Cold start engine control systems and methods

A control system includes a starter control module, a mode setting module, a throttle control module, and a fuel control module. The starter control module initiates cranking of a spark ignition direct injection (SIDI) engine in response to user actuation of an ignition switch. The mode setting module sets a mode of operation to a coldstart mode when an engine coolant temperature is less than a predetermined temperature during the cranking. The throttle control module allows a throttle valve to be biased to a predetermined open position when the SIDI engine is off and, in response to the setting of the mode to the coldstart mode, selectively closes the throttle valve relative to the predetermined open position during the cranking. The fuel control module, in response to the setting of the mode to the coldstart mode, disables direct injection of fuel for a first combustion event during the cranking.

FIELD

The present disclosure relates to internal combustion engines and more particularly to engine control systems and methods for cold engine startups.

BACKGROUND

Internal combustion engines combust air and fuel within cylinders to produce drive torque. Air flow into an engine may be regulated via a throttle valve. A fuel control system controls fuel injection amount and timing. Increasing the amount of air and fuel provided to the cylinders generally increases the torque output of the engine.

Spark ignition direct injection (SIDI) engines have improved fuel economy and increased power over port fuel-injected combustion engines. A fuel injection system for an SIDI engine is operated at high pressure to inject fuel directly into combustion chambers. A fuel pump for supplying the fuel to a fuel rail at high pressure is mechanically driven by the engine.

SUMMARY

A cold start control system for a vehicle includes a starter control module, a mode setting module, a throttle control module, and a fuel control module. The starter control module initiates cranking of a spark ignition direct injection (SIDI) engine in response to user actuation of an ignition switch. The mode setting module sets a mode of operation to a coldstart mode when an engine coolant temperature is less than a predetermined temperature during the cranking. The throttle control module allows a throttle valve to be biased to a predetermined open position when the SIDI engine is off and, in response to the setting of the mode to the coldstart mode, selectively closes the throttle valve relative to the predetermined open position during the cranking. The fuel control module, in response to the setting of the mode to the coldstart mode, disables direct injection of fuel for a first combustion event during the cranking.

A cold start control method for a vehicle, includes: initiating cranking of a spark ignition direct injection (SIDI) engine in response to user actuation of an ignition switch; setting a mode of operation to a coldstart mode when an engine coolant temperature is less than a predetermined temperature during the cranking; and allowing a throttle valve to be biased to a predetermined open position when the SIDI engine is off. The cold start control method further includes: in response to the setting of the mode to the coldstart mode, selectively closing the throttle valve relative to the predetermined open position during the cranking; and, in response to the setting of the mode to the coldstart mode, disabling direct injection of fuel for a first combustion event during the cranking.

DETAILED DESCRIPTION

A spark ignition direct injection (SIDI) engine combusts air and fuel to generate drive torque for a vehicle. The fuel is injected directly into cylinders of SIDI engines. The fuel may be gasoline, a mixture of gasoline and ethanol, or another suitable type of fuel. Engines that can combust gasoline, ethanol, and a mixture of gasoline and ethanol can be referred to as flex fuel engines.

A control module selectively starts an SIDI engine in response to user actuation of an ignition input, such as an ignition key or button, or initiation of an auto-start event. The control module controls various operating parameters during startup of the SIDI engine and while the SIDI engine is ON (running) after startup. For example, the control module controls opening of a throttle valve, fuel injection amount and timing, spark timing, and other suitable operating parameters during startup of the SIDI engine and while the SIDI engine is ON after startup. The control module also selectively shuts down the SIDI engine in response to user actuation of an ignition input or initiation of an auto-stop event.

Different types of fuel have different flash point temperatures. The flash point temperature of a fuel may refer to a minimum temperature at which the fuel can vaporize to form an ignitable mixture in air. At temperatures that are less than the flash point temperature of the fuel that is directly injected into the SIDI engine, the fuel may be unable to vaporize during startup, and the SIDI engine may be unable to start.

One or more auxiliary devices can be added to facilitate startup of the SIDI engine at temperatures that are less than the flash point temperature of the fuel. For example, a block heater and/or a fuel rail heater or a fuel injector heater may be added to warm the fuel. Warming the fuel may enable the fuel to vaporize sufficiently to allow startup of the SIDI engine at temperatures that are less than the flash point temperature of the fuel. For another example, as gasoline has a low flash point temperature relative to other types of fuels, a separate gasoline tank and a gasoline injector can be added for use during startup of engines using a fuel having a high flash point temperature, such as Ethanol. Adding one or more auxiliary devices, however, increases vehicle cost.

According to the present disclosure, no auxiliary devices are added. Instead, at temperatures that are at or less than the flash point temperature of the fuel that is directly injected into the cylinders of the SIDI engine, the control module selectively controls the throttle valve, fueling, and spark during startup of the SIDI engine as to enable startup of the SIDI engine.

Referring now toFIG. 1, a functional block diagram of an example engine system100is presented. The engine system includes an engine102that combusts an air/fuel mixture to produce drive torque for a vehicle. Air is drawn into an intake manifold104through a throttle valve106. The throttle valve106regulates air flow into the intake manifold104. Air within the intake manifold104is drawn into cylinders of the engine102, such as cylinder108.

One or more fuel injectors, such as fuel injector110, inject fuel that mixes with air to form an air/fuel mixture. In various implementations, one fuel injector may be provided for each cylinder of the engine102. The fuel injectors inject fuel directly into the cylinders. Fuel injection may be controlled based on a desired air/fuel mixture for combustion, such as a stoichiometric air/fuel mixture. A fuel system provides fuel to the fuel injectors. The fuel system is discussed further below.

An intake valve112opens to allow air into the cylinder108. A piston (not shown) compresses the air/fuel mixture within the cylinder108. A spark plug114initiates combustion of the air/fuel mixture within the cylinder108. One spark plug may be provided for each cylinder of the engine102. Combustion of the air/fuel mixture applies force to the piston, and the piston drives rotation of a crankshaft (not shown).

The engine102outputs torque via the crankshaft. A flywheel120is coupled to the crankshaft and rotates with the crankshaft. Torque output by the engine102is selectively transferred to a transmission122via a torque transfer device124. The torque transfer device124selectively couples/decouples the transmission122to/from the engine102. The transmission122may include, for example, a manual transmission, an automatic transmission, a semi-automatic transmission, an auto-manual transmission, or another suitable type of transmission. The torque transfer device124may include, for example, a torque converter and/or one or more clutches.

Exhaust produced by combustion of the air/fuel mixture is expelled from the cylinder108via an exhaust valve126. The exhaust is expelled from the cylinders to an exhaust system128. The exhaust system128may treat the exhaust before the exhaust is expelled from the exhaust system128. Although one intake and exhaust valve are shown and described as being associated with the cylinder108, more than one intake and/or exhaust valve may be associated with each cylinder of the engine102.

An engine control module (ECM)130controls various engine actuators. The engine actuators may include, for example, a throttle actuator module132, a fuel actuator module134, and a spark actuator module136. The engine system100may also include other engine actuators, and the ECM130may control the other engine actuators.

Each engine actuator controls an operating parameter based on a signal from the ECM130. For example only, based on signals from the ECM130, the throttle actuator module132may control opening of the throttle valve106, the fuel actuator module134may control fuel injection amount and timing, and the spark actuator module136may control spark timing.

The ECM130may control the engine actuators based on, for example, driver inputs and inputs from various vehicle systems. The vehicle systems may include, for example, a transmission system, a hybrid control system, a stability control system, a chassis control system, and other suitable vehicle systems.

A driver input module140may provide the driver inputs to the ECM130. The driver inputs provided to the ECM130may include, for example, an accelerator pedal position (APP), a brake pedal position (BPP), cruise control inputs, and vehicle operation commands. An APP sensor142measures position of an accelerator pedal (not shown) and generates the APP based on the position of the accelerator pedal. A BPP sensor144monitors actuation of a brake pedal (not shown) and generates the BPP based on a position of the brake pedal. A cruise control system146provides the cruise control inputs, such as a desired vehicle speed, based on inputs to the cruise control system146.

The vehicle operation commands may include, for example, vehicle startup commands and vehicle shutdown commands. The vehicle operation commands may be input by a user via actuation of one or more ignition system inputs148. For example, a user may input the vehicle operation commands by actuating an ignition key, one or more buttons/switches, and/or one or more other suitable ignition system inputs.

An engine speed sensor152measures rotational speed of the engine102and generates an engine speed based on the speed. For example only, the engine speed sensor152may generate the engine speed based on rotation of the crankshaft in revolutions per minute (rpm). A coolant temperature sensor154measures a temperature of engine coolant and generates an engine coolant temperature (ECT) based on the temperature of the engine coolant. The ECM130may also receive operating parameters measured by other sensors156, such as oxygen in the exhaust, intake air temperature (IAT), mass air flowrate (MAF), oil temperature, manifold absolute pressure (MAP), and/or other suitable parameters. In various implementations, ethanol content may be measured using a sensor.

The ECM130selectively shuts down the engine102when a user inputs a vehicle shutdown command. For example only, the ECM130may disable the injection of fuel, disable the provision of spark, and perform other shutdown operations to shut down the engine102in response to receipt of a vehicle shutdown command.

The ECM130selectively starts the engine102. The ECM130starts the engine102in response to receipt of a vehicle startup command or initiation of an auto-start event. The ECM130engages a starter motor160with the engine102to initiate engine startup. The starter motor160may engage the flywheel120or other suitable component(s) that drive rotation of the crankshaft.

A starter motor actuator162, such as a solenoid, selectively engages the starter motor160with the engine102. A starter actuator module164controls the starter motor actuator162and the starter motor160based on signals from the ECM130. For example only, the ECM130may command engagement of the starter motor160when the vehicle startup command is received. The starter actuator module164selectively applies current to the starter motor160when the starter motor160is engaged with the engine102. The application of current to the starter motor160drives the starter motor160, and the starter motor160drives the crankshaft.

Once the crankshaft is rotating, the starter motor160may be disengaged from the engine102, and the flow of current to the starter motor160may be discontinued. The engine102may be deemed running, for example, when the engine speed exceeds a predetermined speed, such as approximately 700 rpm or another suitable speed. The period between when the starter motor160is engaged with the engine102for starting the engine and when the engine102is deemed running may be referred to as engine cranking.

The current provided to the starter motor160may be provided by, for example, a battery170. While only the battery170is shown, the battery170may include one or more individual batteries that are connected together or one or more other batteries may be provided.

The engine system100may include one or more electric motors, such as electric motor (EM)172. The EM172may selectively draw electrical power, for example, to supplement the torque output of the engine102. The EM172may also selectively function as a generator and selectively apply a braking torque to the engine102to generate electrical power. Generated electrical power may be used, for example, to charge the battery170, to provide electrical power to one or more other EMs (not shown), to provide electrical power to other vehicle systems, and/or for other suitable uses.

As mentioned above, the fuel system supplies fuel to the fuel injectors. The fuel system may include a fuel tank174, a low pressure fuel pump176, a high pressure fuel pump178, a fuel rail180, a pressure relief valve182, and/or one or more other suitable components. The low pressure fuel pump176draws fuel from the fuel tank174and provides fuel at low pressures to the high pressure fuel pump178. The low pressures provided by the low pressure fuel pump176are expressed relative to pressurization provided by the high pressure fuel pump178.

The low pressure fuel pump176is an electrically driven fuel pump, and a pump actuator module184may control the application of power to the low pressure fuel pump176based on signals from the ECM130. For example only, the ECM130may command application of power to the low pressure fuel pump176when or before a vehicle startup command is input.

The high pressure fuel pump178pressurizes the fuel received from the low pressure fuel pump176within the fuel rail180. The high pressure fuel pump178is engine driven, such as by the crankshaft or by a camshaft. The high pressure fuel pump178may pump fuel into the fuel rail180, for example, once, twice, or more per revolution of the crankshaft.

The fuel injectors inject fuel from the fuel rail180into the cylinders. The high pressure fuel pump178pressurizes the fuel within the fuel rail180to pressures that are greater than pressure within the cylinder during fuel injection. When a pressure within the fuel rail180is greater than a predetermined maximum pressure, the pressure relief valve182releases fuel back to the fuel tank174.

As fuel is injected directly into the cylinders and combustion is initiated via spark, the engine102may be referred to as a spark ignition direct injection (SIDI) engine. Flex fuel SIDI engines can combust gasoline, a blend of gasoline and ethanol, or ethanol. An ethanol fuel may be referred to using the prefix E and an integer corresponding to an amount of ethanol in the blend by volume. For example, E85 may refer to a blend of gasoline and ethanol that includes 85 percent ethanol by volume, E50 may refer to a blend of gasoline and ethanol that includes up to 50 percent ethanol by volume, etc. Ethanol may be referred to as E100, and gasoline may be referred to as E0. Other types of fuels that may be combusted by SIDI engines include methanol, other alcohol based fuels, liquefied petroleum gas (LPG), propane, butane, etc.

Flash point temperature of a fuel may refer to a minimum temperature at which the fuel can vaporize to form an ignitable mixture in air. Some fuels, such as gasoline, have a flash point temperature that is less than a predetermined minimum temperature, such as −10 degrees Celsius (° C.). Other fuels, however, have a flash point temperature that is greater than the predetermined minimum temperature. For example only, E100 may have a flash point temperature of approximately 18° C. Fuels having a flash point temperature that is greater than the predetermined minimum temperature may be unable to vaporize and/or combust when the engine102is started at or even above the predetermined minimum temperature.

One or more auxiliary devices could be added to the vehicle to enable startup of the engine102at temperatures that are less than the flash point temperature of the fuel within the fuel tank174. For example only, a gasoline injector and a separate gasoline fuel tank can be added, and the gasoline can be injected during engine cranking to enable startup of the engine102. For another example only, an engine block heater and/or one or more other electrical heaters, such as a fuel rail heater or fuel injector heaters, can be added to warm the fuel to enable startup of the engine102. The addition of one or more of these auxiliary, startup enabling devices, however, also increases vehicle cost.

In the present patent application, zero auxiliary devices (e.g, engine block heater, separate gasoline injector, separate gasoline fuel tank, and/or one or more electrical heaters) are included to facilitate engine startup at temperatures that are less than the flash point temperature of the fuel within the fuel tank174. Instead, at temperatures that are less than the flash point temperature of the fuel within the fuel tank174, a startup control module190selectively closes the throttle valve106and controls fueling during engine cranking to enable vaporization of the fuel and to start the engine102.

Referring now toFIG. 2, a functional block diagram of an example implementation of the startup control module190is presented. In response to a user inputting a vehicle startup command204while the engine102is off, a starter control module208commands the starter actuator module164to engage the starter motor160with the engine102and apply power to the starter motor160. The vehicle startup command204may be input by the driver, for example, by actuating one or more ignition inputs.

The starter actuator module164engages the starter motor160with the engine102and applies power to the starter motor160in response to the command. When engaged with the engine102and receiving power, the starter motor160drives rotation of the crankshaft. Power is also applied to the low pressure fuel pump176during engine cranking. Power may be applied to the low pressure fuel pump176beginning before power is applied to the starter motor160. The low pressure fuel pump176may be controlled during engine cranking and while the engine102is running based on providing fuel to the high pressure fuel pump178at a predetermined low pressure. The high pressure fuel pump178increases the pressure of the fuel within the fuel rail180as the starter motor160drives the crankshaft.

A throttle control module212controls opening of the throttle valve106. The throttle control module212may set a desired area216for the throttle valve106, and the throttle actuator module132may actuate the throttle valve106based on the desired area216. A fuel control module220controls amount and timing of fuel injection. The fuel control module220may set desired fueling parameters224(e.g., desired amount, desired timing, desired number of pulses, etc.), and the fuel actuator module134may control the fuel injectors based on the desired fueling parameters224.

While the engine102is off pursuant to receipt of a vehicle shutdown command, the throttle control module212may de-energize the throttle valve106. When de-energized, the throttle valve106may be biased (mechanically) to a predetermined open position. The throttle valve106may be biased against one or more stops. When in the predetermined open position, a predetermined open area is achieved, such as approximately 80 percent open.

The opening of the throttle valve106should be at approximately the predetermined open position at the time when the vehicle startup command204is received. Additionally, pressure within the intake manifold104should be approximately equal to ambient air pressure when the vehicle startup command204is received. As stated above, the fuel within the fuel tank174may be unable to vaporize and the engine102may be unable to start at temperatures that are less than the flash point temperature of the fuel.

A mode setting module228sets a mode232of operation for the engine102. The throttle control module212and the fuel control module220control the throttle valve112and fuel injection, respectively, based on the mode232. Control modules of one or more other engine actuators may also control the other engine actuators based on the mode232.

The mode setting module228may set the mode232to a coldstart mode in response to the receipt of the vehicle startup command204and a determination that a temperature is less than a predetermined temperature. For example, the mode setting module228may set the mode232to the coldstart mode when an ECT (engine coolant temperature)236is less than the predetermined temperature. The predetermined temperature is less than the flash point temperature of the fuel within the fuel tank174. The predetermined temperature may be a predetermined value that is less than or equal to 18 degrees Celsius (° C.) or another suitable temperature below which the fuel within the fuel tank174may be unable to vaporize during engine cranking. When the temperature is not less than the predetermined temperature, the mode setting module228may set the mode232to a start mode for a normal engine startup.

The mode setting module228may set the predetermined temperature (used for determining whether to set the mode232to the coldstart mode) based on the characteristic244. For example only, the mode setting module228may set the predetermined temperature using a function or a mapping (e.g., lookup table) that relates the characteristic244of the fuel within the fuel tank174to the predetermined temperature.

In response to the mode232being set to the coldstart mode, the throttle control module212and the fuel control module220control the throttle valve112and fuel injection for a cold start of the engine102. More specifically, when the mode232is set to the coldstart mode, the throttle control module212selectively closes the throttle valve112relative to the predetermined open position during engine cranking. Closing the throttle valve112increases the vacuum (i.e., lowers the pressure) within the intake manifold104and the cylinders. The lower pressure within the intake manifold104may provide better conditions for vaporization when the fuel is injected into a cylinder.

The throttle control module212may close the throttle valve112to a predetermined fully closed position during engine cranking when the mode232is set to the cold start mode. When the throttle valve112is in the predetermined fully closed position, a predetermined fully closed area is achieved, such as approximately zero percent open.

In various implementations, the throttle control module212may close the throttle valve112based on adjusting the pressure within the intake manifold104to a target pressure when the mode232is set to the cold start mode. The target pressure may be a predetermined pressure that is less than ambient air pressure. The throttle control module212may control the throttle valve112in closed-loop based on measurements provided by a MAP sensor and the target pressure.

When the mode232is set to the cold start mode, the fuel control module220generally provides rich fueling for combustion events. However, the fuel control module220may disable fuel injection for one or more combustion events when the mode232is set to the coldstart mode. The fuel control module220may disable fuel injection, for example, for one or more of the combustion events that would occur soonest after the starter motor160begins cranking the engine102. Disabling fuel injection for a combustion event allows the high pressure fuel pump178to increase the pressure within the fuel rail180. The pressure within the fuel rail180being higher may increase vaporization of fuel injected into a cylinder and increase temperature of the walls and body of the cylinder.

Injection of fuel for a given combustion event may be accomplished using one or more individual injections of fuel. When the mode232is set to the coldstart mode, the fuel control module220may command one injection of fuel for a combustion event of a cylinder be performed while the intake valve(s) of the cylinder is open for the combustion event. The lower pressure within the intake manifold104that is attributable to the closing of the throttle valve112may enable the fuel that is injected while the intake valve(s) is open to vaporize to a greater extent. The fuel control module220may also command one or more other fuel injections for the combustion event be performed after the intake valve of the cylinder is closed for the combustion event. The fuel and air charge temperature increase during the cylinder compression event can therefore occur at a lower pressure due to the lower intake manifold pressure and thus enable the fuel to vaporize to a greater extent.

A spark control module248sets a desired spark timing252, and the spark actuator module136generates spark based on the desired spark timing252. When the mode232is set to the coldstart mode, the spark control module248may disable spark for one or more combustion events. Disabling spark for a combustion event may enable a charge of air and fuel to warm within a cylinder. This may enable more fuel of the charge to vaporize when it is combusted during a later combustion event.

The mode setting module228may transition the mode232from the coldstart mode (or the start mode) to an engine running mode when the engine is running after a startup. The mode setting module228may transition the mode232to the engine running mode, for example, when an engine speed becomes greater than a predetermined speed, such as approximately 700 rpm or another suitable speed. The throttle control module212, the fuel control module220, and the spark control module248may transition to normal control of the throttle valve112, fueling, and spark timing in response to a transition in the mode232to the engine running mode.

Referring now toFIG. 3, a flowchart depicting an example method of performing a cold start of the engine102is presented. Control may begin with304at a time when the engine102is off pursuant to a vehicle shutdown request. At304, control determines whether a user has input a vehicle startup command. If true, control continues with308. If false, control remains at304and waits for a user to input a vehicle startup command. A user may input a vehicle startup command by actuating an ignition switch, an ignition button, etc.

At308, control engages the starter motor160with the engine102and applies power to the starter motor160. The starter motor160drives rotation of the crankshaft of the engine102. The low pressure fuel pump176may be activated to begin pumping fuel to the high pressure fuel pump178before the starter motor160begins driving the crankshaft. The high pressure fuel pump178pumps fuel into the fuel rail180as the starter motor160drives the crankshaft.

Control may obtain a characteristic of the fuel within the fuel tank174at312. The characteristic of the fuel may be, for example, an ethanol concentration of the fuel, a flash point temperature of the fuel, or another suitable characteristic of the fuel. At316, control may set the predetermined temperature used in determining whether the startup of the engine102is a cold start based on the characteristic of the fuel.

At320, control may determine whether the ECT236is less than the predetermined temperature. If true, control may continue with324and perform a coldstart of the engine102. If false, control may perform a normal startup of the engine102at322, and control may end. The predetermined temperature is less than the flash point temperature of the fuel and may be less than or equal to +18° C.

At324, control regulates the throttle valve112, fuel injection, and spark timing for the coldstart of the engine102. More specifically, control closes the throttle valve112from the predetermined open position during engine cranking. Control may close the throttle valve112to the predetermined fully closed position or regulate the throttle valve112based on achieving the target MAP. Control may command an injection of fuel for a combustion event of a cylinder while the intake valve is open for the cylinder. Control may additionally or alternatively disable fuel injections for one or more combustion events during engine cranking. Control may disable spark for one or more combustion events during engine cranking. A combination of one or more of the above may enable fuel injected into the cylinders to vaporize and allow the engine102to start. Control may also alter the injected quantity of fuel on a cylinder event basis.

At328, control may determine whether the engine102is running. If true, control may transition to controlling the throttle valve112, fuel injection, and spark timing in a normal operation mode at332, and control may end. If false, control may return to324and continue controlling the throttle valve112, fuel injection, and spark timing for the coldstart of the engine102. The engine102may be deemed running, for example, when the engine speed is greater than the predetermined speed.