GB2462129A

GB2462129A - Power supply for tractor implement

Info

Publication number: GB2462129A
Application number: GB0813727A
Authority: GB
Inventors: Markus Scholz
Original assignee: AGCO GmbH and Co
Current assignee: AGCO GmbH and Co
Priority date: 2008-07-26
Filing date: 2008-07-26
Publication date: 2010-01-27
Also published as: GB0813727D0; DE202008013955U1

Abstract

An auxiliary power supply system 100 for a tractor comprises an input connected to an electrical power supply 44 and an output connected to a tractor connector 22 for connection with an implement such as a baler. Transistors 80, 82 are arranged to selectively connect the output to the input in response to a signal from an electronic control unit 32. Short circuit protection circuitry 85 may also be provided. The system may be connected to the electronic control unit by a wireless connection.

Description

DESCRIPTION

POWER SUPPLY FOR TRACTOR IMPLEMENT

The invention relates to an auxiliary power supply system on a tractor for providing the power to an attached implement such as a seed drill. In particular, but not exclusively so, the invention is suited to a network structure conforming to the ISO 11783 standard.

As agricultural machinery becomes more complex with advances in technology so does the control systems associated therewith. Historically, the mechanisms of tractor-hauled implements such as balers and seed drills were driven by connections to the axles of the implement. Later on power take-off (FF0) shafts were introduced which provided mechanical power to the implement via a shaft connected to the rear of a tractor, still present on the majority of power machinery today.

As well as a P1'O shaft, modern implements have a control bus which connects to the tractor allowing a driver to control various functions on the implement via a user interface located in the cab of a tractor. The user interface often comprises a display monitor which may have touch input functionality and is often dedicated to a given implement. More recently, the control bus employed between the tractor and the implement has been standardised for example conforming with the ISO 11783 standard. This avoids time consuming changing of the user interface because the same control apparatus are used regardless of the attached implement.

An example known tractor/implement communications network is shown in Figures 1 and 2.

With reference to Figure 1, a baler 10 is hitched to the rear of a tractor 12 via a drawbar 14.

Mechanical power is delivered from the tractor 12 to the baler 10 via PlO shaft 16. A number of hydraulic pipes 18 are connected from the baler 10 to the rear of the tractor 12 at hydraulic spools 19. The hydraulic pipes 18 serve various hydraulic rams (not shown) located in the baler which adjust various operating parameters.

An implement bus breakaway connector 20 is connected to a receiving socket (not shown) in the rear of the tractor. A wiring harness 21 is connected between the implement 10 and the breakaway connector 20. As described above bus cables within the wiring harness 21 communicate control signals from the tractor 12 to the various functions on the baler 10.

With reference to Figure 2, the implement bus breakaway connector 20 is typically a socket which is received by the tractor connector 22 which takes the form of a plug. In the event of the implement 10 becoming unhitched from the tractor 12 the breakaway bus connections are designed to separate without causing damage to the attached cables.

The control system 30 shown in Figure 2 comprises an electronic control unit (ECU) which is connected to two bus lines, or control area network (CAN) lines. A first CAN line CAN_High 34 and a second CAN line CAN_Low 35. The two CAN lines 34, 35 are also connected to a user interface 36 in the form of a touch sensitive monitor for example located in the cab. The ECU 32 and user interface 36 communicate with a computer located on the implement (not shown) via the CAN lines 34, 35 and the breakaway connectors 22, 20.

It will be appreciated that the bus cables 34, 35 within the wiring harness 21 communicate signals in a two-way manner wherein measured parameters on the attached implement 10 are fed back to the tractor 12.

In addition to control signals, the wiring harness 21 also delivers electrical power to the implement 10 from the tractor 12 via the breakaway connectors 22 and 20. The system of Figure 2 includes three output power lines connected to the breakaway socket 22. The two power lines 40, 42 are connected to a battery 44 and generator 45 via respective relays 46, 48 and fuses 50, 52. The battery 44 and generator 45 are grounded by a connection to the tractor chassis 54 to complete the circuit.

When conforming to Part 9 of the ISO 11783 standard, first power line (PWR) 40 has maximum current rating of 30 amps determined by fuse 50 and serves to supply power to any actuators disposed on the implement such as valves and motors. The second power line (ECU_PWR) 42 has a maximum current rating of 15 amps determined by fuse 52 and serves to supply power to any computer located on the implement.

A third power line (TBC_PWR) 43 branches off from the second power line 42 and is connected to the connecter 22 at a respective terminal. This power line 43 supplies the Terminating Bias Circuit of the CANBUS.

The electrical relays 46 and 48 serve to isolate the battery 44 and generator 45 from the tractor connector 22 when the tractor 12 is not running. The ECU 32 is connected to the chassis 54 by signal lines 56 and 58 via the coils of the relays 46, 48. When the power is no longer required by the implement, the tractor ECU 32 drops the voltage on lines 56, 58 so as to drop out the relays 46,48 thus disconnecting the power lines 40, 42 from the battery 44.

The use of separate electrical relays for each power line 40, 42 is considered costly and bulky in an environment where space is at a premium. Also, relays are very sensitive to dust, moisture and ambient temperature making them susceptible to failure in a rough environment.

It is thus an object of the invention to provide an improved auxiliary power supply system for a tractor which is cheaper, consumes less space and is more robust.

In accordance with the invention there is provided an auxiliary power supply system on a tractor comprising an input connected to an electrical power supply, an output connected to a tractor ëonnector for connection with an implement attached to the tractor, and a transistor arranged to selectively connect the output to the input in response to a signal from an electronic control unit. By employing a transistor to selectively connect the output to the input the expense associated with a mechanical relay is avoided. The use of a power transistor allows the auxiliary power supply system to be housed in a relatively small package. Furthermore, transistors are less susceptible to harsh working environments and so deliver improved reliability in the overall system.

Preferably the system further comprises short circuit protection circuitry to disconnect the power supply therefrom in the event of a short circuit occurring resulting in a current flow exceeding a predetermined value. Advantageously, the short circuit protection circuitry removes the requirement for bulky fuses and allows the system to be simply reset by a turn of the ignition key or the push of a button for example. Thus the need to access the fuses and replace such in the event of a short circuit is avoided thus saving time and cost for the operator.

Preferably the short circuit protection circuitry only disconnects the power supply when the current flow exceeds the predetermined value for a predetermined period of time. This introduces intelligence into the short circuit protection circuitry wherein short overloads caused by the routine activation of capacitive loads are ignored whilst large sustained short circuits are protected against by automatic disconnection of the battery. This avoids the need to regularly reset the power supply whilst maintaining sufficient protection for the apparatus.

In a preferred embodiment the output comprises a first power line and a second power line each connected to a respective transistor. This allows each transistor to be independently switchable in response to a respective signal from the electronic control unit (ECU) and thus allowing independent control of the respective power lines. Preferably the first power line has a maximum current rating in the range of 30 to 60 amps and the second power line has a maximum current rating in the range of 15 to 25 amps.

The signal may be provided from the ECU only when the ignition circuit of the tractor is active. Therefore in response to an operator switching off the tractor engine the power to the tractor connector is automatically cut by switching off the transistor. However, in a preferred arrangement the demand for power from the implement is communicated to the ECU from the implement itself via a CANBUS.

The connection between the ECU and the power supply system according to the invention can be either analogue wired, wired over a bus system or wireless.

In a preferred embodiment the system is packaged in a single module thus allowing simple assembly and replacement in the event of failure. Preferably further still, the module is housed within the tractor connector.

The tractor connector preferably conforms with the ISO 11783 CAN BUS standard.

Further advantages will become apparent from reading the following description of a preferred embodiment with reference to the appended drawings in which:-Figure 1 is a perspective view of an implement attached to a tractor which can employ an auxiliary power supply system in accordance with the invention; Figure 2 shows a control system of the tractor of Figure 1 comprising a known auxiliary power supply system; Figure 3 shows a control system of the tractor of Figure 1 comprising an auxiliary power supply system in accordance with the invention; Figure 4 is an enlarged schematic view of the power supply system of Figure 3; and, Figure 5 is a plot of time against current for the trigger characteristics of short circuit protection circuitry included in the power supply system of Figure 3.

The invention delivers an improvement to known auxiliary power supply systems on a tractor.

The power supply system described below with reference to Figures 3 to 5 replaces the mechanical relays 46, 48 and conventional fuses 50, 52 of the system 30 described above with reference to Figure 2. The remaining components, such as the CAN lines, ECU, breakaway connectors, generator and battery are common to both systems. For this reason a detailed description of the features common to both the known and novel system will not be provided.

Furthermore, it will be appreciated that the auxiliary power supply system according to the invention can be fitted to the tractor 12 shown in Figure 1 and as described above.

With reference to Figure 3, a control system 70 fitted to a tractor 12 comprises an auxiliary power supply 100. Power lines 40 and 42 are connected to the battery 44 generator 45 via current carrying terminals of respective power MOSFET transistors 80 and 82. The transistors 80, 82 are each contained in a respective IC module 83, 84, of the type BTS55S available from Infineon Technologies AG, reference to the associated data sheet is invited.

The first power line 40 has a maximum current rating of 60 amps and the second power line 42 has a maximum current rating of 25 amps.

The ECU 32 is connected to the gate of each transistor 80, 82 via a respective connection 76, 78. Therefore, the current flowing between the battery 44 and generator 45 and the respective power lines 40, 42 is controlled by the application of appropriate electrical signals from the ECU 32 to the respective gates of the transistors 80, 82.

In this most simple and preferred embodiment of the invention the voltage applied to the gates of the transistors 80, 82 is taken high, for example 5 volts, by the ECU 32 in response to a received signal from the implement-based computer via the CAN lines 34, 35 and/or an ignition circuit 60 indicating that the tractor is in operation.

In the event that the tractor is switched off, by simple turning of the ignition key for example, and the power demand from the implement ceases, the voltage on lines 76, 78 is dropped to zero volts so as to disconnect the power lines 40, 42 from the battery unit 44.

Furthermore, the power supply system 100 comprises short circuit protection circuitry 85.

With reference to Figure 4, each MOSFET module 80, 82, comprises current measuring means 86, 87 which measures the current flowing between the source and drain of the associated transistor 80, 82 and provides a signal indicative of that measured current to the short circuit protection circuitry via signal lines 88, 89.

The short circuit protection circuitry 85 is connected to the chassis of the tractor 54 via a grounding connection 90. In the event that the circuitry 85 detects a short circuit sustained for a predetermined period of time the appropriate gate signal is interrupted by opening one of switches 91, 92 disposed in lines 76,78 respectively thus switching off the affected transistor 80, 82. The current to the affected power line is therefore switched off thus avoiding any further damage to the power supply system or implement or even person connected thereto.

To reset the short circuit protection circuitry 84 the digital inputs are set to a low voltage by simply switching off the tractor ignition 60. Alternatively, a switch may be provided in the cab which allows resetting of the circuitry without switching off the ignition. This is far quicker and simpler than the replacement of conventional fuses and requires no extra components to be fitted to the tractor 12.

The switch-off function of the short circuit detection circuitry 85 for the 60 Amp power line obeys the time-current relationship shown by the plot of Figure 5. The plot shows duration of current flow (t) verses the magnitudes of the current (I) with shaded area under the plot representing overloads allowed by the short circuit detection circuitry 85.

Relatively small overloads of say 100 amps are allowed to continue for a relatively long duration of say a few seconds. However, as the overload increases in magnitude, the allowed duration reduces according to region A of the curve shown in Figure 5. Hence, an overload of 300 amps is interrupted after one second.

Large overloads which are synonymous with a short to ground are disconnected within ims as shown by region B of the plot.

Therefore, the system 100 goes some way to distinguishing between a routine, harmless overload, which can occur for example when a large motor on the implement is initiated, and a potentially harmful short to ground.

The switch-off function of the short circuit detection circuitry 85 for the 25 Amp power line (and 43) obeys a similar time-current relationship to that shown in Figure 5 except that the allowed overload is significantly lower to protect the more sensitive components connected thereto.

The short circuit detection circuitry comprises analogue components to provide sufficient reaction times to protect the transistors 80, 82 in the event of a short to ground. The components form a resistor-capacitor (RC) circuit to deliver the required time delay in opening switches 91, 92. [Can we include the RC circuit?] Digital components can be employed instead but are less effective at providing sufficient and reliable short-circuit protection.

The power supply system 100 is packed in a single module with suitable terminals to be connected to the associated power lines 40, 42 battery 44 generator 45, grounding line 90 and ECU connections 76, 78.

Although the control lines 76, 78 are herein described as wired connections it is envisaged that a signal may be sent from the ECU to the power supply system via wireless connection.

The power supply system is suitable for use with any communication system between a tractor and implement based on the ISO 11783 standard.

It is envisaged that the status of the short circuit detection circuitry 85 could be communicated to the ECU and displayed to the driver on user interface 36.

Claims

CLAIMSI. An auxiliary power supply system on a tractor comprising an input connected to an electrical power supply, an output connected to a tractor connector for connection with an implement attached to the tractor, and a transistor arranged to selectively connect the output to the input in response to a signal from an electronic control unit.
2. A system according to Claim 1, further comprising short circuit protection circuitry to disconnect the power supply from the tractor connector in the event of a short circuit occurring resulting in a current flow exceeding a predetermined value.
3. A system according to Claim 2, wherein the transistor is disconnected from the power supply when the current flow exceeds the predetermined value for a predetermined period of time.
4. A system according to Claim 2 or 3, wherein the short circuit protection circuitry is reset by switching off an ignition circuit associated with the tractor.
5. A system according to any preceding claim, wherein the output comprises a first power line and a second power line each connected to a respective transistor.
6. A system according to Claim 5, wherein each transistor is independently switchable in response to a respective signal from the engine control unit.
7. A system according to Claim 5 or 6, wherein the first power line has a maximum current rating in the range of 30 to 60 amps and the second power line has a maximum current rating in the range of 15 to 25 amps.
8. A system according to any preceding claim, wherein the signal is provided from the electronic control unit only when an ignition circuit of the tractor is active.
9. A system according to any preceding claim wired to the electronic control unit.
10. A system according to any one of Claims I to 8, connected to the electronic control unit by a wireless connection.
11. A system according to any preceding claim packaged in a single module.
12. A system according to Claim 11, wherein the module is housed within the tractor connector.
13. A system according to any preceding claim, wherein the electrical power supply comprises a battery.
14. A system according to any preceding claim, wherein the tractor connector conforms with the ISO 11783 CAN BUS standard.