Technical field of the invention

The invention is related to isolation valves for fuel tanks in the automotive industry

Background of the invention

Fuel tank vapor and emission control systems are used to control the flow of fuel vapors from a vehicles fuel tank and also to control the relative pressure of the fuel tank. Vapors are vented to a canister or another vapor control structure, where hydrocarbon vapors are stored and which is also connected to the engine air inlet.

Fuel tanks produce fuel vapor during various operating phases and theses vapors are directed to a canister or another component responsible for storing them, and then purging them regularly to the admission header of the engine. Periodic purging of stored vapors is necessary during the operation of the vehicle. In order to control the purge, the fuel system is operated to control the flow of vapor from the storage canister to the engine air inlet, and atmospheric air is admitted to purge the canister.

The document US2010/0051 1 1 6 assigned to Eaton Corporation discloses a vapor isolation valve in fluid communication with a fuel tank. The valve acts as a two-stage exit flow mechanism when venting high pressure from the fuel tank to an exit passage. An inconvenience is that when the pressure difference is high, the switch between the two stages may be too sudden resulting in corking. Summary of the invention

It is an object of the present invention to provide good assembly or methods for reducing the risk of corking or clogging, to improve the customer interface with the vehicle during a refuelling operation in extreme conditions and avoid expulsion of fuel toward the operator while opening the fuel cap.

The above objective is accomplished by a method for controlling the opening speed of a valve connected between a fuel tank and a filter, and configured to relieve the pressure inside the fuel tank into the filter, the method comprising the steps of:

- Measuring a pressure in the fuel tank,

- Measuring or inferring a fuel vapor temperature in the fuel tank,

- Calculating an opening speed of the valve as a function of the pressure and the fuel vapor temperature in the fuel tank,

- Opening the valve at the calculated opening speed in order to avoid corking of another valve of the fuel tank connected between the valve and the fuel tank.

The method comprises also a step of opening includes an electronically operating of the valve in order to open the valve at different opening rates. By iterating the method it is possible to optimize the opening speed of the valve.

The opening rates according to the method are preferably comprised in the range between 0 and 3.3 millimeter(s) per second.

According to a preferred embodiment, the valve is operated with a stepper motor.

According to a further embodiment, the method further comprises a step of filtering the fuel vapor relieved from the valve in order to capture fuel particles.

According to another embodiment, the method further comprises a step of returning filtered fuel vapor to the valve to release latter in the atmosphere.

Another objective of the invention is accomplished by a method of opening a fuel door, accessible by an operator, of a fuel tank which is provided with locking means controlling the opening of the fuel door, the method comprising the step of:

- Monitoring a refuelling request of the operator in order to perform the hereinbefore method for controlling the opening speed of a valve so as to open the valve at the calculated speed;

- Comparing the pressure in the fuel tank to a predefined pressure value so as to determine if the fuel door can be opened, by unlocking the locking means, without risk for the operator.

Thus, the tank is only available for refuelling when the pressure is inferior to a predefined pressure value over which there is a risk that the fuel exits through the fuel door opening when the fuel door is opened. According to a further embodiment, when pressure in the fuel tank is inferior to the predefined pressure value, the method comprises the steps of unlocking a locking element and of setting the valve at a completely opened position in order to facilitate a refuelling of the fuel tank.

According to an embodiment, the predefined pressure value is between

20 and 60 mbar, preferably between 45 and 55 mbar, and most preferably 50 mbar. These values are selected for operator/user security according to customer specification.

According to yet a further embodiment, when the pressure in the fuel tank is superior to the predefined pressure value, and when the time since the last refuelling request is superior to a predefined time value, the method comprises a further step of sending a signal informing of the pressure status to the operator, and then a step of unlocking a locking element. Thus, the operator/user is informed and may take the vehicle to a garage for repair and/or maintenance.

According to a referred embodiment, the predefined time value is 20 seconds. This is the time it takes for a driver to reach the fuel door when he has left his seat.

The herein disclosed methods can be performed by means of a computer program product comprising code means configured to enable the controller to carry out the method.

The above disclosed objects can be obtained by means of an assembly for an automotive vehicle comprising a fuel tank provided with locking means and a fuel tank door, a controller provided with look-up tables, a filter, a temperature sensor for measuring the temperature of the vapor in the fuel tank, a pressure sensor for measuring the pressure in the fuel tank, the temperature sensor and the pressure sensor being connected to the controller, a valve that can be opened and closed at varying opening speed, the valve being connected to the fuel tank on one side and to the filter on the other side, the filter being connected to an engine intake manifold, the controller being able to calculate a suitable opening speed for the valve as a function of values received from the temperature sensor, the pressure sensor and data stored in the look-up tables, the valve being adapted to be opened at various opening and closing speed calculated by the controller, the valve being able to receive and transfer vapors to the filter and air to the atmosphere.

According to an embodiment of the assembly, the valve is an electronically operated valve capable of opening at different rates, e.g. the valve is operated by a stepper motor.

According to a further embodiment of the assembly, the temperature sensor is located in the fuel tank. When the temperature sensor is located in the tank it is easier to obtain precise data concerning the temperature.

According to yet a further embodiment, the fuel tank is provided with a level sensor.

An advantage of having a level sensor is that it can be used to further fine-tune the opening speed of the valve.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

Although there has been constant improvement, change and evolution of devices in this field, the present concepts are believed to represent substantial new and inventive improvements, including departures from prior practices, resulting in the provision of more efficient, stable and reliable devices of this nature.

A further advantage is that the herein disclosed method and assembly prevents damage to and prolong the life expectancy of the fuel systems and particularly the venting valves.

Brief description of the drawings

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings. Fig. 1 is a schematic illustration of a fuel valve system for a fuel tank comprising the assembly according to the invention.

Fig. 2 is a flow chart illustrating the method according to the invention.

Fig. 3 is an example of a look-up table used by the assembly and method according to the invention.

Fig. 4 is a graph showing the variation of pressure P in the same fuel tank with a conventional all-or-nothing valve and with a fuel valve system according to the invention as a function of the time T.

Fig. 5 is a graph showing the aperture A rate of a conventional all-or- nothing valve and of a fuel valve system according to the invention as a function of the time T permitting to obtain the Fig. 4.

Description of illustrative embodiments

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

Furthermore, the terms "first, second, third" and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms "top, bottom, over, under" and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein. It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Similarly, it is to be noticed that the term "coupled", also used in the claims, should not be interpreted as being restricted to direct connections only. The terms "coupled" and "connected", along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression "a device A coupled to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "Coupled" may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the method according to the invention. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The following terms are provided solely to aid in the understanding of the invention.

The term "fuel tank" is understood to mean an impermeable tank that can store fuel under divers and varied environmental and usage condition. An example of this tank is that with which motor vehicle is equipped. The term "Corking" or "Clogging" is understood to define what happens when the force of the rushing fuel vapors physically lifts the float of the valve against the seat, thereby blocking free vapor exit. Or in other words the pressure drop across the float valve is high enough to create a relative vacuum at the outlet port which pulls the float up against the valve seat.

The Malfunction Indicator Lamp (MIL) or CHECK ENGINE light as it is more commonly called, is essentially an emission warning light. If the light comes on, it means the Onboard Diagnostics II system (OBD II) has detected an emissions-related problem.

The term "On-board diagnostics" (OBD) designates an automotive term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle subsystems.

The terms "Refuelling" or "fuelling request" indicate both a request to fill the fuel tank with fuel.

Fig.1 discloses an assembly comprising a valve 1 10 for a fuel tank. The assembly comprises the valve 1 10, a filter 125, a controller 160 provided with look-up tables 1 62, and a fuel tank 1 12 provided with a fuel door 175 and locking means. The function of the locking means is to keep the fuel door 175 closed. The fuel tank 1 12 is provided with means for measuring the pressure (not shown) and means for measuring the temperature (not shown) of the vapor in the fuel tank. The fuel tank 1 12 is also provided with means for detecting a refuelling request (not shown). The fuel tank 1 12 may be provided with means for measuring other parameters in the fuel tank such as the liquid fuel level in the tank.

The fuel tank 1 12 is connected to the valve 1 10, preferably a stepper valve. A stepper valve is composed of two separate chambers, a first chamber and a second chamber. The first chamber is separated from the second chamber by a seal that interfaces with a sliding shaft that drives the two valve poppets in such a way that when the first chamber is open the second chamber is completely closed and vice-versa. A stepper valve is disclosed in the document US961 6744. However, the method according to the invention could function with another valve or a set of valves that provide the function of precisely controlling air flow through a valve, for example with only one selective sealing interface.

The valve 1 10 is on a side opposite of the fuel tank 1 12 connected to the filter 125, preferably a charcoal filter, also called canister. The filter is connected to engine intake manifold 140. The valve 1 10 is connected to the controller 160 and is configured to move between an opened position and a closed position in response to an electronic signal from the controller 1 60. The valve 1 10 may be located or mounted directly on the fuel tank 1 12 or may be mounted remotely. Additional components, such as, without limitation, additional valves (not shown) or passageways (not shown) may be interspersed between the fuel tank 1 12 and the valve 1 10. An exit passage 1 14 is in communication with the vehicle's evaporative system (not shown) and may be referred to as the vent path as this is the path for venting or relieving excess fuel vapor from the fuel tank 1 12.

The fuel tank 1 12 is connected to the controller 1 60 provided with look- up tables 1 62. The controller 1 60 is connected to the valve 1 10. The look-up tables 162 are provided with information regarding suitable opening speeds of the valve 1 10 for specific combinations of temperature and of pressure of the fuel vapor in the fuel tank. The controller 1 60 is provided with means for instructing the valve 1 10 to open and close at predefined speed rates according to information received from the means for measuring the pressure in the fuel tank 1 12 and the means for measuring the temperature in the fuel tank 1 12.

According to a further embodiment, the means for measuring the temperature are located somewhere else in the vehicle and the look-up table is adapted to use data from said means for measuring temperature to deduce the temperature in the tank.

One or more of the following means may be used as locking element between the fuel tank and space accessible to the operator: a fuel flap, a fuel cap, a closure mechanism.

When the motor is running, the valve 1 10 receives vapors provided with fuel particles from the tank and transfers those vapors to the filter 125, that captures the fuel particles and return clean vapors to the valve 1 10. The valve 1 10 then forwards some of the clean vapors to the atmosphere through the exit 1 14 and returns some to the fuel tank 1 12. The valve 1 10 is gradually opened and closed as a function of the pressure and the temperature of the vapors in the fuel tank 1 12.

As the fuel tank 1 12 heats up the gas comprising fuel, vapor and air expands. In order to avoid an overpressure, that could lead to an explosion, the fuel tank 1 12 has to be vented. The gas is vented through the valve 1 10 to the filter 125. The activated carbon in the filter 125 captures the vapor. When the engine is running, the filter 125 is regularly cleaned by means of a vacuum created from the manifold in order to partly reverse the above flow, i.e. to suck the fuel vapors into the engine, thus the clean air is returned to the atmosphere through the valve 1 10 and the exit 1 14. Normally, the fuel tank 1 12 only supply fuel vapors under short time periods as an under pressure is created due to the presence of these vapor, that are let out by the valve 1 10. The architecture of the valve 1 10 provided with the exit passage 1 14 enables to provide the clean air to the atmosphere instead of returning it to the fuel tank 1 12.

By providing a gradual fine-tuned opening speed of the valve 1 10, the wear on the valve 1 10 is reduced. The wear on the remainder of the assembly is also reduced by damping transitions between no vapor flows and high vapor flow. The possibility to fine tune the opening of the valve 1 10 may also reduce the pressure differentials across other valves, such as, without limitation, fill/fuel level vapor valves (FLVV) or grade vent valves (GVV) which are located between the fuel tank 1 12 and the valve 1 10. Reducing the pressure differential across, for example, an FLVV, reduces the likelihood that the FLVV will be improperly closed due to corking or clogging.

Indeed, as it can be seen in Fig. 5, with a conventional all-or-nothing valve (curve with discs "·"), the opening speed is very quick and whatever the pressure P in the fuel tank, latter is released abruptly. As shown in Fig. 4, this quick opening of the conventional all-or-nothing valve (curve with discs "·") does not mean that the pressure P in the fuel tank will decrease rapidly. Thus, the force of the rushing fuel vapors physically lifts the float of the valve against the seat, thereby blocking free vapor exit. Or in other words, the pressure drop across the float valve is high enough to create a relative vacuum at the outlet port which pulls the float up against the valve seat. Consequently, as it can be seen in Fig. 5, with a conventional all-or-nothing valve (curve with discs "·"), due to corking, the pressure P decreases too slowly in the fuel tank incurring a high risk of expulsion of fuel toward the operator if latter opens the fuel cap.

When the controller 1 60 recognizes a refuelling request, the controller collects information concerning the pressure and temperature in the fuel tank 1 12 by means of the temperature sensor and the pressure sensor. The controller uses the look-up table 1 62 comprising predefined data concerning the relationship between pressure and temperature on one hand and suitable opening speed for the valve 1 10 in order to calculate a suitable opening speed. Then, the controller sends an electrical signal to the valve 1 10 instructing the valve 1 10 to open at the calculated speed.

The controller 1 60 continues to receive information concerning the pressure in the fuel tank 1 12 and when the pressure in the fuel tank 1 12 falls below a preselected pressure value, that is stored e.g. in the look-up table 1 62, the controller 160 sends a signal to the locking means to unlock the fuel door 175, so the user can start filling the tank.

Fig. 2 is a flow chart disclosing the different steps of a method according to the invention. At step 200, the controller 160 detects a refuelling request. A refuelling request is made when an operator chooses to refuel and presses a button in the car to begin the depressurization sequence. The controller 1 60 is informed about a refuelling request by grabbing a signal from a serial contact - bus of the vehicle. At step 205, the pressure sensor measures the pressure in the fuel tank 1 12 and sends the measured pressure value to the controller. At step 210, the temperature sensor measures or infers the temperature in the fuel tank and sends the information to the controller 1 60. At step 215, the controller calculates a suitable opening speed for the valve using the measured temperature, the measured pressure and the look-up table 1 62. At step 220, the valve is opened at the calculated opening speed, whereupon the fuel tank is depressurized at a desired speed.

At step 230, the pressure value in the tank is measured. If the pressure value lies below a predetermined pressure value, e.g. 50 mbar, the flow goes to step 235 and the locking element of the fuel tank door 175 is unlocked. The user can thus open the fuel door and fill the fuel tank 1 12 with fuel. The value 50 mbar has been selected as being a suitable pressure balance value for user safety. However, the value is dependent on customer specifications and the height of the filler pipe. A suitable value lies in the range between 20 mbar and 60 mbar, more preferably between 45 mbar and 55 mbar.

If at step 230 the pressure in the fuel tank is higher than the predefined pressure value, the flow goes to step 240. At step 240, the time from the start of the refuelling request is measured. When a predetermined time has elapsed since the refuelling request, e.g. 20 seconds, the flow goes to step 245. The value 20 seconds has been selected as it mimics customer specification, as it is about the time it takes for a user to get out of the car after having stopped the car, and attempt to open the fuel tank door 175 and start the refuelling of the fuel tank 1 12. At step 245, a notification of fault is sent to the vehicle that can be used to trigger a Mil-request, i.e. a light is activated on the on-board diagnostic display in order to inform the user that the pressure in the fuel tank is too high. Typically, it is the manufacturer who decides selects the criteria for activating the MIL-lamp. Then the flow goes to step 235 and the locking element of the fuel tank door is unlocked 175. The user can thus open the fuel tank door and fill the fuel tank 1 12 with fuel.

By preventing the opening of the fuel door when the pressure is under a predefined value, it is possible to limit the risk of fuel exiting the fuel door when the fuel door is opened.

Fig. 3 shows a look-up table used by the method and the assembly according to the invention. It comprises temperature and pressure values and pre-calculated values of opening speed for the valve 1 10 for each combination of pressure value and temperature value. E.g. when the temperature in the fuel tank is 20°C and the pressure in the fuel tank is 200 mbar, the most suitable opening speed of the valve is considered to be 0,8 millimetre per second.

Of course, the controller 1 60 can continue to receive information concerning the pressure and the temperature in the fuel tank 1 12 even after the end of step 220 so that it is able to modify several times the opening speed of the valve 1 10 during the pressure release from the fuel tank 1 12 with help of the look-up table 162. This means that method according to the invention, after the answer "no" in step 240, can flow to step 205 instead of step 230 as shown in Fig. 2. An example of pressure release according to the invention is shown in Figs. 4 and 5. It can be seen that controller 1 60 instructs the valve to open at two different successive opening speeds (see the two successive slopes in Fig. 5 permitting to show the variation of aperture A of the valve). Thus, by comparing curves of a conventional all-or-nothing valve (curve with discs "·") and curves according to the invention, it can be immediately seen that gradual opening speeds of the valve 100 as function of the temperature and pressure in the fuel tank according to the invention allows the pressure in the fuel tank 1 12 to fall more rapidly compared to a conventional all-or-nothing valve (more than two times quicker in this example). Consequently, due to the absence of corking, the risk of expulsion of fuel toward the operator if latter opens the fuel cap is highly decreased notably after the predetermined time of 20 seconds.