Vapor canisters and evaporative emission control systems for vehicles

Abstract

The present invention relates to a vapor canister for a vehicle evaporative emission control system, comprising: a canister housing (20) defining an interior volume (22) for receiving one or more volumes of adsorbent (24.1, 24.2, 24.3) therein; a fuel vapor inlet port (26) for connecting the canister to a fuel tank (16); an exhaust port (28) for drawing fresh air into the canister; a purge port (30) for extracting fuel vapor from the canister; and a pump (50) integrated with the canister housing (20). The integrated pump (50) is actuated to provide an operating pressure or underpressure in the canister. It is used in various operating modes, such as canister purge, leak detection diagnostics, refueling, or engine shutdown.

Description

Technical Field

[0001] The present invention relates generally to the field of fuel emission control in internal combustion engines. More particularly, the present invention relates to an evaporative canister for use in an evaporative emission control canister system for an internal combustion engine to reduce emissions from the fuel system. Background Art

[0002] Gasoline fuel evaporation from motor vehicle fuel systems is a major potential source of hydrocarbon air pollution. Such emissions can be controlled by a canister system that employs activated carbon to adsorb fuel vapors emitted from the fuel system. It is well known that when a vehicle is parked in a warm environment during daytime warming (i.e., diurnal warming), the temperature in the fuel tank increases, resulting in an increase in vapor pressure in the fuel tank. A mixture of fuel vapor and air from the fuel tank enters the canister through the fuel vapor inlet of the canister and diffuses into the adsorbent volume, where the fuel vapor is adsorbed in temporary storage, and the purified air is released to the atmosphere through the vent port of the canister. In certain operating modes of the engine, the canister system is purged with ambient air to periodically remove the adsorbed fuel vapor from the activated carbon to release the fuel vapor from the activated carbon. The regenerated carbon is then ready to adsorb additional fuel vapor.

[0003] A conventional type of tank is disclosed in, for example, EP0899450 or EP2906811.

[0004] Purging the air does not release all of the fuel vapor adsorbed on the adsorbent volume, resulting in residual hydrocarbons, referred to as "roots," that may be emitted to the atmosphere. In addition, the roots, which are in local equilibrium with the gas phase, also permit fuel vapor from the fuel tank to migrate through the tank system as emissions. This emission typically occurs when the vehicle has been stationary and is subject to diurnal temperature changes over a period of several days, and is commonly referred to as "diurnal breathing loss," or DBL.

[0005] DBL is a major concern for motor vehicle manufacturers and also because of regulations adopted by some countries or states.

[0006] In this connection, canister emissions can be reduced by optimizing canister geometry, selecting the proper carbon (a combination of a high capacity carbon adsorbent and a low emission adsorbent), and ensuring good purging of the canister. Unfortunately, with modern engines, it can be difficult to draw sufficient amounts of air through the canister to draw the purged vapors into the engine. Typically, turbocharged engines inherently reduce the points where manifold vacuum is available, limiting purge events to small areas where the engine is operating. Additionally, hybrid powertrains add further limitations to purge activity due to the reduced operating time of the internal combustion engine.

[0007] In addition to reducing the DBL, new evaporative emission systems for US LEVIII and CN6 as well as future EU legislation require testing for:

[0008] - Physical damage to the evaporative emission system, such as housing rupture, etc.;

[0009] -Disconnected hoses, which may release trapped gas into the atmosphere;

[0010] - Damaged or broken wiring that prevents functionality.

[0011] In order to improve the transfer of purge vapors to the engine, it has been suggested to add a purge pump in the purge line connecting the canister and the engine air induction system.

[0012] Furthermore, the above-mentioned diagnostics require the installation of sensors in the evaporative emission system, such as temperature and / or pressure sensors.

[0013] In general, the complexity of the evaporative emission system increases due to the increased number of components.

[0014] Purpose of the Invention

[0015] It is an object of the present invention to improve the design of evaporative emission control systems. Summary of the invention

[0016] According to the present invention, a vapor canister, particularly a vapor canister for a vehicle evaporative emission control system, comprises: a canister housing defining an internal volume for receiving one or more volumes of an adsorbent therein; a fuel vapor inlet port for connecting the canister to a fuel tank; a vent port for drawing fresh air into the canister; and a purge port for extracting fuel vapor from the canister. It is noteworthy that a pump is integrated with the canister housing.

[0017] Thus, the present invention proposes a vapor canister that has integrated therewith a pump that can be selectively operated, particularly by the ECU, to assist in pushing / pulling purged vapors from the vapor canister to the engine during a purge event.

[0018] The immediate advantages of combining the pump and tank into one unit are: reduced complexity (system integration, hoses, wiring harnesses, controllers, assembly steps, etc.); reduced space required and increased packaging flexibility; reduced weight; and reduced cost.

[0019] Advantageously, the pump is configured to be reversible, i.e. it has the ability to generate an overpressure or an underpressure during a certain period of time, which may be useful for certain functions. In particular, the pump can be integrated in the tank to generate an overpressure suitable for a predetermined operating mode, in particular for a purge mode or a leak detection diagnostic. The purge pump can further be integrated in the tank to generate an underpressure suitable for a predetermined operating mode, in particular for a leak diagnostic mode, a refueling mode or an engine shut-off mode.

[0020] As used herein, the terms overpressure and underpressure are used to refer to the pressure difference relative to an initial or reference pressure (e.g., atmospheric pressure). Thus, overpressure, or positive pressure, generally refers to a pressure greater than the reference / atmospheric pressure. Conversely, underpressure, or negative pressure, generally refers to a pressure less than the reference / atmospheric pressure.

[0021] In general, the pump is configured to be able to move air and / or fuel vapor flows in the system. The pump may include a pumping member, such as a pumping wheel or turbine, which is operably connected to a drive motor, particularly an electric motor. Advantageously, the housing of the pump is provided in part by the tank housing and in part by a dedicated pump housing component. The pumping member is an essential component of the pump. The design of the pumping member depends on the pump type. Any pumping technology suitable for moving / compressing gas can be used. In particular, the pump may be a centrifugal pump (e.g. a rotating impeller with blades) or a rotary positive displacement pump (e.g. a pump with rotating gears, wheels or vanes).

[0022] In an embodiment, the drive motor is arranged in a first housing part, while the second housing part is provided by a vapor canister housing designed to receive and accommodate a pumping member of the pump. The canister housing may thus comprise a hole or cavity in the outer wall, which receives the pumping member, while the first housing part protrudes outside the canister housing and is mounted to the canister housing in a sealed manner.

[0023] In other words, the tank housing is configured to form a complementary housing part that accommodates the pumping member. The complementary housing part extends inside the tank. It forms a housing for the pump element and is also configured as a functional part of the pump, cooperating with the pump element. For example, the complementary housing part can have an internal shape configured to cooperate with the pumping member to achieve the desired pumping effect.

[0024] The complementary housing part is preferably operably connected to one or more ports. The complementary housing part may advantageously include inlet and outlet orifices (the function of the orifices may be reversed depending on whether the operation of the pump generates positive or negative pressure). The inlet orifice is connected to the one or more ports by appropriate tube means. The outlet orifice of the complementary housing part may also be in fluid communication with one of the ports or a given area of ​​the tank by tube means.

[0025] In an embodiment, the motor housing is a cup-shaped housing in which the drive motor is arranged and comprises a peripheral flange at its open end by means of which it is fixed in a sealing manner to the outer wall of the tank housing.

[0026] In an embodiment, the canister housing includes an internal passage extending from one of the ports, particularly the fuel vapor inlet port, into the canister and opening into a volume of adsorbent; and the pump is operably coupled to the internal passage to move air and / or vapor therethrough.

[0027] A pump is integrated in the tank in order to generate an overpressure suitable for a predetermined operating mode, in particular a purge mode or a leak detection mode.

[0028] In general, the canister interior volume may include one or more volumes of fuel vapor adsorbent material for temporarily adsorbing and storing fuel vapor entering via the fuel vapor inlet port. The interior volume may include, for example, an initial adsorbent volume and a subsequent adsorbent volume. A skilled person will select an appropriate adsorbent material based on the desired performance of the vapor canister in terms of fuel emissions. Conventional adsorbent materials for vapor canisters typically include activated carbon, which may have various shapes with different adsorption capacities, particularly granules or pellets, as is known in the art.

[0029] In some embodiments, a high capacity adsorbent is preferably used for the initial adsorbent volume, while a so-called low discharge adsorbent is used for the subsequent adsorbent volume. In this regard, the low discharge adsorbent may be available in particulate form or as a monolith (also referred to as a monolith).

[0030] The vapor canister may further include one or more additional adsorbent volumes placed in a separate housing downstream of the vent port, for example, with low-drain monolith(s).

[0031] It may be noted that although the present vapor canister was developed in the context of a motor vehicle, its design principles may be adapted to a variety of applications using internal combustion engines, whether vehicles, stationary applications, or equipment in various fields.

[0032] According to another aspect, the present invention relates to an evaporative emission control system for a vehicle, comprising:

[0033] Fuel tanks for storing volatile fuels;

[0034] A steam cartridge according to any preceding claim;

[0035] a vapor line for directing fuel vapor from the tank into the canister vapor inlet port, the tank valve being disposed in the vapor line;

[0036] a purge line from the tank purge port to an induction system of the internal combustion engine, a purge valve being disposed in said purge line;

[0037] A ventilation line is connected to the ventilation port, and a ventilation valve is arranged in the ventilation line.

[0038] In the following, different methods of using the present evaporative emission control system are disclosed to achieve various functions.

[0039] According to one aspect, a method of purging a canister of the present evaporative emission control system includes, with a vent valve and a purge valve open and a tank valve closed, operating a pump to create an overpressure in the canister to assist in moving fuel vapor from the canister into an engine for consumption therein during combustion.

[0040] According to another aspect, a method of detecting a leak in the present evaporative emission control system includes:

[0041] a) operating a pump for a predetermined amount of time to create an overpressure or underpressure in the system;

[0042] b) monitoring a parameter indicative of fuel vapor pressure in the system during a predetermined monitoring period;

[0043] c) If this parameter changes over time, it is concluded that a leak exists.

[0044] According to a further aspect, a method of operating an evaporative emission control system is disclosed wherein during a refueling event of the tank, a pump is operated to create an underpressure in the system to limit vapor emissions through a fill opening of the fuel tank; and wherein, preferably, when the pump is operated, the vent valve and the purge valve are closed and the tank valve is opened.

[0045] According to other aspects, a method of operating an evaporative emission control system is disclosed wherein, when the engine is off, a pump is operated to create an underpressure in the system to draw gas from an induction system of the engine, and wherein preferably a purge valve is open and a vent valve and a tank valve are closed. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0047] Figure 1 : is a schematic diagram of an evaporative emission control system using an embodiment of a vapor canister of the present invention;

[0048] Figure 2 : is shown Figure 1 Detail sketch of the integration of the pump into the vapor tank. DETAILED DESCRIPTION

[0049] Figure 1 One embodiment of a vapor canister 10 of the present invention is shown for use with an evaporative emission control canister system 12 of an internal combustion engine, generally designated 14 .

[0050] The evaporative emission control canister system 12 includes a fuel tank 16 and a vapor canister 10 for temporarily storing hydrocarbons. The fuel tank 16 typically includes a refueling pipe 16.1 closed by a removable cap 16.2, and a fuel pump and meter unit 16.3 adapted to deliver fuel 18 (gasoline or other fuel for motor vehicles) from the fuel tank 16 to a fuel injection system (not shown) of the engine 14.

[0051] The fuel tank 16 and the vapor canister 10 are connected to each other so that hydrocarbons exhausted from the fuel 18 located in the fuel tank 16 can be stored in the vapor canister 10. The vapor canister 10 contains one or more volumes of adsorbent material in which the fuel vapor (hydrocarbons) accumulate. However, the storage capacity of the vapor canister 10 is limited and therefore must be emptied periodically by taking in fresh air.

[0052] The internal structure of the steam tank 10 is as follows Figure 1 As shown. The steam canister 10 includes a canister housing 20 which defines an interior volume 22 in which one or more volumes of adsorbent 24 are arranged. The adsorbent material may generally include any suitable form of activated carbon. Here, the canister contains three volumes of adsorbent indicated as 24.1, 24.2 and 24.3.

[0053] The canister 10 is configured to define a flow path for air and fuel vapor through the adsorbent volume 24, between the fuel vapor inlet port 26 and the vent port 28. Reference numeral 30 denotes a purge outlet.

[0054] The tank housing 20 includes a partition wall 32, which divides the tank into two chambers 22.1 and 22.2, thereby defining a U-shaped flow path through the tank. The tank 10 generally includes an initial adsorbent volume located on the fuel source side, i.e., close to the fuel port 26, and a subsequent adsorbent volume, such as an adsorbent volume designed for low emissions. The tank here includes an initial adsorbent volume 22.1 in the first chamber 22.1, and the second chamber 22.2 includes a second adsorbent volume 22.2 at its bottom (same as 22.1 for different adsorbent materials). The low-emission adsorbent volume 24.3 is located at the top of the second chamber, before the ventilation port 28. Traditionally, the adsorbent material is maintained by means of a front screen and a support screen. At the bottom of the tank, below the support screen, an air gap is formed that communicates with both chambers 22.1 and 22.2, through which air and fuel vapor can be exchanged; chambers 22.1 and 22.2 are therefore connected in series. The above are only examples of adsorbent material configurations that can be used and should not be understood as limiting. Those skilled in the art will adjust the adsorbent volume and type as well as the retention method and configuration according to the desired application. As this is not the focus of the present invention, it will not be discussed in detail.

[0055] It will be appreciated that the arrangement of an initial adsorbent volume on the fuel source side and one or more subsequent low emission adsorbent volumes implies a predetermined flow path:

[0056] a fuel vapor flow path from the fuel port 26 to the initial adsorbent volumes 24 . 1 , 24 . 2 , towards the subsequent low emission adsorbent volume 24 . 3 and the vent port 28 ; and

[0057] An air flow path from the ventilation port 28 (or ventilation duct) to the subsequent low emission adsorbent volume 24 . 3 , towards the initial adsorbent volumes 24 . 1 and 24 . 2 and the purge port 26 .

[0058] In the evaporative emission control canister system 12, the canister fuel port 26 is connected to the fuel tank 16 via a fuel vapor inlet line 36. A first valve 38 is arranged to open or close flow through the line 36. A fuel vapor purge conduit 40 connects the purge port 30 of the canister 10 to an air intake system 42 of the internal combustion engine 14. Here, a second valve 44 is arranged to open or close flow through the purge conduit 40. A ventilation conduit or line 46 is preferably connected to the canister ventilation port 28 at one end and open to the atmosphere at the other end for ventilating the canister 10 and for receiving purge air, or both. A third valve 48 is arranged on the ventilation line 46 to open or close flow through it. Preferably, a check valve 49 is arranged in the ventilation line 46 to allow flow only toward the vapor canister 10.

[0059] When the engine is off, fuel vapor from the fuel tank 16 enters the canister 12 through the fuel vapor inlet port 26. The fuel vapor diffuses into the initial adsorbent volume 24.1, 24.2, and then into the subsequent adsorbent volume 24.3. When the engine is on, ambient air can be drawn into the canister system 10 through the vent port 28. The purge air flows through the subsequent adsorbent volume 24.3, then through the initial adsorbent volume 24.1, 24.2, and releases the fuel vapor adsorbed on the adsorbent volume before entering the purge tube 40 via the purge port 30. Thus, the vapor-laden purge air is sent to the engine's induction system 42 via the purge tube 40 for combustion therein.

[0060] It is understood that the current steam canister 10 includes a pump 50 integrated with the canister housing 20. The pump 50 is mounted to the outer wall 20.1 of the canister housing 20 and communicates with the internal volume 22 of the canister, thereby generating an overpressure (positive pressure) or underpressure (negative pressure) in the canister and / or system.

[0061] like Figure 2As shown, the mounting of the pump 50 to the tank wall 20.1 is achieved through the hole 20.2 in the outer wall 20.1. The pump 50, here for example of a centrifugal type, comprises a pump wheel 52 (or impeller / turbine) forming a pumping member, which is operatively connected to a motor 54 shown in dotted lines. The pumping member can be directly mounted on the output shaft of the motor or connected thereto by means of a gear reducer. The motor 54 can be of any suitable type, for example brushed or brushless.

[0062] The motor 54 is arranged in a cup-shaped outer housing 56 with a radially extending peripheral flange 58, opposite the closed bottom. The motor housing 56 accommodates the motor 54 and optional control electronics and extends to the base of the pump wheel 52. The flange 58 is thus located at the transition between the motor 54 and the pump wheel 52. Reference numeral 57 denotes an electrical connector protruding at the rear of the motor housing 56. An annular seal 59 is positioned against the flange 58 to surround the base of the pumping member.

[0063] The pump 50 is assembled to the tank housing 20 by introducing the pump wheel 52 through the hole 20.2. The tank housing is configured to form a complementary housing part 61 for the pump wheel. This complementary housing part 61 is formed in Figure 2 61 is shown in dashed lines because, in this embodiment, the complementary housing part 61 is not Figure 2 in the cutting plane and behind it.

[0064] The area of ​​the tank housing receiving the pump 50 comprises a thickened wall portion 20.1 arranged below the fuel port 26, offset from a cylindrical channel (tube) 60 extending from the fuel port 26 into the tank 10, and opening further below the adsorbent volume.

[0065] A bore 20.2 is provided in the portion 20.1 and comprises a stepped inlet section defining inner 20.3 and outer 20.4 radially extending annular surfaces and opening into an inner cavity defined by a complementary housing portion 61. The inner and outer surfaces 20.3, 20.4 are configured to mate with flange 58 and seal 59.

[0066] It will be appreciated that when the pump 50 is introduced through the aperture 20.2, the annular flange 58 abuts the annular surface 20.3, the seal 59 abuts the annular surface 20.4, and the pumping member mates with the complementary housing component 61. The flange 58 is generally used to secure the pump 50 to the housing 20 to form an assembly. The pump 50 may be secured to the tank housing 20 using any suitable securing means, such as fasteners, glue, welding, clamping, heat staking, etc.

[0067] The complementary housing part 61 forms a housing for the pump wheel 52 and is preferably also configured as a functional component of the pump that cooperates with the pump wheel. For example, the complementary housing part 61 has an internal shape that matches the shape of the pump wheel 52 and is preferably configured to provide the desired pumping effect. In other words, the configuration of the inner surface of the complementary housing part 61 can be designed to cooperate with the pump wheel as a functional element of the pump.

[0068] Furthermore, although not disclosed, the complementary housing part 61 comprises inlet and outlet apertures (not shown), at least the inlet aperture being in fluid communication with the fuel port 26. For example, the inlet aperture of the complementary housing part 61 may be in fluid communication with the passage 60 via a suitable tube arrangement (not shown). The outlet of the complementary housing communicates with an opening of the tube arrangement further downstream of the port 26 in the passage 60, or directly into the tank volume.

[0069] Thus, the present vapor canister 10 includes an integrated pump 50 forming a single package, thereby reducing complexity and cost, and increasing integration flexibility for the end customer.

[0070] The pump 50 may be based on any suitable technology suitable for pumping gases, such as air and fuel vapor.

[0071] As will now be described, such a pump 50 can be used to generate overpressure or underpressure, which can be used for different functions or operating modes. The pump 50 is typically controllable by an engine control unit (ECU), which will selectively activate / switch on the pump for the desired function.

[0072] i) Purification Events

[0073] Pump 50 may be activated to generate an overpressure that assists during a purge event, thereby increasing the amount of fuel vapor that is drawn from vapor canister 10 and sent to engine air induction system 42. Typically, the ECU may command pump activation during engine events where insufficient manifold vacuum is available, thereby assisting in drawing vapor from the canister. During such a purge event, valves 44 and 48 are open, while valve 38 is closed.

[0074] ii) Leak detection

[0075] On-board leak detection can be performed with the aid of a pump. The pump is activated for a predetermined amount of time (depending on the system volume) to generate negative or positive pressure. The pressure in the system can then be monitored by any suitable means, electrical feedback from sensors and the like in the tank assembly. Such sensor(s) allow detection of a pressure decay in the system which indicates a leak. This of course requires sealing the system, i.e. closing all valves.

[0076] Figure 1Reference numeral 62 in FIG. 1 denotes a pressure sensor.

[0077] Pressure monitoring may involve measuring the pressure in the system at the moment the pump is turned off after an activation period; this is the reference pressure. The pressure is then measured at one or more predetermined time periods after the pump activation ends, for example after a few minutes to 10, 15 or 30 minutes.

[0078] In summary, leaks in the evaporative emission control system can be detected by a leak detection routine that includes the following steps:

[0079] a) operating a pump for a predetermined amount of time to create an overpressure or underpressure in the system;

[0080] b) monitoring a parameter indicative of fuel vapor pressure in the system during a predetermined monitoring period;

[0081] c) If this parameter changes over time, it is concluded that a leak exists.

[0082] iii) (Fuel) Tank Refueling

[0083] The location of the fuel pump 50 close to the fuel inlet port 26 and the tank line 36 allows a negative pressure to be created in the fuel tank to capture emissions in the air during a refueling event.

[0084] In other words, during a refueling event, the operation of the pump 50 is to create an underpressure to permit the capture of fuel vapors resulting from the addition operation. To this end, the vent valve and the purge valve are closed and the (fuel) tank valve is opened.

[0085] iv) Engine shutdown

[0086] The location of the fuel pump 50 within the tank 10 further allows it to be used to purge unburned hydrocarbons from the engine air induction system 42 .

[0087] Thus, pump 50 may advantageously be activated to create negative pressure during a predetermined period after engine shutdown to draw air emissions in air induction system 42 into canister 10. This further eliminates the need for an additional carbon filter or hydrocarbon absorber in the engine air box.

[0088] During this operating mode, the purge valve is open, while the vent valve and the (fuel) tank valve are closed.

Claims

1. A vapor canister for an evaporative emission control system, comprising: a tank housing (20) defining an interior volume (22) for receiving one or more volumes of adsorbent (24.1, 24.2, 24.3) therein; a fuel vapor inlet port (26) for connecting the canister to a fuel tank (16); a ventilation port (28) for drawing fresh air into the tank; a purge port (30) for extracting fuel vapor from the canister; It is characterized in that A pump (50) is integrated with the tank housing (20), the pump (50) comprising a pumping member (52) operatively coupled to a drive motor (54), the pump being integrated with the outer wall (20.1) of the tank housing such that the pumping member communicates with the tank interior volume to generate an overpressure or underpressure, The pump includes a motor housing (56) that holds the drive motor; The tank housing (20) includes a hole (20.2) in the outer wall through which the pumping member (52) is received into the tank housing; and The motor housing (56) is mounted to the tank housing in a sealing manner, the motor housing (56) protruding from the outer wall (20.1) to the outside of the tank, the tank housing (20) being configured to form a complementary housing part (61), the complementary housing part extending into the interior of the tank housing to accommodate the pumping member (52) therein, and the complementary housing part having an internal shape configured to cooperate with the pumping member to achieve a desired pumping effect.

2. The steam tank according to claim 1, characterized in that The motor housing (56) is a cup-shaped housing, the drive motor (54) is arranged in the cup-shaped housing, and the cup-shaped housing includes a peripheral flange (58) at its open end, and the cup-shaped housing is sealed to the outer wall of the tank housing through the peripheral flange, and the cup-shaped housing protrudes from the outer wall outside the tank.

3. The steam tank according to claim 1, characterized in that The canister housing includes an internal passage (60) extending from one of the ports (26) into the canister and opening to a volume of adsorbent; and the pump (50) is operably coupled to the internal passage to move air and / or vapor through the internal passage.

4. The steam tank according to claim 2 or 3, characterized in that: The complementary housing part (61) is operably connected to one or more of the ports of a vapor canister according to any preceding claim, characterized in that the pump (50) is integrated in the canister to generate an overpressure suitable for a predetermined operating mode, in particular for a purge mode or a leak detection diagnostic.

5. The steam tank according to claim 1, characterized in that The pump (50) is integrated in the tank to generate an underpressure suitable for a predetermined operating mode, in particular a leak diagnosis mode, a refueling mode or an engine shut-off mode.

6. The steam tank according to claim 1, characterized in that The canister contains one or more volumes of fuel vapor adsorbent material within the interior volume for temporarily adsorbing and storing fuel vapor entering via the fuel vapor inlet port.

7. An evaporative emission control system for a vehicle, comprising: a fuel tank (16) for storing volatile fuel; A vapour cartridge (10) according to any preceding claim; a vapor line (36) for conducting fuel vapor from the tank to the canister vapor inlet port (26), a tank valve (38) disposed in the vapor line; a purge line (40) from the tank purge port (30) to an inlet system (42) of an internal combustion engine (14), a purge valve (44) being arranged in the purge line; A ventilation line (46) is connected to the ventilation port (28), and a ventilation valve (48) is arranged in the ventilation line.

8. A method of purging a canister of an evaporative emission control system according to claim 7, comprising: With the vent and purge valves open and the tank valve closed, the pump is operated to create an overpressure in the canister to assist in moving fuel vapor from the canister into the engine for consumption therein during combustion.

9. A method for detecting a leak in an evaporative emission control system according to claim 7, comprising: a) operating the pump for a predetermined amount of time to create an overpressure or underpressure in the system; b) monitoring a parameter indicative of fuel vapor pressure in the system during a predetermined monitoring period; c) If the parameter changes over time, it is concluded that a leak exists.

10. A method of operating an evaporative emission control system as claimed in claim 7 wherein during a refueling event of the tank, the pump is operated to create an underpressure in the system to limit vapor emissions through a fill opening of the fuel tank.

11. The method according to claim 10, characterized in that When the pump is operated, the vent valve and the purge valve are closed, and the tank valve is opened.

12. A method of operating an evaporative emission control system as claimed in claim 7, wherein when the engine is shut down, the pump is operated to create an underpressure in the system to draw gas from an induction system of the engine.

13. The method according to claim 12, characterized in that The purge valve is open and the vent valve and the tank valve are closed.

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