Steering column assembly for vehicle

Abstract

A steering column assembly for a vehicle, comprising: an elongate steering column (14) mounted for rotation about a longitudinal axis (16) thereof and configured for attachment of a steering wheel (18) at one end; a gear (24) connected to the steering column at a position spaced apart from a steering wheel attachment position and configured to rotate together with the steering column; a motor (44) comprising a rotatable output shaft (34); a first worm (30) directly connected to and rotatable with an output shaft (34) of the motor and engaged with the gear (24); a damper (60) comprising a rotatable shaft (36); a second worm (32) directly connected to and rotatable with the shaft (32) of the damper and engaged with the gear (24); and a control device configured to operate the motor.

Description

Technical Field

[0001] The present invention relates to steering column assemblies for vehicles and, more particularly, to such assemblies for use with steer-by-wire steering wheel actuators.

[0002] The invention also relates to a vehicle comprising a steer-by-wire steering wheel actuator according to the invention. Background Art

[0003] In a steer-by-wire arrangement, a steering wheel (steering wheel) is connected to one end of a rotatably mounted shaft, the angular displacement of which is measured to generate a signal for controlling the orientation of the vehicle's steering wheels. The arrangement is also typically provided with an electric motor connected to the shaft to provide a controlled amount of torque in a direction opposite to the torque applied by the driver, in order to provide the driver with a sense of road feel.

[0004] In such an arrangement, typically an electric motor, under the control of an ECU (Electronic Control Unit), drives a worm which engages a worm gear which rotates with a shaft connected to the steering wheel. It is desirable to take steps to ensure that the worm is always engaged with the worm gear in order to reduce gear rattle which may occur when the direction and torque of the motor are reversed. Summary of the invention

[0005] According to a first aspect of the present invention, a steering column assembly for a vehicle comprises:

[0006] an elongated steering column mounted for rotation about its longitudinal axis and configured for attachment of a steering wheel at one end;

[0007] a gear connected to the steering column at a location spaced apart from a steering wheel attachment location and configured to rotate with the steering column;

[0008] a motor comprising a rotatable output shaft;

[0009] a first worm gear directly connected to and rotatable together with an output shaft of the motor and engaged with the gear;

[0010] a damper, the damper comprising a rotatable shaft;

[0011] a second worm gear directly connected to and rotatable together with the shaft of the damper and engaged with the gear; and

[0012] A control device is configured to operate the motor.

[0013] The motor is operated to generate feedback torque to the steering column and steering wheel to provide the driver with a sense of road feel, and the damper increases the motor feedback torque. In addition, in the event of a motor failure, the damper provides passive feedback torque to the driver. Coupling the damper via a second worm gear engaged with a gear connected to the steering column provides a compact package that is easier to fit into a vehicle.

[0014] The damper preferably includes a fluid chamber configured to contain a damping fluid and a body located in the fluid chamber, the body being configured to move with a rotatable shaft of the damper.

[0015] The use of such a viscous damper produces a driver feedback torque that increases with steering speed.

[0016] The body located within the fluid chamber may include a plurality of protrusions and / or recesses.

[0017] The body located within the fluid chamber may be spaced apart from a wall of the fluid chamber.

[0018] The body located within the fluid chamber may include a portion of increased width.

[0019] The body located within the fluid cavity may form part of, or may be attached to, a rotatable shaft of the damper.

[0020] Furthermore, the rotatable shaft of the damper can be displaced longitudinally in the direction of its axis of rotation.

[0021] Providing and damping the axial movement of the rotatable shaft with a damper reduces the noise generated by the clearance between the second worm and the gear attached to the steering column, especially when the rotation direction of the steering column is reversed.

[0022] The rotatable shaft of the damper may be mounted to allow it to pivot or articulate.

[0023] This accommodates any lateral movement of the damper shaft due to its longitudinal displacement.

[0024] Preferably, the steering column assembly comprises a bearing arrangement configured to allow the rotatable damper shaft to pivot or articulate.

[0025] The steering column assembly may further include a biasing device configured to urge the second worm gear toward contact with a gear connected to the steering column.

[0026] This reduces the backlash between the second worm and the gear attached to the steering column and helps to reduce rattling noises that may occur, particularly during torque reversal.

[0027] Preferably, the steering column assembly includes bearing means for rotatably mounting a rotatable shaft of the damper, the biasing means engaging the bearing means.

[0028] The biasing means may engage with the outer race of the bearing means.

[0029] Preferably, the biasing means comprises a spring, such as a leaf spring.

[0030] The steering column assembly may further include a spring acting on the rotatable output shaft of the motor, the spring being configured to apply torque to the motor shaft, and / or a spring acting on the rotatable shaft of the damper, the spring being configured to apply torque to the damper shaft.

[0031] The return spring may be arranged to provide a return torque over the entire angular range of the steering column. The net torque provided by the spring may act in a direction to return the steering column to the straight ahead position. Furthermore, the torque provided by the spring preferably increases as the steering column is further rotated away from the straight ahead position.

[0032] The spring acting on the rotatable output shaft of the motor and / or the spring acting on the rotatable shaft of the damper preferably comprises a helical spring.

[0033] The steering column assembly may further include a motor position sensor device for sensing a rotational position of the motor output shaft, the sensor device including a target member rotatable together with the motor shaft and a sensor for detecting the target member.

[0034] This helps calculate the appropriate feedback torque to be produced by the motor.

[0035] The steering column assembly may further include a position sensor device for sensing a rotational position of the damper shaft, the sensor device including a target member rotatable together with the damper shaft and a sensor for detecting the target member.

[0036] Measurement of the angular displacement and / or angular velocity of the damper shaft improves the prediction of the amount of torque to be produced by the damper and therefore the amount of torque to be produced by the motor.

[0037] The steering column assembly may include a member configured to rotate with a rotatable damper shaft, the damper shaft being displaceable relative to the member along its rotational axis, and the target member being mounted on the member.

[0038] This arrangement accommodates movement of the damper shaft in the axial direction and ensures that a constant spacing exists between the target member and the sensor device.

[0039] For example, the steering column assembly may include a cup-shaped member mounted at one end of the rotatable damper shaft, and the motor position sensor device is mounted on the cup-shaped member.

[0040] The first worm may form part of a motor output shaft and / or the second worm may form part of a rotatable damper shaft.

[0041] The first worm gear and the second worm gear may engage with a gear connected to the steering column at diametrically opposite positions.

[0042] The steering column assembly preferably includes a housing within which the first and second worm gears and a gear connected to the steering column are located.

[0043] The invention also comprises a vehicle comprising a steering column according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0045] Figure 1 is a schematic diagram of a known steer-by-wire system;

[0046] Figure 2 is a partially cut-away perspective view of a first embodiment of a steering column assembly according to the present invention;

[0047] Figure 3 is along Figure 2 Arrow III – Observed in the direction of III Figure 2 A vertical cross-section of a steering column assembly of , wherein portion A is shown in an enlarged scale;

[0048] Figure 4 yes Figure 2 a side view of a steering column assembly;

[0049] Figure 5 yes Figure 2 Schematic diagram of torque control of a steering column assembly;

[0050] Figure 6 is a partially cut-away perspective view of a second embodiment of a steering column assembly according to the present invention;

[0051] Figure 7 is along Figure 6 The arrow VI I–VI I is viewed from the direction Figure 6 A vertical cross-section of a steering column assembly of , wherein portion B is shown in an enlarged scale;

[0052] Figure 8 is a vertical section through a portion of a third embodiment of a steering column assembly according to the present invention, the third embodiment being Figure 6A variation of a steering column assembly;

[0053] Fig. 9 is a partially cutaway perspective view of a fourth embodiment of a steering column assembly according to the present invention, wherein portion C is shown in an enlarged scale;

[0054] Fig.10 is along Fig. 9 Arrow X – Observed in the direction of X Fig. 9 A vertical cross-section of a steering column assembly; and

[0055] Fig.11 is a cross section through a fifth embodiment of a steering column assembly according to the invention, the fifth embodiment being a variant that may be used with any of the preceding embodiments. DETAILED DESCRIPTION

[0056] Figure 1 A known steer-by-wire system S for a vehicle is shown, which includes a steering assembly 10 according to the present invention. The steer-by-wire system S includes a steering wheel actuator in the form of a steering wheel A to allow the driver of the vehicle to provide input steering commands. The steering wheel A is connected to the end of an elongated steering shaft B.

[0057] Steering input applied through the steering wheel A is detected by a steering sensor (at Figure 1 A signal representing the steering input (i.e., the rotation of the steering wheel A and the steering shaft B) is transmitted from the sensor C to an electronic control unit (ECU) D, which in turn controls the steering axle actuator E. The steering axle actuator E applies the steering input to the steering axle F, thereby steering the steering wheels G according to the rotational position of the steering wheel A.

[0058] The electronic control unit D is also configured to supply current to a torque feedback motor H connected to the shaft B, which applies a torque in the opposite direction to the torque applied to the steering wheel A in order to provide the driver with a sense of "road feel".

[0059] exist Figure 1 The damper J shown schematically in FIG. 1 is connected to the steering shaft B and introduces feedback torque to the steering wheel A when a steering input is applied. Figure 1 The damper J is shown mounted halfway along the steering shaft B, ie, between the ends of the steering shaft B, so that the steering shaft B passes through the damper J, but this is not necessary.

[0060] exist Figures 2 to 4 A first embodiment of a steer-by-wire column assembly 10 according to the invention is shown in FIG. The assembly 10 comprises a straight, elongated steer-by-wire steering column 14 (only the lower end of which is shown) which is rotatably mounted about its longitudinal axis 16. Figure 1A steering wheel 18 schematically shown in the figure is fixed to the upper end of the steering column 14, and the driver can turn the steering column 14 through the steering wheel. In the drawings, the steering column 14 is shown as a single shaft, but in reality it may be formed by multiple parts. For example, the steering column may be formed by several telescopic parts and may have a torque sensor (e.g., a torsion bar assembly) located between the steering wheel 18 and the opposite end of the steering column 14.

[0061] The opposite lower end of the steering column 14 is received in a housing 20 in which it is rotatably mounted. Figure 3 As best shown in FIG. 1 , a spur gear (pinion) 24 is fixedly mounted on the lower end of the steering column 14 within the housing 20 and is thereby constrained to rotate with the steering column 14 and the steering wheel 18 .

[0062] Two identical worms 30, 32 are rotatably mounted within the housing 20 and mesh with the spur gear (pinion) 24 at diametrically opposed locations on opposite sides of the gear. Each worm 30, 32 is formed on the surface of a respective shaft 34, 36, which are oriented parallel to each other and perpendicular to the axis of rotation 16 of the steering column 14. The shafts 34, 36 are rotatably mounted within the housing by lower and upper bearings 38, 40 which are positioned just beyond the lower and upper ends of the worms 30, 32 in use.

[0063] like Figure 3 As best shown in the drawings, the first shaft 34 forms the output shaft of the electric motor 44 and is directly driven by the motor. A motion position sensor (MPS) target magnet 48 is securely fixed to the lower end of a mounting cup 50 (the mounting cup 50 is fixed to the lower end of the shaft 34 below the motor 44) so ​​as to rotate with the shaft 34. The rotation of the MPS target magnet 40 is detected by an MPS sensor 52 mounted on the upper surface of an MPS sensor circuit board 54 (which is mounted within the housing 20). An electronic control unit (ECU) (not shown in the drawings) is also mounted on the circuit board 54. The MPS target magnet 48 and the MPS sensor 52 are known, and different types of magnets and sensors can be used depending on the circumstances.

[0064] Further references Figure 3A viscous damper, generally indicated at 60, is mounted on the other shaft 36 at a position below the lower bearing 38. The viscous damper comprises a generally cylindrical block 62 which is rotatably mounted within a complementary cylindrical recess 63 in the housing 20. The recess 63 contains a damping fluid (e.g. silicone fluid) which is retained by an annular lower annular seal 64 and an upper annular seal 65 which are in contact with the lower and upper portions of the cylindrical block 62, respectively. The central portion of the cylindrical block 62 is provided with four identical, equidistant annular grooves 66 which define three identical annular fins 68 whose peripheries are adjacent to but slightly spaced from the walls of the recess 63.

[0065] The torque applied by the viscous damper is a function of the spacing between the perimeter of cylindrical block 62 and the wall of recess 63, the number and size of grooves 66 and annular fins 68, and the viscosity of the damping fluid, as will be discussed further below.

[0066] A motion position sensor (MPS) target magnet 70 is securely fixed to the lower end of a mounting cup 72 (which is fixed to the lower end of the damper shaft 36 below the viscous damper 60) so as to rotate with the shaft 36. The rotation of the MPS target magnet 70 is detected by an MPS sensor 74 mounted on the upper surface of an MPS sensor circuit board 76. The MPS target magnet 70 and the MPS sensor 74 are known, and different types of magnets and sensors may be used depending on the situation.

[0067] The motor 44 provides feedback torque to the steering column 16 (and thus to the steering wheel 18) in response to the driver's demand. The viscous damper 60 also resists the rotation of the steering wheel and applies a feedback torque to the driver that is a function of the rotational speed of the steering wheel. The viscous damper 60 also helps to keep the worm 30 connected to the output of the motor 44 in contact with the spur gear 24 and helps to reduce gear rattle that may occur when the direction and torque of the motor are reversed. In addition, the viscous damper 60 also ensures that a certain degree of feedback torque is always generated even if the motor 44 is not operating.

[0068] The above embodiments can be based on Figure 5 In the following description, "step" is abbreviated as "S".

[0069] In S100, the desired driver feedback torque is calculated in a known manner using information from the angular displacement and angular velocity of a steering wheel actuator (e.g., steering wheel 18). Other inputs may be involved in the calculation process, such as estimated front axle actuator rack force, inputs from vehicle motion sensors (e.g., yaw rate, lateral acceleration, and vehicle speed), etc. In S102, the damper torque is estimated based on the damper angular velocity, which is calculated based on the position of the damper determined by the MPS target magnet 70 and the MPS sensor 74 (e.g., by determining the change in angular position within a certain time interval). Alternatively, the angular velocity of the damper can be estimated in S102 by measuring the movement and / or position of different system components (e.g., motor 44 and / or steering column 14) and inferring the damper angular velocity.

[0070] Then, the damper torque estimated in S102 is subtracted from the total torque demand calculated in S100, and the difference is the torque required to be provided by the motor 44. Alternatively, in S104, a friction compensation torque component may be estimated by a known method based on the torque required to be provided by the motor 44 and a signal representing the speed of the motor 44. The estimated friction compensation torque component is added to the previously calculated torque required to be provided by the motor 44, and the active demand is adjusted according to the gearbox ratio in S106 to determine the torque demand of the motor 44.

[0071] Alternatively, a sensor may be installed in the input shaft 14 / 16 to measure the net torque felt by the driver. In this case, a closed loop may be used to control the active components of the system to achieve the desired driver feedback torque.

[0072] exist Figures 6 to 8 A second embodiment of the present invention is shown in FIG. Many features of the second embodiment are very similar to those of the first embodiment and corresponding features are indicated by the same reference numerals with 200 added.

[0073] The assembly 210 includes a straight, elongated steer-by-wire steering column 214 (only the lower end of which is shown) which is rotatably mounted about its longitudinal axis 216. Figure 1 A steering wheel 218 schematically shown in the figure is fixed to the upper end of the steering column 214, and the driver can turn the steering column 214 through the steering wheel. In the drawings, the steering column 214 is shown as a single shaft, but in fact it may be formed by multiple parts. For example, the steering column can be formed by several telescopic parts and can have a torque sensor (e.g., a torsion bar assembly) located between the steering wheel 18 and the opposite end of the steering column 214.

[0074] The opposite lower end of the steering column 214 is received in a housing 220 in which it is rotatably mounted. Figure 7As best shown in FIG. 2 , a spur gear (pinion) 224 is fixedly mounted on the lower end of the steering column 214 within the housing 220 , thereby being constrained to rotate with the steering column 214 and the steering wheel 218 .

[0075] Two identical worms 230, 232 are mounted in the housing 220 and mesh with a spur gear (pinion) 224 at diametrically opposed locations on opposite sides of the gear. Each worm 230, 232 is formed on the surface of a corresponding shaft 234, 236, which are oriented parallel to each other and perpendicular to the axis of rotation 216 of the steering column 214. The shaft 234 is rotatably mounted in the housing by a lower bearing 238 and an upper bearing 240 positioned just beyond the lower and upper ends of the worm 230 in use. The shaft 236 is rotatably mounted in the housing by a lower bearing 239 located at the lower end of the shaft 236 and an upper bearing 240 positioned just beyond the upper end of the worm 230 in use.

[0076] like Figure 7 As best shown in the drawings, the first shaft 234 forms the output shaft of the electric motor 244 and is directly driven by the motor. A motion position sensor (MPS) target magnet 248 is securely fixed to the lower end of a mounting cup 250 (the mounting cup 250 is fixed to the lower end of the shaft 234 below the motor 244) so ​​as to rotate with the shaft 234. The rotation of the MPS target magnet 240 is detected by an MPS sensor 252 mounted on the upper surface of an MPS sensor circuit board 254 (which is mounted within the housing 220). An electronic control unit (ECU) (not shown in the drawings) is also mounted on the circuit board 254. The MPS target magnet 248 and the MPS sensor 252 are known, and different types of magnets and sensors can be used depending on the circumstances.

[0077] Further references Figure 7 and Figure 8 A viscous damper, generally indicated at 260, is mounted on the other shaft 236 at a position below the worm 232. The viscous damper comprises a generally cylindrical block 262 which is rotatably mounted within a complementary cylindrical recess 263 in the housing 220. The recess 263 contains a damping fluid (e.g., a silicone fluid) which is retained by an annular lower annular seal 264 and an upper annular seal 265 which are in contact with the lower and upper portions of the cylindrical block 262, respectively. The central portion of the cylindrical block 262 is provided with five identical, equidistant annular grooves 266 which define four identical annular fins 268 whose peripheries are adjacent to but slightly spaced from the walls of the recess 263.

[0078] A motion position sensor (MPS) target magnet 270 is securely secured to the lower end of a mounting cup 272. The lower end of the damper shaft 236 is slidably mounted within the mounting cup 272 to allow it to be displaced along its axis of rotation, but is rotationally positioned relative to the mounting cup 272 by a key 273. Thus, the damper shaft 236 rotates with the mounting cup 272, but is axially movable relative to the mounting cup. The rotation of the MPS target magnet 270 is detected by an MPS sensor 274 mounted on the upper surface of an MPS sensor circuit board 276. The MPS target magnet 270 and the MPS sensor 274 are known, and different types of magnets and sensors may be used depending on the circumstances.

[0079] As in the first embodiment, the viscous damper 260 resists the rotation of the steering wheel and applies a feedback torque to the driver that is a function of the rotational speed of the steering wheel. However, in addition, in this embodiment, the damper shaft 236 is also able to move longitudinally coaxially with its axis of rotation so that the damper 260 provides damping in both the rotational and axial directions.

[0080] The upper end of the damper shaft 236 is slidably mounted in the upper bearing 240. As previously described, the lower end of the damper shaft 236 is slidably mounted in the mounting cup 272, but rotationally fixed relative to the mounting cup. Thus, the damper shaft 236 is also able to be displaced along its rotational axis, but by mounting the lower end of the damper shaft 236 within the mounting cup 272, a constant spacing is maintained between the MPS target magnet 270 and the MPS sensor 274 regardless of the axial position of the damper shaft 236.

[0081] It will also be observed that an annular lower compliant support 280 and an upper compliant support 282 are mounted on the damper shaft 236. The lower compliant support 280 is mounted between the lower end of the cylindrical block 262 of the viscous damper 260 and the upper end of the mounting cup 272, and the upper compliant support 282 is mounted between a radially extending annular shoulder 284 just above the upper end of the damper worm 232 and the inner surface of the upper bearing 240. The lower compliant support 280 and the upper compliant support 282 are identical and known, each comprising identical upper and lower cup washers 286 arranged with their concave surfaces facing each other and an elastically deformable (e.g. silicone rubber) annular plug 288 arranged between and separating the concave surfaces of the two washers 286.

[0082] As with the first embodiment, the rotational torque applied by the viscous damper 260 is a function of the spacing between the perimeter of the cylindrical block 262 and the wall of the recess 264, the number and size of the grooves 266 and annular fins 268, and the viscosity of the damping fluid.

[0083] Additionally, in this embodiment, the damper shaft 236 is also capable of longitudinal displacement along its rotational axis, which provides damping in the longitudinal direction and helps reduce noise generated by impact between the spur gear 224 and the worm 232 when the direction of motion of the spur gear changes. The lower compliant support 280 and the upper compliant support 282 provide a flexible impact for the damper shaft 236 at the extreme end of the longitudinal displacement of the damper shaft.

[0084] exist Figure 8 1 and 2, which is a modification of the second embodiment. The third embodiment is very similar to the second embodiment and corresponding features are indicated by the same reference numerals increased by 100. The modification is to the damper body 262 of the second embodiment and therefore only that portion 362 of the third embodiment is shown.

[0085] like Figure 8 As shown, the viscous damper 360 includes a generally cylindrical block 362 that is rotatably mounted in a complementary cylindrical recess 364 in the housing 320. The recess 363 contains a damping fluid (e.g., a silicone fluid) that is retained by an annular lower seal 364 and an upper seal 365 that are in contact with the lower portion 362b and the upper portion 362a of the cylindrical block 362, respectively. The central portion 362c of the cylindrical block 362 is also cylindrical, but has a larger diameter and is separated from the lower portion 362b and the upper portion 362a by peripheral grooves 366a, 366b. The diameter of the central portion 362c is slightly smaller than the inner diameter of the recess 363, so the central portion 362c is slightly spaced from the inner wall of the recess 363.

[0086] As in the second embodiment, the damper 360 is rotationally displaceable and longitudinally displaceable along its rotation axis. When the worm shaft 336 moves axially, the enlarged central portion 362c of the cylindrical block 362 produces a piston effect in the recess 364 by means of fluid transfer between the fluid chambers 367a, 367b on both sides of the central portion 362c.

[0087] The structure and operation of the third embodiment are otherwise the same as those of the second embodiment.

[0088] exist Fig. 9 and Fig.10 A fourth embodiment of the present invention is shown in . Many features of the fourth embodiment are very similar to those of the first embodiment and corresponding features are indicated by the same reference numerals with 400 added.

[0089] The assembly 410 includes a straight, elongated steer-by-wire steering column 414 (only the lower end of which is shown) which is rotatably mounted about its longitudinal axis 416. Figure 1A steering wheel 418 schematically shown in the figure is fixed to the upper end of the steering column 414, and the driver can turn the steering column 414 through the steering wheel. In the drawings, the steering column 414 is shown as a single shaft, but in reality it may be formed by multiple parts. For example, the steering column can be formed by several telescopic parts and can have a torque sensor (e.g., a torsion bar assembly) located between the steering wheel 418 and the opposite end of the steering column 414.

[0090] The opposite lower end of the steering column 414 is received in a housing 420 in which it is rotatably mounted. Figure 3 As best shown in FIG. 4 , a spur gear (pinion) 424 is fixedly mounted on the lower end of the steering column 414 within the housing 420 , thereby being constrained to rotate with the steering column 414 and the steering wheel 418 .

[0091] like Fig.10 As best shown in FIG. 4 , two identical worms 430, 432 are mounted within the housing 420 and mesh with a spur gear (pinion) 424 at diametrically opposed locations on opposite sides of the gear. Each worm 430, 432 is formed on the surface of a corresponding shaft 434, 436, which are oriented parallel to each other and perpendicular to the rotation axis 416 of the steering column 414. The shafts 434, 436 are rotatably mounted within the housing by lower bearings 438a, 438b and upper bearings 440a, 440b. The lower bearing 438b and upper bearing 440b of the motor shaft 434 are positioned just beyond the lower and upper ends of the motor worm 430. The upper bearing 440b of the damper shaft 436 is positioned just beyond the upper end of the damper worm 432, with the lower bearing 438b positioned toward the lower end of the damper shaft 436, which is opposite to the position of the lower bearing of the first embodiment. In this embodiment, the cover plate 451 is also fixed to the housing 420 above the upper end of the damper shaft 436 .

[0092] like Fig. 9 and Fig.10 As shown, a leaf spring 490 is mounted on the exterior of the housing 420. The leaf spring comprises a longer, generally straight portion 491 (although it will bend in use, as will be explained) having an enlarged head 492 at one end by which the leaf spring is secured to the outer surface of the housing 420 by means of bolts 493. A shorter, generally straight second portion 494 extends substantially perpendicularly to the longer portion 491, the two portions joining at a curved junction 495. The shorter portion 494 of the leaf spring 490 passes through a hole 496 in the housing 420 and its free end abuts against an outer race 498 of the upper bearing 440b of the damper shaft 436.

[0093] In use, the leaf spring 490 is mounted on the housing 420 so that the longer portion 491 is bent, thereby applying a radial force to the outer race 498 of the upper bearing 440b of the damper shaft 463 through the free end of the shorter portion 494 to keep the worm 432 in contact with the teeth of the spur gear 424.

[0094] like Fig.10 As best shown in the drawings, the first shaft 434 forms the output shaft of the electric motor 444 and is directly driven by the motor. A motion position sensor (MPS) target magnet 448 is securely fixed to the lower end of a mounting cup 450 (the mounting cup is fixed to the lower end of the shaft 434 below the motor 444) so ​​as to rotate with the shaft 434. The rotation of the MPS target magnet 440 is detected by an MPS sensor 452 mounted on the upper surface of an MPS sensor circuit board 454 (which is mounted within the housing 420). An electronic control unit (ECU) (not shown in the drawings) is also mounted on the circuit board 454. The MPS target magnet 448 and the MPS sensor 452 are known, and different types of magnets and sensors may be used depending on the circumstances.

[0095] Further references Fig.10 , a viscous damper, generally indicated at 460, is mounted on the other shaft 432 at a position located between the lower bearing 438b and the lowermost end of the damper screw 436. The viscous damper 460 includes a generally cylindrical block 462 which is rotatably mounted in a complementary cylindrical recess 463 in the housing 420. The cylindrical block 462 of this embodiment is much longer than the corresponding cylindrical block 62 of the first embodiment and extends at its lower end to and is mounted in the lower bearing 438b. The central portion of the cylindrical block 462 is provided with five identical, equidistant annular grooves 466 which define four identical annular tabs 468 whose peripheries are adjacent to but slightly spaced from the walls of the recess 463. Recess 463 contains a damping fluid (e.g., silicone fluid) which is retained by annular lower and upper annular seals 464, 465 which contact portions of cylindrical block 462 just below and just above annular fin 468. The seals are selected to accommodate movement of shaft 436 as it articulates to maintain contact with spur gear 424.

[0096] As with the previous embodiments, the torque applied by the viscous damper is a function of the spacing between the perimeter of the cylindrical block 462 and the wall of the recess 463, the number and size of the grooves 466 and annular fins 468, and the viscosity of the damping fluid. In this embodiment, the damper is designed to be relatively insensitive to changes in the spacing between the block 462 and the wall 463 that may occur when the shaft 436 articulates.

[0097] A motion position sensor (MPS) target magnet 470 is securely fixed to the lower end of a mounting cup 472, which is fixed to the lower end of the damper shaft 436 below the viscous damper 460, so as to rotate with the shaft 436. The rotation of the MPS target magnet 470 is detected by an MPS sensor 474 mounted on the upper surface of an MPS sensor circuit board 476. The MPS target magnet 470 and the MPS sensor 474 are known, and different types of magnets and sensors may be used depending on the situation.

[0098] The motor 444 provides feedback torque to the steering column 416 (and thus to the steering wheel 418) in response to the driver's demand. The viscous damper 460 also resists the rotation of the steering wheel and applies a feedback torque to the driver that is a function of the rotational speed of the steering wheel. The viscous damper 460 also helps to keep the worm 430 connected to the output of the motor 444 in contact with the spur gear 424 and helps to reduce gear rattle that may occur when the direction and torque of the motor are reversed. In addition, the viscous damper 460 also ensures that a certain degree of feedback torque is always generated even if the motor 444 is not operating.

[0099] Although the use of a spring 490 to bias the damper worm shaft is shown for a particular embodiment, it is equally applicable to all previous embodiments.

[0100] Fig.11 is a cross section through a fifth embodiment of the invention, which is a variation that can be used with any of the previous embodiments. This variation will be described with reference to the first embodiment, but it applies equally to all embodiments.

[0101] Fig.11 Variations include the addition of a return spring acting on the motor shaft 34 , the damper worm shaft 36 , or both. Fig.11 The input shaft 14 is shown meshing with a spur gear (pinion) 24. The spur gear 24 in turn meshes with a motor worm 30 on a motor worm shaft 34 and with a damper worm 32 on a damper shaft 36.

[0102] In this embodiment, a clockwork type coil spring 502 is mounted on the upper end of the motor shaft 34, wherein the inner end of the spring 502 is attached to the motor worm shaft 34 and the outer end of the spring 502 is attached to the housing 20. Similarly, an identical second coil spring 504 is mounted on the upper end of the damper shaft 36, wherein the inner end of the spring 502 is attached to the damper shaft 36 and the outer end of the spring 504 is attached to the housing 20. The coil spring allows a large rotation angle in a small package.

[0103] In this particular embodiment, the two springs 502, 504 are arranged to act partially oppositely. The springs 502, 504 can be preloaded in opposite directions so that they remain tensioned in the same direction throughout their operating range. The preload provides compensation for the backlash between the respective worm 30, 32 and the spur gear (pinion) 24. Therefore, if desired, one or more devices for backlash control in the previous embodiments can be omitted.

[0104] In an alternative construction, only a single spring 504 is used in conjunction with the motor worm shaft 34. In this case, the return spring is arranged to provide a return torque throughout the angular range of the steering wheel 18. The net torque provided by the spring acts in the direction of returning the steering wheel to a straight-ahead angle. In addition, the torque provided by the spring increases as the steering wheel is rotated further away from the straight-ahead angle.

[0105] In all the above embodiments, the damper provides rotational damping to increase the motor feedback torque. In addition, in the event of a motor failure, the damper provides passive feedback torque to the driver.

[0106] Coupling the damper via the second worm shaft provides a compact package that facilitates fitting into a vehicle.

[0107] For those embodiments in which the worm shaft can move axially and can be damped, noise generated by clearance in the worm gearbox is reduced, particularly when the steering wheel direction is reversed.

[0108] As described above with respect to the fifth embodiment, coupling the damper via a second worm shaft and controlling the backlash in the worm gearbox with a spring loaded worm system allows the damper to be included in a compact package with gearbox noise control.

[0109] Providing a preload to the return springs on both the motor shaft and the damper shaft compensates for the worm / worm gear compensation, which may be sufficient to eliminate the need for an additional mechanism.

[0110] The invention is not restricted to the details of the foregoing embodiments.

Claims

1. A steering column assembly for a vehicle, comprising: an elongated steering column mounted for rotation about its longitudinal axis and configured for attachment of a steering wheel at one end; a gear connected to the steering column at a location spaced apart from a steering wheel attachment location and configured to rotate with the steering column; a motor comprising a rotatable output shaft; a first worm gear directly connected to and rotatable together with an output shaft of the motor and engaged with the gear; a damper, the damper comprising a rotatable shaft; a second worm gear directly connected to the damper shaft and rotatable therewith and engaged with the gear; as well as A control device is configured to operate the motor.

2. The steering column assembly according to claim 1, wherein: The damper includes a fluid chamber configured to contain a damping fluid and a body positioned in the fluid chamber, the body configured to move with a rotatable shaft of the damper.

3. The steering column assembly according to claim 2, wherein: The body located within the fluid chamber includes a plurality of protrusions and / or recesses.

4. A steering column assembly according to claim 2 or claim 3, wherein: The body located within the fluid chamber is spaced apart from a wall of the fluid chamber.

5. The steering column assembly according to any one of claims 2 to 4, wherein: The body within the fluid chamber includes a portion of increased width.

6. A steering column assembly according to any one of claims 2 to 5, wherein: The body located within the fluid chamber forms part of a rotatable shaft of the damper.

7. A steering column assembly according to any one of claims 2 to 5, wherein: The body within the fluid chamber is attached to a rotatable shaft of the damper.

8. A steering column assembly according to any one of the preceding claims, wherein: The rotatable shaft of the damper can be displaced longitudinally in the direction of its rotation axis.

9. The steering column assembly according to claim 8, wherein: The rotatable shaft of the damper is mounted to allow it to pivot or articulate.

10. A steering column assembly according to claim 9, including a bearing arrangement configured to allow the rotatable damper shaft to pivot or articulate.

11. A steering column assembly according to any preceding claim, comprising biasing means configured to urge the second worm towards contact with the gear connected to the steering column.

12. A steering column assembly as claimed in claim 9 including bearing means for rotatably mounting a rotatable shaft of said damper, said biasing means engaging said bearing means.

13. The steering column assembly according to claim 10, wherein: The biasing means engages an outer race of the bearing means.

14. A steering column assembly according to any one of claims 11 to 13, wherein: The biasing means comprises a spring.

15. The steering column assembly of claim 14, wherein: The spring comprises a leaf spring.

16. A steering column assembly according to any preceding claim, comprising: a spring acting on a rotatable output shaft of the motor, the spring being configured to apply a torque to the motor shaft; and / or a spring acting on a rotatable shaft of the damper, the spring being configured to apply a torque to the damper shaft.

17. The steering column assembly of claim 16, wherein: The spring acting on the rotatable output shaft of the motor and / or the spring acting on the rotatable shaft of the damper comprises a coil spring.

18. A steering column assembly according to any preceding claim, comprising a motor position sensor arrangement for sensing the rotational position of the motor output shaft, the sensor arrangement comprising a target member rotatable with the motor shaft and a sensor for detecting the target member.

19. A steering column assembly according to any preceding claim, comprising a position sensor arrangement for sensing the rotational position of the damper shaft, the sensor arrangement comprising a target member rotatable with the damper shaft and a sensor for detecting the target member.

20. The steering column assembly of claim 19, comprising a member configured to rotate with the rotatable damper shaft, the damper shaft being displaceable relative to the member along its axis of rotation, and the target member being mounted on the member.

21. A steering column assembly according to claim 20 including a cup-shaped member mounted at one end of the rotatable damper shaft and the motor position sensor means is mounted on the cup-shaped member.

22. A steering column assembly according to any preceding claim, wherein: The first worm forms part of the motor output shaft, and / or wherein the second worm forms part of the rotatable damper shaft.

23. A steering column assembly according to any one of the preceding claims, wherein: The first worm and the second worm engage with the gear connected to the steering column at diametrically opposed positions.

24. A steering column assembly according to any preceding claim, comprising a housing within which the first and second worms and the gear connected to the steering column are located.

25. A vehicle comprising a steering column assembly according to any preceding claim.

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