendicular to the rack shaft 4. The symmetry allows for a simpler structure and improves left-right balance.

[0033] Output shaft 31a of first steering motor 31 and output shaft 36a of second steering motor 36 are provided along rack shaft 4. This makes it possible to reduce protrusion of steering motors 31, 36 in the radial direction of rack shaft 4 compared to when output shafts 31a, 36a are provided along a direction perpendicular to pinion shafts 33, 38.

[0034] Note that output shafts 31a, 36a may be tilted from a state parallel to rack shaft 4 in a direction in which steering motors 31, 36 move closer to rack shaft 4, for example, at an angle less than the angle at which output shafts 31a, 36a become parallel to pinion shafts 33, 38 (for example, an angle within a range in which steering motors 31, 36 do not interfere with housing 5, which will be described later). Also, output shafts 31a, 36a may be tilted from a state parallel to rack shaft 4 in a direction in which steering motors 31, 36 move away from rack shaft 4, for example, at an angle less than the angle at which output shafts 31a, 36a become perpendicular to pinion shafts 33, 38 (for example, an angle at which interference between steering motors 31, 36 and other vehicle-mounted components can be avoided).

[0035] In the former case, the protrusion of steering motors 31, 36 in the radial direction of rack shaft 4 can be further reduced compared to when output shafts 31a, 36a are parallel to rack shaft 4. In the latter case, interference can be avoided if other vehicle-mounted components are located near rack shaft 4. These cases, as well as when output shafts 31a, 36a are parallel to rack shaft 4, are also included in the output shafts 31a, 36a being provided along rack shaft 4.

[0036] First turning motor 31 and second turning motor 36 are provided outside first reduction gear mechanism 32 and second reduction gear mechanism 37 in the axial direction of rack shaft 4. This allows turning motors 31, 36 and reduction gear mechanisms 32, 37 to be positioned closer to the inside than when turning motors 31, 36 are provided inside reduction gear mechanisms 32, 37. Therefore, the axial protrusion of rack shaft 4 as a whole of turning motors 31, 36 and reduction gear mechanisms 32, 37 can be reduced.

[0037] Rack gear 41 has a first rack gear 41a that meshes with first pinion gear 33a, and a second rack gear 41b that meshes with second pinion gear 38a. First rack gear 41a, together with first steering motor 31, first reduction mechanism 32, and first pinion shaft 33, constitutes a first steering mechanism S1 that steers wheels 7 with the driving force of first steering motor 31, and second rack gear 41b, together with second steering motor 36, second reduction mechanism 37, and second pinion shaft 38, constitutes a second steering mechanism S2 that steers wheels 7 with the driving force of second steering motor 36.

[0038] An intermediate portion 42 where no rack gear 41 is formed is provided between the first rack gear 41a and the second rack gear 41b on the rack shaft 4. The intermediate portion 42 is adjacent to the first rack gear 41a and the second rack gear 41b, and separates the first rack gear 41a from the second rack gear 41b. The intermediate portion 42 is provided for the following reasons.

[0039] The rack gear 41 is subjected to induction hardening (direct current heating) in which a high-frequency current is directly passed through it, and during hardening, electrodes are placed on both sides of the rack gear 41 to pass the high-frequency current through them. This allows for localized hardening of the rack gear 41 that requires hardening, thereby suppressing distortion of the rack shaft 4.

[0040] On the other hand, if rack gear 41 becomes too long, it becomes difficult to ensure the quality of the hardening due to the mass effect. For this reason, in steer-by-wire system 100A, by providing intermediate portion 42, rack gear 41 is configured with two rack gears, first rack gear 41a and second rack gear 41b, and hardening is performed separately for rack gears 41a and 41b.

[0041] The rack shaft 4 is accommodated in a housing 5 indicated by a two-dot dash line together with the first reduction mechanism 32, the first pinion shaft 33, the second reduction mechanism 37, and the second pinion shaft 38. The housing 5 has a rack portion 5a that accommodates the rack shaft 4, a first gear box portion 5b that accommodates the first reduction mechanism 32 and the first pinion shaft 33, and a second gear box portion 5c that accommodates the second reduction mechanism 37 and the second pinion shaft 38.

[0042] The housing 5 is manufactured (cast) by die casting as a single housing in which the rack portion 5a and the gear box portions 5b, 5c are integrally molded. When manufacturing the single housing 5 by die casting, the gear box portions 5b, 5c are molded using, for example, a slide core that slides in conjunction with the opening and closing of fixed and movable molds.

[0043] In this case, since it is necessary to configure a slide core in the mold, the layout (inclination angle and axial position) of the pinion shafts 33, 38 is set within a range in which the slide core can be formed. In other words, the layout of the pinion shafts 33, 38 is limited by the die-casting method, which requires that the slide core can be formed.

[0044] The slide core is easier to establish the more gentle the inward inclination of the pinion shafts 33, 38 (as the inclination approaches the vertical direction in FIG. 1), and the more gentle the inward inclination, the further apart the reduction mechanisms 32, 37 are, so it becomes easier to move the steering motors 31, 36 (in other words, the steering mechanisms S1, S2) inward and shorten the distance D.

[0045] On the other hand, if the inward inclination becomes gentler, steering motors 31, 36 will move away from each other and the axial protrusion of rack shaft 4 will increase. Also, if steering mechanisms S1, S2 are moved inward, rack gears 41a, 41b will move closer to each other, so there is a manufacturing method limitation in induction hardening in that intermediate section 42 is required to move pinion shafts 33, 38 inward (in other words, to move steering motors 31, 36 inward).

[0046] Therefore, the layout of the pinion shafts 33, 38 is limited by the manufacturing methods of die casting and induction hardening, and the layout of the pinion shafts 33, 38 is determined taking these limitations into consideration.

[0047] For example, if the limit to which pinion shafts 33, 38 can be moved inward is determined by induction hardening, pinion shafts 33, 38 can be moved inward as far as the limit allowed by the induction hardening process, and then tilted inward around pinion gears 33a, 38a within the range in which the slide core is established. This allows steering motors 31, 36 to be moved inward more than when pinion shafts 33, 38 are tilted outward, and therefore it is possible to prevent steering motors 31, 36 from protruding in the axial direction of rack shaft 4 while moving steering motors 31, 36 (in other words, steering mechanisms S1, S2) inward as far as the limit allowed by the induction hardening process.

[0048] This can also be explained as follows, using distance D as a reference: For example, if the steering mechanisms S1, S2 are moved inward as far as possible within the limits of induction hardening techniques in the state shown in Fig. 1, and the pinion shafts 33, 38 are to be tilted outward around the worm wheels 32b, 37b in the positions shown in Fig. 1, then the rack gears 41a, 41b must be moved inward.

[0049] However, because intermediate portion 42 must have a sufficient length for induction hardening, rack gears 41a, 41b cannot be moved further inward than the position shown in Figure 1. Therefore, to achieve the outward tilt, steering mechanisms S1, S2 must be moved outward, increasing distance D. For this reason, when pinion shafts 33, 38 are tilted outward, steering motors 31, 36 protrude more in the axial direction of rack shaft 4 than when they are tilted inward.

[0050] Note that a retaining core, for example, may be used instead of the slide core, and in this case, since it is not necessary to form a slide core, the layout is not particularly limited by the die casting. Also, the housing 5 may be, for example, a composite housing in which the rack portion 5a and the gear box portions 5b, 5c are molded separately and integrated by bolting or the like, and in this case, since it is not necessary to use a slide core, the layout is similarly not limited.

[0051] In steer-by-wire system 100A configured as described above, first pinion shaft 33 and second pinion shaft 38 are inclined inward. This moves steering motors 31, 36 inward and suppresses protrusion in the direction in which rack shaft 4 extends (the axial direction of rack shaft 4), thereby enabling a compact design.

[0052] Furthermore, since pinion shafts 33, 38 are inclined inward, even if steering motors 31, 36 are moved inward to the limit of the induction hardening manufacturing method, further compactness can be achieved compared to a case where pinion shafts 33, 38 are not inclined inward.

[0053] In steer-by-wire system 100A, output shaft 31a of first steering motor 31 and output shaft 36a of second steering motor 36 are arranged along rack shaft 4. This makes it possible to prevent steering motors 31, 36 from protruding in the radial direction of rack shaft 4, thereby achieving further compactness.

[0054] (First Modification) Fig. 2 is a diagram showing the main parts of steer-by-wire system 100B according to the first modified example, as viewed from the first steering motor 31 side along the axial direction of rack shaft 4.

[0055] As shown in FIG. 2, in steer-by-wire device 100B according to the first modification, first pinion shaft 33 and second pinion shaft 38 are offset from each other in the circumferential direction of rack shaft 4. In other words, pinion shafts 33, 38 are located at different positions along the circumferential direction of rack shaft 4. In this example, when viewed along the axial direction of rack shaft 4 from first steering motor 31, second pinion shaft 38 is offset by 90° clockwise with respect to first pinion shaft 33. Note that rack gears 41a, 41b are also offset from each other in the circumferential direction of rack shaft 4 in accordance with pinion shafts 33, 38 which are offset from each other in the circumferential direction. Pinion shafts 33, 38 may be offset from each other by another angle, for example, 60°.

[0056] This configuration can avoid interference with vehicle-mounted components that may occur due to the inward tilt of first pinion shaft 33 and second pinion shaft 38. Note that the interference that may occur due to the inward tilt of pinion shafts 33, 38 may be interference between reduction mechanisms 32, 37.

[0057] Furthermore, in this case, in the die casting described above using a slide core, the slide core is easier to remove, making it easier to establish the slide core. Therefore, if the limit to how far pinion shafts 33, 38, which are provided at the same circumferential position, can be moved inward is determined by the die casting using a slide core (in other words, if pinion shafts 33, 38 are moved inward up to the limit imposed by the induction hardening process, the slide core cannot be removed in the die casting, and pinion shafts 33, 38 cannot be tilted inward at the desired tilt angle), even if steering motors 31, 36 are moved inward up to that limit, pinion shafts 33, 38 can be tilted inward by the amount that they can.

[0058] (Second Modification) Fig. 3 is a diagram showing a main part of a steer-by-wire system 100C according to a second modification. As shown in Fig. 3, in the steer-by-wire system 100C according to the second modification, the first pinion shaft 33 and the second pinion shaft 38 are arranged point-symmetrically with respect to the center point P of the rack shaft 4, and are thereby offset from each other in the circumferential direction of the rack shaft 4. In other words, this arrangement of the pinion shafts 33, 38 being point-symmetrical is also included in the pinion shafts 33, 38 being offset from each other in the circumferential direction. In this example, the second pinion shaft 38 is arranged so as to be point-symmetric with the first pinion shaft 33.

[0059] The rack gears 41a, 41b are also offset from each other in the circumferential direction of the rack shaft 4 in accordance with the pinion shafts 33, 38 that are offset from each other in the circumferential direction. The rotation direction of the second steering motor 36 and the teeth of the second worm shaft 37a and the second worm wheel 37b can be changed in accordance with the arrangement of the second pinion shaft 38, which is provided point-symmetrically with the first pinion shaft 33.

[0060] Even with this configuration, the slide core can be easily removed in the die casting using a slide core as described above. Therefore, as in the first modified example, when the limit to which pinion shafts 33, 38, which are provided at the same circumferential position, can be moved inward is determined by die casting using a slide core, even if steering motors 31, 36 are moved inward up to that limit, pinion shafts 33, 38 can be tilted inward, and steering motors 31, 36 can be moved further inward by that amount.

[0061] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0062] Steer-by-wire devices 100A, 100B, 100C each having a rack shaft 4 for steering wheels 7 of a vehicle include a first steering motor 31, a first pinion shaft 33 which receives a driving force from first steering motor 31 and meshes with a rack gear 41 of rack shaft 4, a second steering motor 36, and a second pinion shaft 38 which receives a driving force from second steering motor 36 and meshes with a rack gear 41 of rack shaft 4, The pinion shaft 33 and the second pinion shaft 38 are inclined inward toward the axial center of the rack shaft 4 in a direction from the rack gear 41 side toward the first steering motor 31 side and the second steering motor 36 side (i.e., in the case of the first pinion shaft 33, in a direction from the rack gear 41 side toward the first steering motor 31 side, and in the case of the second pinion shaft 38, in a direction from the rack gear 41 side toward the second steering motor 36 side).

[0063] According to this configuration, the inward inclination of the first pinion shaft 33 and the second pinion shaft 38 moves the first steering motor 31 and the second steering motor 36 inward, thereby suppressing protrusion in the direction in which the rack shaft 4 extends (the axial direction of the rack shaft 4), thereby making the system more compact.

[0064] In the steer-by-wire systems 100B and 100C, the first pinion shaft 33 and the second pinion shaft 38 are offset from each other in the circumferential direction of the rack shaft 4.

[0065] According to this configuration, one of first pinion shaft 33 and second pinion shaft 38 is displaced relative to the other, thereby making it possible to avoid interference with vehicle-mounted components that may occur due to an inward inclination.

[0066] In steer-by-wire systems 100A, 100B, 100C, output shaft 31a of first steering motor 31 and output shaft 36a of second steering motor 36 are provided along rack shaft 4.

[0067] According to this configuration, the protrusion of the first turning motor 31 and the second turning motor 36 in the radial direction of the rack shaft 4 is suppressed, thereby making it possible to achieve further compactness.

[0068] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0069] 2 Wheel, 4 Rack shaft, 31 First steering motor (first motor), 31a Output shaft, 33 First pinion shaft, 36 Second steering motor (second motor), 36a Output shaft, 38 Second pinion shaft, 41 Rack gear, 100A, 100B, 100C Steer-by-wire device

Claims

1. A steer-by-wire device having a rack shaft for steering the wheels of a vehicle, a first motor; a first pinion shaft that receives a driving force from the first motor and that meshes with a rack gear of the rack shaft; A second motor; a second pinion shaft that receives a driving force from the second motor and meshes with the rack gear of the rack shaft, the first pinion shaft and the second pinion shaft are inclined inward toward the axial center of the rack shaft in a direction from the rack gear side toward the first motor side and the second motor side, A steer-by-wire system characterized by:

2. 2. The steer-by-wire system according to claim 1, the first pinion shaft and the second pinion shaft are offset from each other in the circumferential direction of the rack shaft, A steer-by-wire system characterized by:

3. 3. The steer-by-wire system according to claim 1 or 2, The output shaft of the first motor and the output shaft of the second motor are provided along the rack shaft. A steer-by-wire system characterized by:

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