MISFUELLING PREVENTION DEVICE

Abstract: A system for preventing the accidentally adding of automotive diesel fuel to the fuel tank of a gasoline fuelled vehicle at retail filling stations. The vapour pressure in the tank to be filled is measured by means of sensors and the difference in vapour pressure between petrol and diesel fuels is used to give a safety cut-off system.

Description: The invention relates to a misfuelling prevention device. Such a device acts to stop specific fuel being accidentally added to the fuel tank of an engine which has not been developed for such specific fuel. For example, such a device acts to stop automative diesel fuel being accidentally added to the fuel tank of a gasoline (petrol) fuelled vehicle at retail filling stations. Automative gas oil is being used in increasing quantities by the private motorist, who can now choose a compression-ignition engine as an option with most ranges of cars. This has encouraged changes in the siting of delivery pumps at retail stations, and whereas previously the diesel pump would be remotely situated it will now often be found on the forecourt next to its gasoline counterparts. The motorist must thus make an active decision as to which pump to select when purchasing fuel, and failure to do so could result in misfuelling. The principal problem arises with the drivers of conventional gasoline-fuelled vehicles who draw up to diesel pumps unaware that any fuel other than gasoline is availa­ ble; the converse problem of drivers attempting to put gasoline into diesel tanks is much rarer, presumably because the drivers of diesel-fuelled vehicles, who are in the minority, are most accus­ tomed to being selective in their refilling. This problem is handled at present by the retail station forecourt attendant, who will normally keep the diesel pump switched off. He can then ask the customers positively to confirm that they require diesel fuel before activating the pump. This system fails, however if the attendant is busy or lax. In addition motorists are unused to being questioned by the attendant, and cases have occurred where the customer has responded positively to the questions put to him, and then solemnly proceeded to refill a gasoline vehicle with diesel fuel. At best this causes considerable disruption to the business of the retail station, and at worst could damage a customers vehicle resulting in a claim for repairs. There are several ways in which this problem could be tackled. Customer education is an obvious one, and with the advent of low-lead gasolines the motorist will soon have to choose between three incompatible fuels and the need to select a pump on this basis rather than at random will become accepted. A more direct alternative would be to ensure physical incompatibility between the fillers of gasoline and diesel cars, so that the nozzle of a diesel pump simply could not be used to refill a gasoline vehicle. This, however, would require the participation of third parties, certainly the vehicle manufacturers to ensure that common standards are agreed and enforced. A third possibility would be to include a sensor to sample the contents of the tank before filling to confirm that the fuel is correct before allowing fresh fuel to be dispensed. Therefore, it is an object of the invention to provide a simple and convenient method and system for misfuelling prevention which can be used as a safeguard against the accidental misfuelling of cars which is becoming more common with the increased use of other fuels than gasoline for vehicles, and which causes great inconvenience and possibly engine damage. The invention therefore provides a method for preventing the misfuelling of a fuel tank characterized by the steps of connecting a fuel delivery pump to the tank to be filled, measuring a quantity representative for the hydrocarbon vapour pressure above the fuel in the tank before delivery of the fuel, comparing the value of the said measured quantity with a predetermined value, deriving from this comparison information concerning the kind of fuel in the tank and disconnecting the fuel delivery pump before filling if the fuel in the tank is different from the fuel to be supplied by the delivery pump. The invention also provides a system for preventing the misfuelling of a fuel tank characterized by means for connecting a fuel delivery pump to the tank to be filled, means for measuring a quantity representative for the hydrocarbon vapour pressure above the fuel in the tank before delivery of the fuel, means for compa­ ring the value of the said measured quantity with a predetermined value, means for deriving from this comparison information concer­ ning the kind of fuel in the tank and means for disconnecting the delivery pump before filling if the fuel in the tank is different from the fuel to be supplied by the delivery pump. The invention is based upon the recognition that the vapour pressure difference between different fuels such as petrol and diesel fuel provides a physical parameter which can be measured using modern sensors to give a safety cut-off system. The vapour above gasoline is predominantly butane, and has a partial pressure of at least 250 mbar (generally 400-500 mbar). That above diesel may contain a wider spread of hydrocarbons, but is at a very much lower partial pressure of perhaps 10 mbar maximum and typically 1 mbar. There is thus at least an order of magnitude difference in the hydrocarbon concentration above diesel compared with that above gasoline. A sensor system could thus be based simply upon hydrocarbon concentration rather than on the precise mix of hydrocarbon components. The tank atmosphere would be sampled before delivery of fuel, and a high hydrocarbon reading, indicating that the tank already contains gasoline, would disable the pump. A simple method of disabling the fuel delivery would be to interrupt the electrical supply to the fuel delivery pump, and only turn it on when the sensor system had registered an all clear. The invention will now be described by way of example in more detail with reference to the accompanying drawing, in which the figure represents schematically the system of the invention. Referring now to the figure, block 1 represents a sensor system 1 which is capable to measure and determine the hydrocarbon vapour pressure in a tank to be filled after a diesel fuel delivery pump has been connected to the tank. For reasons of clarity the filler nozzle, tank and diesel delivery pump have not been shown. The sensor system 1 is connected by any means suitable for the purpose to a processing means 2 comprising means for comparing the measured value of the vapour pressure in the tank to be filled with a predetermined value. From this comparison information can be derived concerning the kind of fuel in the tank. The means 2 can be connected by any suitable means to a display means 3 for displaying the measured value of the vapour pressure. The display means 3 can be located on any suitable location. If the measured value of the vapour pressure is above a predetermined value, which means that the tank to be filled already contains gasoline and that the diesel delivery pump erroneously has been connected to a gasoline fuel tank, the pump is disconnected before filling. The pump can be disconnected in any way suitable for the purpose. The sensor system can be constructed in several advantageous manners. For example, the atmosphere of the tank to be filled can be sampled via a tube (an "aspirated" system) or the sensor itself can be located on the filler nozzle of the delivery pump, and so samples the tank atmosphere directly. An aspirated system would require a tube fed to the end of the filler nozzle, through which gas is drawn through the sensor system using a pump. For example, the sensor in this case could be an infra-red or thermal conductivity type. Such sensors are conventional and will therefore not be described in further detail. Generally it can be said that the vapour is allowed to penetrate to the sensor and then the sensor will respond. An alternative to an aspirated system is the siting of a sensor element close to the end of the filler nozzle, in order directly to sample the tank atmosphere. The advantages of such an approach would be that no delay associated with passage of sampled gas down an aspirating tube would occur. It will be appreciated that any sensor means suitable for the purpose can be used. Experiments have been carried out wherein the response time of typical detector units has been measured by assembling the detectors and exposing them to gasoline and to diesel fuel vapour, as well as to calibration gases. For example, thermal conductivity detectors and infra-red analysers operate well over the 0-50% gas range appropriate to gasoline vapour. The rise time of these detectors is of the order of 5 seconds, however, the time for a significant output to occur is less, for example 2 seconds. Thus, 2 seconds after exposure of the sensor to gas, the output can be used as an indicator of fuel type. In an advantageous filler nozzle mounting embodiment of the invention a system of sensors is applied, based upon infra-red adsorption using a remote light source coupled via fibre optics. The attenuation due to 50% butane at a wavelength of 3.5 µm amounts to some 50% over a 10 mm path length. It will thus be possible to develop a 10 mm open path beam system, which could be installed close to the delivery end of the nozzle. Further, as an alternative an acoustic system could be used, employing an open ended tube excited at resonance by a piezo electric crystal. Such a device could be made to dimensions for example 30 × 10 × 10 mm. The resonant frequency would be affected by the ingress of heavy gasoline vapour, to generate an output signal. Further, semi-conductor sensors could be used, which can be made intrinsically safe, which would allow them to be installed on the filler nozzle. Precautions are required to protect them from liquid which would destroy the sensor, and this could, for example, be achieved by a housing with a shutter which would exclude liquid. It will further be appreciated that the method and system of the invention can also be used for prevention of misfuelling a diesel fuel tank. When a diesel fuel tank erroneously is connected to a gasoline delivery pump, the pump will be disconnected if the measured value of the vapour pressure is below a predetermined value, which means that the tank already contains diesel fuel. It will also be appreciated that the present invention is not restricted to gasoline-diesel misfuelling prevention, but can be used for any fuels having mutually different vapour pressures. Various modifications of the present invention will become apparent to those skilled in the art from the foregoing description and accompanying drawing. Such modifications are intended to fall within the scope of the appended claims.

Claims: 1. A method for preventing the misfuelling of a fuel tank characterized by the steps of connecting a fuel delivery pump to the tank to be filled, measuring a quantity representative for the hydrocarbon vapour pressure above the fuel in the tank before delivery of the fuel, comparing the value of the said measured quantity with a predetermined value, deriving from this comparison information concerning the kind of fuel in the tank and disconnecting the fuel delivery pump before filling if the fuel in the tank is different from the fuel to be supplied by the delivery pump. 2. The method as claimed in claim 1 characterized in that the delivery pump is disconnected before filling, if the value of the said measured quantity is above the predetermined value. 3. The method as claimed in claim 1 characterized in that the delivery pump is disconnected before filling, if the value of the said measured quantity is below the predetermined value. 4. The method as claimed in any one of claims 1-3 characterized by the step of displaying the value of the said measured quantity. 5. The method as claimed in any one of claims 1-4 characterized by the step of measuring the quantity representative for the hydrocarbon vapour pressure above the fuel in the tank by sampling the atmosphere of the tank. 6. The method as claimed in claim 5 characterized in that the said sampling takes place via a tube. 7. The method as claimed in any one of claims 1-5 characterized in that the said quantity representative for the vapour pressure above the fuel in the tank is measured by a sensor. 8. The method as claimed in claim 7 characterized in that the sensor is located on the filler nozzle of the delivery pump. 9. A system for preventing the misfuelling of a fuel tank characterized by means for connecting a fuel delivery pump to the tank to be filled, means for measuring a quantity representative for the hydrocarbon vapour pressure above the fuel in the tank before delivery of the fuel, means for comparing the value of the said measured quantity with a predetermined value, means for deriving from this comparison information concerning the kind of fuel in the tank and means for disconnecting the delivery pump before filling if the fuel in the tank is different from the fuel to be supplied by the delivery pump. 10. The system as claimed in claim 9 characterized by a means for disconnecting the delivery pump before filling, if the value of the said measured quantity is above the predetermined value. 11. The system as claimed in claim 9 characterized by a means for disconnecting the delivery pump, before filling, if the value of the said measured quantity is below the predetermined value. 12. The system as claimed in any one of claims 9-11 characterized by means for displaying the value of the said measured quantity. 13. The system as claimed in any one of claims 9-12 characterized by means for sampling the atmosphere in the tank. 14. The system as claimed in claim 13 characterized by a tube which is fed to the end of the filler nozzle of the delivery pump. 15. The system as claimed in claim 13 characterized by a sensor means located on the filler nozzle of the delivery pump.

Inventors: WATTS, ANDREW JOHN
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: B67D5
IPC codes: B67D7