# Patent

## Title
Electric steering wheel position adjustment apparatus

## Abstract

The electric steering wheel position adjustment apparatus of the present invention comprises: a non-expandable steering shaft 2b; a non-expandable steering column 5b; a column holder 31 that supports the steering column 5b so as to be able to move in the axial direction; a pair of left and right tilt shafts 33 that support the column holder 31 so as to be able to pivotally move around the center axis thereof; and an expandable intermediate shaft 28 that is connected to the steering shaft 2b by way of a universal joint 27b; and a tilt shafts 33 that are arranged so that the center axis thereof is orthogonal to the center axis of the steering shaft 2b. The center axis OC of the pair of left and right tilt shafts 33 is located in a range between the position OF of the center of displacement of the front-end section and the position OB of the center of displacement of the rear-end section of the universal joint 27b.

## Background
TECHNICAL FIELD
The present invention relates to an electric steering wheel position adjustment apparatus, and more specifically to an apparatus that has an electric motor as a drive source and that adjusts the forward-backward position and up-down position of a steering wheel.
BACKGROUND ART
Electric steering wheel position adjustment apparatuses having various kinds of construction are known, and some are already being used as the steering apparatuses of automobiles. FIG. 19 illustrates a first example of conventional construction that was disclosed in JP 2010-116042 (A). The steering shaft 2 to which the steering wheel 1 is fastened has a cylindrical outer shaft, and a circular rod shaped inner shaft 4 that is inserted inside the outer shaft 3 so as to be able to move back-and-forth in the axial direction, and so as to be able to transmit torque. More specifically, there is a spline fit between the middle section to the front-end section of the inner circumferential surface of the outer shaft 3 and the outer circumferential surface of the rear-end section of the inner shaft 4. The steering wheel 1 is fastened to the rear-end section of the outer shaft 3.
The steering shaft 2 is inserted inside a cylindrical shaped steering column 5, and is supported so as to be able to freely rotate. The steering column 5 has a cylindrical outer column 6 that is supported by the vehicle body, and a cylindrical inner column 7 that is inserted inside the outer column 6 so as to be able to move back-and-forth in the axial direction. The portion near the rear end of the middle section of the outer shaft 3 is supported on the radially inside of the rear-end section of the inner column 7 so as to be prevented from displacing in the axial direction, and so as to be able to rotate freely. Moreover, the portion near the front end of the middle section of the inner shaft 4 is supported on the radially inside of the front-end section of the outer column 6 so as to be prevented from displacement in the axial direction, and so as to be able to rotate freely. With this construction, the steering shaft 2 is supported on the inside of the steering column 5 so as to be able to rotate freely, and the outer shaft 3 and inner column 7 are capable of relative movement in the forward-backward direction with respect to the inner shaft 4 and outer column 6.
The apparatus of the first example of conventional construction, as an electric actuator in order to be able to adjust the forward-backward position of the steering wheel 1, has: a gear housing 8 that is fastened to the bottom surface of the outer column 6; a feed nut 9 that is supported on the inside of the gear housing 8 so as to be prevented from displacement in the axial direction, and so as to be able to only rotate; a push-pull arm 10 that is fastened to a portion of the rear-end section of the inner column 7 that protrudes further toward the rear than the outer column 6; a push-pull rod 11 having a male screw section 12 provided on the front half thereof that screws into the feed nut 9, and the rear-end section thereof being linked with the push-pull arm 10; and an electric motor (omitted in the figure) that is connected to the feed nut 9 by way of a worm reducer 13, and that rotates and drives the feed nut 9.
When adjusting the forward-backward position of the steering wheel 1, the feed nut 9 is rotated, which causes the push-pull rod 11 to move in the axial direction. Due to this displacement, the inner column 7, by way of the push-pull arm 10, moves in the same direction as the push-pull rod 11, and by causing the outer shaft 3 that is supported on the inside of the inner column 7 to move in the forward-backward direction together with the inner column, the forward-backward position of the steering wheel 1 is adjusted.
In the electric steering wheel position adjustment apparatus of this first example of conventional construction, there is a possibility that the driver that operates the steering wheel 1 will experience an unpleasant or uncomfortable feeling due to a small space that exist in the area of fit between the rear-end section of the outer column 6 and the front-end section of the inner column 7. In other words, in the electric steering wheel position adjustment apparatus, differing from a manual apparatus, even in the state in which the adjusted position of the steering wheel 1 is maintained, the diameter of the rear-end section of the outer column 6 is not reduced, and a small space remains in the area of fit. Due to this small space, there is a possibility that the inner column 7 that supports the outer shaft 3 to which the steering wheel 1 is fastened will be loose with respect to the outer column 6 that is supported by the vehicle body. Due to this loose fit, the feeling of support rigidity of the steering wheel 1 will decrease, and there is a possibility that the driver that operates the steering wheel 1 will experience an unpleasant feeling. Moreover, this looseness causes the resonant frequency of the members of the electric steering wheel position adjustment apparatus that constitutes the steering column apparatus that includes the steering shaft 2 and steering column 5 to decrease, and when there is small vibration of the vehicle body when traveling over a bad road or the like, there is a possibility that unpleasant noise or vibration will occur in this steering column apparatus.
FIG. 20 and FIG. 21 illustrate a second example of conventional construction that is disclosed in JP 2006-297989 (A). In this second example of conventional construction as well, as in the first example of conventional construction, the steering shaft 2a is supported on the inside of the steering column 5a so as to be able to rotate freely, and the outer shaft 3a and inner column 7a are able move in the forward-backward direction relative to the inner shaft 4a and outer column 6a. 
In this second example of conventional construction, by using a linear motion ultrasonic motor 15 that is supported by the bottom-end section of an installation bracket 14 as an actuator in order to be able to adjust the forward-backward position of the steering wheel 1, it is possible for the inner column 7a to move in the axial direction with respect to the outer column 6a. More specifically, a moving piece 16 of the linear motion ultrasonic motor 15 and inner column 7a are linked by a transmission member 17, and by transmitting the movement of the moving piece 16 to the inner column 7a, it is possible to move the inner column 7a in the forward-backward direction. The base-end section of the transmission member 17 is fastened by screws to the inner column 7a, and the tip-end section of the transmission member 17 is linked to the moving piece 16 by way of a spherical joint 18. The spherical joint 18 has: an engaging concave section 19 that is formed in the moving piece 16; a spacer 20 that fits with and is supported by the engaging concave section 19, and that has an inner circumferential surface that is a spherical concave surface; and a spherical surface engaging section 21 that engages with the inner circumferential surface of the spacer 20.
When adjusting the forward-backward position of the steering wheel 1, the linear motion ultrasonic motor 15 causes the moving piece 16 to move in the axial direction of the steering column 5a. This displacement, by way of the transmission member 17, causes the inner column 7a to move in the same direction as the moving piece 16, which causes the outer shaft 3a that is supported on the inside of the inner column 7a to move in the forward-backward direction together with the inner column 7a. As a result, as illustrated by the two-dot chain line in FIG. 20, it becomes possible to adjust the forward-backward position of the steering wheel 1.
In the case of the construction of this second example of conventional technology, there is a problem in that due to the construction of the engagement area between the moving piece 16 and the transmission member 17, the manufacturing cost for maintaining smooth operation increases. In other words, in order to smoothly perform adjustment of the forward-backward position of the steering wheel 1 without any looseness, it is necessary to properly regulate the fitting strength at the engagement area between the spherical engaging section 21 of the transmission member 17 and the spacer 20. When the fitting strength is to low, a positive gap occurs in this engagement area, and looseness occurs between the spherical engaging section 21 and the spacer 20, which easily causes rattling of the steering wheel 1 in the forward-backward direction. On the other hand, when the fitting strength is too high, pivotal displacement of the spacer 20 with respect to the spherical engaging section 21 cannot be performed smoothly.
In the construction of this second example of conventional technology, the amount of movement in the forward-backward direction of the moving piece 16 is large, and unless there is a good degree of parallel accuracy between the movement direction of this moving piece 16 and the movement direction of the inner column 7a when performing forward-backward position adjustment of the steering wheel 1, as the forward-backward position of the steering wheel 1 is adjusted, the transmission member 17 will move in the axial direction of the transmission member relative to the moving piece 16. This relative displacement causes rubbing in the axial direction of the transmission member 17 between the outer circumferential surface of the spacer 20 and the inner circumferential surface of the engaging concave section 19. In this case, when the fitting strength is too high, and pivotal displacement of the spacer 20 with respect to the spherical engaging section 21 is not performed smoothly, there will be strong rubbing between the outer circumferential surface of the spacer 20 and the inner circumferential surface of the engaging concave section 19, and there is a possibility that noise or vibration will occur, causing the passengers in the automobile to experience an uncomfortable feeling. Particularly, in this state, the surface that allows relative displacement in the axial direction of the transmission member 17 between the transmission member 17 and the moving piece 16 is limited to only one location between the outer circumferential surface of the spacer 20 and the inner circumferential surface of the engaging concave section 19, so the rubbing length easily becomes long, which makes it even easier for noise and vibration to occur.
Performing high precision processing of the inner circumferential surface of the spacer 20, which is a spherical concave surface, and the outer circumferential surface of the spherical engaging section 21, which is a spherical convex section, in order to prevent the occurrence of noise and vibration is connected to higher costs. Moreover, when manufacturing the spherical engaging section 21 with high precision, it is not possible to avoid the outer diameter of the transmission member 17 becoming small on the base-end section of the spherical engaging section 21. It is easy for large stresses to occur in the neck section of this transmission member 17 during adjustment of the forward-backward position of the steering wheel 1, and so such construction as this is not advantageous from the aspect of maintaining sufficient durability when used over a long period of time.
As construction for preventing the occurrence of noise and vibration in the portion of the steering column apparatus, JP 5,076,908 (B2), for example, discloses a mechanism as illustrated in FIG. 22 in which support holes 22 are provided in part in the axial direction of the outer column 6b, and adjustment screws 24 that are screwed into female threads 23 that are formed in the support holes 22 press synthetic resin pads 26 that come in contact with the outer circumferential surface of the inner column 7b by way of disc springs 25, which prevents looseness of the portion that constitutes the steering column apparatus. However, in this mechanism, when the force by which the pads 26 press against the outer circumferential surface of the inner column 7b is made large enough to be able to prevent looseness, the drive load on the electric motor increases, and there is a problem in that the operation noise becomes large.
RELATED LITERATURE
Patent Literature


    [Patent Literature 1] JP 2010-116042 (A)
    [Patent Literature 2] JP 2006-297989 (A)
    [Patent Literature 3] JP 5,076,908 (B2)
    [Patent Literature 4] JP H09-323658 (A)
    [Patent Literature 5] JP H10-119793 (A)
    [Patent Literature 6] JP 2005-255040 (A)
    [Patent Literature 7] JP 2009-006743 (A)
    [Patent Literature 8] DE 10251764 (A1)


SUMMARY OF INVENTION
Problem to be Solved by Invention
The object of the present invention is to provide at low cost construction of an electric steering wheel position adjustment apparatus that improves the rigidity of the portion that constitutes the steering column apparatus, so that the driver operating the steering wheel does not experience an unpleasant feeling, and that is capable of performing position adjustment of the steering wheel stably and smoothly.
Means for Solving Problems
The electric steering wheel position adjustment apparatus of the present invention has: a steering shaft, a steering column, a column holder, a pair of left and right tilt shafts, an intermediate shaft, an electric actuator for forward-backward position adjustment, and an electric actuator for up-down position adjustment. Particularly, in the present invention, the steering shaft that fixes and supports a steering wheel on the rear-end section thereof, and the steering column that supports the steering shaft so as to be able to rotate freely on the inside thereof, both have non-expandable construction in which at least in the normal state, the overall length does not expand or contract.
Moreover, the column holder, by way of the pair of left and right tilt shafts, is supported by a vehicle-side bracket that is supported by a portion that is fastened to a vehicle body, and that supports the steering column so as to be able to move in the axial direction. The pair of left and right tilt shafts are concentric with each other, are arranged so as to have a center axis that is orthogonal to the center axis of the steering shaft, and support the tip-end section of the column holder so as to be able to pivotally move with respect to the vehicle-side bracket.
The intermediate shaft is arranged between the front-end section of the steering shaft and an input shaft of a steering gear unit, and transmits the rotation of the steering shaft to the input shaft of the steering gear unit, and comprises expandable construction such that the overall length is able to expand or contract. The universal joint connects the front-end section of the steering shaft to the rear-end section of the intermediate shaft.
The electric actuator for forward-backward position adjustment has a forward-backward electric drive motor as the drive source, and causes the steering column to move in the axial direction with respect to the column holder. On the other hand, the electric actuator for up-down position adjustment has an up-down electric drive motor as the drive source, and causes the column holder to pivotally move in the up-down direction with the tilt shaft as the pivot center.
In the electric steering wheel position adjustment apparatus of the present invention having this kind of construction performs adjustment of the forward-backward position of the steering wheel by causing the intermediate shaft to expand or contract, which causes the steering column to move in the axial direction and causes the steering shaft to move in the forward-backward direction.
Preferably, the apparatus of the present invention is constructed so that when the position of the center of displacement of the universal joint when the steering wheel is displaced to the front-end position of the adjustable range is taken to be the position of the center of displacement of the front-end side, and the position of the center of displacement of the universal joint when the steering wheel is displaced to the rear-end position of the adjustable range is taken to be the position of the center of displacement of the rear-end side, the center axis of the pair of left and right tilt shafts is located within a range between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side.
Furthermore, the apparatus of the present invention is constructed such that when the distance between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side is taken to be L, the center axis of the pair of left and right tilt shafts is located within a range of length L/5 centered around the center position between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side.
Preferably, in the apparatus of the present invention, the electric actuator for forward-backward position adjustment and the electric actuator for up-down position adjustment are fastened on the bottom side of the column holder and mechanisms that push the steering column downward are provided in at least two locations separated in the forward-backward direction on the top side of the column holder.
Furthermore, preferably, the mechanisms that push the steering column downward each have: a support hole that is formed so as to pass through between the inner circumferential surface and outer circumferential surface of the column holder; and a sliding plate, an elastic member and a cover that are assembled inside the support hole in order from the inside in the radial direction of the column holder, and the elastic member is elastically compressed between the sliding plate and the cover, and the sliding plate pushes the outer circumferential surface of the steering column.
In this case, it is particularly preferred that the arrangement spacing in the axial direction of the mechanisms that push the steering column downward be essentially equal to the maximum range of movement in the axial direction of the steering column.
As the electric actuator for forward-backward position adjustment, it is possible to employ construction that has: a forward-backward feed screw rod that is arranged parallel to the steering column and is rotated and driven by the forward-backward electric drive motor; a moving piece that is screwed onto the forward-backward feed screw rod and that moves in the forward-backward direction according to the rotation of the forward-backward feed screw rod; and a transmission member that has a tip-end section joined to the moving piece and a base-end section joined to the steering column and that transmits the movement of the moving piece to the steering column.
In the electric actuator for forward-backward position adjustment having this kind of construction, preferably an engaging concave section is provided in the moving piece; the tip-end section of the transmission member engages with the engaging concave section of the moving piece by way of a spacer; the engaging concave section of the moving piece has an inner circumferential surface that is a cylindrical concave surface having an inner diameter that does not change in the axial direction of the transmission member; the tip-end section of the transmission member has an outer circumferential surface that is a cylindrical convex surface having an outer diameter that does not change in the axial direction of the transmission member; and the spacer has an outer circumferential surface that is a cylindrical convex surface having an outer diameter that does not change in the axial direction of the transmission member and an inner circumferential surface that is a cylindrical concave surface having an inner diameter that does not change in the axial direction of the transmission member.
Moreover, preferably, the steering column has a middle cylindrical section that is provided in the middle section in the axial direction of the steering column and that has an outer diameter that does not change in the axial direction, and reduced-diameter sections that are provided on both end sides in the axial direction of the middle cylindrical section and have outer diameters that are smaller than the outer diameter of the middle cylindrical section.
In this case, preferably the base-end section of the transmission member is joined and fastened to the middle cylindrical section, and the mechanisms that push the middle cylindrical section of the steering column toward the transmission member are provided at two locations in the axial direction of a portion on the opposite side in the radial direction of the column holder from the transmission member. The above mechanisms are provided so as not to become separated from the middle cylindrical section regardless of displacement in the axial direction of the steering column with respect to the support section.
Effect of the Invention
With the present invention, an electric steering wheel position adjustment apparatus is provided that improves the support rigidity of the steering column and makes it possible to perform position adjustment of the steering wheel smoothly without giving an uncomfortable or unpleasant feeling to occupants including a driver that operates the steering wheel. More specifically, the steering shaft and steering column both have integrated non-expandable construction that in at least the normal state do not allow expansion or contraction of the overall length thereof, so the rigidity of these members is maintained.
In the present invention, a pair of tilt shafts and the steering shaft are arranged such that the respective center axes are orthogonal to each other, so it is possible to perform position adjustment of the steering wheel smoothly. In other words, with the electric steering wheel position adjustment apparatus of the present invention, the steering column has non-expandable construction, so when adjusting the up-down position of the steering wheel, the column holder is pivotally displaced centered around the tilt shafts, and even when the center of displacement of the universal joint that connects the steering shaft and the intermediate shaft is pivotally displaced centered around the tilt shafts, it is possible to keep the amount of expansion or contraction of the intermediate shaft small, so it is possible to suppress causes, such as friction resistance due to expansion or contraction of the intermediate shaft, that hinder smooth operation of the up-down position adjustment of the steering wheel.
Particularly, in the present invention, the position of the center axis of the tilt shaft is regulated by the relationship of the position of the center of displacement of the front side and the position of the center of displacement of the rear side of the universal joint, so when adjusting the up-down position with the steering wheel moved to the front-end position, it is possible to keep the amount of expansion or contraction of the intermediate shaft small and to smoothly perform up-down position adjustment of the steering wheel in this state even when the center of displacement of the universal joint is pivotally displaced centered around the tilt shafts. Moreover, during up-down position adjustment when the steering wheel has been moved to the rear-end position, the load on the electric actuator for up-down position adjustment due to the portion that includes the universal joint is suppressed, so it is possible to make the electric steering wheel position adjustment apparatus more compact and lightweight.
Furthermore, mechanisms that push the steering column downward are provided at two or more locations at the front and rear of the column holder, and the mechanisms elastically push the steering column toward the inner circumferential surface of the column holder, so looseness between the steering column and the column holder is suppressed, and it is possible to increase the rigidity of the area of fit of these members.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical cross-sectional side view illustrating a first example of an embodiment of the present invention.
FIG. 2 is an enlarged view of the right half in FIG. 1.
FIG. 3 is an enlarged view of part A in FIG. 2.
FIG. 4 is an enlarged view of part B in FIG. 2.
FIG. 5 is an enlarged view of part C in FIG. 2.
FIG. 6 is a perspective view illustrating the first example as seen from above in the front.
FIG. 7 is an enlarged view of the right half in FIG. 6.
FIG. 8 is a perspective view that illustrates the first example as seen from above on the opposite side from FIG. 7.
FIG. 9 is a perspective view that illustrates the right half in FIG. 6 as seen from below.
FIG. 10 is a partial cross-sectional drawing that illustrates the first example as seen from the right in FIG. 1 and FIG. 2.
FIG. 11 is a partial cross-sectional drawing that illustrates the first example as seen from the left in FIG. 1.
FIG. 12 is a top view illustrating the first example as seen from above in FIG. 2.
FIG. 13 is a bottom view illustrating the first example as seen from below in FIG. 2.
FIG. 14 is an enlarged cross-sectional drawing of section D-D in FIG. 2.
FIG. 15 is an enlarged cross-sectional drawing of section E-E in FIG. 2.
FIG. 16 is a partial enlarged cross-sectional drawing of the support section of both the front and rear ends of a screw rod for forward-backward position adjustment as seen from the same direction as in FIG. 1 and FIG. 2.
FIG. 17 is a partial enlarged cross-sectional drawing of the support section of both the top and bottom ends of a screw rod for up-down position adjustment as seen from the same direction as in FIG. 1 and FIG. 2.
FIG. 18 is a schematic drawing for explaining the change of the amount of expansion and contraction of the intermediate shaft when adjusting the up-down position of the steering wheel according to the forward-backward position of the steering wheel.
FIG. 19 is a partial vertical cross-sectional side view illustrating a first example of conventional construction.
FIG. 20 is a vertical cross-sectional side view illustrating a second example of conventional construction.
FIG. 21 is an enlarged view of part F in FIG. 20.
FIG. 22 is a partial cross-sectional drawing illustrating a conventional gap adjustment mechanism for adjusting the gap between the outer column and inner column that can be applied to the first example and second example of conventional construction.



MODES FOR CARRYING OUT INVENTION
FIG. 1 to FIG. 18 illustrate an example of an embodiment of the present invention. The electric steering wheel position adjustment apparatus of this example has a steering shaft 2b and a cylindrical steering column 5b, neither of which is expandable or contractible, in a section thereof that functions as a steering column apparatus. In the construction of this example, the forward-backward position and up-down position of the steering wheel (see FIG. 19) that is supported by and fastened to the rear-end section of the steering shaft 2b that protrudes from the opening on the rear end of the steering column 5b can each be adjusted within a specified range, however, forward-backward position adjustment of the steering wheel 1 is achieved by moving the overall steering shaft 2b and steering column 5b in the axial direction.
In the construction of this example, the overall length of the steering shaft 2b does not expand or contract, however the steering shaft 2b is able to move in the axial direction (forward-backward direction) of the steering shaft, so as illustrated in FIG. 1 and FIG. 6, as an intermediate shaft 28 that is linked to the front-end section of the steering shaft 2b by way of a universal joint 27a so as to be able to transmit torque, construction is employed in which the end sections of an intermediate inner shaft 29 and intermediate outer shaft 30 fit together using a spline fit such that torque can be transmitted and the overall length can be expanded and contracted. In other words, by expanding or contracting the intermediate shaft 28, movement in the forward-backward direction of the steering shaft 2b is compensated for. The front-end section of the intermediate shaft 28 is linked to an input shaft (omitted in the figure) of a steering gear unit for applying a steering angle to the steered wheels (front wheels) by way of another universal joint 27b. 
In the construction of this example, the installation position of the universal joint 27a that links the front-end section of the steering shaft 2b and the rear-end section of the intermediate shaft 28 is appropriately regulated such that during position adjustment of the steering wheel 1, the amount of relative displacement between the steering shaft 2b and the intermediate shaft 28 is kept to minimum, and such that the position adjustment of the steering wheel 1 can be performed smoothly. More specifically, in order support a column holder 31 that holds the steering column 5b so as to be able to pivotally move with respect to a vehicle side bracket 32, a pair of left and right tilt shafts 33 (see FIG. 9 and FIG. 11) that are concentric with each other and the steering shaft 2b are located in positions such that the center axes of each are orthogonal with each other. Furthermore, as illustrated in FIG. 3, the center axis OC of the pair of tilt shafts 33 is located in the center position in the forward-backward direction between the center position OF of displacement on the front-end side of the universal joint 27a and the center position OB of displacement on the rear-end side.
The center position OF of displacement on the front-end side is the center position of displacement of the universal joint 27a, or in other words, the center point position of the joint cross 34 of the universal joint 27a, in a state in which the steering wheel 1 is displaced to the front-end position of the adjustable range. The center position OB of displacement on the rear-end side is the center position of displacement of the universal joint 27a in a state in which the steering wheel 1 is displaced to the rear-end position of the adjustable range. In this example, the center axis OC of the pair of tilt shafts 33 is located in the center position of the line segment that connects the center position OF of displacement on the front-end side and the center position OB of displacement on the rear-end side. Therefore, when the length of the line segment that connects the center position OF of displacement on the front-end side and the center position OB of displacement on the rear-end side is taken to be L, the distances between the center axis OC of the pair of tilt shafts 33 and the center position OF of displacement on the front-end side and the center position OB of displacement on the rear-end side are each L/2. However, even when the center axis OC of the pair of tilt shafts 33 is shifted by ±L/10, or preferably by ±L/20, from the position in the figure, the center axis OC of the pair of tilt shafts 33 is located in nearly the center position between the center position OF of displacement on the front-end side and the center position OB of displacement on the rear-end side, so there is no particular problem.
The column holder 31 that holds the steering column 5b so that displacement of the steering column 5a in the axial direction (forward-backward direction) is possible is formed into a hollow body shape, or more specifically, a substantially cylindrical shape by die casting a light metal alloy, for example. The column holder 31 corresponds to a support section that constitutes the section of the steering column apparatus of the present invention. In order to eliminate looseness of the steering column 5b with respect to the column holder 31, support holes 22a are formed in two locations that are separated in the forward-backward direction on the tip surface of the column holder 31 so as to pass through between the inner circumferential surface and outer circumferential surface of the column holder 31. As illustrated in FIG. 4 and FIG. 14, a sliding plate 35, a washer 36 and a disc spring 37 are installed on the inside of the each of the support holes 22a, and the opening section on the top end of each support hole 22a is covered by a screw cover 38. The sliding plate 35 is made of a high polymer material such as a synthetic resin like polyacetal (POM) or a synthetic rubber having excellent sliding properties. In this state, the sliding plates 35 that are located in the end section on the radially inside of the support holes 22a are pressed against the outer circumferential surface (top surface) of the steering column 5b by the elastic force of the disc springs 37, so that the steering column 5b is not loose inside the column holder 31. The spacing in the axial direction of the mechanisms for preventing looseness of the steering column 5b is arbitrary, however, in this example, the spacing in the axial direction of the mechanisms is essentially the same as the maximum movable range in the axial direction of the steering unit.
In this example, from the aspect of maintaining the required rigidity, the steering column 5b is integrally formed into a hollow body shape using an extruded pipe or seam welded pipe made of an aluminum alloy or iron-based alloy. However, it is also possible to employ construction in which plural elements are combined by welding or fitting. In this example, the steering column 5b has a substantially cylindrical shape, but is not limited to this. By performing a drawing process on both end sections in the forward-backward direction of the steering column 5b, reduced-diameter sections 39a, 39b having outer diameters that are smaller than the outer diameter of the middle section in the forward-backward direction are formed. Moreover, the middle section in the forward-backward direction of the steering column 5b is taken to be a middle cylindrical section 40 having an outer diameter that does not change in the axial direction, and both end sections in the forward-backward direction of this middle cylindrical section 40 are continuous with the reduced-diameter sections 39a, 39b by inclined surface sections 41a, 41b. The length in the axial direction of the middle cylindrical section 40 and the installation positions of the support holes 22a are regulated by the relationship with the amount of adjustment in the forward-backward direction of the steering wheel 1, and the sliding plates 35 do not separate from the middle cylindrical section 40 regardless of the displacement in the axial direction of the steering column 5b with respect to the column holder 31.
The steering shaft 2b is integrally formed into a cylindrical shape or circular rod shape using drawn pipe or seam welded pipe made of an iron-based alloy, or an extruded pipe or drawn pipe made of an aluminum alloy, however, as in the case of the steering column 5b, it is also possible to employ construction in which plural elements are combined by welding or fitting. The steering shaft 2b is supported on the radially inside of the steering column 5b by a pair of ball bearings 42a, 42b that are located on both end sections in the forward-backward direction in a state such that displacement in the axial direction with respect to the steering column 5b is prevented.
A pair of angular ball bearings 42a, 42b that have back-to-back contact angles and that are preloaded, are located between the inner circumferential surface of the reduced-diameter sections 39a, 39b, and the outer circumferential surface of the portions near both ends of the middle section of the steering shaft 2b. Therefore, in this example, as illustrated in FIG. 4, the outer rings 43a, 43b of the pair of ball bearings 42a, 42b are fastened around the edge sections on the openings of the reduced-diameter sections 39a, 39b in a state such that displacement in a direction toward each other is prevented. Moreover, the inner ring 44a of the ball bearing 42a on the front side is fastened around the portion near the front end of the middle section of the steering shaft 2b by a retaining ring 45 that is fastened around the steering shaft 2b so that displacement in the forward direction is prevented. On the other hand, the inner ring 44b of the ball bearing 42b on the rear side is fastened around the steering shaft 2b with a loose fit by a push nut 46 in a state such that displacement in the backward direction is prevented. An elastic member 47 such as a disc spring is held between the surface on the front side of the push nut 46 and the rear-end surface of the inner ring 44b, and this elastic member 47 applies an elastic force on the inner ring 44b in the forward direction. With this kind of construction, the steering shaft 2b is supported on the radially inside of the steering column 5b in a state such that displacement in the axial direction is prevented, and so as to be able to rotate freely with no looseness.
In this example, back-to-back angular ball bearings instead of deep-groove ball bearings are used as the pair of ball bearings 42a, 42b, and are installed in a state being preloaded from the axial direction of the steering shaft 2b. Therefore, the preloading makes it possible to prevent looseness of the bearings, and it is possible to reduce the rotation torque of the bearings, so a steering apparatus having good steering stability of the steering wheel 1 is achieved. Moreover, a push nut 46 is used for fastening the inner ring 44b on the rear side, so there is no need to form a fastening groove on the rear-end section of the steering shaft 2b where it is easy for large forces to be applied from the steering wheel 1. Therefore, it is possible to maintain the strength and rigidity of the rear-end section of the steering shaft 2b without having to increase the thickness of the steering shaft 2b. A screw hole 48 is provided on the rear-end section of the steering shaft 2b, and by using this screw hole 48, the steering wheel 1 is fastened to and supported by the steering shaft 2b, and the diameter of the rear-end section of the steering shaft 2b is sufficiently maintained.
As illustrated in FIG. 9 and FIG. 11, the column holder 31 is supported by the vehicle-side bracket 32 by the pair of tilt shafts 33 that are provided on both sides of the front-end section of the column holder so as to be concentric with each other, and the column holder 31 is able to pivotally move around these tilt shafts 33. The vehicle-side bracket 32 is integrally formed by die cast molding of a light metal alloy, for example, and is supported by a portion that is fastened to the vehicle body so that displacement in the forward direction due to an impact load that is applied during a secondary collision is possible. In order for this, a pair of left and right installation plate sections 49 are provided on the vehicle-side bracket 32, long holes 50 that extend in the forward-backward direction are formed in the front sections of the installation plate sections 49, and notches 51 that are open on the rear-end edges of the installation plate sections 49 are formed in the rear-end sections. Sliding plates 52a, 52b are fastened to each of the long holes 50 and notches 51, and by the way of bolts or studs that are inserted in through holes in these sliding plates 52a, 52b, the pair of installation plate sections 49 are fastened to and supported by a portion that is fastened to the vehicle body. In this state, the vehicle-side bracket 32 is always firmly supported by a portion that is fastened to the vehicle body, however, when a large impact load is applied in the forward direction during a secondary collision, the vehicle-side bracket 32 moves in the forward direction within the range that the bolts or studs are able to move inside the long holes 50.
An actuator case 53 that is manufactured separately from the steering column 5b is joined and fastened to a portion of the column holder 31 that is on the bottom side of the steering column 5b using plural bolts. As illustrated in FIG. 2 and FIG. 5, a forward-backward feed screw apparatus 54 and an up-down feed screw apparatus 55 that constitute an electric actuator are provided inside the actuator case 53. In this example, a forward-backward position adjustment actuator is formed by the forward-backward feed screw apparatus 54 and a forward-backward electric drive motor 56. The forward-backward feed screw apparatus 54, with the forward-backward electric drive motor 56 as a drive source, causes the steering column 5b to move in the forward-backward direction, and has a forward-backward feed screw rod 58 that is arranged parallel with the steering column 5b, and a moving piece 16a that has a forward-backward feed nut that screws onto the forward-backward feed screw rod 58. As illustrated in FIG. 5 and FIG. 16, both the front and rear end sections of the forward-backward feed screw rod 58 are supported by the actuator case 53 by way of a pair of ball bearings 59a, 59b such that displacement in the axial direction is prevented, so that only rotation is possible. The forward-backward feed screw rod 58 is connected to the forward-backward electric drive motor 56 by way of a worm reducer, and is rotated and driven by the forward-backward electric drive motor 56. In this example, a forward-backward feed screw apparatus 54 that has the forward-backward electric drive motor 56 as a drive source is used, however, instead of this, it is also possible to use a linear motor that has a brake function, such as a linear motion ultrasonic motor.
The moving piece (forward-backward feed nut) 16a has a base section 60 and a connecting section 61 that is provided above the base section 60. A screw hole 62 that screws onto the forward-backward feed screw rod 58 is formed on the base section 60. The connecting section 61 and the steering column 5b are connected by way of a transmission member 17a so as to be able to transmit force in the forward-backward direction therebetween. The transmission member 17a is formed by performing cold forging on raw material made of an iron-based alloy such as carbon steel or stainless steel, and a male screw section 63 is provided on the base-end section (top-end section), an outward-facing flange section 64 is provided on the middle section, and a circular column section 65 is provided on the tip-end section (bottom-end section). A fastening hole 66 such as a hexagonal hole is formed in the tip-end surface (bottom-end surface) of the circular column section 65 so that the tip-end section of a tool such as a hexagonal wrench can be fastened. In the transmission member 17a of this example, there is no neck section where the outer diameter becomes particularly small.
As illustrated in FIG. 5 and FIG. 14, the transmission member 17a is fastened with screws to the bottom surface of the middle cylindrical section 40 of the steering column 5b so that tilting in the forward-backward direction is sufficiently suppressed. More specifically, with a cylindrical section of a nut plate 68 inserted into a though hole 67 that is formed on the bottom surface of the middle cylindrical section 40 of the steering column 5b, the nut plate 68 is fastened to the circumferential edge section of the through hole 67 by crimping so as to be mounted to the steering column 5b from the inner circumferential surface side thereof. A radially inward side spacer 69 having an outer diameter that is smaller than the outer diameter of the flange section 64 is placed on the top surface of the flange section 64, and an radially outward side spacer 70 is mounted around this radially inward side spacer 69. The radially inward side spacer 69 is made of a hard material such as an iron-based alloy. However, the radially outward side spacer 70 is made of a high polymer material such as synthetic resin, hard rubber, hard vinyl or the like, or a material having a specified hardness but also having large internal loss and a vibration absorbing capability such as a soft metal. With the bottom surface near the radially inside of the radially outward side spacer 70 in contact with the top surface of the portion near the radially outside of the flange section 64, the top surface of the radially inward side spacer 69 and the top surface of the radially outward side spacer 70 are located on the same plane. Furthermore, a filler piece 71 is held between the top surfaces of the radially inward side spacer 69 and the radially outward side spacer 70 and the bottom surface (outer circumferential surface of the bottom-end section) of the steering column 5b. The filler piece 71 is made of a hard material such as an iron-based alloy, and is formed into a circular ring shape or frame shape as a whole with a wedge shaped cross sectional shape. By screwing the male screw section 63 that is provided on the top-end section of the transmission member 17a into the nut plate 68 and further tightening, the transmission member 17a is firmly supported by and fastened to the bottom surface of the middle section of the steering column 5b. The transmission member 17a is supported by and fastened to the middle cylindrical section 40 of the steering column 5b having a relatively large outer diameter, so the transmission member 17a does not hinder the rotation of the steering shaft 2b. Moreover, by combining the radially outward side spacer 70 with the radially inward side spacer 69 made of a hard material, the radially outward side spacer 70 will not be exhausted. Furthermore, even in the case where the radially outward side spacer 70 drops down from the flange section 64 and comes in contact with the moving piece 16a, the occurrence of noise is suppressed since the material of the radially outward side spacer 70 is not hard.
The transmission member 17a that is supported by and fastened to the bottom surface of the middle cylindrical section 40 of the steering column 5b and the moving piece 16a that is screwed onto the forward-backward feed screw rod 58 are combined so as to be able to transmit movement in the forward-backward direction, and so as to be able to move relative to each other in the axial direction of the transmission member 17a. More specifically, an engaging concave section 19a that opens upward is provided in the center section of the connecting section 61 of the moving piece 16a, and the circular column section 65 of the transmission member 17a is inserted into this engaging concave section 19a. A cylindrical shaped spacer 72 is placed between the inner circumferential surface of the engaging concave section 19a and the outer circumferential surface of the circular column section 65 so that there is no looseness, and so that sliding movement in the axial direction of the circular column section 65 is possible. The inner circumferential surface and the outer circumferential surface of the cylindrical spacer 72, except for chamfer sections on both ends in the axial direction, are cylindrical surfaces having no change in the diameter in the axial direction.
In a state that the transmission member 17a and the moving piece 16a are combined, the moving piece 16a does not rotate with respect to the forward-backward feed screw rod 58. When the forward-backward feed screw rod 58 is rotated by the forward-backward electric drive motor 56, the moving piece 16a moves along the forward-backward feed screw rod 58 in a direction that corresponds to the direction of rotation. The direction of movement of the moving piece 16a is basically in the direction of the center axis of the column holder 31, and is parallel to the direction of movement of the steering column 5b. However, due to manufacturing error or assembly error of a product, the direction of the movement of the moving piece 16a and the direction of movement of the steering column 5b may be a little nonparallel. For example, in case that the direction of the abutting section (contact surfaces) between the bottom surface of the column holder 31 and the top surface of the actuator case 53 does not match the direction of movement of the moving piece 16a or the direction of movement of the steering column 5b, these directions of movement may be a little nonparallel. In that case, the transmission member 17a moves in the axial direction of the transmission member 17 relative to the moving piece 16a. This relative displacement is performed while there is slippage at the area of contact between the inner circumferential surface of the cylindrical spacer 72 and the outer circumferential surface of the circular column section 65, and at the area of contact between the outer circumferential surface of the cylindrical spacer 72 and the inner circumferential surface of the engaging concave section 19a. These circumferential surfaces are simple cylindrical surfaces, so the surfaces can be processed with high precision without a large increase in cost, and because the sliding sections of these members are located at two locations, the relative displacement between these members can be performed smoothly. In order that the transmission member 17a can move in the forward-backward direction, a long hole 89 in the forward-backward direction that extends in the axial direction of the column holder 31 is provided in part of the column holder 31.
In this example, an up-down feed screw apparatus 55 and up-down electric drive motor 57 are provided as an electric actuator for up-down position adjustment. With the up-down electric drive motor 57 as a drive source, the up-down feed screw apparatus 55 causes the rear section of the steering column 5b to move (raise or lower) in the up-down direction. In this example, the up-down feed screw apparatus 55 causes the entire column holder 31 to pivotally move with respect to the vehicle-side bracket, with the pair of tilt shafts 33 as the center of rotation. More specifically, as illustrated in FIG. 8 to FIG. 10, a U-shaped support frame 73 is provided at the rear-end section of the vehicle-side bracket 32, and the rear-end section of the column holder 31 is held inside this support frame 73 so as to be able to raise or lower without looseness. The support frame 73 has inside surfaces that are parallel with each other. On the other hand, convex sections 74a, 74b that have outside surfaces that are parallel with each other are provided on both the right and left sides of the rear-end section of the column holder 31 so as to protrude out in the width direction. The outside surfaces of the convex sections 74a, 74b and the inside surfaces of the support frame 73 engage by way of respective sliding plates 75a, 75b. One sliding plate 75a is thicker than the other sliding plate 75b, and by pressing this thick sliding plate 75a toward the other sliding plate 75b using a pressure screw 76, looseness between the support frame 73 and the column holder 31 is eliminated. The pressure screw 76, after being tightened to a specified torque, is prevented from coming loose by a lock nut. In this example, an up-down feed screw apparatus 55 having the up-down electric drive motor 57 as a drive source is used, however, instead of this, it is also possible to use a linear motor having a brake function such as a linear motion ultrasonic motor.
As illustrated in FIG. 5 and FIG. 15, by combining the engaging hole 77 that is provided in the center section in the width direction of the support frame 71 and the up-down feed screw apparatus 55, the rear-end section of the column holder 31 is able to move up or down (raise or lower) according to the power flowing to the up-down electric drive motor 57. As illustrated in FIG. 5 and FIG. 17, both the top and bottom end section of the up-down feed screw rod 78 of the up-down feed screw apparatus 55 is supported by the actuator case 53 by way of a pair of ball bearings 79a, 79b such that only rotation is possible. The up-down feed screw rod 78 is connected to the up-down electric feed drive motor 57 by way of a worm reducer, and is rotated and driven by the up-down electric drive motor 57.
An up-down feed nut 80 screws around the middle section of the up-down feed screw rod 78. The up-down feed nut 80 is formed into a incomplete circular ring shape using a metal material such as an iron-based metal having elasticity, and by adjusting the interference of the screw engagement section with the up-down feed screw rod 78 with a screw 81, it is possible to eliminate any looseness in the screw engagement section. Moreover, the tip-end section of an engaging arm 82 that is integrally provided on the up-down feed nut 80 and the engaging hole 77 can be joined by way of a spherical joint 83 so as to be able to transmit force in the up-down direction and so as to be able to pivotally move. The spherical joint 83 is formed on the tip-end section of the engaging arm 82, and has a spherical engaging section 84 having an outer circumferential surface that is a partial spherical convex surface, and a spacer 85 that is formed into a cylindrical shape using a material such as synthetic resin that slides easily, and has an inner circumferential surface that is a partial spherical concave surface. A screw hole is formed in the center section of the spherical engaging section 84, and a slit in the radial direction is provided thereon, so that the outer diameter of the spherical engaging section 84 can elastically expand or contract. More specifically, by engaging a partial conical shaped convex surface that is formed on the head of an adjustment screw 86 that is screwed into the screw hole in the spherical engaging section 84 with a partial conical shaped concave surface that is formed in the opening section of the screw hole in the spherical engaging section 84, it is possible to adjust the outer diameter of the spherical engaging section 84. By screwing the adjustment screw 86 a proper amount into the screw hole in the spherical engaging section 84, the occurrence of a gap in the spherical joint 83 is prevented. With this kind of construction, movement in the up-down direction is transmitted from the up-down feed nut 80 to the bottom-end section of the support frame 73 without looseness.
As illustrated in FIG. 7 and FIG. 9 reinforcement ribs 90 are provided on both the left and right sides of the front-end section of the vehicle-side bracket 32, and these reinforcement ribs 90 maintain the strength and rigidity of the portion of the vehicle-side bracket where the tilt shaft 33 is located. Moreover, reinforcement ribs 92 are also provided between a pair of left and right pivot support arms 91 that are provided on the front-end section of the column holder 31 in order to pivotally support the column holder 31 by the tilt shaft 33 and the main portion of the column holder 31, and these reinforcement ribs 92 maintain the strength and rigidity of the pivot support arms 91. Therefore, in this example, the strength and rigidity of the pivot support section that supports the column holder 31 with respect to the vehicle-side bracket 32 are sufficiently maintained, and the operational feeling of the steering wheel 1 is sufficiently prevented from becoming deteriorated due to insufficient rigidity of this pivot support section.
In the following, the position adjustment of the steering wheel 1 by the electric steering wheel position adjustment apparatus of this example will be explained. First, when adjusting the forward-backward position of the steering wheel 1, current is allowed to flow to the forward-backward electric drive motor 56, and the forward-backward electric drive motor 56 rotates the forward-backward feed screw rod 58 by a specified amount in a specified direction. With rotation of the forward-backward feed screw rod 58, the moving piece 16a moves in the forward-backward direction along the forward-backward feed screw rod 58, and the steering column 5b, by way of the transmission member 17a, is moved in the forward-backward direction inside the column holder 31. As a result, the forward-backward position of the steering wheel 1 is adjusted. When the steering wheel 1 is moved to an adjustable limit position, the moving piece 16a comes in contact with one of a pair of stoppers 87a, 87b as illustrated in FIG. 16 that are provided at portions near both ends of the forward-backward feed screw rod 58, and the moving piece 16a is prevented from moving any further. In this state, current flowing to the forward-backward electric drive motor 56 is stopped.
When the forward-backward position of the steering wheel 1 is adjusted to a limit position, the portion on the end section in the axial direction of the steering column 5b where the outer ring 43a, 43b of the ball bearing 42a, 42b is fastened inside with an interference fit comes close to the inner circumferential surface of the end section of the column holder 31. There is a possibility that the end sections in the axial direction of the steering column 5b may deform a little due to the outer rings 43a, 43b being fastened inside, or due to the effect of chucking during processing. However, the end sections in the axial direction of the steering column 5b are the reduced-diameter sections 39a, 39b, and there is no rubbing between the end sections in the axial direction of the steering column 5b and the inner circumferential surface of the end sections of the column holder 31. Therefore, even when the forward-backward position of the steering wheel 1 is adjusted to a limit position, unpleasant noise or vibration does not occur due to rubbing between the end section in the axial direction of the steering column 5b and the inner circumferential surface of the end section of the column holder 31.
Next, when adjusting the up-down position of the steering wheel 1, current is allowed to flow to the up-down electric drive motor 57, and the up-down electric drive motor 57 rotates the up-down feed screw rod 78 by a specified amount in a specified direction. As a result, the up-down feed nut 80 moves in the up-down direction along the up-down feed screw rod 78. However, this up-down feed nut 80 does not move in the up-down direction due to engagement between the engaging hole 77 and the spherical engaging section 84, so the up-down feed screw rod 78 moves in the up-down direction, and due to that displacement, the actuator case 53 and column holder 31 that support the up-down feed screw rod 78 pivotally move around the tilt shaft 33. As a result, the up-down position of the steering wheel 1 is adjusted to a specified position. In this case as well, when the steering wheel 1 is moved to a limit position within the adjustable range, the up-down feed nut 80 comes in contact with one of a pair of stoppers 88a, 88b such as illustrated in FIG. 17 that are provided in portions near both ends of the up-down feed screw rod 78, and is prevented from further movement. In this state, electric current flowing to the up-down electric drive motor 57 is stopped.
In the electric steering wheel position adjustment apparatus of this example, the steering shaft 2b and steering column 5b are integrated such that when both are in at least the normal state, the full length is not expanded or contracted, so the rigidity of the steering shaft 2b and steering column 5b is sufficiently maintained. Therefore, it is possible to suppress vibration of the steering wheel 1 and improve the steering performance. Moreover, in this way, the steering shaft 29 having single construction is located inside the non-divided steering column 5b, so an area of fit that is a cause of looseness does not exist in the portion that constitutes the steering column apparatus. Consequently, the occurrence of looseness in the portion that constitutes the steering column apparatus is suppressed, so it is possible to increase the resonant frequency of that portion. As a result, it becomes possible to avoid resonance with traveling vibration that has a low resonant frequency, or engine vibration having large amplitude.
Moreover, the pair of sliding plates 35 that are supported in series at two locations at the front and rear of the column holder 31 and that support the steering column 5b so as to be able to move in the axial direction elastically push the middle cylindrical section 40 of the steering column 5b toward the inner circumferential surface of the column holder 31, so looseness between the steering column 5b and the column holder 31 is eliminated. Particularly, by bringing the outer circumferential surface of the middle cylindrical section 40 having a relatively large diameter in contact with the sliding plates 35, the area of the contact surface between these members becomes large, so it becomes possible to make the force by which the sliding plates 35 push the steering column 5b relatively small. Moreover, the gap in the axial direction in the portion where the sliding plates 35 push the outer circumferential surface of the steering column 5b can be kept as large as possible within the range of movement in the forward-backward direction of the steering column 5b, so the rigidity in the area of fit between the steering column 5b and the column holder 31 is sufficiently maintained. Furthermore, by using the moment that occurs between the sliding plates 35 and the sliding section on the outer circumferential surface of the steering column 5b, it is possible to make the force by which the sliding plates 35 pushes the steering column 5b relatively small. With this kind of construction, it is possible to reduce the load that is applied when moving the steering wheel 1 in the forward-backward direction, so it is possible to lessen the operating noise of the forward-backward electric drive motor 56. Moreover, even when the tolerance for the inner-diameter dimension of the column holder 31 and the tolerance for the outer-diameter dimension of the steering column 5b are the same as in the conventional construction, it is possible to eliminate looseness, so tilting of the steering column 5b and the transmission member 17a can be kept small. Therefore, there is no need to use a spherical shape having a high degree of displacement absorbency for the tip-end section of the transmission member 17a, and it is possible to use a simple shape such as a circular column shape.
In the apparatus of this example, construction does not allow expansion and contraction of the overall length of the steering shaft 2b and steering column 5b, so when adjusting the forward-backward position of the steering wheel 1, the center position of the universal joint 27a, and the joint cross 34, which is the center of displacement of the universal joint 27a, moves in the axial direction of the steering shaft 2b and steering column 5b. On the other hand, when adjusting the forward-backward position of the steering wheel 1, the installation position of the tilt shaft 33 that is provided between the front-end section of the column holder 31 and the front-end section of the vehicle-side bracket 32 does not change even though the forward-backward position of the steering wheel 1 is adjusted.
Therefore, depending on the forward-backward position of the steering wheel 1, a state occurs in which the center position of the joint cross 34 is not located on the center axis of the tilt shaft 33. In this state, when pivotally displacing the column holder 31 centered around the tilt shaft 33 in order to adjust the up-down position of the steering wheel 1, the center position of the joint cross 34 pivotally moves centered around the tilt shaft 33. As the center of this joint cross 34 pivotally moves, the distance between the universal joint 27a on the rear side that includes this joint cross 34 and the universal joint on the front side changes. The change in this distance is absorbed by the expansion or contraction of the intermediate shaft 28. However, in order to expand or contract the intermediate shaft 28, it is necessary to overcome the friction resistance that acts in the area of fit between the intermediate inner shaft 29 and the intermediate outer shaft 30. Due to this kind of friction resistance, the resistance against the pivotal displacement of the column holder 31 becomes large, and there is a possibility that the capability for smooth adjustment of the up-down position of the steering wheel 1 will be lost. The amount that this capability for smooth adjustment is lost becomes more extreme as the amount that the intermediate shaft expands or contracts during adjustment of the up-down position becomes larger, and the resistance that accompanies the expansion or contraction of the intermediate shaft 28 becomes larger.
In the construction of this example, the center axis OC of the tilt shaft 33 is located in the center position in the forward-backward direction between the center position OF of displacement of the front-end side and the center position OB of displacement of the rear-end side. Therefore, even in a state in which the center position of the joint cross 34 is not located on the center axis OC of the tilt shaft 33, it is possible to keep the radius of the pivotal displacement of the center position of the joint cross 34, accompanying the pivotal displacement of the column holder 31 centered around the tilt shaft 33, which is the amount that the center position of the joint cross 34 is shifted from the center axis OC, small. By keeping this radius small, it is possible to keep the amount of expansion or contraction of the intermediate shaft 28 due to adjustment of the up-down position small, and it is possible to keep the resistance due to the expansion or contraction of the intermediate shaft 28 small. As a result, it is possible to smoothly adjust the up-down position of the steering wheel 1 regardless of the forward-backward position of the steering wheel 1.
In FIG. 18, the positions represented by F, C and B indicate the position of the center of displacement of the universal joint 27a when the steering wheel 1 is moved to the front-end position, and the center position and rear-end position of the adjustable range when the up-down position of the steering wheel 1 is in the neutral state. When the forward-backward position of the steering wheel 1 is in the center position, and the position of the center of displacement of the universal joint 27a is located on the center axis of the tilt shaft 33, the universal joint 27a does not raise or lower even when the intermediate shaft 28 expands or contracts as the up-down position of the steering wheel 1 is adjusted. Therefore, the intermediate shaft 28 and universal joint 27a do not resist the adjustment of the up-down position of the steering wheel 1.
On the other hand, when adjusting the up-down position in a state in which the steering wheel 1 has been moved to the front-end position represented by F, the position of the center of displacement of the universal joint 27a moves between fH and fL with fO as the center, and the intermediate shaft 28 expands or contracts due to this displacement. As can be seen from FIG. 18, the amount of expansion or contraction between fH and fL is relatively large. This amount of expansion or contraction increases the longer the distance that the position of the center of displacement of the universal joint 27a is separated from the tilt shaft 33 becomes. In the construction of this example, by locating the position of the center axis OC of the tilt shaft 33 at the center position in the forward-backward direction between the position of the center of displacement OF of the front-end side and the position of the center of displacement OB of the rear-end side, it is possible to suppress the maximum value of the distance that the position of the center of displacement of the universal joint 27a is separated from the tilt shaft 33 more than in the case of construction in which the center axis OC is located further toward the rear than the position of the center of displacement OB of the rear-end side. Therefore, even when adjusting the up-down position when the steering wheel 1 is moved to the very front position, it is possible to keep this amount of expansion or contraction small and it is possible to perform the up-down position adjustment smoothly.
On the other hand, in a state in which the steering wheel 1 has been moved to the rear-end position represented by B, the universal joint 27a that connects the front-end section of the steering shaft 2b and the rear-end section of the intermediate shaft 28 is located further toward the rear than the tilt shaft 33. When up-down position adjustment is performed in this state, the position of the center of displacement of the universal joint 27a moves between bH and bL with bO as the center, and the intermediate shaft 18 expands or contracts due to this displacement. As can be seen from FIG. 18, the amount of this expansion or contraction is kept relatively small. Instead of that, during up-down position adjustment of the steering wheel 1, the portion that includes the universal joint 27a becomes the load on the up-down electric drive motor 57 of the electric actuator for up-down position adjustment. This is because, unlike in the case when the universal joint 27a is located further toward the front than the tilt shaft 33, the weight of the portion of the universal joint 27a is not cancelled out by other portions. Therefore, the load on the up-down electric drive motor 57 during up-down position adjustment of the steering wheel 1 becomes large, so a larger motor must be used, which is disadvantageous from the aspect of making the electric steering wheel position adjustment apparatus more compact and lightweight. This tendency becomes even more extreme the larger the distance that the universal joint 27a is separated from the tilt shaft 33 becomes. However, in this example, the positional relationship of the center axis OC of the tilt shaft 33, and the positions of the center of displacement OF, OB are regulated as described above, so when compared with construction in which the center axis OC is located further toward the front than the position of the center of displacement OF on the front side, it is possible to suppress the maximum value of the distance that the position of the center of displacement of the universal joint 27a is separated from the tilt shaft 33. Therefore, it is possible to keep the amount that the load on the up-down electric drive motor 57 becomes increases low, and thus it is easier to make the apparatus more compact and lightweight.
Locating the center axis OC of the tilt shaft 33 at the center position in the forward-backward direction is also advantageous from the aspect of suppressing fluctuation in the torque required for operating the steering wheel 1, regardless of the adjustment of the forward-backward position of the steering wheel 1. In other words, when the universal joints 27a, 27b, which are both joint cross universal joint, transmit torque in a state in which a joint angle is applied, the torque characteristic (torque loss) changes in accordance with the phase variation in the rotational direction. When this kind of change in the torque characteristic is left as is, the driver that is operating the steering wheel 1 will experience an unpleasant feeling. Therefore, by making the phase in the rotational direction of the universal joints 27a, 27b suitably different, the fluctuations in torque characteristic of these universal joints 27a, 27b will cancel each other out. In this case, it is necessary to make suitable the relationship between the joint angles of the universal joints 27a, 27b and the shift in the phase in the rotational direction, however, in the construction of this example, the position of the universal joint 27a on the rear side shifts as the forward-backward position of the steering wheel 1 is adjusted. As a result, the relationship of the joint angles of the universal joints 27a, 27b shifts from the initial relationship. When this shift is large, it is not possible to sufficiently suppress the fluctuation in the torque characteristic of these universal joints 27a, 27b, and there is a possibility that the driver that is operating the steering wheel 1 will experience an unpleasant feeling. On the other hand, in the construction of this example, it is possible to keep the amount of this shifting small, so it is possible to keep the possibility that driver that is operating the steering wheel 1 will experience an unpleasant feeling low.
Moreover, the sliding plates 35 push the steering column 5b downward toward the forward-backward feed screw apparatus 54, so a moment in the horizontal direction does not occur according to this pushing, and looseness of the steering column 5b inside the column holder 31 that may occur when the forward-backward feed screw apparatus 54 is operated and stopped is suppressed, and up-down movement of the steering column 5b that may occur when inverting the displacement operation is also suppressed. Even in the case where it is necessary to perform a finishing process on the outer circumferential surface of the middle cylindrical section 40 in order to improve the precision of the area of fit between the outer circumferential surface of the steering column 5b and the inner circumferential surface of the column holder 31, the outer circumferential surface of the middle cylindrical section 40 has the largest diameter of the outer circumferential surface of the steering column 5b, so performing a finishing process on the outer circumferential surface of this middle cylindrical section 40 does not effect the other portions, and can be performed easily and efficiently. Moreover, the support rigidity of the steering wheel 1 as well can be easily adjusted by changing the thickness of the metal plate of the steering column 5b and steering shaft 2b. Furthermore, the portions of the steering column 5b that are pushed by the sliding plates 35 are located in the portion of the steering column 5b having the larger diameter, so the surface area of the pushed portions can be made large, and thus it is not necessary to make the force by which the sliding plates 35 push the steering column 5b excessively large. The effect of suppressing looseness is obtained by a small pushing force such as this, so the load during operation is stable and small, and thus it is also possible to reduce the operating noise of the forward-backward electric drive motor 56.
In the construction of this example, the shape of the transmission member 17a and the cylindrical spacer 72 for transmitting the movement of the moving piece 16a of the forward-backward feed screw apparatus 54 to the steering column 5b is simple, so it is possible to use cold forging to manufacture the transmission member 17a and cylindrical spacer 72 at low cost and with high precision.
Moreover, the relative displacement in the axial direction of the transmission member 17a between the transmission member 17a and the moving piece 16a is compensated for at two locations; the inner circumferential surface and outer circumferential surface of the cylindrical spacer 72, and the outer circumferential surface of the tip-end section of the transmission member 17a and the inner circumferential surface of the engaging concave section 19a that is provided on the moving piece 16a. Therefore, even when the direction of movement of the moving piece 16a and the direction of movement of the steering column 5b accompanying adjustment of the forward-backward position of the steering wheel 1 become nonparallel due to bad precision of the engaging bottom surface of the column holder 31 and the top surface of the actuator case 53, and there is relative displacement in the axial direction of the transmission member 17a between the transmission member 17a and the moving piece 16a accompanying the forward-backward position adjustment of the steering wheel 1, there is rubbing at two locations, so the length of each rubbing location can be made short, and thus it is possible to suppress the occurrence of noise and vibration. Furthermore, there is no neck section in the transmission member 17a, that is disadvantageous from the aspect of maintaining strength and rigidity, so the durability and reliability of the forward-backward feed screw apparatus 54 is maintained.
Furthermore, with construction of this example, the up-down feed screw rod 78 of the up-down feed screw apparatus 55 is located directly below the column holder 31 in the radial direction of the column holder 31, so no adverse moment is applied to the column holder 31 during up-down position adjustment of the steering wheel 1. Therefore, it is possible to perform this up-down position adjustment smoothly. Locating the support frame 73 for guidance during up-down position adjustment as far toward the rear as possible within a range that does not interfere with the portion fastened to the steering column 5b is preferred from the aspect of maintaining support rigidity of the column holder 31 as well as maintaining the support rigidity of the steering wheel 1 regardless of the forward-backward movement of the steering column 5b during forward-backward position adjustment of the steering wheel 1. Moreover, preferably the sliding plates 75a, 75b are coated with a lubricant such as grease in order that up-down adjustment of the steering wheel 1 is performed smoothly. Furthermore, preferably arranging the up-down feed screw rod 78 and the forward-backward feed screw rod 58 such that the center axes are orthogonal to each other is preferred from the aspect of being able to smoothly perform up-down adjustment and forward-backward adjustment of the steering wheel 1, and being able to keep the installation space of the forward-backward feed screw apparatus 54 and up-down feed screw apparatus 55 small.
INDUSTRIAL APPLICABILITY
The electric steering wheel position adjustment apparatus of the present invention is not limited to construction for attachment to a vehicle body, or to construction for joining a steering shaft and universal joint as in the embodiment described above, but can be widely applied to electric steering wheel position adjustment apparatuses that are assembled in electric power steering apparatuses in which various kinds of conventionally known construction are employed.
EXPLANATION OF REFERENCE NUMBERS


    1 Steering wheel
    2, 2a, 2b Steering shaft
    3, 3a Outer shaft
    4, 4a Inner shaft
    5, 5a, 5b Steering column
    6, 6a, 6b Outer column
    7, 7a, 7b Inner column
    8 Gear housing
    9 Feed nut
    10 Push-pull arm
    11 Push-pull rod
    12 Male screw section
    13 Worm reducer
    14 Installation bracket
    15 Linear motion ultrasonic motor
    16 Moving piece
    16a Moving piece (forward-backward feed nut)
    17, 17a Transmission member
    18 Spherical joint
    19, 19a Engaging concave section
    20 Spacer
    21 Spherical engaging section
    22, 22a Support hole
    23 Female screw
    24 Adjustment screw
    25 Disc spring
    26 Pad
    27a, 27b Universal joint
    28 Intermediate shaft
    29 Intermediate inner shaft
    30 Intermediate outer shaft
    31 Column holder
    32 Vehicle-side bracket
    33 Tilt shaft
    34 Joint cross
    35 Sliding plate
    36 Washer
    37 Disc spring
    38 Screw cover
    39a, 39b Reduced-diameter section
    40 Middle cylindrical section
    41a, 41b Inclined surface section
    42a, 42b Ball bearing
    43a, 43b Outer ring
    44a, 44b Inner ring
    45 Retaining ring
    46 Push nut
    47 Elastic material
    48 Screw hole
    49 Installation plate section
    50 Long hole
    51 Notch
    52a, 52b Sliding plate
    53 Actuator case
    54 Forward-backward feed screw apparatus
    55 Up-down feed screw apparatus
    56 Forward-backward electric drive motor
    57 Up-down electric drive motor
    58 Forward-backward feed screw rod
    59a, 59b Ball bearing
    60 Base section
    61 Connecting section
    62 Screw hole
    63 Male screw section
    64 Flange section
    65 Circular column section
    66 Fastening hole
    67 Through hole
    68 Nut plate
    69 Radially inward side spacer
    70 Radially outward side spacer
    71 Filler piece
    72 Cylindrical spacer
    73 Support frame
    74a, 74b Convex section
    75a, 75b Sliding plate
    76 Pressure screw
    77 Engaging hole
    78 Up-down feed screw rod
    79a, 79b Ball bearing
    80 Up-down feed nut
    81 Screw
    82 Engaging arm
    83 Spherical joint
    84 Spherical engaging section
    86 Spacer
    87a, 87b Stopper
    88a, 88b Stopper
    89 Long hole in the forward-backward direction
    90 Reinforcement rib
    91 Pivot support arm
    92 Reinforcement rib

## Claims

1. An electric steering wheel position adjustment apparatus, comprising:
a non-expandable steering shaft having a center axis, a front-end section, and a rear-end section which a steering wheel is supported by and fastened to;
a non-expandable steering column supporting the steering shaft so as to be able to rotate freely on an inside thereof;
a column holder supported by a vehicle-side bracket that is supported by a portion fastened to a vehicle body, having a tip-end section, and supporting the steering column so as allow movement in an axial direction of the steering column;
a pair of left and right tilt shafts being concentric with each other, being arranged so as to have a center axis that is orthogonal to the center axis of the steering shaft, and supporting the tip-end section of the column holder so as to be able to pivotally move with respect to the vehicle-side bracket;
an expandable intermediate shaft having a rear-end section, and transmitting rotation of the steering shaft to an input shaft of a steering gear unit;
a universal joint connecting the front-end section of the steering shaft to the rear-end section of the intermediate shaft;
an electric actuator for forward-backward position adjustment having a forward-backward electric drive motor as a drive source, and causing the steering column to move in the axial direction with respect to the column holder; and
an electric actuator for up-down position adjustment having an up-down electric drive motor as a drive source, and causing the column holder to pivotally move in an up-down direction of the column holder with the tilt shaft as a pivot center,
wherein when a position of a center of displacement of the universal joint when the steering wheel is displaced to a front-end position of an adjustable range is taken to be a position of the center of displacement of a front-end side, and a position of the center of displacement of the universal joint when the steering wheel is displaced to a rear-end position of the adjustable range is taken to be a position of the center of displacement of a rear-end side, the center axis of the pair of left and right tilt shafts is located within a range between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side.

2. The electric steering wheel position adjustment apparatus according to claim 1, wherein when the distance between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side is taken to be L, the center axis of the pair of left and right tilt shafts is located within a range of length L/5 centered around the center position between the position of the center of displacement of the front-end side and the position of the center of displacement of the rear-end side.

3. The electric steering wheel position adjustment apparatus according to claim 1, wherein the electric actuator for forward-backward position adjustment and the electric actuator for up-down position adjustment are fastened on a bottom side of the column holder and mechanisms that push the steering column downward are provided in at least two locations separated in a forward-backward direction of a top side of the column holder.

4. The electric steering wheel position adjustment apparatus according to claim 3, wherein each of the mechanisms that push the steering column downward comprise: a support hole that is formed so as to pass through between an inner circumferential surface and an outer circumferential surface of the column holder, and a sliding plate, an elastic member and a cover that are assembled inside the support hole in order from an inside in a radial direction of the column holder; and the elastic member is elastically compressed between the sliding plate and the cover, and the sliding plate pushes the outer circumferential surface of the steering column.