Cam Mechanisms for the Rear Steering Box within Integral Steering of Vehicles with Four- Wheel Steering

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Dominic Mosley
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1 nternational onference on Mechanical, Automoile and ootics Engineering (MA'0) am Mechanisms for the ear Steering Bo within ntegral Steering of Vehicles with Four- Wheel Steering Dragos MAAVEU and Petre ALEXANDU Astract The paper analses and proposes cam mechanisms variants for the rear ale steering o, so that whole integral steering requirements are achieved with a purel mechanical sstem. The paper presents a vehicle with two steering ale, where for increasing the maneuverailit the rear wheels are turning in the same direction as the front wheels, ut with a negative effect on the stailit of the vehicle at high speeds. Greater attention was given to achieving integral steering : while steering in one direction, the rear wheels to e turned in the same direction as the front wheels for increasing the vehicle stailit and in the opposite direction for increasing maneuverailit. S Kewords am mechanisms, integral steering,. NTDUTN N vehicles with two steering ale (fig.), the transmitting of turning action to the rear wheels can e made directl from the front steering rack: rack, / front spindle levers, - longitudinal shaft, rack/sliding lock of the rear steering sstem, / rear spindle levers, φ v steering wheel angle, υ f front ale turning angle, υ s rear ale turning angle, v turning radius, v turning center, S /S - racks displacements (at driving with φ v ), MA - linkage, M - cam mechanisms. B turning υ s in the opposite direction to υ f (fig..a), the turning radius <, while turning in the same direction v v (fig..) the turning radius v > v, with the following consequences: maneuverailit of the vehicle is increasing and the stailit is decreasing and vice versa For a superior ehavior of the vehicle, solutions were searched so that, at high speeds - when vehicle stailit is a priorit - the rear wheels to e turned in the same direction as the front ones, and as the turning radius is increased, the rear wheels to e aligned, and then to e turned in the opposite direction as the front wheels [, ]. This tpe of steering sstem has een called integral steering. Thus, at steering in one direction, as the steering wheel angle φ v increases, the turning angle υ f will increase continuousl corresponding to Dragos MAAVEU is with the Transilvania Universit of Brasov, Brasov, Zip 00 MANA (phone: +0 ; dragosmacaveiu@ahoo.com). Petre ALEXANDU is with the Transilvania Universit of Brasov, Brasov, MANA ( ale.p@unitv.com). - us u f v - us v v + us v v v Fig. Scheme of integral steering mechanisms with cam mechanisms. the wheels of the front ale (S (φ v ) or υ f (φ v )). At the same time, considering that at the eginning of steering a vehicle runs at high speed, the rear wheels should turn in the same direction of the front ones, so at first υ s is "positive" (Fig. ). As the φ v and υ f increases their values, υ s 0, then it ecomes negative. learl, functions must e identical at steering to left / right, namel for φ v in one wa or another. Some mechanisms schemes for the rear ale steering o have een proposed / tested mostl Japanese manufacturers [], [], ut solutions are not generalied due to construction complications.

2 nternational onference on Mechanical, Automoile and ootics Engineering (MA'0) θ θ θ f, s Φ θ f Φ v θ s Fig. Kinematical function of integral steering. Western car manufacturers have een more restrained in taking this steering sstem, recent concerns show an interested into adopting the integral steering with direct electronic command of the rear ale. For a purel mechanical structure, linkages (v.fig..) or cam mechanisms (v.fig..a) can e adopted, highlighting papers [], [], respectivel [], [] in the functionalit proposal / analsis of these mechanical sstems.. AM MEHANSMS F NTEGAL STEENG The possiilit for cam mechanisms to precisel achieve comple laws of motion is ver high; therefore their use in rear ale steering o is a gain. us r p rr u f,s 0 o 0 o u f S 0 o S Fig. Grooved cam for the rear steering ale. The solution with the rotating cam is presented in figure. The cam follower is also a translational slide lock, which is centrall positioned. The rotation of the cam is received through gears from the front steering rack. elated to a circle of a radius which aligns the slide lock to going straight the groove of the cam is moving awa/closer to center of the cam: sector marks the displacement S for the turning υ s in the same direction to υ f, and sector marks the displacement S so that the turning υ s to e in the opposite direction to υ f (fig..). Specified numerical values are given as a rough guide for a particular case. Longitudinal shaft (v.fig..c) can drive the cams directl from the front ale, and the cams can drive a translational slider or a rotational slider (having the role of a cam follower). n figure, vehicle speed, steering to the right, steering to the left. For steering to the right -, slider positioned in the right side of the cam (fig..a ), in point on the circle with the radius - which marks the position for rectilinear movement of the vehicle. f the cam is rotated clockwise, then, for the rear wheels to pivot first to the direction of the front wheels (to the right), slider needs to move awa from the center of the cam, therefore the cam needs a profile outside of the circle with the radius. This is followed the returning profile from which the rear wheels can e steered to the left, therefore slider should move to the left, which means a profile for moving closer to the center of the cam. Thus, the cam profile for steering to the right is otained. For steering to the left, the cam eing rotated counterclockwise, slider needs to move to the left, on profile followed the returning profile - (profiles inside the circle with the radius ); then, the rear wheels are steered in the opposite direction to the front wheels (to the right), which means that slider is moving to the right following the profile that is outside the circle with the radius. Thus, the profile of the cam for steering to the left is otained. B connecting the contours /, the complete profile of the cam will e otained, ut indicating that the angle of rotation of the cam in each direction was considered as eing 0 o and the contact on the profile eing on the right side. Under the same conditions of steering / and rotation of the cam / (clockwise/counterclockwise), ut with the cam follower positioned on the left side of the cam (fig.. a ), the same reasoning a cam profile is otained, smmetrical to variant,a with respect to -ais, the continuous line showing the profile / for steering to the right and the dotted line showing the profile / for steering to the left. n case the rotation of the cam for profile (steering to the right) is counterclockwise and clockwise (fig..), therefore inverse to the previous case, ased on the same reasoning, the profile from figures. /. is otained, smmetric to contours in.a /.a in respect to -ais (slider ais). n diagram., the roller was considered as passing through a profile groove of the cam; in diagram.a, eing a pointed cam follower. n case the rotation of the cam for profile (steering to the right) is counterclockwise and clockwise (fig..), therefore inverse to the previous case, ased on the same reasoning, the profile from figures. /. is otained, smmetric to contours in.a /.a in respect to -ais

3 nternational onference on Mechanical, Automoile and ootics Engineering (MA'0) ' S ' ' ' S ' ' c ' ' (a ) (a ) ' ' ' ' ' ( ) ( ) Fig. The arrangement of cam profiles that are rotated 0 o. (slider ais). n diagram., the roller was considered as passing through a profile groove of the cam; in diagram.a, eing a pointed cam follower. At a rotation c of cam with 90 o in one wa or another (so with a full profile of the cam in 0 o ), the complete profile is shown in figure.a, in terms of.a ( left contact, rotation clockwise, counterclockwise). Due to the profile smmetr with respect to the -ais, in case of left right contact, the profile in figure.a ma e completed as shown in figure., where the two contacts can eist simultaneousl, so that the structure can ecome compact contact with two rollers, locked cam follower as shown in figure.c. The advantage of the structure with two rollers is reduced the condition of the cam rotation limitation at c =90 o, in one wa and the other. onsidering the rotation eing clockwise for the left turn, continuous line profiles are identified as active and dotted line profiles as passive, depending on the slider thrust (fig. ).Similarl, for the steering/ rotation, with a continuous line are the active contours and the dotted line shows the passive ones. The correspond to the increasing polar radius of the cam for active contours and decreasing polar radius for passive contours. Such a cam for integral steering ma drive not onl a translational slider, ut also a central lever of the rear ale steering mechanism. entral lever can e placed verticall (Fig..a) or horiontal (Fig..), driving the steering knuckle rods. ' ' ' ' ' (c) Fig. Arrangement of cam profiles that are rotated 90 o.

4 nternational onference on Mechanical, Automoile and ootics Engineering (MA'0) Fig. Active / passive contours of the cam. Fig. am linkages floating cam follower for integral steering. An imposed law for cam profiling can e given directl as a displacement law of the slider cam follower: to the circle with radius a function is added or sutracted for eample the sine on period 0 - (contour ), followed an addition or sutraction also a sine function on period 0 - / (contour ). S S Fig. Translating cam with contact points. For the cam in fig., the follower has two rollers separated a fied distance, which act as the constraint. NUMEAL APPLATN Thus, as a numerical application, the displacement law is considered S = a sin c, respective S = a sin c, a with = () a φ a - cam rotation angle of the first period, and φ second period, φ c current angle of rotation (fig.). The following values are considered for the application: =0 mm, a = mm, a = mm, φ a =0 o, φ =0 o. The polar radii of the cam are given : r = r0 + S, respective r = r0 S for profile ( ); r = r0 S, respective r = r0 + S for profile ( The cam representation for the cam follower with two rollers and c =90 o in one direction and the other is given in Figure 9.a. ' a a r ' a a S t a c a a Fig.9 Movement phases of the cam. For the cam follower with a single roller, accepting c =0 o in one direction and the other, the cam in figure 9. is otained, angle ccles eing douled if compared to previous case, φ a =0 o, φ =0 o, the rest of the data remaining the same, as well as the resulting values (at angles φ c equal with 0, 0 o, 0 o, 0 o, 0 o and 0 o /0, 0 o /0, 0 o /00, 0 o /0, 00 o /0, 0 o /0, 0 o /0) The numerical data entries a / a, a / are intentionall eaggerated for clear stand out of cam profiles. The advantage of cam with a single roller ma e found in figure 0.a, to which were considered periods of angles a = 0 and φ =0 o ; r a a

5 nternational onference on Mechanical, Automoile and ootics Engineering (MA'0) φ c 0 o o 0 o o 0 o 0 o /0 0 o /0 0 o /0 0 o /0 0 o /0 0 o /0 0 o /90 S S r r i i.e. the maimum cam rotation Φ c =00 (discrete angles of cam φ c =0o, o, 0 o, o, 0 o, 0 o/90, 0 o/0, 90 o /0, 0 o /0, 0 o /0, 0 o /0, 0 o/0). ' For achieve relativel large stokes S, amplitudes a / a must also e large, which can e inconvenient. n case of cam with a single roller there is a possiilit where this is positioned on a rocker (fig.0.), so that the driving point M of the rocker / from the mechanism have a multiplied stroke with the arms ratio. ' 0 Fig.9 Numerical application for the cam profile. ' 0 ' ' Fig.0 am profiling with Φ c =0 0, respectivel rocker driving. ' ' ' ' A M V. NLUSN The integral steering requirements, for turning the rear wheels in the same direction to front wheels and in the opposite direction, can e achieved accuratel using cam mechanisms at the rear ale steering o. The cam profile is determined the imposed law, ut also its direction of rotation and maimum angle rotation. The cam with the framed cam follower, with two concomitant contact points left/right, is formed with a smmetrical profile, ut emphasiing the rotation of 90. The defined cam has areas of active profile when the polar radius is increasing, as passive profile ones, for steering the vehicle to the right ut also for steering to the left. The cam with a single roller can have a rotation angle up to 0 in one direction or another. The cam with a single roller can e linked with a rocker for increasing the driving strokes of the turning of the wheels. The cam for the integral steering o can drive either a slider or a central slewing lever, the lever eing positioned verticall or horiontall. AKNWLEDGMENT Supported NSS-UEFSD, project numer PN- DE 0/00 EFEENES [] Aleandru, P., Aleandru,. Mechanisms for the integral steering. th EAE European Automotive ongress, pg. 99, Bratislava, 009. [] Berkefeld, V., Seifort, G. Four Wheel steering handling and disturance compensation on surface with varius fricions conditions. SAE Papers, no. 90. [] Galtier, L. ear-steering control device for automotive vehicle with four-wheel steering. U.S. Patent, no [] Kido, L Steering mechanism for vehicle rear wheels. U.S. Patent, no [] Sano, S. Steering apparatus for vehicles. U.S. Patent, no..9.. [] Verschoore,. Steering geometr errors induced raking. SAE Papers, no.. [] Visconti, M. Steering device for a motor vehicle with four steered wheels. U.S. Patent, no..9.

LINKAGE MECHANISM FOR THE REAR AXLE STEERING BOX WITHIN THE INTEGRAL STEERING

LINKAGE MECHANISM FOR THE REAR AXLE STEERING BOX WITHIN THE INTEGRAL STEERING ulletin of the Transilvania University of raşov Series I: Engineering Sciences Vol. () No. - 0 LINKGE ECHNIS FR THE RER XLE STEERING X WITHIN THE INTEGRL STEERING D. CVEIU P. LEXNDRU stract: The paper