Tilt adjustable steering apparatus

Abstract: A tilt steering apparatus comprises a lock lever (16) rotatable around the axis (C) of a supporting shaft (15) . When a lock lever (16) is rotated around the axis (C) of the supporting shaft (15 , a cam surface (28) is rotated relative to a cam follower (21). As a result, the cam surface (28) presses the cam follower (21) against side plates (9, 10) of a fixed bracket (8), thereby achieving tilt locking. The cam surface (28) has a plurality of slopes (29, 30) corresponding to a rotation stroke position of the lock lever (16). The operating torque of the lock lever (16) at the time of a locking operation is reduced without increasing the range of the operating angle of the lock lever (16).

Description: The present invention relates to a tilt adjustable steering apparatus according to the preamble of claim 1, as is known from EP 0 600 700 A1. There is a tilt adjustable steering apparatus so adapted that the height of a steering wheel can be changed depending on the physical constitution of a driver, the driving position, or the like. An example of the tilt adjustable steering apparatus is a telescopically adjustable steering apparatus in which the position of a steering wheel is adjusted along the axis of a steering shaft. Conventionally, there has been provided as the tilt adjustable steering apparatus one comprising a fixed bracket fixed to a vehicle, a tilt bracket fixed to a steering column, a supporting shaft penetrating side plates of the fixed bracket and the tilt bracket, a lock lever manually rotated around the axis of the supporting shaft, and a cam mechanism for pressing the side plates of both the brackets as the lock lever is rotated in the locking direction to achieve tilt locking. However, the operating torque of the lock lever in a case where the tilt locking is achieved is increased. On the other hand, the operating torque of the lock lever in a case where the tilt locking is released is small, so that a feeling of operation is bad. The present invention has been made in view of the above-mentioned problems, and has its object to provide a tilt adjustable steering apparatus capable of obtaining a suitable operating torque of a lock lever and having good operability. In order to attain the above-mentioned object, there is provided a steering apparatus according to claim 1, comprising a tilt adjustable steering column comprises a fixed bracket fixed to a body of a vehicle; a tilt bracket fixed to the steering column; a side plate provided in the fixed bracket; a side plate provided in the tilt bracket and sliding along the side plate of the fixed bracket at the time of tilt adjustment; a supporting shaft passing through respective insertion holes of the side plates of the fixed bracket and the tilt bracket; a lock lever rotatable in the locking direction and the locking releasing direction around an axis of the supporting shaft and rotated in the locking direction to lock the steering column to an adjusted tilt position; and a cam surface and a cam follower which are relatively rotated while being brought into sliding contact with each other as the lock lever is rotated. The cam surface includes a plurality of slopes corresponding to a rotation stroke position of the lock lever. The cam surface presses the cam follower as the lock lever is rotated in the locking direction so that the side plates of both the brackets are pressed against each other, resulting in the steering column being locked at the adjusted tilt position. In this mode, the operating force of the lock lever in a case where the lock lever is locked can be reduced without making the range of the operating angle of the lock lever so large by providing the plurality of slopes. It is preferable that the steering apparatus further comprises means for increasing the operating torque of the lock lever at the front of a stroke in the locking releasing direction of the lock lever, the cam surface and the cam follower constituting means for increasing the operating torque of the lock lever. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. Fig. 1 is a partially broken front view of a steering apparatus according to an embodiment of the present invention; Fig. 2 is a partially broken side view of a lock lever and a portion to which the lock lever is attached; Fig. 3A is a front view of a cam including a cam surface, and Fig. 3B is a front view of a surface of a cam follower opposite to the cam surface; Fig. 4 is a cross-sectional view schematically showing a cam and a cam follower; Fig. 5 is a cross-sectional view of a cam in a steering apparatus according to another embodiment of the present invention; Fig. 6A is a front view of a surface, opposite to a cam follower, of the cam shown in Fig. 5, and Fig. 6B is a cross-sectional view taken along a line 6B - 6B shown in Fig. 6A; Fig. 7A is a front view of a cam follower surface opposite to the cam shown in Fig. 5, and Fig. 7B is a cross-sectional view taken along a line 7B - 7B shown in Fig. 7A; Figs. 8A and 8B are cross-sectional views sequentially showing the operations of a cam and a cam follower in a case where a lock lever is fastened in order to achieve tilt locking in the embodiment shown in Fig. 5; Figs. 9A and 9B are cross-sectional views sequentially showing the operations of a cam and a cam follower in a case where a lock lever is loosened in order to release tilt locking in the embodiment shown in Fig. 5; Fig. 10 is a cross-sectional view of a cam and a cam follower in another embodiment of the present invention; Fig. 11 is a cross-sectional view of a cam and a cam follower in still another embodiment of the present invention; Fig. 12 is a cross-sectional view of a cam and a cam follower in a further embodiment of the present invention; and Fig. 13 is a cross-sectional view of a cam and a cam follower in a still further embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described while referring to accompanying drawings. Fig. 1 is a longitudinal sectional view of a steering column in a tilt adjustable telescopic steering apparatus according to an embodiment of the present invention, and Fig. 2 is a partially broken side view of a lock lever and a portion to which the lock lever is attached. Referring to Fig. 1, a tilt adjustable telescopic steering apparatus 1' (hereinafter merely referred to as a steering apparatus 1') comprises a steering column 2 for supporting a steering shaft 1 having a steering wheel fixed to its upper end in the axial direction so as to be rotatable. The steering column 2 comprises a tube 3 (corresponding to an upper jacket) for supporting the steering shaft 1 so as to be rotatable and a tilt bracket 4 fixed to the tube 3. The tilt bracket 4 is in a groove shape opening downward. A vertically long hole (or longitudinal hole) 7 extending along the length of the steering column 2 is formed in left and right side plates 5 and 6 of the tilt bracket 4. A fixed bracket 8 is fixed to a vehicle, and is in the shape of a groove opening downward comprising a pair of side plates 9 and 10 opposite to each other and an upper plate 11 connecting intermediate portions at upper ends of the side plates 9 and 10 to each other. A vertically long hole 12 in the shape of a circular arc is formed in each of the side plates 9 and 10. Reference numerals 13 and 14 denote mounting stays formed by folding upper edges of parts of the side plates 9 and 10 outward. The fixed bracket 8 is fixed to the vehicle by a bolt passing through a screw insertion hole formed in each of the mounting stays 13 and 14, which is not illustrated. A tilt center axis is supported in a supporting hole composed of a round hole provided in each of the side plates 9 and 10 of the fixed bracket 8, and a lower end in the axial direction of the steering column 2 is supported around the tilt center axis so as to be slidable, which is not illustrated. Telescopic adjustment can be made by displacing the tilt center axis backward and forward in a long hole provided in each of the side plates 5 and 6 of the tilt bracket 4 in the steering column 2. Reference numeral 15 denotes a supporting shaft integrally inserted through the side plates 9 and 10 of the fixed bracket 8 and the side plates 5 and 6 of the tilt bracket 4. The supporting shaft 15 is for supporting a lock lever serving as an operation lever manually operated in order to achieve tilt and telescopic locking and release the locking so as to be integrally rotatable. Referring to Fig. 2, the lock lever 16 has a longitudinal main unit 41. A connecting section 23 connected to a cam 22, described later, so as to be integrally rotatable is provided at one end of the main unit 41, and a grip 42 to be griped by a driver is provided at the other end of the main unit 41. Reference numeral 43 is a stopper plate which is screwed to the vicinity of one end of the main unit 41 to abut against a nut 24. The stopper plate 43 penetrates (or prevents) the nut 24 from turning. In Fig. 2, reference numeral 21 denotes a cam follower engaged with the cam 22, and reference numeral 25 denotes a shim. Referring to Fig. 1 again, the supporting shaft 15 is guided to the vertically long hole 12 so that only vertical sliding is allowed with respect to the fixed bracket 8. On the other hand, the vertically long hole 7 allows the steering column 2 including the tilt bracket 4 from moving (or to move) back and forth with respect to the supporting shaft 15. The supporting shaft 15 is composed of a bolt having a head 17, a body 18 composed of a circular cylinder, and a screw portion 19. The body 18 penetrates the side plates 5 and 6 of the bracket 4 and the side plates 9 and 10 of the bracket 8, and the head 17 has a plain washer 20 interposed between the head 17 and an outer surface of the side plate 10 of the fixed bracket 8. On the other hand, the screw portion 19 of the supporting shaft 15 and a part of the body 18 connecting therewith project outward from the side plate 9 of the fixed bracket 8, and an annular cam follower 21 is fitted in a part of the body 18. The cam follower 21 is brought into contact with an outer surface of the side plate 9 of the fixed bracket 8. Further, the cam follower 21 has a projection inserted through the vertically long hole 12 of the side plate 9. Consequently, the rotation of the supporting shaft 15 around a center axis C is bound by the side plate 9 of the fixed bracket 8. An annular cam 22 which is brought into contact with the cam follower 21 is fitted in the screw portion 19 so as to be relatively rotatable. The connecting section 23 of the lock lever 16 is connected to the cam 22 so that the lock lever 16 and the cam 22 are integrally rotated. A nut 24 with a flange is screwed onto the screw portion 19. The nut 24 positions the cam 22 along the axis of the supporting shaft 15 through the annular shim 25 and the connecting section 23 of the lock lever 16. The inner periphery of the annular connecting section 23 may be in a polygonal shape such as a hexagonal shape or a shape having a width across flat on its circumference. The shim 25, the connecting section 23, the cam 22, and the cam follower 21 are interposed between the side plate 9 of the fixed bracket 8 and the nut 24. When the lock lever 16 is rotated, the cam 22 is rotated relative to the cam follower 21, so that the cam follower 21 is pressed against the side plate 9 upon advancing and retreating along the center axis C of the supporting shaft 15 or the pressing thereof is released, thereby achieving tilt locking and telescopic locking and releasing the locking. As shown in Fig. 3A, a pair of a first positioning section 26 for positioning the cam follower 21 at the time of releasing locking and a second positioning section 27 for positioning the cam follower 21 at the time of locking are provided so as to be opposite to each other with a center axis of the cam 22 (i.e., the center axis C of the supporting shaft 15) on a surface 22a, opposite to the cam follower 21, of the cam 22. Referring to Figs. 3A and 4, a cam surface 28 is formed between the first and second positioning sections 26 and 27 which correspond to each other. In Fig. 4, an arrow X indicates the direction in which the cam follower 21 moves relative to the cam 22 when the lock lever 16 is stroked in the locking direction. On the other hand, as shown in Fig. 3B, the positioning sections 26 and 27 of the cam 22 and a pair of projections 31 in the shape of a stand which are brought into sliding contact with a cam surface 28 are formed on a surface 21a, opposite to the cam 22, of the cam follower 21. As shown in Fig. 4, the cam surface 28 comprises a first slope 29 relatively steeply inclined and a second slope 30 relatively gently inclined, and the second slope 30 corresponds to the rear of a stroke in the locking direction of the lock lever. According to the present embodiment, the plurality of slopes 29 and 30 are provided on the cam surface 28, thereby making it possible to reduce the operating force of the lock lever 16 without so enlarging the operating angle of the lock lever 16. Particularly, the cam surface 28 is provided with the second slope 30 relatively gently inclined in correspondence with the rear of a stroke in the fastening direction of the lock lever 16 whose operating torque is liable to be increased. Consequently, the lever ratio of the lock lever at the rear of the fastening stroke (corresponding to the ratio of the amount of displacement of the cam follower 21 to the increment of the operating angle of the lock lever) can be increased. As a result, the operating torque can be reduced, thereby making it possible to significantly improve the operability of the lock lever 16. In the above-mentioned embodiment, the cam surface may be provided with three or more slopes which differ in inclination, for example. In order to smooth the operation, the adjacent slopes may be continued by a smooth curve, or the whole of the slopes may be a smooth curve. Referring now to Fig. 5, the cam 22 has a cylindrical main unit 59 having a center hole 58 through which the supporting shaft 15 is inserted. In the main unit 59, a cam surface 31 is formed on its opposite surface 60 corresponding to the cam follower 21, and a connecting boss 33 is formed on a rear surface 32 of the opposite surface 60. A pair of flat surfaces having a width across flat, for example, is formed on a peripheral surface of the connecting boss 33. The flat surfaces are engaged with the connecting section 23 of the lock lever 16, so that the lock lever 16 and the cam 22 can be integrally rotated. Referring to Fig. 5 and Fig. 6A which is a front view of the opposite surface 60, a plurality of recesses 34 forming a fan shape which are equally spaced in the circumferential direction are formed on the opposite surface 60, and a bottom surface of each of the recesses 34 forms a cam surface 31'. Referring to Figs. 6A and 6B, one of a pair of inner sidewalls of the recess 34 opposite to the cam 22 in the circumferential direction constitutes a first positioning section 35 for positioning the cam follower 21 at the time of releasing locking, and the other thereof constitutes a second positioning section 36 for positioning the cam follower 21 at the time of locking. Referring to Fig. 6B, the cam surface 31 is formed between the first and second positioning sections 35 and 36. The cam surface 31' comprises a flat portion 44, a first forward inclined slope 37 relatively steeply inclined, a second forward inclined slope 38 inclined more gently than the first slope 37, and a third slope 39 serving as an inverse slope inclined in the opposite direction to the first and second slopes 37 and 38. The adjacent slopes are continued by a smooth curve. The inverse slope constituting the third slope 39 constitutes means for increasing torque at the time of releasing, and constitutes a slope adjusting section for adjusting the operating torque of the lock lever at the time of fastening. The third slope 39 is positioned at the rear of the fastening stroke of the lock lever. An angle of inclination A to a plane perpendicular to a center axis C1 of the cam 22 is set to approximately 1°, for example (which may be in the range of 0.5° to 1.5°), and a top 40 is formed between the second slope 38 and the third slope 39. On the other hand, referring to Figs. 7A and 7B, a plurality of projections 46 forming a shape being trapezoidal in cross section which are brought into sliding contact with the cam surface 31 of the cam 22 are equally spaced in the circumferential direction on a surface 45, opposite to the cam 22, of the cam follower 21. A cam follower surface 47 composed of a top surface of the projection 46 is inclined at an angle of inclination (B = A, which is 1°, for example) equal to that of the third slope 39 to a plane perpendicular to a center axis C2 of the cam follower 21. As shown in Fig. 7A, the cam follower surface 47 and the third slope 39 are inclined at an equal angle of inclination in opposite directions and are brought into surface contact with each other. According to the present embodiment, the plurality of slopes 37, 38, and 39 are provided on the cam surface 28, thereby making it possible to reduce the operability of the lock lever 16 at the time of fastening without increasing the range of the operating angle of the lock lever 16. Particularly referring to Figs. 8A and 8B, the third slope 39, serving as a slope adjusting section, which is an inverse slope but is hardly inclined is provided on the cam surface 31 in correspondence with the rear of the stroke in the fastening direction of the lock lever 16 whose operating torque is liable to be increased. Consequently, the lever ratio of the lock lever at the rear of the fastening stroke (corresponding to the ratio of the amount of displacement of the cam follower 21 to the increment of the operating angle of the lock lever) can be increased. As a result, the operating torque can be reduced, thereby making it possible to significantly improve the operability of the lock lever 16. In Fig. 8B, an arrow Y indicates the direction of movement of the cam 22 relative to the cam follower 21 in a case where the lock lever 16 is operated in the locking direction. Moreover, as shown in Figs. 9A and 9B, when the lock lever 16 is operated in the releasing direction, it must move beyond the top 40 during the transition from the third slope 39 serving as an inverse slope inclined in the opposite direction to the second slope 38. Accordingly, the operating torque at the time of releasing can be increased to improve a feel. In Fig. 9B, an arrow Z indicates the direction of movement of the cam 22 relative to the cam follower 21 in a case where the lock lever 16 is operated in the locking releasing direction. Fig. 10 is a cross-sectional view schematically showing a cam and a cam follower in another embodiment of the present invention. Referring to Fig. 10, the present embodiment differs from the embodiment shown in Fig. 9A in that the third slope 39 in the embodiment shown in Fig. 9A is inclined in the opposite direction to the first and second slopes 37 and 38, while a third slope 48 serving as a slope adjusting section in the present embodiment is made inclined in the same direction as first and second slopes 37 and 38 (that is, forward inclined). An angle of inclination D of the third slope 48 is set to 1° (which may be in the range of 0.5° to 1.5°). In the present embodiment, the cam follower surface 47 constitutes means for increasing torque at the time of releasing. Other constituent elements are the same as those in the embodiment shown in Fig. 9A, and are assigned the same reference numerals and hence, the description thereof is not repeated. According to the present embodiment, the same function and effect as those shown in Fig. 9A, and the operating force of the lock lever 16 at the time of fastening can be reduced. The third slope 48 and the cam follower 47 are inclined in opposite directions, and their respective angles of inclination are made different from each other (A ≠ B). When the lock lever 16 is operated in the direction in which locking is released, therefore, an edge 49 of a cam follower 47 serving as means for increasing torque at the time of releasing is cut into the third slope 48. Consequently, the operating torque at the time of releasing can be increased to improve a feeling of operation of the lock lever at the time of releasing. In the present embodiment, the cam follower surface 47 may be a portion having no slope. The present invention is not limited to the above-mentioned embodiments. Various changed modes are considered. For example, in the embodiment shown in Fig. 9B, the cam follower surface 47 may be brought into contact with the third slope 39 of the cam surface 31 at an edge 49, as shown in Fig. 11, by making an angle of inclination B of the cam follower surface 47 larger than an angle of inclination A of the third slope 39 of the cam surface 31 (B > A). In the embodiment shown in Fig. 9B, a portion having no slope 50 serving as a slope adjusting section may be provided in place of the third slope 39 of the cam surface 31, as shown in Fig. 12, by reducing the angle of inclination of the third slope 39 to zero (A = 0). In an embodiment shown in Fig. 13, a recess 52 concaved by providing a step 51 may be provided at the rear of a fastening stroke of the portion having no slope 50, as shown in Fig. 13, the angle of inclination B of the cam follower surface 47 may be also reduced to zero (B = 0) to have no slope, and a projection 53 fitted in the recess 52 may be provided at the rear of the fastening stroke of the cam follower surface 47. Also in this case, when the lock lever 16 is operated in the releasing direction, the projection 53 moves beyond the step 51, so that contact surface pressure between the cam surface 31 and the cam follower surface 47 is increased once, thereby making it possible to increase the operating torque at the time of a lock releasing operation. In each of the embodiments, the cam surface may be provided with a larger number of slopes which differ in inclination. Further, in order to smooth the operation, the adjacent slopes (or the slope and the portion having no slope) may be continued by a smooth curve, or the whole of the slopes may be a smooth curve. In each of the embodiments, the relationship between the cam surface and the cam follower surface may be reversed. The present invention may be applied to a tilt adjustable steering apparatus having no telescopic adjusting function. In addition thereto, various changes can be made in the range of the present invention. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A steering apparatus (1') comprising a tilt adjustable steering column (2), comprising: a fixed bracket (8) fixed to a body of a vehicle; a tilt bracket (4) fixed to the steering column (2); side plates (9, 10) provided in the fixed bracket (8); side plates (5, 6) provided in the tilt bracket (4) and sliding along the side plates (9, 10) of the fixed bracket (8) at a time of tilt adjustment; a supporting shaft (15) passing through respective insertion holes (12, 7) of the side plates (9, 10, 5, 6) of the fixed bracket (8) and the tilt bracket (4); a lock lever (16) rotatable in the locking direction and the locking releasing direction around an axis (C) of the supporting shaft (15) and rotated in the locking direction to lock the steering column (2) to an adjusted tilt position; and a cam surface (28) and a cam follower (21) which are relatively rotated while being brought into sliding contact with each other as the lock lever (16) is rotated, the cam surface (28) including a plurality of slopes (29, 30; 37, 38, 39; 37, 38, 48; 37, 38, 52) corresponding to a rotation stroke position of the lock lever (16), the cam surface (28) pressing the cam follower (21) as the lock lever (16) is rotated in the locking direction so that the side plates (9, 10, 5, 6) of both the brackets (8, 4) are pressed against each other, resulting in the steering column (2) being locked at the adjusted tilt position, the cam follower (21) being moved in a first direction (X; Y) relative to the cam surface (28) when the lock lever (16) is stroked in the locking direction, characterized in that the plurality of slopes (29, 30; 37, 38, 39; 37, 38, 48; 37, 38, 52) of the cam surface (28) include first and second slopes (29, 30; 37, 38) which are upward slopes in the first direction, the second slope (30; 38) being gentler than the first slope (29; 37), and the cam follower (21) slides from the first slope (29; 37) of the cam surface (28) to the second slope (30; 38) thereof when the lock lever (16) is stroked in the locking direction (X; Y). The steering apparatus of claim 1, characterized in that the plurality of slopes (37, 38, 48) of the cam surface (28) include a third slope (48) which is an upward slope in the first direction, the third slope (48) being gentler than the second slope (38), and the third slope (48) corresponds to a rear of a stroke in the locking direction of the lock lever (16), and the cam follower (21) successively slides toward the first, second and third slopes (37, 38, 48) of the cam surface (28) in this order when the lock lever (16) is stroked in the locking direction. The steering apparatus of claim 1, characterized in that the plurality of slopes (37, 38, 39) of the cam surface (28) include an inverse slope (39) which is a downward slope in the first direction, the inverse slope (39) corresponds to a rear of a stroke in the locking direction of the lock lever (16), and the cam follower (21) slides toward the first and second slopes (37, 38) and the inverse slope (39) of the cam surface (28) in this order when the lock lever (16) is stroked in the locking direction. The steering apparatus of claim 1, characterized in that the cam surface (28) and the cam follower (21) constituting means (28, 21) for increasing an operating torque of the lock lever (16) at a front of a stroke in the locking releasing direction of the lock lever (16). The steering apparatus of claim 4, characterized in that the cam follower (21) is moved in a first direction relative to the cam surface (28) when the lock lever (16) is stroked in the locking direction, the cam surface (28) includes an inverse slope (39) which is a downward slope in the first direction, and the inverse slope (39) of the cam surface (28) corresponds to the front of the stroke in the locking releasing direction of the lock lever (16). The steering apparatus of claim 4 or 5, characterized in that the cam follower (21) includes a cam follower surface (47) which is substantially brought into contact with the cam surface (28) at an edge (49) in correspondence with at least the front of the stroke in the locking releasing direction of the lock lever (16). The steering apparatus of claim 6, characterized in that an angle (B) of inclination of the cam follower surface (47) differs from an angle (A; D) of inclination of an area, corresponding to at least the front of the stroke in the locking releasing direction of the lock lever (16) , of the cam surface (28). The steering apparatus of claim 4, characterized in that the cam surface (28) includes an area corresponding to the front of the stroke in the locking releasing direction of the lock lever (16), a recess (52) concaved by providing a step (51) in the area. The steering apparatus of claim 8, characterized in that the cam follower (21) includes a cam follower surface (47) which is brought into contact with the cam surface (28), and the cam follower surface (47) includes a projection (53) which is engaged with the recess (52) of the cam surface (28) in correspondence with a rear of a stroke in the locking direction of the lock lever (16). The steering apparatus of claim 8, characterized in that an area, corresponding to the front of the stroke in the locking releasing direction of the lock lever (16), of the cam surface (28) includes a portion (50) having no slope.

Inventors: KUROUMARU YOSHIKAZU, MINAMOTO NOBORU, KUROUMARU, YOSHIKAZU, MINAMOTO, NOBORU
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 2001
Main classification: B62D1
IPC codes: B62D1