Steering device

Abstract

The steering device has an input shaft (9) connected to a steering wheel and an intermediate shaft (11) connected to the input shaft (9) and outputting a rotational force input from the input shaft (9) to a transmission mechanism side. The intermediate shaft (11) is connected to an electric motor (2) via a reducer (19) composed of a worm gear formed by engaging a worm shaft (21) and a worm wheel (22). The electric motor (2) applies a rotational force to the intermediate shaft (11) via the reducer (19).

Description

Technical Field

[0001] This invention relates to steering devices. Background Technology

[0002] As a steering device, for example, there is a steering device described in Patent Document 1.

[0003] In the steering device described in Patent Document 1, the steering shaft includes a first shaft connected to a steering wheel, a second shaft connected to the first shaft and outputting rotational force input from the first shaft to a transmission mechanism, and a connecting shaft that rotatably houses the first shaft and connects it to the second shaft via a spline. Furthermore, the connecting shaft is connected to an electric motor via a speed reducer.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application 2019-026915 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] In the steering device described in Patent Document 1, since the connecting shaft and the second shaft are connected via a spline, loosening associated with this connection can occur between the connecting shaft and the second shaft. Furthermore, when the electric motor applies a rotational force to the connecting shaft via a reducer, the second shaft may rotate due to a deterioration in responsiveness caused by the aforementioned loosening.

[0009] The present invention was made in view of the prior art, and one of its objectives is to provide a steering device that can improve the responsiveness of rotational force relative to a second axis.

[0010] Technical solutions for solving technical problems

[0011] In one embodiment of the present invention, an electric motor applies rotational force to a second shaft via a reducer.

[0012] The effects of the invention

[0013] According to the present invention, the responsiveness to rotational forces relative to the second axis can be improved. Attached Figure Description

[0014] Figure 1 This is a perspective view of the steering device according to the first embodiment.

[0015] Figure 2 It is along Figure 1 A longitudinal sectional view of the steering device of the first embodiment, cut by line AA.

[0016] Figure 3 yes Figure 2 A magnified sectional view of a portion of the steering mechanism.

[0017] Figure 4 This is a cross-sectional view of the first pressing device according to the first embodiment.

[0018] Figure 5 This is a process diagram showing the fixing process of the fixed shaft portion in the first embodiment.

[0019] Figure 6 This is a process diagram showing the pressing-in process of the worm gear in the first embodiment.

[0020] Figure 7 This is an explanatory diagram showing the first embodiment of the worm gear pressed into the intermediate shaft.

[0021] Figure 8 This is a cross-sectional view of the second pressing device according to the second embodiment.

[0022] Figure 9 This is a process diagram showing the fixing process of the fixed shaft portion in the second embodiment.

[0023] Figure 10 This is a process diagram showing the pressing process of the second embodiment.

[0024] Figure 11 This is an explanatory diagram showing a second embodiment of the worm gear pressed into an intermediate shaft.

[0025] Figure 12 This is a cross-sectional view of the fixed shaft portion of the third pressing device according to the third embodiment.

[0026] Figure 13 This is a process diagram showing the fixing process of the fixed shaft part in the third embodiment.

[0027] Figure 14 This is a process diagram showing the pressing process of the third embodiment.

[0028] Figure 15 This is an explanatory diagram showing a third embodiment of a worm gear pressed into an intermediate shaft.

[0029] Figure 16 This is a process diagram showing the pressing-in process of the worm gear in the fourth embodiment.

[0030] Figure 17 This is a partial longitudinal sectional view of the steering device according to the fifth embodiment.

[0031] Figure 18 This is a partial longitudinal sectional view of the steering device according to the sixth embodiment. Detailed Implementation

[0032] [First Implementation Method]

[0033] (Structure of the steering mechanism)

[0034] Figure 1 This is a perspective view of the steering device according to the first embodiment. Figure 2 It is along Figure 1 A longitudinal sectional view of the steering device of the first embodiment, with line AA cut off. Figure 3 yes Figure 2 An enlarged sectional view of a portion of the steering mechanism. Figures 1-3 For ease of explanation, the length direction of the steering shaft 7 is defined as "axial direction," the direction orthogonal to the steering shaft 7 is defined as "radial direction," and the direction around the steering shaft 7 is defined as "circumferential direction." Furthermore, the side in the axial direction connected to the steering wheel (not shown) (the upper side in each figure) is designated as "one end," and the side connected to the piston 28 (the lower side in each figure) is designated as "the other end." It should be noted that in... Figure 2 and Figure 3 In the diagram, the electric motor 2, EPS controller 3, and worm shaft 21 are represented by dashed lines.

[0035] The steering system is an integrated steering system used in large vehicles, etc. It mainly consists of the steering system body 1, electric motor 2 and EPS controller (ECU) 3.

[0036] The main body of the steering device 1 includes a steering mechanism 4, a sector shaft 5, and a power cylinder 6.

[0037] The steering mechanism 4 is used for input of rotational force from a steering wheel (not shown) and has a steering shaft 7. A portion of the steering shaft 7 is housed within a housing 8. The steering shaft 7 includes an input shaft 9, a connecting shaft 10, an intermediate shaft 11, and an output shaft 12.

[0038] The input shaft 9 is cylindrical, with one end connected to the steering wheel for inputting the driver's steering torque. Additionally, as... Figure 2 and Figure 3 As shown, the other end of the input shaft 9 is inserted into the approximately cylindrical connecting shaft 10. On the outer periphery of the input shaft 9, a first annular receiving groove 9a is formed at the axial center to receive the first needle roller bearing Nb1, and an annular recess 9b is formed at the other axial end to receive the second needle roller bearing Nb2. The input shaft 9 is rotatably supported by the inner circumferential surface of the connecting shaft 10 via the first and second needle roller bearings Nb1 and Nb2.

[0039] The connecting shaft 10 connects the input shaft 9 and the intermediate shaft 11 by receiving the other end of the input shaft 9 at one end and connecting the other end to the intermediate shaft 11 via a spline portion 13. It should be noted that the other end of the connecting shaft 10 may also be connected to the intermediate shaft 11 via a threaded portion instead of the spline portion 13. Figure 3 As shown, the connecting shaft 10 is a continuous cylindrical shape with a stepped diameter reduction from one end to the other, having a large-diameter cylindrical portion 10a located at one end and a small-diameter cylindrical portion 10b integrally formed with the large-diameter cylindrical portion 10a and formed to be smaller in diameter than the large-diameter cylindrical portion 10a. An annular protrusion 10c protruding radially outward is formed at a position slightly above the axial center on the outer periphery of the large-diameter cylindrical portion 10a.

[0040] like Figure 3 As shown, on the radial end face of the annular protrusion 10c, a step 10d with a stepped diameter reduction is provided at one end. A first ball bearing Bb1, which supports the connecting shaft 10 in a rotatable manner, is provided between the step 10d and the inner peripheral wall of the input-side housing 14, which forms part of the housing 8. The first ball bearing Bb1 is fixed to the input-side housing 14 by using the fastening force generated when it is fixed to the input-side housing 14 via bolts 15, which presses the outer ring 17 of the first ball bearing Bb1 against one end of the step portion 14a provided on the input-side housing 14, using a retaining ring 16.

[0041] In addition, the outer periphery of the small-diameter cylindrical portion 10b is fixed to the inner periphery of the small-diameter recess 20b of the cylindrical intermediate shaft 11 (described later) via the spline portion 13.

[0042] One end of the intermediate shaft 11 is rotatably connected to the input shaft 9 via a first torsion bar 18, and the intermediate shaft 11 is used to input the drive torque of the electric motor 2 via the reducer 19 provided on the outer periphery. A receiving recess 20 is formed on one axial end face 11a of the intermediate shaft 11, opening towards one end, to receive a portion of the connecting shaft 10 that is closer to the other end than the annular protrusion 10c. The receiving recess 20 includes a circular large-diameter recess 20a located on one end side, having an inner diameter corresponding to the outer diameter of the large-diameter cylindrical portion 10a of the connecting shaft 10, and a circular small-diameter recess 20b axially adjacent to the large-diameter recess 20a, having an inner diameter corresponding to the outer diameter of the small-diameter cylindrical portion 10b. A reducer 19, which is connected to the electric motor 2 and is composed of a worm gear that meshes with a worm shaft 21 and a worm wheel 22, is provided on the outer periphery of one end of the intermediate shaft 11.

[0043] The worm gear 22 has a cylindrical metal core 23 and a synthetic resin helical tooth 24 disposed on the outer periphery of one end of the metal core 23. It should be noted that the helical tooth 24 can also be formed of metal. The length of the metal core 23 along the axial direction is longer than the length of the helical tooth 24 along the axial direction. By using the first pressing device 48 (described later), the axial end face 23a of the metal core 23 is pressed towards the other end, and the metal core 23 is pressed into the axial region of the outer periphery of one end of the intermediate shaft 11 (more specifically, the outer periphery of the large-diameter recess 20a) and a portion of the outer periphery of the small-diameter recess 20b axially adjacent to this outer periphery. Figure 3 As shown, with the metal core 23 pressed into the outer periphery of the intermediate shaft 11, the axial end face 23a is located on the opposite side from one axial end face 11a of the intermediate shaft 11. Alternatively, the metal core 23 can be installed onto the outer periphery of the intermediate shaft 11 by hot or cold fitting, instead of pressing it into place. Furthermore, the metal core 23 can be installed onto the outer periphery of the intermediate shaft 11 using wedge screws, adhesives, or splines, instead of pressing, hot fitting, or cold fitting. It should be noted that when using splines or the like to install the metal core 23 onto the outer periphery of the intermediate shaft 11, loosening between the intermediate shaft 11 and the metal core 23 can be suppressed by applying resin to the spline or inserting a pin into the spline. The helical tooth 24 meshes with a worm (not shown) formed on the outer periphery of the worm shaft 21.

[0044] Additionally, an annular grease diffusion prevention member 25 is provided on the outer periphery of the other end of the metal core 23 to prevent grease leakage from the meshing portion of the helical gear 24 and the worm gear from intruding into the output shaft 12. The grease diffusion prevention member 25 has an outer diameter larger than that of the helical gear 24, and is fixed to the outer periphery of the lower end of the metal core 23, for example, by press-fitting. It should be noted that the fixing of the grease diffusion prevention member 25 is not limited to press-fitting; it can also be fixed using a screw or other fixing member. Alternatively, instead of screw-fitting, an adhesive can be used to bond the grease diffusion prevention member 25 to the outer periphery of the lower end of the metal core 23.

[0045] Furthermore, the other end of the intermediate shaft 11 is inserted into the opening recess 12a formed in the expanded diameter portion at one end of the output shaft 12. One end of the output shaft 12 is connected to the intermediate shaft 11 in a rotatable manner via the second torsion bar 26, and the output shaft 12 outputs the steering torque input from the intermediate shaft 11 to the piston 28 via the ball screw mechanism 27, which serves as a conversion mechanism.

[0046] The ball screw mechanism 27 comprises an output shaft 12, which serves as a threaded shaft, having a helical groove (ball groove 27a) formed on its outer periphery at one end; a piston 28, which serves as a nut, located on the outer periphery of the output shaft 12 and having a helical groove (ball groove 27b) on its inner periphery corresponding to the ball groove 27a; and a plurality of balls 27c disposed between the piston 28 and the output shaft 12. Figure 2 It consists of (a portion of which is represented by a dashed line).

[0047] A rotary valve 29, known as a control valve, is configured between the intermediate shaft 11 and the output shaft 12. The rotary valve 29 selectively supplies working fluid supplied by a pump device (not shown) mounted on the vehicle to the first and second liquid chambers (pressure chambers) P1 and P2, described later, based on the amount and direction of the torsion of the second torsion bar 26 derived from the relative rotation angle between the intermediate shaft 11 and the output shaft 12.

[0048] The sector shaft 5 has a sector gear 5a, which meshes with the rack teeth 28a of the piston 28 located on the outer periphery of the other end of the steering shaft 7. The sector shaft 5 rotates in tandem with the axial movement of the piston 28. The sector shaft 5 is connected to the steering wheel via a steering arm (not shown) for steering.

[0049] Thus, the aforementioned ball screw mechanism 27, sector shaft 5, and steering arm constitute a transmission mechanism that converts the rotational force (steering force) input to the steering shaft 7 into the steering force of the steering wheel. It should be noted that, in the absence of using a ball screw mechanism 27 or similar components to form a steering device, the aforementioned transmission mechanism can be, for example, a rack or pinion shaft constituting a rack and pinion mechanism.

[0050] The power cylinder 6 is constructed by dividing a pair of liquid chambers, namely the first and second liquid chambers P1 and P2, by a cylindrical piston 28 that is slidably housed in the housing 8. It is a hydraulic actuator that generates auxiliary torque to assist steering torque.

[0051] The electric motor 2 is configured as a three-phase AC brushless motor that applies rotational torque to the intermediate shaft 11 based on the torsion of the first torsion bar 18. For example... Figure 1 As shown, the electric motor 2 and the EPS controller 3 are integrally formed and housed within a motor housing 30, which is integrally formed with the input-side housing 14 that houses the input shaft 9, etc. The electric motor 2 has a motor shaft (not shown), one axial end of which is connected to... Figure 2 and Figure 3 The worm shaft 21 is indicated by an imaginary line. A worm is integrally formed on the outer circumference of the worm shaft 21, which meshes with the helical tooth portion 24 of the worm wheel 22.

[0052] The torque sensor 31 is positioned around the outer periphery of the connecting shaft 10, near one end of the annular protrusion 10c, with the first torsion bar 18 penetrating its interior. The torque sensor 31 mainly consists of a permanent magnet 32, a pair of first and second magnetic yokes 33 and 34, a pair of first and second magnetic collecting rings 35 and 36, and a magnetic sensor 37. The permanent magnet 32, magnetic yokes 33 and 34, and magnetic collecting rings 35 and 36 are all arranged approximately concentrically with the rotation center line of the steering shaft 7.

[0053] The permanent magnet 32 ​​is a magnetic component formed of magnetic material into a generally cylindrical shape and mounted and fixed to the outer periphery of one end of the connecting shaft 10. The permanent magnet 32 ​​is constructed by alternating N poles and S poles along the circumference of the permanent magnet 32 ​​(magnetizing).

[0054] A pair of magnetic yokes 33 and 34 are both formed into a generally cylindrical shape from soft magnetic materials. The magnetic yokes 33 and 34 are arranged in a row along the circumference at one end, which is the side of the intermediate axis 11, and are radially opposite to the permanent magnet 32. On the other hand, the other ends are radially opposite to each other by the first magnetic yoke 33 being arranged on the inner circumference and the second magnetic yoke 34 being arranged on the outer circumference.

[0055] A pair of magnetic collecting rings 35 and 36 are generally circular rings that collect the magnetic flux of the permanent magnets 32 leaking to the other end of the two yokes 33 and 34 within a predetermined range, and are arranged radially between the other end of the yokes 33 and 34. The magnetic collecting ring 35 is arranged on the outer circumference side, and the magnetic collecting ring 36 is arranged on the inner circumference side, and the two face each other radially. A Hall element 38 is arranged between the radially arranged magnetic collecting rings 35 and 36. A magnetic collecting part 35a is provided at a predetermined position in the circumferential direction of the magnetic collecting ring 35, which is pressed radially inward. On the other hand, a magnetic collecting part 36a is provided in the circumferential direction of the magnetic collecting ring 36, which is opposite to the magnetic collecting part 35a, and protrudes radially outward.

[0056] The magnetic sensor 37 comprises a Hall element 38 housed in a radial gap between magnetic collecting sections 35a and 35b, and a connection terminal 40 for connecting the Hall element 38 to a control board 39 positioned above the torque sensor 31. The magnetic sensor 37 detects magnetic flux passing between the magnetic collecting sections 35a and 36a using the Hall effect of the Hall element 38, and outputs a signal corresponding to this magnetic flux to the control board 39. This allows for the calculation of the relative rotation angle between the input shaft 9 and the intermediate shaft 11 in the control board 39, and the calculation of the steering torque based on this relative rotation angle.

[0057] The housing 8 comprises an output-side housing 41, which is cylindrical and defines the first and second liquid chambers P1 and P2, with one end open and the other end closed; an intermediate housing 42, which houses the rotary valve 29 and is provided with one end of the output-side housing 41 closed; and the aforementioned input-side housing 14, which is connected to the intermediate housing 42 and houses the input shaft 9, the connecting shaft 10, a portion of the intermediate shaft 11, and the torque sensor 31. Figure 1 As shown, the output housing 41 and the intermediate housing 42 are fastened to each other by a plurality of fixing units, such as bolts 43. On the other hand, the intermediate housing 42 and the input housing 14 are fastened to each other by a plurality of fixing units, such as screws 44.

[0058] Inside the output-side housing 41, there is a power cylinder main body 41a formed along the axial direction of the steering shaft 7, and a shaft receiving portion 41b formed orthogonally to the power cylinder main body 41a and partially facing the power cylinder main body 41a. A piston 28 connected to the output shaft 12 is housed within the power cylinder main body 41a, defining a first liquid chamber P1 at one end and a second liquid chamber P2 at the other end. Furthermore, a sector-shaped shaft 5, axially connected to the piston 28 at one end and connected to the steering wheel via a steering arm (not shown) at the other end, is housed within the shaft receiving portion 41b.

[0059] Rack teeth 28a and sector gears 5a that mesh with each other are provided on the outer periphery of the piston 28 and the sector shaft 5. Through the meshing of the rack teeth 28a and sector gears 5a, the sector shaft 5 rotates along with the axial movement of the piston 28, thereby pulling the steering arm in the width direction of the vehicle body, thus changing the orientation of the steering wheel. It should be noted that at this time, working fluid from the first fluid chamber P1 is guided into the shaft housing 41b, thereby lubricating the rack teeth 28a and sector gears 5a.

[0060] like Figure 2 As shown, on the inner circumferential side of the intermediate housing 42, a shaft insertion hole 42a for inserting the overlapping intermediate shaft 11 and output shaft 12 extends axially from one end to the other in a stepped diameter-reducing manner. Furthermore, a bearing Bn is provided at the large diameter portion at one end, supporting the output shaft 12 in a rotatable manner. On the other hand, at the small diameter portion at the other end, there is an inlet port 45 communicating with a pump device (not shown), a discharge port 46 for discharging hydraulic pressure introduced from the inlet port 45 to each liquid chamber P1 and P2, and a discharge port 47 for discharging working fluid discharged from each liquid chamber P1 and P2 via the discharge port 46 to a storage tank (not shown). It should be noted that the discharge port 46 communicates with the first liquid chamber P1 via a first discharge passage L1 provided at one end of the expanded diameter portion of the output shaft 12, and communicates with the second liquid chamber P2 via a second discharge passage L2 provided inside the output housing 41.

[0061] The other end portion of the steering device, which has an intermediate housing 42 and an output housing 41, is pre-assembled and combined with the pre-assembled end portion of the steering device, which includes an input shaft 9, via a connecting shaft 10.

[0062] According to this structure, in the steering device, if the driver steers the steering wheel, the working fluid pumped by the pump is supplied via rotary valve 29 to the fluid chambers P1 and P2 on the side corresponding to the steering direction, and the working fluid (remaining amount) corresponding to the supplied amount is discharged from the fluid chambers P1 and P2 on the other side to the reservoir. Furthermore, as a result of the hydraulically driven piston 28, an auxiliary torque based on the hydraulic pressure acting on the piston 28 is applied to the sector shaft 5.

[0063] Figure 4 This is a cross-sectional view of the first pressing device 48 used in the pressing method of the worm gear 22 in the first embodiment.

[0064] The first pressing device 48 includes a fixed shaft portion 49 fixed to the intermediate shaft 11, a pressing portion 50 provided in a manner that allows it to move axially relative to the fixed shaft portion 49 and is used to press the metal core portion 23 of the worm gear 22, a pressing pressure application portion i.e., a nut 51 provided on the fixed shaft portion 49 via a male thread portion 49h and a female thread portion 51a (described later) and capable of applying pressing pressure to the pressing portion 50 by the reaction force of the female thread portion 51a tightening the male thread portion 49h, and a friction reduction portion i.e., a thrust bearing 52 provided between the nut 51 and the pressing portion 50 and reducing the friction between the central shaft portion 49b of the fixed shaft portion 49 (described later) and the inner peripheral surface of the pressing portion 50 during pressing.

[0065] The fixed shaft portion 49 is formed into a cylindrical shape from a metal material. The fixed shaft portion 49 has a cylindrical end-side shaft portion 49a located on one end side in the axial direction, a cylindrical central shaft portion 49b integrally formed with the end-side shaft portion 49a and formed with a larger diameter than the end-side shaft portion 49a, and a cylindrical other-side shaft portion 49c integrally formed with the central shaft portion 49b and formed with a smaller diameter than the central shaft portion 49b.

[0066] The outer periphery of the one-end side shaft portion 49a has a threaded portion 49d that extends from the central shaft portion 49b to near one end in the axial direction and has a male threaded portion 49h that engages with a female threaded portion 51a provided on the inner periphery of the nut 51, and a non-threaded portion 49e that is integrally formed with the threaded portion 49d in a manner smaller than the diameter of the threaded portion 49d and does not have a male threaded portion.

[0067] The other end shaft portion 49c is formed in a stepped diameter reduction shape from the central shaft portion 49b toward the other end side in the axial direction. It has a large-diameter cylindrical portion 49f that is axially adjacent to the central shaft portion 49b and a small-diameter cylindrical portion 49g that is integrally formed with the large-diameter cylindrical portion 49f and is smaller in diameter than the large-diameter cylindrical portion 49f. A male thread portion 49i is formed on the outer periphery of the small-diameter cylindrical portion 49g, which is screwed into the female thread portion 11b provided on the intermediate shaft 11 (described later).

[0068] The pressing part 50 is formed into a cylindrical shape from a metal material. The pressing part 50 has an annular protrusion 50a that protrudes radially inward from the inner circumferential surface of one axial end. The inner diameter of the annular protrusion 50a is set to be slightly larger than the maximum outer diameter (outer diameter of the thread teeth) of the male thread portion 49h of the shaft portion 49a at one end. Furthermore, the inner diameter of the portion of the pressing part 50 excluding the annular protrusion 50a is set to have a size corresponding to the outer diameter of the central shaft portion 49b.

[0069] Furthermore, the other axial end face of the pressing portion 50 has a pressing surface 50b that presses against the axial end face 23a of the metal core 23 when the metal core 23 is pressed into the intermediate shaft 11, and an abutting surface 50c that abuts against one axial end face 11a of the intermediate shaft 11 when the pressing of the metal core 23 is completed. The pressing surface 50b is an annular surface located radially outward of the pressing portion 50. The abutting surface 50c is an annular surface located radially inward of the pressing portion 50 and disposed in a manner offset from the pressing surface 50b toward one axial end face via a step 50d.

[0070] Figure 5 This is a process diagram showing the fixing process of the fixed shaft portion 49 in the multiple processes of the pressing method of the worm gear 22 in the first embodiment. Figure 6 This is a process diagram showing the pressing-in process of the worm gear 22 in the pressing-in method of the worm gear 22 in the first embodiment. Figure 7 This is an explanatory diagram showing the worm gear 22 pressed into the intermediate shaft 11.

[0071] First, such as Figure 5 As shown, the portion of the steering device, which includes the intermediate shaft 11 and the output shaft 12, is arranged such that the receiving recess 20 of the intermediate shaft 11 faces upward.

[0072] Then, using a thread-forming tool (not shown), such as a tap, as... Figure 5 As shown, a female thread 11b is pre-formed at the center of the bottom of the small-diameter recess 20b of the intermediate shaft 11, which engages with the male thread 49i of the small-diameter cylindrical portion 49g of the fixed shaft portion 49.

[0073] Next, in Figure 5In the fixing process of the fixed shaft portion 49 shown, the fixed shaft portion 49 is fixed to the intermediate shaft 11 by screwing the male thread portion 49i of the small-diameter cylindrical portion 49g into the female thread portion 11b of the intermediate shaft 11. Figure 5 As shown, when the fixed shaft portion 49 is fixed to the intermediate shaft 11, the portion of the central shaft portion 49b of the fixed shaft portion 49 is disposed in the receiving recess 20 of the intermediate shaft 11.

[0074] Then, in Figure 6 In the pressing process of the worm gear 22 shown, after the worm gear 22 is arranged around one axial end of the central shaft portion 49b of the fixed shaft portion 49, the pressing part 50 is arranged from one axial end side of the fixed shaft portion 49 such that the pressing surface 50b of the pressing part 50 contacts the axial end face 23a of the metal core portion 23 of the worm gear 22. After the pressing part 50 is arranged, as Figure 6 As shown, the thrust bearing 52 is arranged axially adjacent to one axial end of the pressing part 50. After the thrust bearing 52 is arranged, as... Figure 6 As shown, the nut 51 is arranged so as to be axially adjacent to one axial end of the thrust bearing 52.

[0075] Then, as Figure 6 As shown, rotating the nut 51 in the direction of arrow B, the female thread 51a of the nut 51 is screwed into the other end in the direction of arrow C relative to the male thread 49h of the fixed end shaft 49a. The reaction force generated by this screwing is transmitted to the pressing part 50 via the thrust bearing 52. Then, while the inner circumferential surface of the pressing part 50 slides on the outer circumferential surface of the central shaft 49b, the pressing part 50 presses the metal core 23 in the direction of arrow C, thereby pressing the inner circumference of the metal core 23 into the outer circumference of the intermediate shaft 11. Figure 7 As shown, with the metal core 23 pressed into the outer periphery of the intermediate shaft 11, the contact surface 50c of the pressing part 50 abuts against one axial end face 11a of the intermediate shaft 11, and the axial end face 23a of the metal core 23 is located slightly closer to the other end side than the axial end face 11a of the intermediate shaft 11.

[0076] [Effects of the First Embodiment]

[0077] In the first embodiment, the metal core 23 of the worm gear 22 constituting the reducer 19 is connected to the outer periphery of the intermediate shaft 11, and the electric motor 2 applies rotational force to the intermediate shaft 11 via the reducer 19. If we assume that the metal core 23 is connected to the outer periphery of the connecting shaft 10, the rotational force from the electric motor 2 will be transmitted to the intermediate shaft 11 via the spline 13 between the connecting shaft 10 and the intermediate shaft 11. Therefore, the rotational force from the electric motor 2 will be transmitted to the intermediate shaft 11 along with a deterioration in responsiveness caused by loosening of the spline 13. Thus, in the first embodiment, since the rotational force from the electric motor 2 is transmitted directly to the intermediate shaft 11 without passing through the connecting shaft 10, the responsiveness of the rotational force from the electric motor 2 relative to the intermediate shaft 11 can be improved without the aforementioned deterioration in responsiveness caused by loosening.

[0078] It should be noted that, as is well known, there is a technique of placing a hollow motor on the outer periphery of the intermediate shaft 11 to directly apply rotational force to the intermediate shaft 11. However, such a hollow motor is relatively large, which has the problem of increasing the radial dimension of the housing of the hollow motor surrounding the intermediate shaft 11.

[0079] However, by using the reducer 19 to amplify the rotational force of the electric motor 2 located outside the intermediate shaft 11 as in this embodiment, the radial dimension of the input-side housing 14 that houses the intermediate shaft 11 and the like can be reduced.

[0080] In the first embodiment, the metal core 23 of the worm gear 22 is pressed into the outer periphery of the intermediate shaft 11 using the first pressing device 48. During this pressing, the fixed shaft 49 is fixed to the intermediate shaft 11 by screwing the male thread 49i of the small-diameter cylindrical portion 49g of the fixed shaft 49 into the female thread 11b near the center of the bottom of the small-diameter recess 20b formed on the intermediate shaft 11. Then, the worm gear 22, the pressing part 50, the thrust bearing 52, and the nut 51 are arranged sequentially from one axial end of the fixed shaft 49. The nut 51 is rotated in the direction of arrow B, and the pressing part 50 slides on the outer periphery of the central shaft portion 49b of the fixed shaft 49 while pressing the metal core 23 into the outer periphery of the intermediate shaft 11. By pressing the metal core 23 into the central shaft 49b while sliding the pressing part 50 on the outer periphery of the central shaft 49b, the thrust applied to the intermediate shaft 11 can be reduced compared to the case where the pressing force is applied directly to the metal core 23 without using the fixed shaft 49, thus suppressing damage to the second torsion bar 26 connected to the intermediate shaft 11.

[0081] It should be noted that the electric motor 2 in this embodiment is designed to apply a much larger rotational force compared to the hollow motors of the well-known art described above, and the rotational force transmitted to the intermediate shaft 11 via the reducer 19 is also significantly larger. Therefore, in order to withstand such a large rotational force, a much larger pressure input is required when the metal core 23 is pressed into the outer periphery of the intermediate shaft 11 compared to pressing the hollow motor into the outer periphery of the intermediate shaft. Therefore, in this embodiment, it is particularly important to reduce the thrust applied to the intermediate shaft 11 to suppress damage to the second torsion bar 26.

[0082] Furthermore, in the first embodiment, since the female thread portion 11b is formed near the bottom of the small-diameter recess 20b that extends relatively far from one axial end face 11a of the intermediate shaft 11 towards the other end, compared to the case where the female thread portion 11b is formed near one axial end face 11a, the degree of freedom in designing the recess of the fixed shaft portion 49 within the receiving recess 20 of the intermediate shaft 11 can be increased to adequately ensure the design of the recess.

[0083] Furthermore, in the first embodiment, the input shaft 9 and the intermediate shaft 11 are connected to each other via a first torsion bar 18 and a cylindrical connecting shaft 10 disposed around the first torsion bar 18. The connecting shaft 10 separates the input-side steering unit portion, which includes the input shaft 9, torque sensor 31, and electric motor 2, from the output-side steering unit portion, which includes the intermediate shaft 11, output shaft 12, and power cylinder 6. Therefore, the steering unit can be easily manufactured by properly configuring and fixing the pre-assembled input-side steering unit portion, which is also pre-assembled, only via the connecting shaft 10 to the output-side portion of the steering unit. Conversely, if the connecting shaft 10 is not provided in the steering unit, assembly from the input-side portion to the output-side portion requires a series of operations, and the manufacturing time of the steering unit is relatively long. In addition, during maintenance of the steering unit, compared to a steering unit without the connecting shaft 10, the interior of both the input-side and output-side portions can be easily accessed by disassembling only the output-side portion of the steering unit, allowing for maintenance.

[0084] In addition, in conventional technology, ball bearings are provided at two locations on the outer periphery of one end of the intermediate shaft and the outer periphery of the other end, so that the intermediate shaft is supported in a rotatable manner relative to the housing.

[0085] However, in the first embodiment, the outer periphery of one end of the connecting shaft 10 is rotatably supported by a ball bearing Bb1, while the other end of the connecting shaft 10 is inserted into the receiving recess 20 of the intermediate shaft 11. Therefore, in this embodiment, the other end of the connecting shaft 10 is inserted into the receiving recess 20 more than the other end of the connecting shaft in the prior art, thus preventing the connecting shaft 10 from tilting relative to the intermediate shaft 11.

[0086] Furthermore, unlike conventional technologies, this embodiment does not require a ball bearing to be provided on the outer periphery of the other end of the connecting shaft 10, thus reducing the manufacturing cost of the steering device.

[0087] [Second Implementation]

[0088] Figure 8 This is a cross-sectional view of the second pressing device 53 used in the pressing method of the worm gear 22 in the second embodiment.

[0089] In the second embodiment, unlike the fixed shaft portion 49 of the first pressing device 48 in the first embodiment, the fixed shaft portion 49 of the second pressing device 53 is constructed by connecting a side shaft portion 49a and a central shaft portion 49b with screws. Furthermore, the shape of the other axial end of the pressing portion 50 of the second pressing device 53 in the second embodiment is different from the shape of the other axial end of the pressing portion 50 of the first pressing device 48 in the first embodiment.

[0090] The outer periphery of the one-sided shaft portion 49a has a male thread portion 49h that extends from one axial end to the other axial end. The portion of the male thread portion 49h at the other axial end is fixed to the central shaft portion 49b by screwing it into the female thread portion 49j formed at one axial end of the central shaft portion 49b.

[0091] The central shaft portion 49b is formed such that its axial length is shorter than that of the central shaft portion 49b in the first embodiment, and its outer diameter is approximately equal to that of the intermediate shaft 11. For example... Figure 8 As shown, the central shaft portion 49b has a small-diameter cylindrical shaft portion 49k at the other end in the axial direction. A male thread portion 49n is formed on the outer periphery of the small-diameter cylindrical shaft portion 49k, which is screwed into the female thread portion 11c, which will be described later, on the intermediate shaft 11. The annular surface 49m at the root of the small-diameter cylindrical shaft portion 49k located in the central shaft portion 49b abuts against one end face 11a of the intermediate shaft 11 in the state where it is fixed to the intermediate shaft 11 by the fixed shaft portion 49 in the fixing process of the fixed shaft portion 49 described later.

[0092] The other axial end face of the pressing part 50 has a pressing surface 50b that presses the axial end face 23a of the metal core 23 when the metal core 23 is pressed into the intermediate shaft 11, and a non-pressing surface 50e that does not press the axial end face 23a of the metal core 23 when the metal core 23 is pressed into the intermediate shaft 11. The pressing surface 50b is an annular surface located radially inner to the pressing part 50. The non-pressing surface 50e is an annular surface located radially outer to the pressing part 50 and disposed in a manner offset from the pressing surface 50b toward one axial end side via a step 50f.

[0093] Figure 9This is a process diagram showing the fixing process of the fixed shaft portion 49 in the multiple processes of the pressing method of the worm gear 22 in the second embodiment. Figure 10 This is a process diagram showing the pressing-in process of the worm gear 22 in the pressing-in method of the worm gear 22 in the second embodiment. Figure 11 This is an explanatory diagram showing the worm gear 22 pressed into the intermediate shaft 11.

[0094] First, such as Figure 9 As shown, the portion of the steering device, which includes the intermediate shaft 11 and the output shaft 12, is arranged such that the receiving recess 20 of the intermediate shaft 11 faces upward.

[0095] Then, using a thread-forming tool (not shown), such as a tap, as... Figure 9 As shown, a female thread 11c is pre-formed on the inner circumferential surface of one end of the intermediate shaft 11, which engages with the male thread 49n of the small-diameter cylindrical shaft 49k of the fixed shaft 49.

[0096] Next, in Figure 9 In the fixing process of the fixed shaft portion 49 shown, the fixed shaft portion 49 is fixed to the intermediate shaft 11 by screwing the male thread portion 49n of the small-diameter cylindrical shaft portion 49k into the female thread portion 11c of the intermediate shaft 11. Figure 9 As shown, when the fixed shaft portion 49 is fixed to the intermediate shaft 11, the small-diameter cylindrical shaft portion 49k of the fixed shaft portion 49 is disposed in the large-diameter recess 20a of the receiving recess 20 of the intermediate shaft 11, and the annular surface 49m of the central shaft portion 49b abuts against one axial end face 11a of the intermediate shaft 11.

[0097] Then, in Figure 10 In the pressing process of the worm gear 22 shown, the worm gear 22, the pressing part 50, the thrust bearing 52 and the nut 51 are arranged sequentially from the axial end side of the fixed shaft part 49, similar to the pressing process of the first embodiment.

[0098] Then, as Figure 10 As shown, similarly to the first embodiment, by screwing the nut 51 in the direction of arrow B, the pressing part 50 is moved in the direction of arrow C via the thrust bearing 52, pressing the inner periphery of the metal core 23 into the outer periphery of the intermediate shaft 11. Figure 11 As shown, with the metal core 23 pressed into the outer periphery of the intermediate shaft 11, the axial end face 23a of the metal core 23 is located slightly closer to the other end side than the axial end face 11a of the intermediate shaft 11. The annular surface 50g of the other axial end side of the annular protrusion 50a of the pressing part 50 abuts against the annular opposing surface 49o provided at one axial end of the central shaft part 49b.

[0099] [Effects of the Second Embodiment]

[0100] In the second embodiment, the male thread 49n of the small-diameter cylindrical shaft portion 49k of the fixed shaft portion 49 is screwed into the female thread portion 11c formed near the axial end face 11a of the intermediate shaft 11. Therefore, compared with the case where the female thread portion 11b is formed near the center of the bottom of the small-diameter recess 20b of the intermediate shaft 11 as in the first embodiment, the axial length of the fixed shaft portion 49 is shortened, thus reducing the manufacturing cost of the fixed shaft portion 49.

[0101] Furthermore, the outer diameter of the female thread portion 11c formed near one axial end face 11a, i.e., the female thread portion 11c formed on the inner circumferential surface of the large-diameter recess 20a of the receiving recess 20, is larger than the outer diameter of the female thread portion 11b at the center of the small-diameter recess 20b in the first embodiment. Therefore, compared with the first embodiment, the engagement area with the male thread portion 49n is ensured to be larger. Thus, the female thread portion 11c of the second embodiment can increase the fixing force relative to the fixed shaft portion 49 compared with the female thread portion 11b of the first embodiment.

[0102] [Third Implementation Method]

[0103] Figure 12 This is a cross-sectional view of the fixed shaft portion 49 of the third pressing device 54 used in the pressing method of the worm gear 22 in the third embodiment.

[0104] In the third embodiment, instead of forming the fixed shaft portion 49 by screwing together one end side shaft portion 49a and the central shaft portion 49b as in the second embodiment, the fixed shaft portion 49 is formed by using the central shaft portion 49b, which is configured as a half-cut, to clamp the other axial end of one end side shaft portion 49a.

[0105] One end side shaft portion 49a has an annular protrusion 49p that protrudes radially outward from the outer periphery of the other end in the axial direction.

[0106] The central shaft portion 49b has a first half 55 and a second half 56 formed by dividing a circular plate-like member with relatively thick walls into two in the radial direction.

[0107] The first half 55 has a semi-circular first plate-shaped portion 55a that cooperates with the semi-circular second plate-shaped portion 56a of the second half 56 to form a circular plate-shaped portion; a first end-side protrusion 55b that protrudes axially from the outer periphery of the first plate-shaped portion 55a and cooperates with the semi-circular arc-shaped second end-side protrusion 56b of the second half 56 to form an annular portion; and a first other end-side protrusion 55c that protrudes axially from the outer periphery of the first plate-shaped portion 55a and cooperates with the semi-circular arc-shaped second other end-side protrusion 56c of the second half 56 to form an annular portion.

[0108] A first semi-circular annular groove 55d is formed on the inner circumferential surface of the first end side protrusion 55b in a continuous semi-circular arc shape along the circumferential direction. The first semi-circular annular groove 55d cooperates with the second semi-circular annular groove 56d provided on the second end side protrusion 56b of the second half 56 to form an annular groove into which the annular protrusion 49p of the one end side shaft portion 49a is inserted.

[0109] The first end protrusion 55c has a semi-circular first protrusion 55e that protrudes radially inward from the other end in the axial direction. The first protrusion 55e cooperates with the semi-circular second protrusion 56e of the second half 56 to form an annular protrusion that is embedded into the annular recess 11d formed on the outer peripheral surface of the intermediate shaft 11.

[0110] The second half 56 includes a second plate-shaped portion 56a, a second one-end protrusion 56b, a second other-end protrusion 56c, a second semicircular groove 55d, and a second protrusion 56e, having the same shape as the first plate-shaped portion 55a, the first one-end protrusion 55b, the first other-end protrusion 55c, the first semicircular groove 55d, and the first protrusion 55e.

[0111] Figure 13 This is a process diagram showing the fixing process of the fixed shaft portion 49 in the multiple processes of the pressing method of the worm gear 22 in the third embodiment. Figure 14 This is a process diagram showing the pressing-in process of the worm gear 22 in the pressing-in method of the worm gear 22 in the third embodiment. Figure 15 This is an explanatory diagram showing the worm gear 22 pressed into the intermediate shaft 11.

[0112] First, such as Figure 13 As shown, the portion of the steering device, which includes the intermediate shaft 11 and the output shaft 12, is arranged such that the receiving recess 20 of the intermediate shaft 11 faces upward.

[0113] Then, as Figure 13 As shown, through machining, a continuous annular recess 11d in the circumferential direction is pre-formed on the outer periphery of one end of the intermediate shaft 11.

[0114] Next, in Figure 13 In the fixing process of the fixed shaft portion 49 shown, an end-side shaft portion 49a is positioned at a predetermined distance from one end face 11a in the axial direction of the intermediate shaft 11 towards one end. After the end-side shaft portion 49a is positioned, as shown... Figure 13 As shown, the first half 55 and the second half 56 are moved from the radially outer side to the radially inner side, and then mate with each other. Figure 14As shown, with the first and second halves 55 and 56 connected together, the first protrusion 55e and the second protrusion 56e, which form annular protrusions, are embedded in the annular recess 11d of the intermediate shaft 11. At the same time, the annular protrusion 49p of the side shaft portion 49a is embedded in the annular groove formed by the first semi-annular groove 55d and the second semi-annular groove 56d.

[0115] Then, in Figure 14 In the pressing process of the worm gear 22 shown, similar to the pressing process in the first and second embodiments, the nut 51 is screwed in in the direction of arrow B, and the pressing part 50 is moved in the direction of arrow C via the thrust bearing 52, pressing the inner circumference of the metal core 23 into the outer circumference of the intermediate shaft 11. Figure 15 As shown, with the metal core 23 pressed into the intermediate shaft 11, the axial end face 23a of the metal core 23 is located slightly closer to the other end side than the annular recess 11d of the intermediate shaft 11. The annular surface 50g of the other axial end side of the annular protrusion 50a of the pressing part 50 abuts against the axial end 55f of the first half 55 and the axial end 56f of the second half 56.

[0116] [Effects of the Third Implementation]

[0117] In the third embodiment, the metal core 23 of the worm gear 22 is pressed into the outer periphery of the intermediate shaft 11 using a third pressing device 54. During this pressing, the fixed shaft portion 49 is fixed to the intermediate shaft 11 by inserting the first protrusion 55e of the first half 55 and the second protrusion 56e of the second half 56 into the annular recess 11d provided on the intermediate shaft 11. Therefore, the fixed shaft portion 49 can be easily fixed to the intermediate shaft 11 through a relatively simple interlocking joint, without the need for thread formation or the removal of chips associated with such thread formation.

[0118] Furthermore, after sequentially arranging the worm gear 22, pressing part 50, thrust bearing 52, and nut 51 from one axial end of the fixed shaft portion 49 fixed to the intermediate shaft 11 as described above, the nut 51 is rotated in the direction of arrow B, and the pressing part 50 slides on the outer periphery of the first half 55 and the second half 56 while pressing the metal core 23 into the outer periphery of the intermediate shaft 11. Therefore, compared to directly applying pressing force to the metal core 23 without using the fixed shaft portion 49, the thrust applied to the intermediate shaft 11 can be reduced, and damage to the second torsion bar 26 fixed to the intermediate shaft 11 can be suppressed.

[0119] [Fourth Implementation Method]

[0120] Figure 16 This is a process diagram showing the pressing process of the worm gear 22 in the fourth embodiment.

[0121] In the fourth embodiment, the fourth pressing device 57 has a fixed shaft portion 49 from the fixed shaft portion 49 of the first embodiment, one end of which has a shaft portion 49a removed, and a pressing portion 50 whose shape on one end of the axial direction is different from that of the pressing portion 50 of the first embodiment.

[0122] like Figure 16 As shown, one axial end of the central shaft portion 49b of the fixed shaft portion 49 is suspended from the fixed wall 58 provided in the work area. On the other hand, the other side shaft portion 49c is fixed to the intermediate shaft 11 by the threaded connection between the female thread portion 11b of the intermediate shaft 11 and the male thread portion 49i of the other side shaft portion 49c.

[0123] The pressing part 50 has an expanding end 50h that expands in a stepped manner from one end to the other in an axial direction. The axial end face 50i of the expanding end 50h that is continuous in an annular shape becomes the pressing surface for the pressing force D applied by the pressing machine (not shown).

[0124] In this embodiment, the bottom of the output side housing 41 of the steering device is mounted on the tray 59, and the tray 59 is mounted on the floor 61 of the work area via a spring 60. The spring 60 absorbs the load acting on the intermediate shaft 11 when the worm gear 22 is pressed in.

[0125] In the fourth pressing device 57, a pressing machine (not shown) is used to apply pressing force D to the metal core 23 of the worm gear 22, pressing the axial end face 23a of the pressing part 50 to the other end side, thereby pressing the metal core 23 of the worm gear 22 into the outer periphery of the intermediate shaft 11.

[0126] [Effects of the Fourth Implementation]

[0127] In the fourth embodiment, one axial end of the central shaft portion 49b is suspended from the fixed wall 58, and the bottom of the output side housing 41 of the steering device is mounted to the floor portion 61 via the tray 59 and the spring 60. In this steering device configuration, the metal core 23 of the worm gear 22 can be pressed into the outer periphery of the intermediate shaft 11 using a press. During this pressing, the load acting on the intermediate shaft 11 is absorbed by the spring 60, thus preventing damage to the second torsion bar 26 fixed to the intermediate shaft 11.

[0128] [Fifth Implementation Method]

[0129] Figure 17 This is a partial longitudinal sectional view of the steering device according to the fifth embodiment.

[0130] In the fifth embodiment, the connecting shaft 10 of the first embodiment is eliminated, and the input shaft 9 is directly housed in the receiving recess 20 of the intermediate shaft 11, which has a larger axial length than that of the first embodiment.

[0131] Furthermore, in this embodiment, the metal core 23 of the worm gear 22 is not fastened to the outer periphery of the intermediate shaft 11 by pressing; instead, the metal core 23 is secured via a tapered screw 62 provided at one end and a key 63 provided at the other end. Figure 17 (Indicated by dashed lines) It is mounted and fixed to the outer periphery of the intermediate shaft 11. Moreover, the axial other end face 23b of the metal core 23 is restricted from moving to the other end by a retaining ring 64 provided on the outer periphery of the intermediate shaft 11. Furthermore, the outer periphery of the axial one end of the metal core 23 is rotatably supported by a second ball bearing Bb2 provided on the inner periphery of the input side housing 14.

[0132] [Effects of the Fifth Implementation]

[0133] In the fifth embodiment, the input shaft 9 and the intermediate shaft 11 are connected to each other via the first torsion bar 18 without a connecting shaft, and the electric motor 2 applies a rotational force to the intermediate shaft 11 via the reducer 19. In the steering device of the fifth embodiment configured in this way, the rotational force from the electric motor 2 also acts directly on the intermediate shaft 11, which can improve the responsiveness from the electric motor 2 to the intermediate shaft 11.

[0134] [Sixth Implementation Method]

[0135] Figure 18 This is a partial longitudinal sectional view of the steering device according to the sixth embodiment.

[0136] In the sixth embodiment, a third ball bearing Bb3, which is smaller than the first ball bearing Bb1 in the first embodiment, is used. Furthermore, in the sixth embodiment, the stepped portion 14a of the first embodiment is eliminated, and the input-side housing 14 has an inner circumferential surface 14b formed with a diameter slightly smaller than the outer diameter of the helical tooth portion 24.

[0137] The inner circumferential surface 14b is axially continuous from near the root of the bolt 15 to the position where it radially overlaps with the lower half of the permanent magnet 32. A circular retaining ring groove 14c is formed in the inner circumferential surface 14b slightly below the lower end of the torque sensor 31, into which a spiral retaining ring 65 is embedded, for example. The retaining ring 65 holds the outer ring 17 of the third ball bearing Bb3 in place by pressing it axially against the retaining ring 16 fastened by the bolt 15. A C-shaped retaining ring can also be used for the retaining ring 65.

[0138] The outer periphery of the annular protrusion 10c has an inner ring fitting groove 67 into which the inner ring 66 of the third ball bearing Bb3 is inserted, and a receiving groove 69 axially adjacent to the inner ring fitting groove 67 and accommodating a C-shaped retaining ring 68. The retaining ring 68 holds the inner ring 66 by pressing it toward one end relative to the sidewall of the inner ring fitting groove 67. Figure 18 As shown, with the inner ring 66 held in place, the inner ring 66 overlaps axially with the magnetic collecting ring 35 of the torque sensor 31.

[0139] [Effects of the Sixth Implementation Method]

[0140] In the sixth embodiment, the retaining ring 65 is provided in the retaining ring groove 14c of the input side housing 14, and the outer ring 17 is held in place by pressing the outer ring 17 against the retaining ring 65 using the retaining ring 16.

[0141] Here, if we describe the fixing method of the first ball bearing Bb1 in the first embodiment, in the first embodiment, even if the rated load of the ball bearing is reduced, the support requirement of the connecting shaft 10 is met. However, in order to avoid interference with the worm shaft 21, the first ball bearing Bb1 with a large rated load is used. The first ball bearing Bb1 is abutted against and held against the stepped portion 14a of the input side housing 14 by the retaining ring 16.

[0142] However, if a third ball bearing Bb3 with a small rated load is used as in the sixth embodiment, the stepped portion 14a of the first embodiment is not required. The inner diameter of the inner circumferential surface 14b of the input-side housing 14 becomes narrower, necessitating the provision of a new fixing portion for securing the third ball bearing Bb3 on the inner circumferential surface 14b. Therefore, in the sixth embodiment, a retaining ring groove 14c for inserting the retaining ring 65 is formed on the inner circumferential surface 14b.

[0143] In this way, by eliminating the stepped portion 14a of the first embodiment and fixing it with the third ball bearing Bb3 using the retaining ring 65, the radial dimension of the steering device can be reduced accordingly to the elimination of the stepped portion 14a, thereby reducing the manufacturing cost of the steering device.

[0144] Furthermore, if a small third ball bearing Bb3 is used, interference between the third ball bearing Bb3 and the lower end of the torque sensor 31 can be avoided, and the inner ring 66 of the third ball bearing Bb3 can be positioned further in the radial direction. Therefore, the radial dimension of the steering device can be further reduced, and the manufacturing cost of the steering device can be further reduced.

Claims

1. A steering device comprising: The steering shaft provides the rotational force input from the steering wheel; A transmission mechanism that transmits the rotation of the steering shaft to the steering wheel; A power cylinder having a piston disposed in the transmission mechanism and a pair of liquid chambers defined by the piston, capable of applying a steering force to steer the steering wheel; A rotary valve capable of selectively supplying working fluid to the pair of fluid chambers according to the rotation of the steering shaft; and An electric motor capable of applying rotational force to the steering shaft via a reducer consisting of a worm shaft and a worm wheel. The steering shaft has a first shaft connected to the steering wheel and a second shaft connected to the first shaft. The second shaft outputs the rotational force input from the first shaft to the transmission mechanism side, and is tightly fitted with the worm gear and forms part of the rotary valve.

2. The steering device according to claim 1, The first shaft and the second shaft are connected to each other via a torsion bar.

3. The steering device according to claim 2, The second shaft is formed of a metallic material. The reducer includes a worm gear having a cylindrical metal core made of a metallic material. The metal core is pressed into the outer periphery of the second shaft.

4. The steering device according to claim 3, The second shaft has a receiving recess formed on the axial end face located on the side of the first shaft, and a female thread is provided on the inner circumferential surface of the receiving recess, which engages with the male thread of the pressing device for pressing in the metal core.

5. The steering device according to claim 3, The second shaft has an annular recess formed on its outer circumferential surface, into which a protrusion of a pressing device for pressing in the metal core is embedded.

6. The steering device according to claim 2, The second shaft is formed of a metallic material. The reducer includes a worm gear having a cylindrical metal core made of a metallic material. The metal core is fastened to the outer periphery of the second shaft by hot or cold fitting.

7. The steering device according to claim 1, The first shaft and the second shaft are connected to each other via a torsion bar and a cylindrical connecting shaft disposed around the torsion bar.

8. The steering device according to claim 7, The second shaft is formed of a metallic material. The reducer includes a worm gear having a cylindrical metal core made of a metallic material. The metal core is pressed into the outer periphery of the second shaft.

9. The steering device according to claim 8, The second shaft has a receiving recess formed on the axial end face located on the side of the first shaft, and a female thread is provided on the inner circumferential surface of the receiving recess, which engages with the male thread of the pressing device for pressing in the metal core.

10. The steering device according to claim 8, The second shaft has an annular recess formed on its outer circumferential surface, into which a protrusion of a pressing device for pressing in the metal core is embedded.

11. The steering device according to claim 7, The second shaft is formed of a metallic material. The reducer includes a worm gear having a cylindrical metal core made of a metallic material. The metal core is fastened to the outer periphery of the second shaft by hot or cold fitting.

12. The steering device according to claim 7, The second shaft has a receiving recess formed on an axial end face located on the side of the first shaft, and the connecting shaft is inserted into the receiving recess.

13. The steering device according to claim 7, It also includes a housing for housing the steering shaft, a ball bearing disposed in the housing and supporting the connecting shaft in a rotatable manner, a retaining ring disposed on the inner circumferential surface of the housing and supporting the outer ring of the ball bearing, and a retaining ring pressing the outer ring of the ball bearing against the retaining ring.

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