Patent ID: 12221919

DETAILED DESCRIPTION

The present disclosure is directed toward emission control on turbocharged engines. As is known, an oxygen or lambda sensor, placed intermediate an engine exhaust manifold and the main catalyst measures an oxygen content. The measurement is used to adjust the fuel amount that is sent to the engine by optimizing the air and fuel mixture. An engine system according to the present disclosure includes a cold light off catalyst (CLOC) where a CLOC valve is controlled to divert exhaust gas from the turbine of the turbocharger and through a small catalyst (upstream of the main catalyst) in a CLOC mode. The CLOC can achieve high efficiency quickly to treat the exhaust gas, while a much larger downstream main catalyst is warming up.

During full rerouting of the exhaust from the turbocharger and to the CLOC, the main catalyst inlet gas will ideally have low concentrations of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) which will impact the reactions of the main catalyst. Once the CLOC is deactivated, the main catalyst must be at peak conversion efficiency as it will then be responsible for all emission conversion. The techniques herein require the main catalyst oxygen sensor to be reading stoichiometric or slightly rich before control can command the CLOC to be deactivated to avoid NOx breakthrough after the transition from routing the exhaust to the CLOC in CLOC mode to routing the exhaust to the turbine (e.g., when CLOC mode is deactivated).

Additional techniques disclosed herein include regulating the CLOC valve while in CLOC mode based on a boost torque request. In this regard, in the event that control receives a boost torque request from the engine while in CLOC mode, control can move the CLOC valve to a position wherein all, or some exhaust flow is directed back into turbine (instead of through the CLOC) to build boost pressure back into the turbocharger (e.g., at the compressor to enable increased air flow into the engine intake manifold).

Referring now toFIG.1, a diagram of an example vehicle or vehicle control system100is illustrated. The vehicle100includes an engine104configured to combust an air/fuel mixture to generate drive torque. The engine104includes an intake system108that draws fresh air into an intake manifold (IM)112through an air filter (AF)116and an induction passage120. A throttle valve124regulates a flow of air through the induction passage120. A turbocharger128comprises a compressor132(e.g., a centrifugal compressor) that pressurizes or forces the air through the induction passage120. The compressor132is coupled to a turbine136(e.g., a twin-scroll turbine) of the turbocharger136via a shaft140.

The pressurized air is distributed to a plurality of cylinders156and combined with fuel (e.g., from respective direct-injection or port-injection fuel injectors) to form an air/fuel mixture. While four cylinders are shown, it will be appreciated that the engine104could include any number of cylinders. The air/fuel mixture is compressed by pistons (not shown) within the cylinders156and combusted (e.g., via spark from respective spark plugs) to drive the pistons, which turn a crankshaft (not shown) to generate drive torque. The drive torque is then transferred to a driveline (not shown) of the vehicle100, e.g., via a transmission (not shown). Exhaust gas resulting from combustion is expelled from the cylinders156and into an exhaust manifold (EM)160of the engine104.

The exhaust gas from the exhaust manifold160is provided to an exhaust system164comprising an exhaust passage168. Kinetic energy of the exhaust gas drives the turbine136, which in turn drives the compressor132via the shaft140. A cold light off catalyst (CLOC)172is routed in a bypass passage174around the turbine136. A CLOC valve176selectively controls exhaust flow into the turbine136of the turbocharger128and/or into the CLOC172via the bypass passage174. Explained further, the CLOC valve176moves between a fully open position whereby all exhaust gas is routed to the turbine136, a fully closed position whereby all exhaust gas is routed to the CLOC172, and infinite positions therebetween causing a blend of exhaust to be routed to both of the turbine136and the CLOC172.

As used herein a “CLOC mode” is used to refer to a controller commanding the CLOC valve176to rout at least some exhaust to the CLOC172. A main exhaust gas treatment system184, such as a catalytic converter, treats exhaust gas to decrease or eliminate emissions before it is released into the atmosphere. All exhaust gas regardless of passing through the turbine136or the CLOC172is directed to the main exhaust gas treatment system184. The CLOC172includes a small catalyst that can reach high conversion efficiency quickly and treat the exhaust gas such as when the main catalyst184has yet to reach optimal operating temperature (such as in examples 400 degrees Celsius).

A controller, also referred to herein as an engine controller,190controls operation of the vehicle100. Examples of components controlled by the controller190include the engine104, the throttle valve124, and the CLOC valve176. It will be appreciated that the controller190controls specific components of the vehicle100that are not illustrated, such as, but not limited to, fuel injectors, spark plugs, an EGR valve, a VVC system (e.g., intake/exhaust valve lift/actuation), a transmission, and the like.

An oxygen sensor194is incorporated at the main catalyst194and measures an oxygen content. The measurement is used to adjust the fuel amount that is sent to the engine to optimize the air and fuel mixture. As is known, stoichiometric combustion is the ideal process where the optimal amount of oxygen and fuel are consumed to achieve maximum combustion efficiency. In this regard, stoichiometry results in no excess fuel and no excess air.

As will be described in detail herein, the reading of the oxygen sensor194is used to determine whether the exhaust is reading stoichiometric or slightly rich (more fuel than air). CLOC mode can be deactivated when the reading of the oxygen sensor194is reading stoichiometric or slightly rich to avoid breakthrough emissions.

Lubrication oil from the engine104is routed through an oil line144to the turbocharger128to lubricate components of the turbocharger128. In examples, the oil is sourced from the engine104at the sump.

The controller190controls operation of various components based on measured and/or modeled parameters. Inputs192such as one or more sensors are configured to measure one or more parameters, and communicate signals indicative thereof to the controller190(pressures, temperatures, speeds, etc.) as discussed in greater detail herein. Other parameters could be modeled by the controller190, e.g., based on other measured parameters. The controller190is also configured to perform the engine/turbocharger control techniques.

Referring now toFIG.2, a flow chart of an example method300of operating the engine104having the turbocharger128, CLOC172, and CLOC valve176is illustrated. For explanatory purposes, components of the vehicle100will be referenced, but it will be appreciated that this method300could be used for any engine having a turbocharger and CLOC. Control starts at302. At310, the controller190determines whether the temperature of the main catalyst194is less than a threshold. The temperature of the main catalyst194can be determined such as by the inputs192including a temperature sensor positioned at the main catalyst194. In examples the threshold temperature can be 400 degrees Celsius. It is appreciated that the temperature is merely exemplary and can be different depending upon the makeup of the components in the main catalyst194. If the temperature of the main catalyst194is not less than a threshold, control disables CLOC mode at320. Again, if the temperature of the main catalyst194is not less than a threshold, the main catalyst194is at temperature and can perform the emission reduction without the CLOC. If the temperature of the main catalyst194is less than a threshold, control commands the CLOC172and CLOC valve176to enter CLOC mode at314.

At322control determines whether a boost is required. A boost can be required such as by an accelerator pedal input provided at the inputs192. If a boost is not required, control loops to310. If a boost is required, control determines whether a full turbine input is required to meet the acceleration demand at328. If yes, control disables CLOC mode at320. If control determines that a full boost is not required to meet the acceleration demand, control commands a partial CLOC mode at330. A partial CLOC mode can correspond to the CLOC valve176moving to a position intermediate fully open and closed whereby exhaust flow is blended between the CLOC172(to satisfy emissions) and the turbine136(to satisfy boost request). The exact position of the partial CLOC mode can be determined by the controller190to minimize pollutant emissions versus boost request. Control ends at332.

Referring now toFIG.3, a flow chart of an example method400of operating the engine104having the turbocharger128, CLOC172, the CLOC valve176and oxygen sensor194is illustrated. For explanatory purposes, components of the vehicle100will be referenced, but it will be appreciated that this method300could be used for any engine having a turbocharger and CLOC. Control starts at402. At410, the controller190determines whether CLOC is enabled. Again, CLOC operation can be enabled such as at startup of the engine104when the main catalyst184has not reached optimal operating temperature. If CLOC is not enabled control loops to410. If CLOC is enabled, control determines whether a temperature of the main catalyst184is greater than a threshold at414. In examples the threshold temperature can be 400 degrees Celsius. It is appreciated that the temperature is merely exemplary and can be different depending upon the makeup of the components in the main catalyst194. If not, control loops to414.

At420control determines whether the signal from the oxygen sensor194corresponds to a lean condition (more air than fuel). In examples, control determines whether reactions of the main catalyst correspond to poor conversion efficiency potential based on the oxygen sensor194. If not, control loops to430where the system transitions to turbine mode (CLOC disabled). If the signal from the oxygen sensor194corresponds to a lean condition, control adds enrichment at440. In examples, adding enrichment can include commanding an increased amount of fuel to the engine104. At444control determines whether the signal from the oxygen sensor194corresponds to a stoichiometric condition. If not, control loops to414. If yes, control proceeds to430where the system transitions to turbine mode (CLOC disabled). Control ends at450.

It will be appreciated that the term “controller” as used herein refers to any suitable control device or set of multiple control devices that is/are configured to perform at least a portion of the techniques of the present disclosure. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present disclosure. The one or more processors could be either a single processor or two or more processors operating in a parallel or distributed architecture.

It should be understood that the mixing and matching of features, elements, methodologies and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.