WO2010046905A1

WO2010046905A1 - Traction device

Info

Publication number: WO2010046905A1
Application number: PCT/IN2009/000495
Authority: WO
Inventors: Prashant V. Rao; Alok Kumar Tiwari; Pandharinath Namdeo Khatmode; Saurabh Gupta; Visha Pandey
Original assignee: Deere & Company
Priority date: 2008-09-12
Filing date: 2009-09-10
Publication date: 2010-04-29

Abstract

The invention seeks to provide a four wheel drive, four wheel steered vertical axle tractive device with continuously variable speed obtained through hybrid drive train with electronic control modules. The configuration seeks to provide optimized steering through electric systems generating differential control of wheel speeds. These devices are supported on a multi-layered scalable and flexible hollow chassis with suitable electro-pneumatic suspension with variable responses. The tractive device uses GPS driven location to obtain wheel slip control and electronic control of draft forces with mounted, semi-mounted and trailed implements to enable operation at desired tractive effort and depth of operation. The hitch system seeks to provide a virtual hitch point below and within the four vertical axle configuration for effective distribution of load on driving wheels on all terrains. By the virtue of above configuration the device is able to achieve three modes of steering viz. normal steering; zero turning radius and crab steering.

Description

Traction Device

Field of invention:

This invention relates to a traction devices such as those used in agricultural services, rural transportation and on-road vehicles and more particularly this relates to a multi utility traction device with or without hybrid configuration.

Background of invention:

Traction devices are commonly used for agricultural and off-road applications. Conventional traction device consist of horizontal front and rear axles, steering unit, prime mover, drive train, differential case with fixed final drive and three point linkages. Wherein prime mover is connected to drive train housing and said drive train housing is connected to differential case with fixed final drive, on which traction wheels are mounted.

These traction devices may not be used for all multiutility applications of different agricultural operations because of limitation for variable ground clearance, track width and conventional three point hitch system. Also these devices are not provided with separate suspension systems for supporting driver's work station and merely depend on tire inflation to obtain ground feed back. However, suspensions are provided separately for cabs and driver seat for ride comfort.

These devices use conventional gear train and structural casing/ transmission housing and hence uneconomical due to lot of material cost, manufacturing cost and number of parts. However elimination of conventional gearbox with electric motors and suitable drive trains are available to generate propulsion for cars and commercial vehicles. Presently traction devices used for agricultural purposes are not having system to monitor and control the tire slip which results in lower fuel economy and non uniform movement of the device over different types of terrain. Conventional depth and draft control systems are used to reduce wheel slip. Steering system used on conventional devices incorporate mechanical or hydraulic systems which require more response time and have power losses due to viscosity of oil in their circuits.

Hitches used in the conventional devices attach the trailers to rear of the rear axle center. This location causes weight transfer from the front axle and instability of the device.

For several years emphasis has been given to the problem of reduction of fuel consumption and exhaust emissions for on-road and off-road vehicles. To meet present and future emission norms, costs of conventional technologies are very high and will be difficult for agricultural customers to afford.

Prior art

US 2005/0150700 teaches a hybrid power train for farm tractors, wherein the elements defining at least one of the electric machines are housed in structural casing formed in one piece. Multiple structural casings form an integral part of the supporting structure of the tractor. Hybrid power train comprises a first electrical machine disposed within the first structural casing, an epicyclic gear train disposed within the first cavity of the second structural casing, and a second electrical machine disposed within the second cavity of the second structural casing. The diesel engine of the agricultural tractor is mechanically connected to the Power Take-Off (PTO) mechanism by routing the PTO shaft through a number of hollow shafts for transmitting power from the diesel engine to and from the two electric machines by means of a conventional epicyclic gear train.

US 6,502,654 teaches a utility transport tractor having a cargo box above the rear axle with the operator's platform forward of the rear axle enabling additional seats to be included. To maintain the functionality of a conventional agricultural tractor, the cargo box tail gate and a portion of the cargo box floor can be raised to positions in which they both extend upwardly and forwardly toward the operator. In these positions, the three point hitch at the rear of the tractor is visible to the operator as is typically the case conventional agricultural tractors. US 5,743,347 teaches a lawn end garden tractor having independent electric motors for both driven wheels. The motors are combined with reduction gearboxes, and the wheel is mounted on the output shaft of the gearbox. There is no mechanical axle connection. The power to the motors is controlled by an automatic controller as to wheel speed, power being increased/ decreased in accordance with whether the wheels are under- running or overrunning relative to manually-controlled speed setting. Steering is controlled by potentiometer on a mechanical steering wheel or by joystick control.

US 5,597,172 teaches an agricultural suspension system including four generally identical independent strut suspension assemblies each having a pneumatic spring supported above a strut shaft which is received within a strut journal connected to an adjustable axle.

US 7,219,779 teaches a hydro-pneumatic suspension system for cabs along with suspended seats. The system influences the dependency of the suspension stiffness on the axle load and can be used to adjust the stiffness to ballast conditions and operating or driving states.

Drawbacks associated with conventional devices

Conventional traction devices use horizontal front and rear axles thereby limitation for variable ground clearance and track width.

The devices are not provided with separate suspension systems for supporting driver's work station and merely depend on tire inflation to obtain ground feed back.

These devices use conventional gear train and structural casing/ transmission housing and hence uneconomical due to lot of material cost, manufacturing cost and number of part.

The devices use conventional depth and draft control system to monitor and control the tire slip. Steering system used on conventional devices incorporate mechanical or hydraulic systems which require more response time and have power losses.

Hitches used in the conventional devices attach the trailers to rear of the rear axle center causing weight transfer from the front axle and hence instability of the device.

To meet present and future emission norms, costs of conventional technologies will be high and hence difficult for agricultural customers to afford.

In order to overcome said drawbacks this invention is devised.

Objects of invention:

Main object of this invention is to provide a Traction Device which can generate tractive effort with minimum carried weight.

Yet another object of this invention is to provide a Traction Device with a provision for variable ground clearance and track width.

Yet another object of this invention is to provide a Traction Device with better maneuverability with four wheel drive and four wheel steering with slip control.

Yet another object of this invention is to provide a Traction Device with hitch system to have better stability on slopes/ undulated terrain and improved traction.

Yet another object of this invention is to provide a Traction Device with intelligent operator platform suspension system.

Yet another object of this invention is to provide a Traction Device which is simple in construction, easy to manufacture and cost effective.

Statement of Invention

Traction Device with or without hybrid configuration, with plurality of electric motors and plurality of articulated final drive system wherein individual traction wheel of said device is provided with said electric motor on respective vertical axle to provide continuously variable forward speed and/ or reverse speed, said device is provided with articulated final drive system in between the vertical axle and the traction wheels. Brief description of invention:

Traction Device in accordance with this invention basically comprises of scalable and flexible chassis, operator platform suspension system, electrical steering system, hybrid configuration incorporating engine, generator and controllers, individual wheel electric motors mounted on the vertical axles, self-aligning articulated final drive system, hitch system and Global Positioning System (GPS system). Wherein said scalable and flexible chassis is provided with intelligent operator platform suspension system to provide greater safety and increased operator comfort with better control at relatively higher speeds. Said chassis is provided with electrical steering system to steer the device in a desired manner. Said chassis is also provided with hybrid configuration incorporating engine, generator and controllers. Individual traction wheel of said device is provided with electric motor on vertical axle to provide continuously variable speed and reverse speed with full torque with a provision for regenerative braking. Said device is provided with self-aligning articulated final drive system in between the vertical axle and the traction wheel. Said final drive system comprises of driving pinion and driven final drive gear provided inside the final drive case. Rotation of the driving pinion on said final drive gear provides a mechanical spring suspension. The traction device is provided with unique hitch system with or without ballast weight/ s to provide improved stability on slopes enabling haulage of heavier loads. Said hitch system is connected to the chassis in between the axles to have a hitch geometry which can distribute the weight transfer due to hitched equipments to all the supporting wheels. Said device is also provided with GPS system to monitor the slip of all the traction wheels and correct it within the desired values and to provide improved maneuverability by four wheel electrical steering system with different modes to optimize tractive efficiency and field capacity in the field with a provision for regenerative braking.

Therefore said light weight traction device generates low soil compaction, have better fuel economy and variable ground clearance for movement over crops. Generator coupled with engine in the traction device provides electric current to run the four pneumatic traction tires to generate traction. When the device moves on undulated terrain, sub-frame deflects with respect to the main chassis in a manner to reduce the severity of the deflection of the chassis and provides a more stable platform for the driver seat keeping all its driving wheels in contact with the ground. When the device encounters with an obstruction, articulating final drive pinion climbs up on the final driven gear on driving wheel meeting an obstruction, causing the traction device to assume a position with respect to the ground which helps to reduce the starting torque requirement

he horizontal component of the ground reaction helps to reduce the starting torque requirement. Driver steering input is sensed by a controller which then rotates the wheel axle to achieve the desired steering mode. An electronic controller senses the rpm of each individual wheel and compares it with the GPS speed input. The differential slip value thus obtained is given to the electrical hitch controller which adjusts the depth of the implement to bring the wheel slip within the desired limits. Hitch linkage system below the main chassis enables the draft force to be transferred downwards on all supporting wheels and this helps the device to pull more than its weight with better stability on slopes.

Detail description of invention

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same

Fig.l shows isometric view of multi utility hybrid traction device in accordance with this invention.

Fig.2 shows plan view of the multi utility hybrid traction device.

Fig.3 shows elevation of the multi utility hybrid traction device.

Fig.4 shows plan view of chassis of the multi utility hybrid traction device. Fig.5 shows schematic sketch showing the principal of operation of the sub-frame and the chassis.

Fig.6 shows sectional view of the final drive assembly.

Fig.7 shows schematic view of the final drive assembly.

Fig.8 shows various steering modes.

Fig.9 shows schematic sketch showing the principal of traction of the wheel.

Fig.lO shows schematic sketch showing the hitching system.

Fig.ll shows schematic sketch showing principle of weight distribution to the four final drive assemblies

Now referring from figures 1 to 11

The Traction Device comprises of four pneumatic wheels (8) (Fig.l) with agricultural lugs mounted on vertical axles (16), connected to main chassis (9). Wherein the said main chassis is connected with sub-frame (12) which allows it to deflect with respect to the main chassis. This sub-frame is supported through hinges and pneumatic devices (23) (Fig.4) to the main chassis frame of the vehicle. The Chassis (9) enables continuous contact of the driving wheels (8) (Fig.l) with undulating terrain and provides a stable platform for the driver seat (14). The Chassis also incorporates adjustable means (10) to provide variable track width and adjustable ground clearance (11). Pneumatic devices are connected to air compressor (13) (Fig.4) which gets drive from the engine (1) (Fig.l).

Prime mover (engine) (1) along with its accessories, generator (2), power electronics unit (4) and operator seat (14) with different controllers (3) are mounted on sub-frame (12). Driver seat location is in close proximity to engine with suitable foot and hand control to operate brake and accelerator pedal. Generator (2) coupled with the crankshaft of the engine (1) is controlled by power electronics unit (4), which incorporates power semiconductor devices, converters/ inverters, control unit, switching strategies and packaging of the individual units (not shown).

Four Vertical axles (16) (Fig.l) comprises of inner shaft (17) and housing (17A) . The housings (17A) are connected to the main chassis supports (15) (Fig.2) and inner shafts (17) are connected to the steering arm linkages (19) (Fig.2). The wheels (8) are turned by steering arm (19) welded to the inner shaft (17) within the housing (17A). Individual electric motors (5) are mounted on the vertical axles and connected to the hub (6) provided on the bottom of the vertical axles (16) (Fig.l). These motors (5) give drive to wheels (8) through articulating final case (7) (Fig.l). The articulating final cases (7) are made from cast iron and contain final driven gear and a pinion on motor output shafts. The Vertical axles (16) and the articulating final cases (7) provide high ground clearance (11) (Fig.3). The electronic high voltage distribution controller provides continuously variable speed at all the driven motors (5) with provision for regenerative braking.

Final drive cases (7) are mounted on Vertical Axles (16) (Fig.l). Self-aligning articulating final drive case (7) allows the angular orientation of the supported device to provide optimum utilization of tractive force for forward motion. These articulating final cases (7) can rotate in relation to the lower case (not shown), causing the motor driving pinion to move up on the periphery of the final driven gear (34). The articulating final cases (7) enable maximum axle torque for forward motion. The driving wheels (8) are assembled from steel rims and pneumatic tires which get drive from articulating final case (7).

GPS system (not shown) is used to obtain the forward speed (actual speed) of the traction device (Fig.l) with respect to ground reference. An electronic controller (3) senses the rpm of each individual wheel (8) through the speed sensors (not shown) and thus calculates the theoretical speed of the wheels. Error signal (slip) is calculated from the calculated wheel speed and GFS measured speed. This error signal provides the vertical push requirement on the traction device by adjustment in the electro hydraulic hitch system (Fig.lO).

The traction device (Fig.l) uses an electrical steering system (18), configured with four vertical axles (16) which can be rotated to achieve the desired steering mode viz. normal steering (Fig.8A), zero turning radius (Fig.8B), crab steering (Fig. 8C). The invention uses a hitched linkage system (21) wherein the hitch point (22) is located below the chassis (9) and between the vertical axles (16). The hitch system is raised or lowered by implement lift system (29) connected to hitch linkages with suitable connecting device (28) (Fig.lO) where positions at different angles are controlled. By connecting a load or implement to this hitch system at lower links (24) and top link (27), the load gets distributed to all the four traction wheels (8). Lift link (25) connects the lower link (24) to the lift arm (26) (Fig.lO). Lift arm is pivoted on the main chassis (9). Normal weight on each wheel (8) thus gets increased and thereby increasing the tractive force of the traction device (Fig.ll).

Generator (2) coupled with engine (1) converts the mechanical energy in to electrical energy with the help of controller (3) and generator logic processor module which is used to drive electric motors(5) and also charging the battery pack(not shown) and running onboard electric loads, such as lights, electric Power Take Off (e-PTO) and other electrical accessories. Power electronics controller (4) does the system integration to improve the range of the electric vehicle and fuel economy for efficient and high- performance of the traction device (Fig.l). The motor controller (3) detects the faults such as over voltage, under voltage, over current, gate drive fault, motor (5) over temperature, inverter over temperature and the information is sent to the power electronics controller (4) and appropriate protective action is initiated.

Suitable electro-pneumatic suspension system integrates the hollow frame structured main chassis and sub-frame (12), supporting the operator station (Fig.4). As the vehicle undulates with the terrain (32), electro-pneumatic logic controls (30) monitors the angular variation signals (31) from the horizontal position and minimizes it and enables the traction device to keep all its driving wheels (8) in contact with the ground to generate traction force (T) (Fig.9). The construction of the Sub-frame (12) and the Chassis (9) (Fig.4) allows relative deflection of the members. The Sub-frame (12) (Fig.4) deflects with respect to the chassis in a manner to reduce the severity of the deflection of the chassis (9) providing a more stable platform for the driver seat (14) (Fig.4) on undulating terrain (32).

The tractive force (T) is a function of the normal weight (W), area of contact of the wheel (B x L ), horizontal component of ground reaction force (Fh) and the Vertical component of this force (Fv) (Fig.9). The high torque available at the driving wheels is utilized more efficiently than any other conventional vehicles as the load is directed below the chassis (9) (Fig.lO) and converted by the hitch geometry (Fig. 11) to vertical mass on all the four vertical axles (16). This increases the normal weight (W) (Fig.9). As all four wheels are driven the area of contact (B x L) (Fig.9) is maximum and this generates maximum tractive effort. This tractive effort enables the device to pull more than its weight.

When the traction device (Fig.l) begins to pull against any load, the final driving pinion (33) (Fig.7) climbs up on the final driven gear (34) (Fig.7) causing the traction device to assume a position with respect to the ground by which the horizontal component of the ground reaction to the wheels (Fh) (Fig.9) is greater in proportion than the vertical component (Fv) (Fig.9). These factors then combine to assist the hybrid traction device (Fig.l) to move forward using its motive power with minimum losses, lower starting torque and downscaling rating and size of electric motor (Fig.6). Now, when the driving wheels (8) (Fig.l) encounters uneven terrain (32) (Fig.5), first the final driven gear (34) (Fig.7) causes the articulating final case (7) (Fig.7) to rotate and the assembly moves relative to the driving pinion (33) (Fig.7). This acts like a mechanical spring suspension. With further rotation, the main chassis (9) starts deflecting further from one corner to another. The flexible chassis converts the resistance to deflection of its sections to additional vertical force on the wheel resulting in increased traction.

An electronic controller (3) senses the rpm of each individual wheel (9) (Fig.l) and compares it with the GPS speed input. The differential slip obtained by comparison of these inputs is referred against a set desired slip value. This input is given to the electrical hitch controller (3) which adjusts the depth of the implement to bring the wheel slip within the desired limits where slip data is managed by a microprocessor.

Wheels connected to the four vertical axles (16) are driven by electric motor (5) (Fig.l). Driver steering (19) input is sensed by a controller which then rotates the steering motor axles to achieve the desired steering mode (Fig.8). The steering controller communicates with drive controller to determine the differential speed of the wheels to achieve no slip turning of vehicle.

Wheel (8) speed (all four wheels) input, operator demand (Steering wheel (20)) angular position, torque and rotation direction) is shared from motor drive controller and steering controller. Based on 3D matrix, fed in to the controller, control of electrical steering motor is done. The steering controller provides the angle and direction of rotation of the wheels about the vertical axles (16) of the traction device whereas drive controller controls the individual wheel speed based on the steering angle (e.g. slows the speed for inner wheels with respect to the outer wheels) to provide differential action.

Hitch linkage system (21) wherein the hitch point (22) is located below the chassis and near to the center of gravity enables the draft force to be transferred downwards on all supporting wheels to increase normal weight (W) thereby improving the tractive force (T). As the draft force lends its own weight to the traction device, device need not carry any additional weight for better traction. Hitch height of hitch linkage system is set by a servo controlled electro hydraulic hitch linked to the slip micro controller (not shown). For stability of the traction device during implement transportation, suitable parking arrangement is made for the implement on the chassis (9).

Main advantage of the invention is the multiutility of the traction device having variable ground clearance and track width with intelligent operator platform suspension, unique hitch system with improved tractive effort and electric drive system helping in downsizing the engine and getting better fuel economy, better emission performance and also a mobile electric power source available to run AC appliances in remote areas and improved reliability of the system due to higher efficiency and lower parts as compared to conventional mechanical/ hydraulic drive reducing lot of material cost and manufacturing cost. Other advantages are four wheel drive, four wheel steering with high maneuverability, flexible suspension, articulating final drive, slip control, low soil compaction and stability for uniform operation.

The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that those skilled in the art may practice numerous alterations and modifications without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

Claims

WE CLAIM:

1. Traction Device with or without hybrid configuration, with plurality of electric motors, and plurality of articulated final drive system, wherein individual traction wheel of said device is provided with said electric motor on respective vertical axle to provide continuously variable forward speed and/ or reverse speed, said device is provided with articulated final drive system in between the vertical axle and the traction wheel.

2. Traction Device as claimed in claim 1 wherein said device comprises of scalable and/ or flexible chassis, operator platform suspension system, steering system, self aligning articulated final drive system and hitch system, wherein said scalable and flexible chassis is provided with operator platform suspension system to provide greater safety and increased operator comfort with better control, said chassis is provided with series-hybrid configuration, the traction device is provided with hitch system with or without ballast weight/ s to provide improved stability, said hitch system is connected to the chassis to have a hitch geometry to distribute the weight uniformly to all the supporting wheels.

3. Traction Device as claimed in claim 1 or 2 wherein said device is further provided with Global Positioning System (GPS) to monitor the slip of all the traction wheels.

4. Traction Device as claimed in any of preceding claims 1 to 3 wherein said chassis supports driving wheels, and comprises of a sub-frame supported on it through suitable suspension system to mount prime mover, generator or integrated starter generator, power electronics unit, controllers, driver seat and other accessories.

5. Traction Device as claimed in any of preceding claims 1 to 4 wherein said device comprises plurality of vertical axles, said axle comprises of inner shaft slidingly mounted inside housing, said housings are connected to the main chassis through rotary joint assembly and the housing is also connected to the steering arm linkage.

6. Traction Device as claimed in any of the preceding claims 1 to 5 wherein said final drive system comprises of driving pinion mounted inside final drive case and driven gears supported on shafts provide drive to the axle shaft, on which the individual traction wheel is mounted, final drive pinion climbs up on the final driven gear on driving wheel meeting an obstruction, causing the traction device to assume a position with respect to the ground which helps to reduce the starting torque requirement.

7. Traction Device as claimed in any of the preceding claims 1 to 6 wherein said device is provided with plurality of electronic controllers to sense the rpm of each individual wheel and to compare the theoretical speed with the GPS speed input to obtain differential slip against a set desired slip to raise or drop the implement to maintain the slip or depth/ draft.

8. Traction Device as claimed in any of the preceding claims 1 to 7wherein said device is provided with separate controllers for the steering system and drive system wherein controller for the steering system senses the direction and rotation angle of traction device about its vertical axles and controller for the drive system controls the wheel speeds based on the operator input & steering controller input and thus facilitates the turning of the traction device along a predetermined path with two or four wheel steering mode accompanied with differential action.

9. Traction Device as claimed in any of the preceding claims 1 to 8 wherein said hitch system comprises a electro- hydraulic hitch system linked to the slip micro controller with the hitch point located below the chassis and between the vertical axles in such a way that the draft force is distributed on all axles and contributes to the stability of the vehicle.

10. Traction Device as claimed in any of the preceding claims acting as a mobile electric power source to run electrical appliances.