This invention relates to a cooling system on a vehicle. More specifically, this invention relates to a cooling system for cooling electrical components on an agricultural machine.

It is known in the vehicle industry to provide cooling circuits on vehicles to cool down the engine, or hydraulic oil, or transmission oil.

It is also known to generate electrical energy on a vehicle for powering propulsion systems. For example, electric motors are used to drive the wheels on a vehicle, such as a truck or car. To provide the necessary electrical energy, the vehicle is provided with a rechargeable battery, a fuel cell and a combustion engine connected to a generator.

Typically, such a vehicle will additionally have an electrical network (usually 12V or 24V DC) for supplying components on the vehicle and/or externa! systems, e.g. on a towed trailer, for example lights.

Agricultural machinery, such as agricultural tractors have different electrical energy requirements than passenger vehicles. As well as travelling over ground, a tractor must also provide power to implements attached to the tractor such as trailer, balers or ploughs. The implements require power to drive certain components on the implement, such as drives. The drives are usually powered by the PTO, or an hydraulic circuit.

If a medium voltage supply system, that is a voltage supply greater than 400V (150 kW), is available on the tractor, it is desirable to supply implements attached to the tractor with electrical energy. Electrical motors are cheap and easy to control and if the energy supply for the implement is taken from the tractor it avoids the implement having to generate and store its own electricity.

Medium voltage components require cooling systems to keep the temperatures of the electrical components at an optimum working temperature. Cooling circuits therefore have to be provided to cool electrical components on both the tractor and implement.

It is known to use transformer oil to cool down electrically powered drives and electrical components. Because transformer oil is a non electrical conducting fluid it can flow in direct contact with the electrical components and parts of the drives to be cooled. As a result the electrical components can be designed and housed more compactly than if an electrical conducting cooling fluid is used which must be guided in hoses, or cavities between the components and parts to be cooled.

The disadvantage of transformer oil is that it is harmful to the environment and is highly combustible. This has consequences if any of the transformer oil leaks.

Further, transformer oil is expensive. It can be a serious problem if a cooling system on an implement leaks as it will influence the cooling system on the vehicle.

It is also known to use a water glycol emulsion mixture to cool down electric drives and electrical components. It has the advantage that it is not harmful to the environment, however it is not as efficient as a cooling fluid as transformer oil.

Agricultural machinery and implements are fitted with specific, standard components with specific, recommended cooling requirements. The cooling requirements of two components may be different thus necessitating at least two different cooling systems.

It is an aim of the invention to provide an improved cooling system for cooling electrical components on an agricultural machine and/or an attached implement.

According to the invention there is provided An electrical component cooling system for use on a vehicle, said system comprising at least two cooling circuits each having a respective cooling fluid, characterised in that the system carries at least two different cooling fluids for cooling electrical components located on the vehicle and/or a connected implement.

Preferred features of the invention are set out in the dependent claims.

The invention will now be described by way of example only with reference to the following drawings in which:

Figure 1 shows a side view of an agricultural tractor coupled to a towed implement,

Figure 2 shows a circuit diagram of the cooling system in accordance with the present invention,

Figure 3 shows a circuit diagram of a medium voltage supply unit on an agricultural tractor, Figures 4 to 7 are circuit diagrams of a cooling system in accordance with further embodiments of the invention.

Figure 1 shows an agricultural tractor 1 coupled to a baler implement 2. A

detachable hose and wiring 3 connects implement 2 to the tractor 1 to allow the tractor to power the baler.

Figure 2 is a circuit diagram of a cooling system according to the invention which is used to cool electrical components located on a tractor 1

A combustion engine 10 located on the tractor 1 drives the generator 11a which is located within a medium voltage supply unit . Here a medium voltage supply is taken to be greater than 400 V. Components which are included in the medium voltage supply unit 11 are described later. Generator 11a is positioned within medium voltage supply unit 11 and is connected to an electric motor 12 which drives the tractor's wheels (not shown).

The first cooling circuit 20 comprises a cooling fluid 20c moving in the direction indicated by arrow A, pump 21 , an air to fluid heater core 22, and flow control valves 24a, 24b to control the rate of flow of the cooling fluid 24c in the circuit 20. Air is blown from fan 23 which is driven by combustion engine 10 to heater fluid core 22. Check valves 25a, 25b prevent the fluid flowing between consumers, that is the electrical components to be cooled without passing the heater core. A tractor control unit 100 controls the check valves 24a, 24b, combustion engine 10, generator 11a and electric motor 12.

The cooling fluid 20c is transformer oil although other cooling fluids may be used. Circuit 20 is used to cool the generator 11a and electric motor 12.

A second cooling circuit 30 comprises a pump 31 , an air to fluid heater core 32, control valve 33 and check valve 34. Fan 23 blows air onto core 32. Cooling fluid 30a comprises a water-glycol emulsion although an alternative cooling fluid could be used. Consumer 40 requiring cooling is cooled by circuit 30. Consumer 40 may for example be a low performance electric component such as an electric air compressor. Check valve 41 ensures that only components which are designed for water cooling are cooled by the second circuit 30.

Figure 3 shows an electrical circuit inside medium voltage supply unit 11 for a tractor 1.The medium voltage supply unit 1 is provided with an electric generator 1 1a which is driven by the engine crank shaft 10a of combustion engine 10 and an electronic power unit 11 b (insulated-gate bipolar transistor) connected to the electric generator by wiring. The unit 11 provides protection for the generator and power unit and reduces the risk of persons accidentally coming into contact with these components. Alternatively, the generator and power unit may be placed outside of the unit 1 a different locations on the tractor.

The generator produces AC power with an AC frequency dependent on the combustion engine speed. The electronic power unit 1 b converts the AC power output of the generator 11a to a DC voltage with the defined DC-link voltage level to provide ail units connected to the DC network 1 e.

A brake chopper 11 c is provided to avoid a voltage rise in the DC network 11 e if energy is fed back into the system from other sources than the generator. The chopper comprises an oscillating switch in series with a resistor and, depending on the input voltage overshoot (coming from e.g. the implement via the network) the switch is oscillated to guide the excess voltage into the resistor transforming the voltage into heat. The oscillation is necessary to keep the network active and supplying energy, if the switch was to be closed completely over a longer period, the complete voltage supplied by the system would be destroyed and all consumers would be non operative. By oscillating the switch, only the peaks of the voltage are destroyed and the system is still operative. In addition, the resistors are generally designed to be quite small so they are not capable of receiving a constant high load. Using oscillation enables them to cope with the load. E.g. the nominal voltage of the network is 700 V. The overshoot limitation is 900 V. If peaks greater than 900 V occur the switch is closed in an oscillatory manner.

An insulation monitoring system 1 1d is provided to monitor the resistance in the network to detect electrical malfunctions in the medium voltage system. This is necessary to protect the life of potential users of the system and to prevent damage in electric components of the tractor or implement or other consumers connected to the system.

Medium voltage DC network 11 e (greater than 400V, 150 kW) supplies tractor components such as a battery/supply network 16 via DC/DC converter 16a reducing voltages greater than 400 V to, for example, the standard 12V supply. An electronic unit 11g comprising a heating/ventilating/air conditioning (HVAC) compressor via DC/DC converter

is aiso provided. Similarly a variable cooling fan drive 1 1f is supplied via a DC/AC inverter to provide a variable frequency to vary fan speed.

To supply external consumers (e.g. on implements/ front loaders /stationary devices supplied by the tractor) additional supply means are provided.

Medium voltage DC network 11e is connected to an electronic unit 1 1h for supplying external consumers.

In a first mode, electronic unit 11 h converts high power DC into high power AC at fixed frequency to connectors 1 1i. Alternatively electronic unit 11 h can also supply high power DC to connectors 1k. By having an DC or AC supply, different consumer requirements can be fulfilled. E.g. an electric motor running on constant speed can be supplied with AC at a fixed frequency adequate for the wanted motor speed. If one or more electric motors with variable speed must be supplied, it may be more efficient to supply DC and convert into AC on the implement respectively for every electric motor.

There are two cooling circuits 111 and 1 m. First cooing circuit 111 carries

transformer oil and is used to cool high performance components, for example electric generator 11 a and electric power unit 1 b. A second cooling circuit 1 m carries a water glycol emulsion and is used to cool lower cooling requirement components such as a battery/supply network 11f, HVAC compressor supply 11 g, cooling fan drive supply 1 1 f and electronic units 11 h.

By having two separate cooling circuits, different consumers with different cooling requirements in different locations can be efficiently cooled.

Figure 4 shows a further embodiment of a tractor cooling system. The same reference numerals are used for the same parts already described. Both cooling circuit 20 and 30 are designed as secondary cooling circuits. Air to fluid heater cores 22 and 32 are replaced by fluid to fluid heater cores 222 and 232. Heater core 102 is placed in front of cooling fan 23. Installation space is reduced using this embodiment since heater cores 222 and 232 can be placed arbitrarily on the tractor.

Figure 5 is yet a further embodiment of a tractor cooling system. Figure 5 is based on the system shown in figure 2 extending the cooling system of the tractor 1 so that it can also be used to cool components on an implement 2. To supply the implement 2, the second cooling circuit 30 is connected to the implement 2 and a consumer 50 by self sealing couplings 51 a in the feedline 52a and self sealing couplings 51b in the return line 52b to disassemble the implement 2 without needing to empty the circuit.

By having two separate cooling circuits 20 and 30, any leakage, or failure of the second circuit on the implement will not affect the important circuit 20 on the tractor. Highly efficient cooling is provided on the tractor 1 whilst the lower cooling

requirement of the consumer on the implement is supplied with a fluid which is not harmful, for example a water glycol mixture. Such a fluid is not harmful if it leaks during coupling and uncoupling of the implement to and from the tractor.

Figure 6 shows a further embodiment still of a tractor cooling system. Figure 6 is based on the circuit of figure 5 in which the first cooling circuit 20 comprising a transformer is also supplying a high performance consumer 60 on the implement 2 by self sealing couplings 61a, 61b. The circuit is protected by control valves 62 and a check valve 63 is used to avoid flow of the cooling fluid in the wrong direction. If a sensor (not shown) detects pressure losses on the implement and/or supply lines 64, this information is forwarded to the tractor control unit 100 and the control valve 62 is closed to prevent the whole circuit leaking.

Figure 7 is yet a further embodiment which is based on the cooling circuit of figure 5. The second cooling circuit 300 is provided with a water glycol mixture to supply consumer 301 on implement 2. Secondary cooling circuit is dependent on the first cooling circuit. First cooling circuit 20 and second cooling circuit 300 are exchanging heat by a fluid to fluid heat exchanger 302. The fluid passage to heat exchange 302 can be controlled by control valve 303. The implement supply can be switched on or off. The check valve 304 is provided to avoid flow of the cooling fluid in the wrong direction. A pump 305 pumps the fluid around the circuit in the direction C shown by the arrow.

With the arrangement shown in figure 7, only one heater core 22 is placed in front of the fan 22 thus reducing the amount of space occupied in front of the engine 10. Cooling circuit 300 exchanges heat by an additional heat exchanger 302 which could be located at any convenient location on the tractor 1.

The second cooling circuit 300 can be reversed by using transformer oil whilst connected to the second cooling circuit 30 without having the first cooling circuit 20.