Steering device

Abstract

To reduce the dimension of a first steering mechanism in an axial direction.SOLUTION: A steering device includes: a first steering mechanism 7R that is linked with a steering wheel 9; and a second steering mechanism 7L which is a separate component from the first steering mechanism 7R, and which is not linked with the steering wheel. The first steering mechanism 7R does not include a steering assist mechanism which includes an electric motor, but includes: a first steering shaft 12; a torque sensor 10 that detects the steering torque of the first steering shaft; and a first ball screw mechanism 13 that decelerates the rotation from the first steering shaft 12, while the second steering mechanism 7L includes: a first electric motor 11 and a first reduction gear 48 that form the steering assist mechanism; and a second ball screw mechanism 49 that decelerates the rotation from a second steering shaft 47.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a steering device. [Background technology]

[0002] As a steering device, for example, the steering devices described in Patent Documents 1 and 2 below are known.

[0003] The steering device of Patent Document 1 is configured as an integral type steering device used in large vehicles, etc. In this steering device, an electric motor that applies a steering assist force to the steering shaft and a reducer that reduces the rotational force of the electric motor are arranged on the ground side.

[0004] On the other hand, in the steering device of Patent Document 2, an electric motor that applies a steering assist force to the steering shaft and a reducer that reduces the rotational force of the electric motor are arranged on the driver's seat side. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-156082 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-306317 Summary of the Invention [Problem to be solved by the invention]

[0006] If the electric motor and reducer are placed on the ground side as in the steering device of Patent Document 1, there is a risk that the electric motor and reducer will interfere with peripheral vehicle equipment, which poses a problem of poor mountability of components associated with the steering device.

[0007] Furthermore, if the electric motor and reducer are located on the driver's seat side to solve this problem, as in the steering device of Patent Document 2, the electric motor and reducer must be located while avoiding interference with sensors for the steering shaft, which tends to complicate the internal structure of the steering device and increase the axial dimension of the device.As a result, in the steering device of Patent Document 2, there is a risk that the housing that houses the electric motor and other components will interfere with the floor panel, for example.

[0008] The present invention was devised in consideration of the above technical problems, and one of its objects is to provide a steering device that can shorten the axial dimension of the first steering mechanism connected to the steering wheel. [Means for solving the problem]

[0009] A steering device of the present invention has a first steering mechanism linked to a steering wheel and a second steering mechanism separate from the first steering mechanism and not linked to the steering wheel. The first steering mechanism has a first steering shaft to which rotation from the steering wheel is input, a torque sensor provided on the first steering shaft for detecting steering torque of the first steering shaft, and a first reduction mechanism provided on the first steering shaft for reducing the rotation from the first steering shaft. The second steering mechanism has a second steering shaft, a first electric motor for applying a rotational force to the second steering shaft, a first reduction gear provided on the second steering shaft for reducing the rotational force of the first electric motor, and a second reduction mechanism provided on the second steering shaft for reducing the rotation from the second steering shaft. [Effects of the Invention]

[0010] According to the present invention, the axial dimension of the first steering mechanism can be shortened. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing the configuration of a steering device according to a first embodiment. [Figure 2] FIG. 2 is a longitudinal sectional view of a first steering mechanism according to the first embodiment. [Figure 3]FIG. 3 is a vertical cross-sectional view of a second steering mechanism according to the first embodiment. [Figure 4] FIG. 10 is a vertical cross-sectional view of a first steering mechanism according to a second embodiment. [Figure 5] FIG. 10 is a vertical cross-sectional view of a first steering mechanism according to a third embodiment. [Figure 6] FIG. 10 is a vertical cross-sectional view of a first steering mechanism according to a fourth embodiment. [Figure 7] FIG. 10 is a vertical cross-sectional view of a first steering mechanism according to a fifth embodiment. [Figure 8] FIG. 13 is a vertical cross-sectional view of a second steering mechanism according to a sixth embodiment. [Figure 9] FIG. 13 is a vertical cross-sectional view of a second steering mechanism according to a seventh embodiment. [Figure 10] FIG. 13 is a vertical cross-sectional view of a second steering mechanism according to an eighth embodiment. [Figure 11] FIG. 13 is a vertical cross-sectional view of a second steering mechanism according to a ninth embodiment. [Figure 12] FIG. 22 is a longitudinal sectional view of a second steering mechanism according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a steering device of the present invention will be described with reference to the drawings. In the following embodiment, an example in which the steering device is applied as an integral type steering device used in a large vehicle or the like is shown.

[0013] [First embodiment] FIG. 1 is a diagram showing the configuration of a steering device according to a first embodiment.

[0014] A large vehicle to which the steering device is applied has a first steered wheel 1R, which is the right front wheel, and a second steered wheel 1L, which is the left front wheel. The first steered wheel 1R and the second steered wheel 1L are connected by a tie rod 2 and a first tie rod arm 3R and a second tie rod arm 3L provided on both ends of the tie rod 2. This allows the first steered wheel 1R and the second steered wheel 1L to be steered in conjunction with each other.

[0015] The first steering wheel 1R is connected to the first steering mechanism 7R via a first steering arm 4R, a first drag link 5R, and a first pitman arm 6R. Similarly, the second steering wheel 1L is connected to the second steering mechanism 7L via a second steering arm 4L, a second drag link 5L, and a second pitman arm 6L. The tie rod 2 and the above arms and links form a link mechanism that interlocks a first transmission mechanism 46 (described below) of the first steering mechanism 7R with a second transmission mechanism 78 (described below) of the second steering mechanism 7L.

[0016] The steering device has a first steering mechanism 7R connected to a steering wheel 9 via a steering shaft 8, and a second steering mechanism 7L that is separate from the first steering mechanism 7R and is not connected to the steering wheel 9. The first steering mechanism 7R drives a first pitman arm 6R to steer the first steering wheel 1R in response to operation of the steering wheel 9 by the driver. The second steering mechanism 7L drives a first electric motor 11 provided in the second steering mechanism 7L to rotate based on steering torque detected by a torque sensor 10 (see FIG. 2) provided in the first steering mechanism 7R, thereby driving a second pitman arm 6L to steer the second steering wheel 1L.

[0017] Fig. 2 is a vertical cross-sectional view of the first steering mechanism 7R of the first embodiment. For convenience of explanation, the internal structures of the detection unit 27 and signal processing unit 28 of the torque sensor 10 are omitted from Fig. 2. The detection unit 27 and the signal processing unit 28 will be mainly described with reference to the shapes of the housings that accommodate them.

[0018] The first steering mechanism 7R is mainly composed of a first steering shaft 12 linked to the steering wheel 9, a torque sensor 10 provided around the first steering shaft 12 and detecting the steering torque of the first steering shaft 12, a first ball screw mechanism 13 which is a speed reduction mechanism that reduces the rotation speed of the first steering shaft 12, and a first sector gear 14 which is connected to the first steering shaft 12 via the first ball screw mechanism 13 and is used to drive the first pitman arm 6R.

[0019] Here, in Figure 2, for the sake of convenience, the side of the rotation axis Z1 of the first steering shaft 12 that is connected to the steering wheel 9 (upper side in the figure) will be referred to as the "first end 12a," and the side where the first four-point contact ball bearing 25 is attached (lower side in the figure) will be referred to as the "second end 12b."

[0020] The first steering shaft 12 passes through a cylindrical first housing 15 and a cylindrical first connecting member 16 provided adjacent to the first housing 15, and extends into a cylindrical second housing 17 provided on the opposite side of the first housing 15 with the first connecting member 16 in between. The first steering shaft 12 includes an input shaft 18 to which rotational force from the steering wheel 9 is transmitted, and an output shaft 20 connected to the input shaft 18 via a torsion bar 19.

[0021] The input shaft 18 has a first end shaft portion 18a located on the first end 12a side, an intermediate shaft portion 18b formed integrally with the first end shaft portion 18a and having a larger diameter than the first end shaft portion 18a, and an opposite end shaft portion 18c formed integrally with the intermediate shaft portion 18b and having a smaller diameter than the intermediate shaft portion 18b. An annular dust seal 21 is provided on the outer circumferential surface of the intermediate shaft portion 18b at a position close to the first end shaft portion 18a to prevent dust and dirt from entering the first housing 15 and the like. A cylindrical magnet portion 22, whose magnetic field change is detected by the torque sensor 10, is crimped and fixed to the outer circumferential surface of the intermediate shaft portion 18b at a position axially adjacent to the opposite end shaft portion 18c.

[0022] The output shaft 20 includes a cylindrical first shaft portion 20a located on the first end 12a side, a cylindrical second shaft portion 20b formed integrally with the first shaft portion 20a and having a larger diameter than the first shaft portion 20a, a third shaft portion 20c formed integrally with the second shaft portion 20b and having a larger diameter than the second shaft portion 20b, and a fourth shaft portion 20d formed integrally with the third shaft portion 20c and having a smaller diameter than the third shaft portion 20c. A reduced-diameter portion 27b of a detection unit 27 (described later) of the torque sensor 10 is press-fitted and fixed to the outer circumferential surface of the first shaft portion 20a. A first deep-groove ball bearing 23 is provided on the outer circumferential surface of the second shaft portion 20b to rotatably support the second shaft portion 20b. A first nut 24, which constitutes a part of the first ball screw mechanism 13, is provided around the third shaft portion 20c. Additionally, a first four-point contact ball bearing 25 that rotatably supports the fourth shaft portion 20d is provided on the outer peripheral surface of the fourth shaft portion 20d. Furthermore, a first fixing member 26 that fixes the first four-point contact ball bearing 25 to the third shaft portion 20c is provided on the outer peripheral surface of the fourth shaft portion 20d at a position closer to the second end portion 12b than the first four-point contact ball bearing 25.

[0023] The first housing 15 is formed in a generally cylindrical shape and mainly accommodates the torque sensor 10 provided around the input shaft 18 .

[0024] The first connecting member 16 is made of a metal material and has a generally cylindrical shape. The first connecting member 16 connects an abutment surface 15b on the second end 12b side of an annular flange portion 15a provided on the first housing 15 to an end face 17a on the first end 12a side of the second housing 17, and holds a shielded or rubber-sealed first deep groove ball bearing 23 between the first connecting member 16 and the outer peripheral surface of the second shaft portion 20b of the output shaft 20.

[0025] The second housing 17 is made of a metal material and has a generally cylindrical shape. The second housing 17 has a first nut accommodating portion 17b that mainly accommodates the first nut 24 provided around the output shaft 20, and a first sector gear accommodating portion 17c that communicates with the first nut accommodating portion 17b and accommodates the first sector gear 14.

[0026] The torque sensor 10 is configured as a well-known magnetic torque sensor that uses a magnet portion 22 that is fixed by crimping to the outer circumferential surface of the input shaft 18. The torque sensor 10 has a detection portion 27 that detects a signal corresponding to a change in magnetism of the magnet portion 22 that rotates together with the input shaft 18, and a signal processing portion 28 that is disposed around the detection portion 27 and processes the magnetic flux detected by the detection portion 27 to calculate the steering torque. Note that the signal processing portion 28 may be configured to calculate the steering angle instead of or in addition to the steering torque.

[0027] The detection unit 27 (detection unit housing) is made of synthetic resin and metal and has an annular shape. The detection unit 27 is disposed around the magnet unit 22. A first annular protrusion 27a is formed on the axial end face of the detection unit 27 on the first end 12a side at a position adjacent to the inner circumferential surface of the detection unit 27, protruding toward the first end 12a along the direction of the rotation axis Z1 of the first steering shaft 12. A first reduced diameter portion 27b is formed on the axial end face of the detection unit 27 on the second end 12b side at a position adjacent to the inner circumferential surface of the detection unit 27, protruding toward the second end 12b in a stepped manner. The first reduced diameter portion 27b is press-fitted and fixed to the outer circumferential surface of the first shaft portion 20a of the output shaft 20, and rotates together with the output shaft 20.

[0028] The signal processing unit 28 (a housing of the signal processing unit) is made of synthetic resin and has an annular shape. The signal processing unit 28 is disposed around the detection unit 27. Two cylindrical first rotation restricting portions 28a are formed on the axial end face of the signal processing unit 28 on the second end 12b side at positions adjacent to the outer peripheral surface of the signal processing unit 28. The first rotation restricting portions 28a restrict the signal processing unit 28 from rotating in response to the rotation of the detection unit 27. As shown in FIG. 2, the two first rotation restricting portions 28a are disposed symmetrically in the radial direction of the first steering shaft 12 across the output shaft 20. Each first rotation restricting portion 28a has a columnar first extension portion 28b that protrudes with a constant diameter toward the second end 12b along the direction of the rotation axis Z1 of the first steering shaft 12 and then reduces in diameter in a conical shape, and a columnar first rotation restricting cylindrical portion 28c that protrudes from the tip of the first extension portion 28b toward the second end 12b along the direction of the rotation axis Z1 of the first steering shaft 12. Each first rotation restricting cylindrical portion 28c is inserted into a first circular recess 16b formed on a surface 16a of the first connecting member 16 that faces the torque sensor 10 in the axial direction of the first steering shaft 12. Therefore, the first rotation restricting cylindrical portion 28c engages with the first circular hole portion 16b in the radial direction of the first steering shaft 12, and this engagement holds the signal detecting portion 27 in the first connecting member 16. The bottom of the first circular hole portion 16b has a first conical portion 16c that tapers in diameter conically toward the second end portion 12b.

[0029] The first deep groove ball bearing 23 is a bearing arranged between the second shaft portion 20b of the output shaft 20 and the first connecting member 16 at a position on the first steering shaft 12 adjacent to the torque sensor 10, and receives a radial force acting on the output shaft 20. The first deep groove ball bearing 23 is arranged on the opposite side of the first four-point contact ball bearing 25 in the axial direction of the first steering shaft 12, with the first ball screw mechanism 13 in between.

[0030] Furthermore, an annular groove is formed on the outer circumferential surface of second shaft portion 20b at a position closer to third shaft portion 20c, into which a first O-ring 29, which is an annular sealing member made of, for example, rubber, is fitted. First O-ring 29 provides an airtight seal between the outer circumferential surface of second shaft portion 20b and the inner circumferential surface of first deep groove ball bearing 23.

[0031] The first connecting member 16 has an annular portion 16d, a first annular protrusion 16e protruding toward the first end 12a from a portion of the upper part of the annular portion 16d adjacent to the outer peripheral surface of the annular portion 16d, a second annular protrusion 16g protruding toward the second end 12b from a surface 16f of the annular portion 16d on the second end 12b side at a position closer to the inner peripheral portion of the annular portion 16d, and a first connecting member side protrusion 16h protruding radially outward from the outer peripheral surface of the annular portion 16d.

[0032] A first bolt hole 30 is formed in the first annular protrusion 16e and the annular portion 16d along the axial direction of the first steering shaft 12. A first bolt 31, which is a fixing member, is screwed into the first bolt hole 30 via a first bolt insertion hole 15c in a flange portion 15a provided in the first housing 15.

[0033] Further, a second bolt insertion hole 32 is formed through the first connecting member side overhanging portion 16h along the axial direction of the first steering shaft 12. A second bolt 33 serving as a fixing member passes through the second bolt insertion hole 32 of the first connecting member side overhanging portion 16h and is then screwed into a second bolt hole 34 of the housing side overhanging portion 17d that overhangs the outer periphery of the second housing 17.

[0034] The outer peripheral surface of second annular protrusion 16g has an annular groove into which a second O-ring 35, which is an annular sealing member made of, for example, rubber, is fitted. Second O-ring 35 provides an airtight seal between the outer peripheral surface of second annular protrusion 16g and the inner peripheral surface of second housing 17. The inner peripheral surface of second annular protrusion 16g continues beyond surface 16f toward first end 12a and holds the outer peripheral surface of outer race 23a of first deep groove ball bearing 23.

[0035] The first ball screw mechanism 13 is composed of a first steering shaft-side ball screw groove 36, which is a spiral groove provided on the outer peripheral surface of the third shaft portion 20c of the output shaft 20, a first nut-side ball screw groove 24a, which is a spiral groove provided on the inner peripheral surface of the first nut 24, and a plurality of balls 37 arranged between the ball screw grooves 36 and 24a. The balls 37 support the first nut 24 so as to be rotatable relative to the third shaft portion 20c.

[0036] Additionally, a plurality of first rack teeth 24b are formed on the outer periphery of the first nut 24 on the first sector gear accommodating portion 17c side. These first rack teeth 24b mesh with the first tooth portion 14a formed on the first sector gear 14.

[0037] The first four-point contact ball bearing 25 is disposed around the fourth shaft portion 20d of the output shaft 20 located on the opposite side of the first ball screw mechanism 13 from the torque sensor 10 of the first steering shaft 12. The first four-point contact ball bearing 25 receives both a thrust force acting in the axial direction of the first steering shaft 12, i.e., the direction of the rotation axis Z1, and a radial force acting in the radial direction of the first steering shaft 12. More specifically, a force acting on one of the four contact points of the first four-point contact ball bearing 25, i.e., a force F acting on the second end 12b side of the outer race 38 of the first four-point contact ball bearing 25 as shown in FIG. 2, will be described. This force F can be broken down into a thrust force F1 acting in the direction of the rotation axis Z1 of the first steering shaft 12 and a radial force F2 acting radially outward of the first steering shaft 12. Therefore, the first four-point contact ball bearing 25 receives a thrust force F1 acting via contact point P and a radial force F2 acting via contact point P but smaller than the thrust force F1. In one example, the thrust force F1 is approximately 1.5 to 2 times the radial force F2. Therefore, the first four-point contact ball bearing 25 is configured so that its contribution rate when receiving the thrust force F1 is much larger than its contribution rate when receiving the radial force F2. In a large vehicle having a first sector gear 14 as in this embodiment, the thrust force acting on the first steering shaft 12 is much larger than in a vehicle of average size. Therefore, it is advantageous to use the first four-point contact ball bearing 25 to simultaneously receive such a large thrust force and radial force.

[0038] Furthermore, the first four-point contact ball bearing 25 has an inner race 39 arranged on the outer circumferential side of the fourth shaft portion 20d, an outer race 38 arranged on the outer circumferential side of the inner race 39, and a plurality of balls 40 arranged between the inner race 39 and the outer race 38. The first four-point contact ball bearing 25 is press-fitted into the inner circumferential surface of the second housing 17. Of the inner corners 39a, 39b on the inner circumferential side of the inner race 39, the corner 39a on the first end 12a side abuts against a step 41 formed between the third shaft portion 20c and the fourth shaft portion 20d of the output shaft 20. Meanwhile, of the outer corners 38a, 38b on the outer circumferential side of the outer race 38, the corner 38a on the first end 12a side abuts against a step 42 provided on the inner circumferential surface of the second housing 17.

[0039] The first fixing member 26 is configured as a nut member and has a first fixing member-side internal thread portion 26a formed on its inner circumferential surface. This first fixing member-side internal thread portion 26a is threadedly engaged with a first steering shaft-side external thread portion 43 formed on the outer circumferential surface of the fourth shaft portion 20d of the output shaft 20. This threaded engagement presses a corner portion 39b of the inner race 39, pressing the corner portion 39a of the inner race 39 against a step portion 41 provided on the output shaft 20, thereby fixing the inner race 39 to the output shaft 20.

[0040] A disk-shaped first closing member 44 is provided at a position closer to the second end 12b than the first four-point contact ball bearing 25 in the direction of the rotation axis Z1 of the first steering shaft 12. This first closing member 44 closes the opening of the second housing 17 from the first four-point contact ball bearing 25 side and fixes the outer race 38 of the first four-point contact ball bearing 25 to the second housing 17. The first closing member 44 is made of metal or synthetic resin. The first closing member 44 has a circular plate-shaped bottom wall 44a and a cylindrical peripheral wall 44b that rises from the outer edge of the bottom wall 44a toward the first end 12a.

[0041] Additionally, an annular seal groove is formed in the outer peripheral surface of peripheral wall 44b at a position closer to axial end face 44c, into which a third O-ring 45, which is an annular seal member made of, for example, rubber, is fitted. Third O-ring 45 provides an airtight seal between the inner peripheral surface of second housing 17 and the outer peripheral surface of peripheral wall 44b.

[0042] Furthermore, a first closing member side male thread portion 44d is formed on the outer peripheral surface of the peripheral wall 44b at a position closer to the second end 12b than the third O-ring 45, and this first closing member side male thread portion 44d is threadedly engaged with a first housing side female thread portion 17e formed on the inner peripheral surface of the end portion on the second end 12b side of the second housing 17. This threaded engagement presses an axial end face 38c of the outer race 38, and presses a corner portion 38a of the outer race 38 against a step portion 42 of the second housing 17, thereby fixing the outer race 38 to the second housing 17.

[0043] The first sector gear 14 is provided swingably in a first sector gear accommodating portion 17c provided in the second housing 17. One axial end of the first sector gear 14 is connected to first rack teeth 24b of a first nut 24 via a first tooth portion 14a, and the other axial end is linked to the first steered wheel 1R via a first pitman arm 6R (see FIG. 1). The first tooth portion 14a of the first sector gear 14 and the first rack teeth 24b of the first nut 24 form a first transmission mechanism 46 that steers the first steered wheel 1R in accordance with the output from the first ball screw mechanism 13.

[0044] In this steering device, when the driver turns the steering wheel 9, the input shaft 18 rotates and the torsion bar 19 is twisted, and the resulting elastic force of the torsion bar 19 rotates the output shaft 20. As the output shaft 20 rotates, the first nut 24 moves in the direction of the rotation axis Z1 of the first steering shaft 12, causing the first sector gear 14 to rotate. As a result, the first pitman arm 6R is pulled in the vehicle body width direction, changing the orientation of the first steered wheel 1R.

[0045] FIG. 3 is a vertical cross-sectional view of the second steering mechanism 7L of the first embodiment.

[0046] The second steering mechanism 7L is mainly composed of a second steering shaft 47, a first electric motor 11 that imparts a rotational force to the second steering shaft 47, a first reducer 48 that reduces the rotational force of the first electric motor 11, and a second ball screw mechanism 49 that is provided on the second steering shaft 47 and is a reduction mechanism that reduces the rotation from the second steering shaft 47.

[0047] Here, in Figure 3, for ease of explanation, the side of the second steering shaft 47 in the direction of the rotation axis Z2 where the second deep groove ball bearing 53 is attached (upper side in the figure) is referred to as "one end 47a," and the side where the second four-point contact ball bearing 55 is attached (lower side in the figure) is referred to as "the other end 47b."

[0048] The second steering shaft 47 is housed in a space surrounded by a cylindrical third housing 50, a cylindrical second connecting member 51 arranged adjacent to the third housing 50, and a fourth housing 52 arranged adjacent to the second connecting member 51.

[0049] The second steering shaft 47 has a first medium diameter shaft portion 47c located on the one end 47a side, a large diameter shaft portion 47d formed integrally with the first medium diameter shaft portion 47c and having a diameter larger than that of the first medium diameter shaft portion 47c, a second medium diameter shaft portion 47e formed integrally with the large diameter shaft portion 47d and having a diameter smaller than that of the large diameter shaft portion 47d, a first small diameter shaft portion 47f formed integrally with the second medium diameter shaft portion 47e and having a diameter smaller than that of the second medium diameter shaft portion 47e, and a second small diameter shaft portion 47g formed integrally with the first small diameter shaft portion 47f and having a diameter smaller than that of the first small diameter shaft portion 47f.

[0050] A first core metal portion 62 of a first worm wheel 60 (described later) of the first reducer 48 is press-fitted and fixed onto the outer circumferential surface of the first medium diameter shaft portion 47c. A second deep groove ball bearing 53 that rotatably supports the large diameter shaft portion 47d is provided on the outer circumferential surface of the large diameter shaft portion 47d. A second nut 54 that constitutes a part of the second ball screw mechanism 49 is provided around the second medium diameter shaft portion 47e. A second four-point contact ball bearing 55 that rotatably supports the first small diameter shaft portion 47f is provided on the outer circumferential surface of the first small diameter shaft portion 47f. A second fixing member 56 that fixes the second four-point contact ball bearing 55 to the second steering shaft 47 is provided around the second small diameter shaft portion 47g.

[0051] The third housing 50 is formed in a cylindrical shape with a bottom from a metal material, and mainly houses a first reducer 48 arranged around the first medium diameter shaft portion 47c and a second deep groove ball bearing 53 arranged around the large diameter shaft portion 47d.

[0052] The second connecting member 51 is made of a metal material and has a generally cylindrical shape. The second connecting member 51 connects an end face 50a on the other end 47b side of the third housing 50 to an end face 52a on the one end 47a side of the fourth housing 52, and holds a shielded or rubber-sealed second deep groove ball bearing 53 between the second connecting member 51 and the outer peripheral surface of the large-diameter shaft portion 47d of the second steering shaft 47.

[0053] The fourth housing 52 is made of a metal material and has a generally cylindrical shape. The fourth housing 52 has a second nut accommodating portion 52b that mainly accommodates a second nut 54 provided around the second steering shaft 47, and a second sector gear accommodating portion 52c that communicates with the second nut accommodating portion 52b and accommodates a second sector gear 57.

[0054] The first electric motor 11 is driven and controlled based on steering torque detected by a torque sensor 10 provided in the first steering mechanism 7R, thereby applying a rotational force to the second steering shaft 47 via a first reduction gear 48. The first electric motor 11 is disposed on the opposite side of the second steering shaft 47 from the second sector gear 57, such that a first worm shaft 58 connected to a motor shaft (not shown) of the first electric motor 11 overlaps with a first medium-diameter shaft portion 47c of the second steering shaft 47 in the radial direction of the second steering shaft 47. The first electric motor 11 is housed in a first motor housing 11a having a cylindrical shape with a bottom. As shown in FIG. 3, the first motor housing 11a extends outward beyond the third housing 50 both in the direction of the rotation axis Z2 of the second steering shaft 47 and in the radial direction.

[0055] The first electric motor 11 is controlled and driven by a first control device 59 (see FIG. 1). More specifically, the steering torque detected by the torque sensor 10 of the first steering mechanism 7R is transmitted to the first control device 59, and the first electric motor 11 is controlled and driven based on the transmitted steering torque.

[0056] The first reducer 48 includes a first worm shaft 58 and a first worm wheel 60 that meshes with the first worm shaft 58. The first worm wheel 60 is formed by insert-molding a cylindrical metal first core portion 62 into a synthetic resin first gear forming portion 61. The first core portion 62 is press-fitted onto the outer peripheral surface of the first medium diameter shaft portion 47c of the second steering shaft 47, so that the first core portion 62 abuts against the axial end surface of the one end 47a of the large diameter shaft portion 47d.

[0057] The second deep groove ball bearing 53 is a bearing arranged between the large diameter shaft portion 47d of the second steering shaft 47 and the second connecting member 51, and receives a radial force that is a radial force acting on the second steering shaft 47. The second deep groove ball bearing 53 is arranged on the opposite side of the second four-point contact ball bearing 55 in the axial direction of the second steering shaft 47, with the second ball screw mechanism 49 sandwiched between them.

[0058] Furthermore, an annular groove is formed in the axial center of the outer circumferential surface of the large diameter shaft portion 47d, into which a fourth O-ring 63, which is an annular sealing member made of, for example, rubber, is fitted. The fourth O-ring 63 provides a liquid-tight seal between the outer circumferential surface of the large diameter shaft portion 47d and the inner circumferential surface of the second deep groove ball bearing 53. This allows lubricant to be stored near the first reducer 48 inside the third housing 50, improving lubrication of the meshing portion between the first worm shaft 58 and the first worm wheel 60.

[0059] The second connecting member 51 has a cylindrical main body 51a, an annular protrusion 51b protruding radially outward from the axial center position of the outer peripheral surface of the cylindrical main body 51a, an annular protrusion 51c protruding radially inward from a position on the inner peripheral surface of the cylindrical main body 51a closest to the one end 47a, a cylindrical extension 51d extending from the axial end of the annular protrusion 51c on the one end 47a side toward the one end 47a along the direction of the rotation axis Z2 of the second steering shaft 47, and an annular ceiling wall 51e extending radially inward from a position on the inner peripheral surface of the extension 51d closest to the one end 47a.

[0060] Furthermore, a portion 51f of the annular protrusion 51b, which faces the second sector gear 57 and the second steering shaft 47 in the direction of the rotational axis Z2 with the fourth housing 52 interposed therebetween, is expanded radially outward compared to the remaining portions. A third bolt insertion hole 64 is formed through this portion 51f in the direction of the rotational axis Z2 of the second steering shaft 47. A third bolt 67 serving as a fixing member is screwed into a third bolt hole 66 provided in the fourth housing 52 via the third bolt insertion hole 64 of the portion 51f and a fourth bolt insertion hole 65 in the flange portion 50b provided in the third housing 50, thereby fastening the third housing 50 and the second connecting member 51 to the fourth housing 52 together.

[0061] The inner peripheral surfaces of the annular protrusion 51c and the expansion portion 51d hold the second deep groove ball bearing 53 between them and the outer peripheral surface of the large diameter shaft portion 47d.

[0062] The ceiling wall portion 51e has a radial length sufficient to cover the second deep groove ball bearing 53 from the one end portion 47a side.

[0063] The second ball screw mechanism 49 is composed of a second steering shaft side ball screw groove 68 which is a spiral groove provided on the outer peripheral surface of the second medium diameter shaft portion 47e of the second steering shaft 47, a second nut side ball screw groove 54a which is a spiral groove provided on the inner peripheral surface of the second nut 54, and a plurality of balls 69 arranged between the ball screw grooves 68, 54a. The balls 69 support the second nut 54 so as to be rotatable relative to the second medium diameter shaft portion 47e.

[0064] Additionally, a plurality of second rack teeth 54b are formed on the outer periphery of the second nut 54 on the second sector gear accommodating portion 52c side. These second rack teeth 54b mesh with second teeth 57a formed on the second sector gear 57.

[0065] The second four-point contact ball bearing 55 receives both a thrust force acting in the axial direction of the second steering shaft 47, i.e., in the direction of the rotation axis Z2, and a radial force acting in the radial direction of the second steering shaft 47. The distribution of the thrust force and radial force received by the second four-point contact ball bearing 55 is similar to the above-mentioned forces F, F1, and F2 received by the first four-point contact ball bearing 25 provided in the first steering mechanism 7R.

[0066] Furthermore, the second four-point contact ball bearing 55 has an inner race 70 arranged on the outer circumferential side of the first small diameter shaft portion 47f, an outer race 71 arranged on the outer circumferential side of the inner race 70, and a plurality of balls 72 arranged between the inner race 70 and the outer race 71. The second four-point contact ball bearing 55 is press-fitted into the inner circumferential surface of the fourth housing 52. Of the inner circumferential corners 70a, 70b, the corner 70a on the one end 47a side abuts against a step 73 formed between the second medium diameter shaft portion 47e and the first small diameter shaft portion 47f of the second steering shaft 47. Meanwhile, of the outer circumferential corners 71a, 71b, the corner 71a on the one end 47a side abuts against a step 74 provided on the inner circumferential surface of the fourth housing 52.

[0067] The second fixing member 56 fixes the inner race 70 of the second four-point contact ball bearing 55 to the second steering shaft 47. The second fixing member 56 is configured as a nut member and has a second fixing member-side internal thread portion 56a formed on its inner circumferential surface. This second fixing member-side internal thread portion 56a is threadedly engaged with a second steering shaft-side external thread portion 75 formed on the outer circumferential surface of the second small-diameter shaft portion 47g of the second steering shaft 47. This threaded engagement presses a corner portion 70b of the inner race 70, and presses the corner portion 70a of the inner race 70 against a step portion 73 provided on the second steering shaft 47, thereby fixing the inner race 70 to the second steering shaft 47.

[0068] A disk-shaped second closing member 76 is provided at a position closer to the other end 47b than the second four-point contact ball bearing 55 in the direction of the rotation axis Z2 of the second steering shaft 47. This second closing member 76 closes the opening of the fourth housing 52 from the second four-point contact ball bearing 55 side and fixes the outer race 71 of the second four-point contact ball bearing 55 to the fourth housing 52. The second closing member 76 is made of metal or synthetic resin. The second closing member 76 has a circular plate-shaped bottom wall portion 76a, a cylindrical inner circumferential wall portion 76b that rises from the outer edge of the bottom wall portion 76a toward the one end 47a, an annular protruding portion 76c that protrudes radially outward from the end of the inner circumferential wall portion 76b on the one end 47a side, and a cylindrical outer circumferential wall portion 76d that extends from the outer edge of the annular protruding portion 76c toward the other end 47b.

[0069] Furthermore, the length of the outer peripheral wall portion 76d along the direction of the rotational axis Z2 of the second steering shaft 47 is greater than the length of the inner peripheral wall portion 76b along the direction of the rotational axis Z2 of the second steering shaft 47. An axial end face 74e on the one end 47a side of the outer peripheral wall portion 76d is located closer to the one end 47a than an axial end face 74f on the one end 47a side of the annular protruding portion 76c. Therefore, the axial end face 74e abuts against an axial end face 71c on the other end 47b side of the outer race 71 of the second four-point contact ball bearing 55, while the axial end face 74f is spaced from an axial end face 70c on the other end 47b side of the inner race 70 of the second four-point contact ball bearing 55.

[0070] Furthermore, an annular seal groove is formed in the outer peripheral surface of the outer peripheral wall portion 76d at a position closer to the axial end face 74e, into which a fifth O-ring 77, which is an annular seal member made of, for example, rubber, is fitted. The fifth O-ring 77 provides an airtight seal between the inner peripheral surface of the fourth housing 52 and the outer peripheral surface of the outer peripheral wall portion 76d.

[0071] Furthermore, a second closing member side male thread portion 74g is formed on the outer peripheral surface of the outer peripheral wall portion 76d at a position closer to the other end 47b than the fifth O-ring 77, and this second closing member side male thread portion 74g is threadedly engaged with a second housing side female thread portion 52d formed on the inner peripheral surface of the end portion on the other end 47b side of the fourth housing 52. This threaded engagement presses an axial end face 71c of the outer race 71, and presses a corner portion 71a of the outer race 71 against a step portion 74 of the fourth housing 52, thereby fixing the outer race 71 to the fourth housing 52.

[0072] The second sector gear 57 is provided swingably in a second sector gear accommodating portion 52c provided in the fourth housing 52. One axial end of the second sector gear 57 is connected to the second nut 54 via a second tooth portion 57a, and the other axial end is linked to the second steered wheel 1L via a second pitman arm 6L (see FIG. 1). The second tooth portion 57a ​​of the second sector gear 57 and the second rack teeth 54b of the second nut 54 form a second transmission mechanism 78 that steers the second steered wheel 1L in accordance with the output from the second ball screw mechanism 49.

[0073] In this steering device, when the driver rotates the steering wheel 9, the first electric motor 11 applies a rotational force to the second steering shaft 47 via the first reduction gear 48 in accordance with the steering torque acquired by the torque sensor 10 of the first steering mechanism 7R. As the second steering shaft 47 rotates, the second nut 54 moves in the direction of the rotation axis Z2 of the second steering shaft 47, thereby rotating the second sector gear 57. As a result, the second pitman arm 6L is pulled in the vehicle body width direction, thereby changing the direction of the second steered wheel 1L.

[0074] [Advantages of the first embodiment] As described above, in the first embodiment, the first steering mechanism 7R has the torque sensor 10 and the first ball screw mechanism 13 provided on the first steering shaft 12. The second steering mechanism 7L has the first electric motor 11, the first reduction gear 48, and the second ball screw mechanism 49 provided on the second steering shaft 47. More specifically, since it is generally assumed that the same vehicle model is configured to allow both a right-side steering wheel and a left-side steering wheel to be configured, spaces of approximately the same size for mounting a steering device are provided on both sides of the center of the vehicle in the lateral direction. Therefore, a relatively large space remains on the side where the steering wheel 9 is not provided, i.e., the side of the second steering shaft 47, and there is room to mount components associated with the steering device. Therefore, in this embodiment, the steering shaft is divided into a first steering shaft 12 connected to the steering wheel 9 and a second steering shaft 47 provided on the side where the steering wheel 9 is not provided. The torque sensor 10 and the first ball screw mechanism 13 are disposed on the first steering shaft 12, and the first steering assist mechanism including the first electric motor 11 and the first reduction gear 48, which do not necessarily have to be disposed on the first steering shaft 12 side, and the second ball screw mechanism 49 are disposed on the second steering shaft 47. Therefore, the axial dimension of the first steering mechanism 7R on the driver's seat side can be shortened compared to a steering device in which the first electric motor 11 and the first reduction gear 48 are provided on the steering wheel 9 side. This makes it possible to prevent the first housing 15 from interfering with the floor panel.

[0075] [Second embodiment] FIG. 4 is a vertical cross-sectional view of the first steering mechanism 7R of the second embodiment.

[0076] The first steering mechanism 7R of the second embodiment is mainly configured by replacing the first deep groove ball bearing 23 and the first four-point contact ball bearing 25 of the first steering mechanism 7R of the first embodiment with a first angular contact ball bearing 79 and a second angular contact ball bearing 80. In addition, in accordance with this replacement, in the second embodiment, the first shaft portion 20a and the second shaft portion 20b of the output shaft 20 of the first steering shaft 12 of the first embodiment are replaced with a fifth shaft portion 20e, and the fourth shaft portion 20d of the output shaft 20 of the first embodiment is replaced with a sixth shaft portion 20f whose axial dimension is shorter than that of the fourth shaft portion 20d.

[0077] The first angular contact ball bearing 79 receives both a thrust force acting in the axial direction of the first steering shaft 12, i.e., the direction of the rotation axis Z1, and a radial force acting in the radial direction of the first steering shaft 12. The first angular contact ball bearing 79 is disposed adjacent to the third shaft portion 20c on the outer peripheral surface of the fifth shaft portion 20e provided on the first end 12a side of the output shaft 20. The inner race 81 of the first angular contact ball bearing 79 is disposed on the opposite side of the reduced diameter portion 27b of the detection unit 27 of the torque sensor 10, with a cylindrical spacer member 84 interposed between them, in the direction of the rotation axis Z1 of the first steering shaft 12. An end face 81a of the inner race 81 on the first end 12a side abuts an axial end face 84a of the spacer member 84 on the second end 12b side. Meanwhile, an end face 81b of the inner race 81 on the second end 12b side abuts against a step 85 provided between the fifth shaft portion 20e and the third shaft portion 20c. The outer peripheral surface of the outer race 82 of the first angular ball bearing 79, excluding the second end 12b side, is held by the inner peripheral surface of the second annular protrusion 16g of the first connecting member 16.

[0078] The second angular contact ball bearing 80 has the same size and configuration as the first angular contact ball bearing 79 and receives both thrust and radial forces acting on the output shaft 20. The second angular contact ball bearing 80 is disposed on the outer peripheral surface of the sixth shaft portion 20f of the output shaft 20, which is located on the opposite side of the first steering shaft 12 from the torque sensor 10, with the first ball screw mechanism 13 sandwiched between them. As shown in FIG. 4 , the second angular contact ball bearing 80 is oriented symmetrically to the first angular contact ball bearing 79, with the first nut 24 sandwiched between them, in the direction of the rotation axis Z1 of the first steering shaft 12. A corner 86a on the first end 12a side of an inner race 86 of the second angular contact ball bearing 80 abuts against a step 87 provided between the third shaft portion 20c and the sixth shaft portion 20f of the output shaft 20. An end face 86b of the inner race 86 of the second angular ball bearing 80 on the second end 12b side is located closer to a third closing member 90 (described later) than the second end 12b of the first steering shaft 12. The outer race 88 of the second angular ball bearing 80 is press-fitted into a cylindrical peripheral wall portion 90b of the third closing member 90.

[0079] The steering device of the second embodiment also has a preload adjustment mechanism 89 that adjusts the preload of the first angular contact ball bearing 79 and the second angular contact ball bearing 80. The preload adjustment mechanism 89 has a third closing member 90 and a fixing ring 91.

[0080] The third closing member 90 has a bottom wall base 90a in the shape of a circular plate, and a cylindrical peripheral wall 90b that rises from the outer edge of the bottom wall base 90a toward the first end 12a.

[0081] A recess 90d is formed in the center of a bottom surface 90c located on the first end 12a side of the bottom wall base 90a, recessed from the bottom surface 90c toward the opposite side from the first steering shaft 12. Therefore, the bottom surface 90c is continuous in an annular shape while adjacent to the cylindrical circumferential wall portion 90b. An end face 88a of the outer race 88 of the second angular contact ball bearing 80 on the second end 12b side abuts against this bottom surface 90c. In addition, a pair of rotation locking holes 90f are formed in an outer surface 90e of the bottom wall base 90a on the opposite side from the bottom surface 90c, into which corresponding portions of a preload device (not shown) are fitted. The rotation locking holes 90f contribute to the rotation of the third blocking member 90.

[0082] A third closing member-side male thread portion 90g is formed on the outer peripheral surface of the cylindrical peripheral wall portion 90b on the bottom wall base portion 90a side, and this third closing member-side male thread portion 90g is threadedly engaged with a third housing-side female thread portion 17f formed on the inner peripheral surface of the end portion of the second housing 17 on the second end 12b side. This threaded engagement presses the output shaft 20 toward the first end 12a via the second angular contact ball bearing 80, thereby pressing the inner race 81 of the first angular contact ball bearing 79 and pressing the outer race 82 via the balls 83, thereby adjusting the preload of the first angular contact ball bearing 79. At the same time, the corner portion 86a of the inner race 86 is pressed against the step portion 87 via the outer race 88 and balls 92 of the second angular contact ball bearing 80, thereby adjusting the preload of the second angular contact ball bearing 80.

[0083] After adjusting the preload of the first angular ball bearing 79 and the second angular ball bearing 80, the third blocking member 90 is fixed to the second housing 17 by screwing the ring side female thread portion 91a formed on the inner surface of the fixing ring 91 into the third blocking member side male thread portion 90g of the third blocking member 90.

[0084] Furthermore, an annular seal groove-forming protrusion 17g that protrudes radially inward from the inner circumferential surface of the second housing 17 is formed at a position adjacent to the third-housing-side female thread portion 17f on the inner circumferential surface of the second housing 17. An annular seal groove into which a sixth O-ring 93, which is an annular seal member made of, for example, rubber, is fitted, is formed on the tip surface of the seal groove-forming protrusion 17g. The sixth O-ring 93 provides an airtight seal between the outer circumferential surface of the cylindrical circumferential wall portion 90b of the third closing member 90 and the inner circumferential surface of the seal groove-forming protrusion 17g of the second housing 17.

[0085] [Effects of the second embodiment] As described above, in the second embodiment, the first steering mechanism 7R has the first angular contact ball bearing 79 provided on the first end 12a side of the output shaft 20, and the second angular contact ball bearing 80 arranged on the output shaft 20 on the opposite side from the torque sensor 10 across the first ball screw mechanism 13. The preload of the first angular contact ball bearing 79 and the second angular contact ball bearing 80 can be adjusted by the preload adjustment mechanism 89, so that the bearing of the first steering shaft 12 can be efficiently adjusted according to individual differences in the steering device and the usage conditions.

[0086] [Third embodiment] FIG. 5 is a vertical cross-sectional view of a first steering mechanism 7R according to the third embodiment.

[0087] The first steering mechanism 7R of the third embodiment is configured such that the first ball screw mechanism 13 and the first sector gear 14 of the first steering mechanism 7R of the first embodiment are replaced with a first worm gear mechanism 94. In accordance with this replacement, in the third embodiment, the third shaft portion 20c of the output shaft 20 of the first embodiment is replaced with a seventh shaft portion 20g having a larger diameter than the third shaft portion 20c and an eighth shaft portion 20h having a shorter axial dimension than the third shaft portion 20c. Furthermore, in the third embodiment, instead of the first nut accommodating portion 17b and the first sector gear accommodating portion 17c of the first embodiment, the second housing 17 has a worm accommodating portion 17h formed on the seventh shaft portion 20g and its outer periphery that accommodates a reduction mechanism worm 95, and a worm wheel accommodating portion 17i that accommodates a reduction mechanism worm wheel 96 that meshes with the reduction mechanism worm 95.

[0088] The first worm gear mechanism 94 has a worm 95 for the reduction mechanism formed on the outer periphery of the seventh shaft portion 20g of the output shaft 20, and a worm wheel 96 for the reduction mechanism that meshes with the worm 95 for the reduction mechanism.

[0089] The reduction mechanism worm 95 is formed on most of the outer periphery of the seventh shaft portion 20g, excluding relatively small areas on the first end 12a side and the second end 12b side.

[0090] The reduction mechanism worm wheel 96 is formed by insert-molding a cylindrical metal reduction mechanism core portion 98 into a synthetic resin reduction mechanism gear forming portion 97. A recessed groove 98a into which a key 99 is fitted is formed on the inner peripheral surface of the reduction mechanism core portion 98, and the reduction mechanism core portion 98 is connected via this key 99 to a gear output shaft portion 100, which is a cylindrical shaft. The gear output shaft portion 100 is connected to the first pitman arm 6R (see FIG. 1). The worm wheel 96 does not need to be made of synthetic resin, and may instead be a metal gear.

[0091] [Effects of the third embodiment] As described above, in the third embodiment, the first worm gear mechanism 94 includes the reduction-mechanism worm 95 formed on the outer periphery of the seventh shaft portion 20g and the reduction-mechanism worm wheel 96 that meshes with the reduction-mechanism worm 95. In addition, in the first embodiment, the rotation of the output shaft 20 is decelerated via the first ball screw mechanism 13, and then this decelerated rotation is further decelerated via the meshing of the first rack teeth 24b of the first nut 24 and the first tooth portion 14a of the first sector gear 14. In other words, the rotation of the output shaft 20 is decelerated in two stages. However, in the present embodiment, the rotation of the output shaft 20 is decelerated in only one stage via the meshing of the reduction-mechanism worm 95 and the reduction-mechanism worm wheel 96. Therefore, compared to the first embodiment, the reduction mechanism can be configured more simply, and the manufacturing costs of the steering device can be reduced.

[0092] Furthermore, the first worm gear mechanism 94 of this embodiment does not require a component that strokes in the direction of the rotation axis Z1 of the first steering shaft 12, such as the first nut 24 of the first ball screw mechanism 13 of the first embodiment, and therefore the axial dimensions of the first steering shaft 12 and the steering device can be shortened compared to the first embodiment.

[0093] [Fourth embodiment] FIG. 6 is a vertical cross-sectional view of a first steering mechanism 7R according to the fourth embodiment.

[0094] The first steering mechanism 7R of the fourth embodiment is configured such that the first ball screw mechanism 13 and the first sector gear 14 of the first steering mechanism 7R of the second embodiment are replaced with a first worm gear mechanism 94.

[0095] [Effects of the fourth embodiment] Like the third embodiment, the fourth embodiment can reduce the manufacturing costs of the steering device and shorten the axial dimension, and like the second embodiment, can efficiently bear the first steering shaft 12 according to the individual differences and usage conditions of the steering device.

[0096] [Fifth embodiment] FIG. 7 is a vertical cross-sectional view of a first steering mechanism 7R according to the fifth embodiment.

[0097] The first steering mechanism 7R of the fifth embodiment is configured such that the first worm gear mechanism 94 of the third embodiment is replaced with a second worm gear mechanism 101, which is a well-known double lead worm gear. In accordance with this replacement, in this embodiment, the first blocking member 44 of the third embodiment is eliminated, and a backlash mechanism 102 and a fourth blocking member 103 are newly added.

[0098] The second worm gear mechanism 101 has a dual lead worm 104 formed on the outer periphery of the seventh shaft portion 20g of the output shaft 20, and a reduction mechanism worm wheel 96 that meshes with the dual lead worm 104. The dual lead worm 104 is configured by changing the lead size of the upper and lower tooth surfaces (upper and lower in FIG. 7) of the dual lead worm 104, and when the dual lead worm 104 is moved along the direction of the rotation axis Z1 of the first steering shaft 12, the tooth thickness of the meshing portion 105 between the dual lead worm 104 and the reduction mechanism gear forming portion 97 of the reduction mechanism worm wheel 96 changes, thereby adjusting backlash.

[0099] The backlash mechanism 102 includes an adjusting plug 106 and a lock ring 107. The adjusting plug 106 is cylindrical, and its inner circumferential surface is formed so that its diameter tapers in a stepped manner via a stepped portion 106a as it moves from the first end 12a toward the second end 12b. A corner 38b of the outer race 38 of the first four-point contact ball bearing 25 on the second end 12b side abuts against this stepped portion 106a. A plug-side female thread 106b is formed on the inner circumferential surface of the adjusting plug 106 at a location adjacent to one axial end 106c of the adjusting plug 106 on the first end 12a side. This plug-side female thread 106b threadably engages with a nut-side male thread 108a formed on the outer circumferential surface of a retaining ring 108. This threaded engagement presses the end face 38c of the outer race 38 against the stepped portion 106a, thereby fixing the outer race 38 to the adjusting plug 106.

[0100] An annular seal groove into which a seventh O-ring 109, which is an annular seal member made of, for example, rubber, is fitted, is formed in a position near one axial end 106c of the outer peripheral surface of the adjustment plug 106. The seventh O-ring 109 provides an airtight seal between the inner peripheral surface of the second housing 17 and the outer peripheral surface of the adjustment plug 106.

[0101] A plug-side male thread portion 106d is formed on the outer peripheral surface of the adjusting plug 106 at a position closer to the second end 12b than the seventh O-ring 109. This plug-side male thread portion 106d is threadedly engaged with a first-housing-side female thread portion 17e formed on the inner peripheral surface of the end of the second housing 17 closer to the second end 12b. During this engagement, the adjusting plug 106 is rotated by a backlash adjustment device (not shown). This causes the output shaft 20 to move axially via the adjusting plug 106 and the first four-point contact ball bearing 25, thereby adjusting the backlash to fall within a predetermined value. Then, while maintaining this predetermined value, the ring-side female thread portion 107a of the lock ring 107 is threadedly engaged with the plug-side male thread portion 106d of the adjusting plug 106, thereby fixing the adjusting plug 106 to the second housing 17.

[0102] 7, a pair of fourth bolt holes 106f, into which fourth bolts 110 serving as fixing members are screwed, are formed in an end face 106e of the adjustment plug 106 on the second end 12b side, along the direction of the rotation axis Z1 of the first steering shaft 12. The pair of fourth bolt holes 106f are formed in the end face 106e of the adjustment plug 106 so as to be symmetrical about the rotation axis Z1 of the first steering shaft 12.

[0103] The fourth closing member 103 is formed in a disk shape. The fourth closing member 103 has a disk portion 103a and an annular upright portion 103b that rises from the outer periphery of the disk portion 103a toward the first end 12a. An annular protruding inner wall portion 103c that protrudes from the upright portion 103b toward the first end 12a is formed on the inner edge of the upright portion 103b. The upright portion 103b also has a pair of fifth bolt insertion holes 103d formed therein, through which the fourth bolt 110 is inserted. The pair of fifth bolt insertion holes 103d are formed at positions facing the pair of fourth bolt holes 106f of the adjustment plug 106 in the direction of the rotation axis Z1 of the first steering shaft 12. The fourth closing member 103 is fixed to the adjustment plug 106 by screwing the fourth bolt 110 into the fourth bolt hole 106f through the fifth bolt insertion hole 103d.

[0104] [Effects of the fifth embodiment] In the fifth embodiment, the first steering mechanism 7R includes a second worm gear mechanism 101 that is a dual-lead worm gear. Therefore, when the dual-lead worm 104 is moved along the rotation axis Z1 of the first steering shaft 12, the tooth thickness of the meshing portion 105 between the dual-lead worm 104 and the reduction mechanism gear forming portion 97 of the reduction mechanism worm wheel 96 changes, thereby adjusting backlash. This reduces rattle noise that occurs at the meshing portion 105. More specifically, if the backlash is large, an additional force is applied to the meshing portion 105 from the steering wheel 9 via the first steering shaft 12 while the vehicle is traveling on a rough road. This can cause rattle noise, such as a resonant "clack" noise, at the meshing portion 105. This noise can be reduced. Therefore, by using the second worm gear mechanism 101 that is a dual-lead worm gear as in this embodiment, the backlash can be adjusted appropriately to reduce rattle noise. [Sixth embodiment] FIG. 8 is a vertical cross-sectional view of the second steering mechanism 7L of the sixth embodiment.

[0105] The second steering mechanism 7L of the sixth embodiment is configured by adding a second electric motor 111 and a second reducer 112 to the second steering mechanism 7L of the first embodiment.

[0106] The second electric motor 111 has the same size and configuration as the first electric motor 11. The second electric motor 111 is driven and controlled by a second control device (not shown) that is mechanically and electrically integrated with the second electric motor 111. The second electric motor 111 is driven and controlled by the second control device based on the steering torque detected by a torque sensor 10 provided in the first steering mechanism 7R, and applies a rotational force to the second steering shaft 47 via a second reduction gear 112. The second electric motor 111 is located closer to the one end 47a than the second sector gear 57 in the axial direction of the second steering shaft 47, i.e., in the direction of the rotation axis Z2, and a second worm shaft 113 connected to a motor shaft (not shown) of the second electric motor 111 is disposed so as to overlap the first medium diameter shaft portion 47c of the second steering shaft 47 in the radial direction of the second steering shaft 47.

[0107] The second reducer 112 has a first worm wheel 60 and a second worm shaft 113. A first gear forming portion 61 of the first worm wheel 60 is adapted to mesh with a worm provided on the outer periphery of the second worm shaft 113, and the second reducer 112 reduces the speed of the rotation from the second electric motor 111 via this meshing.

[0108] The second electric motor 111 is accommodated in a second motor housing 111a that is cylindrical and has a size similar to that of the first motor housing 11a. As shown in Fig. 8, the second motor housing 111a extends outward beyond the third housing 50 in both the direction of the rotation axis Z2 of the second steering shaft 47 and the radial direction.

[0109] [Effects of the Sixth Embodiment] As described above, in the sixth embodiment, the first electric motor 11, the first reduction gear 48, the second electric motor 111, and the second reduction gear 112 are provided on the one end 47a side in the axial direction of the second steering shaft 47. As described above, a relatively large space remains on the side where the steering wheel 9 is not provided, i.e., on the second steering shaft 47 side, and there is room to mount components associated with the steering device. Therefore, in this embodiment, there is room to arrange the first electric motor 11 and the second electric motor 111, which are relatively large, and this improves the mountability of components associated with the steering device.

[0110] Furthermore, on the steering wheel 9 side of the vehicle, particularly in a cab-over vehicle where the driver's seat is located above the engine, there is a restriction that the steering mechanism must be arranged in a nearly vertical direction. However, on the side of the vehicle where the steering wheel 9 is not provided (the passenger seat side), the steering mechanism can be arranged in any direction, for example, inclined relative to the vertical direction, as long as the position of one end P1 (see FIG. 1) of the first pitman arm 6R is determined. Therefore, on the second steering shaft 47 side, by adjusting the direction of the second steering mechanism 7L, i.e., the mounting posture, it is possible to further improve the mountability of components associated with the steering device.

[0111] [Seventh embodiment] FIG. 9 is a vertical cross-sectional view of the second steering mechanism 7L of the seventh embodiment.

[0112] The second steering mechanism 7L of the seventh embodiment is configured by eliminating the second closing member 76 from the second steering mechanism 7L of the first embodiment and newly adding a first fixing ring member 114, a third electric motor 115, a third reduction gear 116, and a fifth closing member 117. Furthermore, in the second steering mechanism 7L of the seventh embodiment, the first small diameter shaft portion 47f of the second steering shaft 47 of the first embodiment is replaced with a third small diameter shaft portion 47h that is longer in the axial direction than the first small diameter shaft portion 47f. A second four-point contact ball bearing 55 and a second core portion 121 of a second worm wheel 119 (described later) of the third reduction gear 116, which is located closer to the other end 47b than the second four-point contact ball bearing 55, are arranged around the third small diameter shaft portion 47h.

[0113] The first fixing ring member 114 is an annular member that fixes the outer race 71 of the second four-point contact ball bearing 55 to the fourth housing 52. A ring member-side female thread portion 114a is formed on the outer peripheral surface of the first fixing ring member 114, and the ring member-side female thread portion 114a screws into a second housing-side female thread portion 52e formed on the inner peripheral surface of the fourth housing 52. This screwing presses a corner portion 71a on the side of one end 47a of the outer race 71 against a step portion 42 provided on the inner peripheral portion of the fourth housing 52, thereby fixing the outer race 71 to the fourth housing 52.

[0114] The third electric motor 115 has the same size and configuration as the first electric motor 11. The third electric motor 115 is driven and controlled by a third control device (not shown). The third electric motor 115 is driven and controlled by the third control device based on the steering torque detected by the torque sensor 10 provided in the first steering mechanism 7R, and applies a rotational force to the second steering shaft 47 via a third reduction gear 116. The third electric motor 115 is disposed such that a third worm shaft 118 connected to a motor shaft (not shown) overlaps with the second small diameter shaft portion 47g of the second steering shaft 47 in the radial direction of the second steering shaft 47.

[0115] The third electric motor 115 has a cylindrical shape with a bottom and is housed in a third motor housing 115a. As shown in Fig. 9, the third motor housing 115a extends outward beyond the third closing member 117 in both the direction of the rotation axis Z2 of the second steering shaft 47 and the radial direction.

[0116] The third reducer 116 includes a third worm shaft 118 and a second worm wheel 119 that meshes with the third worm shaft 118. The second worm wheel 119 is formed by insert-molding a cylindrical metal second core portion 121 into a synthetic resin second gear forming portion 120. The second core portion 121 includes a cylindrical first cylindrical base portion 121a, a cylindrical first protrusion portion 121c that protrudes toward the other end 47b from the outermost position on a surface 121b of the first cylindrical base portion 121a that faces the other end 47b, a circular first protrusion portion 121d that protrudes radially outward from the outer circumferential surface of the first protrusion portion 121c, and a cylindrical first support portion 121e that protrudes toward the third blocking member 117 from the outer circumferential portion of the first protrusion portion 121d. Furthermore, a second recessed portion 121g is formed in a ring shape at a position adjacent to the outer peripheral surface of the first cylindrical base portion 121a on the surface 121f of the first cylindrical base portion 121a on the one end 47a side. The surface 121f of the first cylindrical base portion 121a is in contact with an end face 70c of the inner race 70 of the second four-point contact ball bearing 55 on the other end 47b side.

[0117] Furthermore, by threading the fixing member side female thread portion 56a of the second fixing member 56 into the steering shaft side male thread portion 75 formed on the second small diameter shaft portion 47g of the second steering shaft 47, the surface 121b of the first cylindrical base portion 121a is pressed, and the corner portion 70a on the one end portion 47a side of the inner race 70 is pressed against the step portion 73 of the second steering shaft 47 via the first cylindrical base portion 121a, thereby fixing the inner race 70 and the second core portion 121 to the second steering shaft 47.

[0118] The fifth closing member 117 is formed in a cylindrical shape with a bottom, closes the opening on the other end 47b side of the fourth housing 52, and houses a part of the third reducer 116, the second fixing member 56, etc. A closing member flange 117b extending radially outward from a portion 117a of the axial end portion on the one end 47a side of the fifth closing member 117 that overlaps with the second sector gear 57 in the direction of the rotational axis Z2 of the second steering shaft 47 is formed. A sixth bolt insertion hole 117c, through which a fifth bolt 122 is inserted, is formed in the radial center position of this closing member flange 117b and extends in the direction of the rotational axis Z2 of the second steering shaft 47.

[0119] Additionally, a threaded hole forming portion 52f is formed on the outer periphery of the fourth housing 52, expanding radially outward from the outer periphery, and this threaded hole forming portion 52f is adjacent to the closing member flange 117b. A fifth bolt hole 52g is formed in the threaded hole forming portion 52f, into which a fifth bolt 122 is screwed. The fifth closing member 117 is fixed to the fourth housing 52 by screwing the fifth bolt 122 into the fifth bolt hole 52g of the threaded hole forming portion 52f through the sixth bolt insertion hole 117c.

[0120] [Effects of the Seventh Embodiment] As described above, in the seventh embodiment, the first electric motor 11 and the first reduction gear 48 are provided on one end 47a of the second steering shaft 47 in the axial direction, and the third electric motor 115 and the third reduction gear 116 are provided on the other end 47b of the second steering shaft 47 in the axial direction. In this embodiment as well, there is room on the second steering shaft 47 side for mounting components associated with the steering device. Therefore, in this embodiment, there is room for arranging the first electric motor 11 and the third electric motor 115, which are relatively large, and therefore it is possible to improve the mountability of the components associated with the steering device.

[0121] Furthermore, as in the sixth embodiment, the steering mechanism can be positioned in any orientation on the side where the steering wheel 9 is not provided, and therefore, on the second steering shaft 47 side, by adjusting the orientation of the second steering mechanism 7L, i.e., the mounting posture, the mountability of components associated with the steering device can be further improved.

[0122] [Eighth embodiment] FIG. 10 is a vertical cross-sectional view of the second steering mechanism 7L of the eighth embodiment.

[0123] The second steering mechanism 7L of the eighth embodiment is configured by adding part of the configuration of the second steering mechanism 7L of the seventh embodiment, i.e., a third electric motor 115 and a third reducer 116, to the second steering mechanism 7L of the sixth embodiment, and further adding a fourth electric motor 123 and a fourth reducer 124. In addition, with the addition of the fourth electric motor 123, the second blocking member 76 used in the sixth embodiment has been eliminated, and a sixth blocking member 125 has been newly added.

[0124] The fourth electric motor 123 has the same size and configuration as the first electric motor 11, the second electric motor 111, and the third electric motor 115. The fourth electric motor 123 is driven and controlled by a fourth control device. The fourth electric motor 123 is driven and controlled by the fourth control device based on the steering torque detected by the torque sensor 10 provided in the first steering mechanism 7R, and applies a rotational force to the second steering shaft 47 via a fourth reduction gear 124.

[0125] The fourth reducer 124 has a second worm wheel 119 and a fourth worm shaft 126. A second gear forming portion 120 of the second worm wheel 119 is adapted to mesh with a worm provided on the outer periphery of the fourth worm shaft 126, and via this meshing, the fourth reducer 124 reduces the speed of rotation from the fourth electric motor 123.

[0126] The sixth closing member 125 is formed in a cylindrical shape with a bottom, closes the opening on the other end 47b side of the fourth housing 52, and houses the third reducer 116, parts of the fourth reducer 124, the second fixing member 56, etc. An open end 125a of the sixth closing member 125 is fixed to the outer peripheral surface of the fourth housing 52.

[0127] [Effects of the Eighth Embodiment] As described above, in the eighth embodiment, the first electric motor 11, the first reduction gear 48, the second electric motor 111, and the second reduction gear 112 are provided on one end 47a of the second steering shaft 47 in the axial direction, and the third electric motor 115, the third reduction gear 116, the fourth electric motor 123, and the fourth reduction gear 124 are provided on the other end 47b of the second steering shaft 47 in the axial direction. In this embodiment, too, there is room on the second steering shaft 47 side for mounting components associated with the steering device. Therefore, in this embodiment, there is room for arranging the first electric motor 11, the second electric motor 111, the third electric motor 115, and the fourth electric motor 123, which are relatively large, and therefore it is possible to improve the mountability of the components associated with the steering device.

[0128] Furthermore, as in the sixth and seventh embodiments, the steering mechanism can be positioned in any orientation on the side where the steering wheel 9 is not provided, and therefore, on the second steering shaft 47 side, by adjusting the orientation of the second steering mechanism 7L, i.e., the mounting posture, the mountability of components associated with the steering device can be further improved.

[0129] [Ninth embodiment] Fig. 11 is a vertical cross-sectional view of the second steering mechanism 7L of the ninth embodiment. For convenience of explanation, Fig. 11 does not show the internal structure of the main body 128 and the detection unit 129 of the angle sensor 127. Regarding the main body 128 and the detection unit 129, the shape of the housing that accommodates them will be mainly described.

[0130] The second steering mechanism 7L of the ninth embodiment is configured such that an angle sensor 127 is newly added to the second steering mechanism 7L of the first embodiment. In addition, with the addition of this angle sensor 127, the shape of the third housing 50 is partially modified so that it has a sensor accommodating portion 50c. Furthermore, in the ninth embodiment, a fourth small diameter shaft portion 47i formed integrally with the first medium diameter shaft portion 47c is added to the second steering shaft 47.

[0131] The angle sensor 127 detects the rotation angle of the second steering shaft 47 in the event of a failure of the torque sensor 10 of the first steering mechanism 7R. The angle sensor 127 is a well-known angle sensor that, for example, has a main gear that rotates integrally with the second steering shaft 47, transmits the rotation of the main gear to a detection gear, and detects the rotation angle of a magnet mounted on the detection gear using a magnetic sensor. Note that the angle sensor 127 may also detect the rotation angle of the second steering shaft 47 by other means, for example, by counting slits provided in a portion that rotates integrally with the second steering shaft 47 using an encoder. The angle sensor 127 has a main body 128 that has a main gear that rotates integrally with the second steering shaft 47, and a detection unit 129 that detects the rotation of the main body 128. The rotation angle of the second steering shaft 47 detected by the angle sensor 127 is input to a first control device 59 (see FIG. 1) associated with the first electric motor 11. When the torque sensor 10 of the first steering mechanism 7R fails, the first control device 59 applies a steering assist force to the second steering shaft 47 by controlling the drive of the first electric motor 11 based on the rotation angle of the second steering shaft 47. When the torque sensor 10 of the first steering mechanism 7R fails, the rotational force from the first steering mechanism 7R is transmitted to the second steering mechanism 7L via the link mechanism (see FIG. 1) between the first pitman arm 6R and the second pitman arm 6L.

[0132] The main body 128 (housing of the main body) is formed in an annular shape from synthetic resin and metal materials and is fixed to the outer periphery of the second steering shaft 47. A second annular protrusion 128a protruding toward the other end 47b along the direction of the rotation axis Z2 of the second steering shaft 47 is formed on an axial end face of the main body 128 on the other end 47b side at a position adjacent to the inner circumferential surface of the main body 128. Furthermore, a second annular reduced diameter portion 128b protruding in a stepped manner toward the one end 47a is formed on an axial end face of the second steering shaft 47 on the one end 47a side at a position adjacent to the inner circumferential surface of the main body 128. This second reduced diameter portion 128b is press-fitted and fixed to the outer circumferential surface of the fourth small diameter shaft portion 47i of the output shaft 20 and rotates together with the output shaft 20.

[0133] The detection unit 129 (housing of the signal processing unit) is made of synthetic resin and has an annular shape, and is disposed around the main body 128. Two cylindrical second rotation restricting portions 129a are formed on the axial end face of the detection unit 129 on the one end 47a side at positions adjacent to the outer peripheral surface of the detection unit 129, and restrict the rotation of the detection unit 129 due to the rotation of the main body 128. As shown in FIG. 11 , the two second rotation restricting portions 129a are disposed symmetrically in the radial direction of the second steering shaft 47, with the output shaft 20 sandwiched between them. Each second rotation restricting portion 129a has a columnar second expanding portion 129b that protrudes with a constant diameter toward one end 47a along the direction of the rotation axis Z2 of the second steering shaft 47 and then tapers conically, and a columnar second rotation restricting cylindrical portion 129c that protrudes from the tip of the second expanding portion 129b toward the one end 47a along the direction of the rotation axis Z2 of the second steering shaft 47. Each second rotation restricting cylindrical portion 129c engages with a second circular hole 50d formed in the third housing 50 in the radial direction of the second steering shaft 47, and this engagement holds the detection portion 129 in the third housing 50. A bottom portion of the second circular hole 50d has a second conical portion 50e that tapers conically toward the outside of the third housing 50.

[0134] [Effects of the ninth embodiment] As described above, in the ninth embodiment, the second steering mechanism 7L has the angle sensor 127 that detects the rotation angle of the second steering shaft 47 when the torque sensor 10 of the first steering mechanism 7R fails. Therefore, even if the torque sensor 10 of the first steering mechanism 7R fails, the application of steering assist to the second steering shaft 47 can be continued based on the rotation angle detected by the angle sensor 127, thereby providing redundancy to the steering device.

[0135] [Tenth embodiment] FIG. 12 is a vertical cross-sectional view of the second steering mechanism 7L of the tenth embodiment.

[0136] The second steering mechanism 7L of the tenth embodiment is configured such that the second deep groove ball bearing 53 of the second steering mechanism 7L of the first embodiment is replaced with a third four-point contact ball bearing 130. In accordance with the replacement with the third four-point contact ball bearing 130, the first connecting member 16 used in the first embodiment is eliminated, and a second fixing ring 131 and a third fixing member 132 are newly added. In addition, in this embodiment, the first medium diameter shaft portion 47c and the large diameter shaft portion 47d of the second steering shaft 47 used in the first embodiment are eliminated, and a fifth small diameter shaft portion 47j formed integrally with the second medium diameter shaft portion 47e and a sixth small diameter shaft portion 47k formed integrally with the fifth small diameter shaft portion 47j are newly added. Furthermore, in this embodiment, the first core wire portion 62 of the first reducer 48 used in the first embodiment is replaced with a third core wire portion 133 having a shape similar to that of the second core wire portion 121 of the first reducer 48.

[0137] The third four-point contact ball bearing 130 has a configuration similar to that of the second four-point contact ball bearing 55 and rotatably supports the fifth small-diameter shaft portion 47j of the second steering shaft 47. The third four-point contact ball bearing 130 is disposed on the outer circumferential surface of the fifth small-diameter shaft portion 47j at a position adjacent to the second medium-diameter shaft portion 47e in the direction of the rotation axis Z2 of the second steering shaft 47. A corner 134a on the other end 47b side of an inner race 134 of the third four-point contact ball bearing 130 abuts against a step 135 formed between the second medium-diameter shaft portion 47e and the fifth small-diameter shaft portion 47j. In addition, a corner 136a on the other end 47b side of an outer race 136 of the third four-point contact ball bearing 130 abuts against a step 137 formed on the inner circumferential portion of the fourth housing 52.

[0138] The second fixing ring 131 is an annular member that fixes the third four-point contact ball bearing 130 to the fourth housing 52. A second ring-side female thread portion 131a is formed on the outer peripheral surface of the second fixing ring 131. This second ring-side female thread portion 131a screws into a fourth housing-side female thread portion 17j formed on the inner peripheral surface of the end portion of the fourth housing 52 on the one end 47a side. This screwing presses an end face 136b on the one end 47a side of the outer race 136, and presses a corner portion 136a of the outer race 136 against a step portion 135 of the fourth housing 52, thereby fixing the outer race 136 to the fourth housing 52.

[0139] The third core metal portion 133 has a cylindrical third cylindrical base portion 133a, a cylindrical third protrusion portion 133c protruding toward the one end 47a from the outermost position on a surface 133b of the third cylindrical base portion 133a on the one end 47a side, a circular second protrusion portion 133d protruding radially outward from the outer circumferential surface of the third protrusion portion 133c, and a cylindrical second support portion 133e protruding from the outer circumferential portion of the second protrusion portion 133d toward the third housing 50. Furthermore, a second recessed portion 133g that is recessed from the surface 133f toward the one end 47a and continues in an annular shape is formed on a surface 133f of the third cylindrical base portion 133a on the other end 47b side at a position adjacent to the outer circumferential surface of the third cylindrical base portion 133a. A surface 133f of the third cylindrical base portion 133a abuts against an end surface b of the inner race of the third four-point contact ball bearing on the one end 47a side.

[0140] The third fixing member 132 fixes the third four-point contact ball bearing 130 and the third core metal portion 133 of the first reducer 48 to the second steering shaft 47. The third fixing member 132 is configured as a nut member and has a third fixing member-side internal thread portion 132a formed on its inner circumferential surface. This third fixing member-side internal thread portion 132a is threadedly engaged with a third steering shaft-side external thread portion 138 formed on the outer circumferential surface of the sixth small-diameter shaft portion 47k of the second steering shaft 47. This threaded engagement presses a corner portion 134b of the inner race 134, and presses the corner portion 134a of the inner race 134 against a step portion 135 provided on the second steering shaft 47, thereby fixing the third four-point contact ball bearing 130 and the third core metal portion 133 of the first reducer 48 to the second steering shaft 47.

[0141] [Effects of the Tenth Embodiment] As described above, in the tenth embodiment, the second deep groove ball bearing 53 of the second steering mechanism 7L of the first embodiment is replaced with the third four-point contact ball bearing 130, so that the second steering mechanism 7L has the second four-point contact ball bearing 55 arranged on the other end 47b side of the second steering shaft 47 and the third four-point contact ball bearing 130 arranged on the one end 47a side of the second steering shaft 47. In other words, the second steering mechanism 7L has two four-point contact ball bearings. Therefore, the second steering mechanism 7L can withstand thrust forces that are twice as large as those of the first embodiment, which has one four-point contact ball bearing, the second four-point contact ball bearing 55. [Explanation of symbols]

[0142] 9···Steering wheel, 7R···First steering mechanism, 7L···Second steering mechanism, 12···First steering shaft, 10···Torque sensor, 11···First electric motor, 23···First deep groove ball bearing, 25···First four-point contact ball bearing, 47···Second steering shaft, 48···First reduction gear, 79···First angular contact ball bearing, 80···Second angular contact ball bearing, 89···Preload adjusting mechanism, 94···First worm gear mechanism, 95···Worm for reduction mechanism 96...worm wheel for reduction mechanism, 101...second worm gear mechanism, 102...backlash mechanism, 104...double lead worm, 106...adjusting plug, 107...lock ring, 111...second electric motor, 112...second reducer, 115...third electric motor, 116...third reducer, 123...fourth electric motor, 124...fourth reducer, 127...angle sensor, 130...third four-point contact ball bearing

Claims

1. A steering device having a first steering mechanism linked to a steering wheel and a second steering mechanism separate from the first steering mechanism and not linked to the steering wheel, the first steering mechanism includes a first steering shaft to which rotation from the steering wheel is input, a torque sensor provided on the first steering shaft and configured to detect steering torque of the first steering shaft, a first reduction mechanism provided on the first steering shaft and configured to reduce the speed of rotation from the first steering shaft, and a first transmission mechanism configured to steer a first steered wheel in accordance with an output from the first reduction mechanism; the second steering mechanism includes a second steering shaft, a first electric motor that applies a rotational force to the second steering shaft, a first reduction gear that is provided on the second steering shaft and reduces the rotational force of the first electric motor, a control device that controls the first electric motor based on the steering torque acquired by the torque sensor, a second reduction mechanism that is provided on the second steering shaft and reduces the rotation from the second steering shaft, and a second transmission mechanism that steers a second steering wheel in accordance with the output from the second reduction mechanism, The first transmission mechanism and the second transmission mechanism are connected to each other via a link mechanism so as to be interlocked with each other. A steering device characterized by:

2. 2. The steering device according to claim 1, a deep groove ball bearing disposed on the first steering shaft at a position adjacent to the torque sensor and rotatably supporting the first steering shaft; a first four-point contact ball bearing that is arranged on the first steering shaft on the opposite side of the first reduction mechanism from the torque sensor and that rotatably supports the first steering shaft.

3. 2. The steering device according to claim 1, a first angular contact ball bearing that is disposed on the first steering shaft at a position adjacent to the torque sensor and that rotatably supports the first steering shaft; a second angular ball bearing that is arranged on the first steering shaft on the opposite side of the first reduction mechanism from the torque sensor and that rotatably supports the first steering shaft.

4. 2. The steering device according to claim 1, A steering device characterized in that the first reduction mechanism is a worm gear mechanism having a worm formed on the first steering shaft and a worm wheel that meshes with the worm.

5. 5. The steering device according to claim 4, A steering device characterized in that the worm gear mechanism is a double lead worm gear mechanism.

6. 2. The steering device according to claim 1, the first electric motor and the first reduction gear are provided on one end side of the second steering shaft in the axial direction, A steering device characterized in that the second steering mechanism further includes a second electric motor provided on one end side of the second steering shaft in the axial direction and applying a rotational force to the second steering shaft, and a second reducer that reduces the rotational force of the second electric motor.

7. 2. The steering device according to claim 1, the first electric motor and the first reduction gear are provided on one end side of the second steering shaft in the axial direction, A steering device characterized in that the second steering mechanism further includes a third electric motor provided on the other end side of the second steering shaft in the axial direction and applying a rotational force to the second steering shaft, and a third reducer that reduces the rotational force of the third electric motor.

8. 2. The steering device according to claim 1, the first electric motor and the first reduction gear are provided on one end side of the second steering shaft in the axial direction, the second steering mechanism further comprises: a second electric motor provided at one end of the second steering shaft in the axial direction and applying a rotational force to the second steering shaft; a second reduction gear that reduces the rotational force of the second electric motor; a third electric motor provided at the other end of the second steering shaft in the axial direction and applying a rotational force to the second steering shaft; a third reduction gear that reduces the rotational force of the third electric motor; a fourth electric motor provided at the other end of the second steering shaft in the axial direction and applying a rotational force to the second steering shaft; and a fourth reduction gear that reduces the rotational force of the fourth electric motor.

9. 2. The steering device according to claim 1, The steering device according to claim 1, wherein the second steering mechanism further comprises an angle sensor provided on the second steering shaft for detecting an angle of the second steering shaft.

10. 2. The steering device according to claim 1, a second four-point contact ball bearing disposed on the other end side of the second steering shaft in the axial direction and rotatably supporting the second steering shaft; a third four-point contact ball bearing disposed on one end side of the second steering shaft in the axial direction, and rotatably supporting the second steering shaft.

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