Deceleration fuel cutoff control systems and methods

A system for a vehicle includes a rate of change module, a period estimation module, a deceleration fuel cutoff (DFCO) module, and an injection control module. The rate of change module determines a rate of change of an engine speed. While an engine is being fueled, the period estimation module determines an estimated period of a next DFCO event based on the rate of change of the engine speed. The DFCO control module selectively generates a DFCO signal based on the estimated period. The injection control module cuts off fuel to the engine when the DFCO signal is generated.

FIELD

The present disclosure relates to internal combustion engines and more particularly to deceleration fuel cutoff control systems and methods for engines.

BACKGROUND

Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons, which produces drive torque. Air flow into the engine is regulated via a throttle. More specifically, the throttle adjusts throttle area, which increases or decreases air flow into the engine. As the throttle area increases, the air flow into the engine increases. A fuel control system adjusts the rate that fuel is injected to provide a desired air/fuel mixture to the cylinders and/or to achieve a desired torque output. Increasing the amount of air and fuel provided to the cylinders increases the torque output of the engine.

In spark-ignition engines, spark initiates combustion of an air/fuel mixture provided to the cylinders. In compression-ignition engines, compression in the cylinders combusts the air/fuel mixture provided to the cylinders. Spark timing and air flow may be the primary mechanisms for adjusting the torque output of spark-ignition engines, while fuel flow may be the primary mechanism for adjusting the torque output of compression-ignition engines.

Engine control systems have been developed to control engine output torque to achieve a desired torque. Traditional engine control systems, however, do not control the engine output torque as accurately as desired. Further, traditional engine control systems do not provide a rapid response to control signals or coordinate engine torque control among various devices that affect the engine output torque.

Traditional engine control systems control engine output torque using air flow in spark-ignition engines and using fuel flow in compression-ignition engines. When one or more faults are diagnosed, traditional engine control systems transition to engine shutdown. For example only, traditional engine control systems may disable fuel to the engine and prevent airflow into the engine.

SUMMARY

A system for a vehicle includes a rate of change module, a period estimation module, a deceleration fuel cutoff (DFCO) module, and an injection control module. The rate of change module determines a rate of change of an engine speed. While an engine is being fueled, the period estimation module determines an estimated period of a next DFCO event based on the rate of change of the engine speed. The DFCO control module selectively generates a DFCO signal based on the estimated period. The injection control module cuts off fuel to the engine when the DFCO signal is generated.

A method for a vehicle, includes: determining a rate of change of an engine speed; while an engine is being fueled, determining an estimated period of a next deceleration fuel cutoff (DFCO) event based on the rate of change of the engine speed; and selectively generating a DFCO signal based on the estimated period; and cutting off fuel to the engine when the DFCO signal is generated.

DETAILED DESCRIPTION

An engine control module (ECM) controls torque output by an internal combustion engine of a vehicle. In some circumstances, the ECM may disable fuel to cylinders of the engine while the vehicle is running (e.g., key ON), such as during a vehicle deceleration event. Cutting off fuel to the engine during a vehicle deceleration event may be referred to as a deceleration fuel cutoff (DFCO) event.

Generally, the ECM may initiate a DFCO event and cut off fuel to the engine when an engine speed is greater than a predetermined minimum entry speed (e.g., approximately 1500 revolutions per minute) and one or more other DFCO entry conditions are satisfied. Under some circumstances, however, fuel could be cut off during vehicle deceleration when the one or more other DFCO entry conditions are satisfied and the engine speed is not greater than the predetermined minimum entry speed.

For example only, when the vehicle begins traveling down a decline (e.g., a hill), the engine speed may not be greater than the predetermined minimum entry speed. As the vehicle travels down the decline, however, the engine speed may increase and become greater than the predetermined minimum entry speed. The ECM could then initiate a DFCO event and cut off fuel to the engine if the one or more other entry conditions are satisfied. However, fuel may be unnecessarily consumed as the engine speed increases while the vehicle travels down the decline.

The ECM of the present disclosure generates an estimated period of a next DFCO event based on a rate of change of the engine speed. The estimated period corresponds to a potential duration (e.g., in seconds) of the next DFCO event. Instead of selectively initiating a DFCO event when the engine speed is greater than the predetermined minimum entry speed, the ECM selectively initiates a DFCO event based on the estimated period. Relative to initiating a DFCO event when the engine speed is greater than the predetermined minimum entry speed, selectively initiating a DFCO event based on the estimated period may enable fuel to be cut off sooner and provide fuel consumption savings under some circumstances.

Referring now toFIG. 1, a functional block diagram of an example engine system100is presented. The engine system100includes an engine102that combusts an air/fuel mixture to produce drive torque for a vehicle based on driver input from a driver input module104. Air may be drawn into an intake manifold110through a throttle valve112. For example only, the throttle valve112may include a butterfly valve having a rotatable blade. An engine control module (ECM)114controls a throttle actuator module116, which regulates opening of the throttle valve112to control the amount of air drawn into the intake manifold110.

Air from the intake manifold110is drawn into cylinders of the engine102. While the engine102may include multiple cylinders, for illustration purposes only, a single representative cylinder118is shown. For example only, the engine102may include 2, 3, 4, 5, 6, 8, 10, and/or 12 cylinders.

The engine102may operate using a four-stroke cylinder cycle or another suitable operating cycle. The four strokes, described below, may be named the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke. During each revolution of a crankshaft (not shown), two of the four strokes occur within the cylinder118. Therefore, two crankshaft revolutions are necessary for the cylinder118to experience all four of the strokes.

During the intake stroke, air from the intake manifold110is drawn into the cylinder118through an intake valve122. The ECM114controls a fuel actuator module124, which regulates fuel injection to achieve a desired air/fuel ratio. Fuel may be injected into the intake manifold110at a central location or at multiple locations, such as near the intake valve122of each of the cylinders. In various implementations (not shown), fuel may be injected directly into the cylinders or into mixing chambers associated with the cylinders.

The injected fuel mixes with air and creates an air/fuel mixture in the cylinder118. During the compression stroke, a piston (not shown) within the cylinder118compresses the air/fuel mixture. Based on a signal from the ECM114, a spark actuator module126may energize a spark plug128in the cylinder118, which ignites the air/fuel mixture. The timing of the spark may be specified relative to the time when the piston is at its topmost position, referred to as top dead center (TDC).

The spark actuator module126may be controlled by a timing signal specifying how far before or after TDC to generate the spark. Because piston position is directly related to crankshaft rotation, operation of the spark actuator module126may be synchronized with crankshaft angle. Generating spark in a cylinder may be referred to as a firing event.

The spark actuator module126may have the ability to vary the timing of the spark for each firing event. In addition, the spark actuator module126may have the ability to vary the timing of the spark for a given firing event even when a change in the timing signal is received after the firing event immediately before the given firing event.

During the combustion stroke, the combustion of the air/fuel mixture drives the piston down, thereby driving the crankshaft. The combustion stroke may be defined as the time between the piston reaching TDC and the time at which the piston returns to bottom dead center (BDC).

During the exhaust stroke, the piston begins moving up from BDC and expels the byproducts of combustion through an exhaust valve130. The byproducts of combustion are exhausted from the vehicle via an exhaust system134. A catalyst136receives exhaust gas output by the engine102and reacts with various components of the exhaust gas. For example only, the catalyst may include a three-way catalyst (TWC) or another suitable exhaust catalyst.

The intake valve122may be controlled by an intake camshaft140, while the exhaust valve130may be controlled by an exhaust camshaft142. In various implementations, multiple intake camshafts (including the intake camshaft140) may control multiple intake valves (including the intake valve122) for the cylinder118and/or may control the intake valves (including the intake valve122) of multiple banks of cylinders (including the cylinder118). Similarly, multiple exhaust camshafts (including the exhaust camshaft142) may control multiple exhaust valves for the cylinder118and/or may control exhaust valves (including the exhaust valve130) for multiple banks of cylinders (including the cylinder118). In various implementations, the intake valve122and/or the exhaust valve130may be controlled by devices other than camshafts, such as electromagnetic actuators.

The time at which the intake valve122is opened may be varied with respect to piston TDC by an intake cam phaser148. The time at which the exhaust valve130is opened may be varied with respect to piston TDC by an exhaust cam phaser150. A phaser actuator module158may control the intake cam phaser148and the exhaust cam phaser150based on signals from the ECM114. Enablement and disablement of opening of the intake valve122and/or the exhaust valve130may be regulated in some types of engine systems. Lift and/or duration of opening of the intake valve122and/or the exhaust valve130may also be regulated in some types of engine systems.

The engine system100may include a boost device that provides pressurized air to the intake manifold110. For example,FIG. 1shows a turbocharger including a hot turbine160-1that is powered by hot exhaust gases flowing through the exhaust system134. The turbocharger also includes a cold air compressor160-2, driven by the turbine160-1, that compresses air leading into the throttle valve112. In various implementations, a supercharger (not shown), driven by the crankshaft, may compress air from the throttle valve112and deliver the compressed air to the intake manifold110.

Opening of a wastegate162may be controlled to control an amount of exhaust gas allowed to bypass the turbine160-1. Exhaust gas bypassing the turbine160-1may reduce the boost (the amount of intake air compression) of the turbocharger. The ECM114may control the turbocharger via a boost actuator module164. The boost actuator module164may modulate the boost of the turbocharger by controlling the opening of the wastegate162. In various implementations, multiple turbochargers may be controlled by the boost actuator module164. The turbocharger may have variable geometry, which may be controlled by the boost actuator module164.

An intercooler (not shown) may dissipate some of the heat contained in the compressed air charge, which is generated as the air is compressed. The compressed air charge may also absorb heat from components of the exhaust system134. Although shown separated for purposes of illustration, the turbine160-1and the compressor160-2may be attached to each other, placing intake air in close proximity to hot exhaust.

The engine system100may include an exhaust gas recirculation (EGR) valve170, which selectively redirects exhaust gas back to the intake manifold110. The EGR valve170may be located upstream of the turbocharger's turbine160-1. The EGR valve170may be controlled by an EGR actuator module172.

The engine system100may measure the rotational speed of the crankshaft (i.e., engine speed) in revolutions per minute (RPM) using a crankshaft position sensor178. The rotational speed of the crankshaft may be referred to as engine speed. Temperature of engine oil may be measured using an oil temperature (OT) sensor180. Temperature of engine coolant may be measured using an engine coolant temperature (ECT) sensor182. The ECT sensor182may be located within the engine102or at other locations where the coolant is circulated, such as a radiator (not shown).

A pressure within the intake manifold110may be measured using a manifold absolute pressure (MAP) sensor184. In various implementations, engine vacuum, which is the difference between ambient air pressure and the pressure within the intake manifold110, may be measured. The mass flow rate of air flowing into the intake manifold110may be measured using a mass air flowrate (MAF) sensor186. In various implementations, the MAF sensor186may be located in a housing that also includes the throttle valve112.

The throttle actuator module116may monitor the position of the throttle valve112using one or more throttle position sensors (TPS)190. The ambient temperature of air being drawn into the engine102may be measured using an intake air temperature (IAT) sensor192. The ECM114may use signals from one or more of the sensors to make control decisions for the engine system100.

The ECM114may communicate with a transmission control module194to coordinate operation of the engine102and a transmission (not shown). For example only, the ECM114and the transmission control module194may communicate to coordinate shifting gears (and more specifically gear ratio) in the transmission. The ECM114may, for example, adjust engine output torque during a gear shift. The ECM114may communicate with a hybrid control module196, for example, to coordinate operation of the engine102and an electric motor198.

The electric motor198may also function as a generator and may be used to produce electrical energy for use by vehicle electrical systems and/or for storage in an energy storage device (e.g., a battery). The production of electrical energy may be referred to as regenerative braking. The electric motor198may apply a braking (i.e., negative) torque on the engine102to perform regenerative braking and produce electrical energy. The engine system100may also include one or more additional electric motors. In various implementations, various functions of the ECM114, the transmission control module194, and the hybrid control module196may be integrated into one or more modules.

Each system that varies an engine parameter may be referred to as an engine actuator. Each engine actuator receives an associated actuator value. For example, the throttle actuator module116may be referred to as an engine actuator and the throttle opening area may be referred to as the associated actuator value. In the example ofFIG. 1, the throttle actuator module116achieves the throttle opening area by adjusting an angle of the blade of the throttle valve112.

The spark actuator module126may similarly be referred to as an engine actuator, while the associated actuator value may be the amount of spark advance relative to cylinder TDC. Other actuators may include the cylinder actuator module, the fuel actuator module124, the phaser actuator module158, the boost actuator module164, and the EGR actuator module172. For these engine actuators, the associated actuator values may include to number of activated cylinders, fueling rate, intake and exhaust cam phaser angles, boost pressure, and EGR valve opening area, respectively. The ECM114may control actuator values in order to cause the engine102to achieve a target engine output torque.

Referring now toFIG. 2, a functional block diagram of an example implementation of a fuel control module200of the ECM114is presented. A target fueling module204determines a target amount (e.g., mass) of fuel to be injected for a combustion event that will occur within a cylinder of the engine102. The target amount of fuel to be injected for the combustion event will be referred to as a target fuel amount208. The target fueling module204may determine the target fuel amount208for each combustion event of the engine102.

An air per cylinder (APC) determination module212may determine an amount (e.g., mass) of air that will be present for the combustion event of the cylinder. The amount of air that will be present for the combustion event of the cylinder will be referred to as an APC216. The APC module212may determine the APC216for each combustion event of the engine102.

The APC module212may determine the APC216, for example, based on a MAP220measured using the MAP sensor184, an engine speed224, and/or one or more other suitable parameters. In various implementations, the APC module212may determine the APC216based on a MAF226measured using the MAF sensor186. In other implementations, the APC216may be a commanded APC and may be determined, for example, based on one or more driver inputs (e.g., accelerator pedal position).

An engine speed module228may determine the engine speed224based on a crankshaft position232measured using the crankshaft position sensor178. For example only, the engine speed module228may determine the engine speed224based on a change in the crankshaft position232over a period.

The target fueling module204may generate the target fuel amount208for the combustion event, for example, to achieve a target torque236and/or a target air/fuel ratio240with the APC216of the combustion event. The target torque236may be set, for example, based on one or more driver inputs, such as an accelerator pedal position. The target air/fuel ratio240may be set, for example, based on a stoichiometric air/fuel ratio or another suitable air/fuel ratio. The target fueling module204may generate the target fuel amount208for the combustion event, for example, as a function of the target torque236, the target air/fuel ratio240, the APC216, and/or one or more other suitable parameters. An injector control module244may command the fuel actuator module124to selectively control fuel injection for the combustion events of the engine102based on the target fuel amount208.

The target fueling module204also generates the target fuel amount208based on a state of a deceleration fuel cutoff (DFCO) signal260. A DFCO module264(see alsoFIG. 3) sets the DFCO signal260to one of an active state and an inactive state at a given time.

Fueling to the cylinders of the engine102is cut off when the DFCO signal260is in the active state. Fueling to the cylinders of the engine102may be controlled as described above or in another suitable manner when the DFCO signal260is in an inactive state. For example only, the target fueling module204may set the target fuel amount208to zero (such that no fuel will be injected) when the DFCO signal260is in the active state. In this manner, fuel may be cut off to the cylinders of the engine102when the DFCO signal260is in the active state. A spark control module (not shown) may disable spark to the cylinders of the engine102when the DFCO signal260is in the active state.

The DFCO module264could selectively transition the DFCO signal260from the inactive state to the active state when the engine speed224is greater than a predetermined minimum entry speed (e.g., approximately 1500 RPM) and one or more other DFCO entry conditions are satisfied. Under some circumstances, however, fuel could be cut off during vehicle deceleration when the one or more other DFCO entry conditions are satisfied and the engine speed224is not greater than the predetermined minimum entry speed.

For example only, when the vehicle begins traveling down a decline (e.g., a hill), the engine speed224may not be greater than the predetermined minimum entry speed. As the vehicle travels down the decline, the engine speed224may increase and become greater than the predetermined minimum entry speed. Fuel could then be cut off if the one or more other entry conditions are satisfied. However, fuel may be unnecessarily consumed as the engine speed224increases while the vehicle travels down the decline.

For another example only, as the vehicle travels down the decline, the engine speed223may not be greater than the predetermined minimum entry speed and the engine speed224may not increase. As the engine speed224may fail to be greater than the predetermined minimum entry speed while the vehicle travels down the decline, fuel may not be cut off.

The DFCO module264of the present disclosure generates an estimated period of a DFCO event based on a rate of change of the engine speed224. Instead of selectively transitioning the DFCO signal260to the active state based on the comparison of the engine speed224and the predetermined minimum entry speed, the DFCO module264selectively transitions the DFCO signal260to the active state based on the estimated period. Relative to transitioning based on the comparison of the engine speed224and the predetermined minimum entry speed, selectively transitioning the DFCO signal260to the active state based on the estimated period may enable fuel to be cut off sooner and provide fuel consumption savings under some circumstances.

Referring now toFIG. 3, a functional block diagram of an example implementation of the DFCO module264is presented. A first rate of change (ROC) module316determines an engine speed ROC320based on the engine speed224. The engine speed ROC320corresponds a rate of change of the engine speed224over a predetermined period. The engine speed ROC320may be determined, for example, based on a mathematical derivative of the engine speed224or in another suitable manner.

A filtering module324may apply a filter to the engine speed ROC320to generate a filtered engine speed ROC328. For example only, the filtering module324may determine a moving average the engine speed ROC320over a predetermined period or apply another suitable type of filter to generate the filtered engine speed ROC328. The predetermined period may be, for example, approximately 1 second or another suitable period. The moving average may be weighted or non-weighted. The filtering module324may also generate the filtering engine speed ROC328based on a state of a torque converter clutch (e.g., locked, controlled slip, etc.). For example only, the filtering module324may vary a filtering coefficient based on the state of the torque converter clutch.

A period estimation module332generates an estimated DFCO period336based on the engine speed ROC320. The estimated DFCO period336may refer to an estimated period (e.g., seconds) from the present time that fuel could be cut off to the cylinders of the engine102before fueling to the cylinders would be re-enabled. In other words, the estimated DFCO period336may refer to an estimated period (duration) of a next DFCO event.

The period estimation module332may generate the estimated DFCO period336based on the filtered engine speed ROC328, the engine speed224, and a first predetermined (minimum) engine speed. The period estimation module332may generate the estimated DFCO period336using one of a function and a mapping that relates the filtered engine speed ROC328, the engine speed224, and the first predetermined engine speed to the estimated DFCO period336. For example only, the period estimation module332may generate the estimated DFCO period336using the equation:

T=Engine⁢⁢Speed-Pred⁢⁢Engine⁢⁢SpeedFiltered⁢⁢Engine⁢⁢Speed⁢⁢ROC,
where T is the estimated DFCO period336, Engine Speed is the engine speed224, Pred Engine Speed is the first predetermined engine speed, and Filtered Engine Speed ROC is the filtered engine speed ROC328. The first predetermined engine speed may be a fixed value or a variable value. For example only, if the first predetermined engine speed is a variable value, the first predetermined engine speed may be set at a given time based on a state of the torque converter clutch (e.g., locked, controlled slip, etc.), a state of the vehicle, and/or one or more other suitable parameters. The first predetermined engine speed is greater than an idle engine speed. In various implementations, the engine speed ROC320may be used in place of the filtered engine speed ROC328. As the denominator of the above equation approaches zero, the estimated DFCO period336approaches infinity. The estimated DFCO period336may be limited to a predetermined maximum value.

An enabling/disabling module344selectively enables and disables a DFCO control module348. When enabled, the DFCO control module348determines whether to set the DFCO signal260to one of the active state and the inactive state based on the estimated DFCO period336. For example only, the DFCO control module348may set the DFCO signal260to the active state when the estimated DFCO period336is greater than a predetermined minimum DFCO period. As stated above, fueling to the engine102is cut off when the DFCO signal260is in the active state.

Conversely, the DFCO control module348may set the DFCO signal260to the inactive state when the estimated DFCO period336is less than the predetermined minimum DFCO period. For example only the predetermined minimum DFCO period may be approximately 2 seconds or another suitable minimum period of a DFCO event (during which fuel is cut off to the engine102). When disabled, the DFCO signal260is set to the inactive state, thereby preventing the DFCO control module348from initiating a DFCO event.

The enabling/disabling module344selectively enables and disables the DFCO control module348based on an accelerator pedal position (APP)352and a gear ratio356. The enabling/disabling module344selectively enables and disables the DFCO control module348further based on an engine coolant temperature (ECT)360and a transmission control module (TCM) disable DFCO signal364.

For example only, the enabling/disabling module344may disable the DFCO control module348when at least one of the following is true:(i) the APP352is greater than a predetermined resting APP;(ii) the gear ratio356is less than a predetermined ratio;(iii) the ECT360is less than a predetermined temperature;(iv) the engine speed224is less than a second predetermined (minimum) engine speed; and(v) the TCM disable DFCO signal364is in an active state.
Conversely, the enabling/disabling module may enable the DFCO control module348when (i)-(v) are not satisfied.

The APP352may be measured using one or more accelerator pedal position sensors (not shown). When the accelerator pedal is not being depressed, the APP352may be equal to the predetermined resting APP. The APP352may increase relative to the predetermined resting APP as the accelerator pedal is depressed. The gear ratio356may correspond to a gear ratio currently engaged within the transmission and may be determined, for example, by the transmission control module194. The predetermined ratio may be, for example, a third gear ratio, a fourth gear ratio, a fifth gear ratio, or another suitable gear ratio. The ECT360may be measured using the ECT sensor182. The predetermined temperature may be, for example, between approximately 30 degrees Celsius (° C.) and approximately 60° C. or another suitable temperature. The second predetermined engine speed may be, for example, approximately 900-1100 RPM or another suitable engine speed that is greater than the idle engine speed. The transmission control module194sets the TCM disable DFCO signal364to one of the active state and an inactive state at a given time based on a second estimated DFCO period as discussed further below.

The enabling/disabling module344may enable and disable the DFCO control module348, for example, using an enable/disable signal370. For example, the enabling/disabling module344may set the enable/disable signal370to the inactive state to enable the DFCO control module348. Conversely, the enabling/disabling module344may set the enable/disable signal370to the active state to disable the DFCO control module348.

Referring now toFIG. 4, a functional block diagram of an example implementation of the transmission control module194is presented. A second ROC (rate of change) module404determines a vehicle speed ROC408based on a vehicle speed412. The vehicle speed ROC408corresponds a rate of change of the vehicle speed412over a predetermined period. The vehicle speed ROC408may be determined, for example, based on a mathematical derivative of the vehicle speed412or in another suitable manner. The vehicle speed412may be determined, for example, based on one or more wheel speeds generated based on measurements of one or more wheel speed sensors (not shown).

A filtering module416may apply a filter to the vehicle speed ROC408to generate a filtered vehicle speed ROC420. For example only, the filtering module416may determine a moving average the vehicle speed ROC408over a predetermined period or apply another suitable type of filter to generate the filtered vehicle speed ROC420. The predetermined period may be, for example, approximately 1 second or another suitable period. The moving average may be weighted or non-weighted.

A second period estimation module424generates a second estimated DFCO period428based on the vehicle speed ROC408. The second estimated DFCO Period428may refer to an estimated period (e.g., seconds) from the present time that fuel could be cut off to the cylinders of the engine102before fueling to the cylinders would be re-enabled. In other words, the second estimated DFCO period428may refer to an estimated period of the next DFCO event.

The second period estimation module424may generate the second estimated DFCO period428using one of a function and a mapping that relates the filtered vehicle speed ROC420to the second estimated DFCO period428. In various implementations, the second period estimation module424may generate the second estimated DFCO period428based on the vehicle speed ROC408. In such implementations, the second period estimation module424may generate the second estimated DFCO period428using one of a function and a mapping that relates the vehicle speed ROC408to the second estimated DFCO period428. For example only, second period estimation module424may generate the second estimated DFCO period428using the equation:

T2=⁢Vehicle⁢⁢Speed-Prev⁢⁢Vehicle⁢⁢SpeedFiltered⁢⁢Vehicle⁢⁢Speed⁢⁢ROC,
where T2is the second estimated DFCO period428, Vehicle Speed is the vehicle speed412at the present sampling time, Prev Vehicle Speed is the vehicle speed412at the last sampling time, and Filtered Vehicle Speed ROC is the filtered vehicle speed ROC420.

A DFCO disabling module432sets the TCM disable DFCO signal364to one of the active state and an inactive state at a given time based on the second estimated DFCO period428. For example only, the DFCO disabling module432may set the TCM disable DFCO signal364to the active state when the second estimated DFCO period428is less than the predetermined minimum DFCO period. In this manner, the DFCO control module348will be disabled when the second estimated DFCO period428is less than the predetermined minimum DFCO period. Conversely, the DFCO disabling module432may set the TCM disable DFCO signal364to the inactive state when the second estimated DFCO period428is greater than the predetermined minimum DFCO period. In this manner, the DFCO control module348can be enabled when the second estimated DFCO period428is greater than the predetermined minimum DFCO period.

Referring now toFIG. 5, a flowchart depicting an example method500of controlling DFCO is presented. Control may begin with504where control determines the engine speed ROC320based on the engine speed224. Control determines the filtered engine speed ROC328at508based on the engine speed ROC320.

Control determines the estimated DFCO period336at512. Control may determine the estimated DFCO period336based on the filtered engine speed ROC328, the engine speed224, and the first predetermined engine speed. Control may generate the estimated DFCO period336using one of a function and a mapping that relates the filtered engine speed ROC328, the engine speed224, and the first predetermined engine speed to the estimated DFCO period336. For example only, control may generate the estimated DFCO period336using the equation:

T=Engine⁢⁢Speed-Pred⁢⁢Engine⁢⁢SpeedFiltered⁢⁢Engine⁢⁢Speed⁢⁢ROC,
where T is the estimated DFCO period336, Engine Speed is the engine speed224, Pred Engine Speed is the first predetermined engine speed, and Filtered Engine Speed ROC is the filtered engine speed ROC328. In various implementations, the engine speed ROC320may be used in place of the filtered engine speed ROC328.

At516, control may determine whether the gear ratio356is greater than the predetermined ratio, the APP352is equal to the predetermined resting APP, the ECT360is greater than the predetermined temperature, and the engine speed224is greater than the second predetermined engine speed. If false, control may prevent a DFCO event (including cutting off fuel) from beginning at520, and control may end. If true, control may continue with524.

Control may determine whether the TCM disable DFCO signal364is in the inactive state at524. If false, control may prevent a DFCO event from beginning at520, and control may end. If true, control may continue with528. At528, control may determine whether the estimated DFCO period336is greater than the predetermined minimum DFCO period. If false, control may prevent a DFCO event from beginning at520, and control may end. If true, control may initiate a DFCO event and cut off fuel to the engine102at532, and control may end. While control is shown and discussed as ending, the method500may be illustrative of one control loop, and control may perform a control loop at predetermined intervals.

Referring now toFIG. 6, a flowchart depicting an example method600of selectively disabling and allowing entry into DFCO is presented. Control may begin at604where control determines the vehicle speed ROC408based on the vehicle speed412. Control may determine the filtered vehicle speed ROC420at608. At612, control determines the second estimated DFCO period428. Control may determine the second estimated DFCO period428based on one of the filtered vehicle speed ROC420and the vehicle speed ROC408. Control may determine the second estimated DFCO period428using one of a function and a mapping that relates the one of the filtered vehicle speed ROC420and the vehicle speed ROC408to the second estimated DFCO period428.

At616, control determines whether the second estimated DFCO period428is less than the predetermined minimum DFCO period. If true, control may set the TCM disable DFCO signal364to the active state at620, and control may end. If false, control may set the TCM disable DFCO signal364to the inactive state at624, and control may end. In this manner, control may prevent a DFCO event from beginning when the second estimated DFCO period428is less than the predetermined minimum DFCO period and allow fuel to be cut off for a DFCO event when the opposite is true. While control is shown and discussed as ending, the method600may be illustrative of one control loop, and control may perform a control loop at predetermined intervals.