Patent Application
20090150041
The present invention relates to a refueling system and to a method for refueling the fuel tank of a motor vehicle. More specifically, the present invention relates to a refueling system that is safe, accurate and simple in construction thereby decreasing manufacturing costs, while enabling easy refueling.
It is known that the fuel contained in a fuel tank tends to evaporate at ambient temperature and forms a fuel vapour/air mixture filling the headspace of the fuel tank above the surface of the liquid fuel. When most of the fuel has been consumed due to combustion in the engine, the headspace above the surface of the liquid fuel in the tank is comparably large and therefore, a corresponding volume of the fuel vapour/air mixture has filled the headspace of the fuel tank. During refueling, however, nearly the entire volume of the fuel vapour/air mixture is replaced by liquid fuel and the fuel vapour/air mixture must escape from the fuel tank somehow to prevent an increase of the pressure within the fuel tank. Usually, the fuel vapour/air mixture is allowed to escape from the fuel system through a vent valve.
Increasingly stringent environmental standards have resulted in regulations which necessitate a significant reduction in fuel vapours escaping from a vehicle during refueling. These regulations generally strive to essentially eliminate fuel vapour escaping to the atmosphere during refueling. Therefore, in current conventional automobile refueling systems, a float style valve is generally used to vent the fuel tank during refueling. As this valve is submerged in fuel, its float rises, this ultimately seals the fuel tank off so that it can not vent, consequently sending fuel up the fill pipe and tripping the aspirator in the fill nozzle. This type of venting valve has a multitude of names, such as Control Valve (CV), or Fuel Level Vent Valve (FLVV). Control valves generally are rather expensive, due to the number of complex materials needed to create the floats used in the valves. In addition, because the valves are made to control the refueling function, they are submerged in fuel whenever the tank is nearly full. Due to their size, these valves have a certain lack of responsiveness that allows liquid to pass into the vapour path to the carbon canister, consequently contaminating the canister. In the past, a few different methods have been looked at to solve that problem.
One such method is disclosed in U.S. Pat. No. 6,516,835 which describes a tank mounted solenoid valve that is actuated based on signals from tank mounted sensors, such as the level sensor. When the level sensor indicates that the tank is full, the valve shuts, causing a pressure spike in the tank thus ending the refueling process. The advantage to this system is that the valve can stay in the normally closed position at all times, leaving only small orifice vent valves for dealing with dynamic pressure generation while the vehicle is running. As a result, the amount of vapour that can flow to the vapour recovery canister is limited, allowing the canister to be smaller. As mentioned above, by removing the control valve, the risk of liquid carryover into the vapour recovery canister is greatly reduced. The downside to this system is the additional sensors and valves required to perform the refueling functions. These items add additional cost to the system.
U.S. Pat. No. 6,488,015 describes a system that uses the Canister Vent Solenoid or Drain Cut Valve, to control the refueling process. The system uses the vehicle speed sensor to determine if the vehicle is stopped. Once stopped, the Drain Cut Valve will close if the fuel level in the tank is above a prescribed height. The valve remains closed for a prescribed amount of time to allow pressure to build in the tank forcing fluid up the fill pipe and ultimately shutting off the fill nozzle. If after five seconds, the fuel level in the tank is below a prescribed level, the valve opens again allowing for more refueling. Once the fuel level reaches a prescribed level, the cut valve closes and ends the refueling process. This system is effective; however there are a few concerns. First, by using the vehicle speed sensor, refueling can be permitted during an engine on condition. Second, the system is based on a resistor card type fuel level gauge. Based on the poor accuracy of these gauges, consistent fill volumes could be difficult.
In view of the above, there exists a need for an improved refueling system that overcomes the disadvantages in the prior art. In particular, the refueling system should be simple in construction, accurate and safe.
The inventors of the present invention have found that this technical problem can be solved by the subject matter of the present claims, i.e. by a refueling system for a vehicle having a combustion engine, the refueling system comprising:
The main functional differences seen in this system over the one of U.S. Pat. No. 6,488,015 described above is that it is not based on a vehicle speed sensor. By requiring the vehicle to be shut of at the time of refueling, a large amount of risk is eliminated due to lack of moving part that could potentially produce charge concentrations.
The fuel tank of the system according to the invention is a hollow body made of a material which resists chemically to fuels, like a metal a polymeric material. The invention gives good results with fuel tanks made of polymeric material. The polymeric material is preferably selected from the group consisting of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyoxymethylene, polypropylene, elastomers and mixtures of two or more thereof. Preferably, the polymeric material comprises high density polyethylene (HDPE). In a specific embodiment, the hollow element also comprises a layer of barrier material like EVOH (at least partially hydrolysed ethylene—vinyl acetate copolymers). Alternatively, the HDPE may be surface treated (by fluorination, sulphonation or the like) in order to reduce its permeability to fuel.
As explained above, the main characteristic of the present invention is related to the presence of an ignition sensor which is connected to a controller which only opens the drain cut valve (and hence, allows effective venting for the refueling event) when the engine is switched off, and is adapted to close it again at the end of the refueling process or if no refueling occurs. The above mentioned controller may either be the Engine Control Unit (ECU), or a separate ECU designed to control functions only related to the fuel system. The end of refueling or the no refueling event may be determined by the use of a level sensor and a timer which will detect if the level sensor is stationary for a predetermined period of time.
The system according to the invention comprises a canister which is connected, through vapour lines, to the fuel tank in a way such that the fuel vapour/air mixture from the tank is channeled into the canister and adsorbed or partially condensed in the charcoal. The vapour line in such a system is connected to an inlet port located at the top of the canister. A second port on the canister is also provided, known as a “purge” port, from which a line extends to the intake manifold or carburettor of the vehicle's engine. When the engine is running, at a preset frequency, condensed fuel and vapour that is stored in the charcoal is released and sucked into the engine, to be burned.
The canister according to the invention also comprises a third port which is connected to the atmosphere through a canister drain cut valve. When this valve is closed at the end of the refueling process, the tank can be effectively sealed, such that no vapour can escape to the atmosphere, causing fuel to back fill up the filler pipe ultimately ending the refueling process.
The fuel vapour adsorbent material inside the canister according to the invention can be any absorbent. It is preferably charcoal, either pure, granular, pelletized or supported on an adequate support. It may also be agglomerated charcoal in the form of a honeycomb for instance.
As explained above, it is preferred (in order to downsize the canister) to have the venting valve closed when no refueling occurs. Therefore, in one embodiment of the present invention, the refueling system comprises a filler door with a filler door sensor adapted to detect whether the filler door is open or closed. The controller according to that embodiment is then adapted to first open the venting valve when the engine shuts off, but to close it again if or when the filler door closes.
In fuel systems using an OBD (On Board Diagnosis including leak detection tests), usually, when the engine switches off, the CPU (central computer programmed control unit of the engine) starts a leak detection test by closing all valves including the venting valve. Accordingly, the refueling system of the present invention would not be compatible with such fuel systems since the leak test at engine shut off would always be aborted (the venting valve being open), even in the case no refueling occurs.
Therefore, according to a first preferred embodiment of the present invention, the refueling controller is adapted to close the canister drain cut valve after a prescribed period of time t has elapsed, during which both the ignition sensor continuously detects that the ignition is switched off and the filler door sensor continuously detects that the filler door is closed (typical case of engine shut off without refueling). Once the drain cut valve has been closed and the engine is still switched off, the CPU can start the regular leak detection test Usually, the time t is in the range of the minutes, typically in between 1 and 10 minutes, preferably within 2 and 8, more preferably between 3 and 6 minutes.
On the other hand, it would be better to close the venting valve when the tank is at (almost) full state in order to avoid liquid entrainment to the canister. Therefore, according to a second preferred embodiment, the refueling system according to the invention comprises additionally a fuel level detecting device to detect the fuel level inside the fuel tank. More preferably, this device uses a contact-less level sensor, which is more accurate than a conventional resistor card level sensor. Preferred contact-less level sensors are those based on weighing or inductive or Hall effects. The latter give good results. In such systems, the refueling controller is adapted to close the canister drain cut valve when the fuel level detected by the fuel level detecting device reaches a prescribed height h. This height generally corresponds to the maximum fuel level allowed in the tank.
The present invention also concerns a method for refueling a motor vehicle using a refueling system as described above, said method comprising the steps of:
As mentioned above, it is preferable to close said valve again through the controller after refueling or when no refueling occurs.
Therefore, the method preferably comprises the additional step of detecting whether the filler door of the fuel tank is open or closed. This step then conditions in fact the closing of the drain cut valve by the controller and it is performed using the filler door sensor describes above. In this embodiment, the non refueling event is detected by this sensor both if no refueling occurs or if refueling took place but is finished.
According to a more preferred embodiment, in order to reduce the time during which the venting valve remains open while allowing the driver to perform refueling if required and/or allowing leak detection in the case of engine shut off without refueling, the method according to the invention preferably comprises the additional step of closing the canister drain cut valve when the filler door is and remains closed for at least a period of time t (either after engine shut off or after closing the filler door when refueling is finished).
Finally, according to another preferred embodiment, in order to avoid liquid entrained in the canister at (almost) full tank level, the method comprises the additional steps of:
Preferably, the height h is the one corresponding to the full tank level. It is worth noting in that regard that the system and the controller could be adapted as described in U.S. Pat. No. 6,488,015 i.e. to use 2 pre-described levels.
The system and method according to the present invention are illustrated in a non limitative way respectively by
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/55618 | 10/27/2005 | WO | 00 | 4/27/2007 |
| Number | Date | Country | |
|---|---|---|---|
| 60622621 | Oct 2004 | US |
