GB2615292A - Agricultural vehicle with electric drive hub - Google Patents

Abstract

An agricultural vehicle 1 with an electric drive hub is provided. The vehicle 1 comprises: a supporting frame 2; a drive means (10, Figure 2); a ground contacting mobility means 15; a rechargeable electrical power source 7; and a controller 8 to activate or deactivate the drive means 10. The ground contacting mobility means 15 comprises a hub 16 and the drive means 10 comprises an electric motor mounted within the hub 16 and in electrical communication with the power source 7. The drive means 10 may further comprise a brake that is integral with and contained within the drive means 10 and in use of the vehicle 1 the brake is engaged to brake the drive means 10 when the controller 8 deactivates the drive means 10.

Description

AGRICULTURAL VEHICLE WITH ELECTRIC DRIVE HUB

Field of the Invention

The present invention relates to an agricultural vehicle, particularly an agricultural vehicle where the drive means comprises an electric motor.

Background to the Invention

Conventional self-propelled agricultural vehicles, such as crop sprayers, combines or balers use hydrostatic motors to power drive wheels or tracks to enable them to traverse fields or travel on roads. Each wheel usually has its own hydraulic motor to provide independent drive to all wheels. The motors are fluidly connected via a series of flow control valves to a main hydraulic pump which is driven by an internal combustion engine. Conventional hydrostatic design does not include any friction braking either for slowing during motion, or any form of parking brake. Hydrostatically driven vehicles rely on the oil in the system trapped between the motor and control valve to slow the vehicle or hold it stationary. Unfortunately, if a hydraulic pipe bursts, then there is no control of the wheel motor or motors on that pipe's circuit. As a result, all braking effects will be lost. Moreover, when a pipe does burst or motor seal blows, a large quantity of oil is lost onto the field, which generates significant environmental contamination issues.

Furthermore, when a hydrostatic vehicle stalls, for example, when it is climbing a hill, the wheel motor pumps oil back to the pump as the vehicle runs downhill. There have been several recorded instances of runaway self-propelled agricultural vehicles, even though check valves are meant to prevent hydrostatic failure.

To overcome this problem, some manufacturers have mounted conventional disc brakes to the wheel hubs to reduce the vehicle's vulnerability to loss of braking due to hydrostatic failure. However, disc brakes add mechanical complexity to the wheels and weight. Furthermore, they are difficult to maintain in an agricultural environment and have a short service life.

Other manufacturers use oil-immersed brake plates in the axle reduction hubs. These work fine on normal terrain and at legal speed limits on road. However, they often fail if the vehicle is speeding or, heavily loaded, or attempting to perform an emergency stop.

Another downside of the hydrostatic drive is the lack of drive torque at the wheel, especially at slow speed in adverse ground conditions. This is because no torque multiplier gears are usually used. There is also a loss of power between the engine and the transmission system as well as the transmission system and the differential unit.

Also, a considerable amount of energy is lost with the hydrostatic drive as heat. This is because heat is generated as the oil moves back and forth within the pipes and inside the pump under pressure. As the oil and the components get hot, the efficiency of the motors diminishes, resulting in significant power reductions. Although losses due to heating can be reduced using coolers, at least 25 °A, or more of the energy within the oil is lost to heat and cooling.

There has now been devised an agricultural vehicle which overcomes and/or substantially mitigates the above referenced and/or other disadvantages associated with the prior state-of-the-art agricultural vehicles.

Summary of the Invention

In an aspect of the invention, there is provided an agricultural vehicle as defined in claim 1.

The agricultural vehicle according to the invention is advantageous primarily because it does not suffer from any of the above problems.

As this agricultural vehicle uses a hub motor, it can deliver high torque, near instantaneously, to the mobility means for traversing uphill and other difficult ground conditions often seen in fields. This makes the vehicle unusually responsive and can tow or carry surprisingly large implements and loads in unfavourable agricultural environments.

The electric hub motor operates in a cyclic manner; therefore, rarely is the motor at full power. As a result, the motor does not generate anywhere near as much heat as a hydrostatic system. In other words, the conversion of electric energy into the kinetic energy required to drive the ground contacting mobility means is surprisingly more efficient than a hydrostatic system, with less energy wasted as heat.

Notably and surprisingly, the stability of the agricultural vehicle is far superior than that of a vehicle incorporating a hydrostatic drive system. This is postulated due to the precise nature of the delivery of power to the ground contacting mobility means through the drive means. It means that the movement of the vehicle is instantaneous on commands from the controller, and the vehicle does not suffer from minor delays as seen in hydrostatic systems. Therefore, there is less chance of the support structure wobbling, which can happen in hydrostatic vehicles due to the inherent slosh within a fluid based system.

Another advantage of the vehicle, according to the invention, is that the user can site the power for the drive means on any part of the vehicle. In other words, the user is not restricted, based on mechanics, to where the power unit must go. This feature is important to enable the user to control weight distribution and balance.

In addition, the vehicle does not need an internal combustion engine. As a result, there is greater scope for the mounting of implements to the supporting frame.

Furthermore, there are no oil pipes, fluids to contaminate the ground, steering racks, transfer boxes etc that adds weight to the vehicle and clutter up the supporting frame. Overall, these innovative design features make the vehicle surprisingly light with limited maintenance requirements.

Moreover, the vehicle is near silent whilst moving as no combustion engine is used. This makes the vehicle advantageous in agricultural environments bordered by populated areas.

Preferably the drive means comprises a brake that is integral with the drive means and in use of the vehicle the brake is engaged to brake the drive means when the controller deactivates the drive means. This means that, in particular, the brake enables the vehicle to be held under control when the controller deactivates the drive means. Furthermore, as the brake and the electric motors are housed within the drive means, they are well protected from the wear and tear caused by a dirty and harsh agricultural environment.

The ground contacting means may be wheels or tracks or a combination of both.

Preferably the drive means comprises one or more epicyclic gears that are integral with and contained within the drive means. This enables the motor components to be smaller so that they can be assembled within the drive means. It also means that the epicyclic gears are protected from the wear and tear of an agricultural environment. Preferably the epicyclic gears have a gearing ratio of between 10:1 and 40:1 for the drive means motor speed of rotation to ground contacting mobility means rotational rate. More preferably, the gearing ratio is 30:1. Thus epicyclic gears are used to obtain a slow wheel rotation needed for fieldwork whilst allowing the motor to run in the region of 30 times faster. This has the overall effect of maximising the torque produced at the wheels.

As well as being engaged when the controller deactivates the drive means, the brake may also be engaged independently of the motion of the drive means, under command from the controller. It is beneficial to have a brake that is integral to the drive means for protecting it in an agricultural environment. In the context of the invention, the deactivation of the drive means, could be understood to be any reduction in speed of the electric motor contained therein. The power of activation of the brake is proportional to the rate of deceleration of the electric motor commanded by the controller. This means that the brake does not fully activate when only a small change of speed is called for. It provides the control described above with respect to the advantages of the invention.

Preferably the power source is stored electricity in the form of one or more batteries. Other examples of suitable power sources include but are not limited to hydrogen electric or other electric power supply engines. Preferably the electrical power source is a modular rechargeable power source removably mounted to the supporting frame. This enables a replacement power source to be installed when the existing power source has been discharged easily and quickly. In other words, the old, discharged power source can be swapped out easily for a new one. Thus, the user of the vehicle does not have to wait for the recharging of the power source.

The power source may be rechargeable through conventional mains supply or super charging means. The power source may be recharged through solar and/or wind power. Suitable power sources include but are not limited to lead acid, lithium polymer batteries or lithium ion batteries. The power source may also be recharged from electricity from a local anaerobic digester plant. In such a manner the impact on the environment of the vehicle is greatly reduced. The solar and/or wind power may be derived from solar panels and/or wind turbines respectively at or near where the vehicle is located. The solar panels may be carried on the vehicle. This means that the power source can be recharged or the charge at least maintained without having to take it off the vehicle. It also extends the life-time of the power source before a recharge is necessary. The power source may also be recharged by a generator driven by an internal combustion engine carried on the supporting frame.

Preferably, in use of the vehicle, the electric motor provides between 500 and 3200Nm at peak torque. More preferably the electric motor provides between 1200 and 2100Nm peak torque. The drive means configured in this manner can deliver near-instant torque to the ground mobility means, compared to conventional tractors powered by combustion engines where there is a delay in the torque delivered to the wheel.

Preferably, in use of the vehicle, the electric motor delivers between 5 and 50 KW of power based on the operating modes of the vehicle. More preferably, the electric motor delivers between 7 and 20KW during nominal modes of operation. This enables the drive means to drive the ground contacting means with sufficient power to operate most conventional implements attached to the vehicle. It also means that, surprisingly, the vehicle's pulling power is comparable to that of most conventional tractors.

It will be recognised that for improved traction, steerage and stability, there may be a number of ground contacting mobility means. There may be a plurality of drive means each driving respective ground contacting mobility means. Each of the drive means are independently controlled by the controller, so as to enable efficient responsiveness to commands from the controller and to effectively enable the delivery of power to the mobility means.

The invention will now be described by way of example only with reference to the accompanying figures in which like numerals refer to like parts.

Brief Description of the Drawings

Figure 1 shows a side view of an embodiment of the vehicle according to the invention, and Figure 2 shows a perspective view of the vehicle in Figure 1, but without ground mobility means.

Detailed Description of the Illustrated Embodiment

In Figures 1 and 2, an embodiment of the vehicle of the invention is shown. The vehicle is generally designated 1. Vehicle 1 comprises a rectangular support frame 2 having four drive supports 3a, 3b, 3c and 3d (3d not shown). The drive supports 3a and 3b are located on one side of support frame 2, and the drive supports 3c and 3d are located on the opposite side of support frame 2. Both the support frame 2 and the drive supports 3a-d are manufactured from steel. The drive supports 3a and 3d are welded to opposite ends of a rear secondary frame 4, which spans the rear of vehicle 1. The drive supports 3b and 3c are welded to the opposite ends of a forward secondary frame 5, which spans the front of the vehicle 1. Each drive support 3a-d is mounted at right angles to the respective secondary frame and points downwardly from the respective secondary frame towards the surface on which vehicle 1 is used.

The forward secondary frame 5 has a swing arm 5a mounted to it, which is hingedly connected to the mid-point of the support frame 2. The rear secondary frame 4 also has a swing arm 4a mounted to it, which is hingedly connected also to the mid-point of the support frame 2. The secondary frames allow both the front and rear pair of wheels to move up and down together. Separation of the secondary frames from the main support frame is achieved by electric actuators (not shown) mounted between the respective secondary frames 4, 5 and the support frame 2, and controlled by the control unit. The secondary frames, therefore, provide vehicle 1 with suspension needed.

Mounted towards the front of the vehicle 1, on the support frame 2, is the cab 6 and behind cab 6 is a removable battery module 7 (Fig 2). It is noted that in other examples, which are substantially the same as the ones described here, the position of the cab 6 may be altered. Indeed, in some examples, there is no need for a cab 6 at all. Similarly, the battery module 7 position may be varied. The cab 6 comprises a control unit 8, which is operable by a user who sits inside cab 6, whlist vehicle 1 moves.

The battery module 7 is a 1000kg Lead acid pack. Its power rating is 48vDC 600Ah. In other examples, the battery 7 is a LiPo battery pack which is 1/4 size and 1/5 of weight of the Lead acid equivalent.

At the bottom of each drive support 3a-d (i.e. those parts opposite where the secondary frame attaches), there is mounted a drive unit 10a-d (only 10a-c shown). Each drive unit 10a-d extends outwardly of the respective drive support 3a-d, and thus points outwards of the centre of the vehicle, at right angles to the respective drive support 3a-d.

Each drive unit 10a-d comprises a frame mounting portion 11a-d and a wheel mounting portion 12a-d which are rotatable with respect to one another. Each drive unit 10a-d is mounted to the respective drive support 3a-d by the respective frame mounting portion of each drive unit 10a-d. Therefore, only the wheel mounting portions 12a-d of each drive unit 10a-d will rotate with respect to the rest to the other drive units.

Inside each drive unit 10a-d" an electric hub motor and a brake are mounted. Each drive unit 10a-d is in electrical communication via conducting electrical wires (not shown), with the battery module 7 and the control unit 8. Each electric motor includes a stator and a rotor. The stator of each motor is connected to the frame mounting portion 11a-d of the respective drive unit 10a-d. The rotor of each motor is attached to the wheel mounting portion 12a-d of each drive unit 10a-d. In other examples of the invention, vehicle 1 is substantially as described, but the mounting of the rotor and the stator are switched i.e., the rotor is mounted to the frame mounting portion and the stator is mounted to the wheel mounting portion 12a-d.

Mounted to the wheel mounting portion of each drive unit 10a-d is a wheel 15. Moreover, each wheel 15 has a hub 16 that substantially encases the respective drive unit 10a-d. The stator and the rotor of the electric motor are co-axial with one another, and the rotatable and non-rotatable portions of the drive unit are also coaxial with one another. The centre of hub 16 of each wheel 15 lies on the axis of rotation of the respective drive unit. Therefore, the drive from the motor is through the centre of the wheel 15 directly.

Each wheel hub 16 has a 7.50-16 tyre mounted, which has an outside diameter of 805mm. .Each electric motor is approximately an 8 KW motor.

In the example shown, there are attachments 20, 30 at the rear and front of the support frame for attaching implements. These attachments 20, 30 comprise standard conventional linkages. Implements 22, 32 are attached (only implement 22 shown in Figure 1) to these linkages, and in the example shown they are standard furrow devices. Other implements that might be used include but are not limited to trailers of drill subsoilers.

In use of the vehicle 1, the operator sits in the cab and controls vehicle 1 using control unit 8. The control unit 8 in this example is a joystick control, but other types of control units are envisaged suitable and exemplified here, such as a convention steering wheel with forward and backward control levers, just independent forward and backward levers (rather like tank controls) or pushbutton controls. Signals from the control unit 8 cause power to be delivered as required to each of the four drive units 10a-d either independently or as required by the operator (for example, if the operator wants to lock the rear wheels with respect to one another, so that they rotate together at the same speed). The delivery of power to the respective drive unit 10a-d causes the motors therein to operate and the rotor to rotate with respect to the stator. As the rotor is connected to the wheel mounting portion 12a-d, the respective wheel mounting portion 12a-d of the drive unit 10a-d also rotates. Since the wheel 15 is attached to the wheel mounting portion 12a-d, wheel 15 rotates thereby causing vehicle 1 to move.

Steering of vehicle 1 is achieved by controlling the power delivered to the respective drive unit 10a-d. For example, if the operator requires vehicle 1 to turn, then control unit 8 reduces power to the drive units 10a-d on the inside of the turning curve and increases the power to the drive units 10a-d on the out-side of the turn curve. This makes the wheels 15 on the inside of the turning curve rotate slower than those outside the turning curve.

In another example of the invention, vehicle 1 is substantially as described in any of the embodiments above, but further mounted within each respective drive units 10a-d is a series of epicyclic gears. The gears are mounted between the rotor part of the motor and the wheel mounting portion 12a-d. The benefit of this is that the motor can rotate fast whilst the wheels 15 rotate slowly. In this example, the gear ratio is 30:1 between the rotor and the wheel mounting portion 12a-d. It also means that the gears are kept clean from the usually dirty external agricultural environment. In case the rotor is mounted within the vehicle mounting portion, then the gears may alternatively be mounted between the stator and the wheel mounting portion. The gears may alternatively be mounted between the rotor and the stator of the electric motor.

In another example of the invention, vehicle 1 is substantially as described in any of the embodiments above, but steering of vehicle 1 is achieved by having steerable drive supports 3a-d. Each drive support is mounted to the respective secondary frames 4 and 5 using hinges. The hinge is located at the uppermost part of the respective drive support. The hinges allow each drive support to rotate back and forth about an axis that runs longitudinally through the centre of each drive support (i.e. generally at right angles to the support frame). The rotation of each drive support about its hinge is controlled by electric actuators which are mounted at one end to the support frame and at the other end of the actuator to a portion of the drive support which is forwards or backwards of the hinge. Each actuator is connected electrically to the battery module and the control unit. In response to instructions by the operator, the control unit decides which actuators to engage to cause which drive supports to rotate about their respective hinges and thereby which wheels to turn.

In another example of the invention, there is provided a vehicle 1 substantially as described in any of the embodiments above, but an autonomous drive unit replaces the operator. The autonomous drive unit may be integrated with the control unit, or separate. The autonomous drive unit may be programmable or be able to receive signals from an external source, such as radio fre-quency communication, GPS, or WIFI. Upon receiving said signals, the autonomous drive unit then sends instructions to the control unit to operate the vehicle 1, the same way that a conventional operator might perform. This allows vehicle 1 to be remotely or autonomously controlled without having an operator on board.

In another example of the invention, there is provided with a vehicle substantially as described in any of the embodiments above, but the wheels on one side of the vehicle are linked by a continuous track, and the wheels on the opposite side of the vehicle 1 are linked by a separate continuous track. The track is a caterpillar track or chain link track or the like. Vehicle 1 thereby gains traction from the contact of the tracks with the ground rather than the wheels directly. The advantage is that the increased ground contacting surface offers greater traction aiding forward movement of the vehicle..

In another example of the invention, there is provided a vehicle 1 substantially as described in any of the embodiments above, but the implements are suspended below the support frame between the wheels or between the tracks. This prevents vehicle 1 from tipping substantially when the implements are interacting with the ground; this is a typical problem encountered with forward or backward mounted implements.

In another example of the invention, there is provided a vehicle 1 substantially as described in any of the embodiments above, but the implements are mounted on top of the support frame 2. For example, if vehicle 1 is to be used as a sprayer, then the spray unit consisting of the spray tank, boom and pump, are all mounted on the top part of the support frame. Mounting on the top of the support frame does not impinge on the ground clearance achieved below the support frame by having the drive supports suspended from the support frame and the wheels each having their own drive unit (i.e. no through axle linking each wheel).

In another example of the invention, there is provided a vehicle 1 substantially as described in any of the embodiments above, but each drive support 3a-d has its own secondary frame, which is hingedly mounted to the main support frame. Thus, vehicle 1 has complete independent suspension.

In another example of the invention, there is provided a vehicle 1 substantially as described in any of the embodiments above, but there is no secondary frame. The drive supports 3a-d are welded to support frame 2. Steerage is by independent control of each separate drive unit.

Claims (6)

1. CLAIMS1. An agricultural vehicle comprising a supporting frame mounted on ground contacting mobility means, a drive means mounted to the supporting frame to drive the mobility means, a rechargeable electrical power source mounted to the supporting frame, and a controller to activate or deactivate the drive means, wherein the ground contacting mobility means comprises a hub and the drive means comprises an electric motor mounted within the hub and in electrical communication with the power source.
2. 2. An agricultural vehicle, according to claim 1, wherein the drive comprises a brake that is integral with and contained within the drive meansand in use of the vehicle the brake is engaged to brake the drive means when the controller deactivates the drive means.
3. 3. An agricultural vehicle, according to claim 1 or claim 2, wherein the drive means comprises one or more epicyclic gears that are integral with and contained within the drive means.
4. 4. An agricultural vehicle, according to any preceding claim, wherein the power source is a modular rechargeable power source removably mounted to the supporting frame.
5. 5. An agricultural vehicle, according to any preceding claim, wherein in use the electric motor provides between 500 and 3200Nm at peak torque.
6. 6. An agricultural vehicle, according to any preceding claim, wherein in use the electric motor delivers between 5 and 50 KW of power.