Steering shaft

Abstract

[Problem] To provide a steering shaft which has a structure capable of suppressing a change in sliding resistance even when the overall length thereof changes. [Solution] One engaging part among an inner-diameter-side engaging part 19 and an outer-diameter-side engaging part 31 is equipped with one or more non-engaging sections 23 which do not engage the other engaging part and are located in an intermediate section in the axial direction. Therein: an engageable part is positioned on both sides in the axial direction of a non-engaging section 23 of the one engaging part; each of said engageable parts has an effective length X; the non-engaging sections 23 have an axial-direction dimension which is the same length as is the effective length X; and the other engaging part has an effective length Y which has a length 2X which is twice the effective length X.

Description

Technical Field

[0001] The present disclosure relates to a steering shaft.

Background Art

[0002] In recent years, the implementation of autonomous driving technology in vehicles has been progressing. In the near future, it is considered that autonomous vehicles achieving SAE's autonomous driving level 2 (partial driving automation) will become widespread, and the spread of autonomous vehicles achieving autonomous driving level 3 (conditional driving automation) will also progress.

[0003] At autonomous driving level 2, if predetermined conditions are met, the driver can drive the vehicle with their hands off the steering wheel. In autonomous vehicles implementing autonomous driving technology at level 2 or higher, particularly level 3 or higher, the need for the driver to operate the steering wheel is reduced. Therefore, in autonomous vehicles, when autonomous driving is executed, there is little need to keep the steering wheel within reach of the driver's hand, and in order to secure a large space in front of the driver's seat, it is desirable to retract the steering wheel significantly forward.

[0004] In order to retract the steering wheel significantly forward, it is necessary to make the telescopic stroke amount of the steering shaft that fixes the steering wheel longer than the telescopic stroke amount of a conventional-structured steering shaft, and to make the steering shaft have a long stroke.

[0005] The steering shaft includes an inner shaft and an outer shaft, and is configured by spline-engaging a male spline portion provided on the outer peripheral surface of the inner shaft and a female spline portion provided on the inner peripheral surface of the outer shaft. In order to make the steering shaft have a long stroke, it is conceivable to increase the total length of the male spline portion and the female spline portion.

[0006] As a technique applicable to such a structure, Japanese Patent Application Laid-Open No. 2017-052514 discloses covering male spline teeth with a resin coating layer in order to reduce sliding resistance during the telescopic operation of a steering shaft.

Prior Art Document

Patent Document

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Figures 20 and 21 show an unpublished steering shaft 100 that the present inventors considered before completing the present disclosure.

[0009] The steering shaft 100 includes an outer shaft 102 disposed on one axial side and an inner shaft 101 disposed on the other axial side. The inner shaft 101 has a male spline portion 106 that forms an inner diameter side engaging portion at an end of the outer peripheral surface on one axial side. The male spline portion 106 extends in the axial direction and has a plurality of male spline teeth 103 arranged in the circumferential direction.

[0010] The outer shaft 102 has a female spline portion 107 that forms an outer diameter side engaging portion at an end of the inner peripheral surface on the other axial side. The female spline portion 107 engages with the male spline portion 106 so as to be able to transmit torque and to allow relative displacement in the axial direction. The female spline portion 107 extends in the axial direction and has a plurality of female spline teeth 105 arranged in the circumferential direction.

[0011] The male spline portion 106 includes a resin coating layer 104 that covers a range from an end on one axial side to an intermediate portion thereof.

[0012] The effective length of the male spline portion 106 is defined as the axial dimension of the portion of the male spline portion 106 that can engage with the female spline portion 107 via the resin coating layer 104. When the engagement length E between the male spline portion 106 and the female spline portion 107 is X in the state where the overall length of the steering shaft 100 is maximally extended, the effective length of the male spline portion 106 is 3X. The axial dimension of the resin coating layer 104 is substantially the same as the effective length 3X of the male spline portion 106.

[0013] The value of "X" is set to about 20 mm for a steering shaft not intended for long stroke, but is set to 30 mm or more when long stroke of the steering shaft is intended.

[0014] In the illustrated example, the effective length of the female spline portion 107 is 2X.

[0015] In the conventional steering shaft 100, when the overall length is changed, the engagement length E between the male spline portion 106 and the female spline portion 107 changes as shown in FIGS. 21(A) to 21(D).

[0016] FIG. 21(A) shows the state where the overall length of the steering shaft 100 is maximally extended. The engagement length E in the state where the overall length of the steering shaft 100 is maximally extended is X.

[0017] FIG. 21(B) shows the state where the overall length of the steering shaft 100 is reduced by a stroke amount equal to X from the state of FIG. 21(A). When the overall length of the steering shaft 100 is reduced from the state of FIG. 21(A) to the state of FIG. 21(B), the engagement length E gradually increases and finally becomes 2X.

[0018] Figure 21(C) shows the state where the overall length of the steering shaft 100 is further reduced by a stroke amount equal to X from the state of Figure 21(B). When the overall length of the steering shaft 100 is reduced from the state of Figure 21(B) to the state of Figure 21(C), the engagement length E remains unchanged at 2X.

[0019] Figure 21(D) shows the state where the overall length of the steering shaft 100 is most reduced by further reducing the overall length of the steering shaft 100 by a stroke amount equal to X from the state of Figure 21(C). When the overall length of the steering shaft 100 is reduced from the state of Figure 21(C) to the state of Figure 21(D), the engagement length E gradually decreases and finally becomes X.

[0020] As the overall length of the steering shaft 100 changes, the engagement length E changes. When the engagement length E changes, the frictional force at the engagement portion between the male spline portion 106 and the female spline portion 107 changes. Therefore, the sliding resistance between the male spline portion 106 and the female spline portion 107, which depends on the frictional force, also changes in accordance with the change in the engagement length E.

[0021] When the sliding resistance when the engagement length is X is defined as α, the relationship between the sliding resistance and the stroke amount is as shown in Figure 22. That is, the sliding resistance of the steering shaft 100 changes when the engagement length E changes with the increase or decrease of the stroke amount, and becomes constant when the engagement length E is constant regardless of the increase or decrease of the stroke amount. The horizontal axis of Figure 22 indicates the stroke amount from the state where the overall length of the steering shaft 100 is maximally extended, and the vertical axis of Figure 22 indicates the magnitude of the sliding resistance. The engagement length is shown in parentheses beside the stroke amount.

[0022] In a manual steering device in which the sliding resistance changes as the engagement length changes and the driver manually adjusts the front-rear position of the steering wheel, the force required to adjust the front-rear position fluctuates, which may give the driver a sense of discomfort or uneasiness. In an electric steering device in which the front-rear position of the steering wheel is adjusted electrically, the driving noise of an actuator such as an electric motor changes, which may give discomfort to the driver and passengers. When the steering shaft 100 is made to have a long stroke, the amount of change in the engagement length becomes large, so the fluctuation range of the sliding resistance also becomes large, and the above-mentioned problems may become prominent.

[0023] FIG. 23 shows another unpublished steering shaft 100a that the present inventors considered before completing the present disclosure. In the steering shaft 100a, in order to ensure the same expansion and contraction stroke amount as that of the steering shaft 100, the effective length of the male spline portion 106a of the inner shaft 101a is set to 4X, and the effective length of the female spline portion 107a of the outer shaft 102a is set to X.

[0024] According to such a configuration, even when the overall length of the steering shaft 100a is changed, the engagement length E can be made constant at the same length as X without changing the engagement length E, so the sliding resistance can also be made constant. However, since the axial dimension of the male spline portion 106a becomes excessive, bending is likely to occur during manufacturing, and the productivity of the inner shaft 101a may decrease.

[0025] It is also conceivable to set the effective length of the female spline portion of the outer shaft to 4X and the effective length of the male spline portion of the inner shaft to X. However, in this case, since the axial dimension of the female spline portion becomes excessive, there may be a problem that the productivity of the outer shaft decreases.

[0026] The present disclosure aims to provide a steering shaft that can prevent the sliding resistance from changing as the engagement length between the inner shaft and the outer shaft changes when the overall length of the steering shaft is changed, even in a structure where the steering shaft has a long stroke.

Means for Solving the Problems

[0027] A steering shaft according to an aspect of the present disclosure includes an inner shaft having an inner diameter side engaging portion at one end of the outer peripheral surface in the axial direction, an outer shaft having an outer diameter side engaging portion at the other end of the outer peripheral surface in the axial direction, which engages with the inner diameter side engaging portion in a torque transmissible manner and allows relative displacement in the axial direction, and is provided with.

[0028] Either one of the inner diameter side engaging portion and the outer diameter side engaging portion has at least one non-engaging portion in the axial intermediate portion that does not engage with the other engaging portion of the inner diameter side engaging portion and the outer diameter side engaging portion. Each of the engaging portions disposed on both axial sides of the non-engaging portion among the one engaging portion has an effective length X, and the non-engaging portion has an axial dimension having the same length as the effective length X. That is, the one engaging portion has an axial length of three times the effective length X (3X) as a whole and an axial dimension of the engaging portion of two times the effective length X (2X).

[0029] The other engaging portion of the inner diameter side engaging portion and the outer diameter side engaging portion has an effective length Y (= 2X) that is twice the effective length X.

[0030] The effective length X is defined by the axial dimension of the portion that engages with the other engaging portion among each of the engaging portions constituting the one engaging portion, and is equal to the engagement length between the one engaging portion and the other engaging portion in the state where the overall length of the steering shaft is extended to the maximum.

[0031] The one engaging portion can include one non-engaging portion and two engagable portions. In this case, they are arranged axially in the order of engagable portion, non-engaging portion, and engagable portion. Alternatively, the one engaging portion can include two non-engaging portions and three engagable portions. In this case, they are arranged axially in the order of engagable portion, non-engaging portion, engagable portion, non-engaging portion, and engagable portion. Further, the one engaging portion can include three or more non-engaging portions and the number of engagable portions that is one more than the number of the non-engaging portions.

[0032] The inner diameter side engaging portion can be constituted by, for example, a male spline portion, an external tooth portion composed of a plurality of external teeth such as a male serration portion, or an engaging structure in which the cross-sectional contour shape of the outer peripheral surface is non-circular. The outer diameter side engaging portion can be constituted by, for example, a female spline portion, an internal tooth portion composed of a plurality of internal teeth such as a female serration portion, or an engaging structure in which the cross-sectional contour shape of the inner peripheral surface is non-circular.

[0033] In the steering shaft according to one aspect of the present disclosure, the inner diameter side engaging portion can be constituted by the one engaging portion, and the outer diameter side engaging portion can be constituted by the other engaging portion. In this case, the engagable portion constituting the inner diameter side engaging portion can be constituted by the external tooth portion, and the outer diameter side engaging portion can be constituted by the internal tooth portion. Further, the effective length X is defined by the axial dimension of the portion of the plurality of external teeth constituting the external tooth portion that engages with the plurality of internal teeth.

[0034] In the steering shaft according to one aspect of the present disclosure, the non-engaging portion can be constituted by a cylindrical surface having an outer diameter equal to or less than the root circle diameter of the plurality of external teeth.

[0035] In the steering shaft according to one aspect of the present disclosure, the inner shaft can include a shaft body and a resin coating layer having the inner diameter side engaging portion on an outer peripheral surface thereof and covering an outer peripheral surface of an end portion on one axial side of the shaft body. In this case, the inner diameter side engaging portion can have an anti-slip portion that suppresses the resin coating layer from moving relative to the shaft body in the axial direction. The anti-slip portion can be configured by a concave groove, a concave portion, a protrusion, a convex portion, or the like.

[0036] In the steering shaft according to one aspect of the present disclosure, the outer diameter side engaging portion can be constituted by the one engaging portion, and the inner diameter side engaging portion can be constituted by the other engaging portion. In this case, the engagable portion constituting the outer diameter side engaging portion can be constituted by the internal tooth portion, and the inner diameter side engaging portion can be constituted by the external tooth portion. Further, the effective length X is defined by an axial dimension of a portion of the plurality of internal teeth constituting the internal tooth portion that engages with the plurality of external teeth.

[0037] In the steering shaft according to one aspect of the present disclosure, the external tooth portion of the inner diameter side engaging portion is constituted by a male spline portion. In this case, the plurality of external teeth are constituted by male spline teeth. Further, the internal tooth portion of the outer diameter side engaging portion is constituted by a female spline portion. In this case, the plurality of internal teeth are constituted by female spline teeth.

[0038] In the steering shaft according to one aspect of the present disclosure, the external tooth portion of the inner diameter side engaging portion is constituted by a male serration portion. In this case, the plurality of external teeth are constituted by male serration teeth. Further, the internal tooth portion of the outer diameter side engaging portion is constituted by a female serration portion. In this case, the plurality of internal teeth are constituted by female serration teeth.

[0039] In the steering shaft according to one aspect of the present disclosure, the inner diameter side engaging portion is configured by an engaging structure in which the cross-sectional contour shape of the outer peripheral surface is non-circular such as an oval or a polygon, and the outer diameter side engaging portion is configured by an engaging structure in which the cross-sectional contour shape of the inner peripheral surface is non-circular such as an oval or a polygon.

[0040] In the steering shaft according to one aspect of the present disclosure, when the number of the non-engaging portions is one, the effective length X is 30 mm or more, preferably 40 mm or more.

Effects of the Invention

[0041] According to the steering shaft according to one aspect of the present disclosure, even in a structure in which the steering shaft has a long stroke, when the overall length of the steering shaft is changed, it is possible to prevent the sliding resistance from changing along with the change in the engagement length between the inner shaft and the outer shaft.

Brief Description of the Drawings

[0042]

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DETAILED DESCRIPTION OF THE INVENTION

[0043] [First Example] A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 10. In this example, the steering shaft of the present disclosure is applied to a steer-by-wire type steering device for an autonomous vehicle. In the following description, the front-rear direction means the front-rear direction of the vehicle, the vertical direction means the vertical direction of the vehicle, and the width direction means the width direction of the vehicle.

[0044] 〔Overall Configuration of Steering Device〕 The steering device 1 in this example is a steer-by-wire type steering device. As shown in the overall configuration in FIG. 1, the steering device 1 includes 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 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 electrically connected.

[0045] In the steering unit 3, the operation of the steering wheel 2 by the driver is measured by a torque sensor and a steering angle sensor (not shown), and the measurement results are output to the control device 6. Various signals indicating the driving situation such as the steering torque measured by the torque sensor, the steering angle measured by the steering angle sensor, the vehicle speed, the yaw rate, and the acceleration are input to the control device 6. Based on the various signals indicating the driving situation, the control device 6 drives the steering actuator 7 provided in the steering unit 5. As a result, linear members such as the rack shaft and the screw shaft are displaced in the width direction, the pair of tie rods 8 are pushed and pulled, and a steering angle is applied to the pair of steering wheels 4.

[0046] Based on the various signals indicating the driving situation, the control device 6 controls the driving of the reaction force applying motor 62 (see FIG. 2) of the reaction force generating device 10 provided in the steering unit 3, and applies a steering reaction force corresponding to the driving situation to the steering wheel 2.

[0047] Steering unit The steering unit 3 includes a position adjusting device 9 for adjusting the position of the steering wheel 2 and a reaction force generating device 10 for applying a steering reaction force to the steering wheel 2.

[0048] The position adjusting device 9 includes 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. Further, the position adjusting device 9 has a function of largely retracting the steering wheel 2 forward during automatic driving.

[0049] The position adjusting device 9 includes a steering shaft 11, a steering column 12, a lower telescopic actuator 13, an upper telescopic actuator 14, and a tilt actuator 15.

[0050] 〈Steering shaft〉 The steering shaft 11 is configured to be able to expand and contract in its entire length and is rotatably supported inside the steering column 12 by using a plurality of rolling bearings 16.

[0051] A steering wheel 2 is fixed to the rear end of a steering shaft 11. The front end of the steering shaft 11 is connected to an output shaft 63 constituting a reaction force generating device 10 via a torque transmission joint (not shown).

[0052] The steering shaft 11 includes an outer shaft 18 disposed on one axial side and an inner shaft 17 disposed on the other axial side. The inner shaft 17 has an inner diameter side engaging portion 19 at one end of the outer peripheral surface in the axial direction. The outer shaft 18 has an outer diameter side engaging portion 31 that engages with the inner diameter side engaging portion 19 so as to be torque transmissible and axially displaceable relative to each other.

[0053] In this example, one axial side corresponds to the rear side, and the other axial side corresponds to the front side. However, when implementing the present disclosure, one axial side can be the front side and the other axial side can be the rear side.

[0054] The steering shaft 11 is configured to be able to expand and contract its overall length by combining the inner diameter side engaging portion 19 of the inner shaft 17 and the outer diameter side engaging portion 31 of the outer shaft 18. In particular, during automatic driving, the steering shaft 11 has a longer expansion and contraction stroke amount compared to a conventional steering shaft that can only adjust the front - rear position of the steering wheel 2 in order to retract the steering wheel 2 significantly forward.

[0055] 《Inner Shaft》 The inner shaft 17 is integrally formed entirely of an iron - based alloy such as carbon steel, or a light alloy such as an aluminum alloy, a magnesium alloy, or a titanium alloy. The inner shaft 17 is configured in a solid or hollow cylindrical shape.

[0056] In this example, the inner diameter side engaging portion 19 of the inner shaft 17 corresponds to one engaging portion. The inner diameter side engaging portion 19 includes a non-engaging portion 23 that does not engage with the outer diameter side engaging portion 31 of the outer shaft 18 corresponding to the other engaging portion at the intermediate portion in the axial direction. On both axial sides of the non-engaging portion 23, first engaging portions 22a and 22b corresponding to two engagable portions are arranged. Each of the first engaging portions 22a and 22b has an effective length X. The non-engaging portion 23 has an axial dimension with the same length as the effective length X.

[0057] That is, the inner diameter side engaging portion 19 includes one non-engaging portion 23 and two first engaging portions 22a and 22b. In the inner diameter side engaging portion 19, the first engaging portion 22a, the non-engaging portion 23, and the first engaging portion 22b are arranged in this order in the axial direction.

[0058] When implementing the present disclosure, the inner diameter side engaging portion can include two non-engaging portions and three first engaging portions. In this case, they are arranged in the order of the first engaging portion, the non-engaging portion, the first engaging portion, the non-engaging portion, and the first engaging portion. Further, the one engaging portion can include three or more non-engaging portions and a number of first engaging portions that is one more than the number of the non-engaging portions.

[0059] The inner diameter side engaging portion 19 can be constituted by, for example, a male spline portion, an external tooth portion composed of a plurality of external teeth such as a male serration portion, or an engaging portion whose cross-sectional contour shape of the outer peripheral surface is non-circular.

[0060] Each of the first engaging portions 22a and 22b constituting the inner diameter side engaging portion 19 is constituted by an external tooth portion 86 formed by arranging a plurality of external teeth 25 in the circumferential direction. The plurality of external teeth 25 extend in the axial direction and are arranged in the circumferential direction. The circumferential arrangement of the plurality of external teeth 25 in this example is at an equal pitch. The tooth thickness and tooth width of each of the plurality of external teeth 25 are constant over the axial direction.

[0061] Among the first engaging portions 22a and 22b, the first engaging portion 22a arranged on one axial side and the first engaging portion 22b arranged on the other axial side have the same number, pitch, tooth thickness, tooth width, and arrangement phase of the plurality of external teeth 25.

[0062] In this example, the outer tooth portions 86 of the first engaging portions 22a and 22b that constitute the inner diameter side engaging portion 19 are constituted by male spline portions. Each of the plurality of outer teeth 25 is constituted by male spline teeth.

[0063] The first engaging portion 22a on one side in the axial direction has a chamfered portion 26 at the end on one side in the axial direction.

[0064] The non-engaging portion 23 is disposed in the intermediate portion in the axial direction of the first engaging portions 22a and 22b. The non-engaging portion 23 is constituted by a cylindrical surface whose outer diameter does not change in the axial direction. The non-engaging portion 23 has an outer diameter smaller than the bottom circle diameter of the plurality of outer teeth 25 that constitute the first engaging portions 22a and 22b.

[0065] When implementing the present disclosure, the outer peripheral surface shape of the non-engaging portion is not limited to a cylindrical surface, and other shapes can be adopted as long as they do not interfere with the outer diameter side engaging portion provided on the outer shaft. Specifically, the non-engaging portion has a shape that enables relative displacement in the axial direction with respect to the outer diameter side engaging portion and does not engage to enable torque transmission. For example, the non-engaging portion can also be constituted by arranging a plurality of teeth having a tooth height lower than that of the plurality of outer teeth 25 and / or a smaller tooth width in the circumferential direction.

[0066] The inner diameter side engaging portion 19 of this example does not have continuous outer teeth over the entire axial length of the inner diameter side engaging portion 19, but has outer tooth portions 86 composed of outer teeth 25 only on both axial sides excluding the non-engaging portion 23 of the inner diameter side engaging portion 19.

[0067] The first engaging portions 22a and 22b have the same effective length X. The effective length X is defined by the axial dimension of the portion that engages with the outer diameter side engaging portion 31 among each of the first engaging portions 22a and 22b that constitute the inner diameter side engaging portion 19, and is equal to the engagement length between the inner diameter side engaging portion 19 and the outer diameter side engaging portion 31 in the state where the total length of the steering shaft 11 is extended the most.

[0068] Of each of the first engaging portions 22a and 22b, the portion that engages with the outer diameter side engaging portion 31 is a portion that can contribute to torque transmission when torque is transmitted between the inner shaft 17 and the outer shaft 18.

[0069] In this example, the entire axial length of the first engaging portion 22a including the chamfered portion 26 provided at one end on the axial direction side is the effective length X. However, when the chamfered portion 26 does not contribute to torque transmission, the axial dimension of the axial range excluding the chamfered portion 26 in the first engaging portion 22a is defined as the effective length X.

[0070] The non-engaging portion 23 has an axial dimension L that is the same length as the effective length X of each of the first engaging portions 22a and 22b. 23 (L 23 = X).

[0071] In order to achieve a long stroke of the steering shaft 11, the reference dimension "X" is set to a value of 30 mm or more. In this example, "X" is about 50 mm.

[0072] In this example, the inner diameter side engaging portion 19 is provided with a resin coating layer 27. Specifically, the inner shaft 17 is composed of a shaft body 69 and a resin coating layer 27. The shaft body 69 has an inner diameter side engaging core portion 70 provided on the outer peripheral surface of one end on the axial direction side, a connecting portion 20 disposed at the other end on the axial direction side, and an intermediate shaft portion 21 disposed at the intermediate portion in the axial direction. The inner diameter side engaging core portion 70 constituting the shaft body 69 is covered by the resin coating layer 27 over its entire axial length and entire circumference. The inner diameter side engaging portion 19 is composed of the inner diameter side engaging core portion 70 and the resin coating layer 27.

[0073] The inner diameter side engaging core portion 70 includes a non-engaging core portion 72 and first engaging core portions 71a and 71b disposed on both axial sides thereof. Each of the first engaging core portions 71a and 71b is constituted by an external tooth core portion 88 in which a plurality of tooth cores 73 are circumferentially arranged. The plurality of tooth cores 73 extend in the axial direction and are arranged at equal pitches in the circumferential direction. The tooth thickness and tooth width of each of the plurality of tooth cores 73 are constant over the axial direction except for the chamfered portion 83 provided at the distal end portion with respect to the non-engaging core portion 72.

[0074] Among the first engaging core portions 71a and 71b, the number, pitch, tooth thickness, tooth width, and arrangement phase of the plurality of tooth cores 73 are the same for the first engaging core portion 71a disposed on one axial side and the first engaging core portion 71b disposed on the other axial side.

[0075] In this example, the axial dimension L 71b of the first engaging core portion 71b on the other axial side 71a is larger than the axial dimension L 71b of the first engaging core portion 71a on one axial side (L 71a > L 71a ), and is larger than the effective length X (L

[0076] > X).

[0077] The outer peripheral surface of the connecting portion 20 has an uneven shape in the circumferential direction. Specifically, a plurality of male serration teeth 28 extending in the axial direction are circumferentially arranged on the outer peripheral surface of the connecting portion 20.

[0078] A torque transmission joint (not shown) is fixed to the connecting portion 20 so as not to be relatively rotatable. Thereby, the end portion on the other axial side of the inner shaft 17 is connected to the output shaft 63 constituting the reaction force generating device 10 via the torque transmission joint.

[0079] The intermediate shaft portion 21 is provided in the portion between the inner diameter side engaging portion 19 and the connecting portion 20 in the axial direction. Similar to the non-engaging core portion 72, the intermediate shaft portion 21 has an outer peripheral surface in the shape of a cylindrical surface, and has the same cross-sectional shape, outer diameter, and surface properties as those of the non-engaging core portion 72 in terms of cross-sectional shape, outer diameter, and surface properties.

[0080] The manufacturing method of the shaft body 69 is not particularly limited, and it can be manufactured by forging only or cutting only, or it can also be manufactured by appropriately combining forging and cutting. Regarding the non-engaging core portion 72 constituting the inner diameter side engaging core portion 70, since it is not necessary to improve the surface properties, when the shaft body 69 is manufactured by forging, surplus material can be left on the non-engaging core portion 72.

[0081] The resin coating layer 27 on the inner diameter side engaging portion 19 is intended to reduce the sliding resistance of the inner diameter side engaging portion 19 during the telescopic operation of the steering shaft 11. Specifically, the entire axial length of the first engaging core portion 71a on one side in the axial direction and the entire axial length of the non-engaging core portion 72 are each covered by the resin coating layer 27, and the range from the end on one side in the axial direction to the intermediate portion in the axial direction of the first engaging core portion 71b on the other side in the axial direction is covered by the resin coating layer 27. The end on the other side in the axial direction of the first engaging core portion 71b on the other side in the axial direction is exposed without being covered by the resin coating layer 27.

[0082] The resin coating layer 27 has two first engaging core covering portions 74a, 74b that cover the first engaging core portions 71a, 71b, a non-engaging core covering portion 75 that covers the non-engaging core portion 72, and two side plate portions 76a, 76b that are each substantially circular ring-shaped.

[0083] Of the first engaging core covering parts 74a and 74b, the first engaging core covering part 74a on one axial side covers the first engaging core part 71a on one axial side over the entire axial length, and the first engaging core covering part 74b on the other axial side covers the range from the end on one axial side to the middle part in the axial direction of the first engaging core part 71b on the other axial side. The outer peripheral surfaces of the first engaging core covering parts 74a and 74b are constituted by an uneven surface in which concave parts and convex parts are alternately arranged in the circumferential direction.

[0084] The outer peripheral surface of the non-engaging core covering part 75 is constituted by a cylindrical surface whose outer diameter does not change in the axial direction. The outer diameter of the non-engaging core covering part 75 is smaller than the outer diameter of the bottom surface of the concave part among the outer peripheral surfaces of the first engaging core covering parts 74a and 74b.

[0085] The side plate parts 76a and 76b connect the ends on both axial sides of the non-engaging core covering part 75 and the proximal ends of the first engaging core covering parts 74a and 74b with respect to the non-engaging core covering part 75. The outer peripheral surfaces of the side plate parts 76a and 76b are constituted by an uneven surface in which concave parts and convex parts are alternately arranged in the circumferential direction.

[0086] The end surface on one axial side of the non-engaging core covering part 75 and the side surface on one axial side of the side plate part 76a on one axial side are in contact with the end surfaces on the other axial side of the plurality of tooth cores 73 constituting the first engaging core part 71a on one axial side, and the end surface on the other axial side of the non-engaging core covering part 75 and the side surface on the other axial side of the side plate part 76b on the other axial side are in contact with the end surfaces on one axial side of the plurality of tooth cores 73 constituting the first engaging core part 71b on the other axial side. Thereby, even when the resin coating layer 27 is formed by a method that does not use an adhesive for adhering the synthetic resin constituting the resin coating layer 27 to the metal material constituting the shaft body 69, such as injection molding, it is possible to prevent the axial relative displacement of the resin coating layer 27 with respect to the shaft body 69.

[0087] However, in order to improve the bonding strength between the shaft body 69 and the resin coating layer 27, fine uneven portions may be provided on a part or all of the inner diameter side engaging core portion 70 of the shaft body 69 by shot blasting, or an adhesive may be applied.

[0088] The axial dimension L of the resin coating layer 27 27 is substantially the same as three times the effective length X of each of the first engaging portions 22a and 22b (L 27 ≒ 3X). In this example, the axial dimension L of the resin coating layer 27 27 is approximately 150 mm.

[0089] In this example, the effective length X is, more specifically, the axial dimension of the plurality of external teeth 25 that mesh with the plurality of internal teeth 33 when torque is transmitted between the inner shaft 17 and the outer shaft 18. Among the plurality of external teeth 25, when torque is transmitted between the inner shaft 17 and the outer shaft 18, the tooth surfaces (circumferential side surfaces) of the portions that mesh with the plurality of internal teeth 33 are in sliding contact with the tooth surfaces of the plurality of internal teeth 33 when the inner shaft 17 is axially displaced relative to the outer shaft 18. The axial dimension L 71a of the first engaging core portion 71a and the axial dimension L 72 of the non-engaging core portion 72 are regulated such that the axial dimension of the first engaging portion 22a and the axial dimension of the non-engaging portion 23 on one axial side are the effective length X.

[0090] The axial dimension L 71a of the first engaging core portion 71a on one axial side is the size obtained by subtracting the axial dimension of the side plate portion 76a on one axial side constituting the resin coating layer 27 from the effective length X. Also, the axial dimension L 72 of the non-engaging core portion 72 is the sum of the effective length X and the axial thicknesses of the side plate portions 76a and 76b.

[0091] The resin coating layer 27 is made of a synthetic resin having a low coefficient of friction with respect to the metal material constituting the outer shaft 18, such as polyamide resin (PA), polytetrafluoroethylene resin (PTFE), or polyacetal resin (POM).

[0092] As shown in FIG. 8(A), the thickness of the resin coating layer 27 is substantially constant over the entire circumference and is sufficiently smaller than the tooth width and tooth height of the tooth core 73. Specifically, the thickness of the resin coating layer 27 is about 10 μm to 1000 μm. The resin coating layer 27 has a contour shape along the outer shapes of the first engaging core portions 71a, 71b and the non-engaging core portion 72. Such a resin coating layer 27 can be formed, for example, by injection molding using a mold.

[0093] When implementing the present disclosure, the thickness of the resin coating layer 27 can also be changed in the circumferential direction. For example, as shown in FIG. 8(B), among the resin coating layer 27, the thickness of the portion covering the tooth tip surface of the tooth core 73 can be made smaller than the thickness of the portion covering the tooth bottom surface between two adjacent tooth cores 73 in the circumferential direction. Such a resin coating layer 27 can be formed using a fluid dipping method.

[0094] The non-engaging core covering portion 75 constituting the resin coating layer 27 can be formed, for example, by molding synthetic resin around the shaft body 69 and then performing cutting on the outer peripheral surface. Alternatively, when the amount of thermal shrinkage of the synthetic resin molded around the non-engaging core portion 72 is sufficiently larger than the amount of thermal shrinkage of the synthetic resin molded around the first engaging core portions 71a, 71b, the cutting can be omitted.

[0095] That is, since the amount of thermal shrinkage of the synthetic resin increases as the thickness increases, even when the synthetic resin molded around the non-engaging core portion 72 is molded until its outer diameter becomes the same as the outer diameter of the synthetic resin molded around the first engaging core portions 71a, 71b, the amount of thermal shrinkage of the synthetic resin molded around the non-engaging core portion 72 is larger than the amount of thermal shrinkage of the synthetic resin molded around the first engaging core portions 71a, 71b.

[0096] 《Outer Shaft》 The outer shaft 18 has a hollow cylindrical shape. The outer shaft 18 is disposed on one axial side of the inner shaft 17. The outer shaft 18 has a large-diameter cylindrical portion 29 in a range extending from the end portion on the other axial side to the axial intermediate portion, and has a small-diameter cylindrical portion 30 at the end portion on one axial side. The outer shaft 18 has an outer-diameter side engaging portion 31 at the end portion on the other axial side of the inner peripheral surface of the large-diameter cylindrical portion 29. The steering wheel 2 is fixed to the end portion on one axial side of the outer shaft 18. In this example, the outer-diameter side engaging portion 31 corresponds to the other engaging portion.

[0097] The outer-diameter side engaging portion 31 has a second engaging portion 32 over the entire axial length. That is, the outer-diameter side engaging portion 31 is composed only of the second engaging portion 32. The second engaging portion 32 is composed of an internal tooth portion 87 formed by arranging a plurality of internal teeth 33 in the circumferential direction. The plurality of internal teeth 33 extend in the axial direction and are arranged in the circumferential direction. The circumferential arrangement of the plurality of internal teeth 33 in this example is at an equal pitch.

[0098] The tooth thickness and tooth depth of each of the plurality of internal teeth 33 are constant over the axial direction except for the chamfered portion 34 provided at the axial end portion. The internal teeth 33 have a tooth tip circle diameter larger than the outer diameter of the non-engaging portion 23 of the inner shaft 17.

[0099] In this example, the second engaging portion constituting the outer-diameter side engaging portion 31 is constituted by a female spline portion. The plurality of internal teeth 33 are constituted by female spline teeth.

[0100] The second engaging portion 32 engages with the first engaging portions 22a and 22b of the inner-diameter side engaging portion 19 provided on the inner shaft 17 so as to be torque-transmittable and allow relative displacement in the axial direction. Specifically, the plurality of internal teeth 33 constituting the second engaging portion 32 mesh with the plurality of external teeth 25 of the first engaging portions 22a and 22b. Thereby, the outer shaft 18, together with the steering wheel 2, relatively moves in the front-rear direction with respect to the inner shaft 17, and expands and contracts the steering shaft 11.

[0101] The second engaging portion 32 does not engage with the non-engaging portion 23 of the inner diameter side engaging portion 19 provided on the inner shaft 17. Specifically, the tooth tip surfaces of the plurality of internal teeth 33 face the outer peripheral surface of the non-engaging portion 23 with a gap therebetween.

[0102] In this example, among the plurality of internal teeth 33, the effective length Y of the second engaging portion 32, which is the axial dimension of the portion deviated from the chamfered portion 34, is twice the effective length X of the first engaging portions 22a and 22b constituting the inner diameter side engaging portion 19 (2X). In this example, the value of “Y” is about 100 mm.

[0103] However, when contributing to the torque transmission of the chamfered portion 34, the effective length Y is the total axial length including the chamfered portion 34 among the plurality of internal teeth 33.

[0104] When the overall length of the steering shaft 11 in this example is changed, the spline engagement mode between the inner diameter side engaging portion 19 and the outer diameter side engaging portion 31 is switched as shown in FIGS. 9(A) to 9(D).

[0105] FIG. 9(A) shows a state where the overall length of the steering shaft 11 is extended to the maximum. In this state, the plurality of external teeth 25 constituting the first engaging portion 22a on one axial side engage with the plurality of internal teeth 33 constituting the other half on the axial side of the second engaging portion 32. The engagement length E between the plurality of external teeth 25 and the plurality of internal teeth 33 in this state is the same as the effective length X of the first engaging portion 22a.

[0106] FIG. 9(B) shows a state where the overall length of the steering shaft 11 is reduced by a stroke amount equal to X from the state of FIG. 9(A). When the overall length of the steering shaft 11 is reduced from the state of FIG. 9(A) to the state of FIG. 9(B), the plurality of external teeth 25 constituting the first engaging portion 22a on one axial side move axially on one side while remaining engaged with the plurality of internal teeth 33 constituting the second engaging portion 32. Also, the non-engaging portion 23 is inserted radially inside the end portion on the other axial side of the outer shaft 18. In this case, the engagement length E remains unchanged at X.

[0107] FIG. 9(C) shows a state in which the entire length of the steering shaft 11 is further reduced by an amount equal to X from the state of FIG. 9(B). When the entire length of the steering shaft 11 is reduced from the state of FIG. 9(B) to the state of FIG. 9(C), a plurality of external teeth 25 constituting the first engaging portion 22a on one axial side come out of a plurality of internal teeth 33 constituting the second engaging portion 32 on one axial side, and at the same time, a plurality of external teeth 25 constituting the first engaging portion 22b on the other axial side start to mesh with a plurality of internal teeth 33 constituting the second engaging portion 32.

[0108] In this state, a plurality of external teeth 25 of the first engaging portion 22a on one axial side and external teeth 25 of the first engaging portion 22b on the other axial side are simultaneously spline-engaged with a plurality of internal teeth 33. The sum of the engagement lengths between the plurality of external teeth 25 constituting the first engaging portion 22a on one axial side and the plurality of internal teeth 33 and the engagement lengths between the plurality of external teeth 25 constituting the first engaging portion 22b on the other axial side and the plurality of internal teeth 33 is X. Therefore, even while the entire length of the steering shaft 11 is being reduced from the state of FIG. 9(B) to the state of FIG. 9(C), the engagement length E remains unchanged at X.

[0109] FIG. 9(D) shows a state in which the entire length of the steering shaft 11 is most reduced by further reducing the entire length of the steering shaft 11 by an amount equal to X from the state of FIG. 9(C). When the entire length of the steering shaft 11 is reduced from the state of FIG. 9(C) to the state of FIG. 9(D), a plurality of external teeth 25 constituting the first engaging portion 22b on the other axial side move to one axial side while remaining meshed with a plurality of internal teeth 33 constituting the second engaging portion 32. For this reason, even when the entire length of the steering shaft 11 is reduced from the state of FIG. 9(C) to the state of FIG. 9(D), the engagement length E remains unchanged at X.

[0110] Even when the entire length of the steering shaft 11 is changed, the engagement length E between the plurality of external teeth 25 and the plurality of internal teeth 33 can be made constant without change. For this reason, when the sliding resistance when the engagement length is X is α, the relationship between the sliding resistance and the stroke amount is as shown in FIG. 10.

[0111] That is, in the steering shaft 11, regardless of the increase or decrease in the stroke amount, the engagement length E is constant, so the sliding resistance is constant. Note that the horizontal axis in FIG. 10 indicates the stroke amount from the state where the full length of the steering shaft 11 is extended to the maximum, and the vertical axis in FIG. 10 indicates the magnitude of the sliding resistance. Also, the engagement length E is shown in parentheses next to the stroke amount.

[0112] 《Steering Column》 The steering column 12 is configured to be able to expand and contract its full length and is supported by a vehicle body (not shown). The steering column 12 includes a bracket 35 and a column main body 36. The steering column 12 in this example has a two-stage expansion and contraction structure in order to ensure a large expansion and contraction stroke amount in the front-rear direction.

[0113] The bracket 35 is for supporting the column main body 36 on the vehicle body and includes a fixed bracket 37 fixed to the vehicle body and a displacement bracket 38 supported so as to be able to relatively displace in the front-rear direction with respect to the fixed bracket 37.

[0114] The fixed bracket 37 includes a substantially rectangular flat plate-shaped fixing plate portion 39 and a substantially U-shaped fixed-side support frame 40. The fixing plate portion 39 is fixed to the vehicle body using a plurality of mounting bolts 41. The fixed-side support frame 40 is provided at the front end of the fixing plate portion 39 and connects the end portions on both sides in the width direction of the fixing plate portion 39.

[0115] The displacement bracket 38 includes a displacement plate portion 42 arranged so as to overlap the lower surface of the fixing plate portion 39 and a substantially U-shaped displacement-side support frame 43. The displacement plate portion 42 is supported using a linear guide 44 so as to be able to relatively displace in the front-rear direction with respect to the fixing plate portion 39.

[0116] The displacement-side support frame 43 is provided at the rear end of the displacement plate portion 42 and connects the end portions on both sides in the width direction of the displacement plate portion 42. Among the pair of left and right support wall portions 45 constituting the displacement-side support frame 43, a screw shaft (not shown) of the tilt feed screw device 60 constituting the tilt actuator 15 is rotatably supported on the inner surface of one of the support wall portions 45 with the axial direction facing the vertical direction.

[0117] The column main body 36 is entirely configured in a substantially cylindrical shape and is arranged with the axial direction facing the front-rear direction. The column main body 36 includes an outer column 46 arranged at the intermediate portion in the front-rear direction, a lower-side inner column 47 fitted inside the front-side portion of the outer column 46, and an upper-side inner column 48 fitted inside the rear-side portion of the outer column 46.

[0118] The outer column 46 is supported so as to be movable in the vertical direction with respect to the displacement bracket 38. The rear-side portion of the outer column 46 passes through the inside of the displacement-side support frame 43 constituting the displacement bracket 38 in the front-rear direction. A nut (not shown) of the tilt feed screw device 60 constituting the tilt actuator 15 is pivotally supported on the outer peripheral surface of the rear-side portion of the outer column 46. The outer column 46 has a slit (not shown) extending in the front-rear direction at the intermediate portion in the front-rear direction of the lower surface.

[0119] The lower-side inner column 47 is fitted inside the front-side portion of the outer column 46 so as to be relatively displaceable in the front-rear direction. The front end portion of the lower-side inner column 47 is supported and fixed to the fixed bracket 37 via the gear housing 61. Further, an inner shaft 17 is rotatably supported inside the lower-side inner column 47 via a rolling bearing 16.

[0120] The upper-side inner column 48 is fitted inside the rear-side portion of the outer column 46 so as to be relatively displaceable in the front-rear direction. An outer shaft 18 is rotatably supported inside the upper-side inner column 48 via a rolling bearing 16.

[0121] <Lower-side telescopic actuator> The actuator 13 for the lower telescopic part is arranged so as to span between the fixed bracket 37 and the displacement bracket 38, and displaces the displacement bracket 38 in the front - rear direction with respect to the fixed bracket 37. Thereby, the outer column 46 and the lower inner column 47 are relatively displaced in the front - rear direction, and the column body 36 is expanded and contracted.

[0122] The actuator 13 for the lower telescopic part includes a motor 49 for the lower telescopic part and a feed screw device 50 for the lower telescopic part.

[0123] The motor 49 for the lower telescopic part has a motor output shaft (not shown) directed in the vertical direction and is supported and fixed to the side surface in the width direction of the fixed - side support frame 40 that constitutes the fixed bracket 37.

[0124] As shown in FIG. 2, the feed screw device 50 for the lower telescopic part includes a lower screw shaft 51 and a lower nut 52. The lower screw shaft 51 is arranged with its axial direction in the front - rear direction and is rotationally driven by the motor 49 for the lower telescopic part via a speed - reducing mechanism such as a worm speed reducer (not shown). The lower screw shaft 51 is supported by the fixed bracket 37 so as to be rotatable only. The lower nut 52 is screwed onto the lower screw shaft 51 and is supported with respect to the side surface in the width direction of the displacement bracket 38.

[0125] That is, the actuator 13 for the lower telescopic part rotates the motor 49 for the lower telescopic part, thereby displacing the lower nut 52 in the axial direction of the lower screw shaft 51, and relatively displacing the outer column 46 in the front - rear direction with respect to the lower inner column 47.

[0126] 〈Actuator for the upper telescopic part〉 The actuator 14 for the upper telescopic part is arranged so as to span between the outer column 46 and the upper inner column 48, and displaces the upper inner column 48 in the front - rear direction with respect to the outer column 46. Thereby, the column body 36 is expanded and contracted.

[0127] The upper telescopic actuator 14 includes an upper telescopic motor 53 and an upper feed screw device 54.

[0128] The upper telescopic motor 53 is supported below the front end of the outer column 46 with a motor output shaft (not shown) facing in the width direction.

[0129] The upper feed screw device 54 includes an upper screw shaft 55 and an upper nut 56. The upper screw shaft 55 is arranged with its axial direction facing the front-rear direction, and is rotationally driven by the upper telescopic motor 53 via a speed reduction mechanism such as a worm speed reducer (not shown). The upper screw shaft 55 is supported by the outer column 46 so as to be rotatable only. The upper nut 56 is screwed onto the upper screw shaft 55 and is supported via a connector member 57 on the lower surface of the upper inner column 48.

[0130] The connector member 57 is arranged inside a slit provided in the outer column 46 and is fixed to the lower surface of the upper inner column 48. That is, by rotationally driving the upper telescopic motor 53, the upper telescopic actuator 14 displaces the upper nut 56 in the axial direction of the upper screw shaft 55, thereby relatively displacing the upper inner column 48 in the front-rear direction with respect to the outer column 46.

[0131] 〈Tilt actuator〉 The tilt actuator 15 is arranged so as to span between the displacement-side support frame 43 constituting the displacement bracket 38 and the outer column 46, and displaces the outer column 46 in the vertical direction with respect to the displacement bracket 38. Further, a reaction force generating device 10 connected to the front side of the position adjusting device 9 is rotatably supported by a pair of pivot bolts 58 arranged in the width direction with respect to the fixed-side support frame 40. Thereby, the column main body 36 can be swung in the vertical direction around the pivot bolt 58 with respect to the bracket 35.

[0132] The tilting actuator 15 includes a tilting motor 59 and a tilting feed screw device 60.

[0133] The tilting motor 59 is fixed to one support wall portion 45 that constitutes the displacement side support frame 43 with its motor output shaft (not shown) facing the front-rear direction.

[0134] The tilting feed screw device 60 includes a tilting screw shaft (not shown) and a tilting nut. The tilting screw shaft is arranged with its axial direction facing the up-down direction and is rotationally driven by the tilting motor � through a speed reduction mechanism such as a worm speed reducer (not shown). The tilting screw shaft is supported by the one support wall portion 45 so as to be rotatable only. The tilting nut is screwed onto the tilting screw shaft and is pivotally supported on the side surface in the width direction of the outer column 46.

[0135] That is, the tilting actuator 15 rotates the tilting motor 59 to displace the tilting nut in the axial direction of the tilting screw shaft, thereby relatively displacing the outer column 46 in the up-down direction with respect to the displacement bracket 38.

[0136] 《Method for Adjusting the Position of the Steering Wheel》 To adjust the front-rear position of the steering wheel 2 by the position adjusting device 9 of this example, the lower telescopic actuator 13 or / and the upper telescopic actuator 14 is / are driven. When the lower telescopic actuator 13 is driven, the displacement bracket 38 is relatively displaced in the front-rear direction with respect to the fixed bracket 37, and the outer column 46 is relatively displaced in the front-rear direction with respect to the lower inner column 47. When the upper telescopic actuator 14 is driven, the upper inner column 48 is relatively displaced in the front-rear direction with respect to the outer column 46.

[0137] As a result, the entire length of the steering column 12 expands and contracts, and the entire length of the steering shaft 11 expands and contracts, thereby adjusting the front-rear position of the steering wheel 2. After the front-rear position of the steering wheel 2 is adjusted to a desired position, the driving of the lower telescopic actuator 13 or / and the upper telescopic actuator 14 is stopped.

[0138] To adjust the vertical position of the steering wheel 2 by the position adjustment device 9 in this example, the tilt actuator 15 is driven to displace the rear portion of the outer column 46 in the vertical direction with respect to the displacement bracket 38. As a result, the steering shaft 11 rotatably supported inside the column main body 36 swings, and the vertical position of the steering wheel 2 is adjusted. After the vertical position of the steering wheel 2 is adjusted to a desired position, the driving of the tilt actuator 15 is stopped.

[0139] The adjustment of the front-rear position and the vertical position of the steering wheel 2 can be performed simultaneously or independently (before and after in time).

[0140] To retract the steering wheel 2 significantly forward and store the steering wheel 2 in the dashboard or place it away from the driver during automatic driving by the position adjustment device 9 in this example, the lower telescopic actuator 13 and the upper telescopic actuator 14 are each driven. As a result, the displacement bracket 38 is displaced forward relative to the fixed bracket 37, the outer column 46 is displaced forward relative to the lower inner column 47, and the upper inner column 48 is displaced forward relative to the outer column 46.

[0141] By shortening the overall length of the steering column 12 and shortening the overall length of the steering shaft 11 to the state shown in Fig. 9(D), the steering wheel 2 retreats significantly forward. After the steering wheel 2 has retreated significantly forward, the driving of each of the lower telescopic actuator 13 and the upper telescopic actuator 14 is stopped.

[0142] 〈Reaction force generating device〉 The reaction force generating device 10 is disposed in front of the position adjusting device 9 and is fixed to the position adjusting device 9. The reaction force generating device 10 is controlled by the control device 6 and applies a steering reaction force of a magnitude and direction corresponding to the driving conditions such as the steering angle of the steering wheel 2 and the vehicle speed to the steering wheel 2.

[0143] The reaction force generating device 10 includes a gear housing 61, a reaction force applying motor 62, a worm reducer (not shown), and an output shaft 63.

[0144] The gear housing 61 is fixed to the front end of the lower inner column 47 that constitutes the position adjusting device 9. Inside the gear housing 61, the output shaft 63 is rotatably supported.

[0145] The reaction force applying motor 62 is supported and fixed to the gear housing 61. The rotation of the reaction force applying motor 62 is transmitted to the steering shaft 11 via the worm reducer and the output shaft 63.

[0146] The worm reducer includes a worm wheel externally fitted and fixed to the output shaft 63 and a worm fixed to the tip of the motor output shaft of the reaction force applying motor 62.

[0147] The output shaft 63 is arranged with its axial direction facing the front and rear directions and is rotatably supported inside the gear housing 61. The output shaft 63 has a configuration in which a lower output shaft and an upper output shaft arranged coaxially with each other are connected to each other via a torsion bar. Around the upper output shaft, a torque sensor for measuring the steering torque input from the driver to the steering wheel 2 is arranged. The rear end of the upper output shaft is connected to the front end of the inner shaft 17 constituting the steering shaft 11 via a torque transmission joint.

[0148] In order to apply a steering reaction force to the steering wheel 2 by the reaction force generating device 10, for example, the reaction force applying motor 62 is driven by the control device 6 based on various signals indicating driving conditions such as steering torque, steering angle, and vehicle speed. The rotation of the reaction force applying motor 62 is transmitted to the output shaft 63 via a worm reduction gear and is applied to the steering wheel 2 as a steering reaction force via the steering shaft 11.

[0149] According to the steering shaft 11 constituting the steering device 1 of the present example as described above, even in a structure in which the steering shaft 11 has a long stroke, when the overall length of the steering shaft 11 is changed, it is possible to prevent the sliding resistance from changing along with the change in the engagement length between the inner shaft 17 and the outer shaft 18.

[0150] In this example, the inner diameter side engaging portion 19 of the inner shaft 17 includes first engaging portions 22a and 22b having an effective length X, and an axial dimension L 23 equal to the effective length X. The inner diameter side engaging portion 19 is configured such that two first engaging portions 22a and 22b are arranged on both sides of the non-engaging portion 23. Further, the effective length Y of the second engaging portion 32 of the outer diameter side engaging portion 31 provided on the outer shaft 18 is set to a length (2X) that is twice the effective length X, which is equal to the sum of the effective length X and the axial dimension L 23 of the non-engaging portion 23.

[0151] Therefore, when the overall length of the steering shaft 11 is changed, as shown in FIGS. 9(A) to 9(D), the engagement length E between the plurality of external teeth 25 and the plurality of internal teeth 33 does not change as X. Accordingly, even when the overall length of the steering shaft 11 is changed, it is possible to keep the sliding resistance of the steering shaft 11 constant without changing it. As a result, even though the steering shaft 11 in this example has a long stroke, when driving the lower telescopic actuator 13 and the upper telescopic actuator 14 to change the overall length, the change in the driving sound is suppressed, preventing discomfort to the driver and passengers.

[0152] Furthermore, even when the effective length of the plurality of external teeth 25 is X and the effective length of the plurality of internal teeth 33 is 2X, it is possible to secure a telescopic stroke amount of the steering shaft 11 by 3X. For this reason, it is not necessary to excessively increase the axial dimensions of each of the plurality of external teeth 25 and the plurality of internal teeth 33. Accordingly, since it is possible to suppress the occurrence of bending during the manufacture of the inner shaft 17 and the outer shaft 18, it is possible to ensure the productivity of the steering shaft 11.

[0153] In this example, the inner shaft 17 has the inner diameter side engaging portion 19 provided with the resin coating layer 27 by coating one end portion on the axial direction side of the shaft body 69 with the resin coating layer 27. However, when implementing the present disclosure, the resin coating layer can also be omitted.

[0154] [Second Example] A second example of the embodiment of the present disclosure will be described with reference to FIG. 11.

[0155] In this example, the axial dimension L of the first engaging core portion 71a on one axial side, which constitutes the inner diameter side engaging core portion 70 provided on the shaft body 69 71a and the axial dimension L of the first engaging core portion 71b on the other axial side 71b are substantially the same.

[0156] The resin coating layer 27 covers the range from the end on one axial side of the first engagement core portion 71a on one axial side to the end on one axial side of the intermediate shaft portion 21. That is, the first engagement core portion 71b on the other axial side is covered by the first engagement core covering portion 74b over the entire axial length.

[0157] In this example, when forming the resin coating layer 27, first, the shaft body 69 is set in the mold 77. The cavity 78 of the mold 77 has an inner surface shape corresponding to the outer surface shape of the resin coating layer 27 to be formed, that is, an inner surface shape with concavities and convexities opposite to those of the outer surface shape of the resin coating layer 27. Next, the molten synthetic resin is fed into the cavity 78 from the gate 79 disposed on the radially outer side of the end on one axial side of the intermediate shaft portion 21, and the resin coating layer 27 is formed by cooling and solidifying the molten synthetic resin.

[0158] According to this example, after injection molding the synthetic resin around the shaft body 69, there is no need to cut the outer peripheral surface of the portion that becomes the non-engagement portion 23, and the manufacturing of the steering shaft 11 becomes easy. Compared with the structure of the first example, it is easier to accurately regulate the axial dimension of the first engagement portion 22b on the other axial side to the effective length X.

[0159] FIG. 12 shows a modification of the second example. In this modification, a corner R portion 80 having an arcuate cross-sectional shape is provided at the connection portion between the outer peripheral surface and the axial side surface of the side plate portions 76a, 76b.

[0160] According to this modification, it is possible to make it difficult for the axial end portions of the outer peripheral surfaces of the side plate portions 76a, 76b to catch on the inner peripheral surface of the outer shaft 18, and it is possible to prevent the axial relative displacement of the inner shaft 17 with respect to the outer shaft 18 from being inhibited.

[0161] Regarding the configuration and the operational effects of the other parts of the second example, they are the same as those of the first example.

[0162] [Third Example] The third example of the embodiment of the present disclosure will be described with reference to FIGS. 13 to 15(B).

[0163] In this example, the inner diameter side engaging portion 19 has notch recesses 81 at a plurality of circumferential positions at one axial end of the outer peripheral surface. Specifically, the first engaging portion 22a on one axial side has notch recesses 81 at four circumferential positions at one axial end of the outer peripheral surface. Each notch recess 81 has a semi-circular cross-sectional shape and opens to the outer peripheral surface and one axial end surface of the first engaging portion 22a on one axial side.

[0164] In this example, each notch recess 81 is formed in a portion between two adjacent outer teeth 25 in the circumferential direction. Grease is held in each notch recess 81. Thereby, the lubrication state between the inner diameter side engaging portion 19 and the outer diameter side engaging portion 31 can be maintained well for a long period of time, and the resistance when the inner shaft 17 is relatively displaced axially with respect to the outer shaft 18 can be suppressed to be small.

[0165] In this example, when forming the resin coating layer 27, with the shaft body 69 set in the mold, as shown in FIG. 14, by inserting a positioning pin 82 into a part of the portions between the plurality of tooth cores 73 constituting the first engaging core portion 71a on one axial side, the circumferential positioning of the shaft body 69 with respect to the mold is achieved. Next, molten synthetic resin is injected into the mold under pressure. The synthetic resin is cooled and solidified, and the completed inner shaft 17 is taken out of the mold. The synthetic resin in the portion where the positioning pin 82 is arranged among the periphery of the first engaging core portion 71a on one axial side becomes extremely thin compared to other portions, and notch recesses 81 are formed in this portion.

[0166] In this example, the tooth thickness of a part of the outer teeth 25 among the plurality of outer teeth 25 constituting the first engaging portions 22a and 22b is smaller than the tooth thickness of the remaining outer teeth 25. Specifically, the thickness of the synthetic resin covering a part of the plurality of tooth cores 73 is smaller than the thickness of the synthetic resin covering the remaining tooth cores 73.

[0167] When the external teeth 25 with a small tooth thickness transmit torque between the inner shaft 17 and the outer shaft 18, they mesh with the internal teeth 33 that form the outer diameter side engaging portion 31. However, when the inner shaft 17 is relatively displaced axially with respect to the outer shaft 18, the tooth surfaces do not slide in contact with the tooth surfaces of the internal teeth 33. Therefore, the resistance when the inner shaft 17 is relatively displaced axially with respect to the outer shaft 18 can be suppressed to be small.

[0168] In this example, the notch recesses 81 are formed in the portion between the external teeth 25 that are adjacent in the circumferential direction and have a small tooth thickness. Therefore, the influence of the presence of the notch recesses 81 on the resistance when the inner shaft 17 is relatively displaced axially with respect to the outer shaft 18 can be suppressed to be small.

[0169] Regarding the configurations and the effects of the other parts of the third example, they are the same as those of the first example.

[0170] [Fourth Example] The fourth example of the embodiment of the present disclosure will be described with reference to FIG. 16.

[0171] In this example, the structure of the non-engaging core portion 72a that forms the inner diameter side engaging core portion 70a of the shaft body 69a that constitutes the inner shaft 17 is changed from the structure of the first example.

[0172] In this example, only one annular concave groove 64 is formed in the axially intermediate portion of the outer peripheral surface of the non-engaging core portion 72a of the shaft body 69a. By covering the outer peripheral surface of the non-engaging core portion 72a with the resin coating layer 27, the synthetic resin that constitutes the resin coating layer 27 enters the inside of the annular concave groove 64, and the resin coating layer 27 is engaged axially with respect to the annular concave groove 64. That is, the annular concave groove 64 constitutes an anti-slip portion that suppresses the resin coating layer 27 from relatively moving axially with respect to the shaft body 69a.

[0173] In this example, by forming the annular concave groove 64 on the outer peripheral surface of the shaft body 69a, it is possible to suppress the axial relative displacement of the resin coating layer 27 with respect to the inner diameter side engaging core portion 70a. In other words, the holding force of the resin coating layer 27 can be improved. Note that, among the resin coating layer 27, the outer diameter of the portion covering the annular concave groove 64 can be the same as the outer diameter of the portion covering the portion of the shaft body 69a that is out of the annular concave groove 64, or can be made smaller by twice the radial depth of the annular concave groove 64.

[0174] Figures 17(A) to 17(D) show four modified examples of the fourth example.

[0175] In the first modified example shown in Figure 17(A), a plurality (four in the illustrated example) of annular concave grooves 64a are formed on the outer peripheral surface of the non-engaging core portion 72a. The plurality of annular concave grooves 64a are arranged at intervals in the axial direction. The synthetic resin constituting the resin coating layer 27 is allowed to enter inside each of the annular concave grooves 64a, and the resin coating layer 27 is axially engaged with the annular concave grooves 64a. That is, in the first modified example, each of the plurality of annular concave grooves 64a constitutes an anti-slip portion. In the first modified example, compared with the fourth example, the holding force of the resin coating layer 27 can be improved.

[0176] In the second modified example shown in Figure 17(B), a spiral groove 65 is formed on the outer peripheral surface of the non-engaging core portion 72a. The synthetic resin constituting the resin coating layer 27 is allowed to enter inside the spiral groove 65, and the resin coating layer 27 is engaged with the spiral groove 65. That is, in the second modified example, the spiral groove 65 constitutes an anti-slip portion. According to the second modified example, since the spiral groove 65 can be processed with a single chuck, the productivity of the inner shaft 17 can be improved.

[0177] In the third modification example shown in FIG. 17(C), a knurl groove 66 is formed on the outer peripheral surface of the non-engaging core portion 72a. The synthetic resin constituting the resin coating layer 27 is made to enter inside the knurl groove 66, and the resin coating layer 27 is engaged with the knurl groove 66. That is, in the third modification example, the knurl groove 66 constitutes an anti-slip portion. According to the third modification example, the holding force of the resin coating layer 27 can be increased.

[0178] In the fourth modification example shown in FIG. 17(D), a plurality of recesses 67 are formed on the outer peripheral surface of the non-engaging core portion 72a. The plurality of recesses 67 are arranged in two rows spaced apart in the axial direction, and are arranged at equal intervals in the circumferential direction for each row. The synthetic resin constituting the resin coating layer 27 is made to enter inside each of the recesses 67, and the resin coating layer 27 is engaged with the recesses 67. In the fourth modification example, each of the plurality of recesses 67 constitutes an anti-slip portion. According to the fourth modification example, the holding force of the resin coating layer 27 can be increased.

[0179] Regarding other configurations and effects of the fourth example, they are the same as those of the first example.

[0180] [Fifth Example] The fifth example of the embodiment of the present disclosure will be described with reference to FIG. 18.

[0181] In this example, each of the first engaging portions 22a and 22b constituting the inner diameter side engaging portion 19 has a chamfered portion 26a at the proximal end with respect to the non-engaging portion 23. The chamfering angle of the chamfered portion 26a is preferably 45 degrees or less, and is 30 degrees in the illustrated example.

[0182] The second engaging portion 32 has chamfered portions 34 at both ends in the axial direction. The chamfering angle of the chamfered portion 34 is preferably 45 degrees or less, and is 30 degrees in the illustrated example.

[0183] In this example, even when bending deformation occurs in either the inner shaft 17 or the outer shaft 18, it is possible to suppress the axial end portions of the first engaging portions 22a and 22b from riding on the axial end portions of the second engaging portion 32.

[0184] That is, since the chamfered portion 34 is provided at the axial one-side end portion of the second engaging portion 32 and the chamfered portion 26a is provided at the axial other-side end portion of the first engaging portion 22a, when the outer shaft 18 is relatively moved in the axial one-side direction with respect to the inner shaft 17, it is possible to suppress the axial other-side end portion of the first engaging portion 22a from riding on the axial one-side end portion of the second engaging portion 32.

[0185] Also, since the chamfered portion 34 is provided at the axial other-side end portion of the second engaging portion 32 and the chamfered portion 26a is provided at the axial one-side end portion of the first engaging portion 22b, when the outer shaft 18 is relatively moved in the axial other-side direction with respect to the inner shaft 17, it is possible to suppress the axial one-side end portion of the first engaging portion 22b from riding on the axial other-side end portion of the second engaging portion 32.

[0186] In this example, since the chamfered portion 26a is arranged at the proximal-side end portion of each of the non-engaging portions 23 of the first engaging portions 22a and 22b, the chamfered portions are arranged at the portions adjacent to both axial sides of the non-engaging core portion 72 among the plurality of tooth cores 73. These chamfered portions can also be made continuous with the anti-slip portions formed on the outer peripheral surface of the non-engaging core portion 72.

[0187] When implementing the present disclosure, the chamfered portion 34 may be formed only at the axial both-side end portions of the second engaging portion 32, and the two chamfered portions 26a arranged at the proximal-side end portions of the respective non-engaging portions 23 of the first engaging portions 22a and 22b may be omitted.

[0188] Regarding the other configurations and operational effects of the fifth example, they are the same as those of the first example.

[0189] [Sixth Example] The sixth example of the embodiment of the present disclosure will be described with reference to FIG. 19.

[0190] In this example, the outer diameter side engaging portion 31a that constitutes the outer shaft 18a corresponds to one engaging portion. The outer diameter side engaging portion 31a has a stepped shape and includes a non-engaging portion 68 that does not engage with the inner diameter side engaging portion 19a of the inner shaft 17a corresponding to the other engaging element at the axial intermediate portion. On both sides of the non-engaging portion 68, first engaging portions 84a and 84b corresponding to two engagable portions are arranged. Each of the first engaging portions 84a and 84b has an effective length X. The non-engaging portion 68 has an axial dimension with the same length as the effective length X.

[0191] That is, the outer diameter side engaging portion 31a includes one non-engaging portion 68 and two first engaging portions 84a and 84b. In the outer diameter side engaging portion 31a, the first engaging portion 84a, the non-engaging portion 68, and the first engaging portion 84b are arranged axially in this order.

[0192] Each of the first engaging portions 84a and 84b is constituted by an inner tooth portion 87a in which a plurality of inner teeth 33a are arranged in the circumferential direction. The plurality of inner teeth 33a extend axially and are arranged at equal pitches in the circumferential direction. The tooth thickness and tooth width of each of the plurality of inner teeth 33a are constant in the axial direction except for the chamfered portion 34 provided at the axial end.

[0193] Among the first engaging portions 84a and 84b, the number, pitch, tooth thickness, and tooth width of the plurality of inner teeth 33a are the same between the first engaging portion 84a arranged on the other side in the axial direction and the first engaging portion 84b arranged on one side in the axial direction.

[0194] The first engaging portions 84a and 84b have the same effective length X. Specifically, among the plurality of inner teeth 33a that constitute each of the first engaging portions 84a and 84b, the axial dimension of the portion deviated from the chamfered portion 34 is the effective length X.

[0195] The disengaged portion 68 is disposed in the intermediate portion in the axial direction of the first engaging portions 84a and 84b. The disengaged portion 68 has a cylindrical inner peripheral surface. Further, the disengaged portion 68 has an inner diameter larger than the root circle diameter of the plurality of internal teeth 33a constituting the first engaging portions 84a and 84b.

[0196] The disengaged portion 68 has an axial dimension L 68 equal to the effective length X of the first engaging portions 84a and 84b (L 68 = effective length X).

[0197] On the other hand, the inner diameter side engaging portion 19a of the present example has a second engaging portion 85 corresponding to an engagable portion over the entire axial length. That is, the inner diameter side engaging portion 19a is composed only of the second engaging portion 85. The second engaging portion 85 is composed of an external tooth portion 86a in which a plurality of external teeth 25a are arranged in the circumferential direction. The plurality of external teeth 25a extend in the axial direction and are arranged at equal pitches in the circumferential direction. The tooth thickness and tooth height of each of the plurality of external teeth 25a are constant over the axial direction except for the chamfered portion 26 provided at the axial end. The plurality of external teeth 25a have a tip circle diameter smaller than the inner diameter of the disengaged portion 68 of the outer shaft 18a.

[0198] The inner diameter side engaging portion 19a is provided with a resin coating layer 27. Specifically, the entire length range of the second engaging portion 85 is covered with the resin coating layer 27.

[0199] The second engaging portion 85 engages with the first engaging portions 84a and 84b of the outer diameter side engaging portion 31a provided on the outer shaft 18a. Specifically, the plurality of external teeth 25a constituting the second engaging portion 85 engage with the plurality of internal teeth 33a of the first engaging portions 84a and 84b in a torque-transmissible manner and allowing relative displacement in the axial direction. Thereby, the outer shaft 18a moves relative to the inner shaft 17a in the front-rear direction together with the steering wheel 2, and the steering shaft 11a is expanded and contracted.

[0200] The second engaging portion 85 does not engage with the disengaged portion 68 of the outer diameter side engaging portion 31a provided on the outer shaft 18a.

[0201] In this example, among the plurality of external teeth 25a, the effective length Y of the second engaging portion 85, which is the axial dimension of the portion covered by the resin coating layer 27, is twice the effective length X of each of the first engaging portions 84a and 84b that constitute the outer diameter side engaging portion 31a (2X). In this example, the value of "Y" is about 100 mm. In this example, the axial dimension L of the resin coating layer 27 27 is approximately the same as twice the effective length X of each of the first engaging portions 84a and 84b (L 27 ≈ 2X).

[0202] Also in the case of the steering shaft 11a of this example, when the overall length is changed, the engagement length E between the plurality of external teeth 25a and the plurality of internal teeth 33a can be made constant. For this reason, even when the overall length of the steering shaft 11a is changed, the sliding resistance can be made constant. Further, in this example, since the range (axial dimension L 27 ) in which the resin coating layer 27 is formed can be made shorter than the structure of the first example, the manufacturing cost of the steering shaft 11a can be suppressed.

[0203] Regarding the other configurations and operational effects of the sixth example, they are the same as those of the first example.

[0204] As described above, the embodiments of the present disclosure have been explained. However, the present disclosure is not limited to this, and can be appropriately changed without departing from the technical idea of the invention. Also, the structures of the first to sixth examples of the embodiments of the present disclosure and their modified examples can be appropriately combined and implemented as long as there is no contradiction.

[0205] The present disclosure is not limited to an electric steering device that electrically adjusts the front-rear position of the steering wheel, and can also be applied to a manual steering device that manually adjusts the front-rear position of the steering wheel. Also, the present disclosure is not limited to a steer-by-wire type (linkless structure) steering device, and can also be applied to other types of steering devices.

Explanation of Reference Numerals

[0206] 1 Steering device 2 Steering wheel 3 Steering unit 4 Steering wheel 5 Steering gear unit 6 Control device 7 Steering actuator 8 Tie rod 9 Position adjusting device 10 Reaction force generating device 11, 11a Steering shaft 12 Steering column 13 Lower telescopic actuator 14 Upper telescopic actuator 15 Tilt actuator 16 Rolling bearing 17, 17a Inner shaft 18, 18a Outer shaft 19, 19a Inner diameter side engaging portion 20 Connection portion 21 Intermediate shaft portion 22a, 22b First engaging portion 23 Non-engaging portion 25, 25a External teeth 26, 26a Chamfered portion 27 Resin coating layer 28 Male serration teeth 29 Large diameter cylindrical portion 30 Small diameter cylindrical portion 31, 31a Outer diameter side engaging portion 32 Second engaging portion 33, 33a Internal teeth 34 Chamfered portion 35 Bracket 36 Column body 37 Fixed bracket 38 Displacement bracket 39 Fixed plate portion 40 Fixed side support frame 41 Mounting bolt 42 Displacement plate portion 43 Displacement side support frame 44 Linear guide 45 Support wall part 46 Outer column 47 Lower side inner column 48 Upper side inner column 49 Lower side telescopic motor 50 Lower side feed screw device 51 Lower side screw shaft 52 Lower side nut 53 Upper side telescopic motor 54 Upper side feed screw device 55 Upper side screw shaft 56 Upper side nut 57 Connector member 58 Pivot bolt 59 Tilt motor 60 Tilt feed screw device 61 Gear housing 62 Reaction force applying motor 63 Output shaft 64, 64a Annular concave groove 65 Spiral groove 66 Knurled groove 67 Concave part 68 Non-engagement part 69, 69a Shaft body 70a Inner diameter side engagement core part 71a, 71b First engagement core part 72, 72a Non-engagement core part 73 Tooth core 74a, 74b First engagement core part covering part 75 Non-engagement core part covering part 76a, 76b Side plate part 77 Mold 78 Cavity 79 Gate 80 Corner R part 81 Notch concave part 82 Positioning pin 83 Chamfered part 84a, 84b First engagement part 85 Second engagement part 86, 86a Outer tooth part Internal tooth parts 87 and 87a External tooth core part 88 Internal tooth core part 89 Steering shaft 100 Inner shafts 101 and 101a Outer shafts 102 and 102a Male spline teeth 103 Resin coating layer 104 Female spline teeth 105 Male spline parts 106 and 106a<> Female spline parts 107 and 107a

Claims

1. An inner shaft having an inner diameter side engaging portion at one end of the outer peripheral surface in the axial direction, an outer shaft having an outer diameter side engaging portion at the other end of the inner peripheral surface in the axial direction, the outer diameter side engaging portion being engageable with the inner diameter side engaging portion to transmit torque and allow relative displacement in the axial direction, comprising: One of the engaging portions of the inner diameter side engaging portion and the outer diameter side engaging portion has at least one non-engaging portion in the axial intermediate portion that does not engage with the other engaging portion of the inner diameter side engaging portion and the outer diameter side engaging portion, Each of the engagable portions disposed on both axial sides of the non-engaging portion of the one engaging portion has an effective length X, and the non-engaging portion has an axial dimension of the same length as the effective length X, and the other engaging portion has an effective length Y that is twice the length of the effective length X, a steering shaft.

2. The inner diameter side engaging portion is constituted by the one engaging portion, and the outer diameter side engaging portion is constituted by the other engaging portion, The engagable portion constituting the inner diameter side engaging portion is constituted by an external tooth portion formed of a plurality of external teeth, and the outer diameter side engaging portion is constituted by an internal tooth portion formed of a plurality of internal teeth, [[ID=ll]]The steering shaft according to claim 1, wherein the effective length X is an axial dimension of a portion of the plurality of external teeth that engages with the plurality of internal teeth.

3. The steering shaft according to claim 2, wherein the non-engaging portion is constituted by a cylindrical surface having an outer diameter equal to or less than the pitch circle diameter of the plurality of external teeth.

4. The inner shaft includes a shaft body and a resin coating layer having the inner diameter side engaging portion on the outer peripheral surface and covering the outer peripheral surface of one end of the shaft body in the axial direction. The steering shaft according to claim 2 or 3.

5. The steering shaft according to claim 4, wherein the inner diameter side engaging portion has an anti-slip portion that suppresses relative movement of the resin coating layer in the axial direction with respect to the shaft body.

6. The outer diameter side engaging portion is constituted by the one engaging portion, and the inner diameter side engaging portion is constituted by the other engaging portion, The engagable portion constituting the outer diameter side engaging portion is constituted by an internal tooth portion formed of a plurality of internal teeth, and the inner diameter side engaging portion is constituted by an external tooth portion formed of a plurality of external teeth, The steering shaft according to claim 1, wherein the effective length X is an axial dimension of a portion of the plurality of internal teeth that engages with the plurality of external teeth.

7. The external tooth portion of the inner diameter side engaging portion is constituted by a male spline portion, and the plurality of external teeth are constituted by male spline teeth. The steering shaft according to claim 2 or 6.

8. The number of the non-engaging portions is one, and the effective length X is 30 mm or more. The steering shaft according to claim 1.

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