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 provides vinegar Regarding tearing shafts. [Background technology]

[0002] Autonomous driving technology for automobiles has been advancing rapidly in recent years. As a result, it is believed that in the near future, the level of autonomous driving will reach levels where automobiles can drive themselves under certain conditions (Level 3 and 4), and even fully autonomous driving (Level 5). In autonomous vehicles equipped with such autonomous driving technology, the driver will have less need to operate the steering wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-52514 Summary of the Invention [Problem to be solved by the invention]

[0004] During autonomous driving, autonomous vehicles may be required to move the steering wheel significantly forward and store it in the dashboard or away from the driver to ensure ample space in front of the driver's seat.

[0005] In order to move the steering wheel far forward, the telescopic stroke of the steering shaft to which the steering wheel is fixed must be greater than that of steering shafts of conventional construction. Specifically, in a steering shaft that constitutes a steering device in which the fore-aft position of the steering wheel can be adjusted, the telescopic stroke must be greater by the amount required to move the steering wheel far forward, rather than the amount required to adjust the fore-aft position of the steering wheel.

[0006] The steering shaft is configured to be able to extend and retract its entire length by spline-engaging the male spline portion on the inner shaft with the female spline portion on the outer shaft. Therefore, in order to increase the extension stroke of the steering shaft, it is conceivable to increase the overall length of the male spline portion.

[0007] However, the cross-sectional area of ​​the male spline portion in an imaginary plane perpendicular to the central axis of the inner shaft is larger than that of the portion of the inner shaft that is axially offset from the male spline portion. For this reason, if the overall length of the male spline portion is increased in order to increase the extension and contraction stroke of the steering shaft, the weight of the inner shaft tends to increase, which creates a problem in that the weight of the steering shaft also tends to increase.

[0008] Japanese Patent Application Laid-Open Publication No. 2017-52514 (Patent Document 1) discloses a technology for preventing metallic contact between the male spline portion and the female spline portion by covering the outer peripheral 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 Application Laid-Open Publication No. 2017-52514 does not mention at all that any part of the outer peripheral surface of the inner shaft other than the male spline portion is covered with synthetic resin.

[0009] The present invention has been made to solve the above-mentioned 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 extension and retraction of the steering shaft over the entire stroke range. [Means for solving the problem]

[0010] The inventors of the present invention have intensively studied means for solving the above problems and have found that when the fore-and-aft position of the steering wheel is in the driver operation range where the driver operates the steering wheel, it is necessary to be able to transmit a relatively large torque between the inner shaft and the outer shaft, whereas when the steering wheel is in the driver non-operation range where the driver does not operate the steering wheel, it is not necessary to be able to transmit a large torque between the inner shaft and the outer shaft as long as the inner shaft and the outer shaft can be displaced relative to each other in the axial direction.The inventors then came to the idea that if a male spline portion made of synthetic resin is provided on the inner shaft in the driver non-operation range, the metal male spline portion can be omitted, and have completed the present invention. Specifically, the present invention No. The tearing shaft employs the following means:

[0011] According to one aspect of the present invention steering shaft teeth, The transmission has an outer shaft with a female spline portion on its inner peripheral surface, and an inner shaft that is spline-engaged with the outer shaft to enable torque transmission and relative axial displacement, and a steering wheel is fixed to the rear end. The inner shaft is It 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 thereof, and a non-spline portion adjacent to the other axial side thereof, the non-spline portion having a smaller cross-sectional area than the male spline portion. The resin coating portion covers the outer peripheral surface of the shaft body in a range including 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. In a steering shaft according to one aspect of the present invention, when the fore-and-aft position of the steering wheel is located in a driver operation range where the driver operates the steering wheel, the female spline portion engages with the male spline portion via the resin coating layer, whereas when the fore-and-aft position of the steering wheel is located in a driver non-operation range where the driver does not operate the steering wheel, the female spline portion engages with the resin male spline portion. In this specification and claims, unless otherwise specified, a cross section refers to a cross section on an imaginary plane perpendicular to the central axis of the inner shaft.

[0012] According to one aspect of the present invention steering shaftIn the above, the shaft body may have a small diameter shaft portion, the outer diameter of which is smaller than the 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 may cover the outer peripheral surface of the small diameter shaft portion, and a resin retaining portion may be provided around the small diameter shaft portion. In this case, the resin retaining portion can have the same cross-sectional contour as the cross-sectional contours of the resin coating layer and the resin male spline portion.

[0013] According to one aspect of the present invention steering shaft In the above, the shaft body may have 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. In this case, the exposed shaft portion can be provided with a phase determining portion that can be used for phase determination.

[0014] According to one aspect of the present invention steering shaft In the above, the non-splined portion may have a circular cross-sectional shape. In this case, the non-splined portion can have an outer diameter that is the same as the diameter of the tooth root circle of the male splined portion. Alternatively, according to one aspect of the present invention, steering shaft In the above, the non-splined portion may have a non-circular cross-sectional shape. In this case, the non-splined portion may have a protrusion and / or a recessed groove at one or more locations in the circumferential direction of the outer circumferential surface. [Effects of the Invention]

[0015] According to one aspect of the steering shaft of the present invention, the extension stroke of the steering shaft can be increased while suppressing an increase in weight, and sliding resistance during extension and contraction of the steering shaft can be reduced over the entire stroke range. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing a steer-by-wire steering device according to a first example of the embodiment. [Figure 2] FIG. 2 is an end view of the steer-by-wire steering unit as viewed from the rear, relating to the first example of the embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, showing a first example of the embodiment. [Figure 4] FIG. 4 is a perspective view showing a steer-by-wire steering unit according to the first example of the embodiment. [Figure 5] FIG. 5 shows an inner shaft constituting a steering shaft in a first example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view taken along line BB in (A), and (C) is an enlarged cross-sectional view taken along line CC in (A). [Figure 6] FIG. 6 shows the shaft body of the inner shaft constituting the steering shaft in the first example of the embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view taken along line DD of (A), and (C) is an enlarged cross-sectional view taken along line EE of (A). [Figure 7] FIG. 7 is a schematic diagram showing the steering shaft and steering wheel in the first example of the embodiment, where (A) shows the state in which the fore-and-aft position of the steering wheel has been moved to the rearmost position within the driver operation range X, (B) shows the state in which the fore-and-aft position of the steering wheel has been moved to the frontmost position within the driver operation range X, and (C) shows the state in which the fore-and-aft position of the steering wheel has been moved to the frontmost position within the driver non-operation range Y. [Figure 8] FIG. 8 is a cross-sectional view schematically illustrating a method for manufacturing an inner shaft that constitutes a steering shaft according to the first example of the embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view taken along line FF in FIG. [Figure 10]Figure 10 is a diagram corresponding to Figure 5, showing a second example of an embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) taken along line GG, (C) is an enlarged cross-sectional view of (A) taken along line HH, and (D) is an enlarged cross-sectional view of (A) taken along line II. [Figure 11] Figure 11 is a diagram corresponding to Figure 6 showing a second example of an embodiment, where (A) is a plan view, (B) is an enlarged cross-sectional view of (A) taken along line JJ, (C) is an enlarged cross-sectional view of (A) taken along line KK, and (D) is an enlarged cross-sectional view of (A) taken along line LL. [Figure 12] FIG. 12 is a diagram corresponding to FIG. 8 and shows a third example of the embodiment. [Figure 13] FIG. 13 is a schematic diagram showing the order of steps in a method for manufacturing an inner shaft that constitutes a steering shaft according to the fourth example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First example of embodiment] A first example of the embodiment will be described with reference to FIGS. 1 to 9. In this example, No. The steering shaft is applied to a steer-by-wire steering device for an autonomous vehicle. In the following description, the front-rear direction means the front-rear direction of the vehicle, the up-down direction means the up-down direction of the vehicle, and the width direction means the width direction of the vehicle.

[0018] [Overall configuration of steering device] The steering device 1 of this example is a steer-by-wire type steering device. As shown in Fig. 1, the overall configuration of the steering device 1 is provided with a steering unit 3 to which a steering wheel 2 is attached, a steering unit 5 that steers a pair of steered wheels 4, and a control device (ECU) 6. The steering device 1 has a linkless structure in which the steering unit 3 and the steering unit 5 are not mechanically connected but are electrically connected.

[0019] Steering unit 3 measures the operation of steering wheel 2 by the driver using torque sensor 7 (see FIG. 3) and a steering angle sensor (not shown), and outputs the measurement results to control device 6. Various signals indicating the driving situation, such as the steering torque measured by torque sensor 7, the steering angle measured by the steering angle sensor, vehicle speed, yaw rate, and acceleration, are input to control device 6. Based on the various signals indicating the driving situation, control device 6 drives steering actuator 8 provided in steering unit 5. This displaces linearly moving members such as a rack shaft and a screw shaft in the width direction, pushing and pulling a pair of tie rods 9, and applying a steering angle to the pair of steered wheels 4.

[0020] In addition, the control device 6 controls the driving of a reaction force applying motor 72 (see Figure 2) of a reaction force generating device 11 (described later) provided in 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.

[0021] [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 generation device 11 for applying a steering reaction force to the steering wheel 2.

[0022] The position adjustment device 10 has the function of adjusting the front-rear 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 front-rear 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 of this example has the function of significantly retracting the steering wheel 2 forward during autonomous driving.

[0023] The position adjustment device 10 includes a steering shaft 12, a steering column 13, a lower telescopic actuator 14, an upper telescopic actuator 15, and a tilt actuator 16.

[0024] <Steering shaft> The steering shaft 12 is configured so that its entire length can be extended or contracted, and is rotatably supported inside the steering column 13 by a plurality of (two in the illustrated example) rolling bearings 17a, 17b. A steering wheel 2 is fixed to the rear end of the steering shaft 12. A front end of the steering shaft 12 is connected to an output shaft 28 that constitutes the reaction force generator 11 via a torsion bar 30.

[0025] The steering shaft 12 is made up of an inner shaft 18 located at the front and a hollow cylindrical outer shaft 19 located at the rear, which are splined together to enable torque transmission and relative axial displacement. In particular, the steering shaft 12 of this example has a larger extension stroke than conventional steering shafts that only allow adjustment of the fore-and-aft position of the steering wheel 2, in order to allow the steering wheel 2 to be moved forward significantly during automatic driving.

[0026] Inner Shaft As shown in Figure 5, the inner shaft 18 is made of a shaft body 20 made of a metal such as carbon steel, and a resin-coated portion 21 made of synthetic resin. The inner shaft 18 also has splines 22 of the same specifications (equal tooth width and tooth height along the axial direction) that are continuous in the axial direction on the outer peripheral surface of the portion that aligns with the resin-coated portion 21 in the axial direction. The internal structure of the splines 22 is different between one half of the splines 22 on one axial side and the other half of the splines 22 on the other axial side. The axial dimension L of the splines 22 (resin-coated portion 21) 22 is set based on the extension / contraction stroke of the steering shaft 12 required to largely retract the steering wheel 2 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.

[0027] (shaft body) 6, the shaft body 20 has, in order from one axial end, 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 with a resin coating portion 21, and the exposed shaft portion 25 is not covered with the resin coating portion 21 and is exposed to the outside.

[0028] The male spline portion 23 is provided at one axial end of the shaft body 20. The male spline portion 23 has an uneven shape in the circumferential direction. The male spline portion 23 has, on its outer circumferential surface, a plurality of male spline teeth 23a extending in the axial direction of the shaft body 20. The multiple 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 a chamfered portion provided at one axial end.

[0029] Axial dimension L of male spline portion 23 23 As shown in Fig. 7, when the front-rear position of the steering wheel 2 is in the driver operation range X where the driver operates the steering wheel 2, the length dimension is restricted to a value that allows the male spline portion 23 and the female spline portion 35 provided on the outer shaft 19 to be spline-engaged with a sufficient engagement margin via the resin coating layer 31 described later. Specifically, the axial dimension L of the male spline portion 23 is 23 is about 30 mm to 90 mm. In this example, the driver operation range X is a longitudinal position adjustment range in which the driver operating the steering wheel 2 can adjust the longitudinal position of the steering wheel 2.

[0030] The non-splined portion 24 is disposed adjacent to the other axial side of the male splined portion 23, and is provided in the axially intermediate portion of the shaft body 20. With respect to an imaginary 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 root circle diameter d of the male splined portion 23 is b The outer diameter D is the same as 24 (db =D 24 ). For this reason, 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, and may be a non-circular shape such as a broken circle or a polygon. Alternatively, the non-spline portion may have a plurality of teeth with a lower tooth height and / or a smaller tooth width than the plurality of male spline teeth that make up the male spline portion, and / or may have a number of teeth that is fewer than the total number of the plurality of male spline teeth that make up the male spline portion.

[0031] The exposed shaft portion 25 is disposed on the other axial side of the non-spline portion 24 and is provided in the other axial half of the shaft body 20 .

[0032] The exposed shaft portion 25 has an extension shaft portion 26 and a male stopper portion 27 .

[0033] The extension shaft portion 26 is provided at a 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 has an outer diameter D 24 The extension shaft portion 26 has an outer diameter that is the same as that of the non-spline portion 24. Therefore, the extension shaft portion 26 has a round bar shape, just like the non-spline portion 24. In this example, the only difference between the extension shaft portion 26 and the non-spline portion 24 is whether or not it is covered with 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-spline portion may be made different from each other, the outer diameter of the extension shaft portion and the non-spline portion may be made different from each other, or the surface textures may be made different from each other.

[0034] The male stopper portion 27 is disposed 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 circumferentially engages with a female stopper portion 29 provided on the output shaft 28 that constitutes the reaction force generator 11, thereby restricting the relative rotation between the inner shaft 18 and the output shaft 28 within a predetermined angle range and preventing excessive twisting of the torsion bar 30.

[0035] Male stopper portion 27 has a concave-convex shape (gear shape) in the circumferential direction. Specifically, male stopper portion 27 is configured by male side teeth 27a and male side grooves 27b, each of which extends in the axial direction, arranged alternately and at equal pitches in the circumferential direction. In this example, male stopper portion 27 constituting exposed shaft portion 25 functions as a phase determining portion that can be used to determine the phase of shaft body 20.

[0036] (Resin coated part) The resin coating portion 21 is made of a synthetic resin with a low coefficient of friction, such as polyamide resin (PA), polyethylene tetrafluoride (PTFE), or polyacetal resin (POM). The resin coating portion 21 covers the outer peripheral surface of the shaft body 20, 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.

[0037] The resin-coated portion 21 is made up 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.

[0038] The resin coating layer 31 covers the entire uneven surface of the male spline portion 23. The thickness (film thickness) of the resin coating layer 31 is almost 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 approximately 10 μm to 1000 μm. Therefore, the resin coating layer 31 has a contour shape that follows the outer shape of the male spline teeth 23a. The axial dimension L of the resin coating layer 31 31 is the axial dimension L of the male spline portion 23 23 is the same as (L 31 =L 23 ).

[0039] The resin male spline portion 32 covers the entire cylindrical surface of the non-spline portion 24. The resin male spline portion 32 is disposed adjacent to the other axial side of the resin coating layer 31 that covers the male spline portion 23, and is axially connected to the resin coating layer 31. In other words, the resin male spline portion 32 and the resin coating layer 31 are integrally configured.

[0040] The resin male spline portion 32 is configured by a plurality of resin male spline teeth 32a extending in the axial direction of the inner shaft 18 and arranged 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 are the same.

[0041] The tooth thickness and tooth height of the resin male spline teeth 32a are constant along the axial direction. Specifically, the tooth thickness of the resin male spline teeth 32a is equal to the tooth width of the male spline teeth 23a plus twice the thickness of the resin coating layer 31. Furthermore, the tooth height of the resin male spline teeth 32a is equal to the tooth height of the male spline teeth 23a plus the thickness of the resin coating layer 31. Therefore, the tip, bottom, and side surfaces of the resin male spline teeth 32a are smoothly connected in the axial direction to the tip, bottom, and side surfaces of the male spline teeth 23a covered with the resin coating layer 31. Therefore, the cross-sectional contour shape of the resin male spline portion 32 is the same as the cross-sectional contour shape of the resin coating layer 31 with respect to an imaginary plane perpendicular to the central axis of the inner shaft 18.

[0042] Axial dimension L of the resin male spline portion 32 32 The length L of the resin male spline portion 32 is limited to the length required to move the steering wheel 2 forward from the state where it is positioned at the most forward position within the forward position adjustment range, which is the driver operation range X, as shown in FIG. 7(B), to the point where the steering wheel 2 can be stored in the dashboard, as shown in FIG. 7(C).32 is the axial dimension L of the non-splined portion 24 24 is the same as (L 32 =L 24 ), specifically, about 90mm to 130mm.

[0043] In the illustrated example, the axial dimension L of the resin male spline portion 32 32 is the axial dimension L of the resin coating layer 31 31 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). Also, 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. The axial dimension L of the resin male spline portion 32 32 The lower limit is about 90 mm.

[0044] In this example, the male spline portion 23 covered with 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, the one axial half of the spline 22 is made of synthetic resin only on the surface and metal on the inside, whereas the other axial half of the spline 22 is made of synthetic resin from the surface to the inside.

[0045] (outer shaft) The outer shaft 19 has a hollow cylindrical shape. The outer shaft 19 is disposed rearward of 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 peripheral surface of the small-diameter cylindrical portion 33. The steering wheel 2 is fixed to the rear end of the outer shaft 19.

[0046] The female spline portion 35 has a concave-convex shape in the circumferential direction. The female spline portion 35 is configured by arranging a plurality of female spline teeth 35a extending in the axial direction of the outer shaft 19 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 chamfered portions provided at the axial ends.

[0047] 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 Specifically, the axial dimension of the female spline portion 35 is shorter than, for example, the axial dimension L of the resin coating layer 31. 31 It is about 1.5 to 2 times the amount.

[0048] The large diameter cylindrical portion 34 has an inner diameter larger than the diameter of the tooth root circle of the female spline teeth 35a.

[0049] The female spline portion 35 provided on the outer shaft 19 is spline-engaged with the spline 22 provided on the inner shaft 18. As a result, the outer shaft 19, together with the steering wheel 2, moves relative to the inner shaft 18 in the front-to-rear direction, causing the steering shaft 12 to extend and retract.

[0050] In particular, in this example, the spline engagement state between the inner shaft 18 and the outer shaft 19 changes depending on the front-rear position of the steering wheel 2. This will be specifically explained below with reference to FIG. 7A shows a state in which the longitudinal position of the steering wheel 2 has been moved to the rearmost position within the driver operation range X, and FIG. 7B shows a state in which the longitudinal position of the steering wheel 2 has been moved to the frontmost position within the driver operation range X. FIG. 7C shows a state in which the longitudinal position of the steering wheel 2 has been moved to the frontmost position within the driver non-operation range Y.

[0051] As shown in Figures 7A and 7B, when the distance from the driver to the steering wheel 2 is short and the fore-and-aft position of the steering wheel 2 is within the driver operation range X where the driver operates the steering wheel 2, the female spline portion 35 is spline-engaged 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 margin, preferably over the entire length. Therefore, within the driver operation range X, a relatively large torque can be transmitted between the inner shaft 18 and the outer shaft 19. Therefore, the torque input to the steering wheel 2 by the driver and the torque generated by the reaction force generator 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 18 and the outer shaft.

[0052] Even within the driver operating range, the female spline portion 35 may be spline-engaged with one axial side portion of the resin male spline portion 32. However, in this case, the engagement margin 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 margin, so that a large torque is not transmitted to the resin male spline portion 32.

[0053] As shown in Figure 7 (C), when the distance from the driver to the steering wheel 2 is long 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 is spline-engaged with a sufficient engagement margin with the resin male spline portion 32 that constitutes the other axial half of the spline 22. Therefore, 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 relatively displace the inner shaft 18 and the outer shaft 19 in the axial direction. When the female spline portion 35 engages with the resin male spline portion 32, the male spline portion 23 covered with the resin coating layer 31 is inserted inside the large-diameter cylindrical portion 34.

[0054] (Inner shaft manufacturing method) The inner shaft 18 of this example can be manufactured by the following manufacturing method, for example.

[0055] First, a cylindrical blank made of a metal such as carbon steel is machined, and then subjected to plastic processing (spline processing) such as cold forging, hobbing, and rolling, thereby producing a shaft body 20 having, in order from one axial end, a male spline portion 23, a non-spline portion 24, and an exposed shaft portion 25, as shown in Figure 6.

[0056] Thereafter, a step of forming the resin-coated portion 21 by injection molding is performed on the outer peripheral surface of the shaft body 20. For this step, the portion of the shaft body 20 that is on one axial side of the non-spline portion 24 is placed in a cavity 37 of a mold 36. Specifically, as shown in FIG. 8 , the male spline portion 23 and the non-spline portion 24 of the shaft body 20 are placed in the cavity 37 of the mold 36.

[0057] The mold 36 is formed by combining a first mold 38 and a second mold 39, and has a spline-forming portion 40 on its inner surface. The spline-forming portion 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 portion 32, respectively.

[0058] In this example, when the male spline portion 23 and the non-spline portion 24 of the shaft body 20 are placed in the cavity 37 of the mold 36, the male stopper portion 27 provided on the exposed shaft portion 25 is used to match the phases of the male spline portion 23 and the spline-molded portion 40 in the circumferential direction. Specifically, by engaging the first mold 38 and / or the second mold 39 with one or more male groove portions 27b that constitute the male stopper portion 27, the gap between the male spline portion 23 and the spline-molded portion 40 is made uniform over the entire circumference.

[0059] Thereafter, molten resin is injected into the cavity 37 through a gate 41 provided in the first mold 38. The molten resin is then solidified within the cavity 37. As a result, the solidified molten resin forms the resin-coated portion 21. In other words, the resin-coated portion 21 is formed so as to cover the male spline portion 23 and the non-spline portion 24 on the outer circumferential surface of the shaft main body 20. In this example, the inner shaft 18 consisting of the shaft main body 20 and the resin-coated portion 21 is manufactured in this manner.

[0060] Steering column The steering column 13 is configured to be extendable over its entire length and is supported by a vehicle body (not shown). The steering column 13 includes a bracket 42 and a column body 43. The steering column 13 in this example has a two-stage telescopic structure to ensure a large amount of telescopic stroke in the front-rear direction.

[0061] The bracket 42 is used to support 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 capable of relative displacement in the fore-and-aft direction with respect to the fixed bracket 44.

[0062] The fixed bracket 44 includes a fixed plate portion 46 in the shape of a substantially rectangular flat plate, and a fixed-side support frame 47 in a substantially U-shape. The fixed plate portion 46 is fixed to the vehicle body using a plurality of mounting bolts 48. The fixed-side support frame 47 is provided at the front end of the fixed plate portion 46, and connects both ends of the fixed plate portion 46 in the width direction.

[0063] The displacement bracket 45 includes a displacement plate portion 49 arranged so as to be overlapped on the underside of the fixed plate portion 46, and a generally U-shaped displacement-side support frame 50. The displacement plate portion 49 is supported by a linear guide 51 so as to be displaceable relative to the fixed plate portion 46 in the front-to-rear direction. The displacement-side support frame 50 is provided at the rear end of the displacement plate portion 49 and connects both ends of the displacement plate portion 49 in the width direction. Of the pair of left and right support walls 52 that make up the displacement-side support frame 50, a screw shaft (not shown) of a tilt feed screw device 70 that makes up the tilt actuator 16 is rotatably supported on the inner surface of one of the support wall portions 52, with its axial direction facing up and down.

[0064] The column body 43 is configured in a generally cylindrical shape overall, and is disposed with its axial direction facing the front-to-rear direction. The column body 43 includes an outer column 53 disposed in the middle in the front-to-rear direction, a lower-side inner column 54 fitted within the front side of the outer column 53, and an upper-side inner column 55 fitted within the rear side of the outer column 53.

[0065] The outer column 53 is supported relative to the displacement bracket 45 so as to be movable in the vertical direction. The rear side of the outer column 53 is inserted in the front-to-rear direction inside the displacement-side support frame 50 that constitutes the displacement bracket 45. A nut (not shown) of a tilt feed screw device 70 that constitutes the tilt actuator 16 is pivotally supported on the outer peripheral surface of the rear side of the outer column 53. The outer column 53 has a slit 56 (see Figure 3) that extends in the front-to-rear direction in the middle of the lower surface in the front-to-rear direction. The outer column 53 has screw holes 57 at multiple locations on its outer peripheral surface. A screw plug 58, the tip of which is made of a material with a low friction coefficient such as polyacetal (POM), is screwed into each of the screw holes 57.

[0066] The lower-side inner column 54 is fitted within the front portion of the outer column 53 so as to be able to move relatively in the front-to-rear direction. The tip of a screw plug 58 that is threaded into a threaded hole 57 provided in the outer column 53 is pressed against the outer peripheral surface of the lower-side inner column 54. This suppresses rattle of the lower-side inner column 54 relative to the outer column 53.

[0067] The upper-side inner column 55 is fitted within the rear side of the outer column 53 so as to be able to move relatively in the front-to-rear direction. The tip of a screw plug 58 that is threaded into a screw hole 57 provided in the outer column 53 is pressed against the outer peripheral surface of the upper-side inner column 55. This suppresses rattle of the upper-side inner column 55 relative to the outer column 53.

[0068] <Lower telescopic actuator> The lower-side telescopic actuator 14 is disposed so as to bridge between the fixed bracket 44 and the displacement bracket 45, and displaces the displacement bracket 45 in the front-to-rear direction relative to the fixed bracket 44. This causes the outer column 53 and the lower-side inner column 54 to be displaced relative to each other in the front-to-rear direction, causing the column main body 43 to extend and contract.

[0069] The lower telescopic actuator 14 includes a lower telescopic motor 59 and a lower feed screw device 60.

[0070] The lower telescopic motor 59 is supported and fixed to the widthwise side surface of the fixed support frame 47 that constitutes the fixed bracket 44, with the motor output shaft (not shown) facing up and down.

[0071] As shown in Fig. 2, the lower side feed screw device 60 includes a lower side threaded shaft 61 and a lower side nut 62. The lower side threaded shaft 61 is disposed with its axial direction facing the front-to-rear direction, and is rotationally driven by a lower side telescopic motor 59 via a reduction mechanism such as a worm reducer (not shown). The lower side threaded shaft 61 is supported by the fixed bracket 44 so as to be only rotatable. The lower side nut 62 is threadedly engaged with the lower side threaded shaft 61, and is supported by a side surface of the displacement bracket 45 in the width direction. In other words, the lower side telescopic actuator 14 rotationally drives the lower side telescopic motor 59 to displace the lower side nut 62 in the axial direction of the lower side threaded shaft 61, thereby displacing the outer column 53 in the front-to-rear direction relative to the lower side inner column 54.

[0072] <Upper telescopic actuator> The upper telescopic actuator 15 is disposed so as to bridge between the outer column 53 and the upper inner column 55, and displaces the upper inner column 55 in the front-to-rear direction relative to the outer column 53. This causes the column body 43 to extend and retract.

[0073] The upper telescopic actuator 15 includes an upper telescopic motor 63 and an upper feed screw device 64 .

[0074] 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.

[0075] The upper side feed screw device 64 includes an upper side screw shaft 65 and an upper side nut 66. The upper side screw shaft 65 is disposed with its axial direction facing the front-to-rear direction, and is rotationally driven by an upper side telescopic motor 63 via a reduction mechanism such as a worm reducer (not shown). The upper side screw shaft 65 is supported so as to be rotatable only relative to the outer column 53. The upper side nut 66 is threadedly engaged with the upper side screw shaft 65, and is supported on the lower surface of the upper side inner column 55 via a connector member 67. The connector member 67 is disposed 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 rotationally drives the upper side telescopic motor 63 to displace the upper side nut 66 in the axial direction of the upper side screw shaft 65, thereby displacing the upper side inner column 55 in the front-to-rear direction relative to the outer column 53.

[0076] <Tilt actuator> The tilt actuator 16 is disposed so as to bridge between the displacement-side support frame 50 and the outer column 53 that constitute the displacement bracket 45, and displaces the outer column 53 in the vertical direction relative to the displacement bracket 45. In addition, as will be described later, the reaction force generator 11 connected to the front side of the position adjustment device 10 is rotatably supported by the fixed-side support frame 47 by a pair of pivot bolts 68 disposed in the width direction. This makes it possible to swing the column main body 43 in the vertical direction relative to the bracket 42 around the pivot bolts 68.

[0077] The tilt actuator 16 includes a tilt motor 69 and a tilt feed screw device 70 .

[0078] The tilt motor 69 is fixed to one of the support walls 52 that constitute the displacement side support frame 50 with its motor output shaft (not shown) facing in the front-rear direction.

[0079] The tilt feed screw device 70 includes a tilt screw shaft and a tilt nut (not shown). The tilt screw shaft is disposed with its axial direction facing the vertical direction, and is rotationally driven by a tilt motor 69 via a reduction mechanism such as a worm reducer (not shown). The tilt screw shaft is supported on one of the support wall portions 52 so as to be rotatable only. The tilt nut is threadedly engaged with the tilt screw shaft, and is pivotally supported on the side surface of the outer column 53 in the width direction. In other words, the tilt actuator 16 rotationally drives the tilt motor 69 to displace the tilt nut in the axial direction of the tilt screw shaft, thereby displacing the outer column 53 vertically relative to the displacement bracket 45.

[0080] <<How to adjust the steering wheel position>> To adjust the longitudinal position of the steering wheel 2 using the position adjustment device 10 of this example, 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 in the longitudinal direction relative to the fixed bracket 44, and the outer column 53 is displaced in the longitudinal direction relative to the lower inner column 54. On the other hand, when the upper telescopic actuator 15 is driven, the upper inner column 55 is displaced in the longitudinal direction relative to the outer column 53. This causes the overall length of the steering column 13 to expand and contract, and also the overall length of the steering shaft 12 to expand and contract, thereby adjusting the longitudinal position of the steering wheel 2 within the longitudinal position adjustment range, which is the driver operation range X. After the longitudinal position of the steering wheel 2 has been adjusted to the desired position, the drive of the lower telescopic actuator 14 and / or the upper telescopic actuator 15 is stopped.

[0081] To adjust the vertical position of the steering wheel 2 using the position adjustment device 10 of this example, the tilt actuator 16 is driven to displace the rear portion of the outer column 53 in the vertical direction relative to the displacement bracket 45. This causes the steering shaft 12, which is rotatably supported inside the column body 43, to swing, adjusting the vertical position of the steering wheel 2. After the vertical position of the steering wheel 2 has been adjusted to the desired position, the drive of the tilt actuator 16 is stopped. The adjustment of the front-rear position and the adjustment of the up-down position of the steering wheel 2 can be performed simultaneously or independently (at different times).

[0082] Furthermore, in order to retract the steering wheel 2 significantly forward during autonomous driving by using the position adjustment device 10 of this example so that the steering wheel 2 can be stored in the dashboard or positioned away from the driver, the lower telescopic actuator 14 and the upper telescopic actuator 15 are each driven. As a result, the displacement bracket 45 is displaced forward relative to the fixed bracket 44, the outer column 53 is displaced forward relative to the lower inner column 54, and the upper inner column 55 is displaced forward relative to the outer column 53. Then, the overall length of the steering column 13 is shortened, and the overall length of the steering shaft 12 is shortened, thereby retracting the steering wheel 2 significantly forward. After the steering wheel 2 has been retracted significantly forward, the drive of the lower telescopic actuator 14 and the upper telescopic actuator 15 is stopped.

[0083] <Reaction force generating device> The reaction force generating device 11 is disposed 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 to the steering wheel 2 a steering reaction force of a magnitude and direction according to driving conditions such as the steering angle of the steering wheel 2 and the vehicle speed.

[0084] The reaction force generator 11 includes a gear housing 71, a reaction force applying motor 72, a worm reducer 73, an output shaft 28, and a torsion bar 30.

[0085] The gear housing 71 is fixed to the front end of the lower inner column 54 that constitutes the position adjustment device 10. Furthermore, the front end of the inner shaft 18 that constitutes the steering shaft 12 is inserted into the inside of the gear housing 71. As a result, the male stopper portion 27 provided at the front end of the inner shaft 18 is disposed inside the gear housing 71.

[0086] The reaction force applying motor 72 is supported and fixed to the gear housing 71. The rotation of the reaction force applying motor 72 is transmitted to the steering shaft 12 via a worm reducer 73, the output shaft 28, and the torsion bar 30.

[0087] The worm reducer 73 includes a worm and a worm wheel 75. The worm is connected to a motor output shaft (not shown) of the reaction force applying motor 72. The worm wheel 75 is fitted onto the output shaft 28.

[0088] The output shaft 28 is disposed with its axial direction facing the front-rear direction, and is rotatably supported inside the gear housing 71. The output shaft 28 is disposed 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 disposed around the front end of the inner shaft 18 to measure the steering torque input to the steering wheel 2 by the driver.

[0089] To apply a 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 reducer 73, and is applied to the steering wheel 2 as a steering reaction force via the torsion bar 30 and the steering shaft 12.

[0090] According to the inner shaft 18 constituting the steering device 1 of this example as described above, it is possible to increase the extension stroke of the steering shaft 12 while suppressing an increase in weight, and to reduce the sliding resistance during the extension and retraction movement of the steering shaft 12 over the entire stroke range.

[0091] That is, in this example, the metal male spline portion 23 is provided only on the portion of the spline 22 provided on the outer peripheral surface of the inner shaft 18 that engages with the female spline portion 35 when the longitudinal position of the steering wheel 2 is within the driver operation range X. The metal male spline portion 23 is not provided on the portion of the spline 22 that engages with the female spline portion 35 when the longitudinal position of the steering wheel 2 is within the driver non-operation range Y, but instead a synthetic resin male spline portion 32 is provided that has the same cross-sectional contour as the cross-sectional contour of the resin coating layer 31 formed around the male spline portion 23. Furthermore, this resin male spline portion 32 is formed around the non-spline portion 24 that has a smaller cross-sectional area than the male spline portion 23.

[0092] Therefore, according to this example, compared to when the overall length of the male spline portion 23 is increased, the telescopic stroke of the steering shaft 12 can be increased while suppressing an increase in the weight of the inner shaft 18. Furthermore, when the fore-and-aft position of the steering wheel 2 is located in the driver operation range X, the male spline portion 23 and the female spline portion 35 can be spline-engaged via the resin coating layer 31. Furthermore, when the fore-and-aft position of the steering wheel 2 is located in the driver non-operation range Y, the resin male spline portion 32 and the female spline portion 35 can be spline-engaged. Therefore, sliding resistance during the telescopic movement of the steering shaft 12 can be reduced over the entire stroke range of the steering shaft 12. Furthermore, in this example, since there is no need to increase the overall length of the male spline portion 23, an increase in the processing cost of the inner shaft 18 can be suppressed.

[0093] 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 with the mold 36. Therefore, there is no need to provide a dedicated portion for aligning the phase on the shaft body 20, which reduces the manufacturing cost of the inner shaft 18.

[0094] [Second example of embodiment] A second example of the embodiment will be described with reference to FIGS.

[0095] In this example, only the structure of the inner shaft 18a is changed from the structure of the first example of the embodiment.

[0096] The shaft body 20a constituting the inner shaft 18a of this example has, in order from one axial end, 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 disposed adjacent to one axial end of the male spline portion 23, and is provided at the end portion of one axial end of the shaft body 20a.

[0097] The small diameter shaft portion 76 has a diameter d b outer diameter D smaller than 76 (d b >D 76 In this example, the small diameter shaft portion 76 has a circular cross section. That is, the small diameter shaft portion 76 has an outer diameter D of the non-spline portion 24. 24 outer diameter D smaller than 76 The small diameter shaft portion 76 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. Furthermore, the axial dimension of the small diameter shaft portion 76 is sufficiently shorter than the axial dimension of the male spline portion 23.

[0098] The resin coating 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 coating portion 21a has a resin retaining portion 77 around the small diameter shaft portion 76.

[0099] The resin retaining portion 77 covers the entire cylindrical surface of the small diameter shaft portion 76. The resin retaining portion 77 is disposed adjacent to one axial side of the resin coating layer 31 that covers 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 formed. The axial dimension of the resin retaining portion 77 is the same as the axial dimension of the small diameter shaft portion 76.

[0100] The resin retaining portion 77 is configured by a plurality of resin teeth 77a extending in the axial direction of the inner shaft 18a and arranged 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 are the same.

[0101] The tooth thickness and tooth height of the resin teeth 77a are constant along the axial direction. Specifically, the tooth thickness of the resin teeth 77a is equal to the tooth width of the resin male spline teeth 32a. Furthermore, the tooth height of the resin teeth 77a is equal to the tooth height of the resin male spline teeth 32a. Therefore, the tip, bottom, and side surfaces of the resin teeth 77a are smoothly connected in the axial direction to the tip, bottom, and side surfaces of the male spline teeth 23a covered with 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 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. Therefore, the resin teeth 77a form one axial end of the spline 22a. However, when implementing the present invention, the resin teeth may be omitted from the outer peripheral surface of the resin retaining portion.

[0102] The inner shaft 18a of this example as described above can also be manufactured by the same manufacturing method (injection molding) as the first example of the embodiment.

[0103] In this example, a small diameter shaft portion 76 having an outer diameter 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 end face on the other axial end of the resin retaining portion 77 against the end face on one axial end of the male spline portion 23, it is possible to effectively prevent the resin coated portion 21a from slipping out (being displaced relative to) the shaft body 20a on the other axial end. The other configurations and effects are the same as those of the first embodiment.

[0104] [Third example of embodiment] A third example of the embodiment will be described with reference to FIG.

[0105] In this example, only the structure of the shaft body 20b is changed from the structure of the first example of the embodiment.

[0106] The shaft body 20b of this example has a phase determination recess 78 at a portion in the circumferential direction of the extension shaft portion 26 that constitutes the exposed shaft portion 25.

[0107] When manufacturing the inner shaft 18b of this example, the male spline portion 23 and the non-spline portion 24 of the shaft main body 20b are placed in the cavity 37 of the mold 36a with the phasing protrusion 79 of the first mold 38a engaged with the phasing recess 78 of the extension shaft portion 26. This allows the shaft main body 20b and the mold 36a to be phase-matched.

[0108] In the present embodiment described above, phasing relative to the mold 36a can be performed using the phase determining recess 78 provided in the axially intermediate portion of the shaft body 20b, rather than the male stopper portion 27 provided at the other axial end of the shaft body 20b. This allows the mold 36a to be made smaller, thereby reducing the manufacturing cost of the inner shaft 18b. The other configurations and effects are the same as those of the first embodiment.

[0109] [Fourth Example of Implementation Form] A fourth example of the embodiment will be described with reference to FIG.

[0110] In this example, only the manufacturing method of the inner shaft 18 is different from the manufacturing method of the first example of the embodiment.

[0111] In this example, too, a cylindrical material made of metal such as carbon steel is first cut, and then subjected to plastic processing (spline processing) such as cold forging, hobbing, and rolling. This produces the shaft body 20 having, in order from the bottom of Figure 13, the male spline portion 23, the non-spline portion 24, and the exposed shaft portion 25.

[0112] Thereafter, a step of forming a resin-coated portion 21 on the outer peripheral surface of the shaft body 20 is performed by performing a fluidized bed dipping method and cutting. For this, first, as shown in Fig. 13(A), a step of dipping the male spline portion 23 and the non-spline portion 24 of the shaft body 20 into molten resin 80, which is a molten synthetic resin, is performed. As a result, as shown in Fig. 13(B), a resin-coated intermediate material 81 is formed on the lower half of the outer peripheral surface of the shaft body 20.

[0113] Thereafter, a cutting process such as shaving or broaching is performed on the outer peripheral surface of the resin-coated intermediate material 81 to form the resin-coated portion 21 from the resin-coated intermediate material 81. For this purpose, as shown in FIG. 13(C), the shaft body 20, the lower half of which is covered with the resin-coated intermediate material 81, is set in cutting equipment 82. At this time, the male stopper portion 27 provided on the exposed shaft portion 25 is used to match the circumferential phase of the male spline portion 23 with the concave-convex spline processed portion 84 provided on the inner peripheral surface of the cutting tool 83. Specifically, the phase of the male spline portion 23 and the spline processed portion 84 is matched by engaging a phase setting pin 85 provided on the cutting equipment 82 with one or more male groove portions 27b that constitute the male stopper portion 27.

[0114] 13 relative to the shaft body 20, the outer circumferential surface of the resin-coated intermediate material 81 is cut by the spline processing portion 84 provided on the inner circumferential surface of the cutting tool 83. In this way, splines 22 are processed on the outer circumferential surface of the resin-coated intermediate material 81, and the resin-coated portion 21 is formed. In this example, the inner shaft 18 consisting of the shaft body 20 and the resin-coated portion 21 is manufactured in this manner.

[0115] In this example, the inner shaft 18 is manufactured by the manufacturing method described above, and unlike the manufacturing method of the first example of the embodiment, there is no need to use a mold, so the manufacturing cost of the inner shaft 18 can be reduced. The other configurations and effects are the same as those of the first embodiment.

[0116] Although the embodiments of the present invention have been described above, the present invention is not limited to these and can be modified as appropriate within the scope of the technical concept of the invention. Furthermore, the structures of the examples of the embodiments can be combined as appropriate as long as no contradiction occurs.

[0117] In each example of the embodiment, the non-spline portion constituting the shaft body of the inner shaft has been described as having a circular cross-sectional shape, but when implementing the present invention, the cross-sectional shape of the non-spline portion is not limited to a circle, and can be a non-circular shape such as a segmented circle, a polygon, or a gear shape. In this way, when the cross-sectional shape of the non-spline portion is non-circular, the resin male spline portion can be effectively prevented from rotating relative to the non-spline portion. Furthermore, by providing protrusions and / or recessed grooves at some or multiple locations in the circumferential direction of the outer circumferential surface of the non-spline portion, it is also possible to prevent the resin male spline portion from rotating relative to the non-spline portion.

[0118] The present invention is not limited to steer-by-wire steering devices, but can also be applied to retractable steering devices.Furthermore, the present invention is not limited to structures that move a steering wheel electrically, but can also be applied to structures that move a steering wheel manually. [Explanation of symbols]

[0119] 1 Steering device 2 steering wheels 3 Steering unit 4 steering wheels 5. Steering unit 6. Control device 7 Torque Sensor 8. Steering actuator 9 Tie rod 10 Position adjustment device 11 Reaction force generator 12 Steering shaft 13. Steering column 14 Lower telescopic actuator 15 Upper telescopic actuator 16 Tilt actuator 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 part 23a male spline teeth 24 Non-splined section 25 Exposed shaft part 26 Extension shaft 27 Male stopper part 27a Male lateral teeth 27b Male gutter 28 Output shaft 29 Female stopper part 30 Torsion bar 31 Resin coating layer 32 Resin male spline part 32a Resin Male Spline Teeth 33 Small diameter cylinder part 34 Large diameter cylinder 35 Female spline part 35a female spline teeth 36, 36a mold 37 Cavity 38, 38a First mold 39 Second mold 40 Spline forming part Gate 41 42 Bracket 43 Column body 44 Fixing bracket 45 Displacement Bracket 46 Fixed plate part 47 Fixed side support frame 48 Mounting bolts 49 Displacement plate 50 Displacement side support frame 51 Linear guide 52 Support wall section 53 Outer Column 54 Lower inner column 55 Upper side inner column 56 Slit 57 screw hole 58 Screw plug 59 Lower telescopic motor 60 Lower feed screw device 61 Lower screw shaft 62 Lower nut 63 Upper telescopic motor 64 Upper feed screw device 65 Upper screw shaft 66 Upper nut 67 Connector parts 68 Pivot bolt 69 Tilt motor 70 Tilt feed screw device 71 Gear housing 72 Reaction force motor 73 Worm reducer 75 worm wheel 76 Small diameter shaft 77 Resin retaining part 77a Resin tooth 78 Phase determining recess 79 Phase determining protrusion 80 Molten Resin 81 Resin-coated intermediate material 82 Cutting equipment 83 Cutting tools 84 Spline processing part 85 Phase determination pin

Claims

1. A steering shaft having an outer shaft with a female spline portion on its inner peripheral surface and an inner shaft spline-engaged with the outer shaft to enable torque transmission and relative axial displacement, with a steering wheel fixed to the rear end thereof, The inner shaft is 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 including 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, When the longitudinal position of the steering wheel is located in a driver operation range where the driver operates the steering wheel, the female spline portion engages with the male spline portion via the resin coating layer, whereas when the longitudinal position of the steering wheel is located in a driver non-operation range where the driver does not operate the steering wheel, the female spline portion engages with the resin male spline portion. Steering 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.

2. The steering shaft according to claim 1.

3. 2. The steering 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. 4. The steering shaft of claim 3, wherein the exposed shaft portion includes a phase determining portion that can be used for phase determination.

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

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

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

Images