Integrated vapor control valve with full range hydrocarbon sensor

An evaporative fuel vapor control system, purge valve and methods are described. The system includes a fuel supply, internal combustion engine, vapor canister, and a purge valve. The purge valve includes a sensor disposed in the body housing of the purge valve and in communication with the flow passage to provide a signal indicative of the magnitude of chemicals in the fuel vapor being provided to the engine. Various methodologies relating the system, purge valve and sensors are described.

BACKGROUND OF THE INVENTION

Automobiles powered by an internal combustion engines not only emit pollutant emissions via combustion of fuel or via emission of lubricant or fuel in the crankcase, they also produce hydrocarbon emissions via evaporation of fuel stored in the automobiles. It is believed that approximately 20% of all hydrocarbon (HC) emissions from the automobile originate from evaporative sources. To reduce or eliminate this form of emission, modern automobiles store the fuel vapor in a canister and control its release from the canister into the combustion chamber for combustion. Such on-board evaporative emission control system (EVAP) typically includes a charcoal type vapor canister that collects vapor emitted from a fuel tank and a vapor control valve that regulates the amount of vapor permitted to be released from the canister to the engine. The EVAP system is designed to be fully enclosed so as to maintain stable fuel tank pressures without allowing fuel vapors to escape to the atmosphere.

Fuel vapor is generally created in the fuel tank as a result of evaporation. It is then transferred to the EVAP system charcoal canister when tank vapor pressures become excessive. When operating conditions can tolerate additional enrichment, these stored fuel vapors are purged into the intake manifold and added to the incoming air/fuel mixture. The EVAP system delivers these vapors to the intake manifold to be burned with the normal air/fuel mixture. This fuel vapor from the canister is added to the combustion chambers during periods of closed loop operation of the engine when the additional enrichment can be managed by the closed loop fuel control system.

It is believed that inaccurate control of the vapor control valve of the EVAP system may cause a rich air-fuel ratio and hence, driveability problems, as well as failure of the various idle speed tests or enhanced I/M evaporative pressure or purge test. That is, a determination of when to permit fuel vapor to be purged to the engine is believed to be problematic due to the wide variations in the volume of fuel vapors produced in the tank that arises from various factors such as, for example, ambient temperature, pressure, fuel mixture or the volume of fuel in the tank. Moreover, the concentration of hydrocarbons or other chemical constituents in fuel vapor may vary greatly depending on these factors and thus, the tail pipe emission can be outside of acceptable range. Also, the amount of latent energy stored in the fuel vapor may influence the driveability and exhaust emission of the vehicle. And inappropriate over or under purging of the vapor canister may reduce efficiency of the emission system.

It is believed that the prior art provides for a separate sensor in a purge line to determine the suitability of a purge cycle for a vapor purge valve. However, it is believed that such configuration has some drawbacks in that the attendant electrical connector and provisions must be made for separate wire connections with the sensor and purge valve actuator.

SUMMARY OF THE INVENTION

There is provided, in one aspect of the present invention, a fuel vapor control valve that alleviates the drawbacks discussed above. The fuel vapor control valve includes a body housing and a sensor. The body housing defines a flow passage between an inlet and an outlet. The body housing defines a main volume in selective fluid communication with at least one of the inlet and outlet. The sensor is disposed in the body housing and exposed to the main volume so that the sensor provides a signal indicative of a magnitude of chemicals present in the fuel vapor in the main volume.

In a further aspect of the invention, a fuel vapor control valve is provided. The fuel vapor control valve includes a body housing and a sensor. The body housing defines a flow passage between an inlet and an outlet. The body housing defines a main volume in selective fluid communication with at least one of the inlet and outlet. The sensor is disposed in the body and exposed to one of the inlet and outlet volumes so that the sensor provides a signal indicative of a magnitude of chemicals up to 100% by weight present in the fuel vapor in the main volume.

In yet another aspect, an evaporative fuel control system is provided. The system includes a fuel supply, internal combustion engine, vapor canister, and a vapor control valve. The fuel in the fuel supply generates vapor in the supply. The engine is supplied with fuel from the fuel supply. The internal combustion engine has respective intake and exhaust manifolds. The vapor canister includes a vapor passage disposed in selective fluid communication with the fuel supply to retain fuel vapor from the fuel supply and a purge passage disposed in selective fluid communication with one of the intake and exhaust manifolds to release fuel vapor to the engine. The vapor control valve disposed in the purge passage between the engine and the vapor canister. The vapor control valve has a body housing that surrounds a flow passage through the vapor control valve. The vapor control valve includes a sensor disposed in the body housing of the vapor control valve and in communication with the flow passage to provide a signal indicative of the magnitude of chemicals in the fuel vapor being provided to the engine.

In a further aspect of the invention, a method of determining the chemical content of a fuel vapor in a vapor control valve is provided. The vapor control valve has a body housing that surrounds a flow passage through the vapor control valve between an inlet and an outlet. The housing includes a main volume in selective fluid communication with an inlet volume and an outlet volume. The method can be achieved by supplying a first electrical current to provide a heat source for a sensor and a second electrical current to determine changes in resistance of a sensing element of the sensor located in at least one of the main, inlet, or outlet volumes; and sampling the fuel vapor present in the at least one of the main, inlet, or outlet volume to indicate a magnitude of chemicals present in the fuel vapor.

In yet another aspect of the invention, a method of controlling an evaporative fuel emission system is provided. The emission system includes a fuel supply coupled to an internal combustion engine via fuel injectors, a vapor canister and a vapor control valve. The internal combustion engine has respective intake and exhaust manifolds. The vapor canister has a vapor passage disposed in fluid communication with the fuel supply to retain fuel vapor from the fuel supply and a purge passage disposed in selective fluid communication with one of the intake and exhaust manifolds to release fuel vapor to the engine. The vapor control valve is disposed in the purge passage between the engine and the vapor canister. The vapor control valve has a housing that includes a main volume in selective fluid communication with an inlet volume and an outlet volume. The method can be achieved by supplying a first electrical current to provide a heat source for a sensor and a second electrical current to determine changes in resistance of a sensing element of the sensor located in at least one of the main, inlet, or outlet volumes; determining a chemical content of the fuel vapor in at least one of the main, inlet or outlet volumes based on at least one of the first and second electrical current; and controlling one of the vapor control valve and fuel injectors based on the determined chemical content.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3illustrate the preferred embodiments. Referring toFIG. 1, an evaporative fuel vapor control system10according to a preferred embodiment is shown. In particular, the system10includes an internal combustion engine12, a fuel supply14, a vapor canister16and a vapor control or purge valve18.

The fuel supply14can be a suitable fuel tank14athat stores fuel and vapors formed or generated in the fuel tank14a. The internal combustion engine12can be supplied with fuel from the fuel supply14via suitable fuel supply conduits20ato a fuel rail22for injection into the engine12by respective fuel injectors24a,24b,24c,24d. Although not shown, a fuel tank isolation valve can be utilized between the vapor canister16and the fuel supply14.

The internal combustion engine12includes an intake manifold26in which the fuel injector outlets are mounted therein to dispense fuel into the intake manifold26. Alternatively, high-pressure, direct injection fuel injectors can be mounted directly to the cylinder head of the engine12in pressure direct injection applications. The intake manifold26is coupled to an intake air box28that provides filtered air for combustion by the engine12. A purge port30acan be provided on the intake manifold26so that fuel vapors from the fuel tank14acan be drawn by vacuum to the intake manifold26for combustion. Alternatively, a suitable delivery system can be provided for port30bthrough the exhaust manifold32so that fuel vapors can be used to achieve a light-off temperature for faster catalyst action in a close-coupled catalytic converter34. The engine12includes an exhaust manifold32coupled to an exhaust catalytic converter34.

The vapor canister16includes a vapor passage20bdisposed in fluid communication with the fuel supply14to retain fuel vapor from the fuel supply14. The vapor canister16includes a purge passage20ddisposed in selective fluid communication with one of the intake manifold26and exhaust manifold32to release fuel vapor to the engine12via the purge valve. A fresh air vent or inlet36is provided to replace the volume of fuel vapor being purged into the engine12. The purge valve18is disposed in the purge passage20dbetween the intake manifold26and the vapor canister16. Preferably, the vapor canister16is a charcoal type canister with a fresh air inlet36.

Referring toFIG. 2, the purge valve18includes a body housing40that surrounds a flow passage42extending through the purge valve18. The body housing40of the purge valve18includes an inlet portion40a, main body portion40b, and outlet portion40cthat define the flow passage42between the inlet portion40aand outlet portion40c. The inlet portion40acan be coupled to a fuel vapor canister16via pipe20c, and the outlet portion40ccan be coupled to one of the intake manifold26of the engine12via pipe20d. The inlet portion40adefines a preset inlet volume; the main body portion40bdefines a preset main volume; and the outlet portion40cdefines a preset outlet volume.

The body housing40can include an actuator, preferably an electromagnetic actuator18awith a closure member18bthat permits flow of fuel vapor to the engine12in a first position and prevents a flow of fuel vapor to the engine12in a second position of the closure member18b. In this embodiment, the engine intake vacuum is applied to the closure member18b. Although the closure member18bis shown inFIG. 1as occluding the inlet40a, the closure member18bcan be disposed for occluding the outlet40c, as shown inFIGS. 2 and 3.

The purge valve18of the preferred embodiment includes a sensor52disposed in at least one of the inlet, outlet, or main volumes of the purge valve18and in communication with the flow passage42that includes inlet passage42a, body passage42b, and outlet passage42c. Preferably, the sensor52is located in a portion of the purge valve18that is in constant fluid communication with the outlet of the vapor canister16. The sensor52, illustrated in simplified schematic form inFIGS. 2 and 3, can provide a signal indicative of the magnitude of chemicals in the fuel vapor being provided to the engine12. The sensor52can be a semiconductor sensor connected to an electrical connector53, which can also be used to connect an emission control unit (“ECU”) to a suitable actuator for the closure member of the purge valve18.

One example of suitable sensors includes a sensor52that responds to changes in the content of reducing or oxidizing chemicals and requires elevated temperatures proximate a sensing element52ato induce a reaction of chemical vapors to change the electrical resistance of sensing element52asuch as, for example, platinum. The sensing element52acan be configured to operate at high levels, e.g., 95% by weight, of chemicals. Preferably, the chemicals can be hydrocarbons such as, for example, Butane, Hexane, Hexene, Benzene, Toluene, Dimethyl Pentane, Iso-Octane, Ethyl-Benzene, O-Xylene, Nonane or MTBE. More preferably, the chemicals sensed are Butane and Pentane present in the fuel vapor.

The sensing element52acan be formed in any suitable configuration such as, for example, a planar configuration, shown here inFIG. 3. In such configuration, the sensing element52ais mounted on a ceramic substrate. A first group of electrical terminals54and56can be used to energize the heating element with a first electrical current. A second group of electrical terminals58and60can be provided so that a second current can be supplied to the terminals58and60. Hence, a change in the electrical resistance ΔR of the sensing element52acan be determined in relation to the change in the second electrical current Δi. When the sensing element52ais heated via first terminals54and56in the presence of oxidizable or reducible chemicals, the electrical resistance to the flow of the electrons across terminals58and60is increased or decreased (depending on the types of chemical), which can be measured to reflect the concentration level of chemicals in the fuel vapor. In the preferred embodiment, the first electrical current is a generally constant electrical current supplied to the sensor when the engine is operating. All four terminals can be connected to a pair of connecting wires with a switching arrangement so that a single current can be used to provide the heat source and sensing the change in electrical resistance of the sensing element52aor two discrete currents can be supplied to provide the respective heat source and sense the change in resistance in the sensing element52a.

The terminals58and60can be suitably interconnected with the purge valve, fuel pump, fuel injectors, air pump and other actuated devices such that the change in electrical current Δi can be utilized by the vehicle control unit ECU via a suitable connection such as, for example, a direct connection or via a network80based on a suitable interconnected master-slave network protocol (e.g., Controller-Area-Network, a Local-Interconnect-Network, Time-Triggered Protocol for Class A applications). Alternatively, the output from sensor52can be configured, as appropriate, to provide a control signal for pulse-width or frequency modulation of the purge valve18or other vehicle emission related devices such as, for example, the fuel injectors, fuel pump, fuel pressure regulator and ignition system.

The terminals54,56,58, and60are preferably integrated with the terminals62and64of the electromagnetic actuator18ainto a single electrical connector. Alternatively, both the actuator18aand the sensor52can be connected to the ECU by a single wire in the single connector via a multiplexing arrangement. By combining all of the electrical connections for the sensor and solenoid into a single electrical connector, it is believed the drawbacks of the conventional purge valve have been alleviated and that several advantages have also been achieved: (1) a stable air-to-fuel ratio due to the ability to determine a concentration of fuel vapor being added into the engine12; (2) a reduction of hydrocarbons being emitted in the engine exhaust due to intermittent fuel vapor being purged into the engine12; and (3) a reduction in engine stumble due to a spike in air-to-fuel ratio while hydrocarbon vapor is being purged. Additionally, where port30bis utilized, it is believed that a reduction in cold-start emission by purging an appropriate concentration of fuel into the exhaust manifold32so that catalytic light-off of the catalytic converter34can be achieved before the engine12is fully warmed up to operating temperatures.

Signal conditioning circuits can also be preferably provided on the housing of the sensor52to condition the output of the sensor to a suitable voltage level such as, for example, 0 to 5 Volts (digital or analog) that corresponds to chemical concentration level detected by the sensor element52b. Where signal-conditioning circuits are utilized, the circuits are preferably sealed from contamination with the fuel vapor present in the purge valve. It should be noted, however, that the sensor52can be any sensor having the capability to detect the concentration of hydrocarbons such as, for example C3H8, from about 0% to 100% in a fuel vapor environment with an accuracy of ±3% and the ability to provide about 0.04 volt output per approximately 2% increase in hydrocarbons with a calibrated fuel vapor volume within about 300 milliseconds over operating temperatures ranging from −40 degrees Celsius to 150 degrees Celsius. Preferably, the sensor52is a semi-conductor sensor manufactured by Umweltsensortechnik GmbH Geschwenda of Germany having model number 81020000 disposed in the main volume40bof the purge valve18(FIGS. 1-3).

In operation, fuel vapor FV is generated in the fuel supply14due to various conditions such as the ambient temperature, sloshing, vibration, barometric pressure, or the volatility characteristics of the fuel. Build up of fuel vapor FV in a headspace of the fuel supply14forces the fuel vapor FV to flow toward the vapor canister16via vent conduit20b. The vapor canister16retains the fuel vapor so that the fuel vapor is not released to the atmosphere. As the vapor canister16retains more and more of the fuel vapor, it must maximize a purging of the stored vapors during the operation of the engine12. To determine the appropriate conditions at which to purge the vapor canister16without affecting the drivability or controllability of the engine12, the vehicle control computer ECU can sense, via the sensor52, the concentration of various chemicals (e.g., hydrocarbons) in the fuel vapor and determine whether to purge via purge passage20dand if the canister should be purged, the duration of the purging of the fuel vapor into the engine intake.

By virtue of the advantages described above, various methodologies relating to evaporative emission control can be achieved. In particular, a method to determine the chemical content of the fuel vapor FV1in the purge valve18is provided. The method can be achieved by supplying a first electrical current and a second electrical current to the sensor52located in at least one of the inlet, body, and outlet volumes40a,40b, and40cthat provide respective inlet passage42a, body passage42b, and outlet passage42c; and sampling the fuel vapor present in the at least one of the inlet, body, and outlet volumes40a,40b, and40cto indicate a magnitude of chemicals such as, for example, hydrocarbons present in the fuel vapor FV or FV1.

Further, a method of controlling an evaporative fuel emission system is also provided. The method can be achieved by supplying a first electrical current and a second electrical current to a sensor located in at least one of the main, inlet, or outlet volumes40b,40a,40c; determining a chemical content of the fuel vapor in at least one of the main, inlet or outlet volumes40b,40a,40cbased on at least one of the first and second electrical currents; and controlling one of the vapor control valve and fuel injectors based on the determined chemical content. The step of controlling the purging can also include preventing a flow of fuel vapor from the main volume to the outlet volume via a closure member18bof the purge valve18while the sensor52determines the chemical content of the fuel vapor FV1in the main volume40bof the body40. The step of controlling can also include flowing the fuel vapor FV1to one of the intake and exhaust manifolds26or32as a function of the magnitude of the chemical content sensed by the sensor52. Preferably, the sensor52is located in the main volume40bof the body40of the purge valve18.