Engine startup fuel pressure control systems and methods

A fuel pressure control system for a vehicle comprises a pressure regulator module and a pressure increasing module. The pressure regulator module regulates a fuel pressure supplied to an engine to a first predetermined pressure during an engine running period. The pressure increasing module selectively increases the fuel pressure to a second predetermined pressure during the engine running period when a counter value is one of greater than and less than a predetermined final value. The second predetermined pressure is greater than the first predetermined pressure, and the counter value is set to the predetermined final value after the engine is started for a first time after being assembled.

FIELD

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

BACKGROUND

Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons, which produces drive torque. Air flow into gasoline engines 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. Increasing the amount of air and fuel provided to the cylinders increases the torque output of the engine.

The fuel that is combusted by the engine is stored in a fuel tank. A low pressure pump draws fuel from the fuel tank. The low pressure pump pressurizes the fuel and supplies low pressure fuel to a high pressure pump. The high pressure pump further pressurizes the fuel and supplies the pressurized fuel to one or more fuel injectors.

An engine control module (ECM) controls the amount and timing of fuel injection, torque output by the engine, and other parameters. The ECM may also diagnose faults in one or more components of the vehicle. These faults may be used to, for example, notify a driver to seek service and aid a service technician in servicing the vehicle.

SUMMARY

A fuel pressure control system for a vehicle comprises a pressure regulator module and a pressure increasing module. The pressure regulator module regulates a fuel pressure supplied to an engine to a first predetermined pressure during an engine running period. The pressure increasing module selectively increases the fuel pressure to a second predetermined pressure during the engine running period when a counter value is one of greater than and less than a predetermined final value. The second predetermined pressure is greater than the first predetermined pressure, and the counter value is set to the predetermined final value after the engine is started for a first time after being assembled.

In other features, the pressure increasing module determines whether to increase the fuel pressure based on an engine coolant temperature and the engine running period when the counter value is the one of greater than and less than the predetermined final pressure.

In still other features, the pressure increasing module increases the fuel pressure to the second predetermined pressure when the engine coolant temperature is within a predetermined temperature range, the engine running period is less than a predetermined period, and the counter value is the one of greater than and less than the predetermined final pressure.

In further features, the pressure regulator module selectively decreases the fuel pressure to a third predetermined pressure that is less than the first predetermined pressure.

In still further features, the fuel pressure control system further comprises an engine runtime module. The engine runtime module starts the engine running period when an engine speed is greater than a predetermined speed.

In other features, the fuel pressure control system further comprises an engine runtime module. The engine runtime module starts the engine running period when an engine speed is greater than a predetermined speed for a predetermined number of combustion events.

In still other features, the fuel pressure control system further comprises an engine runtime module. The engine runtime module starts the engine running period when an engine speed is greater than a predetermined speed for a predetermined number of consecutive combustion events.

In further features, the first predetermined pressure is approximately four-hundred (400) kPa and the second predetermined pressure is approximately four-hundred, fifty (450) kPa.

In still further features, the second predetermined pressure is approximately twenty (20) percent greater than the first predetermined pressure.

In other features, the second predetermined pressure is approximately thirty (30) percent greater than the first predetermined pressure.

A fuel pressure control method for a vehicle comprises regulating a fuel pressure supplied to an engine to a first predetermined pressure during an engine running period and selectively increasing the fuel pressure to a second predetermined pressure during the engine running period when a counter value is one of greater than and less than a predetermined final value. The second predetermined pressure is greater than the first predetermined pressure, and the counter value is set to the predetermined final value after the engine is started for a first time after being assembled.

In other features, the fuel pressure control method further comprises determining whether to increase the fuel pressure based on an engine coolant temperature and the engine running period when the counter value is the one of greater than and less than the predetermined final pressure.

In still other features, the fuel pressure control method further comprises increasing the fuel pressure to the second predetermined pressure when the engine coolant temperature is within a predetermined temperature range, the engine running period is less than a predetermined period, and the counter value is the one of greater than and less than the predetermined final pressure.

In further features, the fuel pressure control method further comprises selectively decreasing the fuel pressure to a third predetermined pressure that is less than the first predetermined pressure.

In still further features, the fuel pressure control method further comprises starting the engine running period when an engine speed is greater than a predetermined speed.

In other features, the fuel pressure control method further comprises starting the engine running period when an engine speed is greater than a predetermined speed for a predetermined number of combustion events.

In still other features, the fuel pressure control method further comprises starting the engine running period when an engine speed is greater than a predetermined speed for a predetermined number of consecutive combustion events.

In further features, the first predetermined pressure is approximately four-hundred (400) kPa and the second predetermined pressure is approximately four-hundred, fifty (450) kPa.

In still further features, the second predetermined pressure is approximately twenty (20) percent greater than the first predetermined pressure.

In other features, the second predetermined pressure is approximately thirty (30) percent greater than the first predetermined pressure.

DETAILED DESCRIPTION

A fuel system supplies fuel to an engine for combustion. A fuel pump pressurizes fuel within a fuel rail. Fuel injectors supply fuel from the fuel rail to the engine. A fuel pressure control module regulates the pressure of the fuel within the fuel rail (i.e., fuel pressure) based on a predetermined startup pressure when engine startup is initiated.

During vehicle assembly, however, air is trapped within the fuel rail. When the engine is started for a first time (e.g., at an assembly plant), air trapped within the fuel rail may prevent the fuel pressure control module from providing a desired air/fuel mixture. More specifically, air trapped within the fuel rail may be purged from the fuel rail to the engine and cause the air/fuel mixture to be lean. The lean air/fuel mixture may cause, for example, engine misfire, stalling, and/or setting of one or more codes in diagnostic memory.

The fuel pressure control module of the present disclosure selectively increases the fuel pressure to a predetermined purging pressure when the engine is started for the first time. The predetermined purging pressure is greater than the predetermined startup pressure. Increasing the fuel pressure to the predetermined purging pressure decreases the volume of air (i.e., compresses the air) trapped within the fuel rail, which enables the fuel pressure control module to more accurately control the air/fuel mixture.

Referring now toFIG. 1, a functional block diagram of an engine system100is presented. Air is drawn into an engine102through an intake manifold104. A throttle valve106is actuated by a throttle actuator module108to vary the volume of air drawn into the engine102. The throttle actuator module108may include, for example, an electronic throttle controller (ETC). The air mixes with fuel from one or more fuel injector (e.g., fuel injector110) to form an air/fuel mixture. The air/fuel mixture is combusted within one or more cylinders of the engine102, such as cylinder112.

A spark plug114may initiate combustion of the air/fuel mixture within the cylinder112. A spark actuator module116controls the provision of spark by the spark plug114. Although one fuel injector, spark plug, and cylinder are shown, the engine102may include more or fewer fuel injectors, spark plugs, and/or cylinders. For example only, the engine102may include 2, 3, 4, 5, 6, 8, 10, or 12 cylinders. One fuel injector and spark plug may be provided for each cylinder of the engine102. Drive torque generated by combustion of the air/fuel mixture is output from the engine102via a crankshaft118. Exhaust gas resulting from combustion is expelled from the engine102to an exhaust system120.

Before combustion, fuel is stored in a fuel tank122. A fuel pump124draws fuel from the fuel tank122and pressurizes the fuel within a fuel rail126. The fuel rail126supplies pressurized fuel to the fuel injector110. While the fuel injector110is shown inFIG. 1as injecting fuel directly into the cylinder112, the fuel injector110may inject fuel into other suitable locations. For example only, the fuel injector110may inject fuel into the intake manifold104, near an intake valve associated with each of the cylinders, and/or into mixing chambers associated with each of the cylinders.

A fuel actuator module128controls opening of the fuel injector110based on signals from an engine control module (ECM)150. In this manner, the ECM150controls the timing of fuel injection and the amount of fuel injected by the fuel injector110. The ECM150also controls other engine actuators, such as the throttle actuator module108and the spark actuator116.

One or more sensors may also be implemented in the engine system100. For example only, the engine system100includes a crankshaft sensor152. The crankshaft sensor152measures the position of the crankshaft118and outputs the crankshaft position signal accordingly. For example only, the crankshaft sensor152may include a variable reluctance (VR) sensor or another suitable type of crankshaft sensor.

The crankshaft position signal may include a pulse train. Each pulse of the pulse train may be generated as a tooth of an N-toothed wheel (not shown) that rotates with the crankshaft118, passes the VR sensor. Accordingly, each pulse corresponds to an angular rotation of the crankshaft118by an amount equal to 360° divided by N teeth. The N-toothed wheel may also include a gap of one or more missing teeth, and the gap may be used as an indicator of one complete rotation of the crankshaft118.

The engine system100also includes a coolant temperature sensor154. The coolant temperature sensor154measures the temperature of engine coolant and outputs a coolant temperature signal accordingly. The coolant temperature sensor154may be located within the engine102or at another location where the coolant is circulated, such as a radiator (not shown). A fuel pressure sensor156measures the fuel pressure within the fuel rail126and outputs a fuel pressure signal accordingly.

The ECM150controls operation (i.e., activation/deactivation) of the fuel pump124to regulate the fuel pressure within the fuel rail126. For example only, the ECM150may maintain the fuel pressure at a predetermined operating pressure (e.g., approximately 250 kPa) during normal engine operation.

Engine startup commands are relayed to the ECM150by an input module158. An engine startup command may be generated based on, for example, turning of a key or depression of a button (not shown). A starter (not shown) engages and drives rotation of the crankshaft118when an engine startup command is received.

An engine cranking period may be said to begin when the starter engages or when the engine startup command is received. The engine cranking period may extend to when, for example, an engine speed exceeds a predetermined speed (e.g., approximately 500 rpm) for a predetermined number of consecutive combustion events (e.g., four in an engine having four cylinders). When the engine speed exceeds the predetermined speed for the predetermined number of combustion events, an engine running period may be said to begin.

During the engine running period, the ECM150generally controls the fuel pump124to achieve a predetermined startup pressure. The predetermined startup pressure may be calibratable and may be set based on, for example, a maximum fuel pressure that the fuel pump124may sustain over a period of time. For example only, the predetermined startup pressure may be approximately 400 kPa. Once the fuel pressure reaches the predetermined startup pressure, the ECM150may decrease the fuel pressure to the predetermined operating pressure.

Air is trapped within the fuel rail126, however, during assembly of the engine system100. When the engine102is started for a first time (e.g., at an assembly plant), the air trapped within the fuel rail126during assembly may prevent the ECM150from supplying a desired air/fuel mixture to the engine102. More specifically, air trapped within the fuel rail126may be expelled from the fuel rail126into the cylinder112. The injection of air to the cylinder112may cause the air/fuel mixture combusted within the cylinder112to be lean (i.e., have an equivalence ratio (EQR) of less than a stoichiometric EQR of 1.0). The lean air/fuel mixture may cause, for example, engine misfire, stalling, and/or setting of one or more codes in diagnostic memory (not shown).

The ECM150of the present disclosure includes a fuel pressure control module170that increases the fuel pressure during the engine running period when the engine102is started for the first time. The fuel pressure control module170increases the fuel pressure to a predetermined purging pressure that is greater than the predetermined startup pressure. Increasing the fuel pressure to the predetermined purging pressure decreases the volume of air (i.e., compresses the air) within the fuel rail126, which enables the ECM150to more accurately control the air/fuel mixture.

While the fuel pressure control module170is shown and described herein as being located within the ECM150, the fuel pressure control module170may be located in another suitable location. For example only, in other implementations, the fuel pressure control module170may be implemented externally to the ECM150and may be located near the fuel tank122. In such implementations, the fuel pressure control module170may control the fuel pressure based on a desired fuel pressure provided by the ECM150. The ECM150may set the desired fuel pressure to the predetermined purging pressure during the engine running period when the engine102is started for the first time.

Referring now toFIG. 2, a functional block diagram of an exemplary implementation of the fuel pressure control module170is presented. The fuel pressure control module170includes an engine speed module202, an enabling/disabling module204, an engine runtime module206, and a counter module208. The fuel pressure control module170also includes a pressure regulator module210and a pressure increasing module212.

The engine speed module202determines the rotational speed of the engine102(i.e., the engine speed) in revolutions per minute (rpm). In one implementation, the engine speed module202determines the engine speed based on the crankshaft signal provided by the crankshaft sensor152. For example only, the engine speed module202may determine the engine speed based on the period of time between the pulses of the pulse train output by the crankshaft sensor152.

The enabling/disabling module204determines whether the engine running period has begun based on the engine speed. The enabling/disabling module204selectively starts an engine runtime timer when the engine running period has begun. The engine running period begins (and the enabling/disabling module204starts the engine runtime timer) when the engine speed is greater than the predetermined speed for the predetermined number of combustion events.

For example only, the predetermined speed may be approximately 500 rpm and the predetermined number of combustion events may be four consecutive combustion events in engines having four cylinders. The engine runtime timer is reset to a predetermined reset value (e.g., zero) before being started. In this manner, the engine runtime timer tracks how long the engine102has been running (i.e., the engine runtime period).

The pressure regulator module210regulates the fuel pressure within the fuel rail126by controlling the fuel pump124. The pressure regulator module210may use feedback from the fuel pressure sensor156in regulating the fuel pressure.

The pressure regulator module210regulates the fuel pressure based on the predetermined startup pressure during the engine running period. The predetermined startup pressure may be calibratable and may be set based on, for example, a maximum fuel pressure that is sustainable by the fuel pump124. For example only, the predetermined startup pressure may be approximately 400 kPa. Later, the pressure regulator module210may decrease the fuel pressure and regulate the fuel pressure based on the predetermined operating pressure.

The pressure increasing module212selectively increases the fuel pressure to the predetermined purging pressure during the engine running period when the engine102is started for the first time. The pressure increasing module212determines whether to increase the fuel pressure based on whether the engine102has previously been started, the coolant temperature, and the engine runtime period.

The pressure increasing module212may increase the fuel pressure when the engine102is started for the first time, the coolant temperature is within a predetermined temperature range, and the engine runtime period is less than a predetermined period. For example only, the predetermined temperature range may be bounded by temperatures of approximately 10° C. and 60° C. and the predetermined period may be approximately 90 seconds.

The pressure increasing module212may determine whether the engine102has previously been started based on a counter value. The counter value may be obtained from, for example, the counter module208. For example only, the counter value may be implemented in the form of a manufacturer's enabling counter (MEC).

The counter value is initially set (e.g., by an ECM supplier) to a predetermined initial value. For example only, the counter value may be set to the predetermined initial value of 255. The counter value may be adjusted on one or more occasions after the engine102is started for the first time. In one implementation, the pressure increasing module212may determine that the engine102has previously been started when the counter value different than the predetermined initial value.

The counter value may also be set to a predetermined final value after the engine102is started for the first time. In one implementation, the counter value is set to the predetermined final value after the vehicle passes end of assembly diagnostics. For example only, the predetermined final value may be zero. In such an implementation, the pressure increasing module212may determine that the engine102has not previously been started until the counter value is equal to the predetermined final value. Further, the fuel pressure may be increased in some circumstances even after the engine102is started for the first time, such as if the engine102stalls during the first running of the engine102.

When increasing the fuel pressure, the pressure increasing module212increases the fuel pressure to the predetermined purging pressure. For example only, the predetermined purging pressure may be approximately 20-30% more than the predetermined startup pressure or approximately 450 kPa. Increasing the fuel pressure to the predetermined purging decreases the volume of air (i.e., compresses the air) trapped within the fuel rail126and enables the ECM150to more accurately control the air/fuel mixture.

Referring now toFIG. 3, a flowchart depicting an exemplary method300is presented. The method300begins in step302after the engine startup command is received where the method300controls the fuel pressure based on the predetermined startup pressure. The method300determines whether this is the first time that the engine102has been started after being assembled in step304. If true, the method300continues to step306; if false, the method300ends. The method300may determine whether the engine102has previously been started based on, for example, the counter value.

In step306, the method300determines whether the engine102is running. In other words, the method300determines whether the engine speed has been greater than the predetermined speed for the predetermined number of combustion events in step306. If true, the method300continues to step308; if false, the method remains in step306.

The method300starts the engine runtime timer in step308and continues to step310. The method300determines whether the coolant temperature is within the predetermined temperature range in step310. If true, the method300continues to step312; if false, the method300ends.

The method300determines whether the engine runtime period is less than the predetermined period in step312. If true, the method300increases the fuel pressure based on the predetermined purging pressure in step314and returns to step312. If false, the method300ends. In this manner, the method300increases the fuel pressure to the predetermined purging pressure when the engine coolant temperature is within the predetermined range of temperatures and the engine runtime period is less than the predetermined period during the engine runtime period when the engine102is started for the first time after assembly.