DESC:FIELD OF INVENTION
The present invention relates an Electric Power Steering (EPS) system and more particularly the invention relates to fitting of EPS system in the front solid steering column of a three wheeled vehicle as a single column to reduce steering effort of the driver and to achieve about 1:1 steering turn between handle bar and road wheel. Further, the invention provides the assistance to the driver effort such that the driver can provide less effort.

BACKGROUND OF THE INVENTION
The basic aim of steering is to ensure that the wheels are turned in the desired directions. The conventional steering arrangement of delta type three wheeler vehicles is to turn the single front wheel using a handle bar which is positioned in front of the driver, via the solid steering column. These vehicles are normally used for a) Carrying passengers; or b) Carrying goods.

The torque required to steer the vehicle by the driver is varied from 40 Nm to 70 Nm depending upon the varying load of the vehicle. In the worst case scenario, when two passengers sit along with driver in front side of vehicle then the torque required to steer the vehicle goes maximum of up to 95 Nm. That is, if the front wheel load increases then the steering effort required to steer the vehicle also increases.

The conventional Electric Power Steering system used for passenger cars will reduce the driver effort to 3 to 4 Nm on steering wheel. This effort reduction cannot be provided to three wheeled vehicle since more assistance may lead to roll over (topple) of the vehicle. Hence this system cannot be used in three wheeled vehicles.

Moreover, the present EPS for passenger cars will provide the assistance based on only vehicle speed. When the speed increases, then the assistance provided by the system should be reduced. But for three wheeled vehicle, the assistance should be varied depend on the vehicle load as well as the vehicle speed. So, for the three wheeled vehicles the steering effort should be maintain in the range of 30 to 40 Nm irrespective of speed and load of the vehicle, to avoid rollover of vehicle and also reduce the driver fatigue.

The engagement of mechanical backup of conventional EPS comes into picture only after 8 degree of steering rotation in the passenger cars. If the mechanical linking of EPS happened after 8 degree of steering rotation, this will cause a steering play in case of handle bar mechanism which has 1:1 ratio between handle bar and road wheel. This causes misconception for driver during turning of the vehicle in case of handle bar mechanism.

US8781684B2 discloses a steering and control systems for a three-wheeled vehicle. A three-wheeled vehicle that includes: a single front wheel; two rear wheels; a passenger cabin; an electronic steering control unit; and a steering input device configured to send an electronic signal to the electronic steering control unit corresponding to an input received at the steering input device associated with turning the three-wheeled vehicle; wherein the electronic steering control unit is configured to counter-steer the front wheel in response to receiving the electronic signal, wherein the counter-steering of the front wheel initiates a leaning of the passenger cabin a direction of turning of the three-wheeled vehicle. However the front wheel is for counter steering control and the rear wheel is for turning the vehicle.

DE4239831A1 discloses an electrical power-assisted steering for motor vehicle - has motor driven by difference signal between manual steering torque and torque predicted by sensors. An electric power assisted steering system has a sensor to detect the manual torque applied at the steering wheel with an electric motor to assist the operation of the steering rack. There is a sensor for the cross-acceleration of the vehicle and another for the amount of vehicle yaw. A unit deduces the theoretical steering torque for the measured cross-acceleration and yaw and this value is compared to the manual torque. The difference signal is used to drive the electric motor. The theoretical steering torque increases with cross-acceleration and/or yaw and is zero when these parameters are zero. However this system is used for 4 wheeler vehicle and electric power steering system is for rack and pinion steering gear mechanism.

US6000491A discloses an electric power steering apparatus having steering torque sensor integrally assembled in steering device with variable steering ratio. An electric power steering apparatus includes a steering torque sensor assembled integrally with a steering device having a variable steering ratio. The steering device includes an input shaft eccentrically and rotatably mounted in a movable housing rotatably supported on a fixed housing, an output shaft rotatably mounted in the fixed housing in eccentric relation to the input shaft, a coupling relatively non-rotatably interconnecting the input and output shafts while allowing them to move relatively to one another in a perpendicular direction of axes of the input and output shafts, and a drive mechanism for rotating the movable housing relatively to the fixed housing to displace the input shaft relatively to an axis of the movable housing so that the eccentricity between the input and output shafts changes to vary the steering ratio of the steering device. The input shaft includes a first shaft connected to a steering wheel, a second shaft connected to the output shaft via the coupling, and a torsion bar connecting the first and second shafts while permitting relative torsional displacement between the first and second shafts. The steering torque sensor includes a slider engaged with the first and second shafts and axially displaceable in response to relative torsional displacement between the first and second shafts, and a coil attached to the movable housing for converting the amount of axial displacement of the slider into a corresponding electric signal. However the EPS system does not provide assistance directly to the front wheel without any gear device.

US20060185927A1 discloses a power steering system for all-terrain vehicle. To provide a power steering system for an all-terrain vehicle in which a control unit can be favorably protected from water, mud or the like coming from the ground surface at the time of operating of the vehicle on rough terrain or the like. In a power steering system for a saddle ride type four-wheel vehicle in which a rotary shaft of a power assist motor is disposed at right angles to a steering shaft and is inclined so that its upper portion is located on the rear side, a control unit for controlling the power assist motor is disposed on the upper side relative to a meshed portion between the power assist motor and the steering shaft. However the assist motor is fixed on the rear side of the steering shaft and ECU is fixed on the front side of the steering shaft.

US20050236791A1 discloses a steering power assist for 2 or 3 wheel motorcycles. Disclosed herein is an Invention which communicates physical assistance to steering a conventional two wheel or three wheel motorcycles. As it can be used to fine tune a two wheel motorcycle. The invention when applied to a three wheel motorcycle, or also referred to as a tricycle, quite profoundly eases the steering input necessary by the operator. In a three wheel application, steering becomes harder proportionally as the vehicle is turned from straight a head to its maximum turning angle, right or left. However the mechanical device is used to provide the assistance to the driver.

Accordingly, there exists a need for a fitting of EPS system in the front solid steering column of a three wheeled vehicle as a single column to reduce steering effort of the driver.

OBJECTS OF INVENTION
It is the primary object of the present invention to provide an EPS system which reduces steering effort on handle bar for three wheeled vehicles.

It is another object of the invention, wherein the assistance is provided based on the vehicle load and speed instead of only vehicle speed in case of passenger cars.
It is another object of the invention to provide an EPS system which identifies different scenarios of vehicle condition such as less load in static and dynamic condition and more load in static and dynamic condition.

It is another object of the invention, wherein the steering linkages are firmly connected with electric power steering and hence in the event of electric system malfunctioning, the vehicle can be driven with the mechanical system.

SUMMARY OF INVENTION
One or more of the problems of the conventional prior art may be overcome by various embodiments of the system and method of the present invention.

It is the primary aspect of the electric power steering (EPS) system for three wheeler vehicles, comprising of:
an EPS unit [3];
a reduction gear box [3C];
a torque sensor [3D];
a motor [3E]; and
an electronic control unit (ECU),
characterized in that, the EPS unit [3] is fitted in the front solid steering column [1] of a three wheeled vehicle as a single column,
an output shaft [3A] of the EPS unit [3] having an external spline is inserted into the spline bunk [1A],
the front solid steering column [1] in the vehicle comprises of one or more internal splines,
wherein the EPS unit [3] is mounted to the vehicle by interlocking/engagement of the external splines of the EPS unit [3] to the internal splines of the vehicle solid steering column [1],
the reduction gear box [3C], the motor [3E] and the ECU are provided at a steering column [1] of the vehicle for steering assistance,
the steering turn is achieved with 1:1 between a handle bar [4] of the vehicle for steering input device and the road wheel,
the manual torque is given through the handle bar [4] and the motor torque is given through a worm and worm wheel arrangement of the reduction gear box [3C],
the mechanical back up of EPS unit [3] is responded to less than 2 degree of rotation, and
the assistance from the system is varied during run time through a software programmed in the ECU according to the vehicle load, speed condition and the steering input torque.

It is another aspect of the present invention, wherein a housing of the EPS unit [3] is fastened with a vehicle frame [2] on top of the steering column [1].

It is another aspect of the present invention, wherein the EPS unit [3] drives the steering column [1] when the output shaft [3A] of the EPS unit [3] is rotated.

It is another aspect of the present invention, wherein a sleeve [3B] of the EPS unit [3] consists of one or more bearing supports with the EPS unit [3] to withstand the force of the handle bar [4].

It is another aspect of the present invention, wherein the handle bar [4] is connected to the sleeve [3B] of the EPS unit [3].

It is another aspect of the present invention, wherein the input shaft and the output shafts are mounted in the fixed housing of the EPS unit [3] in the same axis.

It is another aspect of the present invention, wherein the assistance can be provided by the electric motor [3E] present in the EPS unit [3] and the torque produced by the motor [3E] are multiplied through the reduction gear mechanism.

It is another aspect of the present invention to provide a method for working of the EPS system, comprises:
sensing the direction of the handle bar [4] turning by the torque sensor [3D] of the EPS unit [3];
sending the torque sensor signal to the ECU of the EPS unit [3];
receiving the vehicle speed and vehicle load signals from other sensors to the ECU of the EPS unit [3];
powering up the motor [3E] by the ECU based on the various input signals;
driving the output shaft [3A] of the EPS unit [3] by the motor [3E] through the worm and worm wheel arrangement of the reduction gear box [3C]; and
turning the steering column [1] by the output shaft [3A] of the EPS unit [3] with combination torques of manual torque and motor torque,
wherein the manual torque is given through the handle bar [4] and the motor torque is given through the worm and worm wheel arrangement of the reduction gear box [3C],
wherein the actual torque required to steer the vehicle is lesser at the handle bar [4], and
wherein when the vehicle load increases in the static condition then the assistance from the system is maximum whereas when the vehicle load is high in the dynamic condition then the assistance is reduced compared to the static condition.

BRIEF DESCRIPTION OF THE DRAWINGS:
So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.
Figure 1: illustrates the schematic diagram of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to one embodiment of the present invention.
Figure 2: illustrates the schematic diagram of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to another embodiment of the present invention.
Figure 3: illustrates the isometric view of the ECU according to one embodiment of the present invention.
Figure 4: illustrates the sectional view of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to one embodiment of the present invention.
Figure 5: illustrates the internal sectional view of the EPS unit according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The present invention relates an Electric Power Steering (EPS) system and more particularly the invention relates to fitting of EPS system in the front solid steering column of a three wheeled vehicle as a single column to reduce steering effort of the driver and to achieve about 1:1 steering turn between handle bar and road wheel. Further, the invention provides the assistance to the driver effort such that the driver can provide less effort.

Referring to Figure 1, the schematic diagram of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to one embodiment of the present invention is illustrated. An electric power steering (EPS) system for three wheeler vehicles is provided, comprising of an EPS unit [3], a reduction gear box [3C], a torque sensor [3D], a motor [3E] and an electronic control unit (ECU). The EPS unit [3] is fitted in the front solid steering column [1] of a three wheeled vehicle as a single column. An output shaft [3A] of the EPS unit [3] having an external spline is inserted into the spline bunk [1A]. The front solid steering column [1] in the vehicle comprises of one or more internal splines. The EPS unit [3] is mounted to the vehicle by interlocking/engagement of the external splines of the EPS unit [3] to the internal splines of the vehicle solid steering column [1]. The reduction gear box [3C], the motor [3E] and the ECU are provided at a steering column [1] of the vehicle for steering assistance. The steering turn is achieved with 1:1 between a handle bar [4] of the vehicle for steering input device and the road wheel. The manual torque is given through the handle bar [4] and the motor torque is given through a worm and worm wheel arrangement of the reduction gear box [3C]. The mechanical back up of EPS unit [3] is responded to less than 2 degree of rotation. The assistance from the system is varied during run time through a software programmed in the ECU according to the vehicle load, speed condition and the steering input torque.

Referring to Figure 2, the schematic diagram of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to another embodiment of the present invention is illustrated. Referring to figure 3, the isometric view of the ECU according to one embodiment of the present invention.
Referring to Figure 4, the sectional view of the EPS unit fitted in the front solid steering column of the three wheeled vehicle according to one embodiment of the present invention is illustrated.

Referring to Figure 5, the internal sectional view of the EPS unit according to another embodiment of the present invention is illustrated. A housing of the EPS unit [3] is fastened with a vehicle frame [2] on top of the steering column [1]. The EPS unit [3] drives the steering column [1] when the output shaft [3A] of the EPS unit [3] is rotated. A sleeve [3B] of the EPS unit [3] consists of one or more bearing supports with the EPS unit [3] to withstand the force of the handle bar [4]. The handle bar [4] is connected to the sleeve [3B] of the EPS unit [3].

The input shaft and the output shafts are mounted in the fixed housing of the EPS unit [3] in the same axis. The assistance can be provided by the electric motor [3E] present in the EPS unit [3] and the torque produced by the motor [3E] are multiplied through the reduction gear mechanism.

A method for working of the EPS system is provided, comprising of the following steps. The direction of the handle bar [4] turning is sensed by the torque sensor [3D] of the EPS unit [3]. The torque sensor signal is sent to the ECU of the EPS unit [3]. The vehicle speed and vehicle load signals are received from other sensors to the ECU of the EPS unit [3]. The motor [3E] by the ECU are powered up based on the various input signals. The output shaft [3A] of the EPS unit [3] is drove by the motor [3E] through the worm and worm wheel arrangement of the reduction gear box [3C]. The steering column [1] is turned by the output shaft [3A] of the EPS unit [3] with combination torques of manual torque and motor torque.

The manual torque is given through the handle bar [4] and the motor torque is given through the worm and worm wheel arrangement of the reduction gear box [3C]. The actual torque required to steer the vehicle is lesser at the handle bar [4]. When the vehicle load increases in the static condition then the assistance from the system is maximum whereas when the vehicle load is high in the dynamic condition then the assistance is reduced compared to the static condition. The assist motor [3E] is fixed on one side of the steering either left or right and the separate ECU is fixed on a vehicle chassis.

Front wheel turns the vehicle and the rear wheel follows the front wheel turn. The Reduction gear box, Motor and ECU is used to provide the steering assistance at the steering column so that driver can provide less effort to turn the vehicle. Handle bar is used as steering input device. This system provides steering assistance to the driver so that the effort is reduced. EPS system for solid column steering system is provided without any additional gear mechanism. The steering input torque, vehicle speed and the vehicle load is used to provide the assistance from the motor. The EPS system provided assistance directly to the front wheel without any gear device. Input shaft and output shafts are mounted in the fixed housing in the same axis. The system doesn't have any gear mechanism and the steering assistance directly transfers to turn the wheel. The assist motor is fixed on one side of the steering shaft either left or right and the separate ECU is fixed on the vehicle chassis. The System steers the front wheel of the three wheeled vehicle. The Electric Motor along with reduction gear box is used to provide the assistance to the driver.

Although, the invention has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. ,CLAIMS:WE CLAIM:
1. An electric power steering (EPS) system for three wheeler vehicles, comprising of:
an EPS unit [3];
a reduction gear box [3C];
a torque sensor [3D];
a motor [3E]; and
an electronic control unit (ECU),
characterized in that, the EPS unit [3] is mounted in the front solid steering column [1] of a three wheeled vehicle as a single column,
an output shaft [3A] of the EPS unit [3] having an external spline is inserted into the spline bunk [1A],
the front solid steering column [1] in the vehicle comprises of one or more internal splines,
wherein the EPS unit [3] is mounted to the vehicle by interlocking/engagement of the external splines of the EPS unit [3] to the internal splines of the vehicle solid steering column [1],
the reduction gear box [3C], the motor [3E] and the ECU are provided at a steering column [1] of the vehicle for steering assistance,
the steering turn is achieved with 1:1 between a handle bar [4] of the vehicle for steering input device and the road wheel,
the manual torque is given through the handle bar [4] and the motor torque is given through a worm and worm wheel arrangement of the reduction gear box [3C],
the mechanical back up of EPS unit [3] is responded to less than 2 degree of rotation, and
the assistance from the system is varied during run time through a software programmed in the ECU according to the vehicle load, speed condition and the steering input torque.

2. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein a housing of the EPS unit [3] is fastened with a vehicle frame [2] on top of the steering column [1].

3. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein the EPS unit [3] drives the steering column [1] when the output shaft [3A] of the EPS unit [3] is rotated.

4. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein a sleeve [3B] of the EPS unit [3] consists of one or more bearing supports with the EPS unit [3] to withstand the force of the handle bar [4].

5. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein the handle bar [4] is connected to the sleeve [3B] of the EPS unit [3].

6. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein the input shaft and the output shafts are mounted in the fixed housing of the EPS unit [3] in the same axis.
7. The electric power steering (EPS) system for three wheeler vehicles as claimed in claim 1, wherein the assistance can be provided by the electric motor [3E] present in the EPS unit [3] and the torque produced by the motor [3E] is multiplied through the reduction gear mechanism.

8. A method for working of the EPS system, comprises:
sensing the direction of the handle bar [4] turning by the torque sensor [3D] of the EPS unit [3];
sending the torque sensor signal to the ECU of the EPS unit [3];
receiving the vehicle speed and vehicle load signals from other sensors to the ECU of the EPS unit [3];
powering up the motor [3E] by the ECU based on the various input signals;
driving the output shaft [3A] of the EPS unit [3] by the motor [3E] through the worm and worm wheel arrangement of the reduction gear box [3C]; and
turning the steering column [1] by the output shaft [3A] of the EPS unit [3] with combination torques of manual torque and motor torque,
wherein the manual torque is given through the handle bar [4] and the motor torque is given through the worm and worm wheel arrangement of the reduction gear box [3C],
wherein the actual torque required to steer the vehicle is lesser at the handle bar [4], and
wherein when the vehicle load increases in the static condition then the assistance from the system is maximum whereas when the vehicle load is high in the dynamic condition then the assistance is reduced compared to the static condition.