DESCRIPTION TECHNICAL FIELD

The present invention relates to a system for feeding an engine of tractor powered by alternative gas fuel and configured to tow an auxiliary unit, e.g. a trailer such as an implement or a range extender.

BACKGROUND OF THE INVENTION

Tractors may be powered by using alternative gas fuel in order to reduce the emissions with respect to other typology of fossil fuels.

One example of alternative gas fuel is Compressed Natural Gas (CNG) (methane stored at high pressure) that is a fuel which can be used in place of gasoline, diesel fuel and propane/LPG.

Another example of alternative gas fuel is Liquefied Natural Gas (LNG) that is a natural gas

(predominantly methane, CH ₄ , with some mixture of ethane C ₂ H ₆ ) that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport.

Today the current design layout of a tractor does not allow to accommodate a main tank large enough for storing of a suitable amount of gas fuel to allow to power the engine for a full working day of the tractor. Accordingly, the tractor has to be used with an auxiliary gas tank that is carried by an auxiliary unit such as a towed implement or a range extender such as the front or rear hitch or fixed to the front on the front axle support. Usually such main tank is used first for feeding the gas engine and, when such tank is almost empty, the auxiliary tank is used for feeding the engine.

However, it may happen that main tank of the tractor has not sufficient gas for returning to its recovery, leaving its user in the fields without possibility of moving away.

Further, implements or range extenders provided with gas tanks are cannot be usually driven on roads because they are not usually homologated for such configuration and therefore, if the auxiliary unit has the entire tank full of gas, it should be left on the fields leading to the danger of explosion in hot/sunny environment.

In view of the above, the need is felt to foresee an optimized system for managing gas between a tractor and an auxiliary unit when such tractor uses gas for feeding its engine .

The present invention is therefore focused to solve the aforementioned problem in an economic and optimized manner.

SUMMARY OF THE INVENTION

The above technical problem is solved by the present invention that relates to a tractor according to the amended set of claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be described in the accompanied drawings that represent a non-limiting example of the invention wherein, in which the only Figure 1 represents schematically a layout of tractor according to the invention. DETAILED DESCRIPTION OF THE INVENTION

Figure 1 discloses a vehicle system in which numeral 1 indicates a tractor (of a known kind) connectable to an auxiliary unit 2, e.g.. a trailer (of a known kind) such as towed implement or a range extender.

Tractor 1 comprises a main tank 4 carried by tractor' s body and configured to house fuel in a form of liquefied or compressed gas to power the internal combustion engine 5 of the tractor 1. The auxiliary unit 2 carries at least one auxiliary tank 6 to house the aforementioned fuel in form of liquefied or compressed gas. As known, example of gas fuels are Compressed Natural Gas (CNG) and Liquefied Natural Gas (LNG) .

According to an aspect of the present invention, a valve

10 is provided with inputs 10-a, 10-b connected respectively with a first supply line 11 originating from the main tank 4 and with a second supply line 12 originating from the auxiliary tank 6; the valve 10 has an output 10-c connected with a fuel supply line of the engine 5 through a third supply line 13.

The valve 10, per se known, is designed to place in fluid communication the output 10-c with the input 10-a or the input 10-b, may be advantageously carried by tractor 1 and may be electrically or fluidically actuated.

Pressure variation means 14, i.e. a pressure regulator for LNG or a pressure reducer for CNG, may be placed along supply line 13 downstream with respect to valve 10 in order to regulate pressure of LNG/CNG from to the value of the pressure in the respective tank 4, 6 to a value suitable for injection in engine 5.

The tractor 1 is further provided with an electronic control unit 16 that is electrically connected to valve 10 to control this latter in order to supply engine 5 only with the fuel contained in the auxiliary tank 6 as a predominant action; preferably such control unit 16 is the ECU of tractor 1. Electronic control unit 16 is configured to control valve 10 to supply the engine 5 with the fuel contained in the main tank 4 when the fuel contained in the auxiliary tank 6 goes below a preset limit, e.g. lower than 10 bar, representing the condition in which the auxiliary tank 6 is almost empty.

More specifically, a pressure sensor 18 is provided on the second supply line 12 to measure the pressure of the gas in the auxiliary tank 6 and a pressure sensor 19 is provided on the first supply line 11 to measure the pressure of the gas in the main tank 4. Both sensors 18 and 19 are electrically connected to control unit 16 which is configured to receive and memorize pressure related values detected by these latter.

Preferably, the control unit 16 is electrically connected to a connection sensor 20 that is provided to detect the connection of the second supply line 12 with the valve 10; the electronic unit 16 is configured to implement the above described strategy when the connection sensor 20 detects the availability of the auxiliary tank 6 and is configured to supply to the engine 5 with the fuel of the main tank 4 when the connection sensor 20 detects the unavailability of the auxiliary tank 6.

Most preferably, the second supply line 12 is provided with a quick coupler 22, per se known, for connecting the auxiliary tank 6 with second line 12 and the connection sensor 20 detects such coupling of the quick coupler 22 Advantageously quick couples 22 and connection sensors 20 are integrated one with the other and are both electrically connected to control unit 16.

Further, a respective non return valve 24,25 is placed on each between first and second supply line 11,12 to avoid exchange of gas between the main tank 4 and the auxiliary tank 6. Indeed, it may happen that, when auxiliary tank 6 is almost empty, gas may flow from main tank 4 to auxiliary tank 6. The operation of the above described tractor 1 is the following .

When the measured pressure in auxiliary tank 6 is greater than the preset limit, i.e. the auxiliary tank 6 is full or partially full, valve 10 is controlled so that the input 10- b is connected with the output 10-c and the engine 5 is supplied with the fuel contained in the auxiliary tank 6 that is used as a fuel source as long as the pressure in the tank is sufficient, i.e. the amount of the contained fuel is sufficient .

Conversely, when the measured pressure becomes lower than the limit, i.e. the auxiliary tank 6 is almost empty, the valve 10 is switched so that the input 10-a is connected with the output 10-c and the engine is supplied with the fuel contained in the main tank 4.

According to the above described logic, it is possible to discharge first the auxiliary tank 6 and then the main tank 4.

The invention is further related to a for controlling fuel feeding to a gas engine 5 of a tractor 1 as described above according to a control method comprising the following steps :

• detecting coupling of auxiliary tank 6 with said second supply line 12;

• if such coupling is realized, starting as predominant action the feeding of gas engine 5 of tractor 1 via auxiliary tank 6 of the auxiliary unit 2 otherwise feeding gas engine 5 from main tank 4;

• detecting pressure of auxiliary tank 6 of the auxiliary unit 2;

• switching feeding of gas engine 5 of tractor 1 from auxiliary tank 6 to main tank 4, when pressure of auxiliary tank 6 decreases below a preset limit. Preferably, as said, the detection of the pressure in the auxiliary tank 6 is made by a closed loop control by pressure sensor 18 and control unit 16.

Advantageously the control unit 16 comprises elaboration means configured to memorize and run automatically the steps of the above described method.

In view of the above, the advantages of a tractor 1 as described is the following.

The auxiliary tank 6 is empty first with respect to main tank 4 and therefore the above described drawbacks are limited .

Indeed, if necessary, auxiliary unit 2 with empty auxiliary tank 6 may be safely parked on field at the end of the working day and the tractor 1 should be always provided with sufficient gas to come back from fields with the remaining fuel contained in the main tank 4.

It is clear that modifications can be made to the described tractor 1 which do not extend beyond the scope of protection defined by the claims.

Auxiliary unit 2 may comprise more than one auxiliary tank 6 and, as said, auxiliary unit 2 may be represented by any possible trailer unit such as an implement or a range extender .

Further, it is clear that valve means 10 may be of any typology and that non return valves 24, 25 may be substituted by equivalent means or being absent.

Similarly quick coupler 22 may be absent or substituted by an equivalent device.