Patent Application
20160297467
The disclosure of Japanese Patent Application No. 2015-078698 filed on Apr. 7, 2015 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to steering systems.
2. Description of the Related Art
A steering position adjustment device is proposed which supports a load such as a steering column and a steering wheel during tilt adjustment by a spring member interposed between a fixed bracket and a movable bracket (see, e.g., Japanese Patent Application Publication No. 2011-168190 (JP 2011-168190 A)). A tilt-telescopic steering system is also proposed in which a spring member is pulled in telescopic adjustment so as to restrain the impact on tilt adjustment (see, e.g., Japanese Patent Application Publication Nos. 2009-61993 (JP 2009-61993 A) and 2002-22061 (JP 2002-22061 A)). In JP 2009-61993 A and JP 2002-22061 A, the tilt-telescopic steering system includes a fixed bracket and a movable bracket which can be adjusted by tilt adjustment and telescopic adjustment, and a spring member is disposed between the fixed bracket and a member that is displaced in a tilt adjustment operation but is not moved in a telescopic adjustment operation.
When the steering wheel is adjusted to the uppermost position in the tilt direction by tilt adjustment, the spring member is minimally stretched and a spring load is reduced. On the other hand, when the steering wheel is adjusted to the lowermost position in the tilt direction by tilt adjustment, the spring member is maximally stretched and the spring load is increased. This is disadvantageous because the operation force that is applied by an operator to move the steering column toward the upper or lower side in the tilt direction varies significantly depending on the tilt adjustment position.
It is one object of the present invention to provide a steering system configured to restrain a change in operation force that is applied when changing a tilt adjustment position.
According to one aspect of the present invention, a steering system includes: a steering shaft having its one axial end coupled to a steering member; a column jacket that supports the steering shaft such that the steering shaft is rotatable and is swingable about a tilt center; a bracket that includes a pair of side plates each having an elongated tilt adjustment hole and that is fixed to a fixed portion; a fastening mechanism that includes a fastening shaft inserted through the elongated tilt adjustment holes of the bracket to move with the column jacket in a tilt direction, and that fastens the pair of side plates by the fastening shaft to lock a position of the column jacket; a fulcrum formation member provided on the fixed portion or the bracket and forming a fulcrum; a first engagement portion provided in the fixed portion or the bracket; a lever link that includes a second engagement portion forming a point of load, an elongated hole in which the fastening shaft is fitted so as to be movable in a longitudinal direction in association with tilt adjustment, and a point of effort located at an edge of the elongated hole directly or indirectly receiving the fastening shaft, and that is swingably supported by the fulcrum formation member; and a biasing member that includes one end engaged with the first engagement portion and the other end engaged with the second engagement portion and that biases the column jacket toward an upper side in the tilt direction via the lever link and the fastening shaft.
The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
Embodiments of the present invention will be described below with reference to the accompanying drawings.
The steering operation mechanism 5 is, e.g., a rack and pinion mechanism that steers steered wheels (not shown) in response to steering of the steering member 2. Rotation of the steering member 2 is transmitted to the steering operation mechanism 5 via the steering shaft 3, the intermediate shaft 4, etc. The rotation transmitted to the steering operation mechanism 5 is converted to axial movement of a rack shaft, not shown. The steered wheels are steered in this manner.
The steering shaft 3 has a tubular upper shaft 6 and a lower shaft 7. The upper shaft 6 is fitted to the lower shaft 7 by, e.g., spline fitting or serration fitting so as to be slidable relative to the lower shaft 7. The steering member 2 is coupled to one end of the upper shaft 6. The steering shaft 3 can be extended and retracted in an axial direction X. The steering system 1 further includes a hollow column jacket 8 that supports the steering shaft 3 such that the steering shaft 3 is rotatable. The steering shaft 3 is passed through the column jacket 8 and is rotatably supported by the column jacket 8 via a plurality of bearings 9, 10.
The column jacket 8 has an inner jacket 11 and an outer jacket 12. The inner jacket 11 is fitted to the outer jacket 12 so as to be slidable relative to the outer jacket 12. The inner jacket 11 is, for example, an upper jacket, and the outer jacket 12 is, for example, a lower jacket. The column jacket 8 can be extended and retracted in the axial direction X. The upper inner jacket 11 is coupled to the upper shaft 6 via the bearing 9 so as to be movable with the upper shaft 6 in the axial direction X. The lower outer jacket 12 supports the lower shaft 7 via the bearing 10 such that the lower shaft 7 is rotatable.
The steering system 1 further includes a fixed bracket 14, a tilt center shaft 15, and a column bracket 16. The fixed bracket 14 is fixed to a vehicle body 13. The tilt center shaft 15 is supported by the fixed bracket 14. The column bracket 16 is fixed to the outer periphery of the outer jacket 12 and is rotatably supported by the tilt center shaft 15. The column jacket 8 and the steering shaft 3 can pivot (tilt) in a tilt direction Y about a tilt center CC as the central axis of the tilt center shaft 15.
The position of the steering member 2 can be adjusted by pivoting (tilting) the steering shaft 3 and the column jacket 8 about the tilt center CC (what is called “tilt adjustment”). The position of the steering member 2 can also be adjusted by extending and retracting the steering shaft 3 and the column jacket 8 in the axial direction X (what is called “telescopic adjustment”). The steering system 1 further includes a bracket 17 and a fastening mechanism 18. The bracket 17 is fixed to the vehicle body 13. The fastening mechanism 18 attains a tilt lock and a telescopic lock. The bracket 17 includes a pair of side plates 22 each having an elongated tilt adjustment hole 23.
As shown in a schematic perspective view of
As shown in
Referring to
The fastening shaft 21 is inserted through the elongated tilt adjustment holes 23 that are formed in the pair of side plates 22 of the bracket 17 so as to extend in the tilt direction Y (only one of the side plates 22 is shown in
As shown in
As shown in
As shown in
The lever link 60 has a second spring engagement portion 62, an elongated hole 63, and a point of effort Q. The second spring engagement portion 62 is a second engagement portion that forms a point of load R. The fastening shaft 21 is fittingly inserted through the elongated hole 63. The point of effort Q is located at an edge 63a of the elongated hole 63. The second spring engagement portion 62 is an engagement hole with which the other hook-shaped end 72 of the spring member 70 is hooked and engaged. The edge of the engagement hole (the second spring engagement portion 62) with which the other end 72 of the spring member 70 is engaged forms the point of load R.
As shown in
As shown in
The present embodiment will be described with respect to an example in which the first spring engagement portion 38 is formed in the side plate 22. However, the first spring engagement portion 38 may be formed in the top plate 25 or the attachment plate 24. The pair of fastened portions 28 of the support portion 19 of the outer jacket 12 are extended from a pair of arc ends 261 of the arc-shaped portion 26. The pair of fastened portions 28 are placed between the pair of side plates 22 and are in the shape of a plate substantially parallel to the pair of side plates 22.
The slit 27 is formed between opposing inner side surfaces 28a of the pair of fastened portions 28. An inner surface 22a of each side plate 22 faces an outer surface 28b of a corresponding one of the fastened portions 28. Each fastened portion 28 of the outer jacket 12 has a circular fastening shaft insertion hole 29 through which the fastening shaft 21 is inserted. When making tilt adjustment, the fastening shaft 21, the outer jacket 12, the inner jacket 11, and the steering shaft 3 move together in the tilt direction Y
The fastening shaft 21 is a bolt that is inserted through the elongated tilt adjustment holes 23 in the side plates 22 of the bracket 17 and the fastening shaft insertion holes 29 in the fastened portions 28 of the outer jacket 12. A large diameter head 21a at one end of the fastening shaft 21 is fixed such that the fastening shaft 21 can rotate together with the operation lever 20. The fastening mechanism 18 is interposed between the head 21a of the fastening shaft 21 and one of the side plates 22. The fastening mechanism 18 includes the force conversion mechanism 30 that converts operation torque of the operation lever 20 to an axial force of the fastening shaft 21 (a fastening force for fastening the pair of side plates 22).
The force conversion mechanism 30 includes the rotary cam 31 and the one fastening member 32. The rotary cam 31 is coupled to the operation lever 20 so as to be rotatable therewith, so that movement of the rotary cam 31 relative to the fastening shaft 21 in a fastening shaft direction J is restricted. The one fastening member 32 is a non-rotary cam that is cam-engaged with the rotary cam 31 and fastens one of the side plates 22. The fastening mechanism 18 further includes the nut 33, the other fastening member 34, and the interposed member 35. The nut 33 is screwed on a threaded portion 21b of the other end of the fastening shaft 21. The other fastening member 34 fastens the other side plate 22. The interposed member 35 is interposed between the other fastening member 34 and the nut 33.
The interposed member 35 includes a washer 36 and a needle roller bearing 37. The washer 36 is interposed between the nut 33 and the other fastening member 34. The needle roller bearing 37 is interposed between the washer 36 and the other fastening member 34. The other fastening member 34 and the interposed member 35 are interposed between the nut 33 and the other side plate 22 of the bracket 17. The rotary cam 31, the one fastening member 32 (the non-rotary cam), the other fastening member 34, and the interposed member 35 are supported by the outer periphery of the fastening shaft 21.
Each of the one fastening member 32 (the non-rotary cam) and the other fastening member 34 has a fastening plate portion 32a, 34a that fastens a corresponding one of the side plates 22, and a boss portion 32b, 34b that is fitted in a corresponding one of the elongated tilt adjustment holes 23. Since the boss portions 32b, 34b are fitted in the elongated tilt adjustment holes 23, rotation of the fastening members 32, 34 is restricted. The lever link 60 of a corresponding one of the biasing mechanisms 50 is interposed between the fastening plate portion 32a, 34a of the fastening member 32, 34 and an outer surface 22b of a corresponding one of the side plates 22 of the bracket 17.
The one fastening member 32 (the non-rotary cam) and the other fastening member 34 are supported by the fastening shaft 21 so as to be movable in the fastening shaft direction J. The rotary cam 31 rotates relative to the one fastening member 32 (the non-rotary cam) according to rotation of the operation lever 20 in a lock direction. The one fastening member 32 thus moves in the fastening shaft direction J, and the pair of side plates 22 of the bracket 17 are held and fastened between (the fastening plate portions 32a, 34a of) the fastening members 32, 34 via the lever links 60 of the pair of biasing mechanisms 50.
Each side plate 22 of the bracket 17 thus fastens a corresponding one of the fastened portions 28 of the support portion 19 of the outer jacket 12. This restricts movement of the outer jacket 12 in the tilt direction Y, whereby a tilt lock is attained. Since both of the fastened portions 28 are fastened, the arc-shaped portion 26 of the support portion 19 of the outer jacket 12 is elastically compressed to reduce its diameter, thereby fastening the inner jacket 11. This restricts movement of the inner jacket 11 in the axial direction X, whereby a telescopic lock is attained.
As the operation lever 20 is rotated in an unlock direction, the one fastening member 32 and the other fastening member 34 release the side plates 22 of the bracket 17. This allows the lever links 60 to move in the tilt direction Y together with the fastening shaft 21 and the members supported by the fastening shaft 21 (the fastening members 32, 34 etc.), so that tilt adjustment can be made. When making the tilt adjustment, the biasing mechanisms 50 operate so that the operation force of the operator does not change so much, regardless of the tilt adjustment position.
As shown in a schematic view of
As shown in
As used herein, the angle of action θ1 refers to the angle between a line segment PR connecting the fulcrum P and the point of load R and an axis 70C of the spring member 70 in the state where the spring member 70 that is an extension spring is minimally stretched to a spring length Si and generates the smallest biasing force F1. The angle of action θ2 refers to the angle between the line segment PR connecting the fulcrum P and the point of load R and the axis 70C of the spring member 70 in the state where the spring member 70 is maximally stretched to a spring length S2 and generates the largest biasing force F2. The angle of action θ1 that is a positive value is larger than the angle of action θ2 and smaller than 90° (0°<θ2<θ1<90°).
The moment component of the smallest biasing force F1 is given by “F1×sinθ1,” and the moment component of the largest biasing force F2 is given by “F2×sinθ2,” where sinθ2 <sinθ1. A change in moment load due to stretching and compression of the spring member 70 in the tilt adjustment range can therefore be restrained. In
In
G2/G1=(F2/F1)×(sinθ2/sinθ1)×(cosβ2/cosβ1)×(D1/D2) (1)
If the biasing mechanism 50 including the lever link 60 is not used, the ratio G2/G1 is equal to the first term (F2/F1) of the above expression (1). In the present embodiment, the following conditions are set: 0°<θ2<θ1<90°, 0°<β1<β2<90°, and D1<D2. Thus, the second term (sinθ2/sinθ1), the third term (cosβ2/cosβ1), and the fourth term (D1/D2) of the expression (1) are smaller than 1.
A change in operation force that is applied by the operator between the uppermost position and the lowermost position in the tilt adjustment range can therefore be reduced. The lever link 60 swings about the fulcrum P and is displaced about the fulcrum P in conjunction with tilt adjustment. As the lever link 60 swings about the fulcrum P, the position of the point of load R is shifted accordingly. The spring load (biasing force) of the spring member 70 therefore changes from the biasing force F1 to the biasing force F2. As the lever link 60 swings about the fulcrum P, the fastening shaft 21 and the elongated hole 63 move relative to each other, so that the distance between the fulcrum P and the point of effort Q changes from the distance D1 to the distance D2. The lever ratio of the lever link 60 changes from the ratio D1/D to the ratio D2/D accordingly. The change in spring load is thus offset by the change in lever ratio, whereby a change in operation force that is applied when changing the tilt adjustment position can be restrained.
The biasing mechanism 50A of the second embodiment in
In the second embodiment in
In the third embodiment, the fulcrum P is located between the point of effort Q and the point of load R in the axial direction X. The point of effort Q is located on the upper side XU of the fulcrum P in the axial direction X. The point of load R is located on the lower side XL of the fulcrum P in the axial direction X. As shown in
A first spring engagement portion 38B is formed in a stay 42 extended from the side plate 22. The first spring engagement portion 38B is located on the lower side YL of the point of load R (RU, RL) in the tilt direction Y. The third embodiment provides the same effects as those of the first embodiment by using a change in distance between the fulcrum P and the point of effort Q (D1<D2) and a change in angle of action of the spring member 70 that is a helical extension spring (θ1>θ2) at the time of tilt adjustment.
In the third embodiment, the point of effort Q and the point of load R in the biasing mechanism 50B may be arranged reversely with respect to the fulcrum P in the axial direction X.
As shown in
An insertion hole 61C through which a fulcrum formation member (not shown) forming the fulcrum P is inserted is formed in the bent portion 93. The bent portion 93 is rotatably supported by the fulcrum formation member. An elongated hole 63C is formed in the lever link 60C so as to extend from a tip end 91b of the first arm 91 toward the bent portion 93. A second spring engagement portion 62C forming the point of load R is formed in a tip end 92b of the second arm 92.
The fourth embodiment provides the same effects as those of the first embodiment by using a change in distance between the fulcrum P and the point of effort Q (D1<D2) and a change in angle of action of the spring member 70 that is a helical extension spring (θ1>θ2) at the time of tilt adjustment. The use of the lever link 60C bent into the hook shape improves flexibility in placement of the spring member 70. In the fourth embodiment, the point of effort Q and the point of load R in the biasing mechanism 50C may be arranged reversely with respect to the fulcrum P in the axial direction X.
The present invention is not limited to the above embodiments. For example, the present invention is also applicable to such steering systems that the pair of side plates 22 of the bracket 17 fasten and fix a pair of fastened side plates of an inner bracket having an elongated telescopic adjustment hole and fixed to the upper jacket. In this case, the lever link may be placed between the side plate 22 and the fastened side plate.
In each of the above embodiments, either a pair of biasing mechanisms 50, 50A-50C may be provided, or a single biasing mechanism 50, 50A to 50C may be provided on one of the side plates 22. The first spring engagement portion 38, 38C may be provided in a fixed portion such as the vehicle body 13. Various modifications can be made to the present invention without departing from the spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-078698 | Apr 2015 | JP | national |
