STEERING EFFORT REDUCTION SYSTEM

FIELD OF THE INVENTION

[0001] The present subject matter relates generally to a steering system, and more particularly, to a steering effort reduction system in an automotive vehicle.

BACKGROUND OF THE INVENTION

[0002] In many countries of the world, an automotive vehicle specially a three wheeled motor vehicle is a significant mode of public transportation. It is vastly used as a passenger carrier providing point to point mode of transportation in rural and urban areas and offering last mile connectivity, as well as also for load carrying applications. The vehicle comprises of a handle bar type steering system with a single steering column tube connecting a front wheel to the handle bar. The steering column allows the driver to maneuver the vehicle along a desired path and is designed in such a way that the single front wheel is exactly in line with the vehicle centerline.

[0003] Such a three wheeled vehicle is often driven over pot holed roads in urban areas and rugged, rough, unmetalled roads in rural areas. Though such vehicle is designed to bear the load of four people, generally it is overloaded and is operated intermittently for 12 to 14 hours a day to enable the driver to maximize his earnings. Operating the vehicle on this type of terrain coupled with excess load causes high stress on the steering column and head tube of the vehicle due to the combined forces acting on the head tube from vertical, left and right directions.

[0004] In light of these conditions, maneuvering such vehicle requires a high steering effort by the driver of the vehicle. With more number of passengers, the steering effort increases further. Moreover, when these vehicles are operated inside a city amidst huge traffic, it becomes even more difficult for the driver to maneuver at low speeds as the steering effort increases. The high steering effort causes steering fatigue and shoulder pain to the driver which is discomforting and troublesome for him, and may have the effect of harming his earning potential.

[0005] Hence, the present subject matter is directed to overcome one or more problems as set forth above. It is therefore an object of the present invention to disclose a steering effort reduction system which assists the rotational effort provided by the driver of a three wheeled vehicle at the vehicle steering means and reduces the overall steering effort. It is another object of the present invention to provide a powered steering effort reduction system for a three wheeled vehicle for efficient steering operation, increased driver satisfaction, reduced driver discomfort and improved operational efficiency. It is yet another object of the present invention to develop a low cost solution to reduce a driver's steering fatigue while operating the three wheeled vehicle for long hours.

SUMMARY OF THE INVENTION

[0006] To this end, the present subject matter discloses a steering effort reduction system for directly assisting the steering effort exerted by a driver of a three wheeled vehicle on a steering column tube through a handle bar, the steering effort reduction system comprising a gear train powered by a motor supported on a first supporting member and positioned anterior to an upper portion of the steering column tube, the said gear train further comprising a drive gear connected to a shaft of the motor and a driven gear secured around the steering column tube below the 'handle bar, the drive gear and the driven gear rotatab'ly connected to each other; a steering angle position sensor positioned atop an extended portion of the upper portion of the steering column tube and supported by a second supporting member; wherein the motor provides torque to the drive gear to assist the rotation of the steering column tube, and wherein further the motor output and its rotational direction is dependent upon the steering angle and steering rate.

[0007] According to an aspect of the present subject matter, one end of the first supporting member is connected to the extended portion of the upper portion of the steering column tube, and the drive gear axis is parallel to the long axis of the steering column tube.

[0008] The foregoing objectives and summary provide only a brief introduction to the present subject matter. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the subject matter and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 shows a side view of a typical three wheeled embodied for passenger carrying application.

FIG. 2 shows the front view of the three wheeled vehicle.

FIG. 3 is a rear view of the three wheeled vehicle showing the internal combustion engine mounted on the posterior side of the three wheeled vehicle.

FIG. 4 shows a perspective view of a steering effort reduction system according to an embodiment of the present invention.

FIG. 5 shows an exploded view of the steering effort reduction system according to the embodiment of the present invention.

FIG. 6(a) and 6(b) respectively show a graphical representation of the steering effort reduction in driver alone condition and gross vehicle weight condition.

DETAILED DESCRIPTION OF THE INVENTION

[00010] It is to be noted that "front" and "rear", and "left" and "right" wherever referred to in the ensuing description, refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the said vehicle. Furthermore, a 'longitudinal axis', except otherwise mentioned, refers to a front to rear axis relative to the vehicle, while a 'lateral axis', except otherwise mentioned, refers generally to a side to side, or left to right axis relative to the vehicle. Various other features of the present subject matter here will be discernible from the following further description thereof, set out hereunder. The detailed explanation of the constitution of parts other than the subject matter which constitutes an essential part has been omitted at suitable places. In the ensuing exemplary embodiments, the vehicle is a three wheeled vehicle for passenger carrying application. However it is contemplated that the concepts of the present invention may be applied to other types of vehicles within the spirit and scope of this invention including load carrying three wheeled vehicle.

[00011] The steering effort reduction system is now described in connection with the rendered drawings. In the supporting figures, the same reference numerals are given to members and parts having the same functions. The drawings are showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

[00012] FIG. 1 describes a side view of a concerned three wheeled automotive vehicle, referenced by the numeral 100, and driven by an internal combustion engine. The vehicle is laterally divided into two halves, along the axis X-Y, an anterior portion A having the driver's seat 107 while a posterior portion P has a long passenger seat 108 with a seating capacity of minimum three passengers. The anterior portion A has a front cowl 101 along with a windscreen 102. The lower portion of the front cowl 101 is connected to a front wheel 104 with a wheel cover 103 stationed in between. A steering means in the form of a handle bar assembly 109 is present behind the front cowl 101 which is used by the vehicle driver to operate/manoeuvre the said three wheeled vehicle 100. In this view, a steering column assembly connected to the handlebar is not visible to an onlooker of the vehicle. Meanwhile, a rear compartment 106 is present in the posterior portion P of the vehicle below the passenger seat 108 and supported on a pair of rear wheels 105 located on either side of the longitudinal axis of the vehicle 100. The rear compartment houses the engine and transmission system along with related vehicular components.

[00013] FIG- 2 illustrates a front view of the three wheeled vehicle with the panels and styling parts removed. The said three wheeled vehicle 100 is supported on a frame structure spanning from the anterior portion A to the posterior portion P of the vehicle. The steering column assembly is connected to the front wheel 104 and comprises a steering column tube 202, front suspension 203 and a trailing arm 204. The steering column tube 202 is rotatably supporting on the front wheel 104. An upper portion of the steering column tube is connected to the handlebar and a lower portion is connected to the front wheel due to which it acts as a mechanical link between the handle bar 109 and the front wheel 104. The steering column tube 202 is engulfed by a head tube 205 on all sides and welded or secured to the head tube. The head tube 205, which is a part of vehicle chassis, usually houses bearings that allow the steering tube 202 to turn freely. A clutch actuation lever 111 is pivotally mounted at a distal end of the handle bar 109 preferably on the left side thereof, such that the user may grip the handle bar 109 to change the gear ratio by retracting and releasing the clutch actuation lever 111.

[00014] FIG. 3 shows the rear view of the said three wheeled vehicle 100 with the rear panel removed and hence showing the otherwise invisible internal combustion engine 300 mounted at the posterior portion of the vehicle frame below the passenger seat 108 and inside the rear compartment 106. The internal combustion engine 300 produces the necessary power which is then transferred to the transmission system. The internal combustion engine can be petrol driven or diesel driven.

[00015] As shown in FIG. 4 and FIG- 5, the upper portion of the steering column tube is extended along its longitudinal axis so as to develop into a steering column tube as represented by the numeral 202'. The extended portion of the steering column tube is shown by 202'a. This modification is done without damaging the steering column of the vehicle. The steering effort reduction system is connected to the steering column tube 202' and mainly comprises of a powered gear train to assist the steering effort of the driver and a steering angle position sensor. The gear train further comprises of a drive gear 402 and a driven gear 403 and derives power from a motor 401, preferably a DC motor, positioned anterior to upper portion of the steering column tube 202'. The DC motor 401 is supported on the steering column tube 202' below the handle bar 109 through a first supporting member 404. One end of the first supporting member 404 is connected to the upper portion of the steering column tube. The drive gear 402 is connected to a shaft of the motor 401 whereas the driven gear 403 is secured around the steering column tube 202' below the handle bar 109. The drive gear 402 and the driven gear 403 are preferably spur gears and are rotatably connected to each other in a predefined gear ratio, preferably 2:1 in the present embodiment.

[00016] The gear train arrangement (drive gear and driven gear) is kept parallel to the long axis of the steering column tube 202' for efficient power transmission. According to an embodiment of the present invention, the centre-to- centre distance from steering column tube rotational axis to drive gear rotational axis is 55 mm which can be adjusted according to the position of the motor 401.

[00017] Further, to sense the steering angle corresponding to the handle bar 109, a steering angle position sensor (SAPS) 406 is provided in the steering effort reduction system. The said SAPS 406 is mounted atop the extended portion 202'a of the upper portion of the steering column tube 202' due to which it is better located to measure the steering angle. The steering angle position sensor 406 is held in this position on the steering column tube through a second supporting member 405 which connects the steering column tube extension 202'a to the posterior surface of the front panel 101 of the vehicle. The second supporting member 405 may be made of any material including sheet metal and is in the form of a narrow strip. It is to be noted that the location of steering angle position sensor 406 and DC motor 401 in the present invention ensure trouble free operation of the steering effort reduction system and does not hinder the vehicle steering operation.

[00018] According to an aspect of the present invention, the motor 401 provides torque to the drive gear 402 to assist the rotation of the steering column tube 202', and the motor output and its rotational direction is dependent upon the steering angle and steering rate. The working of the steering effort reduction system is now explained. The driver of the vehicle 100 exerts a rotational effort or torque on the handle bar 109 in order to steer the vehicle. The steering angle position sensor 406 records the steering angle or the angle by which the driver turns the steering column. The sensor output is then passed on to a control system of the DC motor 401 to develop the torque that is required to assist the driver. The DC motor 401 provides the required torque to the gear train which transfers it to the drive gear 402 through the shaft of the motor 401. The drive gear '402 drives the driven gear 403 which assists the driver of the vehicle. This torque assistance reduces the driver steering effort. The driven gear 403 can assist the torque up to 37.6 Nm to the steering column.

[00019] According to an embodiment of the present invention, the control system has a control logic based on the steering rate and steering angle. The control logic actuates the motor based on the SAPS signal voltage which is the input for the control system. Current from the motor is used as feedback signal. If the steering angle input voltage tends to zero at any time, the feedback system turns off the power supplied to the DC motor. The power required to steer the handlebar without the proposed system decides the power required for steering assistance. Hence, the static steering effort test results may be used as input to create a respective duty cycle for the DC motor.

[00020] The assisting direction of DC motor and duty cycle depends on SAPS input voltage. SAPS input voltage varies between an extreme left position of the handlebar and the extreme right position of the handle bar. If the signal voltage from the SAPS is less than a predetermined voltage, the motor assists the steering column to the left and vice versa. In a preferred embodiment, the cut off voltage for left direction steering support is 2V. However, it may change depending upon the duty cycle and the steering effort reduction required. By setting the range of operating voltage of SAPS, a linear function between voltage and steering angle is obtained which is used by control system to actuate the DC motor. Further, the motor power is obtained by stalling the DC motor. According to an embodiment, to achieve 70 percent assist, the DC motor may be operated at 60 W of power. The DC motor may be stalled for different SAPS voltage values and a duty cycle may be formed. Based on the change in steering angle input signal voltage with respect to time, the control signals from the system then assist the direction of DC motor and provide corresponding duty cycle. The input signals and control signals flow through control cables in the system. When tested, the present steering effort reduction system reduces the steering torque from 56 Nm to 32 Nm in driver alone condition as shown in FIG. 6(a) as well in gross vehicle weight condition as shown in FIG. 6(b).

[00021] From the forgoing description, it will be appreciated that the present invention offers many advantages. The integration of powered gear train with steering column provides a very simple yet efficient mechanism to reduce the steering effort of the driver without affecting the stability of the vehicle. The reduction in steering effort of the driver in turn leads to efficient steering operation even during long driving hours, drop in driver fatigue as well as increased driver satisfaction. The present invention does not decouple the steering column tube into two separately controlled parts or provide indirect assistance to any of the parts of the steering system. The present invention directly assists the steering column by connecting the gearing system directly to the steering column tube. Further, the steering effort reduction system assists and not completely removes the effort provided by the driver of the vehicle. Therefore, the steering system works even in the event of failure of all or any of the components of the steering effort reduction system. Furthermore, the present system offers a low cost solution to reduce the driver's fatigue. The increase in cost is offset by driver's delight, satisfaction and increased operational efficiency.

[00022] The present subject matter is thus described. The description is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

1. A steering effort reduction system for directly assisting the steering effort exerted by a driver of a three wheeled vehicle on a steering column tube through a handle bar, the steering effort reduction system comprising of: a gear train powered by a motor supported on a first supporting member and positioned anterior to an upper portion of the steering column tube, the said gear train further comprising a drive gear connected to a shaft of the motor and a driven gear secured around the steering column tube below the handle bar, the drive gear and the driven gear rotatably connected to each other, a steering angle position sensor positioned atop an extended portion of the upper portion of the steering column tube and supported by a second supporting member, wherein the motor provides torque to the drive gear to assist the rotation of the steering column tube, and wherein further the motor output and its rotational direction is dependent upon the steering angle and steering rate.

2. The steering effort reduction system as claimed in claim 1, wherein one end of the first supporting member is connected to the upper portion of the steering column tube.

3. The steering effort reduction system as claimed in claim 1, wherein the drive gear axis is parallel to the long axis of the steering column tube.

4. The steering effort reduction system as claimed in claim 1, wherein the said motor is a DC motor.

5. The steering effort reduction system as claimed in claim 1, wherein the said three wheeled vehicle includes a three wheeled vehicle for passenger carrying and load carrying applications with handle bar type steering.