Abstract:
A steering column tilt adjusting device allows the tilt of the upper steering column to be adjusted with finer resolution than is normally possible with the same latching hardware. In this case, sets of interengageable teeth of constant pitch are employed. One set of teeth is on a latch plate biased toward latching engagement but releasable by a manually operated lever. The other set of teeth is on a plate linked to the tiltable portion of the steering column. The linkage is such that the plate moves through a smaller angle of displacement than does the movable portion of the steering column. Thus, the teeth on the plate can be relatively coarse while allowing fine adjustment of the steering column position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an automotive steering column tilt adjusting device which allows the steering column to be tilted to match the position of the driver. More specifically, the invention relates to a tilt adjusting device allowing delicate adjustment with a smaller incremental angle. 
     Conventionally, one kind of tilt adjusting device secures a steering column assembly at a selected steering column angular position by way of engagement between two sets of matching teeth. One set of teeth is formed on an edge of a movable section of the steering column and the other set of teeth is formed on a stationary section of the steering column. 
     In such a conventional tilt adjusting device, the increment of the steering column angle is determined by the pitch of the teeth. Therefore, to obtain a smaller incremental angle, it is necessary to reduce the pitch of the teeth or to increase the distance between the pivot of the movable part and the teeth thereof in relation to the distance between the pivot and the steering wheel. In the former case, the smaller teeth may be insufficiently strong. Regarding the latter case, since the space within the vehicle for the steering column assembly is strictly limited, it is not practical to significantly enlarge the size. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a tilt adjusting device for an automotive steering column assembly which allows satisfactorily precise steering column angle adjustment without reducing the pitch of the teeth and without changing substantially the size of the steering column assembly. 
     Another object of the present invention is to provide a tilt adjusting device as described above which also permits the steering column to be temporarily moved and then returned to the previously adjusted position without having to be re-adjusted. 
     According to the present invention, a movable toothed plate is attached to a movable steering column section via a linkage and is rotatable about a pivot axis displaced from the pivot axis of the movable steering column section. The pivot axes of the movable teeth and the movable steering column section are so arranged that the movable teeth move through a larger angle than the movable steering column section as the movable steering column section is adjusted to a desired angle. 
     According to one embodiment of the invention, a tilt adjusting device for an automotive steering column assembly comprises a steering column and tube assembly, the assembly including an upper movable section and a lower stationary section connected for rotation together. The assembly further includes a stationary bracket for fixedly securing the lower stationary section to a vehicle body, and a movable bracket connected to the upper movable section for movement therewith. The movable bracket is pivotable with respect to the stationary brackets. A latching mechanism including interengageable members is provided. Each of the interengageable member has interengagement means for latching the movable bracket at a selected angular position with respect to the stationary bracket. A first member is connected to the movable bracket for movement therewith. The assembly further including a manually operated lever for releasing interengagement of the first and second members for permitting pivotal movement of the movable bracket, and a pivotting means for pivotably supporting the movable bracket and the first member for relative movement with respect to each other. The pivot means includes a first pivot allowing pivotal movement of the movable bracket and a second pivot allowing pivotal movement of the first member, the second pivot being located closer to the interengagement means of the first member than the first pivot is to the interengagement means of the first member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken as limitative to the invention but for elucidation and explanation only. 
     In the drawings: 
     FIG. 1 is an elevation of an automotive steering column assembly including the first embodiment of a tilt adjusting device according to the present invention; 
     FIG. 2 is an enlarged elevation of the tilt adjusting device of FIG. 1; 
     FIG. 3 shows a section taken along line III--III of FIG. 2; 
     FIG. 4 is an explanatory diagram of the angular movements of about the axes of the movable bracket and the toothed plate of the tilt adjusting device of the first embodiment; 
     FIG. 5 is a fragmentary elevation of a modification of the first embodiment; 
     FIG. 6 is a plan view of another modification of the tilt adjusting device of the first embodiment; 
     FIG. 7 is an elevation of the tilt adjusting device of FIG. 6; 
     FIG. 8 shows a section taken along line VIII--VIII of FIG. 7; 
     FIG. 9 is an elevation of a further modification of the tilt adjusting device of the first embodiment; 
     FIG. 10 is an elevation of the steering column assembly including the second embodiment of the tilt adjusting device according to the present invention; 
     FIG. 11 is an enlarged plan view of the second embodiment of the tilt adjusting device of FIG. 10; 
     FIG. 12 is an enlarged elevation of the tilt adjusting device of FIG. 11; 
     FIG. 13 shows a section taken along line XIII--XIII of FIG. 12; and 
     FIG. 14 is an elevation of a modification of the second embodiment of the tilt adjusting device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, particularly to FIG. 1, a steering column assembly generally comprises an upper steering column tube 23 and a lower steering column tube 20. The lower steering column tube 20 has a dash bracket 21 at the lower end remote from the upper steering column tube. The dash bracket 21 is secured to a vehicle body B. A stationary bracket 22 is secured to both the other end of the lower steering column tube 20, and the vehicle body B, specifically a vehicle instrument panel. Thus, the lower steering column 20 is fixedly secured to the vehicle body B by the dash bracket 21 and the stationary bracket 22. 
     The upper steering column tube 23 is formed with an integral movable bracket 24. The movable bracket 24 is essentially channel-shaped in cross-section and pivots about a pivot bolt 25 in the stationary bracket 22. The movable bracket 24 is associated with a tilt adjusting mechanism 10 operated by way of a tilt adjusting lever 36. 
     The upper steering column tube 23 rotatably receives an upper steering column shaft 26b to which the steering wheel 27 is secured. On the other hand, the other steering column tube 20 rotatably receives a lower steering column shaft 26a connected to a steering mechanism (not shown) via a universal joint 28. The upper and lower steering column shafts 26b and 26a are connected to each other via a universal joint (26c in FIG. 6) for transmission of rotational steering force. 
     As shown in FIGS. 2 and 3, the movable bracket 24 engages one end of a coil spring 31, the other end of which engages a hook 30 projecting from the stationary bracket 22. The coil spring 31 thus resiliently biases the movable bracket 24 counterclockwise in FIG. 2. In addition, an elongated opening 32 is formed in the stationary bracket 22 to receive a roller 42 which rotates about a pin 40 projecting from a pair of linkage levers 39. As shown most clearly in FIG. 3, the linkage levers 39 are connected to a pivotable plate 38 with teeth 37 along one edge, which toothed plate 38 is free to pivot about a pivot pin 33 projecting from the stationary bracket 22. The linkage levers 39 are, in turn, pivotably connected to the movable bracket 24 via a connector pin 41. As shown in FIG. 2, the linkage levers 39 engage one end of a coil spring 47, the other end of which engages a hook 48 extending from the tilt adjusting lever 36. 
     The teeth 37 of the toothed plate 38 oppose teeth 44 formed along part of the edge of a latch plate 43. The latch plate 43 is free to pivot about a pivot pin 34 projecting from the stationary bracket 22 and is also formed with a rounded recess 45 with a sloping cam surface 46. 
     The tilt adjusting lever 36 is provided with a roller 35 free to pivot about an axle 35a projecting from the tilt adjusting lever. The roller 35 opposes the recess 45 and is positioned so as to be able to remain in contact with the cam surface 46 throughout its range of movement. In the position illustrated in FIG. 2, the tilt adjusting lever 36 is normally biased by the coil spring 47 in the clockwise direction of FIG. 2 to urge the roller 35 onto the cam surface 46. On the other hand, the movable bracket 24 is biased by the coil spring 31 in the counterclockwise direction of FIG. 2. In this position, the latch plate 43 is biased in the clockwise direction about the pivot pin 34 so as to establish engagement between its teeth 44 and the teeth 37 of the toothed plate 38. The engagement between the teeth 37 and the latch teeth 44 holds the toothed plate 38 in the position illustrated in FIG. 2 and thus holds the linkage lever 39 in the shown position. As a result, the movable bracket 24 of the upper steering column tube 23 is similarly held in the position illustrated. 
     To adjust the tilt of the steering column assembly and thereby adjust the height of the steering wheel 27, the tile adjusting lever 36 is moved in the counterclockwise direction of FIG. 2. The roller 35 is thus moved along the cam surface 46 of the latch plate 43 to the recess 45. Due to the actuating force applied to the tilt adjusting lever 36, the latch plate 43 is pivotted counterclockwise about the pivot pin 34 to release the latch teeth 44 from engagement with the teeth 37 of the toothed plate 38. 
     In accordance with the counterclockwise movement of the tilt adjusting lever 36, the linkage lever 39 is pulled upwardly by the spring force of the coil spring 47 to cause it to pivot about the pin 40 in the counterclockwise direction. This allows the movable bracket 24 to pivot counterclockwise due to the spring force of the coil spring 31. That is, in response to the operation of the tilt adjusting lever 36, the movable bracket 24 and the upper steering column tube 23 are moved to the uppermost position due to the spring force of the coil spring 31. 
     From the uppermost position, the movable bracket 24 with the steering column tube 23 can be manually pivotted in the clockwise direction to lower the steering wheel to the most suitable steering wheel position. After the above steering wheel position adjustment, in other words after adjustment of the tilt of the upper steering column tube 26b, the tilt adjusting lever 36 is released from the counterclockwise force so that the tilt adjusting lever 36 returns to its initial position due to the spring force of the coil spring 47. The roller 35 thus moves out of the recess 45 along the cam surface 46 to bias the latch plate 43 towards the toothed plate 38 so that the latching teeth 44 engage the teeth 37. As a result, the movable bracket 24 and the upper steering column 23 are secured in the adjusted angular position. 
     FIG. 4 is an explanatory diagram of the geometry of the movement of the movable bracket 24, the linkage lever 39 and the toothed plate 38. As is apparent from FIG. 4, when the movable bracket 24 pivots about the pivot bolt 25 through an angle θ 1 , the displacement at the connector pin 41 is a fixed distance l 3 . Therefore, the pivot pin 40 is also displaced by the distance l 3 . If the distance between the connector pin 41 and the pivot bolt 25 is l 1  and the distance between the pivot 33 and the pivot pin 40 are given as l 1  and l 2  respectively, then the angle θ 2  through which the toothed plate 38 pivots l 1  /l 2  times larger than the angle θ 1 . 
     Therefore, as will be appreciated, according to the shown embodiment, the pivotal angle of the toothed plate 38 is greater than the corresponding pivot angle of the movable bracket 24. As a result, even if the teeth 38 and 44 are of a conventional pitch, the minimum angular increment of the steering column assembly tilt can be sufficiently small to allow delicate adjustment. 
     FIG. 5 shows a modification of the foregoing first embodiment of steering column tilt adjusting mechanism according to the present invention. In this modification, the latch plate 49 with teeth 44 is bracketed by a pair of guide members 50 and is formed with an elongated opening 51. As in the foregoing first embodiment, the tilt adjusting lever 36 is free to pivot about the pivot pin 33 projecting from the stationary bracket, as is the toothed plate 38 with the teeth 37. 
     The guide members 50 protrude from the stationary bracket and allow reciprocating, essentially up-and-down movement of the latch plate 49. A projecting pin 52 formed on the tilt adjusting lever 36 engages the elongated opening 51. The axis of the elongated opening 51 is inclined with respect to the axis of motion of the latch member 49 in order to cause reciprocal movement of the latch plate 49 in response to movement of the tilt adjusting lever 36. 
     Even though the movement of the latch plate 49 is different from that of the latch plate 43 in the foregoing first embodiment, the tilt adjusting function to be carried out by this modification is essentially the same as that of the foregoing first embodiment. 
     FIGS. 6 to 8 show another modification of the foregoing first embodiment of the steering column tilt adjusting mechanism according to the present invention. Referring to FIG. 7 this modification, a locking plate 61 is pivotably supported by the pivot pin 33. A roller 35&#39; is rotatably secured to the locking plate 61 for rotation about the roller axle 35a&#39;. As with the roller 35 of the foregoing first embodiment, the roller 35&#39; normally contacts the cam surface 46 of the latching plate 44 and can engage the recess 45 when the tilt adjusting lever 36 is actuated. The locking plate 61 also has a bent strip 63. The bent strip 63 opposes a point 63&#39; along the edge of the tilt adjusting lever 36. A coil spring 66 is stretched between the bent strip portion 63 and a hook 67 projecting from the tilt adjusting lever 36 in order to bias the bent strip portion 63 towards the point 63&#39; of the tilt adjusting lever 36 and establish contact therebetween. 
     The locking plate 61 has a hook 65 to which one end of a coil spring 64 is attached. The other end of the coil spring 64 is attached to the linkage plate 39. The linkage plate 39 has a projection 41&#39; which rotatably supports a roller 68. The roller 68 is adapted to engage a recess 60 formed in the lower edge of the movable bracket 24. 
     On the other hand, the upper edge of the linkage lever 39 opposes the lower edge 62a of the tilt adjusting lever 36 so that the linkage lever 39 will be depressed downward when the tilt adjusting lever 36 is moved clockwise. 
     The roller 35&#39; supported by the locking lever 61 normally contacts the cam surface 46 of the latch plate 43 to cause the latch teeth 44 to engage the teeth 37 of the toothed plate 38. As a result, movement of the linkage lever 39 is restricted. The linkage lever 39 is also biased upwardly by the coil spring 64 to ensure engagement between the roller 68 and the recess 60. Since movement of the linkage lever 39 is restricted due to the interengagement of the latch plate 43 and the toothed plate 38, movement of the movable bracket 24 and the upper steering column 23 is also restricted. Therefore, in the position illustrated in FIG. 7, the movable bracket 24 is held securely in place. 
     As in the foregoing first embodiment, the tilt adjustment can be performed by moving the tilt adjusting lever 36 counterclockwise. In response to counterclockwise movement of the tilt adjusting lever 36, the bent strip 63 of the locking plate 61 is driven to pivot the locking plate in the counterclockwise direction. According to this movement of the locking lever 61, the roller 35&#39; moves along the cam surface 46 to the recess 45. The roller 35&#39;, once within the recess 45, urges the latch plate 43 in the counterclockwise direction to release the engagement between the latch teeth 44 to the latch teeth 37 of the toothed plate 38. 
     At the same time, due to the counterclockwise movement of the locking plate 61, the linkage lever 39 is pulled upwards to pivot counterclockwise about the pin 40 by the spring force of the coil spring 64. Due to the upward movement of the linkage lever, the movable bracket 24 and the upper steering column 23 are moved counterclockwise to be positioned at the uppermost position. Thereafter, a suitable angular position can be selected by gradually lowering the upper steering column 23 and the movable bracket 24 from the uppermost position. 
     When a suitable steering column tilt is determined, the tilt adjusting lever 36 is returned to the initial position by clockwise rotation thereof. In response, the locking plate 61 is moved clockwise so that the roller 35&#39; returns to the cam surface 46 of the latch plate 43. The latch plate 43 is thus moved so that the latch teeth 44 engage the teeth 37 of the toothed plate 38. Due to the interengagement of the latching plate 43 and the toothed plate 38, the linkage lever 39 and movable bracket 24 are held securely in the selected steering column angular position. 
     During this tilt adjusting operation, the universal joint 26c interposed between the upper and lower steering column shafts 26b and 26a permits variation of the angle of the upper steering column shaft with respect to the lower steering column shaft. 
     In addition to the tilt-adjusting capability described above, this embodiment of the present invention also allows the steering column to be moved to its uppermost position and then returned to the previously selected position without having to be readjusted, as described below. 
     When the steering wheel must be moved, for example when the driver of the vehicle gets out of the vehicle or for some other reason, the tilt adjusting lever 36 is moved counterclockwise to release the steering column. Due to the clockwise movement of the tilt adjusting lever 36, the linkage lever 39 is depressed in the clockwise direction against the spring force of the coil spring 64 to release the roller 68 from the recess 60 of the movable bracket 24. As a result, the movable bracket 24 becomes free from the restriction due to the interengagement of the latch plate 43 and the toothed plate 38. The movable bracket 24 is then moved counterclockwise by the spring force of the coil spring 31. The counterclockwise movement of the movable bracket 24 is stopped when a stopper strip 24a formed on the upper edge of the movable member comes into contact with to a stopper edge 22a of the stationary bracket 22. 
     When the tilt adjusting lever 36 is moved clockwise, the point 63&#39; is released from the bent strip 63 so that the engagement between the latching plate 43 and the toothed plate 38 remains unaffected. 
     To return the movable bracket to the previous position, the movable bracket 24 is forced downwards against the force of the spring 31. During this clockwise movement of the movable bracket, a curved surface 24b of the movable bracket contacts the roller 68 to depress the linkage lever 39 downwardly. Therefore, the linkage lever 39 rotates about the pin 40 against the spring force of the coil spring 64. Due to the resilient force of the coil spring 64, the roller 68 moves along the curved surface 24a and enters the recess 60, thus locking the steering column back into the previously selected position. 
     FIG. 9 shows a further modification of the foregoing embodiment of FIGS. 6 to 8 which employs a tilt adjusting lever and a separate lever for temporarily moving the upper steering column upwards. In this modification, the lever 70 allowing temporary upward movement of the upper steering column 23 forms an extension of the linkage lever 39&#39;. The tilt adjusting lever 36 has essentially the same shape as that of the first embodiment of FIG. 1 and is actuable independently of the lever 70. The linkage lever 39&#39; rotatably supports the roller 68&#39; near the end proximal to the lever 70. The roller 68&#39; can rotate about the pin 41 and engage a recess 60 formed in the lower edge of the movable bracket 24. 
     As will be appreciated, the tilt adjusting operation is substantially identical to that illustrated with respect to the foregoing first embodiment. On the other hand, to temporarily move the upper steering column 23 and the movable bracket, the lever 70 is moved in the clockwise direction to release the roller 68&#39; from engagement with the recess 60. As a result, the movable bracket 24 and the upper steering column 23 pivot in the counterclockwise direction due to the spring force of the coil spring 31. At this time, the pin 40 allows rotation of the linkage lever 39&#39; independently of the toothed plate 38. Therefore, the toothed plate 38 remains in engagement with the latch plate 43. 
     As in the foregoing embodiment of FIGS. 6 to 8, returning the steering column to its previous position from the uppermost position is performed by depressing the movable bracket 24 and the upper steering column downwardly. During downward movement of the movable bracket, the curved surface 24b contacts the roller 68&#39; and depresses the linkage lever 29 to rotate clockwise about the pin 40. According to the downward movement of the movable bracket 24, the roller 68&#39; moves along the surface 24b to engage with the recess 60 at the position previously selected. 
     FIGS. 10 to 13 show the second embodiment of the tilt adjusting mechanism for the steering column assembly according to the present invention. As in the foregoing first embodiment, the lower steering column 120 has a dash bracket 121 through which the lower end of the lower steering column 120 is secured to the vehicle body B&#39;. The upper end of the lower steering column 120 is, in turn, secured by the stationary bracket 122. Thus, the lower steering column 122 is fixedly secured on the vehicle body by the stationary bracket 122 and the dash bracket 121. The movable bracket 124 at the lower end of the upper steering column 123 is pivotably connected to the stationary bracket 122 via the pivot bolt 125. 
     The upper and lower steering column shafts 126a and 126b are housed in the upper and lower steering column tubes 120 and 124 for rotation therein. The universal joint 126&#39; is interposed between the upper and lower steering column shafts 126b and 126a for transmission of the rotational steering force and to allow adjustment of the tilt of the upper steering column shaft 126b with respect to the lower steering column shaft 126a. The upper steering column shaft 126b supports a steering wheel 128 for steering operation. On the other hand, the lower end of the lower steering column shaft 126a is connected to the universal joint 129 to transmit the steering force to a steering mechanism (not shown). 
     The movable bracket 124 is biased in the counterclockwise direction in FIG. 12 to be normally urged upwardly by a coil spring 131, one end of which engages the movable bracket and the other end of which engages a hook 130 projecting from the stationary bracket 122. 
     The tilt adjusting lever 136 is pivotally mounted on the stationary bracket 122 via a pivot pin 133. A plate 137 with teeth 138 is also pivotably supported by the pivot pin 133. The toothed plate 137 has a pin 134 projecting therefrom. The pin 134 movably engages an elongated opening 132 formed in the movable bracket 124. Similarly, the pivot pin 133 is free to move along an elongated opening 139. The longitudinal axis of elongated opening 139 is essentially perpendicular to the longitudinal axis of the elongated opening 132. The teeth 138 of the toothed plate 137 oppose the teeth 141 of a latch plate 140 which is free to pivot about a pivot 135. The latch plate 140 is formed with a recess 142a and a cam surface 142b extending along one edge of the recess. A roller 143 rotatably about an axle 144 projecting from a tilt adjusting lever 136 normally remains in contact with the cam surface 142b. 
     The tilt adjusting lever 136 is biased in the counterclockwise direction by a coil spring 147, one end of which engages a hook portion 145 extending from the tilt adjusting lever and the other end engages a hook 146 projecting from the stationary bracket 122. 
     In the normal position, the tilt adjusting lever 136 is biased in the counterclockwise direction to drive the cam surface 142b of the latch plate 140 towards the toothed plate 137 for interengagement of the teeth 138 and 141. As a result, the movement of the movable bracket 124 about the pivot bolt 125 is restricted despite the resilient force provided by the coil spring 131. 
     To adjust the tilt of the steering column assembly, the tilt adjusting lever 136 is move in the clockwise direction in FIG. 12 to release the roller 143 from the cam surface 142b. Due to the rotational movement of the tilt adjusting lever 136, the roller 143 enters the recess 142a and urges the latch plate 140 to release the teeth 141 from engagement with the teeth 138 of the toothed plate 137. The toothed plate 137, thus, can rotate about the pin 133, thereby causing the pin 134 to move along the elongated opening 132 of the movable bracket 124. 
     At this time, the movable bracket 124 moves in the counterclockwise direction along with the upper steering column tube 123 due to the spring force of the coil spring 131. The toothed plate 137 can remain in place while the movable bracket 124 moves upwards since the pin 134 is free to move relative to the elongated opening 139. 
     After the movable bracket 124 and the upper steering column tube 123 reach their uppermost position, the movable bracket 124 can be manually forced downward while holding the tilt adjusting lever in the actuate position to select a suitable tilt position. When the steering column assembly is suitably positioned, the tilt adjusting lever 136 can be released to return to its initial position due to the force of the coil spring 147. During this return movement of the tilt adjusting lever 136, the roller 143 again comes into again contact with the cam surface 142b of the latch plate 140 to establish engagement between the sets of teeth 138 and 141. 
     During this steering column assembly tilt adjusting operation, the pin-and-opening engagement between the pin 133 and opening 139 and the pin 134 and the opening 132 serves to magnify the angular displacement of the toothed plate 137 in relation to the angular displacement of the movable bracket according to the ratio of the distances l 1  and l 2  in FIG. 12. That is, since the toothed plate 137 is pivoted about the pivot pin 134 and the rotational movement of the movable bracket 124 is transmitted by way of the pin 133, the angular displacement of the teeth 138 is l 1  /l 2  times larger than that of the pin 133. Therefore, even though the teeth has a conventional pitch, the minimum angular increment is sufficiently fine to allow precise adjustment. 
     FIG. 14 shows a modification of the foregoing second embodiment of the tilt adjusting device according to the present invention. In this modification, the latch plate 150 is bracketed by a pair of guides 155 for reciprocal movement toward and away from the teeth 138 of the toothed plate 137. The latch plate 150 is formed with an elongated opening 159 with an axis oblique to the axis of the latch plate. A pin 133&#39; projecting from the tilt adjusting lever engages the elongated opening. 
     In this structure, releasing the engagement of the teeth 138 and 151 is performed by moving the pin along the elongated opening 159 of the latch plate 150. In this modification, the tilt adjustment can be performed in essentially the same manner as set forth in the second embodiment.