Inner shaft, manufacturing method thereof, and steering shaft

Abstract

To achieve an inner shat structure capable of increasing an expansion stroke volume of a steering shaft while suppressing an increase in weight and capable of reducing sliding resistance of the steering shaft during an expansion operation in the entire stroke range.SOLUTION: An inner shaft 18 is constituted of a metallic shaft body 20 and a resin coating part 21 made of a synthetic resin. The shaft body 20 has a male spline part 23, and a non-spline part 24 with smaller cross section than the male spline part 23. By covering the male spline part 23 and the non-spline part 24 with the resin coating part 21, a resin coating layer 31 is formed around the male spline part 23, and a resin male spline part 32 having the same section contour shape as that of the resin coating layer 31 is formed around the non-spline part 24.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an inner shaft, a method for manufacturing the same, and a steering shaft equipped with an inner shaft. [Background technology]

[0002] In recent years, autonomous driving technology for automobiles has been advancing rapidly. Therefore, it is believed that in the near future, autonomous driving levels will reach stages where the vehicle drives itself under certain conditions (Levels 3 and 4), and even fully autonomous driving (Level 5). In autonomous vehicles equipped with such technology, the need for the driver to operate the steering wheel will decrease. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-52514 [Overview of the project] [Problems that the invention aims to solve]

[0004] Autonomous vehicles may require that, during autonomous driving, the steering wheel be moved significantly forward and stored in the dashboard, or positioned away from the driver, in order to secure ample space in front of the driver's seat.

[0005] To move the steering wheel significantly forward, the extension and retraction stroke of the steering shaft to which the steering wheel is fixed must be greater than the extension and retraction stroke of a conventional steering shaft. Specifically, in the case of a steering system that allows adjustment of the fore-aft position of the steering wheel, the extension and retraction stroke must be greater than the extension and retraction stroke required to adjust the fore-aft position of the steering wheel, by the amount required to move the steering wheel forward.

[0006] The steering shaft is configured to be extendable and retractable by spline-engaging a male spline section on the inner shaft with a female spline section on the outer shaft. Therefore, to increase the extension and retraction stroke of the steering shaft, it is conceivable to lengthen the overall length of the male spline section.

[0007] However, the cross-sectional area of ​​the male spline section is larger with respect to a virtual plane perpendicular to the central axis of the inner shaft than the portion of the inner shaft that is axially offset from the male spline section. Therefore, if the overall length of the male spline section is increased to increase the extension stroke of the steering shaft, problems arise such as an increase in the weight of the inner shaft and thus the weight of the steering shaft.

[0008] Furthermore, Japanese Patent Publication No. 2017-52514 (Patent Document 1) discloses a technique for preventing metal-to-metal contact between the male spline portion and the female spline portion by covering the outer circumferential surface of the male spline portion with a synthetic resin coating layer, thereby reducing sliding resistance during the extension and retraction of the steering shaft. However, Japanese Patent Publication No. 2017-52514 does not mention covering the portion of the outer circumferential surface of the inner shaft other than the male spline portion with synthetic resin.

[0009] The present invention has been made to solve the above problems, and aims to provide an inner shaft that can increase the extension and retraction stroke of the steering shaft while suppressing an increase in weight, and that can reduce sliding resistance during the extension and retraction operation of the steering shaft throughout the entire stroke range. [Means for solving the problem]

[0010] The inventors of the present invention diligently studied means to solve the above problems and found that when the fore-aft position of the steering wheel is within the driver's operating range where the driver operates the steering wheel, it is necessary to enable the transmission of a relatively large torque between the inner shaft and the outer shaft. However, when the fore-aft position of the steering wheel is within the driver's non-operating range where the driver does not operate the steering wheel, it is not necessary to transmit a large torque between the inner shaft and the outer shaft if the inner shaft and the outer shaft can be displaced relative to each other in the axial direction. Based on this, they concluded that in the driver's non-operating range, if a male spline portion made of synthetic resin is provided on the inner shaft, the metal male spline portion can be omitted, and thus completed the present invention. Specifically, the inner shaft and its manufacturing method, as well as the steering shaft of the present invention, employ the following means.

[0011] An inner shaft according to one aspect of the present invention comprises a metal shaft body and a resin coating made of synthetic resin. The shaft body has a male spline portion on one axial side, and a non-spline portion adjacent to the male spline portion on the other axial side, the non-spline portion having a smaller cross-sectional area than the male spline portion. The resin coating covers the outer circumferential surface of the shaft body in a range that includes the male spline portion and the non-spline portion. The resin-coated portion includes a resin coating layer formed around the male spline portion and a resin male spline portion formed around the non-spline portion and having the same cross-sectional contour shape as that of the resin coating layer. In the present specification and claims, unless otherwise specified, the cross-section refers to a cross-section with respect to a virtual plane orthogonal to the central axis of the inner shaft.

[0012] In the inner shaft according to one aspect of the present invention, the shaft body may have a small-diameter shaft portion adjacent to one axial side of the male spline portion and having an outer diameter smaller than the root circle diameter of the male spline portion. Further, the resin-coated portion may cover the outer peripheral surface of the small-diameter shaft portion and include a resin retention portion around the small-diameter shaft portion. In this case, the resin retention portion may have the same cross-sectional contour shape as the cross-sectional contour shapes of the resin coating layer and the resin male spline portion, respectively.

[0013] In the inner shaft according to one aspect of the present invention, the shaft body may have an exposed shaft portion on the other axial side of the non-spline portion and not covered by the resin-coated portion on the outer peripheral surface. In this case, the exposed shaft portion may include a phase determination portion that can be used for phase determination.

[0014] In the inner shaft according to one aspect of the present invention, the non-spline portion may have a circular cross-sectional shape. In this case, the non-spline portion may have the same outer diameter as the root circle diameter of the male spline portion. Alternatively, in the inner shaft according to one aspect of the present invention, the non-spline portion may have a non-circular cross-sectional shape. In this case, the non-spline portion may have a protrusion or / and a concave groove portion at a part or a plurality of locations in the circumferential direction of the outer peripheral surface.

[0015] A method for manufacturing an inner shaft according to one aspect of the present invention is a method for manufacturing an inner shaft according to one aspect of the present invention, comprising the steps of: placing at least a portion of the shaft body located on one axial side from the non-spline portion in a cavity of a mold having a spline molding portion on its inner surface; and solidifying molten resin injected into the cavity to form the resin coating portion on the outer circumferential surface of the shaft body.

[0016] A method for manufacturing an inner shaft according to one aspect of the present invention is a method for manufacturing an inner shaft according to one aspect of the present invention, comprising the steps of forming a resin-coated intermediate material on the outer surface of the shaft body by immersing at least a portion of the shaft body located on one axial side from the non-spline portion in molten synthetic resin, and forming the resin-coated portion by machining the outer surface of the resin-coated intermediate material.

[0017] A steering shaft according to one aspect of the present invention comprises an outer shaft and an inner shaft spline-engaged to the outer shaft, enabling torque transmission and relative axial displacement, with a steering wheel fixed to the rear end. The inner shaft is an inner shaft according to one aspect of the present invention. [Effects of the Invention]

[0018] According to one aspect of the present invention, the inner shaft can be configured to increase the extension and retraction stroke of the steering shaft while suppressing an increase in weight, and to reduce sliding resistance during the extension and retraction operation of the steering shaft throughout the entire stroke range. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic diagram showing a steer-by-wire steering device according to a first example of the embodiment. [Figure 2]Figure 2 is an end view of a steer-by-wire steering unit as seen from the rear, relating to the first example of the embodiment. [Figure 3] Figure 3 is a cross-sectional view taken along line AA in Figure 2, showing a first example of the embodiment. [Figure 4] Figure 4 is a perspective view showing a steer-by-wire steering unit in relation to a first example of the embodiment. [Figure 5] Figure 5 shows the inner shaft that constitutes the steering shaft in a first example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) along line BB, and (C) is an enlarged cross-sectional view of (A) along line CC. [Figure 6] Figure 6 shows the shaft body of the inner shaft constituting the steering shaft in a first example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) along line DD, and (C) is an enlarged cross-sectional view of (A) along line EE. [Figure 7] Figure 7 is a schematic diagram showing the steering shaft and steering wheel separately for the first embodiment, where (A) shows the steering wheel in the rearmost position within the driver operating range X, (B) shows the steering wheel in the front-rear position within the driver operating range X, and (C) shows the steering wheel in the front-rear position within the driver non-operating range Y. [Figure 8] Figure 8 is a schematic cross-sectional view showing a manufacturing method for the inner shaft constituting the steering shaft, relating to the first example of the embodiment. [Figure 9] Figure 9 is a schematic cross-sectional view of the FF line shown in Figure 8. [Figure 10] Figure 10 is a diagram corresponding to Figure 5, showing a second example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) along the GG line, (C) is an enlarged cross-sectional view of (A) along the HH line, and (D) is an enlarged cross-sectional view of (A) along the II line. [Figure 11]Figure 11 is a diagram corresponding to Figure 6, showing a second example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) along the JJ line, (C) is an enlarged cross-sectional view of (A) along the KK line, and (D) is an enlarged cross-sectional view of (A) along the LL line. [Figure 12] Figure 12 is a diagram corresponding to Figure 8, showing a third example of the embodiment. [Figure 13] Figure 13 is a schematic diagram showing, in order of steps, the manufacturing method of the inner shaft constituting the steering shaft, with respect to the fourth embodiment. [Modes for carrying out the invention]

[0020] [First example of an embodiment] A first example of the embodiment will be described with reference to Figures 1 to 9. In this example, the inner shaft and steering shaft of the present invention are applied to a steer-by-wire steering system for an autonomous vehicle. In the following description, the longitudinal direction refers to the longitudinal direction of the vehicle, the vertical direction refers to the vertical direction of the vehicle, and the width direction refers to the width direction of the vehicle.

[0021] [Overall configuration of the steering system] The steering system 1 in this example is a steer-by-wire type steering system. As shown in Figure 1, the steering system 1 comprises a steering unit 3 to which a steering wheel 2 is attached, a steering unit 5 that steers a pair of steering wheels 4, and a control unit (ECU) 6. The steering system 1 has a linkless structure in which the steering unit 3 and the steering unit 5 are not mechanically connected but electrically connected.

[0022] The steering unit 3 measures the driver's operation of the steering wheel 2 using a torque sensor 7 (see Figure 3) and a steering angle sensor (not shown), and outputs the measurement results to the control device 6. The control device 6 receives various signals indicating the driving conditions, such as steering torque measured by the torque sensor 7, steering angle measured by the steering angle sensor, vehicle speed, yaw rate, and acceleration. Based on these various signals indicating the driving conditions, the control device 6 drives the steering actuator 8 provided in the steering unit 5. This displaces linear motion members such as rack shafts and screw shafts in the width direction, pushing and pulling a pair of tie rods 9 and applying a steering angle to a pair of steering wheels 4.

[0023] Furthermore, the control device 6 controls the drive of the reaction force applying motor 72 (see Figure 2) of the reaction force generating device 11, which will be described later, provided by the steering unit 3, based on various signals indicating driving conditions such as steering torque, steering angle, and vehicle speed, and applies a steering reaction force to the steering wheel 2 according to the driving conditions.

[0024] [Steering Unit] The steering unit 3 includes a position adjustment device 10 for adjusting the position of the steering wheel 2 and a reaction force generating device 11 for applying a steering reaction force to the steering wheel 2.

[0025] The position adjustment device 10 has the function of adjusting the fore-aft position and the up-down position of the steering wheel 2. In other words, the position adjustment device 10 has a telescopic mechanism for adjusting the fore-aft position of the steering wheel 2 and a tilt mechanism for adjusting the up-down position of the steering wheel 2. Furthermore, the position adjustment device 10 in this example has the function of moving the steering wheel 2 far forward during autonomous driving.

[0026] The position adjustment device 10 comprises a steering shaft 12, a steering column 13, a lower telescopic actuator 14, an upper telescopic actuator 15, and a tilt actuator 16.

[0027] <Steering shaft> The steering shaft 12 is configured to be extendable and retractable, and is rotatably supported inside the steering column 13 using multiple (two in the illustrated example) rolling bearings 17a and 17b. The steering wheel 2 is fixed to the rear end of the steering shaft 12. The front end of the steering shaft 12 is connected to the output shaft 28, which constitutes the reaction force generating device 11, via a torsion bar 30.

[0028] The steering shaft 12 is formed by combining an inner shaft 18 located at the front and a hollow cylindrical outer shaft 19 located at the rear, using spline engagement to enable torque transmission and relative axial displacement. In particular, the steering shaft 12 in this example has a larger extension and retraction stroke compared to conventional steering shafts that only allow adjustment of the fore-aft position of the steering wheel 2, in order to move the steering wheel 2 far forward during autonomous driving.

[0029] Inner Shaft As shown in Figure 5, the inner shaft 18 consists of a metal shaft body 20 made of carbon steel or the like, and a resin-coated portion 21 made of synthetic resin. The inner shaft 18 also has a spline 22 on its outer circumferential surface in the portion that aligns with the resin-coated portion 21 in the axial direction, with the same specifications (equal tooth width and tooth height across the axial direction). The internal structure of the spline 22 differs between one axial half and the other axial half. The axial dimension L of the spline 22 (resin-coated portion 21) 22 This is set based on the amount of extension and retraction stroke of the steering shaft 12 required to move the steering wheel 2 far forward. In the following description of the inner shaft 18, one axial side corresponds to the rear side, and the other axial side corresponds to the front side.

[0030] (Shaft body) As shown in Figure 6, the shaft body 20 has, in order from one axial side, a male spline portion 23, a non-spline portion 24, and an exposed shaft portion 25. Of these, the male spline portion 23 and the non-spline portion 24 are covered by a resin coating portion 21, while the exposed shaft portion 25 is exposed to the outside without being covered by the resin coating portion 21.

[0031] The male spline portion 23 is provided at one end of the shaft body 20 on the axial side. The male spline portion 23 has a circumferentially uneven shape. The male spline portion 23 has a plurality of male spline teeth 23a on its outer circumferential surface that extend in the axial direction of the shaft body 20. The plurality of male spline teeth 23a are arranged at equal pitches in the circumferential direction. The tooth thickness and tooth height of the male spline teeth 23a are constant along the axial direction, except for the chamfered portion provided at one end on the axial side.

[0032] Axial dimension L of the male spline section 23 23 As shown in Figure 7, when the fore-aft position of the steering wheel 2 is located within the driver operation range X in which the driver operates the steering wheel 2, the length dimension is restricted so that the male spline portion 23 and the female spline portion 35 provided on the outer shaft 19 can spline engage with sufficient engagement via the resin coating layer 31, which will be described later. Specifically, the axial dimension L of the male spline portion 23 23 This range is approximately 30mm to 90mm. In this example, the driver operation range X refers to the range of fore-aft position adjustment that the driver operating the steering wheel 2 can perform to adjust the fore-aft position of the steering wheel 2.

[0033] The non-splined portion 24 is positioned adjacent to the male splined portion 23 on the other axial side and is located in the axial middle portion of the shaft body 20. With respect to a virtual plane perpendicular to the central axis O of the shaft body 20, the cross-sectional area of ​​the non-splined portion 24 is smaller than the cross-sectional area of ​​the male splined portion 23. In this example, the non-splined portion 24 has a circular cross-sectional shape, and the tooth root circle diameter d of the male splined portion 23 is smaller. b Outer diameter D of the same size 24 (db =D 24 Therefore, the non-spline portion 24 has a round bar shape (cylindrical shape). However, when implementing the present invention, the cross-sectional shape of the non-spline portion is not limited to a circle, but may be a non-circular shape such as a semicircular or polygonal shape. Alternatively, the non-spline portion may have a plurality of teeth that are shorter in height and / or narrower in width than the plurality of male spline teeth constituting the male spline portion, and / or have a number of teeth that is less than the total number of male spline teeth constituting the male spline portion.

[0034] The exposed shaft portion 25 is located on the other axial side of the non-splined portion 24 and is provided on the other axial half of the shaft body 20.

[0035] The exposed shaft portion 25 has an extension shaft portion 26 and a male stopper portion 27.

[0036] The extension shaft portion 26 is provided on the portion adjacent to the other axial side of the non-spline portion 24. In this example, the extension shaft portion 26 has a circular cross-sectional shape and is adjacent to the outer diameter D of the non-spline portion 24. 24 It has the same outer diameter as the non-splined portion. Therefore, the extension shaft portion 26 has a round bar shape, similar to the non-splined portion 24. In this example, the only difference between the extension shaft portion 26 and the non-splined portion 24 is whether or not it is covered by the resin coating portion 21. However, when implementing the present invention, the cross-sectional shape of the extension shaft portion and the cross-sectional shape of the non-splined portion can be made different from each other, the outer diameter of the extension shaft portion and the outer diameter of the non-splined portion can be made different from each other, and the surface properties can be made different from each other.

[0037] The male stopper portion 27 is positioned adjacent to the other axial side of the extension shaft portion 26 and is provided at the other axial end of the shaft body 20. The male stopper portion 27 engages in the circumferential direction with the female stopper portion 29 provided on the output shaft 28 that constitutes the reaction force generating device 11, thereby restricting the relative rotation between the inner shaft 18 and the output shaft 28 to within a predetermined angle range and preventing excessive twisting of the torsion bar 30.

[0038] The male stopper portion 27 has a concavo-convex shape (gear shape) in the circumferential direction. Specifically, the male stopper portion 27 is constituted by alternately and equally pitch arranging male-side tooth portions 27a and male-side groove portions 27b that each extend in the axial direction in the circumferential direction. In this example, the male stopper portion 27 that constitutes the exposed shaft portion 25 functions as a phase determination portion that can be used for phase determination of the shaft body 20.

[0039] (Resin coating portion) The resin coating portion 21 is made of a synthetic resin with a low coefficient of friction, such as polyamide resin (PA), polytetrafluoroethylene resin (PTFE), or polyacetal resin (POM). The resin coating portion 21 covers the outer peripheral surface of the shaft body 20 in the range including the male spline portion 23 and the non-spline portion 24. In this example, the resin coating portion 21 covers the outer peripheral surface of the male spline portion 23 and the outer peripheral surface of the non-spline portion 24, respectively.

[0040] The resin coating portion 21 is composed of a resin coating layer 31 formed around the male spline portion 23 and a resin male spline portion 32 formed around the non-spline portion 24.

[0041] The resin coating layer 31 covers the entire surface of the concavo-convex shape of the male spline portion 23. Also, the thickness (film thickness) of the resin coating layer 31 is substantially constant over the entire circumference and is sufficiently smaller than the tooth width and tooth height of the male spline teeth 23a. Specifically, the thickness of the resin coating layer 31 is about 10 μm to 1000 μm. For this reason, the resin coating layer 31 has a contour shape along the outer shape of the male spline teeth 23a. The axial dimension L of the resin coating layer 31 31 is the same as the axial dimension L of the male spline portion 23 23 (L 31 = L 23 ).

[0042] The resin male spline portion 32 covers the entire cylindrical surface of the non-spline portion 24. The resin male spline portion 32 is positioned adjacent to the resin coating layer 31 covering the male spline portion 23 on the other axial side, and is connected to the resin coating layer 31 in the axial direction. In other words, the resin male spline portion 32 and the resin coating layer 31 are integrally constructed.

[0043] The resin male spline section 32 is constructed by arranging a plurality of resin male spline teeth 32a that extend axially along the inner shaft 18 at equal pitches in the circumferential direction. The resin male spline teeth 32a are provided in the same number as the metal male spline teeth 23a and are arranged at the same pitch as the male spline teeth 23a. Therefore, the phases of the resin male spline teeth 32a and the male spline teeth 23a in the circumferential direction coincide with each other.

[0044] The tooth thickness and tooth height of the resin male spline tooth 32a are constant along the axial direction. Specifically, the tooth thickness of the resin male spline tooth 32a is equal to the tooth width of the male spline tooth 23a plus twice the thickness of the resin coating layer 31. Similarly, the tooth height of the resin male spline tooth 32a is equal to the tooth height of the male spline tooth 23a plus the thickness of the resin coating layer 31. As a result, the tooth tip surface, tooth root surface, and side surface of the resin male spline tooth 32a are smoothly connected in the axial direction to the tooth tip surface, tooth root surface, and side surface of the male spline tooth 23a, which is covered by the resin coating layer 31. Therefore, with respect to a virtual plane perpendicular to the central axis of the inner shaft 18, the cross-sectional profile of the resin male spline portion 32 is the same as the cross-sectional profile of the resin coating layer 31.

[0045] Axial dimension L of the resin male spline portion 32 32 The fore-aft position of the steering wheel 2 is restricted to the length required to move it forward from the forwardmost position within the fore-aft position adjustment range, which is the driver operation range X, as shown in Figure 7(B), to the point where the steering wheel 2 can be stored in the dashboard, as shown in Figure 7(C). The axial dimension L of the resin male spline portion 3232 The axial dimension L of the non-splined portion 24 24 It is the same as (L 32 =L 24 Specifically, this ranges from approximately 90mm to 130mm.

[0046] In the illustrated example, the axial dimension L of the resin male spline portion 32 is shown. 32 The axial dimension L of the resin coating layer 31 is 31 It is slightly larger than that. However, when implementing the present invention, the axial dimension of the resin male spline portion (=axial dimension of the non-spline portion) can be made sufficiently larger or smaller than the axial dimension of the resin coating layer (=axial dimension of the male spline portion). Alternatively, the axial dimension of the resin male spline portion (=axial dimension of the non-spline portion) and the axial dimension of the resin coating layer (=axial dimension of the male spline portion) can be made the same. Axial dimension L of the resin male spline portion 32 32 The lower limit is approximately 90 mm.

[0047] In this example, the male spline portion 23 covered by the resin coating layer 31 constitutes one axial half of the spline 22, and the resin male spline portion 32 constitutes the other axial half of the spline 22. Therefore, one axial half of the spline 22 is made of synthetic resin only on the surface and metal inside, while the other axial half of the spline 22 is made of synthetic resin from the surface to the interior.

[0048] (Outer shaft) The outer shaft 19 has a hollow cylindrical shape. The outer shaft 19 is located behind the inner shaft 18. The outer shaft 19 has a small-diameter cylindrical portion 33 in its front half and a large-diameter cylindrical portion 34 in its rear half. The outer shaft 19 has a female spline portion 35 on the inner circumferential surface of the small-diameter cylindrical portion 33. The steering wheel 2 is fixed to the rear end of the outer shaft 19.

[0049] The female spline portion 35 has an uneven shape in the circumferential direction. The female spline portion 35 is composed of a plurality of female spline teeth 35a extending in the axial direction of the outer shaft 19, arranged at equal pitches in the circumferential direction. The tooth thickness and tooth height of the female spline teeth 35a are constant along the axial direction, except for the chamfered portion provided at the axial end.

[0050] The axial dimension of the female spline portion 35 is equal to the axial dimension L of the resin-coated portion 21. 21 ( =L 31 +L 32 It is shorter than ). Specifically, the axial dimension of the female spline portion 35 is, for example, shorter than the axial dimension L of the resin coating layer 31. 31 It is about 1.5 to 2 times that amount.

[0051] The large-diameter cylindrical portion 34 has an inner diameter larger than the root circle diameter of the female spline tooth 35a.

[0052] The female spline portion 35 on the outer shaft 19 is spline-engaged with the spline 22 on the inner shaft 18. As a result, the outer shaft 19 moves relative to the inner shaft 18 in the front-rear direction together with the steering wheel 2, causing the steering shaft 12 to extend and retract.

[0053] In this particular example, the spline engagement configuration between the inner shaft 18 and the outer shaft 19 switches depending on the fore-aft position of the steering wheel 2. This will be explained in detail below using Figure 7. Figure 7(A) shows the steering wheel 2 in its rearmost position within the driver's operating range X, Figure 7(B) shows the steering wheel 2 in its frontmost position within the driver's operating range X, and Figure 7(C) shows the steering wheel 2 in its frontmost position within the driver's non-operating range Y.

[0054] As shown in Figures 7(A) and (B), when the distance from the driver to the steering wheel 2 is short and the fore-aft position of the steering wheel 2 is within the driver operating range X where the driver operates the steering wheel 2, the female spline portion 35 engages with the male spline portion 23, which constitutes one axial half of the spline 22, via the resin coating layer 31 with a sufficient engagement allowance, preferably over its entire length. Therefore, in the driver operating range X, it becomes possible to transmit a relatively large torque between the inner shaft 18 and the outer shaft 19. Thus, the torque input from the driver to the steering wheel 2 and the torque generated by the reaction force generating device 11 can be transmitted between the inner shaft 18 and the outer shaft 19. If the steering system is equipped with an assist device, the torque generated by the assist device can also be transmitted between the inner shaft and the outer shaft.

[0055] Furthermore, the female spline portion 35 may spline engage with one axial portion of the resin male spline portion 32 even within the driver operating range. However, in this case, the engagement allowance between the female spline portion 35 and the resin male spline portion 32 is sufficiently small, and the female spline portion 35 and the male spline portion 23 are spline engaged with a sufficient engagement allowance, so a large torque is not transmitted to the resin male spline portion 32.

[0056] As shown in Figure 7(C), when the distance from the driver to the steering wheel 2 is large and the fore-aft position of the steering wheel 2 is in the driver non-operation range Y where the driver does not operate the steering wheel 2, the female spline portion 35 splines with a sufficient engagement allowance to the resin male spline portion 32 which constitutes the other half of the spline 22 on the axial side. For this reason, in the driver non-operation range Y, it is not possible to transmit a large torque between the inner shaft 18 and the outer shaft 19, but it is possible to displace the inner shaft 18 and the outer shaft 19 relative to each other in the axial direction. When the female spline portion 35 engages with the resin male spline portion 32, the male spline portion 23, which is covered by the resin coating layer 31, is inserted inside the large diameter cylindrical portion 34.

[0057] (Inner shaft manufacturing method) The inner shaft 18 in this example can be manufactured by, for example, the following manufacturing method.

[0058] First, a cylindrical material made of metal such as carbon steel is machined, and then subjected to plastic deformation (splinting) such as cold forging, hobbing, and rolling. As shown in Figure 6, this creates a shaft body 20 having a male spline portion 23, a non-spline portion 24, and an exposed shaft portion 25 in order from one side in the axial direction.

[0059] Subsequently, a resin coating portion 21 is formed on the outer circumferential surface of the shaft body 20 by injection molding. For this purpose, the portion of the shaft body 20 located on one axial side from the non-spline portion 24 is placed inside the cavity 37 of the mold 36. Specifically, as shown in Figure 8, the male spline portion 23 and the non-spline portion 24 of the shaft body 20 are placed inside the cavity 37 of the mold 36.

[0060] The mold 36 is formed by combining the first mold 38 and the second mold 39, and has a spline molding section 40 on its inner surface. The spline molding section 40 has an uneven shape in the circumferential direction and has a contour shape that matches the cross-sectional contour shapes of the resin coating layer 31 and the resin male spline section 32, respectively.

[0061] In this example, when arranging the male spline portion 23 and the non-spline portion 24 of the shaft body 20 within the cavity 37 of the mold 36, the male stopper portion 27 provided on the exposed shaft portion 25 is used to align the circumferential phase of the male spline portion 23 and the spline forming portion 40. Specifically, by engaging the first mold 38 and / or the second mold 39 with one or more locations of the male side groove portion 27b constituting the male stopper portion 27, the gap between the male spline portion 23 and the spline forming portion 40 is made uniform around the entire circumference.

[0062] Subsequently, molten resin is injected into the cavity 37 through the gate 41 provided in the first mold 38. The molten resin is then allowed to solidify within the cavity 37. This forms a resin coating portion 21 with the solidified molten resin. In other words, the resin coating portion 21 is formed so as to cover the male spline portion 23 and the non-spline portion 24 of the outer circumferential surface of the shaft body 20. In this example, the inner shaft 18, consisting of the shaft body 20 and the resin coating portion 21, is manufactured in this manner.

[0063] Steering column The steering column 13 is configured to be extendable and retractable in length and is supported by a vehicle body (not shown). The steering column 13 comprises a bracket 42 and a column body 43. In this example, the steering column 13 has a two-stage telescopic structure to ensure a large extension and retraction stroke in the front-rear direction.

[0064] The bracket 42 is for supporting the column body 43 on the vehicle body and comprises a fixed bracket 44 that is fixed to the vehicle body and a displacement bracket 45 that is supported so as to be able to move relative to the fixed bracket 44 in the front-rear direction.

[0065] The fixing bracket 44 comprises a roughly rectangular flat fixing plate portion 46 and a roughly U-shaped fixing-side support frame 47. The fixing plate portion 46 is fixed to the vehicle body using a plurality of mounting bolts 48. The fixing-side support frame 47 is provided at the front end of the fixing plate portion 46 and connects the ends on both sides in the width direction of the fixing plate portion 46.

[0066] The displacement bracket 45 comprises a displacement plate portion 49 positioned to overlap the lower surface of the fixed plate portion 46, and a substantially U-shaped displacement-side support frame 50. The displacement plate portion 49 is supported using a linear guide 51 to allow relative displacement in the front-rear direction with respect to the fixed plate portion 46. The displacement-side support frame 50 is provided at the rear end of the displacement plate portion 49 and connects the ends on both sides of the displacement plate portion 49 in the width direction. On the inner surface of one of the pair of left and right support wall portions 52 that constitute the displacement-side support frame 50, a screw shaft (not shown) of a tilt feed screw device 70 that constitutes the tilt actuator 16 is rotatably supported with its axial direction facing up and down.

[0067] The column body 43 is generally cylindrical in shape and is positioned with its axial direction oriented in the front-rear direction. The column body 43 comprises an outer column 53 positioned in the middle of the front-rear direction, a lower inner column 54 fitted into the front side of the outer column 53, and an upper inner column 55 fitted into the rear side of the outer column 53.

[0068] The outer column 53 is supported on the displacement bracket 45 so as to be able to move in the vertical direction. The rear part of the outer column 53 is inserted in the front-rear direction inside the displacement-side support frame 50 that constitutes the displacement bracket 45. A nut (not shown) of the tilt feed screw device 70 that constitutes the tilt actuator 16 is pivotally supported on the outer circumferential surface of the rear part of the outer column 53. The outer column 53 has a slit 56 (see Figure 3) that extends in the front-rear direction in the middle of the front-rear direction on its lower surface. The outer column 53 has screw holes 57 at multiple locations on its outer circumferential surface. A screw plug 58, whose tip is made of a material with a low coefficient of friction such as polyacetal (POM), is screwed into each of the screw holes 57.

[0069] The lower inner column 54 is fitted inside the front part of the outer column 53, allowing for relative displacement in the front-rear direction. The tip of a screw plug 58, which is screwed into a threaded hole 57 in the outer column 53, is pressed against the outer circumferential surface of the lower inner column 54. This suppresses rattling of the lower inner column 54 relative to the outer column 53.

[0070] The upper inner column 55 is fitted inside the rear portion of the outer column 53, allowing for relative displacement in the front-rear direction. The tip of a screw plug 58, which is screwed into a threaded hole 57 in the outer column 53, is pressed against the outer circumferential surface of the upper inner column 55. This suppresses rattling of the upper inner column 55 relative to the outer column 53.

[0071] <Actuator for lower telescopic control> The lower telescopic actuator 14 is positioned to span between the fixed bracket 44 and the displacement bracket 45, causing the displacement bracket 45 to be displaced in the front-rear direction relative to the fixed bracket 44. This causes the outer column 53 and the lower inner column 54 to be displaced relative to each other in the front-rear direction, thereby extending or retracting the column body 43.

[0072] The lower telescopic actuator 14 comprises a lower telescopic motor 59 and a lower feed screw device 60.

[0073] The lower telescopic motor 59 is supported and fixed to the side surface in the width direction of the fixed support frame 47 that constitutes the fixed bracket 44, with its motor output shaft (not shown) facing vertically.

[0074] As shown in Figure 2, the lower side feed screw device 60 comprises a lower side screw shaft 61 and a lower side nut 62. The lower side screw shaft 61 is positioned with its axial direction oriented in the front-rear direction and is rotationally driven by a lower side telescopic motor 59 via a reduction mechanism such as a worm gear reducer (not shown). The lower side screw shaft 61 is supported by the fixed bracket 44 so as to be rotatable only. The lower side nut 62 is screwed onto the lower side screw shaft 61 and is supported by the widthwise side surface of the displacement bracket 45. That is, the lower side telescopic actuator 14 rotates the lower side telescopic motor 59, thereby displacing the lower side nut 62 in the axial direction of the lower side screw shaft 61, and thus displacing the outer column 53 relative to the lower side inner column 54 in the front-rear direction.

[0075] <Actuator for upper telescopic extension> The upper telescopic actuator 15 is positioned to span between the outer column 53 and the upper inner column 55, and displaces the upper inner column 55 in the front-rear direction relative to the outer column 53. This causes the column body 43 to extend or retract.

[0076] The upper telescopic actuator 15 comprises an upper telescopic motor 63 and an upper feed screw device 64.

[0077] The upper telescopic motor 63 is supported below the front end of the outer column 53, with its motor output shaft (not shown) facing in the width direction.

[0078] The upper side feed screw device 64 comprises an upper side screw shaft 65 and an upper side nut 66. The upper side screw shaft 65 is positioned with its axial direction oriented in the front-rear direction and is rotationally driven by an upper side telescopic motor 63 via a reduction mechanism such as a worm gear reducer (not shown). The upper side screw shaft 65 is supported relative to the outer column 53 so as to be rotatable only. The upper side nut 66 is screwed onto the upper side screw shaft 65 and is supported relative to the lower surface of the upper side inner column 55 via a connector member 67. The connector member 67 is positioned inside the slit 56 of the outer column 53 and is fixed to the lower surface of the upper side inner column 55. In other words, the upper side telescopic actuator 15 rotates the upper side telescopic motor 63, thereby displacing the upper side nut 66 in the axial direction of the upper side screw shaft 65, and thus displacing the upper side inner column 55 relative to the outer column 53 in the front-rear direction.

[0079] <Tilt Actuator> The tilt actuator 16 is positioned to span between the displacement-side support frame 50 and the outer column 53, which constitute the displacement bracket 45, and displaces the outer column 53 in the vertical direction relative to the displacement bracket 45. Furthermore, as will be described later, the reaction force generating device 11, which is connected to the front side of the position adjustment device 10, is rotatably supported by a pair of pivot bolts 68 arranged in the width direction relative to the fixed-side support frame 47. This makes it possible to swing the column body 43 vertically around the pivot bolts 68 relative to the bracket 42.

[0080] The tilt actuator 16 comprises a tilt motor 69 and a tilt feed screw device 70.

[0081] The tilt motor 69 is fixed to one of the support walls 52 that make up the displacement-side support frame 50, with its motor output shaft (not shown) facing in the front-rear direction.

[0082] The tilt feed screw device 70 comprises a tilt screw shaft (not shown) and a tilt nut. The tilt screw shaft is positioned with its axial direction oriented vertically and is rotationally driven by a tilt motor 69 via a reduction mechanism such as a worm gear reducer (not shown). The tilt screw shaft is supported by one support wall 52 so that it can only rotate. The tilt nut is screwed onto the tilt screw shaft and is pivotally supported on the widthwise side of the outer column 53. That is, the tilt actuator 16 rotates the tilt motor 69, thereby displacing the tilt nut in the axial direction of the tilt screw shaft, and thus displacing the outer column 53 relative to the displacement bracket 45 in the vertical direction.

[0083] How to adjust the steering wheel position In this example, to adjust the fore-aft position of the steering wheel 2 using the position adjustment device 10, the lower telescopic actuator 14 and / or the upper telescopic actuator 15 are driven. When the lower telescopic actuator 14 is driven, the displacement bracket 45 is displaced relative to the fixed bracket 44 in the fore-aft direction, and the outer column 53 is displaced relative to the lower inner column 54 in the fore-aft direction. Conversely, when the upper telescopic actuator 15 is driven, the upper inner column 55 is displaced relative to the outer column 53 in the fore-aft direction. This extends and retracts the overall length of the steering column 13 and the steering shaft 12, thereby adjusting the fore-aft position of the steering wheel 2 within the fore-aft position adjustment range, which is the driver operation range X. After adjusting the fore-aft position of the steering wheel 2 to the desired position, the driving of the lower telescopic actuator 14 and / or the upper telescopic actuator 15 is stopped.

[0084] In this example, to adjust the vertical position of the steering wheel 2 using the position adjustment device 10, the tilt actuator 16 is driven to displace the rear portion of the outer column 53 vertically relative to the displacement bracket 45. This causes the steering shaft 12, which is rotatably supported inside the column body 43, to swing, thereby adjusting the vertical position of the steering wheel 2. After adjusting the vertical position of the steering wheel 2 to the desired position, the drive of the tilt actuator 16 is stopped. Furthermore, the fore-aft and up-down position adjustments of steering wheel 2 can be performed simultaneously, or independently (in a chronological order).

[0085] Furthermore, in order to move the steering wheel 2 far forward during autonomous driving using the position adjustment device 10 in this example, and to store the steering wheel 2 in the dashboard or position it away from the driver, the lower telescopic actuator 14 and the upper telescopic actuator 15 are driven respectively. This causes the displacement bracket 45 to be displaced forward relative to the fixed bracket 44, the outer column 53 to be displaced forward relative to the lower inner column 54, and the upper inner column 55 to be displaced forward relative to the outer column 53. Then, by shortening the overall length of the steering column 13 and the overall length of the steering shaft 12, the steering wheel 2 is moved far forward. After the steering wheel 2 has been moved far forward, the driving of the lower telescopic actuator 14 and the upper telescopic actuator 15 is stopped.

[0086] <Reaction force generating device> The reaction force generating device 11 is positioned in front of the position adjustment device 10 and is fixed to the position adjustment device 10. The reaction force generating device 11 is controlled by the control device 6 and applies a steering reaction force to the steering wheel 2 of a magnitude and direction corresponding to driving conditions such as the steering angle of the steering wheel 2 and the vehicle speed.

[0087] The reaction force generating device 11 comprises a gear housing 71, a reaction force applying motor 72, a worm gear reducer 73, an output shaft 28, and a torsion bar 30.

[0088] The gear housing 71 is fixed to the front end of the lower inner column 54, which constitutes the position adjustment device 10. The front end of the inner shaft 18, which constitutes the steering shaft 12, is inserted into the inside of the gear housing 71. As a result, the male stopper portion 27 provided on the front end of the inner shaft 18 is positioned inside the gear housing 71.

[0089] The reaction force motor 72 is supported and fixed to the gear housing 71. The rotation of the reaction force motor 72 is transmitted to the steering shaft 12 via the worm gear reducer 73, the output shaft 28, and the torsion bar 30.

[0090] The worm gear reducer 73 comprises a worm and a worm wheel 75. The worm is connected to a motor output shaft (not shown) of a reaction force motor 72. The worm wheel 75 is fitted onto the output shaft 28.

[0091] The output shaft 28 is positioned with its axial direction oriented in the front-rear direction and is rotatably supported inside the gear housing 71. The output shaft 28 is positioned coaxially with the inner shaft 18 that constitutes the steering shaft 12. The output shaft 28 is connected to the inner shaft 18 via a torsion bar 30. A torque sensor 7 is positioned around the front end of the inner shaft 18 to measure the steering torque input from the driver to the steering wheel 2.

[0092] To apply steering reaction force to the steering wheel 2 using the reaction force generating device 11, the control device 6 drives the reaction force applying motor 72 based on various signals indicating driving conditions such as steering torque, steering angle, and vehicle speed. The rotation of the reaction force applying motor 72 is transmitted to the output shaft 28 via the worm gear reducer 73 and applied to the steering wheel 2 as steering reaction force via the torsion bar 30 and steering shaft 12.

[0093] With the inner shaft 18 constituting the steering device 1 in this example as described above, it is possible to increase the extension and retraction stroke amount of the steering shaft 12 while suppressing an increase in weight, and to reduce sliding resistance during the extension and retraction operation of the steering shaft 12 throughout the entire stroke range.

[0094] In other words, in this example, of the splines 22 provided on the outer circumferential surface of the inner shaft 18, a metal male spline portion 23 is provided only in the portion that spline-engages with the female spline portion 35 when the fore-aft position of the steering wheel 2 is located within the driver operating range X. In the portion of the splines 22 that spline-engages with the female spline portion 35 when the fore-aft position of the steering wheel 2 is located within the driver non-operating range Y, a metal male spline portion 23 is not provided. Instead, a resin male spline portion 32 made of synthetic resin is provided, having the same cross-sectional contour shape as the resin coating layer 31 formed around the male spline portion 23. Furthermore, such a resin male spline portion 32 is formed around a non-spline portion 24, which has a smaller cross-sectional area than the male spline portion 23.

[0095] Therefore, according to this example, compared to the case where the overall length of the male spline portion 23 is increased, the increase in the weight of the inner shaft 18 can be suppressed while increasing the extension stroke amount of the steering shaft 12. Furthermore, when the fore-aft position of the steering wheel 2 is located in the driver operating range X, the male spline portion 23 and the female spline portion 35 can be spline-engaged via the resin coating layer 31. Also, when the fore-aft position of the steering wheel 2 is located in the driver non-operating range Y, the resin male spline portion 32 and the female spline portion 35 can be spline-engaged. Therefore, sliding resistance during the extension and retraction operation of the steering shaft 12 can be reduced throughout the entire stroke range of the steering shaft 12. Furthermore, in this example, since it is not necessary to increase the overall length of the male spline portion 23, the increase in processing costs for the inner shaft 18 can also be suppressed.

[0096] Furthermore, in this example, when manufacturing the inner shaft 18, the male stopper portion 27, which prevents excessive twisting of the torsion bar 30, can be used to align the phase of the shaft body 20 and the mold 36. Therefore, there is no need to provide a dedicated part for phase alignment on the shaft body 20, which can reduce the manufacturing cost of the inner shaft 18.

[0097] [Second example of an embodiment] A second example of the embodiment will be described using Figures 10 and 11.

[0098] In this example, only the structure of the inner shaft 18a is changed from the structure of the first example of the embodiment.

[0099] The shaft body 20a constituting the inner shaft 18a in this example has, in order from one axial side, a small-diameter shaft portion 76, a male spline portion 23, a non-spline portion 24, and an exposed shaft portion 25. The small-diameter shaft portion 76 is positioned adjacent to one axial side of the male spline portion 23 and is provided at one axial end of the shaft body 20a.

[0100] The small diameter shaft portion 76 is the root circle diameter d of the male spline portion 23. b Smaller outer diameter D 76 (d b <D 76 In this example, the small-diameter shaft portion 76 has a circular cross-sectional shape. That is, the small-diameter shaft portion 76 has an outer diameter D of the non-spline portion 24. 24 Smaller outer diameter D 76 It has a round bar shape. When implementing the present invention, the cross-sectional shape of the small-diameter shaft portion and the cross-sectional shape of the non-spline portion can be made different from each other. Also, the axial dimension of the small-diameter shaft portion 76 is sufficiently shorter than the axial dimension of the male spline portion 23.

[0101] The resin-coated portion 21a covers not only the male spline portion 23 and the non-spline portion 24 of the shaft body 20a, but also the small-diameter shaft portion 76. The resin-coated portion 21a has a resin retaining portion 77 around the small-diameter shaft portion 76.

[0102] The resin retaining portion 77 covers the entire cylindrical surface of the small-diameter shaft portion 76. The resin retaining portion 77 is positioned adjacent to one axial side of the resin coating layer 31 covering the male spline portion 23, and is connected to the resin coating layer 31 in the axial direction. Therefore, the resin retaining portion 77, the resin coating layer 31, and the resin male spline portion 32 are integrally constructed. The axial dimension of the resin retaining portion 77 is the same as the axial dimension of the small-diameter shaft portion 76.

[0103] The resin retaining portion 77 is constructed by arranging a plurality of resin teeth 77a that extend axially along the inner shaft 18a at equal pitches in the circumferential direction. The resin teeth 77a are provided in the same number as the metal male spline teeth 23a and are arranged at the same pitch as the male spline teeth 23a. Therefore, the phases of the resin teeth 77a and the male spline teeth 23a in the circumferential direction coincide with each other.

[0104] The tooth thickness and tooth height of the resin tooth 77a are constant along the axial direction. Specifically, the tooth thickness of the resin tooth 77a is equal to the tooth width of the resin male spline tooth 32a. Also, the tooth height of the resin tooth 77a is equal to the tooth height of the resin male spline tooth 32a. Therefore, the tooth tip surface, tooth root surface, and side surface of the resin tooth 77a are smoothly connected in the axial direction to the tooth tip surface, tooth root surface, and side surface of the male spline tooth 23a, which is covered by the resin coating layer 31. Consequently, with respect to a virtual plane perpendicular to the central axis of the inner shaft 18, the cross-sectional contour shape of the resin retaining portion 77 is the same as the cross-sectional contour shapes of the resin coating layer 31 and the resin male spline portion 32, respectively. For this reason, the resin tooth 77a constitutes one end of the spline 22a on the axial side. However, when implementing the present invention, the resin teeth can be omitted from the outer circumferential surface of the resin retaining portion.

[0105] The inner shaft 18a of this example, as described above, can also be manufactured by the same manufacturing method (injection molding) as in the first example of the embodiment.

[0106] In this example, a small-diameter shaft portion 76, whose outer diameter is smaller than the root circle diameter of the male spline portion 23, is provided at one axial end of the shaft body 20a, and a resin retaining portion 77 is formed around the small-diameter shaft portion 76. Therefore, by abutting the other axial end face of the resin retaining portion 77 against the axial end face of the male spline portion 23, the resin coating portion 21a can be effectively prevented from coming loose (relatively displacing) in the other axial direction relative to the shaft body 20a. The other configurations and effects are the same as in the first example of the embodiment.

[0107] [Third example of an embodiment] A third example of the embodiment will be described with reference to Figure 12.

[0108] In this example, only the structure of the shaft body 20b is changed from the structure of the first example of the embodiment.

[0109] In this example, the shaft body 20b has a phase-determining recess 78 on a circumferential portion of the extension shaft portion 26 that constitutes the exposed shaft portion 25.

[0110] When manufacturing the inner shaft 18b in this example, the male spline portion 23 and the non-spline portion 24 of the shaft body 20b are placed in the cavity 37 of the mold 36a with the phase-setting protrusion 79 provided on the first mold 38a engaged with the phase-setting recess 78 provided on the extension shaft portion 26. This aligns the phase of the shaft body 20b and the mold 36a.

[0111] In this example, the phase setting relative to the mold 36a can be performed using the phase setting recess 78 located in the axial middle of the shaft body 20b, rather than the male stopper portion 27 located at the other axial end of the shaft body 20b. This allows for miniaturization of the mold 36a. Consequently, the manufacturing cost of the inner shaft 18b can be reduced. The other configurations and effects are the same as in the first example of the embodiment.

[0112] [Fourth example of an embodiment] A fourth example of the embodiment will be described using Figure 13.

[0113] In this example, only the manufacturing method of the inner shaft 18 differs from the manufacturing method of the first embodiment.

[0114] In this example as well, first, a cylindrical material made of metal such as carbon steel is subjected to machining, and then plastic deformation (splinting) such as cold forging, hobbing, and rolling is performed. This produces a shaft body 20 having, in order from the bottom of Figure 14, a male spline portion 23, a non-spline portion 24, and an exposed shaft portion 25.

[0115] Subsequently, a process is carried out to form a resin coating portion 21 on the outer surface of the shaft body 20 by fluid immersion and cutting. To this end, first, as shown in Figure 14(A), the male spline portion 23 and the non-spline portion 24 of the shaft body 20 are immersed in molten synthetic resin 80. As a result, as shown in Figure 14(B), a resin coating intermediate material 81 is formed on the lower half of the outer surface of the shaft body 20.

[0116] Subsequently, a process is carried out to form the resin-coated portion 21 from the resin-coated intermediate material 81 by performing cutting processes such as shaving and broaching on the outer circumferential surface of the resin-coated intermediate material 81. For this purpose, as shown in Figure 14(C), the shaft body 20, whose lower half is covered by the resin-coated intermediate material 81, is set in the cutting equipment 82. At this time, the male stopper portion 27 provided on the exposed shaft portion 25 is used to align the circumferential phase of the spline-processed portion 84 with the uneven shape provided on the inner circumferential surface of the cutting tool 83 and the male spline portion 23. Specifically, the phase of the male spline portion 23 and the spline-processed portion 84 is aligned by engaging the phase-setting pin 85 provided on the cutting equipment 82 with one or more male side groove portions 27b that constitute the male stopper portion 27.

[0117] Subsequently, by moving the cutting tool 83 relative to the shaft body 20 to the upper side as shown in Figure 14, the spline processing section 84 provided on the inner circumferential surface of the cutting tool 83 cuts the outer circumferential surface of the resin-coated intermediate material 81. This processes splines 22 onto the outer circumferential surface of the resin-coated intermediate material 81, forming the resin-coated portion 21. In this example, the inner shaft 18, consisting of the shaft body 20 and the resin-coated portion 21, is manufactured in this manner.

[0118] In this example of manufacturing the inner shaft 18 using the manufacturing method described above, it is not necessary to use a mold, as in the manufacturing method of the first embodiment, and therefore the manufacturing cost of the inner shaft 18 can be reduced. The other configurations and effects are the same as in the first example of the embodiment.

[0119] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. Furthermore, the structures of each example of the embodiments can be combined as appropriate, as long as no contradictions arise.

[0120] In each example of the embodiment, the case in which the non-spline portion constituting the shaft body of the inner shaft has a circular cross-sectional shape has been described. However, when implementing the present invention, the cross-sectional shape of the non-spline portion is not limited to a circle, but can also be non-circular, such as a semicircular, polygonal, or gear-shaped. In this way, when the cross-sectional shape of the non-spline portion is non-circular, relative rotation of the resin male spline portion with respect to the non-spline portion can be effectively prevented. Furthermore, relative rotation of the resin male spline portion with respect to the non-spline portion can also be prevented by providing protrusions and / or grooves at some or more locations in the circumferential direction on the outer surface of the non-spline portion.

[0121] The present invention is not limited to steer-by-wire steering systems, but can also be applied to retractable steering systems. Furthermore, the present invention is not limited to structures that move the steering wheel electrically, but can also be applied to structures that move the steering wheel manually. [Explanation of Symbols]

[0122] 1. Steering system 2 Steering Wheel 3. Steering Unit 4 Steering wheels 5. Steering Unit 6. Control device 7 Torque sensor 8. Steering actuator 9 Tie rods 10 Position adjustment device 11. Reaction force generating device 12 Steering shaft 13. Steering column 14 Lower telescopic actuator 15 Upper telescopic actuator 16 Tilt Actuators 17a, 17b Rolling bearings 18, 18a, 18b Inner Shaft 19 Outer Shaft 20, 20a, 20b shaft body 21 Resin-coated part 22, 22a spline 23 Male spline section 23a Male spline teeth 24 Non-splined section 25 Exposed shaft part 26 Extension shaft 27 Male Stopper Section 27a Male tooth portion 27b Male gutter 28 Output shaft 29 Female stopper section 30 Torsion bar 31 Resin coating layer 32 Resin male spline section 32a Resin male spline teeth 33 Small diameter cylinder part 34 Large diameter cylindrical section 35 Female spline section 35a Female spline teeth 36, 36a mold 37 Cavity 38, 38a First mold 39. Second mold 40 Spline forming section Gate 41 42 brackets 43 Column body 44 Fixing brackets 45 Displacement Bracket 46 Fixed plate part 47 Fixed-side support frame 48 Mounting bolts 49 Displacement plate section 50 Displacement side support frame 51 Linear Guide 52 Support wall section 53 Outer Column 54 Lower Inner Column 55 Upper Inner Column 56 slits 57 screw holes 58 Screw plug 59 Motor for lower telescopic extension 60 Lower side feed screw device 61 Lower threaded shaft 62 Lower side nut 63 Upper telescopic motor 64 Upper side feed screw device 65 Upper side threaded shaft 66 Upper nut 67 Connector components 68 pivot bolts 69. Tilt motor 70 Tilt feed screw device 71 Gear Housing 72 Reaction force applying motor 73 Worm gear reducer 75 Worm Wheel 76 Small diameter shaft section 77 Resin retaining part 77a Resin teeth 78 Phase-determining recess 79 Phase-determining protrusion 80 Molten resin 81 Resin-coated intermediate material 82 Cutting equipment 83 Cutting tools 84 Spline machining section 85 Phase-setting pins

Claims

1. a metal shaft body having a male spline portion on one axial side thereof and a non-spline portion adjacent to the other axial side thereof, the non-spline portion having a cross-sectional area smaller than that of the male spline portion; a resin coating portion made of synthetic resin that covers an outer peripheral surface of the shaft body in a range that includes the male spline portion and the non-spline portion, the resin-coated portion comprises a resin coating layer formed around the male spline portion, and a resin male spline portion formed around the non-spline portion and having the same cross-sectional contour shape as the cross-sectional contour shape of the resin coating layer. Inner shaft.

2. the shaft body has a small diameter shaft portion, the small diameter shaft portion having an outer diameter smaller than a root circle diameter of the male spline portion, in a portion adjacent to one axial side of the male spline portion, The resin coating portion covers the outer peripheral surface of the small diameter shaft portion, and includes a resin retaining portion around the small diameter shaft portion. The inner shaft according to claim 1.

3. 2. The inner shaft according to claim 1, wherein the shaft body has an exposed shaft portion, the outer circumferential surface of which is not covered by the resin coating portion, on the other axial side of the non-spline portion.

4. The inner shaft according to claim 3 , wherein the exposed shaft portion has a phase determining portion that can be used for phase determination.

5. The inner shaft according to claim 1 , wherein the non-splined portion has a circular cross-sectional shape.

6. 6. The inner shaft according to claim 5, wherein the non-splined portion has an outer diameter equal to the diameter of a tooth root circle of the male splined portion.

7. The inner shaft according to claim 1 , wherein the non-splined portion has a non-circular cross-sectional shape.

8. A method for manufacturing an inner shaft according to any one of claims 1 to 7, the step of placing at least a portion of the shaft body that is on one axial side of the non-spline portion in a cavity of a mold having a spline-molding portion on its inner surface, and solidifying molten resin injected into the cavity to form the resin-coated portion on the outer circumferential surface of the shaft body, A manufacturing method of an inner shaft.

9. A method for manufacturing an inner shaft according to any one of claims 1 to 7, a step of forming a resin-coated intermediate material on an outer peripheral surface of the shaft body by immersing at least a portion of the shaft body that is on one axial side of the non-spline portion in molten synthetic resin; and forming the resin-coated portion by performing cutting on the outer peripheral surface of the resin-coated intermediate material. A manufacturing method of an inner shaft.

10. A steering shaft having an outer shaft and an inner shaft spline-engaged with the outer shaft to enable torque transmission and relative axial displacement therebetween, the steering shaft having a rear end to which a steering wheel is fixed, The inner shaft is the inner shaft according to any one of claims 1 to 7. Steering shaft.

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