JP7697676B2 - Shaft connection structure, motor with speed reducer, electric power steering device, and steering unit for steer-by-wire - Google Patents

Description

The present invention relates to a shaft connection structure that connects a pair of shafts. It also relates to a motor with a reduction gear, an electric power steering device, and a steering unit for steer-by-wire, each of which has a shaft connection structure.

Electric power steering devices that use an electric motor as an auxiliary power source to reduce the force required by the driver to operate the steering wheel are widely used. In addition, electric power steering devices often use an electric motor in combination with a worm reduction gear to reduce the size of the electric motor.

In a motor with a reducer that combines an electric motor and a worm reducer, the motor output shaft of the electric motor is connected to the worm that constitutes the worm reducer in a manner that allows torque transmission in order to increase the output torque of the electric motor.

It is widely known that the motor output shaft and the worm are connected using a joint member (coupling), as described, for example, in JP 2016-2926 A (Patent Document 1).

According to the structure described in JP 2016-2926 A, even if a so-called alignment error occurs, in which the central axis of the motor output shaft and the central axis of the worm do not coincide, the alignment error can be absorbed by the coupling member undergoing elastic deformation, etc. Therefore, even if an alignment error occurs, torque can be transmitted between the motor output shaft and the worm. It is also possible to suppress the generation of abnormal noise.

JP 2016-2926 A

In the structure described in JP 2016-2926 A, the coupling member connecting the motor output shaft and the worm is composed of three parts: a first rotating element fixed to the end of the motor output shaft, a second rotating element fixed to the end of the worm, and an intermediate element disposed between the first rotating element and the second rotating element. This increases the number of parts in the motor with a reduction gear, which causes the cost to rise. In addition, because the coupling member is interposed between the motor output shaft and the worm, the overall length of the connection is long, which makes it easier for the motor with a reduction gear, and therefore the electric power steering device, to become large.

The above problems are not specific to the connection between the motor output shaft and the worm, but can occur in the same way at the connection between a pair of shafts that are connected so that torque can be transmitted.

The present invention has been made to solve the above problems, and aims to provide a shaft connection structure that can absorb alignment errors, connect a pair of shafts without increasing the number of parts, and shorten the overall length of the connection, as well as a motor with a reduction gear, an electric power steering device, and a steering unit for steer-by-wire that are equipped with this shaft connection structure.

The shaft connection structure of the present invention comprises a male spline connection portion provided at an end of a first shaft, and a female spline connection portion provided at an end of a second shaft.
The male spline connection portion is formed by forming a plurality of male spline teeth on the outer surface of a partial spherical convex portion.
The female spline connection portion has a plurality of female spline teeth formed on the inner surface of a partial spherical recess.
The partial spherical recess is open only to one end face of the second shaft.
The partial spherical recess has an inner diameter that curves downward from the opening toward the back, and the female spline teeth are formed on the entire inner surface of the partial spherical recess over the axial direction.
The partial spherical convex portion has an outer diameter that curvedly decreases from the base end to the tip end, and the male spline teeth are formed on the entire outer surface of the partial spherical convex portion in the axial direction.
In the shaft connection structure of the present invention, the partial spherical convex portion is inserted inside the partial spherical concave portion, and each of the male spline teeth and each of the female spline teeth are spline-engaged, thereby connecting the first shaft and the second shaft in a manner capable of transmitting torque.
In addition, the partial spherical convex portion includes not only a convex portion (spherical convex portion) having a spherical outer surface formed by cutting a sphere (including an elliptical sphere) with one plane as shown in FIG. 29A, but also a convex portion (spherical truncated convex portion) having a spherical truncated outer surface formed by cutting a sphere with two parallel planes as shown in FIG. 29B. The spherical convex portion has a bow-shaped cross section and a dome-shaped convex surface with a rounded tip on the outer surface. In contrast, the spherical truncated convex portion has a substantially isosceles trapezoidal cross section and a band-shaped convex surface on the outer surface. Among the spherical convex portions, those having a hemispherical outer surface formed by cutting a sphere near the center are particularly called hemispherical convex portions. In addition, the partial spherical concave portion includes not only a concave portion (spherical convex portion) having a spherical inner surface formed by cutting a sphere (including an elliptical sphere) with one plane as shown in FIG. 29B, but also a concave portion (spherical truncated concave portion) having a spherical truncated inner surface formed by cutting a sphere with two parallel planes as shown in FIG. Among the spherical recesses, those having a hemispherical inner surface formed by cutting a sphere near the center are particularly called hemispherical recesses.

In one aspect of the shaft connection structure of the present invention, the male spline connection portion can be constructed by forming a plurality of the male spline teeth on an outer surface of a hemispherical convex portion, and the female spline connection portion can be constructed by forming a plurality of the female spline teeth on an inner surface of a hemispherical concave portion.
Alternatively, in one aspect of the shaft connection structure of the present invention, the male spline connection portion can be constructed by forming a plurality of the male spline teeth on an outer surface of a spherical frustum-shaped convex portion, and the female spline connection portion can be constructed by forming a plurality of the female spline teeth on an inner surface of a spherical frustum-shaped concave portion.

In one aspect of the shaft connection structure of the present invention, at least one of the male spline connection portion and the female spline connection can be covered with a coating layer made of synthetic resin.
Alternatively, a buffer member made of an elastic material can be disposed between the male spline connection portion and the female spline connection portion.

In one embodiment of the shaft connection structure of the present invention, the outer diameter of the portion of the first shaft adjacent to the male spline connection portion can be made smaller than the outer diameter of the male spline connection portion.

The motor with a reducer of the present invention includes a worm reducer and an electric motor.
The worm reducer includes a worm and a worm wheel.
The electric motor has a motor output shaft.
In the motor with a reducer of the present invention, the end of the worm and the end of the motor output shaft can be connected by the shaft connection structure of the present invention.
In this case, the end of the motor output shaft may be provided with the male spline connection portion, and the end of the worm may be provided with the female spline connection portion.
Alternatively, the end of the motor output shaft may be provided with the female spline connection portion, and the end of the worm may be provided with the male spline connection portion.

The electric power steering device of the present invention is equipped with a motor with a reduction gear of the present invention.

The steer-by-wire steering unit of the present invention includes, for example, a steering shaft constituting a position adjustment device, and a reaction force generating device having a reaction force output shaft and for applying a steering reaction force to the steering wheel.
In the steer-by-wire steering unit of the present invention, the end of the steering shaft and the end of the reaction force output shaft can be connected so as to be capable of transmitting torque by the shaft connection structure of the present invention.
In this case, the end of the steering shaft may be provided with the male spline connection portion, and the end of the reaction force output shaft may be provided with the female spline connection portion.
Alternatively, the end of the steering shaft may be provided with the female spline connection portion, and the end of the reaction force output shaft may be provided with the male spline connection portion.

The steer-by-wire steering unit of the present invention includes, for example, a steering shaft constituting a position adjustment device, and a reaction force applying motor having a motor output shaft and for applying a steering reaction force to the steering wheel.
In the steer-by-wire steering unit of the present invention, the end of the steering shaft and the end of the motor output shaft can be connected so as to be capable of transmitting torque by the shaft connection structure of the present invention.
In this case, the end of the steering shaft may be provided with the male spline connection portion, and the end of the motor output shaft may be provided with the female spline connection portion.
Alternatively, the end of the steering shaft may be provided with the female spline connection portion, and the end of the motor output shaft may be provided with the male spline connection portion.

The present invention provides a shaft connection structure that can absorb alignment errors, connect a pair of shafts without increasing the number of parts, and shorten the overall length of the connection, as well as a motor with a reduction gear, an electric power steering device, and a steering unit for steer-by-wire that are equipped with this shaft connection structure.

FIG. 1 is a schematic diagram showing a steer-by-wire steering device according to a first embodiment. FIG. 2 is a side view showing a steer-by-wire type steering unit according to the first example of the embodiment. FIG. 3 is an end view of the steer-by-wire steering unit according to the first embodiment, as viewed from the rear. FIG. 4 is a cross-sectional view taken along line AA of FIG. 3, showing the steer-by-wire steering unit according to the first embodiment with the bracket and the reaction force applying motor omitted. FIG. 5 is an enlarged view of the left side of FIG. FIG. 6 is a side view showing a position adjustment device constituting a steer-by-wire type steering unit according to the first embodiment. FIG. 7 is a front end view of a position adjustment device constituting a steer-by-wire steering unit according to the first embodiment. FIG. 8 is a perspective view showing a position adjustment device constituting a steer-by-wire type steering unit according to the first embodiment. FIG. 9 is a perspective view showing a reaction force generating device constituting a steer-by-wire type steering unit according to the first embodiment, with the reaction force applying motor removed. 10A and 10B are diagrams showing a male spline connection portion constituting a power connection portion of a steer-by-wire type steering unit according to the first example of the embodiment, in which (A) is a side view and (B) is an end view. 11A and 11B are diagrams showing a female spline connection portion constituting a power connection portion of a steer-by-wire type steering unit according to a first example of an embodiment, in which (A) is an end view and (B) is a cross-sectional view taken along line D-D of (A). FIG. 12 is a diagram for explaining the connection structure of the power connection part of a steer-by-wire type steering unit in relation to the first example of the embodiment, where (A) is a partial cross-sectional view showing the state before connection, and (B) is a partial cross-sectional view showing the state after connection. FIG. 13 is an enlarged view of the upper right portion of FIG. FIG. 14 is an enlarged view of part B in FIG. FIG. 15 shows a second example of the embodiment and corresponds to part C in FIG. FIG. 16 is a cross-sectional view showing a connection structure between a connection shaft and a main shaft according to a second example of the embodiment. FIG. 17 is a cross-sectional view showing a shaft coupling that connects the connecting shaft and the main shaft according to the second embodiment. FIG. 18 is an end view showing a shaft coupling that connects the connecting shaft and the main shaft according to the second embodiment. FIG. 19 is a diagram showing a third example of the embodiment, and corresponds to FIG. FIG. 20 is a schematic diagram showing an electric power steering apparatus according to a fourth embodiment. FIG. 21 is a schematic cross-sectional view taken along line EE of FIG. 20 with some parts omitted. FIG. 22 is a diagram showing a modification of the fourth example of the embodiment, which corresponds to FIG. 23A and 23B are diagrams corresponding to FIG. 12 and show a fifth example of an embodiment, in which (A) is a partial cross-sectional view showing the state before connection, (B) is a partial cross-sectional view showing the state after connection, and (C) is a partial cross-sectional view showing the state in which an alignment error has occurred after connection. FIG. 24 is a side view showing a male spline connection portion according to a modified example of the fifth example of the embodiment. FIG. 25 is a diagram showing a sixth example of the embodiment, and corresponds to FIG. 26A and 26B are views showing a male spline connection portion according to a seventh example of an embodiment, in which (A) is a side view and (B) is an end view. 27A and 27B are views showing a female spline connection portion according to a seventh example of an embodiment, in which (A) is an end view and (B) is a cross-sectional view taken along line FF of (A). 28A and 28B are diagrams corresponding to FIG. 12 and show a seventh example of an embodiment, in which (A) is a partial cross-sectional view showing the state after connection, and (B) is a partial cross-sectional view showing the state in which an alignment error has occurred after connection. FIG. 29A is a schematic diagram showing an example of a spherical notch-shaped convex portion, and FIG. 29B is a schematic diagram showing an example of a spherical frustum-shaped convex portion.

[First Example of the Embodiment]
A first embodiment of the present invention will be described with reference to Figures 1 to 14. In this embodiment, the shaft connection structure of the present invention is applied to a steer-by-wire steering device. In the following description, the front-rear direction means the front-rear direction of the vehicle, the up-down direction means the up-down direction of the vehicle, and the width direction means the width direction of the vehicle.

[Overall configuration of steering device]
The steering device 1 of 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 steered wheels 4, and a control device (ECU) 6. The steering device 1 has a linkless structure in which the steering unit 3 and the steering unit 5 are not mechanically connected but are electrically connected.

The steering unit 3 measures the operation of the steering wheel 2 by the driver using a torque sensor 75 (see FIG. 5) and a steering angle sensor (not shown), and outputs the measurement results to the control device 6. Various signals indicating the driving situation, such as the steering torque measured by the torque sensor 75, the steering angle measured by the steering angle sensor, vehicle speed, yaw rate, and acceleration, are input to the control device 6. The control device 6 drives the steering actuator 7 provided in the steering unit 5 based on the various signals indicating the driving situation. This displaces linear motion members such as the rack shaft and screw shaft in the width direction, pushing and pulling a pair of tie rods 8 to impart a steering angle to the pair of steered wheels 4.

The control device 6 also controls the drive of a reaction force applying motor 58 (see FIG. 3) of a reaction force generating device 10 (described later) provided in the steering unit 3 based on various signals indicating driving conditions such as steering torque, steering angle, and vehicle speed, and applies a steering reaction force to the steering wheel 2 according to the driving conditions.

[Steering unit]
Next, a description will be given of the steering unit 3, which is a characteristic part of the steering device 1 of this embodiment. The steering unit 3 includes a position adjustment 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.

The position adjustment device 9 and the reaction force generating device 10 are each sub-assembled and connected to each other at two connection points. Specifically, the position adjustment device 9 and the reaction force generating device 10 arranged in front of the position adjustment device 9 are connected at only two points, the power connection part 11 and the housing connection part 12, as shown in Figures 4 and 5. Therefore, the steering unit 3 of this example is assembled by connecting the position adjustment device 9 and the reaction force generating device 10 at two points, the power connection part 11 and the housing connection part 12. In particular, this example is characterized by the connection structure of the power connection part 11. A detailed explanation of the connection structure of the power connection part 11 will be given after the explanation of the position adjustment device 9 and the reaction force generating device 10.

<Position adjustment device>
The position adjustment device 9 has a function of adjusting the front-rear position and the up-down position of the steering wheel 2. In other words, the position adjustment device 9 has a telescopic mechanism for adjusting the front-rear position of the steering wheel 2, and a tilt mechanism for adjusting the up-down position of the steering wheel 2.

The position adjustment device 9 includes a steering shaft 13, a steering column 14, a lower telescopic actuator 15, an upper telescopic actuator 16, and a tilt actuator 17.

<Steering shaft>
The steering shaft 13 is configured so that its entire length can be extended and contracted, and is rotatably supported inside the steering column 14 by a plurality of (three in the illustrated example) rolling bearings 18a to 18c. The steering wheel 2 is attached to the rear end of the steering shaft 13. The steering shaft 13 is formed by spline-engaging a lower shaft 19 disposed at the front side with a hollow cylindrical upper shaft 20 disposed at the rear side to enable torque transmission and relative axial displacement.

<Female spline connection>
The front end of the lower shaft 19 is provided with a female spline connection portion 21 which constitutes the power connection portion 11 capable of transmitting torque to the reaction force generating device 10. Therefore, in this example, the steering shaft 13 (lower shaft 19) corresponds to the second shaft recited in the claims.

11, the female spline connection portion 21 has a hemispherical female spline structure in which a plurality of female spline teeth 23 are formed on the inner surface of a hemispherical recess 22 that opens into the front end face of the lower shaft 19. The inner diameter of the hemispherical recess 22 curvedly decreases from the opening toward the innermost portion (the center portion of the inner surface), and the innermost portion is located on the central axis of the lower shaft 19. The plurality of female spline teeth 23 are disposed at equal intervals in the circumferential direction, and are formed in radial directions from the innermost portion of the hemispherical recess 22 toward the opening edge.
The hemispherical recess 22 may have any concave shape in which the inner diameter curvedly decreases from the opening to the back. Therefore, the hemispherical recess 22 is not limited to a perfect hemisphere in which the depth dimension from the opening to the back is half the inner diameter of the opening, but includes an approximate hemisphere that is not a perfect hemisphere, a semi-elliptical sphere, and an approximate hemi-elliptical sphere that is not a perfect hemisphere.

Steering column
The steering column 14 is configured to be extendable over its entire length and is supported by a vehicle body (not shown). The steering column 14 includes a bracket 24 and a column body 25. The steering column 14 in this example has a two-stage telescopic structure to ensure a large amount of telescopic movement in the front-rear direction.

The bracket 24 is used to support the column body 25 on the vehicle body, and includes a fixed bracket 26 that is fixed to the vehicle body, and a displacement bracket 27 that is supported so as to be displaceable relative to the fixed bracket 26 in the fore-and-aft direction.

The fixed bracket 26 comprises a fixed plate portion 28 having a substantially rectangular flat shape and a fixed side support frame 29 having a substantially U-shape. The fixed plate portion 28 is fixed to the vehicle body using a number of mounting bolts 30. The fixed side support frame 29 is provided at the front end of the fixed plate portion 28 and connects both ends of the fixed plate portion 28 in the width direction.

The displacement bracket 27 comprises a displacement plate portion 31 arranged so as to be superimposed on the underside of the fixed plate portion 28, and a displacement side support frame 32 having a generally U-shape. The displacement plate portion 31 is supported by a linear guide 80 (see FIG. 3) so as to be capable of relative displacement in the front-rear direction with respect to the fixed plate portion 28. The displacement side support frame 32 is provided at the rear end of the displacement plate portion 31, and connects both ends of the displacement plate portion 31 in the width direction. Of the pair of left and right support walls 33 constituting the displacement side support frame 32, a screw shaft (not shown) of the tilt feed screw device 56 constituting the tilt actuator 17 is supported on the inner surface of one of the support walls 33 so as to be rotatable with its axial direction facing up and down.

As shown in FIG. 4, the column body 25 is generally cylindrical in shape and is disposed with its axial direction in the front-rear direction. The column body 25 includes an outer column 34 disposed in the middle in the front-rear direction, a lower inner column 35 fitted into the front side of the outer column 34, and an upper inner column 36 fitted into the rear side of the outer column 34.

The outer column 34 is supported so as to be movable in the vertical direction relative to the displacement bracket 27. The rear side of the outer column 34 is inserted in the front-rear direction inside the displacement side support frame 32 that constitutes the displacement bracket 27. A nut (not shown) of the tilt feed screw device 56 that constitutes the tilt actuator 17 is pivotally supported on the outer peripheral surface of the rear side of the outer column 34. The outer column 34 has a slit 37 (see FIG. 4) that extends in the front-rear direction at the middle part of the lower surface in the front-rear direction. The outer column 34 has screw holes 38 at multiple locations on the outer peripheral surface. Each screw hole 38 is screwed with a screw plug 39 whose tip is made of a material with a low friction coefficient such as polyacetal (POM).

The lower-side inner column 35 is fitted into the front side of the outer column 34 so as to allow relative displacement in the front-rear direction. The tip of a screw plug 39 that is screwed into a screw hole 38 provided in the outer column 34 is pressed against the outer peripheral surface of the lower-side inner column 35. This suppresses rattling of the lower-side inner column 35 relative to the outer column 34. The lower-side inner column 35 has a cylindrical portion 40 that is arranged inside the outer column 34, and a first housing connection portion 41 that is fitted into and supported by the front end portion of the cylindrical portion 40.

<<First housing connection part>>
The first housing connection part 41 has a cylindrical first connection tube part 42 fitted into the front end part of the cylindrical part 40, and a first connection plate part 43 bent from the front end part of the first connection tube part 42 toward the outside in the radial direction and having an outward flange shape and a substantially rectangular flat plate shape. Each corner part of the first connection plate part 43 is provided with a first through hole 44 penetrating in the front-rear direction. The first housing connection part 41 is disposed inside the fixed side support frame 29. The first through hole 44 may be a simple through hole or may be a screw hole. The first housing connection part 41 is disposed at the front end part of the column main body 25 before the position adjustment device 9 and the reaction force generating device 10 are connected, and therefore functions as a cover when the position adjustment device 9 is delivered or assembled, and can prevent foreign matter from entering the inside of the column main body 25.

The upper inner column 36 is fitted into the rear side of the outer column 34 so as to allow relative displacement in the front-to-rear direction. The tip of a screw plug 39 that is screwed into a screw hole 38 provided in the outer column 34 is pressed against the outer peripheral surface of the upper inner column 36. This prevents the upper inner column 36 from rattling relative to the outer column 34.

<Lower telescopic actuator>
The lower-side telescopic actuator 15 is disposed so as to span between the fixed bracket 26 and the displacement bracket 27 that constitute the bracket 24, and displaces the displacement bracket 27 in the front-rear direction relative to the fixed bracket 26. This causes the outer column 34 and the lower-side inner column 35 that constitute the column body 25 to be relatively displaced in the front-rear direction, causing the column body 25 to expand and contract.

The lower telescopic actuator 15 includes a lower telescopic motor 45 and a lower feed screw device 46.

The lower telescopic motor 45 is supported and fixed to the widthwise side of the fixed support frame 29 that constitutes the fixed bracket 26, with the motor output shaft (not shown) facing up and down.

As shown in FIG. 3, the lower side feed screw device 46 includes a lower side screw shaft 47 and a lower side nut 48. The lower side screw shaft 47 is arranged with its axial direction facing the front-rear direction, and is rotated by the lower side telescopic motor 45 via a reduction mechanism such as a worm reducer (not shown). The lower side screw shaft 47 is supported by the fixed bracket 26 so that it can only rotate. The lower side nut 48 is screwed into the lower side screw shaft 47 and is supported by the side surface of the displacement bracket 27 in the width direction. That is, the lower side telescopic actuator 15 rotates the lower side telescopic motor 45 to displace the lower side nut 48 in the axial direction of the lower side screw shaft 47, thereby displacing the outer column 34 in the front-rear direction relative to the lower side inner column 35.

<Upper telescopic actuator>
The upper telescopic actuator 16 is disposed so as to bridge between the outer column 34 and the upper inner column 36 that constitute the column body 25, and displaces the upper inner column 36 in the front-rear direction relative to the outer column 34. This causes the column body 25 to extend and retract.

The upper telescopic actuator 16 includes an upper telescopic motor 49 and an upper feed screw device 50.

The upper telescopic motor 49 is supported below the front end of the outer column 34 with the motor output shaft (not shown) facing in the width direction.

As shown in FIG. 3, the upper side feed screw device 50 includes an upper side screw shaft 51 and an upper side nut 52. The upper side screw shaft 51 is arranged with its axial direction facing the front-rear direction, and is rotated by the upper side telescopic motor 49 via a reduction mechanism such as a worm reducer (not shown). The upper side screw shaft 51 is supported so as to be rotatable only with respect to the outer column 34. The upper side nut 52 is screwed to the upper side screw shaft 51, and is supported on the lower surface of the upper side inner column 36 via a connector member 53. The connector member 53 is disposed inside the slit 37 of the outer column 34 and fixed to the lower surface of the upper side inner column 36. That is, the upper side telescopic actuator 16 rotates the upper side telescopic motor 49 to displace the upper side nut 52 in the axial direction of the upper side screw shaft 51, thereby displacing the upper side inner column 36 in the front-rear direction relative to the outer column 34.

<Tilt actuator>
The tilt actuator 17 is disposed so as to span between the displacement side support frame 32 and the outer column 34 that constitute the displacement bracket 27, and displaces the outer column 34 in the vertical direction relative to the displacement bracket 27. In addition, as will be described later, the reaction force generating device 10 connected to the front side of the position adjustment device 9 is rotatably supported by a pair of pivot bolts 54 disposed in the width direction relative to the fixed side support frame 29. This makes it possible to swing the column body 25 in the vertical direction relative to the bracket 24 around the pivot bolts 54.

The tilt actuator 17 includes a tilt motor 55 and a tilt feed screw device 56.

The tilt motor 55 is fixed to one of the support walls 33 that constitute the displacement side support frame 32, with the motor output shaft (not shown) facing forward and backward.

The tilt feed screw device 56 includes a tilt screw shaft and a tilt nut (not shown). The tilt screw shaft is arranged with its axial direction facing the vertical direction, and is rotated by the tilt motor 55 via a reduction mechanism such as a worm reducer (not shown). The tilt screw shaft is supported on one of the support walls 33 so that it can only rotate. The tilt nut is screwed onto the tilt screw shaft and is pivotally supported on the side surface of the outer column 34 in the width direction. That is, the tilt actuator 17 rotates the tilt motor 55 to displace the tilt nut in the axial direction of the tilt screw shaft, thereby displacing the outer column 34 in the vertical direction relative to the displacement bracket 27.

How to adjust the steering wheel position
To adjust the longitudinal position of the steering wheel 2 by the position adjustment device 9 of this example, the lower telescopic actuator 15 is driven to displace the displacement bracket 27 relative to the fixed bracket 26 in the longitudinal direction and to displace the outer column 34 relative to the lower inner column 35 in the longitudinal direction, and/or the upper telescopic actuator 16 is driven to displace the upper inner column 36 relative to the outer column 34 in the longitudinal direction. This causes the overall length of the steering column 14 to expand and contract, and also the overall length of the steering shaft 13 to expand and contract, thereby adjusting the longitudinal position of the steering wheel 2. After the longitudinal position of the steering wheel 2 has been adjusted to the desired position, the drive of the lower telescopic actuator 15 and/or the upper telescopic actuator 16 is stopped.

To adjust the vertical position of the steering wheel 2 using the position adjustment device 9 of this example, the tilt actuator 17 is driven to displace the rear portion of the outer column 34 vertically relative to the displacement bracket 27. This causes the steering shaft 13, which is rotatably supported inside the column body 25, to swing, adjusting the vertical position of the steering wheel 2. After the vertical position of the steering wheel 2 has been adjusted to the desired position, the drive of the tilt actuator 17 is stopped.

The adjustment of the fore-aft position and the up-down position of the steering wheel 2 can be performed simultaneously or independently (at different times).

<Reaction force generating device>
The reaction force generating device 10 is disposed in front of the position adjustment device 9, and is connected to the position adjustment device 9 by a power connection part 11 and a housing connection part 12. The reaction force generating device 10 is controlled by the control device 6, and applies to the steering wheel 2 a steering reaction force of a magnitude and direction according to driving conditions such as the steering angle of the steering wheel 2 and the vehicle speed.

The reaction force generating device 10 comprises a gear housing 57, a reaction force applying motor 58, a worm reduction gear 59, and a reaction force output shaft 60.

9, the gear housing 57 includes a lower housing 61, an upper housing 62, and a second housing connection portion 63. The lower housing 61, the upper housing 62, and the second housing connection portion 63 are connected in the front-rear direction by a bolt 81 before the reaction force generating device 10 is connected to the position adjustment device 9. The lower housing 61 is integrally provided with a cup-shaped worm accommodating portion 65 and a cylindrical worm wheel accommodating portion 66. The upper housing 62 is cylindrical and is fixed to the rear side of the worm wheel accommodating portion 66. Both widthwise sides of the upper housing 62 are rotatably supported by a pair of pivot bolts 54 relative to the fixed support frame 29.

<<Second housing connection part>>
The second housing connection portion 63 closes the rear opening of the upper housing 62, and has a cylindrical second connection tube portion 67 and a second connection plate portion 68 bent radially outward from the front end of the second connection tube portion 67 and having a generally rectangular flat plate shape. Each corner of the second connection plate portion 68 is provided with a second through hole 69 penetrating in the front-rear direction. In this example, the lower housing 61 and the upper housing 62 are provided with auxiliary through holes (not shown) penetrating in the front-rear direction in the portions that match the second through holes 69 (of which, in the illustrated example, the upper two positions). Therefore, when the lower housing 61, the upper housing 62, and the second housing connection portion 63 are connected in the front-rear direction by the bolts 81 to form the gear housing 57, the second through hole 69 and the auxiliary through hole are continuous in the front-rear direction to form one continuous hole 79. The second through hole 69 may be a simple through hole or a screw hole. The lower housing 61 and the upper housing 62 are connected to each other by a bolt 87 that is inserted through the auxiliary through-hole from the front side to the rear side.

The reaction force applying motor 58 is supported and fixed to the worm housing 65 that constitutes the gear housing 57. The rotation of the reaction force applying motor 58 is transmitted to the steering shaft 13 via the worm reduction gear 59, the reaction force output shaft 60, and the power connection part 11.

The worm reducer 59 includes a worm 70 and a worm wheel 71. The worm 70 is supported rotatably inside the worm housing 65 and is connected to a motor output shaft (not shown) of the reaction force applying motor 58. The worm wheel 71 is disposed inside the lower housing 61 and is fitted onto a lower output shaft 72 (described below) that constitutes the reaction force output shaft 60.

The reaction output shaft 60 is arranged with its axial direction facing the front-rear direction, and is rotatably supported inside the gear housing 57 via a plurality of (two in the illustrated example) rolling bearings 82a, 82b. The reaction output shaft 60 includes a lower output shaft 72, an upper output shaft 73, and a torsion bar 74. The lower output shaft 72 and the upper output shaft 73 are arranged coaxially with each other and are connected to each other via the torsion bar 74. A torque sensor 75 is arranged around the upper output shaft 73 to measure the steering torque input from the driver to the steering wheel 2. The rear end of the upper output shaft 73 protrudes rearward from the second connection tube portion 67 that constitutes the second housing connection portion 63.

Male spline connection
The rear end of the upper output shaft 73 is provided with a male spline connection portion 76 that constitutes the power connection portion 11 capable of transmitting torque between the position adjustment device 9. Therefore, in this example, the reaction output shaft 60 (upper output shaft 73) corresponds to the first shaft recited in the claims.

As shown in Fig. 10, the male spline connection portion 76 has a hemispherical male spline structure in which a plurality of male spline teeth 78 are formed on the outer surface of a hemispherical protrusion 77 provided at the rear end of the upper output shaft 73. The outer diameter of the hemispherical protrusion 77 curvedly decreases from the base end (bottom) to the tip end (top), and the tip end is located on the central axis of the upper output shaft 73. The multiple male spline teeth 78 are disposed at equal intervals in the circumferential direction and are formed in a radial direction from the tip end to the base end of the hemispherical protrusion 77. In this example, the male spline connection portion 76 is covered with a coating layer made of a synthetic resin having a low friction coefficient, such as polyamide resin.
The hemispherical convex portion 77 may have any convex shape as long as the outer diameter curvedly decreases from the base end to the tip end. Therefore, the hemispherical convex portion 77 is not limited to a perfect hemisphere in which the length from the base end to the tip end is half the outer diameter at the base end, but includes an approximate hemisphere that is not a perfect hemisphere, a semi-elliptical sphere, and an approximate hemi-elliptical sphere that is not a perfect hemisphere.

To apply a steering reaction force to the steering wheel 2 using the reaction force generating device 10, the control device 6 drives the reaction force applying motor 58 based on various signals indicating driving conditions such as steering torque, steering angle, and vehicle speed. The rotation of the reaction force applying motor 58 is transmitted to the reaction force output shaft 60 via a worm reduction gear 59, and is applied as a steering reaction force to the steering wheel 2 via the power connection part 11 that connects the upper output shaft 73 and the lower shaft 19.

In this example, the position adjustment device 9 and the reaction force generating device 10 as described above are connected at two points: the power connection part 11 and the housing connection part 12.

<Power connection part>
The power connection portion 11 is formed by directly connecting, by spline engagement, a female spline connection portion 21 provided at the front end portion of the lower shaft 19 constituting the position adjustment device 9 and a male spline connection portion 76 provided at the rear end portion of the upper output shaft 73 constituting the reaction force generating device 10. For this reason, the power connection portion 11 has a connection structure with a spline structure.

Specifically, as shown in FIG. 12B, the tip half of the hemispherical protrusion 77 constituting the male spline connection part 76 is inserted into the hemispherical recess 22 constituting the female spline connection part 21, and the multiple female spline teeth 23 provided on the inner surface of the hemispherical recess 22 and the multiple male spline teeth 78 provided on the outer surface of the hemispherical protrusion 77 are alternately arranged in the circumferential direction and meshed with each other to form a spline engagement. In this example, the male spline connection part 76 is covered with a coating layer made of synthetic resin, so the female spline teeth 23 and the male spline teeth 78 are spline engaged via the coating layer.

In addition, in this example, the outer surface of the hemispherical convex portion 77 constituting the male spline connection portion 76 is pressed backward (axially) against the inner surface of the hemispherical concave portion 22 constituting the female spline connection portion 21 via the coating layer.

The power connection part 11 connects the steering shaft 13 (lower shaft 19) and the reaction output shaft 60 (upper output shaft 73) in a manner that allows torque to be transmitted based on the meshing of the female spline teeth 23 and the male spline teeth 78, and the frictional force acting between the inner surface of the hemispherical recess 22 and the outer surface of the hemispherical protrusion 77.

In this example, in the power connection part 11, the outer surface of the hemispherical convex part 77 constituting the male spline connection part 76 is pressed backward against the inner surface of the hemispherical concave part 22 constituting the female spline connection part 21. Therefore, a displacement prevention structure is separately provided to prevent the lower shaft 19 equipped with the female spline connection part 21 from being displaced backward.

In this example, as shown in Fig. 13, a rolling bearing 18a for rotatably supporting the lower shaft 19 with respect to the lower inner column 35 is used to prevent the lower shaft 19 from displacing rearward. Specifically, a locking groove 83 is formed in the outer circumferential surface of the lower shaft 19 at a position adjacent to the front side of the portion where the rolling bearing 18a is fitted, and a bevel-shaped retaining ring 84 having a tapered surface is engaged with the locking groove 83. Furthermore, an annular protrusion 86 that protrudes radially inward is provided on the inner circumferential surface of an inward flange-shaped annular wall portion 85 provided on the inner circumferential surface of the lower inner column 35 at a position adjacent to the rear side of the portion where the rolling bearing 18a is fitted. As a result, the rearward pressing force acting on the lower shaft 19 is supported by the lower inner column 35 via the retaining ring 84 and the rolling bearing 18a.

<Housing connection>
The housing connection portion 12 is formed by connecting a first housing connection portion 41 provided at the front end portion of the lower inner column 35 that constitutes the position adjustment device 9 and a second housing connection portion 63 provided at the rear portion of the gear housing 57 that constitutes the reaction force generating device 10 with a plurality of connection bolts 64 (see FIG. 5 ) (four in the illustrated example). Therefore, the housing connection portion 12 has a bolt connection structure.

Specifically, the first connecting plate 43 constituting the first housing connecting portion 41 and the second connecting plate 68 constituting the second housing connecting portion 63 are overlapped in the front-rear direction without any gap, and the first connecting plate 43 and the second connecting plate 68 are joined by a connecting bolt 64 inserted from the rear to the front through the first through hole 44 provided in the first connecting plate 43 and the second through hole 69 (continuous hole 79) provided in the second connecting plate 68. Furthermore, in this example, when the first connecting plate 43 and the second connecting plate 68 are overlapped in the front-rear direction, the second connecting tube 67 is spigot-fitted into the first connecting tube 42. In this example, the lower side inner column 35 constituting the position adjustment device 9 and the gear housing 57 constituting the reaction force generating device 10 are connected in the front-rear direction by such a housing connecting portion 12. In addition, in this example, such a housing connecting portion 12 is disposed near the power connecting portion 11, i.e., slightly forward of the power connecting portion 11.

In the present example as described above, even if a so-called alignment error occurs in which the central axis of the lower shaft 19 and the central axis of the upper output shaft 73 do not coincide with each other in the power connection portion 11, the alignment error can be absorbed (tolerated).
That is, in this example, the power connection portion 11 is configured by inserting the hemispherical convex portion 77 constituting the male spline connection portion 76 into the hemispherical concave portion 22 constituting the female spline connection portion 21, and spline-engaging the female spline teeth 23 provided on the inner surface of the hemispherical concave portion 22 with the male spline teeth 78 provided on the outer surface of the hemispherical convex portion 77. Therefore, by displacing the hemispherical convex portion 77 inside the hemispherical concave portion 22 while keeping the female spline teeth 23 and the male spline teeth 78 in spline engagement, it is possible to absorb alignment errors. Furthermore, the power connection portion 11 can absorb not only alignment errors that occur during the connection work between the lower shaft 19 and the upper output shaft 73, but also alignment errors that occur when the steering device 1 is used (operated).

Therefore, according to the connection structure of the power connection part 11 of this example, even if an alignment error occurs, torque can be transmitted between the steering shaft 13 and the reaction output shaft 60. In addition, it is possible to prevent abnormal noise and a decrease in transmission efficiency caused by an alignment error. In addition, even if a twist occurs between the hemispherical recess 22 and the hemispherical protrusion 77, torque can be transmitted efficiently between the steering shaft 13 and the reaction output shaft 60.

In addition, because the surface of the male spline connection portion 76 is covered with a synthetic resin coating layer, rattling between the male spline teeth 78 and the female spline teeth 23 can be suppressed. In addition, noise caused by metallic contact between the male spline connection portion 76 and the female spline connection portion 21 can be prevented. When implementing the present invention, the female spline connection portion 21 can be covered with a synthetic resin coating layer instead of the male spline connection portion 76, or both the male spline connection portion 76 and the female spline connection portion 21 can be covered with a synthetic resin coating layer. Furthermore, a cushioning member (damper member) made of an elastic material such as rubber or elastomer can be placed between the female spline connection portion and the male spline connection portion without providing a synthetic resin coating layer.

In addition, the power connection part 11 in this example directly connects the female spline connection part 21 and the male spline connection part 76 without using any coupling or joint member. This allows the steering shaft 13 and the reaction force output shaft 60 to be connected so that torque can be transmitted without increasing the number of parts. In addition, the overall length (axial length) of the power connection part 11 can be shortened. This prevents the longitudinal dimension of the steering unit 3 from becoming large.

Furthermore, in the power connection portion 11 of this example, the female spline connection portion 21 and the male spline connection portion 76 can be connected simply by inserting the hemispherical convex portion 77 constituting the male spline connection portion 76 inside the hemispherical concave portion 22 constituting the female spline connection portion 21. Therefore, the connection work between the female spline connection portion 21 and the male spline connection portion 76 and the connection work between the first housing connection portion 41 and the second housing connection portion 63 can be performed simultaneously. In addition, when connecting the first housing connection portion 41 and the second housing connection portion 63, the second connection tube portion 67 is spigot-fitted into the first connection tube portion 42, so that the diameter direction (radial direction) of the female spline connection portion 21 and the male spline connection portion 76 can be easily positioned.

In the illustrated example, the steering shaft 13 is rotatably supported inside the steering column 14 by three rolling bearings 18a to 18c, and the reaction output shaft 60, which is connected to the steering shaft 13 by the power connection part 11 so that torque can be transmitted, is rotatably supported inside the gear housing 57 by two rolling bearings 82a and 82b. However, of the three rolling bearings 18a to 18c that rotatably support the steering shaft 13, the rolling bearing 18b provided between the outer peripheral surface of the front end of the upper shaft 20 and the inner peripheral surface of the front end of the upper inner column 36 can be omitted if the rolling bearing 18a that functions as a displacement prevention mechanism is provided. In this way, by omitting the rolling bearing 18b, the cost of the steering unit 3 can be reduced.

In addition, in this example, the outer column 34 is fitted to the lower inner column 35 to allow relative displacement in the fore-aft direction, and the upper inner column 36 is fitted to the outer column 34 to allow relative displacement in the fore-aft direction, giving the column body 25 a two-stage telescopic structure. This makes it possible to prevent the axial dimensions of the lower screw shaft 47 and the upper screw shaft 51 from becoming excessively large while ensuring a sufficient amount of telescopic movement over the entire length of the steering column 14.

In addition, the position adjustment device 9 of this example can adjust the longitudinal position of the steering wheel 2 using either the lower telescopic actuator 15 or the upper telescopic actuator 16. Therefore, even if a malfunction such as a breakdown occurs in either the lower telescopic actuator 15 or the upper telescopic actuator 16, the longitudinal position of the steering wheel 2 can be adjusted using the other actuator.

Furthermore, the position adjustment device 9 of this example can drive the lower telescopic actuator 15 and the upper telescopic actuator 16 simultaneously, so the adjustment speed of the fore-aft position of the steering wheel 2 can be improved compared to a position adjustment device equipped with only one actuator.

[Second Example of the Embodiment]
The second embodiment will be described with reference to Figures 15 to 18. In this embodiment, the same components as those in the first embodiment are given the same reference numerals as those in the first embodiment, and detailed descriptions thereof will be omitted.

In this example, the lower shaft 19a is divided into a connecting shaft 88 and a main shaft 89, and the connecting shaft 88 and the main shaft 89 are connected by a shaft coupling 90 to form a coupling structure.

The connection shaft 88 has a female spline connection portion 21 at its front end. As in the first embodiment, the female spline connection portion 21 is spline-engaged to the male spline connection portion 76 at the rear end of the reaction force output shaft 60 (upper output shaft 73) of the reaction force generating device 10 so as to transmit torque. In the illustrated example, the upper output shaft 73 has a constriction portion 118 adjacent to the front side of the male spline connection portion 76, the constriction portion 118 having an outer diameter smaller than the outer diameter of the base end of the male spline connection portion 76.

The connecting shaft 88 has a first shaft-shaped portion 91 with a cylindrical outer circumferential surface at its rear end. The main shaft 89 has a second shaft-shaped portion 92 with a cylindrical outer circumferential surface at its front end. Each of the first shaft-shaped portion 91 and the second shaft-shaped portion 92 can also have a notch or key groove formed in a circumferential portion of the outer circumferential surface to prevent rotation.

The shaft coupling 90 includes a first transmission member 93 connected to the first shaft portion 91 so as not to rotate relative to the first shaft portion 91, a second transmission member 94 connected to the second shaft portion 92 so as not to rotate relative to the second shaft portion 92, and an intermediate member 95 disposed between the first transmission member 93 and the second transmission member 94 to transmit torque between the first transmission member 93 and the second transmission member 94.

The first transmission member 93 has an insertion hole 96a penetrating in the axial direction in the center, and has notches 97a extending in the radial direction at two circumferential positions. The first transmission member 93 also has protrusions 98a protruding in the axial direction at multiple circumferential positions. To connect the first transmission member 93 to the first shaft-shaped portion 91, the first shaft-shaped portion 91 is inserted into the insertion hole 96a, and a screw member (not shown) arranged on a portion of the circumferential direction of the first transmission member 93 is tightened using a tool (not shown). This reduces the circumferential width of the notch 97a and the inner diameter of the insertion hole 96a, thereby connecting the first transmission member 93 to the first shaft-shaped portion 91.

The second transmission member 94 has an insertion hole 96b penetrating in the axial direction in the center, and has notches 97b extending in the radial direction at two circumferential positions. The second transmission member 94 also has protrusions 98b protruding in the axial direction at multiple circumferential positions. To connect the second transmission member 94 to the second shaft-shaped portion 92, the second shaft-shaped portion 92 is inserted into the insertion hole 96b, and a screw member (not shown) arranged on a portion of the second transmission member 94 in the circumferential direction is tightened using a tool (not shown). This reduces the circumferential width of the notch 97b and the inner diameter of the insertion hole 96b, thereby connecting the second transmission member 94 to the second shaft-shaped portion 92.

The intermediate member 95 is made of, for example, an elastic material and is configured in a circular ring shape. The intermediate member 95 has circular ring portions 99a, 99b on both axial sides. The circular ring portion 99a has first engagement holes (not shown) at multiple locations in the circumferential direction into which the protrusions 98a provided on the first transmission member 93 can be inserted. The circular ring portion 99b has second engagement holes (not shown) at multiple locations in the circumferential direction into which the protrusions 98b provided on the second transmission member 94 can be inserted.

In this example, the lower shaft 19a has a connecting structure in which the lower side connecting shaft 88 and the upper side main shaft 89 are connected via a shaft coupling 90, so that alignment errors that occur between the lower shaft 19a and the reaction force output shaft 60 can be absorbed not only by the power connection part 11 but also by the shaft coupling 90.
The other configurations and effects are the same as those of the first embodiment.

[Third Example of the Embodiment]
A third example of the embodiment will be described with reference to Fig. 19. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

The power connection part 11a in this example is configured by spline engagement between the male spline connection part 76a provided at the front end of the lower shaft 19b and the female spline connection part 21a provided at the rear end of the upper output shaft 73a. In other words, the front-to-rear positions of the male spline connection part and the female spline connection part of the power connection part 11a in this example are opposite to those of the power connection part 11 in the first example of the embodiment.

In this example, a hemispherical protrusion 77a is provided at the front end of the lower shaft 19b, and multiple male spline teeth 78a are formed on the outer surface of the hemispherical protrusion 77a. A hemispherical recess 22a is provided at the rear end of the upper output shaft 73a, and multiple female spline teeth 23a are formed on the inner surface of the hemispherical recess 22a. The hemispherical protrusion 77a constituting the male spline connection part 76a is inserted into the hemispherical recess 22a constituting the female spline connection part 21a, and each of the multiple female spline teeth 23a provided on the inner surface of the hemispherical recess 22a is spline-engaged with each of the multiple male spline teeth 78a provided on the outer surface of the hemispherical protrusion 77a. In this example, the lower shaft 19b and the upper output shaft 73a are connected to be able to transmit torque by such a power connection part 11a.

Furthermore, in this example, the male spline teeth 78a constituting the male spline connection portion 76a provided at the front end of the lower shaft 19b and the male spline teeth 100 for telescopic adjustment provided on the outer peripheral surface of the lower shaft 19b in the range from the rear end to the middle portion are continuous in the front-to-rear direction. In other words, the male spline teeth 100 for telescopic adjustment are extended to the front end of the lower shaft 19b. Therefore, the lower shaft 19b is provided with male spline teeth over the entire axial length of the outer peripheral surface.

In the present embodiment as described above, the male spline teeth 100 for telescopic adjustment and the male spline teeth 78a that constitute the male spline connection portion 76a can be machined at the same time. This makes it possible to reduce the number of machining steps and therefore the cost of the steering unit 3.
The other configurations and effects are the same as those of the first embodiment.

[Fourth Example of the Embodiment]
A fourth embodiment will be described with reference to Figures 20 and 21. In this embodiment, the shaft connection structure of the present invention is applied to an electric power steering device. In this embodiment, the same components as those in the first embodiment are given the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

The steering device 1a in this example is a column-assist type electric power steering device. The steering device 1a includes a steering wheel 2, a steering shaft 13a, a steering column 14a, a pair of universal joints 101a, 101b, an intermediate shaft 102, a steering gear unit 103, a pair of tie rods 8, and an electric assist device 104.

The steering wheel 2 is attached to the rear end of the steering shaft 13a, which is rotatably supported inside the steering column 14a. The front end of the steering shaft 13a is inserted inside the housing 105, which is fixed to the front end of the steering column 14a, and is connected to the output shaft 106 via a torsion bar 117.

The rotation of the output shaft 106 is transmitted to the pinion shaft 107 of the steering gear unit 103 via a pair of universal joints 101a, 101b and the intermediate shaft 102. The rotation of the pinion shaft 107 is then converted into linear motion of a rack shaft (not shown), which pushes and pulls a pair of tie rods 8 and imparts a steering angle to the steered wheels.

The electric assist device 104 is intended to reduce the force required for the driver to operate the steering wheel 2, and is equipped with a torque sensor (not shown) arranged around the output shaft 106, an ECU (not shown), and a motor 108 with a reduction gear.

The motor with reduction gear 108 includes a worm reduction gear 109 and an electric motor 110.

The worm reducer 109 includes a worm 111 and a worm wheel 112. The worm 111 is supported at both axial ends by a pair of rolling bearings 113 (only one of which is shown in FIG. 21) so as to be rotatable relative to the housing 105. The worm 111 has worm teeth 114 at its axial middle portion. The worm wheel 112 is fitted onto the output shaft 106 and is supported rotatably relative to the housing 105 by a rolling bearing (not shown). The worm wheel 112 has worm wheel teeth 115 on its outer circumferential surface that mesh with the worm teeth 114.

The electric motor 110 is driven and controlled by the ECU and has a motor output shaft 116.

In this example, the connection structure of the power connection part 11b between the motor output shaft 116 and the worm 111 is devised. That is, a female spline connection part 21b is provided at the tip of the motor output shaft 116, in which a plurality of female spline teeth 23b are formed on the inner surface of the hemispherical recess 22b. Also, a male spline connection part 76b is provided at the base end of the worm 111, in which a plurality of male spline teeth 78b are formed on the outer surface of the hemispherical protrusion 77b. Then, the hemispherical protrusion 77b constituting the male spline connection part 76b is inserted into the hemispherical recess 22b constituting the female spline connection part 21b, and each of the multiple female spline teeth 23b provided on the inner surface of the hemispherical recess 22b and each of the multiple male spline teeth 78b provided on the outer surface of the hemispherical protrusion 77b are spline-engaged. This connects the motor output shaft 116 and the worm 111 in a manner that allows torque transmission. In this example, the worm 111 corresponds to the first shaft described in the claims, and the motor output shaft 116 corresponds to the second shaft described in the claims.

In this example, the motor output shaft 116 and the worm 111 can be connected to transmit torque without increasing the number of parts. In addition, the overall length of the power connection part 11b can be shortened, preventing the reduction gear motor 108 and, ultimately, the steering device 1a from becoming larger. In addition, alignment errors between the motor output shaft 116 and the worm 111 can be absorbed.

In addition, in the past, in order to support the worm so that it can oscillate and be displaced, a pair of axial dampers have been arranged on both axial sides of the rolling bearing that rotatably supports the base end portion of the worm. However, in this example, since the tip end of the motor output shaft 116 and the base end of the worm 111 are connected via the power connection part 11b as described above, the axial damper arranged on the electric motor 110 side can be omitted, and it is sufficient to arrange the resin axial damper 128 only between the flange part 127 provided at the axial middle part of the outer circumferential surface of the worm 111 and the rolling bearing 113. Therefore, according to this example, the reduction geared motor 108 can be made smaller.
The other configurations and effects are the same as those of the first embodiment.

[Modification of the fourth example of the embodiment]
A modified example of the fourth embodiment will be described with reference to Fig. 22. In this example, the shaft connection structure of the present invention is also applied to an electric power steering device, and the connection structure of the power connection part 11c between the motor output shaft 116a and the worm 111a is devised.

In other words, in the power connection part 11c of this example, the positional relationship between the male spline connection part and the female spline connection part provided at the tip end of the motor output shaft 116a and the base end of the worm 111a is reversed from that in the fourth example of the embodiment.

In this example, a male spline connection portion 76c is provided at the tip of the motor output shaft 116a, in which a plurality of male spline teeth 78c are formed on the outer surface of a hemispherical convex portion 77c. A female spline connection portion 21c is provided at the base end of the worm 111a, in which a plurality of female spline teeth 23c are formed on the inner surface of a hemispherical concave portion 22c. The hemispherical convex portion 77c constituting the male spline connection portion 76c is inserted into the hemispherical concave portion 22c constituting the female spline connection portion 21c, and each of the multiple female spline teeth 23c provided on the inner surface of the hemispherical concave portion 22c is spline-engaged with each of the multiple male spline teeth 78c provided on the outer surface of the hemispherical convex portion 77c. This connects the motor output shaft 116a and the worm 111a in a manner that allows torque transmission. In this example, the worm 111a corresponds to the second shaft described in the claims, and the motor output shaft 116a corresponds to the first shaft described in the claims.

In addition, a biasing member 129 is provided around the tip end portion of the worm 111a. This biases the tip end of the worm 111a in a direction approaching the worm wheel 112.

In the above-described embodiment, the center O of the rolling bearing 113 that rotatably supports the base end of the worm 111a can be aligned with the axial position of the spline engagement portion between the male spline teeth 78c and the female spline teeth 23c. Therefore, the worm 111a can be oscillated with the center O of the rolling bearing 113 as a fulcrum. This allows the biasing member 129 provided on the tip side of the worm 111a to function efficiently. Therefore, the biasing member 129 can bias the worm teeth 114 toward the worm wheel teeth 115, and the backlash of the meshing portion between the worm teeth 114 and the worm wheel teeth 115 can be reduced. As a result, the occurrence of teeth rattle noise at the meshing portion between the worm teeth 114 and the worm wheel teeth 115 can be suppressed.

In addition, since the power connection portion 11c is constructed by inserting the hemispherical convex portion 77c into the inside of the hemispherical concave portion 22c, the axial dimension of the power connection portion 11c is prevented from increasing, and the reduction gear motor 108 can be made smaller.
The other configurations and effects are the same as those of the first and fourth embodiments.

[Fifth Example of the Embodiment]
A fifth example of the embodiment will be described with reference to Fig. 23. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

In this example, the outer diameter of the axially intermediate portion of the upper output shaft 73a adjacent to (connected to) the male spline connection portion 76 is smaller than the outer diameter of the male spline connection portion 76 (hemispherical convex portion 77). In other words, the upper output shaft 73a has a constriction 118 with a smaller diameter than the male spline connection portion 76 in a portion adjacent to the front side of the male spline connection portion 76. For this reason, in this example, the rear portion of the upper output shaft 73a is shaped approximately mushroom-like.

In this example as described above, even if an alignment error occurs in which the central axis of the upper output shaft 73a and the central axis of the lower shaft 19 do not coincide as shown in FIG. 23C, the front end face of the lower shaft 19 is unlikely to interfere with the outer peripheral surface of the upper output shaft 73a. This makes it possible to sufficiently absorb the alignment error. Also, in this example, even if the central axis of the upper output shaft 73a and the central axis of the lower shaft 19 do not coincide, it is possible to prevent the intersection position between the central axis of the upper output shaft 73a and the central axis of the lower shaft 19 from shifting.

23B, the tip of male spline connection portion 76 (semispherical convex portion 77) and the bottom of female spline connection portion 21 (semispherical concave portion 22) are not in contact with each other, and a space 130 is provided between the tip of male spline connection portion 76 and the bottom of female spline connection portion 21. For this reason, space 130 can also be used as a grease reservoir.
The other configurations and effects are the same as those of the first embodiment.

[Modification of the fifth example of the embodiment]
A modification of the fifth example of the embodiment will be described with reference to FIG.

In the fifth embodiment, as shown in FIG. 23B, when the male spline connection part 76 (semispherical convex part 77) is inserted inside the female spline connection part 21 (semispherical concave part 22), the base end part 131 (area surrounded by a two-dot chain line in FIG. 23A) of the male spline connection part 76, in which the outer diameter of the male spline teeth 78 is constant, protrudes (exposed) in the axial direction from the female spline connection part 21 for the most part. For this reason, in the fifth embodiment, the base end part 131 of the male spline connection part 76 hardly contributes to torque transmission. Therefore, in this example, as shown in FIG. 24, the part in which the outer diameter of the male spline teeth 78 is constant is omitted from the male spline connection part 76d provided at the rear end of the upper output shaft 73b. In other words, the outer diameter of the male spline teeth 78d constituting the male spline connection part 76d changes in a curved manner over the entire axial length.

In this example as described above, the axial dimension of the male spline connection portion 76d can be made shorter than in the structure of the fifth example of the embodiment. Note that the structure of this example can be applied not only to the connection portion between the steering shaft and the reaction force output shaft, but also to the connection portion between the worm and the motor output shaft, for example.
The other configurations and effects are the same as those of the first and fifth embodiments.

[Sixth Example of the Embodiment]
A sixth example of the embodiment will be described with reference to Fig. 25. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

In this example, the position adjustment device 9a that constitutes the steering unit 3a is a manual position adjustment device, rather than an electric position adjustment device as in the structure of the first example of the embodiment. The position adjustment device 9a is capable of adjusting the front-rear and up-down positions of the steering wheel 2 (see FIG. 1), and supports the steering shaft 120 rotatably inside the steering column 119 via a pair of rolling bearings 18d, 18e.

To allow the adjustment of the fore-aft position of the steering wheel 2, the steering column 119 is configured so that the outer column 121 arranged on the lower side is fitted to the inner column 122 arranged on the upper side to allow relative displacement in the fore-aft direction, making the overall length extendable. The steering shaft 120 is configured so that the outer shaft 124 arranged on the upper side is fitted to the inner shaft 123 arranged on the lower side to allow torque transmission and relative displacement in the fore-aft direction, making the overall length extendable. In this example, a rolling bearing 18d is arranged between the outer column 121 and the inner shaft 123, and a rolling bearing 18e is arranged between the inner column 122 and the outer shaft 124.

Furthermore, in order to enable adjustment of the vertical position of the steering wheel 2, the front end portion of the outer column 121, etc., is pivoted relative to the vehicle body by a tilt axis (not shown) arranged in the width direction, and the rear portion of the outer column 121 is supported relative to a support bracket 125 fixed to the vehicle body so as to allow vertical displacement.
To adjust the position of the steering wheel 2, an adjustment lever (not shown) is operated to reduce the tightening force of the support bracket 125 on the outer column 121, and the position of the steering wheel 2 is manually adjusted.

In this example, the reaction force applying motor 58a constituting the reaction force generating device 10a is directly fixed to the front end of the outer column 121 constituting the position adjustment device 9a having the above-mentioned configuration. The male spline connection portion 76 provided at the tip end (rear end) of the motor output shaft 126 of the reaction force applying motor 58a is directly connected to the female spline connection portion 21 provided at the front end of the inner shaft 123 so as to be capable of transmitting torque by spline engagement. Specifically, the tip half of the hemispherical convex portion 77 constituting the male spline connection portion 76 is inserted into the hemispherical concave portion 22 constituting the female spline connection portion 21, and each of the multiple female spline teeth 23 provided on the inner surface of the hemispherical concave portion 22 and each of the multiple male spline teeth 78 provided on the outer surface of the hemispherical convex portion 77 are alternately arranged in the circumferential direction and meshed with each other to perform spline engagement. In this way, in this example, the steering unit 3a is configured as a direct drive type. In this example, the motor output shaft 126 of the reaction force applying motor 58a corresponds to the first shaft described in the claims, and the inner shaft 123 corresponds to the second shaft described in the claims.

According to the steering unit 3a of this example as described above, it is possible to omit a number of components such as the worm reduction gear compared to the structure of the first example of the embodiment, which leads to a reduction in the number of parts, thereby achieving cost reduction and weight reduction.
The other configurations and effects are the same as those of the first embodiment.

[Seventh Example of the Embodiment]
The seventh example of the embodiment will be described with reference to Figures 26 to 28. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as in the first example of the embodiment, and detailed descriptions thereof will be omitted.

In this example, the structure of the power connection portion 11d has been changed from the structures in the first to sixth examples of the embodiment. Specifically, the structure of the male spline connection portion 76e provided at the rear end of the upper output shaft 73c and the structure of the female spline connection portion 21d provided at the front end of the lower shaft 19c have been changed from the structures in the first to sixth examples of the embodiment.

As shown in FIG. 26, the male spline connection portion 76e has a spherical male spline structure in which a plurality of male spline teeth 78e are formed on the outer surface of a spherical frustum-shaped protrusion 132 provided at the rear end of the upper output shaft 73. The spherical frustum-shaped protrusion 132 has a shape like a semi-spherical protrusion with a flat tip, and the outer diameter curvedly decreases from the base end to the tip. The spherical frustum-shaped protrusion is a protrusion having a spherical frustum-shaped outer surface formed by cutting a sphere with two parallel planes, as shown in FIG. 29(B). In other words, the spherical frustum-shaped outer surface can be called a belt-shaped convex curved surface. The spherical frustum-shaped protrusion has a cross-sectional shape that is approximately an isosceles trapezoid. In this example, a partially spherical convex curved portion 133 is provided at the tip of the spherical frustum-shaped protrusion 132, but the convex curved portion 133 can be omitted. The male spline teeth 78e are arranged at equal intervals in the circumferential direction and are formed radially on the outer surface of the spherical frustum-shaped protrusion 132. In this example, the male spline connection portion 76e is covered with a coating layer made of a synthetic resin with a low coefficient of friction, such as polyamide resin.

As shown in FIG. 27, the female spline connection portion 21d has a spherical female spline structure in which multiple female spline teeth 23d are formed on the inner surface of a spherical recess 134 that opens into the front end face of the lower shaft 19c. The spherical recess 134 has a shape similar to a semi-spherical recess with a flat bottom, and the inner diameter curves downward from the opening toward the back. In this example, a partially spherical concave curved portion 135 is provided at the bottom of the spherical recess 134, but the concave curved portion 135 can be omitted. The multiple female spline teeth 23d are arranged at equal intervals in the circumferential direction and are formed radially on the inner surface of the spherical recess 134.

In this example, as shown in FIG. 28A, the entirety of the frustum-shaped protrusion 132 constituting the male spline connection part 76e is inserted into the frustum-shaped recess 134 constituting the female spline connection part 21d, and each of the multiple female spline teeth 23d provided on the inner surface of the frustum-shaped recess 134 is spline-engaged with each of the multiple male spline teeth 78e provided on the outer surface of the frustum-shaped protrusion 132. In this example, since the male spline connection part 76e is covered with a synthetic resin coating layer, the female spline teeth 23d and the male spline teeth 78e are spline-engaged through the coating layer. Furthermore, the convex curved part 133 provided at the tip of the frustum-shaped protrusion 132 is inserted inside the concave curved part 135 provided at the bottom of the frustum-shaped recess 134.

In this example, as shown in FIG. 28B, if an alignment error occurs in which the central axis of the lower shaft 19c and the central axis of the upper output shaft 73c do not coincide, the alignment error can be absorbed by displacing the spherical frustum-shaped convex portion 132 inside the spherical frustum-shaped concave portion 134 while keeping the female spline teeth 23d and the male spline teeth 78e in spline engagement.

In the above-described embodiment, the axial dimension of the power connection portion 11d composed of the male spline connection portion 76e and the female spline connection portion 21d can be shortened. Therefore, the overall size of the device can be reduced. In addition, in the embodiment, the male spline teeth 78e are formed on the outer surface of the frustum-shaped convex portion 132, and the female spline teeth 23d are formed on the inner surface of the frustum-shaped concave portion 134. Therefore, the meshing length of the spline engagement portion can be shortened compared to the structure of the first embodiment, in which the male spline teeth are formed on the outer surface of the hemispherical convex portion, and the female spline teeth are formed on the inner surface of the hemispherical concave portion. Therefore, the generation of swell noise, which is likely to occur when the meshing length is long, can be effectively prevented. In addition, the meshing length can be shortened, and therefore the absorption of alignment can be increased. In other words, the inclination of the upper output shaft 73c and the lower shaft 19c can be increased.
The other configurations and effects are the same as those of the first embodiment.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of each example of the embodiment can be combined as appropriate as long as no contradiction occurs.

When implementing the present invention, the respective shapes of the partial spherical convex portion and the partial spherical concave portion, and the respective numbers and shapes of the male spline teeth and female spline teeth are not limited to the structures of the examples of the embodiments, so long as the partial spherical convex portion can be displaced inside the partial spherical concave portion while keeping the female spline teeth and the male spline teeth in spline engagement. In addition, when implementing the present invention, the male spline engagement portion and the female spline engagement portion can also be reversed in structure to that of the examples of the embodiments.

In addition, when implementing the present invention, the types of the first shaft and second shaft that can be connected by the shaft connection structure of the present invention are not limited to the shafts described in each of the embodiments. In addition, the motor with a reducer of the present invention is not limited to the motor with a reducer that constitutes the electric power steering device described in the fourth embodiment and the modified example of the embodiment, but can also be applied to a motor with a reducer such as a reaction force generating device that constitutes a steer-by-wire type steering device, or a motor with a reducer provided in other devices.

In addition, when implementing the present invention, the position adjustment device to be combined with the reaction force generating device is not limited to an electrically operated position adjustment device as shown in the first embodiment, but a manual position adjustment device as shown in the sixth embodiment can also be used.

REFERENCE SIGNS LIST 1, 1a Steering device 2 Steering wheel 3, 3a Steering unit 4 Steering wheel 5 Steering unit 6 Control device 7 Steering actuator 8 Tie rod 9, 9a Position adjustment device 10, 10a Reaction force generating device 11, 11a, 11b, 11c, 11d Power connection portion 12 Housing connection portion 13, 13a Steering shaft 14, 14a Steering column 15 Lower telescopic actuator 16 Upper telescopic actuator 17 Tilt actuator 18a to 18e Rolling bearing 19, 19a, 19b, 19c Lower shaft 20 Upper shaft 21, 21a, 21b, 21c, 21d Female spline connection portion 22, 22a, 22b, 22c Hemispherical recess [0033] 23, 23a, 23b, 23c, 23d Female spline teeth 24 Bracket 25 Column body 26 Fixed bracket 27 Displacement bracket 28 Fixed plate portion 29 Fixed side support frame 30 Mounting bolt 31 Displacement plate portion 32 Displacement side support frame 33 Support wall portion 34 Outer column 35 Lower side inner column 36 Upper side inner column 37 Slit 38 Screw hole 39 Screw plug 40 Cylindrical portion 41 First housing connection portion 42 First connection cylinder portion 43 First connection plate portion 44 First through hole 45 Lower side telescopic motor 46 Lower side feed screw device 47 Lower side screw shaft 48 Lower side nut 49 Upper side telescopic motor 50 Upper side feed screw device 51 Upper side screw shaft 52 Upper side nut 53 Connector member 54 Pivot bolt 55 Tilt motor 56 Tilt feed screw device 57 Gear housing 58, 58a Reaction force applying motor 59 Worm reducer 60 Reaction force output shaft 61 Lower housing 62 Upper housing 63 Second housing connection portion 64 Connection bolt 65 Worm accommodating portion 66 Worm wheel accommodating portion 67 Second connection cylinder portion 68 Second connection plate portion 69 Second through hole 70 Worm 71 Worm wheel 72 Lower output shaft 73, 73a, 73b, 73c Upper output shaft 74 Torsion bar 75 Torque sensor 76, 76a, 76b, 76c, 76d, 76e Male spline connection portion 77, 77a, 77b, 77c Hemispherical convex portion [0033] 78, 78a, 78b, 78c, 78d, 78e Male spline teeth 79 Continuous hole 80 Linear guide 81 Bolt 82a, 82b Rolling bearing 83 Locking groove 84 Retaining ring 85 Annular wall portion 86 Annular protrusion portion 87 Bolt 88 Connection shaft 89 Main shaft 90 Shaft coupling 91 First shaft-shaped portion 92 Second shaft-shaped portion 93 First transmission member 94 Second transmission member 95 Intermediate member 96a, 96b Insertion hole 97a, 97b Notch 98a, 98b Protrusion portion 99a, 99b Circular ring portion 100 Male spline teeth 101a, 101b Universal joint 102 Intermediate shaft 103 Steering gear unit 104 Electrically-assisted device 105 Housing Reference Signs List 106 Output shaft 107 Pinion shaft 108 Motor with reducer 109 Worm reducer 110 Electric motor 111, 111a Worm 112 Worm wheel 113 Rolling bearing 114 Worm teeth 115 Worm wheel teeth 116, 116a Motor output shaft 117 Torsion bar 118 Narrowed portion 119 Steering column 120 Steering shaft 121 Outer column 122 Inner column 123 Inner shaft 124 Outer shaft 125 Support bracket 126 Motor output shaft 127 Flange portion 128 Axial damper 129 Pressing member 130 Space 131 Base end portion 132 Frustrated spherical convex portion 133 Convex curved portion 134 Frustrated spherical concave portion 135 Concave section

Claims (10)

A male spline connection portion provided at an end of the first shaft, the male spline connection portion having a plurality of male spline teeth formed on an outer surface of a partial spherical convex portion;
a female spline connection portion provided at an end of the second shaft, the female spline connection portion having a plurality of female spline teeth formed on an inner surface of a partially spherical recess;
the partial spherical recess is open only to one end surface of the second shaft,
the partial spherical recess has an inner diameter that curves downward from the opening toward the innermost portion, and the female spline teeth are formed on the inner surface of the partial spherical recess over the entire axial length thereof,
the partial spherical convex portion has an outer diameter that curves downward from a base end to a tip end, and the male spline teeth are formed on the entire outer surface of the partial spherical convex portion in the axial direction,
the partial spherical protrusion is inserted into the inside of the partial spherical recess, and each of the male spline teeth is spline-engaged with each of the female spline teeth, thereby connecting the first shaft and the second shaft in a torque-transmittable manner.
Shaft connection structure.
the male spline connection portion has a plurality of male spline teeth formed on an outer surface of a semi-spherical convex portion,
The female spline connection portion has a plurality of female spline teeth formed on an inner surface of a semispherical recess.
2. A shaft connection structure according to claim 1. the male spline connection portion has a plurality of male spline teeth formed on an outer surface of a spherical frustum-shaped convex portion,
The female spline connection portion has a plurality of female spline teeth formed on an inner surface of a spherical frustum-shaped recess.
2. A shaft connection structure according to claim 1. A shaft connection structure according to any one of claims 1 to 3, in which at least one of the male spline connection portion and the female spline connection portion is covered with a coating layer made of synthetic resin. A shaft connection structure according to any one of claims 1 to 4, in which the outer diameter of the portion of the first shaft adjacent to the male spline connection portion is smaller than the outer diameter of the male spline connection portion. A worm reducer having a worm and a worm wheel;
an electric motor having a motor output shaft;
The end of the worm and the end of the motor output shaft are connected to each other so as to be capable of transmitting torque by the shaft connection structure according to any one of claims 1 to 5.
Motor with reduction gear. The male spline connection portion is provided at an end of the motor output shaft,
The female spline connection is provided at an end of the worm.
A motor with a reducer according to claim 6. An electric power steering device equipped with a motor with a reduction gear as described in claim 6 or claim 7. A steering shaft;
a reaction force generating device having a reaction force output shaft for applying a steering reaction force to the steering wheel,
The end of the steering shaft and the end of the reaction force output shaft are connected to each other in a torque-transmitting manner by the shaft connection structure according to any one of claims 1 to 5.
Steer-by-wire steering unit. A steering shaft;
a reaction force application motor having a motor output shaft for applying a steering reaction force to the steering wheel,
The end of the steering shaft and the end of the motor output shaft are connected to each other in a torque-transmitting manner by the shaft connection structure according to any one of claims 1 to 5.
Steer-by-wire steering unit.

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