Valvetrain fault indication systems and methods using knock sensing

A system for a vehicle includes a knock indication module, a valve control module, and a fault indication module. The knock indication module selectively indicates that knock occurred within a cylinder of an engine. The valve control module controls lifting of a valve of a cylinder of the engine and, in response to the knock indication module indicating that knock occurred within the cylinder, transitions lifting of the valve from one of a low lift state and a high lift state to the other one of the low lift state and the high lift state. The fault indication module selectively indicates that a fault is present in a variable valve lift (VVL) mechanism of the cylinder based on whether the knock indication module indicates that knock occurred within the cylinder after the transition to the other one of the low lift state and the high lift state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. 13/590,369 filed on Aug. 21, 2012. The disclosure of the above related application is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to internal combustion engines and more particularly to systems and methods for identifying faults in a valvetrain.

BACKGROUND

Vehicles include an internal combustion engine that generates drive torque. An intake valve is selectively opened to draw air into a cylinder of the engine. The air mixes with fuel to form an air/fuel mixture. The air/fuel mixture is combusted within the cylinder. An exhaust valve is selectively opened to allow the exhaust gas resulting from combustion to exit the cylinder.

One or more rotating camshafts regulate the opening and closing of the intake and/or exhaust valves. The camshafts include cam lobes that are fixed to and rotate with the camshafts. The geometric profile of a cam lobe determines a valve opening schedule. More specifically, the geometric profile of a cam lobe generally controls the period that the valve is open (duration) and the amount or distance (lift) that the valve opens.

Variable valve actuation (VVA) and variable valve lift (VVL) improve fuel economy, engine efficiency, and/or performance by modifying valve duration and lift, respectively, as a function of engine operating conditions. Two-step VVL systems include VVL mechanisms, such as hydraulically-controlled, switchable roller finger followers (SRFFs). A SRFF associated with a valve (e.g., the intake or exhaust valves) allows the valve to be lifted in two discrete states: a low lift state and a high lift state. The valve lift associated with the high lift state is greater than the valve lift associated with the low lift state.

SUMMARY

A system for a vehicle includes a knock indication module, a valve control module, and a fault indication module. The knock indication module selectively indicates that knock occurred within a cylinder of an engine. The valve control module controls lifting of a valve of a cylinder of the engine and, in response to the knock indication module indicating that knock occurred within the cylinder, transitions lifting of the valve from one of a low lift state and a high lift state to the other one of the low lift state and the high lift state. The fault indication module selectively indicates that a fault is present in a variable valve lift (VVL) mechanism of the cylinder based on whether the knock indication module indicates that knock occurred within the cylinder after the transition to the other one of the low lift state and the high lift state.

A method for a vehicle includes: selectively indicating that knock occurred within a cylinder of an engine; and controlling lifting of a valve of a cylinder of the engine. The method further includes: in response to an indication that knock occurred within the cylinder, transitioning lifting of the valve from one of a low lift state and a high lift state to the other one of the low lift state and the high lift state. The method further includes: selectively indicating that a fault is present in a variable valve lift (VVL) mechanism of the cylinder based on whether the occurrence of knock within the cylinder is indicated after the transition to the other one of the low lift state and the high lift state.

DETAILED DESCRIPTION

An engine combusts an air/fuel mixture within cylinders to generate drive torque. Air flows into a cylinder through an intake valve. Exhaust flows out of a cylinder through an exhaust valve. Each cylinder may include one or more intake valves and one or more exhaust valves.

A variable valve lift (VVL) mechanism enables operation of an associated valve (e.g., an intake valve or an exhaust valve) in two discrete lift states: a high lift state and a low lift state. During operation in the low lift state, the VVL mechanism opens the valve a first distance. The VVL mechanism opens the valve a second distance during operation in the high lift state, and the second distance is greater than the first distance.

A cylinder with a faulty VVL mechanism will have different combustion characteristics (e.g., burn rate) than other cylinders. For example, a cylinder with a faulty VVL mechanism may exhibit a greater level of knock than one or more other cylinders. The present disclosure describes systems and methods for detecting and indicating whether a fault is present in a VVL mechanism of a cylinder based on knock.

Referring now toFIG. 1A, a functional block diagram of an example vehicle system100is presented. An engine102generates torque for a vehicle. Air is drawn into the engine102through an intake manifold104. Airflow into the intake manifold104may be varied by a throttle valve106. A throttle actuator module108(e.g., an electronic throttle controller) controls opening of the throttle valve106. One or more fuel injectors, such as fuel injector110, mix fuel with the air to form a combustible air/fuel mixture. A fuel actuator module112controls the fuel injectors.

A cylinder114includes a piston (not shown) that is coupled to a crankshaft116. Although the engine102is depicted as including only the cylinder114, the engine102may include more than one cylinder. The fuel injectors may inject fuel directly into the cylinders or at another suitable location. One combustion cycle of the cylinder114may include four strokes: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During one revolution of the crankshaft116(i.e., 360 degrees of crankshaft rotation), two of the four strokes can occur. One engine cycle includes each of the cylinders undergoing one combustion cycle and occurs over two revolutions of the crankshaft116(i.e., 720 degrees of crankshaft rotation).

Referring also toFIG. 1B, during the intake stroke, the piston is lowered to a bottom most position, and air and fuel may be provided to the cylinder114. The bottom most position may be referred to as a bottom dead center (BDC) position. During the intake stroke, air enters the cylinder114through one or more intake valves associated with the cylinder114, such as intake valve118. One or more exhaust valves, such as exhaust valve120, are also associated with the cylinder114. While only the intake valve118and the exhaust valve120are shown and discussed, the cylinder114may include one or more additional intake valves and/or one or more additional exhaust valves.

During the compression stroke, the crankshaft116drives the piston toward a top most position. The top most position may be referred to as a top dead center (TDC) position. The intake valve118and the exhaust valve120are both closed during the compression stroke, and the piston compresses the contents of the cylinder114. A spark plug122may ignite the air/fuel mixture. A spark actuator module124controls the spark plugs of the engine102. The spark plugs may be omitted in various types of engines.

Combustion of the air/fuel mixture drives the piston back toward the BDC position during the expansion stroke. The piston drives the crankshaft116. The rotational force (i.e., torque) on the crankshaft116from combustion of the air/fuel mixture may be a source of compressive force for a compression stroke of a combustion cycle of a next cylinder in a predetermined firing order of the cylinders.

Exhaust resulting from the combustion of the air/fuel mixture is expelled from the cylinder114during the exhaust stroke. The exhaust is expelled from the cylinder114via the exhaust valve120. While the engine102is described as a four-stroke, spark ignition engine, the engine102may be another suitable type of engine. One or more electric motors may be provided with the engine102.

The timing of opening and closing of the intake valve118is regulated by an intake camshaft126. An intake camshaft, such as the intake camshaft126, may be provided for each bank of cylinders of the engine102. The timing of opening and closing of the exhaust valve120is regulated by an exhaust camshaft127. An exhaust camshaft (not shown) may be provided for each bank of cylinders of the engine102. Rotation of the intake camshaft(s) and the exhaust camshaft(s) is generally driven by rotation of the crankshaft116, such as by a belt or a chain.

A cam phaser regulates rotation of an associated camshaft. For example only, intake cam phaser128regulates rotation of the intake camshaft126. The intake cam phaser128may adjust the rotation of the intake camshaft126, for example, with respect to rotation of the crankshaft116, with respect to a position of the piston, with respect to another camshaft, etc. For example only, the intake cam phaser128may retard or advance rotation of the intake camshaft126, thereby changing the opening and closing timing of the intake valve118. An exhaust cam phaser129regulates rotation of the exhaust camshaft127. Adjusting rotation of a camshaft with respect to rotation of the crankshaft116may be referred to as camshaft phasing.

A valve actuator module130controls the intake cam phaser128. The valve actuator module130or another actuator module may control operation of the exhaust cam phaser129. A cam phaser may be electrically or hydraulically actuated. Hydraulically actuated cam phasers operate based on pressure of a hydraulic fluid (e.g., oil) supplied to the cam phaser. Electrically actuated cam phasers operate using electrical power.

A variable valve lift (VVL) mechanism136(FIG. 1B) is associated with the intake valve118. For example only, the VVL mechanism136may include a switchable roller finger follower (SRFF) mechanism. While the VVL mechanism136is shown and will be discussed as a SRFF, the VVL mechanism136may include other types of valve lift mechanisms that enable an associated valve to be lifted to two or more discrete lift positions. Further, while the VVL mechanism136is shown and discussed as being associated with the intake valve118, another VVL mechanism may be implemented similarly for the exhaust valve120. For example only, one VVL mechanism may be provided for each valve of each cylinder.

The VVL mechanism136includes a lift adjuster138and a cam follower140. The cam follower140is in mechanical contact with a valve stem142of the intake valve118. A biasing device143biases the valve stem142into contact with the cam follower140. The cam follower140is also in mechanical contact with the intake camshaft126and the lift adjuster138.

The intake camshaft126rotates about a camshaft axis144. The intake camshaft126includes a plurality of cam lobes including low lift cam lobes and high lift cam lobes, such as low lift cam lobe146and high lift cam lobe148. For example only, the intake camshaft126may include one low lift cam lobe and one high lift cam lobe for each intake valve of each cylinder. The exhaust camshaft127may include one low lift cam lobe and one high lift cam lobe for each exhaust valve of each cylinder. While only lifting of the intake valve118will be discussed, the present application is also applicable to exhaust valves and other intake valves.

The low and high lift cam lobes146and148rotate with the intake camshaft126. Air may flow into the cylinder114through an inlet passage150when the intake valve118is open. Airflow into the cylinder114through the inlet passage150is blocked when the intake valve118is closed. The intake valve118is selectively opened and closed via the intake camshaft126. More specifically, one of the low lift cam lobe146and the high lift cam lobe148opens and closes the intake valve118during a given combustion cycle.

A cam lobe contacting the cam follower140applies a force to the cam follower140in the direction of the valve stem142and the lift adjuster138. The cam follower140may also be referred to as a rocker arm. The lift adjuster138is collapsible to allow the intake valve118to be opened to two discrete positions, a low lift position and high lift position. Pressure of a hydraulic fluid152may be controlled to control which one of the low lift cam lobe146and the high lift cam lobe148opens the intake valve118during a given combustion cycle.

During operation of the intake valve118in the low lift state, the low lift cam lobe146causes the VVL mechanism136to pivot in accordance with the geometry of the low lift cam lobe146. The pivoting of the VVL mechanism136caused by the low lift cam lobe146opens the intake valve118a first predetermined amount or distance. During operation in the high lift state, the high lift cam lobe148causes the VVL mechanism136to pivot in accordance with the geometry of the high lift cam lobe148. The pivoting of the VVL mechanism136caused by the high lift cam lobe148opens the intake valve118a second predetermined amount or distance. The second predetermined amount or distance is greater than the first predetermined amount or distance.

A fluid control valve154regulates the pressure of the hydraulic fluid152. The valve actuator module130or another actuator module controls the fluid control valve154to control the pressure of the hydraulic fluid152. The fluid control valve154may also be referred to as an oil control valve (OCV).

A crankshaft position sensor160(FIG. 1A) monitors an N-toothed wheel162and generates a crankshaft position signal based on rotation of the N-toothed wheel162. For example only, the crankshaft position sensor160may include a variable reluctance (VR) sensor or another suitable type of crankshaft position sensor. The N-toothed wheel162rotates with the crankshaft116.

A manifold absolute pressure (MAP) sensor164monitors pressure within the intake manifold104and generates a MAP signal based on the pressure. In various implementations, vacuum within the intake manifold104may be measured, where the vacuum is measured relative to ambient pressure. A mass air flowrate (MAF) sensor166monitors mass flowrate of air flowing through the throttle valve106and generates a MAF signal based on the mass flowrate.

A knock sensor168measures vibration of the engine102and generates a knock signal based on the vibration. For example only, the knock sensor168may include a piezo-electric knock sensor that is in contact with the engine102or another suitable type of knock sensor. While only the knock sensor168is shown and discussed, multiple knock sensors may be included. For example, one knock sensor may be provided for each cylinder of the engine102, one knock sensor may be provided for each cylinder bank, etc. One or more other sensors may also be implemented.

The engine102transfers torque to a transmission170. The transmission170may include a manual type transmission, an automatic type transmission, an auto-manual type transmission, or another suitable type of transmission. The transmission170may transfer torque to one or more wheels (not shown) via a transmission output shaft172and a driveline (not shown).

An engine control module (ECM)180controls operation of the engine102. More specifically, the ECM180controls the throttle valve106via the throttle actuator module108and controls the fuel injectors via the fuel actuator module112. The ECM180controls the spark plugs via the spark actuator module124. The ECM180controls phasing of the intake and exhaust valves via the valve actuator module130. The ECM180may also control lifting of the intake and exhaust valve via the valve actuator module130.

Referring now toFIG. 2, a functional block diagram of an example portion of the ECM180is presented. A driver torque module204may determine a driver torque request208based on one or more driver inputs, such as an accelerator pedal position, a brake pedal position, a cruise control input, and/or one or more other suitable driver inputs. One or more engine operating parameters may be controlled based on the driver torque request208and/or one or more other torque requests.

For example, a throttle control module212may determine a desired throttle opening216based on the driver torque request208. The throttle actuator module108may adjust opening of the throttle valve106based on the desired throttle opening216. A spark control module220may determine a desired spark timing224based on the driver torque request208. The spark actuator module124may generate spark based on the desired spark timing224.

A fuel control module228may determine one or more desired fueling parameters232based on the driver torque request208. For example, the desired fueling parameters232may include fuel injection timing and amount. The fuel actuator module112may actuate the fuel injectors to inject fuel based on the desired fueling parameters232.

A valve control module236may determine desired intake and exhaust phase angles (not shown inFIG. 2) and a desired lift state240based on the driver torque request208. The desired lift state240may be one of the high lift state and the low lift state. The valve actuator module130controls operation of the valves in the high lift state or the low lift state at a given time based on the desired lift state240. The valve actuator module130may control intake and exhaust camshaft phasing based on the desired intake and exhaust phase angles.

A knock indication module244indicates whether knock occurred within the cylinder114based on a knock signal248generated based on output from the knock sensor168. The knock indication module244generates knock data252indicating whether knock occurred within the cylinder114. The knock indication module244determines whether knock occurred in each other cylinder based on knock measured using a knock sensor and generates the knock data252accordingly. The knock indication module244performs the knock detection and indication for each combustion cycle of each cylinder of the engine102.

A cylinder with a faulty VVL mechanism will have different combustion characteristics (e.g., burn rate) than other cylinders. For example, a cylinder with a faulty VVL mechanism may exhibit a greater level of knock than one or more other cylinders. A cylinder with a faulty VVL mechanism may, for example, exhibit knock more frequently (e.g., a greater number of combustion cycles) than cylinders with reliable VVL mechanisms and/or a cylinder with a faulty VVL mechanism may exhibit more observable knock (e.g., more vibration) than cylinders with reliable VVL mechanisms.

When a VVL mechanism is faulty, the associated valve will be stuck in operation in one of the high lift state and the low lift state, regardless of whether the desired lift state240is the high lift state or the low lift state. For example, when the VVL mechanism is faulty, the associated valve may be stuck operating in the high lift state both when the desired lift state240is the high lift state and when the desired lift state240is the low lift state.

A storage module256stores the knock data252for the cylinders and the combustion events. For example, the storage module256may track a number of times that the knock indication module244indicated that knock occurred for each cylinder over a predetermined period or a predetermined number of engine cycles.

A fault detection module260may include a transition command module264and a fault indication module268. In response to occurrence of a greater level of knock in a cylinder relative to a level of knock in one or more other cylinders, the transition command module264commands the valve control module236to transition the desired lift state240to the other one of the lift states. The greater level of knock may include, for example, a greater number of occurrences of knock, more observable knock, or another suitable indicator of a greater level of knock.

When the desired lift state240is set to the high lift state, the valve control module236transitions the desired lift state240to the low lift state in response to the command. When the desired lift state240is set to the low lift state, the valve control module236transitions the desired lift state to the high lift state in response to the command.

The transition command module264may also command the spark control module220to selectively advance the spark timing in response to a greater level of knock in a cylinder relative to a level of knock in one or more other cylinders. The transition command module264may, for example, command the spark control module220to advance the spark timing by a predetermined amount each combustion cycle. Advancing the spark timing may make knock more observable. In advancing the spark timing, the spark control module220may advance the spark timing past a maximum best torque (MBT) spark timing for the operating conditions.

In response to the transition to the other one of the lift states, the fault indication module268monitors whether the cylinder continues to exhibit a greater level of knock than one or more other cylinders. The fault indication module268may wait a predetermined period or a predetermined number of engine cycles after the transition to the other one of the lift states before performing the monitoring.

The fault indication module268indicates whether a fault is present in a VVL mechanism of the cylinder based on whether the cylinder continues to exhibit a greater level of knock than one or more other cylinders after the transition to the other one of the lift states. For example, the fault indication module268may indicate that a fault is present in a VVL mechanism when the cylinder does not exhibit a greater level of knock than one or more other cylinders after the transition. When the cylinder continues to exhibit a greater level of knock than one or more other cylinders after the transition, the fault indication module268may indicate that no fault is present in a VVL mechanism.

In various implementations, a second transition in the desired lift state240may be performed when the cylinder does not exhibit a greater level of knock than one or more other cylinders after the transition to the other one of the lift states. In other words, the desired lift state240may be transitioned back to the original one of the lift states. The second transition may be performed, for example, to verify the presence of a fault in the VVL mechanism by verifying that the cylinder exhibits a greater level of knock during operation in the original one of the lift states and does not exhibit knock during operation in the other one of the lift states.

The fault indication module268may indicate whether a fault is present in a VVL mechanism of the cylinder based on knock of the cylinder after the second transition. For example, the fault indication module268may indicate that a fault is present in a VVL mechanism of the cylinder when the cylinder exhibits a greater level of knock than one or more other cylinders after the second transition. When the cylinder does not exhibit a greater level of knock than one or more other cylinders after the second transition, the fault indication module268may indicate that no fault is present in a VVL mechanism. The fault indication module268may again wait a predetermined period or a predetermined number of engine cycles after the second transition to the other one of the lift states before performing the monitoring.

The fault indication module268indicates whether a fault is present in a VVL mechanism of the cylinder via a VVL mechanism fault indicator272. For example, the fault indication module268may set the VVL mechanism fault indicator272to an active state in memory276when a fault is present in a VVL mechanism of the cylinder. The fault indication module268may set the VVL mechanism fault indicator272to an inactive state when a fault is not present in a VVL mechanism. For example, the VVL mechanism fault indicator272may be a predetermined diagnostic trouble code (DTC) associated with a fault in a VVL mechanism of the cylinder. The fault in the VVL mechanism may be, for example, a broken rocker arm.

The fault indication module268may also generate the VVL mechanism fault indicator272to indicate whether the faulty VVL mechanism is stuck in operation in the high lift state or the low lift state. When the cylinder stops exhibiting knock after the transition and/or exhibits knock after the second transition, the fault indication module268may indicate that the VVL mechanism is stuck operating the associated valve in the original lift state. For example, when the desired lift state240was first transitioned from the low lift state to the high lift state and second transitioned from the high lift state to the low lift state, the fault indication module268may indicate that the VVL mechanism is stuck in the low lift state when the cylinder ceases exhibiting knock after the first transition to the high lift state and/or the cylinder exhibits knock after the second transition to the low lift state.

A monitoring module280may monitor generation of the VVL mechanism fault indicator272and/or one or more other fault indicators. In response to generation of the VVL mechanism fault indicator272, the monitoring module280may, for example, illuminate a malfunction indicator lamp (MIL)284. Based on the VVL mechanism fault indicator272, a vehicle servicer can identify and replace the VVL mechanism that includes the fault and that caused the knock.

One or more other remedial actions may be taken in response to generation of the VVL mechanism fault indicator272. For example only, the valve control module236may limit setting of the desired lift state240to the one of the lift states that the VVL mechanism is stuck. For example, when the fault indication module268indicates that the VVL mechanism is stuck in the low lift state, the valve control module236may set the desired lift state240only to the low lift state and refrain from setting the desired lift state240to the high lift state.

Referring now toFIG. 3, a flowchart depicting an example method of determining and indicating whether a fault is present in a VVL mechanism of a cylinder is presented. Control may begin with304where control determines whether one or more cylinder has a greater level of knock than one or more other cylinders. If true, control may selectively adjust (e.g., advance) the spark timing at308and continue with312. If false, control may remain at304.

At312, control transitions the desired lift state240to the other one of the lift states. For example, if the desired lift state240is in the low lift state, control transitions the desired lift state240to the high lift state, and vice versa. At316, control may determine whether the cylinder has a greater level of knock than one or more other cylinders. If false, control may indicate that a fault is present in a VVL mechanism of the cylinder at320, and control may end. Control may also indicate that the VVL mechanism is stuck in operation in the one of lift states from before the transition at320. For example, if the desired lift state240was in the low lift state before the transition, control may indicate that the VVL mechanism is stuck in operation in the low lift state at320. If true at316, control may indicate that no fault is present in the VVL mechanisms of the engine102at324, and control may end.

One or more remedial actions may be taken when a fault is present in a VVL mechanism of the cylinder. For example, control may limit the desired lift state240to the one of the lift states in which the VVL mechanism is stuck and prevent the desired lift state240from being transitioned to the other one of the lift states. Additionally or alternatively, control may illuminate the MIL284.

Referring now toFIG. 4, a flowchart depicting an example method of determining and indicating whether a fault is present in a VVL mechanism of a cylinder is presented. Control may begin with404where control may determine whether one or more enabling conditions for determining whether a fault is present in a VVL mechanism of a cylinder are satisfied. If true, control may continue with408. If false, control may remain at404.

At408, control may selectively adjust (e.g., advance) the spark timing and continue with412. Control may determine whether one or more cylinders have a greater level of knock than one or more other cylinders at412. If true, control may continue with416-428. If false, control may continue with432-444which are discussed further below.

Control transitions the desired lift state240to the other one of the lift states at416. For example, if the desired lift state240is in the low lift state, control transitions the desired lift state240to the high lift state, and vice versa. At420, control may determine whether the one or more cylinders have a greater level of knock than one or more other cylinders. If false, control may indicate that a fault is present in a VVL mechanism of the cylinder at428, and control may end. Control may also indicate that the VVL mechanism is stuck in operation in the one of lift states from before the transition at428. For example, if the desired lift state240was in the low lift state before the transition, control may indicate that the VVL mechanism is stuck in operation in the low lift state at428. If true at420, control may indicate that no fault is present in the VVL mechanisms of the cylinder at424, and control may end.

As stated above, when412is false, control may continue with432-444. At432, control transitions the desired lift state240to the other one of the lift states. For example, if the desired lift state240is in the low lift state, control transitions the desired lift state240to the high lift state, and vice versa.

At436, control may determine whether one or more cylinders have a greater level of knock than one or more other cylinders while not exhibiting knock before the transition. If true, control may indicate that a fault is present in a VVL mechanism of the cylinder at440, and control may end. Control may also indicate that the VVL mechanism is stuck in operation in the one of lift states from before the transition at440. For example, if the desired lift state240was in the low lift state before the transition, control may indicate that the VVL mechanism is stuck in operation in the low lift state at440. If true at436, control may indicate that no fault is present in the VVL mechanisms of the engine102at444, and control may end.