| CN201844836U | 2011-05-25 |
| Claims [Claim 1] Steering system based on single bilateral rotary steering-torque transmission arm using elliptic bevel gear sets for four wheelers which 1) according to first installation of elliptic bevel gear sets can provide steering to the vehicle according to close approximation to pro-Ackermann geometry for steer angle of inner wheel less than 90 degree and according to second installation of elliptic bevel gear sets can provide steering to the vehicle according to close approximation to antiAckermann geometry for steer angle of outer wheel less than 90 degree; 2) fulfills critical steering requirements according to which while vehicle is cornering the wheels can be steer turned by unequal angles (in a special way as required by either proAckermann or anti- Ackermann condition) as well as reverted back to neutral steer position in predictable fashion; 3) fulfills critical steering requirements by choosing meshing point of each conjugate pairs of elliptic bevel gears, at neutral steer position of front wheels, as appropriate neutral conjugate contact point, where neutral conjugate contact point is a meshing point of conjugate pairs of elliptic bevel gears at which transmission ratio is one, in order to make use of monotonic increasing/decreasing transmission ratio of conjugate pairs of elliptic bevel gears at their meshing point at their respective appropriate region; 4) can rotate wheels by 360 degree; comprises central steering shaft, left steering shaft, right steering shaft, left steering-torque transmission arm and right steering-torque transmission arm, steer support mechanism, one circular bevel gear sets as central steering mechanism, two identical conjugate pairs of elliptic bevel gears as Left wheel bevel gear set and Right wheel bevel gear set, with their vertically oriented bevel-gears mounted on central steering shaft, left steering shaft, right steering shaft respectively, horizontally oriented gears mounted on left steering-torque transmission arm and right steering-torque transmission arm wherein Left steering shaft and right steering shaft are parallel vertically oriented rods connected at their lower end to the inward end of axle of left and right wheel respectively; Central steering shaft is a vertically oriented rod coplanar to, parallel to and located between left steering shaft and right steering shaft and connected at its upper end to handle; Central steering shaft, Left steering shaft and right steering shaft are appropriately rotatably coaxially housed in tubes via ball bearing which in turn is fixedly attached to the chassis of the vehicle; left steering-torque transmission arm, is horizontally oriented rod located between central steering shaft and left wheel steering shaft connecting central steering mechanism to left wheel bevel gear set ; right steering-torque transmission arm, is horizontally oriented rod located between central steering shaft and right wheel steering shaft connecting central steering mechanism to right wheel bevel gear set; left steering-torque transmission arm and right steering-torque transmission arm acts as medium to transmit steering torque of central steering shaft to left steering shaft and right steering shaft via rotation action; asymmetry of elliptic arc with respect to extremity points of equi-conjugate diameters as bifurcation mechanism to convert rotation of steering arms as left side and right side nonparallel (Pro/ Anti Ackermann) steering mechanism; Elliptic bevel gears used are, preferably but not restricted to, of first and second order, and have provision to install suspension system. [Claim 2] Central steering mechanism, claimed in claim 1, consists of 1) a pair of coaxially parallel vertically oriented identical circular bevel gears, as central top bevel gear and central bottom bevel gear coaxially mounted on the central steering shaft with their teeth side facing each other and 2) a pair of coaxially parallel horizontally oriented identical circular bevel gears with their teeth side facing each other, as, central left bevel gear and central right bevel gear wherein central left bevel gear located on left side of central steering shaft is coaxially fixedly mounted on the right end of left steering-torque transmission arm; central right bevel gear located on left side of central steering shaft is coaxially fixedly mounted on the left end of right steering-torque transmission arm; central bottom bevel gear, located at lower side of central right bevel gear is coaxially rotatably mounted on central steering shaft via roller ball bearing whereas central top bevel gear located at upper side of central right bevel gear is coaxially fixedly mounted on central steering shaft; central left bevel gear and central right bevel gear are meshingly engaged with vertically oriented bevel gears central top bevel gear and central bottom bevel gear; central top bevel gear is driving bevel gear while central left bevel gear, central right bevel gear and central bottom bevel gear are driven bevel gears; gear ratio of central top bevel gear (and central bottom bevel gear) with central left bevel gear (and central right bevel gear) is equal to required steering ratio of the steering system. [Claim 3] Conjugate pair of elliptic bevel gears, Left wheel bevel gear set, claimed in Claim 1, is a consists of two identical elliptic bevel gears as Left wheel bull bevel gear and Left wheel pinion bevel gear wherein Left wheel bull bevel gear is driven gear and Left wheel pinion bevel gear is driving gear; Left wheel bull bevel gear a vertically oriented bevel gear is coaxially mounted at its pivot point on the left steering shaft with its teeth facing upward direction; Left wheel pinion bevel gear horizontally oriented bevel located on the right side of the Left steering shaft towards upper side of Left wheel bull bevel gear with teeth facing towards left steering shaft is mounted on left end of left steering-torque transmission arm in such a way that Left wheel bull bevel gear meshingly engaged with Left wheel pinion bevel gear ; Left wheel pinion bevel gear is an elliptic bevel gear, of appropriate size chosen according to requirement of Pro- Ackermann or Anti- Ackermann steering, coaxially fixedly mounted on the left end of left steering-torque transmission arm such that its teeth meshes with left wheel bull bevel gear; Pivot point of Left wheel bull bevel gear and Left wheel pinion bevel gear are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle, which in case of second order elliptic bevel gear can be centrode of pitch curve. [Claim 4] Conjugate pair of elliptic bevel gear, Right wheel bevel gear set, claimed in [Claim 1], consists of a pair of two identical elliptic bevel gears as Right wheel bull bevel gear and Right wheel pinion bevel gear wherein Right wheel bull bevel gear is driven gear and Right wheel pinion bevel gear is driving gear; Right wheel bull bevel gear a vertically oriented bevel gear is coaxially mounted at its pivot point on the Right steering shaft with its teeth facing upward direction; Right wheel pinion bevel gear horizontally oriented bevel located on the right side of the Right steering shaft towards upper side of Right wheel bull bevel gear with teeth facing towards Right steering shaft is mounted on Right end of Right steering-torque transmission arm in such a way that Right wheel bull bevel gear meshingly engaged with Right wheel pinion bevel gear ; Right wheel pinion bevel gear and Right wheel bull bevel gear are identical to Left wheel pinion bevel gear and Left wheel bull bevel gear, respectively; Pivot point of right wheel bull bevel gear and Right wheel pinion bevel gear are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle which in case of second order elliptic Bevel gear can be centrode of pitch curve and in case of first order of elliptic bevel gear can be one of the foci of the pitch curve. [Claim 5] In order that steering system steer the vehicle according to close approximation to Pro-Ackermann steering geometry till inner wheel steering angle, denoted by Ai, is less than 90°, conjugate pairs of elliptic bevel gears need to satisfy additional conditions according to which at neutral position Meshing point of the Left wheel bevel gear set and Right wheel bevel gear set is at the point 1) where transmission ratio between driving and driven gear is one, 2) while steering left side transmission ratio of driving to driven gear of left wheel gear set increases and of right wheel gear set decreases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set decreases and of right wheel gear set increases; left wheel gear set and right wheel gear set are mirror image with respect to vertical longitudinal zero plane of the vehicle. [Claim 6] In order that steering system steer the vehicle according to close approximation to Anti- Ackermann steering geometry till outer wheel steering angle, denoted by Ao, is less than 90°, elliptic bevel gear sets need to satisfy additional conditions according to which at neutral position Meshing point of the left wheel bevel gear set and right wheel bevel gear set is at the point 1) where transmission ratio between driving and driven gear is one, 2) while steering left side transmission ratio of driving to driven gear of left wheel gear set decreases and of right wheel gear set increases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set increases and of right wheel gear set decreases; left wheel gear set and right wheel gear set are mirror image with respect to vertical longitudinal zero plane of the vehicle. [Claim 7] Steer support mechanism, claimed in claim 1, a mechanism with of help which steering system is connected to the vehicle and steering-torque transmission arms can be kept aligned and allowed to rotate whenever required, comprises two tubes, as right steer transmission head tube, left steer transmission head tube, coaxially rotatably housing right steering-torque transmission arm, left steering-torque transmission arm, respectively via ball bearings. [Claim 8] Steering system according to this invention have the provision to provide suspension system, as claimed in Claim 1, by allowing right steering shaft and left steering shaft to be Shock-damping system with axle of the front wheel being attached to outer protecting cover and axle eye attached to fixed link via ball bearing. |
| AMENDED CLAIMS received by the International Bureau on 15 January 2023 (15.01.2023) [Claim 1] Steering system based on single bilateral rotary steering-torque transmission arm using elliptic bevel gear sets for four wheelers which 1) according to first installation of elliptic bevel gear sets can provide steering to the vehicle according to close approximation to pro- Ackermann geometry for steer angle of inner wheel less than 90 degree, 2) according to second installation of elliptic bevel gear sets can provide steering to the vehicle according to close approximation to anti-Ackermann geometry for steer angle of outer wheel less than 90 degree, 3) fulfills critical steering requirements according to which the wheels can be steer turned from neutral steer position by unequal angles (in a special way as required by either proAckermann or anti-Ackermann condition) along the direction of rotation of the steering handle and steer angular displacement of inner wheel from steer neutral position with respect to steer angular displacement of outer wheel from steer neutral position while retracing back to steer neutral position is same as during tracing away from neutral steer position, 4) can rotate wheels by 360 degree, 5) allows installation of suspension system and characterized in comprising Central steering system, which comprises a shaft, lying on plane parallel to midplane of the four wheeler with one end towards the front side of the four wheeler is mounted with a circular bevel gear set, referred to as central gear set, and other end mounted with a steering handle, changes the orientation of axis of rotation steering force applied by steering handle to transverse left and right directions by equal and constant transmission ratio with the help of central gear set, bilateral steer torque transmission mechanism which acts as medium to transfer the rotation steering force transmitted from central steering system towards the left wheel and right wheels via longitudinal axial rotation motion of bilateral steering torque transmission arms, 15 AMENDED SHEET (ARTICLE 19) left wheel steering system which comprises a vertical shaft, referred to as left steerer rod, attached to inward end of axle of the front left wheel mounted with elliptic bevel gear set, referred to as left wheel gear set, receives steering torque from steering handle transmitted via central gear set via steering torque transmission arm and transmits the received steering torque to left steerer rod of left wheel with the help of left wheel gear set after changing the direction of axis of rotation of steering force from transverse horizontal to vertical direction, right wheel steering system which comprises a vertical shaft, referred to as right steerer rod, attached to inward end of axle of the front right wheel mounted with elliptic bevel gear set, referred to as right wheel gear set, receives steering torque from steering handle transmitted via central gear set via steering torque transmission arm and transmits the received steering torque to right steerer rod of right wheel with the help of right wheel gear set after changing the direction of axis of rotation of steering force from transverse horizontal to vertical direction, wherein left wheel gear set and right wheel gear set are identical conjugate pairs of elliptic bevel gears and installed in such a way that if left wheel gear set transmits steering force with continuously increasing transmission ratio then left wheel gear set transmits steering force with continuously decreasing transmission ratio and if left wheel gear set transmits steering force with continuously increasing transmission ratio then left wheel gear set transmits steering force with continuously decreasing transmission ratio; left wheel gear set and right wheel gear set fulfills critical steering requirements by choosing meshing point of each conjugate pairs of elliptic bevel gears, at neutral steer position of front wheels, as appropriate neutral conjugate contact point, where neutral conjugate contact point is a meshing point of conjugate pairs of elliptic bevel gears at which transmission ratio is one, in order to make use of monotonic increasing/decreasing transmission ratio of conjugate pairs of elliptic bevel gears at their meshing point at their respective appropriate region; Left steering shaft and right steering shaft are parallel vertically oriented rods connected at their lower end to the inward end of axle of left and right wheel respectively; Central steering shaft, Left steering shaft and right steering shaft are appropriately rotatably coaxially housed in tubes via ball bearing which in turn is fixedly attached to the chassis of the vehicle; 16 AMENDED SHEET (ARTICLE 19) left steering-torque transmission arm, is horizontally oriented rod located between central steering shaft and left wheel steering shaft connecting central steering mechanism to left wheel bevel gear set; right steering-torque transmission arm, is horizontally oriented rod located between central steering shaft and right wheel steering shaft connecting central steering mechanism to right wheel bevel gear set; left steering-torque transmission arm and right steering-torque transmission arm acts as medium to transmit steering torque of central steering shaft to left steering shaft and right steering shaft via rotation action; asymmetry of elliptic pitch curve of elliptic gears with respect to neutral conjugate contact point as bifurcation mechanism to convert rotation of steering arms as left side and right side non-parallel (Pro/ Anti Ackermann) steering mechanism; elliptic bevel gears used are, preferably, of first or second order. [Claim 2] Steering system for four wheelers, claimed in claim 1, in which Central steering system consists of 1) a pair of coaxially parallel vertically oriented identical circular bevel gears, as central top bevel gear and central bottom bevel gear coaxially mounted on the central steering shaft with their teeth side facing each other and 2) a pair of coaxially parallel horizontally oriented identical circular bevel gears with their teeth side facing each other, as, central left bevel gear and central right bevel gear wherein central left bevel gear located on left side of central steering shaft is coaxially fixedly mounted on the right end of left steering-torque transmission arm; central right bevel gear located on left side of central steering shaft is coaxially fixedly mounted on the left end of right steering-torque transmission arm; central bottom bevel gear, located at lower side of central right bevel gear is coaxially rotatably mounted on central steering shaft via roller ball bearing whereas central top bevel gear located at upper side of central right bevel gear is coaxially fixedly mounted on central steering shaft; central left bevel gear and central right bevel gear are meshingly engaged with vertically oriented bevel gears central top bevel gear and central bottom bevel gear; central top bevel gear is driving bevel gear while central left bevel gear, central right bevel gear and central bottom bevel gear are driven bevel gears; AMENDED SHEET (ARTICLE 19) gear ratio of central top bevel gear (and central bottom bevel gear) with central left bevel gear (and central right bevel gear) is equal to required steering ratio of the steering system. [Claim 3] Steering system for four wheelers, claimed in claim 1, in which Left wheel bevel gear set being a Conjugate pair of elliptic bevel gear, consists of two identical elliptic bevel gears as Left wheel bull bevel gear and Left wheel pinion bevel gear wherein Left wheel bull bevel gear is driven gear and Left wheel pinion bevel gear is driving gear; Left wheel bull bevel gear a vertically oriented bevel gear is coaxially mounted at its pivot point on the left steering shaft with its teeth facing upward direction; Left wheel pinion bevel gear horizontally oriented bevel located on the right side of the Left steering shaft towards upper side of Left wheel bull bevel gear with teeth facing towards left steering shaft is mounted on left end of left steering-torque transmission arm in such a way that Left wheel bull bevel gear meshingly engaged with Left wheel pinion bevel gear; Left wheel pinion bevel gear is an elliptic bevel gear, of appropriate size chosen according to requirement of Pro- Ackermann or Anti -Ackermann steering, coaxially fixedly mounted on the left end of left steering-torque transmission arm such that its teeth meshes with left wheel bull bevel gear; Pivot point of Left wheel bull bevel gear and Left wheel pinion bevel gear are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle, which in case of second order elliptic bevel gear is centroid of pitch curve. [Claim 4] Steering system for four wheelers, claimed in claim 1, in which Right wheel bevel gear set being a Conjugate pair of elliptic bevel gear, consists of a pair of two identical elliptic bevel gears as Right wheel bull bevel gear and Right wheel pinion bevel gear wherein Right wheel bull bevel gear is driven gear and Right wheel pinion bevel gear is driving gear; Right wheel bull bevel gear a vertically oriented bevel gear is coaxially mounted at its pivot point on the Right steering shaft with its teeth facing upward direction; Right wheel pinion bevel gear horizontally oriented bevel located on the right side of the Right steering shaft towards upper side of Right wheel bull bevel gear with teeth facing towards Right steering shaft is mounted on Right end of Right steering-torque transmission arm in such a way that Right wheel bull bevel gear meshingly engaged with Right wheel pinion bevel gear ; Right wheel pinion bevel gear and Right wheel bull bevel gear are identical to Left wheel pinion bevel gear and Left wheel bull bevel gear, respectively; 18 AMENDED SHEET (ARTICLE 19) Pivot point of right wheel bull bevel gear and Right wheel pinion bevel gear are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle which in case of second order elliptic Bevel gear is centroid of pitch curve. [Claim 5] Steering system for four wheelers, claimed in claim 1, claim 3, claim 4, in which, left wheel gear set and right wheel gear set are installed according to first installation so that steering system steer the vehicle according to close approximation to Pro-Ackermann steering geometry till inner wheel steering angle, denoted by Ai, is less than 90°, conjugate pairs of elliptic bevel gears need to satisfy additional conditions according to which at neutral position Meshing point of the Left wheel bevel gear set and Right wheel bevel gear set is at the point 1) where transmission ratio between driving and driven gear is 1 : 1, 2) while steering left side transmission ratio of driving to driven gear of left wheel gear set continuously decreases and of right wheel gear set continuously increases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set continuously increases and of right wheel gear set continuously decreases; left wheel gear set and right wheel gear set are mirror image with respect to vertical longitudinal zero plane of the vehicle. [Claim 6] Steering system for four wheelers, claimed in claim 1, claim 3, claim 4, in which according to second installation in order that steering system steer the vehicle according to close approximation to Anti-Ackermann steering geometry till outer wheel steering angle, denoted by Ao, is less than 90°, elliptic bevel gear sets need to satisfy additional conditions according to which at neutral position Meshing point of the left wheel bevel gear set and right wheel bevel gear set is at the point 1) where transmission ratio between driving and driven gear is 1 : 1, 2) while steering left side transmission ratio of driving to driven gear of left wheel gear set continuously increases and of right wheel gear set continuously decreases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set continuously decreases and of right wheel gear set continuously increases; left wheel gear set and right wheel gear set are mirror image with respect to vertical longitudinal zero plane of the vehicle. [Claim 7] Steering system for four wheelers, claimed in claim 1, in which bilateral steer torque transmission mechanism consists of two steer transmission arms and each of which is a AMENDED SHEET (ARTICLE 19) transverse straight shaft rotatably coaxially housed in a tube referred to as transmission head tube, wherein two steer transmission arms are held in transversely horizontal orientation with one on each side of central bevel gear set and coaxial to each other by attaching transmission head tubes at it outer side to the frame of reverse tricycle; one transmission arm coaxially connects right end of transversely oriented right side central pinion gear, to left end of transversely oriented right wheel bull gear; one transmission arm coaxially connects left end of transversely oriented left side central pinion gear to right end of transversely oriented left wheel bull gear. [Claim 8] Steering system for four wheelers, claimed in claim 1, in which suspension system is provided by allowing right steering shaft and left steering shaft to be Shock-damping system with axle of the front wheel being attached to outer protecting cover and axle eye attached to fixed link via ball bearing. AMENDED SHEET (ARTICLE 19) |
Title of Invention: Ackermann Steering System based on Single Bilateral Rotary Steering- Torque Transmission Arm using Elliptic Bevel Gear Sets
Field of Invention
[01] Steering system for four wheelers satisfying pro/anti Ackermann condition.
Background of Invention
[02] Steering mechanism of automobiles (four wheelers or reverse-trikes) having two front wheels need to satisfy Ackermann condition during low to medium speed drive and antiAckermann conditions during high speed drive. Meeting Ackermann condition is much more required for very low valued wheelbase to track width ratio.
Technical Problem
[03] According to current mechanical Ackermann steering system, which is based on trapezoidal mechanism, rotation motion is converted into linear (reciprocating) motion which is then converted back to steering rotation at the wheel kingpin. Wheels can be turned by maximum of 45 degree.
[04] Mechanism comprises multiple complex linkages which are difficult to manufacture and maintain. Components including recirculating ball screws, ball linkages, track rods, tie rods etc require frequent lubrication with lubrication being challenging exercise each time.
[05] Spare parts inventory is difficult to manage as each component require special manufacturing process. Components including recirculating ball screws, ball linkages etc are uncommon for other industrial or transportation machinery equipment. With each different model these components come in different sizes due to which even two year old models become unserviceable or irreparable. It becomes difficult to find original equipment manufacturers for components with less frequent application.
[06] Portion of Trapezoidal mechanism (with seven bar linkages) for Ackermann steering mechanism or Davis steering mechanism are located away from main chassis and therefore prone to misalignments while driving on uneven roads.
Summary of Invention
SUBSTITUTE SHEETS (RULE 26) [07] Rotation steering action at the handle is transmitted as steering action on the wheel through rotation motion of steer-torque transmission arm and is not converted into planar translation motion as intermediate phase. Therefore steering arms via head tubes can be integrated with the frame of vehicle.
[08] This steering demonstrates all the critical steering features. It is important that while cornering the wheels can be steer turned by unequal angles as well as reverted back to neutral steer position in predictable fashion. Steering of vehicle according to Ackermann geometry require that the inner front wheel steer angle is greater than outer front wheel steer angle with their difference higher for higher steer angle in a special way. Steering of vehicle according to anti- Ackermann geometry require that the outer front wheel steer angle is greater than inner front wheel steer angle with their difference higher for higher steer angle in a special way. Steering system according to this invention can fulfill such a purpose by making use of continuous transmission ratio gradient of conjugate pair of elliptic bevel gear around the neutral conjugate contact point (NCCP). Neutral conjugate contact point (NCCP), in this patent document, is referred to that meshing point at which transmission ratio is equal to one. In case of conjugate pair of second order elliptic bevel gears transmission ratio is maximum (approximately equal to M/m where M is major axis length and m is minor axis length) when vertex of driving gear meshes with covertex of driven gear and is minimum (approximately equal to m/M) when covertex of driving gear meshes with vertex of driven gear. Transmission ratio continuously increases when meshing point moves from vertex to covertex of driven gear. Neutral conjugate contact point (NCCP) lies between covertex and vertex of driven gear as well as driving gear. In case of conjugate pair of second order elliptic bevel gears there are two types of Neutral conjugate contact point (NCCP). For first type contact point on driven gear lies in the quadrant in which transmission ratio increases for clockwise rotation of meshing point and for second type contact point on driven gear lies in the quadrant in which transmission ratio decreases for clockwise rotation of meshing point. In case of conjugate pair of second order elliptic bevel gears, there are two Neutral conjugate contact point (NCCP) of first type separated by angular distance of 180 degree and two Neutral conjugate contact point (NCCP) of second type separated by angular distance of 180 degree.
In case of conjugate pair of first order elliptic bevel gears case is different. Pivot point in this case is foci and transmission ratio is maximum for only one meshing point and minimum only for one meshing point with pivot points with minimum and maximum transmission ratio
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SUBSTITUTE SHEETS (RULE 26) separated by an angular distance of 180 degree. In case of conjugate pair of first order elliptic bevel gears there is only one Neutral conjugate contact point (NCCP) of first type and only one Neutral conjugate contact point (NCCP) of second type. For pro-Ackermann installation of conjugate pairs of elliptic bevel gears, Neutral conjugate contact point (NCCP) of first type is chosen as meshing point for conjugate pair of elliptic bevel gear installed on right wheel and Neutral conjugate contact point (NCCP) of second type is chosen as meshing point for conjugate pair of elliptic bevel gear installed on left wheel. For anti- Ackermann installation of conjugate pairs of elliptic bevel gears, Neutral conjugate contact point (NCCP) of second type is chosen as meshing point for conjugate pair of elliptic bevel gear installed on right wheel and Neutral conjugate contact point (NCCP) of first type is chosen as meshing point for conjugate pair of elliptic bevel gear installed on left wheel. This steering system can rotate the wheels by 360 degree due to which it can be used to maneuver the vehicle out of difficult terrain conditions or parking space.
[09] Steering system, according to this invention is integrated to the chassis (and its components do not project out of the main chassis) of the vehicle due to which it is more robust against alignment problems and therefore require less frequent maintenance. This steering system may lead to reduction of weight and hence increase in fuel efficiency of the vehicle. This steering system also allows more space for installation of other systems like suspension system, cooling system. Additionally, components are concealed from external conditions like dirt, mud and therefore require less frequent maintenance.
[10] Steering system comprises bevel gears, ball bearings, as main components which are in use in multiple equipments and do not require specialized manufacturing process. Spare parts inventory for this steering system is far less challenging.
[11] This steering system has special advantage in situation of configuration for vehicle maneuvering at high speed. For configuring the vehicle for various types of anti- Ackermann condition, one only needs to rotate the left and right shafts by 180 degree whereas in order to replace Ackermann trapezoid mechanism by Davis steering mechanism one needs to change almost all the components which includes bar linkages, rack-pinion gears, bearings, recirculating ball screws etc.
Brief Description of Drawings
SUBSTITUTE SHEETS (RULE 26) [12] Fig. 1 Front view of Steering system with a single bilateral rotary steer-torque transmission arm with elliptic bevel gear sets configured according to Ackermann condition showing gear sets in neutral steer position.
[13] Fig. 2 Steering system configured according to Ackermann condition showing elliptic bevel gear sets after steering rightward direction by 45 degree.
[14] Fig. 3 Steering system configured according to Ackermann condition showing elliptic bevel gear sets after steering leftward direction by 45 degree.
[15] Fig. 4 Steering system with a single bilateral rotary steer-torque transmission arm with elliptic bevel gear sets configured according to anti-Ackermann condition showing gear sets in neutral steer position.
[16] Fig. 5 Schematic diagram of rightward steering of Steering system.
[17] Fig. 6 Schematic diagram of leftward steering of Steering system.
[18] Fig. 7, Fig. 8 and Fig. 9 Pitch curve of elliptic bevel curve from various view points.
Description of Embodiments
[19] As shown in Fig. l, Fig. 2 and Fig. 3, Steering system based on single bilateral rotary steering-torque transmission arm using elliptic bevel gear sets for four wheelers or reverse tricycles, which 1) can be optimally configured to provide close approximation to proAckermann for steer rotation of inner wheel by an angle less than or equal to 90 degree or antiAckermann condition for steer rotation of outer wheel by an angle less than or equal to 90 degree; and 2) can rotate wheels by 360 degree; and comprises central steering shaft (CSS), left steering shaft (LSS), right steering shaft (RSS), left steering-torque transmission arm (LST) and right steering-torque transmission arm (RST), steer support mechanism (SSM), one circular bevel gear set as central steering mechanism (CSM), two identical conjugate pairs of elliptic bevel gears as left wheel bevel gear set (LBS) and right wheel bevel gear set (RBS), with their vertically oriented bevel-gears mounted on central steering shaft (CSS), left steering shaft (LSS), right steering shaft (RSS) respectively, horizontally oriented gears mounted on left steering-torque transmission arm (LST) and right steering-torque transmission arm (RST) wherein
SUBSTITUTE SHEETS (RULE 26) Left steering shaft (LSS) and right steering shaft (RSS) are parallel vertically oriented rods connected at their lower end to the inward end of axle of left and right wheel respectively;
Central steering shaft (CSS) is a vertically oriented rod coplanar to, parallel to and located between left steering shaft (LSS) and right steering shaft (RSS) and connected at its upper end to handle;
Central steering shaft (CSS), Left steering shaft (LSS) and right steering shaft (RSS) are appropriately rotatably coaxially housed in tubes via ball bearing which in turn is fixedly attached to the chassis of the vehicle; left steering-torque transmission arm (LST), is horizontally oriented rod located between central steering shaft (CSS) and left wheel steering shaft (LSS) connecting central steering mechanism (CSM) to left wheel bevel gear set (LBS); right steering-torque transmission arm (RST), is horizontally oriented rod located between central steering shaft (CSS) and right wheel steering shaft (RSS) connecting central steering mechanism (CSM) to right wheel bevel gear set (RBS); left steering-torque transmission arm (LST) and right steering-torque transmission arm (RST) acts as medium to transmit steering torque of central steering shaft to left steering shaft and right steering shaft via rotation action;
Elliptic bevel gears used in steering system as shown in the diagrams are elliptic bevel gears of second order;
Elliptic bevel of other orders like first order can also used, pitch curve of which is shown in Fig. 7, Fig. 8 and Fig. 9.
Central steering mechanism (CSM)
[20] As shown in Fig. l, Fig. 2 and Fig. 3, central steering mechanism (CSM), consists of 1) a pair of coaxially parallel vertically oriented identical circular bevel gears, as central top bevel gear (CB1) and central bottom bevel gear (CB2) coaxially mounted on the central steering shaft (CSS) with their teeth side facing each other and 2) a pair of coaxially parallel horizontally oriented identical circular bevel gears with their teeth side facing each other, as, central left bevel gear (CPI) and central right bevel gear (CP2) wherein central left bevel gear (CPI) located on left side of central steering shaft is coaxially fixedly mounted on the right end of left steering-torque transmission arm (LST); central right bevel gear (CP2) located on left side of central steering shaft is coaxially fixedly mounted on the left end of right steering-torque transmission arm (RST);
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SUBSTITUTE SHEETS (RULE 26) central bottom bevel gear (CB2), located at lower side of central right bevel gear (CP2) is coaxially rotatably mounted on central steering shaft (CSS) via roller ball bearing whereas central top bevel gear (CB1) located at upper side of central right bevel gear (CP2) is coaxially fixedly mounted on central steering shaft (CSS); central left bevel gear (CPI) and central right bevel gear (CP2) are meshingly engaged with vertically oriented bevel gears central top bevel gear (CB1) and central bottom bevel gear (CB2); central top bevel gear (CB1) is driving bevel gear while central left bevel gear (CPI), central right bevel gear (CP2) and central bottom bevel gear (CB2) are driven bevel gears; gear ratio of central top bevel gear (CB1) (and central bottom bevel gear (CB2)) with central left bevel gear (CPI) (and central right bevel gear (CP2)) is equal to required steering ratio of the steering system.
Left wheel bevel gear set (LBS)
[21] As shown in Fig. l, Fig. 2 and Fig. 3, conjugate pair of elliptic bevel gears, Left wheel bevel gear set (LBS), consists of two identical elliptic bevel gears as Left wheel bull bevel gear (LB) and Left wheel pinion bevel gear (LP) wherein
Left wheel bull bevel gear (LB) is driven gear and Left wheel pinion bevel gear (LP) is driving gear;
Left wheel bull bevel gear (LB) a vertically oriented bevel gear is coaxially mounted at its appropriate point on the left steering shaft (LSS) with its teeth facing upward direction;
Left wheel pinion bevel gear (LP) horizontally oriented bevel located on the right side of the Left steering shaft (LSS) towards upper side of Left wheel bull bevel gear (LB) with teeth facing towards left steering shaft (LSS) is mounted on left end of left steering-torque transmission arm (LST) in such a way that Left wheel bull bevel gear (LB) meshingly engaged with Left wheel pinion bevel gear (LP);
Left wheel pinion bevel gear (LP) is an elliptic bevel gear, of appropriate size chosen according to requirement of Ackermann or Anti- Ackermann steering, coaxially fixedly mounted on the left end of left steering-torque transmission arm (LST) such that its teeth meshes with left wheel bull bevel gear (LB);
Pivot point of Left wheel bull bevel gear (LB) and Left wheel pinion bevel gear (LP) are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle, which in case of second order elliptic bevel gear can be centrode of pitch curve.
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SUBSTITUTE SHEETS (RULE 26) Right wheel bevel gear set (RBS)
[22] As shown in Fig. l, Fig. 2 and Fig. 3, conjugate pair of elliptic bevel gears, Right wheel bevel gear set (RBS), consists of two identical elliptic bevel gears as Right wheel bull bevel gear (RB) and Right wheel pinion bevel gear (RP) wherein
Right wheel bull bevel gear (RB) is driven gear and Right wheel pinion bevel gear (RP) is driving gear;
Right wheel bull bevel gear (RB) a vertically oriented bevel gear is coaxially mounted at its appropriate point on the Right steering shaft (RSS) with its teeth facing upward direction;
Right wheel pinion bevel gear (RP) horizontally oriented bevel located on the right side of the Right steering shaft (RSS) towards upper side of Right wheel bull bevel gear (RB) with teeth facing towards Right steering shaft (RSS) is mounted on Right end of Right steeringtorque transmission arm (RST) in such a way that Right wheel bull bevel gear (RB) meshingly engaged with Right wheel pinion bevel gear (RP);
Right wheel pinion bevel gear (RP) and Right wheel bull bevel gear (RB) are identical to Left wheel pinion bevel gear (LP) and Left wheel bull bevel gear (LB), respectively;
Pivot point of Right wheel bull bevel gear (RB) and Right wheel pinion bevel gear (RP) are such that sum of instantaneous cone angle (with respect to every meshing point) is right angle, which in case of second order elliptic bevel gear can be centrode of pitch curve.
Pro-Ackermann Installation
[23] In order that steering system steer the vehicle according to close approximation to ProAckermann steering geometry till inner wheel steering angle, denoted by Ai, is less than 90 degree, gear sets need to satisfy additional conditions according to which at neutral position, as shown in Fig. 1,
Meshing point of the left wheel bevel gear set and right wheel bevel gear set is at the point 1) where transmission ratio between driving and driven gear is one, 2) while vehicle is steering left side, transmission ratio of driving to driven gear of left wheel gear set increases and of right wheel gear set decreases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set decreases and of right wheel gear set increases; left wheel bevel gear set (LBS) and right wheel bevel gear set (RBS) are mirror image with respect to vertical longitudinal zero plane of the vehicle.
Anti-Ackermann Installation
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SUBSTITUTE SHEETS (RULE 26) [24] In order that steering system steer the vehicle according to close approximation to AntiAckermann steering geometry till outer wheel steering angle, denoted by Ao, is less than 90 degree, gear sets need to satisfy additional conditions according to which at neutral position, as shown in Fig. 4,
Meshing point of the left wheel bevel gear set and right wheel bevel gear set is at the point 1. where transmission ratio between driving and driven gear is one, 2) while steering left side transmission ratio of driving to driven gear of left wheel gear set decreases and of right wheel gear set increases and 3) while steering right side transmission ratio of driving to driven gear of left wheel gear set increases and of right wheel gear set decreases; left wheel bevel gear set (LBS) and right wheel bevel gear set (RBS) are mirror image with respect to vertical longitudinal zero plane of the vehicle.
Steer Support Mechanism
[25] As shown in Fig. l, Fig. 2 and Fig. 3, Steer support mechanism (SSM), a mechanism with of help which steer system is connected to the vehicle and steering-torque transmission arms can be kept aligned and allowed to rotate whenever required, comprises two tubes, as right steer transmission head tube (RTH), left steer transmission head tube (LTH), coaxially rotatably housing right steering-torque transmission arm (RST), left steering-torque transmission arm (LST), respectively via ball bearings.
Suspension System
[26] Since all the four wheels of a four wheeler vehicle must roll on the ground to provide uniform steering geometry, suspension system plays a vital role during steering of any four wheeler.
[27] As shown in Fig. l, Fig. 2 and Fig. 3, steering system (1) according to this invention have the provision to provide suspension system (SPN) by allowing right steering shaft (RSS) and left steering shaft (LSS) to be Shock-damping system with axle of the front wheel being attached to outer protecting cover and axle eye attached to fixed link via ball bearing.
Steering operation
[28] As shown via schematic diagrams Fig. 5 when handle is rotated in clockwise direction, central top bull bevel gear rotates in clockwise direction which in turn via central left pinion bevel gear and left wheel pinion bevel gear rotates left wheel bull gear in clockwise direction and via central right pinion bevel gear and right wheel pinion bevel gear rotates right wheel bull
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SUBSTITUTE SHEETS (RULE 26) gear in clockwise direction and therefore results in steering the wheels in leftward direction. If the elliptic bevel gears installed according to Pro- Ackermann transmission ratio of left wheel bevel gear set will continuously increase and transmission ratio of right wheel bevel gear set will continuously decrease. If the elliptic bevel gears installed according to Anti- Ackermann condition, transmission ratio of left wheel bevel gear set will continuously decrease and transmission ratio of right wheel bevel gear set will continuously increase.
[29] As shown via schematic diagrams Fig. 6 when handle is rotated in anti-clockwise direction, central top bull bevel gear rotates in anti-clockwise direction which in turn via central left pinion bevel gear and left wheel pinion bevel gear rotates left wheel bull gear in anti-clockwise direction and via central right pinion bevel gear and right wheel pinion bevel gear rotates right wheel bull gear in anti-clockwise direction and therefore results in steering the wheels in rightward direction. If the elliptic bevel gears installed according to Pro-Ackermann transmission ratio of left wheel bevel gear set will continuously decrease and transmission ratio of right wheel bevel gear set will continuously increase. If the elliptic bevel gears installed according to Anti- Ackermann condition, transmission ratio of left wheel bevel gear set will continuously increase and transmission ratio of right wheel bevel gear set will continuously decrease.
Feasibility of Steering Mechanism
[30] For elliptic gear, with aspect ratio (ratio of length of major axis to minor axis) equal to 1.3, maximum transmission ratio is 1.3 and minimum transmission ratio is 1/1.3. Therefore on rotation of wheels by 45 degree ratio of transmission ratio of elliptic gear sets at inner wheel (which is left wheel during leftward steering and right wheel during rightward steering) to the transmission ratio of outer wheel (which is right wheel during leftward steering and left wheel during rightward steering) continuously rises to 1.69. Therefore elliptic bevel gear sets with each elliptic gear having aspect ratio is sufficient to achieve steering geometry as close approximation to Pro/ Anti Ackerman condition. Four wheeler vehicles can accommodate left wheel and right wheel elliptic bevel gears sets with each elliptic gear having minor axis as 9 inch and major axis as 11.7 inch. In case requirement is only to rotate the wheel by -45 degree to +45 degree, only sector portion of elliptic bevel gear may be installed.
SUBSTITUTE SHEETS (RULE 26)
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