Sterring column for motor vehicle

Abstract: A steering column (22) for a motor vehicle having a gear box (24) of an electric power assist apparatus (20) in front of the steering column. The steering column includes a rigid mast jacket (40) consisting of a short tubular sleeve and a bracket (44) attached to the tubular sleeve having a pair of laterally separated guides (48A,48B) straddling the gear box. A pair of lugs (52A,52B) on the gear box cooperate with a pair of elongated slots (54A,54B) in the guides in connecting the mast jacket to the gear box for vertical pivotal movement and for linear translation. A longitudinally collapsible steering shaft (86) is rotatably supported on the tubular sleeve with a steering hand wheel (96) at one end and a flexible coupling (94) at the other end connecting the steering shaft to an input shaft (26) on the gear box. The tubular sleeve (42) is connected to the vehicle body by a clamp (58) which releases the tubular sleeve for a collapse stroke of the mast jacket. The mast jacket protects the steering shaft against beam bending during the collapse stroke. The unobstructed span in front of the tubular sleeve between the guides (48A,48B) yields a collapse stroke of the mast jacket consistent with acceptable performance of an energy absorber.

Description: TECHNICAL FIELD This invention relates to a steering column for a motor vehicle. BACKGROUND OF THE INVENTION An energy absorbing steering column for a motor vehicle commonly includes a mast jacket consisting of a pair of telescopically related tubular elements, a steering shaft consisting of a pair of telescopically related shaft elements, and a steering hand wheel on the steering shaft. The steering shaft is rotatably supported on the mast jacket and collapses longitudinally with the mast jacket in response to an impact on the steering hand wheel. An energy absorber converts into work a fraction of the kinetic energy of the impact in response to longitudinal collapse of the mast jacket. In such steering columns, the mast jacket must be long enough to accommodate a longitudinal collapse stroke consistent with acceptable energy absorbing performance and the span of the telescopic overlap between the tubular elements thereof must afford enough rigidity in beam bending to substantially isolate the steering shaft from beam bending forces which would otherwise interfere with smooth longitudinal collapse of the steering shaft. In a motor vehicle having a stationary electric power assist apparatus in front of the steering column, the space occupied by the electric power assist apparatus reduces the space available for the mast jacket of such prior steering columns to the extent that the length of the mast jacket may not be consistent with both acceptable performance of the energy absorber and acceptable rigidity in beam bending. A steering column according to this invention has a longitudinal collapse stroke consistent with acceptable energy absorbing performance and has acceptable rigidity in beam bending in a motor vehicle environment including a stationary electric power assist apparatus in front of the steering column. "Research Disclosure - September, 1996" discloses a steering column having a gearbox of an electric power assist apparatus mounted on the body of a motor vehicle in front of the steering column. The disclosed steering column includes a mast jacket including a tubular sleeve and a bracket rigidly attached thereto, and having a pair of separated guides straddling the gear box. Mounting means are provided that are operative to connect the mast jacket to the gear box for up and down pivotal movement about a lateral centerline of the gear box and for linear translation in the direction of a longitudinal centerline of the mast jacket which intersects the lateral centerline of the gearbox. A collapsible steering shaft is supported on the tubular sleeve for rotation about the longitudinal centerline of the mast jacket, and a steering hand wheel is provided thereon at a first end of the mast jacket. A flexible coupling between the laterally separated guides is connected to the steering shaft and to an input shaft of the gearbox. Clamp means rigidly attached to the vehicle body are provided around the tubular sleeve and are operative to define an upper limit position and a lower limit position of vertical pivotal movement of the mast jacket about the gearbox lateral centerline, and to capture by friction the position of the mast jacket between its upper and lower limit positions in response to pivotal movement of a control lever from an unlocked position thereof to a locked position thereof. The steering shaft disclosed by this reference, however, is collapsible only by being provided with a slip joint between its upper and lower steering shaft elements. These elements are at no time, prior or subsequent to steering shaft collapse, linearly fixed together. Rather, these elements rely solely on the clamp means for maintaining their linear positions relative to each other. Further, these positions are only maintained when the control lever is in its locked position. Although this reference contemplates adaptation of the disclosed steering column to a rake (tilt) only assembly by changing the elongated holes in its lower pivot bracket and telescope bracket into net locator holes, such a modification does not then provide for linear translation of the mast jacket through a collapse stroke. Despite what the steering column disclosed by this reference may offer, it is often advantageous to provide a tiltably-adjustable steering column having a collapsible steering shaft of a length that remains fixed at all times prior to steering column collapse. This reference provides no teaching or suggestion, however, for providing such a steering column. U.S. Patent No. 5,673,937 discloses a steering column which does not include an electric power-assist mechanism, but which includes a mast jacket having clamping means thereabout for permitting rake (tilt) adjustment and longitudinal collapse of the mast jacket. This reference fails to disclose, however, a steering shaft which is ordinarily longitudinally adjustable, or longitudinally collapsible responsive to an impact on the steering hand wheel. Indeed, the structure disclosed by this reference is such that telescopic steering wheel adjustment, such as through use of the slip-jointed steering shaft of the above-discussed "Research Disclosure - September, 1996" reference, cannot be accommodated. Despite what the steering column disclosed by this reference may offer, it is often advantageous to provide a collapsible steering shaft in addition to a collapsible steering mast. This reference provides no teaching or suggestion, however, for providing such a steering column. SUMMARY OF THE INVENTION For motor vehicles having a gearbox of an electric power assist apparatus mounted on the vehicle body vehicle in front of the steering column, the shortcomings of previous steering columns are addressed by the present invention. The present invention provides a steering column for a motor vehicle having a gear box of an electric power assist apparatus mounted on a body of the motor vehicle in front of the steering column. The inventive steering column includes a mast jacket having a tubular sleeve, and a bracket rigidly attached to the tubular sleeve and having a pair of laterally separated guides straddling the gear box. A longitudinally collapsible steering shaft is supported on the tubular sleeve for rotation about a longitudinal centerline of the mast jacket, the steering shaft having a steering hand wheel thereon at a first end of the mast jacket. The inventive steering column further includes a mounting means operative to connect the mast jacket to the gear box for up and down pivotal movement about a lateral centerline of the gear box and for linear translation during collapse of the longitudinally collapsible steering shaft in the direction of the mast jacket longitudinal centerline, the mast jacket longitudinal centerline intersecting the gear box lateral centerline. A flexible coupling between the laterally separated guides is connected to the steering shaft and to an input shaft on the gear box. A clamp means is rigidly attached to the body of the motor vehicle around the tubular sleeve and is operative to define an upper limit position and a lower limit position of a vertical pivotal movement of the mast jacket about the lateral centerline of the gear box, and to capture by friction the tilt position of the mast jacket between the upper limit position and the lower limit position thereof in response to pivotal movement of a control lever from an unlocked position thereof to a locked position thereof. The longitudinally collapsible steering shaft includes telescopically-overlapping elements that are, prior to collapse of steering shaft, linearly fixed together regardless of whether the clamp control lever is in its locked or unlocked position. An impact on the steering hand wheel is operative to overpower the friction couple between the clamp means and the tubular sleeve to release the mast jacket from the clamp means for linear translation of the mast jacket through a collapse stroke during which the mounting means controls the position of a second end of the mast jacket opposite to its first end. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational view of a steering column according to this invention on a motor vehicle; Figure 2 is a partially broken-away perspective view of the steering column according to this invention; Figure 3 is a view taken generally along the plane indicated by lines 3-3 in Figure 2; Figure 4 is a sectional view taken generally along the plane indicated by lines 4-4 in Figure 3; Figure 5 is a sectional view taken generally along the plane indicated by lines 5-5 in Figure 4; and Figure 6 is an enlarged sectional view taken generally along the plane indicated by lines 6-6 in Figure 5. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figures 1-5, a body 10 of a motor vehicle has a passenger compartment 12 therein behind a schematically represented vertical panel 14 of the body. A generally flat support panel 16 is rigidly connected to the body 10 of the motor vehicle through a schematically represented bracket 18 behind the vertical panel 14. An electric power assist apparatus 20 is suspended from the support panel 16 adjacent the vertical panel 14. A steering column 22 according to this invention is suspended from the support panel 16 behind the electric power assist apparatus. The electric power assist apparatus includes a fragmentarily illustrated stationary gear box or housing 24 rigidly connected to the support panel 16, a tubular input shaft 26 rotatably supported on the gear box, a tubular output shaft 28 supported on the gear box for rotation relative to the input shaft, and an internal torsion bar 30 connected at one end to the input shaft and at the other end to the output shaft. The output torque of an electric motor 32 mounted on the gear box 24 is applied to the output shaft 28 through reduction gears, not shown, in the gear box. A universal coupling 34 connects the output shaft to an intermediate steering shaft 36 in front of the vertical panel 14. Another universal coupling 38 connects the intermediate steering shaft 36 to a pair of steered wheels, not shown, of the motor vehicle through a conventional steering gear, not shown. As seen best in Figures 2-5, the steering column 22 includes a mast jacket 40 consisting of a tubular sleeve 42 and a U-shaped bracket 44 welded or otherwise rigidly attached to the tubular sleeve so that the mast jacket is effectively a rigid, one-piece structural element of the steering column. The U-shaped bracket 44 has a web 46 and a pair of wide, flat guides 48A,48B straddling the gear box 24 parallel to a longitudinal centerline 50 of the mast jacket. A pair of rigid lugs 52A,52B on the gear box are closely received in respective ones of a pair of elongated slots 54A,54B in the guides 48A,48B. The longitudinal centerline 50 of the mast jacket intersects a lateral centerline 56 of the gear box defined by the lugs 52A,52B so that the lugs cooperate with the elongated slots in connecting the mast jacket to the gear box for up and down pivotal movement about the lateral centerline and for linear translation in the direction of the longitudinal centerline 50 of the mast jacket. A clamp 58 of the steering column 22 includes a pair of vertical brackets 60A,60B on opposite sides of the tubular sleeve 42 attached to the support panel 16. The vertical brackets 60A,60B are perforated by respective ones of a pair of substantially vertical slots 62A,62B. A spacer 64, Figures 4-5, is welded or otherwise rigidly attached to the tubular sleeve 42 between the vertical brackets and includes an undulation defining a lateral slot 66 in the spacer open toward an outboard end 68 of the tubular sleeve. A control shaft 70 of the clamp 58 spans the vertical brackets 60A,60B through the vertical slots 62A,62B and seats in the slot 66 in the spacer 64 so that the control shaft 70 is supported on the tubular sleeve 42 for up and down pivotal movement of spacer 64 and control shaft 70 as a unit with the mast jacket 40 about the lateral centerline 56. The ends of the vertical slots 62A,62B cooperate with the control shaft in defining an upper limit position 50' and a lower limit position 50" of the mast jacket 40. A control lever 72 is rigidly attached to the control shaft 70 outboard of the vertical bracket 60A. The control shaft 70 is pivotable as a unit with the control lever 72 between a locked position of the control lever 72 and an unlocked position thereof shown in solid and broken lines, respectively, in Figure 1. A nut 74 on a screw-threaded end of the control shaft 70 outboard of the other vertical bracket 60B is restrained against rotation relative to the vertical bracket 60B. Pivotal movement of the control lever 72 from its unlocked position to its locked position squeezes the vertical brackets 60A,60B against the ends of the spacer 64 to capture by friction the position of the mast jacket 40 between its limit positions 50',50''. Pivotal movement of the control lever 72 from its locked position to its unlocked position releases the friction couple between the vertical brackets 60A,60B and the ends of the spacer 64 to release the mast jacket for up and down pivotal movement about lateral axis 56 between its limit positions 50',50''. A spring 76, Figure 5, between the spacer 64 and a platform 78 defined by the vertical brackets 60A,60B biases the mast jacket toward its upper limit position 50'. A longitudinally collapsible steering shaft 80 of the steering column 22 includes a solid lower shaft element 82 and a tubular upper shaft element 84 telescopically overlapping the lower shaft element. The solid shaft element has a pair of flat sides 86A,86B cooperating with a corresponding pair of flat sides 88A,88B on the tubular shaft element, Figure 6, in coupling the solid and tubular shaft elements for unitary rotation and for relative linear translation. A plurality of plastic pins 90 are molded-in-place in corresponding passages in the solid and tubular shaft elements 82,84 and resist relative linear translation between the solid and tubular shaft elements 82,84 until the material strength of the pins 90 is exceeded, and shaft 80 collapses. Thus stearing shaft 80 is not telescopically adjustable, but rather its telescopically-overlapping elements 82,84 are, prior to collapse of steering shaft 80, linearly fixed together regardless of whether clamp control lever 72 is in its locked or unlocked position, as shown in Figure 4. A bearing 92 is interference fitted between the tubular shaft element 84 and the tubular sleeve 42 and supports the steering shaft 80 on the mast jacket 40 for rotation about the longitudinal centerline 50 of the mast jacket. A flexible coupling 94 is connected to the solid shaft element 82 and to the input shaft 26 on the gear box 24. A steering hand wheel 96 is attached to the tubular shaft element 84 at the top of the steering column 22. Manual effort applied at the steering hand wheel 96 is transferred by the steering shaft 80 and the flexible coupling 94 to the input shaft 26 and rotates the input shaft relative to the output shaft 28 against a restoring force induced by the torsion bar 30. A control module 98 mounted below the gear box 24 turns the electric motor 32 on and off in accordance with a signal from a torque sensor, not shown, in the gear box. The output torque of the electric motor 32 supplements the manual effort applied to the output shaft 28 through the torsion bar 30 to steer the motor vehicle. The force of an impact on the steering hand wheel 96 represented by a schematic force vector "F 1 " is transferred from the tubular shaft element 84 of the steering shaft to the tubular sleeve 42 of the mast jacket through the bearing 92. With the control lever 72 in its locked position, such force is resisted by the friction couple between the spacer 64 and the vertical brackets 62A,62B. When the friction couple between the vertical brackets 62A,62B and the spacer 64 is overpowered, the spacer 64 slides forward with mast jacket 40, from between the vertical brackets, the control shaft 70 releases from the slot 66 through the open side thereof, and the spring 76 releases from between the spacer and the platform 78. Thereafter, the mast jacket 40 traverses a collapse stroke "S", Figure 4, as the elongated slots 54A,54B in the guides 48A,48B slide over the lugs 52A,52B on the gear box and cooperate in controlling the position of the lower end of the mast jacket during the collapse stroke. An energy absorber, not shown, between the mast jacket 40 and the vehicle body 10 converts into work a fraction of the kinetic energy of the impact on the steering hand wheel 96 in response to linear translation of the mast jacket through its collapse stroke "S". Importantly, because the guides on the mast jacket straddle the gear box and are not in front of the tubular sleeve, the unobstructed span available for linear translation of the tubular sleeve yields a collapse stroke "S" consistent with acceptable performance of the aforesaid energy absorber. At the same time that the spacer 64 releases from between the vertical brackets 62A,62B, the plastic pins 90 fracture longitudinally to release the solid and the tubular shaft elements 82,84 from each other for relative telescopic collapse. Because the input shaft 26 on the gear box 24 and the flexible coupling 94 resist linear translation of the solid shaft 82 in the direction of the impact on the steering column represented by the force vector "F 1 ", the tubular shaft element 84 collapses telescopically over the solid shaft element 82 concurrent with linear translation of the mast jacket 40 through its collapse stoke "S". In the circumstance that an impact on the steering hand wheel 96 represented by a second schematic force vector "F 2 ", Figure 1, thrusts the mast jacket 40 upward during its collapse stroke against the support panel 16 between the vertical brackets 62A,62B, force reactions at the lugs 52A,52B and at the support panel load the mast jacket in beam bending. Because the mast jacket is effectively a rigid, one-piece structural element of the steering column and because of the relatively long span between the lugs and the vertical brackets made possible by the guides 48A,48B straddling the gear box 24, the mast jacket successfully resists significant deflection in beam bending. Accordingly, the mast jacket effectively isolates the steering shaft 80 from force reactions which would otherwise load the steering shaft in beam bending and significantly increase sliding friction between the solid and tubular shaft elements 82,84 during the collapse stroke "S" of the mast jacket.

Claims: A steering column (22) for a motor vehicle having a gear box (24) of an electric power assist apparatus (20) mounted on a body of the motor vehicle in front of said steering column, said steering column including: a mast jacket (40) including a tubular sleeve (42) and a bracket (44) rigidly attached to said tubular sleeve and having a pair of laterally separated guides (48A, 48B) straddling said gear box (24); a longitudinally collapsible steering shaft (80) supported on said tubular sleeve (42) for rotation about a longitudinal centerline (50) of said mast jacket (40), said steering shaft (80) having a steering hand wheel (96) thereon at a first end (68) of said mast jacket (40); a mounting means (52A, 52B, 54A, 54B) operative to connect said mast jacket (40) to said gear box (24) for up and down pivotal movement about a lateral centerline (56) of said gear box (24) and for linear translation during collapse of said longitudinally collapsible steering shaft (80) in the direction of said mast jacket longitudinal centerline (50), said mast jacket longitudinal centerline (50) intersecting said gear box lateral centerline (56); a flexible coupling (94) between said laterally separated guides (42A, 48B) connected to said steering shaft (80) and to an input shaft (26) on said gear box (24); and a clamp means (58) rigidly attached to the body of the motor vehicle around said tubular sleeve (42) and operative to define an upper limit position (50') and a lower limit position (50") of a vertical pivotal movement of said mast jacket (40) about said lateral centerline (56) of the gear box (24) and to capture by friction the tilt position of said mast jacket (40) between said upper limit position and said lower limit position thereof in response to pivotal movement of a control lever (72) from an unlocked position thereof to a locked position thereof; characterized by said longitudinally collapsible steering shaft (80) including telescopically-overlapping elements (82, 84) that are, prior to collapse of steering shaft (80), linearly fixed together regardless of whether said clamp control lever (72) is in its said locked or unlocked position, an impact (F 1 ) on said steering hand wheel (96) being operative to overpower the friction couple between said clamp means (58) and said tubular sleeve (42) to release said mast jacket (40) from said clamp means (58) for linear translation of said mast jacket (40) through a collapse stroke during which said mounting means (52A, 52B, 54A, 54B) controls the position of a second end of said mast jacket (40) opposite to said first end (68) of said mast jacket (40). The steering column for a motor vehicle recited in claim 1 characterized in that said mounting means includes a pair of lugs (52A, 52B) on said gear box (24) defining said lateral centerline (56) of said gear box, and a pair of elongated slots (54A, 54B) in respective ones of said guides (48A, 48B) straddling said gear box (24) closely and slidably receiving respective ones of said pair of lugs (52A, 52B) on said gear box (24). The steering column for a motor vehicle recited in claim 2, wherein said clamp means (58) includes a pair of vertical brackets (60A, 60B) connected to the body of the motor vehicle, said vertical brackets (60A, 60B) being located on opposite sides of said tubular sleeve (42) and each having a substantially vertical slot (62A, 62B) therein, a control shaft (70) rigidly connected to a control lever (72) and traversing said pair of vertical brackets (60A, 60B) and extending through said substantially vertical slots (62A, 62B), said upper and lower limit positions (50', 50") being defined by engagement of said control shaft against opposite ends of said pair of substantially vertical slots, a fastener means (74) operative in response to rotation of said control shaft (70) as a unit with said control lever (72) from said control lever unlocked position to said control lever locked position to tension said control shaft (70) between said pair of vertical brackets (60A, 60B) and thereby squeeze said vertical brackets (60A, 60B) against opposite ends of a spacer (64) rigidly attached to said tubular sleeve (42) between said vertical brackets (60A, 60B), said spacer (64) having a slot (66) therein, said control shaft (70) being pivotable up and down as a unit with said mast jacket (40) about said lateral centerline (56) of said gear box (24) between said upper and lower limit positions (50', 50"); characterized by said spacer slot (66) being open toward said first end (68) of said mast jacket, said control shaft (70) being seated in said spacer slot (66) prior to collapse of said longitudinally collapsible steering shaft (80) and unseated from said spacer slot (66) subsequent to collapse of said longitudinally collapsible steering shaft (80).

Inventors: ESCHENBACHER FLOYD E JR, GATZ LEROY L, LI XIAOYU, ROE KEVIN LAWRENCE, ROSS KEVIN CARLTON, STUEDEMANN RICHARD THOMAS, ESCHENBACHER, FLOYD E, JR., GATZ, LEROY L., LI, XIAOYU, ROE, KEVIN LAWRENCE, ROSS, KEVIN CARLTON, STUEDEMANN, RICHARD THOMAS
Applicants: DELPHI TECH INC, DELPHI TECHNOLOGIES, INC.
Application year: 1999
Main classification: B62D1
IPC codes: B62D1